BIOLOGY.
UBRAPY

BIOLOGY.

BIOLOGY

BY

DR. CHARLES LETOURNEAU.

TRANSLATED BY

WILLIAM MACCALL.

Pro Veritate"

LIBRA |{ V

CALIFORNIA

LONDON: CHAPMAN AND HALL, 193, PICCADILLY.

PHILADELPHIA : J. B. LIPPINCOTT AXD' CO.

1878.

Lf

BIOLOGY

LIBRARY

G

LONDON I
R. CLAY, SONS, AND TAYLOR, PRINTERS,

BREAD STREET HILL,
QUEEN VICTORIA STREET.

UNIVKKS1TY OF

CALIFORNIA.

PREFACE.

THE word Biology, which seems to have been employed for
the first time by Treviranus, is far from bearing in the
scientific vocabulary a completely settled import. It may
not be unprofitable to determine the sense of the word.
Etymologically it signifies literally " science of life," and
embraces everything relating, intimately or remotely, to the
study of organised beings ; that is to say, a whole group of
sciences, among which is comprehended Anthropology, for
instance. It is in this encyclopaedical sense that Auguste
Comte took the word " Biology," though as far as we our-
selves are concerned we intend to give it a sense much more
restricted. • Under the designation " Biology," we merely
place the exposition and the coordination of all the great
facts and great laws of life, or nearly what is usually under-
stood by " General Physiology," when this denomination is
applied to the two organic kingdoms. In this volume we
have simply attempted to state concisely what life is, and
how organised beings are nourished, grow, are reproduced,
move, feel and think.

vi PREFACE.

Even while limiting ourselves to this comparatively re-
stricted domain, we have had to consider, to group, to con-
dense and to classify, an enormous mass of facts derived
from all the natural sciences. Among these facts, numerous
as the stars of the heaven and the sands of the sea, we
have been compelled to make a choice, and to select as much
as possible what was most important, most significative, most
luminous.

We hope that the learned men who devote themselves to
special subjects may find in our modest production some new
combinations, perchance some of those general views which
are sometimes lacking to certain men in other respects very
distinguished, but who abide too closely in this or that district
of knowledge, as happens often in this age when the division
of scientific labour is carried to excess. Nevertheless, we do
not write for scientific men. We wish especially to be read
by the mass of enlightened people, whom our very incom-
plete system of public instruction has left almost unacquainted
with Biology. In effect, our best establishments for secondary
instruction limit their ambition to imparting sufficiently
complete ideas of physics, and very incomplete ideas con-
cerning chemistry ; but they stop too timidly on the threshold
of Biology, the mysteries of which are accessible? only to a
small number of special men. This is a defect exceedingly
deplorable, exceedingly prejudicial to general progress. It is
on account of this defect that so many false and even
pernicious ideas continue to find acceptance and empire in
public opinion ; hence it is, in a great measure, that true
philosophy, or rather that philosophy which is alone solid
and sound, that which flows directly and legitimately from

PREFACE. rii

observation and experiment, has such difficulty in diffusing
itself.

The object of our little book is to remedy this serious
educational deficiency in those who are otherwise enlightened.
It is therefore a work of vulgarisation. Certain scientific
men, too strictly confined within their own circle, and whose
horizon is bounded by the walls of their laboratories, pro-
nounce, with disdain, though unjustly, this term vulgar-
isation. To find the truth is surely a noble labour ; but what
is the value of the discovered truth, if care is not taken to
propagate it, to introduce it into the patrimony of general
knowledge ?

On the other hand, it must be granted that the work of
popularising has been brought somewhat into disrepute by a
crowd of pseudo-scientific publications, the authors of 'which,
trusting too little to the intelligence of the reader, either
administer only an infinitesimal dose of science, or think
themselves obliged to dilute the main idea with a deluge of
light or pleasing words, sacrificing thus at once to the most
amiable and most dangerous of our national peculiarities.
Science only deserves its name upon condition of preserving
a somewhat austere nobleness. For our part we have taken
care not to rob science of that which constitutes its strength,
and for this we trust the reader will give us credit. In our
opinion there is not a person of moderate intelligence who
will not be able, at the cost of a slight mental effort, to read
and comprehend this book ; and we think also that by such
a perusal of it, sufficiently clear and complete ideas of Biology
will have been imparted.

This is not a polemical work, but rather an exposition

viii PREFACE.

of facts. Nevertheless, amongst these facts are some which
are indisputable ; also, when we have met with them, we
have not hesitated to formulate the conclusions or induc-
tions which resulted from them. We have always done this
temperately and with brevity, and without having any other
motive than the love of truth.

We trust that this volume may be read, and that
profitably, and that it may awaken, in a large number
of its readers, love of and respect for science, namely, that
which alone, in these sad times, is at once a refuge and
a hope.

CH. LETOURNEAU.

1

TKlVKKSrVYOF

US

BIOLOGY.

BOOK I.

OF ORGANISED MATTER IN GENERAL.

CHAPTER I.

CONSTITUTION OP MATTER. UNITY OF SUBSTANCE IN THE ORGANIC

WORLD AND IN THE INORGANIC WORLD.

THE sciences of observation demand at the outset from him who
wishes to cultivate them an act of faith^ Though it is per-
fectly incontestable that the exterior world manifests itself to
us solely by exciting in our mind an incessant series of phe-
nomena of consciousness, of phenomena called subjective, we are
nevertheless compelled, unless we wish to plunge into the doubt
applauded by Pyrrho and Berkeley, to believe our senses as
honest and sincere witnesses when they signalise to us the exist-
ence, apart from our own being, of a vast material universe, the
elements whereof, without pause in movement, awaken in us, by
acting on our organism, impressions, sensations, and consequently
ideas and desires.

The exterior world exists independently of our conscious life ;
it was when as yet we were not ; and it will be when we are no

2 BIOLOGY. [Boos i.

more. Without stopping, as a few years ago M. Littre did, to
discuss the point whether the certitude of the existence of the
external world is of first or second quality, leaving aside every
metaphysical refinement, we must first firmly believe in the real
existence of the external world ; because all our senses cease not
to cry to us in every tone that the objective, the Non-He of the psy-
chologists, is not a chimera, because the contrary opinion would
strike with nullity all observation, all experience, all reasoning,
all knowledge.

The reality of the exterior world once admitted, and man
never having been led to doubt that reality, except through a
species of intellectual depravation, people naturally inquired
what could be the internal constitution of the substance of the
universe. They suspected that behind the appearance infinitely
mobile and varied of the exterior phenomena there might exist
a general and related force. Our object in this work not being
to pass in review the opinions or the reveries of the different
philosophical schools, we make haste to expound the most pro-
bable theories and systems, those which observation has confirmed,
and which by slow degrees have conquered in science their right
of citizenship.

Leucippus seems to have been the first to have had the intuition
of the most rational theory on the constitution of the universal
substance. In his opinion this substance is a discontinuous mass
of granules, solid, infinitely small, separated by void spaces. It
is " the void mingled with solid," according to an expression of
Bacon.

Democritus admitted that these primordial granules were full,
impenetrable, moreover insecable, and, for this last reason, he
called them atoms? But the conception of atoms, full and dis-

1 For what is it that Democritus says? — "That there are substances in
infinite number, which are called atoms, because they cannot be divided, which
are, however, different, which have no quality whatever, are impassible, which
are dispersed here and there in the infinite void, which approach each other,
gather themselves together, enter into conjunction ; that from these assem-
blages one result appears as water, another as fire, another as tree, another

CHAP, i.] CONSTITUTION OF MATTER. 3

persed through the limitless void of the universe, did not furnish
a sufficiently precise account of the constitution of bodies.
Epicurus appeared, whose doctrine was so magnificently sung
by the great poet Lucretius. lie immensely improved the
atomic theory of Leucippus and Democritus by vivifying atoms,
and by supposing them endowed with spontaneous movement.
From the mobility of atoms resulted their various aggregations
and the dissemblances of bodies. According to Epicurus, atoms
of necessity mingled together, intertwined, literally caught and
clung to each other. A philosopher who had the talent to
preach and to propagate in France the atomic theoiy without
seeming to offend the orthodoxy of his epoch, which was still
very suspicious, Gassendi, restored to honour the atomic doctrine
of the ancients. He admits, according to the expression of
Epicurus, that "that which is moves in that which is not,"
that is, that atoms are not in contact, but that they are
separated by void spaces.

Thus then, according to this theory, the world is composed
of an innumerable quantity of atoms, mobile, infinitely small,
distant from each other. These atoms are in a perpetual state
of movement, rushing toward each other, repelling each other,
for they have their sympathies and antipathies. It is from
the diversity of their affinities that result their exceedingly
diversified modes of grouping and the variety of the external
world. It is by their vibrations, their oscillations that they
reveal themselves to man by impressing his organs of sense.
They have as essential qualities inalterability, eternity. When
they gather together, new bodies are formed ; when they dis-
aggregate, bodies previously existing dissolve and seem to vanish.
They are unhewn stones which have passed, pass, and are

as man ; that everything consists of atoms, which he also calls ideas, and that
nothing else exists, forasmuch as generation cannot arise from that which is
not while likewise what 'exists cannot cease to be, because atoms are so firm
that they cannot change nor alter nor suffer." — PLUTARCH, Miscellaneous
Works : Against the Epicurean Colotcs; Amyot's translation, Clavier's
edition, vol. xx., Paris, 1803.

B 2

BIOLOGY. [BOOK i.

destined evermore to pass from one edifice to another. Their
totality constitutes the general substance of the universe, and,
in reality, this general substance undergoes no other changes
than modifications in the distribution of its constituent ele-
ments. All the phenomena, all the varied aspects, all the
revolutions of the universe can be referred essentially to simple
atomic displacements.

This grand theory, so admirably simple and seductive, would
be nothing but a brilliant speculation, if facts, numerous and
rigorously observed, did not now serve it as basis and demon-
stration.

We rapidly enumerate the most important of these facts, which
belong for the most part to the domain of Physics and Chemistry.
Wenzel, Bichter, Proust proved first of all that in chemical
compositions and decompositions, bodies combine according to
proportions rigorously defined. Dalton formulated the law of
multiple proportions, and deduced therefrom naturally that
matter is constituted by atoms extended, having a constant
weight, and that those atoms are of various species.

When atoms of the same species come into juxtaposition, we
have what we call simple bodies, such as hydrogen, oxygen,
azote. On the contrary, the bodies called compound result from
the juxtaposition of atoms of diversified nature, whence come
acids, salts, oxides, and also all the unstable and complex
compounds which constitute organic substances.

This is not all : to the law of Dalton the law of Avogadro
and of Ampere is adjoined. This last law establishes that all
gases, temperature and pressure being equal, have the same
elastic force. But as this force is probably due to the shock
of atoms or groups of atoms, molecules, on the sides of the
vessels which imprison the gases, we must admit that in the
conditions aforesaid all gases contain, under the same volume,
the same number of molecules or of atoms.

Finally, Dulong and Petit have been able to show, experi-
mentally, that the atoms of simple bodies all possess the same
specific heat.

CHAP, i.] CONSTITUTION OF MATTER. 5

All these great laws, slowly evolved by observation and ex-
periment, have transformed into a solid scientific theory the
brilliant but vague intuition of the thinkers of ancient Greece.
With ground so firm to rest on, chemistry has been able to
particularise more, to study in some sort the individual cha-
racter of atoms ; in scientific language, it has arrived at the
notion of atomicity.

Atoms have as general characteristics extension, impenetra-
bility, indestructibility, and eternal activity. But these general
characteristics exclude not a number of specific differences.
The progress of chemistry will no doubt show us what amount
of truth there is in the hypotheses of Dumas and of Lockyer,
according to which the simple bodies of chemistry as it now
exists are merely indecomposed bodies. According to this as-
sumption our metals and our metalloids are simple modifi-
cations of a single substance, probably hydrogen, the atoms
thereof forming different molecular groupings. In the present
state of science, these ideas, as yet purely hypothetical, can
be passed by ; and relying for the present on the great laws
of Dal ton, Ampere, Dulong, and Petit, we have the right to
consider the simple bodies of contemporary chemistry as repre-
senting groups of atoms identical among themselves in each
simple body, but specifically different from one simple body
to another. Now each of these atomic species has its individual
energy, its own affinities. In the group of the other atomic
species it has friends, it has indifferents, it has enemies. It
willingly unites itself to the first, neglects the second, refuses,
on the contrary, to combine with the last. Moreover, this faculty
of attracting and of being attracted attains in each atomic
species a different degree of energy. Whence we may conclude
that there are in the different atomic species differences of mass
and of form. In aggregating themselves thus, according to their
affinities, atoms arrange themselves into small systems, having in
each body a special structure. These atomic systems are called
molecules.

The atoms of alkaline metals, such as potassium and sodium,

6 BIOLOGY. [BooK r.

cannot fix each more than one atom of chlorine or of bromine ;
they are monoatomic, as, for instance, hydrogen. Calcium, barium,
strontium, in order that their attractive power may be saturated,
need to fix two atoms of chlorine ; they are diatomic, as, for
instance, oxygen. Phosphorus, which in the perchlorure of
phosphorus succeeds in fixing five atoms of chlorine, is pentatomic.

It is these inequalities in the mode and the power of combina-
tion, in the capacity of saturation, which we call the atomicity of
each atomical species, designating specially by that expression
the maximum capacity of saturation. However, hereby is by no
means implied that a pentatomic species, for instance azote, can-
not combine with less than five atoms. Azote, which fixes five
atoms in the chlorohydrate of ammonia (AzH4Cl), is not more
than triatomic in ammoniac gas (AzH3), and is only diatomic in
the bioxide of azote. For the sake of greater clearness, the
denomination atomicity is reserved to designate the capacity of
absolute saturation. The capacities of inferior saturations are
called quantivalences. Thus then azote is pentatomic, but it is
trivalent in gas ammoniac, and so on.

This notion of atomicity has thrown a great light on the
ultimate texture of bodies, and also on the march hither and
thither of atoms in various combinations. In effect, free or
combined, every atom tends to saturate itself by the annexion of
other atoms. If, for instance, a tetratomic atom has combined
with two atoms only, it ceases not to tend to saturate its attrac-
tive force ; it strives to fix two atoms more. But these two
atoms once found, no other simple body can combine with our
tetratomic atom, unless by displacing one or two of its atoms
and becoming their substitute. If, for instance, we take from
a carburet of saturated hydrogen an atom of hydrogen, the
molecule thus mutilated can unite itself to an atom of chlorine.
But the chlorine is monoatomic ; this, however, does not hinder
it from fixing the complex molecule of the carburet, impoverished
to the extent of an atom of hydrogen. The reason is that
certain atomic groups, certain molecules, can play in combina-
tions the part of a single atom. They are what we call com-

CHAP, i.] CONSTITUTION OF MATTER. 7

pound radicals. This notion of compound radicals has a pre-
dominant importance in the chemistry of organic substances, so
called because nearly altogether they constitute the substance
of living bodies. It simplifies extremely their apparent com-
plexity. It is thus that, according to Mulder, the formula of
albumineis l<XCwH81N5Ou)+88Pk If we limit ourselves to
totalising the atoms, this formula gives C400H310N500120 + S2Ph,
a molecule of frightful complication. But if we admit a com-
pound radical, proteine (C40H31N5012), comporting itself as a
simple atom, the molecular structure of albumine is enormously
simplified : it approaches that which we are accustomed to meet
in the chemistry called mineral. It is probably also from this
notion of compound radicals that we must seek the explanation
of what has been called isomeria. If bodies having the same
elementary composition, such as the tartaric and paratartaric,
malic acid, citric acid, sugars, gums, have nevertheless distinctive
properties, we must probably attribute the dissimilarities to
differences of molecular structure, to the existence, in the very
heart of these isomeric bodies, of dissimilar compound radicals.

There is another notion not less important than that of com-
pound radicals for the easy comprehension of the formulas of
the chemistry called organic, the notion, namely, of autosatura-
tion. In effect, the atomicity of a simple body does not always
expend itself on atoms of a different species ; it may manifest
itself between atoms of the same species. The atoms of carbon,
for instance, can saturate themselves. An atom of carbon, which

l

is tetratomic, — c — , may, by expending merely a quarter of its

atomicity, unite itself with another atom of carbon, which, in its
turn, will neutralise in this combination a quarter of its attrac-
tive energy ; there will result thus therefrom a molecule hexa-
valent, that is to say, capable of still enchaining six atoms :

l l

— c — c —

8 BIOLOGY. [BOOK i.

Let a third atom of carbon then unite itself to this molecule,
we have an octovalent molecule :

I l I

— c — c — c — •

Finally, the adjunction of a fourth atom of carbon gives a
decavalent compound :

c — c — c — c —

This notion of autosaturation has enabled us to systematise a
quantity of facts of organic chemistry, to create rationally new
compounds, to classify and to seriate groups. We owTe to it the
theory of alcohols, and that of hydrocarburets.1

The preceding pages contain the principal notions of general
chemistry, which as we proceed we propose to apply. We must,
however, before ending this chapter say a few words on what
have been called catalyses. Certain bodies brought into contact
with other bodies determine by their presence alone, and without
taking any other part in the reactions, either combinations or
metamorphoses or unfoldings. It seems as if in these cases the
body, intervening, by its presence alone, brings into play an attrac-
tive force sufficient to disturb the atomicity of the body which it
influences, without, however, being able to enter into combination
with that body. For instance, platina determines, by its presence
alone, the combination of oxygen and hydrogen, the formation
of water; it transforms also alcohol into acetic acid by deter-
mining its oxidation.

These are catalyses of combination.

The albuminoidal substances introduced into the stomach
impregnate themselves there with gastric juice, expand, and in

1 Consult for further details, Wurtz, Philosophie Chimique, Chimie nouvdlc,
etc. Haquet, article, Atomique (Theorie) in the Encyclopedic Generate.

CHAP. i.J CONSTITUTION OF MATTER. 9

consequence the organic substance of the gastric juice achieves
in these alimentary substances an isomeric 'modification, which
renders them liquid, absorbable, in short, transforms them into
albuminose. In the same way, under the influence of sulphuric
acid diluted, cane-sugar, cellulose, gums, and fecules are metamor-
phosed first of all into dextrine, and then into glycose, or grape-
sugar.

These are isomeric catalyses.

The hippuric acid of the urines of herbivorous animals
unfolds itself, under the 'influence of the mucous elements
modified by the air, into hippuric acid and sugar of gelatine or
glycocoll.

That is an unfolded catalysis.

In sum, the universe must be regarded as a whole composed
of atoms dissimilar, and variously grouped according to their
affinities. These active atoms are the foundation, the substance,
the cause of all things : to use the expression of Tyndall, they
are giants travestied.

The various aspects of bodies result from the various modes
of aggregation of the constituent elements.

" All the changes accomplished on the surface of the globe are
due to combinations which are made or to combinations which
are unmade." l

All chemical phenomena are consequently the expression of
atomic combinations, and can be included in four general
types:

1. Simple change of molecular structure, or isomeria.

2. Unfolding of compound molecules.

3. Adjunction, addition of atoms, or of molecules not yet
saturated, or, inversely, subtraction of atoms.

4. Substitution of certain atoms, certain molecules for others
in a compound body.

These general characteristics manifestly exclude all ulti-
mate, all radical difference between living organised bodies and

1 Dumas, Traiti de Chimie, t. viii.

10 BIOLOGY. [BOOK i.

inorganic bodies. Is there sufficient reason, however, for distin-
guishing between an inorganic world and an organic world?
What are the dissimilar qualities of these two grand groups?
This is what we propose to examine in the following
chapters.

[Note. — When in this chapter atoms are spoken of as
full, it is in the sense of a plenum excluding a vacuum. —
TRANSLATOR.]

LI B Li A K V

UNI VKKSl'l V OF

CALIFORNIA.

CHAPTER II.

ANORGANIC SUBSTANCES AND ORGANIC SUBSTANCES.

IP, as results from the preceding exposition, the universe is a
whole eternally unstable in form, eternally immutable in sub-
stance, it follows as a matter of course that living or organised
bodies cannot be constituted of aught essentially special. An
integrant part of the medium which environs them, they come
forth from it only to return to it, and there is not an atom of
their substance which does not participate of the eternity of
universal matter, the basis of everything which exists. There
is not one of these atoms which has not played an infinite
number of parts in an infinity of organic and anorganic com-
binations, and which is not destined to play an infinite number
more. Also, in analysing elementarily the most complex of
animals, man, we, in normal conditions, find in him only four-
teen simple bodies of mineral chemistry, the list of which is
herewith given : —

Oxygen,

Hydrogen.

Azote,

Carbon,

Sulphur,

Phosphorus,

Fluor,

Chlorine,

Sodium,

Potassium,

Calcium,
Magnesium,
Silicium,
Iron.

Moreover it must be stated that the mass of the human body
is especially constituted of four of these simple bodies, namely,
azote, carbon, hydrogen, oxygen.

12 BIOLOGY. [BOOK i.

If the results are accepted of elementary chemical analysis by
decomposition, organised beings do not differ in substance from
unorganised beings. But the analogy in substance does not
exclude very important differences in form ; for we know that
the properties of bodies are intimately related to their com-
position, to the mode of aggregation of the substances which
constitute them.

Let us remark, in passing, that of the four simple bodies
occupying the first place in the composition of the body of man
and of the animals, there are two whose affinities of combination
are neither strong nor numerous, and which have a certain degree
of chemical inertia. Carbon, which is completely inert in
ordinary temperatures, unites itself only to a small number of
substances, and often by only a feeble bond. Nevertheless it
largely blends with the constitution of plants, and occupies a
very important place in the constitution of animals. Azote,
more indifferent still than carbon, is found in large quantities in
the vegetal kingdom, in quantities still larger in the animal
kingdom. It is this very inertia shared, though in a less degree
by a third element, hydrogen, which renders these bodies suit-
able to figure in the chemical constitution of living beings.1 In
these beings, in effect, matter is in a state of extreme mobility ;
it is subject to a perpetual movement of combination and decom-
bination ; without repose, without truce, its elements go and
come, have reciprocities of action, aggregate themselves, dis-
aggregate themselves ; there is a real whirl of atoms, in the very
midst of which fixed compounds, with chemical elements solidly
cemented together, can only figure in a secondary fashion. Here
are needed compounds unstable, of a great molecular mobility,
capable of forming, disaggregating, metamorphosing, themselves,
of renewing the woof of the living tissues.

At the very outset the ternary compounds non-azotised, the

aggregates of hydrogen, of oxygen, and of carbon, that is to say,

the fixed oils, the fats, the gums, the starches, the resins, the

sugars, and so on, the constituent principles of plants and

1 See H. Spencer, The Principles of Biology, vol. i.

CHAP, ii.] ANORGANIC AND ORGANIC SUBSTANCES. 13

animals possess a great inertia and a notable instability ; often
they are susceptible of isomeria (sugars, dextrine, and the like).

As regards the more complex compounds, those in which
carbon, hydrogen, azote, sulphur, phosphorus ally themselves to
form the substances called albuminoidal, molecular instability is
earned in them to the maximum ; the unfoldings, the isomeric
modifications are effected with extreme facility. Further on we
shall, in reference to nutrition and digestion, signalise the im-
portant isomeric modifications which transform the insoluble
albuminoidal aliments into soluble substances. Let us call atten-
tion also, by the way, to the still more curious and typical
metamorphoses which the various kinds of virus and miasma
produce in the albuminoidal substances of living bodies. It
deserves remark, besides, that these last substances, when once
modified isomerically, possess the murderous property of trans-
mitting by simple contact to sound organic substances the
molecular alteration they have themselves undergone.

But, finally, we may observe that these actions of contact are
not peculiar to organic substances. They have, like the isomeric
phenomena, their analogues in the chemistry called anorganical.
In effect there is no radical difference, no abruptly settled
frontier between organic chemistry and inorganic chemistry.
The two kinds of chemistry study the same elementary bodies
which are subject to the same laws. Organic substances proceed
from anorganic substances, and return to them incessantly, to
come forth from them anew. For the most part we merely find
in organic substances greater complexity and instability. Also
we see modern chemistry striving more and more to pluck from
living bodies the monopoly of the fabrication of substances called
organic.

Moreover, if we place in a graduated series the mineral and
organic compounds, we discover between the two classes transitory
groups, forming a point of union : these are the carburets of
hydrogen, the alcohols, the ethers, ternary acids, fat bodies, the syn-
thesis of which the chemist is now able to accomplish. Neither is
there anything inalienable or special in the composition of organic

14 BIOLOGY. [BOOK i.

products. We can succeed in substituting magnesia for lime in
the shells of eggs. "We can, in fats, replace hydrogen by chlorine,
without modifying essentially the properties of the compound.
Chemical synthesis has also tried to reproduce the simplest of
the azotic organic substances. There has been a direct repro-
duction of urea, of taurine, of glycocoll in the laboratory ; and
if the true albuminoidal bodies have hitherto defied the efforts
of synthetic chemistry, we may almost with certainty predict
that they will not defy them always. It will then be possible
to appropriate direct from the mineral world fibrine, albumine,
caseine, and so on. that is to say, the special, the most needful
aliments of man. This grand discovery must inaugurate for
civilised communities a new era. It must be for man a real
enfranchisement, by diminishing in a prodigious measure the sum
of muscular labour, to which for more or less duration and
progression he is now doomed.

These preliminaries settled, we are able to enumerate the
various groups of simple or compound substances, which by their
union constitute the bodies of organised beings. M. Ch. Robin
has given an excellent classification of these substances or imme-
diate princifiles.1 According to him, the immediate principles are
the ultimate solid bodies, liquid or gaseous, to which we can
reduce the liquid or solid organised substance, the humours and
the elements. But in order that these ultimate materials may
merit the name of immediate principles, M. Robin thinks they
must be obtained without chemical decomposition, by simple
coagulations and successive crystallisations.

These bodies, which, by their innermost blending, their reci-
procal dissolution, constitute the semi-solid organised substance,
can be grouped into three classes :

1. The first class comprehends the crystallisable or volatile
bodies without decomposition, having a mineral origin and coming
forth from the organism as they had entered it t( water, certain
salts, and so on).

2. The immediate principles of the second class are also

1 Charles Robin, Lefons sur les Hwneurs, Paris, 1867.

CHAP, ii.] ANORGANIC AND ORGANIC SUBSTANCES. 15

crystallisable or volatile without decomposition, but they are found
in the organism itself, and come forth from it direct as excre-
mentitial bodies. They are acids, for instance, the acids tartaric,
lactic, uric, citric ; vegetal and animal alkaloids : creatine, creati-
nine, urea, caffeine, and so on ; fat or resinous bodies ; sugars
of the liver, of grape, of milk, of cane, and the like.

3. In the third class of immediate principles we find bodies
not crystallisable or coagulable. They are formed in the
organism itself ; then, decomposed there, give birth to the imme-
diate principles of the second class. The organic substances,
properly so called, the substances of the third class, constitute
the most important part of the body of organised beings (globu-
line, musculine, fibrine, albumine, caseine, cellulose, starch,
dextrine, gum, and some colouring matters, such as hsematine,
biliverdine.)

It is from the intense union, molecule by molecule, of substances
appertaining to these three groups that organised substance
results, formed of multiple elements, but constituted in great
part of bodies complex, inert, unstable, easily decomposed, either
through the play of chemical affinities, or the action of undula-
tions calorific, luminous, electric.

So far we have occupied ourselves with the materials of
organised bodies only from the point of view of their chemical
composition ; but it is quite as needful to take into consideration
their physical state and physical properties.

An English chemist, justly celebrated, Graham, fell on the
happy idea of grouping all bodies, according to their characteristic
physical state, into two grand classes, that of crystalloids and
that of the colloids.*

The crystalloids comprehend all the bodies which ordinarily
form solutions sapid and free from viscosity. These bodies have
furthermore the property of traversing by diffusion porous
partitions.

The colloids have a consistency more or less gelatinous (gum,
starch, tannin, gelatine, albumine). They diffuse themselves
1 Phil. Transactions, 1861, p. 183 ; Moigno, Physique Moliculaire.

16 BIOLOGY. [Boos i.

feebly and slowly, as the following table indicates, which gives
the time of equal diffusion for some bodies taken in the two

Chlorohydric acid .1

Chlorure of sodium 2, 33

Cane-sugar 7

Sulphate of magnesia 7

Albumine 49

Caramel 98

Herefrom it is seen that chlorohydric acid traverses the porous
membranes forty-nine times faster than albumine, and ninety-eight
times faster than caramel. It is no doubt owing to this feeble
diffusibility that the colloids are savourless when they are pure.
Besides, these colloids do not comprehend merely the complex
organic substances called albuminoids ; certain bodies indubitably
mineral, such as silica, hydrated peroxide of iron, can assume
the colloidal condition. Both the one and the other, moreover,
enter into the composition of organised bodies. A particular
soluble form of the hydrated peroxide of iron, which normally is
an element of the blood, gives, when we dissolve it in water in
the proportion of 1 to 100, a red liquid, condensing into coagulum,
into a sort of rutilant clot, under the influence of traces of acids,
of alkalies, of alkaline carbonates, atid of neutral salts.

Certain colloids, such as gelatine, gum arabic, are soluble in
water ; certain others, such as gum tragacanth, are insoluble
therein. In any case they have as a general characteristic the
power of absorbing a great quantity of water, of augmenting
enormously in volume, and of then losing this water very
rapidly by evaporation. It seems as if in this case they are
merely subject to a sort of capillary imbibition. Yet it must be
admitted that they incorporate more intensely with themselves
a certain quantity of water as an integrant portion. Hence it
appears that there is for colloids a water of gelatinisation, as there
is for crystals a water of crystallisation.

CHAP, ii.] ANORGANIC AND ORGANIC SUBSTANCES. 17

There is not, however, any absolute incompatibility between
colloids and crystalloids. If the colloids are for the most part
complex organic compositions, we have seen above that very
simple mineral compounds can assume the colloidal state ; and
on the other hand Reichert discovered in 1849 that albuminoidal
substances can take the crystalloidal form. We shall be able
to cite examples of this last case when speaking of plants. In
almost all seeds, in effect, we find a white powder, finely grained,
and presenting sometimes crystallised facets, square edged.
The diameter of these particles is from Om,00125 to Om,0375.
They are called particles of aleurone. They are composed of
fibrine, of albumine, of legumine, of gliadine, of gum, of sugar,
and so on. They are aliments in reserve.

These albuminoidal crystalloids are birefringent ; they are all
insoluble and unassailable in water and alcohol.1

We have signalised above the strong diffusibility of the crys-
talloids ; it is so great that they can penetrate the colloids,
blend with them as intensely as with water, while on the con-
trary the colloids can scarcely diffuse themselves into effective
union with each other.

From this enormous difference of diffusibility between colloids
and crystalloids it results that, if we separate by a porous mem-
brane water and a colloid holding in solution a crystalloid, this
last disengages itself from the colloid and traverses the mem-
brane to dissolve in the water. It is thus that we can very
easily with a membrane dialyser extract from a colloidal substance
arsenious acid, digitaline, and so on. This process is made use of
in certain toxicological researches, and also industrially to purify
gums, albumine, caramel, and the like.

The reader has no doubt already the presentiment of the
weight and worth of some preceding statements for the compre-
hension of biological facts. In effect every organised being is a
compound of colloidal bodies holding in solution crystalloidal
bodies. But this organised body is in a state of perpetual reno-
1 Duchartre, Botanique, p. 69 ; Sachs, Traiti de Botaniquc, p. 72.

0

18 BIOLOGY. [BOOK i.

ration. Unceasingly it plays, face to face with the exterior
medium, the part of dialyser, either directly or by the aid of
special apparatus. It forms nutritive soluble substances, and
rejects waste substances, likewise soluble, at least in the liquids
of the organism.

When, for instance, the residuum of the waste of the living
tissues is composed of crystalloid bodies, these bodies can easily
and rapidly traverse the colloidal substance of the tissues to be
expelled from the organism ; but their expulsion leaves in those
same tissues a void which other soluble substances can come to
till by permeability ; and in this fashion the losses undergone
by the living machine are repaired without difficulty.

Finally, the colloidal state is the form the most suitable for
the manifestation of the instability, the molecular mobility of
the complex bodies which constitute organised beings. Under
this form they are really in the dynamical state ; they yield
without difficulty to the shock, to the action of incident bodies.
They can unmake and remake themselves, become the scene of a
perpetual exchange of molecules and of atoms, in a word, of a
vital progression and regression.

CHAPTER III.

CHEMICAL COMPOSITION OF ANIMALS AND PLANTS.

Ix the two living kingdoms, organised substance is, as we
have already seen, constituted by three groups of bodies inti-
mately blended, and which Chevreul was the first to call
immediate principles. It is now needful to compare with each
other the chemical species which enter into the composition of
the plant and into that of the animal. We shall glance very
rapidly at the immediate principles of the first category. In
effect, water, which constitutes in weight the largest part of
organised beings, mineral salts, atmospheric gases, are manifestly
unable to furnish to us sufficiently distinctive characteristics.
But that the results of the comparison may be the more striking
we shall indicate first of all in bold outline what is the chemical
composition of plants, and what is that of animals.

1. Chemical Composition of Plants.

Organised vegetal tissues, when submitted to desiccation,
present a friable residuum, the weight of which is very variable.
Jn the average of terrestrial plants this residuum is from a
fifth to a third of the total weight ; but it rises to eight-ninths
if we take ripe seeds, and can descend to a tenth or a twentieth
in aquatic plants and certain mushrooms. This residuum,
desiccated, offers always to chemical analysis, carbon, hydrogen,
oxygen, azote and sulphur, potassium, calcium, magnesium, iron,
phosphorus. Often, moreover, we find therein sodium, lithium,

c 2

•20 BIOLOGY. [BOOK i.

manganese, silicium, chlore. Finally, in the marine plants we
discover iodine and brome.

Such are the ultimate results of analysis ; but, of course,
during life, these bodies are not, for the most part, in a state of
liberty ; they are combined in various manners. The metals are
usually in the state of salts, of sulphates, of phosphates, of
carbonates, of oxalates, and so on. There is also a certain
quantity of oxygen, of azote, of hydrogen and of carbonic acid
dissolved in the liquids or impregnating the vegetal anatomical
elements. But the true organic compounds are ternary or
quaternary compounds. The ternary compounds are formed of
carbon, of hydrogen, and of oxygen. They constitute the strongest
part of the vegetal texture. Let us mention first of all cellulose,
which forms almost alone the primary part of the vegetal cells,
and then many substances which are isomeric to it, such as in-
uline and xylogen. The first of these isomers of cellulose, inuline,
is found in decomposed roots, in colchicum bulbs, in dahlia
tubers, and so on. As to xylogen, it is the substance which 'gives
rigidity to ligneous tissues. Furthermore, in putting ourselves
at the point of view of chemical composition we have to see the
relation of cellulose to the starches, the sugars and the gums.
To the type of sugars, the sugar of grape, or glycose, has long
been given the formula C12H12012,2HO. Starch is composed of
C12H909,HO. In reality, these ternary bodies have already in a
large measure the characteristics of complexity and instability
peculiar to organic substances, and their definitive formula is
still a subject of discord among chemists. According to M.
Wurtz, for instance, the formula of cellulose would be C6H10Or>,
that of gum arabic C12H£20U, that of starch C H1005, and this
formula would not vary by the isomeric transformation of starch
into dextrine. Saccharine and amylaceous matters bear as chemical
characteristic the inclusion of hydrogen and oxygen in such
proportions that the oxygen could suffice exactly to saturate the
hydrogen and to transform it into water. The general formula
of these groups would therefore be Cm(H20)n.1
1 Wurtz, Chimie Nouvelle.

CHAP, in.] COMPOSITION OF ANIMALS AND PLANTS. 21

To complete the enumeration of the ternary vegetal compounds,
we have to mention the fat vegetal bodies, the non-azotised oils,
which are also compounds in complex molecules of carbon, of
oxygen, and of hydrogen.

After the group of ternary organic substances comes a tribe
of azotised compounds, wrongly, and in virtue of questionable
chemical theories, called quaternary bodies. The molecules of
these last bodies are, it is true, formed for the most part by
atoms of carbon, of oxygen, of hydrogen, and of azote ; but almost
constantly a certain quantity of sulphur and of phosphorus
must be joined to them. These quaternary compounds are the
organic substances by excellence ; we seek in vain their analogues
in the mineral world. They form themselves spontaneously in
the texture of living beings ; whereas the ternary compounds
spoken of above can be brought into relation with the carburets
of hydrogen which connect them with the inorganic world.

The azotised vegetal substances form two principal groups, —
the group of the alkaloids, and that of the albuminoids. The
alkaloids are very complex compounds, capable of combining
as bases with an acid. These bodies, unimportant as to quantity,
are very important as to their physiological or toxical properties;
they are quinine, strychnine, morphine, and so on.

But the substances which, without question, hold the first
rank, the compounds essential to vegetal life as well as to
animal life, are those which form the group of the albuminoids.
We shall see that these substances constitute the nucleus of the
vegetal cells, constitute their internal membrane, that they are
also found in the liquid filling the cells, in the protoplasm.
Among the most important of these substances we must name
gluten or vegetal fibrine, so abundant in the seeds of the cereals.
To it is given as formula, according to the theory of Mulder,
10(C40H31012Az5) -f S.

In relation to gluten we have to view glut in e, an analogous
albuminoidal substance ; it is the coagulable principle of the
sap of plants. It is likewise called vegetal albumine.

•22 BIOLOGY. [BOOK T.

Finally there is extracted from the seeds of the leguminous
plants a third albuminoidal substance, containing, like gluten,
sulphur, and which is called vegetal caseine.

The last substance which we have to mention is the green
matter of plants, chlorophyll. Its physiological agency is 'ex-
tremely curious and interesting ; we shall therefore describe it
in detail in the course of our expositions. Here it suffices to
observe that chlorophyll cannot be placed in the group of the
preceding substances, called proteical. Neither phosphorus nor
sulphur is found therein. It is composed only of carbon, of
hydrogen, of oxygen, of azote, and, what is altogether character-
istic, of iron. Its formula, still however requiring consideration,
would be C18H9AzOs + Fe (in indeterminate quantity).

2. Chemical Composition of Animals.

In a preceding chapter we have enumerated the fourteen
simple bodies entering into the composition of the most complex
of organisms, the human organism.

A glance thrown at this list suffices to show that if the
elementary composition is held in view, and the quality of the
elements is alone considered, there is almost identity between the
vegetal organisms and the animal organisms. But in both kinds
of organism these, elementary bodies are aggregated in various
combinations, with the exception of azote and oxygen, of which
a part is in a state of liberty alike in the animal and the
vegetal organisms.

In every animal organism also we encounter, in a state of
intense blending, immediate principles of the three classes.

The immediate principles of the first class, or mineral
principles, penetrate, entirely formed, into the animal economy ;
and entirely formed they come forth from it : this is the case
with water, azote, certain salts, and so on.

The principles of the second class are in general hydrocar-
bonised ternary compounds such as lactic acid and the lactates,

CHAP, in.] COMPOSITION OF ANIMALS AND PLANTS. 23

uric acid and the urates, fat bodies (olei'ne, margarine, stearine),
animal starch or glycogenous matter of the liver, the glycose of the
same gland, chitine. They comprehend quaternary azotised pro-
ducts, the result of the disassimilation of the organic elements,
such as urea (C2Az2H402), creatine (CsH9Az3O4), creatinine
(C8H7Az307), cholesterine (C52H44O2), and so on. While the
principles of the first class pass merely into the organism by
coming from the exterior world, those of the second form them-
selves in the animal organism, but do not sojourn there.

The immediate principles of the third class are numerous
neither in animals nor plants, but they play in the first a more
important part than in the last. They are the albuminoidal sub-
stances, all likewise colloids, and insatiable in their thirst for
water. These bodies are very unstable compounds, much inclined
to isomeric modifications. They are formed in the animal
economy, never leave it when it is in a healthy state, are renewed
therein molecule by molecule through the nutritive movement,
and from their quantity and from the dominant part they play,
they constitute the very essence of the living organism. Their
formula, as we have already stated, is still undecided. There has
been a disposition to consider them as all formed of the same
radical, proteine, united to atoms of sulphur and phosphorus.

In boiling the epidermic productions, the cartilages, the organic
framework of the bones, the cellular tissue, the tendons, and
so on, we obtain quaternary azotised substances, chondrine,
gelatine, containing less carbon and more azote than the other
albuminoidal substances : moreover, containing no sulphur.

The most important animal albuminoidal substances are
fibrine, albumine, caseine, the analogues of which we have signal-
ised in plants. In the same way that in plants we have found
a special quaternary substance, chlorophyll, containing a metal,
iron, we find also in the superior animals a matter analogous to
albumine, but coagulating much less easily when it is dissolved in
water. This matter is the substance of the globules of the
blood, globuline. Like chlorophyll, it contains iron in its com-

24 BIOLOGY. [BOOK L

position, and, like it, also exerts a special action on one of the
gases of the atmosphere.

How summary soever may be the short enumeration which
precedes, it suffices to establish from a thorough knowledge of the
matter a parallel between the composition of animals and that
of plants, and to give saliency to the analogues and the differences.

3. The Organic Substances of the two Kingdoms.
A supreme fact is evolved from the preceding examination,
namely, that there is in the ternary and quaternary substances a
dominant element common to them all, carbon. Of all organic
substance, carbon is the base. In weight it forms the principal
element thereof. The albumine of the blood contains about fifty
per cent, of carbon. But in organic substances carbon plays a
much more important part still. It is the bond of all the various
atoms, which compose the complex molecules of organised bodies.
W e have already seen that carbon is a tetratomic body, that is to
say, capable of fixing, of keeping wedded to one of its atoms
four atoms of a monoatomic body, such as hydrogen, or two
atoms of a diatomic body, such as oxygen ; and so on. We have
besides remarked that the atoms of carbon could unite with each
other in neutralising reciprocally one only of their affinities, the
others remaining free and fit to satisfy themselves, in attracting
and fixing either atoms of other elements or even aggregates
more or less complex, radicals comporting themselves as a single
atom. But these atoms, these radicals, are often only aggre-
gated to the atom of carbon which attracts them by one of their
affinities, while the others remain active, exciting the aggrega-
tion of new atoms. Let us take, for instance, the iodide of
methyl, that is to say, of carbonised hydrogen, an atom of iodine
taking the place of an atom of hydrogen : —

H

H— C— I

i

CHAP, in.] COMPOSITION OF ANIMALS AND PLANTS. 25

Heating in suitable conditions this body with potash or
hydrate of potassium, we determine the displacement of the
atom of iode, which combines with the potassium and is suc-
ceeded by the oxygen of the potash. But this oxygen is di-
atomic : 'the half only of its affinity is satisfied or neutralised by
this displacement : the rest still remains free. This is why,
without ceasing to form part of the carburet, the atom of
oxygen unites itself on its own account with a molecule of
hydrogen likewise taken from the hydrate of potassium, and we
have thus wood spirit :

H

H— C— (OH)

i

We have taken as example a body in which one atom only
of carbon figures. But if we represent to ourselves a poly-car-
bonised compound we at once see to what a degree of complexity
and mobility such a body can attain ; therefrom we gain a general
idea of what the chemistry of organic bodies is ; we recognise
that modern chemists have the right to call this branch of their
science the chemistry of the compounds of carbon ; and we
willingly subscribe to this proposition of Haeckel : "It is only
in the special chemico-physical properties of carbon, and
especially in the semi-fluidity and instability of the carbonised
albuminoidal compounds, that we must seek the mechanical
causes of the phenomena of particular movements by which
organisms and inorganisms are differentiated, and which is called
in a more restricted sense Life" l

The general statements given above apply equally to organic
vegetal substances, and to organic animal substances, forasmuch
as we have seen that as regards quality, as regards general

1 E. Haeckel, Histoire de la Creati&n Naturelle. Paris, 1874.

26 BIOLOGY. [BOOK i.

chemical composition, the two classes of substances are manifestly
identical. Consequently, there is no radical difference between
the organic substances of the vegetal kingdom and those of the
animal world. Nevertheless these are notable dissimilarities ;
they bear on the relative quantity of the ternary compounds
non-azotised, and the quaternary compounds azotised, in both
the realms of Nature. In effect, the albuminoidal substances
whidh constitute the chief part of any veritable animal organism
are from the quantitative point of view little more than
accessories. The great mass of every true plant is especially
constituted by the non-azotised carburetted substances. Azote,
though forming an essential element of the intracellular vegetal
protaplasm and of the alkaloids, represents often in weight less
than a hundredth of the dry matters : rarely the proportion rises
to three hundredths. To sum up, the vegetal kingdom is,
quantitatively considered, the kingdom of ternary carburetted
substances, while the animal kingdom is that of carburetted
substances azotised or quaternary. Consequently there is -in
the animal world a greater degree of chemical complexity and
instability, that is to say, a superior vital activity.

Nevertheless, there is no radical difference. "We must hence-
forth reject that idea of complete antagonism between the two
kingdoms, which has so long prevailed in science. We must no
longer consider every plant as an apparatus of reduction specially
charged to form, all in a lump, at the expense of the mineral
world, ternary and quaternary compounds for the nourishment of
animals. We must cease to see in every animal an apparatus of
combustion whose mission is to destroy those compounds with-
out being able to form any. Cl. Bernard has demonstrated that
the cells of the liver fabricate at the expense of the blood an
amylaceous matter possessing, according to the analysis of
M. Pelouze, the same composition as vegetal starch, and, like it,
transforming itself into sugar. Finally, M. Kouget has found
this amylaceous matter, glycogen or zooamyline, in the muscular
tissue, in the lung, in the cells of the liver, in the placenta, in j

CHAP, in.] COMPOSITION OF ANIMALS AND PLANTS. 27

the amniotic cells, the epithelial cells, the cartilages, &c., of
the vertebrates.1

For a long time cellulose was considered a substance exclusively
vegetal ; but after a while, under the name of chitine, or tunicine,
it was found in the tegumentary envelope of the tunicates, in
the exterior skeleton of the anthropods, and so on ; and M. Ber-
thelot has succeeded in transforming into sugar this tunicine,
this animal cellulose, for ebullition and acids metamorphose
it into glycose.2

Even chlorophyll, that vegetal substance by excellence, has
been found in certain rudimentary animals.

Therefore, once more we declare that there is no radical
difference, no chasm between the two living kingdoms, from
the point of view of the composition and formation of the
organic substances. In this respect there is no reason why
the two kingdoms should not be included under the denomina-
tion of Organic Empire, as Blainville proposed.

NOTE. — Both as a substantive and as an adjective^ vegetal is a good old
English word which is often for obvious reasons preferable to vegetable or
plant. — Translator.

1 J. Gasarrat, Phenome'nes Physiques de la Vie^ p. 196.

2 J. Gasarrat, loc. cit.

CHAPTER IV.

OF LIFE.

LIFE has long been the mystery of mysteries ; and in modern
times it has been the last refuge, the citadel of supernaturalism.
In fact, so long as there were no clear ideas regarding the con-
stitution of bodies, or the composition of chemical aggregates, so
long as so-called organic substances appeared radically different
from mineral substances, it was impossible to unravel the
mystery of life. We now know that organised bodies do not
contain a material atom which was not first derived from, and
afterwards restored to, the exterior medium. We have made an
enumeration of the immediate principles which constitute living
bodies; we have been able to reproduce a certain number of
these in our chemical laboratories. We know in what physical
state, under what blended conditions, they are found within
organised and living bodies. We know, moreover, that the
entire universe contains an always active matter, that what
is called force cannot sever itself from what is called matter,
that consequently there can no longer be any question of a
vital principle, of an archeus, superadded to living beings, and
regulating their phenomena. Even these simple general facts
authorise us to affirm that vital phenomena are simply the result
of the properties of living matter. To give a just idea of life,
it remains to us then to determine what are its properties, and
also what are the principal conditions of their manifestation.

We prove then, first of all, that life depends strictly upon the
exterior medium, that an alteration in the composition of the

CHAP, iv.] OF LIFE. 29

aerian or aquatic medium determines the cessation or suspension
of the vital movement. We can even at will suspend and
reanimate life in certain organised beings.

M. Yilmorin succeeded in reviving, by means of moisture, a
dried fern sent from America. By drying and then moistening
certain infusoria we may arrest and revive the course of life in
them. In America and Northern Russia frozen fishes, brought,
from great distances, are revivified by being plunged into water
of the ordinary temperature.

In Iceland, in 1828-9, Gaymard in ten minutes revivified
frozen toads in tepid water.

In the case of dried organisms, the organic substances jiave
been deprived, by evaporation, of their water of gelatinisation,
and thereby of their molecular mobility, the instability indis-
pensable to the realisation of atomic changes ; in fact, they have
been separated from the exterior world, yet without decompo-
sition ; whence their easy revival.

In congealing organisms, an analogous result is obtained. By
the solidification of water substances lose their colloidal state.
They are, in some degree, chemically paralysed, but can never-
theless revive, if congelation has produced neither chemical
decomposition of the substances, nor morphological destruction
of the tissues and of their anatomical elements.

These facts suffice by themselves to prove that the principal
condition of life is the interchange of materials between the
living body and the exterior world ; but, fortunately, we are not
limited to such commonplace demonstrations. Yital activities
have been minutely scrutinised, watched, and followed step by
step, as we shall see further on. "We have been enabled to note
the incessant amalgamation with the organism of substances
derived from the exterior world, to observe the modifications
and transformations which these substances undergo and promote
in the midst of living matter ; the results of all these biological
operations have been summed up, and establish approximately
the .balance of gain and loss. In short, it is now known that

30 BIOLOGY. [BOOK i.

the principal vital phenomenon, that which serves as a support
to all the others, is a double movement of assimilation and of dis-
assimilation, of renovation and of destruction, in the midst of living
matter ; that this matter may be either in a semi-solid state, and
without structure, as in certain inferior organisms; or that it
may be in a liquid state more or less viscous, like the blood and
lymph of the superior animals ; or finally, that it may be
modelled into anatomical elements, into cells and fibres bathed
with liquids and gases, as in the bodies of all the superior animal
and vegetal organisms.

The living substance is thus a chemical laboratory in constant
action. It is the physical or chemical properties of this sub-
stance, diversely modified, which underlie all the vital properties,
nutrition, growth, reproduction, the chlorophyllian attribute, motility,
and innervation. \

Now the six properties w^ich we have just enumerated are
the six principal modes of living activity, the six categories
under which all biological phenomena group and class them-
selves. The chlorophyllian property is almost exclusively vegetal ;
but the five other fundamental properties represent, when united,
the highest, the most complete expression of life. But they are
far from being always united ; they are also far from having the
same importance. Some of them are primordial, some secondary.

The most important of all is evidently nutrition, the double
and perpetual movement of molecular renovation of the living
substance. Without nutrition there can be no growth, no repro-
duction, no movement, no conscious sensitiveness, no thought.

In truth, life can be conceived of as reduced to its most simple
expression, to mere nutrition. A being capable of nourishing
itself, and destitute of every other property or function, lives
still ; but if it has not the faculty of reproduction, which, as we
shall see, is only a simple extension of the nutritive property,
its life will be only an individual life ; a moment will come
when the nutritive exchanges will slacken, when the nutritive'
residue, incompletely expulsed, will impregnate the living tissues

CHAP, iv.] OF LIFE. 31

and liquids, obstructing them, so to speak ; then the colloidal
plasmatic substances will cease to restore themselves, to regene-
rate themselves. Soon the retardment will end in complete
arrest ; then the organised being will have ceased to live ; the
complex elements which composed it will change, will break
asunder, and the groups of their molecules and of their atoms will
re-enter the exterior medium, the mineral world.

If, on the contrary, the nutritive property of a living being
is sufficiently energetic to rise, as it were, to excess, even to
growth and reproduction, the being is sure of living in its
offspring ; it fills its place in the innumerable crowd of living
beings, and can even, if the doctrine of evolution is as true as
it is probable, become the source of a superior organised type,
can ascend in the hierarchy of life.

In fact, many of the inferior organisms are endowed only with
the properties of nutrition, growth, and reproduction. At a
greater degree of complication and perfection a new property
appears, motility, subordinated likewise to nutrition, when it
concerns the individual, to reproduction when it concerns the
series. £so one is ignorant that large numbers of animals are
endowed solely with these four properties, nutrition, growth,
reproduction, and motility, which are possessed by a number of
plants also, as we shall see hereafter.

Nutrition, growth, and reproduction are truly fundamental
properties. They belong to the entire organic world, to every-
thing which lives and lasts. Above these properties must rank
three others, all naturally subordinate to the primordial property,
nutrition. These three are, the chlorophyllian property, motility,
and innervation.

The chlorophyllian property is, with rare exceptions, confined
to plants. Motility is, in a measure, common to animals and
vegetals. Finally, the last vital property, innervation, is limited
to the superior animals. It is also the most delicate, the most
subordinated to, the most closely connected with, the integrity of
nutrition, the most dependent, directly or indirectly, upon the

82 BIOLOGY. [BOOK i.

other vital properties. Let but the nutritive liquids impregnated
with oxygen cease to reach the nervous cells, to bathe them,
to excite them, to renew them, immediately motility, sensibility,
and thought vanish ; the animal re-descends, for a time, or for
ever, to the level of unconscious organised beings.

From this physico-chemical point of view we can now, without
much difficulty, form an idea of the totality of the molecular
movements which form the essential basis of life. Every living
being is constituted, in a general manner, of colloidal substances
more or less fluid, more or less solid, holding in solution salts,
gases, and so on. A portion of these salts and gases has been
introduced from without, and is ready to combine itself with the
unstable colloidal substances ; some are the result of combina-
tions already effected ; but this process of combination and
separation cannot stop ; for the atoms of atmospheric oxygen
mingle themselves ceaselessly with the organic molecules, separate
them, disaggregate them by virtue of their powerful affinities
for certain elements which form part of their complex molecules.
After a time more or less short, the oxygen, by a slow oxydation,
would have thus destroyed the living substance, if food had not
likewise been introduced from without into the texture of the
living being. These renovating substances, after having often
undergone preparatory chemical changes, after having become
nutriments, that is to say, after having acquired a chemical com-
position and a physical state which assimilate them to the living
substance, identify themselves with it. One by one their mole-
cules take the place of those which have been destroyed. The
living being, thus incessantly restored, lasts, continues to live,
and would live indefinitely, if this molecular movement never
slackened.

But we now know, through the magnificent generalisations of
modern chemistry and physics, that in the world there are. only
atoms in some degree animated, that these atoms transmit to each
other mutually the movement which impels them, or which they
engender, and that this movement, without ever being annihi-

CHAP, iv.] OF LIFE. 33

lated, transforms itself in a thousand ways. These transmuta-
tions of movement take place also naturally in living beings,
and the impulsions, so complex and varied, of the molecules
transmit themselves to the different organic apparatus, producing,
here the generation of new anatomical elements, there, the
movements of totality of the living substance, elsewhere the
nervous phenomena of consciousness, everywhere a certain
elevation of temperature and, doubtless, electric phenomena.

It has been said, and may be admitted as a general principle,
that the animal world lives at the expense of the stores of matter
and of movement accumulated by the vegetal world. We
shall have to show, at a future time, what amount of truth there
is in this generalisation. We content ourselves, at present, with
remarking that these vegetal accumulations are formed under
the influence of solar radiation, that is to say, of the vibrations
radiated by the central star of our planetary system, and that,
consequently, the dynamic solar source is the great reservoir of
force, the great motive power, which gives the impulse to the
vital movement, and sustains the impulse given.

And now can we define life 1 For that purpose it will evi-
dently be sufficient if we summarise the preceding facts into as
clear, and at the same time as brief, a formula as possible ;
for it is not our intention to pass in review the very numerous
definitions which have been given of life, long before its pheno-
mena were scientifically analysed.

The definition now most commonly adopted in France is that
given by Blainville : "Life is a twofold movement, at once general
and continuous, of composition and decomposition." This defini-
tion, as H. Spencer judiciously points out,1 is at the same time
too comprehensive, and not comprehensive enough. It is too
comprehensive, because it is applicable to that which occurs in
an electric pile or in the flame of a wax taper, as well as in the
primordial nutritive phenomena ; it is too restricted, because it
leaves out the highest, the most delicate vital activities, the
1 Principles of Biology, voL i.

D

34 BIOLOGY. [BOOK I.

cerebral or psychical activities. Lewes says : " Life is a series of
definite and successive changes of structure and of composition,
which act upon an individual without destroying his identity."
In speaking of structure, this definition excludes the activities of
purely mineral chemistry, which the first does not, but it also
forgets the cerebral activities, and besides it does not embrace
the vital acts that take place in the plasmatic liquids, such as
the blood, the lymph, which, though destitute of structure, are
endowed with life, as we shall presently see.

The definition of H. Spencer, " The continual agreement
between interior and exterior relations," has the fault of being
too abstract, and of soaring so high above facts, that it ceases to
recall them. Besides, just by reason of its vague generality, it
might also be applied to certain continuous chemical phenomena.

It would be better to descend nearer to the earth, and to limit
ourselves to giving a short summary of the principal vital facts
which have been observed. Doubtless life depends upon a two-
fold movement of decomposition and renovation, simultaneous and
continuous ; but this movement produces itself in the midst of
substances having a physical state, and most frequently a morpho-
logical state quite peculiar to them. Finally, this movement
brings into play diverse functions in relation with this morpho-
logical state of the living tissues, habitually composed of cells
and fibres endowed with special properties.

Let us say then that '* life is a twofold movement of simul-
taneous and continual composition and decomposition, in the
midst of plasmatic substances, or of figurate anatomical elements,
which, under the influence of this in-dwelling movement, perform
their functions in conformity to their structure."

CHAPTER V.

ANATOMICAL CONSTITUTION OF ORGANISED BODIES.

EVERYWHERE and always, as we have already expounded, the
living or organised bodies are constituted by complex substances,
in part albuminoidal, and in that special physical state which is
called colloidal. The fundamental matter of these living bodies
is uncrystallisable. " To live and to crystallise," says Ch. Robin,
" are two properties which are never united " (Elements Ana-
tomiques, p. 17). It is enough in effect for a body to be endowed
with the humblest of vital properties, nutrition, not to be
crystallisable. At the same time living substances are im-
pregnated with crystalloidal solutions and with gases : this is a
general attribute ; but in the form this attribute is extremely
diversified. At the lowest degrees of the organic world we find
beings without structure, amorphous : for instance, the genus
Amoeba and the genus Monas ; they are small contractile albu-
minoidal masses whose form is modified incessantly. Such are
also the simplest rhizopods, living masses rather more con-
siderable, but without definite form ; we see them emitting and
reabsorbing tentaculifonn prolongations of varying length. But
if even in a small degree we study by the help of the microscope
'the structure of beings more elevated in the living hierarchy, we
instantly see that the fundamental mass has lost its homogeneous-
ness, that it has fractionised itself into corpuscles generally
invisible to the naked eye. These small bodies, these living
bricks which by their aggregation constitute every organic edifice
a little complex, have been called anatomical elements or histologicai
elements.

D 2

36 BIOLOGY. [BOOK i.

Finally, these anatomical elements float more or less directly
in living liquids, which are called blastemas. For instance, the
freshwater polypus, celebrated on account of the curious experi-
ments of regeneration to which it has given occasion, is solely
composed of corpuscles living, spherical, of cells swimming in an
intercellular liquid, which is a blastema. This is also the texture
of certain infusoria, for example, of the Paramsecia, and likewise
of a number of plants.

Besides in plants, and especially in superior animals, exist
systems of canals serving for the circulation of liquids as
living as the figurate anatomical elements. These liquids, which,
like the blastemas, to distinguish them from which there has
been a wrong attempt, are both receptacles of disassimilated
products and reservoirs of assimilable products, have been called
plasmatic liquids, or plasmas.

We have successively to describe living substance under the
two general forms which it assumes, namely, the histological form
and the blastematic and plasmatic form.

1. Of the Figurate Elements in General.

The science of the figurate elements of living bodies, whose
real origin only remounts to the end of the last century, has
long borne the name of General Anatomy. It was not till 1819
that Mayer published a treatise of General Anatomy under the
title of Treatise on Histology, and a New Division of the Body
of Man. The word Histology has had eager acceptance, no
doubt because it is derived from the Greek, and it is now in
general use.

The first elementary histological form which organised matter
assumes is the cellular form. "We must understand by cell a
microscopical corpuscle, having a sort of independence, an indi-
vidual life, assimilating and disassimilating on its own account.
The cell has generally a form more or less spherical. It is consti-
tuted by a substance more or less soft. When it is complete it

CHAP, v.] CONSTITUTION OF ORGANISED BODIES. 37

contains another cellular element which is smaller, a nucleus in
which the living activity of the cell usually attains its maximum
of power. Moreover, it often happens, especially in plants, that
the exterior surface of the cellular corpuscle hardens. This
hardened surface then constitutes what is called the cellular
membrane.

The observations and the inductions of palaeontology, of em-
bryology, of the systematic natural history of organised beings,
authorise us in considering the organic cell as the corner-stone
of the living world, the common mother of all other histological
elements. In effect the first figurate living beings have been
monocellular, or composed of cells resembling each other, and
simply juxtaposed. At the origin of nearly the whole of living
beings, animals or plants, we find a simple cell. Finally, when
we hierarchically class the innumerable organised beings which
people our globe, we encounter, at the lowest, the humblest
degree, beings composed of a single cell, or of a small number
of identical and juxtaposed cells.

The cellular theory which we have just in summary fashion
sketched, is one of the grandest views of Biology. Bichat was
the first to attempt the anatomical analysis of living beings, by
trying to resolve each organised being into tissues anatomically
and physiologically special. Schwann, carrying analysis further,
decomposed the tissues themselves into microscopical elements,
and was the first to formulate the cellular theory in his work
entitled Microscopical Researches on the Conformity of Structure
and of Growth of Animals and Plants. 1838.1

The cellular theory contested at present, or rather differently
interpreted on certain points by M. Ch. Robin and his school,
nevertheless keeps its ground as a whole. It is not easy to
understand without it the genesis and the evolution of organised
beings. Finally, this theory has led Physiology to scrutinise

1 Mikroskopische Uiitersuchungen uber die Ubereinstimmung in der Struktur
und dem Wachsthum der Thiere und Pflanzen. — De Mirbel had already shown
that the tissue of plants is composed of utricles and cells. 1831-1832.

38 BIOLOGY. [Boox i.

more profoundly the mechanism of the vital acts ; it has taught
it to refer them to their ultimate agents, that is, to the histo-
logical elements themselves, which vary in function and in form
in complex beings, and which we must consider as playing a part
in the mechanism of organised beings, analogous to that of atoms
in chemical aggregates. As Schwann has said, " Forasmuch
as the primary elementary forms of all organisms are cells,,
the fundamental force of all organisms reduces itself to the
fundamental force of cells." (Mikroskopische Untersuchungen,
1838.)

The cell, properly so called, of which we have given above a
succinct description, is a sort of schematic type, scarcely existing
in anything except rudimentary beings and tissues. If we study
the cell either as a complex organism, or in the hierarchical
series of organisms, we see it in effect modifying itself, putting
on different forms when assuming diversified functions. Finally,
another type of histological element appears : it is the fibre, a
microscopical element likewise, springing evidently from the cell
in certain cases, where the cells have merely been elongated by
juxtaposing and cementing themselves end to end. These deri-
vative fibres exist manifestly in plants, in which they often
hollow a passage for themselves as canals. According to Ch.
Robin, there is a different process in animals. Here the fibres,
with all their essential attributes, would seem to be present at
the very dawn of the embryonic life, forming themselves spon-
taneously by genesis, at the expense of the blastematic liquids
secreted by cells. As there are various species of cells, there
are also various species of fibres ; but the true typical fibres, well
specialised, are found scarcely anywhere except in the animal king-
dom. We purpose speaking further on at greater length of cer-
tain species of fibres, muscular fibres, nervous fibres, and so on.

In sum, passing by some amorphous organised types, points of
union of a sort between the living world and the non-organised
world, we must consider every complex organism as being con-
stituted by a great number of individuals, living, microscopic.

CHAP, v.] CONSTITUTION OF ORGANISED BODIES. 39

having each special activity and special functions. These ana-
tomical elements are conformed in accordance with a small number
of types, and in the superior organised beings they are grouped
in tribes, and thus form, tissues, charged each to fulfil such and
such great physiological function, which is the total of all the
elementary activities (muscular tissue, nervous tissue, osseous
tissue, chlorophyllian tissue of plants).

As a matter of course the degree of differentiation in plants is .
very variable. It is an organic law that this differentiation of
the anatomical elements is earned the further the more the
organised individual is perfect. In other words, the great law
of the division of labour reigns everywhere in the organised
world. Besides, the elements themselves have a more complicated
structure the more their function is complex (muscular fibre,
nervous fibre). Finally, the more the organisation of an animal,
taken as a whole, is simple, the simpler is also the structure of
each of the orders of anatomical elements. Thus the muscular
fibres of the radiata, the annulata, the mollusca, the nervous
tubes, the ganglionic cells of lampreys, are simpler than the
same elements in the crab.1

But in every superior organism there is a differentiated blend-
ing of anatomical elements, having varied functions and varied
degrees of structure. We could therefore, in every individual,
group the elements in series, according to their degree of perfec-
tion, of complication, and we should have a complete scale going
from the elements, confused and even amorphous, of the inferior
beings up to the elements with complex structure of the superior
beings.2

At the foot of the organic scale we find monocellular infusoria
(polytoma, difnugia, enchelys, monas, amoeba) formed of a single
homogeneous substance. Some of them are constituted of a sub-

1 Ch. Robin, Elements Anatomiques.

2 Ch. Bernard, Rapporteur lesprogrteet lamarchede la
en France. Paris, 1867.

40 BIOLOGY. [BOOK i.

stance slowly contractile, which seems to be the rudiment, still
undivided, of the muscular fibre ; it is a sort of non-figurate
muscular matter. This matter is called sarcode.

There seems to be in inferior beings, a confusion of organic
materials and functions. Many of the infusoria are endowed
with motility and sensibility, with a sort of instinct, and yet
they are destitute of muscular elements and nervous elements.

We can place in a degree immediately superior the plants and
the animals simply polycellular, that is to say, constituted of a
certain number of cells similar to each other and grouped. They
are beings formed of a single tissue.

On the other hand, at the outset of their embryological exist-
ence, the beings the most complex, the superior animals, man
not excepted, commence by being monocellular, then pass through
the polycellular state, the most rudimentary ; finally, in a last
period, their histological elements differentiate.

This gradual histological differentiation, which is observed in
the embryological development of superior beings, can also be
demonstrated in the palseontological succession of the organised
beings on our globe. In fine, it is easy to encounter it anew by
grouping living beings hierarchically, from the simplest to the most
complex. It is in this triple coincidence that the grand doctrine
of evolution, founded by Lamarck and Darwin, finds its most,
brilliant confirmation.

In the animal kingdom the figurate elements can be classed in
two great groups : the group of the constituent elements, which
forms the basis, the framework of every organised being, and that of
the produced elements, which plays a part more or less secondary,
and has an existence more or less provisional. It has been ob-
served that the constituent elements were generally situated in
the interior of the body, and the produced elements on the surface.
But this division, to which M. Charles Robin first of all, and Mr.
H. Spencer afterwards, accorded a supreme importance, is only,
like most classifications, a commodious arrangement for grouping
the elements. If it were literally accepted— and indeed it is so

CHAP, v.] CONSTITUTION OF ORGANISED BODIES. 41

accepted by M. C. Robin — it would be necessary to class among
the constituent elements the globules suspended in the blood,
the kaematia, which yet are evidently elements produced, and of
brief duration.

From the point of view of ultimate physical constitution, of
the mode of molecular collocation, we must consider every living
element as being formed by a blending, molecule by molecule,
of immediate principles, belonging to the three classes already
indicated. All these immediate principles are dissolved in one of
them, in water, which in weight is by far the most important
body. In effect, living elements need a certain minimum of con-
stituent water without which they can neither get nutriment nor
as a result perform their functions.

In the vegetal elements, as Sachs remarks,1 we can prove
this intimate blending of the immediate principles, by extracting
from those elements, by the aid of certain solvents, substances
chemically determined, without thereby changing the form of
the histological skeleton.

There exists between the anatomical vegetal elements and the
animal elements an important difference in the degree of chemi-
cal stability. The animal elements are much more easily alter-
able by physical and chemical agents. In plants there is a
certain degree of mineral fixity manifestly in relation with
their smaller degree of vital perfection and activity. MM.
Naegeli and Schwendener, studying carefully the play of pola-
rised light in the vegetal cellular membranes, the particles of
starch, and also in the vegetal crystalloidal bodies, have found
that in these vegetal tissues and elements there must be crystal-
lised molecules birefringent and with double optical axes. These
facts are perfectly in accordance with the difference of chemical
composition of tissues in the two organised kingdoms. We shall
see in effect that the most characteristic chemical element of
organised substances, azote, enters in relatively feeble propor-
tion into the composition of plants. Now the presence of azote
1 J. Sachs, Traite de E'ltanique, p. 768. Paris, 1874.

42 BIOLOGY. [BOOK i.

coincides always in living beings, with a more elevated degree of
vitality, a greater molecular mobility.

The action of certain chemical and physical agents on the
anatomical elements is in manifest ' relation with their constitu-
tion. In effect brought into contact with solutions of bichlorure
of mercury, of perchlorure of iron, of chromate of potash, of
alcohol, and of other substances eager in their thirst for water,
the anatomical elements lose their form and condense ; for they
then lose their constitutive water.1 It is for this reason that
alcohol definitively arrests the movements of the most resistant
of the animal elements, of the vibratile cells, of which we have
presently to speak, and that it kills in like manner the vibrions
and the spermatozoaries.

Heat, on the contrary, first of all accelerates the vital pheno-
mena ; under its influence the mobile cells move with more
rapidity, the functions of plants are accomplished with a greater
energy ; for a certain elevation of temperature facilitates the
chemical reactions and renders the osmosis more rapid. In like
fashion diffusion increases with temperature. For chlorohydric
acid we have in effect the following gradation : —

Diffusion at 15°5C= 1

„ 27° = 1-3545

„ 38° = 1-7732

75 » • • • •

49° = 2-1812

But if the temperature continues to rise, the functional exci-
tation promptly reaches a maximum point, beyond which it first
of all decreases and soon is annihilated. Because the heat
diminishes by evaporation the constitutive water of the elements,
and alters the composition of the albuminoidal substances when
it does not coagulate them ; a result which is irremediable. Sub-
jected to a temperature too elevated, the anatomical element soon
dies ; while cold, which likewise slackens and stops the nutritive
phenomena, does not always destroy them, sometimes merely

1 Ch. Robin, Elements Anatomiques, p. 20.

CHAP, v.] CONSTITUTION OF ORGANISED BODIES. 43

suspends them. The reason is that the vital activities- and pro-
perties are directly and solely derived from the physico-chemical
properties in the midst of the anatomical elements. Consequently
we see them grow stronger, or languish, vanish, reappear, or
hasten to final extinction, from the sway of the molecular move-
ments and mutations of which they are the expression.

2. Histology of Plants.

The vital functions are less numerous, less specialised in the
plant than in the animal, it being understood of course that we
except the most inferior organisms in the two kingdoms. We are
therefore justified in supposing, a priori, a less sharp specialisa-
tion in the form of the elements. This is what is actually the
case. While in the superior animal we find varied histological
types very clearly distinguished from each other ; in the plant,
on the contrary, the elementary forms are less decided, less dis-
similar, and sometimes they can be supplemented physiologically.

It is from the microscopical anatomy of plants that has sprung
the cellular theory, so contested at present in France, but gene-
rally admitted in Germany, and according to which every ana-
tomical element, vegetal or animal, has as direct origin a simple
cell. In effect, in the vegetal world, the utricular, the cellular
type greatly predominates. Every plant, from the simplest to
the most complex, is formed by an aggregation of cells, or of fibres
manifestly originating in cells.

Every complete anatomical vegetal element is a cell formed of
a double wall, of a content, and of one or more nuclei.

The external cellular envelopment is constituted, chemically,
by a ternary substance united to certain salts ; this is the cellu-
lose, composed of carbon, of hydrogen, and of oxygen. The
chemical formula of the cellulose is analogous to that of sugars.
It is C12 H10O10. When the histological element is complete, this
external membrane is interiorly lined with another very thin
vesicle ; but the second contains azote : it is albuminoidal. This
azotised membrane englobes a semi-liquid substance and one or

44 BIOLOGY. [BOOK i.

two small spherical or ovoidal bodies, likewise azotised. These
are the nuclei, in which are often included one or two nucleoles.
These azotised portions of the cell appear to be the seat of a
nutritive movement more intense than the others. They appear
also to be bound up with the period of development ; for
when the cell has lost its fluid content or protoplasm, it becomes
incapable of growth and of multiplication.

The contents of the vegetal cells are normally liquid or solid.
Liquid they can be formed of oil or of water, holding in sus-
pension either molecular azotised granulations, or particles of
fecula, or drops of oil or of resin, or finally, small green bodies,
very interesting, called chlorophyllian bodies. It is to these last
corpuscles that the green parts of plants owe their colour.

The liquid contents, non-oleose, are generally called protoplasm
by the botanists. According to certain botanists, this proto-
plasm is the really important part of the cell ; it secretes the
enveloping membranes, and the nuclei come forth from it by
diffe rentiation.

In any case, this protoplasm is assuredly albuminoidal, for it
precipitates through the chemical agents which precipitate
albumine, and iodine communicates to it the yellow coloration
which it gives to azotised organic substances.

The internal vesicle, the protoplasm, and the nuclei form an
albuminoidal whole, which Dutrochet was the first to succeed in
isolating, by destroying the external membrane with nitric acid
or dilute caustic alkalis.

To constitute the diverse vegetal tissues, the cells assume
various forms. For instance, the vegetal vessels by which, espe-
cially in plants, the liquids and the gases circulate, are at the
outset formed of cells juxtaposed longitudinally. After taking
this linear arrangement the cells are cemented, and their walls
are reabsorbed at the points where there is contact. The com-
munication once established, the contents of the cells in their
turn disappear, and the canal is formed. If the vascular bundle
is perfect, every trace of cellular cementation completely dis-

CHAP, v.] CONSTITUTION OF ORGANISED BODIES. 45

appears ; but in the case where the fusion of the elements has
been less complete, the vessel remains nodose, being fashioned in
the likeness of a chapelet.1 It is then called utmculous. Some-
times, instead of being juxtaposed in linear series, the formative
cells assume the shape of a vascular network.

According to M. Ch. Robin,2 we are able in vegetal tissues to
distinguish as clearly as in animal tissues a small number of
histological types. These types have as origin a cell ; but from
their advent they bear a distinct physiognomy, and they are
never seen undergoing or accomplishing mutual transformation.

The first of these types is that of cells properly so called,
ottering moreover a certain number of varieties according as
they are spheroidal, ovoidal, fibroidal, stellated, or cylindroidal.
It would be needful to range in this class the cells of the
epidermis of plants, those of the cork-tree, of cambium, and of
marrow. "We might naturally add the monocellular plants, such
as the red utricles which sometimes give a red tinge to the snow
of the Alps (protococcus nivcdis of Saussure), and the diatomous
plants. The second type is that of the filamentous cells, all
more or less cylindrical, and eight or ten times longer than they
are broad. We may cite as an example of filamentous tissues
the cells forming the mycelium of the cryptogams, and also
certain monocellular infusoria, such as the bacteria and the
vibrions, if indeed we admit that botany can claim as belonging
to its domain these dubiously-defined organisms.

Every plant solely composed of the two histological types
spoken of above, is a cellular plant.

The fibrous cells represent the third type. These are they
which, juxtaposed lineally, form the ligneous fibres of wood and
of liber.

Finally, the vascular cells form the fourth type. These are
they which by their linear juxtaposition and the partial reab-
sorption of their walls, constitute canalicules — vessels. To the

' In the sense of rosary or string of beads. — Translator.
8 £Uments Anatomiques.

46

BIOLOGY.

type of vascular cells belong the trachean cells with spiral filament,
the punctuated cells, and the laticiferous cells.

Ill
HI

y
!i

:is

Hi

-8} »-—

CHAP, v.] CONSTITUTION OF ORGANISED BODIES. 47

We are disinclined to admit that this classification, so sharp,
so decided, can be admitted in all its inflexible rigour ; but we
may accept it as giving a good general view, as grouping under a
small number of heads a great variety of vegetal and hisfcological
elements.

3. Histology of Animals.

The anatomical animal elements differ in general from the
vegetal elements in the threefold point of view of chemical
composition, of structure, and of form.

In effect, while in plants the anatomical element is in chief
part constituted by a non-azotised ternary substance, the cellulose ;
the animal elements, on the contrary, are formed especially by
the quaternary albuminoidal substances. No doubt we en-
counter in animals ternary substances analogous to the starch
and the cellulose of plants, but partially, secondarily, and in
small quantity. It is thus that we find in the tegument of the
arthropods, and even in all classes of the invertebrates, a matter
very analogous to the vegetal cellulose, chitine, which can trans-
form itself into glucose. But these points of detail do not
weaken the value of the grand general fact enounced above.

The general differences of structure are perhaps in proportion
to the differences of chemical composition. The albuminoidal
substances are in effect essentially colloidal, and consequently
must tend to a more unfixed morphology. Thus, while in the
vegetal cell we generally find an enveloping membrane with the
exactest limits, this membrane is often lacking in the anato-
mical animal elements. In the latter case the element is a small
figurate glomerule, approaching more or less the type fibre or the
type cell, and usually furnished with one or more nuclei and
nucleoles.

From the point of view of form, the difference between the
histological animal elements and the histological vegetal elements
is more marked still. The vegetal histological types are few,
and are all related directly and visibly to the cell. But the

48 BIOLOGY. [BOOK i.

anatomical animal elements have forms much more varied. In
those of them which merit the name of fibre*, there is often no
longer any trace of the cellular form ; and the animal fibres are
not even derived from original cellular elements, if we admit
with M. Ch. Robin the spontaneous genesis of the anatomical
elements in the blastemas.

This theory of the spontaneous apparition of the anatomical
elements in the living liquids has hitherto been rejected in
Germany, where is adopted in all its rigour the axiom of M.
Virchow — Omnis celhda e cellula.

In accordance with the terms of the German cellular theory,
every anatomical element, whatever it may be, has as origin
a cell ; it comes forth from it by gemmation or segmentation ;
and every element which departs from the cellular form is simply
a metamorphosed cell. It is not easy to understand how asser-
tions so directly opposed should be passionately maintained on
both sides by observers equally skilful. We are compelled to
admit that on each side there is a portion of truth. We
shall see when treating of generation that the French school
wishes to reject reproduction by division and gemmation in the
vegetal kingdom, in the initial period of embryonic animal life,
and in certain produced elements. According to this school, most
of the elements called constituent, that is to say, forming really
the framework of the animal organism, spontaneously arise, by
synthesis, by genesis in the living liquids, alike in the embryon
and the adult.

Let this be as it may, the cellular theory is convenient for
classifying the anatomical elements. In effect, while the parti-
sans of spontaneous genesis admit no bond of direct kinship
among most of the anatomical elements, strive especially to note
dissemblances and to multiply species, the partisans of the cellular
theory, preoccupied with the idea of a common origin, dwell
especially on resemblances, and thus arrive at forming a very
small number of elementary histological groups. According to
them there are only four types of anatomical elements and of

CHAP, v.] CONSTITUTION OF ORGANISED BODIES. 49

animal tissues, namely : 1. The elements of the cellular or con-
nective tissue ; 2. The cells remaining autonomous, that is to
say, the epitheliums and the glandular cells, to which might be
added the globules of the blood ; 3. The elements of the mus-
cular tissue ; 4. The elements of the nervous tissue.

The first of these tissues forms the general gangue, the support
of all the other tissues and elements. It is essentially composed
of cells called stellated cells, having a diameter of from Om ra, 050
to Om m, 060. These cells enclose a nucleus containing a
nucleole. They emit fibrillary prolongations concurring to form
the fibres of the cellular tissue, and which often seem to be
anastomotically connected with each other. Other fibres called
laminous fibres, because they are slightly flattened, form them-
selves in that same cellular tissue round elongated nuclei,
called embryoplaatic nuclei. The whole resembles a long wire-
drawn spindle. The laminous fibres emanating from those cells
form the chief part of the cellular tissue. They are very long,
grouped in bundles, and with an average breadth of Omm, 001.

According to this theory, we regard as appertaining to cellular
tissue the cartilaginous cells and the osseous cells. All these
cells are1 nucleated. The first are round or ovoid, the second
are irregular, and emit in every direction filiform prolongations,
anastomotically intertwined. These last cells, which form the
living mechanism of the osseous skeleton, have been called
stellated osseous corpuscles.

The cells called autonomous comprehend the globules of the
blood, which we shall describe further on, and the epitheliums.
Of these last elements, some serve to line, while protecting,
the animal membranes, the skin and the mucous membranes,
while the others play in the secretions an extremely important
part, to which we shall have occasion to return.

The epitheliums have as their first division the pavimentmis
Epithelium*, large cells flattened, and usually polyhedrical,
because they are subject to reciprocal compression. They
contain a nucleus and a nucleole, and their whole aspect vividly

E

50 BIOLOGY. [BOOK i.

recalls a pavement of hexagonal bricks. In animals they clothe
the mucous membrane with many conduits, and play especially
the part of a protecting varnish. As related to them may be
regarded the epidermic cells. Other epithelial cells are cylindrical
or cylindro- conical. Sometimes the free surface of these cells is
furnished with fine and mobile cilia. In that case the epithe-
lium is called vibratile epithelium.

We have besides to mention the globulous, the spherical
epithelium. We find it especially in the glands where its
function is to form, at the expense of the plasmas and the
blastemas, the special bodies destined to be secreted.

Finally, we signalise here for the sake of remembrance the
muscular elements, distinguished into fibre-cells and into fibres
properly so called ; then the elements of the nervose tissue, fibres,
and cells. We shall have elsewhere to describe in detail the
form, the structure, the functions of these elements, which may
be characterised as aristocratic.

CHAPTER VI.

OF LIVING LIQUIDS.

FOR centuries the humourists and the solidists have filled the
world, we mean the small physiological and medical world, with
their discords, with their furious strifes. As in all long wars,
there has been in this many a peripetia. Sometimes the triumph-
ant humours submerged their adversaries ; sometimes these, offer-
ing resolute front with their serried ranks, seemed to have fixed
victory for ever to their banners. Observation and experience
have ended by imposing on the belligerents their sovereign
arbitrament. It is at present demonstrated that between the
solids and the liquids of every organism there is less difference
than had long been believed. The solids come forth from the
liquids ; they come forth from them incessantly and return unto
them. Finally, between the solids or anatomical elements and
the living liquids, that is to say, the blastemas [blastemata] and
the plasmas [plasmata], there is a great analogy of composition.

The name of blastema is given to every living liquid, that is to
say, endowed with nutritive mollecular movement and interposed
between anatomical elements. The plasmas are also living liquids,
but circulating in canals, the blood and the lymph of animals
thus circulating. Blastemas and plasmas have a great analogy
with each other if we look at them in a general manner. They
both are living ; they both equally contain materials of assimi-
lation destined for the anatomical elements, and materials of
disassimilation which come forth therefrom, crystalloidal sub-
stances in process of transforming themselves to become assimi-
lable or organisable albuminoidal substances; and albuminoidal

E 2

52 BIOLOGY. [BOOK i.

substances tending to become ciystalloidal and to be expelled
from the organism. The vitality of the blastemas is naturally,
greater than that of the plasmas ; they may almost be considered
as elements which have lost their forms ; physically, they are
viscous liquids in which, generally, granulations are interspersed.
They are the organisable liquids by excellence. It is in the
midst of the blastematic liquids that the anatomical elements
of the embryons, or of the tissues constituted in process of
development or regeneration, have their origin, for instance,
after a wound.

1. — Vegetal Blastemas.

The plants, even the most perfect, the dicotyledons, have no
special circulatory system. In the dicotyledonous tree, the terres-
trial sap mounts through the tissues of the wood, filling the
intercellulary spaces, the canals, and passing by endosmosis
from cell to cell, from fibre to fibre. Arriving at the leaves it
undergoes an important modification, with which we shall have
to occupy ourselves ; then it redescends by the more superficial
tissues, and especially by the young intermediary tissues between
the bark and the wood. The descending sap, that which has
been elaborated in the leaves, must be considered as a living
liquid, as a blastema ; also, as it goes along we see it organising
itself either in a direct manner or through the agency of pre-
existent anatomical elements. In truth it is a liquid holding a
middle position between the plasmas and the blastemas.

The blastematic liquid, whence spring the buds, is thoroughly
comparable with the animal blastemas. Like these last it is
in part exuded by the anatomical elements, that is to say by the
vegetal cells which it drains off and dissevers. This mode of
formation recalls that of the vegetal and animal embryonary
blastemas.

The true vegetal blastemas resemble much the semi-liquid
azotised content of the vegetal cells, namely, that intracellular
substance endowed with spontaneous movements, having its

CHAP, vi.] OF LIVING LIQUIDS. 53

special molecular affinities, refusing, for instance, as long as it is
living, to let itself be imbibed by colouring matters. Now we
know that this intracellular protoplasma offers all the chemical
reactions of the true albuminoidal matters (albumine, fibrine,
easeine). Iodine gives it a yellow colour ; alcohol, the mineral
acids, and heat coagulates it.

Chemically, the vegetal blastemas are constituted by water,
by albuminoidal substances, and by some salts.

2. — Animal Blastemas.

There has been a wish to limit the name of blastemas, in the
animal economy, to the interstitial liquids alone in which new
anatomical elements are formed, that is to say, to the intercellu-
lar liquids of the animal embryons, before the formation of the
vessels, to the organisable liquids which are produced in a wound
in process of cicatrisation, finally to the liquids of the serous
cavities. But in biology, as in all other natural sciences, if it is
useful to divide, to classify, it is wise not to accord to divisions
and classifications an absolute value. The frontiers which we are
obliged here and there to mark out in the vast field of the living
world to aid the feebleness of our memory have only a relative
value. In effect, in the organic world, even taken generally, all
is gradual modification, gradual transition. If this is true, as
incontestably it is, in the classifications of natural history,
properly so-called, how much more must it be so when the aim is
to ascertain the constituent parts of one and the same organism 1
If we reserve the name of blastemas to the small number of
liquids living, interstitial, organisable, and generative, what are
we to do with the other interstitial liquids, with those which
bathe the elements of the tissue called conjunctive [connective],
of that tissue comparatively coarse in its morphology which
serves as gangue and as support to all the others ? And in most
tissues, wherever the elements do not touch each other at every
point of their surface, is there not an interstitial liquid, coming

54 BIOLOGY. [BooK I,

on the one hand from the tissues, and on the other from the
exterior medium 1 But these tissues constantly grow larger from
birth to the adult state or age, that is to say, that incessantly
during this lapse of time new elements arise and gain place in
the midst of the old. Evidently these elements are formed at
the expense of the interstitial liquid, which consequently then
becomes a true formative blastema.

Let a freshwater polypus be sectionised into several frag-
ments : immediately each of these fragments strives to complete
itself, strives to remake a complete individual; but this new in-
dividual once formed is not more voluminous than the fragment
whence it took its birth. It has therefore modelled and consti-
tuted itself at the expense of the interstitial liquid, bathing the
cellular tissue of the hydra ; therefore this liquid is formative ;
therefore it is a blastema. But blastema is likewise the inter-
cellulary liquid of the grey cerebral substance, that of the umbili-
cal cord, that of the marrow of the bones, and so on.

The chemical composition of the animal blastemas is a little
better known than that of the vegetal blastemas. Like these
last, they are composed of albuminoidal substances, of salts, and
of regressive crystalloidal substances ; lastly, of a great quantity
of water. But besides these general characteristics it has been
successfully demonstrated that the blastemas of the superior
animals have a composition different from that of the blood and
the lymph, from which chiefly they are derived. They possess
fibriiie and alburnine in smaller quantity. Largely albumine
takes iji'them its chemical, soluble, and assimilable form ; it be-
comes albuminose ^ no longer coagulates from heat, and coagulates
imperfectly and with difficulty through the acids. Fibrine is no
longer found therein, and nothing is more natural, for we know
that to become assimilable, nutritive, fibrine needs to be trans-
formed isomerically into albuminose.

There has been a desire to make of the chemical instability of
the blastemas a distinctive characteristic. No doubt the blaste-
mas are in a state of perpetual mutation ; they are never iden-

CHAP, vi.] OF LIVING LIQUIDS. 55

tical for two moments of duration. But we can say quite as much
of the blood, of the lymph, of the histological elements them-
selves, forasmuch as the movement of continuous renovation is
the primordial condition of life.

On the whole, between the anatomical elements, the blastemas,
and the plasmas, there is from the chemical point of view, merely
the difference in the proportion and the nature of constituent
immediate principles, but a difference graduated from each to
jeach. They are three forms of living matter, analogous to each
other and engendering each other.

3. — Of tJie Plasmas.

In the plant, the imperfect division of physiological labour, and
the confusion of functions, are so great that we find it difficult to
classify the organic liquids. We have signalised the liquids
evidently blastematic of the vegetal embryon, of the buds, the
liquid semi-blastematic and semi-plasmatic which is called sap.
Further on we shall say some words in reference to the secretion
of the vegetal glands and of their secreted products ; and thus
we shall have passed in review all the vegetal organic liquids.
The thing is less simple in animals, or at least in the superior
animals. The division of labour is more advanced in the tissues
and the liquids, and we must carefully classify both of them.

In the superior animal the organic liquids can first of all be
divided into two great groups corresponding to the two great divi-
sions of the solid elements ; they are the group of the constituent
humours, and that of the produced humours.

The chemical composition of each group, and even of the
humours of each group, is very various ; but in a general manner
we can say, that they all contain immediate principles of the
three orders : *

1 . Principles of mineral origin (water and dissolved salts) ;

2. Principles of organic origin, some crystallisable, others
coagulable (urea, creatine, lactates, choleates, and so on) j

1 Ch. Robin, DCS humeurs, p. 20, 21, 8vo.

56 BIOLOGY. [BOOK i.

3. Principles non-crystallisable, but coagulable, met with in all
the humours, except the bile, the urine, and the sudor. These last
immediate principles are the albuminoidal substances properly so
called, and the saccharine substances, both of them having the
property of dissolving certain mineral or mineralised compounds
little or not at all soluble in water. It is thus that albumine
fixes silica, phosphate of lime, urates, and so on.

The humours produced or humours of secretion, are formed in the
economy at the expense of the constituent humours, and generally
by special organs called glands. By and by we shall have occa-
sion to study their process of formation. They comprehend the
extremely aqueous liquids, produced on the surface of the mem-
branes, called serous, which cover certain viscera (brain, heart,
lungs, intestines, and so on) ; the liquids bathing the articular
surfaces or synovial liquids ; lastly the sperm, the milk, the muci,
the salivae, the bile, the intestinal juice, and so on.

In connection with the produced humours we may view the
liquids simply excreted, that is to say, separated from the con-
stituent humours without chemical modifications (sudor, urine,
amniotic liquid, allantoi'dian liquid, pulmonary exhalation).

All these liquids, save three, are alkaline. The three liquids
habitually acid are the gastric juice, the sudor, and the urine.
However, this last liquid is sometimes alkaline, sometimes acid,
sometimes neutral, in man, at the different stages of digestion.
In the herbivorous mammifers it is normally alkaline. But here
also the alkalinity depends on the digestion. In effect the urine
of the herbivora becomes acid if we feed them on animal ali-
ments, or, which comes to the same thing, if dieting them, subject-
ing them to inanition, we force them to live at the expense of their
own substance. The alkalinity of the animal humours is usually
due to salts of bibasic or tribasic soda ; but free soda we never
meet with in them.

In connection with secretion and excretion we shall speak in
detail of the produced humours, contenting ourselves here with
indicating their principal distinctive characteristics.

CHAP, vi.] OF LIVING LIQUIDS. 57

We have now to describe the humours of the first order, the
humours constituent, living, those which may be regarded in
some sort as liquefied anatomical elements. These liquids, which
exist with supreme distinctness only in animals with complex
structure, furnished with circulating apparatus well denned, are
only two in number, the blood and the Lymph ; for we must con-
sider the chyle, that is to say, that ultimate product of digestion
circulating in the lymphatic vessels, a dependency of the lymph.

The blood and the lymph are contained in circulatory systems,
ramified and inclosed in every direction. These circulatory systems
imprison the liquids which are formed in them, without, normally,
permitting them to break forth in mass. But across their walls
they leave an easy passage to many materials coming either from
the tissues, or from the ambient medium and to many others which
escape from the blood and the lymph, either to nourish the tissues,
or to be expelled as unworthy from the frontiers of the organism.

This double movement of coming and going, of exchange of
materials, is effected simultaneously, like the nutritive assimila-
tion and disassimilation in the solid elements. In truth the
blood and the lymph are living liquids, in process of perpetual
renovation. Incessantly they are formed in the system of the
canals where they circulate without being destroyed.

The vascular walls which contain the constituent liquids do
not seem notably to modify the chemical composition of the sub-
stances which traverse them. The part they play is especially
physical, osmotic. Therefrom it results that the blood and the
lymph borrow their constituent materials already formed from
an ambient medium, either from the grand cosmic medium, the air
for example, or from the organic medium, the tissues, the
myriads of anatomical elements which compose the body of the
superior animals.

Considered as organised liquids, the constituent humours neces-
sarily contain immediate principles of the three classes ; but those
of the third class, the albuminoids of organic origin, not crystal-
lisable or coagulable, predominate therein. They are albumins

5S BIOLOGY. [BOOK i.

or rather serine,1 and plasmine, which severed from the living
organism, evolves itself into fibrine spontaneously coagulable and
into fibrine called liquid. To these albuminoidal substances we
must add variable proportions of peptones and albuminose, that
is to say, of albuminoidal alimentary substances liquefied and
absorbable.

The blood and the lymph are not homogeneous, physically
simple liquids. We meet with, in them, floating bodies which
are true free anatomical elements. ' These bodies have been called
globules. The liquids in which these globules swim in immense
numbers have received the special name of plasmas.

These plasmas isolatedly considered are endowed with nutrition ;
they are consequently living. They contain in proportions almost
equal, immediate principles of the three orders ; nevertheless
the coagulable principles predominate. If nutrition ceases in a
plasma, that is to say, if this liquid dies, its composition immedi-
ately changes ; the albuminoidal principles which it contains
evolve into a liquid portion and another portion spontaneously
coagulable. It is this which, in animals provided with a circula-
tory system, produces the cadaveric rigidity.

The office of the plasmas is of supreme importance ; but to
obtain a complete notion thereof we must figure to ourselves
what every complete organism is from the point of view of tex-
ture. At the lowest degree of life and organisation, we find
rnonocellular beings, free anatomical elements, simple infusoria,
living habitually in the water ; for directly or indirectly, the
anatomical elements are generally aquatic entities. These the
monocellular organism absorbs and assimilates, disassimilates, and
secretes, directly borrowing materials from the ambient me-
dium, or restoring them to it. In beings a little more complex
composed merely of cells identical with each other, and simply
juxtaposed, the nutritive process is scarcely more complicated.
In effect, the polycellular organism, with cells which resemble
each other, is definitively nothing more than a collection of juxta-
1 Ch. Robin, DCS Tissus, p. 21.

CHAP, vi.] OF LIVING LIQUIDS. 59

posed monocellular organisms. However there is usually a gene-
ral enveloping membrane and afterwards an interstitial liquid,
a sort of blastema, playing, in respect to the anatomical elements
of the polycellular organism, the part of an artificial medium.
The cells now no longer plunge direct into the cosmic medium ;
they are protected and isolated by an organic, an elaborated
liquid. In the extremely complex organisms, for instance, in the
superior animals, the intrication of the texture is much greater.
Here the anatomical elements are not formed in one mould only ;
they are differentiated according to multiple types, and each type
assumes a diverse function. One, for instance the epithelial type,
supplies to the living membranes a protecting varnish ; to the
glands a special agent of secretion; another, for example, the
tissue called cellular, serves as gangue, as bond, as support to all
the tissues, apparatus and organs, while opening besides a passage
to blastematic liquids. A third, exemplified in the osseous
element, furnishes to the organism a solid framework. Lastly,
the muscular fibre and cell impress on the pieces of the living
apparatus the necessary movements, while the nervose fibre and
cell endow the organism with sensibility, with will, with thought,
and are the sentient soul of the entire being, of which they
assume the conscious direction, and so on. But in order that
these anatomical elements so diverse, so numerous, grouped into
tissues, into organs, into apparatus, into special systems, may
live, may perform their functions, may co-operate, it is needful for
them to be almost completely withdrawn from the rough and
capricious influences of the exterior world ; they must perform
their functions in an artificial medium, alive like themselves, in
which they find a temperature little variable, a magazine always
well provisioned with substances elaborated and assimilable, suited
to repair their losses ; Lastly, a place of discharge, into which they
throw their used materials, that have become unfit to figure
in the vital movement. These nutritive media, artificial, liquid,
consequently appropriate for the aquatic life of the anatomical
elements, are the plasmas, always in movement, always renewed,

60 BIOLOGY. [BOOK i.

yielding incessantly materials to the exterior world and to the
tissues, and incessantly taking them back, having a temperature
nearly equal, as long as that of the exterior medium does not
suffer very great oscillations. For the anatomical elements, the
plasmas are a veritable living atmosphere.

4.— Of the Blood.

In the vertebrates the most important of the plasmas, the
blood, is a red sap unceasingly circulating with greater or lesser
activity. In the invertebrates the blood is animated by a much
slower movement of translation. It is contained in apparatus
not so well constructed, and is generally colourless and trans-
parent like lymph. Often even the blood and the lymph of the
iiwertebrates are confounded ; where there are distinct san-
guineous cavities and lymphatic cavities, as happens in some
annelate worms, the blood is tinted with a special colour —it is
sometimes red, sometimes yellow, green, violet, or bluish. The
sanguineous cells which it sometimes in that case conveys, are
almost always colourless. However, there are sanguineous,
coloured globules in the terebella and the cephalopods.1

The blood of the vertebrates, with which we have especially
to occupy ourselves, is, according to a felicitous comparison of
Cl. Bernard,2 an interior medium, in which live the anatomical
elements as the fishes live in the water. These anatomical
elements, moreover, retain in the blood their physiological inde-
pendence, and- though drawing their nutritive materials from the
sanguineous plasma, they do not allow themselves to be imbibed
by it, which is an essential condition of endosmotic exchanges.
Consequently we see, for example in the blood of the vertebrates,
potash dominating in the globules, and soda in the plasma.

The physical qualities of the blood of the superior vertebrates

1 R. Wagner, quoted by Fr. Leydig (Traite d'ffistologic de VHomme et das
Animaux, p. 509, Paris, 1866.)

a Cl. Bernard, Lemons sur Ics Proprieles des Tissus vivants, pp. 55-58.
Paris, 18C6, Svo.

CHAP, vi.] OF LIVING LIQUIDS. 61

are well known. In these perfected organisms the blood is a
liquid slightly viscous, of a purple red in the arteries ; that is to
say, when it is freshly impregnated with aerian oxygen, but of a
blackish tint, more or less deep in the veins ; that is to say,
when from contact with the tissues it has exchanged its oxygen
for carbonic acid. It is well known that the temperature of
these two bloods differs, that of the venous blood being a little
more elevated in the right ventricle of the heart and in the
deeper veins — an elevation which we must evidently attribute to
the chemical reactions of nutrition, the residua of which the
venous blood collects.

It is also known that the blood, as soon as it is drawn from
the vessels, separates into two parts— a red coagulum containing
the globules, and a liquid part of a lemon yellow, which is called
tenon.

The blood, we haye said, is a medium from which all the
anatomical elements of the organism derive the materials needful
to their life; and into which they pour all their nutritive residua ;
its chemical composition must therefore be very complex. We
find therein in effect immediate principles of the three classes, and
we find therein in great number. We must content ourselves,
therefore, with signalising the chief of them.

The principles of the first class, wholly mineral, are first of
all water, which quantitatively is the most important element,
as, moreover, the figure for the density of the blood shows, which
on an average is only 1,050. In quantity, water in man repre-
sents from 905 to 910 thousandths of the blood. The proportion,
however, notably varies ; it is more considerable in the infant,
the young man, the pregnant woman ; in short, wherever the
formation of new anatomical elements necessitates the fixation
of many solid materials. In this liquid mass all the other
immediate principles are dissolved, and the globules travel along.

The immediate gaseous principles of the first class are oxygen,
azote, and hydrogen. The first of these gases, which is by far
the most important, comes from the exterior air from which it is

62 BIOLOGY. [BOOK i.

borrowed by the respiratory organs, as we shall see when speak-
ing of respiration. It is oxygen which, combining with the
globules or hsematia, gives them the vermilion tint which they
have in the arterial blood. But the globules do not keep their
oxygen long. Elaborated in the fine circulatory vessels, where
they are in almost immediate contact with the anatomical ele-
ments, they surrender to them their vivifying oxygen, indispensable
to the chemical reactions of nutrition. In exchange they take
back the gaseous residuum of the oxydation of the tissues, the
carbonic acid, which gives them a blackish tinge, that of the
venous blood. It must be observed that the sanguineous globules
never completely despoil themselves of one of these gases to
impregnate themselves completely with the other. They retain
them simultaneously, oxygen predominating in the arterial blood,
carbonic acid in the venous blood. It suffices, besides, for the
gases to be in equal quantity in the blood for the globules to
become blackish. The change in the proportion of the two gases
is not effected suddenly, but by degrees— in proportion as the
arterial blood goes away from the lungs and the heart to approach
the tissues, the oxygen gradually yields the place to the car-
bonic acid.

The water of the blood is not normally free ; it is found com-
bined with albuminoidal matters. This is why it cannot nitrate
mechanically through the vascular walls. Almost in totality it
comes from the aliments, for it is doubtful whether any notable
quantity thereof is formed in the organism.

The immediate saline principles of the first class which are
contained in the blood are the chlorures, the chlorohydrates, the
sulphates, the carbonates, the phosphates, and so on. Of all the
salts, the chlorure of sodium is by far the most abundant in
the blood of man. The proportion of the salts varies, besides,
according to the animal species.

The phosphates predominate in the blood of the carnivora, but
yield the superiority to the carbonates of soda and of potash in
the herbivora. This is, after all, as we have remarked in refer-

CHAP, vi.] OF LIVING LIQUIDS. 63

ence to urine, a pure affair of alimentation. It is to the basic
phosphate of soda and to the carbonate of soda that the blood
owes its alkaline reaction.

M. Ch. Robin l remarks that the different salts of the blood
serve as mutual solvents, and that the phosphates and carbonates
of soda permit the sanguineous liquid to dissolve a great quantity
of carbonic acid. In the economy, in effect, the blood is never
saturated with carbonic acid. Venous blood brought into contact
with carbonic acid, still suffices to dissolve thereof Omg> 48 in 100.
Thus it always seeks this gas eagerly, and is ready to disengage
therefrom the anatomical elements.

We must cite, by way of remembrance, traces of silica, of
manganese of lead, of copper, fortuitous mineral elements, little
or not at all useful to nutrition, but drawn along with the others
into the living organisms. It is otherwise with iron, which
seems to play an important part, to form a really constituent
portion of the sanguineous globules, though it exists in a very
small quantity, for the total quantity of iron in the blood of an
adult man is reckoned to be not more than one gramme.2

Other salts, the salts of soda, of potash, of lime, belong like
the preceding to the immediate principles of the second class.
They are organic salts, nutritive wastes. Let us mention the
urates and inosates of soda, of potash, and so on, which probably
result from the disassimilation of the muscular tissue, &c.

But the disassimilation of the anatomical elements gives birth
to many other principles more complex, more organical, to sorts
of alkaloids. These crystallisable principles, always in a state
of liberty in the blood, are urea, creatinine, creatine, inosite.
There has been an attempt to determine the place of origin of
these diverse products. It is said that creatine and creatinine
come from the muscles, urea from the tissues, fibrous, laminous,

serous.3

•

1 Ch. Robin, Des Humeurs.

2 A French gramme is nearly equivalent to nineteen grains English. —
Translator. * G. See, Du Sany et dcsaiUmies.

.
64 BIOLOGY. [BOOK i.

We may view in connection with these substances cholesterine
and seroline, formed probably in the nervous tissue.

All these bodies pass by osmosis through the fine capillary
vessels, and sojourn in the blood till they are secreted or excreted
therefrom.

The other azotised substances of the blood belong to the third
class of immediate principles. They are the albuminoidal sub-
stances, properly so called. Urea, creatine, creatinine, and so
on, are azotised regressive principles, residua of disassimilation :
they form part of the material current coming forth from the
organism. On the contrary, the other albuminoidal substances
are the residuum of the alimentary elaboration. They are des-
tined to repair the waste of the tissues, and form part of the
material current entering the economy.

When the blood of a mammifer is drawn from the vessels, and
allowed to rest, it separates into a red clot and a yellowish liquid.
The 'clot is composed of an azotised complex substance, which
has been called fibrine, because it has then a fibrillary aspect, and
this coagulated substance retains in its meshes the red globules.
The ambient liquid contains in solution another azotised sub-
stance, denominated albumine, because it has affinity with the
albumen of the egg, though containing a half less sulphur. For
a long time there was an erroneous belief that fibrine and albu-
mine have as distinct existence in the economy as in the blood
when drawn. Fibrine and albumine are, however, isomeric,
albumine merely containing a little more water. From important
analyses of the blood made by Denis, of Commercy,1 it results
that in effect the blood contains albumine, which Denis prefers
to call serine ; but instead of fibrine there is in the blood another
analogous azotised substance, which he calls plasmine. This
plasinine, he thinks, evolves itself in the blood when drawn, and
thanks to the intervention of the globules, into a coagulable part
called fibrine, and into another soluble albuminoidal substance,

1 Denis, Comptes rendus des Seances de r Academic des Sciences. Paris, 1S5G
and 1858. — Memoire sur le Sang, Paris, 1859, 8vo.

CHAP, vi.] OF LIVING LIQUIDS. 65

which remains in the serum with the albumine or serine and
can be separated therefrom. That all these determinations of
contemporaneous chemistry are destined to be maintained intact
in the future we do not believe.

In effect, the albuminoidal substances are extremely unstable ;
those of the economy are probably isomeric, or nearly so. Their
chemical formula has not even yet been determined. They are
not naturally absorbable, except on condition of being soluble ;
the fibrine and the albumine of the aliments are transformed by
digestion into isomeric substances called peptones, albuminose,
whose degree of relationship with the plasmine and the serine
of Denis has not yet been determined. In short, these are
questions the precise solution of which must be reserved for the
chemistry of the future.

To conclude what we have to say on the principal organic
materials of the blood, let me mention the fine guttulse of fat
matter floating in the blood after digestion, in the state of emul-
sion. These fat bodies are absorbed by the tissues, which yield
them afterwards to the sanguineous liquid, in the state of com-
bination, saline, saponaceous, and soluble (butyrates, phosphorised
fat matters). Let me mention, lastly, a certain quantity of glucose
or sugar of grape.

The mineral substances dissolved in the blood are not all in
the state of simple blending. If we inject into the blood first
of all a solution of a salt of iron, then a solution of prussiate
of potash, we do not obtain the characteristic reaction of the salts
of iron, the formation of Prussian blue, because the albuminoidal
substances of the blood have at the very outset fixed the salt of
iron. On the contrary, we obtain Prussian blue if we inject
first of all the prussiate of potash, because the albuminoidal
substances leave this salt free (Claude Bernard).

5. — Of the Red Sanguineous Globules.

If we examine in the microscope a guttula of blood, we find
small floating bodies, extremely numerous, pressed against each

F

BIOLOGY.

[BOOK i.

other, and every one of which seems to be an isolated cell. A
more attentive examination soon shows that these bodies are
rather glomerules than real cells, for they have neither nuclei
nor enveloping membranes. They are small flattened disks,
depressed in the centre on their two faces, an arrangement which
often simulates a nucleus. Their diameter is from Omm, 006 to
Omm, 907, in the adult man. But their form varies in the series
of the vertebrates, and also in man and the mammifers if we
remount to the first stage of the embryological life. In effect,
at the epoch when the embryon has only a length of Om, 02 to
Om, 03, where the globules begin to appear, they are white, and
have a veritable nucleus. According to some authors they then
multiply by segmentation. They are now much longer, and their
diameter attains Omm, 010, to Omm, Oil.

In the animal series we also observe very notable differences
in the form, the volume, and the struc-
ture of the sanguineous globules. As
long as we are simply considering the
class of the mammifers, these differences
are slight. However, the sanguineous
globules of the camel and of the llama
have an ovalar ellipsoidal form, and re-
semble those of birds and reptiles. In
the elephant and in the didactylus sloth
we also find sanguineous globules much
longer than in the other mammifers.

In the other classes of vertebrates the
differences grow more striking. In all
the vertebrates the globules are, as in
Frog.- a and 6 front view and' man, of a red colour by reflection, and

profile of a red globule ; c, . , . , , , , , , TIT • •

white globule, 500 diameters, it IS to them that the blood OW6S its
Man. — d and e, front view and ,.-, ,. , T -, ,-, 111

profile of a sanguineous gio- rutilant tint. In general the red glob-

of the mammifers are less volu-

of the chyle, 800 diameters. minous than those Qf the other clasges Qf

vertebrates. They are elliptical and nucleated in the classes of

CHAP, vi.] OF LIVING LIQUIDS. 67

birds, of amphibia, and of fishes : elliptical only in the class
of reptiles. There is no absolute rule, however. The fact of the
existence of globules in the blood of an animal is very important ;
but their form is much less so. We have seen that certain
mammifers have elliptical sanguineous globules like those of
birds. On the other hand, the humblest of the vertebrates, fishes
of an inferior order, such as the genera myxine and petromyxon,
having affinity with the celebrated Amphioxus lanceolatus, have
like man sanguineous globules, circular and with double depres-
sion. Lastly, as a second link of the chain between the branch-
iostoma without globules,1 as an invertebrate, and the fishes with
globular blood, is found a fish with white, colourless globules,
the leptocephalus. But, on the whole, in spite of some exceptions,
the red globules, or h&matia, are found in the blood of nearly all
the vertebrates ; they are the anatomical and physiological sign
of a complete organisation, of a more active respiration, of a
higher vitality.

In the blood of man and of the mammifers, the sanguineous
globules are in immense number. According to Schumann,
Andral, and Gavaret, the red globules in the humid state form
in volume the half of the mass of the blood.2 Furthermore,
Yierordt has counted, in a cubic millimetre of blood, from
4,180,000 to 5,551,000 globules.

The younger the individual the greater is the proportion of
haematia. The blood of the adult man contains 302 thousandths
according to Ch. Robin.3 There is much more in younger persons,
and in the new-born child the proportion rises to 600, to 680,
and even to 700 thousandths. A German anthropologist, Dr.
Welcker, has demonstrated that from the point of view of the
form and the proportions of the cranium and of the face,
woman holds an intermediate position between the adult man
and the infant. In regard to the hsematia, the relative propor-
tion is the same, rising in women to 320 and to 400 thousandths.

1 Eetzius, J. M tiller, De Quatrefages. 2 G. See, Du Sang et des An6mies, p. 15.
3 Ch. Robin, Des Humeurs.

p 2

«8 BIOLOGY. [Boos i.

The hsematia are veritable histological elements floating in the
sanguineous plasma. Like everything which lives, they assimilate
and disassimilate incessantly. Each of them has probably only a
brief duration. According to the German cellular doctrine, they
spring in the embryon, from pre^existent cells, and multiply after-
wards by segmentation, by cellular division : but the point is not
one which direct observation has yet elucidated. It is certain,
however, that the hsematia are remade in the blood, for a few
weeks or a month suffice to cure the anaemia caused by too copious
blood-letting or by excessive haemorrhage. In an animal sub-
jected to abstinence, the globules diminish in number, lose their
shape, and shrink. It is probable that incessantly the more aged
of the hsematia dissolve in the blood, and are replaced by hsema-
tia of new formations. These fresh growths have their birth
either in the lymphatic glands, or in the special glands (thyroid
body, spleen, and so on).

The physiological characteristic of the hoematia is the property
they possess of absorbing liquids with a great energy. This
property is inherent in their very substance, independently of
their form. In effect, a solution of this substance grows red in
contact with oxygen, and becomes less rutilant from contact with ;
carbonic acid. The affinity of the substance of the globules for
oxygen is quite comparable with that of the green matter of
leaves, chlorophyll, for the carbon of aerian carbonic acid. It,
is by reason of this powerful affinity for oxygen that in the'
sanguineous transfusion practised in men and the mammifers the
injection of mere globules suffices to provoke real resurrections.
The blood extracted from the vessels continues to appropriate
oxygen and to exhale carbonic acid. From contact with oxygen
the hsematia swell, and tend to lose their double depression.
Carbonic acid, on the contrary, makes them shrink.

In like fashion in the vertebrated organisms, the function of
the hsematia is to imbibe many volumes of oxygen during their
passage through the respiratory organs. Once impregnated with
oxygen, the globules give to the blood a tint rutilant, vermilion.

CHAP, vi.] OF LIVING LIQUIDS. 69

The blood is then called arterial: thereupon the globules are
conveyed with their provision of oxygen into the circulatory
apparatus. Soon they find their way to the finest vessels of
this system, where they are almost in contact with the anatomical
elements of the tissues. Between the globules and the anatom-
ical elements an exchange of gas is there accomplished which is
one of the primordial acts of nutrition.

In effect, the vital condition by excellence for every anatom-
ical element is to be oxydized, more or less slowly. But this
process of oxydation produces, along with other chemical com-
pounds, carbonic acid gas, which, if it was not eliminated in the
degree of its formation, would soon bring death to the anatomical
element. The function of the red globules of the blood is pre-
cisely to take back that carbonic acid, and to furnish in exchange
their vivifying oxygen.

The visible sign of this gaseous exchange is the change of
coloration of the globule, which becomes blackish when it has
parted with its oxygen to charge itself with carbonic acid. This
black or venous blood contains much less oxygen than the arterial
blood. According to Magnus, there is in the arterial blood
38 of oxygen to 100 of carbonic acid, and the proportion is only
22 to 100 in the venous blood. The venous blood is blood im-
poverished by nutrition ; it contains fewer globules, less fibrine,
and on the contrary more salts, a certain number of which are
nutritive residua.1

Every anatomical element transforms oxygen into carbonic
acid by the mere agency of nutrition ; but it consumes a much
greater quantity when it exercises a special function, and then
the absorption of oxygen is rigorously in proportion to the
degree of activity of the chemical element. For instance, if
we cut all the veins which are distributed to a muscle, all volun-
tary contraction becoming for it now impossible, the arterial
blood traverses it, losing only a small part of its oxygen, and
it is red when it passes into the veins (Ch. Bernard). But if
1 Longet, TraiU de Physiologic, t. I., p. 581.

70 BIOLOGY. [BOOK r.

afterwards, exciting one of its nerves by an electric current, we
contract the muscle, immediately a certain consumption of
oxygen responds to the contraction ; in the passage the globules
are charged with carbonic acid ; they grow black ; they become
venous. Analogous phenomena are observed for the same reason
during the hibernal sleep, during syncope ; and the case must be
the same for the blood traversing the veins during dreamless
slumber.

Claude Bernard has shown that we can produce at will the
changes of coloration in the blood by the section and the excita-
tion of certain nerves.

Essentially in all these special cases of organic atony, there is
a general phenomenon : the inaction or the diminished action of
the tissues, and of the organs; hence the superabundance of
oxygen in the blood. We see therefore that in a certain sense
we only need to determine the absorption of oxygen by a tissue
to measure the degree of its functional activity.

The exchange of gas between the tissues and the globules
is probably accomplished by osmosis and diffusion. We must
nevertheless remark that in all likelihood the oxygen is in the
state of combination with the substance of the globule and the
hsematoglobuline. In effect, an organic acid, the pyrogallic acid,
which is greedy of oxygen, and absorbs it with special ease and
eagerness when it is in solution in the alkaline liquids, succeeds
not however in despoiling thereof the globules of the blood.
These globules indeed have for oxygen such affinity, that in the
arterial blood they absorb it almost in totality, and rob thereof
almost completely the plasma. Like all chemical phenomena, the
combination of the globules and of the oxygen is influenced by
the temperature. At a low temperature it ceases to be accom-
plished : — for instance in the body grown cold of a mammifer
in the state of hibernal sleep. On the contrary, when the
temperature rises, the fixation of the oxygen becomes easy,
proceeding as far as 40 to 45 degrees. [Centigrade scale.]
Beyond that point the oxydation of the globules tends to

CHAP, vi.] OF LIVING LIQUIDS. 71

taggeration : there is stable combination, something analogous
to what takes place when the globules are in contact with the
oxyde of carbon, their special poison : the globule then loses its
precious osmotic qualities ; it is killed.1

6. — Of the White Globules of tht Blood.

The white globules of the blood, or leucocytes, are pale spherical
globules, sarcodic, amceboidal, having a diameter of Omm, 008 to
Omm, 014.

Water and acetic acid pale them and enable us to perceive from
one to four granulous masses or nuclei. In the foetus the substance
of the leucocyte is less dense, and not granulous ; we see
therein one or two granulous nuclei. We find also in the blood
free or globuline nuclei from Omm, 003, to O^ 005 in diameter,
granulous, without nucleoles.

In the blood of Man they are in the proportion of about 1 to
300 red globules : but- we meet with them in greater number in
woman (1 to 250). They are the more numerous the younger
the person is.

From one to two years old . . . . 1 in 100

Newborn children 1 in 100 to 130

Human embryon 1 in 80 to 100

We thus see that in relation to the number of leucocytes the
woman takes position anew between the man and the infant.2

1 The proteic matters of the globule differ completely from the surrounding
fibrine. They Lave even their special inorganic compounds. The alkaline
phosphates predominate in the globules, and have especially a potassic base.
In the serum, soda and lime hold sway. The globule contains ten times more
phosphates, two times less chlorure, ten times more potash, and three times
less soda, lime, and magnesia than serum.

"We likewise behold the predominance therein of fats, especially of phos-
phorised fats, analogous to those of the nervose substance.

Lastly, we know that the iron contained in the blood is entirely confined to
the globules. Besides, the substance of the globule, though albuminoidal, is
crystallisable. (G. See, Du Sang et des Anbnies.)

* Ch. Robin, Des Hnmeurs.

72 BIOLOGY. [BOOK i.

Sometimes the leucocytes are in considerable number in the
blood, to which they communicate a greyish tint or the tint of
wine lees. Their number in such cases attains and even sur-
passes the infantine and embryonary proportion. It is important
to remark that in such instances of leucocythcemia, there is
generally a swelling either of the liver, or of the spleen, or of
the lymphatic glands.

The leucocytes are not met with merely in the blood : they are
also found in the living plasma, which we have yet to study, in
the lymph, and then it is observable that they are more
numerous in that liquid when it is examined beneath the
lymphatic glands.

Lastly the leucocytes float in variable numbers in most of the
humours of the economy. We can view them in relation to the
granulous corpuscles existing so numerously in pus. However,
in these last globules the amoeboidal movements are less evident,
and the nuclei not so easily seen.

The leucocytes are met with in the blood of all the mammifers
and also in that of birds, of reptiles, and of fishes. However,
while the red globule is peculiar to the vertebrates, the white
globules, on the contrary, exist also in the invertebrates.

"We have signalised the presence of the leucocytes in pus ; but
we also find them in the blastema of cicatrices, in what is called
the plastic lymph.

We can only make conjectures more or less plausible on the
office of the white globules. Peradventure we may regard them
as a transitory, primitive, state of the red globules.

We know in effect that the first embryonary globules, those
which we cannot help regarding as the first pattern of the red
globules, are nearly colourless, like the white globules, that like
them they have a nucleus, and lastly, that certain inferior verte-
brates have only colourless globules. The abundance of the
leucocytes in the blood of the mammiferous embryon comes also
as a confirmation of this hypothesis. If this manner of regard-
ing the subject had a solid foundation, then by bringing into

CHAP. vi.l OF LIVING LIQUIDS. 73

fellowship with it the presence of the leucocytes in the lymph,
their greater number after that this lymph has passed through
the ganglions, the swelling of these ganglions, either of the
liver or of the spleen in leucocythsemia, we should be tempted
to consider these glands and these ganglions as the original
sources, as the centres of creation of the sanguineous globules,
which before taking the red tint, before growing retractile, to
assume the form of hseniatia, begin by being leucocytes.

In leucocythremia there would seem to be a superabundance
of globular formation, while these elements are more voluminous,
blended with a great number of free globulines. Hence the
difficulty of their transformation into red globules.

l.—Of the Lymph.

It is a familiar fact that besides the grand circulatory system,
composed of arteries, of veins, in which a propulsive organ, the
heart, drives incessantly the blood on, there exists in the superior
vertebrates a second circulatory system, without central organ of
propulsion. This system, composed of an immense and fine
network, which is bestrewn with special glands, called ganglions,
has its origin partly in the mechanism of the tissues, and
especially on the surface of the membranes, partly around the
thinnest sanguineous vessels, the capillaries. In this lymphatic
system circulates slowly a yellowish, transparent plasma, convey-
ing white globules, and containing, like the blood, immediate
principles of the three classes : it is the lymph. The materials
of the lymph come, in chief part, like those of the blood, from
anatomical elements, and they come from them likewise by
osmotic process. The portion of the network clothing the
stomachal and intestinal mucous membrane absorbs direct the
nutriments, and especially the emulsionized fats, which, during
digestion, give it a lacteous tint.

The lymph is not borne on in an endless circuit like the blood.
In effect the whole system ends, in man, in two principal trunks,

74 BIOLOGY. [BOOK i.

throwing itself into two huge venous vessels, the right and the
left subclavian veins.

The lymphatic plasma, so analogous to the sanguineous plasma,
acts exactly like it when drawn from the vessels. There is
ovolvement of plasniine and the formation of a fibrinons clot.

Like the blood, the lymph is alkaline. It contains nearly the
same immediate principles, but in smaller quantity, and more
diluted. As its course is very slow, a result is that it has not
everywhere, like the blood, a composition observably uniform.
On the contrary, this composition varies with every region, with
the hour of digestion, and so on. In general the lymph is the
more charged with substances, the nearer our examination
extends to its chief trunks of communication with the sanguineous
system.

In the mammifers the lymph is a liquid essential, indispensable
to the duration of life. If in these animals we form a fistula
in the largest lymphatic trunk, the thoracic canal, the lymph
being no longer able to blend with the blood in sufficient quantity,
we see the patients rapidly grow lean and die, even while
continuing to take food.

What is the special province of the lymph and of the lymphatic
circulation1? This is still a very obscure point of physiology.
Evidently the lymphatic is an adjuvant of the circulatory
system ; it connects the immediate principles in the digestive
system and in the mechanism of the tissues, then pours them
into the whole grand circulation. Its special function the most
probable is to form white globules and to convey them to the
great sanguineous current. The fact that a fistula of the thoracic
canal is followed by death, proves conclusively that the lymphatic
system is not a mere ornamental apparatus, and that it plays in
the economy one of the most important parts.

BOOK II.

OF THE PRIMORDIAL PHENOMENA OF LIFE.
CHAPTER I.

OF NUTRITION.

WE cannot form a precise idea of the mechanism of nutrition,
unless we have thoroughly present to our mind the general laws
of diffusion and those of osmosis, especially between crystalloids
and colloids.

We know that two solutions of different density, put separately
into a diffusion vessel and consequently in contact only on a
small surface, mingle by degrees intensely, to such a point indeed
that after a given lapse of time, the blending has everywhere an
identical composition.

We also know that every substance has a degree of special
diffusibility, and that generally the colloidal substances have a
diffusibility infinitely inferior to that of the crystalloidal
substances. A glance at the following table furnishes a complete
idea of this difference : —

QUANTITIES DIFFUSED IN EQUAL TIMES.

Chlorure of Sodium 58,68

Sulphate of Magnesia 27,42

Nitrate of Soda , . . 51,56

7$ BIOLOGY. [BOOK n.

Sulphuric Acid 69,32

Sugar Candy . 26,74

Barley Sugar 26,21

Molasses of Cane Sugar 32,55

Sugar of Starch 25,94

Gum Arabic 13,24

Albumine , 3,08

Furthermore, these colloids, so slow to blend and to be diffused,
are easily penetrated by the crystalloids, while their analogues
cannot traverse them except by taking, through isomeric modifica-
tion, an altogether special state of solubility. For instance, we
shall see when speaking of animal digestion that the albuminoidal
substances of the elements, in order to pass into the circulatory
system, need previously to be transformed into soluble albuminose.

We must also remember that two substances, incapable of
chemical combination, and possessing different degrees of
diffusibility, separate to a certain point, when they are put in
a blended state, in a diffusion vessel, for then the more diffusible
of the two passes out more rapidly than the other.

The application of the preceding data to nutrition is achieved
almost of itself, so to speak. In effect, from the simply physical
point of view, organised beings are merely masses of colloidal
substances, holding in solution crystalloidal substances. This
definition is strictly true for a number of rudimentary organisms,
for instance the amoebae and most of the infusoria ; in general,
for all those beings, neither vegetal nor animal, of which Haeckel
has made his group of monera. It applies even to a number of
zoophytes, and also to every histological element of the superior
organisms, isolatedly considered. Let us take the small amorphous
mass of contractile albuminoid substance which constitutes an
amceba, a rhizopod, or monocellular beings such as the Protococcus
nivalis, many infusoria, lastly the globules of the blood of the
mammifers, and even the cells and fibres, grouped into tissues to
form the body of plants and of the superior animals ; we see

CHAP, i.] OF NUTRITION. 77

that in some, every element living, ultimate, isolated, or associated
to other analogous elements is only a small mass of colloidal
substance. But like all colloidal bodies, this substance is
capable of imbibing water and aqueous solutions ; it may be said
greedily to seek them ; thus there is established in the midst of
its molecules an incessant aqueous current, which conveys to
them soluble substances, modified crystalloids or albuminoids,
and which at the same time seizes back other substances, usually
crystalloidal, which have become unfitted to form a part of the
living body.

The phenomena of diffusion however are not by any means
peculiar to the liquid state. In a gaseous medium the diffusion
of liquids is simply replaced by gaseous diffusion direct or
indirect. We have seen besides that analogous phenomena
are produced even in the midst of living liquids, in the blood
and the lymph of the superior animals.

But if the physical condition of nutrition is simple diffusion
in amorphous beings not yet composed of cells or of fibres, it is
a little more complex in the others, if we proceed from the
monocellular organisms to the superior mammif ers, constituted by
fibres and cells cemented or grouped in tissues. Here the diffusion
is accompanied by the passage of the liquids through a membrane,
that is to say, that there is osmosis, and naturally osmosis with
a double current from without to within, and from within to
without, endosmosis and exosmosis.

We must needs do for osmosis what we have done for diffusion,
that is to say, briefly recall the principal facts appertaining
thereto. Osmosis, discovered by Dutrochet,1 then studied
especially by Graham, who gave it the name of dialysis, is, as is
well known, the blending of two unequal densities, separated by
a membrane. Definitively it is diffusion in special mechanical
conditions, which permit the superposition of the liquids, whereby

1 J.-B. Dutrochet, De I'Endosmose, in Mimoires pour servir d VHistoire
anatomique des Vegetaux ct des Animaux, t I. Paris, 1837.

78 BIOLOGY. [BOOK n.

for instance the more dense can be placed above the less dense.
As essentially there is a very great analogy between diffusion and
osmosis, it follows as a matter of course that the substances
which osmosis finds the most sluggish must be the colloidal
substances ; and that is exactly what experience confirms. In
osmosis, the membranous partition, usually organic, which
separates the liquids, is 'traversed simultaneously by a double
current ; and commonly the stronger current goes from the less
dense liquid to the more dense liquid. There are however
exceptions. For instance, if water and alcohol are separated by
a fragment of bladder, the water passes in greater quantity
towards the alcohol. It has been supposed that in this case
the direction of the current depends on the inequality of the
capillary attractions between the liquids and the two faces of the
membrane. The water moistening the membrane better than the
alcohol, rises by capillarity in its pores, while on the contrary if
we substitute for the bladder a layer of collodium, which is better
moistened by the alcohol than by the water, the direction of the
osmosis is reversed. All the membranes with which osmotic
experiments have been made are in .effect really and thoroughly
perforated (bladder, collodium, paper, parchment, and so on).
But this explanation does not suit all cases, and especially the
cases of osmosis through living liquids. In effect, so far as our
most powerful microscopes permit us to -assure ourselves thereof,
the surfaces of the animal and vegetal cells and fibres are
absolutely homogeneous. We find no trace of pores. No doubt
we are compelled to admit molecular and atomic intervals across
which the passage of the solutions must be effected ; but in this
case the osmosis is accompanied by a chemical action exercised
on the dialysing membrane. The liquids, gases, or vapours, which
traverse the cellular or fibrillary walls unite themselves, as they
pass along, molecule by molecule, to the chemical elements
constituting this wall; then, as on the other side of the
membrane they find themselves in contact with a new fluid, they
forsake forthwith the elements of the wall to combine with those

CHAP. L] OF NUTRITION. - 79

of the fluid which they encounter. This explanation, proposed
by M. Ch. Robin, would, if well founded, furnish an explanation
of an extremely important fact. It would make us understand
why in the organisms themselves the composition of the fluid
absorbed is no longer on the hither side of the membrane or
living wall what it was on the thither side ; a phenomenon
peculiar to the biological osmosis, and never produced in the
endosmometers and the dialysing apparatus.

But, well founded or not, this explanation seems to me by no
means needful to furnish a reason for the changes occasioned
in the composition of the fluids by physiological absorption. It
Eunices to explain this metamorphosis to take into account
chemical phenomena at the same time as physical phenomena-
Hitherto almost all the osmotic experiments effected in the
laboratories have borne upon liquids miscible indeed, but exercising
on each other no chemical action. Obviously this is not what
happens in the living tissues. There the fluids which have
traversed a living wall hold in solution unstable substances,
which are by the very fact of the osmosis in contact with other
fluids composed of substances of analogous complexity and of
different composition. There are evidently at the time of this
conflict, exchanges of molecules, chemical reactions; the new
substances arising repair the waste of the old, and for that
purpose are forced to enter into alliance and combination with
them. The residuum of these functions and that of the waste
of the substances previously organised are a blending of diverse
crystalloidal bodies, which is promptly dragged away from the
histological elements, the fibres, and the cells, to be afterwards
definitively expulsed from the organism. We have seen that
nothing is easier than to separate with a dialyser a crystalloidal
substance from a colloidal substance. It is very evident
nevertheless that the cellular wall is not inert in all this labour
of molecular mutation. It is as living as that which it contains,
and must consequently in like fashion participate in the
phenomena of transformation.

80 BIOLOGY. [BOOK ii.

We could surely in osmotic experiments draw much nearer to
what comes to pass in the organised bodies by making to react
on colloidal substances oxydant bodies, capable of giving birth
thus to crystalloidal bodies, and so on.

The curious experiments of Traube on artificial cells have
taught us that it is possible to imitate in a certain measure the
physical and chemical phenomena of life.1 Assuredly we hither-
to are far from having imitated within the domain and the range
of the possible, the phenomena of animal physics, and of vegetal
physics, which form the esssnce, the support of the vital acts.
]STo doubt the lack of initiative, which, in regard to this matter,
experimentalists have displayed, must in a large degree be at-
tributed to the metaphysical and mystical ideas which have been
conceived of life. As long as the vital phenomena were considered
as of an order altogether apart, as having no relation with the
physical or chemical phenomena ; as long as there was a belief
that to explain what was called " the miracle of life " there had
to be invoked directing entities, independent of the bodies, a
kind of immaterial gods set over the physiological government of
every organism, an archeus, a vital principle, and so on, it was
naturally almost impossible that the idea of reproducing arti-
ficially the principal physico-chemical acts of life should occur to
experimentalists. In our days there is, fortunately, a complete
change, and we see men of science venturing on paths which they
would never have dreamed of entering half a century ago.

M. Traube has based his experiments on two principal facts.
The first of these facts has been established by Graham ; it is,
that the colloids dissolved are incapable of penetrating by diffu-
sion through the colloidal membranes. The second fact is, that
the precipitates of the colloidal substances are themselves col-
loidal. Starting from these facts, M. Traube has been able,
artificially, to make cells, the wall of which was formed of
tannate of gelatine. He takes a drop of gelatine, which, by an

1 ExpcrimenU zur Theorie der Zdlbildung und Endosmosc (ArcJiiv fur
Anztomie, &e., von Reichert und Dubois-Reymond, 1867, p. 87).

CHAP, i.] OF NUTRITION. 81

ebullition of thirty-six hours has lost its coagulability. He lets
it dry in the air for several hours, and by the help of a rod fixed
in the cork of a vessel half filled with a solution of tannin, he
plunges it into this liquid. Then the small quantity of gelatine
which dissolves on the surface of the drop combines with the
tannin, and the result is a closed cellular membrane. But this
membrane is homogeneous, unperf orated, as the organic membranes
are. Also the diffusion which is established between its contents
and the exterior liquid must be effected osmotically across the
molecular interstices. The osmosis is produced very energetically.
The membrane distends more and more ; as a consequence the
constituent molecules sever from each other : at a given moment
when the molecules of the two liquids brought face to face can
easily be introduced into the molecular interstices and blend, they
form anew molecules of tannate of gelatine. Consequently, the
membrane grows by intussusception. In effect, it suffices to arrest
all increase, to substitute water for the solution of tannin.

M. Traube forms also, in the same manner, endosmotic mem-
branes, very curious, impermeable by certain substances, very
permeable by others ; in a word, exercising on the substances
in contact with them an elective action, such as the living
membranes exercise.

According to M. Traube, every precipitate whose molecular
interstices are smaller than the molecules of its components
must take the form of a membrane.

Lastly, the endosmosis across the membranes depends solely
on the attraction of the body which is dissolved for its solvent.

These experiments are infinitely interesting; nevertheless,
they imitate very imperfectly what takes place in the living
cells. It is something to have obtained by simple chemical
processes a membrane which grows by intussusception, foras-
much as, from time immemorial, this mode of growth has
been considered peculiar to living bodies. But in the living
cell there is something more ; the contents are as little inert as

G

82 BIOLOGY. [BOOK n.

the enveloping membrane ; they are modified and renewed un-
ceasingly, molecule by molecule, without being destroyed.

In the primordial phenomena of nutrition there are, in effect,
two acts, or rather two principal aspects of the same phenomenon,
assimilation and disassimilation. To assimilation relate the facts
of absorption and endosmosis ; with disassimilation are connected
the facts of secretion and exosmosis. We must remember that
disassimilation has, as result, the transformation of the colloidal
substances of living bodies into crystallisable substances, occupy-
ing, after a fashion, a middle position between organic substances
and mineral substances.

It is now invincibly demonstrated that these primordial facts
of nutrition are identical in all the living universe, as well in
the animal world as in the vegetal world. It is also known,
moreover, that the principal agent of all these transformations,
of all these exchanges, is the oxygen of the air.

In the most rudimentary beings, amorphous or monocellular,
oxygen is diffused direct in the midst of the molecules of the
living substance ; it oxydises this substance by a sort of slow
combustion, and determines the formation of diverse organic
crystallisable bodies, and of a gas — carbonic acid ; the whole is
afterwards expulsed.

In the being whose structure is more complex, where there is
an aggregation of cells, of fibres, in a word, of diverse histological
elements, each having its special form and special functions,
while the whole are, moreover, grouped in particular tissues, the
oxygen of the air, and generally all the substances which penetrate
into the organism and come forth from it, have to undergo a sort
of gradatory process before being assimilated or excreted. In
the simplest cases when the organism is merely constituted by
histological elements of kindred nature, more or less straitly
joined together, and bathing in an interstitial liquid, a circulatory
system, a respiratory system, a digestive system being wholly
lacking, the nutritive substances and the disassimilated substances
dissociate themselves in the intercellular blastema. It is in this

CHAP, i.] OF NUTRITION. 83

liquid, impregnated as moreover it is with oxgyxm and carbonic
acid gas dissolved, that the histological elements choose the
materials which suit them and reject those which are no longer
suitable. At a more exalted degree of structure are superadded
special apparatus, systems more or less ramified with canals, in
which circulate the liquids and the gases. But even then the
interstitial, intercellular liquid ceases not to exist ; it merely
renews, revivifies, purifies itself without pause, seeking suste-
nance in the circulatory fluids, and ridding itself there, in its
turn, of the substances destined to elimination.

In sum, the intercellular liquid acts toward the circulatory
fluids as the histological elements act toward itself.

We see that it is by a peculiarity of construction that almost
all organised beings live in the air. In truth, all the histological
elements constituting the complex organisms are aquatic ; they
bathe in a special liquid, in a living medium, which is alike their
essential cause and the result of their nutritive activity. Cl.
Bernard has much contributed in these last years to propagate
this felicitous idea of the interior media, such as the blood of
animals, the sap of plants, and so on : "that ensemUe of all the
interstitial liquids, that expression of all the local nutritions,
that source and confluent alike of all elementary changes." 1 We
may admit, with the eminent physiologist, though with restric-
tions and exceptions for the living beings that are wholly rudi-
mentary, that there is no direct nutrition, and that, for instance,
the fragment of a fresh- water polypus, when it is reconstituted
and completed to the point of re-becoming an entire polypus,
avails itself principally of the nutritive interstitial fluid which
impregnated at the outset the separated fragment. "

Thus, for every complex organised being there are three
superposed media, the cosmic medium, ae'rian, or aquatic — but in
this last case holding the air in solution ; the sanguineous, or
sap-filled medium ; lastly, the interstitial, intercellular medium.
Naturally, the internal media need, like the external media, to
1 Revue Scientifique, 1874.

G 2

84 BIOLOGY. [BOOK n.

maintain themselves in what we call a suitable state of purity,
that is to say, in a state of composition sufficiently equilibrated
for the histological elements to find therein at every instant their
food. We shall see in the course of this exposition that in the
complex organisms special apparatus of exhalation, of secretion,
and of excretion are charged to keep up incessantly across
these media renovating currents, exactly as other apparatus,
for instance, the digestive apparatus and certain glands, pour
in suitable nutriments.

These general data accepted, we can now analyse the acts, the
phases of nutrition. We know that this biological property
exercises itself in all living substances, figurate or not, as well in
the plasmas and the blastemas as in the figurate elements. In
both it depends in part on physical conditions of endosmosis,
exosmosis, and diffusion, and in part on the physical affinities of
substances brought into relation. In all this there is not the
smallest place for a metaphysical agent. We have simply to do
with physical and chemical phenomena producing themselves in
conditions of complexity and simultaneousness entirely special,
yet narrowly bound to the variations of the ambient medium.
We see in effect these phenomena intensified or enfeebled accord-
ing as the air is more or less oxygenised, according as the
temperature is higher or lower, and so on.

Though the nutritive phenomena are simultaneous and unin-
terupted, we can, for the convenience of exposition, divide them
into phenomena of assimilation and phenomena of disassimi-
lation.

It is by endosmosis that the immediate principles reach the
substance of the anatomical elements, reach the living liquids.
The principles of the first class, that is to say, the mineral
substances, often arrive without modification by simple dissolution,
and it is thus, for example, that the chlorures and the alkaline
sulphates arrive. Certain of these substances combine with
the organic matters, as, for instance, the phosphate of lime com-
bines with osse'ine in the bones ; but then, in opposition to the

CHAP, i.] OF NUTRITION. 85

laws of non-living chemistry, the combination does not seem to
be accomplished in definite proportions. It is a sort of alloy.

In plants the power of assimilation seems more energetic. It
is in the mineral medium, in effect, that the plant must seek
its aliments direct ; consequently we see the green parts of
plants assimilate at once the carbon of aerian carbonic acid, and
incorporate it immediately with complex organic substances,
ternary and quaternary. The same synthetical power is exercised
in certain circumstances on the azote of the air, and, normally,
on the azote of the ammoniac salts drawn by the roots of plants
from the soil.

In the animal, the true phenomena of assimilation are generally
exercised at the expense of albuminoidal substances already
elaborated. It is an important and remarkable fact that the
organic assimilated substances have never, previously, the same
composition as those which form the assimilative anatomical
elements. The musculine. the elasticine, and the like, peculiar to
every species of cell, of fibre, and so on, are, in effect, met with
nowhere apart from the elements which they constitute and
reconstitute incessantly ; they are formed in the animal organism
at the expense of the living liquids, by isomeric catalyses.1

The anatomical elements can assimilate a great number of
substances, but they have necessarily their own special affinities,
entirely analogous to those of the bodies of mineral chemistry.
Thence result a choice and a selection, which, for a long time,
appeared intelligent, though here intelligence no more enters
than in the affinity of chlore for hydrogen, of anhydrous sul-
phuric acid for water, and so on. These chemical combinations
formed in the substance of the anatomical elements have excessive
instability, and they are the more unstable the more life rises to
a superior degree, the more it is animalised. Thus chemical
instability is much greater in the anatomical animal elements
than in the vegetal elements.2 In these last we cannot dissever

1 Ch. Robin, Anatomic Microscojnque des J&f6ments Anafamiques. Svo.
Paris, 1868. 2 Ch. Robin, loc. cit. p. 65.

86 BIOLOGY. [BOOK n.

the chemical combinations but by the aid of energetic chemical
agents. Moreover, it is much less easy to interrupt the vital
movement in the plant than in the animal. But in them
both, chemical instability, in various degrees, is the very
condition of life. Every combination too stable is the equivalent
of death.

Nutritive assimilation has naturally, as a condition, a corre-
sponding disassimilation. In order that new substances may
incorporate themselves with an anatomical element it is abso-
lutely necessary that other substances yield their place to them.
In effect, incessantly a portion of the substances which formed
part of the anatomical element ceases to resemble the fundamental
substances, and severs itself from them. The substances thus
have not, by reason of the severance, ceased to be complex
albuminoidal substances, but generally they have become more
oxydised, and have passed into the state of crystallisable matters,
— they have taken a step to return to the mineral world.

As to the mineral substances expulsed from the anatomical
element, certain of them merely pass through without undergoing
any change. This is* the case with sundry salts, azote, water,
and so on. Other mineral compounds, however, are formed
therein by direct combination, just as they would have been
formed in a retort. In this fashion are produced in animals,
the alkaline carbonates, the lactates, the ammoniaco-magnesian
phosphates, the phosphates of lime, the urates, carbonic acid, and
so on.

The nutritive exchange is not effected in all the tissues with
the same energy. In general it is in the cell, properly so called,
or in tissues formed by cellular aggregations, that this double
current attains its maximum of power. Nutrition can often be
effected without the succour of special circulatory apparatus.
The exchange of nutritive materials frequently is achieved in
this case from step to step with sufficient rapidity. Things take
place thus in certain inferior organisms simply polycellular, in
the crystalline of the eye of mammifers, and so on.

CHAP, i.]

OF NUTRITION.

87

If a tissue is at the same time constituted by cells and furnished
with a rich vascular network, it is in conditions specially favour-
able, and the nutrition thus is rapid and energetical : this is
what takes place in the mammifers, in the medullary tissue of
the bones, in the grey substance of the brain, and so on.

After the exposition of the general facts to which we have
devoted this chapter, it will be now more easy for us to
present successively in the two organic kingdoms the history of
nutrition, that is to say, of the vital property which is the
support and the essential cause of all the others.

f I I > I > \ I > '••'
lj 1 1> It A n 1.

UN J V K US MY <>

CHAPTER II.

VEGETAL NUTRITION.

IN the composition of every plant we find mineral substances,
ternary substances non-azotised and proteic substances. Now
plants not eating each other direct, like animals, it is needful for
the vegetal organic substances to be habitually created by the
plant itself, at the expense of the mineral medium which
environs it. Brought back to their primary mineral elements,
the complex organic substances yield carbon, oxygen, hydrogen,
azote, and a certain quantity of sulphur and of phosphorus. If
we add to these elements chlore, calcium, silicium, potassium,
sodium, magnesium, lithium, iron, often manganese, and in the
marine plants, iodine and brome, we have nearly the whole
elementary sources of alimentation in the vegetal kingdom.
Naturally the metals which we have just enumerated form bases
which combine with the acids which they encounter, to consti-
tute sulphates, silicates, chlorures, often organic salts, for
instance, oxalates, and so on.

To form a sufficient idea of vegetal nutrition, we must follow
these mineral elements, note how they enter into the plant,
indicate the combinations which they form there, finally, leave
them only when, having played out their part in the vegetal
organism, they are finally expulsed from it.

Of these chemical elements, some, for example, are derived
from the air, others from the soil. The mineral elements taken
direct from the ambient air by the plant are hydrogen, oxygen,
carbon. Hydrogen and oxygen are absorbed and fixed by the

CHAP. IL] VEGETAL NUTRITION. 89

plant, either simultaneously in the state of water, or isolatedly.
It is probable, in effect, that the green parts of plants have the
power of decomposing water, which they draw in a small part
from the atmosphere, but in enormous quantity from the soil.
The chlorophyllian parts would effect the decomposition of water,
whatsoever its source, and would fix direct its elements in the
complex combinations of which we have spoken. This, however,
is a point which has not yet been well studied. Certain, at least,
it is, that the greater part of the oxygen absorbed by the plant
is taken from the atmosphere direct, and a little by all parts of
the vegetal organism. As to carbon, which forms in weight the
chief part of every desiccated plant, it also is derived by the
green portions of the plants from the carbonic acid of the air.
This is one of the most interesting, one of the best studied points
of vegetal physiology. All the other mineral matters, and
almost the whole of the water, are absorbed by the roots of the
plant, penetrate into the vegetal tissues, there ascend, there meet
with, especially in the leaves, the mineral substances derived from
the air, and some of them form complex combinations.

Vegetal physiology is still so confused, the division of labour
in the plant is so ill-distinguished, that it is not easy to mark out
therein functions thoroughly determinate, functions very dif-
ferent from each other. Everything is connected, everything
blends, everything forms the link of a chain. Nevertheless, for
clearness of exposition, we are obliged to make divisions more or
less natural ; we must, in effect, speak of phenomena mingled,
entangled, proceeding sometimes simultaneously in the same
tissues or organs. We have to tell how penetrate into the
plant the numerous mineral substances which chemical analysis
, discovers there, how those substances have infiltrated themselves
into the tissues, what compounds they have formed there under
the powerful action of the nutritive movement, finally how and
in what proportion they were eliminated during the life of the
plant after becoming unsuitable to figure in the nutritive
, process.

90 BIOLOGY. [BOOK n.

1. Formation and Circulation of the Sap.

Let us take as type a complete plant, a dicotyledon, plung-
ing its roots into the ground, displaying its branches in the air.
In the spring such a plant impregnates itself incessantly with
the materials which it appropriates from the exterior medium.
It absorbs them by the roots, by the leaves, by the bark. It is
by the osmotic process that the roots draw from the soil the
first materials of the sap. It is the delicate cells of the
extremities of the roots, radicellular spongioles, which are
the principal agents of absorption. These cells contain a pro-
toplasm dense and albuminous, coagulable by nitric acid ;
they are in contact with the soil by means of their cellular
membrane, by means of the hairs which garnish them ; they are
thus in conditions very favourable to osmotic absorption. It is,
moreover, easy to prove that is owing to the process entirely
physical of endosmosis, that the roots saturate themselves with
the humidity of the soil, for all that is needful to arrest their
work of absorption is to plunge them in a saccharine and dense
solution. In the soil, on the contrary, the water, relatively little
charged with dissolved substances, moistens the extremities of
the roots, penetrates by endosmosis into their anatomical ele-
ments, and mingles there with their protoplasm, bringing with it
ammoniac salts, phosphates, salts of potash, and so on.

But to accomplish their office the hairs of the roots need, like
all organised cells, nourishment, that is to say, need to be
oxydised, to absorb oxygen, and to exhale carbonic acid. Con-
sequently, the penetration of the air into the soil into which
the roots plunge is indispensable to the maintenance of the life
of plants. The exhalation of the carbonic acid by the roots has
also its utility. In effect it is from the presence of this carbonic
acid that certain salts become soluble in water and can thus
penetrate into the radical cells. The case is the same, for
example, with certain phosphates, and no doubt also for silica,
and so on. Once introduced into the cells of the spongioles, of

rnAp. IL] VEGETAL NUTRITION. 91

the radical hairs, the substances, borne on by the water which
holds them in solution, pass from cell to cell, each borrowing
from each, in proportion as the nutritive waste goes on. In
plants with roots, this ascensional movement of the liquids
drawn from the soil is facilitated by the presence of those vessels
and vascular bundles we have previously described ; there are
indeed no roots except in the plants whose cellular tissue is
traversed by vessels. In the spring the flow of the sap is so
abundant that it invades everything ; cells, fibres, vessels, even
the interstices of the cells or intercellular meatus. This flow
thus ascends from the root to the leaves, but circulates more
rapidly in the vessels, where it encounters fewer obstacles, and
is, in a certain measure, raised by capillarity. The grand
movement of ascension is accomplished through the central part,
through the ligneous body, or through its exterior zone, younger
and less incrusted if the vegetal is already aged. Very certainly
; multiple causes, endosmosis, diffusion, capillarity, the nutritive
fixation of the alible materials in the buds, evaporation on the
surface of the leaves, co-operate in the ascension of the sap; but the
| most powerful cause is assuredly the absorption exercised by the
ascensional cells of the roots. In effect a plant can live and ac-
tively live when its radical extremities alone are placed in water.
Besides this grand general movement of the sap there are
others more interesting perhaps, those, namely, of the contents of
the cell, of the protoplasm. This liquid, which we know to be
habitually an albuminoidal liquid, is granulous, and we see in
nearly all plants its granulations execute along the walls of
; the cell or of the fibre-cell a gyratory movement. They mount
t on one side and re-descend on the other. This protoplasmic
i movement is a vital movement connected probably with the
molecular exchanges and reactions of nutrition. It is accom-
plished only within determinate thermometrical limits. The
minimum limit approaches 0 degree, the maximum limit is from
, 45 to 47 degrees. It is toward 35 to 37 degrees that the speed
» of the protoplasmic current attains its maximum. When it is the

92 BIOLOGY. [BOOK ir.

cold which arrests this gyratory movement, we can by treating
the soil put the liquid again into motion.1

With respect to this manifest action of heat it is curious to
see that light seemingly influences little or not at all the pro-
toplasmic movement which is accomplished without apparent
modification even when the plant is kept in darkness.

After gyrating in the cells, travelling in the vessels and the
meatus, after taking from or giving to the elements, which it
has traversed or passed beside, certain of the matters which it
conveys, the sap arrives at the part truly aerian of the vegetal.
There it undergoes very important modifications, thanks to the
special action of a substance of which we have now to speak.
This substance is the green matter of the leaves, the chlorophyll.

2. — Chlorophyllian Property.

Chlorophyll is the substance to which all the green parts of
plants owe their colour. In the cells of certain lichens and of
certain algae, the chlorophyll sometimes presents itself in the
amorphous state, colouring all the protoplasm, sometimes in irre-
gular masses ; but habitually in all the vascular plants it has a
definite form, that of green granulations of from Omm, 001 to
0""n, 005 in diameter, of homogeneous appearance and without
nuclei. We can obtain from this green matter fat crystallisable
bodies, stearine, margarine and so on, and an immediate azotised
principle, chlorophyll properly so called, the elementary analysis
of which gives oxygen, hydrogen, azote, carbon, and iron. By
an appropriate chemical treatment Fremy was able to separate
chlorophyll into two substances ; the one yellow, phylloxanthine,
and the other blue, phyllocyanine.

Chlorophyll rises spontaneously in the cellular protoplasm.
First of all are formed colourless or yellow particles, which
grow green afterwards, if the cell in which they are contained
is exposed to the light. The chlorophyllian particles, born in

1 Nageli, quoted by Sachs, Traite de Botanique, pp. 855, 856.

CHAP. H.] VEGETAL NUTRITION. 93

the darkness, remain yellow, but under the action of even a
feeble light and a somewhat elevated temperature, of from 20
to 30 degrees, they grow green. All the rays of the solar
spectrum suffice to make the colourless chlorophyllian particles
green, but by far the. most active are the yellow rays.

Once formed, the chlorophyllian particles, if they are favoured
by good conditions, increase in size, and at a given moment can
multiply by binary division. The solar light does not merely
influence the formation of the chlorophyllian particles ; their
whole evolution is subjected thereto. The particles veridified and
subjected to an intense light during a long space of time form
in their very substance particles of starch, which are most
manifestly the result of a nutrition too active, an aliment in
reserve. This starch besides re-dissolves and re-forms according
as the green cell is withdrawn from the solar light or exposed to
it anew. From a long sojourn in darkness the particles of
chlorophyll themselves lose their shape, suffer atrophy, and
disappear, dissolving into the colourless protoplasm.

We have seen that all the rays of the solar spectrum have the
power to render green the chlorophyll ; but all are not capable
of impressing on it enough of nutritive activity to form the
starch in its particles. That is a faculty limited naturally to
the rays the most stimulating, the yellow rays.

Light being the determinating agent of the chlorophyllian
formation, it is natural for the chlorophyllian particles to
accumulate specially on the best illuminated cellular wall ; and
i this, in reality, is what takes place.1

In the persistent leaves, heat appears to have a great influence
on the position of the particles of chlorophyll. In effect, when
the temperature lowers they quit the wall to accumulate inter-
. volved in the centre of the cell. In spring, or whenever the
» plant is subjected to a certain elevation of temperature, they,
whether in darkness of in light, resume their parietal position.
Lastly, toward the end of the vegetative period, the precious
1 Franck, Botanische Zeitung, 1872.

94 BIOLOGY. [BOOK n.

chlorophyllian substance in a great measure escapes destruction
in the perennial plants. It re-dissolves along with the starch
which it englobes, and the whole, passing through the petiole,
and carrying along even the phosphoric acid and the potash,
wanders toward the permanent organs of the plant.1

Before we speak of the special properties of chlorophyll, it is
opportune to signalise the importance of the metallic element
which it contains. The atoms of iron which enter into its com-
position constitute in effect an integrant part of it ; without
them it is not endowed with its special properties. Another metal,
potassium, though not figuring in the complex molecule of the
chlorophyll, seems to play an important part in its nutrition.
When the plant does not absorb chlorure of potassium, or at least
nitrate of potash, the particles of chlorophyll have less vitality
and are incapable of forming starch.

We have succinctly described the morphological evolution of
chlorophyll. It remains for us now to speak of its function.

Priestley was the first to observe that the green parts of
plants exhale oxygen. He put under a receiver in confined air,
where mice had died asphyxiated, some mint plants, which lived
and flourished energetically there. The chlorophyllian property
was thus discovered ; but it was Ingenhouz who attributed the
disengagement of vital air operated by plants to its true cause,
the action of light.2 The same observer demonstrated also the
inverse action of the flowers and of the roots, which night and
day exhale carbonic acid and vitiate the atmosphere.

Every terrestrial or aquatic plant furnished with chlorophyllian
cells, and exposed to the solar light, borrows from the air carbonic
acid, and restores to the air an equivalent volume of oxygen.

For most plants, the activity of the phenomenon is in proportion
to the intensity of the light. Though the chlorophyllian function
has need in almost all plants of full light, it still exercises:
itself, feebly indeed, in diminished light, and there are even

1 J. Sachs, Traite de Botanique.

2 Ingenhouz, Experiences sur les Vegetaux, 1780.

CHAP, ii.] VEGETAL NUTRITION. 95

plants, mosses, for example, living in the shade of the woods,
which cannot, without dying, bear an intense light. But in
diverse degrees, light is indispensable to the green parts of all
plants. At night, or in darkness, chlorophyll ceases to act, and
the plant simply exhales carbonic acid.

The property of decomposing the carbonic acid of the air and
of absorbing carbon specially appertains to chlorophyll, just as
that of fixing a great quantity of oxygen specially appertains to
the hsemoglobuline of the haematia. Chlorophyll has also, like
haemoglobuline, its poisons. Thus, as Boussingault has demon-
strated, mercury introduced into a receiver where a plant is
destroys the chlorophyllian property.

It seems to result from the experiments of Dutrochet,1 that a

part of the oxygen put at liberty by the chlorophyllian action

is not immediately expulsed, but penetrates previously into the

mechanism of the tissues. The oxygen exhaled direct is merely

air overplus. The rest is impelled into the aerian cavities, into

1 the globulous vessels, into the punctuated tubes, and especially

into the tracheae. In this way it descends into the petioles of

[ the leaves, into the stem, and serves there probably the real

: respiratory function, the oxydation of the tissues, and the

production of the carbonic acid disengaged by the plant.

It is by the stomata that this expulsion and this absorption of
air seem especially to be accomplished ; nevertheless, the mosses
and the coniferse, which have no stomata, exhale carbonic acid.

We might be astonished that the small proportion of carbonic
iacid contained in the air suffices for the alimentation in carbon
of the -whole vegetal kingdom, if we did not think on the
great density of the atmosphere, and on the considerable restitu-
tions that are made to the atmosphere by the vegetal kingdom
on the one hand, and by the entire animal kingdom on the other,
i This last, in effect, incessantly consumes oxygen, and exhales
torrents of carbonic acid. Moreover, we must add to these
principal sources of carbonic acid all the combustions, the
1 Dutrochet, De I'Endosmose, p. 357.

96 BIOLOGY. [BOOK n. J

volcanic exhalations, and so on. As to the rest, in calculating
in accordance with the presumed height of our atmosphere and
the proportion of four ten-thousandths of carbonic acid for a
given volume of air, we arrive in estimating the quantity of
carbon existing in the ae'rian medium at the enormous figure of
1,500 billions of kilogrammes.

It is also probable that the air is not the only source of the
carbonic acid absorbed by the plant. There is assuredly some
produced by the oxydation of the sap and of the anatomical
elements, and there is no reason for supposing that the plant
does not also undergo the decomposing action of the chlorophyll.
As the carbonic acid is, when light acts, incessantly de-
composed by the chlorophyll, there results a sort of carbonicj
void in the portion of the air in contact with the green cells, and!
consequently by degrees and by diffusion new quantities of acicB
arrive. The alimentation in carbon is therefore never lacking. 1
Though the decomposition of acid is effected in all the green
cells, nevertheless, the upper surface of the leaves seems to play
the predominant part in the chlorophyllian act, for if we turn the:
leaves so as to expose to the sun their under-surface, the carbonic;
action diminishes, and in a few days ceases.1

Let this be as it may, the exhalation of carbonic acid, little
perceptible during the day and relatively active during the nighty
is far from compensating the absorption. M. Boussingault had
calculated that in twelve hours of the night one square deci-l
metre of green surface burns Og,214 of the carbon of the tissues J
while in twelve hours of the day it assimilates 3*,416.

If we allow the light to reach plants, only by allowing it to;
pass through glass coloured with the colours of the prism, wd
see that all the visible rays can put chlorophyll into activity,
but that the rays capable of exciting its appearance in thcfj
protoplasm are also those which stimulate chlorophyll most.
These are, in effect, the yellow rays, which determine the most
abundant disengagement of carbonic acid.

1 Dutrochet, De l'£ndosmose, p. 355.

CHAP. IT.] VEGETAL NUTRITION. 97

If we attentively regard the undulatory amplitude of the
luminous rays suitable for making the chlorophyll operate, we
see that those active rays have as highest limit Om,0006886, and
as lowest limit Om,00039968. They are rays feebly refrangible.1

The rays most strongly refrangible, the blue and the violet,
as well as the ultra-violet invisible rays, influence especially the
rapidity of growth, the movements of*the protoplasm and of the
zoospores, and so on.

We have recently compared, in passing, chlorophyll and the
ha?matoglobuline of the blood. The parallel is so curious that we
must consecrate a few lines to it.

Chlorophyll and hsematoglobuline are both quaternary sub-
stances. They both exercise an elective action on a mineral gas.

They both are habitually moulded into globules, without
nucleus.

The special property, however, which characterises them
seems in both to be independent of the form which they assume.
We have seen that a solution of h<ematoglobuline absorbs oxygen,
and that amorphous chlorophyll, dissolved in the cellular proto-
plasm of certain plants, continues, nevertheless, to absorb
molecules of carbon.

Chlorophyll and haematoglobuline equally seem to form only
a temporary association with the mineral element which with
special avidity they seek. In effect, the sanguineous globules
yield to the anatomical elements of animals their provision of
oxygen almost as soon as they have taken it, and, in return, they
charge themselves greedily with carbonic acid, thus holding
kinship with the chlorophyllian globules in this aspect of their
physiology. •

Chlorophyll, though absorbing, like every living substance, the
quantity of oxygen necessary to its nutritive movement, does not
seem to have a great affinity for that gas. It is probable that
in the night it ceases purely and simply to exercise its special
action without assuming another ; but it is certain that it does

1 J. Sachs, TraiU de Botcmiquc, p. 878.

B

93 BIOLOGY. [BOOK 11.

not fix more than for a moment the carbon derived from the
carbonic acid. As this carbon does not accumulate in the
chlorophyllian tissues, as the composition of chlorophyll is always
perceptibly the same, the molecules of carbon assimilated by it
must be instantly surrendered to the sap to which they bring the
supply needful to the formation of complex substances, ternary
and quaternary. Whence, besides, could the tissues take the
carbon which constitutes the half of their weight, if they had
not, to provision themselves, this perpetual supply? We shall
have some words to say on this living chemistry. Let us occupy
ourselves for the moment with the vegetal function, comparable
in everything with what is called respiration in animals, that is
to say, with the absorption of oxygen.

=

3. Absorption of Oxygen or Vegetal. Respiration.

A green phanerogamous plant is asphyxiated in a mediu
of hydrogen, of azote, and even of carbonic acid, and if its
sojourn in this artificial atmosphere is too prolonged it loses
for ever the chlorophyllian property.1

Besides, M. de Saussure had already remarked, when extract-
ing by the aid of a pneumatic machine the air impregnating the
tissues of plants, that this air contained notably less oxygen
than the ambient atmosphere. The proportion is very variable ;
that found by Saussure was 85 of azote and 15 of oxygen.2
Moreover it has long been known that during the day when
in darkness, and consequently during the night, plants disengage
carbonic acid. Ingenhouz had already observed that this dis-
engagement of carbonic gas was constantly operated by flowers
and 'roots. Finally, in our own day, Boussingault, Garreau,
Sachs have been able to demonstrate that this exhalation is a
permanent and general fact, that it is effected even by the leaves
exposed to the sun. In truth we have here to deal with an act
indispensable to everything which lives. Without this continual

1 Boussingault, Annales de Chimie et de Physique. IV6 serie, 1868, t. XIII.
8 Th. de Saussure, Eecherches Chimiques sur la Vegetation. 1804.

CHAP, n.] VEGETAL NUTRITION. 99

labour of slow oxydation organised substances could not
accomplish their metamorphoses, operate the exchanges of
matter which constitute the fundamental act of life.

As Dutrochet said in reference to this point : " Life is one ;
the differences are not fundamental, and when we follow the
phenomena to their origin the differences disappear." l

This absorption of oxygen correlative to a disengagement of
carbonic acid, is the act called respiratory in animals, and we
can give it the same name in plants, forasmuch as the essential
fact is identical in the two kingdoms. Animal and plant absorb
ai:rian oxygen : animal and plant, while producing heat,
water, and carbonic acid, burn their fat and amylaceous matters.
We even find in the vegetal cells a substance analogous to the
principal residuum of the combustion of the albuminoids in
animals, urea : namely asparagine, immediate azotised and
crystalloidal principle.

The respiratory property is essential to life : it is indispensable
even to the chlorophyllian cells, which become incapable of
reducing the carbonic acid when they lack oxygen, and this is
why they are asphyxiated in an atmosphere of pure carbonic
acid.

Every living element is at hirst for oxygen, and to such a
degree that sometimes certain organisms steal it even from
stable chemical compounds.

Vibrionians, studied by M. Pasteur, decompose the tartrate of
lime and transform lactic acid into butyric acid to procure for
themselves oxygen. It is besides by an analogous process that
in most of the vertebrates the anatomical elements deoxydise
the haematoglobuline of the haematia.

In the plant oxygen combines in totality with the carbon of
the tissue : for in pure oxygen there is perfect equivalence.

Modern researches the most exact have shown that vegetal
growth operates only through the aid of the absorption of
oxygen by the tissues of plants, and that this absorption

1 Dutrochet, De VEndosmose, p. 326.

H 2

100 BIOLOGY. [BOOK n.

is proportional to the growth. It is, for example, very consider-
able in germination. Thus seeds and buds absorb, in evolution,
many times their weight of oxygen. It is the same with flowers.
Mowers, like all the parts not green of plants, manifestly absorb
oxygen ; but they absorb it in great quantity, and, a curious
thing, in the monoical plants, the male flowers absorb more
oxygen than the female flowers. A fact deserving of remark is,
that in all the organic vegetal combinations, oxygen is always
in smaller proportion than would be needful for the complete
combustion of their carbon and of their hydrogen, for their
total transformation into water and into carbonic acid ; and the
fact is wholly in accordance with the theory of respiration.

It is known well, that one of the constant effects of oxydation
is a certain production of heat, and that the oxydation of the
tissues is the principal source of animal heat. Though less
active, vegetal oxydation produces likewise perceptible calorific
effects, especially in germination and florescence. Barley grains
heaped up for the preparation of malt heat much. In the
spadix of the aroidese, at the time of fecundation, the excess of
temperature above the exterior medium may amount to 10 or 12
degrees. The same fact is observed, but in a less degree, in the
isolated flowers of the Cucurbita, Bignonia radicans, Victoria
regia, and so on.1

However, the respiratory oxydation, and the nutritive or
assimilative movement which results therefrom, are not effected
except within certain limits of temperature. The minimum is
variable as the species varies. According to M. Boussingault 2
the leaves of the larch decompose carbonic acid at 0°, 5 to
2°, 5 j those of the grass of the meadows between 1°, 5 and 3°, 5.
According to MM. Cloetz and Gratiolet, the carbonic assimilation
commences above 6 degrees in the Vallisneria, between 10 and
15 degrees in the Potamogeton.

This absorption of oxygen is by no means comparable with

1 J. Sachs, Traite de Botanique, p. 847.

* Boussingault, Comptes Rendus de VAcad. des Sciences, LXVIII.

CHAP. IL] VEGETAL NUTRITION. 101

that which is produced after the death of the plant, and which
has for result the mineralisation more and more complete of the
organised tissues, deprived of life. In the last case special
chemical combinations are produced : first of all, a ternary
compound, ulmine (C40 H16 O14), which is transformed into a
series of derived products more and more oxygenised (ulmic
acid, humine, humic acids, and so on). Such of these products
as are acid join themselves to the ammonia formed also during
the cadaveric decomposition of the plant ; they then constitute
soluble salts, which can be reabsorbed by the roots, and thus be
restored to the vital movement.

To terminate this abridged description of vegetal respiration,
it remains for us to indicate by what paths the air introduces
itself into the mechanism of the vegetal tissues.

In the inferior plants, the mosses and the conf ervse, there is no
aerian circulation, no special apparatus. The oxygen is absorbed
direct by the cells. In the complex plants, having true roots,
true aerian leaves, canals, there is a commencement of functional
specialisation. The air is absorbed a little by the bark, but
especially by the leaves. Th. de Saussure, when analysing the
interstitial air of plants, found that the air the least modified,
the least poor in oxygen, is that of the leaves ; that of the stems
is less oxygenised, and that of the roots still less.

The air probably penetrates into the phanerogamous plant by
the stomata of the inferior surface of the leaves. Thus if we
plunge leaves into water and if we subject them to the action of
the pneumatic pump, we see the air escaping regularly in bubbles
by the section of the vessels of the petiole (Dutrochet). Once intro-
duced by the stomata, the air circulates in the lacunae, the inter-
cellular meatus, especially in the tracheae and the punctuated
tubes, when the first flow of sap in spring has forsaken them.

In the aquatic leaves destitute of epidermis and of stomata
the aerian water acts direct on the cells, with thin walls, of the
parenchyma. When there are stomata the process is the same
as in the open air.

102 BIOLOGY. [BooK ir.

In the complex plant, the air is therefore subjected to a sort
of circulation, which Dutrochet justly compares with the aerian
circulation in the tracheae of insects which are likewise
furnished with stomata. Once introduced into the vegetal
tissues, the air is absorbed by the anatomical elements, and by
the sap or the blastemas which it contributes to elaborate.
Finally it is probable that a part of the oxygen resulting from
the reduction of the carbonic acid by the green parts, and which
is consequently in the nascent state, that is to say, eager to
enter into new combinations, is also forthwith absorbed, or even
mechanically driven into the canals and cellular interstices.

4. Sap Elaborated or Descendent.

The water of the soil, more or less charged with the sub-
stances in dissolution, penetrates by endosmosis into the cells of
the spongioles, and thence is impelled into the vessels, the
mea'tus, the anatomical elements, step by step. Finally it is in
some sort inhaled by the whole of the tissues, which all have
need of nourishment, and more specially by the leaves and the
green parts. These chlorophyllian tissues are the special
exhaling and assimilative organs, in the midst whereof the sap
undergoes a very important elaboration, and in a fashion passes
into the state of true blastema. So far in effect the sap was
nothing more than a simple mineral solution. In the leaves the
sap is vitalised, it becomes an organisable liquid. It is only
after this metamorphosis of the sap that new anatomical elements
can be formed at its expense, that the organism expands and
grows. This sap thus modified has been called sap descendent,
because its ordinary course is from the leaves to the roots. It is
interesting to follow the flow of this elaborated sap, to see how
it passes and distributes itself from the leaves to the root of the
plant.

It is needful for us here to take anew into account the effect
of the endosmosis, which plays moreover such a foremost part in

CHAP, n.] VEGETAL NUTRITION. 103

all the nutritive mechanism of the plant. Besides their special
chlorophyllian function, and perhaps in consequence of that
function, the leaves exercise on the sap a double propulsion :
they aspire it from below to above, and they drive it back, after
elaboration, from above to below. This is doubtless a kind of
circulation, but rudimentary, without regularity, effected little by
little, sometimes by one route, sometimes by another. The cells
of the leaves, whose contents are dense and albuminoidal, are well
arranged for absorbing by endosmosis the ascending lymphatic
sap, to determine there, when it has penetrated into their cavity,
synthetic chemical phenomena, to carbonise it, that is to say, to
enrich it with atoms of carbon, thanks to their special property,
then finally to expulse it by exosmosis. At the same time they
concentrate it by depriving it of a notable portion of its aqueous
vehicle, which is exosmosed, and escapes by evaporation.

Experience has demonstrated that this exhalation is an active
phenomenon, the result of a vital act, probably chlorophyllian,
and not a passive evaporation. The confirmatory facts are
numerous. Hales was the first to discover that light augments
the aqueous exhalation on the surface of the leaves. The
phenomenon depends on the solar light and very little on heat :
for, simple light diffused, slightly calorific, suffices, whilst in the
shade a heat equal or even very inferior does not act much, and
at night the aqueous exhalation stops.

If of two simple plants one is exposed to the light, and the
other is kept in darkness, the first absorbs much more water than
the second.

Sennebier has shown that leafy boughs dipped in water at
their lower extremity aspire much more water in light than in
darkness. He observed also that heat in darkness has little
influence on this sort of suction, and that the results vary
according to the species of plants. In general the plants which
in the light resist the most the desiccating action of the
atmosphere are those which in darkness resist it the least, and
reciprocally. The intense contact of the air with the cells of

104 BIOLOGY. [BOOK n.

the leaves is necessary to this aqueous aspiration, as the following
fact proves.

Dutrochet having plunged into water a leaved stalk of Pisum
sativum, deprived it of its interstitial air by means of a pneumatic
pump. The aerian cavities, once purged of air, were promptly
invaded by water. The plant was then taken from the water
and the extremity of its stalk was alone kept in it. It was, in
this state, exposed to the diffused light, but it had become inca-
pable of aspiring water, and was asphyxiated, or rather it was
incapable of aqueous aspiration because it was asphyxiated.

From the preceding facts it clearly results that the ascension
of the sap is bound in a certain measure to the functionment of
the leaves, and that this functionment, which comprehends simple
aqueous exhalation, is subordinated, like every physiological act,
to the absorption of oxygen by the anatomical elements, to
respiration.

We must note a fact, whose explanation is however easy,
namely, that the absence of light has not on the green corollse
the action which it exercises on the chlorophyllian leaves.
As these corollse respire simply after the manner of the animal
anatomical elements, by absorbing oxygen and without acting on
the carbonic acid, the absence of light does not hinder them from
living, from aspiring sap, and so on.

Once elaborated and concentrated by the special action of the
leaves, the sap comes forth from the cells by exosmosis, and just
as the endosmotic action of the radical spongioles has driven the
lymphatic sap from below to above, toward the branches and the
buds, the exosmotic impulsion drives back the elaborated sap
from above to below, from the leaves to the roots. We have
seen that the ascension was especially accomplished through the
ligneous centre, or at least through its youngest, peripheric part ;
the descent of the sap, on the contrary, is more habitually
achieved through the bark. In ascending it enriches itself more
and more, either carrying along with it the substances contained

CHAP. II.] VEGETAL NUTRITION. 105

in the cells which it bathed in its passage, or by the special action
of the green leaves ; l in descending it is impoverished, on the
contrary, more and more, for in going along, either it relinquishes
organisable substances at the expense of which anatomical
elements are formed, or it simply deposits in already prepared
cavities masses of nutrimentary or organisable matters.

We haye just described, in a fashion, the schematic mode of the
circulation of the sap ; doubtless there are numerous irregularities,
and the sap undergoes in its course diverse impulsions, diverse
deviations. The exosmotic impulsion is not the sole cause of
the descendent propulsion. We must likewise take into account,
as for the ascending sap, the relative void, made by the fixation
of a duliquid part, by the nutrition and the formation of the
tissues, and lastly, mechanical influences. For instance, it has
been remarked that the agitation of the stems by the wind
favours the growth of plants. Knight made on this subject
precise experiments by immobilising certain stems. We are
justified in thinking that the waving and the bending of the
stems have as a result local pressions which aid the march of the
sap in the canals. This descendent march of the elaborated sap
must be slower than that of the aqueous sap : for this time we
have before us a liquid, denser, more viscous, even sometimes
differentiated. In effect there are assuredly diverse species of
sap ; for we must consider as such the milky liquid called latex,
existing in great abundance in the cortical system of lettuce, of
the fig-tree, of the euphorbise, and so on. The gum of trees of
the Pinus kind, and so on, the resin of the conifers, are probably
also sap residua.

1 Knight collected in the spring at various heights the sap of the sycamore
and of the birch. These are the variations of specific weight which he
observed on the sycamore :—

Level of the soil 1,004

At seven feet 1,008

At twelve feet 1,102

In the last case the sap had moreover a sugary savour.

106 BIOLOGY. [BOOK ir.

The sap can descend by the aubier or by the ligneous tissue of the
central system. Knight having decorticated circularly a stem of
Solanum tuberosum, saw the subterranean tubes developing them-
selves indeed less, yet still developing themselves; in which
case the sap could only have descended by the bark.

The same observer has demonstrated that the elaborated sap
can take an ascending movement when it is dissolved and carried
on by the lymphatic sap.1

Furthermore the lymphatic sap can take a descendent
movement, for example, when it forms in the leaves, absorbing
the water which moistens them. When we cut the stem of a
plant containing abundance of liquids, for example a milky plant,
we see the latex flowing from the two surfaces of section There
is here a simple sap movement, determined by the elastic pression
of the canals primitively distended, turgid through the action
of the endosmosis. In sum, the sap, elaborated or not, passes
where it can. A root which had become naked Dutrochet cut,
during winter, lower down than a shoot which it had produced ;
he saw, the following spring, this shoot continue to live. The
development of the leaves had not yet taken place ; consequently
the shoot lived without elaborated sap, by the mere help of the
lymphatic sap, driven now from above to below. Knight having
cut off from a forward variety of Solanum tuberosum the runners
which produce the tubers, there resulted in the stem a plethora
of elaborated sap. The plant, which, usually is not florescent, had
flowers, fruits, and even small tubers were developed on many of
the aerian parts of the plant.

If in the spring we cut a vine-root we see the lymphatic sap
flowing from the superior or central trongon as from an aerial
stem.

Dutrochet observed that the trunk of a tree cut down during
winter and completely stripped of its branches presents never-
theless in spring an outflow of elaborated sap under its bark.
This sap existed therefore in the central part of the vegetal
i Knight, Philosophical Transactions, 1805.

CHAP, ii.) VEGETAL NUTRITION. 107

tissue, forasmuch as it came neither from the leaves nor from
the roots. It had been already prepared, and must have
reached the periphery by means of the transversal medullary
radii.

It is probably because the monocotyledonous plants have none
of these transversal medullary radii that there is not in them
any flow of sap between the cortical system and the central
system, and consequently no growth at the point of junction of
these two systems.1

In sum, there is no true -circulation of sap, forasmuch as the
course of the nourishing liquid is at the mercy of a number of
accidents. There are only two principal sources of the sap :
the spongioles of the roots, which introduce into the plant the
aqueous or lymphatic sap, and the leaves, which elaborate this
sap already thickened and enriched, to impel it afterwards to the
lower part of the plant, by all the paths that are practicable.

5. Algce and Mushrooms.

"We have just presented a rapid picture, or rather given the
enumeration, of the different phases of nutrition in a complex
plant having roots, stems, and leaves. Naturally things come to
pass otherwise in the inferior plants, composed almost wholly of
cellular tissues, in what are called in these days Thallophytes, in
the algae and mushrooms.

Here there are neither true vessels nor true roots. The
aliments are absorbed by the cells which are in contact with
them, and transmitted by endosmosis from point to point.

Nevertheless the algae have still fellowship with the higher
plants by the presence of chlorophyll, even in the coloured algae,
where it is masked by colouring matters (nostochineae, and so on).
Chlorophyll acts there as it acts everywhere ; it absorbs and
assimilates carbon, and only operates in the light.

In many thallophytes the elementary cell has taken the
1 Dutrochet, De VEndosmose, p. 387.

108 BIOLOGY. [BOOK n.

elongated form of a filament, simple in certain intermediary algae
(phycomyceta), divided transversely by partitions in others, and
sometimes ramified (mucedinese).

The nutritive characteristic of the mushrooms is the absence
of chlorophyll. Through this characteristic the mushrooms
resemble the animal organisms. They are incapable of
assimilating direct the aerian carbon, and have no need of light.
We can even see some of them living under the soil, as for instance
the truffles, and so on. From the absence of chlorophyll it also
results that the mushrooms, like animals, have need of aliments
wholly prepared, of combinations carbonised, assimilated by other
organs. Thus when they are not parasites they have to live at
the expense of organic matters in process of decomposition.

Furthermore, and this is a general characteristic, they are
incapable of forming a single granule of starch. This fact
explains in a certain measure the office of chlorophyll in the
synthetic chemistry of the vegetal organism, and serves us as
transition to pass to the following chapter.

CHAPTER III.

VEGETAL ASSIMILATION AND DISASSIMILATION.

1. Organic Substances.

BEFORE speaking of the chemical transformations of which the
vegetal organism is the seat and the agent, it will not be useless
to enumerate the various bodies which penetrate into the living
plant from the ambient medium.

"We have seen the roots, and sometimes the leaves, absorb
water, of which the plant has an imperious need. We know
that the water absorbed by the roots is loaded with substances
in solution. Among these substances, some are terreous, and we
shall pass them under review at a future time in this exposition
(salts of lime, soda, potash, ammonia, &c.). It is through the
roots that the larger part of the azote which is necessary to the
plant penetrates into it. This azote is introduced into the plant
in the form of salts of ammonia and especially of a series of
substances produced from the slow oxydation of the organic
detritus. The type of these substances is a compound of C40,
H!6, O14, ulmine, which, according to Miilder, is transformed by
a gradual sur-oxygenation into ulmic acid, humine, humic and
geic acids, &c. The acids of this series eagerly absorb ammonia,
and compose with it soluble salts. They form also soluble
alkaline salts, and terreous salts, which would be insoluble if the
ammonia did not form therein an aggregation of double salts.
According to Miilder, water co-operates with these formations,

110 BIOLOGY. [BOOK n.

being decomposed to oxydize these matters, and a part of its
hydrogen combines itself with the azote of the air and forms
ammonia. Plants raised in ulmic acid and powdered charcoal,
entirely deprived of ammonia, shut up in an atmosphere and
watered with water which was also destitute of it, have yielded
to analysis a double or treble quantity of azote to that which
their seed contained at the commencement of the experiment.
In this case, the plant being deprived of ammonia, it is very
possible that it had absorbed the azote directly from the air.
The following facts render this a very probable eventuality : —

Schroeder sowed cereals in flower of sulphur watered with
distilled water, and contained in vessels of glass or porcelain
covered with a receiver. The seeds germinated, and produced
halms from 2 to 14 inches in length, bearing short ears, which
however flowered. When dried, they were five times the weight
of those seeds from which they sprang.

Boussingault sowed twenty-nine seeds of clover in sand
previously reddened in the fire. The plants which they produced
weighed 67 grains at the end of three months. (Annales de
Chimie, t. Ixxvii.)

Peas treated in the same way yielded in the same space of
time plants weighing 72 grains, loaded with flowers and perfect
seeds, &c. (Quoted by Burdach, Traite de Physiologie, t. ix. p.
255.) Finally, as we shall see further on, recent experiments of
M. G. Ville put the normal absorption of atmospheric azote by
the plant almost beyond doubt.

If the anatomical elements of plants bring about many
chemical syntheses, they are also very capable of disaggregating
mineral compounds. We know that chlorophyll decomposes the
carbonic acid of the air. It has been also observed, that seeds
germinating in water decompose it, and absorb a portion of its
hydrogen.

The oxygen contained in a plant comes in a large degree from
the ae'rian medium ; a notable portion of it from the decomposi-
tion of the carbonic acid by chlorophyll. The plant also

CHAP, in.] VEGETAL ASSIMILATION AND DISASSIMILATION. Ill

procures it in another way. In general, as we have seen, the
nutritive substances absorbed by the roots are veiy rich oxygenised
compounds ; on the contrary, the assimilated substances, forming
a large portion of the dry matter of plants, are either poor in
oxygen, or do not contain it at all. Assimilation must then be
specially an act of dis-oxygenation ; now we know that it takes
place particularly in the chlorophyllian cell. We have then here,
as Sachs justly remarks, the place, the conditions, and the time
of this dis-oxygenation.1

In fact, it is in the chlorophyllian cells that assimilation, or
rather the vitalization, of various substances introduced into the
plant takes place. It is towards this living and active laboratory
that they converge ; it is there that they enter into conflict with
each other. The chlorophyllian cell is a powerful apparatus of
synthesis, effecting organic combinations which still defy the
power of contemporary chemistry. The molecules of azote,
carbon, oxygen, hydrogen, &c., penetrate the cellular cavity, some
free, others entangled in combinations more or less complex.
There they are mixed together, dragged into the circular current
of the cellular protoplasm, subject to the attraction exercised
upon them by the chlorophyll, and, on the other hand, shaken
by the undulations of the yellow rays of solar light which add
their impulsion to the vibrations by which they are already
animated. The atoms and the molecules yield to these united
influences ; those particles which are involved in combinations
abandon them, resume their liberty, and all unite to form living
organic substances, ternary and quaternary substances.

We have already said a few words upon the advent and aspect
of one of these substances, one of the most important in vegetal
physiology, starch. Starch is especially formed in the green cells,
and even in the interior of the chlorophyllian bodies. We have
seen that its formation is in direct dependence upon the chemical
operation of the chlorophyll, consequently upon light. It

1 J. Sachs, loc. cti., p. 821.

112 BIOLOGY. [BOOK ir.

appears under the influence of light, and in its absence re-
dissolves. We seize here chemical synthesis in some degree in
the very act.

Assuredly proteic substances are also formed in the chlorophyl-
lian cell. Doubtless the phenomenon is less evident here ; but we
know that the sap reaches the leaves in the state of a fluid still
very slightly charged, and that it issues from them as a living
liquid in the state of nutriment and blastema.

We have just said that chemical synthesis, exercised upon the
chlorophyllian cell, had probably resulted in a subtraction, an
emission of oxygen ; but there are, on the contrary, organic
compounds that result from super-oxydation ; these are the
vegetal acids. Their molecule contains more oxygen and hydrogen
than are required to form water. Oxalic acid, one of the most
frequent, contains three atoms of oxygen to two of carbon
(C2O3). In laboratories, it i§ obtained by oxydizing sugar and
fecula with azotic acid. In the plant, it is probably produced by
the direct action of oxygen upon the same substances. Oxalic
acid, in fact, as well as the ternary, acetic, citric, and malic acids,
and so on, is not formed in the synthetic laboratory of the
chlorophyllian cells, but in those parts which are not green, or
which are sheltered from the light

Organic vegetal substances are naturally subject in a high
degree to isomerism and instability, like all aggregates of this
kind ; they also often undergo metamorphoses during the course
of the nutritive process. Their molecular mutations succeed and
engender each other.

The spores, seeds, bulbs, tubers, rhizomas, the vivacious shoots
of ligneous plants are in truth nutritive reservoirs, where the
organised sap deposits organic substances, utilizable at a later
time, either for germination or for nutrition, when the flow of
lymphatic sap reappears in spring. These substances are then
drawn away, and furnish materials for the development of the
folial and floral buds, for the nutrition of the tissues, which could
not otherwise obtain aliment, f rondation not yet existing ; but

CHAP. IJL] VEGETAL ASSIMILATION AND DIS-ASSIMILATION. 113

before being drawn away and utilized, these substances in reserve
often undergo metamorphoses.

The fecula, deposited in autumn in the ligneous body of the
trees, is often in spring transformed into sugar, which, in certain
plants, the maple, for example, mixes largely with the ascending
sap. MM. Payen and Persoz have shown that there is first of
all produced a matter called by them diastasis. This matter has
the property of rendering the fecula soluble, by transforming it
first into dextrine, then into sugar. It produces this isomeric
transformation by means of very small quantities, for it is capable
of rendering soluble five thousand times its own weight of fecula.

As to the albuminoidal substances in reserve in expectation of
the spring sap, such as starch, sugar, inuline, and fat, certain
among them, not having lost any of their solubility, are simply
seized anew, drawn away, and finally assimilated. Others also
undergo their isomeric modifications, specially in germination.
Thus, during the germination of the leguminous plants, caseine
is metamorphosed into albumine in the cotyledons. In the
gramineous plants, the gluten of the endosperm, which is insoluble
in water, is dissolved during germination, and is conveyed into
the plantule. The energetic oxydation which always accompanies
germination also determines the formation of regressive sub-
stances, for example, asparagin, which is perhaps re-assimilated
at a later period.

A certain portion of carbonated hydrates is also totally burned,
• converted into water and carbonic acid by vital oxydation. In
this case, the hydrates are burned either in the anatomical
elements, or in the sap of the plant, as they are in the blood of
the animal, proving once more that there is no antagonism
between the vegetal kingdom and the animal kingdom, and that
essentially the primordial phenomena of life are identica.1 in the
two kingdoms.

As Cl. Bernard has very well observed, if an animal eats the
sugar accumulated in beet-root, that does not prove that this
sugar was made for him. On the contrary, it was destined (if

i

114 BIOLOGY. [BOOK 11.

we may employ this word in speaking of blind organic finality)
— it was destined to be burned by the beet-root itself during the
second year of vegetation, when florescence and fructification are
developing themselves.

However this may be, the nutritive substances, when suf-
ficiently elaborated, are assimilated ; that is to say, their molecules
intercalate themselves between the organic molecules already
formed, either to replace those which have been destroyed, or to<
bring about the enlargement of the cell ; others spontaneously
organize themselves in the blastemas.

We may form some probable conjectures as to the special office
of the various categories of organic substances. It is probable
that the hydrates of carbon and the fatty bodies are especially
transformed into cellular membranes^ these membranes being prin-
cipally constituted of cellulose, the molecule of which is almost
indentical with that of starches, sugars, and fats. Thence come
also without doubt the vegetal acids, tannin, and the colouring
matters.

The proteic substances are probably employed in the formation
of internal azotized utricles included in the cells, and of the
cellular protoplasm and the chlorophyllian particles.

They also furnish, but by incomplete oxydation, by degradation,
asparagin, of which we have spoken, and without doubt the
vegetal alkaloids (quinine, morphine, strychnine, &c.), quaternary
but not proteic substances, and of which the molecule, very
complex, very rich in carbon, and tolerably rich in hydrogen,
contains also a notable proportion of oxygen and very little
azote.

2. Inorganic Substances.

Besides atmospheric gases, a number of mineral substances are
introduced into the plant through the roots. The principal are
alkaline and terreous bases : potash, soda, ammonia, magnesia,
lime, generally salified by sulphuric, azotic, phosphoric, silicious
and carbonic acids. Many of these substances do not contribute

CHAP, in.] VEGETAL ASSIMILATION AND DIS- ASSIMILATION. 115

anything to the nutrition of plants ; they are mechanically driven
by the water which penetrates into the plant, and are deposited
in the deep tissues, after having formed insoluble salts with the
vegetal acids.

Habitually, these mineral particles are uniformly intercalated
between the organic molecules } also by incineration, or by
treating the vegetal anatomical elements with certain acids, we
may succeed in destroying the organic substances which they
contain, preserving only the mineral skeleton, but nevertheless
keeping the form of the destroyed anatomical element.

Often the mineral salts also form true crystals in the vegetal
tissues and even in the cells. Such, for example, are fine granulous
incrustations of carbonate of lime, bundles of spars of oxalate of
lime, or even tolerably voluminous crystals.

The amount of mineral matters in a plant is proportioned to
its age, and also to the quantity of water which flows through it ;
in short, to the activity of the vegetation. The proportion of
soluble substances may undergo certain variations. As to the
insoluble substances, they accumulate ceaselessly, mineralizing
the plant more and more, and contracting the range of action of
life. If most of the mineral substances drawn from the soil
are of little use in the development and nutrition of plants, yet
some of them are very important, for example, ammonia, the
phosphates and the sulphates. Others again appear sometimes
necessary to one plant or group of plants, sometimes to another.

Most plants which grow on the sea shore contain much soda,
and this soda is necessary to them ; for they grow only upon the
sea-coast or near saline deposits inland.

"We always find in the tissues of plants of certain very natural

families, the same mineral substances. They have thus chosen

i them in a certain degree. We may mention the gramineous

plants, the stems of which, without exception, contain silica,

"whilst the fruits contain phosphate of magnesia and of ammonia.

But often the same plants contain different salts, according as
they grow in various soils.

I 2

116 BIOLOGY. [BOOK n.

Let us notice, however, that it is possible, under the condi-
tions of artificial culture, to rear, without silica, plants which
habitually contain much of it, maize for example.

Lime seems to be indirectly useful to plants, by serving as a i
vehicle to the sulphuric and phosphoric acids, and by neutralizing
the oxalic acid, hurtful to the plant in which it is formed ; but
any other base could do as much.

3. Influences of Light, Heat and Electricity.

We have already spoken at length upon the influence of solar
light upon vegetal nutrition. It is such, that, without this
influence, nearly the whole of the vegetal world would cease to
exist. In consequence, the animal kingdom, which, in the
continental parts of the globe, lives, directly or not, at the
expense of the vegetal kingdom, would also become extinct, at
least in its higher branches, on the surface of these terrestrial
regions. In effect, without solar light, mushrooms alone, of all
plants, could still live upon the continents.

But animal life would probably find refuge in the sea. A
number of the lower marine animals are nourished and live
without the help of plants. Now these rudimentary organisms,
to which we must grant the faculty of synthetising complex
organic substances, after the manner of plants, could themselves
furnish alimentation for higher aquatic animals, as often actually
happens. All this aquatic fauna can thus live without light.
This is even the case now, as the dredgings and soundings made, ;
during the last few years, at the bottom of the ocean and of
large lakes has proved.

Solar light only penetrates the sea to a very small depth.
Below 50 fathoms (1 fathom = lm '82,) a very sensitive photo-
graphic paper is no longer impressed. At this depth also, the
vegetal kingdom is only represented by rare specimens, and
below 200 fathoms it absolutely disappears. Now the bottom of
the Atlantic ocean, which is as much as 1400 and 1500 metres

CHAP, in.] VEGETAL ASSIMILATION AND DIS-ASSIMILATION. 117

deep, is covered with organized beings, all belonging to the group
of the Protozoa of Haeckel. This bottom is everywhere car-
peted with those little sarcodic, gelatinous, contractile organ-
isms, called by Huxley Bathybius Hceckelii. Amongst these
bathybians live foraminifers, rhizopods, radiolites, sponges.1

"We therefore must admit that certain of these rudimentary
animal organisms can decompose water, carbonic acid, and
ammonia, or assimilate the numerous organic detritus in suspen-
sion in the marine waters, arising from the dejections of animals,
and from the decomposition of their dead bodies. It is only thus
that they can live, can multiply, and can aliment more complex
animals.

Analogous facts have been observed by MM. de Candolle,
Forel, and Dufour, in the Lake of Geneva. There also the most
sensitive photographic paper ceases to take an impression beyond
the small depth of 50 or 60 metres in summer, and 40 or 50 in
winter. Nevertheless, at the bottom of the lake live from
thirty-five to forty species of lower animals.

The idea of a necessary solidarity between the two organic
kingdoms must then be abandoned. This solidarity only exists,
in a very large measure, in the organized terrestrial world.
There, we may admit, as a general thesis, that the vegetal
kingdom is necessary to the animal kingdom. Now nearly the
whole of plants cannot live without light. But the calorific and
chemical solar rays are not less necessary to the maintenance of
life. Solar irradiation is then one of the grand causes of the
production, development, and duration of organized beings. The
great theory of the transmutation and correlation of physical
forces is therefore applicable to biology. We must guard,
however, against making this application with a mathematical
and inflexible rigour which the subject does not allow of. We
think also that there has been too great an inclination of late
years to consider solar irradiation as the unique and universal

i The Depths of the Sea, by C. Wyville Thomson. 8vo. London, 1873.
French Translation ; Les Abimes de la Mer, 8vo. Paris, 1875.

118 BIOLOGY. [BOOK n.

cause of life upon the surface of the globe. With these reser-
vations, we cannot deny that solar irradiation is fixed, accumulates
in the plant, and that, in the infinitely numerous cases in which
the plant serves as animal alimentation, this irradiation is
treasured up by it, transforms itself into various series of
molecular vibrations, into heat, movement, thought, etc.

We have not to return here to the chief office fulfilled by
light in the nutrition of plants ; but, besides the phenomena of
synthetic chemistry accomplished by chlorophyll, light also
produces in plants certain secondary phenomena, which probably
depend upon the chlorophyllian property. Thus many plants
sleep in the night, that is to say, droop their leaves or follicles
more or less, or rather gather them up along the stem or
principal petiole. This phenomenon assuredly depends upon
the light, since De Candolle was able to make sensitive plants
sleep in the day in artificial darkness, and, on the other hand,
succeeded in waking them at night by the light of lamps.1 This
so-called slumber, this sinking down of the leaves, arises probably
from a diminution of the turgescence of the tissues, and this
diminution is assuredly the result of the inaction of the
chlorophyllian cells, which, no longer exhaling, no longer
forming organic syntheses, summon less water into the petiolary
canals, the meatus, and so on.

If the luminous undulations are, as it were, the soul of vegetal
life, caloric undulations are not less indispensable to the nutrition
of plants. Above and below a certain temperature, vegetal life
ceases. Speaking generally, the thermometric limits of vegetal
life are 0 degree and 50 degrees.2 It must be noticed that the
cellular juices, being liquids very full of substances in solution,
do not congeal at 0 degree. M. Uloth has seen seeds of Acer
platano'ides and triticum germinate between the fragments of ice

1 Memoir e sur I 'Influence de la Lumiere artificielle sur les Plantes (Mem, des
Savants Strangers de Vlnstitut, t. i. )

2 Sachs, Ueber die obere Temperaturgrenze der Vegetation (Flora, 1864).

CHAP, in.] VEGETAL ASSIMILATION AND DIS-ASSIMILATION. 119

in a glacier, and send down numerous roots, several inches in
length, into ice destitute of crevices.1 It is then probable that
germination can still take place at 0 degree, and, as it always
develops a remarkable quantity of heat, the result must have
been, in the case mentioned by M. Uloth, the partial fusion of
the ice, whence it became possible for the roots to penetrate.

We have given the limits of temperature, but these vary-
according to species. Most plants succumb after remaining for
ten minutes in water at from 45 to 46 degrees. In the air,
phanerogams are killed after remaining from ten to thirty
minutes in a temperature of from 50 to 51 degrees. To produce
a lasting alteration, it is sometimes necessary that the tempe-
rature should reach 60 degrees. Death then takes place through
the coagulation of the albuminoidal substances.

Dried vegetal tissues (seeds) can naturally support more
extreme temperatures of heat or cold. Thus, tissues full of
sap are killed at 50 degrees, whilst dried seeds of Pisum sativum
may be heated with impunity to 70 degrees for an hour.

In every plant each function has its special limits of tempe-
rature. We cannot enter here into the enumeration of facts
in detail. Moreover, we have already stated the temperatures
necessary for the operation of chlorophyll.

In cells killed either by congelation or by too high a tempe-
rature, the cellular membranes become permeable ; liquids filter
through : consequently turgescence ceases. First of all, the pro-
toplasm becomes immovable, takes a sombre tint, and rapidly
loses its water by passive evaporation.

Life is not sufficiently active in plants for them to have, like
the higher animals, a temperature of their own, independent in
some degree of that of the exterior medium. The small aquatic
plants, and the subterraneous parts of terrestrial plants, have
generally the temperature of the ambient medium. On account
of their volume, the massive stems follow more slowly the

1 Uloth, Flora, 1871.

120 BIOLOGY. [BOOK n.

exterior thermometric variations, and consequently, they may
be hotter or colder than the exterior medium.

Electricity seems to exercise very little influence upon the
nutritive movement of plants. Feeble constant currents, small
sparks of induction, have no apparent effect either upon the
movement of the protoplasm, or upon that of the mobile leaves.
A too powerful current, a spark too strong, causes either the
arrest of the protoplasm or that of the tissue. Thirty Grove
elements instantly stop the protoplasmic movement.

As to the electric state of the tissues, it is curious to observe
in the plants phenomena very analogous to those which have
been observed in the nerves and muscular fibres of animals, and
have served as a basis for many theories. In effect, in a cut
stem, there is a current from the surface of the stem to the
centre of section.1 The electric currents, which, without doubt,
result from the chemical assimilative and dis-assimilative reac-
tions of nutrition, are not peculiar to such and such a vegetal
or animal tissue. There again the two organic kingdoms touch
and intermingle,

1 Buff, Annal. der Chimie und Pharmacie, 1854, Band 89. Jurgensen, StU'
dien des Physiologisches Instituts zu £reslau, 1861, Heft I. — Heidenhain, ibid.,
1863, Heft II.

[NOTE. — A French metre is equal to 39^^ English inches, or
to rather more than a yard. The small g occasionally occurring
indicates gramme ; the small m, metre ; the small mm a millimetre.
— TRANSLATOR.]

LI i; i; A u i

UNI VKHSITY OF

CALIFORNIA. J

CHAPTER IV.

OF ANIMAL NUTRITION.

AFTER what has been already said concerning the chemical and
anatomical constitution of animals and plants, nutrition in
general, and the nutrition of plants, it will be possible to
abridge considerably the general exposition of the phenomena
of nutrition amongst animals. In effect, if nutrition is traced
back to its fundamental activities, that is to say, to assimilation
and dis-assimilation within a living matter, amorphous or figurate,
the principal phenomena are plainly similar in both kingdoms ;
and, even if we only consider certain rudimentary animal
organisms, for example the gregarine, we can say that there is
an identity of process, not certainly with that which takes
place in the superior plants, where there already exists a high
degree of differentiation in tissue and of division of labour, but
with the nutritive mode of purely cellular plants. In effect,
the dissimilarity between plants and animals decreases in pro-
portion as we compare the inferior types of the two kingdoms.

Correctly speaking, we should rather compare the gregarine, a
parasitical animal without organic differentiation, to a mushroom.
In effect, as mushrooms live by assimilating the products of
decomposed organisms, and seem powerless to effect the chemical
synthesis of which complete plants are the agents, in the same
way the gregarine absorbs and assimilates direct in the intestines
of articulated animals and worms, where it lives upon the
complex organic substances which it would be incapable of

122 BIOLOGY. [BOOK ir.

forming. The same general remark may be applied to a number
of infusoria, the amoebae, and the rhizopods.

At a later period we shall have to describe the principal
modes of anatomical and physiological differentiation, by means
of which the complex animal organisms prepare the way for
interior nutrition, and we shall see them gradually working,
becoming more and more complicated in proportion as we rise
in the animal series. For the present, we have only to consider
the general nutritive phenomena ; the principal exchanges of
matter, which are accomplished between a complex animal and
the exterior world.

In such an organism, there is no direct interchange between
the anatomical elements and the ambient medium ; intermediary
liquids, which may be compared to the elaborated sap of superior
plants, have the office of receiving the different kinds of nutriment
fully prepared for assimilation, of conveying them — of presenting
them, as it were, to the anatomical elements ; the latter, by
virtue of their innate constitution, of their affinities, draw from
these interior and living mediums the substances which suit
them, and reject those of their molecules which are altered by
the action of life.

We have already shown what is the composition of those
living mediums called plasmas and blastemas. We know that
therein are found three orders of immediate principles, mineral
substances, ternary matters, amyloidal, saccharine, fatty, finally
and especially substances proteic or albuminoiidal. Naturally,
the diverse chemical compounds of living liquids are so much
the more numerous, the more varied, in proportion to the
complexity and differentiation of the animal, since in every
organism each kind of anatomical element has its special
alimentary preferences. Also, whilst amongst the superior
plants we find some products of dis-assimilation little varied,
as for instance asparagin, and perhaps some vegetal acids; we
see among the superior animals the proteic substances alone
furnishing, when the anatomical elements reject them after

CHAP, nr.] OF ANIMAL NUTRITION. 123

having oxydized them, urea, urates, creatine, creatinine, inosie
acid, inosates, and so on.

A very general fact, and one which it is very important to
point out, is that all truly animal organisms cannot live without
constantly absorbing complex organic substances, and that they are
powerless to create these themselves, at least in sufficient quantity,
from the mineral world, whence it is necessary that they should
draw a supply, either from other animals or from vegetals.

The blood of the superior animals is the great mart in which
the anatomical elements provide themselves with the substances
which are necessary to them, and reject those which encumber
them. As a consequence of its office in the vital movement, the
blood is itself necessarily subject to a perpetual exchange of
materials. It gives to, and takes from, the anatomical elements
on the one hand, and on the other, to and from the ambient
medium. It borrows oxygen from the outer air by means of
the respiratory organs ; it receives from the digestive organs
immediate principles, restorative nutriments liquefied or dissolved.
Finally, the totality of the lymph, when it exists, continually
diffuses itself in the blood. On the other hand, the tissues
yield to it the dissolved or liquid residues of vital combustion.

The expenditure of the blood balances its acquisitions. It
exhales, by means of the lungs and skin, water, carbonic acid,
and azote ; it expels through diverse special channels, water
and complex organic substances. Of the latter the most part
are purely regressive, and destined to be returned to the
mineral kingdom; the others are modified by special secreting
organs, and become fit to play a more or less important part in
the various physiological functions. Finally, on the other hand,
the blood yields to the anatomical elements the three orders
of immediate principles indispensable to their conservation, the
oxygen which burns and vivifies them, the water which soaks
them, diverse mineral salts, hydro-carbonic ternary substances,
new prote'ic matters which, in each anatomical element, replace,
molecule by molecule, the exhausted materials.

124 BIOLOGY. [Boo* n.

This double movement of acquisition and expenditure is
simultaneous in the blood, as the twofold movement of assimila-
tion and dis-assimilation is simultaneous in the anatomical
elements.

After this general sketch of the nutritive going and coming
within the complex animal, we can now occupy ourselves with
each of the three groups of immediate principles which enter
into the composition of the body of every animal, and indicate
in bold outline under what form they enter the organism, and
under what form they leave it.

[NOTE. — A word which frequently occurs in the French
original is intime. To the Latin intimus, the French intime, the
German innig3 in their scientific import, there is not any exact
English equivalent, though ultimate and other words are employed
in lack of better. — TRANSLATOR.]

CHAPTER Y.

OF ASSIMILATION AMONGST ANIMALS.

1. Mineral Principles.

THE mineral principles which ceaselessly introduce themselves
into animal organisms are, gases of the air, a large quantity of
water, and dissolved composite solids, of which the principal are
phosphate of lime, phosphate of magnesia, bi-carbonate of lime,
fluoride of calcium, silicious acid, chlorure of sodium, carbonate
of soda, alkaline phosphates, oxyde of iron, etc. Amongst the
lower organisms, the two chief gases of the air penetrate direct
through the limiting surface of the animal. Amongst others,
apparatus exist, varying according to species and medium, but
whose office is limited in final analysis to bringing the outer air
into contact with the black or venous blood, without other
barrier than a very thin organic membrane — that is to say, to
realizing in a special part of the organism the conditions of
osmotic absorption which exist over the whole surface of the
bodies of inferior animals.

Of the two principal gases of the blood, the one, azote, is
absorbed in smaller quantity, and seems normally to exercise no
function in the animal economy. It is rejected as it was
absorbed, and by the same channels. Nevertheless, the animal,
in a state of inanition, fixes a certain portion of it in its tissues.
Probably there is then a direct synthesis. As a compensation,
when the animal enjoys an abundant azotic alimentation it

126 BIOLOGY. [BOOK n.

rejects all the aerian azote, and, in addition, a certain portion in
excess, arising from the reduction of the aliments.1

Oxygen has a very different part to play in the exercise of
physiological functions. It penetrates into the blood, is con-
veyed by it into contact with the tissues which impregnate
themselves with it, and burn, thanks to its assistance, the
immediate principles which constitute them, particularly the
complex organic substances. Finally, the anatomical elements
in return restore to the sanguineous medium an equal volume
of carbonic acid, of which a large portion is exhaled, particularly
through the respiratory surfaces, a smaller part forming alkaline
carbonates, by combining itself with the bases previously existing
in the tissues.

This oxydation of anatomical elements is one of the primordial
phenomena of life. It must take place, under pain of death, in
every living substance, figurate or amorphous, vegetal or animal.
It is a fundamental, biological phenomenon, and all the reactions
of living chemistry depend upon it. Without its intervention,
there can no longer be either assimilation or dis-assimilation in
any organized substance, and the anatomical elements become
incapable of exercising their special functions ; the chlorophyllian
cell then ceases its chemical synthesis, the muscular animal
fibre no longer contracts, the nervous cell becomes incapable of
feeling, volition, or thought ; there is no longer either maintenance,
or development, or generation of the anatomical elements.

Amongst the invertebrated animals, whose blood does not
contain globules, it is the sanguineous plasma itself which
conveys the dissolved oxygen to the tissues. Amongst almost,
the whole of the vertebrates, on the contrary, this office principally.,
devolves upon the red sanguineous globules, as we have alreadyi
indicated. The substance of these globules, which has a great
affinity for oxygen, imbibes it, fixes many volumes of it, and
becomes vermilion. The oxygen thus flowing on with the

1 Ch. Eobin, Des Humeurs.

-

.v.] OF ASSIMILATION AMONGST ANIMALS. 327

globules is conveyed even into the finest capillary ramifications
of the circulatory system. There the globules meeting the waves
of carbonic acid, the expulsed residuum of the oxydation of
anatomical elements exchanges with this acid its oxygen, with
which it had only made a shifting combination. The oxygen
thus yielded goes, by endosmosis, to re- vivify the tissues, whilst
the carbonic acid, carried away in its turn by the globules, to
which it has imparted a sombre red tinge, is exchanged by them
for a fresh provision of oxygen, in the capillary vessels of the
special organs called respiratory. The respiration of the most
complex animals is summed up then in a series of very simple
acts : absorption by the red globules of aerian oxygen, cession
of this oxygen to the anatomical elements, in exchange for a
residuum of carbonic acid, finally the exchange of this carbonic
acid for a fresh supply of aerian oxygen. It is a ceaseless
circuit, which stops only with death.

Almost the whole of the water contained in such large
proportion in the animal organism penetrates it from without,
either through the general surface of the body, as in inferior
organisms, or by that of the organs called digestive, as in the
complex animals. Nevertheless, it is probable that a considerable
quantity of water forms itself in the interior of the living
tissues themselves, by the complete oxydation of certain ternary
hydro-carbonated matters. The water besides conveys along
with it into the economy important quantities of calcareous,
alkaline, and ferruginous salts, and also a ceitain quantity of
air, which it holds in solution. Boussingault has stated that
the quantity of mineral substances imbibed each day at the
drinking trough by a milch-cow rises to 50 grammes.

In weight, water forms the major part of every animal
organism, of every plasma, of every anatomical element. The
albuminoidal substances retain a notable quantity as constituent
water, another portion as water of imbibition. Water does
not seem to be directly decomposed amongst animals, and its
office is specially mechanical, but none the less important. It

128 BIOLOGY. [BooK IT,

is water which furnishes to the immediate principles the fluid
medium, indispensable to nutritive exchanges, which maintains in
the tissues the same principles in a state of solution and emulsion,
in a word, of needful molecular division, so that the chemical
reactions indispensable to life may be accomplished. Deprived
of their water, living substances lose their mobility and their
instability, and become in a measure mineral. We know that
certain infusoria, rotiferous, tardigrade, and anguillule, lose or
recover their physiological functions according as they are dried
or moistened.1

Water issues from the economy in various ways. It is
exhaled through the external cutaneous or mucous surfaces
directly in contact with the exterior medium, either in the
state of vapour or in a liquid state. But, amongst complex
animals, it is especially through certain secretory or excretory
organs, particularly through the renal and sudorific glands, that
the water of the organisms escapes and returns to the mineral
kingdom.

A quantity of mineral salts, oxydes, etc., penetrates into the
economy either with the water, or with the aliments, whatever
they may be. The principal are phosphates of lime, of magnesia,
of soda, of potash, sulphates and carbonates of lime, of silica,
of chloride of sodium, alkaline carbonates, salts of iron, etc.

Many of these salts, though insoluble in water, are dissolved
in the blood, by means of the albuminoidal substances, the
carbonic acid, and other salts, which act upon them as solvents.
Once in the blood, they pass into the substance of the anatomical
elements ; thus, in the muscular flesh, we find phosphate of lime,
phosphate of magnesia, and tribasical phosphate of soda. The
alkaline carbonates are also met with in most of the solids and
liquids of the economy.

Certain of these salts form themselves within the tissues by
the process merely of nutrition ; thus carbonic acid, the result

1 J. Gavarret, Nouvelles Experiences sur les Rotiferes (Journal du Progres,
t. IV., p. 421 ; t. V. p. 1).

CHAP, v.] OF ASSIMILATION AMONGST ANIMALS. 129

of the oxydation of the anatomical elements, combines itself
with alkaline bases ; the oxydation of the proteic substances
causes, specially in the nervous tissue, the formation of phos-
phoric acid, which combines itself also with the alkaline bases,
united with less powerful acids, ete.

Tribasic phosphate of lime, which is dissolved in the blood, or
combined with the albuminoids of this humour, is deposited in a
solid state in the bones, the teeth, and the hair.

There is a remarkable proportion of chlorure of sodium in the
blood, and in all the liquids and solids of the economy. Its
office is not yet correctly defined, but its presence seems neces-
sary. It cannot help figuring in the alimentation of men and
animals. Livingstone, during his travels across the African
continent, having to live for whole months without animal food
and milk, relates that he was seized with a violent desire to eat
sea-salt ; he adds, that after thus abstaining from them, animal
food and milk had at first, to him, a very salt taste.

Though there is in the blood a very small quantity of iron, it
is a substance absolutely necessary. We have 'seen that it forms
part of the haemoglobine of the blood. Its curative office in
anaemia is as beneficial as it is well known.

2. — Hydro-carbonized Principles.

The hydro-carbonized principles, that is to say, specially the
1 amyloidal and saccharine substances, seem only to penetrate into
the circulation, and consequently the anatomical elements, after
having been transformed into dextrine or glycose, in the same
way that amongst plants the amylaceous masses are saccharified
before being made use of for nutrition. In the blood, and also
in the anatomical elements, these ternary substances meet the
oxygen, which reduces them, when the oxydation is complete, to
water and carbonic acid. This transformation of hydro-carbonized
substances leaves no organic residuum, but develops heat, and
contributes powerfully to facilitate all the reactions, all the

K

130 BIOLOGY. [BooK u.

exchanges of material which are the very foundation of nutrition.
01. Bernard has proved that a portion of these ternary compounds
form themselves direct, by synthesis, in animal tissues as well as
in those of plants. The liver of animals forms in its cells
an amyloidal matter denominated glycogene, which is afterwards
transformed into sugar. The placenta of the larger number of
mammifers is also a producer of glycogene. The placenta of
ruminants seems to form an exception, but the glycogenical
function is then fulfilled by platings, by special villosities of
the amnios. We also find sugar in the muscles of the foetus,
in the larger portion of the epithelial cells covering its mucous
membranes, in the bones and the cartilages. In the crab, where
development is achieved by sudden bounds, by moultings, the
liver only contains glycogenical matter during these periods of
rapid growth.

It seems certain that the glycogenical cells of the liver, and
all the analogous cells, can synthetically form glycogenical matter
at the expense of the aliments, whatever they may be ; but it
seems also incontestable that they directly utilize substances of
a similar composition contained in the aliments. M. W. Pavey
has, in effect, shown that in dogs fed exclusively upon animal
aliment, the mean proportion of glycogenical matter was 6 -9 7 in
the 100, whilst it rose to 17 '23 per 100 in dogs fed upon boiled
potatoes, barley-meal, and bread. Finally, the proportion was
14*5 in the 100 when a considerable portion of sugar was added
to the ration of animal food.1

We have said that the combustion of hydro-carbonized matters
in the organisms developed heat, which was afterwards utilized
in the reactions of living chemistry. We shall see farther on
that a portion of this heat can also transform itself direct into
muscular movements. In effect, we find sugar in the muscles of
the foatus, in the tissue of muscles immobilized by the section
of their motory nerves, and in the muscles of animals in the

1 The Influence of the Diet on the Liver. London. (Guy's Hospital Reports,
1859.)

CHAP, v.] OF ASSIMILATION. AMONGST ANIMALS. 131

sleep of hibernation. Finally, we find, in the juice extract-
ed from the muscles, lactic acid and inosite, which seem
products derived from the oxydation of hydro-carbonized
substances.

We must remark also, that during the last stage of intra-
nt erine life, when the muscles already contract frequently, only
lictic acid is met with in their tissue, as in the adult. We
know, moreover, that when a muscle is immobile, only a very
small part of the arterial blood is transformed therein into
venous blood. It seems then that, in effect, , muscular action
may be one of the principal causes of the oxydation of hydro-
carbonized substances contained in the blood and in the tissues.
A«J to the question of the direct transmutation of heat into
movement by the muscle, the subject is so complex as to demand
a separate chapter.

Substances analogous to the amyloi'dal and saccharine substances,
fat bodies, also enter the blood in a state of very fine division
—a state of emulsion. In the superior animals, this emulsion
is accomplished by special liquids, bile and the pancreatic juice ;
the latter passes with these matters into the blood and decom-

' poses them into glycerine and into fatty acids ; for they do not
seem to be always utilized in nature. In the blood the fatty
bodies evolve themselves by forming fatty acids, oleic, stearic, etc.,
which become oleates and stearates of soda and potash ; besides,

( cholic and cholele acids, whence are formed cholates and choleates ;

; finally, cholesterine, and a fat phosphoric substance, cerebrine.
It is probable, moreover, that like the larger portion of amyloidal
in utters, they also end by being oxydized, in developing utilizable
heat. We know that the alimentation of the inhabitants of the

, polar regions contains an enormous quantity of fatty matters,

\ and that, under the same conditions, European sailors have found
the advantage of adopting the same kind of alimentation as the
natives.

It is also certain that animal organisms can produce fat from
saccharine matters. MM. Dumas and Milne-Edwards, having

132 BIOLOGY. [BooK n. I

fed bees exclusively upon honey, obtained thus an overplus
of wax.1

Whatever may be * their source, the fatty matters of the
economy, when in excess, are deposited in the meshes of the
cellular tissue, and generally in the larges quantity where
the organic activity is the least.

3. — Albumino'idal Substances.

Are protei'c substances completely formed, by chemical synthesis,
in the economy? That is possible, but not sufficiently proved.
It is most probable that the albuminoidal substances of the
anatomical elements are derived by means of multiple isomeric
elaborations and modifications from the compounds of the same
kind existing in the aliments. These substances the inferior
animals, without differentiated anatomical systems, absorb direct
from the ambient medium ; the other kinds of animals find
them already prepared in other organisms. According to a
general formula, which has for a long time found acceptance,
it is the vegetal kingdom which is forced to provide for the
animal kingdom. We have seen that probably the marine
fauna forms an important exception to this formula, which is
correct as regards a very large majority of the terrestrial
animals.

But, finally, whether the first origin of organic substances be
vegetal or animal, it is not the less true that the least complex
animal has need to borrow from other organisms non-mineral
aliments, without which it cannot live. If, as we have just
seen, the fact may in a certain degree be contested as regards
the albuminoidal and saccharine compounds, it is undeniable in
regard to the more important materials of living beings, the
protei'c substances.

The animal never either absorbs or assimilates directly these
substances ; it is necessary that they should undergo, before
1 Comptes Eendusde V Academic des Sciences, 1843, t. xvii. p. 531.

CHAP, v.] OF ASSIMILATION AMONGST ANIMALS. 183

absorption, important isomeric modifications, due, in the superior
animal, to the action of fermentescible agents called pepsine,
pancreatine, etc., which are secreted by certain portions of the
digestive apparatus. Under the influence of these agents, the
albuminoidal vegetal and animal bodies undergo an isomerical
transformation. All become soluble and incoagulable by heat ;
they are then peptones, and it is under this form that they enter
the circulation. Amongst the vertebrates, the intestinal capil-
1? tries, and consequently the intestinal veins, are the principal
channel for the absorption of the albuminoids. Once in the
blood, these substances pass from the state of peptones, or
albuminose, to that of albumine, of plasmine or fibrinogenous
matter. This complicated elaboration is necessary : thus a
solution of albumine of egg injected into the lungs, into the
serous vessels, into the cellular tissue of an animal, into one of
its veins, is never assimilated, and passes intact into the urine.1

The peptones were not coagulable by heat, but the azotised
principles which result from them, and which at last form
themselves in the blood, become again coagulable. Electively
absorbed by the anatomical elements, they incorporate them-
selves therewith molecule by molecule, after having undergone
a final isomeric modification. In effect, justifying the title of
prote'ic which has been given to them, they become, in final
result hsemoglobine, keratine, syntonine, osseine, etc., all these
substances having a chemical composition analogous to that
which produces them, but being endowed with very different
properties.

But the albuminoidal substances do not alone penetrate the
web of living tissues. They bring with them a number of mineral
matters, upon which they act as solvents, — for example, calcareous
salts, silica, etc.2

The peptones, which have the same property, incorporate with
themselves in some degree, certain dissolved substances. In

1 Cl. Bernard, Progrls et Marche de la Physiologic Generate en France, p. 197.

2 Ch. Robin, Lefonssur les Humeurs, pp. 103, 104.

184 BIOLOGY. [BOOK n.

effect, artificially digested, and mixed then with much sugar,
they nevertheless offer no reaction if treated with the reactive
of Trommer.1

The complex azotised matters assimilated by the tissues are not
the only ones which the blood furnishes. Other azotised substances
are formed by means of the coagulable principles of the blood,
through special secretory organs called glands. These substances
are destined to be the specially active agents, the source of]
various liquids to which we shall have to refer. Let us cite, as
examples, the digestive ferments, pepsine and pancreatine, of
which we have just spoken.

It will be seen from the preceding remarks, how difficult it is
to strike the balance of the nutrition of an animal. The
alimentary substances are, in fact, only utilized after having
undergone a succession of elaborations, of metamorphoses, and,
as we shall see, before being eliminated, they are elaborated
anew. For the anatomical element is not a passive element
allowing itself to imbibe like a filter : it is a living agent,
endowed with special needs, which it satisfies, under penalty of
death, by choosing amongst the substances in contact with it,
by forming sometimes completely the substances indispensable to
its nutrition, then by decomposing and rejecting them ; it is an
agent at once of synthesis and of chemical reduction.

It is especially within the nucleus of the anatomical element
that its power of chemical attraction and repulsion seems to
dwell. In the glycogenical cell, according to 01. Bernard, the
sugar only accumulates while the nucleus is persistent ; and in
the muscular fibres, the nucleus is persistent as a regulator of
the nutrition.2

On the contrary, the degeneracy and death of the element
would be the consequence of the disappearance of the nucleus.

1 M. Sohiff, Digestion, t. ii. p. 154.

2 Cl. Bernard, Progres et Marche de la Physiologic, etc., p. 99.

CHAPTER VI.

OF DIS-ASSIMILATION AMONGST ANIMALS.

WHEN once the nutriments are elaborated and assimilated, the
first half of the nutritive movement is accomplished ; but in
the living substance there is never any repose, and these same
materials, employed so far in a work of reparation, of recon-
struction, are in their turn worn out ; in their turn they become
unfit to figure in a living tissue, and are eliminated under various
forms.

The substances expulsed from the animal mechanism, the
elements of regression, may be divided into three great categories ;
(1), mineral substances ; (2;, mixed substances, altogether mineral
in their properties, but not formed spontaneously apart from
animal organisms ; (3), finally, complex, azotized, but crystallizablo
compounds. No truly proteic substances are met with. These
last are not normally expulsed from the animal organisms.

The mineral substances are either gaseous, or liquid, or solids
in solution. The gases in almost all animals are azote, oxygen,
and carbonic acid. A small part of the azote is produced by the
complete combustion of a portion of the azotized substances ;
the larger part is simply aerian azote which, after having
penetrated the tissues, is expulsed from them without having
fulfilled any appreciable function. But the experiments of M.
liegnault have shown that animals, even when in a state
of complete repose, and particularly when they have a richly
azotized diet, exhale a small proportion of azote, the residuum

136 BIOLOGY. [BooK n.

of the complete combustion of a small quantity of albuminoidal
matters.1

The exhaled oxygen also no doubt is derived from the outer
air. It is an overplus which cannot be utilized. So far, at
least, it has not been shown that the chemical reactions of
nutrition set at liberty oxygen gas.

As to the carbonic acid abundantly exhaled from the general
surface of the bodies of animals, and especially through their
respiratory organs, it is almost wholly derived from the slow
combustion, the oxydation, of the tissues. In effect, we cannot,
in striking the nutritive animal balance, place any value upon
the small proportion of carbonic acid contained in the atmosphere.
The carbonic acid exhaled by the animal is a true principle of
dis-assimilation ; formed in the very substance of the anatomical
elements, it is first sent into the circulatory torrent of saiiguiferous
animals, to be finally restored to the ae'rian medium. The inmost
mode of formation of the carbonic acid is besides far from be-
ing well known. Thus the quantity of carbonic acid exhaled by
the lungs does not exactly correspond to the quantity of oxygen
absorbed. It seems then that we have not here a simple question
of combustion.2 It has been possible to compare, in the various
tissues and organs, the power of the formation of carbonic acid,
that is to say, to estimate, in a certain degree, the relative
energy of oxydation in the superior animals. The parenchymas
of certain very active glands, such as the liver and the kidneys,
yield a strong proportion of carbonic acid. The muscular tissue
furnishes less of it, and the nervose tissue less still.

It is not in the blood that the greater part of the exhaled
carbonic acid is produced, but in the histological elements them-
selves ; also we find that the blood has always a lower temperature
than the tissues from which it proceeds.

As a mineral substance, and an exhaled liquid, we have to
mention water, excreted specially through the skin and kidneys

1 J. Gavarret, Des Phenomenes Physique* de la Vie, pp. 177, 178.

8 Cl. Bernard, Progres et Mar die de la Physiologic Generate en France, p. 191.

CHAP, vi.] OF DIS-ASSIMILATION AMONGST ANIMALS. 137

in a liquid form, through the respiratory organs as vapour. Let
us note, by the way, that this pulmonary vapour is charged with
putrescible, azotized particles.

But water, in its liquid state, is not excreted alone ; it carries
with it a quantity of mineral substances, mostly saline, some
acid. The salts in solution in the water are carbonates, sul-
phates, phosphates, etc., certain of which have only traversed
the organism to leave it as they entered it; some of them,
however, are directly formed in the organism. Carbonic acid,
for example, so abundant in living solids and liquids, can unite
with the bases which it meets there. On the other hand, it is
probable that the combustion of proteic matters in nutrition
leads to the formation of 'sulphuric and phosphoric acids, which,
on their side, also combine with the bases, either directly, or
by displacing weaker acids. It is certain, in fact, that these
salts always come together in the ashes of protei'c matters
directly burned. Finally, it has been proved that all prolonged
intellectual labour in man corresponds to an abundant excretion
of phosphates through the kidneys, and it is known that the
nervose tissue is very rich in phosphorus.1

To the mineral acids must be added organic acids ; some, not
azotized, such as the lactic acid (C6H505,HO) probably result
from the oxydation or evolvement of the hydrocarburets of the
fats ; others are azotized, and proceed from the oxydation of
protei'c matters. These acids, which have a fixed formula, like
mineral acids, are only formed in the tissues of animals, and
once constituted, they act exactly like the ordinary mineral acids,
and unite with the bases to form salts, which are also expulsed
by the ordinary ways. The principal of these azotized organic
acids are uric acid (C40H4Az4O6) very abundant in man, the car-
nivorous mammifers, birds and reptiles ; and hippuric acid (C18H8
O8Az,HO), which is met with most in the herbivorous mammifers.

1 Byasson, Essai sur le Rapport qui Existe, d, lEtat Physioloyique, entre
VActiviti Cbrtbrale et la Composition des Urines. (Theses de la Faculte de
Medecine de Paris, 1868, n° 162.)

138 BIOLOGY. [BOOK n.

It is in the anatomical elements themselves that the urates
are formed, and thence they afterwards pass into the blood.
They are created particularly in the fibrous and muscular tissues.
The formation of uric acid seems to respond to an incomplete,
imperfect oxydation of the tissues, at least in man, and yet we
find an enormous quantity of this acid in the urine of birds,
whose respiration is extremely active, — a paradoxical fact, of
which there are many in biology, proving that much remains to
be done by physiologists.

We must put in the same category with uric acid a substance
yet more important, urea (C2Az'2H4O2), proceeding, like the uric
acid, from an oxydation of the albuminoi'dal substances, but a
deeper and more complete oxydation. It is necessary to guard
against considering urea as an alimentary residuum ; this sub-
stance is incessantly and regularly formed, and is produced by
the dis-assimilation of the anatomical elements themselves. It is
produced even during abstinence, since Lassaigne found it in the
urine of a man executed after eighteen days of absolute absti-
nence ; and it exists also in the urine of the newly-born. As
it is constantly forming, it is also constantly met with in the
blood, which appropriates it afresh from the tissues.

Urea and urates are not the only products of the molecular
dis assimilation of the anatomical elements. There is a whole
series of analogous compounds ; for, each kind of anatomical
element, having its own composition, assimilates and dis-assimi-
lates particular substances. The principal azotized quaternary
substances proceeding from protelc dis-assimilation are creatine,
creatinine, leucine, inosic acid, and inosates. All these sub-
stances are crystallizable. They are more specially produced by
such or such a tissue. Thus creatine seems to be almost
exclusively the product of the dis-assimilation of the muscular
substance. Leucine is found rather in the tissue of the glands,
with or without an excretive canal, in the lymphatic ganglions,
and also in the grey substance of the brain.1

L Ch. Robin, loc. tit., pp. 686—688.

CHAP, vi.] OF DIS- ASSIMILATION AMONGST ANIMALS. 139

Oxygen is certainly the determinating agent in the composition
of all these regressive bodies. Nevertheless, according to
M. Robin, there is not here simple oxydation, but oxydation
with evolution, and often simple evolvent catalysis, in technical
terms. It would even be necessary, in relation to this, to
establish a kind of antagonism between assimilation and dis-
assimilation. The one would operate through metamorphic
catalysis, and the other through evolvent catalysis. These are
data which can only be admitted with considerable reservation.
In fact we can, in a certain degree, note in passing the substances
which enter into an animal organism, and those which issue from
it ; but, from the ingress to the egress, a succession of reactions
and transformations has taken place, which we are far from
having traced step by step, since we have not yet even succeeded
in giving the definitive formula of the albuminoTdal substances.

CHAPTER VII.

ULTIMATE PHENOMENA OF ANIMAL NUTRITION.

M. CL. BERNARD has recently expressed some general views upon
the phenomena of nutrition, supported only by a very small
number of facts, but certainly true in a degree, and highly
interesting.

According to him, we must altogether reject the idea of direct
alimentary assimilation. The histological element he thinks
acts not upon the complex substances absorbed by the animal
organism, but upon the elements of these substances, which it
thus decomposes, not uniformty, but according to its needs, by
selecting, as a chemist does in his laboratory, and drawing forth
the elements which are indispensable to it from complex
compounds with very diversified formulas. The following fact,
quoted by Burdach, would support this view : — " John has seen
seeds perish when sown in powdered silica, with potash and
fresh white of egg ; they only germinated when this last was
already putrified. Here organic matter only acts as an aliment
when it is on the point of returning entirely to inorganic
nature." l M. Cl. Bernard has himself observed that, without
doubt, the saccharine aliments introduced into alimentatipn
favoured the production of the glycogenic*al matter of the liver,
but that other bodies altogether different,, such as glycerine,
chloroform, etc., did not favour it less. All these bodies simply
acted as nutritive excitatives. The hepatic cell appears at first
1 Burdach, Physiologic, t. ix. p. 392.

CHAP, vii.] ULTIMATE PHENOMENA OF ANIMAL NUTRITION. 141

in the liver without determinate characteristics ; then we see an
amidonised product forming in its cavity, as starch forms in the
chlorophyllian cell, and without doubt by an analogous chemical
synthesis.

The larva of the fly, the asticot, may be considered as a bag of
glycogenical matter ; now this larva is developed and nourished
especially by animal food in a state of putrefaction, tending to
decomposition, to mineralization. Accurate experiments seem
to have shown that this larva develops itself, not at the expense
of animal food in general, but of a small part of the extractive
substance ; nevertheless it fabricates glycogenical matter with
this azotized substance.

The glycogenical function is diffuse in the lower animals, and
specialised in man and the higher mammifers. M. Cl. Bernard,
concludes from this that the case must be the same in the
formation of albuminoidal substances, that consequently there
must be animal cells, where the synthesis of protei'c matters is
specially accomplished at the expense of the dissevered elements
of the nutriments.1

It is very certain that the various species of histological
elements fabricate varied quaternary substances, since each of
them has its special chemical composition, and their assimilation
is carried on at the expense of the same sanguineous plasma.
But where are the special agents of the albuminoidal fabrication
in the complex animal organism 1 No one yet knows. Besides,
it is incontestable that the animal cannot live without azotized
aliments, already containing, in a prepared state, substances
analogous to those which constitute the web of its tissues. No
animal can aliment itself simply with distilled water and air,
in which however it finds wherewith to compose, elementarily,
ternary and quaternary substances.

The precise amount of our knowledge of this very interesting

1 Cl. Bernard, Des Ph&nomenes de la Vie Communes aux Animaux ct O.MM
Vigttaux (Revue Scientifique, 1874).

142 BIOLOGY. [BOOK IT.

question it is very easy to show : verily the chlorophyllian cell
makes starch, and probably protei'c substances, by combining the
elements of the atmosphere and those of the ascending sap.
Verily, also, there are in animal organisms cells which fabricate
an amyloidal substance, either by isomeria or by synthesis. All
the rest is in a state of hypothesis.

A very certain fact is, that animals cannot aliment themselves
without substances already elaborated either by plants or by
other animals, and that it will be the same with man, as long as
chemistry cannot fabricate completely, synthetically, the im-
mediate organic and complex principles of which he stands
in need.

The synthesis of albuminoidal substances seems as if it would
baffle the science of the chemist for some time longer. Never-
theless, these substances are supremely the materials of life ;
but their mobility, their instability, that is to say the very
qualities which render them suitable to form living anatomical
elements, are serious obstacles not only to their artificial fibrica-
tion, but even to the determination of their formula, and, up to
the present time, chemistry has only succeeded in synthetizing
hydrocarburates, or regressive azotized bodies, of which urea is
the type.

A very important property of the coagulable albuminoidal
substances proceeds from their very mobility ; it is the faculty
M-hich they have of transmitting to each other in living organisms
and by simple contact their molecular conditions. These are only
simple isomeric changes, and it is by this process that each
anatomical element, whatever may be its composition, fabricates,
at the expense of the plasmas, of the common nutritive juices,
the special compounds which it must assimilate.1

After the same manner also we may explain the action of the
different kinds of virus, as well as hereditary transmission and
morbid contagion.

We may observe analogous phenomena in protei'c substances
1 Ch. Robin, loc. tit., Introduction, p. xiii,

CHAP, vii.] ULTIMATE PHENOMENA OF ANIMAL NUTRITION. 143

deprived of life. It is thus, for example, that muscular flesh
and blood putrefy with great rapidity when brought into contact
with the organic particles called miasmata, and that we obtain,
by condensation, aqueous vapour from the atmosphere of marshes,
or from confined air vitiated by agglomerations of men or
animals.1

We have spoken, in one of our first chapters, of the great
affinity shown for water by albuminoldal substances. We conse-
quently comprehend what extreme importance this property has
in the scheme of nutrition. It is, in effect, one of the principal
conditions of absorption and assimilation. In reality, all the
anatomical elements of animals, even of those which live in the
air, are aquatic organisms. They live in the plasmas and
blastemas,' as marine animals live in the water. They have their
inner liquid mediums, which are their safeguards from the
destructive action of the exterior aerian medium. It is in these
inner mediums that they take their nutriments and throw off
their secretions. Also all the animal membranes lose their vital
properties by drying, and the aerian animals, as well as the
aquatic animals, can only respire through the intermediation of
tissues incessantly lubrified.

After what we have already said of the chemical composition
of animals and plants, as well as of nutrition in general, it is
self evident that the ultimate phenomena of nutrition, already sc
analogous in the two organic kingdoms, are identical in the
animals called Jierbivoruus and in those called carnivorous. There
is only a difference in the constitution of the apparatus charged
with the preparation of the alimentary materials. We know
besides that many animals are herbivorous or carnivorous indif-
ferently ; and we shall see further on that the transformation of
a herbivorous animal into a carnivorous one is only a pastime for
the physiologist. This transformation takes place spontaneously
under the influence of abstinence. Then the urine of herbivorous

1 Ch. Robin, loc. cit., Introduction, pp. 195—199.

144 BIOLOGY. [BOOK n.

animals, normally muddy and alkaline, becomes clear and acid
like that of the carnivorous animals. Besides, if we compare
each day the quantity of oxygen absorbed by an animal in a
state of inanition, by respiration, with the quantity of the same
gas which enters into the composition of the carbonic acid
exhaled, we see the proportion established first of all as if the
animal had been subjected to an alimentation of fat, then as if
it had been exclusively nourished on animal food, but in an
insufficient quantity.1

In effect, assimilable, complex, ternary, and quaternary sub-
stances are necessary to the anatomical elements of animals ;
but it matters very little whether these substances are derived
from the vegetal kingdom or the animal kingdom, provided they
have undergone a suitable preparation. If these aliments of
exterior origin fail, the nutritive movement continues never-
theless for a longer or shorter time in complex animals, but
then it is exercised at the expense of the living substance itself ;
the organism literally eats itself. The blood first yields all that
it can yield of assimilable substances, and repairs its losses at
the expense of the tissues, and of the anatomical elements, of
which it previously furnished the materials. It takes back
what it gave. This is called physiological abstinence.

This abstinence may be provoked by various causes. .Every-
thing which can disturb the internal mutations of the tissues in
such a way as to cause the nutritive expenditure to predominate
over the receipts is a cause of physiological abstinence; for
example, an ill-chosen alimentation, even if it be copious, to
which is wanting any one of the constituent principles indis-
pensable to the organism ; or an incomplete reparation, whether
it be a pathological defect of the organs, or an alteration of the
exterior air (encumberment, confined air, etc.). Abstinence bears
simply upon the oxygen then; but we have seen that this gas
is indispensable to the utilization of alimentary materials.

In the lowest scale of the organized world, in beings formed of
1 G. See, Le Sang et les Anemies.

CHAP. VIL] ULTIMATE PHENOMENA OF ANIMAL NUTRITION. 145

one cell, or of a group of identical cells, abstinence causes the
dissolution of the organisms in the ambient medium, the direct
return to the mineral world. This is what indeed takes place in
the most complex beings ; but here the scene is more varied ; for
the body of the superior animals is an aggregate of various
organs and apparatus, constituted by the grouping, the intrication
of anatomical elements dissimilar to each other, peculiar in form
and function. The body of the higher mammifers must then be
considered as a republic hierarchically organised with division of
labour. To one tissue is attached secretion, to another movement,
to another sensibility, motility, thought, &c., to all life ; that is to
say, the movement of assimilation and dis-assimilation, but more
or less tenacious, rapid, and energetic. The result is that towards
abstinence each of these tissues takes a different attitude, that
when once the food is cut or furnished in an insufficient quantity,
our histological citizens are more or less slowly re-absorbed and
perish. Those which are first destroyed are either the least
robust, or those which have the most urgent nutritive needs,
those which, from their essence, are the seat of the most rapid
mutations. They dissolve, and the immediate principles which
constituted them are re absorbed and pass back into the circu-
latory torrent ; for there is circulation in all the very complex
animals. The blood gives back to the tissues that which it has
just taken from them ; but it takes from some to give to others ;
it first satisfies the most exacting to the detriment of the more
patient. In short, the more voracious and active of the anato-
mical elements devour those which are more feeble, and live at
their expense.

According to Chossat,1 whose work is the authority upon this
question, the death of an animal from total or gradual abstinence
takes place when the animal has lost about forty-hundredths of
its total weight, or sometimes fifty-hundredths, if the animal is
fat. The following table will indicate the unequal repartition of
loss in the different organs :

1 Chossat, liecherches Exptrimcntales sur V Inanition, 4°, Paris, 1S43.

L

146 BIOLOGY. [BOOK n.

Parts losing more than the average. Parts losing less than the average.

0,400 . 0,400

.Fat 0,933 Stomach 0,397

Blood 0,750 Pharynx, oasophagus . 0,342

Spleen 0,714 Skin 0,338

Pancreas ..... 0,641 Kidneys 0,319

Liver 0,520 Respiratory apparatus . 0,223

Heart 0,448 Osseous system . . .0,167

Intestines 0,424 Eyes 0,100

Locomotive muscles . . 0,423 Nervous system . . . 0,019

A very curious fact arising out of this table, is the feeble
deperdition undergone by the nervous centres, even at the
moment of death. We may say that, before dying, they have
really devoured the other organs, and it is to their almost
complete integrity that we must trace the relative integrity of
the intellectual faculties observed in men in a state of inanition
up to the moment of death.

The physiological disturbances proceeding from abstinence are
not less interesting to study. The temperature of the body
gradually lowers, in proportion as the nutritive movement isj
retarded. Chossat, experimenting upon various animals, guinea-
pigs, rabbits, crows, turtle-doves, pigeons, chickens, has found
3 degrees to be the daily average lowering of the temperature,
with a more considerable depression the last day. At the
moment of death, the average heat of the body falls to 24°'9.

Normally the nutritive movement is retarded during the night,
and the temperature, which strictly depends upon it, falls in hot-
blooded animals to about 0°'74; but during abstinence this
oscillation is always augmented with regard to amplitude and
duration, and the thermometric depression reaches 30<28.

The secretions and excretions are also closely connected with
the nutritive movement, since their principal function is defini-
tively to expulse the products of dis-assimilation or to favour the

CHAP. VIL] ULTIMATE PHENOMENA OF ANIMAL NUTRITION. 147

absorption of the aliments ; it is then very natural that during
abstinence they should be diminished or suppressed. The liver
ceases to form animal starch, which normally contributes to its
fabrication of sugar (Cl. Bernard). The urine still contains urea,
the principal residuum of the combustion of the protelc sub-
stances of the tissues ; but naturally, it contains less and less
of it.

The digestive tube shrinks ; sometimes even it becomes
ulcerated by the local re-absorption of its anatomical elements.

Vital combustion being gradually extinguished, respiration,

which furnishes it with the necessary quantity of oxygen, or at

least with the major part of this oxygen, performs its functions

with gradually decreasing energy. The movements of the

muscles are retarded. It is the same with the beatings of the

heart, which, in a man in a state of inanition, have been known

I to fall to 38 per minute. The wearing out and rapid re-absorption

| of the very tissue of the heart is now added to the general

nutritive depression.

The functional disturbances of the nervous centres are still
very imperfectly determined. They are sometimes absolutely
wanting in man. In animals, however, notice has been taken of
insomnia, first a period of agitation, then a period of stupor,
finally one of fury ; in man, there are often hallucinations.1

Abstinence is naturally better supported when the movement
of life is less energetic. Burdach 2 has in an interesting manner
i connected with this subject some facts observed in the most
various animals. After six weeks of abstinence, a snail had only
lost an eleventh part of its weight ; fresh- water polypi can live
without food for five and even ten years ; toads, two years ;
Chinese gold-fish, several years; salamanders, six months; a
toad shut up in a porous vessel tightly closed, the vessel being
surrounded with earth saturated with humidity, was still living,
though very thin, at the end of two years. It had been kept in

I l Collard de Martigny, Journal de Magendie, t. viii.

* Traitt de Physiologic.

L 2

148 BIOLOGY. [BOOK n.

an almost uniform exterior temperature.1 On the contrary, birds,
whose nutritive movement is intense and rapid, succumb very
quickly. One day of abstinence kills a sparrow, three days a
thrush, &c. The same law is verified in the same animal organ-
ism, according to the various ages. Thus, in middle life, man can
resist complete abstinence for one or two weeks. The child
succumbs sooner, and the old man much later.

Everything which retards the quickness of the nutritive
exchanges helps to support abstinence ; for example, repose in
bed, sleep, and the substances which provoke it.

Without having for the animal the primordial importance
which it has for the plant, solar light is nevertheless a powerful
excitative of life in the animal kingdom also. Moreover, absti-
nence is better supported in darkness. Eight miners shut up
for thirty-six hours in a coal-pit without food said they had
not suffered from hunger.

Nevertheless, in all animals death is sooner or later the
result of abstinence, and in all, it takes place when the organism
has lost a part of its weight, always perceptibly the same for all
the species. If the animals known as cold-blooded live much
longer than others, it is only because their diurnal loss is normally
much less. They expend less, and consequently their capital is
not so soon exhausted.

1 Cl. Bernard, Lcyom sur Us Proprietes des Tissus Vimnts, p. 49.

CHAPTER Vlll.

OF THE MODIFYING AGENTS OF NUTRITION.

, VARIOUS influences modify the nutritive movement, more or
less, for better or worse. These influences dwell either in the
organism itself, or outside it.

: A. It might be said that nutrition is the object of life, if life
has an object ; but it has none, since it is simply the result of
a fortuitous concurrence of cosmical, geological, climacteric, and
even orological facts. It has not always existed on the surface
of our little planet. It will be extinguished there one day.
But, if we cannot say that nutrition is the object of life, we
are justified in saying that it is the basis thereof. A given
organism lasts, prospers, develops and reproduces itself the
more surely the better nourished it is, and it is the better
nourished the better organised it is, that is to say, in more
complete harmony with the exterior medium. Also, as we shall

' see hereafter, the various organic systems of every complex
animal are regulated with regard to nutrition. The result of
the special functionment of each of them is to render nutrition
possible and easy. Here is a series of organic harmonies, of
which we shall give an exposition farther on. We shall see
that there are systems of organs adapted, some to render the
aliments absorbable, others to convey the nutritive substances to
the tissues ; whilst certain others have the function of ventilating
to some extent the anatomical elements, furnishing them with
oxygen, and relieving them of their carbonic acid. Finally,

150 BIOLOGY. [BOOK n.

upon others devolves the task of relieving the animal organism
of the non-volatile residue of denutrition, &c.

But in order that the action, the utility, of these varied or-
ganic mechanisms, their influence on nutrition, may be thoroughly
comprehended, it is first of all necessary to describe them, which
shall be done in its place. We only wish to point out here, in
passing, some interesting facts relative to the influence of the
nerves and nervous system upon nutrition ; for it would be
difficult to place these facts elsewhere.

It is certain that nutrition is, to some extent, independent of
the nervous system. In effect, we see it in operation in the
plants, in the lower animals, destitute of a nervous system, and
in the embryo, which, as yet, has none.

Professor Schiff has seen absorption carried on by the
stomachal mucous membrane, after the section of nearly all
the nerves which communicate with the stomach1 (solar plexus
destroyed, section of the threads of the pneumo-gastric nerve
which are joined to the O3sophagus).

Claude Bernard has likewise observed that the section of the
nerves in the wing of a pigeon does not prevent the feathers
from shooting.

But there are very curious contradictory facts. "We shall see
farther on that the expenditure, the afflux of blood in the finest
sanguineous canalicules, the capillary vessels, is regulated by the
influence of certain special nervous threads, called for this reason
vaso-motors. Under the influence of these nerves, the capillary
vessels contract or dilate ; now these vessels form a net-work of
meshes more or less compact in the web of nearly the whole of
the organs and tissues, and the afflux of the nutritive sanguineous
plasma is more or less abundant, according as their calibre
enlarges or contracts. Here then, the influence of the nerves is
necessary. Moreover, if we paralyze, by section, the vaso-motory
nerves of an organ, we see that this organ can no longer support
abstinence as easily as the others. It seems that it may become
1 M. Schiff, Lefons sur la Physiologic de la Digestion, 1867, t. ii. p. 404.

CHAP, viii.] OF THE MODIFYING AGENTS OF NUTRITION. 151

accustomed to a more abundant nourishment, and if this fails,
it becomes inflamed and suppurates.1

That paralysis of the capillary vessels, and consequently their
persistent dilatation, occasions an excessive afflux of sanguineous
plasma, is proved by the following experiments of Professor
Schiff. He cut one of the lower maxillary nerves of a mam-
miferous animal; then, at the end of a certain time, having
killed the animal, he discovered an increase of volume in the
bone of the jaw, with rarefaction of the osseous tissue.

In a dog two months old, the same physiologist cut the two
principal nerves of one of the posterior members, the sciatic and
crural nerves. Four months afterwards the bones of the member
were hypertrophied, and new osseous productions had formed in
the foot. This result is due to the section and consequent
paralysis of the nervous vaso-motory fibres intermixed with the
other fibres of the nerve.

The same experimentalist has also observed paralysis of the
vaso-motory fibres of the ear of a rabbit cause abundance of
hairs to grow upon that ear.

B. The exterior medium also powerfully influences nutrition
by its principal physical modalities, especially by light and heat.

Doubtless, light has not that primordial importance for animals
that it has for chlorophyllian plants. The animal kingdom has
representatives at the bottom of the Atlantic, at a depth of
nearly two kilometres, whither a solar ray never penetrates, but
there it is only represented by inferior animals. Nevertheless,
in the fauna of caverns, vertebrated species are found j but they,
are modified, and modified for the worse, by the absence of light.
Very commonly, the organs of sight are atrophied. Besides,
very frequently, the skin of the animals of caverns is destitute
of the colouring pigment, as has been observed in a blind fish of
the cavern of the Karstgebirge, and in the proteus anguimts of
the Mammoth Cave.2

1 Cl. Bernard, Rapport sur les Progrls de la Physiologic Gtntralc, p. 215.
8 Ley dig, Histiologie Comparte, p. 94, 95.

152 BIOLOGY. [BooK n.

Every one knows that a man obliged to live, not in complete
darkness, but only in a dim weak light, grows pale, languid,
etiolated. In this case, as we have proved above, when speaking
of abstinence, the nutritive exchanges are retarded.

.To the animal, heat is much more important than light.
Without wishing at present to approach the study of animal
heat, we can already prove that animal and vegetal life is
only possible between certain limits of exterior temperature.
Doubtless animals, and especially the superior animals, do not
yield with a readiness as perfect as that of plants to the;
temperature of the exterior medium, but they only resist itl
up to a certain point. In all animals life is extinguished when
the interior temperature, that of the anatomical elements, re-
mains for some time below zero, for then the humours congeal.
In the higher mammifers death takes place even sooner. The
child in that state of slow asphyxia which has been called oedema
of the newly-born, dies when its temperature descends to about
20 degrees centigrade.1 Experimentalists also indicate this
temperature of 20 degrees as being the minimum of inner
temperature. Nevertheless, the temperature of the blood may
descend to two or three degrees with impunity in a hibernating
animal, just as this animal can then sojourn without injury in
an irrespirable gas ; this is because the nutritive exchanges are
in this case extremely retarded. The anatomical elements can
consequently be satisfied with a small nutritive ration, which,
at a higher temperature, would not suffice to keep them alive.2

Neither is the superior limit very high. A cold-blooded
animal dies when a temperature 30 degrees above zero penetrates
its anatomical elements. For the mammifers the highest limit
is 45 degrees ; it rises to 50 degrees for birds. Without doubt,
an animal can live a certain time in these extreme temperatures,
but only a very short time, and on condition that the ambient

1 Ch. Letourneau, Quelques Observations sur les Nouveau-nte, 1858. (Theses
de la FacuUd de Medicine de Paris. )

2 Cl. Bernard, Lefons sur les Proprietes des Tissus Flvants, p. 50 — 53.

. viii.] OF THE MODIFYING AGENTS OF NUTRITION. 153

atmosphere is dry. Then, in fact, cutaneous evaporation produces
a certain degree of coolness, which makes a momentary compen-
sation. Thus, a mammiferous animal, in a dry hot-house will
support, during some minutes, temperatures of 80, 100, and
even 120 degrees, but only when its inner temperature does not
exceed by more than five degrees the normal temperature. It
first pants; then at the end of a very short time, it falls
instantaneously dead, without agony. When a temperature of
45 degrees has thus invaded the anatomical elements the
muscular sap coagulates, and the animal dies in that state which
is known as cadaveric rigidity. A. thermometer then quickly
introduced into the heart marks about 45 degrees.1

1 01. Bernard, loc. cit., p. 231.

NoTE. A kilometre, that is to say, a measure of a thousand
metres, is equal to rather more than five hundred fathoms. —
TRANSLATOR.]

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UNI VKUSlTY OK

CALIFORNIA.

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CHAPTER IX.

OF THE MEANS OF ANIMAL NUTRITION.

EVERY organised being is the seat of an incessant and double
movement of assimilation and dis-assimilation. In order that this
double movement may be accomplished, and this is the funda-
mental condition of life, it is necessary that it should be
constantly alimented by substances so composed, that they can
be incorporated in the organism.

In almost all vegetals, and in a certain number of the lower
animals, the work is relatively simple, since they draw food
direct, and without preparation from the ambient medium. In
the superior animals, the phenomena are complicated. Before us
are then brought very diversified organisms, where the division
of physiological labour is pushed farther and farther. But in-
this case, the anatomical elements seem to have lost, in vegetative
energy what they have gained in fineness. In order to live, they
need to absorb highly elaborated organic substances, and, for
this purpose, the organism is furnished with a special apparatus,
whose office consists in forming a kind of physiological kitchen,
to modify the elements, to accomplish the first chemical trans-
formation, which renders them more suitable for assimilation.
This apparatus is the digestive system.

But this chemical elaboration would be useless if the alimen-
tary substances, once modified and transformed into nutriments,
did not come in contact with all the anatomical elements, super-
ficial or hidden, in the suitable physical and chemical conditions,
if the residua unfit to sustain the vital movement were not

CHAP, ix.] OF THE MEANS OF ANIMAL NUTRITION. 155

given back to the elements in the degree of their formation. A
special apparatus performs the task of conveying to each
anatomical element, whatever may be the situation and function
of that element in the organism, new materials, while at the
same time it carries away, sweeps off the nutritive residua.
This apparatus is the circulatory system.

Moreover, an incessant atmospheric ventilation is an indis-
pensable condition of the ultimate nutritive exchange. Every
living substance needs to combine with the oxygen of the air,
and to exhale carbonic acid, which is one of the principal products
of this combination. The special apparatus which provides an
easy entrance and issue to the circulating gases in the complex
organism has been called the respiratory system.

But the respiratory apparatus can only provide an issue for
gaseous products ; now denutrition, as we have seen, originates a
whole family, yea, even several families, of regressive products,
salts, quaternary substances. These bodies are taken afresh from
the anatomical elements by the circulatory system; but this
system would be incapable, by itself, at least in a very complex
organism, of removing them definitively beyond the frontiers of
the living histological federation, which constitutes every superior
•organism. For this there must be special apparatus, excretory
glands. *

For the sake of clearness of exposition, we are obliged thus
to cut the complex organism into a certain number of great
divisions ; but in reality, in the living being, all these functions
are bound up together, are indispensable to each other, and are
carried on simultaneously, to such a point, indeed, that, to under-
stand the working of one of them, it is almost necessary to know
the working of them all. Consequently, in giving an exposition
of them successively in the order of our enumeration, we shall
be compelled to leave behind us, on the way, many gaps, many
obscure points, which will only disappear in the course of the
exposition. Finally, when we shall have passed in review
digestion, circulation, respiration, and excretion, it will remain

156 BIOLOGY. [BOOK ir.

for us, in order to complete the description of the adjuvant
means of nutrition, to examine the organs of motility and
innervation, which, while being more specially consecrated to tho
life of relation, are, in one sense, not less indispensable to the
exercise of the great functions mentioned before. For, in
complex organisms, each anatomical element, while having its
own existence, and a certain degree of nutritive and functional
independence, nevertheless does not cease to be closely and,
wholly united to the other histological citizens of the confedera-
tion. There is unity in diversity.

Before commencing the exposition of the great physiological
functions, we have yet a general remark to formulate. In
organised beings, from the lowest to the highest, the most
differentiated, there is a graduated hierarchy. From the physio-
logical confusion which exists at the lowest step of the ladder,
we pass, step by step, through a series of organic models, better
and better finished, to the most perfect specialisation. Nothing
is more interesting than this seriation of organs, especially from
the point of view of the great doctrine of evolution, still so much
discussed, but which more and more vivifies all the branches of
natural history. Now, however succinct may be the general
picture of life which we have undertaken to draw in this book,
the reader will nevertheless find there all the great features, the
principal outlines of the animated world. We shall try then
to describe briefly, but clearly, the various degrees, the successive
advances of each great function in the animal world, the only
one in which organic specialisation has attained a high degree of
perfection. Apart from all application to the doctrine of
evolution, the result of this mode of proceeding will be to give
a more complete and exact idea of each function.

CHAPTER X.

OF THE DIGESTIVE APPARATUS IN THE ANIMAL SERIES.

DIGESTION is the introduction in mass of aliments into a special
organic cavity where these aliments are analysed, elaborated, and
absorbed, leaving usually a residuum which is afterwards expulsed.
We see that this function does not exist normally in the vegetal
kingdom. At the most, we can make a slight exception for the
carnivorous plants. It is very interesting to follow along the
animal series, the specialisation more and more perfect of this
grand function.

FIG. 3.

Amceba Sphrerococcus at the different degrees of its evolution. A, amoeba encysted. Proto-
plasmic mass (c) containing nucleus (b) and nucleole (a); enveloping membrane (d); B,
arrueba coine forth from the enveloping membrane ; C, amoeba commencing to divide ; Do
and Db, amoaba totally divided into two independent amrebse.

In certain very inferior organisms, in certain protozoaries,
digestion is as completely lacking as in the vegetal kingdom.
In the gregarine, for example, the alimentary substances are
absorbed in the state of solution by all the points of the surface
indifferently.

158

BIOLOGY.

[BOOK ii.

In the amrebse we behold the very birth of the digestive
function. Alimentary particles glue themselves on the viscous
surface of the amoeba at any point whatever of this surface ; then
penetrate by degrees into the central parts of this elementary
organism, by digging for themselves, in some sort, a temporary-
digestive canal, which closes behind them. Finally, the aliment
dissolves ; its molecules incorporate themselves gradually with
the substance of the amo3ba and the residuum not assimilable
is expulsed through some point of the surface. The same
alimentary process is observable in the rhizopods with this
difference, that the viscous prolongations or pseudopods of the
animal roll themselves, first of all, round the alimentary par-
ticle. Things take place exactly in the same way in the actino-
sphcerium which, however, is an organism differentiated into
cells. (Fig. 4).

In the acinetous infusoria the radiating appendices clasp the

prey, which is usually another
infusorium whose soft substance
lets itself be liquefied and passes
along the appendices as along
tubes, to come finally to accu-
mulate in droplets in the par-
enchyma of the animal.

The specialisation which com-
mences already to be discernible
in -the acinetous infusoria takes
increased point and pith in other
animals of the same class. There
is not yet any digestive appar-
atus : but there is a special
orifice of ingress and sometimes
also a special orifice of egress. The aliments penetrate by the
orifice consecrated to that use, and which is furnished with
vibratile cilia, making for themselves a way through the paren-
chyma as in the previous case ; then the residuum is expulsed.

FIG. 4.

Actinospfuzrivm. a, alimentary fragment
penetrating into the cortical layer ;
6, c, central parenchyma; d, globules
of nourishment ; e, pseudopods of the
cortical layer.

CHAP, x.] DIGESTIVE APPARATUS IN THE ANIMAL SERIES. 159

It is thus that digestion is effected in the infusoria, very common
in vegetal infusions, — the paramaecia. (Fig. 5.)

In young sponges, thqre is a permanent cavity which is also
the general cavity of the body. This cavity, which at first had
no special covering, clothes itself afterwards with
vibratile cilia, and ramifies into anastomosed canals
by which circulate the alimentary matters. It is,
as we see, a rude model of digestive system, and
of circulatory system, which are still confounded
(nardon). In other sponges there are a mouth, a
canal and fine ramifications debouching on the
surface of the animal by smaller orifices (sycon,
Ic).

Gegenbaur, whom we chiefly follow in this
description,1 places after the sponges the inferior
animals, to which he and Haeckel give the name schema ^Vtbe di-
of cselenterates (KO~I\OS, Ivrtpov). The morphological
characteristic of these animals is a body with
constant cavity, which may be considered a
digestive cavity, sometimes ill differentiated, how-
ever ; for the freshwater polypus, for example, if
we turn it inside-out, after the fashion of a glove-finger, and
keep it thus by means of a thread, can digest with what was
previously its exterior surface. Nevertheless in many hydrarians
we already see developed the division of the digestive tube into
three parts, an cesophagian portion, a dilated portion, and a
narrowed portion, terminating in a caecum.

The organised beings live as they can, become what circum-
stances permit them to become, and all processes are good to
what we call nature, provided they attain their object. Thus the
hydrarian polypi living in colonies, have an intestinal tube in
common, prolonging itself through the whole tribe, and realising
thus the most perfect communism.

In the colonies of Siphonophores the specialisation has taken a
1 Gegenbaur, Manuel d' Anatomic Oomparte.

gestive cavity in
iheparamaedum.
a, cavity of the
body filled with
soft protoplasm ;
t, buccal open-
ing ; c, anus ;
d, -d, contractile
cavities.

160

BIOLOGY.

[BOOK ii.

form more strange still. In them has been established a division
into castes, as in our old human communities : but the caste in
question is a physiological caste. Certain members of the colony
specially adapt themselves for the digestive function. For that
purpose they come to bear the form of dilatable sacs, and are in

communication interiorly with
the digestive cavity common
to all the tribe.

In the medusae, and also the
actiniae, the digestive and cir-
culatory systems are still con-
founded, reducing itself to a
median cavity, whence star!
canals which unite on thj
edge of the ombrelle to fornv
a circular canal. (Figure 6.) J
The bryozoaries have a
mouth surrounded with ten-
tacles, an enlarged intestine,
sometimes furnished with
dentiform projections des-
tined to mastication. Occa^
sionally there exists a sort of
stomach with orifices of inl
gress and egress (cardia and?
In the annelid we

Fm.

Half of aurelia aurita seen underneath, a,
marginal curpuscules ; t, marginal tentacles ;
b, buccal arms ; v, stomachal cavity ; gv, pylorus),
canals of the gastro-vascular system, which **7
ramify toward the edges and throw them- find a digestive tube nearly
selves into the circular canal ; ov, ovaries.

complete with two orifices.

The digestive tube of the lumbric has a powerful muscular
portion useful to an animal which feeds on the humus of the soil.
In the tunicates we meet with an oesophagus, a portion
enlarged, stomachal, and a rectum. The mouth is often at the
bottom of a large sac, whose walls serve at the same time for
respiration. It is another instance of physiological confounding.
We have mentioned above, tribes of animals bearing an intestine

CHAP, x.] DIGESTIVE APPARATUS IN THE ANIMAL SERIES. 1C1

in common : in the compound ascidia there is likewise a cloaca in
common where meet all the anus of the colony.

Differentiation takes a sufficiently important step forward in
the bryozoaries and the tunicates.. The elaboration of the
aliments has in them become more complex by the existence of
glandular sacs though these are still isolated and rudimentary.

In a, certain group of echinoderms the progress continues.
Sometimes the buccal edges, hardened, play the part of masti-
catory apparatus : sometimes (echinoids) there are complicated
apparatus of mastication. Besides a special secretion proceed*
on the internal surface of the intestine, where we remark a
coverin of coloured cells.

Fio. 7. FIG. 8.

FIG. 7.— Astericus vemumlftius, open at the dorsal face, a, anus; i, stomach expanded in

form of rosette ; h, radiating and tubular appendices of the intestine ; g, genital glands.
FIG. 8. — Digestive organs of a spider, ee, oesophagus ; c, superior cesophagian ganglion,

cerebroidal ; v, stomach ; V, lateral prolongations ; v", appendices directed upwards ; i,

median intestine ; r, intestinal extremity enlarged into cloaca ; hh' openings of the liver

into the intestine ; e, urinary canals.

The asteroids, properly so called are without anus, and have
a stomach stellated like their body. The stomach is in effect
furnished with caecal appendices extending by pairs in each
radius. (Fig. 7.)

162 BIOLOGY. [BOOK n.

In the sea-urchins and the holothuria there are a mouth, teeth,
jaws, a distinct intestine, an anus.1

In the grand class of the arthropods (crustaceans, arachnida,
myriapods, insects), there exists a digestive apparatus regularly
and definitively constituted. (Fig. 8). Often, especially in
the crustaceans and the insects, the intestinal epithelium
is clothed with a hard layer of chitin, sometimes emitting
projections destined to crush the aliments. In the crus-
taceans, certain anterior parts become buccal pieces. The
glandular system is enriched and diversified. The crustaceans
have a voluminous liver, full of a yellow-greenish bitter juice.
This liver decomposes into ramose cylinders.2 Most insects have
also cesophagian glands tubulated, enrolled, lobated, ramified,
and which are supposed to be salivary. Other glands forming
simple or ramified tubular sacs, debouch into the median in-j
testine ; it is conjectured' that they represent the liver of the
superior animals. In insects, the secretion has still a mis-
cellaneous character. In the long slender and flexuous tubes,
which are usually inserted at two distinct points of the intestine,
and which are called the vessels of Malpighi, there is secreted by
the side of the urine, another matter probably of a bilious
nature. The yellowish canals are believed to represent the;
biliary canals.3

In many arthropods we already remark that the alimentation
considerably influences both the form and the dimension of the
digestive apparatus. Carnivorous animals have a digestive
apparatus conspicuously and comparatively short. The larva of
the butterfly, which makes an enormous consumption of aliments,
has a very wide intestine, while the butterfly itself, which eats
little, and only liquid aliments, has a long and slender digestive
tube.

Certain insects (bombyx, ephemerides, oastri), which are very
voracious in the state of larvae, are, in the adult state, destitute

, Physiologic Compares. 2 Dugks, loc. tit.

* Leyd.ig,Histologie Comparee, p. 336. Duges, loc. tit., t. III. p. 400.

CHAP, x.] DIGESTIVE APPARATUS IN THE ANIMAL SEKIES. 163

of organs of manducation. Wholly destined for generation, they
cannot take any nutriment; hence the brief duration of their
life.1

If we except the brachyopods, whose intestine terminates in an
imperforated caecum, the mollusks have a very complete digestive
system, and comparable, in a certain measure, with that of the
vertebrates. In the cephalopods, we find a long oesophagus, an
enlarged stomach, an intestine with circumvolutions, and a
rectum. In the littorine we observe an arrangement of the
stomach, which exists in certain vertebrates ; there are a cardiac
part and a pyloric part, separated by a salient fold. Sometimes
the stomach is furnished with triturating booklets of varied
form. But it is especially by the development of the glandular
appendices that the stomach of the mollusks is distinguished
from that of the animals hierarchically inferior. These organs,
in effect, go on perfecting and complicating themselves more and
more in the diverse families of mollusks, and especially in the
most advanced of the mollusks, the aquatic cephalopods (Cuvier),
there are cesophagian salivary glands with short caecums, a liver
developed, compact, divided into lobes, provided each of them
with an excretory conduit, and all these conduits open togethei
or separately at the origin of the median intestine, or into the
stomach. The liver of the mollusks functionates essentially
like that of the vertebrates. That gland is in this class very
voluminous, and it fabricates sugar at the expense of the blood
i though in the mollusks this liquid is destitute of globules.

From the point of view of the general form of the digestive
tube, properly so called, the vertebrates have signal fellowship
with the mollusks. However in them the degree of organic
specialisation is more elevated still. Thus the buccal cavity
. which is not divided in fishes and the amphibians, commences in
reptiles to be sectionised into two divisions, a nasal or aerian
division and a buccal or digestive division.

Corneous teeth, analogous to the appendices of the same kind
1 Duges, Physiologie Compare, p. 279.

M 2

164

BIOLOGY.

[BOOK TI.

existing in the inferior animals, — are also found on the buccal
orifice, in form of a cupping-glass, of the cyclostomes. The
amphibians have likewise analogous organs on the edge of their

jaws.

In the fishes, the ganoids and the teleostians, there are teeth on
the jaws, the palatal bones, the vomer, the hyoid bone and the
bronchial arcs ; the selacians have none except on the jaws.'
(Fig. 10.)

A

Fio. 9.

Digestive tube of fishes. A, gobius melano-
stomus, B, salmon; o, oesophagus ; v, sto-
mach ; i, median intestine ; ap, pyloric
appendices ; r, rectum.

Fro 10.

Buccal opening of the pdro-
myzon marinus, with corneous
teeth.

The teeth of fishes, of amphibians, of reptiles fall and are
renewed during the whole of life.

The three divisions of the digestive tube, properly so called,
grow gradually more perfect in proportion as the animal rises in
the hierarchy of the vertebrates.

In fishes the first part of the digestive tube has direct
continuity to the stomach without difference of diameter (Fig. 9).

CHAP, x.] DIGESTIVE APPARATUS IN THE ANIMAL SERIES. 165

This first portion or cesophagian portion is only distinguished
from the stomachal portion by characteristics drawn from the
structure of the mucous membrane. Its function, however, is
still imperfectly specialised. In effect, at its origin, in the portion
which may be called pharyngian, the cavity is in part circum-
scribed by the branchial arcs and has consequently respiratory
uses.

The proteus (amphibian) has a conformation more inferior still ;
there is no trace in the animal of stomachal dilatation.

The first portion of the digestive tube of birds is characterised
by diverse dilatations : the first, annexed to the oesophagus, is
the crop. Two other divisions are more specially stomachal.
They are the gizzard, very rich in glands, thec another very

FIG. 11.

Stomachs of different mammifers. A, seal. B, liycena. C, hamster.
D, lamentine. E, camel. F, sheep. 1. paunch. 2. bonnet 3.
manyplies. 4. caillette. c, cardia, pt pylorus.

muscular dilatation, especially in the granivorous birds, and
? which is sometimes clothed with a corneous layer. This last
pouch fulfils especially a mechanical office.

It is only in the mammifers that the stomach becomes
regularly transversal (Fig. 11). At the same time it has
enlarged, and its walls have not everywhere the same structure.
, Therein are distinguished, as in man, a cardiacal portion connected
with the oesophagus, and a pyloric portion debouching into the
intestine. But in certain families of mammifers the division is
not merely, as in man, characterised by a difference of structure.
Every one knows the stomach with four compartments of the

166 BIOLOGY. [Boox n.

ruminants : the paunch, the bonnet, the manyplies and the
caillette, this last division being more specially charged with the
secretion of the gastric juice (Fig. 11).

The stomach of the vertebrates debouches into the intestine
properly so called, or rather into the first part of that intestine,
the duodenum, and has continuation in the small intestine. It
is however distinctly separated from it by a membranous fold
called the valvula of the pylorus.

In its region nearest to the stomach the intestine receives the
excretory conduits of two of the most important glands, the
liver and the pancreas. The median or small intestine is, with
some exceptions, longer in the herbivorous than in the carnivorous
vertebrates. There are exceptions to this rule, but they are
more apparent than real ; for, in effect, the development ini
width usually comes to compensate for the defect in length. The
mole, the cetaceans, though carnivorous, have very long, but at
the same time very narrow intestines.

Caterpillars have an intestinal tube, which is not much longer
than their body, but it is nearly as wide.

The last portion of the digestive tube, the large intestine, really
develops itself in length and breadth only in the amphibia.
Beginning with reptiles, the large intestine is furnished on its
passage with a dilatation called caecum, much more developed in
herbivorous than in carnivorous animals.

In the termination of the intestine we likewise remark an
unequal differentiation in the diverse vertebrated groups. In the
selacians, the amphibians, the reptiles, the birds, and the mono-
trematous mammifers, the large intestine opens into a cavity
called cloaca, into which debouch the urinary conduits, and the
genital conduits.

We have not here to give a detailed description of the
structure of the digestive tube, and we content ourselves with
recalling that, in the vertebrates, its walls are composed funda-
mentally of three tunics encased in each other, and intimately
connected. They are, from within to without, a mucous

CHAI-. x.] DIGESTIVE APPARATUS IN THE ANIMAL SERIES. 167

membrane sometimes furnished with tufts or villosities clothed
besides with cells comparable with the cells of the epidermis,
and called epithelial cells : a muscular layer of which the
contractile elements are in part longitudinal, in part arranged as
a ring round the digestive tube : a layer of cellular tissue, which
gives a surface of insertion to the contractile elements, and to the
canal a sufficient degree of solidity and of resistance. It deserves
remark that the villose tufts which garnish the internal face of
the stomachal and intestinal mucous membrane, to the number of
many thousands the square inch in man, are lacking in the
invertebrates. Lastly to the digestive apparatus are annexed
glands, some of them voluminous, having their body outside of
the digestive wall, which only their secretory conduits traverse,
others in the very substance of that wall.

To conclude the very general morphological description of the
digestive tube, it remains for us to say a few words on those
glands.

Of the Glands of the Digestive Apparatus.

It is especially by the glandular apparatus that the digestive
system of the vertebrates in general and of the mammifers in
particular is distinguished from that of the inferior animals.
The digestive glands, in effect, are more numerous, more dif-
ferentiated as to function, and of a more complex structure.

The salivary glands are numerous, in clusters granulous and
closely pressed. Already in the tortoise we find under the
tongue a pair of glands which are probably salivary glands.
Analogous glands, but larger still, exist in birds. In the mam-
mifers they are distinguished into three couples, the matfillary,
the suUingual, and the parotid glands. It is in the herbivorous
mammifers that the three pairs of salivary glands attain their
greatest volume, and we shall see that this fact is in relation to
the kind of alimentation.

As Claude Bernard has shown, these salivary glands, though

168 BIOLOGY. [BOOK IT.

very analogous to each other, secrete salivas of diverse species.
In general the salivary glands are wholly lacking in the aquatic
animals.

In the salivary glands, the organs of secretion, the glandular
elements are agglomerated ; but in the stomach of the superior
vertebrates these elements are separated and hidden in the
substance of the mucous membrane. Their number, moreover,
is immense ; they are blind glands and separated from each other
only by a thin layer of cellular tissue. These small glands arei
related and proportioned to the numerous capillary vessels, and!
to the nervose threads. Besides the glandules of the stomach
there are many others, scattered over the whole extent of the
digestive canal. They assume variable forms : sometimes they
are simple depressions, small purses, small tubes : sometimes they
ramify.

But the most imporfcarit glandular appendix of the digestive
canal of the vertebrates is assuredly the liver.

In the most inferior vertebrate, the one which in a certain
measure connects the vertebrates with the mollusks, the am-\
phioxus, the liver is represented only by a caecum of a greenish
tint, reminding us of the simple culs-de-sac, short, not ramified,
which seem to play the part of liver in the invertebrates. It is^
also under an analogous form, under the form of a pointed cone,
that the liver originates in reptiles, birds, and mammifers.1 In
the superior mammifers, the liver — very voluminous — is, abstrac-
tion being made of the cellular tissue, essentially constituted by
vessels and nerves, first of all by special cells, charged, as we
have seen, to fabricate a glycogenous matter. These cells are
irregular, rounded, or polygonal, have a simple or double
nucleus with nucleole (Figs. 13 and 14). Their contents, finely
granulous, can include accessorily granules of fat. Between these
cells pass very fine capillaries, emanating from the great venous
trunk, or vena portse, coming from the intestine (Fig. 12).

1 Leydig, Histologie Comparte, pp. 401 — 410. — Gegenbaur, Manuel
tomie Comparte, p. 752.

AP x.] DIGESTIVE APPARATUS IN THE ANIMAL SERIES. 169

Such is, schematically, the elementary structure of the gly-
cogenous hepatic organ, forming in itself the major part of the
liver. But by the side of
this organ, the former of
sugar, and which we must
consider as a gland without
excretory conduit, a san-
guineous gland, there is
another organ, the secreter of

: bile, constituting, schemati-
cally also, a gland of clus-
tering form. It consists of
small groups of glandular
csecums, agglomerated in the
fashion of fern leaves, and
dispersed along the branches
of a greatly ramified excretory
conduit, into which they open
and secrete. The wall of the
glands and of the conduits
is clothed with epithelial
cells of divers form.

Between the glycogenous elements and the biliary elements
there is only a relation of juxtaposition. The superior verte-

'. brates offer us, therefore, here an example of organic inter-

( mingling such as we find so many of in the inferior animals.

! In them the liver has separated itself from the renal glands,
with which it is confounded in certain invertebrates; but it
remains still joined to the glycogenical gland. If, as some
partisans of the doctrine of evolution believe, the present

' superior vertebrate is not yet the last term of organic progress
and differentiation on the earth, the two glandular apparatus
may separate in the future in the more perfect being destined
to arrive as successor.

The hepatic biliary conduit or choledochal canal, debouches into

Capillary network of the liver, injected from
the super-hepatic veins.

170

BIOLOGY.

[BOOK ii.

the first portion of the small intestine or duodenum. In this
same region and very near the origin of the choledochal canal
opens, in man, the principal excretory canal of another and
very important gland of cluster-shape, formed also of small
clusters or acini, each diverticule whereof is terminated in a
cul-de-sac. It is also clothed with epithelial cells. ~VVe shall
have to speak of the digestive office of this gland called
pancreatic.

In certain vertebrates the pancreatic canal opens at a certain

FIG 13.

Isolated cells of the
liver ; a, with simple
nucleus, 6, with
double nucleus.

FIG. 14.

Arrangement of the cells of the liver in a lobule cut
tran sversally, with the section of the hepatic vein
in the centre.

distance from the hepatic canal, but generally below, abou
from 30 to 50 centimetres (rabbit, hare, beaver, porcupine
ostrich).

The pancreatic gland already exists in the most inferioi
vertebrates— the fishes : but in them it is generally smaller
and of a simpler structure. Its culs-de-sac [blind ends] are
wider, more or less independent. The pancreas of divers ver-
tebrates (lizard, and so on) is joined to the spleen as in the
superior mammifers, the biliary gland is joined to the glycogenic

CHAP, x.] DIGESTIVE APPARATUS IN THE ANIMAL SERIES. 171

gland. A degree of glandular entanglement is observable in
the chimaera monstruosa, in which the pancreas adheres alike to
the spleen and the liver.

After the pancreas no large gland figures in the rest of the
digestive tube. There are merely small mucous glands scattered
here and there. We have already said a few words about them,
and, when treating of digestion, we shall have to indicate the
part they play.

CHAPTER XI.

OF ALIMENTATION IN GENERAL.

WHETHER animals absorb the complex organic substances,
in their cruder state, after simple isomeric modifications, whether,
in final analysis, they resolve them into their ultimate elements,
certain it is that the most complex substances are at the same
time the most easy to assimilate, and also those which have the
greatest alible value.

The most important constituent principles of the animal ana-
tomical elements are chemically formed by azotized quaternary
compounds, and it is indispensable that analogous principles
should be found in a considerable quantity in their aliments;
now we know that these quaternary substances are relatively
weak in vegetals, that, moreover, they are therein combined with
mineral substances. It is then from the animal kingdom itself
that animals must especially derive their nourishment. " Eat
each other " is for them one of the most imperious nutritive
rules. Nevertheless, some of them are herbivorous, but then
they must, like the ruminants, have a complex, differentiated
digestive tube, a perfected nutritive alembic.

Most of the lower animals, whose rudimentary digestive tube
we have briefly described, are limited almost exclusively to
animal nourishment. Many of them, moreover, are marine
animals, that is to say, living in the midst of a vast organic
dilution, full of detritus, dissolved, diluted, or fragmentised.
Those among them which are fixed, the polypi, the cirrhopods,

CHAP. XL] OF ALIMENTATION IN GENERAL. 173

even the bivalvous mollusks, are forced to content themselves
with sucking in the dissevered organic molecules as these pass
along, or sometimes the animal cula, which the aqueous medium
brings them. Some aid chance by causing a current of water to
pass incessantly into their digestive cavities.

In short, most invertebrated animals live upon animal sub-
stances, excepting always the majority of insects ; but these
latter have moreover a complete digestive system, already
differentiated, at the adult age. In the state of larvae, on the
contrary, they often feed upon animal matters. Fish, and even
reptiles, are also, for the most part, carnivorous. We must
come to birds and to mammifers to find important groups of
animal species, living habitually upon vegetals.

A general fact, strange at first sight, arises out of the com-
parative examination of the digestive system in marine herbivora,
whatever may be their place in the animal hierarchy. In effect,
in the tsrrestrial animals, the herbivorous digestive tube is more
differentiated, more complex, furnished with gastric, pouches,
with csecums vaster and more numerous than the carnivorous
digestive tube possesses. The porcupine has as many as fourteen
stomachic cavities. * Now we observe precisely the contrary in
aquatic animals, in which we see herbivorous alimentation
generally coinciding with a simplified digestive system. Thus
in the herbivorous cyprinus there is not even any stomachal
distention ; and it is the same in the tadpole. The cetaceous
herbivora (the lamentine, dugong, &c.) have only one stomach
with simple or double dilatation, while the cetaceous carnivora,
(dolphin, whale, &c.) have three, four, five stomachs, and tho
squalus peregrimc* many stomachal cavities.

The explanation of this anatomical paradox seems to us easy
to give. The general principle is, not that every herbivorous
animal must have a more complex stomach, but that every
animal must possess a digestive system more differentiated in
proportion as its alimentation is more varied ; now, in the
1 J. W. Draper, Human Physiology, &c., p. 59.

174 BIOLOGY. [BOOK IT.

aquatic mediums, the flora is little diversified. It is almost
entirely composed of sea-weeds, plants of very simple structure,
of a soft consistency, and of a chemical composition everywhere
almost identical. The digestive apparatus of the marine
herbivora has then only a uniform work, of relative simplicity,
to accomplish, while, on the contrary, the aquatic fauna being
extremely varied, the alimentation which it furnishes resembles
it ; and consequently necessitates a digestive system adapted to
render absorbable, aliments very dissimilar from each other.

Alimentary variety seems even to be a necessity for certain
herbivora, and Magendie has seen rabbits only live fifteen days,
that is die of inanition, when compelled to live solely upon one
of the vegetals which constituted their ordinary alimentation
(carrots, cabbages, barley, &c.).

Besides, we must guard against attaching an absolute value to
the denominations herbivora and carnivora. As M. Schiff points
out in his excellent Traite de la Digestion,1 there is no essential
difference between the gastric juice of herbivora and that of]
carnivora. Both disaggregate the vegetal or animal aliments,
both dissolve the albuminoidal substances, and everything that
is soluble in acidulated water. The herbivorous gastric juice is
only a little less active, and, though of equal weight, it digests
fewer albuminoidal matters than the carnivorous gastric juice.
But, by causing a rabbit to absorb, either through the blood or
through the stomach, various soluble substances (peptogens)
which have the property of rendering the gastric juice more
active, we succeed in making the stomach of a rabbit functionate
like the stomach of a dog or a cat. At all events the peptones
prepared at the expense of the albumine by the stomach of a
herbivorous animal are directly assimilable by the tissues of a
carnivorous animal, and if we inject them either into its stomach,
or direct into its veins, they are perfectly absorbed, and we do
not find them again in the urines, as happens with every non-
assimilated substance.

1 T. II., pp. 183, 184.^

OF ALIMENTATION IN GENERAL 175

The identity of the process and the result of digestion in
herbivora and carnivora being demonstrated, there is no cause
for astonishment in the facility with which a herbivorous animal
can become a carnivorous animal, and inversely.

The herbivora especially become accustomed without much
difficulty to an animal diet. Organised for the greater, it costs
them little to accommodate themselves to the less.

Numerous facts of this kind have in science an almost com-
mon-place notoriety. Spallanzani had accustomed a pigeon to
eat meat to such a point that it afterwards refused seeds.

The cows and horses of Iceland feed willingly upon dried fish.
Horses and oxen accustomed to feed upon fish have been seen to
enter the water to fish for themselves.1 Besides, all the herbi-
vorous mammifers are necessarily carnivorous during the period
of lactation. Also, during this period, the rumen of ruminants
is not yet developed.2

Amongst the carnivora, the most robust, the most typical
sometimes actually refuse vegetal nourishment. The tiger, the
lion, the eagle, habitually allow themselves to die of hunger
rather than touch it. Nevertheless, Spallanzani had accustomed
an eagle to eat and digest bread.

Native repugnances can be most frequently overcome by call-
ing in the help of the culinary art. It is, moreover, in a great
.measure to this circumstance that man owes his omnivorous
Character. Dogs and cats do not eat corn, but they will eat
i bread. The rabbit refuses large pieces of raw meat, but it
willingly accepts and digests meat minced or boiled.

Certain animals are at once carnivorous and herbivorous, as,
for instance, a number of birds. Others are frugivorous in
, winter, and insectivorous in summer. The small frugivorous
•monkeys eat insects, and seek eagerly for eggs and for little birds
scarcely hatched.3

1 Burdach, Physiologic, t. IX., p. 241.

9 Gegenbaur, Manuel d? 'Anatomic Comparte, p. 748.

3 M. Schiff, Digestion, t. II., p. 187.

176 BIOLOGY. [BOOK TI.

Moreover, animal species very closely connected in the tax-
inomy differ in their mode of alimentation. The polypi, like
most inferior animals, usually feed exclusively upon animal
matters. Even the hydras habitually reject vegetal substances,
which their rudimentary organization does not permit them to
assimilate \ but the tiibularia gelatinosa nevertheless feeds upon
the flowers and seeds of the water lentil.

Among the coleoptera, the plantigrades, and the cetaceans,
certain kinds are carnivorous, and others of the same group are
herbivorous, &c.

We have already said above that during abstinence every
animal becomes carnivorous. It consumes its own tissues, an<fi
even its stomach becomes charged, at the expense of these tissues,
with a carnivorous gastric juice, destined for the absent aliments
(L. Corvisart).

Before concluding this very incomplete sketch, it will not be
useless to say a few words on geophagy.

The earth-worms, the naids, swallow the humus of the soil ; ,
this humus- is kneaded by a kind of musculous gizzard, probably
diluted with a secretion, and the residuum is rejected in pulpy
cords. According to Swammerdam, the larva of the ephemeris
eats clay only. Its colour even varies with the colour of the
clay.

Among the lower beings, geophagy easily explains itself. The
vegetal humus, which the earth-worms eat, the moist clay, which
the larvae of the ephemerides also swallow on the banks of the
rivers where they live, contain a large quantity of organic detri-
tus and of soluble salts, which alone are absorbed. Geophagy is
less easily comprehended in man ; nevertheless, independently of
pathological cases, there are numerous examples of it.

The Otomacs eat, or rather ate, every day, a pound and a half
of unctuous and ferruginous clay.

Spix and Martius l have observed analogous cases amongst
various tribes on the banks of the Amazon. According to
1 Reise in Brasilien, t. II.

CHAP. XL] OF ALIMENTATION IN GENERAL. 177

Lal>illardiere, the New Caledonians ate a white and friable
steatite, etc., but only in time of famine.

We may certainly admit that the human stomach, like that of
the earthworm, can separate certain mineral substances from
organic remains and from salts, but in very small quantity, and
it is probable that here geophagy only plays a fictitious alimen-
tary part. It simply distends the stomach, neutralizes more or
less its gastric juice, mechanically deadens the feeling of hunger,
as carbonic acid, for example, or any inert gas does.

CHAPTER XII.

OF DIGESTION.

A. THE object of digestion is the preparation of assimilable
substances. The processes are the mechanical division followed
by a chemical transformation of the aliments. In final analysis
absorption is only exercised on liquefied and dissolved substances.

True digestion, therefore, does not exist among the beings
rudimentary, not differentiated, that form the first stage
of the animal kingdom. In an inferior degree it exists
animals with a simple digestive tube, having neither at tl
orifice of the alimentary canal, nor at any point of its cavity,
organs suitable for tearing, lacerating, and crushing, and cons
quently not being able to assimilate easily almost anything bi
aliments liquefied apart from their organism.

Among animals possessing buccal, pharyngian teeth, or appai
tus which occupy the place thereof, there exists usually a specif
glandular apparatus charged to render alimentary trituration moi
easy by imbibing the aliments with a liquid called salivary. In
more general manner we may say that some kind of saliva exisi
often when there is an apparatus for the prehension of aliment
Thus the fly emits on the particles it is about to draw in wM
its proboscis a brownish liquid which dilutes them. Naturally
the saliva is the more abundantly secreted the harder is tl
habitual aliment. Thus the saliva is null or scanty in aquatic
animals, whatever they may be (crustaceans, fishes, crocodiles

CHAP. XIL] OF DIGESTION. 179

palmipedes, birds, carnivorous cetaceans). It is, on the contrary,
very abundant in the granivorous and herbivorous animals.
Schultz observed in a horse that a single parotid gland produced
in twenty-four hours 1,678 grammes of saliva.

It is especially in the terrestrial vertebrates that the secretory
glandular apparatus exists well developed. It furnishes a liquid,
transparent, slightly viscous, usually alkaline, sometimes acid or
neutral.

In the superior mammifers, and in man, there are three pairs
of salivary glands, called sublingual, submaxillary, and parotid.
Claude Bernard has shown that these glands do not secrete an
identical liquid. In effect ,the liquid secreted by the glandules
of the buccal mucous membrane seems incapable of transforming
starch into sugar, when it is blended with the parotidian saliva.
But it accomplishes very easily this transformation when it is
mixed with submaxillary saliva.1

The chemical agent of this isomeric transformation is a sort oi
special ferment, ptyaline. It is formed in the midst of the closed
cells which originate in the substances of the acini of the
gland ; these, breaking, surrender to the purely excretory liquid
the product of their elaborations. Thus we can easily obtain by
maceration of the glandular tissue an artificial salivation.

The diversity of the products of secretion of glands in appear-
ance identical permits us to range in the category of the salivary
glands the venomous glands of serpents, which seem indeed to
form part thereof anatomically. The same reason authorises
us not to reject with too much disdain the facts, seemingly
^legendary according to which the human saliva itself can
acquire venomous properties under the influence of a violent
burst of anger. The substances produced by living chemistry
; undergo with an extreme facility isomeric metamorphoses : and
these metamorphoses bring along with them new properties.

It is especially during mastication, when there is rapid contact

1 Draper, loc. cit. p. 43. — CL Bernard, Lefonssur les Liquides dc VOrganisme,
t. II., p. 239. "

K 2

180 BIOLOGY. [BOOK n.

of the aliments with the mucous membrane, that saliva is
secreted abundantly, and assumes all its characteristics. Mitscher-
lich observed that the parotidian saliva of man was acid in the
state of comparative repose of the gland, but became alkaline
during mastication. The accidental acidity of the saliva is
probably due to a secondary modification of the starch which
becomes first of all sugar under the influence of the salivary
diastasis, then evolves into lactic acid. In its turn this acid is
carried with the aliments into the stomach, where it contributes
its share to the gastric digestion.

The alimentary mass, more or less impregnated with saliva,
passes from the mouth into the first portion of the digestive
canal, into the pharynx when there is one, lined in certain
reptiles with a vibratile epithelium destined to aid in the transfer
of the alimentary particles, but clothed in man alone with a
simple epidermoidal epithelium called pavimentous. From the
oesophagus the alimentary mass passes into the stomach, where
the most important digestive acts are accomplished.

B. Gastric Digestion. — The gastric digestion is the principal
act of the digestive function, since, as we are about to see, the
stomach is the grand laboratory where is principally operated the
transformation of the albuminoidal alimentary matters into
absorbable peptones. The state, still so imperfect, of comparative
physiology does not permit us to draw here a complete picture
of albuminoidal digestion in the whole of the animal kingdom.
Nevertheless we know that in the inferior organisms, the in-
vertebrates, for example, are for the most part carnivorous. It
is manifest that, spite of the imperfection of their digestive
system, they must succeed in effecting this transformation of
albuminoids into peptones, which is achieved among the superior
vertebrates only in a differentiated stomach provided with special
secretory apparatus. In the transparent invertebrates we can
demonstrate the transformation undergone by the aliments.
Dug&s has thus seen, through the tissues, in the planaries and
the clepsines the blood swallowed losing by degrees its red

. XIL] OF DIGESTION. 181

colour in the stomach and changing into a greyish homogeneous
matter.1 "While worms swallowed by the hydras underwent a
similar transfigurement.

Moreover, Schweiger found in the digestive cavity of polypi,
and in the canals connecting the individuals aggregated as a
colony, a lactescent liquid, probably a nourishing liquid. It is
this liquid which is absorbed by the animal, and which circulates
through its organism, there where the stomach emits canalicules
with csecums, or even a sort of complete system of canals, as in
the medusa.2

The isomeric metamorphosis of the albuminoids is therefore
accomplished even in the rudimentary beings, but it demands
for that purpose a time so much the longer as the living labora-
tory is the more imperfect. Thus after seven or eight days of
abstinence food is still found in the digestive tubs of caterpillars.
Schweiger says that he found in the intestine of leeches blood
sucked two-and-a-half years before. This extreme slowness of
the digestive labour in the inferior animals helps us to under-
stand how they are able to resist abstinence so long.

Absorption is slow in the digestive cavity of the inferior in-
vertebrates, and, naturally, the movement of the alimentary
mass is also very slow there. The contractility of the walls is
aided in many of these animals by vibratile cilia, that is to say,
epithelial cells, furnished with long mobile ciliary prolongations.
These filiform appendices form on the stomachal and intestinal
surface of numerous invertebrates a sort of living meadow where
each blade is animated by a regular oscillatory movement,
effected always in the same direction, and powerfully aiding the
conveyance of the alimentary substances. This arrangement of
the intestinal epithelium, frequent among the invertebrates, is
also observed in the foetal state among the selacians, the batra-
chians, and so on; but it is regularly lacking in birds and
mammifers even at the embryonary period.3

1 Dug&s, loc. cit., p. 331. 2 Handbuch der NaturgescJiicMe.

3 Leydig, loc. tit., pp. 348, 375.

182 BIOLOGY. [BOOK n.

Nevertheless, at very different degrees of the zoological
hierarchy the same mode of alimentation seems to bring with it
the same structure. Thus the internal surface in certain carni-
vorous coleoptera, for instance the stag-beetle, has a reticulated
aspect wholly analogous to that of the stomach of the mammifers.
It is true that we have here to deal with a superior invertebrate
in which the vitality is active, energetic, and the digestive system
strongly differentiated.

Some other facts come to prove the feeble digestive power of
the stomach in the inferior invertebrates. Trembley observed
that the hydra neither altered nor digested one of its arms when
it swallowed it along with a prey. The actinia devoured by a
larger individual of its own species is often revomited safe and
sound. It therefore resists digestion as the entozoa resist.
The fact is not, however, general ; and frequently shell
mollusks, and whole crustaceans, swallowed by the actinice and
the asterioe are completely digested excepting the shells or
the carapace, which are afterwards rejected.

The facts of resistance opposed to digestion by certain
living animals are evidently due to the defect of energy in the
digestive liquids secreted, that is to say, to the imperfection of the
glandular system. Among the mammifers things go on dif-:
ferently, and thoroughly living tissues are promptly attacked
and digested by the stomachal secretion unless they are pro-
tected by a thick epidermic or epithelial varnish. Claude
Bernard having introduced into the stomach of a dog, through
a gastric fistula, the posterior portion of a frog, saw that
portion dissolved and digested, while the anterior portion con-
tinued to live.

The agent of this curious dissolution is a very active juice
secreted by the stomachal glandules, and of which we have
now to speak.

When the aliments are introduced into the stomachal cavity
of a mammifer the mucous membrane is congested, grows red,
arid we see streaming out, when there is a gastric fistula, as in

CHAP, xii.] OF DIGESTION. 183

Beaumont's famous Canadian, or in an animal prepared by vivi-
section, a juice abundant, liquid, limpid, acid, gathering into
droplets and flowing along the wall : it is the gastric juice.
This liquid attacks more or less energetically the aliments.
It has not much action on the vegetal substances, and limits
itself to dissolving the azotised substance of the cells. It is
especially the albuminoidal aliments which more or less rapidly
it dissevers and dissolves. It commences by saturating the
animal tissues, which swell. The muscular fibres become more
friable, grow softer, and their striae disappear. The cellular
tissue dissolves, and then the muscular fibrils are disaggregated,
and end by being converted into a brownish pap. l The tendons,
the aponeurosic membranes, are changed into a gelatiniform pap.
The nervous glandular elements are also dissevered and softened.
The bones themselves are attacked and pulverised ; their organic
mechanism is extracted and dissolved, and by degrees the
terreous parts are likewise attacked and pulverised. A piece
of beef-bone which an eagle was forced to swallow every day,
and which he regularly vomited, disappeared in twenty- five days.
The portion of the aliments merely softened swells, is saturated
by the gastric juice holding in solution the substances already
transformed into peptones, and the whole forms a species of soft
mass called chyme, which gradually, in portions, after flowing
for some time in the stomach itself, from the cardia or oasophagian
orifice to the pylorus or intestinal orifice, ends by passing into
the intestine.

The agent of this transformation, the gastric juice, owes its
digestive properties principally to two substances, an acid and a
ferment. It would be more correct to say, to acids — the lactic
acid, and the chlorohydric acid ; but the first, the lactic acid,
comes in part from the evolvement of the starch, or rather from
the sugar which proceeds from it, under the influence of the
salivary ptyaline. The other acid is secreted by the glandules.
Among animals with multilocular stomach, one of the parts
1 Schiff, Digestion, loc. tit., p. 145. ,

184 BIOLOGY. [BOOK n.

is specially entrusted with this acid secretion. Thus the
stomachal juice is alkaline in the paunch and the bonnet of
ruminants : it is acid, on the contrary, in the caillette.

In the mammifers, provided as man is, with a single stomachal
pouch, the differentiation, which no longer exists in the general
form of the stomach, continues in its apparatus of secretion.
The innumerable glandules of the stomachal mucous membrane
have not then the same function, and we can determine approxi-
matively what region of the stomach secretes acid mucus, what
other secretes fermented mucus, or peptic mucus.

In effect, if we subject to hot infusion in acidulated water
the stomach of a mammifer, a part of the stomach disappears
at the end of an hour or an hour-and-a-half : it is disaggregated
first and liquefied afterwards. The other part, which is always
the pyloric region, dissolves only with extreme tardiness. The
part easily dissolved has probably the office of secreting the acid
mucus.1 The anatomical examination of the glandules in the
one region and the other confirms this view. The glands of
the region supposed to be peptic are almost always ramified
into two or three small conduits interiorly lined with cells
of cylindrical epithelium, but filled in the recesses by cells of
globulous epithelium. These are the secreting cells, and we find
their analogues in the caillette of the ruminants. The glands
probably mucous are more rarely ramified, and do not contain
cells of globular epithelium. We have seen that the mucous
glands occupy especially the pyloric region of the stomach : as
to the peptic glands they are especially abundant in the middle
region.

The globular cells contained in the cul-de sac of the peptic
glands secrete during stomachal digestion a mucus, holding in
solution a faint albuminoidal ferment, which has been called
pepsine. According to M. Schiif pepsine is not secreted at the
expense of the elements of the blood, except when this fluid is
previously charged with substances which he calls peptogens.
1 M. Schiff, loc. cit., t. II., p. 238.

CHAP. XIL] OF DIGESTION. 185

Dextrine, bread, the gelatine of bone, divers peptones, are
peptogens.

The normal absorption of peptogenical substances into the small
intestine has not apparently the result of charging with pepsine
the stomachal glands, and yet this effect seems to be obtain-
able by the injection of these substances into the serous vessels,
the subcutaneous cellular tissue, the stomach, and the rectum.

Pepsine is the special agent for the transformation of albu-
minoidal alimentary substances into peptones isomeric, but
soluble, assimilable, and no longer coagulating through heat.

The two agents, acid and peptic, evaporate, moreover, in their
transformation, and are both necessary. Without the acid the
pepsine has no longer any action. Also when the alkaline
bile accidentally renews into the stomach and neutralises the
gastric juice, the work of digestion is suddenly arrested. The
acid disaggregates and softens the albuminoidal substances, and
by this preparatory modification renders the peptic action
possible.

By observing the phases and phenonmena of digestion in the
stomach through the process of gastric fistulse, and, better still,
by recurring to artificial digestions, experimenters have succeeded
in determining with sufficient precision the action of pepsine on
the diverse categories of aliments.

In effect digestion is merely the result of simple, physical, and
chemical phenomena, which are accomplished very well apart
i from the stomach. It is to Reaumur that the honour is due of
'being the first to make trial of artificial digestions.1 But Spallan-
zani was the first who made successful trial thereof. Eberle
prepared artificial gastric juice by softening a stomachal mucous
membrane in water at 30° Reaumur, then in adding drop by drop
chlorohydric acid, or acetic acid. Miiller, Schwann, Tiedeinann,
iand Gmelin, Bur kin je, Pappenheim, Lauret and Lassaigne, made
analogous experiments, which have since been often repeated.

It is generally of the caillette of a ruminant that we must
1 Hlttoirc dcs I' Academic des Sciences, 1752.

186 BIOLOGY. [Boox IL

make use to obtain the necessary gastric ferment. M. Schiff,
who has occupied himself a great deal with these artificial diges-
tions, employs often the stomach of animals which are not
ruminants.1 In that cases he detaches only the median por-
tion, called peptic ; he infuses it in from 500 to 600 grammes of
acidulated water, and lets it rest for five or six days. The liquid
thus obtained has the property of transforming the albuminoidal
aliments into peptones isomerical, but soluble in water and even
diluted alcohol, moreover incoagulable by heat, and no longer
forming insoluble compounds with the metallic salts: In addition,
when these peptones are mingled with sugar, they, as we have
already maintained, mask the reaction of Trommer.

All the processes of absorption which we have just enumerated
enable us surely to demonstrate that the only aliments trans-
formed by the gastric juice are the albuminoidal substances. The
stomach absorbs besides a number of other substances contained
in the aliments, but on condition that they are soluble in acidu-
lated water, for the stomach does not modify them (salts, and so
on). The fat bodies, starch, are scarcely altered by the gastric
juice ; they pass with the ehyme into the intestine, where, more-
over, the transformation of the proteic substances saturated with
gastric juice is gradually finished.2

According to M. Schiff,3 and in opposition to an idea generally
received, the liquid albumine is more slowly digested than the
solid albumine ; it demands more acid for its transformation.
Moreover the stomachal acid is incapable of coagulating albu-
mine.

On the contrary, liquid caseine is promptly coagulated by the
gastric juice, and its previous coagulation is even a condition of
its transformation into peptones.

Vegetal legumine dissolves without difficulty in the acids, and
is afterwards transformed.

1 M. Schiff, loc. cit., t. I., p. 78.
• 2 M. Schiff, loc. cit., t. II., pp. 123, 124.
3 Kid. t. II., p. 150.

CHAP, xii.] OF DIGESTION. 187

We have seen that the albuminoidal vegetal substances are
generally contained in a membrane constituted by the cellulose ;
that is to say, that the vegetal aliments yield less easily than the
animal aliments their proteVc principles. Jn effect, the digestive
juices must first of all dissolve more or less the refractory
envelopments.

If we are willing to depart from rigorous and literal strictness
in definitions, there is a large amount of truth in the following
general formula of digestion — Stomachal digestion is histogene-
tical, that is to say, that it prepares the quaternary azotised
bodies destined to incorporate themselves with the anatomical
elements. On the contrary, but in a more general manner still,
intestinal digestion is therniogenetical ; it renders absorbable
principally the carburets of hydrogen, the ternary substances,
destined in great part to undergo in the economy a complete oxy-
dation, to be afterwards transformed into water and carbonic
acid in producing heat.

Divers experiments of M. Schili seem to prove that peptic

secretion does not depend on the central nervous system. After

the section of the pneumogastric nerves the pepsine does not the

less continue to form itself in the glandular culs-de-sac, and the

stomachal absorption itself is not diminished.1 The case seems

* to be different in the acid secretion, and this explains how Wilson

Phillip, Brachet, Breschet, Milne-Edwards were able to see

[ digestion stop after the section of those same pneumogastric

i nerves. The first of these experimenters affirms even that he

succeeded in restablishing the digestive activity by galvanising

? the peripheric trongon of the cut nerves.

Besides, other experiments of M. Scheff show that the general

functions of the stomach are far from being independent of the

< nervous centres. On dogs subjected to cerebral vivisections, to

1 lamisections of the optic layers and of the cerebral peduncles,

this physiologist demonstrated that the capillary vessels of the

stomachal mucous membrane dilated in places, that at those

1 M. Schiff, loc. a/., p. 415.

188 BIOLOGY. [BOOK n.

points were produced first of all sanguineous stases, thereupon a
softening of the mucous membrane, which then became incap-
able of resisting the action of the gastric juice, and was digested,
whence ulcerations and even perforations of the stomach.

Certain general states influence, moreover, the peptic secretion j
for example, according to the observations of M. Schiff, fever com-
pletely abolishes this secretion. The stomach is then absolutely
incapable of digesting ; it absorbs, but it requires aliments'
directly assimilable, such as dextrine glycose, the artificial
peptones of Corvisart.1

0. Intestinal Dif/estion. — Intestinal digestion exists really, that
is to say, with its distinctive characteristics, there only where
exist also its true agents, that is to say, the hepatic and pancreatic
glands. "We have seen that the secretory elements of the bile
seem to be at first in the echinoids, simple epithelial cells lining
the internal surface of the intestine. The epithelial hepatic cells
are, definitively, everywhere and always the creators of bile in
the whole of the animal kingdom ; but in proportion as we rise in
the zoological series we see these cells becoming more and more
numerous, and accumulating in special apparatus more and more
complex They are first of all simple csecums, in the heart of
which the cells have birth, fill themselves with bile, which they
afterwards allow to escape, by dissolving, or, as in the insects,
there are tubes in which urine and bile are generated side by
side.

In the arthropods there exists a voluminous liver, especially
in the crustaceans and the insects. The mollusks are also pro-
vided with a voluminous liver, dividing into lobes, fabricating at
the same time sugar and bile like that of the superior vertebrates.

In these last the bile is secreted abundantly, sojourns in part
at least in a special pouch called biliary vesicle, and is finally
poured into the first part of the small intestine, the duodenum.
The bile is, as every one knows, a yellowish or greenish liquid,
bitter, holding in solution a colouring matter, the biliverdine,
1 M. Sehiff, loc. tit., p. 269.

CBAF. XIL] OF DIGESTION. 189

phosphates, chlorates, organic salts of soda, cholesterine, and so
pn. It is alkaline, but only during digestion. In addition, we
do not find in bile any albuminoidal substance ' and it does not
coagulate through heat, the acids, the metallic salts.

We have seen that the liver of the superior mainmifers is
formed by the assemblage of two apparatus, the one glycogenical,
the other biliary. The first acts at the expense of the venous
blood, charged with nutriments brought to it by the vena portse,
that is to say, the common trunk of the intestinal veins. The
secretory organ of the bile, on the contrary, elaborates its secre-
tion at the expense of the general arterial blood, and we stop
the biliary secretion by binding the hepatic artery. The same
thing, moreover, takes place by absolute necessity in the inferior
animals whose liver is not in contact with any vena portse.
Poured on the aliments the bile seems to act on the fat bodies
which it emulsionises, and also on the albuminoidal matters im-
pregnated with gastric juice. It neutralises them first of all,
then stimulates their dissolution. But it seems to acquire all its
properties only after blending with another liquid, the pancreatic
juice.

t Does the pancreas exist in the invertebrates ? This is a ques-
tion of comparative physiology which still waits for a reply.
We have seen that we do not begin clearly to recognise the
pancreas except in fishes, and then only in a rudimentary state.
In the superior vertebrates, it is a large gland cluster-like,
jpouring an abundant liquid into the intestine through a conduit
'which sometimes anastomoses with the' biliary or choledochal
canal, and sometimes opens direct into the intestine, generally
in immediate proximity to the biliary conduit, sometimes at a
considerable distance from that conduit and below it. The
"pancreas secretes a colourless limpid, viscous and alkaline liquid.
This liquid contains a special albuminoidal substance called
pancreatine, and this substance is in such quantity there, that
through heat or alcohol the pancreatic juice coagulates in mass
1 Ch. llobin, Leyons sur Us Humeurs, p. 501.

190 BIOLOGY. [BOOK n.

and entirely. After being thus coagulated and dried the pan-
creatine is susceptible of being redissolved into water, and
we can by this means obtain an artificial pancreatic juice, and
hereby the study of the properties of the pancreatic juice is
much facilitated. As the pancreatic juice like the gastric juice
is wholly formed in the cells of the pancreatic gland, we can
also by simple infusion of the glandular tissue obtain an artificial
pancreatic juice.1

First of all this liquid emulsionises the fat bodies surely and
promptly. In addition it evolves in part some neutral fats
(butyrine, olei'ne, margarine, stearine) into glycerine and butyric
acid.

Moreover the pancreatic juice transforms almost instan-
taneously the fecules into soluble glycose.

Lastly it accomplishes the liquefaction of the proteic sub-
stances of the chyme.

We have seen that the bile by itself has a somewhat feeble
fluidifying action on the chyme : but from its union with the
pancreatic juice, which is besides more active, results a liquid
endowed with very energetic properties.

It is easy for us now to form a sufficiently exact idea of in-
testinal digestion. The chyme impregnated with gastric juice,
containing proteic matters already attacked by the stomachal
liquid, and in addition amyloidal and fat substances not modified,
passes the pyloric orifice of the stomach and arrives in the first
portion of the small intestine, the duodenum, where in most of
the vertebrates it is saturated by the biliary and pancreatic
juices. These two liquids being alkaline, the gastric acid is
neutralised : the chyme itself becomes alkaline. Moreover in
the intestine, as in the stomach, the presence of the alimentary
mass causes the congestion of the mucous membrane, an
abundant glandular secretion, and more vigorous movements of

1 Ch. Robin, Lemons sur Us Humeurs, pp. 532, 535.— Cl. Bernard, Memoire
sur le Pancreas, etc. (Supplement aux Comptes Rendus de VAcademie des
Sciences, t. I.)— L. Corvisart, Sur une Fonction peu Connue du Pancreas.

CHAP. XIL] OP DIGESTION. 191

the digestive walls. The afflux of the biliary and pancreatic
liquids finishes and completes the chemical elaboration com-
menced in the superior portion of the digestive tube. The
amyloidal and saccharine substances are metamorphosed into
dextrine and glycose : the protei'c are transformed into peptones.
The fat bodies are emulsionised.

All these important chemical modifications are effected, little
by little, 'in the degree that by the action of its muscular layer
the intestine contracts and thus makes the demi-liquid alimentary
mass march on. By degrees the aliments become assimilable
substances, veritable nutriments, Now these substances are in
contact in the intestine with the villosities so richly vascular :
they are therefore absorbed by endosmosis and thus pass into the
circulation. It is possible, however, that the vascular absorption
is not direct. There seems, in effect, to be incessantly on the
intestinal surface a generation of epithelial cells, which on the
one hand protect the mucous membrane, and on the other
absorb the nutritive liquids, elaborate them perhaps, then sur-
render them by endosmosis to the capillary vessels of the
intestine.1

The emulsionised fat bodies seem to be more specially seized
by the fine lymphatic canalicules, then to be driven thence into
the secondary lymphatic network. Therefore they give to this
network the milky aspect, fill it with chyle, which, drawn into
the grand lymphatic circulation, goes finally to pour itself into
the venous blood.

The gastric biliary and pancreatic liquids are unquestionably
the principal chemical agents of the transformation of the
aliments : but they are not the only ones. Numerous small
glands of diverse forms are disseminated in the substance of
the intestinal mucous membrane. These glands secrete an
important digestive liquid, the intestinal juice, and also simple
mucus. It results from various experiments that the intestinal
juice is the auxiliary of the other digestive liquids already
1 Cl. Bernard, Rapport sur les Progrte de la Physiologic, etc. p. 199.

192 BIOLOGY. [BOOK n.

described. It transforms the fecula into dextrine and glycose :
it emulsionises the fat matters ; it metamorphoses isomerically
the prote'ic substances. But its digestive action diminishes
and gradually ceases in the last portion of the intestine, the
large intestine. Nevertheless the lymphatic vessels of this
region are still charged with chyle exactly like those of the
small intestine.

The origin of the large intestine is distinguished by a dilata-
tion called ccecum, where the chymic mass sojourns for a longer or
shorter period. This caecal cavity acquires considerable dimen-
sions in the herbivorous animals, and this is conformable to the
general law according to which the digestive system must be so
much the more complex the less assimilable are the aliments.
Now nothing is less assimilable than the vegetal cellulose, which
traverses in great part the digestive tube without being modified,
not only in man but even in the herbivorous animals.

We have now indicated in large outline the diverse digestive
processes, the principal metamorphoses which the alimentary sub-
tances undergo to become absorbable and assimilable, to become
nutriments after being simple aliments. We must next occupy
ourselves with the second preparatory phase of nutrition, see by
what series of anatomical and physiological processes the assimil-
able matters elaborated by digestion are brought into intimate
contact with the tissues, with the histological elements, that is to
say, give a general description of the circulation.

CHAPTER XIII.

CIRCULATION.

1. — General HorpJiology of the Circulation.

IF we embrace with a complete and comprehensive glance the
anatomy of the circulatory apparatus in the whole animal king-
dom, we still see, as in other cases, specialisation gradually
effected. Nature, as it was formerly the fashion to say. did not
arrive at perfection at a bound. She made numberless attempts,
long she groped, adding successively new pieces to the system, or
complicating little by little those which existed already. In
modern language, the circulatory apparatus, like all others, was
perfected and differentiated more and more under the influence
of the struggle to live, and of natural selection.

A first fact results from comparative anatomy, namely, that

the circulatory system only shapes itself in living organisms,

after the digestive system, of which at the outset it may be

^viewed as the appendix.

In the protozoa l there is not yet either digestion or circulation.
The nutritive liquids absorbed pass direct into the nearly homo-
geneous parenchyma of the body. The liquids expulsed come
forth in the same fashion by a sort of insensible perspiration.

Jn the rhizopods the intimate contact of the substances absorbed

with the living substance is aided by the sarcodic contractions, by

1 Gegeubaur, Anatomie Comparte, p. 103.

194

BIOLOGY.

[BOOK ii.

the emission and the retraction of the pseudopods. Liquid currents
charged with granules are visibly produced.

In some infusoria we observe a rotatory movement, in a con-
stant direction, of the intra-cellular liquid, that is to say, a
phenomenon completely comparable with the intra-cellular gyra-
tion of the vegetal protoplasm (Paramsecia).

Immediately after the protozoa come the animals a little more
complex, having a digestive cavity, but no other. These are the
coral polypi or anthozo'ids, the hydromedusce, the clenophores.
In a certain number of animals of this group we see the first
rude beginning of the circulatory
apparatus, consisting of ramifications
more or less complex, emanating from
the digestive cavity and communicating
with it (medusae, and so on, — see Figure
6). The digestion and the circulation
being still confounded, we may charac-
terise the whole of the system as
g astro-vascular. The content of the
apparatus is not yet specialised : it ia
chyme diluted with water.

An organic progress is accomplished
in the ncemathelmintlis. For the first
time the nourishing liquid elaborated
by the digestive apparatus is, before

An;enor extremity of the body J

of a nasmertian (Boriasia ca- being assimilated, collected in a special

milla) : a opening of the

cavity distinct from the digestive system,
and surrounding it more or less com-
pletely. Figurate elements, a sort of
sanguineous globules, float in this liquid
in some nsematods. In the ncemertians
we already see appearing some vascular
canals. (Figure 15.) In the annelates there is a tolerably regular
network ; there are also longitudinal vessels connected with each
other, and of which one, very constant, is dorsal. This last is

trornpe ; p, troinpe ; c, vihratile
depressions ; n, cervical gang-
lion ; n', lateral nervous sys-
tem ; I, sanguineous lateral
trunks, which bend forward in
order to unite : before this
union they send round the brain
a branch which joins that op-
posite in order to form the
dorsal vessel d.

CHAP, xiii.]

CIRCULATION.

195

I

always contractile, and it drives the blood from behind forward.
The liquid of the rperienteric cavity is colourless, and we find in
it figurate elements.

In the hirudinates the perienteric cavity exists only among the
young. Habitually this cavity communicates with
the exterior, and consequently the liquid which
it contains is more or less mixed with water.
In many of the hirudinates and of the annelids
the blood is yellewish or more or less red.
(Figure 16.)

In the tunicate* there is constantly an impul-
sive organ, a heart, situated on the passage of the
ventral trunk.

The circulatory system of the echinoderms id
constituted by two vascular rings surrounding
the orifice of the digestive tube. These rings
are connected with each other, they emit radi-
ating ramifications, and one of. them receives
vessels coming from the intestine.

In the arthropods (crustaceans, arachnida,

insects) there is still, as in all the preceding

groups, a general cavitv filled with blood. In all

there exists an impulsive or cardiacal organ,

whence proceed efferent vessels, called for that

reason arterial. The blood returns to the heart

by the lacunar spaces situated between the

organs. These conduits without special walls

debouch into a pericardiacal reservoir, and the

blood penetrates afterwards into the heart by

] cardiacal clefts. In the decapod* (Figure 17)

I the blood before returning to the heart is

oxydised in passing through the branchiae. In

j insects the vascular system with well determined walls is almo&t

' limited to the contractile dorsal vessel.

All the mollusks have a sanguiferous organ contractile or car-

02

Anterior portion of
the vascular san-
guineous system
of a young Sce-
nuris varUgata ;
d, dorsal vessel;
v, ventral vessel ;
c, transversal an-
astomosis enlarg-
ed ; heart. The
arrows indicate
the direction of
the blood.

196

BIOLOGY.

[BOOK ii.

diactile, they have even sometimes several. (Figure 18.) There
has been an attempt to show the distinct existence in the heart

of the mollusks of a ventricle and
of auricles; but the ventricle is
only a dilatation of the dorsal
trunk, and the auricles are only
dilatations of the transversal vessel
debouching into the pretended ven-
tricle. In the cephalopods the dorsal
vessel curves like a curl, the bran-
chial veins debouch thereinto by
dilating. The heart sends forth
two arteries, the one cephalic, the
other abdominal. There is a true
network of fine capillaries between
the last ramifications of the venous
and arterial systems. Most of the
cephalopods have cardiacal mus-
cular dilatations on the branchial
arteries. Spite of the relative per-
fection of this apparatus, the cavity
of the body constitutes always a
huge lacuna full of blood, which
bathes the organs direct. This cavi-
ty communicates with the vessels j
veins debouch direct thereunto.

The circulatory system attains its
completion in the vertebrates, but
it is sti11 Vei7 imperfect in the first

ojf them, the amphlOXUS. In effect

in this animal, which Haeckel
wishes to regard as a connect-
ing point between the mollusks and the vertebrates, there
is still no heart, and the impulsion is impressed on the san-
guineous liquid by all the larger vessels, which are contractile.

FIG. 17.

Schematic figure of the circulatory
apparatus of the lobster : o, eyes ; a e,
exterior antennae ; a i, interior anten-
nas ; b r, branchiae ; c, heart ; p c,

T 1 • J • '

liver; a p, posterior artery of
body ; a, trunk of ventral artery ; a v,
anterior \ entral artery ; v, ventral
venous sinus ; v "b r, branchial veins.
The arrows indicate the direction of
the sanguineous currents.

CHAP. XIIL]

CIRCULATION.

197

In the other vertebrates there is a heart, but we see it perfecting

c

*~l U_ ^i ' I? ^ * ^> SsVO //«'• / *>

^-i r-*-<: £*- ^l r? NML-- v

FIG. 18.

Schematic figures showing the comparison of the modifications of the circulatory centres
in the mollusks : A, part of the dorsal trunk and of the transversal vessels of a worm ;
B, heart and auricle of a nautilus ; C, heart and ventricle of a lammelibranchian or loliginate ;
D, the same organ in an octopus ; E, heart and auricle of a gasteropod ; v, ventricle ; a,
auricle ; a c, cephalic artery ; a i, abdominal artery. The arrows indicate the direction
of the sanguineous current.

itself little by little. The simplest form of the heart in verte-

FIG. 19.

Schema of the framework of
the great trunks, of the dif-
ferentiated apparatus of the
branchial vessels ; a, arterial
bulb ; 1 — 5, arterial arcs ;
o a", aorta ; c, carotid artery.

FIG. 20.

Heart, branchial arteries, and opercu-
lary branchia of the Lepidosteus
osseus; y, ventricle ; A A, auricle;
B, arterial muscular bulb ; a, trunk
of the branchial arteries ; 1, accessory
branchia (operculary) ; p, pseudo-
"branchia (vent branchia) ; 2, 3, 4, 5,
branchiae of the arcs. The arrows
indicate the direction of the blood.

L

brates exists in fishes. There, the cardiacal dilatation is merely

BIOLOGY.

[BOOK ir.

divided into two parts, an auricle and a ventricle. The first part
receives the venous blood coming from the rest of the body, and
impels it into the second cavity, whence it is sent forth again by
a system of vessels into the respiratory or branchial organs. In
the branchial folds the blood traverses a system of fine capillary
vessels ; it is there charged with oxygen, and is afterwards poured
into the general circulation to return anew to the heart. (Figures
19 and 20.)

When lungs take the place of branchiae the heart commences
to divide longitudinally into four
cavities more or less incompletely
separated. There are, first of all,
in the auricles a reticulated tissue ;
in the ventricle protuberances, mus-
cular projections (lepidosiren). In
the reptiles there are three cardi-
acal cavities ; two auricles, the one
receiving the venous blood of the
body, the other the blood returning
from the respiratory organs. The
separation of the ventricle into two
cavities is indicated only by a re-
fciculated tissue. Sometimes, how-
ever, these two reticulated halves
do not contract simultaneously (tor-
toises). Here still, as in the inferior
crustaceans and the arachnida, the
totality of the blood is not constrained
to traverse the respiratory surfaces before returning to the
heart.

In birds the longitudinal separation of the heart is complete ;
there are two auricles, two ventricles. The blood vivified,
oxygenised, returning from the lungs> the arterial blood, is no
longer mingled in the heart with the blood which has served for
nutrition, the venous blood, black and charged with carbonic

\

FIG. 21.

Heart airl large vessels of Sctlaman-
dra maculosa. The first arc of the
aorta, c, in direct continual ion with
the carotid ; w, x, y, z, apparatus of
the hyoid bone j c, carotidian
glands.

CHAP, xm.] CIRCULATION. 199

acid. The case is naturally the same with the mammifers ; in a
cetacean, the dugong, the two hearts exist, but they are almost
entirely separate. In proportion as the cardiacal cavities take
distinct shape they subdivide each into two secondary cavities by
means of membranous valves not contractile. Other valves of
analogous structure are found at the orifice of the large vessels
which go from the heart or debouch into it.

The circulatory system of the vertebrates forms an ensemble
of closed canals, containing a special liquid. There are no
longer any lacunae, or at least they are merely exceptional and
partial (Fig. 21). From the heart goes a system of efferent or
arterial canals, while to the heart comes another afferent or
venous system. Lastly, these two systems of canals, which in
the superior vertebrates have a different structure, are connected
with each other by very fine canalicules, called capillary vessels,
with very thin walls. These capillary vessels can be classed in
three principal networks, among the superior vertebrates. One
of these networks extends on the surface of the respiratory
organs : it is the one which gives issue outwardly to the carbonic
acid : it is the one which gives at the same time access to the
oxygen : it is the network of the respiratory capillaries. The
second grand network of capillary canals exists in the liver : it
springs from the subdivision of the intestinal venous system.
The vasculary ramuscules which constitute it intertwine round
the glycogenical cells of the liver, then unite anew to form
veins (hepatic veins), which pour their contents into the general
venous system. The group of the capillaries of the liver may be
called the network of the glycogenical capillaries. The ensemble
of all the other capillaries, belonging neither to respiration nor
to glycogenesis, may be denominated the network of the nutritive
capillaries. The capillaries of this last network plunge into the
mechanism of all the organs, even into that of the respiratory
organs and of the liver; it is through their walls that the
nutritive exchange is effected, that the anatomical elements
receive their assimilable substances, and reject their disassimi-

•200

BIOLOGY.

[BOOK n.

CHAP, xiii.] CIRCULATION. 201

lated products. To be complete we must besides mention the
numerous small capillary networks serving the secretions not
glycogenical.

Assuredly in this summary, so rapid and so incomplete, we

cannot have the pretension to expound in detail the physiology

of the diverse organs and apparatus. Our duty is to keep to

generalities, while merely borrowing from particular facts those

of them which are indispensable to our exposition. Nevertheless,

it will be opportune to describe briefly the mechanism of the

circulation in the superior vertebrates. We shall thus have

to speak of the heart, of the arteries, of the capillary vessels,

and finally of the veins. But previously it will not be without

utility to present in a few lines the idea of ensemble which

springs from our rapid summary of comparative anatomy. The

movement of the fluids is evidently a primordial law of nutrition.

I It is effected alike in the monocellular being and in man. First

I of all it is by direct absorption through the exterior wall of the

i cell. It has been observed that an active and visible exchange,

\ when the protoplasm conveys granulations, is carried on between

the nucleus and the protoplasm (hairs of the Tradescantid Virginia).

, Here the circulation rigorously depends on the nutritive exchange,

! on the summons to action of the assimilable materials, on the

'rejection of the waste materials. In the polycellular organism,

; little or not at all differentiated, each cell acts nearly as if it

(were alone, and we have seen that, in plants, there is a rotatory

movement of the protoplasm in each cell. In the inferior

•animal, in which already the nutritive labour begins to break

'into parts, there exists a gastro-vascular apparatus. A substance

more or less assimilable passes into a system of fine canals in

direct communication with the digestive pouch. Then these

.canals separate from the digestive apparatus. As in a system so

complex, the nutritive appeal made by the anatomical elements

and the capillarity would no longer suffice to impress on the

; nutritive liquid the requisite mtovement, the canals became more

or less contractile. Then by a new specialisation the contractile

202 BIOLOGY. [BOOK n,

power accumulates after a fashion at special points, where a.
muscular tissue more or less rich appears. Generally, then,,
there is a respiratory apparatus more or less complete, and as a
result there are two species of blood more or less distinct, a blood
oxygenised, and a blood which has need to be so. These two,
species of nutritive liquids finally separate, while there is pro-
gressive improvement, and though the second always comes from
the first, it no longer blends with it. Then the propulsive agents
are multiple. They are the nutritive call of the anatomical
elements, the reflex impressed by them on the waste substances,
the general contractility of the vessels, contractility more)
accentuated in the arteries, that is to say, in the canals which
convey the vivified blood. Lastly, there exists a central pro-:
pulsive organ, a hollow muscle, first with two, then with three,
then with four cavities, communicating with each other two by two,
but separated by valves which hinder the reflex. Each pair of j
these cardiacal cavities is, truth to speak, a special heart. One-i
of these hearts is venous, that is to say, charged to impel rapidly j
the black blood returning from the tissues toward the respira-j
tory apparatus, where it obtains a supply of oxygen. The other'
heart is arterial, and has for function to impel toward thej
tissues the oxygenised blood which is indispensable to them.

Naturally, the nutritive system is the better specialised, the ;
better closed and the better differentiated the system is which !
contains it. First of all it is not distinguished from the aliment I
itself, then from the chyme ; then it becomes an elaborated ;
chyme ; finally we meet with, therein, floating figurate elements.
These elements, which at the outset are simple epithelial cells,
become special globules, characterised by a particular form, a(
particular colour, — hsematia, — as greedy for oxygen as they are
prompt to relinquish it to the anatomical elements.

A. Of the Heart. — We have seen that the heart of the superior
vertebrates is, in the animal series, bound to the contractile
sanguiferous organs by a long chain of gradations. Moreover
the same seriation is individually reproduced in the embryological

CHAP, xiii.] CIRCULATION. 203

development of every vertebrate. In these days it is merely to
1 utter a commonplace to recall that the heart of every vertebrate
appears first of all, in the embryon, under the form of a simple
contractile vesicle, and represents tolerably well, in its ulterior
1 development, first, the cardiacal type of the fish, then that of
the reptile.

• Further on we shall see that the anatomical muscular elements
1 are distinguished into muscles of the life of relation and muscles
of the nutritive life. The first constitute the muscular masses
i which obey the will ; the others form the contractile elements of
the viscera not subject to that influence. Now, by exception,
! the heart, the organ of the organic and independent life of the
I will, is constituted by muscular fibres of the animal life, by fibres
I called striated. This is the case among mammifers, birds, and
: reptiles. Nevertheless these cardiacal muscular fibres are not
I absolutely identical with those of the muscles of the animal life.
I They are thinner, have a granulous aspect ; besides, they have a
i reciprocity of ramification and anastomosis. Striation, but of a
1 very fine kind, is also seen on the cardiacal muscles of many in-
! vertebrates, especially insects, spiders, and crustaceans : in short,
1 among the arthropods. There likewise the muscular fibres have
a granulous texture and a more sombre hue.

The nervous apparatus of the heart is also altogether peculiar.
' By and by we shall find that the peripheric part of the nervous
system is composed of afferent or motory fibres, of efferent or
sensitive fibres, and lastly of a nervous network having some
; special anatomical features, and called the system of the sympa-
thetic nerves. Now the heart, already singular by the nature of
its muscular fibres, is also innervated in a particular fashion. It
receives equally sympathetic fibres with ganglionary expansions
and smooth fibres of the animal life. Finally, the distribution
of all these nervous fibres is not made uniformly among the
muscular fibres. If, employing a suitable sodic solution, we
Tender transparent considerable portions of the auricles and the
ventricles, we find therein few or no nerves. It is in proximity

204 BIOLOGY. [BOOK n.

to the valves that these seem to be concentrated. Nevertheless
sympathetic threads furnished with ganglionaiy expansions
penetrate here and there into the muscular substance.

This structure of the heart is in perfect harmony with the
functions of that organ. It is true that this organ belongs to
the department of the nutritive life ; but it has to contract with
rapidity. Now the smooth muscular fibres of the animal life
contract slowly. It was needful then that in animals with a
circulation active in a degree, however small, the propulsive organ
of the blood should be constituted by striated fibres. Further-
more it was indispensable for 'these fibres to have a great
functional independence. In effect, the heart, which commences
to beat the very first day of the embryonic life, does not definitively
stop till death. Contrariwise to what takes place in all the
organs of relation and in a considerable number of nutritive
organs, the heart has no normal intermittence ; it has no need of
reparative repose. It is an indefatigable worker, and the labour
it accomplishes during the life of a man is truly prodigious.
From birth to death, it can without reposing contract three billion
times, and impel into the tissues about 150 millions of kilogrammes
of blood. If during sleep its movements are somewhat slower,
it is because many organs at that time repose and so expend less.
During the hibernal sleep when the nutritive movement falls to
the minimum, and when the consumption of oxygen diminishes
nineteen-twentieths (marmot), the number of beatings of the heart
diminishes nine-tenths. If the heart were strictly enslaved to the
nervous system, if it always obeyed it with docility, and waited
always for a first, excitation from it, then the heart would share
the functional feebleness of the nervous system, which is the
most intermittent of the organic systems : but this is far
from being the case. The heart severed from the organism
still beats for a longer or shorter period according to the
species. Thus Scoresby saw the heart of a shark beating
some hours after it had been torn from the body (Burdach,
vi. 303). The heart commences to beat (punctum saliens) before

CHAP, xiii.] CIRCULATION. 205

.there is in the embryon the smallest trace of nervous system,
and at a later period, in the adult, when the motory nervous
system is killed by the help of the poison curare, the heart
continues nevertheless to palpitate. It is even totally freed
from dependence on the nervous centres, and we no longer
succeed, as in the heart's normal state, in suspending the
cardiacal beatings by irritating one of the principal sources
of the heart, the pneumogastric nerve.1

In effect, in the state of integrity of the organism, the
heart, spite of its independence, is bound by its nervous system
;to the rest of the organism, and specially to the brain. The
rapid ingestion of a very cold drink into the stomach provokes
' & contraction of the vessels of the brain, thence anaemia of
, that organ, and sometimes stoppage of the beatings of the
i heart, whence death can result.2 A sudden stoppage of the
j beatings of the heart can also be provoked by a shock on the
j epigastrium : it is produced when the, heart and the viscera of
a frog, being laid bare, we strike a violent blow on the abdominal
viscera.3 A sharp pain on the passage of a sensitive nerve
i produces the same effect.4 If we electrise any nerve whatever
i the heart stops in its state of dilatation, in diastole. The
! result is the same in a frog, if we electrise the origin of the
I spinal marrow, the medulla oblongata.5 But the stoppage of
| the heart in diastole is produced more surely still if we electrise
| the nerves which connect it direct with the brain, the pneumo-
gastric nerves.

Moral impressions produce the same effect. Syncope fre-
quently follows a strong emotion. This is a fact of common
I observation. Sometimes, on the contrary, emotions provoke a

'• J Saissy, Regnault. — See also Gavarret, DCS PMnomZncs Physiques de la,
[Tie, p. 227.

? 2 R. Ganz, Ueber die Gefahr des Jcalten Trunkes bci erhitztcm Kdrper
(Pfliiger's Archiv, 1870).

3 Brown -Sequard, Archives Generate de Mtditine, 1856, t. VIII.
I 4 Cl. Bernard, Sur la Physiologic du Cceur.

6 Vulpian, Legons sur la Physiologic du Systtme Nerveux, p. 853.

206 BIOLOGY. [BOOK n.

tumultuous acceleration of the cardiacal beatings, either primi-
tively, or consecutively to a retardment. We can also directly
excite precipitate beatings by touching the internal wall of a
ventricle with a foreign body, for instance, a thermometer intro-
duced into the heart. (01. Bernard.)

Apart from all these causes of perturbation, the heart exercises
on the blood contained in its cavities a constant and very uni-
form pression. In the mammifers this pression is equivalent to
scarcely more than a force capable of raising a column of mer-
cury of 150 millimetres. Contrarily to all prevision, this pres-
sion is strikingly inferior to that which the blood undergoes in
the arteries ; and yet the blood is rapidly driven from the heart
into the arterial canals. M. Schiff has given an ingenious ex-
planation of this physiological paradox, by demonstrating expe-
rimentally, that the predominance of the cardiacal impulsion is
due to the combined action of the shock, and of the elasticity of
the walls of the heart.1

We can now form a sufficiently clear idea of the functional
activity of the heart. The cardiacal cavities contract in couples,
the auricles first of all, and together, then the ventricles.

In the simple heart of fishes the heart is never traversed except
by venous blood, which flows first of all into the auricle, is
driven by it into the ventricle, and thence by a ventricular con-
traction into the respiratory organs, the branchiae. In the rep-
tiles, in which there are two auricles and a single ventricle, the
arterialised blood returning from the respiratory surfaces, and
the venous blood charged with carbonic acid coming from the
tissues, blend in this ventricle common to them both.

In the birds and the mammifers the venous blood penetrates
into the right auricle, passes thence into the right ventricle, which
drives it into the lungs. There it is oxygenised, becomes ver-
milion, arterial, returns to the heart ; but this time, into the
left heart. It penetrates into the auricle of that side, which
sends it forth once more into the corresponding ventricle ; whencs
1 M. Schiff (unpublished work).

CHAP, xin.] CIRCULATION. 207

tit is impelled into the general arterial system, whither we have
now to follow it.

B. Arteries. — The arteries, that is to say, all the vessels going
'by ramification from the heart to the capillaries, have all an
elastic and contractile wall. Long there was a controversy re-
garding the nature of the contractile elements of the arteries till
the moment, when in 1840, Henle demonstrated that the arterial
'contractility is due to anatomical elements identical with those
of the muscles of organic life.1 They are fusiform fibro- cells
transversely placed relatively to the axis of the vessel, and fur-
nished with a nucleus. They have a length of from five to seven
Ihundredths of a millimetre, and have a breadth of from five to
: six thousandths of a millimetre on the level of the nucleus The
mode of contraction is naturally in strict relation with the
• nature of these anatomical elements. The contractions of the
; fibro cells is effected slowly, progressively, after an excitation of a
I certain duration. But in requital, they persist during from ten
i to fifteen seconds at the least, and the artery returns slowly to
| its primitive state. This muscular layer is in general the thicker,
the larger the calibre of the vessel is. It diminishes in the
degree of the ramification of the arteries, and ceases altogether in
! the capillaries.

The arterial contractility is less independent of the nervous

system than that of the heart. The experimental researches of

modern physiology have, in effect, demonstrated the existence of

I motory nerves of the vessels, or vaso-motories. We shall have to

I speak of them at tolerable length. Their action determines the

paralysis of the vessels, which dilate ; for they then lose their

j tonicity, the state of demi-contraction which keeps always the

: arterial calibre in a certain degree of "narrowness. If we cut in

, a rabbit's neck the cord of the great sympathetic nerve whence

I emanate the vaso-motor nerves of the ear, we see ceasing the

rhythmical beatings of the auricular artery, which normally are

effected five or six times a minute. The excitatory nervous

1 Henle, Wochenschri/l fiir die gesammte Hdlkunde, 1840 (No. 21).

208 BIOLOGY. [BOOK n.

centre of these movements, as well as of almost the totality of
the vaso-motory nervous network, seems to be situated in the up-
per part of the spinal marrow. According to experiments of M.
Schiff the section of the cervical marrow abolishes in the rabbit
the rhythmical movements of which we have spoken. The com-
plete section abolishes them on the two sides ; the hemisection
abolishes them only on the sectionised side.1

If we can paralyse the vessels, especially the arteries, by sec-
tionising the nerves which animate them, or the excitatory centre
of those nerves, we can inversely excite arterial contractions by
diverse means. The mere action of cold suffices to determine
the contraction even of large arteries. Thus we can in a sheep
stop the haemorrhage produced by the section of the carotid
artery by applying to this section a simple sponge saturated
with cold water.2 In an amputated limb, Kb'lliker determined
the contraction of the poplitic artery, and of the tibial artery, by
help of a magneto-electrical apparatus of induction.3 This is an
effect which we obtain in all the arteries by electrising them with
interrupted currents. M. Yulpian has observed the contraction
effected slowly at the outset between the two electrodes applied
to the vessel, then propagated to the last peripheric ramifications,
The continuous electric currents, whatever their direction might
be, would act in an analogous manner.4

The arteries, like the heart, never rest during life. Their
action appears even to survive that of the heart, which thus no
longer deserves to be called uttimum moriens, a name long given to
it. When the heart has ceased to beat the arteries still contract,
and as their action is no longer counterbalanced by the cardiacal
impulse, they tend to drive the blood into the capillaries and into
the veins. Then when their muscular coat is dead in its turn, they

1 Sc'hiff, Sur un Cceur Artifidel Accessoire dans Us Lapins (Comptes RenduS
de VAcad. des Sc., t. XXXIX. 1834).

2 Vulpian, Legons sur VAppareil Faso-moteur, p. 63.
» Kolliker, Zeitschrift fur Wisscnsch. Zoologie, 1849.
4 Vulpian, loc. tit., p. 56.

CHAP, xiii.] CIRCULATION. 209

dilate ; and that is the cause of their vacuity in the dead
body.1

It seems idle at the present day to debate whether the arteries
dilate when they are traversed by the sanguineous stream which
each contraction or systole of the cardiacal ventricles drives into
their canals. But the fact at one time was the subject of contro-
versy among physiologists. Spallanzani demonstrated the dila
tation of the great arterial trunks, and especially of the general
trunk of the arterial tree, the aorta, by surrounding this vessel
with a metallic ring.2 He saw that during the cardiacal systole
the aortical diameter augmented a third, in immediate proximity
to the heart, and a twentieth only in the rest of its passage.
Other* experimentalists have demonstrated by analogous means
similar facts in the large arterial trunks, for instance, the carotid ;
but the dilatation becomes less and less considerable in proportion
as the artery is more distant from the heart and of a narrower
calibre. In the small arterial branches, as Magendie has re-
marked, the dilatation is no longer perceptible.3

If the arterial dilatation is unquestionable in arteries of con-
siderable calibre, and if it assuredly depends on the passage of the
sanguineous stream, we may ask oursejves whether the pulsation,
the arterial pulse has the same cause. Tho older physiologists,
Haller, Spallanzani, and so on, have pretended, and wrongly,
that the pulsation is simultaneous in the whole arterial tree, and
consequently could not be attributed to the movement of trans-
lation of the sanguineous fluid, but rather to the shock, to the
transmission from point to point in the liquid column, of the
rapid agitation of the vibratory wave determined by the ventri-
cular systole. We now know that the isochronism of the arterial
beatings does not exist; but it is nevertheless probable that
the vibratory transmission contributes its part to the production
of the pulse.

1 Yulpian, loc. cit., p. 324.

2 Spallanzani, Experiences sur la Circulation.

3 Magendie, Journal de Physiologie, t. I., p. 113.

P

210 BIOLOGY. [BOOK n.

We can now form a sufficiently exact idea of the arterial
circulation. At every ventricular systole a certain quantity of
blood, on an average fifty grammes in man, is driven from the
heart into the arteries. The valves situated at the orifice of the
arterial trunks in the heart, the sigmoidal valves, rise to let the
flow pass, and afterwards fall to hinder the reflux. The elasticity
and the contractility of the arteries, vanquished by this sudden
afflux, yield ; the calibre of the vessels abruptly augments ; but
the muscular fibro-cells of the arterial walls, excited by their
vaso-motory nerves, instantly re-act ; the artery contracts, and
impresses on the sanguineous wave a new impulsion. Naturally
it is the large trunks, those which receive the shock the most
directly, that dilate the most ; but the sanguineous impulsion is
expended in part for this dilatation ; the arterial contraction
which it has provoked comes to its aid, is a supplement thereto
in a certain measure, and it acts with the more continuity the
more distant the arterial vessel is from the heart, and is influenced
less by the sudden effort of the cardiacal impulsion. Thus in th©
fine arterial ramifications the sanguineous current is perceptibly
continuous and uniform ; dilatation and pulsation scarcely exist
in them. This is why we observe in these small vessels a con-
siderable diversity of operation. Of two arterial ramuscules
emanating from a common trunk, one is the seat of a rapid cir-
culation, the other of a slow circulation. Other differences seem
to depend on the organs, in the tissue whereof the arteries pro-
ceed to distribute themselves. If these organs are the seat of a
great nutritive expenditure, of important material exchanges, the
arterial contractions are the more energetic; for they must
maintain a more active sanguineous current. Also the arteries
of the brain, of the marrow, of the glands obey the artificial
excitations better than tha others ; they contract more rapidly
and more vigorously.1

The circulation varies also in a general manner in the different
parts of the arterial tree ; the course of the blood slackens in the
1 Vulpian, loc. cit., p. 64.

CHAP, xni.] CIRCULATION. 211

degree that it approaches the capillaries. It slackens, on the
one hand, because the cardiacal impulsion is transmitted with a
diminishing intensity; on the other hand, because the total
capacity of the arterial ramifications is greater than that of the
trunks whence they emanate.

At last the arterial blood, in a continuous and uniform current,
reaches the fine capillary ramifications, penetrating into the web
of the tissues, and connecting the arterial tree with the venous
tree. But this fine capillary network is the seat of pheno-"
mena very important, and entirely bound up with the primordial
acts of nutrition.

C. Capillary Vessels. — In many invertebrates, as we have seen,

the circulatory system is composed solely of some principal

1 vessels, beyond which the blood circulates in the interstices of

the organs, in lacunae, without peculiar membraneous partitions.

| On the contrary, in other invertebrates there are true capillary

i vessels. Thus it is, for example, in the annelates (annulata), in

I which the finest vascular ramifications have their autonomy. In

I certain insects there exist also fine canalicules, comparable with

the capillaries. In the cephalopal mollusks, we see, at many

points of the body, the arteries terminating in veritable capillaries

formed of a homogeneous membrane, which is bestrewn with

elongated nuclei.

Such is, verily, the texture of the true capillaries in the
I vertebrates. They are fine canalicules, having nearly the
1 diameter of a sanguineous globule. The slimmest allow the
I globules only to pass in file. Their diameter varies between
Omm,007 and Omm,030 ; they are constituted solely by a single
| coat, with a thickness varying from Omm,001 to Omm,002. This
I coat, everywhere homogeneous, is besprinkled with ovoid nuclei,
I the main diameter whereof is directed toward the axis of the
I vessel. If we follow the capillaries, either in the direction of
the arteries or in the direction of the veins, we see their diameter
) enlarging little by little. It passes from Omm,030 to Omm,.070,
' and a second membrane, or coat, clothes the first at the exterior. .

p 2

212 BIOLOGY. [BOOK n.

This second membrane, closely joined to the first, contains fibre-
cells, this time transversal, which already indicate the rise of
the contractile tunic of the larger vessels. Finally, these
capillaries, with their transversal fibro-cells, are continued along
with vessels still larger, from Omm,060, to Omm,140, which, besides
the two preceding tunics, have a third external tunic, a coating
of laminous longitudinal fibres. These last vessels, already
visible to the naked eye, have direct continuance in the arterioles
and the veinules.

In diverse regions of the body, the arteries have, apart from
the capillaries, transversal channels of communication, which
connect them direct with the veins. These are small vessels
furnished with a muscular layer, comparatively thick. If these
vessels contract, the blood is compelled to pass through the
muscular network ; if, on the contrary, the last contractile rings
of the arterioles shrink up and cause the occlusion of the capil-
laries, the blood passes through the collateral vessels, and, in
that case, it is no longer serviceable to nutrition. This mechanism
is observable in certain glands, and notably in the venous
apparatus of the liver, where it serves to regulate the glyco-
genical secretion, to deprive of blood the secreting cells, or to
allow the adequate ration thereof to reach them.1

We can now form a general idea of the province of the capil-
laries in nutrition. The sanguineous stream, driven first of all
by the heart, then by the arteries, directs ifcs course toward the
capillary network, for a time in an abrupt and pulsatile fashion,
then more and more regularly. Arriving at the capillaries, the
arterial blood moves at a moderate and uniform rate, at least in
the normal state. We have seen that in the finest canalicules
the globules only pass one by one, and so to speak, by friction.
Then they and the plasma which bathes them and carries them
on are only separated from the anatomical elements constituting
the tissues by a thin homogeneous membrane of which we have
spoken. The osmotic conditions are therefore very favourable

1 Cl. Bernard, Legons sur les Proprietes des Tissus vivants, pp. 415, 416.

CHAP, xiii.} CIRCULATION. 213

to the exchanges of fluids and of gases. Besides the blood is sub-
jected to a tolerably strong pression. To these conditions already
so favourable to the osmotic exchanges are added electro motory
actions. This exceedingly interesting point of the physiology of
the capillaries has been elucidated by M. Becquerel in a series
of important papers.1 If by means of a voltaic pile we decom-
pose water contained in a vessel divided into two compartments
by a membrane, we see the level rise in the negative compart-
ment. There is therefore material transport from the positive
pole to the negative pole. Something analogous takes place in
the capillaries. In consequence of the incessant chemical muta-
tions which are effected in the tissues and the vessels, electrical
currents are produced. The capillary vessel is electrised nega-
tively on the exterior, and positively in the interior of its wall.
The oxygen traverses the wall, and is deposited on the external
surf ace. As to the globules, they enter into contact with the posi-
tive internal wall. The oxygen, once infiltrated into the tissues,
oxydises them, gives rise to the production of carbonic acid,
which the electrical current tends to impel into the interior of
the capillary. In other terms, and leaving aside the old notion
of the two 'electric fluids, there is between the contents of the
capillary vessels and the histological elements of the tissues a
circular current, an electrical circuit, which carries the oxygen
to the outside of the vessels, and brings back the carbonic acid.
We shall have to expound in detail what relates to the special
office of the capillaries in the respiratory surfaces, and in the
liver ; we must content ourselves here with speaking of the
capillaries distinctively nutritive, of those instrumental in the
general exchanges between the blood and the tissues. But on
this point our work is already done, and it is sufficient to refer
the reader to the preceding chapters, in which nutrition has been
discoursed of in a general manner. We have indicated there
\\ hat substances come forth from the capillaries to be assimilated
by the anatomical elements, what others are yielded to the blood
1 Mi-moires d Comptes Rcndus de FAcad&nie des Sciences, from 1867 to 1870.

214 BIOLOGY. [BOOK 11.

by those anatomical elements ; and when, speaking of diffusion
and osmosis, we have passed in review the principal physical
conditions of this nutritive barter. 01. Bernard very justly
compares the anatomical elements to animals fixed at the bottom
of the sea, and the oxygenised sanguineous wave to the flood which
comes incessantly to bathe these animals, bringing to them
aliments and respirable air.

The diverse manifestations of life, and life itself, are intimately
dependent on the passage of this nourishing stream. If it is for
a moment interrupted in an organ, the functions of that organ
are at once suspended, and if the interruption is of some dura-
tion, the death of the anatomical elements is inevitable. A liga-
ture applied to the general trunk of the arterial tree, the aorta,
in an animal, paralyses the animal instantaneously. Inversely,
we can make to revive members amputated and already in a state
of cadaveric rigidity ; we resuscitate an animal's head severed
from the trunk by injecting into the arteries, and consequently
into the capillaries, either complete blood, or even denbrinised
but oxygenised blood.1

But the capillary networks, exquisitely fine, are not rigid and
inextensible. If they are not contractile, they are assuredly
elastic. They can dilate or narrow, according as the sanguineous
torrent which traverses them is more or less abundant. Now we
have seen that the origins of the capillary vessels themselves, and
especially the arterioles whence they spring, are furnished with a
contractile tunic. Consequently the calibre of these vessels, and
therefore the amount of the sanguineous current in the capillaries,
must be very variable ; and in truth this is what happens. But
the history of the principal conditions of these variations forms
one of the most interesting chapters of general physiology, and
also one of the most important, forasmuch as it is, so to speak,
the mechanism of nutrition which is here concerned.

Numerous agents can produce either the contraction or the

1 Brown-Sequard, RecJwrches sur le Retablissement de V Irritabiliti Muscu-
laire, (Comptes Eendus et Memoir es de, la Societe de Biologic, 1851).

CHAP, xiii.] CIRCULATION. 215

dilatation of the capillaries. Physical, chemical, mechanical
irritants can redden the skin, that is to say, cause the dilatation
of the capillaries. The application of a refrigerant mixture pro-
vokes first of all the dilatation of the capillaries, then their con-
traction. The skin becomes pale and exsanguine. On the
contrary, heat dilates the capillaries and congests them.

Bright light acts as heat acts. An electric light produced by
1 20 Bunsen elements has . been seen to cause a cutaneous ery-
thema. From diverse experiments made by M. Bouchard with
prisms and lenses, it results that it is the chemical rays of the
luminous spectrum which produce redness and vesication soonest.

The dilatation of the capillaries can be provoked by direct
irritation without the intervention of the nervous system ; for in
the embryon of a chicken still destitute of nerves we need only
deposit a drop of nicotine on the area vasculosa to produce a
very beautiful congestion.1

This fact seems to demonstrate that the capillaries, though
lacking muscular fibro cells, have a contraction peculiarly their
own. At all events, the capillaries with simple homogeneous
wall dep nd on larger capillaries, furnished with fibre-cells, and
especially on the arterioles and arteries, which are most evidently
contractile. It is therefore very natural that in acting on the
nervous system we can cause either the contraction or the dila-
tation of the capillaries. A sharp irritation of the skin, or a
violent pain, brings on the contraction of nearly all the capillaries.2
If we excite in a dog the central end of the sciatic nerve sec-
t ionised, we see contracting first the vessels of the other member,
then those of the whole body.

On applying ice to the cubital nerve Waller saw the little
finger and the fourth finger grow red, and their temperature
rise. The sanguineous vessels depend, then, in a large measure
on the nervous system. Modern physiology has put beyond
doubt this interesting fact, and it has demonstrated the existence

1 Vulpian, Lefons sur VAppareil Vaso-moteur, t.»I., p. 171.

2 Ibid. p. 217.

216 BIOLOGY. LDOOK n.

of special nerves, of motory nerves of the vessels, or va.so-
motories. The function of the vaso-motory nerves is of such
importance that it is indispensable briefly to describe it.

The vague notion of nerves specially charged to regulate the
distribution of blood in the vessels is very old in science.
Already even in 1727, Pourfour du Petit had noted the fact
Avhich in our own days has led M. Schiff in Germany, and M.
Cl. Bernard in France, to the discovery of the vaso-motory
nerves. Whosoever has opened a treatise on anatomy knows
that the peripheiic parts of the nervous system, situated apart
from the nervous column — the nerves, properly so called — are
distinguished into two great categories. One of these categories
comprehends cords, smooth, cylindrical, and appertains to motility
and to sensibility. The other is composed of cords along whose
passage enlargements or ganglions are found ; this is the ga-ng-
llonary nervous system, which has for a long time been called
the sympathetic nervous system or the system of organic life,
because its principal branches are especially distributed to the
riscera. We propose to give further on a somewhat less
succinct description of the ganglionary nervous system. For
the moment we must satisfy ourselves with saying that as a
whole it is composed of two chains of ganglions placed on each
side of the vertebral column.

These ganglions, connected with each other by vertical nervous
cords, are, on the one hand, united by other nervous branches
to the spinal marrow, and send forth numerous branches,
distributing 'themselves to the viscera, penetrating even to all
the tissues and organs of the body, and clinging more or less
straightly to the arteries. In the cervical region in man, we
count three cervical sympathetic ganglions, of which the higher
one sends forth fibres which adhere to the intracranian and
extracranian arterial branches. Now, as early as 1727, Pourfour
clu Petit had remarked that the section of the great sympathetic
nerve in the nec£ provoked congestion of the eye and the redness
of the ocular conjunctiva. To think that the cutting of the

CHAP, xm.] CIRCULATION. 217

nerve had paralysed the vessels, and that consequently vaso-
motory nerves existed, there was only a step, apparently easy,
to take ; and yet that step was not taken till our own day. The
priority of precise and well-interpreted observations and experi-
ments seems to belong to M. Schiff (1845).1 In France, M. Cl.
Bernard, who appears to have been ignorant at that time of the
labours of his predecessor, was the first to give a theory of the
vaso-motory nerves complete, demonstrative, and based on well-
made experiments.2 We have now to indicate, without restricting

I ourselves to follow the chronological order, the typical facts and
their signification.

The section of the sympathetic nerve in the neck, or rather
the outpl ucking of the higher cervical ganglion, causes the dilata-
tion of the capillaries of the cerebral pia mater, of the con-

I junctiva, of the ear of the corresponding side, and so on. This
dilatation is accompanied by a very notable elevation of local
temperature (5, 10, 15 degrees), demonstrated for the pia mater
and the brain ; in short, by all the phenomena, of simple conges-

i tion, without inflammation. A wound in the ear of the side thus
injured bleeds more rapidly and more abundantly. The blood in
the veins of the side affected contains more oxygen and less car-
bonic acid than the ordinary venous blood. The sensibility is at
the same time intensified. Analogous phenomena are observed
in all the organs whose sympathetic nerves are cut, the liver, the
•eins, the lungs, the intestines, &c.3

This congestion is not inflammatory. It persists for days and
for weeks without modification, and we might without temerity
affirm that it results from a paralysis, if we merely relied on the
facts which we have just enumerated ; but,the counter-proof has
been made, and leaves no room for doubt. If, in a dog whose

1 De Vi Motoria Baseos Encephali, Bockenhemii, 1845.

2 Cl. Bernard, Influence du Grand Sympathique sitr la Sensibility et la
Calorification (Comptes Rendus de la Sotiett de Biologie, 1851).

3 Vulpian, Lemons su/r les Nerfs Faso-moteurs, t. I., pp. 94, 95, 106, 112,
531, 561.

218 BIOLOGY. [BOOK. n.

great cervical sympathetic nerve we have sectionised, we provoke
the redness of the ocular conjunctiva by instilling into the eye
a drop of ammonia, we can dissipate this redness by galvanising
the higher end of the cut nerve. In the same way the electrisa-
tion of the great cervical sympathetic nerve, or rather of the
higher cervical ganglion, determines the contraction of the pia
mater of the same side.1 In dogs M. Yulpian has seen the
section of the renal nerves followed by red colouration of the
kidney, and by polyuria, with the passage of the albumine of
the blood in the urine. Inversely the electrisation of the
nerves made the renal gland grow pale and abolished the secre-
tion. In short, the electrisation of the sympathetic nerves
and ganglions produces results diametrically opposed to those
of their section and of their destruction, that is to say, paleness,
the lowering of the temperature, the abolition of the secretions,
the diminution of the sensibility.

These phenomena are invariable. They are observed every-
where and always in all the vertebrates. There are consequently
vaso-motory nerves ; and M. Schiff thinks they should be
divided into vaso-constrictor nerves and vaso-dilatator nerves.

Anatomically the remote vaso-motory nervous filaments have
been investigated as far as the capillaries of the second degree,
already furnished with nbro-cells. Evidently the nerves cannot
have direct action on the finest capillaries altogether destitute of
contractile elements. It is in acting on the arteries, the arterioles,
and the capillaries of the second and third degree that they
obstruct or facilitate more or less completely the passage of the
sanguineous current, modifying thus more or less the alimentary
ration of the organic elements.

We have seen above that the ganglionary or grand sympathetic
nervous system, draws from the spinal marrow numerous and

1 Nothnagel, DCS Nerfs Vaso-moteurs des Vaisseaux du Cerveau (analysed in
Gazette Hebdomadaire, 1867), and Callenfels, Ueber den Einfluss der vaso-
motorischen Nervens auf den Krewlauf und die Temperatur (Zeitschrift fur
ration. Med., 1855).

CHAP, xiii.] CIRCULATION. 219

important roots. It is therefore very natural that lesions of
the nervous centres should react on the vaso-motory nerves, and
that diverse excitations should be able to transmit themselves
indirectly to those nerves, by reflecting themselves on the nervous
centres, that is, by reflex action.

In truth, a lesion of the cerebral peduncles and of the optical
layers determines a dilatation of the abdominal capillaries,
especially of those of the liver and of the stomach. The elec-
trisation of the marrow on the level of the first dorsal vertebrae
acts exactly as the direct electrisation of the cervical and sympa-
thetic cord acts. It provokes the contraction of the vessels of
the head, the lowering of the temperature, the dilatation of the
ocular pupil, and so on. The electrisation of the spinal marrow
at its origin, the rachidian bulb, determines the constriction of
all the vessels of the body (Bezold-Ludwig. etc.).1 On the
contrary, puncturing, chemical agents cause a general dilatation
of the arterioles. It is for this reason that Cl. Bernard, by
puncturing the roof of the fourth cerebral ventricle, was able to
occasion saccharine diabetes, and so on. By practising from
below to above hemisections and total sections of the spinal
marrow, M. Schiff was led to consider the rachidian bulb as the
general centre of all the vaso-motory nerves of the body.

As the vaso-motory nerves have their excitatory centre in the
bulb and the marrow, or at least have very intimate bonds with
those regions, it is very natural that they should be very
susceptible of undergoing reflex actions ; and in effect all exci-
tations of the central end of a sectionised nerve reacts on the
vaso-motory nerves, generally by determining vascular contrac-
tions. Analogous effects are moreover produced incessantly,
normally, and without the slightest vivisection, in every verte-
brated organism. All sensitive excitation a little strong, having
its point of departure either from the cutaneous surface or from
a mucous surface, or from one of the organs of the senses, can
react on the capillary circulation. All the world knows that
1 Vulpian, loc. cit., pp. 210, 218, 220, 221.

220 BIOLOGY. [Boox n.

strong moral impressions, that emotions produce the same
effects ; the change of the coloration of the cheeks is a familiar
sign of strong emotions, especially in the young and in women ;
that is to say, when the impressionability is the more intense and
the reflex actions the more easy. The changes of coloration are
far from coinciding always with the abnormal cardiacal pulsa-
tions ; their physiological reason is a reflex vaso-motory action.

In physiology and in pathology the office of the vaso-motory
nerves and of the capillaries is enormous. The variations in the
calibre of the small vessels regulate the distribution of the blood
even in the innermost part of the tissues, and thus act direct on
nutrition, and consequently on the operation of the organs. As
a general rule any moderate dilatation of the capillaries of
an organ has for effect the superactivity of that organ, whatever
it may be, gland, muscle, brain, and so on. On the contrary,
every contraction too great brings with it a nutritive retardment
and a functional diminution, forasmuch as it lessens the quantity
of arterial blood passing in a given time within range of the
anatomical elements, and consequently the proportion of liquid
and gaseous exchanges of which the capillaries are the principal
seat.

After having, by circulating in the capillaries, supplied the
anatomical elements with assimilable materials, and retaken the
waste substances ; after having yielded at the same time the
oxygen needful to the nutritive chemical transformations, and
received in return the carbonic acid, product of the vital com-
bustions, the arterial blood, formerly vermilion, becomes venous
blood, black blood, and passes from the capillaries into vessels
more and more voluminous. These vessels are at first similar
to the ultimate arterioles which pass into the capillaries ; then
little by little their muscular and elastic tunics grow thinner ;
some longitudinal contractile fibres cross the circular fibres ; the
vascular walls grow less rigid ; the vessels have become venous.
They go on thus anastomosing each other, augmenting always
in calibre, to reduce themselves in the mammifers to twTo great

CHAT, xm.] CIRCULATION. 221

trunks called vente caver. Of these two trunks the higher one
receives the venous blood of the higher part of the body ; the
other is the general trunk of the veins of the lower half. Both
throw themselves into the right auricle of the heart, whence
the venous sanguineous wave passes into the corresponding ven-
tricle, which drives it in its turn into the lungs, where it is oxy
genised, arterialised, to return into the right auricle, to pass into
the ventricle of the same side, and recommence the cycle.

The impulsion of the heart, not very perceptible in the
capillaries, where the blood moves in an unintermitting flow,
seems to be almost null in the veins. There the causes of the
circulation are especially the reflux of the liquids exhaled by the
anatomical elements, and principally the elasticity and the
contractility of the venous canals, in most of which, besides,
all retrogradation of the sanguineous current is rendered im-
possible by valves arranged in such a manner that they leave
the path free in the direction of the heart, but can shut- it in the
direction of the capillaries.

The grand system of sanguineous irrigation which we have
just described functionates consequently without repose, without
pause, as long as life endures. Unceasingly a stream of
nourishing blood traverses it. This stream wastes its strength
in the tissues, regains its strength at the expense of the sub-
stances elaborated by the digestive apparatus, renews its vivifying
gas in the respiratory capillaries, exhausts itself in the capillaries
of the glands. It is literally a living river. But by the side of
the grand sanguineous system exists another network with which
we have now to occupy ourselves.

/"LIU HA K v ,

UK1V.KKSITY OF j

CALIFORNIA. ,

CHAPTER XIY.

LYMPHATIC CIRCULATION.

THE lymphatic circulation does not seem to exist in the jn ver-
tebrates, unless we consider as lymph the colourless nutritive liquid
which travels along the rudimentary vessels in many of them.
Nevertheless certain persons have professed to recognise a
lymphatic circulation in the hirudinates, which are moreover
provided with a tolerably complete circulatory system.1

The lymphatic apparatus is assuredly an apparatus of per-
fectionment ; for it is entirely lacking in the amphioxus, and
does not appear in the vertebrated embryon till the late period
when the venous and arterial networks are already differen-
tiated.2 The manner in which the lymphatic system com-
plicates itself by degrees in the veins of the vertebrates is
interesting ; for it suggests conjectures respecting the physio-
logical province of this system.

In the inferior vertebrates, the lymphatic vessels are especially
represented by a kind of sheaths, surrounding the sanguineous
vessels, especially the arteries (Fig. 23). In fishes and the
batrachians we find this arrangement extending even to
the aorta. In all the vertebrates, furthermore, the fine lym-
phatic networks, the radical networks, a kind of lymphatic
capillaries, are joined to the sanguineous capillaries,- so that
these last form a part of their walls. In all the vertebrates,

1 Leydig, Traiti tf Histologie de VHomme et dcs Animaux.

2 Gegenbaur, loc. cit., p. 9.

CHAP, xiv.]

LYMPHATIC CIRCULATION.

223

too, the lymphatic vessels sheathe the sanguineous vessels of
the nervous centres which they isolate thus from the nervous
substance. It is this intimate union of the sanguineous and
lymphatic networks which made many anatomists believe that
the brain had no lymphatic vessels.1

But the fine lymphatic canals do not seem to have always
walls of their own; in that case they must be a kind of
lacunae of the conjunctive tissue.

FIG. 23

Fragment of the aorta of a
tortoise (chelydra) sur-
ronnded by a large lym-
phatic cavity: a, aorta;
b, external wall of the
lymph.itic cavity removal
at b' ; trabecules fastening
the sanguineous vessel to
the walls of the lymphatic
cavity.

FIG. ^4.

a a, caudal sinus ; b,
transversal anasto-
mosis ; c, lateral
vessels ; d origin of
the caudal vein in
the silurus glanis.

In the inferior vertebrates the lymphatic vessels communicate
with the veins by numerous branches. In the reptiles the
principal lymphatic vessels have just got so far as to have some
rare and insufficient valves.

Numerous reptiles have lymphatic hearts, which we find,
moreover, in certain fishes, in amphibians, and even birds
(Fig. 24). These hearts are partial dilatations of the vessels,
1 Ch. Robin, loc. cit., pp. 214, 315.

224 BIOLOGY. [BooK n.

and are animated by regular pulsations. Sixty beatings a j
minute have been counted in a frog. In these special points the
lymphatic wall, which elsewhere has nearly the same anatomical
texture as the veins, is clothed with a muscular layer thick and
striated.

It is well known that in the mammifers and in man the lym-
phatic system is constituted by very fine capillary networks,
situated in the depth of the organs, in the various membranes,
and in the skin. From these networks proceed vessels which
throw themselves into each other, forming trunks larger and
larger, and less and less numerous. Finally all the system is
connected with the venous system by two canals. The smallest
of these canals receives the lymph from the right half of the
trunk and of the head ; it throws itself into the subclavial vein
on the same side. The other, larger, known under the name of
thoracic canal, receives the lymph from the rest of the body, and
has its conflux in the left subclavial vein. In man the lymphatic
network does not seem to have any other direct communications
with the sanguineous system.

After every repast, the lymphatic vessels of the intestine, the
chyliferous vessels, swell and become lactescent. If we bind
the lymphatic canal we see it swelling below the ligature ; and if
we prick it we see the lymph spurt out. This alone suffices to
prove that the lymph pours itself into the blood ; and the arrange-
ment of the lymphatic valves also confirms this fact. But on its
passage the lymph encounters special organs, distentions, or closed
glands, from which it seems to obtain a supply of white globules.
These important organs are also subject to the law of gradual
differentiation. In fishes we find at distant intervals, on the
passage of some lymphatic vessels, simple enlargements, where
globules form in meshes of cellular tissue.

In the reptiles there are already more prefect formative
organs ; they are the closed follicles or Peyer's glands, disseminated
in the depth of the intestinal mucous membrane. These follicles
are constituted by closed vesicles filled with nucleated cells;

CHAP, xiv.] LYMPHATIC CIKCULATION. 225

they are more numerous in the mammifers, and largely aided
in their cellular production by organs of analogous structure,
varying in size from that of a lentil to that of a nut, and dis-
seminated along the passage of the lymphatic vessels ; they are
lymphatic ganglions, which are met with already in birds, in the
region of the neck. The lymphatic vessels are subdivided into
fine afferent canalicules before approaching a ganglion, and on
the other side of the gland the vessel only forms again at the
expense of analogous efferent canalicules. As to the ganglions
they are like the Peyer's glands, essentially constituted by
vesicles, at least the tenth of a millimetre large, and filled with
nucleated cells, with a diameter of about five-thousandths of a
millimetre. By the rupture of the vesicles the cells become free
and are borne along by the lymphatic plasma.

As we have seen, the lymph is a living liquid, playing in
nutrition an important part ; thus it is that the ligature of the
thoracic canal causes the rapid emaciation of the mammifers, and
their death at the end of a small number of days.

Trusting to the preceding data, we can form conjectures suf-
ficiently probable respecting the physiological province of the
lymphatic system. The lymph has in the vertebrated organism
a double origin. A notable fraction of the substances which
constitute it is drawn from the intestinal mucous membrane.
It is principally in this way that the fat, emulsionised bodies
penetrate into the circulation. But the networks, lymphatic in
origin, of the rest of the body, appear to gather a part of the
plasma completely elaborated, which pierces by osmosis through
the wall of the vessels, and especially of the fine arteries and
capillaries. To this sanguineous plasma comes probably to join
itself a part of the intercellular blastema, that is to say, of
the assimilable liquid which bathes the anatomical elements
apart from the vessels. The whole forms, first of all, a sort of
blood destitute of globules, a limpid plasma ; but at the expense
of this plasma white globules form in the ganglions. Then the
lymph is complete, and it has the greatest analogy of chemical

Q

226 BIOLOGY. [BOOK n.

and morphological composition with the blood, in which it ends
by throwing itself. Red globules are lacking thereto; but it
is probable that these are formed in the sanguineous vascular
system at the expense of the white globules of the lymph, and
of those which are generated in diverse closed glands, and of a
general texture analogous to that of the ganglions. We allude
to the glands called sanguineous, to the spleen, to the thyroid
gland, and so on.

The metamorphosis of the white lymphatic globules into red
sanguineous globules is almost directly established by the fol-
lowing fact : —

Burdach, having placed on a watch-glass some drops of the
blood of a dog, plunged the whole in a vessel filled with oxygen,
which he closed hermetically. He says that at the end of
twenty-four hours there was coagulation, and a red clot floated
in the serum. Burdach further says that through the help of
the microscope he saw in this clot globules, yellowish, ovalar,
biconvex, smaller than the sanguineous globules.1

On the whole, the lymphatic system is an auxiliary of the
venous system, with which, moreover, it largely communicates
in the inferior vertebrates. But its function is not simply to
convey to the heart and to the respiratory organs blood
vitiated by the activity of nutrition ; it furthermore undertakes
the duty of making up for the imperfections of the sanguineous
circulatory system by gathering a part of the plasma not
utilised, and finally, at the expense of this plasma, and of the
assimilable liquids obtained in the intestine, it fabricates white
globules.

The movement of the lymph in the lymphatic vessels is so
curious as to deserve remark. Of the causes of propulsion which
we have indicated in the sanguineous circulation, one, the car-
diacal contraction, is here absent. Nevertheless the lymph
marches, and even with a notable swiftness, since it bursts out
when we prick the thoracic canal below a ligature. Now its
1 Burdach, Traite de Physiologic, t. II., p. 541.

CHAP, xiv.] LYMPHATIC CIRCULATION. 227

movement of translation has only two possible causes, the
pression exercised by the absorption itself in the fine canalicules,
the vis ct, tergo, and, as an auxiliary force, the contraction of the
walls ; that is to say, the principal agents of circulation in the
veins. We may therefore, by analogy, conclude that in the
sanguineous circulatory system the heart is simply a reinforcing
organ, and that a very great part of the propulsive labour is
accomplished by the vessels themselves.

Q 2

CHAPTER XY.

OF THE RESPIRATORY ORGANS IN THE ANIMAL KINGDOM.

THE fundamental phenomenon of respiration is very simple :
it is merely the exchange of the carbonic acid and the water
contained in an organism for the aerian oxygen. It is a
physical phenomenon governed in its ensemble by the laws of
osmosis. In respiration, the water which escapes from the
organised body is in the state of vapour. But the carbonic acid
expulsed results from the oxydation of the organised substance ;
consequently respiration is very intimately related to nutrition.
It has for object to ventilate the organism, to renew the air of
the interior medium. As there is no nutrition without absorp-
tion of oxygen, respiration is a primordial function ; it is effected
as an essential act of every living substance. It has been
objected to the generality of this law that certain infusoria, for
instance, certain vibrions, and so on, can live in a medium
charged with carbonic acid and destitute of oxygen. The excep-
tion cannot be admitted without solid proofs which are still
lacking. Of these pretended animalcules some are provided
with chlorophyll, and are rather to be regarded as plants. If
the statement were true for the others we should simply have to
conclude that they have the faculty of taking their oxygen from
the carbonic acid itself, by decomposing it. The whole organised
world absorbs oxygen and needs to absorb it. Not without
reason the ancients made synonyms of the verbs to breathe and
to live. Every organised being, vegetal or animal, dies more or

CHAP, xv.] RESPIRATORY ORGANS IN ANIMAL KINGDOM. 22y

less rapidly when it is robbed of air ; and ae'rian abstinence is
always supported for an infinitely shorter period than alimentary
abstinence ; always it is the more rapidly mortal, the richer the
nutrition.

In the protozoa the exchange of gases is made by the whole
body. The oxygen impregnates the small protoplasmic mass,
transforms itself there into carbonic acid, and comes out as it
went in by the simple action of osmosis. Moreover, the proto-
plasmic movement, especially where there are emission and
retraction of pseudopods, aids much the accomplishment of the
phenomenon, by multiplying the contacts. This process, infinitely
simple, does not essentially differ from the . processes with
' complex differenciation so much as at first sight might appear.
i Definitively, in superior organisms, every anatomical element
holds the same relation to the air which is observable in the
i amorphous or monocellular protozoa. "What constitutes the dif-
| ference is the apparatus thanks to which the anatomical element
is brought into contact with the* exterior atmosphere.

Every organised substance not clothed with an impermeable
glaze, natural or artificial, respires more or less.

Placing in closed vessels reptiles from which he had torn the
lungs, Spallanzani discovered that in these animals the skin acted
as a respiratory organ more vigorously than the lungs themselves.

W. Edwards saw some frogs, whose lungs had been plucked
out, and whose neck was tightened by a ligature, live from twenty
to forty days when placed on humid sand in a chamber whose
temperature was +12 degrees. If, on the contrary, the frogs
were plunged in water when their teguments were no longer
in contact with the dissolved air, they perished in three
days.

Humboldt and Provencal kept in vessels thoroughly separated
the body and the head of a tench, and they found that the body
absorbed oxygen, — in a word, respired.

Even in mammifers in which exists a respiratory apparatus
voluminous and with a vast surface, the skin plays an important

230 BIOLOGY. [BOOK n.

respiratory part. A mammifer grows cold and dies when its skin
is covered with an impermeable varnish.1 If in a mammifer we
keep by means of a receiver air in contact with the skin, this air
is modified as absolutely as in the lungs.

But, as we have previously seen, the fine capillary vessels are
of all the parts of the body of complex animals the best organised
for the exchanges, whatever they may be, between the interior
medium and the exterior medium. Consequently an organic
surface in contact with the atmosphere breathes the more
freely and energetically the better provided it is with capillary
vessels and the more immediate the contact of these vessels is
with the exterior air. (Fig. 34). Rich capillary vascular-
isation, easy contact with the aerian gases; such are the two
principal conditions of a good respiratory surface. And these
conditions can be met with apart from the respiratory organs,
properly so called. It is thus that the pond leech (Colitis possilis)
breathes in part through the intestine. In this animal, the
intestinal mucous membrane being excessively vascular, almost
entirely constituted by sanguineous capillaries connected by a
small quantity of conjunctive substance, the animal makes use
of this substance as of a respiratory organ ; he swallows the air,
which, in contact with the intestinal capillaries, is exchanged
for the carbonic acid which the intestine expulses.2

Nevertheless, every animal in any degree complex has points
of his exterior or interior surface specially charged with the
respiratory gaseous exchange. It follows, as a matter of course,
that for the respiratory system, as for all others, specialisation
is the more perfect, the higher the animal is exalted in the
hierarchy. Before passing in review, in this respect, the diverse
groups of the animal kingdom, it is useful to define some terms
often recurring in the description.

The name of branchice is usually given to all the appendices,

1 Fourcault, Influence des Enduits Impermeables, etc. (Comptes Eendus de
V Academic des Sciences, t. XVI.)

2 Leydig, Traite d? Histologie, etc., p. 417.

CHAP, xv.] RESPIRATORY ORGANS IN ANIMAL KINGDOM. 231

all the vascular surfaces serving aquatic respiration, all the
apparatus specially charged to absorb the oxygen dissolved in the
water, and to relinquish in exchange carbonic acid. The organs
of aerian respiration can be divided in a general manner into two
categories, the tracheae and the lungs. The tracheae are canals
more or less ramified, always open, plunging into the interior
of the body, and communicating with the exterior air only by
narrow openings. The lungs are internal sacs, sometimes simple,
sometimes subdivided into compartments more or less numerous ;
they communicate also with the exterior air by orifices or
conduits more or less narrow.

Like all organic classifications, that of the respiratory ap-

J9.

FIG. 25.

Transversal sections of annulated worms, to show the homology existing between the
branchis and the cirrhi.— A, section of Eunice; B, section of Myrianide; p, abdominal
parapod ; p1, dorsal parapod ; br, branchiae ; br, cirrhi.

paratus suffers a number of exceptions. There are mixed forms,
transitory or confused types. Thus the tracheae are aerian
respiratory organs according to the definition. But we can bring
into affinity with them the vascular ramified systems, in which
the water circulates in many of the invertebrates. The lungs
of spiders can be considered as modified tracheae ; and so on.

In many of the inferior invertebrates (turbellariates, nsemer-
tians, annelidse) there are no special organs appertaining to the
respiration. The gaseous exchange is effected by the teguments,
furnished often with vibratile cilia. This last anatomical arrange-
ment is found, as we shall see, in the mucous membrane of the
respiratory passages of many superior animals. "When water
penetrates into the cavity of the body the surface of this cavity

232

BIOLOGY.

[BOOK ir.

plays also a respiratory part, a part the more important the more
rapid the renewal and the circulation of the water are.

The branchiae appear in the annelates. They are, as in most
of the invertebrates, appendices projecting from the external
tegument. Different organs, particularly the dorsal cirrhi, grow
vascular and become branchial in tufts more or less ramified
(Fig. 25).

FIG. 26.

Intestinal canal and ramified organs of a Iwlothurion: o, mouth ; t, intestinal tube; d,
cloaca ; a, amis ; c, ramified stony canal ; p, Poll's vesicle ; rr, arborescent organs ; /,
their union at the point of intersection above the cloaca ; m, longitudinal muscles of the

In the tunicians there is a sort of respiratory pouch ; it is the
anterior part of the digestive tube. This portion dilates into a
sac, at the bottom of which the true digestive tube commences.

In the holothuria exists a system of aquiferous canals,
probably respiratory ; it is a double tree, the two orifices whereof
open into the cloaca. This cloaca receives the water, and projects
it vigorously outwards, on an average three times a minute

CHAP. xv.J RESPIRATORY ORGANS IN ANIMAL KINGDOM. 233

(Fig. 26). Analogous systems exist in many other echinoderms,
and often they are bedecked with vibratile cilia.1

The crustaceans breathe through the branchiae, which often are
external appendices. Sometimes
they are abdominal appendices,
sometimes they are claws, or por-
tions of claws modified. In the
decapods we find branchiae inclosed
in cavities furnished with eddying
organs, making the water cir-
culate.

In a certain number of arach-
nida, in the myriapods, and espe-
cially in the insects, respiration
is accomplished by means of the
tracheae, which the nutritive liquid
of the animal bathes exteriorly
(Fig. 28). The tracheae form
then a system of canals, whose
ultimate ramifications constitute
a fine network, analogous, as to
arrangement, to the capillary net-
works.2 The principal trunks are
kept open by a chitineous bande-
lette rolled spirally and following
the skeleton of the tracheae. These
tracheae communicate outwards by
means of determinate orifices
called stigmata. The introduc-
tion and the expulsion of the air of the tracheae seem
to be helped by regular movements of the abdominal
walls. These rhythmical movements are frequent; we can
count on an average twenty-five in the stag-beetle, and from

1 Dugfcs, loc. cit., t. II. p. 355.

2 Leydig, loc. cit., p. 440.

FIG. 27.

A, transversal section of a phyllopod
(Limnetis), The section passes through
the part which bears the first pair of
feet. — i, intestinal canal ; c, heart ;
7i, ventral marrow ; d, folding of the
teguments forming a shell conceal-
ing the members ; 6r, natatory feet.
— B, transversal section of squalla
(through the abdomen), i, c, n, as in
A ; m, muscles ; d, tegumentary fold ;
p, external lamellary parts ; j/, inter-
nal lamellary parts ; &r, branchiae.

234

BIOLOGY.

[ROOK II.

fifty to fifty-five in the green locust. Spite of the compara-
tive perfection of their respiratory apparatus and the activity
of their life, insects resist asphyxia a long time. Thus Lyonnet
saw caterpillars revive which had remained under water for
eighteen days.

FIG. 28.

A, posterior part of the larva of Ephemera vulgata :—a, longitudinal trachean trunk ; b, in-
testinal canal ; c, trachean branchiae ; d, pluinous appendices of the tail. — B. larva of
jEschna grandis (the dorsal part of the teguments is removed) :— a, superior longitudinal
trachean trunks ; b, thin anterior extremity ; c, their superior part ramifying above the
rectum ; o, eyes.— The figure C in the middle represents the intestine of the same larva,
seen sidewise :— d, inferior lateral trachean trunk : e, communications with the superior
trunk ; a, b, c, as in figure J5.

Must we, with Blainville, consider as aerian branchiae the
wings of insects, which are often the seat of an active circula-
tion 1

The mollusfo, being for the most part aquatic, breathe through

CHAP, xv.] RESPIRATORY ORGANS IN ANIMAL KINGDOM. 235

the branchiae, which, in general, are visibly prolongations,
cutaneous appendices. These appendices are sometimes simple
folds, sometimes foliated or pectiniform prolongations. They
are usually traversed by vessels whose blood afterwards returns
to the heart (Figs. 29 and 30). When the vessels are lacking
there are at least lacunar cavities. But though these branchise
are visibly respiratory organs, they are far from being the only

FIG. 29.

Schematic vertical sections of the types
pteropod (A) and cepkdlopod (B). The
heart is directed downward, c, cepha-
lic part with indication in A of the
fins, which form part thereof, in B of
the arms ; tr, intestinal canal ; br,
branchiae, p, foot.

FIG. 30.

Polyce.ro, cristate, seen on
the dorsal side : — a. anal
orifice; br, branchiae; t,
tentacles.

j organs performing the work of respiration. The skin comes to

! their aid and respires also. Sometimes there are no branchise ;

1 the respiration is wholly effected by the cutaneous surface and

by the intestinal canal. This last surface is, moreover, clothed

with a vibratile epithelium, like that of the branchise, and the

oscillatory movements of these cilia are continued from the anus

to the stomach. The anus opens and shuts by a rhythmical

236

BIOLOGY.

[BOOK n.

movement, and an uninterrupted current penetrates to the vicinity
of the stomach (Gegenbaur).

In a small group of mollusks the pul-
monary organ appears. In these pul-
monate mollusks the lung is only a simple
sac, a cutaneous depression communicating
with the exterior by an orifice. Some,
as for instance the ampullaria, have at the
same time a branchia and a pulmonary
sac with contractile orifice. Of these
pulmonate mollusks some are terrestrial,
the others aquatic ; and these last of ten
come to the surface of the water to
breathe. They need the free atmosphere,
and in a closed vessel, as Spallanzani saw,
they, without immediately suffering as-.'
phyxia, transform into carbonic acid the
whole of the oxygen contained in the
confined medium.

The two chief respiratory modes, the
branchial mode and the pulmonary mode,
are observable in the vertebrates, but in a
higher degree of perfectionment. Here
the external tegument still respires but
accessorily, and the chief part of the
function is accomplished by special organs.
Nevertheless the respiratory apparatus is
always more or less connected with the
intestinal canal ; it seems to be a diver-
ticulum thereof. In fishes, in which the
branchial apparatus attains its maximum
of development, it is supported by arcs
appertaining to the visceral skeleton (Figs.
31 and 32). The water penetrates by the mouth of the animal,
and is not expulsed till it has traversed the branchial clefts, and

FIG.. 3).

Respiratory organs of the
Myxine glutinosci seen on
the ventral side ; o, oeso-
phagus ; i, internal bran-
chial canals ; ~br, branchial
sacs ; Tyr', external bran-
chial canals uniting in a
reral branchial conduit
s; e, oesophagq-cuta-
neous canal ; a, auricle of
the heart ; v, ventricle ;
ab, branchial artery send-
ing a branch to each bran-
chia ; d, wall of the body
thrown outward and back-
ward.

CHAP. xv.J RESPIRATORY ORGANS IN ANIMAL KINGDOM. 237

bathed the surface of the respiratory mucous membrane. The
amphibians have external branchiae under the form of foliations
or of ramified filaments, supported by the branchial arcs.

The lung, in its most elementary form, is a
simple vascular sac. It appears first of all
among the amphibians, where it co-exists with
the branchiae, of which we have spoken above,
and which are sometimes temporary, some-
times permanent (perennibranchials). The
lungs of the proteus tribe are not more than
elongated sacs. Many reptiles have also
simple lungs. In the anourians the lung
is already subdivided into secondary cavities
or alveoli, which augment considerably the
respiratory surface.

There has been a disposition to consider
as a rudimentary respiratory organ the
velatory bladder of fishes (Fig. 33). It is
certain that we find in this cavity carbonic
acid, azote, and hydrogen ; we also meet with
enormous proportions of oxygen. According
to Biot and Laroche, this proportion can rise
to 70 in 100 in the fishes caught at more than
50 metres deep, and only to from 26 to 29
in 100 in the others, though the deep layers
of water are not more oxygenised than the
layer on the surface.

In reality, and making abstraction of the
general form of the apparatus, there is no
fundamental difference between the bran-
chiae and the lungs. The branchiae can even act in the open
air on the single condition of being kept in a state of sufficient
humidity, and on the other hand, the surface of the pulmonary
mucous membranes is constantly lubrified by a liquid secretion.
We can feed carps in the open air, in moss saturated with water ;

FIG. 32.

Vascular distribution in
the branchial laminar*:
o, section of osseous
branchial arc ; 6ft, the
branchial lamellae ; c,
branchial arteries ; c',
ramuscules of the
arteries in the lamel-
Ise ; d, branchial
veins ; d', d', venous
ramuscules in the la-
mellae.

238 BIOLOGY. [BOOK n.

we can even thus make them travel considerable distances without
killing them. Branchial surfaces and pulmonary surfaces absorb
oxygen, exhale carbonic acid, and transform more or less perfectly
arterial blood into venous blood. This double current can be
seen, so to speak, when we examine, by means of the microscope,
the branchiae plunged in water. There is established, from their
contact, in the liquid medium a sort of circular movement ; the
corpuscules floating in the water seem to be attracted on one side
and refilled on the other.1

rv
}

FIG. 3:J.

Diverse forms of natatory bladders :— A, Polypterus bichir ; 5, Johnius lobahis ; C, Con
trii-pinosa ; a, annexes of the bladder ; 6, its orifice.

We have not here to describe in detail the pulmonary
paratus of the superior vertebrates. Let us merely say that
more the animal is perfect the more the pulmonary pouch is
divided and subdivided into lobes, lobules, terminal cids-de-sac
or cells, in ever increasing number, whence in the superior
mammifers an enormous respiratory surface (Fig. 34). At the
same time that the pulmonary sac grows more perfect it separates
1 Duges, loc. tit, t. II., p. 522.

CHAP, xv.] RESPIRATORY ORGANS IN ANIMAL KINGDOM. 239

•

more and more from the digestive tube ; it acquires aerian canals
more and more long and ramified, kept constantly open by a
cartilaginous skeleton, and supporting at one or more points of
their passage the organs of the voice. Over all its surface, the
aerian tree, trachea, and bronchi, is clad with vibratile epithelium ;
and this is the case for all surfaces in the whole animal kingdom.
The vibratile vestment is lacking only on the surface of the cells
or pulmonary alveoli.

Muscles, more or less numerous, impress on the costal frame

>-4* y

FIG. 34.
Capillary network of the pulmonary vesicles.

which covers the lungs and keeps them dilated alternative move-
ments of inspiration and expiration; but the diaphragmatic
partition which so powerfully aids inspiration in man and the
mammifers is completely lacking in reptiles, and is only in a
very rudimentary state in birds.

We are compelled, that we may not indulge in a parergon, to
renounce all detailed anatomical description. Nevertheless we
must dwell at rather more length on the physiological province
of respiration, on the indispensable aid which it brings to the
work of nutrition in the complex animals.

CHAPTER XYI.

OF THE PHYSIOLOGICAL OFFICE OF RESPIRATION.

IT is necessary to distinguish between the fundamental biological
fact of the absorption of oxygen, which is one of the first con-
ditions of nutrition, and the physiological function properly so
called, which is simply the physiological process employed to.
render this absorption possible and easy. The absorption of
oxygen is a general fact ; every organised being absorbs oxygen
under penalty of death ; this is true as regards the most humble
vegetal and animal organisms, as well as the highest. It is true
of every living being in all the stages of its existence. William
Edwards and Colin 1 have shown that seeds do not germinate in a
vacuum, and it was sufficient for Reaumur to cover an egg with an
impenetrable varnish to prevent the embryon from developing.2
But respiration, properly so called, only and truly exists in those
cases where a special branchial, trachean, or pulmonary apparatus
is the means of furnishing with respirable air the entire organ-
ism, and of exhaling those gases which are hurtful to or useless
for the maintenance of life.

Whatever may be the diversity of the organological pro-
cesses, the object of all respiratory apparatus is to bring the
capillary vessels containing blood more or less vitiated by nutri-
tion into as easy contact as possible with the atmosphere. If
we were to employ the language of the ancient natural philoso-

1 Comptes Eendus de V Academic des Sciences, 1838.

2 Ibid., year 1735.

CHAP, xvi.] % PHYSIOLOGICAL OFFICE OF RESPIRATION. 241

phers, who attributed intentions to nature, we should say that
this was the idea of respiration.

The most easy conditions of the exchange of gases being best
realised amongst the higher mammifers, we can take as a type
respiration in man, the only one indeed which has yet been
thoroughly studied. Moreover it will be easy for us to indicate,
in the course of this exposition, the analogies or differences
observable in the remainder of the animal kingdom.

The capillary vessel is preeminently the seat and agent of
material exchanges in the animal organism. "Wherever it may
be, it adapts itself readily to the osmotic phenomena. In the
web of the tissues, when the capillary partition separates liquids,
it is these liquids which mingle through the thin intermediate
membrane. In the lungs of man, the wall of the capillaries
separates the sanguineous liquid, holding gases in solution, from
the exterior atmosphere, and the exchange is made between the
gases.

In the capillaries of the lungs (Fig. 34), as in those of the
tissues, the electro-motor currents play an important mechani-
cal part. But whilst in the tissues they are the agents of the
expulsion of the oxygen across the wall of the capillaries, in the
lungs they are precisely the reverse. In effect, in the lungs, the
oxygen is situated outside the circulation ; consequently the
direction of the electric current is inverse. The electro-motory
capillary- current tends therefore to cause the expulsion of the
carbonic acid.1

In spite of the action of breathing in the lungs of the verte-
brated animals, and especially of the mammifers, though there
are constantly and regularly an alternate entrance and exit of gas
in the pulmonary cavity, respiration, gaseous exchange through
the capillary wall, is nevertheless a continuous uninterrupted
phenomenon. In effect, at each expiration the lungs expulse
only a very small portion of their gaseous contents. According

1 Becquerel, loc. cit.t and Des Forces Physico-chimiques, 8vo. Paris, 1875.
Onimus, Des Phenom&nes Electro-capillaires (Eevue Scientijique, 1870, n° 42).

B

242 BIOLOGY. [BOOK n«

to the calculations of Menzies, Goodwin, Davy, <fec., this portion
may be valued at a fifth, a seventh, even an eighth of the pul-
monary capacity. The absolute volume of gaseous contents varies
remarkably, like the pulmonary capacity, according to individuals
and ages. Hutchinson has given the following averages of this
capacity : — 1

litres

From 15 to 25 years 3'590

25 to 30 , 3-623

35 to 40
40 to 45
50 to 55
55 to 60

3720
3-459
3-215

2-970

In a gigantic and athletic American the pulmonary capacity rose
to 7-082 litres.

The pulmonary capacity, then, bears a very obvious and con-
stant relation to youth and strength, or more generally to the
degree of vitality. Of this Hutchinson' s American is a striking
example. After two years of idle and dissolute life, his enor-
mous pulmonary capacity fell first to 6*364 litres, then to 5-222
litres, and finally, a little later, he succumbed to a tubercular
malady.

The mean volume of gas inhaled at each inspiration may be
estimated at about one-third of a litre, or from nine to ten cubic
metres in twenty-four hours. As to the volume expired, it
naturally is much the same as the volume inspired, with a slight
diminution of a fiftieth to a seventieth ; for there are other
outlets.

Evidently the pulmonary gases, expelled at each inspiration,
are especially those nearest to the outside, those which fill the
trachea and the large bronchise. As to the air inclosed in the
pulmonary cells and in the fine bronchial ramifications, it renews
itself by diffusion, by the gaseous mingling from point to point ;
so that at last the respiring ; surface, the vascular wall of the

1 Hutchinson, On the Spirometer, 1846 (analysed in Arch. Gen. de Med.,
1847.)

CHAP, xvi.] PHYSIOLOGICAL OFFICE OF RESPIRATION. 243

pulmonary cells, is in contact with a gaseous mixture of which
the composition is obviously always the same. The exchange of
gases can, then, be effected regularly without interruption, and
even without any sudden variation.

The lungs receive the exterior air, that is to say, a gaseous
mixture of about 21 of oxygen and 79 of azote, besides a small
quantity of vapour of water and about four ten- thousandths of
carbonic acid. They restore to the atmosphere air remarkably
impoverished of oxygen, since it scarcely contains more than
18 in 100 (Duges), but impregnated instead with carbonic acid
and the vapour of water.

From numerous observations, among which we must first cite
those of Lavoisier, next those of Regnault and Reiset,1 it is
proved that the quantity of oxygen contained in the carbonic
acid exhaled by the lungs is sensibly inferior to the quantity of
atmospheric oxygen absorbed. Lavoisier had already noted this
interesting fact. MM. Eegnault and Reiset saw that this pro-
portion varied very little in the same animal species, living under
normal condition^. The proportion between the oxygen of the
carbonic acid exhaled and the oxygen absorbed has been, accord-
ing to their observations, from 0'743 to 0750 in the dog, 0 920
in the rabbit, &c. Atmospheric oxygen indeed ought to be
considered as a true aliment ; it combines with the plasmas,
with the matter of the anatomical elements, in a word, with the
living substance ; it enters into numerous compounds, and is
eliminated through diverse channels. The organism only takes
from the atmosphere that quantity of oxygen which is necessary
for it : it rations itself. In an atmosphere containing 40 and
even 60 in 100 of oxygen, the absorption of this gas is not
sensibly more considerable than in the common air, unless there
is variation in the regimen. In this last case, on the contrary,
the quantity of oxygen absorbed varies ; for there must be more
or less of it, according to the variation in the proportion and
the nature of the substances to be assimilated in the sanguineous

1 Annales de Chimie et de Physique, 2° serie, t. XXVI.

R 2

244 BIOLOGY. [BOOK n.

liquid. Thus, the deficit in the quantity of oxygen given back
to the air by the exhalation of carbonic acid is greater in the
carnivora than in the herbivora. If animals are fed on grain,
the proportion is sometimes inverse ; there is then an excess
in the exhaled oxygen.

The exchange of gases through the pulmonary membrane
is much more a physical phenomenon than a physiological
one ; the azote must, then, also penetrate the blood through
the wall of the capillaries ; this is, in effect, what happens. But
here, reversing what takes place in the case of oxygen, the
pulmonary exhalation restores to the air more azote than it
has borrowed from it, at least in most cases.

Regnault and Reiset found that all animals subjected to their
habitual regimen always generated an excess of azote. Despretz
demonstrated the same thing by more than two hundred experi-
ments.1 Boussingault, proceeding by the indirect method, that
is to say, by comparing the quantity of azote introduced by
the aliments with the quantity expelled in the solid and liquid
matters, observed that the first was always greater than the
second.2 We can thence infer that a certain portion of the azote
of the aliments is exhaled by the lungs. In effect, if an animal
is made to respire in an atmosphere composed of seventy-nine
parts of hydrogen, and twenty-one parts of oxygen, there are
seen to be a simultaneous absorption of hydrogen, and an exhala-
tion of azote. In this case the production of azote must
evidently be ascribed to the organism. Besides, the absorption
of hydrogen changes into certainty the great probability of the
absorption of azote in the normal air. We must, then, admit, with
Edwards, that in the ordinary atmosphere the disengagement and
absorption of azote by the pulmonary surface always take place
simultaneously, and that the only variation is caused by the
augmentation or diminution in the quantity of azote exhaled.

In effect, it is the quantity of azote exhaled which varies ;

1 Annales de Chimie et de Physique, 2e terie, XXVI.

2 Economic Rurale, t. II.

CHAP, xvi.] PHYSIOLOGICAL OFFICE OF RESPIRATION. 245

sometimes there is an excess, sometimes a deficit. Thus, there
is a retention of azote in the organism during inanition, and even
several days after its cessation. It is the same when the animal
under observation is suffering, perhaps because then it submits
itself spontaneously to a relative inanition.

The pulmonary membrane, offering to contact with the air a
large surface at a tolerably high temperature, is naturally the
seat of transpiration, of an abundant aqueous evaporation.
Lavoisier and Seguin, whom we must always quote when respira-
tion is in question, have estimated at 7*90 grammes in an hour,
or about 569 grammes, the quantity of water exhaled in twenty-
four hours by the pulmonary surface of man.1 The average of
the numerous experiments of Valentin2 is 540 grammes ; conse-
quently, very nearly the number indicated by Lavoisier and
Seguin. This quantity is besides very variable. It may be
augmented at will in animals, for example by injecting water
into their veins.

Complex reactions take place in the blood, still as little known
as those which cause the elaborated sap in plants. The grand
fact is the fixation of oxygen ; but we have seen that there were
also the absorption and exhalation of azote. Lavoisier and Seguin
had already deduced from their observations that a portion of
the water exhaled by the pulmonary surface was directly formed
in the blood by the oxydation of the hydrogen. Modern obser-
vations have confirmed this view, which may, with great likeli-
hood, be extended to aqueous excretion in all its forms ; for the
lung is only one of the numerous channels through which water
goes forth from animal organisms.

The most complete researches have been made, touching the
physical phenomena of respiration, especially with regard toanimals
having lungs, birds and mammifers ; but these phenomena, viewed
in a general manner, differ little in branchial respiration. On the

1 Premier Memoire sur la Transpiration (Memoires de I" Academic des
Sciences de Paris (1790), and Annales de Chimie, t. XC.).
3 Lehrbuch der Physiologic, t. I.

246 BIOLOGY. [BOOK n.

surface of the branchiae, as on the surface of the lungs, there is
a continual exchange of gas between the sanguineous liquid and
the aquatic medium. The quantity of air dissolved in water is
not considerable ; but this air is respired by cold-blooded
animals, and it is besides much richer in oxygen than the atmo-
spheric air. In effect, the air dissolved in the water is composed
of 29-8 of oxygen, 6 6 '2 of azote, and 4 of carbonic acid. Now
Humboldt and Provencal observed this air to contain only 2 '3
of oxygen, 63*9 of azote, and, in compensation, 33*8 of carbonic
acid, after having been respired a certain time by some fishes.1

If observation has been able to scrutinize and measure the
respiratory phenomena, properly so-called, that is to say, the
exchange of gases through the capillary membrane, it has not
succeeded so well as regards the nutritive part of the respiration.
Nevertheless, interesting facts have been collected, and they
permit us already to form a general idea of the office which ab-
sorbed oxygen fulfils, and of the succession of chemical trans-
formations with which they co-operate.

The first and most striking phenomenon is the sadden change
of colour which the sanguineous liquid undergoes immediately
after absorbing the atmospheric oxygen. The blood, which
arrived in the capillaries in the state of black or venous blood,
becomes rutilant and vermilion, as soon as it has exchanged its
carbonic acid for oxygen ; it is then called red or -arterial blood.
The change of colour is instantaneous. For example, the blood
in the carotid artery of an animal blackens and reddens alter-
nately arid suddenly, according as we prevent or permit the
access of air to the respiratory apertures.

Of the oxygen absorbed by the blood, a part remains in a state
of solution in the sanguineous plasma, and probably co-operates
with the oxydations in the isomeric transformations of the
nutriments ; but the larger portion of this oxygen is fixed by
the hrematia. These corpuscules absorb many vojlumes of it;
they are truly the vehicles of the oxygen. They impregnate
1 Mgmoires de la Societt d'Arcucil, t. II. '

CHAP, xvi.] PHYSIOLOGICAL OFFICE OF RESPIRATION. 247

themselves with it, and convey it to the capillary vessels of fine
calibre, which penetrate the very web of the tissues. But tnis
part of the system of circulation is the special Jfold of nutritive
exchanges. There, in effect, the blood is no longer separated
from the anatomical elements and the liquids which bathe them,
except by the thin homogeneous partition of the capillaries.
The blood then yields to the tissues assimilable materials and
takes back disassimilated materials. In the first category is
comprehended oxygen ; in the second, carbonic acid. Without
the incessant access of the first, without the incessant expulsion
of the second, the succession of chemical reactions and transfor-
mations, which, as a whole constitute nutrition, would cease to
take place ; the whole vital movement would be retarded and
stopped.

The oxygen is not simply dissolved in the substance of the
sanguineous globule ; it seems to be combined with this substance.
In effect, if we inject into the veins of a dog an eager absorbent
of oxygen, for example, pyro-gallic acid, the animal does not ap-
pear sensible of it ; its globules do not part with their provision
of oxygen.1 On the contrary, certain substances, which are
capable of yielding oxygen, are deprived of it in the blood ; the
globules carry it away from them. Thus, per-oxyde of iron
injected into the circulation, is found again in the urine as pro-
toxyde. The globules may be considered as condensers of
oxygen ; they are pre-eminently the exciting agents of life ; also, in
the operation of transfusion it is sufficient to inject into the veins
defibrinated blood; probably the globules alone would suffice.
Certain substances have the property of killing the globules,
of rendering them for ever unfit for the absorption of
oxygen. Such is particularly oxyde of carbon ; but even in cases
of poisoning, by this substance, persons have often succeeded in
reviving the poisoned animals, in resuscitating them by having
recourse to transfusion, that is to say, by replacing the dead
globules with living ones.

1 Cl. Bernard, Lemons sur lesLiquides de VOrganisme.

248 BIOLOGY. [BOOK IT.

The nutrimentary matters, prepared by the labour of digestion
and diffused into the circulation, are exchanged through the wall
of the capillaries with the products of denutrition. These last
are the result of an oxydation, the principal seat of which is
probably in the very substance of the anatomical elements, and
not in the capillaries themselves, as is still affirmed in a number
of special treatises. The capillaries are organs marvellously
adapted to the exchanges between the blood and the anatomical
elements ; but these last are the laboratory itself, where the
principal transformations are accomplished. The comparison of
the two kinds of blood permits us to fix, in some degree, the
balance of gain and loss. After having served as nutrition, the
ternary matters not azotized are brought back to the state of
carbonic acid and water; their combustion is, then, complete.
They have attained their maximum of oxydation. On the
contrary, the quaternary or albuminoidal substances only
undergo an incomplete combustion, of which the product is a
certain quantity of carbonic acid and water, besides a residue
of crystallizable quaternary elements, of which we have already
spoken, and which are eliminated by the various emunctories of
the economy.

From the comparison of the two kinds of blood springs another
interesting fact, namely, that the arterial blood has a composition
sensibly identical in the various regions of the organism, whilst
the composition of the venous blood varies much according to
different organic localities. In effect, the arterial blood is the
general nutritive reservoir; from it each anatomical element
satisfies its needs ; but these needs vary according to the chemical
constitution and function of the elements. Each anatomical
element, then, takes, according to its affinities, one substance in
preference to another. Besides, and above all, it makes the
matters which it absorbs undergo a special elaboration, and
restores to the circulation also a special nutritive residue,
whence results necessarily the local diversity of the venous
blood.

CHAP, xvi.] PHYSIOLOGICAL OFFICE OF RESPIRATION. 249

On an average, respiration, or at least the primordial fact of
respiration consists, according to Regnault and Reiset, of an
absorption of oxygen, varying from 10 grammes to 0*09 in an
hour, and in a kilogramme of living matter. Besides, this
. oxygen transforms itself into carbonic acid and water in the
i proportion of 0*800 of a gramme combined with the carbon,
and of 0'200 of a gramme combined with the hydrogen. Finally,
there is an exhalation of azote representing about six-thousandths
of the weight of the oxygen consumed. These rough figures
must be accepted with great caution. Respiratory combustion
does not simply produce water and carbonic acid. These two
la.st bodies only result from the combustion of ternary substances ;
but quaternary substances oxydize themselves also, and their
oxydation gives birth to crystallizable, azotized elements,
eliminated by other outlets besides the pulmonary surface.

However this may be, an important general fact results from

the observations of Regnault and Reiset, corroborated besides by

.1 those of many others ; namely, that the energy of the vital com-

i bustion has a close connection with the nutritive and functional

I movement.

Thus, the quantities of oxygen absorbed, and of carbonic acid

and azote exhaled, are about seven times greater amongst birds

; than amongst mammif ers. In compensation, respiratory intensity,

estimated after the same manner, is nearly ten times stronger in

the mammifers than in reptiles (Regnault and Reiset).

The respiration of insects, when these animals are in full
activity, has plainly the same energy as that of the mammifers,
whilst the earthworms do not respire more than reptiles ; but in
these comparisons the size of the animal must be taken into
account. In effect, the smaller the animal the larger the pro-
portion which the surface bears to its bulk ; consequently oxyda-
tion, which, as we shall see, is the principal source of animal
heat, must be more active since the coldness caused by peripheric
radiation is greater.

Andral and Gavarret have made some very excellent observa-

250 BIOLOGY. . [Boos n.

tions upon respiration in man.1 These observations bear upon
man from sixteen to thirty years of age, the experiment lasting
from eight to thirteen minutes, between one and two o'clock in
the day, during the same interval between repasts, and under the
same conditions of muscular exertion. According to them the
consumption of carbon in an hour undergoes, in proportion to
age, the variations indicated in the following table : —

From 8 to 15 years it is 70'42

15 to 20 10'76

20 to 30
30 to 40
40 to 50

12
11
9-17

„ 50 to 60 11-07

,, 60 to 70 10-25

In an old man of 76 years, it is 6

92 „ 8-5

„ 102 „ 5-9

Andral and Gavarret not having noted the weight of the
persons under observation, the figures above quoted lose much of
their value ; nevertheless, they furnish the confirmation of the
general law which we have enunciated above, namely, that the
respiratory activity varies in proportion to the intensity of the
nutritive movement, that is to say, of life.

The observations of Scharling complete those of Andral and
Gavarret, for they furnish an indication of the weight of the
persons. Now these observations prove that oxydation is more
energetic in the child than in the adult. A child of nine years
consumed by kilogramme and by hour 0'25 of a gramme of carbon ;
adults of from twenty-five to twenty-eight yearsonly consumed
on an average 0' 12 of a gramme.

Also, according to Scharling, the difference of sex influences
the energy of vital combustion, even before puberty ; in the
human species girls consume less carbon than boys. But Andral
and Gavarret have moreover shown that the difference is notable

1 Recherches sur la Quantitt d'Acide Carbonique ExhaU par le Poumon (Ann.
de Chim. el de Phys., 2e serie, 1843).

CIIAP. xvi.] PHYSIOLOGICAL OFFICE OF RESPIRATION. 251

at the middle period of life. During the whole period of ovula-
tion, from the first appearance of the menses to their cessation,
the exhalation of carbonic acid is less in woman than in man ;
but the equality is sensibly re established during pregnancy and
after the critical age.

Many other causes vary the exhalation of carbonic acid. Thus,
in animals having a fixed temperature or hot blood, it augments
in proportion as the exterior temperature decreases. On the
contrary, in cold-blooded animals, respiratory combustion
diminishes in proportion as the temperature is lowered. This
is because the first resist refrigeration by a more active combus-
tion, whilst the second, being incapable of producing a sufficient
internal warmth, grow gradually colder till the moment when
they fall into a state of hibernal sleep or die.

Every functional activity, whatever it may be, has as corollary,
or rather cause, a more active combustion within the organ or
functional apparatus.

' After having eaten copiously insects respire more energetically,
and they also die more promptly in confined air, or in an irre-
spirable gaseous medium.

It has been observed that there is a proportion between the
digestive activity in frogs and the quantity of oxygen contained
in the ambient medium.

According to Yierordt, Yalentin, Scharling, and Horn, the
exhalation of carbonic acid augments rapidly in man after a
repast. Analogous facts have been stated by Spallanzani con-
cerning snails when fasting, by Story of various insects, and by
Boussingault of turtle-doves.

In inanition, there is a lesser absorption of oxygen, and like-
wise a lesser exhalation of carbonic acid. The animal derives
from the atmosphere more oxygen than it restores to it. This
is simply because then it nourishes itself at the expense of its
own tissues ; it eats itself, and consequently respires as a car-
nivorous animal, but one badly nourished. In efiect, Regnault
and Ileiset have seen that animals fed upon butcher's meat and

252 BIOLOGY. [BOOK n.

aliments rich in fatty matters, exhale less carbonic acid, and,
consequently, burn more hydrogen.

The fewer the functions exercised by an inanitiated animal
the less carbon it expends. This is the reason why Bidder and
Schmidt have observed that when animals were deprived of sight
the degree of their diurnal carbonic exhalation tended to equal
that of their nocturnal exhalation.

Moleschott has shown that the action of light upon the skin
notably augments the intensity of the respiratory phenomena.1

During the day, under the influence of various kinds of
activity, the production of carbonic acid is, according to Schar-
ling, less by a quarter than during the nocturnal slumber. But
it is especially during the. hibernal sleep that the absorption of
oxygen is reduced to its minimum. Regnault and Reiset have
seen it fall to a twentieth part of what it was in a waking state.

Contraction and muscular effort demand a large absorption of
oxygen, as Lavoisier and Seguin had already observed.. This is
because^ in a given weight of living matter, respiratory combus-
tion increases in direct proportion to the muscular activity.

Behind every biological activity there is an oxydation of
the anatomical elements. No organ escapes this law, and the
nervous centres are as much in subjection to it as the other
organic apparatus. Every thought, every volition, every sen-
sation, corresponds to an oxydation of the living substance, as
well as every secretion, every movement, &c.

In speaking of innervation, we shall have to consider, in con-
nection with it, the cerebral functionment. Lavoisier, after
having pointed out the relation which exists between muscular
activity and the exhalation of carbonic acid, wrote thus : " This
kind of observations leads us to compare the displays of force,
between which no connection would seem to exist. We may
know, for example, to how many pounds in weight the efforts of
a man reciting a discourse, of a musician playing an instrument
would correspond. We can even estimate how much there is of
1 Wiener MediciniscJie Wochenschrift, 1855.

LP. xvi.] PHYSIOLOGICAL OFFICE OF RESPIRATION. 253

mechanical in the labour of the philosopher who reflects, of
the literary man who writes, of the musician who composes.
,These effects, considered as purely moral, yet possess some
•physical and material attribute, which permits us to compare
ithem with the efforts of the labouring man. It is therefore not
iwithout justice that the French language has included under the
general denomination of labour, the efforts of the mind as well as
i those of the body, the labour of the cabinet and the labour of the
artisan, "i

Truly it is singular and regrettable that, even in our days, and

: in spite of the brilliant triumph of the doctrine of the correlation

I of the physical forces, no physiologist has brought this beautiful

'idea of Lavoisier into the domain of facts, rigorously and

i minutely observed. The last champions of vitalism and animism

always repeat that thought escapes the law of the correlation of

i physical forces, that its mechanical equivalent cannot be deter-

; mined. Now it is incontestable that every cerebral activity

answers to an absorption of oxygen, which manifests itself by

a larger exhalation of carbonic acid, and by the renal excretion

of certain products of oxydation. It would surely be possible

to estimate approximately in calories, and consequently in kilo-

grammetres, this process of oxydation. Thus the mechanical

equivalent of thought, and even of the different modes of

thought, would be determined.

In vertebrated animals with lungs, the movement of the venti-
lating apparatus of the lungs, of the thoracic frame, are generally
executed automatically ; but they are much more subject than the
movements of the heait, to the will, which can accelerate, retard,
or suspend them ; it is, then, natural that certain lesions of the
nervous centres immediately affect, not directly indeed the ex-
change of gases on the pulmonary surface, but the alternate
movements of the thoracic frame. In effect, certain wounds of
the spinal marrow, in rabbits and guinea-pigs, cause a slackening
of the respiration, and a gradual coldness ; in a word, a state very
1 Lavoisier, Memoires de V Academic des Sciences, 1789.

254 BIOLOGY. [Boox n.

analogous to hibernation. In the mammifers it is a very limited
region, situated at the origin of the spinal marrow, in the
rachidian bulb on a level with the Y of grey substance, compre-
hended in the posterior angle of the fourth ventricle. Now the
integrity of this region is so necessary to the accomplishment of
the respiratory movements that a section performed at this point
at once destroys both respiration and life. This celebrated point
in the spinal marrow is known as the nodus vitalis. Galen, had
already pointed it out ; but only in our days, through the minute
researches of Flourens, has its precise position been determined.

In reptiles, the cutting of the nodus vitalis has a much less
striking effect than in the mammifers ; it effectually destroys
the respiratory movements, but does not immediately kill the.
animal, a result very easy to comprehend, and which is attri-
butable to the feebler centralization, the smaller energy of the
respiratory apparatus. Here the skin comes to the aid of the
lungs in a great measure ; whence batrachians are of all reptiles
those which survive the longest the cutting of the nodus vitalis.
This section besides, not only destroys the respiratory move-
ments, but also the whole of the voluntary movements of the
trunk, the members, and the head, since it interrupts most of
the conscious and voluntary communications between the brain
and nearly the whole of the other organs.

Our object being, not to write a special treatise on physiology,
but rather to give a general idea of the process by which nutrition
is accomplished in the animal kingdom, we shall here terminate
this brief but adequate description of respiration. We have now
seen how the animal organism elaborates and absorbs the
materials which it borrows from the outer world ; how these
materials, having become assimilable, circulate throughout the
whole of the animal mechanism, and how atmospheric oxygen,
indispensable to the accomplishment of the primary phenomena
of nutrition, is absorbed. It remains for us to examine how the
organisms free themselves from the non-gaseous products of dis-
assimilation ; how also they fabricate, at the expense of the

CHAP. xvi. ] PHYSIOLOGICAL OFFICE OF RESPIRATION. 255

plasmas, certain substances destined afterwards to play more or
less important parts in the different functions. Thus it is that
we have to speak of excretion and secretion.

NOTE.

A litre is about a quart English. A kilogramme is a thousand grammes,
j According to the new system of weights and measures introduced into France
, at the Revolution, deci as a prefix means tenth ; centi, hundredth ; milli,
thousandth, when the principal unit is progressively fractionised : — deca as a
1 prefix means tenth ; Jiecto, hundredth ; kilo, thousandth, when the principal unit
1 is progressively augmented or multiplied. Thus millimetre is the thousandth
; part of a metre; hectogramme a hundred grammes, and so on. In Professor
j Roscoe's Lessons in Elementary Chemistry a comparison of the French
I metrical with the common measures is given. — Translator.

CHAPTER XVII.

OF SECRETION AND EXCRETION IN. GENERAL.

EVERY organised and living element assimilates and dissimilates
incessantly. But in proportion as the organism is complicated
and differentiated, the conditions of assimilation become more
difficult; and this- function needs for its accomplishment the
auxiliary apparatus, digestion, circulatory and respiratory, which
we have passed in review. Besides, assimilation would be im-
possible if the waste of the immediate principles were not expulsed
in the degree of its production. In short, dissimilation is the
indispensable corollary of assimilation, and like this last it needs
special apparatus wherever the structure of the organism is too
complex. These special apparatus are the glands of which we
have by and by to give a general description. Nevertheless along
with the special organs of expulsion, the elementary property of
simple exhalation still continues. The most marked example of
this primitive mode of elimination is certainly the gaseous and
aqueous exhalation, which is so extensively effected by means of
the lung.

But besides the glands serving for simple expulsion, there are
others whose distinctive office consists in forming, at the expense
of the nutritive liquids, special substances, destined to play a
part in the accomplishment of one of the grand functions of the
living organism. The glands of the first type are called glands
of excretion, the others, glands of secretion. "We may give as ail
example of the first the glands which excrete urine and sweat,

CHAP, xvii.] OF SECRETION AND EXCRETION IN GENERAL. 257

that is to say the kidneys and the sudoriparous glands. The
salivary glands and the liver represent well t'he glands of the
second type.

The higher the perfection of an organised being the more its
organs of excretion and secretion are numerous and specialised.
From this general proposition, applicable moreover to all organic
apparatus, we may infer that the organs of elimination are very
rudimentary in the vegetal kingdom. Lacking there completely
are the complex glandular organs, furnished with canals of dis-
charge, such as exist in animals. We might bring the vegetal
glands into relation with the glands closed or without the excretory
conduits of animals. In both cases, in effect, the secretory organ
is represented by cells elaborating at the expense of the nutritive
liquids special substances, which come forth from the cells, either
by exosmosis or by rupture of the cells which have formed them,
but are not then received into special conduits ; for the network,
called network of secretion, into which is poured the essential
oil of the helianthus, the resinous gum of certain umbelliferse,
the limpid balm of the conifers and the terebinthaceae, is merely
composed of meatus more or less ramified, due to simple ecarte-
ments of cells.

The secreting cells of vegetals are sometimes isolated and
sometimes grouped. As example of the first we may cite the
spherical cell, filled with a viscous or odorous substance, which
terminates certain vegetal hairs. Other glandular cells, isolated,
are dispersed over the parenchyma of the tissues, for instance the
camphoric cells of the leaves of the CampJiora officinarum. Often
the glandular cells are grouped in small masses, for instance, that
which contains the essential odoriferous oil in the rind cf the
citron. Sometimes the walls of these cells open or are reabsorbed,
and the place they occupied is transformed into a reservoir. But
these are special secretions. As to the form under which are
eliminated the products of disassimilation of the plant, it is
still very little known. Must we regard as products of excretion
the matters resinous, cereous, or slimy, and so on, which are

8

253 BIOLOGY. [BOOK u.

spread over the surface of certain plants ? But we do not find them
in all plants 1 yet all plants must excrete. Must we admit, with
certain botanists, that the products of disassimilation are borne
along with the descending sap, and expulsed by the roots them-
selves? But all this is very improbable. In reality vegetals
disembarrass themselves ill and imperfectly of their disassimi-
lated products. Water indeed is exhaled on the surface of the
leaves and of the stalk. Certain semifluid substances are also
expulsed by simple exosmosis. But considerable residua, notably
a great quantity of mineral substances, remain in the vegetal
tissues, encumber them, and determine the death of the ana-
tomical elements which they contain. This is probably the
cause of the death and the fall of the leaves, of the decay and
disappearance from within to without of the ligneous elements
in the centre of the dicotyledonous trees. Also the blackish
cadaveric detritus which often bathes the internal wall of hollow
trees contains products of decomposition, ulmine and its
derivatives.

It is in the animal kingdom alone that we find organs of secre-
tion numerous and perfectionated. Here the life is more intense,
and special organic agents are necessary to regulate the expulsion
of the disassimilated products, and form humours or substances
indispensable to the accomplishment of physiological acts of the
first order.

As we have already remarked, a distinction is made between
the secretion which fabricates new principles, and the excretion,
which merely furnishes passage to the materials of disintegra-
tion. But the secretion itself is effected according to two
principal modes. It is operated either by glands without excretory
conduits, or by glands with excretory conduits.

The difference between these two glandular types is however
purely . morphological. In the glands, with excretory conduits,
the product of the secretion is poured by a special canal on the
surface of the body, or of a mucous membrane (Fig. 35).
On the contrary, the closed glands act on the composition of the

CHAP, xvii.] OF SECRETION AND EXCRETION IN GENERAL. 259

plasmas j they fabricate, at the expense of the blood, special
products, which pass afterwards into the circulation by osmosis.
But essentially closed glands and glands with canals are very
analogous. In both the secreting elements are cells, anatomically
comparable with the epithelial cells covering the mucous mem-
branes and the skin. The mode of action of these cells has,
moreover, nothing exceptional. Every anatomical element is a
living laboratory, borrowing by election from the nutritive liquids
materials which it fashions and transforms. This is what the
glandular epithelial cells do (Fig. 35) ; but as in them the vege-
tative properties are very energetic, they transform with a greater
activity. The special substance, as soon as elaborated, is expulsed
from the secreting cell either by simple osmosis or set at liberty

FIG. 35.
Human gastric gland, with, acid secretion, as example of simple gland.

by rupture or resorption of the cellular wall. In the closed
glands the product of the secretion traverses the wall of the
capillaries, which are in contact with the secreting cells, and is
afterwards conveyed into the circulation. This is what takes
place, for instance, with the glycogenical cells of the liver, which
we have already mentioned. The cells elaborate the materials
which the blood of the intestine brings them, and restore to the
fine capillaries in contact with them those same materials
metamorphosed into sugar, which serves for the general nutrition.
But if the glycogenical function of the liver is now well eluci-
dated, this is far from being the case with many other closed
glands. It would be needful to make for each of those glands

a 2

260 BIOLOGY. [BOOK IL

the precise and methodical researches, thanks to which Professor
Maurice Schiff has thrown so much light on the function of the
spleen, or at least on one of its functions.

That the spleen and the pancreas could co-operate for the
same general function might be deduced from comparative
anatomy, as in certain vertebrates these two glands form only
one. But the physiological bond uniting them was most difficult
to discover.

Excellent experiments of Corvisart had already established
that the pancreatic juice and even the infusion of the pancreas
had the faculty of transforming the albuminoidal substances into
peptones incoagulable by heat. In addition Meissner had shown
that the formation of the pancreatine in the pancreas is inter-
mittent, and that when a person is fasting the pancreas has no
longer any digestive power. The case is moreover the same with
the stomachal pepsin, which is formed intermittently at
the expense of the peptogens introduced into the blood. But the
formation of the pancreatine is subjected to physiological condi-
tions far more complex ; forasmuch as it is absolutely dependent
on the integrity of the spleen. After the extirpation of this
last gland, in effect : —

1. The neutral or acidulated pancreatic infusion no longer
digests the smallest trace of albumine, whether the pancreas is
taken in a fasting animal or an animal in full digestion ;

2. In these conditions, albumine introduced by a fistula into
the duodenum, when this is bound at its two extremities, no
longer transforms itself into peptone, either in the fasting animal
or the animal in full digestion ;

3. Finally, always after the extirpation of the spleen the
albumine introduced into the bound duodenum is well digested
slowly by the duodenal juice, but is no longer transformed
rapidly into peptone after the first hour of stomachal digestion,
as happens always in animals still possessing a spleen.

To make amends, the peptic glands finding in the blood a richer
provision of peptogens, forasmuch as the pancreas no longer

CHAP, xvii.] OF SECRETION AND EXCRETION IN GENERAL. 261

absorbs any, secrete with much greater activity, and thus com-
pensate in a large measure for the inaction of the pancreatic
gland.1

These valuable researches, which put beyond doubt the
fact of the intimate solidarity between the spleen and the
pancreas, show how very complex the phenomenon of secretion
can be. The cells of the spleen do not fabricate pancreatic
ferment, and there is no trace of this ferment in the blood ; never-
theless the function of the pancreas is abolished when the spleen
is extirpated. In order that the pancreatic glands may elaborate
pancreatine at the expense of the albuminoidal substances, or of
certain of these substances, it is needful, previously, for the
materials, absorbed by election into the pancreatic gland, to
undergo, in the cells of the spleen, a first modification, a first
process, the nature of which is still unknown.

But who can say how many of these physiological correlations
are still unknown, and how fertile the study of the other closed
glands may be, undertaken from that point of view 2

The glands with excretory conduit must be considered as folds,
as diverticules of the cutaneous or mucous teguments. The
labour of specialisation bears especially on the epithelium or the
epidermis of the tegumentary membrane ; the mode of nutrition
of this epithelium is modified, and its cells acquire the faculty
of elaborating at the expense of the blood, here saliva, there
gastric or pancreatic juice ; at one point bile, elsewhere spermatic
liquid, and so on.

The humours secreted have all two general characteristics : —

1 . None of the humours is living ; none is endowed with the
property of continuous renovation which we have signalised in
the plasmas. Their water is in great part free ; it is not a
constituent water, and it is charged with salts directly dis-
solved.

2. All these humours contain one or more quaternary principles,

1 A. Herzen, Sulla Digestion* deW Albumina Effettuata dal Succo Pancre*
atico e sulla Funzione della Milza.

262 BIOLOGY. [Boox n.

which we do not find in the blood (peptine, pancreatine, and so
on).1

In reality, the secreting glands are at the same time organs of
excretion. All of them take from the blood water and salts,
substances to which they offer a passage without in any respect
changing them. But besides they form, at the expense of the
sanguineous materials, a 'special azotised product. Yery habitually
the agent of these chemical transformations is the epithelial cell.
Sometimes, however, the metamorphosis can be accomplished in
the wall itself of the gland, as is the case, for instance, with the
mammary gland.2 But the secreting element by excellence is
the epithelial cell, whose numerous varieties have each their
special affinities.

When neither the wall of the glandular organ, nor the epithelial
cells which are contained therein, exercise any modifying action
on the materials of the blood, but fulfil simply the office of a
filter, offering a passage to certain substances and refusing it to
others, there is merely excretion. Excretion is a biological act
more simple than secretion, and comparable with the exhalation
which goes on, for instance, on the pulmonary surface.

The excretory glands are never closed. Always they pour the
humour which they' filtrate on some point of the tegumentary,
cutaneous, or mucous surface, and this humour is destined
to co-operate with no ulterior physiological function. It is a
dead product, whose expulsion is necessary, and whose retention
in the organism would be fatal. It is the residuum of nutrition.

The excrementitial humours, of which the sweat and the urine
are the types, are solely constituted by the water, holding in
solution saline principles, and also crystallisable azotised sub-
stances, which, formed in the anatomical elements themselves by
disassimilation, pass first of all into the blood, whence they are
extracted and excreted by the glands.

1 Ch. Robin, Legons sur les Humeurs Normales et Morbides, pp. 29, 30, 32,
and Introduction, p. xxvi., xxvii.

2 Ch. Robin, loc. cit., pp. 17, 18.

CIIAP. xvii.] OF SECRETION AND EXCRETION IN GENERAL. 263

Neither the secreted humours nor the excreted humours are
living, but the first have a composition perceptibly stable, re-
actions nearly fixed. On the contrary, the composition of the
excreted liquids is variable, according to the greater or lesser
activity of the gland, the proportion and the nature of -the
substances absorbed by digestion, the state of activity or of
inaction of such or such organic apparatus, and so on.

We can range in graduated series the diverse modes of elimina-
tion, of excretion, and of secretion realised in the organisms.

The mode the most simple, the only one existing in most
vegetals and inferior animals, is the direct passage of the expulsed
substances across the tissues, without the intervention of any
special organ ; it is simple transudation or exhalation, such as
continues to be in the superior animals on the pulmonary surface.

Then comes the excretory mode, that is to say, a sort of trans-
udation through particular glands; such are the urinary and
sudorific excretions.

At the degree, immediately superior, is found the secretion
which is called direct. In effect, the gland drains, direct from
the general mass of the materials of the blood, substances which
it transforms and which have a physiological use. We may cite,
as example, the salivary and biliary secretions.

The mode the least simple is that in which the open gland,
furnished with a canal, needs the co-operation of a closed gland
which prepares materials for it. The only example well demon-
strated of this mode of secretion so complex, is that offered us
by the pancreas and the spleen. But it is very possible that
other correlations of the same kind exist in the superior
organisms, that the salivary secretion, for example, is connected
with the thyroidal body, and so on ; and that the most of the
closed and open glands are thus coupled together.

CHAPTER XVIII.

OF THE SECRETIONS AND EXCRETIONS IN PARTICULAR.

No exposition of a subject as a whole can attain a sufficient
degree of clearness, unless it rests on the description of some
particular facts. It is therefore not unsuitable after the general
outline, contained in the preceding chapter, to consecrate some
pages to the most important and most typical particular secre-
tions and excretions.

Evidently we must place in the first line the hepatic secretion,
of all the most complex. In effect, in the liver, the division of
labour is far enough from being distinct, and this gland is simul-
taneously a closed gland, a secretory gland with excretory
conduit, and a gland of excretion. Comparative anatomy,
moreover, reveals to us a still higher degree of confusion. In
truth, while in diverse vertebrates, for instance, the lizard, the
spleen is merely adjoined to the pancreas, in the Chimcera mon-
struosa liver, splesn, and pancreas are united into one mass.

In the mollusks the same epithelial cells seem to be charged
to secrete at the same time both sugar and bile ; for this last
humour always contains sugar. Besides there is no vena portse,
and the saccharo-biliary secretion is accomplished at the expense
of the still badly arterialised blood.

In the superior mammifers the glycogenical cells of the liver
are sometimes rounded, sometimes polyhedrical ; their diameter
is about 0.02 of a millimetre (Fig. 36). They contain granula-
tions and one or two nuclei furnished with nucleoles. These

CHAP. XVHI.] SECRETIONS AND EXCRETIONS IN PARTICULAR. 265

cells are in contact with the finest capillaries of the vena portse,

from which they borrow the materials necessary for the fabrica-

: tion of their amylaceous product (Fig. 37). This product,

denominated glycogen, is analogous to the cellulose of vegetals ; it

is uncrystallisable, like starch, and, like starch, susceptible of

transforming itself isomerically into glycose, fermentiscible and

crystallisable. Once formed by the hepatic cell, the glycogen is

) yielded by it to the blood of the super-hepatic capillaries, and

• transforms itself into glycose, which normally is either destroyed

FIG 36.

Isolated cells of the
liver ; a, with simple
nucleus, b, with
double nucleus.

FIG. 37.

Arrangement of the cells of the liver in a lobule cut
transversally, with the section of the hepatic vein
in the centre.

by oxydation in the blood or utilised for the nutrition of the
anatomical elements.

It is by no means certain that the glycogenical cells do not
also contribute their share to the secretion of the bile. If they
are in contact with the sanguineous capillaries, they are likewise
in contact with the fine ramuscules of the biliary canals, a sort
J of excretory capillaries. Finally, we sometimes find in the
normal state, often in the pathological state, yellowish granules

266 BIOLOGY. [Boox n

and fine droplets of the same tint, which seem to be the colouring
matter of the bile.

But this contribution, if it exists, is assuredly accessory, for the
bile is specially formed in the fine culs-de-sac or acini whence
go forth the biliary canals. These culs-de-sac receive thin arterial
ramuscules, from which their walls and the epithelial cells, which
clothe them, borrow the materials which they elaborate and
transform into bile.

Between the glycogenical cells and the secretory acini of the
bile there is not a very intimate physiological bond. In effect
the blood of the vena portse is indispensable to the activity of
the glycogenical cells. But a ligature of this vein by no means
stops the biliary secretion, alimented almost exclusively by the
capillaries of the hepatic artery.1 Inversely the ligature of the
hepatic artery dries up the biliary secretion.

The glycogenical formation and the biliary secretion do not
suffice to exhaust the functional activity of the liver. From the
researches of M. Flint, it results that one of the substances
poured out with the bile is so by an act of simple excretion.
We mean a ternary substance, very rich in carbon, which is
likewise found in the vegetal kingdom among the mushrooms.
This substance is cholesterine, which, among the vertebrates,
seems to be especially a product of disassimilation of the nervous
system. The venous blood returning from the brain, that of the
jugular vein, for instance, contains 0,801 of cholesterine, while
the arterial blood darted from the heart towards the encephalon,
that of the primitive carotid, contains only 0,774. Now this
excrementitial product, which can be met with, moreover, in
diverse secretions, is especially taken from the blood by the liver,
which excretes it into the biliary liquid. There is here an act of
simple election. The liver lets the cholesterine filter through,
in the same way that to certain salts, for instance the iodide of
potassium, it offers that free passage which it refuses to certain
others, notably calomel.

1 Ore, Journal de VAnatomie et de la Ptysiologie, Paris, 1864.

CHAP, xviii.] SECRETIONS AND EXCRETIONS IN PARTICULAR, 267

The function of the salivary glands is much more simple than
that of the liver. The culs-de-sac or acini of the salivary glands
in cluster are lined with epithelial cells whichhave a single nucleus,
i These cells, flattened and pavimentous, in the state of repose
of the gland, swell and soften during the period of secretion.
Jt is then that they take from the blood the materials necessary
for the fabrication of ptyaline; also they become loaded with
granulations, which give them a slighly opaque look.

Though identical in appearance, the diverse salivary glands
of man and of the superior mammifers secrete, that is to say
fabricate, coagulable substances specially appertaining to each
:gland. There are here imperceptible particularities, belonging
:to the molecular acts themselves of nutrition. The fact becomes
Imore striking still if we range the poison glands of reptiles
with the salivary glands ; a classification justified moreover by
anatomy.

The salivary cells swell assuredly during the period of
iglandular activity, but it is especially during repose that they
seem to detach themselves from the partition and to accumulate
in the culs-de-sac. Then, when the gland commences to operate,
jia liquid flow, borrowed from the blood, traverses the wall of
tthe acini, and goes to dissolve and to carry along the salivary
Iferment previously formed. Analogous phenomena are produced
'in the lactiferous glands, and perhaps in most of the glands.
jln the lacteal glands the secretory cells load themselves with
j droplets of fat, which their rupture sets at liberty.

The fundamental structure of the excretory glands does not
'perceptibly differ from that of the secretory glands. The
J mechanism of their functions is also the same. In excretion as
Jin secretion there are always cells, called epithelial, which borrow
: from the blood of the capillaries certain substances ; but the
1 secretory cells content themselves with giving a passage to the
: substances substracted without perceptibly modifying them.
1 The most important of all the excretions is certainly the urinary
' or renal excretion.

268 BIOLOGY. [BOOK n.

Organs analogous by function to the kidneys of the superior
vertebrates exist in many invertebrates, notably in insects and
the arachnida. In these animals the secretory cells are even
sometimes very voluminous. Those of the Coccus ffesperidum,
for instance, are so large that they can only place themselves in
single file in the vessel of Malpighi, to which they give a knotted
aspect. These uriniferous cells dissolve and set at liberty the
numerous granulations of uric acid and of urate which they
contain.

The schema of the kidney of the vertebrates is found in the
myxinoids.1 The apparatus is composed of a long canal com-
parable with the ureter, that is to say, with the long and
narrow conduit, which, in the superior vertebrates, unites the
kidney to the bladder. In the myxinoids this canal shows from
distance to distance culs-de-sacs narrowed at the neck. At
the bottom of every cul-de-sac is found one of those small
clusters, consisting of intricated capillaries, which are called
glomerules of Malpighi, in the kidney of the superior vertebrates
(Fig. 38). This arrangement of the renal capillaries has for
result to slacken the course of the blood in the glands, to
multiply the contacts of the vessels with the excretory cells,
and consequently it is very suitable for facilitating the urinary
excretion. Tn effect this excretion is of supreme importance,
forasmuch as it represents a grand current of expulsion, thanks
to which the principal mass of the mineral principles and of the
quaternary azotised principles, disassimilated, useless or hurtful,
is driven from the animal economy.

The urinary liquid represents the residuum the most general
and most abundant of disassimilation, that is to say, that its com-
position is alike very complex and very variable. With the
exception of a small quantity of colouring matter or some pro-
ducts of vesical secretion in the animals that have a bladder, we
find in it no immediate principles of the third class. It is
merely a solution much charged with mineral or mineralised
1 Leydig, loc. cit.

: CHAP, xviu.] SECRETIONS AND EXCRETIONS IN PARTICULAR, 269

substances, whose proportion incessantly varies. We find in it
i a quantity of mineral salts, first of all chlorure of sodium, then
j chlorure of potassium, chlorohydrate of ammonia, 'sulphates of

soda and potash, phosphates of lime, of soda, of potash, of mag-
i nesia, ammoniaco-magnesian phosphate, carbonates of lime, of
i potash. The organic salts and the quaternary products resulting
I from the disassimilation are lactates of soda, of potash, of lime,

urates of lime, of magnesia, of soda, of potash, of ammonia, a

FIG. 38.

Schematic representation of a Malpighi glomerule of the bladder : — a, sanguineous vessel
entering ; b, sanguineous vessel leaving ; c, clusters of the capillary vessels in the
. interior of the glomerule ; d, lower part of the capsule drawn without its epithelium ;
f «, commencement of the urinary canal ; /, internal epithelium of the mass of the capil-
» laries ; g, internal epithelium of the capsule.

little uric acid, and besides, especially in the herbivorous animals,
hippuric acid and hippurates. Finally, we must add to this
long, though incomplete list, the most important products of
excretion, urea, creatine, creatinine, immediate principles of the
second class derived direct from the oxydation of the albumin-
oidal substances in the concatenation of the tissues.

The composition of urine varies under the influence of all the
causes capable of acting on the nutrition of the animal organism.

270 BIOLOGY. [BOOK n.

It is denser, more charged, more coloured during digestion, more
colourless, on the contrary, and holding in solution fewer pro-
ducts of excretion during the first infancy, when assimilation
predominates over disassimilation, and when the needs of growth
fix in the economy, in great quantity, the nutriments which
penetrate thereinto.

After violent exercise, the urea, the phosphates, and the sul-
phates notably augment in the urine; for there is a greater
consumption of albuminoidal substances.

Abstinence brings the same results; for then the animal is
nourished at the expense of his own tissues ; but in this last
case the augmentation of the phosphates and sulphates is simply
relative.

Excellent observations and analyses, especially those of Dr.
Byasson, have put it beyond doubt, that all intellectual activity,
how little soever energetic, has as corollary a corresponding
augmentation of the urinary phosphates. Every organic act has,
in truth, for basis an oxydation of the tissue, of the anatomical
element which operates. The brain is subject to this law, like
every other organ ; but, as we shall see by and by, it is very
rich in phosphates. It is therefore perfectly natural that its
disassimilation should give birth to phosphorised products of
excretion.

As we have already mentioned in a preceding chapter, the
urine of the herbivora is generally alkaline, and richer in hip-
puric acid and in hippurates. That of the carnivora is habitually
acid, and the urates and the uric acid are in larger proportion
therein. But, as we have indicated, there is nothing fixed and
immutable. Every herbivore, subjected to an animal alimenta-
tion, has the urine of a carnivore, and simple abstinence itself
suffices to produce this result.

An abundant animal alimentation has for result greater pro-
duction and excretion of uric acid and urates. On the contrary,
in abstinence the uric acid disappears and the urea is excreted
in greater quantity. The urea, product of an oxydation more

CHAP, xviii.] SECRETIONS AND EXCRETIONS IN PARTICULAR. 271

iprofound of the organic substances, is formed by disassimilation
>in the anatomical elements themselves. Possibly, however, the
luric acid, the result of an incomplete oxydation, is produced for
ithe most part in the blood itself, when the fluid is surcharged
with peptones which the tissues are not able to assimilate.

But how can we explain the fact that uric acid is found in
such enormous proportion precisely in those of the vertebrates
'which are endowed with an extreme respiratory activity, namely,
in birds, which, however, as regards uric secretion, resemble
i testaceous reptiles ? Yerily in both the uric acid is found in so
i great a quantity, that it is concreted and crystallised even in the
; interior of the urinary canals, and gives to the urine the appear-
ance of a whitish pulp. Among the invertebrates, concretions
i and crystals of like nature are not met with even in the cells of
I the urinary glands.

We can view as having affinity to the urinary excretion the
isudoral excretion, operated by millions of cutaneous glandules,
i each of which may be considered as a small kidney excreting an
j aqueous solution, charged with substances analogous to those
I which are found in the urine. But the sudoral excretion is
1 much less rich in salts and in organic matters than the urine.
I "We usually find in it urea, but no uric acid or urates.

Secretion; we have said, can be traced back to phenomena of
nutrition, that is to say, to molecular acts, effected in the midst
I of glandular cells, which means that it can be accomplished
{ without the intervention of the nervous system. Such is evi-
i dently the case with vegetal secretions. But in the superior
I animals, having a complete nervous system and suitable capillary
I vessels, the secretion evidently depends on the degree of reple-
tion of these vessels, and on the rapidity with which the
| sanguineous current traverses them. It is therefore indispen-
1 sable that the secretion should be influenced by the vaso-motory
: nerves ; and this is in effect what experiment demonstrates.
Normally, secretion is always accompanied by a dilatation of the
capillaries of the gland, by a congestion, and every congestion

272 BIOLOGY. [BOOK n

artificially provoked by the secretion of the vaso-motory nerve
or by the excitation of the vaso-dilatatory nerves, which seem t
exist at least in certain glands, has for result a greater secretor
activity.

Incitations arising or provoked in the nervous centres, eithe
directly or by reflex action, can also transmit themselves to th-
glandular vaso-motory nerves, and react on the secretion. Thm
we determine an abundant secretion in a dog, chained an<
famished, by placing a piece of roast meat before him. All tht
world knows likewise with what facility certain strong e'motion;
act on the biliary secretion. These are examples of reflex phy
siological acts. The direct excitations of the nervous centres
can, in their turn, modify or trouble the secretions. As early as
•1845 M. Schiff had demonstrated that lesions of the cerebral
peduncles render the urine acid and albuminous. Punctures oi
the roof of the fourth cerebral ventricle provoke saccharine
diabetes (Cl. Bernard). Lesions of the isthmus and of the lower
part of the cervical marrow can abolish the urinary excretion,
can produce anuria.

Brief and incomplete though it may be, the exposition which I
precedes suffices to make the mechanism and the importance ofi
secretion understood. We have therefore now passed in review
everything relating to nutrition, to its modes, to the di verse i
biological contrivances which render it possible in the essential
being o'f complex organisms. Consequently we can forthwith
enter on the exposition of the chief properties of organised
matter. "We know how organised beings are nourished ; let us.
now see how they grow, and how they are reproduced.

LIB u .AH v

OHIVKU8ITY OF

CALIFORNIA.

BOOK III.

GROWTH.

CHAPTER I.

OF THE PROCESSES OF GROWTH.

THE organised individual, vegetal or animal, is perpetually
mutable and always perishable. It is born, it grows, it dies,
after having more or less painfully maintained its organic
equilibrium in the midst of the exterior medium. We have ere
long to formulate the general laws of the birth, of the generation,
of organised beings. Let us now see how these beings grow.
Every living creature being definitively constituted by ana-
tomical elements, it can only increase in volume by the growth
or the multiplication of those elements.

As to the development in volume of anatomical elements
j already existing, the phenomenon is relatively simple. There is

• scarcely anything more before us than a particular case of nutri-
\ tion with a certain predominance of movement of assimilation
J over that of disassimilation. The anatomical element or elements

acquire more than they lose, and their mass more or less aug-
ments. If a complex or organised being is concerned the growths
of the elements, isolately considered, totalise themselves, and the

* whole individual grows and greatens.

But evidently this mode of growth is insufficient to account
for the phases which every organised being traverses from birth

274 BIOLOGY. [BOOK in.

to death ; for putting aside for the present the cases of spon-
taneous generation with which we have not to occupy ourselves
here, every complex individual of the two organic kingdoms
springs from a simple cell. Growth can therefore be effected
only by an enormous multiplication of the anatomical elements.
This, in effect, is what happens. But as to the mode of genera-
tion of these histological elements, we find ourselves in the
presence of two great rival theories which we have already
signalised. The one more especially defended in Germany is the
theory of cellular generation. The other, maintained chiefly in
France by M. Ch. Robin and his school, is that of spontaneous
genesis.

FIG. 39.

"Reproduction by segmentation of an elementary organism, amoneron : A, entire moneron
(protamceba) ; J5, the same moneron divided into two halves by a median fissure ; C, the
two halves have separated, and constitute now independent individuals.

According to the cellular theory, maintained in all its vigour
by M. Virchow, and still admitted by the majority of German
naturalists and physiologists, every cell comes directly and
strictly from a pre-existing mother cell. Omnis cellula e cellula ;
such is the formula which sums up the doctrine. Whatever
the biological process may be, simple division (Fig. 39), or the
budding from the mother cell, &c., there is always proliferation
alike in the animal kingdom and in the vegetal kingdom.

The doctrine of spontaneous genesis is less exclusive. With-
out denying the fact of cellular proliferation, which is very
generally observed in the vegetal kingdom, at the outset of the

CHAV. i.] OF THE PROCESSES OF GROWTH. i'/f,

embryological evolution, as well as for certain species of his-
tological elements, the partisans of spontaneous genesis, sup-
ported moreover by numerous and precise observations, affirm
that for the most part in the animal kingdom, and here and
there in the vegetal kingdom, new histological elements appear
spontaneously in the intercellular blastemas.

Even if we admit that the defenders of spontaneous genesis
have generalised a little too much the application of their doctrine,
it is certainly on their side that there is the largest amount of
truth. We must, in any case, admit two grand processes of his-
tological generation : proliferation, or multiplication by extension
and division of substance and genesis, or multiplication by a sort
of living precipitation in the heart of the blastemas. The two
processes are observable in the two organic kingdoms, but in
very different degrees, each of these two great modes of his-
tological multiplication being dominant in the one kingdom
and exceptional in the other. In short, proliferation and genesis
are the rule, the first in the vegetal kingdom, the second in the
animal kingdom.

CHAPTER II.

OF GROWTH IN THE VEGETAL KINGDOM.

CELLULAR proliferation is far from being accomplished in a uniform
manner. It results from various processes, which sometimes
even are more or less combined, but of which the principal
may be arranged under the following heads — 1, simple division or
segmentation, scission ; 2, budding, germination or surculation ; 3,
copulation or conjugation ; 4, endogenous generation.

In cellular segmentation it is first of all the azotized utricule,
the inner envelope of the cellular protoplasm, which depresses
itself, narrows itself into a circular furrow. Afterwards, the
external tunic in cellulose places itself in its turn in the depres-
sion, which, becoming deeper and deeper, at last forms ft
partition at first incomplete and pierced with a circular hole,
afterwards complete. While this division is taking place, a
second nucleus appears in that one of the two cavities which was
primitively destitute of it. The result of this very simple evolu-
tion is the formation of a new cell, which divides itself in its
turn. M. Mohl was the first to observe closely this cellular1
unfolding in the terminal cell of the confervse. It has since
been affirmed regarding most of the vegetal tissues. It is thus
that the ligneous cell of the phanerogams form their layers and
their fibrous bundles ; it is thus that the cells multiply themselves
in the sporangia, and the spores of the algoe, &c., &c. Sometimes,
as in the cells of the pith of the dicotyledons, the division of the
nucleus precedes that of the cell.

CHAP. ii.J OF GROWTH IN THE VEGETAL KINGDOM. 277

In germination, the cell emits from one point of its surface
a prolongation, a kind of protoplasmic rupture, which acquires
a nucleus, separates itself by partitionment from the rest of the
parent cell, and lives afterwards an independent life. It is by
this process that certain unicellular plants, for example the
Vaucherias, reproduce themselves.

In the monocellular algse the spores and sexual cells, con-
taining antherozo'ids, analogous to the spermatic animalcules,
form themselves by the terminal partitionment of one of the
ramifications emitted by the cell.

It is also in the algae, the conjugated diatomous algse, that the
phenomenon of conjugation is especially remarkable. Two
neighbouring cells each emit a prolongation; these projections
meet ; their partitions are reabsorbed at the point of contact ;
the protoplasms of the two cells intermingle ; soon the cells are
completely amalgamated. They then form only one cell, which
is a reproductive one, a spore or zygospore (spirogyra longata).

The multiplication of the cells, by endogenesis, is characterised
by the formation of a greater or lesser number of daughter cells,
which grow, burst the tunic of the parent cell, and live in their
turn an independent life. This mode of reproduction exists in
some unicellular vegetals, for example, in the protococcacese.1

To sum up, all these diverse modes of proliferation do not
essentially differ from eath other. In every case the essence is
the same ; it is a particle of living matter, individualised, which
assimilates beyond what is necessary for its own maintenance,
and becomes a true organic centre. Thus is produced an
exuberance of force and matter ; whence the tendency to the
formation of fresh centres.

The growth of a vegetal, by the simple increase of volume of
the histological elements, may be considered as the first step, the
prelude to that development by cellular multiplications which we
have just described. Here also there is a predominance of the
movement of absorption, of assimilation. The nutritive liquids
1 Kaegeli, Gattungen einzcllingen A Igen, Zurich, 1847.

278 BIOLOGY. [BOOK in.

diffuse themselves into the substance of the anatomical elements ;
living molecules of new formation intercalate themselves by
intussusception with the molecules primitively existing; the
cellular membrane extends ; the protoplasm grows ; then the
form of the histological elements often modifies itself. It is in
this manner, for example, that the ligneous fibres form themselves.
The cells, at first spherical, elongate, and become cylindrical ;
their extremities adhere to each other, either squarely or
obliquely. Concentric layers deposit themselves successively on
the inner surface of the partition, which they thicken.1

In other tissues the spherical or polyhedrical cell grows simply
by increasing in age without losing its first form. Sometimes,
even, we can determine the relative ages of the cells of a tissue
by the variations in volume. In the pith of many plants the
cells go on regularly and gradually decreasing in volume from the
central region, where they are the most aged, to the circum-
ference, where they are youngest. The same fact may be
observed in comparing the medullary cells of the same stem at
different heights. Dutrochet has observed that in certain plants
the gradual decrease of the diameter of the stem from the base
upwards is owing solely to the decreasing volume of the medul-
lary cells, beginning at the neck of the root.2 In effect, slices
of the pith of the elder-tree, cut at different heights, contained
manifestly the same number of cells.

In the inferior vegetals, especially in certain families of algje
(conjugated, diatomous, siphonated), there is neither division
of labour nor specialisation of tissue. ' The cell then lends itself
to various functions, metamorphoses itself, adapts itself tu
multifarious uses. Besides, whatever may be the degree of
complication of its structure, it generally preserves the faculty
of segmenting itself, of multiplying itself. It is quite otherwise

1 Ch. Eobin, Des EUments Anatomiqiws (BiUiotlilque des Sciences
Naturelles).

3 Dutrochet, Mdmoires pour Servir a VHistoire Physiologique et Anatomique
des Animaux et des Vegetaux, t. II.. p. 139.

CHAP, ii.] OF GROWTH IN THE VEGETAL KINGDOM. 27&

with the complex phanerogamous plants. There the faculty of
self-multiplication by division is in some degree the special
appanage of incompletely developed cells, always young. These
are the cells which issue from the mother cells, which diversify
themselves and form the different histological vegetal types, of
which we have before given a succinct account. From them
issue the tubes, the ligneous cells, the chlorophyllian cells ; but
all these derived and special elements have, on the other
hand, habitually lost the faculty of division and of multi-
plication.

Growth is only an exaggeration, an outcome of nutrition ; that
is to say, it is dependent upon the grand conditions of the
medium which regulate this primordial property of organized
matter.

Nevertheless, it appears only to depend indirectly upon light.
In effect, it is often in the night that seem to go on most strongly
the growth and segmentation of the vegetal cells. The necessary
conditions are simply the previous existence, in the tissues of
the plant, of a store of materials, elaborated, assimilable, and
of a sufficient quantity of aqueous vehicle to dilute and convey
these materials.

The action of light on the chlorophyll is necessary to the
formation of the immediate assimilable principles in the plant ;
but assimilation, properly so called, is carried on very well in
darkness. In effect, the subterranean parts of plants live and
• develop themselves ; the phenomena of germination are perfectly
accomplished in darkness; truffles and all tuberaceous plants
effect subterraneously all the phenomena of their development ;
mushrooms, deprived of chlorophyll, assimilate even when the
organic materials are prepared by other organized beings.

Light seems even to retard the development of the plant. It
is in the morning, towards sunrise, that the internode in its
process of growth offers its maximum of horary augmentation.
If a stem receives upon different sides of its surface luminous
rays varying in intensity, it curves itself towards the side on

280 BIOLOGY. [Boos in.

which there is most light, because on that side the anatomical
elements increase and multiply least actively. It is only the
very refrangible rays, blue, violet, and ultra-violet, which exercise
this retarding action. Nevertheless, the mean elongation is
ordinarily greater during the twelve hours of the day than
during the twelve hours of the night; but this result is due
to the mean elevation of the diurnal temperature, and it is
always in the morning at sunrise that growth reaches its
maximum.1

A. de Candolle, De Yries, Koppen, Sachs, &c., have occupied
themselves with the influence of the temperature upon the ger-
mination and elongation of different parts of plants. Below 0
and above 50 degrees, vegetal life is generally impossible, and
it is ordinarily at about 30 degrees that it attains its maximum
of activity. This proposition has, however, only a general appli-
cation, as, for each species, there are special maximal and
minimal temperatures, and also a certain temperature particularly
favourable.

At this suitable temperature, development is as rapid as
possible j nevertheless it still takes place above and below it,
within sufficiently wide limits, but much more slowly.

From observations made by M. Boussingault upon grains of
barley, it has been concluded that to develop itself, a vegetal
requires a given and nearly uniform degree of heat. 2 This given
quantity of calorific vibrations transforms itself into nutritive
and evolutive equivalents. A lower temperature produces the
same effect as the more favourable temperature, but naturally
in a longer time. According to this hypothesis, very high
temperatures must be considered as agents of perturbation, as
forces too great, hurtful by their very excess, and of a nature to
shackle the phenomena of nutritive chemistry.

In treating of nutrition and respiration, we have stated what

1 Sachs, Traite de Botaniquc, pp. 886-890.

2 Boussingault, Exnwmie Hurale, Considiree dans ses Rapports avec la CMmic,

1 la Meteorologie, t. II.

CHAP, ii.] OF GROWTH IN THE VEGETAL KINGDOM. 281

an indispensable part is filled by the atmosphere in the life of
organised beings. It is evident that in an atmosphere unsuitable
for the maintenance of life, or in a vacuum, growth is arrested,
the floral and foliaceous buds no longer develop themselves, as
Saussure and many other experimentalists have moreover shown.

The principal facts and general conditions of vegetal growth
being determined, we can now describe or point out a certain
number of particularities connected therewith.

The epoch of blossoming often coincides with a more or less
rapid acceleration of growth^ and, at that time, we see, in the
greenhouses, agaves lengthen by more than two decimetres in
twenty four hours. The Corypha umbraculifera has been seen to
grow forty-five times more during the four months preceding its
blooming than it had done in the same lapse of time in thirty-
five years.1 Mushrooms grow with extreme rapidity. In three or
four days the Lycoperdon giganteum develops into a sphere three
decimetres in diameter. Certain algse, for example the confervse,
formed of a single row of cells juxtaposed, end to end, lengthen
almost visibly by cellular division.

In the most complex vegetals, growth has been closely studied.
It is produced by the descending and elaborated sap. In the
arborescent dicotyledons, the duramen, the ligneous portion, is
no longer traversed by the descending sap ; moreover, the fibres
which compose this ligneous portion are half mineralized ; they
have ceased to multiply themselves, and even to grow. It is
between the wood and the bark that the flow of descending sap
finds an easy passage, and it is there, in fact, that every year a
layer of fresh tissue is formed. Most botanists admit that the
creation of the new histological elements takes place by simple
division of the old, especially of those which constitute the inner-
most layer of the bark, since, according to the experiments of
Duhamel, a shred of bark, only connected with the rest by its
upper part, or else separated from the aubier by a plate of pewter,
still effused cambium on its inner surface. According to M.
1 Tieviranus, Biologic.

282 BIOLOGY. [BOOK in..

Tre*cul, there is probably also an advent of new elements by
spontaneous genesis.1 In the opinion of this observer, when the
buds are produced, there is also an effusion of gelatiniform
blastema between the bark and the aubier. This effusion forms
a mamelon ; then in this mamelon appear little cells. M. Ch.
Robin goes farther. According to him differentiated histological
elements spring forth also by genesis in the centre of the cellulous
mamelon. We should observe the appearance of ovoid cells
arranged in a single cluster, and having from the beginning a
reticulated aspect ; then afterwards cells with a spiral thread
spring forth. When once the evolution of the bud is more
advanced, when once the leaves are formed, the primitive, single
cluster ramifies to send little clusters into each leaf.2

The pith grows energetically when it is not imprisoned in a
rigid ligneous tissue, which isolates it from the cortical system.
In this last case, on the contrary, it often dies, is destroyed, and
the stem becomes fistulous. But when the pith is bound by
transverse radii to the bark and to the cambium, it most fre-
quently grows by cellular division. Notwithstanding, Dutrochet
has affirmed that he saw new cells spring forth, by spontaneous
genesis, in the cellular interstices of the pith. The medullary
cells are generally soft, and very osmotic ; they readily imbibe
water or sap, become turgescent, and fit to produce generative
blastemas.

The duramen is a kind of senile state. Trees which are desti-
tute of it, as the poplar and the maple, grow generally with
greater rapidity than others ; for growth then takes place
throughout the whole thickness of the trunk, and not only
between the bark and the aubier. In fact, there is growth
wherever the elaborated sap penetrates. Dutrochet cites, as an
example, the radiciform stem of the beetroot, composed of layers
of loose cellular tissue, between which the cambium circulates.3

1 Trecul, Anncdes des Sciences Naturelles, 1846.

2 Ch. Robin, loc. cit., p. 39.

3 LOG. cit., t. II. p. 162.

CHAP, ii.] OF GROWTH IN THE VEGETAL KINGDOM. 283

The development of the plant in length is accomplished in two

ways ; on the one hand by terminal elongation, due to the evolu
;tion of the bud, which produces internodes or merithalli of new
'formation ; on the other, an elongation is effected of the merithalli,
'already formed, by the lengthening of their vascular or cellular

organs.

The roots scarcely lengthen except from the point, since two
I ligatures placed across their course near their extremity never

separate from each other (Duhamel).

Most vegetals grow during the whole of their life, either
'specially in length, as the monocotyledons, or in both dimensions,
!as the dicotyledons. Growth only slackens more and more in

proportion as the vegetal tissues become mineralised, and its
(complete cessation generally coincides with the death of the

vegetal. Death, besides, may be partial. In effect, there is no
j centralisation in the plant. Every vegetal may be compared to
| a polypier. Each bud has its individuality, its own existence ; it
'attracts and elaborates the nutritive fluids ; also when a terminal
Ibucl dies the branch which bears it dies also.

The fall of the decayed leaves is determined much less by the
•autumnal cold than by the termination of the foliaceous growth,
•due, doubtless, to an excessive degree of mineralization. Many
j decayed leaves fall before the appearance of the cold. As to

the leaves termed persistent, they scarcely differ in this respect

from the so-called caducous leaves. Instead of falling in a
1 mass, they fall one by one, when their growth has reached its
[bound.

Jn the ligneous stems of the dicotyledons, to speak correctly,
| death incessantly accompanies life. Every year a certain number
I of anatomical elements lose the faculty of growth, of multiplica-
! tion, and at last of receiving nutriment. They become first what
' are called definitive tissues, then little by little are destroyed ;

but, on the surface of the aubier, where the flow of cambium,
• of elaborated sap, passes, a new living stratum is formed. In
1 proportion as death invades the centre of the stem, vitality takes

284 BIOLOGY. [BOOK m

refuge and renews itself on the surface, and these two regiom
are bound together by a graduated succession of layers, more
vitalized in proportion as they approach the bark, more dead ic
proportion as they approach the centre.

NOTE.

The French, word aulier expresses better than any English word the white,
fresh tender wood between the body of the tree and the bark. — Translator.

CHAPTER III.

OP GROWTH IN THE ANIMAL KINGDOM.

JWnEN molecularly the male fecundating substance has blended
with that of the female ovulum (Fig. 40), has impregnated it, the
work of evolution, that ia to say, of generation and multiplication of
the anatomical elements, has commenced

in that ovulum. Growth commences

*in the ovulum by the inferior process
of segmentation or fractionment (Fig.

'41). Cells, all like each other, juxta-

»jpose themselves to form a membrane,
in a point of which appears the rudi-
ment of the embryon. The primitive
membrane is the blastoderm; the first

Vindication of the embryon is called Anovum
the embryonary spot. In this point the g^™ S?3±ft

iblastodermic membrane is double; it ^T^ffS^

sm, y
jping
in the

I is composed of an external vestment, 8tance or protoplasm, yolk of

7 ovum ; d, enveloping mem-

serous or animal ; and of an internal brane of *he y°* ]n *he mam~

mifers : it is called Membrana

Vestment. muCOUS Or vegetative. From pellucicla, on account of its trans-
parency.

the first vestment specially proceed,

in the vertebrates, the teguments and the organs of the life

of relation ; the second vestment gives, above all, birth to the
, apparatus of vegetative life. These first phenomena of develop-
iment are perceptibly the same in the whole animal kingdom,

from the lowest point to the highest.

286 BIOLOGY. [BOOK in.

This preparatory labour once accomplished in the ovulum, the
process of segmentation makes way before the process of genesis.
The cells of the blastoderm gradually disappear in proportion
as spring up among them by genesis the anatomical elements
destined to constitute definitively the new individual. It is
between the two blastodermic vestments that arise these first
elements. Thenceforth the difference is marked between the
invertebrated animals and the vertebrated animals. In these

FIG. 41.

First stadium of the evolution of a mammifer, " segmentation of the ovum," multiplica
tion of the cells by reiterated scissions : A, the ovum divides by a first fissure into two
cells ; B, the two cells divide into four cells ; C, these last divide into eight cells ; D the
segmentation, indefinitely reiterated, has produced a spherical mass of numerous cells.

last, in effect, we soon see traced the rudiment of the vertebral
column, the cells of the notocord (Fig. 42). This notocord en-
sheaths itself. Then we behold the formation of the first cartila-
ginous bodies of the vertebrates, and of the first elements of the
central nervous axis ; and so on. All the tissues and all the
organs thus appear little by little. At the moment of their
birth the anatomical elements are already for the most part well
characterised. Nevertheless they undergo another evolution;
they develop themselves ; azotised granulations, nucleoles, are
formed little by little in their substance ; their volume augments.
But, once arrived at their complete development, they are stable,
or at least no longer modify themselves, except regressively, to
disappear and perish. Never is an animal histological species

,CHAP. in.] OF GKOWTH IN THE ANIMAL KINGDOM.

287

, metamorphosed into another ; never, for example, does a mus-
cular fibre become a nervous fibre, &C.1

The nucleus is usually the centre of genesis and of evolution of
the anatomical element. It is the nucleus which habitually
appeal's the first ; it is after the nucleus that the nucleoles show
i themselves. Most of the elements destined to a prompt destruc-
tion, such as the haematia, the leucocytes, have no nucleus. If

FIG. 42.
Ovum of dog. The embryon in form of a shoe sole is in rudimentary shape : a, dorsal fissure ;

6, dorsal plates ; c, clear (or bright) area ; d, opaque gerininative area ; e, membrane of

the germinative vesicle.
The small superior figure is of natural size. The inferior figure is magnified.

the primitive hsematia, those which show themselves first of all
in the embryon, are furnished with a nucleus, it is probably
because they have those functions of which, at a later period,
they are deprived. In effect, in the embryon, at the moment of
the genesis of the first hsematia, there are not yet any of those
sanguineous glands called closed glands, in which new hsematia
are subsequently to be fabricated. Also the first hsematia are
completer elements, endowed with an intenser vitality, and
1 Ch. Kobin, DCS EUmcnts Anatomiqucs, pp. 47 — 54.

288 BIOLOGY. [BOOK in.

capable of engendering by segmentation other hsematia similar
to themselves.

In the animal, moreover, the histological multiplication by
scission, by segmentation, is scarcely observable, except in
elements not much differentiated ; for example, in the haematia,
the leucocytes, the epithelial cells. The superior histological
elements, the nervous cell, the muscular fibre-cell, are never
segmentised.1

When segmentation is observable, it is produced only in
elements fully developed, adult in some fashion. The small
nuclei, the small cells are not segmentised. In truth, in every
anatomical element growth has two phases : the first, during
which the element augments! merely in volume ; the second,
during which it multiplies. Both of them have equally as cause
an excess of assimilation. But in order that the second may be
produced, the anatomical element must naturally have attained
its limit of growth, and can no longer assimilate into its sub-
stance molecules of new formation.

In the adult vertebrate, the genesis of the white globules, the
leucocytes, is especially produced in the lymphatic ganglions ;
and in the sanguineous closed ganglions, the spleen, for example.
Kecent observations have shown that the venous blood coming
forth from the spleen is much richer in globules than the arterial
blood entering it.

There is great probability that the new red globules proceed
simply from the modification, the transformation of the white
globules. Thus, the venous blood of the spleen contains numerous
globules intermediate between the leucocytes and the hse-
matia. These mixed forms are met with also in great number
in the blood after a haemorrhage, or frequent bleedings, when the
sanguineous liquid is in process of regeneration.

We have previously cited a curious fact observed by Burdach,
the coloration into red of a lymphatic clot. Analogous facts
have been noted by Yirchow and Friedreich. These physiologists
have likewise seen the lymph redden in the air.
1 Ch. Robin, TUd.

CHAP, in.] OF GROWTH IN THE ANIMAL KINGDOM. 289

It would seem at the first glance as if the question of knowing
whether the anatomical elements arise by scission or by genesis
, belonged purely to the domain of science, and were dependent
solely on observation and e-xperiment. This however is by no
, means the case. This is one of the subjects which have the
j privilege of bringing into play passions by no means scientific.
, In effect, the spontaneous genesis of the anatomical elements in
. the blastemas seems to have a close connection with the theory
I of spontaneous generation, which by some is so much execrated
and mocked. But if we contemplate the matter with composure
all this fury seems to have very little justification. Two facts
. are very certain : the first, that anatomical elements multiply ;
iithe second, that they multiply by diverse processes, but in
ij general conditions which are identical. These principal facts
(dominate all others. Little it matters whether a cell arises by
I scission, by germination, by endogenesis, or by genesis. Defini-
tively the contents of an anatomical element do not differ
;• essentially from the environing blastema ; in both cases there are
)| organised substances, in the midst of which is effected the inces-
; sant molecular movement which constitutes the fundamental
i! phenomenon of life. If assimilation prevails over disassimilation
• there must necessarily result the formation of new living centres,
I of new anatomical elements, and from the philosophical point
of view it matters little whether this new formation is effected
I without or within a cell.

Observation in effect shows that in the living tissues the

I processes of scission and of genesis are sometimes associated,

I and sometimes succeed each other. Nuclei, cells even, arising

J from genesis, for instance leucocytes, can afterwards multiply by

segmentation and germination.1

According to M. Robin the advent of epithelial layers on the
surface of the cutaneous dermis and the mucous membranes

1 Ch. Robin, loc. cit., pp. 47, 48.

290 BIOLOGY. [BOOK in.

begins by the genesis of the nuclei. Between the nuclei it
produced a layer of amorphous matter, which is segmentised after-
wards and individualised into cells. As to the aristocratic
elements, such as the nervous cells, the fibre cells, they are more
the seat of this proliferation by scission.

CHAPTER IT.

OP THE GENERAL CONDITIONS OF GROWTH.

GROWTH is essentially the result of the predominance of assimi-
ilation over disassimilation, that is to say, it cannot be effected
'without the concurrence, the immediate presence of a sufficient

provision of assimilable materials. But the living anatomical
; elements seem sometimes capable of profoundly modifying and

metamorphosing these materials in a great degree. According

to M. Cl. Bernard, the larvae of flies form their organised
{tissues from substances soluble in alcohol, and consequently

deprived of albuminoidal substances, properly so called. Not-
I withstanding, as a general rule, a certain analogy of chemical

construction is necessary between the different kinds of histo-
1 logical elements and the blastemas, at the expense of which
fi these elements live and develop themselves. If, for example,
8 we transplant, by animal grafting, the anatomical elements of
|one animal to another, the operation will be likely to succeed
'in proportion as the animal species are analogous.

As to the general conditions of heat, light, oxygenation, and
; alimentation, we must refer to the chapters treating of nutrition,
«and limit ourselves to pointing out the particular facts relating
• directly to growth itself.

It has been pretended that certain animals, certain tissues, can
[live and develop themselves without oxygen. These paradoxical
if acts must only be received with extreme reserve. They have,
! without doubt, been insufficiently observed, badly elucidated, and

are included probably in the general law, according to wliich

u 2

292 BIOLOGY. [BOOK TIT. !

oxygen is indispensable to the nutrition, ancTconsequently to the
life of organised beings and their anatomical elements. Truly,
we may say of oxygen, as the ancients did of the air in general,
that it is the pabulum mice.

Like the vegetal anatomical elements, the animal elements can
only develop and multiply within certain limits of temperature.
There are, for animal and vegetal development, thermic cardinal
points which seem very near each other. The temperature of
from 30 to 35 degrees seems to be one of the most favourable,
since it is this which animals, with warm blood, maintain, in spite
of the thermic variations of the exterior medium. In his experi-
ments in embryogeny, M. Dareste has observed that elevated
temperatures constantly determine, first an acceleration of the
evolutive phenomena, then their premature stoppage ; whence
nanism. On the contrary, lower temperatures much retard the
progress of development ; they even stop the evolution, and do
not permit the embryon to advance beyond a certain period.1

The influence of the seasons is attended by analogous results.
In man, and most animals, the maximum of grow this in summer,
and the minimum in winter.

If, by means of an artificial hatching apparatus, we, as M.
Dareste has done, limit the influence of the source of heat to a
fixed point of the embryon, we can, by varying the position of
the ovum, obtain all the types of simple monstrosities described
in the treatises on teratology.

The rapidity of nutritive exchanges, and consequently of
growth, is closely connected with the abundance of liquids within
the living tissues. In ligneous vegetals, the fibres have less
vitality in proportion as they harden. Plants, with loose tissues,
loaded with juices, grow more quickly than vegetals with dense
tissues,

In the same way, amongst animals, the histological elements
are less impregnated with humidity in proportion as the animal

1 Expost, des Titres et des Travaux Scientifiques de M. Camille Dareste.
Paris, 1868.

CHAP, iv.] OF THE GENERAL CONDITIONS OF GROWTH. 293

is aged. The muscular fibre of a young animal contains 26 in
100 of water; that of an adult of the same species only 23,5.
Haller, comparing the different degrees of cohesion of human
hair according to age, found that at eight years of age this
cohesion was represented by 10, at twenty-two by 17, and at
fifty-five by 25.1

The degree of fluidity of the anatomical elements is great in
proportion to the youth of the animal, and the rapidity of reno
vation and of growth is correlative with it. According to the
tables of Quctelet, the growth of man is two-fifths the first year,
a seventh the second, an eleventh the third, a fourteenth the
fourth, a fifteenth the fifth, and eighteenth the sixth and seventh.
It is only a sixty-eighth at eighteen years, and a two hundredth
at nineteen.

Upon the subject of the advantageous influence of suitable
humidification upon growth, Burdach points out that, in many
aquatic animals, fishes, amphibious, and cetaceous animals, growth
lasts as long as life, and is only gradually and more and more
retarded.

The nutritive characteristic of youth is the rapidity and
facility of nutritive exchange. This is why the phenomena of
colouration and discolouration of the bones by madder are effected
with much greater rapidity when the animal is young.

With the advance of age, all the secretions are impoverished,
especially the cutaneous perspiration ; at the same time the
general oxydation of the tissues lessens, the production of heat
diminishes ; all the functions become less energetic ; some are
extinguished by degrees, especially those of the most differen-
tiated histological elements, those most noble, least vegetative,
those of the nervous and muscular elements. Strength decreases,
and intelligence is blunted.

This is because the ruling property of the living substance
gradually declines. Nutrition becomes less and less active, and
all the other properties of which it is the support decline with
1 Burdach, TraiM de Physiologic, t. V. p. 491.

294 BIOLOGY. [Boos in.

it. In the higher vertebrates this decline of nutrition is im-
mediately attended by slackening of the pulse and of the
respiration. The animal offers less resistance to low tempera-
tures, often succumbs to them.

During youth, assimilation prevails over disassimilation. In
old age the case is reversed. The tables published by Quctelet
show that the weight of the body diminishes from the fiftieth
year in man, and the sixtieth in woman. At ninety years this
weight is reduced in the former from 136 to 123 Ibs., in the
latter from 120 to 103 and a half.

The average duration of life varies, in the two organic king-
doms, with the species.

In general, the lower organisms live a shorter time than the
higher organisms. Less richly endowed with organs and ap-
paratus, less differentiated, they harmonise less readily with the
exterior medium and its variations. At the longest, mushrooms
only live a few days. The infusoria sometimes complete the
cycle of their life in a few hours, and most of the invertebrated
animals have only a short existence.

In general, life is short in proportion to the rapidity of growth
and of embryonary evolution. Aptitude for generation being in
some degree a sign of the full development of the organised
being, it is natural that its tardy appearance should be connected
with greater longevity. In fact, this is the case with most of
the vertebrated animals. In many invertebrated animals the
appearance of the generative functions is, on the contrary, the
forerunner of death. Numbers of insects die immediately after
having procreated. The male butterflies die even sometimes in
accomplishing the act of generation. The ephemerides live one
or two years in the state of larvse, and only a few hours as
perfect insects.

In plants, fructification is also a supreme act, presaging a
complete and speedy death in herbaceous plants, a partial death
in the perennial vegetals. The celebrated saying of Proudhon,
" Love is death," is then in this case an exact expression of the

CHAP, iv.] OF THE GENERAL CONDITIONS OF GROWTH. 295

truth. So true is it, that we may sometimes abridge or lengthen
life by accelerating or retarding the moment of reproduction.
If, by means of a rich manure, we cause biennial plants to
fructify during the first year of their existence, they die that
same year. On the contrary, the mignonette is rendered ligneous
and long-lived by cutting its flowers before the formation of the
j seed.1

Insects themselves live much longer when they are prevented
from pairing.

Death may be general or partial. This latter is frequent in
all organisms with a feeble physiological centralisation, in vegetals
and in many lower animals. It is even not uncommon in the mam-
mifers. Inversely, in these latter, the partial life of certain
elements, especially of the epitheliums, often continues after
general death, characterised by the cessation of the three pri-
mordial functions, circulation, respiration, and innervation.

Death may ensue through simple old age, in consequence of an
extremely gradual slackening of the molecular movements of
nutrition. It then takes place without pain, without illness,
without agony, sometimes without consciousness, and may even
be accompanied by a certain feeling of comfort ; it is then the
eutlianasia of Plato.

Pinel has observed that at the Salpetriere most of the nona-
genarian women died without any shock, and often in their sleep.

Death is, in fact, only a final cessation of nutritive exchanges.
Every being, every anatomical element which ceases to assimilate
and disassimilate, returns consequently to the mineral world.
The materials which constituted it then undergo purely chemical
unfoldings, decompositions, and disaggregations.

During the life of a complex organism, many of its histological
elements perish, without their death being in any way prejudicial
to the life of the whole. Sometimes the elements of certain tissues
become mutually compressed, and thus, by simple pressure, cause
the gradual disappearance of some of them. Sometimes the
1 De Candolle, Organographie Vegetale, t. II.

296 BIOLOGY. [BOOK in.

anatomical elements liquefy, as the embryonary cells do nor-
mally : this is what is called ulceration. On the surface of the
skin and of the mucous membranes and in the glands, thousands
of epithelial cells incessantly detach themselves, fall, and
dissolve.

Even in the web of the deep tissues, a number of histological
elements disappear by simple resorption, and are either replaced
or not by elements of new formation.

All that has gone before shows clearly that life is a thing
modifiable and variable in intensity and duration. , In certain in-
dividuals it is prolonged two or three times beyond the average
life of their species. Thomas Parr was married at a hundred
and forty-two years, and was still fit to accomplish the act of
generation. He died at the age of a hundred and fifty-two ; and
Harvey, who made the post-mortem examination, found his
muscles still full and well developed, the viscera in a good state,
and no ossification of the cartilages.1

A large number of examples are on record of partial rejuven-
escence in old men. White hair has become again black, and
new teeth have appeared. In other cases, with aged women,
the menses and the aptitude for fecundation have reappeared.
We have ourselves seen once, in the case of a woman more than
sixty, white hair replaced by black, after erysipelas of the hairy
scalp.

In truth, death is a necessity to all the organised beings of
our planet ; but it is not a fatality. As Ch. Robin says,2 " No
scientific contradiction would hinder our conception of a perfect
equilibrium between assimilation and disassimilation indefinitely
repeated in all existing beings, without interrupting the con-
tinuity of that molecular renovation, and without a decomposition
of the organised substance ensuing .... The anatomical ele-
ment or organism, once produced, once born, may be supposed to
present a perfect equilibrium of indefinite duration between the

1 Philosophical Transactions, 1669.
« Ch. Robin, EUm. Anat., p. 96.

CHAP, iv.] OF THE GENERAL CONDITIONS OF GROWTH. 297

act of assimilation and that of disassimilation. " Condorcet had
already written : " Would it be absurd now to suppose that the
perfectionment of the human species may be regarded as sus-
ceptible of indefinite progress, that a time must come when
death will only be the effect either of extraordinary accidents,
or of the more or less gradual destruction of the vital forces, and
that finally, the duration of the average interval between birth
and this destruction has no assignable term ? Doubtless, man
will not become immortal ; but may not the distance between
the moment when he begins to live and the ordinary epoch
when naturally, without illness, without accident, he experiences
the difficulty of existing, be ceaselessly increased ? " l

To dare now to assert that it is not impossible to conquer
death, the great enemy, is to expose ourselves to an accusation
of madness. The animist and vitalist doctrines fail ; they have
lost all credit with science ; but a yoke borne for a long time
always leaves a permanent impress, and, in the domain of
opinion, the effect often long survives the cause. For centuries
life has been considered as a mysterious, miraculous fact, beyond
all investigation. Each organism was regarded as a monarchy
despotically governed by a metaphysical entity. It was believed
that the problem of life must eternally defy the power of human
science. It was &fatum, against which it was useless to struggle.
Such is still the prevailing opinion ; but it exists only by force
of habit. The phenomenon of life has been analysed. We know
that it is the result of simple molecular exchanges, comparable
to those that take place in an electric pile. That there is in the
vital phenomena something immutable, predestined, no one can
now maintain. Every living being conserves itself as long as
there is in it a certain nutritive equilibrium, as long as assimi-
lation and disassimilation are almost equally balanced. Now it
is certain that the duration of this equilibrium depends upon
an infinity of causes, internal and external. Of two children
born, one may live ar hour, the other half a century. There is
1 Coadorcet, Progres de I'Esprit Humain.

298 BIOLOGY. [BOOK in.

neither law nor rule when the course of life is abandoned to the
hazard of events, as always happens. A priori, it is surely not
impossible, an organised being given, to maintain indefinitely in
it the tide of life at a constant watermark, and it seems to us
that science is now sufficiently armed to attack boldly this
great problem. It would be necessary to bring observation and
experiment to bear first of all upon very simple organisms, whose
normal life is very short. We should commence by determining
the average duration of that life when the organism is abandoned
to itself. Then, being guided as much as possible by scientific
facts already acquired, we should vary in a hundred ways the
light, the temperature, the alimentation, the composition of the
atmosphere, &c., &c., noting carefully the effect of each new
factor, of each variation of medium.

Furthermore, we should scrutinise the conditions of life and
of organism in the species remarkable for their longevity, then
in individuals whose duration is exceptionally long. Evidently
the investigation itself would suggest new modes of research.
We should fail, or we should succeed. In any case, something
useful would result from this labour.

In fact, biology will not be a complete science till it has
learned to comprehend life. A man of science, who cannot
without injustice be accused of philosophical temerity, has
already proclaimed this : " The physico-chemical actions, which
manifest and regulate the phenomena belonging to living beings,
are included in the ordinary laws of general physics and
chemistry" (p. 4).

" . . . . There is only one system of mechanical philosophy,
only one system of physics and of chemistry, which comprehend in
their laws all the phenomena which take place around us, either
in machines living or machines dead. Under the physico-
mechanical relation, life is only a modality of the general
phenomena of nature ; it engenders nothing, it borrows its forces
from the outer world, and only varies its manifestations in
thousands and thousands of ways " (p^ 135).

CHAP, iv.] OX THE GENERAL CONDITIONS OF GROWTH. 299

"By modifying the inner nutritive and evolutive mediums,
and by taking the organised matter in some degree from its
birth, we may hope to change its evolutive direction, and conse-
quently its final organic expression. In a word, I think that we
can produce scientifically new organised species in the same way
that we create new mineral species, that is to say, that we can
cause the appearance of organised forms, which exist virtually in
the organogenic laws, but which nature has never yet realised"
(p. 113).

" Life is extinguished, and natural death takes place, only
because the production of the plastic element stops, and because
then the passive tissues become impregnated and incrusted with
mineral and other matters, which cramp their functions, and
lessen more and more the nutrition, or the genesic formation of
the active histological elements" (p. 126).

" To sum up, what the physiologist wants, is to be able experi-
mentally to direct the evolutive phenomena in such a way as to
modify the nutrition of the organised matter, in order thereby
to change more or less the duration, the intensity, or even the
nature of its vital properties" (p. 129).

" Up to the present time, physiology has been struggling with
transitory ideas, which will disappear in proportion as science
advances. With regard to physiology, we are just at the point
where alchemy was before the foundation of chemistry. The
views which may now be expressed with relation to the modes
of action of the physiological experimentalist will only be the
result of gropings more or less vague ; but, nevertheless, these
acts will not be less positive, and the scientific principle of
general physiology cannot remain doubtful or uncertain. Phy-
siology, like all the terrestrial sciences whose phenomena are
within our reach, must become in time an active experimental
science upon the phenomena of life" (p. 219).

" When the progress of general physiology shall have shown
the experimentalist the special organic elements upon which ho
acts, and he shall have learned to master the conditions of their

300 BIOLOGY. [Boon in.

activity, then he will have acquired the power of scientifically
modifying and regulating the phenomena of life. He will ex-
tend his dominion over living nature, as the natural philosopher
and the chemist have acquired their power over the phenomena
of inert nature. ' ' 1

1 Cl. Bernard, Rapport sur Us Prorjres de la Physioloyie Ginirale en France.

NOTE.

The reader is anew reminded that when degrees of heat are mentioned the
Centigrade scale is always implied, so that thirty and thirty-five degrees
Centigrade correspond respectively to eighty-six and ninety-five degrees
Fah renheit — Translator.

V

BOOK IV.

OF GENERATION.
CHAPTER I.

OF THE ORIGIN OF ORGANISED BEINGS.

WITHOUT remounting to the cosmogonies so fascinating and so
probable of Kant and of Laplace, we must admit, with con-
temporary geology, that the earth was formerly in the state of
incandescent globe ; that during numerous cycles it was absolutely
uninhabitable for the organised world we now know. We are
compelled therefore to admit that the first living beings spon-
taneously organised themselves at the expense of mineral matter.
The first inhabitants of the earth were, we know, of an extremely
simple structure. The monera of Haeckel, some types of in-
fusoria, the rhizopods perhaps — such are the existing organised
beings which best recall to us those primitive ancestors of the
organic world. But the Darwinian doctrine, which results with
such evidence from palaeontology, from embryology, from the
well hierarchised classification of the organisms, demands as its
indispensable complement spontaneous formation, without germs,
without parents, of the first examples of the living world.

In the scientific domain any logical and necessary deduction or
induction ought to be admitted without contest, though it may
shock old ideas and shatter old dogmas. This is far, however,

302 BIOLOGY. [Boon iv.

from being the case. The same religious and metaphysical pre-
judices which have been so deeply disquieted by the doctrine of
organic evolution are still more alarmed and annoyed by the
idea of spontaneous generation of any kind. It is only step by
step that those antiquated theories yield the ground to scientific
demonstrations. First of all it was denied that organised matter
had in itself the faculty of living. The equilibrium was only
maintained, it was thought, in every organised being through the
perpetual intervention of an entity, of an archeus, of a vital
principle, of a soul, and so on, guiding and governing the vital
phenomena as a charioteer conducts a chariot, to use the expres-
sion of Tertullian. It becomes, however, unavoidable to admit
that there is no metaphysical dualism in the plant and in the
animal, but that they both live because they both combine in
themselves the conditions necessary and sufficient for an inces-
sant nutritive renovation. The doctrine of evolution has had
the same destiny. Not many years ago all naturalists, or almost
all, believed in the perfect immutability of the organised species,
and, as every epoch had its special fauna and flora, it was neces-
sary to recognise, with Cuvier, as in effect was done, a series of
successive creations, of visible or organic changes. When God,
irreverently compared to the machinist of an opera, whistled
once, an implacable cataclysm annihilated all the living world ;
when he whistled a second time, but creatively, a new fauna and a
new flora rose to life. Thus had things to go on at every geo-
logical epoch. From the tribolite to the mammoth every species
had thus to be formed by magical crystallisation. Assuredly
there was here a spontaneous generation of the most astonishing
kind, but it shocked no one, because it was in more or less tacit
accordance with metaphysical and religious ideas. But little by
little the idea of miracle has been driven from this domain as
from so many others. It became inevitable to confess that the
geological epochs had not been separated by abysses, that the
cataclysms, where there had been any, had only been partial ;
that the modifications and transformations of the soil had been

CHAP, i.] ON THE ORIGIN OF ORGANISED BEINGS. 303

produced little by little, slowly, by this patient labour of accu-
mulated ages. But this new geological doctrine was incompatible
with the sudden destructions and creations of the organised
world. If the habitat had been slowly modified, it was necessary
to believe that the inhabitant had been slowly modified too.
The grand doctrine of organic revolution created by Lamarck,
completed by Darwin, has come then to demonstrate the muta-
bility of the organised species, and to furnish the genealogy
thereof. It was a real revolution, and many naturalists have not
decided for or against it ; but nevertheless, the tide is gradually
rising. The doctrine of evolution is already almost triumphant.
There scarcely remains for the recalcitrants any other resources
than to demonstrate its perfect agreement with the dogmas they
are not willing to abandon. The thing is in process of execution.
The interpreters are skilful, the sacred texts obliging, the
metaphysical theories ductile, malleable, and flexible. Courage !
We must be very narrow-minded indeed not to recognise in the
first chapter of Genesis a succinct exposition of the Darwinian
theory.

But if the doctrine of evolution makes us descend step by
step to the most rudimentary organised beings, it does not go
further ; and we must admit, at least here, the intervention of a
spontaneous generation. This consequence is revolting to many
men of science who accept all the rest. They reject the notion
that matter has in itself the power of self -organisation in certain
given conditions. Yet many of these rebels formerly believed
in the spontaneous generation of the mammoth at a time when
the doctrine of successive creations was in vogue. But now,
rather than resign themselves to the cruel necessity of admitting,
even as a simple possibility, spontaneous generation, they prefer
resuscitating the old theory of errant germs.. The interplanetary
spaces are, they think, bestrewn with germs, born we know not
how, coming we know not whence, and waiting we know not how
long, for a passage to a planet sufficiently mature to serve them
as nourishing receptacle, as matrix.

804 BIOLOGY. [BOOK rv.

Such puerilities as these are surely far more difficult to admit
than the spontaneous formation of some very simple living types
at the outset of the organic world, even though many observa-
tions and experiments do not plead very eloquently in favour
of spontaneous generation even at our epoch. Certain vegetal
parasites develop themselves under the epidermis of living
plants. Whence can come the seeds of these entophytes which
appear even in plants destitute of stomata 1 l Microscopic mush-
rooms spring up and live in the citrons. The forester Hartig
found some in the cavities of the ligneous part of trees, under
numerous sound annual layers. Marklin has seen the white of
a hen's egg converted into sporotrichum. Very recently vibrions
were met with in the pus of a closed abscess. In his Histoire
des Helmintlies, M. Dujardin speaks of the rhabditis aceti, which
dwells exclusively in wine vinegar, and is found neither in the
vine nor in grapes. Whence then does it come ? And especially
where were its germs when man made neither wine nor vinegar ?

The cause of generation spontaneous, equivocal, heterogenical
has moreover never ceased to have partisans. No one has de-
fended it with more force, perseverance, and talent than F.-A.
Pouchet, from whom we now propose to borrow some arguments.

Most of the organic macerations abandoned to themselves, at
a suitable temperature, at the end of a time which varies, but is
tolerably short, are peopled by vegetal and animal proto-organisms.
According to the adversaries of lieterogenesis, these myriads of
new beings proceed from germs floating in the air. But whoso
says germ says ovulum, that is to say, cell of a diameter perfectly
appreciable in the miscroscope, for the ovulum of certain ciliated
rnicrozoa varies from Omm0028 to Omm,0420 in diameter.

Now, if by the aid of the aeroscope of Pouchet, we examine
microscopically one cubic decimetre of air, by making it pass
through an orifice of a quarter of millimetre of section, that is
to say by drawing it out to a length of 4000 metres, it is only

1 F.-A. Pouchet, Nouvelles Experiences sur la Giniration Spontanee et sur la
Resistance Vitale, p. 117.

CHAP, i.] ON THE ORIGIN OF ORGANISED BEINGS. 305

very exceptionally that we find the ovum of a ciliated microzoon
or the spore of a mucedinate.

If, by the help of an eight-horse motive power, we project on
diverse macerations of plants 6 million litres of that atmospheric
air which is said to be full of germs, we see that the macera-
tions, exposed to this torrent of ovula, do not become richer
in infusoria than those which are imprisoned in a single cubic
decimetre of air.

"We obtain spontaneous generations by making use of artificial
water and air, and even of oxygen, instead of air.

When we mingle together two different fermentiscible liquids,
we find, in the mixture, organised beings different from those
which the liquids when separate contain.

In experimenting simultaneously with calcined air, a body
heated 200 degrees, and water which has undergone ebullition,
we obtain animal and vegetal proto-organisms. Now not one of
the reproductory bodies resists boiling water. But the following
experiment is assuredly more convincing still.

A vessel of crystal Om,30 in diameter is washed with sulphuric
acid and filled with distilled boiling water. Then we plunge
therein 10 grammes of filaments of flax heated for two hours to
150 degrees. We cover it afterwards with a receiver, and we
place it in the centre of another large vessel Om,50 in diameter,
filled with distilled water. We keep it at a temperature of 28
degrees, and at the end of four days the maceration is filled
with paramsecia, while we do not find one of these animals, and
not even one of their ova, in the large vessel.1

But why do the so-called floating germs persist so obstinately
in being invisible 1 In effect, atmospheric micrography finds in
the air nothing but particles of fecula of wheat or some very small
particles of silex. The ovula, the spores are so rare that
habitually we do not meet with a single one in a cubic decimetre
of air.

Ae'rian germs being sc rare can only very slowly people infu-

1 F.-A. PoucLet, loc. cit., p. 122.

X

306 BIOLOGY. [BOOK iv.

sions. Some ovula may fall thereinto first* of all, be evolved, and
give birth to organisms which may multiply little by little.
Now in a fermentiscible liquid, we see at the outset a very thin
mucous pellicle forming on the surface. Then suddenly appear
in this pellicle many small lines, pale, immobile, ranged side
by side in a certain disorder. These lines have the form and
the diameter of bacteriums, and in effect, at the end of some
hours we see them take animation and become living bacteriums,
moving rapidly in a straight line.

Gerard had noted, at the time of the appearance of proto-
organisms in the macerations, a certain evolutive order. In the
maceration of hay we see, the second day, specimens of the
bacterium termo simple, whose articulations augment little by
little. Then come monads, and at the end of fifteen days we
find trichods, colpods, the proteus tribe closing the series.1

F.-A. Pouchet has likewise demonstrated this evolution, % and
has drawn from it a whole theory.2 According to him there
appears, first of all in the macerations, an ephemeral population
of vibrions and monads. These proto-organisms die. Their
debris and their dead bodies mount to the surface, fall asunder,
dissolve more or less, and all these detritus form a sort of
membrane, which organises itself anew, engendering ovula of
superior infusoria, microzoa with vibratile cilia. At certain
points of this pellicle, which Pouchet calls proligerous membrane,
we see granulations accumulate, mass themselves into a kind of
spheroidal nebulae. Then this nebulous substance becomes a true
ovular cell, surrounding itself with a translucid membrane, with
& bright zone. Finally this ovulum is evolved. We observe
therein the gyration of the content or vitellus, the formation of
the embryon, and the fifth day comes forth a rameciate.

The same maceration gives, or does not give, birth to ciliated
microzoa, according as its pioligerous pellicle is more or less
thick.

1 Gerard, Dictionrtairc d' Histoire Naturelle, art. GENERATION.

2 F.-A. Poucbot, loc. cit., p. 110.

CHAP, i.] OF THE ORIGIN OF ORGANISED BEINGS. 307

If we place the hatf of a given liquid in a vessel with a
narrow surface, and the other half in a vessel with a broad
surface, the proligerous pellicle of the narrow vessel is much
thicker than that of the broad vessel. For in the one vessel and
in the other has been produced an equivalent generation of
vibrions and of monads ; but in the broad vessel the residua have
been obliged to spread themselves over a larger surface. They
have not, for this reason, been able to form a proligerous
membrane sufficiently compact, and no ciliated infusorium is
created.

Certainly these are very eloquent facts. A last fact let us
cite. There was poured into a porcelain basin with a flat bottom
the paste of boiling flour, about a centimetre in thickness. Then,
when this paste commenced to congeal, there was written on its
surface, with a pencil, imbibed with a strong maceration of
gall nut powder, previously examined in the microscope and
nitrated, these two words : — gentratio spontanea. The basin was
then covered with a sheet of glass, and left to itself for four days.
The temperature was 24 degrees on an average, and the pression
0,76 during this space of time, at the end of which the words
generatio spontanea were seen traced in black. These characters
were formed by crowded tufts of a microscopic mushroom
absolutely unknown, with stalklets simple, cylindrical, not articu-
lated, and with capitula of a beautiful black. M. G. Pennetier
proposes to call this new organic species Aspergillus primigenius,1
Many other topical facts can be found in the publications of F.-
A. Pouchet, and of his rivals MM. G. Pennetier and Mantegazza,
Joly and Musset, to which we must content ourselves with refer-
ring. The short extracts we have just given suffice to show that
the doctrine of spontaneous generation does not merit the vulgar
disdain with which it is assailed. Its partisans are able to rely
on serious arguments drawn from observation and experiment.
It ;s evidently not enough to oppose to them dogmatic contradic-
tions and some questionable chemical experiments.
1 G Pennetier, Origines de la Vie.

x 2

308 BIOLOGY. [BOOK iv.

The facts observed by F.-A. Pouchet lender moreover spon-
taneous generation much more intelligible. In effect, the birth
of infusoria, at least of the more complex infusoria, seems to be
preceded by the formation of a sort of living blastema, in the
heart of which the ovula originate, exactly as they originate by
spontaneous genesis in the blastemas of animals and plants.

What radical difference is there between the formation of the
ovula in the proligerous pellicle of F.-A. Pouchet and the for-
mation of cellular elements under the microscope in saccharine
serum ? It is one of the adversaries of spontaneous generation,
M. Cl. Bernard, who affirms that he had observed this last fact
of veritable heterogenesis.1 We must allow him to speak him-
self : — " I have observed that in saccharine serum, under the
influence of a mild temperature, there are developed amyloidal

productions perfectly analogous to the white globules

In a drop of saccharine serum, completely transparent, and in
which the microscope reveals to us nothing, there are soon formed
leucocytes,. or globules of beer yeast."

1 Cl. Bernard, Rapport sur les Progrte de la Physiologic, &c., pp. 210, 217.

I CHAPTER IT.

OF GENERATION IN THE TWO KINGDOMS.

GROWTH is only an excess of nutrition, and generation is only
an excess of growth. Growth and generation have for cause a
superabundance of nutritive materials. This superabundance
has for effect first of all to carry the anatomical elements to
their maximum volume, then to provoke the formation of new
elements. As long as the individual has not attained all the
development compatible with the plan of his being, the elements,
newly born, remain aggregated to the pre-existent elements.
When the limit of growth is attained, when there is no longer
room in the organised individual for a new adjunction of histolo-
gical elements, the newcomers detach themselves from their
organic stem and constitute independent individuals which
evolve in their turn.

Generation is so much a continuous growth, that its processes
are identical with or analogous to those of growth. Definitively,
in growth as in generation, those processes reduce themselves
to two : the process of segmentation and that of genesis, which
however can aid each other and combine their action.

Division (scissiparity, fissiparity, and so on) is observable in
the majority of the lowest representatives of the two kingdoms.
It is habitually the division into two parts which is then in
use, bipartition, sometimes longitudinal as in the vorticels,
sometimes transversal, as in the hydrae, the acalephans (Fig. 43).

310 BIOLOGY. [BOOK iv.

It is by bipartition that the polypiers are produced and the
humblest seaweeds and mushrooms -multiply.

FIG. 43.

Reproduction by segmentation of an elementary organism, amoneron: A, entire moneron.
(protamoeba) ; B, the same moneron divided into two halves by a median fissure ; C, the
two halves have separated, and constitute now independent individuals.

At a higher degree of organisation it is no longer the
whole organism which is divided. The function is localised.
There is formed, often by genesis, a special cell, the ovulum,
charged to reproduce a new organic individual. This cell
always commences its labour of organic construction with a
series of bipartitions, with a segmentation ; whence result
numbers of new cells, of bricks, which are the first materials
of the future edifice. But usually to be fit to traverse its whole
evolutive cycle, the ovular cell needs a special impulsion. It has
to blend with another anatomical element, likewise special. The
element which segmentises and multiplies itself is called female.
That which impresses on it the evolutive impulsion is called
male element, and the process of union is one of the simplest :
it is the process of conjugation of which we have previously
given an example. The two cells come into contact : the female
element absorbs the male element, impregnates itself therewith,
and from that moment it is fecundated, and pursues the course of
its formative labour. In the two kingdoms everywhere there
are sexuality and fecundation ; whatever may be the complica-
tion o£ accessory organic apparatus, the fundamental fact

CHAP. IL] OF GENERATION IN THE TWO KINGDOMS. 311

reduces itself always and everywhere to the conjugation of two
cells, and the absorption of one by the other. The names
change, but the phenomenon is essentially the same, whether
we contemplate the oosphere and the anther ozoids of the algae, the
embryonary sac and the pollen of the phanerogams, the ovulum
and the spermatozoaries of the animals. The oosphere, the em-
bryonary sac, the ovulum are simple varieties of the female
element, as the antherozoids, the pollinical cells, the sperma-
tozoaries are varieties of the male element.

Between the organisms in which reproduction is effected by
simple bipartition, and those in which it is only possible after
the fusion of a female cell and a male cell, that is to say, after
a fecundation we can place the cases of parthenogenesis, the most
celebrated example of which is that of the aphides. Here the
intervention of the male cell is only necessary after long
intervals. If it has once taken place it suffices for the forma-
tion of a series of ovula, to which it is no longer indispensable,
and the female can afterwards engender, without the co-operation
of the male, a whole line of young. But little by little the
field of evolution is abridged for each new ovulum : the pro-
ducts are more and more imperfect, more and more incomplete :
finally the evolutive force of the ovula is extinguished, is
exhausted, and their revivification by a new sexual, impregna-
tion becomes the very condition itself of generation.1

In most plants, in a great number of inferior bisexuate
animals, the male and female apparatus are united in the same
individual. Then autofecundation is often possible : sometimes
also it is impossible. But even in the first case the diversity of
origin of the male and female sexual elements is a condition
most frequently favourable, sometimes indispensable to fecunda-
tion. The observations and experiments of Sprengel and Darwin
have demonstrated that nearly all hermaphrodite plants need, to
fructify, a cross fecundation. To use the expression of Darwin,

1 See Cl. Bernard, Des Phinomlnes de la Vie communs aux Animaux ct aux
(Kevue Scienttfque, 1874).

312 BIOLOGY, [BOOK iv.

" Nature tells us in the most evident manner that she has horror
of a perpetual atitofecundation."

The female ovulum can be fecundated at various moments of
its evolution, at various degrees of maturity, and it is probable
that the epoch of fecundation has an influence on the future
direction of this evolution, which has not an immutable character.
"We shall see in effect, further on, that disturbing causes, even
though slight, acting on the fecundated ovum, can make the
embryonary development vary in a very large measure. That
even the production of the one sex or the other may be connected
with the degree of maturity of the fecundated ovulum is not, a
priori, an inadmissible supposition.

Girou de Buzareingues demonstrated in the female slips of
phanerogamous dioic plants with the flowers in clusters, that the
male or pollinical cells, when they fell on the whole cluster and
fecundated all the flowers thereof, produced very various results
according to the degree of maturity of the ovula. At the lower
part of the cluster, where the most advanced flowers are found,
the fructification gave male seeds, while the flowers less ripe,
those at the top of the cluster, produced female seeds.

Starting from this idea, and supposing that the complete
maturity of a female ovulum might be very favourable to the
production of the male sex, and inversely, M. Thury, of Geneva
(1863), caused cows to be impregnated, sometimes at the com-
mencement, sometimes at the end, of the rutting period. In the
first case he obtained female calves ; in the second, male calves.
The experiment was recommenced by a Swiss agriculturist, M.
Cornay, who, twenty-nine times in twenty-nine cases, succeeded
in producing at will such or such a sex.1 These are positive facts
which are not weakened in any considerable degree by contra-
dictory observations, almost all susceptible of different inter-
pretations ; and assuredly the question deserves to be taken up
afresh and seriously studied.

In the preceding fact an observation made on ovular develop-
1 Cl. Bernard, loc. tit.

CHAP, ii.] OF GENERATION IN THE TWO KINGDOMS. 313

ment in the vegetal kingdom has been extended and applied to
the animal kingdom. In truth, if we remount to the primordial
phenomenon of sexual generation, we find it nearly identical in
the two kingdoms. The animal ovulum and the vegetal ovulum
are rigorously comparable.

The animal ovulum is a cell, which, at first, is not distinguished
from many other histological elements by any observable
characteristic. This cell is composed essentially of an envelop-
ing wall, of a protoplasmic content, of a nucleus. It has been a
mistake therefore to give to these diverse plants of the ovular
cell special names, tending to give the notion that they represent
things without analogy, when in reality the differences are
purely virtual. The faculty of reproduction, of generation,
considered in a general manner, by no means specially appertains
to the ovular cell. It is merely developed more and more with
a longer range in the ovulum than in the other cells.

Let this be as it may, it is indispensable to know the names
given by the embryologists to the diverse parts of the ovular
cell. The enveloping membrane, which is hyaline and trans-
parent, and whose projection has, in the microscope, the appear-
ance of a ring, has been called transparent zone, zona pellucido.
The content or cellular protoplasm of this envelopment, a
substance more or less viscous and granulous, has been called
vitellus. The ovular protoplasm or vitellus contains a nucleus
which hollows for itself a way from a cavity and then bears the
names of germinative vesicle, vesicle of Purkinje. Finally, this
nucleus contains a nucleole, which is the germinative spot.

In the most perfect of the sexual vegetals, the phanerogams,
that which habitually is called ovulum is nearly equivalent to
the ovarium of animals. In the cellular tissue with polyhedrical
elements which this ovary contains, and which is called nucula,
is found the real ovulum, which has been called the embryonary
sac. It is an oval cell, whose wall represents the vitelline membrane
of the animal ovulum. Its content is a mucous, granulous, and
greyish protoplasm, manifestly equivalent to the vitellus. Finally,

314 BIOLOGY. [BOOK iv.

the nucleus or embryonary vesicle of the botanists is comparable
with the germinative vesicle. "We distinguish besides therein
a nucleole, which seems thoroughly to correspond to the germi-
native spot. The differences between the embryonary sac of
plants and the ovulum of animals bear only on the dimensions
or the number of the nuclei. The embryonary sac has in effect
dimensions relatively considerable, and it contains sometimes
two or three nuclei or embryonary cells.

With regard to generation as with regard to all the grand
biological facts, we see evermore revealed the unity of life. We
shall have to signalise many other analogies in the pages which
have to follow and which are to be consecrated to a descrip-
tion of the principal phenomena of generation in the two
kingdoms.

CHAPTER IIT.

OF VEGETAL GENERATION.

ASEXUATE generation is observable in certain algae, especially the
confervae. It is accomplished by endogenesis. The protoplasm of
certain cells contracts first of all, by separating from the wall, and
usually divides afterwards, segmentises into many new cells.
Then the enveloping membrane of the mother cell opens and
is reabsorbed. The daughter cells escape and swim in the
water, eddying, thanks to the movements of two or more
vibratile cilia. These zoospores, as they are thus called, end
by fixing themselves and germinating (Fig. 44).

Other algae are endowed with sexuate generation, either in
its simplest mode, which is conjugation, or in its complete mode,
with male cell, female cell, and fecundation. In the first case
(ulothrix, chlamydococcm, pandorina) two cells analogous to the
zoospores in movement meet and melt into each other. When
there is sexuality, the phenomena still offer great simplicity
The female element is represented by a cell, whose protoplasm
contracts while separating from the cellular wall. This small
protoplasmic mass, thus modified, and ready to evolve, is called
oosphere, and the envelopment is called oogon. In other cells
the protoplasm transforms itself into mobile elements very
analogous to the spermatozoaries of animals. These fecunda-
tory elements are denominated anther ozoids, and the cell which

316

BIOLOGY.

1 [BOOK iv.

contains them and has engendered them is called antheridion
(Fig. 45). Once set at liberty, the antherozoids penetrate into the
oogon, by a special opening, and confound themselves with the
mass of the oosphere which they impregnate.1

1)

FIG. 44.

A, zoospore covered with vibratile cilia.

B, zoospores furnished only with two vibratile cilia.

C, evolution of a zoospore of Vaucheria : a, filament before the fructification ; &, at the
extre mity of the ii lament an accumulation of protoplasm has formed, whence is to proceed
the zoospore ; c, zoospore, almost completed, and already furnished with its enveloping
membrane, projects beyond the filament.

D, Numerous zoospores set at liberty.

Apart from the abundance of organs, of apparatus, which in
the highest animals are the means of generation, the same
description of fecundation could serve equally for the algse and

1 Sachs, TraiU de Botanique. p. 285.

CHAP, in.]

OF VEGETAL GENERATION.

317

for man. So great is essentially the simplicity of biological
i phenomena of the first order.

When the oosphere has absorbed some antherozoaries, generally

of a volume much inferior to its own, it has become capable of
i pursuing the course of its evolution : it is fecundated. We see

it then envelop itself with a solid membrane, fix itself, and

germinate. It has, in a word, become an oospore.

FIG. 45.

A, extremity of an antheridion filament formed of cells juxtaposed and containing each

an antherozoid.
B and C, antherozoids in the state of liberty.

D, antherozoid of an aquatic fern.

E, fragment of an antherozoid of Vaucheria twisted spirally (a 9. From the extremity of this
antheridion come forth antherozoids having the form of short rods. By the side of the
antheridion is found the oogonion (s), or saclike cavity full of ovular corpuscles. At a
point of the oogonion situated in face of the extremity of the antheridion is formed an
orifice by which penetrate these antherozoids. Then these antherozoids impregnate the
ovula, which evolve or cover themselves with an enveloping envelope ; in short
become oospores.

The modes of reproduction of mushrooms are very varied, as
regards the accessory apparatus : but essentially the processes of
generation are perfectly comparable with those of which we have
just spoken. Sometimes the reproductory bodies, or spores, are
formed without fecundation ; sometimes fecundation is necessaiy.
These spores are sometimes immobile, sometimes mobile, and

318 BIOLOGY. [BooK iv.

furnished with vibratile cilia; consequently they are in every
respect similar to the zoospores of the algae. But definitively,
the spores are formed at the expense of certain cells, and if they
are multiple they result from a repeated bipartition of this proto-
plasm. What matters it, after this, that they are produced or
not on the filaments of a mycelium, that they are gathered
together or not in the cavity of a receptacle, or sporangium, of
this form or of that ?

The system of reproduction by oospheres and mobile anthero-
zoids exists also in the characese, the muscineae, and the ferns.
The form of the antherozoid varies, but usually it is a filament
more or less elongated, mobile, furnished or not with vibratile
cilia. Always the antherozoid is formed at the expense of the
protoplasm of special cells or antheridia whose wall is torn or
reabsorbed. Before the dehiscence or disappearance of this wall,
each antherozoid, habitually alone in the mother cell, is rolled two
or three times on itself (Fig. 45). As to the apparatus containing
the female corpuscules, they vary much in form, and have for that
reason received diverse names ; but generally the antherozoid s do
not penetrate into the receptacles of the oospheres (archegons)
except through a soft mucilaginous substance. Once in contact
with the oosphere or oospore, the antherozoid confounds itself
with it, and as happens usually after all fecundation, the oospore
segmentises itself by bipartition, and the embryonary develop-
ment follows its course.1

The phenomena of reproduction and fecundation are manifestly
the same in the phanerogams. We have already spoken of the
embryonary sac, of the embryonary cells which it contains. The
fecundating agent is no longer here an antherozoid ; it is the
granulated viscous substance (favilla) contained in the particles
of pollen. These particles are of very varied form, but have all
a double enveloping membrane (endhymenine, exhymenine). It
is well known that from contact with the humidity of the stigma,

1 J. Sachs, loc. tit., pp. 391, 318, 401, 439.

CHAP, in.] OF VEGETAL GENERATION. 319

the particle of pollen swells by endosmosis, that its internal
membrane forms a hernia filled with f avilla (pollinised content),
and penetrates thus to the embryonary cells. The fecundation
• is made by the intense blending of the f avilla, and of the contact
of the embryonary cell. The fecundated cell always develops
itself, and forms by division a mass of spherical cells, whence
proceed the cotyledons and the embryon.

1,1 It \{ A U V

UNI VKKSITY OF

CALIFORNIA.

X

CHAPTER IV.

OF ANIMAL GENERATION.

THE two living kingdoms were probably identical originally, as
the naturalists, partisans of evolution, try to demonstrate by
patient researches and ingenious pictures of affinity. Assuredly
there still exist many points of union between the two grand
divisions of the organic world, and there is no differential
characteristic constant and applicable to all animal and vegetal
species. We must therefore expect to meet with a great anal-
ogy between the principal phenomena and even the grand
processes of reproduction in the two kingdoms.

At the lowest degrees of the animal hierarchy, in the beings
little or not at all differentiated, for example in the polypi, the
morphological centre of the whole creature seems to exist in
each of the cells, and any portion whatsoever of the body can
reproduce the whole animal. It is in the species thus endowed
with an enormous power of reparation, of regeneration, that
fissiparous reproduction is especially observable. The individual,
on attaining his maximum of growth, overflows, so to speak,
beyond his natural limits ; he unfolds himself, and forms, by
simple division, a new individual (Fig. 46). This process of
multiplication acquires sometimes an extreme energy, if it is
true, as M. Balbiani affirms, that in forty-two days a paramecium
can produce, by fissiparity, 1,384,116 new individuals, that is to
say, that a single animal, Omm,2 long grows 277 metres in bulk.
We see then the body of the infusorium lengthen, thereupon

CHAP, iv.] OF ANIMAL GENERATION. 321

narrow toward the middle, and form thus a couple conducted
by the anterior individual. l Finally the separation is effected,
and each of the halves completes itself. The na'ids divide them-
selves in the same manner transversally into two parts, of which

FIG. 46.

Amoeba sphcerococcus, in the different stages of its evolution. A, encysted amoeba. Proto-
plasmic mass (c). containing nucleus (fe), nucleole (a), and enveloping membrane (d). B,
amoeba freed from the enveloping membrane ; C, amoeba commencing to divide itself ;
L>a and D6, amoeba totally divided into two independent parts.

i the anterior remakes itself into a head, and the posterior into
I a tail.

It is by germination or gemmiparity, that is to say, by a
'variety of fissiparity, that are formed the aggregations, the
colonies of the zoantharies. Sometimes the bud detaches itself,
playing the part of a vegetal spore or bulbille, and goes to form
an independent individual.

Many monadaries seem to reproduce themselves solely by
gemmiparity. This mode of generation exists sometimes alone,
sometimes associated with sexuality, sometimes alternating with
this last in many inferior animals. In the hydras or fresh-water
polypi we easily see the young hydras budding on the mother
hydra. Their body at first communicates with the cavity of that
of the mother, and is nourished at the expense of the same until
the moment when the new individual is in its turn furnished with
prehensile tentacles capable of seizing its prey.

* Dugfes, Physioloyie Comparte, t. I. p. 213.

322 BIOLOGY. [BOOK iv.

Internal gemmiparity, endogenesis, is observable in the olvoces,
the acephalocystes, and so on. The cavity of the animal fills
itself with vesicular animals similar to the mother vesicle.
Certain of these newcomers, those the most developed, contain
themselves other individuals, which in their turn contain others ;
so that three generations are thus inclosed one within the
other.

According to M. Balbiani many fissiparous or gemmiparous
species are at the same time capable of sexuality, but of an
alternant sexuality. 1 In the green paramecium (Paramecium
bursaria) the sexuate cells pre-exist ; they enlarge at a given
moment. In the largest of these cells ovula with a nucleus and
a nucleole are formed. In the smallest the intercellular sub-
stance divides into small bacilla, which are spermatozoaries
charged with fecundation.

This hermaphrodite sexuality enters into action at a determi-
nate epoch. The scissiparous process would exhaust itself little by
little, would end by no longer producing any but puny, imperfect
individuals, and would lead to absolute sterility, if sexuality did
not come to give to the reproductive property a new vigour.

The lowest mode of sexual reproduction, conjugation, i»
observable in the colpods. Two individuals unite, encyst them-
selves, and blend into one common mass. Then this common
mass reproduces by fractionment new individuals.

The mode of copulation of the green paramecium recalls still,
though faintly, conjugation. In its sexual phase, each para-
mecium is provided with reproductory bodies male and female,
as we have recently seen ; but nevertheless, — a thing, however,
frequent among the hermaphrodites, — the fecundation is mutual.
Two individuals juxtapose themselves mouth to mouth during a
duration of many days, and they exchange their spermatozoids.
It is an example of the horror which Nature has of autofecun-
dation, to use Darwin's expression. Many hermaphroditical

1 Balbiani, Sur T Existence d'une Generation Sexuelle chez les Infusoires
(Comptes Jtendus de I'Academie des Sciences, t. XLVI).

CHAP, iv.]

OF ANIMAL GENERATION.

323

i invertebrates are provided with the genital apparatus of the two
i sexes ; but these apparatus are so arranged that autofecundation
is almost impossible.

Sometimes, however, especially in the bivalvous mollusks, for
j the most part fixed and immovable, there is autofecundatory
hermaphrodi sm.

On the whole, a general fact results from the examination
of generation among the inferior animals, — the great diversity
of processes, and also a sort of confusion in their employment.
The species are still ill differentiated ; there is in the plan ofc
their organism a sort of indecision. Nature, to use the language
of Darwin and of many others, seems to hesitate, to grope ; she
has not yet found the best way, and tries all ways simulta-
neously. But when the sexuality is well marked, when there is
formation of a male cell and a female cell, the primary acts of
reproduction and fecundation assume an almost uniform character.
In all animals, the female cell, the ovulum, is nearly identical.
At first the ovulum differs in nothing from an ordinary cell, if
we do not allow ourselves to be led astray by the special names
invented by the embryologists. The
complete ovulum is composed in effect of
an enveloping membrane, the vitelline mem-
brane, or zona pellucida, of a content or
protoplasm, the vitellus, of a nucleus or

, . • 7 p 11 •

germinative vesicle, or a nucleole or germi-
native spot (Fig. 47).

According to M. Van Beneden, there FIG. 47.

are in the ovulum an accessory part and ovulum of woman magnified

, . -i mi , i-ii 250 times : a. pellucid zone ;

an essential part. The last, which he &, vitellus ; c, germinative
calls cell-ovum, has in all the animal Sative^^ ** ger"
kingdom an identical evolution, and

is represented solely by the nucleus of the ovulum, by the
germinative vesicle, and a small part of the vitellus which sur-
rounds it.1 It is certain, at all events, that the germinative
1 Cl. Bernard, loc. tit.

Y 2

324 BIOLOGY. [BocK iv.

vesicle is the least variable part of the ovum. It can be double,
and then gemelliparity seems constantly to result therefrom.
This is what takes place at least in certain species, especially in
the Vortex balticus, in which this duplicity of the germinative
vesicle is the rule.1

The cellular content or vitellus is likewise called yellow, very
improperly, however, for its colour is very variable. In effect, it
is, according to species, white, yellow, red, brown, green, violet,
and so on, and is usually composed of a liquid more or less
viscous, holding in suspension granules, and often fatty globules.

The vitelline or enveloping membrane is also exceedingly
diverse. Often it is a transparent, anhysted membrane ; some-
times it is a simple albuminous layer. In certain species it is
covered with designs, with grooves, with reliefs. At other
times, as happens in the ovulum of fishes, it is pierced with
holes, with micropylse, which facilitate the impregnation of the
ovulum by the spermatozoaries.2

We must then consider the nucleus of the ovulum as a germ
englobed in a mass purely nutritive, which is the vitellus.

The ovulum of viviparous animals differs very little as to
volume, whatever the size of the animals may be. That of the
oviparous anynals is much larger, is sometimes indeed very
voluminous ; but the increase bears on the nutritive portion of
the ovulum, the vitellus, whicn in birds acquires an enormous
development.

What distinguishes the ovulum from every other cell, even
before fecundation, is the rapidity of its evolution. There is
a whole series of phases, of modifications, through which it
passes in a very short space of time, without even undergoing
the fecundating impulsion. Soon, in the whole animal series,
the ovulum loses its first differentiation ; the nucleus and the
nucleole (vesicle and germinative spot) disappear, and seem to
melt into the vitellus. The ovulum is then nothing more than

1 Leydig, TraiU d'ffistologie, p. 620.

2 Leydig, loc. tit., pp. 616, 617.

CHAP, iv.]

OF ANIMAL GENERATION.

325

an imperfect cell composed of an enveloping membrane and of
a mass of granulations.

At the same time the vitellus is drawn back toward the centre
of the cell, and a transparent zone then separates the cellular
membrane from the granulous content (Fig 48 A). Another phe-
nomenon, the utility of which is not yet well known, is afterwards
produced. It can take place also independently of fecundation.
It is the emergence of the polar globules. According to M. Ck
Robin, these globules are formed by a sort of vitelline germination.
We see successively appear on the surface of the vitellus two

FIG. 48.
A, ovum of she dog immediately before the B, ovum of she dog some hours later. The epi

commencement of segmentation. Tlie
contraction has given to the vitellus a
polyhedrical form.— a, epithelial colls ;
c, space between the contracted vitellus
(d) and the vitelline membrane or pellucid

thelial cells are further diminished ; the
vitellus separated into two segments or
spheres of fractionment. Between these
two halves are seen the bright vesicles (c)
called vesicles of direction. The letters as
before.

or three projections, which take the hemispherical form, and
separate by division from the mass which has engendered them,
remaining interposed between the cellular membrane and the
vitellus. These are the polar globules (Fig. 49, A e).

All the evolutive phenomena which we have just signalised
can be accomplished before fecundation ; they can also be posterior
thereto. But in certain species the spontaneous ovular evolution
goes much further, since, in the cases of parthenogenesis the
whole development of the embryon is effected without the succour
of fecundation. This ovular generation, without males, this
parthenogenesis, which the doctors of Catholic theology are sure

326 BIOLOGY. [BOOK iv.

to invoke one day in support of their mysteries the most impor-
tant and the most improbable, is not rare in the animal kingdom.
Many examples thereof can be cited, of which the most celebrated
is the parthenogenesis of the pucerons, signalised first of all by
Bonnet.

But for the most part the spontaneous evolution of the
ovulum does not go further than the emergence of the polar
globules. If then the fecundation does not intervene, the ovulum
withers and dissolves. In the contrary case, it undergoes the
important phenomenon of fractionment, that is to say, a series
of fissiparous divisions, of bipartitions. Fissiparity has certainly

FIG. 49.

First stadium of the evolution of a mammifer, " segmentation of the ovum," multiplica-
tion of the cells by reiterated scissions : A, the ovum divides by a first fissure into two
cells ; U, the two cells divide into four cells ; C, these last divide into eight cells ; D, the
segmentation, indefinitely reiterated, has produced a spherical mass of numerous cells.

been the first process of reproduction of the rudimentary
organisms, and it still exists in the state of transitory phase, of
organic tradition, in sexuate generation. The phenomenon is one
of the simplest. After the disappearance of the vesicle, the
retraction of the vitellus, the emergence of the polar globules, the
vitellus narrows in the middle, and is thus severed into two granu-
lous masses, of which each is divided in its turn into two halves,
and so on in succession, till the moment when the whole vitelline
mass is transformed into a heap of globules, spherical, granulous,
destitute at first of enveloping membranes and of nuclei, then

CHAP, iv.] OF ANIMAL GENERATION. 327

completing themselves little by little. They axe then vitelline
cells, the agglomeration of which gives to the ovular surface the
appearance of a mulberry (Figs. 49 and 50).

Soon after their appearance the vitelline cells displace them-
selves ; they come and fix themselves on the internal face of the
ovular membrane (vitelline), and thus form a membrane, limiting
a hollow sphere full of an albuminous liquid. This membrane
has been called blastoderm, and the
cells which compose it become the
llastodermic cells (Fig. 50). It is
at their expense that the embryon
forms itself.

The vitelline fractionment is a
general phase of ovular evolution ;
but it is not always accomplished
uniformly. In birds, in fishes, in
testaceous reptiles, in the cephalo-
podal mollusks, it is partial ; a por-
tion only of the vitellus takes part

therein. Then the blastodermic Orum of rabbit taken in the uterus.—

, . , £ £ a, pellucid zone; ft, blastodermic vesi

membrane, instead OI forming a cie formed of hexagonal cells, in sym-

, TT -, -, . , metrical conjunction like the bricks

noilOW spnere, becomes a Simple f0f a pavement] ; c, accumulation of

spherical calotte, and the portion ™ie™lc<

of the vitellus not employed plays merely the part of a nutritive

substance.

i

In the ovum of insects, of the arachnida, of certain crusta-
ceans, there is produced, instead of a regular series of biparti-
tions, an irregular cleaving, whence results the formation of
unequal fragments. But these fragments end by grouping
themselves into polyhedrical masses.

Whatever besides may be the form and the extent of the blas-
todermic membrane, it is not long in unfolding into two super-
posed membranes. This division is especially perceptible at
the point of the blastoderm, whither go to form themselves the
first lineaments of the embryon. The external blastodermic

328 BIOLOGY. [BOOK iv.

vestment has been called serous or animal vestment, because it
is the rudiment of most of the apparatus and organs of the
animal life. The internal vestment is called mucous or vegetative
vestment. From it proceed the nutritive apparatus.

Finally the cells accumulate at a point of the blastoderm, and
form there a sort of spot called the embryonic spot. It is there
that the embryon develops itself.

In their ensemble the phenomena we have just described are
common to all vertebrated and invertebrated animals, endowed
with sexuate ovulation. But, starting from the formation of
the embryon, differences arise corresponding first of all to the
two great branches of the animal kingdom. To follow step by
step these differences would be evidently to go beyond the limits
assigned to us. "We must content ourselves with indicating
some general facts.

The division of the animal kingdom into the vertebrated and
invertebrated branches is of all the most general, the most im-
portant. Also it is marked at the very outset of the embryonary
x,e volution. In the vertebrated ovulum the embryonary spot
elongates into an ellipse, rises in the middle after the fashion of
a buckler, and at this point the serous vestment hollows out for
itself a rectilinear furrow (primitive line, nota primitiva). The
edges of the furrow rise more and more, and in the depth is formed
a solid cellular cord, a sort of provisional scaffolding, round which
the vertebral column is to be formed. This cord is the notocord or
dorsal cord (Figs. 51 and 52).

It is to special treatises that the reader must go to follow the
ulterior phenomena of development, the formation of the um-
bilical vesicle, of which the content serves still for the nutrition
of the young being, that of the amnios, which envelopes it in
an aqueous medium, the origin of the placenta or of the vascular
organ, which, in the superior viviparous vertebrates, establishes
a communication between the circulatory system of the mother
and that of the embryon, when this last has exhausted the
nutritive resources of the vitellus.

CHAP, iv.]

OF ANIMAL GENERATION.

329

A very important general fact, of which the partisans of the
evolutive or Darwinian doctrines make great use, and with y
justice, is the identity of the embryonary forms at the outset J
in all the vertebrates, and the appearance in a regular and/

FIG. 51.

Ovum of dog. The embryoa in form of

shoe sole is outlined.
o, dorsal fissure ;
fc, dorsal plates ;

c, clear area ; *

d, opaque germinative area ;

e, membrane of the germinative vesicle.
The small superior figure is of natural size.

The inferior figure is magnified.

FIG. 52.

Embryon of a dog's ovum, twenty days old.
Dorsal fissure widely open and surrounded
everywhere with a bright edge, which indi-
cates the first deposit of the nervous sub-
stance on the depth and the walls of the
fissure. In the depth is seen on the median
line the chorda dorsalis represented by a
darker stripe. — a, ft, c, rudiments of the cere-
bral vesicles ; e, posterior rhomboidal sinus ;
d, body of primordial vertebrae ; /, lateral
plates ; g, middle and external vestments of
the blastodermic vesicle, still united; h,
mucous vestment; i, body of the embryon.

successive order of the characteristics of each type. We may
compare the embryons of the vertebrates to a group of travellers
starting from the same place, and entering first of all a vast
general route, which they forsake to enter roads of more and more
secondary importance, and diverging less and less. It is first of

830 BIOLOGY. [BOOK iv.

all fishes which differentiate themselves; then reptiles, then
birds, then mammifers ; finally the diverse mammiferous types.
The less individuals are to differ in the adult state, the more
tardily their embryons differentiate themselves. It is at the
last period of development, for instance, that the embryon of a
monkey can be distinguished from the embryon of a man, and
there is a moment when both do not differ more from the em-
bryons of a fowl or of a tortoise than they differ from each
other.1 It is difficult not to see here, as the partisans of evolu-
tion are inclined to see, a sort of living palaeontology, an abridged
picture of the formation of diverse animal types, such as has
been accomplished in the course of the cycles which have rolled
away.

The development of the fecundating element is at first so
analogous to that of the ovulum, properly so named, that it has
not unjustly been called the male ovulum. Wherever sexuate
reproduction exists in the two kingdoms, the male element is
primitively a complete cell, containing a protoplasm comparable
with the vitellus and a nucleus analogous to the germinative
vesicle.

These male ovula, according to the testimony of many ob-
servers, seem usually to be formed by spontaneous genesis, as
well in the anther of phanerogamic giants, as in the special
apparatus of animals.

Once the male cell formed and arrived at a certain degree of
maturity, its granulous protoplasmic content undergoes, spon-
taneously, a phenomenon, which vividly recalls the fractionment
of the fecundated female ovulum. The last elements of that
f ractionmeiit, which are generally in an even number, resemble
each other much in most of the cryptogamic plants, and in all
the animal kingdom. They are cells, whence comes forth finally
a mobile corpuscule, called spermatozoid in the vegetal kingdom,
and spermatozoary, or zoosperm, in the animal kingdom. The cells
of fractionment, each of which produces, as a male, only one of
1 Huxley, Man's Place in Nature.

CHAP, iv.] OF ANIMAL GENERATION. 331

these fecundating corpuscles, have been called, always by
analogy, male embryonary cells.

In the phanerogamic plants the male ovula are the great cells,
•which are called pollinical utricles, and the products of their
fractionment are pollinical cells, each of which ends by represent-
ing a particle of pollen. It is the content of these particles of
pollen, or favilla, which is the fecundating substance. The evolu-
tion is here less complete than that of the male embryonary cells.
In effect, these last resemble at first, almost identically, the
pollinical cells. But arrived at a higher degree of maturity, they
differenciate themselves more, and their content becomes sper-
matozoary, or spermatozoid. If the content of the particles of
pollen does not organise itself into corpuscles, endowed with a
movement of totality, it is not, nevertheless, completely im-
mobile, and the granulations observable therein are animated by
movements comparable besides with those which are effected in
many other vegetal cells. Whatever, moreover, may be the
apparent dissemblance between the favilla of the particle of
pollen and the mobile fecundating corpuscle, spermatozoary or
spermatozoid, the phenomenon of fecundation does not, on that
account, change in its essence. On the whole, the fecundating
substance penetrates always into the ovulum, and when once it
has arrived there its molecules sever and untimately blend with
those of the female ovulum.

The form of the spermatozoaries and of the spermatozoids is
somewhat variable. These fecundating elements are globulous
in some vegetals ; they are also globulous in the myriapods and
some crustaceans. But in general they are more or less filiform,
and at one point swelled out. They have already this form in
the male embryonary cells, when, before the rupture of those
cells, they are seen to be rolled spirally (Fig. 53).

As a rule the enlarged part of the spermatozoary is at one of
its extremities. This part is of variable form, cylindrical, spheri-
cal, oval, elongated to a point, and so on. The spermatozoaries
of the mammifers have a somewhat short head and a caudal

332 BIOLOGY. [BOOK iv.

filament long and thin. But the form of the spermatozoary
seems to be secondary, for certain animals have simultaneously
zoosperms of two different forms, (Paludina vivi-
© <* © para.)1 The filiform part is the locomotory organ
of the spermatozoary. The movements produced
by this sort of vibratile cilium are moreover very
varied. They are sometimes movements of repta-
tion, sometimes movements of torsion, sometimes
flutterings, sometimes spirally penetrating move-
ments.2 There are no immobile spermatozoariea
among the vertebrates. They seem, however, to be
very numerous among certain invertebrates, especially
| the crustaceans. But probably their rigidity is only
FIG. 53. apparent, and ceases as soon as they penetrate into
ofrnraan T^a, the body of the female. It is certain that even the
e,6tai£ &> b° 7 ' mobile spermatozoaries of man and of the mammif erg
move with much more velocity when they enter the
mucus of the uterine neck or body. Their rate of progression)
however, is infinitely less than it appears in the microscope,
According to Henle it is only eighteen hundredths of a milli-
metre a second in man. The rate of progression varies muct
with the nature of the ambient medium. It increases in ar
alkaline solution, — diminishes, on the contrary, in an acid
medium.

Since the discovery of the spermatozoaries, by Leuwenhoeck,
the question has often been asked whether the spermatozoariej
were or were not animals. Certain micrographers, partisans ol
the first opinion, have gone so far as to assert that the sperma-
tozoaries of the mammifers are differentiated animals. Some
have even thought that they had testicles. Judged by our present
instruments of observation, the spermatozoaries are absolutely
without structure, are very inferior in this respect to the vibratile
epithelial cells, with which they have been compared. We must
consider them special anatomical elements, superior to most of
1 Leydig, loc. cit., p. 600. 2 Ibid., p. 554.

CHAP, iv.] OF ANIMAL GENERATION. 333

the other histological elements by their motility, and especially
by their fecundating property, veiy inferior on the other hand by
their structure.

All the particles of pollen, all the spermatozoids and sperma-
tozoaries are endowed with the fecundating property. But it seems
established by experiments of artificial fecundation, that a single
particle of pollen, a single spermatozoary cannot alone fecundate
an ovulum. The ovum needs veritably and literally to be impreg-
nated with fecundating molecules. There is a certain minimum
which does not suffice to give the necessary impulsion.

We have seen what great analogy exists between the male
ovulum and the female ovulum. In the inferior animals and
even in the superior animals, at a certain period of embryonary
evolution, the analogy extends to the whole male and female
generative apparatus. At a particular moment of the intra-
uterine life it is impossible to distinguish the male embryon from
the female embryon, and in many invertebrates the difficulty
persists during the whole duration of life, to such a point indeed
that men like Cuvier, Carus, and Blainville never succeeded in
distinguishing from each other the ovarium and the testicle of
the gasteropods.1

The ovulum and the sperm atozoaries have another property in
common, the property of reviviscence. Spermatozoaries desiccated
can get back their motility after a very long time, when they are
humected anew ; and M. Davaine was able to keep for five
years, without killing them, in a solution of chromic acid, at
2 in 100, the eggs of the lumbricoid ascarides of the Greek
tortoise. As for the vegetal seeds, we know that some of
them can still germinate after thousands of years.
1 Duges, loc. cit.t t. I., p. 231.

CHAPTER V.

OF REGENERATION.

IT is impossible to terminate an exposition of generation without
saying some words on regeneration, which essentially does not
differ from it. We must satisfy ourselves with mentioning
the general laws of regeneration, without describing the innu-
merable series of particular facts which everybody knows.

It seems to result from modern micrographical observations
that there is identity between primordial phenomena of the first
generation of the tissues in the embryon, and those of their
regeneration in the adult. In both cases the elements of the
newborn tissues are formed by spontaneous genesis in the midst
of an organisable blastema. In the animal embryon this forma-
tive blastema results from the liquefaction of the embryonary
cells : in the adult animal it is formed by the anatomical elements
of the conservated tissues. But in both cases the spinal tissues
do not appear all at once : they are first of all preceded by a
transitory generation of nuclei and of cells called embryoplastic,
to which at last succeed the special histological elements.

The lower an animal is placed in the hierarchy, the greater the
degree of regenerative faculty he possesses. In this case there
is still physiological confusion. There are no elements specially
charged with reproduction. Every histological element pos-
sesses then in the state of indi vision, the fundamental properties
of nutrition, of development, of reproduction. All the world
knows that in the inferior animals we can make with full

CHAP, v.] OF REGENERATION. 335

success artificial fissifarity. The Polypus brachiatus, the earth-
worms, the naids, the planaries can be sectionised with impunity.
Each isolated fragment lives its own life, completes itself, and
becomes an entire animal.

We can even thus create monsters. For instance, by section-
ising longitudinally a planary to the half of its length, Duges
was able at the end of a few days to obtain a bicephalous
planary.

When an inferior animal is sectionised transversally into two
parts, it is the more differentiated, the more centralised the part
which completes itself the first. In a Polypus brachiatus it is
the buccal portion which first renews itself. In the earthworm
the anterior fragment remakes for itself a tail before the pos-
terior part succeeds in. refashioning a head.

In all cases the organs of new formation are regenerated at
the expense of the blastemas of the portion which they complete.
When a snail remakes a head, when the tail of a lizard grows
again, when, as Spallanzani has observed, a salamander regene-
rates a new tail with the nerves, the muscles, the vertebrae, the
vessels, the skin thereof — when it creates anew claws, the lower
jaw, and so on, all this labour of reconstruction is achieved
without augmenting the weight of the trunk which has remained
alive. The animal has become again entire and complete, but it
is enfeebled, diminished. This is why it is impossible to renew
indefinitely the operation without causing death. The head of
the earthworm, for example, cannot be reproduced more than
twice or thrice. This is also the reason why the regenerated
is often smaller than the old and more imperfectly fashioned
part.

By an inexplicable singularity regeneration is sometimes the
more certain, the larger the portion taken away is. When
Reaumur merely broke one or two joins of the anterior claw of a
crab, the loss was not repaired. On the other hand, the whole
claw was regenerated when it had been entirely removed.1
1 Reaumur, Memoires de V Academic des Sciences, 1712.

336 BIOLOGY. [BOOK iv.

Regeneration being simply, like generation, an exaggeration of
the property of nutrition, it is natural for it to be the prompter
and easier the younger the individual is. It is operated, in
effect, more easily in youth than in the period of maturity,
and more easily in the larva than in the complete animal. The
young salamanders reproduce their claws more easily and more
completely than the old. The sectionised tail of the tadpole
grows again the faster the younger the animal is. The perfect
insect does not reproduce its antennae, while this regeneration is
accomplished with facility in its larva ; and so on.

The faculty of regeneration — and this is a very singular fact
at the very outset — seems to be almost peculiar to the animal
kingdom. It exists little, or not at all, in plants. A leaf or a
branch when cut is not remade. This fact comes in support of
the theory which considers every complex vegetal as an aggrega-
tion, a sort of colony of polypiers, of which the diverse parts have
their own, their individual life. Every leaf, every bud lives
on its own. account, and the diverse parts of the vegetal are
connected with each other by a very feeble solidarity.

In the superior animals and in man we do not see, as in the
inferior animals, an entire organ, complex, composed of diverse
tissues, reproduce itself in totality. But all the tissues, except
perhaps the striated muscular fibre, can be reproduced isolately
and in small portions.

It is a factr of vulgar notoriety and often utilised in surgical
therapeutics, that great quantities of osseous tissue can be
regenerated, and even very promptly, provided the vascular
membrane of the bone, the periosteum is uninjured.

The regeneration of a tissue is the easier the more this tissue is
differentiated, the more delicate and noble are the functions to
which it appertaineth. Yet, in conflict with this general pro-
position, the muscular striated tissue can be little if at all
regenerated, while the reproduction of the nervous tissue is not
rare. A sectionised or even a resectionised nerve remakes
itself from the injured point to its furthest ramifications, and

CHAP, v.] OF REGENERATION. 337

according to M. Ranvier it regenerates itself by traversing all the
phases through which it has already passed from the beginning
of its foetal development. The nervous centres, the central
hemispheres even, seem to be able to restore themselves in a
certain degree. How otherwise explain a large number of incon-
testable cases of complete re-establishment of the intellectual
faculties after serious lesions, and even after notable losses of
substance of the encephalon ?

No doubt, the biological facts, like all the phenomena of the
universe, obey laws, true laws, inflexible, and without exception.
But those facts are so complex, so intermingled, the ensemble of
their causes forms a skein so entangled, that the most of our
pretended biological laws are simply imperfect generalisations,
suffering many exceptions and always subject to revision.

BOOK V.

OF MOTILITY.
CHAPTER I.

OF THE BBOWNIAN MOVEMENTS.

THE general properties of organised matter, with which we have
so far been occupied, are closely connected with the truly funda-
mental biological property, nutrition ; to speak correctly, they
are only its dependencies. It is otherwise with that which we
have now to examine. Doubtless, the faculty of movement is
subordinate to nutrition, which is the very essence of life, but it
differs from it ; it is, as it were, superadded to it.

Before proceeding further, it is important to distinguish care-
fully between motility, an organic property, and movements,
essential attributes of every organic and inorganic matter. At
the present time, most men of science, and a certain number of
thinkers, have finally broken with the old metaphysical distinc-
tion, which, with one stroke, cut the universe into two parts,
having between them only relations of contingency. We have
ceased to abstract the active qualities of the material substance
from the substance itself ; we no longer figure the world to our-
selves as constituted by an extended substance, but in itself
perfectly inert, ceaselessly incited and put in motion by an im-
palpable agent called force. The ancient divorce no longer

340 BIOLOGY. [BOOK v.

exists. Force is espoused anew to matter, from which moreover
it was never separated, except in the brain of metaphysicians.
There tis no longer inertia in the universe. Behind all these
phenomena is concealed an extended substance, never immobile,
and which is itself its own mover. If we still often speak of
forces, it is from pure habit, or by pure artifice of language. In
final analysis, the idea of force may always be brought back to
movements of an active material substance.

Without speaking even of the planetary movements, which
carry everything along, we know that those bodies most solid
and immovable in appearance resolve themselves into atoms
and molecules, ceaselessly animated with rapid movements.
Naturally, these molecular movements also take place in organ-
ized bodies. There, they are varied very differently, since
these bodies are nourished, that is, are the seat of incessant
molecular exchanges, and are decomposed without intermission
to be recomposed.

The molecular movements are, then, effectuated in every living
substance, but all living bodies are not endowed with motility.
Motility may be defined as the property which certain organized
bodies have, either of totally changing their position in space,
or of contracting, or of becoming shorter, or of modifying for
the moment their form, spontaneously and independently of any
mechanical action of exterior origin.

Definitions, with whatever precision we may endeavour to
give them, are always adjusted with difficulty to all the peculiar
facts which they embrace. There are certain movements, for
example, which we do not very well know how to classify ; we
wish to speak of movements still incompletely studied, and
known under the name of Brownian movements. The botanist,
Robert Brown, was the first to prove that the fine particles of
mineral dust, well pounded, moved, apparently spontaneously,
when held in suspension in a liquid medium. In fact, all
corpuscles having from three to four thousandths of a millimetre
in diameter, execute in liquids, under the microscope, a kind of

CHAP, i.] OF THE BROWNIAN MOVEMENTS. 341

oscillation, with an alteration in position of from four to five
times their diameter. It is difficult to attribute to simple liquid
currents, as has often been done, these movements, which seem
rather due to phenomena of attraction at a short distance, and
must be brought back to the domain of capillarity. Now almost
similar movements are also observed in certain organic sub-
stances. Thus, when leucocytes or infusoria are disaggregated,
they resolve themselves into granulations animated with very
lively Brownian movements. Must we consider these move-
ments as organic or inorganic? "We scarcely know; and the
distinction becomes still more embarrassing with regard to the
movements of the pollinical favilla, of which we have already
said a few words.

A number of observers, Needham, Amici, Guillemin, &c., &c.,
have occupied themselves with the movements of the favilla, or
rather of its corpuscles. The last of the observers whom we
have just named has even attempted to compare them with the
movements of the spermatic animalcules. Robert Brown had
already observed these movements, and he had also seen them
in pollinical particles, especially in the ovoid and transparent
particles of the pollen of gramineous plants. These movements
have even a singular persistency, since R. Brown said that he
found them still in particles of pollen preserved in a herb-
arium for twenty- five years. Moreover, Alex. Brongniart has
noticed some interesting peculiarities regarding them. In one
case, particles of pollen having burst in water, the granulations
of the favilla of the pepo were still animated with their ordinary
oscillatory movements, and were displaced. The pollinical
granulations of several other species (hibiscus palustris and
syriacus, rosa bractea, &c.), curved inwards and changed their
form.

Doubtless, there is nothing organic in the Brownian move-
ments of mineral particles, but they are nearly similar to the
Brownian movements of the debris of white globules, and of
disaggregated infusoria, and these last resemble the oscillations

342 BIOLOGY. [BOOK v.

of the favilla, which, in certain species mentioned by Brongniart,
have truly the appearance of spontaneous and organic move-
ments, since the granulations not only incurve and change in
form, but are, besides, paralysed by contact with alcohol and
various other substances, which nev«r happens to the mineral
particles.

It seems, then, that there may be, in the phenomena which we
have just mentioned, a kind of gradual transition from inorganic
movement to organic motility. But many purely organic move-
ments take place in the two living kingdoms, and it remains for
iis to enumerate them, and to indicate, as far as possible, their
conditions and laws.

CHAPTER II.

OF MOVEMENTS IN THE VEGETAL KINGDOM.

shall first of all set aside, as foreign to our subject, the
slow insensible movements of the stems and roots, which depend
upon development, growth, &c., and whence result, for example,
the direction of the stems towards the sky, of the roots into the
soil, the spiral twisting of certain stems, &c.

On the contrary, the movements of certain species of confervse
strongly recall those of animals. In fact their filaments balance,
lower, raise themselves, twist themselves, and oscillate ; and so
on. Heat and light accelerate them ; cold and darkness retard
them. Acids, alkalis, alcohol, &c., suppress them.

We have already pointed out the movements of the spores and
of the antherozoids. In a number of phanerogamic species, the
various parts of the flower execute extended movements. Certain
flowers open in the day and shut in the night, or inversely.
This phenomenon even takes placfe habitually, in each species, at
a certain hour, so that by choosing suitable species, Linnaeus could
form what he called Fiords clock.

The movements of the petals depend much upon heat and light.
It is only between 8 and 28 degrees that the flower of the crocus
opens. Below this it does not open at all ; above, it shuts. At
a constant temperature, any abrupt variation of light tends to
decide the blowing of the flowers of the crocus, the tulip, and of
compound flowers ; every abrupt diminution tends to close them.

In cellars, lighted at night by lamps, and kept in darkness

344 BIOLOGY. [BooK v.

during the day, De Candolle has seen flowers, habitually diurnal,
open in the evening and shut in the morning. Flowers of
nocturnal habits changed also inversely.1

Movements of the stamens are also common and generally
more rapid than those of the petals. The best known are those
of the stamens of the berberis vulgaris. When irritated by any
kind of contact, these stamens bend towards the pistil, and
scatter their pollen upon the stigma ; after which they stand
upright again, and approach the petals. The movement of the
stamens is sometimes spontaneous and successive ; thus Humboldt
has seen the stamens of the Parnassia palustris approach each
other one by one, and by jerks of the pistil, scatter their pollen
three times over the stigma, and resume their first position.
Certain venomous substances abolish these movements of flowers.
Flowering branches of species having petals or mobile stamens
are paralysed, when their stems are plunged into various solutions
(prussic acid, water of bitter almonds, alcohol, ether, acetic acid,
ammonia, &c.). The movements stop as soon as the venomous
liquid, by absorption, reaches the mobile organs.2

When once fecundation is accomplished, the vitality of the
flower diminishes, and the movements cease.

Many plants have leaves which execute each day a regular and
periodical movement. They have a diurnal position, a nocturnal
position, and pass slowly from one to the other. Moreover,
certain of them are excitable by various contacts, mechanical
agents, light, &c., so that accidental movements are superadded
to the diurnal movements. It is peculiarly in the leguminous
plants, especially the mimosas and oxalidese, that the slow move-
ments of wakefulness and slumber are most easily observed.
They are caused by the variations of the luminous intensity, and
are specially due to the action of the most refrangible rays.3

The species most celebrated for the mobility of their leaves

1 Memoires preseiites k 1'Institut.

2 Goeppert, De acidi hydrocyanic! vi in plantis comvientatio. Breslau, 1827.

3 J. Sach's, loc. cit., p. 1029-1031.

CHAP. IL] OF MOVEMENTS IN THE VEGETAL KINGDOM. 345

are the Dioncea muscipula, the Oxalis sensativa of Java, and the
Mimosa pudica. The leaves of the dionsea are furnished with
true darts, which transpierce the insects as soon as they come in
contact with them. As to the Oxalis sensitiva, its mode of action is
nearly like that of the Mimosa pvdica, which we s^hall take as a type.

The periodical movement is very marked in the Mimosa pudica.
According to the observations of MM. P. Bert and Millardet1 it
is effected thus. In the evening the petiole of the compound
leaf is much lowered ; then it begins to rise again towards mid-
night, consequently without any luminous excitation, and before
sunrise it has attained its maximum of uprightness. At sun-
rise it begins to lower itself very rapidly, whilst the folioles
separate and spread themselves out. At the commencement of the
night, the petiolary depression is at its maximum, and the folioles
are close to the petiole. But, in addition to this slow periodical
movement, the leaf has extreme sensitiveness, and all contact,
all mechanical or chemical irritation, causes it instantly to
assume its nocturnal position.

It is towards 30 degrees that the sensitiveness of the mimosa
pudica attains its maximum. Below 15 degrees it is null. At
40 degrees the folioles become rigid in an hour, at 45 in half-an-
hour, from 48 to 50 in a few minutes. Up to this point they
may still recover their sensitiveness in a lower temperature, but
at 52 degrees they lose it finally. Below 15 degrees, or after
having remained some days in darkness, the folioles also become
rigid, but transitorily.2

Ingenhouz and Humboldt have seen the motility of the sensitive
plant disappear when the plant was plunged into carbonic acid,
azote, &c., but this was only because it could no longer respire.
On the contrary, they have seen it naturally persist in oxygen.
An electric current causes the depression of the leaves. On the
contrary, chloroform and ether abolish the motility.

1 Bert, Recherches sur Us Mouvements de la Sensitive. Paris, 1867.

2 Sachs, loc. tit., p. 855, 1035, 1037; and Dutrocliet, Memoires pour aennrt
&c., t. I. p. 524.

346 BIOLOGY. [BOOK v.

Lindsay, ' Dutrochet, and, after them, many other observers
have proved that the principal agent in the movements of the
sensitive plant is the bourrelet at the base of the petiole. Ac-
cording to Dutrochet, this bourrelet acts, as if it were composed of
two springs, an upper and a lower. The first lowers the petiole,
the second raises it again. The action of the bourrelet would
coincide with its distension, its turgescence, and would be due,
according to certain botanists, to an afflux of sap. But how is
this afflux of sap produced? How can the movement of the
folioles be explained 1 Above all, how can we comprehend that
an excitation may be transmitted from one leaf to another, some-
times even to a distant leaf, missing the nearer leaves, sometimes
across the entire plant, since all the leaves contract successively,
when a drop of sulphuric acid is sprinkled upon the roots.1

We must admit here the intervention of the anatomical ele-
ments of contractile tissues, analogous to those which exist in
animals. In effect, M. Yulpian has found, at the junctions of
the folioles, and at the base of the petioles, cells containing a
finely granulated jelly, which he compares to the substance of
muscular fibres, and which he says he has seen contract under
various excitive influences. M. Cohn, of Breslau, has found
analogous histological elements in the filaments of the anthers
of the cynarese ; that is to say, elongated cells, longitudinally
striated when at rest, contracting under the influence of various
excitants, and then presenting transverse striae, of a very vivid
kind.

These anatomical elements may possibly be the agents of the
local movements, directly provoked. As to the indirect move-
ments, transmitted to leaves non-excited, we cannot account
for them without admitting a certain contractility of the sap
vessels, along which the stimulus is transmitted from one to
the next. This kind of vascular contractility is rather animal

1 Vulpian, Lemons sur la Physiologic Comparee du Syst&me Nerveux, p.
31, 32.

CHAP, ii.] OF MOVEMENTS IN THE VEGETAL KINGDOM. 347

:than vegetal ; nevertheless it exists in a large number of
•Vegetals, if the facts observed by Goeppert are exact. According
to what this observer says, branches cut from plants rich in
milky juices (Cfalidonium majus, Lactuca perennis, Euphorbia esula,
etc.) no longer pour forth liquids when plunged into prussic acid.
Here then we have a property common to the two kingdoms,
'which, moreover, touch at many other points. The manner in
which the spores and the antherozoids of the cryptogams move,
'forms a new feature of union. Here is no longer analogy, but
'identity. "We know that many infusoria alter their position by
means of vibrations, oscillations of one or many filiform ap-
pendages called mbratile cilia, which are also found in animals on
a variety of epithelial cells, hence called mbratile epithelium.
Now these animal vibratile cilia in no wise differ from those
which serve as propulsive agents to the spores and antherozoarjes
of sea-weeds and of certain mushrooms, &c. Our classifications,
with their arbitrary divisions, are never the exact expression of
nature. Everything is connected ; everywhere there are transi-
tions and shadings.

f L I B 11 A It V

UNIVKKS1TY OK

CAL1 FOILS'! A..'

CHAPTER III.

OF MOVEMENTS IN THE ANIMAL KINGDOM.

WITHOUT, as we have seen, specially appertaining to the animal
kingdom, motility is nevertheless a property infinitely more
spread and developed in the animal kingdom than in the vegetal
kingdom. There is scarcely any animal species which is not
more or less endowed therewith : but it is not a property inherent
in organised matter : for many hJstological elements are destitute
thereof, and when the animal is perfectionated, differentiated in
some small degree, motility is the attribute and the function ol
a special tissue, at least in its most perfect mode.

At the lowest degree of animality, when all is still confused
in the living substance, it is the whole body of the animal which
is constituted by a substance, contractile, homogeneous, chang-
ing form perpetually, emitting and retracting expansions unceas-
ingly. This contractile, amorphous substance has been called
sarcode. It is sarcode which forms exclusively the body of the
amoebse of the lowest monerians (Bathybius haeckelii), also of the
rhizopods which move in emitting and retracting sarcoclical
expansions.

The first effort of differentiation seems to be the formation of
vibratile cilia. Here the mobile expansions are no longer
transitory. They have a fixed, definite form. They are per-
sistent organs, constituting, as we have seen, the principal agent
of locomotion in the infusoria.

In the hydroids, the hydra properly so-called excepted, there

ICHAP. in.] OF MOVEMENTS IN THE ANIMAL KINGDOM. 349

is already a certain differentiation of tissue and a thin con-
tractile layer exists, on the periphery of the body, beneath the
epithelial lining. This tissue is already composed of long and
fine fibres.1

On the contrary, the substance of sponges is formed of cor-
puscles, amibiform, amorphous, and contractile.

In many animals, especially in numbers of worms, in the first

[period of life, the only locomotory organs are still vibratile

; cilia : but at the adult age there is developed under the external

s tegument a muscular layer constituted by fibres confusedly

interlaced (Fig. 54).

FIG. 54.

Section of Hirudo. c, cuticular layer; m, muscular layer ; r, lateral line with the excretory
organ ; p, pt median lines, superior and inferior ; g', oblique fibres ; v, intestine ; d,
dorsal vessel ; I, lateral vessel ; s, vesicle of the excretory organ ; n, ventral ganglionary
chain.

Already in the echinoderms the case is different. Here the
contractile apparatus always forms a subtegumentary tube : but
the fibres which compose it are regularly grouped.2

In respect to the muscular apparatus, the mollusks represent
a well-marked link of transition. During the first phases of
their development they often move by means of vibratile cilia.
At the adult age they are furnished alike with a superficial

I ! Gegenbaur, Manuel d1 Anatomic Comparee, p. 118

2 Ibid., p. 169, 170.

350 BIOLOGY. [BOOK v.

muscular envelopement and distinct muscles, traversing the;
cavity of the body and serving to open and to shut the valves.
The most of the muscular fibres constituting the motory ap-
paratus have still as in worms, the form of long filaments a
little flattened, which sometimes are subdivided into fibrils. A
certain number of those fibres are however slightly striated
transversally.1 We perceive therein also some nuclei, which are
probably the last vestiges of the primitive embryoplastic cells,
at the expense of which the fibre has been developed.

A new and decisive progress is accomplished in the arthro-
pods. No longer any contractile envelopement. The muscular
fibres are all grouped into distinct masses, having a definite form,
into muscles, which are inserted into such and such a part of the
body by means of fibrous tendons. Lastly those muscles are almost
solely formed of fibres bearing very numerous transversal striae.2
Under the microscope they scarcely differ from those which
constitute the muscles of animal life in the vertebrates, that is1
to say, muscles charged to excite the voluntary movements.

The voluntary muscles of the vertebrates represent the most
perfect form of contractile substance. They are supported by
the diverse pieces of the osseous framework, into which they insert
themselves, and on which they impress the movements which the
will commands. The cutaneal muscular apparatus disappears,
unless we are disposed to see vestiges thereof in the small
muscles which put in movement the scales of serpents, the
pilose bulbs, and the hair of the mammifers, the feathers of
birds, in those which act on the skin of the human face, and so
on. Yet according to Gegenbaur, these dermic muscles are
completely lacking in fishes, and do not at all represent the
contractile tube of the inferior animals.

From the point of view of elementary form the contractile
substance which may be called muscular presents itself under
many aspects. There is first of all the amorphous or sarcodical

1 Gegenbaur, loc. tit., p. 465.

2 Leydig, loc. cit., p. 152.

CHAP, in.] OF MOVEMENTS IN THE ANIMAL KINGDOM. 351

state, that of the amoeba, for example ; then the cellular form ;
finally the form in tubes. According to a certain number of
histologists and physiologists, there is under all these varied
forms an identical substance. Doubtless the form can be
dominated by the essence and the same organised substance
may, strictly, constitute anatomical elements diversely configured.
Nevertheless, almost always, the morphological differences corre-
spond to functions more or less dissimilar. Even the diverse
varieties of figurate muscular elements have each, as we shall
see by and by, their special mode of contractility. As to the
amorphous contractile substance, we can, at the most, only con-
sider it as a first outline of the muscula'r element. It is semi-
fluid, coagulates at 40 degrees, while the true muscular substance
is solid. We can bring it into affinity with the semifluid and
vitreous substance contained in the large contractile cells of
the hydras, and also with the substance which constitutes first
of all the heart of the vertebrated embryon.1

It is only in the form called fibro-cellular that the muscular
substance acquires a veritable autonomy. It is then represented
by fusiform cells, more or less flattened, provided with one or
two Duclei and capable of compressing or of swelling themselves
out by contraction. There are often fine granulations round
nucleus. The length of the fibre-cell can vary from some hun-
dredths of a millimetre to half a millimetre. These fibro-cells
are found in great number in man and in the mammifers, in the
muscular coats of the intestine, of the veins, and of the arteries,
in the excretory conduits, under the skin in diverse regions,
especially under the pilose follicles, which they put in move-
ment, under the scrotum, and so on. This type of contractile
element is found with variations in all the vertebrates, and
in a great number of invertebrates. In both cases it usually

1 Recently it has been pretended that the sarcode is semifluid, even in the
striated muscular fibre, and that this substance is contained in tubes. And it
has been said that a dermatoid was seen marching in every direction in the
very heart of a muscular fibre as if in a liquid.

352 BIOLOGY. [BOOK v.

co-exists with fibrous contractile elements, which are themselves
of varied species.

According to the strict interpretation of the cellular doctrine
generally admitted in Germany, every muscular fibre comes
originally from cells, which are simply developed in length by
end being joined to end. The nuclei, which we observe here
and there along the course of the fibres in the adult, are in that
case, the last vestiges of that primitive cellular state.

Let this be as it may, the typical muscular fibres are of two
histological species, connected however with each other by a
series of transitory forms. They are smooth or striated. The
smooth fibres must be considered in man and the superior verte-
brates as fibro-cells very much elongated. In many invertebrates,
on the contrary, they seem to be very fine threads without
nuclear enlargements and without divisions. It is those fine
filiform elements, cylindrical and smooth, which constitute
exclusively the muscular apparatus of the inferior invertebrates.
Among the mollusks, we already in certain organs, for instance
in the pharynx of certain gasteropods, meet with those muscular
fibres striated crosswise, which constitute the voluntary muscu-
lar apparatus of the arthropods (crustaceans, arachnida, insects)
and of the vertebrates.

This striated muscular apparatus or apparatus of the animal
life, resolves itself, in final analysis under the microscope, into very
thin fibrils, about the thousandth part of a millimetre in diameter
and offering alternately in the direction of their length transparent
parts and dark parts of the same extent. These fibrils juxtapose
themselves in larger or smaller numbers to form striated muscu-
lar bundles, contained in an elastic transparent sheath called
sarcolemma or myolemma. In the bundle the fibrils are placed
in such fashion, that that there is nearly exact correspondence
between their bright parts and their dark parts, whence the
striated appearance of the bundle. The volume of these bundles
is very variable, according to the animal species, and in the
same species according to the regions. It is these bundles which

CHAP, in.] OF MOVEMENTS IN THE ANIMAL KINGDOM. 353

in vertebrates constitute the flesh, properly so called, the muscu-
lar mass, obeying the orders of the will, obeying the volitions
formulated in the brain. It is, in effect, a constant character-
i istic of the striated muscular fibre, and likewise of the fibro-icell,
that of being in relation, in contact more or less immediate, with
central nervous masses. On the contrary, the elementary sarcodic
substance contracts of itself, obeying direct exterior impressions.
In the same way the vibratile cilia oscillate independently of all
nervous incitation, even in the superior animals, for even the
death of the individual does not suspend their movement. In
certain inferior animals, in which the nervous system is not yet
differentiated, there already exist smooth muscular fibres con-
tracting as spontaneously as the sarcodical substance.

In the vertebrates, in which the two systems of smooth fibres
and striated fibres are largely represented, there is between them
a certain division of labour. The smooth fibres, or fibre-cells,
appertain in a general manner to the apparatus and to the organs
of nutritive life, while the striated muscles are the servants of
the conscious will, the muscles of the life of relation. Thence
the classical division into muscular system of the organic life and
muscular system of the animal life.

This division, however, is true only to a certain degree. Here,
as everywhere in biology, there is no absolutely determined dis-
tinction. We find striated fibres in the intestine of the tench,
in the gizzard of birds, in the pharynx of some gasteropods.
Finally, the wall of the heart of all vertebrates is formed of
striated fibres.. But those cardiacal fibres have an arrangement
in some sort transitory. They anastomose into each other, as do
the smooth fibres in certain invertebrates.

To the anatomical differences of the two orders of fibres,
correspond differences of functions, physiological differences.
Contractility, that is to say, the shortening and the widening of
the fibre, is effected according to different modes in the smooth
muscles and in the striated muscles. In the first it is slow and
durable : in the second it is prompt and instantaneous, and does

A A

354 BIOLOGY. [Boox \r.

not continue longer than the excitation itself which has provoked
it. This law is verified in the diverse apparatus of the verte-
brates ; it is verified still more visibly in invertebrates. Those
of them, for instance the mollusks, whose muscular system is
almost entirely composed of smooth fibres, move slowly. On
the other hand, the arthropods, which have a striated muscula-
ture, have movements vivacious, vigorous, and precise.

Contractility is a property inherent in the muscular fibre, and
can be brought into play by diverse excitants. It exists in the
inferior invertebrates, and in the vertebrate d embryon when it
has not yet a nervous system. It persists in the superior and
adult vertebrate, when the nervous system has been killed by a
special poison.

Like all the organic properties, contractility has nutrition for
necessary basis. It cannot be accomplished without influencing
the double assimilation and disassimilation movement indispen-
sable to the maintenance of the life of the muscular tissue. Every
contraction corresponds to a more energetic oxydation, to a more
active assimilation, to the formation and the elimination of dis-
assimilated products. The result is manifested immediately, in
the vertebrates, by changes in the colour, the composition and the
temperature of the blood which comes from the muscle, the
muscular venous blood. If a muscle is at rest, the venous blood
which comes from it is almost as rutilant as the fresh and oxy-
genised blood brought by the artery. The phenomenon is more
marked still in the case of paralysis, in certain maladies which
produce muscular atony, in syncope. The explanation is that the
muscle, in its state of rest, is at its minimum of consumption,
of life, of contraction ; it absorbs nothing more than is strictly
necessary to its maintenance.

On the other hand, when the muscle contracts, it wears itself,
it expends itself ; it absorbs and eliminates more. Hence the
venous blood which comes forth from it becomes immediately
black.1

1 01. Bernard, Leyons sur Us Proprietes des Tissus Vivants, pp. 220-274.

CHAP, in.] OP MOVEMENTS IN THE ANIMAL KINGDOM. 355

We know that this change of coloration is the indication of
important chemical mutations. Thus, the venous muscular blood
which, in the state of repose, contains only 6,75 per cent of car-
bonic acid more than the arterial blood, contains 10*79 per cent,
after the contraction.

An experiment of Matteucci has demonstrated in another
manner that muscular contraction corresponds to an oxydation of
the fibre. In two glass vessels of the same size the same number
of frogs, skinned and prepared, was suspended. In one of these
vessels the frogs were suspended to metallic hooks, .through which
was made to pass an electric current, which determined contrac-
tions. At the end of five minutes the frogs were taken out of
the vessels, into each of which the same quantity of limewater
was poured. Thus resulted in the two vessels precipitates of
carbonate of lime. But the precipitate was very slight in the
vessel where the frogs had remained immobile ; on the contrary,
it was very abundant in the other.

All oxydation, in some degree energetic, has, for effect, a
certain development of heat. Thus it can be demonstrated, that
during contraction the muscular venous blood is hotter than the
arterial blood.

But the production of carbonic acid in the living tissues
results from and is accompanied by many other chemical muta-
tions ; also we see that the contractions alter the composition of
the muscular juice bathing the fibre. In the state of repose,
when the muscle is not fatigued, this muscular juice is abundant
and its reaction is neutral or alkaline. The existence of this
liquid and alkaline medium is necessary to contractility. In
effect, a muscle into which a liquid even slightly acid is injected,
loses the faculty of contraction.

The alkaline muscular juice of the muscle in repose contains
oxygen, creatine, creatinine and other analogous substances,
which are products of oxydation of the albuminoids.1 We find
therein also sugar, lactic acid and potash. It is this last substance
1 Cl. Bernard, loc. tit., pp. 226, 227, 170.

A A 2

S56 BIOLOGY. [BOOK v.

which gives to the muscular juice its alkaline reaction. In pro-
portion as a muscle is fatigued its reaction becomes less and less
alkaline, and finally passes into acidity. At the same time the
muscle furnishes a quantity greater and greater of soluble sub-
stances. According to Helmholtz, there is in a fatigued muscle
0'73 per cent, of parts soluble in water: there is only 0'65 per
cent, in a muscle which has rested.

Some hours after death the muscle becomes rigid. It is then
spoken of as in a state of cadaveric tenseness, which seems due to
the spontaneous coagulation of the contractile or syntonine sub-
stance ; for we can provoke the rigid state by plunging a muscle
into a liquid at 45 degrees.1

At the outset we can also make the rigidity disappear by
letting a sanguineous current pass into the vessels.

As the muscle in cadaveric rigidity generally offers an acid
reaction due to the lactic acid, it has been believed that the
coagulation of the syntonine was due to the presence of the
acid ; but Cl. Bernard saw in crabs the muscles of the tail in a
state of cadaveric rigidity, though they still presented an alka-
line reaction. Finally, he observed that the acid reaction is
often lacking in the bodies of animals that have died after a
long abstinence.

We have already remarked that muscular irritability is a
property inherent in the muscular element, wholly distinct from
the excitant which brings it into play, without excepting the
most important of those excitants, the nervous system. The
fact is demonstrated either by killing the excito-motory nervous
fibres, as we do, for instance, by means of the curare* poison, or
inversely by abolishing the contractility of the fibre, with the
help of certain substances which do not act on the nerves. The
muscular poisons the most in use are the sulpho-cyanuret of
potassium, the sulphate of copper, tne sulphate of mercury, and
also certain organic poisons which act first of all on the

1 Cl. Bernard, loc. tit., p. 230.

CHAP, in.] ' OF MOVEMENTS IN THE ANIMAL KINGDOM. 357

cardiacal muscular tissue ; for example, the upas tieute, digitaline,
and so on.

From what precedes it results that there is no essential differ-
ence in the contractions, whatever the excitant may be which
has provoked them. Little it matters whether this excitant is
mechanical, chemical, physical or physiological. But there are
individual differences in the muscles ; all are not equally sensi-
tive to the same excitants. The contact of an irritant chemical
substance, a slight puncture made with the point of a scalpel,
and so on, determines the contraction of most of the muscles,
when -laid bare, of the animal life. The smooth fibres of the
stomach, of the intestine, &c., appear on the other hand more
sensitive to the variations of the temperature. The muscular
fibres of the scrotal dartos, the testicular cords, contract, under
the influence of a sudden variation of the temperature, more or
less. The tissues with smooth fibres of the stomach, of the intes-
tine, seem in a certain measure to revive under the influence of
an elevation of the temperature. In effect, if we plunge into
an atmosphere of hot vapour an animal which has just died, we
see when the body is heated to 20 degrees, the stomach and the
intestines execute for half-an-hour and even an hour, peristaltic
movements.1

Light, which seems to have little or no action on any of the
muscles, impresses notwithstanding the contractile fibres of the
iris, direct and without the succour of a reflex action. Thus two,
and even three, days after death the iris of eels still contracts
under the influence of luminous rays, provided care is taken to
humect the eye, and prevent its dessication.

But the most important physical excitant, the excitant which
acts most surely on the smooth fibres and the striated fibres, is
electricity. When a muscle is maintained in suitable conditions
of humidity, of temperature, of medium, it contracts under the
influence of the continuous electrical currents and of the induced
currents with frequent interruptions. It was with the help of
1 CL Bernard, loc. tit., pp. 189, 190.

358 BIOLOGY. [BOOK v.

a feeble continuous current that Helmholtz formerly determined
the duration of muscular contractions by means of very simple
experiments which had at the time a certain notoriety. He
made to pass along a frog's muscle detached from the animal
a current, which the fact itself of the contraction interrupted.
A galvanometer made it possible to appreciate to a certain degree
the duration of the different phases of contraction. The total
duration of the contraction was in these conditions 0",305, and
decomposed itself into three parts. In a first phase, which Helm-
holtz calls the pose, and which continued 0",20, there was no
appreciable effect. The action of electricity on the muscular
fibre is not therefore instantaneous. In this period of incu-
bation contraction succeeded; it continued 0",180, gradually
augmenting in intensity ; finally came a period of slackening,
which amounted to Q",105. If the contractions are thus reiterated
a certain number of times, the muscle is fatigued, is exhausted :
it contracts with a force gradually decreasing, and the duration
of the period of slackening grows longer and longer.

The electrical current seems to act on the muscular fibre by
determining in it a change of molecular state. In effect, if the
current passes during a certain time without interruptions, we
see the muscle contract, especially at the commencement of the
passage of the current, and at the moment of its interruption.
On the other hand, the induced currents provoke a permanent
contraction. With an induced current of 32 interruptions a
second, Helmholtz obtained the tetanic contraction of the masseter
muscle.

Not only the muscular fibre contracts under the influence of
electricity, but it is itself a sort of electric pile, as M. Dubois-
Reymond discovered. If, in effect, by the help of a conductor
and a galvanometer, we establish a communication between a
point of the surface of a muscular fibre and its section, we see
that there is an electrical current going from the exterior
surface to the section, and that this current ceases during the
contraction of the fibre.

CHAP, in.] OF MOVEMENTS IN THE ANIMAL KINGDOM. 359

This fact is observed alike in the striated fibres and the smooth
fibres. But according to the observations of M. Dubois-Rey-
mond the intensity varies in the different muscles. It seems
therefore certain that every muscular fibre is electrised positively
at its surface, and negatively at its centre.

At the moment when the muscle enters into the state of
cadaveric rigidity, the current is interverted \ it ceases finally
when the fibre commences to decompose.

In like fashion the heart of a frog is electrised, positively at
its point, and negatively at its base. Similar phenomena are
observed, moreover, in the nervous fibres, and analogous ones
have been observed in vegetal fibres. We must content our-
selves with mentioning in passing these cuiious facts, of which
no satisfactory scientific explanation has yet been given.1

Of all the excitants of muscular contractility, which we
have just passed under review, there is none which equals in
power the special physiological excitant, the nervous fibre.
The excitants, not themselves physiological, act on the muscle
with a hundred-fold energy when they borrow the aid of the
nervous threads which are distributed in the muscle. It results,
in effect, from the observations and the measurements of
Matteucci, that during its contraction a muscle accomplishes a
mechanical labour at least 27,000 times greater than the chemical
labour, whence has come the excitation of the nerve.2 Now in
the complex animals all the muscles receive nervous fibres, con-
nected with the central nervous system, and the influence of
these nervous centres on the muscular movements is the greater
the more perfect the animal is. But in order to form an idea of
the relations of the muscular system and the nervous system, it
is indispensable to study the last and the noblest of the general
properties of organised matter, that is to say, innervation.

1 Cl. Bernard, loc. tit., pp. 205, 207.

5 Matteucci, Theorie Dynamique de la Chaleur (Revue Scuntifique, 1866,
n°. 51.

BOOK V7.

OF INNERVATION.
CHAPTER I.

THE NERVOUS SYSTEM IN THE ZOOLOGICAL SERIES.

WE have now arrived at the most elevated point of elementary
differentiation of organised matter, and at the most aristocratic
properties of that matter. Every living substance is nourished.
Certain histological elements are nourished, move and contract
themselves. Certain others, the elements of the nervous tissue,
posses*, besides the fundamental property of nutrition, a
whole group of special properties. Thus, the nervous cells
can excite the contraction of the muscular elements ; they
have motricity. Moreover they have the consciousness of the
action exercised on them by the ambient mediums ; they feel
pain and pleasure. They can also, by means of the organs of
the senses, classify, select the excitations bearing on the extremi-
ties of the nervous fibres, with which they are anatomically
related. They have sensibility. Finally, they can treasure up,
combine in a thousand manners the sensations perceived ;
they can think and will. It is the totality of these primordial
properties which constitutes innervati.on.

As we see, innervation is a very complex whole. Also the
anatomical tissue which is endowed therewith, and the systems

362 BIOLOGY. [BOOK vi.

which this tissue forms, present a . number of varieties in
structure and in form. In certain beings innervation is rudi-
mentary ; it reduces itself to the single faculty of exciting
movements and connecting them with each other ; that is to say,
to motridty. In others sensibility is joined to motricity. Finally,
the most perfect animals possess alike motricity, sensibility,
thought, in, however, very numerous degrees of perfection and
imperfection.

In passing by for the moment the varieties of the nervous
elements, we can consider every nervous tissue or nervous system
as reducible to two histological types. Invariably, every nervous
apparatus is composed of fibres and cells. Always the fibres
continue direct with the cells, and always they connect those
cells with a motory or sensitive organ. We shall soon have to
describe the form and the function of the diverse nervous fibres
and cells. At present it is enough for us to mention that the
fibres are especially the conductors of impressions and of incita-
tions, while the cells act on the impression which is transmitted
to them, either to send it back, or to reflect it simply from one
fibre to another, or to transform it into phenomena of conscious-
ness. Finally, the cells can, in their turn, become centres of
excitation, and then, without any exterior impressiorJ, they
provoke movements or combine thoughts.

Like all other organic systems, the nervous system complicates,
perfectionates, diversifies itself gradually in the animal series.

No trace of nervous system in the rhizopods, the sponges, in
the monerions, the infusoria, unless we admit, with some romantic
naturalists, a diffused nervous tissue, disaggregated, or rather
not yet aggregated, invisible nervous molecules, infused and
latent in a living gangue not yet differentiated. But all this is
pure fancy. Neither is there any nervous system in the hydroids,
the lucernaries, the anthozoaries. In the medusae we meet with
a nervous ring formed of a cord, following the edge of the disk,
and offering, from distance to distance, cellular enlargements
called gcmglionaries. This is already the schema of all the

CHAP, r.] THE NERVOUS SYSTEM IN THE ZOOLOGICAL SERIES. 363

nervous systems, more complex and more perfect, which we are
about to pass under review, for there are, even in this rudimen-
tary network, conducting cords composed of fibres, and receptive
and excitation centres composed of cells. The existence of a
nervous system is problematical in certain radiata. A nervous
system seems, however, to exist in the holothuria, namely, an
cesophagian. fibrous collar, emitting radii
at points of which there are ganglionary
enlargements.

M. D. Quatrefages found, in' the
planaries, a nervous ganglion, situated
on a median line, and formed of two
small masses joined together.

The rotifera have also a central
ganglionary mass, situated on the
pharynx. This mass, sometimes divided
into two portions, emits nervous fila-
ments.

In the colonies of bryozoaries, every
colonist is provided with a cerebroidal
ganglion, and besides, as Fritz Muller
has shown, there is a system of cords
connecting all the individual ganglions,
that is to say, a colonial nervous
system.

The plathelminths have, in this anterior
part of the body, two nervous masses, re-
latively large, and united by a nervous
commissure. The position of these ganglions has made them be
called cerebral. The trompe passes as if into a ring, between the
two cords of the commissure. From these ganglions go forth
two longitudinal fibrous trunks which follow the lateral edges
of the body, and are provided with small ganglionary enlarge-
ments emitting nervous filaments (Fig. 55).

This nervous system, so simple, is the rough model of that of

a, opening of the trompe ; p,
trompe ; c, vibratile fossettes ;
n, cervical ganglion ; n't lateral
nervous system ; I, lateral san-
guineous trunks, which bend
forward in order to join ; before
this junction they send round
the brain a branch which unites
with that opposite to form the
dorsal vessel (d).

364

BIOLOGY.

[BOOK vi.

most of the articulated invertebrates (worms, annelates, arthro-
pods), especially when the lateral cords approach each other on
the ventral face, as is the case with some species.

According to M. Blanchard, the nematoids (ascarides, strongyli
filarians, and so on) have, at the origin of the O3sophagus, four

FIG. 56.

A, nervous system of Serpula contortuplicata : a, pharyngian ganglions superior ; b, inferior;
&', ventral trunk ; n, nerves of the mouth ; t, nerves of the antennae.

B, nervous system of Nereis regia : o, eyes reposing on the cesophagian ganglion superior-
The other designations as in the preceding figure.

small ganglions, situated two at the right, two at the left, and
connected by commissures forming an ossophagian collar.

This cesophagian collar is found in all the annelates and arthro-
pods, but it is usually formed of a super-cesophagian ganglionary

CHAP, i.] THE NERVOUS SYSTEM IN THE ZOOLOGICAL SERIES. 365

mass, sometimes connected by fibrous commissures, sometimes
joined together direct. From the inferior ganglion go forth two
abdominal cords directed from the front to the back, and bearing
each a series of ganglions, whence radiate nervous threads. The
ganglions of each cord usually face each other, and thus form, by
their juxtaposition, pairs of nervous centres of which each corre-
sponds to a segment of the body (Fig. 57). If many segments

... A

.'•

FIG. 57.

A, B, C, NERVOUS SYSTEMS OF INSECTS.

A, termites; B, coleopter (dytiscus) ; C, fly: gs, cesophagian ganglion superior (eerebroidal
ganglion) ; gi, cesophagian ganglion inferior ; gr, g%, g%, united ganglions of the ventral
chain ; o, eyes.

blend together in the course of the development, the correspond-
ing nervous ganglions do the same, and thus constitute a more
important nervous mass.1

The more voluminous of the ganglions is the more anterior of
the super-o2sophagian ganglion. It is called cerebral or eerebroidal
1 Gegenbaur. loc. ctt*

366

BIOLOGY.

[BOOK vi.

ganglion, and it usually furnishes nerves to certain organs of the
senses and regularly to the eyes.

As a rule, the ganglions are constituted exclusively of cells,
and the cords exclusively of nervous fibres.

FIG. 58.

A, nervous system of a crab (Carcinus mcenas) ; gs, cerebral ganglion ; o, ocular nerve ; a,
nerve of the antennae ; c, oesophagian commissure ; transversal connection of this com-
missure ; gi, fusionated ventral chain.

B, nervous system of a cirrhipod (Coronula diadema) seen in the ventral face : gs, c, gi, as
in A ; a, antennary nerves which distribute themselves over the mantle and the shell.
Between them is situated the ocular ganglion, in connection with the brain ; m, nerve of
the stomach ; s, visceral nerve which unites itself in a plexus s" with a second visceral
nerve *', coming from the anterior part of the- oesophagian ring. The abdominal ganglion
emits -forward the first cirrus, and rearward (nc) the other cirri.

The body of the myriapods, and that of the grub or larva of
the insects, being formed of very numerous segments, the nervous
system of those animals is also very richly provided with gan-
glions. On the other hand a concentration, a coalescence, of

CHAP, i.] THE NERVOUS SYSTEM IN THE ZOOLOGICAL SERIES. 367

nervous enlargements, takes place in the arachnida, the insects
(Fig. 57), the crustaceans. The cerebral ganglion and the central
chain of these last sometimes fuse into a single mass, whence
radiate the nervous cords (Fig. 58). This mass is merely divided
into two parts by the foramen, the cesophagian ring.1 There is
here a degree of concentration of the ganglionary cells, greater,
in some respects, than in the vertebrates themselves. It is one
of those paradoxical facts which show how far from absolute our
pretended biological laws are. Nervous concentration, which we
have accustomed ourselves to consider one of the signs, of the
means, and of the results of organic perfectionment, is better
realised in the crustaceans than in man.

There is, however, another law which does not seem to suffer
exception ; it is that of the predominance, greater and greater
of the cerebral ganglion, in proportion as the intelligence is
developed. One of the reasons of this development is assuredly
the greater perfection and the more important office of the
organs of the special senses, forasmuch as certain crustaceans,
for instance the large-eyed amphipods, have a very voluminous
cerebral ganglion, lobed, and emitting optical nerves. In like
fashion, and for the same reason, the large-eyed libellulas, many
dipterans, hymenopters, the lepidoptera (Fig. 59 g s) have a
powerful cerebroidal ganglion.2 Nevertheless the degree of de-
velopment is closely related to the volume of the cerebral
ganglion. The brain of the spinning spiders, of ants, of bees, is
remarkable for its volume, and even for its conformation.
Though the bee is much smaller than the cockchafer, it possesses
a brain much more developed, and relatively three times larger,
if we take into consideration the difference of size. The brain
of the ant is proportionally larger still. Besides, the surface of
these cerebroidal ganglions so much developed is mammilated ;
we find there bourrelets, something analogous to what are cir-
cumvolutions in the brains of the vertebrates. In the bee, accord-
ing to Dujardin, the brain has a very singular form. We perceive
1 Gegenbaur, loc. tit., p. 348. a Ibid.

368

BIOLOGY.

[BOOK vi.

a disk with stellated strise surmounting like a hood the superior
ganglion.1 According to some experiments of M. Faivre, the
cerebral ganglion has, like the cerebral hemispheres of the
vertebrates, the property of being insensible to punctures and
lacerations.2

Already we can discover in many of the arthropods the
existence of a special nervous network, destined for the digestive
system. In general, this visceral nervous
or sympathetic system springs from the
central ganglion by a single trunk. Then
it ramifies, and its branches are furnished
along their course with small ganglionary
enlargements. (Fig. 59, r, r'). Duges
saw this visceral nervous system in the*
spiders : Andouin and Edwards and others
found it in the crustaceans : Lyonnet,
Cuvier, Brandt demonstrated its presence
in the insects.

Essentially, and spite of the apparent
irregularity of its general arrangements,
the nervous system of the mollusks is merely
rQ a kind of copy of that of the arthropods.

Here we still find the oesophagian ring,

(Esophagian ganglion supe-
rior with visceral nervous emitting from its central portion a ganglion-
system of a lepidopter

s, cephalic ary peripheric nervous system, distributing

nglion superior (cere- ., -A , ,, ,. , , .,,

broid);a, antennary nerve : itself to the diverse Organs, but Without
o, optical nerve ; r, impair .,

trunk of the visceral nervous regularity, without symmetry, as moreover

system; r1, the root springing , , „ . „ .. . ,

from the assophagian gang- the general conformation of the body

lion superior ; s, nerves in. -, , m., i

pairs with their ganglionary demands. The super-cesophagian or cere-
ts «',*". kj.gj gangiion js naturally very small

in the lamellibranchians which have not a head provided with
organs of the senses : it is, on the other hand, very large for
the contrary reason, in the cephalophores.

1 Anndles des Sciences Naturelles, 1850.

2 Faivre, Annales des Sciences Naturelles, 4<* serie, t. -VIII. et IX.

CHAP, i.] THE NERVOUS SYSTEM IN THE ZOOLOGICAL SERIES. 369

The visceral nervous system of the mollusks, is like their
general nervous system, a copy of that of the arthropods.

On the other hand the cerebral ganglion of certain cephalopods
has affinity in some respects with the brain of the vertebrates.
There exists in these animals a cephalic cartilage, forming a sort
of cranian cavity, and hollowed with a fossette destined to be
occupied by the cerebroidal ganglion. This cartilage is the
rudiment of an orbit and lodges the organs of hearing.

The super-oesophagian ganglion of the mollusks seems also to
have special functions. If we remove this ganglion in the snail
the animal survives the operation four or five weeks, but remains
completely without movement. On the other hand, the extirpa-
tion of the sub-cesophagian ganglion kills the animal in twenty-
four hours.1

The excitation of the cerebroidal ganglion of the mollusks
produces little or no effect. It is the same with its galvanisa-
tion. But the case is altogether different with the sub-cesophagian
ganglion. Its irritation provokes a vigorous muscular agitation :
its galvanisation by the continuous currents has often f of* effect
to stop the heart in its state of dilatation, or of diastole, exactly
as happens with the galvanisation of the pneumogastric nerves
in the vertebrates.

These facts tend to confirm the opinion of the German evolu-
tionists, who wish to connect genealogically the vertebrates with
the mollusks. However, if we take into account nothing but the
general conformation and distribution of the nervous system, the
analogy, remote though it may be, exists rather between the arthro-
pods and the vertebrates. In effect the nervous system of the
acranian vertebrates can be strictly considered as a very co-
alescent ganglionary nervous system. The most imperfect of the
acranian vertebrates, the amphioxus, has as central nervous system
merely a nodose spinal marrow, that is to say, offering a series
of enlargements, each of which corresponds with the origin of a

1 Vulpian, Lemons sur la Physiologic G6n6rale et Comparie du Syst&me
Nerveux, pp. 757-761.

B B

370

BIOLOGY.

[BOOK vi.

pair of nerves. An enlargement which may be compared with
the central ganglion of the arthropods terminates, forwards,
their spinal marrow. It does not perceptibly differ from the
others, but emits five pairs of nerves, among which are the
optic nerves and the auditive nerves.

The great difference consists in the complete absence of
cesophagian ring. In the vertebrate it is no longer merely
the cerebral enlargement, it is the whole central nervous
system which is above the digestive system. In saying that the
arthropod may be compared with a vertebrate reversed, marching
on the back, it has been thought that the
difficulty was got rid of : but it merely
changed its place. In effect, in supposing that
the arthrppod is a vertebrate reversed, we cer-
tainly put thesub-oesophagian ganglionary chain
above the digestive system, but on condition
of making to descend below it the sub-ceso-
phagian ganglion, that is to say the analogue
of the brain. Better it is, spite of the
Hseckelian theories, which are still a little

60

A, brain and spinal mar. rash, to confess that the genealogy of the

row of Orthagoriscus . . „ . .

moia. B, brain and vertebrates is far from being elucidated.

commencement of the T . ., . , ., . . ,.

marrow of Trigia adri- .Let this be as it may, we cannot deny the
analogy of the spinal marrow of the craniote
or acranian vertebrates with the ganglionary chain of the arthro-
pods. Rudimentary expansions continue to be found even in
man, and histologically and physiologically, the ganglionary chain
of the arthropods as well as the spinal marrow of the verte-
brates are cellular centres endowed with a certain sum of
independence.

In the craniote vertebrates the spinal marrow ends, forwards,
in an enlarged portion, in a brain properly so called. But here
still, the transition is graduated, and we pass with no remark-
able suddenness from the type acranian to the type cranian,
even if we compare merely the adult animals (Figs. 60 and 61).

CHAP, i.] THE NERVOUS SYSTEM IN THE ZOOLOGICAL SERIES. 371

If we follow step by step the embryological evolution of any
superior vertebrate the transition is more graduated still : for
we see the nervous centres begin with the acranian form, then
assume by degrees the complete cerebral type, passing through
intermediate forms very analogous to those which persist in the
fishes and in the reptiles.

In these two last classes the encephalic
nervous centres are represented by a
series of vesiculiform expansions (Figs.
60 and 61). In like fashion the ence-
phalon of the superior vertebrates is
composed first of all of five vesicles,
which have been called, going successively
from the front to the back, anterior
brain, intermediary brain, median brain,
posterior brain, and terminal brain
(Figs. 62, 63, 64, 65). With the inferior
face of the anterior brain are connected
the olfactory bulbs, which furnish the
nerves of smell.1

The anterior brain is divided by an
antero-posterior fissure into two hemi-
spheres, which, continuing to increase in
size, become the principal cerebral mass,

, ., , Brain and marrow of the frog :

the cerebral hemispheres, and cover tne A, upper aspect ; B, nether

, . , , . . , , aspect ; a, olfactory bulbs ; &,

Other encephalic expansions, tne more anterior brain; c, median
,, , , • • . IT brain; d, posterior brain; e,

the vertebrate is intelligent.

elongated marrow ; i, infundi-
bulum; s, rhomboidal fosse;
m, spinal marrow; t, its ter-
minal thread.

The intermediary brain divides also
into two masses, which, as we shall see
ere long, play a very important part in the cerebral functionment.
These are the optical expansions or optical layers.

The median brain reduces itself more and more, and is no
longer represented in the human brain by anything but four
small tubercles, called quadrigeminous tubercles.
1 Gegenbaur, loc. tit. pp. 681-690.

B B 2

372

BIOLOGY.

[BOOK vr.

The posterior brain becomes the cerebellum.

The surface of the cerebral hemispheres, at first completely
smooth in the embryon of the superior vertebrates and in the
inferior vertebrates (marsupials, edentals, &c.), goes into folds in
proportion to the evolutive or hierarchical progress. In most of

Em Dry on of dog seen from the back, with
outline of the central nervous system, of
which the medullary sheath (6) forms a
furrow open above. Three primitive
vesicles (a) form the same number of
expansions ; the posterior part of the
marrow enlarges into the rhomboidal
sinus (of) ; c, lateral sheaths limiting
the outline of the body ; d, germinative
vestment external and msdian ; /, mu-
cous vestment.

FIG. 63.

Vertical sections through the brains
of some vertebrates : A, young
selacian (heptanchns) ; B, embryon
of adder ; C, embryon of she-goat ;
a, anterior brain ; 1), intermediary
brain ; c, median brain ; d, pos-
terior brain ; e, terminal brain ; s,
primitive cleft; h, hypophysis.

the mammifers it is moulded into cords sinuous, hemicylin-
droidal, juxtaposed, called cerebral circumvolutions.

The circumvolutions, gathered always into regular groups, are
usually so much the more flexuous, so much the more compli-
cated, the more the animal is intelligent. They are, for instance,
very richly developed in the elephant, the arthropoid apes, and.

CHAP, i.] THE NERVOUS SYSTEM IN THE ZOOLOGICAL SERIES. 373

in man. But here there are exceptions, and the cerebral hemi-
spheres of the beaver, like those of all the rodentia, for instance,
are almost smooth, while in the sheep exists a somewhat complex
system of circumvolutions.

We have seen that in the arthropods the cerebroidal ganglion
has the privilege of furnishing always the optical nerves, and

FIG. 64.

Differentiation of the anterior brain ; A, brain of tortoise • B, brain of a foetus of calf; C,
brain of a cat. In A and in B has been removed on the left the roof of the cavity of the
anterior brain ; and on the right the four-pillared fornix. In C has been removed on the
right side all the lateral and posterior portion of the anterior brain, and on the left
enough to permit the curvation toward the base of the Cornu Amrnonis to be seen. In
all the figures 1 represents the anterior brain ; II, the intermediary ; III, the median ;
IV, the cerebellum ; V, the spinal cord ; ol, the olfactory bulb (its communication with
the cerebral cavity figured in A) ; st, striated body; /, four -pillared fornix ; h, large foot
of the hippocampus ; sr, rhomboidal sinus ; g, geniculated protuberance.

sometimes other nerves of the special senses. In like fashion,
in the vertebrates, the olfactory, optical, auditive, gustatory
nerves, in short all the nerves of the special senses, have their
original centre in the encephalon (optical layers), that is to say
in the grand conscious nervous centre. Most of the other
nervous branches have, at least apparently, their origin in the
spinal marrow.

874

BIOLOGY.

[BOOK vi.

Like the arthropods and the mollusks the vertebrates have a
special nervous network for the apparatus of the vegetative life.
This network has been called in its ensemble sympathetic
nervous system, and we are obliged, to render what follows
intelligible, to give a succinct description thereof.

Here still there is no essential difference between the superior
invertebrates and the vertebrates. The dissemblances bear on

FIG. 65.

Brain of rabbit ; A, upper aspect ; B, nether aspect ; lo, olfactory lobe ; I, anterior brain ;
HI, median brain ; IV, posterior brain (cerebellum) ; V, elongated marrow ; h, hypophy-
sis ; 2, optical nerve ; 3, oculo-motor nerve ; 5, trigeminus nerve ; b, abductor nerve ;
7, 8, facial and acoustic nerves. In A has been removed the roof of the right hemisphere
to show the interior of the lateral ventricle, the striated bodies which are found therein
before and behind the four-pillared fornix with the commencement of the Hippocampus
major.

the exterior arrangement, on the morphology. In sum, in the
invertebrates and in the vertebrates there is a special nervous
network destined for the organs, systems, and apparatus of the
vegetative life : namely, for the digestive tube, for the respira-
tory organs, for the circulatory system, for the genito-urinary
organs. In both the invertebrates and vertebrates this system
lias its origin, or at least its roots, in the great nervous centres.
Following the distribution of the sympathetic branches to their
furthest extremities, we see that their fibres are distributed
wherever there are vegetative contractile elements, smooth

CHAP, i.] THE NERVOUS SYSTEM IN THE ZOOLOGICAL SERIES. 375

fibro cells. In ultimate analysis the great sympathetic can be
denominated nervous system of the vegetative muscles. Such at
least is its physiological characteristic. "We shall see that his-
tologically it is pre-eminently composed of special nervous fibres,
like the office which is assigned to them. With these special
fibres are blended a small number of fibres similar to those of
the nervous system of the animal life. These last are probably
charged with the sensitive function. They gather the impressions
on the surface of the mucous membranes, and so forth.

The sympathetic network is remarkable, morphologically, for
the very great number of ganglionary expansions which exist on
its plexus. Always in the vertebrates, it is connected with
the nervous centres, the spinal marrow, the brain, by numerous
roots. These roots throw themselves into the ganglions which
are connected with each other by cords, and whence set forth
other ganglionary cords, which go to form networks, complicated
plexus in the viscera.

The sympathetic system is not much developed in fishes. It
seems even to be wholly absent in the more inferior fishes, and
to have its place supplied by simple intestinal ramifications.

We shall have to return to the very interesting functions of
the great sympathetic ; but before going further it is needful to
expound with some detail the histological structure of the diverse,
parts of the nervous system, and of the diverse types of nervous
systems, of which we have just given a general morphological
description.

CHAPTER II

OP CELLS AND OF NERVOUS FIBRES.

ALL nervous system resolves itself under the microscope into cells
and fibres. All the nervous cords are almost exclusively com-
posed of fibres. On the other hand, the cells exist in very great
numbers in all the distended parts, in all
the central or ganglionary masses of the
diverse types of nervous systems.

Though there are diverse varieties of cells
and of fibres, yet as the differences concern
only the details, it is possible to give of
them all a general description.

The nervous cells are corpuscles of a
somewhat irregular form, and are more or
less spheroidal (Fig. 66). They have a
wall, a content, a nucleus, and a nucleole.
This last, of a brilliant and yellowish

a, Bipolar nervous cell of the colour, is included in a large transparent
and spherical nucleus, which itself is sur-

FIG. 66.

cSn"iouiaSrnucS rounded on all sides by a granulous and
SttSvVS'SS "M substance. Usually a somewhat
S^onnSve^tlssue^nd ^ick cellular membrane covers the whole,
containing nuclei. According to M. Ch. Bobin this mem-

brane is lacking in the cells of the nervous centres of the
superior vertebrates. The diameter of the nervous cells varies
considerably. It is on an average from Oram,020, to Omm,050.

CHAP, ii ] OF CELLS AND OF NERVOUS FIBRES.

377

The nervous cells continue always with one or more fibres.
They are thus called, according to the number of these fibrous
prolongations, unipolar, bipolar, multipolar. Cells called apolar,
without nervous prolongations, are long admitted : but their

FIG. 67.

Ganglionary multipolar cell of the spinal marrow of the ox, with a rounded nucleus and a
nucleole : a, cylinder axis ; b, prolongations of the cell finely striated and fibrillary.—
Very greatly magnified.

existence is very problematical. The nervous cells having a
greyish tint, which they owe to their contents, the regions of
the nervous centres when they are gathered together in great
number have the same colour. Thus is constituted the grey
nervous substance, which we find on the surface of the brain and
in the central part of the spinal marrow in the mammifers, and
so on.

378

BIOLOGY.

[BOOK vi.

The nervous fibres continue direct with the cells. They are
in some sort tentacles which these project to connect themselves
with the other organs.

The fundamental part of every nervous fibre is a very thin
filament solid and flexible (Fig. 68, h). This filament, called
cylinder axis, cylindraxis, is chemically constituted by a quater-
nary azotised substance. It continues direct with the granulous
content of the nervous cell. This filament is the truly essential
part of the nervous fibre : it is the soul thereof. It is the con-
ducting portion, the telegraphic wire which puts the nervous
cell in relation with the other organs.

In the complete fibre the axile filament is enveloped by a
protecting manica. It occupies then the centre of a tube, of

Nervous fibres magnified 350 times ; e, fine fibre ; /, fibre of middle size ; g, broad fibre
with dark edge, and in the fresh state, taken from the nerve of a rabbit ; h, fibre of the
spinal marrow of man ; visible therein are the bright cylinder axis and the contracted
sheath ; i, analogous fibre of the brain of man : k, passage from the fixed cerebral fibre
to the sheathed fibre; fibre taken from the brain of the torpedo.

an elastic sheath, filled with a sort of viscous oil. This sub-
stance, which Kolliker has compared with turpentine, but which
belongs rather to the family of fat bodies, is transparent. Like
all transparent bodies, rich in carbon, it strongly refracts the
light. Also, under the microscope, the nervous fibres with oily

CHAP, ii.] OF CELLS A3STD OF NERVOUS FIBEES. 379

envelopments seem limited by two dark parallel lines. For
this reason the name of fibres with double contour has been given
to them (Fig. 68).

It is these fibres which, united in bundles with a general
fibrous envelopment, constitute all the nervous cords, the nerves
properly so called, at least those of the animal life, those which
in man and the superior vertebrates distribute themselves to
the skin, to the organs of the special senses, to the muscles.
Seen with the naked eye, all the regions or portions of the
nervous system in which they dominate are white. This white
tint is due to the oily substance of the fibres with double contour.

Physiology has demonstrated that certain of these fibres seem
to transmit to the muscles motory excitations arising in the
nervous centres : that certain others, on the contrary, carry from
the periphery to the nervous centres the sensitive excitations.
On this account, the first have been called motory fibres, the
second sensitive fibres. There is however no decided anatomical
difference between these two orders of fibres. But there is seen
on the course of the nervous fibres, shortly before they reach
the nervous centres, a ganglionary expansion, a nervous cell
(Fig. 69 p).

In most of the nervous cords, motory fibres and sensitive
fibres are mingled and confounded under the general neuro-
lemma. "We have however to except the nervous cords, specially
transitive, which proceed to the organs of the senses.

We have seen that usually the special sensitive nerves proceed
direct to the cerebroidal ganglion of the invertebrates and to the
brain of the vertebrates. The others, the mixed nerves, take
their course, in the arthropods, to the ganglions of the abdominal
chain, and in the vertebrates to the spinal marrow (Fig. 69, q,
and Fig. 71). But in this last case the two orders of fibres
separate a little, before arriving at the marrow, into an anterior,
cylindrical root and into a posterior ganglionary root, that is to
say, expanded at a point where are found united the cells of all
the sensitive fibres of the nervous cord (Fig. 69).

380

BIOLOQY.

[BOOK vi.

It is only by the, presence of this cellular expansion at a point
of their course that the sensitive fibres are distinguished from
the motory fibres. In a general manner they seem also to be
less voluminous j but the diameter of the nervous fibres of every
kind is a very variable thing.

A third variety of fibres exists especially in the cords of the
great sympathetic nerve. These are the grey, gelatiniform,

Section magnified and schematic of the spinal marrow of man at the commencement of
the lumbar region ; a, posterior fissure ; ft, anterior fissure ; c, central canal; d, posterior
cord* ; e, lateral cords ; /, anterior cords ; g, anterior commissure of the white sub-
stance ; h, posterior horns ; i, anterior horns ; k, posterior commissure ; I, anterior com-
missure of the grey substance ; m, gelatinous substance ; n, posterior roots ; and o, anterior
roots of the nerves ; p, ganglion of the posterior root ; q, mixed nerve from the union of
the two roots.

Remak's fibres. They constitute almost the totality of all the
cords or grey threads of the great sympathetic, and are on the
other hand rare or absent in the white branches of the same
system. These fibres are thin (Omm,003), pale, greyish, be-
strewn with fine granulations of the same colour, and even
with elliptical nuclei (Fig. 70). They dominate in the threads
of the great sympathetic, and are lacking in the others. As
M. Ch. Robin remarks, they seem to be fo3tal nervous fibres.
In effect all the white fibres of the animal life assume in the
first* phase of their histological evolution the form of gelatini-

CHAP. n.l OF CELLS AND OF NERVOUS FIBRES.

381

form fibre : and it is the same with the fibres which regenerate
themselves in the adult after a lesion. According to Remak,
who discovered them, the gelatiniform fibres differ especially
from the others by the absence of the oily envelopment, the
medullary substance. Moreover they are constituted also by an
axile filament and a delicate envelopment. The lack of oily
envelopment is the cause of their grey colour.

These diverse degrees of perfection in the structure of the
nervous fibre in the vertebrate, suggest naturally the idea of

Fio. 70.

Ganglionary network of the muscular membrane of the small intestine of the guinea pig ;
o, nervous network ; ft, ganglion ; c and d, lymphatic vessels.

an evolution. No doubt some imagination is needed to find, as
Hseckel finds, all the genealogical links from man to the gastrula,
that is to say to the animal reduced to be nothing more than a
simple digestive pouch. But it is certain, nevertheless, that if
we classify hierarchically all the types of the animal kingdom,
we see, from the foot to the top of the scale, the vegetative life
adjoin to itself little by little the animal life, which gradually
expands in its turn. Now in the superior vertebrate all these
phases have left their impress behind, without speaking of the
embryological evolution which reproduces them all in epitome.

382 BIOLOGY. [BOOK vi.

The superior mammifer is a sort of summary of the entire king-
dom. In him are combined all the tissues, all the apparatus
scattered through the entire series : he has a special nervous
system, but he possesses nevertheless a portion of the ganglionary
system of the invertebrates, and in him as in them this gangli-
onary system is constituted especially by gelatiniform fibres.

In effect the nervous fibre with double contour is not common
among the invertebrates. It is absolutely lacking in the inferior
invertebrates : it appears, but it is still rare, in the arthropods.
Even the nervous system of the inferior vertebrates, the cyclo-
stomes, is constituted especially by granulous fibres, enveloped
with a delicate sheath and destitute of oily covering. In this
case, as in many others, is verified the current saying : Natura
non facit saltus.

There is 110 sudden bound, no hiatus, between the grey nervous
fibres and the nervous fibres with large diameter. The connecting
link is formed by the thin nervous tubes. These are nervous fibres
with double contour, of a diameter much smaller than that of
the other fibres. Some of them moreover seem to appertain to
motricity, others to sensibility : for certain of them are provided
with a cellular expansion, which is also of small size. The thin
nervous tubes are met with to some extent everywhere in the
nervous system : but they abound especially in the great sym-
pathetic. This authorises us to consider them as the first stadium
of perfectionrnent of the gelatiniform fibres.

The complete fibres despoil themselves habitually of their
accessory parts, in their terminal portions, and reduced then to
their axile threads, they have a considerable affinity with the
gelatiniform fibres.

According to recent researches of Dr. Luys, the nervous cells
and even their nuclei appear, when much magnified under the
microscope, to turn themselves into intricate fibrils (Fig. 67).
But the experiments of Dr. Luys having been generally made
on specimens hardened by chromic acid, it is possible that this
fibrillary severance is merely the result of the chemical agent,

CHAP, ii.] OF CELLS AND OF NERVOUS FIBRES. 383

and till there is more convincing proof it is wise to consider the
cell and the nervous fibre as the ultimate elements of the nervous
tissues.

On the whole, every nervous system, invertebrated or verte-
brated, resolves itself into a number more or less great of cells,
and into a number more or less great of fibres, which connect the
cells or end therein.

The regions of the system where the cells accumulate in great
number are the nervous centres. The parts almost wholly com-
posed of fibres form the nervous cords, and if we embrace at
a glance the ensemble of the kingdom, we see that the cellular
centres are the more voluminous and the less numerous, the
more exalted the animal is in the hierarchy.

It is in the superior vertebrates and especially in man that the
cellular concentration attains its maximum (Fig. 65). It is here
also that unfold themselves in all their plenitude the special
properties of the nervous system, sensibility, motricity, and
thought.

"We have not to describe here in their infinite details the
nervous centres of the superior mammifers. It suffices to figure
them to ourselves schematically. The spinal marrow (Figs. 69
and 71) is essentially a column of grey substance, that is to say
of multipolar cells, emitting or receiving three orders of fibres :
sensitive fibres radiated in all the organs, and especially
the skin ; motory fibres, setting forth from the cells, to arrive at
the muscles ; finally, intermediary fibres, serving solely to
connect the cells with each other, to solidarise them, to make
of all the grey substance of the marrow a harmonious whole,
able, in a certain degree, to vibrate in unison.

As the mixed nerves, before arriving at the marrow, break
into posterior or sensitive bundles, and anterior or motory
bundles (Fig. 69), men of science have considered as sensitive the
posterior cells of the spinal marrow, which receive direct the
sensitive fibres. On the other hand they have regarded as
motory the anterior cells, whence go forth the motory fibres. It

384 BIOLOGY. [BOOK vr.

has been remarked at the same time that the cells, probably
sensitive, are of smaller dimensions.

But the cells of the spinal marrow are not merely solidarised
among themselves : they are also solidarised with the central
cells. In what concerns the anatomical relations of the spinal
marrow and of the brain, and also the repartition in the ence-
phalon, of the cells, and of the fibres, we are indebted to the
brilliant labours of Dr. Luys for a picture of the whole subject
as simple as it is fascinating.1

According to this anatomist all the sensitive fibres of the
spinal marrow, whether they have or have rnot encoun-
tered on their passage the cells of this first centre, lead into,
first of all, two masses of cells, situated at the inferior part of
the brain, the optical layers [Thalami nervorum optiqoruvi].
Then having passed through this secondaiy centre, they
radiate toward the surface of the brain, the grey covering
of the circumvolutions. This covering is formed of numerous
layers of triangular cells, superposed by veins, like geological
strata, having all their ridges at high point and being all
connected by fibrous points of union.

The sensitive fibres, radiated from the optical layers, traverse
from below to above all these cortical layers, to reach the more
superficial strata, formed of cells analogous by their volume to
the sensitive cells of the spinal marrow.

Beneath these layers of small cells, we find beds, superposed,
of cells more or less voluminous in proportion to their distance
from the periphery of the brain. The last strata, the deepest,
are constituted by voluminous cells, analogous to the cells,
called motory, of the marrow.

From these last cells set forth descending fibres, which all
converge towards two cellular masses, situated also toward the
base of the brain, in the vicinity of the optical layers. These
masses of grey substance have been called in anatomy striated
bodies.

1 T. Luys, Reck, sur le Syst. Nerv. C6r6bro-spinal, Paris, 1865.

CHAI>. ii.] OF CELLS AND OF NERVOUS FIBRES.

385

i
FIG. 71.

Central nervous system of man seen from the ventral face : a, brain ; fe, anterior lobe of the
brain ; c, median lobe ; d, posterior lobe nearly covered by the cerebellum ; e, cerebellum ;
/', elongated marrow ; /, spinal marrow ; 1, olfactory nerve ; 2, optic nerve ; 3, oculo-
motory nerve ; 4, pathetic nerve ; 5, trigeminous nerve ; 6, abductor nerve of the eye ;
7, facial nerve and auditive nerve ; 9, glosso-pharyngial nerve ; 10, pneuinogastric or
vagus nerve; 11, accessory nerve and hypoglossal nerve; 13 to 16, the first four cervical
nerves ; g. nerves of the neck forming the brachial plexus ; 25, dorsal nerves ; 33, lumbar
nerves ; h, lumbar and sciatic nerves uniting to form the lumbar plexus ; i, the last
nerves forming what is called the horse's tail (Cauda equvna) ; j, impair terminal nerve
of the spinal marrow ; Jk, sciatic nerve.

C C

380 BIOLOGY. [BOOK vi.

From the striated bodies travel descending fibres, which en-
counter on their path the motory cells of the spinal marrow,
then radiate thence into the nervous cords and threads, and
end their journey at the contractile elements, the elements of
muscular tissue.

"We can thus follow along its whole anatomical career and in
all its physiological metamorphoses the impression received by
the terminal extremity of a sensitive nervous fibre. If, for
example, a hard body strikes violently any point of the cutaneous
envelopment, the molecules of the nervous fibres, harshly
touched, enter from point to point into vibration ; the shock com-
municates itself first of all to the cells of the marrow, then to
those of the optical layers, then to the cells of the cerebral cir-
cumvolutions. No doubt this shock is modified in a fashion not
known in its passage through these nervous centres. Let this
be as it may, on reaching the superficial cells of the circumvolu-
tions, the shock, the vibration, the molecular movement, what-
ever may be the form thereof, awakens in these cells an altogether
special phenomenon, a phenomenon of consciousness, or sensation.
But we are only yet at the half of the circuit. The sensitive
nerves which have incurred the shock communicate in their turn
the agitation to the subjacent cellular strata. These last cells, a
little larger than the superficial or sensitive cells, a little smaller
than the deep, or motory cells, are probably the thinking cells.
In these the molecular shock is transformed into ideas. The
ensemble of these thinking cells constitutes the soul of the
organism. They take account of the causes of pain, com-
bine the means of preventing the return thereof, and their
decision, communicated to the deepest cortical layers, is there
metamorphosed into volitions. In effect the deep cells of the
cortical layers are motory, or rather volitive. They ordain the
muscular movements necessary to prevent the return of the
painful shock, and to ward off danger. The command is
transmitted along the convergent central fibres, then through the
cells of the striated bodies and of the spinal marrow. Finally,

CHAP, ii.] OF CELLS AND OF NERVOUS FIBRES. 887

by the motory cells of the peripheric nervous cords, this com-
mand arrives at the muscles charged to execute it. The cycle is
then complete, and the mechanical stimulation of the extremities
of some sensitive nervous fibres has, like a succession of gun-
discharges, determined a sensation, a ratiocination, a volition,
movements.

Such is the complete series, but it is not always so distinct.
The one or the other, even the one and the other of the two first
periods, may be lacking. That depends on the organisms and
the organs. Assuredly each of the three stages of this nervous
circulation desires a small special study. We have therefore
now to occupy ourselves with motricity, with sensibility, and
with thought.

c c 2

CHAPTER III.

OF MOTRICITY.

IN the case we have just mentioned at the end of the preceding
chapter, the series of phenomena may, spite of its complexity, be
summed up in a brief formula. A peripheric excitation is trans-
mitted by nervous fibres to multipolar cells, which transform it
and send it back under the form of motory incitations aloi
other nervous threads. We may in a sort of rough way compai
the agitated nervous cell with a mirror which reflects an incident
ray. But when the shock is transmitted through the brain, its
reflection is not accomplished so simply, and along the path are
awakened phenomena altogether special, conscious psychical
phenomena. It is wholly otherwise when the conscious nerv-
ous centres do not come into play. Then everything comes to
pass silently ; the molecular shock comes from the periphery,
and is sent back thereto, but its passage is not seen. There is
thus truly what is called in physiology a reflex action. As a very
great number of nervous phenomena of every order may be
regarded as simple reflex actions, it is indispensable to speak
with some detail of these primordial acts of the physiology of
the nervous system.

Three principal cases can present themselves : the centre,
which is the seat of the motory reflection, is either a simple
multipolar cell, or a ganglionary nervous centre, or the spinal
marrow of a vertebrate.

ClIAP. Ill]

OF MOTRICITY.

389

The first case is observed in certain rudimentary protozoaries,
in which the nervous system is reduced to some scattered cells,
forming with a fine fibre a network scarcely perceptible. The
second is found normally and
frequently in a number of in-
vertebrates with a ganglionary
nervous system. In the verte-
brates it is the ordinary mode
of functionment of the sympa-
thetic nervous network. In
effect it is by virtue of uncon-
scious reflex acts, going on in
the sympathetic ganglions (Fig.
72), that the motory incita-
tions are transmitted to the
smooth fibres of the intestine,
of the stomach, of the bladder,
of the sanguineous vessels ; and,
in sum, almost all the move-
ments of the apparatus of the
vegetative life in the verte-

brates are achieved bv virtue

of reflex ganglionary actions.

The cells of the spinal marrow (Fig. 73) do not seem, spite
of what has been pretended, endowed with conscious sensibility ;
nevertheless they are very active, and the spinal marrow must
be considered one of the most important reflex centres, especially
for the muscles of the life of relation. It holds in effect under
its sway a very great number of muscles, which owe to it that
permanent half contraction which is called tonicity, and which is
the cause of the constant contraction of the sphincters, of the
antagonist muscles ; and so on. This tonus depends so much on
the spinal marrow, that it is instantaneously abolished by the
destruction of the marrow, whence the nerves of the muscles
indicated derive their motricity.

FIG. 72.

from the ganglion ; d, multipolar ganglion-
ary cells ; e, unipolar cells ; /, apolar cells.

390

BIOLOGY.

[BOOK vi.

The same effect moreover is produced by the simple section of
the corresponding sensitive nerves. The muscular tonus results
consequently from a veritable reflex action, in which the brain
does not at all participate, forasmuch as, by its separation
from the encephalon, the spinal marrow, so far from losing its
reflex power, possesses it on the contrary in a very high degree.

Multipolar ganglionary cell of the spinal marrow of the ox : a, cylinder-axis ; 6, prolongations
of the substance terminating in fibres excessively fine.

If, for instance, we pinch the foot of a decapitated frog, the
animal immediately withdraws it with much more energy than he
did in his state of integrity. If we pinch with more force the
reflex action is irradiated on the other members. In a frog
poisoned by strychnine and decapitated, the smallest contact at

CHAP, in.] OF MOTRICITY. 391

any point of the skin determines convulsive movements almost
general, while in the perfect animal, we can sometimes touch the
central end of a cut nerve without exciting the smallest reflex
movement.

In many vertebrates decapitation by no means hinders reflex
movements, complex and associated, having all the appearance of
voluntary movements. All the world has heard the celebrated
experiments of Flourens spoken of, so often repeated and varied
since. Deprived of its cerebral hemispheres, a pigeon still flies
when we throw it into the air, swallows grain when we put it
into its mouth ; and so on. The experiment is always the more
striking, the more the vertebrate is inferior, and the less brain
it consequently possesses. For instance, a fish without brain
swims as well as a normal fish. If we pinch the skin near the
anal orifice of a decapitated frog, we see the posterior feet of
the animal directed towards the irritated point, then extended
suddenly, as if to repel the aggressor. If we pinch laterally the
skin of the posterior part of a triton, consisting mainly of the
trunk and of the two posterior members, this fragment, when
pinched, curves laterally as the intact animal would do to with-
draw the irritated point from the irritant body.1

Analogous facts have been observed by M. Ch. Robin on the
body of a decapitated man. He says : — " The right arm of the
executed man, being extended obliquely on the side of the
trunk, the hand being 25 centimetres apart from the hip, I
scratched the skin of the breast with a scalpel, on a level with
the aureola of the mamma, to an extent of from 10 to 11 centi-
metres, without interfering with the subjacent muscles. We
saw immediately the great pectoral muscle, the biceps, the
anterior brachial muscle, and the muscles covering the epi-
trochlea contract successively and rapidly. The result was a
movement of approach of the whole arm toward the trunk, with
rotation of the arm on the inside, and demiflexion of the forearm

1 Vulpian, Lemons sur la Physiologie Gten&rale et Compare du Syst&nw
Ncrveux, p. 417.

392 BIOLOGY. [Boos vi.

on the arm, a true movement of defence, which projects the hand
from the side of the chest to the pit of the stomach. " x

It is assuredly the grey, that is to say cellular substance,
which serves as centre to these reflex acts : for it is indispensable
and it is sufficient that these substances exist, for these reflex
actions to be produced. After making almost complete hemi-
sections of the marrow Yan Deen still obtained reflex actions of
the four members. We have seen Professor Schiff interrupt by
many alternate hemisections the continuity of the white sub-
stance of the marrow in a cat, which did not hinder him from
still obtaining contractions of the iris, by pinching the animal's
tail.

As the celebrated experiments of Legallois have demonstrated,
the diverse regions of the marrow correspond each to a special
region of the body. They have a certain independence, and after
a section can live a long time, by retaining their reflex excita-
bility, provided their capillary circulation is not fettered. This
sort of federation of the diverse regions of the spinal marrow
confirms the opinion which regards this nervous centre of the
vertebrates as a fusionated ganglionary chain.

We know moreover that apart from all vivisection, there are
in the marrow normal functional centres. Such is the nodus
mtalis of the superior vertebrates, that joint some millimetres in
thickness, situated at the origin of the marrow, and whose
destruction has for result instantaneous death, due to the aboli-
tion of the respiratory muscular movements. Such is also the
cilio-spinal centre, situated as high as the two first nervous roots
of the dorsal marrow, and holding under its empire almost
all the capillary circulation of the head. Such finally is the
genito-spinal centre, situated in the lumbar region in man.

Like all the tissues, the nervous tissue only works on condition

of being fed : also its vitality is intimately dependent on the

integrity of the sanguineous circulation among its elements.

But more than all other tissues, it is intermittent in its mode of

1 Ch. Robin, Journal de Physiologic, Paris, 1869.

CHAP, in.] OF MOTRICITY. 393

functionment. A large expenditure of motricity exhausts for a
time the nerves and the marrow. For them as for the muscles
it has been demonstrated that their chemical reaction, neutral
in the state of repose, becomes acid after labour.

To sum up, the spinal marrow- is an unconscious nervous
centre, a grand source of reflex acts. It probably holds under
its dominion a quantity of associated movements, harmonious
in appearance, but which in reality are for the most part effected
without the intervention of the conscious centres, of the cerebral
centres. This is why the young of many vertebrates run about
as soon as they are born, when the cerebral hemispheres act
little or not at all, in any case cannot consciously command
complicated movements, which the young animal has not yet
learned to execute.

The brain, on the other hand, is charged to accomplish reflex
acts of another order, which often trouble in their execution the
unconscious acts of the marrow. This is why this last nervous
centre acts with more energy and is more excitable when by
vivisection it has been in some sort delivered from the interven-
tion of its mobile neighbour.

UNIVERSITY <»K

CALIFORNIA.

CHAPTER IV.

PROPERTIES OF NERVOUS FIBRES.

THAT the cellular element is, in every nervous tissue, tl
important agent, that which plays the principal part, is beyoi
doubt j nevertheless it would give an incomplete idea of tl
nervous fibre to see in it only a conducting thread, which maj
be motory or sensitive indifferently, and solely by reason of its
terminal insertions. For example, it is not because the optical
nerve leads to the eye that it transmits or awakens only visual
sensations, since, after the section of this nerve, all excitation
conveyed to its central point arouses in the nervous centres
exclusively special sensations. We must therefore attribute to
the various orders of nervous filaments peculiar properties, in-
herent in their very structure, or rather in their molecular con-
stitution. This diversity is disclosed even by the manner
in which the nervous fibres die. Each order of fibres has its
peculiar kind of death. If, for example, we kill the nerves by
stopping circulation, we see the sensitive element die first, and
losing its properties from the periphery to the centre. Then
the motory element succumbs, but from the centre to the
periphery. The functional and nutritive centre of the motory
fibre is, then, the centre in which it ends. The fact is still more
clearly demonstrated by the section of a motory nerve. We see
then, as in the case of the stoppage of the circulation, this nerve
die from the centre to the periphery. To obtain movements by

CHAP, rv'.] PROPERTIES OF NERVOUS FIBRES. 395

exciting the cut nerve, we must in fact bring excitation to bear
upon a point nearer and nearer the terminal extremities, till we
reach the muscles themselves. This gradual abolition of mo-
tricity corresponds> in this case, to an appreciable alteration in
the constitution of the nerve, that is to say, a progressive
coagulation of the medullary substance, the myeline of the
rnervous fibre. But, while the peripheric tron£on of the nerve
thus dies little by little, the central end, which is always in
continuity with the central cell, lives intact, preserving all its
properties.

How is this curious influence of the central cell upon the fibre
exercised ? What is, essentially, the character of the molecular
shocks transmitted by the central cell to the motory fibre ?
These are questions which still wait for an answer. Though
electricity is produced in the nervous tissue as in every living
tissue, it is not likely that the molecular shock which runs along
the motory fibres is of an electric nature. In effect, a simple
ligature, placed upon its course, is sufficient to stop it completely,
by disorganising the nervous fibre at a single point, whilst it
opposes no obstacle to the passage of an electric current.
Finally, the rate of propagation of the motory excitation along
a nerve is extremely slow. In fact it is proved by the experi-
ments of Helmholtz, Dubois-Reymond, &c., that in the motory
nerve of a warm-blooded animal this rate is only from 50 to 60
metres in a second. In a nerve cooled to zero it diminishes by
nine -tenths, and we can even arrest all conductibility in the
sciatic nerve of a frog by applying ice to one point of this
nervous trunk.1 After that, it is very natural to see the
speed of nervous transmission retarded in cold-blooded animals,
whose temperature is at once lower and more variable than
that of warm-blooded animals. In effect, in the frog, for
example, this speed does not exceed from 15 to 20 metres in a
second.

1 E. Onimus, De la Thtorie Dynamique de la CJialeur dans les Sciences
Biologiques. Paris, 1866, p. 70.

396 BIOLOGY. [BOOK vi.

If we are still ignorant as to what the molecular vibration,
formerly called nervous influx, is, in its essence, we are not better
instructed as to the manner in which this vibration is transmitted
to the contractile muscular elements. By what mechanism do
the dissociated nervous fibres, divested of their protecting
envelopment, when they are insinuated between the muscular
fibres of the animal life, between the fibre-cells ,of the
sanguineous vessels and the apparatus of nutritive life, succeed
in modifying the state of these elements, determining their
contraction, and that with much greater energy than would be
exercised by an excitation bearing upon the contractile element
itself? One more unsolved problem to be added to so many
others.

In most questions relating to the method in which the nervous
tissues live and act, we must therefore content ourselves with
recording plain facts, of which we are unable to give any satis-
factory explanation. If physiologists are unable to tell us why
the nervous cell excites the motory fibre, how the latter
transmits this excitation to the muscular fibre, neither can
they explain how curare specially kills the motory nervous fibre,
sparing the sensitive fibre. Certainly we have here a fresh proof
of radical diversity between these two orders of nervous
conductors.

The wourara, or curare, of which the South American Indians
make use to poison their arrows, has, in fact, the very curious
property of selecting, to some extent, the motory nervous fibres.
Once introduced into the circulatory system of any vertebrated
animal, in a very small quantity, it strikes with paralysis the
whole of the motory network, leaving perfectly unimpaired the
whole of the sensitive network. Its action is first disclosed by
slight convulsive movements, followed by the progressive extinc-
tion of all the movements of the life of relation. The effect of
curare, whilst more manifest and prompt in vertebrated animals,
nevertheless is not peculiar to them. In fact, curare also acts
upon the aquatic larvae of insects, upon naids, and mollusks,

CHAP, iv.] PROPERTIES OF NERVOUS FIBRES. 397

but slowly. It produces no apparent effect upon planaries,
asterias, and fresh water polypi1 In short it is specially
upon the white fibres of animal life that its action is
prompt and sure. The gelatiniform fibres resist it better.
In man even, the sympathetic nerve is difficult to touch,
and those organs which, like the heart, receive simultane-
ously white and grey fibres, are the last to be smitten. As
the chief difference between the white fibres and those named
after Remak seems to consist in the presence of a manica of
myeline in the first, which is absent in the others, we should be
tempted to believe that the curare acts specially upon this
medullary substance ; but in this case, as in so many biological
phenomena, the conditions are too complex to lend themselves
readily to such simple explanations. In fact, it is from the
periphery to the centre that curare effects the toxication of the
nerve ; the peripheric extremities of the nerve are first and
perhaps solely struck, since a motory nerve, separated from the
marrow by section, is still poisoned by the curarised blood which
bathes its extremities.2 Now exactly by penetrating into the
muscles, the nervous motory fibres divest themselves of their
oily envelopment, and assume in some degree the aspect of the
fibres of Remak. It has been supposed that curare* did not
provoke profound lesions in the nervous fibre. In fact, the
living nervous fibre, like the muscular fibre and certain vegetal
fibres, produces an electric current, going from the surface to its
centre of section; now the nervous fibre, physiologically de-
stroyed by curare, is still the seat of the ordinary electric
phenomena ; consequently, life has never quitted it, and the
nutritive exchange is always taking place. Here then we must
admit either delicate and invisible molecular perturbations, or
perhaps a simple depression of the nutritive energy, sufficient to
abolish the special function, but not yet reaching the funda-
mental basis of life.

1 Vulpian, loc. cit., p. 201.

2 CL Bernard, Rapport sur Us Progrte de la Physiologie, p. 19.

398 BIOLOGY. [BOOK vi.

We cannot pass over in absolute silence the electric properties
of the nerves ; but we shall speak of them briefly. It seems to
us that, in physiology, far too much importance has been
attached to this secondary question. People have allowed
themselves to be drawn too far by the idea and desire of
establishing a connection between the electric agent and the
nervous agent. But all identification between these two forces,
or rather these two modes of molecular vibration, is manifestly
erroneous. It is true that the electric currents bring nervous
motricity into play with great energy, but many other
mechanical, physical, and nervous excitants do as much.

As to the electric current which, as M. Dubois-Eeymond has
shown, is established between two electrodes placed, one on the
external surface of a nerve, the other on its sectionised surface,
it is not peculiar to the nervous tissue, and always establishes
itself from the external surface to the section; it is simply
the result of nutritive chemical actions. Also, it appears indif-
ferently and in the same manner, whether the nervous fibre is
motory or sensitive. A nerve which has just been crushed with
blows of a hammer, and has lost its motricity, nevertheless
engenders an electric current ; for, in spite of the violence of the
lesion, which haa destroyed the form of the nervous fibres, their
substance still lives some time, or at least certain parts of this
substance ; for example, the nervous sheaths and the neurolemma.

Nevertheless a nervous current is established throughout the
length of the nerve, and is perceptible in the galvanometer,
when we have excited by a continuous current a portion only of
this nerve, not comprehended in the circuit of the galvanometer.
This is what M. Dubois-Reymond has too pompously named the
electro-tonic force of the nerves. Is this faculty of electric
irradiation peculiar to the nervous fibres, as M. Dubois-Eeymond
would assert ? It does not seem that this so-called special
property has been sufficiently sought for in the other fibrous
tissues, and Matteucci has demonstrated it, though with more
difficulty, in a piece of cotton soaked in a conductor liquid.

CHAP, iv.] PROPERTIES OF NERVOUS FIBRES. 399

As to the action of electricity upon the motory nerves, it also
presents some interesting peculiarities.

As a general rule, every interrupted current, or every strong
continuous current, applied to a motory nerve still in relation
with the muscles, provokes a muscular contraction, more or less
tetanic.

On the contrary, the application of a feeble continuous current
causes one contraction at the moment of closing, and another at
the moment of opening. In the interval there is no appreciable
effect.1

According to M. Cl. Bernard the current acts only by
abruptly changing the electric condition of the nerve. In fact,
in certain cases, electricity causes the muscular contraction to
disappear. The galvanisation of the pneumogastric stops the
heart in the act of dilatation, of diastole. The tetanic con-
traction of a frog's foot, following the application of sea salt
to the nerve, ceases when the two points of galvanic pincers
are placed upon the lumbar nerve. Finally, all medical men,
however little acquainted with electro-therapeutics, know that
in man the passage of a continuous current often causes the
contraction of certain muscles to disappear instantaneously. For
our own part, we have several times had occasion to verify
this interesting fact.

Long and very frequently reiterated excitations abolish, at
least for a time, the excitability of the nerve ; but if, for
example, we have employed a continuous current, it is then
sufficient to reverse its direction to awaken this exhausted con-
tractility, and the experiment may be repeated many times.
These voltaic alternatives, as they have been called, show plainly
that there is something altogether special in nervous motricity,
and that there exists in the inmost constitution of the axillary
cord a mobility, a molecular instability, which no other tissue
possesses.

1 Vulpian, loc. tit., p. 71-73.

400 BIOLOGY. [BOOK vi.

The persistent vitality of the fibrillary nervous tissue is not
less remarkable.

A nerve exposed to the free air dries up, and soon loses its
properties, but, within a certain time, it may recover them by
simple imbibition, in the same manner that certain desiccated
infusoria revive.

If we cut the anterior rachidian or motory roots of a mixed
nerve, the peripheric end will not be long in losing its motricity,
and it gradually wastes even as far as its finest terminal ramifi-
cations. If we cut the posterior or sensitive root, above the
ganglion, it is the central end which wastes.

Under such conditions, the nervous fibres lose their excita-
bility, in the mammifers, at the end of about four days, whilst
the irritability of the muscles lasts nearly three months. The
structure of the nervous fibre is therefore altered, but not
fundamentally. In effect, the nerve has only lost its oily en-
velopment; but its axile cord lasts and persists, apparently
intact, covered only by the Schwann's sheath, shrivelled and
folded round it. Professor Schiff has found the axile filament,
still intact, five months after the section of a nerve ; M. Yul-
pian has seen the same thing after six months. But things do
not remain in this state. At the end of an indefinite time,
shorter if the animal is young, longer if the animal is old, or of
variable temperature, or cold-blooded, the nerve is restored, the
anatomical and physiological continuity is re-established between
the trongons of the cut nerve, if they have been kept in contact ; it
is sometimes re-established even when there has been a resection
of a nervous segment of from 1 to 2 centimetres. In this last case,
we see a bundle of grey fibrils, budding, shooting at the central
end, and joining at the peripheric end. At the same time,
myeline is reproduced in the Schwann's sheaths, and, finally, the
entire nerve is restored ; for a long time, however, its fibres have
a very small diameter.1

This property of restoration is constant, inherent in the
1 Schiff, Vulpian, Phelippeaux.

CHAP, iv.] PROPERTIES OF NERVOUS FIBRES. 401

essence of the nervous fibre ; since even nervous fragments trans-
planted and grafted under the skin of dogs waste and are
regenerated, as they would be after a simple section.

How many things are still unexplained in this singular nervous
restoration ! How can we comprehend the influence of the
motory and sensitive cells upon the fibres ? Why, some days
after the section of the motory nerve, does the motricity of the
nerve disappear, since the axile filament, which is the essential
part of the fibre, apparently preserves its integrity 1 It is
generally admitted that the genesis of nervous fibres is only
possible in the embryon; it would necessitate, it is said, very
complex blastemas, which the simple process of nutrition is
powerless to produce. Nevertheless, in cases of nervous restora-
tion, after resection, there is generation of nervous fibres.
Finally, the nervous medullary substance, or myeline, is a
ternary, hydrocarbonised body; now, in the case of nervous
regeneration, it is necessarily secreted, either by the Schwann's
sheath, or by the axile cord. Here then is a fresh case
of synthesis of a carbonised ternary matter in an animal
tissue.

D D

CHA.PTEK V.

OF SENSIBILITY IN GENERAL.

HOWEVEE accustomed we may be to see the adage Natura non
facit saltus ceaselessly verified, and from whatever point we view
the world, to meet with graduated series of facts, we are compelled
to recognise in conscious sensibility a quality altogether peculiar,
manifesting itself suddenly, and without any link to connect it
with the other properties of inorganic or organic matter. With-
out doubt, there are degrees in sensibility. In following the
animal hierarchy, we see this property, at first confused, gaining
little by little in intensity, in clearness, then subdividing into
various departments ; but there is, nevertheless, a point where
sensibility abruptly starts up, for between unconsciousness and
consciousness there is no bridge. Here then we are in the pre-
sence of a new fact, quite as peculiar and unknown in its essence
as gravity is. But just as the want of any clear idea on the
subject of the inner nature of gravity has not hindered natural
philosophers from studying and formulating the laws of this
great property of matter, so, though ignorant as to what nervous
sensibility is in itself, we can indicate its modes and conditions.

Conscious sensibility is a property inherent in certain nervous
fibres and cells. This is a general fact, which can be verified
from the highest to the lowest degree of the animal scale. Never-
theless, we must here point out the apparent exception in the
case of the infusoria. Many of them, in fact, according to the
evidence of our microscopes, have no nervous system, yet seem to
experience sensations. We see them move, to all appearance
voluntarily, avoid obstacles, &c., &c. Must we, to explain these

CHAP, v.] OF SENSIBILITY IN GENERAL. 403

paradoxical facts, admit, with some physiologists, the existence
of an amorphous nervous substance, impregnating as it were the
entire bodies of these animals 1 There is nothing to authorise such
hypotheses. In the whole animal kingdom we see the precision of
the sensitive perceptions correspond to clearly denned nervous ap-
paratus, aided by special organs called organs of the senses, having
the office of choosing amongst the shocks, the movements, the
vibrations, &c., in short, the physical impressions of the exterior
medium, all that can awaken in the nervous centres of the conscious
being the tactile, olfactory, gustatory, auditive, and visual sensa-
tions. How admit that special sensations, which, to be produced in
the superior animals, require diverse and complex apparatus, may,
nevertheless, be experienced in a state of organic confusion and
indivision 1 It is much more simple here to accuse the imperfec-
tion of our means of investigation, and to reserve till we have
more ample information those exceptional cases, destined pro-
bably to be included one day in the general law.

With the aid of this restriction we can now sketch the picture
of nervous sensibility. This sensibility has its seat in the nervous
cells and fibres, of which we have already, given a brief descrip-
tion. That there may be nervous cells specially sensitive having
consciousness of impressions exercised upon the terminal extre-
mities of their fibres, no one has ever attempted to deny.

It has not been the same with the nervous fibres, properly
so-called, and upon the authority of some experiments, either
erroneous or insufficient, the indifference of the nervous fibres
was for some time believed in. According to this theory, the
nervous fibres are all identical. It would be necessary to regard
them as simple conducting threads, indifferent to the kind of
excitations which they transmit. Sensitive, when they bring an
organ of sense into communication with the sensitive central
cells, the nervous fibres become motory by simple displacement,
by the single fact of connecting a muscle with the motory cells.
No trustworthy experiment comes to the support of this theory,
which is brilliantly refuted by the evident speciality of the optic,

D D 2

404 BIOLOGY. [Boox vi.

acoustic, &c., nerves. In fact, every irritation which touches
either the course of these nerves or their central portion, after
section, only awakens in the nervous centres special sensations,
glimmerings, sounds, &c. In the same way in the vertebrates
the posterior roots of the rachidian nerves are sensitive ; further-
more, every excitation bearing upon any point whatever of their
course between the teguments and the nervous centres determines
sensitive perceptions, touch, pain, &c.

There are then systems of fibres and cells physiologically quite
different from the motory cells and fibres, in spite of great analogy
in form and structure. Besides, this sensitive nervous system is
habitually armed, at the extremity of its fibrous irradiations, with
special apparatus destined to collect, to concentrate upon the ter-
minal nervous fibres excitations from without. These apparatus
are the organs of the senses, which we must now briefly describe
throughout the animal series.

We shall merely mention in passing the protozoa. They have
no organs of the senses, any more than the rhizopods, the sponges,
the infusoria, since these rudimentary organisms are absolutely
destitute of nervous system, and the organs of the senses are
simply excitatory apparatus, means of reinforcing exterior im-
pressions, instruments by the aid of which the sensitive nervous
system palps the ambient medium. Can it be said that all the
special senses may be concentrated in one, that of touch 1 We
cannot deny that thei^e is some truth in this generalisation.
Under the apparent diversity of special sensations, there is always
the same cause, namely, the shock, the agitation of the sensitive
nervous extremities by molecules belonging to the exterior medium;
but as each sense selects from these multiplied excitations those
which correspond to its anatomical construction, we must admit
special senses.

If certain physiologists have wished, with some appearance of
reastm, to reduce all the senses to one, others, on the contrary,
have capriciously tried to multiply their number. The ancients
admitted five senses; touch, tasjbe, smell, hearing, and sight.

CHAP, v.] OF SENSIBILITY IN GENERAL. 405

Buffon wished to add the genesic sense. Ch. Bell has imagined
a muscular sense, another sense adapted to estimate weight,
consistence. According to Carus, supported in this by several
contemporary physiologists, there is a special sense for tempera-
ture. Many physiologists admit doloriferous nerves. But the
sensitive enumeration of the ancients is surely the most simple
and accurate ; there is only a special sense where there is a special
apparatus to gather certain impressions to the exclusion of others.
The appreciations of weight, pressure, temperature, consistence,
pain, &c., evidently belong to the domain of the sense of touch ;
otherwise it would be necessary, by analogy, to subdivide the
other senses, those of sight, hearing, smell, taste, into a crowd
of distinct senses, corresponding to all the varieties of colours,
sounds, odours, and savours. If in certain maladies the percep-
tion of pain is abolished, while touch seems intact, it is simply
because the nerves of touch have become insensible to certain
agitations, as the eye sometimes becomes incapable of perceiving
such and such a colour.

But if the five classic senses suffice to represent the great de-
partments of sensibility in man and the vertebrated animals, it
is not impossible that it may be otherwise with the invertebrated
animals. The aerian waves are only sonorous to the human ear
within certain limits of number, length, and rapidity. In the
same way the chemical rays of the solar spectrum awaken in
us no sensations. But sensitive apparatus differently adapted
from ours may probably perceive those vibrations which are
insensible to us. The inverse is more probable still. Many
of the invertebrated animals seem, from the point of view of
special senses, much less favoured than man and the higher
mammifers, and consequently may be destitute of one or more
of our five senses. This question of comparative physiology has
been little studied yet. Nevertheless from some experiments
made by M P. Bert we may infer that as regards visual per-
ceptions there is no radical difference between man and insects,
in spite of the dissemblance of the perceptive organs.

CHAPTER VI.

OF TOUCH.

TOUCH is the most simple of all the senses, the least differen-
tiated. The tactile sensations result from a shock, a pressure,
an agitation bearing almost directly upon the extremities of the
sensitive fibres. Where these fibres are very numerous, tactile
sensibility is strongly developed. It is habitually at certain
points of the teguments, skin, or mucous membrane that these
agglomerations of sensitive nervous terminations are found.
Ordinarily then these terminal extremities are clothed with an
envelopment, a kind of hood ; sometimes they are terminated
by a nervous cell. There are then what are called corpuscles of
touch.

The sense of touch is in some measure distributed everywhere
among the higher mammifers ; but it exists, more or less
developed, in the whole of the animal series. As it is the least
perfect of the- senses, it is also the one which offers the least
variety in the different animal classes, compared amongst them-
selves.

In the hydral polypi and the anthozoaries, the tentacula which
surround the mouth are considered as tactile organs. The
annelates, the hirudinates, have as organs of touch tegurnentary
cells, which have the form of bristles, baculi, in connection with
•sensitive fibres. According to Leydig, these tactile cutaneous
organs are sometimes, in the hirudinates, grouped in large
numbers at the bottom of cupuliform depressions.

CHAP, vi.] OF TOUCH. 407

In the echinoderms, the tentacula situated in the neighbourhood
of the buccal orifice, and receiving the nerves, are considered as
tactile organs.

The mollusks have as instruments of touch cutaneous cells
with setiform prolongations, disseminated where the body is not
covered with hard pieces.1

When we can trace the cutaneous nerves of the mollusks, in
the transparent species, for example, we see that these nerves are
clear, pale, offering here and there ganglionary expansions. It
seems then that here the sense of touch is exercised by grey
fibres.

The articulated appendages or palpi situated near the mouth
in the crustaceans, the arachnida, and the insects, are tactile
organs- In the crustaceans there are, on the antennae and other
appendages, filiform prolongations, " tactile baculi," which also
exist in the myriapods, the insects.2 Besides these special organs,
we are forced to admit, in the crustaceans, the arachnida, and the
insects, sensitive organs disseminated in the skin. In effect, in
spite of the envelopment, the varnish of chitine, which covers
them, these animals feel strongly the contact of the exterior
bodies at any point whatever of their own bodies. The soft
membrane which lines this bed of chitine is therefore sensitive, as
is also the subungual dermis of man.

The general structure of the skin is perceptibly the same in
all vertebrated animals, but nevertheless the manner of termi-
nation of the nervous fibres varies. Often the fibres end in
expansions, some of which are called corpuscles of Paccini ;
others, corpuscles of touch. The first are observed in man,
birds, &c. In the corpuscle of touch, the sensitive fibre con-
ducts to an ovoid nucleus. The corpuscules of touch, in man,
have a special form, which is nevertheless met with also in the
hand of the monkey, and in the lingual papillae of the elephant.
Every one knows that these corpuscles are extremely numerous
1 Gegenbaur, loc. tit., pp. 122, 302, 479. » IKd, p. 361.

408 BIOLOGY. tBooK vi.

on the palmary and plantary faces of the hand and foot of man,
where, by their juxtaposition, they trace curved lines, crowded
and regular. On the palmary face of the ungual joint of the
forefinger, Meissner counted eight hundred corpuscles of touch
in the space of a square line.

These corpuscles are of ovoid form, and each of them is
constituted by a dermic bed, covering a small mass of conjunc-
tive tissue. A sensitive nervous cord penetrates the corpuscle
at its base. It is certain that these tactile corpuscles are
apparatus which reinforce sensation, but are not indispensable
to it. The different tactile sensations are still experienced by
the skin in the regions where the corpuscles are wanting, but
much less clearly. The internal surfaces of the terminal joints
of the fingers, for example, feel the two points of a compass at
a distance of seven-tenths of a line, while on the level of the
dorsal spine a distance of twenty-four lines is required to keep
the two sensations from being confounded.1 At the tip of the
tongue, on the contrary, the two sensations are still received at a
distance of half a line.

1 E. J. Weber, De Subtilitate Tactus, in the work entitled : De Pulsu,
Itesorptione, Auditu, et Tactu. Annotations Anat. et PhysioL, Lipsise, 1834.

CHAPTER VIL

OF THE SENSES OF TASTE AND OF SMELL.

THE fact of the extraordinary tactile sensibility of the point of
the tongue proves conclusively that the cutaneous corpuscules
tactile are not special sensitive apparatus. In effect these cor-
puscles do not appear to exist in the lingual mucous membrane.

The sense of touch has not therefore in man, in whom it has
especially been studied, any localisation well denned, any
specialisation very distinct. We see it also transforming
itself in the tongue, passing gradually into the sense of taste.
For the papillary projections of the point of the tongue which
are so tactile are at the same time gustatory. To convince
ourselves thereof we have merely to excite them with a feeble
electrical current. The effect however is the same when we
merely excite the parts of the point of the tongue which are
destitute of papillae.

So far we know nothing positive with regard to the seat or
even the existence of taste among the invertebrates and even
among many of the vertebrates. The buccal mucous membrane
of fishes is covered with small teeth, pointed and hooked, and
seems very ill organised for gustation. The tongue, which in
the vertebrates seems to be the special, or the most special,
seat of taste is rudimentary and dry in many reptiles. Never-
theless the chelonians and the lizards, which chew their food, have
a tongue, soft, rich in papillae.

410 BIOLOGY. [BOOK vi.

So far as taste is concerned birds seem to be very badly
provided. They probably swallow without tasting : for their
tongue, usually destitute of muscular tissue; is dry and carti-
laginous.

It is among the vertebrates that the sense of taste is de-
veloped, but very unequally, according to species. The rodents,
which feed on fruits or animal substances, have a soft tongue,
without appendices. Those, on the other hand, which gnaw
roots and barks, have on the tongue a kind of integument,
garnished sometimes even with denticulated scales. Certain
carnivorous animals, especially of the genera Ftlis and Hycena,
have also a tongue bestrewn with papillae conical, voluminous, and
covered with a horny sheath.

In dogs, monkeys, men, the tongue is voluminous, musculous,
flexible. On the superior surface and on the edges the mucous
membrane which crosses it is made rough with dermic projections,
rich in nervous threads. These papillae, denominated, according
to their varying aspect, caliciform, fongiform, corolliform, hemi-
spherical, seem to have for result and for function to multiply the
surfaces of contact with the sapid bodies. These last act only
in the state of solution. Their molecules severed and in suffi-
cient number must put themselves into intimate contact with the
gustatory papillae. Sapidity has very different degrees of energy,
according to the substances. Water containing in solution a
hundredth of cane sugar is insipid, while a solution of sea salt
to the extent of an eight-hundredth has still savour, and it is
enough for a solution to contain a thousandth of sulphuro-
hydric acid or of sulphate of quinine to be still sapid. We can
always, indeed we must, view in their relations the sense of
taste and the sense of touch : but taste is a special tactility, less
gross, more varied also, for the number of savours perceptible by
man is extremely numerous. The division of the sensitive labour
is for taste more evident than for touch. It seems as if there
were special nervous threads for certain savours. Many sapid
bodias, especially salts, produce different sensations, according

CHAP, vii.] OF THE SENSES OF TASTE AND OF SMELL. 411

as they are applied to the anterior part or the posterior part of
the tongue.1

The essential structure of the gustatory papillae is still imper-
fectly known. Certain anatomists think that the nervous fibres
terminate freely in the papillae. Others are of opinion that they
anastomose with fine filamentous prolongations emanating from
epithelial cells. It is supposed that this arrangement has been
observed on the tongue of the frog (Billroth), an animal however
in which taste is probably very little developed.
. In touch, sensibility is brought into play by the simple shock
or contact of bodies. The sense of taste, on the other hand, is
only impressionable by solutions, molecules severed in a liquid.
But smell demands a matter more attenuated still. In eifect,
liquids impregnated with odorous substances awaken no olfactory
sensation, at least in man, when they bathe the organ of
smell. Substances alone in the state of gases, of vapours, or of
line particles suspended in the atmosphere, can provoke olfactory
sensations, at least in the superior mammifers.

In the animal series the anatomical sense of smell is rather
better known than that of taste.. Leydig found, in the hirudi-
iiates, at the bottom of cupuliform depressions, compact bundles
of rigid prolongations, analogous to the tactile baculi. He met
with analogous organs in the cephalopodal mollusks. Thinking
that he recognised therein olfactory organs, he called these
prolongations olfactory baculi. He gave the same name, and
attributed the same function to analogous bundles existing on
the pair of anterior antennae of certain crustaceans.2

In all vertebrates, in which the sense of smell is better and
more certainly known, it is also constituted by depressions of
varying form and volume situated in the head ; these cavities
are usually clothed with vibratile epithelium. In the amphioxus

1 J. Guyot et Admyrault, Archives Gtnirales de Medcdne, 2e ser., t. XIII.,
y. 51.

2 Gegenbaur, Anatomie Compare, p. 190. — Leydig, Histologie Comparee,
pp. 250, 361.

412 BIOLOGY. [BOOK vi.

the organ of smell seems to exist spite of the absence of brain.
It is represented by one or two depressions with vibratile
epithelium.1

In every class of vertebrates, man not excepted, the nervous
olfactory threads are composed of pale fibres, finely granulous,
without envelopment of myeline : in short of grey fibres,
which all, in the craniote vertebrates, emanate from two special
and intracranian nervous expansions called olfactory bulbs.
These masses of nervous substance, very little developed in man,
are much more so in the other vertebrates. In many mammifersand
vertebrates, moreover, the sense of smell is much more developed
than in man. It controls the sense of sight, often comes to
its aid, and sometimes takes its place. The olfactory bulbs of
many mammifers are very voluminous, situated in advance of
the brain : often they are hollow, and communicate with the
lateral ventricles. The mole, which is almost blind,2 has
enormous olfactory bulbs. In many birds and reptiles also the
olfactory bulbs form an important cerebral expansion. The
olfactory bulb of fishes is often as large as the cerebral lobe,
properly so called. Sometimes even it is much larger, and this
conformation is no doubt in relation with the difficulty of
olfaction in an aquatic medium.

The olfactory nerves are nervous threads, proceeding in great
number from those bulbs, and ramifying into the superior portion
of the nasal cavities. The mucous membrane of those cavities,
habitually clothed with vibratile cilia, is destitute thereof
precisely in the portion, somewhat limited, where it receives the
olfactory threads. There it is furnished with a cylindrical epithe-
lium, whose cells terminate in fine filaments, which go to lose
themselves in the dermis of the mucous membrane. Beneath
these epithelial cells are other special cells, surmounted each

1 Huxley, Anatomia Comparata dei Vertebrati. Italian translation of E.
Giglioli. Gegenbaur, Anatomic Comparfo, p. 709.

2 On the contrary, the mole is said to have rery sharp sight, though its eyes
are peculiarly placed. — Translator.

CHAP. VIL] OF THE SENSES OF TASTE AND OF SMELL.

413

with a thin bacillum (or bacillarium), with a transparent and
crystalline extremity (Fig. 74). At their inferior part, these
cells emit nodose filaments, which
continue with the fine ramifica-
tions of the olfactory nerves.1

The sense of olf action, even in
man, is of very great delicacy. An
air charged with a ten-thousandth
of its volume of vapour of essence
of roses has nevertheless for us an
extremely appreciable odour. The
keenness of the sense of smell is
far greater still in many animals,
capable of catching numerous
scents which escape us.

In reality, spite of the vola-
tility of scented substances, the
manner in which these substances
enter into relation with the ol-
factory elements does not differ
essentially from what takes place
for the sense of taste. The ol-
factory mucous membrane being
constantly lubricated by a secre-
tion, it is always in the state of
solution that the scented particles
come into contact with it. Also
the groups of olfactory and gus-
tatory sensations are very near
neighbours, and it is not without
difliculty that physiologists are
able to distinguish them. In sum,
smell is akin to taste, and taste is akin to touch. Strictly, we

PIG. 74.

Microscopical elements of the olfactory
mucous membrane : 1, of the frog ; a,
cylindrical nucleated epithelial cell,
terminating at its base with a ramified
filament ; &, nucleated cell of the olfac-
tory bacillum, c, which terminates at its
extremity with a bundle of long vibra-
tile cilia, e, while the cell bears at its
base a fine nodose filament, which con-
tinues with the fibres of the olfactory
nerve. — 2, of man : a, the epithelial
caudal cells, between which are the
cells, 6, with their olfactory bacilla, c,
their terminations gemmate, e, and their
internal filaments, d, communicating
with the fibres of the olfactory nerve.
—3, fibres of the olfactory nerve of the
dog, dividing themselves into very fine
fibrils.

1 C. Vogt, Lcttr&s Physiologiques, p. 419.

414 BIOLOGY. [Boox vr.

may consider these three varieties of sensibility as three modes,
three degrees of the same sense.

From the point of view of dignity, of psychological nobleness,
touch, taste, and smell are coarse, inferior senses. In man they
have no special memory. The sensations and impressions which
they procure leave no durable traces, and the imagination by
itself is powerless to revive them.

With the two special senses of which we have now to speak
it is far otherwise.

CHAPTER

OF THE SENSE OF HEARING.

BETWEEN the three preceding senses, which may be called tactile
senses, and the senses of hearing and of sight, there is an impor-
tant difference in the mode of generation of the sensations. For
the tactile senses, the direct contact of the bodies capable of
exciting the sensation is indispensable. On the other hand, for
hearing and sight, the sensitive organ is agitated indirectly by
simple vibrations transmitted to fluid or solid media. As I have
not here to write a treatise on acoustics, it is enough for me to
recall that any sonorous body is only a body of which the •
molecules vibrate more or less regularly, and communicate to
the ambient media movements which from point to point go to
agitate the auditory organs.

The physiology of the invertebrates is still so imperfectly
known that we are unable to say whether in a number of
them the sense of hearing exists. Guided by anatomical facts
and analogies, men of science have thought that they recognised
auditory organs in all the groups of the invertebrates. In
worms the auditory organ seems to be a vesiculiform capsule,
full of liquid, and containing solid concretions, analogous to
those which we meet with in the internal ear of the verte-
brates. These ototitks are put into vibratory movement by
cilia lining the wall of the auditory sac.1

Certain echinoderms seem to be provided with auditive
1 Gegenbaur, loc. tit., p. 197.

416 BIOLOGY. [BOOK vi.

vesicles, in which float powerfully refracting homogeneous granu-
lations. These vesicles receive nerves, and sometimes even rest
on the central ganglions of the nervous system.1

There is the same structure of the auditory organs in the
mollusks. Those organs are always small bags full of liquid and
containing otoliths formed of an organic basis,
impregnated with calcareous substance. These
otoliths sometimes amount to many hundreds
(Fig. 75).

The auditory organs of the arthropods are
more varied, and are known only in some
FIG. 75. divisions of the crustaceans and of the insects.

Auditory organ of Cy- In the crustaceans, the auditory vesicles are
suie';°' &e, epithelial sometimes open. The closed vesicles contain
cilia3; o™toiith. W1 otolithical concretions fixed by fine hairs regu-
larly arranged. According to Hensen, auditory
hairs, free, sometimes exist outside of the vesicles. These hairs
even enter into vibration, isolately, when musical sounds are
produced. Each of these vibrates in the water according to a
special musical sound.

The organs of hearing proceed in the vertebrates from an
invagination which is produced from the two sides of the head
at the commencement of the embryonary life. This vesicle, at
first in extensive communication with the exterior, closes little
by little. The most inferior of the vertebrates, the amphioxus,
seems destitute of auditory organs.2 According to Schultze, the
auditory organ of the cyclostomes appears to be first of all a
vesicle containing a rounded otolith.3

Most fishes have as organs of hearing ampullae full of liquid
and imperfectly divided by an incomplete partition, on which
the nervous terminations are spread. The internal face of the wall

1 Leydig, toe. cit., p. ai6.

2 Huxley, Anatomia, Cbmparata dei Vertebrati, p. 71. (Jtalian transla-
tion of En. Giglioli.)

3 Entweilung von Petromyzon Planeri, Harlem, 1 856. '

CHAP, viii.]

OF THE SENSE OF HEARING.

417

is lined with cylindrical epithelial cells. Beneath are found other
, cells sending bacilla between the epithelial cells. At this base
these cells emit fine filaments which seem to be in relation with
the nerves (Fig. 76). It is a structure very analogous to that
of the olfactory membrane.

In man and the superior vertebrates the auditory or<*nn is
composed, as is well known, of three
parts, namely : — the external ear,
comprehending the pavilion of
the ear and the external auditory
conduit, shut by the membrane of
the tympanum : the median ear,
composed of the cavity of the
tvmpanum, communicating with
the throat through the Eustachian
tube and traversed by the chain
of the ossicles ; finally, the internal
ear, constituted schematically by
an ampulla full of liquid, and
containing otoliths. It is also
known that this internal ear is Fio _6

subdivided into vestibule. semi- Microscopical preparation taken from the

partition of the auditory ampulla of the

Circular Canals, and into a part clavated ray rJJaja elamta): a, cylindii-

cal nucleated cell, forming- the internal
epithelium ; 6, nucleated cells terminal
ing in fine filaments and resting on the
cartilage traversed by the nervous
fibres, /, which terminate in very fine
ramifications, g; the ramifications con-
tinue very probably in the fine filaments,
e, with which commence the nucleated
cells c, of which the terminations in
auditory bacilla, d, are placed between
'the cells, o, of the epithelium.

rolled spirally, the cochlea. The

fundamental portion of all this

complicated apparatus is evidently

the internal ear, in which are

formed the terminal threads of the

auditory nerve. The other parts

are accessory, and are more or less lacking in many vertebrates.

The internal ear is simplified more and more in proportion as we

descend in the series. The aquatic mammifers and birds have

no external ears. The median ear gradually disappears in reptiles

and the amphibia. Already in the inferior vertebrates the cochlea

loses its usual shape. Instead of the spiral cochlea birds

E E

418 BIOLOGY. [Boos vi.

have a small pyriform sac. Deserving of remark is this last fact,
completely in contradiction with the modern theories of the office
of the cochlea in man, in whom it is supposed to have the ap-
preciation of musical sound for function. Such an organ ought to
be extremely developed in singing birds. There is no cochlea in
the internal ear of reptiles and of fishes. The most inferior fishes
have not even any semicircular canal, and consequently their
ear has much affinity with that of the invertebrates.

From this rapid anatomical summary it manifestly results,
that the truly essential part of the organ of hearing is the
internal ear, that is to say a vesicle full of liquid holding in
suspension otoliths, and into which lead the terminal threads of
the auditory nerve. The shock of the aerian sonorous waves puts
in movement the liquid of the auditory ampulla, and the vibra-
tions of the molecules of this liquid agitate and impress the threads
of the auditory nerve. In the superior mammifers and in man
these threads are very numerous ; also the auditory ampulla has
grown complicated ; it is furnished with appendices, with circular
canals, and especially with the labyrinth, that is to say, with a
tubular cylindrical prolongation, rolled on itself spirally, and the
windings whereof go on gradually decreasing (Fig. 77). The
nervous auditory threads penetrate into the stem of this cochlea,
and come forth therefrom successively, spreading themselves in
the partition which separates from each other the spiral windings.
These nervous threads of the cochlea are composed of nervous
fibres, which, at first white, and with double contour, have con-
tinuance with the ganglionary cells, become afterwards fine
and pale, and end their course in small cells emitting each an
extremely fine filament, a sort of auditory bacillum.

As the spiral windings go on decreasing, the length of the
terminal nervous threads diminishes also gradually, and their
regular arrangement recalls that of the strings of a harp or of a
piano, with which they have often been compared. An accessory
organ, the organ of Corti, lodged in the spiral partition itself,
has been compared to the fingerboard of this living piano. But

CHAP. VIIL] OF THE SENSE OF HEARING. 419

the nervous fibres do not vibrate after the manner of strings, and
the portion of each of these fibres, included in the partition of
the cochlea, represents only a very small part of the total fibre.
The analogy is therefore forced. There is nothing to prove that
in this order of decrease each of these fibres has the duty of seiz-
ing a special tone higher and higher, and the construction of the
cochlea mav be nothing more than an organical device having the

FIG. 77.

Vertical section of the cochlea of a foetus of calf. The central stem or columella and the
spiral lamina are not yet ossified. We see distinctly in each spiral winding the three
cavities as well as the thickening due to the organ of CortL

advantage of furnishing to the extension of the nervous threads a
surface relatively large under a small volume. It is not the less
certain that the ear of man discerns musical tones and semitones
with great facility; but observations of pathological anatomy
prove that this faculty of appreciating musical tones can persist
after the destruction of the cochlea. Finally, as we have had occa-
sion to remark in passing, singing birds have no spiral cochlea.

Let this be as it may, the ear can seize an infinite variety
of tones of every kind, apart from the musical sounds, the
number of which is somewhat limited. As regards the wealth
of the sensitive field, hearing is very superior to the three
tactile senses, and is inferior only to the most delicate, the
most intellectual of the senses, the sense of sight.

£ £ 2

CHAPTER IX.

OF THE SENSE OF SIGHT.

ALREADY we have remarked how in going from touch to
taste, from taste to smell, from smell to hearing, the excitants
of the special sensations, the modes according to which the
exterior medium impresses the organs of the senses, always go on
attenuating themselves. At the outset it is the shock, the coarse
contact : then it is the sapid particle ; afterwards comes the
odoriferant effluvium ; finally, the simple vibration, the sonorous
nerve. From hearing to sight the series continues. In effect,
to excite the optical nerve, an undulation of gaseous liquid or
solid molecules is no longer needful. The normal excitant of the
sense of sight is the most impalpable of all : it is the vibration
of the ether, a body, doubtless, not penetrable, as was long
believed, for everything which is material is extended and im-
penetrable, but at least a gas so rarefied and light, that for
our rough clumsy instruments ot physics it has no appreciable
weight.

The eye, whatever may be the type of its structure, may be
considered, when it is furnished with its essential parts, as a
transparent and refractive apparatus, suitable for concentrating
the luminous rays on the expansions of the optical nerve. But
the eye is far from being always" complete, and it is very curious
to see it perfecting itself little by little as we ascend the animal
series. How many pages overflowing with a bombastic admira-
tion have been written to vaunt the structure pretendedly

CHAP, ix.]

OF THE SENSE OF SIGHT.

421

marvellous of the eye in man and the superior vertebrates 1 It
has been praised as a perfect instrument, necessarily the work of
an intelligent artificer anxious to adapt means to ends, and so
forth. "We now know that, considered as an optical apparatus,
the eye is a tolerably good instrument, but by no means perfect.
Moreover, comparative anatomy and embryology prove to us
that, spite of its complicated construction, the eye is like all the
other organs, merely the result of a slow labour of perf ectiomnenc
and accommodation.

In effect, the rudimentary eye is only a simple drop of black
pigment, reposing on nervous elements. Such it is in the inferior
medusse, in which we find at
the base of the tentacles pig-
mentary spots. These spots
are the first rudiment of the
eyes : for sometimes we meet
therein with crystalline rods.
In other cases the construc-
tion of the optical apparatus
takes an additional step, and
we encounter in the masses
of pigment a transparent and

rpfvanfivft ' hn^^r /T?iV 7«\
.nactlVG body (Xlg. 1&).

In certain species, nervous

bundles penetrate manifestly into the capsule.1

Many planaries have first of all in the embryonary state pig-
mentary spots in the place where are to be at a later period eyes
with rods or crystalline cones. The absence or the presence of the
organs of vision is often subordinated to the kind of life. Eyes,
for example, are sometimes lacking in the annelids which live in
the darkness. These eyes have not, in this case, been the object
of selection or differentiation, for they are useless.

1 For all questions of evolutive anatomy, consult especially the Manuel
d' Aticutomie ComparSe of Gegenbaur, one of the few treatises composed in
harmony with the results of traiisformism.

peduncles; c, canal thereof; d, ampulla; e,
sac with crystais; /, pigment; g, body in

formoflens-

422 BIOLOGY. [BooK vi.

The eyes of the asterise are situated at the extremity of the
radii. They are spherical bodies reposing on a nervous mass.
They are surrounded by an envelopment of pigment, and covered
with an epithelial cuticle.

Visual organs are met with in the mollusks at all degrees of
development. They are absent in the fixed mollusks. Certain
of these last, which in the state of mobile larvae had eyes, lose
them by organic degradation when they have become immobile.
Certain species of lamellibranchians have as organs of vision
sometimes pigmentary spots, sometimes brilliant organs, dissemi-
nated on the edge of the mantle and receiving nerves.

The eyes of the cephalopods and cephalophores are always two
in number, and placed usually at the base of the tentacles,
sometimes at the extremity of special tentacles. They are more
over very irregularly developed. Sometimes they are simple
pigmentary spots situated on the cesophagian ganglion; some-
times, for example, they are complex organs, comparable with
the eyes of the vertebrates. They then rest on a ganglionary
nervous expansion, have a retina, a layer of optical bacilla,
separated from the deep layer of the retina by a pigmentary
stratum. On this retina rests a sort of vitreous body, in front
of which is a lens, covered by a cornea. A thin integument
covers all the apparatus. The eye of the sepia is constructed
on this plan, but with great perfection (Fig. 79). *

In sum, the complete eye is composed first of all of optical
bacillaria, that is to say of small special organs, destined to
receive, or rather to select the luminous waves, and to transmit
the molecular agitation to the optical nervous threads. That is
the essential part of the organ of vision. In advance of these
bacillaria, refractive media concentrate the luminous rays, and
thus intensify the impression. Finally, a pigmentary envelop-
ment isolates, more or less perfectly, the sensitive elements.

How remarkable soever the compound eyes of many arthro-
pods may at first sight appear, these organs do not differ
essentially from those of the other zoological groups. The eye

CHAP, ix.]

OF THE SENSE OF SIGHT.

423

of the arthropods is, schematically, composed of a crystalline
bacillum, wrapped in a pigmentary mass, and covered exteriorly
with a transparent chitinous lamina. This lamina connects with
the general tegnmentary envelopment, and sometimes bombates
within so as to form a plano-convex lens. Sometimes this

FIG. 79.

Schematic horizontal section of the eye of a sepia, ; KK, cephalic cartilage ; C, cornea ; L,
crystalline humour ; ct, ciliary body ; R, internal layer of the retina ; p, pigmentary layer ;
o, optical nerve ; go, ganglion of the optical nerve ; fc', cartilage of the globe of the eye ;
ik, cartilage of the iris ; w, white body ; ae, external argentine layer (after Hensen).

chitinous crystalline substance bombates also outwards, and then
it is bi-convex. This simple eye, with a simple bacillum, exists
in the inferior crustaceans.

In the arachnida many bacilla group themselves, cling
together ; they are habitually covered with one and the same

424 BIOLOGY. [BooKvi.

cornea. But it is in the superior crustaceans, and especially the
insects, that this compound eye attains its maximum of develop-
ment. Then it is constructed by the aggregation of a great

number of simple eyes, some-
times many thousands, radia-
ting round a nervous expan-
sion, pressed against each
other, which gives them a
hexagonal form. The external
chitinous tegument , the cornea,
has then the aspect of a
hexagonal network, exactly
Fl°- 80- resembling tulle (Fig. 80 £).

.1, schematic section through the compound eye . , ..

of an arthropod; n, optical nerve; g, its ThlS has been Called the JO.-

ganglionary expansion ; r, crystalline bacilla ,-„. oriX

coming forth from the ganglion; c, facetted cetted eye (-fig. oU).

cornea formed by the teguments, each facette, T . , ,, £ ,,

in consequence of its internal convexity, ap- In principle trie eye OI the
pearing to be a refractive organ (lens). , •, j , . IY-

L, some facettes of the cornea seen on the upper Vertebrates does not diner

C, "crystalline bacilla(r), with the corresponding essentially from that of the
cornean lens (c) of the eye of a coleopter. invertebrates and even of the

arthropods. At the outset it is represented in the adult amphioxus,
and even in the first stages of development in the cyclostomes,
only by a pigmentary spot reposing on the nervous centres.

In all the other vertebrates the eye is first of all constituted,
in the embryological state, by a double vesiculiform expansion of
the intermediary cerebral cell. These expansions join themselves
to the epithelial cells of the epidermis, winch at this point multiply,
modify themselves, repel the vesicular nervous wall, depressing
it into the form of a cup. Then the epidermoidal expansion
which penetrates into this depression differentiates itself there
and forms the crystalline humour (Fig. 81). At the same time,
the expansions of the optical nerve spread themselves over the
segment of the ocular globe thus formed, and their terminal
threads connect themselves with the retinian bacilla in very large
number.1 Finally, we have the complete eye of the superior
1 Huxley, loc. cit.

CHAP, ix.]

OF THE SENSE OF SIGHT.

426

vertebrate (Fig. 82), that is to say a vitreous globe, receiving
in the rear a voluminous nerve, and containing a retina reposing
on a pigmentary layer, then divers refractive media, which go
from back to front ; the vitreous humour, the crystalline, enchased
in a contractible and vascular apparatus, called ciliary process,
and protected in front by a coloured contracted screen, the iris.
This screen pierced in the centre by a circular opening, the pupil.

FIG. 81.

A , transversal and vertical section of an embryon of fish ; c, brain ; a, primitive ocular
vesicle ; b, its stem by which it communicates with the medullary tube ; d, dermic layer.

B, ulterior state, formation of the secondary layer ; p, anterior wall (pigmentary layer) ; r,
posterior wall (layer of the retina) of the secondary ocular vesicle ; e, cornean layer (epi-
dermis) emitting into the secondary vesicle the crystalline humour ; I, the vitreous body
behind.

merges into a liquid medium, the aqueous humour, which bathes
also the anterior face of the crystalline on the one hand, and
the posterior face of the transparent cornea on the other. We
have not here to describe in all its details the complex structure
of the eye of the vertebrates. In sum this retina is formed of
bacilla connected behind with cells, into which the optical
nervous fibres seem to pass (Fig. 82).

If we are willing to disregard accessory parts, the eye of man
does not differ essentially from that of the arthropods. Each of
the bacilla of the human retina is comparable with one of the
voluminous optical bacilla of the insects, &c., and the eye of the
mammifers may be brought into relation with the compound eye,

BIOLOGY.

[BOOK vi

with single cornea, of many arachnida. \Ve still therefore find
here an essential uniformity under an apparent variety.

But we can generalise still more. In effect, there is a great
analogy of conformation in the terminations of the sensitive
nervous fibres. For the optical, auditory, olfactory fibres the
morphological resemblance is striking. Each of these fibres
ends, at the periphery, in a cell connected with a special organ,
or bacillum, whose function probably is to select among the

FIG. 82.

Transversal and horizontal section, magnified, of the globe of the eye ; a, sclerotic ; o, cor-
nea ; c, lamella of the conjunctiva passing over the cornea ; d, circular vein of the iris ;
e, choroid with its pigmentary layer ; /, ciliary muscle ; g, ciliary process ; h, iris in the
middle of the pupil ; I, optical nerve ; k, anterior edge of the retina (ora serrata retinae) ;
I, crystalline lens surrounded by its capsule ; m, membrane of Descemet lining the in-
terior chamber of the eye ; n, internal layer of the retina; o, membrane of the vitreous
body; p, canal of Petit.

molecular vibrations of the ambient world those which are
adapted to the special sensibility of the fibre which it terminates.
The organs of the senses with complicated structure, such as
the eye and the ear, are only accessory apparatus, which render
more easy the function of the bacillum, by concentrating on it
such or such a kind of excitation. In effect in proportion as we

CHAP, ix.]

OF THE SENSE OF SIGHT.

427

Fio. 83.

A, Elements of the retitia. — The trellis, isolated, of the supporting fibres : a, membrane, i
tremely fine, which separates the bacillated layer from the other layers ; e, vertical suppc
ing fibres, with lateral prolongations and intercalated nuclei (cO visible especially in 1

, ex-
Sport-
ing fibres, with lateral* prolongations and intercalated nuclei (cf) visible especially in the
median layers ; d, intermediary layer ; g, molecular layer ; t, internal limiting membrane,
where the supporting fibres have their origin.

B, The nervous elements, isolated, of the retina : Z>, bacilla -vrith external granules (?/) ; c.
cones with their granules (cO ; d, intermediary layer with fibrils extremely fine ; /, layer
with internal granules ; g, trellis of nervous fibres, very fine, in the molecular layer ; h,
ganglionary cells ; h', nervous fibres which proceed thereto ; i, fibres of the optic nerve.

428 BIOLOGY. [BOOK vi.

descend in the animal series, we see the apparatus, the organs
of the senses simplify, and even disappear, leaving desquamated
the nervous terminations and their bacilla.

As to the tactile fibres and the gustatory fibres, which are
only a variety thereof, their function is much more simple ; also
they have not usually any terminal cells. Neither do they lead to
true bacilla, but to corpuscles, dermic projections, appendices of
varied form.

The nature of the sensations transmitted to the conscious
nervous centres by the sensitive fibres is, however, altogether
independent of the terminal appendices and apparatus. In effect
any sensitive nerve excited on its passage awakens in the nervous
centres solely and specially the kind of sensation which it has
the function to provoke. Every excitation, physical, mechanical,
chemical, and so on, any lesion, puncture, contusion, section of a
sensitive nerve, have as repercussion in the nervous centres
sensations tactile or painful, gustatory, olfactory, auditory,
optical, according as the nerve affected appertains to touch, to
taste, to smell, to hearing, or to sight.

It remains for us now, after having passed in review the
peripheric organs of sensibility, the apparatus which are the
gatherers of sensations, to consider the receptive centres, the
nervous parts, in which the mechanical agitation of the terminal
sensitive fibres determines a physical fact, a phenomenon of con-
sciousness. Recently some unsuccessful efforts have been made
to apply here the theory of the transformation of forces. But
there is not here any transformation of the molecular movement
in the habitual sense of the expression. When a luminous undu-
lation comes to agitate the nerves of the retina, the central
sensation which results therefrom is by no means a direct trans-
formation of the ethereal vibration. This undulation has been
simply the occasional cause of a whole series of physiological
phenomena, the nutritive oxydation of the tissues being the real
cause. The mechanical agitation of the sensitive nervous ex-
tremities plays in sensation the part of a trigger in a firearm.

CHAP, ix.] OF THE SENSE OF SIGHT. 429

Now no one dreams of seeing in the deflagration of the powder and
the propulsion of the ball which succeed the shock from the dis-
charge of a musket, the direct transformation of the movement
operated by that discharge. It would be just as little logical to
wish to find in the conscious phenomenon of sensation the
mechanical agitation which has brought into play the sensitive
apparatus. In the firearm and in the nervous system, the exterior
shock has simply determined a perturbation of equilibrium ; it has
let loose forces which neutralised each other ; it has acted as a
force of disengagement.

CHAPTER X.

OF THOUGHT.

WE are now about to explore a biological department which has
for centuries been the exclusive domain of metaphysical phantasy,
and which is still its sanctuary, its last refuge. The fact is, that
scientific investigation could not undertake with any success the
analytical study of conscious biological facts without being armed
at all points. It was first of all necessary to acquire, by patient
and innumerable researches, a just idea of organisation and of
life ; it was necessary to prove that the living world and
the mineral world are only diverse modes of an identical sub-
stance; to watch, step by step, the circular movement of
the material molecules ; to see them vitalised, then mineral-
ised, in the nutritive vortex ; to distinguish and co-ordinate
the great organic properties. At the same time, it was neces-
sary to unravel the anatomical structure and texture of all
living beings, to resolve them into systems, apparatus, organs,
tissues, and anatomical elements. That done, it was possible to
classify the functions, as we have classified the organs, and
especially to connect the fundamental properties of the living
substance with the tissues. "We have seen that all the anatomical
elements grow, are nourished and reproduced ; but that on this
general substance are grafted properties peculiar to each histo-
gical species, that the epithelial cell secretes, that the muscular
fibre contracts, that the nervous fibre conducts the motory and
sensitive incitations; finally, that all the phenomena of con-

CHAP, x.] OF THOUGHT. 431

sciousness have their seat in the nervous cells. In effect, where-
ever there are phenomena evidently conscious, there are nervous
centres. Thought is assuredly a property of the nervous cell.
There are conscious nervous cells, and without them there is no
psychical phenomenon humble or sublime. This is the idea
which the Greek expressed in an ingenious allegory, by making
Minerva spring from the brain of Jupiter. The existence of
these nervous cells is a necessary condition to the production of
the phenomena of consciousness, but the mode in which they are
grouped is only a secondary condition of thought. The latter
exists with all its principal modes in the nervous ganglionary
chapelet of the ant as well as in the brain of the mammif ers.
Nevertheless, it is a biological law, that the concentration of
nervous cells in great masses is favourable to the development
and intensity of the psychical phenomena. The caterpillar has
more ganglions than the perfect insect ; the more intelligent the
insect is, the larger the cerebroidal ganglion. Finally, in the
vertebrated animals, the intellectual development is large in
proportion as the encephalon is more voluminous.

Must we consider the nervous ganglions of the invertebrated
animals as so many little brains ? Has each swelling of the
central nervous chain, in insects, for example, the faculty of
feeling, thinking, wishing, on its own account 1 Is all this gang-
lionary concatenation a nervous federation, each member of which
enjoys a certain independence, and presides over the conscious
life of the segment of the body which corresponds with it ? In
this case, there would be a kind of regional division of conscious
nervous labour, and the cerebroidal or superoesophagian ganglion
would scarcely have any advantage over the others but that of
presiding over vision, and of being in consequence intrusted with
the guidance of the whole cohort drawn up behind it. l A cele-
brated experiment of Duges seems at first to solve the question
affirmatively : " I rapidly cut off," he says, " with scissors, the
protothorax or protodere of the Mantis rdigiosa ; the posterior
1 Dugks, Physiologic ComparSe, t. I. p. 343.

432 BIOLOGY. [BOOK vi.

troncon, still supported upon its four feet, resists the impulsions
by which we try to overturn it, rises up and resumes its equili-
brium if we overcome this resistance, and at the same time, by
the trepidation of the wings and elytra, testifies a lively feeling
of anger, as it would during the integrity of the animal, when
provoked .by being touched or threatened. But this posterior
troncon contains a considerable part of the chain of ganglions.
"We can carry on this experiment in a more striking manner :
the long corselet, which has been detached from the other seg-
ments, contains a bi-lobed ganglion, which sends nerves into the
arms or anterior feet, armed with powerful claws (snatching
feet) ; let the head be detached, and this isolated segment will
live nearly an hour with its single ganglion ; it will agitate its
long arms, and is quite capable of turning them against the
fingers of the experimentalist who hold the troncon, and seizing
them so as to inflict pain. This single thoracic, or deric gang-
lion, then, feels the fingers which press the segment to which
it belongs, recognises the point by which it is held, wishes to
free itself from it, and directs towards it the members which
it animates."1

At first sight, the experiment of Duges seems decisive ; but
the co-ordination of the movements, their apparent intention, do
not necessarily prove that they are conscious. Many very com-
plicated reflex, but perfectly unconscious movements co-ordinate
perfectly. We observe many of these apparently voluntary
movements, even in the vertebrated animals, and even in the
mammifers, where nevertheless the coalescence of the nervous
centres is incomparably greater. A fish, or a frog, deprived of
the brain, still executes a series of movements, apparently com-
bined. It was the same with the pigeons whose brain Flourens
had removed.2 Finally, reflex, co-ordinate movements still take
place in a decapitated human corpse. The spinal marrow seems

1 Duges, Physiologic Comparee, p. 337.

2 Flourens, Recherches Exp&rimentales sur les Propriitis et Us Fonctions
du Syst&me Nerveux, &c., Paris, 1824.

CHAP, x.] OF THOUGHT. 433

to be a source of automatic nervous activity, an unconscious
nervous centre. It may then be the same with the nervous
ganglions of the arthropods, &c.,'in which, besides, the prepon-
derance of the cerebroidal ganglion is much less evident, and
surely much less absolute than in the brain of vertebrated
animals.

In the latter, the brain is the principal, and very probably
the only conscious organ. In traversing the series, from lower
to higher, we see the cerebral hemispheres grow large in propor-
tion as the species is better endowed and more intelligent.
There are first simple nervous ampullae, scarcely to be distin-
guished from the other nervous intracranian expansions (see
Book I., ch. VI). Then gradually these cerebral vesicles grow,
and end by dominating and covering, more or less completely,
the other encephalic nervous ganglions ; their surface, almost
exclusively formed of nervous cells, becomes furrowed, is folded
in flexuous digitations called circumvolutions. The more in-
telligent the animal, the more numerous generally are these
circumvolutions. Their object, like that of the pecten, which
thrusts, in the eye, from back to front, the retina of certain
birds, is to multiply surface under a small volume. At the
same time that their number and ramifications augment, the
grey substance, the cellular cortex, which covers them, and is
the conscious part of the brain, augments in thickness. In man,
we must estimate at many thousands the number of nervous cells
superposed in strata in a square millimetre of cortical cerebral
substance, and the number of these strata is greater at the
anterior part of the brain, in the frontal lobes, which seem to
be the headquarters of intelligence.1

In a preceding chapter, we have summarised the beautiful
anatomical systematization of the cells and fibres of the human
nervous centres, for which we are indebted to M. Luys. We
have seen that thousands of sensitive and peripheric fibres of

1 J. Luys, Etiides de Physiologic et de Pathologic Cirtlrales, p. 11. Paris,
1874.

F F

434 BIOLOGY. [BOOK vi.

each half of the body, first conduct to a cellular nucleus, tJie
optic thalamus ; that thence they radiate towards the cortical
cells of the circumvolutions ; that other fibres start from these
cortical cells, and converge towards another cellular nucleus,
the striated body, whence finally irradiates the whole system
of peripheric motory fibres, connected, in addition, with the
cells of the cerebellum, which seems to be simply a co-
ordinating centre of the movements. As the cortical cells of
the two cerebral hemispheres are united by transverse fibres, the
result is that the hemispheres, the two optic layers, the two ;
striated bodies, form a complete system, the different parts of
which are anatomically and physiologically connected. If the
man is a healthy adult, then the instrument is harmonic, and
vibrates accurately : the circumvolutions are swollen, and
dilated ; their summits rise equally to the surface of the hemi-
spheres ; a cortical, cellular layer, several millimetres in
thickness, covers them. On the contrary, in senility, insanity,
and mental maladies, certain circumvolutions give way and break
down; they are notes which no longer sound.1

On the whole, every nervous system, however little developed,
in the invertebrated animals as well as the vertebrated, may be
traced to a conscious cellular part, in continuous relation with
two fibrous systems, the one afferent, through which sensitive
excitation is conveyed, the other efferent, by which motory
incitation is transmitted. The schema of such a system would
be a conscious cell furnished with a single afferent fibre and a
single efferent fibre.

But the mode of operation of a system thus arranged is
evidently reflex action, and, in effect, there is not a central
nervous act, from the protozoon to man, which cannot be traced
to reflex acts ; thus it is infinitely interesting to follow
through all its principal phases the gradual transformation and
complication of the reflex nervous act.

1 J. Luys, Le Cerveau (Revue Scientifique, No. 35, 1875).

CHAP, x.] OF THOUGHT. 435

First of all, the reflex action is absolutely unconscious. There
is an agitation of the afferent fibres, excitation of the cells, which
react upon the efferent fibres. At a higher degree, the nervous
cell sensibilises : it becomes conscious of the vibration of its
molecules; it experiences the sensations of touch, taste, &c.,more
or less varied and numerous according as the organ is more or
less perfect. At the same time it has impressions of pain or of
pleasure. At this stage the conscious being is still very inferior ;
each sensation, each impression, dies as soon as it is born ; there
is no chain of conscious phenomena, no link, no relation in the
psychical life. But everything changes, when the nervous cell
preserves the trace of the reflex act of which it has been the
centre. It is, so to speak, impregnated with it, as certain phos-
phorescent substances catch the luminous rays, as a plate of
•prepared collodion stores up the luminous waves.1 From that
moment, the conscious phenomena are linked together ; those
which come last find in the nervous centres the echo of those
which have preceded them. Speaking in the language of the
psychologists, we may say that the faculties are now born. The
traces of past sensations and impressions become recollections;
there is memory. Then these recollections are disunited, group
themselves capriciously, forming complex pictures, fictitious as a
whole, though formed of old sensations and impressions ; this is
imagination. But from persistent impressions of pain and pi
sure spring desires to escape the former, to feel the latter.
Impressionability, sensibility, imagination, gather round these
desires, and are more or less vigorously incited by them. This
co-ordination of impressions, sensations, images, with the attain-
ment of one object in view, becomes ratiocination, and the
faculty of effecting this co-ordination is what psychologists have
called understanding, intelligence, reason ; in the same way that
the conscious result of every confrontation, every comparison,
amongst themselves, of impressions, sensations, &c., is called
idea, thought. Finally, every desire preceded and accompanied
1 J. Luys, Itecherches sur le Syst&me Nerveux, etc., p. 270.

F F 2

436 BIOLOGY. [BOOK vi.

by reasoning, by a relative estimate of the motive, becomes a
volition ; whence the will of the psychologists.

But behind all this labyrinth of psychical phenomena there
are simply reflex acts, transformed sensations and impressions.
Moreover, all this mental labour, of which the excessive compli-
cation in man has so long defied observation, is simply the result
of the special properties of the nervous tissue. In effect, every
sensation is accompanied by an elevation of the temperature of
the nerve and a disturbance of its electric condition, by a
negative oscillation of the nervous current. Besides, in order
that it may take place, a considerable time is necessary, corre-
sponding to an elevation of temperature in the cells which are
its seat,1 coinciding with a sur-oxydation, a waste of the sub-
stance of those cells which eliminate a much greater quantity of
phosphates, &c., &c.2

Finally, comparative anatomy, anthropology, pathological
anatomy furthermore lend their valuable co-operation to physio-
logy ; they show us that the moral and intellectual faculties are
completely in subjection to the nervous centres ; that they follow
with docility their variations, more or less, to better or to worse ;
that they develop, diminish, or change with them. The pheno-
mena of consciousness are, then, throughout the animal kingdom,
not excepting man, functions, acts of the nervous cell. Upon
this point doubt is impossible.

But we are not confined to this simple declaration. A young
Italian physiologist, Dr. Mosso (of Turin), has just opened up to
experimental psychology a track altogether new, by providing it
with an apparatus which may aptly be called a psychometer.
Our readers will surely be grateful to us for giving here a
summary of the still unpublished work of Dr. Mosso.

It has long been known that there was a certain connection
between the contractility of the vessels, especially of the capillary
vessels, and certain agitations of the nervous centres, for example,

1 Schiff, Archives de Physiologic, t. II., 1870, and Lombard, id., t. II., p. 670.
3 Byasson, loc. cit.

CHAP, x.] OF THOUGHT. 437

that impressions, strong emotions, modify the beatings of the
heart, the colouration of the cheeks, &c. (see p. 220). It was this
interesting fact which served M. Mosso as a starting-point. He
formed the design of finding a practical experimental means of
measuring with some precision this influence of the nervous
centres upon the vaso-motory nerves. For this purpose he made
use of a large glass cylinder, closed at one of its extremities,
open at the other, a kind of large cylindrical flask, sufficiently
wide to accommodate easily the hand and entire forearm. A
large armlet of caoutchouc fixes the tube to the bend of the
elbow ; at the same time shutting the upper orifice, while exer-
cising only the most moderate compression. The wall of the
cylinder is furnished with three orifices. One, which is closed
with a stopper, serves to fill the vessel with tepid water. A
second opening permits the introduction of the ball of a thermo-
meter, which indicates the temperature of the water. To the
third is adjusted a curved tube, very analogous to the hsemo-
dynamometer of Poiseuille. This tube communicates with the
cavity of the cylinder, and is so arranged that a small column
of water rises therein. Finally, it is furnished at its upper
extremity with a movable needle, adapted to note the oscilla-
tions of this column upon the paper of a registering tambour.
Things being thus arranged, it is easy to see that the slightest
sanguineous afflux in the forearm will diminish the volume of
the member, and consequently will cause a part of the liquid
column of the hsemodynamometer to flow back into the receiver.
Every congestion, every dilation of the vessels will produce
an inverse effect. In both cases the needle will write upon
the registering paper the oscillations of the liquid column.

With this apparatus Dr. Mosso has been able to prove that
every cerebral phenomenon has its repercussion upon the peri-
pheric circulation. The following are the principal facts which
he has observed with regard to man during wakefulness and
slumber.

In the waking state, every sensation, every moral or physical

438 BIOLOGY. [BOOK vi.

impression, every intellectual labour is accompanied by strong
contractions of the peripheric vessels, and the degree of con-
traction is proportioned to the effort made. Thus, while a young
man was translating successfully Latin and Greek, the liquid
level sank less during the translation of the former than of
the latter, because the translator knew the Latin language well,
the Greek imperfectly.

The facts observed during slumber are not less curious.
Already, in certain cases of loss of substance by the bones of the
skull, Blumenbach first, and afterwards Dr. Pierquin had
remarked that dreaming corresponds with a congestion of the
cerebral substance : " A woman," says Pierquin, "had in conse-
quence of a syphilitic affection lost a large portion of the hairy
scalp, of the bones of the skull, and of the dura-mater. The
corresponding portion of the brain was exposed. When her
sleep was without dreams, the brain was immobile, and remained
in its osseous case. But when agitated by dreams, the turgescent
brain projected from the skull. This turgescence was evidently
in this case the result of vascular excitation."

The observations made with the apparatus of M. Mosso fully
confirm that of Pierquin. At the beginning of sleep, there is a
peripheric sanguineous afflux ; the vessels of the members dilate.
Any sound whatever always provokes, in the vascular peripheric
system, considerable contractions in the sleeping man. Dreams
are always accompanied by a peripheric contraction, even when
they leave no remembrance. The return of conscious life, at the
end of sleep, is always preceded by a vascular contraction on the
periphery of the body.

A general fact springs out of these observations, namely, that
there is an alternacy, or rather antagonism between the action of
the brain and that of the other organs. The active congestion of
the first involves the relative anaemia of the others, and this
gives us the explanation of some noteworthy facts ; for example,
the sedative action of intellectual occupations upon the physical
functions and instincts, the debilitating influence of mental

CHAP, x.] • OF THOUGHT. 439

labour upon the general constitution, the difficulty there is in
being at once a man of action and a man of thought.

It is evident that the psychometrical process which we have
just described is one of the most fortunate applications of physio-
logy to the study of the cerebral functions. This process will
surely be perfected and largely utilised, and we may predict
that it will bear yet more fruit.

As we have already remarked, sensorial excitation at the
terminations of the sensitive nerves only provokes a rupture of
equilibrium, setting at liberty forces which counterbalance each
other. It is the spark which kindles the powder. Doubtless,
it is very hazardous to assert, with M. Wundt, that the sensation
grows like the logarithm of the excitation which produced it.1
The facts of biology, with their diversity, their infinite variability,
are very ill adapted to the inflexibility of mathematical formulas.
But leaving logarithms aside, it is unquestionable that sensation
is not contained in the peripheric excitation, and that its
intensity increases more rapidly than that of the external cause
which has provoked it.

Sensibility is, then, a property inherent in the nervous cell, and
the sensations, or to speak more generally, the facts of conscious-
ness, are phenomena which interpose between the afferent and
efferent currents of the reflex action, and which, once produced,
persist, have a kind of separate existence, can revivify, combine,
aggregate themselves to fresh impressions and sensations, are
awakened according to the impulsion of the desires, forming
finally a mental amalgam which constitutes the psychical indi-
viduality. But definitively, in spite of the extreme complication
of the mental microcosm, the muscular movements which follow
our volitions are only the last point of a reflex series, of which
the direct or indirect origin is always an excitation bearing upon
the extremities of the sensitive nerves.

Surely this is one of the most important services rendered by

1 Wundt, Menschen und ThierseeU (analysed by Th. Ribot, in the Revu*
Sdentifique, 1875, No. 31).

440 BIOLOGY. , [BOOK vi.

modern physiology, to have reduced to such a simple formula the
apparently entangled skein of the psychical phenomena ; but the
labour of analysis has been carried still farther, and after
having demonstrated that every conscious movement is the result
of a reflex nervous action, the fact has been established, that
there is in the brain a localisation of the reflex properties.

The division of labour is already made manifest in the optic
layer, where, in man, we can isolate four clusters of nervous
cells, four receptive centres.1 The first of these nuclei, the
anterior, is the olfactory centre, highly developed in the animal
species, which possess large olfactory nerves. Behind is the
optical nucleus, the most voluminous of all in man, and, on the
contrary, very little developed in the species which live habitually
in darkness, as the mole. The third nucleus, or median centre,
from front to back, receives the non-special tactile fibres.
Finally, the fourth is the receptive centre of the acoustic fibres,
the acoustic centre. The special office of these nervous centres is
established : 1st, by comparative anatomy, which shows each of
them to be more voluminous when the corresponding sense is
more developed in such or such an animal species ; 2nd, by patho-
logical anatomy, which proves the coincidence of their isolated
atrophy with the disappearance of the senses whose sensitive
agitations they receive ; 3rd, by experimentation, since M. E.
Fournier has succeeded, by making irritant injections in the web
of the optic layer, in destroying at will this or that category of
sensitive impressions.

In the cortical substance of the hemispheres, perceptive
departments of sensation and impression answer to these optical
receptive centres. On the brain of individuals who had suffered
amputation long before, Dr. Luys has proved local atrophies of
circumvolutions.2 In these later times, Dr. Ferrier 3 has observed

1 Arnold, Jcanes Cerebri et Medullce Spinalis, Turici, 1858. Luys, Revue
Scientifique, No. 37, 1875. 2 Luys, ibid.

3 Terrier (Progres Medical, 1873, No. 28, and 1874, No. 1) Reclierches Ex-
perimentales sur la Physiologic ct la Pathologic Cerebrates.

CHAP, x.] OF THOUGHT. 441

that in exciting by electricity this or that region of the grey
cerebral cortex of animals, a contraction of this or that group of
muscles is caused ; that we can at will make the eyes, the tongue,
&c., move. Mr. Robert Batholon, Professor in the Medical
College of Ohio, has obtained the same results by experimenting
upon a man whose brain was laid bare by a large loss of osseous
substance. Professor .Schiff: himself has seen that in animals
the cerebral substance grew heated in such or such a locality
according as it was agitated by such or such a category of
sensorial excitations.1 We may compare this nervous mechanism
to a piano, the sensitive peripheric fibres being the key-board,
the isolated centres of the optic layers the hammers, and the
various cortical regions the cords.

A physiological note responds to each touch : here a secretion,
there a palpitation, a contraction or a dilatation of capillary
vessels ; elsewhere a sensation, such or such a sensation :
somewhere else, by reflex action, such or such a movement.

The more voluminous the peripheric nervous cords are, the
more developed will be the nuclei of the optic layers, and the
stronger the current of the sensations and impressions, and the
more vigorously agitated will be the cortical perceptive centres,
the nervous elements which have consciousness of sensations,
which weigh them, compare them, register them ; consequently
the more difficult will be their ponderatory labour. If at the same
time these cortical layers have little surface and depth, in other
terms, if the cerebral hemispheres are little developed, the
animal or the man will be peculiarly instinctive ; will instantly
and blindly obey the actual impression. If, on the contrary, the
perceptive centres dominate, then the being will be intelligent,
reflective, master of itself. It is by virtue of this law that the
inferior vertebrates, in which the nervous intracranian vesicles,
olfactory, optical, &c., are as voluminous as the cerebral
vesicles (anterior brain; see Figs. 60, 61), have a rudimentary
intelligence.

1 M. Schiff, Archives de Phyyiologie, 1870.

442 BIOLOGY. [BOOK vi.

It is easy enough to explain why a particular man, having
otherwise little intelligence, is nevertheless endowed with this
or that sensitive aptitude. It is enough that the external ear
be well shaped, the nucleus of the optic layer which corresponds
(with it voluminous, the fraction of cortical substance in relation
/with this nucleus rich in cells, in order that the individual,
though otherwise ill endowed, should have musical aptitudes.
We thus comprehend singular facts, which have seemed abnorma]
to many observers ; for example, that many idiots have shown a
taste and even an aptitude for music.

The importance of these generalisations will escape no one.
They shed light upon the most obscure, the most mysterious
domain of biology. They snatch psychology from the hands of
dreamers to give it a true scientific basis; they undermine a
number of deeply-rooted prejudices, of myths illegitimately
revered ; they are the true and solid foundations upon which the
science of the moral man will one day rise.

/ L1BUA U V ;

I UNIVERSITY OF

CALIFORNIA

BOOK VII.

OF THE PHYSICAL FORCES IN BIOLOGY

CHAPTEE I.

OF ORGANIC HEAT.

CHEMICAL reactions, which have not for corollary a certain
development of heat, are noted as rare exceptions. But life is
only maintained by perpetual material exchanges, by combinations
and decombinations, incessant molecular mutations ; we must,
then, expect to see organised bodies present, during their life,
calorific combinations altogether peculiar to them.

A general fact already results from the thermometric observa-
tions gathered in the two living kingdoms ; namely, that the
elevation of the temperature is habitually so much the greater
in proportion as the organic structure is more complex, more
differentiated, more perfect.

Plants nearly follow the thermal variations of the ambient
medium. This is the conclusion at which M. Rameaux, of
Strasburg, and also M. Becquerel have arrived.1 The first of
these observers made holes in the trunks of trees, into which he
introduced thermometers ; the second made use of very sensitive
thermo-electric apparatus. These observations, however, must
only be accepted with caution. We must first of all throw aside
hibernal observations. In winter, the life of the vegetal is
1 Des PhbiomZnes Physico-Chimiques.

444 BIOLOGY. [Boox VH.

reduced to its minimum; it is a hibernant slumber much more
profound than that of animals. The nutritive exchanges are
then, in most cases, too unimportant to determine an appreciable
elevation of the temperature. As to estival observations, they
must also be cautiously judged. The plant has not, like even the
lowest animal, a perfected circulatory system, which everywhere
equalises the temperature. In the vegetal, each region, each
tissue, each organ, enjoys a sufficiently large independence;
the federative rule is there much more accentuated than in
the animal.

The centre of trees, the hardened ligneous part, is half
mineralised, and any thermometrical instrument introduced
into this half dead region can indicate little or no elevation of
temperature. It would be necessary to take in summer, during
full vegetative movement, the temperature of the cambium, of
the intermediary layer between the aubier and the bark. It is
certain that, at all times when, in any part whatever of a vegetal,
the phenomena of nutrition, .of development, of transformation,
acquire a certain degree of intensity, the local temperature rises
much. It is sufficient to signalise, in support of this assertion,
the thermometric phenomena which accompany germination and
florescence.

However, it is specially in the animal kingdom that the thermic
independence of the organised being is clearly indicated. But
here again the distinctive temperature of the animal is higher,
less subject to exterior thermometric fluctuations, in proportion
to the perfection of the species. Professor Yalentin, who has
noted the numerical proportions of the organic temperature in the
principal invertebrated groups has found on an average the excess
of the animal temperature over the exterior medium to be : —
In the Polypi 0° 20

Meduste 0

Echinoderms . . . . 0

Mollusks ...... P

Cephalopoda . . . . 0

Crustaceans. 0

CHAP, i.] OF ORGANIC HEAT. 445

Nobili and Melloni. taking observations with a thermo-electric
apparatus, have always found in insects a positive temperature
of a fraction of a degree, or even of some degrees. Reaumur
observed in a beehive a positive temperature of 12°, 5, when the
thermometer marked 3°, 75 outside it.1

But if the temperature of invertebrated animals almost always
preserves a more or less notable excess over the outer temperature,
it varies, absolutely, in very large proportions. Ordinarily, it
follows, more or less readily the exterior thermometric oscillations,
rising in the day in summer, falling at night in winter. During
the'latter season, and in cold climates, most invertebrated animals
which are not killed by the lowness of the temperature become
benumbed, and fall into hibernation, subject as they are tc
climaterie vicissitudes.

That which we have just said of invertebrated animals might
almost be applied to the two lower classes of the vertebrates.
Like the invertebrated animals, fishes and reptiles have a
temperature which varies with that of the ambient medium,
whilst generally higher than the latter ; like the invertebrated
animals again, most of them are benumbed in winter. Never-
theless, their overplus of temperature is habitually higher than
that of the invertebrated animals. Moreover, it is very variable.
In fishes it has sometimes been found to be only 0°,20, sometimes
3°, 88. In the fishes of the Sea of Marmora, Davy has even
observed a thermal excess much more considerable. In taking
the temperature of the abdomen and that of the dorsal muscles,
he has found the former 6°,11, and the second 7°, 22 in excess
of that of the sea.

In reptiles the surplus temperature may sometimes be stated
as still greater; though sometimes only 00<04 in the frog, it
has been seen to rise to 8% 12 in theLacerta agilis.

In the vertebrated animals of the two higher classes, in bircU

1 Consult J. Gavarret, Les Phdnom&nes Physiologiques de la Vie, and the
article on " Chaleur Animale," in the Dictionaire Eneycloptdique des Sciences
Medicales.

446 BIOLOGY. [BOOK vn.

and mammifers, where the respiratory and circulatory systems
are better constructed, where the two kinds of blood are not
mingled, where respiration is more active, the organic tempera-
ture shakes off in some degree the yoke of the outer temperature,
and if we except some rare species, which are still subject to
hibernation, it is proved that the superior vertebrates enjoy a
temperature of their own tolerably high, and only varying to a
small extent, in spite of climates and seasons. The temperature
of adult and well-fed birds varies from 38 to 45 degrees. This
variation of some degrees corresponds with specific, individual,
even sexual differences ; in fact, Professor Martins has seen, in
the duck species, that the temperature of the female was sensibly
higher and also more variable than that of the males.

The temperature of the mammifers is lower by some degrees
than that of birds, but is invariable, like this latter. Thus, in
the Arctic regions, Parry has found the temperature of a fox
exceed the ambient medium by 76°,7.

The temperature of the ambient medium oscillates between 36
and 40 degrees. That of man varies between 36°,50 and 37°,50,
and differs according to age and sex ; it is higher in the child
than in the adult, higher in the adult than in the menstruous
woman, and lower perceptibly in the old man, during sleep,
&c., &c., besides following with sufficient fidelity the oscillations
of the respiratory energy. (See Book II., Chap, xiv.)

From the series of facts which we have just enumerated, it
results that there are no cold-blooded animals in the literal sense
of the expression, and neither are there any animals with an
invariable temperature in the strict meaning of the word. In the
whole animal kingdom, the organic temperature, and especially
that of the blood, is normally higher than the exterior tempera-
ture. Moreover in the whole animal kingdom the organic
temperature oscillates and varies. But these thermic variations
decrease in proportion as the animal is higher in the series, and
in the well-nourished bird and mammifer, the temperature of the
interior medium, the blood, only varies within narrow limits ;

CHAP, i.] OF ORGANIC HEAT. 447

it depends then much more upon tho biological conditions of the
individual than upon the ambient medium. If it resist refrigerant
influences, it can also, in a certain degree, resist those of warmth,
and maintain itself for a certain time below the exterior tem-
perature when the latter is excessive. The principal means of
resistance to heat is evaporation, which proceeds on the cutaneous
and respiratory surfaces.

The maintenance of the median temperature of the blood in birds
and mammifers is a primordial condition. Thermic deviations, even
when very slight, immediately put life in peril. The tempera-
ture of the blood cannot with impunity go beyond 43 degrees
in the mammifers, and 50 degrees in birds. At 42 degrees the
blood may already coagulate in the vessels ; at 49 or 50 degrees
the muscular substance coagulates ; the muscles are then rigid
and acid.1

As the composition of the albuminoidal substances is much
less alterable by cold than by heat, the lowering of the organic
temperature is less dangerous than its elevation; at least
there is, herein a larger margin. Small mammifers (rabbits,
guinea-pigs) make cold rapidly in ice, die when the temperature
of their rectum descends to 18 or 20 degrees. But, by proceeding
slowly, gradually, it is possible to lower their temperature much
more without killing them, since, in marmots, the temperature of
the rectum during hibernation is only 4 or 5 degrees.

We know that all animals absorb oxygen in quantities which
vary according to determinate laws, with the class, the zoo-
logical species, the physiological conditions. We know, on the
other hand, that this absorbed oxygen is the principal agent in
the chemical mutations and transformations which are at once
the effect and the cause of nutrition. Now all combustion is
developed from heat. We can, then, taking the foregoing general
facts as our sole basis, assign as the cause of the production and
maintenance of organic temperatures, the oxydation, the slow.

1 Cl. Bernard, Rapport sur les Progres de la Physiologic, p. 45, and Her-
mann, Elements de Physiologic, Paris, 1869.

448 BIOLOGY. [BOOK vn.-

combustion of living substances, and say with Lavoisier : —
"The animal machine is governed by three regulating principles,
respiration, which consumes hydrogen and carbon and furnishes
caloric; transpiration, which augments or diminishes, according,
as it is necessary to get rid of more or less caloric; finally,,
digestion, which restores to the blood what it loses by respiration
and transpiration." *

But, thanks to the progress of modern physics, chemistry, and
physiology, we can follow, step by step, minutely, these impor-
tant phenomena, indicate what processes organisms employ to
produce, according to need, heat and cold, state what organisms
are the most active producers of heat ; finally, specify the office
of the aliments, and apply to the working of living machines
the great law of the correlation of physical forces.

1 Lavoisier, Mtmoires de I'Academie des Sciences, 1789.

CHAPTER IL

OF THE PROCESSES OF OEGANIC CALORIFICATION.

IF we must consider the chemical reactions of nutrition as the
principal source of organic heat, if this heat is a function of
nutrition, it must augment or decrease according as the exchange,
the molecular mutations, are made with more or less activity.
Now, every organic functionment has always as its effect, or
rather cause, an acceleration of the double nutritive movement
of assimilation and disassimilation ; consequently the local tem-
perature of each organ must incessantly vary. In effect, this
inductive conclusion is confirmed by observation ; for it is a
general law that every organ grows warm while accomplishing
its special function, to grow cold afterwards in the intervals of
repose.

This fact can be proved, either by taking directly the tem-
perature of the organs, by the help of thermo-electric needles, or
by comparing the temperature of the blood which enters an
organ with that of the blood which issues from it. This experi-
ment is practicable, for example, in the arteries and the veins of the
glands. It has been made in the kidneys, the salivary glands,
and also in the afferent and efferent vessels of the liver. It has
thus been proved that the liver is the warmest organ in the
economy, that its efferent veins are warmer than its afferent
veins ; that in glands with intermittent functionment, like the

O G

450 BIOLOGY. [BOOK yn.

salivary glands, the venous blood issuing from the gland grows
always warm when this gland is in a state of activity.1

The observations thus made upon the sanguineous glandular
vessels have besides brought into prominence one of the most
interesting physiological phenomena, namely, that if the oxyda-
tion of the living tissues and substances is the principal cause of
organic heat, it is not the only one. In effect the glandular
venous blood, which is black and oxydised during the repose of
the glands, becomes, on the contrary, rutilant when the gland
becomes again active, and at the same time its temperature
rises. It is then less burned, contains more oxygen, and less
carbonic acid. The venous blood of glands with intermittent
functionment, like the salivary glands, thus passes alternately
from black to red, according as the glands are in a state of
repose or in movement. On the contrary, the venous blood of
glands perpetually active, like the kidney, is always warm
and vermilion. Slow oxydation, organic combustion, is here
only a secondary agent of temperature, of which the principal
causes are the isomerias, the catalyses, the evolvements taking
place in the substance of the glandular organs.2

In all the other organs it is oxidation which prevails; the
efferent or venous blood is always black, and it is the blacker,
the more burned in proportion as the organ has functionated
with greater activity. Thus the brain, so rich in capillary
vessels, has normally a very high temperature. Professor Schiff
has proved directly that the temperature of the cerebral hemi-
spheres rises when they functionate ; we know also that these
organs are the seat of a kind of vascular erection, of active
congestion, while, on the contrary, during dreamless sleep the
brain is pale and anaemic. Observations made upon trepanned
animals, and also upon man, in cases of loss of substance of the
bones of the skull, have put these interesting facts beyond

1 Cl. Bernard, Chaleur Animale, in Revue Scienfifique, 1872, No. 45.

2 Cl. Bernard, loc. tit., No. 47.

CHAP, ii.] OF THE PROCESSES OF ORGANIC CALORIFICATION. 451

doubt.1 It is known besides that intellectual activity in a
healthy man and the cerebral sur-excitation in the lunatic are
accompanied by a sur-oxydation of the nervous substance, which
is betrayed by a greater production and excretion of phosphates.
Finally, it has been proved that the venous blood coming from
the brain, the blood of the jugular vein, had normally a higher
temperature than that. of the carotid artery, and that cerebral
activity had as corollary a super-elevation of this venous tem-
perature.

Professor Schiff has also, with the aid of thermo-electric
needles, seen the temperature rise in excited nervous cords, but
rise less in proportion as the animal was near death.

All the anatomical elements, all the tissues, all the organs,
co-operate, then, in the production and maintenance of organic
heat, without which, on the other hand, they could not continue
to live; but in the vertebrates, and probably in the higher
invertebrates also, it is certainly the muscular system which
furnishes the most powerful calorific tribute. The muscles are,
in effect, the seat of very important nutritive exchanges, and
besides, in the mammifers, they represent about a third of the
weight of the body.

Reaumur, Huber, Newport, <fec., have seen the temperature
rise in a bocal containing insects, when these animals were put
in movement by disturbing them. Dufour has proved that
during the repose of the Sphinx atropos, the temperature of that
insect is only eight degrees above that of the ambient air, while,
at twilight, when the animal is in a state of activity and flies,
the difference may reach ten degrees. M. Maurice Girard has
seen the temperature of the Acherontia atropos almost equal that
of warm-blooded animals after a prolonged flight. The ambient
air being at 2 3°, 4, he has found in the abdomen of the sphinx
25°,5, and in the thorax 32, and even 37 degrees.

1 Pierqnin, quoted by Gratiolet, Anatomie Compare* du Sysltme Nerceux
dans ses Rapports avec I' Intelligence.— Blumenbach, in Archives de Medetine,
1861, t. I.

G G 2

452 BIOLOGY. [BOOK vn.

The muscular temperature in man has especially been deeply
studied by M. Becquerel. With thermo-electric needles he has
seen the muscular temperature rise 1 degree and some tenths,
after violent exercise. At the same time, the venous blood
issuing from the muscle, and which, during the period of repose,
was moderately black, becomes of an intense black, and its
temperature rises. On the contrary, in paralysis by nervous
section, when the tonic muscular contraction is itself abolished,
the blood issues from the muscle rutilant, and scarcely oxydised.

The production of heat, during muscular contraction, is then
manifestly dependent upon oxydation. It is demonstrated also
by compressing the nutritive artery of the muscle, which imme-
diately causes a remarkable coldness (Becquerel) ; by paralysing
the muscular system of a dog with curare, which lowers the
temperature of the animal several degrees in an hour (id.) ; by
causing the muscles of a frog confined in a bocal to contract by
means of electricity, and by proving that these contractions have
caused the production of carbonic acid (Matteucci).

This last fact proves, besides, that the muscle can contract,
oxydise itself, and engender heat, without being traversed by a
sanguineous current. The interfibrillary muscular juice, and
perhaps the substance itself of the contractile fibre, are for some
time sufficient to produce the indispensable chemical reactions.
These reactions, which always necessitate a certain absorption of
oxygen, have been variously interpreted. It is certain that the
resting muscle is alkaline, and that contraction acidifies the
muscular juice. The acid is lactic or sarcolactic acid. The
alkaline principle is creatinine, which transforms itself into
creatine. According to another explanation, the muscular fibre
does not wear itself out through labour (Yoit), which is very
improbable. There is in the resting muscle an azotised sub-
stance, inogen, which, during contraction, evolves into carbonic
acid, lactic acid, and an albuminoidal substance, myosine. It is
myosine which in solidifying produces rigidity of the muscle.
The development of heat, and also the production of mechanical

CHAP, ii.] OF THE PROCESSES OF ORGANIC CALORIFICATION. 453

force result from these reactions. There has even been an
attempt to prove that the quantity of lactic acid produced was
proportional to the muscular labour accomplished, and to the
temperature developed (Heidenhain). Oxygen is besides indis-
pensable to contraction, and to the reparation of the muscular
forces.1 In effect, repose alone does not suffice to restore
muscular energy; it is necessary, in order to reconstitute the
contractile force, that an oxygenised reparatory liquid should
circulate through the muscle. In the living body it is the
arterial blood which performs this office. We can, however, in a
certain degree, substitute for the blood in an isolated muscle the
injection of a solution largely composed of oxygen, for example,
a solution of permanganate of potash.

If muscular contraction produces heat, inversely heat provokes
contractions ; it is a peculiar case of the great law of transforma-
tion of physical forces, of which we shall shortly speak. The
beatings of the heart are accelerated when hot water is injected
into a vein, even when the temperature of the blood is very little
raised thereby. Inversely, under the slowly graduated influence
of cold, the intestines and the hearc contract with less and less
energy, then finally stop. This is one of the causes of the
hibernal sleep.

The chemical phenomena which produce organic calorification
are accomplished, on the one hand, in the sanguineous and lym-
phatic plasmas, since these liquids are living ; on the other, in the
tissues, in the anatomical elements themselves, the nutrition of
which is moreover closely connected with the quantity and quality
of the blood which circulates in the capillaries. We must, then,
now briefly describe the physiological mechanism which regulates
the local sanguineous circulation, the consumption of the san-
guineous aliment, and. consequently, tha production of organic
heat.

The regulating agent of the local capillary circulations is the
nervous vaso-motory network, the large sympathetic nerve. After
1 Hermann, Elements de Physiologic, p. 231.

454 BIOLOGY. [BOOK vn.

the section of a nervous sympathetic cord, the venous blood
coming from the organs whose circulation was controlled by this
nervous branch becomes redder, warmer, and more coagulable.
It is less burned, and contains more oxygen, but it has been
the seat of active chemical reactions, for it contains less fibrine
than ordinaiy venous blood ; besides, it springs from the vein
in isochronal jerks, corresponding to the pulsations of the
heart.

This is because the capillaries are dilated, and allow the san-
guineous current to pass with five or six times more than its
ordinary rapidity. Generally, there is in the organ whose vaso-
motors are paralysed a sanguineous congestion, and always an
elevation of the local temperature. Let the sectionised nerve be
electrised, and immediately the capillaries contract, congestion
disappears, the local temperature falls, the venous blood becomes
again black, and no longer flows except foamingly.1

Since by paralysing the vaso-motory branches the elevation of
the local temperatures is provoked, we are authorised in conclud-
ing therefrom that the nervous network of the large sympathetic
performs the function of moderating local combustions, of re-
straining the nutritive expenditure, of rationing the anatomical
elements, of creating coldness.2

But we have seen that the sympathetic nervous network is
only a dependency of the general nervous system, that it is
anatomically connected with the nervous centres, and that there
is, in the upper part of the spinal marrow, a general vaso-motory
centre. It will, then, be easy to comprehend that excitations,
direct or reflex, but having their seat in the nervous centres, can
make all. or nearly all, the capillary vessels of the body contract
synergetically ; and, in fact, by wounding or cutting the spinal
marrow at a particular point, we can provoke in the mammifers,
for example rabbits and guinea-pigs, a general coldness,3 which
throws these animals into a state resembling hibernal sleep. The

1 Cl. Bernard, Revue Scientifique, 1872, No. 23. 2 Ibid.

8 Cl. Bernard, Rapport sur les Progrls de la Physiologic, p. 183.

CHAP, ii.] OF THE PROCESSES OF ORGANIC CALORIFICATION. 455

animal has then become cold-blooded. Moreover, we can obtain
the same result by various processes : by directly and gradually
cooling the animal,1 by rendering it immobile for a considerable
time, by subjecting it to rocking movements, by covering it with
an impenetrable varnish.

The action of physical and psychical sensibility also tells upon
the capillary circulation through the medium of the spinal
marrow and of the vaso-motory nerves. Experiments made by
Professor P. Mantegaaza upon man and animals have proved
that physical pain provokes a lowering of the temperature. It is
often the same with moral pain, sombre passions, prolonged
griefs, which sometimes end by impairing the nutrition of the
tissues and cause organic degenerations.

Organic heat, then, is the result of nutrition, of life itself.
Every organised body, especially every animal, is a fireplace,
where diverse substances, mostly ternary or quaternary, burn
slowly, developing heat which, in its turn, provokes or forms the
exchanges, the chemical metamorphoses necessary to life. A
very large proportion of organic heat is engendered by the action
of oxygen upon the living solids and liquids. It is this dominant
chemical action which gives the impulse to all the others, when
it is not directly the only calorific source. Many other chemical
reactions take place in the organisms, and also engender heat.
" The albuminoidal substances produce decided calorific pheno-
mena, at the time of their hydratation with evolvement, or of
their dehydratation with combination. The hydrates of carbon
(sugar, starch, &c., &c.) can disengage heat by simple evolvement
independently of any oxydation. Finally, the neutral fat bodies
can also give heat in evolvement by simple hydratation, as
appears to take place under the influence of the pancreatic
juice."2

1 Fourcault, Influence desEiidutts Imperm6ables (Oomptes Rendus de VAcad.
des Sc., t XVI.).

3 Berthelot, De la Chaleur Animale (Journal XAnat. et de PhysioL, t. II.,
p. 671).

456 BIOLOGY. [BooK vn.

Heat, then, is produced in every organised body, in a feeble
quantity in vegetals and the lower animals, with more energy
in the higher organisms. It is produced in all the organs,
tissues, and anatomical elements ; but very unequally, according
to the conditions of time and place. It is the general circulation
which levels, in a certain degree, the various local temperatures,
which distributes with a certain equality the created heat, which,
moreover, thanks to the vaso-motory nerves, regulates the ex-
penditure and temperature of each organ.

The quantity of heat thus produced is variously employed.
One part is dissipated and lost by conductibility, radiation,
evaporation; another part serves to maintain the organic
temperature at a proper degree ; finally a last part is directly
transformed into mechanical labour, as happens, in steam
engines, with the heat developed by the combustion of carbon,
for, in spite of their complexity, their mobility, the biological
phenomena, like physical phenomena, all are included in the
law of the correlation and transformation of forces, as we shall
show in the following chapter.

CHAPTER III.

THE TRANSFORMATION OF FORCES IN BIOLOGY.

IN its incessant efforts to conquer scientific truth, humanity has
proceeded as it did in its mythological conceptions. As the
numerous gods of polytheism have little by little given place to
monotheism and pantheism, so observation has shown that
the physical forces formerly imagined and invoked to explain the
universe have undergone incessant transformations, and were
only, correctly speaking, diverse manifestations of a single force.
We think that scientific language would gain much by finally
banishing this word force, which expresses a conception alto-
gether metaphysical of an unknown something lurking behind
the material elements, and controlling them as a horseman guides
his horse. In truth there are in the world only matter and
movement, or rather, as movement is only an act of matter, there
is only matter in movement. When we say, for example, that
heat is transformed into electricity, we are simply understood to
say that the atomic vibration called calorific changes its mode
and becomes the vibration which we call electric. When a body,
falling freely through space, is abruptly arrested in its fall by
an obstacle, and immediately grows warm in proportion to the
rapidity of its fall, it is not a force, called weight, which is
transformed into another force called heat ; it is the movement
of totality of the falling body which is changed into a special
vibratory movement of the molecules of this body, <fcc., <fec. Ail

458 BIOLOGY. [BOOK vn.

becomes clear if we substitute the word movement, which has a
clear and definite meaning, for the word force, which is nebulous
and metaphysical. .

Movement is essential to matter, and the atoms of all bodies,
as well those of the impalpable ether as those of our hardest
metals filling space, are animated with violent and varied move-
ments, which, according to .the modes of their rapidity, direction,
amplitude, &c., &c., produce upon our senses diverse impressions.
But as in their origin these movements are essentially analogous,
they are very easily transformed into each other, since for that
purpose it is sufficient for them to change their type.

We must here recall the principal points of this great doctrine
of the unity of forces, founded by Dr. Mayer, and which has
totally revolutionised physics.

The English natural philosopher Joule has demonstrated that
every body undergoing mechanical violence, friction, a shock,
&c. , grows warm in proportion to the gravity of labour expended,
that is to say that the movement of totality which has shaken
its mass is then entirely transformed into calorific molecular
vibrations. We can then determine with exactitude the mechani-
cal equivalent of heat, that is to say, find how many kilometres
are necesary to raise by 1 degree the temperature of 1 kilo-
gramme of water. All know that the kilogrammetre represents
the labour necessary to raise a weight of 1 kilogramme to a
height of 1 metre. Joule found that 424 kilogrammetres were
necessary to obtain this result. The mechanical equivalent of
heat in relation to water is, then, according to this calculation,
424. Reciprocally, 1 kilogramme of water, falling freely from a
height of 424 metres, and abruptly arrested in its fall, will give
1 degree Centigrade of temperature.

Furthermore, the amount of heat necessary to raise by 1
degree the temperature of 1 kilogramme of water has been
called calory.

The calory is, then, about equivalent to 424 kilogrammetres.

But it is easy to show by very numerous experiments that the

CHAP, m.] THE TRANSFORMATION OF FORCES IN BIOLOGY. 459

calorific movement may be transformed into an electric move-
ment, into a luminous movement, into a molecular chemical move-
ment, even into sound, as the beautiful experiment of singing
flames proves. Reciprocally, all these movements may be trans-
formed into heat, or into each other. "We can, then, affirm theo-
retically that there are mechanical equivalents for electricity,
light) sound, molecular movements which are effected in the
chemical reactions, and, as the mechanical equivalent of heat is
known, it would suffice to transform these diverse movements into
a determinate quantity of heat to have their mechanical equiva-
lent. This labour has not yet been performed with sufficient
precision. However, Father Secchi has found approximately
that the amount of electricity which decomposes 106 milli-
grammes of water can raise by 1 degree the temperature of
38 grammes of the same liquid.1 If then we take as electric
the amount of electricity capable of raising 1 kilogramme of
water from 0 to 1 degree, we shall see, by a simple proportion,
that this quantity of electricity is that which can decompose
2^,789 of water :

1 A£

0*106 : 38 : : x : 1000* : x, whence x = _ = 2*,789.

38

Consequently, this quantity of electricity is equivalent to 1
calory, or to 424 kilogrammetres.

Similar determinations we can theoretically conceive to be
possible with regard to sound and light, but, in spite of several
attempts, the mechanical equivalents of sound and light are yet
to be determined.

Chemical combinations also obey the great law of the correlation
of physical forces. It is clear that every chemical combination or
decombination reduces itself essentially to movements of atoms and
molecules. In every chemical combination, millions of atoms are
precipitated towards each other, clash against each other, till
they have reached a state of stable equilibrium. But here the
infinite variety of phenomena renders difficult the calculation of
1 A. Secchi, UUnitt des Farces Physiqius, p. 328 (2C. e"dit. 1874).

460 BIOLOGY. [BOOK vn.

the mechanical equivalents with relation to water. A step how-
ever has been taken in this direction by determining the heat of
combustion of a certain number of bodies. The following table
indicates the number of calories developed by the combustion,
the oxydation of some simple or compound bodies : —

Kilogrammes of water raised
from 0 to 1 degree by com-

Oxydised Substances. bination with the oxygen

of 1 kilogramme of each
substance.

Hydrogen 34,135

Carbon 7,990

Sulphur 2,263

Phosphorus 5,747

Zinc 1,301

Iron 1,576

Tin 1,233

Olefiant Gas 11,990

Alcohol 7,016

Inversely, when once these bodies are saturated with oxygen,
their decomposition by an electric current necessitates the absorp-
tion of a force equivalent to the number of calories which
develops their combustion.

These observations prove that, in principle, the atomic move-
ments are included in the general law of the unity of physical
forces ; but how powerless they are still to permit us to note
exactly all the transformations of the molecular movements
which take place in the interior of organised bodies !

Without doubt there is, in these last bodies, nothing which
does not proceed from, the mineral world ; but these elements of
mineral production, in ultimate analysis, group themselves in the
living organism into compounds infinitely complex, and in a state
of incessant metamorphosis. Though these chemical transforma-
tions take place in sufficiently regular series, according to a kind
of chemical rhythm, nevertheless it is very difficult to follow them
through all their phases, and most frequently we are thereby
reduced, in order to form an idea of the chemical acts of organ-
isms, to a comparison of the absorbed bodies with the eliminated

CHAP, in.] THE TRANSFORMATION OF FORCES IN BIOLOGY. 461

bodies. But, in the animal machine, the most important chemical
acts are oxydations, combustions. The alimentary matters intro-
duced into an animal organism represent molecular systems
containing forces of tension, that is to say, groups of molecules, in
which the atomic attractions mutually balance each other. Once
transfused in the nutritive vertex, from contact with the aerial
oxygen, these bodies oxydate, their molecular equilibrium is
destroyed ; they then set at liberty vival forces, that is to say,
that the molecular attractions no longer neutralise each other ; the
atomic movements may be communicated to the ambient medium,
and consequently be transformed into heat, into electricity, into
movement, mechanical, or of totality.1 In fact these are the
three principal methods of transformation of the molecular move-
ments in the essence of the animal tissues. We know that in
the nervous and muscular fibres there is an electric current from
the surface to the centre, and this current results directly from
oxydation ; for it is still more clearly produced, as M. Becquerel
has proved, in muscular tissue when mangled, which then oxy-
dates, or rather respires, more energetically than in its normal state.
We have pointed out, in their place and order, the electric phenomena
which take place in the capillary vessels. Analogous electric
currents are probably developed in all the living tissues.

It is much easier to prove organic heat than electricity. It is,
moreover, the form which the greater part of the vival forces of
the free molecular movements takes in the animal machine. We
have seen that this heat maintained the bodies of the higher
vertebrates at a temperature of from 36 to 40 degrees.

Ingenious experiments have proved that muscular movements
as well as organic heat have their source in the chemical com-
binations of the animal machine. It has been observed that
muscular activity corresponded to an augmentation of the con-

1 In biology, the expression vival forces must be taken simply in a meta-
phorical sense, in the sense of free forces, of living forces, as Helmholtz calls
them (Lebendige Kriifte). Biological mechanik is not yet sufficiently ad-
vanced for us to give to the expression vival force the value which it has in
mechanik, that of the product of the mass by the square of the velocity.

462 BIOLOGY. [BOOK vn.

sumption of oxygen proportional to the expenditure of force, and
finally that, for a given consumption of oxygen, the developed
heat and the muscular labour were in inverse proportion to each
other. The force expended in heat is not expended in mechanical
labour; and inversely. This is exactly what happens in the
experiments of pure physics. For example, when an electro-
magnetic motor raises a weight represented by 131 kilogram-
mitres, it gives, for the same chemical labour in a calorimeter,
308 calories less than in all the experiments.1 In the same way,
every muscular effort corresponds to a greater consumption of
oxygen, and an appreciable development of sensible heat ; but
this quantity of sensible heat is so much less, for the same weight
of absorbed oxygen, in proportion as the mechanical labour
accomplished has been more considerable. This general proposi-
tion is derived from various experiments, amongst which the
most important are certainly those of M. Hirn, of Colmar,2 who
has studied, with regard to the production of heat and of power,
men ascending upon a revolving wheel, the steps of which moved
on under their feet. He noted the quantity of carbonic acid ex-
haled by the lungs, first in the state of repose, then during labour.
He also measured the quantity of air inspired and respired,
and simultaneously the total product in kilogrammetres.

The experiments of M. Y. Kegnault have shown that, in a
dog subjected to a mixed alimentation, out of 100 parts of oxygen
absorbed, 7 are employed to form water, by combining with the
hydrogen of the organic substances. Now the degrees of heat
from the combustion of carbon and hydrogen are known ; we can,
then, the quantity of extracted carbonic acid being given, estimate
the amount of heat produced, and compare it with the kilogram-
metres of exterior labour. We thus find that man can utilise in
exterior labour about a fifth of the total heat developed by internal
combustions.

1 Matteucci, Revue Scientifique, 1866, No. 50.

2 Bulletin de la Societt d'Histoire Naturelle de Colmar, 4« aiinee, 1863.

CHAP, in.] THE TRANSFORMATION OF FORCES IN BIOLOGY. 463

The figures obtained by the process we have just described are
evidently only approximative. The oxygen exhaled by the lungs
under the form of carbonic acid, even when the quantity of oxygen
employed in the formation of water is added, according to the
observations of M. Regnault, does not represent all the oxygen
absorbed. The cutaneous surface also respires and exhales car-
bonic acid. Finally, a very important part of oxygen serves to form,
at the expense of the albuminoidal substances, on the one hand,
the immediate azotised, regressive crystallisable principles, such
as urea ; and, on the other hand, sulphates, phosphates, <fec. ; all
bodies eliminated by the kidneys, perspiration, &c.

To approach the truth more nearly, we must add to this direct
study of* pulmonary exhalation the comparative study of the
aliments and of the excrementitious matters; this is what M.
Boussingault has called the indirect method.

We can, for example, ascertain the comparative quantities of
the ingesta and excreta of a bird inclosed in a receiver, by placing
the receiver in a calorimeter. We thus prove that the heat
developed is notably greater than that corresponding to the
combustion of the carbon and of the hydrogen. The excess is
due, without doubt, to the oxydation of the albuminoids, the
true combustible power of which is still imperfectly understood.

Nevertheless, Frankland has given a table of the calorific and
mechanical energy developed by the combustion of diverse ali-
mentary substances. According to these statements, fat alimen-
tary matters furnish more disposable heat and force than
saccharine and amylaceous matters, and the latter produce more
than food composed of beef, veal, pork, or fish.

According to Frankland, 1 kilogramme of dried muscular
substance, purified in ether, and transformed into urea by com-
bustion, develops 4368 units of heat.1

There are then no respiratory aliments exclusively destined to
be burned, thus furnishing heat, and plastic aliments exclusively
destined to be assimilated and to furnish useful labour, as Liebig
1 Revue de Cours Scieniiftqiies, 1866-1867, p. 81.

464 BIOLOGY. [BOOK vn.

had pretended. All the aliments, all the organic substances become
oxydised while furnishing energy. This last proposition has been
put beyond doubt by MM. Fick and Wislicenus in their celebrated
ascent of the Faulhorn.1

These observers, after having previously ascertained the weight
of their bodies, and having subjected themselves during thirty-
six hours to a non azotised alimentation, ascended the Faulhorn,
taking care to ascertain the current of the urea expulsed during
the ascent, and the amount during the six hours following.

Knowing their weight, and the height of the mountain above
the Lake of Brienz, they had the sum of the kilogrammetres, of
the units of labour. The weight of the excreted urea gave, ac-
cording to the figures of Frankland, the heat develope'd by the
combustion of the albuminoidal substances, and especially of the
muscular tissue. Now, the two experimentalists found that the
oxydation of azotised matters could not have supplied, at the
maximum, more than the half of the exterior labour accom-
plished, without taking into account frictions, the contractions
of the heart, thoracic movements, &c.

Furthermore, Dr. Yerloren has remarked that many insects
feed specially upon albuminoidal matters at the time when they
accomplish little muscular labour, and, on the contrary, have an
alimentation almost exclusively ternary and non-azotised when
they labour much. He remarked also that bees and butterflies
feed upon substances very slightly azotised.

The preceding facts permit us then to arrive at a proper
appreciation of the office and value of the diverse categories of
alimentary substances.

1 Philosophical Magazine, t. XXXI.

NOTE.

It is not easy to express in English the distinction between forces vives and
forces vivantes. To lessen, not to vanquish, the difficulty the word vival his
been employed. Now and then in the translation of this work, French words
or expressions have, modified or unmodified, been from necessity used. —
TRANSLATOR.

CHAPTER IV.

OF ALIMENTS.

ALIMENT fills a double office in organised beings : it furnishes
substance and energy. The molecular movement is incontest-
ably the very essence of life ; every organised and living sub-
stance is a vortex incessantly engulfing and expelling new
materials ; these materials failing, the organism is destroyed, it
devours itself. We must then reject the opinion of some modern
physiologists who, dazzled by the grandeur of the principle of
the unity of physical forces, have ended by seeing only the
dynamic side of phenomena, by enthroning spiritualism anew in
biology, and pretending, for instance, that the muscular fibre
contracts without decaying.

There is no organic functionment without decay of the organs,
there is no durable life without the repair of this waste by
aliments.

But neither are there clearly defined categories among the
alimentary substances. Some furnish more force or movement
than substance, others more substance than force ; but all furnish
at the same time both substance and force, with the exception of
water and certain inoxydable salts. Water serves especially as
a vehicle, as water of imbibition, of composition. Certain salts,
such as the chlorure of sodium, are employed solely in stimula-
ting absorption, in accelerating the nutritive movements. These
are mineral aliments.

H H

466 BIOLOGY. [BooK vii. |

As to the organic aliments, all are at once respiratory and
plastic. The ternary or hydro- carbonised aliments themselves
can be fixed, under the form of fat, in the animal tissues, but it
is certain that a large proportion of them burn, leaving as the
residuum of their complete combustion water and carbonic acid.
They evidently represent the great source of the calorific move-
ment. As to the azotised quaternary aliments, they burn for the
most part incompletely, it is true, furnishing at once assimilable
materials, which lodge for a time in the organism, and also
sensible heat and dynamic movement. Moreover, there is no
impassable barrier between these two groups of aliments, since
Cl. Bernard and Lehmann have proved that the albuminoidal
aliments can be partially metamorphosed into sugar, and thus
form substances totally oxydable, — respiratory aliments. Ordi-
narily, however, these substances only undergo incomplete
oxydations, evolvements, isomeric metamorphoses, catalyses.
These varied reactions, which, however, produce heat, leave as
excrementitious residua azotised compounds much more oxydised
than the quaternary substances whence they are derived. These
azotised wastes are composed of leucine, tyrosine, of creatine, of
uric acid, lastly of urea, which is the most azotised product of the
series. Thus for 1 equivalent of oxygen, albumine contains 3|
equivalents of carbon, creatine 2 equivalents, uric acid 1J, and
urea only 1 equivalent.1

The value of aliments depends therefore, on the pne hand, on
the quantity of movement and of force : on the other, on the
quantity of assimilable molecules which they can furnish.

A ternary aliment has the more value, the less oxygen, and
the more hydrogen and carbon it contains.

A quaternary aliment has the more value, the richer it is in
azote, carbon and hydrogen, the poorer it is in oxygen.

Every substance completely oxydised can, from the alimentary
point of view, play in the economy only a secondary part (water,

\ G. See, D& V Alimentation (Revue Scientifiquc, 1866, No. 35).

CHAP. IT.] OF ALIMENTS. 467

sea salt). Likewise urea, which contains still a great deal of
azote, has no alimentary value.

Experiments have demonstrated that the animal machine needs
alike ternary aliments and quaternary aliments. Diet exclu-
sively non-azotised and diet exclusively azotised equally produce
the same disorders as abstinence. The equilibrium between the
azote absorbed and the azote expended is maintained on the sole
condition that the same equilibrium is also maintained as regards
carbon (Yoit, Boussingault).1

Man requires therefore a mixed diet, compensating at the
same time the losses of movement and the losses of substance.
The greater the expenditure of muscular force and the lower the
temperature, the larger must the proportion of ternary substances
be which enter into the alimentation. The inhabitants of hot
countries have need of few aliments. On the contrary, the Es-
quimaux of the Arctic regions eat every day 8 kilogrammes of
raw flesh, containing about a third of fat ; they drink seal-oil,
and swallow pieces of congealed whale-oil. Dr. Hayes states that
his European mariners, passing the winter in the polar regions,
had to restrict themselves to the diet of the Esquimaux.

But the dynamical value of quaternary substances is never-
theless very considerable. In his Traite de Zootechnie,2 M. A.
Sanson has tried to determine the dynamical coefficient of these
substances. For that purpose he compared the sum of kilo-
grammetres furnished in a day by the omnibus horses and the
post horses of Paris with the weight of albuminoidal substances
contained in their alimentary ration. Deduction made of the
portion of albuminoids necessary to the simple maintenance of
the animal, conformably to empirical data, he thought that he
had nothing more to do than to divide the sum of the kilogram -
metres by the number of grammes of albuminoids consumed by
labour. By proceeding thus it is found that in the horse 1
kilogramme of albuminoidal substances produces in round

1 Annales de Chimie et de Physique, 3* serie, 1846, t. XVI U.

2 A Sanson, Traite de Zootechnie, &c., 2e edit., 1874, t. I.

H H 2

463 BIOLOGY. [BOOK vn.

numbers, 16,000,000 utilisable kilogramme tres. But this figure
is evidently far too high, forasmuch as M. Sanson has not taken
into account the dynamic value of the ternary substances con-
tained in the ration.

Among all the alimentary substances which man uses, milk
alone, which contains in nearly equal proportions proteic matters,
fat and sugar, is a complete aliment ; and if the animals exclu-
sively carnivorous nevertheless live, it is because they always
find in the body of their prey reserves of fatty and saccharine
matters.

"We have now arrived at the end of our long exposition. The
reader will pardon us for having made it especially a long
enumeration of facts. Science has in our days abjured the
errors of its youth, and nourishes itself with scarcely anything
but observations and experiments. Philosophy is on the way to
imitate science, of which it is destined one day to be the crown.
More and more men are persuaded that without observation and
experiment there is no real knowledge.

To terminate our work it remains for us to say a few words
of a vast general theory, now almost everywhere admitted. We
mean the general law of balancement between the two organic
kingdoms. That there is much truth in this view as a whole
cannot be denied. It is certain in a general manner that the
vegetal kingdom fabricates the aliments of the animal kingdom.
But we must not formulate this proposition too strictly. First of
all we must regard as withdrawn from the law of alternancy the
mushroom family on the one hand, and the fauna of the oceanic
depths on the other. Moreover, there is no complete antagonism
between the vegetal machine and the animal machine. The
comburent function does not devolve solely on the animal. The
vegetal tissues oxydise themselves like the animal tissues, like
everything that lives. .

Finally, the animal likewise fabricates starches and sugars.

CHAP, iv.] OF ALIMENTS. 469

It is still more unwise to fix the attention exclusively on one
alone of the nutritive acts of the plant, to take account only of
the decomposition of the carbonic acid. No doubt the chloro-
phillian plant dissevers the elements of the carbonic acid ; no
doubt, moreover, the chlorophillian function depends strictly on
the solar light, and we have a right to regard the labour accom-
plished by the chlorophillian cell as a dynamic transformation of
the radiation of the sun. But the decomposition of the carbonic
acid does not represent all the labour effected by the green parts
of plants. These organs are assuredly apparatus of organic
synthesis; laboratories where are found at the same time both
ternary compounds and quaternary compounds. M. G. Ville l
has shown that seeds sown in calcinated sand and watered with
distilled water, and cultivated in a receiver with glass walls
yields an excess of azote at the time they have ripened and are
gathered. Nevertheless he had added to the sand in which the
roots grew nothing but phosphate of lime, some potash, some
lime, oxide of iron, sulphate of lime. Moreover, the same
experimentalist found normally an overplus of azote in many of
our domestic plants when gathered. Finally, he was able to
conclude from his observations and experiments, that during
germination any vegetal needs to find within reach a certain
provision of azote completely prepared. It is in their cotyledons
that certain species, for example the leguminosse, take this
quantity of azote, this azote of development. As to the plants
less fortunately endowed, they need to find in the soil, in the
form of manure, the azote which is indispensable to them, and
which they are powerless to procure otherwise. But when the
germination is terminated, when the plant is furnished with
chlorophillian leaves, it assimilates direct azote taken from the
grand atmospheric reservoir. It is then that it forms by
synthesis both the starches and the albuminoidal substances
which it needs for growth and reproduction. That the green

1 G. Ville, Assimilation de ? Azote par Us Plantes (Revue Scienttfque, 186(5,
Xo. 8).

470 BIOLOGY. [BOOK vir.

leaves fabricate albuminoidal substances is shown by the single
fact that the ascending sap conveys none to the chlorophillian
cells, and that nevertheless the descending sap carries some
away.1

The important chemical elaboration of the chlorophyllian cells
is therefore much less simple than at first sight it seems : it is
alike a labour of disseverment and of composition, of analysis
and of synthesis. _No doubt, if it is not completely certain that
solar radiation furnishes to the leaf all the mechanical energy
which the leaf displays, seeing that every atom and every mole-
cule possess affinities of their own, nevertheless it is the vibra-
tions emanating from the sun which give the impulse to all this
mechanical labour, and which are the principal agents thereof.
We are therefore justified in a very considerable degree in saying
that the plant treasures up solar radiation, that is to say move-
ment, which the animal afterwards utilises while transforming
it. The result of the combustions which are accomplished in
our tissues and wherever we make fire figure is truly the setting
at liberty of energies immobilised by the plant. All the acts,
all the movements, all the .facts of consciousness of animals and
of man are, at least in a considerable degree, transformations of
solar energy.

But in this vast conception which contains so much truth, it
is needful that force should not cause matter to be forgotten.
In effect there is in the universe something besides dynamism.
No doubt, organised beings receive from the sun by the help of
interplanetary media impulsions, movements, which they utilise
and transform. But the substance of these beings has also its
own existence, its own sphere of activity.

In reality there is in the universe neither force distinct from
matter, nor matter destitute of force. If the dynamik of the

1 The ascending sap of the vine (the tears of the vine) does not, through
heat, yield albumin o:is precipitate ; through distillation a notable quantity of
gum is formed therein ; appropriate reactions reveal the presence of some
saline substances.

CHAP, iv.] OF ALIMENTS. 471

universe shows us everywhere a single force, a single movement
changing always in mode and in rhythm, without ever
being annihilated, there is also everywhere a single extended
substance, veritable Proteus, flowing into an infinity of combina-
tions, but eternally, and without being able to grow immobile or
to disappear. Definitively, thus, as is superabundantly proved by
all the natural sciences and by the long analytical exposition
contained in this volume, there is unity of matter as there is
unity of force, or rather, movement is inherent in matter, the
universe is constituted by a substance in movement.

INDEX.

ABSTINENCE, 143, 148

Acid, aerian carbonic (Quantity of
the), 95

Acids, organic, secreted by the ani-
mal, 137

Acid, carbonic, of disassimilation,
136

Actinosphoerium (Digestion in the),
158

Action, reflex, 388, 433

(Office of the grey sub-
stance of the spinal marrow in the)
392

Albumine of the blood, 64

Albuminoids, albuminoidal sub-
stances, 13

Albuminose, 65

Algie and mushrooms, 107

Alimentation in general, 172

Aliments (of the), 465

Aliment, complete, 468

Aliments, quaternary, 466

Aliments, ternary, 466

Amoebae (Digestion of the), 157

Amphioxus (Absence of hearing in
the), 416

Amphioxus (Circulation in the), 196

Amphioxus (Smell in the), 411

(Nervous svstem of the),

369

Animals (Histological types), 48

Animals, cold-blooded, 446

Annelates (Circulation in the), 194

Annelates (Branchial respiration of
the), 432

Annelates (Touch in the), 406

Antheridion, 316

Antherozoids, 316

Apparatus, digestive, in the animal
series, 157

Arachnida (Respiration of the), 233

Arteries, 207

(Nerves of the), 207

(Contractile nbro-cells of

the), 207

Arthropods (Circulation in the), 211

Arthropods (Muscular fibres of the),
350

Arthropods (Sense of hearing in the),
416

Arthropods (Digestive system of the),
162

Arthropods (Compound eyes of the),
422

Arthropods (Touch in the), 407

Assimilation, 82, 86

animal, 1 25

Assimilation of the albuminoid sub-
stances by animals, 132

Assimilation of the hydrocarbonised
substances by animals, 129

Assimilation and absorption of mine-
ral salts in the animal, 128

Assimilation of mineral substances
by animals, 125

Assimilation and disassimilation,
vegetal, 109

Assimilation, chlorophyllian, 111

Assimilation of azote by plants,
110, 469

Asterise (Eyes of the), 422

Atomicity, 5

474

INDEX.

Atomic (Combinations), 9
Autofecundation, 311
Autosaturation, 8
Avogadro and Ampere (Law of), 5
Azote in the two living kingdoms,
14

B.

BACILLA, sensitive, 426

Beings, organised (Origin of), 301

Berberis vulgaris (Movements of),

344
Bile (Action of the), 188

— (Formation of the), 265
Birds (Taste in), 410

(Temperature of), 445

Bladder, natatory, 237
Blastemas, 36, 56

animal, 53

chemical composition of,

54

Blastemas, vegetal, 52
Blastoderm, 327
Blastodermic (Cells), 327
Blastodermic (Coatings), 285, 327
Blood (Of the), 60
(Chemical composition of the),

61
Blood, black or venous, 69

venous (Temperature of the),

450

Blood (Office of the), 123
Bodies, striated, 384, 434
Body, vitreous, 425
Brain (Functionment of the), 440
Brain (Temperature of the), 450
Branchia?, 230
Bryozoaries (Digestive system of the),

161
Bryozoaries (Nervous system of the),

363

C.

CALORIE, 458

Calorification, organic (Processes of),

449

Canals, semi-circular, auditory, 417
Capillary (Vessels), 211
Carbon in the organic substances, 24

Cell (Of the), 36

Cells and nervous fibres, 374

Cells, artificial, of Traube, 80

nervous (Fibrils of the), 382

— nervous, thinking, 386
Cells, nervous, 376

. Properties of, 361

Cell, vegetal, 43

Cellular (Theory), 37

Cellulose, 43

Centre, nervous, cilio-spinal, 392

genito-spinal, 392

Cephalopods (Sense of smell of the),

411

Cephalopods (Eyes of the), 422
Chlorophyl, 92
(Action of the light on),

92, 96

Chlorophyl (Oxydation of), 97
and haematoglobuline

(Parallel), 97
Chlorophyllian (Organic syntheses),

112, 469
Chlorophyllian (Bodies), 44

(Property), 92

Choledocal (Canal), 169
Cilia, vibratile, 347
Circumvolutions, cerebral, 372
Circulation, 193

— arterial, 210

(Morphology of), 193

Ccelenterates, 159

Cold (Its influence on the small marn-

mifers), 447
Colloidal (Bodies), 15
Collar, oesophagian, 364
Composition, chemical, of animals,

22

Composition of plants, 19
Confervse (Movements of the), 343
Conjugation, 276
Constitution, anatomical, of organised

bodies, 35
Contagion, 142
Contractility, muscular, 353
Contraction, muscular (Duration of),

358, 452
Contraction (Its influence on the

temperature), 452
Contractility, vascular, of vegetals,

452
Cornea, transparent, 425

ITsDEX.

475

Corpuscules, stellate, osseous, 49

' of Paccini, 407

Crustaceans (Respiration of the),

233

Crystalline, 425
Ciystalloidal (Bodies), 15
Curare", 396

Current, nervous (Eate of), 395
Cyelostomes (Hearing of the), 416
Cylinder axis, 378

D.

D ALTON (Law of), 4
Death, 295

— not a fatality, 296
partial, 295

— natural (Euthanasia), 295

Democritus (Atomic theory of), 2
Dialysis, 77
Diaphragm, 239
Diastasis, vegetal, 113
Differentiation of the tissues (Law

of), 39

Diffusibility (Degrees of), 75
Digestion (Of), 178
Digestions, artificial, 185
Disassimilation, 82, 86

in animals, 135

Disassimilation, of the quaternary

substances, 138
(Predominates in old

age), 294

Dulong and Petit (Law of), 5
Duramen, 282

EAB, internal, or cochlea, 417

Ear, auditory, or cochlea (Function
of), 417

Echinoderms (Circulation of the),
195

Echinoderms (Digestive system of
the), 168

Echinoderms (Sense of hearing of
the), 415

Echinoderms (Touch in the), 407

Electricity, muscular, 358

(Its action on the muscu-
lar fibre), 358

Electricity (Its action on plants), 120

Electric, 459

Electromotricity in the capillaries,

212

Element, anatomical (Its constitu-
tion), 36, 43

Elements, anatomical, 35
— constituent

and produced, 40
Elements, anatomical (fluid in

youth), 293
Elements (Influence of health on their

growth and multiplication), 292
Elements, chemical, of the human

body, 11

Elements, figurate, in general, 36
Embryonary (Spot), 328
Embryoplastic (Cells), 334
Encephalon, vesiculous, of fishes and

reptiles, 371
Endogenesis, 277
Endosmosis, 77
Epithelium, 49

(Genesis of the), 289

Equivalents, mechanical, of the

aliments, 467
Equivalents, mechanical, of heat,

458

Excrementitial (Humours), 262
Exosmosis, 77
Eye, 420

. (Embryology of the), 424

Eyes, compound, 423

F.

Faculties, intellectual, 535
Fauna of the caves, 151
great ocean

depths,

116

Favilla, 319, 331
Fecundation, 310
by the antherozoids,

317

Fecundation by the ptollen, 318
Fibres, smooth muscular, 352

striated muscular, 352

nervous, 378

nervous motory, 380

grey nervous, gelati inform, or

Remak's, 380

476

INDEX.

Fibres, sensitive, 380

— (Properties of the), 394
Fibrine of the blood, 64
Fibro-cell, muscular, 351
Fishes (Circulation of the), 197

Respiration of the), 229

(Taste in), 409

• (Organ of hearing in), 416

Auditory nerves of), 416

Flora (Clock of), 343

Force (Meaning of the word), 457

inseparable from substance, 457

Forces, physical in Biology, 443
Forces (Are modes of movement),

340

Forces, of tension, 461
Forces, living, 461

GANGLIONS, cerebroidal of the inver-
tebrates, 365, 369

Ganglions, nervous, of the inver-
tebrates (Their functions), 431

Ganglions, lymphatic, 389

Gastric (Juice), 182

Gastric (Digestion), 180

Gastrula of Haeckel, 381

Generation, 801

Generation in the two organic king-
doms, 309

Generation (Proceeds like growth),
309

Generation, by division, 309

ovuJar, 310

— vegetal, 315
animal, 320

— fissipary, 320

by conjugation, 322

Generation, cellular (Theory of),

274

Generation (Presages often death),
294

Generation, spontaneous, 301, 308

Genesis, spontaneous, of the ana-
tomical elements, 48

Genesis (Theory of), 274

Geophagy, 176

Germination, cellular, 276

Glands, of the digestive apparatus,
167

Glands of excretion, 256

of secretion, 256

with excretory

258

conduits,

closed, 258

Globules, red, of the blood, 65

— white, of the blood, 71
Globules (Proportion of the), 72
— metamorphosed into i ed

globules, 226, 288
Globules, red, of the blood (Their

origin), 288

Glomerules of Malpighi, 268
Glycogen, 130
Growth (Oi), 273

Growth (General conditions of), 291
Growth (Processes of), 273
Growth in the animal kingdom, 285
Growth in the vegetal kingdom, 276
Growth, persistent of the aquatic

animals, 293
Growth, vegetal, during florescence,

281

Growth, vegetal, diurnal, 280
Growth, nocturnal, 279

H.

H;EMATIA, 67

(Function of the), 69,

70
Heat (Its influence on vegetal growth ),

279
Heat (Its influence on the life of

plants), 119
Heat (Its action on animal life),

152, 153

Heat (Can coagulate the blood), 447
Heat, organic, 513
Heat (Results from nutrition), 455
Heats, of combustion, 459

of combustion of the aliments,

463
Heart (Of the), 202

(Activity of the), 204

(Influence of the nervous sys-
tem on the), 205
Herbivora compared with carnivora,

143, 174
Herbivora (Digestive tube of the),

174

INDEX.

477

Herbivora (Urine of the), 270
Hermaphrodism,autofecundatory,323
Hirudinates (Circulation in the), 195

(Sense of smell in the),

411
Histology of vegetals, 43

of animals, 47

Histologicai (Elements), 3£
Hojothuria (Respiration of the), 432,
Humours, 55

(Chemical composition of

the), 55
Humours (Produced), 56

(Constituent), 57

(Secreted), 261

Humour, aqueous, of the eye, 425
Hydroids (Movements in the), 348

I.

INFLUX, nervous, 396

In nervation, 361

Insects (Temperature of), 445

(Respiration of), 231

Intestinal (Digestion), 188
Intestinal (Juice), 191
Invertebrates (Temperature of), 444

LAW of definite proportions, 4
Layers, optical, 371, 373, 384, 434
Layers, optical (Centres receptive of),

440

Leaves (Cause of the fall of), 283
Leucippus (Atomic theory of), 2
Leucocytes, 71
Leucocythapmia, 72
Life (Of), 28

Life (Temporary suspension of), 29
Life (Definition of), 33, 3i
Life (Primordial phenomena of), 72
Life (Is less lasting when the organism

is less differentiated), 294
Life (Variable duration of), 296
Liquids, living, 51
Liver (Capillaries of the), 169

- (Cells of the), 168
Lungs, 231, 237
(Capillaries of the), 241

Lungs, Gas of the), 241

(Change of colouration of

blood in the), 246
Lymph (Of the), 73
Lymph, plastic, 72
Lymphatic system (Functions of the),

74, 226

Lymphatic (Circulation), 222
Lymphatic (Glands) of Peyer, 224

M.

MAMMIFERS (Taste in the), 410
(Temperature in the),

446

Marrow, spinal, 383
Matter, organised, in general, 1
Matter (Constitution of), 1
Media (Of), 83
Media (Interior) 83
Medusae (Digestive system of the),

160
Medusae (Nervous system of the),

362
Medusae (Rudimentary eye of the),

421
Mimosa pudica (Movements of the),

345

Mimosa pudica (Causes of the move-
ments of the), 346
Molecules, 5
Mollusks (Digestive system of the),

163

Mollusks (Circulation of the), 195
— (Respiration of the). 234
(Muscular fibres of the),

349
Mollusks (Nervous system of the),

368
Mollusks (Sense of touch in the),

407
Mollusks (Sense of hearing in the),

416

Mollusks (Eyes of the), 422
Monstrosities, artificial, 292
Motility, 339
Motricity (Of), 388
Movements, vital, molecular, 32
Movements, Brownian, 339
Movements, in the vegetal kingdom,

343

478

INDEX.

Movements of the petals, 343

— of the leaves, 344

— ill the animal kingdom,
348

Movements, muscular (Source of),

452
Muscle (Is oxydised in contraction),

355

Myriapods (Respiration of the), 233
(Nervous system of the),

366

N.

N^EMATOIDS (Nervous system of the),

364
Naemathelminths (Circulation of the),

194
Nerves (Electric currents of the),

398
Nerves (Electro-tonic force of the),

398
Nerves (Regeneration of the), 400

vasomotory (Their influence

on nutrition), 150

Nodus vitalis, 254, 392
-Notocord, 286, 328>
Nucleus of the cell (Function of the),

37

Nutriments, 154
Nutrition (Of), 75
Nutrition, vegetal, 88
animal, 121,140

(Modifying agents of), 149

Nutrition, animal (Means of), 154

0.

OOGONE, 315

Oosphores, 315

Osmosis, 77

Otoliths, 415

Ovulum, animal (Constitution of the),
313, 323

Ovulum, vegetal (Its structure), 313

Ovulum (Evolution of the), 324

Ovulum, male, 330

Oxydation of the anatomical ele-
ments, 126

Oxygen (Its province in animal
disassiniilation, 139

r.

PAIN (Its influence on the tempera-
ture), 455
Pancreas (Functional relations of the,

with the spleen), 260
Paucreatine, 189
Pancreatic (Juice), 189
Papillce, gustatory, 410
Paraniflecia (Digestion in the), 159

(sexuality of the), 322

Parthenogenesis, 311

Pepsine, 185

Peptogens, 185

Peptones, 65, 133, 134

Plasmas, 51, 55, 58

Plasmine of the blood, 64

Planaries (Nervous system of the), 363

Planaries (Eyes of the), 421

Plathelminths (Nervous system of

the), 363
Pollen, 319, 331
Principles, immediate, 14, 15
Processes, ciliary, 425
Proliferation, cellular (Modes of),

276

Properties, vital, 30
Proteiue, 7

Proteic (Substances), 22
Protoplasm, vegetal, 44

(Intracellular movements

of the), 91

Protozoaries (Circulation of the), 193
Protozoaries (Respiration of the),

229

Psychometer of Dr. Mosso, 436
Pupil, 425

Q.
QUATERNARY (bodies), 23

R.

RADICALS, compound, 7
Regeneration, 334

(In the inferior ani

rnals), 320, 334

Regeneration (Processes of), 335
feeble in vegetals, 336

INDEX.

479

Regeneration (Is in inverse propor-
tion to differentiation), 336

.Reptiles (Circulation of), 198

Reptiles (Cutaneous respiration of),
229

Eeptiles (Taste in), 409

Respiration, vegetal, 94

intestinal respiration of

pondloach, 230

Respiration, tegumentary, of the
inferior vertebrates, 231

Respiration (Physiological province
of), 240

Respiration, diurnal, 252

Respiratory (Organs), in the animal
kingdom, 228

Retina of the eye of vertebrates,
425

Rhizopods (Circulation of the), 193

Rigidity, cadaveric, 153, 356

Rotifers (Nervous system of the), 363

S.

SALIVA (Formation of the), 267
Salivary digestion, 179
Salts excreted by the animal, 137
Sap (Formation and Circulation of

the), 90
Sap, elaborated or descending, 102,

107, 281, 470
Sarcode, 348, 350
Secretion and excretion in general,

256

Secretion, vegetal, 257
Secretion and excretion in particular,

264

Secretions (Diminish with age), 293
Segmentation (Cellular), 276

of the animal ovulum,

285
Segmentation of the histological

elements, 288
Senses (Number of the), 404

(Organs of the), 403

Senses of taste and of smell, 409

Sense of hearing, 415

Senses, tactile, 415

Senses of sight, 420

Sensations, 439

Sensibility in general, 402, 439

Sepia (Eye of the), 422
Serine of the blood, 64
Serum of the blood, 61
Sexes (Production of), 312
Sleep of plants, 118
Smell (Sense of), 411

(Nerves of the sense of), 412

Spermatozoaries, 330
Spermatozoaries (Reviviscence of the),

333
Spleen (Its action on the Pancreas),

260

Sporangium, 318

Subjectivity of the exterior world, 1
Substances, anorganic and organic,

11
Substances, inorganic, of vegetals,

114

Substances, organic of vegetals, 109
Substance, grey nervous, 377
Surculation, 276
Systems, colonial digestive, 159
System, nervous, in the zoological

series, 361
System, sympathetic nervous, of

insects, 368
System, smypathetic nervous of the

vertebrates, 374

T.

TEMPERATURE, constitutional, of ani-
mals, 444, 446

Temperature of plants, 119

Ternary (Compounds), 12

Texture of the organisms, 59

Theory, cellular, 48

Thoracic canal, 224

Thought (Of), 430

Tissues, anatomical, 39

Tissue, animal cellular, 49

Tissue, connective, 53

Tonicity, 389

Touch (Sense of), 406

Tracheae, 231

Transformation of sugars into fats by
animals, 131

Transformation of the forces in
Biology, 457

Tubes, thin nervous, 382

Tubercles, quadrigeininous, 371

480

INDEX.

Tunicates (Digestive, system of the), Vertebrates, superior (Lungs of the),

160
Tunicates (Respiration of the), 232

IT.

UNITY of substance in the universe,

3, 470
Urea, 138

Urine (Composition of the), 268
(Formation of the), 267

V.

VASO-MOTORY nerves (Function of

the), 216, 219
Vaso-motories (Their influence on the

local temperatures), 453
Vegetals (Histological types), 45

(Mineralisation of), 101, 283

(Temperature of), 443

Vertebrates (Digestive System of

the), 163

Vertebrates (Circulation of the), 199
-. — (Respiration of the), 236 ZOOSPORES, 3] 5

238

Vertebrates (Muscles of the), 350

(Sense of Smell in the),

411

(Formation of the Audi-
tory Organs), 417

Vessels, .vegetal (Formation of the),
44

Vessels, capillary (Classification of
the), 199

Vesicle, germinative, 323

Vestibule, auditory, 417

Villosities, intestinal, 167

Vitellus, 323

Vitelline (Cells), 327

W.

WATER (Its proportion in the body of

animals), 127
Water (Its office in assimilation), 127

TH3 END.

LONDON : R. CLAY, SONS, AND TAYLOR, PRINTERS.

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