Zygomatico-auricularis, 749
of ox, 747
Zygomaticus muscle of dog, 318
of horse, 215
of ox, 295
of pig, 311
-----
Footnote 1:
Only the gross structure is discussed here. For the microscopic
structure reference is to be made to histological works.
Footnote 2:
Only a brief general statement of osteogenesis can be made here;
details must be sought in embryological literature.
Footnote 3:
As might be expected from the history of anatomy, a good many of these
terms are more or less interchangeable; furthermore, a given skeletal
feature may differ greatly in various species.
Footnote 4:
The term is employed here, as is usual in descriptive anatomy, to
designate only the bony part of the rib (Os costale); morphologically
it includes the cartilaginous part also.
Footnote 5:
The manubrium sterni of man is equivalent, strictly speaking, to the
cariniform cartilage + the first osseous segment of the horse.
Footnote 6:
The long axis of the skull is considered to be horizontal in these
descriptions.
Footnote 7:
The occipital crest of this description is equivalent to the external
occipital protuberance and superior nuchal line of man. A curved line
a little lower down, which is continued on the paramastoid process,
represents the inferior nuchal line of man.
Footnote 8:
Other terms for these parts are basioccipital (basilar part),
exoccipitals (lateral parts), and supraoccipital (squamous part). It
should be noted, however, that the lines between the basioccipital and
exoccipitals pass through the lower part of the condyles.
Footnote 9:
This foramen might well be called a canal, since it is an inch or more
in length.
Footnote 10:
The cavity so formed may be termed the sphenopalatine sinus. The
sphenoidal sinus may be a separate cavity which communicates only with
the ventral ethmoidal meatuses; this arrangement exists in about a
third of the cases, according to Paulli.
Footnote 11:
This is also called the subsphenoidal canal or pterygoid foramen.
Footnote 12:
On account of its deep situation, and the fact that it cannot be
separated from its surroundings, the ethmoid must be studied by means
of appropriate sagittal and transverse sections of the skull.
Footnote 13:
According to Martin, there are originally four centers, two anterior
and two posterior (smaller) ones, which fuse in a variable manner.
Footnote 14:
This is commonly termed the styloid process. It is not the homologue
of the styloid process of man.
Footnote 15:
This foramen is somewhat variable in position, but is commonly
opposite the corner incisor. Smaller inconstant foramina are often
present.
Footnote 16:
The alveolus for the temporary canine is commonly formed in the
maxilla alone.
Footnote 17:
This bone is really a greatly developed first ethmoturbinal.
Footnote 18:
In the Stuttgart Nomenclator Anatomicus (S. N. A.) the body (Corpus)
is the part which bears the teeth, and is divided into a pars incisiva
and a pars molaris. The ramus is the rest of the bone.
Footnote 19:
These correspond to the great cornua of man.
Footnote 20:
This relation varies with age; in the young horse the third tooth, in
the old subject the fourth, lies below the end of the crest.
Footnote 21:
This bone is probably equivalent to the fourth and fifth carpals of
forms in which five carpal elements are present in the lower row.
Footnote 22:
It is also called the large pastern bone or os suffraginis.
Footnote 23:
This bone is also called the small pastern bone or os coronæ.
Footnote 24:
This bone is also called the os pedis or coffin bone.
Footnote 25:
The upper and lower divisions of the wing are sometimes termed the
basilar and retrossal processes respectively.
Footnote 26:
This is termed the lacrimal sinus by some authors. It is similar in
location and in the position of its orifice to the turbinal part of
the frontal sinus of the horse, with the important difference that it
does not communicate with the frontal sinuses in the ox.
Footnote 27:
This third bone was termed the phacoid in the cat by Strauss-Durckeim,
and is regarded by some authors as the vestige of an additional digit,
the prepollex.
Footnote 28:
It is doubtful whether the synovia is a true secretion or a transudate
containing products of friction. The view given above is that which is
more commonly accepted.
Footnote 29:
This classification makes no claims to scientific accuracy, but is
simply a statement of the terms in general use. A grouping based on
mechanical principles seems desirable, but appears to be almost
impossible on account of the great variety and irregularity of form of
the articular surfaces.
Footnote 30:
The movements in some of these joints are more extensive and varied
than in some diarthroses. To illustrate this we may compare the
movements of the cervical or coccygeal vertebræ with those possible in
the carpo-metacarpal or the sacro-iliac joints.
Footnote 31:
In dissecting-room subjects these bursæ and the adjacent structures
are commonly the seat of pathological changes. They appear to be the
starting-point of “poll evil” and “fistulous withers.”
Footnote 32:
No natural line of demarcation exists between the ligamentum nuchæ and
the lumbo-dorsal continuation of the supraspinous ligament, since the
change from the purely elastic to the white fibrous structure is
gradual.
Footnote 33:
The term is a very unfortunate one, since it is a distinct
misapplication of the name as it is used in regard to man. It is,
however, very firmly established, and appears likely to persist
indefinitely in the absence of a convenient popular equivalent.
Footnote 34:
This is often called the Y-shaped ligament—a rather
undesirable name, since it is not bifurcate.
Footnote 35:
It is also called the V-shaped ligament.
Footnote 36:
This should be noted in regard to resection of the lateral cartilage
or other operations in this vicinity.
Footnote 37:
These are termed the postero-lateral ligaments by M’Fadyean. They may
well be called, as by German authors, the suspensory ligaments of the
navicular bone.
Footnote 38:
In this figure the patella is pushed up above the trochlea—a position
which it does not occupy normally.
Footnote 39:
This section consists necessarily only of a brief statement of the
most important differences in the joints of the other animals.
Footnote 40:
These movements are best seen in man, in whom the back of the hand may
be turned forward (pronation) or backward (supination).
Footnote 41:
The student will note in dissection that transition forms occur; also
that the same sheath may belong to two or more tendons in common, _e.
g._, the sheath of the two flexors on the back of the carpus. In such
cases the synovial membrane is reflected from one tendon to the other,
and may form a secondary mesotendon.
Footnote 42:
This muscle is probably the homologue of the sternal portion of the
sterno-cleido-mastoid of man. On account of the differences in its
insertion in the various animals, it seems desirable to adopt the name
sterno-cephalicus.
Footnote 43:
The upper part of this maybe separated from the scalenus proper, and
is then termed the cervicalis ascendens or ilio-costalis cervicis—a
continuation in the neck of the transversalis costarum.
Footnote 44:
This seems due to pressure produced by pathological changes in the
supra-atloid bursa, which are frequently extensive in dissecting-room
subjects.
Footnote 45:
The lumbar part of this muscle is subject to variation. It may, in
quite exceptional cases, extend as far as the ilium.
Footnote 46:
The muscle as here described includes the spinalis and semispinalis
components, as the separation of these is largely artificial in the
horse.
Footnote 47:
The function of the intercostal muscles is still a subject of much
discussion. The statements made above seem to represent the view most
commonly held in regard to their action.
Footnote 48:
It should be noted, however, that in the embryo the diaphragm appears
as a paired structure, extending from the lateral walls of the cœlom
to fuse with the septum transversum.
Footnote 49:
In order to get a clear idea of the relative positions of these
foramina and of the form of the diaphragm, the thoracic surface of the
latter should be examined while the abdominal viscera remain _in
situ_.
Footnote 50:
It is narrow and slit-like in the natural condition, but may appear
oval in the dissecting-room, especially if the hind limb is drawn back
and abducted.
Footnote 51:
It must be admitted that the term “ring” is rather misleading as
applied to the abdominal opening of the canal, since normally it is a
mere dilatable slit. The ring-like constriction which exists here in
the male is constituted by the peritoneum, which descends into the
canal to form the tunica vaginalis. This peritoneal ring is termed the
=vaginal ring= (Annulus vaginalis), and must not be confused with the
subperitoneal ring, _i. e._, the internal inguinal ring.
Footnote 52:
As might be expected, the cremaster usually undergoes more or less
atrophy, and is paler in the castrated subject. In the mare the muscle
is small, and ends in the connective tissue in the lower part of the
inguinal canal.
Footnote 53:
The term canal is somewhat misleading; it is rather a slit-like
passage or space between the two oblique muscles, since the inguinal
ligament is that part of the aponeurosis of the external oblique
muscle which stretches between the external angle of the ilium and the
prepubic tendon.
Footnote 54:
The obliquity of the tendon and the angle which it forms with the
pelvic floor are of clinical importance in regard to manipulation of
the fœtus in obstetrical cases. The slope varies in different
subjects. In some cases the tendon forms about a right angle with the
pubic bones.
Footnote 55:
The terms dorsal and ventral are here used in the topographic and not
in the morphological sense. All the muscles of the group are ventral
in the latter sense.
Footnote 56:
This is regarded as a vestige of the clavicle. On this basis the
portion of the muscle from the vestige to the arm represents the
clavicular part of the deltoid of man.
Footnote 57:
Günther states that this muscle assists in extension or flexion
according to the position of the head of the humerus relative to the
glenoid cavity.
Footnote 58:
M’Fadyean and Vaughan term this muscle the scapulo-ulnaris, while
Arloing and Lesbre term it “Ancone accessoire du grand dorsal.” The
above name seems to agree best with the chief insertion and action,
although it certainly arises largely from the tendon of insertion of
the latissimus dorsi.
Footnote 59:
This is considered to represent the part of the common extensor for
the fourth and fifth digits.
Footnote 60:
Martin considers that this muscle represents the extensor indicis
proprius and the part of the common extensor for the second digit.
Footnote 61:
In man the muscle is an extensor of the hand.
Footnote 62:
On account of the intimate union between the psoas major and iliacus
they are frequently considered a single muscle, to which the name
ilio-psoas is applied; some anatomists include the psoas minor also
under this term.
Footnote 63:
By some anatomists the portion inserted into the crest is termed the
gluteus accessorius, but Lesbre considers this the deep gluteus,
homologous with the gluteus minimus of man. The portion inserted into
the trochanteric ridge apparently represents the piriformis of man.
Footnote 64:
Apparently the muscle represents the biceps, together with part of the
gluteus superficialis of man. Hence the names gluteo-biceps and
paramero-biceps have been suggested.
Footnote 65:
This muscle was incorrectly designated the adductor magnus by
Percivall and Strangeways. Its name, however, is not at all
descriptive of its structure in the domesticated animals.
Footnote 66:
It has been customary to describe two adductors—a parvus or brevis,
and a longus or magnus. This division is largely artificial, and has
been abandoned in the new nomenclature—a return to the views of
Bourgelat and Girard.
Footnote 67:
This has been termed by various authors the adductor parvus or brevis.
Footnote 68:
Termed by various authors the adductor magnus or longus.
Footnote 69:
The iliac head is described by some authors as a separate muscle, and
termed the pyriformis. This does not seem desirable, especially since
it is at least probable that the homologue of the pyriformis of man is
that portion of the middle gluteus which is inserted into the back of
the trochanteric ridge.
Footnote 70:
The name is based on the arrangement in man, in whom the muscle
consists of two fasciculi forming a groove between them for the tendon
of the obturator internus. In the horse it is undivided, and is
grooved for the obturator tendon, so that at first sight it appears to
be double. The gemellus may be regarded as the extrapelvic head of the
obturator internus (Gegenbaur).
Footnote 71:
While it is true that the separation of the intermedius is probably
never entirely a natural one in the horse, it varies in individual
cases, and is usually clear on cross-sections. In some subjects it is
possible to separate another slip which may represent the articularis
genu of man.
Footnote 72:
It seems inadvisable to retain the old nomenclature, since it is
inapplicable to other domesticated animals in which the muscle is well
developed (_e. g._, ox, pig).
Footnote 73:
The soleus may, therefore, be included with the two heads of the
gastrocnemius under the name triceps suræ.
Footnote 74:
The origins of these heads are given in the order in which they may be
most conveniently dissected, not in order of size and importance.
Footnote 75:
This is probably the homologue of the subclavius of man.
Footnote 76:
Movements of individual digits are specified with regard to the axis
of the manus (hand, paw), and not to the median plane of the body.
Footnote 77:
The term “mouth” is commonly used to signify either the oral cavity
(Cavum oris) or the entrance to it (Rima oris).
Footnote 78:
The epiglottis may be either in front of or behind the soft palate;
most often it is prevelar.
Footnote 79:
In the undisturbed state of the parts there is no space between the
tongue and the rami of the lower jaw; consequently the tongue must be
drawn aside to see the sublingual crest.
Footnote 80:
It will be noted that this definition of crown and root does not agree
exactly with the popular view that the crown is the free portion and
the root the embedded portion. The objection to the latter statement
lies in the fact that it is not capable of general application. Thus
the morphological crown of the permanent molars in the horse is
extremely long, and is, for the most part, embedded in the bone in the
young animal. The root proper begins to form at four or five years of
age, and continues its growth for about eight years. As the exposed
part of the crown wears down, the embedded part pushes out of the
alveolus, thus preventing deficiency of length. On the old basis we
should have to say that successive portions of the root become crown,
while in point of fact it is only in very extreme age that the true
root comes into wear.
Footnote 81:
Ellenberger found, as the result of extensive observations (8000
subjects), that about 2 to 3 per cent. of mares have erupted canines
in both jaws; that 6 to 7 per cent. have them in the upper jaw; while
20 to 30 per cent. have them in the lower jaw.
Footnote 82:
It is interesting to notice that vestigial canines are not at all
uncommon in mares, especially in the lower jaw. They are very small,
and do not usually erupt; their presence is indicated in the latter
case by a prominence of the gum. This is in conformity with the fact
that they were present in both sexes in Eocene and Miocene ancestors
of existing equidæ.
Footnote 83:
It is common in veterinary works to call all the cheek teeth molars,
since, in the horse particularly, the premolars are molariform, _i.
e._, do not differ materially from the true molars in size or form.
The term cheek teeth conveniently includes the premolars and molars.
Footnote 84:
The student is advised to amplify these very general statements by the
examination of heads of subjects of varying ages. It may also be noted
that the position of the septum between the two divisions of the sinus
varies much.
Footnote 85:
Careful observations (especially on frozen subjects and those in which
the organs have been hardened _in situ_) show that there is no
abdominal part of the œsophagus in the strict sense of the term. The
stomach here lies directly on the diaphragm, so that the last inch or
so of the œsophagus is placed obliquely in the hiatus œsophageus, and
is partly covered by the pleura, but not by peritoneum. In soft
subjects the weight of the stomach, or traction on it, draws part of
the œsophagus into the abdomen, inclosed in a collar of peritoneum.
Footnote 86:
The potential lumen is difficult to determine at all accurately. When
distended, its diameter (according to Rubeli) varies from 5.7 cm. at
its origin to 4 cm. at its cardiac end. The thickness of the wall
varies (inversely as the lumen) from 4 mm. to 1.2 cm. or more.
Footnote 87:
At the origin of the tube muscular bundles arise on the raphé
pharyngis and blend with the crico-pharyngeus. Ventrally fibers come
from the depression between the cricoid and arytenoid cartilages.
Bundles of striped fibers may be continued in the superficial part of
the muscular coat as far as the cardia.
Footnote 88:
This method of division, although long in use, is of very little value
for accurate description. It is mentioned here chiefly because
agreement on a more useful topographic method has not been arrived at.
Footnote 89:
Only a general account of the arrangement of the peritoneum is given
in this section, since a detailed description cannot be understood
without a knowledge of the viscera concerned.
Footnote 90:
This is the position in the expiratory phase as usually seen in the
dead subject. In inspiration the saccus cæcus lies under the upper
parts of the sixteenth and seventeenth ribs.
Footnote 91:
This occlusion is usually so complete that distention of the stomach
by air or fluid forced in through the pylorus may be carried far
enough to rupture the stomach without ligating the œsophagus.
Footnote 92:
No natural line of demarcation exists, but there is a marked increase
of the thickness of the wall toward the terminal part. Other
differences will be noted in the further description.
Footnote 93:
It will be noticed that the mesoduodenum is not continuous with the
great mesentery, but ends by a free edge. The mesentery begins on the
opposite surface of the end of the duodenum, so that the bowel is
attached by two peritoneal folds at this point.
Footnote 94:
Abnormal displacement, _e. g._, torsion of the left parts, is not
rare, and is liable to produce death if not promptly reduced.
Footnote 95:
There is no natural line of demarcation between the small colon and
rectum: the plane of the pelvic inlet is selected for convenience of
description.
Footnote 96:
The anterior part of the rectum is very variable in position and
relations. It is not often median, but may be deflected either to
right or left. Most often it is pushed to the left by the pelvic
flexure of the colon. In other cases—especially when empty—it may lie
against the right wall, and the space to the left is occupied by the
small colon. The amount covered by peritoneum dorsally and laterally
is very variable, and appears to be in inverse proportion to the
fullness of the bowel.
Footnote 97:
A descriptive method based on that in use in human anatomy cannot be
applied with clearness to the organ in the horse.
Footnote 98:
These impressions are not evident on the soft organ. In hardened
material they are clearly mapped out, although of course variable in
size, in conformity with the degree of fullness of the various hollow
viscera. The cæcal impression may not be evident if, as often happens
in old horses, the right lobe of the liver is much atrophied.
Footnote 99:
Flower and Ruge describe the mammalian liver as being primarily
divided by the umbilical fissure into two parts, the right and left
lobes. Secondary fissures on either side may subdivide each of these
primary lobes. On this basis we may recognize in the liver of the
horse right lateral, right central, left central, and left lateral
lobes. In the young foal these four lobes are distinctly recognizable.
The two central lobes would correspond to the middle lobe of the
foregoing description, and the right central lobe would be the
equivalent of the quadrate lobe of man.
Footnote 100:
In the young foal the interlobular tissue is more abundant and the
lobulation correspondingly distinct.
Footnote 101:
The hepatic veins may be recognized on section from the fact that they
remain open, being connected closely with the parenchyma.
Footnote 102:
The ductless glands are organs which elaborate substances which pass
directly into the veins or lymphatics, instead of being conveyed away
by ducts. This process is termed internal secretion. The ductless
glands include the lymph glands, which are described with the organs
of circulation; the thyroid and thymus bodies, described usually with
the respiratory organs; the adrenal or suprarenal bodies, described
with the urinary organs; the pineal and pituitary bodies, described
with the brain; and the spleen, described with the digestive system as
a matter of convenience. The spleen is not, strictly speaking, a gland
at all: it is not epithelial in origin or structure, but is
mesenchymatous.
Footnote 103:
The student is strongly recommended to study the peritoneum of a foal
or other small subject when the opportunity occurs, as in these the
viscera are easily handled, and the course of the peritoneum can be
followed without difficulty.
Footnote 104:
The passage is subject to a good deal of variation in caliber and is
sometimes completely occluded.
Footnote 105:
In dissecting-room subjects (which are usually aged) the omentum often
exhibits pathological changes, such as adhesions, rents, tumors,
formation of twisted strands, etc.
Footnote 106:
The student will note here the difference between the structure and
behavior of the brachydont (short-crowned) incisors of the ox and the
hypsodont (long-crowned) type of the horse.
Footnote 107:
In popular language these are conveniently regarded as so many
stomachs, and termed accordingly “first,” “second,” etc. Other names
are in common use, _e. g._, paunch, honeycomb, manifold or manyplies,
and rennet or true stomach.
Footnote 108:
It has been customary to term the sacs left and right respectively,
but these do not represent the relations as they exist _in situ_ and
as they are presented on frozen sections.
Footnote 109:
It is important to notice that the reticulum is separated from the
pericardium by an interval of about 1 to 1½ inches (ca. 2 to 4 cm.)
only, since foreign bodies which are often swallowed by cattle lodge
in the reticulum, and not rarely (if sharp) perforate the reticulum
and diaphragm.
Footnote 110:
The epiglottis in the pig seems to be constantly retrovelar. The pig
frequently breathes through the mouth, and this is no doubt possible
only when the soft palate is raised; it seems probable that it is also
shortened.
Footnote 111:
The canines of the pig are “permanent pulp” teeth and therefore
capable of continued growth, and are without roots in the strict
sense.
Footnote 112:
It is usually stated that the cardiac end is funnel-shaped, but it is
not so in formalin-hardened cadavers nor in frozen sections. The
hiatus œsophagus is a long slit in the right crus of the diaphragm,
and the terminal part of the œsophagus, which lies in it, is flattened
transversely.
Footnote 113:
It will be noted that the fundus gland region does not extend up to
the lesser curvature; here the cardiac mucosa joins the pyloric.
Footnote 114:
The description here given is based mainly on the appearance of the
organ as hardened _in situ_, which differs radically from that of the
soft organ, as is seen on comparison of the annexed figure (Fig. 321).
Footnote 115:
In the bulldog, which is very prognathic (“undershot”), the lower
canines are opposite to or slightly in front of the plane of the upper
incisors, and the upper canines are about opposite to the first lower
cheek teeth. In the epignathic (“overshot”) dachshund the lower
canines are under or slightly behind the upper ones.
Footnote 116:
Increase in number also occurs, the supernumerary teeth being at
either end of the series.
Footnote 117:
The valve does not seem to be efficient, since experience shows that
rectal injections can be made to pass beyond it. This may be partly
due also to the fact that the terminal part of the ileum runs
horizontally forward, and the ileo-cæcal orifice faces into the
beginning of the colon.
Footnote 118:
Ellenberger and Baum state that the cæcum may reach a length of 20 cm.
in very large dogs.
Footnote 119:
When the stomach is very full, it pushes the left portion of the colon
over to the right, producing an acute angle in place of a transverse
branch. The terminal part of the colon is thus oblique in direction.
Footnote 120:
An external nose (Nasus externus), such as exists in man, forming a
projection distinctly marked off from the rest of the face, does not
exist in the domesticated animals.
Footnote 121:
The septal cartilage is to be regarded as an unossified part of the
mesethmoid. It will be noted that the line of demarcation between the
bone and the cartilage is irregular and varies with age; extensive
ossification for calcification) of the cartilage is commonly found in
old animals. The process often results in the formation of calcareous
islands in the cartilage.
Footnote 122:
In the ordinary position of the head and neck, and while the parts are
at rest, about half of the larynx lies between the branches of the
mandible; when the head and neck are extended, proportionately more of
the larynx lies behind a plane through the posterior borders of the
rami. It is here described in the position it occupies when the head
and neck are extended.
Footnote 123:
The term glottis is commonly used to designate the interval between
the vocal bands and arytenoid cartilages or the structures that
inclose that space.
Footnote 124:
In so-called œdema glottidis this loose submucous tissue becomes
infiltrated with fluid, in some cases causing occlusion of the
vestibule.
Footnote 125:
The arrangement of the muscles should be noted, since the space
inclosed by the divergence of the sterno-cephalici and the convergence
of the omo-hyoidei is the area of election for the operation of
tracheotomy.
Footnote 126:
The student should bear in mind that these terms are employed simply
as a matter of convenience in description; all the parts, though
differently named, form a continuous whole.
Footnote 127:
The apertures do not exist in the fœtus, and are sometimes absent in
the adult subject. Some of them may be produced in dissection by the
necessary disturbance of the parts. Clinicians state that a serous
exudate formed in one pleural sac usually passes through to the other
side in the horse.
Footnote 128:
A correct idea of the natural form and size of the lung cannot be
obtained from a specimen in this state. The lungs should be hardened
_in situ_ for this purpose.
Footnote 129:
Some authors consider each lung to be divided into anterior and
posterior lobes by the cardiac notch, so that the right lung would
have three lobes and the left lung two lobes.
Footnote 130:
In fœtal lung the lobulation is much more distinct. Pigmentation of
the lung is sometimes seen in horses, and in such cases the pigment is
deposited mainly in the interlobular tissue, thus mapping out the
lobules.
Footnote 131:
It must not be inferred from the necessarily brief account here given
that the two sets of vessels are quite distinct. On the contrary,
competent observers state that numerous small branches of the
bronchial arteries anastomose with pulmonary vessels. Part of the
blood conveyed to the lungs by the bronchial arteries is returned by
the pulmonary veins. In the horse bronchial veins are absent or
inconstant.
Footnote 132:
The cervical part of the gland is very variable. The thoracic lobe of
one side may have no cervical continuation; the other lobe may then
give off a single prolongation which bifurcates. The thoracic part in
the new-born foal occupies most of the space which is later taken up
by the apices of the lungs. Its two lobes are in contact, and its deep
surface is molded on the anterior part of the pericardium and the
large vessels.
Footnote 133:
It is therefore often termed the precardiac lobe.
Footnote 134:
The arrangement here is one of the most striking features of the pig’s
larynx. The short, thick middle hyo-epiglottic ligament and the
anterior part of the thyro-hyoid membrane are inelastic, while the
posterior part of the membrane is thin and elastic and allows the
epiglottis to be separated by a considerable interval from the thyroid
cartilage. Moreover, the borders of the epiglottis are connected with
the thyroid cornua of the hyoid bone by lateral hyo-epiglottic
ligaments.
Footnote 135:
The kidneys are soft, plastic organs, and hence an accurate knowledge
of their form can be gained only from a study of specimens which have
been hardened _in situ_. The description here given is based on this
method. For this purpose subjects should be hardened in the standing
position to avoid artefacts.
Footnote 136:
The most instructive sections are those made in the horizontal and
transverse planes, through the pelvis in each case.
Footnote 137:
The fœtal kidney is divided by furrows into a number of polygonal
areas, each of which is the base of a pyramidal lobe or renculus.
These furrows usually disappear before or soon after birth in the
foal, although traces of them are sometimes seen in the adult.
Footnote 138:
In the kidney of the horse the renal columns dip in between the
pyramids very superficially as compared with the arrangement in the
human kidney. Breuer states that the pyramids are 40 to 64 in number,
and are arranged in four rows. Only the middle ones are distinct.
Footnote 139:
The crest is the result of fusion of the papillæ or apices of the
pyramids in the embryo.
Footnote 140:
This is commonly termed the fundus by veterinarians, but is not the
homologue of the fundus of the human bladder.
Footnote 141:
This would correspond to the fundus vesicæ of man.
Footnote 142:
From the standpoint of comparative anatomy the term “adrenal” seems
decidedly preferable to “suprarenal.”
Footnote 143:
This is a remnant of the gubernaculum testis of the fœtus.
Footnote 144:
The tunica vaginalis is not a part of the scrotum in the strict or
narrow sense of that term, but is included here on practical grounds.
Footnote 145:
Sometimes one vesicula or both are very large in the gelding. The
writer has seen four cases in the dissecting room, three of which were
bilateral, the other unilateral. The vesicula resembled the urinary
bladder in appearance and contained about a quart of thick,
amber-colored secretion.
Footnote 146:
It has been customary to divide the pelvic part of the urethra into
prostatic and membranous parts. These terms apply well in human
anatomy, but have no special value in comparative anatomy. In the
horse a prostatic part hardly exists, unless we assume that it and the
neck of the bladder together are only about an inch in length. There
is no membranous part in the sense in which that term is used in
regard to man.
Footnote 147:
The statement often made that it acts as a sphincter of the bladder is
a hypothesis of doubtful plausibility. In material hardened _in situ_,
in which the internal urethral orifice is tightly closed, the urethral
muscle apparently takes no part in the closure.
Footnote 148:
This is clinically important, since enlargement of the prostate may
interfere with micturition.
Footnote 149:
These terms apply properly only when the adjacent viscera are removed
and the ovaries are actually “suspended” by the broad ligaments. When
the ovary is in its natural position, the surfaces are dorsal and
ventral, the former corresponding to the “external” surface if the
free border is directed outward, to the “internal” if the free edge is
medial.
Footnote 150:
The Fallopian tubes may be regarded, both in structure and morphology,
as prolongations of the uterus (McMurrich).
Footnote 151:
The arrangement is the only exception to the general rule that the
serous cavities are closed. In this case the mucous membrane of the
fimbriated extremity is continuous with the adjacent peritoneum, a
persistence of the embryonic relations of the Müllerian duct.
Footnote 152:
In formalin-hardened subjects there is frequently a pronounced
ring-like constriction at the beginning of the vulva.
Footnote 153:
The term vulva is used here in the sense in which it is understood
generally by English and French veterinarians. In the German works it
is applied only to the labia and other structures around the external
orifice of the urogenital sinus, while the sinus itself is termed the
vestibule of the vagina (Vestibulum vaginæ).
Footnote 154:
Lesbre states that the cornua may attain a length of 45 to 50 cm.
Footnote 155:
The pericardium is described before the heart since it must be
examined first in the laboratory.
Footnote 156:
This is termed the tubercle of Lower in human anatomy and the
tuberculum intervenosum by German veterinary anatomists.
Footnote 157:
These vessels will be described later in their systematic order.
Footnote 158:
The relation to the guttural pouch is not constant. In some
cases—especially when the head and neck are extended—the artery lies
behind the pouch. The backward extension of the latter is variable.
Footnote 159:
By some authors the term facial is applied to the artery only after it
turns around the lower border of the jaw.
Footnote 160:
The artery is conveniently placed at its inflection for taking the
pulse, since it is superficial and lies directly on the bone.
Footnote 161:
This vessel appears to represent both the supraorbital and frontal of
man.
Footnote 162:
The term axillary is often applied to the artery from the first rib to
the point of origin of the subscapular branch.
Footnote 163:
The pulse can be taken where the artery lies on the lateral ligament,
since the pectoral muscle is thin here.
Footnote 164:
This vessel is also termed the A. metacarpea volaris superficialis or
the palmar metacarpal artery.
Footnote 165:
In the great majority of subjects this vessel and some of its branches
are the seat of more or less extensive verminous aneurysm, produced by
the Sclerostomum armatum. In the author’s experience an entirely
normal specimen is quite exceptional in adult horses.
Footnote 166:
The left branch is a descriptive convention rather than a reality,
since the arteries of the small intestines spring from the mesenteric
trunk either directly or by short common stems with an adjacent
vessel.
Footnote 167:
The obliteration in the adult extends a variable distance from the
vesical end toward the origin, but usually involves only a small part.
Footnote 168:
Most of the veins are depicted in the illustrations of the section on
the arteries, to which reference is to be made.
Footnote 169:
Chauveau says “the bronchial veins, which ramify on the bronchi like
the arteries of which they are satellites, open into the great
coronary vein very near its mouth, after having united to form a
single vessel, which sometimes opens directly into the atrium.”
Ellenberger and Baum state that the bronchial and œsophageal veins
open into the vena azygos separately or by a common trunk. Martin
describes a short broncho-œsophageal trunk, but the vein which he
figures as the bronchial does not come from the lungs, but is a small
mediastinal vessel. The author finds such a vessel entering the
terminal part of the œsophageal vein, but no distinct bronchial vein
in the horse.
Footnote 170:
M’Fadyean records a case in which the vein lay on the deep face of the
omo-hyoideus with the carotid artery.
Footnote 171:
The venous angle formed by this junction indicates the position of the
thyroid gland.
Footnote 172:
These are termed by Chauveau and M’Fadyean the subsphenoidal
confluents.
Footnote 173:
The place and mode of termination is quite variable. It may disappear
from the surface of the thigh at any point above the distal third. In
some cases it passes through the anterior part of the gracilis instead
of dipping in between that muscle and the sartorius.
Footnote 174:
This often joins the posterior femoral or the popliteal vein.
Footnote 175:
The term chyle is often applied to the lymph carried by the efferent
vessels of the intestine when it contains products of digestion, and
these vessels may be designated as lacteals or chyle vessels.
Footnote 176:
The lymph vessels of these organs appear to vary considerably in their
mode of termination, and the arrangement needs further study. Some
ducts from the stomach, liver, and spleen open directly into the
cistern.
Footnote 177:
Abscess here can be reached readily by an incision between the vein
and the omo-hyoideus.
Footnote 178:
It is, of course, only the pericardium which comes in contact with the
wall, but it is customary as a matter of convenience to speak of the
relation of the heart as though it were direct.
Footnote 179:
Only the most important differential features of the arrangement of
the vessels as compared with those of the horse will be considered.
Footnote 180:
The homologies of the vessels of the lower parts of the limbs are
still uncertain. The account given here is mainly based on the views
of Sussdorf and Baum.
Footnote 181:
It is difficult to make the arrangement of these vessels clear in a
brief textual description, but a reference to the schematic figure
will explain the main facts.
Footnote 182:
Most of the differences in the veins of the ox are correlated with
those of the arteries of which they are satellites and will not be
described. The account here given consists chiefly of those
differential features which could not be deduced from a knowledge of
the arteries.
Footnote 183:
The upper series is continuous with the posterior mediastinal
(œsophageal) glands and the lower or tracheal glands with the
bronchial. Hence we might well designate the mediastinal glands as
œsophageal (anterior and posterior) and tracheo-bronchial.
Footnote 184:
When enlarged, as is often the case in tuberculosis, this gland
frequently causes difficulty in swallowing and in rumination and
produces chronic or recurrent bloating.
Footnote 185:
The relative weight is subject to wide variation. It is large in
hunting dogs and such as are trained for speed or worked.
Footnote 186:
Limitations of space and the purpose of this work preclude
consideration of the finer structure of the nervous system, for which
ample literature is available.
Footnote 187:
The description given here is intended to present the chief facts in
regard to the brain as they may be studied in the dissecting room. The
vessels and membranes which must be examined first have been
described.
Footnote 188:
Unless care is used in removing the brain the infundibulum is likely
to be torn and the pituitary body left in the cranium. In this case
there is a small opening which communicates with the third ventricle.
Footnote 189:
The fossa corresponds in position to the locus perforatus anticus of
the human brain, but is not pierced by numerous openings for vessels
in the horse.
Footnote 190:
The decussation varies superficially in different specimens. In some
there is a distinct superficial crossing of fibers so that the median
fissure is practically effaced at this point.
Footnote 191:
In the new nomenclature the term lamina quadrigemina is applied to the
dorsal mass of the mid-brain, and the four eminences which it bears
are the corpora quadrigemina.
Footnote 192:
In man a distinct superior brachium connects the superior pair with
the lateral geniculate body, but in the domesticated animals the union
with the optic thalamus is too direct to allow of any definite arm
being recognized.
Footnote 193:
On a strictly embryological basis the optic part of the hypothalamus,
comprising the anterior part of the third ventricle and the structures
associated with it, belong to the telencephalon, but will be
considered here as a matter of convenience.
Footnote 194:
This backward projection of the thalamus is equivalent to the pulvinar
and lateral geniculate body of man, which are not superficially
divided in the domestic animals.
Footnote 195:
In order to study the configuration of the hemisphere it should be
separated from its fellow by median section and from the brain stem by
cutting across the mid-brain. Material for this purpose should be
hardened _in situ_.
Footnote 196:
Termed by Lesbre the parietal fissure and by M’Fadyean the great
oblique fissure.
Footnote 197:
Just above this point is a lobe which is homologous with the insula of
man. When the overhanging gyri which partly conceal it—forming the
operculum—are removed, there are disclosed several short, deeply
placed gyri (Gyri breves).
Footnote 198:
By some authors this is regarded as the homologue of the cruciate
fissure of the dog, but it seems likely that the latter is represented
by a short and inconstant sulcus situated further forward.
Footnote 199:
From the morphological point of view other structures should be
included, but in descriptive anatomy it is usual to limit the
application of the term to the parts enumerated above.
Footnote 200:
It is generally believed that these constitute an olfactory path.
Footnote 201:
It is hardly possible to get an accurate idea of the shape of the
ventricle except by studying a cast of it. The size of the ventricles
varies in different subjects, and it is not rare to find more or less
disparity between the two ventricles of the same brain.
Footnote 202:
The term arose from the striated appearance of the mass in sections
cut in certain planes, the gray matter being cut up into strands by
tracts of white fibers.
Footnote 203:
Although this nerve springs directly from the ganglion, it contains
motor as well as sensory fibers.
Footnote 204:
This ganglion appears to be equivalent to the jugular or superior and
petrous ganglia of man.
Footnote 205:
In some cases the left vagus passes back below the junction of the
jugular veins and the termination of the left brachial vein. It then
runs backward and somewhat dorsally across the left face of the
anterior vena cava to reach its usual position.
Footnote 206:
The nerve lies here about a finger’s breadth above the thyroid gland.
If, however, the gland is enlarged it may come in contact with the
nerve. The same is true in regard to the relation to the anterior
cervical lymph glands.
Footnote 207:
In order to examine the plexus and the origins of its chief branches
conveniently and with as little disturbance of relation as possible,
the subject should be suspended in imitation of the natural position
and the fore limb abducted as much as is necessary.
Footnote 208:
Morphologically the last-named muscle belongs to the extensor group.
In man and in the dog and many other animals it is an extensor in
function.
Footnote 209:
In veterinary works these are frequently termed plantar nerves, which
is an unfortunate misnomer. The writer inclines to the use of the old
term metacarpal or common digital to designate the nerves as far as
their divisions, and the term digital beyond this.
Footnote 210:
The special statements of this description refer to the system of the
horse. A few important differential features will be mentioned in the
account of the nervous system of the other animals.
Footnote 211:
The right and left plexuses communicate with each other, so that both
lungs receive fibers from both vagi.
Footnote 212:
It has been customary to designate these in veterinary works as the
semilunar or cœliac ganglia, but in the horse they evidently include
the anterior mesenteric ganglia as well.
Footnote 213:
A good preparation of the ganglia in the horse is often difficult to
obtain on account of aneurysm of the artery and the formation of a
quantity of connective tissue about it.
Footnote 214:
Only the most salient differences as compared with the horse will be
mentioned.
Footnote 215:
The origin of the lacrimal nerve is such that Ellenberger-Baum and
Martin describe it as a branch of the maxillary nerve.
Footnote 216:
Lesbre terms this the tracheo-œsophageal branch, and considers that it
must be regarded as an accessory or internal recurrent nerve.
Footnote 217:
This belongs to the upper eyelid, but is described here on account of
its position.
Footnote 218:
According to Piersol the system of spaces and canaliculi in the
substantia propria is completely filled by the cells and their
processes, upon which the nutrition of the cornea largely depends. The
lamina elastica anterior, formerly described as a distinct layer
between the corneal epithelium and the substantia propria, does not
exist as such, but there is a condensation of the superficial part, of
the latter, which Rollett termed the anterior limiting layer; it is
not elastic.
Footnote 219:
In albinos the pigment is absent here, as elsewhere, and the iris is
pinkish in color.
Footnote 220:
For the minute structure of the retina reference must be made to
histological works.
Footnote 221:
Ellenberger and Baum regard this as the homologue of the transversus
and obliquus auriculæ of man.
Footnote 222:
There is, strictly speaking, no osseous part of the tube such as
occurs in man. In the horse the cartilage extends to the tympanic
orifice.
Footnote 223:
For the finer structure reference is to be made to the histological
literature.
Footnote 224:
This muscle has been described in the Myology.
Footnote 225:
To prevent a possible misapprehension, it may be stated that the
epidermis primarily molds the corium, and that the glands and
hair-follicles are invaginations of the epidermis.
Footnote 226:
The hoof may be loosened and removed intact by allowing the foot to
macerate or by boiling it.
Footnote 227:
The term foot is used here in the popular sense, _i. e._, to designate
the hoof and the structures inclosed within it.
Footnote 228:
The wide groove at the heels, however, contains chiefly the matrix of
the periople.
Footnote 229:
The lower punctum lacrimale is frequently absent and the corresponding
duct therefore blind. There is often a duct or its remnant which opens
below the inferior turbinal fold, but is not connected behind with the
functional duct.
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