Produced by Sonya Schermann and the Online Distributed
Proofreading Team at http://www.pgdp.net (This file was
produced from images generously made available by The
Internet Archive)
Transcriber’s Note
When italics were used in the original book, the corresponding text has
been surrounded by _underscores_ Mixed fractions have been displayed
with a hyphen between whole number and fraction for clarity.
Superscripted characters are preceded by ^ and when more than one
character is superscripted, they are surrounded by {}.
Some corrections have been made to the printed text. These are listed in
a second transcriber’s note at the end of the text.
ON
MOLECULAR AND MICROSCOPIC SCIENCE
VOLUME THE SECOND
LONDON: PRINTED BY
SPOTTISWOODE AND CO., NEW-STREET SQUARE
AND PARLIAMENT STREET
_Fig. 118, p. 107._
[Illustration: GALEOLARIA LUTEA.]
[_Frontispiece to Vol. II._
ON
MOLECULAR
AND
MICROSCOPIC SCIENCE
BY MARY SOMERVILLE
AUTHOR OF ‘THE MECHANISM OF THE HEAVENS’ ‘PHYSICAL GEOGRAPHY’
‘CONNECTION OF THE PHYSICAL SCIENCES’ ETC.
_Deus magnus in magnis, maximus in minimis_—St. Augustine
IN TWO VOLUMES—VOL. II.
WITH ILLUSTRATIONS
LONDON
JOHN MURRAY, ALBEMARLE STREET
1869
_The right of translation is reserved_
CONTENTS
OF
THE SECOND VOLUME.
PART III.
ANIMAL ORGANISMS.
SECT. PAGE
I. FUNCTIONS OF THE ANIMAL FRAME 1
II. PROTOZOA 13
III. HYDROZOA ZOOPHYTES 81
IV. ANTHOZOA ZOOPHYTES 119
V. ANNULOSA, OR WORMS 144
VI. ECHINODERMATA 169
VII. THE CRUSTACEA 188
VIII. CIRRIPEDIA 213
IX. BRYOZOA, OR POLYZOA 218
X. TUNICATA, OR ASCIDIANS 222
XI. MOLLUSCA 229
INDEX 253
ILLUSTRATIONS
TO
THE SECOND VOLUME.
FIG. PAGE
118. Galeolaria lutea (_Voght_) _frontispiece_
86. Amœba princeps 14
87. Actinophrys sol 17
88. Acanthometra bulbosa } _to face_ 19
89. Eucyrtidium cranoides } (_Haeckel_)[A] _frontispiece to vol. i._
90. Dictyopodium trilobum } _to face_ 20
91. Podocyrtis Schomburgi 20
92. Aulocantha scolymantha } _to face_ 21
93. Actinomma drymodes } (_Haeckel_) _to face_ 21
94. Haliomma echinaster } _to face_ 21
95. Simple Rhizopods 22
96. Gromia oviformis 26
97. Various forms of Foraminifera 28
98. Simple disk of Orbitolites complanatus 34
99. Animal of Orbitolites complanatus 34
100. Rosalina ornata (_Voght_) _to face_ 41
101. Section of Faujasina 45
102. Interior of the Operculina 46
103. Section of Sponge 59
104. Paramœcium caudatum 69
105. Kerona silurus 69
106. Noctiluca 73
107. Vorticellæ 76
108. Acineta 77
109. Thread-cells and darts 82
110. Hydra fusca 84
111. Syncoryna Sarsii with Medusa-buds 90
112. Thaumantia pilosella 92
113. Otolites of magnified Thaumantias 93
114. Development of Medusa-buds 95
115. Rhizostoma 98
116. Cydippe pileus and Beroë Forskalia 102
117. Praya diphys } _to face_ 103
118. Galeolaria lutea } (_Voght_)[B] _frontispiece_
119. Apolemia contorta } _to face_ 108
120. Physophora hydrostatica } 109
121. The Physalia 112
122. Velella spirans (_Voght_) 115
123. Alcyonian polypes, highly magnified 120
124. Polype of Alcyonidium elegans 120
125. Spicula of Alcyonium digitatum 121
126. Red coral branch 126
127. Red coral greatly magnified 127
128. Tubipora musica 130
129. Actinian polype 131
130. Lobophylla angulosa 135
131. Nervous system of Leech 151
132. Foot of Naïs 152
133. Terebella conchilega 154
134. Pushing poles of Serpula 155
135. Foot of a Polynoë 160
136. Brachionus pala 163
137. Common Rotifer 167
138. Section of shell of Echinus 177
139. Sucker-plate of Sea-Egg 179
140. Section of a sucker-plate 179
141. Spine of Echinus miliaris 181
142. Pluteus of the Echinus 181
143. Larvæ of Echinus in various stages of development 182
144. Skeleton of Synapta 185
145. Wheel-like plates of Chirodota violacea 186
146. Ear of Crab 191
147. Section of a Crab 193
148. Young of Carcinus mœnas in various stages of development 195
149. Lucifer, a stomapod crustacean 200
150. Female Cyclops 205
151. Cypris 207
152. Section of Daphnia pulex 208
153. Balanus culcatus 213
154. Tentacles or feet of the Balanus 214
155. Section of Lepas anatifera 215
156. Development of Balanus balanoïdes 216
157. Lepas 217
158. Cells of Lepraliæ 219
159. Cellularia ciliata and Bugula avicularia 220
160. Magnified group of Perophora 222
161. Highly magnified Perophora 223
162. Ascidia virginea 225
163. Salpa maxima 227
164. Young of Salpa zonaria 227
165. Cardium or Cockle 230
166. Foot of Cockle 231
167. Section of shell of Pinna transversely to the direction of
its prisms 233
168. Membranous basis of the shell of the Pinna 233
169. Section of nacreous lining of the shell of
Avicula margaritacea (pearl oyster) 234
170. Tongue of Helix aspersa 237
171. Palate of Trochus zizyphinus 237
172. Granulated Trochus 238
173. Tongue of Limpet 238
174. Whelk 240
175. The Crowned Eolis 240
176. Tongue-teeth of Eolis coronata 241
177. Hyalæa and Clio 243
178. Clione borealis 243
179. Cuttle Fish 245
180. Arm of Octopus 247
Footnote A:
From Dr. Ernst Haeckel’s ‘Radiolarien.’
Footnote B:
From Voght’s ‘Syphonophores de la Mer de Nice’.
MOLECULAR AND MICROSCOPIC SCIENCE.
PART III.
ANIMAL ORGANISMS.
SECTION I.
FUNCTIONS OF THE ANIMAL FRAME.
ALTHOUGH animal life is only known to us as a manifestation of divine
power not to be explained, yet the various phases of life, growth, and
structure in animals, from the microscopic Monad to Man, are legitimate
subjects of physical inquiry, being totally independent of those high
moral and religious sentiments which are peculiar to Man alone.
The same simple elements chemically combined in definite but different
proportions form the base of animal as well as of vegetable life. But
besides the elementary gases and carbon, many substances, simple and
compound, are found in the animal frame; the phosphate and carbonate of
lime, iron which colours the blood, and common salt which, with the
exception of water, is the only article of food we use in a mineral
state. Animals derive their nourishment, both directly and indirectly,
from vegetables. Their incapacity to change inert into living matter is
one of the most characteristic distinctions between the animal and
vegetable kingdoms.
Protoplasm was shown to be rudimentary formative vegetable matter: so
Sarcode, or rudimentary flesh, forms the whole or part of every animal
structure. It is a semi-fluid substance, consisting of an albuminous
base, mixed with particles of oil in a state of very fine division. It
is tenacious, extensile, contractile, and diaphanous, reflecting light
more than water, but less than oil. It is rendered perfectly transparent
by citric acid, and is dyed brown by iodine. This substance, in a
homogeneous state, constitutes the whole frame of the lowest grade of
animal life; but when gradually differentiated into cell-wall and
cell-contents, it becomes the origin of animal structure from that which
has little more than mere existence to man himself; in fact, cellular
origin and cellular structure prevail throughout every class of animal
life. Unicellular plants and animals live for themselves independently
and alone; but the cells which form part of the higher and compound
individuals of both kingdoms, may be said to have two lives, one
peculiarly their own, and another depending on that of the organized
beings of which they form a part.
Flesh or muscle, which is organized sarcode, consists of two parts,
namely, bundles of muscular fibre imbedded in areolar tissue. Nervous
matter also consists of two parts, differing much in appearance and
structure, the one being cellular, the other fibrous. The vital activity
of the nerves far surpasses that of every other tissue; but there is an
inherent irritability in muscular fibre altogether independent of
nervous action: both the nervous and muscular tissues are subject to
decay and waste.
The blood, which is the ultimate result of the assimilation of the food
and respiration, conveys nourishment to all the tissues during its
circulation; for with every breath, with every effort, muscular or
mental, with every motion, voluntary or involuntary, at every instant of
life, asleep or awake, part of the muscular and nervous substances
becomes dead, separates from the living part, is returned to the
circulation, combines with the oxygen of the blood, and is removed from
the system, the waste being ordinarily in exact proportion to the
exertion, mental and physical. Hence food, assimilated into blood, is
necessary to supply nourishment to the muscles, and to restore strength
to the nervous system, on which all our vital motions depend; for, by
the nerves, volition acts upon living matter. Waste and repair is a law
of nature, but when nature begins to decay, the waste exceeds the
supply.
However, something more than food is necessary, for the oxygen in the
blood would soon be exhausted were it not constantly restored by
inspiration of atmospheric air. The perpetual combination of the oxygen
of the air with the carbon of the blood derived from the food is a real
combustion, and the cause of animal heat; but if the carbonic acid gas
produced by that chemical union were not continually given out by the
respiratory organs, it would become injurious to the animal system. Thus
respiration and the circulation of the blood are mutually dependent; the
activity of the one is exactly proportional to that of the other: both
are increased by exercise and nervous excitement.
External heat is no less essential to animals than to vegetables; the
development of a germ or egg is as dependent on heat as that of a seed.
The amount of heat generated by respiration and that carried off by the
air is a more or less constant quantity; hence, in hot countries, rice
and other vegetable diet is sufficient, but as the cold increases with
the latitude, more and more animal food or hydrocarbon is requisite for
the production of heat.
The waste of the tissues, and the aëration of the vital juices, that is,
the exchange of the respiratory gases, are common to all animals. The
heart, upon whose expansions and contractions the circulation of the
blood depends, is represented in the lower animals by propelling organs
of a variety of forms; and the organs of respiration differ exceedingly,
according to the medium in which the animals live. Water, both fresh and
salt, though a suffocating element to land animals, contains a great
deal of air, not only in the state of gas, but also in solution, the
quantity in solution being directly as the pressure; so that animals
living in the deepest recesses of the ocean breathe as freely as those
that live on land, but with respiratory organs of a very different
structure. In the lowest classes, which have no respiratory organs at
all, the gases are exchanged through their thin delicate skins.
The mechanical forces act within the living being according to the same
laws as they do in the external world: the chemical powers too, which
are the cause of digestion, heat, and respiration, follow the same laws
of definite and quantitative proportion as they do in inert matter; but
neither the mechanical forces, nor the physical powers, could create a
germ; nor could they even awaken its dormant state to living energy,
unless a vital power existed in it, the origin of which is beyond the
reach of man.
Animals are endowed with nerve-force, in addition to mechanical force
and the physical powers which are common to them and vegetables; a force
which constitutes their prime distinction, which is superior to all the
other powers from its immediate connection with mind, and which becomes
more evident, and more evidently under the control of the animal, in
proportion as the animal approaches the higher grades of life, and only
attains its perfect development in the human race.
The bones of man and the higher animals are clothed with a system of
muscles, so attached that the head, eyes, limbs, &c., can be moved in
various directions. In each of these muscles the fibres of two sets of
nerves ramify, namely, the sensory and the motor nerves.
The sensory nerves convey external impressions to the brain, and by them
alone the mind is rendered conscious of external objects. The
impressions made by light and sound upon the eye and the ear, or by
mechanical touch on the body, are conveyed by the sensory nerves to the
brain, where they are perceived, though the impressions take place at a
distance from it. Conversely, the mind or will acts through the brain on
the motor nerves, which by alternately contracting, relaxing, and
directing the muscles, produces muscular motion. Thus the motor nerves
convey the emotions of the mind to the external world, and the sensory
nerves convey the impressions made by the external world to the mind. By
these admirable discoveries, Sir Charles Bell has proved that ‘we are
placed between two worlds, the invisible and the material;’ our nervous
system is the bond of connection. The connection, however, between the
mind and the brain is unknown: it has never been explained, and is
probably inexplicable; yet it is evident that the mind or will, though
immaterial, manifests itself by acting on matter; that is, as a power
which stimulates the nerves, the nerve-force acting on the muscles.
Mental excitement calls forth the most powerful muscular strength, and
an iron will can resist the greatest nervous excitement. The nervous and
muscular forces are perpetually called into action, because, for
distinct perception, the muscles require to be adjusted. Mind is passive
as well as active: we may see an object without perceiving it, and we
may hear a sound without attending to it. We must look in order to see,
listen in order to hear, and handle in order to feel; that is, we must
adjust the muscular apparatus of all our senses, of our eyes, ears, &c.,
if we would have a distinct perception of external exciting objects: and
that is accomplished by the power of mind acting upon matter.
Dr. Carpenter has shown that it is by a series of forces acting upon
matter that man conveys his ideas to man, the sonorous undulations of
the atmosphere being the medium between the two. On one side the will,
or power of mind, acts upon the nerves, nerve-force acts upon the
muscles of speech, and these muscles, while in the act of speaking,
produce sonorous undulations in the atmosphere. On the other side, these
undulations are communicated by the mechanism of the ear to the auditory
nerves, exciting nerve-force, and nerve-force acts upon the mind of the
hearer. ‘Thus the consciousness of the speaker acts upon the
consciousness of the hearer by a well-connected series of powers.’
Nerve-force generates, directly or indirectly, light, heat, chemical
power, and electricity. When the optic nerve is pressed in the dark, a
luminous ring is seen round the eye, and a blow on the face excites a
flash of light. Nervous excitement, by accelerating respiration,
increases the chemical combination of the oxygen of the air with the
carbon of the blood, and thus produces animal heat. But the development
of electricity by nervous and muscular force, is one of the most
unexpected and singular results of physiological research.
MM. Matteucci and Du Bois Reymond have proved that the intensity of the
nervous and muscular forces is at a maximum when the muscles are
contracted; and that if each arm of a man be put in contact with a wire
of a galvanometer so as to form an electric circuit, an instantaneous
deviation of the needle will take place, now in one direction and now in
the other, according as he contracts his right arm or his left. The
electricity thus evolved, when conveyed to the needle through several
miles’ length of coiled insulated wire, will cause a deflection
amounting to sixty or seventy degrees, according to the strength of the
man—that is, according to his muscular and nervous force; the amount of
the electricity being exactly in proportion to the amount of muscular
force.
It appears that the electric currents in the nerves are eight or ten
times stronger than those in the muscles. M. Helmholtz found that the
time required to contract a muscle, together with the time required to
relax it again, is not more than the third of a second, and is a
constant quantity, for the compensation of energy prevails also in
organic nature. He also found that the motion or velocity of the
electric current in a man is at the rate of 200 feet in a second. The
electric equivalent, as determined by M. Helmholtz, is equal to the
electricity produced in a voltaic battery by the seven millionth part of
a milligramme of zinc consumed in the ten-thousandth part of a second, a
milligramme being the 0·015432 part of a grain.
The contraction and muscular action or mechanical labour produced by the
passage of an electric current through a nerve is 27,000 times greater
than the mechanical labour which results from the heat disengaged by the
oxidation of that small quantity of zinc requisite to generate the
electricity; that is to say, the mechanical labour really produced by
the contraction of the muscles is enormously greater than the labour
corresponding to the zinc oxidized. In fact, the electric excitement of
a nerve is analogous to an incandescent particle or electric spark that
sets fire to a great mass of gunpowder. This result, and the association
between the greatest activity of respiration and the intensity of the
muscular energy, led M. Matteucci to suspect that a chemical action must
take place in the interior of a muscle during its contraction; and he
found by experiment that there actually is what he calls a muscular
respiration, namely, that the muscles themselves absorb oxygen, and give
out carbonic acid gas and nitrogen when contracted. This kind of
respiration is more or less common to all animals; if impeded, the blood
is imperfectly oxygenized, and loss of animal heat is the consequence.
The heat that is perpetually escaping from animals is replaced, by the
combustion of the carbon of the tissues or of the food with the oxygen
inhaled by the lungs and the skin.
In the highest class of animal life the brain is at once the seat of
intelligence and sensibility, and the origin of the nervous system. In
the lower animals intelligence and sensibility decrease exactly in
proportion to the deviation of their nervous system from this high
standard. The forms of the nervous system are more and more degraded as
the animals sink in the scale of being, till at last creatures are found
in which nerves have only been discovered with the microscope; others
apparently have none, consequently they have little or no sensibility.
The brain and the spinal cord enclosed in the vertebræ of the backbone
form a nervous system, which in the vertebrated creation is equal to all
the contingencies and powers of these animated beings, but is beyond all
comparison most perfect in the human race. The brain alone is the seat
of consciousness, for the spinal cord, though intimately connected with
it, and of a similar ‘mysterious albuminous electric pulp,’ appears to
have no relation to the faculties of perception and thought, yet it is
essential to the continuance of life. It is a distinct nervous centre
which generates muscular energy in man and animals corresponding to
external impressions, but without sensation, and is entirely independent
of the will; the vegetative functions of respiration, the contractions
of the heart, circulation of the blood, and digestion, are carried on
under every circumstance, even during sleep. The reason of their being
independent of sensation and the will is, that the nerves in the organs
performing these functions never reach the brain, which is the seat of
intelligence and sensation, but they form what is called the reflex
system; for any impressions made upon them are carried to the upper part
of the spinal cord alone, and are reflected back again to the muscles of
the heart, lungs, &c., which, by their contractions, produce these
involuntary motions. For instance, the flow of blood into the cavities
of the heart while dilating, acts upon the nerves, and these excite a
rhythmical movement in the muscular fibres of the heart. For there is a
vital contractility in muscular tissue which is one of the most
universal attributes of living beings, and is probably the sole cause of
motion in the lowest grades of life, and the movements produced by it in
the higher grades are in all cases the most directly connected with the
vegetative functions. The involuntary reflex system of nerves
constitutes the chief locomotive power in a number of the lower animals;
but it forms a continually decreasing portion of the whole nervous
system in proportion as animals rise in the scale of life, till in man
its very existence has been overlooked. If the spinal cord were
destroyed, instant death would be the consequence; whereas infants born
without brain have sucked and lived for a day or two.
There are numerous actions, especially among the lower animals, as
little under the influence of the will or intelligence as the reflex
nerves, which nevertheless depend upon sensation for their excitement.
The sensation may call the muscular apparatus into action without any
exertion of reason or will, in such a manner as to produce actions as
directly and obviously adapted to the well-being of the individual as
the reflex system. For example, a grain of dust irritates the nostrils,
and involuntarily excites the complicated muscular movements concerned
in the act of sneezing. This class of actions, which is called
sensori-motor, or consensual, includes most of the purely instinctive
motions of the lower animals, which, being prompted by sensations,
cannot be assigned to the reflex group.
Purely emotional movements are nearly allied to the preceding. Sensation
excites a mental feeling, or impulse, which reacts upon the muscular
system without calling either the will or the instinct into exercise.
These emotional movements are often performed in opposition to the
strongest efforts of the will, as when a sense of something ridiculous
may excite irresistible laughter at an improper time. It is probable
that the strong emotions exhibited by many of the lower animals, which
have been ascribed to instinct, are referable to this group.[1]
The movements of such animals as have no nerves are merely owing to the
vital contractility of muscular fibre.
In the highest province of animal life, which includes the mammalia,
birds, reptiles, and fishes, the general structure of the nervous system
consists of a double lobed brain, from whence a spinal cord proceeds,
protected by articulated bones, which extend along the back of the
animals, and from thence nerve-fibres extend to every part of the body.
But in order to suit a great variety of forms, this system undergoes
many modifications. In all the lower grades of life that have nerves,
the system chiefly consists of small globular masses, or nuclei, of
nervous matter, technically called ganglia, which are centres of nervous
energy, each of which is endowed with its own peculiar properties; the
nervous cords and filaments proceeding from them are merely organs of
transmission. The arrangement of these centres of nerve-force is
symmetrical, or unsymmetrical, according to the form of the animal.
In the lower portion of Articulated animals, such as insects, crustacea,
annelids, worms, &c. &c., there is a double cord extending along the
ventral side of the animal, united at equal intervals by double
nerve-centres, or ganglia. These two cords diverge towards the upper
end, surround the gullet, and unite again above that tube to form a
distinct bilobed principal nerve-centre or brain. A third form of the
nervous system is only a ring round the gullet; the points in it from
whence the nerves radiate are swollen nerve-centres, or ganglia. Those
on the sides and upper parts of the ring represent the brain, and supply
the eyes, mouth, &c., with nerves: other centres, connected with the
lower side of the ring, send nerves to the locomotive organs, viscera,
and respiratory organs. In animals of a still lower grade there are
single nuclei irregularly scattered, but in every case they are centres
of energy from whence filaments are sent to the different parts of the
creature. The last and lowest system consists of filamentous nerves,
chiefly microscopic.
Intelligence, or the mental principle, in animals differs in degree,
though not in kind, from that in the human race. It is higher in
proportion as the nervous system, especially the brain, approximates in
structure to that of man; but even in many of the lower orders may be
traced the dawn of that intelligence which has made man supreme on
earth. Every atom in the human frame, as well as in that of other
animals, undergoes a periodical change by continual waste and
renovation; but the same frame remains: the abode is changed, not the
inhabitant. Yet it is generally assumed that the living principle of
animals is extinguished when the abode finally crumbles into dust, a
tacit acknowledgment of the doctrine of materialism; for it is assuming
that the high intelligence, memory, affection, fidelity, and conscience
of a dog, or elephant, depend upon a combination of the atoms of matter.
To suppose that the vital spark is evanescent, while there is every
reason to believe that the atoms of matter are imperishable, is
admitting the superiority of matter over mind: an assumption altogether
at variance with the result of geological sequence; for Sir Charles
Lyell observes, that ‘sensation, instinct, the intelligence of the
higher mammalia bordering on reason, and lastly the improvable reason of
man himself, presents us with a picture of the ever-increasing dominion
of mind over matter.’
The physical structure of a vast number of animals has been investigated
from such as are a mere microscopic speck to the highest grade of animal
life; but very little is comparatively known of their intelligence and
means of communication. We know not by what means a pointer and
greyhound make an agreement to hunt together; nor how each dog is not
only aware that his companion possesses a property which he has not, but
that by their united talents they might accomplish their purpose, which
is merely sport, for they never eat the game.[2] The undulations of the
air and water are no doubt the means by which most animals communicate;
but there is reason to believe that many inhabitants of the earth, air,
and water are endowed with senses which we do not possess, and which we
are consequently incapable of comprehending.