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BOUGHT WITH THE INCOME
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GIVEN IN

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DATE DUE -

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http://www.archive.org/details/cu31924024760799

ZOOLOGICAL PHILOSOPHY

MACMILLAN AND CO., LimITED

LONDON - BOMBAY + CALCUTTA
MELBOURNE

THE MACMILLAN COMPANY

NEW YORK BOSTON - CHICAGO
DALLAS - SAN FRANCISCO

THE MACMILLAN CO, OF CANADA, Ltp,
TORONTO

ZOOLOGICAL
PHILOSOPHY

AN EXPOSITION WITH REGARD TO THE
NATURAL HISTORY OF ANIMALS

THE DIVERSITY OF THEIR ORGANISATION AND THE FACULTIES WHICH THEY

DERIVE FROM IT; THE PHYSICAL CAUSES WHICH MAINTAIN LIFE WITHIN

THEM AND GIVE RISE TO THEIR VARIOUS MOVEMENTS; LASTLY, THOSE WHICH
PRODUCE FEELING AND INTELLIGENCE IN SOME AMONG THEM

BY

J. B. LAMARCK

TRANSLATED, WITH AN INTRODUCTION, BY

HUGH ELLIOT

AUTHOR OF “MODERN SCIENCE AND THE ILLUSIONS OF PROFESSOR BERGSON”
EDITOR OF ‘‘THE LETTERS OF JOHN STUART MILL,” ETC., ETC.

MACMILLAN AND CO.,, LIMITED
ST. MARTIN’S STREET, LONDON

I9gIl4
Bay

A.Rq4 34

COPYRIGHT

ees

nee

eae

TABLE OF CONTENTS

PAGE
INTRODUCTION - - - : Z Z - = - xvii
Life—The Philosophie Zoologigque—Zoology—Evolution—In-

heritance of acquired characters—Classification—Physiology—
Psychology—Conclusion.

PREFACE - - - - = 2 z z ‘ < 3 1

Object of the work, and general observations on the subjects
dealt with in it.

PRELIMINARY DiscouRSsE = = - - - = - 9

Some general considerations on the interest of the study of
animals and their organisation, especially among the most
imperfect.

PART I. :

CONSIDERATIONS ON THE NATURAL HISTORY OF ANIMALS, THEIR
CHARACTERS, AFFINITIES, ORGANISATION, CLASSIFICATION

AND SPECIES.
~~
fo

- T.\On Artiricist DEVICES IN DEALING WITH THE PRro-
DUCTIONS OF NaTURE - - - - - 19

How schematic classifications, classes, orders, families, genera
and nomenclature are only artificial devices.

Tr IMPORTANCE OF THE CONSIDERATION OF AFFINITIES - 29
How a knowledge of the affinities between the known natural
productions lies at the base of natural science, and is the funda-
mental factor in a general classification of animals.

TII. Or Species amone Livine Bopigs, aND THE IDEA THAT
WE SHOULD ATTACH TO THAT WORD --— - - 35
That it is not true that Species are as old as Nature, and have
all been in existence for an equal period; but that it is true that
they have been formed one after another, that they have only a rela-
tive constancy, and are only invariable temporarily.

vill

CHAP.

IV.

VII.

TABLE OF CONTENTS

GENERAL PRINCIPLES CONCERNING ANIMALS - - -

The actions of animals only take place by means of movements
that are stimulated, and not transmitted from without. Irri-
tability is a faculty which they all possess, and is not found except
in animals: it is the source of their actions. It is not true that
all animals possess feeling, nor the faculty of carrying out acts
of will.

On THE TRUE ARRANGEMENT AND CLASSIFICATION OF
ANIMALS - - ne i. 086
That animals may be arranged, as regards their larger groups,
in a series which exhibits a gradually increasing complexity of
organisation ; that the knowledge of the affinities between the
various animals is our only guide in determining this series, and
that the use of this method dispenses with arbitrary judgments ;
lastly, that the number of the lines of demarcation, by which
classes are established, has to be increased in correspondence with
our knowledge of the different systems of organisation, so that the
series now presents fourteen distinct classes, of great service in
the study of animals.

. DEGRADATION AND SIMPLIFICATION OF ORGANISATION,

FROM ONE EXTREMITY TO THE OTHER OF THE ANI-
MAL CHAIN, PROCEEDING FROM THE MOST COMPLEX
TO THE SIMPLEST - - - - - - -

That it is a positive fact that on following the animal chain in
the usual direction from the most perfect to the most imperfect
animals, we observe an increasing degradation and simplification
of organisation; that, consequently on traversing the animal
scale in the opposite direction, that is to say, in the same order
as Nature’s, we shall find an increasing complexity in the organisa-
tion of animals, a complexity which would advance with evenness
and regularity, if the environmental conditions, mode of life, etc.,
did not occasion many anomalies in it.

OF THE INFLUENCE OF THE ENVIRONMENT ON THE
Activities AND Hasrrs or ANIMALS, AND THE
INFLUENCE OF THE ACTIVITIES AND HABITS OF THESE
Livine BopIEs IN MODIFYING THEIR ORGANISATION
AND STRUCTURE - - - - - -

How the environment acts upon the organisation, general form
and structure of animals; how changes subsequently occurring
in their environment, mode of life, etc., involve corresponding
changes in the activities of animals; lastly, how a change in the
activities, which has become permanent, involves on the one
hand more frequent use of certain parts of the animal, thus
developing and enlarging them proportionally; while, on the
other hand, this same change diminishes and sometimes abolishes

PAGE

47

56

68

106

TABLE OF CONTENTS

‘0k CHAP,

4] the use of certain other parts, thus acting unfavourably on their
development, reducing them, and finally causing their disappear-
ance.

(See the Additions at the end of Part I.)

VIII. OF tae NaturaL ORDER oF ANIMALS, AND THE WAY
IN WHICH THEIR CLASSIFICATION SHOULD BE DRAWN
UP, SO AS TO BE IN CONFORMITY WITH THE ACTUAL
ORDER oF NaturE - -

That the natural order of animals constitutes a series, which
we should traverse from the most imperfect animals to the most
perfect, in order to be in harmony with the order of Nature; for
Nature did not bring them all into existence at the same moment.
Since she had to form them in turn, she was obliged to begin with
the simplest, and only produced at the end those with the most
complex organisation. That the classification presented here-
with is unquestionably the one that approaches most nearly to
the order of Nature; so that if there are any corrections to be
made in it, it can only be in matters of detail; I believe, for
instance, that the Naked Polyps should form the third order of
the class, and the Floating Polyps the fourth.

ADDITIONS TO THE SUBJECT-MATTER oF CHaps. VII. anp VIII.

? PART II.

ix

PaGk

128

173

AN ENQUIRY INTO THE PHYSICAL CAUSES OF LIFE, THE CON-
DITIONS REQUIRED FOR ITS EXISTENCE, THE EXCITING FORCE
OF ITS MOVEMENTS, THE FACULTIES WHICH IT CONFERS ON
BODIES POSSESSING IT, AND THE RESULTS OF ITS PRESENCE

IN THOSE BODIES.

INTRODUCTION - - eee

Some general considerations on nature, and her power to create

life and organisation, and subsequently to increase the complexity

of the latter. In all these operations, she works only by the action

of various moving fluids on supple bodies, which are modified,
organised, and animated by these fluids.

I. Comparison oF InorGANIC Bopirs wits Livine Boptss,
FOLLOWED BY A PARALLEL BETWEEN ANIMALS

AND PLANTS - - - - - - - -

That there is a great difference between living bodies and inor-

ganic bodies. That animals are essentially distinguished from

: plants by Irritability, which is possessed exclusively by the former,

and which enables their parts to make sudden movements, repeated

! as often as they are stimulated by exciting causes,—a peculiarity
which does not occur in any plant.

106

183

191

x

CHAP,

IT,

Il.

IV.

Vv.

TABLE OF CONTENTS

Or LIFE, WHAT IT CONSISTS OF, AND THE CONDITIONS OF
Its EXISTENCE IN A Bopy - -

That life in itself is a purely physical phenomenon, which
gradually gives rise to many other phenomena, and which is due
exclusively to the relations existing between the adapted con-
taining parts of a body, the contained fluids moving in them, and
the exciting cause of the movements and changes which take
place in the body.

Or THE Exciting CausE oF Orncanic MovEMENTS~ -

That the organic movements, as also the movements which
constitute the actions of animals, are not communicated, but
stimulated by the activity of an exciting cause, which is not part
of the bodies it animates and does not perish like them; that
this cause resides in the invisible, subtle, expansive fluids, con-
stantly in agitation, which penetrate into, or are incessantly
being developed in the bodies which they animate.

OF OrGAsM AND IRRITABILITY - - -

That the exciting cause of organic movements sets up in the
supple parts of living bodies, especially of animals, an orgasm
which is essential for the preservation of life; and which, in the
case of animals, confers on the parts which possess it the faculty of
being irritable.

That Irritability is a faculty belonging exclusively to the supple
parts of animals, that it confers on them the power of producing
local manifestations which are repeated as often as the instigating
cause is brought to bear; lastly, that this faculty is essentially
distinct from that of feeling.

Or CELLULAR TISSUE, REGARDED AS THE MaTRIx IN
WHICH ALL ORGANISATION HAS BEEN CAST = -
That cellular tissue is the universal matrix of all organisation,
and that the movement of fluids in this tissue is the means employed

by nature for the creation and gradual development of the organs,
at the expense of the tissue in question.

. OF Direct or SPONTANEOUS GENERATION - - é

That, since all living bodies are productions of nature, she
must herself have organised the simplest of such bodies, endowed
them directly with life, and with the faculties peculiar to living
bodies.

That by means of these direct generations formed at the
beginning both of the animal and vegetable scales, nature has
ultimately conferred existence on all other living bodies in turn.

VII. Or tae IMMepiate Resutts or Lire 1n a Bopy - 7

That it is not true that living bodies have the faculty of resisting
the laws and forces to which all non-living bodies are subject, nor

TABLE OF CONTENTS xi

Pack
that they are controlled by laws peculiar to themselves; but, on

Hl the contrary, that it is true that the laws, which regulate the

changes occurring in bodies, meet with very different conditions

‘ in living bodies from those that they find in lifeless bodies, and

hence work upon the former results very different from those
worked upon the latter.

That living bodies have the faculty of building up their own

substance for themselves and thus forming combinations which

would never have come into existence without them; hence their

remains furnish the material which serves for the formation of the
u various minerals.

TH. Or tHe Facutties CcoMMON To ALL Livine Boprzs - 259

That life endows all bodies which possess it with certain faculties
in common, and that the production of these faculties requires no
special organ whatever, but only such a state of things in the
parts of these bodies as may enable life to exist in them.

MTX. Or toe FacvLties PECULIAR TO CERTAIN Livinc Bopres 265

That, in addition to the faculties conferred by life on all living
bodies, some living bodies have faculties which are altogether
peculiar to themselves. Now observation shows that these latter
faculties only arise, when special organs, capable of producing
them, exist in the animals possessing such faculties.

UMMARY OF Part II. - - - - - - - - 280

, PART III.

N ENQUIRY INTO THE PHYSICAL CAUSES OF FEELING, INTO THE
FORCE WHICH PRODUCES ACTIONS, AND LASTLY INTO THE
ORIGIN OF THE ACTS OF INTELLIGENCE OBSERVED IN
VARIOUS ANIMALS.

oh
{TRODUCTION - - - 5 5 = 285

Some general observations on the means possessed by nature,
for giving rise in living bodies to the phenomena known as sensa-
tions, ideas and the various acts of intelligence.

J. Or rae Nervous System, irs ForMaTION, AND THE 291
VARIOUS SORTS OF FUNCTIONS THAT IT CAN FULFIL
945 That the system of organs, called the nervous system, is limited

to certain animals, and that among those which possess it, it is
| found in different degrees of complexity and perfection; that

t

xii

CHAP.

II.

III.

IV.

TABLE OF CONTENTS

this system confers on some animals only the faculty of muscular
movement, on others this faculty together with that of feeling,
and on others again these two faculties together with that of forming
ideas, and of carrying out by this means various acts of intelli-
gence.

That the system of organs under examination fulfils four very
different kinds of functions, but only when it has reached a com-
plexity sufficient to give it the power of doing so.

Or tHE Nervous FiLuiIp -

That there is developed in the bodies of certain animals a very
subtle, invisible, containable fluid, remarkable for the rapidity
of its movements; that this fluid has the faculty of exciting
muscular movement, and that by its means nerves which are
affected produce feeling ; that, when its entire mass is agitated, it
gives rise to inner emotions; and that finally it is the singular
agent by which ideas and all intellectual acts are formed.

Or PuysicaL SENSIBILITY AND THE MECHANISM OF
SENSATIONS

That it is not true that any matter, or any part of a living body,
can have in itself the faculty of feeling; but that it is true that
feeling is a phenomenon resulting from the functions of a special
system of organs capable of giving rise to it.

That feeling is the result of action upon the subtle nervous
fluid of an affected nerve, which is propagated throughout the
nervous fluid of the sensitive system, and is terminated by a
general reaction which is carried back to the individual’s inner
feeling and to the point affected.

Or tHE INNER FEELING, THE EMOTIONS THAT IT MAY
EXPERIENCE, AND THE POWER WHICH IT THENCE
DERIVES FOR THE PRODUCTION oF ACTIONS

That the inner feeling results from the totality of internal
sensations produced by the vital movements, and from the fact
that all parts of the nervous fluid are in communication so as to
form a single though divided whole, which is capable of acquiring
those general agitations termed emotions.

That this inner feeling is the bond of union between the
physical and moral, and the origin of both; that the feeling in
question on the one hand acquaints the individual with sensations
that he experiences (whence the physical); and, on the other
hand, gives him consciousness of his ideas and thoughts (whence
the moral) ; and lastly, as a result of emotions aroused by needs,
causes the individual to act without any participation of his will
(whence instinct).

CHAP.

TABLE OF CONTENTS

V. OF THE ForcE WHICH PRODUCES THE ACTIONS oF ANI-

MALS, AND OF CERTAIN PECULIAR FACTS RESULTING
FROM THE USE OF THIS FORCE

That since muscular action is a power fully adequate for the
production of the movements performed by animals, and since
nervous influence is able to excite that muscular action, such
animals as have physical feeling possess in their inner feeling a
power quite capable of driving to the muscles the fluid which
excites their movements; and it is in fact by its emotions that
this feeling obtains the force to work the muscles.

Or THE CoNSUMPTION AND DRAINAGE OF THE NERVOUS
FLuIp In THE PRopucTion oF ANIMAL ACTIONS -

OF THE ORIGIN OF THE PROPENSITY TOWARDS REPEATING
THE SAME ACTIONS

Or Instinct in ANIMALS

Or SKILL IN CERTAIN ANIMALS

OF THE WILL -

That, since the will always results from a judgment, and since
a judgment necessarily arises from a comparison of ideas, a
thought, or some impression that causes it, every act of will is
an act of intelligence, and that consequently only animals with
a special organ for intelligence can carry out acts of will.

That, since the will always depends on a judgment, not only
is it never really free, but, since judgments are liable to numerous
causes of error, the will resulting from them is less reliable than
instinct in the inner feeling driven by some need.

VII. Or THE UNDERSTANDING, ITS ORIGIN, AND THE ORIGIN

or IpEas -

That all acts of the understanding require a special system of
organs for their execution; that acquired ideas are the material
of all operations of the understanding ; that although every idea
is originally a sensation, every sensation need not become an
idea, since a special organ is necessary for its formation, and the
sensation, moreover, has to be noticed ; finally, that, in all acts of
intelligence, the nervous fluid is the only active factor, in that it
moves in the organ concerned, while the organ itself remains
passive, simply providing for the diversity of the operations by
the diversity of its parts.

xiii

PAGE

343

348

349

350

353

355

362

xiv TABLE OF CONTENTS

CHAP.
VIII. OF toe Principat Acts or THE UNDERSTANDING, OR
THOSE OF THE First ORDER FROM WHICH ALL THE
REST ARE DERIVED - + - = -

That the principal acts of the understanding are attention, a
special preparatory state of the organ, without which none of its
acts could be produced; thought, from which spring complex
ideas of all orders; memory, whose acts, named recollections,
recall ideas of any kind, by bringing them again to the inner
feeling, or consciousness of the individual ; and judgments, which
are the most important acts of the understanding, and without
which no reasoning, or act of will could be produced, nor any
knowledge be acquired.

Or ImacInaTION 3

Or REASON, AND ITs CoMPARISON WITH INSTINCT

INDEX - x

GLOSSARY

Giving the original French of some of the more important words
used in the course of this translation.

ENGLISH,

’ affective,

affinities,

amphibian,
analytic,
arbitrary opinion,
argument,
artificial devices,
centre of communication,
classification,
complexity,
crude,

crura cerebri,
digression,

ego,

environment,
erethism,

exciting cause,
factor,

faculty,

feeling,

function,

fungus,
ganglionic longitudinal cord,
hypocephalon,
inclination,
inference,

inner feeling,
integral molecule,
intellect,

kinship,
laburnum,
lacteals,

limb,

main medullary mass,
matrix,

FRENCH,
affectant.
(biol.) rapports.
(chem.) affinités.
amphibie.
décomposant.
arbitraire.
raisonnement.
parties de Vart.
centre de rapport.
distribution, classification.
composition.
brut.
pyramides du cerveau.
écart.
mot.
ctrconstances, milieux environnants, ete.
éréthisme.
cause excitatrice.
cause influente, cause essentielle, etc.
Saculté.
sentiment.
(zool.) faculté, fonction.
champignon.
moelle longitudinale noueuse.
hypocéphale.
penchant.
conséquence.
sentiment intérieur.
molécule intégrante.
intelligence.
parenté.
cytise.
vaisseaux chyleux.
membre.
masse médullaire principale.
gangue, matrice.

Xvi

ENGLISH.
medulla oblongata,
mind,
monas,
natural order,
need,
nucleus (of sensations),
orgasm,
peduncles of the cerebellum,
pelvis,
procedure of nature,
propensity,
proteus,
reproduction,
rudiment,
scale of nature,
schematic classification,
sensibility,
sensitive,
serum,
skill,
soft radiarian,
soul,
spinal cord,
spirits,
spontaneous generation,
stage,
synthetic,
radiarian,
root-collar,
unguiculate,
ungulate,
vital knot,
vital principle,
volatile,
zoological philosophy,

GLOSSARY

FRENCH.
moelle allongée.
esprit.
monade.
ordre naturel.
besoin.
Soyer.
orgasme.
jambes du cervelet.
bassin.
marche de la nature,
penchant.
protée.
génération.
ébauche.
échelle de la nature.
distribution systématique.
sensibilité.
sensible.
sante,
industrie.
radiaire molasse.
dme.
moelle épiniére.
esprits.
génération directe or spontanee.
degré.
composant.
radiatre.
collet de la racine.
onguiculeé.
ongulé.
neud vital.
arché-vitale.
coercible,
philosophie zoologique.

INTRODUCTION.

§ 1. Lire.

JEAN-BaPTISTE-PIERRE-ANTOINE DE Monet DE LaMaRCK
was born on Aug. Ist, 1744, at Bazantin, a village in Picardy,
now known as the Department of the Somme. He was
the eleventh and youngest child of his parents, and belonged
to a family of nobility which had for generations past been
devoted to military pursuits. A number of his brothers
carried on the family tradition by entering the French
army ; but Jean himself was destined by his father for an
ecclesiastical career, and was entered as a student at the
Jesuit College at Amiens. Yet he himself had no inclination
to the calling desired by his father; and on the death of
the latter in 1760, he made immediate use of his new liberty
to leave the Jesuit College and join the French army, which
was then in Germany, near the end of the Seven Years’ War.
He bought a horse and rode through France and part of
Germany, until he reached the French lines on the eve of
the Battle of Fissingshausen. He carried with him a letter
of introduction to the colonel of one of the infantry regiments ;
and on the following morning placed himself in a company
of Grenadiers. The battle of Fissingshausen was fought and
lost: the French retreated: all the officers of Lamarck’s
company were killed, and the command fell upon him. His
courage was such that his colonel took him that very evening
to the Field-Marshal, by whom he was appointed an officer.

1 This at least is the story told by all Lamarck’s biographers. I venture nevertheless

to suggest that it can hardly be accepted in the unquestioning way usually followed.
The story is founded upon Cuvier’s Eloge de M. de Lamarck, and that again is doubtless
b

xviii INTRODUCTION

Shortly afterwards Lamarck was promoted to the rank
of lieutenant. Peace being declared, he spent five years in
garrison, first at Toulon, then at Monaco. While at Monaco,
one of his comrades in horseplay lifted him up by the head.
Inflammation of the lymphatic glands of the neck ensued.
He had to abandon his profession, and proceeded to Paris,
where after some delay a complicated operation was per-
formed, which cured him at the expense of deep and per-
manent scars.’

Lamarck was now thrown upon the world at the age of
22, damaged in health, and with no other resources than a
pension of 400 francs a year. For a year he lived in a garret
in Paris, and earned a living as a clerk ina bank. Then he
entered upon a course of medicine lasting, according to
Bourguin, four years, during part of which time he lived
with his eldest brother in a village near Paris. While in
garrison, Lamarck had already acquired an interest in
botany, and when studying medicine, developed his know-
ledge of it. It was through this means that he came into
contact with Jean-Jacques Rousseau; and the two
philosophers made botanical excursions together. It was
possibly through Rousseau’s influence that Lamarck thought
of devoting himself entirely to music ; but he was dissuaded
by his brother. Botany, however, absorbed him to such
an extent that he abandoned medicine, and entered upon
a course of botanical study lasting ten years, at the end of
which. he published his Flore Francaise, with a preface by
Daubenton.

France was now at the zenith of her philosophic career.
Scientific and philosophic subjects were discussed even in
the world of fashionable society: and the publication of
Lamarck’s work, in which also Buffori had assisted, brought

based upon a letter written by Lamarck’s son in 1830, shortly after his death, giving
Cuvier certain biographical particulars. This letter was only published in 1909:
I have read it, and find in it every disposition towards magnifying Lamarck’s achieve-
ments and enhancing the family glory. I do not wish to throw doubt on a pleasing
story: I merely wish to indicate that it comes from a distinctly biassed source, and
scarcely justifies the confident relation of it hitherto given by Lamarck’s biographers.

1 This is Cuvier’s account, which differs somewhat from that of Lamarck’s son,

LIFE xix

him into immediate fame. In 1779 he was elected into the
Academy of Sciences over the head of Descemet.

Two years later Buffon obtained for Lamarck a commis-
sion from the king to visit a number of foreign botanical
gardens and museums. In company with Buffon’s son he
travelled through Germany, Hungary and Holland, collecting
rare plants, meeting eminent foreign botanists, and making
notes for the use of the Jardin du Roi at Paris. On his
return in 1782, when he was 38, he still had no salaried
position, but was shortly afterwards appointed keeper of
the Herbarium at the Jardin du Roi, with the wretched
salary of 1000 francs a year. But even this position was
very insecure, and in 1790 its suppression was recommended
by the Comité des Finances to the Assemblée Nationale.
Lamarck published two pamphlets to emphasise the necessity
for continuing the office; to state his own claims for being
restored to it; and to submit to the Assemblée a general
scheme for the reorganisation of the Jardin du Roi, by which
it should become of general use to science, the arts and
commerce.

For another two or three years he appears to have held
some botanical position in the Jardin du Roi, or, as it became
about this time, the Jardin des Plantes. But at last, in 1793,
the scheme of reorganisation was carried by the National
Convention, and the Muséum @ Histoire Naturelle was founded.

There is not much clue to Lamarck’s views on the Revolu-
tion, although it is stated by de Mortillet that the change
of name of the Jardin du Roi was at the instigation of
Lamarck. There is no doubt, moreover, that Lamarck’s
scheme of reorganisation, written in 1790, was to a great
extent embodied in the scheme actually voted by the Con-
vention three years later: under which the Muséum
@ Histoire Naturelle received the constitution which it
still possesses at the present day. Two chairs of zoology
were created : one of which was devoted to mammals, birds,
reptiles and fishes, while the other was devoted to the
“inferior animals” (the insects and worms of Linnzeus),

XX INTRODUCTION

or, as Michelet called it, “Pinconnu.” To the first chair,
Geoffroy Saint-Hilaire was appointed, then a young man of
22. For the second chair, containing the unknown part of
the Animal Kingdom, there were no obviously suitable
candidates. Lamarck was a botanist of 25 years standing,
but the chair of botany had passed to Desfontaine, and
there now seemed nothing suitable remaining for him except
this chair of zoological remnants, to which accordingly he
was appointed at a salary of 2868 livres, 6 sous, 8 deniers.
The record of persons attached to the Muséum d Histoire
Naturelle in 1794 contains the title of his chair: ‘“‘ Lamarck
—fifty years old; married for the second time; wife
enceinte ; six children; professor of zoology, insects, worms’
and microscopic animals.” + Nevertheless, Lamarck passed
the remainder of his life in straitened circumstances: he
married altogether four times, and had seven children.

The collection of invertebrate animals already accumulated
at the Museum was immense, and Lamarck soon found that
his share of the Animal Kingdom included by far the greater
number of all existing species. His knowledge of zoology
was limited to the sphere of conchology, where he had
acquired some information, partly through intercourse with
his friend Bruguiere, and partly through a collection of
shells that he had formed for himself. From the date of
his appomtment, however, he practically abandoned botany,
and threw himself fervently into the study of invertebrate
zoology. The results of his researches were published in
seven volumes in his great work Histoire Naturelle des
Animaux sans vertébres, 1815-1822. Lamarck’s other works
included a number of publications on meteorology, a subject
in which he had taken an interest from early days, when
from his garret window at the top of a high house in Paris,
he could see nothing but the clouds passing by, and lay
speculating on their varied shapes and movements. But,
like Goethe with his Farbenlehre, Lamarck failed on this
subject either to reach any important conclusion or to secure

1 Lamarck, by A. 8. Packard, New York, 1901.

LIFE Xxi

the approval of his contemporaries. He attacked the
chemistry of Lavoisier and Berthollet, which further com-
pleted the discredit in which his excursions outside biology
involved him. His only remaining great work is the
Philosophie Zoologique, published in 1809, the translation of
which is herewith presented to the public, and to which I
shall confine the remaining sections of my Introduction.
Lamarck died at the end of 1829, at the age of 85. The
end of his life was passed in melancholy circumstances.
During his last ten years, he became totally blind; this was
due, it was said, to constant strain of eyesight in microscopic
work. But he was faithfully attended by his two daughters,
to one of whom he dictated the final portion of the Anmmaua
sans vertébres. The scientific world of his time rejected his
theories of transformism ; Cuvier, who was firmly convinced
of the fixity of species, became the most famous and fashion-
able biologist of the time, and Lamarck’s influence was
completely overshadowed. Arago, in his Histoire de ma
Jeunesse, relates the story of his meeting with Napoleon.
The Emperor was receiving the Members of the Institute
at the Tuileries, and Lamarck attended, carrying with him
his latest work, which happened to be the Philosophie
Zoologique, to present to Napoleon. Napoleon first spoke to
Arago, who had just been elected to the Institute, and then
passed to Lamarck. “Napoleon,” says Arago, “ passed
from me to another member of the Institute: a naturalist
famous for his brilliant and important discoveries, M.
Lamarck. The old man presented Napoleon with a book.
‘What is this?’ said the Emperor. ‘Is it your absurd
Météorologie with which you are disgracing your old age ?
Write on natural history, and I will receive your works with
pleasure. This volume I only accept out of consideration
for your grey hair. Here!’” and he handed the book to
an aide-de-camp. Lamarck, who had been vainly endeavour-
ing to explain that it was a work on natural history, was
weak enough to burst into tears.
1 Lamarck, par G. Revault D’Allonnes, Paris.

xxii INTRODUCTION

On his death, no permanent grave was provided for him.
His remains were carried to the cemetery of Montparnasse ;
but for some reason no burial lot was obtained. His body
was placed in a trench, cleared out once every five years
for the reception of new bodies. No monument marked the
site: but an unknown hand wrote on the margin of the
register: ‘‘ To the left of M. Dassas.” The position of the
trench is thus known, but Lamarck’s bones have probably
long since been removed, and their identity irretrievably
lost among vast quantities of others thrown together in
the Catacombs of Paris.

§2. Tue PaitosoPHiz ZOoOLOGIQUE.

Few names have been so extensively quoted in modern
biological controversies as that of Lamarck; yet of those
who quote him scarcely any have taken the trouble to read
his work. His name has come to be associated almost
bee with the doctrine of the inheritance of acquired
characters: the modern upholders of that doctrine are
commonly referred to as neo-Lamarckians, and among those
there are some who look up to Lamarck as the greatest
biological teacher that has ever lived. Partly on these
grounds, and partly on the grounds of the great historical
interest attaching to the work, it has been held desirable to
publish a complete English translation of his famous
philosophical treatise. For it is to be observed that the
Zoological Philosophy, from the purely historical stand-
point, represents the most advanced philosophical position
taken up by men of science in the pre-Darwinian era. We
most of us in these days do not believe in the inheritance of
acquired characters; but we all of us believe in evolution.
The Zoological Philosophy was published exactly half a
century before the Origin of Species: and by far its most
outstanding feature is its defence of the theory of the muta-
bility of species against the theory of special creations for
each species, then almost universally current. That inherit-

PHILOSOPHIE ZOOLOGIQUE xxiii

ance of acquired characters was one of the main factors
supposed by Lamarck to account for that evolution, I do
not wish to deny ; but that the reputation of Lamarck is to
stand or fall by that one theory is a suggestion which can
scarcely be made by anyone who closely studies the present
translation. But to that I shall come shortly.

Before beginning the translation, I had to consider on
what principles I should carry it out. The style of writing
and the mode of thinking that prevailed a century ago are
radically different from those that prevail at the present day.
As regards the style, Lamarck is lucid but ponderous. His
sentences are of great length, carrying numbers of sub-
ordinate clauses: his language is precise and carefully in
accordance with logical forms. All this is novel and more
or less disagreeable to modern readers. The formality of his
language soon becomes tedious ; we get lost in the relentless
prolixity of his sentences ; we do not care a snap for logical
forms. One further characteristic of Lamarck’s style—and
this one unquestionably a vice—is that of redundancy.
Many favourite doctrines are repeated with such insistence,
and in so many different forms, that the student finds the
most abundant justification for frequent skipping.

The mode of thought is not less contrasted with modern
modes, than is the style of writing. Every sort of scientific
or literary production is a product of its age, almost as much
as of the individual who attaches his name to them. In
the literature of any period there are current a certain
number . of more or less established ideas. Those ideas
circulate through society, undergoing changes but slowly.
Each new book that is issued represents certain of those
ideas in a setting that is perhaps more or less new; and if
it is an original work, of somewhat rare order, it may even
contain one or two ideas not previously current in society.
And these ideas, not being previously current, are not
understood; if they advance at all, they can only do so

slowly.
Hence the difficulty with which we are confronted on

Xxiv INTRODUCTION

plunging into a scientific work of more than a century
ago. We are suddenly in an entirely new miliew; for
in science, above all things, the rapidity of advance has
been immense. We find ourselves in the presence not merely
of one or two ideas that are new and therefore difficult to
us; but we are surrounded on all sides by strange and
unfamiliar conceptions, embodied in a language that is
modelled on a scheme we have never heard of. And the
associations which we carry with us from our own age are
often misleading. The difficulty is comparable to that of
learning the elements of a new science or of a new language.

Here then are very substantial and solid reasons to account
for the undoubted fact that Lamarck, although extensively
referred to, is scarcely ever read at the present day. And
these reasons had to be carefully considered in deciding upon
the mode in which the work was to be presented to the
English-reading public. Yet I could not disguise from myself
the fact that the main interest of this translation is historical,
and that any tampering with the text, in the hope of making
it more intelligible, would gravely damage its value from
the historical standpoint. I therefore determined to carry
out what should be in the main an extremely literal trans-
lation, and to leave its natural asperities of thought and
style without softening. On the other hand, I determined
to write by way. of introduction a brief précis of the whole
work, stating as far as possible the sum of Lamarck’s doc-
trines in my own words for the use of persons accustomed
to the style of writing and to the mode of thought prevalent
in this twentieth century.

I have said that the translation is extremely literal; yet
it is not absolutely so. I have not hesitated, especially in
the earlier part of the work, to break up some of the longer
sentences, in accordance with modern taste. I have even
translated such a word as “génération” by “ reproduc-
tion,” in all cases where Lamarck meant by the former word
exactly what we mean by the latter. I am aware of course
that the connotations of these two words are not precisely

PHILOSOPHIE ZOOLOGIQUE ey

the same, and indeed that the more modern word superseded
the older, in correspondence with the growth of a more
correct theory of the process indicated. But as a general
rule, Lamarck does not intend the word “ génération” to
imply any theory excluded by the word “ reproduction ” :
to translate it by “ generation” would at the present day
carry suggestions which are irrelevant to his issue, and be
more confusing than the name which has now become
familiar. But of course where he does intend it to carry a
connotation, not borne by the word “ reproduction,” I have
translated it accordingly.

Other difficulties arise from the need for expressing the
forgotten concepts of a century ago in a language adapted
for the conveyance of the concepts of to-day. Lamarck’s
concept embodied in the French word distribution long ago
became extinct ; the word itself has since come to be utilised
for a wholly different purpose, with geographical connota-
tions: its extinct meaning has now to be expressed by a
periphrasis or some other single word, intrinsically less suit-
able, but more comprehensible. In other cases, a certain
alliteration in the original has to be sacrificed for the sake
of clearness. It would be impossible to translate “ parties
de art” as “ parts of the art”; for few biologists would
guess what the part of an art might be.

The Zoological Philosophy is divided into three parts, the
first of which is devoted to zoology, the second to physiology,
and the third to psychology, using these three terms in their
modern sense. I shall now proceed without further pre-
liminaries to a description of Lamarck’s doctrines on these
subjects.

§ 3. ZooLoey.

‘The first doctrine set forth by Lamarck is that animals
in nature are arranged in a “natural order,” to discover
which is the duty of the systematic zoologist. Lamarck
held that if all living species of animals were known, they
would be found to fall into a linear series, exhibiting a few

XXVi INTRODUCTION

small collateral branches: a characteristic of this series
would be that each species would differ from the neighbouring
species by gradations so small as to be imperceptible. From
species to species, however, organisation gradually develops,
so that there are conspicuous differences discernible when
we compare two animals situated at some little distance
from one another in the scale of nature. The scale begins
with Monas and ends with Man: these two infinitely different
creatures being connected by the entire series of animal
spécies, each one differing from its neighbours only in minute
details. Lamarck attributed the large gaps which appear
in various parts of the scale to undiscovered species ; for,
as we shall shortly see, he did not believe that species had
ever become extinct. Between the various orders of birds
or mammals, for instance, there often seems no obvious
connecting link: and the gap between these two classes
themselves is a wide and apparently impassible one. The
discovery at the end of the eighteenth century of Ornitho-
rhyncus and Echidna, which possess many of the characters
both of mammals and birds, naturally appeared to Lamarck
strong confirmation of his theory that the gaps existing in
the linear series of animals, merely represent the existence
of living species, hitherto undiscovered, either because
they belong to unexplored lands or to the bottom of the
ocean. Lamarck’s scale of nature was thus to a certain
extent analogous with the modern periodic classification of
the elements. In each case, gaps occur which are liable,
as knowledge advances, to be filled up by new species or
new elements, possessing properties that can be prophesied
in advance. |

If there is in reality no hiatus or gap in the progressive
linear series of animals, then, argued Lamarck, there cannot
be any isolated groups of animals, nor is there any objective
justification for breaking up the animal kingdom into classes,
orders, families, genera, etc. In fact, all such classifications
must be purely arbitrary. They may indeed set forth any
portion of the animal series, arranging the species in their

ZOOLOGY xxvii

true order ; and in so far as they do this, they are valid and
useful. But the lines of demarcation between these groups
are regarded by Lamarck as wholly arbitrary. You may,
for instance, take the first hundred species of the scale and
call it Class I.: the second hundred species you may call
Class II.: but you would have been equally justified in
taking the first 120 species and calling them Class I., and
the second 120 Class II. In short, there is no real division
or break in the scale of animal nature.

"Hence, Lamarck refers to classes, orders, families, genera
as “ parties de l’art,” or devices introduced by art for human
convenience, and not corresponding to anything real in
nature. Yet he regarded these devices as absolutely essential
for introducing order into what would otherwise be a chaotic
jumble. We are thus forced to adopt either a schematic
classification or a “natural” classification: the former is
a mere grouping of animals by respect to certain characters
of no fundamental taxonomic importance ; the latter repre-
sents the series of species in their true order, and is only
artificial, says Lamarck, in so far as it breaks them into
groups. Since such subdivision of the series is a practical
necessity, he held that it is wise to apportion our classes,
orders, etc., in such a way that the gaps in our knowledge
fall between them, and do in fact create apparent groupings
in the animal world.”

" Lamarck then proceeds to trace the essentials of a natural
classification, which shall be in correspondence with the
order of nature. The guiding principle must be the true
affinities (rapports) between animals. Their contiguity in
the series is to be determined, mainly by the resemblance:
existing between their most “essential” organs, and to a.
lesser degree by the resemblance between less “ essential ”
systems of organs. By “ essential’? Lamarck means, in the
case of animals, essential to the maintenance of individual
life, and in the case of plants essential to reproduction.
He says that the most essential system, in the determination
of affinities, is the ‘‘ organ of feeling,” or nervous system ;

XXviii INTRODUCTION

after that comes the respiratory system; and third, the
circulatory system.’ This order of importance is arrived at
in the following way. Starting from the higher extremity
of the animal series, where man is placed, he descends the
series of gradually simplifying animals. One after another,
he finds the different systems of organs dying out: and the
importance of each system is judged by the distance he has
to travel down the series before that system becomes extinct.
Thus the circulatory system extends throughout Lamarck’s
eight highest classes, viz. :—mammals, birds, reptiles, fishes,
molluscs, cirrhipedes, annelids and crustaceans, and there
ends. The respiratory and nervous systems extend through
these and also the two succeeding classes of arachnids and
insects. They are therefore held to be more essential than
the circulatory system. Of these two again, the nervous
system is the more essential, since “it has produced the most
exalted of animal faculties, and is necessary to muscular
activity.” I confess it is not obvious why the alimentary
system does not take precedence of all others, for it is
described as extending through the three further classes
of worms, radiarians and polyps, only ending at the in-
fusorians. Since Lamarck (as I shall shortly explain)
believed in an evolution from the simplest to the most com-
plex animals, he naturally assumed that the earliest system
of organs to be developed in the course of that evolution
must be the system most essential to life in the higher animals.
The least essential of the features to be considered in the
determination of affinities are, in his opinion, the external
characters of animals: differences of external characters
are therefore to be used only for the determination of species.
For more fundamental distinctions, more essential characters
are to be considered.

* Lamarck found the “ productions of nature ”’ commonly
divided into the three kingdoms of animal, vegetable and
mineral. He proposed the abolition of this scheme, and the
substitution of another in which all bodies were to be divided
into organic and inorganic. For the science which deals

ZOOLOGY xxix

with organic bodies, both Lamarck and Treviranus proposed
the name “ biology” in the year 1802. Lamarck further
commits himself to the statement that all inorganic sub-
stances are derived from the exuvie of living bodies. He
believed that nature originally created only the most
elementary forms of life. These by evolution upwards led
to the animal and plant kingdoms: the decomposition of
these two types of organism gave rise to the third kingdom,
chiefly composed of minerals.

He then has to define the difference between animals and
plants: he finds that «rritability, or the power of response to
external stimuli, is a universal property of animals, and a
property which is invariably lacking in plants. Mvzmosa
pudica, the sensitive plant, gives him a certain amount of
trouble, but the apparent exception is explained by an
Ingenious though (even for his time) highly speculative
theory. True irritability, characterised by an immediate
contraction on contact with a foreign body, is a property
which according to Lamarck is found in some part of every
living animal. In the second line of differentiation, he
names digestion and the power of locomotion as being charac-
teristic of the great majority of animals and wholly absent
in plants.

Lamarck sees a new instance of the wisdom of the “ sub-
lime author of all things” im the arrangements made for
preventing overpopulation of the earth by any. one species.
Small animals, though multiplying with great rapidity, are
kept down by an immense mortality, in which they are
involved by the accidents of life, more especially the acci-
dent of being eaten by a larger animal. The larger animals,
which are not liable to serve as food for others, are main-
tained within their proper limits by a low rate of reproduc-
tion. Man alone might well multiply to cover the surface
of the earth: but he is himself his own executioner; for
with the development of intellect comes the development of
passions, which ever lead to the reduction and limitation of
his own species. ”

XXX INTRODUCTION

§ 4. EvoLutIon.

The most fundamental purpose of Lamarck’s zoological
work was to controvert the belief in fixity of species. It
was at that time almost universally held that all species
had been created at the beginning of the universe by special
acts of creation. They were thus supposed to be all of
equal antiquity, and to be “‘as old as Nature.” They were
supposed further to have subsisted without any sort of
structural change since the moment of their creation.

These propositions Lamarck attacks. He holds that
species can only maintain their constancy of form so long
as their environment remains constant. Any change in the
environment necessitates a corresponding change in th
species. In support of this doctrine, he cites the case of
domesticated animals, and the altered shape which has in
their case followed upon an altered environment: the same
thing is found in cultivated plants. He draws attention
further to the linear series of animals arranged in order of
gradually-increasing complexity, so as to form a continuous
whole, strongly suggesting development. He is far from
wishing to attack the conceptions of theology. If “ the
sublime author of the universe” can create all the different
species by separate acts of creation, so too, says Lamarck,
he can surely create one or two species to begin with, and
confer upon them the power of evolving into the rest.

Lamarck held that as long as the environment remained
unaltered, the species living in it might also remain unaltered.
Geoffroy Saint-Hilaire had recently brought from Egypt an
extensive collection of mummified animals of great antiquity.
An examination of these animals revealed the fact that they
were in every respect identical with the existing fauna of
that country ; and this discovery was used as an argument
in favour of the permanent fixity of species. Jamarck’s
position, however, was unaffected by it: for he pointed out
that there was every reason to believe that there had been
no change in the climate and conditions prevailing in Egypt

EVOLUTION XXxi

during the last few thousand years: hence no change need
have been expected in the animals living there.

Lamarck then considers the question whether it is true
that any species have ever become extinct. The evidencé’
of fossils certainly seems to suggest it, for they exhibit
innumerable forms no Jonger found among living animals.
Yet Lamarck finds it very difficult to believe that nature
could be so imperfect as to permit of the complete extinction
of any species. He was not wholly emancipated from that
vicious tendency—of which Plato was the prototype—towards| ?
imagining, that because a thing was not beautiful, or har-
monious, or otherwise agreeable, it could not be true. Hence
he inferred that, in the case of many fossils of sania
extinct species, the species would still be found living in‘
unexplored countries, or on the sea-bottom, or other unknown |

regions. He believed furthermore that many of these fossils
had evolved into existing known species ; but that the}
changes undergone during evolution, in correspondence with ;
a changing environment, had been so great that the ite,
species were no longer recognisable as descendants of the
fossils. nee
If any species have become extinct it is, he said, at all
events only the larger species of land animals, such as
Cuvier’s Palaeotherium, Anoplotherium, Mastodon, etc. : and
their extermination, if a fact, is exclusively due to human
agency. But no species of water animals, nor any of the
smaller species of land animals, can possibly have become
extinct. Lamarck very shrewdly perceived that the fossils
showing most analogy with living forms are usually the
least ancient. And this strange admixture of good and
bad philosophy then ends in an attack upon the theory of
a general catastrophe in nature—a theory invoked to explain
among other things the divergence of fossils from existing
forms of life. Throughout this part of Lamarck’s work, we
find much in which his philosophy was several generations
in advance of his contemporaries, and indeed was not far
short of our own: mixed with much else in which his

Xxxii INTRODUCTION

philosophy was far bebind that taught by many of his greater
contemporaries and forerunners.

The method by which Lamarck believed evolution to have
been brought about was by the inheritance of minute
variations: and he was altogether opposed to any belief in
those larger variations which we now call mutations. “ If

the procedure of nature is attentively examined,” he writes,

“it will be seen that in creating or giving existence to ea
productions, she has never acted suddenly or by a single
leap, but has always worked by degrees towards a gradual
and imperceptible development.” For the explanation of
this belief we have to remember that the current notions of
his time were of the catastrophic type. Species were sup-
posed to have been individually created by single and
instantaneous acts: the surface of the earth was likewise
regarded as having been exposed to a series of violent
catastrophes, so that the changes which have visibly enough
come over it were due, not to slow and gradual processes,
but to a succession of sudden large breaks.

Now those who upheld the standard of uniformitarianism
were inclined to state their position in the most uncom-
promising way. They adduced such maxims as “ Natura
non facit saltum,” and endeavoured to show that evolution
proceeded invariably by minute and imperceptible gradations.
It is possible that they went too far: nevertheless, we have
to remember that they never envisaged the modern problem
of the mutation theory. For them the antithesis was
between catastrophic transformations and transformations
by imperceptible gradations. Even should the doctrine
of Bateson and De Vries be well founded, the evolutionists
of a century ago must be held as its ancestors in a direct
line.

In the same way that uniformitarianism, though a true
principle, was not propounded in precisely correct terms, so
also transformism tended to be asserted in somewhat too
extreme a fashion. By reaction against the doctrine that

species were immutable, the evolutionists of the time under

EVOLUTION Xxxiii

consideration believed in a greater mutability than has been
found to be the case. Lamarck believed that an alteration
of the environment would within a few generations effect a
permanent alteration in the structure of a species. Of
this I shall adduce a number of instances in the following
section. He perceived how easily domestic races evolved
out of wild species; but he apparently did not know how
easily they also lapsed into the wild state; nor that varia-
tions, so conspicuous to the eye, are highly unstable and
superficial. By reaction against the doctrine of the per-
manent stability of species, he adopted an altogether exag-
gerated view of their instability. Indeed, his views on this
subject are scarcely consistent: and Sir Ray Lankester
has already urged that his first and second laws are
incompatible.

Given the fact of evolution, the question at once arose as
to what are the physical causes of it. Of natural selection
Lamarck had not the slightest conception. The only passage
that is even remotely suggestive of it, is when he deplores
the inequality of intellectual capacity among men; for
those with higher intellects gain an advantage over the
others, and hence these others, constituting the great
majority, must suffer. He regarded the equalisation of
intellectual capacity as the greatest social reform required.
It is plain how little he guessed at the theory of natural
selection.

He held that evolution was due to the co-operation of
two factors, eh first and most fundamental was due to
of structure : this tendency cy being conferred upon the low-
or Surucuuy
hest animals at the moment of their spontaneous generation.
I shall describe Lamarck’s opinion as to the physical causes
of the tendency, as also of spontaneous generation itself, in
a later section dealing with his physiology. For the present,
it suffices to observe that Lamarck believed that variou
portions of inorganic matter are constantly being vitalise
or endowed with life by a process of spontaneous generation

: c

XXXIV INTRODUCTION

\that in this way worms and infusorians come into being,
| and that these organisms are at the same moment endowed
| with a tendency to evolve, till they ultimately give rise to
‘all the higher races of animals.

The second factor, which, according to Lamarck, operated
in the evolution of species, is that with which his name has
come to be so closely associated, namely, the inheritance of|
acquired characters. This doctrine appears to have been
first enunciated in detail by Lamarck himself: it is natural
therefore, that he should dwell upon it at great length in
the present work. We must, however, recollect that he
looked upon it as subordinate to the main factor, just as
Darwin invoked it as subordinate to natural selection!
His position was far indeed from that occupied, for instance,
by Herbert Spencer in 1852, when some evolutionists en-
deavoured to account for evolution with exclusive reference
to direct action of the environment. I shall deal with this
alleged factor in my next section: for the present I confine
myself to an account of Lamarck’s views of the evolutionary
process.

Lamarck held, then, that if it were not for the effects of
jenvironmental influences, the innate tendency to develop
‘would be the exclusive factor in operation. We should
then see the linear series of animals to be a perfectly regular
and even progress in complexity of organisation from Monas
termo to man. Hach animal born would presumably be
shghtly more complex than its parent. If we could trace
the ancestry of man, we should find as we went backwards
that each individual was to an excessively small degree less
complex than its immediate neighbour, till finally we ended
with the infusorians. All existing animals are on the road
of development from Monas to man, and man’s ancestors
include every existing species of animal. Not only had he
bird, reptile and fish ancestors, but also arachnid, insect,

1 Professor Charles Martins in his introduction to the 1873 reprint of the Philosophie
Zoologique is so intent upon making out a case for inheritance of acquired characters,
that he omits to make any mention whatever of Lamarck’s primary factor. He has
thus helped to perpetuate a common error regarding Lamarck’s views.

EVOLUTION XXXV

worm, starfish, etc., ancestors! He passed through the

stage of being a scorpion and a spider. He traversed in

turn every known species of insect. He was a tapeworm,

a sea-anemone, a polyp and an amoeba. For myself, I fail
to see how he could have been an intestinal worm when

there were no such things as intestines, or a liver-fluke

when there were no such things as livers. His existence as

a flea must have been precarious, when there was nothing

more substantial to live upon than jelly-fishes, starfishes,

and parasitic worms. Indeed, the doctrine is wholly absurd

the moment it is consistently thought out. It was to remedy _
absurdities of a somewhat different kind that Lamarck in-

vented his factor of use-inheritance: and it is that factor

which he would have at once invoked to explain away such

difficulties as I have named.

The fact remains however that, leaving aside for the
moment the influence of environment, Lamarck assumed a
perfectly even development to proceed in a straight line
throughout the animal scale: and he assumed that this
development was due to an innate power conferred upon the
lowest of animals at the moment of their spontaneous genera-
tion. Accordingly, one of the longest chapters in the whole
work is devoted to an account of the gradual progress in
organisation observed as we pass along the animal scale.
In point of fact, Lamarck inverts the natural order, and
begins with the highest mammals, proceeding to the lowest
infusorians. Thus, instead of a gradually increasing com-
plexity, he finds a gradually diminishing complexity, as he
passes along, or as he calls it a “ degradation of organisation.”
That Lamarck should have traversed the series in the wrong
direction is doubtless due to the fact, that from the time
of Aristotle to the time of Lamarck, every systematist,
including even Linneus, had commenced his classification
with the highest animals and finished it with the lowest.

1 J am here alluding to the classification presented in the main work. This classifica-
tion was greatly improved in the “‘ Additions ’’ to Part I., as I shall show later; and
many of these animals were then referred by Lamarck to collateral branches, off the
main line of development leading to man.

XXXVi INTRODUCTION

Lamarck was merely following a precedent, of which he
fully realised the inappropriateness. In his own classi-
fication, he strikes out a new line, and begins his animal
scale with the simplest existing animals.

The degradation noted by Lamarck as he passed along the
scale from mammals to infusorians is traced throughout the
various systems of organs. The skeleton is lost, on passing
the fishes; the nervous system, on passing the insects ;
respiration comes to an end with the radiarians, and so on
with the circulatory, digestive and other systems. So, too,
the lungs of mammals gradually deteriorate through the birds
to the reptiles and fishes, where they are replaced by “ less
perfect ” respiratory organs, in the shape of gills. These
again vanish farther on, and give place to the still more
imperfect system of trachez in the insects and arachnids:
while lower down the scale, respiration is entirely lost.

The bilateral symmetry which characterises all animals
down to the insects similarly gives way to a radiating shape
in Lamarck’s class of “ radiarians,” and these merge into
amorphous infusoria. Polyps represent the intermediate
state: for they have radiating tentacles around the mouth,
but are not otherwise of definite shape. Nature has, accord-
ing to Lamarck, just started in them that radiating form,
which is carried to its highest perfection in the echinoderms.

A few observations on special pots may be made before
I pass on to the subject of use-inheritance. Lamarck, as
we shall see in dealing with his physiology, assumed the
existence of “subtle, invisible fluids,” which like spirits in
the past, and like vital forces or biotic energy in the present,
served to explain anything which remained a mystery before
materialistic methods. They were useful for instance for
explaining the physical origin of the radiating form of cer-
tain animals. “ The subtle surrounding fluids which enter
the alimentary canal are expansive, and must by incessant
repulsion from the centre towards every point of the circum-
ference give rise to this radiating arrangement of the parts.”

In much the same way he explains why birds have feathers

EVOLUTION XXXVii

instead of hair. When a bird flies, it fills its lungs with air
“in order to increase their volume and make itself lighter.”
But the lung being warm causes the air to expand, and
piercing through the lung, penetrate every region of the
body, including the bones and hair. The result of the
expansion of air within the bird’s hair is to make it blossom
forth into feathers. Lamarck did not fail to see the diffi-
culties of his theory. Why have bats not got feathers ?
Because they have a complete diaphragm, which prevents
the swelling and piercing of the lungs. Why then have
flying insects not got feathers? Hach difficulty is met by
Lamarck with unshaken confidence in his hypothesis.

Lamarck did not believe in spontaneous generation,
except in the most elementary animals, but he held that
among them it is always in progress. Like much else in
his work, this is a deduction based on false premises. All
infusorians, he says, die in cold weather: they are much
too delicate either to survive or to leave any spores or ger-
minal material that could last through a winter. Yet, on
the return of warm weather, we find them swarming in
stagnant water and other places: hence they are spon-
taneously generated. )

The progress made towards “ perfection” of organisa-
tion as we advance along the animal scale must be
understood to mean a progress in the direction of human
organisation. For Lamarck the organisation of man is the
type of perfection; and perfection or imperfection of
organisation is judged by its approach towards or depar-
ture from the human. Lamarck recognised, however, that
a high organisation was characterised by the concentra-
tion of organs and functions in special places, whereas in a
lower organisation they tend to be more generalised through-
out the body. He thus anticipated von Baer’s famous law,
that development proceeds from the homogeneous to the
heterogeneous, upon which was founded one of the most
important clauses in Spencer’s formula of evolution.

It must have been quite obvious from the first that the

XXXViil INTRODUCTION

kind of evolution above described could not possibly account
for all the varied shapes of existing animals. The series 1s
full of anomalies. Birds, for instance, are lower in the
scale than mammals. Yet their pectoral muscles and
sternum are developed out of all proportion to their proper
place in the series. Then, again, whales have no legs; yet
legs reappear farther down the series, for birds have them,
and so do many reptiles, not to speak of lower animals.
If evolution was solely as hitherto described, we should
expect legs to vanish gradually as we passed down the
scale; and having vanished, not to reappear again.

Within a single class, such as reptiles, the same anomaly
is seen. Frogs (for Lamarck included amphibians with
reptiles) breathe by gills when first born: hence they are
inferior to snakes which never have anything but lungs.
Yet snakes have no legs, while frogs have legs: that is to
say, the lower animal is better off for legs than the higher.
Whence these numerous anomalies? It is to Lamarck’s
solution of this problem that we must now turn our attention.

§5. INHERITANCE OF ACQUIRED CHARACTERS.

Acquired modifications, as distinct from the so-called
spontaneous variations, are of two different kinds. In the
first place, there are those modifications which are due to
the direct action of the environment, without reference to
any active efforts on the part of the organism. Such, for
instance, are various modifications in colour, etc., of the
superficial layer of the body, due to the application of light
or heat: such, again, are mutilations. In the second place,
there are those modifications which arise from the greater
or lesser use of any part, due to some environmental cause,
which requires the organism to exert certain parts to a
greater or lesser extent than the average. This latter type is
referred to as functionally-produced modifications, and their
inheritance is often called use-inheritance. It is this latter
type alone that Lamarck regarded as being a factor in

ACQUIRED CHARACTERS XXx1x

organic evolution; he expressly excludes direct action as
an operative cause. But before dealing with Lamarck’s
general views on this subject, I propose to cite a number of
the facts upon which he relied for the proof of his theory.

Domestic races, both of animals and plants, are very
different from the ancestral wild races from which they spring.
When the environment is greatly altered, the structure of
the organism undergoes a corresponding alteration. Take,
for instance, the various races of dogs. They are, according
to Lamarck, all descended from an animal something like a
wolf. They became domesticated by man, and were trans-
ported by him to different parts of the earth, where the
environment was very different from their natural home.
Accordingly, they underwent modifications in each locality,
which brought them into harmony with the conditions pre-
vailing in that locality. These modifications, being inherited
through many generations, acquired comparative stability ;
and the new varieties, when imported into a new country
or great city, would for a long period retain their general
characteristics. These would be further complicated by
inter-breeding, and thus give rise to the many different
varieties with which we are acquainted. So argued Lamarck.
‘ Where an animal does not use its teeth, these dwindle
and disappear. Such, for instance, is the case with right-
whales and ant-eaters, although Geoffroy Saint-Hilaire dis-
covered rudimentary teeth in the foetus of right-whales.
The same applies to birds, where teeth have become still
more completely extinct.

Animals which do not use their eyes, such as moles, after
a time lose the use of that organ either completely or
partially.

Snakes would be impeded by legs, and have consequently
lost them. Their mode of life requires them to hide in
grass, and to pass through narrow crevices. Hence, urges
Lamarck, their bodies become narrow and long. Long legs
would greatly interfere with their mode of life: short legs
would be incapable of supporting them, since (being reptiles)

xl INTRODUCTION

they could not have more than four. Similarly, insects
which do not fly have undergone a degeneration of the
wings.

Birds, to continue Lamarck’s examples, acquire webbed
feet by constant efforts to swim. In the course of these
efforts, the skin uniting the base of the digits is constantly
on the stretch. It therefore develops, and, in course of
many generations, birds are produced with complete webs.

Other birds perch on trees, and by continual effort to
grasp the branches, develop long hooked claws. Others,
again, feed on water-animals or plants, but have a strong
objection to wetting their bodies. Hence they are constantly
stretching their legs, to keep their bodies above water when
standing in it. After many generations, long legs become
established, without feathers and adapted for standing in
water. For the same reason long necks were developed by
constant stretching. In the case of birds like swans, which
have no objection to swimming on the water, long necks
are established without long legs.

Where the tongue is much used for reaching objects in
front, it also lengthens, as in the ant-eater or woodpecker :
where it has to grasp.or palpate such objects, it becomes
cleft, as in humming-birds, lizards, and snakes.

Flat fishes normally swim in the vertical plane, with one
eye on each side of their heads. In certain species, however,
the fish desires to come as near as possible to the shore ;
and in the case of a shelving beach, it can approach much
nearer land by turning on to its side and swimming in the
horizontal plane. One eye, being then on the under-surface,
where there is really nothing worth looking at, is perpetually
being strained or twisted round to see what is going on
overhead. Hence, after many generations, it moves bodily
round to the upper side, as in soles, turbots and dabs.

Herbivores are commonly massive because they spend
all their time eating: some, however, such as gazelles, are
liable to be pursued by carnivores, and hence acquire legs
capable of rapid locomotion ; others, such as deer, develop.

ACQUIRED CHARACTERS xli

in a similar manner, owing to pursuit by man. All these
creatures are liable to fits of anger, in which they desire to
fight; but, since neither their legs nor their mouths are
suitable for use as weapons, they are reduced to butting
each other with the crowns of their heads. This causes an
additional flow of fluids to that region, with a deposit of
horny matter: hence the development of horns and antlers.

Giraffes live in barren countries, where the only available
food is in the leaves of trees. By constantly stretching
their necks to reach these leaves, they acquire the strange
conformation characteristic of them. Kangaroos likewise
acquire a powerful pair of hind-legs and tail.

The sloth is drawn upon likewise for an explanation of
its slovenly habits. Originally a dweller on the ground,
and then capable of moving with the ordinary rapidity,
it took to climbing trees, where food was found in such
abundance as to require very little movement. More move-
ment than necessary would be injurious, partly owing to
the heat of the climate in which it lives, and partly because
by sitting still and doing nothing it would run fewer risks
of falling off and hurting itself. By constant disuse of its
locomotive structures, continues Lamarck, it gradually lost
the power of moving on the ground, where it is said to be
able to take not more than fifty steps in a day.

Lamarck even adduces an instance from man himself.
One, Tenon, had recently stated that the intestine of habitual
drunkards is greatly shortened. Now habitual drunkards
(he continues) consume a smaller quantity of solid food than
ordinary people : there would be less work for their intestine
to do, and a corresponding diminution in its length. Such
are the facts on which Lamarck bases his theory of the
inheritance of functionally-produced modifications.

Now it is quite clear that all these facts can be explained
as easily or more easily on the theory of natural selection,
than on that of the inheritance of acquired characters. If
it is true that rapid moving among trees is dangerous to
sloths, then natural selection would soon ordain that all

xlii INTRODUCTION

sloths should become inactive. Rash sloths, which moved
about rapidly and hence fell to the ground, would be injured
and more or less incapacitated for reproduction. They
therefore leave no progeny of rash sloths, similar to them-
selves. Cautious sloths, on the other hand, which move
as little as possible, run fewer risks of falling off and getting
hurt; they are therefore likely to leave progeny, and this
progeny will consist of cautious sloths like their parents.
Thus there is a perpetual tendency for the species to be
recruited from the cautious and prudent sloths, and for the
extinction of the rash sloths. In course of time, none but
cautious sloths will remain.

The case is similar with the giraffe’s neck. In time of
stress, giraffes with unusually long necks will have access to
a better supply of food than giraffes with short necks. The
latter will die out, while the former will survive. On this
assumption, there is no necessity for any inheritance of
acquired characters. The unusual length of neck is a
spontaneous congenital variation, arising by pure chance ;
it is preserved and inherited.

From the @ priori view, there does not seem a great deal
to choose between the theories ; and it was the @ priori view
that was adopted by Lamarck. Many of the known facts of
evolution might be accounted for either by use-inheritance
or by natural selection. Jf it is true that acquired characters
are inherited, then the giraffe might well have developed his
neck through that agency. The hypothesis fits the facts.
But so also does the hypothesis of special creation; for if
God manufactured the giraffe, neck and all, just as we find
him, we immediately reach the goal of our researches on the
matter. Similarly, again, natural selection is equally satis-
factory as an & priort hypothesis. Jf congenital variations
are inherited, and 2f favourable variations have a real sur-
vival-value for the individual, then natural selection might
well have been the true method.

The fact is, of course, that the above mode of reasoning
is a grave abuse of the deductive method. Few, indeed, are

ne

ACQUIRED CHARACTERS xiii

the people who are competent to judge of the correct use of
deduction in difficult biological inquiries. It is not enough
to invent a hypothesis, which covers the facts, and then
regard it as true without further study. In the present case
the facts are covered by at least three different and mutually-
exclusive hypotheses, special creation, inheritance of acquired
characters and natural selection. The @& priori method
breaks down hopelessly, and we must resort to the & posteriori
method.

Now, no one has ever seen or heard of a genuine instance
of special creation. The doctrine of creation is a pure inven-
tion, fabricated to explain the facts. I think it could very
easily be proved that as a matter of fact it does not afford
the least glimmerings of an explanation of any of the facts ;
but that is by the way. It implies a disruption in nature ;
it is directly and immediately opposed to everything that
we know of natural phenomena; it has deservedly fallen
to the last degree of discredit among all who have the slightest
knowledge of the subject. Special creation may be left out
of account, because it is an unknown factor in natural events.

Inheritance of acquired characters is a hypothesis that
may be dealt with on the same lines. Many are the attacks
which have been levelled against the theory that acquired
characters can be inherited. One of the most famous is
that of Weismann, with his theory of the continuity of the
germ-plasm. The germinal material, or germ-plasm, he
said, is totally separate and cut off from the body-material
or soma-plasm. Hence, he argued, modifications of the
soma during life cannot by any possible means affect the
germ-plasm: there can be no use-inheritance, because there
is no way in the organism by which it could be accomplished.

This again is a pure deduction: and a dangerous one.
It does not follow in biology that because we cannot see
how a thing works, therefore it cannot work. Some physio-
logists indeed do think they see how the soma-plasm may
specifically affect the germ-plasm. But while we remain
in our present ignorance as to the causes of development,

xliv INTRODUCTION

and of the extraordinary and specific influence which the
pituitary, thyroid, reproductive and other glands exert upon
remote parts of the body, and indeed of many other remark-
able correlations existing between apparently disconnected
parts, our empirical knowledge is surely far too slight to
offer any kind of firm basis for a large-reaching deduction
like that of Weismann.’

The advocates of use-inheritance have in all cases devoted
themselves to proving that it mght be the true factor in
evolution: they have then assumed that it 7s the true
factor. Weismann equally has opposed them on the first
ground, denying that it might be the true factor. From
this shifting and dubious morass of argumentation, we may
advisedly transfer our attention to the simple question of
fact and experience. And once on this solid ground we
find that not one single proved genuine instance of use-inheri- _
tance has ever at any tume been discovered. ‘

I have not forgotten, indeed, about the guinea-pigs of
Brown-Séquard, and am well acquainted with the numerous
alleged facts brought forward by investigators of all kinds.
Not one of them but is susceptible of some other explanation. |
It is difficult to deny that use-inheritance often appears the
easiest and most straightforward method: it is just that
very facility of explanation which gives it such an enormous
hold on untrained minds. Yet the trained biologist will
attach not the slightest importance to that straightforward
and plausible air, for he well knows that nature’s methods
are rarely of the kind that a human being regards as simple
or straightforward. In short, all this is simply going back
to the tiresome question as to whether use-inheritance
might happen. We do not want the production of cases in

1 Since the above was printed, I have received advance proofs of Professor MacBride’s
forthcoming work on the Embryology of the Invertebrates, through the courtesy of
Mr. Walter Heape, F.R.S., the general editor of a series of text-books of Embryology
shortly to be published. Professor MacBride suggests that the discovery of hormones
by Professor Starling may afford a clue as to a possible modus operand: of the inheritance
of acquired characters. He quotes Professor Langley to the effect that if an animal
changes its structure in response to a changed environment the hormones produced
by the altered organs will be changed: and these altered hormones circulate in the
blood and bathe the growing and maturing genital cells,

ACQUIRED CHARACTERS xlv

which use-inheritance might be the factor concerned, for we
are prepared to admit all along that it may be a factor.
What we want is one indubitable instance that it 7s a factor—
one case in which the process takes place under our eyes,
in which use-inheritance is not claimed merely as the most
probable of several rival explanations, but in which it is
obviously the only real and true explanation. Nothing
short of this is of the slightest use for throwing light on the
problem before us.

Use-inheritance is so plausible a theory, that if a single
case were brought forward to prove that it is actually a
process occurring in nature, it might well be accepted thence-
forward as an important factor in evolution. At present,
the inductive philosopher must not only refuse to accept it ;
he must regard it as being in contradiction to the probabilities
of the case. | For the search for supporting facts has now
_ been long in progress. The theory was suggested by Lamarck
more than a century ago; and in the last half-century it
has been discussed with the greatest detail and publicity.
The fact that no instances have been discovered cannot but
suggest, as a reason, that there are none to discover.

The third factor which I named, that of natural selec-
tion, differs profoundly in this respect from the other two.
A priori, it is quite satisfactory': it unquestionably might
explain organic evolution. But we can go much farther:
“we know that new races actually do arise by selection ;
‘we are able to witness the actual process. Hence, selection
is proved to be a vera causa. Like use-inheritance it is
competent theoretically to account for a great part of the
evolutionary process ; unlike use-inheritance it is not invented
for the occasion, but is a process which may actually be
observed to take place. \

Lamarck committed the error, eminently excusable in
the age in which he lived, of assuming that when he has
formed a theory which will fit the facts, and when he can
think of no other theory which will also fit the facts, then
that theory must be true. I shall adduce an even more

xlvi INTRODUCTION

striking instance of this tendency when I come to deal with
his physiology ; for in physiology it led him to views much
more conspicuously erroneous than it did in zoology; yet
we shall find it still harder to condemn him for this particular
paralogism in physiology, since there are a few physiologists
even at the present day (as I shall show) who are addicted
to false reasoning of a similar kind.

That Lamarck should have believed in the inheritance of
acquired characters was, indeed, almost inevitable. Not
only so, but the invention of this hypothesis was a very
remarkable and honourable achievement. Before a true
theory is discovered, the usual routine is for many hypo-
theses to be invented and tested. The discovery of a true
hypothesis is only effected after the rejection of a multitude
of false hypotheses. The invention of a hypothesis such as
the inheritance of acquired characters required a genius of
no ordinary kind: had it not been for this invention, bio-
logists might not yet have reached a knowledge of the great
importance attaching to the discrimination between acquired
and congenital characters. Consider how the facts must
have presented themselves to Lamarck. He saw that all
progeny possess a structure closely resembling that of their
parents : he saw that when one of the parents possessed some
striking feature, not peculiar to its species, some variation
in short, that variation was very commonly transmitted
to the offspring ; once again, he saw that use or disuse of
any part by an individual affected the structure of that
part in that individual, causing it to increase or diminish
in physical size and capacity, so as to produce a variation
from the normal, not distinguishable by any external examina-
tion from the congenital variations. Is it not then perfectly
natural that he should have assumed such acquired variations
to be inheritable ? What possible grounds can he have had
for supposing that variations from the normal are of two
utterly different kinds, one of which is capable of being
inherited, while the other is not? Is not this just one of
those traps which, as Darwin remarked, nature seems to

ACQUIRED CHARACTERS xlvii

have set up for the express purpose of deceiving investigators,
and which a pioneer is almost dead certain to fall into ?
Why should it have occurred to Lamarck to inquire whether
the origin of a variation may affect its heritability? In
point of fact it never did occur to him. The problem of
inheritance of acquired characters never presented itself to
his mind: he never differentiated them from congenital
variations. There was for him no antithesis between the
two: the antithesis to use-inheritance was for him special
creation and fixity of species. It was these latter doctrines
that he mainly desired to attack, in the interests of an
evolutionary theory; and he could not understand how
evolution could have occurred without use-inheritance.
But he never had before him the elements of the problem,
as presented to modern minds. Had he lived in modern
times, it is just as likely that he would have been a neo-
Darwinian as a neo-Lamarckian. He saw that structures
were adapted to their functions: hence, he argued, either
the structure must create the function, involving special
creation and design, or else the function must create the
structure, involving inheritance of acquired characters.
When once the problem is stated in this way, we see that
Lamarck unquestionably chose the less untenable and
more plausible of the two theories.

How natural this oversight was, is borne in upon us by
the fact that at the present time almost everyone who is
not a biologist holds just the same opinion as Lamarck did,
on hearing the theory stated for the first time. Disbelief
in the inheritance of acquired characters is almost limited
to trained biologists, though among them it is almost universal.
Lamarck then committed an exceedingly natural and par-
donable oversight, when he failed to observe that variations
from the mean specific type are not all on a par, but are of
two wholly different kinds. And it may even be that the
future will determine that the two kinds are not after all
so different as is commonly held. We now believe that
the congenital variations—strictly called variations—are

xlviii INTRODUCTION

spontaneous, while the variations acquired by the action of
the environment during life—strictly called modifications—are
due to the definite influence of surrounding circumstances.
But it is of course merely a facon de parler to call any variation
spontaneous. A variation must have some cause, and that
cause must be of physico-chemical nature: this is one of
the most fundamental axioms of science. Darwin, when
he spoke of variations as spontaneous, did not mean that
they rose up like a phoenix out of nothing: he meant that
they occurred in a purely fortuitous manner, without any
reference whatever to the preservation either of the species
or of the individual which developed them. He meant that
they had no purpose or design behind them, and in fact
used the word in opposition to finalism or teleology in the
old sense. Nevertheless, congenital variations must have
some physico-chemical cause, and it yet remains to be
proved that that physico-chemical cause is of different
character from the cause which produces acquired modifica-
tions. It may indeed be pointed out that modifications
are purposive, or adapted to meet the individual’s special
needs, whereas variations are fortuitous. But the observa-
tion is of no relevance: for natural selection would speedily
extinguish all races where the modifications acquired were
not adapted to the individual’s special needs; moreover,
the distinction between purpose and chance is at best a
shallow and subjective one.

It may further be pointed out that the factor causing
an acquired modification acts on a particular organ or tissue,
whereas in a congenital variation it acts upon the undif-
ferentiated protoplasm of the germ. For inheritance to
take place in the former case, the somatic modification
would have to be conveyed to the germ-plasm, whereas
in the latter case it is impressed there from the first. But
this is merely a repetition of Weismann’s argument that it
is very difficult to see how a somatic modification can affect
the germ-plasm in a corresponding specific sense: it is
difficult to see, no doubt; but nature’s methods are not

ACQUIRED CHARACTERS xlix

limited to those that we may easily discern. We do not
at present know the determining factor and immediate
physico-chemical cause of growth and development. We
know only the mediate or more remote causes, such as
nutrition, increased blood-supply, ete. Hence it may quite
well turn out that the immediate cause of an acquired modifi-
cation is of the same nature as that which impresses on the
germ-plasm the tendency towards a specific variation.

If the development of an individual is controlled by ae
environmental factors, and if those factors are in the last
analysis of physico-chemical nature, then there seems reason
to suspect that the fundamental difference between a varia-
tion and a modification is not related to any difference in
their aetiology, or in the factors which produce them, but
is dependent almost wholly on the period of the individual’s
life at which these factors operate. If they come into
action after birth or before it in the course of development,
they produce a modification apparently not heritable. If
they come into action before development begins, they
produce a variation which 1s heritable.

Now, if we define the span of an individual’s life as the
period contained between the moment of fertilisation of
the ovum and the moment of death, it is obvious that the
rate of development is exceedingly different at different
periods of this life. Take, for instance, a mammal. While
still in the uterus, it passes through every stage of develop-
ment from the protozoon to its own specific type. Before
it is even born, it has traversed with extreme rapidity and
many short-cuts the various stages passed through in the
course of past evolution by the species to which it belongs.
If therefore we judge of the maturity of an individual, not
by the time elapsed since fertilisation, but by the stage of
development attained at any given moment, it is clear that
a mammal, when born, has already passed through by far
the greater part of its life-journey: its career has already
reached the final stage, and verges on complete maturity.
The remainder of its Hnidepencert career is doubtless, when

1 INTRODUCTION

measured by time, by far the longer portion : but it is really
a mere lingering over the final stage of maturity : as measured
by development, the animal’s career at the moment of birth
is very near its termination. The various tissues and organs
are set hard in very nearly their final shape: the morpho-
logical polarisation can no longer be altered except in minute
details. Now it is in this developmentally late stage of an
animal’s career that modifications due to environment
are chiefly acquired. How, then, is it to be supposed that
such modifications should leave a deep organic impress ?

Supposing once more we shift attention from the life of
the individual to the life of the race; and regard a species
as synonymous, not with the mature individuals composing
it, but with the germ-plasm from which they sprout. This
germ-plasm is potentially immortal. Countless millions of
years ago that same germ-plasm which we now carry in our
bodies was already in existence: but it had not then the
power of budding forth a mammal. It had originally
no power of budding forth anything at all. It was
a protozoon, and perpetuated itself as it still does
by division of the one cell into two. But gradually new
qualities were added to this aboriginal germ-cell. The
daughter-cells were not in all cases completely separated
from their parent, and excrescences came to be formed on
the germ-cell, as the evolution of the metazoa was attained.
It is these excrescences only that are mortal. In the progress
of evolution, the character of the excrescence growing from
the germ-cell has greatly altered; until in some cases it
has assumed the shape of a mammal. But the germ-cell of
the mammal is just the same germ-cell as that which existed
at the outset of evolution. It has innumerable times been
divided in half, and one half has been cast away: but there
has been no other discontinuity either in the individuality
or substance of the cell.

Hence we may regard the germ-cell of a mammal as
having lived and preserved its personality for myriads of
years. During that time it has greatly changed the kind

ACQUIRED CHARACTERS li

of soma that grows upon it: its soma-growing potentialities
have radically altered. These potentialities have been
acquired and modified by intercourse with the environment
through many million years: using the term environment
in the widest possible sense to denote any kind of physico-
chemical cause that produces variation in the germ-cell.
If now some modification is impressed upon the soma of
any individual, and if that modification does really induce
a corresponding alteration of the germ-plasm, it would appear
that such alteration could only be of infinitesimal extent,
since it is brought into contact with a germ-plasm whose
constitution has been moulded into its present form by
factors which have worked for many million years. An
analogy will make my meaning clear.

Suppose that a bullet was fired from one of the nearest
fixed stars such as « Centauri directly at the centre of London,
and suppose that it travelled the entire distance in a straight
line. Now, when it is starting its journey, suppose that
a new environmental force operates in such a way as slightly
to deflect the bullet from its course. Suppose that this
variation is so excessively small that after travelling on-
wards for a further quarter of a million miles, it is still only
one inch out of its original course. Yet the total journey
before it is so inconceivably great, that it is easy to calculate
that this minute deflection may cause the bullet, not only
to fail striking London, but to miss the Earth altogether.

Now we may compare the career of this bullet through
space with the career of the germ-plasm through time. We
may compare the successive miles accomplished by the
bullet with the successive generations of its parasitic somata.
We may compare the force which deflects it from its course
with the factor that causes a variation in the germ-plasm.
And the application is at once obvious. Environmental
factors which have been in operation millions of generations
have caused in the germ-cell a great and permanent varia-
tion : environmental factors which have only just come into
operation will influence the germ-cell to an infinitely minute

lii INTRODUCTION

extent ; and even the continued operation of those factors
through a long succession of generations will cause the
germ-cell to swerve quite inappreciably from its inherited
career.

I do not adduce this analogy for the purpose of defending
the inheritance of acquired characters: far from it. I
adduce it for the following purpose. We find that the
bodies of animals and plants are adapted to their environ-
ment, and we may affirm that they have been moulded into
their present shape by exposure to the forces of the environ-
ment throughout vast periods of time. We may affirm this
without raising any question of the process by which the
moulding occurs :—whether it is exclusively of an indirect
character (like natural selection), or whether more direct
factors are in operation. In any case the structure of the
organism is an expression of the sum-total of the forces
which have acted upon the germ-cell, ever since that early
time when it first became differentiated from inorganic
matter. Now an acquired modification, impressed upon the
soma, can affect the germ, if at all, only as one new force,
whose individual effects will surely be totally obscured
amidst the multitude of the older forces. Yet those effects
may be registered in the hereditary qualities of the germ:
and a gradual repetition of them in the course of innumerable
generations may give rise to a specific and visible variation.

That a functionally-produced modification should so deeply
impress the germ-cell as to leave visible effects on the soma
of the next generation is at present a discredited hypothesis.
Indeed, the direct environmental influence has to be con-
tinued for some little time before it can produce any functional
reaction or modification of the soma at all. A physiological
somatic modification can only be caused by a factor which
operates for an appreciable proportion of the life of the
soma. Now the organism consists of two parts :—of the
newly-developed and ephemeral soma, and of the germ-cell
which has existed from the most extreme antiquity. If
such germ-cell can be affected by direct specific influence,

ACQUIRED CHARACTERS liii

we may perhaps assume that that influence has likewise
to be maintained in operation for an appreciable proportion
of the life of the germ: and no proportion would be appreci-
able, at all events among the higher animals, unless it extended
over many thousand somatic generations.

I am fully aware of the hazardous character of such a
speculation. Indeed, it would scarcely be worth mentioning
at all were it not for the suggestion which it involves, that
inheritance of acquired characters, if not entirely fictitious,
is likely to be true only to this extremely mitigated degree.
It suggests, moreover, that the search for evidence would be
more fruitful among protozoa and the lower types of metazoa
than among more complex forms: for in these primitive
animals the soma (where there is one) is less remote from
the germ: it has travelled a far shorter way on its develop-
mental career. It is indeed among such animals and among
plants that the most plausible cases have been cited. But
until the process can be actually observed to occur in at
least one undoubted instance, use-inheritance must continue
to be regarded as an altogether illegitimate hypothesis, and
to be rigidly excluded from our account of the factors of
organic evolution.

§ 6. CLASSIFICATION.

i In his classification of animals, Lamarck had recourse to
two fundamentally different methods. If animals in nature
fall into a linear series, it is obviously a matter of first-rate
importance to ascertain the true order in which the species
are arranged in this series. In so doing, no divisions or
groups of any kind are needed. All that has to be done is
to determine the position of each species with reference to
other species, and to ascertain the exact point of the series
which must be allotted toit. This is what Lamarck means by
a distribution générale of animals.

A second important function of his classification is to
draw the lines in the series, which mark off genera,

liv INTRODUCTION

families, orders and classes from one another. This is
what Lamarck calls classification. Since the series represents
an even and regular progress in complexity of organisation,
the selection of the points on the scale where our lines of
demarcation shall be drawn is purely arbitrary : such divisions
have no objective reality. Thus classification, as Lamarck
conceived it, is not a science, but an art: it involves a
question not of truth or error, but merely of convenience.
Distribution, on the other hand, is a genuine science, not
dependant on our convenience: our attempts at distribu-
tton are either true or false: if true, they correspond to
an order which has actual objective existence.

The word “classification”? in modern biology does not
exactly correspond to either of these two terms. We no
longer believe in a linear series of animals: on the other
hand, the groupings and divisions which we make among
animals are not regarded as subjective conveniences, but as
objective realities. The entire collection of living animals
is broken up into discontinuous groups: and the gaps
between these groups are not gaps in our minds, but gaps
in external nature. Hence, modern classification is a true
science. To this extent it resembles Lamarck’s distribution
and differs from his classification. I have allowed myself a
certain degree of latitude in deciding when either of these
words is to be translated by the English “ classification,”
a word that inevitably carries with it to modern readers all
its modern biological connotations.

It remains only to indicate the services which Lamarck
rendered to classification ; and they were undoubtedly very
great. It was certainly unfortunate that he should have
adopted the conception of a linear series. He not only adopts
it, but most energetically defends it :

“Man is condemned to exhaust all possible errors when
he examines any set of facts, before he recognisestthe truth.
Thus it has been denied that [animals] can really be arranged
in a true series according to their affinities. ... Several
naturalists have imagined that the affinities among animals

CLASSIFICATION lv

may be represented something after the manner of the
different points of a compass. This idea, which some modern
writers think sublime, is clearly a mistake, and is certain to
be dispelled when we have a deeper and wider knowledge of
organisation.” Yet it is now known to represent the
facts much more nearly than the linear arrangement of
Lamarck.

\The first great service of Lamarck to classification was
in establishing the distinction between vertebrates and
invertebrates. Aristotle, indeed, had detected the profound
difference between these two groups: but he had taken as
his standard of differentiation the presence or absence of
blood: a highly defective standard which was not to any
great extent improved by Linneus. It was reserved for
Lamarck, in his course of lectures at the Muséum in 1794, to
direct attention to the immense taxonomic importance of
the vertebral column, and to set up that great primary
division of the animal kingdom, which was long regarded
as final.

The remainder of Lamarck’s achievements in classification
he within the realm of Invertebrata: for it was with these
animals that his professional work at the Muséum was
exclusively concerned. At the time when he assumed the
task of organising the vast collection of animals accumulated
there, Linnzeus’s classification of invertebrates into insects
and worms was still current. In that same course of lectures
in 1794, he broke up the class of worms to form four new
classes: molluscs, worms, echinoderms, and polyps. These
divisions had already been suggested by Bruguiere as orders
in the old class of worms. Lamarck did not then touch
Linnzus’s class of insects, which comprised the whole phylum
of arthropods. .

The arrival of Cuvier in Paris in 1795 produced a general
stimulation of biology, from which Lamarck was not slow
to profit. The meduse and other radiating ccelenterates
had been grouped by Linnzus with the molluscs, and that
classification was still maintained. Lamarck removed them

lvi INTRODUCTION

from the molluscs, and combined them with his class of
echinoderms to form the class of radiarians.*

In 1799 Lamarck removed the crustaceans from among
the insects, and erected them into a separate class. This
innovation was not recognised for some years. In the follow-
ing year he performed a still more remarkable achievement,
in separating the arachnids from the insects, and conferring
class-distinction on them also. Up to the date of publica-
tion of the Philosophie Zoologique, this class had not been
admitted in the work of any other naturalist. Lamarck
further reduced the old class of worms by separating from
them the new class which he called annelids. This important
innovation likewise took some years before it received general
recognition. Lastly, he established the class of infusorians,
as distinct from his previous class of polyps. Lamarck’s
infusorians correspond of course to what we now call Proto-
zoa; but there was a good deal of confusion as to what
animals were infusorians and what polyps, owing to deficiency
of observation. Minor improvements in classification were
also numerous. He removed the cirrhipedes, for instance,
from the neighbourhood of annelids and molluscs: he
recognised the gastropod affinities of pteropods, etc., etc.

In the present work, Lamarck gives a list of all genera
known at his time, arranged in their proper order and
classification. The names of the genera are not given in
Latin, but in French; and for a large number of them
Lamarck himself appears to have invented popular names,
based on the scientific names. It has therefore been ‘a
matter of considerable difficulty to ascertain precisely to
what animals he is alluding in each case. The difficulty is
still further increased by the fact that many of these genera
are no longer recognised: a large proportion of them in
fact are far more allied to what we should call families than

1 Professor Packard, who some years ago published in America extremely literal
translations of certain parts of Lamarck’s work, translates radiaires as radiata. This
is somewhat ambiguous; for Cuvier’s class of radiata is far wider than Lamarck’s
class of radiaires, and includes infusorians, polyps and many worms. The correct
translation is radiarian. I preserve the popular style.

CLASSIFICATION lvii

to modern genera. Lamarck did not intend his list to be
precise, or indeed do more than give a general idea of the
extent of the animal kingdom. Hence his use of trivial
names. In order to find out what animals he meant by
these names, I have in the case of invertebrates referred to
each one in Lamarck’s later work, Animaux sans Vertéebres,
second edition, 11 vols., where the French name is almost
always given in conjunction with the Latin name. For
vertebrates I have used Duméril’s Zoologie Analytique,
1806. In a few cases, I have traced the meaning through
Cuvier’s Réegne Animal, or through the Encyclopédie Méthod-
aque, 196 vols., 1782-1832, to which Lamarck himself con-
tributed. Having ascertained to what genus Lamarck
refers, I have translated it by the current English name,
where there is one, so as to preserve the resemblance to the
French original. In other cases, I have employed the Latin
generic name to which Lamarck’s French name was intended
to correspond. As I have already said, it often corresponds
to no genus now recognised, as, for instance, the “ Pongo”;
in other cases it much more resembles a family than a genus.
Readers must not therefore expect to find any precision in
this classification that would satisfy modern standards.
The names are often not precise enough to designate clearly
any particular group, and the groups themselves are often
similarly vague and undetermined, or even altogether
mythical. As an instance, let me take Lamarck’s genus
“ fasciole,” belonging to the order of “flat worms.” I find
that the generic name which he intended to suggest was
“ Fasciola,’ and I find further that this was a genus
founded by Linneus, and applied by him to three different
animals, the liver-fluke, a cestode, and a triclad, which he
confused together, on account of a superficial resemblance.

Lamarck’s first class is that of infusorians, with its two
orders of naked and appendiculate infusorians. The former
mainly correspond to our Protozoa: the latter includes
Cercaria, now known to be a larval form of trematodes.
Lamarck also regarded the human spermatozoon as an

lviii INTRODUCTION

infusorian :—a view which continued to subsist down to the
early researches of Kolhker.

His second class is that of polyps, the first order of which
is the rotifers: among them he includes Vorticella, which is
areal infusorian. The second order include the polyps, which
form polyparies. This corresponds to a mixture of Hydro-
zoa and Anthozoa with Polyzoa. It includes the sponges
as one genus, a few Algae, including Corallina, an echinoderm,
an arthropod, the ascidian Botryllus, etc. The last genus
of polyps, the genus therefore which Lamarck regarded as
having advanced farthest in development, is the sea-anemone.

Lamarck’s third class are the radiarians, with two orders.
The first order, or soft radiarians, contain all varieties of
coelenterates, except Anthozoa. They are grouped together
on account of their radiating structure, with the medusa as
a type. This order includes also the tunicate Pyrosoma.
The second order of radiarians are the echinoderms. La-
marck includes Sipunculus—a gephyrean—as an _ echino-
derm, on account of its resemblance to holothurians: and
this classification was still retained as late as 1841 by Forbes
in his British Starfishes. It constitutes Lamarck’s highest
genus of radiarians.

Class IV. contains the worms, divided into three orders
of round worms, bladder-worms, and flat-worms. Among
the latter is included Linguatula (an arthropod), and Fasciola
already mentioned. The round worms are chiefly nematodes,
but include also turbellarians, cestodes, etc., and one genus
“ Scolez”’ (the tape-worm’s head). Among the bladder-
worms is placed an animal under the name of bicorne. On
reference to the Animaux sans Vertébres, I find it alluded
to as Ditrachyceros. I believe that the separate segments of
tape-worms were referred to under this name, being taken for
independent individuals. At a certain stage, the segments do
sometimes show two horn-like processes.

Class V. contains the insects, divided into much the same
orders as at the present day... The next higher class, Class

1 There are a few minor inaccuracies, such as the statement that the Hemiptera

CLASSIFICATION lix

VI., consists of the arachnids, established for the first time
by Lamarck himself. It comprises two orders, the first of
which corresponds to our modern class of arachnids, while
the second (“arachnids with antenne”’) includes our
modern myriapods, together with one or two insects such
as the louse and silver-fish.

Class VII. are the crustaceans, divided into the two orders
of those whose eyes are at the end of stalks, and those whose
eyes are sessile. In the next class, that of the annelids,
Lamarck discerns the commencement of a tendency on the
part of nature to abandon the articulatory type in favour
of the vertebrate type. Thus he finds that annelids no
longer have jointed legs, as in the classes immediately pre-
ceding. The class is divided by Lamarck into two orders,
of which the first—the Cryptobranch annelids—is a mixture
of various ill-assorted animals, including a triclad and two
copepods.’ The order includes Lumbricus and Nats: though
curiously enough, in his later and more systematic work,
Lamarck restored Nais to his class of worms, removing it
from the annelids. The second order, the Gymnobranch
annelids, consists of polychaets, with the addition of two
molluscs at the end.

Class IX. are the cirrhipedes, with only four known genera.
They are intermediate between the annelids and Class X.
containing the molluscs. Lamarck regarded the molluscs
as the highest class of invertebrates. For some time, he
says, Nature had been making preparations for originating
the vertebrate plan of organisation. In the molluscs those
preparations are completed. The articulatory system ac-
cordingly vanishes: and the slow movements of molluscs
are due to the fact that the class is midway on the road of
development from an external to an internal skeleton, and
therefore possesses the advantages of neither. It is to be
noted that Lamarck had a very clear conception of the

have three setz in their sucking-organ. Asa matter of fact they always have four ;
though two are often united together, so as to give the appearance of only three.

1The triclad (Planaria) is removed to its proper position in the Animaux sans
Vertébres,

Ix INTRODUCTION

arthropod type, and if his scheme of classification had
admitted of groups superior to classes, there is no doubt
that he would have combined the insects, arachnids and
crustaceans into one phylum, altogether separate from the
molluscs, though the annelids and cirrhipedes are regarded
by him as intermediate forms.

Lamarck divides molluscs into two orders of Cephalic and
Acephalic. The latter of course consist mainly of the
modern lamellibranchs. One section of this order, however,
contains the brachiopods, and another section the tunicates,
which he took to be molluscs. Lamarck’s Order II. are the
Cephalic molluscs. It is divided into the three sections of
pteropods, gastropods and cephalopods. Nearly half the
animals included by Lamarck under the name of cephalopods,
consist of Foraminifera ; most of the remainder are genuine
cephalopods. One of the Foraminifera, which Lamarck
mistook for a cephalopod, is Orbulites, which here occurs
for the second time in his animal scale; for this animal had
already been once named as belonging to the polyps.

These are the main features of Lamarck’s classification of
the invertebrates. That he should have evolved these ten
classes, with their various orders, out of Linnzeus’s insects
and worms is an achievement of no small magnitude. We
now come to the vertebrates, to whose classification Lamarck
never made any contribution. I may therefore rapidly
run through the classification which he here adopts from
what he believed to be the best authority of his time.

Class XI. contains the fishes. They are divided into two
orders of Cartilagmous and Bony fishes; though Lamarck
includes among the Cartilaginous fishes a number of our
modern ganoids and teleosts. This order commences with
the hagfish and lamprey, correctly placed together as cyclo-
stomes: Linnzus had previously regarded the hagfish as
a worm. The second order of Bony fishes mainly consist of
“ Holobranchs,” or fishes with complete gills. These holo-
branchs are divided into thirty sections, largely determined
by the character and position of the fins, as also by the gills,

CLASSIFICATION lxi

opercula, general shape, etc. This classification has now
been altogether discarded, and the modern subdivisions of the
Fishes are on quite different lines. Lamarck terminates the
class with the ‘“ ophichthians ” or “ snake-fishes,” doubtless
because they seem to come nearest to the next class of reptiles.

The reptiles, Lamarck’s Class XII., are divided by him
into four orders. The first order of ‘“‘ Batrachian reptiles ”
are what we now call amphibians, and are not reptiles at
all. The second order is the snakes, the third lizards, and
the fourth chelonians or tortoises, which apparently Lamarck
regarded as the nearest approach to Birds. The birds to
which Class XIII. is devoted were divided by Lamarck into
the seven orders of Climbers, Birds of Prey, Passeres, Col-
umbe, Galliaceans, Waders and Palmipeds. The further
subdivisions of these orders are largely dependent on the
character of the beak. The four orders which Lamarck
placed first, and therefore regarded as most primitive or
“least perfect,’ contain birds which depend on their parents
for food, etc., after being hatched. The last three orders,
which he regarded as the highest, contain the birds which
can look after themselves as soon as they are out of the
egg. He thus completely inverted the true significance of
this particular criterion of development ; for we now know
that it is the most highly evolved animals in which the young
are least capable of looking after themselves. In the case
of man, it is many years before the new individual can reach
a state of independence.

Following the birds, Lamarck introduces the monotremes,
including Ornithorhyncus and Echidna, as being half-way
between birds and mammals. His fourteenth, and last class,
contains the mammals, which are divided into the four
orders of exungulate, amphibian, ungulate and unguiculate
mammals. The exungulate are what we call the cetaceans.
The amphibians comprise the seal, walrus, dugong and
manatee. The ungulates correspond to the modern order
of that name; and the remainder of the mammals are
included among the unguiculates. The sub-divisions of

Ixii INTRODUCTION

this order are not uninteresting. He recognised the families
of edentates, rodents, and Chiroptera, and referred genera
to these families, on the whole with fair accuracy. He also
recognised the marsupials, under the name of Pedimana.
His highest, or “‘ quadrumanous,” family corresponds to
our Primates. But the remainder of the exunguiculate
mammals are divided into tardigrade, plantigrade and
digitigrade, according to their method of walking. The
tardigrade or slow-walker contains the solitary genus of the
sloth, which Lamarck thus separated from the edentates,
although placing it in contiguity with that group. The
plantigrade and digitigrade mammals are those which walk
respectively on their whole feet, or on their toes. Lamarck
thus had no conception either of the Carnivora or of the
Insectivora. The Carnivora he divides up among the planti-
grades and digitigrades. The Insectivora fall to the family
of plantigrades, with the exception of Galeopithecus, which
he somewhat excusably referred to the Chiroptera. The
anthropoid apes are represented by the ‘‘ Pongo” and the
“Orang,” both very vague genera. There were said to be
two species of Orang, the Orang of the Indies, and the Orang
of Angola, the latter no doubt being the Chimpanzee.

It is not quite clear how Lamarck thought that man was
related to the animal scale. Throughout the work he con-
stantly refers to man and animal in antithetical terms. He
did not regard man as an animal, in the same sense as other
animals; but he perceived that by confining his attention
entirely to a study of structure, man might be classified as
one family of mammals. This family he calls “ Bimanous,”’
and divides into six varieties-—Caucasian, Hyperborean, Mon-
golian, American, Malayan, and Ethiopian or Negro.

It appears highly probable that Lamarck recognised the
common origin of man and other animals, but that he did
not venture to proclaim it. He elaborates a hypothesis as
to how man might have developed, if he were only distinguished
from other animals by his structure and organisation. Ac-
cording to this hypothesis, the evolution of man would be

CLASSIFICATION lxiii

due to inheritance of acquired characters. Lamarck supposes
that some race of apes conceived a desire to obtain distant
views over the country, and for that reason contracted the
habit of standing up on their hind legs, to get a better view.
The constant assumption of this posture would, according
to Lamarck, produce suitable modifications of structure,
which would be inherited: in course of many generations,
the erect position would become the normal one. The modi-
fications of feet and jaws are accounted for on similar lines.
Lamarck assumes that as the human race became dominant,
it would everywhere be brought in contact with a new
environment, develop new wants, and make efforts for the
satisfaction of these wants. These efforts would result in
corresponding structural alterations, which would be inherited.
Thus, he regards the origin of language as due to the constant
efforts to impart ideas. These efforts, by use-inheritance,
would cause the necessary development of the throat, mouth
and lips. When once language had been acquired, and
conventional signs agreed upon, man had scattered over the
earth, varieties of the original language had arisen, until
ultimately the existing diversity of languages was attained.
Meanwhile the development of other races of apes would be
hindered by that of man, for man would persecute them and
drive them from the hospitable regions of the earth. But
all this is merely put forward as an hypothesis, to explain
how the structure of man might have been derived from
simian ancestry by ordinary biological laws: but Lamarck
cautiously repudiates at the end any suggestion that he did
arise from simian ancestry.

In his later classification, printed in the ‘“ Additions” to
Part I., Lamarck made certain improvements in his classifica-
tion, in the direction of abandoning the linear series. He
held that the animal kingdom originated by spontaneous
generation in two independent roots, the infusorians and
the worms. From the former were derived the polyps and
radiarians alone. The worms, on the other hand, or at

Ixiv INTRODUCTION

least the aquatic worms, as opposed to the parasitic worms,
Gordius, for instance,’ led straight to the annelids, and
through them to the cirrhipedes and molluscs. Other
aquatic worms took to the air and gave rise to the insects
via gnats and mayflies. Insects, adopting solitary habits,
became arachnids; and arachnids, taking once again to
water, became crustaceans.

The molluscs, continuing Lamarck’s exposition, led to the
fishes through a regular gradation of other molluscs still
remaining to be discovered: and the fishes to the reptiles.
The reptiles, he said, were differentiated by environmental
action into two divisions, of which one led to the birds,
via the chelonians or tortoises, and thence to the mono-
tremes; while the other led to the Amphibian mammals
via the saurians, especially of the crocodile type. Of the
Amphibian mammals, some took to feeding on grass on the
sea-shore, like the walrus and manatee,? and so brought
about the development of the ungulates. Others, such as
the seal, confined themselves to an animal diet, and thus
led to the unguiculates.

§ 7. PHystoLoey.

On approaching a work of philosophical physiology written
a century ago, the point to which we look with the greatest
interest is the attitude of the writer towards the ancient
problem now bearing the modern name of vitalism. Through-
out last century, controversy was ever returning to that
great and fundamental question as to whether organic pro-
cesses or functions are due exclusively to the ordinary laws
of physics and chemistry, or whether those laws are sup-
plemented by others of a spiritual or non-material character.
When the problem is looked at with an exclusively physio-
logical interest, the opposite schools are referred to as vitalism

1 He referred, no doubt, to the free sexual form.

2 This is, of course, a mistaken observation. The walrus is almost or completely
carnivorous, while the manatee feeds exclusively on aquatic plants below the surface
of the water. Neither animal has the habit alleged by Lamarck.

PHYSIOLOGY Ixv

and mechanism. But this physiological question has a far
deeper philosophical interest; and when the problem is
regarded from that wider point of view, the opposite schools
are those loosely described as spiritualism and materialism.

The method of science is now, and always has been,
exclusively materialistic : that is to say, the sole data of its
investigations are matter and energy; every event, that
receives a scientific explanation, is analysed into some par-
ticular combination of matter and material energy. Now it
happened at the dawn of civilisation that men began to
speculate about the causes of things long before they had
any science or organised knowledge to guide them; long,
therefore, before there was any possibility of their finding
those causes. In this position the mental craving was met
by the invention of a new kind of entity, different from
matter, and called spirit. All difficulties were immediately
levelled: What causes disease? An evil demon. Why do
the winds blow? A spirit is responsible. What is the
origin of the universe ? A god or gods made it ; and so on.
Thus all things received an easy explanation. I need not
recite the oft-told story of the decline of spirits and the rise
of materialism in conjunction with the advance of civilisa-
tion. In no instance did the progress of knowledge reveal
the true existence of any entity apart from matter. One by
one the spirits were driven from the field of explanation: at
the present time they are all but banished from scientific
method, and survive only in extremely mitigated form in
the imaginations of the vulgar.

Nowhere has the struggle been more strenuous than in
the region of physiology. Of all subjects which have excited
the curiosity of man, few are more enthralling, and few more
beset with difficulties, than the causes of the manifestations
of life and movement by which certain portions of matter,
named organisms, are differentiated from inorganic matter.
The difficulty was of course met in olden times by the hypo-
statisation of a new entity, often called the soul, but assuming

a vast variety of different shapes and conditions according
é

Ixvi INTRODUCTION

‘to the:fancy'of the inventor. There is no longer any reason
to doubt that:physiological processes are exclusively material,
dike'‘all other ‘processes in the universe ; and that there exists
no: imdependent entity of this character, as was assumed in
times of ignoratice. Nevertheless, so highly complex is the
stibject)sand so-pressing is the demand for some immediate
explanation, that there are still a few physiologists remaining
who invoke ‘spirits to assist them in accounting for certain
phenomena'that have yet been scarcely reached by the
rising tide of materialistic science. It is true that they are
not often tash enough to invoke an actual spiritual sub-
stance. «They prefer to speak of “ biotic energy” or ‘ vital
force”? » that’ is to say, they invent a spiritual form of
energy,” rather’ than a spiritual form of substance. But
there is‘no’ essential difference whatever between the two.
‘Tfthey affirm ‘the existence of any kind of vital or spiritual
force, ‘of nonsmaterial character, they are inexorably com-
mitted to a belief in souls or some such spiritual bodies.
Notwithstanding their protestations to the contrary, they
have: no logical escape from the position. These physio-
logists'urge vitalism almost exclusively on the grounds that,
without the assumption of a vital force, it is impossible to
explain. certain of the more complex manifestations of

intelligence;!voluntary movement, choice, etc. Now it is

‘but a short'time back that even quite simple nervous pro-
cesses; suchds reflex action, were impossible to explain by
mechanical‘ or: physico-chemical methods. It is now known
that these simple processes are in point of fact of a purely
mechanical nature ; and it is also very widely believed by
thesgreat majority of physiologists that the more complex
cerebral! dperations are based entirely upon the reflex prin-
ciple, .aiidsindeéd are nothing more than reflex action,
multiplied and compounded to a high degree of complexity.
So:far then:from there being any apparent impossibility
ape Ȏxplaining the highest mental manifestations on

sat ya i B of re { tire
ae ‘On this point, 2 oy article in Bedrock for October, 1912, with the ensuing con-
troverby. 9 POOL

PHYSIOLOGY Ixvii

mechanical principles, those principles would appear, even
at the outset of the discussion, to offer by far the most pro-
bable solution. But, in any case, the argument from impossi-
bility is one that has no weight whatever.

I take it that one of the chief values of a historical study

such as the present is to establish a comparison between the
methods of the past and the methods of the present, so that
we may know not only where our ancestors failed, but why
they failed, and how we may avoid a similar fate. ‘“ Nur
durch Werden wird das Gewordene erkannt.” In describing
Lamarck’s physiological philosophy, I shall therefore pay
special attention to certain instances of the modern use of
the same type of argument, which led in his hands to so
miserable a failure.
" Lamarck held that three things are necessary for the
constitution of life. There must be the solid parts of the
organism, the liquid parts, and the “exciting cause” of
“organic movement.” The solid and liquid parts require
little illustration. Lamarck describes the solid parts as
being “supple ”’ and “ containing,” and the liquid parts as
“contained.” Life is constituted by organic movements,
or movements of the contained liquids through the containing
solid tissues. The liquids to which he referred were of
course the blood and other visible fluids of the organism.
But in order to maintain this movement an “ exciting cause ”
or stimulus was needed, and to this exciting cause we must
pay further attention."

Let me do Lamarck the justice to say that he repudiated
altogether a ‘‘ vital principle.” ~ “ The ancient philosophers,”
he says, “ felt the necessity for a special exciting cause of
organic movements; but not having sufficiently studied
nature, they sought it beyond her; they imagined a vital
principle, a perishable soul for animals, and even attributed
the same to plants; thus in place of positive knowledge,
which they could not attain from want of observations, they
created mere words to which are attached only vague and
unreal ideas.

Ixviii INTRODUCTION

\\ ;
‘“‘ Whenever we abandon nature, and give ourselves up to

the fantastic flights of our imagination, we become lost in
vagueness and our efforts culminate only in errors. The
only knowledge that it is possible for us to acquire is and
always will be confined to what we have derived from a
continued study of nature’s laws; beyond nature all is
bewilderment and delusion : such is my belief.” 7 /

“Lamarck thus affirms the mechanistic position, but he
goes on to say that the “exciting cause” is composed of
two factors, caloric and electricity. These he regarded as
subtle, invisible fluids which penetrate every part of the
organism. Its life is mainly due, he says, to caloric, and
its active movements to the electric fluid, or, in the case
of the more complex, to the galvanic fluid. These fluids
may indeed be somewhat specialised within the organism,
and other subtle invisible fluids may co-operate with them,
but Lamarck looked upon it as quite certain that they
were the chief components of the exciting cause, that en-
dows bodies with life.” Now this exciting cause is obviously
analogous to those spiritual factors, which Lamarck is so
careful to exclude. It is descended directly from the
“animal spirits’? of more ancient writers, like Galen, and
it has strong vitalistic implications; he goes so far as to
refer to heat, the most important of the subtle, invisible
fluids, as the “ material soul of living bodies.” Yet we
must remember that the so-called subtle, invisible fluids
were recognised by the physics of Lamarck’s day. When
invoking the aid of these fluids for the explanation of physio-
logical phenomena, he was drawing on what he believed to
be a purely physical source, and he constantly impresses upon
the reader that his explanations are exclusively physico-
chemical, The fact is that physics was at that time
imperfectly differentiated from metaphysics: Lamarck de-
rived his “exciting cause”? from metaphysical elements,
which have since been entirely discarded: and he fell into
a semi-vitalistic mode of explanation, in spite of his desire
to keep free from it. Lamarck comes nearest to the modern

ce

PHYSIOLOGY lxix

vitalistic writers when he attempts to describe the physiology
of the nervous impulse. He attributes it to a “ nervous
fluid,” and this, he says, is no other than electric fluid which
becomes modified and “ animalised ” on entering into the
bodies of the higher animals.

By what reasoning did Lamarck reach this conclusion ?
The facts before him consisted mainly in the rapid trans-
mission of some kind of impulse from or to the brain from
remote regions of the body. Lamarck considers how this
transmission could be accomplished: he passes in review
all possible alternatives: Richerand had refuted the sugges-
tion that some vibration of the nerves conveyed the mysterious
impulse: there remained only two possible alternatives :
(1) that the impulse should be carried by the visible or
“ essential ” fluids of the animal, such as blood and lymph ;
(2) that it should be carried by invisible fluids analogous or
identical with the electric, galvanic and magnetic fluids.
The first alternative is ruled out by many facts: in the
first place no such movement of the visible fluids can be
detected in nervous action: in the second place, the visible
fluids are too gross and heavy to move with the required
velocity, which Lamarck affirms (quite wrongly of course) to
be nearly equal to that of light: and soon. All conceivable
alternatives being thus ruled out, it follows, says Lamarck,
that the one remaining unrefuted possibility must be the
true explanation: there must be a subtle, invisible fluid of
the character named above.

Now I wish to point out that this argument is identical
in every particular with that by which Hans Driesch and all
other vitalists of our time prove the existence of a vital force.
Driesch names the argument per exclusionem. Like Lamarck,
he takes three or four conceivable alternatives; though-I
need hardly say that the conceivable alternatives of to-day
are radically different from the conceivable alternatives of
a hundred years ago. He then refutes all possible alterna-
tives but one: and thereupon announces that that one (the
vital or spiritual force) is the true explanation, conferring

lxx INTRODUCTION

upon his argument the title of a “ proof of vitalism.” Now
this argument per exclusionem is sound, upon one condition
only ; and that is that all possible alternatives have really
been marshalled together at the outset of the argument.
This is a condition which, in the present state of physio-
logy, is entirely impossible to satisfy. It is interesting to
note that, of the various possibilities named by Lamarck,
not one figures in the list of possibilities named by Driesch.
A century has swept them all away, and brought out a
whole series of new possibilities, never dreamt of by Lamarck.
Few students of the history of science can doubt that another
century, or much less (for things move faster now) will
sweep away no less effectively Driesch’s list of possibilities.
In order to name every conceivable mode of explanation of
any phenomenon, it is necessary to know infinitely more
about the conditions of that phenomenon than is at present
possible in any branch of physiology. We have to know
that we have exhausted every possible alternative ; we have
to know that there is nothing more to be known; and that
is a condition of the most extreme stringency. This argu-
ment, or some attempt at it, has served as proof of every
kind of erroneous explanation of the universe, and all things
in it, great and small. The ancients vaguely used that
method when they affirmed the existence of animal spirits:
by the same method, Lamarck proved the existence of a
subtle, invisible nervous fluid racing up and down the
nervous system: by this method again, Driesch proves the
existence of a vital force. I challenge anyone to find the
slightest difference between Lamarck’s method of proving
the existence of the nervous fluid, and Driesch’s method of
proving the existence of the vital force. This logical method,
dignified by the name of per exclusionem, is indeed a method
of argument by which nearly all untrained minds, and a
great many trained minds, are wont to establish propositions
they desire, in place of the disagreeable confession of ignorance
or agnosticism. It is at the bottom of every vitalistic theory.
“* Here is a process difficult to explain: it cannot be caused

PHYSIOLOGY Ixxi,

this way, or that way, or the other way ::herice! the: orily
remaining conceivable explanation must bé the:itrie ane.’?,
And then ensues some ridiculous theory, always: fepending:on:
a new, mysterious, and invisible agency : it has:to be invisible!
of course, since no power of microscope or.balgnce can -dis-
cover it. Hence we get spirits, animal spitits,'souls; subtle;
fluids, vital forces and other “‘ monstrous products begotten
by the imagination,” as Lamarck himself;' well:-ealls;.them:
elsewhere. These agencies are in turn relegated: to~:the
sphere of superstition, as science grows. Lamareki claimed;
the support of science for the existence of;subtlé invisible:
fluids: science has entirely disposed of themis; The nérvous
‘impulse is still not properly explained: ands doubtless until.
it is, it will continue to be regarded as a suitable playground,
for spiritualistic fancies and desires. Butyyear’. by .year:
these phantoms find it harder to discoven; any: dark:.and
unexplored corners of science, where they: may:.obtaim»a
momentary respite from the ever-advancing tide: of material-,
istic knowledge. infits "an yee ot

To do Lamarck justice, his theory was notiso, dutragedus
as is that of the modern vitalists. He invoked-a: factory
which he imagined (wrongly no doubt) to be-equallysinsteu-
mental in the inorganic world. His subtleefiuid Wasi:not:
invented ad hoc; it was recognised as a neal exisbéenee! by:
many physicists of his time. But the sanodernrwitalistsi
invent a factor that is wholly and unutterablpnew to science}:
and to every branch of knowledge or history. .-!Fheir plunge:
into the unknown is far wilder and more furious :than:hns.:
Their search for a hypothesis has led them to;the:most remote:
regions of primitive superstition ; it has ledithem to: invent
a factor out of hand for the purposes of theirsdwn :theorisa-:
tion—a factor unknown to any branch of;science;: a factor
unrecorded in any trustworthy history, a factox which!breaks:
down utterly and immediately under analysis, andlastly 1a:
factor which, so far from explaining the fatts it-18 supposed;
to explain, throws over them an impenetrable: eloud of:
mystery and obscurity. \ de edt to Gorse 1

lxxii INTRODUCTION

\\
Lamarck begins his physiological section with an account

of the distinguishing features between the organic and the
inorganic. He reduces the differences to nine. An organism
has an individuality of its own: it is necessarily heterogene-
ous: it comprises solid parts and fluid parts: its different.
parts are mutually dependent on one another: it undergoes
what we should now term metabolism: it grows, not by
external accumulation of matter, but by “‘intro-susception ”’ ;
it feeds; it reproduces itself; and it dies. None of these
peculiarities, says Lamarck, are exhibited by inorganic
matter. Lamarck’s next task is to differentiate between
animals and plants. The most important distinction, he
says, is that the former possess irritability, while the latter
do not. By irritability, he means an immediate reaction to.
contact of a foreign body: the point of the organism where
the contact occurs, contracts with neighbouring parts: but
upon cessation of the stimulus, the parts are immediately
restored to their former condition, ready to respond again
to any new stimulus. !!

"“ Lamarck’s theory of irritability is based upon his theory
of “orgasm.” I have already said that he regarded an
organism as essentially composed of solid and supple “ con-
taining” parts, through which travel the “ contained ”
visible fluids. Now the solid and supple parts were regarded
by Lamarck as being permanently in a state of distention,
due to the presence within them of caloric and other subtle
invisible fluids. These fluids were “expansive”; so that
the supple parts to which they had penetrated were thrown
into a condition of distention, or, as Lamarck calls it,
“ orgasm.” "When very intense, the orgasm gives rise to
erethism : when insufficiently intense, to atony.

From his theory of orgasm, naturally flowed his theory of
irritability. On contact of a foreign body, the subtle invisible
fluids are promptly dispersed in the neighbourhood of the
point touched. The orgasm or distention is relieved, and
the parts concerned immediately collapse or contract. On
cessation of the stimulus, the subtle fluids promptly suffuse

PHYSIOLOGY Ixxiii

once more the part in question, and restore to it its orgasm
and readiness for a new contraction on application of a new
stimulus.

Lamarck regarded life as synonymous with “ vital move-
ments,” that is to say, with the movements of the visible
contained fluids through the supple containing parts. The
function of the “‘ exciting cause ” is purely to keep the fluids
moving, though exactly how it does this is left unexplained.
But the entire phenomena of life, its origin, development,
and evolution, are attributed by Lamarck to the movement
of the fluids through the solids, under the mysterious influence
of the exciting cause.

\ As regards the origin of life, Lamarck held that it came
about in this way: gelatinous or mucilaginous particles are
lying about in nature: it happens that some of these consist
of solid and fluid parts, and are in all other respects fitted
for the reception of life; thereupon the subtle invisible
fluids, which he imagined to be spread everywhere over the
surface of the earth penetrated these particles, and acted as
the “ exciting cause ” which starts the visible fluids moving
through the supple solid parts: and that is the commence-
ment of life. The particles of gelatinous character become
primitive animals; those of mucilaginous character become
primitive plants. 7 i

't When once the fluids begin to move, they soon create hollow
spaces or “cells”? within the solid matter; and Lamarck
very warmly defended the theory that all organic matter is
either cellular or the product of cells. In this respect he
entirely anticipated Schwann; unfortunately his cellular
theory was mixed up with too many crudities to secure
the scientific approval of his time. This is but one instance
of many in which Lamarck anticipated the knowledge of
a future age. /"

\ Lamarck, having accounted for the origin of life by
means of the “ vital movement” of the visible or essential
fluids, proceeds to account for development on the same
principle. The fluids carve out canals and hollows of all

La

Ixxiv INTRODUCTION

kinds: whence we get the various vessels and cavities of
the interior. Moreover, they deposit certain substances,
formed within them. These deposited substances begin to
accumulate in special places, giving rise to the formation of
organs.”’

‘\ Lamarck held that spontaneous generation took place in
the way described above. He held that it still continues to
take place, wherever there happens to be lying about a
particle of matter of gelatinous or mucilaginous consistency,
suitable for vitalization by the ubiquitous invisible fluids. He
held that the organisms at the beginning of the animal and
vegetable scales are produced by spontaneous generation,
which as regards animals he was at first inclined to limit to the
infusorians, but subsequently extended to the worms. At first
the reproduction was by buds or gemme; subsequently it
became sexual. Lamarck regarded sexual fertilisation not as
the initiating point of development, but as a preliminary opera-
tion by which a gelatinous or mucilaginous particle of matter
was rendered fit for the reception of life. He considered that
it did not even confer life: the unfertilised ovum was not a
living thing, nor capable of “ possessing life”’: after fer-
tilisation, it was still not living, though now it had become
fit for life. Life itself, he believed, was conferred by the
subsequent application of a gentle warmth of the nature of
incubation. This view naturally follows from the identifica-
tion of life with a movement of the contained fluids."

It is not clear how Lamarck supposed that fertilisation
prepared the ovum for the reception of life. He conceived
that fertilisation consisted in the emanation of a “ subtle
penetrating vapour”? which escaped from the sperm and
penetrated the ovum. This “invisible flame or subtle and
expansive vapour ” was the “ aura vitalis,”’ which Spallanzani
had long previously disproved. Spallanzani clothed a male
frog during cohabitation in a pair of trousers through which
subtle penetrating vapours could pass, but no organic matter :
no fertilisation was found to ensue. Spallanzani thus com-
pletely proved the materiality of the process of sexual

PHYSIOLOGY Ixxv

reproduction, and Lamarck’s revival of the “ aura vitalis ”
or semi-spiritual theory constitutes a grave indictment of
his scientific judgment. It is possible, however, that he
was not aware of Spallanzani’s experiment, though he
mentions that savant in another connection.

Lamarck’s chemistry was that which prevailed before
Dalton had formulated the Atomic theory, and is con-
sequently by no means easy for a modern reader to
understand. It is enough, however, to observe that he
regarded the sum-total of living things as being (as indeed
they are) an immense and ever-active laboratory. He held
that all substances, organic and inorganic, were the produce
of organisms. In their bodies, he says, are elaborated all
known complex substances ; from their decomposing remains
spring all inorganic and mineral substances. How the first
gelatinous or mucilaginous corpuscle came to be lying about,
when there was nothing for it to lie about on, is unexplained :
but perhaps it is unfair to approach too nearly to first causes.

The subtle invisible fluids which become the “ exciting
cause” of life, and hence of chemical synthesis in organic
matter, behave in exactly the opposite way in inorganic
matter, which they ever tend to decompose into its elements
or “principles.” Lamarck’s theory as to the causes of
death is not without interest. The solid parts of the organism
are composed of various substances, and are subject to a
constant metabolism. In the course of katabolism, the less
solid and more volatile parts would be given off most freely.
In anabolism, the new substances brought would be only of
the average consistency. Since the most volatile parts are
thus constantly being replaced by less volatile parts, the
substance of the organism tends to an increasing rigidity
and hardness; it can support only a diminished distention
from orgasm, and finally becomes incapable of the further
maintenance of life.

The rest of Lamarck’s physiology is of no special interest.
He held that there are certain “ faculties”? common to all
living bodies, such as growth, nutrition, reproduction ; and

lxxvi INTRODUCTION

that there are others limited to some living bodies only, such
as respiration, circulation, sexual reproduction, intelligence,
etc. Each of these “ faculties” begins at a certain point
in the animal scale. Subsequent to that point it develops
with tolerable regularity in its progress towards perfection ;
anterior to that point it is completely wanting.

§ 8. PsycHoLoGy.

Of the various philosophical questions agitated among the
group of materialists in the latter half of the eighteenth cen-
tury, none occurred more frequently than this: ‘“‘ Can matter
think 2”? A man is made of matter; a man can think:
hence matter must be able to think. A syllogism of this kind
was at the basis of the question. Yet it was found very hard
to admit that matter can think. The question was mainly
agitated among the men of science and the materialistic
philosophers: the spiritualistic philosophers got out of the
difficulty by inventing a new entity, to which they gave the
name of soul, spirit or mind, and saying that it is this entity
which thinks.

Of course, by this facile method, there need never remain
any difficulty in any possible sphere of inquiry. All things
are susceptible of “explanation” by the invention of a
factitious entity of non-material qualities. Lamarck, how-
ever, knew too much to slide out of the idfficulty by such
discredited methods. Holding his views, it was inevitable
that one of his earliest psychological problems must have
been the old question: “Can matter think?” He put it
squarely to himself, and decided that matter did not think ;
thought was only an “ effect.”’ Although probably the whole
subject remained rather vague in his mind, as it is in his
writings, he scarcely could have got farther in his time.

Lamarck’s psychology is of the kind that is spoken of at
the present day as physiological psychology. He did not
indeed employ the experimental method introduced by Helm-
holtz, Fechner and Wundt; but he based his psychology

PSYCHOLOGY Ixxvii

on such knowledge as he possessed of the physiology of the
nervous system. Doubtless that knowledge was scanty and
almost evanescent: even in our time physiology is only
just beginning to reach a development sufficient for the
foundation of a thoroughly scientific psychology. Lamarck
went far in the direction of materialism, though the
imperfect physiology of his day led him into a materialism
almost as crude as was the spiritualism of his day. He
denied the existence of the “ peculiar entity called mind”
(esprit). “In this factitious entity,” he continues, “ which
is not like anything else in nature, I see a mere invention for
the purpose of resolving the difficulties that follow from
inadequate knowledge of the laws of nature.” Mental mani-
festations are simply “ effects’? of cerebral processes, not
manifestations of a separate entity. He could hardly have
expressed it better. The whole of Lamarck’s psychology is
thus reduced to an investigation of the physical or cerebral
processes which are correlated with mental processes.

So far, Lamarck’s method is admirable. His classification
of the functions of the nervous system is also excellent: he
says there are four: (1) the production of muscular move-
ment, (2) of sensation, (3) of emotion, (4) of intellect; a
classification which is obviously in close correspondence with
the modern tripartite division of mind. More especially is
he to be praised for the prominence which he gives to emo-
tion :—the importance of which has always been grotesquely
underestimated or altogether overlooked by the metaphysical
schools of psychology.

But, having said so much, I have said about all that can
be said for Lamarck’s psychology. He wished to base his
psychology on the physiology of the nervous system: and
so far he was right. But his knowledge of that physiology
was worse than non-existent: his ideas on the subject were
extensively and radically erroneous ; the greater part of his
positive statements are altogether untrue.

Lamarck held that the nervous system consisted of three
kinds of substance, the medullary pulp, the aponeurotic

Ixxviii INTRODUCTION

investment, and the nervous fluid. The medullary pulp cor-
responds to the grey and white matter of the brain and
spinal cord, and the nervous tissue generally ; all he says
says about it is that it consists of an “‘ albumino-gelatinous ”’
substance. The aponeurotic investment is, I suppose, the
pia mater. But the entire body of Lamarck’s psychology is
based on the assumption of the existence of the third kind
of substance, namely the nervous fluid, which, as I have
already said, was electric fluid supposed to become modified
and “ animalised”’ on entering into the bodies of the higher
animals. The main result of this animalisation is apparently
that, instead of being uncontainable, and free to permeate
the whole of the animal’s body, it becomes containable ;
that is to say, there are certain tissues that it cannot traverse,
and the most important of such tissues is the aponeurotic
investment in which the entire medullary pulp is enclosed.
It can, however, still move rapidly within the medullary
pulp itself, without needing any visible channels. The
nervous fluid is thus encased within the aponeurotic invest-
ment of the nervous system: it precisely corresponds to the
“animal spirits ” of the ancients.

Lamarck held that in animals more primitive than insects
any nervous system which might exist had no other function
than that of exciting muscular movement. The system, he
imagined, then consisted of isolated ganglia, from which
nerves travelled to the muscles. He attributed the origin
of nerves to the expansive efforts of the nervous fluid within
the ganglia ; long nervous threads being thus thrust out by
the nervous fluid in its efforts to escape. In the insects
according to his view, the nervous system became sufficiently
integrated to endow the animal with feeling or sensation.
But it is not until we reach the lowest vertebrates, that is
to say, the fishes, that any kind of intellectual operation or
intelligent activity can be carried out. The existence of
sensation begins when the nervous system is united into one,
with a “main medullary mass” and a common nucleus
(foyer) for all the afferent nerves. The existence of intelli-

PSYCHOLOGY Ixxix

gence begins with the appearance of the cerebral hemispheres.
Lamarck cites direct introspection as evidence that thought,
etc., takes place in the anterior region of the hemispheres.

In dealing with the force in animals which confers upon
them the power of activity, Lamarck finds that it has two
distinct sources. In animals that have no nervous system,
the activating power is stated to be the subtle fluids of the
environment, notably caloric and electricity. These keep
the visible or “essential” fluids in motion, and entirely
dispense with any need for a nervous system to excite activity.
But Lamarck, influenced no doubt by Descartes, believed
that all such animals were pure machines, that had no feeling,
and were fatally driven by their environment into one or
other form of activity. They had no muscular system, but
only possessed irritability, aroused by contact with an external
object. As nervous and muscular systems were acquired,
however, the source of their motion gradually ceased to
be the subtle fluids of the environment, and the nervous
fluid was substituted for them.

In this second form of activity, therefore, Lamarck speaks
of nature as having transferred the source of motion from
being outside the animal, to within it. He held that there
was a central “‘ reservoir’? of the nervous fluid; and that
when any muscles were to be acted upon, the process con-
sisted in the simple despatch of nervous fluid from the
reservoir down the nerve which led to the muscle in question.
When the muscular contraction was no longer desired,
the nervous fluid returned to the reservoir by a natural
recoil,

Lamarck next had to consider by what physical processes
the reservoir could issue some of its fluid to the correct
muscles. He says it is by means of “emotions”: and that
the emotions again are due either to sensation or to thought,
to physical sensibility or to moral sensibility. We are thus
brought face to face with Lamarck’s curious theory of the
physical aspects of sensation, emotion, and thought ; which
I shall now endeavour to indicate.

Ixxx INTRODUCTION

In addition to the reservoir of nervous fluid already men-
tioned, Lamarck imagined a nucleus (foyer) at which all the
afferent nerves meet. It is to be understood that he con-
sidered what we should now call the afferent and efferent
portions of the nervous system to be two entirely distinct
systems, though with a channel of communication for the
passage of nervous fluid between them. The efferent nerves
issued from their common reservoir; the afferent nerves
terminated in a common nucleus, situated, he believed, in the
medulla oblongata. The relation between the nucleus and
the reservoir is nowhere definitely stated.

Lamarck’s idea of sensation, then, was as follows: some
stimulus affects a nerve-ending in some part of the body ;
say the stimulus of contact by some foreign body. The
nervous fluid at the termination of the nerve affected is
immediately thrown into agitation ; and this agitation travels
up the nerve till it reaches the nucleus. Thereupon it is
propagated through the nucleus into every other sensitive
or afferent nerve in the body. The disturbance is carried
down all these nerves to their endings; it then recoils and
returns along them till once more it arrives at the nucleus.
Hence there is a simultaneous reaction upon the nucleus by
all the afferent nerves, save that which brought in the original
agitation. This nerve alone remains passive, while the rest
are undergoing the action and reaction of the disturbance
which it aroused. Hence when the reaction reaches the
nucleus, and thus throws it for the second time into agitation,
the entire effect of that second agitation is concentrated on
the single nerve, which alone had not reacted because it
brought the original impression. The agitation now travels
back along that nerve to its ending, where the original
stimulus was applied. Hence the location of sensation at
the point of the body first stimulated: but such localisation
is regarded by Lamarck as an illusion, for sensation is a
general effect depending upon an agitation throughout every
portion of the sensitive system, and not upon processes
occurring in any single part of that system. It is worth

PSYCHOLOGY lxxxi

noting that Lamarck presumed the quantity of sensation to
be proportional to the strength of the stimulus, and thus at
all events formulated one of the greatest problems of physio-
logical psychology in later times. It is now known that the
presumption is incorrect. It is more accurate to say that
the quantity of sensation is proportional to the logarithm of
the stimulus, but even this is only a very rough approxima-
tion, and the latest researches tend to limit more and more
the sphere of application of the law. When Lamarck speaks
of feeling, he means sensation, not emotion.

Coming now to emotions, Lamarck postulated for their
explanation the existence of an entity which he variously
calls the “feeling of existence,” the “inner feeling,” the
“mov” orego. Even so close a student as Professor Packard
seems doubtful what Lamarck meant by this “ feeling.”
It is stated to be due to the summation of a large number of
indefinite sensations reaching the nucleus from all parts of
the body: the summation of these stimuli, individually
very weak, gives rise to an “inner feeling ” of appreciable
magnitude. An emotion was understood by Lamarck to be
an affection or condition of this inner feeling, and he usually
speaks of it as an “ emotion of the inner feeling.”

I cannot resist from drawing attention once more to that
constantly alluring temptation to explain difficulties by the
manufacture of a psychical entity. Lamarck fails to under-
stand what an emotion is: he therefore invents an “ inner
feeling’ and affirms that emotion is a special state of this
entity. I am far indeed from wishing to raise the question
of the true existence of an “ inner feeling,” which has been
defended by William James and many other psychologists.
But unquestionably it has no such peculiar relation to the
emotions as that alleged by Lamarck, and for which purpose
he invented it. An emotion is not rendered more intelligible
by being regarded as a special state of some psychical entity.
The point is exactly analogous to the postulate of “ mind”
as a special entity, in modern psychology. We are ac-
quainted with various mental processes, such as emotions,

Ixxxii INTRODUCTION

perceptions, reasoning, memory, will, etc. We cannot
straight away explain them ; and hence we immediately postu-
late an entity called ‘“ mind,” of which they are special states.
To the physiologist, the additional entity merely cumbers
the ground: it explains nothing: it stands in the way of
true physiological explanations of those ‘mental pro-
cesses’: and, worst perhaps of all, it litters up the whole
subject with a false system of terminology. The very name
“mental process,” which I am compelled to use, implies a
process of an entity called mind, whose existence I am
compelled to deny. When once false ideas become current
in any subject, the terminology of that subject becomes
correspondingly false. The false ideas become frozen into
a permanent language: and their displacement is far more
difficult than in a fluid condition.

The influence of language upon thought is largely, I should
suppose, in the direction which it mevitably gives to the
attention of the student. When he comes fresh to the new
subject, all is disorder and confusion. The terminology
comprises, however, a system of names which indicate or
should indicate the prominent and significant facts and
principles to be noted in reducing the subject to order. Now,
if that terminology is wrong, the whole subject will be
wrongly focussed: what should be prominent remains
unnoticed: what is really insignificant is held to be an
important foundation principle: the attention is wrongly
directed throughout.

These remarks apply with overwhelming force to psycho-
logy. Until recent times, the relative importance of different
sections of the subject were grossly misinterpreted. The
accents were all on the wrong parts. People gaped at the
problem of free-will and determinism: they thought it a
fundamental and genuine issue: they ranged themselves as
free-willists and necessitarians. In point of fact, the problem
is neither fundamental nor genuine : it does not even indicate
a true cleavage of opinion among philosophers. It is a
factitious paradox, as foolish as that of Achilles and the

PSYCHOLOGY lxxxiii

tortoise. You can create difficulties about almost anything,
even about a running man overtaking a tortoise. Such
difficulties are analogous to those mechanical puzzles, which
are often extremely difficult to make out, though based on
the most simple and elementary of principles: the main
law to be observed in making a puzzle (as also in conjuring)
is to draw attention off the significant feature, and, if
possible, to direct it on to insignificant features.

Now this is just precisely what has happened in psychology.
Attention is thrown on to the irrelevant, and withdrawn
from the relevant : and the language of centuries has securely
fixed the resulting false outlook. Hence we do not find, on
studying psychology, a set of simple laws and great principles
such as we meet with in physics and chemistry. We find a
collection of puzzles of the free-will type—which are only
puzzles because they so ingeniously draw attention from
every relevant feature in the discussion. And what should
be a mere psychological toy becomes the heading of an
important chapter of the science.

Modern psychologists have many such vexatious follies to
deal with. We have inherited a psychology that is sodden
with metaphysics, and perpetually haunted with unreal
entities. We have to discuss it in a terminology framed by
our opponents, and wholly unsuited to a true science. Let
us firmly assail the pestilential and slovenly habit of attri-
buting all things unknown to some psychical entity, invented
by ourselves for the occasion, or more usually inherited from
our savage ancestors. Lamarck offers us at any rate a
valuable object lesson. Convinced as he was of the fallacy
to which I have been alluding; earnest as he was in his
attempt to avoid it; he yet constantly fell into it. He
materialised a nervous fluid, with a reservoir, a nucleus, etc.
He materialised an “inner feeling’? to explain emotions,
just as we materialise a “ mind” to explain the various
so-called mental processes. He materialised “ nature ” in
much the same way that Bergson does “time,” as though
they were so many material Pa Truly the materialism

Ixxxiv INTRODUCTION

of science is far from the grosser materialism of the common
beliefs.

Lamarck believed that “emotions of the inner feeling ”
might be aroused either through sensation or through thought.
The physical characteristic of an emotion aroused by sensa-
tion is simply an agitation or “emotion” of the nervous
fluid in the nucleus. An emotion differs from a sensation
in that it involves no reaction from other sensitive nerves.
The original agitation is conveyed to the nucleus by a single
nerve, as in a sensation; and the commotion or emotion
there produced has no further active effect. If it acts on
any nerves, it is upon motor nerves which give rise to muscular
action. Every need (besoin) excites an emotion, either
through the medium of sensation or of thought. The
emotion, then acting upon the motor nerves, gives rise to
just those actions necessary for the satisfaction of the
need felt.

Lamarck explains habit by the tendency of the subtle
fluids constantly to traverse the same routes through the
organism. The first passage of the fluids facilitates sub-
sequent passages along the same channel, so that similar
actions tend to be repeated. He regarded instinct as originat-
ing in acquired habits. The habit once acquired would,
according to Lamarck, be inherited, and in course of
time become an instinct. In both these doctrines, he
anticipated two of the leading principles in Spencer’s
Principles of Psychology. The idea of instinct as habit,
acquired and inherited, is indeed almost universally attri-
buted to Spencer. There is but little interest in determin-
ing the priority, however; for the idea itself is certainly
erroneous.

Lamarck also based upon his nervous fluid a theory of
fatigue. The fluid, he says, is used up while functioning,
and has to be made good. Hence the necessity for rest
before further activities can be undertaken.

Lamarck regarded the will as an intellectual faculty,
though not in the first rank of importance. Here again he

PSYCHOLOGY Ixxxv

deserves great credit; for throughout the history of philo-
sophy, almost up to modern times, the will has been accorded
an altogether undue prominence and significance. He placed
it approximately in its correct rank: he pointed out that
the extraordinary instincts of various insects has nothing
whatever to do with will or any conscious effort : he rightly
affirmed that conscious will has infinitely less to do with
initiating even human activities than it is supposed to
have. He denied the so-called free-will altogether, saying
that any volition flowed as necessarily from antecedent
conditions as the quotient in an arithmetical sum. In
all this he has been thoroughly justified by modern
knowledge.

Lamarck regarded the cerebral hemispheres, which he
called the hypocephalon, as the special intellectual organ,
and to a great extent cut off from the remainder of the
brain. He held that “ideas”? were the material of every
kind of intellectual operation : and with that restless craving
for the manufacture of semi-material entities to explain away
difficulties, he affirmed that an idea was a tracing or engraving
actually impressed physically upon the soft substance of the
hemispheres. He recognised that the white matter of the
hemispheres is composed of nerve-fibres, which he imagined
to be hollow tubes containing the nervous fluid. He believed
that each fibre terminated in a minute cavity in the cortex,
too small to be visible. Now, when some impression is made
on our external senses, say the sight of a fish, the nervous
fluid contained in the optic nerve becomes agitated, as I
have already mentioned in describing Lamarck’s views of
sensation. Now, Lamarck continues, if attention is turned to
the cause of the sensation, the sensation does not immediately
pass away, but, by a second reaction, subsequent to that
constituting the sensation, it reaches the brain, and there
becomes pigeon-holed as an idea. The agitation in the
original afferent nerve, in this case the optic nerve, passes
up to the cerebral cortex, and there (if I understand Lamarck
aright) engraves on the walls of the cavity at the end of the

Ixxxvi INTRODUCTION

nerve, an exact image of the fish which caused the sensation.
On this theory, therefore, the hemispheres become a vast
storehouse of miniature engravings, containing all the ideas
which the individual has ever formed.

Let not the reader too hastily deride this fantastic specula-
tion. Its difficulties, and indeed absurdities, are in our day
so obvious that it is hard to remember that they were
not always obvious. Nearly all Lamarck’s errors may be
matched by similar errors current at the present day, and
not always confined to vulgar people. His present error is
no exception. It is not uncommon to hear people of passable
education exhibiting exactly the same ignorance as to the
relations of the physical and the psychical. An external
object, at which we look, forms an image on the retina:
and since the light has to pass through the lens, the image
is inverted. Now it is quite a common thing to hear people
wondering how the inverted image on the retina can give
rise to an optical sensation of the object as being right
way up. It is even said very often that we do see
the object upside down, and rectify it unconsciously and
automatically.

Now people who argue thus, or who see any unusual
difficulty in the matter, are in no better case than Lamarck
was a century ago, with his engravings in cavities of the
cerebral cortex. In each case, the psychical image is con-
fused with a physical image of the object: and whatever
the relation of psychical to physical may be, it is certainly
infinitely different from any such elementary analogy as
the above. Both illustrate that vicious tendency to hypo-
statisation, or manufacture of spiritual, material, or spirito-
material entities, which I have already so often endeavoured
to stigmatise.

Lamarck was a follower of Locke and the empirical school.
He believed that all ideas were acquired, and that there
were no such things as innate ideas. Since he traced all
intellect to ideas, and all ideas to sensations, he must be
reckoned as a sensationalist ; probably he was influenced by

PSYCHOLOGY lxxxvii

Condillac. But he is careful to say that though every idea
is derived from a sensation, not every sensation yields an
idea. It is only when attention is fixed upon the sensation,
at the moment when it is experienced, that an idea of more or
less permanence remains.

On this theory of physically-existing ideas Lamarck bases
his whole theory of intellect. When the nervous fluid
traverses the outlines of an idea in the cortex, it is thrown
once more into the same type of agitation as when
it first engraved that idea. This agitation, being con-
veyed back to the nucleus of sensations, gives rise to a
fainter repetition of the original sensation: thus we have
memory.

When the nervous fluid passes over several graven ideas
at the same time, each portion of the fluid is agitated in a
mode corresponding to the idea traversed. When these
different streams of fluid, each with its special agitation or
mode of motion, reach the nucleus at the same moment,
their motions are compounded so as to form a “ complex ”
idea, which is then laid down in the cortex separately from
its constituents. Complex ideas may be further combined,
and thus Lamarck endeavours to give a physical interpreta-
tion of comparison and reasoning. Dreaming is accounted
for as an aberrant or haphazard wandering of the nervous
fluid, owing to failure of control by the “inner feeling.”
Delirium and syncope are similarly explained. But it is
needless to enter into further detail on Lamarck’s psychology,
or to follow out all his applications of the general principles
cited above.

§ 9. CoNcLUSION.

It is an unhappy but necessary characteristic of social
evolution that those great leaders of thought and action,
who at one time exercise profound influence over their
generation, are apt to be unduly criticised by those of
a succeeding generation. The works of great men are

Ixxxviii INTRODUCTION

commonly such as to arouse emotion, as often disagreeable
as agreeable. Their writings cannot be studied with indiffer-
ence: they do not leave us cold, as do the works of lesser
men. If we agree with them, we agree warmly; if we
disagree with them, we are animated by a desire to attack
or abuse them.

The application of this tendency to Lamarck is obvious.
He defended the doctrine of organic evolution at a time
when it was opposed not only to the entire authority of the
Church and people, but also to the judgment of the leading
men of science. For half a century his writings stood as
almost the only public representation of a belief which
no one now questions. Then came the Origin of Species :
a work which naturally and immediately superseded every
earlier publication, a work moreover which perhaps aroused
more emotion than any other work of science ever published.
Almost inevitably, discipleship of Darwin engendered anta-
gonism to Lamarck. Once evolution became an accepted
fact, no one studied Lamarck to be convinced of it. His
arguments in favour of it ceased to excite interest: and
attention became concentrated on minor details as to the
process itself. Lamarck was at once seen to have offered
a very different account from that of Darwin, and the whole
energy of Darwinian discipleship was roused to antagonism
by the concentration of attention on the anti-Darwinian
elements of the older theory.

The scene has now changed once more: the reaction has
in various quarters turned against Darwin, while Lamarck
himself is slowly entering upon the final stage of oblivion.
The time is ripe for appreciating his true position in the
history of knowledge.

As a philosopher, he was decidedly of the second rank.
He appears to have been an agnostic by reason, and a deist
by desire. “Since I can have no positive knowledge on
this subject,” he writes, ““I prefer to think that the whole
of nature is only an effect: hence I imagine and like to
believe in a first cause or in short a supreme power which

CONCLUSION Ixxxix

brought nature into existence and made it such as it is.”
He regarded the universe as having some goal or purpose,
known only to its sublime author. His philosophy throughout
is far inferior to that of many of his elder contemporaries,
such as Diderot or d’Holbach.

As a pure zoologist, he has not the reputation of
Cuvier. At the same time his judgment and method were
of a very high order, as shown by the groups established
by him and still recognised at the present day; eg.
Annelids, Arachnids, Myriapods, Vertebrates. We must,
remember that he upheld against overwhelming odds the
banner of organic evolution. There can be no justifica-
tion for the contempt with which many people now
speak of Lamarck, merely because his idea of the
evolutionary process differed from ours. So great a truth
can only be discovered by the efforts of several genera-
tions. While therefore he was not a first-class philosopher
or perhaps zoologist, yet he derived a certain advantage
and width of view from the combination of these two
interests. He was able to draw his conclusions from a
wider basis than would have been possible to a more limited
specialism.

I am aware that there are many who repudiate all sug-
gestion of a philosophical treatment of scientific problems.
Such a view cannot for a moment be defended. It arises
from the fact that the name philosophy is so often used
as synonymous with metaphysics: and that the most in-
accessible problems of science have been so often treated to
bushels of high-sounding words from which no genuine
solutions can issue. Yet it remains indisputable that only
by a large knowledge of general principles, as well as of
details, can any true progress result. A man may be in-
timately versed in the anatomy, physiology, classification
and distribution of earwigs, and yet be entirely destitute
of biological judgment: just as a mechanic may know the
minutest details of his machine, and yet be wholly unable
to improve it; while the engineer who has never seen it

xe INTRODUCTION

before, but is guided by the general laws and principles
of mechanics, will quickly succeed in raising its efficiency.
So it is in science: a knowledge of the great general
principles confers a judgment and grasp of essentials, which
is denied to the mere scientific artisan.

In the foregoing pages I have endeavoured to draw certain
tules of scientific method from an analysis of the causes of
the errors into which Lamarck fell. These rules are neither
new nor startling ; yet their importance is so great as to bear
almost endless repetition.

The first principle is one which has never ceased to be
preached since the time of Bacon: it emphasises the truth
that the methods of science are those of observation and
experiment: and that as soon as we travel outside these
methods, we become involved in hopeless error and confusion.
The second follows from the first: it enjoins upon us the
principle, never to seek the explanation of some difficult
problem by the manufacture of a new and unknown
entity. In every case where Lamarck abandoned this rule
he came to grief. I do not mean that we should only believe
in the existence of what we can see or feel; I mean that
when we form some hypothesis to explain a process or event,
and when that hypothesis involves us in the assumption of
some existence not appreciable to our senses, that existence
must be invested with similar properties to those possessed
by other existences which are appreciable to our senses.
That is to say, it must either have the properties of matter,
or of material force or energy: and therefore must be
capable, theoretically at least, of being some day removed
from the sphere of hypothesis to that of observation. To
this rule there has never been any exception in the history
of science. Wherever any suggested hypothesis has included
any factor of a different order from those known to us by
observation and experiment, that hypothesis has ultimately
decayed or been refuted. The unbroken record of history
suffices in itself to establish this general philosophic law,
which indeed is thrust upon us with equal force from many

CONCLUSION xci

other sides. Yet it is disregarded every day, even by men
of science ; and science suffers in consequence. How then
can it be denied that some knowledge of the philosophy
of science is essential to true advance and to sound
judgment ?

Undoubtedly, however, too much stress on the philosophy
or general principles is no less dangerous than too much
application to the details. The former error leads to pre-
mature generalisations and excessive deduction: the latter
to a heavy weight of meaningless and undigested facts, not
qualitatively different from the crammed learning of a well-
flogged schoolboy. The unfortunate truth remains that either
of these subjects—an apprehension of the essential prin-
ciples on the one hand, and a mastery over the facts on the
other hand—is in itself a sufficient task for any ordinary
man. They cannot be fruitfully combined, except by a
fine genius, and then only with a life of hard and unremitting
toil. Whatever we may think as to the former, there is no
doubt that Lamarck abundantly satisfied the latter condi-
tion. He never exploited science for his own advantage.
At all times there are many who follow science with the
view of gaining from it money or honour: there are others,
who have derived from nature a curious and inquiring mind,
and who are wholly bound up with the desire to discover
new truth, and to know new things, merely and solely for
the interest of them. Such a one was Lamarck: he
fulfilled the true function of the philosopher by wandering
over all the sciences and prying into every corner of nature,
with the hope of grasping certain general principles or out-
lines of natural laws. He fulfilled the true function of the
man of science by an intimate and minute study of the
details known in a single part of the sphere of possible know-
ledge. Whether his powers were equal to so vast and uni-
versal an inquiry is a question that may properly be asked :
at any rate, he gave to the work all that any man can give:
he shattered his health, lost his eyesight, and abandoned
his reputation in his immovable resolve to find the truth.

xcii INTRODUCTION

Had he been a soldier, and suffered thus for the sake of his
country, how great would have been the honour that would
have rewarded so deep a devotion! But he was the soldier
of no country: he was the soldier of humanity and truth
alone. To my pen falls the lot of vindicating the memory
of one who, if he had laboured to destroy his fellow-men
instead of to enlighten them, would have received all the
glories of a national hero.

H. E.

PREFACE.

EXPERIENCE in teaching has made me feel how useful a philosophical
zoology would be at the present time. By this I mean a body of
rules and principles, relative to the study of animals, and applicable
even to the other divisions of the natural sciences; for our know-
ledge of zoological facts has made considerable progress during the
last thirty years.

I have in consequence endeavoured to sketch such a philosophy
for use in my lessons, and to help me in teaching my pupils ; nor had
I any other aim in view. But in order to fix the principles and
establish rules for guidance in study, I found myself compelled to
consider the organisation of the various known animals, to pay attention
to the singular differences which it presents in those of eagh family,
each order, and especially each class; to compare the faculties which
these animals derive according to its degree of complexity in each
race, and finally to investigate the most general phenomena presented
in the principal cases. I was therefore led to embark upon successive
inquiries of the greatest interest to science, and to examine the most
difficult of zoological questions.

How, indeed, could I understand that singular degradation which
is found in the organisation of animals as we pass along the series
of them from the most perfect to the most imperfect, without en
quiring as to the bearings of so positive and so remarkable a fact,
founded upon the most convincing proofs? How could I avoid
the conclusion that nature had successively produced the different
bodies endowed with life, from the simplest worm upwards? For
in ascending the animal scale, starting from the most imperfect animals,
organisation gradually increases in complexity in an extremely remark-
able manner.

I was greatly strengthened in this belief, moreover, when I recognised
that in the simplest of all organisations there were no special organs
whatever, and that the body had no special faculty but only those
which are the property of all living things. As nature successively

A

2 ZOOLOGICAL PHILOSOPHY

creates the different special organs, and thus builds up the animal
organisation, special functions arise to a corresponding degree, and
in the most perfect animals these are numerous and highly developed.

These reflections, which I was bound to take into consideration,
led me further to enquire as to what life really consists of, and what
are the conditions necessary for the production of this natural pheno-
menon and its power of dwelling in a body. I made the less resistance
to the temptation to enter upon this research, in that I was then con-
vinced that it was only in the simplest of all organisations that the
solution of this apparently difficult problem was to be found. For
it is only the simplest organisation that presents all the conditions
necessary to the existence of life and nothing else beyond, which might
mislead the enquirer.

The conditions necessary to the existence of life are all present
in the lowest organisations, and they are here also reduced to their
simplest expression. It became therefore of importance to know
how this organisation, by some sort of change, had succeeded in giving
rise to others Jess simple, and indeed to the gradually increasing com-
plexity observed throughout the animal scale. By means of the two
following principles, to which observation had led me, I believed I
perceived the solution of the problem at issue.

Firstly, a number of known facts proves that the continued _use of
any organ leads to its development, strengthens it and even enlarges
it, while permanent disuse of any organ is injurious to its develop-
ment, causes it to deteriorate and ultimately disappear if the disuse
continues for a long period through successive generations. Hence
we may infer that when some change in the environment leads to a
change of habit in some race of animals, the organs that are less used
die away little by little, while those which are more used. develop
better, and acquire a vigour and size proportional to their use.

Secondly, when reflecting upon the power of the movement of the
fluids in the very supple parts which contain them, I soon became
convinced that,iaccording as this movement is accelerated, the fluids
modify the cellular tissue in which they move, open passages in them,
form various canals, and finally create different organs, according
to the state of the organisation in which they are Lote

Arguing from these two principles, I looked upon it as certain
that, firstly, the movement of the fluids within animals—a move-
ment which is progressively accelerated with the increasing complexity
of the organisation—and, secondly, the influence of the environment,
in so far as animals are exposed to it in spreading throughout all
habitable places, were the two general causes which have brought
the various animals to the state in which we now see them. |

PREFACE © 3

I have not merely confined myself in the present work to setting
forth the conditions essential to the existence of life in the simplest
organisations, and the causes which have given rise to the growing
complexity of animal organisation from the most imperfect to the most
perfect of animals; but, believing that there is some possibility of
recognising the physical causes of feeling, which is possessed by so
many animals, I have not hesitated to take up this question also.

I was indeed convinced that matter can never possess in itself
the property of feeling; and I imagined that feeling itself is only a
phenomenon resulting from the workings of an orderly system capable
of producing it. I enquired therefore what the organic mechanism
might be which could give rise to this wonderful phenomenon, and I
believe I have discovered it.

On marshalling together the best observations on this subject, I
recognised that for the production of feeling the nervous system
must be highly complex, though not so highly as for the phenomena
of intelligence.

Following out these observations, I have become convinced that
the nervous system, when it is in the extremely imperfect condition
characteristic of more or less primitive animals, is only adapted to
the excitation of muscular movements, and that it cannot at this
stage produce feeling. In this particular stage it consists merely of
ganglia, from which issue threads. It does not present any gang-
lionic longitudinal cord, nor any spinal cord, the anterior extremity
of which expands into a brain which contains the nucleus of sensations
and gives origin to the nerves of the special senses, or at least to some
of them. When the nervous system reaches this stage, the animals
possessing it then have the faculty of feeling.

Finally, I endeavoured to determine the mechanism by which
a sensation was achieved; and I have shown that nothing more
than a perception can be produced in an individual which has no
special organs, and moreover, that a sensation produces nothing
more than a perception whenever it is not specially remarked.

I am in truth undecided as to whether sensation is achieved by a
transmission of the nervous fluid starting from the point affected,
or merely by a communication of movement in that fluid. The fact,
however, that the duration of certain sensations is dependent upon
that of the impressions which cause them, make me lean towards
the latter opinion. My observations would not have thrown any
satisfactory light upon the subjects treated, if I had not recognised
and been able to prove that feeling and irritability are two very different
organic phenomena. They have by no means a common origin, as
has been supposed ; the former of these phenomena constitutes a

4 ZOOLOGICAL PHILOSOPHY

faculty peculiar to certain animals, and demanding a special system
of organs, while the latter, which does not require any special system,
is exclusively the property of all animal organisation.

So long therefore as these two phenomena continue to be confused
as to their origin and results, it will be only too easy to make mistakes
in proffering explanations of the causes of the general phenomena
of animal organisation. It will be so especially in making experiments
for the purpose of investigating the principle of feeling and of move-
ment, and finally the seat of that principle in the animals which possess
these faculties.

For instance, if we decapitate certain very young animals, or cut
the spinal cord between the occiput and the first vertebra, or push
in a probe, there occur various movements excited by the pumping
of air into the lungs. These have been taken as proof of the revival
of feeling by dint of artificial respiration; whereas these effects
are due partly to the irritability not being extinct, for it is known that
it continues to exist sometime after the death of the individual, and
partly to certain muscular movements which can still be excited
by the inhalation of air when the spinal cord has not been altogether
destroyed by the introduction of a long probe right down its
canal.

I recognised that the organic act which gives rise to the movement
of the parts is altogether independent of that which produces feeling,
although in both cases nervous influence is necessary. I notice
that I can work several of my muscles without experiencing any
sensation, and that I can receive a sensation without any movement
resulting from it. But for these observations, I too might have taken
the movements occurring in a young decapitated animal, or in one whose
brain had been removed, as signs of feeling, and I should have fallen
into error.

I think that if the individual is disabled by its nature or otherwise
from giving an account of a sensation which it experiences, and that
if it only indicates by cries the pain which it is made to undergo,
we have no certain sign for inferring that it receives sensation except
from knowing that the system of organs which gives it the faculty
of feeling is not destroyed, but retains its integrity. Muscular move-
ments excited from without cannot in themselves prove an act
of feeling.

Having fixed my ideas on these interesting objects, I gave attention
to the inner feeling, that is to say, that feeling of existence which is
possessed only by animals which enjoy the faculty of feeling. I
brought to bear on the problem such known facts as are relevant, in
addition to my own observations, and I soon became convinced

PREFACE 5

that this inner feeling constituted a power which it was essential to
take into consideration.

| Nothing in fact seems to me so important as the feeling which I
have named, considered both in man and in the animals which possess
a nervous system capable of producing it. It is a feeling which can
be aroused by physical and moral needs, and which becomes the source
whence movements and actions derive their means of execution.
No one that I know had paid any attention to it; and this gap in our
knowledge of one of the most powerful causes of the principal pheno-
mena of animal organisation rendered all explanations inadequate
to account for these phenomena. We have, however, a sort of clue
to the existence of that inner power when we speak of the agitations
which we ourselves are constantly experiencing ; for the word emotion,
which I did not create, is often enough pronounced in conversation
to express the observed facts.

When I had considered that the inner feeling was susceptible of
being aroused by different causes, and that it then constituted a
power capable of exciting actions, I was so to speak struck by the
multitude of known facts which attest the actual existence of that
power; the difficulties which had long puzzled me with regard to the
exciting cause of actions appeared to me entirely surmounted.

Admitting that I had been fortunate enough to alight upon a
truth in attributing to the inner feeling of animals which have it the
power which produces their movements, I had still only surmounted
a part of the difficulties by which this research is hampered. For
it is obvious that not all known animals do or can possess a nervous
system; consequently, all animals do not possess the inner feeling
of which I am speaking ; and in the case of those which are destitute
of it, the movements which they are seen to execute must have another
origin.

I had reached this point when I reflected that without internal
excitations plant life would not exist at all, nor be able to maintain
itself in activity. I recognised the fact that the same consideration
applied to a large number of animals; and as I had very frequently
observed that nature varies her means when necessary in order to
attain the same end, I had no further doubt about the matter.

I think therefore that the very imperfect animals which have no |
nervous system live only by the help of excitations which they receive
from the exterior. That is to say, subtle and ever moving fluids
contained in the environment incessantly penetrate these organised
bodies and maintain life in them, so long as the state of these bodies
permits of it. Now this thought is one which I have many times
considered, which many facts appear to me to confirm, against which

6 ZOOLOGICAL PHILOSOPHY

none of those that are known to me seem to conflict, and finally which
appears to me obviously borne out by plant life. It was therefore
for me a flood of light which disclosed to me the principal cause which
maintains movements and the life of organised bodies, and to which
animals owe all that animates them.

I combined this consideration with the two preceding ones, namely,
that which concerns the result of the movement of fluids in the interior
of animals and that which deals with the effects of a change that is

/ maintained in the environment and habits of these beings. I could

/ thus seize the thread which connects the numerous causes of the

phenomena presented in animal organisation, and I soon perceived

the importance of this power in nature which preserves in new in-

\ avi all the changes in organisation acquired by their ancestors
as a result of their life and environment.

Now I remarked that the movements of animals are never directly
communicated, but that they are always excited ; hence T recognised
that nature, although obliged at first to borrow from the environ-
ment the excitatory-power for vital movements and the actions of
imperfect animals, was able by a further elaboration of the animal
organisation to convey that power right into the interior of these
beings, and that finally she reached the point of placing that same
power at the disposal of the individual. |

Such are the principal conclusions which I have endeavoured to
establish and develop in this work.

This Zoological Philosophy thus sets forth the results of my studies
on animals, their characters both general and special, their organisa-
tion, the causes of their development and diversity, and the faculties
which they thence derive. In its composition I have made use of
the bulk of the material which I was collecting for a projected work
on living bodies under the title of Biology. This work will now remain,
so far as I am concerned, unwritten.

The facts which I name are very numerous and definite, and the
inferences which I have drawn from them appeared to me sound
and necessary ; I am convinced therefore that it will be found difficult
to replace them by any others.

The number of new theories expounded in the present work are
likely to give the reader an unfavourable impression, if only from
the fact that the commonly received beliefs do not readily give
way to any new ones which tend to contradict them. Now, since
the predominance of old ideas over new favour this prejudice,
especially when there is some contributory personal interest, it follows
that, whatever difficulties there may be in the discovery of new truths
in nature, there are still greater difficulties in getting them recognised.

PREFACE 7

But these difficulties, arising from various causes, are on the whole
more advantageous than otherwise to the general progress of know-
ledge. By means of a rigorous hostility to the admission of new
ideas as truths, a multitude of more or less specious but unfounded
ideas which appear, soon after fall into oblivion. Sometimes, on
the other hand, excellent opinions and solid thoughts are for the same
reasons discarded or neglected; but it is better that a truth once
perceived should have a long struggle before obtaining the attention
it deserves, than that all that is produced by the ardent imagination
of man should be too readily received.

The more I meditate on this subject, and particularly on the numerous
causes which may bring about a change in our opinions, the more am
I convinced, that except for the physical and moral facts! that no
one can question, all else is but opinion or argument; and we well
know that arguments can always be met by others. Thus, although
it is obvious that there are great differences in the probability and
even the value of the opinions of different men, it seems to me that
we should be wrong to blame those who refuse to adopt our own.

Should we recognise as well founded only those opinions that are
most widely accepted? Experience shows clearly enough that
persons with the most developed intellect and the highest wisdom
constitute at all times an extremely small minority. The fact can
scarcely be questioned. Authorities in the sphere of knowledge
should weigh one another’s worth and not count one another’s numbers,
although indeed a true estimation is very difficult.

Seeing how numerous and rigorous are the conditions required
for forming a sound judgment, it is still uncertain whether the judg-
ment of individuals who have been set up as authorities by public
opinion is perfectly sound on the topics on which they pronounce.

There are then few positive truths on which mankind can firmly
tely. They include the facts which he can observe, and not the in-
ferences that he draws from them ; they include the existence of nature,
which presents him with these facts, as also the laws which regulate
the movements and changes of its parts. Beyond that all is un-
certain, although some conclusions, theories, opinions, etc., have much
greater probability than others.

We cannot rely on any argument, inference or theory, since the
authors of these intellectual acts can never be certain that they have
taken into account the true data, nor that they have admitted these

1By moral facts I mean mathematical truths; that is to say, the results of
calculations whether of quantities or forces, and the results of measurements ; since
it is through intelligence and not through the senses that these facts become known

to us. Now these moral facts are just as much positive truths as are those relating
to the existence of bodies that we can observe.

8 ZOOLOGICAL PHILOSOPHY

only. There is nothing that we can be positive about, except the
existence of bodies which affect our senses, and of the real qualities
which belong to them, and finally the physical and moral facts of
which we are able to acquire a knowledge. The thoughts, argu-
ments and explanations set forth in the present work should therefore
be looked upon merely as opinions which I propose, with the intention
of setting forth what appears to me to be true, and what may indeed
actually be true.

However this may be, in giving myself up to the observations
from which my theories have arisen, I have obtained the pleasure
which their resemblance to truth has brought me, and I have obtained
also the recompense for the fatigues entailed upon me by my studies
and meditations. In publishing these observations, together with
the conclusions that I have drawn from them, my purpose is to invite
enlightened men who love the study of nature to follow them out,
verify them, and draw from them on their side whatever conclusions
they think justified.

This path appears to me the only one that can lead to a knowledge
of truth or of what comes nearest it, and it is clear that such know-
ledge is more profitable to us than the error which might fill its place.
I cannot doubt therefore that it is this path which we must follow.

It may be noticed that I have dwelt with special pleasure on the
exposition of the second and especially of the third part of this work,
and that I have been greatly interested in them. None the less,
the principles bearing on natural history which I have studied in
the first part should be looked upon as possibly the most useful to
science, since they are in general most in harmony with the opinions
hitherto received.

I might have considerably extended this work by developing under
each heading all the interesting matter that it permits of; but I
have preferred to confine myself to such exposition as is strictly
necessary for the adequate comprehension of my observations. I ~
have thus spared my readers’ time without exposing them to the
risk of failing to understand me.

I shall have attained my end if those who love natural science
find in this work any views and principles that are useful to them ;
if the observations which I have set forth, and which are my own,
are confirmed or approved by those who have had occasion to study
the same objects; and if the ideas which they succeed in giving
rise to, whatever they may be, advance our knowledge or set us on
the way to reach unknown truths.

PRELIMINARY DISCOURSE.

To observe nature, to study her productions in their general and
special relationships, and finally to endeavour to grasp the order
which she everywhere introduces, as well as her progress, her laws,
and the infinitely varied means which she uses to give effect to that
order: these are in my opinion the methods of acquiring the only
positive knowledge that is open to us,—the only knowledge moreover
which can be really useful to us. It is at the same time a means to
the most delightful pleasures, and eminently suitable to indemnify
us for the inevitable pains of life.

And in the observation of nature what can be more interesting
than the study of animals? There is the question of the affinities
of their organisation with that of man, there is the question of the
power possessed by their habits, modes of life, climates and places
of habitation, to modify their organs, functions and characters. There
is the examination of the different systems of organisation which are
to be observed among them, and which guide us in the determina-
tion of the greater or lesser relationships that fix the place of each
in the scheme of nature. There is finally the general classification
that we make of these animals from considerations of the greater
or lesser complexity of their organisation; and this classification
may even lead us to a knowledge of the order followed by nature in
bringing the various species into existence.

Assuredly however, it cannot be disputed that all these enquiries,
and others also to which the study of animals necessarily leads, are
of very great interest to anyone who loves nature and seeks the
truth in all things.

It is a peculiar circumstance that the most important phenomena
for us to consider have only been available since the time when
attention was devoted to the study of the least perfect animals, and
since the researches on the various complications in the organisation
of these animals became the main object of study.

It is no less curious that the most important discoveries of the

10 ZOOLOGICAL PHILOSOPHY

laws, methods and progress of nature have nearly always sprung from
the examination of the smallest objects which she contains, and from
apparently the most insignificant enquiries. This truth, already
established by many remarkable facts, will receive in the course of this
work a new accession of evidence, and should convince us more than
ever that in the study of nature no object whatever can be dis-
regarded.

The purpose of the study of animals is not merely to ascertain their
different races, nor to determine all the distinctions among them by
specifying their special characters. This study further aims at
acquiring a knowledge of the functions which animals possess, the
causes of the presence and maintenance of life in them, and of the
remarkable progression which they exhibit in the complexity of their
organisation, as well as in the number and development of their
functions.

At bottom, the physical and moral are without doubt one and the
same thing. Itis by a study of the organisation of the different orders
of known animals that this truth can be set in the strongest light. Now
since these products from a common origin, at first hardly separated,
become eventually divided into two entirely distinct orders, these
two orders when examined at their greatest divergence have seemed
to us and still seem to many persons to have nothing in common.

The influence of the physical on the moral has however already
been recognised, but it seems to me that sufficient attention has not
yet been given to the influence of the moral on the physical. Now
these two orders of things which have a common origin re-act upon
one another, especially when they appear the most widely separated ;
and we are now in a position to prove that each affects the variations
of the other.

It seems to me that we have gone the wrong way to work in the en-
deavour to show the common origin of the two orders of results which,
in their highest divergence, constitute what is called the physical
and the moral.

For the study of these two kinds of objects, apparently so distinct,
has been initiated in man himself. Now his organisation, having
reached the limit of complexity and perfection, exhibits the greatest
complication in the causes of the phenomena of life, feeling and
function. It is consequently the most difficult from which to infer
the origin of so many phenomena.

After the organisation of man had been so well studied, as was the
case, it was a mistake to examine that organisation for the purposes of

1See the interesting work of M. Cabanis entitled Rapport du physique et du
moral de Vhomme.

PRELIMINARY DISCOURSE Il

an enquiry into the causes of life, of physical and moral sensitiveness,
and, in short, of the lofty functions which he possesses. It was first
necessary to try to acquire knowledge of the organisation of the other
animals. It was necessary to consider the differences which exist
among them in this respect, as well as the relationships which are
found between their special functions and the organisation with which
they are endowed.

These different objects should have been compared with one another
and with what is known of man. An examination should have been
made of the progression which is disclosed in the complexity of organisa-
tion from the simplest animal up to man, where it is the most complex
and perfect. The progression should also have been noted in the
successive acquisition of the different special organs, and consequently
of as many new functions as of new organs obtained. It might then
have been perceived how needs, at first absent and afterwards gradually
increasing in number, have brought about an inclination towards
the actions appropriate to their satisfaction; how actions becoming
habitual and energetic have occasioned the development of the organs
which execute them; how the force which stimulates organic move-
ments can in the most imperfect animals exist outside of them and
yet animate them ; how that force has been subsequently transported
and fixed in the animal itself; and, finally, how it has become the source
of sensibility, and last of all of acts of intelligence.

I may add that if this method had been followed, feeling would
certainly not have been looked upon as the general and immediate
cause of organic movements. It would never have been said that
life is a consequence of movements executed by virtue of sensations
received by various organs or otherwise; nor that all vital move-
ments are brought about by impressions received by sensitive parts
(Rapport du physique et du moral de Vhomme, pp. 38 to 39, and 85).

This cause would appear to be justified up to a certain point in the
most perfect animals, but if it held good with regard to all bodies
which enjoy life, they would all possess the faculty of feeling. Now
it could hardly be shown that this is the case in plants ; it could hardly
even be proved that it is the case in all known animals.

The supposition of such a general cause does not seem to me justified
by the real methods of nature. When constituting life, she had no
power to endow with that faculty the imperfect animals of the earlier
classes of the animal kingdom.

With regard to living bodies, it is no longer possible to doubt that
nature has done everything little by little and successively.

Hence, among the various subjects which I intend to discuss in
the present work, I shall endeavour to make clear by the citation

12 ZOOLOGICAL PHILOSOPHY

of recognised facts that nature, while ever increasing the complexity
of animal organisation, has created in order the different special organs,
as also the functions which the animals possess.

The belief has long been held that there exists a sort of scale or
graduated chain among living bodies. Bonnet has developed this
view ; but he did not prove it by facts derived from their organisa-
tion; yet this was necessary especially with regard to animals. He
was unable to prove it, since at the time when he lived the means did
not exist.

In the study of all classes of animals there are many other things
to be seen besides the animal complexity. Among the subjects of
greatest importance in framing a rational philosophy are the effect
of the environment in the creation of new needs ; the effect of the needs
in giving rise to actions, and of repeated actions in creating habits
and inclinations; the results of increased or diminished use of any
organ, and the means adopted by nature to maintain and to perfect
all that has been acquired in organisation.

But this study of animals, especially of the least perfect animals,
was long neglected ; since no suspicion existed of the great interest
which they exhibit. Moreover, what has been started in this respect
is still so new that we may anticipate much more light from its further
development.

When the study of natural history was actually begun, and
naturalists inquired into both kingdoms, those who devoted their
researches to the animal kingdom studied chiefly the vertebrate animals,
that is to say mammals, birds, reptiles and, lastly, fishes. In these
classes of animals the species are in general larger, and have their
parts and functions better developed and more easily ascertainable
than the species of invertebrate animals. Their study, therefore,
seemed to present more of interest.

In fact the majority of invertebrate animals are extremely small,
their functions are limited, and their organs much more remote from
those of man than is the case of the more perfect animals. As a
result, they have been to some extent despised by the vulgar, and
down to our own time have only realised a very moderate amount
of interest on the part of most naturalists.

We are beginning, however, to get over a prejudice so harmful to
the progress of knowledge. During the few years that these singular
animals have been closely examined, we have been compelled to
recognise that the study of them is highly interesting to the naturalist
and philosopher, because it sheds light, that could scarcely be other-
wise obtained, on a number of problems in natural history and animal
physics. It has been my duty in the Natural History Museum to

PRELIMINARY DISCOURSE 13

attend to the exhibit of the animals which I called invertebrate,
on account of the absence in them of a vertebral column. My re-
searches on these numerous animals, the accumulated observations
and facts, and finally the increased knowledge of comparative anatomy
which I gained from them, soon inspired me with the highest interest
im the subject.

The study of invertebrate animals must, in fact, be of special interest
to the naturalist for four reasons :—(1) The number of the species
of these animals in nature is much greater than that of vertebrate
animals. (2) Since they are more numerous, they are necessarily
more varied. (3) The variations in their organisation are much
greater, more sharply defined and more remarkable. (4) The order
observed by nature in the successive formation of the different organs
of animals is much better expressed in the mutations which these
organs undergo in invertebrate animals. Moreover, their study is
more fertile in helping us to understand the origin of organisa-
tion, with its complexity and its developments, than could possibly
be the case in more perfect animals such as vertebrates.

Convinced of these truths I felt that, in the instruction of my
pupils, I should not plunge into detail straight away, but should
above all show them the general principles which hold good of all
animals. I tried to give them a view of the whole and of the essentials
which appertained to it, with the intention of taking subsequent
note of the main groups into which that whole appears to be divided
for purposes of comparison and more intimate knowledge.

The real way, no doubt, of acquiring a thorough knowledge of an
object, even in its smallest details, is to begin by inspecting it in its
entirety. We should examine first its bulk, extent, and the various
parts which compose it. We should enquire into its nature and
origin, and its connection with other known objects. In short, we
should enquire into the general principles involved, from all possible
points of view. The subject is then divided into its chief parts for
separate study and examination in all the bearings likely to be in-
structive. By further dividing and sub-dividing these parts, and
inspecting each successively, we arrive at the smallest, where we do
not neglect the least details. Once these researches finished, the effects
have to be deduced from them, so that little by little the philosophy
of science is established, modified and perfected.

It is by this method alone that human intelligence can gain know-
ledge (in any science) that is at once vast, solid and coherent. It
is solely by this kind of analysis that science makes real progress,
so that allied objects are never confused, but can be perfectly

known.

14 ZOOLOGICAL PHILOSOPHY

Unfortunately this method is not sufficiently used in the study
of natural history. The recognised necessity for close observation
of special objects has produced a habit of not going beyond these
objects with their smallest details. They have thus become for most
naturalists the chief subjects of study. This would, however, not
really be a drawback for natural science, were it not for the steady
refusal to see in the observed objects anything besides their form,
dimensions, external parts, colour, etc., but those who give themselves
up to such a study are contemptuous of the higher ideals, such as the
enquiry into the nature of the objects which occupy them, into the
causes of the modifications or variations which these objects undergo,
and into the relations of these same objects with each other and with
all other known objects, etc., ete.

It is because the method which I have just named is insufficiently
followed out that we find so much divergence in what is taught on
this subject, both in works on natural history and elsewhere. Those
who have gone in exclusively for the study of species find it very
difficult to grasp the general affinities among objects; they do not
in the least appreciate nature’s true plan, and they perceive hardly
any of her laws.

I am convinced that it is wrong to follow a method which so greatly
limits ideas. I find myself on the other hand obliged to bring out
a new edition of my Systéme des animaux sans vertébres, since the
rapid progress of comparative anatomy and the new discoveries of
zoologists, together with my own observations, enable me to improve
that work. I have accordingly collected into a special work, under
the title of Zoological Philosophy, (1) the general principles at stake
in the study of the animal kingdom; (2) the observed facts which
require to be considered in that study; (3) the principles which
regulate the most suitable classification of animals, and an arrange-
ment of them in their natural order; (4) lastly, the most important of
the results which flow naturally from the accumulated observations
and facts, and which constitute the true foundation of the philosophy
of science.

The Zoological Philosophy is nothing but a new edition, re-cast,
corrected and much enlarged, of my work entitled Recherches sur
les corps vivants. It is divided into three main divisions, and each
of these divisions is broken up into separate chapters.

Thus, in the first division, which sets forth the essential observed
facts and the general principles of the natural sciences, I shall begin
by a discussion of what I call artificial devices used among the sciences
in question. I shall deal with the importance of the consideration
of affinities, and with the notion that should be conveyed, when

PRELIMINARY DISCOURSE 15

we speak of species among living bodies. Afterwards, when I have
treated of the general principles which concern animals, I shall adduce
proof of the degradation of organisation which runs through the entire
animal scale, placing the most perfect animals at the anterior extremity
of that scale. On the other hand I shall show the influence of en-
vironment and habit on the organs of animals, as being the factors
which favour or arrest their development. I shall conclude this
division by a discussion of the natural order of animals, and by an
account of their most suitable arrangement and classification.

In the second division I shall put forward my ideas as to the order
and state of things which constitute the essence of animal life; and I
shall indicate the conditions necessary for the existence of this wonder-
ful natural phenomenon. Afterwards, I shall endeavour to ascertain
the exciting cause of organic movements; of orgasm and of irrita-
bility ; the properties of cellular tissue; the sole condition under
which spontaneous generation can occur; the obvious effects of vital
actions, etc.

Lastly, the third division will state my opinion as to the physical
causes of feeling, of the power to act, and of the acts of the intelligence
found in certain animals.

In this division I shall treat: 1st, the origin and formation of the
nervous system; 2nd, the nervous fluid, which can only be known
indirectly, but whose existence is attested by phenomena that it
alone can produce; 3rd, physical sensibility and the mechanism
of sensations; 4th, the reproductive power of animals; 5th, the
origin of the will and the faculty of willing; 6th, ideas and the different
kinds of them; 7th, lastly, certain peculiar acts of the understanding,
such as attention, thoughts, imagination, memory, etc.

The reflections set forth in the 2nd and 3rd divisions doubtless
comprise subjects that are very difficult to examine, and may
even appear insoluble; but they are so full of interest that such
attempts may possibly be profitable, either in the disclosure of un-
perceived truths or in pointing out the direction in which they may
be sought.

PART I.

CONSIDERATIONS ON THE NATURAL HISTORY OF ANIMALS,
THEIR CHARACTERS, AFFINITIES, ORGANISATION,
CLASSIFICATION AND SPECIES.

CHAPTER I.

ON ARTIFICIAL DEVICES IN DEALING WITH THE
PRODUCTIONS OF NATURE.

THROUGHOUT nature, wherever man strives to acquire knowledge
he finds himself under the necessity of using special methods, Ist,
to bring order among the infinitely numerous and varied objects
which he has before him; 2nd, to distinguish, without danger of
confusion, among this immense multitude of objects, either groups
of those in which he is interested, or particular individuals among
them ; 3rd, to pass on to his fellows all that he has learnt, seen and
thought on the subject. Now the methods which he uses for this
purpose are what I call the artificial devices in natural science,—devices
which we must beware of confusing with the laws and acts of nature
herself.

It is not merely necessary to distinguish in natural science what
belongs to artifice and what to nature. We have to distinguish as
well two very different interests which incite us to the acquisition
of knowledge.

The first is an interest which I call economic, because it derives
its impetus from the economic and utilitarian needs of man in deal-
ing with the productions of nature which he wants to turn to his
own use. From this point of view he is only interested in what
he thinks may be useful to him.

The other, very different from the first, is that philosophic interest
through which we desire to know nature for her own sake, in order
to grasp her procedure, her laws and operations, and to gain an idea
of what she actually brings into existence. This, in short, is the kind of
knowledge which constitutes the true naturalist. Those who approach
the subject from this point of view are naturally few; they are in-
terested impartially in all natural productions that they can observe.

To begin with, economic and utilitarian requirements resulted
in the successive invention of the various artificial devices employed

20 ZOOLOGICAL PHILOSOPHY

in natural science. When the interest of studying and knowing
nature was first felt, these artificial devices continued to be of assist-
ance in the prosecution of that study. These same artificial devices
have therefore an indispensable utility, not only for helping us to a
knowledge of special objects, but for facilitating study and the pro-
gress of natural science, and for enabling us to find our way about
among the enormous quantity of different objects that we have to
deal with.

Now the philosophic interest embodied by the sciences in question,
although less widespread than that which relates to our economic
requirements, compels us to separate what belongs to artifice from
what is the sphere of nature. We have to confine within reason-
able limits the consideration due to the first set of objects, and attach
to the second all the importance that they deserve.

The artificial devices in natural science are as follows :

(1) Schematic classifications, both general and special.

(2) Classes.

(3) Orders.

(4) Families.

(5) Genera.

(6) The nomenclature of various groups of individual objects.

These six kinds of devices, commonly used in natural science, are
purely artificial aids which we have to use in the arrangement and
division of the various observed natural productions; to put us in
the way of studying, comparing, recognising and citing them. Nature
has made nothing of this kind: and instead of deceiving ourselves
into confusing our works with hers, we should recognise that classes,
orders, families, genera and nomenclatures are weapons of our own
invention. We could not do without them, but we must use them
with discretion and determine them in accordance with settled
principles, in order to avoid arbitrary changes which destroy all the
advantages they bestow.

It was no doubt indispensable to break up the productions of nature
into groups, and to establish different kinds of divisions among them,
such as classes, orders, families and genera. It was, moreover, necessary
to fix what are called species, and to assign special names to these
various sorts of objects. This is required on account of the limitations
of our faculties ; some such means are necessary for helping us to fix
the knowledge which we gain from that prodigious multitude of
natural bodies which we can observe in their infinite diversity.

But these groupings, of which several have been so happily drawn
up by naturalists, are altogether artificial, as also are the divisions
and sub-divisions which they present. Let me repeat that nothing

ARTIFICIAL DEVICES 21

of the kind is to be found in nature, notwithstanding the justification
which they appear to derive from certain apparently isolated portions
of the natural series with which we are acquainted. We may, there-
fore, rest assured that among her productions nature has not really
formed either classes, orders, families, genera or constant species,
but only individuals who succeed one another and resemble those
from which they sprung. Now these individuals belong to infinitely
diversified races, which blend together every variety of form and degree
of organisation; and this is maintained by each without variation,
so long as no cause of change acts upon them.

Let us proceed to a few brief observations with respect to each
of the six artificial devices employed in natural science.

Schematic classifications —By schematic classifications, general or
special, I mean any series of animals or plants that is drawn up un-
conformably to nature, that is to say, which does not represent
either her entire order or some portion of it. It is consequently
not based on a consideration of ascertained affinities.

The belief is now thoroughly justified that an order established by
nature exists among her productions in each kingdom of living bodies:
this is the order on which each of these bodies was originally formed.

This same order is individual and essentially without divisions
in each organic kingdom. It becomes known to us through the
affinities, special and general, existing among the different objects
of which these two kingdoms consist. The living bodies at the two
extremities of that order have essentially the fewest affinities, and
exhibit the greatest possible differences in their organisation and
structure.

It is this same order, as we come to know it, that will have to replace
those schematic or artificial classifications that we have been forced
to create in order to arrange conveniently the different natural
bodies that we have observed.

With regard to the various organised bodies recognised by observa-
tion, there was at first no other thought beyond convenience and ease
of distinction between these objects; and it has taken the longer to
seek out the actual order of nature in their classification, inasmuch
as there was not even a suspicion of the existence of such an
order.

Hence arose groupings of every kind, artificial systems and methods,
based upon considerations of such an arbitrary character that they
underwent almost as many changes in their principles and nature as
there were authors to work upon them.

With regard to plants, the sexual system of Linneus, ingenious
as it is, presents a general schematic classification : and, with regard

22 ZOOLOGICAL PHILOSOPHY

to insects, the entomology of Fabricius presents a special schematic
classification. All the progress made in recent times by the philo-
sophy of natural science has been necessary, in France at least, to carry
the conviction that the natural method should be studied. Our
classifications should conform to the exact order found in nature,
for that order is the only one which remains stable, independent of
arbitrary opinion, and worthy of the attention of the naturalist.

Among plants, the natural method is extremely difficult to
establish, on account of the obscurity prevailing in the character
of the internal organisation of these living bodies, and of the differences
presented by plants of different families. Since the learned observa-
tions of M. Antoine-Laurent de Jussieu, however, a great step has
been made in botany in the direction of the natural method; many
families have been constituted with direct reference to their affinities ;
but the general position of all these families among themselves, and
consequently of the whole order, remains to be determined. The fact
is that we have found the beginning of that order; but the
middle, and especially the end, are still at the mercy of arbitrary
opinion.

The case is different with regard to animals; their organisation
is much more pronounced, and presents different systems that are easier
to grasp. The work has, therefore, in their case made greater pro-
gress; as a result, the actual order of nature in the animal kingdom
is now sketched out in its main outlines in a stable and satisfactory
manner. It is only the boundaries of classes and their orders, of
families and genera, that are still abandoned to arbitrary opinion.

If schematic classifications are still found among animals, these
classifications are only minor, since they deal with objects belonging
to one class. Thus, the hitherto received classifications of fishes and
birds are still schematic classifications.

With regard to living bodies, the farther one descends from the
general to the particular the less constant become the characters
serving to determine affinities, and the more difficult to recognise
is the actual order of nature.

Classes.—The name class is given to the highest kind of general
divisions that are established in a kingdom. The further divisions
of these receive other names: we shall speak of them directly. The
more complete is our knowledge of the affinities between the objects
composing a kingdom, the better and more natural are the classes
established as the primary divisions of that kingdom, so long
as attention has been paid to recognised affinities in forming them.
Nevertheless, the boundaries of these classes, even the best of them,
are clearly artificial; they will therefore continue to undergo

ARTIFICIAL DEVICES 23

arbitrary variations at the hands of authors so long as naturalists
will not agree and submit themselves to certain general principles
on the subject.

Thus, even though the order of nature in a kingdom should be
thoroughly known, the classes which we are obliged to establish
in it will always be fundamentally artificial divisions.

It is true, especially in the animal kingdom, that several of these
divisions appear to be really marked out by nature herself; and it is
certainly difficult to believe that mammals, birds, etc., are not sharply
isolated classes formed by nature. This is none the less a pure illusion,
and a consequence of the limitation of our knowledge of existing
or past animals. The further we extend our observations the more
proofs do we acquire that the boundaries of the classes, even appar-
ently most isolated, are not unlikely to be effaced by our new discoveries.
Already the Ornithorhyncus and the Echidna seem to indicate the exist-
ence of animals intermediate between birds and mammals. How
greatly natural science would profit if the vast region of Australia

: and many others were better known to us! ,

Tf classes are the first kind of division that can be established in a
kingdom, it follows that the divisions which can be established among
the objects of one class cannot themselves be classes ; for it is obviously
inappropriate to set up class within class ; that, however, is just what
has been done: Brisson, in his Ornithologie, has divided the class of
birds into various special classes.

Just as nature is everywhere governed by laws, so too artifice should
be subjected to rules. If there are none, or if they are not followed,
its products will be vacillating and its purpose fail.

Some modern naturalists have introduced the custom of dividing a
class into several sub-classes, while others again have carried out the
idea even with genera; so that they make up not only sub-classes
but sub-genera as well. We shall soon reach not only sub-classes
but sub-orders, sub-families, sub-genera and sub-species. Now this
is a thoughtless misuse of artifice, for it destroys the hierarchy and
simplicity of the divisions, which had been set up by Linneus
and generally adopted.

The diversity of the objects belonging to a class either of animals or
plants is sometimes so great as to necessitate the formation of many
divisions and sub-divisions among the objects of that class; but it
is to the interest of science that artificial devices should always have
the greatest possible simplicity. Now that interest allows, no doubt,
of any divisions and sub-divisions that may be necessary; but it is
opposed to each division having a special denomination. A stop
must be put to the abuses of nomenclature; otherwise the nomen-

24 ZOOLOGICAL PHILOSOPHY

clature would become more difficult to understand than the objects
themselves.

Orders.—The name order should be given to the main divisions of
the first rank into which a class is broken up. If these divisions
leave scope for the formation of others by further sub-division, these
sub-divisions are no longer orders; and it would be very inappro-
priate to give them the name.

The class of molluscs, for example, are easily divided into two large
main groups, one having a head, eyes, etc., and reproducing by
copulation, while the other has no head, eyes, etc., and carry out no
copulation to reproduce themselves. Cephalic and acephalic molluscs
should be regarded as the two orders of that class; meanwhile, each
of these orders can be broken up into several remarkable groups.
Now this fact is no sufficient reason for giving the name order or
even sub-order to each of the groups concerned. These groups, there-
fore, into which orders are divided should be regarded as sections
or as large families, themselves susceptible of still further sub-
divisions.
' Let us maintain in our artifical devices the great simplicity and

beautiful hierarchy established by Linneus. If we are under the
necessity to make many sub-divisions of orders, that is to say, of the
principle divisions of a class, by all means let us make as many as
may be necessary, but do not let us assign to them any special
denomination.

The orders into which a class is divided should be determined
by the presence of important characters extending throughout the
objects comprised in each order; but no special name should be
assigned to them that is applicable to the objects themselves.

The same thing applies with regard to the sections that we have
to form among the orders of one class.

Families.—The name family is given to recognised parts of the
order of nature in either of the two kingdoms of living bodies. These
parts of the natural order are, on the one hand, smaller than classes
and even than orders, but, on the other hand, they are larger than
genera. But however natural families may be and however well
constituted their genera are according to their true affinities, the
boundaries of these families are always artificial. The more indeed
that the productions of nature are studied, and new ones observed,
the greater the continual variations in the boundaries of families
that are made by naturalists. Some divide one family into several
new ones, others combine several families into one, while others
again make additions to a family already known, increase it, and thus.
thrust back the boundaries which had been assigned to it.

ARTIFICIAL DEVICES 25

If all the races (so-called species) belonging to a kingdom of living
bodies were thoroughly known, as well as their true affinities, so that
the sorting out of these races and their allocation in various groups
were in conformity with their natural affinities, the classes, orders,
sections and genera would be families of different sizes, for all these
divisions would be larger or smaller parts of the natural order.

On such an assumption, nothing doubtless would be more difficult
than to assign the boundaries between these different divisions;
arbitrary opinion would produce incessant variation, and there would
be no agreement except where gaps in the series made clear demarca-
tions.

Fortunately for the practicability of the artifice which we have to
introduce into our classifications, there are many races of animals
and plants that are still unknown to us, and will probably remain so,
since insuperable obstacles are placed in our way by the places where
they live and other circumstances. The gaps thence arising in the
series, whether of animals or plants, will leave us for a long time still,
and perhaps for ever, the means of setting up the majority of the
divisions.

Custom and indeed necessity require that a special name should
be given to each family and to each genus so as to be applicable to
the objects it contains. It follows that alterations in the boundaries,
extent and determination of families will always cause a change in
their nomenclature.

Genera.—The name of genus is given to combinations of races or
so-called species that have been united on account of their affinities,
and constitute a number of small series marked out by characters
arbitrarily selected for the purpose.

When a genus is well made, all the races or species comprised in it~
resemble one another in their most essential and numerous characters.
They differ only among themselves in characters less important,
but sufficient to distinguish them.

Well made genera are thus really small families, that is to say, real
parts of the actual order of nature.

Now we have seen that the series to which we give the name of
family are liable to vary as to their boundaries and extent, according
to the opinions of authors who arbitrarily change their guiding
principles. In the same way the boundaries of genera are exposed
to infinite variation because different authors change at will the
characters employed to determine them. Now a special name has to
be assigned to each genus; and every change in the constitution
of a genus involves nearly always a change of name. It is difficult
therefore to exaggerate the injury done to natural science by

26 ZOOLOGICAL PHILOSOPHY

perpetual alterations of genera, which multiply synonymy, overburden
nomenclature, and make the study of these sciences difficult and
disagreeable.

When will naturalists agree to abide by general principles for uniform
guidance in the constitution of genera, etc., etc.? The natural
affinities, which they recognise among the objects which they have
brought together, mislead them nearly all into the belief that their
genera, families, orders and classes actually exist in nature. They
do not notice that the good series which they succeed in forming
by study of affinities do in truth exist in nature, for they are large
or small parts of her order, but that the lines of demarcation which
they are obliged to set up at intervals do not by any means so exist.

Consequently, genera, families, sections of various kinds, orders
and even classes are in truth artificial devices, however natural may
be the series which constitute these different groups. No doubt they
are necessary and have an obvious and indispensable utility ; but if
the advantages, which these devices bring, are not to be cancelled
by constant misuse, the constitution of every group must be in accord-
ance with principles and rules that naturalists once for all have agreed
to follow.

Nomenclature-—We come now to the sixth of the artificial devices
which have to be employed in natural science. By nomenclature
is meant the system of names assigned either to special objects,
such ag a race or a species, or to groups of these objects, such as a
genus, family or class.

Now nomenclature is confined to the names given to species, genera,
families and classes. It has therefore to be distinguished from that
other artificial device called technology, which refers solely to the
denominations applied to the parts of natural bodies.

“All the discoveries and observations of naturalists would
necessarily have fallen into oblivion and been lost to society, if the
objects observed and determined had not each received a name to serve
as a recognition mark when speaking of them or quoting them.”
(Dict. de Botanique, art. “‘ Nomenclature.’’)

It is quite clear that nomenclature in natural history is an artificial
device, and is a means that we have to resort to for fixing our ideas in
the sphere of natural observed productions, and to enable us to pass
on either these ideas or our observations on the objects concerned.

No doubt this artificial device should like the others be controlled
by settled rules that are generally adhered to; but I am bound to
remark that its universal misuse, of which complaints are so justly
made, arises principally from extrinsic causes which daily increase
also in the other artificial devices already named.

ARTIFICIAL DEVICES 27

In fact, lack of settled rules as to the formation of genera, families
and even classes, exposes these artificial devices to all the vagaries
of arbitrary judgment; nomenclature undergoes a continuous succession
of changes. It never can be fixed so long as this lack of rules con-
tinues ; and synonymy, already immense, will continue to grow and
become more and more incapable of repairing a confusion which
annihilates all the advantages of science.

This would never have happened if it had been recognised that
all the lines of demarcation in the series of objects composing a king-
dom of living bodies are really artificial, except those which result
from gaps to be filled. But this was not perceived: there was not
even a suspicion of it. Almost to the present day naturalists have
had no further object in view than that of setting up distinctions.
Here is evidence of what I mean:

“In fact, in order to procure and keep for ourselves the services of
all natural bodies within our reach, that we can subordinate to our
needs, it was felt that an exact and precise determination of the
characters of each body was necessary, and consequently that the
details of organisation, structure, form, proportion, etc., etc., should
be sought out and determined, so that they could for all time be
recognised and distinguished from one another. This is what
naturalists are now doing up to a certain point.

“This part of the work of naturalists has made the most advance.
Immense efforts have rightly been made for about a century and a
half to perfect it, because it assists us to a knowledge of what
has been newly observed, and serves as reminder of what was
previously known. Moreover, it fixes our knowledge with regard
to objects whose properties are or will hereafter become of use
to us.

“But naturalists attach too much weight to forming lines of
demarcation in the general series both of animals and plants; they
devote themselves almost exclusively to this kind of work, without
considering it under its true aspect or coming to any agreement as
to the framing of settled rules in this great enterprise for fixing the
principles of determination. Hence the intrusion of many abuses ;
for each one arbitrarily changes the principles for the formation of
classes, orders and genera: and numerous different groupings are
incessantly being set before the public. Genera undergo continual
variation without limit, and the names given to nature’s pro-
ductions are constantly being changed as a result of this thoughtless
proceeding.

“As a result, synonomy in natural history is now terribly wide-
spread. Science every day becomes more obscure ; she is surrounded

28 ZOOLOGICAL PHILOSOPHY

by almost insurmountable difficulties; and the finest effort of man
to set up the means of recognising and distinguishing the works of
nature is changed into an immense maze, into which most men
naturally hesitate to plunge.’ (Discours d’ouvert. du cours de 1806,
pp. 5 and 6.)

Here we have a picture of the results of omitting to distinguish
what really belongs to artifice from what is in nature, and of not having
endeavoured to discover rules for the less arbitrary determination
of the divisions which have to be established.

CHAPTER II.
IMPORTANCE OF THE CONSIDERATION OF AFFINITIES.

Among living bodies the name affinity has been given to features of
analogy or resemblance between two objects, that are compared in
their totality, but with special stress on the most essential parts.
The closer and more extensive the resemblance, the greater the
affinities. They indicate a sort of kinship between the living bodies
which exhibit them; and oblige us in our classification to place
these bodies in a proximity proportional to their affinities.

How great has been the progress of natural science since serious
attention began to be given to affinities, and especially since their
true underlying principles have been determined !

Before this change, our botanical classifications were entirely at
the mercy of arbitrary opinion, and of artificial systems of any
author. In the animal kingdom the invertebrate animals comprising
the larger part of all known animals were classified into the most
heterogeneous groups, some under the name of insects, some under the
name of worms; where the animals included are from the point of
view of affinity widely different from one another.

Happily this state of affairs is now changed; and, henceforth, if
the study of natural history is continued, its progress is assured.

The principle of natural affinities removes all arbitrariness from
our attempts at a methodical classification of organised bodies. We
have here the law of nature which should guide us to the natural
method. Naturalists are forced to agree as to the rank which they
assign, firstly to the main groups of their classification, and after-
wards to the individuals of which these groups are composed ; finally,
they are obliged to follow the actual order observed by nature in
giving birth to her productions.

Thus, everything that concerns the affinities of the various animals
should be the chief object of our researches, before making any division
or classification among them.

30 ZOOLOGICAL PHILOSOPHY

The question of affinities does not apply only to species; for we
have also to fix the general affinities of all the orders into which groups
are united or divided from the comparative point of view.

Affinities, although possessing very different values according to the
importance of the parts exhibiting them, can none the less be extended
to the conformation of the external parts. If the affinities are so great
that not only the essential parts, but also the external parts present
no determinable difference, then the objects in question are only
individuals of the same species. If on the other hand, notwith-
standing a large degree of affinity, the external parts exhibit appreci-
able differences, though less than the essential resemblances; then
the objects in question are different species of the same genus.

The important study of affinities is not limited to a comparison
of classes, families, or even of species; it includes also a considera-
tion of the parts of which individuals are composed. By comparison
together of corresponding parts we obtain a firm basis for recognis-
ing either the identity of individuals of the same race or the difference
between individuals of distinct races.

It has, in truth, been noted that the proportions and relations of
the parts of all individuals composing a species or a race always
remain the same, and so appear to be preserved forever. From this
it has been rightly inferred that, by examining detached parts of an
individual, one could decide to what species, old or new, these parts
belong.

This power is very favourable to the progress of knowledge at the
present time. But the conclusions drawn from it can only hold good
for a limited period; since the races themselves undergo changes
in their parts, in proportion to any considerable change in the circum-
stances: which affect them. As a matter of fact, since these changes
only take place with an extreme slowness, which makes them always
imperceptible, the proportions and relations of the parts always appear
the same to the observer, who does not really see them change.
Hence, when he comes across any species which have undergone
these changes, he imagines that the differences which he perceives
have always existed.

It is none the less quite true that by a comparison of corresponding
parts in different individuals, their affinities, nearer or more remote,
can be easily and certainly determined. It can therefore be known
whether these parts belong to individuals of the same race or of
different races.

It is only the general inference that is unsound, having been drawn
too hastily. This I shall have more than one opportunity of proving
in the course of the present work.

IMPORTANCE OF AFFINITIES 31

Affinities are always incomplete when they apply only in an isolated
case; that is to say, when they are decided from an examination
of a single part taken by itself. But, although incomplete, the value
of affinities based upon a single part depends upon the extent to which
the part from which they are taken is essential, and vice versa.

There are then determinable differences among affinities, and various
degrees of importance among the parts which display them; in
fact, the knowledge of affinities would have had no application or
utility unless the more important parts of living bodies had been
distinguished from the less important, and unless a principle had been
found for estimating the true values of these important parts.

The most important parts for exhibiting the chief affinities are,
among animals, the parts essential to the maintenance of life, and
among plants, the parts essential to reproduction.

In animals, therefore, it is always the internal organisation that will
guide us in deciding the chief affinities. And in plants, it will be
in the parts of fructification that affinities will be sought.

But in both cases the parts most important for seeking out affinities
vary. The only principle to be used for determining the importance
of any part, without arbitrary assumptions, consists in enquiring
either how much use nature makes of it, or else the importance to the
animal of the function of that part.

Among animals, whose affinities are mainly determined by their
internal organisation, three kinds of special organs have rightly been
chosen from among the others as the most suitable for disclosing
the most important affinities. They are, in order of importance, as
follows :

(1) The organ of feeling. The nerves which meet at a centre, either
single as in animals with a brain, or multiple as in those with a
ganglionic longitudinal cord.

(2) The organ of respiration. The lungs, gills and tracheae.

(3) The organ of circulation. The arteries and veins, which usually
have a centre of action in the heart.

The first two of these organs are more widely used by nature, and
therefore more important than the third, that is to say, the organ of
circulation ; for the latter disappears in the series after the crustaceans,
while the two former extend to animals of the two classes which follow
the crustaceans.

Finally, of the two first, the organ of feeling has the more import-
ance from the point of view of affinities, for it has produced the most
exalted of animal faculties, and moreover without that organ muscular

activity could not take place.
If I were to'refer to plants, among which the reproductive parts

32 ZOOLOGICAL PHILOSOPHY

alone are of importance in deciding affinities, I should set forth these
parts in their order of importance as follows :

(1) The embryo, its accessories (cotyledons, perisperm) and the
seed which contains it.

(2) The sexual parts of flowers, such as the pistil and stamens.

(3) The envelopes of the sexual parts; the corolla, calyx, etc.

(4) The pericarp, or envelope of the seed.

(5) The reproductive bodies which do not require fertilisation.

These generally received principles give to natural science a coherence
and solidity that it did not previously possess. Affinities are no longer
at the mercy of changes of opinion ; our general classifications become
necessary inferences; and according as we perfect them by this
method they approach ever more closely to the actual order of
nature.

It was, in fact, due to the perception of the importance of affinities that
the attempts of the last few years were originated to determine what
is called the natural method; a method which is only a tracing by
man of nature’s procedure in bringing her productions into existence.

No importance is now attached in France to those artificial systems
which ignore the natural affinities among objects; for these systems
give rise to divisions and classifications harmful to the progress of
natural knowledge.

With regard to animals, there is no longer any doubt that it is purely
from their organisation that their natural affinities can be determined.
It is, in consequence, chiefly from comparative anatomy that zoology
will obtain the data for such determination. But we should pay
more attention to the facts collected in the works of anatomists than
to the inferences which they draw from them ; for too often they hold
views which might mislead us and prevent us from grasping the
laws and true plan of nature. It seems to be the case that whenever
man observes any new fact he is always condemned to rush headlong
into error in attempting to explain it; so fertile is his imagination
in the creation of ideas. He is not sufficiently careful to guide his
judgment by the general principles derived from other facts and
observations.

When we consider the natural affinities between objects, and make
a sound estimate of them, we can combine species on this principle,
and associate groups with definite boundaries forming what are
called genera. Genera can be similarly associated on the principle of
affinities, and united into higher groups forming what are called
families. These families, associated in the same way and on the same
principle, make up orders. These again are the primary divisions of
classes, while classes are the chief divisions of each kingdom.

IMPORTANCE OF AFFINITIES 33

We must then be guided everywhere by natural affinities in composing
the groups which result by dividing each kingdom into classes, each
class into orders, each order into sections or families, each family
nee genera, and each genus into different species if there is occasion

or it.

There is thorough justification for the belief that the complete series
of beings making up a kingdom represents the actual order of nature,
when it is classified with direct reference to affinities; but, as I have
already pointed out, the different kinds of divisions which have to
be set up in that series to help us to distinguish objects with greater
ease do not belong to nature at all. They are truly artificial although
they exhibit natural portions of the actual order instituted by
nature.

It should be added that in the animal kingdom, affinities should
be decided mainly from a study of organisation. The principles
employed for settling these affinities should not admit of the smallest
doubt. We shall thus obtain a solid basis for zoological philosophy.

It is known that every science must have its philosophy, and that
it cannot make real progress in any other way. It is in vain that
naturalists fill their time in describing new species, in grasping all
the shades and small details of their varieties, in enlarging the immense
list of catalogued species, in establishing genera, and in making incessant
changes in the principles which they use. If the philosophy of science
is neglected her progress will be unreal, and the entire work will
Temain imperfect.

It is indeed only since the attempt has been made to fix the extent
of affinity between the productions of nature that natural science
has obtained any coherence in its principles, and a philosophy to make
it really a science.

What progress towards perfection is made every day in our classi-
fications since they were founded upon the study of affinities !

It was through the study of affinities that I recognised that in-
fusorian animals could no longer be put in the same class as polyps ;
that radiarians also should not be confused with polyps; and that
soft creatures, such as medusae and neighbouring genera, which
Linneus and even Bruguiére placed among the molluscs, were essen-
tially allied to the echinoderms, and should form a special class with
them.

It was again the study of affinities which convinced me that worms
were a separate group, comprising animals very different from
radiarians, and still more from polyps ; that arachnids could no longer
be classed with insects, and that cirrhipedes were neither annelids nor

molluscs.
c

34 ZOOLOGICAL PHILOSOPHY

Finally, it was through the study of affinities that I succeeded in
effecting a number of necessary alterations even in the classification
of molluscs, and that I recognised that the pteropods, which are closely
allied to but distinct from the gastropods, should not be placed
between the gastropods and the cephalapods, but between the ace-
phalic molluscs and the gastropods; since these pteropods, like all
acephalic animals, have no eyes and are almost without a head, not
even excepting Hyalea. (V. the special classification of molluscs
in Chap. VIII, at the end of Part I.)

When the study of affinities among the different known families
of plants has made us better acquainted with the rank held by each
in the general series, then the classification of these living bodies
will leave nothing more to arbitrary judgment, but will come more
closely into conformity with the actual order of nature.

The study of the affinities among observed objects is thus clearly
so important that it should now be regarded as the chief instrument
for the progress of natural science.

CHAPTER III. ==
OF SPECIES AMONG LIVING BODIES AND THE IDEA THAT WE
SHOULD ATTACH TO THAT WORD.

Ir is not a futile purpose to decide definitely what we mean by the
so-called species among living bodies, and to enquire if it is true that
species are of absolute constancy, as old as nature, and have all existed
from the beginning just as we see them to-day ; or if, as a result of
changes in their environment, albeit extremely slow, they have not
in course of time changed their characters and shape.

The solution of this question is of importance not only for our
knowledge of zoology and botany, but also for the history of the
world.

T shall show in one of the following chapters that every species has
derived from the action of the environment in which it has long been
placed the habits which we find in it. These habits have themselves
influenced the parts of every individual in the species, to the extent
of modifying those parts and bringing them into relation with the
acquired habits. Let us first see what is meant by the name of species.

Any collection of like individuals which were produced by others
similar to themselves is called a species.

This definition is exact ; for every individual possessing life always
resembles very closely those from which it sprang ; but to this definition
is added the allegation that the individuals composing a species never
vary in their specific characters, and consequently that species have
an absolute constancy in nature.

It is just this allegation that I propose to attack, since clear proofs
drawn from observation show that it is ill-founded.

The almost universally received belief is that living bodies con-
stitute species distinguished from one another by unchangeable
characteristics, and that the existence of these species is as old as
nature herself. This belief became established at a time when no
sufficient observations had been taken, and when natural science

36 ZOOLOGICAL PHILOSOPHY

was still almost negligible. It is continually being discredited for
those who have seen much, who have long watched nature, and who
have consulted with profit the rich collections of our museums.

Moreover, all those who are much occupied with the study of natural
history, know that naturalists now find it extremely difficult to decide
what objects should be regarded as species.

They are in fact not aware that species have really only a constancy
relative to the duration of the conditions in which are placed the
individuals composing it; nor that some of these individuals have
varied, and constitute races which shade gradually into some other
neighbouring species. Hence, naturalists come to arbitrary decisions
about individuals observed in various countries and diverse con-
ditions, sometimes calling them varieties and sometimes species. The
work connected with the determination of species therefore becomes
daily more defective, that is to say, more complicated and confused.

It has indeed long been observed that collections of individuals
exist which resemble one another in their organisation and in the
sum total of their parts, and which have kept in the same condition
from generation to generation, ever since they have been known.
So much so that there seemed a justification for regarding any col-
lection of like individuals as constituting so many invariable species.
Now attention was not paid to the fact that the individuals of the
species perpetuate themselves without variation only so long as the
conditions of their existence do not vary in essential particulars.
Since existing prejudices harmonise well with these successive
regenerations of like individuals, it has been imagined that every
species is invariable and as old as nature, and that it was specially
created by the Supreme Author of all existing things.

Doubtless, nothing exists but by the will of the Sublime Author
of all things, but can we set rules for him in the execution of his will,
or fix the routine for him to observe? Could not his infinite power
create an order of things which gave existence successively to all that
we see as well as to all that exists but that we do not see ?

Assuredly, whatever his will may have been, the immensity of his
power is always the same, and in whatever manner that supreme
will may have asserted itself, nothing can diminish its grandeur.

I shall then respect the decrees of that infinite wisdom and con-
fine myself to the sphere of a pure observer of nature. If I succeed
in unravelling anything in her methods, I shall say without fear of
error that it has pleased the Author of nature to endow her with that
faculty and power.

The idea formed of species among living bodies was quite simple,
easy to understand, and seemed confirmed by the constancy in the

OF SPECIES 37

shapes of individuals, perpetuated by reproduction or generation.
Such are a great number of these alleged species that we see every day.

Meanwhile, the farther we advance in our knowledge of the various
organised bodies which cover almost every part of the earth’s surface,
the greater becomes our difficulty in determining what should be
regarded as a species, and still more in finding the boundaries and
distinctions of genera.

According as the productions of nature are collected and our
museums grow richer, we see nearly all the gaps filled up and the lines
of demarcation effaced. We find ourselves reduced to an arbitrary
decision which sometimes leads us to take the smallest differences
of varieties and erect them into what we call species, and sometimes
leads us to describe as a variety of some species slightly differing
individuals which others regard as constituting a separate species.

Let me repeat that the richer our collections grow, the more proofs
do we find that everything is more or less merged into everything
else, that noticeable differences disappear, and that nature usually
leaves us nothing but minute, nay puerile, details on which to found
our distinctions.

How many genera there are both among animals and plants, among
which the number of species referred to them is so great that the study
and determination of these species are well nigh impracticable! The
species of these genera, arranged in series according to their natural
affinities, exhibit such slight differences from those next them as to
coalesce with them. These species merge more or less into one another,
so that there is no means of stating the small differences that dis-
tinguish them.

It is only those who have long and diligently studied the question

‘of species, and who have examined rich collections, that are in a
position to know to what extent species among living bodies merge
into one another. And no one else can know that species only appear
to be isolated, because others are lacking which are close to them
but have not yet been collected.

I do not mean that existing animals form a very simple series,
regularly graded throughout ; but I do mean that they form a branch-
ing series, irregularly graded and free from discontinuity, or at least
once free from it. For it is alleged that there is now occasional dis-
continuity, owing to some species having been lost. It follows that
the species terminating each branch of the general series are connected
on one side at least with other neighbouring species which merge into
them. This I am now able to prove by means of well-known facts.

I require no hypothesis or supposition; I call all observing
naturalists to witness.

38 ZOOLOGICAL PHILOSOPHY

Not only many genera but entire orders, and sometimes even classes,
furnish instances of almost complete portions of the series which I
have just indicated.

When in these cases the species have been arranged in series, and
are all properly placed according to their natural affinities, if you
choose one, and then, jumping over several others, take another a little
way off, these two species when compared will exhibit great differ-
ences. It is thus in the first instance that we began to see such of
nature’s productions as lay nearest to us. Generic and specific dis-
tinctions were then quite easy to establish ; but now that our collec-
tions are very rich, if you follow the above-mentioned series from the
first species chosen to the second, which is very different from it, you
reach it by slow gradations without having observed any noticeable
distinctions.

I ask, where is the experienced zoologist or botanist who is not
convinced of the truth of what I state ?

How great the difficulty now is of studying and satisfactorily
deciding on species among that multitude of every kind of polyps,
radiarians, worms, and especially insects, such as butterflies, Phalaena,
Noctua, Tinea, flies, Ichnewmon, Curculio, Cerambiz, chafers, rose-
chafers, etc.! These genera alone possess so many species which
merge indefinably into one another.

What a swarm of mollusc shells are furnished by every country
and every sea, eluding our means of distinction and draining our
resources.

Consider again, fishes, reptiles, birds and even mammals; you
will see that except for gaps still to be filled, neighbouring species
and even genera are separated by the finest differences, so that we have
scarcely any foothold for setting up sound distinctions.

Is there not an exactly similar state of affairs in the case of botany,
which deals with the other series, consisting of plants ?

How great indeed are the difficulties of the study and determina-
tion of species in the genera Lichen, Fucus, Carex, Poa, Piper,
Euphorbia, Erica, Hieracium, Solanum, Geranium, Mimosa, etc., etc.

When these genera were constituted only a small number of species
belonging to them were known, and it was then easy to distinguish
them; but now that nearly all the gaps are filled, our specific
differences are necessarily minute and usually inadequate.

Let us see what are the causes which have given rise to this un-
doubted state of affairs ; let us see if nature affords any explanation,
and whether observation can help us.

We learn from a number of facts that, according as the individuals
of one of our species change their abode, climate, habits, or manner

OF SPECIES 39

of life, they become subject to influences which little by little alter the
consistency and proportions of their parts, their shape, properties and
even their organisation ; so that in course of time everything in them
shares in these mutations.

In the same climate, very different habitats and conditions at first
merely cause variations in the individuals exposed to them; but
in course of time the continued change of habitat in the individuals
of which I speak, living and reproducing in these new conditions,
induces alterations in them which become more or less essential to
their being; thus, after a long succession of generations these in-
dividuals, originally belonging to one species, become at length
transformed into a new species distinct from the first.

Suppose, for example, that the seeds of a grass or any other plant
that grows normally in a damp meadow, are somehow conveyed
first to the slope of a neighbouring hill where the ground although
higher is still rich enough to allow the plant to maintain its existence.
Suppose that then, after living there and reproducing itself many times,
it reaches little by little the dry and almost barren ground of a mountain
side. If the plant succeeds in living there and perpetuating itself
for a number of generations, it will have become so altered that botanists
who come across it will erect it into a separate species.

The same thing happens in the case of animals that are forced
by circumstances to change their climate, habits, and manner of
life: but in their case more time is required to work any noticeable
change than in the case of plants.

The idea of bringing together under the name of species a collection
of like individuals, which perpetuate themselves unchanged by re-
production and are as old as nature, involved the assumption that the
individuals of one species could not unite in reproductive acts with
individuals of a different species.

Unfortunately, observation has proved and continues every day to
prove that this assumption is unwarranted ; for the hybrids so common
among plants, and the copulations so often noticed between animals
of very different species, disclose the fact that the boundaries between
these alleged constant species are not so impassable as had been
imagined.

It is true that often nothing results from these strange copulations,
especially when the animals are very disparate; and when any-
thing does happen the resulting individuals are usually infertile ;
but we also know that when there is less disparity these defects do not
occur. Now this cause is by itself sufficient gradually to create
varieties, which then become races, and in course of time constitute
what we call species.

40 ZOOLOGICAL PHILOSOPHY

To assist us to a judgment as to whether the idea of species has
any real foundation, let us revert to the principles already set forth ;
they show :

(1) That all the organised bodies of our earth are true productions
of nature, wrought successively throughout long periods of time.

(2) That in her procedure, nature began and still begins by fashion-
ing the simplest of organised bodies, and that it is these alone which
she fashions immediately, that is to say, only the rudiments of
organisation indicated in the term spontaneous generation.

(3) That, since the rudiments of the animal and plant were
fashioned in suitable places and conditions, the properties of a com-
mencing life and established organic movement necessarily caused
a gradual development of the organs, and in course of time produced
diversity in them as in the limbs.

(4) That the property of growth is inherent in every part of the
organised body, from the earliest manifestations of life; and then
gave rise to different kinds of multiplication and reproduction, so
that the increase of complexity of organisation, and of the shape and
variety of the parts, has been preserved.

(5) That with the help of time, of conditions that necessarily were
favourable, of the changes successively undergone by every part of
the earth’s surface, and, finally, of the power of new conditions and
habits to modify the organs of living bodies, all those which now exist
have imperceptibly been fashioned such as we see them.

(6) That, finally, in this state of affairs every living body underwent
greater or smaller changes in its organisation and its parts; so that what
we call species were imperceptibly fashioned among them one after
another and have only a relative constancy, and are not as old as nature.]

But objections may be raised to the allegation that nature has
little by little fashioned the various animals known to us by the aid
of much time and an infinite variation of environment. It may be
asked whether this allegation is not refuted by the single fact of the
wonderful variety observed in the instinct of various animals, and in
the marvellous skill of all kinds which they exhibit.

Will anyone, it may be asked, venture to carry his love of system
so far as to say that nature has created single-handed that astonishing
diversity of powers, artifice, cunning, foresight, patience and skill,
of which we find so many examples among animals? Is not what
we see in the single class of insects far more than enough to convince
us that nature cannot herself produce so many wonders; and to
compel the most obstinate philosopher to recognise that the will of the
Supreme Author of all things must be here invoked, and could alone
suffice for bringing into existence so many wonderful things ? C

OF SPECIES 41

No doubt he would be a bold man, or rather a complete lunatic,
who should propose to set limits to the power of the first Author of all
things; but for this very reason no one can venture to deny that
this infinite power may have willed what nature herself shows us it
has willed.

This being so, if I find that nature herself works all the wonders
just mentioned ; that she has created organisation, life and even
feeling, that she has multiplied and diversified within unknown limits
the organs and faculties of the organised bodies whose existence she
subserves or propagates; that by the sole instrumentality of needs,
establishing and controlling habits, she has created in animals the
fountain of all their acts and all their faculties, from the simplest
to instinct, to skill, and finally to reason; if I find all this, should I
not recognise in this power of nature, that is to say in the order of exist-
ing things, the execution of the will of her Sublime Author, who was
able to will that she should have this power ?

Shall I admire the greatness of the power of this first cause of every-
thing any the less if it has pleased him that things should be so,
than if his will by separate acts had occupied itself and still continued
to occupy itself with the details of all the special creations, variations,
developments, destructions and renewals, in short, with all the muta-
tions which take place at large among existing things ?

Now I hope to prove that nature possesses the necessary powers.
and faculties for producing herself that so much excite our wonder.

The objection is still raised however that everything we see in living—~
bodies indicates an unchangeable constancy in the preservation of
their form. It is held that all animals whose history has come down
to us for two or three thousand years have always been the same, and
neither lost nor acquired anything in the perfection of their organs
and the shape of their parts.

Not only had this apparent stability passed for an undoubted fact,
but an attempt has recently been made to find special proofs of it
in a report on the natural history collections brought from Egypt
by M. Geoffroy. The authors of the report express themselves as
follows : _

“The collection has in the first place this peculiarity, that it may
be said to contain animals of all periods. It has long been asked
whether species change their shape in the course of time. This
question, apparently so futile, is none the less necessary for the history
of the world, and consequently for the solution of innumerable other
questions which are not foreign to the gravest subjects of human
worship.

“We have never been in so good a position to settle this question,

42 ZOOLOGICAL PHILOSOPHY

in so far as concerns a large number of remarkable species and some
thousands that are not remarkable. It appears as though the super-
stition of the ancient Egyptians were inspired by nature for the purpose
of leaving a record of her history.”

“Tt is impossible,” continue the authors of the report, “‘ to control
our flights of imagination, on seeing still preserved with its smallest
bones and hair, perfectly recognisable, an animal which two or three
thousand years ago had in Thebes or Memphis its priests and altars.
But without giving rein to all the ideas suggested by this approach
to antiquity, we shall confine ourselves to the announcement that
this part of M. Geoffroy’s collection shows that these animals are
exactly similar to those of to-day.” (Annales du Muséum d Hist.
natur., vol. i. pp. 235 and 236.)

I do not refuse to believe in the close resemblance of these animals
with individuals of the same species living to-day. Thus, the birds
that were worshipped and embalmed by the Egyptians two or three
thousand years ago are still exactly like those which now live in that
country.

It would indeed be very odd if it were otherwise ; for the position
and climate of Egypt are still very nearly what they were in those
times. Now the birds which live there, being still in the same conditions
as they were formerly, could not possibly have been forced into a change
of habits.

Furthermore, it is obvious that birds, since they can travel so easily
and choose the places which suit them, are less liable than many other
animals to suffer from variations in local conditions, and hence
less hindered in their habits.

Indeed there is nothing in the observation now cited that is con-
trary to the principles which I have set forth on this subject; or
which proves that the animals concerned have existed in nature for
all time; it proves only that they inhabited Egypt two or three
thousand years ago; and every man who has any habit of reflection
and at the same time of observing the monuments of nature’s
antiquity will easily appreciate the import of a duration of two or three
thousand years in comparison with it.

ence we may be sure that this appearance of stability of the
things in nature will by the vulgar always be taken for reality;
because people in general judge everything with reference to themselves.

For the man who forms his judgment only with reference to the
changes that he himself perceives, the eras of these mutations are
stationary states which appear to him to be unlimited, on account
of the shortness of the existence of individuals of his own species.

OF SPECIES : 43

Moreover, we must remember that the records of his observations,
and the notes of facts which he has been able to register, only extend
back a few thousand years; which is a time infinitely great with
reference to himself, but very small with reference to the time occupied
by the great changes occurring on the surface of the earth. Every-
thing seems to him to be stable in the planet which he inhabits ;
and he is led to repudiate the signs which exist everywhere in the
monuments heaped up around him, or buried in the soil which he
tramples underfoot.

Magnitudes are relative both in space and time: let man take that
truth to heart, and he will then be more reserved in his judgments
on thestability which he attributes to the state of things that he observes
in nature. (See the Appendix, p. 141, of my Recherches sur les corps
vivants.)

In order to admit the imperceptible changing of species, and the
modifications which their individuals undergo according as they
are forced to change their habits and contract new ones, we are
not reduced to a mere consideration of the very short spaces of
time comprised in our observations; for, in addition to this induc-
tion, a number of facts collected many years ago throw enough light
on the question to free it from doubt; and I can now affirm that our
observations are so far advanced that the solution sought for is
patent.

Indeed not only do we know the results of anomalous fertilisations,
but we also now know positively that a compulsory and sustained
alteration in the habitats and manner of life of animals works after
a sufficient time a very remarkable mutation in the individuals exposed
to it.

Consider the animal which normally lives in freedom in plains
where it habitually exerts itself by swift running; or the bird which
is compelled by its needs to pass incessantly through large spaces
in the air. When they find themselves imprisoned, the one in the
dens of a menagerie or in our stables, the other in our cages or back
yards, they undergo in course of time striking alterations, especially
after a succession of generations in their new state.

The former loses a great part of his swiftness and agility ; his body
thickens, the strength and subtleness of his limbs diminish, and his
faculties are no longer the same; the latter becomes heavy, can
scarcely fly, and takes on more flesh in all his parts.|

In Chapter VI. of this Part I., I shall have occasion to prove by
well-known facts the power of changes of conditions for giving to
animals new needs, and leading them on to new actions; the power
of new actions when repeated to induce new habits and inclinations ;

44 ZOOLOGICAL PHILOSOPHY

finally, the power resulting from the more or less frequent use of any
organ to modify that organ either by strengthening, developing and
increasing it, or by weakening, reducing, attenuating it, and even
making it disappear.

With regard to plants, the same thing may be seen as a result of
new conditions on their manner of life and the state of their parts ;
so that we shall no longer be astonished to see the considerable changes
that we have brought about in those that we have long cultivated.

Thus, among living bodies, nature, as I have already said, definitely
contains nothing but individuals which succeed one another by
reproduction and spring from one another; but the species among
them have only a relative constancy and are only invariable tem-
porarily.

Nevertheless, to facilitate the study and knowledge of so many
different bodies it is useful to give the name of species to any col-
lection of like individuals perpetuated by reproduction without change,
so long as their environment does not alter enough to cause varia-
tions in their habits, character and shape.

eye ee
OF THE SpEcIES ALLEGED TO BE Lost.

I am still doubtful whether the means adopted by nature to ensure

the preservation of species or races have been so inadequate that entire
races are now extinct or lost.
“Yet the fossil remains that we find buried in the soil in so many
different places show us the remains of a multitude of different animals
which have existed, and among which are found only a very small
number of which we now know any living analogues exactly alike.

Does this fact really furnish any grounds for inferring that the species
which we find in the fossil state, and of which no living individual
completely similar is known to us, no longer exist in nature? There
are many parts of the earth’s surface to which we have never pene-
trated, many others that men capable of observing have merely
passed through, and many others again, like the various parts of the
sea-bottom, in which we have few means of discovering the animals
living there. The species that we do not know might well remain
hidden in these various places.

If there really are lost species, it can doubtless only be among the
large animals which live on the dry parts of the earth; where man
exercises absolute sway, and has compassed the destruction of all
the individuals of some species which he has not wished to preserve
or domesticate. Hence arises the possibility that animals of the genera
Palaeotherium, Anoplotherium, Megaloniz, Megatherium, Mastodon,
of M. Cuvier, and some other species of genera previously known,

OF SPECIES 45

are no longer extant in nature: this however is nothing more than
a possibility.

But animals living in the waters, especially the sea waters, and
in addition all the races of small sizes living on the surface of the earth
and breathing air, are protected from the destruction of their species
by man. Their multiplication is so rapid and their means of evading
pursuit or traps are so great, that there is no likelihood of his being
able to destroy the entire species of any of these animals.

It is then only the large terrestrial animals that are liable to exter-
mination by man. This extermination may actually have occurred ;
but its existence is not yet completely proved.

Nevertheless, among the fossil remains found of animals which
existed in the past, there are a very large number belonging to animals
of which no living and exactly similar analogue is known ; and among
these the majority belong to molluscs with shells, since it is only the
shells of these animals which remain to us.

Now, if a quantity of these fossil shells exhibit differences which
prevent us, in accordance with prevailing opinion, from regarding
them as the representatives of similar species that we know, does it
necessarily follow that these shells belong to species actually lost? Why,
moreover, should they be lost, since man cannot have compassed their
destruction ? May it not be possible on the other hand, that the fossils
in question belonged to species still existing, but which have changed
since that time and become converted into the similar species that we
now actually find. |The following consideration, and our observations
throughout this work, will give much probability to such an assumption.

Every qualified observer knows that nothing on the surface of the
earth remains permanently in the same state. Everything in time
undergoes various mutations, more or less rapid according to the
nature of the objects and the conditions; elevated ground is
constantly being denuded by the combined action of the sun, rain-
waters and yet other causes; everything detached from it is carried
to lower ground ; the beds of streams, of rivers, even of seas change
in shape and depth, and shift imperceptibly ; in short, everything on
the surface of the earth changes its situation, shape, nature and appear-
ance, and even climates are not more stable.

Now I shall endeavour to show that variations in the environment
induce changes in the needs, habits and mode of life of living beings,
and especially of animals; and that these changes give rise to modi-
fications or developments in their organs and the shape of their parts.
Tf this is so, it is difficult to deny that the shape or external characters
of every living body whatever must vary imperceptibly, although
that variation only becomes perceptible after a considerable time]

46 ZOOLOGICAL PHILOSOPHY

Let us then no longer be astonished that among the numerous fossils
found in all the dry parts of the world, and constituting the remains
of so many animals which formerly existed, there are so few of which
we recognise the living representatives.

What we should wonder at, on the contrary, is finding amongst
these numerous fossil remains of once living bodies, any of which the
still existing analogues are known to us. This fact, proved by our
collections of fossils, suggests that the fossil remains of animals whose
living analogues we know are the least ancient fossils. The species
to which each of them belongs doubtless has not had time to undergo

——variation. MO

Naturalists who did not perceive the changes undergone by most
animals in course of time tried to explain the facts connected with
fossils, as well as the commotions known to have occurred in different
parts of the earth’s surface, by the supposition of a universal
catastrophe which took place on our globe. They imagined that
everything had been displaced by it, and that a great number of the
species then existing had been destroyed.

Unfortunately this facile method of explaining the operations of
nature, when we cannot see their causes, has no basis beyond the
imagination which created it, and cannot be supported by proof.

Local catastrophes, it is true, such as those produced by earth-
quakes, volcanoes and other special causes are well known, and we
can observe the disorder ensuing from them.

But why are we to assume without proof a universal catastrophe,
when the better known procedure of nature suffices to account for
all the facts which we can observe ?

Consider on the one hand that in all nature’s works nothing is done
abruptly, but that she acts everywhere slowly and by successive
stages ; and on the other hand that the special or local causes of dis-
orders, commotions, displacements, etc., can account for everything
that we observe on the surface of the earth, while still remaining subject
to nature’s laws and general procedure. It will then be recognised
that there is no necessity whatever to imagine that a universal
catastrophe came to overthrow everything, and destroy a great part
of nature’s own works. |

I have said enough on a subject which presents no difficulty. Let
us now consider the general principles and essential characters of
animals,

CHAPTER IV.
GENERAL PRINCIPLES CONCERNING ANIMALS.

ANIMALS in general are living beings with very curious properties,
well calculated to astonish us and excite our study. These beings,
infinitely varied in shape, organisation, and faculties, are capable of
moving themselves or some of their parts without the impulse of any
movement from without. Their irritability is due to an exciting
cause which in some originates from within, while in others it comes
entirely from without. Most of them possess the property of loco-
motion, and all have parts that are highly irritable.

We find that in their movements some crawl, walk, run or leap;
others fly, rising into the atmosphere and passing through wide spaces ;
others again live in the waters and swim about there freely.

Animals are not, like plants, able to find close by within their reach
the material on which they feed; and the predatory animals are
actually obliged to go forth and to hunt, chase and seize their prey.
It was necessary therefore that they should have the power of motion
and even of locomotion, in order to procure the food which they
require.

Moreover, those among animals which multiply by sexual repro-
duction are not hermaphrodite enough to be sufficient to themselves.
Hence it was farther necessary that they should be able to travel
about for the purpose of effecting acts of fertilisation, and that the
environment should provide facilities for it to those which, like
oysters, cannot change their position.

Thus the needs of animals have endowed them with the property
of moving parts of their bodies, and of carrying out locomotion which
subserves their own survival and that of their races.

In Part II. we shall enquire into the origin of this extraordinary
faculty, as of the other important faculties found among them ;
but it suffices at present to draw attention to certain obvious

points.

48 ZOOLOGICAL PHILOSOPHY

(1) Some only move themselves or their parts when their irrita-
bility has been stimulated; but they experience no feeling: these
are the most imperfect animals ;

(2) Others, in addition to the movements that their parts can
undergo through stimulated irritability are capable of experiencing
sensations, and possess a very vague inner feeling of their existence ;
but they only act by the internal impulse of an inclination which
leads them towards some or other object ; so that their will is always
dependent and controlled ;

(3) Others again not only exhibit in some of their parts movements
resulting from their stimulated irritability ; not only are they capable
of receiving sensations, and possess an inner feeling of their existence,
but they have besides the faculty of forming ideas, although confused
ones, and of acting by a free will, subject however to inclinations which
lead them exclusively towards certain special objects ;

(4) Finally, others (and these are the most perfect) possess in a
high degree all the aforementioned faculties; in addition they are
able to form clear and precise ideas of the objects which affect their
senses and attract their attention; to compare and combine their
ideas up to a certain point; to form judgments and complex ideas ;
in short to think, and to have a will that is less bound down and permits
them to introduce more or less variation into their activities.

Life in the most imperfect animals has no energy of movement ;
and irritability alone suffices for the execution of vital movements.
But since vital energy increases in proportion to complexity of organisa-
tion, there arrives a time when nature has to improve her methods
in order to provide for the necessary activity of vital movements ;
for this purpose she has utilised muscular activity in establishing the
circulatory system, so that the fluids can move with greater rapidity.
This rapidity itself is increased in proportion to the increase of the
muscular power which works it. Finally, since no muscular activity
can take place without nervous influence, this has become every-
where necessary for the acceleration of the fluids in question.

Thus nature has been able to add muscular activity and nervous
influence to an irritability which was no longer adequate. But this
nervous influence, which gives rise to muscular activity, never does
so by means of feeling, as I hope to show in Part II. I shall then
prove that sensibility is by no means necessary to the execution

vital movements, even in the most perfect animals.

The various animals which exist are thus clearly distinguished '
from one another, not only by peculiarities of external shape, con-
sistency of body, size, etc., but, in addition, by the faculties which
they possess. Some, such as the most imperfect, are extremely limited

GENERAL PRINCIPLES 49

in that respect, having no other faculty but those of life in general,
and being unable to move except by a power outside them; while
others have faculties, progressively more numerous and important,
up to the most perfect animals, which exhibit 2, capacity calculated
to excite our wonder.

These remarkable facts no longer surprise us, when we recognise
that every faculty is based upon some special organ or system of organs,
and when we observe that organisation gradually becomes more
complex as we pass from the most imperfect animal, which has no
special organ whatever and consequently no faculty but those of
life in general, to the most perfect and richly endowed animal. Thus '
all the organs, even the most important, arise one after the other in,
the animal scale, and afterwards become successively more perfect
through the modifications impressed on them, by which these organs
come to harmonise with the state of organisation of which they are
part. Hence, by their combination in the most perfect animals,
they constitute the highest degree of organisation, giving rise to the.
most numerous and important faculties. -

The examination of the internal organisation of animals; of the
various systems presented by that organisation in the animal-scale ;
and, finally, of the special organs, is then the subject of study most
deserving of our attention.

If animals, considered as productions of nature, are rendered
extremely remarkable by their faculty.of locomotion, a great many of '
them are still more so by their faculty of feeling.

I have said that this faculty of locomotion is very limited in the most
imperfect animals, among which it is not voluntary and is only carried
out by external stimuli. It then becomes gradually more ‘perfect
and ultimately takes its source within the animal itself, and becomes
at length subject to its will. { In just the same way, the faculty of feeling '
is still very obscure and limited in the animals among which it begins
to exist; but it then develops gradually, and when it has reached its
highest development it ultimately gives rise in the animal to the
faculties which constitute intelligence. =

Indeed the most perfect among animals have simple and even com-
plex ideas ; they have passions and memory and they dream, that is
to say, they experience involuntary recurrences of their ideas and
even of their thoughts; and they are up to a certain point capable
of learning. How wonderful is this result of the power of nature!

Nature thus succeeds in endowing a living body with the faculty
of locomotion, without the impulse of an external force ; of perceiving
objects external to it; of forming ideas by comparison of impres-

sions received from one object with those received from others; of
D

50 ZOOLOGICAL PHILOSOPHY

comparing or combining these ideas, and of forming judgments which
are merely ideas of another order; in short, of thinking. Not only is
this the greatest marvel that the power of nature has attained, but it
is besides a proof of the lapse of a considerable time; since nature
has done nothing but by slow degrees.

As compared to the periods which we look upon as great in our
ordinary calculations, an enormous time and wide variation in successive
conditions must doubtless have been required to enable nature to bring
the organisation of animals to that degree of complexity and develop-
ment in which we see it at its perfection. If an inspection of the
numerous diverse strata composing the external crust of the earth
furnishes unimpeachable testimony of its great antiquity ; if the very
slow but continuous displacement of the sea-bottom,' certified by the
numerous monuments left everywhere about, gives further confirmation
of its prodigious antiquity ; then the belief is justified that the state of
perfection at which the organisation of the most perfect animals has
arrived, contributes to exhibit that truth in the strongest possible light.

But in order that this new proof may be securely based, it will first
be necessary to bring into evidence the facts concerning the actual
progress of organisation; it will be necessary to verify if possible
the reality of that progress; finally, it will be necessary to collect
the best established facts and to identify nature’s methods in bring-
ing her productions into existence.

—~—Méanwhile, let us note that although the term productions of nature
is generally accepted for indicating the beings which constitute each
kingdom, it seems none the less that no definite idea is attached to that
expression. Apparently, prejudices of special origin prevent the
recognition of the fact that nature possesses the faculty of herself
bringing so many different beings into existence ; of causing incessant
though very slow variations in living races; and of maintaining
everywhere the general order that we observe.

Let us leave aside all opinion whatever on these great subjects ;
and to avoid any error of imagination let us everywhere consult
nature’s own works.

In order to be able to bring under our attention the totality of exist-
ing animals, and to place these animals under an aspect easily under-
stood, we must remember that all the natural productions that we can
observe have long been divided by naturalists into three kingdoms,
under the name of animal kingdom, vegetable kingdom and mineral
kingdom. By this division, the existences comprised in each of these
kingdoms are compared together under a common standard ; although
some have a very different origin from others.

1 Hydrogéologie, p. 41 et seq.

x

GENERAL PRINCIPLES 51

For some time past I have found it more convenient to employ
another primary division which is better calculated to give an idea
of the beings dealt with. Thus, I distinguish the natural productions
comprised in the three aforementioned kingdoms into two main
branches :

1. Organised living bodies ;
2. Crude bodies without life.

Living beings, such as animals and plants, constitute the first of these
two branches of the productions of nature. They possess, as every-
one knows, the faculties of alimentation, development, reproduction,
and they are subject to death.

But what is not known so well, since the fashionable hypotheses
do not permit of the belief, is that living bodies form for themselves
their own substances and secretions, as a result of the activity and
functions of their organs and of the mutations wrought in them
by organic movements (Hydrogéologie, p. 112). What is still less
known is that the exuviae of these living bodies give rise to all the
composite matters, crude or inorganic, that are to be found in nature,
matters of which the various kinds increase in course of time and
according to the conditions, by reason of the disintegration which
they imperceptibly undergo. For this disintegration simplifies them
more and more, and after a long period leads to the complete
separation of their constituent principles.

These are the various crude and lifeless matters, both solid and
liquid, which compose the second branch of the productions of
nature, and most of which are known under the name of minerals.

It may be said that an immense hiatus exists between crude matters
and living bodies, and that this hiatus does not permit of a linear’
arrangement of these two kinds of bodies, nor of any attempt to
unite them by a link, as has been vainly attempted.

All known living bodies are sharply divided into two special kingdoms,
based on the essential differences which distinguish animals from
plants ; and in spite of what has been said I am convinced that these
two kingdoms do not really merge into one another at any point,
and consequently that there are no animal-plants, as implied by the

word zoophyte, nor plant-animals, ~~

Irritability in all or some of their parts is the most general charac-
teristic of animals; it is more general than the faculty of voluntary
movements and of feeling, more even than that of digestion. Now
all plants, as I have elsewhere shown, are completely destitute of
irritability, not even excepting the so-called sensitive plants nor those
which move certain of their parts on being touched or brought into
contact with the air.

52 ZOOLOGICAL PHILOSOPHY

It is known that irritability is a faculty essential to the parts or to
certain parts of animals, and that it is never suspended or annihilated
so long as the animal is alive and the part possessing it has suffered
no injury. Its effect is seen in a contraction which takes place
instantly throughout the irritable part on contact with a foreign
body ; a contraction which ends with its cause, and which is renewed
whenever the part after relaxation is irritated by new contacts. Now
nothing of this kind has ever been observed in any other part of
plants.

When I touch the extended branches of the sensitive plant (Mimosa
pudica), instead of a contraction I observe in the joints of the disturbed
branches and petioles a relaxation, which permits these branches and
petioles of the leaves to droop, and causes the leaflets themselves to
sink down upon one another. When once that sinking has been
produced it is useless to touch again the branches and leaves of this
plant; no effect follows. A longish time is required, unless it is
very hot, for the distension of the joints of the small branches and
leaves of the sensitive plant ; when all these parts will again be raised
and spread out, ready to fall together once more upon a contact or
slight shaking.

I cannot see in this phenomenon any relation to the irritability
of animals. I reflected however that during growth, especially
when it is hot, there are produced in plants many elastic fluids,
part of which are incessantly being exhaled. Hence I conceived
that in leguminous plants these elastic fluids might accumulate,
especially in the joints of the leaves, before being dispelled, and that
they might then distend these joints and keep the leaves or leaflets
spread out.

In this case, the slow dissipation of the elastic fluids in question set
up in leguminous plants by the approach of night; or the sudden
dissipation of the same fluid set up in Mimosa pudica by a slight shaking,
will give rise for leguminous plants in general to the phenomenon
known under the name of sleep, and for the sensitive plant to that
wrongly attributed to irritability.1

It follows from the observations which I shall set forth below, and
from the inferences which I have drawn from them, that in general

1] have developed in another work (Hist. Nat. des végétaux, édition Déterville,
vol. i. p. 202) other analogous phenomena observed in plants such as Hedysarum
girans, Dionaea muscipula, the stamens of the flowers of Berberis, etc.; and I have
shown that the curious movements observed in the parts of certain plants chiefly
in hot weather are never the result of a real irritability essential to any of their fibres ;
but that they are sometimes hygrometric or pyrometric effects, sometimes the results
of elastic relaxations which take place under certain circumstances, and sometimes

of a swelling and drooping of parts by the local accumulations and more or less rapid
dissipations of elastic and invisible fluids which are being exhaled.

GENERAL PRINCIPLES 53

it is not true that animals are sensitive creatures endowed without
exception with the power of producing acts of will, and consequently
with the faculty of voluntary locomotion. Hence the definition
of animals hitherto given to distinguish them from plants is altogether
unsuitable ; in consequence, I have already proposed to substitute
the following as more in harmony with the facts, and more suitable
to characterise the beings which compose the two kingdoms of living

bodies. 2 koe
DEFINITION oF ANIMALS.

Animals are organised living bodies, which have irritable parts
at all times of their lives; which nearly all digest the food on which
they live; and which move, some by acts of will, either free or
dependent, and others by stimulated irritability.

DEFINITION OF PLANTs.

Plants are organised living bodies whose parts are never irrit-
able, which do not digest or move either by will or true irritability.

We see from these definitions, which are much sounder and more
accurate than those hitherto received, that animals are primarily
distinguished from plants by the irritability which all or some of
their parts possess, and by the movements that they can produce
in these parts, or which are set up by external causes as a sequence
of their irritability.

It would doubtless be wrong to agree to these new ideas merely
on authority ; but I think that every unprejudiced reader who takes
into consideration the facts and observations which I shall set forth
in the course of the present work will be unable to deny them pre-
ference over the ancient ones for which I am substituting them ;
since the latter are obviously contrary to all observation.

We shall terminate this general outlook upon animals by two some-
what curious considerations: one concerning the extreme multiplicity
of animals on the surface of the earth and in the waters, the other
concerning the means adopted by nature to ensure that their number
shall never become injurious to the preservation of her productions
and of the general order which should exist.

Of the two kingdoms of living bodies that comprising the animals
appears much richer and more varied than the other: at the same
time it exhibits more wonderful phenomena in its organisation.

The surface of the earth, the waters, and to some extent even the air
are populated by an infinite multitude of diverse animals, the races
of which are so varied and numerous that a large proportion of them

54 ZOOLOGICAL PHILOSOPHY

will probably always evade our researches. This is rendered the more
likely since the enormous extent of water, its depth in many places,
and the prodigious fertility of nature in the smallest species will doubt-
less be for all time an almost insuperable obstacle to the progress
of knowledge.

A single class of the invertebrate animals, such as insects for instance,
equals the entire vegetable kingdom in the number and diversity of
its contained objects. The class of polyps is apparently much more
numerous still, but we shall never be able to flatter ourselves that

__we know all the animals which make it up.

As a result of the rapid multiplication of the small species, and
particularly of the more imperfect animals, the multiplicity of in-
dividuals might have injurious effects upon the preservation of races,
upon the progress made in perfection of organisation, in short, upon
the general order, if nature had not taken precautions to restrain that
multiplication within limits that can never be exceeded.

Animals eat each other, except those which live only on plants;
but these are liable to be devoured by carnivorous animals.

We know that it is the stronger and the better equipped that eat
the weaker, and that the larger species devour the smaller. Neverthe-
less, individuals rarely eat others of the same race as themselves ;
they make war on different races.

The multiplication of the small species of animals is so great, and
the succession of generations is so rapid, that these small species would
render the globe uninhabitable to any others, if nature had not set
a limit to their prodigious multiplication. But since they serve
as prey to a multitude of other animals, and since the duration of
their life is very short and they are lulled by any fall of temperature,
their numbers are always maintained in the proper proportions for
the preservation of their own and other races.

As to the larger and stronger animals, they might well become
dominant and have bad effects upon the preservation of many other
races if they could multiply in too large proportions; but their races
devour one another, and they only multiply slowly and few at a time ;
and this maintains in their case also the kind of equilibrium that
should exist.

Lastly, man alone, considered apart from all that is special to him,
seems to be able to multiply indefinitely, for his intelligence and powers
protect him from any limit of multiplication due to the voracity of
any animal. He exercises a supremacy over them, so that instead of
having to fear the larger and stronger races of animals, he is capable
rather of extinguishing them, and he is continually keeping down
their numbers.

GENERAL PRINCIPLES 55

But nature has given him numerous passions which unfortunately
develop with his intelligence, and thus set up a great obstacle to the
extreme multiplication of individuals of his species.

It seems, in fact, that man is himself responsible for continually
keeping down the numbers of his kind; for I have no hesitation in
saying that the earth will never be covered by the population that
it might support; several of its habitable regions will always be
sparsely populated in turns, although the period of these fluctuations
are, so far as we are concerned, immeasurable.

By these wise precautions, everything is thus preserved in the
established order; the continual changes and renewals which are
observed in that order are kept within limits that they cannot pass ;
all the races of living bodies continue to exist in spite of their variations ;
none of the progress made towards perfection of organisation is lost ;
what appears to be disorder, confusion, anomaly, incessantly passes
again into the general order, and even contributes to it; everywhere
and always the will of the Sublime Author of nature and of everything
that exists is invariably carried out.

Before devoting ourselves to showing the degradation and simplifica-
tion existing in the organisation of animals, when we proceed according
to custom from the most complex to the simplest, let us examine
their true arrangement and classification, as well as the principles
employed for this purpose. It will oe easier for us to recognise

the proofs of the degradation in question. {

CHAPTER V.
ON THE TRUE ARRANGEMENT AND CLASSIFICATION OF ANIMALS.

For the progress of zoological philosophy and the object that we have
in view, it is necessary to enquire into the true arrangement and
classification of animals; to consider how such an arrangement
came about; to ascertain what principles should be observed in set-
ting up that general arrangement; and, finally, to investigate what
remains to be done in order to bring that arrangement into the closest
harmony with the actual order of nature.

ut in ordér that our studies may be profitable, we must first deter-
mine the essential aims of an arrangement and of a classification of
animals ; for these two aims are very different in nature.

The aim of a general arrangement of animals is not only to possess
a convenient list for consulting, but it is more particularly to have an
_ order in that list which represents as nearly as possible the actual
order followed by nature in the production of animals; an order con-
spicuously indicated by the affinities which she has set between them.

The aim of a classification of animals, on the other hand, is to furnish
points of rest for our imagination, by means of lines of demarcation
drawn at intervals in the general series; so that we may be able
more easily to identify each race already discovered, to grasp its
affinities with other known animals, and to place newly discovered
species in their proper position. This device makes up for our own
shortcomings, facilitates our studies and our knowledge, and is
absolutely necessary for us; but I have already shown that it is a
produce of artifice, and that despite appearances it corresponds to
nothing real in nature.

An accurate determination of affinities between objects will always
begin by fixing in our general arrangements the place of the large
groups or primary divisions ; then that of the lesser groups, and lastly
that of the species or special races that have been observed. Now
here is the inestimable advantage accruing to science from a know-

ARRANGEMENT AND CLASSIFICATION 57

ledge of affinities. Since these affinities are the actual work of nature,
no naturalist will ever be able or indeed desire to alter the consequences
of a recognised affinity. The general arrangement will thus become
ever more perfect and less arbitrary, according as our knowledge
of affinities becomes greater.

The case is different with classifications: that is to say, with the
various lines of demarcation that we have to draw at intervals in the
general list both of animals and plants. In truth, so long as there are
gaps remaining to be filled in our list owing to many animals and plants
not having yet been observed, we shall always find these lines of
demarcation, which appear to be drawn by nature herself; but this
illusion will vanish as our observations accumulate. Have we not
already witnessed the effacement of a great number, at least in the
smaller divisions, by reason of the numerous discoveries of naturalists
during the last half century? Except for the lines of demarcation
resulting from gaps to be filled, those which we shall always have to
draw will be arbitrary and therefore changeable, so long as naturalists
do not adopt some conventional principle for their guidance.

In the animal kingdom such a principle is that every class should
comprise animals distinguished by a special system of organisation.
The strict execution of this principle is quite easy, and attended only
with minor inconveniences.

In short, although nature does not pass abruptly from one system
of organisation to another, it is possible to draw boundaries between
each system, in such a way that there is only a small number of animals
near those boundaries and admitting of doubt as to their true class.

The other lines of demarcation which sub-divide classes are usually
more difficult to establish, since they depend on less important
characters; and for this reason are more arbitrary.

Before examining the true classification of animals, let me endeavour
to show that the list of living bodies should form a series, at least as
regards the main groups; and not a branching net-work.

a

]
CLASSES, SHOULD FORM A SERIES IN THE ARRANGEMENT

oF ANIMALS.

Man is condemned to exhaust all possible errors when he examines
any set of facts before he recognises the truth. Thus it has been denied
that the productions of nature in each kingdom of living bodies can
really be arranged in a true series according to their affinities; and
that there exists any scale in the general arrangement either of animals
or plants.

Naturalists, for instance, have noticed that many species, certain
genera and even some families appear to a certain extent isolated

58 ZOOLOGICAL PHILOSOPHY

in their characters; and several have imagined that the affinities
among living beings may be represented something after the manner
of the different points of a compass. They regard the small well-
marked series, called natural families, as being arranged in the form
of a reticulation. This idea, which some modern writers think sub-
lime, is clearly a mistake, and is certain to be dispelled when we have
a deeper and wider knowledge of organisation ; and especially when
the distinction is recognised between what is due to the influence
of environment and habits and what is due to the greater or less
progress in the complexity or perfection of organisation.

Meanwhile I shall show that nature, by giving existence in the course
of long periods of time to all the animals and plants, has really formed
a true scale in each of these kingdoms as regards the increasing com-
plexity of organisation; but that the gradations in this scale, which
we are bound to recognise when we deal with objects according to
their natural affinities, are only perceptible in the main groups of the
general series, and not in the species or even in the genera. This
fact arises from the extreme diversity of conditions in which the various
races of animals and plants exist ; for these conditions have no relation
to the increasing complexity of organisation, as I shall show; but they
produce anomalies or deviations in the external shape and characters
which could not have been brought about solely by the growing com-
plexity of organisation.

We have then only to prove that the series constituting the animal
scale resides essentially in the arrangement of the main groups com-
posing it, and not in that of species, nor always even of genera.

The series to which I have alluded can then only be made out among
the larger groups ; since each of these groups, constituting the classes
and bigger families, comprises beings whose organisation is dependent
on some special system of essential organs.

Thus each distinct group has its special system of essential organs ;
and it is these special systems which undergo a degradation as we pass
from the most complex to the simplest. But each organ taken by
itself does not proceed so regularly in its degradations: and less so
in proportion to its lesser importance and greater susceptibility to
modification by environment.

In fact, the organs that have little importance or are not essential
to life are not always at the same stage of perfection or degradation ;
so that if we follow all the species of a class we shall see that some
one organ of any species reaches its highest degree of perfection,
while some other organ, which in that same species is quite un-
developed or imperfect, reaches in some other species a high state
of perfection.

ARRANGEMENT AND CLASSIFICATION 59

These irregularities in the perfection and degradation of inessential
organs are found in those organs which are the most exposed to the
influence of the environment; this influence involves similar irregu-
larities in the shape and condition of the external parts, and gives
rise to so great and singular a diversity of species that, instead of being
arranged like the main groups in a single linear series as a regularly
graduated scale, these species often constitute lateral ramifications
around the groups to which they belong, and their extremities are
in reality isolated points.

A much more powerful and lasting set of conditions is necessary to
modify any internal system of organisation than to alter the external
organs.

I observe, however, that in cases of necessity nature passes from one
system to another without a break, if they are closely allied; it is
indeed by this faculty that she succeeded in fashioning them all in
turn, passing from the simplest to the most complex.

So true is it that she has this faculty, that she even passes from one
system to another not merely in two different allied families but in
one individual.

Those systems of organisation in which respiration is carried on by
true lungs are nearer to the systems requiring gills than to those requir-
ing tracheae ; thus, nature not only passes from gills to lungs in allied
classes and families, as is seen among fishes and reptiles, but she does
so even during the existence of one individual: which possesses in
turn first one and then the other system. It is known that the frog,
in its imperfect condition of tadpole, breathes by gills; while in its
more perfect condition of frog it breathes by lungs. But nowhere
does nature pass from the system of tracheae to the pulmonary
system.

It may then be truly said that in each kingdom of living bodies the
groups are arranged in a single graduated series, in conformity with the
increasing complexity of organisation and the affinities of the object.
This series in the animal and vegetable kingdoms should contain the
simplest and least organised of living bodies at its anterior extremity,
and ends with those whose organisation and faculties are most perfect.

Such appears to be the true order of nature, and such indeed is
the order clearly disclosed to us by the most careful observation and
an extended study of all her modes of procedure.

We have seen the necessity of paying attention to the question of
affinities, in drawing up our arrangements of the productions of nature ;
hence we are no longer able to arrange the general series in any way
we like. Our knowledge of nature’s methods continues to increase
in proportion to our studies of the affinities between objects or various

60 ZOOLOGICAL PHILOSOPHY

groups of objects; and this knowledge compels us to conform to her
order.

The first result obtained from the use of affinities in placing the groups.
in a general scheme is that the two extremities of the order must be
occupied by the most dissimilar beings, since they are the most distant
from one another from the point of view of affinities, and consequently
of organisation. Hence it follows that if one of the extremities of
the order is occupied by the most perfect of living bodies, having the
most complex organisation, the other extremity of the order must
necessarily be occupied by the most imperfect of living bodies, namely,
those whose organisation is the simplest.

In the general arrangement of known plants according to the natural
methods, that is according to affinities, only one extremity is thoroughly
known; and that is occupied by the cryptogams. If the other ex-
tremity is not determined with equal ‘certainty, it is due to the fact
that our knowledge of plant organisation is much less advanced than
our knowledge of the organisation of a great number of known
animals. Hence it follows that in the case of plants we have as yet
no certain guide to the affinities between the large groups, as we have
to those among genera and families.

The same difficulty does not exist in the case of animals, and both
extremities of their general series are thus definitely fixed ; for as long
as importance is attached to the natural method, and hence to
affinities, the mammals will of necessity occupy one extremity of
the order, while the infusorians will be placed at the other.

For animals then, as well as for plants, there exists in nature an
order arising, like the objects which it calls into existence, from powers
conferred by the Supreme Author of all things. Nature is herself
only the general and immutable order created everywhere by this
Sublime Author; she is the sum total of the general and special laws
to which that order is subject. By these powers, which she continues
unchangeably to make use of, she has given and still continues to give
existence to her productions ; she is incessantly varying and renewing
them, and thus maintains everywhere the entire order which results.

We were obliged to recognise this order of nature in each kingdom
of living bodies; and we are already in possession of various parts
of it, in our better constituted families and genera. We shall now
see that in the animal kingdom it is established in its outlines in a
way that leaves no scope for arbitrary opinion.

But the great number of divers animals that we have come to know,
and the brilliant light shed by comparative anatomy on their organisa-
tion, now place it in our power definitely to draw up the general list
of all known animals, and to assign definitely the rank of the main

ARRANGEMENT AND CLASSIFICATION 61

divisions that may be established in the series which they constitute.
This it behoves us to recognise ; it would indeed be difficult to dispute.

Let us now pass to the actual arrangement and classification of
animals.

Tue TRUE ARRANGEMENT AND CLASSIFICATION OF ANIMALS.

Since the purpose and principles both of a general arrangement
and of a classification of living animals were not at first perceived
when these subjects were studied, the works of naturalists long suffered
from this imperfection of our ideas. The same thing happened in
the science of natural history as has happened in all others to which
much attention was given, before any principles had been thought out
to constitute a basis and to guide their labours.

Instead of subjecting the classification which had to be made in
each kingdom of living bodies to an arrangement which should be quite
unfettered, attention was entirely devoted to disposing objects in
convenient classes, so that their arrangement was thus abandoned
to arbitrary opinion.

The affinities among the larger groups in the vegetable kingdom,
for example, were very difficult to grasp; and artificial systems were
long made use of in botany. They facilitated the making of convenient
classifications based upon arbitrary principles, so that every author drew
up a new one according to his fancy. Thus the proper arrangement of
plants according to the natural method was then always sacrificed. It
is only since we have recognised the importance of the parts concerned
with fruiting, and the greater importance of some than others that the
general arrangement of plants began to make progress towards perfection.

As the case of animals is different, the general affinities which
characterise the main groups are much easier to perceive: so that
several of these groups were identified at the very beginning of the
study of natural history.

Aristotle indeed divided animals primarily into two main divisions
or, as he called it, two classes, viz. :

1. Animals that have blood :
Viviparous quadrupeds.
Oviparous quadrupeds.
Fishes.

Birds.

2. Animals that have no blood :

Molluscs.
Crustaceans.
Testaceans.
Insects.

62 ZOOLOGICAL PHILOSOPHY

This primary division of animals into two main groups was fairly
good, but the character taken by Aristotle for discrimination was
bad. That philosopher gave the name of blood to the chief fluid in
animals which has a red colour. He imagined that all animals which
he placed in his second class only possessed white or whitish fluids ;
and he thereupon regarded them as having no blood.

Such apparently was the first outline of a classification of animals ;
it is at any rate the oldest of which we have any knowledge. But
this classification also furnishes the earliest example of an arrange-
ment, though in the opposite direction from the order of nature; since
we may notice in it a progression, though a very imperfect one, from
the most complex to the simplest.

That erroneous direction has been generally followed ever since
in the arrangement of animals; and this has clearly retarded our
knowledge of nature’s procedure.

Modern naturalists have endeavoured to improve upon Aristotle’s
division by giving to the animals in the first class the name of red-
blooded animals, and to those in his second class that of white-blooded
animals. It is now well known how defective is this character ; since
there are some invertebrate animals (many annelids) which have
red blood.

In my opinion the essential fluids of animals do not deserve the name
of blood, except when they circulate in arteries and veins; for the
other fluids are so degraded, and the combination of their principles
so imperfect, that it would be wrong to assimilate them to fluids which
have a true circulation. One might as well attribute blood to a plant
as to a radiarian or polyp.

In order to avoid ambiguity and hypothesis, I divided the entire
known animal world in my first course of lectures at the Museum
in the spring of 1794 (the year II. of the republic) into two perfectly
distinct groups, viz. :

Animals that have vertebrae.
Animals without vertebrae.

I called the attention of my pupils to the fact that the vertebral
column, among animals provided with it, indicates the possession
of a more or less perfect skeleton and of a plan of organisation on the
same plane; whereas its absence among other animals not only
distinguishes them sharply from the first, but shows that their whole
plan of organisation is very different from those of vertebrate animals.

From Aristotle to Linneus nothing of note appeared with regard
to the general arrangement of animals; but in the course of last
century naturalists of the highest distinction made a large number
of special observations on animals, and especially on many inverte-

ARRANGEMENT AND CLASSIFICATION 63

brate animals. Some recorded their anatomy with greater or less
fulness, while others gave an accurate and detailed history of the
metamorphoses and habits of a great number of these animals; as a
result of their valuable observations, we have become acquainted
with many facts of the greatest importance.

At length Linneus, a man of high genius and one of the greatest
of naturalists, after having marshalled the facts and taught us the
necessity for great accuracy in the determination of all kinds of
characters, gave us the following classification for animals.

He divided known animals into six classes, based upon three stages
or characters of organisation.

CLASSIFICATION OF ANIMALS, ESTABLISHED BY LINNZUS.

Classes, First Stage.
I. Mammals. Heart with two ventricles: bluod red and
II. Birds. warm.
III. Amphibians (Reptiles). Second Stage.
IV. Fishes. ee with one ventricle: blood red and cold.
V. Insects. Third Stage.
VI. Worms. A cold serum (in place of blood).

Except for the inversion displayed by this arrangement as by all
others the four first divisions proposed are now definitely established,
and will henceforth always obtain the assent of zoologists as to their
position in the general series. For this we are primarily indebted to
the illustrious Swedish naturalist.

The case is different with regard to the two final divisions of the
arrangement in question; they are wrong and very badly disposed.
Since they comprise the greater number of known animals of the
most varied characters, they should be more numerous. Hence it
has been necessary to re-constitute them and substitute others.

We have seen that Linnzeus, and the naturalists who succeeded him,
gave very little attention to the necessity for increasing the number
of divisions among animals which have a cold serum in place of blood
(invertebrate animals), and whose characters and organisation are so
greatly varied. Hence they have divided these numerous animals
into two classes only, viz. insects and worms; so that everything
which was not regarded as an insect, that is to say all invertebrate
animals that have not jointed legs, were referred without exception
to the class of worms. They placed the class of insects after the fishes,
and the worms after the insects. According to this arrangement of
Linneus, the worms constituted the final class of the animal kingdom.

These two classes are still maintained in the same order in all the
editions of the Systema Naturae published subsequently to Linneus.
The essential vice of this arrangement, as regards the natural order of

y

vs

64 ZOOLOGICAL PHILOSOPHY

animals, is obvious ; it cannot be denied that Linnzus’s class of worms
is a sort of chaos in which the most disparate objects are included.
Yet the authority of that savant carried so much weight among
naturalists, that no one dared to change this monstrous class of worms.

With a view to bringing about some useful reform in this respect,
I suggested in my first course the following arrangement for inverte-
brate animals, which I divided not into two classes, but into five in
the following order.

ARRANGEMENT OF INVERTEBRATE ANIMALS SET FORTH
IN my First COouRSE.

Molluscs ;
Insects ;
Worms ;
Echinoderms ;
. Polyps.

These classes were then identical with some of the orders which
Bruguicre had suggested in his arrangement of worms (which J did not
adppt), and with the class of insects as defined by Linnzus. |

he arrival of M. Cuvier in Paris however, towards the middle of
the year ITI. (1795), drew the attention of zoologists to the organisa-
tion of animals. I then saw with much satisfaction the conclusive
evidence which he produced in favour of the priority of rank accorded
to molluscs over insects in the general series. This I had already
impressed in my lessons’ but it had not been favourably received by
the naturalists of this capital.

The change which | had thus instituted, from a consciousness of the
inadequacy of the prevailing arrangement of Linneus, was thoroughly
consolidated by M. Cuvier by the most definite facts, several of which, it
is true, were already known but had not attracted ourattention in Paris.

I took advantage of the light shed since his arrival by this savant
over every section of zoology, and particularly over invertebrate
animals which he called white-blooded animals. I then added in
turn new classes to my arrangement; I was the first to establish
them; but, as we shall see, such of those classes as were adopted were
only adopted reluctantly.

The personal interests of authors are doubtless a matter of complete
indifference to science, and also apparently to those who study it.
Nevertheless, a knowledge of the history of the changes undergone
during the last fifteen years by the classification of animals is not
without its uses: the following are those which I have instituted.

First, I changed the name of my class of echinoderms to radiarians, /
in order to unite with them the jelly-fishes and neighbouring genera.

GLa So Bo

ARRANGEMENT AND CLASSIFICATION 65

This class, notwithstanding its utility and inevitableness, has not yet
been adopted by naturalists.

In my course in the year VII. (1799) I established the class of
| crustaceans. At that time M. Cuvier, in his Tableau des animauz,
p. 451, still included crustaceans with insects; and although this

class is essentially distinct, yet it was not till six or seven years later
that a few naturalists consented to adopt it.

The following year, that is to say, in my course of the year VIII.
(1800) I suggested the arachnids as a class by itself, easy and necessary to
distinguish. From that time its characters have constituted a sure indi-
cation of an organisation peculiar to these animals ; for it is impossible
to believe that they arose from an organisation exactly similar to the
insects. Insects undergo metamorphosis, propagate only once in the
course of their life, and have only two antennae, two eyes with facets and
six jointed legs; while the arachnids never undergo metamorphosis, and
exhibit various characters besides which differentiate them from insects.
This fact has since been partly confirmed by observation. Yet this class
of arachnids is still not admitted into any other work than my own.

M. Cuvier had discovered the existence of arterial and venous vessels
in various animals, which used to be confused under the name of
worms with other animals of very different organisation. I immediately
took this new fact into consideration for the improvement of my
classification ; and in my course in the year X. (1802) I established
the class of annelids, placing them after the molluscs and before the
crustaceans, as required by their organisation.

By giving a special name to this new class I was able to keep the
old name of worms for the animals which have always borne it, and
whose organisation was remote from the annelids. So I continued
to place the worms after the insects, and to distinguish them from the
radiarians and polyps with which they can never again be united.

My class of annelids, published in my lectures and in my Recherches
sur les corps vivants (p. 24), was several years before being admitted
by naturalists. For the last two years however this class has begun
to gain recognition ; but since it is held desirable to change the name of
it and to call it by the name of worms, they do not know what to do
with the worms properly so-called which have no nerves or circula-
tory system. In this difficulty they combine them with the class of

w~é&

These instances of perfection at first attained in a classification,\ —. ~

polyps, although their organisation is very different. "

then destroyed and subsequently re-established by the necessity of
things, are not rare in natural science. =
Linneeus in fact united several genera of plants which Tournefort

had formerly distinguished as in the case of Polygonum, Mimosa,
E

‘,
Ps,

SK

66 ZOOLOGICAL PHILOSOPHY

Justicia, Convallaria, and many others; and now botanists are re-
establishing the genera which Linnezus had destroyed.

Finally last year (in my course of 1807) I established among in-
vertebrate animals a new class—the tenth—that of infusorians ; because
after a careful examination of the characters of these imperfect animals,
I was convinced that I had been wrong to place them with the polyps.

Thus, by continuing to collect facts from observation and from the
rapid progress of comparative anatomy, I instituted successively
the various classes which now compose my arrangement of inverte-
brate animals. These classes, to the number of ten, are arranged.
in order from the most complex to the simplest as usual, viz. :

CLassEs OF INVERTEBRATE ANIMALS.

Molluscs. Insects.
Cirrhipedes. Worms.
Annelids. Radiarians.
Crustaceans. Polyps.
Arachnids. Infusorians.

I shall show, when I come to deal with each of these classes, that
they constitute necessary groups, since they are based upon a study
of organisation ; and that although races may, nay must, exist near
the boundaries, half way between two classes, yet these groups are the
best attainable by artifice. They will therefore have to be recognised,
so long as the interest of science is our chief concern.

By adding to these ten classes into which the invertebrates are
divided, the four classes of vertebrate animals identified and deter-
mined by Linnzus, we shall have a classification of all known animals
into the following fourteen classes, set out once more in the opposite
order to that of nature.

1. Mammals.
a Se | Vertebrate animals.
4, Fishes.
5. Molluscs.
6. Cirrhipedes.
7. Annelids.
8. Crustaceans.
9. Arachnids.
10. Insects.
11. Worms.
12. Radiarians.
13. Polyps.
14, Infusorians.

\ Invertebrate animals.

ARRANGEMENT AND CLASSIFICATION 67

The above represents the true arrangement of animals, and also
the classes established among them.

We now have to examine a very important problem, which appears
never to have been fathomed nor discussed ; but the solution of which
is necessary ; it is this:

All the classes, into which the animal kingdom is divided, necessarily
form a series of groups arranged according to the increasing or decreas-
ing complexity of their organisation. In drawing up this series, ought
we to proceed from the most complex to the simplest, or from the
simplest to the most complex ?

We shall endeavour to give the solution of this problem in Chap.
VIII. which concludes this part; but we must first examine a very
remarkable fact, most worthy of our attention, which may lead us
to a perception of (nature’ 8 procedure; when bringing her diverse
productions into existence. _refer to that remarkable degradation of
organisation which is found on traversing the natural series of animals,
starting from the most perfect or the most complex towards the simplest
and most imperfect.

Although this degradation neither is nor can be finely graduated as
I shall show, it so obviously and universally exists in the main groups,
including even the variations, that it doubtless depends on some
general law which it behoves us to discover and consequently to
search for.\

CHAPTER VI.

DEGRADATION AND SIMPLIFICATION OF ORGANISATION FROM
ONE EXTREMITY TO THE OTHER OF THE ANIMAL CHAIN,
PROCEEDING FROM THE MOST COMPLEX TO THE SIMPLEST.

Amone the problems of interest for zoological philosophy, one of the
most important is that which concerns the degradation and simpli-
fication observed in animal organisation on passing from one extreme
to the other of the animal chain, from the most perfect animals to
those whose organisations are the simplest.

Now the question arises whether this is a fact that can be established ;
for, if so, it will greatly enlighten us as to nature’s plan and will set
us on the way to discover some of her most important laws.

I here propose to prove that the fact in question is true, and that
it is the result of a constant law of nature which always acts with
uniformity ; but that a certain special and easily recognised cause
produces variations now and again in the results which that law
achieves throughout the animal chain.

We must first recognise that the general series of animals arranged
according to their natural affinities is a series of special groups which
result from the different systems of organisation employed by nature ;
and that these groups are themselves arranged according to the de-
creasing complexity of organisation, so as to form a real chain.

We notice then that except for the anomalies, of which we shall
ascertain the cause, there exists from one end to the other of this chain
a striking degradation in the organisation of the animals composing it,
and a proportionate diminution in the numbers of these animals’
faculties. Thus if the most perfect animals are at one extremity
of the chain, the opposite extremity will necessarily be occupied by
the simplest and most imperfect animals found in nature.

This examination at length convinces us that all the special organs
are progressively simplified from class to class, that they become
altered, reduced and attenuated little by little, that they lose their

DEGRADATION OF ORGANISATION 69

local concentration if they are of the first importance, and that finally
they are completely and definitely extinguished before the opposite
end of the chain is reached.

As a matter of fact, the degradation of which I speak is not always
gradual and regular in its progress, for often some organ disappears
or changes abruptly, and these changes sometimes involve it in peculiar
shapes not related with any other by recognisable steps.

Often again some organ disappears and re-appears several times
before it is definitely extinguished. But we shall see that this could
not have been otherwise ; for the factor which brings about the pro-
gressive complexity of organisation must have had varied effects,
owing to its liability to modification by a certain other factor acting
with great power. We shall however see that the degradation in
question is none the less real and progressive, wherever its effects
can be seen.

If the factor which is incessantly working towards complicating
organisation were the only one which had any influence on the shape
and organs of animals, the growing complexity of organisation would
everywhere be very regular. But it is not; nature is forced to submit |
her works to the influence of their environment, and this environment |
everywhere produces variations in them. This is the special factor |

which occasionally produces in the course of the degradation that we |
are about to exemplify, the often curious deviations that may be |
observed in the progression.

We shall attempt to set forth in full both the progressive degra-
dation cf animal organisation and the cause of the anomalies in the
progress of that degradation, in the course of the animal series.

It is obvious that, if nature had given existence to none but aquatic
animals and if all these animals had always lived in the same climate,
the same kind of water, the same depth, etc., etc., we should then
no doubt have found a regular and even continuous gradation in the
organisation of these animals.

But the power of nature is not confined within such limits.

It first has to be observed that even in the waters she has established
considerable diversity of conditions: fresh-water, sea water, still or
stagnant water, running water, the water of hot climates, of cold
climates, and lastly shallow water and very deep water; these provide
as many special conditions which each act differently on the animals
living in them. Now the races of animals exposed to any of these
conditions have undergone special influences from them and have
been varied by them all the while that their complexity of organisation
has been advancing.

After having produced aquatic animals of all ranks and having

70 ZOOLOGICAL PHILOSOPHY

caused extensive variations in them by the different environments
provided by the waters, nature led them little by little to the habit
of living in the air, first by the water’s edge and afterwards on all
the dry parts of the globe. These animals have in course of time
been profoundly altered by such novel conditions ; which so greatly
influenced their habits and organs that the regular gradation which
they should have exhibited in complexity of organisation is often
scarcely recognisable.

These results which I have long studied, and shall definitely prove,
lead me to state the following zoological principle, the truth of which
appears to me beyond question.

Progress in complexity of organisation exhibits anomalies here and
there in the general series of animals, due to the influence of environment
and of acquired habits.

An examination of these anomalies has led some to reject the obvious
progress in complexity of animal organisation and to refuse to recognise
the procedure of nature in the production of living bodies.

Nevertheless, in spite of the apparent digressions that I have just
mentioned, the general plan of nature and the uniformity of her pro-
cedure, however much she varies her methods, are still quite easily
distinguished. We have only to examine the general series of known
animals and to consider it first in its totality and then in its larger
groups; the most unequivocal proofs will then be perceived of the
gradation which she has followed in complexity of organisation; a
gradation which should never be lost sight of by reason of the afore-
mentioned anomalies. Finally, it will be noticed that whenever there
have been no extreme changes of conditions, that gradation is found to
be perfectly regular in various portions of the general series to which
we have given the name of families. This truth becomes still more
striking in the study of species; for the more we observe, the more
difficult, complicated and minute become our specific distinctions.

The gradation in complexity of animal organisation can no longer
be called in doubt, when once we have given positive and detailed
proof of what we have just stated. Now since we are taking the
general series of animals in the opposite direction from nature’s actual
order when she brought them successively into existence, this grada-
tion becomes for us a remarkable degradation which prevails from
one end to the other of the animal chain, except for the gaps arising
from objects which are not yet discovered and those which arise
from anomalies caused by extreme environmental conditions.

Let us now cast an eye over the complexity and totality of the animal
series, in order to establish positively the degradation of organisation
from one extremity to the other; let us consider the facts presented

DEGRADATION OF ORGANISATION 71

and let us then pass rapidly in review the fourteen classes of which
it 1s primarily composed.

The general arrangement of animals set forth above is unanimously
accepted as a whole by zoologists: who dispute only as to the boundaries
of certain classes. In examining it I notice a very obvious fact which
would in itself be decisive for my purpose; it is as follows:

At one extremity of the series (that namely which we are accustomed
to consider as the anterior) we find the animals that are most perfect
from all points of view, and have the most complex organisation ;
while at the opposite extremity of the same series we find the most
imperfect that exist in nature—those with the simplest organisation
and to all appearances hardly endowed with animality.

This accepted fact, which indeed cannot be questioned, becomes
the first proof of the degradation which I propose to establish; for
it is a necessary condition of it.

Another fact brought forward by an examination of the general
series of animals and furnishing a second proof of the degradation
prevailing in their organisation from one extremity to the other of
their chain, is the following :

The first four classes of the animal kingdom contain animals that
are in general provided with a vertebral column, while the animals of
all the other classes are absolutely destitute of it.

It is known that the vertebral column is the essential basis of the
skeleton, which cannot exist without it; and that wherever there is a
vertebral column there is a more or less complete and perfect
skeleton.

It is also known that perfection of faculties is a proof of perfection
of the organs on which they rest.

Now although man may be above his rank on account of the extreme |
superiority of his intelligence as compared with his organisation, )
he assuredly presents the type of the highest perfection that nature
could attain to: hence the more an animal organisation approaches |
his, the more perfect it is. =

Admitting this, I observe that the human body not only possesses
a jointed skeleton but one that is above all others the most complete
and perfect in all its parts. This skeleton stiffens his body, provides
numerous points of attachment for his muscles and allows him an
almost endless variation of movement.

Since the skeleton is a main feature in the plan of organisation of
the human body, it is obvious that every animal possessed of a skeleton
has a more perfect organisation than those without it.

Hence the invertebrate animals are more imperfect than the ver-
tebrate animals; hence, too, if we place the most perfect animals

72 ZOOLOGICAL PHILOSOPHY

at the head of thé animal kingdom, the general series exhibits a real
degradation in organisation; since after the first four classes all
the animals of the following classes are without a skeleton and con-
sequently have a less perfect organisation.

But this is not all: Degradation may be observed even among
the vertebrates themselves ; and we shall see finally that it is found
also among the invertebrates. Hence this degradation follows from
the fixed plan of nature, and is at the same time a result of our follow-
ing her order in the inverse direction ; for if we followed her actual
order, if, that is to say, we passed along the general series of animals.
from the most imperfect to the most perfect, instead of a degradation
in organisation we should find a growing complexity and we should
see animal faculties successively increasing in number and perfection.
In order to prove the universal existence of the alleged. degradation, let.
us now rapidly run through the various classes of the animal kingdom.)

MAMMALS.

Animals with mammae, four jointed limbs, and all the organs essential
to the most perfect animals. Hair on certain parts of the body.

Mammals (Mammatza, Lin.) should obviously be at one extremity
of the animal chain, viz. that which contains the most perfect animals
and the richest in organisation and faculties ; for among them alone
are found those with the most developed intelligence.

If perfection of faculties is a proof of that of the organs they are
based upon as I said above, all mammals (and they alone are truly
viviparous) must have the most perfect organisation, since it is agreed
that these animals have more intelligence, more faculties and a more:
perfect set of senses than any others; moreover their organisation
approaches most nearly to that of man.

Their organisation exhibits a body whose parts are stiffened by a.
jointed skeleton, which is generally more complete in these animals
than in the three other classes of vertebrates. Most of them have four
articulated limbs appended to the skeleton; and all have a dia-
phragm between the chest and abdomen ; a heart with two ventricles
and two auricles; red warm blood; free lungs, enclosed within the
chest, through which the blood passes before being driven to the other
parts of the body; lastly, they are the only viviparous animals, for
they are the only animals in which the foetus although enclosed within
its membranes is always in communication with its mother and develops
at the expense of her substance, and in which the young feed for some
time after their birth on the milk of her mammae.

DEGRADATION OF ORGANISATION 73

It is then the mammals that must occupy the first rank in the animal
kingdom by virtue of their perfection of organisation and greatest
number of faculties (Recherches sur les corps vivants, p. 15). After
the mammals we no longer find a definitely viviparous reproduction,
nor lungs limited by a diaphragm to the chest and receiving all the
blood which has to be driven to the rest of the body, etc., etc.

Among the mammals themselves it is in truth not easy to distinguish
what is really due to degradation from what is the effect of environ-
ment, manner of life and long-established habits.

Nevertheless, traces of the general degradation of organisation
may be found even among them; for those whose limbs are
adapted for grasping objects have a higher perfection than those whose
limbs are adapted only for walking. It is among the former that
man is placed in respect of his organisation. Now it is clear that since
the organisation of man is the most perfect, it should be regarded
as the standard for judging of the perfection or degradation of the
other animal organisations.

Thus the three divisions, into which the class of mammals is unequally
broken up, exhibit among themselves, as we shall see, a conspicuous
degradation in the organisation of the animals they contain.

First division: unguiculate mammals; they have four limbs, flat
or pointed claws at the end of their digits but not investing them.
These limbs are in general adapted for grasping objects or at least
for hooking on to them. It is among these that the animals with
the most perfect organisation are found.

Second division: ungulate mammals; they have four limbs and
the extremity of their digits is completely invested by a rounded
horn called a hoof. Their feet serve no other purpose than that of
walking or running on the ground, and cannot be employed either
for climbing trees, or for grasping any object or prey, or for attack-
ing and rending other animals. They feed exclusively on vegetable
substances.

Third division: exungulate mammals; they have only two limbs
and these limbs are very short, flat and shaped like fins. Their digits
are invested by skin and have no claws or horn. Their organisation
is the least perfect of all mammals. They have no pelvis, nor hind
feet; they swallow without previous mastication; finally they
habitually live in the water ; but they come to the surface to breathe
air. They have received the name of cetaceans.

Although the amphibians also live in the water, coming out of it
occasionally to crawl] upon the shore, they really belong to the first
division in the natural order, and not to that which comprises the

cetaceans.

74 ZOOLOGICAL PHILOSOPHY

Henceforth we have to distinguish the degradation of organisation
which arises from the influence of environment and acquired habits,
from that which results from the smaller progress in the perfection or
complexity of organisation. We must be careful therefore about going
into too much detail in this respect; because asI shall show the environ-
ment in which animals habitually live, their special habitats, the habits
which circumstances have forced upon them, their manner of life, etc.,
have a great power to modify organs; so that the shapes of parts
might be attributed to degradation when they are really due to other
causes.

It is obvious for example that the amphibians and cetaceans must
have greatly shortened limbs, since they live habitually im a dense
medium where well-developed limbs would only impede their move-
ments. It is obvious that the influence of the water alone must
have made them such as they are, by interfering with the movements
of very long limbs with solid internal parts; and that consequently
these animals owe their general shape to the influence of the medium
they inhabit. But with regard to that degradation which we are
seeking among the mammals themselves, the amphibians must
be far removed from the cetaceans because their organisation is much
less degraded in its essential parts. Amphibians then have to be joined
to the unguiculate mammals, while the cetaceans should form the last
order of the class, as being the most imperfect mammals.

We now pass to the birds; but I must first note that there is no
gradation between mammals and birds. There exists a gap to be filled,
and no doubt nature has produced animals which practically fill this
gap, and which must form a special class if they cannot be comprised
either among the mammals or among the birds.

This fact has just been realised, by the recent discovery in Australia
of two genera of animals, viz. :

Ornithorhyncus
Echidna

These animals are quadrupeds with no mammae, with no teeth
inserted and no lips; and they have only one orifice for the genital
organs, the excrements and the urine (a cloaca). Their body is covered
with hair or bristles.

They are not mammals, for they have no mammae and are most
likely oviparous.

They are not birds; for their lungs are not pierced through and
they have no limbs shaped as wings.

Finally, they are not reptiles; for their heart with only two ven-
tricles removes them from that category.

They belong then to a special class.

| Monotremes (Geoff.).

DEGRADATION OF ORGANISATION 75

BIRDS.

Animals without mammae, with two feet and two arms shaped as wings ;
the body covered with feathers.

The second rank clearly belongs to the birds ; for while we do not
find among these animals so many faculties or so much intelligence
as among the animals of the first rank, they are the only ones except
the monotremes which have like mammals a heart with two ventricles
and two auricles, warm blood, the cavity of the cranium completely
filled by the brain, and the trunk always enclosed by ribs. They have,
then, qualities common to mammals, but not found elsewhere; and
consequently affinities with them that are not to be found in any
animals of the posterior classes.

But the birds when compared with the mammals display an obvious
degradation of organisation which has nothing to do with the influ-
ence of the environment. They are for instance naturally devoid of
mammae, organs with which only animals of the highest rank are
provided and which belong to a system of reproduction that is no
longer found in the birds nor in any of the animals of subsequent
ranks. In short they are essentially oviparous; for the system
of truly viviparous animals, which is adapted to animals of the first
rank, is not found in the second nor does it again re-appear. Their
foetus is enclosed in an inorganic envelope (the egg-shell) and soon
ceases communication with the mother and can develop without
feeding on her substance.

The diaphragm, which among canine completely separates some-
what obliquely the chest from the abdomen, here ceases to exist, or
becomes very incomplete.

The vertebrae of the neck and tail are the only mobile parts in the
vertebral column of birds. Since movements of the other vertebrae
of that column are not necessary to the animal, they are not performed
and they thus place no obstacle to the large development of the
sternum which now makes such movement almost impossible.

The sternum of birds indeed gives attachment to the pectoral
muscles, which have become very thick and strong by reason of their
energetic and almost continuous movements. The sternum has thus
become extremely large and carinate in the middle. This, however,
is due to the habits of these animals and not to the general degra-
dation that we are investigating. The truth of this is exemplified by
the fact that the mammal called a bat has also a carinate sternum.

All the blood of birds passes through their lungs before reaching
the other parts of the body. Thus they breathe exclusively by lungs

76 ZOOLOGICAL PHILOSOPHY

like the animals of the first rank; and this is not the case with any
known animal after them.

We now come to a very strange peculiarity which is connected
with the environment of these animals. They live more than other
vertebrates in the air, and are almost continually rising into it and pass-
ing through it in every direction. They have adopted a habit of swelling
their lungs with air in order to increase their volume and make them-
selves lighter; and this habit has caused the organ to adhere to the
sides of the chest so that the air within, being rarefied by the heat
of the place, has had to pierce through the lung with its investing
membranes and to penetrate every part of the body even to the inside
of the great bones which are hollow, and to the quills of the large
feathers.1 It is, however, only in the lungs that the blood of birds
undergoes the necessary influence of the air; for the air which
penetrates to the other parts of the body has another use than that
of respiration.

Thus the birds, which have been rightly placed after the mammals,
exhibit an obvious degradation in their general organisation: not
because their lung has a peculiarity not found among the former,
for this is due like their feathers only to their acquired habit of launch-
ing themselves into the air; but because they no longer have the
system of reproduction proper to the most perfect animals, but only
that which characterises most of the animals of the posterior classes.

It is very difficult to ascertain among the birds themselves the
degradation of organisation which we are now studying; our know-
ledge of their organisation is still too vague. Hence it has hitherto
been a matter of convention which order should be placed at the head
of this class and which at the end.

We may reflect however that aquatic birds (like the palmipeds),
as also the waders and gallinaceans, have this advantage over all
other birds that their young on coming out of the egg can walk and
feed. We may pay special attention to the fact that among the pal-
mipeds, the penguins and king-penguins, whose almost featherless
wings are merely oars for swimming and of no use for flight,

If it is true that in the case of birds the lungs are pierced through and the hair
changed into feathers as a result of their habit of rising into the air, I may be asked
why bats have not also feathers and pierced lungs. I reply that it seems to me pro-
bable that bats, which have a more perfect organisation than birds, and hence «.
complete diaphragm to impede the swelling of their lungs, have not been able to
pierce them through nor to swell themselves out with air sufficiently for that fluid
even by an effort to reach the skin and so to give to the horny matter of the hair
the faculty of branching out into feathers. Among birds, in fact, air is introduced
as far as the hair bulbs; changing their bases into quills and compelling this same
hair to break up into feathers; an event which cannot occur in the bat, where the
air does not penetrate beyond the lung.

DEGRADATION OF ORGANISATION 77

thus approximate in some ways to the monotremes and cetaceans.
We shall then recognise that the palmipeds, waders, and gallinaceans
should constitute the first three orders of birds, and that the doves,
passerines, birds of prey and climbers should form the last four orders
of the class. Now, from what we know of the habits of the birds
of these last four orders, we find that their young on coming out of
the egg can neither walk nor feed by themselves.

On this principle the climbers are the last order of birds; more-
over, they are the only ones which have two posterior digits and two
anterior. This character, which they possess in common with the
chameleon, appears to justify us in placing them near the reptiles.

REPTILES.

Animals with only one ventricle in the heart and still possessing a pul-
monary respiration though incomplete. Their skin is smooth or

provided with scales.

In the third rank are naturally and necessarily placed the reptiles ;
and they will furnish us with new and stronger proofs of the degrada-
tion of organisation from one extremity of the animal chain to the
other, starting from the most perfect animals. In fact, their heart,
which has only one ventricle, no longer displays that conformation
which belongs essentially to animals of the first and second ranks,
and their blood is cold, almost like that of the animals of the posterior
ranks.

We find another proof of the degradation of the organisation of reptiles
in their respiration. In the first place they are the last animals to
breathe by true lungs; for after them we find no respiratory organ
of this nature in any of the succeeding classes, as I shall endeavour
to show when speaking of molluscs. Next, the lung has in their case
usually very large chambers, proportionally less numerous, and is
already much simplified. In many species this organ is absent in
youth and is then replaced by gills, a respiratory organ which is never
found in animals of the anterior ranks. Sometimes the two kinds
of respiratory organs are present together in the same individual.

But the strongest proof of degradation in the respiration of reptiles
is that only part of their blood passes through the lungs, while the rest
reaches the parts of the body without having undergone the influence
of respiration.

Finally, among reptiles the four limbs essential to the most perfect
animals begin to be lost, and indeed many of them (nearly all the
snakes) lack them altogether.

78 ZOOLOGICAL PHILOSOPHY

Independently of the degradation of organisation indicated by the
shape of the heart, by the temperature of the blood which scarcely
arises above the level of the environment, by the incomplete respira-
tion and by the almost regular simplification of the lung, it is found
that reptiles differ considerably among themselves ; so that there are
greater differences of organisation and external shape among the:
animals of the various orders of this class than among those of the
two preceding classes. Some habitually live in the air, and of these,
such as have no legs can only crawl; others live in the water or on
its banks, sometimes withdrawing into the water and sometimes.
going into open places. There are some that are clothed in scales.
and others that have a naked skin. Lastly, although they all havea
heart with one ventricle, in some there are two auricles, while in
others there is only one. All these differences are due to environment,
manner of life, etc.; conditions which doubtless act more strongly
upon an organisation that is still remote from the goal to which nature
is tending, than they could do on one more advanced towards per-
fection.

Reptiles are oviparous animals (including even those in which
the eggs are hatched in the body of the mother); their skeleton is.
modified and usually very degraded ; their respiration and circulation
are less perfect than those of mammals and birds; and they all
have a small brain which does not fill the cavity of the cranium.
Hence they are less perfect than the animals of the two preceding
classes, and in their turn confirm the fact that the degradation
of organisation increases, according as we approach the most
imperfect animals.

Within this class of animals themselves, independently of the modi-
fications in their parts due to environment, we find in addition traces
of the general degradation of organisation; for in the last of their
orders (the batrachians) the individuals, when they are first born,
breathe by gills.

If the absence of legs observed among snakes were regarded as a
result of degradation, the ophidians ought to be the last order of
reptiles ; but it would be a mistake to suppose this. The fact is that
snakes are animals which for purposes of concealment have adopted
the habit of crawling directly on the ground, and their body has thus
acquired a considerable length, out of proportion to its size. Now
elongated legs would have impeded their efforts in crawling and
concealing themselves; while very short legs, of which there could
only be four since these animals are vertebrates, would have been
incapable of moving their body. Thus the habits of these animals
have caused the disappearance of their legs ; although the batrachians,

DEGRADATION OF ORGANISATION 79

ru have legs, are more degraded in organisation and nearer to the
es.

The proofs of the important principle which I am stating will be
based upon positive facts; they will consequently always hold good
mn contact with the arguments that are brought against them.

FISHES.

Animals breathing by gills, with a smooth or scaly skin ; the body
provided with fins.

On following the course of that degradation undergone by organisa-
tion as a whole and of the diminution in the number of animal faculties,
we see that the fishes must of necessity be placed in the fourth rank,
that is, after the reptiles. Their organisation in fact is even less
advanced towards perfection than is that of reptiles, and is conse-
quently more remote from that of the most perfect animals.

It is true no doubt that their general shape, the absence of a con-
striction between the head and body to form a neck, and the various
fins which for them take the place of limbs, are results of the influence
of the dense medium they inhabit, and not of the degradation of
organisation. But that degradation is none the less real and very
great, as we may convince ourselves by an examination of their
internal organs; so that we are forced to assign to fishes a lower
tank than to reptiles.

We no longer find in them the respiratory organ of the most perfect
animals; for they have no true lung, and in its place have only gills
or vascular pectinate folds arranged on both sides of the neck or head,
four altogether on each side. The water which these animals breathe
goes in by the mouth, passes between the folds of the gills, and bathes
the numerous vessels which run there. Now since the water is mixed
with air or contains it in solution, that air although small in quantity
acts upon the blood of the gills and there achieves the function of
respiration. The water then issues through open holes on either
side of the neck.

Note that this is the last time that the respired fluid enters by the
animal’s mouth in order to reach the organ of respiration.

These animals, like those of the posterior ranks, have no trachea
or larynx or true voice (including even those called grondeurs *)
or eyelids, etc. These organs and faculties are here lost and are not
again found throughout the animal kingdom.

Yet the fishes are still part of the division of vertebrate animals ;

1[The Grey Gurnard. H.E.]

80 ZOOLOGICAL PHILOSOPHY

but they are the last of them and they terminate the fifth stage of
organisation, being in common with reptiles the only animals which have:
A vertebral column ;
Nerves, terminating in a brain, which does not fill the cranium ;
A heart with one ventricle ;
Warm blood ;
Lastly, a completely internal ear.

Fishes thus display an oviparous reproduction; a body without
mammae, of a shape adapted for swimming; fins which are not
all invariably analogous with the four limbs of the most perfect
animals; a very incomplete skeleton curiously modified and rudi-
mentary in the last animals of this class; only one ventricle in the heart
and cold blood ; gills instead of lungs; a very small brain; the sense
of touch incapable of giving knowledge of the shapes of bodies; and
apparently without any sense of smell, for odours are only conveyed
by air. It is clear that these animals strongly confirm in their turn
also the degradation of organisation that we have undertaken to
follow throughout the animal kingdom.

We shall now see that fishes are primarily divided into what are
called bony fishes, which are the most perfect of them, and cartilaginous
fishes, which are the least perfect. These two facts confirm the de-
gradation of organisation within the class itself; for among the
cartilaginous fishes the softness and cartilaginous condition of the
parts intended to stiffen their bodies and aid their movements
indicate that it is among them that the skeleton ends or rather that
nature has sketched its first rudiments.

By continually following the order of nature in the inverse direction,
the eight last genera of this class should include the fishes whose
branchial apertures have no operculum or membrane and are nothing
but holes at the sides or under the throat; finally the lampreys and
hag-fishes should terminate the class, for these fishes differ greatly
from all others by the imperfection of their skeleton and in having a
naked slimy body without lateral fins, etc.

OBSERVATIONS ON THE VERTEBRATES.

The vertebrate animals, although differing greatly from one another
as regards their organs, appear to be all formed on a common plan
of organisation. On passing from the fishes to the mammals, we find
that this plan becomes more perfect from class to class and that it
only reaches completion in the most perfect mammals; but we may
also notice that this plan while approaching perfection has undergone
numerous modifications, some of them very large, through the influence
of the environment of the animals and of the habits which each

DEGRADATION OF ORGANISATION 81

race has been forced to contract by the conditions in which it is
placed.

Hence we see, on the one hand, that if vertebrates differ markedly
from one another in their organisation, it is because nature only started
to carry out her plan in their respect with the fishes; that she made
further advances with the reptiles; that she carried it still nearer
perfection with the birds, and that finally she only attained the end
with the most perfect mammals.

On the other hand, we cannot fail to recognise that if the perfection
of the plan of organisation of the vertebrates does not everywhere
show a regular and even gradation from the most imperfect fishes
to the most perfect mammals, the reason is that nature’s work has
often been modified, thwarted and even reversed by the influence
exercised by very different and indeed conflicting conditions of life

upon animals exposed to them throughout a long succession of
generations.

ANNIHILATION OF THE VERTEBRAL COLUMN.

On reaching this point in the animal scale the vertebral column
becomes entirely annihilated. Since this column is the basis of
every true skeleton, and since this bony framework is an important
part of the organisation of the most perfect animals, it follows that all
the invertebrate animals, which we are about to investigate in turn,
must have an organisation still more degraded than that of the four
classes that we have just passed in review. Henceforth, therefore,
the supports for muscular activity will no longer reside in any internal
parts.

Moreover, none of the invertebrate animals breathes by cellular
lungs; none of them has any voice nor consequently any organ
for this faculty; finally they mostly appear devoid of true blood,
that is to say, of that fluid which in the vertebrate is essentially red,
but which only owes its colour to the intensity of their animalisation,
and proves especially a real circulation. How grave an abuse of words
it would be to give the name of blood to the thin and colourless fluid
which moves slowly through the cellular substance of the polyps!
We might as well apply the name to the sap of plants.

Besides the vertebral column, we also lose here the iris which is
characteristic of the eyes of the most perfect animals; for such of the
invertebrates as have eyes have no distinct irises.

Kidneys in the same way are only found among the vertebrates,
and fishes are the last animals where this organ is met with. Hence-
forward there is no more spinal cord, no more great sympathetic

nerve.
F

82 ZOOLOGICAL PHILOSOPHY

A final very important observation is that among vertebrates, and
especially in the neighbourhood of that extremity of the animal scale
where the most perfect animals are found, all the essential organs
are isolated or have each an isolated seat in as many special places.
We shall soon see that the complete contrary holds good according
as we approach the other extremity of the scale.

It is then obvious that all the invertebrate animals have a less
perfect organisation than any of those which possess a vertebral
column ; while the organisation of mammals is that which from all
aspects includes the most perfect animals and is beyond question
the true type of the highest perfection.

Let us now enquire whether the classes and large families into
which the long series of invertebrate animals is divided also exhibit,
when we compare them together, an increasing degradation in the
complexity and perfection of their organisation.

INVERTEBRATE ANIMALS.

On reaching invertebrate animals we enter upon an immense series
of diverse creatures, the most numerous of any existing in nature,
the most curious and interesting with regard to the variations observed
in their organisation and faculties.

On observing their condition, we are convinced that in bringing
them successively into existence, nature has proceeded gradually
from the simplest to the most complex. Now since the purpose
in view has been to attain a plan of organisation which should admit
of the highest perfection (that of the vertebrates)—a plan very
different from those which nature had hitherto used to reach this point
—we may be sure that among these numerous animals we shall not
meet with a single system of organisation progressively perfected,
but with various quite distinct systems, each one taking its start
at the point where each organ of highest importance began to exist.

For instance, when nature attained to the creation of a special organ
for digestion (as in the polyps) she then gave for the first time a special
constant shape to the animals provided with it; seeing that the in-
fusorians with which she began everything could not possess either
the faculty endowed by this organ, or the kind of shape and organisa-
tion favourable to its functions.

She subsequently established a special organ for respiration, and
in proportion as she varied this organ in order to perfect it and to
accommodate it to the animal’s environment, she diversified their
organisation, in so far as the existence and development of the other
special organs rendered it necessary.

DEGRADATION OF ORGANISATION 83

_ When afterwards she succeeded in producing the nervous system,
it then immediately became possible to create the muscular system.
Thereupon, fixed points for the attachments of the muscles became
necessary, and also paired parts so as to constitute a symmetrical
shape. Hence have resulted various schemes of organisation due to
the environment and to the parts acquired, which could not previously
have come about.

When finally she secured sufficient movement in the contained
fluids of the animal to permit a circulation to be organised, there
again resulted important peculiarities of organisation which dis-
tinguished it from the organic systems in which there is no
circulation.

In order to perceive the truth of what I have stated and to furnish
evidence of the degradation and simplification of organisation (since
we are following the order of nature in the inverse direction) let us
rapidly run through the various classes of invertebrate animals.

MOLLUSCS.

Soft unjointed animals which breathe by gills and have a mantle. No
ganglionic longitudinal cord; no spinal cord.

The fifth rank, as we descend the graduated scale of the animal
series, necessarily belongs to the molluscs ; for they have to be placed
a stage lower than the fishes since they have no vertebral column,
but they are yet the most highly organised of invertebrate animals.
They breathe by gills, which vary greatly not only in their shape and
size, but in their position within or without the animal according
to the genera, and the habits of the races comprised in these genera.
They all have a brain; nerves without nodes, that is to say, without
a row of ganglia stretching down a longitudinal cord. They have
arteries and veins and one or several single-chambered hearts. They
are the only known animals which, although possessing a nervous
system, have neither a spinal cord, nor a ganglionic longitudinal
cord.

Gills, which are essentially intended by nature to carry out re-
spiration during immersion in the water, have been subjected to modi-
fication both in function and shape in those aquatic animals which
have been constantly exposed for generations to contact with the air,
and even in some cases have stayed in it altogether.

The respiratory organ of these animals has imperceptibly become
accustomed to the air ; and this is no mere supposition : for it is known
that all the crustaceans have gills and yet there are crabs (Cancer

84 ZOOLOGICAL PHILOSOPHY

ruricola) which habitually live on land and breathe air quite naturally
with their gills. Eventually this habit of breathing air with gills
became a necessity to many molluscs which acquired it: it even
modified the organ in such a way that the gills of these animals,
having no further need for so many points of contact with the respired
fluid, became adherent to the walls of the cavity which contains
them.

As a result we may distinguish among molluscs two kinds of
gills.

The first kind consist of networks of vessels running through the
skin of an internal cavity which is not protruded and can only breathe
air: these may be called aerial gills.

The second kind are organs nearly always protruded either within
or without the animal and forming fringes or pectinate lamellae or
edgings, etc.: these can only achieve respiration by means of the
contact of fluid water, and may be called aquatic gills.

If the differences in the habits of animals produce differences in their
organs, it will be useful in describing the special characters of certain
orders of molluscs to distinguish those which have aerial gills from
those whose gills can only breathe water; but in any case they are
always gills and it appears to us quite improper to say that the molluscs
which breathe air possess a lung. How often the abuse of words
and wrong applications of names have served to distort objects and
lead us into error!

After all, is the difference so great between the respiratory organ
of Pneumoderma, which consists in a vascular network running over
an external skin, and the vascular network of snails, which runs over
an internal skin? Yet Pnewmoderma appears to breathe nothing but
water.

Let us further enquire for a moment if there are any affinities between
the respiratory organ of air-breathing molluscs and the lung of verte-
brates.

A lung is essentially a peculiar spongy mass composed of more
or less numerous cells into which air is always entering in nature.
The entrance is effected through the animal’s mouth and thence by a
more or less cartilaginous canal called the trachea, which usually
sub-divides into branches known as bronchi, culminating in the cells.
The cells and bronchi are alternately filled and emptied of air by
successive swellings and shrinkings of the cavity of the body contain-
ing the mass; so that distinct alternate inspirations and expirations
are characteristic of alung. This organ can only tolerate the contact
of air and is highly irritated by water or any other material. It is
therefore different in character from the branchial cavity of certain

DEGRADATION OF ORGANISATION 85

molluscs, which is quite peculiar, exhibits no alternate swelling and
shrinking, never has a trachea or bronchi and in which the respired
fluid never enters by the animal’s mouth.

A respiratory cavity which has neither trachea nor bronchi nor
alternate swelling and shrinking, and in which the respired fluid
does not enter by the mouth, and which is adapted either for air or
water, cannot be a lung. To confuse such different things by the
same name is not to advance science but to retard it.

The lung is the only respiratory organ that can give the animal
the faculty of having a voice. After the reptiles no animal has a
lung; nor therefore a voice.

TI conclude that it is not true that there are molluscs which breathe
by lungs. If some in nature breathe air, so also do certain crustaceans
and all insects; but none of these animals has true lungs, unless the
same name is to be given to very different objects.

The molluscs also furnish proof of the progressive degradation that
we are investigating in the animal chain ; for their general organisation
is less perfect than that of fishes. But it is not so easy to recognise
the same degradation among the molluscs themselves ; for it is difficult
to distinguish in so numerous and varied a class what is due to the
degradation in question, from what is caused by the environment
and habits of these animals.

The only two orders into which the large class of molluscs is
divided, are strongly contrasted by the importance of their dis-
tinctive characters. The animals of the first of these orders (cephalic
molluscs) have a very distinct head, eyes, jaws or a proboscis and
reproduce by copulation.

All the molluscs of the second order (acephalic molluscs) on the con-
trary are destitute of a head, eyes, jaws, proboscis; and they never
copulate for the purpose of reproduction.

Now it can hardly be denied that the second order of molluscs
is inferior to the first as regards perfection of organisation.

It is important, however, to remember that the absence of head,
eyes, etc., in the acephalic molluscs is not wholly due to the general
degradation of organisation, since we find again at lower stages of
the animal chain, animals which have a head, eyes, etc. We have here
again apparently one of those deviations in the progress of perfection
of organisation that are produced by environment, and consequently
by causes foreign to those which make for a gradual increase of com-
plexity in animal organisation.

When we come to consider the influence of the use of organs and of
an absolute and permanent disuse, we shall see that a head, eyes,
etc., would in fact have been of very little use te molluscs of the second

86 ZOOLOGICAL PHILOSOPHY

order, because the large development of their mantle would have
prevented the functioning of these organs.

In conformity with that law of nature which requires that every
organ permanently disused should imperceptibly deteriorate, become
reduced and finally disappear, the head, eyes, jaws, etc., have in fact
become extinct in the acephalic molluscs: we shall see elsewhere
many other examples of the same thing.

In the invertebrates nature no longer finds in the internal parts
any support for muscular movement; she has therefore supplied
the molluscs with a mantle for that purpose. Now the strength and
compactness of this mantle of the molluscs is proportional to the
necessity entailed by their locomotion and means of support.

Thus in the cephalic molluscs, where there is more locomotion
than in those which have no head, the mantle is closer, thicker and
stronger ; and among the cephalic molluscs, those which are naked
(without shells) have in addition a cuirass in their mantle which is
stronger than the mantle itself and greatly facilitates the locomotion
and contraction of the animal (slugs).

But if, instead of following the animal chain in the opposite direc-
tion from the actual order of nature, we followed it from the most
imperfect animals to the most perfect, we should then easily per-
ceive that nature when she was about to start the plan of organisation
of the vertebrates, was forced in the molluscs to abandon the use of a
crustaceous or horny skin as a support for muscular action, and to
prepare to transfer these fulcra into the interior of the animal. In
this way the molluscs are to some extent in the midst of this change
of system of organisation; they have in consequence only feeble
powers of locomotive movements and they all carry out such move-
ments with remarkable slowness.

CIRRHIPEDES.

Animals without eyes which breathe by gills and have a mantle and jointed
arms with a horny skin.

The cirrhipedes, of which only four genera! are yet known, should
be considered as a special class, since these animals cannot belong to
any other class of invertebrate animals.

They approach the molluscs by their mantle and should be placed
immediately after the acephalic molluscs, since like them they have
neither head nor eyes.

Yet the cirrhipedes cannot be a part of the class of molluscs; for

1 Anatifa, Balanus, Coronula, and Tubicinella.

DEGRADATION OF ORGANISATION 87

their nervous system is characterised like the animals of the three
following classes by a ganglionic longitudinal cord. They have more-
over jointed arms with a horny skin and several pairs of transverse
jaws. They are therefore of lower rank than molluscs. Their fluids
move by a true circulation with arteries and veins.

These animals are fixed on marine bodies and in consequence carry
out no locomotion ; their principal movements are those of their arms.
Now although they have a mantle like the molluscs, nature could not
obtain from it any assistance for the movements of their arms, and
was forced to create in the skin of those arms fulcra for their muscles.
Hence the skin is coriaceous and almost horny like that of crustaceans
and insects.

ANNELIDS.

Animals with elongated annulated bodies without jointed legs, breathing
by gills and having a circulatory system and a ganglionic longi-
tudinal cord.

The class of annelids necessarily comes after that of cirrhipedes,
because no annelid has a mantle. We are moreover compelled to place
them before the crustaceans, because they have no jointed legs and it
would not do to interpose them in the series of those which have; nor
does their organisation permit us to place them lower than the insects.

Although these animals in general are still very little known, the
rank to which their organisation entitles them proves that in their case
again the degradation of organisation is continued; for from this
aspect they are inferior to the molluscs in that they have a ganglionic
longitudinal cord; they are inferior also to the cirrhipedes, which
have a mantle like molluscs ; and the fact that they have not jointed
legs prevents us from interposing them in the series of those which
are so organised.

Annelids owe their elongated form to their habits of life, for they
either live buried in damp earth or in mud or actually in the water,
mostly in tubes of various materials which they enter and leave at
will. Thus they are so like worms that all naturalists hitherto have
confused the two.

Their internal organisation shows a very small brain, a ganglionic
longitudinal cord, arteries and veins in which circulates blood that is
usually coloured red; they breathe by gills, sometimes external and
protruding, and sometimes internal and hidden or invisible.

88 ZOOLOGICAL PHILOSOPHY

CRUSTACEANS.

Animals with a jointed body and limbs, crustaceous skin, a circulatory
system, and breathing by gills.

We now enter upon the long series of animals, whose body and
limbs are jointed, and whose integuments are hard, crustaceous,
horny or coriaceous.

The solid or hard parts of these animals are all on the exterior.
Since nature created the muscular system very little in advance
of the earlier animals of this series, and since she had need of solid
support to endow it with energy, she was obliged to establish the
method of articulation in order to secure the possibility of movement.

All the animals that exhibit this method of articulation were held
by Linnzeus and subsequently as forming only a single class, to which
was given the name of insects; but it was at length recognised that
this large series of animals has several important divisions which
roust be distinguished.

The class of crustaceans, which had thus been confused with that
of insects, although all the ancient naturalists had always kept it
apart, is a division indicated by nature and must be maintained.
It should follow immediately upon the annelids and occupy the
eighth rank in the general series of animals; this is required by their
organisation and is not a matter of arbitrary opinion.

The crustaceans indeed have a heart, arteries and veins; a trans-
parent and almost colourless circulating fluid, and they all breathe
by true gills. This is unquestionable and will always constitute a
difficulty in the way of those who persist in placing them among the
insects on account of their having jointed legs.

If the crustaceans are completely distinguished from the arachnids.
and insects by their circulation and respiratory organ, and if their
rank is therefore obviously superior, they yet share one trait of
inferiority of organisation with the arachnids and insects as compared
with the annelids ; that, namely, of being a part of the series of animals.
with jointed limbs: a series in the course of which the circulatory
system and consequently the heart, arteries and veins are seen to-
diminish and disappear, and in which again the branchial system
of respiration is likewise lost. The crustaceans therefore again confirm
the continuous degradation of organisation in the direction in which
we are following the animal scale. The transparency and extreme
thinness of the fluid which circulates in their vessels, like that of
insects, is a further proof of their degradation.

As to their nervous system, it consists of a very small brain and a

DEGRADATION OF ORGANISATION 89

ganglionic longitudinal cord. This is a sign of poverty of that system
observed among the animals of the two preceding and the two following
classes ; for the animals of these classes are the last in which a nervous
system is still to be seen.

It is in the crustaceans that the last traces of an organ of hearing have
been identified ; after them it is no more found in any animal.

OBSERVATIONS.

Here ends the existence of a true circulatory system, that is to say,
of a system of arteries and veins, which is part of the organisation of the
most perfect animals and with which those of all the preceding classes
are provided. The organisation of the animals of which we shall now
speak is still more imperfect than that of the crustaceans, which are
the last in which a circulation is actually to be found. The degradation
of organisation is thus clearly in progress; since according as we
advance along the series of animals, all features of resemblance are
successively lost between the organisation of those we come to and
that of the most perfect animals.

Whatever may be the nature of the movement of the fluids in
the animals of the classes that we are about to traverse, that move.
ment is secured by less active methods, and constantly tends to
become slower.

ARACHNIDS.

Animals breathing by limited tracheae, undergoing no metamorphosis,
and having throughout their lives jointed legs and eyes in their
head.

On continuing the order that we have hitherto followed, the ninth
rank in the animal kingdom necessarily belongs to the arachnids ;
they have so much affinity with the crustaceans that we shall always
have to bring them together, immediately following one another.
They are however entirely distinct; for the arachnids furnish us
with the first example of a respiratory organ lower than gills,—one
never met with in animals which have a heart, arteries and veins.

Arachnids in fact breathe only by stigmata and air-carrying tracheae,
which are respiratory organs analogous to those of insects. But
these tracheae, instead of extending throughout the body as in the
insects, are limited to a small number of sacs: this shows that nature
is bringing to an end in the arachnids the method of respiration
which she had to employ before the establishment of gills, just as she
brought to an end in the fishes or later reptiles that which she had to
make use of, before she could form a true lung.

90 ZOOLOGICAL PHILOSOPHY

If the arachnids are quite distinct from the crustaceans, through
not breathing by gills but by very limited air-carrying tracheae,
they are also to be distinguished from the insects. It would be quite
as improper to combine them with the insects of which they lack
the classic character and from which they differ even in internal
organisation, as it would be to confuse the crustaceans with the insects.

The arachnids, indeed, although having strong affinities with the
insects are essentally distinct from them:

1. In that they never undergo metamorphosis, that they have at
birth the shape and all the parts of an adult and that, consequently,
they have eyes in their head and jointed legs throughout their lives.
This is an order of things that follows from the nature of their internal
organisation and therein differs greatly from that of insects ;

2. In that in the arachnids of the first order (pedipalp-arachnids)
we begin to see the outlines of a circulatory system ; }

3. In that their respiratory system, although of the same order
as that of insects, is nevertheless very different ; since their tracheae
are limited to a small number of sacs, and do not constitute the very
numerous air-canals extending throughout the animal’s body that are
witnessed in the tracheae of insects ;

4. Lastly, in that the arachnids procreate several times in the course
of their life; a faculty which the insects do not possess.

These considerations suffice to show how faulty are those arrange-
ments in which the arachnids and insects are combined into one class,
through paying exclusive regard to the joints in these animals’ legs,
and the more or less crustaceous skin which covers them. It is almost
as if we were to consider only the more or less scaly integuments of
reptiles and fishes, and thus to combine them into one class.

The general degradation of organisation that we are seeking through-
out the entire animal scale is extremely obvious in the arachnids: these
animals indeed breathe by an organ inferior in organic perfection
to lungs and even to gills, and have only the rudiments of a circulation
apparently not yet finished off. They thus confirm in their turn the
continuous degradation in question.

This degradation may even be observed in the series of species
belonging to that class; for the arachnids with antennae, making up
the second order, are sharply distinguished from the others, are very
inferior to them in progress of organisation, and come close to the
insects; they differ from the latter however in undergoing no meta-

1“ Tt is especially in the spiders that this heart may be easily observed: it may
be seen beating through the skin of the abdomen in species that are not hairy. On
removing this skin, a hollow oblong organ is seen, pointed at the two ends, with the

anterior end directed towards the thorax and from the sides of which there issue
visibly two or three pairs of vessels” (Cuvier, Anatom. comp. vol. iv. p. 419).

DEGRADATION OF ORGANISATION 91

morphosis ; and as they never launch themselves into the air, it is
very probable that their tracheae do not generally extend through-
out all parts of their bodies.

INSECTS.

Animals which undergo metamorphoses, and have in the perfect state
two eyes and two antennae in their head, six jointed legs and two
tracheae which extend throughout their body.

As we continue to follow the inverse order from that of nature,
the insects necessarily succeed the arachnids. They constitute that
immense series of imperfect animals which have no arteries or veins ;
which breathe by air-carrying tracheae not limited to special parts ;
lastly, which are born in a state less perfect than that in which they
reproduce ; and which consequently undergo metamorphoses,

In their perfect state all insects without exception have six jointed
legs, two antennae and two eyes in their head, and most of them
also have wings.

The insects necessarily occupy the tenth rank of the animal kingdom
in the order that we are following; for they are inferior to the arachnids
in perfection of organisation since they are not born like these latter in
their perfect state, and they only procreate once in the course of their
life. It is particularly in the insects that we begin to observe that the
organs essential to maintenance of life are almost equally distributed,
and in most cases situated throughout their bodies instead of being
isolated in special places, as is the case in the most perfect animals.
The exceptions to this rule gradually disappear, so that it becomes
ever more striking in the lower classes of animals.

Nowhere hitherto has the general degradation of organisation
been more manifest than in the insects, whose organisation is less
perfect than that of the animals of any of the preceding classes.
This degradation comes out even within the various orders into which
insects are naturally divided; for those of the three first orders
(Coleoptera, Orthoptera, Neuroptera) have mandibles and mazxillae
jn their mouths; those of the fourth order (Hymenoptera) begin to
possess a sort of proboscis ; finally, those of the four last orders (Lepi-
doptera, Hemiptera, Diptera and Aptera) have really nothing more
than a proboscis. Now paired maxillae are nowhere found again
in the animal kingdom, after the insects of the three first orders.
With regard to wings, the insects of the six first orders have four,
all of which or only two serve for flight. Those of the seventh and
eighth have only two wings or else they are quite aborted. The

92 ZOOLOGICAL PHILOSOPHY

larvae of the insects of the two last orders have no legs and are like
worms.

It appears that the insects are the last animals which have a quite
distinct sexual reproduction and are probably oviparous.

Lastly, we shall see that insects are rendered highly remarkable
by what is called their skill; but this alleged skill is far from being
the product of any thought or any combination of ideas on their
part.

OBSERVATION.

Just as among the vertebrates the fishes display in their general
conformation and anomalies of organisation the product of the action
of their environment ; so the insects among the invertebrates exhibit,
in their shape, organisation and metamorphoses, the obvious effects
of the action of the air in which they live; for most of them launch
themselves into it and habitually maintain themselves there like
birds.

If the insects had had lungs, if they had been able to swell them-
selves out with air, and if the air which penetrates into every part
of their body could have there become rarefied like that which is intro-
duced into the body of birds, their hair would no doubt have changed
into feathers.

Lastly, if among invertebrate animals we are surprised to find so
few affinities between the insects which undergo remarkable meta-
morphoses and other classes of invertebrates, let us remember that
these are the only invertebrate animals which launch themselves into
the air and there execute movements of progression; we shall then
no longer be surprised that such peculiar conditions and habits must
have produced peculiar results.

The insects are allied only to the arachnids by their affinities, and in
fact these two are in general the only invertebrate animals that live in
the air; but no arachnid has the faculty of flight; none therefore
undergoes metamorphosis ; and when I come to treat of the influence
of habits, I shall show that these animals, being accustomed to remain
on the surface of the earth and to live in retreats, must have lost a
part of the faculties of insects and acquired characters which con-
spicuously distinguish the two groups.

EXTINCTION OF SEVERAL ORGANS ESSENTIAL TO THE
Most Prerrect ANIMALS.

After the insects it appears that there is a rather large gap in the
series remaining to be filled by animals not yet observed ; for in this
part of the series several organs essential to the most perfect animals

DEGRADATION OF ORGANISATION 93

suddenly drop out and are really annihilated, since they are not found
again in the classes which remain to be considered.

DISAPPEARANCE OF THE NeERvous SysTEM.

Here for instance the nervous system (the nerves and their centre
of communication) completely disappears, and is no more found in
any of the animals of the succeeding classes.

In the most perfect animals, this system consists of a brain which
appears to serve for carrying out acts of intelligence. At its base is
the nucleus of sensations from which issue nerves and also a dorsal
spinal cord which sends out other nerves to various parts.

Among the vertebrates the brain becomes regularly reduced, and
as its volume diminishes the spinal cord becomes larger and seems to
take its place.

Among the molluscs which constitute the first class of the inver-
tebrates the brain still exists, but there is no spinal cord nor a gan-
ghonic longitudinal cord, and as ganglia are rare the nerves do not
appear to have nodes.

Lastly, in the five following classes the nervous system is approach-
ing its end and is reduced to the very small rudiments of a brain and
to a longitudinal cord from which issue nerves. Thereafter there is
no longer a separate nucleus for sensations, but a multitude of small
nuclei scattered throughout the length of the animal’s body.

Hence among insects, the important system of feeling comes to an
end; a system which at a certain stage of development gives birth
to ideas and which in its highest perfection can produce all the acts
of intelligence; which, lastly, is the source whence muscular action
derives its power and without which sexual reproduction apparently
could not exist.

The centre of communication of the nervous system is situated
in the brain or at its base or in a ganglionic longitudinal cord. There
is still a longitudinal cord when there is no longer any obvious brain ;
but when there is neither a brain nor a longitudinal cord, the nervous
system ceases to exist.

DISAPPEARANCE OF THE SEXUAL ORGANS.

Here again all traces of sexual reproduction disappear; indeed
among the animals about to be cited it is no longer possible to recognise
organs for true impregnation. We shall, however, still find among
the animals of the two following classes kinds of ovaries, abounding
in oviform corpuscles that are alleged to be eggs; but I look upon
these supposed eggs which can develop without previous fertilisation

94 ZOOLOGICAL PHILOSOPHY

as buds or internal gemmules; they establish a connection between
internal gemmiparous reproduction and sexual oviparous reproduction.

The strength of habit is so great that man always perseveres in the
same view of things, even when it is contrary to the evidence.

Thus botanists, accustomed to observing the sexual organs of a
great number of plants, affirm that all without exception have such
organs. Consequently several botanists have made every conceivable
effort to discover stamens and pistils in cryptogamic or agamic plants ;
and they have preferred to attribute arbitrarily and without proof
these functions to parts of whose use they are ignorant, rather than
admit that nature may attain the same end by different means.

It was believed that every reproductive body is a seed or egg, that is
to say, a body which must undergo the influence of sexual fertilisa-
tion in order to be reproductive. This is what caused Linneus to
say: Omne vivum ex ovo. But we now know well plants and animals
which reproduce entirely by means of bodies that are neither seeds
nor eggs, and which consequently do not require sexual fertilisation.
These bodies are therefore differently fashioned and develop in another
manner.

The following is the principle to be observed in judging of the method
of reproduction in any living body.

Any reproductive corpuscle which without having any investment
to break through lengthens, grows and becomes a plant or animal
similar to that from which it sprang, is not a seed nor an egg; it
undergoes no germination and does not hatch after beginning to
grow, and its formation requires no sexual fertilisation: thus it does
not contain an embryo in an investment which has to be broken
through, as does the seed or egg.

Now, if you follow attentively the development of the reproductive
corpuscles of algae, fungi, etc., you will see that the result of the lengthen-
ing and growth of these corpuscles is to take imperceptibly the shape
of the plant from which they spring; that they do not break through
any investment as does the embryo in the seed or egg.

Similarly, if you follow the gemma or bud of a polyp like a hydra,
you will be convinced that this reproductive body does nothing but
lengthen out and grow; that it breaks through no investment; in short,
that it does not hatch like a chicken or silkworm coming out of its egg.

It is then clear that all reproduction of individuals does not come
about by means of sexual fertilisation ; and that when sexual fertilisa-
tion does not occur there is not really a true sexual organ. Now as no
organ for fertilisation is to be distinguished in the four classes follow-
ing the insects it appears that this is the point in the animal chain
at which sexual reproduction ceases to exist.

DEGRADATION OF ORGANISATION 95

DISAPPEARANCE OF THE ORGAN OF SIGHT.

Here again the organ of sight, so useful to the most perfect animals,
is entirely extinguished. This organ began to be deficient in some
of the molluscs and cirrhipedes and in most of the annelids, and is
only found afterwards in the crustaceans, arachnids and insects in a
very imperfect state and of little or no use; after the insects it does
not re-appear in any animal.

Here again, finally, the head altogether ceases to exist,—an essential
part of the body of the most perfect animals and the seat of the brain
and nearly all the senses; for the swelling at the anterior extremity
of the body of some worms like Taenia is caused by the arrangement
of their suckers and is not the seat of a brain nor of any organ of
hearing, sight, etc., since there are no such organs in the animals of
the neighbouring classes. Hence this swelling cannot be considered
as a true head.

We see that at this part of the animal scale the degradation of
organisation becomes extremely rapid, and strongly foreshadows the
greatest simplification of animal organisation.

WORMS.

Animals with soft elongated bodies, without head, eyes or jointed legs,
and no longitudinal cord or circulatory system.

We now come to worms, which have no vessels for circulation ; in-
cluding those known under the name of intestinal worms, and some
others not intestinal whose organisation is quite as imperfect. They
are animals with soft more or less elongated bodies, which undergo no
metamorphosis and are all destitute of a head, eyes and jointed legs.

The worms should be placed immediately after the insects and before
the radiarians, and occupy the eleventh rank in the animal kingdom.
It is among them that we note the origin of the tendency of nature
to establish the system of articulations, a system that she subsequently
carried to completion in the insects, arachnids and crustaceans. But
the organisation of the worms is less perfect than that of the insects,
since they have no longitudinal cord, head, eyes or true legs, so that we
are forced to place them after the insects; lastly, the new kind of shape,
which nature initiates in them on passing from a radiating arrange-
ment of the parts to the system of articulations, shows that the worms
should be placed even before the radiarians. After the insects, more-
over, the plan followed by nature in the animals of preceding classes
is lost sight of, viz. that general shape of the animal which consists

96 ZOOLOGICAL PHILOSOPHY

of a bilateral symmetry of the parts, so that each part is opposite to
another exactly like it.

In the worms we no longer find this bilateral symmetry, nor do
we yet witness the radiating arrangement of the organs both internal
and external which characterises the radiarians.

After I established the annelids, some naturalists called them by
the name of worms; and as they did not then know what to do with
the animals now under discussion, they united them with the polyps.
I leave the reader to imagine what may be the affinities and classic
characters that justify the union in one class of Taenia or Ascaris with
a hydra or any other polyp.

Several worms still appear to breathe like insects by tracheae of
which the external openings are kinds of stigmata ; but there is reason
to believe that these limited or imperfect tracheae are water-carrying
and not air-carrying like those of insects; because these animals
never live in the open air, but are continuously in the water or bathed
by fluids which contain water. :

As no organ for fertilisation is distinguished in them, I suppose
that sexual reproduction does not occur in these animals. It may be
however that, just as there exists a primitive circulation in arachnids
so there may exist a sexual reproduction in the worms, as is suggested
by the various shapes of the tail of Strongylus; but observation has
not yet fully established such reproduction in these animals.

Objects which are found in some of them and supposed to be ovaries
(as in Taenia) appear to be merely clusters of reproductive corpuscles
which do not require fertilisation. These oviform corpuscles are
internal, like those of sea-urchins, and not external like those of
Coryne, etc. Polyps exhibit similar differences in the situation of their
gemmules; it is therefore probable that the worms are internally
gemmiparous.

Animals like the worms, which have no head, eyes, legs or perhaps
sexual reproduction, provide further evidence in their turn of the con-
tinuous degradation of organisation that we are seeking throughout
the animal scale.

RADIARIANS.

Animals with regenerating bodies, destitute of a head, eyes or jointed
legs ; with the mouth on the inferior surface and a radiating arrange-
ment of the parts both internal and external.

In the usual order the radiarians occupy the twelfth rank in the
lengthy series of known animals, and constitute one of the three last
classes of invertebrates.

DEGRADATION OF ORGANISATION 97

When we reach this class we find animals with a general shape
and arrangement of the parts and organs, both internal and external,
that nature has not employed in any of the animals of the anterior
classes.

The radiarians indeed conspicuously exhibit in their internal and
external parts that radiating arrangement around a centre or axis,
which constitutes a special shape not hitherto used by nature. Its
rudiments are found in the polyps, which accordingly come next.

Nevertheless, the radiarians form a stage in the animal scale quite
distinct from the polyps; so that we can no more confuse radiarians
with polyps than we can class crustaceans with insects or reptiles
with fishes. Among the radiarians indeed, not only do we find again
organs apparently intended for respiration (tubes or kinds of water-
bearing tracheae), but we discover in addition special organs for
reproduction, such as kinds of ovaries of various shapes to which
there is nothing analogous in the polyps. Moreover, the intestinal
canal of the radiarians is not generally a cul-de-sac with a single
opening as in all the polyps; their mouth is always on the inferior
surface and displays a special arrangement which is quite different
from that commonly found in polyps.

Although the radiarians are very remarkable animals, and as yet
little known, what we do know of their organisation plainly points to
the rank which I am assigning to them. Like the worms, radiarians
have no head, eyes, jointed legs, circulatory system or perhaps nerves.
Yet the radiarians necessarily come next to the worms, for the latter
have nothing in the arrangement of their internal organs that suggests
a radiating shape, and it is among them that the system of articulations
begins.

Tf the radiarians are destitute of nerves, they cannot have the faculty
of feeling, but are simply irritable; this fact seems to be confirmed
by observations made on living star-fishes, whose arms have been cut
off without their showing any sign of pain.

In many radiarians fibres may still be distinguished; but can we
call these fibres muscles? Not unless we are justified in saying
that a muscle can function without nerves. Do not plants show us
that cellular tissue may be reduced to fibres? Yet we cannot possibly
regard these fibres as muscular. In my opinion it does not follow
that because a living being has distinguishable fibres, it must therefore
have muscles; I hold that where there are no nerves, there is no
muscular system. There is reason to believe that in animals without
nerves the fibres which are still to be found possess the faculty by mere
irritability of producing movements which replace those of the muscles,

although less energetically.
G

98 ZOOLOGICAL PHILOSOPHY

Not only does it appear that the muscular system has ceased to
exist in the radiarians, but also there seems to be no sexual repro-
duction. There is indeed nothing to show or even to suggest that the
little oviform bodies, the clusters of which are called ovaries in these
animals, undergo any fertilisation or are true eggs: this is rendered
still less probable by the fact that they are found in all individuals
alike. Hence I regard these little oviform bodies as already perfected
internal gemmules, and the clusters of them in special places as nature’s
preliminary step towards sexual reproduction.

The radiarians in their turn contribute to prove the general degrada-
tion of animal organisation; for on reaching this class of animals
we find a shape and a new arrangement of the parts and organs that
are far removed from the animals of the preceding classes. Further-
more they appear to be destitute of feeling, muscular movement and
sexual reproduction; among them the intestinal canal no longer has
two exits, the clusters of oviform corpuscles disappear, and the body
becomes completely gelatinous.

OBSERVATION.

It appears that in very imperfect animals such as the polyps and
radiarians, the centre of movement of the fluids does not exist except
in the alimentary canal ; it is here that it is first established, and it is
through this canal that the subtle surrounding fluids enter, mainly
for the purpose of stimulating the movement of the fluids which belong
to these animals themselves. What would plant life be without
external stimuli? What indeed would be the life of the most imperfect
animals without this factor, that is, without the caloric and electricity
of the environment ?

The radiating form has no doubt been acquired as a consequence
of this method, which nature employs feebly at first in the polyps
and afterwards with greater vigour in the radiarians; for the subtle
surrounding fluids which enter the alimentary canal are expansive
and must by incessant repulsion from the centre towards every point
of the circumference give rise to this radiating arrangement of the
parts.

This is the reason why in the radiarians the intestinal canal, although
still very imperfect, since it has usually only one opening, is none the
less provided with numerous radiating vasculiform and often branched
appendages.

This again is no doubt the reason why in the soft radiarians, such as
jelly-fishes, etc., we may observe a continual isochronous movement,
a movement which very probably results from the alternative move-
ments of the masses of subtle fluids, which penetrate into the interior

DEGRADATION OF ORGANISATION 99

of these animals and escape again, after having spread throughout
all their parts.

Let it not be said that the isochronous movements of the soft radi-
arians are signs of respiration; for nature does not exhibit in any
animal after the vertebrates those alternate and measured movements
of inspiration and expiration ; whatever the respiration of radiarians
may be, it is extremely slow and involves no appreciable movement.

POLYPS.

Animals with sub-gelatinous and regenerating bodies, with no special
organ but an alimentary canal with only one opening. Terminal
mouth supplied with radiating tentacles or a ciliated and rotatory
organ.

With the polyps we reach the penultimate stage of the animal scale,
that is to say, the last but one of the classes which have to be established
among animals.

Here the imperfection and simplicity of organisation are very
striking, ‘so that the animals of this group have scarcely any faculties
left, and their animal nature has long been doubted.

They are gemmiparous animals with homogeneous bodies, usually
gelatinous, and with very regenerative parts, not displaying the
radiating shape (for it is only here that nature began it) except in
radiating tentacles around their mouth, and having no special organ
but an intestinal canal, which has only one opening and is therefore
incomplete.

The polyps may be described as much more imperfect animals
than any of those which make up the preceding classes, for they have
no brain, longitudinal cord, nerves, special respiratory organs, vessels
for the circulation of fluids nor ovary for reproduction. The substance
of their body is to a great extent homogeneous and composed of
a gelatinous and irritable cellular tissue in which fluids move slowly.
Lastly, their viscera are entirely reduced to an imperfect alimentary
canal, rarely folded on itself or provided with appendages, and usually
resembling a mere elongated sac, always with a single opening which
serves at once for mouth and anus.

There can be no justification for the statement that, although
we find in these animals no nervous system, respiratory organ
or muscle, etc., yet these organs still exist infinitely reduced and
distributed or dissolved throughout the general substance of the
body, and equally divided up in every molecule instead of being
collected in special places; consequently that every point in their

100 ZOOLOGICAL PHILOSOPHY

body can experience every kind of sensation, muscular movement,
will, ideas and thought; this would be an altogether gratuitous,
baseless and improbable supposition. On such a supposition a hydra
must have in every part of its body all the organs of the most perfect
animals, and hence every point in the body of this polyp must see,
hear, distinguish odours, tastes, etc.; and also must have ideas,
form judgments, think and, in short, reason ; each molecule of the body
of a hydra or any other polyp would in itself be a perfect animal ; and
the whole hydra would be a more perfect animal even than man.
since each of its molecules would be equivalent, as regards the com-
pletion of organisation and faculties, to an entire individual of the
human species.

There is no reason why such an argument should not be extended to
the Monas—the most imperfect of known animals—and even to plants
themselves, which also possess life. We should then attribute to each
molecule of a plant all the aforementioned faculties, though restricted
within limits set by the nature of the living body of which it is part.

Assuredly it is not to this that the study of nature leads us. This
study teaches us, on the contrary, that wherever an organ ceases to
exist, the function depending on it ceases likewise. Any animal which
has no eyes or whose eyes have been destroyed cannot see; and
although in the last analysis the various senses derive their origin
from touch, of which they are only special modifications, yet no animal
which is without nerves, the special organ of feeling, could experience
any kind of sensation ; for it has not the intimate feeling of its existence,
it has not the central nucleus to which sensation has to be conveyed,
and consequently it could not feel.

Thus the sense of touch, which is the basis of the other senses and is
spread throughout every part of the bodies of animals which have
nerves, no longer exists in those which, like the polyps, have no nerves.
Among the latter, the parts are nothing more than merely irritable ;
they are so in a very high degree, but they are devoid of feeling and
hence of every kind of sensation. In order that a sensation may
arise, an organ is first necessary to receive it (nerves); and then some
central nucleus must exist (a brain or ganglionic longitudinal cord)
to which this sensation may be conveyed.

A sensation is always the sequel of an impression received and
immediately conveyed to an internal nucleus, where the sensation
is formed. Interrupt the communication between the organ which
receives the impression and the nucleus where the sensation is formed,
and all feeling will immediately cease. This principle can never be
disputed.

No polyp can really be oviparous; for it has no special organ for

DEGRADATION OF ORGANISATION 101

reproduction. Now in order to produce true eggs, it is necessary not
only that the animal should have an ovary, but in addition that it or
some other individual of its species should have a special organ for
fertilisation, and it cannot be shown that the polyps have such organs ;
in place of them we are well aware of the buds which some of them
produce for purposes of multiplication; and on paying them a little
attention we note that these buds are themselves nothing more than
somewhat isolated portions of the animal’s body,—portions less
simple than those employed by nature for the multiplication of the
animalcules which compose the last class of the animal kingdom.

Polyps, being highly irritable, only move by external stimuli foreign
tothemselves. All their movements are necessary results of impressions
received, and are in general carried out without any act of will; they
are thus without any possibility of choice, since they cannot have
any will.

They invariably and inevitably move towards the light, just like
the branches and leaves or flowers of plants, although in their case the
movement is slower. No polyp pursues its prey, nor seeks for it with
its tentacles; but when some foreign body touches these same ten-
tacles, they hold it and carry it to the mouth, and the polyp swallows
it without making any distinction as to its suitability or the reverse.
It digests and feeds on the body if it is capable of being digested,
but rejects it entirely if it remains some time untouched in the
alimentary canal ; finally, it brings up such of the débris as can be no
more broken up; but in all this, there is the same necessity in the
action and never any possibility of choice to vary it.

The distinction of the polyps from the radiarians is very wide and
glaring ; nowhere in the interior of the polyps is the radiating arrange-
ment to be found: their tentacles alone have this arrangement, thus
resembling the arms of the. cephalapod molluscs, with which however
they certainly cannot be confused. Moreover the polyps have a
superior terminal mouth, while the mouth of the radiarians is other-
wise situated.

It is altogether improper to give the polyps the name of zoophytes,
which means animal-plants ; because they are entirely and completely
animals. They have faculties absent in plants, that, for instance, of
true irritablity and generally of digestion ; and, lastly, their nature
has nothing essentially in common with that of a plant.

The only affinities existing between polyps and plants are: (1) A
similar simplification of organisation ; (2) the faculty possessed by
many polyps of adhering to one another with a common conmunica-
tion by their alimentary canal, and of forming compound animals ;
(3) the external shape of the groups formed by these combined polyps,

102 ZOOLOGICAL PHILOSOPHY

a shape which has long caused these groups to be taken for true plants,
since they are often branched almost in the same way.

Whether polyps have one or several mouths, there is always an
alimentary canal to which they lead and consequently an organ for
digestion, of which all plants are destitute.

If the degradation of organisation that we have observed in all classes
starting from the mammals is anywhere obvious, it is assuredly among
the polyps, whose organisation is reduced to an extreme simplification.

INFUSORIANS.

Infinitely small animals with gelatinous, transparent, homogeneous
and very contractile bodies ; with no distinct special organ internally,
but often oviform gemmules ; and having externally no radiating
tentacles nor rotatory organs.

At length we reach the last class of the animal kingdom, comprising
the most imperfect animals from all points of view; that is, those
which have the simplest organisation, possess the fewest faculties and
seem all to be mere rudiments of animal nature.

Hitherto I have placed these small animals in the class of polyps,
of which they constituted the last order under the name of amorphous
polyps, since they have no constant shape peculiar to them all;
but I have recognised the necessity of separating them to form a class
apart, though this in no wise changes the rank that I had assigned
tothem. The only result of this change is to establish a line of demarca-
tion which appears to be called for, on account of the greater sim-
plicity of their organisation and their lack of radiating tentacles and
rotatory organs.

Since the organisation of the infusorians becomes ever more simple
as we pass down their genera, the last of these genera shows us in some
degree the limit of animality, the limit at all events of what we can
reach. It is especially in the animals of the second order of this class
that we can verify the entire disappearance of any trace of an intestinal
canal and mouth; so that they have no special organ whatever nor
any digestion.

They are only very tiny gelatinous, transparent, contractile and
homogeneous bodies, consisting of cellular tissue, with very slight
cohesion and yet irritable throughout. These tiny bodies, which look
like animated or moving points, feed by absorption and continual
imbibition ; and they are doubtless animated by the influence of the
subtle surrounding fluids, such as caloric and electricity, which stimu-
late in them the movements constituting life.

DEGRADATION OF ORGANISATION 103.

If we were to imagine that such animals possess all the organs
known in other animals, but that these organs are dissolved throughout
their bodies, how absurd such a supposition would be !

The extremely slight cohesion between the parts of these tiny
gelatinous bodies is an indication that such organs cannot exist, since
they could not possibly carry on their functions. It is clear that in
order that any organs may have the power of reacting on fluids and
of carrying on their appropriate functions, their parts must have
enough cohesion and firmness to give them strength ; now this is not
to be imagined in the case of these fragile animalcules. It is exclu-

sively among the animals of this class that nature appears to carry |

yh

out direct or spontaneous generations, which are incessantly renewed

whenever conditions are favourable; and we shall endeavour to
show that it is through this means that she acquired the power after
an enormous lapse of time to produce indirectly all the other races of
animals that we know.

Justification for the belief that the infusorians or most of them owe
their existence exclusively to spontaneous generation is found in the
fact that all these fragile animals perish during the reduction of tem-
perature in bad seasons ; and it surely will not be suggested that such
delicate bodies could leave any bud sufficiently hardy to be preserved
and to reproduce them in warm weather.

Infusorians are found in stagnant waters and infusions of plant
or animal substances, and even in the seminal fluid of the most perfect
animals. They are found just the same in all parts of the world, but
only in conditions suitable for their existence.

Thus on examining in turn the various systems of organisation of
animals from the most complex to the simplest, we have seen the
degradation of animal organisation beginning even in the class that
comprises the most perfect animals and thence advancing progressively
from class to class, although with anomalies due to environment,
and finally ending with the infusorians. These last are the most
imperfect animals and the simplest in organisation,—the animals
in which the degradation that we have traced reaches its limit.
Animal organisation is then reduced to a simple homogeneous gela-
tinous body with very slight cohesion, destitute of special organs, and
entirely formed of a very delicate and primitive cellular tissue, which
appears to be vivified by subtle surrounding fluids incessantly penetrat-
ing it and exhaling from it.

We have seen each special organ in turn, including even the most
essential, become slowly degraded till it is less special, less isolated,
and finally completely lost and gone, long before reaching the other
extremity of the order we are tracing; and we have noticed that it is

104 ZOOLOGICAL PHILOSOPHY

chiefly among the invertebrate animals that the extinction of special
organs occurs.

It is true that even before leaving the division of vertebrates, we
already witness great changes in the perfection of organs ; while some
even disappear altogether, such as the urinary bladder, the diaphragm,
the organ of voice, the eyelids, etc. The lung, for instance, which is
the most perfect respiratory organ, begins its degradation in the reptiles
and ceases to exist in the fishes, not to reappear again in any inver-
tebrate animal. Finally, the skeleton, the appendages of which
constitute the basis of the four extremities or limbs possessed by most
vertebrates, begins its deterioration mainly in the reptiles and comes
entirely to an end with the fishes.

But it is in the division of invertebrates that the extinction takes
place of the heart, brain, gills, conglomerate glands, vessels for circula-
tion, the organs of hearing and sight, that of sexual reproduction
and even that of feeling, as also of movement.

As I have already said, we should vainly seek in a polyp, such as the
hydra or most animals of that class, the slightest vestiges either of nerves
(organs of feeling) or of muscles (organs of movement)! Irritability,
with which every polyp is highly endowed, alone replaces the faculty of
feeling which no polyp possesses, since it has not the essential organ forit.

It also replaces the faculty of voluntary movement, since all will

‘is an act of the organ of intelligence, and this animal is absolutely

destitute of any such organ. All its movements are necessary results

' of the impressions on its irritable parts of external stimuli; and they

are carried out without any scope for choice.

Put a hydra in a glass of water, and set this glass in a room where
daylight only enters by one window and therefore only from one side.
When this hydra has fixed on some point of the sides of the glass,
turn the glass so that the light strikes it on the opposite side to that
where the animal is. You will then always see the hydra go with
a slow movement and place itself where the light strikes, and stay there
so long as you do not change this point. This is the same in those parts
of plants which, without any act of will, lean towards the side from
which the light comes.

Doubtless wherever a special organ no longer exists, the function
which it supports also ceases to exist; and we may furthermore
clearly observe that according as an organ is degraded and reduced,
the function resulting from it becomes proportionally more vague
and imperfect. Thus, we find that on descending from the most
complex towards the simplest, the insects are the last animals which
have eyes; but there is sound reason for the belief that they see very
dimly and make little use of them.

DEGRADATION OF ORGANISATION 105

Thus on traversing the chain of animals from the most perfect to
the most imperfect, and on examining in turn the various systems
of organisation distinguished in the course of this chain, the degrada-
tion of organisation and of each organ up to their complete disappear-
ance is seen to be a positive fact which we have now verified.

This degradation comes out even in the nature and consistency of
the essential fluids and flesh of animals. For the flesh and blood of
mammals and birds are the most complex and animalised materials
that can be obtained from the soft parts of animals. Hence after
the fishes these materials are progressively degraded until in the soft
radiarians, the polyps and the infusorians, the essential fluid has only
the consistency and colour of water and the flesh is nothing more than
a gelatinous scarcely animalised material. The bouillon made from
such flesh would scarcely be found very nourishing or strengthening
by any one who tried to live upon it.

Whether or no we recognise these interesting truths, they will never-
theless always be forced upon the attention of those who closely
observe facts, and who, overcoming prevailing prejudices, consult the
phenomena of nature and study her laws and regular procedure.

We shall now pass to the examination of another kind of subject,
and shall endeavour to prove that the environment exercises a great
influence over the activities of animals, and that as a result of this
influence the increased and sustained use or disuse of any organ are
causes of modification of the organisation and shape of animals and
give rise to the anomalies observed in the progress of the complexity
of animal organisation.

CHAPTER VII.

OF THE INFLUENCE OF THE ENVIRONMENT ON THE ACTIVITIES
AND HABITS OF ANIMALS, AND THE INFLUENCE OF THE
ACTIVITIES AND HABITS OF THESE LIVING BODIES IN MODI.
FYING THEIR ORGANISATION AND STRUCTURE.

WE are not here concerned with an argument, but with the examina-
tion of a positive fact—a fact which is of more general application than
is supposed, and which has not received the attention that it deserves,
no doubt because it is usually very difficult to recognise. This fact
consists in the influence that is exerted by the environment on the
various living bodies exposed to it.

f It is indeed long since the influence of the various states of our

/ organisation on our character, inclinations, activities and even ideas

| has been recognised ; but I do not think that anyone has yet drawn
attention to the influence of our activities and habits even on our
| organisation. Now since these activities and habits depend entirely

‘| on the environment in which we are habitually placed, I shall endeavour

|| to show how great is the influence exerted by that environment on the
| general shape, state of the parts and even organisation of living bodies.

- It is, then, with this very positive fact that we have to do in the
present chapter.

«- If we had not had many opportunities of clearly recognising the
result of this influence on certain living bodies that we have trans-
ported into an environment altogether new and very different from
that in which they were previously placed, and if we had not seen
the resulting effects and alterations take place almost under our very
eyes, the important fact in question would have remained for ever
unknown to us.

The influence of the environment as a matter of fact is in all
times and places operative on living bodies; but what makes this
influence difficult to perceive is that its effects only become percep-
tible or recognisable (especially in animals) after a long period of time.

INFLUENCE OF ENVIRONMENT 107

Before setting forth to examine the proofs of this fact, which deserves
our attention and is so important for zoological philosophy, let us
sum up the thread of the discussions that we have already begun.

In the preceding chapter we saw that it is now an unquestionable
fact that on passing along the animal scale in the opposite direction
from that of nature, we discover the existence, in the groups composing
this scale, of a continuous but irregular degradation in the organisa-
tion of animals, an increasing simplification in their organisation,
and, lastly, a corresponding diminution in the number of their
faculties.

This well-ascertained fact may throw the strongest light over the
actual order followed by nature in the production of all the animals
that she has brought into existence, but it does not show us why the
increasing complexity of the organisation of animals from the most
imperfect to the most perfect exhibits only an irregular gradation, in
the course of which there occur numerous anomalies or deviations
with a variety in which no order is apparent.

Now on seeking the reason of this strange irregularity in the increas-
ing complexity of animal organisation, if we consider the influence
that is exerted by the infinitely varied environments of all parts of the
world on the general shape, structure and even organisation of these
animals, all will then be clearly explained.

It will in fact become clear that the state in which we find any animal,
is, on the one hand, the result of the increasing complexity of organisa-
tion tending to form a regular gradation; and, on the other hand,
of the influence of a multitude of very various conditions ever tending
to destroy the regularity in the gradation of the increasing complexity
of organisation.

I must now explain what I mean by this statement : the environment
affects the shape and organisation of animals, that is to say that when the
environment becomes very different, it produces in course of time
corresponding modifications in the shape and organisation of animals.

It is true if this statement were to be taken literally, I should be |
convicted of an error; for, whatever the environment may do, it —
does not work any direct modification whatever in the shape and
organisation of animals.

But great alterations in the environment of animals lead to great
alterations in their needs, and these alterations in their needs neces-
sarily lead to others in their activities. Now if the new needs become
permanent, the animals then adopt new habits which last as long
as the needs that evoked them. This is easy to demonstrate, and
indeed requires no amplification.

It is then obvious that a great and permanent alteration in the

108 ZOOLOGICAL PHILOSOPHY

environment of any race of animals induces new habits in these
animals.

Now, if a new environment, which has become permanent for some
race of animals, induces new habits in these animals, that is to say,
leads them to new activities which become habitual, the result will
be the use of some one part in preference to some other part, and in
some cases the total disuse of some part no longer necessary.

Nothing of all this can be considered as hypothesis or private opinion ;
on the contrary, they are truths which, in order to be made clear, only
require attention and the observation of facts.

We shall shortly see by the citation of known facts in evidence,
in the first place, that new needs which establish a necessity for some
part really bring about the existence of that part, as a result of efforts ;
and that subsequently its continued use gradually strengthens,
develops and finally greatly enlarges it; in the second place, we shall
see that in some cases, when the new environment and the new needs
have altogether destroyed the utility of some part, the total disuse
of that part has resulted in its gradually ceasing to share in the
development of the other parts of the animal; it shrinks and wastes
little by little, and ultimately, when there has been total disuse for
a long period, the part in question ends by disappearing. All this is
positive; I propose to furnish the most convincing proofs of it.

In plants, where there are no activities and consequently no habits,
properly so-called, great changes of environment none the less lead to
great differences in the development of their parts; so that these
differences cause the origin and development of some, and the shrinkage
and disappearance of others. But all this is here brought about by
the changes sustained in the nutrition of the plant, in its absorption
and transpiration, in the quantity of caloric, light, air and moisture
that it habitually receives ; lastly, in the dominance that some of the
‘various vital movements acquire over others.

Among individuals of the same species, some of which are continually
well fed and in an environment favourable to their development,
while others are in an opposite environment, there arises a difference
in the state of the individuals which gradually becomes very remark-
able. How many examples I might cite both in animals and plants
which bear out the truth of this principle! Now if the environment
remains constant, so that the condition of the ill-fed, suffering or
sickly individuals becomes permanent, their internal organisation is
ultimately modified, and these acquired modifications are preserved
by reproduction among the individuals in question, and finally give
rise to a race quite distinct from that in which the individuals have been
continuously in an environment favourable to their development.

INFLUENCE OF ENVIRONMENT 109

A very dry spring causes the grasses of a meadow to grow very
little, and remain lean and puny; so that they flower and fruit after
accomplishing very little growth.

A spring intermingled with warm and rainy days causes a strong
growth in this same grass, and the crop is then excellent.

But if anything causes a continuance of the unfavourable environ-
ment, a corresponding variation takes place in the plants: first in
their general appearance and condition, and then in some of their
special characters.

Suppose, for instance, that a seed of one of the meadow grasses In
question is transported to an elevated place on a dry, barren and ston y.,
plot much exposed to the winds, and is there left to germinate ; at :
the plant can live in such a place, it will always be badly nourished,
and if the individuals reproduced from it continue to exist in this
bad environment, there will result a race fundamentally different from
that which lives in the meadows and from which it originated. The
individuals of this new race will have smal] and meagre parts; some
of their organs will have developed more than others, and will then be
of unusual proportions.

Those who have observed much and studied large collections, have
acquired the conviction that according as changes occur in environ-
ment, situation, climate, food, habits of life, etc., corresponding changes
in the animals likewise occur in size, shape, proportions of the parts,
colour, consistency, swiftness and skill.

What nature does in the course of long periods we do every day
when we suddenly change the environment in which some species of
living plant is situated.

Every botanist knows that plants which are transported from their
native places to gardens for purposes of cultivation, gradually undergo
changes which ultimately make them unrecognisable. Many plants,
by nature hairy, become glabrous or nearly so; a number of those
which used to lie and creep on the ground, become erect; others
lose their thorns or excrescences; others again whose stem was
perennial and woody in their native hot climates, become herbaceous
in our own climates and some of them become annuals; lastly, the
size of their parts itself undergoes very considerable changes. These
effects of alterations of environment are so widely recognised, that
botanists do not like to describe garden plants unless they have been
recently brought into cultivation.

Is it not the case that cultivated wheat (Triticum sativum) is a plant
which man has brought to the state in which we now see it? I should
like to know in what country such a plant lives in nature, otherwise
than as the result of cultivation.

110 ZOOLOGICAL PHILOSOPHY

Where in nature do we find our cabbages, lettuces, etc., in the same
state as in our kitchen gardens? and is not the case the same with
regard to many animals whieh have been altered or greatly apociied

Pee 2 ~,

How many different races of our domestic fowls and pigeons have
we obtained by rearing them in various environments and different
‘. countries ; birds which we should now vainly seek in nature ?
~~Those which have changed the least, doubtless because their
domestication is of shorter standing and because they do not live in a
foreign climate, none the less display great differences in some of their’
parts, as a result of the habits which we have made them contract.
Thus our domestic ducks and geese are of the same type as wild
ducks and geese; but ours have lost the power of rising into high
regions of the air and flying across large tracts of country ; more-
over, a real change has come about in the state of their parts, as com-
pared with those of the animals of the race from which they come.

Who does not know that if we rear some bird of our own climate
in a cage and it lives there for five or six years, and if we then return
it to nature by setting it at liberty, it is no longer able to fly like its
fellows, which have always been free? The slight change of environ-
ment for this individual has indeed only diminished its power of flight,
and doubtless has worked no change in its structure; but if a long
succession of generations of individuals of the same race had been
kept in captivity for a considerable period, there is no doubt that even
the structure of these individuals would gradually have undergone
notable changes. Still more, if instead of a mere continuous captivity,
this environmental factor had. been further accompanied by a change
to a very different climate; and if these individuals had by degrees
been habituated to other kinds of food and other activities for seizing
it, these factors when combined together and become permanent
would have unquestionably given rise imperceptibly to a new race
with quite special characters.

Where in natural conditions do we find that multitude of races of
dogs which now actually exist, owing to the domestication to which
we have reduced them? Where do we find those bull-dogs, grey-
hounds, water-spaniels, spaniels, lap-dogs, etc., etc.; races which
show wider differences than those which we call specific when they
occur among animals of one genus living in natural freedom ?

No doubt a single, original race, closely resembling the wolf, if
indeed it was not actually the wolf, was at some period reduced by
man to domestication. That race, of which all the individuals were
then alike, was gradually scattered with man into different countries
and climates; and after they had been subjected for some time to

\

INFLUENCE OF ENVIRONMENT 111

the influences of their environment and of the various habits which
had been forced upon them in each country, they underwent remark-
able alterations and formed various special races. Now man travels
about to very great distances, either for trade or any other purpose ;
and thus brings into thickly populated places, such as a great capital,
various races of dogs formed in very distant countries. The crossing
of these races by reproduction then gave rise in turn to all those that
we now know.

The following fact proves in the case of plants how the change of
some important factor leads to alteration in the parts of these living
bodies.

So long as Ranunculus aquatilis is submerged in the water, all its
leaves are finely divided into minute segments; but when the stem
of this plant reaches the surface of the water, the leaves which develop
in the air are large, round and simply lobed. If several feet of the same
plant succeed in growing in a soil that is merely damp without any
immersion, their stems are then short, and none of their leaves are
broken up into minute divisions, so that we get Ranunculus hederaceus,
which botanists regard as a separate species.

There is no doubt that in the case of animals, extensive alterations
in their customary environment produce corresponding alterations
in their parts; but here the transformations take place much more
slowly than in the case of plants; and for us therefore they are less
perceptible and their cause less readily identified.

As to the conditions which have so much power in modifying the
organs of living bodies, the most potent doubtless consist in the
diversity of the places where they live, but there are many others
as well which exercise considerable influence in producing the effects
in question.

It is known that localities differ as to their character and quality,
by reason of their position, construction and climate: as is readily
perceived on passing through various localities distinguished by
special qualities ; this is one cause of variation for animals and plants
living in these various places. But what is not known so well and
indeed what is not generally believed, is that every locality itself
changes in time as to exposure, climate, character and quality, although
with such extreme slowness, according to our notions, that we ascribe
to it complete stability.

Now in both cases these altered localities involve a corresponding
alteration in the environment of the living bodies that dwell there,
and this again brings a new influence to bear on these same bodies.

Hence it follows that if there are extremes in these alterations,
there are also finer differences: that is to say, intermediate stages

112 ZOOLOGICAL PHILOSOPHY

which fill up the interval. Consequently there are also fine distinctions
between what we call species.

It is obvious then that as regards the character and situation of the
substances which occupy the various parts of the earth’s surface,
there exists a variety of environmental factors which induces a
corresponding variety in the shapes and structure of animals, inde-
pendent of that special variety which necessarily results from the
progress of the complexity of organisation in each animal.

‘In every locality where animals can live, the conditions constituting
any one order of things remain the same for long periods : indeed they
alter so slowly that man cannot directly observe it. It is only by an
inspection of ancient monuments that he becomes convinced that in
each of these localities the order of things which he now finds has
not always been existent; he may thence infer that it will go on

changing.

» Races of animals living in any of these localities must then retain
their habits equally long: hence the apparent constancy of the races
that we call species,—a constancy which has raised in us the belief
that these races are as old as nature.

But in the various habitable parts of the earth’s surface, the character
and situation of places and climates constitute both for animals and
plants environmental influences of extreme variability. The animals
living in these various localities must therefore differ among themselves,
not only by reason of the state of complexity of organisation attained
in each race, but also by reason of the habits which each race is forced
to acquire; thus when the observing naturalist travels over large
portions of the earth’s surface and sees conspicuous changes occurring
in the environment, he invariably finds that the characters of species
undergo a corresponding change.

Now the true principle to be noted in all this is as follows:

1. Every fairly considerable and permanent alteration in the environ-
ment of any race of animals works a real alteration in the needs of that
race,

2. Every change in the needs of animals necessitates new activities
on their part for the satisfaction of those needs, and hence new habits.

3. Every new need, necessitating new activities for its satisfaction,
requires the animal, either to make more frequent use of some of its
parts which it previously used less, and thus greatly to develop and
enlarge them; or else to make use of entirely new parts, to which
the needs have imperceptibly given birth by efforts of its inner feeling ;
this I shall shortly prove by means of known facts.

Thus to obtain a knowledge of the true causes of that great diversity
of shapes and habits found in the various known animals, we must’

INFLUENCE OF ENVIRONMENT 113

reflect that the infinitely diversified but slowly changing environment
in which the animals of each race have successively been placed,
has involved each of them in new needs and corresponding alterations
in their habits. This is a truth which, once recognised, cannot be
disputed. Now we shall easily discern how the new needs may have
been satisfied, and the new habits acquired, if we pay attention to the
two following laws of nature, which are always verified by observation.

First Law.

In every animal which has not passed the limit of its development,
a more frequent and continuous use of any organ gradually strengthens,
develops and enlarges that organ, and gives it a power proportional to
the length of time it has been so used; while the permanent disuse of
any organ imperceptibly weakens and deteriorates it, and progressively
dinunishes its functional capacity, until it finally disappears.

Sreconp Law.

All the acquisitions or losses wrought by nature on indwiduals, through
the influence of the environment in which their race has long been placed,
and hence through the influence of the predominant use or permanent
disuse of any organ ; all these are preserved by reproduction to the new
individuals which arise, provided that the acquired modifications are
common to both sexes, or at least to the individuals which produce the

young.

Here we have two permanent truths, which can only be doubted
by those who have never observed or followed the operations of nature,
or by those who have allowed themselves to be drawn into the error
which I shall now proceed to combat.

Naturalists have remarked that the structure of animals is always
in perfect adaptation to their functions, and have inferred that the
shape and condition of their parts. have determined the use of them.
Now this is a mistake: for it may be easily proved by observation
that it is on the contrary the needs and uses of the parts which have
caused the development of these same parts, which have even given
birth to them when they did not exist, and which consequently have
given rise to the condition that we find in each animal.

If this were not so, nature would have had to create as many different
kinds of structure in animals, as_ there are different kinds of environ-
‘ment in which they have to live ;. and neither structure nor environ-
ment would ever have varied.

This is indeed far from the true order of things. If things were

really so, we should not have race-horses shaped like those in England ;
H

114 ZOOLOGICAL PHILOSOPHY

we should not have big draught-horses so heavy and so different from
the former, for none such are produced in nature; in the same way
we should not have basset-hounds with crooked legs, nor grey-hounds
so fleet of foot, nor water-spaniels, etc.; we should not have fowls with-
out tails, fantail pigeons, etc. ; finally, we should be able to cultivate
wild plants as long as we liked in the rich and fertile soil of our gardens,
without the fear of seeing them change under long cultivation. 4

A feeling of the truth in this respect has long existed; since the
following maxim has passed into a proverb and is known by all,
Habits form a second nature.

Assuredly if the habits and nature of each animal could never vary,
the proverb would have been false and would not have come into
existence, nor been preserved in the event of any one suggesting it.

If we seriously reflect upon all that I have just set forth, it will be
seen that I was entirely justified when in my work entitled Recherches
sur les corps vivants (p. 50), I established the following proposition :

“Tt is not the organs, that is to say, the nature and shape of the
parts of an animal’s body, that have given rise to its special habits
and faculties; but it is, on the contrary, its habits, mode of life and
environment that have in course of time controlled the shape of its body,
the number and state of its organs and, lastly, the faculties which it
possesses.”

If this proposition is carefully weighed and compared with all the
observations that nature and circumstances are incessantly throwing
in our way, we shall see that its importance and accuracy are sub-
stantiated in the highest degree.

Time and a favourable environment are as I have already said
nature’s two chief methods of bringing all her productions into exist-
ence: for her, time has no limits and can be drawn upon to any
extent.

As to the various factors which she has required and still constantly
uses for introducing variations in everything that she produces, they
may be described as practically inexhaustible.

The principal factors consist in the influence of climate, of the vary-
ing temperatures of the atmosphere and the whole environment,
of the variety of localities and their situation, of habits, the com-
monest movements, the most frequent activities, and, lastly, of the
means of self-preservation, the mode of life and the methods of
defence and multiplication.

Now as a result of these various influences, the faculties become
extended and strengthened by use, and diversified by new habits
that are long kept up. The conformation, consistency and, in short,
the character and state of the parts, as well as of the organs, are

INFLUENCE OF ENVIRONMENT 115

imperceptibly affected by these influences and are preserved and
propagated by reproduction.

\‘t These truths, which are merely effects of the two natural laws
stated above, receive in every instance striking confirmation from
facts; for the facts afford a clear indication of nature’s procedure in
the diversity of her productions.

But instead of being contented with generalities which might be
considered hypothetical, let us investigate the facts directly, and
consider the effects in animals of the use or disuse of their organs
on these same organs, in accordance with the habits that each race
has been forced to contract.

Now I am going to prove that the permanent disuse of any organ
first decreases its functional capacity, and then gradually reduces
the organ and causes it to disappear or even become extinct, if this
disuse lasts for a very long period throughout successive generations
of animals of the same race.

I shall then show that the habit of using any organ, on the con-
trary, in any animal which has not reached the limit of the decline
‘of its functions, not only perfects and increases the functions of that
organ, but causes it in addition to take on a size and development
which imperceptibly alter it; so that in course of time it becomes
very different from the same organ in some other animal which uses
it far less.

The permanent disuse of an organ, arising from a change of habits,
causes a gradual shrinkage and ultimately the disappearance and even
extinction of that organ.

Since such a proposition could only be accepted on proof, and not
on mere authority, let us endeavour to make it clear by citing the chief
known facts which substantiate it.

The vertebrates, whose plan of organisation is almost the same
throughout, though with much variety in their parts, have their jaws
armed with teeth; some of them, however, whose environment has
induced the habit of swallowing the objects they feed on without any
preliminary mastication, are so affected that their teeth do not develop.
The teeth then remain hidden in the bony framework of the jaws,
without being able to appear outside ; or indeed they actually become
extinct down to their last rudiments.

In the right-whale, which was supposed to be completely destitute
of teeth, M. Geoffroy. has nevertheless discovered teeth concealed
in_the jaws of the foetus of this animal. The professor has moreover
discovered in birds the groove in which the teeth should be placed,
though they are no longer to be found there.

116 ZOOLOGICAL PHILOSOPHY

Even in the class of mammals, comprising the most perfect animals,
where the vertebrate plan of organisation is carried to its highest
completion, not only is the right-whale devoid of teeth, but the
ant-eater (Myrmecophaga) is also found to be in the same condition,
since it has acquired a habit of carrying out no mastication, and has
long preserved this habit in its race.

Eyes in the head are characteristic of a great number of different
animals, and essentially constitute a part of the plan of organisation
of the vertebrates.

Yet the mole, whose habits require a very small use of sight, has
only minute and hardly visible eyes, because it uses that organ so
little.

Olivier’s Spalax (Voyage en Egypte et en Perse), which lives under-
ground like the mole, and is apparently exposed to daylight even less
than the mole, has altogether lost the use of sight: so that it shows
nothing more than vestiges of this organ. Even these vestiges are
entirely hidden under the skin and other parts, which cover them up
and do not leave the slightest access to light.

The Proteus, an aquatic reptile allied to the salamanders, and living
in deep dark caves under the water, has, like the Spalaz, only vestiges
of the organ of sight, vestiges which are covered up and hidden in the
same way.

The following consideration is decisive on the question which I
am now discussing,

Light does not penetrate everywhere; consequently animals which
habitually live in places where it does not penetrate, have no oppor-
tunity of exercising their organ of sight, if nature has endowed
them with one. Now animals belonging to a plan of organisation of
which eyes were a necessary part, must have originally had them.
_ Since, however, there are found among them some which have lost

the use of this organ and which show nothing more than hidden and
covered up vestiges of them, it becomes clear that the shrinkage and
even disappearance of the organ in question are the results of a per-
manent disuse of that organ.

This is proved by the fact that the organ of hearing is never in this
condition, but is always found in animals whose organisation is of the
kind that includes it: and for the following reason.

The substance of sound,! that namely which, when set in motion by
the shock or the vibration of bodies, transmits to the organ of hearing

1 Physicists believe and even affirm that the atmospheric air is the actuai sub-
stance of sound, that is to say, that it is the substance which, when set in motion
by the shocks or vibrations of bodies, transmits to the organ of hearing the impression

of the concussions received.
That this is an error is attested by many known facts, showing that it is impossible

INFLUENCE OF ENVIRONMENT 117

the impression received, penetrates everywhere and passes through
any medium, including even the densest bodies : it follows that every
animal, belonging to a plan of organisation of which hearing is an
essential part, always has some opportunity. for the exercise of this
organ wherever-it-may live. Hence among the vertebrates we do not
find any that are destitute of the organ of hearing; and after them,
when this same organ has come to an end, it does not subsequently
recur in any animal of the posterior classes.

It is not so with the organ of sight; for this organ is found to
disappear, re-appear and disappear again according to the use that
the animal makes of it.

In the acephalic molluscs, the great development of the mantle
would make their eyes and even their head altogether useless. The
permanent disuse of these organs has thus brought about their dis-
appearance and extinction, although molluscs belong to a plan of
organisation which should comprise them.

Lastly, it was part of the plan of organisation of the reptiles, as of
other vertebrates, to have four legs in dependence on their skeleton.
Snakes ought consequently to have four legs, especially since they are
by no means the last order of the reptiles and are farther from the
fishes than are the batrachians (frogs, salamanders, etc.). ;

Snakes, however, have adopted the habit of crawling on the ground
and hiding in the grass; so that their body, as a result of continually
repeated efforts at elongation for the purpose of passing through
narrow spaces, has acquired a considerable length, quite out of pro-
portion to its size. Now, legs would have been quite useless to these
animals and consequently unused. Long legs would have interfered

that the air should penetrate to all places to which the substance producing sound
actually does penetrate.

See my memoir On the Substance of Sound, printed at the end of my Hydrogéologie,
p. 225, in which I furnished the proofs of this mistake.

Since the publication of my memoir, which by the way is seldom cited, great efforts
have been made to make the known velocity of the propagation of sound in air tally
with the elasticity of the air, which would cause the propagation of its oscillations
to be too slow for the theory. Now, since the air during oscillation necessarily under-
goes alternate compressions and dilatations in its parts, recourse has been had to
the effects of the caloric squeezed out during the sudden compressions of the air and
of the caloric absorbed during the rarefactions of that fluid. By means of these
effects, quantitatively determined by convenient hypotheses, geometricians now account
for the velocity with which sound is propagated through air. But this is no answer
to the fact that sound is also propagated through bodies which air can neither traverse
nor set in motion. ‘

These physicists assume forsooth a vibration in the smallest particles of solid
bodies ; a vibration of very dubious existence, since it can only be propagated through
homogeneous bodies of equal density, and cannot spread from a dense body to a
rarefied one or vice versd. Such a hypothesis offers no explanation of the well-known
fact that sound is propagated through heterogeneous bodies of very different densities

and kinds. :

118 ZOOLOGICAL PHILOSOPHY

with their need of crawling, and very short legs would have been
incapable of moving their body, since they could only have had four.
The disuse of these parts thus became permanent in the various races
of these animals, and resulted in the complete disappearance of these
same parts, although legs really belong to the plan of organisation of
the animals of this class.

Many insects, which should have wings according to the natural
characteristics of their order and even of their genus, are more or less
completely devoid of them through disuse. Instances are furnished
by many Coleoptera, Orthoptera, Hymenoptera and Hemiptera, etc.,
where the habits of these animals never involve them in the necessity
of using their wings.

But it is not enough to give an explanation of the cause which has
brought about the present condition of the organs of the various
animals,—a condition that is always found to be the same in animals
of the same species ; we have in addition to cite instances of changes
wrought in the organs of a single individual during its life, as the
exclusive result of a great mutation in the habits of the individuals
of its species. The following very remarkable fact will complete the
proof of the influence of habits on the condition of the organs, and of
the way in which permanent changes in the habits of an individual
lead to others in the condition of the organs, which come into action
during the exercise of these habits.

M. Tenon, a member of the Institute, has notified to the class of
sciences, that he had examined the intestinal canal of several men who
had been great drinkers for a large part of their lives, and in every
case he had found it shortened to an extraordinary degree, as compared
with the same organ in all those who had not adopted the like
habit.

It is known that great drinkers, or those who are addicted to drunken-
ness, take very little solid food, and eat hardly anything; since the
drink which they consume so copiously and frequently is sufficient
to feed them.

Now since fluid foods, especially spirits, do not long remain either
in the stomach or intestine, the stomach and the rest of the intestinal
canal lose among drinkers the habit of being distended, just as among
sedentary persons, who are continually engaged on mental work and
are accustomed to take very little food; for in their case also the
stomach slowly shrinks and the intestine shortens.

This has nothing to do with any shrinkage or shortening due to a
binding of the parts which would permit of the ordinary extension,
if instead of remaining empty these viscera were again filled; we
have to do with a real shrinkage and shortening of considerable extent,

INFLUENCE OF ENVIRONMENT 119

and such that these organs would burst rather than yield at once to
any demand for the ordinary extension.

Compare two men of equal ages, one of whom has contracted the
habit of eating very little, since his habitual studies and mental work
have made digestion difficult, while the other habitually takes much
exercise, is often out-of-doors, and eats well; the stomach of the first
will have very little capacity left and will be filled up by a very small
quantity of food, while that of the second will have preserved and
even increased its capacity.

Here then is an organ which undergoes profound modification in
size and capacity, purély on account of a change of habits during the
life of the individual.

The frequent use of any organ, when confirmed by habit, increases the
functions of that organ, leads to its development and endows it with a
size and power that it does not possess in animals which exercise it less.

We have seen that the disuse of any organ modifies, reduces and
finally extinguishes it. I shall now prove that the constant use of
any organ, accompanied by efforts to get the most out of it, strengthens
and enlarges that organ, or creates new ones to carry on functions
that have become necessary.

The bird which is drawn to the water by its need of finding there
the prey on which it lives, separates the digits of its feet in trying to
strike the water and move about on the surface. The skin which unites
these digits at their base acquires the habit of being stretched by these
continually repeated separations of the digits ; thus in course of time
there are formed large webs which unite the digits of ducks, geese,
etc., as we actually find them. In the same way efforts to swim,
that is to push against the water so as to move about in it, have
stretched the membranes between the digits of frogs, sea-tortoises,
the otter, beaver, etc.

On the other hand, a bird which is accustomed to perch on trees
and which springs from individuals all of whom had acquired this habit,
necessarily has longer digits on its feet and differently shaped from those
of the aquatic animals that I have just named. Its claws in time be-
come lengthened, sharpened and curved into hooks, to clasp the
branches on which the animal so often rests.

We find in the same way that the bird of the water-side which does
not like swimming and yet is in need of going to the water’s edge
to secure its prey, is continually liable to sink in the mud. Now this
bird tries to act in such a way that its body should not be immersed
in the liquid, and hence makes its best efforts to stretch and lengthen
its legs. The long-established habit acquired by this bird and all

120 ZOOLOGICAL PHILOSOPHY

its race of continually stretching and lengthening its legs, results in
the individuals of this race becoming raised as though on stilts, and
gradually obtaining long, bare legs, denuded of feathers up to the
thighs and often higher still. (Syst¢medes Animauax sans vertebres, p. 14.)

We note again that this same bird wants to fish without wetting
its body, and is thus obliged to make continual efforts to lengthen
its neck. Now these habitual efforts in this individual and its race
must have resulted in course of time in a remarkable lengthening,
as indeed we actually find in the long necks of all water-side birds.

If some swimming birds like the swan and goose have short legs
and yet a very long neck, the reason is that these birds while moving
about on the water acquire the habit of plunging their head as deeply
as they can into it in order to get the aquatic larvae and various
animals on which they feed ; whereas they make no effort to lengthen
their legs.

If an animal, for the satisfaction of its needs, makes repeated efforts
to lengthen its tongue, it will acquire a considerable length (ant-eater,
green-woodpecker) ; if it requires to seize anything with this same
organ, its tongue will then divide and become forked. Proofs of my
statement are found in the humming-birds which use their tongues
for grasping things, and in lizards and snakes which use theirs to
palpate and identify objects in front of them.

Needs which are always brought about by the environment, and the
subsequent continued efforts to satisfy them, are not limited in their
results to a mere modification, that is to say, an increase or decrease
of the size and capacity of organs; but they may even go so far as
to extinguish organs, when any of these needs make such a course
necessary.

Fishes, which habitually swim in large masses of water, have need of
lateral vision; and, as a matter of fact, their eyes are placed on the
sides of their head. Their body, which is more or less flattened
according to the species, has its edges perpendicular to the plane
of the water; and their eyes are placed so that there is one on each
flattened side. But such fishes as are forced by their habits to be
constantly approaching the shore, and especially slightly inclined or
gently sloping beaches, have been compelled to swim on their flattened
surfaces in order to make a close approach to the water’s edge. In
this position, they receive more light from above than below and stand
in special need of paying constant attention to what is passing above
them; this requirement has forced one of their eyes to undergo a
sort of displacement, and to assume the very remarkable position
found in the soles, turbots, dabs, etc. (Pleuronectes and Achirus). The
position of these eyes is not symmetrical, because it results from an

INFLUENCE OF ENVIRONMENT 121

incomplete mutation. Now this mutation is entirely completed in
the skates, in which the transverse flattening of the body is altogether
horizontal, like the head. Accordingly the eyes of skates are both
situated on the upper surface and have become symmetrical.

Snakes, which crawl on the surface of the earth, chiefly need to see
objects that are raised or above them. This need must have had its
effect on the position of the organ of sight in these animals, and accord-
ingly their eyes are situated in the lateral and upper parts of their
head, so as easily to perceive what is above them or at their sides ; but
they scarcely see at all at a very short distance in front of them. They
are, however, compelled to make good the deficiency of sight as regards
objects in front of them which might injure them as they move forward.
For this purpose they can only use their tongue, which they are
obliged to thrust out with all their might. This habit has not only
contributed to making their tongue slender and very long and con-
tractile, but it has even forced it to undergo division in the greater
number of species, so as to feel several objects at the same time ;
it has even permitted of the formation of an aperture at the extremity
of their snout, to allow the tongue to pass without having to separate
the jaws.

Nothing is more remarkable than the effects of habit in herbivorous
mammals.

A quadruped, whose environment and consequent needs have for
long past inculcated the habit of browsing on grass, does nothing but
walk about on the ground; and for the greater part of its life is
obliged to stand on its four feet, generally making only few or moderate
movements. The large portion of each day that this kind of animal
has to pass in filling itself with the only kind of food that it cares for,
has the result that it moves but little and only uses its feet for support
in walking or running on the ground, and never for holding on, or
climbing trees.

From this habit of continually consuming large quantities of food-

“material, which distend the organs receiving it, and from the habit
of making only moderate movements, it has come about that the body
of these animals has greatly thickened, become heavy and massive
and acquired a very great size: as is seen in elephants, rhinoceroses,
oxen, buffaloes, horses, etc.

The habit of standing on their four feet during the greater part of
the day, for the purpose of browsing, has brought into existence a
thick horn which invests the extremity of their digits; and since
these digits have no exercise and are never moved and serve no other
purpose than that of support like the rest of the foot, most of them
have become shortened, dwindled and, finally, even disappeared.

122 ZOOLOGICAL PHILOSOPHY

Thus in the pachyderms, some have five digits on their feet invested
in horn, and their hoof is consequently divided into five parts ; others
have only four, and others again not more than three; but in the
ruminants, which are apparently the oldest of the mammals that are
permanently confined to the ground, there are not more than two
digits on the feet and indeed, in the solipeds, there is only one (horse,
donkey).

Nevertheless some of these herbivorous animals, especially the
ruminants, are incessantly exposed to the attacks of carnivorous
animals in the desert countries that they inhabit, and they can only
find safety in headlong flight. Necessity has in these cases forced
them to exert themselves in swift running, and from this habit their
body has become more slender and their legs much finer ; instances
are furnished by the antelopes, gazelles, etc.

In our own climates, there are other dangers, such as those con-
stituted by man, with his continual pursuit of red deer, roe deer and
fallow deer ; this has reduced them to the same necessity, has impelled
them into similar habits, and had corresponding effects.

Since ruminants can only use their feet for support, and have little
strength in their jaws, which only obtain exercise by cutting and
browsing on the grass, they can only fight by blows with their heads,
eins one another with their crowns.

In the frequent fits of anger to which the males especially are subject,
tthe efforts of their inner feeling cause the fluids to flow more strongly
towards that part of their head; in some there is hence deposited
a secretion of horny matter, and in others of bony matter mixed with
horny matter, which gives rise to solid protuberances: thus we have
the origin of horns and antlers, with which the head of most of these
animals is armed.

It is interesting to observe the result of habit in the peculiar shape
and size of the giraffe (Camelo-pardalis): this animal, the largest of
the mammals, is known to live in the interior of Africa in places where
the soil is nearly always arid and barren, so that it is obliged to browse
on the leaves of trees and to make constant efforts to reach them.
From this habit long maintained in all its race, it has resulted that
the animal’s fore-legs have become longer than its hind legs, and that
its neck is lengthened to such a degree that the giraffe, without standing
up on its hind legs, attains a height of six metres (nearly 20 feet).

Among birds, ostriches, which have no power of flight and are raised
on very long legs, probably owe their singular shape to analogous
circumstances.

The effect of habit is quite as remarkable in the carnivorous mammals
as in the herbivores; but it exhibits results of a different kind.

INFLUENCE OF ENVIRONMENT 123

Those carnivores, for instance, which have become accustomed to
climbing, or to scratching the ground for digging holes, or to tearing
their prey, have been under the necessity of using the digits of their
feet : now this habit has promoted the separation of their digits, and
given rise to the formation of the claws with which they are armed.

But some of the carnivores are obliged to have recourse to pursuit
in order to catch their prey : now some of these animals were compelled
by their needs to contract the habit of tearing with their claws, which
they are constantly burying deep in the body of another animal in
order to lay hold of it, and then make efforts to tear out the part seized.
These repeated efforts must have resulted in its claws reaching a size
and curvature which would have greatly impeded them in walking or
running on stony ground: in such cases the animal has been compelled
to make further efforts to draw back its claws, which are so pro-
jecting and hooked as to get in its way. From this there has gradually
resulted the formation of those peculiar sheaths, into which cats,
tigers, lions, etc. withdraw their claws when they are not using them.

Hence we see that efforts in a given direction, when they are long
sustained or habitually made by certain parts of a living body, for
the satisfaction of needs established by nature or environment, cause
an enlargement of these parts and the acquisition of a size and shape
that they would never have obtained, if these efforts had not become
the normal activities of the animals exerting them. Instances are
everywhere furnished by observations on all known animals.

Can there be any more striking instance than that which we find
in the kangaroo? This animal, which carries its young in a pouch
under the abdomen, has acquired the habit of standing upright, so
as to rest only on its hind legs and tail; and of moving only by means
of a succession of leaps, during which it maintains its erect attitude
in order not to disturb its young. And the following is the result:

1. Its fore legs, which it uses very little and on which it only supports
itself for a moment on abandoning its erect attitude, have never
acquired a development proportional to that of the other parts, and
have remained meagre, very short and with very little strength.

2. The hind legs, on the contrary, which are almost continually
in action either for supporting the whole body or for making leaps,
have acquired a great development and become very large and strong.

3. Lastly, the tail, which is in this case much used for supporting
the animal and carrying out its chief movements, has acquired an
extremely remarkable thickness and strength at its base.

These well-known facts are surely quite sufficient to establish the
results of habitual use on an organ or any other part of animals. If
on observing in an animal any organ particularly well-developed,

‘

124 ZOOLOGICAL PHILOSOPHY

strong, and powerful, it is alleged that its habitual use has nothing to
do with it, that its continued disuse involves it in no loss, and finally,
that this organ has always been the same since the creation of the species
to which the animal belongs, then I ask, Why can our domestic ducks
no longer fly like wild ducks? I can, in short, cite a multitude of in-
stances among ourselves, which bear witness to the differences that
accrue to us from the use or disuse of any of our organs, although these
differences are not preserved in the new individuals which arise by
reproduction: for if they were their effects would be far greater.

I shall show in Part IT., that when the will guides an animal to any
action, the organs which have to carry out that action are immediately
stimulated to it by the influx of subtle fluids (the nervous fluid),
which become the determining factor of the movements required.
This fact is verified by many observations, and cannot now be called
in question.

_Hence it follows that numerous repetitions of these organised
activities strengthen, stretch, develop and even create the organs

necessary to them. We have only to watch attentively what is

happening all around us, to be convinced that this is the true cause
of orgahic development and changes.

Now every change that is wrought in an organ through a habit
of frequently using it, is subsequently preserved by reproduction,
if it is common to the individuals who unite together in fertilisation
for the propagation of their species. Such a change is thus handed
on to all succeeding individuals in the same environment, without
their having to acquire it in the same way that it was actually created.

Furthermore, in reproductive unions, the crossing of individuals
who have different qualities or structures is necessarily opposed _to
the permanent propagation of these qualities and structures. Hence
it is that in man, who is exposed to so great a diversity of environment,
the accidental qualities or defects which he acquires are not preserved
and propagated by reproduction. If, when certain peculiarities
of shape or certain defects have been acquired, two individuals who
are both affected were always to unite together, they would hand on
the same peculiarities; and if successive generations were limited
to such unions, a special and distinct race would then be formed. But
perpetual crossings between individuals, who have not the same
peculiarities of shape, cause the disappearance of all peculiarities
acquired by special action of the environment. Hence, we may be sure
that if men were not kept apart by the distances of their habitations,
the crossing in reproduction would soon bring about the disappear-
ance of the general characteristics distinguishing different nations.

If I intended here to pass in review all the classes, orders, genera

INFLUENCE OF ENVIRONMENT 125

and species of existing animals, I should be able to show that the
conformation and structure of individuals, their organs, faculties,
etc., etc., are everywhere a pure result of the environment to which
each species is exposed by its nature, and by the habits that the
individuals composing it have been compelled to acquire; I should
be able to show that they are not the result of a shape which existed
from the beginning, and has driven animals into the habits hey are
known to possess.

It is known that the animal called the ai or sloth (Bradypus ee
is permanently in a state of such extreme weakness that it only executes
very slow and limited movements, and walks on the ground with
difficulty. So slow are its movements that it is alleged that it can only
take fifty steps in a day. It is known, moreover, that the organisation
of this animal is entirely in harmony with its state of feebleness and
incapacity for walking; and that if it wished to make other movements
than those which it actually does make it could not do so.

Hence on the supposition that this animal had received its organisa-
tion from nature, it has been asserted that this organisation forced
it into the habits and miserable state in which it exists.

This is very far from being my opinion; for I am convinced that
the habits which the ai was originally forced to contract must
necessarily have brought its organisation to its present condition.

If continual dangers in former times have led the individuals of
this species to take refuge in trees, to live there habitually and feed
on their leaves, it is clear that they must have given up a great number
of movements which animals living on the ground are in a position
to perform. All the needs of the ai will then be reduced to clinging
to branches and crawling and dragging themselves among them,
in order to reach the leaves, and then to remaining on the tree in a
state of inactivity in order to avoid falling off. This kind of inactivity,
moreover, must have been continually induced by the heat of the
climate; for among warm-blooded animals, heat is more conducive
to rest than to movement.

Now the individuals of the race of the ai have long maintained this
habit of remaining in the trees, and of performing only those slow
and little varied movements which suffice for their needs. Hence
their organisation will gradually have come into accordance with
their new habits; and from this it must follow:

1. That the arms of these animals, which are making continual
efforts to clasp the branches of trees, will be lengthened ;

2. That the claws of their digits will have acquired a great length
and a hooked shape, through the continued efforts of the animal to
hold on ;

126 ZOOLOGICAL PHILOSOPHY

3. That their digits, which are never used in making independent
movements, will have entirely lost their mobility, become united
and have preserved only the faculty of flexion or extension all
together ;

4. That their thighs, which are continually clasping either the trunk
or large branches of trees, will have contracted a habit of always being
separated, so as to lead to an enlargement of the pelvis and a back-
ward direction of the cotyloid cavities ;

5. Lastly, that a great many of their bones will be welded together,
and that parts of their skeleton will consequently have assumed an
arrangement and form adapted to the habits of these animals, and
different from those which they would require for other habits.

This is a fact that can never be disputed; since nature shows
us in innumerable other instances the power of environment over
habit and that of habit over the shape, arrangement and proportions
of the parts of animals.

Since there is no necessity to cite any further examples, we may
now turn to the main point elaborated in this discussion.

It is a fact that all animals have special habits corresponding to
their genus and species, and always possess an organisation that is
completely in harmony with those habits.

It seems from the study of this fact that we may adopt one or other
of the two following conclusions, and that neither of them can be
verified.

Conclusion adopted hitherto: Nature (or her Author) in creating
animals, foresaw all the possible kinds of environment in which they
would have to live, and endowed each species with a fixed organisa-
tion and with a definite and invariable shape, which compel each
species to live in the places and climates where we actually find them,
and there to maintain the habits which we know in them.

My windwidual conclusion: Nature has produced all the species
of animals in succession, beginning with the most imperfect or simplest,
and ending her work with the most perfect, so as to create a gradually
increasing complexity in their organisation; these animals have
spread at large throughout all the habitable regions of the globe,
and every species has derived from its environment the habits that
we find in it and the structural modifications which observation
shows us.

The former of these two conclusions is that which has been drawn
hitherto, at least by nearly everyone: it attributes to every animal
a fixed organisation and structure which never have varied and never
do vary ; it assumes, moreover, that none of the localities inhabited
by animals ever vary; for if they were to vary, the same animals

INFLUENCE OF ENVIRONMENT 127

could no longer survive, and the possibility of finding other localities
and transporting themselves thither would not be open to them.

The second conclusion is my own : it assumes that by the influence
of environment on habit, and thereafter by that of habit on the state of
the parts and even on organisation, the structure and organisation
of any animal may undergo modifications, possibly very great, and
capable of accounting for the actual condition in which all animals
are found. <

In order to show that this second conclusion is baseless, it must.
first be proved that no point on the surface of the earth ever under-
goes variation as to its nature, exposure, high or low situation, climate, |
etc., etc. ; it must then be proved that no part of animals undergoes .
even after long periods of time any modification due to a change of |
environment or to the necessity which forces them into a different
kind of life and activity from what has been customary to them. _

Now if a single case is sufficient to prove that an animal which has
long been in domestication differs from the wild species whence it
sprang, and if in any such domesticated species, great differences
of conformation are found between the individuals exposed to such a
habit and those which are forced into different habits, it will then be
certain that the first conclusion is not consistent with the laws of
nature, while the second, on the contrary, is entirely in accordance
with them.

Everything then combines to prove my statement, namely: that
it is not the shape either of the body or its parts which gives rise to
the habits of animals and their mode of life; but that it is, on the con-
trary, the habits, mode of life and all the other influences of the environ-
ment which have in course of time built up the shape of the body and
of the parts of animals. With new shapes, new faculties have been
acquired, and little by little nature has succeeded in fashioning animals
such as we actually see them.

Can there be any more important conclusion in the range of natural
history, or any to which more attention should be paid than that
which I have just set forth ?

Let us conclude this Part I. with the principles and exposition of
the natural order of animals.

CHAPTER VIII.

OF THE NATURAL ORDER OF ANIMALS, AND THE WAY IN WHICH
THEIR CLASSIFICATION SHOULD BE DRAWN UP SO AS TO BE
-.. IN CONFORMITY WITH THE ACTUAL ORDER OF NATURE.

IT nave already observed that the true aim of a classification of animals
should not be merely the possession of a list of classes, genera and species,
but also the provision of the greatest facilities for the study of nature
and for obtaining a knowledge of her procedure, methods and laws.

I do not hesitate to say, however, that our general classifications of
animals up to the present have been in the inverse order from that
followed by nature when bringing her living productions successively
into existence; thus, when we proceed from the most complex to the
simplest in the usual way, we increase the difficulty of acquiring a
knowledge of the progress in complexity of organisation; and we
also find it less easy to grasp both the causes of that progress and of
the interruptions in it.

When once we have recognised that a thing is useful and indeed
indispensable for the end in view and that it is free from drawbacks,
we should hasten to carry it into execution although it is contrary
to custom.

This is the case with regard to the way in which a general classi-
fication of animals should be drawn up.

We shall see that it is not a matter of indifference from which end
we begin this general classification of animals, and that the beginning
of the order is not a mere matter of choice.

The existing custom of placing at the head of the animal kingdom
the most perfect animals, and of terminating this kingdom with the
most imperfect and simplest in organisation, is due, on the one hand,
to that natural prejudice towards giving the preference to the objects
which strike us most or in which we are most pleased or interested ;
and, on the other hand, to the preference for passing from the better
known to what is less known.

NATURAL ORDER OF ANIMALS 129

When the study of natural history began to occupy attention,
these reasons were no doubt very plausible; but they must now
yield to the needs of science and especially to those of facilitating
the progress of natural knowledge.

With regard to the numerous and varied animals which nature
has produced, if we cannot flatter ourselves that we possess an exact
knowledge of the real order which she followed in bringing them
successively into existence, it is nevertheless true that the order
which I am about to set forth is probably very near it: reason and
all our acquired knowledge testify in favour of this probability.

——~Tf indeed it is true that all living bodies are productions of nature,
we are driven to the belief that she can only have produced them
one after another and not all in a moment. Now if she shaped
them one after another, there are grounds for thinking that she
began exclusively with the simplest, and only produced at the very
end the most complex organisations both of the animal and vegetable
kingdoms.

The botanists were the first to set an example to the zoologists as
to the proper way of drawing up a general classification in order to
represent the actual order of nature; for it is with the Acotyledons
or agamous plants that they constitute the first class among plants,
that is to say, with the simplest in organisation and the most imperfect
under every aspect, plants in short which have no cotyledons, no
recognisable sex, no vessels in their tissue, and which in fact are com-
posed of nothing but cellular tissue more or less modified according
to their various expansions.

What botanists have done in the case of plants, we should now do
with regard to the animal kingdom; and we should do it, not only
because nature herself indicates it and reason demands it, but also
because the natural order of classes in accordance with their growing
complexity of organisation is much easier to determine among animals
than it is in the case of plants.

While this order represents most closely the order of nature, it also
makes the study of objects much easier, advances our knowledge of
the organisation of animals with its increasing complexity from class
to class, and exhibits still more clearly the affinities existing among the
various stages of complexity of animal organisation, and the external
differences that we commonly utilise for the characterisation of classes,
orders, families, genera and species.

To these two principles, whose validity can scarcely be questioned,
J add another, viz. : that if nature, who has not succeeded in endowing
organised bodies with eternal existence, had not had the power of

giving these bodies the faculty of reproducing others like themselves
I

130 ZOOLOGICAL PHILOSOPHY

to carry on and perpetuate the race in the same way, she would have
been forced to create directly all races, or rather she would only have
been able to create a single race in each organic kingdom, viz. the
simplest and most imperfect animals and plants.

Moreover, if nature had not been able to endow the organising activity
with the faculty of gradually increasing the complexity of organisation
by accelerating the energy of the movement of the fluids and hence
that of organic movement, and if she had not preserved by repro-
duction all the progress made in complexity of organisation and
all acquired improvements, she would assuredly never have produced
that infinitely varied multitude of animals and plants which differ
so greatly from one another both in their organisation and in their
faculties.

Finally, she could not create at once the highest faculties of animals,
for they are only found in conjunction with highly complex systems.
of organs: and she had to prepare slowly the methods by which such
systems might be brought into existence.

Thus, in order to establish the state of affairs that we now see in
living bodies, the only direct production that is required from nature,
that is to say, the only production that occurs without the co-operation
of any organic activity, is in the case of the simplest organised bodies,
both of animals and plants; these she continues to produce every
day in the same way at favourable times and places. Now she endows
these bodies, which she has herself created, with the faculties of feeding,
growing, multiplying, and always preserving the progress made in
organisation. She transmits these same faculties to all individuals
organically reproduced throughout time and the immense variety of
ever-changing conditions. By these means living bodies of all classes
and orders have been successively produced.

In the study of the natural order of animals, the very definite grada-
tion existing in the growing complexity of their organisation and in the
number and perfection of their faculties is very far from being a new
truth for it was known even to the Greeks ;1 but they could not set
forth its underlying principles and proofs, because they lacked the
necessary knowledge.

Now, in order to facilitate an acquaintance with the principles
which have guided me in the exposition that I am about to give,
and in order to bring home more closely the gradation observed in
the complexity of organisation from the most imperfect animals at
the head of the series to the most perfect at the end of it, I have
divided into six distinct stages the various modes of organisation
recognised throughout the animal scale.

1See the Voyage du jeune Anacharsis, by J. Barthélemy, vol. v. pp. 353, 354,

NATURAL ORDER OF ANIMALS 131

Of these six stages of organisation, the first four comprise the in-
vertebrate animals, and consequently the first ten classes of the animal
kingdom according to the new order that we are going to follow; the
two last stages comprises all the vertebrate animals and consequently
the four (or five) last classes of animals.

By this method it will be easier to study and follow the procedure
of nature in the production of the animals that she has brought into
existence ; to recognise throughout the animal scale the progress
made in complexity of organisation and everywhere to verify both
the accuracy of the classification and the propriety of the rank
assigned by examining such characters and facts of organisation as
are known.

In lecturing on invertebrates at the Museum, I have for some years
past followed this plan of always proceeding from the simplest to
the most complex.

In order to bring out more clearly the arrangement and totality
of the general series of animals, I shall first present a table of the
fourteen classes into which the animal kingdom is divided, confining
myself to a very brief account of their characters and of the stages
of organisation which they include.

TABLE

OF THE ARRANGEMENT AND CLASSIFICATION OF ANIMALS
ACCORDING TO THE ORDER MOST IN CONFORMITY WITH
THE ORDER OF NATURE.

INVERTEBRATE ANIMALS.

CLASSES
I. INFUSORIANS. >
Amorphous animals, reproducing by fission or
budding; with bodies gelatinous, transparent,
homogeneous, contractile and microscopic; no
radiating tentacles, or rotatory appendage ; no
‘special organ, even for digestion. lst Stage.

II. Poryes. . No nerves; no

Reproducing by budding; bodies gelatinous vessels ; no special-

and regenerating, but with no other internal ised internal organ

organ than an alimentary canal with a single | except for digestion.
aperture.

Terminal mouth, surrounded by radiating
tentacles or furnished with ciliated or rotatory
organs.

They mostly form compound animals. y,

132

CLASSES

ITI,

VI.

VII.

Vill.

IX.

ZOOLOGICAL PHILOSOPHY

RADIARIANS.

Suboviparous animals, free, with regenerating
bodies, destitute of head, eyes, or jointed legs ;
parts arranged radially. Mouth on inferior
surface.

. Worms.

Suboviparous animals, with soft regenerating
bodies; undergoing no metamorphosis, and
never having eyes, jointed legs, nor a radial
arrangement of the internal parts.

. INSECTS.

Oviparous animals, which undergo meta-
morphosis, and have, in the perfect state, eyes
in their heads, six jointed legs, and tracheae
which spread everywhere; a single fertilisation
in the course of their life.

ARACHNIDS.

Oviparous, having always jointed legs, and
eyes in their heads, and undergoing no meta-
morphosis. Limited trachae for respiration; a
primitive circulation; several fertilisations in
the course of their life.

CRUSTACEANS.

Oviparous, with jointed body and _ limbs,
crustaceous skin, eyes in their head, and usually
four antennae; respiration by gills; a ganglionic
longitudinal cord.

ANNELIDS,

Oviparous, with elongated and ringed bodies ;
no jointed legs, rarely any eyes; respiration by
gills ; a ganglionic longitudinal cord.

CIRRHIPEDES.

Oviparous, with a mantle and jointed arms,
the skin of which is horny; no eyes; respira-
tion by gills; ganglionic longitudinal cord.

. MoLLuscs.

Oviparous, with soft moist bodies, unjointed,
and with a variable mantle; respiration by
gills of various shapes and situations; no spinal
cord, nor ganglionic longitudinal cord, but nerves
terminating in a brain.

2nd Stage.

No ganglionic
longitudinal cord;
\'no vessels for cir-
culation; a few in-
ternal organs in addi-
tion to those of
digestion.

3rd Stage.

ing in a ganglionic
- longitudinal cord ;
respiration by air-
carrying tracheae;
circulation absent or
imperfect.

4th Stage.

Nerves terminat-
ing in a brain or a
‘ganglionic longitud-
inal cord; respira-
tion by gills ; arteries
and veins for circu-
lation.

Nerves terminat-

CLASSES

NATURAL ORDER OF ANIMALS

VERTEBRATE ANIMALS.

133

XI. FisHss.
Oviparous, and without mammae; respiration
complete and always by gills; two or four 5th Stage.
primitive limbs; fins for locomotion; no hair
or feathers on the skin. Nerves terminat-
ing in a brain which
XII. Reprizzs. [ is far from filling the
Oviparous, and without mammae ; respiration cranial cavity; heart
incomplete, usually by lungs which exist either | With one ventricle,
throughout life or during the latter part of it; | 2nd the blood cold.
four limbs, or two, or none; no hair or feathers
on the skin.
XIII. Brrps.
Oviparous, and without mammae; four jointed 6th Stage.
limbs, two of which are shaped as wings ; respira-
tion complete, by adherent lungs, which are Nerves terminat-
pierced through ; feathers on the skin. ing in a brain which
‘ rfills the cranial
XIV. Mammats.! cavity; heart with
Viviparous, and possessing mammae; four | two ventricles, and
jointed limbs, or two only; respiration com- | the blood warm.
plete, by lungs not pierced through; hair on
some part of the body.

The above is a table of the fourteen classes of known animals arranged
in the order most in conformity with that of nature. The arrangement
of these classes is such that we shall always be obliged to adhere to it
even though we may refuse to adopt the lines of demarcation between
them ; because this arrangement is based on a study of the organisa-
tion of the living bodies concerned, and because this highly important
study reveals affinities among the objects comprised in each division,
and determines the rank of each division throughout the series.

For these reasons no solid grounds can ever be found for changing
the general features of this classification, though changes may be
made as to detail, particularly in the divisions that are subordinate
to the classes ; because the affinities between the objects comprised
in the sub-divisions are more difficult to determine and leave more to
arbitrary opinion.

Now in order to bring home more closely the conformity of this
arrangement of animals with the actual order of nature, I shall set
forth the general series of known animals divided into its main groups,
proceeding from the simplest to the most complex according to the
principles indicated above.

134 ZOOLOGICAL PHILOSOPHY

My object in the exposition is to enable the reader to recognise the
rank in the general series that is occupied by the animals which I have
often had occasion to cite in the course of the present work, and to
save him the trouble of having recourse to other works on zoology
for this purpose.

I shall, however, here give merely a list of genera and of the main
groups; but this list will suffice to show the extent of the general
series, the arrangement of it that is most in conformity with nature,
and the places necessarily occupied by classes and orders as well perhaps
as by families and genera. We must of course refer to the good works
on zoology that we possess for a study of the details of all the animals
named in this list, for that does not come within the scope of the
present work.

GENERAL CLASSIFICATION OF ANIMALS.

Forming a series in conformity with the actual order of nature.

INVERTEBRATE ANIMALS.

They have no vertebral column and consequently no skeleton; those
which have fulcra for the movement of their parts have them under
the integument. They lack a spinal cord and exhibit great variety
in the complexity of their organisation.

FIRST STAGE OF ORGANISATION.

No nerves or ganglionic longitudinal cord ; no vessels for circulation ;
no organs of respiration ; no specialised internal organ but that for
digestion.

(Infusorians and Polyps.)

INFUSORIANS.
(Class I. of the Animal Kingdom.)

Amorphous animals, reproducing by fission ; with bodies gelatinous,
transparent, homogeneous, contractile, and microscopic; no radiating
tentacles, or rotatory appendage ; internally no special organ, even for
digestion.

OBSERVATIONS.

Of all known animals the infusorians are the most imperfect, the
most simply organised and possessed of the fewest faculties; they
certainly have not the faculty of feeling.

GENERAL CLASSIFICATION 135

Infinitely minute, gelatinous, transparent, contractile, almost homo-
geneous and incapable of the possession of any special organ on
account of the very delicate consistency of their parts, the infusorians
are in truth mere rudiments of animalisation.

These fragile animals are the only creatures which do not have to
carry on any digestion when feeding, and which in fact only feed by
absorption through the pores of their skin and by an internal
imbibition.

In this they resemble plants, which live entirely by absorption,
carry on no digestion and in which the organic movements are only
achieved by external stimuli; but the infusorians are irritable and
contractile and perform sudden movements which they can repeat
several times running ; this it is that indicates their animal nature and
distinguishes them essentially from plants.

TABLE OF INFUSORIANS.
ORDER 1.—NAKED INFUSORIANS.

They are destitute of external appendages.

Monas. —_—
Volvox. Bursaria.
Proteus [Amoeba. H. E.]. Colpoda.
Vibrio.

ORDER 2.—APPENDICULATE JNFUSORIANS.

They have projecting parts, like hair, kinds of horns or a tail.
Cercaria [Trematode. H. E.}.
Trichocerca.
Trichoda.

Remarks. The monas, and especially Monas termo, is the most
imperfect and simplest of the known animals, since its extremely
minute body is nothing but a point which is gelatinous and trans-
parent, but contractile. This animal then must be the one with
which the animal series begins, when arranged according to the
order of nature.

POLYPS.
(Class II. of the Animal Kingdom.)

Gemmiparous animals, with gelatinous, regenerating bodies, and having
no internal organ except an alimentary canal with a single aperture.

Terminal mouth, surrounded by radiating tentacles, or furnished with
ciliated or rotatory organs. They mostly adhere together, are im com-
munication by their alimentary canal, and then form compound

animals.

136 ZOOLOGICAL PHILOSOPHY

OBSERVATIONS.

We have seen that the infusorians are infinitely small and fragile
animalcules without coherence, without a shape peculiar to their
class, without any organs and hence without a distinct mouth and
alimentary canal.

In the polyps the simplicity and imperfection of organisation,
although very conspicuous, are less than in the infusorians. Organisa-
tion has clearly made some progress ; for nature has already obtained
a permanent and regular shape for the animals for this class; they
are all provided with a special organ for digestion, and consequently
with a mouth which leads into the alimentary sac.

Imagine a small, elongated gelatinous, highly irritable body, which
has at its superior extremity a mouth furnished either with rotatory
organs or with radiating tentacles serving as the entrance to an alimen-
tary canal which has no other opening: and we shall have a good
idea of a polyp.

Add to this that many of these little bodies become adherent and
live together in a common life, and we shall then know the most general
and curious fact that concerns them.

The polyps are more imperfect in organisation than the animals
of the following classes, since they have no nerves for feeling, no special
organs for respiration and no vessels for the circulation of their
fluids.

TABLE OF POLYPS.
OrpDER 1.—ROoOTIFER POLyYps.
They have ciliated and rotatory organs at their mouths.

Urceolaria.

Brachionus (?).

Vorticella [Infusorian. H. E.].
ORDER 2.—POLYPS WHICH FORM POLYPARIES.
[Hydrozoa, Anthozoa, Polyzoa, Sponge, etc. H. E.]

They have radiating tentacles around the mouth, and are fixed in a
polypary which does not float upon the waters.

(1) Polypary membranous or horny, without distinct bark.

Cristatella. Cellaria.

Plumatella. Flustra.

Tubularia. Cellepora.

Sertularia. Botryllus [Ascidian. H. E.].

(2) Polypary with a horny axis, covered with an encrustation.
Acetabulum [Alga. H. E.]. Alcyon.
Corallina [Alga. H. E.]. Antipathes (black coral).
= Gorgonia (sea-fan).
Sponge.

GENERAL CLASSIFICATION 137

(3) Polypary with an axis partly or wholly stony, and covered
with a bark-like encrustation.

Isis.
Coral.

(4) Polypary wholly stony, and without encrustation.

Tubipora (organ-pipe coral). Pavonia.
Lunulites. Meandrina.
Ovulites. Astrea.
Siderolites. Madrepora.
Orbulites. Caryophyllia.
Alveolites. Turbinolia.
Ocellaria. Fungia (mushroom-coral).
Eschara. Cyclolites.
Retepora. Dactylopora.
Millepora. Virgularia.
Agaricia.

ORDER 3.—FLoaTiInG PoLyps.

A free, elongated, polypary floating in the waters, with a horny or bony axis,
covered with flesh that is common to all the polyps ; radiating tentacles around
the mouth,

Funiculina. Encrinus [Echinoderm. H. E.}.
Veretillum. Umbellularia.
Pennatula (Sea-pen).

ORDER 4.—NakED POLYPS.

They have radiating tentacles, often multiple, at the mouth,
and form no polypary.

Pedicellaria. Zoantha.
Coryne. Actinia (Sea-anemone),
Hydra.

SECOND STAGE OF ORGANISATION.

No ganglionic longitudinal cord; no circulatory vessels; a few
special internal organs (either tubes or pores, which draw in water
or kinds of ovaries) in addition to those of digestion.

(Radiarvans and worms.)

RADIARIANS.
(Class III. of the Animal Kingdom.)

Subgemmiparous animals, free or vagrant ; with regenerating bodies
and a radiating arrangement of the parts both internal and external and
a complex digestive organ ; mouth underneath, simple or multiple.

No head, eyes or jointed legs; a few internal organs in addition to

those of digestion.

138 ZOOLOGICAL PHILOSOPHY

OBSERVATIONS.

This is the third main line of demarcation which has to be drawn
in the natural classification of animals.

We here find altogether new forms which, however, belong in general
to one type, viz. the radiating arrangement of the parts both internal
and external.

We have no longer to deal with animals with elongated bodies,
a superior terminal mouth, usually fixed in a polypary, and living
together in great numbers which share a common life, but we have to
deal with animals whose organisation is more complex than that of the
polyps and which are not compound but always free, which have a
conformation peculiar to themselves and assume in general the
inverted position.

Nearly all the radiarians have tubes which draw in water and appear
to be water-bearing tracheae, and in a great many of them are found
peculiar bodies resembling ovaries.

From a memoir which I lately heard read at a meeting of the
professors of the Museum, I learn that a skilful observer, Dr. Spix, a
Bavarian doctor, has discovered the apparatus of a nervous system in
star-fishes and sea-anemones.

Dr. Spix affirms that he has seen in the red star-fish, under a tendinous
membrane which is suspended over the stomach like a tent, a plexus
consisting of whitish nodules and threads, and in addition, at the origin
of each arm, two nodules or ganglia communicating together by a
thread and giving rise to other threads which go to the neighbouring
parts. Among these are two very long ones which traverse the entire
length of the arm and send out branches to the tentacles.?

According to the observations of this savant there are in each arm
‘two nodules, a short prolongation of the stomach (caecum), two hepatic
lobes, two ovaries and tracheal canals.

In sea-anemones Dr. Spix observed at the base of these animals
below the stomach several pairs of nodules arranged about a centre
-and communicating together by cylindrical threads. These give rise
‘to others which pass to the upper parts: he found moreover four
ovaries surrounding the stomach, from the base of which issue canals
which unite together and open at a point within the alimentary
cavity.

It is surprising that the apparatus of such complicated organs should
have escaped the notice of all those who have studied the organisation
-of these animals.

If Dr. Spix is correct in what he describes ; if he is not mistaken by

1[Tube-feet. H. E.]

GENERAL CLASSIFICATION 139

attributing to these organs a nature and functions that do not really
belong to them (as has happened to so many botanists who imagined
they saw male and female organs in nearly all the cryptogams), then
the following result ensues :

1. That we must no longer refer the beginning of the nervous
system to the insects ;

2. That this system must be regarded as existing in a rudimentary
form in the worms, radiarians and even in the sea-anemone, the last
genus of the polyps ;

3. That this however is no reason why all the polyps should possess
the rudiments of this system ; just as it does not follow that because
some reptiles have gills, therefore they must all have them ;

4, Finally, that the nervous system is none the less a special organ,
not common to all living bodies; for, not only is it absent in plants,
but it is absent also in some animals. As I have shown the infusorians
cannot possibly have it, nor assuredly can it be possessed by the
majority of polyps; thus we should seek it in vain in the hydras
which belong nevertheless to the first order of polyps, that, namely,
which is nearest to the radiarians, since it comprises the sea-anemones.

Thus, whatever truth there may be in the facts named above, the
considerations set forth in this work as to the successive formation
of the various special organs hold good at whatever point in the animal
scale each of these organs begins ; and it remains true that the various
faculties of animals only take their origin from the existence of the
organs underlying them.

TABLE OF RADIARIANS.
OrpER 1.—Sorr RADIARIANS.
[ Various Coelenterates, exclusive of Anthozoa. H. E.]

Bodies gelatinous ; soft, transparent skin without jointed spines ;

no anus.

Stephanomia. Physsophora.
Lucernaria. Physalia.

Velella. Aequorea.
Porpita. Rhizostoma.
Pyrosoma [Tunicate. H. E.]. Medusa (jelly-fish).

Beroé.

ORDER 2.—ECHINODERM RADIARIANS.

Opaque, crustaceous or coriaceous skin, provided with retractile tubercles, or
spines articulated on tubercles, and pierced with holes in series.

(1) Stellerides. Skin not irritable, but mobile ; no anus.
Ophiura (brittle-star).
Asterias (star-fish).

140 ZOOLOGICAL PHILOSOPHY

(2) Echinoids. Skin neither irritable, nor mobile; an anus.

Clypeaster (cake-urchin). Galerites.
Cassidites. Nucleolites.
Spatangus (heart-urchin). Sea-urchin.
Ananchytes.

(3) Fistulides. Elongated body, skin irritable and mobile ; an anus.

Holothuria (sea-cucumber).
Sipunculus [Gephyrean. H. E.].

Remark. Sipunculus is an animal very similar to the worms, but
its recognised affinities with the holothurians have caused it to be
placed among the radiarians, although it has not the characters of
that group and must therefore be placed at the end of it.

As a rule, in a thoroughly natural classification the first and last
genera of the classes are those in which the standard characters are
least pronounced. Since the lines of demarcation are artificial, the
genera which are close to these lines display the characters of their
class less conspicuously than the others.

WORMS.
(Class IV. of the Animal Kingdom.)

Suboviparous animals with soft elongated bodies, no head, eyes, legs,
or bundles of setae ; destitute of a circulation, and having a complete,
intestinal canal, that is, with two openings.

Mouth consisting of one or several suckers.

OBSERVATIONS.

The general shape of worms is quite different from that of radiarians,
and their mouth, which is always formed as a sucker, has no analogy
with that of polyps, where there is merely an aperture associated with
radiating tentacles or rotatory organs.

The worms in general have an elongated body, very slightly con-
tractile, although quite soft; and as regards their intestine they are
no longer limited to a single aperture.

In the fistulide radiarians nature has begun to abandon the radiating
structure and to give an elongated shape to the bodies of animals,
the only shape which could conduct towards the end she had in view.

After having fashioned the worms, she will henceforth tend to
establish a type that is symmetrical as regards parts in pairs. She
could not have attained this type except through the type of articu-
lations; but in the somewhat ambiguous class of worms, she has
merely sketched out the rudiments of certain features of it.

GENERAL CLASSIFICATION 141

TABLE OF WORMS.
ORDER 1.—CyYLINDRICAL WoRMSs.

[Nematodes, cestodes, and other flat and round worms. H. E.]

Gordius [Nematode. H. E.]}. Cucullanus.

Filaria (guinea-worm). Strongylus.

Proboscidea [Turbellarian. H. E.]. Scolex [head of tapeworm. H. E.}.
Crino. Caryophyllaeus [Cestode. H. E.}.
Ascaris [Nematode. H. E.]. Tentacularia.

Fissula. Echinorhyncus

Trichocephalus [Nematode. H. E.]. (Acanthocephala. H. E.].

ORDER 2.—BLADDER WoRMS.

« Bicorne.”
Hydatis.

OrnpER 3.—FLAT Worms.

Taenia [Cestode. H. E.]. Lingula [doubtless a misprint for
Ligula, a Cestode. H. E.].
Linguatula [Arthropod. H. E.]. Fasciola [v. Introd. H. E.].

THIRD STAGE OF ORGANISATION.

Nerves terminating in a ganglionic longitudinal cord; respiration
by air-carrying tracheae ; circulation absent or imperfect.

(Insects and Arachnids.)

INSECTS.
(Class V. of the Animal Kingdom.)

Oviparous animals which undergo metamorphoses, which may have
wings, and which have in the perfect state six jointed legs, two antennae,
two eyes with facets and a horny skin.

Respiration by air-carrying tracheae which spread everywhere ; no
circulatory system; two distinct sexes; a single copulation in the
course of their life.

OBSERVATIONS.

On reaching the insects we find among the extremely numerous
animals comprised in this class a state of affairs very different from
what we have met with in the animals of the four preceding classes ;
so instead of a gradual progress in the complexity of animal organisa-
tion we find on reaching the insects that a considerable leap has been
made.

142 ZOOLOGICAL PHILOSOPHY

Here for the first time, animals from the outward aspect exhibit a
distinct head; very remarkable, although still imperfect, eyes; jointed
legs arranged in two rows; and that symmetrical form of paired and
opposed parts that we shall henceforth find employed by nature up
to and including the most perfect animals.

On examining the interior of insects, we also see a complete nervous
system, consisting of nerves which terminate in a ganglionic longitudinal
cord; but although complete, this nervous system is still very imper-
fect, since the nucleus to which sensations are conveyed appears much
broken up, and the senses themselves are few and ill-developed ; lastly,
we see a true muscular system, and sexes which are distinct but which
as in plants can only provide for a single fertilisation.

It is true that we do not yet find any circulatory system ; and we
shall have to pass higher up the animal chain before we meet with
this improvement in organisation.

It is characteristic of all insects to have wings in their perfect state ;
so that those which have none owe their condition to the fact that their
wings have become habitually and permanently aborted.

OBSERVATIONS.

In the table which I shall now give, the number of genera is greatly
reduced from what has been hitherto constituted among the animals
of this class. Such a reduction appears to me to be required in the
interests of study, and also of simplicity and clearness of method.
I have not carried it so far as to be detrimental to our knowledge
of the animals. If we were to utilise every appreciable peculiarity
in the characters of animals and plants for indefinitely multiplying
their genera, we should, as I have already said, merely encumber and
darken science instead of serving it; we should make the study of
it so complicated and difficult that it would only be practicable for
those who were willing to devote their entire life to gaining a knowledge
of the immense nomenclature and the minute characters selected for
marking the distinctions between these animals.

TABLE OF INSECTS.
(A) Suckine Insects.

Their mouth has a sucking-organ with or without a sheath.

OrpER 1.—AprTERous INSECTS.
A bivalve, three-jointed, proboscis, enclosing a sucking-organ of two setae.
Wings generally abortive in both sexes ; larva without legs ; pupa motionless,
in a@ cocoon.
Flea.

GENERAL CLASSIFICATION 143

ORDER 2.—DreteRovs INsEcTs.

An unjointed proboscis, straight or elbowed, sometimes retractile.
Two naked, membranous, veined wings; two balancers; larva worm-like,
usually without legs.

Hippobosca (horse-fly).
Oestrus.

Stratiomys.

Syrphus (hover-fly).
Anthrax.

Fly.

Tabanus (gad-fly).
Bhagio.

Gnat.

Stomoxis.

Myopa.

Conops.

Empis.

Bombylus.

Asilus.

Tipula (crane-fly).
Simulium (sand-midge).
Bibio.

OrpER 3.—HeEmiPTEROUS INSECTS.

Sharp, jointed beak, curved under the breast, serving as a sheath for a sucking-
tube of three setae.
Two wings hidden under membranous elytra ; larva hexapod ; the pupa walks

and eats.

Dorthesia.
Cachineal insect.
Psylla.
Plant-louse.
Aleyrodes.
Thrips.

Cicada.

Fulgora.
Tettigonia.

Scutellera.

Pentatoma.

Bed-Bug.

Coraeus.

Reduvius.

Hydrometra.

Gerris.

Nepa (water-scorpion).

Notonecta (water-boat-
man).

Nancoris.

Corixa (water-bug).

ORDER 4.—LEPIDOPTEROUS INSECTS.

Sucking tube in two pieces, without a sheath, resembling a tubular proboscis,

and rolled spirally when not in use.
Four membranous wings, covered with coloured and flour-like scales.
Larva with eight to sixteen legs ; motionless chrysalis.

(1) Antennae subulate or setaceous [moths. H. E.}.

Pterophorus.
Orneodes.
Cerastoma.
Tinea.
Noctua.
Phalaena.

Alucita.

Adella [Trichoptera. H. E.].
Pyralis.

Hepialus.

Bombyx (silk-worm).

(2) Antennae swollen at some part of their length.

Zygoena (burnet-moth).
Butterfly.

Sphinx (hawk-moth).
Sesia (clear-wing).

144 ZOOLOGICAL PHILOSOPHY

(B) Biting Insects.

The mouth exhibits mandibles, usually accompanied by mazillae.

ORDER 5.—HyYMENOPTEROUS INSECTS.

Mandibles, and a sucking-tube of three more or less elongated pieces, whose base
as enclosed in a short sheath.

Four wings, naked, membranous, veined and unequal; anus of the females
armed with a sting or provided with a boring-apparatus ; pupa motionless.

(1) Anus of the females armed with a sting.

Bee. Ant.
Monomelites. Mutilla (solitary ant),
Nomada. Scolia.
Eucera. Tiphia.
Andrena, Bembex.
— Crabro (digging-wasp).
Wasp. Sphex.
Polistes.

(2) Anus of the females provided with a boring-apparatus.

Chrysis. Chalcis.
Oxyurus. Cinips.

— Diplolepis.
Leucopsis [Diptera. H. E.]. Ichneumon.

= Wood-wasp.
Evania. Oryssus.
Foenus. Tenthredo (saw-fly).

= Cimbex (saw-fly).

ORDER 6.—NEUROPTEROUS INSECTS.

Mandibles and mazillae.
Four wings, naked, membranous and reticulated ; abdomen elongated, without
sting or boring-apparatus ; larva hexapod ; metamorphosis variable.

(1) Pupa motionless.

Perla. Hemerobius.
Nemoura. Ascalaphus.
Caddis-fly. Myrmeleon.

(2) Pupa active.

Nemoptera. Raphidia.
Panorpa. Ephemera.
Psocus. —
Termes (white ant). Agrion.
— Aeshna (dragon-fly).
Corydalis. Libellula (dragon-fly).

Chauliodes.

GENERAL CLASSIFICATION 145

ORDER 7.—ORTHOPTEROUS INSECTS.
Mandibles, maxillae and galeae covering the maxillae.

Two straight wings, folded longitudinally, and covered by two almost membranous
elytra.

Larva like the perfect insect, but with no wings or elytra ; pupa active.

Grasshopper. Locust.
Acheta. Truxalis.
Mantis (praying-insect). Cricket.
Phasma (stick- and leaf-insects). Cockroach.
Spectrum. Earwig.

ORDER 8,—COLEOPTEROUS INSECTS.

Mandibles and mazillae.

Two membranous wings, folded longitudinally when at rest, under two hard or
coriaceous but shorter elytra. Larva hexapod, with a scaly head and no eyes;
pupa inactive.

(1) Two or three segments in all the tarsi.

Pselaphus. Lady-bird.
_— Eumorphus.

(2) Four segments in all the tarsi.

Erotylus. Prionus.

Cassida. Spondilus.
Chrysomela. _—

Galeruca. Bostrichus.

Crioceris. Mycetophagus.
Clythra. Trogossita.
Cryptocephalus. Cucujus.

Leptura. Bruchus (pea-beetle).
Stencorus. Attelabus.

Saperda. Brentus.

Necydalis. Curculio.

Callidium. Brachycerus[Diptera. H.E.].
Cerambix.

(3) Five segments in the tarsi in the first pairs of legs, and
four in those of the third pair.

Opatrum. Mordella.
Tenebrio (meal-worm beetle). Rhipiphorus.
Blaps. Pyrochroa (cardinal-beetle).
Pimelia. Cossiphus.
Sepidium. Notoxus.
Scaurus. Lagria.
Erodius. Cerocoma.
Chiroscelis. Apalus.

— Horia.
Helops. Mylabris.
Diaperis. Cantharis.

— Melée (oil-beetle).
Cistela.

146

ZOOLOGICAL PHILOSOPHY

(4) Five segments in all the tarsi.

Lymexylon. Oxyporus (rove-beetle).
Telephorus. Poederus (rove-beetle),
Malachius. =
Melyris. Cicindela (tiger-beetle).
Lampyris (glow-worm). Elaphrus.
Lycus. Scarites.
Omalysus. Manticora.
Drilus. Carabus.
— Dyticus (water-beetle),
Melasis. —
Buprestis. Hydrophilus(water-beetle).
Click-beetle. Gyrinus (whirligig-beetle).
— Dryops.
Ptilinus. Clerus.
Death-watch. —
Ptinus. Necrophorus (burying-
beetle).
—_— Carrion-beetle.
Staphylinus (rove-beetle). Nitidula.
Ips. Goliathus.
Dermestes. Cockchafer.
Anthrenus. Lethrus.

Byrrhus (pill-beetle).
Hister.

Geotrupes (dor-beetle).
Copris (dung-beetle).

Sphoeridinus. Scarabaeus (chafer).
a Passealus.
Trox. Lucanus (stag-beetle).

Cetonia (rose-chafer).

ARACHNIDS.
(Class VI. of the Animal Kingdom.)

Oviparous animals which have jointed legs throughout their lives and
eyes in their head ; they undergo no metamorphosis and never have wings
or elytra.

Stigmata and limited tracheae for respiration ; a rudimentary circula-
tion ; several fertilisations in the course of their life.

OBSERVATIONS.

The arachnids, which come after the insects in the order that
we have established, display obvious progress in the perfection of
organisation.

Sexual reproduction, for instance, is found among them, and for the
first time in its full capacity, since these animals copulate and pro-
create several times in the course of their life; whereas in the
insects the sexual organs, like those of plants, can only achieve a

GENERAL CLASSIFICATION 147

single fertilisation. Moreover, the arachnids are the first animals in
which we find a rudimentary circulation, for according to M. Cuvier
they have a heart, from the sides of which issue two or three pairs of
vessels.

Arachnids live in the air like insects which have attained their
perfect state ; but they undergo no metamorphosis, never have wings
or elytra (nor is this due to any mere abortion), and they generally
keep hidden or live in solitude, feeding on other animals or sucking
blood.

In the arachnids, the method of respiration is the same as in the
insects, but this method is on the verge of changing ; for the tracheae
of arachnids are very limited, and do not extend throughout the body.
These tracheae are reduced to a small number of vesicles, as we learn
from M. Cuvier again (Anatom. vol. iv. p. 419) ; and after the arachnids
this method of respiration does not recur in any of the succeeding
classes.

This class of animals should be treated with much caution: many of
them are venomous, especially those living in hot climates.

TABLE OF ARACHNIDS.

OrpER 1.—ARACHNIDS WITH PEDIPALPS.

No antennae, but only pedipalps ; the head fused with the
thorax ; eight legs.

Mygale. Phrynus.
Spider. Thelyphonus.
Scorpion. Trombidium.
Chelifer. Hydrachna.
Galeodes. Bdella.
Harvestman. Mite.
Trogulus. Nymphon.
Elais. Pycnogonum.

ORDER 2.—ARACHNIDS WITH ANTENNAE.
[Myriapods and‘a few insects. H. E.]

Two antennae; the head distinct from the thorax.
Louse [Hemiptera. H. E.]. —

Ricinus. Centipede.

— Scutigera.
Silver-fish [Aptera. H. E.]. Julus (millipede).
Spring-tail.

148 ZOOLOGICAL PHILOSOPHY

FOURTH STAGE OF ORGANISATION.

Nerves terminating in a ganglionic longitudinal cord, or in a brain
without a spinal cord ; respiration by gills; arteries and veins for the
circulation.

(Crustaceans, annelids, cirrhipedes and molluscs.)

CRUSTACEANS.
(Class VII. of the Animal Kingdom.)

Oviparous animals with jointed body and limbs, a crustaceous skin,
several pairs of maxillae, eyes and antennae in the head.
Respiration by gills; a heart and vessels for circulation.

OBSERVATIONS.

The great changes that we find in the organisation of the animals
of this class, indicate that in forming the crustaceans, nature has
succeeded in making great progress in animal organisation.

In the first place, the method of respiration is altogether different
from that employed in the arachnids and insects; and this method,
which is characterised by the organs called gills, continues as far as
the fishes. Tracheae will appear no more, and gills themselves dis-
appear as soon as nature can form a cellular lung.

Then again the circulation, of which only rudiments are found in
the arachnids, is thoroughly established in the crustaceans; for in
them we find a heart and arteries for the dispatch of blood to the various
parts of the body, and veins which bring back this fluid to the chief
organ which sets it in motion.

We still find in the crustaceans the type of articulations, always
used by nature in the insects and arachnids, to facilitate muscular
movement by means of the induration of the skin; but hereafter
nature abandons this type to establish a system of organisation in
which it is no longer required.

Most crustaceans live either in brackish or salt water. Some,
however, keep on land and breathe air with their gills: they all feed
on animal substances.

GENERAL CLASSIFICATION 149

TABLE OF CRUSTACEANS.

ORDER 1.—SESSILE-EYED CRUSTACEANS.
Eyes sessile and immovable.

Wood-louse. Cephaloculus.

Ligia. Amymone.

Asellus. Daphnia.

Cyamus (whale-louse). Lynceus.

Shrimp. Osole.

Caprella. Limulus [Apus, not the
modern Limulus. H. E.].

— Caligus.
Cyclops (water-flea). Polyphemus.

Zoea [Decapod larva. H. E.].

ORDER 2.—STALK-EYED CRUSTACEANS.
Two distinct eyes, raised upon movable stalks.
(1) Elongated tail, furnished with swimming blades, or hooks or setae.

Branchiopod. Pagurus (hermit-crab).
Squilla. —

Palaemon. Ranina.

Crangon. Albunea.

Palinurus (rock-lobster). Hippa (sand-crab).
Scyllarus. Corystes.

Galathea. Porcellana.

Cray-fish.

(2) Tail short, without appendages, and applied to the lower surface
of the abdomen.

Pinnotheres. Dorippe.
Leuccsia. Plagusia.
Arctopsis. Grapsus.
Maia. Ocypode.

_— Calappa.
Matuta. Hepatus.
Orithyia. Dromia.
Podophthalmus. Cancer.
Portunus.

ANNELIDS.

(Class VIII. of the Animal Kingdom.)
Oviparous animals with soft elongated bodies, with transverse rings ;
they rarely have eyes or a distinct head and are destitute of jointed legs.
Arteries and veins for circulation ; respiration by gills ; a ganglionic
longitudinal cord.
OBSERVATIONS.

We find in the annelids that nature is striving to abandon the type
of articulations which she always used in the insects, arachnids and

150 ZOOLOGICAL PHILOSOPHY

crustaceans. Their soft elongated body, which in most of them simply
consists of rings, makes these animals appear as imperfect as the
worms with which they used to be confused. Since, however, they
have arteries and veins and breathe by gills, these animals are quite
distinct from the worms and should be placed with the cirrhipedes

between the crustaceans and the molluscs.
They have no jointed legs,! and most of them have on their sides

setae or bundles of setae which take the place of legs: they nearly all
have suckers and feed only on fluid substances.

TABLE OF ANNELIDS.

OrpER 1.—CRYPTOBRANCH ANNELIDS.

Planaria [Triclad. H. E.]. Furia (?).
Leech. Nais.
Lernea [Copepod. H. E.]}. Lumbricus.

Clavella [Copepod. H. E.]. Thalassema.

OrpER 2.—GYMNOBRANCH ANNELIDS.
[Polychaets. H. E.]

Arenicola. —_
Amphinoma. Terebella.
Aphrodite. Amphitrite.
Nereis. Sabellaria.

— Siliquaria [molluse. H. E.].
Serpula. Dentalium [mollusc. H. E.}.
Spirorbis.

CIRRHIPEDES.
(Class IX. of the Animal Kingdom.)

Oviparous and testaceous animals without a head or eyes, but having
a mantle which covers the inside of the shell, jointed arms whose skin
is horny, and two pairs of maxillae.

Respiration by gills ; a ganglionic longitudinal cord ; vessels for cir-
culation.

OBSERVATIONS.

Although only a small number of genera belonging to this class are
yet known, the character of the animals contained in these genera is so

1In order to perfect these animals’ organs of locomotion, nature had to abandon
the system of jointed legs, which are independent of a skeleton, and to establish the
system of four limbs depending on an internal skeleton, which is characteristic of
the most perfect animals; this is what she has done in the annelids and molluscs,
where she has paved the way for commencing with the fishes the type of organisation
peculiar to vertebrates. Thus in the annelids she has abandoned jointed legs, and
in the molluscs she has gone still farther,—she has discarded the use of a ganglionic
longitudinal cord.

GENERAL CLASSIFICATION 151

fee that we have to set them apart as constituting a special
class.

Seeing that the cirrhipedes have a shell, a mantle and no head or
eyes they cannot be crustaceans ; their jointed arms prevent us from
placing them among the annelids, and their ganglionic longitudinal
cord does not allow us to unite them with the molluscs.

TABLE OF CIRRHIPEDES.

Tubicinella. Balanus.
Coronula. Anatifa.

Remark. We see that the cirrhipedes still resemble the annelids
by their ganglionic longitudinal cord ; but in these animals nature is
preparing to form the molluscs, since they have like them a mantle
covering the inside of their shell.

MOLLUSCS.
(Class X. of the Animal Kingdom.)

Oviparous animals with soft unjointed bodies, and having a variable
mantle.

Respiration by very diversified gills ; no spinal cord, nor ganglionic
longitudinal cord, but nerves terminating in an imperfect brain.

The majority are enclosed in a shell; others have one that is more or
less completely embedded within them, and others again have none at all.

OBSERVATIONS.

The molluscs are the most highly organised of invertebrates ; that
is to say, their organisation is the most complex and the nearest to
that of the fishes.

They constitute a numerous class which terminates the invertebrates,
and which is sharply distinguished from the other classes by the fact
that the animals composing it are the only ones which, although
having a nervous system like many others, have neither a ganglionic
longitudinal cord nor a spinal cord.

Nature is here about to begin the formation of the system of organisa-
tion of the vertebrates ; and appears to be preparing for the change.
Hence the molluscs, which have altogether lost the type of articula-
tions, and the support given by a horny skin to animals belonging to
this type, are very slow in their movements and appear in this respect
even more imperfectly organised than the insects.

Finally, since the molluscs constitute a link between the inverte-
brates and the vertebrates, their nervous system is intermediate,

152 ZOOLOGICAL PHILOSOPHY

and exhibits neither the ganglionic longitudinal cord of the inverte-
brates which have nerves, nor the spinal cord of the vertebrates.
This is highly characteristic of them, and clearly distinguishes them
from the other invertebrates.

TABLE OF MOLLUSCS.

OrpeER 1.—AcEPHALIC MoLuuscs.

(First group, Brachiopods; last group, T'unicates; the rest,
Lamellibranchs. H. E.]

No head ; no eyes ; no organ of mastication ; they reproduce without copulation.
The majority have a shell with two valves which articulate at a hinge.

Brachiopods.
Lingula.
Terebratula.
Orbicula.
Ostracians,
Radiolites. Oyster.
Calceola. Gryphaea.
Crania [Brachiopod. H. E.]. Plicatula.
Anomia. Spondylus.
Placuna. Pecten.
Vulsella.
Byssifera.
Pedum. Crenatula.
Lima. Perna.
Pinna. Malleus.
Mytilus (mussel). Avicula.
Modiola (?).
Chamaceans.
Etheria. Corbula.
Chama. Pandora.
Diceras. —
Naiads.
Unio (fresh-water mussel).
Anodonta.
Arcaceans.
Nucula. Cucullaea.
Petunculus. Trigonia.
Arca. —_
Cardiads.
Tridaena. Isocardia.
Hippopus. Cardium (cockle).

Cardita.

GENERAL CLASSIFICATION 153

Conchs.
Venericardia. Lucinia.
Venus. Cyclas.
Cytherea. Galathea.
Donax. Capsa.
Tellina.
Mactraceans.
Erycina. Lutraria.
Ungulina. Mactra.
Crassatella. —
Myarians.
Mya.
Panorpa.
Anatina.
Solenaceans.
Glycimeris. Petricola.
Solen. Rupellaria.
Sanguinolaria. Saxicava.

Pholadarians (Boring-mussels).

Pholas. Aspergillum.
Teredo. =<
Fistulana.
Ascidians.
Ascidia.
Salpa.
Mammaria.

OrpDER 2.—CEPHALIC MoLuuscs.

A distinct head and eyes, and two or four tentacles in the majority, jaws or a
proboscis at the mouth ; reproduction by copulation.
The shell of those, which have one, never consists of two valves articulated at a
hinge.
(1) Pteropods.
Two opposite, swimming fins.
Hyalea.
Clio.
Pneumoderma.

(2) Gastropods.

(A) Straight body, united to the foot throughout the whole or nearly the
whole of its length.
Tritonians.

Glaucus. Tritonia.
Aeolis. Tethys.
Scyllaea. Doris.

154

ZOOLOGICAL PHILOSOPHY

Phyllidsans.
Pleurobranchus.
Phyllidia.
Chiton.

Laplysians.
Laplysia (sea-hare).
Dolabella.

Limacians.
Onchidium.
Limax (slug).
Parmacella.

Patella (limpet).
Fissurella.
Emarginula.

Bullaea.
Sigaretus.

Vitrina (glass-snail).
Testacella.

(B) Body spiral ; no syphon.

Amphibulimus,
Achatina.
Pupa.

Planorbis.
Ampullaria.

Melania.
Limnaea,

Nerita.
Natica.

Scalaria.
Turritella.
Vermicularia (?).

Solarium,
Trochus.

Pyrula.
Fusus.

Colymaceans.
Helix (snail).
Helicina.
Bulimus.
Orbaceans.
Cyclostoma.
Vivipara [Paludina. H. E.].
Auriculaceans.
Auricula,
Melanopsis.
Neritaceans.
Neritina.
‘Navicella.
Stomataceans.
Haliotis.
Stomatia.
Stomatella,
Turbinaceans.
Phasianella.
Turbo.
Monodonta.
Delphinula.
Heteroclites.
Volvaria.
Bulla.
Janthina,
Calyptraceans.
Crepidula.
Calyptraea.
(C) Body spiral: a syphon.
Canalifera.
Cerithium.
Pleurotoma.
Turbinella.

Fasciolaria.

Murex.

GENERAL CLASSIFICATION 155

Wing-shells.
Rostellaria.
Pteroceras.
Strombus.

Purpuraceans.
Cassis (helmet-shell).
Harpa (harp-shell)
Dolium (tun).
Terebra (auger-shell).

Eburna.
Columellarians.
Cancellaria.
Marginella.
Columbella.
Convolutes.

Ancilla [Ancillaria. H. E.).
Oliva (olive-shell).
Terebellum.

(3) Cephalopods.

Buccinum (whelk).
Concholepas.
Monoceros.
Purpura.

Nassa.

Mitra (mitre-shell).
Voluta.

Ovula.
Cypraea (cowry).
Conus (cone-shell).

(A) With multilocular test.
Lenticulaceans. [Foraminifera. H. E.]

Miliola.
Gyrogonita.
Rotalia.
Renulites.

Intuolaceans.
Litucla | {Foraminifera HE.
Spirolinites ae
Spirula [Cephalopod. H. E.].

Nautilaceans.

Baculites.
Turrilites.
Ammonoceras.

Discorbina.
Lenticulina.
Nummulites.

Orthoceras [Cephalopod. H. E.].
Hippurites [Lamellibranch. H. E.].
Belemnites [Cephalopod. H. E.].

Ammonites.
Orbulites,
Nautilus.

(B) With unilocular test.
Argonautaceans,

Argonauta.
Carinaria [Gastropod. H. E.].

(C) Without test.
Sepiated.

Octopus.
Calamary.
Cuttle-fish.

156 ZOOLOGICAL PHILOSOPHY

VERTEBRATE ANIMALS.

They have a vertebral column consisting of a number of short articu-
lated bones following one another in succession. This column serves
to support their body, it is the basis of their skeleton, constitutes a
sheath for their spinal cord, and terminates anteriorly in a bony case
containing the brain.

FIFTH STAGE OF ORGANISATION.

Nerves terminating in a spinal cord and a brain which does not
fill up the cavity of the cranium; heart with one ventricle and cold
blood.

(Fishes and Reptiles.)

FISHES.
(Class XI. of the Animal Kingdom.)

Oviparous vertebrate animals with cold blood ; living in water, breathing
by gills, covered with a skin either scaly or almost naked and slimy, and
having for their locomotive movements only membranous fins supported
by a bony or cartilaginous framework.

OBSERVATIONS.

The organisation of the fishes is much more perfect than that of the
molluscs and animals of the anterior classes, since they are the first
animals to have a vertebral column, the rudiments of a skeleton, a
spinal cord and a cranium enclosing the brain. They are also the first
in which the muscular system derives its support from internal
parts.

Nevertheless their respiratory organs are still analogous to those of
the molluscs, cirrhipedes, annelids and crustaceans; and like all the
animals of the preceding classes, they are still without a voice and have
no eyelids.

The shape of their body is adapted to their necessity for swimming ;
but they maintain the symmetrical shape of paired parts started in the
insects ; lastly, among them as among the animals of the three follow-
ing classes, the type of articulations is altogether internal, and only
occurs in the parts of their skeleton.

N.B.—In the preparation of the tables of vertebrate animals I
have used M. Duméril’s work entitled Zoologie Analytique, and I
have permitted myself to make but few changes in his arrangement.

GENERAL CLASSIFICATION 157

TABLE OF FISHES.

ORDER 1.—CarTILAGINous FIsHES.

Vertebral column soft and cartilaginous ; no true ribs in a great
number.

(1) No operculum over the gills, and no membrane.

Trematopneans. [Hole-breathing. H. E.]
Respiration through round holes.

1. Cyclostomes.
Gasterobranchus (hagfish, myxine).

Lamprey.
2. Plagiostomes.
Torpedo. Squatina (angel-fish).
Skate. Squalus.
Bhinobatus. * Aodon.

(2) No operculum over the gills, but a membrane.
Chismopneans. ([Cleft-breathing. H. E.]
Gills opening by clefts at the sides of the neck ; four paired fins.

Batrachus [‘Teleost. H. E. }. Balistes [Teleost. H. E.].
Lophius (frog-fish) [Teleost. H. E.]. Chimaera [Elasmobranch. H. E.].

(3) An operculum over the gills, but no membrane.
Eleutheropomes. [Free operculum. H. E.]
Four paired fins ; mouth under the snout.

" Pelyodon [Ganoid. H. E.].
Pegasus [Teleost. H. E.].
Accipenser (sturgeon) [Ganoid. H. E.}.

(4) An operculum and a membrane over the gills.
Teleobranchs. [Complete gills. H. E.]
[Teleosts. H. E.]

Gills complete, with an operculum and a membrane.

5. Aphyostomes. [Sucking-mouth. H. E.]

Macrorhyncus.
Solenostoma.
Centriscus (snipe-fish).

6. Pteroptera. [United fins. H. E.]

Cyclopterus (lump-sucker).
Lepadogaster.

158 ZOOLOGICAL PHILOSOPHY

7. Osteoderms. [Bony skin. H. E.]

Ostracion (copper-fish). Diodon (porcupine-fish).
Tetraodon (globe-fish). Spherodon.
Ovoides. Syngnathus.

ORDER 2.—Bony FISHEs.
Vertebral column with bony vertebrae, that are not flexible.

(1) An operculum and membrane over the gills.
Holobranchs. [Complete gills. H. E.]
Apode Holobranchs.

No inferior paired fins. [Eel-shaped. H. E.]

8. Peropterous holobranchs. [Finless. H. E.]

Coecilia [Amphibian. H. E.]. Notopterus.
Monopterus. Ophisurus.
Leptocephalus [immature eel. H. E.]. Apteronotus.
Gymnotus (Electric eel). Regalecus.
Trichiurus.

9. Pantopterous Holobranchs. [With all unpaired fins. H. E.]
Muraena (eel). Anarrhichas (sea-wolf).
Ammodytes (sand-eel). Comephorus.
Ophidium. Stromataeus.
Macrognathus. Rhombus.

Xiphias (sword-fish).

Jugular Holobranchs.
Inferior paired fins situated under the throat, or in front of thoracic fins.

10. Auchenopterous Holobranchs. [Fins on neck. H. E.]

Murenoid. Batrachoides.
Calliomorus. Blenny.
Uranoscopus. Oligopod.
Weever. Kurtus.

Cod. Chrysostrome.

Thoracic Holobranchs.
Inferior paired fins situated under the pectorals.

1l. Petalosome Holobranchs. [Blade shaped. H. E.]

Lepidopus. Bostrichthys.
Cepola (band-fish). Bostrichoid.
Taenioid. Gymnetrus.

12. Plecopod Holobranchs. [Inferior fins united. H. E.]

Gobius (goby).
Gobioid.

13. Eleutheropod Holobranchs. [Inferior fins free.. H. E.]

Gobiomore.
Gobiomoroid.
Echeneis.

GENERAL CLASSIFICATION 159

14. Atractosome Holobranchs. ([Spindle-shaped. H. E.]

Scomber (mackerel). Scomberomorus.
Scomberoid. Gasterosteus (stickleback).
Caranx (horse-mackerel), Centropodus.

Trachinote. Centronotus.
Caranxomorus. Cephalacanthus.

Caesio. Istiophorus.

Caesiomorus. Pomatomus.

15. Letopome Holobranchs. [Smooth-operculed. H. E.]

Hiatula. Chilinus.

Coris (rainbow wrasse). Cheilodipteron.
Gomphosus. Ophiocephalus.
Osphronemus. Hologymnosa.
Trichopod. Sparus.
Monodactyl. Dipterodon.
Plectorhyncus. Cheilio.
Pogonias. Mullet.

Labrus (wrasse).

16. Osteostome Holobranchs. [Bony-mouthed. H. E.]

Scarus.
Ostorhincus.
Leiognathus.

17. Lophionotous Holobranchs. [Crested-back. H. E.]

Coryphaena. Taenionotus.
Emipteronota. Centrolophus.
Coryphaenoid. Eques.

18. Cephalotous Holobranchs. [Large-headed. H. E.]

Gobiesox. Cottus.
Aspidophora. Scorpaena (scorpion-fish),
Aspidophoroides.

19. Dactylous Holobranchs. [Pectorals in distinct rays, like fingers. H. E.]
Dactylopterus. Trigla (gurnard).
Prionotus. Peristedion.
20. Heterosomatous Holobranchs. [Irregular-shaped. H. E.]

Pleuronectes.
Achirus.

21. Acanthapome Holobranchs. [Spiny opercula. H. E.]

Lutjanus. Sciaena.
Centropomus. Micropterus (black bass).
Bodianus. Holocentrum.

Taenianotus. Perca (perch).

160

25. Oplophore Holobranchs.

ZOOLOGICAL PHILOSOPHY

22. Leptosome Holobranchs.

Chetodon.
Acanthinion.
Pomadasis.
Pomacanthus.
Holacanthus.
Enoplosus.
Glyphisodon.
Acanthurus.
Aspisurus.

[Slender-bodied. H. E.]

Chetodipteron.
Pomacentrus.
Acanthopod.
Selene.
Argyriosus.

Zeus.

Galeoides.
Chrysostose.
Capros (boar-fish).

Abdominal Holobranchs.
Inferior paired fins placed a litile in front of the anus.

23. Siphonostome Holobranchs.
Fistularia.

[Tube-like mouths. H. E.]

Aulostoma.
Solenostoma.

24. Cylindrosome Holobranchs.

Cobitis.
Misgurnus.
Anableps.
Fundulus.
Colubrine.

Silurus,
Macropteronotus.
Malapterurus.
Pimelodus.
Doras.
Pogonathus.
Cataphractus.
Plotosus.

26. Dimerid Holobranchs.
Cirrhites.
Cheilodactylus.

27. Lepidome Holobranchs.

Mugil (grey mullet).
Mugiloid.

28. Gymnopome Holobranchs.

Argentina.
Atherina.
Hydrargyrus.
Stolephorus.
Buro.

Clupea (herring).
Mystus.

[Cylindrical. H. E.]

Amia [Ganoid. H. E.].

Butirinus.
Tripteronotus.
Ompolk.

{Armed. H.E.] [Catfishes. H. E.]

Ageniosus.

Macrorhamphosus (snipe-

fish).
Centranodon.
Loricaria.
Hypostome.
Corydoras.
Tachysurus.

[Two-membered. H. E.]

Polynemus.
Polydactylus.

[Scaly opercula. H. E.]

Chanos,
Mugilomorus.

[Naked opercula. H. E.]
Clupanodon.
Gasteropleucus.
Mene.
Dorsuaria.
Xystera.
Cyprinus (carp).

GENERAL CLASSIFICATION 161

29. Dermopterous Holobranchs. [Skin-fins. H. E.]

Salmo. Characinus. 4
Osmerus vt aon H. E.]} Serracalino, }{Characinidae. H. E.]

Corregonus.

30. Stagonote Holobranchs. [Long-jawed. H. E.]

Elops. Sphyraena.

Megalops (tarpon). Lepisosteus.

Esox. Polypterus [Ganoid. H. E.].
Synodon. Scombresox.

(2) An operculum over the gills, but no membrane.
Sternoptyges. [Bent sternum. H. E.]

3].

Sternoptyx.

(3) No operculum over the gills, but a membrane.
Cryptobranchs. [Gills hidden. H. E.]

eh RiaCAd ateiadesaldees sige ecb sata 9 a
Mormyrus.
Stylophorus.
(4) No operculum nor membrane over the gills: no inferior
paired fins.
Ophichthians. [Snake-fishes. H. E.]
GBe., sin! seme ce aie inl icra ea elena ee
Unibranch aperture. Murenophis.
Sphagebranchus. Gymnomuraena,

Remark. Seeing that the formation of a skeleton begins in the
fishes, those called cartilaginous are probably the least perfect fishes.
Consequently the most imperfect of all should be Gasterobranchus,
which Linneus, under the name of myzine, had regarded as a worm.

Thus, in the order that we are following, the genus Gasterobranchus
must be the first of the fishes, because it is the least perfect.

REPTILES.
(Class XII. of the Animal Kingdom.)

Oviparous vertebrate animals with cold blood ; breathing incompletely
by a lung, at all events in later life; and having the skin smooth or
else covered either with scales or with a bony shell.

OBSERVATIONS.

Progress in the perfection of organisation is seen to be very remark-

able in the reptiles when they are compared with fishes ; for it is among
L

162 ZOOLOGICAL PHILOSOPHY

them that we find lungs for the first time, and we know that it is the
most perfect respiratory organ since it is the same as that of man;
but it is still only rudimentary and indeed some reptiles do not have
it in early life: as a matter of fact they only breathe incompletely,
for it is only a part of the blood that passes through the lung.

It is also among them that for the first time we distinctly see the
four limbs, which are included in the plan of the vertebrates and are
appendages of the skeleton.

TABLE OF REPTILES.

OrpER 1.—BaTRACHIAN Reptites [Ampuipians. H. E.].

Heart with one auricle: skin naked : two or four legs: gills during
immaturity : no copulation.

Urodela.
Siren. Triton.
Proteus. Salamander.
Anura.
Tree-frog. Pipa.
Frog. Toad.

ORDER 2.—OPHIDIAN REPTILES (OR SNAKES).
{Snakes and Apodal Lizards. H. E.]
Heart with one auricle: elongated narrow body without legs or fins :

no eyelids.
Homoderms.
Coecilia [Amphibian. H. E.]. Ophisaurus.
Amphisboena. Slow-worm.
Acrochordus. Hydrophis (sea-snake).
Heteroderms.
Crotalus. Erix.
Scytale. Viper.
Boa. Coluber.
Erpeton. Platurus.

ORDER 3.—SauRIAN REPTILES.
(Legged Lizards and Crocodiles. H. E. ]
Double-auricled heart ; body scaly and having four legs ; claws on the
digits ; teeth in the jaws.

Tereticauds [Round-tailed. H. E.].

Chalcides. Agama.
Scincus. Lacerta.
Gecko. Iguana.
Anolis. Stellio.

Dragon. Chamaeleon.

GENERAL CLASSIFICATION 163

Planicauds [Flat-tailed. H. E.].

Uroplates, Lophura.
Tupinambis. Dracaena.
Basiliscus. Crocodile [Crocodilia. H. E.].

ORDER 4.—CHELONIAN REPTILES.

Double-auricled heart ; body with a carapace and four legs ; jaws
without teeth.

Chelonia. Emys.
Chelys. Tortoise.

SIXTH STAGE OF ORGANISATION.

Nerves terminating in a spinal cord, and in a brain which fills up
the cavity of the cranium ; heart with two ventricles and warm blood.

(Birds and Mammals.)

BIRDS.
(Class XIII. of the Animal Kingdom.)

Oviparous vertebrate animals with warm blood ; complete respiration
by adherent and pierced lungs ; four jointed limbs, two of which are
shaped as wings ; feathers on the skin.

OBSERVATIONS.

Assuredly birds have a more perfect organisation than reptiles or
any other animals of the preceding classes, since they have warm blood,
a heart with two ventricles, and their brain fills up the cavity of the
cranium,—characters which they have in common only with the most
perfect animals composing the final class.

Yet the birds are clearly only the penultimate step of the animal
scale; for they are less perfect than the mammals, in that they are
still oviparous, have no mammae, are destitute of a diaphragm, a
bladder, etc., and have fewer faculties.

In the following table it may be noticed that the first four orders
include birds whose young can neither walk nor feed themselves,
when they are hatched; and that the last three orders, on the other
hand, comprise birds whose young walk and feed themselves as soon as
they come out of the egg ; finally, the 7th order, that of the palmipeds
seems to me to contain those birds which are most closely related to
the first animals of the following class.

164 ‘ZOOLOGICAL PHILOSOPHY

TABLE OF BIRDS.

ORDER ].—CLIMBERS.
Two digits in front, and two behind.

Levirostrate Climbers. [Slender-billed. H. E.]

Parrot. Touraco.
Cockatoo. Trogon.
Macaw. Musophaga(plantain-eater).
Puff-bird. Toucan.
Cuneirostrate Climbers. [Wedge-shaped beaks. H. E.]
Woodpecker. Ani.
Wryneck. Cuckoo.
Jacamar.

OrpER 2.—BrirRDs OF PREY.
A single digit behind ; anterior digits entirely free ; beak and claws

hooked.
Nocturnal Birds of Prey.
Owl.
Eagle-owl.
Surnia.
Bare-necked Birds of Prey.
Condor.
Vulture.
Feather-necked Birds of Prey.
Griffon. Buzzard.
Secretary-bird. Goshawk.
Eagle. Falcon.

ORDER 3.—PASSERES.
A single digit behind ; the two front external ones united ; tarsus of
medium height.

Crenirostrate Passeres. [Notched beaks. H. E.]

Tanagra. Ampelis (wax-wing, etc.).
Shrike. Thrush.
Flycatcher.
Dentirostrate Passeres. [Tooth-beaked. H. E.]
Hornbill.
Motmot.

Phytotoma (plant-cutter).

Plenirostrate Passeres. [Full-beaked. H. E.]
Grackle. Crow.
Bird of Paradise. Pie.
Roller.

GENERAL CLASSIFICATION 165

Conirostrate Passeres. [Conical beaks. H. E.]

Ox-pecker. Crossbill.
Glaucopis. Grosbeak.

Oriole. Colius (mouse-bird).
Cacicus. Finch.

Starling. Bunting.

Subulirostrate Passeres. [Subulate beaks. H. E.]

Mannakin. Lark.
Titmouse. Wagtail.
Planirostrate Passeres. [Flat-beaked. H. E.]

Martin.

Swallow.

Nightjar.
Tenuirostrate Passeres. [Slender-billed. H. E.]
Kingfisher. Bee-eater.
Tody. Humming-bird.
Nuthatch. Creeper.
Orthorincus. Hoopoe.

ORDER 4.—COLUMBAE.
Soft, flexible beak, flattened at the base ; brood of two eggs.
Pigeon.

ORDER 5.—GALLINACEANS.
Solid, horny beak, rounded at the base ; brood of more than two eggs.

Alectride Gallinaceans. [Fowl-like. H. E.]

Bustard. Guinea-fowl.
Peacock. Curassow.
Tetras. Penelope.
Pheasant. Turkey.
Brachypterous Gallinaceans. (Short-winged. H. E.]
Dodo. Rhea.
Cassowary. Ostrich.

ORDER 6.—WADERS.

Tarsus very long, and denuded of feathers as far as the leg, external
digits united at their base (waterside birds).

Pressirostrate Waders. [Narrow-beaked. H. E.]

Jacana. Moorhen.
Rail. Coot.
Oyster-catcher.

e Cultrirostrate Waders. [Cutting-beaked. H. E.]
Bittern. Crane.
Heron. Mycteria.

Stork. Tantalus.

166 ZOOLOGICAL PHILOSOPHY

Teretirostrate Waders. [Round-beaked. H. E.]

Avocet. Dunlin.
Curlew. Plover.
Woodcock.
Latirostrate Waders. [Broad-beaked. H. E.]
Boatbill.
‘Spoonbill.

Phoenicopterus (flamingo).

ORDER 7.—PALMIPEDS.

Digits united by large membranes ; tarsus of low height (Aquatic
birds, swimmers).

Penniped Palmipeds. [Fin-footed. H. E.]

Anhinga. Frigate-bird.
Phaéton. Cormorant.
Gannet. Pelican.

Serrirostrate Palmipeds. [Serrated beaks. H. E.]

Merganser.
Duck.
Flamingo.

Longipen Palmipeds. {Long-winged. H. E.]

Gull. Avocet.

Albatross. Tern.

Petrel. Scissor-bill.
Brevipen Palmipeds. [Short-winged. H. E.]

Grebe. Penguin.

Guillemot. King-penguin.

Auk.

MONOTREMES. (Geoff.)

Animals intermediate between birds and mammals. These animals
are quadrupeds without mammae, without any teeth inserted, without lips,
and with only one orifice for the genital organs, the excrement and the

urine ; their body is covered with hair or bristles.

ORNITHORHYNCHUS.
ECHIDNA.

N.B.—I have already spoken of these animals in Chapter VI., page
74, where I showed that they are neither mammals, birds nor

reptiles.

GENERAL CLASSIFICATION 167

MAMMALS.
(Class XIV. of the Animal Kingdom.)

Viviparous animals with mammae ; four jointed legs or only two ;
complete respiration by lungs, not pierced through externally ; hair on
parts of the body.

OBSERVATIONS.

Nature clearly proceeds from the simplest to the most complex in
her operations on living bodies; hence the mammals necessarily
constitute the last class of the animal kingdom.

This class undoubtedly comprises the most perfect animals, with
the greatest number of faculties, the highest intelligence and, lastly,
the most complex organisation.

Since the organisation of these animals approaches most nearly to
that of man they display a more perfect combination of senses and
faculties than any others. They are the only ones that are really
viviparous, and have mammae to suckle their young.

The mammals thus exhibit the highest complexity of animal organ-
isation, and the greatest perfection and number of faculties that
nature could confer on living bodies by means of that organisation.
They should thus be placed at the end of the immense series of existing
animals.

TABLE OF MAMMALS.

ORDER 1.—ExXUNGULATE MAMMALS.

Two limbs only: they are anterior, short, flattened, suitable for swimming,
and have neither claws nor hoofs.

Cetaceans.
Right-whale. Narwhal.
Rorqual. Anarnak.
Physale. Delphinapterus.
Cachalot. Dolphin.
Sperm-whale. Hyperodon.

ORDER 2.—AMPHIBIAN MAMMALS.
Four limbs: the two anterior short, fin-like, with unguiculate digits; the
posterior directed backwards, or united with the extremity of the body,
which is like a fish’s tail.

Wrairus f{Pinnipeds. HE.

Dugong

Macere, (Siren. H. E.}.

Observation.
This order is only placed here, on account of the general shape of the animals
it contains. (See my observation, p. 74.)

168 ZOOLOGICAL PHILOSOPHY

ORDER 3.—UNGULATE MAMMALS.

Solipeds.
Horse.

Ruminants or Bisulcates.

Ox. Deer.

Antelope. Giraffe.

Goat. Camel.

Sheep. Musk-deer.
Pachiderms.

Rhinoceros. Pig.

Hyrax. Elephant.

Tapir. Hippopotamus.

ORDER 4.—UNGUICULATE MAMMALS.

Four limbs ; flattened or pointed nails at the extremity of their digits,
which do not envelop them.

Tardigrades.
Sloth [Edentate H. E.].
Edentates.

Ant-eater. Aardvark.
Pangolin. Armadillo.
Rodents.

Kangaroo [Marsupial. H. E.]. Spalax.
Hare. Squirrel.
Coendu. Dormouse.
Porcupine. Hamster.
Aye-aye [Lemur. H. E.]. Marmot.

Phascolomys [Marsupial. H. E.]. Vole.
Hydromys (Australian Water-rat). Musk-rat.

Beaver. Rat.
Cavy.
Pedimana (Marsupials. H. E.].

Opossum. Wombat.

Bandicoot. Coescoés.

Dasyurus. Phalanger.

Plantigrades.
Mole [Insectivore. H. E.]. Badger [Carnivore. H. E.].
Shrew [Insectivore. H. E.]. Coati [Carnivore. H. E.].
Bear (Carnivore. H. E.]. Hedgehog [Insectivore. H. E. ].
Kinkajou [Carnivore. H. E.]. Tenrec [Insectivore. H. E.].
Digitigrades. [All carnivores. H. E.].

Otter. Cat.

Mongoose. Civet.

Skunk. Hyaena.

Weasel. Dog.

GENERAL CLASSIFICATION 169

Chiroptera.

Galeopithecus [Insectivore. H.E.]. Noctilio.
Rhinolophus. Bat.
Phyllostome. Flying Fox.

Quadrumana.
Galago Baboon.
Tarsius Sapajou.
Loris ;{Lemurs. H. E.}. Cebus.
Makis African Baboon.
Indris Pongo.
Guenon (Old-world Monkey). Orang.

Remark. According to the order which I have adopted, the quad-
rumanous family comprises the most perfect of known animals, and
especially the later genera of this family; and as a matter of fact
the genus orang (Pithecus) is at the end of the entire order, just as
the monas is at the beginning of it. How great is the difference in
organisation and faculties between these two genera !

Naturalists who have considered man exclusively according to the
affinities of his organisation, have formed a special genus for him
with six known varieties, thus making him a separate family which
they have described in the following manner.

BIMANA.

Mammals with differentiated unguiculate limbs ; with three kinds of
teeth and opposable thumbs on the hands only.

Man.

Caucasian.
Hyperborean.
Mongolian.
American.

Malayan.

Ethiopian or Negro.

Varieties.

This family has received the name of Bimana, because in man it
is only the hands that have a separate thumb opposite to the fingers
while in the Quadrumana the hands and feet have the same character
as regards the thumb.

Some Observations with regard to Man. |

If man was only distinguished from the animals by his organisation,
it could easily be shown that his special characters are all due to long-
standing changes in his activities and in the habits which he has

170 ZOOLOGICAL PHILOSOPHY

adopted and which have become peculiar to the individuals of his
species.

As a matter of fact, if some race of quadrumanous animals, especially
one of the most perfect of them, were to lose, by force of circumstances or
some other cause, the habit of climbing trees and grasping the branches
with its feet in the same way as with its hands, in order to hold on to
them; and if the individuals of this race were forced for a series of
generations to use their feet only for walking, and to give up using
their hands like feet ; there is no doubt, according to the observations
detailed in the preceding chapter, that these quadrumanous animals
would at length be transformed. into bimanous, and that the thumbs
on their feet would cease to be separated from the other digits, when
they only used their feet for walking.

Furthermore, if the individuals of which I speak were impelled by
the desire to command a large and distant view, and hence endeavoured
to stand upright, and continually adopted that habit from generation
to generation, there is again no doubt that their feet would gradually
acquire a shape suitable for supporting them in an erect attitude ;
that their legs would acquire calves, and that these animals would
then not be able to walk on their hands and feet together, except with
difficulty. ,

Lastly, if these same individuals were to give up using their jaws
as weapons for biting, tearing or grasping, or as nippers for cutting
grass and feeding on it, and if they were to use them only for mastica-
tion; there is again no doubt that their facial angle would become
larger, that their snout would shorten more and more, and that finally
it would be entirely effaced so that their incisor teeth became vertical.

Let us now suppose that a quadrumanous race, say the most perfect,
acquired through constant habit among all its individuals the con-
formation just described, and the faculty of standing and walking
upright, and that ultimately it gained the supremacy over the other
races of animals, we can then easily conceive:

1. That this race having obtained the mastery over others through
the higher perfection of its faculties will take possession of all parts
of the earth’s surface, that are suitable to it;

2, That it will drive out the other higher races, which might dispute
with it the fruits of the earth, and that it would compel them to take
refuge in localities which it does not occupy itself ;

3. That it will have a bad effect on the multiplication of allied
races, and will keep them exiled in woods or other deserted localities,
that it will thus arrest the progress of their faculties towards per-
fection ; whereas being able itself to spread everywhere, to multiply
without obstacle from other races and to live in large troops, it will

GENERAL CLASSIFICATION 171

create successively new wants, which will stimulate its skill and
gradually perfect its powers and faculties ;

4. Finally, that this predominant race, having acquired an absolute
supremacy over all the rest, will ultimately establish a difference
between itself and the most perfect animals, and indeed will leave
them far behind.

The most perfect of the quadrumanous races might thus have become
dominant ; have changed its habits as a result of the absolute sway
exercised over the others, and of its new wants; have progressively
acquired modifications in its organisation, and many new faculties ;
have kept back the most perfect of the other races to the condition
that they had reached; and have wrought very striking distinctions
between these last and themselves.

The orang of Angola (Simia troglodytes, Lin.) is the most perfect of
animals : it is much more perfect than the orang of the Indies (Simia
satyrus, Lin.), called the orang-outang; yet they are both very inferior
to man in bodily faculties and intelligence.1 These animals often
stand upright; but as that attitude is not a confirmed habit, their
organisation has not been sufficiently modified by it, so that the
standing position is very uncomfortable for them.

We know from the stories of travellers, especially as regards the
orang of the Indies, that when it has to fly from some pressing danger
it immediately falls on to its four feet. Thus, it is said, the true
origin of this animal is disclosed, since it is obliged to abandon a
deceptive attitude that is alien to it.

No doubt this attitude is alien to it, since it adopts it less when
moving about, and its organisation is hence less adapted to it; but
does it follow that, because the erect position is easy to man, it is
therefore natural to him ?

Although a long series of generations has confirmed the habit of
moving about in an upright position, yet this attitude is none the less
a tiring condition in which man can only remain for a limited period,
by means of the contraction of some of his muscles.

If the vertebral column were the axis of the human body, and kept
the head and other parts in equilibrium, man would be in a position
of rest when standing upright. Now we all know that this is not
the case; that the head is out of relation with the centre of gravity ;
that the weight of the chest and belly, with their contained viscera,
falls almost entirely in front of the vertebral column ; that the latter
has a slanting base, etc. Hence it is necessary as M. Richerand
observes, to keep a constant watch when standing, in order to avoid

1See in my Recherches sur les corps vivants, p. 136, some observations on the
orang of Angola.

172 ZOOLOGICAL PHILOSOPHY

the falls to which the body is rendered liable by the weight and
arrangement of its parts.

After discussing the questions with regard to the erect position of
man, this observer expresses himself as follows: “ The relative weight
of the head, and of the thoracic and abdominal viscera, gives a forward
inclination to the axial line of the body, as regards the plane on which
it rests; a line which should be exactly perpendicular to this plane,
if standing is to be perfect. The following fact may be cited in support
of this assertion: I have observed that children, among whom the
head is bulky, the belly protruding and the viscera burdened with fat,
find it difficult to get accustomed to standing upright; it is only at
the end of their second year that they venture to trust their own
strength ; they continue liable to frequent falls and have a natural
tendency to adopt the position of a quadruped ” (Physiologie, vol.
il., p. 268).

This arrangement of parts, as a result of which the erect position
is a tiring one for man, instead of being a state of rest, would disclose
further in him an origin analogous to that of the other mammals,
if his organisation alone were taken into consideration.

‘~~ Tn order to follow out the hypothesis suggested at the beginning
of these observations, some further considerations must now be added.

The individuals of the dominant race in question, having seized all
the places of habitation which were suitable to them and having
largely increased their needs according as the societies which they
formed became larger, had to multiply their ideas to an equivalent
extent, and thus felt the need for communicating them to their fellows.
We may imagine that this will have compelled them to increase and
vary in the same degree the signs which they used for communicating
these ideas ; hence it is clear that the individuals of this race must have
made constant efforts, and turned all their resources towards the crea-
tion, multiplication and adequate variation of the signs made necessary
by their ideas and numerous wants.

This is not the case with other animals; for although the most
perfect of them such as the Quadrumana mostly live in troops, they
have made no further progress in the perfection of their faculties
subsequent to the high supremacy of the race named ; for they have
been chased away and banished to wild and desert places where they
had little room, and lived a wretched, anxious life, incessantly com-
pelled to take refuge in flight and concealment. In this situation
these animals contract no new needs and acquire no new ideas ; their
ideas are but few and unvaried; and among them there are very few
which they need to communicate to others of their species. Very
few different signs therefore are sufficient to make themselves under-

GENERAL CLASSIFICATION 173

stood by their fellows ; all they require are a few movements of the
body or parts of it, a few hissings and cries, varied by simple vocal
inflections.

Individuals of the dominant race already mentioned, on the other
hand, stood in need of making many signs, in order rapidly to com-
municate their ideas, which were always becoming more numerous
and could no longer be satisfied either with pantomimic signs or
with the various possible vocal inflections. For supplying the large
quantity of signs which had become necessary, they will by various
efforts have achieved the formation of articulate sounds. At first
they will only have used a small number, in conjunction with inflexions
of the voice ; gradually they will have increased, varied and perfected
them, in correspondence with the growth in their needs and their
gain of practice. In fact, habitual exercise of their throat, tongue
and lips in the articulation of sounds will have highly developed that
faculty in them.

Hence would arise for this special race the marvellous faculty of
speaking ; and seeing that the remote localities to which the individuals
of the race would have become distributed, would favour the corrup-
tion of the signs agreed upon for the transmission of each idea, languages
would arise and everywhere become diversified.

In this respect, therefore, all will have been achieved by needs alone:
they will have given rise to efforts, and the organs adapted to the
articulation of sounds will have become developed by habitual use.

Such are the reflections which might be aroused, if man were dis-
tinguished from animals only by his organisation, and if his origin
were not different from theirs. |

ADDITIONS TO THE SUBJECT MATTER OF
CHAPS. VII. AND VIII.

During the last few days of June 1809 the menagerie of the Museum
of Natural History received a seal known under the name of sea-calf
(Phoca vitulina) which was sent alive from Boulogne; and I had an
opportunity of observing the movements and habits of this animal.
Thereupon I acquired a still stronger conviction that this amphibian
is much more allied to the unguiculate mammals than to the other
mammals, notwithstanding the great differences in general shape
between it and them.

Its hind legs, although very short like the fore-legs, are quite free
and separate from the tail, which is small but quite distinct, and they
can move easily in various ways; they can even grasp objects like
true hands.

174 ZOOLOGICAL PHILOSOPHY

I noticed that this animal is able to unite its hind feet as we join
our hands, and that on then separating the digits between which there
are membranes, it forms a fairly large paddle, which it uses for travelling
about in the water in the same way as fishes use their tail as a fin.

This seal drags itself about on the ground with some speed by means
of an undulatory movement of the body, and without any help from
its hind legs, which remain inactive and are stretched out. In thus
dragging itself about, it derives help from its fore-legs only by support-
ing itself on the arms up to the wrists, without making any special
use of the hands. It seizes its prey either with its hind feet or with
its mouth, and although it sometimes uses its hands to rend the prey
that it holds in its mouth, these hands appear to be used principally
for swimming or locomotion in the water. Finally, as this animal often
remains under water for a longish time and even feeds there in comfort,
I have noticed that it easily and completely closes its nostzils just as
we close our eyes ; this is very useful to it when immersed in the liquid
that it inhabits.

As this seal is well known, I shall give no description of it. My
purpose here is simply to remark that the amphibians have their
hind legs set on in the same direction as the axis of their body, for the
simple reason that these animals are compelled to use them habitually
as a caudal fin by uniting them and by separating the digits so as to
form a large paddle. With this artificial fin they are then able to
strike the water either to the right or left, and thus move rapidly in
various directions.

The two hind legs of seals are so often united and used as a fin that
they would not simply have this backward direction in continuance
of the body but would be permanently united as in the walruses,
were it not for the fact that the animals in question also use them very
frequently for seizing and carrying off their prey. Now the special
movements required by these actions prevents the hind legs of seals
from becoming permanently united, and only allow them to be joined
together momentarily.

Walruses, on the contrary, which are accustomed to feeding on grass,
which they come and browse on the shore, only use their hind legs
as a caudal fin; so that in most of them these legs are permanently
united with one another and with the tail, and cannot be separated.

We find here a new proof of the power of habit over the form and
state of the organs, a proof that I may add to all those already set
forth in Chapter VII.

I might add still another very striking proof drawn from mammals.
The faculty of flight would seem to be quite foreign to them; yet I
can show how nature has gradually produced extensions of the animal’s

ADDITIONS 175

skin, starting from those animals which can simply make very long
jumps and leading up to those which fly perfectly ; so that ultimately
they possess the same faculty of flight as birds, though without having
any affinities with them in their organisation.

Flying squirrels (Sciwrus volans, aerobates, petaurista, sagitta, volu-
cella) have more recently acquired this habit of extending their wings
when leaping, so as to convert their body into a kind of parachute; they
can do no more than make a very long jump by throwing themselves
to the bottom of a tree, or leaping from one tree on to another at a
moderate distance. Now by frequent repetition of such leaps in the
individuals of these races, the skin of their flanks is dilated on each
side into a loose membrane, which unites the hind-legs to the fore-
legs and embraces a large volume of air; thus saving them from a
sudden fall. These animals still have no membranes between the
digits.

The galeopithecus (Lemur volans) doubtless acquired this habit
earlier than the flying squirrels (Pteromis, Geoftir.) ; the skin of their
flanks is still larger and more developed ; it unites not only the hind-
legs with the fore-legs but also the tail with the hind-legs and the
digits with each other. Now these creatures make longer leaps than
the preceding, and even perform a sort of flight.

Lastly, the various bats are mammals which probably acquired
still earlier than the galeopithecus the habit of extending their limbs
and even their digits to embrace a great volume of air, and sustain
themselves when they launch forth into the atmosphere.

From these habits, so long acquired and preserved, bats have derived
not only lateral membranes but also an extraordinary lengthening of
the digits of their four legs (except the thumb) which are united by
very large membranes ; so that these membranes of the hands, being
continuous with those of the flanks and those which unite the tail to
the two hind-legs, constitute in these animals great membranous wings
with which they fly perfectly as we all know.

Such then is the power of habit: it has a remarkable influence on
the shape of the parts and endows animals, which have long contracted
certain habits, with faculties not possessed by those which have
adopted different habits.

With regard to the amphibians, of which I spoke above, I should
like here to communicate to my readers the following reflections that
have been raised in me and ever more strongly confirmed by all the
subjects I have dealt with in my studies.

I do not doubt that mammals originally came from the water, nor
that water is the true cradle of the entire animal kingdom.

We still see, in fact, that the least perfect animals, and they are the

176 ZOOLOGICAL PHILOSOPHY

most numerous, live only in the water, as I shall hereafter mention
(p. 246); that it is exclusively in water or very moist places that
nature achieved and still achieves in favourable conditions those direct
or spontaneous generations which bring into existence the most simply
organised animalcules, whence all other animals have sprung in turn.

We know that the infusorians, polyps, and radiarians live exclusively
in the water; and that some worms even live in it while the rest dwell
only in very moist places.

Now the worms appear to form one initial branch of the animal
scale, and it is clear that the infusorians form the other branch. We
may suppose therefore that such worms as are completely aquatic
and do not live in the bodies of other animals, Gordius, for instance, and
many others that we are not yet acquainted with, have doubtless
become greatly diversified in the water ; and that among these aquatic
worms, those which afterwards became accustomed to exposure to
the air have probably produced the amphibian insects such as gnats,
mayflies, etc., etc., while these in turn have given existence to all the
insects which live altogether in the air. Several races of these again
have changed their habits as a result of their environment and con-
tracted a new habit of living hidden away in solitude: hence the origin
of the arachnids, nearly all of which live also in the air.

Finally, those arachnids that frequented water, and gradually became
accustomed to live in it until at last they altogether ceased to live
in the air, led to the existence of all the crustaceans ; this is clearly
indicated by the affinities which connect the centipedes with the
millipedes, the milipedes with the woodlice, and these again with
Asellus, shrimps, etc.

The other aquatic worms, which are never exposed to the air,
would have developed in course of time into many different races with
a corresponding advance in the complexity of their organisation. They
would thus have led to the formation of the annelids, cirrhipedes and
molluscs, which form together an unbroken portion of the animal
scale.

There seems to us to be a great hiatus between the known molluscs
and the fishes; yet the molluscs whose origin I have just named
have led to the existence of the fishes through the medium of other
molluscs that have yet to be discovered, and it is manifest that the
fishes again have given rise to the reptiles.

As we continue to examine the probable origin of the various animals,
we cannot doubt that the reptiles, by means of two distinct branches,
caused by the environment, have given rise, on the one hand, to the
formation of birds and, on the other hand, to the amphibian mammals,
which have in their turn given rise to all the other mammals.

ADDITIONS 177

After the fishes had led up to the formation of the batrachian
reptiles and these to the ophidian reptiles, both of which have only one
auricle in their hearts, nature easily succeeded in giving a heart with a
double auricle to the other reptiles, which became divided into two sepa- -
rate branches; subsequently she easily achieved the formation of a heart
with two ventricles in animals originating from both these branches.

Thus among the reptiles which have a heart with a double auricle,
the chelonians appear to have given existence to the birds; for, in
addition to their various unmistakable affinities, if I were to place
the head of a tortoise on the neck of certain birds, I should find hardly
any incongruity in the general appearance of the factitious animals ; in
the same way the saurians, especially the planicauds, such as croco-
diles, seem to have led to the existence of the amphibian mammals.

If the chelonian branch has given rise to the birds, we may suppose
that the aquatic palmipeds, and especially the brevipens, such as the
penguins and king-penguins, have brought about the formation of the
monotremes.

Lastly, if the saurian branch gave rise to the amphibian mammals,
it is highly probable that from this branch all the mammals have
taken their origin.

I think the belief is justifiable, that the terrestrial mammals originated
from those aquatic mammals that we call amphibians. These were
divided into three branches by reason of the diversity arising in their
habits in the course of time; one of these led to the cetaceans, another
to the ungulate mammals, and the third to the various known un-
guiculate mammals.

Those amphibians indeed which preserved the habit of going on to
the beach became divided, owing to their different manner of feeding.
Some of them, being accustomed to browsing on grass, as for instance
the walruses and manatees, gradually led to the formation of the
ungulate mammals such as the pachyderms, ruminants, etc. ; the others
as, for instance, the seals, having acquired the habit of feeding ex-
clusively on fishes and marine animals, brought about the existence
of the unguiculate mammals through the medium of races which
as they diversified became altogether terrestrial.

Those aquatic mammals, however, which acquired the habit of
never coming out of the water and of only coming to the surface to
breathe, probably gave rise to the various cetaceans with which we
are acquainted, The cetaceans have been greatly modified in organisa-
tion by having dwelt for so long a period exclusively in the sea ; hence
it is now very difficult to recognise whence they derive their origin.

In consequence of the immense lapse of time during which these

animals have lived in the sea without ever using their hind-legs for
M

178 ZOOLOGICAL PHILOSOPHY

grasping objects, these unused legs have entirely disappeared, in-
cluding their bones, and even the pelvis which served for their support
and attachment.

The degeneration in the limbs of cetaceans under the influence of
the environment and acquired habit is also seen in their fore-feet,
which are entirely invested by skin so as not even to show the digits
at the end of them; they thus consist of one fin on each side contain-
ing the skeleton of a concealed hand.

Seeing that the cetaceans are mammals, it is assuredly a part of
their plan of organisation to have four limbs like all the rest, and
consequently a pelvis for the support of their hind-legs. But, here as
elsewhere, the loss of these parts is the result of an abortion due to a
long disuse of them. When we remember that in seals which still
have a pelvis, this pelvis is impoverished, reduced and does not pro-
trude from their haunches, we shall feel that the cause must be the
moderate use which these animals make of their hind-legs, and that,
if they were to give up using them altogether, the hind-legs and even
the pelvis would ultimately disappear.

The arguments which I have just adduced will doubtless seem to be
mere guesses, since it is not possible to establish them on direct
positive proofs. If we pay attention, however, to the observations
set forth in the present work, and if we then closely examine the
animals which I have cited and also the effects of their habits and
environment, we shall find as a result of this examination that these
guesses acquire a high degree of probability.

The table on p. 179 may facilitate the understanding of what I
have said. It is there shown that in my opinion the animal scale
begins by at least two separate branches, and that as it proceeds it
appears to terminate in several twigs in certain places.

This series of animals begins with two branches, where the most
imperfect animals are found; the first animals therefore of each of
these branches derive existence only through direct or spontaneous
generation.

There is one strong reason that prevents us from recognising the
successive changes by which known animals have been diversified
and been brought to the condition in which we observe them ; it is
this, that we can never witness these changes. Since we see only the
finished work and never see it in course of execution, we are naturally
prone to believe that things have always been as we see them rather
than that they have gradually developed.

Throughout the changes which nature is incessantly producing in
every part without exception, she still remains always the same in her
totality and her laws; such changes as do not need a period much

ADDITIONS 179

TABLE
SHOWING THE ORIGIN OF THE VARIOUS ANIMALS.

Worms. Infusorians,
Polyps.
Radiarians,

ad Insects.
er Arachnids.

Rinciiie. Crustaceans.

Cirrhipedes.

Molluscs.
Fishes.
Reptiles.

Birds.
Monotremes.
Amphibian Mammals.

a

Cetacean Mammals.
Ungulate Mammals.

Unguiculate Mammals.

180 ZOOLOGICAL PHILOSOPHY

longer than the duration of human life are easily recognised by an
observer, but he could not perceive any of those whose occurrence
consumes a long period of time.

To explain what I mean let me make the following supposition.

If the duration of human life only extended to one second, and if
one of our ordinary clocks were wound up and set going, any individual
of our species who looked at the hour hand of this clock would detect
in it no movement in the course of his life, although the hand is not
really stationary. The observations of thirty generations would
furnish no clear evidence of a displacement of the hand, for it would
only have moved through the distance traversed in half a minute and
this would be too small to be clearly perceived; and if still older
observations showed that the hand had really changed its position,
those who heard this proposition enunciated would not believe it,
but would imagime some mistake, since they had always seen the hand
at the same point of the dial.

I leave my readers to apply this analogy to the subject in hand.

Nature—that immense assemblage of various existences and bodies,
in all whose parts continually proceeds an eternal cycle of movements
and changes controlled by laws—an assemblage that is only immutable
so long as it pleases her Sublime Author to continue her existence—
should be regarded as a whole made up of parts, with a purpose that
is known to its Author alone, but at any rate not for the sole benefit
of any single part.

Since each part must necessarily change and cease to exist to make
way for the formation of another, each part has an interest which is
contrary to that of the whole; and if it reasons, it finds that the whole
is badly made. In reality, however, this whole is perfect, and com-
pletely fulfils the purpose for which it is destined.

PART II.

AN ENQUIRY INTO THE PHYSICAL CAUSES OF LIFE, THE
CONDITIONS REQUIRED FOR ITS EXISTENCE, THE
EXCITING FORCE OF ITS MOVEMENTS, THE FACULTIES
WHICH IT CONFERS ON BODIES POSSESSING IT, AND
THE RESULTS OF ITS PRESENCE IN THOSE BODIES.

INTRODUCTION.

Natore, that word so often spoken as though it referred to a special
entity, cannot be for us more than the totality of objects comprising :
(1) all existing physical bodies; (2) the general and special laws,
which regulate the changes of state and position to which these bodies
are hable ; (3) lastly, the movement distributed at large among them,
which is continually preserved or being renewed, has infinitely varied
effects, and gives rise to that wonderful order of things which this
totality embodies.

All physical bodies whatever—solid, fluid, liquid or gaseous—are
endowed with properties and faculties peculiar to themselves; butasa
result of the movement distributed among them, these bodies are liable
to different relations and transformations in their state and position.
They are liable to contract with one another various kinds of union,
combination or aggregation, and then to undergo all kinds of altera-
tions, such as complete or incomplete separation from their other
components or from their aggregates, etc.; these bodies thus derive
new properties and faculties from the condition in which each of them
is placed.

As a further result of the arrangement or position of these same
bodies, of their special condition at any period of time, of the faculties
possessed by each, of the laws of all the orders which regulate their
changes and effects, and, lastly, of the movement which never leaves
them in absolute rest, there continually reigns throughout the whole
of nature a mighty activity, a succession of movements and trans-
formations of all kinds, which nothing could arrest or annihilate,
unless it be the power which has made all things exist.

The idea of nature as eternal, and hence as having existed for all
time, is for me an abstract opinion without foundation, finality or
probability, and with which my reason could never be satisfied. Since
I can have no positive knowledge on this subject, and no power of
reasoning about it, I prefer to think that the whole of nature is only
an effect: hence, I imagine and like to believe in a First Cause or, in

184 ZOOLOGICAL PHILOSOPHY

short, a Supreme Power which brought nature into existence and
made it such as it is.

As naturalist and physicist, however, I am only concerned in my
studies of nature with the bodies that we know or that have been
observed, with the qualities and properties of these bodies, with the
relations that they may have to one another under different condi-
tions, and finally, with the effects of these relations and of the diverse
movements which are distributed and ever preserved among them.

This method, which is the only one open to us, makes it possible
to obtain a glimpse of the causes of those multitudinous phenomena
which nature exhibits in her various parts, and to arrive at an under-
standing of the causes of the wonderful phenomena presented by living
bodies, in short, the causes of life.

It is no doubt a very ee matter to enquire into the nature
necessary for its ex existence ; whet i is the origin of that remarkable force
which gives rise to vital movements so long as the state of organisation
allows ; lastly, how the various phenomena resulting from the con-
tinued presence of life in a body may achieve their result and endow
this body with the faculties observed in it; but of all the problems
which man can suggest these are beyond question the most difficult to
solve.

It seems to me that it was much easier to determine the course of
the stars observed in space, and to ascertain the distance, magnitudes,
masses and movements of the planets belonging to our solar system,
than to solve the problem of the origin of life in the bodies possessing
it, and, consequently, of the origin and production of the various
existing living bodies.

“However difficult may be this great enquiry, the difficulties are not
insuperable ; for in all this we have to deal only with purely physical
phenomena. Now it is obvious that the phenomena in question are,
on the one hand, only direct effects of the mutual relations of different
bodies, and only the result of an order and state of things which give
rise to these relations among some of them ; and, on the other hand, it
is obvious that these phenomena result from movements set up in the
parts of these bodies by a force whose origin it is possible to ascertain.

These early results of our enquiries are unquestionably of very great:
interest, and give us a hope of obtaining other results no less important.
But however well founded they may be, it will perhaps yet still be long
before they obtain the attention which they deserve ; because they have
to contend with one of the most ancient preconceptions, they have to
destroy inveterate prejudices, and present a new field of study very
different from any that we are accustomed to.

INTRODUCTION 185

It is apparently reflections of this kind which caused Condillac to
say that “reason has very little force and makes very slow progress,
when it has to destroy errors from which no one is exempt” (Traité
des Sensations, vol. 1., p. 1108).

M. Cabanis unquestionably established a very great truth by a
series of unexceptionable facts, when he said that the moral and the
physical both spring from a common origin; and when he showed that
the operations called moral are directly due, like those called physical, to
the activity either of certain special organs, or of the living system as a
whole ; and, finally, that all the phenomena of intelligence and will take
their origin from the congenital or fortuitous state of the organisation.

But in order to see more clearly how firmly this great truth is based,
we must not confine ourselves to seeking the proofs of it by an examin-
ation of the highly complicated organisation of man and the more
perfect animals; proof will be obtained still more easily by studying
the diverse progress in complexity of organisation from the most
imperfect animals up to those whose organisation is the most complex ;
for this progress will then exhibit in turn the origin of every animal
faculty and the causes and developments of these faculties. We
shall then acquire a renewed conviction that those two great branches
of our existence called the physical and the moral, which exhibit two
orders of phenomena apparently so distinct, have a common basis in
organisation.

This being so, it is in the simplest of all organisations that we should
open our inquiry as to what life actually consists of, what are the
conditions necessary for its existence, and from what source it derives
the special force which stimulates the movements called vital.

As a matter of fact it is only by a study of the simplest organisa-
tions that we can attain a knowledge of the true conditions for the
existence of life in a body ; for in a complex organisation all the principal
internal organs are necessary for the maintenance of life on account
of their close connection with other parts of the system, and because
the system itself is formed on a plan which requires these organs ;
but it does not follow that these same organs are essential to the
existence of life in all living bodies whatsoever.

This is very important to remember when we are enquiring what
are the real conditions for the constitution of life ; otherwise we might
thoughtlessly attribute to some special organ an existence that is
indispensable for the manifestations of life.

The peculiarity of vital movements is to be started and maintained
by stimulus and not by transmission. These movements are the only
ones of this character in nature, except perhaps for those of fermenta-
tion; they differ however from the movements of fermentation in

186 ZOOLOGICAL PHILOSOPHY

that they can be maintained almost unchanged for a limited period,
and in that they lead to a growth subsequently maintained for some
time of the body in which they work, whereas those of fermentation
irreparably destroy the body subjected to it and increase up to the
limit that annihilates them.

Since vital movements are never transmitted but always stimulated,
we must enquire what is their exciting cause, that is to say, from what
source living bodies derive the peculiar force which animates them.

Whatever may be the state of organisation of a body and of its
essential fluids, active life could assuredly not exist in that body
without a special cause capable of exciting its vital movements. What-
ever hypothesis we may form in this matter, we are always obliged to
recognise that some special cause must be present for the active mani-
festations of life. Now it can no longer be doubted that this cause
which animates living bodies is to be found in the environment of those
bodies, and thus varies in intensity according to places, seasons, and
climates. It is in no way dependent on the bodies which it animates,
it exists before they do and remains after they have been destroyed.
Lastly, it stimulates in them the movements of life, so long as the state
of these bodies allows ; and it ceases to animate them when that state
opposes obstacles to the performance of the movements which it
stimulates.

In the most perfect animals this exciting cause of life is developed
within themselves, and suffices to animate them up to a certain point ;
but it still needs the co-operation of that provided by the environment.
In the other animals, and in all plants it is altogether external to them ;
so that they can only obtain it from their environment.

When these interesting facts have been ascertained and settled,
we shall enquire how the first outlines of organisation come to be
formed, how spontaneous generation can have occurred and in what
part of the two series of living bodies.

If, indeed, bodies which possess life are really productions of nature,
she must have had and still have the faculty of producing some of them
spontaneously. She must then have endowed them with the faculty
of growth, multiplication and increasing complexity of organisation
and the power of varying according to time and circumstances. She
must have done this if all those that we now observe are really the
products of her power and efforts.

After recognising the necessity for these acts of direct creation,
we must enquire which are the living bodies that nature may produce
spontaneously, and distinguish them from those which only derive
their existence indirectly from her. Assuredly the lion, eagle, butter-
fly, oak, rose, do not derive their existence immediately from nature ;

INTRODUCTION 187

they derive it as we know from individuals like themselves who
transmit it to them by means of reproduction ; and we may be sure
that if the entire species of the lion or oak chanced to be destroyed
in those parts of the earth where they are now distributed, it

would be long before the combined powers of nature could restore
them.

I propose then to show what is the method apparently used by nature oe

for forming, in favourable places and conditions, the most simply
organised living bodies and through them the most perfect animals ;
how these fragile animals, which are the mere rudiments of animality
directly produced by nature, have developed, multiplied and become
varied; how at length, after an infinite series of generations, the
organisation of these bodies has advanced in complexity and has
extended ever more widely the animal faculties of the numerous
resulting races. |

We shall find that every advance made in complexity of organisation
and in the faculties. arising from it-has been _ preserved and transmitted
to other individuals by means of reproduction, and that by this pro-

cedure maintained for very many centuries nature has succeeded |

in forming successively all the living bodies that exist.

We shall see, moreover, that all the faculties without exception are |
purely physical, that is, that each of them is essentially due to activities

of the organisation ; so that it will be easy to show how, from the
humblest instinct, the origin of which can be easily ascertained,
nature has attained to the creation of the intellectual faculties from
the most primitive to the most highly developed.

My readers must not expect to find here a treatise on physiology :

the public is already in possession of excellent works of this character.

in which I have few alterations to suggest; but I must marshal
together the general facts and well-established fundamental truths on
this subject, because I find that their association leads to new light
which has escaped those who have occupied themselves with details,
and because this light clearly shows us what the bodies endowed with
life really are, why and how they exist, and in what manner they develop
and reproduce ; lastly, by what methods the faculties observed in them
have arisen, and been transmitted and retained in the individuals of
each species.

If we wish to grasp the chain of physical causation which brought
living bodies into existence, we must pay attention to the principle
which I embody in the following proposition :

It is to the influence of the movements of various fluids in the more
or less solid substances of our earth that we must attribute the forma-
tion, temporary preservation, and reproduction of all living bodies

188 ZOOLOGICAL PHILOSOPHY

observed on its surface, and of all the transformations incessantly
undergone by the remains of these bodies.

If we neglect this important principle, we become involved in an
inextricable confusion, and the general cause of observed facts and
objects cannot be perceived; our knowledge of this subject then
remains without value, coherence or progress, so that instead of com-
prehensible truths we shall continue to set up those phantoms of our
imagination and that love of the marvellous, in which the human
mind takes so much delight.

Tf, on the other hand, we pay to this proposition all the attention to
which its importance entitles it, we shall then see that there naturally
flow from it a number of subordinate laws which furnish an explanation
of all the well-known facts concerning existence, nature, and the various
faculties ; and, lastly, concerning the transformations of living bodies,
and the other more or less complex bodies that exist.

As to the constant but variable movements of the fluids that I am
about to discuss, it seems quite clear that they are permanently main-
tained on our earth by the influence of the sunlight. Sunlight is
incessantly causing modifications and displacements of great masses
of these fluids in certain regions of the earth, and forcing them to
undergo a kind of circulation and various sorts of movements, so
that they are able to produce all the observed phenomena.

To establish the accuracy of this statement, I shall merely have to
introduce order into my citation of the facts and their relations, and
into the application of these principles to observed phenomena.

In the first place it is necessary to distinguish the visible fluids,
which are contained in living bodies and there undergo constant
change and movement, from certain other subtle fluids which are always
invisible but which animate these bodies and are indispensable to the
existence of life.

Next, when considering the effects of the activity of the invisible
fluids, to which I refer, on the solid, fluid and visible parts of living
bodies, we shall easily discern that the organisation of these different
bodies and all their movements and modifications are entirely due
to the movements of the various fluids occurring in these bodies ;
that the fluids in question have by their movements organised these
bodies, modified them in various ways and modified themselves also,
so as gradually to have produced the state of things now observed.

In short, if we give sustained attention to the various phenomena
presented by organisation, and especially to those concerned with the
development of that organisation mainly in the most imperfect
animals, we shall reach the following convictions :

1. That the entire work of nature in her spontaneous creations

INTRODUCTION 189

consists in organising into cellular tissue the little masses of gelatinous
or mucilaginous material which she finds at hand under favourable
circumstances ; in filling these little cellular masses with fluids and in
vivifying them, by setting these contained fluids in motion by means
of the stimulating subtle fluids which are incessantly flowing in from
the environment ;

2. That cellular tissue is the framework in which all organisation
has been built, and in the midst of which the various organs have
successively developed by means of the movement of the contained
fluids which gradually modifies the cellular tissue ;

3. That the function of the movement of the fluids in the supple
parts of the living bodies which contain them, is to cut out paths and
establish depots and exits, to create canals and afterwards various
organs ; to cause variation in these canals and organs by means of a
diversity either in the movements or in the nature of the fluids which
produce and modify them ; finally to enlarge, elongate, divide and
solidify gradually these canals and organs by substances which are
formed and incessantly separated off from the essential fluids in move-
ment there; substances of which one part becomes assimilated and
united with the organs while the other is thrown out ;

4, That, lastly, the function of organic movement is not merely
the development of organisation, and the increase and growth of the
parts, but also the se of organs: and of the function which

_they fulfil. __ [ae

After having expounded these great principles which seem to me
unquestionable truths although not hitherto recognised, I shall enquire
what faculties are common to all living bodies and consequently to
all animals ; I shall then pass in review the chief of the faculties which
are peculiar to certain animals but are not possessed by the rest.

I vénture to affirm that grave injury results to the progress of
physiological knowledge by the thoughtless supposition that all
animals without exception possess the same organs and enjoy the
same faculties; as though nature were everywhere forced to employ
the same methods to attain her end. Seeing that nothing more than
an active imagination is needed for setting up principles if we do
not pause to consider facts, it is an easy supposition that all living
bodies possess the same organs and hence enjoy the same faculties.

Another subject which I must not neglect in this second part of my
work is the question of the immediate results of life in a body. Now
I am in a position to show that these results give rise to combinations
between principles which, except for this factor, would never have been
united together. These combinations accumulate more and more
according as the vital energy increases, so that in the most perfect

190 ZOOLOGICAL PHILOSOPHY

animals there is a high complexity and great intricacy in the combina-
tion of principles. Living bodies thus constitute, by their possession
of life, nature’s principal means for bringing into existence a number
of different compounds which would never otherwise have arisen,

It is vain to imagine that living bodies find ready formed in the
substances on which they feed all the material required for building
up the various parts of their bodies; they only find in these food
substances, materials suitable for entering into the combinations
which I have mentioned, and not the combinations themselves.

It is no doubt owing to an insufficient study of the power of life in
the bodies which possess it, and the failure to perceive the results
of this power, that it has been alleged that living bodies find in their
ordinary food the material ready prepared which serves for building
up their bodies and that these materials have existed in nature for all
time.

Such are the subjects which compose the second part of this work :
their importance would no doubt justify considerable expansion ;
but I have confined myself to a concise exposition of what is necessary
in order that my observations may be understood.

CHAPTER I.

COMPARISON OF INORGANIC BODIES WITH LIVING BODIES, FOL-
LOWED BY A PARALLEL BETWEEN ANIMALS AND PLANTS.

I Lone ago conceived the idea of making a comparison between
organised living bodies and crude inorganic bodies. I then noticed
the extreme difference existing between these two, and I became
convinced of the necessity for examining the kind and amount of this
difference. It was at that time the general custom to present the
three kingdoms of nature arranged in a line, with class distinctions
between them; and the enormous difference apparently was not
perceived between a living body and a crude lifeless body.

Yet if we wish to arrive at a real knowledge of what constitutes
life, what it consists of, what are the causes and laws which control
so wonderful a natural phenomenon, and how life itself can originate
those numerous and astonishing phenomena exhibited by living bodies,
we must above all pay very close attention to the differences existing
between inorganic and living bodies ; and for this purpose a comparison
must be made between the essential characters of these two kinds of
bodies.

COMPARISON BETWEEN THE CHARACTERS OF INORGANIC BoDIES
AND THOSE oF Livine Boptrss.

1. No crude or inorganic body possesses individuality except in its
integral molecule; the solid, fluid or gaseous masses that may be formed
by a collection of integral molecules have no limits; and the large or
small size of these masses neither adds nor subtracts anything that
can alter the nature of the body concerned; for this nature is ex-
clusively dependent on that of the integral molecule of the body.

Every living body, on the other hand, possesses an individuality
throughout its mass and volume; and this individuality, simple in
some and compound in others, is never confined in living bodies to that
of their component molecules.

192 ZOOLOGICAL PHILOSOPHY

2. An inorganic body may present a truly homogeneous mass or it
may constitute a heterogeneous mass ; the aggregation or combination
of similar or dissimilar parts can occur without these bodies ceasing to
be crude or inorganic. In this respect there is no essential necessity
for the masses of this body to be more homogeneous than hetero-
geneous or vice versd; it is by chance that they are as we observe
them.

All living bodies, on the contrary, even those with the simplest organi-
sations, are necessarily heterogeneous, that is to say, composed of dis-
similar parts: they have no integral molecules, but are formed from
molecules of a different character.

3. An inorganic body may constitute either a perfectly dry, solid
mass or a completely liquid mass or a gaseous fluid.

The contrary holds good in the case of all living bodies; for no
body can possess life unless it is formed from two kinds of necessarily
co-existing parts, the one solid, but supple and capable of holding
liquids ; the other liquid and contained in the first, but quite inde-
pendent of the invisible fluids which penetrate the body and develop
within it.

The masses which constitute inorganic bodies have no special specific
shape; for whether these masses have a regular shape, as in the case
of crystals, or whether they are irregular, their shape does not remain
permanently the same; it is only the integral molecule which has in

‘each kind an invariable shape.+

Living bodies, on the contrary, nearly all exhibit a shape peculiar
to their species and one which cannot vary without giving rise to a
new race.

4. The integral molecules of an inorganic body are entirely inde-
pendent of one another; for even when they are combined into a
solid, liquid or gaseous mass, each of them continues to exist by itself
and to be constituted by the number, proportions, and character of
combination of its principles; its existence is neither conditioned
nor increased by the similar or dissimilar molecules in its neighbour-
hood.

The molecules of a living body, on the other hand, and consequently
all the parts of that body, are dependent for their character upon one
another; because they are all subjected to the influence of a factor

1The integral molecules which constitute a compound substance all result from
combinations of the same number of principles in the same proportions, with exactly
the same character of combination: hence they all have the same shape, density
and special properties.

But when any causes have produced a variation either in the number of the com-
ponent principles of these molecules, or in the proportions of the principles, or in

the character of their combination, these integral molecules then acquire another
shape, density and special properties: they then belong to another species.

INORGANIC AND LIVING BODIES 193

which animates them and gives them activity, and because this factor
requires their co-operation for a common end both in the separate
organs and in the entire individual ; because, moreover, the variations
in this same factor work similar effects in the state of each molecule
and each part.

5. No inorganic body needs any movement in its parts for its
preservation ; on the contrary, so long as the parts remain at rest
the body is preserved without disintegration and might exist in this
condition for ever. But as soon as any factor begins to act upon this
body and produce movements and changes in its parts, the body at
once loses either its shape or its coherence, if the movement and changes
produced in its parts merely affect its mass or some part of its mass ;
and it loses even its fundamental character or is destroyed, if the
movements and changes in question penetrate as far as its integral
molecules.

Every body possessing life, on the other hand, is permanently or
temporarily animated by a special force, which incessantly stimulates
movements in its internal parts and uninterruptedly produces changes
of state in these parts, at the same time effecting restorations, re-
newals, developments and a number of phenomena that are entirely
peculiar to living bodies; so that in their case the movements stimu-
lated within them produce disintegration and destruction followed by
recuperation and renewal. This prolongs the life of the individual
so long as the equilibrium between these two opposed elements is not
too rudely disturbed.

6. In all organic bodies an increase of volume and mass is always
accidental and has no necessary limits. This increase only takes
place by juxtaposition, that is to say, by the addition of new parts to
the external surface of the body in question.

The growth of every living body, on the contrary, is always necessary
and limited, and only takes place by intussusception, that is to say, by
internal penetration, or the introduction into the individual of sub-
stances which have to be added to it and make part of it after being
assimilated. Now this growth is a true development of parts from
within outwards, and is exclusively the property of living bodies.

7. No inorganic body has to feed in order to be preserved; for
it need never lose any of its parts, and when it does it has no means of
restoring them.

All living bodies, on the contrary, necessarily experience in their
internal parts successive and constantly renewed movements, changes
in the state of the parts, and, lastly, continual losses of substance
through the separations and dissipations involved by these changes.

Hence no such body can maintain life if it is not constantly feeding,
N

194 ZOOLOGICAL PHILOSOPHY

that is to say, if it is not incessantly making good its losses by sub-
stances introduced into its interior, in short, if it does not take food
whenever it needs it.

8. The masses of inorganic bodies consist of separate parts which
are united by accident ; these bodies are not born, nor are they ever
the produce of a germ or bud whose development gives rise to an
individual exactly similar to that from which it springs.

All living bodies, on the contrary, are really born, and are the pro-
duce either of a germ which has been vivified and prepared for life by
fertilisation, or else simply of anexpansible bud. In either of these cases
new individuals arise exactly like those which have produced them.

9. Lastly, no inorganic body can die, inasmuch as no such body
possesses life. Death is a necessary result of the existence of life in
a body, for it is only the complete cessation of organic movements,
following upon some disturbance which makes these movements hence-
forth impossible.

All living bodies, on the contrary, are subject to an inevitable death ;
for it is a property of life or of the movements constituting life in a
body, to bring about after a certain period a condition of the organs
which makes it impossible for them to carry on their functions,
and which therefore destroys the faculty of performing organic
movements.

Hence between crude or inorganic bodies and living bodies there
exists an immense difference, a great hiatus, in short, a radical dis-
tinction such that no inorganic body whatever can even be approached
by the simplest of living bodies. Life and its constituents in a body
make the fundamental difference that distinguishes this body from all
those that are without it.

How great then is the error of those who try to find a connection
or sort of gradation between certain living bodies and inorganic bodies !

Although M. Richerand in his interesting Physiologie has dealt
with the same subject that I am now treating, I have had to reproduce
his views together with modifications of my own; since his studies
are very important on the subjects which I still have to set forth.

A comparison between plants and animals does not immediately
concern my thesis in this Part IT. ; nevertheless, as such a comparison
assists in the general purpose of this work, I propose here to state a
few of its most prominent characteristics. But first let us see what
plants and animals actually have in common, in their capacity as
living bodies.

The only point in common between animals and plants is the pos-
session of life; hence they both fulfil the conditions of its existence,
and possess the general faculties to which it gives rise.

INORGANIC AND LIVING BODIES 195

Hence in both cases they are bodies composed essentially of two kinds
of parts, the one solid but supple and containing ; the other liquid and
contained, but independent of the invisible fluids which penetrate and
develop within them.

All these bodies possess individuality, either simple or compound ;
have a shape peculiar to their species; are born at the moment
when life begins to exist in them or when they are separated from
the body whence they spring; are permanently or temporarily ani-
mated by a special force which stimulates their vital movements ; are
only preserved through nutrition which more or less restores their
losses of substance ; grow for a limited period by internal development ;
form for themselves the compound substances of which they are made ;
reproduce and multiply so as to carry on the species like themselves ;
lastly, all reach a period when the state of their organisation no longer
permits of the maintenance of life within them.

Such are the faculties common to these two kinds of living bodies.
Let us now compare the general characters by which they are dis-
tinguished from each other.

CoMPARISON BETWEEN THE GENERAL CHARACTERS OF PLANTS
AND ANIMALS.

Plants are organised living bodies, not irritable in any of their parts,
incapable of performing sudden movements several times in succession,
and the vital movements of which are only performed by means of
external stimuli, that is to say, by an exciting cause provided by the
environment and acting chiefly on the contained and visible fluids
of these bodies.

In animals, some or all of the parts are essentially irritable, and have
the faculty of performing sudden movements which may be repeated
several times in succession. The vital movements are in some per-
formed by means of external stimuli, and in others by a force develop-
ing within them. The external stimuli and internal stimulating
force affect the irritability of the parts, act upon the visible contained
fluids and give rise in all cases to the performance of vital movements.

It is certain that no plant whatever has the faculty of suddenly
moving its external parts and repeating such movement several times
in succession. The only sudden movements that certain plants dis-
play are movements of relaxation or collapse of some part (v. p. 52) ;
hygrometric or pyrometric movements also are sometimes performed
by certain filaments when suddenly exposed to the air. As to the
other movements performed by the parts of plants, such as those
which make them bend towards the light, those which cause the
opening and closing of flowers, those which give rise to the erection

196 ZOOLOGICAL PHILOSOPHY

or depression of stamens or peduncles or to the twining of climbing
stems and tendrils, finally, those constituting what is called sleeping
and waking in plants; none of these movements are ever sudden ;
they are carried out so slowly as to be altogether imperceptible ;
and they are only known by their finished results.

Animals, on the contrary, possess the faculty of performing very
obvious sudden movements, by means of some of their external parts,
and of repeating them several times in succession with or without
variation,

Plants, especially those which live partly in the air, grow in a remark-
able manner in two opposite directions, in such a way as to exhibit
an ascending vegetation and a descending vegetation. These two kinds
of vegetation start from a common point which I have elsewhere +
named the vital knot, because in this point life is specially concentrated
when the plant loses its structures, and because the plant only really
dies when life ceases to exist in this part. The organisation of this
vital knot, otherwise known as the root-collar, is altogether peculiar ;
from the vital knot the ascending vegetation produces the stem,
branches and all the parts of the plant that are in the air; and from
the same point the descending vegetation gives birth to roots which
are buried in the soil or in water. Finally, in germination, which
brings the seeds into life, the early development of the young plant
requires ready prepared juices, which the plant cannot yet draw from
the soil or from the air; these juices then appear to be furnished by
the cotyledons, which are always attached to the vital knot; they
suffice for starting the ascending vegetation of the plumule and the
descending vegetation of the radicle.

Nothing of the kind is observed in animals. Their development
is not limited to two special directions only, but takes place on all
sides and in all directions, according to their requirements ; finally,
their life is never concentrated in an isolated point butis spread through-
out the essential special organs, if there are any. In animals in which
there are no essential special organs, life is not concentrated in any
one part; for when we divide their bodies life is preserved in each
separate part.

Plants in general rise perpendicularly, not to the plane of the earth
on al] occasions, but to that of the horizon ; so that according as they
grow they shoot upwards towards the sky like a sheaf of rockets in a
firework display. Although the twigs and branches which form their
tops do not follow the direction of the stem, they always form an
acute angle with the stem at their point of insertion. It appears
that the stimulating force of the vital movements in these bodies is

1 Histoire Naturelle des Végétaux, édition de Déterville, vol. i., p. 225.

ANIMALS AND PLANTS 197

chiefly directed upwards and downwards, and that this is the reason
of the peculiar shape and arrangement of these living bodies, in short,
of their ascending and descending vegetation. From this it follows
that the canals, in which move the essential fluids of these bodies,
are parallel to one another and to the longitudinal axis of the plant ; for
it is always parallel, longitudinal tubes that are formed in their cellular
tissue, and these tubes do not diverge except to form the flattened
expansions of leaves and petals, or to be distributed in the fruit.

Nothing of all this is found in animals. The longitudinal axis of
their bodies is not necessarily directed towards the sky, on the one
hand, and the centre of the earth, on the other hand ; the force which
stimulates their vital movements does not work exclusively in two
directions ; lastly, the internal canals which contain their visible
fluids are turned about in various ways and present no sort of
parallelism.

The food of plants consists only of the liquid or fluid substances
which they absorb from the environment: this food includes water,
atmospheric air, caloric, light, and various gases which they decom-
pose and convert to their own use; hence they never have to carry
on digestion, and for this reason they have no digestive organs. Seeing
that living bodies themselves elaborate their own substance, it is they
which form the first non-fluid combination.

Most animals, on the contrary, feed on substances which are already
compound and which they introduce into a tubular cavity suitable
to receive them. Hence they have a digestion in order to bring about
the complete solution of these substances; they modify existing
combinations and load them heavily with new principles; so that it
is they which form the most complex combinations.

Lastly, the final residue of destroyed plants is very different from
that which emanates from animals, showing that these two kinds of
living bodies are indeed of an entirely distinct nature.

In plants, as a matter of fact, solids exist in larger proportion than
fluids, mucilage constitutes their softest parts, and carbon predomi-
nates among their component principles; whereas in animals fluids
are more abundant than solids, gelatine abounds in their soft parts
and even in the bones of such as have any, while among their com-
ponents nitrogen is specially conspicuous.

Moreover, the strata formed out of the residue of plants is chiefly
argillaceous and often contains silica, whereas those formed from
animals consist either of the carbonate or phosphate of lime.

198 ZOOLOGICAL PHILOSOPHY

Some Features OF ANALOGY BETWEEN ANIMALS AND PLANTs.

Although the nature of plants is very different from that of animals,
and although the bodies of the one always possess faculties and even
substances that would vainly be sought in the other, the fact remains
that they are both living bodies and that nature obviously followed a
uniform plan of operations in producing them. In point of fact,
nothing is more remarkable than the analogy observed between
certain of her operations in these two kinds of living bodies.

In both of them, the most simply organised only reproduce by
gemmae or buds. These are reproductive corpuscles which are like
eggs or seeds, but require no preliminary fertilisation, and which
indeed contain no embryo which has to break through its invest-
ments before being able to complete its development. Yet in both
animals and plants, when the complexity of organisation was sufficiently
advanced to permit of the formation of organs of fertilisation, the
reproduction of individuals then became exclusively or chiefly sexual.

Another very remarkable feature of analogy, in the operations of
nature, between animals and plants, is the more or less complete
suspension of active life, that is to say, of vital movements, which is
experienced in certain climates and seasons by a large number of living
bodies of both kinds.

In the winter of cold climates, indeed, the woody perennial plants
undergo a more or less complete suspension of vegetation, and hence
of organic or vital movements; their fluids, which are at these periods
less abundant, remain inactive: during these conditions, there occur
in the plants no losses or absorptions of food or any alterations or
development; in short, their active life is altogether suspended,
their bodies become torpid and yet they are not lifeless. Since the
truly simple plants can only live for a year, they hurriedly produce
their seeds or reproductive corpuscles in cold climates and die on the
approach of the bad season.

The phenomena of the more or less complete suspension of active
life, that is, of the organic movements composing it, are also witnessed
in many animals in very curious forms.

In the winter of cold climates life comes to an end in the most
imperfect animals ; and among those which retain life, a great many
become more or less completely torpid, so that in some all the internal
or vital movements are suspended, while in others they still exist
but are only performed with extreme slowness. Thus although nearly
all the classes contain animals which undergo this more or less com-
plete suspension of active life, it is particularly noticeable in the
ants, bees, and many other insects; in the annelids, molluscs, fishes,

ANIMALS AND PLANTS 199

reptiles (especially snakes), and, lastly, in many mammals such as
the bat, marmot, dormouse, etc.

The last feature of analogy that I shall name is no less remarkable ;
it is this: just as there are simple animals constituting separate
individuals, and compound animals adhering together, communicating
at their base and sharing a common life such as most of the polyps,
so also there are simple plants living as individuals and there are com-
pound plants where several live together, are grafted on to one another
and share a common life.

The general rule among plants is to live until they have produced
flowers and fruit or reproductive corpuscles. Their lives rarely last
for more than a year. Their sexual organs, if they have any, are only
of use for a single fertilisation; so that when plants have reached
the goal of reproduction (seeds), they die and are completely
destroyed.

In the case of a simple plant, death takes place after the production
of fruit; and it is difficult, as we know, to propagate it otherwise than
by seeds or gemmae.

Annual or biennial plants all appear to be in this position; they
are simple plants; and their roots, stems and branches are simply
vegetative products ; it is by no means every plant however that is
in this position, for the greater number of those that are known are
in reality compound plants.

Thus, when I see a tree, shrub or perennial, it is not simple plants that
I have before me, but a multitude of plants living together upon one
another and all sharing a common life.

So true is this that if I were to graft the shoot of a cherry tree on
to the branch of a plum tree, and an apricot shoot on to another
branch of the same tree, these three species would live together and
share a common life while yet remaining distinct.

The roots, trunk, and branches of such a plant consist purely of the
vegetable products of this common life, and of separate but adherent
plants which live upon it ; just as the general substance of a madrepore
is the animal product of numerous polyps which live together through
successive generations. But every bud in a plant is itself an individual
plant, which shares in the common life of all the rest, develops its flower
or inflorescence once a year, then produces fruit and may finally give
rise to a branch already supplied with other buds, that is, other in-
dividual plants. Each of these individual plants either fruits, in which
case it does so only once, or produces a branch which gives rise to
other similar plants. Any such composite plant is thus a vegetable
product, which continues to live after the destruction of all the in-
dividuals which have combined to produce it.

200 ZOOLOGICAL PHILOSOPHY

By separating off parts of a plant, containing one or more buds or
including undeveloped elements, we can form at pleasure a number
of new living individuals similar to those from which they are taken,
without any necessity for taking the fruit. This in fact is just what
horticulturists do when they take slips, layers, etc.

Now just as nature has made compound plants, so too she has made
compound animals; and for this purpose she has made no change in
the nature of either animals or plants. It is quite as absurd to call
compound animals by the name of plant-animals, as it would be to
call compound plants by the name of animal-plants.1

If the name of zoophyte were given a century ago to compound
animals of the class of polyps, the error was excusable ; the low state
of knowledge then existing about animal nature made this term
less obnoxious; but now things have altered, and it cannot be a
matter of indifference that a class of animals should receive a name
which embodies a false notion of the objects indicated.

Let us now enquire what life is, and what are the conditions for its
existence in a body.

1 When we confine our attention to the substances produced by vegetation or
by animals, we often find cases where it is difficult to decide whether they belong to
the plant or animal kingdom ; chemical analysis of these bodies sometimes decides
in favour of animal substances when their shape and organisation are suggestive of
true plants. Several genera referred to the family of algae provide examples of
this difficulty : it would thus seem to follow that there is an almost imperceptible
transition from plants to animals.

I do not think so: on the contrary, I am thoroughly convinced that if it were
possible to examine the actual animals which form the membranous or filamentous
polyparies so closely resembling plants, the uncertainty as to their true nature would.
at once be removed.

CHAPTER IL

OF LIFE, WHAT IT CONSISTS OF, AND THE CONDITIONS
OF ITS EXISTENCE IN A BODY.

Lire, said M. Richerand, is a collection of phenomena which succeed
one another for a limited period in organised bodies.

He should have said, life is a phenomenon which gives rise to a
collection of other phenomena, etc. ; for it is not these other phenomena
that constitute life, but they are themselves caused by life.

A study of the phenomena resulting from the existence of life in a
body provides no definition of life, and shows nothing more than
objects that life itself has produced. The line of study which I am
about to follow has the advantage of being more exact, more direct
and better fitted to illuminate the important subject under considera-
tion ; it leads, moreover, to a knowledge of the true definition of life.

Life when studied in living bodies is exclusively due to the relations
existing between the three following objects: the parts of the body
adapted for containing liquids, the contained liquids moving in them,
and the exciting cause of such movements and changes as are carried
out. ,

Whatever efforts we may make by the most profound thought and
meditation to decide as to what life consists of, we shall necessarily
be compelled to fall back on the principle just enunciated as soon as
we pay attention to the teaching of observation on the matter; in
fact, life consists of nothing else.

A comparison drawn between life and a watch in active movement
is inadequate, to say the least of it; for in the watch there are only
two main points to consider: (1) the wheels and machinery of
movement; (2) the spring which by its tension and elasticity keeps
up the movement so long as that tension continues.

But in a living body, instead of two chief points for study, there are
three: (1) the organs or supple containing parts; (2) the essential
contained fluids which are always in motion; (3) lastly, the exciting

202 ZOOLOGICAL PHILOSOPHY

cause of vital movements, from which arises the action of the fluid
on the organs and the reaction of the organs on the fluids. It is then
purely from the relations between these three objects that the move-
ments, changes, and all the phenomena of life result.

In order to improve the comparison between a watch and a living
body we should have to compare the exciting cause of organic move-
ments with the spring of the watch, and regard the supple containing
parts, together with the essential contained fluids, as the machinery
of the movement in question.

It will then be clear, in the first place, that the spring (exciting cause),
is the essential motive power, without which the whole remains in-
active, and that its variations of tension must be the cause of the
variations of energy and rapidity of movements.

In the second place, it will be obvious that the machinery of move-
ment (the organs and essential fluids) must be in a state and arrange-
ment suitable for the performance of the movements which it has to
carry out ; hence, when this machinery gets out of order the effective
power of the spring is lost.

From this point of view the parallel is complete; a living body
may be compared with a watch; and I can easily show the close
accuracy of this comparison by reference to known facts and observa-
tions.

As to the machinery of movement, its existence and faculties are
now well known, as also most of the laws which control its various
functions.

But as to the spring, the essential motive power and originator
of all movements and activities, it has hitherto escaped the researches
of observers: I believe, however, that I shall be able to describe it in
the next chapter, in such a way that it cannot in future be neglected.

But first let us continue the enquiry as to what essentially con-
stitutes life.

Seeing that life in a body results exclusively from the relations
existing between the containing parts in an appropriate condition,
the contained fluids moving in them, and the exciting cause of the
movements, activities and reactions which take place, we may include
what essentially constitutes life in the following definition.

Life, in the parts of any body which possesses it, 1s an order and state
of things which permit of organic movements ; and these movements
constituting active life result from the action of a stimulating cause which
excites them.

This definition of life, either active or suspended, includes all the
positive facts which have to be expressed in it, and covers all special
cases. It appears to me impossible to add or subtract a single word

OF LIFE 203

without destroying the integrity of the essential ideas contained in it ;
lastly, it is based on the known facts and observations which have
reference to this wonderful natural phenomenon.

To begin with, in this definition active life is kept distinct from that
hfe which, without ceasing to exist, is suspended and appears to be
maintained for a limited time without perceptible organic movements ;
and this, as I shall show, is in accordance with observation.

Then it brings out the fact that no body can possess active life
except when the two following conditions are satisfied.

The first is the necessity for a stimulating cause which excites
organic movements.

The second is the necessity that a body in order to possess and main-
tain life should be so ordered in its parts as to possess the property
of responding to the action of the stimulating cause and of producing
organic movements.

In the animals whose essential fluids are quite simple, such as the
polyps and infusorians, if the contained fluids of any of these animals
are suddenly removed by a rapid desiccation, such desiccation may
be carried out without any disintegration of the organs or containing
parts of this animal or any destruction of the order existing in them :
in this case life is altogether suspended in the desiccated body; no
organic movement occurs in it and it appears no longer to be a
living body. Yet it cannot be called dead, for its organs or con-
taining parts have retained their integrity, and if the internal fluids
are restored to this body, the stimulating cause, assisted by a gentle
warmth, soon excites movements, activities, and reactions in its parts
and henceforth it returns to life.”

The rotifer of Spallanzani, which was several times reduced to a
state of death by rapid desiccation, and afterwards restored to life on
being plunged into tepid water, shows that hfe can be alternately
suspended and renewed: it is therefore only an order and state of
things in a body, by means of which vital movements can occur when
stimulated by a special cause.

In the plant kingdom, the algae and mosses exhibit the same pheno-
mena as the rotifer of Spallanzani; mosses rapidly desiccated and
kept in a herbarium even for a century may return to life and fresh
vegetation, if they are placed in moisture at a moderate temperature.

Complete suspension of vital movements without degeneration of
the parts, and hence with a continued possibility of a return of these
movements, may also occur in man himself, though only for a very
short time.

We learn from observations made on people that have been drowned,
that if anyone falls into the water and is pulled out again after an

204 ZOOLOGICAL PHILOSOPHY

immersion of three-quarters of an hour or even an hour, he is
asphyxiated to the extent that no movement whatever takes place
in his organs. Yet it may still be possible to restore him to active
life.

If he is left in this condition without any assistance, orgasm and
irritability soon become extinct in his internal parts, and thereafter
the essential fluids and the softest parts begin to decompose, and this
is the sign of death ; but if, immediately after his extraction from the
water and before the extinction of irritability, the usual aid is adminis-
tered to him, if, in short, it is possible by means of the usual stimulants
to excite in time contractions in his internal parts, and produce move-
ments in his organs of circulation, then all the vital movements quickly
resume their course, and active life no longer remains in suspense but
ig promptly restored.

But when degenerations and disorders of a living body, either in
the order or in the state of its parts, are large enough to prevent these
parts from yielding to the influence of the exciting cause and producing
organic movements, then life is quickly extinguished, and the body
henceforth is no longer included among the living.

From what I have just said, it follows that if in a body any disturb-
ance or degeneration affects the order and state of things which endow
it with active life, and if this disturbance is of a nature to prevent the
performance of organic movements or their restitution after suspension,
the body then loses its life, that is to say, it undergoes death.

A disorder resulting in death may be brought about in a living body
through various accidental causes ; but nature becomes the necessary
cause at the end of a certain period ; and, in fact, it is a property of life
to bring the organs imperceptibly to a condition in which they cannot
perform their functions, so that death inevitably ensues ; the reason
of this I shall explain.

When therefore we affirm that life, in all bodies which possess it,
consists only of an order and state of things in the parts of the body,
by which these parts are subject to the influence of a stimulating cause
and carry out organic movements, we are not expressing a mere con-
jecture but a fact universally attested, susceptible of many proofs and
never liable to be seriously disputed.

This being so, we are only concerned to know what is the order and
state of the parts which make a body capable of possessing active life.

But as no precise knowledge of this subject can be directly acquired,
let us first investigate the conditions essential to the existence of this
order and state of things in the parts of the body, in order that it may
possess life.

OF LIFE 205

—_—*

CONDITIONS ESSENTIAL TO THE EXISTENCE OF THE ORDER AND
STRUCTURE OF A Bopy IN ORDER THAT IT MAY PossEss LIFE.

First condition. No body can possess life unless it consists essentially
of two kinds of parts, viz. supple containing parts and contained
fluid substances.

As a matter of fact, no body that is perfectly dry can be alive,
nor can any body whose parts are fluid be in possession of life. The
first condition essential to life in a body therefore is that it should
consist of a mass with two kinds of parts, the one solid and containing,
but soft and more or less cohesive, the other fluid and contained.

Second condition. No body can possess life unless its containing »
parts are cellular tissue or formed out of cellular tissue.

Cellular tissue, as I shall show, is the matrix in which all the organs
of living bodies have been successively formed; and the movement of
fluids in this tissue is the means adopted by nature for the gradual
creation and development of these organs.

Every living body is thus essentially a mass of cellular tissue in which
more or less complex fluids move more or less rapidly ; so that if the
body is very simple, that is, has no special organs, it appears homo-
geneous and consists only of cellular tissue containing fluids which are
slowly moving ; but if its organisation is complex, all its organs with-
out exception are invested in cellular tissue down to their smallest
parts, and are even essentially formed of it.

Third condition. No body can possess active life except when an
exciting cause of its organic movements works within it. Without
the impulse of this active stimulus, the solid containing parts of an
organised body would be inert, the contained fluids would remain
at rest, organic movements would not take place, no vital function
would be carried out, and consequently active life would not exist. __

Now that we know the three conditions essential to the existence of
life in a body it becomes easier for us to ascertain wherein consist
the order and state of things necessary to a body for the maintenance
of life,

For this purpose, we must not limit our enquiries to living bodies
with a highly complex organisation ; for we should never learn from
them to what cause life is to be attributed, and we might select at
hazard factors of no fundamental importance.

But if we fix our attention on that extremity, either of the animal or
plant kingdom, in which are found living bodies with the simplest
organisations, we shall notice, in the first place, that in each individual
the body consists only of a gelatinous or mucilaginous mass of cellular
tissue of the feeblest coherence, the cells of which are in communication,

206 ZOOLOGICAL PHILOSOPHY

and the various fluids of which undergo movements, displacements,
dissipations, subsequent renewals, changes of state, and finally deposit
parts which become fixed there. We shall then observe that an
exciting cause of varying activity, but never entirely absent, in-
cessantly animates the very supple containing parts of these bodies,
as well as the essential fluids contained in them, and that this cause
keeps up all the movements constituting active life, so long as the parts
which have to acquire these movements are in a condition to do so.

INFERENCE.

The order of things necessary for the existence of life in a body is
then essentially as follows :

1. A cellular tissue (or organs formed of it) endowed with great
suppleness and animated by orgasm, the first result of the exciting
cause ;

2. Various more or less complex fluids contained in this cellular
tissue (or in the organs built up from it), and undergoing as a second
result of the exciting cause, movements, displacements, various
changes, etc.

In animals the exciting cause of organic movements acts powerfully
both on the containing parts and on the contained fluids; it maintains
an energetic orgasm in the containing parts, puts them in a condition
to react on the contained fluids and hence makes them highly irritable ;
as to the contained fluids, the exciting cause involves them in a kind of
rarefaction and expansion, which facilitate their various movements.

In plants, on the contrary, the exciting cause in question only acts
powerfully on the contained fluids, and produces in these fluids such
movements and alterations as they are adapted to undergo; but its
only effect on the containing parts of these living bodies, even on their
most supple parts, is an orgasm or slight erethism which is too feeble
to permit of any movement or to cause a reaction on the contained
fluids or consequently to endow these parts with irritability. The
result of this orgasm has been badly named latent sensibility ; I shall
speak of it in Chapter IV.

In animals, which invariably have parts that are irritable, the vital
movements are kept up in some solely by the irritability of the parts,
and in others by a combination of irritability with muscular activity
of the organs themselves.

In fact, in those animals whose very simple organisation only requires
slow movements in the contained fluids, the vital movements are carried
out exclusively through the irritability of the containing parts and the
agitation produced by the exciting cause in the contained fluids. But
as the vital energy increases in proportion to complexity of organisa-

OF LIFE 207

tion, there soon arrives a time when irritability and the exciting cause
are no longer sufficient by themselves for the acceleration needed in the
movements of the fluids ; nature then makes use of the nervous system
which increases the effects of the irritability of the parts by adding
the activity of certain muscles; and when this system permits of
muscular movement, the heart becomes a powerful motor for accele-
rating the movement of the fluids; finally, after the establishment
of pulmonary respiration muscular movement is once again necessary
to the performance of vital movements on account of the alternate
dilatations and contractions occurring in the cavity which contains
the respiratory organ and without which there could be no inspirations
or expirations,

“Doubtless we are not called upon,” says M. Cabanis, “‘ to prove
again that physical sensibility is the origin of all the ideas and habits
constituting the moral existence of man; Locke, Bonnet, Condillac
and Helvetius have pushed this truth to the last stage of demonstra-
tion. Among educated persons who use their reason there is now no
one who can throw the smallest doubt upon the matter. From
another standpoint, physiologists have proved that all vital movements
are the result of impressions received by sensitive parts, etc.” (Rapports
du Physique et du Moral de ? Homme, vol. i., pp. 85, 86).

I too recognise that physical sensibility is the source of all ideas, but
I am very far from admitting that all vital movements are the result
of impressions received by sensitive parts: that at most can only be
true with regard to such living bodies as possess a nervous system ;
for the vital movements of those which have no such system cannot
be the result of impressions received by sensitive parts: this is quite
obvious.

If we wish to make a true analysis of life, we must necessarily
examine the facts which it presents in all bodies possessing it. Now
as soon as we deal with the subject in this way we see that what is
really essential to the presence of life in one plan of organisation is
by no means essential in another.

No doubt nervous influence is necessary to the maintenance of life
in man, and in all animals which have a nervous system; but this
does not prove that vital movements, even in man and in animals
provided with nerves, are due to impressions made on sensitive parts :
it only proves that their vital movements cannot occur without the
help of nervous influence.

It is clear from the above exposition that life in general may exist in
a body, although the vital movements are not produced by impressions
received by the sensitive parts and although there is no muscular
activity ; it may even exist when the body possessing it has no

3

208 ZOOLOGICAL PHILOSOPHY

irritable parts whose reaction could assist its movements. It is enough,
as we see in plants, that a body possessing it should present internally
an order and state of things with regard to its containing parts and
contained fluids which permit of the excitation of the characteristic
movements and changes, by means of a special force.

But if we consider life in special cases, that is, in various selected
bodies, we shall then see that whatever is essential to the plan of
organisation of these bodies has also become necessary to the main-
tenance of life in them.

Thus in man and the most perfect animals, life cannot be maintained
without irritability of the reacting parts, without the involuntary
muscles to keep up the rapid movement of the fluids, without the
nervous influence which by quite a different route from feeling pro-
vides for the performance of the functions of the muscles and other
internal organs; lastly, without the influence of respiration to restore
continually the essential fluids which are so rapidly disintegrated
in these systems of organisation.

Now this nervous influence, which is undoubtedly necessary, is
exclusively that which sets the muscles in action and not that which
produces feeling ; for it is not by means of sensations that the muscles
act. In fact, no feeling whatever is aroused by the cause which pro-
duces the movements of systole and diastole in the heart and arteries ;
and if we do sometimes perceive the beats of the heart it is when they
are stronger and more rapid than usual ; this muscle, which is the chief
motive power of circulation, then strikes neighbouring sensitive parts.
Finally, when we walk or perform any action we never feel the move-
ment of the muscles nor the impulse which drives them.

Hence it is not through the medium of feeling that the muscles
carry on their functions, although nervous influence is necessary to
them. But since nature was obliged, in order to accelerate the move-
ment of fluids in the most perfect animals, to add the muscular move-
ment of the heart, etc., to the irritability which they possess in common
with the rest, nervous influence has become necessary to the main-
tenance of life in these animals. There can, however, be no justification
for the statement that their vital movements are only due to impressions
received by sensitive parts, for if their irritability was destroyed they
would immediately lose their life; and their feeling, if it still survived,
could not alone suffice for its preservation. Moreover, I hope to prove
in Chapter IV. of this part that sensibility and irritability are not
only quite distinct faculties, but that they have not even a common
origin and are due to very different causes.

“ Living is feeling,’ said Cabanis: yes, doubtless for man and the
most perfect animals and probably too for a great number of inver-

OF LIFE 209

tebrates. But since the faculty of feeling weakens in proportion to
the lower development of the system of organs on which it is based
and in proportion to the inferior concentration in the cause which
makes this faculty active, we must say that life is rudimentary feeling
for those invertebrates that have a nervous system; because this
system of organs, especially in the insects, gives them only a very
dim feeling.

As to the radiarians, if the nervous system still exists in them, it
must be very rudimentary indeed and adapted only to the excitation
of muscular movement.

Lastly, since it is impossible that the great majority of polyps or
any of the infusorians should possess a nervous system, we must say
of them and even of the radiarians and worms, that living is not
feeling ; as we are obliged also to say in the case of plants.

In dealing with nature, nothing is more dangerous than generalisa-
tions, which are nearly always founded on isolated cases : nature varies
her methods so greatly that it is difficult to set bounds to them.

According as animal organisation becomes more complex, the order
of things essential for life does the same, and life is specialised in each
of the principal organs. But all specialised organic life depends on the
general life of the individual, just as the latter depends on the specialized
life of the principal organs, for there is an intimate connection between
each organ and the rest of the organisation. The order of things
essential to life in any animal is thus only determinable by a description
of that order itself.

In accordance with this principle, it is quite clear that in the most
perfect animals, such as mammals, the order of things essential to life
includes a system of organs for feeling, consisting of a brain, spinal
cord, and nerves, a system of organs for complete pulmonary respira-
tion, a system of organs for circulation with a bilocular heart which
has two ventricles, and a muscular system for the movement of internal
and external parts, etc.

No doubt each one of these systems of organs has its special life,
as Bichat has shown: and on the death of the individual, life be-
comes extinct in them all. Nevertheless none of these systems of
organs could preserve its special life independently, nor could the
general life of the individual continue if any of them had lost its own.

From this state of affairs, already generally recognised in the case
of mammals, it by no means follows that the order of things essential
to life in other bodies, includes a system of organs for feeling, another
for respiration, another again for circulation, etc. Nature shows
us that these various systems of organs are only essential to life in

animals where they form a necessary part of the organisation.
co)

210 ZOOLOGICAL PHILOSOPHY

These, I think, are truths against which can be set no known facts.
and no authoritative observation.

The following i is a summary of the principles set forth in this canis

1. Life is an organic phenomenon which gives rise to many others;
this phenomenon results exclusively from the relations existing between
the containing parts of the body, the contained fluids moving in them,
and the exciting cause of the movements and changes there occurring ;

2. Consequently life in a body is an order and state of things which
permits of organic movements, and these movements constituting
active life result from the action of a cause which excites them;

3. Without the stimulating and exciting cause of vital movements,
life could not exist in any body, whatever the state of its parts ;

4. The exciting cause of organic movements acts in vain if the state
of things in the parts of the organised body is so disordered that these
parts can no longer respond to the action of this cause nor produce
the special movements called vital. Life would then be extinct in
the body, and could no more be restored ;

5. Lastly, in order that the relations between the containing parts
of the organised body, the fluids contained in them, and the cause
which excites vital movements in them, may produce and maintain
the phenomenon of life, the three conditions named in this chapter
must be completely fulfilled.

Let us now pass to an examination of the exciting cause of organic
movements.

CHAPTER III.

OF THE EXCITING CAUSE OF ORGANIC MOVEMENTS.

WE have seen that life is a natural phenomenon which itself produces
several others, and that it results from the relations existing between
the supple containing parts of an organised body and the contained
fluids of that body. We cannot conceive the production of this
phenomenon, that is to say, the presence and continuance of the move-
ments constituting active life, unless we imagine a special exciting
cause of these movements, a force which animates the organs, controls
the activities and all the organic functions,—a spring, in short, of which
the permanent though variable tension is the driving energy of all
vital movements.

There can be no doubt that the visible fluids of a living body and the |
solid parts which contain them are irrelevant to the cause that we are
here seeking. All these parts together constitute the machinery of
movement, if I may revert to the parallel already drawn; and it is
not the function of any of them to supply the force in question, that is,
the motive power or exciting cause of the movements of life. '

We may be certain that if there were no special cause to stimulate
and maintain orgasm and irritability in the supple and containing
parts of animals, and to produce in plants an obscure orgasm by
promoting direct movement of their contained fluids, the blood of
animals which have a circulation and the transparent whitish serum
of those that have not, would remain at rest and would rapidly
decompose together with the solid parts.

In the same way, if there were no exciting cause of vital movements,
if there were no force or spring to endow a body with active life, the
sap and special fluids of plants would remain motionless, would de-
generate and be exhaled, and finally compass the death and desiccation
of these living bodies.

The ancient philosophers felt the necessity for a special exciting
cause of organic movements; but not having sufficiently studied

212 ZOOLOGICAL PHILOSOPHY

nature, they sought it beyond her; they imagined a vital principle, a
perishable soul for animals, and even attributed the same to plants ;
thus in place of positive knowledge, which they could not attain from
want of observations, they created mere words to which are attached
only vague and unreal ideas.

Whenever we abandon nature, and give ourselves up to the fan-
tastic flights of our imagination, we become lost in vagueness, and
our efforts culminate only in errors. The only knowledge that it is
possible for us to acquire is and always will be confined to what we have
derived from a continued study of nature’s laws; beyond nature all
is bewilderment and delusion: such is my belief.

If it were true that it is really beyond our powers to ascertain the
exciting cause of organic movements, it would be none the less obvious
that such a cause exists and that it is physical, since we can observe its
effects and nature has all the means of producing it. Do we not know
that it spreads and maintains movement in all bodies, and that none
of the objects submitted to nature’s laws really possesses an absolute
stability ?

I do not wish to go back to the consideration of first causes, nor of
all the movements and changes observed in physical bodies of all
kinds. We shall confine ourselves to a study of the immediate re-
cognised causes acting on living bodies, and we shall see that they
are quite sufficient to maintain in these bodies the movements
constituting life, so long as the appropriate order of things is not
destroyed.

It would doubtless be impossible to ascertain the exciting cause of
organic movement if the subtle, invisible, uncontainable, incessantly
moving fluids which constitute it were not disclosed to us in a great
variety of circumstances ; if we had not proofs that the whole environ-
ment in which all living bodies dwell are permanently filled with them ;
lastly, if we did not know positively that these invisible fluids penetrate
more or less easily the masses of all these bodies and stay in them for a
longer or shorter time; and that some of them are in a constant
state of agitation and expansion, from which they derive the faculty
of distending the parts in which they are insinuated, of rarefying the
special fluids of the living bodies that they penetrate, and of com-
municating to the soft parts of these same bodies, an erethism or
special tension which they retain so long as their condition is
favourable to it.

But it is well known that the question at issue is not insoluble ;
for no part of the earth inhabited by living beings is destitute of
caloric (even in the coldest regions), of electricity, of magnetic fluid,
etc. These fluids, some of which are expansive and the others agitated

[I

THE EXCITING CAUSE 213

in various ways, are incessantly undergoing more or less regular dis-
placements, renewals or replacements and perhaps in the case of some
of them there may actually be a genuine circulation.

We do not yet know how numerous may be these subtle invisible
fluids which are distributed in constant agitation throughout the
environment. But we do perceive in the clearest manner that these
invisible fluids penetrate every organised body and there accumulate
with constant agitation, finally escaping in turn after being retained
for a longer or shorter period. They thus stimulate movements and
life, when they come in contact with an order of things permitting of
such results.

With regard to such of these invisible fluids as chiefly constitute
the exciting cause under consideration, two of them appear to us to be
the essential elements of this cause, viz. caloric and the electric fluid.
They are the direct agents which produce orgasm and the internal
movements which in organised bodies constitute and maintain life.

Caloric appears to be that of the two exciting fluids in question
which causes and maintains the orgasm of the supple parts of living
bodies ; and the electric fluid is apparently that which provides the
cause of the organic movements and activities of animals.

My justification for this division of the faculties assigned to the two
fluids in question is based on the following principles.

In inflammations, the orgasm acquires an excessive energy which is
at length even destructive of the parts. This is clearly in consequence
of the extreme heat developed in inflamed organs : it is, then, especially
to caloric that the orgasm must be attributed.

The rapidity of the movements of caloric throughout the bodies
which it penetrates is very far from equalling the extraordinary speed
of the movements of the electric fluid. Hence this latter fluid must
be the cause of the movements and activities of animals; it must be
more particularly the genuine exciting fluid.

It is possible, however, that other active invisible fluids combine
with the two already named in the composition of the exciting cause ;
but what appears to me beyond question is that caloric and electricity
are the two chief components, and perhaps even the only components
of this cause. |

In animals with low organisations, the caloric of the environment
seems to be sufficient by itself for the orgasm and irritability of their
bodies ; hence it arises that in extreme reductions of temperature and
in the winters of climates in high latitudes, some entirely perish while
others become more or less completely torpid. In these same animals
the ordinary electric fluid provided by the environment appears to be
sufficient for the organic movements and activities.

214 ZOOLOGICAL PHILOSOPHY

The caseis different with regard to animals of highly complex organisa-
tions: in these, the caloric of the environment merely completes or
rather aids and favours the power which these living bodies themselves
possess of constantly producing caloric within them. It is probable
even that this internally produced caloric has undergone modifications
in the animal as a result of which it is specialised ; and rendered alone
suitable for the maintenance of orgasm; for when the state of the
organisation has greatly enfeebled the orgasm and irritability, the
external caloric arising either from our fires or from a rise of tempera-
ture cannot take the place of internal caloric.

The same observation appears to be applicable also to the electric
fluid which excites the movements and activities of animals with
highly complex organisations. It appears indeed that this electric
fluid, which is introduced through the medium of respiration or of
food, has undergone some modification in the animal’s interior and
become transformed into nervous or galvanic fluids.

As to caloric, it is unquestionably one of the principal elements
of the exciting cause of life, and is particularly instrumental in pro-
ducing and maintaining orgasm, without which life could not exist.
So true is this that a great reduction of temperature would exterminate
all living bodies long before reaching the point of absolute cold. Asa
matter of fact, the cold of our winters, especially when it is extreme,
causes the death of a great many of the animals exposed to it. But
we know that on no part of the earth’s surface and at no period of the
year do we ever find a total absence of caloric.

Let me repeat that without a special exciting cause of orgasm and
vital movements—without the force which alone can produce such
movements—life could not exist in any body. Now this exciting
cause has nothing to do with the visible fluids of living bodies, nor
with the solid containing parts of these bodies. This is a fact that can
no longer be questioned since it is justified by all observation.

This same exciting cause is also the cause of fermentation, the mani-
festations of which it alone brings about in all compound non-living
matter, whose parts are favourable to it. Thus in great reductions
of temperature the activities of life and fermentation are suspended
more or less completely, in proportion to the intensity of the cold.

Although life and fermentation are two very different phenomena,
they both derive from the same origin the movements by which they
are constituted ; and in both cases it is necessary that the state of
the parts, whether of the organic body capable of life or of the inorganic
body capable of fermentation, should be favourable to the performance
of these movements. But in bodies possessing life, the existing order
and state of things are such that every decomposition of principles

THE EXCITING CAUSE 215

is subsequently made good by new and closely similar combinations
as a result of continued movements, whereas in the unorganised or
disorganised fermenting body, the decompositions which occur cannot
be made good by a continuance of fermentation.

As soon as an individual dies, its body, which is then disorganised
in reality though often not in appearance, immediately joins the class
of bodies liable to fermentation, particularly as regards the more
supple of its parts. The exciting cause which gave it life then hastens
the decomposition of such of its parts as are capable of fermentation.

We learn then from the principles set forth above that the exciting
cause of vital movements must necessarily be sought in the invisible,
subtle, penetrating and ever active fluids with which the environment
is always supplied; and that the chief element of this cause is the
element which maintains an orgasm essential to the existence of life,
and, in fact, that it is no other than caloric; as the following
observations will further bring out.

I need not cite any special instances on this subject, since the general
fact concerned is well known. We are aware that a certain quantity
of heat is generally necessary to all living bodies and especially animals.
When it is reduced below a certain point, the irritability of animals
becomes less intense, their organisation less active and all their
functions flag or are performed slowly, especially in those animals
where there is no production of internal caloric. When it becomes
still further reduced, the most imperfect animals die and a great
many of the rest fall into a torpid lethargy and undergo a suspension
of life; it cannot be doubted that they would in turn all lose their
lives, if this reduction of heat were to be carried much further in the
environment.

When the temperature rises, on the contrary—that is, when the heat
increases and is distributed everywhere—we constantly notice, if this
state of things continues, that life revives and seems to acquire new
strength in all living bodies, that the irritability of the internal parts
of animals rises proportionally in intensity, that the organic functions
are carried on with more energy and promptitude, that the various
stages of life succeed each other with greater rapidity, and that life .
itself comes sooner to an end, but that the new generations are more
frequent and abundant.

Although heat is everywhere necessary for the maintenance of life
especially in animals, its intensity should not much exceed certain
limits; for if it did animals would suffer greatly from it, and in the
case of the highly complex would be exposed at the slightest cause to
rapid diseases, which would quickly result in death.

We may then be sure that not only is heat necessary to all living

216 ZOOLOGICAL PHILOSOPHY

bodies, but that when it reaches a certain degree without exceeding
the proper limits, it markedly animates all the activities, is favourable
to reproduction and appears to expand life everywhere in a wonder-
ful way. ;

The ease, rapidity, and abundance with which, in tropical countries,
nature produces and multiplies the simplest animals are facts in
support of this statement. The multiplication of these animals is in
fact specially noticeable in favourable times and places, that is to say,
in hot climates and in the case of countries of high latitudes in the
warm season, especially when there are other conditions favourable
to fertility.

Indeed at certain times and in certain climates, the earth (especially
at its surface where caloric always accumulates the most) and the
body of the waters teem with animated molecules, that is to say,
with animalcules of extremely varied genera and species. These
animalcules, like many other imperfect animals of different classes,
reproduce and multiply with an astonishing fertility—far greater
than that of larger animals with a more complex organisation. So
rapid are the results of this prodigious fertility, that matter seems.
to become everywhere animalised. Hence, if it were not for the huge
immolation which overtakes the animals of the first orders of the animal
kingdom, they would soon overwhelm and perhaps extinguish the more
perfect animals of the later classes and orders of this kingdom—so
great is the difference between them in the capacity and ease of multi-
plication !

The above statement as regards the necessity for animals of a caloric
distributed throughout the environment, and varying within certain
limits, is entirely applicable to plants; but in their case heat only
maintains life under certain necessary conditions.

The first and most important condition is that the roots of the plant.
should have constant access to moisture; for the greater the heat,
the more necessary does water become to the plant, to make good
the heavy losses of its fluids due to transpiration; and the less the
heat, the less it needs moisture, which would then be injurious to
its preservation.

The second condition for the elaboration of its products by a plant,
is that the plant in addition to heat and water should also have plenty
of light. :

The third, lastly, makes it dependent upon air, from which it pro-
bably appropriates oxygen and the other gases which it finds there,
immediately decomposing them and making use of their principles.

From the above statement, it is quite clear that caloric is the first
cause of life, in that it produces and maintains orgasm without which

THE EXCITING CAUSE 217

no living body could exist. In this it succeeds so long as the state of
the parts of the living body does not prevent it.

We find, moreover, that this expansive fluid, especially when its
abundance gives it some intensity of action, is the principal factor
in the enormous multiplication of living bodies of which I have just
spoken. Hence it is universal that in the hot climates of the earth the
animal and plant kingdoms exhibit an extremely remarkable wealth
and abundance, whereas in the frozen regions of the earth they only
exist in a state of the greatest poverty.

A further fact in favour of the principle just established is that there
is a great difference between the summer and winter of our own
climates as regards the number of animals and plants. _

Although caloric is really the first cause of life in the bodies which
possess it, yet it could not alone account for its existence nor keep up
the movements which constitute it; there is needed in addition,
especially for animals, the influence of a fluid to excite their acts of
irritability. Now we have seen that electricity possesses all the
properties necessary for constituting this exciting fluid, and that it
is distributed sufficiently widely notwithstanding its variations, to
ensure that living bodies shall always be provided with it.

It may be that some other invisible fluid combines with electricity
in making up the cause which is able to excite vital movements and all
the organic activities ; this is quite possible, but I see no need for sup-
posing it.

It seems to me that caloric and the electric substance together are
quite sufficient to constitute the essential cause of life, the one by
setting the parts and internal fluids in a proper condition for the
existence of life, and the other by arousing in the course of its move-
ments through the body the various stimuli which give rise to the
organic activities and the active part of life.

If we were to try to explain how these fluids work, and to determine
definitely the number of those that enter into the composition of the
exciting cause of all organic movements, we should be abusing the
power of our imagination and arbitrarily creating explanations which
we have no means of verifying.

It is enough to have shown that the exciting cause of the movements
which constitute life does not reside in any of the visible fluids in the
interior of living bodies, but that it takes its origin as follows :

1. From caloric, which is an invisible penetrating, expansive, ever-
active fluid that percolates slowly through the supple parts, dis-
tending them and making them irritable; and that is constantly
being dissipated and renewed and is never entirely absent from any

body that possesses life ;

218 ZOOLOGICAL PHILOSOPHY

2. From the electric fluid, either the ordinary electric fluid in the
case of plants and imperfect animals, or the galvanic fluid for those
with very high organisation ;—a subtle fluid, moving with extra-
ordinary speed, which instigates sudden local dissipations of the caloric
which distends the parts, and thus excites acts of irritability in the
non-muscular organs, and movements in the muscles when it extends
its action to them.

If the two fluids named above thus combine their special activities,
there must ensue in the case of organised bodies submitted to their
influence, a powerful cause or force which works effectively, and is
controlled by the organisation,—that is, by the regular shape and
arrangement of the parts,—and keeps up movements and life so long
as there exists in these bodies an order of things which allows of such
effects.

This apparently is the mode of action of the exciting cause of life ;
but it cannot be regarded as established, until it is possible to find
proofs of it. The two named fluids may be the only principles con-
tributing to the production of this cause; but that again is a belief
of which we cannot be certain. What is quite positive in this respect
is that the source, from which nature derives this cause and the result-
ing force, is to be found in the subtle invisible fluids among which the
two just named are unquestionably the chief.

I shall confine myself to the statement that the active and expansive
fluids, composing the exciting cause of vital movements, penetrate
into or are constantly developing in the bodies which they animate,
pass all through them, while harmunising their movements with the
nature, order and arrangement of the parts, and are then constantly
being exhaled by an imperceptible transpiration. This fact is un-
questionable and sheds the brightest light over the causes of life. }

Let us now enquire into the special phenomenon that I call orgasm
in living bodies, and afterwards into the irritability which this orgasm
produces in animals, where the nature of their bodies permits it to be
highly developed.

CHAPTER IV.

OF ORGASM AND IRRITABILITY.

Ir is not the special affection called orgasm that we are now about to
‘discuss, but the general condition known under the same name and
characteristic of the supple internal parts of animals during life; a
condition which is natural to them, since it is essential to their pre-
servation, and which necessarily comes to an end at or soon after death.

It is certain that, among the solid internal parts of animals, those
that are supple are animated throughout life by an orgasm or peculiar
kind of erethism, from which they derive the faculty of collapsing
and being promptly restored on the receipt of any impression.

An analogous orgasm also exists in the most supple of the solid parts
of plants, so long as they are alive; but it is so faint that the parts
endowed with it do not derive therefrom any faculty for immediate
restoration, after the impressions that they have received.

The orgasm of the supple internal parts of animals contributes to |
some extent to the production of their organic phenomena; it is
maintained by an invisible, expansive, penetrating fluid (possibly
several), which slowly passes through the parts affected and produces
in them the tension or sort of erethism just mentioned. The orgasm
resulting from this state of things in the parts, is maintained
throughout life with a strength that is proportional to the favour-
able disposition of the parts; it is the stronger according as they
are more supple and less dried up.,

It is this same orgasm, the necessity for which has been recognised
for the presence of life in a body, that some modern physiologists
have looked upon as a kind of sensibility; hence they have alleged
that sensibility is a property of all living bodies, that such bodies
are both sensitive and irritable, that all their organs are impregnated
with these two necessarily co-existing faculties, in short that they
are common to every living thing both animal and plant. Cabanis,
who shared this opinion with M. Richerand and apparently others,
aid indeed that sensibility is the general fact of living nature.

220 ZOOLOGICAL PHILOSOPHY

M. Richerand, however, who has in particular developed this opinion
in the prolegomena of his Physiologie, admits that the sensibility,
which gives us the power of receiving sensations and depends on
nerves, is not the same thing as that more general kind of sensibility
for which no nervous system is necessary. For the former he suggests
the name of perceptibility and for the latter that of latent sensibility.

Since these two faculties are different in their origin and results,
why should we give a new name to the phenomenon, long known as
sensibility, and transfer the name of sensibility to a more recently
observed phenomenon of altogether special nature? Surely it is more
convenient to give a particular name to the general phenomenon on
which life depends: and this is what I have done by calling it orgasm.

It is probable that without orgasm (latent sensibility), no vital
function could go on; for wherever it exists, there can be no true
inertia in the parts; they are no longer merely passive. This is the
element of truth in the idea that all the living parts feel and act in
their own way, that they distinguish among the fluids which bathe
them whatever is suitable for their nutrition, and that they separate
from them those substances which affect their special type of sensi-
bility.

Although we are not definitely aware how each vital function is
performed, we should not gratuitously attribute to the parts a know-
ledge and power of choice among the objects which they have to
separate out, and retain or evacuate. We should rather reason thus:

1. The organic movements aroused are simply due to the action
and reaction of the parts ;

2. From these actions and reactions it follows that the state and
nature of the parts undergo alterations, decompositions, new com-
binations, etc. ;

3. As a result of these alterations, there occur secretions which
are favoured by the width of the secretory canals; depots are estab-
lished which are sometimes kept isolated and sometimes attached to
these same parts; lastly, there are various evacuations, absorptions,
resorptions, etc.

All these operations are mechanical and subject’to physical laws ;
they are carried out by means of the exciting cause and of orgasm,
which keeps up the movements and activities ; so that by these means
and by the shape, arrangement and situation of the organs, the vital
functions are varied and controlled, and each works in its special
way.

The orgasm dealt with in this chapter is a definite fact, which what-
ever we call it can no longer be neglected. We shall see that it is
very weak and faint in plants where its powers are very limited, but.

ORGASM AND IRRITABILITY 221

that in animals on the contrary it is very conspicuous ; for it produces
in them that remarkable property called irritability by which they are
distinguished.

Let us first study it in animals.

—_—!

Or AnimaL Orcas.

By animal orgasm, I mean that curious condition of the supple
parts of a living animal, in which there exists at every point a peculiar
tension, of such strength that the parts are able immediately to react
to any impression that they may experience, and do in fact react on
the moving fluids which they contain.

This tension, the degree of which varies in the different parts, con-
stitutes what physiologists call the tone of the parts; it seems to be
due as I have already said to the presence of an expansive fluid which
penetrates these parts, remains in them for a certain period and keeps
their molecules separated to some distance from one another though
without destroying their coherence ; some of the fluid suddenly escapes
on any contact, leading to a contraction, but it is promptly restored
again.

Thus at the moment of the dissipation of the expansive fluid dis-
tending any part, this part subsides on itself as a result; but it is
promptly restored to its previous distention by the arrival of new
expansive fluid. Hence it follows that the orgasm of this part gives
it the property of reacting on the visible fluids which affect it.

This tension in the soft parts of living animals does not go so far
as to break up the cohesion of their molecules, or to destroy their
adhesiveness, agglutination and firmness, so long as the intensity of
orgasm does not exceed a certain point. But the tension prevents
the falling together and collapse of the molecules which would occur
if this tension did not exist ; for the soft parts do actually subside in a
remarkable way as soon as the tension is removed.

Indeed among animals, and even among plants, the extinction of
orgasm, which only occurs on the death of an individual, gives rise
to a relaxation and subsidence of the supple parts, making them
softer and more limp than in the living state. This has given rise to
the belief that these limp parts found in old people after death have
escaped the rigidity which gradually comes over the organs during
life.

The blood, and especially the arterial blood, of animals whose
organisation is highly complex, itself possesses a sort of orgasm ;
for it is during life suffused with various gases which develop within
it and become modified there. Now these gases may also contribute
to the stimulation of the organic acts of irritability, and consequently

222 ZOOLOGICAL PHILOSOPHY

to the vital movements, when the blood affected flows to the
organs.

The excessive tension of orgasm under certain conditions in some
or all of the soft parts of an individual, although not great enough
to break up the cohesion of those parts, is known under the name of
erethism. When it is very strong it produces inflammation, whereas
when the orgasm is extremely reduced, though not to the point of
disappearance, it is generally designated by the name of atony.

The tension which constitutes orgasm may vary within certain
limits, without on the one hand destroying the cohesion of the parts,
or on the other hand ceasing to exist. This variation renders possible
those sudden contractions and distensions which occur when the cause
of orgasm is momentarily removed and then restored. This seems to

me to be the chief cause of animal irritability.

The cause which produces orgasm, or that peculiar tension of the
supple internal parts of animals, is no doubt an element in what I
have called the exciting cause of organic movements. It is to be found
principally in caloric, either in that provided by the environment, or
in this combined with the caloric that is constantly being produced
in the interior of many animals.

Indeed an expansive caloric is continually emanating from the
arterial blood of many animals, and constitutes the principal cause of
the orgasm in their supple parts. It is especially in the warm-blooded
animals that the continual emanation of caloric becomes remarkable.
This expansive fluid is constantly being dissipated from the parts which
it distends, but it is as constantly being renewed by the emanations
always being given off from the animal’s arterial blood.

An expansive fluid, similar to that which we are discussing, is dis-
tributed throughout the environment and incessantly provides for the
orgasm of living animals, either by completing what was wanting to
the internal caloric, or achieving it alone.

As a matter of fact, the caloric of the environment assists more or
less in the orgasm of the most perfect animals and suffices by itself
for that of the rest ; it is especially the cause of orgasm in all animals
which have no arteries or veins, that is to say, no circulatory system.
Hence all organic movement becomes gradually weaker in these animals,
according as the temperature of the environment becomes lower ;
and if this reduction of temperature continues indefinitely their orgasm
is extinguished and they die. We have only to recall the torpidity
that overtakes bees, ants, snakes and many other animals when the
temperature falls below a certain point, and we shall then be in a
position to judge whether my statement has not some deans

The reduction of temperature which causes many animals to become

ORGASM AND IRRITABILITY 223

torpid works this result by weakening their orgasm and hence by
slackening their vital movements. If this reduction of temperature
goes too far, I have already observed that it extinguishes the orgasm
and causes the death of the animal; but I may remark on this subject,
with regard to the effects of cooling, not carried far enough to kill
the individual, that there is a certain peculiarity in the case of warm-
blooded animals and perhaps of all animals that have nerves: it is
as follows.

It is known that no very great fall of temperature is required to bring
about the torpid state of apparent sleep in certain mammals, such as
marmots, bats, etc. If the heat returns, it penetrates, revives, awakes,
and restores them to their usual activity; but if on the contrary
the cold increases still further after these animals have become torpid,
they do not pass imperceptibly from their condition of apparent
sleep into death. If the increase of cold is considerable, it causes an
irritation in their nerves which awakes and agitates them, and revives
their organic movements and hence their internal heat. If the increase
of cold then continues, it soon throws them into a state of disease,
ending in death unless heat is quickly restored to them.

Hence it follows that, for warm-blooded animals and perhaps for
all animals with nerves, a mere weakening of their orgasm may reduce
them toa torpid state. In this case the orgasm is not totally destroyed,
since if the cold were great enough for that purpose, it would begin
by irritating them, giving them pain and end by killing them.

In the case of animals without nerves, it seems that a reduction of
temperature sufficient to weaken their orgasm and make them torpid,
may if it increases result in their passing through their stage of lethargic
sleep to that of death, without any temporary return of activity.

Those who imagine that the first result of a moderate degree of cold
is to slacken the respiration, have mistaken the effect for the cause.
Thus the torpid state, into which various animals fall when the tempera-
ture is lowered, has been attributed to a direct slackening of the
respiration of these animals ; whereas in point of fact the slackening
of respiration is itself due to another effect of the cold, namely, the
enfeeblement of their orgasm.

As regards animals which breathe with lungs, those that fall into a
torpid state in certain degrees of cold doubtless undergo a considerable
slackening of respiration ; but here it is clearly only the result of a
great enfeeblement in their orgasm. Now this enfeeblement slackens
all the organic movements and all the functions. It diminishes also the
production of internal caloric and the losses which these animals are
subject to, during their customary activity. Their need for restoration
during their lethargy is thus very slight or next to nothing.

224 ZOOLOGICAL PHILOSOPHY

Animals breathing with lungs undergo alternate swellings and con-
tractions of the cavity containing their respiratory organ. Now these
movements are carried out with greater or less facility, according
as the orgasm of the supple parts is more or less energetic. Thus
several mammals, such as the marmot and dormouse, and many
reptiles, as the snakes, fall into a torpid state on certain reductions of
temperature, because they then have a greatly weakened orgasm,
from which results secondarily a slackening of all their organic functions
including that of respiration.

If this decline in the energy of their orgasm did not take place, there
would be no reason why any less air should be breathed by these animals
when it is cold. In bees and ants which breathe by tracheae and
undergo no alternative swellings and contractions, it cannot be said
that they breathe less when it is cold; but there are sound reasons
for the belief that their orgasm is then greatly enfeebled, and thus
accounts for the torpid state which they undergo in these conditions.

Finally, in warm-blooded animals their internal heat is almost
entirely produced within their bodies, either as a result of the decom-
position of air in respiration as is generally held, or because it is con-
stantly given off from the arterial blood while changing into venous
blood, as I myself believe; in either case the orgasm gains or loses
energy, according as the internal caloric increases or diminishes in
quantity.

As regards the explanation which I am giving of orgasm, it is a matter
of indifference whether the caloric produced in the interior of warm-
blooded animals, is the result of the decomposition of air in respiration
or is an emanation from the arterial blood as it changes into venous
blood. If, however, it is desired to consider this question, I should
put forward the following suggestions :

If you drink a glass of spirits, the resulting warmth that you feel
in your stomach assuredly does not spring from increased respiration.
Now if caloric may be given forth from this liquor as it undergoes
changes in your organ, so too it may be exhaled from your blood
when it undergoes changes in its component parts.

In fever when the internal heat is greatly increased, it is observed
that respiration is also faster, and hence it is inferred that the con-
sumption of air is greater. This supports the view that the internal
caloric of warm-blooded animals results from the decomposition of
the respired air. I know of no experiment to show definitely whether
the consumption of air during fever is really greater than in health.
I doubt whether it is so; for if respiration were faster in this diseased
condition it may be compensated for by each inspiration being less,
owing to the constraint of the parts. What I do know is that when

ORGASM AND IRRITABILITY 225

I have some local inflammation like a boil or any other inflamed
tumour, caloric issues in extraordinary abundance from the blood of
the parts affected. Yet I do not see how any increase of respiration
can in this case have given rise to the local concentration of caloric ;
I should say on the other hand that the blood, being compressed
and concentrated in the diseased part, is liable to disturbances and
decompositions (as also the supple parts containing it) which involve
the productions of the observed caloric.

I cannot admit that atmospheric air includes in its composition a
fluid, which when freed is an expansive caloric; I have elsewhere
stated my views on this matter. In point of fact, I believe that air
is composed of oxygen and nitrogen; and I know that it contains
caloric within it, because absolute cold does not exist anywhere on
our earth. Iam fully convinced that the component fluid which when
freed is changed into expansive caloric was previously a constituent
part of our blood; that this fluid in combination is always being
partially set free and that by its liberation it produces our internal
heat. Evidence that this internal heat does not come from our
respiration is furnished by the fact that if we were not constantly
making good the losses in our blood by means of food, and hence of
a chyle always being renewed, our respiration would not restore to
our blood the qualities which it must possess for the maintenance
of our existence.

The utility of respiration to animals is not in question; by this
method their blood derives a restoration which they could not do
without ; and the belief appears to be justified that it is by appro-
priating oxygen from the air that the blood derives one of its most
necessary restorations. But in all this there is no proof that caloric
comes from the air or its oxygen, rather than from the blood itself.

The same thing may be said with regard to combustion: the air
in contact with burning substances may be decomposed, and its dis-
engaged oxygen may be fixed in the residue of combustion ; but that
is no proof that the caloric then produced comes from the oxygen in
the air rather than from the combustible substances, with which I
hold that it was previously combined. All the known facts are better
and more naturally explained on this latter assumption than on any
other.

However this may be, the positive fact remains that in a great many
animals an expansive caloric is constantly being produced within
them, and that it is this invisible penetrating fluid which maintains
the orgasm and irritability of their supple parts; while in other
animals orgasm and irritability are chiefly the result of the caloric

of the environment.
P

226 ZOOLOGICAL PHILOSOPHY

To refuse to recognise the orgasm of which I have spoken, and to
regard it as a hypothetical fact, that is to say a product of the imagina-
tion, would be to deny to these animals the existence of that tone
in the parts which they possess throughout life. Now death alone
extinguishes this tone, as also the orgasm which constitutes it.

PLant ORGASM.

In plants the exciting cause of organic movements seems to act
chiefly on the contained fluids, and sets them alone in motion ; while
the cellular tissue of the plant, whether simple or modified into vasculi-
form tubes, only acquires from it an ill-defined orgasm giving rise to
a very slow general contractility, which never acts in isolation or
suddenly.

If, during the warm season, a plant grown in a pot or box needs
watering, we notice that its leaves, the ends of its branches and young
shoots hang down as though about to fade: yet life still continues to
exist in them; but the orgasm of the supple parts is then greatly
enfeebled. If this plant is watered, we see it gradually erect its
drooping parts and show an appearance of life and vigour which it
did not present when it had no water.

This restoration of the vigour of the plant is doubtless something
more than a mere result of the introduction of new fluids into the
plant. It is also the result of a revived orgasm, since the expansive
fluid causing this orgasm penetrates the parts of the plant with much
greater ease when the juices or contained fluids are abundant.

The ill-defined orgasm of living plants thus causes a slow general
contractility in their solid parts, especially in the newest,—a sort of
tension which various facts justify us in accepting, although there are
no sudden movements. This plant-orgasm does not endow the organs
with any faculty for instantaneous reaction on contact with objects
which might affect them, and hence it has no power of causing irrit-
ability in the parts of these living bodies.

It is not true indeed, as has been alleged,1 that the canals in which
move the visible fluids of these living bodies are sensitive to impressions
of stimulating fluids, or that they become relaxed or distended by a
prompt reaction in order to achieve the transport and elaboration of
their visible fluids ;—in short they have no true tone.

Finally, it is not true that the peculiar movements observed at
certain periods in the reproductive organs of various plants, nor the
movements of leaves, petioles or even the small twigs and plants
called sensitive, are the product and proof of an irritability existing

1 Richerand, Physiologie, vol. i., p. 32.

ORGASM AND IRRITABILITY 227

in these parts. I have observed and watched these movements and
am convinced that they have nothing in common with animal
irritability. See what I have already said, pp. 51-53.

Although nature has doubtless only one general plan for the pro-
duction of living things, she has everywhere varied her means, when
diversifying her productions, according to the circumstances and
objects on which she worked. But man is always striving to confine
her to the same methods ; for the idea that he has formed of nature is
still indeed far from that which he ought to entertain.

How great are the efforts that have been made to discover sexual
reproduction everywhere throughout the two kingdoms of living bodies ;
and in the case of animals to attribute to all of them nerves, muscles,
feeling and even will, which is necessarily an act of intelligence!
How profoundly different nature would be, if she was really limited
in the ways that we imagine !

We have just seen that orgasm has very different degrees of intensity,
and consequently has effects that vary according to the nature of
the living bodies in which it occurs, and that in animals alone does it
give rise to irritability. We now have to enquire into the nature of
this remarkable phenomenon.

IRRITABILITY.

Irritability is the faculty possessed by the irritable parts of animals,
of producing sudden local manifestations which may occur at any
point on the surface, and may be repeated as often as the exciting
cause acts upon the susceptible regions.

The manifestations consist in a sudden contraction and shrinkage of
the irritated point, a shrinkage characterised by the closing in of
neighbouring points upon that which is affected, but soon followed
by a contrary movement, that is to say by a distension of the irritated
point and neighbouring parts; so that the natural condition of the
parts distended by orgasm is promptly re-established.

I said at the beginning of this chapter that orgasm is formed and
maintained by caloric, that is a penetrating expansive invisible fluid
which passes slowly through the soft parts of animals and produces
in them a tension or kind of erethism. Now if some impression is made
upon any such part so as to instigate a sudden dissipation of the in-
visible fluid distending it, the part immediately shrinks and contracts :
but if a new supply of expansive fluid is instantly developed and
distends it afresh, it then reacts immediately and so produces the
phenomenon of irritability.

Lastly, since the parts in the neighbourhood of the point affected
themselves suffer a slight dissipation of the expansive fluid distend-

228 ZOOLOGICAL PHILOSOPHY

ing them, their consecutive shrinkage and restoration throw them
momentarily into a condition of quivering.

Thus a sudden contraction of the part affected, followed by an equally
sudden distension which restores the part to its original condition,
constitutes the loca] phenomenon of irritability.

The production of this phenomenon does not need any special
organ ; for the state of the parts and the instigating cause are sufficient
in themselves ; it is in fact observed in the simplest of animal organisa-
tions: moreover the impression giving rise to the phenomenon is not
conveyed by any special organ to a centre of communication or nucleus
of activity; the whole process is confined to the immediate site of
the impression ; every point of the surface of irritable parts is capable
of producing it and of repeating it always in the same way. This
phenomenon is obviously quite different from that of sensations.

From these principles it will be clear that orgasm is the source from
which irritability arises; but this orgasm exhibits very different
degrees of intensity, according to the nature of the bodies in which it
is produced.

In plants, where it is ill-defined and devoid of energy, and where it
works extremely slowly in causing the shrinkages and distensions of
the parts, it has no power to produce irritability.

In animals on the contrary, where orgasm is highly developed on
account of the nature of their body-substance, it rapidly produces
the contractions and distensions of the parts on the stimulus of the
exciting causes; in them it constitutes a marked irritability.

Cabanis, in his work entitled: Rapports du physique et du moral
de Vhomme, has endeavoured to prove that sensibility and irritability
are phenomena of the same nature and have a common origin (Histoire
des sensations, vol. i., p. 90); his intention no doubt was to reconcile
what we know of the most imperfect animals with the ancient and
universally received belief that all animals without exception possess
the faculty of feeling.

The arguments adduced by this savant for showing the identity of
nature between feeling and irritability, appear to me neither clear nor
convincing; hence they do not affect the following propositions by
which J distinguished these two faculties.

Irritability is a phenomenon peculiar to animal organisation,
requiring no special organ, and continuing to subsist some time
after the death of the individual. This faculty may exist just the same
whether there are or are not any special organs, and it is therefore
universal for all animals.

Sensibility on the contrary is a phenomenon peculiar to certain
animals; it can only be manifested in those which have a special

ORGASM AND IRRITABILITY 229

organ essentially distinct, and adapted solely for producing it; and
it invariably ends with life or even slightly before death.

We may be sure that feeling cannot occur in an animal without the
existence of a special organ adapted for producing it,—that is without
a nervous system. Now this organ is always quite discernible; for
it cannot exist without a centre of communication for the nerves,
and hence could not remain unperceived when it is present. This
being so, seeing that many animals have no nervous system, it is
obvious that sensibility is not a faculty common to all animals.

Finally, feeling as compared with irritability presents in addition
this distinctive peculiarity, that it comes to an end with life or even
a little before ; whereas irritability is still preserved some time after
the death of the individual, and even after it has been divided into
fragments.

The time during which irritability is preserved in the parts of an
individual after death varies no doubt with the system of organisation
of that individual ; but in all animals it is probably true that irritability
continues to be manifested after the cessation of life.

In man the irritability of his parts scarcely lasts more than two or
three hours after death, or even less, according to the cause of death :
but thirty hours after having removed a frog’s heart it is still irritable
and capable of producing movements. There are insects, in which
movements are manifested still longer after they have been deprived
of their internal organs.

From the above account, we see that irritability is a faculty peculiar
to animals ; that all animals possess it in a high degree in some or all
of their parts and that an energetic orgasm is the source of it: we see
moreover that this faculty is entirely distinct from that of feeling ;
that the one is of very different character from the other, and that since
feeling can only result from the functions of a nervous system provided
as I have shown with its centre of communication, it only occurs in
those animals which possess the required system of organs.

Let us now consider the importance of cellular tissue in all kinds of
organisation.

CHAPTER V.

OF CELLULAR TISSUE, REGARDED AS THE MATRIX IN WHICH
ALL ORGANISATION HAS BEEN CAST.

As we observe the facts presented to us in the various parts of nature,
it is curious to remark how the simplest causes of observed facts are
often those which remain the longest unperceived.

It is no new discovery that all the organs of animals are invested
by cellular tissue, even down to their smallest parts.

It has indeed been long recognised that the membranes which form
the investments of the brain, nerves, vessels of all kinds, glands,
viscera, muscles and their fibres, and that even the skin itself are all
the produce of cellular tissue.

Yet in this multitude of harmonious facts, nothing more appears
to have been seen than the mere facts themselves; and no one
that I know of has yet perceived that cellular tissue is the universal
matrix of all organisation, and that without this tissue no living body
could continue to exist.

Thus when I said 1 that cellular tissue is the matrix in which all the
organs of living bodies have been successively formed, and that the
movement of fluids through it is nature’s method of gradually creating
and developing these organs out of this tissue, I was not afraid of
coming upon any facts which might testify to the contrary ; for it
is by examining the facts themselves that the conviction is acquired
that every organ whatever has been formed in cellular tissue, since it is
everywhere invested with it even down to its smallest parts.

Hence we see that in the natural order, both of animals and plants,
those living bodies whose organisation is the simplest and which are
consequently placed at one extremity of the order, consist only of a
mass of cellular tissue in which there are to be seen neither vessels,
nor glands nor any viscera ; whereas those bodies, whose organisation

1 Opening address of the course of invertebrate animals delivered in 1806, p. 33.
Since the year 1796, I have stated these principles in the early lessons of my course.

CELLULAR TISSUE 231

is the most complex and which are therefore placed at the other
extremity of the order, have their organs so deeply imbedded in cellular
tissue that this tissue always forms their investments and constitutes
for them a bond of communication. Hence the possibility of those
sudden metastases, so well known to those who practice the art of
medicine.

Compare the very simple organisation of the infusorians and polyps,
presenting nothing more than a gelatinous mass of cellular tissue,
with the highly complex organisation of the mammals, which still
presents a cellular tissue though enveloping a large number of different
organs ; you will then be in a position to judge whether the principles,
which I have drawn up on this important subject, are merely the
results of an imaginary system.

Compare in the same way in plants the very simple organisation
of the algae and fungi with the more complex organisation of a big
tree or any other dicotyledonous plant, and you will perceive that the
general plan of nature is everywhere the same, notwithstanding the
infinite variations of her individual operations.

Take for instance the algae which grow under water, such as the
widely spread Fucus which constitutes a great family with different
genera, and such as the Ulva, Conferva, etc.; their scarcely modified
cellular tissue is conspicuous enough to prove that it alone forms the
whole substance of these plants. In several of these algae, the move-
ments of the internal fluids in this tissue have not yet given rise to
any signs of a special organ, and in the others they have only traced
out a few canals through which food is supplied to thos2 reproductive
corpuscles, which botanists take for seeds because they often find
them invested in a capsular vesicle in the same way as the gemmae
of many known examples of Sertularia.

We may then convince ourselves by observation that in the most
imperfect animals, such as the infusorians and polyps, and in the
least perfect plants, such as the algae and fungi, there sometimes
exists no trace of any vessels and sometimes only a few rudimentary
canals ; lastly, we may recognise that the very simple organisation of
these living bodies consists only of a cellular tissue, in which slowly
move the fluids which animate them; and that these bodies being
destitute of special organs only develop, grow, and multiply or repro-
duce themselves by a faculty of growth and separation of reproduc-
tive parts; for they possess this faculty in a very high degree.

In plants indeed, even including those with the most perfect organisa-
tion, there are no vessels comparable to those of animals which have a

circulatory system.
Thus the internal organisation of plants really consists only of a

232 ZOOLOGICAL PHILOSOPHY

cellular tissue more or less modified by the movement of fluids, a tissue
which is very slightly modified in the algae, fungi and even the mosses,
whereas it is much more modified in the other plants and especially
in the dicotyledons. But everywhere, even in the most perfect animals,
there is really nothing in their interior but a cellular tissue modified
into a large number of different tubes, most of which are parallel to
one another in consequence of the ascending and descending move-
ment of the fluids. Yet the structure of these tubes is not comparable
to that of the vessels of animals which possess a circulatory system.
Nowhere do these vegetable tubes intertwine or form those special
groups of vessels, folded and interlaced in infinite variety, that we call
conglomerate glands in animals which have a circulation. Finally
in all plants without exception, there is no special organ within their
bodies: there is nothing but more or less modified cellular tissue,
longitudinal tubes for the movement of fluids, and harder or softer
fibres also longitudinal, for strengthening the stem and branches.

If we admit on the one hand that every living body whatever is a.
mass of cellular tissue, in which are embedded various organs of a
number proportionate to the complexity of organisation ; and if on
the other hand we also admit that all bodies contain within them fluids
that move faster or slower according as the state of organisation
allows of a more or less active or energetic life, we are forced to the
conclusion that it is to the movement of fluids in the cellular tissue
that we have primarily to attribute the formation of every kind of
organ in the midst of this tissue, and hence that each organ must be
invested by it both in its gross outlines and in its most minute parts,
as indeed we actually find.

With regard to animals, I have no need to show that in various of
their internal parts the cellular tissue is squeezed aside by the moving
fluids, which open a passage through it; and that in these regions
it has been forced back upon itself; it has then been compressed and
transformed into investing membranes round about these running
streams of fluid; while on the outside these living bodies are inces-
santly compressed by the environing fluids (either water or atmospheric
fluids) and modified by external impressions and by deposits upon
them. Their cellular tissue has thus come to form that universal
investment of every living body, that is called skin in animals and
bark in plants.

I was then fully justified when I said “‘ that the function of the move-
ment of fluids in the supple parts of living bodies, and especially in
the cellular tissue of the simplest among them, is to carve out routes,
places of deposit and exits, to create cunals and thereafter diverse
organs, to vary these canals and organs in accordance with the

CELLULAR TISSUE 233

diversity of the movements or character of the fluids causing them,
finally to enlarge, elongate, divide, and gradually solidify these canals
and organs. This is effected by the substances which are incessantly
being formed in the fluids, and are then separated from them, and
in part assimilated and united to the organs, while the remainder is
rejected” (Recherches sur les corps vivants, pp. 8 and 9).

I was equally justified when I said “ that the state of organisation
in every living body has been gradually acquired by the increasing
influence of the movement of fluids (firstly in the cellular tissue and
afterwards in the organs formed in it), and by the constant changes
in the character and state of these fluids owing to the continual wastage
and renewals proceeding within them.”

Lastly, I was authorised by these principles in saying “ that every
organisation and every new shape, acquired by this agency and contri-
buting circumstances, were preserved and transmitted by reproduction,
until yet further modifications had been acquired by the same method
and in new circumstances” (Recherches sur les corps vivants, p. 9).

It follows from the above that the function of the movement of
fluids in living bodies, and consequently of organic movement, is not
merely the development of organisation, for this development continues
so long as the movement is not weakened, through the hardness which
overtakes the organs during life; but that this movement of fluids
has in addition the faculty of gradually increasing the complexity
of organisation and of multiplying the organs and their functions
according as new modes of life or new habits acquired by individuals
stimulate it in various ways, create a necessity for new functions, and
consequently for new organs.

Let me add that the faster the movement of fluids in a living body,
the more does it complicate the organisation, and the greater the branch-
ing of the vascular system.

It is from the uninterrupted co-operation of these factors and of
long periods of time, combined with an infinite variety of environment,
that all the orders of living bodies have been successively formed.

VEGETABLE ORGANISATION IS ALSO CAST IN A CELLULAR TISSUE.

Imagine a cellular tissue in which, for various reasons,! nature
could not establish irritability, and you will have an idea of the matrix
in which all vegetable organisation has been cast.

If we then reflect that the movements of fluids in plants are only

1 Chemical analysis has shown that animal substances abound in nitrogen, while
vegetable substances are destitute of this material or contain only very small pro-
portions of it. Hence there is a distinct difference between animal and vegetable

substances: now this difference may be the reason why the factors which produce
orgasm avd irritability in animals cannot establish these faculties in living plants.

234 ZOOLOGICAL PHILOSOPHY

excited by external influences, we shall be convinced that in this kind
of living bodies life can only have a feeble activity, even in times and
climates when vegetation is rapid; and consequently that their com-
plexity of organisation is necessarily confined within very narrow limits.

Infinite pains have been taken to become acquainted with the details
-of plant organisation: search has been made in them for peculiar
or special organs of the same kind as some of those known in animals ;
-and the results of all these researches have done no more than show
us that the containing parts consist of a more or less compressed cellular
‘tissue, with elongated cells that communicate with each other by
pores and by vascular tubes of various shape and size, mostly having
lateral pores or sometimes clefts.

All the details ascertained on this subject furnish little in the way
of clear general ideas, and the only ones which we need recognise are
as follows :

1. Plants are living bodies with less perfect organisation than
animals and with less active organic movements; their fluids move
more slowly and the orgasm of the containing parts is very faint ;

2. They are essentially composed of cellular tissue ; for this tissue
is to be found in every part of them, and indeed it is found almost by
itself and with very slight modifications in the simplest of them
(algae, fungi and probably all the agamous plants) ;

3. The only change undergone by cellular tissue in monocotyledons
and dicotyledons as a result of the fluids moving within them, consists
in the transformation of certain parts of this cellular tissue into
vascular tubes of varied size and shape open at the extremities, and
mostly having lateral pores.

Let me further add that since the movement of fluids in plants is
either upwards or downwards their vessels are naturally almost always
longitudinal, and approximately parallel to one another and to the
directions of the stem and branches.

Lastly, the outer part of that cellular tissue, which constitutes the
bulk of every plant and the matrix of its low organisation, is squeezed
and compressed by the contact, pressure and collision of the environ-
ment, and is thus thickened by deposits and transformed into a general
integument 1 called bark which is comparable to the skin of animals.
Hence we may understand how the external surface of this bark,
being even more disorganised than the bark itself by the causes named,

1 If the stems of palms and some ferns appear to have no bark, it is because they
are only elongated root collars, the exterior of which shows a continuous succession
of scars left by old leaves that have fallen; this prevents the possibility of a con-
tinuous or uninterrupted bark; but it cannot be denied that each separate part of
this exterior has its special bark, although more or less imperceptible on account of
the small size of these parts.

CELLULAR TISSUE 235

comes to constitute that outer pellicle called epidermis both in animals
and plants.

If then we study plants from the point of view of their internal
organisation, all that we can find is, among the simplest, a cellular
tissue without vessels but variously modified and stretched or com-
pressed according to the special shape of the plant; and in the more
complex, an assemblage of cells and vascular tubes of various sizes,
mostly with lateral pores, and a varying number of fibres, resulting
from the compression and hardening that a portion of the vascular
tubes has undergone. This is all that the internal organisation of plants
presents, as regards their containing parts; even their pith is no
exception.

But if we study plants from the point of view of their external
organisation, the most general and essential points to observe are as
follows :

1, Their various peculiarities of shape, colour and consistency,
both in them and their parts ;

2. The bark which invests them, and gives communication by pores
with the environment ;

8. The more or less complex organs which develop on the exterior
in the course of the plant’s life, and serve for reproduction; they
perform their functions once only, and are highly important in the
determination of the characters and true affinities of each plant.

It is then in the study of the external parts of plants, and especially
in that of their reproductive organs, that the means must be sought
for describing the characters of plants and determining their natural
affinities.

Since the above exposition is a positive result of knowledge acquired
by observation, it is obvious that on the one hand the true affinities
among animals can only be determined by their internal organisation,
which provides the only features of real importance; and that on the
other hand these affinities cannot be similarly determined among plants,
as regards any of the divisions which mark their classes, orders, families
and genera. In their case affinities can only be determined by a study
of their external organisation; for their internal organisation is
insufficiently complex, and its various modifications too vague, to
provide the means for fulfilling this purpose.

We have now seen that cellular tissue is the matrix, in which all
organisation was originally cast ; and that it was by means of the move-
ment of the internal fluids of living bodies that all their organs were
created in this matrix and out of its substance. We have now to
enquire briefly whether we are justified in attributing to nature the
power of forming direct generations.

CHAPTER VI.
OF DIRECT OR SPONTANEOUS GENERATION.

Lire and organisation are products of nature, and at the same time
results of the powers conferred upon nature by the Supreme Author
of all things and of the laws by which she herself is constituted: this
can no longer be called in question. Life and organisation are thus
purely natural phenomena, and their destruction in any individual is
also a natural phenomenon, necessarily following from the first.

Bodies are incessantly undergoing transformations in their con-
dition, combination and character; in the course of which some are
always passing from the inert or passive condition to that which permits
of the presence of life in them, while the rest are passing back from the
living state to the crude and lifeless state. These transitions from life
to death and from death to life are evidently part of the immense
cycle of changes of every kind to which all physical bodies are liable
as time goes on.

Nature, as I have already said, herself creates the rudiments of
organisation in masses where it did not previously exist ; subsequently,
use and the vital movements cause the development and increasing
complexity of the organs (Recherches sur les corps vivants, p. 92).

However extraordinary this proposition may appear, we shall be
obliged to abandon any opinion to the contrary if we take the trouble
to examine and reflect seriously upon the principles which I am about.
to advance.

The ancient philosophers had observed the power of heat, and noted
the extreme fertility which it confers on the various parts of the earth’s
surface in proportion to its abundance; but they omitted to reflect
that the co-operation of moisture is the essential condition for making
the heat so fertile and necessary to life. Since however they perceived
that life in all living bodies derives its support and activity from
heat, and that the privation of heat everywhere results in death,
they concluded with justice not only that heat was necessary for

SPONTANEOUS GENERATION 237

the maintenance of life, but that it could even create both life and
organisation.

They recognised then that direct generations do occur, that is
to say, generations wrought directly by nature and not through the,
intermediary of individuals of a similar kind: they called them
somewhat inappropriately spontaneous generations; and perceiving’
as they did that the decomposition of animal or vegetable substances!
provided nature with conditions favourable to the direct creation of’
new organisms, they wrongly imagined that such organisms were the.
produce of fermentation.

I am in a position to show that the ancients were not mistaken when
they attributed to nature the faculty for direct generation ; but that
they were very much mistaken in applying this moral truth to a number
of living bodies, which neither are nor can be produced by this sort
of generation.

Asa matter of fact, sufficient observations had not then been collected
on this subject ; and it was not known that nature, by means of heat
and moisture, directly creates only the rudiments of organisation.
This direct creation is confined to those living bodies which are at the
beginning of the animal and vegetable scales, and perhaps of some of
their branches. Thus the ancients, of whom I speak, thought that all
the animals with low organisations—which they called for this reason
imperfect animals—were the result of these spontaneous generations.

Lastly, since natural history in those times had scarcely advanced
at all, and very few facts had been observed as to the productions of
nature, the insects and all the animals then designated as worms were
generally regarded as imperfect animals, which are born in favourable
times and places, as a result of the action of heat on various decaying
substances.

It was then believed that putrid flesh directly engendered larvae,
which were subsequently metamorphosed into flies; that the extra-
vasated juice of plants, which, as a result of pricks by insects, gives
tise to gall nuts, directly produced the larvae which are transformed
into Oinips, ete., etc. : all of which is without foundation.

Thus the mistake of the ancients in assuming direct generations
jn cases where they do not occur, was propagated and transmitted
from age to age; it was bolstered up by the erroneous beliefs named
above, and-became the cause of a new mistake for moderns after they
had recognised the old one.

When people perceived the necessity for collecting facts and making
precise observations as to what actually occurs, the mistake into which
the ancients fell was disclosed: men famous for their attainments
and powers of observation, such as Rhedi, Leuwenhoek, etc., proved

238 ZOOLOGICAL PHILOSOPHY

that all insects without exception are oviparous or sometimes apparently
viviparous, that worms are never found to appear on putrid meat,
except when flies have been able to deposit their eggs on it ; and lastly
that all animals, however imperfect they may be, themselves have the
power of reproducing and multiplying the individuals of their species.

But unfortunately for the progress of knowledge we are nearly
always extreme in our opinions, as we are in our actions; and it is
only too common for us to compass the destruction of an error, and then
throw ourselves into the opposite error. How many examples I might
cite in illustration, even in the present state of accredited opinions,
if such details were not foreign to my purpose !

It was thus proved that all animals without exception have the power
of reproducing themselves ; it was recognised that the insects and all
the animals of the later classes only do so by the method of sexual
generation ; bodies resembling eggs had been seen in the worms and

_tadiarians ; and lastly the fact had been verified that the polyps re-

' produce themselves by gemmae or kinds of buds. Hence the inference
was drawn that the direct generations attributed to nature never take
place, but that every living body springs from a similar individual
of its own species, by a generation that is either viviparous, oviparous
or even gemmiparous.

This conclusion is erroneous in being too universal : for it excludes
the direct generations wrought by nature at the beginning of the animal
and vegetable scales, and perhaps also at the beginning of certain

_branches of those scales. Moreover, supposing that the bodies, in which
nature has established life and organisation directly, obtain at the
same time the faculty of reproducing themselves, does it necessarily
follow that these bodies spring only from individuals like themselves ?
Unquestionably no ; and this is the mistake into which we have fallen,
after recognising that of the ancients.

Not only has it been impossible to demonstrate that the animals.
with the simplest organisation, such as the infusorians and among
them especially Monas, and also the simplest plants such perhaps.
as the Byssus of the first family of algae, have all sprung from indi-
viduals similar to themselves; but moreover there are observations.
which go to show that these extremely small and transparent animals
and plants, of gelatinous or mucilaginous substance, of very slight
coherence, curiously ephemeral, and as easily destroyed by environ-
mental changes as brought into existence, are unable to leave behind
them any permanent security for new generations. It is on the con-
trary far more probable that their new individuals are a direct result.
of the powers and faculties of nature, and that they alone perhaps are
in this position. Hence we shall see that nature has played only an

SPONTANEOUS GENERATION 239

indirect part in the existence of all other living bodies, since they are
all derived one after the other from the original individuals ; mean-
while in the course of long periods, she wrought changes and an increase
of complexity in their organisation, and ever preserved by reproduction
the modifications acquired and the development attained.

If it is admitted that all natural bodies are really productions of
nature, it must be quite clear that in bringing the various living bodies
into existence, she must necessarily have begun with the simplest, that
is with those which are in truth the veriest rudiments of organisation
and which we scarcely venture to look upon as organised living bodies.
But when by means of the environment and of her own powers, nature
has set going in a body the movements constituting life, the repetition
of these movements develops organisation in it and gives rise to nutri-
tion, the earliest of the faculties of life ; from the latter soon arises the
second of the vital faculties, namely, growth of the body.

Excess of nutrition in causing growth of this body prepares in it
the material for a new being with a similar organisation ; and thus
provides it with the power to reproduce itself. Hence originates the
third of the faculties of life.

Finally, the continuance of life in a body gradually increases the
hardness of its containing parts and their resistance to the vital move-
ments: it proportionally enfeebles nutrition, sets a limit to growth,
and finally compasses the death of the individual.

Thus as soon as nature has endowed a body with life, the mere
existence of life in that body, however simple its organisation may be,
gives birth to the three faculties named above; and its subsequent
stay in this same body slowly works its inevitable destruction.

But we shall see that life, especially in favourable conditions, tends.
incessantly by its very nature to a higher organisation, to the creation
of special organs, to the isolation of these organs and their functions,
and to the division and multiplication of its own centres of activity.
Now since reproduction permanently preserves all that has been
acquired, there have come from this fertile source in course of time
the various living bodies that we observe; lastly, from the remains
left by each of these bodies after death, have sprung the various
minerals known to us. This is how all natural bodies are really pro-
ductions of nature, although she has directly given existence to the
simplest living bodies only.

Nature only establishes life in bodies that are at the time in a
gelatinous or mucilaginous state, and that are sufficiently soft to respond
easily to the movements which she communicates to them by means
of the exciting cause that I have spoken of, or of another stimulus
which I shall hereafter endeavour to describe. Thus every germ, at

240 ZOOLOGICAL PHILOSOPHY

the moment of its fertilisation, that is at the instant when by an organic
act it is rendered suitable for the possession of life, and every body
which derives immediately from nature the rudiments of organisation
and the movements of the most elementary life, are at that time
necessarily in a gelatinous or mucilaginous state; although they are
yet composed of two kinds of parts, the one containing and the other
contained, the latter being essentially fluid. ;

COMPARISON BETWEEN THE ORGANIC ACT CALLED FERTILISATION,
AND THAT Act oF NATURE WHICH GIVES RISE TO DriREcT
GENERATIONS.

However little we may know of the two phenomena that I am now
about to compare, it is quite obvious that they are related, for the
results accruing from them are almost identical. Indeed the two acts
in question both give origin to life; or give it the power of establishing
itself in bodies where it was not previously found, and which could
not possess it except through their agency. Thus a careful comparison
between them cannot but enlighten us to a certain extent on the real
nature of these acts.

T have already said ! that in the reproduction of mammals, the vital
movement in the embryo appears to follow immediately upon fertilisa-
tion ; whereas in oviparous animals there is an interval between the
act of fertilising the embryo and the first vital movement induced by
incubation ; and we know that this interval may sometimes be very
longé

Now during this interval the fertilised embryo cannot yet be reckoned
among living bodies ; it is ready no doubt for the reception of life, and
to that end requires only the stimulus of incubation ; but so long as
organic movement has not been originated by this stimulus, the
fertilised embryo is only a body prepared for the possession of life
and not actually possessing it.

If the fertilised egg of a fowl or any other bird is preserved for a
certain time without incubation or any increase of temperature, it is
not found to contain a living embryo; in the same way, the seed of
a plant, which is really a vegetable egg, does not enclose a living
embryo unless it has been exposed to germination.

Now if, owing to special circumstances, there occurs no incubation
or germination to start the vital movement in the egg or seed, the
result is that after a period, dependent on the species and the environ-
ment, the parts of this fertilised embryo degenerate; the embryo,
since it has never actually had life, will not suffer death; it will

1 Recherches sur les corps vivants, p. 46,

SPONTANEOUS GENERATION 241

merely cease to be in a condition for receiving life and will ultimately
decompose.

I have already shown in my Mémoires de Physique et d’ Histoire
naturelle, p. 250, that life may be suspended for some time and after-
wards resumed.

I here wish to observe that preparation for life may be made either
by an organic act, or by the direct agency of nature without any such
act; so that certain bodies, without possessing life, are yet made
ready for its reception by an impression, which does no doubt trace
out in these bodies the earliest outlines of organisation.

What indeed is sexual reproduction but an act for achieving ferti-
lisation ? What again is fertilisation but an act preparatory to life,
an act in short which disposes the parts of a body for the reception
and enjoyment of life ?

We know that in an unfertilised egg we yet find a gelatinous body
which presents a complete external resemblance to a fertilised embryo,
and is indeed nothing else than the germ previously existing in the egg
although it has not been fertilised.

Yet what is the unfertilised germ of an egg but an almost inorganic
body,—a body not prepared internally for the reception of life and
incapable of acquiring life even by the most complete incubation ?

The fact is generally known that every body which receives life,
or which receives the first outlines of organisation preparing it for the
possession of life, is at the time necessarily in a gelatinous or muci-
laginous state; so that the containing parts of this body have the
weakest coherence and the greatest flexibility possible, and are con-
sequently in the highest possible condition of suppleness.

This must necessarily have been the case: the solid parts of the body
must have been in a state closely allied to fluids, in order that the
disposition, which makes the internal parts of the body ready for
life, may be easily achieved.

Now it seems to me certain that sexual fertilisation is nothing else
than an act for establishing a special disposition in the internal parts
of a gelatinous body; a disposition which consists in a particular
arrangement and distension of the parts, without which the body in
question could not receive life.

For this purpose it is enough that a subtle penetrating vapour,
which escapes from the fertilising material, should be insinuated into
the gelatinous corpuscles capable of receiving it ; that it should spread
throughout its parts and by its expansive movement break up the
adhesion between these parts, and so complete the organisation
already begun and dispose the corpuscles for the reception of life,
that is of the movements constituting life.

Q

242 ZOOLOGICAL PHILOSOPHY

It appears that there is this difference between the act of fertilisa-
tion which prepares an embryo for the possession of life, and the act
of nature which gives rise to direct generations ; that the former acts
upon a small gelatinous or mucilaginous body, in which the organisation
was already outlined, whereas the latter is only carried out upon a
small gelatinous or mucilaginous body, in which there was no previous
trace of organisation.

In the first case, the fertilising vapour which penetrates the embryo
merely breaks asunder by its expansive movement the parts which
in the rudiments of organisation ought no longer to adhere together,
and arranges them in a particular way.

In the second case, the subtle surrounding fluids, which are intro-
duced into the mass of the small gelatinous or mucilaginous body,
enlarge the interstices within it and transform them into cells ; hence-
forth this small body is only a mass of cellular tissue, in which various
fluids can be introduced and set in motion.

This small gelatinous or mucilaginous mass, transformed into
cellular tissue, may then possess life, although not yet having any
organ whatever; since the simplest living bodies, both animal and
plant, are really only masses of cellular tissue which have no special
organs. On this subject, I may observe that, whereas the indis-
pensable condition for the existence of life in a body is that the body
shall be composed of non-fluid containing parts and of contained fluids
moving in these parts, the condition is fulfilled by a body consisting
of a very supple cellular tissue, the cells of which communicate by
pores: the possibility of this is attested by the fact.

If the small mass in question is gelatinous, it will be animal life that
is established in it; but if it is simply mucilaginous, then vegetable
life only will be able to exist in it.

With regard to the act of organic fertilisation, if you compare the
embryo of an animal or plant that has not yet been fertilised with the
same embryo after it has undergone this preparatory act of life, you
will observe no appreciable difference between them: because the
mass and consistency of these embryos are still the same and the two
kinds of parts which compose them are extremely vaguely marked
out.

You may then conceive that an invisible flame or subtle and ex-
pansive vapour (aura vitalis) which emanates from the fertilising
material, and which penetrates a gelatinous or mucilaginous embryo,
that is, enters its mass and spreads throughout its supple parts, does
nothing more than establish in these parts a disposition which did not
previously exist there, break up the cohesion at the proper places,
separate the solids from the fluids in the way required by the

SPONTANEOUS GENERATION 243

organisation, and dispose the two kinds of parts in this embryo for
the reception of the organic movement.

Lastly, you may conceive that the vital movement, which follows
immediately on fertilisation in mammals but which is on the contrary
only set up in oviparous animals and in plants by incubation of various
kinds for the former and by germination for the latter, must subse-
quently develop by slow degrees the organisation of individuals
endowed with it.

We cannot penetrate farther into the wonderful mystery of fertilisa-
tion; but the principle which I have just set forth is indisputable,
and rests on definite facts which I think cannot be called in question.

It is important then to note that, in a different state of affairs,
nature in her direct generations imitates her own procedure for fertilisa-
tion which she employs in sexual generations ; and that for this purpose
she does not require the assistance or produce of any pre-existing
organisation.

But we must first remember that a subtle penetrating fluid in a
more or less expansive condition, and apparently very analogous to
the fluid of the fertilising vapours, is distributed everywhere through-
out the earth, and that it provides and ever maintains the stimulus
which like orgasm is at the base of every vital movement ; so that we
may rest assured that in places and climates where the intensity of
action of the fluid is favourable to organic movement, this movement
never ceases until the changes which come over the organs of the living
body no longer permit these organs to lend themselves to continuous
movement.

Thus in hot climates where this fluid abounds, and especially in
places where a considerable dampness acts as a co-operating agency,
life seems to be born and multiply everywhere ; organisation is formed
directly in any appropriate mass where it did not previously exist ;
and in those where it did exist, it develops rapidly and runs through
its various stages in each individual with very remarkable speed.

It is known indeed that in very hot times and climates, the more
complex and perfect the organisation of animals may be, the more
rapidly does the influence of a high temperature make them traverse
the various stages of their existence; this influence accelerates the
various stages and the termination of their life. It is well known
that in tropical countries, a girl becomes nubile very early, and that
she also reaches very early the age of decay or senility. It is, lastly,
an admitted fact that intensity of heat increases the danger of the
various known diseases, by causing them to run through their stages
with astonishing rapidity.

From these principles, we may conclude that any great heat is

244 ZOOLOGICAL PHILOSOPHY

universally injurious to animals living in the air, because it greatly
rarefies their essential fluids. It has thus been noted that in hot
countries, especially at the time of day when the sun is most powerful,
the animals appear to suffer, and hide themselves so as to avoid too
strong a glare.

Aquatic animals, on the other hand, derive from heat, however
great it may be, results that are invariably favourable to their move-
ments and organic development. Among them, it is especially the
most imperfect such as the infusorians, polyps and radiarians that
benefit the most, since the condition is advantageous to their
multiplication and reproduction.

Plants, which only possess a faint and imperfect orgasm, are in
absolutely the same condition as the aquatic animals of which I have
spoken: for, however great the heat may be, so long as these living
bodies have enough water at their disposal, they vegetate all the more
vigorously.

We have now seen that heat is indispensable to the most simply
organised animals ; let us enquire if there are not grounds for the belief
that it may itself, with the co-operation of a favourable environment,
have fashioned the earliest rudiments of animal life.

Nature, by means of heat, light, electricity and moisture, forms direct
| or spontaneous generations at that extremity of each kingdom of living
. bodies, where the simplest of these bodies are found.

_ This proposition is so remote from the current notion on this matter,
that for a long time to come it is likely to be rejected as an error, and
even to be regarded as a product of imagination.

But since men who are free even from the most ubiquitous pre-
judices, and who are observers of nature, will sooner or later perceive
the truth contained in this proposition, I wish to contribute towards
their perception of it.

I believe I have shown by a collection of comparative facts, that
nature under certain circumstances imitates what occurs in sexual
fertilisation and herself endows with life isolated portions of matter
which are in a condition to receive it.

Why indeed should not heat and electricity, which in certain countries
and seasons are so abundantly distributed throughout nature, especially
at the surface of the earth, not work the same result on certain sub-
stances of a suitable character and in favourable circumstances, that
the subtle vapour of the fertilising substances works on the embryos
of living bodies by fitting them for the reception of life ?

A famous savant (Lavoisier, Chimie, vol. i., p. 202) said with truth
that God, when he made light, distributed over the earth the principle
of organisation, feeling and thought.

SPONTANEOUS GENERATION 245

Now light is known to generate heat, and heat has_been justly
regarded as the mother of all generations. These two distribute over
our earth at least, the principle of organisation and feeling ; and since
feeling in its turn gives rise to thought as a result of the numerous
impressions made on its organ by external and internal objects through
the medium of the senses, the origin of every animal faculty may be
traced to these foundations. ”

This being the case, can it be doubted that heat, that mother of
generations, that material soul of living bodies, has been the chief
means employed directly by nature for working in appropriate material
the rudiments of organisation, a harmonious arrangement of parts,
in short, an act of vitalisation analogous to sexual fertilisation ?

Not only has the direct formation of the simplest living bodies
actually occurred, as I am about to show, but the following principles
proves that such formations must still be constantly carried out and
repeated where the conditions are favourable, in order that the existing
state of things may continue.

I have already shown that the animals of the earliest classes (in-
fusorians, polyps, and radiarians) do not multiply by sexual repro-
duction, that they have no special reproductive organ, that fertilisation
does not occur in them and that consequently they lay no eggs.

Now if we consider the most imperfect of these animals, such as
the infusorians, we shall see that in a hard season they all perish, or at
least those of the most primitive orders. Now seeing how ephemeral
these animalcules are, and how fragile their existence, from what
or in what way do they regenerate in the season when we again see
them? Must we not think that these simple organisms, these rudiments
of animality, so delicate and fragile, have been newly and directly
fashioned by nature rather than have regenerated themselves? This
is a question at which we necessarily arrive, with regard to these singular
creatures.

It cannot then be doubted that suitable portions of inorganic matter,
occurring amidst favourable surroundings, may by the influence of
nature’s agents, of which heat and moisture are the chief, receive an
arrangement of their parts that foreshadows cellular organisation,
and thereafter pass to the simplest organic state and manifest the
earliest movements of life.

If it is true that unorganised and lifeless substances, whatever they
may be, could never by any concurrence of circumstances form directly
an insect, fish, bird, etc., or any other animal which has already a
complex and developed organisation ; such animals certainly can only
derive their existence through the medium of reproduction, so that no
fact of animalisation can concern them.

246 ZOOLOGICAL PHILOSOPHY

But the earliest outlines of animal organisation, the earliest acquisi-
tion of a capacity for internal development, namely, by intus-susception,
lastly, the earliest rudiments of the order of things and of the internal
movement constituting life, are formed every day under our very eyes,
although hitherto no attention has been paid to it, and give existence
to the simplest living bodies which are placed at one extremity of each
organic kingdom.

It is useful to note that one of the conditions, essential to the
formation of these earliest outlines of organisation, is the presence of
moisture and especially of water in a fluid mass. So true is it that
the simplest living bodies could not be formed or perpetually be
renewed except in the presence of moisture, that none of the in-
fusorians, polyps or radiarians are ever met with except in water ;
so that we may regard it as an undoubted fact that the animal
kingdom originated exclusively in this fluid.

Let us continue the enquiry into the causes which have created the
earliest outlines of organisation in suitable masses, where it did not

lously exist.
/ If, as I have shown, light generates heat, heat in its turn generates
the vital orgasm that is produced and maintained in animals,
where the cause of it is not within them; thus heat may create the
earliest elements of orgasm in suitable masses, which have attained
the earliest stages of organisation.

When we remember that the simplest organisation needs no special
organ distinct from other parts of the body and adapted to a special
function (as is made clear by the simplification of organisation
observed in many existing animals), we can conceive that such
organisation may be wrought in a small mass of matter which has
the following qualification.

The body that 1s most fitted for the reception of the first outlines of life
and organisation 1s any mass of matter apparently homogeneous, of
gelatinous or mucilaginous consistency, and whose parts though cohering
together are in a state closely resembling that of fluids, and have only
enough firmness to constitute the containing parts.

Now the subtle expansive fluids, distributed and constantly moving
throughout the environment, incessantly penetrate and are dispersed
in any such mass of matter; in passing through it they regulate
the internal arrangement of its parts; they convert it into the cellular
state; and they make it fit for continually absorbing and exhaling
the other environmental fluids which may penetrate within it, and are
capable of being contained there.

We have indeed to distinguish the fluids, which penetrate living
bodies, in two categories :

SPONTANEOUS GENERATION 247

1. Containable fluids, such as atmospheric air, various gases, water,
etc. The nature of these fluids does not permit them to pass through
the walls of the containing parts, but only to go in and escape through
the exits ;

2. Uncontainable fluids, such as caloric, electricity, etc. These
subtle fluids are naturally capable of passing through the walls of
investing membranes, cells, etc., and hence cannot be retained or pre-
served by any body, except for a brief period. |

From the principles set forth in this chapter, it appears to me certain +
that nature does herself carry out spontaneous or direct generations,
that she has this power, and that she utilises it at the anterior extremity
of each organic kingdom, where the most imperfect living bodies are
found ; and that it is exclusively through their medium that she has
given existence to all the rest.

To me then it seems a truth of the highest certainty, that nature
forms direct or so-called spontaneous generations at the beginning of
the plant and animal scales. But a new question presents itself: is it
certain that she does not give rise to similar generations at any other
point of these scales? I have hitherto held that this question might
be answered in the affirmative, because it seemed to me that, in order
to give existence to all living bodies, it was enough for nature to have
formed directly the simplest and most imperfect of animals and
plants.

Yet there are so many accurate observations, so many facts known,
which suggest that nature does form direct generations elsewhere than
at the beginning of the animal and vegetable scales, and we know that
her resources are so wide and her methods so varied in different cir-
cumstances, that it is quite possible that my view, according to which
the possibility of direct generations is limited to the most imperfect
animals and plants, has no true foundation.

Why indeed should nature not give rise to direct generations at
various points in the first half of the animal and plant scales, and even
at the origin of certain separate branches of these scales? Why should
she not establish, in favourable circumstances, in these diverse rudi-
mentary living bodies, certain special systems of organisation, different
from those observed at the points where the animal and vegetable
scales appear to begin ?

Is it not plausible, as able naturalists have believed, that intestinal
worms which are never found except in the body of other animals,
are direct generations of nature; that certain vermin, which cause
diseases of the skin or pullulate there as a result of such diseases, also
have a similar origin? And why should not the same hold good among
such plants as moulds, the various fungi, and even the lichens, which

248 ZOOLOGICAL PHILOSOPHY

are born and multiply so abundantly on the trunks of trees and on
rocks favoured by moisture and a mild temperature ?

Doubtless as soon as nature has directly created an animal or plant,
the existence of life in this body not only endows it with the faculty
of growth, but also with that of separating off some of its parts, and in
short of forming granular corpuscles suitable for reproducing it. Does
it follow that this body which has just obtained the faculty of pro-
pagating individuals of its own species must necessarily have sprung
itself from corpuscles similar to those that it forms? This is a question
which in my opinion is well worthy of examination.

Whether the kind of direct generations, here referred to, do or do not
actually take place, as to which at present I have no settled opinion,
it seems to me certain at all events that nature actually carries out
such generations at the beginning of each kingdom of living bodies,
and that she could never, except through this medium, have brought
into existence the animals and plants which live on our earth.

Let us now pass to an enquiry as to the immediate results of life in
a body.

CHAPTER VIL.
OF THE IMMEDIATE RESULTS OF LIFE IN A BODY.

TuE laws controlling all the transformations that we observe in nature,
although everywhere the same and never in contradiction with one
another, produce very different results in living bodies from what they
cause in lifeless bodies. The results indeed are quite opposite.

In the former, by virtue of the order and state of things characteristic
of living bodies, these laws are constantly striving and succeeding
in forming combinations between principles which otherwise would
never have been joined together, and in complicating these combina-
tions and adding to them a superfluity of constituent elements; so
that the totality of living bodies may be regarded as an immense
and ever active laboratory from which all existing compounds were
originally derived.

In the latter, on the contrary, that is to say in bodies without life,
where there is no force to harmonise their movements and maintain
their integrity, these same laws are incessantly tending to decompose
existing combinations, to simplify them or reduce the complexity of
their composition ; so that in course of time they disengage nearly
all their constituent principles from their state of combination.

This line of thought leads to developments, which when thoroughly
understood and applied to all the known facts, cannot but show more
and more the truth of the principle which I have been setting forth.

This course of study however is very different from that which has
hitherto occupied the attention of savants ; they had observed that the
results of the laws of nature in living bodies were quite different from
those produced in lifeless bodies, and they attributed the curious
facts observed in the former to special laws, although in reality they are
only due to the difference of the conditions between these bodies and
in bodies that are destitute of life. They did not see that the nature
of living bodies, that is, the state and order of things which produce
life in them, give to the laws which regulate them a special direction,

250 ZOOLOGICAL PHILOSOPHY

strength and properties that they cannot have in lifeless bodies ; so

that, by their omission to reflect that one and the same cause

necessarily has varied effects when it acts upon objects of different

nature and in different conditions, they have adopted for the

explanation of the observed facts a route altogether opposite from
hat they ought to have followed.

It has indeed been said that living bodies have the power of resisting
the laws and forces to which all non-living bodies or inert matter are
subject, and that they are controlled by laws peculiar to themselves.

Nothing is more improbable, and nothing moreover is so far from
being proved as this alleged property of living bodies for resisting
the forces to which all other bodies are submitted.

This doctrine, which is very widely accepted, and is to be found set
forth in all modern works on this subject, appears to me to have been
invented in the first place to escape from the difficulty of explaining
the causes of the various phenomena of life, and in the second place
to afford some explanation of the faculty which living bodies possess
of forming for themselves their own substance, of making good the
wastage undergone by the material composing their parts, and lastly
of giving rise to combinations which would never have existed without
them. Thus in the absence of any solution, the difficulty has been
shelved by the invention of special laws, without any effort being
made to ascertain what they are.

In order to prove that bodies possessing life are subject to a different
set of laws from that followed by lifeless bodies, and that the former
possess in consequence a special force of which the chief property is
said to be their release from the sway of chemical affinities, M. Richerand
cites the phenomena presented by the living human body, viz. : “ the
decomposition of food by the digestive organs, the absorption of their
nutritive material by the lacteals, the circulation of these nutritive
juices in the blood, the changes which they undergo in the lungs and
secretory glands, the capacity for receiving impressions from external
objects, the power of approaching or flying from them, in short all
the functions carried on in the animal economy.” In addition to these
phenomena, this savant names as more direct proofs, sensibility and
contractility, two properties with which are endowed the organs that
carry out the functions of the animal economy (£léments de Physiologie,
vol. i., p. 81).

Although the organic phenomena just mentioned are not universal
to living bodies nor even to animals, they are yet characteristic of a
great number of the latter and of the living human body; and they
do undoubtedly show the existence of a special force animating living
bodies ; but this force in nowise results from laws peculiar to these

\

RESULTS OF LIFE 251

bodies ; it finds its origin in the exciting cause of vital movements.
Now this cause, which in living bodies may give rise to the force in
question, could not produce it in crude or lifeless bodies, nor could
it animate them, even though it acted upon them to the same
extent.

Moreover, the force in question does not altogether withdraw
the various parts of living bodies from the sway of chemical affinity ;
and M. Richerand himself agrees that there occur, in the living
machinery, effects that are quite obviously chemical, physical, and
mechanical; but these effects are always influenced, modified, and
weakened by the forces of life. To M. Richerand’s reflections on this
subject I may add the remark that the decompositions and alterations
produced in living bodies by chemical affinities which tend to break
up the state of things adapted for the maintenance of life, are incessantly
being repaired, although more or less completely, by the results of
the vital force which acts on these bodies. Now in order to bring
this vital force into existence and endow it with its recognised properties,
nature has no need of special laws; those which control all other
bodies are amply sufficient for the purpose.

Nature never uses more complex methods than necessary: if it
was possible for her to produce all the phenomena of organisation
by means of the laws and forces to which all bodies are universally
subjected, she has doubtless done so; and did not create laws and
forces for the control of one section of her productions, opposite to
those that she uses for the control of the rest.

It is enough to know that the cause, which produces the vital force
in bodies whose organisation and structure permit that force to exist
and excite the organic functions, could not give rise to any such
power in crude or inorganic bodies, where the state of the parts does
not permit of the activities and effects observed in living bodies. This
cause, of which I have just spoken, only produces in the case of crude
bodies or inorganic substances a force which incessantly works towards
their decomposition, and which regularly achieves it by mingling
its effects with that of the chemical affinities, when the closeness of
their combination does not prevent it.

There is then no difference in the physical laws, by which all living
bodies are controlled ; but there is a great difference in the circum-
stances under which these laws act.

The vital force, we are told, keeps up a perpetual struggle against the
forces which lifeless bodies obey ; and life is only a prolonged combat
between these different forces.

For my own part, I see in both cases only one force, which is synthetic
in one order of things and analytic in another. Now since the conditions

252 ZOOLOGICAL PHILOSOPHY

established by these two orders of things are always combined in living
bodies, though not in the same parts at the same time, and since they
follow each other in turn as a result of the incessant changes wrought by
the vital movements, there does exist in these bodies throughout life a
perpetual struggle between those conditions which make the vital
force synthetic, and those others, always being renewed, which make it
analytic.

Before developing this doctrine, let us consider several principles
which should not be lost sight of.

If all the activities of life, and all the organic phenomena, without
exception, are merely the result of the relations existing between the
containing parts in an appropriate state and the contained fluids
set in movement by a stimulating cause, the effects named below must
necessarily ensue from the existence of this order and state of things
in a body.

In point of fact as a result of these relations and of the movements,
actions and reactions produced by the stimulating cause, there do
incessantly occur the following events in all bodies possessing an active
life :

1. Changes in the state of the containing parts of this body
(especially the most supple), and in that of its contained fluids ;

2. Real losses in these containing parts and contained fluids, caused
by the changes wrought in their state or nature; losses which give
rise to deposits, dissipations, evacuations and secretions of substances,
some of which can be no more utilised, while others may be turned
to various purposes ;

3. The constant need for making good the losses undergone; a
need which perpetually requires the introduction of new and suitable
substances into the body, and which is actually assuaged by food in
animals, and by absorptions in plants ;

4. Lastly, various kinds of combinations, which the conditions
and results of the various activities of life are alone able to bring
about; combinations which, but for these results and conditions,
would never have occurred.

Thus throughout life in a body, combinations are incessantly formed
which are as heavily loaded with priticiples as the organisation of the
body is adapted for ; and among them also, decompositions are always
taking place, and ultimately destructions which perpetually give rise
to the losses experienced.

This is the main positive fact, that is always confirmed by a close
observation of vital phenomena.

Let us now return to the study of the two important principles of
which I spoke above, and which furnish us to some extent with the key

RESULTS OF LIFE 253

to all the phenomena connected with complex bodies. These principles
are as follows :

The first deals with a universal and ever active factor, which more or
less rapidly destroys all existing compounds.

The second concerns a power which is incessantly forming combina-
tions, increasing their complexity and adding new principles to them,
according as the circumstances are favourable.

Now although these two powers are in opposition, they both derive
their origin from laws and forces which are certainly not opposed,
but which work out very different effects on account of the very
different circumstances.

I have already established the fact in several of my works,! that,
by means of nature’s laws and forces, every combination and every
compound substance tends to be destroyed ; and that this tendency
is greater or less, faster or slower in its realisation, in proportion to the
nature, number, proportions, and closeness of combination between the
principles composing it. The reason of this is that some of these
principles in combination have been forced into that condition by
an external force, which modifies them while fixing them; so that
these principles have a constant tendency to liberate themselves; a
tendency to which they give effect, on the advent of any favouring
factor.

Hence, but little attention is necessary to convince us that nature
(the activity of movement established in all parts of our earth) works
unceasingly towards the destruction of all existing compounds, the
liberation of their principles from the combined state by constantly
bringing forward factors which make for such liberation, and the re-
storation of these principles to that state of freedom, in which they
recover their special faculties and which they tend to preserve for
ever; this is the first of the two doctrines enunciated above.

But I have shown at the same time that there also exists in nature
a peculiar, powerful, and ever active cause, which has the faculty of
forming combinations, of increasing and varying them, and which
incessantly tends to add to them new principles. Now this powerful
cause, which is comprised by the second of the two doctrines cited,
resides in the organic activityf living bodies, where it is always
forming combinations that would never have existed without it.

This special cause is not found in any laws adapted to living bodies,
and opposite to those which regulate other bodies; but it takes its
origin in an order of things essential to the existence of life, and
especially in a force which results from the exciting cause of organic
movements. Hence the special cause, which builds up the complex

1 Mémoires de Physique et d’ Histoire naturelle, p. 88; Hydrogéologie, p. 98 et seq.

254 ZOOLOGICAL PHILOSOPHY

substances of living bodies, is due to the sole condition capable of
giving it existence.

In order to be understood, I should mention that two hypotheses
have been tried with a view of explaining all the facts bearing on
existing compounds and their transformations, and on the ele-
mentary combinations that we can ourselves form, break up and
then re-establish.

The one generally received is the hypothesis of affinities: it is
well known.

The other, which is my own special theory, rests on the assumption
that no simple substance whatever can have a tendency of its own
to combine with any other, that the affinities between certain substances
should not be regarded as forces but as harmonies which allow of the
combination of these substances, and lastly, that they can never
combine except when constrained by a force external to themselves,
and then only when their affinities or harmonies permit of it.

According to the received hypothesis of affinities, to which chemists
attribute active special forces, the whole environment of living bodies
tends to their destruction ; so that unless these bodies possessed within
them a principle of reaction, they would soon succumb to the action of
surrounding substances. For this reason men have been unwilling
to admit the fact that there exists an exciting force of movements
in the environment of every body, living or inanimate ; and that among
the former it succeeds in setting up the phenomena which they present,
whereas among the latter it brings about a series of changes permitted
by the affinities and finally destroys all existing combinations. The
supposition is preferred that life only maintains and develops that series
of phenomena found in living bodies, because these bodies were sub-
jected to laws that were altogether peculiar to them.

It will no doubt be recognised some day that affinities are not forces,
but that they are harmonies or kinds of relationships between certain
substances, which enable them to enter into a more or less close com-
bination through the agency of a general force outside themselves
which constrains them to it. Now since the affinities vary between
different substances, those substances which displace others from
their combinations only do so because they have a greater affinity
with certain of the principles in those combinations; they are
assisted in this act by that general exciting force of movements
and by that which works for the approximation and union of all
bodies.

As to life, all that ensues from it during its residence in a body results,
on the one hand, from a tendency of the constituent elements of com-
pounds to free themselves from their state of combination, especially

RESULTS OF LIFE 255

those which have been forced into it, and, on the other hand, from the
results of the exciting force of movements. It is indeed easily per-
ceived that in an organised body, this force regulates its activity in
all the organs of the body, that it preserves harmony in its activities
through the connection of these organs, that so long as they maintain
their integrity it everywhere makes good the wastage wrought by the
first cause, that it profits by the changes taking place in the compound
moving fluids to appropriate from these fluids the assimilated substances
which they carry and to fix them in their right positions, lastly, that
by this order of things it always conduces to the preservation of life.
This same force also conduces to growth of the parts in a living body ;
but this growth soon comes to an end in almost every part, for a special
reason which I shall state in its proper place ; and it then endows the
body with the faculty of reproducing itself.

Let me repeat then that this singular force, which is derived from the
exciting cause of organic movements, and which in organised bodies
brings about the existence of life and produces so many wonderful
phenomena, is not the result of any special laws but of certain con-
ditions and of a certain order of things and acts which give it the power
of producing such effects. Now among the effects to which this force
gives rise in living bodies, we must include that of building up diverse
combinations, of making them more complex, of loading them with
such principles as can be forced into combination, and of incessantly
creating substances which, but for it and but for the combination of
circumstances in which it works, would never have existed in
nature. /

It is true that the trend of arguments, generally received by the
physiologists, physicists and chemists of our century, is very different
from that of the principles which I have set forth and developed
elsewhere.! It is however not my purpose to endeavour to change
this tendency of thought, and thus convert my contemporaries; but
I was obliged to state here the two doctrines concerned, because they
complete the explanation that I have given of the phenomena of life,
and because I am convinced of their accuracy, and know that without
them we shall always have to imagine for living bodies laws contrary
to those which regulate the phenomena of other bodies.

It appears to me beyond question, that if we enquire sufficiently
as to what happens in the objects concerned, we shall soon be con-
vinced :

That the organic functions of all living beings confer on them the
faculty, in some cases (plants) of forming direct combinations, that is,
of uniting free elements after modification, and of immediately pro-

1 Hydrogéologie, p. 105.

256 ZOOLOGICAL PHILOSOPHY

ducing compounds; in other cases (animals) of modifying these
compounds and altering their character by the addition of new
principles to a remarkable extent.

I must then again impress the fact that living bodies form for them-
selves, by the activity of their organs, the substance of their bodies
and the various secretions of their organs; and that they neither
find this substance ready formed in nature, nor the secretions, which
come purely from them alone.

It is by means of food, which animals and plants are obliged to use
for the preservation of their life, that the organs of these living bodies
work their effects. These effects consist in a modification of the food
resulting in the formation of special substances, which would never
have existed without this cause, and in building up by perpetual
alterations and renewals of these substances, the entire body which
they constitute, as also its products.

Whereas all animal and vegetable substances are composed of prin-
ciples in very complex combinations, and many of which have been
forced into these combinations, man has no power to do the like;
all that he can do is to decompose, alter, or destroy them, or to
convert them into various special combinations, always less and less
complex. It is only the movements of life that can produce these
substances.

Thus plants, which have no intestinal canal nor any other organ for
digestion, and which consequently use for food only fluid substances
or substances whose molecules are not aggregated (such as water,
atmospheric air, caloric, light, and the gases that they absorb), yet
form out of such material, by means of their organic activity, all the
juices that are proper to them, and all the substances of which their
body is composed ; that is, they form for themselves the mucilages,
gums, resins, sugar, essential salts, fixed and volatile oils, feculae,
gluten, extractive and woody matter; all of them substances arising
direct from immediate combinations, and none of which can ever be
formed by art.

Plants certainly cannot take from the soil by means of their roots ....

the substances which I have just named: they are not there, and those
which are there are in a more or less advanced condition of degra-
dation or decomposition ; lastly, if there were any in a state of com-
plete integrity, plants would not be able to make use of them without
having previously decomposed them.

Plants then have formed directly the substances to which I refer ;
but when they are outside plants, these substances can only be useful
as manure; that is to say, only after being altered in nature, broken
up, and having undergone the necessary degradation to fit them for

RESULTS OF LIFE 257

manure, the essential function of which is to keep up a favourable
moisture round about the roots of plants.

Animals cannot build up direct combinations like plants: hence
they use compound substances for food; they have to carry out
digestion (at least nearly all of them), and they consequently have
organs for this purpose.

But they also form for themselves their own substance and secre-
tions : now for this purpose they are not obliged to use as food either
these secretions, or a substance like their own: out of grass or hay
the horse forms by the action of its organs its blood and other humours,
its flesh and its muscles, the substances of its cellular tissue, vessels
and glands, its tendons, cartilages and bones, and lastly the horny
matter of its hoofs, and the hair of its body, tail and mane.

It is then in forming their own substance and secretions, that animals
build up to a high degree the combinations that they produce, and give
to these combinations the astonishing number of principles that enter
into animal substances.

Let us now remark that the substance of living bodies, as also the
secretions which they produce by their organic activity, vary in
quality according to the following circumstances :

1. The actual nature of the living being which forms them: thus
vegetable productions are in general different from animal productions ;
and among the latter the productions of vertebrates are in general
different from those of invertebrates.

2. The nature of the organ which separates them from other sub-
stances after their formation: the secretions of the liver are not the
same as those of the kidneys, etc.

3. The vigour or debility of the organs of the living being and of
their action: the secretions of a young plant are not the same as those
of the same plant when it is very old; nor are those of a child the
same as those of a grown man.

4, The integrity of the organic functions : the secretions of a healthy
man cannot be the same as those of a diseased man.

5. The abundance of caloric which is continually formed on the sur-
face of the earth although in quantities varying in different climates,
and which favours the organic activity of the living bodies which it
penetrates ; or the rarity of caloric, as a result of which this organic
activity is greatly enfeebled: as a matter of fact in hot climates the
secretions formed by living bodies are different from those that they
produce in cold climates ; and in cold climates again the secretions
of these bodies differ among themselves, according as they are formed in
the hot season or during the rigours of winter.

T shall not here further emphasise the fact that the organic action
R

258 ZOOLOGICAL PHILOSOPHY

of living bodies incessantly builds up combinations, which would not
have arisen without it: but I shall again repeat that if it is true, as
can hardly be doubted, that all compound mineral substances such as
earths and rocks, and all metallic, sulphurous, bituminous, saline
substances, etc., arise from the remains of living bodies,—remains
which have undergone successive decompositions on and under the
surface of the earth and waters; it is equally true to say that living
bodies are the original source from which all known compound sub-
stances have arisen. (See my Hydrogéologie, p. 91 et seq.)

It would thus be a vain task to try to make a rich and varied collection
of minerals in certain regions of the earth, such as the vast deserts
of Africa, where for many centuries there have been no plants and only
a few stray animals.

Now that I have shown that living bodies form their own substance
for themselves as well as the various matters that they secrete, I must
say a word about the faculty of feeding and growing which all these
bodies possess within certain limits, since these faculties again are
the result of vital activities,

CHAPTER VIII.
OF THE FACULTIES COMMON TO ALL LIVING BODIES.

Ir is a well-known and established fact that living bodies have faculties
which are common to all of them and belong to them as a consequence
of life itself.

But I think that little attention has been paid to the fact that those
faculties common to all living bodies do not need any special organs
as a basis, whereas those faculties which are peculiar to certain bodies
only, are necessarily based on some special organ capable of producing
them.

Doubtless no vital faculty can exist in a body without organisa-
tion ; and organisation is itself simply a collection of organs in com-
bination. But those organs, whose combination is necessary for the
existence of life, are not peculiar to any one portion of the body they
compose ; they are, on the contrary, distributed throughout this body,
and they bring life to every part of it, as also the essential faculties
which spring from life. Hence the faculties common to all living
bodies are exclusively due to the same causes which lead to the exist-
ence of life.

The case is different with the special organs that give rise to the
faculties belonging only to certain living bodies : life can exist without
them; but when nature achieved their creation, the chief of them
have so close a connection with the order of things existing in the body,
that they then become necessary for the maintenance of life in that
body.

Thus it is only in the simplest organisations that life can exist with-
out special organs; these organisations are then incapable of pro-
ducing any other faculty than those common to all living bodies.

On starting an investigation as to the essential properties of life,
we must distinguish the phenomena belonging to all bodies which
possess life, from those which are peculiar to some of those bodies :
and since the phenomena presented by living bodies are a measure of

260 ZOOLOGICAL PHILOSOPHY

their faculties, we may usefully adopt this method of distinguishing
the faculties common to all from those that are peculiar to some.

The faculties common to all living bodies,—that is, the only faculties
that they have in common, are as follows :

1. Feeding, by means of incorporating food substances; the con-
tinual assimilation of a part of these substances ; lastly, the fixation
of the assimilated substances, which repair at first plentifully and after-
wards less completely the loss of substance which these bodies undergo
at all periods of their active life.

2. Building up their bodies ; that is to say, forming for themselves
the substances of which they are made by means of materials which
only contain the principles of these substances, and which are mainly
supplied in the form of food.

3. Developing and growing, up to a certain limit which varies
according to the species ; this growth being more than a mere aggrega-
tion of matter added externally.

4, Lastly, reproducing themselves, that is producing other bodies
which are exactly like them.

Whether a living body, animal or plant, has a very simple or very
complex organisation, whatever may be its class, order, etc., it
necessarily possesses the four faculties enumerated above. Now since
these faculties are the only ones common to all living bodies, they
may be regarded as constituting the essential phenomena presented
by these bodies.

Let us now enquire how much we can ascertain with regard to nature’s
methods for the production of these phenomena.

If nature only creates life directly in bodies which did not previously
possess it ; if she only creates the simplest type of organisation (Chapter
VI.); lastly, if she only maintains organic movements by means of
an exciting cause of these movements (Chapter III.); we may ask
how the movements kept up in an organised body, can give rise to
the nutrition, growth and reproduction of that body, and at the
same time confer on it the faculty of forming its own substance
for itself.

I have no desire to provide an explanation of all the details of this
wonderful work of nature; for such an attempt would expose us to
the probability of error and might discredit the main truths yielded
by observation. I believe that the question propounded above is
sufficiently answered by the following observations and reflections :

The activities of life, or the organic movements, necessarily produce
alterations of state both in the containing parts and in the contained
fluids of a living body, as a result of affinities and of the decomposition
of principles previously in combination: such decomposition being

THE COMMON FACULTIES 261

due to these organic movements and the penetration of subtle fluids.
Now from these alterations which give rise to various new combina-
tions, there result different kinds of substances; some of which are
dissipated or evacuated as the vital movement continues, while
others are merely separated from parts, which do not thereby
suffer any fundamental change. Among these separated substances
some are deposited in particular parts of the body or are reabsorbed
through canals and serve certain purposes; such are lymph, bile,
saliva, the generative substance, etc.; but the rest acquire a special
character, and are carried off by the general force which animates
all the organs and drives all the functions, and are then fixed in similar
or corresponding parts, either solid or supple and containing. They
make good the wastage of these and enlarge their size, in proportion
to their abundance and the possibilities of the case.

It is therefore by means of these assimilated substances, which have
become adapted to particular regions, that nutrition is carried out.
Nutrition, the first of the faculties of life, is thus essentially a mere
restoration of the losses undergone ; it is merely a means for reversing
the tendency towards decomposition, which all compound substances
are liable to. Now this reformation is achieved by means of a force
which conveys the newly assimilated substances to their destined
positions, and not by any special law, as I have already endeavoured
to show. In fact, each kind of part in the animal body appropriates
and stows away, by a true affinity, the assimilated molecules capable
of being incorporated with #

But nutrition is more or less abundant according to the state of
organisation of the individual.

During youth, nutrition is exceedingly abundant in all organised
living bodies ; and it then does more than repair losses, for it adds to
the size of the parts.

Indeed in a living body all the newly formed containing parts are
extremely supple and of weak consistency, as a result of the causes of
their formation. Nutrition under these conditions is carried on so
easily as to be excessive. Not only does it completely make good the
losses ; but by an internal fixation of assimilated particles, it adds
successively to the size of the parts and gives rise to growth of the
young individual.

But after a certain period, varying with the organisation in each
race, the parts, including even the most supple parts of this individual,
lose much of their suppleness and vital orgasm; and their faculty
of nutrition is then proportionally diminished.

Nutrition in this case is limited to the restoration of losses; the body |
maintains a stationary condition for some time; it is indeed in the

262 ZOOLOGICAL PHILOSOPHY

height of its vigour, but it grows no more. Now the surplus of the
parts prepared, being of no further use for nutrition or growth, is
destined by nature to another purpose, and becomes the source
through which she arranges for the reproduction of new individuals
like the others.

Hence reproduction, the third of the vital faculties, derives its
origin like growth from nutrition, or rather from the materials pre-
pared by nutrition. But this faculty of reproduction only acquires
intensity when the faculty of growth begins to decline: this fact is
confirmed by common observation, since the reproductive organs
(sexual parts) both in plants and animals only begin to develop when
the growth of the individual is nearing an end.

I should add that, since the materials prepared for nutrition are
assimilated particles of as many different kinds as there are parts in the
body, the union of these diverse particles left over from nutrition and
growth constitute the elements of a very small organised body, exactly
similar to that from which it sprang.

In a very simple living body with no special organs, when nutrition
has attained the limit of growth for the individual, the excess is then
diverted to the formation and development of a part which thereupon
separates from the organism and continues to live and grow, constitut-
ing a new individual like the old one. Such indeed is the method of
reproduction by fission and by gemmae or buds, which occurs without
any need for a special organ.

Ultimately after a still longer period—a period that varies even in
the individuals of one race according to their habits and climate—
the most supple parts of the living body acquire so great a rigidity and
suffer so great a diminution of orgasm, that nutrition thereafter repairs
the losses only incompletely. The body then gradually wastes away ;
and if some slight accident or some internal disorder, that the diminished
vital forces cannot cope with, do not put an end to the individual,
its increasing old age is necessarily terminated by a natural death
which supervenes when the existing state of things no longer permits
of the performance of organic movements]

This rigidity of the soft parts, which increases during life, has been
denied on the ground that after death the heart and other soft parts
of an old man shrink more and become more flaccid than in a child or
young man who has just died. But the fact has been overlooked that
orgasm and irritability which still continue sometime after death,
lasts longer and is more intense in young individuals than in the old,
among whom these faculties are greatly weakened and are extinguished
almost simultaneously with life. This cause alone gives rise to the
observed effects.

THE COMMON FACULTIES 263

This is the place to show that nutrition cannot be carried out, with-
out slowly increasing the consistency of the parts restored.

All living bodies, and especially those in which internal heat is
developed and maintained throughout life, continually have a part
of their humours and even of their bodily tissue in a real state of de-
composition ; hence they are incessantly undergoing real losses, and
it cannot be doubted that it is to the effects of degradations of the
solids and fluids of living bodies, that the various substances formed
in them are due. Of these, some are secreted and deposited or
retained, while others are evacuated by various routes.

These losses would soon lead to degeneration of the organs and
fluids of the individual, if nature had not given to living bodies a faculty
essential to their preservation: that of making good the losses. Now
as a result of these continuous losses and repairs, it follows that after
a certain period the body cannot have in its parts any of the molecules
which originally composed it.

It is known that the repairs are effected by means of nutrition ;
but they are more or less complete according to the age and state of
the organs of the individual, as I remarked above.

Besides this inequality in the relation of losses to restorations accord-
ing to the ages of the individuals, there exists another which is very
important, and which yet appears to have received no attention. It
concerns the constant inequality between the substances assimilated
and fixed by nutrition, and those which are liberated as a result of
the continual degradation above mentioned.

T have shown in my Recherches (vol. ii., p. 202) that the cause of
this inequality is as follows :

Assimilation (the nutrition resulting from it) always provides more
solid principles or substances, than are removed or dissipated by the
losses.

The successive losses and repairs, which never cease in living bodies,
have long been recognised ; and yet it is only during the last few years
that the conviction has grown that these losses are due to degradations
continually being undergone by the fluids and even the solids of the
body. Some people still have a difficulty in believing that the forma-
tion of the various secretions is the result of these degradations and
changes or combinations always going on in the essential fluids of living
bodies: but this fact I have already established.*

Now if it is true, on the one hand, that the losses of the body consist
less of solid, earthy and concrete substances than of fluid substances
and especially volatile substances ; and if, on the other hand, it is also

1 Mémotre de Physique et @Histoire naturelle, pp. 260-263; and Hydrogéologie,
pp. 112-116.

264 ZOOLOGICAL PHILOSOPHY

true that nutrition gradually provides the parts with more solid sub-
stances than fluid and volatile substances ; it will follow that the organs
will gradually acquire increasing rigidity, making them less fitted for
carrying out their functions, as is actually the case.

It is far from being true that the whole environment of living bodies
tends to their destruction, as is repeated in all modern physiological
works. JI am convinced that, on the contrary, they only maintain
their existence by means of external influences, and that the cause
leading to the death of the individuals is within them and not without
them.

Indeed I see clearly that this cause is due to the difference between
the substances assimilated and fixed by nutrition, and those thrown
out or dissipated by the continual wastage to which living bodies are
subject, since volatile substances are always the first and the easiest
to be freed from their state of combination.

I see, in short, that. this cause, which brings about old age, decrepi-
tude, and finally death, resides in the progressive hardening of the
organs ; a hardening which gradually produces rigidity, and which
in animals reduces to a corresponding extent the intensity of orgasm
and irritability, stiffens and narrows the vessels, and imperceptibly
destroys the action of the fluids on the solids, and vice versd. Lastly,
it disturbs the order and state of things necessary to life, which
ultimately is entirely extinguished.

I believe I have proved that the faculties common to all living
bodies are those of feeding ; of building up for themselves the various
substances of which their bodies are composed ; of developing and
growing up to a certain limit that varies in each case ; of propagating,
that is, of reproducing other individuals like themselves ; lastly, of
losing their life by a cause that is within themselves.

I shall now examine the faculties that are peculiar to some living
bodies ; and shall confine myself, as I have just done, to an exposition
of the general facts without any attempt to enter into the details that
may be found in works on physiology.

CHAPTER IX.
OF THE FACULTIES PECULIAR TO CERTAIN LIVING BODIES.

Just as there are faculties common to all bodies that enjoy life, as I
have shown in the preceding chapter, so too we find in certain living
bodies faculties peculiar to themselves and not shared by the rest.

We are now confronted with a circumstance of capital importance,
to which the utmost attention should be paid if further progress is to be
made in natural science ; it is this.

It is quite clear that both animal and vegetable organisation have,
as a result of the power of life, worked out their own advancing com-
plexity, beginning from that which was the simplest and going on to
that which presents the highest complexity, the greatest number of
organs, and the most numerous faculties; it is also quite clear that
every special organ and the faculty based on it, once obtained, must
continue to exist in all living bodies which come after those which
possess it in the natural order, unless some abortion causes its dis-
appearance. But before the animal or plant which was the first to
obtain this organ, it would be vain to seek either the organ or its faculty
among simpler and less perfect living bodies; for neither the organ
nor its faculty would be found. If this were otherwise, then all known
faculties would be common to all living bodies ; every organ would be
present in each one of these bodies, and there would be no progress
in complexity of organisation.

It is, on the contrary, well established that organisation exhibits an
obvious progress in complexity, and that all living bodies do not possess
the same organs. Now I propose to show that, from want of sufficient
study of nature’s order in her productions and of the remarkable
progress that occurs in complexity of organisation, naturalists have
made altogether fruitless attempts to trace in certain classes, both of
animals and plants, organs and faculties which could not possibly be
there.

We must then first determine the point in the natural order, say of

266 ZOOLOGICAL PHILOSOPHY

animals, at which some organ began to exist, in order to save ourselves
from seeking that organ in much earlier points of the order. Other-
wise science would be retarded by our hypothetically referring to parts
with which we are little acquainted, faculties which they could not
have.

Thus several botanists have made useless attempts to find sexual
reproduction in agamous plants (the cryptogams of Linneus), and
others have thought that they had found, in what are called the tracheae
of plants, a special organ for respiration. In the same way several
zoologists have wanted to prove the existence of lungs in certain
molluscs, a skeleton in star-fishes, gills in jelly-fishes : lastly, a learned
society has this year set, as a prize subject, the question whether there
exists a circulation in radiarians.

Such attempts prove indeed how little we are yet impressed by the
natural order of animals, by the progress in the complexity of their
organisation, and by the general principles which result from the
knowledge of that order. In a matter of organisation, moreover,
when the objects dealt with are very small and unknown, people
think they actually see what they want to see, and they thus find
whatever they want: as, for instance, already happens in the arbitrary
reference of faculties to parts of whose nature and function we are
ignorant.

Let us now enquire what are the chief faculties peculiar to certain
living bodies and let us see at what point in the natural order of animals
and plants each of these faculties, with its attached organ, began to
exist.

The chief of the faculties peculiar to certain living bodies, and con-
sequently not shared by the rest, are as follows :

(1) The digestion of food ;.:

(2) Respiration by a special organ ; ~

(3) The performance of acts and movements by muscular organs ;
(4) Feeling, or the capacity for experiencing sensations ;

(5) Multiplication by sexual reproduction ;

(6) A circulation of their essential fluids ;

(7) The possession of a certain degree of intelligence.

There are many other special faculties, of which examples are found
among living bodies and especially among animals; but I shall con-
fine myself to the consideration of these few, because they are the most
important, and because what I have to say about them is sufficient
for my purpose.

The faculties which are not common to all living bodies are based
in every case without exception on special organs which cause them,
and hence on organs that are not possessed by all living bodies; and

THE PECULIAR FACULTIES 267

the acts which make up these faculties are functions of those
organs.

I shall consequently not enquire whether the functions of such
organs are being performed uninterruptedly or only intermittently,
nor shall I consider whether these functions subserve the preservation
of the individual or of the species, nor whether they act as links between
the individual and surrounding bodies that are foreign to it. I shall
merely state briefly my views on the organic functions which give rise
to the seven faculties named above. I shall prove that each of them
is limited to particular animals, and cannot be common to the entire
animal kingdom.

Digestion. This is the first of the special faculties, and is possessed
by the greater number of animals. It is at the same time an organic
function carried on in a central cavity of the individual; a cavity
which, although varying in shape in different races, is generally like
a tube or canal, which is sometimes open at one of its extremities
only, and sometimes at both.

This function, which acts only on compound substances, called
alimentary substances and not a part of the individual, consists firstly
in destroying the aggregation of the component molecules of the ali-
mentary substances, introduced into the digestive cavity ; and then of
changing the state and properties of these molecules, in such a way
that part of them become fitted for the formation of chyle, and for
renewing or restoring the essential fluid of the individual.

Various liquids, delivered into the digestive organ by the excretory
ducts of various glands in the neighbourhood, liquids which are chiefly
poured forth when digestion has to be performed, facilitate in the first
place the dissolution, that is to say, the destruction of the aggregation
of the molecules of the food substances ; and then contribute to bring-
ing about the changes which these molecules have to undergo. There-
after, such of the molecules as have been adequately altered and pre-
pared, are suspended in the digestive and other liquids, and penetrate
through the absorbent pores of the walls of the alimentary or intestinal
tube into the lacteals or subordinate canals, and there constitute that
precious fluid which is destined to restore the essential fluid of the
individual.

All the molecules or coarser parts, which are of no use for the
formation of chyle, are afterwards rejected from the alimentary
cavity.

Thus the special organ of digestion is the alimentary cavity, whose
anterior opening by which food is introduced bears the name of mouth,
while that of the posterior extremity, when there is one, is called the
anus.

268 ZOOLOGICAL PHILOSOPHY

It follows from the foregoing that no living body, which lacks an
alimentary cavity, ever has any digestion to perform; and since all
digestion works on compound substances and breaks down the aggre-
gation of the food molecules into solid masses, it results that such
living bodies as have no digestion, can only feed on fluid, liquid or
gaseous material.

This applies to all plants; they have no digestive organ, nor as a
matter of fact do they have any digestion to perform.

Most animals, on the contrary, have a special organ for digestion ;
but this faculty is not, as has been alleged, common to all animals,
and cannot be cited as one of the characters of animality. The
infusorians indeed do not possess it; and we should vainly seek an
alimentary cavity in a monas, volvox, proteus, etc.; there is none to
be found.

The faculty of digesting is then only common to the greater number
of animals.

Respiration. This is the second of the faculties peculiar to certain
animals, for it is less general than digestion ; its function is carried
on in a distinct special organ, which varies greatly in different races
and different requirements.

This function consists in a restoration of the essential fluid, which
in these individuals becomes too rapidly degraded; a restoration
for which the slower alternative of food is not sufficient. The restora-
tion in question is effected in the respiratory organ by means of the
contact of a special fluid that is breathed in, and decomposes and
communicates restorative principles to the individual’s essential fluid.

In those animals whose essential fluid is quite simple and only moves
slowly, the degradation of this fluid is also slow, and then the method
of food alone suffices for the restorations ; the fluids capable of provid-
ing certain necessary restorative principles penetrate into the individual
by this route and also by absorption ; and their influence is sufficient
without any need for a special organ. Hence the faculty of breathing
by a special organ is not necessary to these living bodies. This is the
case with all plants and also with a considerable number of animals,
such as those that compose the class of infusorians and that of polyps.

The faculty of breathing then should only be attributed to those
living bodies that possess a special organ for the purpose; for if
those which have no such organ require for their essential fluid any
influence analogous to respiration (which is very doubtful), they
apparently derive it through some slow general route like that of
food or of absorption through external pores, and not by a special
organ. Hence these living bodies do not breathe.

The most important of the restorative principles furnished by the

THE PECULIAR FACULTIES 269

fluid breathed to the animal’s essential fluid, appears to be oxygen. |
It is liberated from the respired fluid, combines with the essential fluid
of the animal, and restores to the latter qualities which it had lost.

There are, as we know, two different respiratory fluids which pro-
vide oxygen for breathing. These fluids are air and water; in general
they are the media in which living bodies are immersed, or by which
they are surrounded.

Water indeed is the respiratory fluid of many animals which live
permanently in its depths. It is believed that this fluid does not de-
compose when giving up oxygen; but that it always has a certain
amount of air mixed up with it, and that it is this air which is decom-
posed in the act of breathing, and thus provides oxygen for the essential
fluid of the animal. This is the way in which fishes and many aquatic
animals breathe; but this respiration is less active, and yields its
restorative principles more slowly, than that which takes place in free
alr.

Free atmospheric air is the second respiratory fluid, and that which
is breathed by a large number of animals which live permanently
in it or within reach of it: it is promptly decomposed in the act of
breathing, and thereupon yields up its oxygen to the essential fluid of
the animal. This kind of breathing, which is characteristic of the
most perfect animals and many others, is the most active: and its
_ activity is proportional to the development of the organ in which it is
' carried out.

It is not enough to discuss the existence of a special organ for breath-
ing; we must pay attention to the character of this organ, in order to
judge of the height of the animal’s development, by means of the faster
or slower recurrence of the necessity for restoring its essential fluid.

In proportion as the essential fluid of animals becomes more complex
and animalised, the degradations which it suffers during life are greater
and more rapid, and the restorations required gradually develop in
proportion to the changes experienced.

In the simplest and most imperfect animals, such as the infusorians
and polyps, the essential fluid is so elementary, so little animalised,
and becomes so slowly degraded, that the restorations of the food
are sufficient. But soon afterwards, nature begins to require a new
method for preserving the essential fluid of animals in a proper con-
dition. It is then that she creates respiration ; but at first she only
sets up a very weak and inactive respiratory system,—that namely
furnished by water, which has itself to convey its influence to every
part of the animal.

Nature subsequently varies the type of respiration in accordance
with the progressive increase of the requirement. She makes this

270 ZOOLOGICAL PHILOSOPHY

function ever more active, and ultimately endows it with the highest
energy.

Since water-born respiration is the least active, let us examine it
first. We shall find that water-breathing organs are of two kinds,
which again differ as regards activity ; we shall afterwards note the
same thing in the case of air-breathing organs.

Water-breathing organs are divided into water-bearing tracheae
and gills, just as air-breathing organs are divided into air-breathing
tracheae and lungs. It is indeed quite obvious that water-bearing
tracheae are to gills what air-breathing tracheae are to lungs. (Systéme
des Animaux sans Vertebrés, p. 47.)

Water-bearing tracheae consist of a certain number of vessels which
ramify and spread in the animal’s interior, and open on the outside by a
number of small tubes which absorb the water: by this means water
continually enters by these tubes, undergoes a kind of circulation all
through the animal’s interior, carries the respiratory influence there,.
and appears to issue forth again through the alimentary cavity.

These water-bearing tracheae constitute the most imperfect, the least
active, and the earliest respiratory organ created by nature; that
moreover which appertains to animals whose organisation is so low
that their essential fluid still has no circulation. Striking examples
are found in the radiarians, such as the sea-urchins, star-fishes,.
jelly-fishes, etc.

Gills are also a water-bearing organ, which may moreover become
accustomed to breathing free air ; but this respiratory organ is always
isolated either within or without the animal, and only occurs in animals.
whose organisation is sufficiently advanced to have a nervous and a
circulatory system.

Trying to find gills in radiarians and worms merely because they
breathe water, is like trying to find lungs in insects because they breathe
air. The air-breathing tracheae of insects constitute therefore the most
imperfect of the air-breathing organs; they extend throughout all
parts of the animal, carrying with them the valuable influence of
respiration ; whereas lungs, like gills, are isolated respiratory organs
which at their highest development are more active than any other.

For the thorough appreciation of the foregoing doctrine, some
attention must be given to the two following principles.

Respiration, in animals which have no circulation of their essential
fluid, is carried out slowly without any perceptible movement, and in a
system of organs which is distributed to almost every part of the ani-
mal’s body. In this type of respiration, the respired fluid itself conveys.
its influence to the parts ; the animal’s essential fluid goes nowhere in
advance of it. Such is the respiration of the radiarians and worms,

THE PECULIAR FACULTIES 271

in which water is the respired fluid; and such again is the respiration
of the insects and arachnids, in which the respired fluid is atmospheric
air.

But the respiration of animals, which have a general circulation, is
of a very different type; it is effected more rapidly, it gives rise to
special movements which in the highest animals become regular,
and it is carried out in a simple, double or compound organ that is
isolated and does not spread throughout the body. The essential fluid
or blood of the animal then goes beyond the respired fluid, which only
penetrates as far as the respiratory organ: the blood therefore has to
undergo in addition to the general circulation a special circulation that
I may call respiratory. Now since it is sometimes only a part of the
blood that travels to the organ of respiration before being despatched
throughout the animal’s body, and since in other cases the whole
of the blood passes through this organ before its journey in the body,
the respiratory circulation is accordingly said to be either complete
or incomplete.

Now that I have shown that there are two quite different types of
respiration in those animals which have a distinct respiratory organ,
I think that the name of general respiration may be given to the first
type, such as that of the radiarians, worms, and insects ; and that the
name of local respiration should be applied to the second type, which
belongs to animals more perfect than insects, including perhaps the
limited respiration of arachnids.

The faculty of breathing is thus peculiar to certain animals; and
the nature of the organ by which they breathe is so well adapted
to their needs and to the stage of development of their organisation,
that it would be very unreasonable to expect to find in imperfect
animals the respiratory organ of more perfect animals.

The Muscular System. This confers upon the animals which possess
it, the faculty of performing actions and movements, and of controlling
these activities either by the inclination due to habit, or by the inner
feeling, or, lastly, by the operations of the intellect.

Since it is admitted that no muscular activity can occur without
nervous influence, it follows that the muscular system must have
been formed after the rise of the nervous system, at all events in its
first outlines. Now if it is true that that function of the nervous
system, of which the purpose is to dispatch the subtle fluid of the
nerves to the muscular fibres or bundles and set them in action, is
much simpler than that other function of producing feeling (as I
hope to prove), it must follow that as soon as the nervous system had
reached the stage of a medullary mass in which terminate the various
nerves, or as soon as it was provided with separate ganglia sending

272 ZOOLOGICAL PHILOSOPHY

out nervous threads to various parts, it was henceforth capable of
giving rise to muscular excitation without however being able to
produce the phenomenon of feeling.

From these principles I believe I am justified in drawing the con-
clusion that the formation of the muscular system is subsequent to
that of the earliest stages of the nervous system, but that the faculty
of carrying out actions and movements by means of muscular organs
is in animals prior to that of experiencing sensations.

Now since the origin of the nervous system is anterior to that of
the muscular system, and since its functional existence only dates
from the time when it was composed of a main medullary mass from
which issue nervous threads, and since no such system of organs can
exist in animals with organisations as simple as the infusorians or most
polyps, it clearly follows that the muscular system is peculiar to
certain animals, that it is not possessed by all, and yet that the faculty
of acting and moving by muscular organs exists in a greater number
of animals than does the faculty of feeling.

For deciding as to the presence of a muscular system in animals
in doubtful cases, it is important to consider whether there are in
these animals any points of attachment for muscular fibres, of a
certain strength or firmness; for, being constantly under stress, these
points of attachment become gradually stronger.

It is certain that the muscular system exists in insects and all animals
of subsequent classes; but has nature established this system in
animals that are more imperfect than insects? If she has, it can
hardly be (as far as the radiarians are concerned) anywhere but in
the echinoderms and fistulides: it cannot be in the soft radiarians :
perhaps there are rudiments of it in the sea-anemones ; the coriaceous
substance of their bodies makes this belief plausible, but its presence
cannot be supposed in the hydra nor in most other polyps, and still
less in the infusorians.

It is possible that, when nature set out to establish some special
system of organs, she selected conditions favourable to their creation ;
and that consequently there are several interruptions in our scale of
animals near the point at which the system is established, and due
to the existence of cases in which its formation was impracticable.

Attentive observation of the operations of nature in the light of these
principles will doubtless teach us many things that we do not yet
know on these interesting subjects, and may perhaps disclose the fact
that although nature was able to begin the muscular system with the
radiarians, yet the worms which follow them are still devoid of it.

If this principle is well-founded, it will confirm what I have already
urged with regard to worms, viz.: that they appear to constitute a

THE PECULIAR FACULTIES 273

special branch of the animal chain that has started afresh by spon-
taneous generation (Chapter VI., p. 247).

The plainly marked and well-known muscular system in insects
is everywhere found afterwards in animals of the following classes.

Feeling is a faculty which must take the fourth rank among those
that are not common to all living bodies; for the faculty of feeling
appears to be still less general than those of muscular movement,
respiration and digestion.

We shall see farther on that feeling is only an effect; that is to
say, the result of an organic act and not a faculty inherent in any of
the substances, which enter into the composition of a body that can
experience it.

None of our humours and none of our organs, not even our nerves,
have the faculty of feeling. It is only by an illusion that we attribute
the singular effect, that we call sensation or feeling, to a definite part
of our body; none of the substances composing this part does or can
really feel. But the very remarkable effect called sensation or, when
more intense, pain, is the product of the function of a very special
system of organs, the activity of which is dependent on the circum-
stances which provoke it.

I hope to prove that this effect, constituting feeling or sensation,
is an undoubted result of an affective cause which excites action in
any part of the special system of organs adapted to it; this action
by a repercussion, that is swifter than light and affects every part of
the system, delivers its general effect in the common nucleus of sensation
and the sensation is then propagated to the point of the body that was
affected.

I shall endeavour to describe in the third part of this work, the
wonderful mechanism of the effect which we call feeling: I shall here
merely remark that the special system of organs for producing such an
effect, is known under the name of the nervous system ; and I may add
that this system only acquires the faculty of giving rise to feeling,
when it is so far developed as to have numerous nerves meeting in a
common nucleus or centre of communication.

It follows from these principles that no animal, which does not possess
a nervous system of the kind named, can experience the remarkable
effect in question, nor consequently can it have the faculty of feeling.
A fortiori, any animal which does not have nerves, terminating in a
main medullary mass, must be destitute of feeling.

The faculty of feeling therefore cannot be common to all living
bodies, since it is universally admitted that plants have no nerves and
can therefore have no feeling. It has however been held that this

faculty is common to all animals; this is clearly a mistake, for all
s

274 ZOOLOGICAL PHILOSOPHY

animals neither have nor can have nerves; moreover, those in which
nerves are just arising, do not yet possess a nervous system that fulfils
the conditions for the production of feeling. It is probable indeed
that, in its origin or primitive imperfection, this system has no other
faculty than that of exciting muscular movement. The faculty of
feeling therefore cannot be common to all animals.

If it is true that every faculty that is limited to certain living
bodies is based upon a special organ, as is everywhere found to be
the case, it must also be true that the faculty of feeling, which is
clearly limited to certain animals, is exclusively the product of a
special organ or system of organs, whose activities produce it.

According to this principle, the nervous system constitutes the special
organ of feeling when it is composed of a single centre of communica-
tion and of nerves terminating it. Now it seems probable that it is
only in the insects that the nervous system attains a development
sufficient for the production of feeling, although still of a vague kind.
The faculty recurs in all animals of later classes in a regular progress
towards perfection.

But in animals less perfect than insects, such as worms and radiarians,
if we do find traces of nerves and separated ganglia, there are strong
reasons for the presumption that these organs are only adapted to the
excitation of muscular movement, the simplest faculty of the nervous
system.

Finally, in animals still more imperfect, such as the majority of
polyps and all the infusorians, it is quite certain that they cannot
possess a nervous system capable of giving them the faculty of
feeling, nor even that of moving by muscles: for them, irritability
alone takes its place.

Thus feeling is not a faculty common to all animals, as has been
generally held.

Sexual Reproduction. This is a special faculty which is in animals
nearly as general as feeling; it results from an organic function, not
essential to life, the purpose of which is to attain the fertilisation of
an embryo which then becomes fitted for the possession of life, and
for constituting after development an individual like that or those
from which it sprang.

This function is performed at particular periods, sometimes regular
and sometimes not, by the co-operation of two systems of organs
called sexual, one being the male organs and the other female.

Sexual reproduction is observed in animals and plants, but it is
limited to particular animals and plants and is not a faculty common
to all these living bodies; nature could not have made it so, as we
shall see.

THE PECULIAR FACULTIES 275

In the production of-living bodies, both animal and plant, nature
was originally obliged to create the simplest organisation in the most
fragile bodies, where it was impossible to establish any special organs.
She soon had to endow these bodies with the faculty of multiplying,
for otherwise she would everywhere have been occupied with creations,
and this is beyond her power. Now since she could not give her
earliest productions the faculty of multiplying by any special system
of organs, she hit upon the plan of giving it through the medium of
growth, which is common to all living bodies. She conferred the faculty
of undergoing divisions, at first of the entire body, and afterwards
of certain projecting portions of the body ; in this way were produced
gemmae and the various reproductive bodies, which are only parts
that grow out, become separated, and continue to live after their
separation, and which need no fertilisation, form no embryo, develop
without the rupture of any membrane, and yet after growth resemble
the individuals from which they spring.

Such is the method employed by nature for the multiplication of
those animals and plants, to which she could not give the complicated
apparatus of sexual reproduction; it would be in vain to seek any
such apparatus in the algae and fungi, or in the infusorians and polyps.

When the male and female organs are united in the same individual,
that individual is said to be hermaphrodite.

In this case a distinction must be drawn between perfect herma-
phroditism, which is sufficient to itself, and that which is imperfect
and not sufficient to itself. Indeed many plants are hermaphrodites,
in which the individual suffices to itself for fertilisation ; but in animals,
which combine the two sexes, it is not yet proved by observation that
the individuals are sufficient to themselves ; and it is known that many
truly hermaphrodite molluscs none the less fertilise one another.
It is true that, among hermaphrodite molluscs, those which have a
bi-valve shell and are fixed, like oysters, must apparently fertilise
themselves : it is however possible that they may fertilise one another
mutually through the medium in which they are immersed. If this
is so, there are among animals only imperfect hermaphrodites ; and
it is known that, among vertebrates, there are not even any true
hermaphrodites at all. Perfect hermaphrodites will thus be confined
to plants.

The character of hermaphroditism consists in the combination of
the two sexes in one individual, but it seems that the monoecious
plants constitute an exception ; for although a monoecious shrub or
tree carries both sexes, its individual flowers are none the less uni-
sexual.

I_may remark in this connection that it is wrong to give the name

276 ZOOLOGICAL PHILOSOPHY

of individual to a tree or shrub or even to herbaceous perennials ;
for a tree, shrub, etc., is in reality a collection of individuals which live
on one another, communivate together, and share a common. life, in
the same way as the compound polyps of madrepores, millipores,
etc.; as I have already proved in the first chapter of this second part.

Fertilisation, the essential result of an act of sexual reproduction,
must be divided into two different kinds, one of which is higher or more
eminent than the other, since it belongs to the most perfect animals
(mammals). This comprises the fertilisation of viviparous animals,
while the other, which is inferior and less perfect, includes that of
oviparous animals.

The fertilisation of viviparous animals immediately vivifies the
embryo exposed to it, and this embryo forthwith continues to live,
and feeds and develops at the expense of its mother, with which it
remains in communication up to birth. No interval is known be-
tween the act which prepares it for the possession of life and the
reception of life itself; moreover, this fertilised embryo is enclosed
in a membrane which contains no stores of food within it.

The fertilisation of oviparous animals, on the other hand, only
prepares the embryo for the reception of life, but does not actually
confer life. Now this fertilised embryo of oviparous animals is en-
closed with a store of food in investments, which cease to communicate
with the mother before being separated from her ; and it only receives
life when a special factor, which may come sooner or later according
to circumstances, or may not come at all, communicates to it the vital
movement.

This special factor, which confers life on the embryo of an oviparous
animal after it has been fertilised, consists as regards animals’ eggs in a
mere rise of temperature, and as regards the seeds of plants in the co-
operation of moisture with a gentle penetrating warmth. In birds’
eggs, for instance, incubation causes this rise of temperature, and in
many other eggs a gentle warmth of the atmosphere is enough ; lastly,
circumstances that favour germination vitalise the seeds of plants.

But eggs and seeds adapted for giving existence to animals and
plants must of necessity contain a fertilised embryo enclosed in in-
vestments, whence it can only emerge after breaking through them:
such eggs and seeds are therefore products of sexual reproduction,
since reproductive bodies otherwise originating do not have any
embryo enclosed in investments which have to be broken through at
the outset of development. Gemmae and the more or less oviform
reproductive bodies of many animals and plants cannot assuredly
be compared with them: it would be a waste of time to search for —
sexual generation where nature has had no means for establishing it.

THE PECULIAR FACULTIES 277

Sexual reproduction is thus peculiar to certain animals and plants :
consequently the simplest and most imperfect living bodies cannot
possess any such faculty.

Circulation. This is a faculty which only exists in certain animals,
and which is much less general in the animal kingdom than the five
others of which I have already spoken. This faculty springs from an
organic function whose purpose is the acceleration of the movements of
the essential fluid of certain animals,—a function which is performed
by a special system of organs adapted to it.

This system of organs is essentially composed of two kinds of
vessels, viz. arteries and veins, and almost always in addition a
thick and hollow muscle, which occupies about the centre of the
system, which soon becomes the principal motive power of it, and
which is called the heart.

The function carried out by this system of organs consists in driving
the animal’s essential fluid, which is here known by the name of blood,
from an almost central point occupied by the heart (when there is
one), through the arteries into every part of the body ; whence it returns
to the same point by the veins, and is then dispatched anew throughout
the body.

It is this movement of the blood, always being driven into every
part and always returning to its starting point throughout the duration
of life, that has received the name of Circulation. It should be qualified
as general in order to distinguish it from the respiratory circulation,
which is undertaken by a special system likewise composed of arteries
and veins.

Nature, when initiating organisation in the simplest and most im-
perfect animals, was only able to give their essential fluid an extremely
slow movement. This no doubt is the case in the very simple and
scarcely animalised essential fluid that moves in the cellular tissue of
infusorians. But afterwards she gradually animalised and developed .
the essential fluid of animals in proportion as their organisation be-
came more complex and perfect; and she accelerated its movement
by various methods.

In the polyps, the essential fluid is nearly as simple and has scarcely
more movement than that of the infusorians. The regular shape of
the polyps, however, and especially their alimentary cavity begin to
furnish means to nature for somewhat increasing the activity of their
essential fluid.

She probably took advantage of this in the radiarians, to establish
in their alimentary cavity the centre of activity of their essential
fluid. The expansive surrounding subtle fluids, in fact, which consti-
tute the exciting cause of these animals’ movements, penetrate chiefly

278 ZOOLOGICAL PHILOSOPHY

into their alimentary cavity ; and by their incessant expansions have
greatly developed this cavity, have induced the radiating form of
these animals both internally and externally, and moreover cause
the isochronous movements observed in the soft radiarians.

When nature had established muscular movement, as she has in
the insects and perhaps even a little before, she had a new means for
increasing the movement of their serum or essential fluid ; but on reach-
ing the organisation of the crustaceans, this means no longer sufficed,
and a special system of organs had to be created for accelerating the
essential fluid or blood of these animals. It is indeed in the crustaceans
that we find for the first time a complete general circulation ; for this
function is only rudimentary in the arachnids.

Every new system of organs acquired is permanently preserved in
subsequent organisations ; but nature continues to work towards its
gradual perfection.

The general circulation is thus at first provided only with a heart
with one ventricle, and indeed in the annelids even a heart is un-
known : it is at first accompanied only by an incomplete respiratory
circulation, viz. one in which all the blood does not pass through the
organ of respiration before being despatched to the parts. This is
the case with animals which have imperfect gills ; but in fishes, where
the branchial respiration is perfect, the general circulation is accom-
panied by a complete respiratory circulation.

When nature subsequently created lungs for breathing, as she did
in the reptiles, the general circulation was of necessity accompanied
only by an incomplete respiratory circulation; because the new
respiratory organ was still too imperfect, and because the general
circulation still had a heart with only one ventricle and also because
the new fluid breathed is by itself more effectively restorative than
water, so that a complete respiration was not needed. But when
nature reached that perfection of pulmonary respiration seen in the
birds and mammals, the general circulation came to be accompanied
by a complete respiratory circulation ; the heart necessarily had two
ventricles and two auricles ; and the blood gained its highest velocity ;
the high animalisation became capable of raising the animal’s internal
temperature above that of the environment, and, lastly, the blood
became subject to rapid decomposition requiring corresponding
restoration.

The circulation of the essential fluid of a living body is then an
organic function peculiar to certain animals: it first becomes complete
and general in the crustaceans, and is afterwards found gradually be-
coming more perfect in animals of the following classes ; but it would
be vain to seek it in the less perfect animals of the anterior classes.

THE PECULIAR FACULTIES 279

Intelligence. Of all the faculties peculiar to certain animals, this is
the one that is the most limited as regards the numbers which possess
it, even in a very imperfect form; but it is also the most wonderful,
especially when highly developed ; and it may then be regarded as
the high-water-mark of what nature can achieve by means of organisa-
tion.

This faculty arises from the activities of a special organ which can
alone produce it, and which is itself highly complex when it has acquired
all the development of which it is capable.

As “ws ues is actually distinct, from that which produces feeling
Se as of intelligence ‘is not ‘only not common to all animals
but is not even common to all those that can feel; for feeling may
exist without intelligence.

The special organ in which are produced the acts of the under-
standing appears to be only an accessory of the nervous system ;
that is, a part added on to the brain, and containing the nucleus or
centre of communication of the nerves. The special organ in question
is thus adjacent to the nucleus; the nature of the substance of which
it is composed appears moreover to differ in no way from that of the
nervous system ; in it alone, however, acts of intelligence are performed ;
and it is a special organ, for the nervous system may exist without it.

In the third part I shall take a general survey of the probable
mechanism of the functions of this organ. In vertebrates it is con-
fused with the medullary mass under the name of brain, although it
only consists of the two wrinkled hemispheres which cover it over.
It is sufficient here to note that of those animals which have a nervous
system, it is only the most perfect that actually possess the two cerebral
hemispheres; probably all invertebrates, except perhaps some of
the last order of molluscs, are destitute of it, although a great many
of them have a brain to which run directly the nerves of one or more
special senses, and although this brain is generally divided into two
lobes separated by a furrow.

In accordance with this view the faculty of performing acts of
intelligence has only just begun in the fishes or, at the earliest, in
the cephalopod molluscs. It is in these animals in a state of extreme
imperfection ; some development has been achieved in the reptiles,
especially in the later orders ; much more has been made in the birds,
and the faculty reaches its highest point in the latest orders of
mammals.

Intelligence is then a faculty limited to certain animals which are
able to feel; but the faculty is not common to all those that possess
feeling: indeed, as we shall see, among the latter, those that have no

280 ZOOLOGICAL PHILOSOPHY

special organ for performing acts of intelligence can only have simple
perceptions of the objects which affect them, but can form no idea
of them, do not make comparisons or judgments, and are guided in
all their actions by their habitual needs and inclinations.

Summary oF Part II.

By confining myself in the nine preceding chapters solely to the
observations with which I was concerned, I have avoided entering
into a quantity of details which are doubtless very interesting, but
may be found in the good works on physiology already accessible
to the public: the principles which I have advanced appear to me
sufficient to prove :

1, That life in every body which possesses it consists only of an
order and state of things, by which the internal parts can be influenced
by an exciting cause and perform movements called organic or vital,
from which are produced according to the species the recognised
phenomena of organisation ;

2. That the exciting cause of vital movements is external to the
organs of all living bodies ; that the elements of this cause are always
found, although in varying abundance, wherever there is life; that it
is provided to living bodies by the environment either in whole or
part ; and that without this same cause no such body could possess
life ;

3. That every living body whatever is necessarily composed of two
kinds of parts, viz.: containing parts consisting of a very supple
cellular tissue, in which and out of which every kind of organ has been
formed ; and visible contained fluids capable of moving about and of
undergoing various changes in their condition and nature ;

4, That animal nature does not differ essentially from vegetable
nature as regards the special organs of these two kinds of living bodies,
but chiefly as regards the nature of the substances of which they are
composed: for the substance of every animal body is such that the
exciting cause can establish in it an energetic orgasm and irritability ;
whereas the substance of all vegetable bodies merely gives the exciting
cause the power of setting in motion the visible contained fluids, while
only permitting in the containing parts of a faint orgasm, not enough
to produce irritability or to cause any sudden movements by the parts;
- 5, That nature herself produces direct or so-called spontaneous
generations by creating organisation and life in bodies which did not
previously possess them ; that she must of necessity have this faculty
in the case of the most imperfect animals and plants at the beginning
of the animal and vegetable scales, and also perhaps of some of their
branches; and that she only performs this strange phenomenon in

SUMMARY OF PART II 281

tiny portions of matter, gelatinous in the case of animals and muci-
laginous in the case of plants, transforming these portions of matter
into cellular tissue, filling them with visible fluids which develop within
them, and setting up in them various movements, dissipations, restora-
tions and alterations by means of the exciting cause provided by the
environment ;

6. That the laws which control the various transformations in bodies,
of whatever nature they may be, are everywhere the same; but that
these laws in living bodies work results altogether opposite to those
achieved in crude or inorganic bodies, because in the former they find
an order and state of things which give them the power to produce all
the phenomena of life, while in the latter they find a very different
state of things and produce very different effects: so that it is not
true that nature has special laws for living bodies, opposite to those
which control the transformations observed in lifeless bodies ;

7. That all living bodies of both kingdoms and all classes have
certain faculties in common; these are the property of the general
organisation of such bodies, and of the life which they contain ; hence
these faculties, common to all living things, need no special organ for
their existence ;

8. That in addition to the faculties common to all living bodies,
some of these bodies, especially among animals, have faculties peculiar
to themselves and not found among the rest ; but these special faculties
are in every case the product of a special organ or system of organs,
so that no animal without that organ or system of organs can possibly
possess the faculty which it confers on those that have it ; 1

9. Lastly, that the death of every living body is a natural pheno- ’
menon, which necessarily results from the presence of life and is brought
about by natural causes, unless some accidental cause intervenes first ;
this phenomenon is nothing else than the complete cessation of vital
movements, resulting from some disturbance in the order and state of
things necessary for the performance of these movements ; in animals
with highly complex organisations, the principal systems of organs
possess to some extent a life of their own, although closely bound up
with the general life of the individual. The death of an animal thus
takes place gradually in the separate parts, so that life becomes succes-

1In this connection I may observe that plants in general have no special organs
within them for particular functions. Every part of a plant contains the organs
essential to life, and may therefore either live and vegetate separately, or as a result
of grafting share with another plant a life common to both; lastly, from this order
of things in plants it follows that several individuals of the same species, or even only
of the same genus, may live on one another in the enjoyment of a common life.

I may add that the latent buds found on the branches and even the trunk of woody

plants are not special organs, but the rudiments of new individuals, awaiting favour-
able conditions for their development.

282 ZOOLOGICAL PHILOSOPHY

sively extinct inthe principal organs in a regular and constant order ;
and the moment at which life ceases in the last organ is that which
completes the death of the individual.

On such difficult subjects as those of which I have been treating,
we are closely confined within the limits of knowledge and to the
sphere of what we can learn from observation. Everything has
reference to the conditions essential to life in a body; conditions
established in compliance with facts which prove their necessity.

If things are not really as I have described, or if it is held that the
conditions named and the admitted facts which testify to the true
foundation of these matters, are not adequate proofs to justify us in
admitting them, we shall then have to abandon altogether the enquiry
into the physical causes which give rise to the phenomena of life and
organisation.

PART III.

AN ENQUIRY INTO THE PHYSICAL CAUSES OF FEELING,
INTO THE FORCE WHICH PRODUCES ACTIONS, AND,
LASTLY, INTO THE ORIGIN OF THE ACTS OF INTELLI-
GENCE OBSERVED IN VARIOUS ANIMALS.

INTRODUCTION.

In the second part of this work, I have endeavoured to throw light on
the physical causes of life, on the conditions necessary for its existence,
and on the origin of that exciting force of vital movements, without
which no body could actually possess life.

I now propose to enquire what feeling may be, how the special
organ giving rise to it (the nervous system) produces the wonderful
phenomenon of sensations, how sensations themselves produce ideas
through the medium of the brain, and how ideas cause in that organ
the formation of thoughts, judgments and reasoning ; in short, of acts
of intelligence that are still more wonderful than sensations.

“ But,” it is said, “the functions of the brain are of a different order
from those of the other viscera. In the latter causes and effects are
of the same nature (physical nature)... .

“The functions of the brain are of quite a different order: they
consist in receiving sense impressions through the nerves, in transmit-
ting them immediately to the mind, in preserving the traces of these
impressions, and in reproducing them with varying rapidity, clearness
and fulness whenever the mind needs them in its operations or the
laws of association of ideas recall them ; lastly, in transmitting to
the muscles again through the medium of nerves the commands of
the will.

“Now these three functions involve a mutual influence, which has
always remained incomprehensible, between divisible matter and the
indivisible ego. This has always constituted an impassable hiatus in
the system of our ideas, and the stumbling block of all philosophies ;
they involve us moreover in a further difficulty that has no necessary
connection with the first: not only do we not understand nor ever
shall understand how impressions on the brain can be perceived by the
mind and produce images in it; but however refined our means of
investigation, these traces cannot be made visible in any way ; and we
are entirely ignorant of their nature, although the effect of age and
diseases on the memory leave us in no doubt either as to their

286 ZOOLOGICAL PHILOSOPHY

existence or their seat.” (Rapport a UInstitut sur wn Mémoire de
MM. Gall et Spurzheim, p. 5.)

It is, I think, a little rash to fix limits to the conceptions which the
human intellect may reach, or to specify the boundaries and the powers
of that intellect. How indeed can we know that man will never

obtain such knowledge, nor penetrate these secrets of nature? Do
we not know that he has already discovered many important truths,
some of which seemed to be entirely beyond him ?

It is more rash, I repeat, to try to determine positively what man
may know and what he never can know, than to study the facts,
examine the relations existing between various physical bodies, draw
all possible inferences, and then make continuous efforts to discover
the causes of natural phenomena; even when the coarseness of our
senses does not allow us to reach anything more than moral certainties.

If we were concerned with objects outside nature, with phenomena
that are neither physical nor the result of physical causes, the subject
would doubtless be beyond the human intellect; for it can never
obtain a grasp of anything external to nature.

Now, since in this work we are dealing mainly with animals, and since
observation teaches us that there are among them some which possess
the faculty of feeling, which form ideas and judgments and carry out
intelligent acts, which, in short, have memory, I wish to ask what is
the peculiar entity called mind in the passage cited above ; a remark-
able entity which is alleged to be in relation with the acts of the brain,
so that the functions of this organ are of a different order from those
of the other organs of the individual.

In this factitious entity, which is not like anything else in nature, I
see a mere invention for the purpose of resolving the difficulties that
follow from inadequate knowledge of the laws of nature: it is much
the same thing as those universal catastrophes, to which recourse is
had for giving answers to certain geological questions. These questions
puzzle us because the procedure of nature, and the different kinds of
transformations that she is always producing, are not yet ascertained.

With regard to the traces impressed on the brain by ideas and
thoughts, what matters it that these traces cannot be perceived by
our senses, if, as is agreed, observations exist which leave us in no
doubt as to their presence and their seat: do we see any more clearly
the way in which other organs perform their functions, and, to take
a single example, do we see any more clearly how the nerves set the
muscles in action? Yet we cannot doubt that nervous influence is
indispensable for the performance of muscular movements.

In the sphere of nature, knowledge is extremely important for us
and yet very difficult to obtain in any better form than moral

INTRODUCTION 287

certainties ; such knowledge can, I believe, only be attained by the
following method.

Do not let us be imposed upon by dogmatic utterances which are
nearly always ventured with little thought; let us carefully collect
such facts as we can observe, let us make experiments wherever we can,
and when experiment is impossible let us marshal all the inferences that
we can draw from analogy, and let us nowhere make a dogmatic
pronouncement : by this method we shall be able gradually to attain
a knowledge of the causes of many natural phenomena, including
perhaps even those that now appear to us the most incomprehensible.

Since, then, the limits of our knowledge as to what occurs in nature
neither are nor can be fixed, I shall endeavour, by the use of such facts
as have been collected, to determine in this third part what are the
physical causes which confer on certain animals the faculty of feeling,
of producing for themselves the movements which constitute their
actions, and, lastly, of forming ideas and of comparing these ideas, so as
to obtain judgments: in short, of performing various intelligent acts.

The principles which I shall set forth on this matter will as a rule
be such as to fill us with an inward moral conviction, although it is
impossible to prove positively their accuracy. It seems that, with
regard to many natural phenomena, this order of knowledge is alone
possible for us; and yet its importance cannot be called in question
in innumerable cases where we are called upon to form judgments.

f the physical and the moral have a common origin, if ideas, thought
and even imagination are only natural phenomena, and therefore really
dependent on organisation, then it must be chiefly the province of
the zoologist, who makes a special study of organic phenomena, to
investigate what ideas are, and how they are produced and preserved,
in short, how memory renews them, recalls them and makes them
perceptible once more; from this it is only a short way to perceiving
what are thoughts themselves, for thoughts can only be invoked by
ideas; lastly, by following the same method and building up from
original perceptions, it may be possible to discover how thoughts
give rise to reasoning, analysis, judgments and the will to act, and how
again numerous acts of thought and judgments may give birth to
imagination, a faculty so fertile in the creation of ideas that it even
seems to produce some which have no model in nature, although in
reality they must be derived from this source.

If all the acts of the intellect, into the causes of which I am now
enquiring, are only phenomena of nature, that is to say, acts of the
organisation, may I not hope, by acquiring a thorough knowledge
of the only means by which the organs perform their functions, to
discover how the intellect may give rise to the formation of ideas and

288 ZOOLOGICAL PHILOSOPHY

preserve their traces or impressions for a longer or shorter period, and
finally, by means of these ideas, carry out thought, etc., etc. ?

It cannot now be doubted that the acts of the intellect are exclusively
dependent on organisation, since it is known that even in man dis-
turbances in the organs which produce these acts involve others in
the acts themselves. :

An investigation of the causes of which I spoke above appears
therefore to me to be obviously possible: I have given attention to
the subject; I have devoted myself to an investigation of the only
method by which nature can have brought about the phenomena in
question; and it is the result of my meditations on this subject
that I am now about to present.

The essential point is that, in every system of animal organisation,
nature has but one method for making the various organs perform
their appropriate functions.

These functions indeed are everywhere the result of the relation
between fluids moving in the animal, and the parts of its body which
contain these fluids.

There are everywhere moving fluids (some containable, others
uncontainable) which act upon the organs; and there are also every-
where supple parts, which are sometimes in erethism and react on
the fluids which affect them, and which are sometimes incapable of
reacting ; but in either case they modify the movement of the fluids
taking place among them.

Thus, when the supple parts of organs are capable of being animated
by orgasm and of reacting on the contained fluids which affect them,
the various resulting movements and changes, both in the fluids and the
organs, produce phenomena of organisation which have nothing to do
with feeling or intelligence; but when the containing parts are so
soft as to make them passive and incapable of reacting, the subtle:
fluid moving in these parts, and modified by them in its movements,
gives rise to the phenomena of feeling and intelligence as I shall
endeavour to prove in this Part.

- We have therefore to deal only with the relations existing between
the concrete supple and containing parts of an animal, and the moving
fluids (containable or uncontainable) which act on these parts.
~ This well-known fact has been for me as a beam of light ; it guided
me in the research that I have sketched out, and I soon perceived that
the intelligent acts of animals are, like their other acts, phenomena
of animal organisation, and that they take their origin from the rela-
tions existing between certain moving fluids and the organs which
produce these wonderful acts.
What matters it that these fluids, whose extreme tenuity prevents

INTRODUCTION 289

us from seeing them or even keeping them in a vessel for making
experiments with, only manifest their existence by their effects ?
These effects constitute a cogent proof that no other cause could have
produced them. It is, moreover, easily ascertained that the visible
fluids, which penetrate the medullary substance of the brain and nerves,
are only nutritive and adapted for secretion; but that they are too
slow in their movements to give rise to the phenomena either of
muscular movement, feeling, or thought.

In the light of these principles, which restrain the imagination within
its proper limits, I shall first show how nature originally succeeded in
creating the organ of feeling, and by its means the force productive
of actions : I shall afterwards proceed to consider how (by means of a
special organ for intellect), ideas, thoughts, judgments, memory, etc.,
may have arisen in the animals which possess such an organ.

CHAPTER I.

OF THE NERVOUS SYSTEM, ITS FORMATION, AND THE VARIOUS
SORTS OF FUNCTIONS THAT IT CAN FULFIL.

THE nervous system, in man and the most perfect animals, consists
of various quite distinct special organs and even systems of organs,
which are closely connected and form a very complicated whole. It
has been supposed that the composition of this system is everywhere
the same, except for its greater or lesser development, and the differ-
ences of size, form, and situation involved by the various types of
organisation. On this theory the various sorts of functions, to which
it gives rise in the most perfect animals, were all regarded as being
characteristic of it throughout all animal organisation.

This manner of regarding the nervous system throws no light on
the nature of the organs in question, on the mode of their origin, on
the growing complexity of their parts in proportion to the complication
and perfection of animal organisation, nor, lastly, on the new faculties
which it confers on animals in proportion to its development. On
the contrary, instead of enlightening physiologists on these matters,
it leads them to attribute everywhere to the nervous system in various
degrees of concentration the faculties which that system confers on
the most perfect animals, and this is entirely without foundation.

I shall therefore endeavour to prove: (1) That this system of organs
cannot be a property of all animals; (2) that at its origin, that is,
at its greatest simplicity, it only confers on the animals which possess
it the one faculty of muscular movement ; (3) that afterwards, when
more highly developed, it endows animals not only with muscular
movement but also with feeling; (4) that lastly, on reaching completion,
it confers on the animals which possess it the faculties of muscular
movement, of experiencing sensations, and of forming ideas, com-
paring them together, and producing judgments ; in short, of having
an intellect whose development is proportional to the perfection of
organisation.

292 ZOOLOGICAL PHILOSOPHY

Before setting forth the proofs of these theories, let us see what
general idea we can form of the nature and arrangement of the various
parts of the nervous system.

This system, wherever it occurs in animals, presents a main medullary
mass, either divided into separate parts or concentrated into a single
whole of varying shape, and also nervous threads which run into this
mass.

All these organs are composed of three kinds of substances of very
different character, viz. :

1. A very soft medullary pulp of peculiar character.

2. An aponeurotic investment, which surrounds the medullary
pulp and provides sheaths to its prolongations and threads, including
even the finest. The nature and properties of this investment are
different from those of the pulp which it encloses.

3. A very subtle invisible fluid, which moves in the pulp without
requiring any visible cavity, and which is kept in at the sides by
the sheath, through which it cannot pass.

Such are the three kinds of substances which compose the nervous
system, and which produce the most astonishing of all organic pheno-
mena as a result of their arrangement, relations and the movements of
the subtle fluid contained within the system.

It is known that the pulp of these organs is a very soft medullary
substance, white on the inside, greyish on its outer layer, not sensitive,
and apparently albumino-gelatinous in character. It forms, by means
of its aponeurotic sheaths, threads and cords which proceed to the
larger masses of this medullary substance containing the nucleus
(simple or divided), or centre of communication of the system.

Both for the performance of muscular movement and for sensations,
it is necessary that this system of organs should have a nucleus or
centre of communication for the nerves. As a matter of fact, in the
first case the subtle fluid which acts upon the muscles issues from a
common nucleus and travels towards the parts which it has to actuate ;
and, in the second case, the same fluid, being set in motion by the
affective cause, starts from the extremity of the affected nerve and
travels towards the centre of communication, there producing the
disturbance which gives rise to sensations.

A nucleus or centre of communication, in which the nerves terminate,
ig therefore absolutely necessary in order that the system may carry
on any of its functions; and indeed we shall see that without it the
individual would not become cognisant of the acts of the organ of
intellect. Now this centre of communication is situated in some part
of the main medullary mass, which always constitutes the basis of the
nervous system.

THE NERVOUS SYSTEM 293

The threads and cords of which I spoke above are nerves; and the
main medullary mass, which contains the centre of communication of
the system, consists in some invertebrates either of separate ganglia
or of a ganglionic longitudinal cord ; in the vertebrates, it forms the
spinal cord and the medulla oblongata which is united to the brain.

Wherever a nervous system exists, however simple or imperfect it
may be, there is always a main medullary mass in some form or other ;
for it constitutes the basis of the system and is essential to it.

It is in vain to deny this truth by such arguments as the following:

1. That it is possible to remove entirely the brain of a tortoise or
a frog, which nevertheless continue to exhibit movements showing
that they still have sensations and a will: I reply, that this operation
only destroys a part of the main medullary mass, and not that part
which contains the centre of communication or sensorium commune ;
for this is not contained in the two hemispheres which form the bulk
of what is called the brain ;

2. “That there are insects and worms, which when cut into two
or more pieces, promptly form so many new individuals, each having
its own system of sensation and its own will”; I reply again, that as
regards insects the alleged fact is untrue, that no experiment has shown
that when an insect is cut in two there may result two individuals
both capable of life; and even if it were so, each half of the insect
would still possess a main medullary mass in its share of the ganglionic
longitudinal cord ;

3. “That the more evenly the nervous substance is distributed,
the less essential is the rdle of the central parts.”1 I reply, for the last
time, that this assertion is erroneous; that it has no facts to support
it; and that it is only made through ignorance of the functions of the
nervous system. Sensibility is neither the property of nervous sub-
stance nor any other substance, and the nervous system can only
enter upon its functional existence when it is composed of a main
medullary mass from which nervous threads take rise.

Not only can the nervous system have no functional existence
unless it is composed of a main medullary mass which contains one or
more nuclei for starting muscular excitement and from which various
nerves proceed to the parts, but we shall also see in Chapter IIT. that
the faculty of feeling in any animal can only arise when the medullary
mass contains a single nucleus or centre of communication, to which
the nerves of the sensitive system travel from all parts of the body.

It is true that the extreme difficulty of following these nerves to their
centre of communication, has led some anatomists to deny the existence

1See L’ Anatomie comparée of M. Cuvier, vol. ii., p. 94; and the Recherches sur le
Systeme nerveux of MM. Gall and Spurzheim, p. 22.

294 ZOOLOGICAL PHILOSOPHY

of any common nucleus that is essential to the production of feeling ;
they consider feeling to be an attribute of all the nerves, including even
their smallest parts; and, to strengthen their view as to the absence
of any centre of communication in the sensitive system, they allege
that the need for finding a definite situation for the soul has caused
the invention of this common nucleus or circumscribed locality to
which all sensations are conducted.

/ It is quite enough to believe that man possesses an immortal soul ;
‘there j is no occasion for us to study the seat and limits of this soul
in the individual body, nor its connection with the phenomena of
organisation : all that we can ever say on this subject is baseless and
purely imaginary.

If we are studying nature she alone should occupy our attention ;
and we should confine ourselves exclusively to the examination of the
facts which she presents, in our endeavour to discover the physical
laws which control the production of these facts; lastly, we ought
never to introduce into our theories any subjects that are outside
nature, and about which we shall never be able to know anything
positive.

For my own part, I only study organisation in order to arrive at an
understanding of the various faculties of animals. I am convinced
that many animals possess feeling, and that some of them also have
ideas and perform intelligent acts ; and I hold that the causes for these
phenomena should be sought in purely physical laws. J always make a
rule of this in my own researches, and I may add that I am not only
convinced that no kind of matter can in itself possess the faculty of
feeling, but I am also convinced that this faculty in such living bodies
as possess it consists only in a general effect which is set up in an
appropriate system of organs, and that this effect cannot occur unless
the system possesses a single nucleus or centre of communication,
in which terminate all the sensitive nerves.

In the case of vertebrates, it is at the anterior extremity of the spinal
cord, in the medulla oblongata itself or perhaps its annular protuber-
ance, that the sensoriwm commune is lodged ; that is to say, the centre
of communication of the nerves which give rise to the phenomenon
of sensibility ; for it is towards some point at the base of the brain
that these nerves appear to converge. If the centre of communication
were farther forward in the interior of the brain, acephalic animals,
whose brain had been destroyed, would be devoid of feeling and
unable even to live.

But this is not the case: in animals which possess any faculty of
intelligence, the nucleus for feeling is confined to some part of the base
of what is called their brain; for this name is given to the entire

THE NERVOUS SYSTEM 295

medullary mass contained within the cranial cavity. The two
hemispheres, however, which are confused with the brain, should be
distinguished from it; because they form together a special organ
added on to the brain, have special functions of their own and do not
contain the centre of communication of the sensitive system.

Although the true brain, that is to say, the medullary part which
contains the nucleus of sensations and to which the nerves lead from
the special senses, is difficult to identify and define in man and intelligent
animals, on account of the contiguity or union between this brain and
the two hemispheres which cover it, it is none the less true that these
hemispheres constitute an organ specially related to the functions that
it performs.

Indeed it is not in the brain properly so-called that ideas, judgments,
thoughts, etc., are formed ; but it is in the organ superimposed on it,
consisting of the two hemispheres.

Nor is it in the hemispheres that sensations are produced; they
have no share in it, and the sensitive system exists satisfactorily
without them ; these organs may therefore undergo great degeneration
without any injury to feeling or life.

T now revert to the general principles concerning the composition
of the various parts of the nervous system.

The nervous threads and cords, the ganglionic longitudinal cord, \
the spinal cord, the medulla oblongata, the cerebellum, the cerebrum
and its hemispheres ;—all these parts have, as I have already observed,
a membranous and aponeurotic investment which serves as a sheath,
and which by its peculiar nature retains within the medullary sub-
stance the special fluid that moves about there ; but at the extremities
of the nerves where they terminate in the parts of the body, these
sheaths are open and allow the nervous fluid to communicate with
the parts.

Details about the number, shape and situation of the parts I have
referred to, belong to the sphere of anatomy; an exact description
may be found in works which deal with this sphere of our knowledge.
Now since my purpose here is simply to investigate the general prin-
ciples and faculties of the nervous system, and to enquire how nature
first conferred it on such animals as possess it, I need not enter into any
of the details that are known about the parts of this system.

ForMATION OF THE NERVOUS SYSTEM.

We certainly cannot positively determine the manner in which
nature brought the nervous system into existence; but it is quite
possible to ascertain the conditions which were necessary for this
purpose. When once we have ascertained and studied these con-

296 ZOOLOGICAL PHILOSOPHY

ditions, we may be able to conceive how the parts of the system were
formed, and how they were filled with the subtle fluid which moves
within them and enables them to carry out their functions.

We may suppose that when nature had advanced so far with animal
organisation that the essential fluid of animals had become highly
animalised, and the albumino-gelatinous substance been formed, this
substance would be secreted from the animal’s chief fluid (blood, or
its substitute) and deposited in some part of the body : now observation
shows that this first occurs in the shape of several small separate masses,
and afterwards as a larger mass which becomes lengthened into a
ganglionic cord and occupies nearly the whole length of the body.

The cellular tissue is modified by this mass of albumino-gelatinous
substance, and so provides it with its investing sheath, and that of its
various prolongations or threads.

Now on examining the visible fluids which move or circulate in the
bodies of animals, I find that, in the animals with the simplest organisa-
tions, these fluids are much less complex and contain much fewer
principles than is the case in the more perfect animals. The blood of
a mammal is a more complex and animalised fluid than the whitish
serum of insects; and this serum again is a more complex fluid than
that watery matter which moves in the bodies of polyps and
infusorians.

This being so, I am justified in the belief that those invisible and
uncontainable fluids which keep up irritability and vital movements
in the most imperfect animals, are the same as those existing in animals
with a highly complex and perfected organisation. In the latter,
however, they undergo so great a modification as to be changed into
containable fluids, though still invisible.

It appears indeed that an invisible and very subtle special fluid,
which is modified during its presence in the blood of animals, is con-
tinually separating out to spread through the nervous medullary
masses, and incessantly makes good the wastage due to the various
activities of this system of organs.

The medullary pulp of the nervous system, and the subtle fluid
moving within it, will thus only be formed when the complexity of
animal organisation has reached a sufficient development for the manu-
facture of these substances.

Just as the internal fluids of animals are progressively modified,
animalised and compounded in correspondence with the progress in
the complexity and perfection of organisation ; so too the organs and
solid or containing parts of the body are gradually compounded and
diversified in the same way and by the same cause. Now the nervous
fluid, which becomes containable after its secretion by the blood,

THE NERVOUS SYSTEM 297

is distributed in the albumino-gelatinous substance of the nerve
tissue, for this substance is a natural conductor of it and is adapted
for holding it and letting it move freely about; the fluid is kept in
by the aponeurotic sheaths which invest this nervous tissue, since
these sheaths do not permit of the passage of the fluid.

Thereafter, when the nervous fluid is distributed throughout that
medullary substance which was originally arranged in separate ganglia
and afterwards in a cord, its movements probably thrust out portions
which become elongated into threads and it is these threads which
constitute the nerves. It is known that they spring from their centre
of communication, and issue in pairs either from a ganglionic longi-
tudinal cord or a spinal cord at the base of the brain, and that they
then proceed to their termination in the various parts of the body.

This no doubt was the method employed by nature for the formation
of the nervous system : she started by producing several small masses
of medullary substance when the animal organisation had advanced
sufficiently to enable her to do so: she then collected them into one
chief mass; through this mass immediately spread the nervous fluid,
which had become containable and was kept in by the nervous sheaths :
it was then that its movements gave rise to the medullary mass in
question, and to the nervous threads and cords which issue from it to
the various parts of the body.

In accordance with this theory, nerves cannot exist in any animal
unless there is a medullary mass containing their nucleus or centre of
communication ; hence those isolated whitish threads which do not
lead to a medullary mass are not to be regarded as nerves.

I may add to these reflections on the formation of the nervous
system, that if the medullary substance has been secreted by the chief
fluid of the animal, it is through the agency of the capillary extremities
of certain arterial vessels in red-blooded animals; and since the ex-
tremities of these arterial vessels must be accompanied by the ex-
tremities of venous vessels, all these vascular extremities, containing
coloured blood, are buried in the medullary substance which they have
produced, and give rise to the greyish colour, which this medullary
substance presents in its external layer : sometimes, indeed, as a result
of certain evolutions taking place in the encephalon as it develops, the
nutritive organs have penetrated so deeply that the greyish medullary
substance is central in some localities, and surrounded in great part
by that which is white.

I may add further, that if the extremities of certain arteries have
secreted and then maintained the medullary substance of the nervous
system, these same vascular extremities may likewise have deposited
the nervous fluid which separates off from the blood and is continually

298 ZOOLOGICAL PHILOSOPHY

poured into that medullary substance which is so well adapted to
contain it.

Lastly, I shall conclude these reflections by some remarks on the
development of the main medullary mass and of the swellings and
expansions which are found in certain parts of that mass. These
expansions are proportional to the formation and development of the
special systems which compose the common and perfected nervous
system.

In the main medullary mass of every nervous system, the particular
part which to some extent gave origin to the rest, need not necessarily
be larger than the other parts which have grown from it; for the
thickness and size of these other parts are always dependent on the use
which the animal makes of the nerves that issue from them. I have
given sufficient proof of this in the case of all the other organs: the
more they are exercised the more they become developed, strengthened,
and enlarged. It is because this law of animal organisation has not
been recognised, or because no attention had been paid to it, that
it is believed that the part of the medullary mass which produces the
other parts must of necessity be larger than them.

In vertebrates, the main medullary mass consists of the brain and
its accessories, the medulla oblongata and the spinal cord. Now it
appears that the part of this mass which produced the rest is really
the medulla oblongata ; for it is from this part that issue the medullary
appendages (the peduncles and crura) of the cerebellum and cerebrum,
the spinal cord, and, lastly, the nerves of the special senses. Yet the
medulla oblongata is in general smaller or less thick than the brain
which it has produced, or the spinal cord which proceeds from it.

Whereas, on the one hand, the brain and its hemispheres are employed
in acts of feeling and intellect, while the spinal cord only serves for the
excitation of muscular movements! and the performance of organic
functions; and whereas, on the other hand, the continued use or exercise
of the organs causes in them a remarkable development; it must
follow that in man, who is continually exerting his senses and intellect,
the brain and hemispheres should become much enlarged while the
spinal cord, which in general is little used, can only acquire moderate
dimensions. Finally, since the chief muscular movements of man are
those of the arms and legs, we should expect to find a conspicuous
swelling in his spinal cord at the exits of the crural and brachial
nerves, and this is confirmed by observation.

In those vertebrates, on the contrary, which make but little use of

1 With regard to the function of the spinal cord in providing nervous influence
to the organs of movement, recent experiments have shown that poisons which act
on this cord do actually cause convulsions and attacks of tetanus before producing
death.

THE NERVOUS SYSTEM 299

their senses and particularly of their intellect, and which are chiefly
given up to muscular movement, the brain and especially the hemi-
spheres should have undergone slight development, whereas the spinal
cord is likely to acquire considerable dimensions. Thus fishes, which
are largely confined to muscular movement, have a very large spinal
cord and a correspondingly small brain.

Among the invertebrates some have a ganglionic longitudinal cord,
instead of a spinal cord, throughout their length, such as the insects,
arachnids, crustaceans, etc.; because these animals carry out much
movement, and the cord is thereby strengthened and swollen where
each pair-of nerves issues. -

Lastly the molluscs, which have only feeble supports for their muscles
and generally only carry out slow movements, have no spinal cord nor
longitudinal cord, and exhibit nothing more than a few scattered
ganglia from which issue nervous threads.

In accordance with this theory, we may conclude that in the verte-
brates the nerves and main medullary mass cannot have been developed
from above downwards, that is, from the superior terminal part of
the brain ; any more than the brain itself can be a production of the
spinal cord, that is, of the inferior or posterior part of the nervous
system ; but that these various parts spring originally from one which
produced the rest. Probably this one is the medulla oblongata.
Some point in the neighbourhood of its annular protuberance must
have given origin to the cerebral hemispheres, the cerebellar
peduncles, the spinal cord and the special senses.

It matters not that the medullary bases of the hemispheres are
narrowed and much less bulky than the hemispheres themselves ;
and that the same applies to the peduncles of the cerebellum, ete. It
is plain to all that the gradual development of these organs, in pro-
portion to their more frequent use, may have caused in them an
expansion which makes them much larger than their roots !

These reflections on the formation of the nervous system are doubtless
somewhat indefinite; but they suffice for my purpose, and seem to
me interesting, because they are accurate and in accordance with the
observed facts.

Functions or THE Nervous System.

The nervous system of the most perfect animals is, as we know,
highly complicated, and may consequently fulfil various kinds of
functions, which confer on the animals possessing them as many
special faculties. Now before proving that this system is limited to
certain animals and not common to all; and before stating what are
the faculties conferred by it in the various degrees of complexity of

300 ZOOLOGICAL PHILOSOPHY

animal organisation, we must say a word about its functions and the
faculties resulting from them. They are of four different kinds, viz. :

1. That of instigating muscular activity ;

2. That of giving rise to feeling or to the sensations which con-
stitute it;

3. That of producing the emotions of the inner feeling ;

4. That, lastly, of forming ideas, judgments, thoughts, imagination,
memory, etc.

T shall endeavour to show that the functions of the nervous system
which give rise to these four kinds of faculties are very different in
character, and that they are not all performed by the animals which
possess this system.

The activities of the nervous system which give rise to muscular
movement are altogether distinct from and even independent of those
which produce sensations : thus we may experience one or more sensa-
tions without any muscular movement ensuing, and we may set in
action various muscles without any resulting sensation. These facts
are worthy of note and they are unquestionably well-founded.

Muscular movement cannot be executed without nervous influence ;
and although we do not know how this influence works, we are justified
by many facts in the belief that it may be by an emission of nervous
fluid which starts from a centre or reservoir and travels down the nerves
to the muscles which have to be actuated. In this function of the
nervous system then, the movements of the subtle fluid which works
the muscles take place from some centre or nucleus towards the parts
that have to carry out some action.

It is not only to set the muscles in action that the nervous fluid
travels from its nucleus or reservoir towards the parts which have to
carry out movements; this emission also takes place apparently in
order to assist various organs in the performance of functions, where
no distinct muscular movement is involved.

Since these facts are well known I shall not dwell further upon them ;
but shall adopt the conclusion that the nervous influence, which
gives rise to muscular activity and which aids various organs in the
performance of their functions, works by an emission of nervous
fluid which travels from some centre or reservoir to the parts requiring
to be actuated.

On this subject I may record a well-known fact that is relevant
to the matter now in hand. It is as follows:

With regard to the nervous fluid which leaves its reservoir on its way
to the parts of the body, one portion of this fluid is subject to the will
of the individual who starts it moving, by means of the emotions
of his inner feeling, when stimulated by some requirement ; whereas

THE NERVOUS SYSTEM 301

the other portion is regularly distributed, independently of the indivi-
dual’s will, to those parts of the body which have to be kept incessantly
in action for the preservation of life.

It would be highly inconvenient if the movements of our heart
or arteries, or the functions of our viscera or secretory or excretory
organs, were dependent on our will; but it is equally important for
the satisfaction of all our requirements that we should have at our
disposal some portion of our nervous fluid, for despatching to the regions
that we wish to actuate.

It appears that the nerves which continually convey the nervous
influence to the vital organs and to the muscles that are independent
of the individual, have a firmer or denser medullary substance than the
other nerves ; or have some other distinguishing peculiarity, as a result
of which not only does the nervous fluid move less rapidly and less
freely, but is also to a great extent protected from those general agita-
tions caused by the emotions of the inner feeling. If it were other-
wise, every emotion would interfere with the nervous influence necessary
to the essential organs and vital movements, and would endanger the
life of the individual.

Those nerves, on the contrary, which convey the nervous influence
to the muscles dependent on the individual, allow to the subtle fluid
which they contain every liberty and rapidity of movement, so that the
emotions of the inner feeling easily set these muscles in action.

Observation justifies us in the belief that the nerves which serve
for the excitation of muscular movement issue from the spinal cord
in vertebrates, from the ganglionic longitudinal cord in such inverte-
brates as have one, and from the separate ganglia in those which have
neither a spinal cord nor a ganglionic longitudinal cord. Now these
nerves, destined for muscular movement, have no close connection
with the sensitive system, in animals which have feeling, and when
they are injured they produce spasmodic contractions and do not
interfere with the system of sensations.

Hence there are grounds for the belief that, of the various special
systems which compose the nervous system at its highest perfection,
that which is engaged in muscular excitation is distinct from that which
serves for the production of feeling.

Thus the function of the nervous system, which consists in producing
muscular activity and the performance of the various vital functions,
can only be fulfilled by the dispatch of the subtle fluid of the nerves
from the reservoir to the various regions.

But that other function of the nervous system which induces feeling
is of quite a different character; for the production of a sensation
cannot occur without nervous influence, and it requires that the subtle

302 ZOOLOGICAL PHILOSOPHY

fluid of the nerves should always travel from the point of the body that
is affected towards the nucleus or centre of communication of the
system and there start an agitation which affects all the nerves
serving for feeling; their fluid then reacts and sensation is produced.

Not only do these two sorts of functions of the nervous system differ,
in that there is no sensation produced by any muscular movement and
that there is not necessarily any muscular movement for the production
of a sensation; but these functions differ also, as we have just seen,
by the fact that in one the nervous fluid is driven from its reservoir
to the parts, whereas in the other it is driven from the parts to the
nucleus or centre of communication of the system of sensations. These
facts are manifest, although we cannot witness the movements which
cause them.

The function of the nervous system which consists in bringing
about emotions of the inner feeling, and which works by means of a
general disturbance of the free mass of nervous fluid—a disturbance
which is followed by no reaction and therefore produces no distinct
sensation—is yet quite peculiar and very different from the two that
T have named; in the account that I shall give of it (Chapter IV.)
we shall find that its study is very curious and interesting.

Whereas the function, by which the nervous system sets the muscles
in action and assists the performance of organic functions, is different
from the function by which this system produces feeeling as also from
that which constitutes the emotions of the inner feeling, I have now to
remark that when the system is sufficiently developed to have obtained
that special accessory organ constituted by the wrinkled cerebral
hemispheres, it then has the faculty of performing a fourth kind of
function, very different from the three others.

Indeed, by means of the accessory organ that I have mentioned,
the nervous system gives rise to the formation of ideas, judgments,
thoughts, will, etc. ; phenomena which assuredly could not be produced
by the first three kinds of functions. Now the accessory organ, in
which are carried out functions capable of giving rise to these pheno-
mena, is only a passive organ, on account of its extreme softness ;
and it receives no excitation because none of its parts would be capable
of reacting; but it preserves the impressions received, and these
impressions modify the movements of the subtle fluids in its numerous
parts.

An ingenious idea, though destitute of proof or any adequate basis,
has been expressed by Cabanis, who said that the brain acts on the
impressions which the nerves conveyed to it as the stomach acts on
the food poured in from the oesophagus; that it digests them in its
own way, and that when agitated by movement transmitted to it, it

THE NERVOUS SYSTEM 303

reacts and that this reaction gives birth to a perception which there-
after becomes an idea.

This does not appear to me to be based on a study of the faculties
of the cerebral pulp; and I cannot convince myself that so soft a
substance is really active, or that it can truly be said to react and
give rise to perception when agitated by the movements transmitted
to it.

This mistake arises, in the first place, from the fact that Cabanis
took no note of the nervous fluid, and was obliged in his mind to
attribute the functions of that fluid to the nervous tissue in which it
moves; and in the second place, from the fact that he confused
sensations with intelligence, whereas the nature of these two organic
phenomena is essentially different, and demands in each case an
individual system of organs for its production.

Thus there are four very different kinds of functions carried on by
the perfected nervous system, that is, when it is completely developed
and provided with its accessory organ; but seeing that the organs
which give rise to these various functions are not the same, and seeing
that they have only come into existence successively, nature formed
those which are adapted to muscular movement before those which
give rise to sensation, and these latter before setting up the means
for producing emotions of the inner feeling; she at length completed
the perfection of the nervous system by making it capable of produc-
ing the phenomena of intelligence.

We shall now see that all animals neither have nor can have a nervous
system, and, moreover, that those which possess this system do not
necessarily derive from it the four kinds of faculties named.

Tue Nervous SYSTEM IS LIMITED TO CERTAIN ANIMALS.

Doubtless it is only in animals that the nervous system can exist ;
but does it follow thence that they must all possess it? There are
certainly many animals whose organisation is such that they could
not possibly have this system of organs; for the system consists
necessarily of two kinds of parts, viz.: a main medullary mass, and
various nervous threads which unite with it. Now this cannot exist
in the elementary organisations of a great many known animals.
It is obvious, moreover, that the nervous system is not essential to life,
since all living bodies do not possess it, and it would be vainly sought
among plants. This system, then, can only have become necessary
to those animals in which nature was able to establish it.

In Chapter IX. of Part II., p. 273, I have already shown that the
nervous system is peculiar to certain animals: I shall now give a
further proof of it by showing the impossibility that all animals should

304 ZOOLOGICAL PHILOSOPHY

possess this system of organs; whence it follows that those which
have not got it can enjoy none of the faculties which it produces.

When people have said that, in animals without nervous threads
(such as the polyps and infusorians), the medullary substance which
yields sensations was distributed and dissolved in every part of the body,
instead of being collected into threads ; and that from this it followed
that each fragment of these animals became an individual endowed
with its particular ego; they have probably paid no attention to the
invariable characteristic organic function, which is always due to
relations between the containing parts and contained fluids, and to
the movements resulting from these relations. There was no adequate
knowledge of the essential facts with regard to the functions of the
nervous system; it was not known that these functions only worked
by causing the movement or transport of a subtle fluid, either from a
nucleus towards the parts or from the parts towards the nucleus.

The nervous system cannot then exist, nor fulfil the least of its
functions, unless it consists of a medullary mass with a nucleus for
the nerves, and also of nervous threads which run into this nucleus.
Moreover the medullary matter, or any other animal substance, cannot
possess in itself the faculty of producing sensations, as I hope to prove
in the third chapter of this part; hence this medullary substance
when dissolved as alleged in every part of an animal’s body would not
give rise to feeling.

If the nervous system at its greatest simplicity is necessarily com-
posed of two kinds of parts, viz. a main medullary mass and nervous
threads running into it; we may feel how great was the progress
required in the complexity of animal organisation, starting from the
Monas, which is the simplest and most imperfect of known animals,
before nature could have attaimed the formation of such a system of
organs even in its greatest imperfection. Yet when this system begins,
its complexity and perfection are still very far from what we find in
the most perfect animals; and before it could begin, animal organisa-
tion had already made much progress in development and complexity.

To convince ourselves of this truth, let us examine the products of
the nervous system at its chief stages of development.

Toe Nervous System IN ITs SimpLtest STATE PRODUCES
NOTHING BUT MuscuLaR MovEMENT.

I have, it is true, nothing more than a mere opinion to offer on this
subject ; but it is based on considerations of such importance and
weight that it may at least be regarded as a moral truth.

If the procedure of nature is attentively examined, it will be seen
that in the creating or giving existence to her productions, she has

THE NERVOUS SYSTEM 30

never acted suddenly or by a single leap, but has always worked b:
degrees towards a gradual and imperceptible development: conse-
quently all her products and transformations are everywhere clearly
subject to this law of progress.

If we follow the operations of nature, we shall indeed see that she
created by successive stages all the tissues and organs of animals,
that she gradually brought them to completion and perfection, and that
in the same way by slow degrees she modified, animalised, and com-
pounded all the internal fluids of the animals she had brought into
existence ; so that in course of time they were brought to the condition
in which we now see them.

The nervous system at its origin is assuredly in its greatest simplicity
and least perfection. This kind of origin is common to it, as to all
the other special organs, which also began in their most extreme state
of imperfection. Now it cannot be doubted that, in its greatest
simplicity, the nervous system gives to the animals possessing it less
numerous and lofty faculties than it bestows on the more perfect
animals, where it has reached its highest complexity and acquired
its accessories. We only have to observe the facts to recognise the
truth of this statement.

I have already proved that when the nervous system is in its greatest
simplicity, it necessarily has two kinds of parts, viz.: a main medullary
mass and nervous threads which run into this mass; but this same
medullary mass may at first exist without giving rise to any special
sense, and it may be divided into separate parts, to each of which
Tun nervous threads.

Such appears to be the case in animals of the class of radiarians,
or at least in those of the division of echinoderms in which a nervous
system is supposed to have been discovered; the system would be
reduced to separate ganglia, communicating together by threads and
sending out others to the parts.

If the observations, which affirm this state of the nervous system,
are well-founded, we have here the system in its greatest simplicity.
It possesses several centres of communication for the nerves, that is
to say, as many nuclei as there are separate ganglia; lastly, it does
not give rise to any of the special senses, not even to sight, which is
certainly the first to show itself unequivocally.

By special senses I mean those which result from special organs
such as sight, hearing, smell, and taste; as to touch, it is a general
sense, a type no doubt of all the rest, but needing no special organ and
incapable of being yielded by the nerves until they are competent to
produce sensations.

When I come to describe in Chapter ITI. the mechanism of sensations,
U

306 ZOOLOGICAL PHILOSOPHY

we shall see that none of them can be produced except when the whole
animal shares in the general effect, by reason of the complexity of its
nervous system and of the single common nucleus for the nerves.
If this is the case, it follows that in animals with the most elementary
nervous systems, where there are different nuclei for the nerves, no
effect or agitation can become generalised through the individuals,
no sensation can be produced, nor can the separate medullary masses
give rise to any special sense. If these separate medullary masses
communicate together by threads, it is in order to secure the free
distribution of the nervous fluid within them.

Yet as soon as the nervous system exists, however simple it may
be, it must be capable of performing some function ; we may therefore
hold that it has an effective action, even when it cannot yet give rise
to feeling.

If we reflect that, for the excitation of muscular movement, which is
the least of the faculties of the nervous system, a lower degree of
complexity and less extent of its parts are required than for the pro-
duction of feeling, and moreover that separate centres of communica-
tion are no bar to the nervous fluid conveying its influence to the
muscles from the individual nuclei, it will then appear very probable
that the animals with the simplest nervous systems derive from it the
faculty of muscular movement, while yet being destitute of feeling.

Thus on starting the nervous system, nature appears to have formed
at first only separate ganglia, communicating together by threads and
dispatching other threads to the muscular organs. These ganglia are the
main medullary masses; and although they communicate by threads,
the separation of the nuclei prohibits the general effect necessary for
constituting sensation, though it is not opposed to the excitation of
muscular movement: hence the animals which possess such a nervous
system are devoid of any special sense.

Having now seen that the nervous system in its extreme simplicity
can only produce muscular movement, we shall go on to show that
when nature has developed, compounded, and further perfected this
system, she proceeded to endow it not only with the faculty of exciting
muscular action but also with that of producing feeling.

Tue Nervous System oN REACHING A HicHEeR CoMPLEXITY PRO-
DUCES BOTH MuscuLaR MovEMENT AND FEELING.

Of all the systems of organs the nervous system is doubtless that
which confers upon animals the most lofty and the most marvellous
faculties ; but unquestionably it only reaches this point after having
acquired its highest possible complexity and development. Prior to
this stage, the animals which have nerves and a main medullary

THE NERVOUS SYSTEM 307

mass present all degrees of perfection in the faculties derived from
them.

I have already said that in its greatest simplicity the nervous system
appears to have its main medullary mass divided into several separate
parts, each of which contains an individual nucleus for the nerves
running into it. In this condition the system is not adapted for pro-
ducing sensations, though it has the faculty of setting the muscles
in action: now, does this very imperfect nervous system, which is
alleged to have been identified in the radiarians, also exist in the
worms? I do not know; and yet there are grounds for the belief,
unless the worms are a branch of the animal scale started afresh by
spontaneous generation. All I know is that in animals of the class
which follow the worms, the nervous system has reached a much
higher stage of development, and is quite easy to see and possesses a
very definite form.

Indeed, as we follow the animal scale from the most imperfect to
the most perfect animals, the first appearance of the nervous system
has hitherto seemed to be in the insects; because in all the animals of
this class it is very clearly defined, and presents a ganglionic longitudinal
cord, which as a rule extends throughout the animal’s length and is
greatly diversified in shape according to the species of insect and to the
state of larva or perfect insect. This longitudinal cord, which ends
anteriorly in a subbilobate ganglion, constitutes the main medullary
mass of the system, and from its ganglia, which vary in size and
proximity, nervous threads proceed to the various parts of the
body.

The subbilobate ganglion at the anterior extremity of the ganglionic
longitudinal cord of insects has to be distinguished from the other
ganglia of the cord, since it gives rise directly to a special sense—that
of sight. This terminal ganglion is, then, really a small and very
imperfect brain, and doubtless contains the centre of communication
of the sensitive nerves, since the optic nerve runs into it. Perhaps the
other ganglia of the longitudinal cord are in the same way special
nuclei, which provide for the action of the animal’s muscles: if these
nuclei exist, they would not prevent the general effect which alone,
as I have proved, can produce feeling, since they are united by the
nervous cord.

Thus in the insects, the nervous system begins to present a brain
and single centre of communication for the production of feeling.
These animals, by the complexity of their nervous system, possess then
two distinct faculties, viz.: that of muscular movement and that of
experiencing sensations. These sensations are probably still only
simple and fugitive perceptions of the objects which affect them,

308 ZOOLOGICAL PHILOSOPHY

but they suffice at least to constitute feeling, although incapable
of producing ideas.

This state of the nervous system, which gives rise in insects only
to these two faculties, is almost the same in the animals of the five
following classes, viz.: arachnids, crustaceans, annelids, cirrhipedes,
and molluscs; there are apparently no other differences than those
involved by a higher development of the two faculties named.

T have not a sufficient number of observations to be able to indicate
which of the animals possessing a nervous system, capable of support-
ing sensations, are liable to experience emotions of their inner feeling.
It may be that as soon as the faculty of feeling exists, that which
produces emotions arises also; but the origin of the latter is so vague
and imperfect that I believe it can only be recognised in vertebrates.
Let us then pass on to a determination of the point in the animal scale
at which begins the fourth kind of faculty of the nervous system.

When nature had supplied the nervous system with a true brain,
that is, with an anterior medullary swelling, capable of giving rise
immediately to at least one special sense such as sight, and of con-
taining in a single nucleus the centre of communication of the nerves,
she had not yet completed the development of the system. Indeed
she long continued to be concerned with the gradual development of
the brain, and started the rudiments of the senses of hearing in the
crustaceans and molluscs. But it still continues to be a very simple
brain, appearing to be the basis of the organ of feeling, since the
sensitive nerves and those of the existing special senses proceed to
unite with it.

Indeed the terminal ganglion, which constitutes the brain of insects
and of the animals of the following classes up to and including the
molluscs, although as a general rule divided by a furrow and to some
extent bilobate, still shows no trace of the two wrinkled hemispheres,
so susceptible of development, which in the most perfect animals
cover over the true brain, viz. that part of the encephalon which
contains the nucleus of the sensitive system; hence the functions,
for which these new accessory organs are adapted, cannot be per-
formed in any of the invertebrates.

THe Nervous System In 1Ts CompLETE STATE GIVES RISE TO
MuscutaR Movements, Fee.tinec, THE INNER EMOTIONS AND
INTELLIGENCE.

It is only among the vertebrates that nature has arrived at the
completion of every part of the nervous system ; and it is probably
in the most imperfect of these animals (viz. the fishes) that she started
the rudiments of the accessory organ of that brain which consists

THE NERVOUS SYSTEM 309

of two wrinkled hemispheres, situated opposite one another but united
at their base. The hemispheres are commonly confused with the brain
properly so called, but this name should be confined to that region
which contains the sensitive centre.

The accessory organ which, when highly developed, confers mar-
vellous faculties on animals, rests upon the brain and covers it over
entirely, so as commonly to be confused with it ; for as a rule the name
of brain is given to the entire medullary mass enclosed in the cavity
of the cranium. We should however distinguish between the brain
properly so called and its accessory organ, however difficult the dis-
tinction may be; for the accessory organ fulfils altogether special
functions, and is neither essential to the brain nor even to the
maintenance of life. It therefore deserves a special name, and I
propose to call it the hypocephalon.

Now this hypocephalon is the special organ in which ideas and all
acts of intelligence are carried out; no such phenomena could take
place in the true brain, viz. that part of the main medullary mass
which contains the centre of communication of the nerves, and where
also the nerves of the special senses meet.

If we regard the brain as that medullary mass which serves as the
meeting place for the various nerves, contains their centre of communi-
cation, and, in short, comprises the nucleus from which nervous fluid is
dispatched to the various parts of the body and to which it is returned
when it evokes any sensation, it will then be true to say that the brain
even of the most perfect animals is always very small. But when the
brain is provided with two hemispheres which cover it over and are
more or less confounded with it, and when these wrinkled hemispheres
become very large, it is customary to give the name of brain to the
whole medullary mass enclosed within the cranial cavity. Hence the
whole of this medullary mass is generally regarded as consisting of

only a single organ, whereas the fact is that it contains two, whose
functions are essentially distinct.

~~ Not only are the hemispheres special organs accessory to the brain,
but they are in no way essential to the existence of the brain; this
is placed beyond doubt by many known facts, showing that lesions
may occur in them or that they may even be destroyed. With regard
to the functions fulfilled by the hemispheres, there must be an emission
of nervous fluid, which travels to these organs from its common reservoir
or nucleus and enables them to carry out the functions for which they
are adapted. Thus we may be sure that it is not the hemispheres
themselves which dispatch to the nervous system the special fluid
by which it works; for in that case the entire system would be

dependent on them; which it is not.

310 ZOOLOGICAL PHILOSOPHY

From these principles it follows: that all animals which have a
nervous system need not necessarily have a brain, since the latter is
characterised by the faculty of giving immediate rise to some sense,
at all events the sense of sight; that all animals which have a brain
need not also have two wrinkled hemispheres, for the smallness of the
brain in the last six classes of invertebrates shows that it can only
serve for the production of muscular movement and feeling, and not
for acts of intelligence; lastly, that all animals, whose brains are
provided with two wrinkled hemispheres, possess the power of muscular
movement and of feeling, the faculty of experiencing inner emotions,
and, in addition, that of forming ideas, making comparisons and judg-
ments and, in short, of carrying out various acts of intelligence,
corresponding to the degrees of development of the hypocephalon.

On paying careful attention to the matter we shall feel that the
operations which give rise to thoughts, meditations, etc., occur in the
superior and anterior part of the brain, that is, in the two wrinkled
hemispheres. We can, moreover, make out that these operations are
not carried out either in the base of the brain, or in its posterior and
inferior part. The two cerebral hemispheres composing what I call
the hypocephalon, are therefore really special organs in which acts of
intelligence are produced. Thus when we are thinking and fix our
attention too long on one subject, we feel a pain in the head, especially
in the part that I have mentioned.

It follows from these various principles that among animals which
have a nervous system :

1. Those which have no brain, and consequently no special senses
nor single centre of communication for the nerves, do not possess
feeling but only the faculty of moving their parts by true muscles ;

2. Those which have a brain and special senses, but not the wrinkled
hemispheres which constitute the hypocephalon, only derive two or
three faculties from their nervous system, viz. those of performing
muscular movements, of experiencing sensations, that is to say, simple
and fugitive perceptions when any object affects them, and perhaps
also of experiencing inner emotions ;

3. Lastly, those which have a brain together with its accessory
hypocephalon enjoy the capacity for muscular movement, feeling,
and emotion, and can moreover, by means of an essential condition
(attention) form ideas, which are impressed on the organs, compare
these ideas together, and produce judgments; and if their hemi-
spheres are developed and perfected, they can think, reason, invent,
and perform various intelligent acts.

No doubt it is very difficult to imagine how the impressions are
formed that correspond to ideas; nothing whatever can be seen to

THE NERVOUS SYSTEM 311

indicate their existence in the brain. But surely the only conclusion
to be drawn from this, is the extreme fineness of the marks, and the
limitations of our own faculties. Will any one say that nothing
exists but what man can perceive? It is enough for us that
memory is a certain testimony of the existence of these impressions
in the brain.

If it is true that nature does nothing suddenly or at a single swoop,
she must have created successively all the organs which give rise to the
faculties observed in the most perfect animals; and this is just what
she has done, with the help of time and favourable conditions.

This assuredly has been her procedure, and we cannot substitute
any other for it unless we abandon the positive ideas that we derive
from the observation of nature.

Thus in the animal organisation, the nervous system was created
in its turn like the other special systems, and this can only have occurred
when the organisation was sufficiently developed for the three sorts
of substances composing this system to have been formed and
deposited in their proper situations.

It is therefore absurd to expect to find this system with its
dependent faculties in animals so simply organised and so imperfect
as the infusorians and polyps; for it is impossible that such complex
organs could exist in these creatures.

Let me repeat that just as the special organs in animals were formed
one after the other, so too each of them was gradually compounded,
completed and perfected in correspondence with the increasing com-
plexity of organisation ; so that the nervous system presents in different
animals the three following principal stages.

At its origin, when it is in its highest imperfection, the system
appears to consist merely of various separate ganglia, which have
communicating threads and from which issue other threads to certain
parts of the body : it then shows no brain and cannot give rise either
to sight, hearing, or possibly any true sensation; but it already
possesses the faculty of exciting muscular movement. Such apparently
is the nervous system of the radiarians, if there is any truth in the
observations cited in Part I. of this work (Chapter VIII., p. 138).

At its next stage, the nervous system presents a ganglionic longitudi-
nal cord and nervous threads which terminate in the ganglia of that
cord : henceforward the ganglion at the anterior extremity of the cord
may be regarded as a rudimentary brain, since it gives rise to the organ
of sight and subsequently to that of hearing ; but this small brain is
still simple and has no hypocephalon or wrinkled hemispheres with
special functions. Such is the nervous system of insects, arachnids,
and crustaceans,—animals which have eyes and in the latter case even

312 ZOOLOGICAL PHILOSOPHY

some traces of hearing: such again is the nervous system of annelids
and cirrhipedes, some of which possess eyes, while others are destitute
of them for the reasons named in Chapter VII. of Part I.

The molluscs, although having a higher organisation than the
animals just mentioned, are in the midst of a change of plan on nature’s
part, and have no ganglionic longitudinal cord nor spinal cord; but
they have a brain and some of them seem to possess the most perfect.
of the simple brains, that is, of brains without a hypocephalon : since
the nerves of several special senses terminate in them. If this is the
case, then the nervous system produces muscular movement and feeling
in all animals from the insects to the molluscs inclusive, but it does not.
permit of the formation of ideas.

Lastly, at a far more perfect stage, the nervous system of vertebrates
presents a spinal cord, nerves and a brain, of which the superior and
anterior part is provided with two accessory wrinkled hemispheres
whose development is proportional to the stage of progress of the new
plan. This system then gives rise not only to muscular movement,
feeling and inner emotions, but also to the formation of ideas, the
clearness and number of which are proportional to the development
of the hemispheres.

How can any one suppose that nature, who in all her productions
invariably proceeds by gradual stages, could have endowed a nervous
system at once with all the faculties which it possesses when it has
attained its ultimate completion and perfection ?

Moreover, since the faculty of feeling is not the property of any
substance of the body, we shall see that the mechanism necessary for
its production is so complex that the nervous system in its extreme
simplicity could have had no other faculty than that of exciting
muscular movement.

I shall endeavour to ascertain in Chapter IV. what is the power that
causes and directs the emissions of nervous fluid to the hemispheres
or other parts of the body. I shall merely say here that the dispatch
of this fluid to the cerebral hemispheres arouses in them functions very
different from those aroused in the muscles and vital organs.

I have now given a brief general account of the nervous system, the
nature of its parts, the conditions that were required for its formation,
and the four kinds of functions that it fulfils when it has attained its
perfection.

Without undertaking any enquiry as to how nervous influence may
set the muscles in action and cause the performance of their functions
by various organs, I may observe that the explanation is probably
to be found in a stimulus to the irritability of the parts.

But in the case of that function of the nervous system through which

THE NERVOUS SYSTEM 313

feeling is produced and which is rightly regarded as the most astonish-
ing and difficult to conceive, I shall endeavour to describe the
mechanism in Chapter III. I shall then do the same for the fourth
function of the nervous system by which it produces ideas, thoughts
etc., a function still more extraordinary than that which gives rise
to feeling.

Since, however, I do not wish to set forth in this work anything
that is not based on adequate facts or observations, I shall first
consider the nervous fluid, and show that, so far from being a product
of imagination, this fluid is made manifest by effects which cannot

be otherwise produced, and which leave not the slightest doubt as to
its existence.

CHAPTER II.

OF THE NERVOUS FLUID.

N A SUBTLE substance, remarkable for the rapidity of its movements and
receiving little attention because it cannot be directly observed,
collected, nor experimentally examined ; a substance of this character
is the very strange and wonderful agent that nature employs for
producing the muscular movement, feeling, inner emotions, ideas, and
acts of intelligence, which many animals are able to carry out.

Now since we can only know this substance through the effects
that it produces, we must begin by discussing it at the outset of the
third part of this work; this fluid is the only substance capable of
causing the phenomena which so much excite our wonder; and if
we refuse to admit its existence and powers, we shall be forced to
abandon all search for physical causes for these phenomena and to
have recourse once more to vague and baseless theories for the satis-
faction of our curiosity.

With regard to the necessity for investigating this fluid by means
of its effects, is it not now an admitted fact that there exist in nature
various kinds of substances, imperceptible to our senses, that we cannot
take hold of, nor collect and examine as we should like; substances
so attenuated and so subtle that they can only manifest their existence
under certain circumstances, and through the medium of some of their
results, which we succeed by careful attention in identifying; sub-
stances, in short, whose nature we can only ascertain up to a certain
point by means of inductions and analogies, guided by a large number
of observations ? The existence of these substances is however proved
by certain effects which can be produced in no other way; effects
which we have to study carefully in various phenomena whose causes
we seek,

It may be said by some that since we possess so few means for
determining with precision the nature and qualities of these sub-
stances, every wise man who is concerned only with exact knowledge
should leave them out of account.

THE NERVOUS FLUID 315

I may be mistaken, but I confess that I am of quite a different
opinion ; I am firmly convinced that these same substances play an
important part in most of the physical facts that we observe, and
especially in the organic phenomena presented by living bodies; and
hence that their investigation is of the greatest importance for the
progress of knowledge on these subjects.

Thus, although we cannot know directly all the subtle substances
existing in nature, yet if we were to abandon all enquiry with regard to
some of them, we should in my opinion be rejecting the only clue that
can lead to a knowledge of natural laws; we should be giving up the
hope of real progress in our knowledge of living bodies, as also of the
causes of the phenomena that we observe in their functions ; we should
at the same time be relinquishing the only path that can lead to the
perfection of our physical and chemical theories.

It will soon be clear that these remarks are not irrelevant to my
purpose, and indeed that they are entirely applicable to that nervous
fluid about which we so greatly desire information.

Since our observations are now too advanced to permit of any real
doubt as to the existence of a subtle fluid which circulates and moves
about in the substance of the nerves, let us see how far we are led, on so
delicate and difficult a subject, by the actual state of knowledge.

But before speaking of the nervous fluid, it is very important to
establish the following proposition :

All the visible fluids contained in an animal’s body, such as the
blood or substitute for the blood, the lymph, secreted fluids, etc., move
too slowly in the canals or parts which contain them, to be capable of
conveying with sufficient rapidity the movement or cause of move-
ment which produces actions in animals; for these actions are carried
out in many animals with an amazing rapidity and vivacity, and the
animals can interrupt them, start them again, and vary them with all
possible degrees of irregularity. The slightest reflection should suffice
to convince us that it is absolutely impossible that fluids so gross as
those just mentioned, and whose movements are usually so regular,
can be the cause of the various actions of animals. Yet everything
that passes in them results from relations between their contained
fluids, or such as penetrate into them, and their containing parts, or
the organs affected by these contained fluids.

Assuredly it can only be a fluid, moving almost with the swiftness
of light, that could work such effects as those I have named ; now we
have some knowledge of fluids which possess this faculty.

All action is the product of movement, and the nerves certainly
act by a movement of some sort; the opinion of those who regarded
the nerves as vibrating cords has been discussed and effectually refuted

316 ZOOLOGICAL PHILOSOPHY

by M. Richerand in his Physiologie (vol. ii., p. 144 et seqg.). “ This
hypothesis,” he says, “‘is so absurd that there is reason for astonish-
ment at the favour that it has long enjoyed.”

The same thing might well be said of the hypothesis of vibration
among molecules so soft and inelastic as those of the medullary sub-
stance of nerves, if anyone were to suggest it.

“Tt is much more reasonable,’’ M. Richerand continues, “‘ to believe
that the nerves act by means of a subtle, invisible, impalpable fluid
to which the ancients gave the name of animal spirits.”

Farther on, when examining the special properties of the nervous
fluid, this physiologist adds: “‘ Have not these conjectures acquired
some degree of probability, since the analogy between galvanism and
electricity, originally suggested by their discoverer, has been confirmed
by those remarkable experiments of Volta, which are at this moment
being repeated, discussed and expounded by all the physicists in
Europe ?”

However manifest may be the existence of the subtle fluid by means
of which the nerves work, there will be for a long time and perhaps
for ever, men who dispute it because it cannot be proved except by
effects which could not be produced in any other way.

Yet it seems to me that when all its effects unite to demonstrate
its existence, it is wholly unreasonable to deny it on the mere grounds
that we cannot see the fluids. It is particularly unreasonable to do so,
seeing that we know that all organic phenomena result exclusively
from relations between moving fluids and the organs concerned. It
is still more unreasonable when we remember that the visible fluids
(blood, lymph, etc.) which travel to the nerves and brain and penetrate
their substance are too gross and move too slowly to be capable of
giving rise to actions of such swiftness as those involved in muscular
movement, feeling, ideas, thought, etc.

As a result of these reflections, I recognised that in every animal
which possesses a nervous system there exists in the nerves and in the
medullary nuclei where the nerves terminate, a very subtle, invisible,
containable fluid, that is but little known since there are no means for
examining it directly. This fluid, which I call nervous fluid, moves
with extraordinary rapidity in the substance of the brain and nerves,
and yet does not form any visible channels in them for the transmission
of its movements.

It is by means of this subtle fluid that the nerves work, that muscular
movement is set going, that feeling is produced, and that the cerebral
hemispheres carry out those acts of intelligence to which they give
rise in proportion to their development.

Although the actual nature of the nervous fluid is little known to us

THE NERVOUS FLUID 317

since we can only appreciate it by its effects, yet since the discovery of
galvanism, it has become increasingly probable that it is closely
analogous to the electric fluid. I am convinced even that it és electric
fluid, which has been modified in the animal economy and to some
extent animalised by its residence in the blood, and which has there
undergone sufficient change to have become@ontainable)and to remain
entirely within the medullary substance of the nerves and brain, to
which it is incessantly provided by the blood.

I base this statement, viz. that the nervous fluid is only electricity
modified by its residence in the animal economy, on the fact that
this nervous fluid, although its effects closely resemble some of those
produced by the electric fluid, is yet distinguished from it by some
peculiar properties, among which that of being retained within an
organ and moving about there, sometimes in one direction and some-
times in another, appears to be characteristic.

The nervous fluid is therefore quite distinct from the ordinary
electric fluid, since the latter passes through every part of our body at
its usual velocity and without any pause, when we complete a circuit
in the discharge of a Leyden jar or electric conductor.

It is different even from the galvanic fluid obtained from Volta’s

pile: the latter indeed, which is still only electric fluid acting in a
smaller quantity, density and activity than the electric fluid of a Leyden
jar or charged conductor, derives from its special circumstances
certain properties or faculties which distinguish it from the electric
fluid collected and condensed by our ordinary methods. This galvanic
fluid therefore has more action on our nerves and muscles than the
ordinary electric fluid: yet since it is not animalised, that is to say,
has not undergone the influence imparted by a residence in the blood
(especially of warm-blooded animals), it does not possess all the qualities
of the nervous fluid.
* The nervous fluid of cold-blooded animals, being less animalised,
is more allied to the ordinary electric fluid and especially the galvanic
fluid. This is the reason why our galvanic experiments produce very
energetic effects on the tissues of cold-blooded animals like frogs ;
and also why in certain fishes such as the torpedo, the electric eel, and
the trembling catfish, a large electrical organ generates electricity
which is completely adapted to the animal’s needs. (See the interest-
ing Memoir of M. Geoffroy on these fishes in the Annales du Muséum
@ Histoire naturelle, vol. i., p. 392.)

In spite of the modifications by which the electric fluid is converted
into nervous fluid, it still preserves to a great extent its extreme
subtlety and rapidity of movement ; qualities which render it suitable
for performing its functions in the animal.

318 ZOOLOGICAL PHILOSOPHY

This electric fluid is incessantly penetrating into the blood, either by
respiration or some other method, and is there gradually modified
and animalised so as to acquire at length the properties of the nervous
fluid. Now we may probably regard the ganglia, spinal cord, and
especially the brain with its accessories, as the organs which secrete
this animal fluid.

There is indeed reason to believe that the substance of the nerves,
which, on account of its albumino-gelatinous nature, is a better con-
ductor of the nervous fluid than any other substance of the body,
and far better than the aponeurotic membranes which invest the
nervous threads and cords, continually draws off the subtle fluid in
question from the minute arteries circulating in it. It is no doubt
these minute arteries and veins that give rise to the grey colour of the
external or cortical layer of the medullary substance.

In this way, there is incessantly produced in animals with a nervous
system the subtle and invisible fluid which moves in the substance
of their nerves and in the medullary nuclei where these nerves terminate.

This fluid works in the nerves by two kinds of movements in opposite
directions; and the activities of the cerebral hemispheres suggest
that it carries out many and varied movements in them that are
beyond our powers of ascertaining.

In the nerves which give rise to sensations, we know that the fluid
moves from the periphery of the body towards the centre, or rather
towards the nucleus that produces these sensations; and since the
individuals which have a nervous system may also experience internal
impressions, the fluid in these cases moves in the nerves of the internal
regions, but still in the direction of the nucleus of sensations.

In the nerves which produce muscular movement, on the contrary,
whether voluntary or involuntary, the nervous fluid moves from the
centre or common nucleus towards the parts which have to be moved.

In both these cases where the nervous fluid moves in the nerves,
and also in the case of its various movements in the brain, the activity
of this fluid consumes a certain part of it, which is thereby dissipated
and lost. This loss necessitates a restoration, which is continually
being made by healthy blood.

The following is a very important observation for understanding
the phenomena of organisation :

Individuals, which use their nervous fluid only for the production
of muscular movement, make good their losses with interest, so that
their strength is increased ; since this muscular movement accelerates
the circulation and other organic movements, and the secretions
which make up for the used fluid are copious at the periods of rest.

Individuals, on the other hand, who use their nervous fluid only in

THE NERVOUS FLUID 319

the production of acts depending on the hypocephalon, such as con-
tinuous thought, deep meditation, mental agitation produced by
passions, etc., make good their losses slowly and often incompletely ;
for muscular movement is then slight, the organic movements are
enfeebled, the organic faculties lose their energy, and the secretions,
which make up for the nervous fluid used, become less copious, and
mental repose very difficult.

The nervous fluid in the brain does not merely convey sensations
from their nucleus, and move about in various ways, but it also stamps
impressions on the organs, and these impressions last longer or shorter
according to their depth.

This statement is not one of those monstrous products begotten by
the imagination: in a brief review of the chief acts of intelligence,
I shall endeavour to show that it is well-founded, and that we are
obliged to recognise it as one of those truths, that can still only be
attained by irrefutable inductions.

T shall conclude my remarks on this singular fluid by some observa-
tions which may throw much light over the various organic functions
fulfilled by means of this fluid.

All parts of the nervous fluid are in communication, in the system
of organs which contains them ; so that, according to the causes which
excite it, either a part of the fluid may be set in motion, or nearly the
whole fluid, or at least such part of it as is free.

The occasions when motion occurs only in parts of it, which may
even be quite small, are as follows :

1. When it stimulates muscular activity, either dependent or
independent of the will of the individual ;

2. When it performs some act of intelligence.

The same fluid, on the contrary, moves as a whole (so far as it is
free) :

1. When it produces any sensation by some general movement of
reaction ;

2. Whenever it causes emotions of the inner feeling by a general
agitation that does not constitute a reaction.]

These details as to the movements of the nervous fluid cannot be
proved by individual experiments; at least I do not see how; but
the reader will probably think them justified, if he closely follows my
observations on the functions of the nervous system in this third part
of my Zoological Philosophy. In particular, the following facts should
be considered :

1. That the nervous influence which moves the muscles only demands
a simple emission of a part of the nervous fluid towards the muscles
which have to act, and that the fluid here acts only as a stimulus ;

320 ZOOLOGICAL PHILOSOPHY

2. That, in acts of intelligence, the organ of understanding is only
passive and is prevented from reacting by its extreme softness; it
acquires no activity from the nervous fluid but merely impressions,
of which it preserves the tracings; the part of the fluid, which works
in the various portions of this organ, is modified in its movements
by the tracings already present, and at the same time traces more ;
so that the organ of understanding, which has only a narrow channel
of communication with the rest of the nervous system, uses only a
part of the whole fluid of the system. Moreover this narrow channel
of communication preserves that part of the nervous fluid, contained
in the organ of intelligence, from the general agitation which occurs
in emotions of the inner feeling, and in the formation of sensations,
except when that agitation is of great intensity, in which case nearly all
the functions and faculties of the system are disturbed.

On these grounds, it appears probable that the entire mass of nervous
fluid secreted and contained in the system is not at the disposal of the
inner feeling of the individual, but that some of it is held in reserve
to provide for the continuance of the vital functions. Hence, just as
there are muscles independent of the will, and others which only enter
into activity when excited by the inner feeling driven by the will or
some other cause ; in the same way, no doubt, one part of the nervous
fluid is less at the service of the individual than the other, lest the
whole fluid should be drained away from the vital functions.

Indeed, since the nervous fluid is never used without a proportional
amount of loss, it follows necessarily that the individual is only free to
use up a certain part of it: untoward effects ensue even when this part
is run too low, for then some of that held in reserve becomes available
and the vital functions suffer accordingly.

I shall have further opportunities later on for extending these
various remarks on the nervous fluid; but let us first enquire what
is the mechanism of sensations, and how the marvellous faculty of
feeling is produced.

CHAPTER III.

OF PHYSICAL SENSIBILITY AND THE MECHANISM OF
SENSATIONS.

How are we to conceive that certain parts of a living body can possess
the faculty of feeling, when no kind of matter whatever does or can
enjoy any such faculty !

It was indeed a great mistake to imagine that animals, even the most
perfect, were endowed with feeling in certain of their parts. Assuredly
the various humours and fluids of living bodies can no more possess
the faculty of feeling than the solid parts.

It is only by a real hallucination that the separate parts of our body
appear to be sensitive; for it is our entire being that feels or rather
undergoes a general effect, on the stimulus of some affective cause.
Since this effect is always referred to the part affected, we promptly
derive from it a perception to which we give the name of sensation ;
and we are misled into the belief that it is the affected part of our
body that feels an impression, whereas it is a commotion throughout
the entire sensitive system which conveys to that part its general
effect.

These considerations may appear strange and even paradoxical,
for they are far removed from the common opinion on this subject.
Yet if the reader will suspend his judgment until he has examined the
grounds on which I base my opinion, he will doubtless abandon the
idea of attributing the faculty of feeling to any individual part of a
living body. But before stating my views, it must first be determined
what animals possess the faculty of feeling and what animals have no
such faculty.

Let me first enunciate the following principle: Every faculty possessed
by animals is necessarily the product of an organic act and consequently
of some movement ; if the faculty is special, it results from the function
of some special organ or system of organs; but no part of the animal

body that remains motionless could possibly give rise to any organic
=

322 ZOOLOGICAL PHILOSOPHY

phenomenon, not even to the smallest faculty. Hence feeling, which
is a faculty, is not a property of any individual part, but the result
of an organic function.

I infer from the above principle that every faculty, that arises
exclusively from the functions of some especial organ, is confined to
animals which possess that organ. Thus just as no animal can see
unless it has eyes, so no animal can feel unless it has a nervous
system.

It is useless to object that light does make impressions on certain
living bodies that have no eyes, and affects them in spite of that
deficiency : it still remains true that plants and a number of animals,
such as polyps and many others, do not see although they move
towards the light ; and that all animals are not endowed with feeling,
although they may perform movements when irritated in special
ways.

No sort of sensibility (conscious or latent) can, then, be ascribed to
animals that have no nervous system, on the mere grounds that they
have irritable parts; I have already shown in Part II., Chapter IV.,
that feeling and irritability are very different in character, and are due
to quite unlike causes. Indeed the conditions required for the pro-
duction of feeling are of altogether another nature from those necessary
for the presence of irritability. The former demand a special organ
which is always distinct, complex, and extended throughout the
animal’s body, whereas the latter demand no special organ and give
tise only to an isolated and local phenomenon.

But animals, which possess a sufficiently developed nervous system,
possess at the same time their natural irritability and also the faculty
of feeling; they have, without being conscious of it, the intimate
feeling of their existence, and though they are still liable to excitations
from without, they act by an internal power that we shall shortly
examine.

In some, the activities of this internal power are guided by instinct,
that is, by inner emotions produced by their needs and habits; while
in others they are guided by a will that is more or less free.

Thus the faculty of feeling is exclusively the property of animals
which have a sensitive nervous system ; and since it gives rise to the
intimate feeling of existence, we shall see that this latter feeling
endows animals with the faculty of acting by emotions which cause
them internal excitations, and permit them to produce for themselves
the movements and actions necessary for the satisfaction of their
needs.

But what is physical sensibility or the faculty of feeling? What
again is the inner feeling of existence? What are the causes of these

PHYSICAL SENSIBILITY 323

wonderful phenomena? Lastly, how can the feeling of existence or
general inner feeling give rise to a force that produces action ?

I have conscientiously considered these matters and the wonders
that flow from them, and now state my opinion on the first of these
interesting questions.

The faculty of receiving sensations constitutes what I call physical
sensibility, or feeling properly so called. This sensibility must be
distinguished from moral sensibility which is quite a different thing,
as I shall show, and which is only excited by emotions raised in us
by our thoughts.

Sensations arise in us, on the one hand, from the impressions that
external objects make on our senses; and, on the other hand, from those
made on our organs by disordered internal movements which have an
injurious effect and produce internal pains. Now these sensations
affect our physical sensibility or faculty of feeling, bring us into com-
munication with the outer world, and acquaint us vaguely with what
is happening within us.

Let us now enquire into the mechanism of sensations, and let us
begin by showing the harmony which exists in all the parts concerned
of the nervous system, and afterwards the result on the entire system
of any impression on a single part of it.

MEcHANISM OF SENSATIONS.

Sensations, which by an illusion we refer to the actual places where
the impressions that cause them are made, are based upon a system
of special organs belonging to the nervous system and called the system
of sensations or of sensibility.

The system of sensations is composed of two essential and distinct
parts, viz. :

1. A special nucleus, that I call the nucleus of sensations, and must
be regarded as a centre of communication to which are conveyed all
the impressions which act upon us ;

2. A large number of simple nerves which start from all the sensitive
parts of the body and proceed to their destination in the nucleus of
sensations.

It is with this system of organs, whose harmony is such that all or
nearly all parts of the body share equally in an impression made on
any one part, that nature succeeds in giving, to all animals with a
nervous system, the faculty of feeling both what affects them internally
and also impressions made upon their senses by external objects.

It may be that the nucleus of sensations is broken up and multiple
in animals which have a ganglionic longitudinal cord; yet we may
suspect that the ganglion at the anterior extremity of the cord is a

324 ZOOLOGICAL PHILOSOPHY

small rudimentary brain, since it gives rise immediately to the sense
of sight. But in the case of animals which have a spinal cord, there
can be no doubt that the nucleus of sensations is simple and indivisible ;
this nucleus is apparently situated at the anterior extremity of the
spinal cord, at the base of what is called the brain and therefore below
the hemispheres.

The sensitive nerves arriving from all parts and terminating in a
centre of communication, or in several such nuclei connected together,
constitute the harmony of the system of sensations, for they spread
throughout the system all the impressions, whether isolated or
generalised, that the individual may experience.

To form a clear conception of the wonderful mechanism of this
sensitive system, we must recall what I said before, viz. that an ex-
tremely subtle fluid, whose movements of translation or oscillation
are nearly as rapid as light, is contained in the nerves and their nucleus,
where it moves freely without escaping.

If we now consider that harmony which unites all parts of the system
of sensations, we see that every impression, internal or external, that
any individual receives, immediately causes an agitation throughout
the system or the subtle fluid contained in it, and consequently through-
out the entire body, although it may pass unperceived. Now this
sudden agitation promptly gives rise to a reaction, which is brought
back from all parts. to the common nucleus, and there sets up a
singular effect, in short, an agitation, which is thereafter propagated
through the one nerve, that does not react, to the point of the
body that was originally affected.

Man, who possesses the faculty of forming ideas out of what he
experiences, has formed one out of this singular effect produced at
the nucleus of sensations and propagated to the point affected, and
has given it the name of sensation, in the belief that every part
that receives an impression possesses in itself the faculty of feeling.
Feeling, however, does not exist anywhere but in the actual idea or
perception which constitutes it, simce it is not a faculty belonging to
any part of our body nor any of our nerves, nor even to the nucleus
of sensations, but is purely the result of an emotion of the whole
sensitive system which becomes perceptible in some point of our
body. Let us examine in further detail the mechanism of this
singular effect of the system of sensibility.

In the case of animals which have a spinal cord, there start from
every part of their body, the most deeply situated as well as the most
superficial, nervous threads of extreme fineness, which without any
division or anastomosis proceed to the nucleus of sensations. Now
these threads, in spite of junctions which they form with others,

PHYSICAL SENSIBILITY 325

travel without any discontinuity to their nucleus, always retaining
their individual sheaths. This does not prevent the nervous cords,
which arise from the junctions of several such threads, from having
their own sheath as well; and the same applies to the still larger
cords formed by the union of several of these.

Each nervous thread may thus be distinguished by the name of the
part where it starts, for it only transm‘ts impressions made on that
part.

We are here dealing exclusively with nerves serving for sensations :
those destined for muscular movement start apparently from some
other nucleus, and constitute a special system within the nervous
system, distinct from that of sensations; in the same way that the
latter is distinct from the system providing for the formation of ideas
and acts of the understanding.

It is true that in consequence of the close connection between the
system of sensations and that of muscular movement, paralysis usually .
extinguishes both feeling and movement in the parts affected ; never-
theless cases are seen where sensibility is quite extinct in certain parts
of the body which still possess freedom of movement,1 and this proves
that the systems of sensation and movement are really distinct.

The special mechanism which constitutes the organic act giving rise
to feeling, consists therefore in the following process :

When an impression is received at the extremity of a nerve, the
movement thereupon set up in the subtle fluid of that nerve is trans-
mitted to the nucleus of sensations, and from there to all the nerves
of the sensitive system. But the nervous fluid immediately reacts
from all the nerves together, and brings back this general move-
ment to the common nucleus, where the only nerve which brought
no reaction receives the entire product of all the rest and transmits
it to the point of the body originally affected.

For greater clearness let us take a special example of the details
of this mechanism.

1M. Hébréard records in the Journal de Médecine, de Chirurgie et de Pharmacie
that a man fifty years of age had suffered, ever since he was fourteen, from an absolute
insensibility in the right arm. Yet this limb retained its activity, size and usual
strength. A phlegmon grew upon it, causing heat, swelling and redness, but no pain
even when squeezed or pressed.

While working, this man fractured the bones of his fore-arm in their lower third.
At first he only heard a crack, and thought that he had broken the spade which he
held in his hand; but it was intact, and he only discovered his accident, because he
could not continue his work. The next day the site of the fracture had swollen, and
the temperature of the fore-arm and hand had risen: yet the patient experienced
no pain even during the extensions necessary for reducing the fracture, etc.

The author concludes from this fact and from similar experiences by other doctors,
that sensibility is absolutely distinct and independent from contractility, etc., etc.
(Journal de Médecine pratique, 15th June, 1808, p. 540).

326 ZOOLOGICAL PHILOSOPHY

If I am pricked in the little finger of one of my hands, the nerve of
the part affected runs in its special sheath and without communica-
tion with others to the common nucleus, where it delivers the agitation
it has received; this agitation is immediately propagated thence to
the fluid in all the other nerves of the sensitive system: then by a
true reaction or repercussion this agitation flows back from all points
to the common nucleus, where it produces a shock and a compression
of the agitated fluid on all sides save one. This total effect produces a
perception, the result of which is carried back by the single nerve
which did not react.

In point of fact, the nerve which brought in the original impression,
and thus set up the agitation of fluid in all the rest, is the only one
which gives no reaction ; for it is the only one that is active while all
the rest were passive. The whole effect of the shock produced in the
common nucleus and passive nerves, as also the resulting perception,
must therefore be carried off by this active nerve.

An effect of this kind resulting from a general movement throughout
the individual, necessarily advertises him of an event passing within ;
and this individual, though he cannot make out any details, derives
from it a perception to which he gives the name of sensation.

The strength of this sensation is presumably proportional to the
intensity of the impression, and its character would correspond with
the actual nature of the impression received ; it appears to be produced
in the very part affected, simply because the nerve of that part is the
only one affected by the general disturbance that is set up.

Thus every shock produced in the nucleus or centre of communica-
tion of the nerves, due to an impression received, is felt throughout
the body though always appearing to us to take place in the very
part which received the impression.

With regard to this impression, there is necessarily an interval
between the moment at which it is made and that when sensation is
produced, but this interval is so short, on account of the rapidity of
the movements, that it is impossible for us to perceive it.

Such, in my opinion, is the wonderful mechanism underlying physical
sensibility. Let me repeat that it is not matter that feels, for matter
has no such faculty ; it is not even a part of the individual’s body,
for the sensation experienced in any such part is only an illusion,
as many facts combine to prove; but it is a general effect, produced
throughout the body, which is entirely concentrated on the same
nerve that first caused it, and which is necessarily felt by the individual
at the extremity of that nerve where the impression was made.

All that we perceive is within ourselves: this is now a well-estab-
lished truth. For a sensation to arise, it is absolutely necessary that

PHYSICAL SENSIBILITY 327

the impression received by the part affected should be transmitted to
the nucleus of the system of sensations; but if the whole action
ended there, there would be no general effect, and no reaction would
be conveyed to the point which received the impression. As regards
the transmission of the original movement impressed, it doubtless
only takes place through the nerve which was affected and by means
of the nervous fluid moving in its substance. We know that, if by a
ligature or tight compression of the nerve, we intercept communica-
tion between the portion arriving from the part affected and that
passing on to the nucleus of sensations, no transmission of movement
is effected.

The ligature or tight compression interrupts the continuity of the
soft substance of the nerve by binding together the walls of its sheath,
and thus suffices to intercept the passage of the nervous fluid ; but, as
soon as the ligature is removed, the elasticity of the nervous substance
permits of restoration of continuity in the nerve, and sensation can
then be produced again.

Although therefore it is true that we only feel what is within our-
selves, yet the perception of the objects which affect us does not occur,
as has been held, in the nucleus of sensations, but at the extremity
of the nerve which received the impression ; and all sensation is thus
actually felt in the part affected, because it is there that the nerve of
this part terminates.

But if this part no longer exists, the nerve, which ran there, continues
to exist although it is shortened ; if therefore this nerve receives an
impression a sensation is experienced which appears by illusion to be
in the part that is no longer possessed.

It has been observed that people who have lost a leg, feel, when the
stump has healed, at changes of the weather, pains in the foot or leg
which they no longer possess. It is obvious that in these individuals
there is an error of judgment as to the actual site of their sensation ;
but this error is due to the fact that the nerves affected were just those
which were originally distributed in the foot or leg of these individuals ;
in reality the sensation is produced at the extremity of the shortened
nerve.

The nucleus of sensations only serves for the production of the general
disturbance set up by the nerve which received the impression, and for
bringing back into this nerve the reaction from all the rest; hence
there results at the end of the affected nerve an effect, which all parts
of the body combine to produce.

Cabanis seems to have had some notion of the mechanism of sensa-
tions, for although he did not work out the principles of it clearly, and
although he wrongly suggests a mechanism analogous to that by which

328 ZOOLOGICAL PHILOSOPHY

the nerves excite muscular action, yet he obviously had a general idea
of what actually occurs in the production of sensations ; he expresses
himself as follows :

“The operations of sensibility may be regarded as being made up
of two phases. In the first place the extremities of the nerves receive
and transmit the original impression either to the entire sensitive
organ, or, as we shall see later, to one of its isolated systems ; the sen-
sitive organ then reacts on the nerve endings, so that the sensibility,
which in the first phase seems to have travelled from the periphery
to the centre, returns in the second phase from the centre to the
periphery ; and the nerves, to put it briefly, exert a real reaction on
themselves for producing feeling, just as they do on the muscular parts
for producing movement.” (Rapports du Physique et du Moral, vol. i.,
p. 143.)

The only deficiency in the above statement is the omission to state
that the nerve at whose extremity the original impression was received
is the only one which does not subsequently react ; and that for this
reason the general reaction from the other nerves of the system, on
reaching the common nucleus, is necessarily transmitted into the only
nerve that is at the moment in a passive state, and thus conveys to
the point first affected the general effect of the system, that is to say,
sensation.

As to the statement of Cabanis that the nerves exert a similar reaction
on the muscular parts for setting them in motion, I believe that this
comparison between two very different acts of the nervous system has no
true foundation ; but that a simple emission of the fluid of the nerves
from its reservoir to the muscles is a sufficient explanation: there is no
necessity to assume any nervous reaction.

I shall conclude my observations on the physical causes of feeling
by the following reflections, for the. purpose of showing that it is a
mistake to confuse the perception of an object with the idea that may
be called up by the sensation of that object, and also to imagine that
every sensation necessarily yields an idea.

To experience a sensation and to distinguish it are two very different
things: the former without the latter constitutes only a simple per-
ception ; whereas the latter, which is never found apart from the former,
alone gives rise to the idea.

When we feel a sensation from some external object and distinguish
that sensation, although we only feel what is within ourselves and
although we have to make one or more comparisons in order to differ-
entiate the object from our own existence and form an idea of it, we
carry out almost simultaneously by means of our organs two acts of
essentially different kinds, one of which makes us feel while the other

PHYSICAL SENSIBILITY 329

makes us think. We shall never succeed in disentangling the causes
of these organic phenomena, so long as we confuse the entirely dis-
tinct facts which constitute them, and fail to recognise that they
cannot both have a common origin.

A special system of organs is certainly needed for producing the
phenomenon of feeling, since this is a faculty peculiar to certain animals
and not general for all. So too a special system of organs is necessary
for carrying out acts of the understanding ; for thought, comparison,
judgment, reasoning are organic acts of a very different character
from those producing feeling. Hence, when we think, we do not
feel any sensation, although our thoughts impress the inner feeling or
ego of which we are conscious. Now since all sensation arises from a
special sense, it follows that the consciousness of one’s thoughts is not
a sensation, but differs radically from it, and must be kept distinct.
In the same way, when we feel a simple sensation that constitutes
perception, and thus passes unnoticed, no idea of it is formed and no
thought produced, so that the sensitive system alone is in action. We
may therefore think without feeling, and feel without thinking. Hence
for each of these two faculties there is a separate system of organs ;
just as there is a separate system for movements which is independent
of the other two, although one or other of them is the remote cause
which sets the latter in action.

Thus it is wrong to confuse the system of sensations with the
system that produces acts of the understanding, and to imagine
that the two kinds of organic phenomena arising from them can be
the result of a single system of organs. This is why men of the highest
capacity and knowledge have been mistaken in their arguments on
subjects of this nature.

‘A creature,” says M. Richerand, “ absolutely destitute of sen-
sitive organs would have a purely vegetative existence ; if it acquired
one sense it still would not possess any understanding, since, as Condillac
has shown, the impressions produced on this single sense could not be
compared ; it would have nothing more than an inner feeling of its
existence, and it would believe that all things which affect it are part of
itself.” (Physiologie, vol. ii., p. 154.)

We see from this quotation that the senses are considered, not merely
as sensitive organs, but also as organs of the understanding ; since, if
instead of a single sense the creature had several, then according to
the received opinion the mere existence of these senses would endow
it with intellectual faculties.

There is even a contradiction in the passage above cited ; for it is
there stated that a creature which had only one sense would still not
possess understanding, and farther on it is said, with reference to the

330 ZOOLOGICAL PHILOSOPHY

impressions which it would experience, that the whole effect would be
limited to an inner feeling of its existence, and it would believe that
all things which affect it are part of itself. How can this being think
or form judgments, if it possesses no understanding ? For to believe
anything is to form a judgment.

As long as we fail to distinguish the facts connected with feeling
from those connected with intelligence, we shall often make mistakes
of this character. It is an established fact that there are no innate
ideas, but that every simple idea arises exclusively from a sensation.
But I hope to show that not every sensation produces an idea;
indeed that it need cause no more than a perception, and that for the
production and impression of a permanent idea a special organ is
needed, as well as compliance with a certain condition not involved
in the organ of sensations.

It is a long way from a simple perception to an impressed and per-
manent idea. Indeed no sensation, which causes only a simple percep-
tion, makes any impression on the organ; it does not need the essential
condition of attention, and can do no more than excite the inner feeling
of the individual and give it momentary perceptions of objects, without
the production of any thought. Moreover memory, whose seat can
only be in the organ where ideas are traced, can never bring back a
perception which did not penetrate to this organ, and therefore left
no impression on it.

I regard perceptions as imperfect ideas, always simple, not graven
on the organ and needing no condition for their occurrence; and this
is a very different state of affairs from what prevails in the case of true
and lasting ideas. Now these perceptions, by means of habitual
repetitions which cut out certain channels for the nervous fluid, may
give rise to actions which resemble those of memory. Examples are
furnished us by the manners and habits of insects.

I shall hereafter revert to this subject; all that I had here to
remark was the necessity of distinguishing perception, which results
from every unnoticed sensation, from an idea, which, as I hope to
show, requires a special organ for its formation.

From the foregoing principles I think we may conclude :

1, That the phenomenon of feeling is not more miraculous than any
other phenomenon in nature, that is, any phenomenon produced by
physical causes ;

2. That it is not true that any part of a living body, or any substance
composing it, has in itself the faculty of feeling ;

3. That feeling is the result of an action and reaction, which become
general throughout the nervous system, and are performed with
rapidity by a very simple mechanism ;

PHYSICAL SENSIBILITY 331

4. That the general effect of this action and reaction is necessarily
felt by the individual’s indivisible ego, and not by any separate part of
his body ; so that it is only by illusion that he thinks that the effect
is entirely wrought at the point where the impression was received ;

5. That whenever an individual notices a sensation, identifies it,
and distinguishes the point of its body on which it takes effect, the
individual then has an idea, thinks, carries out an act of intelligence,
and must therefore possess the special organ for producing it ;

6. Lastly, that, where the system of sensations exists without the
system of understanding, the individual performs no act of intelligence,
has no ideas, and only derives from its senses simple perceptions
which it does not notice, although they may arouse its inner feeling
and make it act.

Let us now endeavour if possible to form a clear idea of the emotions
of the inner feeling of any individual possessing physical sensibility,
and to ascertain what power this individual gains from it, for carrying
out its actions.

CHAPTER IV.

OF THE INNER FEELING, THE EMOTIONS THAT IT MAY Ex.
PERIENCE, AND THE POWER WHICH IT THENCE DERIVES
FOR THE PRODUCTION OF ACTIONS.

My purpose in the present chapter is to treat of one of the most
remarkable faculties conferred by the nervous system on all animals in
which it is highly developed ; I mean that singular faculty, with which
certain animals and man himself are endowed, consisting in the capacity
to experience inner emotions called forth by the needs and various
causes external or internal; from this faculty arises the power for
performing diverse actions.

Nobody, so far as I know, has yet considered the interesting subject
with which I am about to deal; yet, unless we fix our attention on this
subject, we shall never be able to account for the numerous phenomena
presented by animal organisation, which have their origin in the afore-
mentioned faculty.

We have seen that the nervous system consists of various organs
which are all in communication with one another ; consequently every
part of the subtle fluid contained within this system is in communication
with every other part, and is therefore liable to undergo a general
agitation in the presence of certain causes adapted for exciting it.
We have here an essential principle that we must keep in mind
throughout our enquiries; its accuracy cannot be questioned since
proofs of it are furnished by the observed facts.

Yet the whole of the nervous fluid is not always sufficiently free to
take part in the agitation under consideration, for in ordinary cases
it is only one portion of the fluid (no doubt a large portion) that is
capable of undergoing this agitation when aroused by certain emotions.

It is certain that in various circumstances, the nervous fluid under-
goes movements in more or less isolated parts of its mass: portions of
this fluid are thus dispatched to the various parts for muscular action,
and for the vivification of organs, without the whole fluid being set in

THE INNER FEELING 333

motion ; in the same way portions of a fluid may be agitated in the
cerebral hemispheres, while the rest of the fluid remains still: these
are truths that cannot be called in doubt. But if it is manifest that the
nervous fluid may receive movements in a certain part of its mass,
it is no less so that special causes may agitate almost the entire mass
of this fluid, since all its parts are in communication. I say almost the
entire mass, because in the ordinary inner emotions, that portion of the
nervous fluid which serves for the excitation of muscles independently
of the individual, and often also that portion contained in the hemi-
spheres of the brain, are sheltered from the agitations which constitute
emotions.

The nervous fluid may therefore undergo movement in its separate
parts, or as a whole; it is these latter movements which constitute
the general agitations of the fluid, that we are about to discuss.

General agitations of the nervous fluids are of two kinds, viz. :

1. Partial agitations which become general and end by reactions ;
it is this kind of agitation which produces feeling. We have dealt
with it in Chapter IIT. ;

2. Agitations which are general from the first and form no reaction :
it is these which constitute the inner emotions, and it is exclusively
with them that we shall now deal.

But a word must first be said about the feeling of existence, since it
is in this feeling that the inner emotions take their rise.

Or THE FEELING OF EXISTENCE.

The feeling of existence, which I shall call inner feeling, so as not
to imply a universality which it does not possess, is a very obscure
feeling possessed by animals whose nervous system is sufficiently
developed.

This feeling, obscure as it is, is none the less very powerful ; for it is
the origin of the inner emotions, and consequently of that singular
force which enables individuals to produce for themselves the move-
ments and actions which their needs demarid. Now this feeling,
regarded as a very active motive power, works simply by dispatching
to the required muscles the nervous fluid which is to excite them.

The feeling in question is now well recognised, and results from
the confused assembly of inner sensations which are constantly
arising throughout the animal’s life, owing to the continual impres-
sions which the movements of life cause on its sensitive internal
parts.

Indeed, as a result of the organic or vital movements taking place
in every animal, those which possess an adequate nervous system
derive from it physical sensibility and are incessantly being affected

334 ZOOLOGICAL PHILOSOPHY

by impressions throughout their sensitive internal parts; the animal
feels these all confused together, without being able to distinguish
any one.

As a matter of fact, all these impressions are very weak; and although
they vary in intensity according to the health of the individual, they are
usually very difficult to distinguish, because they are not liable to any
sudden interruption or renewal. Yet the sum-total of these impressions,
and the confused sensations resulting from them, constitute in all
animals subject to them a very obscure but real inner feeling that has
been called the feeling of existence.

This continuous and intimate feeling, which is not appreciated
because it is not noticed, is general, in that all the sensitive parts of
the body share in it. It constitutes that ego with which all animals
that are merely sensitive are imbued without knowing it, while those
which also possess an organ of intelligence may notice it, since they
have the facuties of thought and attention. Finally, it is in both cases
the source of a power, which the needs can evoke, which only acts
effectively by emotion, and from which movements and actions derive
their motive force.

The inner feeling may be considered under two quite different
aspects Viz. :

1. In so far as it is the result of obscure sensations which continue
without cessation in all sensitive parts of the body: from this aspect
T call it simply inner feeling ;

2. In its faculties: for the general agitations of the subtle fluid
confer upon animals the power of producing movements and actions
for themselves.

This feeling, which forms a very simple whole, is susceptible of being
stirred by various causes. When it is aroused, it can excite movements
in the free portions of the nervous fluid, direct those movements, and
convey the stimulating fluid to one or another muscle or to any part of
the cerebral hemisphere ; it then becomes a power for exciting action
or thought. From this second aspect therefore we may regard the
inner feeling as the fountain from which the force that produces actions
derives its energy.

It is necessary for a comprehension of the phenomena produced, to
examine this feeling from the two aspects named above; for by its
very nature as a feeling of existence it is always in action throughout
the waking period ; and by its faculties it gives rise to a force which
causes action.

Finally, the inner feeling only manifests its power and produces actions
when there exists a system for muscular movement: this system is
always dependent on the nervous system and cannot exist without it.

THE INNER FEELING 335

It would therefore be inconsistent to look for muscles in animals which
obviously had no nervous system.

Let us now turn to a discussion of the chief facts about the emotions
of the inner feeling.

Or THE Emotions or THE INNER FEELING.

We now have to investigate one of the most important phenomena
of animal organisation, viz. those emotions of the inner feeling which
lead to action in animals and even in man, sometimes without any
effort of their will; emotions long ago recognised, but as to the origin
or causes of which no one seems to have paid any attention.

Observation leaves no room to doubt that the general inner feeling
experienced by animals which possess the requisite nervous system,
is susceptible of being stirred by causes which affect it; now these
causes always consist in the need either of assuaging hunger or of
flying from danger, or avoiding pain, or seeking pleasure, or what is
agreeable to the individual, etc.

The emotions of the inner feeling can only be known by man,
since he alone can notice and mark them ; but he only perceives those
which are strong, and which agitate, so to speak, his whole being ;
close attention and thought is necessary before he can recognise that
he experiences them in all degrees of intensity, and that it is exclusively
the inner feeling that under various circumstances stirs up in him
those inward emotions which lead him to the execution of some action.

I have already said, at the beginning of this chapter, that the inner
emotions of a sensitive animal consist in certain general agitations
of all the free parts of the nervous fluid, and that since the agitations
are followed by no reactions they produce no distinct sensation. Now
we may easily imagine that, when these emotions are weak or moderate,
the individual may dominate them and control their movements ; but
that when they are sudden and powerful he is then mastered by them :
this is a very important consideration.

The positive fact of the existence of these emotions is no mere
hypothesis. Who has not noticed that a loud and unexpected noise
makes us start or give a sort of jump, and execute corresponding
movements that our will had not determined ?

Some time ago I was walking in the street with my left eye covered
by my pocket-handkerchief, because it was in pain and irritated by
the sunlight. A horse and rider that I did not see suddenly fell,
quite close to me on my left: I instantly found myself transported two
steps towards the right by a movement or bound, in which my will
had not the smallest share, and before I had any idea of what was
happening close to me.

336 ZOOLOGICAL PHILOSOPHY

Everybody is acquainted with these kinds of involuntary move-
ments, for everybody has experienced the like; and they are only
noticed because they are extreme and sudden. But we pay no attention
to the fact that everything, which affects us, stirs our emotions pro-
portionally, that is to say, stirs to some extent our inner feeling.

We are moved by the sight of a precipice, of a tragic scene, either
real or on the stage or even on a picture, etc., etc.: and where is the
power of a fine piece of music well executed, if not in producing emotions
of our inner feeling? Consider again the joy or sorrow that we suddenly
feel on hearing good or bad news about something that interests us :
what is it but the emotion of that inner feeling, which is very difficult
to master on the spot ?

I have several times seen pieces of music played on the piano by a
young lady who was deaf and dumb: her playing was far from
brilliant and yet it was passable ; she kept good time, and I perceived
that her entire personality was stirred by regular movements of her
inner feeling.

I gathered from this that the mner feeling in this young person
took the place of the organ of hearing, which was of no use. Her
music-master too told me that he had practised her in keeping time
by measured signs, and I soon became convinced that these signs had
stirred within her the feeling in question ; hence I inferred that what
we attribute entirely to the highly trained and delicate ears of good
musicians belongs rather to their inner feeling, which from the first
bar is stirred by the kind of movement necessary for the performance
of a piece.

Our habits, temperament, and even education, modify this faculty
of undergoing emotion; so that in some individuals it is very weak
while in others it is very strong.

A distinction should be drawn between the emotions aroused by the
sensation of external objects and those which come from ideas, thoughts,
or acts of our intellect; the former constitute physical sensibility,
whereas the latter characterise the moral sensibility, that we shall now
turn to consider.

Mora SENSIBILITY.

Moral sensibility is very different from the physical sensibility that
I have already mentioned ; the former is only excited by ideas and
thoughts which move our inner feeling, while the latter only arises
from impressions produced on our senses ; for these can likewise stir
our inner feeling.

The seat of moral sensibility has been wrongly supposed to be in the
heart, on the ground that the functions of that viscus are more or less

THE INNER FEELING 337

affected by the different manifestations of sensibility. But in reality
moral sensibility is nothing more than a very delicate susceptibility
to emotion, which is aroused in the inner feeling of certain individuals
on the sudden presentation of suitable ideas and thoughts. These
individuals are then said to be highly sensitive.

This sensibility, when developed to the extent attainable to a
perfected intellect, appears to me a product and even a benefaction
of nature. It then forms one of the finest qualities of man, for it is
the source of humanity, kindness, friendship, honour, etc. Sometimes,
however, circumstances make this quality almost as baneful to our-
selves as its presence in others is beneficial : in order to derive from it
the benefits without the disadvantages, we simply have to moderate
its transports by methods which nothing but a good education can
indicate.

A good education shows us the necessity on innumerable occasions
for repressing our sensibility up to a certain point, in order not to fall
short in the respect which man in society owes to his fellows, as also
to the age, sex, and rank of those with whom he consorts : hence result
that decorum and amenity in the expressions used in conversation,
in short, that careful restraint in the expression of ideas which gives
pleasure without ever wounding, and confers a quality of high
distinction to those that possess it.

Up to this point our conquests can only turn to the general advantage.
But the limits are sometimes passed ; and we abuse the power, given
us by nature, of stifling to some extent the finest of the faculties that
we draw from her.

Indeed, many men possess certain propensities which lead them
constantly to resort to dissimulation ; it has become necessary for them
habitually to restrain the emotions of their inner feeling, and carefully
to hide their thoughts and such of their actions as may lead to the end
they have in view.

Now since every faculty, that is not used, gradually degenerates
until it almost becomes extinct, the moral sensibility which we are
here discussing is almost absent in them; and they do not even
esteem it in persons who still possess it in a moderate degree.

Just as physical sensibility is only brought about by sensations
which, when they give birth to some need, immediately produce an
emotion in the inner feeling and thus drive the nervous fluid to the
muscles which have to act; so too moral sensibility is only brought
about by the emotions which thought produces in this inner feeling ;
and when the will, which is an intellectual act, determines some
action the feeling aroused by that act guides the nervous fluid towards

the suitable muscles.
Y

338 ZOOLOGICAL PHILOSOPHY

The inner feeling acquires its various emotions through one or other
of two very different routes, viz.: that of thought and that of physical
feeling or sensations. The emotions of the inner feeling may therefore
be divided :

1. Into moral emotions, such as those raised by certain thoughts ;

2. Into physical emotions, such as those derived from certain
sensations.

Since, however, the results of the first kind of emotion belong to
the sphere of moral sensibility, while those of the second kind depend
on physical sensibility, it is enough to abide by the first distinction
that we established.

Nevertheless, I shall take this opportunity of making a few remarks
which seem to me not without interest.

A moral emotion when very powerful may temporarily extinguish
physical feeling, disturb the ideas and thoughts, and cause some
enfeeblement in the functions of several of the most essential organs.

It is known that distressing news, when unexpected, as also news
which causes extreme joy, produces emotions whose consequences
may be of this kind.

It is also known that among the minor effects of these emotions
are digestive troubles or pains ; and that, in the case of elderly people,
when the emotions are at all strong, they may be dangerous and even
fatal.

Lastly, the power of the moral emotions is so great as often to
dominate physical feeling. Fanatics, for instance, are people whose
moral feeling is so exalted as to overcome the impressions of the
tortures, which they are forced to undergo.

Although as a general rule the moral emotions are more powerful
than the physical emotions, yet the latter when very strong may also
disturb the intellectual faculties; they may even cause delirium and
throw the organic functions out of order.

I shall conclude these remarks with a reflection that I believe to be
well-founded, viz.: that the moral feeling exercises in course of time
a greater influence on the organisation than the physical feeling is
capable of working.

Indeed, almost any disturbance may be produced in the organic
functions, especially in the abdominal viscera, by deep and prolonged
Sorrow.

Cabanis held that individuals, who are always sad and melancholy,
often without any real cause, are victims of a sort of degeneration in
the abdominal viscera ; whence he concluded that the melancholy of
these individuals must be attributed to this kind of degeneration,
and therefore that these viscera contribute to the formation of thought.

THE INNER FEELING 339

It seems to me that this savant has pushed too far the conclusions
to be drawn from his observations.

No doubt any degeneration of organs, and especially of the
abdominal viscera, frequently corresponds to degeneration of the
moral faculties and does actually contribute to it. But this con-
dition, in my opinion, cannot be regarded as assisting in the forma-
tion of thought ; it merely gives the individual a propensity towards
some one kind of thoughts rather than some other.

Now it is known that the moral feeling may act strongly on the state
of the organs and may affect them for a long period in some particular
way; it thus appears to me that constant and real griefs in any
individual may set up degeneration of the abdominal viscera ; and that
these degenerations, once started, may in their turn perpetuate the
inclination to melancholy, even when there is no longer any real
cause for it.

Reproduction, indeed, may transmit a tendency of the organs or a
state of the viscera adapted for giving rise to any special temperament,
inclination, or characteristic; but it is essential that circumstances
should favour the development of this tendency in the new individual ;
for otherwise the individual would acquire another temperament,
inclinations, and characteristics. It is only in animals of very low
intelligence that reproduction transmits almost without variation the
organisation, inclinations, habits and special peculiarities of each
race.

I should travel too far afield if I were to discuss these matters
further ; I now therefore return to my subject.

I may sum up my observations on the inner feeling, by saying that this
feeling is the source of movements and actions for beings that possess
it; these occur, either when sensations, which awake needs, arouse
emotions in it, or when thought similarly awakes a need or points
out a danger, etc., and thus stirs it more or less strongly. These
emotions, however aroused, promptly agitate the available nervous
fluid: and since every need that is felt, causes the resultant emotion
to affect the parts which have to act, movements are invariably
carried out by this method, and are always in relation to the
individual’s needs.

Lastly, since these inner feelings are very obscure, the individual in
whom they are working does not perceive them; yet they are real ;

and if man, who has a highly developed intellect, were to pay them
some attention, he would soon recognise that all his acts are due to
emotions of his inner feeling, some of which are inspired by ideas,
thoughts, and judgments, thus making him feel certain needs, and
exciting his will to action; while the others result immediately from

340 ZOOLOGICAL PHILOSOPHY

sudden and pressing needs, and cause him to carry out actions quite
independently of his will.

I may add that, since the inner feeling may produce the agitations
in question, it follows that if-the individual governs the emotions of
that inner feeling, he may repress or moderate them and even prevent
their effects. This is how the inner feeling of any individual is a
power, which leads him to act according to his needs and customary
inclinations.

But when the emotions in question are so powerful as to cause an
agitation in the nervous fluid sufficient to affect the movements of
the portion contained in the cerebral hemispheres and also that which
controls the involuntary muscles, the individual then loses conscious-
ness, and suffers from syncope; and the functions of his vital organs
are more or less deranged.

Here then we seem to have reached great truths, which the philo-
sophers could never discover because they have not sufficiently
observed nature, and which the zoologists did not perceive because
they were too much occupied with matters of detail. We may at all
events affirm that the physical causes, indicated above, would be
capable of accounting for the phenomena of organisation into which
we are enquiring.

In compliance with the ordinary rules for the exposition of ideas,
I now have to establish a fundamental distinction of the first im-
portance: I have already said that the inner feeling derives its
emotions from two quite different causes :

1. From some intellectual operation culminating in an act of
will ;

2. From some sensation or impression, which causes a need to be
felt or a propensity to be followed, independently of the will.

These two kinds of causes, which stir the inner feeling of the in-
dividual, show that there is really a distinction to be drawn among
the factors which control the movements of the nervous fluid in the
production of actions.

In the first case, the emotion arises from an act of intelligence,
that is to say, from a judgment, which determines the will to act;
and the emotion then directs the movements of the available nervous
fluid in the direction impressed on it by the will.

In the second case, on the contrary, the intelligence has no share
in the emotion of the inner feeling ; and this emotion directs the move-
ments of the nervous fluid in the direction demanded by the needs,
to which the sensations have given rise, and in the direction of the
acquired propensities,

There is another fact to be named no less important than the fore-

THE INNER FEELING 341

going: it is that the inner feeling may be suspended either entirely
or in part.

During sleep, for instance, the feeling is suspended or nearly so ;
the free part of the nervous fluid is in a kind of repose, and no longer
undergoes a general agitation; nor does the individual any longer
enjoy his feeling of existence. The system of sensations is not exercised,
and none of the actions dependent on the individual are carried out ;
the muscles necessary for their production are no longer excited,
but fall into a kind of relaxation.

If sleep is imperfect, and if there exists some cause of irritation
which agitates the free part of the nervous fluid, particularly that in
the cerebral hemispheres, the inner feeling (being suspended) no longer
directs the movements of the fluid in the nerves, and the individual
is then abandoned to dreams, that is, to involuntary recurrences of his
ideas following one another in characteristic disorder and confusion.

In the waking state, the functions of the inner feeling may be
greatly disturbed either by too strong an emotion which cuts off the
nervous fluid as it flows towards the involuntary muscles, or by some
deep irritation affecting chiefly the fluid of the brain. It then ceases
to direct the movements of the nervous fluid; syncope supervenes
if the trouble comes from a strong emotion, or delirium if it is caused
by severe irritation or some act of lunacy, etc., etc.

In accordance with the above principles, it seems to me obvious
that the inner feeling is the only factor that produces actions in man
and such animals as possess it; that this feeling only works when
prompted by its emotions; that it is moved sometimes by acts of
intelligence, sometimes by a need or sensation acting suddenly upon
it; that in men, its weak emotions may be controlled since in-
telligence is highly developed, but that in animals this can only be
done with great difficulty and never in those that lack intelligence ;
that its functions are suspended during sleep, and that then it no longer
directs the movements of the free part of the nervous fluid; that its
functions may also be interrupted and disturbed during the waking
state; finally, that it is the product, on the one hand, of the individual’s
feeling of existence, and, on the other hand, of the harmony in the
parts of the nervous system, as a result of which the free portions of
the subtle nervous fluid are all in communication and capable of undez-
going a general agitation.

On the same principles, it also appears to me obvious that moral
sensibility only differs from physical sensibility, in that the former
results exclusively from emotions prompted by acts of the intelligence ;
while the latter is produced only by emotions aroused by sensations
and the needs which they evoke.

342 ZOOLOGICAL PHILOSOPHY

If these principles are well founded, they appear to me to be of the
highest importance ; for not only do they correct our mistakes as to
the phenomena of life and organisation and the faculties to which these
phenomena give rise, but they set a limit to the marvels created by
our imagination ; and they give a truer and higher idea of the Supreme
Author of all existing things, by disclosing to us the simple method
that he has adopted for working the wonders of which we are witnesses.

Hence the intimate feeling of existence possessed by animals which
have the faculty of feeling but not that of intelligence, confers upon
them at the same time an inner power, which only works through the
emotions called up by the harmony of the nervous system, and which
causes them to carry out actions without any co-operation of the will.
But such animals as possess both the faculty of feeling and that of
intelligence, have this advantage over the first: that the inner power,
which inspires their actions, is susceptible of receiving its driving
emotions either through sensations produced by internal impressions
and wants that are felt, or through a will which, though more or less
dependent, is always the result of some act of intelligence.

We shall now consider more attentively this singular internal power,
which confers the faculty of acting on such animals as possess it:
the next chapter, which is devoted to this purpose, may be regarded
as a completion of the present.

CHAPTER V.

OF THE FORCE WHICH PRODUCES THE ACTIONS OF ANIMALS,
AND OF CERTAIN PECULIAR FACTS RESULTING FROM THE
USE OF THIS FORCE.

ANIMALS, independently of their organic movements and of the
functions essential to life, carry out yet other movements and
actions of which it is very important to ascertain the cause.

We know that plants can satisfy their needs without changing their
position or making any sudden movement: the reason of this is that
every plant in a favourable situation finds in its neighbourhood the
substances which it requires for food; so that it only has to absorb
them and profit by some among them.

The case is different with animals: for, with the exception of
the most imperfect animals at the beginning of the animal chain,
the food on which they live is not always at hand, and they are obliged
to carry out movements and actions in order to procure it. Moreover,
most of them have other wants to be satisfied as well, which in their
turn demand other movements and other actions.

Now the question at issue was how to identify the source from which
animals derive the faculty of making comparatively sudden movements
of their parts ;—in short, of carrying out the various activities by means
of which they satisfy their needs.

I noted, in the first place, that every action is a movement, and that
every movement necessarily has some cause which produces it: the
question was therefore reduced to ascertaining the nature and origin
of this cause.

Thereupon, when I reflected that the movements of animals are
never communicated nor transmitted, but merely exited, their cause
appeared to be revealed to me in the clearest and most decisive manner ;
and I became convinced that these movements are really in every case
the product of some power which excites them.

Indeed in certain animals, muscular activity is a force fully adequate

344 ZOOLOGICAL PHILOSOPHY

for the production of such movements; and nervous influence is no
less adequate for exciting that activity. Now I recognised that in
animals, which possess physical sensibility, the emotions of the inner
feeling constitute the power which drives the exciting fluid to the
muscles, and the problem thus seemed to be solved as far as these
animals are concerned; in the case of animals so imperfect as to
possess no physical sensibility, stimuli arriving from without are
obviously sufficient for their movements, for they are just as irritable
or even more irritable in their parts than the others.

In my opinion, this clears up a mystery which seemed indeed difficult
to penetrate; nor does this solution seem to me to rest on mere
hypothesis : for in the case of sensitive animals, muscular power and
the need for nervous influence to excite that power are not hypo-
thetical ; and the emotions of the inner feeling, which I regarded as
being capable of driving to the muscles the fluid that excites their
activity, appeared to me too manifest to be regarded as conjectural.

If now we closely consider all existing animals, including the state
of their organisation, the consistency of their parts, and the various
circumstances under which they live, it will be difficult not to admit
that the most imperfect of them, which have no nervous system and
hence no muscular activity to help their movements and actions,
move by a force that is outside them, that is to say, one which they do
not possess themselves and is not available at will.

It is true that it is in the interior of these delicate bodies that the
subtle fluids, entering from without, set up the agitations witnessed in
their parts; nevertheless it is impossible for these fragile creatures,
on account of their weak coherence and extreme softness, to contain
within themselves any power capable of producing their movements.
It is only as a result of their organisation that these imperfect animals
act in a methodical manner, which they could in no wise originate for
themselves.

Now, nature has wrought her various productions by slow and gradual
stages ; she has created the various organs of animals in turn, varying
the shape and situation of these organs according to circumstances
and progressively improving their faculties. Hence we feel that she
must have begun by borrowing from without, that is, from the environ-
ment, the force which produces the organic movements and those of
the external parts; that she afterwards transferred that force within
the animal itself, and that finally, in the most perfect animals, she made
a great part of that internal force available to their will, as I shall
shortly show.

If we do not carefully note the gradual order followed by nature
in the creation of the various animal faculties, I believe that we shall

ACTIONS OF ANIMALS 345

find it hard to explain how she could have brought feeling into existence,
and still harder to conceive how simple relations between material
substances can give rise to thought.

We have just seen that animals, which do not yet possess a nervous
system, cannot contain within themselves the force which produces
their movements, but that this force must be outside them. Now
seeing that the intimate feeling of existence is entirely absent in these
animals, and seeing that this feeling is the source of that internal
power which produces movements and actions in those that possess
it, its privation and the privation of the power resulting from it,
necessitate the existence of a force to excite movements, from sources
that are altogether external.

Hence in imperfect animals the force which produces both vital
and bodily movements is wholly outside them: they do not even
control it; but they do control to some extent, as I said above, the
movements which it impresses on them, and this they do by means of
their organisation.

This force is the result of subtle fluids (such as caloric, electricity,
and perhaps others) which incessantly penetrate these animals from
the environment, set in motion the visible and contained fluids of their
bodies, and by exciting the irritability of their containing parts, give
rise to the various movements of contraction which they produce.

Now these subtle fluids moving incessantly in the interior of their
bodies soon carve out special routes which they always follow till
new ones are open to them. Hence the similarity of the movements
observed in these animals; and hence again the appearance of an
irresistible propensity to carry out movements which, when continued
or repeated, give rise to habits.

As a mere statement of principles is not enough, let us endeavour
to elucidate the arguments on which they rest.

The most imperfect animals, such as the infusorians and especially
Monas, only feed by means of absorption which they carry out
through the pores of their skin, and by an internal imbibition of the
absorbed substances. They have no power of seeking their food nor
even of seizing it, but they absorb it because it is in contact with every
point of their surface, and the water in which they live provides it in
sufficient abundance.

These fragile animals, in which the subtle fluids of the environment
are the stimulating cause of orgasm, irritability, and organic move-
ments, carry out, as I have said, movements of contraction which,
being incessantly prompted and varied by this stimulating cause,
facilitate and hasten the absorptions. Now in these animals the
movements of the visible contained fluids are still very slow, and the

346 ZOOLOGICAL PHILOSOPHY

absorbed substances make good the losses which they suffer as a
consequence of life, and serve in addition for the individual’s growth.

I have said that the subtle fluids which move in the interior of these
living bodies cut out special routes which they continually follow, and
thus begin to establish definite movements which become habits. Now
if we reflect that organisation develops as life goes on, we shall under-
stand how new routes must have been cut out, increased in number,
and progressively varied for the furtherance of the movements of
contraction; and how the habits to which these movements give
tise then become fixed and irresistible to a corresponding extent.

Such, in my opinion, is the cause of movements in the most imperfect
animals ; movements that we are led to attribute to their own initiative,
and to regard as a result of their faculties, because we know that in
other animals the source of them is within their bodies ; movements,
in short, which are carried out without any will on the part of the
individual, and which yet, from being very irregular in the most
imperfect of these living bodies, gradually become more regular and
are always the same in animals of the same species.

Finally, just as reproduction transmits acquired forms both internal
and external, so too it transmits at the same time an aptitude for
certain specialised types of movement and corresponding habits.

Or THE TRANSFERENCE OF THE ForCE, WHICH PRODUCES MovE-
MENTS, INTO THE INTERIOR OF ANIMALS.

If nature had confined herself to her original method, that is, to a
force entirely external and foreign to the animal, her work would
have remained very imperfect; animals would have been simply
passive machines, and nature never would have produced in such
organisms the wonderful phenomena of sensibility, the intimate
feeling of existence, the power of acting and, lastly, ideas, by means of
which she has created the most astonishing of all, viz. thought or
intelligence,

With the intention of reaching these great results, she gradually
prepared the way by increasing the coherence of the internal parts of
animals, by diversifying their organs, and by multiplying and com-
pounding their contained fluids, etc.; thereafter she was able to
transfer into the interior of these animals that force productive of
movements and actions, which in truth they did not originally control,
but which was in great part rendered available for them as their
organisation became more perfect.

Indeed, when the complexity of animal organisation had gone so
far as to establish a nervous system of a certain development, as among
the insects, then animals provided with this organisation were endowed

ACTIONS OF ANIMALS 347

with the intimate feeling of their existence; and henceforward the
force productive of movements was transferred into the interior of
the animal itself.

I have already shown that this internal force, which produces
movements and actions, finds its origin in the intimate feeling of
existence possessed by animals which have a nervous system, and that
this feeling when aroused by the needs sets in motion the subtle fluid
contained in the nerves, and drives it to the muscles which have to
act ; thus are produced the actions which the needs demand.

Now every need that is felt, produces an emotion in the individual’s
inner feeling; and from this emotion springs the force which gives
rise to the movements required. I furnished evidence of this in
setting forth the communication and harmony existing throughout
the nervous system, and the way in which the inner feeling on being
stirred may excite muscular activity.

Hence, in animals which contain within them the force productive
of movements and actions, the inner feeling which gives rise to that
force puts it in action, whenever some need is felt, and thus excites
movements in the subtle fluid of the nerves (called by the ancients
animal spirits) ; the force directs that fluid towards such of the organs
as have to act, and finally causes a reflux of the fluid into its usual
reservoirs, when the needs no longer require the organ to act.

The inner feeling then takes the place of will; for it now becomes
important to remember that every animal which does not possess
the special organ in which or by means of which thoughts, judgments,
etc., are produced, has really no will, does not choose, and therefore
cannot control the movements, prompted by its intimate feeling.
Instinct directs these movements, and we shall see that this direction
always results from emotions of the inner feeling, in which the intellect
has no share, and from the organisation as modified by habit; so
that the needs of such animals being necessarily limited and always
the same in the same species, the intimate feeling always produces
the same actions.

The case is different in animals which nature has endowed with an
additional special organ (two wrinkled hemispheres surmounting the
brain), for the performance of acts of intelligence, and which con-
sequently carry out comparisons, judgments, thoughts, etc. These
animals control their power of acting in proportion to the perfection
of their organ of intelligence; and although they are still strongly
subordinated to the habits which have modified their organisation,
they yet enjoy a will that is more or less free; they can choose, and
introduce variation into their actions or at least into some of them.

We shall now say a word about the consumption of the nervous

348 ZOOLOGICAL PHILOSOPHY

fluid which takes place in proportion as it works towards the production
of animal actions.

Or THE CONSUMPTION AND DRAINAGE OF THE Nervous FLUID IN
THE PRopUCTION OF ANIMAL ACTIONS.

The nervous fluid, set in motion by the animal’s inner feeling, is
thus the motive power of the actions of these living bodies ; hence it
is used up in working its effects, and it would ultimately be exhausted
and incapable of producing any further activity, if the individual’s
will kept it continually at work.

The nervous fluid, which is constantly being formed throughout
life, is as constantly being consumed by the use which the individual
makes of it.

One part of this fluid is kept occupied independently of the animal’s
will in the maintenance of vital movements and of the functions
necessary to life.

The other part of the fluid is at the service of the individual and can
be used either for the production of its acts and movements, or for the
performance of its various acts of intelligence.

The individual thus uses up its invisible fluid in a degree proportional
to the duration of the action which it produces, or to the effort which
that action requires ; and it would exhaust the whole of the available
part, if it continued too long to carry out actions which required
much of it.

Hence arises the need of rest after a certain period of action: the
individual falls asleep while the exhausted fluid is recuperated.

The loss of strength, and consequently of the nervous fluid which
gives strength, becomes manifest therefore in all actions that are too
prolonged or are painful, and for that reason called fatiguing.

If you take too long a walk, you become fatigued after a period
relative to your strength; if you run, you become fatigued much
sooner, for you dissipate the principle of your strength much more
rapidly and copiously ; lastly, if you take a weight of fifteen or twenty
pounds, and hold it out with your arm extended horizontally, you will
at first find the action quite easy because you have the wherewithal
to do it, but as your motive principle is rapidly used up, the weight
soon seems heavier and harder to hold, and in a short time the action
becomes altogether impossible.

Your organisation, however, remains the same throughout, for, if it
were to be examined, no change would be found in it from the first
moment, when the action was started, to the moment when you could
no longer support the weight in question.

Is it not obvious that the real difference is only in the dissipation

ACTIONS OF ANIMALS 349

of an invisible fluid, which we cannot perceive owing to the limita-
tion of our available resources ?

The consumption and exhaustion of the subtle fluid of the nerves
in prolonged or painful actions, is certainly a fact that can never be
disputed, since reason and organic phenomena afford the strongest
proof of it.

Although it is true that one part of an animal’s nervous fluid is
constantly employed, independently of its will, in the maintenance of
its vital movements and of such functions as are necessary to its
existence, yet when the individual uses up too much of the free fluid
available to it, the functions of its vital organs suffer. For in these
circumstances the unavailable part of the nervous fluid fills the place
of the available fluid that has been dissipated. It is therefore run too
low, and provides inadequately for the operations of the vital organs ;
thereupon the functions of these organs flag to some extent, and are
imperfectly fulfilled.

It is chiefly man—who is allied to animals by his organisation—
that uses up his physical strength in this way ; for, of all his actions,
those that use the most nervous fluid are the prolonged acts of his
understanding, thoughts, meditations, and, in short, the continued
efforts of his intellect. The digestion is then impaired, and the physical
strength is proportionally diminished.

The consumption of nervous fluid in the movements and actions
of animals is so well known that I need not dwell upon it longer ;
but I may say that this by itself would be a sufficient proof of the
existence of the fluid in the most perfect animals, if there were not
many others of equal cogency.

OF THE ORIGIN OF THE PROPENSITY TOWARDS REPEATING THE SAME
ACTIONS, AND ALSO OF INSTINCT IN ANIMALS.

It is assuredly worth while to investigate the cause of the well-
known phenomenon which compels nearly all animals always to repeat
the same actions, and which gives rise even in man to a propensity
towards any action that has become habitual.

If the principles expounded in this work are really well-founded, the
causes which we seek may be very easily deduced from them; so
that we shall cease to be astonished by phenomena seemingly so
mysterious, when once we have recognised the simplicity of their
origin.

Let us see, then, how we can account for the phenomena in question,
in accordance with the principles enunciated above.

Every action is caused by some movement in the fluid of the nerves.
Now when this action has been several times repeated there is no doubt

350 ZOOLOGICAL PHILOSOPHY

that the fluid cuts out a route which becomes specially easy for it to
traverse, and that it acquires a readiness to follow this route in pre-
ference to others.

How great is the light shed by this simple and fertile principle on
the power of habit—a power from which even man can only escape
with great difficulty by the help of his highly developed intellect !

Who can now deny that the power of habits over actions is inversely
proportional to the intelligence of the individual, and to the develop-
ment of his faculty of thinking, reflecting, combining his ideas, and
varying his actions ?

Animals, which are only sensitive, and have not yet acquired the
organ in which are produced comparisons between ideas, as also
thoughts, reasonings and the various acts constituting intelligence,
have nothing but perceptions (often very confused), do not reason,
and can make little variation in their actions. They are therefore
permanently subject to the power of habit.

Thus insects, which have the least developed nervous system of
any animals that possess feeling, experience perceptions of the objects
which affect them, and seem to possess a memory gained through a
repetition of these perceptions. They can, however, neither vary
their actions nor alter their habits, since they possess no organ to
give them this power.

Or Instinct In ANIMALS.

By instinct is meant the fixed tendencies displayed by animals in
their actions; and many people have held that these tendencies are
the produce of a reasoned choice, and therefore the fruit of experience.
Others, as Cabanis said, prefer to think, in common with observers
of all ages, that many of these tendencies cannot be referred to any
sort of reasoning, and that, although taking their origin in physical
sensibility, they are usually formed without any share of the individual’s
will, beyond that of improving their execution.

If attention had been paid to the fact that all animals which can
feel have an inner feeling capable of being stirred by their needs, and
that the resulting movements of their nervous fluid are always con-
trolled by this inner feeling and by habit, it would then have been
apparent that in all such animals that are devoid of intelligence, the
tendencies of action can never be the product of a reasoned choice or
judgment or experience turned to account, or will, but that they are
subject to needs, excited by certain sensations, which then awake
irresistible propensities. Even in animals which possess some degree
of intelligence, the actions are still commonly controlled by the inner
feeling and by habit.

ACTIONS OF ANIMALS 351

Lastly, although the motive power of movements and actions, as
also their directive cause, are exclusively internal, we must not, as
has been done,! limit the original or prompting cause of these acts
to internal impressions, with the view of attributing all acts of intelli-
gence to external impressions; a slight knowledge of the facts is
enough to show that in both cases the causes, which stimulate
actions, are sometimes internal and sometimes external, and yet
that they do actually give rise to impressions which only act
internally.

According to the common notion attached to the word instinct, it
is regarded as a torch which lights and guides animals in their actions,
and which is for them what reason is for us. Nobody has shown that
instinct may be a force that induces action, nor that it does induce
action without any intervention of the will but only under the control
of acquired propensities.

The view of Cabanis that instinct arises from internal impressions,
while reasoning is the produce of external sensations, cannot be justified.
It is in ourselves that we feel; our impressions can only be internal ;
and the sensations of external objects, derived from our special senses,
cannot produce in us any but internal impressions.

When my dog is out for a walk and sees in the distance another
animal of his own species, he undoubtedly experiences a sensation
from that external object through the intermediary of sight. There-
upon his inner feeling, aroused by the impression received, guides his
nervous fluid in the direction of a tendency acquired in all the indi-
viduals of his race; by a kind of involuntary impulse, his first move-
ment is towards the dog that he sees. This is an act of instinct,
excited by an external object, and many others of the same kind
may similarly be carried out.

With regard to these phenomena, of which we find so many examples
in animal organisation, it seems to me that a true and clear idea of
their cause can only be found when we have recognised: (1) That
the inner feeling is a very powerful generalised feeling, which has the
faculty of exciting and controlling the movements of the free part
of the nervous fluid and of making the animal carry out various actions ;
(2) that this inner feeling is capable of being moved either by acts of
intelligence culminating in a will to act, or by sensations which evoke
needs which in their turn immediately excite it, so that it guides the
productive force of actions in the direction of some acquired propensity
without the co-operation of any act of will.

There are thus two kinds of causes which may move the inner
feeling, viz. those depending on intellectual operations, and those

1 Richerand, Physiologie, vol. ii., p. 151.

352 ZOOLOGICAL PHILOSOPHY

which excite it immediately to guide its power of acting in the direction
of the acquired propensities.

It is purely these last kind of causes that constitute instinct ; and
seeing that they are not the produce of any deliberation, thought,
or judgment, instinctive actions always satisfy surely and unerringly
the wants felt and the habits acquired.

Hence instinct in animals is a compelling tendency, prompted by
sensations in giving rise to needs; and it causes the execution of
actions without the intervention of any thought or act of will.

This propensity is a part of the organisation acquired by habit ;
it is excited by impressions and needs, which move the individual’s
inner feeling, and cause it to dispatch nervous fluid to the appropriate
muscles as required by the propensities.

I have already said that the habit of using any organ or any part of
the body for the satisfaction of constantly recurring needs, gives the
subtle fluid so great a readiness for moving towards that organ where
it is so often required, that the habit becomes inherent in the nature
of the individual.

Now the needs of animals with a nervous system vary in proportion
to their organisation, and are as follows:

1, The need of taking some sort of food ;

2. The need for sexual fertilisation, which is prompted in them by
certain sensations ;

3. The need for avoiding pain ;

4. The need for seeking pleasure or well-being.

For the satisfaction of these needs they acquire various kinds of
habits, which become transformed in them into so many propensities ;
these propensities they cannot resist nor change of their own accord.
Hence the origin of their habitual actions and special inclinations,
which have received the name of instinct.+

This propensity of animals to the preservation of habits, and to the
repetition of the resulting actions when once it has been acquired, is
propagated to succeeding individuals by reproduction so as to preserve
the new type of organisation and arrangement of the parts; thus the
same propensity exists in new individuals, before they have even begun
to exert it.

Hence it is that the same habits and instinct are handed on from

1 Just as all animals do not possess the faculty of will, so too instinct is not a pro-
perty of all existing animals ; for those which have no nervous system have no inner
feeling, and cannot therefore have any instinct for their actions.

These imperfect animals are entirely passive, do nothing of their own accord, feel
no needs, and are provided for by nature in everything just as in the case of plants.
Now since their parts are irritable, nature causes them to carry out movements,
which we call actions.

ACTIONS OF ANIMALS 353

generation to generation in the various species or races of animals,

without any notable variation so long as no alteration occurs in their
environment.

OF SKILL IN CERTAIN ANIMALS.

In animals which have no special organ for intelligence, the name skill,
applied to certain of their actions, is scarcely deserved ; for it is only
by illusion that we ascribe to them a faculty they do not really possess.

Propensities acquired and transmitted by reproduction, together
with the resulting habits of carrying out complicated actions, in the
face of various difficulties which are regularly and habitually overcome
by emotions of the inner feeling: these constitute the sum-total of
actions, always the same in individuals of the same race, to which we
carelessly give the name of skill.

The instinct of animals consists in the habit of satisfying the four
kinds of needs named above, and results from propensities acquired
long previously, which constrain to act in a way predetermined for
each species. It subsequently happened, in the case of some animals,
that a complication in the actions required for the satisfaction of these
four kinds of needs or of some of them, combined with various difficulties
which had to be overcome, gradually forced the animal to increase
and develop its methods, and led it to the performance of various
new activities, without any choice or act of intelligence, but solely by
emotions of the inner feeling.

Hence the origin in certain animals of various complicated actions,
which people call skill, and which they are never tired of enthusiastically
admiring because they always imagine, tacitly at least, that these
actions are the result of thought and calculation ; this, however, is an
obvious mistake. They are merely the result of a necessity which has
developed and guided the habits of animals, until they reach the point
at which we find them.

What I have just said is especially applicable to the invertebrates,
which can carry out no act of intelligence. None of these animals
indeed has any power to vary its actions, or to abandon its so-called
skill in favour of some other method.

There is then nothing more wonderful in the alleged skill of the
ant-lion (Myrmeleon formica leo) which digs out a hole in loose sand
and then waits until some victim falls into the bottom of a hole by the
slipping of the sand, than there is in the operation of the oyster, which
for the satisfaction of all its needs has only to open slightly and close
its shell. So long as their organisation remains unchanged they will
both continue to do just what they do now, without any intervention

of will or reasoning.
Zz

354 ZOOLOGICAL PHILOSOPHY

It is only among the vertebrates, and particularly among the birds
and mammals, that we find the characteristics of a true skill; for in
difficult situations their intelligence may assist them to vary their
actions notwithstanding their subjection to habit. These character-
istics however are not common and it is only in a few races that we
often witness them.

Let us now enquire what constitutes the determining motive of action,
called will: and let us consider if it is actually, as has been supposed,
the motive of all the actions of animals.

CHAPTER VI.
OF THE WILL.

In the present chapter I propose to show that the will, which has been
regarded as the source of all actions in animals, can only be present in
those which possess a special organ for intelligence ; and that even in
these, which include man himself, it is not always the motive of the
actions performed.

On considering the matter, we find indeed that the will is the
immediate result of an active intelligence: for it is always the
effect of a judgment and hence of an idea, thought, comparison or
choice; lastly, we perceive that the faculty of willing is nothing else
than that of determining by thought, that is by an operation of the
organ of understanding, to perform some action, combined with the
faculty of exciting an emotion of the inner feeling which can produce
that action.

Thus the will is a determination towards some action, and is achieved
by the intelligence of the individual : it always results from a judgment,
and this judgment itself necessarily springs from an idea or thought
or from some impression giving rise to such idea or thought, so that it
is purely by an act of intelligence that the will, which determines an
individual to some action, can be developed.

But if the will is nothing else than a determination following upon a
judgment, and hence only the result of an intellectual act, it becomes
clear that animals which have no organ for intelligence cannot carry
out any acts of will. Yet all these animals carry out movements,
which constitute their actions. There are then several different
sources from which the actions of animals may be derived.

Now since the movements of all animals are excited and not com-
municated, there must be different kinds of exciting causes for these
movements. Indeed we have seen that in certain animals these causes
come entirely from without, that is to say, from the environment ;
while in others, which possess an inner feeling, there is a motive power
sufficient for the production of the requisite movements.

356 ZOOLOGICAL PHILOSOPHY

But the inner feeling, which only becomes a power when moved by a
physical cause, acquires its emotions by two very different routes :
in animals which have no organ for the will, the inner feeling can only
be moved by means of sensations; whereas in those which have an
organ for intelligence, the emotions of the inner feeling may either be
the exclusive result of sensations, or that of a will born from an operation
of the understanding.

Hence we have three distinct sources for the actions of animals,
viz.: (1) The external causes which excite the irritability of animals ;
(2) the inner feeling moved by sensations; (3) the inner feeling
moved by the will.

The actions or movements arising from the first of these three sources
take place without the intermediary of muscles; for the muscular
system does not exist in animals of this character ; and when it begins
to be developed, excitations from without still take the place of the
non-existent inner feeling; but the actions or movements which
originate from the emotions of the individual’s inner feeling are only
carried out through the intermediary of muscles excited by nervous
fluid.

Thus when the will determines an individual towards some action,
its inner feeling promptly receives an emotion, and the resulting move-
ments are directed in such a way that the nervous fluid is immediately
dispatched to the required muscles.

As to the animals which are endowed with physical sensibility,
while yet possessing no organ for intelligence, and which therefore
cannot carry out any act of will, their needs always result from some
sensation, that is, from some perception that makes itself felt and not
from any idea or judgment ; and this need or perception immediately
affects the individual’s inner feeling. From this it follows that these
animals, before acting, do not deliberate or form a judgment, and come
to no preliminary determination. Their inner feeling is directly
stirred by the need, and its movements are thereafter controlled by the
nature of this need, so that it promptly puts in action those parts which
have to move. The actions therefore which arise from this source
are not preceded by a true will.

Whereas this is a necessity in the case of the animals under con-
sideration, it is still the most frequent factor in those that are
endowed with intellectual faculties ; for nearly all the needs of these
latter are due to sensations, which revive certain habits and thus
immediately stir the inner feeling, causing these animals to act
without any previous thought. Even man carries out actions of
this character when the needs which prompt them are pressing. If,
for instance, you absent-mindedly take up a piece of iron which

OF THE WILL 357

unexpectedly turns out to be very hot, the pain caused by the heat
of the iron promptly moves your inner feeling ; and before you have
had time to think what you ought to do, your muscles have already
carried out the action which consists in letting go the hot iron that
you were holding.

From these observations it follows that actions carried out in
consequence of needs prompted by sensations which immediately
affect the mdividual’s inner feeling, are in nowise the result of any
thought, judgment, or act of will; while those which are wrought in
consequence of needs aroused by ideas or propensities are exclusively
the result of those acts of intelligence which also affect immediately
the inner feeling and enable the individual to act by a manifest will.

This distinction between actions of which the immediate cause is in
some sensation and those which result from a judgment or act of intelli-
gence, is of great importance for the avoidance of confusion and error
in our investigations of these wonderful phenomena. It is because
the distinction had not been drawn that animals have been usually
credited with a will in the performance of their actions; and people
have supposed, on the analogy of man and the most perfect animals,
that all animals have the faculty of voluntary movement. Yet this
is not so, even in those that possess a nervous system, and still less in
those that do not.

It is certain that animals which have no nervous system cannot
possess the faculty of will; so far from it are they, that they cannot
even have the feeling of their existence : the infusorians and polyps are
in this position.

Those which have a nervous system capable of yielding the faculty
of feeling, but which have no hypocephalon or special organ for in-
telligence, possess indeed an inner feeling—the mainspring of their
actions—and form confused perceptions of the objects which affect
them ; but they have no ideas, do not think, compare or judge, and
hence carry out no act of will. There is reason to believe that this
is the case in the insects, arachnids, crustaceans, annelids, cirrhipedes,
and even molluscs.

The inner feeling, aroused by some need, is the source of all the
actions of these animals. They act without any deliberation or pre-
liminary determination, and always in the one direction to which the
need drives them; and when they encounter some obstacle while
acting, if they avoid it or turn aside and seem to choose, it 1s only
because a new need has aroused their inner feeling. Thus the new
action does not result from any combination of ideas, or comparison
between objects, or judgments, since these animals cannot carry out
any operations of the intelligence, having no organs for the purpose ;

358 ZOOLOGICAL PHILOSOPHY

the new action is purely a sequence of some emotion of their inner
feeling.

It is therefore only the animals which, in addition to a nervous
system, possess the special organ for complex ideas, thoughts, com-
parisons, judgments, etc., that possess the faculty of will and can carry
out acts of will. This apparently is the case with the vertebrates :
and since the fishes and reptiles have so imperfect a brain as not com-
pletely to fill up the cranial cavity—an indication that their acts of
intelligence are extremely limited—it is mainly in the birds and
mammals that the faculty of will is to be found; for they obviously
carry out various acts of intelligence, and certainly have the special
organ which renders them capable of such acts.

But as I have already observed : in the case of animals which have a
special organ for intelligence, all the actions do not result exclusively
from a will, that is, from a preliminary intellectual determination
which excites the motive power of actions. Some of them are no doubt
the product of the faculty of will, but many others simply arise from a
direct emotion of the inner feeling, which is excited by sudden needs and
causes the animal to carry out actions that are not preceded by any
determination or thought.

Even in man, how many actions there are that are exclusively
prompted and carried out by an emotion of the inner feeling, without
any intervention of the will! Do not many of our actions owe their
origin to instantaneous and uncontrolled movements; and what are
these movements but results of the inner feeling ?

If, as I said above, there is no true will in animals which have a
nervous system without any organ for intelligence, and if this is the
reason why such animals only act by emotions produced by their
sensations, this truth applies still more to animals that have no
nerves. It appears therefore that these latter only move by an
excited irritability, and as an immediate result of external excitations.

It is easy to imagine from the above exposition that, after nature
had transferred the power of acting into the interior of animals, that
is, after she had created the inner feeling based on the nervous system
as the origin of the force for producing actions, she then perfected
her work by creating a second internal power, that, viz. of the will,
which arises from acts of intelligence and is the only faculty that can
cause any variation in the habitual actions.

For this purpose, nature was obliged to add a new organ to the
nervous system, in which acts of intelligence might be carried on;
and she had to separate the nucleus of sensations or perceptions from
the organ of ideas, comparisons, judgments, reasonings, thoughts.

Thus in the most perfect animals the spinal cord provides for the

OF THE WILL 359

muscular movement of the parts of the body, and for the maintenance
of the vital functions ; while the nucleus of sensations, instead of being
situated throughout the length, or in any isolated part of the spinal
cord, becomes concentrated at its superior or anterior extremity in
the inferior part of the brain. This nucleus of sensations is therefore
quite close to the organ in which are carried out the various acts of the
intelligence, and is yet separate from it.

When animal organisation has reached the limit of perfection implied
by an organ for acts of intelligence, the individuals which possess such
an organisation have simple ideas, and may form complex ideas. They
possess a will, free in appearance, which determines some of their
actions; they have passions, that is, heightened inclinations which
draw them towards certain kinds of ideas and actions beyond their
control; lastly, they are endowed with memory and have the faculty
of calling up ideas previously traced in their organ, a process which
is due to the nervous fluid passing over, and being acted on by, the
impressions or traces implanted by these ideas.

It seems probable that the disturbed agitations of the nervous fluid
in contact with these traces are the cause of dreams, which often call
up ideas in animals during sleep.

Animals which have intelligence yet carry out most of their actions
by instinct and habit, and in this respect they never make a mistake ;
when they act by will, that is, as the effect of a judgment, they still
make no mistakes, or, at least, very rarely so; because the elements
which enter into their judgments are few in number and usually
furnished by sensations, and still more because in any one race there
is no inequality in the intelligence and ideas of individuals. Hence
it follows that their acts of will are determinations which lead them
always unerringly to the satisfaction of their needs. For this reason
it has been said that instinct is for animals a torch which lights them
better than our reason.

The truth is that animals are less free than ourselves to vary their
actions and more subject to habit, and hence that they find in their
instinct a compelling necessity, and in their acts of will only a cause
the elements of which are invariable, unmodified, quite simple and
always the same in individuals of the same race; so that it has in
all an equal power and extent. Finally, since there is no inequality
in the intellectual faculties of individuals of the same species, their
judgments and their will, resulting from these judgments, cause them
always to carry out the same actions in the same circumstances.

I shall conclude these theories on the origin and results of the will
by some remarks on this faculty in man. We shall then see that things
are quite different in his case from what they are in the case of animals ;

360 ZOOLOGICAL PHILOSOPHY

for although his will seems to be much freer than theirs, it is not really
so; and yet, for a reason that I shall try to explain, individuals of his
species act very differently under similar circumstances.

Since the will is always dependent on some judgment it is never
really free; for the judgment which gives rise to it is a necessary
result of the union of its component elements, like the quotient in an
arithmetical operation. But the produce of a judgment must vary
in different individuals for the reason that the elements which enter
into the formation of this judgment are apt to be quite different in
different individuals.

In fact, so many and various elements enter into the formation of
our judgments, so many are present which ought not to be present,
and of the proper elements so many are unnoticed or rejected from
prejudice, or are affected by our disposition, health, age, sex, habits,
propensities, state of our knowledge, etc., that the union of these
elements gives rise to very different judgments on the same subject in
different individuals. {The fact that our judgments depend on so many
inappreciable elements has given rise to the belief that our determina-
tions are free, although in reality they are not so, seeing that the
judgments which produce them are not free themselves. /”

The diversity of our judgments is so remarkable that it often happens
that a subject gives rise to as many individual judgments as there are
persons to discuss it. This variation has been taken for a freedom of
determination, and a mistake has thus been made; for it is only the
result of the difference between the elements entering into the judgment
of each person.

Yet there are subjects so simple and straightforward that the judg-
ments passed upon them are in almost universal agreement. But
these subjects are almost exclusively confined to what is outside of
us, and only known by the sensations which they excite or have excited
on our senses. Our judgments with regard to them involve scarcely
any elements other than those furnished by sensation together with the
comparisons which we draw between these and other known bodies.
Lastly, for this class of judgment there is very little call upon our
understanding.

One result of the immense number and variety of the causes which
affect the elements entering into the formation of our judgments,
especially those which require various intellectual operations, is that
these judgments are usually erroneous and inaccurate; and that
on account of the inequality between the intellectual faculties of
individuals these same judgments are commonly as varied as the
people who form them, each one importing different elements into
them. Hence it follows, moreover, that disorders of these acts of

OF THE WILL 361

intelligence necessarily involve others in our wills and consequently in
our actions.

If the scope of the present work permitted, I might adduce many
instances in support of these observations; I might even make
remarks that would not be without interest.

I might show, for instance, that while man derives great advan-
tages from his highly developed intellectual faculties, the human
species in general suffers from them at the same time considerable
disadvantages ; since these faculties confer the means for doing harm
as easily as good, and their general effect is always to the disadvantage
of those individuals who make least use of their intelligence, and this
is necessarily the case of the greater number. It would appear there-
fore that the main evil in this respect resides in the extreme inequality
of intelligence between individuals, an inequality that cannot be
entirely destroyed. Nevertheless it may be inferred with still greater
certainty that the thing most important for the improvement and
happiness of man is to diminish as far as possible this enormous
inequality, since it is the origin of most of the evils to which he is
exposed.

Let us now endeavour to ascertain the physical causes at work in
acts of the understanding: we shall try at least to determine what
are the necessary conditions of the organisation in order that these
wonderful phenomena may be produced.

CHAPTER VII.

OF THE UNDERSTANDING, ITS ORIGIN, AND THE ORIGIN OF
IDEAS.

Tuts is the most curious and interesting, and at the same time the
most difficult subject presented to man in his studies of nature; it
is the subject in which it is most important for him to possess positive
knowledge, while yet offering the fewest facilities for its acquisition.

The question is, how purely physical causes, that is to say, simple
relations between different kinds of matter, can produce what we
call ideas; how, out of simple or direct ideas, complex ideas may be
formed ; how, in short, out of ideas of any kind, faculties can arise, so
astonishing as those of thought, judgment, analysis and reasoning.

He indeed is more than bold who undertakes such a research, and
flatters himself that he has found in nature the origin of these wonder-
ful phenomena.

Assuredly, I have not the presumption to suppose that I have dis-
covered their causes; but I started with the conviction that all acts
of intelligence are natural phenomena and hence derive their source
exclusively from physical causes. Seeing that the most perfect animals
enjoy the faculty of producing them, I thought that by careful observa-
tion, attention, and patience, I might reach, especially through induc-
tion, ideas of great moment on this important subject ; I now have to
present my conclusions.

Under the title of understanding or intelligence I include all known
intellectual faculties, such as those of forming ideas of various kinds,
of comparing, judging, thinking, analysing, reasoning, and, lastly, of
recalling ideas previously acquired as well as past thoughts and reason-
ings; this faculty constituting memory.

All these faculties unquestionably result from acts peculiar to the
organ of intelligence, and each such act is necessarily the product of
relations subsisting between that organ and the nervous fluid moving
in it.

OF THE UNDERSTANDING 363

The special organ in question, to which I have given the name of
hypocephalon, consists of two wrinkled pulpy hemispheres, investing
or covering that medullary region which I call more strictly the brain,
and which contains the nucleus or centre of communication of the
nervous system and gives rise to the nerves of the special senses ; the
cerebellum is a mere appendage of it.

This region (the brain properly so-called, including the cerebellum)
and the hypocephalon are quite distinct from each other, especially as
regards their functions, although they are commonly confused together
under the general name of brain or encephalon. Now it is in the func-
tions of the hypocephalon alone that I shall seek the physical causes of
the various intellectual faculties, because this organ is the only one
that has the power of giving rise to them.

Though not easily recognised, there is a real differentiation in the
parts of this organ. This differentiation and the varied movements
of the contained subtle fluid are the only origin of the different
intellectual acts which I have named. This is the general idea, which
I propose briefly to develop.

At the outset, in order to introduce some order into our discussions
we must posit or recall the two following principles which are at the
base of all legitimate hypotheses on this subject.

First principle: All intellectual acts whatever originate from ideas,
acquired either at the time or previously, for these acts may always
be reduced to ideas, or relations between ideas, or operations on
ideas.

Second principle: Every idea of any kind originates either directly
or indirectly from a sensation.

Of these two principles, the first is fully confirmed by an investiga-
tion as to what the various acts of the understanding really consist
of; in all such acts, ideas are invariably the subject or material of the
operations carried out.

The second of these principles had been recognised by the ancients,
and is perfectly expressed in that axiom, which Locke has so success-
fully sustained, viz.: That there is nothing in the understanding which
was not previously in sensation.

Hence it follows that every idea must in the last analysis be resolved
into an image perceived, and that since whatever is in our understand-
ing came there vd sensation, all that issues from it and can find no
perceptible object to fasten upon is absolutely chimerical. This is the
obvious conclusion drawn by M. Naigeon from Aristotle’s axiom.

The axiom however is not yet universally admitted, for many people
hold, on account of certain facts whose causes they do not perceive,
that there really are innate ideas. They persuade themselves that they

364 ZOOLOGICAL PHILOSOPHY

have found a proof of it in the child which a few minutes after birth
tries to suck, and seems to look for its mother’s breast, although it
can still have no knowledge of it through freshly acquired ideas. I
shall refrain from citing the alleged case of a kid which when dragged
from its mother’s breast selected laburnum from several plants offered
it. It is well known that this was a mere imagination, which cannot
have been well-founded.

When once we have recognised that habits are the source of pro-
pensities, that continued exercise of these propensities modifies the
organisation in a corresponding direction, and that they are then
transmitted to new individuals by reproduction, we shall see how the
newly born child may try to suck by pure instinct, and may take the
breast offered it without having the slightest idea of it, or carrying out
any thought, judgment, or act of will; and we shall further see that
the child performs this action exclusively through the slight emotion
which the need raises in its inner feeling, so as to make it act in the
direction of an acquired propensity without any previous experience ;
we shall see in the same way that the duckling just out of the egg, if
it is in the neighbourhood of water, immediately runs to it and swims
about on the surface, without having any idea of it or knowing what it
does. The animal does not perform this action by any intellectual
deliberation, but by a transmitted propensity evoked by its inner
feeling without any call upon the intelligence.

I lay down, then, as a fundamental principle and unquestionable
truth, the proposition that there are no innate ideas, but that all ideas.
whatever spring either directly or indirectly from sensations which
are felt and noticed.

From this principle it follows that the organ of intelligence, being the
ultimate perfection which nature has bestowed on animals, can only
exist in those which already possess the faculty of feeling. Hence the
special organ in which are carried out ideas, judgments, thoughts,
etc., only begins to be formed in animals with a highly developed
system of sensations.

All intellectual acts occurring in an individual are due therefore to a
combination of the following causes, viz. :

1. The faculty of feeling ;

2. The possession of a special organ for intelligence ;

3. The relations subsisting between this organ and the nervous fluid
moving freely about in it;

4. Lastly, the fact that the results of these relations are always con-
veyed to the nucleus of sensations, and therefore to the individual’s
inner feeling.

This is the chain which is in harmony throughout, and constitutes

OF THE UNDERSTANDING 365

the developed physical cause of the most wonderful of natural
phenomena.

To set up a reasonable opposition to the views stated above, it would
be necessary to show that the harmony existing throughout the nervous
system is not capable of producing sensations and the individual’s
inner feeling; that intellectual acts, such as thoughts, judgments,
etc., are not physical acts, and do not result immediately from relations
between a subtle agitated fluid and the special organ containing it ;
lastly, that the results of these relations are not transmitted to the
individual’s inner feeling. Now the physical causes named above are
the only ones that can possibly give rise to the phenomena of intelli-
gence. If therefore the existence of these causes is denied, and if
consequently it is denied that the resulting phenomena are natural,
it will then be necessary to seek another source of these phenomena
outside nature. It will be necessary to substitute for the physical
causes rejected, fantastic ideas of our own imagination, ideas that are
always baseless since it is quite obvious that we can have no other
positive knowledge than that derived from the actual objects which
nature presents to our senses.

Since the marvels which we are investigating, and whose causes
we are seeking, are based upon ideas, and since in acts of intelligence
we are dealing only with ideas and operations on ideas ; before enquir-
ing what ideas themselves are, let us illustrate the gradual formation
of the organs which give nse firstly to sensations and the inner feeling,
then to ideas and, lastly, to the operations performed upon them.

The very imperfect animals of the earlier classes, having no nervous
system, are simply irritable and merely have habits without feeling
any sensations or ever forming ideas. But the less imperfect animals,
which have a nervous system without, however, the organ of in-
telligence, have instinct, habits and propensities and feel sensations,
while yet forming no ideas. I venture to affirm that where there is
no organ for a faculty, that faculty cannot exist.

Now if we admit that every idea originates from a sensation, which
indeed cannot seriously be disputed, I hope to show that it does not
follow that every sensation necessarily yields an idea. The organisa-
tion must have reached a state favourable to the formation of the idea,
and, moreover, the sensation must be accompanied by a special effort
of the individual, in short, by a preparatory act which renders the special
organ of intelligence capable of receiving the idea, that is, of retaining
impressions.

Indeed, if it is true that in creating organisation, nature necessarily
began by forming it in extreme simplicity without the intention of
giving living bodies any other faculties than those of feeling and

366 ZOOLOGICAL PHILOSOPHY

reproducing, those bodies which were endowed by her with organisa-
tion and life could have no other organs than those necessary for the
maintenance of life. This fact is confirmed by observation of the
most imperfect animals, such as the infusorians and polyps.

But when she subsequently complicated the organisation of these
earliest animals and created, with the help of long periods of time
and an infinite diversity of circumstances, the multitude of different
forms which characterise the later classes, nature formed successively
the various organs which animals possess and the different faculties
to which these organs give rise. She produced them in an order that
I have determined in Part I., Chapter VIII., and from this order it
may be seen that the hypocephalon, consisting of the two wrinkled
hemispheres covering the brain, is the last organ which she brought
into existence.

Long before creating the hypocephalon, or special organ for the
formation of ideas and of all the operations carried out upon them,
nature had established in a great number of animals a nervous system,
which gave them the faculty of exciting muscular activity, and after-
wards of feeling and acting by the emotions of their inner feeling.
Now although for this purpose she had multiplied and scattered the.
nuclei for muscular movement either by establishing separate ganglia,,
or by distributing these nuclei throughout the length of a ganglionic
longitudinal cord or spinal cord, yet she concentrated the nucleus of
sensation in a special locality and fixed it in a small medullary mass,
which gives direct origin to the nerves of some special senses and which
has received the name of brain.

It was therefore only after having wrought these various perfections
of the nervous system that nature put the finishing touch on her work
by creating, in close proximity to the nucleus of sensations, the hypo-
cephalon, that remarkable and interesting organ in which ideas are
graven and where all the operations constituting intelligence are carried
out.

It is exclusively these operations that we shall study, in our
endeavours to determine their most probable physical causes, by
careful inductions and a knowledge of the conditions required.

Let us now investigate how an idea comes to be formed, and under
what conditions a sensation can produce it; let us even enquire, at
least in outline, in what way acts of the intelligence are carried out in
the hypocephalon.

It is a very singular circumstance that the special organ now under
consideration never exerts any action itself in any of the acts or pheno-
mena to which it gives rise, and that it does nothing more than receive
and preserve for a longer or shorter period the images transmitted to it

OF THE UNDERSTANDING 367

and the impressions graven upon it. This organ, together with the
brain and nerves, differs from all the other organs of the animal body
in that it is not active, and does no more than provide the means for the
nervous fluid to carry out its various phenomena.

Indeed, when I remember the extreme softness of the medullary
pulp constituting the nerves, brain, and hypocephalon, I cannot think
that in the relations of the nervous fluid with the medullary parts,
the latter are capable of exerting the slightest action. Beyond doubt
these parts are entirely passive and unable to react upon anything that
affects them. Hence it results that the medullary parts, of which
the hypocephalon consists, receive and preserve the traces of all the
impressions made upon them by the movements of the nervous fluid ;
so that the only active element in the functions of the hypocephalon
is the nervous fluid itself; or to express the matter more precisely,
the organ carries out no function, the nervous fluid by itself carries
out all; but this fluid could in nowise give rise to them without the
existence of the organ in question.

I may be asked how it is possible to conceive that any fluid, however
subtle and varied its movements, can by itself give rise to that astonish-
ing variety of acts and phenomena characteristic of the intellectual
faculties. To this I reply, that the entire marvel is in the composition
of the hypocephalon itself.

The medullary mass constituting the hypocephalon, that is, the two
wrinkled hemispheres which cover over the brain,—this mass, I say,
which seems to be only a pulp, whose parts are continuous and coherent
throughout, consists, on the contrary, of an inconceivable number of
separate and distinct parts, from which result a vast quantity of
cavities of infinitely varied size and shape and appearing to occupy
distinct regions, equal in number to the intellectual faculties of the
individual; lastly, however it may come about, the composition
of the organ is different in each region, for each is devoted to some
individual faculty of the intelligence.

The examination of the white medullary part of the hypocephalon
has disclosed numerous fibres in it : now it is probable that these fibres
are not, as elsewhere, organs of movement ; their consistency would not
permit of it: there is more reason to believe that they are so many
individual canals, each terminating in a cavity which would be in the
form of a cul-de-sac unless they communicate together by lateral paths.
These cavities, which are imperceptible to us, are as innumerable as the
tubular threads leading to them; and it may be presumed that it is
on their internal walls that the impressions brought by the nervous
fluid are engraved ; there may also be little medullary plates or leaves

for the same purpose.

368 ZOOLOGICAL PHILOSOPHY

Since we cannot know what is actually the case on this subject, I
believe I have attained my purpose by showing what may be the case
or even probably is the case: for I can do no more.

The wonderful composition of the hypocephalon, both in its main
features and in its individual regions, which are all duplicated, one
being in each hemisphere, is more than a mere hypothesis, in spite of
the fact that we lack the means for seeing it and assuring ourselves of
it. The organic phenomena constituting the intelligence, and the fact
that each of these phenomena requires a special locality in the organ
and indeed a special organ, so to speak, for its production, should give
us a moral conviction that the composition of the hypocephalon is as
I have represented it.

Certainly, individuals are not born in possession of all their possible
intellectual faculties, for the organ of intelligence, like the rest,
develops according to its use. The same applies with each special
kind of intellectual faculty: it is brought into existence in the
appropriate region of the hypocephalon by the needs that are felt ;
and in correspondence with the frequency of the repetition of these
acts, the special organ adapted to them develops and enlarges its
faculty.

It is therefore not true that any of our intellectual faculties are
innate; and this applies also to those of our propensities which depend
on the faculty of thought. These faculties and propensities grow and
strengthen according to the exercise which we give to their underlying
organs. We may indeed derive certain tendencies from our inherited
organisation: but unless we exercise these faculties and inclinations
ourselves we gradually lose the aptitude for them.

Dr. Gall having noticed that some individuals had particular
faculties, more developed and conspicuous than others, conceived the
idea of enquiring whether any part of their body might not present
some external signs by which this faculty could be recognised.

He does not seem to have studied any faculties but those connected
with the intelligence ; for if he had he would have met with abundant
evidence that any part which is much exerted and has acquired a highly
developed faculty, always exhibits manifest signs of it in its size, shape,
and vigour. We cannot look at the posterior extremities and tail of a
kangaroo, without being convinced that these much used parts possess
great power of action, a fact which also applies to the posterior legs
of grasshoppers, etc. In the same way, when we reflect upon the
immense growth of the elephant’s nose, which has been transformed
into an enormous trunk, we cannot help recognising that the habitual
exercise of this organ, which is used by the animal as a hand, is account-
able for its size, strength, and wonderful suppleness, etc., etc.

Ul THE UNDERSTANDING 369

But M. Gall seems to have particularly devoted himself to a search
for the external signs which might indicate a high eminence of in-
tellectual faculties in certain individuals. He recognised that all these
faculties are based upon functions of the cerebral organ, and therefore
directed his attention to the encephalon. After some years of research,
he became convinced that those of our intellectual faculties, which are
greatly developed and have acquired a high degree of complexity,
may be recognised by external signs consisting of certain protuber-
ances of the cranium.

M. Gall certainly founded his theory on a sound principle: for if
it is true, as I have sufficiently proved in Part L., Chapter VIL., that all
parts of the body which are vigorously and constantly used, acquire
a characteristic development and strength of function, the same must
hold good equally for the organ of understanding in general, and even
for each of the special organs which compose it : so much is certain and
easy to demonstrate by many established facts.

M. Gall’s underlying principle therefore is beyond criticism; but
the results of enquiries into the doctrines taught by this savant give
tise to the belief that he misapplied his theory, as regards most of the
inferences which he drew from it.

As a matter of fact, in the case of the special organs which enter into
the composition of the two cerebral hemispheres and give rise to the
different kinds of intellectual faculties, the principle seems to me to be
much less applicable than M. Gall supposes ; and indeed it can only be
in a very small number of extreme cases that certain faculties which
have acquired extraordinary power may present indubitable external
signs of their existence. In such cases I should not be in the least
surprised at the discovery of some such signs, since they have a true
natural cause. But with regard to our intellectual faculties, M. Gall
has lost sight of the larger distinctions, to embark upon a crowd of
details, including even the gradations between these faculties; and
this in my opinion is an instance of a very ordinary abuse of the
imagination, which destroys the value of our discoveries in the study
of nature. And now because M. Gall wanted to prove too much, the
public have fallen into the opposite extreme and rejected the whole.
Such is the usual progress of the human mind in its various acts ; the
good that has been done is most often spoilt by excess and abuse.
The exceptions to this rule are only found in a small minority of
persons who by the aid of a powerful reason set limits to the

imagination. which tends _to-carry them away

To regard certain propensities which have become altogether
dominant as innate in the human species, is not only a dangerous

belief but also a genuine mistake. We may no doubt possess at birth
2A

370 ZOOLOGICAL PHILOSOPHY

special tendencies transmitted from the organisation of our parents,
but it is certain that if we did not strongly and habitually exercise the
faculties favoured by these tendencies, the special organs concerned
would never have developed.

In truth, every individual, from the moment of his birth, is in the
midst of a set of circumstances altogether peculiar to himself, which
to a large extent contribute to make him what he is at the different
stages of his life, and which put him in the way of exerting or not
exerting one or other of his faculties or inherited tendencies ; so that
it may be said in general that we only have quite a moderate share in
bringing about the condition in which we find ourselves throughout
our existence, and that we owe our tastes, propensities, habits,
passions, faculties, and knowledge to the infinitely varied but special
circumstances in which each of us has been placed.

From our earliest infancy, those who bring us up sometimes leave us
entirely at the mercy of surrounding circumstances, or themselves
create circumstances highly disadvantageous to us by their mode of
life, thought, and feeling; and sometimes by ill-advised weakness they
spoil us and let us acquire many pernicious faults and habits, whose
consequences they do not foresee. They laugh at what they call our
tricks, and make jokes over all our follies, in the belief that they will
be able later on easily to change our vicious inclinations and correct
our faults.

It is difficult to conceive how great is the influence of early habit
and inclinations on the propensities which will some day dominate
us, and on the character which we form. The very pliable organisa-
tion of early youth yields readily to the habitual movements of our
nervous fluid in one or other direction, in correspondence with our
inclinations and habits. The organisation thence acquires a modifi-
cation which may increase under favourable circumstances, but which
can never be entirely obliterated.

It is in vain that after our infancy, we make efforts to guide our
inclinations and actions by means of education towards whatever
may be useful to us, in short, to give ourselves principles to form our
reason and manner of judging, etc. We meet with so many circum-
stances that are difficult to master, that we are each of us, so to speak,
constrained by them and gradually acquire a mode of life in which we
ourselves have only had a very small share.

I need not here enter upon the numerous details which form a special
environment for each individual, but I must observe, since I am con-
vinced of it, that everything tending to make any of our actions
habitual modifies our internal organisation in favour of that action’;
so that as a result this action becomes a sort of necessity for us.

OF THE UNDERSTANDING 371

Of all parts of our organisation, that which most readily undergoes
modifications, due to some acquired habit of thought, idea, or action,
is our organ of intelligence. IN ow the region which is modified is neces-
sarily that concerned with the ideas or thoughts which habitually
occupy us. I repeat, then, this region of our intellectual organ when
vigorously exercised acquires a development which may finally
become noticeable by external signs.

We have dealt with the general principles concerning the organ
which gives rise to intelligence; we shall now pass on to a enquiry
into the formation of ideas.

ForRMATION OF IDEAS.

My purpose here is not to undertake any analysis of ideas, nor to
show how they become compounded and increased, nor, in short, how
the understanding is perfected. Many celebrated men since Bacon,
Locke, and Condillac, have dealt with these matters and greatly
illuminated them. I need not therefore stay to consider them.

My purpose is simply to indicate by what physical causes ideas may
be formed, and to show that comparisons, judgments, thoughts, and
all operations of the understanding are at the same time physical
acts, which result from the relations between certain kinds of matter
in action, and which are carried out in a special organ which has
gradually acquired the faculty of producing them.

All that I have to say on this important subject is entirely a matter
of probabilities. All is a product of imagination ; limited however by
the necessity for admitting nothing but physical causes compatible
with the known properties of matter, nothing, in short, but causes
which may be and probably are correct. With regard to the physical
acts which I shall endeavour to analyse, none of them can be witnessed
and none therefore can be proved.

I should mention that ideas are of two distinct kinds, viz. :

Simple or direct ideas; complex or indirect ideas.

By simple ideas I mean those which spring immediately and ex-
clusively from the noticed sensations that are impressed upon us by
objects either within or without us.

By complex ideas I mean those which are found within us as a result
of some operation of our: understanding, performed on previously
acquired ideas; they therefore require no immediate sensation.

Tdeas of all kinds are the result of images or special outlines of objects
which have affected us; these images or outlines only become ideas
for us, when they have been traced on some part of our organ; and
the nervous fluid then passes over them and carries back the result
to our inner feeling, by which we become conscious of it.

372 ZOOLOGICAL PHILOSOPHY

Not only do ideas originate in two different ways, but a distinction
has also to be drawn between those which only become perceptible
to us in company with the sensation which produced them, and those
which are presented to our consciousness without any accompanying
sensation.

The former I call physico-moral ideas, and the latter moral cdeas simply.

Physico-moral ideas are clear, vivid, and sharply defined, and are
felt with all the force that they derive from their accompanying
sensation. Thus the sight of a building or any other object under my
eyes to which I pay attention, gives rise in me to one or several ideas
by which I am vividly affected.

Moral ideas, on the other hand, both simple and complex, of which
we only become conscious as the result of an operation of our under-
standing excited by our inner feeling, are very vague and ill-defined
and do not affect us with any vividness, although we are sometimes
stirred by them. Thus, when I recall an object that I have seen and
noticed, a judgment that J have formed, a reasoning which I have
carried out, etc., the idea only affects me in a weak and vague manner.

We must then beware of confusing what we experience when we
have the consciousness of some idea, from what we experience when
a sensation affects us and we pay attention to it.

All that we are conscious of only comes to us through the organ of
intelligence, and whatever causes sensation in us works firstly through
the sensitive organ and afterwards through the idea that we form of
it, if we happen to pay attention to it.

It is essential, therefore, to distinguish moral from physical feeling,
since experience of the past teaches us that a failure to recognise that
distinction has led men of the highest ability to draw up theories
which now have to be destroyed.

No doubt both feelings are physical, but the difference in the terms
that I use to distinguish them is sufficient for the purpose that I have
in view, and moreover they are the terms in common use.

By moral feeling I mean the feeling that we experience when an
idea or thought or any act of our understanding is transmitted to our
inner feeling, so that we then have consciousness of it.

By physical feeling I mean the feeling which we experience from some
sensation due to an impression on any of our senses and compelling
our attention.

These clear and simple definitions must show that the two things are
quite different from one another, both as regards their origin and
their effects.

It is however through confusing them, as Condillac had done, that
M. de Tracy has said :

OF THE UNDERSTANDING 373

“Thinking is only feeling, and feeling is for us the same thing as
existing ; since it is sensations that tell us of our existence. Ideas
or perceptions are either true sensations or recollections, or affinities
that we perceive, or indeed the desire that may be raised in us by these
affinities : the faculty of thought is thus sub-divided into true sensi-
bility, memory, judgment, and will.”

In all this there is clearly a confusion between sensations and the
consciousness of our ideas, thoughts, judgments, etc. It is a similar
confusion between moral feeling and physical feeling that has led to the
belief that every creature, which possesses the faculty of feeling, also
has that of intelligence ; for this is certainly ill-founded.

Sensations no doubt tell us of our existence, but only when we pay
attention to them. That is to say, we have to think of them, and this
is an act of intelligence.

Thus, in the case of man and the most perfect animals, sensations
that are noticed acquaint them with existence and give ideas ; but in
the case of the more imperfect animals, such for instance, as the insects,
in which I recognise no organ for intelligence, sensations cannot be
remarked, nor yield ideas ; and they can only form simple perceptions
of the objects which affect the individual.

Yet the insect possesses an inner feeling capable of emotions which
make it act; but since there is no idea connected with it, it cannot be
conscious of its existence; in short, it never experiences any moral
feeling.

In the case of all creatures endowed with intelligence, we must
therefore say: to think is to feel morally, or to have consciousness
of one’s ideas and thoughts, and also of one’s existence; but this is
not the same as physical feeling, for the latter is a product of the
system of sensations while the former comes from the organic system
of intelligence.

StmpeLeE [pEas.

A simple idea, arising from a sensation of some object affecting one
of our senses, can only be formed when the sensation is remarked,
and when the result of the sensation is transmitted to the organ of
intelligence and traced or graven on some part of it; this result is
perceived by the individual because at the same moment it affects his
inner feeling.

Indeed every individual which possesses the faculty of feeling and
also an organ for intelligence, promptly receives in this organ the image
or outlines brought by the sensation of any object, if the organ is
prepared for it by attention. Now these outlines or image of the
object reach the hypocephalon by means of a second reaction of the

374 ZOOLOGICAL PHILOSOPHY

nervous fluid, which, after having produced sensation, carries into
the intellectual organ the particular agitation which it derived from
that sensation, impresses on some part of it the characteristic outlines
of its movement, and finally renders them perceptible to the individual
by transmitting their effects to his inner feeling.

The ideas formed on seeing a sky-rocket for the first time, on hearing
a lion’s roar, and on touching the point of a needle are simple ideas.

Now the impressions which these objects make upon our senses
immediately excite in the fluid of the corresponding nerves an agitation
which is different in each case; the movement is propagated to the
nucleus of sensations; the whole system immediately shares in it; and
sensation is produced by the mechanism that I have already explained.

Thus, if our attention has prepared the way, the nervous fluid
instantly conveys the image of the object or some of its outlines to our
organ of intelligence, and impresses that image or those outlines on
some part of the organ; the idea traced is then immediately carried
back by it to our inner feeling.

In the same way that the nervous fluid by its movements is the
agent for carrying to the nucleus of sensations the impressions of
external objects that affect our senses, so too this subtle fluid is the
agent for conveying from the nucleus of sensations to the organ of
intelligence the product of each sensation that is raised, for tracing its
outlines there or impressing them on it by its agitations if the organ
has been prepared by attention, and for subsequently carrying back
the resultant to the individual’s inner feeling.

Thus, in order that the outlines or image of the object which has
caused the sensation may reach the organ of understanding and be
impressed on some part of it, it is necessary that the organ should
first be prepared by an act of attention for receiving the impression,
or that this act should open the way by which the product of that sen-
sation may travel to the organ where the outlines of the object may be
impressed : in order that any idea may arise or be recalled in conscious-
ness, it is necessary again by means of attention that the nervous fluid
should convey its outlines to the individual’s inner feeling; this idea
then becomes perceptible to him and may be recalled at the will of the
individual for a longer or shorter period.

The impression which forms the idea is thus actually traced and
graven on the organ, since memory can recall it at the will of the
individual and make it perceptible once more.

This in my opinion is the probable mechanism of the formation of
ideas ; the mechanism by which we recall them-at will until time
has obliterated or blurred their outlines so that we can no longer
remember them.

OF THE UNDERSTANDING 375

To try to determine how the agitations of the nervous fluid trace or
engrave an idea on the organ of understanding, would be to court the
risk of committing one of those numerous errors to which the imagina-
tion is liable ; all that we can be sure of is that the fluid in question is
the actual agent which traces and impresses the idea; that each kind
of sensation gives a special agitation to this fluid and consequently
causes it to impress equally special outlines on the organ; and,
lastly, that the fluid acts upon an organ so soft and delicate and
finds its way into such narrow interstices and tiny cavities, that it
can impress on their delicate walls traces more or less deep of every
kind of movement by which it may be agitated.

Do we not know that in old age, when the organ of intelligence has
lost some of its delicacy and softness, ideas are graven less deeply and
with greater difficulty ; that memory, which is gradually being lost,
only recalls ideas graven long ago upon the organ, since they were
then more easily and deeply impressed ?

Moreover, with regard to the organic phenomenon of ideas, we are
dealing exclusively with relations between moving fluids and the
special organ which contains them. Now for operations so swift as
ideas and all intellectual acts, what other fluid could produce them but
the subtle and invisible fluid of the nerves, a fluid so analogous to
electricity ; and what organ could be more appropriate for these delicate
operations than the brain ?

Thus a simple or direct idea is formed, whenever the fluid of the
nerves is agitated by some external impression or even by some internal
pain, and conveys the agitation to the nucleus of sensations, and when
attention has prepared the way for the further conveyance of that
agitation to the organ of intelligence.

As soon as these conditions are fulfilled, the impression is immediately
traced upon the organ, the idea comes into existence and is at once
perceived because the individual’s inner feeling is affected by it;
lastly, the idea may be called up afresh by memory, although obscurely,
whenever the individual directs the nervous fluid over the subsisting
traces of that idea.

Every idea recalled by memory is therefore much vaguer than when
it was formed; because the fact which renders it perceptible does
not then result from a present sensation.

CompLex IpzEas.
By a complex or indirect idea, I mean one that does not arise immedi-
ately from the sensation of some object, but is the result of an act of

intelligence working on ideas already acquired.
The act of understanding which gives rise to the formation of a

376 ZOOLOGICAL PHILOSOPHY

complex idea is always a judgment ; and this judgment itself is either
a consequence or a determination of a relationship. Now this act
appears to me to be due to the resultant movement of the nervous
fluid which has been broken up by the inner feeling into separate
streams, each of which traverses previously made impressions of certain
ideas, and thence undergoes special kinds of modifications in its move-
ments. When the streams reunite their individual movements are
then combined into this resultant movement.

It is then by means of this movement of the nervous fluid, which
is really due to compared ideas or to relations between them, that the
subtle fluid makes its impressions on the organ and at the same
moment transfers the effect to the individual’s inner feeling.

Such is in my opinion the physical cause and precise mechanism
which give rise to the formation of all kinds of complex ideas. These
complex ideas are quite distinct from simple ideas, since they do not
result from any immediate sensation or impression on any of our senses,
but originate from several ideas already impressed, and, further, are
exclusively due to an act of the understanding in which the sensitive
system has no share.

There is this difference between the act of understanding which forms
a judgment whence arises a complex idea, and that called a recollection
or act of memory, which merely consists in recalling ideas to the
individual’s inner feeling: that in the former case the ideas employed
take part in an operation resulting in a new idea, whereas in the second
case the ideas employed take part in no operation, give rise to no new
idea, but merely become present to the individual’s consciousness.

If it is true that the emotions of our inner feeling give us the faculty
and power of acting, and that they enable us to put our nervous fluid in
motion and direct it over the impressions of various ideas made upon
different parts of the recipient organ, it is obvious that this subtle
fluid, while passing over the tracings of any idea, will undergo a special
modification in its mode of agitation. We may suppose that, if the
nervous fluid simply brings back this special modification of its agitation
to the individual’s inner feeling, it only makes the idea perceptible or
present to the individual’s consciousness ; but if the fluid, instead of
merely passing over the tracings or image of a single idea, divides into
several streams, each of which travels over some individual idea, and
if the streams then all reunite, the resultant movement of the combined
fluid will impress on the organ a new and complex idea, and will then
transfer its effect to the individual’s consciousness.

If we form complex ideas out of pre-existing simple ideas, we shall
have, as soon as they are impressed on our organ, complex ideas of the
first order: now it is obvious that if we compare together several

OF THE UNDERSTANDING 377

complex ideas of the first order by the same organic means with which
we compared simple ideas, we shall obtain a resultant judgment of
which we form a new idea ; this will be a complex idea of the second
order, since it arises from several previously acquired complex ideas
of the first order. In this way complex ideas of various orders
may be multiplied almost to infinity, as indeed we see in most of
our reasonings.

Thus there are carried out in the organ of intelligence various physical
acts which give rise to the phenomena of comparison, judgment,
analysis of ideas, and reasoning, and these different acts are only opera-
tions on ideas already traced, due to the resultant movement acquired
by the nervous fluid when it impinges on their tracings or images :
and since these operations on pre-existing ideas and even on series of
ideas, taken in turn or all together, are only relations sought out by
thought through the inner feeling between the various kinds of ideas,
these same operations culminate in results which we call judgments,
inferences, conclusions, etc.

In the same way, intellectual phenomena are physically produced in
the most perfect animals. They are no doubt of a very inferior order,
but they are altogether analogous to those described above ; for these
animals do receive ideas and have the faculty of comparing them and
drawing judgments from them. Their ideas are therefore actually
traced or impressed on the organ on which they are formed, since they
evidently have a memory, and when asleep may often be seen dreaming,
that is, experiencing involuntary recurrences of their ideas.

As regards the signs, so necessary for the communication of ideas,
and so useful for increasing their number, J am compelled to confine
myself to a simple explanation, with reference to the double service
that they render us.

“Condillac,” said M. Richerand, “has acquired an immortal glory,
in being the first to discover and to prove irrefutably that signs are
as necessary to the formation as to the expression of ideas.”

I am sorry that the limits of the present work do not permit me to
enter into the detail necessary for showing that there is an obvious
error in a use of terms which suggests that signs are necessary to the
direct formation of ideas; for this cannot have the slightest foundation.

I do not yield to M. Richerand in admiration of the genius and the
profound thoughts and discoveries of Condillac, but I am quite con-
vinced that the signs which have to be used for the communication of
ideas are generally only necessary to their formation, because they
furnish an indispensable means for increasing their number and not
because they actually contribute to their formation.

No doubt a language is as useful for thinking as for talking; we have to

378 ZOOLOGICAL PHILOSOPHY

attach conventional signs to the conceptions we acquire, in order that
these conceptions may not remain isolated, but may be associated and
compared, and their relationships determined. But these signs are
artificial aids, infinitely useful in helping us to think, and not immediate
causes of formation of ideas.

Signs of whatever kind do no more than assist our recollection of
conceptions acquired recently or long ago, furnish us means of bringing
them back into consciousness, and thereby facilitate the formation of
new ideas.

Condillac has successfully proved that without signs man could never
have extended his ideas as he has done and still does; but it does
not follow that signs are themselves elements in ideas.

I greatly regret that I cannot continue the important discussion
which this subject demands; but probably some one will see the
mistake to which I have drawn attention, and furnish a complete proof
of it. Then while recognising all that we owe to the art of signs, we
shall recognise at the same time that it is only an art and consequently
outside nature.

From the observations and considerations set forth in this chapter
I conclude :

1. That the various acts of the understanding require a special organ
or system of organs, just as one is required for feeling, another for move-
ment, and a third for respiration, etc. ;

2. That in the performance of acts of intelligence the movement of
the nervous fluid is the only active factor, while the organ remains
passive though contributing to the diversity of the operations by a
corresponding diversity of its parts and of the impressions preserved
upon them ;—a diversity that cannot be calculated since it increases
up to infinity according as the organ is used ;

3. That acquired ideas are the material of all operations of the under-
standing ; that with this material the individual who habitually exerts
his intellect may be continually forming new ideas, and that the only
means open to him for this extension of his ideas consists in the art of
signs to assist his memory, an art which man alone can use, which he
makes more perfect every day, and without which his ideas would
inevitably remain very limited.

To throw further light on the subject under discussion, I shall now
pass to an examination of the principal acts of the understanding,
that is to say, those of the first order from which all the rest are
derived.

CHAPTER VIII.

OF THE PRINCIPAL ACTS OF THE UNDERSTANDING, OR THOSE
OF THE FIRST ORDER FROM WHICH ALL THE REST ARE
DERIVED.

TuE subjects which I propose to treat in the present chapter are so
vast as to make it impossible for me, within the limits which I have set
myself, to exhaust all the problems and topics of interest which they
present. I shall therefore confine myself to an attempt to show how
all the acts of the understanding, and all the phenomena that result
from them, originate in the physical causes which I have expounded
in the previous chapter.

The special organ which gives rise to the wonderful phenomena of
intelligence is not limited to a single function ; it clearly performs four
essential functions ; and in proportion to its development, these func-
tions acquire more capacity and energy, or are subdivided into many
others ; so that when the organ is highly developed the intellectual
faculties are numerous and some of them attain an almost infinite
capacity.

Hence man, who alone furnishes instances of this latter event, is
the only kind of being who is enabled by his lofty intellectual faculties
to give himself up to the study of nature, to perceive and wonder at
the invariable order, even to discover some of her laws, and finally to
ascend in thought to the Supreme Author of all things.

The principal functions performed in the organ of intelligence are
four in number, and consequently give rise to four very different kinds
of acts, viz. :

1. The act which constitutes attention ;

2. That which gives rise to thought, from which spring complex ideas

of all orders ;
3. That which recalls acquired ideas and is named recollection or

memory ;
4. Lastly, that which constitutes judgments.

380 ZOOLOGICAL PHILOSOPHY

We shall enquire therefore what really are the acts of the understand-
ing which‘constitute attention, thought, memory, and judgments.
We shall find that these four acts are the principal ones, the type or
source of all the rest, and that it is wrong to place in the first rank
will, which is only a result of certain judgments, desire which is only a
moral need, and sensations which have nothing to do with intellect.

In saying that desire is only a need or the consequence of a need
that is felt, I rely on the fact that needs may be divided into physical
needs and moral needs.

Physical needs are those which arise in consequence of some sensation,
such as those for escaping from pain or discomfort and for satisfying
hunger, thirst, etc.

Moral needs are those which arise from thoughts, and in which sensa-
tions have no share, such as those for seeking pleasure or comfort,
of fleeing from danger, of indulging one’s interests or vanity, or any
passion or inclination, etc., etc. ; desire is of this order.

Both these kinds of needs arouse the individual’s inner feeling in
proportion as he feels them, and this feeling promptly sets in movement
the nervous fluid so as to produce actions, either physical or moral,
suitable for satisfying them.

Let us now examine each of the faculties of the first order which
when combined constitute the understanding or intellect.

OF ATTENTION.
THe First oF THE PRINCIPAL FAcuLtTIES oF THE INTELLECT.

I now come to one of the most important subjects of study for
understanding how ideas and all intellectual acts come to be formed,
and how they result exclusively from physical causes; I refer to
attention.

Let us then enquire what attention is, and whether the definition of
it that I am about to give is confirmed by the known facts.

Attention is a special act of the inner feeling; it takes place in the
organ of intelligence and enables that organ to carry out its functions,
for which indeed it is indispensable. Attention is therefore not in
itself an operation of the intelligence but of the inner feeling, and
prepares the organ of thought or some part of it for carrying out its
acts.

It may be described as an effort of an individual’s inner feeling,
sometimes prompted by a need arising in consequence of some sensa-
tion, and sometimes by a desire called up by the memory of an idea
or thought. This effort, by transporting and directing the available
part of the nervous fluid towards the organ of intelligence, prepares

THE PRINCIPAL ACTS 381

some part of that organ, so that it is ready either to re-awake ideas
already impressed upon it or to receive the impression of new ideas.

It seems to me manifest that attention is not a sensation, as Senator
Garat has said,} and that it is not an idea, or any operation upon
ideas ; consequently that it is not an act of will, since this is always the
result of a judgment; but that it is an act of the individual’s inner
feeling, by which some part of the organ of understanding is prepared
for an intellectual operation, and by which that part becomes fitted to
receive impressions of new ideas, or recall to the individual ideas which
had previously been traced.

Indeed I can prove that when the organ of understanding is not
prepared by that effort of the inner feeling called attention, no sensation
can arise; or if one does arise, it leaves no impression but merely
skims over the organ without producing any idea, or recalling to con-
sciousness any that had been previously traced.

I was justified in the statement that although every idea is derived
in the first instance from a sensation, every sensation does not neces-
sarily yield an idea. The citation of certain well-established facts will
suffice to justify this proposition.

When you are reflecting, or your thoughts are occupied with some-
thing, although your eyes are open and external objects are constantly
affecting your vision by the light which they emit, you do not see any
of these objects or at least you do not distinguish them, because the
effort of your attention guides the available portion of your nervous
fluid over the outlines of the ideas which are occupying you, and because
the part of your intellectual organ that is adapted to the reception of
sensations of external objects is not at the time prepared to receive these
sensations. Thus the external objects which affect your senses from all
sides produce no idea within you.

The fact that your attention is directed to the other points of your
organ, where the ideas that occupy you are traced, and where perhaps
you are still tracing new and complex ones by your reflections, puts
these other points in the state of tension or preparation necessary for
the working of your thoughts. Hence, under these circumstances,
although your eyes are open and receive the impression of external
objects, yet you form no idea of them, because the sensations ensuing
from them cannot penetrate to your organ of intelligence, which is not
prepared to receive them. In the same way you do not hear, or at
least do not distinguish, the sounds which strike your ear.

Finally, if somebody speaks to you, although distinctly and in a
loud voice, at a moment when you are engrossed in some particular

1 Course of lectures on the analysis of the understanding for the Ecole normale,
p 145.

382 ZOOLOGICAL PHILOSOPHY

subject, you hear everything and yet grasp nothing, and you are entirely
ignorant what has been said because your organ was not prepared by
attention to receive the ideas communicated to you.

How often it happens that we read an entire page of a work, when
thinking of something different from what we are reading, and without
taking in anything of what we have completely read. To this state of
intellectual preoccupation is given the name of distraction.

But if your inner feeling, on being aroused by some need or interest,
suddenly causes your nervous fluid to flow towards the point of your
intellectual organ that corresponds to the sensation of some object
before your eyes, or some sound that affects your ear, or some body
that you are teaching, your attention then prepares this point of your
organ to receive the sensation of the object in question and you immedi-
ately acquire some idea of that object ; if you pay it enough attention,
you even acquire all the ideas that its shape, size, and other qualities
can impress on you through the medium of the various sensations.

Itis, then, only noticed sensations, that is, those which arrest attention,
that give rise to ideas: thus every idea of whatever kind is the real
produce of a noticed sensation, or of an act which prepares the in-
tellectual organ to receive the characteristic outlines of that idea ; and
every sensation, that is not noticed, but finds the organ of intelligence
unprepared by attention, fails to form any idea.

Mammals have the same senses as man and, like him, receive sensa-
tions of whatever affects them. But since they do not dwell on most
of these sensations, nor fix their attention upon them, but only notice
those that are immediately related to their usual needs, these animals
have but a small number of ideas, which are always more or less the same
with little or no variation.

Hence except for objects which may satisfy their needs and give
rise to ideas in them through being noticed, everything else is non-
existent for these animals.

Nature offers to the eyes of the dog or cat, horse or bear, etc., nothing
that is wonderful, curious, or interesting, but only what ministers
directly to their needs or comfort ; these animals see everything else
without noticing it, that is to say without fixing their attention on it ;
consequently they can acquire no idea of it. Nor could this be other-
wise so long as circumstances do not compel the animal to vary its
intellectual acts, to develop the organ which produces them, and to
acquire by necessity ideas different from those that their usual needs
produce. The results of the education forced upon certain animals are
well known.

I am therefore justified in the statement that these animals dis-
tinguish scarcely anything of what they perceive, and that everything

THE PRINCIPAL ACTS 383

that they do not notice is for them non-existent, although most of the
surrounding objects act upon their senses.

How great is the light thus thrown over the question why animals
which possess the same senses as man have yet so few ideas, think
so little, and are always subjected to the same habits !

Shall I go on to say how many men there are also who remain un-
conscious of nearly all that nature presents to their senses? Now in
consequence of this method of employing their faculties, and limiting
their attention to a small number of objects that interests them, these
men only exert their intellects very little, make small variation in the
subjects of their thoughts, have very few ideas, like the animals that we
have spoken of, and are strongly subjected to the force of habit.

In the case of men who have not been compelled by early education
to exert their intellects, the needs are confined to what they think
necessary for their preservation and physical well-being, but are
extremely limited as regards their moral well-being. The ideas which
they form are almost entirely reduced to ideas of self-interest, property,
and a few physical enjoyments ; their whole attention is absorbed by
the few subjects which promote the satisfaction of these needs. What-
ever is irrelevant to the physical needs of such a man, to his ideas of
self-interest, and his very limited physical and moral enjoyments, is
as good as non-existent for him, since he never does nor can notice it,
having acquired no habit of varying his thoughts.

Finally education, which so wonderfully develops the human in-
tellect, only achieves this result by imbuing a habit of thinking and
of fixing attention on the numerous and varied objects which may affect
the senses, on all that can increase his physical and moral well-being,
and, consequently, on the true aspects of men’s relations with one
another. ;

By fixing attention on the various objects which may affect our
senses, we establish distinctions between these objects and determine
their differences, affinities, and individual qualities: hence the origin
of the physical and natural sciences.

In the same way, by fixing attention on the interests of men in rela-
tion to one another, we form moral ideas both as to right conduct in
the situations that arise in the course of social life, and as to the
progress of useful knowledge: hence the origin of the political and
moral sciences.

Education thus inculcates a habit of exciting the intellect and vary-
ing the thoughts, and this greatly increases the power of giving attention
to numerous different objects, of forming comparisons, of carrying
out judgments with a high degree of accuracy, and of multiplying ideas
of every kind, but especially complex ideas. Lastly, this habit of

384 ZOOLOGICAL PHILOSOPHY

exerting the intellect, when the circumstances of life are favourable,
enables a man to extend his knowledge, to enlarge and guide his genius,
in short, to see things on a large scale, to embrace in thought almost
an infinity of objects, and to obtain from the intellect the most solid
and permanent enjoyments.

I shall conclude this subject with the remark that although the
attention works only by means of the individual’s inner feeling when
aroused by a need, usually a moral need, it is nevertheless one of the
essential faculties of the intellect, and is only carried on in the organ
which produces these faculties. Hence there is justification for the
belief that no being which is destitute of this organ could give attention
to any object.

This section on attention might well be extended, for the subject
seems to me very important to investigate, and I am firmly convinced
that without a knowledge of the necessary condition under which a
sensation can produce an idea, we should never have been able to
grasp the matters connected with the formation of ideas, thoughts,
judgments, etc., nor the cause why most animals which have the same
senses as man only form very few ideas, vary them with difficulty,
and are dominated by the influence of habit.

There is therefore good ground for the belief that no operation of
the organ of the understanding can take place unless the organ is
prepared by attention; and that our ideas, thoughts, judgments,
and reasonings, only continue so long as the organ, in which they are
carried on, is maintained in a proper condition for producing them.

Since the nervous fluid is the chief instrument in an act of attention,
a certain quantity of it is consumed when that act is in progress. Now
if it lasts too long, the individual becomes so fatigued and exhausted,
that the other functions of his organs suffer proportionally. Hence
men who think much, and are constantly meditating, and have acquired
the habit of straining their attention almost incessantly on things
that interest them are much enfeebled in their digestive faculties and
muscular power.

Let us now pass on to an examination of thought, the second of the
principal intellectual faculties, though the earliest and most universal
of its operations.

OF THOUGHT.

THe SECOND oF THE PrincipaL FacutTies oF THE INTELLECT.

Thought is the most universal of intellectual acts, for if we exclude
attention, which is the condition of thought, and the other acts of the
understanding, thought really embraces all the rest and yet deserves to
be especially distinguished.

——_

THE PRINCIPAL ACTS 385

; Thought must be regarded as an action carried out in the organ of
intelligence by movements of the nervous fluid. It works on ideas
already acquired, either by restoring them unchanged to the conscious-
ness of the individual, as in memory ; or by comparing some of these
ideas together so as to draw judgments from them, or to ascertain
their relations, which are also judgments, as in reasoning; or by
methodically dividing and decomposing them as in analysis; or
lastly, in creating new ideas on the model of the old, or in contrast
to them, and thence new ideas again, as in the operations of the
imagination.

Is every thought either an act of memory or a judgment? I at
first thought so ; in that case thought would not be a special intellectual
faculty, distinct from recollections and judgments. I believe, however,
that we should classify this act of the understanding as one of its
special primary faculties, for the thought which constitutes reflection
and consists in the inspection or examination of an object, is more than
an act of memory and yet is not a judgment. Indeed comparisons
and investigations of relations between ideas are not mere recollec-
tions, nor are they judgments, although these thoughts nearly always
terminate in one or more judgments.

Although all acts of the understanding are thoughts, we may yet
regard thought itself as the result of a special intellectual faculty,
since some of its acts cannot be ranked either as memory or judgments.

If it is true that all intellectual operations are thoughts, it is also
true that ideas are the raw material of these operations and that the
nervous fluid is the sole agent which gives immediate rise to them,
as I have already explained in the previous chapter.

Thought, being an operation of the understanding wrought on
previously acquired ideas, can alone give rise to judgments, reasonings,
and acts of the imagination. In all this, ideas are the raw material of
the operation and the inner feeling is always the stimulating and
controlling cause, for it sets the nervous fluid in motion in the
hypocephalon.

This act of understanding is sometimes produced as a result of some
sensation, which gives rise to an idea and thence to a desire; but it
is usually carried out without any immediately preceding sensation,
for the recollection of an idea, giving rise to a moral need, is enough
to stir the inner feeling and incite it to stimulate the act.

The organ of intelligence thus sometimes carries out its functions
as a result of an external cause, which evokes some idea and stirs
the individual’s inner feeling; while sometimes the organ enters into
activity of its own accord, as when some idea recalled by memory

gives rise to a desire, that is, to a moral need, and subsequently to an
2B

386 ZOOLOGICAL PHILOSOPHY

emotion of the inner feeling which leads it to produce some act of
intelligence or several such acts in succession.

As in every other bodily activity, thought is achieved only by an
excitation of the inner feeling, so that, except for organic movements
essential to the preservation of life, acts of intelligence and those of
the muscular system are always excited by the individual’s inner
feeling and should really be regarded as the product of that feeling.

Seeing that thought is an action, it follows that it can only be carried
out when the inner feeling excites the nervous fluid of the hypocephalon
to produce it, and that, considering the passive condition of the cerebral
pulp, the fluid in question must be the only active body that takes a
share in this action.

Since a being, endowed with an organ of intelligence, has the
faculty of setting its nervous fluid in motion, and of guiding that fluid
over the impressed outlines of some previously acquired idea, such a
being immediately becomes conscious of this idea when the action is
excited. Now this act is a thought, although a very simple one, and
it is at the same time an act of memory. But if, instead of recalling
a single idea, the individual recalls several, and carries out operations
on these ideas, he then forms thoughts less simple and more prolonged,
and he can thus carry out various intellectual acts and indeed a long
succession of such acts.

Thought is therefore an action, which may be complicated by a great
many others of the same kind carried out successively or sometimes
almost simultaneously; it may also embrace a large number of ideas
of all kinds.

Not only do the operations of thought include ideas already in
existence or traced in the organ, but they may also produce ideas
which did not previously exist. The results of comparisons, the rela-
tions ascertained between different ideas, and, lastly, the products of
the imagination, are so many new ideas for the individual ; they are
generated by his thought, impressed on his organ, and subsequently
iransferred to his inner feeling.

Judgments, for example, which are also called inferences, because
they result from comparisons or calculations, consist both of thoughts
and of acts subsequent to thoughts.

The same thing holds good with regard to arguments, for we know
that several judgments drawn in turn from compared ideas constitute
what we call an argument; now arguments, being only series of in-
ferences, likewise consist of thoughts and of acts subsequent to
thoughts.

It follows from all this that no creature which is destitute of ideas
could carry out any thought or judgment, and still less any argument.

THE PRINCIPAL ACTS 387

To meditate is to carry out a succession of thoughts, to sift by
successive thoughts either the affinities between several objects that
are under consideration, or the different ideas that may be obtained
from a single object.

A single object may indeed provide an intelligent being with a
number of different ideas, such as those of its mass, size, shape, colour,
consistency, etc.

If the individual becomes conscious of some of these ideas when the
object is not present, he is said to be thinking of that object ; and indeed
he actually does carry out one or more successive thoughts with regard
to it; but if the object is present he is then said to observe it and
examine it, in order to derive from it all the ideas that his method of
observation and capacity for attention permit of.

Just as thought works on direct ideas, that is, on ideas obtained by
sensations that are noticed, so too it works on the complex ideas that
the individual possesses, and may restore them to consciousness.

Hence the object of a thought or succession of thoughts may be
material or include various material objects; but it may also be
constituted out of a complex idea or several ideas of this character.
Now, by means of thought, the individual may obtain still further
ideas from these two different kinds, and so on indefinitely. Hence we
get imagination, which originates in the habit of thinking and forming
complex ideas, and which creates by similarity or analogy special
ideas on the model of those yielded by sensations.

I shall now bring my remarks on this subject to a close: for I do
not propose to undertake any analysis of ideas, as has already been
done by abler men and more profound thinkers ; I shall have attained
my purpose if I have made clear the true mechanism by which ideas and
thoughts are formed in the organ of intelligence, in response to excita-
tions of the individual’s inner feeling.

I shall merely add that thought is always accompanied by attention,
so that when the latter ceases the former promptly comes to an
end.

I shall further add that since thought is an action, it uses up the
nervous fluid, and consequently, that when it is maintained too long,
it causes fatigue, exhaustion and injury to all the other organic func-
tions and especially that of digestion.

I shall conclude with the following remark, which I believe to be
well-founded, viz.: that the available portion of our nervous fluid
becomes larger or smaller in accordance with certain conditions, so
that it is sometimes abundant and more than sufficient for the
production of prolonged thought and attention, while sometimes it
is sufficient and cannot provide for a succession of intellectual acts,

388 ZOOLOGICAL PHILOSOPHY

except at the expense of the functions of the other organs of the
body.

Hence those rises and falls in the activity of thought noted by
Cabanis; hence that facility at certain times and difficulty at other
times of fixing attention and following out a line of thought.

In one who is weakened as a result of disease or age, the functions
of the stomach are carried out with difficulty, and use up a large part
of the available nervous fluid. Now if during this labour of the stomach
you divert nervous fluid from the digestion towards the hypocephalon,
if, that is to say, you give yourself up to close study and a succession
of thoughts which require profound and continued attention, you
damage your digestion and endanger your health.

In the evening, when one is more or less exhausted by the various
fatigues of the day, especially when one is no longer in the vigour of
youth, the available portion of the nervous fluid is generally less abun-
dant and less fitted to provide for continued thought : in the morning,
on the contrary, after the recuperation of a good sleep, the available
portion of the nervous fluid is very abundant, and can adequately
meet the demands that are made upon it by intellectual operations
or bodily exercises. Finally, the more you consume of your nervous
fluid that is available for intellectual operations, the smaller is your
capacity for bodily labour and exercise, and vice versd.

In consequence of these causes and many others, there are remarkable
fluctuations in our faculty for following a line of thought, meditating,
reasoning, and especially exerting our imagination. Among these
causes, variations in our physical condition and the influence upon
it of atmospheric changes are not the least powerful.

Since acts of imagination are at the same time thoughts, this is the
right place to speak of them.

IMAGINATION.

The imagination is that faculty for creating new ideas that the
organ of intelligence acquires by means of its thoughts. Itis dependent
on the presence of many ideas, out of which new complex ideas are
constantly being formed.

The intellectual operations, which give rise to acts of the imagination,
are excited by the individual’s inner feeling, carried out like other
acts of thought by the movements of his nervous fluid, and controlled
by judgments.

Acts of imagination consist in creating new ideas by comparisons
and judgments of previous ideas, these being taken either as models
or as contrasts; so that with this material the individual can form

end. ales ete

THE PRINCIPAL ACTS 389

for himself a number of new ideas which are impressed on his organ,
and out of these many more again, with no limit to this infinite creation
beyond that suggested by his endowment of reason.

I have said that the previously acquired ideas which furnish the
material for acts of the imagination are employed in these acts either
as models or as contrasts.

In fact, if we consider all the ideas produced by human imagination,
we shall see that some, including the larger number, are modelled on
simple ideas which have arisen immediately from sensations, or on
complex ideas based upon the simple ideas, and that the rest originate
in contrast or opposition to the simple or complex ideas that had been
acquired.

Since man cannot form any true idea, except of objects or things in
the likeness of objects, his intellect would have been limited to the
elaboration of this one kind of idea, if it had not possessed the faculty
of taking these ideas either as models or contrasts, and forming from
them ideas of another kind.

It is by contrast to simple or complex ideas, that man imagined the
infinite, basing it on his idea of the finite ; when he had conceived the
idea of a limited duration, he imagined eternity or an unlimited dura-
tion ; when he had formed the idea of a body or of matter, he imagined
mind or an immaterial being, etc., etc.

It is not necessary to show that every product of the imagination,
which does not present a contrast to some simple or complex ideas
originally acquired through sensations, is necessarily modelled upon
some such idea. How many citations I might make, if I wished to
show that wherever man has tried to create ideas, his materials have
always been in the likeness of previously acquired ideas or in contrast
to them !

It is a truth borne out by observation and experience, that the
intellectual organ is in the same case as all the other bodily organs ;
the more it is exercised the more it develops and the more its faculties
extend.

Those animals, which are endowed with an intellectual organ, never-
theless lack imagination, because they have few needs, vary their
actions but little, and hence acquire but few ideas, and especially be-
cause they rarely form complex ideas and then only of the first order.

But man, who lives in society, has so largely increased his needs
that he has been obliged to increase his ideas to a corresponding
extent; so that of all thinking creatures he is the one who can most
easily exercise his intellect, vary his thoughts the most and, lastly,
form the greatest number of complex ideas: hence we have reason to
believe that he is the only creature that can have imagination.

390 ZOOLOGICAL PHILOSOPHY

If, on the one hand, imagination can only exist in an organ which
already contains many ideas, and only originates from the habit of
forming complex ideas ; and if, on the other hand, it is true that the
more the organ of intelligence is exercised, the more it develops, and
the more its faculties extend and increase, we shall perceive that
although all men might possess this fine faculty called imagination,
yet there are only very few who could have it to any high degree.

How many men there are, even excluding those that have had no
education, who are forced by their condition of life to occupy themselves
daily during the chief part of their lives with the same kinds of ideas
and to carry out the same work, and who as a result are scarcely at
all able to vary their thoughts! Their habitual ideas revolve in a little
circle which is nearly always the same and they make but few efforts
to enlarge it, because they have no great interest in doing so.

Imagination is one of the finest faculties of man: it ennobles and
elevates his thoughts and relieves him from the domination of minute
details; and when it reaches a very high development, it makes him
superior to the great majority of other people.

Now genius in an individual is nothing else but a high imagination,
guided by exquisite taste and a well-balanced judgment, and nurtured
and enlightened by a vast knowledge, and controlled in short by a
high degree of reason.

What would literature be without imagination! It is useless for
the man of letters to be a perfect master of his language ; it is useless
for him to cultivate a purified diction and faultless style ; if he has no
imagination, he is cold, lacks thought and images, rouses no emotion
or interest, and all his efforts are futile.

How could poetry, that beautiful branch of literature, and how even
could rhetoric dispense with imagination ?

For myself, I hold that literature, that beautiful produce of the human
intellect, is the noble and sublime art of arousing our passions, elevating
and widening our thoughts, and transporting them out of their usual
routine. This art has its rules and precepts, but imagination and taste
are the exclusive source of its finest products.

Since literature arouses, animates, and charms every man who is
able to appreciate it, science is to that extent inferior ; for she teaches
coldly and stiffly: but science is superior in this, that not only does
she serve all the arts and furnish us with the best means of providing
for all our physical needs, but that she also greatly broadens our
thoughts by showing us everywhere what is really there and not
what we want to find there.

The purpose of the former is to give pleasure; that of the latter
ig to collect all practicable positive knowledge.

THE PRINCIPAL ACTS 391

This being so, imagination is as much to be feared in the sciences
as it is indispensable in literature; for its aberrations in the latter
are merely a lack of taste and reason, whereas its aberrations in the
former are errors; for the imagination nearly always gives rise to
errors, when it is not controlled and limited by learning and reason ;
and if these errors are captivating, they inflict upon science an injury
which is often very difficult to repair.

Yet without imagination there is no genius, and without genius
there is no possibility of discovering anything but facts, without
drawing any satisfying inferences. Now since every science is a body
of principles and inferences carefully deduced from observed facts,
genius is absolutely necessary for stating these principles and drawing
their inferences; but it has to be guided by a sound judgment, and
kept within the limits imposed by a high degree of enlighten-
ment.

Thus, although it is true that imagination is to be feared in the
sciences, this only holds good when it is not controlled by a lofty and
enlightened reason ; when it is so controlled, it is one of the essential
factors in the progress of science.

Now the only means of limiting our imagination, so that its aberra-
tions may not affect the advancement of knowledge, is to allow it to
work only on real natural objects; since such objects are all that
we can possibly know positively ; its various acts will then possess
a reliability that is proportional to the number of facts considered in
the object concerned, and to the excellence of our judgment.

I shall conclude this section with the remark that if it is true that
we derive all our ideas from nature, and have none that do not come
originally from her, it is also true that we can modify these ideas in
various ways by means of our imagination, so as to create new ones
entirely foreign to nature; but these latter are always either contrasts
to acquired ideas, or else more or less distorted images of objects the
knowledge of which we derive from nature alone.

Even in the most exaggerated and extraordinary ideas of man, it
is impossible not to recognise their origin, by means of a close
examination.

OF MEMORY.

Tue THirp OF THE PRINCIPAL FACULTIES OF THE INTELLECT.

Memory is a faculty of the intellectual organs; the recollection of an
object or thought is an act of this faculty ; and the organ of the under-
standing is the seat where this wonderful act occurs, while the nervous
fluid by its movements in that organ is the sole agent of its occurrence.

392 ZOOLOGICAL PHILOSOPHY

This I propose to prove ; but first let us consider the importance of the
faculty in question.

Memory may be described as the most important and necessary of
the intellectual faculties, for without memory what could we do?
how could we provide for our various needs, if we could not recall
the different objects, that we have come to know or to use for their
satisfaction ?

Without memory, man would have no kind of knowledge ; he would
be absolutely destitute of science ; he could cultivate no art ; he could
not even have a language for the expression of his ideas ; and seeing
that, in order to think or even to imagine, he must, in the first place,
have ideas and, in the second place, institute comparisons between
these ideas, he would be altogether deprived of the faculty of thought
and imagination if he had no memory. When the ancients said that
the muses were daughters of memory, they proved that they were
conscious of the importance of this intellectual faculty.

We saw in the preceding chapter that ideas spring from sensations
which we have experienced and noticed, and that with the ideas thus
impressed upon our organ we can form others which are indirect and
complex. Since the time of Locke, it has been recognised that all
ideas whatever originate from sensations and that none have any
other origin.

We shall now see that memory can only come into existence after
ideas have been acquired, and consequently that no individual could
display any act of memory unless he had ideas impressed on the
organ which is the seat of it.

If this is so, nature can have given to the most perfect animals and
even to man nothing but memory ; she cannot give prescience, that is
to say, a knowledge of future events.!

Man would no doubt be very unhappy, if he knew definitely what
was going to happen to him, the precise date of the end of his life, etc.,
but the real reason why he has not this knowledge is that nature could
not give it to him; it was impossible for her. Seeing that memory is
only the recollection of past events, of which we were able to form
ideas, and seeing that the future will give rise to events which do not
yet exist, we cannot form any idea of it, except in the case of such facts
as belong to certain ascertained parts of the order followed by nature.

1 With regard to future events, those which flow from comparatively simple causes
and from the laws which man has discovered in his studies of nature, are capable of
being foreseen by him, and up to a certain point of being referred in advance to more
or less definite dates. Thus astronomers can prophesy the future date of an eclipse,
or when some star will be in some particular position; but this foreknowledge of
certain facts is confined to a very small number of objects. Yet many other future
events of a different kind are also known to him: for he knows that they will occur:
without being able to specify precisely when.

— a ee —t—*#=e

THE PRINCIPAL ACTS 393

Let us now enquire what the mechanism of this wonderful faculty
may be; I shall endeavour to show that the operation of the nervous
fluid, which gives rise to an act of memory, consists in the acquisition
of a special movement by that fluid as it passes over the impressions
of some acquired idea, and in the transference of that movement to
the individual’s inner feeling.

Since ideas are the material of all intellectual acts, memory pre-
supposes ideas already acquired ; and it is obvious that an individual
who had never had an idea could not possess any memory. Hence
the faculty called memory only begins to exist in an individual who
possesses ideas.

Memory throws light on the nature of ideas, and even suggests the
answer to the question as to what they really are.

Now I have pointed out that the ideas which we have formed through
the medium of sensations, and those that we have acquired later by
means of thought, consist of specific images or outlines graven or
impressed more or less deeply on some part of our organ of intelligence.
These ideas are recalled by memory, whenever our nervous fluid,
aroused by our inner feeling, comes in contact with their images or
outlines. The nervous fluid then transmits the effects to our inner
feeling and we immediately become conscious of these ideas: that
is how acts of memory take place.

The inner feeling, which controls the movement of the nervous fluid,
may direct it over one only of the previously traced ideas or over
several of them; hence memory may recall one idea alone, or several
ideas in succession, according to the individual’s desire.

It follows from the above that if our ideas, both simple and complex,
were not impressed more or less deeply on ‘our organ of intelligence,
we should be unable to recall them and memory could not therefore
exist.

Suppose that some object strikes our attention, a fine building,
for instance, which has caught fire and is being burnt up before our
eyes. Now for some time after, we can recall that object perfectly
without seeing it ; for this purpose an act of thought is quite sufficient.

This process must be due to the fact that our inner feeling sets our
nervous fluid in motion, and drives it into our organ of intelligence
over the outlines impressed by the sensation of the conflagration ;
and that the modification, acquired by our nervous fluid in its
movements as it passes over these particular outlines, is promptly
transmitted to our inner feeling and thereupon restores to clear
consciousness the idea that we are seeking to recall; although the
idea is less vivid than when the conflagration was actually taking

place before our eyes.

394 ZOOLOGICAL PHILOSOPHY

We likewise recall any person or object that we have previously
seen and noticed ; and in the same way we recall complex ideas that
we have acquired.

Our ideas, then, are specific images or outlines impressed on some
part of our organ of intelligence, and we only become conscious of these
ideas when our nervous fluid is set in motion and transmits to our
inner feeling that modification of its movement which it acquired while
passing over these outlines. So true is this, that if during sleep our
stomach ig disordered or we suffer from some internal irritation,
our nervous fluid acquires an agitation which is propagated into our
brain. It is easy to conceive how this fluid, when its movements are
no longer controlled by our inner feeling, follows no order in passing
over the outlines of the various ideas impressed upon it, but brings
them into consciousness in the greatest confusion, usually distorting
them by strange associations and unbalanced judgments.

During perfect sleep, the inner feeling undergoes no emotion, and
for practical purposes ceases to exist; consequently it no longer
controls the movements of the available portion of the nervous fluid.
Thus a sleeping individual is as though he did not exist. He no longer
possesses feeling, although the faculty of it is intact; he no longer
thinks, although he still has the power to do so; the available portion
of his nervous fluid is in a state of rest, and since the factor which
produces actions (the inner feeling) is no longer active, the individual
also can do nothing.

But if sleep is imperfect, owing to some internal irritation which
stimulates an agitation of the free part of the nervous fluid, the move-
ments of the latter are not controlled by the inner feeling ; they there-
fore occasion disordered ideas and strange and motley thoughts, owing
to the haphazard association of ideas that have no relation to one
another. Thus are formed the various dreams which we have, when
our sleep is not perfect.

These dreams, or the disordered ideas and thoughts which constitute
them, are nothing but acts of memory occurring at random and in
confusion ; they are irregular movements of the nervous fluid in the
brain, whereby consciousness is filled with disconnected ideas, since
the inner feeling no longer exerts its functions during sleep nor guides
the movements of the nervous fluid.

This is why we have dreams when digestion is very difficult, or when
we have been much agitated by some great interest or by objects
which have stirred us. These produce during sleep a great agitation
of our spirits, that is, of our nervous fluid.

Now these disordered acts are always wrought upon ideas that have
been acquired and impressed on the organ of intelligence: an individual

THE PRINCIPAL ACTS 395

could never have an idea in a dream, that he had not had when awake,
nor recall an object of which he was previously ignorant.

If someone were to be confined from his childhood in a room where
daylight was only admitted from above, and if all necessaries were
supplied to him without communication, he would assuredly never see
in his dreams any of those objects which affect men so strongly in
society.

Thus dreams disclose to us the mechanism of memory, just as memory
teaches us the mechanism of ideas; when I see my dog dreaming,
barking in his sleep, and giving unequivocal signs of the thoughts
which agitate him, I become convinced that he too has ideas, of
however limited a kind.

It is not only during sleep that the functions of the inner feeling
may be suspended or disturbed. While we are awake, a sudden
strong emotion sometimes suspends altogether the functions of this
feeling, and even all movement in the free part of the nervous
fluid; we then suffer from syncope, that is to say, we lose all con-
sciousness and power of action; sometimes also an extensive irritation,
such as occurs in certain fevers, similarly suspends the functions of
the inner feeling and yet agitates the free portion of the nervous fluid
in such a way as to call up disordered ideas and thoughts, and lead to
actions no less disordered : in such a case we suffer from what is called
delirium.

Delirium therefore resembles dreams as regards the disorder of ideas,
thoughts and judgments, and it is clear that this disorder in both cases
arises from the fact that the functions of the inner feeling are sus-
pended, so that it no longer controls the movements of the nervous
fluid.t

But the violence of the nervous agitation causing delirium is the
reason for believing that this phenomenon is not only the product of
a strong irritation, but sometimes also of a powerful moral affection ;
so that individuals experiencing it then obtain very little advantage
from their knowledge, for their inner feeling, whose functions are
disturbed and suspended, no longer guides the nervous fluid in a way
suitable for correct ideas.

Indeed, when moral sensibility is very great, the emotions produced
in the inner feeling by certain ideas or thoughts are sometimes so
considerable, that the functions of this feeling are disturbed, and it is
unable to guide the nervous fluid towards the performance of the new

1 With regard to the faint delirium or kind of dizziness, commonly experienced
when we are falling off to sleep, it is probably due to the fact that the inner feeling,

which is losing control of the movements still taking place in the nervous fluid, resumes
and again gives up that control several times alternately, until complete sleep has

supervened.

396 ZOOLOGICAL PHILOSOPHY

thoughts which ought to be produced; the intellectual faculties are
then suspended or in disorder.

We shall see that lunacy is also due to a very similar cause, which
prevents the inner feeling from directing the movements of the nervous.
fluid into the hypocephalon.

In fact, when any accidental injury has caused some disturbance in
the organ of intellect, or when a powerful emotion of the inner feeling
has left upon this organ traces deep enough to produce some degenera-
tion in it, the inner feeling no longer controls the movements of the
nervous fluid in that organ, and the ideas raised in the individual by
the agitations of the fluid present themselves without any order or
connection. He gives expression to whatever occurs to him, and his
actions are of a corresponding kind. But we see from the acts of this
individual that he is always affected by ideas previously acquired
and then brought into consciousness. In point of fact memory,
dreams, delirium, acts of lunacy, never bring out any ideas beyond
those already possessed by the individual.

There are some acts of lunacy which follow from a disorder of certain
special organs of the hypocephalon, while the others maintain their
integrity ; it is then only in these special organs that the inner feeling
cannot control or direct the movements of the nervous fluid. People
who are affected in this way only perform acts of lunacy with regard to
certain subjects that never vary: they appear to be in possession of
their reason on all other subjects.

I should travel beyond my province if I tried to follow all the dis-
tinctions observed in the disorder of ideas, and to ascertain their causes.
It is enough to have shown that dreams, delirium, and lunacy in general
are only disordered acts of memory which always work upon ideas
previously acquired and impressed on the organs, but which are beyond
the control of the individual’s inner feeling, because the functions of
this power are suspended or disturbed, or because the state of the
hypocephalon does not permit of their performance.

Cabanis had no idea of the strength of the inner feeling, nor did he
perceive that this feeling constitutes in us a power that can be stirred
by any need, or by the smallest desire, or by a thought, and that it is
then able to set in motion the free portion of the nervous fluid and to
direct its movements either into our organ of intelligence, or towards.
muscles which require to be actuated. Yet he was forced to recognise
that the nervous system often enters into activity of its own accord,
without the stimulus of external impressions, and that it can even
disregard these impressions and escape from their influence, since
concentrated attention or deep thought suspend the activity of the
external organs of feeling.

THE PRINCIPAL ACTS 397

“Tt is thus,” said Cabanis, “that operations of imagination and
memory are performed. The motions of the objects recalled and
represented are, it is true, usually provided by impressions received
in the various organs: but the act which recalls their image, which
presents them to the brain in their correct form, which puts that organ
in a condition to form numberless new combinations, often depends
entirely on causes situated within the sensitive organ.” (Histoire
des Sensations, p. 168.)

This appears to me quite true; it is all the result of the power of
the inner feeling of the individual, for this feeling can be aroused by
a simple idea which gives rise to that moral need called desire; and
we know that desire includes and leads to the performance both of
those actions which set up muscular movement, and of those which
give rise to our thoughts, judgments, reasonings, philosophical
analyses, and to the operations of our imagination.

Desire creates the will to act in one or other of these two ways:
now this desire, together with the will which it evokes, arouses our inner
feeling, so that it dispatches nervous fluid either into some part of the
muscular system, or of the organ which produces acts of intelligence.

If Cabanis, whose work on the Rapporis du Physique et du Moral
is an inexhaustible mine of observations and interesting discussion,
had recognised the power of the inner feeling; if he had guessed
the mechanism of sensations, and not mistaken physical sensibility
for the cause of intellectual operations; if he had recognised that
sensations do not necessarily yield ideas, but mere’ perceptions, which
is a very different thing; if, lastly, he had distinguished what is
due to irritability from what is the product of sensations; how great
would have been the light which his interesting work might have
shed! As it is, this work presents the best means for advancing that
sphere of human knowledge now in question, on account of the
multitude of facts and observations which it comprises. But I am
convinced that these facts can only be made useful by fixing our ideas
on the essential distinctions drawn in the course of the present
work,

By paying attention to what I have said in the present section, we
shall probably reach the conviction :

1. That the seat of memory is the organ of intelligence itself, and that
the operations of memory are simply acts which recall to consciousness
ideas already acquired ;

9. That the outlines or images of these ideas are necessarily already
graven in some part of the organ of understanding ;

3. That the inner feeling, when stirred by any cause, drives the avail-
able nervous fluid over such of the impressed outlines as may be selected

398 ZOOLOGICAL PHILOSOPHY

by the emotion which it has derived either from a need or inclination,
or from an idea which awakes a need or inclination; and that it
promptly brings them into consciousness, by carrying back to the
sensitive nucleus the modifications of movement which the nervous
fluid has acquired from these outlines ;

4. That when the functions of our inner feeling are suspended or
disturbed, it ceases to direct the movements which may then set our
nervous fluid in motion; so that if some cause then agitates this fluid
in our intellectual organ, its movements bring back to the sensitive
nucleus disordered ideas, strangely mixed and without any connection
or sequence; hence dreams, delirium, etc.

We thus see that the phenomena in question everywhere result from
physical acts which depend on the organisation and its condition, and
on the circumstances in which the individual is placed, as well as on the
variety of causes, likewise physical, which produce these organic acts.

Let us pass to an examination of the fourth and last kind of the
principal operations of the intellect, viz. those operations which con-
stitute judgments.

OF JUDGMENT.

Tue FourtH oF THE PrRincieaL FACULTIES OF THE INTELLECT.

The operations of the intellect which constitute judgments are the
most important to the individual of any that his understanding can
perform; they are those which can least easily be dispensed with, and
which he is most often called upon to use.

It is in this faculty of judgment that the will takes its origin ; it is
also this faculty which gives rise to moral needs such as desires, wishes,
hopes, anxiety, fear, etc. ; lastly, it is always as a result of judgments
that those of our actions, in which our understanding has had some
share, are performed.

We cannot carry out any series of thoughts without forming judg-
ments; our reasonings and analyses are pure results of judgments ;
the imagination itself has no power, except through its judgments,
with regard to the models or contrasts used in the creation of ideas ;
finally, any thought, which is neither a judgment nor accompanied
by a judgment, is a mere act of memory or else constitutes a barren
inspection or comparison.

How important it is then for every being endowed with an intellectual
organ to accustom himself to use his judgment, and to endeavour
gradually to improve it by means of observation and experience ;
for he is then exercising his understanding at the same time, and he
increases its faculties to a proportional extent !

THE PRINCIPAL ACTS 399

Yet if we consider the great majority of men, we find that whenever
there is no pressing need or danger they rarely judge for themselves
but rely on the judgments of others.

This obstacle to the progress of individual intelligence is not merely
due to idleness, carelessness, or lack of means; it is due further to
the habit impressed on individuals, during their childhood and youth,
of believing what they are told and of always submitting their
judgment to some authority.

Now that we have briefly indicated the importance of judgment,
and especially of developing it by use and gradually improving it by
experience, let us enquire what it is itself and by what mechanism it
works.

A judgment is a very peculiar act, carried out by the nervous fluid
in the intellectual organ ; its result is then traced upon that organ
and is immediately brought back to the individual’s inner feeling ;
in other words, is brought into consciousness. Now this act is always
the result of some comparison made, or some relation sought, between
ideas previously acquired.

The following is probably the mechanism of this physical act :
for it is the only mechanism which seems to me capable of giving rise
to it, and is in harmony with the known effects of the law of united
or combined movements.

Hach idea that is graven doubtless occupies a special site in the
organ : now when the nervous fluid is agitated and traverses the outlines
of two different ideas at the same moment, as occurs in a comparison
of two ideas, it is then necessarily divided into two separate streams,
one of which passes over the first of the two ideas while the other
passes over the second. In each case these two streams of nervous
fluid undergo a modification of movement, which is caused by the
outlines they pass over and which is peculiar to the idea in question.
Hence we may imagine that, if these two streams are subsequently
united into one, their movements will also be combined, so that the
common stream will have a compound movement which is the resultant
of the two kinds of movements brought into combination.

The physical act giving rise to a judgment is therefore probably
constituted by the movements of the nervous fluid, when spread over
the impressed outlines of ideas that are being compared; and it
appears to consist of as many special movements of the fluid, as there
are ideas compared and separate streams of fluid passing over the
outlines of these ideas. Now these separate streams of the same
fluid, each with its special movement, all unite to form a single stream
whose movement is compounded of all the special movements named ;
and this compound movement then impresses new outlines on the

400 ZOOLOGICAL PHILOSOPHY

organ, that is to say, a new idea which is the judgment in
question.

This new idea is instantly brought back to the individual’s inner
feeling ; he has a moral feeling of it ; and if it awakes in him any need,
which is likewise moral, it evokes his will to act in order to satisfy it.

In addition to inexperience, and to the consequences of the almost
universal habit of judging in imitation of others, numerous factors
combine to affect our judgments, that is to say, to make them less
well-balanced.

Some of these factors are due to an imperfection in the comparisons
that are made, and to the preference given by the individual to one
idea over another, according to his knowledge, special tastes, and con-
dition ; so that the true elements which should enter into the formation
of these judgments are incomplete. In all ages there are but few
men who are capable of profound concentration, and who, being
accustomed to think and to learn from experience, can escape from
these factors which tend to affect their judgments.

The others, which it is difficult to avoid, take their origin: (1) In the
actual state of our organisation, which affects the sensations originating
ideas; (2) in the error in which some of our sensations frequently
involve us; (3) in the influence that our inclinations or passions exert
on our inner feeling, leading it to give to the movements, which it
impresses on our nervous fluid, a different direction from what it would
have given them without that influence, etc., etc.

Since I have already treated of the judgment in Chapter VI. of this
part, I should travel beyond the limits of my plan if I were to enter
into the details of the numerous factors which combine to affect our
judgment. It is sufficient, for the purpose that I have in view, to
observe that many factors are apt to affect the value of the judg-
ments that we form; and that in this respect there is as great a
diversity in the judgments of men, as there is in their physical
condition, environment, inclinations, knowledge, sex, age, etc.

Let us not be astonished then at the permanent but not universal
disagreement noticed in the judgments that are passed on some thought,
argument, work, or any other subject, in which no one can see anything
but what he has decided for himself and what he can imagine to
himself as a result of the character and extent of his knowledge;
nothing, in short, but what he can understand, in accordance with the
amount of attention that he pays to the subjects presented to him.
How many persons there are, too, who have formed a habit of judging
scarcely anything for themselves, and consequently of falling back
in almost everything on the judgment of others !

These considerations, which seem to me to prove that judgments are

THE PRINCIPAL ACTS 401

subject to different degrees of correctness, and that this correctness
is relative to the individual’s circumstances, naturally lead me to say

a word about reason, to enquire what it is, and to compare it with
instinct.

OF REASON.
AND ITS COMPARISON WITH INSTINCT.

Reason is not a faculty ; still less is it a torch or entity of any kind ;
but it is a special condition of the individual’s intellectual faculties ;
a condition that is altered by experience, gradually improves and con-
trols the judgments, according as the individual exercises his intellect.

Reason therefore is a quality that may be possessed in different
degrees, and this quality can only be recognised in a being that
possesses certain intellectual faculties.

In the last analysis, it may be said that for all individuals endowed
with intelligence, reason is nothing more than a stage acquired in the
rectitude of judgments.

No sooner are we born-than we experience sensations, mainly from
external objects affecting our senses; we quickly acquire ideas, which
are formed in us as a result of noticed sensations ; and we soon com-
pare almost mechanically the objects we have noticed and thus form
judgments.

But we are then new to the whole of our environment, destitute of
experience, and deceived by some of our senses, so that we judge badly ;
we are mistaken as to the distances, shapes, colours, and consistency
of the objects that we notice, and we do not grasp the relations existing
between them. It is necessary that several of our senses should
combine gradually to destroy our errors and rectify our judgments ;
lastly, it is only with the help of time, experience, and attention paid
to the objects which affect us, that rectitude is slowly attained in our
judgments.

The same thing is true with regard to our complex ideas, and the
useful truths, rules, or precepts communicated to us. It is only by
means of much experience, and memory in collecting all the elements
for an inference; only by means of the greatest use of our under-
standing, that our judgment on these matters is gradually improved.

Hence the wide difference existing between the judgments of child-
hood and those of youth ; hence again the difference found between
the judgments of a young man of twenty and those of a man of forty
or more, when the intellect in both cases has always been regularly
exercised.

Since the extent of our reason is proportional to the rectitude of our
2c

402 ZOOLOGICAL PHILOSOPHY

judgment on all things, and especially on the ordinary affairs of life
and our relations with our fellows, it follows that this quality is
only a certain stage acquired in the rectitude of judgments ; and seeing
that environment, habit, temperament, etc., involve a great diversity
in the exercise of our understanding, that is to say, in our way of
thinking, investigating, and judging, it follows that there are real
differences between the judgments that are formed.

Thus reason is not an individual object or entity that we may or
may not possess, but it is a condition of the organ of understanding,
from which results a greater or smaller degree of rectitude in the in-
dividual’s judgments ; so that every being who possesses an organ of
understanding, who has ideas and performs judgments, must possess a
certain degree of reason corresponding to his species, age, habit, and
the various circumstances which combine to retard or advance or
to keep stationary the progress made in rectitude of judgments.

Seeing that it is only by paying attention to the objects producing
sensations in us, that these sensations can give rise to ideas, it is clear
that the more we use this faculty of attention, and the deeper and more
sustained it is, the clearer become our ideas, the more accurately are
they defined, and the more correct are the judgments that we form
from them.

Hence it follows that the highest stage of reason is that which comes
from extreme clearness in the ideas, and from an almost invariable
soundness of judgments.

Man, who is much more capable than any other intelligent being
of this profound and continuous attention, and can fix it on a great
many different objects, is the only one who can have an almost infinite
variety of clear ideas and whose judgments consequently possess the
highest rectitude ; but for this purpose he has to exercise his intellect
vigorously and perpetually, and his circumstances have to be favourable
for it.

It follows from the above, that since reason is only a stage in the
rectitude of judgments, and since every intelligent being can carry
out judgments, they must all possess a certain degree of reason.

Indeed, if we compare the ideas and judgments of an intelligent
animal, which is still young and inexperienced, with the ideas and
judgments of the same animal when it has reached the age of acquired
experience, we shall find that the difference between these ideas and
judgments is quite as discernible in the animal as it is in man. A
gradual improvement in the judgments, and an increasing clearness
of the ideas, fill up in both cases the interval between the time of their
childhood and that of their maturity. The age of completed experience
and development is clearly distinguished from that of inexperience

THE PRINCIPAL ACTS 403

and low development of the faculties in such an animal, just as it is in
man. In both cases the same features are to be recognised, and an
analogous progress in the acquirements; it is only a matter of more
or less in the different species.

In animals possessing a special organ for intelligence, there are there-
fore various degrees in the rectitude of judgments and hence various
degrees of reason.

Doubtless the highest degree of reason gives man a perception of
the propriety or impropriety both of his own ideas and beliefs, and of
the ideas and beliefs of others; but this perception, which is a judgment,
is not a property of all men. Those who do not possess it substitute a
false perception in place of that just perception which arises from a
highly trained intellect ; and, since the former is the best they can
attain, they believe it to be just. Hence arises that diversity of
opinions and judgments in individuals of the human species; a
diversity which will always stand in the way of a real agreement
between the ideas and judgments of individuals, owing to the fact
that men are situated in very different circumstances and therefore
cannot attain the same degree of reason.

If we now compare reason with instinct, we shall see that the
former to some extent gives rise to determinations to act, originating
in the intellect, that is to say, in ideas, thoughts, and judgments ;
whereas instinct, on the contrary, is a force which impels towards an
action, without any previous determination or intellectual act.

Now, since reason is only a stage acquired in rectitude of judgments,
the determinations of action which spring from it may be wrong or
unsuitable when the judgments producing them are erroneous ; they
may be false in whole or in part.

But instinct, which is simply an impelling force and arises from the
inner feeling when stirred by some need, never makes a mistake in
the action to be performed; for it does not choose, nor does it result
from any judgment, and there are not really different degrees of it.
All action caused by instinct is therefore invariably due to the kind
of excitation produced by the individual’s inner feeling, just as all
movement communicated to a body is made up, both in direction and
strength, by the power which communicated it.

There is nothing either clear or really exact in Cabanis’ idea of
attributing reasoning to external sensations, and instinct to internal
impressions. All our impressions are invariably internal, although the
objects causing them may be either external or internal. Observation
of the facts should convince us that it is more just to say:

That the reasonings and determinations, following from judgments,
take their origin from intellectual operations ; whereas instinct, in

202

404 ZOOLOGICAL PHILOSOPHY

causing some action, takes its origin from the needs and propensities
which arouse immediately the individual’s inner feeling and make him
act, without any choice or deliberation, or, in short, any participation
of the intellect.

The actions of certain animals are therefore sometimes based on
tational determinations, but more often on an instinctive force.

If we pay attention to the facts and arguments presented in the
course of the present work, we shall perceive that there must be animals
which have neither reason nor instinct, such as those which are destitute
of the faculty of feeling ; that there must be others which have instinct
but possess no degree of reason, such as those which have a sensitive
system, but lack the organ for intelligence; lastly, that there must
be others again which have instinct together with some degree of reason,
such as those which possess a system for sensations and another for
acts of the understanding. The instinct of these last is the source
of nearly all their actions, and they rarely make use of such degrees
of reason as they possess. Man, who comes next, also has instinct
which in certain circumstances makes him act; but he is capable of
acquiring much reason, and of using it to control the greater part of
his activities.

Besides the indwidual reason of which I have been speaking, there is
established, in every country and region of the earth, in proportion
to the knowledge of the men who live there and to certain other factors,
a public reason, which is almost universal, and which is upheld until
new and sufficient causes operate to change it. In both cases, the
individual and the public reason are always constituted by a certain
degree of rectitude in the judgments.

It is true that in a society or nation, errors and false beliefs may
be as much matters of general assent as ascertained truths; so that
various errors, prejudices, and truths go to make up the degree of
rectitude of judgment, both in individuals and in the received
opinions of societies, groups, and nations, according to the age or
period considered.

We have therefore to recognise different stages of advance in the
reason of a people or society, as in that of an individual.

Men who strive in their works to push back the limits of human
knowledge know well that it is not enough to discover and prove a
useful truth previously unknown, but that it is necessary also to be
able to propagate it and get it recognised; now both individual
and public reason, when they find themselves exposed to any alteration,
usually set up so great an obstacle to it, that it is often harder to secure
the recognition of a truth than it is to discover it. I shall not dwell
on this subject, because I know that my readers will see its implica-

THE PRINCIPAL ACTS 405

tions sufficiently, if they have any experience in observation of the
causes which determine the actions of mankind.

In concluding this chapter on the principal acts of the understanding,
I terminate at the same time all that I propose to present to my readers
in the present work.

In spite of the errors into which I may have been led, the work may
possibly contain ideas and arguments that will have a certain value
for the advancement of knowledge, until such time as the great sub-
jects, with which I have ventured to deal, are treated anew by men
capable of shedding further light upon them.

Tue ENp.

INDEX

Affinities, 29; method of determining,
31; necessity for studying, 33 ; chemi-
cal, hypothesis of, 254.

Alimentary canal, effects of drink upon,
118.

Animals, study of, 10; constitute a
linear series, 38; locomotion of, 47;
main faculties of, 48 ; definition of, 53 ;
limits of their multiplication, 54;
fourteen classes of, 131-133; table
showing their origin, 179; their dif-
ferentiation from plants, 195; food of,
197; torpidity in, 198-9.

Annelids, first established, 65; definition

of, 87; classification of, 149-150;
origin of, 176.

Ant-eater, its tongue, 120.

Ant-lion, its habits, 353.

Aponeurotic sheath, its function, 297.

Arachnids, first established, 65 ; definition
of, 89; distinction from insects, 90 ;
classification of, 146-147; origin of,
176.

Aristotle's Classification, 61 ;
direction of, 62.

Artificial devices in natural science, 19 ;
enumeration of, 20.

Attention, 380-384.

Aura vitalis, 242.

erroneous

Bark, origin of, 234.

Bats, flight of, 175.

Bimana, definition of, 169.

Birds, definition of, 75; effects of domes-
tication on, 110; use-inheritance in,
120; classification of, 163-166 ; origin
of, 177.

Brain, derived from medulla oblongata,

299.

Cabanis, on the relations of moral and
physical, 185, 207; on life and feeling,
208; on sensibility and_ irritability,
228 ; on the functions of the brain, 302 ;
on sensation, 328 ; on melancholy, 338 ;

on instinct, 351; on memory, 397; on
reasoning, 403.

Caloric, see Subtle fluids.

Carnivores, shape of, 123.

Cellular theory, 230 et seq.

Circulation, organ of, as indicating
natural affinities, 31; not found below
crustaceans, 89 ; a special faculty, 277 ;
its development, 277-278.

Cirrhipedes, definition of, 86; classifica-
tion of, 150-151 ; origin of, 176.

Class, definition of, 22.

Classification, schematic, 21; uses of, 56 ;
direction of, 128; of animals, 131-133.

Condillac, on the progress of reason, 185 ;
on language, 377.

Crustaceans, first established, 65; defini-
tion of, 88; classification of, 148-149 ;
origin of, 176.

Cultivation, effects of, on plants, 109.

Death, peculiar to living bodies, 194;
causes of, 264.

Degradation of organisation, 68.

Delirium, cause of, 395.

Digestion, physiology of, 267-268.

Disuse, effects of, 108; law of, 115; in
whales’ teeth, 115 ; in moles’ eyes, 116 ;
never affects organ of hearing, 116;
in molluscs’ heads, 117 ; in snakes’ legs,
117; in insects’ wings, 118.

Dogs, origin of, 110.

Dreams, causes of, 341; their relation to
memory, 394.

Drowning, effects of, 204.

Echidna, see Monotremes.

Echinoderms, 139.

Education, errors of, 370; effects of, 383.

Electricity, see Subtle fluids.

Emotion, a function of the nervous system,
308; how produced, 332, 335; two
kinds of, 338; effects of, 338; causes
of, 340.

Environment, affects organisation, 70;

408

influence of, 106, etc.; affects the
shape of animals, 107; effect of un-
favourable, 109.

Erethism, definition of, 222.

Evolution, factors of, 2; towards higher
complexity, 49, 265; necessity of long
periods for, 50, 69; method of, 130;
of nervous system, 311-312. See also
Inheritance of acquired characters, Dis-
use.

Exciting cause of organic movements, 211
et seq.; its components, 213 ; necessary
to life, 214.

Hyes, of flat-fishes, 120.

Family, definition of, 24.

Fatigue, causes of, 348 ; effects of, 349.

feathers, origin of, from hair, 76.

Feeling. organ of, as indicating natural
affinities, 31; not necessary to life,
208-209 ; as a faculty of animals, 273-
274; a function of the nervous system,
306, 322; a general effect, 321; due
to physical causes, 330.

Fermentation, compared with life, 185-
186 ; 214.

Fertilisation, nature of, 240; effects of,
276.

Fishes, definition of, 79 ; primary division
of, 80; classification of, 156-161;
origin of, 173.

Flying squirrels, their wings, 175.

Fossils, explanation of, 46.

Galeopithecus, 175.

Gall and Spurzheim, on the functions of
the brain, 285 ; criticism of, 368-369.

Galvanism, see Subtle fluids.

Genius, nature of, 390.

Genus, definition of, 25.

Geoffroy de St. Hilaire, his Egyptian
collections, 41.

Giraffe, neck of, 122.

God, power of, 36, 41; purpose of, 180;
methods of, 342.

Gordius, 176.

Grasses, effect of environment on, 109.

Growth, peculiar to living bodies, 193,

261.

Habit, nature of, 350.

Heart, development of, 278.

Heat, the first cause of life, 216; its
effects on animals, 243-244; a material
soul, 245.

Hemispheres, cerebral, see Hypocephalon.

Herbivores, size of, 121.

Hermaphrodites, characters of, 275.

Horns, origin of, 122.

Hypocephalon, the organ of intelligence,

INDEX

309; distinct from the brain, 363;
structure of, 367.

Ideas, formation of, 371; two kinds of,
371; difference from sensation, 372;
production of, 373 ; physical nature of,
374-375 ; nature of complex, 375-376.

Imagination, nature of, 388-391.

Inflammation, due to concentration of
caloric, 213.

Infusorians first established, 66; defini-
tion of, 102; arise by spontaneous
generation, 103; classification and list
of genera, 134-135; origin of animal
scale, 176; have no respiration, 269 ;
nutrition of, 345.

Inheritance of acquired characters, first
and second law of, 113; in cultivated
plants, 109; in birds, 110; in dogs,
110; in horses, 113; factors of, 114;
accounts for webs of duck’s feet, 119;
for legs of waders, 120; for long necks,
120; for long tongues, 120; for
asymmetrical eyes, 120; for the size of
herbivores, 121; for giraffes’ necks,
122; for the claws of carnivores, 123 ;
for the shape of kangaroos, 123; in
sloths, 125 ; in seals and walruses, 174 ;
in flying squirrels and bats, 175; in
cetaceans, 178. See also Evolution,
Disuse.

Innate ideas do not exist, 330, 364, 369-
370.

Inner feeling, nature of, 333 ; functions of,
334; powers of, 336; the source of
movements, 339.

Inorganic bodies, their origin, 51, 239,
258; comparison with living bodies,
191-194.

Insects, definition of, 91; distinction
from arachnids, 90; degeneration of
wings among, 118; classification of,
141-146.

Instinct, in animals, 350; due to inherited
habits, 352-353, 364; a true guide, 359 ;
cp. with Reason, 403.

Intelligence, the highest animal faculty,
279; absent from invertebrates, 279 ;
connected with the hemispheres, 279 ;
disadvantages of, 361; various kinds
of, 362; basis of, 363: causes of, 364 ;
physical nature of, 377: due to
nervous fluid, 378; based upon ideas,
378 ; principal function of, 379.

Invertebrates, Lamarck’s earliest classifica-
tion of, 64; general remarks on, 82.

Irritability, the most general character-
istic of animals, 51; not found in
plants, 195: nature of, 227-229;
different from sensibility, 228.

INDEX

Judgment, diversity of, 360, 400; as an
intellectual faculty, 398-401.

Lamarck, projects a work on biology, 6 ;
his earliest classification of inverte-
brates, 64; establishes radiarians, 64 ;
crustaceans, 65; arachnids, 65; an-
nelids, 65; infusorians, 66.

Language, see Speech.

Life, its difference from fermentation,
185-186, 214; characters of, 201;
definition of, 202; conditions for its
existence, 205; origin of, 241-242.
See also Organic bodies.

Linneus, his classification, 63.

‘Interature, cp. with Science, 390.

Living bodies, see Organic bodies.

Locke, on the Understanding, 363.

Locomotion of animals, 47.

Lunacy, cause of, 396.

Magnetism, see Subtle fluids.

Main medullary mass, necessary to
nervous system, 293; development
of, 298.

Mammals, definition of, 72; their posi-
tion in the animal scale, 72; degrada-
tion of, 73; classification of, 167-169;
origin of, 177.

Man, varieties of, 169; origin of erect
position in, 170; development of, 170 ;
origin of speech in, 173.

Manatees, lead to ungulates, 177.

Medulla oblongata, its development, 298 ;
origin of nervous system, 299.

Memory as an intellectual faculty, 391-
398.

Metabolism,
263.

Mimosa pudica, 52.

Mind, a factitious entity, 286.

Minerals, see Inorganic bodies.

Moles, degeneration of their eyes, 116.

Molluscs, definition of, 83; primary
division of, 84; respiratory organ of,
84; acephalic, 117; classification of,
151-155 ; origin of, 176.

Monotremes, a special class, 74; classi-
fication of, 166.

Moral sciences, origin of, 383.

Moral sensibility, nature of, 337; exalta-
tion of, 337; distinguished from
physical sensibility, 341.

Movement, how produced, 344; three
sources of, 356.

Movements, muscular, how produced,
300; the first function of the nervous
system, 304. :

Muscular system, physiology of, 271-273 ;
later than nervous system, 272.

254, etc.; description of,

409

Natural history, method of, 13-14.

Nature, productions of, main division of,
51; permanence of, 183.

Needs, controlled by environment, 112 ;
cause emotions, 347.

Nervous fluid, nature of, 314; proof of
its existence, 315-316; derived from
electricity, 317 ; functions of, 319-320 ;
division of, 348; in attention, 384; in
thought, 388.

Nervous system, not found lower than
insects, 93, 304; components of, 292 ;
formation of, 295 et seg. ; functions of,
300 ; of insects, 307.

Nomenclature an artificial device, 26.
Nucleus, necessary to nervous system,
292; its site, 294; of sensation, 324.
Nutrition, peculiar to living bodies, 193,

261.

Orang, 171.

Order, definition of, 24.

Organic bodies, characteristics of, 191-
194; consist of three parts, 201; cp.
with a watch, 202; nature of, 206;
constitute a laboratory, 249; con-
trolled by ordinary physical laws, 250 ;
their common faculties, 260; their
peculiar faculties, 266. See also Life.

Organs, formation of, 232; absent in the
simplest animals, 259.

Orgasm, causes of, 219 et seg. ; necessary
to life, 220; among animals, 221;
among plants, 226.

Ornithorhyncus, see Monotremes.

Phrenology, see Gall and Spurzheim.

Plants, how to determine their affinities,
32; definition of, 53 ; effects of cultiva-
tion on, 109; their differentiation from
animals, 195; growth of, 196; food
of, 197; suspension of life in, 198;
compound, 200; have no _ special
organs, 232, 281 (note); composed of
cellular tissue, 234; general character-
istics of, 235.

Polyps, definition of, 99; classification
and list of genera, 136-137.

Productions of nature, main division of,
51.

Psychology, a department of zoology, 287.

Radiarians, first established, 64; defini-
tion of, 96; origin of their shape,. 98 ;
classification of, 139-140.

Reason, nature of, 401 ; ep. with instinct,
403; public, 404.

Reproduction, derived from nutrition, 262.
See also Sexual reproduction.

Reptiles, definition of, 77; degradation

410

of, 77-78; classification of, 161-163 ;
origin of, 176.

Reservoir of nervous system, 300.

Respiration, organ of, as indicating
natural affinities, 31; physiology of,
268-271.

Richerand, on the erect position of man,
172; on the characters of life, 194;
his definition of life, 201 ; on sensation,
329.

Rotifers, 203.

Scale of animals, 58; regularity of, 70.

Sea-anemones, nervous system of, 138.

Seals, affinities of, 173 ; hind legs of, 174 ;
habits of, 174.

Sensation, mechanism of, 322 ef seq.; the
origin of ideas, 363.

Sensorium commune, site of the, 294.

Sexual reproduction, not found lower than
insects, 93; nature of, 241-242; ab-
sent in primitive animals, 245; and in
cryptogams, 268; a special faculty,
274.

Sight, not found lower than insects, 95.

Sipunculus, 140.

Skill, in animals, 353 ; only found among
vertebrates, 354.

Skin, origin of, 232.

Sleep, nature of, 341.

Sloth, 125.

Snakes, why they have no legs, 78, 117.

Soul, our ignorance of the, 294.

Sound, substance of, 116 (note).

Spallanzant, his rotifer, 203.

Species, definition of, 35; belief in per-
manency of, 35-36; merge into one
another, 37; transformation of, 39;
not affected by Geoffroy’s collections,
40; extinction of, 44; constitute a
linear series, 58.

Speech, origin of, 173; value of, 378.

Spinal cord, function of, 298.

Spontaneous generation, conditions for,
237; reality of, 238; when it occurs,
244; where it occurs, 246; necessity
for, 248.

INDEX

Spurzheim, see Gall.

Star-fishes, nervous system in, 138.

Sublime Author of the Universe, see God.

Subtle fluids, movements of, 188; ubi-
quity of, 212; constitute the exciting
cause of organic movements, 213;
produce animal movements, 344.

Synonymy, evils of, 27.

Systema naturae, 63.

Teeth of whales, loss of, 115.

Tenon, on the effects of drink, 118.

Thought as an intellectual faculty, 384-
388.

Torpidity, in animals, cause of, 222-223.

Tracheae, description of, 270.

Tracy, de on ideas, 373.

Triticum sativum, a product of cultiva-
tion, 109.

Understanding, see Intelligence.

Use, effects of, 119; see also Inheritance
of acquired characters.

Use-inheritance, see Inheritance of acquired
characters.

Vertebral column, annihilation of, 81.

Vertebrates, first recognised, 62; degra-
dation of, 81.

Vital force, 251.

Vital principle, absurdity of, 212.

Walruses, habits of, 174; lead to ungu-
lates, 177.

Whales, loss of teeth by, 115.

Wheat, see Triticum sativum.

Will, nature of the, 355; conditioned by
intelligence, 356; based on nervous
system, 357; confined to vertebrates,
358 ; freedom of the, 360 ; of secondary
importance, 380.

Woodpecker, its tongue, 120.

Worms, definition of, 95 ; classification of,
140-141 ; give rise to insects, 176.

Zoophyte an improper term, 51, 200.

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