*Transcriber’s notes*:
The text of this complex e-book has mostly been preserved in
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capitalisation, hyphenation and diacritics; however, some such flaws
have been corrected silently. A list of spelling corrections is
appended at the end of the book. Multiple levels of headings and
subheadings, not all of which are consistently formatted, can make it
difficult to follow the text coherently. The author has used [square
brackets] to identify his personal additions but these are not always
readily detectable and can be confused with similar brackets used for
other purposes.
The book contains numerous illustrations that vary in size and
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approximate indication of their location.
In this plain text e-version, italic text is denoted by _underscores_
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One incorrect index page reference has been changed, viz. 730 → 369
‘pigment of the skin’
TRANSLATIONS
OF
FOREIGN BIOLOGICAL MEMOIRS
II
London
HENRY FROWDE
[Illustration]
Oxford University Press Warehouse
Amen Corner, E.C.
THE
ANATOMY OF THE FROG
BY
Dr. ALEXANDER ECKER
PROFESSOR OF HUMAN AND COMPARATIVE ANATOMY
IN THE UNIVERSITY OF FREIBURG
Translated, with numerous Annotations and Additions
BY
GEORGE HASLAM, M.D.
SCIENTIFIC ASSISTANT IN THE MEDICAL DEPARTMENT IN THE UNIVERSITY
OF ZÜRICH; FORMERLY ASSISTANT LECTURER IN PHYSIOLOGY IN THE
OWENS COLLEGE, VICTORIA UNIVERSITY, MANCHESTER
_ILLUSTRATED WITH MANY WOOD ENGRAVINGS_
_AND TWO COLOURED PLATES EXECUTED BY HOFMANN, WÜRTZBURG, BAVARIA_
Oxford
AT THE CLARENDON PRESS
1889
[_All rights reserved_]
TRANSLATOR’S PREFACE.
I undertook the publication of a translation of Ecker’s ‘Anatomie des
Frosches’ at the suggestion of Professor A. Gamgee while I was working
under his superintendence in the physiological laboratory of the Owens
College. The work was subsequently accepted by the Delegates of the
Clarendon Press, as one of the series of ‘Foreign Biological Memoirs,’
published by them. Early in the progress of the work it became evident
that a mere translation would be unsatisfactory, and that it would
be desirable to recast and modify several portions of the book. It
was deemed advisable to give greater completeness to the work by
descriptions of the minute structure of the several organs. For these
purposes the appearance of the work has been unavoidably delayed.
I have done my best to bring the book up to date by including the
results of recent researches, to which I have added many facts derived
from my own personal investigations. All such additions are enclosed
within square brackets [ ]. More than a hundred new figures, of which
one-third are original, have been added; and copious, though it is
feared still incomplete, lists of references to frog-literature have
been drawn up. By these additions the size of the book has been
considerably increased.
In the several sections into which the book is divided the following
points may be more particularly noticed:--
Sect. I. The Bones and Joints. The nomenclature of Parker and Bettany
has been adopted throughout.
Sect. II. The Muscles. This section remains in its original form.
Sect. III. The Nervous System. The chapters on the central
nervous system and the sympathetic system have been rewritten.
The description of the arteries of the brain is entirely new,
while the chapters on cranial and spinal nerves have received
many smaller additions, and have been rearranged to facilitate
reference.
Sect. IV. The Vascular System. The chapter on the heart is
practically new, and many additions and alterations have been made
in the descriptions of the blood-vessels and lymphatics.
Sect. V. The Alimentary Canal, with its appendages, the Spleen and
the Peritoneum. In this section much new material has been added:
the descriptions of the blood-vessels of the liver, the ducts
of the liver and pancreas, etc., being the results of original
investigation.
Sect. VI. The Respiratory Organs, the Thymus and Thyroid Glands.
These organs have been carefully studied and numerous new details
are noted. The lymphatic glands of the hyoid region have, after
some hesitation, been designated tonsils.
Sect. VII. The Urino-Genital Organs. A very large number of
preparations have been made to investigate the vessels and
uriniferous tubes of the kidneys; and the descriptions of the
remaining organs of this section have received large additions
from recent publications.
Sect. VIII. The Skin and the Sense-Organs. This section has, with the
exception of very small portions, been re-written and very much
enlarged.
Before concluding this preface, I must thank my friend Professor A.
Milnes Marshall, of the Owens College, for all the help and kindness
he has extended to me before and during the time this work has been
in hand; to him I am indebted not alone for the loan of books,
pamphlets, etc., and for much useful information, but also for the care
and patience with which he has read and corrected the whole of the
proof-sheets.
To Professor G. Lunge, of Zürich, I am indebted for the use of the
library of the Gesellschaft der Naturforscher of Zürich; and to my
friend Mr. C. Herbert Hurst, of the Owens College, for the drawings
for figures 132, 133, 134, and 136; also to Dr. Max Köppen, of
Strasburg, for the proof-sheets of his valuable paper, ‘Zur Anatomie
des Froschgehirns’: to these gentlemen I beg to express herewith my
heartiest thanks. Lastly, I must express my sense of indebtedness to
the Delegates of the Clarendon Press, who have kindly allowed me to
alter the original plan of the book, and to make extensive additions
far beyond the limits originally intended.
A second edition of the original German work is in course of
publication. The first part, on the bones and muscles, has already
appeared.
GEO. HASLAM.
Zürich, 1888.
PREFACE TO THE FIRST PART.
The idea of this manual on the anatomy of the frog, of which I now
offer the first part to physiologists and to those who would become
such, occurred to me during the preparation of the plates for my
‘Icones Physiologicae.’ I was then convinced of the necessity of such
a book. I regret that many direct and indirect causes have hindered
its earlier completion; fortunately, however, its appearance is still
opportune, as the need for the book has not diminished. I am conscious
that the book requires a recommendation to the indulgent judgment of
my fellow-workers, since almost every one has studied the frog for one
purpose or another, and each will closely criticize in that department
with which he is most familiar. Although I shall not be able to satisfy
all, still I hope that my work may serve as a useful basis for further
investigations, and I would apply to it the words with which Sömmering
prefaced his anatomy: ‘Ich wünschte ein Handbuch zu liefern und seine
Einrichtung so zu treffen, dass man künftig an ihm als einer Basis nach
Erforderniss leicht ändern, wegnehmen und zusetzen könnte[1].’
[Footnote 1: ‘I wished to furnish a manual so arranged that it might
serve as a basis easily altered, pruned, or enlarged as the future
might need.’]
Lest more be anticipated from the book than it is intended to supply,
I would observe that I have throughout had in mind only a descriptive
anatomy of the indigenous (German) frog; a comparative anatomy of
Batrachians was as foreign to my intention as were developmental
or histological questions: hence morphological details must not be
expected. Any hope of formulating a systematic nomenclature of the
muscles has been abandoned; as neither one based upon their mode of
action, of which we know so little, nor one based upon their origins
and insertions, as demonstrated by the unpronounceable names of
Chaussier and Dugès, is really practicable. I have therefore preferred
to avail myself, as far as possible, of the received names, which have
been chosen partly according to mode of action, partly according to
origin and insertion, and partly according to position and form; while
in the choice of new names I have given preference to the simplest.
The figures are, with few exceptions, original, and drawn by myself.
Their careful execution in woodcut has added a very necessary neatness
to that correctness, which alone I claim as mine.
ALEXANDER ECKER.
Freiburg,
_February, 1864_.
PREFACE TO THE SECOND PART.
Sixteen years have elapsed since the first portion of this anatomy of
the frog appeared; this second portion, therefore, requires a somewhat
apologetic introduction.
The nervous and vascular systems have, in substance, been known for
some years; still, certain points required a thorough revision: this
seemed especially necessary with regard to the cranial nerves. In
consequence of my anthropological investigations, and particularly
through undertaking the editorship of the ‘Archiv für Anthropologie,’
my attention was drawn into another channel, and I found it impossible
to work out this chapter: consequently the whole was deferred, and
would have been still longer delayed had I not received assistance.
At my request Professor Wiedersheim undertook to investigate afresh the
cranial nerves, the brain, the spinal cord, and the sympathetic system;
and the descriptions of these parts are the result of his work alone. I
regard it as most advantageous to this second part that so experienced
an investigator in the anatomy of Amphibia should have given me his
help.
The remaining portions appear almost unaltered as written several
years ago; and the majority of the illustrations date from the same
period. I had neither the time nor the zeal necessary to re-examine the
whole; besides, it is doubtful whether eyes some twenty years older
would improve matters.
This somewhat neglected book is therefore commended to the indulgence
of my fellow-workers, with the hope that it may at least form a basis
upon which further work may easily be done; to proffer more than this,
as I stated, with a quotation from Sömmering, in the preface to the
first part, I have never even hoped.
The final part of the work, on the viscera and sense-organs, has been
undertaken by Professor Wiedersheim, and will appear in the Spring of
1882.
ALEXANDER ECKER.
Freiburg,
_August, 1881_.
CONTENTS.
PAGE
INTRODUCTION 1
SECTION I. THE BONES AND JOINTS 11
" II. THE MUSCLES 53
" III. THE NERVOUS SYSTEM 121
" IV. THE VASCULAR SYSTEM 203
" V. THE ALIMENTARY TRACT WITH ITS APPENDAGES, THE
SPLEEN, AND THE PERITONEUM 267
" VI. THE LARYNX, LUNGS, VOCAL SACS, THYMUS AND THYROID
GLANDS, AND THE LYMPHATIC GLANDS (TONSILS?) OF
THE HYOID REGION 307
" VII. THE URINO-GENITAL SYSTEM, THE ADRENALS, AND THE
FAT-BODIES 325
" VIII. THE SKIN AND THE SENSE-ORGANS 351
ADDENDA, ETC. 425
INDEX 441
ILLUSTRATIONS.
FIGURE PAGE
1. The Green water-frog, _Rana esculenta_, L. 4
2. The Brown grass-frog, _Rana temporaria_, L. 8
3. Femur of _Rana esculenta_ 16
4. Vertebrae of do. 17
5. Vertebral column of do. 18
6, 7. Section through a vertebra of _Rana esculenta_ 20
8, 9. Urostyle of _Rana esculenta_ 21
10–14. Skull of do. 22, 23, 25, 28
15. Nasal Cartilages of frog 29
16, 17. Skull of _Rana esculenta_ 29, 30
18. Origin of suspensory cartilage from the skull 32
19, 20. Skull of _Rana esculenta_ 32, 33
21. Mandible of _Rana esculenta_ 34
22. Hyoid of _Rana esculenta_ 35
23. Omosternum of _Rana esculenta_ 36
24. Shoulder-girdle and sternum of do. 36
25. Shoulder-girdle of the frog 37
26, 27. Suprascapula of _Rana esculenta_ 38
28. Left scapula of _Rana esculenta_ 38
29. Scapula seen from behind 38
30. Left coracoid 39
31. Clavicle of the left side 39
32. Right shoulder-girdle of _Rana esculenta_ 40
33. Hinder border of the scapula and coracoid 40
34. Clavicular cartilage of _Rana esculenta_ 40
35. Humerus of _Rana esculenta_ (female) 41
36. Do. (male) 41
37. Do. (female) 41
38. Radio-ulnar of _Rana esculenta_ 43
39, 40. Bones of the forearm and hand of _Rana esculenta_ 44, 46
41, 42. Pelvis of _Rana esculenta_ 48
43. Horizontal section through the iliac bones, etc. 49
44. Femur of _Rana esculenta_ 49
45. Tibio-fibula of do. 50
46. Section of the tibio-fibula 50
47. Right foot of _Rana esculenta_ 51
48–50. Eye-muscles of do. 55, 56
51. Skull and orbital cavities of _Rana esculenta_ 57
52. M. levator bulbi of _Rana esculenta_ 57
53. Eye-muscles of _Rana esculenta_ 58
54. Facial muscles of do. 59
55. Muscles of the back and shoulder 60
56, 57. Muscles of the lower jaw of _Rana esculenta_ 61, 62
58. Muscles of the throat, chest, and abdomen of do. 63
59. Muscles of the hyoid bone and the tongue of do. 64
60. Do. (from below) 65
61. Do. (from right side) 66
62. Muscles of the throat, chest, and belly of _Rana esculenta_ 68
63. Muscles of trunk of _Rana esculenta_ (from the right side) 69
64. Second layer of abdominal muscles of _Rana esculenta_,
from right side and below 70
65. M. obliquus internus 71
66. Muscles of the back and shoulder blade 72
67. Muscles of the back and pelvic girdle of _Rana esculenta_ 74
68. Muscles of the shoulder, from below 77
69. Muscles of the right shoulder and upper arm 78
70. Right shoulder, from below 79
71. Muscles of the back and shoulder 79
72. Muscles of the chest, throat, and belly of _Rana esculenta_ 81
73. Muscle of right shoulder and upper arm 83
74. Muscles of the right arm of _Rana esculenta_ 84
75. Do. (deep layer) 85
76. Muscles of forearm of _Rana esculenta_ 86
77. Muscles of hand of _Rana esculenta_, volar surface 88
78. Second layer of muscles on volar surface of hand of
_Rana esculenta_ 88
79. Muscles of hand of _Rana esculenta_ 92
80. Muscles of left thigh of do. 95
81, 82. Do. (ventral surface) 98, 99
83. Deep muscles of left thigh of _Rana esculenta_ 100
84. Do. (Dorsal view) 101
85. Left half of pelvis of _Rana esculenta_ 101
86. Muscles of the right leg and foot of _Rana esculenta_
(Dorsal view) 103
87. Do. (seen from below) 105
88. Do. (Dorsal view) 106
89–91. Muscles of the plantar surface of foot of
_Rana esculenta_ 107, 111, 112
92–94. Dorsal view of muscles of foot of
_Rana esculenta_ 115, 117, 118
95. Pectoral region of _Rana esculenta_ 119
96. Hind portion of back and thigh of _Rana esculenta_ 120
97. The nervous system of _Rana esculenta_, from the
ventral surface 136
98. Dorsal view of brain of _Rana esculenta_ 143
99. Transverse section through hinder end of Medulla
oblongata 144
100. Do. at the point of origin of the abducens nerve 145
101. Do. of the auditory nerve 146
102. Ventral view of brain of _Rana esculenta_ 149
103. Lateral do. 150
104. Transverse section through the anterior portion of
the optic lobes opposite the origin of the
motor-oculi nerve. 151
105. Horizontal section through the brain to show the
ventricles 153
106. Section through the lower division of the pituitary body 157
107. Transverse section through the hinder portion of the
cerebral hemispheres 158
108. Transverse section near the middle of the cerebral
hemispheres 158
109. From a transverse section through one of the cerebral
hemispheres 159
110. Diagram to show the Vena spinalis posterior, etc. 164
111. Dorsal view of the orbit, etc. (deep dissection)
(_coloured_) Plate I.
112. Do. (superficial do.) (_coloured_) Plate I.
113. View of roof of mouth; mucous membrane, etc.
(_coloured_) Plate I.
114. Lateral dissection of head, etc. (_coloured_) Plate I.
115. Dissection of the floor of the mouth (_coloured_) Plate I.
116. Right half of skull of _Rana esculenta_ 174
117. The nervous system of _Rana esculenta_, from the
ventral surface 176
118. Ventral view of the brain and spinal cord, to show the
points of exit of the spinal nerves 178
119. Ventral view of the spinal ganglia 179
120. Schema of spinal ganglion 179
121. Dorsal branches of the spinal nerves 181
122. The brachial plexus 184
123, 124. Nerves of the ventral surface of the arm 185, 186
125. The N. radialis 186
126. Ventral view of the brain and spinal cord 188
127. The sciatic plexus 190
128. Distribution of the sciatic nerve 193
129. Nerves of the leg and sole of the foot 194
130. Distribution of the N. peroneus 196
131. Sympathetic cord 198
132. The heart and blood-vessels, seen from the ventral
surface 213
133. The heart, seen from above 214
134. The frog’s heart, seen from the ventral surface 215
135. Dissection of a case in which the auricular septum
is placed more to the left than is normal 215
136. Dissection of the heart from the left side 216
137 I. Transverse section through the junction of the hinder
and middle thirds of the ventricle of _R. temporaria_ 217
137 II. Transverse section through junction of the middle
and anterior thirds of the same heart 217
138. Portion of a transverse section through the middle
of the ventricle of _R. temporaria_ 218
139. Course of the cardiac nerves in the auricular septum 219
140. Group of nerve-cells on the cardiac nerve, from the
auricular septum 220
141_a_. Small group of nerve-cells from the auricular septum 221
141_b_. Isolated nerve-cells from frog’s heart 221
142. Arteries and veins of the Truncus arteriosus of _Bufo
vulgaris_ 222
143. Schema of the arterial system of _Rana esculenta_ 223
144. Right carotid gland 224
145. Arterial system of Rana esculenta 225
146. Transverse section at level of the larynx 226
147. Dissection to show the occipito-vertebral and the
cutaneous arteries 227
148. Branches of the occipito-vertebral and cutaneous
arteries in the head 228
149. Dissection to show the occipito-vertebral and the
cutaneous arteries 229
150. Subclavian artery of the left side 231
151. Arteries of the palmar surface of the hand 232
152. Arteries of the dorsal surface of the hand 232
153. Arterial system of _Rana esculenta_ 234
154. The urinogenital arteries 235
155. Bifurcation of the aorta and the iliac arteries 236
156. Arteries of the hinder extremity 237
157. Arteries of the dorsal surface of the foot 239
158. Arteries of the sole of the foot 240
159. Schema of the veins of _Rana esculenta_ 242
160. Distribution of the internal jugular vein and the
anterior portion of the cutaneous vein 243
161. The anterior caval vein and its branches 244
162. Course of the cutaneous vein as seen from the side 245
163. Veins in the region of the kidney 246
164. Veins of the liver 248
165. Veins of the hinder extremity 250
166. Transverse section of a septum with the attached skin 252
167. The sinus abdominalis lateralis 252
168. Sinus thoracicus transversus 253
169. The lymph-sacs of _Rana esculenta_ (seen from the
dorsal surface) 254
170. Do. (seen from the ventral do.) 256
171. Do. (seen from the side) 257
172. Transverse section through the trunk in the region
of the iliac lymph-sac 258
173. Dissection to show the iliac lymph-sac 259
174. Plan of attachments of the inferior femoral etc. septa 259
175. Transverse section of the thigh 260
176. The anterior lymph-hearts 261
177. The posterior lymph-hearts 261
178. The roof of the mouth 276
179. The floor of the mouth 277
180. The capillaries of the submucous layer (_coloured_) Plate II.
181 I. Transverse section of the premaxillary bone, to
show attachment of the teeth 279
181 II. Dentine and enamel 279
181 III. Enamel 279
182, 183. Muscles of the tongue 281, 282
184. The alimentary canal 283
185. The abdominal viscera of _Rana esculenta_ 284
186. Longitudinal folds of stomach of _Rana temporaria_ 285
187. The cells at the mouth of the gland of the fundus
of the stomach. (_coloured_) Plate II.
188. The mucous membrane of the pyloric end of the stomach
of _Rana esculenta_ 286
189. Mucous membrane of the pyloric end of stomach and
duodenum 288
190. Isolated fold of mucous membrane of small intestine of
_Rana temporaria_ 291
191. Fold of mucous membrane of _Rana temporaria_ 291
192. The large intestine of _Rana temporaria_ 292
193. Large intestine of _Rana esculenta_ 293
194. The liver 295
195. The pancreas and bile-canals 296
196 I. }
} The hepatic veins (_coloured_) Plate II.
196 II. }
196 III. The hepatic arteries (_coloured_) Plate II.
197. Liver-cells 299
198. The bile-capillaries 299
199. The pancreas and bile-canals 300
201. The peritoneum of _Rana esculenta_ 305
202. The position and relations of the larynx 311
203. The cartilaginous skeleton of the larynx 312
204. The larynx and surrounding parts 313
205. The muscles of the larynx 314
206. Three sections through the larynx of _Rana esculenta_ 316
207. The Rima glottidis 317
208. The lung of _Rana temporaria_ (_coloured_) Plate II.
209. The vocal sac of the right side 320
210. The thymus gland 321
211. The thymus gland of _Rana esculenta_ 321
212. The thyroid gland of _Rana esculenta_ 323
213. The lymphatic gland of _Rana esculenta_ 324
214. The male urino-genital organs 331
215. The right kidney 332
216. The blood vessels and lymphatics of the kidney 333
217. Vertical sections through the kidney (_coloured_) Plate II.
218. The uriniferous tubes 335
219. A gold preparation of the kidney of _Rana esculenta_
(_coloured_) Plate II.
220. Transverse section of the kidney 338
221. The bladder 339
222. The male reproductive organs 341
223. Various preparations from the testis 342
224. The female reproductive organs 344
225. Preparations from ovary and oviduct 346
226. The male urino-genital organs 348
227. The fat-body of _Rana esculenta_ 349
228. The epidermis from the head of _Rana esculenta_ 367
229. Vertical section through the skin of the back 368
230. Surface view of epidermis of _Rana temporaria_ 368
231. Nerve terminations of the branched pigment-cells of
the cutis 368
232. The temporary papillae in _Rana temporaria_ 371
233. The epidermis of the supplemental toe of
_Rana esculenta_ 375
234 I. Fore-foot of a male frog 375
234 II. The swelling on the supplemental toe of a male frog 375
235. The blood-vessels and lymphatics of the skin 376
236. Lateral sense-organ of tadpole of frog 378
237. Various parts from the fungiform papillae 381
238, 239. Frontal sections through the nose of two tadpoles 384
240 I A. Bowman’s glands _in situ_ from _Rana temporaria_ 386
240 I B. Section of Bowman’s gland 386
240 II. Vessels of nasal mucous membrane of _Rana esculenta_ 386
241. Separations from the olfactory mucous membrane of _Rana
temporaria_ 388
242. The tympanic membrane of _Rana esculenta_ 389
243. The columella 391
244. Antero-posterior section through the capsule of the
right labyrinth of _Rana esculenta_ 392
245. The membranous labyrinth of _Rana esculenta_ 394
246. Part of the outer wall of the perilymphatic space 395
247, 248. The right membranous labyrinth of _Rana esculenta_ 397
249, 250. The membranous labyrinth of _Rana esculenta_ 399, 401
251. Preparations from the ear of _Rana esculenta_ 402
252. The nerve-terminations in the membranous labyrinth of
_Rana esculenta_ 404
253. Endothelium from the inner surface of the sclerotic coat 406
254, 255. Preparation from cornea of _Rana esculenta_ 407, 408
256. The vessels of the choroid and iris 410
257. Fibres from the lens of the frog 414
258. Vertical section through retina of frog 415
259. Various preparations from the eye of the frog 417
260. The vessels of the vitreous body 421
261. Preparations from the nictitating membrane of _Rana
esculenta_ 423
INTRODUCTION.
There is no occasion, now-a-days, to offer a lengthened apology for
devoting a treatise solely to the anatomy of the frog, which enjoys
the doubtful honour of being, κατ' εξοχήν, the physiological domestic
animal. It is kept in every physiological laboratory, and is daily
sacrificed in numbers upon the altar of science. The physiologist has
recourse to it, not only to obtain answers to new questions, but for
the sake of demonstrating easily and quickly the most important known
facts of the science. These unlucky batrachians are to be had in any
number, and are specially adapted for experimental investigation: they
have consequently fallen under a harsher tyrant than the stork in the
fable, and their prophetic outcry in the frog-chorus of Aristophanes,
δεινὰ πεισόμεσbθα, has been literally fulfilled.
As the history of the most important physiological discoveries is
closely related with the employment of the frog in physiological
research, it will not be without interest to review briefly the history
of its use in scientific, especially in physiological, investigations,
and to record the services which it has already rendered to science.
Swammerdam (1637–1685), as du Bois-Reymond justly remarks, was the
first to make known the frog as an important means of research; he
says concerning it:--‘An den Thieren, die das heisseste Blut haben,
ist die Bewegung der Muskeln nicht so merklich oder hält vielmehr
nicht so lange an, als an Thieren die mit kälterem Blute begabt
sind. Dergleichen sind die Fische und viele andere Wasserthiere, wie
auch solche, die so wohl im Wasser als auf dem trocknen Lande leben
können. Deswegen habe ich insonderheit mit dem Frosch meine Versuche
angestellt. Denn an diesem Thiere sind die Sehnen sehr sichtbar und
lassen sich leicht entdecken und entblössen[2].’ Swammerdam made the
earliest experiments on the contraction of muscle by means of chemical
and mechanical stimulation of its nerves; thus laying the basis of our
present nerve and muscle physiology, which has been built up within
rather less than two hundred years; though during the first half of
this period but little advance was made.
[Footnote 2: ‘In animals with warm blood the action of the muscles is
neither so apparent nor so long continued as in those animals which
have cold blood, such as fishes and many other aquatic animals, and
those also which live both in water and on dry land. On this account I
have made my investigations chiefly on frogs, for in them the nerves
are very distinct, and are easily found and exposed.’ Buch der Natur,
Leipzig, 1752, p. 330.]
From the famous September evening of the year 1786, on which Galvani
first observed the twitchings of a frog’s leg suspended by a metallic
hook to an iron balcony, the frog has, down to the present time,
afforded almost the only material for the investigation of the
excitability of nerve and its associated electromotive changes,
and also no inconsiderable part of the remaining nerve and muscle
physiology. It was not until Müller devised the method of operating
on the frog that Bell’s law became capable of easy proof; and much
of our knowledge of the functions of the spinal cord is derived from
experiment upon it. Again, the muscles of frogs served, from the time
of Swammerdam to that of Eduard Weber and his followers, for the
investigation of the phenomena and the conditions of contraction;
and in almost all other branches of physiology there are important
doctrines which were first definitely established by experiment upon
the frog. But for the web of the foot of this animal (and the gills and
tail of its tadpole, in which Leeuwenhoek[3] describes the phenomena
most clearly) we should not, perhaps for a long time, have arrived
at a satisfactory knowledge of the existence and the conditions of
the capillary circulation. As is well known, an accurate acquaintance
with the constituents of the blood directly concerned in nutrition
has been obtained by observation on the frog, as well as important
facts in the physiology of the blood and lymph, such as the intimate
knowledge of the corpuscles of both fluids, and the coagulability
of the plasma; while in no less degree have experiments on these
animals served to establish the laws of the heart’s action. Moreover,
physiology is not the only science indebted to the frog: in histology
many important results have been obtained from observations on it, and
for histological instruction it is now indispensable. To it we owe much
of our knowledge of the structure of nerve fibres, their origin and
termination, especially in muscle, their relations within the ganglia,
and even the structure of muscular fibre itself. For the study of
reproduction and development the frog has, next to the chick, afforded
the most important material: one need but refer to the investigations
on impregnation from the time of Spallanzani to that of Newport[4], the
phenomena of cleavage, and many others.
[Footnote 3: Leeuwenhoek, Arcana Naturæ III, epist. 65 ad Reg. Soc.
Lond., p. 158.]
[Footnote 4: It may be well to remind the reader that this introduction
was written in 1864.]
Thus with progress of time the field in which the frog has been
submitted to observation and experiment, whether for the demonstration
of established facts to students or for the solving of new problems,
has vastly increased, and this batrachian has indeed become, as we have
stated, the physiologist’s domestic animal.
That, for these manifold uses, a more exact anatomical knowledge of
the frog is very necessary is self-evident. The majority of students
commencing the study of physiology have little more than a superficial
knowledge of the sciatic nerve and the leg-muscles; at most, of the
spinal cord and its nerve-roots; and only acquire any further knowledge
in a disconnected manner. For this they can scarcely be reproached,
the literature of the anatomy of the frog being so widely scattered in
monographs and journals that reference to it involves the expenditure
of much time. This attempt, therefore, to produce a complete anatomy
of the frog, based throughout upon my own observations, cannot be
considered superfluous; it is rather to be feared it may be thought
insufficient.
The European frogs[5] alone are treated of in the following
description, _i.e._ the two species, _Rana esculenta_, L., and _R.
temporaria_, L., the former being more particularly described, though
such differences in structure as occur are noted. This is not the place
to discuss the exact systematic characters of the two species, yet they
cannot be ignored entirely. The species were, from their habitats,
long ago distinguished by C. Gessner[6], and named _Rana rubeta_, _s.
gibbosa_, the garden or grass-frog, and _Rana aquatica_, _s. innoxia_,
the water-frog; at least, from his figure, the former can be no other
than _R. temporaria_, though Gessner, probably expecting to find in it
the _rubeta_ of older writers, adds that it ‘ist für giftig zu halten.’
[Footnote 5: For purposes of comparison other than European frogs
were examined, especially American species of _Rana_, for which I am
indebted to the kindness of my much esteemed friend Agassiz. These were
_Rana Catesbyana_, Shaw (_R. mugiens_, Catesby--_R. pipiens_, Harlan);
_R. sylvatica_, Leconte; _R. clamitans_, Daudin; _R. palustris_,
Leconte; _R. halecina_, Leconte. To these, however, no further
reference will be made in the text.]
[Footnote 6: C. Gessner, Thierbuch. Zürich. Fol., p. 157.]
Leeuwenhoek[7] also correctly distinguished between them, but it is to
Rösel[8] that we are chiefly indebted for a careful discrimination and
an accurate knowledge of the life-histories of the two species.
[Footnote 7: Leeuwenhoek, Arcana Naturæ, Vol. III of Ecker’s edition.
Leyden, 1722. Epist. 65 ad Reg. Soc. Lond., p. 154.]
[Footnote 8: Rösel, Naturgeschichte der Frösche Deutschlands, ed.
Schreber. Nürnberg, 1815, p. 36.]
[Illustration: Fig. 1.
The green water-frog, _Rana esculenta_ L.]
*Rana esculenta*, L. The green water-frog, Fig. 1, usually attains a
larger size[9] and is more active than the other species, and for this
reason is better adapted to the purposes of the physiologist; hence I
have chosen it for description.
[Footnote 9: The extreme sizes are much more pronounced in this
species. I have never found _R. temporaria_ of the size attained by
large specimens of the water-frog.]
The head is flat, as broad as it is long, and triangular with an
obtuse snout in front. The upper surface of the head, _i.e._ the space
between the eyes, is slightly concave, grooved, and narrower than in
_R. temporaria_. The tympanic membrane is circular, and relatively to
the eye is larger. The upper eyelids have several transverse folds in
their hinder part. The pupil is oval, with the long axis horizontal.
The vomerine teeth are arranged in two clusters, which are relatively
larger than in _R. temporaria_ and lie exactly between the posterior
nares, without however touching them. The openings of the Eustachian
tubes do not exceed in size the posterior nares to so great an extent
as they do in _R. temporaria_. The male possesses a vocal sac on
either side, which reaches the surface beneath the tympanic membrane
through a cleft placed behind the angle of the mouth, and is, in
well-developed specimens, about the size of a cherry. The hind limbs
are relatively longer. The toes are long, and taper towards their tips:
the webs between the toes are cut out semicircularly, and that of the
longest or fourth toe is continued to the tip of the last phalanx. The
supplemental toe is an oval prominence of cartilaginous hardness. The
skin of the back has wart-like tubercles arranged longitudinally in
raised lines; one of these lines runs on each side from the posterior
canthus as far as the thigh, and is very constant: in the male a second
line surrounds the posterior margin of the vocal sac; a corresponding
line exists in the female.
The skin of the belly is quite smooth, the colour presenting many
variations which appear to depend upon very diverse circumstances. It
varies with changes in the physiological condition of the animal. Von
Wittich[10] has shown that a bright green specimen changes to a dark
leafy green colour on exclusion of light; also, that dark specimens
become almost a lemon-yellow colour on exposure to bright sunlight;
and he has pointed out that this brightening of the skin is an active
condition dependent upon contraction of the stellate pigment-cells. It
is therefore not surprising, as the same inquirer observes, that one
should sometimes find specimens of _R. esculenta_ in which the ground
colour is almost a greenish yellow (as in Rösel’s figure, Pl. XIII),
whilst in others it can only be distinguished from the dorsal black
patches by a faint greenish shade. There is no doubt that difference
of habitat influences the colour; but this may again be modified by
light[11], as has been established in the case of fish by direct
observation[12]. Apparent varieties may this occur.
[Footnote 10: Von Wittich, Müller’s Archiv, 1854, p. 41.]
[Footnote 11: Lister, On the Cutaneous Pigmentary System of the Frog.
Phil. Trans., 1857, p. 627.]
[Footnote 12: Agassiz et Vogt, Histoire naturelle des poissons d’eau
douce (Neuchatel, 1839), Pl. IV, mention that the colour of trout is
very variable and that in shaded and deep-lying brooks and rivers a
variety is found which is black.]
In frog-tanks such diversities of colour may not unfrequently be
observed in the same individual, as for example when the lower part
of the body immersed in muddy water is dark, while the part above the
water is bright. That the process of casting the skin exercises an
influence on the brightness of the colouring is certain, yet there are,
as von Wittich has correctly remarked, other alterations of colour
which are in no way connected with this process, and are evidently
more of a pathological nature; such as when the frog assumes a dirty
green spotted appearance, the green fading more and more, until all
the patches which are usually green appear of a dirty greyish-brown
with a faint bronze shimmer. According to this author these changes are
most readily brought about by starvation. The dark colour which frogs
exhibit after hibernation is perhaps to be ascribed to the co-operation
of several of the causes mentioned above.
The usual colouring of healthy animals is as follows: the back is
bright green with three golden yellow longitudinal stripes, one median
and two lateral, and a number of irregular brown or black stripes of
approximately uniform width: on the head are a pair of black stripes
which pass from the angles of the eyes across the nares to the tip of
the nose; now and then the tympanic membrane and surrounding parts
have also a black patch, as in _R. temporaria_: another black stripe
is found on the anterior surface of the arm, in the region of the
shoulder: and on the thighs are black, yellow, and white mottlings.
The whole of the under-surface is white or yellowish. At times the
yellow stripes of the back are wanting or are indistinct. It has
already been mentioned that many varieties may occur; and these have
in all probability given rise to the descriptions of reputed new
species, such as _R. maritima_, Risso, found in South Europe; _R.
alpina_, Risso, found in the high-lying Alpine lakes; _R. hispanica_ of
Fitzinger and Bonaparte, and _R. calcarata_ of Michahelles, the last
three of which certainly cannot be retained. It is not improbable
that the water-frog, which Spallanzani[13] used in his experiments on
impregnation, was the _R. maritima_ of Risso. He says, one must not
confound his frog with that which Rösel calls the green water-frog;
the former being much smaller, without the three dorsal golden-yellow
stripes, and the spawning season (in Lombardy) occurring during April
and May. Rusconi[14] also describes two varieties in Northern Italy.
[Footnote 13: Spallanzani, Versuche über Erzeugung der Thiere and
Pflanzen. Leipzig, 1786, p. 5.]
[Footnote 14: Rusconi, Développ. de la Grenouille. Milan, 1826, p. 6.]
*Rana temporaria*, L., the brown or grass-frog, is so named from the
large black patch in the temporal region, _i.e._ between the eye and
the shoulder. While the separation of the preceding species into
several varieties does not seem to be well founded, it appears that two
distinct species have been included under the name of _R. temporaria_.
Millet of Angers[15] first described, in his Fauna du département de
Maine-et-Loire, as ‘grenouille rousse,’ a species differing from _R.
temporaria_, and gave the species previously known as _R. temporaria_
the name of _R. flaviventris_, ‘grenouille à ventre jaune.’ No further
notice, however, was taken of this observation, not even by Duméril and
Bibron in their ‘Erpétologie.’ Quite independently Steenstrup[16], in
the year 1846, pointed out that two frogs, differing in structure and
habits, had been confounded under the name _R. temporaria_; these he
distinguished as _R. platyrhinus_ and _R. oxyrhinus_. Von Siebold[17],
and also Schiff[18] in part, have confirmed these statements. My
own observations lead me to a like conclusion; I shall therefore
distinguish two species, viz.:--(1) _Rana temporaria_, L., _Rana
platyrhinus_, Steenstrup; (2) _Rana oxyrhinus_, Steenstrup.
[Footnote 15: Annales des Sciences naturelles. Zoologie, IV Série,
Vol. IV, 1855, p. 368.]
[Footnote 16: Amtl. Bericht über die 24. Versammlung deutscher
Naturforscher in Kiel, 1846, p. 141; Wiegmann’s Archiv, 1847, Vol. II,
p. 341; Steenstrup, Oversigt K. Danske Selsk. Forhandlgr., 1846, p. 92.]
[Footnote 17: Wiegmann’s Archiv, 1852, Vol. I, p. 14.]
[Footnote 18: Annales des Sciences naturelles. Zoologie, IV Série,
Vol. IV, 1885, p. 368.]
[Illustration: Fig. 2.
The brown grass-frog, _Rana temporaria_, L.]
*Rana temporaria*, L.; _Rana platyrhinus_, Steenstrup. The brown
grass-frog, Fig. 2, does not attain the dimensions of _R. esculenta_,
L., but is, however, always larger than _R. oxyrhinus_. The head is
somewhat broader than long, and the upper surface of the skull is not
grooved, as in _R. esculenta_, but is flat. The space between the
eyes is wider (according to Duméril, equal to the width of the upper
eyelid, whereas in _R. esculenta_ it is just two-thirds this width):
the fronto-parietal bones are wide and flat. The tympanic membrane,
in comparison with the eye, is smaller than in _R. esculenta_, and is
usually less distinguishable from the surrounding parts as regards
colour and transparency. The apertures of the Eustachian tubes are,
relatively to the posterior nares, larger than in the water-frog. The
vomerine teeth are comparatively small and lie in two groups placed
obliquely to each other, their anterior ends diverging from each other
and being prolonged as ridges to the anterior margins of the posterior
nares. The two groups do not lie between the nasal apertures, but
behind a line drawn transversely through their posterior margins. Vocal
sacs are absent in both sexes. The hind legs are relatively shorter:
the toes are not so evenly tapered off, indeed they are slightly
swollen: the fourth toe, as compared with the third and fifth, is
somewhat longer than in _R. esculenta_; the web of this toe does not
extend to the tip of the toe, but terminates in both sexes at the last
phalanx but one; the web on the third toe is less developed on the
thumb side than on the other: on the remaining toes also the margins
of the web are less developed than in _R. esculenta_, so that the
free borders appear more crescentic. The supplemental toe forms only
a soft and inconspicuous prominence. The back is mostly smooth; the
raised glandular ridge, which extends along each side from the eye to
the thigh, is present, but is much narrower and less prominent than in
_R. esculenta_; another ridge passes from the angle of the mouth to the
shoulder. The colouring in general, and especially the ground colour
of the dorsal surface, varies from the brightest tints to the darkest
brown-black; the conditions causing these variations being, no doubt,
the same as those described above in _R. esculenta_. A dark-brown
specimen taken from a dark frog-tank is usually yellowish red on the
following day. The black patch between the angle of the mouth and the
shoulder has given this species the name of _R. temporaria_, and is
constant. A black stripe passes from the eye across the nostril to
the tip of the snout, and a similar one is found upon the anterior
surface of the upper arm. On the hind legs the bands are chiefly
transverse. The ventral surface is yellowish, and sometimes spotted.
The thighs have a granular appearance, and these as well as the belly
and the neighbourhood of the anus have frequently a reddish coloration
presenting the appearance of an irritated surface.
*Rana oxyrhinus*, Steenstrup. This species is always smaller and more
elegant in shape than the preceding one. The head is conical, with
the pointed snout projecting beyond the lower jaw; a feature which is
especially evident on looking from below. The space between the eyes
is narrower than in _R. temporaria_, and is not grooved, but convex;
the fronto-parietal bones are narrow and arched. With respect to the
arrangement of the vomerine teeth and the sizes of the apertures of the
Eustachian tubes, this species holds an intermediate position between
the other two. Next to the pointed snout, the greatest difference
between this species and _R. temporaria_ is the presence of a much
larger supplemental toe, which is of cartilaginous hardness, compressed
from side to side, and contains a larger bone[19]. The vocal sacs
are absent. In the males the web of the longest toe reaches to the
last phalanx but one; in the females, on the contrary, the last three
phalanges project freely beyond the web. The extremities of the toes
are more pointed than in _R. temporaria_, in which respect, as also
in several others, it approaches _R. esculenta_. In colouring, _R.
oxyrhinus_ resembles _R. temporaria_; the throat, however, is usually
pure white, at least in the males, the breast dusky white and spotted,
while in _R. temporaria_ the throat and breast are more uniformly
coloured and yellowish. V. Siebold has remarked that, during the
pairing-season, the males are covered with a bluish bloom[20]; and, the
whole ground colour being bright at this period, very beautiful tints
result. V. Siebold[21] moreover states that the note which the males
produce during the pairing-season is different in the two species.
On the whole, _R. oxyrhinus_ appears to stand midway between _R.
esculenta_ and _R. temporaria_.
[Footnote 19: According to Steenstrup, _l. c._, the size of the
supplemental toe is in _R. temporaria_ one-half and in _R. oxyrhinus_
two-thirds of that of the next toe.]
[Footnote 20: I do not find, however, that this disappears when the
animals are on land; in fact I have animals before me in a glass in
which it is plainly seen.]
[Footnote 21: _l. c._, p. 15.]
Thomas[22], in addition, distinguishes another species, _R.
agilis_, which however may be the ‘grenouille rousse’ of Millet.
Schlotthauber[23] has described a frog which, in marking and colouring,
might hold a middle place between _R. esculenta_ and _R. temporaria_;
in my opinion this is probably a cross between the two. That attempts
at copulation are made, despite the difference of the pairing-season,
is well known; Pontallié[24] mentions this, and I have myself often
found males of _R. temporaria_ in conjunction with females of _R.
esculenta_.
[Footnote 22: Annales des Sciences naturelles. Zoologie, IV Série,
Vol. IV, 1855.]
[Footnote 23: Wiegmann’s Archiv, Vol. I, 1844, p. 255.]
[Footnote 24: Annales des Sciences naturelles. Zoologie, III Série,
Vol. XVIII, 1852, p. 243.]
* * * * *
I use the following terminology. I suppose the animal to be in its
natural position, the belly towards the ground, the back upwards; a
horizontal plane passing from the snout to the anus divides the body
into a superior or dorsal half and an inferior or ventral half. The
terms superior and inferior, dorsal and ventral, indicate positions
with relation to this plane. I call that part anterior which looks
towards the head, and that posterior which looks towards the anus. A
vertical plane at right angles to the middle of the longitudinal axis
of the body, divides it into an anterior or cephalic and a posterior
or caudal half. All sections and planes which lie parallel to this, as
well as this itself, are frontal. Lastly, by a perpendicular section
along the middle line of the body the animal is divided into right and
left halves; this plane is the median plane; and the position relative
to this plane is expressed by the terms median or lateral. Planes
parallel to the median plane are termed sagittal.
SECTION I.
THE BONES AND JOINTS.
THE BONES AND JOINTS.
LITERATURE.
*van Altena*, Commentatio ad quæst. zoologicam in academia
Lugduno-Batav. a. MDCCCXXVIII propositam, qua desideratur ut
systematice enumerentur species indigenæ reptilium ex ordine
batrachiorum addita unius saltem speciei anatomia et præsertim
osteographia accurata. Lugd. Bat. 1829. 4^o. With 4 Plates.
*Ange, Martin St.*, Recherches sur les organes transitoires des
batraciens. Annales des Sciences naturelles. 1^{re} Série.
Vol. XXIV. 1831.
*Bell*, Article Amphibia, in Todd’s Cyclopaedia of Anatomy and
Physiology. Vol. I, p. 90. 1835–1836.
*Born, Dr. Gustav*, Ue.d. Nasenholen u.d. Thränennasengang der
Amphibien. Leipzig, 1877.
*Bruch, G.*, Beiträge zur Naturgeschichte und Klassification der
nackten Amphibien. Würzburger Naturzeitschrift, 1862.
*Bruch, G.*, Neue Beobachtungen zur Naturgeschichte der einheimischen
Batrachier. Würzburger Naturzeitschrift, 1863.
*Cuvier*, Recherches sur les ossements fossiles. Vol. V. Pt. II.
Paris, 1825.
*Cuvier*, Leçons d’anatomie comparée. Paris, 1835. Vol. I.
*Cuvier*, Ueber die Rückenwirbel der Reptilien und Amphibien,
Froriep’s Notizen. Vol. XIII, p. 74. 1826.
*Daudin*, Histoire naturelle des Rainettes, Grenouilles et des
Crapauds. Paris, 1802.
*Ducrotay de Blainville*, Ostéographie ou description iconographique
comparée du squelette et du système dentaire des cinq classes
d’animaux vertébrés. Paris, 1841.
*Dugès*, Recherches sur l’ostéologie et la myologie des batraciens à
leurs différents âges. Paris, 1834. 4^o. With 20 Plates.
*Duméril et Bibron*, Erpétologie générale ou Histoire complète des
Reptiles. 1836.
*Gegenbaur*: 1. Ueber Bau und Entwicklung der Wirbelsäule bei
Amphibien überhaupt und beim Frosche insbesondere. Abhandlungen
der naturforschenden Gesellschaft zu Halle, Vol. VI. Halle, 1861.
2. Untersuchungen zur vergl. Anatomie der Wirbelsäule bei
Reptilien und Amphibien. Pt. I. Leipzig, 1862. (Carpus and
Tarsus.) With 4 Plates. 4^o.
*Gegenbaur*, Untersuchungen zur vergl. Anatomie der Wirbelthiere.
Pt. II. Schultergürtel. 1865.
*Günther*, Ueber geschlechtliche Differenzen in Knochen von lebenden
und fossilen Fröschen und Fischen. Annals of Natural History.
1859. Vol. III.
*Hallmann*, Die vergleichende Osteologie des Schläfenbeins, etc.
Hannover, 1837. 4^o. With 3 Plates.
*Hoffmann, C. K.*, Beiträge zur Erkenntniss des Beckens der Amphibien
und Reptilien. Leyden, 1876.
*Hoffmann, C. K.*, Bronn’s Klassen und Ordnungen des Thierreichs,
Vol. VI. Amphibien. Leipzig, 1873–8.
*Huxley*, On the Theory of the Vertebrate Skull; Croonian Lecture,
Proc. Royal Society, p. 381. 1858.
*Huxley*, Article Amphibia, Encyclopædia Britannica, IXth Edition.
1875.
*Huxley*, Lectures on the Elements of Comparative Anatomy.
*Huxley*, Handbuch der Anatomie der Wirbelthiere. Deutsche Ausg. von
T. Ratzel. 1873.
*Kehrer, G.*, Beiträge zur Kenntniss d. Carpus und Tarsus d.
Amphibien, Reptilien, und Säuger. Berichte d. naturf. Gesell. z.
Freiburg. 1886.
*v. Klein*, Beiträge zur Anatomie der ungeschwänzten Batrachier.
Jahres-Heft. Würtemberg, 1850.
*Köstlin*, Der Bau des knöchernen Kopfs. Stuttgart, 1844. 8^o.
*Leukart*, Zwischenkiefer. Valentins Repertoire. 1841, p. 155.
*Marshall, A. M.*, The Frog. Manchester and London. 2nd Edit., 1885,
pp. 45–59.
*Mayer, A. F.*, Beiträge zu einer anatomischen Monographie der Rana
pipa. Acad. Caes. Leop. Nov. Acta. 1825. Vol. XII, p. 527; and
Isis v. L. Oken. 1825. col. 317.
*Meckel*, System der vergleichenden Anatomie. II. Thl. I. Abthlg.
Halle, 1824. 8^o.
*Meckel*, Ueber das Zungenbein der Amphibien. Meckel’s Arch. f.
Physik. 1818. Vol. IV, p. 60.
*Mertens*, Anatomiæ batrachiorum prodromus sistens observationes
nonnullas in osteologiam batrachiorum nostratium. Halæ, 1820. 8^o.
*Mivart*, On the Classification of the Anurous Batrachians. Proc.
Zool. Soc. 1869.
*Morren*, Observations ostéologiques sur l’appareil costal des
batraciens. Bulletins de l’Acad. de Bruxelles, 1835, II.--Mémoires
de l’Académie, 1837. Tome X.
*Müller*, Beitrag zur Anat. d. Amph. Zeitschrift f. wissenschaftliche
Zoologie. Vol. IX. 1858, p. 178.
*Parker, W. K.*, Structure and Development of the skull of the common
frog. Phil. Trans. 1871, p. 137.
*Parker, W. K.*, Skull of Batrachia. Phil. Trans. 1876, p. 601.
*Parker, W. K.*, and *Bettany, G. T.*, Morphology of the Skull.
London, 1877.
*Pouchet*, Note sur les différences que le sexe imprime au squelette
des grenouilles. Comptes rendus. Vol. XXV, p. 761. 1847.
*Reichert, K. B.*, Vergleichende Entwicklungsgeschichte des Kopfs der
nackten Amphibien nebst den Bildungsgesetzen des Wirbelthierkopfs
im Allgemeinen und seinen hauptsächlichen Variationen durch die
einzelne Wirbelthier-Classe. Königsberg, 1838.
*Remak*, Untersuchungen über die Entwicklung der Wirbelthiere.
Berlin, 1855.
*Rösel, von Rosenhof*, Historia naturalis ranarum nostratium.
Nörnberg, 1758.
*Rudolphi and Breyer*, Observationes anatomicae circa fabricam Ranae
pipae. Berolini, 1811.
*Rusconi*, Développement de la grenouille commune. Milan, 1826.
*Rusconi*, Sulle metamorfosi delle osse della testa della rana.
Annali di Bologna. 1^{re} Série, Vol. II, p. 357.
*Schneider*, Historia amphibiorum. Jenae, 1799.
*Shaw*, General Zoology. London. Vol. II, Pt. I, p. 167.
*Stannius*, Zootomie der Amphibien (Handb. der Zootomie der
Wirbelthiere, 2. Buch). 2nd Edit. Berlin, 1856. 8^o.
*Stricker*, Untersuchungen über die Entwicklung des Kopfes der
Batrachier. Arch. f. Anat. u. Physiol. 1864, pp. 52–76.
*Stricker*, Beiträge zur Biologie der Batrachier. Verhandl. der
Wiener Akademie. 1866. Vol. XVI, pp. 451–456.
*Townson, R.*, Facts and Observations in Natural History. London,
1799.
*Troya*, Mémoire sur la structure singulière du tibia et du cubitus
des grenouilles et des crapauds. Mémoires de mathématique et de
physique présentées à l’acad. de Paris. Vol. IX. 1780.
*Wagner*, Icones Zootomicae. Leipzig, 1841.
*Wagner*, Lehrbuch der vergleichenden Anatomie. Leipzig, 1834–1835.
*Wiedersheim, R.*, Lehrbuch d. vergleichenden Anatomie der
Wirbelthiere auf Grundlage d. Entwickelungsgeschichte. Jena, 1886.
2nd Edit.
*Wiedersheim, R.*, Elements of Comparative Anatomy of Vertebrates,
translated by W. Newton Parker. London, 1886.
THE BONES AND JOINTS.
The consideration of the differences in form, number, and histological
structure, which the parts of the skeleton present during the various
stages of development does not fall within the scope of this book: we
have here but to deal with the adult frog.
The skeleton is made up of histologically different materials;
these are:--(1) bone, (2) hyaline cartilage, and (3) so-called
calcified cartilage. Concerning the last it is necessary to make some
observations. I have chosen for it the name calcified cartilage in
place of the more usual names ‘cartilaginous bone’ or ‘primordial
ossification,’ as by this term its nature appears to be expressed
without any ambiguity[25]: it is hyaline cartilage in which calcareous
particles have been deposited to a greater or less extent: in the fresh
state it has the appearance of moderately firm cartilage; when dry it
becomes opaque and white, like the calcareous crusts on the cartilages
of the Plagiostomata. The calcareous material is deposited in the
cartilage in finer or coarser granules; after removal of the lime by
means of acids, the cartilaginous structure becomes apparent although
not so perfectly as in unchanged cartilage.
[Footnote 25: Compare Müller, Zeit. f. wissen. Zoolog., Vol. IX.]
This calcified cartilage is widely distributed in the frog’s skeleton:
very many parts, which in higher animals consist only temporarily of
this substance during the transition from cartilage to bone, are in
the frog formed of it throughout life. It is especially well-marked
in the epiphyses of the long bones in the hand and foot, in the
bones of the shoulder-girdle, etc. To avoid repetition later on I
will briefly describe it as found in the first-mentioned situation.
Dugès[26] has described its external appearance, while Bruch[27] has
made us acquainted with its histological peculiarities. If a long
bone of the frog be dried, the femur for example, the middle part is
found to differ considerably from the epiphyses in colour and in other
particulars. The shaft alone has the appearance of bone, the epiphysis
consisting of a white, opaque, firm substance, resembling plaster of
Paris or lime, but which in the fresh moist state is exactly like
cartilage. The epiphyses, which are fitted to the ends of the diaphysis
like the cap of a stick-handle, have sharply defined margins (Fig. 3),
as is well seen in Figs. 36, 39, 45, and 46. If a section be made
through the epiphysis and part of the diaphysis, the long tube of true
bone is seen to cease abruptly above _o_, Fig. 3, and over the end of
it the epiphysis _E_ is fixed. This epiphysis consists almost entirely
of calcified cartilage _c′_, and has merely a superficial layer of
hyaline cartilage _A_. The bony cylinder of the diaphysis _o_, which
contains the marrow _M_ in its interior, is shut off from the epiphysis
by hyaline cartilage, the cells of which are arranged in transverse
layers, _o_.
[Footnote 26: Dugès, Recherches sur l’ostéologie et la myologie des
batraciens à leurs différents âges, p. 116.]
[Footnote 27: Bruch, Beiträge zur Entwicklungsgeschichte des
Knochensystems. Schweiz. Denkschriften, p. 118.]
[Illustration: Fig. 3.
Longitudinal section through the upper extremity of the femur of _Rana
esculenta_, magnified.
_A_ Hyaline cartilage (articular cartilage).
_c_ Hyaline cartilage closing end of bony cylinder.
_c′_ Calcified cartilage of epiphysis.
_D_ Bony cylinder of diaphysis.
_E_ Epiphysis.
_M_ Marrow cavity.
_o_ End of diaphysis.
]
I. THE VERTEBRAL COLUMN.
The _vertebral column_ of the frog consists of ten bones, _viz._ nine
true vertebrae, and the rod-shaped urostyle, which alone is almost as
long as all the remaining vertebrae.
I. GENERAL DESCRIPTION OF THE NINE VERTEBRAE.
*a.* The _bodies_ of the vertebrae are compressed from above downwards;
the posterior surface of each body, with the exception of the eighth,
presents an articular head covered with cartilage; the anterior
surfaces, with the exception of the ninth, present corresponding
articular depressions, covered with cartilage.
*b.* The _arches_, which have somewhat sharp margins both before and
behind, bear the following processes:-- *1.* The *articular processes*
(Figs. 4 and 5 _o o_) are similarly placed to those of the dorsal vertebrae
of man: they project horizontally, the cartilaginous articular surfaces
on the posterior processes being directed downwards, those on the
anterior upwards.
[Illustration: Fig. 4.
Vertebrae of _Rana esculenta_, seen from below, twice the natural size.
1 to 9 First to ninth vertebræ.
_c_ Urostyle.
_o o_ Articular processes.
_sc_ The two facets for articulation with the urostyle.
]
*2.* The *transverse processes* (Figs. 4 and 5 _t t′_) are strong,
flat, and of very varying size and direction. The transverse processes
of the fourth vertebra are the longest, those of the third only a
little shorter; the shortest are those of the seventh and eighth.
The atlas has no transverse processes. Those of the second and third
vertebrae project directly outwards and slightly downwards; those of
the fourth, fifth, and sixth upwards and backwards. The seventh and
eighth project more directly outwards and at the same time backwards;
the ninth upwards and markedly backwards. All the transverse processes
have cartilaginous epiphyses; the largest are those of the second,
third, fourth, and ninth vertebrae.
*3.* The *spinous processes* are generally small, but individually of
varying size, appearance, and direction. The longest are those of the
third, fourth, and fifth vertebrae; these are, in transverse section,
of a three-sided prismatic form, as in the dorsal vertebrae of man;
they are directed backwards and provided with cartilaginous epiphyses.
The spinous processes of the sixth and seventh are shorter, compressed
from side to side, project directly upwards, and are usually without
cartilaginous epiphyses; that of the eighth is still shorter. As
regards the spinous processes, those of the third, fourth, and fifth
vertebrae resemble those of the dorsal vertebrae in man; those of the
sixth, seventh, and eighth, lumbar vertebrae. The ninth has either
no spinous process or only a rudimentary one. The first and second
vertebrae may be looked upon as cervical vertebrae: the second has a
short spinous process with a cartilaginous epiphysis. In the first,
the cartilage which unites the two halves of the arch represents the
rudiment of a spinous process.
[Illustration: Fig. 5.
Vertebral column of _Rana esculenta_, from above, twice nat. size.
1 to 9 First to ninth vertebræ.
_c_ Urostyle.
_o o_ Articular processes.
_sc_ Facets for articulation with the urostyle.
_t t′_ Transverse processes.
]
II. DESCRIPTION OF PARTICULAR VERTEBRAE.
*1.* The *atlas* or *first vertebra* has a thin body, compressed from
above downwards, and an arch. The body has posteriorly a slightly
raised, cartilaginous, articular head, which is broader transversely:
in front it has two oval articular facets, which are separated from
each other by a median projection. Each facet is concave, and directed
forwards, outwards, and slightly upwards. The arch is completed above
by cartilage, which projects slightly to form the rudiment of a spinous
process. The hinder margin of the arch bears two articular processes.
Transverse processes are wanting.
*2.* The *second vertebra* presents all the general characters of an
ordinary vertebra, except that the transverse processes are directed
somewhat downwards.
*3.* The transverse processes of the *third vertebra* are longer than
those of the second: each is directed downwards, is broader at its
extremity than at its base, and bears a hammer-shaped cartilaginous
epiphysis larger than those of the remaining transverse processes.
*4.* The transverse processes of the *fourth vertebra* are the longest:
each is broader at its free end than at its base, is directed upwards
and backwards, and provided with a cartilaginous epiphysis.
*5*, *6*, *7*. The transverse processes of the *fifth*, *sixth*,
and *seventh vertebrae* are smaller, contracted towards their free
extremities, and directed upwards.
*8.* The *eighth vertebra* is distinguished from the rest by its body
possessing no articular head. It presents, at each end, a concave
articular depression. The transverse processes resemble those of the
seventh.
*9.* The *ninth vertebra* unites the vertebral column with the
hip-bones, and is hence to be regarded as a *sacrum*. The body bears on
its anterior surface an articular head for articulation with the eighth
vertebra: on its posterior surface are two small rounded and closely
approximated processes (Figs. 4 and 5 _sc_) for articulation with the
urostyle. The transverse processes are strong, broader at the free ends
than at their origin, directed upwards and backwards, and provided with
cartilaginous epiphyses.
III. ARTICULATIONS OF THE VERTEBRAE.
The articular heads and depressions of the vertebral bodies, together
with the joint surfaces of the articular processes, are covered with
hyaline cartilage. The periosteum of the bodies, as also that of
the articular processes, forms true capsular joint ligaments. The
articulations of the vertebrae are still further strengthened by
longitudinal fibres, which extend along the anterior and posterior
surfaces of the vertebrae, and correspond to the _ligamentum vertebrale
commune anticum et posticum_ of man. Between the vertebral arches are
membranes which represent the _ligamenta intercruralia_. Between the
spinous processes are bands of connective tissue which form _ligamenta
interspinalia_. (For the articulation of the atlas with the occiput,
see page 24.)
IV. STRUCTURE OF THE VERTEBRAE[28] (Figs. 6 and 7).
[Footnote 28: Cf. Gegenbaur, (1) Über Bau u. Entwicklung der
Wirbelsäule bei Amphibien überhaupt u. beim Frosch insbesondere.
Abhand. d. Naturforsch. Gesell. zu Halle, vol. vi, 1861; (2)
Untersuch. zur vergleich. Anat. d. Wirbelsäule bei Amphibien u. Rept.,
Leipzig, 1862. As regards the adult animal I can bear out Gegenbaur’s
observations. The scope and limits of this book forbid me to go further
into the developmental history.]
[Illustration: Fig. 6.
Transverse section through a vertebra of _Rana esculenta_, magnified.
_c_ Cancellous bone.
_Ch_ Chorda dorsalis.
_Ch′_ Sheath of chorda dorsalis.
_o_ Compact bone on the upper and lower surfaces of the body.
]
Each vertebral body consists of a cylinder of compact bone, which is
directly continued into the bony substance of the arch. In the interior
of the cylinder is found an isolated persistent vestige of the _chorda
dorsalis_ (_Ch_): this is surrounded by cancellous bone (_c_), which
extends backwards towards the articular head and forwards directly into
the articular cartilage, compact bone being absent in these parts. In
a transverse section of a vertebral body the following parts are seen
(Fig. 6):--*a.* An outer layer of compact bone (_o_) (the transverse
section of the above-mentioned cylinder), which is formed of parallel
lamellae of varying thickness. These, according to Gegenbaur, and as
I can confirm, are arranged in well-defined groups, each of five to
eight lamellae. The number of the secondary lamellae increases with the
age of the animal. *b.* In the interior, in the form of a cylinder, is
the remnant of the _chorda dorsalis_. It consists of a double sheath
(_Ch′_) and contents (_Ch_) composed of chorda-cells. *c.* Immediately
around the persistent portion of the chorda lies the central part of
the vertebral body, formed by transformation of the vertebral cartilage
and of the bases of the original cartilaginous arches. At each side of
the _chorda_ are large marrow-spaces (_c_), filled with cells, from
which proceed narrower canals, winding in various directions, and
anastomosing freely with one another both before and behind. Their
walls are constituted partly of true bone, partly of cartilage.
[Illustration: Fig. 7.
Longitudinal section through the posterior half of the body of a
vertebra of _Rana esculenta_.
_a_ Cartilage of the head.
_c_ Cancellous bone.
_o_ Shell of compact bone.
]
V. THE UROSTYLE (Figs. 8 and 9).
The *urostyle* is a long, median, rod-like bone, which projects
backwards, midway between the two hip-bones, and terminates over the
anus. The anterior end (Fig. 8 _a_) is the thicker and broader part of
the bone, and has two articular depressions (Fig. 9) for articulation
with the two facets of the ninth vertebra. The hinder end is pointed
and cylindrical, and terminates in a cartilage, which is fixed in the
tubular end of the bone. The middle portion is almost cylindrical, and
has a groove along the ventral surface which gradually becomes less
marked behind. The dorsal surface bears a ridge (Figs. 8 and 9 _s_),
which is high and thick in front, becomes sharper and less prominent
as it proceeds backwards, and gradually disappears towards the
hinder third of the bone, so that in transverse section the anterior
two-thirds of the bone appear triangular, with a ventral and two
lateral surfaces: while the hinder third is cylindrical. The anterior
portion of the bone contains a canal, _canalis vertebralis_ (Fig. 9
_c.v._), which is a continuation of the vertebral canal, along which
the hindermost spinal nerves pass. On each side of the anterior portion
of the urostyle are small apertures (Fig. 8 _c.c._), which lead into
canals (_canales coccygei_), which open into the vertebral canal, and
through which the coccygeal nerves pass. In front of these openings
and partly overhanging them are small triangular projections (Fig. 8)
(_processus transversarii_): these, however, are not constant, and are
more often found in _R. esculenta_ than in _R. temporaria_, in which
latter species the openings are smaller.
[Illustration: Fig. 9.
Urostyle of _Rana esculenta_, seen from the side, twice nat. size.
_c_ Ventral border.
_c.v._ Canal. vertebralis.
_s_ Dorsal ridge (pr. spinos.).
]
[Illustration: Fig. 8.
Urostyle of _Rana esculenta_, seen from the side, twice nat. size.
A bristle is passed through the _canal. vert._ and out through the
_canal. coccyg._ of the right side.
_a_ Anterior extremity.
_c.c._ Canal. coccyg.
_s_ Dorsal ridge (pr. spinos.).
]
II. THE SKULL.
The flat form of the frog’s head, as in batrachians generally, depends
upon the wide separation of the jaw-bones of the two sides, and on the
large size of the orbital cavities and the horizontal direction of
their floors. The outer circumference of the head forms a parabolic
frame (Figs. 10 and 11), composed of the maxillary (_m_), premaxillary
(_i_), and quadratojugal bones (_j_). In the middle of this curved
framework lies the elongated prismatic cranium. Anteriorly, this is
attached to the fore-part of the frame by means of the cartilaginous
skeleton of the organs of smell (Fig. 11 _e′_); posteriorly, it
widens out into two transverse arms (_p_), which contain the organs
of hearing. From this base, on either side, a bony strut, composed
of the posterior arms of the squamosal (_t′_) and of the pterygoid
bones, passes backwards to the hinder end of the frame. The anterior
arm of the squamosal bone (_t_) does not quite reach the framework,
but is attached to it by ligament alone. Between the last-named
arm posteriorly, the cranium on the inner side, and the maxillary
frame-work laterally, is a large space representing the orbital and
temporal fossae of human anatomy.
[Illustration: Fig. 10.
Skull of _Rana esculenta_, seen from above, twice natural size.
_e_ Sphenethmoid.
_fn_ Nasal.
_f.p._ Fronto-parietal.
_i_ Premaxillary.
_j_ Quadrato-jugal.
_m_ Maxillary.
_o_ Exoccipital.
_op_ Opisthotic.
_p_ Prootic.
_pt_ Pterygoid.
_pt′_ Posterior limb of pterygoid.
_t_ Squamosal.
_t′_ Posterior arm of the same.
]
[Illustration: Fig. 11.
Skull of _Rana esculenta_, seen from below, twice natural size.
_c_ Cartilaginous wall of skull.
_e_ Sphenethmoid.
_e′_ Cartilaginous skeleton of nose.
_h′_ Stylo-hyoid.
_i_ Premaxillary.
_m_ Maxillary.
_m′_ Quadrate tract.
_o_ Exoccipital.
_p_ Prootic.
_p′_ Anterior arm of prootic (_ala magna_ autt.).
_p″_ Trigeminal foramen.
_pl_ Palatine.
_pt_ Pterygoid.
_pt′_ Posterior arm of pterygoid.
_s_ Parasphenoid.
_v_ Vomer.
]
A. THE CRANIUM.
The cranium of the frog is a prismatic tube, wide behind, narrow in
front, and formed in great part of cartilage (Figs. 15 and 17). Our
indigenous species are characteristically distinguished from one
another by peculiarities in the form of the cranium. In _R. esculenta_
it is long and narrow, in _R. temporaria_ short and wide. The superior
surface in the former is markedly concave, while in the latter it is
flat, and in _R. oxyrhinus_ arched. These differences are readily
recognised in the living animal.
*The Bones of the Cranium.*
*1.* The *exoccipital bones*, _ossa occipitalia lateralia_, Cuvier
(Figs. 10, 11, 12, 14, 16 _o_).
*Cuvier*, _l. c._, p. 387, Pl. XXIV, bb.--*Dugès*, _l. c._, n.
14.--*Parker* and *Bettany*, _l. c._, p. 166, exoccipitals.
[Illustration: Fig. 12.
Skull of _Rana esculenta_, seen from behind, twice natural size.
_a_ Stapes.
_a′_ Columella auris.
_a″_ Extrastapedial.
_c_ Condyles of exoccipitals.
_h_ Stylo-hyoid.
_o_ Exoccipitals.
_p_ Prootic.
_p′_ Process to which the jaw is attached.
_t_ Squamosal.
]
These paired bones form the hinder part of the cranium; they bound the
_foramen magnum_, and articulate with the vertebral column. They are
imbedded in the cartilaginous matrix of the skull, and are separated
above by an unossified part of this matrix (_occipitale superius_,
Dugès), which represents the tabular portion of human anatomy: below
they are separated by a similar part (_occipitale basilare_, Dugès)
which represents the body of the occipital bone. They therefore
properly represent only the condylar portions (_partes condyloideae_)
of the human occipital bone. Each possesses a cartilaginous articular
head, for articulation with the first vertebra: these converge below,
and surround the lower half of the circumference of the _foramen
magnum_. This latter has, in _R. esculenta_, a transversely oval
outline; in _R. temporaria_, a somewhat heart-shaped outline, with
the apex directed upwards: in accordance with this the whole bone is
wider than high in the first species; and in the latter it is higher
than it is wide. From the upper and outer border of the _foramen
magnum_ on each side a ridge runs obliquely outwards and downwards,
in which lies the suture between this bone and the prootic bones. This
bony ridge (_processus mastoideus_, autt.) is usually cartilaginous
in _R. esculenta_, even in old animals; in _R. temporaria_, even in
young specimens, it is bony. In the latter species the bones unite
very early, while in the former they remain separated by the primitive
cartilage. Between this crest and the _processus condyloideus_
there is a depression (_fossa condyloidea_), with a hole (_foramen
condyloideum_) through which the vagus nerve leaves the cranium. The
exoccipital take part in the formation of the labyrinth of the ear, as
will be noticed later on.
_Articulation of the Exoccipital Bones with the Atlas._ From the middle
of the anterior surface of the body of the atlas a ligament arises,
representing to a certain extent the _lig. suspensorium dentis_, and
attached to the basal portions of the exoccipital bones.
*2.* The *prootic bones*, _ossa petrosa_, Cuvier (Figs. 10, 11, and
12 _p_).
*Cuvier*, rocher, _l. c._, p. 388, Pl. XXIV, ee.--*Dugès*, n. 12,
rupéo-ptéréal.--*Stannius*, ala temporalis.--*Meckel*, Schädelstück
des Schläfenbeins.--*Parker* and *Bettany*, _l. c._, prootic.
These paired bones lie at the sides and in front of the exoccipital
bones. As already explained, they remain in _R. esculenta_ separated
from these by cartilage, while in _R. temporaria_ they early enter
into bony union with them; this is due to the complete ossification
of the _processus mastoideus_ in the latter species, as stated above.
The prootics form the lateral expansions of the posterior part of the
skull in which the organs of hearing are placed. The large cavity which
contains the ear labyrinth is completed by the exoccipital: internally
it opens freely into the skull, and externally on the posterior wall
of the skull through the _foramen ovale_, which is formed by both
these bones. The postero-lateral part of the prootic usually remains
cartilaginous: at the side and in front of the _foramen ovale_ this
cartilage is pierced by a small opening, through which passes the
_nervus facialis_ or _ramus tympanicus n. vagi_ (Volkmann). At the
side there is a process to which the suspensorium of the lower jaw is
attached (Fig. 12 _p_): behind this is a hollow in which the auditory
ossicles lie, and which may be designated _fossa tympanica_ (Fig. 12
_t_). The anterior border of the bone forms the hinder and inner
walls of the orbit. Here also is the trigeminal foramen (Fig. 11
_p″_) through which the _N. trigeminus_ and the several nerves for
the muscles of the eye pass; it represents the _foramen ovale_, _for.
rotundum_, and the _fissura orbitalis superior_ (sphenoidal fissure) of
the human sphenoid bone. The foramen is sometimes, especially in young
animals, only a notch, which is completed by cartilage. On account of
the relation of this part (Fig. 11 _p′_) of the bone to the nerves
which pierce it, the whole bone has been named by Stannius the _ala
magna_ or _temporalis_ of the sphenoid; it has been also looked upon as
a bone which contains these elements, as by Dugès, who on this account
calls it rupéo-ptéréal.
[Illustration: Fig. 13.
Skull of _Rana esculenta_, seen from below, twice natural size.
_c_ Cartilaginous wall of skull.
_e_ Sphenethmoid.
_e′_ Cartilaginous nasal skeleton.
_h′_ Stylo-hyoid.
_i_ Premaxillary.
_m_ Maxillary.
_m′_ Quadrate tract.
_o_ Exoccipital.
_p_ Prootic.
_p′_ Anterior arm of prootic.
_p″_ Trigeminal foramen.
_pl_ Palatine.
_pt_ Anterior arm of pterygoid.
_pt′_ Posterior arm of pterygoid.
_s_ Parasphenoid.
_v_ Vomer.
]
_Appendages of the Prootic Bones._
1. The *styloid cartilage*. From the cartilaginous portion of the
prootic the styloid cartilage runs downwards, backwards, and inwards,
and is continued directly into the anterior cornu of the hyoid bone
(Figs. 11 _h′_ and 12 _h_).
2. The *auditory ossicles*.
_a._ A thick cartilaginous disc, the _operculum_ (Fig. 12 _a_),
closes the _foramen ovale_.
_b._ To the operculum is attached a bony, club-shaped piece, the
_columella auris_ (Fig. 12 _a′_), which has at its inner, thicker end
a cartilaginous epiphysis, the *interstapedial*; it lies transversely
with the apex directed outwards, and this longer portion is the
*mediostapedial*.
_c._ To the apex of the mediostapedial is attached, at an obtuse
angle, the third cartilaginous piece, the *extrastapedial* (Fig. 12
_a″_). It is attached to the tympanic membrane, and by its upper
portion is fastened to the cartilaginous tympanic ring by a smaller
piece, the *suprastapedial*.
3. The *tympanic ring* (_annulus tympanicus_) is an annular
cartilaginous frame; or more exactly, has the shape of a short,
truncated cone, as it narrows towards the middle line: it is attached
to the squamosal bone. (See Organ of hearing.)
*3.* The *parasphenoid*, _os sphenoideum_, Cuvier (Figs. 11 and 16
_s_).
*Cuvier*, _l. c._, p. 388, Pl. XXIV, d.--*Dugès*, n. 8.--*Meckel*,
Theil des Grundbeins.--*Parker* and *Bettany*, _l. c._,
parasphenoid.
A large portion of the base of the cranium is taken up by this
cruciform bone. Of the two longitudinal median processes, the
posterior is by far the shorter, and lies in front of and partly
below the cartilaginous _os occipitale basilare_. The anterior longer
longitudinal arm closes in the greater part of the cranium from below,
and articulates by its outer edges with that part of the prootic bones
often described as the _alae magnae_, and also with the cartilage
lying in front, which forms the greater part of the lateral walls of
the cranium. The anterior extremity of the bone articulates with the
palatine bones. The transverse arms lie on the under surface of the
exoccipitals and of the prootics.
The greater width of the cranium in _R. temporaria_ is associated with
the greater relative width of the anterior arm of this bone.
4. The *fronto-parietal bones*, _ossa fronto-parietalia_, Cuvier
(Figs. 10 and 14 _fp_).
*Cuvier*, _l. c._, p. 387, Pl. XXIV, c. c.--*Dugès*, n.
1.--*Parker* and *Bettany*, _l. c._, fronto-parietal.
These are a pair of somewhat long, flat bones, which form the principal
part of the upper wall or roof of the cranium, and cover in superiorly
the cartilaginous cranium, which is here, in great part, persistent.
They are united in the middle line by the sagittal suture; posteriorly
they articulate with the exoccipital and prootic bones; anteriorly with
the sphenethmoid, which they overlap like tiles. The outer margin of
each bone is bent somewhat downwards (Fig. 16 _fp_), and between it and
the parasphenoid there is a space in the wall of the cranium which is
closed in by cartilage and connective tissue only.
These bones are narrower in _R. esculenta_, and along the sagittal
suture are depressed into a groove: where the superior surface bends
down to become lateral the edges are much more prominent. In _R.
temporaria_ the bones are broader and flat or even somewhat arched. The
latter condition is still more marked in _R. oxyrhinus_.
*5.* The *sphenethmoid*, _os ethmoideum_ (Figs. 10, 11, 14, and 16
_e_).
*Cuvier*, os en ceinture, _l. c._, p. 387, Pl. XXIV, a.--*Dugès*,
n. 15.--*Rathke*, anterior or sphenoidal wing (Vortr. z. vergl.
Anat. d. Wirbelthiere, Leipzig, 1862, p. 42).--*Meckel*, Riechbein,
_l. c._, p. 502.--*Parker* and *Bettany*, _l. c._, ethmoid.
The long tubular cranium is completed anteriorly by a single bone,
which forms at once the roof, floor, and lateral walls. It is
consequently more or less ring-shaped, on which account it has been
named ‘os en ceinture’ by Cuvier. Only the posterior portion is
annular, however: the anterior portion forms a double canal, with a
median partition, for the passage of the nerves of smell, and as these
canals are widened out anteriorly, this part of the bone helps to
complete the nasal cavities, which, however, are bounded for the most
part by cartilage, as described below. In some species of frogs (as for
example _R. occellata_, Rathke) this cartilage is partly ossified.
The sphenethmoid has on each side a small bony canal, running forwards
and inwards, through which the _ramus nasalis_ of the first division of
the trigeminal nerve passes.
The *cartilaginous skeleton of the nose* (Figs. 14 and 16 _n_, _n″_,
_n‴_, _n⁗_). The anterior borders of the funnel-shaped cavities of
the sphenethmoid pass into cartilage, which forms two capsules,
separated from each other by a median cartilaginous septum, and opening
laterally. We can distinguish, (_a_) a cartilaginous septum, forming
a continuation of the bony one; (_b_) the floor of the nasal cavity,
narrower behind, wider in front; (_c_) a roof somewhat narrower
than the floor. The floor and roof are united in front by an arched
surface. From this cartilaginous capsule various processes project,
which unite it to other portions of the facial skeleton: firstly, from
the most posterior portion of the capsule there passes transversely
outwards a bar of cartilage (_sn_), which, widening, becomes continuous
with the cartilage (_sp″_) forming the basis of the anterior arm of
the pterygoid bone. From the anterior angle a cartilaginous process
passes outwards (Figs. 14, 16 _n″_), which is attached to a projection
on the anterior end of the maxillary bone; from the same spot a
horn-shaped cartilaginous process (_n″_, _n‴_) curves round backwards
and towards the middle line. This projection bounds the nasal cavity
externally, sending off a free process (_n‴_) on the way, and ends with
a double point on the roof of the cartilaginous nasal cavity (_n⁗_).
On the floor of the nasal capsule, on either side, is a knob-shaped
cartilaginous eminence, running from behind, forwards and outwards;
this may be regarded as an indication of a turbinated bone. From the
anterior wall there passes into each nasal cavity an almost horizontal,
partly ossified plate (_c.n._), ending posteriorly in a free pointed
border. These are the _cornets_ of Dugès (_l. c._, p. 12, Pl. I,
Figs. 1, 5), who correctly regarded them as turbinated bones. Cuvier
described them as rudimentary nasal bones[29].
[Footnote 29: Cuvier (Ossem. fossil., V, 2. 388) says that these little
bones are fixed outside the nasal cavity, so that we may suppose that
he confounded them with the nasal cartilages found in this situation.
Dugès correctly indicates their position to be inside of the nasal
capsule. Meckel (Vergl. Anat. II, 504) also regards them as nasal
bones. Bruch (Würzb. naturwiss. Zeitschrift, vol. II, 1861, p. 213)
could not find them in any frog-skull, doubtless because he did not
look inside the nasal capsules.]
[Illustration: Fig. 14.
Cartilaginous basis of the skull of _Rana esculenta_, from above, twice
natural size. Cartilage shown by stippling.
_a.n._ Wings of nasal cartilage.
_c.n._ Concha narium.
_e_ Sphenethmoid.
_ff′_ Foramina of cranium.
_fn_ Nasal.
_fp_ Fronto-parietal.
_i_ Premaxillary.
_j_ Quadrato-jugal.
_m_ Maxillary.
_n_, _sn_ Cartilaginous nasal skeleton.
_n′_, _n″_, _n‴_ Processes of the cartilage.
_o_ Exoccipital bones.
_p_. Prootic.
_pt_ Anterior arm of pterygoid.
_pt′_ Posterior arm of pterygoid.
_s′_ Cartilaginous cranium.
_sp_ Cartilage of suspensorium.
_sp′_ Cartilage under the squamosal.
_sp″_ Cartilage under the pterygoid.
_t_^1 Anterior }
_t_^2 Middle } arm of the squamosal.
_t_^3 Posterior }
]
The alar cartilages of the nose have still to be described. They are
(_a.n._) shell-shaped cartilages, hollowed out on the inner sides and
decreasing in width from before backwards. They are movably attached
by their anterior broader ends to the tips of the projecting portions
of the premaxillary bones, and are so arranged as to bound the lateral
margins of the nasal apertures, which they overlap.
[Illustration: Fig. 15.
Nasal cartilages of frog, front view.
_an_ Concha narium.
_i_ Premaxillary bones.
_i′_ Ascending process of same.
_m_ Upper jaw.
_m′_ Lower jaw.
_n_ Olfactory capsule.
]
*6.* The *cartilaginous basis of the skull*, _Primordial cranium_
(Figs. 14, 16).
*a.* If the fronto-parietals be removed, (Figs. 14, 16), a cartilage
(_s′_) is found which partially closes the cranial cavity, and which is
usually perforated on either side by a foramen (_f′_). More anteriorly
in the median line is found a space (_f_) which extends to the
sphenethmoid bone, and is only closed by connective tissue: posteriorly
the cartilage extends between the exoccipitals as far as the _foramen
magnum_, representing the _os occipitale superius_.
*b.* The base of the cranium is (Fig. 16) also partly cartilaginous. If
the parasphenoid (_s_) be removed we find above it a cartilage (_s′_)
which passes backwards between the exoccipitals, and extends as far
back as the _foramen magnum_: it corresponds to the _os occipitale
basilare_.
[Illustration: Fig. 16
Cartilaginous skull of _Rana esculenta_, from below, twice natural
size. Cartilage shown by stippling.
_c_ Cartilage of prootic.
_e_ Sphenethmoid.
_fp_ Fronto-parietal.
_i_ Premaxillary.
_j_ Quadrato-jugal.
_m_ Maxillary.
_n_, _sn_ Cartilaginous nasal skeleton.
_n′_, _n″_, _n‴_, _n⁗_ Processes of nasal cartilage.
_o_ Exoccipital.
_p_ Prootic.
_pl_ Palatine.
_pt_ Pterygoid.
_pt′_ Articular surface for pterygoid.
_r_ Optic foramen.
_r′_ Foramen for N. abducens.
_s_ Parasphenoid.
_s′_ Cartilaginous cranium.
_sp_ Cartilage of suspensorium.
_sp′_ Cartilage under squamosal.
_sp″_ Cartilage under pterygoid.
_v_ Vomer.
]
*c.* The sides of the cranium are formed almost entirely of cartilage.
This cartilage fills the space bounded by the nasals above, the
parasphenoid below, the so-called _ala magna_ of the prootic bone
behind, and the sphenethmoid in front; and has in its posterior part
an aperture (_r_) through which passes the _nervus opticus_, and below
this a smaller one (_r′_) for the _nervus abducens_. The extent of
the cartilage in the antero-posterior direction is greater in _R.
esculenta_ than in _R. temporaria_, or in other words the sphenethmoid
stretches further back in the latter than in the former.
B. THE BONES OF THE FACE.
[Illustration: Fig. 17.
Cartilaginous basis of the skull of _Rana esculenta_, from above, twice
natural size. Cartilage shown by stippling.
_a.n._ Wings of nasal cartilage.
_c.n._ Concha narium.
_e_ Sphenethmoid.
_ff′_ Foramina of cranium.
_fn_ Nasal.
_fp_ Fronto-parietal.
_i_ Premaxillary.
_j_ Quadrato-jugal.
_m_ Maxillary.
_n_, _sn_ Cartilaginous nasal skeleton.
_n′_, _n″_, _n‴_ Processes of the cartilage.
_o_ Exoccipital bones.
_p._ Prootic.
_pt_ Anterior arm of pterygoid.
_pt′_ Posterior arm of pterygoid.
_s′_ Cartilaginous cranium.
_sp_ Cartilage of suspensorium.
_sp′_ Cartilage under the squamosal.
_sp″_ Cartilage under the pterygoid.
_t^1_ Anterior }
_t^2_ Middle } arm of the squamosal.
_t^3_ Posterior}
]
The *Suspensorium*.
7. The *squamosal bones*, _ossa tympanica_, Cuvier (Figs. 10, 14 _t_).
*Cuvier*, _oss. foss._, V, 2. 390, Pl. XXIV, Figs. 1, 2
n.--*Dugès*, _temporo-mastoidien_, n. 10.--*Meckel*, Articular part
of temporal.--*Hallmann* and others, quadrate-bone.--*Parker* and
*Bettany*, _l. c._, squamosal.
The suspensorium, which forms the articulation between the cranium and
the lower jaw, is T shaped; and consists of cartilage covered by bone.
Of the three arms of the T the anterior has a free pointed extremity
(Fig. 14 _t^1_) at the postero-lateral margin of the temporo-orbital
fossa: it forms a true _processus zygomaticus_, and is bound to the
upper jaw by ligaments. In _R. temporaria_ it is comparatively much
shorter than in _R. esculenta_. The posterior upper arm (_t^2_)
articulates with the prootic bone: the third or lower arm (_t_^3),
supported by a cartilage[30], runs backwards and downwards to unite
with the side of the broad hinder extremity of the quadrato-jugal bone.
[Footnote 30: This cartilage is the quadrate cartilage of Parker;
others regard it as the upper end of the cartilaginous mandibular arch,
of which Meckel’s cartilage is the lower distal part.]
The cartilaginous basis[30] of the suspensorium (Fig. 17 _sp_, _sp′_)
is a direct continuation of the cartilaginous basis of the cranium,
and proceeds from it to the outer extremity of the prootic; from this
point the cartilage runs backwards and divides into two branches; of
these, one (_sp′_) retains the original course backwards and outwards
towards the articulation of the lower jaw, and in conjunction with the
quadrato-jugal (_j_) forms this joint. The other (_sp″_) is directed
forwards along the anterior arm of the pterygoid bone; it widens in
front (_sn_), and becomes directly continuous with the cartilaginous
strut described above as projecting from the hinder part of the
cartilaginous olfactory capsule.
*8.* The *quadrato-jugal bones*, _ossa jugalia_, Cuvier (Figs. 10,
17, 19 _j_).
*Dugès*, _tympano-malléal_, n. 11.--*Cuvier*, _l. c._, p. 399,
Pl. XXIV, Figs. 1 2 o.--*Hallmann*, quadrato-jugal bone, _l. c._,
p. 39.--*Parker* and *Bettany*, _l. c._, quadrato-jugal.
This is a small process of bone, likened by Dugès to a comma, which
rests by its posterior broader extremity on the cartilage of the
mandibular arch[1], and forms with it a portion of the articular
head for the lower jaw. The anterior extremity is pointed, directed
forwards, and attached by ligament to the maxillary bone.
*9.* The *pterygoid bones*, _ossa pterygoidea_ (Figs. 10, 11, 17, 19
_pt_).
*Cuvier*, _l. c._, p. 389, Pl. XXIV, Figs. 1, 2 m m.--*Dugès*, n.
9.--*Parker* and *Bettany*, _l. c._, pterygoid bones.
These bones, shaped like the Greek letter λ, possess each three arms:
of these the middle one is attached to the under surface of the prootic
bone by a cartilaginous process (Fig. 18 _sp_); the hinder grooved arm
lies upon the under surface of the cartilaginous suspensorial arch
(Fig. 18 _sp′_); and the anterior arm (_pt_) runs forwards along the
inner border of the anterior ramus of the suspensorium (_sp″_), in
contact with the maxillary, palatine, and nasal bones.
The cartilage just mentioned, by means of which the middle arm of the
pterygoid is connected with the cranium (compare Fig. 18), proceeds
from the cranial origin of the cartilaginous arch (_sp_), turns
downwards and then forms a sort of articular head (_cpt_), which is
articulated to an oval flat elevation of the prootic cartilage by a
movable joint. Externally the articular head curves somewhat abruptly
into the bony substance (Fig. 18 _pt_) of the pterygoid bone.
[Illustration: Fig. 18.
Origin of the suspensory cartilage (_sp_) from the skull, with
attachment of the pterygoid; front view. Cartilage shown by stippling.
_cpt_ Cartilaginous epiphyses of the pterygoid bone, from the cartilaginous suspensorium.
_j_ Quadrato-jugal bone.
_pt_ Pterygoid bone.
_sp_ Origin of suspensorial cartilage from the skull.
_sp′_ Hinder arm of same.
_sp″_ Anterior arm of same.
]
[Illustration: Fig. 19.
Cartilaginous skull of _Rana esculenta_, from below, twice natural
size. Cartilage shown by stippling.
_c_ Cartilage of prootic.
_e_ Sphenethmoid.
_fp_ Fronto-parietal.
_i_ Premaxillary.
_j_ Quadrato-jugal.
_m_ Maxillary.
_n_, _sn_ Cartilaginous nasal skeleton.
_n′_, _n″_, _n‴_, _n⁗_ Processes of nasal cartilage.
_o_ Exoccipital.
_p_ Prootic.
_pl_ Palatine.
_pt_ Pterygoid.
_pt′_ Articular surface for pterygoid.
_r_ Optic foramen.
_r′_ Foramen for N. abducens.
_s_ Parasphenoid.
_s′_ Cartilaginous cranium.
_sp_ Cartilage of suspensorium.
_sp′_ Cartilage under squamosal.
_sp″_ Cartilage under pterygoid.
_v_ Vomer.
]
*10.* The *maxillary bones*, _ossa maxillaria superiora_, Cuvier
(Figs. 10, 11, 17, 19 _m_).
*Cuvier*, _l. c._, p. 389, Pl. XXIV, Figs. 1, 2 k k.--*Dugès*, n.
4, _maxillo-jugal_.--*Parker* and *Bettany*, _l. c._, maxillary
bones.
These are elongated, curved bones, narrower behind, broader in front,
and forming with the quadrato-jugals the bony support of the face. The
superior surface is convex and directed outwards, the inferior surface
is grooved and bears teeth along the outer edge of this groove. From
the upper and inner border of the anterior half of this bone a process
(_processus frontalis_) passes upwards, which articulates with the
nasal bone. The anterior extremity of the bone articulates with the
premaxillary bone, the posterior with the quadrato-jugal.
The maxillary bone articulates at its anterior end (Fig. 19 _n″_) with
a process of the cartilaginous capsule of the nose. The broad plate of
cartilage (Fig. 19 _n_), under cover of the _processus frontalis_,
connects the hindermost transverse portion of the nasal cartilage
with the cartilage which runs forwards from the suspensorium upon the
anterior arm of the pterygoid.
*11.* The *nasal bones*, _ossa fronto-nasalia_, Dugès (Figs. 10, 17
_fn_).
*Cuvier*, _frontale anterius_, _l. c._, h.--*Dugès*, n.
2.--*Meckel*, nasal bone.--*Parker* and *Bettany*, _l. c._, nasal
bones.
These flat, triangular bones, which rest upon the nasal cartilages
(_n_), assist to bound the orbital cavities in front, and are connected
by their external angles with the maxillary bone on either side[31].
[Footnote 31: For _os nasale_, Cuvier (_l. c._, g), _cornet_
(_concha_), Dugès, see cartilaginous nasal capsule, p. 27.]
*12.* The *premaxillary bones*, _ossa intermaxillaria_ (Figs. 10, 11,
17, 19 _i_).
*Cuvier*, _l. c._, p. 388, Pl. XXIV, Figs. 1, 2 f f.--*Dugès*, n.
3.--*Parker* and *Bettany*, _l. c._, premaxillary bones.
These two bones are united in the middle line: each consists of a
tooth-supporting portion, which completes the maxillary arch, and
an ascending process, to the apex of which the nasal cartilage is
articulated by a movable joint (_an_). As muscles are attached to this
process, it becomes a lever, by which movements are effected.
[Illustration: Fig. 20.
Skull of _Rana esculenta_, seen from below, twice natural size.
_c_ Cartilaginous wall of skull.
_e_ Sphenethmoid.
_e′_ Cartilaginous nasal skeleton.
_h′_ Stylo-hyoid.
_i_ Premaxillary.
_m_ Maxillary.
_m′_ Quadrate tract.
_o_ Exoccipital.
_p_ Prootic.
_p′_ Anterior arm of prootic.
_p″_ Trigeminal foramen.
_pl_ Palatine.
_pt_ Anterior arm of pterygoid.
_pt′_ Posterior arm of pterygoid.
_s_ Parasphenoid.
_v_ Vomer.
]
*13.* The *palatine bones*, _ossa palatina_ (Figs. 19, 20 _pl_).
*Cuvier*, _l. c._, p. 389, Pl. XXIV, Figs. 1, 2 i i.--*Dugès*, n.
7.--*Parker* and *Bettany*, _l. c._, palatine bones.
Are two transverse bony bars, situated under the anterior portion of
the sphenethmoid bone on either side: each extends outwards from the
apex of the parasphenoid to the maxillary bone, where this gives off
its ascending process to the nasal bone.
*14.* The *vomers*, _vomer_ (Figs. 19, 20 _v_).
*Cuvier*, _l.c._, p. 389, Pl. XXIV, Figs. 1, 2 l l.--*Dugès*, n.
6.--*Parker* and *Bettany*, _l.c._, vomer.
A pair of flat bones, placed horizontally on the under surface of
the cartilaginous nasal capsule in the triangular space between the
palatine bone and the anterior portion of the arch of the jaw. They
limit the outer border of the floor of this capsule, which lies in a
groove on the dorsal surface of the bone. The outer border of each bone
has three processes, and between them two notches; the hinder of these
notches bounding the posterior nares. The inner borders of the two
bones touch, and the under surface of each bears a transverse row of
small, pointed teeth.
*15.* The *mandible*, _maxilla inferior_ (Fig. 21).
*Cuvier*, _l.c._, p. 398, Pl. XXIV, Figs. 1, 2 _rst_.--*Dugès*, n.
16, 17, 18, 19.--*Parker* and *Bettany*, _l.c._, mandibular arch.
[Illustration: Fig. 21.
_A_ Mandible of _Rana esculenta_, from above, nat. size.
_B_ External view of left side, } twice nat. size.
_C_ Angulosplenial, }
1. Angulosplenial.
2. Dentary.
3. Mentomeckelian.
4, 4′ Meckel’s cartilage.
_a._ Rudimentary _processus coronoideus_.
_b._ Groove for Meckel’s cartilage.
]
The mandible consists of two bony arches united by ligament in the
middle line, and each formed of four pieces. These are, (1) the
*angulosplenial*, a strong, bony piece (Fig. 21 _C_, _B_1, _A_1),
which forms the inferior and internal part of the lower jaw; below,
it extends posteriorly, as far as the articulation; in front, it is
attached to the dentary. In the greater part of its length it has
a groove directed upwards and outwards (_C_, _b_), and above has a
process which represents the _processus coronoideus_: (2) the *dentary*
(_A_ 2, _B_ 2), a bony lamella which rests on the outer surface of
the anterior half of the angulosplenial, and articulates in front with
*Meckel’s cartilage*; it is a thin, flat lamella of bone; (3) in the
groove of the angulosplenial is found a cartilage occupying its entire
length (_A_ 4, _B_ 4), *Meckel’s cartilage*; it is broader behind,
and here forms the articular fossa of the lower jaw; anteriorly it is
covered by the dentary, and articulates with the (4) *mentomeckelian*
(_A_ 3, _B_ 3) at its anterior end, which is bound to its fellow of the
opposite side by ligaments, and unites the two halves of the lower jaw.
The upper part of Meckel’s cartilage, which forms the joint with the
suspensorium, must be regarded as the _articulare_; to this also
belongs the anterior, ossified portion of the mentomeckelian[32];
the dentary, which covers Meckel’s cartilage, must represent the _os
dentale_[33]; the first and largest bone, the angulosplenial, which
lies on the inner side of the cartilage, must be considered as the _os
operculo-angulare_, Dugès, for it contains the elements of these bones.
[Footnote 32: Dugès, _os dentale_.]
[Footnote 33: Dugès, _surangulaire_.]
[Illustration: Fig. 22.
Hyoid of _Rana esculenta_, twice nat. size.
_H_ Body; _h h′_ processes.
_H′_ Anterior horn.
_H″_ Posterior horn.
]
*16.* The *hyoid bone*, _os hyoideum_ (Fig. 22).
*Parker* and *Bettany*, _l.c._, hyoid.
This consists of a broad, thin, cartilaginous plate, with processes
passing from it as represented in the figure. We distinguish in
it:--(*a*) the body (_H_), somewhat oblong, and wider in front than
behind. From the anterior angles there projects on either side a blunt
rounded process (_h_); from either posterior angle a more pointed
process (_h′_). (*b*) The anterior cornua (_H′_) (_cornua styloidea_)
project from the anterior border of the body, first in a forward
direction, then in a curve backwards and upwards (compare Fig. 12),
to unite with the cartilage of the prootic bone. Where the direction
of these _cornua_ is changed each sends off a short blunt process.
(*c*) The posterior cornua (_cornua thyroidea_) (_H″_) are bony rods
which run from the hinder margin of the body, diverge posteriorly, and
enclose the larynx.
III. THE STERNUM (Fig. 24 _es_, _hs_).
*Cuvier*, _l. c._, p. 401, Pl. XXIV, Fig. 31 _e f_.--*Dugès*, n.
27, 28.--*Parker* and *Bettany*, _l. c._, sternum.
The bones of the sternum are in very close relationship with the
shoulder-girdle, and some difference of opinion exists as to the
relations of the several parts.
[Illustration: Fig. 23.
Omosternum of _Rana esculenta_, twice nat. size.
_a_ Anterior,
_p_ Posterior extremity.
]
The following parts must be regarded as undoubtedly belonging to the
sternum:--
*1.* An anterior part, consisting of a bony and a cartilaginous portion.
_a._ The *omosternum* (Figs. 23, 24 _e.s._) is a bony rod, wider
behind, narrower in front, and supports
_b._ The *episternum* (Fig. 24 _es′_), a semicircular plate of
calcified cartilage, with a thin free border of unchanged hyaline
cartilage.
*2.* A posterior part, which also consists of a bony and a
cartilaginous portion.
[Illustration: Fig. 24.
Shoulder-girdle and sternum of _Rana esculenta_, twice nat. size. The
scapula and suprascapula are turned outwards.
_c._ Connecting cartilage.
_cl._ Clavicles and precoracoids.
_co_ Coracoid.
_es._ Omosternum.
_es′_ Episternum.
_h_ Hyaline cartilage.
_hs._ Sternum proper.
_hs′_ Xiphisternum.
_o_ Bone.
_o′_ Calcified cartilage.
_sc._ Scapula.
_sc′_ Suprascapula.
]
_a._ The *sternum proper* (Fig. 24 _h.s._), a rod of cartilage
ensheathed in bone, broader in front and narrower behind. To its
posterior extremity is attached
_b._ The cartilaginous *xiphisternum* (Fig. 24 _hs′_), a plate, the
shape of which is best understood by referring to Fig. 24, and the
structure of which is similar to that of the episternum.
*3.* The *epicoracoids*[34] lie between the episternum and the sternum
proper: they are a pair of narrow cartilages, closely applied to each
other and placed between the ventral ends of the precoracoids and
coracoids, see p. 40.
[Footnote 34: Dugès, _l.c._, p. 61, regards the cartilaginous laminae
as _os episternale_ and _proc. xiphoideus_, and the two bones _e.s._
and _h.s._ (Fig. 24) as sternum.]
IV. THE BONES OF THE ANTERIOR EXTREMITY.
A. BONES OF THE SHOULDER-GIRDLE.
The shoulder-girdle of the frog (Fig. 25) consists of four bones, two
in the upper or *scapular portion*, and two in the lower or *coracoid
portion*.
*1.* The *scapular portion*.
*a.* The *suprascapula*, _pars suprascapularis scapulae_, _scapula
superior s. omolita_ (Figs. 25 _s′_, 26, 27). This forms the upper,
thinner portion. It is trapezoid in shape, its narrowest, thickest,
and lowest border articulating with the scapula. The remaining
three borders are free; the posterior and superior borders are very
considerably thinned out, the inferior surface is curved towards the
ventral surface. Only the thin upper and hinder borders (_hh_) are of
hyaline cartilage; the middle portion (_co_) consists of calcified
cartilage; the lateral part (_o_) and the anterior border (_o′_) of
true bone.
[Illustration: Fig. 25.
Shoulder-girdle of the frog in transverse section, diagrammatic.
_c_ Connecting cartilage.
_c′_ Epicoracoids.
_cl_ Clavicles.
_h_ Humerus.
_s_ Scapula.
_s′_ Suprascapula.
_ss_ Articulation of these two.
_v_ Vertebra.
]
The bony part forms a thin plate striated both radially and
concentrically with the margin. The anterior border (_o′_) is bent on
itself so as to form a groove (Fig. 27). The dorsal surface of this
bony plate is quite smooth, and covered only by periosteum; the ventral
surface, on the contrary, is for the most part covered by an even layer
of calcified cartilage (Fig. 27 _co′_). This passes directly into the
second portion of calcified cartilage (_co_); so that if the whole be
dried, the thin hard lamina of bone can easily be split away from the
underlying parchment-like cartilage. The layer of calcified cartilage
is, however, not so complete that the _suprascapula_ can be said to
consist of calcified cartilage.
[Illustration: Fig. 26.
Suprascapula of _Rana esculenta_, from above, twice nat. size.
_co_ Calcified cartilage.
_h_ Hyaline cartilage.
_o_ Bony portion.
_o′_ Anterior curved border.
]
[Illustration: Fig. 27.
Suprascapula of _Rana esculenta_, from below, twice nat. size.
_co_ Calcified cartilage.
_co′_ Layer of calcified cartilage on the under surface of the bone.
_h_ Hyaline cartilage.
_o_ Bony portion.
_o′_ Anterior curved border.
]
[Illustration: Fig. 28.
Left scapula of _Rana esculenta_, from below, twice nat. size.
_a_ Anterior border.
_c.a._ _Cavitas articularis._
_l_ Outer border.
_m_ Inner border.
_p_ Posterior border.
]
[Illustration: Fig. 29.
Scapula seen from behind, twice nat. size.
_c.a._ _Cav. articularis._
_d_ Dorsal process.
_v_ Ventral process.
]
*b.* The *scapula* (Figs. 25 _s_, 28, 29) is a long, flat,
four-cornered plate of compact bone, contracted in the middle, and
wider at either end. From above (Fig. 28 _l_) it descends to the
shoulder-joint with a slight curvature, with the convexity directed
outwards. The inferior or ventral border (Fig. 28 _m_), which assists
in the formation of the shoulder-joint, is cleft into two processes,
a ventral and a dorsal. This may be best seen by looking at the
border of the bone from behind or before (as in Fig. 29). The lower
ventral process (Fig. 29 _v_) may be regarded as the _acromion_, or
at least as a rudiment of the acromion, _i. e._, _spina scapulae_.
The upper dorsal process evidently represents a rudimentary _processus
coracoideus_. The anterior border (Fig. 28 _a_) is free, somewhat
sharp, and slightly concave; the posterior (Fig. 28 _p_), also concave,
is free externally; while internally, where the division of the ventral
border commences, it takes part in the formation of the articular
cavity of the shoulder (Figs. 28 and 29 _c.a._).
_Articulation with the suprascapula._ The scapula consists of a shell
of compact bony tissue and an inner portion of cancellous tissue; this
latter passes, at the boundary between this bone and the suprascapula,
through an intermediate layer of calcified cartilage, which is directly
continuous with the cartilage of the suprascapula. The compact
superficial layer ceases where the calcified cartilage begins, and the
periosteum of the scapula passes directly into the perichondrium of the
suprascapula.
*2.* The *ventral portion* of the shoulder-girdle consists of three
parts, which lie one behind the other.
*a.* The larger and posterior bone, the *coracoid* (Figs. 24 _co_,
30), is contracted in the middle, and expanded at either end,
especially at the sternal end. The inner half is flattened from above
downwards; externally it becomes more cylindrical. The anterior and
posterior borders are markedly concave; the outer border (Fig. 30 _l_)
articulates by means of a cartilage with the _proc. coracoideus_ of
the scapula; the inner border (_m_) is separated from its fellow of
the opposite side by the epicoracoids. This inner border is so broad,
that it almost touches the inner end of the clavicle (Fig. 24 _cl._). A
*coracoid foramen* is thus formed between the two bones, similar to the
_foramen ovale_ of the pelvis.
[Illustration: Fig. 30.
Left coracoid, twice nat. size.
_a_ From below.
_b_ From behind.
_l_ Outer extremity.
_m_ Inner extremity.
]
[Illustration: Fig. 31.
Clavicle of the left side, twice nat. size.
_l_ Outer extremity.
_m_ Inner extremity.
]
*b.* The small anterior bones of the ventral portion of the
shoulder-girdle (Figs. 24 _cl._, 31), I, like Cuvier and others,
regard as *clavicles*. Dugès (n. 33) names them ‘_acromial_.’ Each
bone is narrower than the coracoid, smaller internally (_m_), broader
externally (_l_), and articulates by this broader end with the
cartilage uniting the dorsal and ventral portions; the inner extremity
rests upon the epicoracoid. The clavicle is grooved on its superior
and posterior surfaces in almost its whole length; the groove widens
externally (_l_), and contains
*c.* The *precoracoid* (Fig. 34 _cl′_), a slender bar of cartilage,
connecting the anterior edge of the scapula with the sternum.
[Illustration: Fig. 32.
Right shoulder-girdle of _Rana esculenta_, from above.
_ca_ Cav. articularis.
_c c_ Cartilage.
_cl_ Clavicle.
_co_ Coracoid.
_sc_ Scapula.
_sc′_ Suprascapula.
]
[Illustration: Fig. 33
Hinder border of the scapula and coracoid, with the connecting
cartilage and shoulder-joint, twice nat. size.
_c_ Connecting cartilage.
_d_ Dorsal process.
_co_ Coracoid.
_sc_ Scapula.
_v_ Ventral process.
]
[Illustration: Fig. 34.
Clavicular cartilage of a young specimen of _Rana esculenta_, enlarged
to the adult size.
_c_ Connecting cartilage.
_e_ Epicoracoids.
_c′_ Ligament between the two cartilages.
_cl_ Clavicle.
_cl′_ Clavicle and precoracoid.
_co_ Coracoid.
_co′_ Cartilage of same.
_es_ Omosternum.
_hs_ Sternum proper.
]
*Cartilages* of the shoulder-girdle (Figs. 24, 32, 34). A cartilage
(_c_), described by Dugès as the ‘paraglénal,’ connects the scapula
with the coracoid, and converts the notch between the two processes
(_s_ and _v_) on the inner border of the scapula into an aperture
opening posteriorly into the glenoid cavity, and which is filled up by
the lining cartilage. This cartilage connects the two processes with
the coracoid; being thicker between this and the _proc. coracoideus_,
it takes an important share in the formation of the floor of the
glenoid cavity. At the outer extremity of the clavicle the cartilage
projects and is then continued in the groove on this bone towards
the middle line (Figs. 32, 34), where it widens out, and is united by
its external margin with the sternum, thus forming the precoracoid as
already described, see p. 40. These connections are best seen in young
animals, as is shown in Fig. 34.
The clavicle (_cl_) is of ossifying cartilage; the cartilage (_c_),
the epicoracoid, is very large, and hyaline, and at _cl_ runs directly
into the epicoracoids, which are here united mesially by ligament. In
the fully developed animal the whole of the epicoracoid changes to
calcified cartilage, as also does the precoracoid lying in the groove
of the clavicle.
B. BONES OF THE FORE LIMB.
*1.* The *arm* has but one bone.
[Illustration:
Fig. 35. Fig. 36. Fig. 37.
Humerus of _Rana Humerus of _Rana, Humerus of _Rana
esculenta_, female, esculenta_ male, esculenta_, female,
seen from below. seen from below. outer side.
Figures twice natural size.
_c_ Anterior extremity. _c_′ Posterior extremity. _cd_ Crista
deltoidea. _cm_ Crista medialis. _t_ trochlea.]
The *humerus*, _os humeri_ (Figs. 35, 36, 37). The shaft of the humerus
is, on the whole, cylindrical, the middle part being the narrowest;
its dorsal surface is slightly concave, the ventral surface convex. In
the upper half the cylindrical form is indistinct, from the presence
of a well-marked crest (_crista deltoidea_) upon the under or ventral
surface. The hinder half of the bone has very different shapes in
the two sexes: in the female it remains cylindrical as far as the
elbow-joint; in the male, on the posterior surface, where the _crista
deltoidea_ ceases, a marked ridge (_crista medialis_) arises, which
gradually winds inwards and terminates at the inner condyle. This
sexual difference is found in all the three species described in the
Introduction, and it would seem that this ridge increases in height
during the pairing season. The muscle which arises from this process
is the _flexor carpi radialis_ (Fig. 74 _Fc_), and it attains, in the
males, a very large size at the same period; indeed, it is at its
origin twice as broad as in the female. Dugès[35] has incorrectly
stated that this _crista_ is a peculiarity of _Rana temporaria_, and is
wanting in _Rana esculenta_. Pouchet[36] first observed that it was a
sexual distinction.
[Footnote 35: _l. c._, p. 68.]
[Footnote 36: Compt. rend. vol. XXV, 1847, p. 761.]
The anterior articular extremity presents a rounded head, which is
somewhat flattened externally. The inferior ventral border is sharp,
and developed into the above-mentioned bony crest (_crista deltoidea_);
the free border is arched and curved outwards. Above, on the outer
surface of the head, is found an eminence which may be a rudimentary
_tuberc. maius_. The inner half of the head is articular.
The posterior articular extremity consists of a rounded head (_c′_),
attached to the posterior extremity of the shaft; internal to this is
a small _trochlea_ (_t_), placed upon the inner condyle. The external
condyle is but small. The head is embraced by these condyles. Upon the
under surface, above the head, is the _fossa cubitalis anterior_. The
structure of the two articular extremities of the humerus differs; the
upper, as in long bones generally (see page 16), consists of hyaline
cartilage surrounded by calcified cartilage, which again is covered by
hyaline articular cartilage; the lower extremity is composed of spongy
bone, with roundish marrow spaces, and for the most part covered by a
layer of calcified cartilage.
The *shoulder-joint*. The socket is formed by the posterior border of
the scapula, by both the processes of that bone, the outer portion of
the coracoid, and besides these by cartilage, which forms the articular
surface already described (Fig. 33). In the macerated bone the floor
of the socket opens dorsally into a fossa between the processes of the
scapula (Fig. 32). This opening, in the natural condition, is closed by
synovial membrane only; the cartilage covering the rest of the space
being absent (the sac may easily be inflated, either from the joint
itself or through the opening). The margin of the socket consists of
a _labrum_, partly fibrous and partly cartilaginous, which is easily
removed entire. The capsule, which is attached beneath the _caput
humeri_, arises from this. From the articular cartilage of the ventral
margin of the socket, and from the adjacent part of the scapula,
proceeds a strong band, which is inserted into the flattened outer
surface of the head.
*2.* The *forearm*.
[Illustration: Fig. 38.
Radio-ulnar of the right side of _Rana esculenta_, twice nat. size.
_r_ Radius.
_r_′ Capitulum radii.
_u_ Ulna.
_u_′ Olecranon.
]
The *radio-ulnar*, _os antibrachii_ (Fig. 38). The two bony elements
of the forearm are fused into one, which, however, shows traces of its
compound character. Of these two bones, that which forms the inferior
(in man anterior) border is the radius, the other the ulna. The
relative positions of the bony elements are such that they appear to be
in a state of semi-pronation; by this the thumb-border of the arm is
directed downwards (in man forwards). The two bones so united form a
flattened, tube-like bone, the grooved surfaces of which are directed
inwards and outwards respectively; the borders being dorsal and
ventral. The shaft of the bone is narrower above, becoming gradually
wider below. In the upper half, the groove showing the line of junction
of the two bony elements is scarcely visible, and it appears as
though this part consisted of ulna alone, the radius not reaching so
far; below the groove is more marked. The upper articular extremity
appears to consist of an _olecranon_ (Fig. 38 _u′_) and a _processus
coronoideus_ (_r′_), between which is the greater sigmoid cavity
(_cavitas sigmoidea major_) for the _processus cubitalis humeri_. A
more careful examination shows this to be incorrect: the portion of the
concave articular surface, which lies in the immediate neighbourhood
of the ventral border, undoubtedly represents the articular surface of
the _capitulum radii_, and the upper portion of the articular surface
(at _u′_) belongs to the _ulna_ and articulates with the _trochlea_
(Figs. 35, 36 _t_) of the humerus. The inner border of the upper
extremity of the bone articulates with the groove _t_ of the humerus.
The inferior extremity forms one of the usual cartilaginous epiphyses,
enclosing the two bones. That part of the extremity corresponding with
the radius is triangular and convex, it is prolonged upon the inner or
under surface of the bone by means of a process; the ulnar portion of
the bone forms a _capitulum_. The structure of the inferior extremity
is that of epiphyses in general, except that there are two medullary
cavities in a common sheath of calcified cartilage; the anterior head
consists of cancellous tissue, with a covering of calcified cartilage.
*3.* Bones of the *hand* (Fig. 39).
*Dugès*, Pl. VIII, Figs. 37, 38, 39, 40, 41, 42, 43, 52.
*a.* Bones of the *wrist*, _ossa carpi_. These are arranged in two
rows, proximal and distal. The proximal or anterior row has three
bones, viz.:--
1. _Os lunatum_, the middle bone (Fig. 39 _l_), Dugès, n. 38,
articulates with the radial part of the articular surface of the
radio-ulnar by a concave surface; with the large bone of the second
row (_hc_) it articulates by means of a rounded head; and with the
two other bones of this row, _os naviculare_ (_n_) and _pyramidale_
(_p_), with the former by a saddle-shaped surface, with the latter
chiefly by ligament. The bone is irregularly cuboid; the dorsal and
palmar surfaces are non-articular. With Dugès I regard this bone as _os
lunatum_; Mertens[37] regards it as _os naviculare_.
[Footnote 37: Mertens, _l. c._]
[Illustration: Fig. 39.
Bones of the forearm and hand of _Rana esculenta_, right side, dorsum,
twice nat. size.
_a_ Os antibrachii.
_hc_ Os capitato-hamatum.
_l_ Os lunatum.
_m_ Ossa metacarpi.
_n_ Os naviculare.
_p_ Os pyramidale.
_r_ Radial portion of the radio-ulnar.
_t_ Os multangulum majus or trapezium.
_t′_ Os multangulum minus or trapezoides.
_u_ Ulnar portion of the radio-ulnar.
_I_-_V_ First to fifth fingers, the fifth only
of os metacarpi, the second and third of
two, fourth and fifth of three phalanges.
]
2. _Os pyramidale_ (Fig. 39 _p_), Dugès, n. 37, articulates with the
ulnar part of the posterior articular extremity of the radio-ulnar.
Anteriorly the bone has a facet which receives the _capitulum ulnae_,
and alongside this a small flat surface which articulates with the
radius. Posteriorly, opposite to the second row, it presents a long
raised articular surface, extending from the dorsum to the palmar
surface; and on the palmar aspect of the bone is a ridge running from
before backwards. Mertens names this bone _os lunatum_.
3. _Os naviculare_ (Fig. 39 _n_), Dugès, n. 39. The third bone of the
first row does not articulate with the bones of the forearm. It is
connected with the _os lunatum_ by a saddle-shaped surface, posteriorly
with the _os capitatum_ by means of a concave surface. On the inner
surface is a small concave articular facet for the _os multangulum
minus_ or _trapezoides_ (Fig. 39 _t′_). The convex palmar surface of
the bone articulates with the _os multangulum majus_ (_t_); the radial
side is non-articular, and with the _os lunatum_ forms a ridge directed
forwards. Mertens names this bone _os triquetrum_. It is evident,
however, that if the arrangement in man obtains as a standard, the
nomenclature of Dugès, which I have here used, is correct; but the _os
naviculare_ is no longer in contact with the articular surface of the
_os antibrachii_.
The second or distal row also consists of three bones:--
4. _Os capitato-hamatum_ (Fig. 39 _hc_), Dugès, n. 40, 41, 42,
corresponds with the _os capitatum_ and _hamatum_[38], which are here
fused together. It is the largest bone, and articulates with all three
bones of the first row; it is crescentic, with the concavity directed
posteriorly, and on the convex surface has three facets for the three
outer _ossa metacarpi_.
[Footnote 38: Dugès thinks that _os trapezoides_ is also included.]
5. _Os multangulum minus_, _s. trapezoides_ (Fig. 39 _t′_), Dugès, n.
43, is a small bone lying next to the foregoing; it articulates with
the _os metacarpi II_, and anteriorly with the _os naviculare_. Dugès
considers it to be the _os trapezium_.
6. _Os multangulum majus_, _s. trapezium_ (Fig. 39 _t_), is a small
bone, which is placed on the convex palmar auricular side of the _os
naviculare_. Dugès regards this bone as _os metacarpi pollicis_ (Dugès,
n. 44), Mertens as _multangulum minus_. It appears to me that the
interpretation here given is justified, because it articulates with the
rudiment of the thumb, and as it possesses no resemblance to a long
bone it cannot be regarded as an _os metacarpi_.
*Structure of the carpal bones.* All the carpal bones consist of
calcified cartilage, though variations due to age occur in the amount
of the deposit.
*Wrist joint.* As stated above, the _os lunatum_ and _os pyramidale_
are articulated with the forearm. In addition to the capsules uniting
the parts, there are strengthening ligaments, two of which require
special mention. One of these arises from the palmar surface of the
posterior extremity of the ulna, and passes to the sharp palmar ridge
of the _os pyramidale_, where it is attached, and is inserted into the
_os capitato-hamatum_; the second ligament passes in a similar manner
on the palmar surface from the radius to the _os naviculare_. Between
the two ligaments there is on the volar surface a deep excavation.
[Illustration: Fig. 40.
Bones of the forearm and hand of _Rana esculenta_, right side, dorsum,
twice nat. size.
_a_ Radio-ulnar.
_hc_ Os capitato-hamatum.
_l_ Os lunatum.
_m_ Ossa metacarpi.
_n_ Os naviculare.
_p_ Os pyramidale.
_r_ Radial portion of the radio-ulnar.
_t_ Os multangulum majus or trapezium.
_t′_ Os multangulum minus or trapezoides.
_u_ Ulnar portion of the radio-ulnar.
_I_-_V_ First to fifth fingers, the first only
of a metacarpal, the second and third of
two, fourth and fifth of three phalanges.
]
*Movements* of the hand. The two bones of the forearm being firmly
united, pronation and supination, as in man, are impossible. The
normal position, as already remarked (see radio-ulnar), is that of
semi-pronation (compare Figs. 2 and 74). If the animal be in its
natural posture, with the arm bent at the elbow (Fig. 1) it can touch
the ground with the ulnar border only; but when the whole surface of
the hand rests upon the ground, the action is brought about as follows:
the plane of the carpus is in extension parallel with that of the
forearm; in flexion, almost at right-angles with that plane (Fig. 74)
The _os lunatum_ glides on the prolongation of the articular surface
on the inner palmar surface of the radius, while the _os pyramidale_
is held firmly by the ligament just described. The hand follows the
movement of the _os lunatum_, and at the same time the three outer
_ossa metacarpi_ gliding with it inwards, the fingers of the hand turn
inwards.
*b.* The Bones of the *metacarpus*, _ossa metacarpi_ (Fig. 40 _m_).
Of these there are five: the *second* to the *fifth* are of about
equal length; the first, forming the rudiment of the thumb, hidden
beneath the skin, is much shorter. This metacarpal bone of the *thumb*
is regarded by Dugès and others as the first phalanx. My reason for
describing it as a metacarpal has already been given. This bone
also presents differences in the two sexes. Meckel’s[39] observation
that it exists only in the male is incorrect; it is a large, broad
and sickle-shaped mass of calcified cartilage or even true bone,
while in the female it is simply a small cartilaginous rod; as this
almost entirely disappears in dried specimens, Meckel’s statement is
explained. The *second* finger has in the frog assumed the functions
of the thumb, and, in the males, in the breeding season swells and
undergoes an essential alteration of structure. The metacarpal of
this finger also displays differences in the sexes, being in the male
stronger, broader, and on the inner side provided with a spine-like
prolongation, for the tendon of the _abductor digiti II (pollicis)
longus_, which attains an unusual development during the breeding
season. The remaining metacarpal bones, the *third*, *fourth*, and
*fifth*, are of similar form, the last being provided with a tubercle.
The anterior articular extremities are rather broad and concave, and
the posterior have rounded heads.
[Footnote 39: _l. c._, II, 464.]
*c.* The *phalanges*, _phalanges digitorum_. The hand has four fingers
and the rudiment of a fifth, which latter is completely hidden under
the skin, and as already explained, consists of a metacarpal only. Of
the four fingers, the fourth is the longest, the third the shortest,
the second and fifth of intermediate and about equal length; the fourth
and fifth fingers have each three phalanges, the second and third have
each two. Their shape is not unlike that of the human phalanges.
V. THE BONES OF THE HINDER EXTREMITY.
A. BONES OF THE PELVIC GIRDLE (Fig. 41).
The *pelvis* has a characteristic V-shape, the pubic and ischiatic
bones of the two sides together forming a vertical plate (_a p_), which
divides anteriorly into the two iliac bones (_il_). The pubic and
ischiatic bones being united by their median surfaces, one can only
speak of the pelvic cavity as the space between the two ilia.
*1.* The *ilia*, _ossa ilii_ (Fig. 42 _il_). In these a broader part
or body can be distinguished, which takes part in the formation of the
_acetabulum_ (_a_). The hinder and broadest part of the bone is joined
to the corresponding portion of its fellow by ligament; anteriorly the
two diverge, bounding a cone-shaped cavity, the pelvis. The suture, by
which the body of the iliac bone is united with the ischiatic and pubic
bones, runs from above downwards through the middle of the _acetabulum_
(Fig. 42, from _p_ through the _acetabulum_ to _is_). Inferiorly and
in front the united _ilia_ form a prominence (_s_), which represents
the _symphysis oss. pub._ of man. The expanded portions of the ilium
rest directly over the articular cavity by means of a somewhat
constricted part or root. The _ala_ is a sabre-like bone, with the
sharper, more convex border directed upwards; the more concave, thicker
border downwards. The two surfaces, of which the inner is grooved,
are directed respectively inwards and outwards. The broader part of
the blade springs directly from the neck or root (at _il′_), and at
this end of the sharp convex border is a process, _process. sup._,
from which the tendon of the _m. vastus externus_ arises. The anterior
end of the blade is a hollow cylinder, containing cartilage, movably
articulated to the transverse process of the last vertebra or sacrum.
[Illustration: Fig 41.
Pelvis of _Rana esculenta_, from below, nat. size.
_a_ Acetabulum.
_il_ Iliac bone.
_p_ Pubic bone.
]
[Illustration: Fig. 42.
Pelvis of _Rana esculenta_, left side, twice nat. size.
_a_ Acetabulum.
_d_ Upper sharp border.
_il_ Iliac bone.
_il′_ Superior process.
_is_ Ischium.
_is′_ Tuber ischii.
_p_ Os pubis.
_s_ Inferior process of the ilium.
_v_ Lower border of same.
]
*2.* The *ischia*, _ossa ischii_ (_is_), are irregular, four-cornered
plates of bone, united together by the whole extent of their inner
surfaces. The vertical plate formed by the union of the two bones takes
only a very small share in the formation of the articular cavity.
Above, it has a somewhat sharp border, continued with the ilium into
a process (_is′_) corresponding with the united _tubera ischii_; the
hinder border, which is united below with the pubic cartilage, is
curved.
[Illustration: Fig. 43.
Horizontal section through the iliac, pubic, and ischiatic bones.
_a_ Acetabulum.
_il_ Ilium.
_is_ Ischium.
_p_ Pubic cartilage.
_s_ Ligaments which unite the bones of opposite sides.
]
*3.* The *pubes*, _os pubis_ (Figs. 41, 42, 43 _p_). Ossified pubic
bones do not exist; even in old animals they are composed of calcified
cartilage. Each is a triangular cartilage, wedged between the ilium and
ischium, but also taking part in the formation of the _acetabulum_. The
pubes of opposite sides are, as shown in section in Fig. 43, united by
ligaments in the median plane.
B. BONES OF THE HIND-LIMB.
*1.* The *thigh*.
The *femur*, _os femoris_ (Fig. 44). The shaft is cylindrical, with a
slight double or S-shaped curve. In the anterior portion the convexity
is directed upwards, in the two hinder thirds downwards. Towards the
hinder extremity it is flattened from above downwards. The anterior
extremity is a rounded articular head placed directly on the shaft
like that of the _humerus_. This head is somewhat flattened from side
to side; and in structure resembles that of the humerus. The inferior
extremity is rounded below, but flattened above (towards the hollow of
the knee) and behind.
*Hip-joint.* The articular cavity is deepened by a fibrous ring,
_labrum cartilagineum_, which fits closely upon the _caput femoris_;
from this _labrum_ the joint-capsule arises, to be inserted behind the
head; close to the lower border of the cavity a _ligamentum teres_
arises, which is inserted into the _caput femoris_.
*2.* The *leg*.
[Illustration: Fig. 44.
Femur of _Rana esculenta_, right side, twice nat. size.
_a_ Anterior extremity.
_p_ Posterior extremity.
]
*Tibio-fibula*, _os cruris_ (Fig. 45). This consists of a single bone,
the _os cruris_; it is often called the _tibia_, but presents, however,
distinct indications of being formed of two bones, the _tibia_ and
_fibula_. The shaft is not quite straight; it is thinner in the middle
and flattened from above downwards. On the upper as also on the lower
surface of the bone is a groove, passing from the middle towards each
extremity; this deepens as it proceeds, and is an indication of the
compound nature of the bone. In the middle of each surface of the bone
is the opening of a canal, through which a bristle may be passed: the
canal has bony walls. The medullary cavity is, for the most part,
double, being single only in the middle. The anterior extremity is
articular, and presents a median groove, which is prolonged on to the
under surface. The posterior extremity forms a transverse condyle,
which has at its inner part a notch for the tendon of the _m. tibialis
posticus_.
[Illustration: Fig. 45.
Tibio-fibula of _Rana esculenta_, twice nat. size, seen from below.
_a a_ Grooves.
_f_ Foramen nutritium.
_t_ Anterior articular extremity.
_t′_ Posterior articular extremity.
_t″_ Groove on malleolus internus for tendon of _m. tibialis posticus_.
]
The *knee-joint* consists of a capsule strengthened by the insertions
of numerous tendons. Within this the articular surfaces of the _femur_
and tibio-fibula are connected by means of fibro-elastic bands, which
spring from the latter bone and cross each other, thus representing the
_lig. cruciata_. The articular surfaces are moreover deepened by loose
semilunar cartilages, corresponding with the inter-articular cartilages
of the knee-joint of man. In addition, on either side of the joint, are
found auxiliary ligaments.
[Illustration: Fig. 46.
Section of the tibio-fibula through the under extremity.
_a_ Cartilaginous epiphysis.
_m_ Marrow cavities.
_t″_ Connecting mass.
_t t′_ The two cylinders of bone.
]
*3.* The *foot* (Fig. 47).
*a.* The *ankle*, _ossa tarsi_. The *tarsus* consists of two rows of
bones.
α. The *proximal row* consists of two long tubular bones (Fig. 47
_ac_), which are parallel to each other, and undoubtedly correspond
with the *astragalus* (_talus_) and *calcaneum*. The bones are
separated in the middle, but approach each other at either end. The
outer of these bones (_c_) I have named calcaneum, following Cuvier
and Dugès; the inner, astragalus (_a_). The two bones are surrounded
and enclosed at their anterior and posterior extremities in a common
epiphysis of calcified cartilage, which has the usual structure found
elsewhere. The _ligamentum calcanei_, which will be described below
(see Muscles of Foot, Fig. 88 _lc_), may be regarded as an unattached
process of the heel[40].
[Footnote 40: Meckel, _l. c._, II, p. 488, regards the cartilage in the
_tendo Achillis_ as such.]
β. The *distal* row of the tarsals are all composed of calcified
cartilage. They are:--
1. _Os cuboideum_ (Fig. 47 _cb_), a flat plate of cartilage, concave
in front, convex behind, placed between the common epiphysis of the
astragalus and calcaneum (_ac_) and the _ossa metatarsi II_ and _III_.
This corresponds, as Dugès suggests, with the separated _os cuboideum_
and _cuneiforme III_ of other batrachians, _e. g._ Bufo.
2. On the inner side of the above, between the _astragalus_ and
_metatarsus I_ lies a small body, concave in front, convex behind,
which we may regard, with Dugès, as the analogue of the _os naviculare_
(Fig. 47 _n_).
[Illustration: Fig. 47.
Right foot of _Rana esculenta_, palmar surface, twice nat. size.
_a_ Astragalus.
_ac_ Common epiphysis.
_c_ Calcaneum.
_cb_ Os cuboideum.
_h_ First, _h′_ second cartilage of supplemental toe.
_m_ Ossa metacarpi.
_n_ Os naviculare.
_I_ to _V_ First to fifth toe.
]
3. This latter supports a cartilage which forms a projection on the
inner border, covered with skin. This consists of closely-united
pieces, a small round, basal piece (_h_), and a flattened beak-like
piece (_h′_). Dugès considers these pieces as the first and second
_ossa cuneiformia_; I rather incline to Meckel’s opinion that they
represent a rudimentary hallux, the first being the _os metatarsi_, the
second a _phalanx_. Both are composed of calcified cartilage; in _R.
temporaria_ the lime-deposit seems to be less than in _R. oxyrhinus_
and _R. esculenta_, and the projection consequently softer[41].
[Footnote 41: In the text these two cartilages are termed the
‘supplemental toe.’]
*b.* The *metatarsal bones*, _ossa metatarsi_ (Fig. 47, _m_ _I_-_V_).
The five _ossa metatarsi_ are long, thin tubular bones, the anterior
articular extremities of which are broader above and narrow below,
hence are wedge-shaped, and anteriorly present flat surfaces for
articulation with the _tarsus_. The shafts are long and thin; the
posterior extremities have rounded heads. The comparative length of
these is as follows: the fourth is the longest, then come the third,
fifth, second, and first in order. In structure they resemble other
tubular bones.
*c.* The *phalanges*, _phalanges digitorum_ (Fig. 47). The total
lengths of the separate toes correspond with that of the _ossa
metatarsi_, but the distinctive differences are increased, partly by
the difference in number and partly by the varying lengths of the
phalanges. The first and second toes have each only two phalanges, the
third and fifth have each three, the fourth, which is the longest, has
four. The terminal phalanges are somewhat hooked towards the plantar
surface.
SECTION II.
THE MUSCLES.
THE MUSCLES.
LITERATURE.
Anonymous, Ueber das Schultergerüst der Schildkröten mit den
daran sitzenden Muskeln. Isis, 1827. (Contains remarks on the
shoulder-muscles of the frog.)
*Carus*, *C. G.* (1) Lehrbuch der vergleichenden Zootomie. 2nd Edit.
Leipzig, 1834. (2) Erläuterungstafeln zur vergleichenden Anatomie.
1 Part. 1826. (Muscles of the Leg.)
*Chappuis*, Morphologische Stellung der kleinen hintern Kopfmuskeln.
Zeit. f. Anat. u. Entwickl. 1876. Vol. II, pages 287–297.
*Cuvier*, Leçons d’anatomie comparée. Paris, 1835. Vols. I, II.
*Dugès*, Recherches anatomiques et physiologiques sur la déglutition
dans les Reptiles. Ext. des Annales des Sciences naturelles.
Paris, 1827.
*Dugès*, Leçons d’anatomie comparée. Paris, 1835.
*Duméril and Bibron*, Erpétologie générale ou Histoire complète des
Reptiles. 1836.
*Führbringer*, Zur vergleichenden Anatomie d. Schultermuskeln.
Jenaische Zeitschr. 1873. Vol. VII.
*Klein*, Beiträge zur Anatomie der ungeschwänzten Batrachier (Rana
temporaria, L.): in Jahrshefte des Vereins für vaterländische
Naturkunde in Würtemburg. 6 Jahrgang. 1850. Page 1.
*Kuhl*, Beiträge zur Zoologie der Rana esculenta: in Beitr. z. Zool.
Frankfurt, a. M. 1820. Page 115.
*de Mann*, Vergelykende myologische en neurologische studien over
Amphibien en Vogels. Acad. Proefschrift. 1873.
*de Mann*, Myologie comparée de l’extrémité post. chez les
amphibiens. Niederl. arch. f. Zool. 1874. Vol. II.
*Marshall*, The Frog. London and Manchester. 2nd Edit. 1885. Pages
60–71.
*Martin St. Ange*, Annales des sciences naturelles. Vol. XXIV. 1831.
Page 393.
*Meckel*, System der vergleichenden Anatomie. Halle, 1828. Vols. III
and IV.
*Pfeiffer*, Zur Anatomie des Schultergürtels und der Schultermuskeln
bei Säugethieren, Vögeln und Amphibien. Giessen, 1854.
*Rymer Jones*, Article ‘Reptiles’ in Todd’s Cyclop. of Anatomy and
Physiology. 1847–1852. Vol. IV. Page 263.
*Stannius*, Handbuch der Anatomie der Wirbelthiere. Vol. II. Zootomie
der Amphibien. Berlin, 1856.
*Wagner*, Icones Zootomicae. Leipzig, 1841.
*Wagner*, Lehrbuch der vergleichenden Anatomie. Leipzig, 1834–35.
*Zenker*, Batrachomyologia. Diss. Jena, 1825.
THE MUSCLES.
I. MUSCLES OF THE HEAD.
I. MUSCLES OF THE EYE.
*1.* _M. rectus inferior_ (Fig. 48 _ri′_).
*Dugès*, post-orbito-sous-oculaire, n. 12.--*Zenker*, _depressor
oculi_.
This muscle arises by a very thin, almost thread-like tendon from the
parasphenoid, near the _foramen opticum_, and becomes rapidly broader;
it lies beneath the tendon of the _membrana nictitans_ and a part
of the _m. retractor bulbi_: then runs forwards and outwards to be
attached into the lower part of the circumference of the eyeball.
[Illustration: Fig. 48.
Eye muscles of _Rana esculenta_, from below.
On the right side (_i. e._ in the left eye) the lev. bulbi (_l_) is
taken away; on the left side it is still present.
_l_ M. levator bulbi.
_l.a_ M. lev. anguli scapulae
_oi_ M. obliquus inferior.
_os_ M. obliquus superior.
_p_ M. pterygoideus.
_r_ M. retractor bulbi.
_re_ M. rectus externus.
1 First cervical vertebra.
]
*2.* _M. rectus externus_ (Fig. 48 _re_).
*Dugès*, post-orbito-ex-oculaire, n. 14.
Arises by a thin, thread-like tendon from the parasphenoid near the
_foramen opticum_, internal to and a little behind the _m. rectus
inferior_: it then passes obliquely outwards over the _m. retractor
bulbi_ and the tendon of the _membrana nictitans_, to be inserted into
the outer and hinder part of the circumference of the eyeball.
*3.* _M. rectus internus_ (Fig. 48 _ri_).
*Dugès*, post-orbito-in-oculaire, n. 13.
A long, thin muscle, which arises by a thread-like tendon from the
parasphenoid at the inner and hinder angle of the orbit, passes along
its inner wall, and is inserted into the antero-internal part of the
circumference of the eyeball.
*4.* _M. rectus superior_ (Fig. 49 _rs._).
*Dugès*, post-orbito-sous-oculaire.
Arises by a slender tendon from the fronto-parietal bone, widens
rapidly, and runs forwards and outwards to be inserted into the upper
part of the circumference of the _bulbus_.
[Illustration: Fig. 49.
Eye-muscles of _Rana esculenta_, from above.
_n_ Membrana nictitans.
_n′_ Tendon of membrana nictitans.
_p_ M. pterygoideus.
_rs._ M. rectus superior.
_t_ M. temporalis.
]
*5.* _M. obliquus inferior_ (Fig. 48 _oi_).
*Dugès*, pré-sous-orbito-oculaire.
This muscle arises near the floor of the orbital cavity, at the inner
and anterior angle, from the palatine bone by a thin and long tendon,
runs under Harder’s gland outwards and backwards, and is inserted,
almost at a right angle with the axis of the eye, into the anterior
part of the circumference of the eyeball.
*6.* _M. obliquus superior_ (Fig. 48 _os_).
*Dugès*, pré-sus-orbito-oculaire, n. 7.
The tendon of this small muscle arises from the inner end of the
palatine bone, near the origin of the _m. obliquus inferior_, runs
upwards, backwards, and outwards, and passes into a flat muscle, which
rapidly becomes broader, and is inserted into the upper surface of the
eyeball.
[Illustration: Fig. 50.
Eye-muscles of _Rana esculenta_, from below, the m. recti and obliqui
have been removed.
_n′_ Tendon of membrana nictitans.
_r_ M. retractor bulbi, lower part.
_r′_ Second part of same.
]
*7.* _M. retractor bulbi_ (Figs. 48 _r_, 50 _r_, _r′_).
*Dugès*, orbito-post-oculaire or choanide, n. 10.--*Zenker*, _m.
opticus_.
This muscle surrounds the optic nerve, and is situated within the
cone formed by the four recti muscles; it consists of three portions,
which take their broad and fleshy (the _recti_ and _obliqui_ arise
by thin tendons) origins from the under surface of the parasphenoid.
The first portion (Fig. 50 _r_) arises from the under surface of the
parasphenoid, nearly as far as the middle line, is broad and fleshy,
and covers, from below, the tendon of the _rectus externus_, then runs
forwards and outwards. The second portion (_r_′), which lies over
this and the tendon of the _m. rectus externus_, has also a broad and
fleshy origin, but runs more directly forwards, slightly crossing the
preceding. The third portion arises above the two others by a strong
thin tendon from the parasphenoid: it runs almost in the direction of
the _m. rectus internus_, but more directly forwards. The first two
portions pass more to the upper surface of the eyeball, the third more
to the under surface; consequently the whole muscle forms a sheath
surrounding the eyeball. The fibres to the upper surface of the eyeball
are inserted somewhat in front of the equator of the eyeball, those to
the under surface somewhat behind it.
*8.* _M. levator bulbi_, Dugès (Figs. 48 _l_, 51 _l_, 52 _l_).
*Dugès*, fronto-pterygoidien, n. 9.--*Klein*, _sustentator bulbi_.
[Illustration: Fig. 51.
Transverse section through the skull and orbital cavities of _Rana
esculenta_.
_b_ Bulb of eye.
_c_ Skull cavity.
_g_ Mucous membrane.
_l_ M. levator bulbi.
_m_ Upper jaw.
_n_ Membrana nictitans.
_n_′ Continuation of same to the lower eyelid.
_p_ Upper eyelid.
]
[Illustration: Fig. 52.
_M. levator bulbi_ of _Rana esculenta_, seen from above; the eyeball
which rests on it has been removed.
_d_._p_ M. depressor palpebrae inferioris.
_l_ M. levator bulbi.
_n_ Membrana nictitans.
_p_ M. pterygoideus.
_t_ M. temporalis.
]
There is no bony floor to the orbital cavity, and the oral and orbital
cavities are only separated by soft tissues; these are:--the mucous
membrane of the mouth, a thin fascia, and above this the muscle under
consideration. The fibres of this muscle run from before and from the
inner side obliquely backwards and outwards, below all the remaining
muscles of the eye, with the exception of the origin of the _m.
retractor bulbi_, and the tendons of the _m. obliquus inferior_, and
the _m. pterygoideus_; they arise on the inner side from the upper
and outer border of the fronto-parietal bone (Fig. 51), also from the
transverse portion of the parasphenoid and pterygoid bones, anteriorly
from the sphenethmoid and palatine bones; they run first downwards,
then, in the direction indicated, underneath the eye; and are inserted
externally by means of tendinous fibres into the superior border of the
upper jaw.
*9.* From the foregoing muscle certain fibres pass to the lower
eyelid, which may be regarded as a *depressor palpebrae inferioris*
(Fig. 52 _d.p_).
Manz[42] has described a muscle as _depressor palpebrae inferioris_
which arises in the neighbourhood of the external angle of the eye,
somewhat behind and below the lower border of the orbit, thence
passes obliquely upwards to be inserted into the lower eyelid. This
description is right as regards the insertion, but needs correction as
regards the origin. The muscle is attached to the orbital border in so
far that the tendinous expansion, into which the _levator bulbi_ passes
at its external border, is attached into the upper jaw; this bundle
splits off from the upper surface of the _levator bulbi_ at its middle,
and runs outwards on the under surface of the eyeball to the hinder
part of the lower eyelid.
[Footnote 42: Manz, Berichte der naturf. Gesellschaft zu Freiburg, 2
Band, 4 Heft, 1862, p. 391.]
[Illustration: Fig. 53.
Eye-muscles of _Rana esculenta_, from below, the m. recti and obliqui
have been removed.
_n_′ Tendon of membrana nictitans.
_r_ M. retractor bulbi, lower part.
_r_′ Second part of same.
]
*10.* Tendon of the _membrana nictitans_[43] (Fig. 53 _n_′).
The pigmented free border of the nictitating membrane passes, at the
inner and outer angles of the eye, into a tendon which passes for some
distance through fibrous tissue, then descends to the under surface
of the eyeball and joins that of the opposite side, so that the free
border of the eyelid, together with this tendon, form a complete ring.
The tendinous part of the ring, which is thin and thread-like, is found
on the under surface of the eyeball, and lies under the _m. retractor
bulbi_, and is bound to this muscle by connective tissue. Manz is
right in saying that the two muscles described by Dugès as _levatores
palpebrae inferiores_ (orbito-palpebral anterieur and posterieur, n. 5
and 6) do not exist; as is also the suggestion that he has confounded
the tendon of the nictitating membrane with these; this is clearly
shown in the figure in Plate VI of Dugès. With regard to the *actions*
of these eye-muscles, it is plain that the four straight and two
oblique muscles rotate the eyeball about three axes, one the axis of
the eye, one vertical, and the third passing from behind forwards and
inwards. The _m. retractor_ pulls the eyeball into the orbital cavity
backwards and downwards, while the _levator_ raises it.
[Footnote 43: Compare Manz, _l. c._]
There is less agreement about the movements of the eyelids, or rather
of the lower eyelid, for the upper has no independent movements.
Dugès (_l. c._) says that the two muscles, which he considers to be
_levatores palpebrae inferiores_, and which, according to him, are
connected with the _m. retractor bulbi_, draw up the lid as it is being
drawn backwards and downwards by the latter muscle. The depression
of the lid on the relaxation of the retractor and projection of the
eyeball is due simply to elasticity. Manz[44], on the contrary,
has shown that the sinking of the eyeball by the contraction of
the _retractor_ must necessarily cause a rising of the nictitating
membrane, as its tendons are attached to that muscle and so must follow
its movements.
[Footnote 44: _l. c._, p. 4.]
The depression of the lower lid occurs simultaneously with the raising
of the eyeball by means of the _m. levator bulbi_, through the
contraction of the _m. depressor palpebrae inferioris_, which proceeds
from that muscle; this is easily understood, as they are but parts of
the same muscle.
II. MUSCLES OF THE FACE.
*11.* _M. intermaxillaris s. dilatator narium_ (Fig. 54 _im_).
*Dugès*, intermaxillaire, n. 1.--*Zenker*, intermaxillaris medius.
This small muscle lies in the space between the vertical processes of
the two premaxillary bones, and consists of obliquely-crossing fibres
arising from the one bone and inserted into the opposite one. It brings
together the processes of the intermaxillary bones, so that their upper
extremities approach each other. At the same time, the cartilaginous
nasal coverings or wings (_an_) diverge and the nares expand; hence we
may regard this muscle as corresponding to a _dilatator narium_.
[Illustration: Fig. 54.
Facial muscles of _Rana esculenta_.
_an_ Cartilaginous nasal alae.
_i_′ Vertical process of premaxillary bone.
_im_ M. intermaxillaris.
_ln_ M. lateralis narium.
_n_ Cartilaginous nose capsule.
]
*12.* _M. lateralis narium_ (Ecker), (Fig. 54 _ln_).
*Zenker*, _m. intermaxillaris lateralis_.--*Klein*, _m. nasalis
inferior_.--*Dugès*, sus-maxillo-pré-nasal, n. 2.
This small muscle occupies the space between the anterior portion
of the maxillary bone and the ascending process of the premaxillary
bone. It arises from the maxillary, and ascends obliquely forwards
to be inserted into the outer border of the ascending process of the
premaxillary bone. It is antagonistic to the foregoing.
A third muscle is described by Dugès as _sus-maxillo-post-nasal_, n.
3 (_nasalis externus_, Klein); according to him it passes from the
_proc. nasalis_ of the maxillary bone to the outer border of the nasal
opening, which it widens. According to Klein (_l. c._, p. 9), this
muscle in _R. temporaria_ runs to the upper border of the maxillary
bone beneath the lower eyelid, and is long and narrow. I have, however,
never been able to find muscular fibre in this situation.
III. MUSCLES OF THE LOWER JAW.
[Illustration: Fig. 55.
Muscles of the back and shoulder.
_c_ M. cucullaris.
_dm_,_dm_ M. depressor maxillae, arising from the fascia dorsalis.
On the right side it is cut through and reflected.
_fd_ Fascia dorsalis.
_fd_′ Same cut near the spinous processes.
_i_ M. infraspinatus.
_l.a_ M. levator anguli scapulae.
_ld_ M. latissimus dorsi.
_r_ M. retrahens scapulae.
_sc_ M. sternocleidomastoideus.
]
*13.* _M. depressor maxillae inferioris_, Carus, Zenker (Figs. 55,
56, 63 _d.m_.).
*Cuvier*, _l. c._, II, 141, _digastricus_.--*Dugès*,
sus-occipitodorso-angulaire, 32.
This is a strong, triangular muscle, wide above, pointed below. It
is placed between the head and the shoulder-blade. It arises in two
portions; the greater, from the _fascia dorsalis_ (_fd_), covers the
scapula, and passes inwards and backwards over the muscles of the back;
anteriorly it passes over the _m. temporalis_ and is attached to the
fronto-parietal and squamosal, being continued to the fascia of the
upper eyelid. The second part is smaller, and arises by fleshy fibres
from the postero-superior arm of the squamosal, and from the posterior
and inferior border of the cartilaginous tympanic ring. The two parts
unite and are inserted into the hinder angle of the lower jaw. Cuvier
correctly considers that only the anterior portion corresponds to the
_digastricus_, the posterior answering to the _m. cervico-maxillaris_
of snakes. It draws the lower jaw down and opens the mouth.
*14.* _M. temporalis_ (Figs. 49, 52, 56, 57 _t_).
*Cuvier*, _m. temporalis_, I, _l. c._, p. 138.--*Dugès*,
sous-rupéo-temporo-coronoidien.
This muscle, together with the _M. pterygoideus_, occupies the space
between the prootic and the eyeball; it arises by the greater part of
its fibres from the upper surface of the prootic; it passes, narrowing,
beneath the anterior arm of the squamosal, then over the pterygoid
bone, between this and the maxillary and quadrato-jugal, receiving
on the way other fibres which arise from the anterior border of the
inferior arm of the squamosal and from the anterior circumference of
the tympanic ring. The collected fibres end in a broad, flat tendon,
which is inserted into the inner surface of the so-called _proc.
coronoideus_.
[Illustration: Fig. 56.
Muscles of the lower jaw of _Rana esculenta_.
_d_ M. deltoideus.
_dm_ M. depressor maxillae, its origin where covering
the m. temporalis reflected at *.
_ld_ M. latissimus dorsi.
_m_ M. masseter.
_t_ M. temporalis, origin.
_t_′ Lower portion of same.
]
*15.* _M. pterygoideus_ (Figs. 49 _p_, 52, 57 _pt_).
*Cuvier*, _m. temporalis_, II, _l. c._--*Zenker*,
_m. massetericus_, _l. c._, p. 25.--*Dugès*,
pré-rupéo-pterygo-maxillaire, 31.
This is partly covered by the foregoing, and lies between it and
the eyeball. It arises at the inner wall of the orbit from the
fronto-parietal, and from that portion of the prootic which may be
regarded as the _ala magna_, above the _m. retractor bulbi_. The muscle
is broad, and compressed from before backwards: it runs downwards
covered by the _m. temporalis_, and soon passes into a long, thin
tendon (Fig. 57 _pt_), which is inserted, behind the _m. temporalis_
and immediately in front of the joint, into the inner surface of the
lower jaw.
*16.* _M. masseter_ (Figs. 56, 57 _m_).
*Dugès*, zygomato-maxillaire, n. 29.
Arises as a somewhat broad muscle from the horizontal process of the
quadrato-jugal and is inserted into the outer side of the lower jaw,
opposite the insertion of the _m. temporalis_.
[Illustration: Fig. 57.
Muscles of the lower jaw of _Rana esculenta_.
_dm_ M. depressor maxillae cut through and reflected.
_la_ M. levator anguli scapulae.
_l.d._ M. latiss. dorsi, cut through and reflected.
_m_ M. masseter.
_pt_ M. pterygoideus.
_s_ Scapula.
_s_′ Suprascapula.
_s.c._ M. sternocleidomastoideus.
_t t_ M. temporalis cut through and reflected.
]
*17.* _M. submaxillaris_ (Figs. 58, 59, 61 _sm_, _sm_′).
*Cuvier*, _m. mylo-hyoideus_, _l.c._, II, 536.--*Zenker*,
_mylo-sternoideus_, p. 25.--*Dugès*, sous-maxillaire, n. 15.
This muscle forms the floor of the mouth as does the _mylo-hyoideus_ in
man; it is, however, not inserted into the hyoid bone.
It arises--1. From the whole of the inner surface of the upper border
of the lower jaw[45], except near the angle (Fig. 58 _sm_);
[Footnote 45: A second origin from the lower border of the mandible,
described by Klein, is not to be found. The appearance is due to the
exit of vessels and nerves from the groove between the mandible and the
muscle.]
2. By a small portion (Figs. 58, 59, 61 _sm_′) near the skull, from
the cartilaginous anterior cornu of the hyoid-bone which projects from
the cartilaginous part of the prootic bone. This portion descends
along the cornu to unite with the other portion. The two together form
a membranous layer, the fibres of which run transversely and meet in
a band of connective tissue along the middle line, forming a kind of
_linea alba_. The sheath runs forwards to the most projecting part of
the lower jaw superficially to the _m. submentalis_. Slightly in front
of its posterior border the muscle is attached in its whole breadth to
the skin of the throat by a fine lamella of connective tissue, which
is not always complete. The posterior border of the muscle is attached
to a fascia, which passes between the deeper muscles and is attached
to these. It is known that this muscle plays an important part in the
movements of respiration and swallowing; but its precise action has not
yet been worked out.
*18.* _M. submentalis_ (Fig. 59 _smt_).
*Cuvier*, _transversus_, _l. c._, p. 588.--*Dugès*, 4,
sous-mentonnier.--*Zenker*, _m. lingualis_ (incorrectly brought
into connection with _m. hyoglossus_).
This small muscle lies in the anterior angle of the lower jaw between
the dentary bones. It consists of transverse fibres which pass from one
bone to the other. Below it is covered by the most anterior portion of
the _m. submaxillaris_.
[Illustration: Fig. 58.
Muscles of the throat, chest, and abdomen of _Rana esculenta_.
_sm_ M. submaxillaris.
_sm_′ Hinder portion of same arising from
the anterior cornu of the hyoid bone.
(For other references see page 68.) ]
Its action is to approximate the sides of the lower jaw: according to
Dugès (_l. c._, p. 123), it assists in closing the nostrils, by drawing
together the sides of the lower jaw and thus raising the premaxillae.
IV. MUSCLES OF THE HYOID BONE AND THE TONGUE.
*19.* _M. geniohyoideus_ (Figs. 59 _gh_, 60 _gh_).
*Cuvier*, IV, 1, 536.--*Dugès*, n. 16.--*Zenker*, p. 30.--*M. St.
Ange*, _l. c._, Pl. XXVI, f. 1, 13, p. 423.
Arises from the lower jaw in two portions, the one from near the middle
line above the _m. submentalis_, the other more externally from the
upper border of the lower jaw. The two parts unite to form a long,
flat muscle, which lies on the ventral surface of the body of the
hyoid bone, and divides posteriorly into two portions. One of these,
the median (Figs. 59, 60 _gh_″), is inserted into the inner border of
the posterior horn of the hyoid bone, and is here attached to a fascia
which covers the _m. hyoglossus_ from beneath. By the same fascia the
muscles of opposite sides are connected in the space between the two
posterior cornua. The lateral division (Figs. 59, 60 _gh_′) is attached
to the posterior cartilaginous process of the hyoid bone.
[Illustration: Fig. 59.
Muscles of the hyoid bone and the tongue of _Rana esculenta_.
The m. submaxillaris has been removed close to its insertion.
_cm_′ Origin of the hinder portion of same from the hyoid bone.
_gh_ M. geniohyoideus.
_gh_′ External portion of same.
_gh_″ Internal portion of same.
_H_ Body of hyoid bone.
_H_′ Anterior horn.
_hg_ M. hyoglossus.
_oh_ M. omohyoideus.
_ph_ Mm. petrohyoidei.
_sh_ M. sternohyoideus.
_sh_′ External origin of same.
_sh_″ Internal origin of same.
_sm_ M. submaxillaris.
_sm_′ Origin of hinder portion of same.
_smt_ M. submentalis.
]
*20.* _M. sternohyoideus_ (Figs. 59 60 _sh_).
*Cuvier*, IV, 1, 538 (_pubio-hyoideus_).--*Dugès*, n. 17,
sterno-xipho-hyoidien.--*Zenker*, p. 30.
This muscle forms the cervical part of the _m. rectus abdominis_
and is, in fact, a direct continuation of it. It arises by an inner
portion (Fig. 59 _sh_″) from the upper surface of the inner extremity
of the coracoid and from the xiphisternum, while the outer portion
(_sh_′) is an immediate continuation of the _m. rectus abdominis_,
which passes into this muscle at about the fifth _inscriptio tendinea_.
The muscle passes forwards on the upper surface of the coracoid
and of the clavicle, under the pericardium towards the hyoid bone;
here the muscle, hitherto horizontal, suddenly becomes (compare
Fig. 60) vertical, and passes between the two insertions of the _m.
geniohyoideus_, and is inserted for a considerable length into the
lower surface of the hyoid bone and the anterior extremity of the
posterior cornu.
[Illustration: Fig. 60.
Muscles of the tongue and of the hyoid bone of _Rana esculenta_, from
below.
_gh_ M. geniohyoideus.
_gh_′ External origin }
_gh_″ Internal origin } of same.
_H_ Body of hyoid.
_H_′ Anterior cornu.
_H_″ Posterior cornu.
_hg_ M. hyoglossus.
_hg_′ Hinder origin of same.
_oh_ M. omohyoideus.
_ph_. 1, 2, 3, 4, first, second, third, and fourth
m. petrohyoideus.
_sh_ M. sternohyoideus.
]
*21.* _M. omohyoideus_ (Figs. 59, 60 _oh_).
*Cuvier*, _l.c._, p. 539.--*Dugès*, n. 18, interscapulo-hyoidien ou
omohyoidien.-- *Zenker*, p. 31.--*M. St. Ange*, _l.c._
Arises from the anterior border of the bony scapula, and is inserted
into the outer part of the ventral surface of the body of the hyoid: it
is partially covered by the _m. sternohyoideus_.
*22.* _M. petrohyoideus anterior_ (Ecker), (Fig. 61 _ph_1).
*Dugès*, 10, rupéo-cérato-hyoidien.--*Zenker*, _m. petro-ceraus_?
p. 30.-- *Klein*, _basio-hyoideus_, _l.c._, p. 71.
A thin, flat muscle, narrow above, but broadening rapidly below,
which arising from the outer extremity of the prootic bone, partially
surrounds the pharynx below, into which some of its fibres are
inserted; it is attached to the ventral surface of the body of the
hyoid bone, near the lateral notch. The chief action of this muscle
appears to be that of a _m. constrictor pharyngis_.
*23, 24, 25.* _Mm. petrohyoidei posteriores_ (Ecker), (Figs. 61
_ph_ 2, 3, 4).
*Cuvier*, _mm. stylohyoidei_, _l. c._, p. 537.--*Dugès*, 20, 21,
22, masto-hyoideus (Fig. 4).--*Zenker*, _petro-hyoideus superior_
and _inferior_.--*Klein*, _stylo-hyoideus_, _l. c._, p. 18.
These are three long, thin muscles, which lie nearly parallel
to one another, and run from the prootic bone to the posterior
cornu of the hyoid bone. All three arise, covered by the _m.
sternocleidomastoideus_, from the lateral extremity of the prootic,
pass round the pharynx and are attached, the _m. petrohyoideus
posterior primus_ (Fig. 61 _ph_ 2) to the anterior extremity, the
_secundus_ (Fig. 61 _ph_ 3) to the middle; and the _tertius_ (Fig. 61
_ph_ 4) to the hinder extremity of the posterior horn of the hyoid bone.
*26.* _M. hyoglossus_ (Figs. 59, 60, 61 _hg_).
*Cuvier*, _l. c._, p. 588.--*Dugès*, 24, hyo-glosse.
Arises from the bony posterior extremity of the hinder process of the
hyoid bone (_hg_′). The muscles of the two sides pass forwards and
converge to the middle line, where they unite. The azygos muscle thus
formed runs forwards on the ventral surface of the hyoid bone, between
the _mm. geniohyoidei_, over the anterior border of the hyoid, and
passes into the tongue, where it turns backwards and runs to the tip.
(For action, see tongue.)
[Illustration: Fig. 61.
Muscles of the hyoid bone of _Rana esculenta_, seen from the right side
and below.
_H_′ Anterior cornu.
_H_″ Posterior cornu.
_hg_ M. hyoglossus.
_H H_ Body of hyoid bone.
_ph_ 1 M. petrohyoideus anterior.
_ph_ 2, 3, 4 Mm. petrohyoidei posteriores.
_sm_ M. submaxillaris.
_sm_′ Hinder portion of same.
]
*27.* _M. genioglossus._
*Cuvier*, _l. c._, p. 587.--*Meckel*, _l. c._, IV, 339.--*Dugès*,
23, genio-glosse.
Arises above the insertion of the _m. geniohyoideus_ on either side
near the middle line from the two anterior bones of the lower jaw. The
two origins quickly unite to form a thick, very firm muscular belly,
which in its course backwards rapidly thins, and is distributed by
numerous bundles; decussating with the fibres of the _m. hyoglossus_ at
an acute angle, it runs on to the anterior extremity of the tongue.
II. MUSCLES OF THE TRUNK.
I. MUSCLES OF THE ABDOMEN.
In the formation of the abdominal wall the following muscles take
part:--(1) _m. rectus abdominis_, (2) _m. obliquus externus_, (3)
_m. obliquus internus_, (4) the _portia abdominalis_ of the _m.
pectoralis_. Above, the _m. obliquus internus_ forms a kind of
*diaphragm*, partially separating the abdominal from the thoracic
cavity (p. 70).
*28.* _M. rectus abdominis_ (Fig. 62 _r_).
*Dugès*, pubio-thoracique, n. 52.
These muscles, situated on either side of the middle line of the
abdomen, are as a rule traversed by five notched _inscriptiones
tendineae_. Each muscle arises, by a narrow, strong tendon, from the
inferior border of the pubes, passes forwards, and quickly widening,
divides at the second _inscriptio tendinea_ (counting from behind) into
two portions.
(_a_) The Outer portion (Fig. 62 _r_) runs into the _portio
abdominalis_ of the _m. pectoralis_, and forms the greater lateral
division of that muscle.
(_b_) The Inner (_r_′) continues as the _m. rectus abdominis_ and
gradually narrows anteriorly. At the sternum some of the fibres (the
median) are inserted into the dorsal surface of the cartilaginous plate
of the xiphisternum, while the greater part of the muscle continues
forwards over the coracoid to become the _m. sternohyoideus_ at about
the fifth _inscriptio tendinea_ (p. 64).
*29.* _M. obliquus externus_ (Fig. 63 _oe_, _oe_′).
*Zenker*, _l. c._, p. 31, _m. obliquus_.--*Dugès*,
dorso-sous-abdominal, n. 54.
The _m. obliquus externus_ arises from--
(_a_) The aponeurosis covering the long muscles of the back, and by
this from the spinous processes. The anterior edge of the _m. obliquus
externus_ covers the posterior edge of the _m. latissimus dorsi_,
which arises from the inferior, ventral surface of the aponeurosis.
The aponeurosis also divides laterally into two parts, one of which,
the posterior, passes into the _obliquus externus_, while the anterior
forms the tendon of origin of the _depressor maxillae inf._ (_dm_)
(compare Fig. 66).
(_b_) A second, narrow portion, _portio omo-abdominalis_ (Fig. 63
_oe_′) (_m. xipho-adscapulaire_, Dugès, n. 62), arises from the
posterior border of the scapula by a thin tendon, and becomes broader
as it runs downwards and backwards, to join the anterior border of the
other and larger portion.
[Illustration: Fig. 62.
Muscles of the chest, throat, and belly of _Rana esculenta_.
_ch_ M. coraco-humeralis.
_d_ M. deltoideus.
_oi_ M. obliquus abdom. internus.
_oe_ M. obliq. abdom. externus.
_oe_′ Scapular portion of same.
_oh_ M. omohyoideus.
_p_′ Port. sternalis anterior of m. pectoralis.
_p_″ Port. sternalis posterior of same.
_p_‴ Port. abdominalis of same.
_r_ M. rectus abdominis.
_r_′ Inner portion of same.
_sh_ M. sternohyoideus.
_sm_ M. submaxillaris.
_sm_′ Hyoid origin of same.
_sr_ M. sternoradialis.
]
The whole muscle is attached by its most anterior fibres to the
cartilage of the xiphisternum, the rest passing into an aponeurosis
which, inseparably connected with the _inscriptiones tendineae_,
traverses the lower surface of the _m. rectus abdominalis_ to the
_linea alba_.
[Illustration: Fig. 63.
Muscles of trunk of _Rana esculenta_, from the right side.
_cd_ M. cutaneus femoris.
_d_ M. deltoideus.
_d.m._ M. depressor maxillae.
_i_ M. infraspinatus.
_ld_ M. latiss. dorsi.
_oe_ M. obliquus abdom. externus.
_oe_′ Scapular origin of same.
_ss_ M. subscapularis.
_t_ M. triceps brachii.
]
*30.* _M. obliquus internus_ (and _transversus_), (Figs. 64, 65
_oi_).
*Dugès*, ileo-transverso-sous-sternal, p. 53.--*Zenker*,
_transversus_, _l. c._, p. 31.--*Kuhl*, _transversus_, _l. c._,
p. 116.
This muscle corresponds with the combined _obliquus internus_ and
_transversus_, and has therefore been described either as the one or
the other, by various authors.
The fibres arise tendinously--
*a.* From the transverse processes of the vertebrae from the fourth
backwards, and from the fascia covering the _mm. intertransversarii_.
*b.* From the iliac bone, by a strong tendon from its upper border, and
by a few weaker fibres from its outer surface. The latter fibres are
covered by the former, and these end posteriorly in a sharp concave
border.
The muscular bundles diverge from these points, some running forwards,
some backwards; the former are only partially covered by the _portio
omo-abdominalis_ of the _m. obliquus externus_ (compare Figs. 62, 63),
in front of the anterior edge of that muscle. The posterior border of
the muscle is uncovered.
[Illustration: Fig. 64.
Second layer of abdominal muscles of _Rana esculenta_, from the right
side and below. The m. obliquus externus and the right anterior
extremity has been removed.
_dm_ M. depressor maxillae.
_hg_ M. hyoglossus.
_ld_ M. latissimus dorsi and infraspinatus.
_oi_ M. obliquus internus.
_oi_′ Insertion of third portion of same.
_oi_″ Second portion inserted into the pharynx.
_pc_ Pericardium.
_ph^4._ M. petrohyoideus quartus.
_r_ M. rectus abdominis.
_ss_ M. subscapularis.
]
The insertions of the muscle are very various, and as a consequence
very various functions are accomplished by it.
*a.* The most anterior part of the muscle (Fig. 65 _oi_‴), the fibres
of which run forwards, is attached--
1. Partly to the xiphisternum and the coracoid.
2. A second portion, _viz._ that arising from the transverse processes
of the fourth vertebra (Fig. 64 _oi_″), surrounds the pharynx like a
diaphragm (Fig. 65 _oe_), and is attached to its side as far as the
dorsal aspect (Fig. 65 _oi_′). This portion is lightly separated from
the following.
3. A third portion, placed behind the preceding, runs from the pharynx
over the pericardium (Fig. 64 _pc_), and is attached to this nearly
as far as the middle line (Figs. 64 _oi_′ and 65 _oi_″), resting on
the sternum, the _m. rectus_ and _m. sterno-hyoideus_. The lines of
insertion of the muscles of opposite sides form an angle, open in
front. In the thin borders of this portion the muscular bundles lie
almost entirely in simple layers, and they are therefore well adapted
for microscopical purposes.
*b.* The middle and posterior portions of the muscle pass downwards
and slightly backwards, towards the outer border of the _m. rectus_;
there they pass into a tendon which, for the most part, runs on the
upper surface of the _rectus_ to the _linea alba_.
II. MUSCLES OF THE BACK.
The muscles of the back are covered by a fascia, the *fascia dorsalis*
(Fig. 66 _fd_), attached to the spinous processes of the vertebrae.
Anteriorly, where it covers the _m. temporalis_, it is attached to the
fronto-parietal and squamosal bones, posteriorly to the superior border
of the iliac bones and the extremity of the urostyle. The posterior
part, which covers the origins of the _m. longissimus dorsi_, of the
_m. coccygeo-iliacus_, and of the _coccygeo-lumbaris_, is especially
strong. From the anterior part several muscles arise laterally, viz.
a portion of the _m. obliquus abdominalis externus_, of the _m.
latissimus dorsi_, and of the _m. depressor maxillae inferioris_. In
the uppermost layer, immediately covered by the _fascia dorsalis_, lie
the _m. cucullaris_, the _m. retrahens scapulae_, the _m. latissimus
dorsi_ arising from the fascia itself, and the scapula with its
muscles; then come the long muscles of the back; and in the third and
deepest layer the short muscles of the back.
[Illustration: Fig. 65.
M. obliquus internus, showing its attachments superiorly.
_h_ Xiphisternum.
_oe_ Oesophagus.
_oi_ M. obliquus internus.
_oi_′ Fibres of m. obliq. int., which are inserted
into the oesophagus.
_oi_″ _oi_‴ Fibres of same, which are attached to
coracoid and xiphisternum.
_p_ Pericardium.
_r_ M. rectus abdominis.
]
The individual muscles are as follows:--
A. _LIMB MUSCLES OF THE BACK_ (for moving the shoulder-girdle and arm).
*31.* _M. cucullaris_ (Fig. 66 _c_).
*Cuvier*, _angularis_.--*Dugès*, n. 38, sous-occipito
adscapulaire.--*Zenker*, _levator scapulae sublimis_.
In order to see this muscle, it is necessary to separate the _fascia
dorsalis_ from the spines of the vertebrae and to turn it back with
the _m. depressor maxillae inf._ arising from it. It is then seen to
rise from the posterior surface of the exoccipital as far as the middle
line; the muscles of the two sides run backwards, diverging each from
the other, so as to form an angle, and are then attached on each side
to the anterior superior angle of the suprascapula at its under surface
and median border.
Cuvier considers this muscle as the analogue of the _m. levator anguli
scapulae_. Dugès and Meckel consider it to be the anterior part of the
_m. cucullaris_, the former thinking the posterior part of the muscle
to be the _m. rhomboideus_. I cannot agree with these opinions, and I
regard the muscle as simply representing the _m. cucullaris_ of man
(Ecker).
*32.* _M. latissimus dorsi_ (Figs. 56, 66 _ld_).
*Dugès*, n. 66, lombo-huméral.--*Zenker*, _depressor brachii_.
This thin, triangular muscle arises from the ventral surface of the
_fascia dorsalis_, and is posteriorly covered in part by the anterior
border of the _m. obliquus abdominis externus_. The muscle becomes
narrower towards the sides, and passes into a flat tendon, which
blends with that of the _m. infraspinatus_, and is attached to the
outer surface of the _crista deltoidea_ of the humerus by a triangular
expansion.
*33.* _M. retrahens scapulae_ (Ecker), (Fig. 66 _r_).
*Dugès*, n. 59, lombo-adscapulaire.--*Klein*, _m. rhomboideus_, _l.
c._, p. 26.--*Zenker*, _omoplateus rectus_? p. 37, _l. c._--*Kuhl*,
_l. c._, 124, _retrahens rhomboideus_.
[Illustration: Fig. 66.
Muscles of the back and shoulder-blade.
_c_ M. cucullaris.
_dm_ M. depressor maxillae arising from the fascia dorsalis,
cut through and reflected on the right side.
_fd_ Fascia dorsalis.
_fd_′ Same cut through at the spines.
_i_ M. infraspinatus.
_l.a_ M. levator anguli scapulae.
_ld_ M. Latissimus dorsi.
_r_ M. retrahens scapulae.
_sc_ M. sternocleidomastoideus.
]
This flat, oblong muscle arises from the transverse process of
the fourth vertebra, and is connected with the third tendinous
inscription (counting from before) of the _m. longiss. dorsi_.
Posteriorly its origin forms a convex border, whence it runs forwards
and to the side; it is inserted into the ventral surface of the
suprascapula, near its inner border. This muscle lies near the _m.
serratus_ or _transv. scap. tertius_ (Fig. 68 _ts_″), and has an
analogous position. It would, therefore, possibly be more correct
to regard it also as a _m. serratus_. It arises from parts which
represent ribs, and is inserted into the scapula. It has, at any
rate, no analogy to the _m. cucullaris_, with which Dugès connects
it, nor with the _m. rhomboideus_, which Klein holds it to be, as it
does not arise from spinous processes.
B. _LONG MUSCLES OF THE BACK._
*34.* _M. extensor dorsi communis_ (Fig. 67 _lg.d._).
*Dugès*, n. 33–40, masse des muscles surspinaux devisée en
huit faisceaux principaux: 1. vertebro-sus-occipital, 2–5.
transverso-spinaux, 6. transverso-coccyg., 7. sacro-coccygien,
8. ileo-coccygien. The muscles 1–7 form the lombo-costal, 8 the
ischicoccyg., Cuv.--*Zenker*, _m. sacrolumbaris_.--*Klein*,
_longiss. dorsi_, _coccygeo-lumb._, _coccyg.-iliac_.
This muscular mass is covered by the _fascia dorsalis_, the _m.
cucullaris_ and _retrahens scapula_, and the suprascapula: it
corresponds with (1) the _m. ileo-costalis_ and _longissimus dorsi_,
_dorsi_ and _cervicis_ (Henle); (2) the _semispinalis_ and _spinalis_
(Henle).
The following separate portions may be made out:--
*35.* (1) _M. longiss. dorsi_ (Fig. 67 _lg.d._).
This muscle arises from the most anterior part of the urostyle, runs
forwards near the middle line, separated from the muscle of the
opposite side by the spinous processes of the vertebrae. The inner
portion passes over the posterior spinous processes without being
connected with them, as far as the fifth, it is then inserted into
the succeeding spines as far as the exoccipital bone. The lateral
portion runs outwards and forwards to be attached to the transverse
processes and oblique processes of all the vertebrae, from the sixth
forwards, while accessory muscular slips arise from the transverse
processes and from the anterior spinous processes which, merging in
the general muscle-mass, are inserted with this into the occiput.
The muscle is subdivided by a series of wavy, tendinous partitions
(Fig. 67), which arise from the transverse processes, and traverse
the muscle in planes, the upper surfaces of which are directed
upwards and forwards. This arrangement of the muscle indicates
its relation with the lateral trunk muscles of fish and fish-like
amphibians.
*36.* (2) _M. coccygeo-sacralis_ (Fig. 67 _c.l._).
This muscle is partially covered by the preceding, it arises
from the lateral surfaces of the anterior half of the urostyle;
from this origin the fibres pass forwards and outwards to be
inserted in two portions, the anterior set into the arch and the
posterior set into the transverse process of the last vertebra. The
former may be regarded as _m. intercruralis_, the latter as _m.
intertransversarius_.
*37.* (3) _M. coccygeo-iliacus_ (Fig. 67 _c.i._).
This muscle arises from nearly the whole length of the lateral
surface of the urostyle, the anterior portion being concealed by
the preceding muscle. The fibres pass outwards and forwards to be
inserted into the anterior two-thirds of the inner surface of the
ilium.
[Illustration: Fig. 67.
Muscles of the back and pelvic girdle of _Rana esculenta_.
_c.i._ M. coccygeo-iliacus.
_c.l._ M. coccygeo-sacralis.
_g.l._ M. glutaeus.
_i_ MM. intertransversarii.
_i′_ MM. intercrurales.
_i.c.i._ M. intertransv. capitis inferior.
_i.c.s._ M. intertr. cap. sup.
_il._ M. ilio-lumbaris.
_lg.d._ M. longissimus dorsi.
_o.i._ M. obliq. internus.
_t_ M. temporalis.
]
*38.* _M. ilio-lumbaris_ (Klein), (Fig. 67 _il._).
*Dugès, n.* 51, transverso-iliaque.--*Cuvier*, *Zenker*, etc.,
_quadr. lumborum_.
Evidently represents the _quadratus lumborum_ of human anatomy;
it takes its origin from the anterior extremity of the ilium, and
runs forwards to be inserted into the transverse processes of the
vertebrae from the seventh to the fourth.
C. _SHORT MUSCLES OF THE BACK._
*39.* _M. intertransversarius capitis superior_ (Ecker), (Fig. 67
_i.c.s._).
*Dugès*, n. 41, ex-occipito-transversaire sup.
A small muscle arising from the prootic: it lies above the _levator
anguli scapulae_, and is inserted into the transverse process of the
second vertebra.
*40.* _M. intertransversarius capitis inferior_ (Fig. 67 _i.c.i._).
*Dugès*, n. 42, ex-occipito-transv. inf.
This muscle lies on the ventral surface of the preceding one, but is
easily separable from it; it arises from the angle of the prootic and
is inserted, together with the preceding muscle, into the transverse
process of the third vertebra. The _n. vagus_ passes outwards between
these two muscles.
*41.* _MM. intertransversarii dorsi_ (Fig. 67 _i_).
*Dugès*, n. 43 to 50, intertransversaires.
Seven small muscles, placed between adjacent transverse processes of
the vertebrae; from the second to the last, in continuity with the
muscles last mentioned.
*42.* _MM. intercrurales_ (Ecker), (Fig. 67 _i_′).
*Klein*, p. 29, interspinales, interobliqui.
Those muscular fibres found between the arches of adjacent vertebrae
are so named. On account of the shortness of the spinous processes
they can scarcely be named _m. interspinales_.
III. MUSCLES OF THE ANTERIOR EXTREMITY.
I. MUSCLES OF THE SHOULDER-GIRDLE.
A. _DORSAL MUSCLES OF THE SHOULDER-BLADE_.
(I.) Muscles arising from the head or trunk, and inserted into
the scapulae, which they act upon primarily, and upon the
shoulder-girdles secondarily.
Some of these muscles, such as _m. cucullaris_ and _retrahens_,
are situated on the back, and have already been described with
the muscles of that region. Others are attached partly to the
under-surfaces of the scapulae and are only visible from below; they
are best seen in such a preparation as is shown in Fig. 68, made by
cutting through the sternum in the middle line, and reflecting each
half outwards.
(*a*) _Muscles which arise from the skull_.
*43.* _M. levator anguli scapulae_ (Fig. 68 _la_).
*Dugès*, sous-occipito-adscapulaire, n. 60.--*Zenker*, _protractor
scapulae_, Pl. I, Fig. 5.--*Cuvier*, Leçons I, p. 379, describes
this muscle as part of the _m. serratus anticus magnus_.
A fairly strong muscle, which has a broad origin from the prootic
and exoccipital bones as far as the _foramen magnum_, a few fibres
are also attached to the lateral portions of the parasphenoid. The
fibres run backwards and outwards, first in a frontal plane and then
in a sagittal plane, to be inserted into the under surface of the
suprascapula near the posterior border, where it encloses the hinder
border of the _m. interscapularis_.
Its action is to draw the shoulders forwards and inwards, or the head
downwards.
*44.* _M. sternocleidomastoideus_ (Fig. 68 _sc_).
*Dugès*, scapulo-mastoidien, n. 65.--*Cuvier*,
sterno-mastoidien.--*Zenker*, _protractor scapulae_, Pl. I, Fig. 5,
1.
A narrow muscle placed in front of and externally to the preceding
muscle; its general direction resembles that of the _m. levator ang.
scap_.
The fibres arise from the most external part of the prootic and
from the hindermost part of the squamosal, under cover of the
_m. digastricus maxillae_, and from the hinder portion of the
cartilaginous tympanic ring. Covered by these muscles, it passes
backwards and downwards to be inserted into the concavity of the
anterior border of the scapula; externally to the origin of the
deltoid.
The action of this muscle is to draw the shoulder forwards and
towards the middle line, or to bend the head downwards.
*45.* _M. protrahens scapulae_ (Fig. 68 _ps_).
*Dugès*, *Zenker*, _protractor acromii_, Pl. I, Fig. 5, 3.
This muscle lies to the outer side of the _rectus capitis inferior_:
it arises from the prootic, and runs backwards and outwards upon the
_levator anguli scapulae_, to be inserted into the scapula.
It pulls the scapula forwards.
(*b*) _Muscles which arise from the vertebrae._
*46.* _M. transverso-scapularis major_ (Ecker), (Fig. 68 _ts_).
*Dugès*, transverso-interscapulaire, n. 63.--*Cuvier*,
_l. c._, p. 380, probably regarded as a portion of the
_serratus_.--*Zenker*, Pl. I, Fig. 5, 3; _depressor acromii_,
Pl. II, Fig. 3, 15.--*Klein*, _depressor scapulae_.
This muscle arises by tendon from the cartilage of the transverse
process of the fourth vertebra and by a slip from the cartilage of
the transverse process of the third vertebra. Diminishing in size,
the muscle passes outwards, forwards, and upwards to be inserted
into the posterior border of the scapula, opposite the insertion
of the _m. sternocleidomastoideus_. It draws the shoulder inwards,
backwards, and downwards.
*47.* _M. transverso-scapularis minor_ (Ecker), (Fig. 68 _ts_′).
*Dugès*, transverso-adscapulaire, n. 61.--*Cuvier*, regarded as
part of the _serratus_.--*Zenker*, Pl. I, Fig. 5, 7, _detractor
scapulae_.
This is much shorter than the muscle just described; it arises under
cover of the _m. levator scapulae_, from the transverse process of
the third vertebra in front of the _transverso-scapularis major_; and
runs outwards and forwards to be inserted into the ventral surface of
the cartilage of the scapula. The action of the muscle is to draw the
shoulder inwards, backwards, and outwards. Dugès regards this muscle
as a portion of the _serratus anticus magnus_, the remainder of which
he considers is to be found in the _portio scapularis_ of the _m.
obliquus externus_ (xipho-adscapulaire, Dugès, n. 62).
[Illustration: Fig. 68.
Muscles of the shoulder, from below; the sternum has been cut through
and the sides drawn apart.
_d_ Deltoideus.
_is_ Interscapularis.
_it_ Intertransversarii.
_la_ Lev. anguli scapulae.
_ps_ Protrahens scapulae.
_sc_ Sternocleidomastoideus.
_ss_ Subscapularis.
_ts_ Transverso-scap. major.
_ts_′ Transverso-scap. minor.
_ts_″ Transverso-scap. tertius.
]
*48.* _M. transverso-scapularis tertius s. serratus_ (Ecker),
(Fig. 68 _ts_″).
This is larger than the muscle just described; arising by a broad
and flat origin from the transverse processes of third and fourth
vertebrae, it runs upwards and inwards to be inserted into the
ventral surface of the cartilaginous scapula near its inner border.
In position, course, and action the muscle most nearly represents the
_m. serratus anticus_ of human anatomy.
(II.) Muscles on the scapula, that is, arising from the scapula and
inserted into the scapula or humerus.
(*a*) _Muscles on the deeper surface._
*49.* _M. interscapularis_ (Fig. 69 _i.s._).
*Dugès*, interscapulaire, n. 64.
[Illustration: Fig. 69.
Muscles of right shoulder and upper arm. The coracoids (_co_) and
the clavicles (_cl_) have been drawn apart after cutting through the
sternum.
_c.h._ M. coraco-humeralis.
_cl_ Clavicle.
_c.o._ Coracoid.
_d_ M. deltoideus.
_d_′ Clavicular portion of m. deltoideus.
_i_ M. infraspinatus.
_i.s._ M. interscapularis.
_l.a._ M. levator anguli scapulae.
_l.d._ M. latissimus dorsi.
_p_′ Sternal portion of m. deltoideus.
_p_″ Anterior sternal portion of the m. pectoralis.
_p_‴ Posterior sternal portion of the m. pectoralis.
_s_ Scapula.
_s.r._ M. sternoradialis.
_t.r._ M. triceps brachii.
]
One end of this muscle is tendinous, and is attached to the outer
extremity of the suprascapula; from this the muscle, becoming fleshy
and narrower, runs towards the middle line to become attached to
the ridge on the ventral surface of the scapula, from which the _m.
deltoideus_ and the _m. subscapularis_ arise, and between which it
passes. It approximates the scapula and suprascapula and lessens the
angle between them.
*50.* _M. subscapularis_ (Fig. 70 _ss_).
*Dugès*, sous-scapulo huméral, n. 72.
This muscle is situated on the upper or visceral surface of the
scapula. It arises from a bony ridge found on the upper surface of
the coracoid and of the _proc. coracoideus_ of the scapula. The
muscle runs outwards and is inserted, after widening, into the inner
surface of the _crista deltoidea_ of the humerus; it is antagonistic
to the deltoid, and draws the raised arm backwards and towards the
trunk.
[Illustration: Fig. 70.
Right shoulder, from below, arm strongly abducted.
_cl_ Clavicle.
_co_ Coracoid.
_d_ Deltoideus.
_d_′ Clavicular portion of deltoid.
_h_ Humerus.
_ss_ Subscapular muscle.
]
(*b*) _Muscles on the superficial surface._
*51.* _M. infraspinatus_ (Fig. 57, between _ld_ and _dm_, Fig. 71
_i_).
*Dugès*, adscapulo-huméral, n. 67.
The _m. infraspinatus_ represents the _m. infraspinatus_, _teres
major_ and _minor_ of human anatomy. It is of triangular form, with
the broad base directed inwards; it arises from the whole of the
upper surface of the suprascapula except along the inner border which
is formed of hyaline cartilage alone: from this origin the fibres
converge outwards to a flat tendon which unites with that of the _m.
latissimus dorsi_ to be inserted into the _crista deltoidea humeri_,
by means of a thin, triangular, tendinous expansion.
[Illustration: Fig. 71.
Muscles of the back and shoulder.
_c_ M. cucullaris.
_dm_ M. depressor maxillae.
_fd_ Fascia dorsalis.
_fd_′ Fascia dorsalis reflected.
_i_ M. infraspinatus.
_l.a_ M. levator anguli scapulae.
_ld_ M. latissimus dorsi.
_r_ M. retrahens scapulae.
_sc_ M. sternocleidomastoideus.
]
*General arrangement of the muscles of the shoulder-blade.*
The muscles attached to the scapula and suprascapula are:
1. Muscles of the back (_m. cucullaris_ and _m. retrahens scap._).
2. Muscles of the neck (_m. omohyoideus_).
3. Muscles of the abdomen (_portio scapularis_ of the _m. obliquus
externus_).
4. True shoulder muscles (_m. levator anguli scapulae_; _m.
sternocleidomastoideus_; _m. protrahens scapulae_; _mm.
transverso-scapularis major_, _minor_, and _tertius s. serratus_; _m.
interscapularis_; _m. subscapularis_; and the long head of the _m.
triceps_).
*From above* the following are visible: _m. cucullaris_, a portion of
the _m. subscapularis_, and the _transverso-scapularis maior_.
*From below* (after cutting through and drawing aside the
two halves of the sternum) may be seen: the _omohyoideus_,
_sternocleidomastoideus_, _levator anguli scapulae_, _protrahens
scapulae_, _transverso-scapularis minor_ and _tertius_,
_interscapularis_ and _subscapularis_.
B. _VENTRAL MUSCLES OF THE SHOULDER (PECTORAL MUSCLES)_
These arise from the sternum or shoulder-girdle and are inserted
either into the humerus or into the radio-ulnar.
*52.* _M. pectoralis_ (Fig. 72).
This is placed on the ventral surface of the shoulder-girdle and
consists of the following parts:
(α) _Portio sternalis anterior_ (Ecker), (Figs. 72, 73 _p_′).
*Dugès*, clavi-huméral, n. 70 (port. clavic. du grand pectoral).
This is the anterior portion of the _m. pectoralis_, it arises from
the sternum proper and the epicoracoids. Broad at the origin, it
becomes narrower as it runs outwards into a tendon attached to the
_crista deltoidea humeri_.
(β) _Portio sternalis posterior_ (Ecker), (Figs. 72, 73 _p_″).
*Dugès*, sterno-huméral, n. 71 (port. sternal du grand
pectoral).--*Klein*, _humero-sternalis_.
This muscle is placed immediately behind the _portio sternalis
anterior_, it has a somewhat broad origin from the sternum and
xiphisternum; the muscle runs outwards and slightly forwards to be
inserted into the groove beside the _crista deltoidea humeri_. The
tendon of the _m. sterno-radialis_ passes between these two portions
of the _m. pectoralis_.
(γ) _Portio abdominalis_ (Figs. 72, 73 _p_‴).
*Dugès*, abdomino-huméral, n. 69 (port. costal du grand
pectoral).--*Zenker*, _brachio-abdominalis_.--*Klein*,
_humero-abdominalis_.
[Illustration: Fig. 72.
Muscles of the chest, throat, and belly of _Rana esculenta_.
_ch_ M. coraco-humeralis.
_d_ M. deltoideus.
_oi_ M. obliquus abdom. internus.
_oe_ M. obliq. abdom. externus.
_oe_′ Scapular portion of same.
_oh_ M. omohyoideus.
_p_′ Port. sternalis anterior to m. pectoralis.
_p_″ Port. sternalis posterior to same.
_p_‴ Port. abdominalis of same.
_r_ M. rectus abdominis.
_r_′ Inner portion of same.
_sh_ M. sternohyoideus.
_sm_ M. submaxillaris.
_sm_′ Hyoid origin of same.
_sr_ M. sternoradialis.
]
This portion represents that part of _m. pectoralis major_ of
human anatomy which arises from the costal cartilages, and more
particularly that part which is connected with the aponeurosis of
the _m. obliquus abdominis externus_. The muscle arises (1) from
the _m. rectus abdominis_ (Fig. 72 _r_), that is, it forms a direct
continuation of the outer portion of this muscle; (2) the inner,
smaller part arises from the superficial surface of the aponeurosis
of the _m. obliquus abdominis_. The muscle becomes narrower as it
courses outwards and forwards, the outer fibres being longer and more
oblique than the inner. The action of this muscle will necessarily
vary according to the part or parts which are brought into action;
speaking generally, the anterior extremities will be drawn downwards
and towards each other.
*53.* _M. coraco-humeralis_ (Dugès), (Figs. 72, 73 _c.h._).
*Dugès*, n. 72.--*Klein*, _adductor humeri_.
A long, narrow muscle, lying upon the posterior border of the
coracoid and the lowest part of the _m. subscapularis_. By its
position it corresponds most nearly with the _m. pectoralis minor_,
although its insertion does not. It has a narrow origin from the
coracoid near the sternum, whence it courses outwards, under cover
of the _port. sternalis anterior_ and _posterior_ of the _m.
pectoralis_, to be inserted into the middle of the humerus between
the deltoid and internal head of the triceps. It draws the limb
towards the trunk.
*54.* _M. sternoradialis_ (Cuvier), (Figs. 72, 73 _s.r._).
*Dugès*, pré-sterno-clavi-radial, n. 74.
This muscle evidently represents the biceps of man, it lies in front
of the _portio sternalis anterior_ of the _m. pectoralis_, its hinder
border being under cover of the latter muscle. It takes origin from
the episternum, omosternum, and the epicoracoid; from this broad
origin the fibres converge while coursing backwards and outwards
to be attached to a strong tendon. This tendon plays in a groove
along the _crista deltoidea_, and is held in position by tendinous
bands arising from the insertion of the _m. pectoralis_; it then
pierces the lower portion of the muscular belly of the deltoid, and
is inserted into the anterior extremity of the radial side of the
radio-ulnar. The muscle is a powerful flexor of the forearm.
*55.* _M. deltoideus_ (Figs. 70, 72, 73 _d_).
*Dugès*, pré-sterno-scapulo-huméral, n. 68.
It is placed in front of and external to the _m. sternoradialis_, and
represents both the _m. deltoideus_ and _supraspinatus_ of man. The
muscle has two points of origin:--
(*a*) _Portio scapularis_, the larger, external portion is attached
to the outer end of the clavicle, and to the anterior process of the
precoracoid, but it arises chiefly from the dorsal surface of the
scapula (from the same ridge as the _m. subscapularis_), and lastly
from the anterior border and ventral surface of the scapula. The
fibres pass outwards over the shoulder-joint.
[Illustration: Fig. 73.
Muscle of right shoulder and upper arm. The coracoids (_c.o._) and
the clavicles (_cl_) have been drawn asunder after cutting through
the sternum.
_c.h._ M. coraco-humeralis.
_cl_ Clavicle.
_c.o._ Coracoid.
_d_ M. deltoideus.
_d_′ Clavicular portion of m. deltoideus.
_i_ M. infraspinatus.
_i.s._ M. interscapularis.
_l.a._ M. levator anguli scapulae.
_l.d._ M. latissimus dorsi.
_p_′ Sternal portion of m. deltoideus.
_p_″ Anterior sternal portion of the m. pectoralis.
_p_‴ Posterior sternal portion of the m. pectoralis.
_s_ Scapula.
_s.r._ M. sternoradialis.
_t.r._ M. triceps brachii.
]
(*b*) _Pars clavicularis_ (_musc. cleido-humeralis_, Klein) arises
from the inner extremity of the clavicle and from the omosternum and
joins the _portio scapularis_.
The muscle is inserted into the humerus, the under part of the
_portio scapularis_ being attached to the upper portion of the
_crista deltoidea_; the outer fibres of this part, together with
those of the _pars clavicularis_, are attached to the extremity of
the _crista deltoidea_ and to the inner surface of the humerus as
far as the distal extremity; just before its insertion the muscle is
pierced by the tendon of the _m. sternoradialis_. The deltoid draws
the limb forwards.
II. MUSCLES OF THE FORE-LIMB.
A. _MUSCLES OF THE ARM._
_M. sternoradialis (biceps)._ See page 82.
*56.* _M. triceps brachii_ (Fig. 73 _t.r._).
*Dugès*, scapulo-huméro-olecranien, n. 75.--*Capes*, *Zenker*, _m.
anconaeus_.
This muscle lies on the upper or dorsal surface of the arm, and
has relations similar to those of the corresponding muscle in man.
The long head arises from the posterior border of the scapula at
the upper border of the glenoid cavity, and is here attached to
the capsule of the joint; the inner head arises from the upper and
inner surfaces of the anterior half of the humerus as far as the
extremity; the outer head arises from the outer surface of the
humerus. Additional fibres, which may be regarded as a fourth origin
(_m. subanconaeus_), arise from the upper surface of the hinder
half of the humerus. The fibres from these several origins unite
to form a strong muscle, which covers the upper, inner, and outer
surfaces of the bone, and then passes into a tendon. This tendon is
attached to the capsule of the elbow-joint and inserted into the
proximal extremity of the radio-ulnar. A cartilage, representing the
olecranon, is found in the capsule at the point of attachment of the
tendon.
B. _MUSCLES OF THE FOREARM._
(I.) Muscles of the flexor surface.
The muscles of this surface are arranged in two groups, so as to
form, at the elbow-joint, a triangular depression (_plica cubiti_),
into which the tendon of the _m. sternoradialis_ sinks.
A. Muscles of the Inner Group.
*57.* _M. flexor carpi I s. radialis_ (Fig. 74 _Fc_).
*Dugès*, sous-huméro-carpien, n. 83.
This represents either the _flexor carpi radialis longior_ or
_radialis brevior_ of man; it has a broad origin from the inner
border of the humerus above the epicondylus medialis. It becomes
narrower as it passes downwards to be inserted by a tendon into the
_os semilunare_ and _naviculare_. The muscle is much stronger in
males than in females, and the crest from which it takes origin is
correspondingly larger in the former sex (p. 42). Tendinous fibres
connect it with the following muscles:--
*58.* _M. flexor carpi II s. ulnaris_ (Fig. 74 _Fc_′).
*Dugès*, epitrochlo-carpien, n. 84.
This muscle represents the _flexor carpi ulnaris_ or _ulnaris
anterior_, and is close to the inner side of the foregoing. It arises
from the _epicondylus medialis_, being connected by fibres with the
_flexor digitorum communis_, and is inserted into the _os naviculare_.
[Illustration: Fig. 74.
Muscles of the right arm of _Rana esculenta_.
_ed_ M. extens. digitorum communis.
_ei_ M. abductor digiti II longus.
_Fa_′ M. flexor antibrachii lateralis superficialis.
_Fc_ M. flexor carpi radial.
_Fc_′ M. flexor carpi ulnar.
_Fd_ M. flexor digitorum communis.
_sr_ Tendon of the M. sternoradialis.
]
*59.* _M. flexor digitorum communis_ (Figs. 75, 76, 77 _Fd_).
*Dugès*, epitrochlo-sous-phalangettien, n. 118.
This muscle lies most internally, and corresponds to the _m. flexor
digitorum sublimis_ of man. It arises in common with the foregoing
muscle from the _epicondylus medialis_, and runs downwards to the palm
of the hand. At its entrance into this it diminishes and passes into
the flat _aponeurosis palmaris_. (See hand, B.)
*60.* _M. flexor antibrachii medialis_ (Ecker), (Fig. 75 _Fa_).
*Dugès*, epitrochlo-sous-radial, n. 79. (Frequently described as the
_pronator rotundus_, a description which cannot be retained, as the
implied movement does not occur in the frog.--Ecker.)
This muscle lies deeply on the inner side of the forearm, covered by
the _flexores carpi_; it arises tendinously from the _epicondylus
medialis_ and is inserted into the inner surface of the radial side of
the radio-ulnar as far as the inferior articular extremity.
*61.* _M. flexor antibrachii lateralis superficialis_ (Ecker),
(Figs. 74, 75 _Fa_′).
*Dugès*, premier ex-huméro-radial, n. 76. (Usually described as
_supinator longus_, this, for reasons similar to those in the case
of _m. flexor antibrachii medialis_, cannot be retained.)
The situation of this muscle corresponds with that of the _supinator
longus_ of man; it lies to the outer side of the tendon of the _m.
sternoradialis_, and arises by two heads, the one, above from the
outer edge of the humerus, the other deeper from the _epicondylus
lateralis_. They unite and pass into a tendon which, running over the
lower articular extremity of the radio-ulnar, is partly attached to
the carpus and partly connected with the tendon of the _m. extensor
digiti II proprius longus_. From its position and insertion, this
muscle evidently flexes the forearm and extends the hand.
[Illustration: Fig. 75.
Muscles of the right arm of _Rana esculenta_, deep layer.
_ed_ Extensor digit. communis.
_Fa_ Flexor antibrachii medialis.
_Fa_′ Flexor antibrachii lat. superficialis.
_Fa_″ Flexor antibr. lat. profundus.
_Fc_ Flexor carpi radialis.
_Fc_′ Flexor carpi ulnaris.
_Fd_ Flexor digitorum communis.
]
*62.* _M. flexor antibrachii lateralis profundus_ (Ecker), (Fig. 75
_Fa_″).
*Dugès*, epicondylo-sus-radial, n. 78.--*Klein*, _flexor
antibrachii_. (_Supinat. brevis_ autt.)
This muscle arises under cover of the foregoing, from the
_epicondylus lateralis_ of the outer surface of the humerus, it
becomes broader and is inserted into the whole length of the lower
(volar) ridge of the radio-ulnar. It is a powerful flexor of the
forearm.
(II.) Muscles of the extensor surface.
*63.* _M. extensor digitorum communis longus_ (Fig. 75 _ed_).
*Dugès*, huméro-sus-digital, n. 95.
This muscle lies on the outer border of the forearm; it arises
in common with the short head of the _flexor antibr. lateralis
superficialis_ from the _epicondylus lateralis_, and from the surface
above it; it runs downwards along the outer side of the forearm,
in order to pass into an aponeurosis on the back of the hand,
which expands upon the third, fourth, and fifth fingers, and ends
between them in a free concave border. This aponeurotic expansion is
connected with the tendons of the _extensor brevis digitorum_.
*63*.* _M. abductor digiti II_ (_i. e. pollicis_) _longus_ (Fig. 74
_ei_).
**Dugès*, cubito-métacarpien, n. 87.
This muscle lies between the foregoing and the _flexor antibrachii
lateralis superficialis_, and appears superficially in the interval
between them. It arises from the lateral surface of the radio-ulnar,
and runs obliquely over the _m. flexor antibrachii lateralis
profundus_ and the hinder extremity of the radio-ulnar towards the
second finger into the metacarpal bones of which it is inserted.
*64.* _M. extensor carpi ulnaris s. ulnaris post._ (Fig. 76 _ec_).
*Dugès*, epicondylo-sous-carpien, n. 85.--*Klein*, _abductor carpi
internus_.
This muscle has a somewhat narrow origin from the _epicondylus
lateralis_; during its course through the forearm, where it lies
between the _mm. anconaei_ on the one side and the _extensor
digitorum communi_ on the other, it becomes broader and is inserted
into the outer surface of the carpus in the following manner. By
one tendinous slip it is attached to the palmar border of the
_os pyramidale_, by a second slip to the outer border of the _os
capitato-hamatum_. This latter slip is usually connected in its
dorsal portion with the _extensor digitorum communis brevis_.
[Illustration: Fig. 76.
Muscles of forearm of _Rana esculenta_, dorsal view.
_aa_ M. anconaei.
_ec_ M. extens. digit. communis.
_Fd_ M. flex. digit.
]
*65, 66.* _M. anconaei s. extensores antibrachii_ (Fig. 76 _aa_).
*Dugès*, epicondylo-cubital and epitrochlo-cubital, n. 80, 81.
Both these muscles lie on the extensor side of the forearm; they
spring, the one from the _epicondylus lateralis_, the other from the
_epicondylus medialis_; converging, they run downwards, enclose the
olecranon, and are inserted into the upper (dorsal) border of the
ulna, each forming a penniform muscle. They are extensors of the
forearm and assist the _m. triceps_.
C. _MUSCLES OF THE HAND._
(I.) Muscles on the palmar surface.
(1) Muscles common to all the digits.
*67.* _M. flexor digitorum communis_ and _m. palmaris brevis_
(Fig. 77 _fd_, _pb_).
The origin and course of this muscle has been described above. At
its entrance into the palm it suddenly diminishes in size and passes
into a triangular aponeurosis, _aponeurosis palmaris_. Into the outer
border of this aponeurosis is inserted the _m. palmaris brevis_
(Fig. 77 _pb_); this latter muscle arises from the posterior or ulnar
border of the lower extremity of the radio-ulnar below the insertion
of the _mm. anconaei_, and runs obliquely downwards to this insertion.
From the lower free border of the aponeurosis a number of muscles
arise which will be described with the rest of the digital muscles.
(2) Muscles of the rudimentary thumb.
*68.* _M. abductor pollicis_ (Figs. 77, 78 _ap_).
*Dugès*, cubito-pollicien, n. 100.
This short muscle arises from the upper border of the lower extremity
of the radio-ulnar, passes transversely outwards, and is then
inserted into the anterior border of the rudimentary thumb.
*69.* _M. adductor pollicis_ (Figs. 77, 78 _ad.p_).
*Dugès*, sous-carpo-pollicien, n. 101.
This lies more superficially than the last, it arises from the palmar
surface of the _os capitato-hamatum_, and is inserted together
with the _abductor pollicis_ into the thumb. Several fibres of the
_extens. dig. II brevis_ are also inserted into the thumb. As this
member is completely covered with skin, the motions of which it is
capable are very limited.
(3) Muscles of the second finger, which serves the purposes of a
thumb.
*70.* _M. flexor digiti II longus s. sublimis_ (Fig. 77 _f2_).
*Dugès*, sous-carpo-phalangettien de l’index, n. 133.
[Illustration: Fig. 77.
Muscles of hand of _Rana esculenta_, volar surface, larger than
nature.
_A_ Aponeurosis palmaris.
_ab5_ M. abductor dig. V primus.
_ab5_′ M. abductor dig. secundus.
_ac_ MM. anconaei.
_adp_ M. adductor pollicis.
_ap_ M. abductor pollicis.
_ec_ M. extensor digitorum communis.
_e5_ M. extens. dig. commun. brevis.
_f2_ M. flexor dig. II longus.
_f3_ M. flexor dig. III longus.
_f4_ M. flexor dig. IV longus.
_f5_ M. flexor dig. V longus.
_fb2_ M. flexor dig. II brevis.
_fb3_ and _fb3_′ MM. flexores dig. III breves.
_fb4_ and _fb4_′ MM. flexores dig. IV breves.
_fb5_ M. flexor dig. V primus.
_fd_ M. flexor digitorum communis.
_o_ M. opponens.
_pb_ M. palmaris brevis.
I First finger, rudimentary thumb.
II Second finger, functions as thumb.
III-V Third to fifth fingers.
]
This is a flat muscle, which arises for the most part by fleshy
fibres from the hinder free border of the _aponeurosis palmaris_,
also by a smaller part from the palmar surface of the _os
capitato-hamatum_. It quickly passes into a thin long tendon which is
inserted into the terminal phalanx of the thumb (second finger).
[Illustration: Fig. 78.
Second layer of muscles on volar surface of hand of _Rana esculenta_,
larger than nature.
_ab5_ M. abductor dig. V primus.
_ab5_′ M. abductor dig. V secundus.
_ad2_ M. adductor dig. II.
_ad.p_ M. adductor pollicis.
_ap_ M. abductor pollicis.
_ec_ M. extensor carpi.
_fb2_ M. flexor dig. II brevis.
_fb2_′ M. flexor dig. II tertius.
_fp_ MM. flexores proprii phalangum.
_i3_ }
_i4_ } MM. interossei volares.
_i4_′}
_i5_ }
_o_ M. opponens dig. II.
_o_′ M. opponens dig. V.
_tt_ ′ MM. transversi metacarpi.
I-V as in Fig. 77.
]
*71.* _M. flexor digiti II brevis s. profundus_ (Fig. 77 _fb2_).
*Dugès*, sous-carpo-phalangien de l’index, n. 102.
This flat muscle, covered by the preceding, has a tendinous origin
from the palmar surface of the _os capitato-hamatum_, together with
one head of the _flexor sublimis_, and is inserted into the basal
phalanx.
*72.* _M. flexor digiti II tertius_ (Fig. 78 _fb2_′).
*Dugès*, tendini-phalangien de l’index, n. 103.
A small, thin muscle which arises close to the foregoing from the _os
capitato-hamatum_, and is inserted into the basal phalanx (see below,
_m. interosseus volaris I_).
*73.* _M. adductor digiti II_ (Fig. 78 _ad2_).
*Dugès*, métacarpo-métacarpien de l’index, n. 90.
This muscle represents the _adductor pollicis_ of man; it arises
from the base of the third os metacarpal and is inserted into the
metacarpal of the second finger, which latter it draws towards the
third finger.
*74.* _M. opponens digiti II_ (Figs. 77 and 78 _o_).
*Dugès*, sous-carpo-métacarpien de l’index, n. 90.
This muscle represents the muscle of like name in man. It arises from
the palmar process of the _os capitato-hamatum_ by a narrow tendon
and passes into a broad, flat muscle, which is inserted into the
under surface and outer border of the metacarpal of the second finger
throughout its length. It has, undoubtedly, the same action as the
corresponding muscle in man.
(4) Muscles of the third finger.
*75.* _M. flexor digiti III longus s. sublimis_ (Fig. 77 _f3_).
The smaller portion of this muscle arises from the free border of the
_aponeurosis palmaris_, the chief portion, together with the _flexor
brevis_, from the palmar surface of the _os capitato-hamatum_. The
two portions pass into one long tendon, which is inserted into the
last phalanx.
*76, 77.* _MM. flexores digiti III breves s. profundi I, II_
(Fig. 77 _fb3_ and _fb3_′).
*Dugès*, tendini-phalangiens du medius, n. 104, 105.
These two muscles arise in part from the free border of the
_aponeurosis palmaris_, in part from the volar surface of the _os
capitato-hamatum_, and pass backwards on either side of the muscle
last described, to be inserted into the basal phalanx. Dugès regards
these as analogues of the _mm. lumbricales_.
*78.* _M. flexor metacarpi dig. III._
This is a somewhat strong muscle, which arises by fleshy fibres from
the palmar surface of the _os capitato-hamatum_, and is inserted into
the palmar surface of the metacarpal bone.
(5) Muscles of the fourth finger.
*79.* _M. flexor digiti IV longus s. sublimis_ (Fig. 77 _f4_).
It arises at the free border of the _aponeurosis palmaris_, and is
inserted into the terminal phalanx by a thin tendon.
*80, 81.* _MM. flexores digiti IV breves s. profundi I, II_
(Fig. 77 _fb4_ and _fb4_′).
*Dugès*, tendini-phalangiens de l’annulaire, n. 108, 109.
Dugès regards these also as analogues of the _m. lumbricales_; they
arise on either side of the foregoing muscle from the free border
of the _aponeurosis palmaris_, and are inserted by tendons into the
basal phalanx.
*82.* _M. flexor proprius phalangum dig. IV_ (Fig. 78 _fp_).
*Dugès*, phalango-phalangien, n. 115.
A small muscle which arises by two slips from the palmar surface
of the basal phalanx, and is inserted into the base of the middle
phalanx.
*83.* _M. flexor metacarpi dig. IV_ (Fig. 78 _i4_).
This somewhat strong muscle arises from the _os capitato-hamatum_,
and is inserted into the palmar surface of the metacarpal bone.
(6) Muscles of the fifth finger.
*84.* _M. flexor dig. V longus s. sublimis_ (Fig. 77 _f5_).
This corresponds exactly with the corresponding muscle of the fourth
finger.
*85.* _M. flexor dig. V brevis_ (Fig. 77 _fb5_).
This muscle arises from the free border of the aponeurosis and is
inserted into the basal phalanx.
*86.* _M. flexor proprius phalangum dig. V_ (Fig. 78 _fp_).
*Dugès*, phalango-phalangien, n. 17.
It corresponds exactly with the corresponding muscle of the fourth
finger.
*87.* _M. opponens dig. V_ (Fig. 78 _o_′).
*Dugès*, deuxième sous-carpo-métacarpien du digitule, n. 92.
This muscle has a narrow origin from the palmar surface of the _os
capitato-hamatum_, it widens and is inserted into the outer border of
the metacarpal of the small finger. It draws this finger towards the
thumb.
*88.* _M. abductor dig. V primus_ (Figs. 77 and 78 _ab5_).
*Dugès*, sous-pyro-pré-métacarpien du digitule, n. 93.
This muscle arises from the palmar border and the outer surface of
the _os pyramidale_, and is inserted into the basal phalanx by a thin
tendon.
*89.* _M. abductor dig. V secundus_ (Figs. 77 and 78 _ab5_′).
*Dugès*, sous-pyro-post-métacarpien du digitule, n. 94.
It arises from the posterior part of the _os pyramidale_, is short,
and is inserted into the outer side of the metacarpal.
(II.) Muscles on the dorsal surface.
_M. extensor digitorum communis longus_ (Figs. 75 _ed_ and 77 _ec_).
*90.* _M. extensor digitorum communis brevis_ (Fig. 79 _e_3, _e_4,
_e_5).
*Dugès*, sous-pyro-phalangettien du III, IV, V, n. 124, 128, 131.
Covered by the foregoing, this muscle arises from the _os pyramidale_
in conjunction with the _extensor pollicis_ and from the _os
capitato-hamatum_. The part destined for the third finger, together
with that for the fourth, arises from the _os pyramidale_, passes
obliquely backwards into a tendon which runs along the inner side
of the corresponding finger to be inserted into the last phalanx.
That for the fifth finger arises from the inner projection of _os
capitato-hamatum_ being here attached to the insertion of the _m.
extensor carpi ulnaris_, and is inserted in a similar manner into the
terminal phalanx of the fifth finger.
*91.* _M. abductor digiti II_ (_i.e._ _pollicis_) _longus_
(Figs. 74 _ei_ and 79 _ab.2_).
For the origin and course of this muscle in the forearm see No. 63.
The muscle passes obliquely over the wrist-joint from the little
finger towards the inner side and from before backwards, it is
inserted into the metacarpal of the second finger (thumb). The place
of insertion of this muscle into the metacarpal (compare p. 47) is,
in the males, developed into a ridge and process, the muscle itself
is enlarged during the breeding season. This muscle abducts the thumb
and by this means presses upon the chest of the female when clinging
to her.
*92.* _M. extensor digiti II proprius longus_ (Fig. 79 _e2_, _e2_′).
*Dugès*, cubito-radio-sous-phalangien de l’index, n. 96.
[Illustration: Fig. 79.
Muscles of hand of _Rana esculenta_. Dorsal view, twice natural size.
_ab.2._ M. abductor dig. II longus.
_ab.2_′ M. abductor dig. II brevis.
_ad.2_ M. adductor dig. II.
_e2_ }
_e2_′ } M. extensor dig. II longus.
_e3_ }
_e4_ } M. extensor digitorum communis brevis.
_e5_ }
_eb2_ M. extensor dig. II proprius brevis.
_ec_ M. extensor carpi ulnaris.
_fa_ M. flexor antibr. lat. superficial.
_i_′3 }
_i_′4 } MM. interossei.
_i_′5 }
II-V as in Fig. 77.
]
This muscle lies obliquely on the back of the hand, parallel with
the _m. abductor digiti II_. It arises by two heads, one from the
tendon of the _flexor antibr. lat. superf._ (n. 60) upon the hinder
extremity of the radio-ulnar. This tendon conceals the hinder end
of this bone by means of a patella-like thickening, and sends forth
three tendinous prolongations; of these, the one is attached to the
ulnar border of the radio-ulnar, the second to the _os naviculare_,
while the third constitutes that portion of the _m. extens. dig. II
proprius long._ which is under consideration. The second head arises
from the _os pyramidale_ in connection with the _extensor digitorum
communis brevis_ (n. 90). The heads unite to form a long muscle,
which runs obliquely towards the second finger, passes into a tendon,
which, after forming connections by some muscular fibres with the
metacarpal, is inserted into the terminal phalanx.
*93.* _M. extensor dig. II proprius brevis_ (Fig. 79 _eb2_).
*Dugès*, sus-luno-phalangettien de l’index, n. 120.
This muscle lies between the preceding muscle and the _abductor dig.
II longus_. It arises from the _os naviculare_, and also includes
some fibres which arise from the second metacarpal. The tendon runs
along the radial side and is inserted along with the last muscle into
the terminal phalanx.
*94.* _M. abductor dig. II brevis_ (Fig. 79 _ab._2′).
*Dugès*, sus-luno-métacarpien de l’index, n. 88.
This represents the _abduct. pollic. brevis_ of man, lies on the
outer side of the hand, arises from the _os naviculare_, and is
inserted into the second metacarpal.
*95.* _M. extensor dig. III proprius._
*Dugès*, sus-luno-phalangettien du médius, n. 122.
This muscle has two heads of origin, from the _os naviculare_ and
_lunatum_. These form one muscular belly, which rapidly diminishes
and passes into a tendon; this, after receiving a few muscular fibres
from the second metacarpal, runs to the outer part of the dorsal
surface of this finger as far as the terminal phalanx, where it is
inserted.
*96.* _M. extensor dig. IV proprius._
*Dugès*, sus-pyro-phalangettien de l’annulaire, n. 128.
By a somewhat broad base, this muscle arises from the _os naviculare_
and _lunatum_. The tendon receives fibres from the fourth metacarpal
and runs on the outer half of the dorsal surface of this finger as
far as the middle phalanx, where it is inserted.
(III.) _MM. interossei._
*97, 98.* [*a.*] _MM. transversi metacarpi_ (Ecker), (Fig. 78 _t_,
_t_′, _ad2_).
These lie transversely between the metacarpals. There are three; the
first has been already described as _m. adductor digiti II_ (n. 73);
the second is stretched between the third and fourth metacarpals, and
the third between those of the fourth and fifth fingers.
*99, 100, 101.* [*b.*] _MM. interossei volares._
One may regard as such, four long, thin muscles, which take origin
near one another on the palmar surface of the carpal bones, and
diverge from this towards the second and fifth fingers.
1. The first of these muscles (Fig. 78 _fb2_′) has already been
described above as the _m. flexor digiti II tertius_ (n. 72).
2. The second (Fig. 78 _i3_) passes from the origin already described
to the palmar surface of the basal phalanx of the third finger.
3. The third (Fig. 78 _i4_) runs, in like manner, to the fourth
finger.
4. The fifth (Fig. 78 _i5_) to the fifth finger[46].
[Footnote 46: Whether these muscles may be regarded as _mm.
interossei_ is open to discussion, as they appear to act more as _mm.
opponentes_.]
*102* to *108*. _MM. interossei dorsales._
These arise in common from the metacarpals, and are inserted into the
basal phalanx of the corresponding surface on the finger.
1. The _third_ finger has two, one to the radial side (Fig. 79
_i_′3), one to the ulnar side.
2. The _fourth_ finger has three, the third (Fig. 79 _i_′4) arises
from the carpus, and perhaps ought rather to be regarded as an
extensor.
3. The _fifth_ finger has two.
IV. MUSCLES OF THE HINDER LIMB.
I. MUSCLES OF THE THIGH.
General arrangement (Figs. 80, 81).
*a.* The _m. triceps femoris_ forms the _outer border_ of the thigh,
and extends on to both the dorsal and ventral surfaces. The outer
border therefore corresponds with the anterior surface of the thigh
of man, in consequence of the thigh in the frog being normally
rotated outwards.
*b.* The _m. vastus internus_ (_v.i._) and a portion of the _adductor
longus_ (_ad_′), the _sartorius_ (_s_), a portion of the _adductor
magnus_ (_ad_‴), and the _rectus internus major_ (_r.i_′) are found
on the _inner surface_ of the thigh.
*c.* The _rectus internus minor_ (_r.i_″) forms the _inner border_.
*d.* On the _dorsal surface_ are to be seen, nearest the trunk,
the _glutaeus_ (_gl_), on the outer border the _vastus externus_
(_v.e._), the _pyriformis_ and _biceps_ (_p_ and _b_), then the
_semimembranosus_ (_sm_), and lastly the _rectus internus minor_
(_ri_″).
*e.* By reflecting the _rectus internus major_ (compare Fig. 82)
there are exposed to view: the _semitendinosus_ (_st_), the whole
length of the _adductor longus_, _magnus_ (_ad_′ and _ad_‴), and
_brevis_ (_ad_″). By reflecting the triceps, one sees (Figs. 84,
85) the _ilio psoas_ (_ip_), and beneath the _semimembranosus_, the
_quadratus_ (_qf_), and _capsularis femoris_ (_og_).
_Description of the separate Muscles._
(A.) Muscles of the dorsal surface.
*109.* _M. glutaeus_ (Fig. 80 _gl_).
*Dugès*, ex-ilio-trochantérien.--*Zenker*, _glutaeus maior_.
The tendinous origin of this muscle is found on the outer surface
and upper border of the two hinder thirds of the iliac bone. Thence
it runs outwards and backwards between the head of the _m. vastus
externus_ (_ve_) on the one side, and the _ilio-psoas_ and _rectus
anticus_ (_ra_) on the other, to be inserted into a tubercle
(trochanter) of the femur.
*110.* _M. Pyriformis_ (Fig. 80 _p_).
*Cuvier*, pyramidal.--*Dugès*, coccy-fémoral, n. 136.
A narrow, slender muscle, arising from the apex of the coccyx; it
passes obliquely outwards and backwards to the thigh, to be inserted
deeply between the _m. vastus externus_ and the _biceps_, into the
inner surface of the femur, but towards the ventral surface.
_M. triceps femoris s. extensor cruris communis_ (Fig. 80).
*Dugès*, pelvi-fémoro-rotulien, n. 145, 146, 147.
This is a large, strong muscle, having three heads of origin, and
inserted by a tendon into the tibio fibula. The three heads are the
_caput longum_ or the _rectus femoris anticus_ (_r.a._), the _caput
externum_ or the _vastus externus_ (_v.e._), and the _caput internum_
or the _vastus internus_ (Fig. 82 _vi_); of these, the first is
situated on the outer border of the thigh, the second on the dorsal
surface, and the third on the ventral surface.
[Illustration: Fig. 80.
Muscles of left thigh of _Rana esculenta_. Dorsal view.
_b_ M. biceps.
_ci_ M. coccygeo-iliacus.
_g_ M. gastrocnemius.
_gl_ M. glutaeus.
_p_ M. pyriformis.
_pe_ M. peroneus.
_r.a._ M. rectus anterior.
_ri_″ M. rectus internus minor.
_sm_ M. semimembranosus.
_t.a._ M. tibialis anticus.
_tr._ M. triceps fem.
_v.e._ M. vastus externus.
]
*111.* [*a.*] _M. rectus femoris anticus_ (Figs. 80, 82 _ra_).
This arises from the under (ventral) surface of the iliac bone about
its middle and beneath the _m. glutaeus_. The muscular belly quickly
passes into an aponeurosis, which covers the other two muscular
masses and combines with their tendons.
*112.* [*b.*] _M. vastus externus_ (Fig. 80 _v.e._).
It arises from the upper and hinder extremity of the iliac bone
(Fig. 42 _il_′) behind the _glutaeus_, which here sinks in between
this muscle and the _rectus anterior_.
*113.* [*c.*] _M. vastus internus_ (Figs. 81, 82 _vi_).
It arises from the whole of the under and outer surfaces of the
hip-joint capsule, and from tendinous slips which pass from this
capsule downwards on the under surface of the muscle, (from the
pubis and the femur I have not seen any fibres of origin, as stated
by others). Anteriorly the _vastus_ may easily be separated into
two heads. The two _vasti_ unite and form one muscular belly, in
the formation of which, as above stated, the _rectus anticus_ takes
no part. This united muscle passes into a tendon which, without the
mediation of a patella, passes over the knee-joint to be inserted
into the anterior extremity of the tibio fibula, and is prolonged
into the fascia of the leg.
*114.* _M. ilio-fibularis s. biceps_ (Fig. 80 _b_).
*Dugès*, ilio-péronien, n, 149.--*Zenker*, flexor externus tibiae,
p. 42.
This is a long, somewhat narrow muscle, which lies to the inner side
of, and partly covered by, the _vastus externus_, between which and
the semimembranous it is placed. It arises by a tendon between the
_ilio-psoas_ and _pyriformis_ from the ilium above the acetabulum
and behind the origin of the _vastus externus_. From here it passes
backwards, separated from the _vastus externus_ by a strong _ligam.
intermusculare_. On the inner side of this muscle, between it and
the _m. semimembranosus_, run the vessels of the thigh and the _N.
ischiadicus_. The muscle then divides into two portions, of which
one is inserted high up on the inner and under surface of the femur.
This is probably the muscle which Klein (_l. c._, p. 61) describes as
the _extensor brevis_. The other long muscular belly passes into a
thin tendon, opposite the hinder extremity of the thigh, it divides
into two portions; the anterior is inserted into the dorsal surface
of the hinder extremity of the femur, the other into the dorsal
surface of the tibio-fibula. Between the two is stretched an arch
with the concavity outwards. This insertion of the biceps is covered
by the stronger tendon of origin of the _m. gastrocnemius_ (compare
Fig. 87).
*115.* _M. semimembranosus_ (Figs. 80, 86 _sm_).
*Dugès*, sus-ischio-poplité, n. 148.--*Klein*, p. 60, _extensor
femoris sublimis_.
This muscle lies on the dorsal surface of the thigh, to the inner
side of the _biceps_ and _pyriformis_: it is a broad muscle, which
takes a tendinous origin from the hinder and upper angle of the
_symphysis ossis ilei_, and is inserted by a flat tendon into the
dorsal surface of the ligaments of the knee-joint, and through these
into the tibio-fibula. The tendon is formed rather abruptly from
the muscle, and is surrounded (Fig. 86) by the concave arch, which
forms the tendon of origin of the _gastrocnemius_ (_q. v._). A little
behind its middle (compare Fig. 81) the muscle is divided obliquely
into an anterior and a posterior portion by an aponeurotic septum. As
all the fibres are interrupted by this structure, the muscle may very
easily be torn through.
(B.) Muscles on the ventral surface.
*116.* _M. sartorius_ (Figs. 81, 82 _s_).
*Dugès*, sous-iléo-tibial, n. 150.--*Klein*, _gracilis_.
This long, flat muscle lies along the middle of the ventral surface
of the thigh; it arises by a tendon from the anterior inferior angle
formed by the symphysis of the innominate bones, and terminates in a
tendon behind the knee-joint, forming a kind of _pes anserinus_ in
the fascia of the leg, similar to that of the _semitendinosus_[47].
[Footnote 47: The sartorius has lately been used by Kühne in his
researches on the nerve-endings in muscle and on muscle contraction
without nerve supply (du Bois-Reymond’s and Reichert’s Archiv, 1859.
Page 314).]
*117.* _M. rectus internus major_ (Ecker), (Figs. 81 _r.i_′, 82
_ri_′).
*Dugès*, post-ischio-tibial profond, n. 152.--*Klein*,
_semimembranosus_.
This is a broad and flat muscle, thinned out at either extremity;
it occupies the inner half of the ventral surface of the thigh,
and is in relation with the _adductor magnus_ externally and
anteriorly, with the _sartorius_ posteriorly, and the _rectus minor_
muscle internally. The muscle arises by a tendon from the pubic
symphysis; it covers in its course the _semitendinosus_, then passes
into a strong tendon, which blends with the tendon of the _rectus
minor_, to be inserted by a slip into a process of the tibio-fibula
representing the _tuberositas tibiae_; first passing between the
tendons of the _sartorius_ and _semimembranosus_, which here form
an aponeurotic arch; a second slip passes under the tendon of the
_m. semitendinosus_ to be inserted into the upper surface of the
tibio-fibula, under it passes the _N. tibialis_. A third thread-like
tendon passes to the _m. semimembranosus_. Somewhat behind its middle
(Fig. 82) the muscle is traversed by an _inscriptio tendinea_, by
which the whole of the fibres are interrupted.
[Illustration: Fig. 81.
Muscles of left thigh of _Rana esculenta_. Ventral surface.
_ad_′ M. adductor longus.
_ad_″ M. adductor brevis.
_ad_‴ M. adductor magnus.
_e.c._ M. extensor cruris.
_f.t._ M. flexor tarsi.
_g.c._ M. gastrocnemius.
_r.i_′ M. rectus internus major.
_r.i_″ M. rectus internus minor.
_s_ M. sartorius.
_t.a._ M. tibialis anticus.
_t.p._ M. tibialis posticus.
_v.i._ M. vastus internus.
]
*118.* _M. rectus internus minor_ (Ecker), (Figs. 80, 81 _r.i_″).
*Dugès*, post-ischio-tibial superficiel, n. 151.--*Zenker*, _flexor
tibiae magnus_.--*Klein*, _ischio-tibialis_.
Situated entirely on the inner surface of the thigh, this narrow
muscle arises by a tendinous band which runs the whole length of the
pubic symphysis, and is connected posteriorly with the _sphincter
ani_, anteriorly with the _rectus abdominis_; posteriorly it passes
into a thin tendon which is also connected with the muscle just
described (117). In its course this muscle is attached to the skin
by strands of vessels and connective tissue.
The vastus internus major and minor together undoubtedly correspond
with rectus internus or gracilis of human anatomy. The rectus
internus major is, however, regarded as corresponding with the
adductor magnus by Dugès, and with the semimembranosus by Klein; by
considering the position and attachments of these muscles one must
arrive at a different conclusion.
_MM. adductores femoris._
*119.* [*a*] _M. adductor longus_ (Fig. 82 _ad_′).
*Dugès*, sous-ilio-fémoral, n. 141.
Without further dissection this muscle is only partially visible
between the _m. sartorius_ and _vastus internus_ (Fig. 81 _ad_′). The
muscle is flat and long, and arises by a tendon from the anterior
inferior angle of the pubic symphysis (Fig. 42 _s_), partially
covered by the origin of the _sartorius_. Thence the muscle passes
between the _vastus internus_ and the _adductor magnus_, and finally
is inserted below the middle of the femur, together with the latter
muscle.
[Illustration: Fig. 82.
Muscles of the left thigh of _Rana esculenta_. Ventral surface.
_ad_′ M. adductor longus.
_ad_‴ M. adductor magnus.
_gl_ M. glutaeus.
_ip_ M. ilio-psoas.
_ra_ M. rectus fem. anticus.
_ri_′ M rectus int. major.
_s_ M. sartorius.
_st_ M. semitendinosus.
_vi_ M. vastus internus.
]
*120.* [*b*] _M. adductor magnus_ (Figs. 81, 82 _ad_‴).
*Dugès*, sous-ischio-pubi-fémoral (adductor 1 and 2), n. 142,
143.--*Klein*, _adductor magnus_ and _extensor femoris profundus_.
This muscle is visible between the _sartorius_ and _rectus internus
major_ in the anterior half of the thigh, posteriorly it is covered
by these muscles. It arises by a tendon from (_a_) the pubic
symphysis and _ischii_, and is in this position divided into two
portions, between which passes the tendon of one head of the _m.
semitendinosus_ (Fig. 83 _st_″); (_b_) a second part arises from
this same tendon (Fig. 83 _st_‴) and joins with the first part. Thus
formed the muscle passes to be inserted into the distal half of the
inner surface of the femur as far as the condyle. Near its hinder
extremity, however, it passes on to the dorsal and outer surfaces,
and thus forms a kind of muscular sheath surrounding the distal
portion of the bone.
*121.* [*c*] _M. adductor brevis_ (Figs. 81, 83 _ad_″),
and
*122.* [*d*] _M. pectineus_ (Fig. 83 _pe_).
*Dugès*, sous-pubio-fémoral (analogue of the _pectineus_, possibly of
the _add. brevis_ also).
These two small muscles which lie under cover of the _sartorius_,
_adductor longus_ and _magnus_, appear externally as one muscle, but
may easily be separated (Fig. 83). They arise close together from
the pubic symphysis, and are inserted into the inner surface of the
anterior half of the femur. They are not attached to the _adductor
magnus_.
[Illustration: Fig. 83.
Deep muscles of left thigh of _Rana esculenta_.
_ad_′ M. adductor longus.
_ad_″ M. adductor brevis.
_ad_‴ M. adductor magnus.
_ip_ M. ilio-psoas.
_pe_ M. pectineus.
_ra_ M. rectus anticus,
_ri_′ M. rectus internus major }
_ri_″ M. rectus internus minor } cut through.
_s_ M. sartorius.
_st_ Belly of m. semitendinosus.
_st_′ M. semitendinosus (cap. posticum).
_st_″ M. semitendinosus (cap. anticum).
_st_‴ Fibres passing into the adductor magnus.
_vi_ M. vastus internus.
]
*123.* _M. semitendinosus_ (Fig. 83 _st_, _st_′, _st_″).
*Dugès*, bis-ischio-tibial, n. 153.--*Zenker*, _biceps_.
This is a long thin muscle, only visible after removal of the _m.
rectus internus_, by which it is entirely covered. It arises by two
long thin tendons, one (_caput posticum_, _st_′) from the pubic
symphysis, the other (_caput anticum_, _st_″) from the hollow between
the symphysis and the acetabulum. The latter passes through a slit
in the _adductor magnus_, and so affords this muscle another point of
origin; then backwards between the _adductor magnus_ and the _rectus
internus major_ and under the lower third of the thigh, and unites
with the posterior head of origin. The muscle so formed passes into
a thin tendon, and, together with that of the _sartorius_, forms an
aponeurotic arch, connected with the fascia of the leg, under which
the tendons of the _rectus internus major_ and _minor_ pass.
(C.) Deep muscles of the thigh.
To these, in addition to the _adductor brevis_, _pectineus_, and the
portion of the _biceps_ already described, belong also the following:
[Illustration: Fig. 84.
Deep muscles of the left thigh of _Rana esculenta_. Dorsal view.
_ad_′ M. adductor brevis.
_ci_ M. coccygeo-iliacus.
_cx_ Coccyx.
_gl_ M. glutaeus.
_il_ Ileum.
_ip_ M. ilio-psoas.
_o.g._ M. obturatorius.
_qf_ M. quadratus femoris.
]
[Illustration: Fig. 85.
Left half of pelvis of _Rana esculenta_. Thigh turned forwards under
the abdomen.
_gl_ M. glutaeus.
_og_ M. obturatorius.
]
*124.* _M. ilio-psoas_ (Figs. 82, 83, 84 _ip_).
*Dugès*, intra-ilio-fémoral (*_iliacus_ and _psoas_).--*Cuvier*,
*Zenker*, *Klein*, _iliacus internus_.
The fibres of this muscle take a broad origin from the pelvic surface
of the ilium, pass outwards over the lower margin of the bone and
form a flat muscle with its apex pointed posteriorly. It crosses the
hip-joint between the _m. rectus_ and _vastus internus_, covering
the hinder part of the _m. glutaeus_, and is inserted into the outer
surface of the middle third of the femur.
*125.* _M. quadratus femoris_ (Fig. 84 _qf_).
*Dugès*, post-ilio-fémoral (Homologue of the _glutaeus maximus_), n.
197.--*Zenker*, _glutaeus minor_, p. 42.
This muscle is of a somewhat elongated, triangular shape, and
arises, under cover of the _pyriformis_, from the ilium behind the
acetabulum; it passes backwards over the joint to be inserted into
the inner and under surfaces of the femur, between the _pyriformis_
and _ilio-psoas_; below, it is in direct relation with the _adductor
brevis_.
*126.* _M. obturatorius_ (Figs. 84, 85 _og_).
*Dugès*, ischio-pubi-fémoral, n. 139 (?).--*Zenker*, _m. capsularis
femoris_.
This small muscle is deeply situated upon the hip-joint, and covered
by all the other muscles that arise from the symphysis. Its origin
from the innominate bone extends from the superior posterior angle of
the _symph. ossis ilii_ to about the middle of the pubic symphysis;
the muscle fills the space between the crest of the symphysis and the
acetabulum. The fibres converge to pass into a strong tendon, which
is inserted into the posterior and anterior surfaces of the head of
the femur. The muscle appears to represent collectively the small
rotators of human anatomy, _m. obturator externus_ and _internus_ and
the _gemelli_.
II. MUSCLES OF THE LEG.
_General description._
On the outer surface (the anterior of man), covered by the _fascia
cruris_, into which the tendon of the _extensor communis cruris_ or
_triceps_ is prolonged, are found the following muscles: nearest to
the bone, the _m. extensor cruris brevis_ (_ec_); externally, the
_m. tibialis anticus_ (_ta_) and the _m. peroneus_ (_pe_). On the
inner surface (the hinder of man) lie the _gastrocnemius_ (_gc_) and
_tibialis posticus_ (_tp_), and deeply the _flexor tarsi sup._ (_ft_).
*127.* _M. gastrocnemius_ (Figs. 80, 81, 86).
*Dugès*, bi-fémoro-plantaire, n. 159.
This important muscle arises by two tendinous heads. The one (Fig. 86
_g_′) rather nearer the middle line of the popliteal space, is
by far the stronger: it arises by a broad, tendinous expansion,
which covers the knee-joint, and is attached to the femur and the
tibio-fibula by anterior and posterior bands respectively; it ends
internally in a concave aponeurotic arch: the second head is a thin,
tendinous slip, arising from the common tendon of the _triceps_ as
this lies on the knee-joint. The muscle is thickest near its origin,
and then gradually diminishes in size as it passes backwards; the
superficial surface is convex, the deep surface is flat. By tracing
the tendons of origin, they are seen soon to unite and form a common
flat tendinous surface, broad in front, contracted behind; this
aponeurosis lies in a plane running obliquely from the deep surface
towards the superficial surface, without, however, reaching this.
The muscular fibres arise from both surfaces of the aponeurosis, the
fibres of the two sides diverging slightly as they pass backwards
so as to be inclined at a small angle to each other. The fibres
are inserted into a fibrous expansion (_Ap_) which lies on the
superficial surface of the muscle; thin and slight in front, this
aponeurosis rapidly thickens posteriorly until it passes into the
_tendo Achillis_.
[Illustration: Fig. 86.
Muscles of the right leg and foot of _Rana esculenta_. Dorsal view.
_a.h._ M. abductor hallucis.
_a.l1_ M. abductor longus digiti I.
_A.p._ Aponeurosis plantaris.
_b_ M. biceps.
_e.t._ M. extensor tarsi.
_F.l._ M. flexor digitorum III, IV, V longus.
_F.l_′. M. flexor digitorum I and II longus.
_g_ M. gastrocnemius, drawn towards the right.
_g_′ Tendon of origin of gastrocnemius.
_l.c._ Ligamentum calcanei.
_p_ M. plantaris.
_r.i._ MM. internus maior and minor.
_s.m._ M. semimembranosus.
_s.t._ M. semitendinosus.
_t.A._ Tendo Achillis.
_t.A_′. Thickening of tendo Achillis.
_t.p._ M. tibialis posticus.
_v.e._ M. vastus externus.
_v.i._ M. vastus internus.
]
*128.* _M. tibialis posticus_ (Fig. 86 _t.p._).
*Dugès*, cruro-astragalien, n. 160.
Covered by the _gastrocnemius_ this muscle occupies the whole of the
inner and upper surfaces of the tibio-fibula, from which it arises
by numerous fibres. Opposite the hinder extremity of the bone the
muscle becomes free and passes somewhat abruptly into a tendon, which
courses behind and over the _malleolus internus_, on to the dorsum
of the foot, and is here inserted into the anterior extremity of the
_astragalus_. I cannot agree with Dugès that this muscle corresponds
with the _soleus_ (Ecker).
*129.* _M. extensor cruris brevis_ (Fig. 87 _ec_).
*Dugès*, pré-fémoro-tibial, n. 154.
Covered by the strong _fascia cruris_, and lying between the _m.
tibialis anticus_ and the tibio-fibula, this muscle arises by a long
tendon from the inner condyle of the femur; it passes backwards in
the groove on the anterior extremity of the tibio-fibula, covered by
the tendon of the triceps femoris, and is then inserted by muscular
fibres into the outer surface of the tibio-fibula almost as far as
the posterior third of the bone. (Dugès regards this muscle as the
upper, i. e. anterior, portion of the _tibialis anticus_.)
*130.* _M. tibialis anticus_ (Figs. 80, 81, 87 _ta_).
*Dugès*, pré-fémoro-astragalien and pré-fémoro-calcanien, n. 156 and
157; the former he regards as one part of the _tib. anticus_, the
latter as the _peroneus longus I_.--*Zenker*, _tib. ant. biceps_.
The tendon of origin of this muscle is attached to the femur
near the tendon of the _m. extensor cruris brevis_, and to the
joint-ligaments. The muscle is placed under the _fascia cruris_, its
long tendon of origin passing beneath the tendon of the _triceps_
in a special sheath through the joint; the tendon then gains a
muscular belly which bifurcates at about the middle of the leg,
forming two muscular masses, coursing along the outer and the inner
side of the leg respectively. The latter is inserted into the dorsal
surface of the _astragalus_ by a tendon, and the former into the
dorsal surface of the _calcaneus_ in a similar manner. The muscle
extends the foot and flexes the tarsus; the latter movement is very
distinct on account of the insertion of the muscle being so near the
_hypomochlion_.
*131.* _M. flexor tarsi anterior_ (Ecker), (Fig. 87 _Ft_).
*Dugès*, ex-tibio-astragalien, n. 155.--*Zenker*, _tibialis anticus
simplex_.
This muscle arises where the insertion of the _extensor cruris
brevis_ ceases, from the middle of the under surface of the
tibio-fibula, and passes backwards between the two tendons of the _m.
tibialis anticus_ along the outer side of this muscle, to be inserted
by a tendon into the inner side of the anterior articular extremity
of the _astragalus_ and the _fascia dorsalis pedis_.
[Illustration: Fig. 87.
Muscles of leg and foot of _Rana esculenta_, seen from below.
_a.b.5_ M. abductor dig. V longus.
_ec_ M. extensor cruris brevis.
_e.d.1_ M. extensor digit I longus.
_e.d.4_ M. extensor digit IV longus.
_e.d.5_ M. extensor digit V longus.
_Ft_ M. flexor tarsi anterior.
_Ft_′ M. flexor tarsi posterior.
_g_ M. gastrocnemius.
_p_ M. peroneus.
_ta_ M. tibialis anticus.
_tF_ M. triceps femoris.
]
*132.* _M. peroneus_ (Figs. 80 _pe_, 87 _p_).
*Dugès*, génio-péronéo-calcanien, n. 158.
This is a strong muscle which is attached by a long tendon of
origin to the hinder extremity of the femur and the ligaments of
the knee-joint. The tendon runs in a sheath through the joint and
posteriorly becomes muscular; the muscle passes downwards on the
outer side of the tibio-fibula to be inserted into the _malleolus
externus_ of this bone and into the anterior extremity of the
_calcaneus_. It has an action similar to that of the _m. tibialis
anticus_.
III. MUSCLES OF THE FOOT.
A. _MUSCLES ON THE PLANTAR SURFACE._
*133.* _Aponeurosis plantaris_ (Fig. 88 _A.p._).
As already mentioned, the tendon of the _m. gastrocnemius_ is, at
the heel, continued into a strong aponeurosis, and possesses at this
place a thickening[48]. The aponeurosis is of triangular form, the
base directed towards the toes and attached to these. The lateral
borders of this triangle are continued into weaker _fasciae_, which
are attached to the two long tarsal bones. The inner border in
particular gives a strong bundle of fibres to the astragalus, and is
thus connected with the fascia of the dorsum of the foot; externally
this aponeurosis is attached to a cartilage (Dugès, os sesamoïde, _l.
c._, n. 66), situated on the plantar surface of the joint between the
_calcaneus_ and the _os metatarsi IV_.
[Footnote 48: Lehmann, Ueber den Knorpel in der Achillessehene des
Frosches, Zeitschs. f. U. Zool. XIV, p. 109. (See also literature on
cartilage, Sect. VII.)]
*134.* _Ligamentum calcanei_ (Ecker), (Figs. 88, 89 _l.c._).
If the _tendo Achillis_ be divided and the _aponeurosis plantaris_
reflected towards the toes, there is seen, arising from the posterior
head of the tibio-fibula, in its whole breadth, a ligament (between
the _tib. posticus_ and _peroneus_). This ligament forms a firm
surface on which the thickened portion of the _tendo Achillis_ may
move, and which evidently represents the tuberosity of the heel bone.
I have therefore named the entire structure the _ligamentum calcanei_.
[Illustration: Fig. 88.
Muscles of the right leg and foot of _Rana esculenta_. Dorsal view.
_a.h._ M. abductor hallucis.
_a.l_I M. abductor longus digiti I.
_A.p._ Aponeurosis plantaris.
_b_ M. biceps.
_e.t._ M. extensor tarsi.
_F.l._ M. flexor digitorum III, IV, V longus.
_F.l._′ M. flexor digitorum I and II longus.
_g_ M. gastrocnemius, drawn towards the right.
_g_′ Tendon of origin of gastrocnemius.
_l.c._ Ligamentum calcanei.
_p_ M. plantaris.
_r.i._ MM. internus maior and minor.
_s.m._ M. semimembranosus.
_s.t._ M. semitendinosus.
_t.A._ Tendo Achillis.
_t.A_′. Thickening of tendo Achillis.
_t.p._ M. tibialis posticus.
_v.e._ M. vastus externus.
_v.i._ M. vastus internus.
]
Several muscles arise from this ligament, viz.:--
*135.* _M. extensor tarsi_ (Klein), (Figs. 88, 89 _e.t._).
*Dugès*, tibio-sous-astragalien (regarded by him as the homologue of
the _tibialis posticus_).
Covered by the two succeeding muscles, this muscle arises from the
_ligamentum calcanei_, runs backwards, and is inserted into the whole
length of the plantar surface of the _astragalus_. It extends the
foot.
*136.* _M. plantaris_ (Figs. 88, 89 _p_).
This takes its origin from the _ligamentum calcanei_ to the inner
side and below the last muscle. It passes backwards and is inserted
into the dorsal surface of the _aponeurosis plantaris_.
[Illustration: Fig. 89.
Muscles of the plantar surface of foot of _Rana esculenta_, twice
natural size.
_A.p._ Aponeurosis plantaris, divided.
_ab.5._ M. abductor dig. V.
_ad.5._ M. adductor dig. V.
_ad.l.1._ M. adductor longus dig. I.
_e.t._ M. extensor tarsi.
_F.5._ M. flexor brevis dig. V.
_F.l._ M. flexor digitorum III, IV, V longus.
_F.l_′. M. flexor digitorum I, II longus.
_l.1._}
_l.2._}
_l3_ }
_l3_′ } Musculi lumbricales.
_l4_′ }
_14_″ }
_l.5._}
_l.c._ Ligamentum calcanei.
_p_ M. plantaris.
_t.A._ Tendo Achillis.
_t.A_′. Thickening in tendo Achillis.
_t.p._ M. transversus plantae posterior.
_t.p._′ M. transversus plantae anterior.
]
*137.* _M. flexor digitorum III_, _IV_, _V longus_ (Ecker),
(Figs. 88, 89 _F.l._).
*Dugès*, péronéo-sous-phalangettien (_flexor dig. longus_).
This muscle also arises from the _ligamentum calcanei_ to the outer
side of the _m. plantaris_. It runs backwards over the _aponeurosis
plantaris_, and at the free margin of this passes somewhat suddenly
into a strong tendon, which traverses an aponeurotic canal, formed by
fibres of the aponeurosis passing above and below the tendon, from
the cartilaginous enlargement in the tendon to the median border of
the aponeurosis. The tendon forms three slips for the fifth, fourth,
and third toes: these are slightly attached to the aponeurosis,
but reach beyond its free border to be inserted into the terminal
phalanges of the toes mentioned, and are held down by fibrous bands.
(The small _m. lumbricales_ arising from these tendons are described
below.)
*138.* _M. flexor digitorum I_, _II longus_ (Ecker), (Figs. 88, 89
_F.l_′.).
The tendons, by means of which the terminal phalanges of the first
and second toes are flexed, arise directly from the posterior border
of the aponeurosis.
*139, 140.* _MM. transversi plantae_ (Ecker), (Fig. 89 _t.p._,
_t.p_′.).
The movements of the aponeurosis and through it the movements of
the tendons attached to it are influenced not only by the _m.
gastrocnemius_ and _plantaris_, but also by two other muscles, which
together have been described as the _flexor dig. longus internus_
(Klein), or as the tarso-sous-phalangettien (Dugès, 221).
*a.* _M. transversus plantae posterior_ (_t.p._).
This takes its origin from the plantar cartilage, widens as it
courses backwards and inwards to be inserted into the dorsal surface
of the _aponeurosis plantaris_; from this the tendons for the first
and second toes (_flexor dig. longus I_ and _II_) arise, thus there
is no direct connection between the muscular fibres of the two
muscles.
*b.* _M. transversus plantae anterior_ (_t.p_′.).
This muscle is covered by the last; broader anteriorly, it arises
from the calcaneum, and is inserted to the inner side of the last
muscle into the dorsal surface of the aponeurosis. This muscle, like
that just described, is not continued directly into the tendon of the
flexor of the toes, they cannot therefore be regarded as flexors of
the toes.
*141* to *149*. _Musculi lumbricales_ (Fig. 89 _l.1–5_).
(A.) From the posterior border of the _aponeurosis plantaris_ arise:--
(1) _M. lumbricalis digiti I_ (_l.1_).
*Dugès*, tendini-sous-phalangien de pouce, n. 185.
This is inserted into the anterior extremity of the proximal phalanx.
(*2*) _M. lumbricalis digiti II_ (_l.2_).
*Dugès*, tendini-sous-phal. du I doigt, n. 186 (and 187), double
according to Dugès.
Similarly inserted.
(*3* and *4*) _MM. lumbricales digiti III_ (_l.3_).
*Dugès*, tendini-sous-phal. du III doigt, n. 188, single according to
Dugès.
One of these (_l3_) is inserted into the anterior extremity of the
basal phalanx, the other (_l3_′) into a corresponding position on the
middle phalanx.
(*5*) _M. lumbricalis digiti IV._
*Dugès*, tendini-sous-phal. du IV doigt.
Inserted into the anterior extremity of the basal phalanx.
(B.) Arising from the tendons of the _flexor longus III_, _IV_, _V_:
(*6* and *7*) _MM. lumbricales digiti IV_ (_l.4_′. and _l.4_″.).
*Dugès*, tendini-sous-phalanginien du IV doigt, n. 201, 202.
The first (_l.4_′) is inserted into the posterior end of the basal
phalanx, the second (_l.4_″) in a similar position into the second
phalanx.
(*8*) _M. lumbricalis digiti V_ (_l.5._).
*Dugès*, tendini-sous-phalangien du V doigt, n. 203.
This arises from the tendon for the fifth toe, runs backwards as a
thin tendon alongside that of the flexor, and is inserted into the
middle phalanx.
_Special Muscles of the Separate Toes._
(I.) Muscles of the rudimentary great toe.
*150.* _M. abductor hallucis_ (Figs. 88 _a.h._, 90).
*Dugès*, tibio-sous-tarsien, n. 163.
This muscle arises from the inner border of the _aponeurosis
plantaris_, at the spot where the _m. plantaris_ is inserted, it may
therefore almost be regarded as a continuation of this muscle; it is
inserted into the anterior border of the rudimentary toe.
(II.) Muscles of the great and first toes.
*151.* _M. adductor longus digiti I_ (Figs. 89, 90 _ad.l1_).
*Dugès*, calcanéo-scaphoidien, n. 164.
This powerful muscle arises from the plantar surface of the calcaneum
and astragalus; its fibres converge towards a tendon lying in its
middle, which becomes free towards its posterior end; the tendon
passing inwards under the _ligamentum tarsi transversum_ through
a groove on the hinder extremity of the astragalus in an arched
direction, to be inserted into the _os naviculare_, which bears the
rudimentary great toe and the _os metatarsi I_.
(III.) Muscles of the first toe.
*152.* _M. abductor longus digiti I_ (Figs. 88 _al.1_, 90 _a.b.1_).
It takes its origin from the inner border of the _aponeurosis
plantaris_, and lies on the plantar surface of the _abductor
hallucis_. Its tendon runs in the hollow which the great toe forms,
and is inserted into the inner side of the _os metatarsi I_.
*153.* _M. flexor brevis digiti I_ (Fig. 90 _F.b.1_).
A small, thin muscle, which arises from the anterior extremity of
the _os metatarsi II_, and is inserted into the basal phalanx of the
first toe. In this small muscle, and also in the _m. lumbrical. dig.
V_ (Fig. 89 _l.5._), the nerve distribution may be very well seen.
*154.* _M. opponens dig. I_ (Fig. 90 _op_).
*Dugès*, sous-metatarso-phalangien du pouce, n. 192.
This is situated to the inner side of the preceding muscle, arises
from the _os metatarsi II_ somewhat narrow, widens in a fan-like
manner towards the _os metatarsi I_, into the anterior half of which
it is inserted.
(IV.) Muscles of the second toe.
*155.* _M. flexor metatarsi dig. II_ (Fig. 90 _F.m.2_).
*Dugès*, sous-tarso-metatarsien du II doigt.--*Klein*, extensor
metatarsi.
By a narrow origin from the hinder end of the calcaneum, posteriorly
this muscle becomes broader and is inserted, somewhat thinned out,
into the plantar surface of the second _os metatarsi_.
*156.* _M. flexor dig. II proprius_ (Fig. 90 _F.p.2_).
*Dugès*, sous-metatarso-phalangien, n. 194.
It arises from the plantar surface of the _os metatarsi II_, and
is inserted by a thin tendon into the plantar surface of the first
phalanx.
Dugès describes this and the analogous muscles of the third, fourth,
and fifth toes (_F.p.3_, _4_, _5_) as the _interossei plantares_, a
nomenclature which, to me, does not appear correct, as these muscles
lie entirely on the plantar surface, and do not adduct or abduct the
toes, but flex them.
(V.) Muscles of the third toe.
*157.* _M. flex. metatarsi dig. III_ (Ecker), (Fig. 90 _F.m.3_).
*Dugès*, sous-calcaneo-métatarsien du III doigt, n. 174.--
*Klein*, _extensor metatarsi_.
Like the corresponding muscle of the second toe (n. 155), this
arises by a small tendon from the hinder extremity of the calcaneum,
runs backwards and is inserted into the plantar surface of the _os
metatarsi III_. The greatest portion of the muscle lies beneath
the _m. transversus metatarsi_ (_tm_), the most anterior portion,
however, lies above this. Dugès has described this latter portion as
a special muscle (n. 176, metatarso-métatarsien du III), the same
description holds good for the second toe (n. 177, Dugès).
*158.* _M. flexor dig. III proprius_ (Ecker), (Fig. 91 _Fp3_).
*Dugès*, sous-métatarso-phalangien du III doigt, n. 195.
Like the corresponding muscle of the second toe, this arises from
the plantar surface of the _os metatarsi III_, and is inserted by a
thin tendon into the plantar surface of the anterior extremity of the
first phalanx.
[Illustration: Fig. 90.
Muscles of plantar surface of foot of _Rana esculenta_.
_a.b.1_ M. abductor longus digiti I.
_ab5_ M. abductor digiti V.
_ad.l.1_ M. adductor longus digiti I.
_a.h._ M. abductor hallucis.
_F.b.1_ M. flexor brevis digiti I.
_F.m.2_, _3_, _4_ M. flexores metatarsi II, III, IV.
_F.p.2_, _3_, _4_, _5_ MM. flexor. proprii digit. 2, 3, 4, 5.
_F.ph.3_, _4_, _4_′, _5_ MM. flexor. phalang. digit. 3, 4, 5.
_op_ M. opponens digiti I.
_t.m_′ }
_t.m_″ } MM. transversi metatarsi 1, 2, 3.
_t.m_‴ }
]
*159.* _M. flexor phalangum proprius digiti III_ (Ecker), (Fig. 91
_F.ph.3_).
*Dugès*, phalango-phalangien, n. 204.
This arises by tendon from the plantar surface of the basal phalanx,
and is inserted into the anterior extremity of the terminal phalanx.
(VI.) Muscles of the fourth toe.
*160.* _M. flexor metatarsi dig. IV_ (Fig. 91 _F.m.4_).
*Dugès*, métatarso-métatarsien, n. 175.
Similarly to the corresponding muscle of the third toe, this one
arises from the hinder extremity of the calcaneum, and is inserted
into the anterior portion of the plantar surface of the _os metatarsi
IV_, but not into the greater portion of this surface, as in the
second and third _os metatarsi_.
*161.* _M. flexor dig. IV proprius_ (Fig. 91 _Fp4_).
*Dugès*, sous-métatarso-phalangien du IV doigt (_interosseus
plantaris_), n. 196.
The origin and insertion are similar to those of the muscles of the
second and third toes.
[Illustration: Fig. 91.
Muscles of plantar surface of foot of _Rana esculenta_.
_a.b.1_ M. abductor longus digiti I.
_ab5_ M. abductor digiti V.
_ad.l.1_ M. adductor longus digiti I.
_a.h._ M. abductor hallucis.
_F.b.1_ M. flexor brevis digiti I.
_F.m.2_, _3_, _4_ M. flexores metatarsi II, III, IV.
_F.p.2_, _3_, _4_, _5_ MM. flexor. proprii digit. 2, 3, 4, 5.
_F.ph.3_, _4_, _4_′, _5_ MM. flexor. phalang. digit. 3, 4, 5.
_op_ M. opponens digiti I.
_t.m_′ }
_t.m_″ } MM. transversi metatarsi 1, 2, 3.
_t.m_‴ }
]
*162.* _M. flexor brevis dig. IV._
A small muscle, which arises with the _m. flexor brevis_ of the fifth
toe, from enlargement of _aponeurosis plantaris_, and is inserted
into the basal phalanx of the fourth toe.
*163.* _M. flexor phalangum proprius dig. IV anterior_ (Fig. 91
_F.ph.4_).
*Dugès*, phalango-phalanginien, n. 205.
It resembles the corresponding muscle of the third toe.
*164.* _M. flexor phalangum proprius posterior_ (Fig. 91 _F.ph.4_′).
*Dugès*, phalangino-phalangettien, n. 209.
This extends from the plantar surface of the second phalanx to the
anterior extremity of the third.
(VII.) Muscles of the small toe.
*165.* _M. abductor dig. V_ (Fig. 91 _a.b.5_).
*Dugès*, calcanéo-ex-métatarsien du digitule, n. 169.
This muscle arises from the hinder extremity of the calcaneum, and is
inserted into the outer surface of the fifth metatarsal.
*166.* _M. adductor dig. V_ (Fig. 89 _a.d.5_).
*Dugès*, sous-tarso-in-phalangien, n. 191.
This arises from the cartilage of the plantar aponeurosis, and is
inserted into the hinder end of the fifth metatarsal.
*167.* _M. flexor brevis dig. V_ (Fig. 89 _F.5_).
*Dugès*, sous-tarso-ex-phalangien, n. 190.
Arising from the same place as the preceding, it extends to the basal
phalanx.
*168.* _M. flexor dig. V. proprius_ (Fig. 91 _F.p._5).
(Analogues of Muscles, n. 156, 158, 161; see note at n.
156).--*Dugès*, sous-métatarso-phalangien, n. 197 (*_inteross.
plant._).
This muscle arises from the plantar and inner surfaces of the fifth
metatarsal, and is inserted into the basal phalanx.
*169.* _M. flexor phalangum proprius_ (Fig. 91 _F.ph.5_).
*Dugès*, phalango-phalanginien, n. 206.
Its origin and insertion are as in the corresponding muscles of the
second, third, and fourth toes, n. 159, 163, 164, 169.
*170* to *172*. _MM. interossei_ (Fig. 91 _t.m._).
*Dugès*, 1, 2, and 3, intermétatarsien, n. 170, 171, 172.
These are three muscles with their fibres arranged transversely,
which occupy the anterior portion of the spaces between the
metatarsals, and approximate these. The first arises (_tm_′) from the
edge of the plantar surface of the first metatarsal, and is inserted
into the corresponding part of the second: the second (_tm_″) passes
from this point to the third, and the third (_tm_‴) to the fifth.
B. _MUSCLES OF THE DORSAL SURFACE._
*173.* _M. flexor tarsi posterior_ (Ecker), (Fig. 92 _F.t._).
*Dugès*, péronéo-sus-astragal, n. 161.
This is a strong muscle, which has a narrow origin from the outer
side of the tibio-fibula, directly over the distal extremity, and is
inserted into the dorsal surface of the astragalus from the middle to
the distal extremity.
Muscles of the first toe.
*174.* _M. extensor longus dig. I_ (Fig. 92 _e.l.1_).
*Dugès*, calcanéo-sus-métatarsien du pouce, n. 166.
This lies to the outer side of and near the foregoing muscle; it
arises by a long, strong head from the middle of the calcaneum, runs
obliquely backwards and inwards to unite with a small head which
arises from the common epiphysis of the astragalus and calcaneum, in
common with the _m. extensor dig. II_. The muscle so formed passes
into a flat tendon to be inserted into the basal phalanx of the first
toe.
*175.* _M. extensor brevis dig. I_ (Fig. 92 _e.b.1_).
A small, short muscle which arises from the _os naviculare_ and is
inserted into the dorsal surface of the first metatarsal.
*176.* _M. abductor brevis dig. I_ (Fig. 92 _a.b.1_).
*Dugès*, ex-tarso-métatarsien du pouce, n. 168.
This small muscle is situated near the preceding; it arises from the
first bone of the supplemental toe, and is inserted into the inner
side of the first metatarsal.
Muscles of the second toe.
*177.* _M. extensor dig. II longus_ (Fig. 92 _e.l.2_).
*Dugès*, calcanéo-sus-phalangien du II doigt, n. 182.
This arises from the calcaneum, in common with the _m. extensor
longus_ of the third toe, and is inserted into the basal phalanx of
the second toe by a tendon.
*178.* _M. extensor dig. II brevis_ (Fig. 92 _e.b.2_).
*Dugès*, astragalo-sus-phalangien du II, n. 183.
This is partly covered by the preceding muscle: it arises from the
astragalus, and unites with the tendon of the preceding muscle.
Muscles of the third toe.
*179.* _M. extensor dig. III longus_ (Fig. 92 _e.l.3_).
*Dugès*, sus-astragalo-phalangien du médius, n. 199.
This arises with the _extensor longus_ of the second toe from the
calcaneum: its tendon unites with that of the following muscle.
*180.* _M. extensor dig. III brevis_ (Fig. 92 _e.b.3_).
*Dugès*, astragalo-sus-phalangien du médius, n. 181.
This muscle arises from the astragalus, and is inserted with the
tendon of the preceding muscle into the dorsal surface of the basal
phalanx.
[Illustration: Fig. 92.
Dorsal view of muscles of foot of _Rana esculenta_.
_a.b.1_ M. abductor brevis dig. I.
_e.b.1_ M. extensor brevis dig. I.
_e.b.2_ M. extensor brevis dig. II.
_e.b.3_ M. extensor brevis dig. III.
_e.b.4_ M. extensor brevis 1 dig. IV.
_e.b.4_′ M. extensor brevis 2 dig. IV.
_e.b.5_ M. extensor brevis dig. V.
_e.l.1_ M. extensor longus dig. I.
_e.l.2_ M. extensor longus dig. II.
_e.l.3_ M. extensor longus dig. III.
_e.l.4_ M. extensor longus dig. IV.
_e.l.5_ M. extensor longus dig. V.
_F.t_ M. flexor tarsi posterior.
_i.2_ to _i.10_ MM. interossei.
]
Muscles of the fourth toe.
*181.* _M. extensor longus dig. IV_ (Fig. 93 _e.l.4_).
*Dugès*, péroneo-sus-phalangien du IV, n. 178.
A narrow muscle arising in common with the _flexor tarsi inf._, but
external to it. It is inserted into the tendinous expansion on the
dorsum of the toe.
*182.* _MM. extensores dig. IV breves_ (Fig. 93 _e.b.4_ and
_e.b.4_′).
*Dugès*, calcanéo-sus-phalangien and sus-calcanéo-phalanginien, n.
179 and 198.
These two small muscles arise from the calcaneum: one is inserted
into the basal phalanx, the other, by means of a long thin tendon,
passes along with the tendon of the corresponding _m. interosseus_ to
the second phalanx, to which it is attached.
Muscles of the fifth toe.
*183.* _M. extensor dig. V longus_ (Fig. 93 _e.l.5_).
*Dugès*, calcanéo-sus-métatarsien, n. 165.
A strong muscle which covers almost the whole length of the
calcaneum; it arises from the anterior extremity of this bone,
runs backwards to the outer side of the dorsum of the foot, and is
attached to the outer surface of the fifth metatarsal.
*184.* _M. extensor dig. V brevis_ (Fig. 93 _e.b.5_).
*Dugès*, calcanéo-sus-phalangien du V, n. 180.
This is a long thin muscle, which, together with the muscle last
described, arises from the calcaneum and is inserted into the basal
phalanx of the fifth toe.
*185.* _M. abductor dig. V brevis_ (Fig. 93 _i.10_).
This, the last _m. interosseus_, arises from the outer side of the
fifth metatarsal, and is inserted into the hinder extremity of the
second phalanx of the same toe.
*186* to *195*. _MM. interossei dorsales_ (Fig. 93 _i.1_ to _i.10_).
First toe.
(1) The analogue of the first _m. interosseus_ is the _m. abductor
brevis dig. I_ (_a.b.1_).
(2) The second _m. interosseus_ (_i.2_) arises from the outer side
of the first metatarsal, and is inserted into the outer surface of
the second phalanx of the same toe, dorsally to the _m. opponens_ and
_flexor brevis dig. I_.
Second toe.
(3) The third _m. interosseus_ (_i.3_) takes origin from the anterior
part of the outer surface of the first metatarsal by a thin tendon;
it is inserted into the inner surface of the second phalanx by a
similar tendon.
(4) The fourth _m. interosseus_ (_i.4_) arises from the outer side of
the second metatarsal, and is inserted into the outer surface of the
second phalanx.
Third toe.
(5) The fifth _m. interosseus_ arises from the outer surface of the
second metatarsal, and is inserted by a thin tendon into the inner
surface of the second phalanx of the same toe.
(6) The sixth arises from the outer surface of the third metatarsal,
and is inserted laterally by a thin tendon into the hinder extremity
of the second phalanx of the same toe.
[Illustration: Fig. 93.
Dorsal view of muscles of foot of _Rana esculenta_.
_a.b.1_ M. abductor brevis dig. I.
_e.b.1_ M. extensor brevis dig. I.
_e.b.2_ M. extensor brevis dig. II.
_e.b.3_ M. extensor brevis dig. III.
_e.b.4_ M. extensor brevis 1 dig. IV.
_e.b.4_′ M. extensor brevis 2 dig. IV.
_e.b.5_ M. extensor brevis dig. V.
_e.l.1_ M. extensor longus dig. I.
_e.l.2_ M. extensor longus dig. II.
_e.l.3_ M. extensor longus dig. III.
_e.l.4_ M. extensor longus dig. IV.
_e.l.5_ M. extensor longus dig. V.
_F.t_ M. flexor tarsi posterior.
_i.2_ to _i.10_ MM. interossei.
]
Fourth toe.
(7) The seventh _m. interosseus_ (_i.7_) arises by a thin tendon from
the hinder extremity of the astragalus, and by fleshy fibres from
the hinder extremity of the fourth metatarsal; it is inserted by a
thin tendon into the inner surface of the second phalanx of the same
toe.
[Illustration: Fig. 94.
Dorsal view of muscles of foot of _Rana esculenta_.
_a.b.1_ M. abductor brevis dig. I.
_e.b.1_ M. extensor brevis dig. I.
_e.b.2_ M. extensor brevis dig. II.
_e.b.3_ M. extensor brevis dig. III.
_e.b.4_ M. extensor brevis 1 dig. IV.
_e.b.4_′ M. extensor brevis 2 dig. IV.
_e.b.5_ M. extensor brevis dig. V.
_e.l.1_ M. extensor longus dig. I.
_e.l.2_ M. extensor longus dig. II.
_e.l.3_ M. extensor longus dig. III.
_e.l.4_ M. extensor longus dig. IV.
_e.l.5_ M. extensor longus dig. V.
_F.t_ M. flexor tarsi posterior.
_i.2_ to _i.10_ MM. interossei.
]
(8) The eighth _m. interosseus_ (_i.8_) takes its origin from the
outer surface of the fourth metatarsal and from the inner surface of
the fifth: it is inserted into the hinder extremity of the second
phalanx.
Fifth toe.
(9) The ninth _m. interosseus_ (_i.9_) arises from the inner surface
of the fifth metatarsal, and is inserted into the hinder extremity of
the second phalanx.
(10) The tenth _m. interosseus_ has already been described as the
_abductor digiti V brevis_ (Fig. 94 _i.10_).
If we take the fourth toe as the axis of movement, the first, third,
fifth, seventh, eighth, and tenth _mm. interossei_ will abduct from
an imaginary line which runs through this toe. The second, fourth,
sixth, and ninth will adduct towards this line. If we compare them
with those of man (in whose case the second toe affords the central
line), those of the first group must be regarded as _mm. interossei
dorsales_, of the latter as _plantares_. Dugès holds all these
_interossei_ (with the exception of the first, _abductor brevis dig.
I_) to be _mm. interossei dorsales_ (métatarso-sus-phalangettiens, n.
210, 211, 212, 214, 215, 216, 218, 219). Those which I have described
as _flexores proprii digitorum_, he regards as _interossei volares_.
V. MUSCLES OF THE SKIN.
*196.* _M. cutaneus pectoris_ (Fig. 95 _cp_).
*Dugès*, abdomino-guttural, n. 53.--*Klein*,
abdomino-cutaneus.--*Zenker*, subcutaneus pectoris.
This is an elongated quadrangular muscle, attached by its hinder
margin to the side of the xiphisternum, and to the superficial
surface of the aponeurosis of the _m. obliquus externus_. The fibres
course forwards and slightly outwards to be inserted, at a very acute
angle, into the skin: lying between the two muscles and attached
to them on either side is a thin fascia, which, together with the
muscles and the _septum thoracicum_, assists in closing a triangular
space between these structures and the deeper muscles.
The thinness and transparency of this muscle render it especially
suitable for the investigation of nerve-terminations[49].
[Footnote 49: Kölliker, Mikrosk. Anatomie, 1866, vol. II. 1,
p. 247; Reichert, Müller’s Archiv, 1851, p. 29, Pl. I; Kölliker,
Untersuchungen über die letzten Endigungen der Nerven in den Muskeln
des Frosches; Leipzig, Engelmann, 1862.]
[Illustration: Fig. 95.
Pectoral region of _Rana esculenta_.
_cp_ M. cutaneus pectoris.
_p_″ Port. abdominalis of the m. pectoralis.
]
*197.* _M. cutaneus dorsi_ (Fig. 96 _cd_).
*Dugès*, pubio-dorso-cutané, n. 56.--*Zenker*, _cutaneus iliacus_.
This muscle has a narrow origin in the space between the muscles of
the belly and of the thigh, and is here inserted into the fasciae,
which are attached to the pubic symphysis; it passes inwards and
upwards to the outer side of the anterior insertion of the _m. rectus
femoris anticus_, then widens and is inserted by diverging fibres
into the inner surface of the skin of the hinder portion of the back.
*198.* _M. coccygeo-cutaneus._
*Dugès*, coccy-dorso-cutanés, n. 57.
The muscular fibres which Dugès has described under this name, lie
covered by the _m. pyriformis_, behind the _m. coccygeo-iliacus_,
etc., and above the muscles of the rectum. They arise from the hinder
extremity of the urostyle: they appear to be connected with the
rectal muscles, and pass outwards to be attached to the skin.
Among the cutaneous muscles may perhaps be included the _m.
submaxillaris_ (p. 62).
The fibrils passing from the flexor tendons to the warty bodies on
the plantar surface of the toes are described[50] with the skin
(p. 373).
[Footnote 50: Compare Klein, Beiträge zur Anatomie der ungeschwänzten
Batrachier (R. temporaria, L.): Jahreshefte des Vereins für
vaterländische Naturkunde in Württemberg, 1850, p. 72.]
[Illustration: Fig. 96.
Hind portion of back and thigh of _Rana esculenta_.
_cd_ M. cutaneus dorsi.
_cx._ Coccyx.
_gl._ M. glutaeus.
_H_ Skin reflected to left side.
_oc_ M. obliquus externus.
_rf_ M. rectus femoris anterior.
_sm_ M. semimembranosus.
_v.e_ M. vastus externus.
]
SECTION III.
THE NERVOUS SYSTEM.
THE NERVOUS SYSTEM.
LITERATURE.
*Ahlborn, F.*, Ueber die Bedeutung der Zirbeldrüse. Zeit. f. wiss.
Zool. 1884. Vol. XL, pp. 331–337.
*Allen, H.*, The Spinal Cord in Batrachia and Reptilia. Proc. Acad.
Nat. Sci. Philadelphia. 1883, pp. 56–57.
*Arndt, A. W.*, Untersuchungen über die Ganglienkörper des Nervus
sympathicus. Arch. f. mikrosk. Anat. 1874. Vol. X, pp. 208–241.
*Arndt, R.*, Untersuchungen über die Endigung der Nerven in den
quergestreiften Muskelfasern. Arch. f. mikrosk. Anat. 1873.
Vol. IX, p. 481.
*Arndt, R.*, Untersuchungen über die Ganglienkörper der
Spinalganglien. Arch. f. mikrosk. Anat. 1875. Vol. XI, p. 140.
*Arnold, J.*, Zur Histologie der Lungen des Frosches. Virchow’s Arch.
1863. Vol. XXVIII, p. 433.
*Arnold, J.*, Histologische Verhältnisse des Frosch-Sympathicus.
Centralbl. f. d. med. Wiss. 1864, p. 657.
*Arnold, J.*, Ueber die feineren histologischen Verhältnisse der
Ganglienzellen in dem Sympathicus des Frosches. Virchow’s Arch.
1865. Vol. XXXII, p. 1.
*Arnold, J.*, Die Spinalfasern im Sympathicus des Frosches. Arch. f.
Anat. und Physiol. 1866, p. 398.
*Arnold, J.*, Das Gewebe der organischen Muskeln. Leipzig, 1869; and
Chap. IV in Stricker’s Handbook.
*Arnstein, C.*, and *Gonjaew*, *K.*, Ueber die Nerven des
Verdauungskanals. Bericht. f. Physiol. u. Histologie. Mittheilung.
aus. d. 4 Vers. wissensch. Naturforsch. zu Kasan. Pflüger’s Arch.
d. ges. Physiol. 1874. Vol. VIII, pp. 614–615.
*Aubert, H.*, Die Innervation der Kreislaufsorgane, Hermann’s
Handbuch der Physiologie. Leipzig, 1880. Vol. IV, Pt. I, p. 377.
*Axmann*, De Gangliorum systematicis structura persitiori eiusque
functionibus. Berolini, 1847.
*Axmann*, Beiträge zur mikroskopischen Anatomie und Physiologie des
Ganglien-nervensystems. 1853, p. 20.
*Baculo, B.*, Nuove ricerche intorno l’apparechio ganglionare
intrinseco dei cuori linfatici. Naples, 1885.
*Balfour, F. M.*, Treatise on Comparative Embryology. London, 1880.
*Balfour, F. M.*, Handbuch der vergleichenden Embryologie. Aus dem
Englischen von B. Vetter. Jena, 1880.
*Beale, L. S.*, On the Structure and Formation of the so-called
Apolar, Unipolar, and Bipolar Nerve-cells of the Frog. Phil.
Trans. 1863, p. 543. (Hyla arborea.)
*Beale, L. S.*, Further observations in favour of the view that
nerve-fibres never end in voluntary muscle. Proc. Roy. Soc. 1863.
Abstract in Quart. Journ. Micros. Sci. 1863. Vol. XII, p. 668.
*Beale, L. S.*, New observations upon the structure, etc. of certain
nervous centres. Proc. Roy. Soc. 1860. Vol. III.
*Beale, L. S.*, On the Distribution of Nerves to the elementary
fibres of Striped Muscle. Phil. Trans. 1864, p. 611.
*Beale, L. S.*, Of very fine nerve-fibres ramifying in certain
fibrous tissues and trunks, and plexuses consisting entirely
of very fine nerve-fibres in the bladder of the frog. Beale’s
Archives of Medicine, 1864. Vol. IV, pp. 19–251.
*Beard, J.*, The Ciliary or Motor-oculi ganglion and the Ganglion
of the ophthalmicus profundus in Sharks. Anatom. Anzeiger. 1887.
Vol. II, p. 565.
*Beck, K.*, Zur Kenntniss der Herznerven. Arch. f. mik. Anat. 1885.
Vol. XXIV, pp. 11–19.
*Bellonci, G.*, Intorno alla struttura e alle connessioni dei
lobi olfattorii negli arthropodi superiori e nei vertebrati.
Atti Accad. Lincei Ann. 279 Mem. Accad. Bologna, Vol. XIII,
pp. 555–564: and in Arch. Ital. Biol. 1883; Vol. III, pp. 191–196.
*Bellonci, G.*, Sulla terminazione centrale del nervo ottico nei
mammiferi. Mem. Accad. Bologna, Vol. VI, pp. 199–205: and in Arch.
Ital. Biol. 1884, Vol. VI, pp. 405–411.
*Bidder, F. H.*, Die Endigungsweise der Herzzweige des N. vagus beim
Frosch. Arch. f. Anat. u. Physiol. 1839, p. 1.
*Bidder, F. H.*, Zur Lehre von dem Verhältniss der Ganglienkörper
zu den Nervenfasern. Nebst einem Anhange von Dr. A. W. Volkmann.
Leipzig, 1847.
*Bidder, F. H.*, Zur Lehre vom Verhalten der Ganglienkörper, u. s. w.
Leipzig, 1847.
*Bidder, F. H.*, Ueber functionelle verschiedene und räumlich
getrennte Nerven-centra im Froschherzen. Arch. f. Anat. u.
Physiol. 1852, p. 163.
*Bidder, F. H.*, Endigungsweise der Herzzweige des N. vagus beim
Frosch. Arch. f. Anat. und Physiol. 1868, p. 1.
*Bidder, F. H.*, Zur näheren Kenntniss des Froschherzens und seiner
Nerven. Arch. f. Anat. u. Physiol. 1866, p. 1.
*Bidder, F. H.*, and *Kupffer*, Untersuchungen über die Textur des
Rückenmarks. Leipzig, 1857.
*Bidder, F. H.*, and *Volkmann*, *A. W.*, Die Selbständigkeit des
sympathischen Nervensystems, durch anatomische Untersuchungen
nachgewiesen. Leipzig, 1842.
*Bidder* and *Gregory*, Beiträge zur Physiologie der Herzbewegung
beim Frosche. Dorpat, 1865.
*Bikfalvi, K.*, Ueber die Hornscheide der markhaltigen Nervenfasern.
Orvoster-meszettudomanyi Ertesito, 1884, p. 133. Abstract in
Centralbl. f. d. med. Wiss. 1886, p. 34.
*Biroege, E. A.*, Die Zahl der Nervenfasern u. der motor.
Ganglienzellen im Rückenmark des Frosches. Arch. f. Anat. u.
Physiol. 1882. Physiol. Abth., p. 435.
*Bischoff*, Nervi accessorii Willisii anatomia et physiologia.
Heidelberg, 1832.
*Blasius, G.*, Gerardi Blasii Anatomia Animalium. Amstelodami, 1681.
*Blattmann, A.*, Mikrosk. anatom. Darstellung der Centralorgane des
Nervensystems bei den Batrachiern. Dissert. Zürich, 1850.
*Boll, F.*, Studj sulle immagini microscopiche della fibra nervosa
midollare. Atti della R. accademia dei Lincei, 1876–1877. Vol. II.
*Boll, F.*, Ueber Zersetzungsbilder der markhaltigen Nervenfasern.
Arch. f. Anat. u. Physiol. 1877, p. 288.
*Bojanus*, Testudinis anatomia. 1819.
*Bosse*, De ganglior. spinal. vi in nutr. radic. poster. nervor.
spinal. Dissert. 1859.
*Boveri, T.*, Beiträge zur Kenntniss der Nervenfasern. Abhandl. d.
bayr. Akad. d. Wiss. 1885. Vol. XV, p. 421.
*Bremer, D. L.*, Die Nerven der Capillaren, der kleinen Arterien und
Venen. Arch. f. mik. Anat. Vol. XXI. 1882, p. 663.
*Bremer, L.*, Ueber die Muskelspindeln sowie über Structur,
Neubildung u. Innervation der quergestreiften Muskelfaser.
Waldeyer’s Arch. 1883. Vol. XXII, p. 2.
*Bremer, L.*, Ueber die Endigungen der markhaltigen und marklosen
Nerven im quergestreiften Muskel. Arch. f. mikrosk. Anat. 1882.
Vol. XXI, p. 165.
*Brenner, A.*, Ueber das Verhältniss des nervus laryngeus inferior
vagi zu einigen Aortenvarietäten des Menschen und zu dem
Aortensystem der durch Lungen athmenden Wirbelthiere überhaupt.
His u. Braune’s Arch. 1883, pp. 373–397.
*Budge, J.*, Ueber den Verlauf der Nervenfasern im Rückenmark des
Frosches. Arch. f. Anat. u. Physiol. 1844, p. 160.
*Budge, J.*, Ueber die Bewegung der Iris. (Concerning ganglia of
motor-oculi, p. 36.)
*Budge, J.*, Wagner’s Handwörterb. d. Physiologie. 1846. Vol. III,
p. 451.
*Burdon-Sanderson, J.*, Circulation of the Blood. Handbook for the
Physiological Laboratory. London, 1873.
*Calberla, E.*, Ueber die Endigungsweise der Nerven in den
quergestreiften Muskeln bei Amphibien. Zeit. f. wiss. Zool. 1874.
Vol. XXIV, p. 164.
*Calberla, E.*, Studien über die Entwicklung der quergestreiften
Muskeln und Nerven der Amphibien und Reptilien. Arch. f. mik.
Anat. 1875. Vol. XI, p. 442.
*Carus*, Versuch einer Darstellung des Nervensystems und Gehirns.
Leipzig, 1814.
*Champness, F.*, The septum atrium of the Frog and Rabbit. Journ. of
Anat. and Physiol. 1874.
*Christmas-Dirckinck-Holmfeld, J.*, Experimentaluntersuchungen über
den Bau der Regio olfactoria. Nord. med. ark. 1883. Vol. XV, No. 3.
*Ciaccio, G. V.*, On the nerves of the Cornea, and their distribution
in the corneal tissue of man and animals. Proc. Roy. Soc. 1863.
Abstract in Trans. Micros. Soc. London, 1863. Vol. XI, pp. 77–93.
*Ciaccio, G. V.*, On the distribution of nerves to the skin of the
frog, with physiological remarks on the ganglia connected with the
cerebro-spinal nerves. Quart. Journ. Micros. Sci. 1864. Vol. IV,
pp. 15–31.
*Ciaccio, G. V.*, Intorno alla minuta fabbrica delle pelle Rana
esculenta. Giornale di Scienze naturali ed economiche. Palermo,
1866. Vol. II, p. 103.
*Clarke, J. Lockhart*, Ueber den Bau des Bulbus olfactorius und der
Geruchsschleimhaut. Zeit. f. wiss. Zool. 1862. Vol. XI, p. 31.
*Cornil* and *Ranvier*, A Manual of Pathological Histology. London,
1880, p. 359, Fig. 199 (Ganglia of heart).
*Courvoisier, G.*, Beobacht. über den sympathischen Gränzstrang.
Arch. f. mik. Anat. 1866. Vol. II, p. 13.
*Courvoisier, L. G.*, Ueber die spinalen und sympathischen Zellen des
Frosches. Centralbl. f. d. med. Wiss. 1867, p. 897.
*Courvoisier, G.*, Ueber die Zellen der Spinalganglien, sowie des
Sympathicus beim Frosch. Arch. f. mikrosk. Anat. 1868. Vol. IV,
p. 125.
*Cuvier*, Leçons d’anatomie comparée. 2nd Edit. Vol. II.
*Cyon*, Ueber die Nerven des Peritoneum. Berichte über die
Verhandlungen d. königl. sächs. Gesellsch. d. Wissensch. zu
Leipzig. Math.-physik. Classe. 1868. Vol. XX, p. 119.
*Czermak, J. N.*, Ueber die Hautnerven des Frosches. Arch. f. Anat.
u. Physiol. 1849, p. 252. Leipzig, 1869.
*Czermak, J. N.*, Ueber die Herznerven des Frosches, Rana temporaria.
Arch. f. Anat. u. Physiol. 1851, p. 160.
*v. Darkschewitsch, L.*, Zur Anatomie der Glandula pinealis. Neurol.
Cent. Bl. 1886. Vol. V, p. 29.
*v. Deen*, De differentia et nexu inter nervos vitae animalis et
vitae organicae. Diss. inaugur. Lugduni-Bat., 1834.
*v. Deen*, Over de zijdelingsche Takken dar swervende zenuw van
den Proteus anguineus, aus Bijdragen tot de Naturkundige.
Wettenschappen, 1834.
*v. Deen*, Ueber den Ramus lateralis n. vagi bei den Batrachiern.
Arch. f. Anat. u. Physiol. 1834, p. 477 (abstract from Diss.
inaugur. De differentia et nexu inter nervos vitae animalis et
vitae organicae). Lugduni-Bat.
*Deiters, O.*, Untersuchungen über Gehirn und Rückenmark.
Braunschweig, 1865.
*Denissenko, G.*, Zur Frage über den Bau der Kleinhirnrinde bei
verschiedenen Klassen von Wirbelthieren. Arch. f. mikrosk. Anat.
1877. Vol. XIV, p. 203.
*Dietl, M. J.*, Beobachtungen über Theilungsvorgänge an Nervenzellen.
Wiener Sitzungsber. 1874. Vol. LXIX, Pt. III, p. 71.
*Dietl, M. J.*, Casuistische Beiträge zur Morphologie der
Nervenzellen. Wiener Sitzungsber. 1874. Vol. LXIX, Pt. III, p. 80.
*Dogiel, J.*, Die Ganglienzellen und Nerven des Herzventrikels beim
Frosche. Arch. f. mikrosk. Anat. 1877. Vol. XIV, p. 470.
*Dogiel, J.*, Die Ganglienzellen des Herzens bei verschiedenen
Thieren und beim Menschen. Arch. f. mikrosk. Anat. 1877.
Vol. XVII, p. 471.
*Dogiel, J.*, Die Nervenzellen und Nerven des Herzventrikels beim
Frosche. Arch. f. mikrosk. Anat. 1882. Vol. XXI, p. 21.
*Duméril, A. M. C.*, and *Bibron, G.*, Erpétologie générale ou
histoire naturelle complète des reptiles. Paris, 1841.
*Eberth*, Untersuchungen zur normalen und pathologischen Anatomie der
Froschhaut. Leipzig, 1869.
*Ecker, A.*, Icones physiologicae. Leipzig, 1851 to 1859.
*Eckhard, C.*, Beiträge zur Anatomie und Physiologie. Giessen, 1860.
Vol. II.
*Eckhard, C.*, Experimentale Physiologie des Nervensystems. Giessen,
1867, p. 208 (Ganglion cells of heart).
*Edinger, L.*, Nachtrag zu dem Bericht über Leistungen auf dem
Gebiete der Anatomie des Centralnervensystems. Schmidt’s Jahresb.
1887.
*Egorow, W.*, Ueber die Nervenzellen der Lungen. Centralbl. f. med.
Wiss. 1879. Vol. XVII, p. 305.
*Eichholtz*, De piscium atque amphibiorum nudorum lobis opticis atque
olfactoriis. Berolini, 1841.
*Engelmann, T. W.*, Zur Physiologie des Ureter. Pflüger’s Arch. f. d.
ges. Physiol. 1869. Vol. II, p. 243. (Treats also of histological
details of frog’s bladder.)
*Engelmann, T. W.*, Ueber die Discontinuität des Axencylinders und
den fibrillären Bau der Nervenfasern. Pflüger’s Arch. f. d. ges.
Physiol. 1880. Vol. XXII, p. 1.
*Engelmann, T. W.*, Der Bulbus aortae des Froschherzens. Pflüger’s
Arch. f. d. ges. Physiol. 1882. Vol. XXIX, p. 425.
*Fischer, E.*, Ueber die Endigung der Nerven im quergestreiften
Muskel der Wirbelthiere. Arch. f. mik. Anat. 1876. Vol. XIII,
pp. 365–390.
*Fischer, J. G.*, Amphibiorum nudorum neurologiae specimen primum.
Berlin, 1843; and Arch. f. Anat. u. Physiol. 1844, p. 57.
*Fowelin, C.*, De causa mortis post nervos vagos dissectos instantis.
Inaug. Dissert. Dorpati, 1851.
*Frenkel, S.*, Nerv und Epithel am Froschlarvenschwanze. Arch. f.
Anat. u. Physiol. 1886. Physiol. Abth., p. 405.
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THE NERVOUS SYSTEM.
I. THE CENTRAL NERVOUS SYSTEM.
_(Re-written by the translator.)_
A. THE SPINAL CORD (Fig. 97).
*1.* *External form.* The spinal cord is, in comparison with the
brain, somewhat small; the two organs are directly continuous, and
present no distinct line of demarcation: the point of origin of
the first spinal nerve is, therefore, arbitrarily accepted as the
anterior limit of the spinal cord; posteriorly it terminates in the
_filum terminale_.
The spinal cord is flattened dorso-ventrally, and is constricted at
a point (_pars media_, Reissner) somewhat anterior to its middle: in
consequence of this constriction the cord has two enlargements; an
anterior smaller, and a posterior larger (_intumescentiae anterior v.
posterior_), from which arise the nerves of the brachial and lumbar
plexuses respectively. At about the sixth or seventh vertebra, the
hinder enlargement diminishes rather abruptly to form the so-called
_conus medullaris_; this is continued into the _filum terminate_,
which enters the cavity of the urostyle. The hinder portion of the
lumbar nerves forms a _cauda equina_, the constituent nerves of which
surround the _filum terminale_.
A *dorsal longitudinal fissure* (_sulcus longitudinalis superior_)
is well marked in the middle line of the dorsal surface of the
posterior enlargement; anteriorly and posteriorly it rapidly fades
away, its position being merely indicated by a small amount of
connective-tissue and a blood-vessel.
The *ventral longitudinal fissure* (_sulcus longitudinalis inferior_)
is well marked throughout the length of the cord. Neither fissure
can be traced in the hinder part of the _conus medullaris_ or in the
_filum terminale_.
Ten pairs of nerves arise from the spinal cord, each nerve arising
by two roots, a ventral and a dorsal (anterior and posterior), from
points near the ventral and dorsal longitudinal sinuses respectively:
the two roots unite at their point of exit from the vertebral canal
through the intervertebral foramen; each dorsal root possesses a
ganglion.
[Illustration: Fig. 97.
The nervous system of _Rana esculenta_, from the ventral surface.
(From Icones physiologicae by A. Ecker. Pl. XXIV, Fig. 1.)
_F_ Facial nerve.
_G_ Ganglion of pneumogastric nerve.
_He_ Cerebral hemisphere.
_Lc_ Optic tract.
_Lop_ Optic lobe.
_M_ Boundary between medulla oblongata and spinal cord.
_M1–10_ Spinal nerves.
_MS_ Connection between fourth spinal nerve and
sympathetic chain.
_N_ Nasal sac.
_Ni_ Sciatic nerve.
_No_ Crural nerve.
_o_ Eyeball.
_S_ Trunk of sympathetic.
_S1–10_ Sympathetic ganglia.
_Sm_ Rami communicantes of sympathetic.
_Sp_ Continuation of sympathetic into head.
_I_ Olfactory nerve.
_II_ Optic nerve.
_III_ Motor oculi nerve.
_IV_ Trochlear nerve.
_V_ Trigeminal and facial nerves.
_Va_ Ramus ophthalmicus of trigeminal.
_Vc_ Ramus maxillo-mandibularis of trigeminal.
_Vd_ Mandibular branch of trigeminal.
_Ve_ Hyomandibular branch of facial.
_Vg_ Gasserian ganglion.
_Vs_ Upper end of sympathetic trunk in connection with
Gasserian ganglion.
_VI_ Abducens nerve.
_VII_ Facial nerve.
_VIII_ Auditory nerve.
_X_ Glossopharyngeal and pneumogastric nerves.
_X1_ Ramus anterior of glossopharyngeal.
_X2_ Ramus Posterior of glossopharyngeal.
_X3–4_ Branches of pneumogastric.
]
*2.* *Internal structure.* As in other vertebrates, the spinal cord
consists of white and grey matter, the latter being surrounded by
the former; the relative amount of the one to the other varies in
different parts of the cord.
A *transverse* section of the cord presents the same general
characteristics as a similar section from a bird or mammal. The grey
matter lies in the middle, surrounding the central canal, and is
prolonged into each half of the section by ventral and dorsal horns
or _cornua_. The grey matter is surrounded by the white, but is not
so sharply marked off from this in amphibia as in birds and mammals.
A section through the *anterior enlargement* is almost quadrangular
in outline, and somewhat broader below than above; the ventral
longitudinal fissure is well marked and deep, while the dorsal is
indistinct. The dorsal horns are narrow and short, the ventral longer
and much broader. The space between the dorsal horns is narrow and
deep, that between the ventral shallow; the outer boundary of the
grey matter is almost straight, and the central canal is placed above
the centre of the section.
In the *constricted portion* of the cord (_pars media_) the relative
proportion of the white matter is increased at the expense of the
grey; the horns are less distinct, the dorsal being directed outwards
and the ventral somewhat flattened. The central canal is in the
centre of the section.
The *posterior enlargement* shows the ventral horns projecting
outwards, very much enlarged, and approaching the periphery; the
space between them is semilunar. The dorsal horns are well developed,
especially at their upper parts; the space between them is narrow and
deep. The outer margin of the grey matter is again nearly a straight
line. The central canal is below the centre of the section.
The arrangement of the parts in the _conus medullaris_ approaches
that in the _pars media_: the horns are much diminished in size, and
posteriorly they entirely disappear, the ventral horns persisting
longer than the dorsal. The central canal approaches the lower
surface.
No cornua can be recognised in the _filum terminale_ behind the
origin of the last pair of spinal nerves. The grey matter has here
a circular outline, with the exception of a very slight indentation
below; the white matter is almost absent: the central canal is on the
lower border of the section in the anterior part, while posteriorly
it occupies almost the entire space below the _pia mater_.
The *Central Canal* lies in the median line, and always presents a
distinct lumen; in the two enlargements this lumen forms a vertical
ellipse[51], while in the _pars media_ it is circular. The canal is
lined by a single layer of ciliated columnar epithelium, the cells
of which are usually conical, with their bases directed towards the
lumen; but other forms may be noticed. These cells average about
0·040 mm. in length and about 0·002 mm. in width at their broadest
part. The peripheral extremities of the cells have processes, which,
in the case of the cells above and below the cord, may often be
traced as far as the _pia mater_; the processes of the lateral cells
are less distinct and seem to be shorter. Anteriorly the central
canal opens into the floor of the fourth ventricle. The termination
of the central canal, posteriorly, has been described by Masius and
Vanlair. According to these observers, the canal towards the hinder
end of the _filum terminale_ increases very gradually in width, until
its epithelial cells are immediately underneath the _pia mater_,
its walls then converge somewhat more sharply to close the cavity.
From the point where the canal commences to increase in width, a
change takes place in its epithelial wall, which, instead of having a
single layer of cells, now possesses two to three layers; towards the
posterior end it is again thinned out to a single layer.
[Footnote 51: v. Kölliker states that the lumen is everywhere
circular.]
The *grey matter* varies in different parts of the cord and
in different parts of the same section. In a section through
the anterior enlargement a portion of the grey matter, placed
immediately above the central canal, is easily distinguished by its
vertically-placed, elliptical outline, and by its transparency: it
is known as the _substantia reticularis_. It consists of a mesh-work
of branched cells, through which course distinctly contoured fine
commisural fibres which are derived chiefly from the dorsal cornua,
the vertical from the epithelial cells of the roof of the central
canal. In a series of sections the _substantia reticulosa_ may be
seen to originate indistinctly in the most anterior part of the cord;
in the anterior enlargement it already possesses the elliptical form
mentioned, and in the _pars media_ it commences to send off lateral
processes to either side. In the posterior enlargement it reaches
its greatest absolute development, as it here surrounds the central
canal; while further backwards it encroaches until, together with the
remaining grey matter, it constitutes almost the whole of the _filum
terminale_.
Immediately underneath the central canal is a narrow band, which
immediately connects the grey matter of the two sides; above it is
bounded by the epithelium of the central canal, below by medullated
fibres. This _septum medium_ (Reissner) may be traced backwards from
the anterior extremity of the cord to the posterior enlargement. It
consists chiefly of transverse fibres, together with vertical fibres
derived from the epithelial cells on the floor of the canal, and
like the _substantia reticulosa_, is distinguished by its greater
transparency from the rest of the grey matter.
The grey matter consists of connective-tissue and nervous elements,
which are very intimately united; each of these elements including
its special cells and fibres. The *nerve-cells* vary much in size and
appearance. A prominent group of large cells in the ventral cornua,
the *lateral group* (Stieda), is very conspicuous. The individual
cells are seldom rounded, but are usually spindle-shaped or angular,
and each possesses one to five processes, which may often be traced
through considerable distances. These cells have an average length of
0·040 mm., and are about 0·016 mm. broad; they are somewhat larger
in the anterior enlargement than in the posterior, and are also
more numerous in a section from the anterior enlargement than in a
section from the posterior. In the terminal filament they gradually
disappear. Some of their processes are continued into the lateral
columns (Köppen).
Smaller, spindle-shaped or triangular cells are scattered irregularly
throughout the grey matter, without forming distinct groups, though
for descriptive purposes those of the centre have been named the
*central group*. In a stained, transverse section of the cord are
seen numerous *nuclei*; these undoubtedly belong both to small
nerve-cells and to connective-tissue cells, but except under the
most favourable conditions the two are indistinguishable. The larger
nerve-cells present the usual characters of nerve-cells: more or
less granular contents, nucleus, well-marked nucleolus, more or less
marked fibrillation; their processes are usually more homogeneous.
The cells are frequently pigmented.
The *processes* of the cells belonging to the lateral group radiate
in all possible directions, but certain well-marked processes
directed towards the middle line can always be made out. From
the lowest part of this group a few processes may be traced into
the ventral roots. The small cells seem to be chiefly arranged
vertically, although their processes radiate in all directions
(Stieda).
The *Fibres of the grey substance* are nearly all non-medullated.
They may be traced in all directions, but the best-marked groups are
either vertical or transverse. The vertical fibres appear to arise
from the central grey matter, and to ascend in larger or smaller
bundles towards the periphery. The transverse fibres are arranged
chiefly in the two commissures: the dorsal commissure (_commissura
superior_) is the smaller; the fibres are parallel, and show no trace
of decussation; externally they radiate in various directions to
the dorsal horns. The ventral commissure is composed of two layers,
the upper grey (_commissura inferior grisea_), the lower white
(_commissura inferior alba_): both are interrupted by the _septum
medium_. A well-marked decussation of the fibres is seen in the
middle line; the exact mode of termination of these fibres has not
been made out, but many appear to communicate with the large cells of
the ventral horns.
The *white matter* consists chiefly of longitudinal, medullated
fibres, in which various columns may be distinguished. The dorsal
columns are separated from the lateral by a process of neuroglia,
continued from the general investment of neuroglia lying under the
_pia mater_. The line of separation between the lateral and ventral
columns is not well marked; it is about the line which would be
formed by prolonging the ventral horns to the surface.
The fibres vary in size, and fibres of all sizes may be found in any
particular part of a transverse section; still the fibres of the
ventral columns have an average greater diameter than those of the
lateral columns, and the fibres of the dorsal columns are finer than
those of the lateral. The largest fibres of the ventral column are
placed near the ventral fissure and on its lower border; they attain
their greatest development in the posterior enlargement; these fibres
frequently contain two or three axis-cylinders each. Köppen suggests
that they may represent the _formatio reticularis_ of higher animals.
In the lateral columns the larger fibres are placed close to the
grey matter, these columns also receive fibres from the cells of the
lateral group.
In the dorsal columns the radiating root-fibres never reach the
median plane, but leave an area of purely longitudinal fibres on each
side of the dorsal fissure; these represent Goll’s columns, and have
a club-shaped outline in transverse section.
The white matter is pierced in all directions by fine
connective-tissue fibres and bundles of fibres which radiate from
the grey matter; some branch and join with others to form a network,
others pass almost uninterruptedly to the periphery. From the
connective-tissue cells of the _pia mater_, processes pass into the
white matter and assist in completing the connective-tissue matrix
for the nervous elements.
*Dorsal roots* of the spinal nerves. Each root consists of a single
bundle of nerve fibres, which suddenly bends at the periphery of the
cord in order to descend vertically through the white matter towards
the dorsal horn; the fibres divide into three sets, one to the dorsal
commissure, a second to the upper horn itself, and the third helps to
form the dorsal columns.
*Ventral roots* of the spinal nerves. Each ventral root consists of
three or four delicate threads, which may be traced to the ventral
cornua, which they reach after a vertical or very slightly oblique
course through the white matter. Other fibres arise from the ventral
columns, but these oblique fibres never extend to the median plane.
*Pigment* is found distributed irregularly through a section from any
part of the spinal cord; it is increased in amount in those parts in
which there is an increased amount of grey matter. The pigmentation
is always found more marked in the lower parts of the ventral horns
than in other parts.
B. THE BRAIN (Figs. 98, 102, 103, and 105).
*1.* *General description.* From behind forwards, the *dorsal*
surface of the brain presents the following parts for examination:
the _medulla oblongata_, the _cerebellum_, the optic lobes, the
thalamencephalon, the cerebral hemispheres, and the olfactory lobes.
The _medulla oblongata_ is a direct continuation of the spinal cord;
it is wider anteriorly than posteriorly, and is separated in front
from the optic lobes by a vertical plate of nervous matter, the
_cerebellum_. The optic lobes are two symmetrical ovoid bodies touching
each other in the median plane, and together forming the widest part
of the brain. In front of the optic lobes is the thalamencephalon,
with a thick vascular membrane, the choroid plexus, lying on its upper
surface, and connected with the pineal gland; the thalamencephalon
extends forwards between the posterior ends of the cerebral
hemispheres. The cerebral hemispheres are two symmetrical ovoid bodies,
narrow in front, wider and slightly diverging behind: each hemisphere
is prolonged forwards to form an olfactory lobe.
The *ventral* surface has in front the olfactory lobes, then the
cerebral hemispheres, behind these the _lamina terminalis_, the _tuber
cinereum_, the optic chiasma, the pituitary body, the _crura cerebri_,
and lastly the _medulla oblongata_, in the order here given.
The various *cranial nerves* (Figs. 102 and 103) may be seen to arise
as follows:--The olfactory nerve (_I_, _I_′, _L.ol_′) arises directly
from the anterior end and outer side of the corresponding olfactory
lobe, and from the cerebral hemisphere. The optic nerve (_To_ and
_II_) arises, as the optic tract, from the side of the brain below the
optic lobe, whence it passes to the chiasma on the under surface of
the brain. The oculo-motor (_III_) takes its origin from the ventral
surface close to the median line and between the _crura cerebri_.
The pathetic or trochlear nerve (_IV_) is attached to the dorsal
surface between the optic lobes and the _cerebellum_. The trigeminal
nerve (_V_) arises from the side and anterior part of the _medulla
oblongata_. The _abducens_ (_VI_) arises behind the pituitary body
close to the median line from the ventral surface of the medulla
halfway between the _sulcus_ and the origin of the _vagus_. The
facial and auditory (_VII_ and _VIII_) nerves arise from the _medulla
oblongata_ behind the trigeminal nerve, the facial being in front of
the auditory nerve. The glossopharyngeal (_IX_) nerve arises, in common
with the pneumogastric nerve (_X_), behind the auditory nerve.
*2.* *The several parts of the brain.*
*a.* The _medulla oblongata_ (Figs. 98, 102, and 103 _Mo_)--α.
*External form.* The _medulla_ is limited behind by the origin of the
first pair of spinal nerves, at which point a very faint constriction
is sometimes found: it extends forwards as far as the _cerebellum_. It
gradually widens as it passes forwards until just before it reaches its
anterior limit, where it presents a shallow but sharp constriction. The
*dorsal surface* is characterised by the presence of a deep, triangular
fossa, the *fourth ventricle* (Fig. 98 _S.r_), (_ventriculus quartus_,
Stieda; _sinus rhomboideus s. sinus triangularis_, Reissner; _fossa
rhomboidalis_); the sides of the triangle are, however, not quite
straight, but are slightly bent outwards just before they converge
towards the posteriorly-directed apex; the base of the triangle is
formed by the _cerebellum_. By careful examination, the ventricle is
seen to be continued for a short distance under the _cerebellum_,
where it opens into the Sylvian aqueduct. In the floor of the fourth
ventricle is a well-marked median longitudinal fissure (_sulcus
centralis_), (Fig. 98 _S_). Into the posterior part of the ventricle
opens the central canal of the spinal cord. As the fourth ventricle is
formed by the white matter passing to either side, and the simultaneous
flattening of the grey matter, the floor of the fourth ventricle is
composed of grey matter.
The fourth ventricle is closed in by a highly vascular membrane,
the *choroid plexus* of the fourth ventricle (_plexus choroideus
ventriculi quarti_, Reissner; _velum medullare posterius_). The
blood-vessels of the plexus will be described together with the
other vessels of the brain (p. 162). They are supported by a
connective-tissue matrix, and the whole covered with flattened
epithelium, which in the fourth ventricle is ciliated and often
pigmented.
The *ventral surface* of the _medulla oblongata_ (Fig. 102 _Mo_) has
a median ventral longitudinal fissure, a direct continuation of that
of the cord; in the anterior part of the _medulla oblongata_ there is
also to either side of this a lateral fissure, continued on to the
_crura cerebri_; these fissures correspond to the positions of the two
_rami posteriores_ of the internal carotid arteries; they are always
well seen in microscopical sections. The _medulla oblongata_ is so
intimately connected with the _pars commissuralis_ (pp. 149, 150) that
the minute anatomy of the two is best described at the same time.
β. *Internal structure.* Examined by means of serial sections, the
_medulla oblongata_ is seen to have, in comparison with the cord, an
increased amount of grey matter; this is especially the case in its
anterior part. The floor and inner parts of the walls of the ventricle
are formed of grey matter, in which the largest-sized cells have
disappeared, to be replaced by medium-sized cells. Traced from behind,
the ventral horns of the cord are seen to increase in size and to be
more widely separated until they form two isolated masses, while the
dorsal horns gradually diminish; at the same time they are forced
outwards and upwards, until they lie under the floor of the ventricle,
and so extend to the _pars peduncularis_.
[Illustration: Fig. 98.
Dorsal view of brain of _Rana esculenta_.
_Ad_ Choroid plexus.
_C_ Cerebellum.
_f_ Groove between cerebral hemispheres and olfactory lobes.
_G_ Opening in the roof of the third ventricle.
_Gp_ Pineal body.
_Hc_ Cerebral hemispheres.
_I_ Olfactory nerve.
_Li_ Wall of fourth ventricle.
_L.ol_ Olfactory lobe.
_L.op_ Optic lobe.
_Mo_ Medulla oblongata.
_S_ Longitudinal fissure of the fourth ventricle.
_S.r_ Fourth ventricle.
_Tho_ Thalamencephalon.
]
*Grey matter.* The _substantia reticularis_ is not present, but the
_septum medium_ extends forwards as far as the _pars peduncularis_.
The central canal extends upwards at the expense of the tissue above
it, and is here pear-shaped; at the same time the dorsal longitudinal
fissure deepens until the two meet in the fourth ventricle; beyond this
point one cannot speak of dorsal and ventral horns.
[Illustration: Fig. 99.
Transverse section through hinder end of _Medulla oblongata_ (magnified
30–80)[52], from Stieda.
[Footnote 52: In these diagrams, from Ludwig Stieda’s Studien über das
centrale Nervensystem der Wirbelthiere, the outline of the diagram is
magnified thirty times, while the details are magnified eighty times.]
_b_ Inferior commissure.
_f_ Dorsal horns.
_g_ Ventral horns.
_h_ Fourth ventricle.
_i_ Nucleus centralis.
_k_ Isolated mass of grey matter in which longitudinal
fibres of the pneumogastric nerve course.
]
Small nerve cells are irregularly distributed throughout the whole of
the grey matter and cannot be grouped; the larger cells, on the other
hand, are arranged in distinct groups which have special relations with
the nerves arising from the part. Occasionally these groups are not so
isolated as usual; in this case processes of one group can be traced
into another group (Reissner). Of these groups the chief are:
1. The _nucleus centralis_ (upper inner group, Reissner), _nucleus
medullae oblongatae_, Stieda (Fig. 99 _i_), is a group of cells found
towards the hinder end of the _medulla oblongata_, on either side of
and below the central canal; the group can be traced under the floor
of the fourth ventricle to about its middle. The cells are rounded or
spindle-shaped, the processes directed upwards, downwards, or outwards;
their average size is 0·040–0·048 mm. long by 0·020 mm. broad.
2. The *auditory nucleus* (_nucleus acusticus_, Reissner, Stieda),
(Fig. 100 _n_) is a large group of cells found in the wall of the
fourth ventricle opposite the point of origin of the auditory
nerve. The cells are rounded, pear-shaped, or of spindle form, and
interspersed between the nerve fibres; these cells have an average
length of 0·040 mm., and are about half as broad. The fibres of the
auditory nerve radiate from their superficial origin in all directions
through the grey matter towards these cells, and evidently communicate
with them (Fig. 101 _p_). One small group (Fig. 101 _r_) passes to
a lower level than the rest, and is regarded by Stieda as the true
auditory centre. Köppen considers that the auditory nerve has a
threefold origin: (1) from small cells on the median surface of the
auditory area; (2) from the large cells between the above; (3) from a
group of free nuclei on the dorsal surface of the auditory area.
[Illustration: Fig. 100.
Transverse section through the _Medulla oblongata_ at the point of
origin of the abducens nerve, from Stieda. (Magnified 30 x 80.)
_h_ Fourth ventricle.
_m_ Abducens nerve.
_n_ Auditory nucleus.
_o_ Abducens nucleus.
]
3. The *trigeminal nucleus* (_nucleus trigeminus_), (Fig. 101 _q_) lies
in part beneath the auditory nucleus but extends further forwards. It
forms a rounded group of cells placed under the outer angle of the
grey matter. The cells are somewhat crowded together, and are chiefly
of an elongated spindle-form, with their processes directed obliquely
downwards and outwards. The fibres of the trigeminal nerve separate
into two groups; the upper group is best traced in a horizontal
section, the fibres curving round to join the longitudinal fibres
continued from the dorsal columns of the cord. The fibres of the lower,
smaller group pass transversely inwards to the trigeminal nucleus.
According to Reissner the latter fibres are motor, the former sensory.
Probably other nerves are connected with the hinder part of this group.
4. The *abducens nucleus* (Fig. 100 _o_). From its superficial origin,
the fibres of the abducens nerve may be traced vertically upwards to a
small, rounded, grey mass; at this point the mass is somewhat isolated,
but further forwards it may be traced as belonging to the central grey
matter; it contains small spindle cells.
[Illustration: Fig. 101.
Transverse section of the _Medulla oblongata_, at the point of origin
of the auditory nerve, from Stieda. (Magnified 30 x 80.)
_h_ Fourth ventricle.
_n_ Auditory nucleus.
_o_ Abducens nucleus.
_p_ Auditory nerve.
_p_′ Ganglion of auditory nerve.
_q_ Hinder portion of trigeminal nerve.
_r_ Bundle of fibres arising from trigeminal nucleus
and joining the auditory nerve.
]
5. The *pneumogastric nucleus*. The pneumogastric, with its numerous
irregular roots, arises from the side of the _medulla oblongata_. The
hindermost fibres can be traced as a small bundle, passing almost
transversely through the white matter to the outer margin of the grey
matter. The larger portion of the fibres is placed in front of these;
part of this seems to be directly continuous with the longitudinal
fibres of the white matter; a second part, however, can be traced from
the surface transversely through the white matter to the grey matter.
These latter fibres, together with those of the group first described,
do not arise from the grey matter in this part of the _medulla
oblongata_, but curve round and run backwards longitudinally through
the grey matter, thus forming a rounded bundle of fibres (Fig. 99 _k_).
Between these fibres are interspersed small nerve-cells and nuclei
which disappear as the fibres approach the white matter. The vagus
undoubtedly receives fibres from the grey matter throughout a long
course, and again receives a large bundle just before leaving the grey
matter. The more exact origin of the various fibres has not been traced.
6. The _nucleus magnus_ (Reissner and Stieda) is a very peculiar group
of cells placed on either side, in the most anterior portion of the
_pars commissuralis_, that is, immediately underneath the _valvula
cerebelli_. The large cells are arranged in a transverse section in a
single row so as to enclose a pear-shaped space on either side, which
has its long axis directed from above, downwards and outwards, the
narrower end being above. In longitudinal section the line of cells is
seen to be open in front. The space enclosed by these cells is occupied
by a granular ground-substance which contains only few nuclei. Bellonci
is of opinion that these nuclei represent the _corpora quadrigemina
posteriora_ of higher animals.
*White matter.* In the hinder part of the _medulla oblongata_ the
arrangement of the white matter resembles that of the white matter
of the spinal cord; further forwards the white matter of the dorsal
surface commences to pass to either side, and ultimately it forms the
outer part of the walls of the fourth ventricle. The fibres of the
white matter of the ventral surface are unchanged in direction as they
proceed forwards. The fibres of the anterior part of the medulla are
thinner than those of the posterior portion (Stieda), according to
Reissner they gradually thin as they pass forwards. The fibres are
nearly all longitudinal, such transverse and oblique fibres as are
present being chiefly in connection with the various nerve-roots and
the commissures.
The _commissura superior_ is naturally lost in consequence of the
opening of the central canal into the fourth ventricle; the _commissura
inferior_ is increased in the anterior half and decreased in the
posterior half of the _medulla oblongata_; in the latter the fibres
become more and more oblique, and decussate very freely; ultimately
they seem to be either continued as longitudinal fibres or to join the
ganglia.
Near the _pars commissuralis_ is a transverse arched band of fibres,
passing from the under surface of one half of the cord over the ventral
longitudinal fissure through the _septum medium_ to the under surface
of the opposite half; part of the fibres are continued upwards along
the periphery to the _cerebellum_, part to the _nucleus magnus_.
Vertical, straight, or slightly arched fibres are found in the walls of
the fourth ventricle.
A section from the _medulla oblongata_ has a larger amount of *pigment*
than a section from the spinal cord, and the anterior portion of the
_medulla oblongata_ contains more than the posterior portion. The
pigment is chiefly found in a curved line, placed in the lower and
outer parts of the grey matter; the amount present varies in different
specimens.
*b.* The _Cerebellum_ and _Valvula cerebelli_.
α. *External form.* The _cerebellum_ is a thin, semilunar plate,
which projects between the optic lobes and the fourth ventricle, its
base covering the most anterior part of the ventricle; the posterior
surface possesses a very faint median fissure (Reissner). The _valvula
cerebelli_ (_Velum medullare anterius_, Reissner) is the thin lamella
which connects the anterior surface of the _cerebellum_ with the optic
lobes.
β. *Minute structure.* By means of longitudinal, vertical sections,
the posterior surface of the _cerebellum_ is seen to be covered with
epithelium; in the lower part of the surface this is columnar or
conical, above it is flattened: immediately beneath, that is in front
of this is a finely granular layer, with very closely packed and
granular nuclei. In front of these is a stratum of nerve-fibres forming
the second layer of the cerebellum.
Still more anteriorly is the third layer of the cerebellum, an
irregular double layer of large cells (Purkinje’s cells, Denissenko);
the cells have an average length and breadth of 0.040 mm. and 0.015 mm
respectively; they are pear-shaped or of spindle-form, and possess
usually two well-marked processes, one passing into the layer behind,
the other forwards into the anterior layer to be immediately described,
while other less distinct processes radiate irregularly in all
directions. The fourth and most anterior layer of the cerebellum is a
thick stratum of nerve fibres with numerous nuclei (0.006 to 0.008 mm.
diameter). The fibres are for the most part arranged transversely, but
some course in various directions. These fibres underlie the flattened
epithelium which covers the anterior surface of the cerebellum.
The fibres of the second layer course, for the most part, in an almost
vertical plane; they connect the _cerebellum_ with the optic lobes
(_processus cerebelli ad corpora bigemina_) and with other parts of the
brain.
The fibres of the fourth layer receive numerous long processes from the
large cells of Purkinje; they form a large commissural system, which
can be followed ventrally on each side into the _pars commissuralis_.
A part of the fibres ends here in the grey matter, a second portion
enters the auditory area and forms a descending auditory root, a third
part joins the lateral columns (in the _medulla oblongata_), and
more anteriorly some join the ventral columns. The descending fibres
from the _cerebellum_, together with the _fibrae arcuatae_ found in
the ventral columns, indicate the presence of a _pons Varolii_. The
fibres of this ventral commissure decussate only on its dorsal surface
(Köppen).
The _Valvula cerebelli_ contains a few medullated fibres and the roots
of the trochlear nerves; these pass from the _medulla oblongata_ into
the _valvula cerebelli_, cross in the median line, and then proceed
forwards as the trochlear nerves.
The *pigment* in the _pars commissuralis_ is arranged in a curved line
similar to that found in the _medulla oblongata_, but the line is
shortened at either extremity, and consequently does not extend into
the _cerebellum_.
*c.* The *optic lobes* and _Crura cerebri_. (_Corpora geminata_ and
_Pars peduncularis_, Reissner; _Lobus opticus_, Stieda; Vierhügel,
Tiedemann; Vierhügel (Zweihügel) and _Pedunculi cerebri_, Schiess;
Mesencephalon, Huxley.)
[Illustration: Fig. 102.
Ventral view of brain of _Rana esculenta_.
_Cho_ Optic chiasma.
_Hc_ Cerebral hemispheres.
_Hy_ Pituitary body.
_L.ol_ Olfactory lobe.
_L.ol^1_ Origin of olfactory nerve from
the cerebral hemisphere.
_Lt_ Lamina terminalis.
_Mo_ Medulla oblongata.
_To_ Optic tract.
_Tu.c_ Tuber cinereum.
_I_ 1st }
_I^1_ 2nd } root of the olfactory nerve.
_II_ Optic nerve.
_III_ Oculo-motor nerve.
_IV_ Trochlear nerve.
_VI_ Abducens nerve.
_V_, _VII_, _VIII_ Trigeminal, facial, and
auditory nerves.
_IX_, _X_, _XI_ Glossopharyngeal, pneumogastric,
and accessory nerves.
]
α. *External form* (Figs. 98, 102, 103 _L.op_). The optic lobes are two
prominent ovoid bodies placed immediately in front of the _cerebellum_,
and connected with it by the _valvula cerebelli_; posteriorly they
touch each other in the median plane, while anteriorly they diverge
and thus constitute the widest part of the brain; in the angle thus
formed is the thalamencephalon. The optic lobes are always more darkly
pigmented than any other part of the central nervous system.
[Illustration: Fig. 103.
Lateral view of brain of _Rana esculenta_.
_Ad_ Choroid plexus.
_C_ Cerebellum.
_Gp_ Pineal body.
_Hc_ Cerebral hemisphere.
_Hy_ Pituitary body.
_L.ol_ Olfactory lobe.
_L.ol_^1 Disc at origin of second root.
_L.op_ Optic lobe.
_Mo_ Medulla oblongata.
_Tho_ Thalamencephalon.
_To_ Optic tract.
_Tu.c_ Tuber cinereum.
_I_ 1st }
_I^1_ 2nd } root of olfactory nerve.
_II_ Optic nerve.
_IV_ Trochlear nerve.
_V_ Trigeminal nerve.
_VII_ Facial nerve.
_VIII_ Auditory nerve.
_IX_, _X_, _XI_ Glossopharyngeal, pneumogastric,
and accessory nerves.
]
The _Crura cerebri_ are two columns of white matter, placed beneath
the optic lobes, and partly hidden by the pituitary gland. At their
junction with the _medulla oblongata_, or rather with the _pars
commissuralis_, is a very slight transverse fissure; at the same point
the ventral longitudinal fissure is interrupted by an extremely small
grey tubercle (Stieda).
β. *Internal structure.* From the anterior extremity of the fourth
ventricle a canal, the Sylvian aqueduct (_Aqueductus Sylvii_, _iter
a tertio ad quartum ventriculum_), may be traced forwards under the
cerebellum, in the median line of this section of the brain. At about
opposite the middle of the length of the optic lobes the canal is
dilated and communicates with the cavities or ventricles (_Ventriculi
lobi optici_, Stieda) enclosed by these; a general cavity is formed,
which in transverse section has something of the form of the letter T.
The roof of the cavity is thinner than the floor; this is especially
the case in the median plane opposite the superior longitudinal fissure
between the optic lobes; the floor is thinned in the middle line by the
descending portion of the cavity. The cavity of each optic lobe extends
both forwards and backwards beyond its point of communication with the
dilated Sylvian aqueduct, hence in a transverse section taken in front
of this point (Fig. 104 _h_′) the cavity of either side appears to be
isolated; in a horizontal and longitudinal section (Fig. 105 _Aq_) the
general arrangement of the parts may be well seen.
The grey matter is chiefly arranged in a layer so as to surround the
cavity (Fig. 104), this layer being deeper on either side of the
descending portion of the cavity than elsewhere. For the rest the grey
matter is much interspersed among the white matter, except at the
circumference of the section, which is entirely formed of white matter.
It contains a large number of small cells, of which the nuclei are
alone visible; in the parts mentioned where the layer is most marked
these cells are arranged in oblique rows, between which pass fine
bundles of medullated fibres (Fig. 104, between _u_ and _h_′). A group
of large cells (Fig. 104 _u_) is found on either side of the middle
line and under the floor of the cavity; the cells are about 0.032 mm.
long, and 0.016 mm. broad; the oculo-motor nerve may be traced to
this group, which is the *oculo-motor nucleus*. A small commissure of
decussating fibres connects the nuclei of opposite sides (Köppen).
[Illustration: Fig. 104.
Transverse section through the anterior portion of the optic lobes
opposite the origin of the motor-oculi nerve; from Stieda (magnified
30–80).
_h_ Lower portion of cavity.
_h_′ Lateral portion of cavity.
_u_ Ganglia of oculi-motor nerve.
_v_ Oculo-motor nerve.
_w_ Large cells of the optic lobe.
_x_ Roof of optic lobe.
_y_ Posterior commissure.
_z_ Anterior diverticulum of the cavity.
]
The substance of the roof of the optic lobes (Fig. 104 _x_) is arranged
in very distinct layers: above is a layer free from cells; the fibres
of this layer are extremely fine and delicate, and have not been
accurately traced; under this is a nuclear layer; a second layer of
fine fibres follows, which is succeeded by a second layer of nuclei in
a granular matrix, and lastly epithelium (Stieda). (Reissner describes
three nuclear layers in _Bufo variabilis_, and this is also the case in
_R. temporaria_, G. H.; according to Köppen, the number is variable.)
In the anterior portion of the roof a distinct bundle of fibres may be
made out; externally they bend downwards, and can be traced as far as
the _crura cerebri_.
Fibres corresponding with the commissural and arched fibres of the
_medulla oblongata_ are continued into the hinder portion of the _crura
cerebri_, the change from _pars commissuralis_ to _crura cerebri_ being
very gradual. The longitudinal white fibres are much increased in
number in the _crura cerebri_, and a portion of them can be traced to
the _nucleus magnus_.
A peculiar irregular group of large cells (Fig. 104 _w_) is found where
the roof meets the _crura cerebri_; these vary in diameter from 0.024
to O.040 mm., and their processes are very indistinct.
The fibres of the optic tracts arise, according to Köppen, from two
different origins: the one lies on the hindermost part of the optic
lobe; from this point the fibres curve downwards and forwards to form
longitudinal fibres; this root Köppen names the ventral ascending root,
it can be traced through the entire length of the organ. The second
root arises in the _tectum opticum_ near the longitudinal fissure; it
is smaller than the foregoing, and has been named the dorsal ascending
optic root. The fibres of these two roots unite anteriorly near the
posterior commissure, at which point they receive additional fibres
(Köppen). Bellonci traces a large proportion of the fibres of the optic
tract to the _nucleus magnus_, which pair of nuclei, as already stated,
he regards as the posterior pair of _corpora quadrigemina_ of higher
animals.
The _pars peduncularis_ is the continuation of the _pars commissuralis_
underneath the optic lobes; a gelatinous mass lying in the median plane
and containing numerous isolated nuclei (_Ganglion interpedunculare_)
divides it into two lateral halves. The longitudinal fibres are
ungrouped posteriorly, but arranged in rounded strands in the middle,
especially dorsally; anteriorly the grouped arrangement is lost and the
number of fibres diminished.
The *pigment* of this region has, in a transverse section, an outline
which has something the form of a lyre; commencing on either side of
the median line, and underneath the deepest portion of the cavity,
the pigment line passes, first, directly outwards; then suddenly turns
upwards and slightly outwards parallel with the wall of the deeper part
of the cavity; it then curves outwards to pass below the cavity of the
optic lobe, where it divides, one portion passing outwards, the other
between the Sylvian aqueduct and the ventricle of the optic lobe.
*d.* The *Thalamencephalon* (Huxley), (_Lobus ventriculi tertii_,
Stieda; _Thalami optici_, Reissner; _Thalamus opticus s. Lobus
ventriculi tertii_, Stannius; Ganglien der Haemisphaeren, Carus).
α. *External form.* From above (Fig. 98 _Tho_) the thalamencephalon
is seen as a lozenge-shaped mass lying in front of the optic lobes,
and behind and between the diverging posterior ends of the cerebral
hemispheres; it is covered by a thick vascular membrane, the *choroid
plexus*, through which passes the pedicle of the *pineal body*
(_Glandula pinealis_). On removing the choroid plexus a small aperture
is seen in the roof of the thalamencephalon, connecting the hollow
pedicle of the pineal gland with the *third ventricle*. The ventricle
appears as a narrow slit in the median line, its walls being formed
by the optic thalami. By pressing aside the cerebral hemispheres the
*posterior commissure* (_Commissura posterior_) may be seen lying quite
in front and deep in the cleft of the ventricle. Immediately behind the
pedicle of the pineal body is a slight but well-marked depression (Fig
98 _G_), the origin of which has not been investigated (Wiedersheim).
The choroid plexus is continued forwards between the cerebral
hemispheres (Figs. 98, 103 _Ad_) for some distance, and terminates in a
fine thread of connective-tissue.
The under surface of the thalamencephalon (Fig. 102) is divided
into two parts by the *optic chiasma* (_Cho_): the anterior portion
(_Lt_) is the _lamina terminalis_ (_Substantia cinerea anterior_);
the posterior (_Tu.c_) the _tuber cinereum_. The _lamina terminalis_
is bounded on either side by the cerebral hemispheres. The _tuber
cinereum_ (Figs. 102, 103 _Tu.c_) is a small median swelling
immediately behind the optic chiasma, and caused by the depression
of the floor of the third ventricle to form the _infundibulum_
(_Diverticulum infundibuli_, Reissner).
[Illustration: Fig. 105.
Horizontal section through the brain to show the ventricles.
_Aq_ Ventricles of optic lobes and the aqueduct of Sylvius.
_Dv_ Third ventricle.
_MF_ Foramen of Monroe.
_Sv_ Lateral ventricle.
_Vv_ Fourth ventricle.
]
The *pituitary body* (_Hypophysis cerebri_) is a flattened sac, placed
behind the _tuber cinereum_ and continuous with it by means of the
_infundibulum_.
β. *Internal structure.* The aqueduct of Sylvius, after communicating
with the ventricles of the optic lobes, again contracts (Fig. 105),
but still remains somewhat larger than before. In the thalamencephalon
the Sylvian aqueduct opens into the third ventricle, which gradually
assumes the form of a vertical slit with the walls bulging slightly
outwards in their upper parts. The thin roof of this ventricle, where
complete, contains a band of transverse fibres. The floor is depressed
both before and behind the part immediately above the optic chiasma,
the posterior depression lying above the _tuber cinereum_, which here
descends towards the _infundibulum_: a transverse section through this
portion of the third ventricle has the form of a square standing on one
angle, the superior angle being produced into the vertical slit of the
general cavity. The anterior depression is formed by the general cavity
being prolonged downwards and forwards to the _lamina terminalis_ in
the form of a narrow and shallow slit.
The white and grey matter of the thalamencephalon are only so far
distinct in that the portion immediately surrounding the cavity is
darker than the rest of the section. In the immediate neighbourhood
of the cavity are many small cells and nuclei, which become scarcer
further from the ventricle; they are arranged in rows, separated by a
fibrillated matrix. On either side is a distinct bundle of longitudinal
fibres, the ‘round bundle’ of Köppen, which come from the optic lobes
but appear to arise from either the _pars commissuralis_ or the
_medulla oblongata_, and to receive additional fibres from the optic
thalami; they pass forwards to the base of the cerebral hemispheres
(Stieda). A second set of longitudinal fibres arises in the substance
of the _tuber cinereum_ and passes forwards to the hemispheres (strand
of the _Tuber-cinereum_ and _Thalamus_, Köppen); this band, together
with the ‘round bundle,’ form a _crus cerebri_ (Köppen).
The commissural fibres of the thalamencephalon are: (1) a _commissura
transversa Halleri_ in the posterior portion of the organ; (2) an optic
commissure, consisting of fibres arising from the thalamencephalon
(thalamencephalic root) and crossing the median line to join the optic
tract of the opposite side; (3) a probable commissure between the optic
nerves just in front of the _chiasma opticorum_; the existence of the
latter is not yet proved beyond doubt; (4) the large commissure of
transverse fibres found in the roof of the third ventricle; whether the
fibres decussate or not is uncertain (Köppen).
The fibres of the large commissure of the roof are, in part, continued
into the strand of the _Tuber-cinereum_ above mentioned, and thus
conducted to the posterior parts of the hemispheres (Köppen). A group
of fibres (Meynert’s band, Köppen) is found in each lateral wall of
the third ventricle; they pass from the region of the _nucleus parvus_
downwards in a curved course almost parallel with the external border
of the thalamencephalon.
A distinct group of cells may be noted in this section of the brain,
an arciform or circular group (_Nucleus parvus_, Reissner; ganglion
of the _habenula_, Köppen) of large spindle cells (average diameter
0.016 mm.), placed under the upper border close to the third ventricle;
the group extends alongside the whole length of the ventricle. A second
group lying in the middle and posterior parts beneath the ventricle,
Köppen names the ‘ventral nucleus’ of the thalamencephalon.
The *pigment* in the posterior part of the thalamencephalon is arranged
in a manner similar to that in the optic lobes and _crura cerebri_;
anteriorly where the third ventricle is prolonged forwards and
downwards the arrangement is different; the pigment lies in a curved
line above the process of the ventricle, with its concavity directed
downwards, each end bifurcating, in order that one branch may pass
upwards, the other downwards.
The *pineal body*[53] is a small vesicle placed underneath the skin
above the fronto-parietal bones; in the embryo it is connected with
the third ventricle by means of the pedicle[54] already mentioned; the
skin covering the body is always paler than the surrounding skin, and
the usual cutaneous glands are absent in this part; the paler spot on
the head may always be found, but is more distinct in _Rana temporaria_
than in _Rana esculenta_. The structure on the roof of the third
ventricle, which is usually known as the pineal body, is nothing more
than a thickened portion of the choroid plexus, and consists of a group
of convoluted vessels surrounded by _pia mater_, which is described
by Wyman as being covered with ciliated epithelium (_R. pipiens_).
The true pineal body is a small body with an outer connective-tissue
capsule, derived from the _pia mater_; this encloses an irregular
mass of epithelial cells; according to de Graaf a twig of the _ramus
supramaxillaris_ reaches it subcutaneously, and a blood-vessel
accompanies the pedicle through the _foramen parietale_. According to
Darkschewitsch, the pedicle contains medullated nerve-fibres derived
directly from the brain.
[Footnote 53: Compare Ehlers, Ueber die Zirbel der Haifische, Zeit.
f. wiss. Zool. 1878, Vol. XXX; and Balfour, Development of the
Elasmobranch Fishes, chap. ix.]
[Footnote 54: Wiedersheim states that the pedicle is hollow, and
regards the part formerly known as the pineal body as a thickened
portion of this pedicle.]
The *pituitary body* (Figs. 102, 103 _Hy_) when examined with a lens
is seen to consist of two portions: an anterior, superior, and smaller
white portion, and a larger, inferior, posterior, and reddish portion.
The anterior portion has the form of a very small, flat disk, and is
enclosed in a connective-tissue capsule which sends in larger and
smaller processes. In either transverse or longitudinal section it
is seen to be formed of two horizontal layers separated by a line
of blood-vessels and connective-tissue. The upper layer consists of
a granular and reticular matrix, containing many nuclei (averaging
0.006 to 0.010 mm. diameter), and divided into irregular rounded or
polyhedral spaces by bands of tissue derived from the capsule. This
layer is more vascular than the lower. The lower layer consists of
a mass of clear, nucleated rounded or polyhedral cells (0.016 to
0.024 mm. in diameter; nuclei from 0.008 to O.012 mm. in diameter,
Reissner), pierced by very fine connective-tissue septa derived
from the capsule. The septa are, for the most part, vertical and
longitudinal (Reissner), the blood-vessels are very few.
The posterior larger portion of the pituitary body (Fig. 106) is also
compressed from above downwards, and in transverse section as an oval
outline. It possesses an external thin connective-tissue capsule,
which sends in fine processes to support a mass of convoluted tubes,
between which course a few blood-vessels; these tubes possess an outer
nucleated basement-membrane, and are lined with a single layer of
more or less cylindrical epithelium, which entirely fills the tube;
hence the tubes possess no lumen. The tubes are from 0.04 to 0.08 mm.
in diameter; the cells are clear or granular, and possess distinct,
rounded nuclei.
*e.* The *Cerebral Hemispheres* and *Olfactory Lobes*. The cerebral
hemispheres (_Lobi hemisphaerici_, Stieda; _Lobi cerebrales_, Reissner;
Centralmasse des Geruchssinns, Carus; Hemisphaeren des grossen Hirns,
Tiedemann; Grosse Hemisphaeren, Schiess; Prosencephalon, Huxley). The
olfactory lobes (_Tubercula olfactoria_, Stieda; _Lobi olfactorii_,
Reissner; Riechkolben, Schiess; Rhinencephalon, Huxley).
α. *External form* (Figs. 98, 102, 103 _Hc_ and _L.ol_). The two
cerebral hemispheres form together the largest section of the brain;
from above they are seen to be separated by a dorsal longitudinal
fissure, which is here well marked: each hemisphere is an ovoid
body with the smaller end directed forwards and continuous with the
corresponding olfactory lobe; the posterior end forms one half of the
anterior boundary of the thalamencephalon. The olfactory lobes are two
elongated, rounded bodies directly continuous with the corresponding
cerebral hemispheres, and likewise partially separated in the median
line by a dorsal longitudinal fissure: at the point of union of the
cerebral hemispheres and olfactory lobes is a faintly marked transverse
depression.
[Illustration: Fig. 106.
Section through the lower division of the pituitary body (magnified 360
times); from Stieda.
_a_ Tubes lined with epithelium.
_b_ Blood-vessels.
]
On the ventral surface the parts are again marked off from one another
by a corresponding ventral longitudinal fissure and a transverse
groove; the two longitudinal fissures being continuous, anteriorly,
between the olfactory lobes. The cerebral hemispheres appear to be
more widely separated behind (Fig. 102) than is the case on the dorsal
surface, and in the space so formed is the _lamina terminalis_ (_Lt_).
Seen from the side, the slight depression of the upper surface, between
the cerebral hemispheres and the olfactory lobes, is seen to be
continued downwards and slightly backwards to join the corresponding
groove on the inferior surface.
The longitudinal fissures are shallow and do not meet, except at one
point, at about the middle of the cerebral hemispheres (Fig. 105). The
olfactory bulbs arise superficially (Figs. 102, 103 _I_′ and _L.ol_)
from the whole length of the olfactory lobe, between the anterior
extremity (_I_′) and the posterior (_L.ol_), where they are also
attached to the cerebral hemispheres.
β. *Internal structure.* The cerebral hemispheres and olfactory lobes
are hollow, the common cavity of each side being known as the lateral
ventricle (_Ventriculus lateralis_); these ventricles communicate
with each other, and with the third ventricle (Fig. 105). The narrow
aperture by which the lateral ventricles communicate is known as the
*Foramen of Monro* _(MF_); it communicates with the third ventricle
posteriorly, and with the space between the cerebral hemispheres
anteriorly, and thus forms a common cavity (_Ventriculus communis
loborum hemisphaericorum_, Stieda).
In general terms, each ventricle may be said to be a semilunar cavity,
prolonged backwards and forwards (Fig. 107 _c_); the outer wall is
always more or less concave, while the inner varies according to
the part of the hemisphere examined. At the anterior and posterior
extremities the inner wall is convex and bulges into the cavity
(Fig. 107); in the middle portion of the cavity the inner wall
presents a longitudinal groove (_Ventriculi lateralis cornu internum_,
Reissner), (Fig. 108 _d_), and consequently the inner wall has here two
rounded masses, an upper and a lower (_Corpus striatum_, Wiedersheim),
projecting into it. By tracing them backwards and forwards, the lower
swelling is seen to increase at the expense of the upper, while at the
same time the lateral grooves disappear; the outline of the cavity
shown in Fig. 107 is then obtained. The roof of the ventricle is arched
and broader than the floor, which, in the middle part, exists only as
a vertical slit (Fig. 108), (_Ventriculi lateralis cornu inferius_,
Reissner): towards the anterior and posterior extremities it widens and
becomes shallower (Fig. 107).
[Illustration: Fig. 107.
Transverse section through the hinder portion of the cerebral
hemispheres; from Stieda.
_c_ Lateral ventricle.
_c_′ Common ventricle of Stieda.
_d_ Longitudinal fibres.
_f_ Anterior prolongation of the third ventricle.
]
The cerebral hemispheres and olfactory lobes are composed of a fine
granular matrix, enclosing spindle-shaped, rounded, or pear-shaped
nerve cells and nuclei, and containing very fine fibres. The cells
(Fig. 109 _b_) are more numerous towards the ventricle, and somewhat
sparse towards the superficial surface. The cells are of two chief
sizes, the smaller and more numerous average 0.004 mm. to 0.008 mm. in
diameter; they are found chiefly in the deeper portions of the section,
but also form a very thin irregular layer beneath the _pia mater_: the
larger cells have an average diameter of 0.010 mm. to 0.012 mm., and
are placed towards the periphery, especially in the dorsal part of the
inner wall.
[Illustration: Fig. 108.
Transverse section near the middle of the cerebral hemispheres.
_c_ Lateral ventricle.
_d_ Groove on the inner wall.
]
In this irregular collection of cells the following centres have been
described: (1) The nucleus, through which the _corpus callosum_ passes
(Köppen); (2) the lower internal or median cell-area (Osborne),
situated above the foregoing nucleus in the posterior and middle
portions of the hemispheres; (3) the upper internal cell-area (Osborne)
is the area of large cells in the dorsal part of the inner wall; (4)
the _Corpus striatum_ (Osborne) is a mass of cells between the _corpus
callosum_ and the _commissura anterior_; Köppen doubts the correctness
of Osborne’s opinion, and suggests that a group of cells found in the
wall of the third ventricle in front of ‘Meynert’s band’ may perhaps be
a _corpus striatum_.
[Illustration: Fig. 109.
From a transverse section through one of the cerebral hemispheres; from
Stieda. (Magnified 360 times.)
_a_ Epithelium of lateral ventricle.
_b_ Nerve cells.
_c_ Connective-tissue processes from the Pia mater.
]
A bundle of longitudinal medullated nerve-fibres, the ‘round bundle,’
is found on either side of the median line (Fig. 107 _d_), and near
the lower border in the posterior portion of this region; these fibres
can be traced from the posterior section of the thalamencephalon; they
diminish in number as they course through the base of the cerebral
hemispheres, and are ultimately lost in the lower anterior part of the
outer walls. A second strand of longitudinal fibres is the continuation
of that of the _Tuber-cinereum_ above described, which can be followed
to the outer wall of the posterior part of the ventricles, and to the
anterior commissure.
The commissures are: (1) The _corpus callosum_, a large bundle of
transverse fibres, seen best in a transverse section, at the point of
junction between the _lamina terminalis_ and the cerebral hemispheres,
forming an arch over the roof of the anterior prolongation of the third
ventricle. The fibres course to the inner and anterior parts of the
hemispheres, and are situated chiefly behind the _foramen Monroi_.
To this commissure must be added those fibres which unite the two
olfactory lobes, and possibly the fibres (_Commissura posterior_)
found in the roof of the third ventricle (Köppen). (2) The _Commissura
anterior_ (Stieda), a smaller set, found immediately under the floor
of the common ventricle, forming in their course outwards a curve,
with the concavity directed downwards. This commissure connects the
‘round bundles’ of opposite sides, and those fibres coursing with the
‘round bundles’ to the olfactory lobes constitute the _pars olfactoria_
of the _commissura anterior_. To this commissure must also be added
some fibres found on the ventral surface of the _commissura anterior_
and connecting the two strands of the _Tuber-cinereum_; an unusually
coarse strand of these fibres can be traced to the inner wall of the
ventricle, and is termed the _pars olfactoria interna_ by Osborne.
The general structure of the olfactory lobes resembles that of the
hemispheres; the olfactory nerves arise each by two roots, an outer
and inner. The outer root arises from the outer wall near the groove
between the corresponding hemisphere and olfactory lobe; the inner or
anterior root arises from the anterior surface of the olfactory lobe.
Both roots have a peculiar method of origin from the extremely fine
fibrillar network of the matrix (Nerve-fibre-conglomerate, Köppen), in
which are rounded dark bodies known as ‘glomeruli;’ in the ‘glomeruli’
dark points and nuclei are seen, between larger and smaller bands of
nerve-fibres. Köppen holds that all the sensory nerves of the brain
arise in a similar manner.
A decussation takes place between the two inner roots of the olfactory
nerves; possibly the external roots are connected by means of the
_commissura anterior_.
Very little *pigment* exists in the cerebral hemispheres or olfactory
lobes, the greater portion is found in the upper part of the inner
walls of the cerebral hemispheres.
The *epithelium* of the *ventricles of the brain*, like that of the
central canal of the *spinal cord*, consists of conical cells with
their bases directed towards the cavity, and their apices directed
peripherally and prolonged into distinct processes (Figs. 104, 109
_a_). In such situations, as the choroid plexuses, where nervous
tissue is absent and the cavity is completed by _pia mater_ alone, the
epithelial cells are flattened. Everywhere else it is ciliated[55]
and possesses distinct round nuclei which are as broad as the cells
themselves. The epithelium is somewhat irregularly and sparsely
pigmented; the ventral parts of the central canal of the spinal cord,
of the fourth ventricle, and of the Sylvian aqueduct are always more
pigmented than the dorsal parts.
[Footnote 55: Schmidt (_l. c._) states that the epithelium of the
central canal of the spinal cord is not ciliated.]
PLAN OF THE ARRANGEMENT OF THE NERVE-FIBRES OF THE CENTRAL NERVOUS
SYSTEM, ACCORDING TO KÖPPEN.
NERVE FIBRE NERVE-FIBRE COMMISSURES. NERVE-FIBRES
STRANDS IN STRANDS IN WHICH CONNECT
THE WHITE THE GREY THE STRANDS OF
MATTER. MATTER. WHITE FIBRES.
{1. The ventral 1. Longitudinal 1. The ventral
{ columns, fibres in commissure.
{ including the dorsal 2. The dorsal
{ the strand portion of commissure
{ of coarse the grey (rudimentary).
The { fibres. matter.
spinal {2. The lateral
cord. { columns.
{3. The dorsal,
{ columns
{ including
{ Goll’s
{ column.
{1. The ventral 1. Longitudinal 1. The ventral 1. The fibrae
{ columns, fibres of the commissure: arcuatae.
{ including Substantia _a._ Dorsal
{ the strand gelatinosa portion.
{ of coarse Rolandi, and _b._ Ventral
{ fibres which give portion.
{ dorsal off ascending 2. (The dorsal
{ longitudinal vagal and commissure
{ strand. trigeminal is wanting.)
{2. The lateral roots.
{ columns,
The { which give
medulla { off an as-
oblongata.{ cending
{ (recurrent)
{ vagus-root.
{3. The dorsal
{ columns.
{ _a._ Ascending
{ trigeminal
{ root.
{ _b._ Auditory
{ root.
{ _c._ Descending
{ auditory
{ root.
{1. The ventral 1. Longitudinal 1. The ventral 1. The fibrae
{ columns, fibres of the commissure. arcuatae.
{ including grey matter. 2. The dorsal
{ the dorsal Small ascend- commissure,
{ longitudinal ing trigeminal cerebellar
{ strand (the root. commissure
{ strand of and trochlear
{ coarse fibres decussation.
The { has dis-
cere- { appeared).
bellum {2. The lateral
and the { columns (each
pars { receives a
commis- { strand from
suralis. { the cere-
{ bellum).
{3. The dorsal
{ columns.
{ _a._ Large as-
{ cending tri-
{ geminal root.
{ _b._ Descending
{ auditory
{ root.
{1. The ventral (Wanting.) 1. The ventral 1. The fibrae
{ columns, commissure. arcuatae.
{ including the 2. The dorsal
{ dorsal longi- commissure.
{ tudinal _a._ Commissura
{ strand. posterior.
{2. (The lateral _b._ Marginal
The { columns can- commissure.
optic { not now be
lobes. { distinguished
{ from the ven-
{ tral columns.)
{3. The dorsal
{ columns: two
{ ascending
{ opticus-roots.
{1. The ventral (Wanting.) 1. The ventral 1. The fibrae
{ and dorsal commissure: arcuatae.
The { columns. _a._ Commissura
thalam- { _a._ Fibres from transversa
enceph- { the optic Halleri.
alon and { lobes. _b._ Commissura
the cere- { _b._ The ‘round anterior.
bral hemi-{ bundle.’ 2. The dorsal
spheres. { _c._ The ‘Thal- commissure,
{ amus-Tuber- the corpus
{ cinereum callosum.
{ strand.’
C. THE COVERINGS OF THE BRAIN AND SPINAL CORD.
1. The _Pia mater_ closely invests the whole of the brain and spinal
cord; it may, in fact, be regarded as the flattened, outermost layer
of the connective-tissue material which supports the nervous elements;
fine processes (Fig. 109 _c_) pass radially from its inner surface to
join the general connective-tissue matrix or neuroglia. It is usually
pigmented, those portions covering the optic lobes and spinal cord
being especially deeply pigmented: on the cerebral hemispheres it
contains very little pigment; at times, indeed, in _R. temporaria_,
pigment is absent from this part.
The _pia mater_ is continued on to the choroid plexuses and pituitary
body, and on to the pineal body by means of the pedicle; the membrane
is very vascular, and forms, especially for the cerebral hemispheres
and the olfactory lobes, a very important source for the direct supply
of blood-vessels.
2. The _Dura mater_, or lining membrane of the cranial cavity and
vertebral canal, is a connective-tissue membrane containing many
very much branched, pigmented cells. This membrane is not so deeply
pigmented as the _pia mater_, except in that portion covering the
cerebral hemispheres and the olfactory lobes, which is much darker than
the corresponding portion of the _pia mater_.
3. The *arachnoid membrane* is the layer of endothelial cells covering
the inner surface of the _dura mater_: by means of the blood-vessels
and nerves, etc., it is continued on to the _pia mater_ of the spinal
cord and brain, which it in like manner closely invests. Masses
of *calcareous crystals* are found between the epineurium and the
arachnoid (Wiedersheim) on each spinal nerve at its exit from the
intervertebral foramen, also on the trigeminal nerves in the cranium.
Additional smaller and more irregular masses are found on the dorsal
part of the _dura mater_ of the spinal cord.
D. THE VESSELS OF THE BRAIN AND SPINAL CORD. (Fig. 110.)
The arteries of these organs are derived from the internal carotids and
the _arteriae vertebrales_. As soon as the internal carotid arteries
reach the cranial cavity each divides into two branches, an anterior
(_Ramus anterior_, Schöbl[56]) and a posterior (_Ramus posterior_,
Schöbl); the anterior branches course forwards on the lower part
of the surface of the brain as far as the anterior portion of the
thalamencephalon, where they again divide; one division, _arteria lobi
hemisphaerici inferior externa_ (Schöbl), continues forwards along the
outer surface of the cerebral hemisphere and of the olfactory lobe
as far as the olfactory bulb, where it may still be distinctly seen;
it gives off branches to the adjacent parts in its course forwards.
The vessels of the two sides communicate with each other by means of
delicate transverse vessels (_Arteriae communicantes anteriores_).
The second division, _arteria lobi hemisphaerici superior interna_
(Schöbl), of the _ramus anterior_ courses on the thalamencephalon to
the dorsal surface, gives a large branch to the choroid plexus of the
fourth ventricle, and runs forwards in the dorsal longitudinal fissure;
it supplies vessels to all the neighbouring parts.
[Footnote 56: These names are those adopted by Schöbl for corresponding
vessels in the newt, the translator has accepted them as being
suitable, with slight modification, to the vessels of the frog.]
The _rami posteriores_ converge as they course backwards, and
ultimately unite to form an _arteria basilaris_, which is continued in
the median line of the under surface of the spinal cord as the _arteria
spinalis anterior_. The _ramus posterior_ gives off, in its course,
many small vessels to the neighbouring parts, and two larger vessels
on either side, one of which, the _arteria lobi optici_ (Schöbl), is
distributed to the optic lobes, while the other passes to the pituitary
body.
The branches of these vessels form a network in the _pia mater_, from
which the nervous tissue is supplied; they also send numerous branches
directly into the brain and cord, and these have a similar arrangement
for all parts of the brain with the exception of the cerebral
hemispheres and olfactory lobes; more or less vertical branches arise
from the posterior parts of the upper borders of the _rami anteriores_,
from the whole of the _rami posteriores_, and from the _arteria
basilaris_; these course upwards from their place of origin into the
corresponding part of the brain, give off a few branches in the white
matter, and then branch freely, and at somewhat sharp angles, in the
grey matter. In the _pars commissuralis_ a large branch may be traced
from the _ramus posterior_ on either side upwards into the cerebellum
almost to its upper border. The vessels of the cerebral hemispheres
and olfactory lobes seem to possess no other definite arrangement than
that described above. The grey matter seems, on the whole, to be more
vascular than the white; the vessels of the latter are chiefly arranged
radially to the surface, and run in courses which are more or less
straight; the vessels of the grey matter are more irregular and sinuous.
The _Arteria spinalis anterior_ courses along the whole length of the
spinal cord, giving off lateral branches and communicating with _rami
spinales_ (branches of the _Arteria vertebralis_). These branches form
a plexus in the _pia mater_, from which vessels pass at irregular
points into the cord; one set of small vessels, described by Reissner,
pass in a straight course from the superior longitudinal sinus towards
the _substantia reticularis_, where they divide. Other branches pass
directly from the _arteria spinalis anterior_, through the ventral
longitudinal fissure, and there divide; the twigs as a rule avoiding
the _septum medium_ and passing in greater part towards the ventral
horns. The vessels in the white matter are for the most part radial and
straight, while in the more vascular grey matter they are irregular and
more sinuous in their course.
[Illustration: Fig. 110.
Diagram to show the _Vena spinalis posterior_, the _Venae spinales
superiores_, and the origin of the _Vena jugularis interna_.
_H_ Hemispheres.
_ji_ Internal jugular.
_op_ Optic lobes.
_mo_ Medulla oblongata.
_spp_ Vena spinalis posterior.
]
The choroid plexus of the third ventricle (_Plexus choroideus
ventriculi tertii_, Reissner) lies, as already described, on the roof
of the third ventricle; it is somewhat triangular in form (_Plexus
venosus triangularis_, Schöbl), and is evidently a prolongation of
the _pia mater_, with an increased supply of vessels. It receives,
at its anterior angle, veins from the cerebral hemispheres and the
adjacent parts. The under surface is covered with a layer of ciliated
pavement epithelium. At the posterior angles of the plexus the veins
communicate on either side (Fig. 110) with the anterior lateral
prolongation of the _vena spinalis superior_, and with the internal
jugular vein. The small body usually named the pineal body, and placed
on the roof of the ventricle, is only a small thickened portion of
the plexus, and consists of a group of convoluted blood-vessels. This
plexus sends a considerable bunch of vessels into the upper part of the
third ventricle. The choroid plexus of the fourth ventricle (_Plexus
choroideus ventriculi quarti_, Reissner) is a triangular membrane,
slightly attached to the borders of the fourth ventricle. Its upper
surface is flat and bounded at either side by a large vein, the _vena
spinalis superior_; anteriorly it is bounded by the _cerebellum_.
The under surface is not flat; in the middle line is a slight furrow
corresponding to the position of a median vessel, which may, when
injected, be seen from the dorsal surface; from it a number of short
vessels pass outwards and slightly backwards to the outer border. The
connective-tissue between these vessels is pushed down into the cavity;
in this manner one obtains a double row of flattened villous-looking
bodies, which frequently have their tips pigmented. The under surface
of the plexus is clothed with flattened, ciliated epithelium.
On either side of the pituitary body is another small venous plexus
(_Plexus lateralis_, Schöbl); it communicates above with the posterior
angle of the choroid plexus of the third ventricle; externally, with
the internal jugular vein; and internally with its fellow of the
opposite side by more or less irregular transverse vessels, which,
together with a median vein from the fissure between the cerebral
hemispheres, form an irregular _circulus venosus_ around the pituitary
body. These plexuses receive blood from the lower part of the cerebral
hemispheres, the thalamencephalon, the optic lobes, and from the
pituitary body. The veins of the spinal cord open into the dorsal,
_vena spinalis posterior_ (Fig. 110 _spp_), which bifurcates at the
posterior angle of the fourth ventricle, one division passing to either
side and forming, as already described, the outer border of the choroid
plexus; anteriorly it opens into the internal jugular vein (Fig. 110
_ji_).
The blood-vessels, both arteries and veins, are irregularly pigmented,
both on the surface and in the interior of the central nervous system;
those of the cerebral hemispheres and olfactory lobes have very little
or no pigment.
DESCRIPTION OF THE FIGURES ON PLATE I.
Fig. 111. Dorsal view of the orbit, etc.; deep dissection.
_c_ Course of the palatine nerve.
_db_ Fibrous plate.
_dm_ M. depressor maxillae.
_ef_ Terminal branches of the ophthalmic nerve.
_F_ Facial with R. anterior of the glossopharyngeal.
_g,g,g_ Terminal twigs of the ophthalmic nerve.
_h_ Muscular twigs of the Ram. maxillaris.
_ics_ M. intertransversar. capitis superior.
_ii_ Twigs of upper eyelid.
_K_ Terminal twigs of the Ram. maxillaris.
_la_ M. levator anguli scapulae.
_pt_ M. pterygoideus.
_sc_ M. sterno-cleido-mastoideus.
_Sp_ Sympathetic nerve.
_t_ M. temporalis.
_tr_ Nasal branch.
Union of facial nerve with Ram. anterior of the glossopharyngeal
nerve.
_I_ Olfactory nerve.
_II_ Optic nerve.
_III_ Motor oculi nerve.
_IV_ Trochlear nerve.
_Vb_ R. palatinus }
_Vc_ R. maxillo-mandibularis } of the trigeminal
_Vc_′ R. maxillaris } nerve.
_Vd_ R. mandibularis }
_Ve(VII)_ Facial nerve.
_Vg_ Gasserian ganglion.
_VN_ Trigeminus.
_VS_ Sympathetic nerve.
_VI_ Abducens nerve.
_VII_′ Facial nerve.
_VIII_ Auditory nerve.
_X1_ Ram. anterior of the glossopharyngeal.
_X2_ Glossopharyngeal nerve.
_X3_ Pneumogastric nerve.
_XG_ Ganglion nervi vagi.
_XI_ Accessory nerve.
Fig. 112. Dorsal view of the orbit, etc.; superficial dissection.
_e_ External branch of the ophthalmic nerve.
_f_ Internal branch of the ophthalmic nerve.
_g,g,g_ Terminal twigs of the ophthalmic nerve.
_II_ Optic nerve.
_III_ Motor oculi nerve.
_IV_ Trochlear nerve.
_Va_ Ophthalmic nerve.
_Vc_ R. maxillo-mandibularis.
_Vc_′ R. maxillaris of the trigeminal nerve.
_Vd_ R. mandibularis of the trigeminal nerve.
_VI_ Abducens nerve.
_VI_′ Ciliary nerves.
Fig. 113. View of roof of mouth; mucous membrane, etc., removed.
_a_ Branch of the Ram. palatinus to the Harderian gland.
_b_ Branch of the Ram. palatinus to the intermaxillary gland.
_c_ Inosculating-branch of the Ram. palatinus.
_Ch_ Internal naris.
_d_ Cutaneous branch of the Ram. palatinus.
_db_ Fibrous plate.
_F_ Ramus mandibularis of the facial nerve.
_Gl_ Intermaxillary gland.
_HD_ Harderian gland.
_l_ Eyeball.
_m_ M. masseter.
_Ms.ob.i._ M. obliquus inferior.
_OK_ Upper jaw.
_r_ M. retractor bulbi.
_ri_ M. rectus internus.
_ri_′ M. rectus inferior.
_sc_ M. sterno-cleido-mastoideus.
_uk_ Mandible.
† Terminal branch of Ram. palatinus.
* Union of facial nerve with Ram. anterior of the
glossopharyngeal.
_III_ Motor oculi nerve.
_Vb_ Ramus palatinus of trigeminal nerve.
_Vc_ Ramus maxillo-mandibularis of the trigeminal nerve.
_Vc_′ Ramus maxillaris of the trigeminal nerve.
_Vd_ R. mandibularis.
_Ve(VII)_ Facial nerve.
_X_ Pneumogastric nerve.
_X1_ Glossopharyngeal nerve.
Fig. 114[57]. Lateral dissection of head, etc., to show the cranial
nerves, etc.
[Footnote 57: The branches of the vagus which are represented in this
figure as crossing the petrohyoid muscles ought to be underneath
them.--_Trans._]
_c_ Cardiac nerve.
_F_ Union of facial and Ram. anterior of the
glossopharyngeal nerve.
_h_ Ram. hyoideus of the glossopharyngeal nerve.
_la_ M. levator angi scapulae.
_lgd_ M. longissimus dorsi.
_m_ M. masseter.
_mt_ Ram. mandibularis of the glossopharyngeal nerve.
_M1_ Hypoglossal nerve.
_M2_ Brachial nerve.
_Oh_ Anterior cornu of the hyoid bone.
_oi_ M. obliquus internus.
_ph1_ M. petrohyoideus I.
_ph2_ M. petrohyoideus II.
_ph3_ M. petrohyoideus III.
_ph4_ M. petrohyoideus IV.
_pp_ Pharyngeal branches of the pneumogastric nerve.
_tt_′ M. temporalis.
_us_ Muscular twigs of the Ram. mandibularis of the
trigeminal nerve.
_Z_ Tongue.
_Va_ Terminal twigs of the ophthalmic nerve.
_Vc_ Ram. maxillaris of the trigeminal nerve.
_Vd_ Ram. mandibularis of the trigeminal nerve.
_Ve(VII)_ Facial nerve.
_X1_ Ram. anterior of the glossopharyngeal nerve.
_X2_ Glossopharyngeal nerve.
_X3_ Pneumogastric nerve.
_X3g_ Ram. gastrici of the pneumogastric nerve.
_X3l_ Ram. laryngeus.
_X3p_ Ram. pulmonales of the pneumogastric nerve.
_XI_ Accessory nerve of the pneumogastric nerve.
Fig. 115. Dissection of the floor of the mouth.
_dm_ M. depressor maxillae.
_F_ United facial nerve and Ram. anterior of the
glossopharyngeal nerve.
_gh_ } M. geniohyoideus.
_gh_′ }
_h_ Ram. hyoideus of the glossopharyngeal nerve.
_H_ Heart.
_Lg_ Lung.
_m_′ Ram. mandibularis of the glossopharyngeal nerve.
_M1_ Hypoglossal nerve.
_M2_ Brachial nerve.
_Oh_ Anterior cornu of the hyoid bone.
_oh_ Momohyoideus.
_ph1_ M. petrohyoideus I.
_ph2_ M. petrohyoideus II.
_ph3_ M. petrohyoideus III.
_ph4_ M. petrohyoideus IV.
_sc_ M. sterno-cleido-mastoideus.
_sh_ M. sterno-hyoideus.
_sm_ M. mylohyoideus (submaxillaris).
_smt_ M. submentalis.
_TT_ Thyroid.
_uk_ Mandible.
_us_ Muscular twigs of the Ram. mandibularis.
_X2_ Glossopharyngeal nerve.
_X3_ Pneumogastric nerve.
_X3c_ Rami cardiaci of pneumogastric nerve.
_X3l_ Ram. laryngeus of the pneumogastric nerve.
_X3p_ Ram. pulmonalis of the pneumogastric nerve.
II. THE PERIPHERAL NERVOUS SYSTEM.
E. THE CRANIAL NERVES.
(To facilitate reference the original arrangement of this part has been
altered.)
[There are ten pairs of cranial nerves in the frog, which are numbered
in order from before backwards. The mode of origin of these nerves, and
their deeper relations with the respective parts of the brain to which
they belong, have already been described.]
*1.* The *olfactory nerve* (_N. olfactorius_), [(Figs. 97, 98, 102,
103, 111 _I_) runs a very short course only a few lines in length,
and escapes from the cranium by an opening in the cartilage of the
sphenethmoid into the nasal cavity, where it divides into two branches,
each of which breaks up into a brush of filaments, to be distributed
in the olfactory mucous membrane. The nerve contains no white fibres].
(See organ of smell, p. 385.)
*2.* The *optic nerve* (_N. opticus_), (Figs. 97, 102, 103, 111 _II_)
[arises, as already described, by the optic tract, and joins with its
fellow at the optic chiasma or commissure, where part of the fibres
pass over to the opposite side (according to Michel all the fibres
cross). Each optic nerve then courses outwards, piercing the cartilage
of the cranium and so reaching the eyeball]. (See organ of sight,
p. 408.)
*3.* The *motor oculi* (_N. oculomotorius_, _Oculo-motor_, _Motor
communis_), (Figs. 102, 111, 112, 113 _III_). From its origin it
courses outwards and forwards, perforating with a slight obliquity
the cartilaginous wall of the cranium, just in front of the Gasserian
ganglion (Fig. 116 _III_); on reaching the orbit it divides into two
branches, between the _Levator bulbi_ and the _Rectus internus_ and
_inferior_. One branch, _Ramus superior_, runs over and parallel to
the _Ramos ophthalmicus Trig._ and enters the under surface of the
_Rectus superior_; the second, lower branch, _Ramus inferior_, supplies
filaments to the _Rectus internus_ and _inferior_ and to the _Obliquus
inferior_. Apparently it exchanges fibres with the ophthalmic division
of the trigeminal nerve.
[That portion of the motor-oculi between its branch to the _Rectus
superior_ and to that to the _Rectus internus_ contains a number of
nerve cells; according to Schwalbe (_l. c._, p. 235 and Pt. XII,
Fig. 4) these cells are arranged in four groups or ganglia; the second
group forms a very slight prominence, and is covered by a very fine
layer of nerve fibres, it also gives off some extremely fine nerves to
the eyeball; this is perhaps a ciliary ganglion (_Ganglion ciliare_,
Schwalbe). Beard, however, names it ‘mesocephalic ganglion.’ The other
three groups are simply clusters of cells between the fibres of the
nerve.]
*4.* The *pathetic* or *trochlear nerve* (_N. trochlearis_,
_patheticus_), (Figs. 102, 103, and 112 _IV_). From its origin it
courses forwards with and then crosses the motor-oculi; it perforates
very obliquely the cartilaginous lateral wall of the cranium, in
front of the motor oculi but above and very slightly behind the optic
foramen (Fig. 116); it runs parallel to and in company with the _Ramus
opthalmicus trigemini_, and appears to exchange a few fibres with it,
which, however, according to de Watteville, Stannius, Cuvier, and
Wyman, is not really the case. In this course it lies first to the
inner, then to the outer side of the ophthalmic, over which it passes
to supply the _Rectus superior_. [The pathetic and ophthalmic nerves
are sometimes enclosed in a common sheath (de Watteville).]
*5.* The *trigeminal nerve* (_N. trigeminus_), (Figs. 97, 102, 103,
111, 112, 113, and 114 _V_) is the largest of the cranial nerves in
the frog; from its origin it runs outwards and forwards to the skull
wall, and just before reaching this enters the large _Gasserian
ganglion_. It then passes through the cranial wall immediately in
front of the auditory capsule, and divides at once into two main
branches (Fig. 111 _Vg_, etc.), the _Ramus ophthalmicus_ and the _Ramus
maxillo-mandibularis_.
The Gasserian ganglion is a large, yellow, oval ganglion placed in
a depression in the outer wall of the cranium; it is covered by a
‘periganglionic gland,’ which is similar in structure to that of
a spinal ‘periganglionic’ gland (see p. 180), the fibrous capsule
being stronger. This ganglion receives three other nerves besides the
trigeminal, _viz._ the sixth and seventh nerves, and branches of the
sympathetic.
According to de Watteville, these nerves are arranged on the lower
surface of the ganglion, so that the sympathetic is below, the
sixth above it, then the seventh, while the fifth is uppermost;
the sympathetic splits into several bundles which join the various
branches of the ganglion; the sixth divides into two bundles, one of
which usually joins the ophthalmic, while the other makes its exit
independently; the seventh splits into two bundles, one of which
leaves the ganglion as the hyomandibular branch, the other gives some
fibres to the palatine branch of the trigeminal nerve, and is then
continued as the palatine branch of the facial.]
*a.* The _Ramus ophthalmicus_ (_Ramus nasalis_, Fischer; Ophthalmic
or Orbital Branch, Wyman; Orbito-nasal or Ophthalmic Nerve, de
Watteville), (Figs. 111 and 112 _Va_). After leaving the Gasserian
ganglion the nerve is directed forwards parallel to the side of the
cranium, between this and the eyeball. It lies beneath the _Rectus
superior_, but above all the other muscles of the eyeball and the optic
nerve. At the anterior end of the orbit it divides into two branches
(_e_ and _f_) which pass through apertures (_Foramen pro ramo nasali_)
in the cartilage of the sphenethmoid, to reach the nasal cavity, where
they lie between the cartilage and mucous membrane. In this position
the nerves supply branches to the mucous membrane and then pierce the
skull to appear on the surface (Figs. 111, 112 _g,g,g_, 114 _Va_), the
skin of which they supply. The branches inosculate with each other and
communicate with the anterior twigs of the _Ramus maxillaris_ (Fig. 114
_Vc_) and with those of the _Ramus palatinus_ (Fig. 113 _Vb_).
In its course through the orbit the _Ramus ophthalmicus_ gives off:--
(1) Near the Gasserian ganglion one, two, or three small branches,
which communicate with the trochlear nerve, and may then be traced to
the sclerotic of the eyeball; some of the twigs enter near the optic
nerve, others nearer the cornea. They are regarded as _Ciliary nerves_
(_Nervi ciliares_).
(2) A large branch, the *palatine nerve* (_Ramus palatinus_),
(Figs. 111 and 113 _Vb_, _b_). This nerve, after receiving the palatine
branch of the facial, descends on the inner border of the _Levator
bulbi_ to the mucous membrane of the mouth, to which it gives numerous
filaments; it then runs parallel and near to the median line, lying on
the base of the skull; and near the front of the orbit it divides into
three branches. The smallest (_a_) supplies the Harderian gland (_HD_);
the second (_b_) continues in the course of the original nerve, pierces
the vomer, and divides, giving filaments to the mucous membrane in its
whole course, while the terminal twigs supply the intermaxillary gland
(_Gl_) and the surrounding structures. One of these (†) ascends on the
anterior border of the sphenethmoid to the intermaxillary (internasal,
Born) space to supply the numerous glands and to inosculate by one or
two twigs with the nasal branch (_tr_) of the trigeminal. The third
branch of the palatine nerve (_c_) curves directly outwards, just
behind the palatine bone, to the inner surface of the maxillary bone;
it then courses backwards, pierces the fibrous plate (_db_) between the
eyeball and the pterygoid bone, and ultimately unites with superior
maxillary division of the trigeminal nerve (_Vc_′). Just before
piercing the fibrous plate it gives off a tolerably large nerve (_d_)
to the mucous membrane, and in its whole course it gives off twigs to
the mucous membrane and surrounding structures; many of these twigs
inosculate with other terminal twigs of the trigeminal.
[This nerve has been minutely described by Stirling and Macdonald;
these observers find that the branches form a very fine and
close plexus in the mucous membrane, etc.; fibres were traced to
blood-vessels, glands, etc., and ganglion cells were found scattered
along the nerves. The fibres are both medullated and non-medullated,
and many of the cells are described as ‘spiral cells’ (see page 201)
such as those described by Arnold in the sympathetic system of the
frog.]
*b.* The _Ramus maxillo-mandibularis_ (_Ramus maxillaris_, Ecker and
Hoffmann; Supra-maxillary, Humphry; Upper Maxillary Branch, Wyman),
(Figs. 111, 112, and 113 _Vc_). This nerve is the largest division
of the trigeminal; it runs directly outwards behind the eyeball, in
front of the auditory capsule, and between the temporal and pterygoid
muscles. After a very short course it divides into the maxillary and
mandibular nerves. The nerve gives off before its division a few fine
filaments (_i,i_) to the hinder half of the upper eyelid and to the
surrounding skin, also a branch (_h_) [not correctly drawn in Fig. 111]
which divides to supply twigs to the temporal and pterygoid muscles.
(1) The _Ramus maxillaris_ (_Ramus supramaxillaris_, Ecker; _Ramus
maxillaris superior_, Hoffmann; Upper Maxillary Branch, Wyman;
Supramaxillary, Humphry and de Watteville), (Figs. 111, 112, 113, and
114 _Vc_) runs outwards and then forwards, between the eyeball and
the outer wall of the orbit, to the margin of the upper jaw (_K_); a
large portion terminates in a number of small branches for the supply
of the skin of the lower eyelid, the upper lip, and of the parts
between the tympanic membrane and the external nares. Some of these
twigs inosculate with twigs of the palatine and ophthalmic nerves. The
second portion of the nerve unites with the palatine nerve, as already
described.
(2) The _Ramus mandibularis_ (_Ramus maxillaris inferior_, Hoffmann;
Mandibular or Lower Jaw Branch, Wyman; Inframaxillary, Humphry and de
Watteville), (Figs. 111, 112, 113, 114, and 115 _Vd_, _us_). As far as
the outer margin of the eyeball, this nerve runs parallel to and behind
the _Ramus maxillaris_, in which course it supplies branches to the
temporal and pterygoid muscles; it then curves backwards, outwards, and
downwards to the under surface of the squamosal bone, where it supplies
a twig to the _Depressor maxillae_, and then perforates the _Masseter_:
in this manner it reaches the outer surface of the mandible, just
behind the insertion of the temporal muscle; it then courses forwards,
under the skin, to the _Symphysis menti_. In this course the nerve
gives off numerous branches to the skin and surrounding parts, it also
supplies the mylo-hyoid and submental muscles; one branch (Figs. 114
and 115 _us_) is larger than the rest, and supplies the under surface
of the floor of the mouth and lower lip.
*6.* The *abducens nerve* (_Nervus abducens_, Ecker and Hoffmann;
included in the trigeminal, Wyman), (Figs. 111 and 112 _VI_). This very
slender nerve courses along the inner wall of the cranium from its
origin to the Gasserian ganglion (_q.v._) which it joins, and leaves
this in contact with the ophthalmic division of the trigeminal nerve:
the nerve then bifurcates in the orbit; the outer branch supplies
the _Rectus externus_, the inner inosculates with small twigs of the
ophthalmic division of the trigeminal, and then gives off a number of
small ciliary nerves, already described, and one special branch to the
_Retractor bulbi_.
*7.* The *facial nerve* (_N. facialis_, Ecker and Hoffmann; _Facialis_
(_Portio dura_), Wyman; Facial or Jugular Nerve, Stannius), (Figs. 111,
113, and 114 _Ve_ _VII_) arises immediately behind the trigeminal, and
runs forwards, first in company with the auditory nerve, then alone, to
the Gasserian ganglion (_q.v._), with which it unites; it again appears
at the posterior angle of the ganglion, and escapes from the cranium in
company with, and immediately behind, the _Ramus mandibularis_ of the
trigeminal, and divides at once into two branches.
*a.* The _Ramus palatinus_ at once unites with the palatine branch of
the ophthalmic division of the trigeminal nerve. Wiedersheim doubts
this arrangement, and holds that the two portions arise in common
from the Gasserian ganglion; neither has Wyman (_Rana pipiens_)
described this branch of the facial. [De Watteville states that the
_Ramus palatinus_ and the palatine branch of the ophthalmic nerve
are separated by the carotid artery. In urodeles the two nerves are
distinct.]
*b.* The _Ramus hyomandibularis_ (_Ramus jugularis_, Hoffmann;
Facial Nerve, Wyman), (Figs. 113 and 114, _Ve_ _VII_). The nerve is
directed outwards and backwards so as to pass around the bony wall
of the auditory capsule, it then crosses over the inner end of the
columella, with which it is in close contact, and is then joined, under
cover of the _sterno-cleido-mastoideus_ (_sc_), by a branch (_Ramus
communicans_) of the glossopharyngeal (see Fig. 111 *). The single
trunk (_F_) so formed is directed downwards in the posterior wall of
the Eustachian tube to just above the angle of the mandible, where it
divides into three branches, or sometimes into two, in which case a
third nerve is supplied by one of the others, usually by the _Ramus
hyoideus_.
(1) The _Ramus mandibularis_ (_Ramus mentalis_, Hoffmann; Third Trunk
of the Facial, Wyman), (Figs. 114 _mt_ and 115 _m_′) passes inside the
angle of the jaw and courses forwards, between the skin and mylo-hyoid
muscle, parallel to the _Ramus mandibularis_ of the trigeminal nerve,
as far as the symphysis. It supplies small twigs to the neighbouring
parts of the mucous membrane of the mouth.
(2) The _Ramus hyoideus_ (_Ramus jugularis_, Hoffmann; Second Trunk of
the Facial, Wyman), (Figs. 114, 115 _h_) is the largest division of
the facial; it courses forwards subcutaneously over the _deltoideus_
and the hinder fibres of the _mylo-hyoideus_ to the anterior cornu of
the hyoid bone, supplying its muscles and the skin of the throat and
sternal region.
(3) The _Ramus auricularis_ (First Trunk of the Facial, Wyman); is a
small branch, directed outwards; it supplies a branch to the walls of
the tympanic cavity, and is finally distributed in the skin under the
tympanic membrane and behind the angle of the mouth.
*8.* The *auditory nerve* (_N. acusticus_, Ecker, Hoffmann; Auditory
Nerve, Wyman). This nerve has a very short course in the cranium;
it reaches the auditory organ by a foramen (Fig. 116 _VIII_) in the
auditory capsule, and is then distributed in the ear, with which it
will be described.
*9.* The *glossopharyngeal nerve* (_N. glossopharyngeus_, Ecker;
_Ramus glosso-pharyngeus_, Hoffmann; Glossopharyngeal, Wyman;
Glossopharyngeal of the Vagus, Müller), (Figs. 102 and 103 _X_, 111,
113, 114, and 115 _X_^2) arises in common with the pneumogastric nerve,
and quits the skull with it through an opening (_Canalis nervi vagi_)
immediately behind the auditory capsule, and at once divides into two
branches; both of which lie under the _MM. intertransversarii capitis_
and are covered by the _Depressor mandibulae_.
*a.* The _Ramus anterior_ (Verbindungsast des Glossopharyngeus,
Wiedersheim; _Ramus communicans_, Hoffmann; Uniting Branch, Wyman;
Laryngeal Branch of the Vagus, Volkmann; _Communicans ad facialem_,
de Watteville), (Figs. 111, 113, and 114 _X^1_). This nerve curves
downwards and forwards around the auditory capsule and beneath the
_Depressor mandibuli_ to join the facial nerve, as already described.
*b.* The _Ramus posterior_ (_N. glossopharyngeus_, Wiedersheim; _Ramus
lingualis_, Hoffmann), (Figs. 111, 113, and 114 _X^2_). This nerve
runs downwards and forwards to the ventral surface of the pharynx,
dips underneath the _Petrohyoideus IV_, to appear again, after a short
interval, by piercing the _Petrohyoideus II_ or _III_, courses parallel
to and behind the anterior cornu of the hyoid bone, and thus reaches
the floor of the mouth. The nerve then runs forwards in a very sinuous
course, close to the median line, and between the _Geniohyoideus_
and _Hyoglossus_; in its course on the floor of the mouth it crosses
the hypoglossal nerve. It supplies the petrohyoid muscles, and gives
numerous small branches to the mucous membrane of the pharynx (_Ramus
pharyngeus_, Hoffmann).
*10.* The *pneumogastric* or *vagus nerve* (_Vagus_; _Ramus
intestinalis nervi vagi_, Fischer, Hoffmann; Vagal Trunk, Wyman;
Vaso-sympathetic, Gaskell), (Figs. 111, 113, 114, and 115 _X_^3). This
nerve arises in common with the glossopharyngeal; the two nerves leave
the skull together by an opening in the exoccipital bone (_Canalis
nervi vagi_); immediately outside the skull they acquire a ganglionic
enlargement (_Ganglion condyloideum_, _Ganglion nervi vagi_), (Fig. 111
_XG_); in this course the glossopharyngeal lies in front of the
pneumogastric, which it then leaves. The pneumogastric lies first upon
the _M. levator anguli scapulae_, then running backwards and downwards
along the hinder border of the _Petrohyoideus IV_ it comes to the side
of the pharynx; it is covered by the trapezius, and passes between the
hypoglossal nerve and the _Aorta ascendens_; arriving at the _Arteria
pulmonalis_, it gives off its terminal branches. [Gaskell has proved
that this nerve contains both sympathetic and vagal elements, and that
it is therefore really a vago-sympathetic.]
[Illustration: Fig. 116.
Right half of skull of _Rana esculenta_, seen from within.
_II_ Optic nerve.
_III_ Motor oculi nerve.
_IV_ Trochlear nerve.
_VN_ Root of the trigeminal nerve.
_Vg_ Gasserian ganglion.
_VS_ Sympathetic nerve.
_VI_ Abducens nerve.
_VII^1_ Facial nerve.
_VIII_ Auditory nerve.
_X^{1–3}_ Pneumogastric and glossopharyngeal nerves.
]
The branches and communications of the pneumogastric nerve are:--
*a.* Communications between the ganglion of the pneumogastric and the
sympathetic system (Fig. 111 _Sp_), which again connect it with the
Gasserian ganglion of the trigeminal nerve (Fig. 111 _VS_, _Vg_); (see
sympathetic system).
*b.* [The _Ramus cutaneus dorsalis_ (Fischer) is considered by Stannius
and Fürbringer to be the homologue of the _Ramus auricularis_; it
passes outwards between the _digastricus_ and _temporalis_ to be
distributed in the skin of the suprascapular region. This nerve is the
persistent portion of the _N. lateralis nervi vagi_ of the tadpole.]
*c.* During its course over the _petrohyoidei_ the vagus gives off a
few twigs (Fig. 114 _pp_), which form a fine plexus to supply these
muscles and the pharynx [also a twig to the trachea, according to
Hoffmann].
*d.* The _Ramus accessorius_ (Fürbringer, Hoffmann, Ecker), (Fig. 114
_XI_) is usually a single small nerve which runs between the
_intertransversarii_ muscles and the _trapezius_: it supplies the under
surface of the latter muscle.
*e.* The _Ramus scapularis_ (Hoffmann) is a very slender nerve arising
near the _Ramus accessorius_; it passes along the under surface of the
_trapezius_ to the inner surface of the _interscapularis_, which it
supplies.
*f.* The _Ramus laryngeus_ (_Recurrens vagi_), (Figs. 114 and 115
_X3l_) runs for some distance parallel to the pneumogastric, separated
from it by the _petrohyoideus IV_; arriving at the hinder cornu of the
hyoid bone the nerve loops round the _Arteria pulmonalis_, and divides
into two branches for the supply of the larynx.
*g.* The _Rami gastrici_ (Fig. 114 _X3g_) are usually two in number:
they pierce the partial diaphragm formed by the anterior fibres of the
_M. obliquus internus_ and terminate in the walls of the stomach.
*h.* The _Rami pulmonales_ (Figs. 114 and 115 _X3p_) also perforate the
partial diaphragm, and then course along the pulmonary arteries to the
lungs.
*i.* The _Ramus cardiacus_ (Figs. 114 and 115 _X3c_). This nerve is
usually smaller on the right side than on the left; it passes along the
dorsal surface of the pulmonary artery and _Vena cava superior_ to the
_Sinus venosus_; in this course it gives off two or three twigs to the
roots of the lungs: the two nerves communicate just before reaching the
heart and pass on to the auricular septum, whence they are distributed
to the heart.
*j.* A slender *Laryngeal nerve* arises from the vagus alongside the
_Ramus cardiacus_; it courses along the hinder end of the greater cornu
of the hyoid to the outer side of the pharynx, which it pierces to pass
to the larynx.
F. THE SPINAL NERVES.
I. *General description.* Ten pairs of nerves arise, as already
described (p. 135), from the spinal cord; each nerve has two roots, a
ventral or anterior, and a dorsal or posterior, which unite at their
points of exit from the intervertebral foramen: just before, and for a
short distance beyond this union, each dorsal root bears a ganglionic
enlargement.
*a.* The length and direction of the various *Nerve-roots* vary
greatly; the roots of the anterior spinal nerves run a very short
course, almost transversely outwards, from their points of origin to
the intervertebral foramina: the roots of the middle and posterior
nerves, in consequence of the vertebral column being considerably
longer than that part of the cord belonging to it, pass obliquely
backwards to the foramina, the hinder nerves of the _Cauda equina_
running for a considerable distance in the vertebral canal (Fig. 116).
The relations of these roots are as follows:--
(1) The roots of the first nerve (_N. hypoglossus_) arise from the
spinal cord at a point between the first and second vertebrae; they run
transversely outwards to escape between the first and second vertebrae.
The dorsal root is extremely slender.
[Illustration: Fig. 117.
The nervous system of _Rana esculenta_, from the ventral surface. (From
Icones physiologicae by A. Ecker. Pl. XXIV, Fig. 1.)
_F_ Facial nerve.
_G_ Ganglion of pneumogastric nerve.
_He_ Cerebral hemisphere.
_Lc_ Optic tract.
_Lop_ Optic lobe.
_M_ Boundary between medulla oblongata and spinal cord.
_M1–10_ Spinal nerves.
_MS_ Connection between fourth spinal nerve and
sympathetic chain.
_N_ Nasal sac.
_Ni_ Sciatic nerve.
_No_ Crural nerve.
_o_ Eyeball.
_S_ Trunk of sympathetic.
_S1–10_ Sympathetic ganglia.
_SM_ Rami communicantes of the same.
_Sp_ continuation of sympathetic into head.
_I_ Olfactory nerve.
_II_ Optic nerve.
_III_ Motor oculi nerve.
_IV_ Trochlear nerve.
_V_ Trigeminal and facial nerves.
_Va_ Ramus ophthalmicus.
_Vc_ Ramus maxillaris.
_Vd_ Mandibular branch of trigeminal.
_Ve_ Hyomandibular branch of facial.
_Vg_ Gasserian ganglion.
_Vs_ Upper end of sympathetic trunk in connection with
Gasserian ganglion.
_VI_ Abducens nerve.
_VII_ Facial nerve.
_VIII_ Auditory nerve.
_X_ Glossopharyngeal and pneumogastric nerves.
_X1_ Ramus anterior of glossopharyngeal.
_X2_ Ramus posterior of glossopharyngeal.
_X3, 4_ Branches of pneumogastric.
]
(2) The roots of the second nerve (_N. brachialis_) arise at the level
of the second vertebra and leave the vertebral canal between the second
and third vertebrae.
(3) The roots of the third nerve arise from the cord between the
second and third vertebrae, and pass out between the third and fourth
vertebrae.
(4) The fourth nerve arises by its two roots at the level of the fourth
vertebra, and quits the vertebral canal between the fourth and fifth
vertebrae.
(5) The fifth nerve arises opposite the fourth vertebra, and passes
outwards and slightly backwards to the foramen between the fifth and
sixth vertebrae.
(6) The roots of the sixth nerve are attached to the cord opposite the
fourth vertebra, and leave the vertebral canal between the sixth and
seventh vertebrae.
(7) The seventh nerve arises from the cord at a point between the
fourth and fifth vertebrae, and leaves the canal between the seventh
and eighth vertebrae.
(8) The eighth nerve quits the cord at a point opposite the
articulation between the fifth and sixth vertebrae, then runs backwards
to the eighth vertebra, and escapes between this and the ninth vertebra.
(9) The ninth nerve arises at the level of the sixth vertebra, and
passes out between the sacrum (ninth vertebra) and the urostyle.
(10) The tenth nerve (_N. coccygeus_) arises from the cord immediately
behind the ninth nerve and opposite the sixth vertebra, and courses
alongside the terminal filament to pass out through a foramen in the
urostyle (_canalis coccygeus_).
*b.* [The *Spinal ganglia* (_Ganglia intervertebralia_).
At their exit from the intervertebral foramen the two roots of each
nerve unite and bear a ganglionic enlargement, which is in intimate
connection with the dorsal root, but is merely in contact with
the ventral root. The ganglia lie[58] in the large intervertebral
depressions, upon the under surface of the _Proc. obliqui_, above and
behind, being in relation with the bodies of the vertebrae internally,
and the _Musculi intertransversarii_ externally (Fig. 119); ventrally
the ganglia are, more or less, covered by the ‘periganglionic glands.’
The ganglia vary much in size; that of the first spinal nerve is the
smallest. The ganglion is not attached to the dorsal root alone but
is prolonged a short distance beyond the point of union of the two
roots; this is best seen in the nerves of the lumbar plexus. Each
ganglion is a yellowish-white rounded or oval body, with an outer thick
(sometimes 0.15 mm. thick) sheath of connective-tissue, connected by
the epineurium of the nerve roots with the _Dura mater_. This sheath is
composed of bundles of parallel, wavy, white, connective-tissue fibres,
which enclose a large number of connective-tissue corpuscles, and here
and there contains brown pigment.
[Footnote 58: The _Gangl. coccygeum_ is in the urostyle.]
[Illustration: Fig. 118.
Ventral view of the brain and spinal cord, to show the points of exit
of the spinal nerves.
_M1–10_ Spinal nerves.
_VG_ Trigeminal ganglion.
_W1–10_ Vertebrae.
_XG_ Ganglion of vagus.
]
By means of longitudinal and transverse sections it may be seen
that the ganglion surrounds the ventral root, but that it forms a
thinner layer on that side, where the dorsal root joins the ventral;
although at this point the two roots and the ganglion are firmly
united together, the thick fibrous sheath of the ganglion prevents any
communication between the nervous elements of the ventral root and
those of the ganglion.
The sheath contains nerve-cells and fibres, and sends in a few fine
processes to support these structures. The fibres of the posterior
root enter and pass out of the ganglion without suffering any changes,
except that the nerve fibres are slightly separated by the presence of
a few nerve-cells, and that a distinct increase in the number of nerve
fibres takes place. The nerve-cells, of which the ganglion is chiefly
composed, and upon the number of which its size directly depends, are
arranged chiefly around the fibres of the dorsal root; such few as lie
between the fibres are smaller than the rest and vary more in their
relative numbers; at times one or two isolated cells are found in the
capsule or even in the adjoining ‘periganglionic gland.’ The cells near
the capsule are somewhat smaller than the deeper cells.[59] Each of
these cells, which are usually pear-shaped, possesses only one process;
the cell membrane is thick, resistant, and possessed of an external
nucleated, endothelial covering, the space around being probably
a pericellular lymph-space; it often contains one to three small
fat-globules; the protoplasm of these has, according to v. Lenhossék, a
concentric fibrillation; the nucleus is round, clear, and distinct, and
relatively larger the smaller the nerve-cell; it is usually placed in
the centre of the cell.
[Footnote 59: Larger cells of deeper layer 80 µ to 90 µ in diameter,
sometimes one or two as large as 0·1 mm. v. Lenhossék.]
[Illustration: Fig. 119.
Ventral view of the spinal ganglia; on the right side they are still
hidden by the ‘periganglionic glands.’ ]
[Illustration: Fig. 120.
Schema of spinal ganglion.
_A_ Ventral root.
_C_ Ramus communicans.
_G_ Ganglion
_O_ Dorsal division.
_P_ Dorsal root.
_R_ Ventral division.
]
In that portion of the cell towards the process is a portion brighter
and less easily stained than the rest of the cell (Polarkernen,
Courvoisier); this apparently possesses one or two nuclei, and is
regarded as a cell by Lenhossék (Polarzellen); the process of each cell
soon acquires a medullated sheath, and after a short course, 0.09 mm.
to 0.35 mm., divides usually about the third constriction (Lenhossék).
These processes all pass peripherally, even those which appear at first
to pass in the opposite direction curve round again; it is chiefly due
to these fibres that the spinal nerve is larger than its two roots.
In addition to the above, smaller, irregular cells from 5 µ to 7 µ in
length are found; Rawitz regards them as young cells, Lenhossék as
cells capable of (entwicklungsfähige) developing into nerve-cells. The
ganglia contain only few blood-vessels.]
The above description is founded upon that of Lenhossék, and has been
confirmed by the translator in every particular, except that only
very indistinct and unsatisfactory indications of the concentric
fibrillation so clearly delineated by Lenhossék were obtained; the
structure of the Gasserian ganglion was found to correspond exactly
with the description here given of the structure of the spinal ganglia.
The nucleus was oftener at the side than at the centre of the cell.
*c.* The ‘*Periganglionic Glands*’ (Periganglionäre Kalkdrüsen, v.
Lenhossék; Kalksäckchen, Ecker, and others; Crystal capsules, Wyman;
Calcareous Sacs or Masses, of other writers), (Fig. 119). These bodies
are found on the ganglia of all the spinal nerves and on the Gasserian
ganglion of the trigeminal nerve; they have recently been carefully
investigated by v. Lenhossék. According to his description there are
usually two to each ganglion, lying on its sides and ventral surface;
each consists of a connective-tissue capsule which sends in a few fine
trabeculae to support a system of glandular tubes: these usually run
parallel to the long axis of the gland, and are about 14 µ to 15 µ in
diameter; each tube is lined with a single layer of somewhat columnar
epithelium, the cells of which have sharp, distinct outlines and oval
nuclei.
A _membrana propria_ was not made out with certainty; the lumen of
the tubes is wide and contains a milky fluid, which gives the whole
structure its characteristic appearance; it has long been known
(Blasius, 1681, mentions the fact, _l.c._, p. 291) that this fluid
contains calcareous matter, which effervesces and dissolves in the
presence of hydrochloric acid; the crystals vary in form but are
chiefly oval (Wyman).
These glands bear no definite proportion to the size of the nerves to
which they are attached (Fig. 118); they already contain calcareous
matter during the tadpole stage before the limbs are developed
(Stannius, Wyman). No ducts have been traced to these glands. This
description, founded upon that of Lenhossék, can be confirmed by the
translator in every particular; his sections, however, would lead him
to believe that the glands are far more vascular than the description
and the drawings of Lenhossék imply.]
*d.* The *Branches* of the complete spinal nerves formed by the union
of the dorsal and ventral roots with the ganglion (Fig. 120) are
usually described as two, a dorsal and a ventral branch, which latter
at once gives off a _Ramus communicans_ to the sympathetic system;
these two branches are given off almost immediately beyond the ganglion.
II. The Individual Nerves.
A. The Dorsal Branches (Fig. 121).
[Illustration: Fig. 121.
Dorsal branches of the spinal nerves. The _Fascia dorsalis_ is
dissected, removed from the left side.
_rc_ Rami cutanei.
_rm_ Rami musculares.
]
The dorsal branches are smaller than the ventral; they pass upwards
between the inner borders of the _Musc. intertransversarii_ and the
articular processes of the vertebrae to reach the under surface of the
_M. longissimus dorsi_; the general course of these nerves is very
similar for all; each nerve gives off--
(_a_) A twig to the _Musc. intertransversarius_ and then divides into
two branches.
(_b_) A _Ramus muscularis_ (Fig. 121 _rm_), which passes outwards to
supply the _M. longissimus dorsi_.
(_c_) A _Ramus cutaneus_ (Fig. 121 _rc_); this nerve continues under
the extensor muscle of the back, running on the arch of the vertebra
towards the middle line; it then pierces the muscle and Fascia dorsalis
to reach the large dorsal lymph-sac (_Sacc. cranio-dorsalis_), through
which it courses to end in the skin. In its course through the sac the
nerve is connected with a small artery and vein by a small amount of
connective-tissue, the whole being enclosed in a sheath of endothelium
continuous with that of the general cavity.
The three anterior cutaneous nerves pierce the _Fascia dorsalis_ near
the spinous processes, the fourth a little to the side, the fifth
perforates the _M. coccygeo-iliacus_ at about the junction of its
anterior and middle thirds; the sixth and seventh perforate the same
muscle, but more posteriorly. There are seven of these _Rami cutanei_,
the first coming from the second spinal nerve, the rest from the
succeeding six spinal nerves.
B. The Ventral Branches.
The ventral branches of the spinal nerves are larger than their
corresponding dorsal branches: each nerve gives off immediately a
_Ramus communicans_ to the sympathetic system (Figs. 117 _SM_, 120
_C_); these _Rami communicantes_ will be described with the sympathetic
system; the remaining portions of the ventral divisions of the original
spinal nerves are usually known as the spinal nerves; they will be
described as such in detail.
*1.* The *hypoglossal nerve*[60] (_N. hypoglossus_, _N. spinalis I_),
(Figs. 114 115, and 117 _M1_), or first spinal nerve, is of small
size; it leaves the vertebral canal between the first and second
vertebrae to lie between the _Musculi intertransversarii_ and the
pharynx, where it has in front the _Arteria vertebralis_, behind the
_Arteria_ and _Nervus brachialis_; passing under the _Levator anguli
scapulae_, it touches the _Aorta ascendens_ and crosses the _Vagus_
and the Carotid-gland, and thus reaches the space between the _Musculi
sterno-hyoidei_ and the _Petro-hyoideus_; then curving forwards sharply
it turns under the _Mylo-hyoideus_ to course between the fibres of the
_Genio-hyoideus_ to the root of the tongue, where it ends. It first
lies to the inner and then to the outer side of the glossopharyngeal
nerve. In its course the nerve gives off the following branches:--
[Footnote 60: [Observers have differed considerably as to the relations
of this nerve: Volkmann describes it as the first nerve of the neck,
and describes a ganglion on its dorsal root; Vogt denies the presence
of this ganglion, and regards it as a true cranial nerve; Stannius
asserts that no ganglion exists, and holds the nerve to represent the
first two spinal nerves; Wyman describes the two roots and regards it
as a spinal nerve; Hoffmann regards this nerve as the second spinal
(N. spinalis II); Fürbringer as the representative of two spinal
nerves; de Watteville describes two roots and names it first spinal
nerve.--TRANS.]]
(_a_) One or two communicating twigs (Figs. 114 and 122) to the second
spinal nerve.
(_b_) Muscular twigs to the _Longissimus dorsi_, _Intertransversarii
capitis_, _Levator anguli scapulae_, and the _Retrahens scapulae_.
(_c_) When near the glossopharyngeal it supplies twigs to the
_Geniohyoideus_, _Sternohyoideus_, and _Omohyoideus_, where it
bifurcates.
(_d_) One of the branches passes inwards to supply the _Hyoglossus_.
(_e_) The other terminal branch passes forwards with the _Ramus
lingualis_ and the glossopharyngeal, between the fibres of the
_Geniohyoideus_, which it partially supplies, and sends twigs to the
neighbouring parts.
(_f_) [Hoffmann describes a communicating branch to the pneumogastric
nerve, which the translator has not been able to discover, and which no
other observer has mentioned.]
*2.* The *second spinal* or *brachial nerve* (_N. brachialis_, _N.
spinalis II_), (Fig. 122) is a large nerve, leaving the vertebral canal
between the second and third vertebrae; it then accompanies the _Art.
axillaris_ along the anterior border of the transverse process of the
third vertebra, over the hinder end of the _Musc. levator scapulae_ and
the anterior end of the _m. transverso-scapularis major_, to the inner
border of the _Musc. subscapularis_, under which it passes into the
arm. In this course it gives off or receives the following branches:--
(_a_) It first receives a branch from the second spinal nerve.
(_b_) It gives off a large branch, the _N. coraco-clavicularis_
(Fig. 122 _Cc_), which first accompanies a branch of the _Art.
axillaris_ on the _Musc. levat. scapulae_, then courses forwards and
outwards over the _Musc. subscapularis_ to pass from above into the
_Foramen ovale_ between the clavicle and coracoid bones. It gives off
two branches:
(1) One immediately beyond its origin, which runs backwards over the
_Musc. subscapularis_ to supply the _Musc. obliq. abdominis internus_
(Fig. 122 _Cc_′).
(2) While in the _Foramen ovale_, the _N. coraco-clavicularis_
bifurcates; the anterior twig runs forwards and outwards to the
_deltoideus_ and also supplies a recurrent filament to the _Musc.
sterno-radialis_; the posterior twig enters the upper surface of the
_Musc. stero-radialis_.
(_c_) At the outer extremity of the _Musc. transverso-scapularis_ the
brachial nerve gives off a posterior branch, which at once bifurcates:
(1) The first branch passes into the under surface of the _Musc.
latissimus dorsi_ (_ld_), giving a twig to the _Infraspinatus_.
(2) The second is the _Ramus cutaneus axillaris_ (_IIc_); it passes on
the under surface and posterior border of the _Musc. latissimus dorsi_
to the skin of axilla and dorsal surface of the upper arm.
(_d_) Several small branches are given off from the upper and anterior
surfaces of the brachial nerve near the _Foramen ovale_; they
accompany an artery to pass forwards and upwards between the _Musc.
subscapularis_ and the _M. transverso-scapularis_ on the one side, and
the long head of the _M. triceps brachialis_ on the other, and are lost
in the _M. deltoideus_ and the _M. infraspinatus_.
[Illustration: Fig. 122.
The brachial plexus.
_Cc_ N. coraco-clavicularis.
_Cc_′ Nerve to musc. obliq. abdom internus.
_d_ Deltoid muscle.
_la_ Musc. lev. ang. scap.
_ld_ Musc. lat. dorsi.
_oi_ Musc. obliq. abdom. intern.
_sc_ Musc. sterno-mastoid.
_ss_ Musc. subscapularis.
_SI_ First spinal nerve.
_SII_ Second spinal nerve.
_SIII_ Third spinal nerve.
_IIc_ Ramus cutaneus axillaris.
_IIIc_ Ramus cutaneus abdominalis.
]
The _N. brachialis_ continues its course by passing between the long
and inner heads of the _M. triceps_, reaches the arm and splits into
two nerves, the _N. ulnaris_ and the _N. radialis_.
[*I.*] The _N. ulnaris_ (Fig. 123 _U_) escapes from cover of the long
head of the _M. triceps_ and runs obliquely over its inner head
towards the outer side of the _Plica cubiti_; in this course it
supplies four branches:
α. The _Ramus subscapularis_ passes dorsally to the _M. subscapularis_.
β. A _Ramus pectoralis_ (Fig. 123 _up_), passes forwards to the _M.
abdomino-pectoralis_ and to the skin of the pectoral region (_R.
cutaneus pectoralis_).
γ. The _N. cutaneus antibrachii superior s. medialis_ (_uc_) passes to
the skin of the inner side of the forearm; this and the two following
nerves are given off near the _Plica cubiti_.
[Illustration: Fig. 123.
Nerves of the central surface of the arm. The hand pronated.
_rc_ Upper cutaneous branch of the N. radialis.
_rc_′ Lower cutaneous branch 4-,f the N radialis
_U_ N. ulnaris.
_uc_ R. cutan. sup. of the N. ulnaris.
_uc_′ R. cutan. inf. of the N ulnaris.
_up_ R. pectoralis of the N. ulnaris.
]
δ. The _N. cutaneus antibrachii inferior s. dorsalis s.
musculo-cutaneus_ (_uc_′) at once supplies branches to the _M. flexor
carpi radialis_[61], and then runs downwards upon the muscle and
bifurcates:--
[Footnote 61: As this muscle increases in size during the breeding
season. it would be interesting to know whether a corresponding change
takes place in the nerve.]
[1] The _R. lateralis_ is distributed, by two twigs, in the _M. flexor
carpi ulnaris_ and in the skin of the second finger, to which it
supplies the _Rami digitales volaris_ and _dorsalis_.
[2] The _R. dorsalis_, after giving a cutaneous twig to the second
finger, is distributed by numerous twigs to the skin of the dorsal
surface of the hand.
The _N. ulnaris_ then passes between the _M. flexor carpi radialis_ and
the tendon of the _M. sterno-radialis_, sinks deeply into the _Plica
cubiti_, where it lies between the _M. flexor carpi radialis_ and
the _Flexor carpi ulnaris_, then between the latter and the _Flexor
anti-brachii medialis_ on the one side and the _Flexor digitorum
communis_ on the other: it supplies branches to all these muscles, and
while still in the forearm divides into two terminal branches:--
α. The _R. ulnaris medialis_ is the smaller; it runs inwards, passes
under the tendon of the _M. extensor carpi ulnaris_ into the palm of
the hand and ends as the _N. volaris digiti V medialis_.
β. The _R. ulnaris lateralis_ passes near the thumb-rudiment, covered
by the _M. abductor pollicis_, deeply into the palm of the hand, and
supplies by bifurcating branches the adjacent sides of the second,
third, fourth, and fifth fingers (_R. volares_); it also gives twigs to
the muscles of the palm.
[II.] The _N. radialis_ (Figs. 123, 124, and 125 _R_) passes immediately
beyond its origin from the _N. brachialis_, between the humerus and the
_M. triceps_, runs along the bone to its outer side; in this course it
gives off:--
[Illustration: Fig. 124.
Nerves of the ventral surface of the arm. The hand supinated, and the
superficial layer (Flex. carpi rad. and uln., Flex. dig. commun.) has
been removed.
_R_ N. radialis.
_u_ N. ulnaris.
_uc_ R. cutan. inf. of the N. ulnaris.
_um_ Bifurcation of the N. ulnaris.
]
α. _Rami musculares_ to the separate parts of the _M. triceps_.
β. The _Ramus cutaneus superior_ (Fig. 125 _rc_) to the skin of the
outer surface of the upper arm and forearm.
The nerve then sinks deeply under the origins of the _M. extensor carpi
ulnaris_ and the _M. extensor digitorum communis_, where it bifurcates
after giving off some small twigs:--
γ. Small muscular twigs to the extensor muscles of the hand and fingers.
[Illustration: Fig. 125.
The N. radialis.
_ec_ M. extensor carpi ulnaris.
_ed_ M. extensor digit. comm.
_R_ N. radialis.
_R1_ R. lateralis.
_R2_ R. medialis.
_rc_ R. cutaneus superior.
_rc_′ R. cutaneus inferior.
]
δ. The _R. radialis medialis_ (_R2_), the smaller terminal branch,
supplies a branch to the _M. extensor digit. comm. longus_ and the skin
over the carpus (_Ramus cutaneus inferior_, _rc_′), and ends on the
muscles of the little finger as the _R. dorsalis digiti V medialis_.
ε. The _R. radialis lateralis_ (_R_), the larger of the two branches,
supplies the extensor muscles of the fingers and gives bifurcating
branches, _Rami digitales dorsales_, to the adjacent sides of the
second, third, fourth, and fifth fingers (the _Ramus dorsalis
lateralis_ of the second finger is supplied by the _N. ulnaris_).
*3.* The *third spinal nerve* (_N. spinalis III_) (Fig. 122 _SIII_)
leaves the vertebral canal by the foramen between the third and fourth
vertebrae, and runs outwards and forwards upon the large transverse
process of the third vertebra to the brachial nerve (_N. spinalis II_).
Its behaviour at this point is subject to considerable variation; at
times it joins the brachial nerve completely, at other times the two
nerves are simply in contact; or lastly, it may send a small twig to
the brachial nerve. Externally to this point the two nerves supply a
number of small branches, which may belong almost entirely to either
one nerve or the other; these nerves again inosculate in a variable
manner, to form an axillary plexus. The more constant branches are:--
(1) One or more twigs to the _Musc. transverso-scapularis major_.
(2) Several branches, usually two larger and one smaller; they course
in the _M. obliq. abdom. internus_ (Fig. 122 _oi_) to the _M. rectus_,
where they give off branches, then pierce the muscle to reach the skin
(_R. cutaneus abdominalis_), (Fig. 122 _IIIc_).
*4.* The *fourth spinal nerve* (_N. spinalis IV_) (Fig. 126 _M4_)
appears between the fourth and fifth vertebrae; it runs on the ventral
surface of the transverse process of the fifth vertebra and upon the
_Musc. intertransversarius_ obliquely outwards and downwards, and
reaches the deeper surface of the _Musc. obliquus internus_, into which
it descends, about opposite the articulation between the eighth and
ninth vertebrae; it then bifurcates into:--
(1) A _Ramus cutaneus abdominalis_, which pierces the muscle and
supplies the skin.
(2) A _Ramus muscularis_, which supplies the broad abdominal muscle and
the _M. rectus abdominis_.
*5.* The *fifth spinal nerve* (_N. spinalis V_) (Fig. 126 _M5_)
emerges through the foramen between the fifth and sixth vertebrae,
runs obliquely downwards and outwards over the transverse processes
of the sixth and seventh vertebrae and the corresponding _M.
intertransversarii_, and at a point nearly opposite the middle of the
urostyle pierces the _M. obliquus internus_.
The rest of its course corresponds exactly with that of the fourth
spinal nerve.
*6.* The *sixth spinal nerve* (_N. spinalis VI_) (Fig. 126 _M6_),
after escaping from the vertebral canal between the sixth and seventh
vertebrae, runs obliquely downwards and outwards on the under
surfaces of the transverse processes of the seventh, eighth, and
ninth vertebrae, then under the iliac bone to a point opposite the
hinder half of the urostyle, where it descends under cover of the _M.
obliquus abdom. internus_. In the rest of its course it repeats the
corresponding courses of the fourth and fifth spinal nerves.
[Illustration: Fig. 126.
Ventral view of the brain and spinal cord, to show the points of exit
of the spinal nerves.
_M1–10_ Spinal nerves.
_VG_ Trigeminal ganglion.
_W1–10_ Vertebrae.
_XG_ Ganglion of the vagus.
]
*7*, *8*, *9*, and *10*. The *seventh*, *eighth*, *ninth*, and *tenth
spinal nerves* (_Nervi spinales VII_, _VIII_, _IX_, and _N. spinalis X
s. N. coccygeus_) (Figs. 126 and 127 _M7_, _M8_, _M9_, and _M10_) are
best described together, as they are intimately associated to form the
sciatic plexus (_Plexus ischiadicus_, _Plexus cruralis_).
Within the vertebral canal the roots of these nerves form the _Cauda
equina_; the seventh nerve leaves the canal between the seventh and
eighth vertebrae, the eighth nerve between the eighth and ninth
vertebrae, the ninth between the sacrum or ninth vertebra and the
urostyle, and the tenth by the _Canalis coccygeus_ in the urostyle;
from these points the four nerves run obliquely on the ventral surface
of the _M. ilio-coccygeus_ to the pelvis, where they form the sciatic
plexus. Although subject to some variation, the usual arrangement is
that the seventh and eighth nerves unite to form a trunk, which then
receives the ninth nerve; the large nerve so formed is the sciatic
nerve: a branch of the tenth usually then joins either the sciatic
plexus or the sciatic nerve; the plexus gives off or receives the
following branches:--
(_a_) Like other spinal nerves, these nerves give off _Rami
communicantes_ (see Sympathetic System).
(_b_) The _M. ilio-hypogastricus_ (Fig. 127 _M7a_). This arises
from the seventh spinal nerve, before its union with the eighth
spinal nerve; it runs obliquely outwards and downwards on the _Musc.
ilio-coccygeus_ and under the border of the _M. obliquus abdom.
internus_, where it bifurcates:--
(1) One branch, the _Ramus cutaneus abdominalis_, pierces the _M.
obliq. abdom. internus_ in the same fashion as the cutaneous branches
of the fourth, fifth, and sixth spinal nerves; it supplies the skin of
the abdomen.
(2) The second or _Ramus muscularis_ supplies the flat abdominal
muscles and the _M. rectus abdominis_.
(_c_) The _M. cruralis_ (Fig. 127 _M7b_) also arises from the seventh
spinal nerve at or just beyond its point of union with the eighth
spinal nerve. It accompanies the _A. cruralis_ on the pelvic wall to
the thigh, where it lies upon the _M. ilio-psoas_ in a triangle between
the _M. rectus fem. anterior_ and the _M. adductor longus_, and divides
into two main branches:--
(1) Muscular twigs to the _M. ilio-psoas_, _M. rectus femoris anticus_,
_MM. adductores longus_ and _brevis_.
(2) The _Ramus cutaneus femoris_, which runs downwards in the hinder
wall of the Lymph-sac (_Saccus iliacus_), and supplies the skin of the
under and outer surfaces of the thigh.
[Illustration: Fig. 127.
The sciatic plexus, from a drawing by Wiedersheim.
_a_ Communicating nerve from the ninth spinal nerve.
_a_′ Nerve to musc. lev. ani.
_b_ Nerve to oviduct.
_c_ Urostyle.
_cc_ Communicating twig from the ninth spinal nerve.
_ci_ M. coccygeoiliacus.
_c.I_ M. coccygeosacralis.
_d_ Nerve to bladder.
_d_′ Twig to the m. iliacus.
_e_ Twig from sciatic plexus to coccygeal plexus.
_i_ M. intertransversarius.
_il_ M. ilio-coccygeus.
_ip_ M. ilio-psoas.
_lev_ M. lev. ani.
_oi_ M. obliq. abdom. internus.
_t_′ Transverse process of sacrum.
_Ao_ Aorta.
_Com_ Point of union of nerves _a_ and _cc_.
_Is_ Ischium.
_M5_ Fifth spinal nerve.
_M6_ Sixth spinal nerve.
_M7_ Seventh spinal nerve.
_M8_ Eighth spinal nerve.
_M9_ Ninth spinal nerve.
_M10_ Tenth spinal nerve.
_M7a_ M. iliohypogastricus.
_M7b_ M. cruralis.
_Ni_ Sciatic nerve.
_Ovd_ Oviduct.
_Rect_′ Rectum.
_S7_, _S8_, _S9_, _S10_ Rami communicantes of seventh,
eighth, ninth, and tenth spinal nerves.
_Ves_ Bladder.
8, 9 Eighth and ninth vertebrae.
]
(_d_) The _Ramus dorsalis_ is a very small nerve; according to Waldeyer
it possesses only twenty nerve-fibres. It arises from the coccygeal
nerve immediately beyond the _Canalis coccygeus_, perforates the _M.
ilio-coccygeus_, and runs on its dorsal surface obliquely over the
lymph-heart, without supplying it; the nerve then pierces the fascia to
supply the skin of the back and thigh.
(_e_) The _Ramus abdominalis_ also arises from the coccygeal nerve; it
is larger than the _R. dorsalis_, and arises at the same point; the
nerve runs on the ventral surface of the _M. ilio-coccygeus_ towards
the lymph-heart, and inosculates with the sympathetic. It is from this
nerve that the branch to the sciatic plexus is usually given off; it
further supplies a varying number of branches, which with branches
derived directly or indirectly from the sciatic nerve, form a plexus
(_Plexus coccygeus_); the two plexuses may together be regarded as a
_Plexus ischio-coccygeus_ or a _Plexus sacro-coccygeus_.
(_f_) In addition to the _Rami communicantes_ given off by the spinal
nerves near the vertebral column, the sciatic plexus supplies a few
twigs, usually two (Fig. 127).
(_g_) Other small twigs pass from the sympathetic system forwards and
outwards to join the sciatic plexus or the sciatic nerve. According to
Waldeyer two of these are very constant.
(_h_) Branches to the oviduct (Fig. 127 _b_).
(_i_) Branches to the rectum (Fig. 127 _cc_).
(_k_) Branches to the bladder (Fig. 127 _d_).
(_l_) Branches to the _M. levator ani_ (Fig. 127 _a_′).
(_m_) A branch to the lymph-heart, which runs along the anterior border
of the _M. lev. ani_, on to its dorsal surface, and then direct to the
lymph-heart.
*Variations* in the *sciatic plexus*. The arrangement of the nerves
in the sciatic plexus is subject to many variations; according to
Wiedersheim most of these variations belong to two chief classes:
either the _N. coccygeus_ inosculates directly with the ninth
spinal nerve by one or several branches, or it joins the ninth
nerve indirectly by uniting with its branches. A case of the latter
arrangement is seen in Fig. 127, and is thus described by Wiedersheim:--
‘After cutting through the pelvic symphysis and drawing to one side
the contained viscera, namely, the hinder end of the oviduct, the
rectum, and the bladder, one sees a row of small twigs (_a_, _b_, _cc_,
_d_, and _e_) arising from the inner, hinder, and anterior surfaces
of the ninth spinal nerve: the first (_a_) runs backwards parallel
with the _N. coccygeus_ over the _M. ilio-coccygeus_ to join this
nerve at the point marked _Com_. The twig _cc_ behaves in like manner
after receiving a twig from _b_. The twig _b_ arises from the inner
surface of the ninth nerve between the two foregoing and close to its
union with the eighth spinal nerve; from this origin twig _b_ passes
almost transversely outwards to the hinder extremity of the oviduct
(“uterus”), and partly to the rectum, crossing in its course twig _a_,
the sciatic nerve, and the urostyle. Its branches form a net-like
plexus with the terminal branches of the last sympathetic ganglion and
with a branch _cc_ from the point of union _Com_.
‘A second branch (_a_′), arising from the point of junction _Com_, is
a continuation of the _N. coccygeus_ (_M10_); it passes vertically
downwards towards the hinder end of the cloaca and at the upper border
of the _Levator ani_, divides into two branches, which are distributed
to the inner and outer surfaces of this muscle and to the cloaca. Other
branches pass dorsally to the lymph-hearts, while a third set pass to
the hindermost part of the bladder.
‘These three sets of nerves, to the _M. coccygeus_, _M. levator
ani_, and to the lymph-hearts, are not supplied entirely by the _N.
coccygeus_, as this is reinforced by one or more branches (_e_) from
the sciatic plexus: this branch (_e_) supplies twigs to the _M.
ilio-coccygeus_, which is also supplied anteriorly from the trunk of
the _N. coccygeus_.
‘The bladder receives a special branch (_d_), which arises from the
sciatic plexus at the junction of the eighth and ninth spinal nerves;
this nerve gives a twig (_d_′) to the _M. iliacus_.’
*I.* The *sciatic nerve* (_N. ischiadicus_) (Fig. 128 _I_) is the
largest nerve of the body; it passes under the _M. coccygeus_, between
the origins of the _M. vastus externus_ and of the _M. pyramidalis_:
lies then between the _M. biceps_ and the _M. pyramidalis_, and later
between the _M. biceps_ and the _M. semimembranosus_; lastly, it
bifurcates under the _M. biceps_ to form the _N. tibialis_ (_II_) and
the _N. peroneus_ (_III_). In this course it gives off:--
(_a_) A twig to the _M. coccygeo-iliacus_, while still in the pelvis.
(_b_) The _N. cutaneus femoris posterior_ (Fig. 128, 2), which passes
between the _M. pyramidalis_ and the _M. vastus externus_, to appear
behind and beneath the former; it accompanies an artery of like name to
supply the skin of the hinder and inner surfaces of the thigh.
(_c_) A little below the foregoing it gives off a collateral branch
(Fig. 128, 3), which passes under the _M. pyramidalis_ and divides to
form--
(1) A branch to the upper third of the _M. semimembranosus_.
(2) A branch to the _Rectus internus minor_. A twig of this branch
(_bb_) pierces the muscle transversely in company with the _Arteria
cutanea_, and passes to the skin of the middle of the inner surface of
the thigh.
(3) Branches to both heads of the _semitendinosus_.
(4) Branches to the _M. adductor magnus_.
(_d_) Branches covered by the _M. pyramidalis_ to the _M. quadrat.
femoris_ and _M. obturator_.
(_e_) A branch (5) forwards to the _M. biceps_.
(_f_) A branch (6) which accompanies the _Art. circumflexa genu
lateralis sup._ forwards to the _M. extensores cruris_, the _M. vastus
externus_, and the _M. rectus anterior_.
[Illustration: Fig. 128.
Distribution of the sciatic nerve.
_I_ The sciatic nerve.
_II_ N. tibialis.
_III_ N. peroneus.
1 Branches to the M. pyramidalis.
2 N. cut. fem. posterior.
3 Large collateral branch.
5 Branch to the M. biceps.
6 Branch accompanying the art. circumfl. genu lateralis sup.
7 Branch of tibial nerve to the M. gastrocnemius.
8 N. suralis.
_ad_‴ M. adductor magnus.
_b_ M. biceps.
_bb_ Twig accompanying the art. cutanea.
_ci_ M. coccygeo-iliacus.
_cp_ N. cut. cruris lateralis.
_ct_ R. cut. cruris posterior.
_g_ M. gastrocnemius.
_gl_ M. glutaeus.
_p_ M. pyramidalis.
_pe_ M. peroneus.
_ra_ M. rectus anterior.
_ri_′ M. rectus internus minor.
_sm_ M. semimembranosus.
_st_ M. semitendinosus.
_ve_ M. vastus externus.
]
*II.* The _Nervus tibialis_ (Figs. 128 _II_, 129 _T_) passes backwards
and inwards to supply the extensors of the foot and the flexors of the
toes. Its branches are:--
(_a_) The _R. cutaneus cruris posterior_ (Figs. 128 and 129 _ct_),
accompanied by an artery and vein, passes to the skin of the calf.
(_b_) A twig to the upper part of the gastrocnemius (Fig. 129 _g_′).
The main nerve, after supplying this twig, bifurcates to form the next
two nerves.
(_c_) The _Nervus suralis_ (Figs. 128 8; 129 _s_) runs downwards on the
inner border of the _M. gastrocnemius_ and gives off:--
(1) A twig (_g_″) to the upper third of the muscle.
[Illustration: Fig. 129.
Nerves of the leg and sole of the foot.
_ab5_ Branch to the M. abduct. digit. V.
_ad5_ Branch to the M. adduct. digit. V.
_ar_ M. rectus anterior.
_b_ M. biceps.
_cs_ Ramus cutaneus medius.
_ct_ Ramus cutaneus cruris posterior.
_dvI_ Ramus digitalis volaris I.
_dvII_ Branch supplying R. digit. volaris I and II.
_dvIII_ Second branch of the N. tibialis.
_F5_ Branch to the M. flex. brev. digit. V.
_flp_ Branches to the M. plantaris and the M. flexor digitorum.
_g_′ Branch to the M. gastrocnemius.
_g_″ Branch to the M. gastrocnemius.
_pc_ N. peroneus.
_s_ N. suralis.
_sm_ M. semimembranosus.
_T_, _t_ Nervus tibialis.
]
(2) The _Ramus cutaneus medius_ (_cs_) is given off below the middle
of the _M. gastrocnemius_; it passes to the skin of the lower third
of the leg. After giving off the latter branch, the _N. suralis_
runs downwards along the inner aspect of the _Tendo achillis_ to the
_Aponeurosis plantaris_ of the sole of the foot as far as the calcar,
and gives off:--
(3) Branches (_flp_) to the _Musc. plantaris_ and the _M. flexor
digitorum_.
(4) A branch to the _M. abductor hallucis_.
(5) The _R. digitalis volaris I_ (_dvI_) supplies the inner side of the
first toe by its terminal twig.
(_d_) The _Nervus tibialis_ (Fig. 129 _t_) passes downwards on the
hinder surface of the tibio-fibula, sinks into the _M. tibialis
posticus_ to appear again at its hinder border; it then runs over the
ankle-joint into the sole of the foot, where it lies midway in the
space between the two _Ossa tarsi_ and between the _M. extensor tarsi_
and the _M. abductor digiti I longus_; the nerve then runs downwards in
the groove of the small _Os tarsi_ and divides to form three branches:--
(1) The first branch (_dvII_) runs to the space between the second and
third fingers, where it bifurcates:--
(α) The _Rami digital. volaris I_ run transversely over the muscles of
the second toe, supply the muscles of the first toe, and bifurcate to
form the _R. digital. volaris I_ and _II_.
(β) The _Ram. digit. volar. II_ divides in the space between the second
and third fingers to supply the _Flex. phalang._ and the adjacent sides
of these toes.
(2) The second branch (_dvIII_) runs over the _M. flex. metatarsi_
of the third toe to the space between the third and fourth toes, and
bifurcates to supply the adjacent sides of these toes and the web
between them.
(3) The third branch at once divides to supply:--
(α) The _M. transv. metatarsi_.
(β) The _MM. lumbricales_ of the fourth toe.
(γ) The _M. abductor digit. V_ (_ab5_), the _M. flexor brevis dig. V_
(_F5_), and the _M. adductor dig. V_ (_ad5_); it then ends as--
(δ) A bifurcating branch forming the _R. digit. volar._ of the fourth
and fifth toes.
*III.* The _Nervus peroneus_ (_N. peroneus communis superior_,
Ecker), (Fig. 130 _pc_) is the second division of the sciatic nerve;
it passes between the outer head of origin of the _M. gastrocnemius_
and the tendon of insertion of the _M. biceps_, it then lies on the
tibio-fibula between the _M. gastrocnemius_ and the _M. peroneus_,
where it is accompanied by the _Vena tibialis postica_, then runs
downwards upon the _M. extensor cruris_ and the _Flexor tarsi ant._,
and passes under the _M. tibial. anticus_ and bifurcates; its branches
are:--
*a.* The _N. cutaneus cruris lateralis_ (Fig. 128 _cp_); which, like
other cutaneous nerves, runs in a common sheath together with an artery
and vein to the skin. It arises close to the sciatic nerve.
*b.* Muscular branches to the _MM. peroneus_, _tibialis anticus_,
_extensor cruris brevis_, and the _flexor tarsi anterior_.
[Illustration: Fig. 130.
Distribution of the _N. peroneus_.
_A_ Inner terminal twig of N. peron. comm. inf.
_B_ Outer terminal twig of N. peron. comm. inf.
_cpl_ N. cutaneus dorsi pedis lateralis.
_pc_ N. peroneus.
_pci_ N. peroneus communis inferior.
_pl_ N. peroneus lateralis.
_pm_ N. peroneus medialis.
]
*c.* The _N. peroneus medialis_ (Fig. 130 _pm_) is the smaller of
the two terminal branches of the _N. peroneus_; it courses with the
_Art. tibialis antica_ under the _MM. flexores tarsi anterior_ and
_posterior_ and supplies the latter.
*d.* The _N. peroneus lateralis_ (Fig. 130 _pl_) is the larger terminal
branch of the _N. peroneus_; it passes downwards between the heads of
the _M. tibialis anticus_ to the tendon of origin of the _Flexor tarsi
posterior_, where it gives off two branches (Nos. 1 and 2); the nerve
then unites with the _N. peroneus lateralis_ to form a common stem, the
_N. peroneus communis inferior_ (Ecker). The _N. peroneus lateralis_
gives off:--
(1) The _N. cutaneus dorsi pedis lateralis_ (_cpl_), which passes to
the skin of the outer side of the dorsum of the foot.
(2) A second branch to the _M. extensor_ of the fourth and fifth toes.
*e.* The _N. peroneus communis inferior_ (Fig. 130 _pci_) runs on
the dorsum of the foot in company with the _Art. dorsalis pedis_,
underneath the _MM. extensores digiti I_ and _II_; it supplies several
branches and then bifurcates. It gives off:--
(1) Branches to the _MM. extensor longus_ and _brevis digiti I_.
(2) _Rami digitales dorsales_ to the adjacent sides of the first and
second toes.
(3) Branches to the _MM. extensores digiti II_.
(4) The inner, terminal branch (Fig. 130 _A_) at once divides:--
(α) The outer branch runs between the third and fourth toes as far as
the commencement of the web, where it bifurcates to form two _Rami
cutanei_, which course along the adjacent sides of these toes as far as
their apices.
(β) The inner branch passes to the extensor muscle, and, in part, to
the adjacent sides of the third and fourth toes.
(5) The outer, terminal branch (Fig. 130 _B_) of the _N. peroneus
communis inferior_ passes to the muscles of the fourth and fifth toes,
and supplies _Rami cutanei dorsales_ to the outer side of the fourth
and inner side of the fifth toes.
Cutaneous branches of the _N. tibialis_ supply the outer side of the
fifth and inner side of the first toe.
G. THE SYMPATHETIC SYSTEM (_Sympathicus_).
_(Re-written by the translator.)_
The *sympathetic cord* or *chain* is a row of nervous ganglia
(vertebral or lateral ganglia), connected by nerve-fibres, and lying
on either side of the vertebral column (Figs. 117 and 131); with the
exception of the last spinal nerve there is usually one sympathetic
ganglion associated with each spinal nerve; in the case of the tenth
spinal nerve there may be only one ganglion or as many as twelve.
The first ganglion (Figs. 111, opposite _ics_; 117 _S_1) is placed on
the hypoglossal nerve just as it emerges from the first intervertebral
foramen; it is large, but smaller than the second; its _Ramus
communicans_ is represented by several fine and very short fibres,
which connect the ganglion with the nerve. This ganglion is connected
with the second by two or three nervous threads, between which passes
the subclavian artery, a true _Annulus Vieussenii_ being thus formed
(de Watteville). The other ganglia are connected by single bands of
fibres. The first ganglion supplies also branches to the axillary
artery and to the cardiac plexus.
The second ganglion (Figs. 117 and 131) is the largest, and is closely
applied to the brachial nerve; as in the case of the first ganglion and
hypoglossal nerve, it is attached to the second spinal nerve without a
distinctly marked _Ramus communicans_.
The third ganglion (_Ganglion cardiacum basale_, Gaskell and Gadow)
is sometimes fused with the second, but is usually close to the third
spinal nerve: it has a short but distinct _Ramus communicans_.
[Illustration: Fig. 131.
Sympathetic cord. From Ecker (Icones physiologicae, Pl. XXIV, Fig. 3).
The heart, lungs, and liver have been removed; the stomach, intestine,
kidneys, and testes drawn to the right side; the left sympathetic cord
is thus pulled to the right side to expose the Rami communicantes.
_S_ Sympathetic cord attached to the ganglion of the vagus.
The numbers refer to the ganglia, which are enumerated from before
backwards.
]
Behind the third ganglion the sympathetic cord is continued backwards
along the corresponding aortic arch, then parallel with and close
to the abdominal aorta (Figs. 117, 127, and 131), receiving _Rami
communicantes_, which are long and well marked, from each of the spinal
nerves; the fourth, fifth, and sixth nerves usually supply each one
_Ramus communicans_, the seventh two, and the eighth and ninth each
two or three: from the tenth nerve it receives three or more, as many
as twelve having been noted. The ganglia are usually more or less
spindle-shaped or flattened and triangular; the hinder part of the cord
usually receives in addition two or three branches from the sciatic
plexus and twigs from the _R. abdominalis_ of the _N. coccygeus_.
The branches and communications of the sympathetic cords are as
follows:--
*a.* Communicating branches between the two cords; these are extremely
numerous and irregular, forming a net-like plexus, which surrounds the
abdominal aorta and other adjacent structures, and gives off numerous
small twigs to the neighbouring vessels and organs.
*b.* Communications with the cranial nerves; these are two branches
(Wiedersheim), (Figs. 111 and 116) which pass from the first ganglion
to the _Ganglion nervi vagi_, where one terminates, the other leaves
the ganglion to pass on to the Gasserian ganglion (Figs. 111 and 116
_VS_): according to Gaskell a _single_ nerve passes from the first
ganglion to the _Ganglion nervi vagi_, whence one portion of its fibres
is continued to the Gasserian ganglion, the remainder accompanying
the pneumogastric nerve without any connection with the ganglion;
he therefore names this nerve the vago-sympathetic. (See Gasserian
ganglion, p. 168.)
*c.* Communications with the spinal nerves; these are:--
(1) The _Rami communicantes_.
(2) Communications between the sympathetic ganglia or their branches
and the spinal nerves or their branches (Fig. 117); by means of these
connections, fibres of the sympathetic system are conducted by the
spinal nerves and their branches to all parts of the body.
*d.* Branches to the heart, which form the following ganglia:--
(1) A relatively large plexus lies on the auricles in the median plane
immediately beneath the division of the _M. hyoglossus_. It supplies a
network of fibres to the auricles and the adjacent large vessels. It is
said to communicate at various points with the pneumogastric nerve.
(2) A smaller ganglion of oval form, supplies twigs to the neighbouring
vessels and a communicating branch to the hypoglossal nerve
(Wiedersheim).
*e.* Branches to the abdominal viscera; these form intricate plexuses
by which the organs are supplied: the one best known is the solar
plexus (Fig. 131); it is formed chiefly from branches derived from the
third, fourth, and fifth ganglia, and supplies the stomach, etc.; other
plexuses for the various viscera are known by corresponding names, such
are the _Plexus hepaticus_, _renalis_, _genitalis_, _haemorrhoidalis_,
and _vesicalis_.
The sympathetic system is characterised by the fact that the branches
form intricate plexuses, which include numerous ganglia and which are
very irregular; it is also characteristic that most of its fibres are
non-medullated. According to the investigations of Gaskell, the fibres
of the sympathetic system arise in mammalia as very fine medullated
fibres from the posterior vesicular (Clarke’s) columns (Mason has
recently described cells in the frog’s spinal cord, which he holds to
be homologous with the cells of these columns); they leave the cord by
both the ventral and dorsal roots of the spinal nerves, and are thus
connected with two sets of ganglia, (1) with the ganglia of the dorsal
roots, and (2) through the _Rami communicantes_ with the sympathetic
ganglia (vertebral or lateral ganglia); these two sets of ganglia
Gaskell terms proximal. By means of the branches from the sympathetic
ganglia (_Rami efferentes_) part of the fibres pass to another set
of ganglia, the solar plexus, etc., which he terms prevertebral or
collateral; from these the fibres pass to be distributed to the various
viscera and blood-vessels, where a fourth set of very small ganglia
(terminal ganglia) is found. The prevertebral and terminal ganglia
are together classed as distal ganglia. Gaskell holds that the fine
medullated fibres from the cord lose their medullary sheath in one or
other of these ganglia according to the function they fulfil.
The inhibitory fibres of the heart and vaso-dilator fibres of the
blood-vessels continue as white fibres along the vago-sympathetic and
spinal nerves to the distal ganglia (Bidder’s ganglion, etc.), where
the medullary sheath disappears: whereas the ‘augmentor’ fibres of
the heart and vaso-constrictor fibres of the blood-vessels lose their
medullary sheath in the proximal ganglia and pass on as non-medullated
fibres. In the same way the nerve-fibres that bring about contraction
of the circular muscle fibres of the hollow viscera lose their
medullary sheaths in the proximal ganglia, while those fibres, the
influence of which negatives the former, become pale fibres in the
distal ganglia.
Waters has demonstrated that in the frog the various spinal nerves
have each a localised physiological action upon the blood-vessels and
muscular walls of various parts of the alimentary canal: he shows that
The third spinal nerve supplies the oesophagus.
The fourth spinal nerve supplies the stomach.
The fifth spinal nerve supplies the upper third of the small intestine.
The sixth spinal nerve supplies the lower two thirds of the small
intestine.
The seventh spinal nerve supplies the large intestine.
The eighth spinal nerve supplies the bladder, this supply being,
however, not so definite as the others given above.
It has long been known that the branches of the spinal ganglia (ganglia
of the posterior roots) are together larger (one-third, Lenhossék),
and contain more fibres than the ventral and dorsal roots together;
this is supposed to be in part due to an acquisition of new fibres
derived from the ganglia. The majority of recent observers hold that
each ganglionic cell has only one process, which, however, soon
bifurcates; whether any of the fibres so formed pass as far as the cord
or beyond its blood-vessels is doubted by most observers, and denied by
Gaskell. These remarks and the description of the cells of the spinal
ganglia (p. 176) hold good for the lateral or vertebral ganglia and the
prevertebral ganglia (solar ganglion, etc.) of the sympathetic system;
the terminal ganglia will be described with the organs in which they
are found.
H. HISTOLOGICAL NOTES ON THE NERVOUS SYSTEM.
(In order to render the foregoing description of the nervous
system more complete, the following notes have been added by the
translator.)
[The histological elements of the nervous system are nerve-cells
and nerve-fibres; of these the nerve-cells have been described with
the parts in which they occur; it may simply be remarked that later
observers have been unable to discover the ‘spiral cells’ described by
Beale, Arnold, and others. The nerve-fibres, as in most other animals,
are of two kinds, medullated and non-medullated.
*1.* Medullated nerve-fibres or white fibres are found in all cranial
and spinal nerves, with the exception of the olfactory nerves, and in
many of the sympathetic nerves (see Sympathetic System); also in the
white matter of the brain and spinal cord; examined microscopically
the fibres are seen to consist of an external sheath or neurilemma, a
medullary sheath, and an axis-cylinder:--
*a.* The neurilemma (Sheath of Schwann, Outer or Primitive Sheath) is a
nucleated endothelial layer covering the nerve-fibre; it is continuous
with the corresponding coat of the nerve-cells, and is uninterrupted
throughout the length of the nerve; at the nodes, however, it dips down
towards the axis-cylinder, the circular groove so formed being filled
with cement substance.
*b.* The medullary sheath (White substance of Schwann); the presence of
this sheath is the chief cause of the whiteness of these nerves; the
thickness of the sheath varies considerably, and towards the ultimate
distribution of the nerve it is entirely lost. At more or less regular
intervals along the course of the nerve-fibre the continuity of the
medullary sheath is broken, and gives the fibres the appearance of
being constricted at these places; such constrictions are known as
nodes of Ranvier; the portion between two such nodes being termed
an internode. Each internode possesses an oval, flattened, granular
nucleus at about its middle and placed between the neurilemma and the
medullary sheath; the nucleus has a nucleolus. In the fresh state the
medullary sheath seems to be fluid; it is of a fatty nature.
Medullary segments are caused by breaks in the continuity of the
medullary sheath, which are seen only in nerves which are no longer in
their normal condition, and are especially well marked after treatment
with osmic acid. The breaks are oblique; hence the conical end of one
segment fits into the funnel-shaped end of the next. How far they
correspond to pre-existent structures is uncertain. The segments in the
frog vary in length from 0.010 to 0.040 mm.
*c.* The axis-cylinder is the essential part of every nerve-fibre;
it shows a longitudinal striation corresponding to the fine fibrils
(primitive fibrillae) of which it consists; these fibrils often exhibit
minute varicosities: at times it has the appearance of being invested
with a very delicate structureless sheath. It is continuous through the
nodes of Ranvier.
*2.* Non-medullated nerve-fibres (Grey or Varicose Fibres; Fibres of
Remak); these occur chiefly in branches and plexuses of the sympathetic
system; they consist of a neurilemma and an axis-cylinder, which agree
exactly with the corresponding elements found in the medullated fibres.
The nerve-fibres, whether medullated or non-medullated, are bound
together by connective-tissue to form nerves. A number of fibres bound
together by connective-tissue to form a slender cord is known as a
funiculus; a small nerve may consist of one such funiculus; the sheath
surrounding it is known as the perineurium, and sends in supporting
processes between the fibres (endoneurium): when several funiculi are
bound together to form a large nerve the common sheath is known as
the epineurium. These sheaths support nerves (_nervi nervorum_) and
vessels (_vasa vasorum_) supplying the nervous elements, and their
intercellular spaces form lymph-canals. The whole nerve is surrounded
by an endothelial coat, which helps to form a lymph-space, which more
or less completely surrounds the nerve.
The ultimate distribution of the nerve-fibres will be included in the
description of the various organs in which they end.]
SECTION IV.
THE VASCULAR SYSTEM.
THE VASCULAR SYSTEM.
LITERATURE.
THE HEART AND BLOOD-VESSELS.
*Aeby*, Ueber den feineren Bau der Blutcapillaren. Centralbl. f. d.
med. Wiss. 1865, p. 209.
*Altmann, R.*, Ueber Corrosion in der Histologie. Centralbl. f. d.
med. Wiss. 1878, p. 245.
*Aubert, H.*, Die Innervation der Kreislaufsorgane. Hermann’s
Handbuch der Physiologie. Leipzig, 1880. Vol. VI, Pt. I, p. 377.
*Beck, K.*, Zur Kenntniss der Herznerven. Arch. f. mik. Anat. 1884.
Vol. XXIV, pp. 11–19.
*v. Bezold*, Untersuchungen über die Innervation des Herzens.
Leipzig, 1863.
*Bidder, F.*, Ueber functionell verschiedene und räumlich getrennte
Nervencentra im Froschherzen. Arch. f. Anat. u. Physiol. 1852,
p. 163.
*Bidder, F.*, Zur näheren Kenntniss des Froschherzens und seiner
Nerven. Arch. f. Anat. u. Physiol. 1866, p. 1.
*Bidder, F.*, Endigungsweise der Herzzweige des N. vagus beim
Frosche. Arch. f. Anat. u. Physiol. 1868, p. 1.
*Bidder, F.*, and *Gregory*, Beiträge zur Physiologie der
Herzbewegung beim Frosche. Dorpat, 1865.
*Boas, J. E. V.*, Ueber den Conus arteriosus und die Arterienbogen
der Amphibien. Morph. Jahrb. 1881. Vol. VII, pp. 271–273.
*Boas, J. E. V.*, Beiträge zur Angiologie der Amphibien. Morph.
Jahrb. 1882. Vol. VIII, pp. 169–187.
*Bobretzky, C.*, Ueber die Entwickelung der Capillargefässe.
Centralbl. f. d. med. Wiss. 1885, p. 769.
*Bremer, L.*, Die Nerven der Capillaren der kleinen Arterien und
Venen. Arch. f. mik. Anat. 1882. Vol. XXI, p. 663.
*Brenner, A.*, Ueber das Verhältniss des N. laryngeus inferior vagi
zu einigen Aortenvarietäten des Menschen und zu dem Aortensystem
der durch Lungen athmenden Wirbelthiere überhaupt. Arch. f. Anat.
u. Physiol. 1883, pp. 373–397.
*Brücke, E.*, Ueber Mechanik des Kreislaufes des Blutes bei Fröschen.
Wiener Sitzungsb. 1851. Vol. VI, p. 61; also p. 114.
*Brücke, E.*, Beiträge zur vergl. Anatomie u. Physiologie des
Gefässsystems der Amphibien. Denkschriften d. Wiener Academie.
1852. Vol. III, p. 335.
*Burdon-Sanderson, J.*, Circulation of the Blood, in Handb. for the
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*Donders* and *Moleschott*, Holländische Beiträge. 1848, p. 361.
*Eberth, C. J.*, Ueber die Vermehrung der rothen Blutkörperchen nach
Untersuchungen von W. Aly. Fortschritte d. Med. 1885. Vol. III,
pp. 1–7.
*Fuchs, E.*, Beitrag zur Kenntniss des Froschblutes und der
Froschlymphe. Virchow’s Arch. 1877. Vol. LXXI, p. 78.
*Gaule, J.*, Beobachtungen der farblosen Elemente des Froschblutes.
Arch. f. Anat. u. Physiol. 1880, pp. 375–392.
*Gulliver, G.*, Measurements of the red blood-corpuscles of
Batrachians. Proc. Zool. Soc. London, 1873, p. 162.
*Hewson, W.*, On the figure and composition of the red Particles
of the Blood, commonly called Globules. Phil. Trans. 1773.
Vol. LXIII, Pt. I, p. 303.
*Home, E.*, On the changes the blood undergoes in the act of
coagulation. Phil. Trans. 1818, p. 172.
*Kollmann, J.*, Bau der rothen Blutkörperchen. Zeitschr. f. wiss.
Zool. 1874. Vol. XXIII, p. 462.
*Kusnezoff, F.*, Ueber blutkörperhaltige Zellen der Milz. Wiener
Sitzungsb. 1873. Vol. LXVII, Pt. III, pp. 58–67.
*Moriggia, A.*, Ueber den Durchtritt der farblosen Blutkörperchen
durch die Blutgefässwandungen, etc. Moleschott’s Untersuchungen.
1876. Vol. XI, p. 470.
*Neumann, E.*, Zur Histologie der rothen Blutkörperchen. Centralbl.
f. d. med. Wiss. 1865, p. 481.
*Owsjannikow, P.*, Zur Histologie der Blutkörperchen. Bullet. de
l’acad. science de Pétersbourg. 1865. Vol. VIII, pp. 561–572.
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Amphibien. Centralbl. f. d. med. Wiss. 1879, pp. 673–675.
*Ranvier, L.*, Traité technique d’histologie, pp. 148–224.
*Rollett, A.*, Versuche und Beobachtungen am Blute. Wiener Sitzungsb.
Vol. XLVI, Pt. II, pp. 65–98.
*Stricker*, Beobachtungen über die Entstehung des Zellkernes. Wiener
Sitzungsb. 1878. Vol. LXXVI, Pt. III, p. 7.
*Thoma, R.*, Die Ueberwanderung farbloser Blutkörperchen von dem Blut
in das Lymphgefässsystem. Heidelberg, 1873.
*Welcker, H.*, Grösse, Zahl, Volum, Oberfläche und Farbe der
Blutkörperchen bei Menschen und Thieren. Henle u. Pfeuffer’s
Zeitschr. 1864. Vol. XX, pp. 258–307.
PART 1.
THE HEART AND BLOOD-VESSELS.
I. THE HEART.
(The original arrangement of this section has been modified.)
The heart is situated in the middle line above the central portion of
the shoulder-girdle and _M. sternohyoideus_, and below the oesophagus;
the apex is directed backwards and lies between the lobes of the liver,
the base is directed forwards and lies a short distance behind the
larynx. The heart is surrounded by the pericardium.
A. The *Pericardium* [is a very thin membranous sac, which completely
encloses the heart; it is attached, at some distance, to the large
vessels passing to and from the heart, and has inserted into it some
fibres of the _M. obliquus abdominis internus_ (see page 70). A fold
of the pericardium extends from the dorsal surface to the truncus
arteriosus, and through it courses the vena cardiaca.
[Illustration: Fig. 132.
The heart and blood-vessels, seen from the ventral surface; after Howes.
_AC._ Left anterior caval vein.
_C′._ Carotid arch.
_LA._ Left auricle.
_P′._ Right pulmo-cutaneous arch.
_RA._ Right auricle.
_S′._ Left systemic arch.
_TA._ Truncus arteriosus.
_V._ Ventricle.
]
The pericardium is a connective-tissue membrane, and is lined on
either side with endothelium, which is in part ciliated (Leydig); the
endothelium of the inner surface is continued on to the heart and so
forms a closed lymph-sac. The pericardium is more or less pigmented,
and contains both vessels and nerves; it may contain fat-cells].
B. The *Heart*.
[The heart is a hollow muscular organ, composed of: (1) two auricles,
forming the wider anterior portion; (2) the ventricle, placed
behind the auricles; (3) the sinus venosus, situated dorsally; and
(4) the truncus arteriosus, lying ventrally. Examined while still
living, the auricles are seen to be much darker in colour than the
ventricle, due to the blood being seen through their thinner walls;
between the auricles and the ventricle is a distinct groove, the
auriculo-ventricular groove. The whole organ is more or less pigmented,
especially the ventricle (_R. temporaria_ has much less pigment).]
[Illustration: Fig. 133.
The heart, seen from above, and dissected to show the opening from the
Sinus venosus to the right auricle; after Howes.
_C′._ Right carotid arch.
_IC._ Posterior caval vein.
_LA._ Left auricle.
_P′._ Right pulmo-cutaneous arch.
_PV._ Pulmonary vein.
_RA._ Right auricle.
_S′._ Right systemic arch.
_SV._ Sinus venosus.
_SV′._ Opening of Sinus venosus into the right auricle.
_V._ Right anterior caval vein.
]
*a.* The *Sinus venosus* (_Sinus venarum cavarum_), (Fig. 133 _SV._)
is a thin-walled sac lying on the dorsal surface of the heart, and
very slightly to the right side (Hoffmann). It is somewhat triangular
in form, receiving an anterior caval vein at each anterior angle
(_V._), and the posterior caval vein (_IC._) at the posterior angle.
The ventral wall has a transverse opening (_SV′._), by which it
communicates with the right auricle; the opening possesses two valves,
an anterior and a posterior, and is placed close to the auricular
septum.
*b.* The *auricles* [are not always separated, as the septum which
usually brings about the separation is in some cases incomplete, and in
rare instances appears to be absent (Hoffmann)]; according to Ecker,
the auricular septum is sometimes placed so far to the left side
that it appears to be absent (Fig. 135). The septum is attached to
the walls of the auricles so as to form two distinct cavities, which
communicate at the auriculo-ventricular opening, where the septum has
a free concave border (Fig. 134). The right auricle is much larger
than the left, and receives the systemic venous blood from the sinus
venosus by the opening (Figs. 133 and 134 _SV._) already described.
The left auricle receives the blood from the lungs by the pulmonary
vein (Fig. 133 _PV._), which opens into the auricle near the septum
(Fig. 134 _PV._): [the openings from the sinus venosus and from the
pulmonary vein may be so closely approximated as to be separated by the
septum only. The septum is much thinner than the auricular walls]. Both
auricles open into the ventricle by the auriculo-ventricular opening
(Fig. 134).
[Illustration: Fig. 134.
The frog’s heart seen from the ventral surface, and dissected so as to
show its structure. The ventral walls of the truncus arteriosus and of
the auricles and ventricle have been removed. From a drawing by Mr.
Hurst.
_A._ Auriculo-ventricular aperture and valve.
_B._ Aperture leading from ventricle to truncus arteriosus.
_C._ Left carotid arch.
_LA._ Left auricle.
_P._ Left pulmo-cutaneous arch.
_P′._ Style passed down right pulmo-cutaneous arch into the
truncus arteriosus, _T._
_PV._ Opening of pulmonary vein.
_RA._ Right auricle.
_S._ Left systemic arch.
_SA._ Septum atriorum.
_SV._ Opening of Sinus venosus into right auricle.
_V._ Ventricle.
]
*c.* The *ventricle* (Figs. 132, 134, and 136 _V._), examined while
still living, is seen to be bluntly conical in shape and darker on the
left side than on the right; this is due to the ventricular wall of the
right side, near the truncus arteriosus, being somewhat thinner. The
inner wall is not smooth but possesses muscular ridges (_Trabeculae_).
At its base the ventricle communicates with the auricles by the
auriculo-ventricular opening (Figs. 134 and 136), and with the truncus
arteriosus by a separate opening (Fig. 134 _A._). The ventricle is
lined by a layer of endocardial endothelium.
[Illustration: Fig. 135.
Dissection of a case in which the auricular septum is placed more to
the left than is normal.
_S_ Septum.
_SS_ Left auricle.
_V_ Opening into the Sinus venosus.
]
[Illustration: Fig. 136.
Dissection of the heart from the left side; after Howes.
_A._ Auriculo-ventricular opening.
_AC._ Anterior caval veins.
_IC._ Posterior caval vein.
_LA._ Left auricle.
_PV._ Pulmonary vein.
_RA._ Right auricle.
_SV._ Sinus venosus.
_TA._ Truncus arteriosus.
_V._ Ventricle.
]
The *auriculo-ventricular opening* (Fig. 134 _A._) is a large aperture
guarded by two valves, a dorsal and a ventral: each valve is formed
by a reduplication of the endothelium, and contains a small amount of
connective-tissue; its free margin is bound down by a number (about
twelve) of fibrous cords, the _chordae tendineae_, which are attached
by their posterior extremities to the trabeculae.
*d.* The *truncus arteriosus* (Figs. 132 _TA._, 134 _A._) arises at the
base of the ventricle, on the right side of its ventral surface, then
passes forwards and to the left, across the auricles, to reach their
anterior border near the median line, where it divides to form two
vessels.
Internally it is incompletely divided into two compartments by a spiral
valve (Fig. 134); the valve is attached to the dorsal surface and is
free ventrally: when the vessel is fully dilated (artificially), the
valve extends two-thirds of its diameter. The opening of the vessel
into the ventricle is guarded by two semilunar valves (Fig. 134 _A._),
the free margins of which are bound to the inner surface of the tube by
_chordae tendineae_. The distal extremity has a semi-lunar valve in the
left compartment (Fig. 134), which is attached by a delicate band to
the spiral valve (Ecker).
C. *The minute structure of the Heart.*
[The heart consists chiefly of muscle, but possesses also nerve-fibres,
nerve-cells, endothelium, and connective-tissue; the truncus arteriosus
has, in addition, blood-vessels.
*a.* The *muscular structure* of the heart.
(1) The *arrangement* of the *muscle-fibres* varies in the different
portions of the heart. That of the ventricle will be easily understood
by reference to Fig. 137. A layer of circular fibres (_CM_) extends
round the whole ventricle, and from it more or less radial or
transverse bands (_TM_, also Fig. 138 _TM_) pass inwards; these, in the
apical portion of the ventricle, seem to extend almost transversely
across; towards the base they are directed onwards and forwards towards
the auricles. Of these bands some, near the apex, can be traced
directly to the opposite side, others join the wall more anteriorly,
and still others join bands of muscular fibres (_LM_), which may be
described as longitudinal, and form the _Musculi papillares_. In the
anterior portion of the ventricle the same arrangement holds good, but
is modified to form a central cavity; still more anteriorly, at the
junction of auricles and ventricle, the trabecular structure is much
less apparent, the fibres being closer and mainly circular.
[Illustration: Fig. 137.
I. Transverse section through the junction of the hinder and middle
thirds of the ventricle of _R. temporaria_. II. Transverse section
through junction of middle and anterior thirds of the same heart. Occ.
I, Syst. 1, Leitz. The heart was freely distended[62] with dilute
spirit, and so hardened.--G. H.
_CC_ Central cavity.
_CM_ Circular muscle.
_LM_ Longitudinal muscle.
_TM_ Transverse muscle.
]
[Footnote 62: The base of the ventricle measured, when distended, 8 mm.
by 5 mm.]
In the auricles the muscular fibres are chiefly arranged in circular
rings which cross one another; on the inner surface, however, traces
of an arrangement similar to that in the ventricle may be made out. In
the heart, from which the sections in Fig. 137 were drawn, transverse
bands (cut longitudinally), 0.33 mm. in length, were numerous; their
central ends terminated in bands, the fibres of which were cut
transversely. The auricular septum (Fig. 141 a _M_) also possesses
muscular fibres which cross one another in its substance.
The fibres of the truncus arteriosus resemble those of an ordinary
artery; those of the sinus venosus are arranged in rings, mostly
transverse, but others oblique, and a few longitudinal.]
(2) The *structure* of the *cardiac muscle-fibres* (Figs. 138 and 141
a).
[The cardiac muscle of the frog consists of spindle-shaped cells, which
as Pohl-Pincus pointed out, are of two kinds; the main difference
between the two being in the size of the nucleus, which is much broader
in one than in the other.
[Illustration: Fig. 138.
Portion of a transverse section through the middle of the ventricle of
_R. temporaria_. From same heart as the sections in Fig. 136. Oc. I.
Syst. 7, Leitz.--G. H.
_A_ Rod-shaped nuclei of muscle fibre.
_B_ Oval nuclei of muscle fibre.
_CM_ Circular layer of muscle.
_CT_ Connective-tissue.
_E_ Endothelium of the epicardium.
_TM_ Transverse bands of muscle.
]
α. Cells with a broad nucleus (Fig. 138 _B_): the nucleus is lenticular
or egg-shaped, 4 to 7 µ broad, 8 to 14 or 18 µ long; the ratio of
length to breadth being 1 : 2.
β. Cells with a narrow nucleus (Fig. 138 _A_): the nucleus is
rod-shaped, 2·5 to 3·5 µ broad and 25 to 43 µ in length. The ratio
of length to breadth varying from 1 : 8 to 1 : 16. These cells are
more frequent in the right half of the base of the ventricle than the
former variety. In the trabeculae the second variety is more numerous
(Pohl-Pincus).
The muscle-fibre may be simple (Fig. 141 a _M_) or possess branches
(Fig. 138); the fibres are all more or less spindle-shaped, and
striated transversely and longitudinally, but possess no sarcolemma.
The protoplasmic contents of the cell are finely granular; the nucleus
much more coarsely granular and possessing one or more distinctly
marked nucleoli. The striations are due to the presence of a network,
which has been carefully described by Messrs. B. Melland and C. F.
Marshall[63], and is similar to that of ordinary voluntary muscle (see
histology of muscle).]
[Footnote 63: I have had opportunity of examining Mr. Marshall’s slides
and have convinced myself of the correctness of his observations.]
*b.* The *nerves* of the *heart*.
The nervous supply of the heart is derived from the sympathetic system
and from the cardiac branches of the pneumogastric nerve; the course of
which has already been traced (page 175) to the roots of the anterior
caval veins, where they form a simple plexus by means of a connecting
link (Fig. 139). The plexus possesses nerve-cells and sends off two
nerves into the auricular septum; the one (_d_) lies dorsally and is
shorter and thicker than the other (_v_), which lies ventrally in the
septum. They course backwards to the posterior border of the septum,
and there distribute fine branches to the base of the ventricle and
surrounding parts.
[Illustration: Fig. 139.
Course of the cardiac nerves in the auricular septum.
_d_ Dorsal nerve.
_v_ Ventral nerve.
]
[In the whole of their course in the heart they have numerous
nerve-cells, either imbedded between their fibres or attached to the
nerves and their branches.
The nerve-fibres are both medullated and non-medullated. The
nerve-cells (Figs. 139, 140, 141) are usually oval, and are unipolar
or rarely bipolar; sometimes two cells exist in the same envelope,
forming the ‘twin-cells’ of Dogiel (Fig. 141 b II). According to the
recent observations of Lavdowsky and Dogiel each cell receives one
medullated fibre and gives off a fine non-medullated fibre; the two run
together for a short distance, after which the non-medullated fibre
separates to supply muscle-fibres.
[Illustration: Fig. 140.
Group of nerve-cells on the cardiac nerve, from the auricular septum.
Stained with picrocarmine. Occ. III, Syst. 3, Hartnack; after Dogiel.
_F_ Fibres of the cardiac nerve.
_G_ Nerve-cells.
]
Two large clusters of nerve-cells have received special names.
*Remak’s ganglion* is a large group of nerve-cells in the wall of the
sinus venosus.
*Bidder’s ganglion* is formed, collectively, by groups of cells in the
auriculo-ventricular groove, the chief groups being attached to the two
cardiac nerves.
No nerve-cells have been discovered behind that portion of the
ventricle near the auriculo-ventricular groove, nor has a direct
connection between the cells or their processes with the fibres of the
pneumogastric nerve been made out.
Nerve-fibres have been described as existing in all parts of the
ventricle and being connected with the muscle-fibres (Openchowsky and
others); this cannot, as yet, be accepted as proved.
The truncus arteriosus also possesses nerve-fibres and nerve-cells
(Pagliani, Löwit, and others), but their arrangement seems to be very
irregular. Löwit did not succeed in finding the nerve-cells in all
cases examined; and Engelmann denies their occurrence.]
*c* and *d*. [The *endothelium* and *connective-tissue* of the heart.
The connective-tissue of the heart exists only in very small quantity.
A fine layer on the outer surface of the ventricle, especially towards
the auriculo-ventricular groove, can easily be seen (Fig. 138 _CT_);
the various valves, the auricular septum, and more particularly the
truncus arteriosus, all contain connective-tissue. In the latter part
the spiral valve is wholly formed of this tissue.
[Illustration: Fig. 141 a.
Small group of nerve-cells from the auricular septum. Stained with
picrocarmine and silver nitrate, after Dogiel.
_E_ Endothelium (endocardium).
_G_ Nerve-cells.
_M_ Muscle-fibres.
_N_ Nucleus.
_N_′ Nucleolus.
]
[Illustration: Fig. 141 b.
Isolated nerve-cells from frog’s heart. I. Usual form of nerve-cell.
II. ‘Twin-cell.’
_C_ Capsule.
_N_ Nucleus.
_N_′ Nucleolus.
_P_ Process.
]
The whole of the inner surface is lined with endothelium
(endocardium), which covers the various trabeculae; the external
surface of the heart is likewise covered with an epicardial layer of
endothelium (Fig. 138 _E_).]
[Illustration: Fig. 142.
Arteries and veins of the Truncus arteriosus of Bufo vulgaris, after
Hyrtl.
_a_ Arteria bulbi.
_b_ Truncus arteriosus.
_h_, _i_ Hepatic portal veins.
_t_ Right and left synangium.
_v_ Vena bulbi anterior.
_vi_ Left innominate vein.
_vc_ Vena bulbi posterior (V. cardiaca).
_A_ Right auricle.
_A_′ Left auricle.
_V_ Ventricle.
]
*e.* The blood-supply to the heart.
With the exception of the _truncus arteriosus_, no part of the heart
possesses blood-vessels (Hyrtl). [The _truncus arteriosus_ (Fig. 142
_b_) has a rich anastomosis, which receives its blood by the _arteria
bulbi_ (_a_), a branch of the carotid arch. Two veins connect this
anastomosis with the systemic veins, and with the hepatic portal veins:
the former, _vena bulbi anterior_ (_v_), passes over the auricles to
open into the left innominate vein (_vi_); the latter, the _vena bulbi
posterior_ (_vc_) or _vena cardiaca_, as it is more usually named,
passes from the _truncus arteriosus_ in a fold of pericardium, and then
courses backwards to open into the anterior-abdominal vein.]
II. THE ARTERIES.
(The original arrangement of this section has been modified.)
The _Truncus arteriosus_ divides to form two vessels (Figs. 132, 134);
each of these is divided by two partitions into three compartments,
which after a short course together separate to form three distinct
vessels, the carotid, systemic, and pulmo-cutaneous arches.
*1.* The *carotid arch* (_Canalis carotico-lingualis_, Brücke; _Ductus
caroticus_), (Fig. 143 _I_) is the most anterior of the three arches:
it winds round the side of the oesophagus as far as the carotid gland,
where it divides to form two branches; the right carotid arch gives off
a small branch to the _Truncus arteriosus_, the _Arteria bulbi_ (see
above).
[Illustration: Fig. 143.
Schema of the arterial system of Rana esculenta.
_A_ Dorsal aorta.
_c_ Cutaneous artery.
_ca_ Carotid artery.
_d_ Carotid gland.
_ic_ Iliac arteries.
_ie_ External iliac artery.
_ii_ Internal iliac artery.
_J_ Mesenteric artery.
_l_ Lingual artery.
_o_ Occipital artery.
_ov_ Occipito-vertebral artery.
_P_ Pulmonary artery.
_s_ Subclavian artery.
_T_ Truncus arteriosus.
_ug_ Urinogenital arteries.
_v_ Vertebral artery.
_I_ Carotid arch.
_II_ Systemic arch.
_III_ Pulmo-cutaneus arch.
]
The *carotid gland* (Fig. 144 _c_′) is a dilated portion of the vessel.
The interior contains bands or trabeculae of muscle, which give its
walls a more or less spongy structure; the muscle-fibres are not
transversely striated (Hoffmann).
*a.* The *lingual artery* (_Arteria lingualis_, _Arteria
hyoidea-lingualis_, _Arteria hyoidea_), (Figs. 143 _l_, 144 _L_) arises
by two roots from the inner surface of the carotid gland, and courses
forwards and inwards, supplying branches to the thyroid gland and the
_Musculi geniohyoidei_, to the ventral surface of the hyoid; another
continues forwards on the outer border of the _M. hyoglossus_ to supply
branches to the hyoid and tongue.
*b.* The *carotid artery* (_Arteria carotis communis_), (Figs. 143
_ca_, 144 _c_″) arises by several roots from the outer wall of the
carotid gland; and passes over the _Musculus petrohyoideus I_ to the
anterior end of the oesophagus, round which it courses towards the
vertebral column, and then runs forwards to the base of the skull.
The artery then courses forwards, lying immediately above the mucous
membrane and underneath the transverse arm of the parasphenoid, which
it crosses about midway between its back and external end; [at this
point the artery gives off two palatine arteries, then ascends in the
orbit to the origin of the _M. pterygoideus_, and divides into two
branches, the internal carotid artery and the ophthalmic artery]. The
branches are:--
(1) The pharyngeal artery (_Arteria pharyngea ascendens_), (Fig. 145
_p_) which runs towards the opening of the Eustachian tube,
distributes branches to the pharynx, and anastomoses with the _Arteria
pharyngeo-maxillaris_ of the cutaneous artery, and with the _Ramus
inframaxillaris_ of the occipital artery.
[Illustration: Fig. 144.
Right carotid gland.
_c_ Carotid arch.
_c_′ Carotid gland.
_c_″ Carotid artery.
_L_ Lingual artery.
]
(2) [The posterior palatine artery (_Arteria palatina posterior_,
Virchow) immediately divides into a number of small twigs to supply the
mucous membrane of the hinder and outer parts of the gums.]
(3) The anterior palatine artery (_Arteria palatina anterior_, Virchow;
_Arteria palatina_, Ecker), (Fig. 145 _p_′) runs forwards, between
the _Musc. levator bulbi_ and the mucous membrane, with the _Ramus
palatinus_ of the trigeminal nerve. [On reaching the palatine bone,
it curves outwards to the outer anterior angle of the orbit, where it
gives off a branch backwards along the upper jaw to the hinder portion
of the orbit.] In its course it supplies twigs to the surrounding
tissues, but chiefly to the mucous membrane and Harder’s gland.
[Illustration: Fig 145.
Arterial system of _Rana esculenta_.
_A_ Dorsal aorta.
_Ad_ Right systemic arch.
_As_ Left systemic arch.
_c_ (opposite fore-limb) Carotid artery.
_c_ (in abdomen) Coeliac artery.
_cm_ Cutaneous artery.
_e_ Lingual artery.
_H_ Heart.
_H_′ Harderian gland.
_L_ Liver.
_Lu_ Lung.
_m_ Mesenteric artery.
_M_ Stomach.
_M_′ Spleen.
_o_ Ophthalmic artery.
_p_ Pharyngeal artery.
_p_′ Anterior palatine artery.
_S_ Subclavian artery.
_I_ Carotid arch.
_II_ Systemic arch.
_III_ Pulmo-cutaneous arch.
]
(4) The internal carotid artery (_Art. cerebralis_, Virchow); see
Arteries of Brain, p. 162.
(5) The ophthalmic artery (_Art. ophthalmica_), (Fig. 145 _o_) [is
larger than the internal carotid artery at this point; it crosses the
origins of the _M. rectus externus_ and of the _M. retrahens bulbi_
and reaches the optic nerve; the artery then runs forwards along the
under surface of this nerve and of the eyeball, lying close to the
sclerotic coat as far as a little beyond the equator, where it pierces
the sclerotic coat so obliquely that the choroid coat is only reached
at the ciliary processes. In its course the artery supplies:--
α. Muscular branches, given off at the point where the artery reaches
the eyeball.
β. Two arteries (_AA. ciliares_) to the choroid, given off at the same
point as the foregoing.
γ. Two arteries to the iris.
δ. The _Art. hyaloidea_, the terminal portion of the ophthalmic artery.
(For further description of these vessels, see Eye.)].
*2.* The *systemic arch* (_Ductus aorticus_), (Figs. 132, 143, and 145
_II_) is the middle arch of the three; it arises from the middle canal
of the _Ductus arteriosus_, and winds obliquely round the oesophagus
between the _MM. petrohyoidei I_ and _II_ towards the vertebral
column, which it reaches at about the level of the sixth vertebra. The
right systemic arch is continued as the dorsal aorta, the left arch
communicates with it merely by a small opening, and is then continued
as the coeliaco-mesenteric artery.
Branches of the systemic arch:--
*a.* The *laryngeal artery* (_Arteria laryngea_), (Fig. 146 _lg_)
arises from the inner border of the systemic arch before it reaches the
oesophagus; it passes forwards and inwards to be distributed in the
larynx and pharynx. According to Brücke this artery possesses a valve
at its point of origin.
[Illustration: Fig. 146.
Transverse section at level of the larynx.
_C_ Carotid gland.
_G_ Glottis.
_lg_ Laryngeal artery.
_S_ Subclavian artery.
_I_ Carotid arch.
_II_ Aortic arch.
]
*b.* The *oesophageal arteries* (_Arteriae oesophageae_) pass from the
upper part of the arch to the dorsal surface of the oesophagus.
*c.* The *occipito-vertebral artery* (Ecker), (_Art.
occipito-vertebralis_), (Fig. 147 _o_, _v_) [arises from the systemic
arch immediately in front of the transverse process of the second
vertebra, and ascends immediately in contact with the body of the first
vertebra, which it separates from the _MM. intertransversarii capitis_
and the sympathetic cord]. Immediately under the most anterior portion
of the _M. longissimus dorsi_ the artery divides into two branches, the
vertebral and occipital arteries:--
(1) The *vertebral artery* (_Arteria vertebralis_ or
_supra-vertebralis_) (Fig. 147 _v_) courses backwards lying
on the transverse processes of the vertebrae and on the _MM.
intertransversarii_, under cover of the _M. longissimus dorsi_. In this
course it is close to the oblique processes, and may even be partially
covered by these; it extends beyond the sacrum, and gives off:--
α. The _Rami spinales_, which pass through the intervertebral foramina
to the spinal cord (see Arteries of Spinal Cord, p. 162).
[Illustration: Fig. 147.
Dissection to show the occipito-vertebral and the cutaneous arteries.
The skin of the back has been divided by a median incision and drawn to
either side; the right arm dislocated and removed through the opening
in the skin (at _A_). On the left side the extensor muscles of the back
have been removed.
_c.m._ Cutaneous artery.
_c.p._ Arteria cutanea pectoris.
_o_ Occipital artery.
_s_ Scapular artery.
_v_ Vertebral artery.
]
β. The _Rami dorsales_; these supply the muscles of the back and send
branches to the skin, which accompany the cutaneous branches of the
spinal nerves through the _Saccus lymphaticus cranio-dorsalis_.
γ. The _Rami intercostales_ are distributed in part to the _MM.
intertransversarii_; other twigs pass ventrally to the periganglionic
glands; the longest branches accompany the anterior divisions of the
spinal nerves to the muscles and skin of the belly (Fig. 145).
(2) The *occipital artery* (_Arteria occipitalis_), (Figs. 147 and 148
_o_), the anterior branch of the occipito-vertebral artery, pierces
the _M. longissimus dorsi_; then courses forwards under cover of the
_Fascia dorsalis_ and upon the _M. temporalis_, and divides, behind the
eyeball [at the anterior border of the _M. temporalis_, Virchow], into
two branches:--
α. The _Ramus orbito-nasalis_ (Fig. 148 _on_) accompanies the
ophthalmic nerve along the wall of the cranium, and passes through the
sphenethmoid, with the nasal branch of the ophthalmic nerve, to the
nose, where it divides into two branches supplying the mucous membrane
of the nose. In its course through the orbit the artery supplies
branches to the Harderian gland and neighbouring parts, and anastomoses
with the ascending branch of the _Arteria palatina_.
β. The _Ramus maxillaris communis_ (_Art. temporalis_, Virchow),
(Fig. 148 _m_) runs downwards and outwards along the anterior border of
the _M. temporalis_, and passes under the anterior arm of the squamosal
bone to course backwards on the upper jaw. At this point the _Ramus
maxillaris superior_ (_m_′) is given off. The main artery continues its
backward course to the tympanic membrane, where it divides into its
three terminal branches:--
[Illustration: Fig. 148.
Branches of the occipito-vertebral and cutaneous arteries in the head;
side view. The skin (_H_) has been reflected downwards.
_c.m._ Cutaneous artery.
_l.a._ M. levator scapulae.
_m_ Art. maxillaris communis.
_m_′ Art. maxillaris superior.
_m_″ Art. maxillaris inferior.
_o_ Occipital artery.
_on_ Art. orbito-nasalis.
_p.m._ Art. pharyngo-maxillaris.
_v_ Vertebral artery.
]
[(1) The _Ramus maxillaris superior_ (_AA. maxillares superiores_,
Virchow), usually not a single artery but a number of small twigs,
which supply the space between the eye and the upper jaw.
(2) A small ascending branch to the tympanic membrane (Virchow).
(3) A _Ramus auricularis_ (Virchow), which forms a rich anastomosis
on the hinder wall of the tympanic cavity, and supplies a twig to the
tympanic membrane. This passes from the upper border of the membrane
to the point of attachment of the _Columella auris_ (extrastapedial),
round which it forms a circular anastomosis. The _Ramus auricularis_
also anastomoses with the cutaneous artery.
[Illustration: Fig. 149.
Dissection to show the occipito-vertebral and the cutaneous arteries.
The skin of the back has been divided by a median incision and drawn to
either side; the right arm dislocated and removed through the opening
in the skin (at _A_). On the left side the extensor muscles of the back
have been removed.
_c.m._ Cutaneous artery.
_c.p._ Arteria cutanea pectoris.
_o_ Occipital artery.
_s_ Scapular artery.
_v_ Vertebral artery.
]
(4) A branch passing inwards to the fat-body, and lying immediately in
front of the deltoid muscle (Virchow).
(5) A small branch running on to the inner surface of the angle of the
jaw and then forwards (Virchow).
(6) A larger vessel, the _Ramus maxillaris inferior_ (Fig. 148 _m_″),
which arises from the _Ramus maxillaris superior_ under cover of the
tympanic membrane, and accompanies the _Ramus mandibularis_ of the
trigeminal nerve through the _M. masseter_, or between this muscle and
the _M. temporalis_ to the mandible, and then courses forwards to the
chin. A large cutaneous branch is given off half-way along the floor
of the mouth. The artery gives off many small twigs to supply the
neighbouring structures.]
3. The *pulmo-cutaneous arch* (_Ductus pulmo-cutaneus_), (Figs. 132
143, and 145 _III_) is the hindmost (fifth embryonic) of the three
persistent arches; it passes upwards and forwards on the oesophagus,
and at the level of the carotid gland divides into two branches, the
pulmonary artery and the cutaneous artery.
a. The *pulmonary artery* (_Arteria pulmonalis_) runs backwards to the
root of the lung, along the outer surface of which it is continued in a
sinuous course. It supplies the lung.
b. The *cutaneous artery* (_Arteria cutanea magna_), (Fig. 149
_c.m._) [passes along the deeper surface of the _M. petrohyoideus
III_ until near the prootic bone; in this course it travels forwards,
outwards, and upwards, crosses the outer border of the muscles,
and appears between the _M. levator anguli scapulae_ and the _M.
sternocleidomastoideus_. At this point the artery curves sharply round
to reach the angle of the jaw, the hinder border of the _M. depressor
maxillae inferioris_. The curve so formed and the descending limb are
covered by the _M. depressor maxillae inferioris_. The artery then
passes backwards to form a rich anastomosis in the skin almost as far
as the posterior end of the trunk. It supplies the following branches:--
(1) The _Ramus dorsalis_ (Virchow) arises immediately in front of the
curve of the main artery; it ascends behind the _M. temporalis_, and
passes along the anterior border of the _M. depressor maxillae_ to the
skin, where it curves backwards. It supplies small twigs forwards as
far as the eyelids.
(2) The _Ramus auricularis_ (Virchow) also arises in front of the
curve in the cutaneous artery; sometimes it arises from the _Ramus
dorsalis_. The artery winds around the _M. petrohyoideus III_ near its
insertion, and so reaches the posterior wall of the tympanic cavity,
where it anastomoses with the _R. auricularis_ of the _Ramus maxillaris
communis_.]
(3) The _Arteria pharyngo-maxillaris_ (Fig. 148 _p.m._) is a small
branch running forwards and outwards to supply the mucous membrane of
the larynx, Eustachian tubes, gums, the lower jaw, and the skin under
the mouth. It forms a rich anastomosis with branches of the _Ramus
maxillaris inferior_ of the occipital artery, and with others from the
pharyngeal branch of the carotid artery; a large branch passes forwards
to supply the skin of the throat and floor of the mouth.
(4) The _Arteria cutanea pectoris_ (Fig. 149 _c.p._) is distributed to
the skin of the breast.
*4.* The *subclavian artery* (_Arteria subclavia_), (Fig. 150 _s_). The
subclavian artery arises from the systemic arch immediately behind the
occipito-vertebral artery at the level of the second or third vertebra.
The artery then runs outwards alongside and in front of the brachial
nerve, between the _M. subscapularis_ and the _M. triceps_ to the arm,
where it is known as the brachial artery; in its course it gives off:--
*a.* The _Arteria costo-cervicalis_ (Fig. 150, 1). This artery arises
near the systemic arch, and runs backwards, parallel to the vertebral
column, over the brachial nerve, and across the transverse processes of
the vertebrae. It is distributed more especially to the _M. obliquus
internus_.
*b.* The _Arteria coraco-clavicularis_ (Fig. 150, 2) arises more
externally than the last artery; it accompanies the coraco-clavicular
nerve on the dorsal surface of the ventral portion of the
shoulder-girdle, and passes between the _M. deltoideus_ and _M.
subscapularis_ into the _Foramen ovale_, where it divides to supply
these muscles and the _M. pectoralis_.
[Illustration: Fig. 150.
Subclavian artery of the left side.
_A_ Systemic arch.
_A_′ Dorsal aorta.
_c_ Arteria cutanea medialis superior.
_c_′ Arteria cutanea medialis inferior.
_ls_ M. levator scapulae.
_o.v_ Occipito-vertebral artery.
_p_ Arteria pectoralis.
_R_ Radial artery
_s_ Subclavian artery.
_U_ Ulnar artery.
1 Arteria costo-cervicalis.
2 Arteria coraco-clavicularis.
3 Arteria scapularis posterior.
4 Arteria scapularis superior.
5 Cutaneous artery.
6 Arteria subscapularis.
]
*c.* The _Art. scapularis posterior_ (Fig. 150, 3), a small branch
arising opposite at the tip of the second transverse process and
passing backwards over the _MM. transverso-scapulares_, to which it is
distributed.
[Illustration: Fig. 151.
Arteries of the palmar surface of the hand.
_B_ Ulnar artery.
_ci_ R. cutaneus medialis inferior.
_d_ Digital branches.
_F_ M. flexor digitorum communis.
_II_ Thumb.
_V_ Fifth finger.
]
[Illustration: Fig. 152.
Arteries of the dorsal surface of the hand.
_B_ Ulnar artery.
_cri_ R. cutan. rad. inferior.
_R_ Radial artery.
_II_ Thumb.
_V_ Fifth finger.
]
*d.* The _Art. scapularis superior_ (Fig. 150, 4) accompanies several
nerves between the _M. subscapularis_, _M. transverso-scapularis
major_, and the long head of the _M. triceps_ towards the dorsal
surface, where it is distributed to the _MM. infraspinatus_,
_latissimus dorsi_, etc.
*e.* The _Ramus cutaneus maxillaris_.
*f.* The _Art. subscapularis_ (Fig. 150, 6) is distributed in the
subscapular muscle.
A. The *brachial artery* (_Arteria brachialis_), (Fig. 150) accompanies
the brachial nerve under cover of the long head of the _M. triceps_ and
over its inner head to the _Plica cubiti_, into which it sinks near the
tendon of the _M. sternoradialis_; beyond this point it is continued as
the ulnar artery. In its course the brachial artery gives off:--
*a.* The _Arteria pectoralis_ (Fig. 150 _p_).
*b.* The _Arteria cutanea medialis superior_ (Fig. 150 _c_).
*c.* The *radial artery* (_Arteria radialis_), (Fig. 150 _R_) which
winds round the humerus with the radial nerve between the muscles of
the outer side of the forearm, to which it gives branches: in the palm
of the hand it passes between the _M. extensor carpi ulnaris_ and the
_M. flexor antibrachii_ to the dorsal surface of the hand, where it
anastomoses with the ulnar artery. In its course it supplies:--
(1) Muscular branches to the surrounding muscles.
(2) The _Ram. cut. radialis inferior_, which arises from the radial
artery towards the distal end of the forearm, and passes underneath the
_M. flexor carpi ulnaris_ to the skin.
B. The *ulnar artery* (_Arteria ulnaris_), (Figs. 150 _U_, 151 _B_)
accompanies the ulnar nerve towards the hand, passes between the _M.
flexor digitorum communis_ and the _M. anconeus_ to the palm of the
hand, and then winds round the outer side to the dorsal surface of the
carpus to form its terminal branches. The branches are:--
(1) The _Ram. cutan. med. inferior_ (Fig. 151 _ci_); it arises near the
wrist-joint and supplies (α) twigs to the skin of the inner surface;
(β) a branch downwards, which courses along the inner side of the
second finger to its tip; and (γ) a branch which passes upwards to
anastomose with the _R. cutaneus medialis superior_.
(2) In the palm of the hand a branch (Fig. 151 _d_) is given off,
which divides to form _Arteriae digitales volares_: one for the second
finger, two for the third finger, two for the fourth finger, and one
for the fifth finger.
(3) Given off on the dorsum of the hand (Fig. 152) it supplies branches
corresponding exactly with those of the palmar surface.
*5.* The *dorsal aorta* (_Aorta communis s. abdominalis_) (Fig. 153
_A_). The two systemic arches unite at about the level of the sixth
vertebra to form the dorsal aorta: as already mentioned the union is
very incomplete, the dorsal aorta being practically a continuation of
the right systemic arch, and only communicating with the left by means
of a small opening. The branches are as follows:--
*a.* The *coeliaco-mesenteric artery* (_Arteria intestinalis
communis_), (Fig. 153), the true continuation of the left systemic
arch, at once divides to form the gastric and mesenteric arteries.
(1) The *gastric artery* (_Arteria gastrica s. coeliaca_) (_c_)
immediately divides into two branches:--
α. The _Ramus dexter s. anterior_; this artery gives off the _Arteria
hepatica_ to the liver and gall-bladder and passes to the right
(anterior) surface of the stomach, running along the attachment of
the mesentery and supplying branches forwards to the oesophagus and
backwards towards the intestine.
β. The _Ramus sinister s. posterior_ passes to the left (posterior)
surface and behaves like the _Ram. dexter_.
(2) The *mesenteric artery* (_Arteria mesenterica superior_ and
_inferior_, and the _Arteria splenica_), (Fig. 153 _m_) supplies:--
α. The superior mesenteric artery, which supplies the upper part of
the intestine, and gives off a recurrent branch to the stomach, which
anastomoses with the gastric arteries.
[Illustration: Fig. 153.
Arterial system of _Rana esculenta_.
_A_ Dorsal aorta.
_Ad_ Right systemic arch.
_As_ Left systemic arch.
_c_ (opposite fore-limb) Carotid artery.
_c_ (in abdomen) Coeliac artery.
_cm_ Cutaneous artery.
_e_ Lingual artery.
_H_ Heart.
_H_′ Harderian gland.
_L_ Liver.
_Lu_ Lung.
_m_ Mesenteric artery.
_M_ Stomach.
_M_′ Spleen.
_o_ Ophthalmic artery.
_p_ Pharyngeal artery.
_p_′ Anterior palatine artery.
_S_ Subclavian artery.
_I_ Carotid arch.
_II_ Systemic arch.
_III_ Pulmo-cutaneous arch.
]
β. The splenic artery to the spleen.
γ. The inferior mesenteric artery to the lower part of the intestine.
All the arteries to the intestine course in lymph-spaces.
*b.* The *urinogenital arteries* (_Arteriae urino-genitales_),
(Fig. 154 _ug_) are four to six small arteries arising from the ventral
surface of the aorta between the kidneys: they immediately divide into
right and left branches to supply the kidneys, fat-bodies, reproductive
organs, and their ducts (see kidney).
*c.* The *lumbar arteries* (_Arteriae lumbales_), are small paired
vessels to the neighbouring muscles, and send branches through the
intervertebral foramina to the vertebral canal. Sometimes these
arteries arise from the _Art. spinalis_ or _Art. vertebralis_, etc.;
in the former case they pass outwards from the vertebral canal to the
surrounding structures.
*d.* The *haemorrhoidal artery* (_Art. mesenterica inf. s Art.
haemorrhoidalis superior_) is a small median artery running from the
posterior end of the aorta to the large intestine.
*6.* *Bifurcation of the aorta.* *The iliac arteries* (_Arteriae
iliacae communes_). Opposite the middle of the urostyle the aorta
bifurcates to form the iliac arteries; each of these courses on the
corresponding sciatic plexus to the thigh, beyond which it is continued
as the sciatic artery. The branches of the iliac artery are:--
*a.* The *vesico-epigastric artery* (_Arteria epigastrico-vesicalis_),
(Fig. 155 _ev_); it arises near the bifurcation, passes outwards on the
plexus, and divides into two branches:--
(1) The epigastric artery (_Arteria epigastrica_) (_e_) immediately
gives off a recurrent branch to the iliac bone and the _M.
ilio-coccygeus_; it then continues to the ventral muscles of the
abdominal wall, where it runs forwards on the deeper surface of the _M.
obliquus internus_, and is distributed more especially to this muscle.
[Illustration: Fig. 154.
The urinogenital arteries.
_A_ Dorsal aorta.
_H_ Testis.
_N_ Kidney.
_ug_ Urinogenital arteries.
]
(2) The hypogastric artery (_Arteria vesicalis_) (_v_) winds downwards
around the sciatic plexus to reach the mesentery, along which it
courses to the bladder, where it forms a rich anastomosis.
*b.* The *femoral artery* (_Arteria femoralis s. cruralis_), (Fig. 155
_f_) is the representative of the femoral artery of man, although it
does not perform the same functions. The artery passes under the hinder
free border of the _M. obliquus internus_ to the thigh, where it lies
upon the _M. ilio-psoas_, and sends twigs to the neighbouring muscles,
the skin, and lymph-sac (_Lamina inguinalis_), and then divides into:--
(1) A twig, which runs forwards on the ventral surface of the iliac
bone and is covered by the epigastric artery.
(2) A twig, running forwards and downwards on the _MM. ilio-psoas_,
_vastus internus_, and _sartorius_, to send branches to the hip-joint.
*c.* The *spermatic artery* (_Arteria spermatica_), which arises, in
males, from the iliac artery, and ascends to the _Vesicula seminalis_.
[Illustration: Fig. 155.
Bifurcation of the aorta and the iliac arteries.
_e_ Epigastric artery.
_ev_ Vesico-epigastric artery.
_f_ Femoral artery.
_o_ Internal oblique muscle.
_v_ Vesical artery.
]
*7.* *Arteries of the hinder extremity.*
A. The *sciatic artery* (_Arteria ischiadica_), (Fig. 156 _i_) is
the continuation of the iliac artery; it leaves the pelvis between
the hinder (outer) border of the _M. coccygeo-iliacus_ and the inner
surface of the origin of the _M. ilio-psoas_, then lies between the
former muscle and the origin of the _M. vastus externus_. It appears
on the thigh between the _M. vastus externus_ (in front) and the _M.
pyriformis_ (behind); it is the main arterial trunk for the hinder
extremity. The artery courses backwards, lying upon the sciatic
nerve and between the _M. biceps_ and the _M. semimembranosus_; in
this course it runs in a lymph-space placed in the _Septum femorale
superius_ (see page 259). Arrived at the popliteal space the artery
bifurcates to form the peroneal and tibial arteries; near the pelvis
it gives off two branches (*a*) and (*b*), and in its course along the
thigh two branches (*c*) and (*d*).
*a.* The _Art. haemorrhoidalis inferior_ (_h_) runs backwards and
inwards under the _M. pyriformis_ to be distributed in the _M.
sphincter ani_ and the skin of the anus.
*b.* The _Art. cutanea femoris posterior v. superior_ (_cf_′) runs
with the corresponding nerve and the _M. pyriformis_, and over the _M.
semimembranosus_ to the skin of the inner and hinder surfaces of the
thigh.
*c.* The _Rami musculares_ supply the _M. semimembranosus_, the _M.
biceps_, and the _MM. extensores auris_; the branch to the _M. rectus
inferior major_ pierces the muscle in company with the nerve, and is
continued as:--
*d.* The _Art. cutanea femoris media_ (_cf_″) to the skin of the middle
of the inner surface of the thigh. Several small twigs pierce the _M.
rectus internus minor_, reach the skin, and communicate with this
artery.
[Illustration: Fig. 156.
Arteries of the hinder extremity.
_cc_ Art. cutanea calcanei.
_cf_ Cutaneous branch of the femoral artery.
_cf_′ Art. cutanea fem. post. superior.
_cf_″ Art. cutanea femoris media.
_cgl_ Art cut. genu lateralis superior.
_cgl_′ Art. circumflexa genu lateralis inferior.
_cgm_ Art. circumflexa genu superior medialis.
_cgm_′ Art. circumflexa genu inferior medialis.
_ci_ M. coccygeo-iliacus.
_g_ M. gastrocnemius.
_gl_ M. glutaeus.
_h_ Art. haemorrhoidalis inferior.
_i_ Sciatic artery.
_ml_ Art. malleolaris lateralis.
_mm_ Art. malleolaris medialis.
_p_ Art. peronea.
_p_′ Muscular branch to the M. peroneus.
_P_ M. pyramidalis.
_ra_ M. rectus anterior.
_ri_″ M. rectus internus.
_sm_ M. semimembranosus.
_su_ Art. suralis.
_t_ Tibial artery.
_to_ Aperture in tibio-fibula.
_tr_ Art. tarsea.
_ve_ M. vastus externus.
]
B. The *peroneal artery* (_Art. peronea_), (Fig. 156 _p_) runs
outwards under cover of the tendon of the _M. biceps femoris_, and
accompanies the peroneal nerve downwards to give off:--
*a.* The _Art. circumflexa genu lateralis superior_, which runs
forwards on the outer side of the knee, gives a twig to the joint, and
is continued as:--
*b.* The _Art. cutanea genu lateralis superior_ (_cgl_) to the skin of
the anterior and outer sides of the knee. It anastomoses with branches
of the _Arteriae circumflexae genu mediales_ to form a rich anastomosis
(_Rete articulare genu_): other branches pass upwards to inosculate
with the _Art. cutanea femoris anterior_ (_cf_), and others downwards
to anastomose with the next artery.
*c.* The _Art. circumflexa genu lateralis inferior_ (_cgl_′) runs under
the tendon of origin of the gastrocnemius to the outer side of the
knee, and terminates in the skin as the _Art. cutanea genu lateralis
inferior_. Some of the cutaneous twigs pass upwards to anastomose with
the _Art. cut. genu lat. superior_, others downwards to anastomose with
the _AA. malleolares_.
*d.* A muscular branch (_p_′) for the _M. peroneus_; it is the real
continuation of the peroneal artery, and runs behind the outer tendon
of origin of the gastrocnemius to be distributed in the _M. peroneus_.
C. The *tibial artery* (_Arteria tibialis_), (Fig. 156 _t_), arises at
the bifurcation of the sciatic, and runs inwards, meeting the tibial
nerve between the tendons of origin of the _M. gastrocnemius_, and
deep in the popliteal space under cover of the calf-muscles. It then
pierces the _M. tibialis posticus_, and leaves this to perforate the
tibio-fibula (see p. 50), appearing again on the anterior surface as
the anterior tibial artery. Before meeting the tibial nerve this artery
gives off the following branches:--
*a.* The _Art. circumflexa genu superior medialis_ (_cgm_), which winds
round to the front of the knee-joint, and gives off a cutaneous branch,
the _Art. cutanea genu medialis superior_, which is distributed in the
skin of the inner side of the knee and anastomoses above with the _Art.
cutanea femoris media_, below with the following branches (*b*, *c*,
and *d*).
*b.* The _Art. circumflexa genu inferior medialis_ (_cgm_′) supplies
twigs to the knee-joint, and passes to the skin of the knee and inner
surface of the calf as the _Art. cutanea inferior medialis_.
*c.* Muscular twigs to the _M. gastrocnemius_.
*d.* The _Art. suralis_ (_su_); this accompanies the _N. suralis_
downwards along the calf-muscle, and is distributed in the skin of the
inner side of the heel.
*e.* While passing between the fibres of the _M. tibialis posticus_,
the tibial artery gives off muscular twigs; one larger than the rest is
known as the _Ramus descendens_.
D. The *anterior tibial artery* (_Arteria tibialis antica_), (Fig. 157
_t.a._) is the continuation of the tibial artery after piercing the
tibio-fibula. It runs downwards on the anterior surface of the leg,
then between the two heads of the _M. tibialis anticus_ to the dorsum
of the foot, where it is continued as the _Arteria dorsalis pedis_. It
supplies:--
[Illustration: Fig. 157.
Arteries of the dorsal surface of the foot.
_c.c._ Art. cutanea calcanei.
_c.c.i._ Art. cutanea cruris inferior.
_Ft_′ M. flexor tarsi.
_h_ Art. cutanea hallucis.
_i1_ Art. interossea dorsalis I.
_i2_ Art. interossea dorsalis II.
_i3_ Art. interossea dorsalis III.
_i4_ Art. interossea dorsalis IV.
_ml_ Art. malleolaris lateralis.
_m.m._ Art. malleolaris medialis.
_t.a._ Anterior tibial artery.
_ta_* Bifurcation of the dorsalis pedis artery.
_tr_ Art. tarsea.
]
*a.* _Rami musculares_ to the _M. peroneus_, _M. extensor cruris_, and
to the _M. flexor tarsi anterior_.
*b.* The _Art. cutanea cruris inferior_ (_c.c.i._) passes between the
two heads of the _M. tibialis anticus_ to the skin of the anterior and
outer sides of the leg.
*c.* The _Art. cutanea calcanei_ (_c.c._) is given off at the
ankle-joint; it runs outwards on the lower end of the tibio-fibula,
giving branches to the joint, then backwards between the tibio-fibula
and the _M. peroneus_ to be distributed to the skin of the heel. Above
it anastomoses with the _A. circumflexa genu inf. lateralis_, and below
with the malleolar arteries.
*d.* The _Art. malleolaris lateralis_ (_ml_) arises a little beyond
the last artery; it runs outwards under the origin of the _M. flexor
tarsi_, gives branches to the joint and muscles, and terminates in the
skin of the outer border and dorsal surface of the foot.
*e.* The _Art. malleolaris medialis_ (_m.m._) arises at about the
same level as the _Art. malleolaris lat._ from the inner border
of the anterior tibial artery. It supplies branches to the joint,
gives numerous branches to the skin, which anastomose with the _Art.
suralis_, and passes to the inner border of the foot, where it ends by
distributing branches to the _M. plantaris_, the extensor aponeurosis,
and, as the _Art. cutanea plantaris_, to the skin of the sole of the
foot.
E. The *dorsal artery* of the foot (_Art. dorsalis pedis_), (Fig. 157
_t.a._) runs under the _M. flexor tarsi posterior_ to the point _ta_*,
where it is superficial; the artery then bifurcates; the branches are:--
[Illustration: Fig. 158.
Arteries of the sole of the foot.
_i_ Art. interossea.
_pf_ Rami perforantes.
]
*a.* The _Art. tarsea_ (_tr_) which arises from the dorsal artery of
the foot while under cover of the _M. flexor tarsi posterior_; it
passes to the _M. extensor digiti V_ and to the skin of the dorsum and
outer border of the foot. One branch courses along the outer border of
the fifth toe to its tip; another passes upwards to anastomose with the
neighbouring vessels.
*b.* The inner branch, formed by the bifurcation of the dorsal artery
of the foot, at once divides to form:--
(1) The _Art. cutanea hallucis_ (_h_) to the supplemental great toe.
(2) The _Art. interossea dorsalis I_ (_i^1_), which at once bifurcates
to form two _Rami digitales_ for the first and second toes; these
inosculate with the _Art. cutanea plantaris_, and send twigs to the
skin of the inner border of the foot.
*c.* The outer branch formed by the bifurcation of the dorsal artery
divides to form the _Arteriae interossei dorsales II_, _III_, and _IV_
(_i^2_, _i^3_, _i^4_); they are distributed in a rich anastomosis to
the web.
*d.* The _Arteria interossea_ (Fig. 158 _i_) arises from the dorsal
artery of the foot at the tarsus, and perforates the membrane between
the astragalus and calcaneum to reach the sole of the foot. It forms a
rich subcutaneous plexus on the calcar, and anastomoses with the _Rami
perforantes_ (Fig. 158 _pf_), which pass above the upper borders of the
_Musculi interossei_ to reach the plantar surface, where they give off
small _Rami interossei volares_ to anastomose with the _AA. interosseae
dorsales_.
III. THE VEINS.
(The arrangement of this section has been modified.)
The blood, distributed to the body by means of the arteries, is
returned to the heart by the veins, which conduct the blood directly or
indirectly to the auricles. The pulmonary vein opens directly into the
left ventricle, the three _Venae cavae_ open into the _Sinus venosus_.
A. *Vein opening into the left auricle.*
The *pulmonary vein* (_Vena pulmonalis communis_), (Fig. 159 _vp_).
The blood returning from each lung is gathered into a vessel lying
along the inner side of the root of the lung. That of the right side
is somewhat longer than the left; the two vessels (_Venae pulmonales
dextra et sinistra_) run above the corresponding anterior caval veins
to form a common trunk, the pulmonary vein, which opens into the left
auricle (see p. 215).
B. *Veins opening into the* _Sinus venosus_.
The veins opening into the _Sinus venosus_ are the three caval veins;
of these the two anterior open into the anterior angles of the _Sinus
venosus_, the posterior into the posterior angle.
*1.* The *Anterior Caval Veins* (_Vena cava superior_), (Figs. 133 _V_,
159 _C a_) are a pair of large veins opening into the _Sinus venosus_
and returning to it blood from the fore-limbs and sides of the head.
Each vein is formed by the union of a small vein, the external jugular,
with two large veins, the innominate and the subclavian veins.
*a.* The *external jugular vein* (_Vena jugularis externa_), (Fig. 159
_je_) is formed, at the outer border of the hyoid bone, by the union of
two veins:--
(1) The lingual vein (_Vena lingualis_) (Fig. 161 _l_). This originates
at the tip of the tongue and passes in a very tortuous course along the
ventral surface of the hyoid; it receives numerous branches from the
tongue and hyoid muscles.
(2) The mandibular vein (_Vena maxillaris inferior_), (Fig. 161 _m_)
runs along the insertion of the _M. submaxillaris_, and turns inwards
at its hinder border to join the lingual vein.
*b.* The *innominate vein* (_Vena anonyma_), (Fig. 160 _A_) is formed
by the union of the internal jugular and the subscapular veins. By
tracing the innominate vein upwards between the suspensorium and the
shoulder-girdle, the internal jugular vein will be seen to receive
the vertebral vein at the outer border of the _M. levator scapulae_.
The left innominate vein receives the _Vena bulbi anterior_ from the
_Truncus arteriosus_ (p. 222).
[Illustration: Fig. 159.
Schema of the veins of _Rana esculenta_.
_a_ Subclavian vein.
_ab_ Anterior abdominal vein.
_Ad_ Right auricle.
_As_ Left auricle.
_Ca_ Anterior vena cava.
_Cp_ Posterior vena cava.
_cm_ Cutaneous vein.
_d_ Vena dorso-lumbalis.
_D_ Intestine.
_f_ Femoral vein.
_i_ Sciatic vein.
_ic_ Vena communicans iliaca.
_je_ External jugular vein formed by lingual and maxillary
veins _l_ and _m_.
_ji_ Internal jugular vein.
_L_ Hepatic veins.
_N_ Kidney.
_o_ Oviducal veins.
_P_ Hepatic portal vein.
_raI_ Renal portal vein.
_raII_ Secondary renal portal veins.
_re_ Renal veins.
_s_ Subscapular vein.
_SC_ Sinus venosus.
_va_ Innominate vein.
_vc_ Vena bulbi posterior (cardiac vein).
_vp_ Pulmonary veins.
]
(1) The *internal jugular vein* (_Vena jugularis_), (Fig. 160 _J_)
can be traced from the border of the _M. levator scapulae_ upwards
and forwards to the hinder part of the prootic bone: it then passes
forwards under the lateral process of the prootic, in a groove on the
anterior surface of the same bone, towards the hinder angle of the
orbit, where it receives the veins from the cranial cavity (see vessels
of brain, p. 165), and also a branch from the orbit.
[Illustration: Fig. 160.
Distribution of the internal jugular vein and the anterior portion of
the cutaneous vein.
_A_ Innominate vein.
_c.m._ Cutaneous vein.
_f_ Nasal vein.
_h_ Harderian gland.
_H_ Skin, reflected downwards.
_J_ Internal jugular vein.
_L_ Anterior lymph-heart.
_l_ M. levator scapulae.
_O_ M. obliquus internus.
_o_ Vena orbitalis anterior.
_o_′ Vena orbitalis posterior.
_P_ Lateral process of the prootic bone.
_S_ Subscapular vein.
_S_′ Shoulder-girdle.
_T_ Tympanic membrane.
_V_ Vertebral vein.
_2_ Transverse process of the second vertebra.
_3_ Transverse process of the third vertebra.
_4_ Transverse process of the fourth vertebra.
]
α. [The _Vena orbitalis media_ (Virchow); it arises from the anterior
internal angle of the orbit, from the Harderian gland, the nasal
cavity, or from other veins on the anterior wall of the orbit. The
vessel lies close to the cranium, immediately underneath the _Arteria
nasalis_, and sinks under the _M. rectus superior_ to join the internal
jugular vein. In its course it receives the _Vena bulbi superior_ (see
eye), and near its termination communicates with the _Vena orbitalis
posterior_.]
β. The _Vena vertebralis_ (Fig. 160 _V_) arises posteriorly and runs
forwards over the transverse processes of the vertebrae, the _Musculi
intertransversarii_, and the _M. levat. scapulae_, to join the internal
jugular vein. In its course it receives branches (_Venae spinales_)
from the vertebral canal through the intervertebral foramina, and
cutaneous branches which accompany the corresponding arteries and
nerves through the dorsal lymphatic sac. The vein pulsates in
consequence of its connection with the anterior lymph-heart (Müller).
(2) The *subscapular vein* (_Vena subscapularis_), (Fig. 160 _S_). This
vein arises in the transverse abdominal muscles and the muscles of the
shoulder girdle; it unites with the internal jugular vein under the
shoulder-girdle.
*c.* The *subclavian vein* (_Vena subclavia_), (Fig. 159) passes
backwards from the anterior caval vein on the dorsal surface of the
coracoid bone and the clavicle, and then under cover of the _Portio
sternalis_ of the _M. pectoralis major_, to the internal border of the
_Portio abdominalis_ of the _M. pectoralis major_, where it is formed
by the union of the cutaneous vein and the brachial vein.
[Illustration: Fig. 161.
The anterior caval vein and its branches.
_a_ Innominate vein.
_c.m._ Cutaneous vein.
_c.s._ Anterior cava vein.
_i_ Internal jugular vein.
_i_′ External jugular vein.
_l_ Lingual vein.
_m_ Mandibular vein.
_s_ Brachial vein.
_s.c._ Subscapular vein.
]
(1) The cutaneous vein (_Vena cutanea magna_, Ecker; _Vena
musculo-cutanea_, Gruby), (Figs. 160, 161, and 162 _c.m._). This vein
arises by small branches in the head; these are:--
α. The _Vena nasalis_ (Virchow); it arises by an upper and a lower
branch from around the nostril, and courses backwards along the
superior maxillary bone to about the middle of the orbit, where it
joins the facial vein.
β. The _Vena orbitalis anterior_ (Virchow), (_Vena ophthalmica
anterior_, Ecker), (Fig. 160 _o_) commences at the Harderian gland from
a rich anastomosis, receives branches from the floor and anterior wall
of the orbit, and joins the facial vein with the _Vena nasalis_.
[Illustration: Fig. 162.
Course of the cutaneous vein as seen from the side.
_c.m._ Cutaneous vein.
_d_ M. depressor maxillae.
_i_ M. infraspinatus.
]
γ. The _Vena orbitalis posterior_ (Virchow), (_Vena ophthalmica
posterior_, Ecker), (Fig. 160 _o_′) arises on the posterior wall of
the orbit on the _M. pterygoideus_; it passes under the _Processus
zygomaticus_ to join the facial vein, and in its course receives the
_Vena ophthalmica_ (see eye), and communicates with the _Vena orbitalis
medialis_ and the internal jugular vein.
δ. The _Vena facialis_ (Fig. 160) is formed about the middle of the
orbit by the union of the _Vena nasalis_ and the _Vena orbitalis
anterior_; it courses backwards towards the angle of the jaw. On
reaching the _M. depressor maxillae_, about 4 mm. in front of the angle
of the jaw, it passes on to the skin. It receives in its course the
_Venae palpebrales_ (Fig. 162) and the _Vena orbitalis posterior_.
The musculo-cutaneous vein is the direct continuation of the _Vena
facialis_ after this has left the upper jaw; it immediately receives
one or more twigs (_Venae tympanicae_), (Fig. 162) from the tympanic
membrane and the tympanic cavity.
The vein then courses backwards in the outer wall of the lateral
lymph-sac as far as the middle of the trunk, where it passes, by
means of the _Septum abdominale_, to the outer border of the _Portio
abdominalis_ of the _M. pectoralis_; here the vein curves round to pass
forwards between the fibres of this muscle to its inner border where it
terminates by joining the brachial vein. In the whole of this lengthy
course the vein receives numerous branches from the neighbouring parts.
[Illustration: Fig. 163.
Veins in the region of the kidney.
_a_ Renal portal vein.
_a_′ Dorso-lumbar veins.
_abd_ Anterior abdominal vein.
_d_ Intestine.
_f_ Femoral vein.
_i_ Sciatic vein.
_N_ Kidney.
_o_ Right ovary, drawn to the left.
_o_′ Oviduct.
_ov_ Oviducal veins.
_p_ Mesenteric veins.
_r_ Renal veins.
_V_ Bladder.
_v.c.i._ Posterior vena cava.
_Vv_ Vesical veins.
]
(2) The *brachial vein* (_Vena brachialis_) is formed in the _Plica
cubiti_ by the union of two veins.
α. The *radial vein* (_Vena radialis_) arises on the dorsum of the hand
from a venous arch, the distal convexity of which receives the _Venae
digitales dorsales_: the vein courses superficially along the outer
side of the forearm to the elbow.
β. The *ulnar vein* (_Vena ulnaris_) arises from the veins in the
palm of the hand, and courses towards the elbow, lying deeply between
the muscles of the inner and outer surfaces of the forearm. In
the elbow the vein becomes superficial near the tendon of the _M.
sterno-cleidoradialis_, and joins the radial vein to form the brachial
vein.
The cutaneous veins of the fore-limb follow courses corresponding with
those of the arteries.
*2.* The *Posterior Caval Vein* (_Vena cava inferior_), (Fig. 159
_Cp_, 163 _v.c.i._). The posterior caval vein is a median vein
which, commencing between the kidneys, runs forwards to open into the
posterior end of the _Sinus venosus_. It receives the hepatic, renal,
and ovarian or spermatic veins.
*a.* The hepatic veins (_Venae hepaticae_), (Fig. 164 _v.h._) are
two in number, one from either side of the liver; they open into the
posterior caval vein near the _Sinus venosus_.
*b.* The *renal veins* (_Venae renales_ or _Venae revehentes_),
(Fig. 163 _r_) are four or five small vessels on each side; they pass
from the inner border of the kidney inwards and forwards, to form,
by their union, the posterior caval vein. The most anterior receive
branches from the fat-bodies (see kidney).
*c.* The *spermatic* or *ovarian veins* are four or five in number on
each side; they open into the posterior caval vein between the renal
veins.
*3.* The *Portal Systems*.
[There are, in the frog, two portal systems; the renal and the
hepatic. Each of these receives vessels which are derived, directly or
indirectly, from the veins of the hinder extremity.
The femoral vein on entering the pelvis divides to form two branches;
an iliac vein placed dorsally, and a pelvic vein placed ventrally; the
two pelvic veins converge to the middle line of ventral wall of the
abdomen, where they unite to form the anterior abdominal vein.]
*a.* The *renal portal vein* (_Vena renalis advehens princeps_),
(Fig. 163 _a_). This vein is formed by the union of the sciatic and the
iliac veins; it courses forwards to the outer border of the kidney, and
is distributed, by numerous branches, to that organ, chiefly on its
dorsal surface. It receives the following veins:--
(1) The *iliac vein* (_Vena iliaca externa_); this is the dorsal branch
formed by the bifurcation of the femoral vein.
(2) The *sciatic vein* (_Vena ischiadica_), (Figs. 163 and 165 _i_)
arises at the popliteal space, courses upwards in company with the
sciatic nerve between the _M. semitendinosus_ and the _M. biceps_, then
passes, still with the nerve, between the _M. vastus externus_ and the
_M. pyramidalis_ into the pelvis. It continues forwards to join the
iliac vein. At the root of the thigh this vein communicates with the
femoral vein by the _Ramus communicans iliacus_.
(3) The *dorso-lumbar vein* (_Vena dorso-lumbalis_), (Fig. 163 _a_′)
is a vein (or more usually several) arising by twigs in the dorsal and
outer walls of the abdomen; it joins the renal portal vein opposite the
kidney.
(4) The *oviducal veins* (Fig. 163 _ov_) are irregular veins from the
oviducts, which open either into the dorso-lumbar vein, or into the
renal portal vein.
*b.* The *hepatic portal system*.
The liver receives blood from two sources: (1) from the hind-limbs by
means of the anterior abdominal vein, and (2) from the alimentary canal
by the hepatic portal vein.
[Illustration: Fig. 164.
Veins of the liver.
_AA_ Auricles.
_aa_ Right and left branches of anterior abdominal vein.
_b_ Ramus descendens.
_c_ Vena bulbi (Vena cardiaca).
_D_ Intestine.
_G_ Gall-bladder.
_L.l._ Left lobe of liver.
_L.r._ Right lobe of liver.
_P_ Hepatic portal vein.
_P_′ Intestinal veins.
_P_″ Gastric veins.
_S_ Sinus venosus.
_V_ Ventricle.
_Va_ Anterior abdominal vein.
_V.c.i._ Posterior vena cava.
_v.h._ Hepatic veins.
]
The *anterior abdominal vein* (_Vena abdominalis_), (Figs. 159 _ab_,
164 _Va_) is formed, a little in front of the symphysis pubis, by
the union of the two pelvic veins. It courses forwards along the
middle line of the ventral body-wall until opposite the liver, where
it ascends and divides into three branches, of which two enter the
right and left lobes of the liver respectively. The third, the _Ramus
descendens_, joins the hepatic portal vein. The anterior abdominal vein
receives the following veins:--
α. The vesical vein (_Vena vesicalis_), (Fig. 163 _Vv_); a median vein
arising in the groove between the lobes of the bladder from lateral
branches, which extend outwards on the bladder. This vein communicates
above with other vesical twigs which open into the haemorrhoidal vein.
β. Parietal veins, which join the anterior abdominal vein in its course
along the ventral body-wall.
γ. A cardiac vein (_Vena cardiaca_), (Figs. 142, 159 _vc_, 164 _c_),
which joins the anterior abdominal vein just before its division (see
p. 222).
The *hepatic portal vein* (_Vena portarum_), (Figs. 159, 164 _P_) is
formed by the union of the gastric, intestinal, splenic, and one of
the haemorrhoidal veins. The large vein so constituted passes forwards
towards the liver, receives the _Ramus descendens_ from the anterior
abdominal vein, and then passes into the left lobe of the liver. Its
branches are the following:--
(1) The *gastric veins*. The stomach has three veins:--
α. [The _Vena coronaria ventriculi_, which receives blood from the
hinder end of the oesophagus and anterior portion of the stomach.
β and γ. Two other veins which form an _Arcus coronarius_ on the
concave surface of the stomach; the hinder receiving in addition the
small _Venae pancreaticae_ and the _Vena duodenalis_; the trunk so
formed receives the _Vena coronaria ventriculi_ (Hoffmann).
(2) The *intestinal veins*; the veins of that portion of the alimentary
canal between the middle of the duodenum and the anterior end of the
large intestine open into a common vein which joins the hepatic portal
vein.
(3) The *splenic vein* joins either the hepatic portal vein or one of
the intestinal veins.
(4) The *haemorrhoidal veins* are three in number; the anterior opens
into the splenic vein, the remaining two into the portal veins through
the agency of the intestinal veins.]
*4.* *The Veins of the Hinder Extremity.*
The hinder extremity has two venous trunks, the sciatic vein and the
femoral vein.
*a.* The *femoral vein* (_Vena femoralis_), (Fig. 165 _f_) is the
larger venous trunk of the hinder extremity. It arises in the popliteal
space as a direct continuation of the posterior tibial vein, courses
upwards in company with the sciatic artery and nerve, then leaves
these to wind forwards and outwards, and appears between the origins
of the _M. vastus externus_ and of the _M. rectus anterior_. The vein
here gives off the _Ramus communicans iliacus_ to the sciatic vein,
and turns forwards and downwards around the _M. glutaeus maximus_ to
reach the floor of the pelvis, near the femoral artery. The vein then
bifurcates to form the pelvic and iliac veins.
[Illustration: Fig. 165.
Veins of the hinder extremity, half schematic.
_c.i._ Vena communicans iliaca.
_f_ Femoral vein.
_i_ Sciatic vein.
_i_′ Vena cutanea cruris medialis.
_r.a._ M. rectus anterior.
_s.m._ M. semimembranosus.
_v.e._ M. vastus externus.
]
(1) The _Ramus communicans iliacus_ (Fig. 165 _c.i._) forms a
communication with the sciatic at the base of the thigh.
(2) The posterior tibial vein (_Vena tibialis postica_), of which the
femoral is a continuation, arises on the dorsal surface of the toes and
foot. It runs superficially on the _M. extensor longus digiti primi_
over the ankle-joint, courses upwards and winds round the outer surface
of the tibio-fibula to the flexor surface. It receives, in its course,
muscular branches, and at the knee a large cutaneous branch.
*b.* The *sciatic vein*: this vein has already been described (see
p. 247), but the vein from which it arises requires description.
The *anterior tibial* vein (_Vena tibialis antica_) arises on the
dorsum of the foot by twigs from the toes; it courses under the _M.
extensor longus digiti primi_, then upwards on the anterior surface
of the leg, and enters the canal in the tibio-fibula to appear on its
hinder surface. The vein then receives twigs from the _M. peroneus_,
the _M. tibialis posticus_, the _M. gastrocnemius_, and a large
cutaneous branch.
α. The _Vena cutanea cruris medialis_ (Fig. 165 _i_′) receives branches
from both above and below, and enters the popliteal space to join the
anterior tibial vein.
β. The anastomosis on the dorsum of the foot, from which the anterior
tibial vein arises, receives perforating twigs from the plantar surface.