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ARISTOTLE
ON THE PARTS OF ANIMALS.

ARISTOTLE

ON

THE PARTS OF ANIMALS.

TRANSLATED, WITH INTRODUCTION AND NOTES,

W. OGLE, M.A., M.D., F.R.C.P.

SOMETIME FELLOW OF CORPUS CHRISTI COLLECB, OXFORD.

Praclare cum illo agittir, qui non mentiens dicit, quod ab Aristotele
responsuin est sciscitanti Alexandra, quo docente profiteretur se
scienteni: ' rebus,^ inquii, * ipsis, quce Jton norunt tnenii7'i,' — Varro.

LONDON:
KEGAN PAUL, TRENCH & CO., PATERNOSTER SQUARE.

1882.

PREFACE.

The biological treatises of Aristotle are more often quoted
than read ; and, it may be added, more often misquoted than
quoted correctly. None perhaps have fared worse than the " De
Partibus Animalium," which forms the central portion of that
great trilogy, in which are set forth successively, the phenomena
presented by animals in life, the causes that have determined
their structure, and the process of their generation and develop-!
ment. The crabbed and obscure style in which this treatise is
written, its corrupt text, and, generally, the difficulties of language
have kept off the biologist, while the simple Aristotelian has
been deterred by a subject-matter, as a rule alien to his tastes.
Yet to both the treatise offers much of interest. In it the
Aristotelian will find some of the best examples of his master's
method ; while the biologist can scarcely be void of curiosity
as to the first serious attempt to assign its function to eachl
separate part of the animal body. It has been hoped therefore*
that this volume may be welcome to both ; offering to the one
a faithful and intelligible rendering of the text, and to the other
a body of notes, which have been made much fuller than would
have been necessary, had they been meant for those only, who
had already some acquaintance with physiology.

iv!C4^671

vr Preface.

In neither part of this undertaking can I hope to have escaped
many a blunder. It is indeed the consciousness of this that has
caused me to keep the following sheets in my desk unpublished,
though written many years ago. And even now, when I have
been induced by friends to venture on publication, I do so
with extreme diffidence and misgiving. Of this, however, I feel
assured ; that those persons, who are most competent to detect
my shortcomings, will also be those most disposed to make full
allowance for them. For they will best know, how difficult a
task the preparation of a volume of this kind is in reality, easy
and simple as it may seem to one who has never tried it.

THE TRANSLATOR.

N.B. — The references in the introductory essays and in the
notes are to Bekker's octavo edition of Aristotle, published by
the Clarendon Press. At the bottom of each page of the trans-
lation there has also been added a reference to the correspond-
ing place in the Berlin quarto edition.

CONTENTS.

PAGE

Preface v

Introduction i

The Main Groups of Animals xxi

Synopsis xxxv

Translation. — Book I i

.» II 19

» ni 57

„ IV 92

Notes. — Book I. 141

» II 150

„ III. 186

» IV 217

Errata 254

Index to Notes 255

INTRODUCTION.

How came these adaptations about, is a question coeval, we may be
sure, with the first recognition of the adaptations themselves. The
answers to it fell of old, as ever since, into two main divisionsj One"*;
group of philosophers there was, who fancied that they found an J- ,
adequate £ause for the phenomena io^he necessary operations of the\
inherent properties of matter ; while-^bther sought a solution in thdv n
intelligent action of a benevolent and foreseeing agent, whom theyj
called God, or Nature, as the case might be. Look, for instance, sai^
these latter, at the back-bone. See how marvellously it has been con-
structed to suit the animal's requirements ; not made of one solid mass,
as is the femur or the humerus, but subdivided into small pieces, so as
to allow of the animal making such motions and bendings as it may
require ; while at the same time, in spite of its subdivision, so firmly
bound together are its parts, as to supply a rigid support to the frame.'
Or look again at the alimentary canal and at the blood-vessels. Each)
part requires a supply of matter for its due nourishment. What but
foresight and intelligent purpose can have made these channels through-
out the body to meet that necessity ? Or see again your hand. Notice
how admirably it is made ; what an exquisite instrument for the purposes
of an intelligent animal, and how useless for one without such mental
capacity; and then consider that it is man, and man alone, that has
been endowed with it. Is it possible not to discern a foreseeing
intention in this limitation of the organ to the creature that alone can
use it with advantage ? In all this, said the materialist, you are mis-
taken. The foetus in its mother's womb is straitened for space, and
forced to lie in a bent attitude. Its backbone gives way to the bendings,
and is necessarily broken up into a series of short pieces.^ The animal
then makes the best use of it it may. As for the stomach, the intestines,
and the blood-vessels,' they are simply formed by the fluid in the animal
substance, driven hither and thither by the motions of that substance,

1 D. P. ii. 9, 4. 2 D. P. i. I, 16. 3 D, p, j. j^ 21.

ii INTRODUCTION.

making channels for itself where it can most easily escape. The hand,
again, was not given to man because he was already intelligent ; but an
animal among the millions of possibilities chanced to develop a hand,
and, having it, made use of it, and by its means became intelligent.^
But, said the teleologist, if this be so, if all be due to chance combina-
tions which the multiform play of the laws of matter brings about, how
"Incomes it that we everywhere see adaptations ? Combinations there
should be without adaptations ; combinations, even, where the organs
and the life are ill suited for each other. And are there not such, said
the materialist, partly anticipating Darwin, as before he had partly
anticipated Herbert Spencer ; are there not such about you on every
side .'' You have but to open your eyes and you will see them every-
where. When the rain falls in seed-time you say the gods send it that
the crops may grow ; but you shut your eyes to the storms that come
in harvest and wreck the farmers' hopes. The rain, whether it do good

! or harm, is alike the result of necessity. So also is it with things that
live. All kinds of combinations are produced, but those alone survive

j that have the necessary conditions of survival ; the rest perish.^ Even
of such as are able to survive, is it true that all are suited for their life,
in the sense that your hypothesis of an intelligent creative power would
require ? Do we not see on all sides living monstrosities and deformi-

Tties, whose existence is incompatible with design, and only explicable if
referred to blind necessity ? These, if such there be, are no more, said
the teleologist, much as Paley ' said after him, than the blunders of an
artist. You will find errors in the composition of the best writer ; faults

1 D. P. iv. lo, 19.

2 Cf. Phys. ii. 8, 4, where is a remarkable passage in which A. thus states the material-
istic view. "Why, however, it must be asked, should we look on the operations of
Nature as dictated by a final cause, and intended to realise some desirable end ? Why
may they not be merely the results of necessity, just as the rain falls of necessity, and not
that the corn may grow ? For the uprising of the watery vapour, its cooling when thus
raised, and its fall as rain when cooled, are all matters of necessity ; and though the rain
makes the com grow, it no more occurs in order to cause that growth, than a shower which
spoils the farmer's crop at harvest-time occurs in order to do that mischief. Now, why

f may not this, which is true of the rain, be true also of the parts of the body ? Why, for
instance, may not the teeth grow to be such as they are merely of necessity, and the fitness
of the front ones with their sharp edge for the comminution of the food, and of the hind
ones with their flat surface for its mastication, be no more than an, accidental coincidence,
*and not the cause that has determined their development ? And so witli all the other
parts, wherever there is an appearance of final causes? In short, whenever accident
caused all the parts of the body to be developed spontaneously in this suitable manner,
to be developed, that is, just as they would have been had design presided over the
formation, the resulting wholes survived ; but when this was not the case they perished,
and still do perish, as Empedocles insists when speaking of certain monstrosities."

The explanation suggested in this passage will be found recurring in after-ages. A
similar hypothesis, for instance, is started in Diderot's " Letter on the Blind for the use
of those who can See," where it is put in the mouth of the blind Sanderson. The relation in
which the hypothesis stands to that of Darwin may thus be expressed ; the old philosopher
insists on the survival of the fit, Darwin on the survival of the fittest. What a vast
difference underlies the apparent similarity in the introduction of a single short syllable
scarcely needs to be pointed out.
» Nat. Theol. i. 2.

INTRODUCTION. iii

in the work of the best sculptor.* But the presence of these will not
prevent you from believing that writer and sculptor worked with a pre-
conceived intention and for a definite end.

So began, and so was carried on, that venerable strife, which ever
since has divided thinking men into two factions, and which still, though
twenty centuries have passed away, is fought with unchanged weapons,
and with increasing bitterness, and in which neither side has ever suc-
ceeded in reducing an opponent to submission, while each has never
failed to claim complete victory.

Between these two opposite views Aristotle had now to decide. He
had already in his Historia Animalium set forth the i^henomena of
animal life. He had now to consider to what cause or causes these
phenomena were attributable. Were they due to mere necessity, or to
the action of intelligent foresight, or at any rate of some principle that
acted as intelligent foresight would do ? To neither, he says, exclu-
sively, but to both, though in very unequal degrees. The motions of
the heavenly bodies are governed by necessity, and by necessity alone.
But in the works of Nature, that is in the phenomena of terrestrial life,
this necessity is a comparatively unimportant factor. Most is the out-
come of design. Still some part, though but a small one, is the result
of necessity. There is indeed one sense in which everything in the
animal body may be said to be the result of necessity. When a man
builds a house, he must, in order to realise his plan, of necessity have
walls, roof, and the like. To have these he must first have bricks,
stones, mortar, and what not ; and, again, to furnish these, clay, lime,
and the other necessary materials must be previously forthcoming. So
is it with the animal body. The design of Nature cannot be carried
out without the necessary antecedents.^ In this sense then all the parts
of the body, and all the successive stages by which they are developed
one after the other, may be said to be the result jof necessity; for all
must necessarily be there, if the plan of Nature is to be realised.

This "hypothetical or conditional necessity" is, however, clearly not
what is meant by Democritus and the Materialists when they say that
all organisms are the result of necessity. They speak of absolute, not I
of hypothetical necessity. They mean, that is to say, that organisms
are evolved as necessary consequences of the inherent properties of
matter ; not merely that the existence of the organism implies the
pre-existence of the necessary conditions for its production ; in short,
that the antecedents determine the end, and not the end the antece-
dents. Is this, asks Aristotle, in any degree true 7 In some measure,
he answers, it is ; but that measure, as already said, is but a small one.

1 Phys. ii. 8, II. * D. P. i. i, I2.

iv INTRODUCTION.

Nature in making plants and animals can but use such material sub-
stances as exist. Now these substances have many properties. Suppose
then that Nature has selected one or more of them for a given purpose,
in virtue of their having this or that suitable property ; she must take
them not only with this desirable property, but with all their other
characters, whatsoever these may be ; and these other properties, which
were not the cause of the selection, will afterwards assert themselves,
and give rise to necessary consequences not included in her design.
Thus " we must not expect to find everything in the body made for a

I purpose. Its parts are mostly the result of final causes ; but their
material constitution entails as necessary consequences much that is
incidental and undesigned."^ These incidental and unforeseen results
may be perfectly useless,^ nay, may even sometimes be baneful;' but,
on the other hand, they may be laid hold of by Nature, and incorporated
in her scheme, though not originally included within it.* The excreta,
for instance, are the result of necessity ; for the body wears away, and
the products of its decay, together with the surplus and the indigestible
parts of the food, must necessarily be eliminated. But these excreta
are in many cases utilised, and converted into means of defence.' Or,
to give another example ; the formation of the skin is the necessary
consequence of the exposure of the external surface to friction and
evaporation,* and the growth of hair upon the scalp is the necessary
and incidental consequence of certain arrangements in the skull, which
were intended by Nature to answer another purpose.'' But this skin
when once formed, and this growth though undesigned, are utilised
by Nature, and turned to account in furnishing a protection to the parts
beneath against excess of heat or cold. In other words, then. Nature
does the best she can with the materials that are at hand ; but the
I properties of those materials are beyond her control, and such con-
sequences as follow upon those properties are the results of necessity.*

^ D, P. iv. 2, 8. So also De Anima, iii. 12, 2 : " Everything given by Nature is either
itself given for an end, or is the incidental accompaniment of something else which is
given for an end."

^ Those characters of an organism, says A. (D^ Gen. v. i.) that are essential, that is,
that form part of its natural design, are fixed and immutable ; those that are unessential,
casual, and outside the plan, are variable. Thus, an eye is essential to an animal that is
intended by Nature to see, and is invariably present in such ; but the precise colour of the
eye is, speaking generally, unessential, and therefore variable, being left to the imcontrolled
action of material causes.

' D. P. iii. 2, 19.

* D. P. iii. 2, 15. "The necessary results of existing material conditions are made
available by rational nature for a final cause."

* Cf. iii. 2, note 8. « D. G. ii. 6, 26. ' D. P. ii. 14, 6, and ii. 7, 19.

' " Magnopere hallucinantur, quicumque eas (Jina/ causes) physicis causis adversari aut
repugnare putent. Nam causa reddita, quod palpebrarum pili oculos muniant, nequicquam
repugnat altera ilia, quod pilositas soleat contingere humiditatum orificiis. Neque causa
reddita, quod coriorum in animalibus firmitudo pertinet ad cceli injurias prepulsandas,
adversatur illi alter!, quod ilia firmitudo fit ob contractionem pororum in extimis corporum
per frigus et depraxlationem aeris, etc." — Bacons De Augin. Sclent, iii. 4.

INTRODUCTION. V

A similar notion of the limitation of creative power runs through the
whole of the Timaeus. The gods in making man and animals do the
best they can, but they deal with a more or less intractable material,
which often baffles their efforts. " Let us always, and in all that we
say," says Plato, " hold that God made them as far as possible the
fairest and best, out of things which were not fair and good."^

Galen, also, some centuries later, took much the same position, when
criticising the Mosaic cosmogony.'' Moses, he says, teaches us that
the Creator is lord over the necessary properties of matter, and that
he can suspend or modify them at his will. He tells us that the Creator
can make an animal of any matter he may please, a man from a stone,
an ox from dust. This we deny. The laws of matter are antecedent
to the Creator, and obligatory upon him. He can only work in
harmony with them. He can choose the best which they allow, but J
not the best ab^s^utely. j

Aristotle, then, admits that necessity is a factor in the world of life ;
and this not merely in the sense that living bodies consist throughout
of ordinary matter, retaining its original properties unaltered ; but also
in the sense that some parts of living structures are the simple outcome/
of such properties, uncontrolled and undirected by design or final cause.' Ci/hf^^
What he denies is that the whole organism, or more than an incon-*| ^ ^j
siderable part of it, can thus be explained. It is ridiculous, he saysf-" - jaA«
to suppose that such phenomena as those of organic life are merely ""f

the result of chance ; meaning by chance, as I understand him, no
separate mysterious agency, but such uncoordinated combinations of
necessary causes as are too tangled for man to unravel, and whose
results are therefore not to be predicted. The very essence of chance is[^
its uncertainty. Chance is the principle of the inconstant. But the
p'henomena in question present a high degree of constancy, and can
be foretold with more or less precision. It is quite plain that besides
the necessary forces of matter, there is something else at work which
guides and coordinates these, so as to make them converge to a pre-
determined end. If a man cannot see this, it is absurd to argue with
him ; as well try and convince a man born blind, who denies the
existence of colour.^ You see a house or a ship, and without hesitation
you infer that such house or ship was made for the purposes to which
ships and houses are subservient. Why .'' Because they are manifestly
adapted to those purposes. Why, then, when you see a plant or an
animal with equally manifest adaptations, do you hesitate to draw a
similar inference .-' True, in one case you can see the agent at work,
while in the other the agency is yivisilile. But, why should this make

^ Jowett's Transl. ii. 546. ^ £)e Ugy part. xi. 14. ^ Phys. ii. I, 5-

vi INTRODUCTION.

any difference ? The agency in the latter case is invisible, because it
is an internal force, a something acting inside the material. It is as
though the visible shipwright were away, and his art were inherent in
the timber itself. It is the case of a physician getting well, not that
of a physician curing another person. Moreover, if the agency itself
be out of sight, the model from which it works is visible enough ; is
as visible and palpable as the model of the ship or the plan of the house,
and, like them, examinable before either is constructed. For the germ
jor seed will not develop after any chance pattern,^ but will grow in the
Ukeg^ess of its parent. Nature's model is that parent form. The seed
of an olive will not produce any chance plant, but an olive like that
/from which it came. Man gives rise to man, and horse to horse. The
doctrine of Empedocles ignores this fact.^ You say, or Empedocles
said, that the multiform interaction of the countless combinations of
matter gives rise to every conceivable form of being ; but that those
forms alone survive that have the necessary conditions of survival.'^ Be
it so. But the olive and the man are not the only beings that have
these conditions. Why, then, do they always produce offspring like
themselves ? * Why not any one of the other countless possible forms
of life ? Clearly because there is something else than the chance
combinations of necessary properties of matter, guiding and directing
these to a preconcerted end. This something else is what I call Nature.
I grant that, as Nature is invisible, her existence is an hypothesis, but
her works are visible and the hypothesis is founded upon the contem-
plation of these.' If you ask me whether this hidden force acts, as
the builder or the shipwright, with conscious deliberation, and conscious
adaptation of means to ends, I do not know. Even art is not always
deliberative." The highest art goes straight to its end without delibera-
tion. So, too, the swallow builds its nest and the spider its web without
deliberation, and yet each in nicest adaptation to its wants.'' Why may
Thot Nature be a similar force implanted in matter, undeliberating though
\guiding to a rational end } All I assert is, that there is something
at work in living bodies more than the common necessary properties
of inanimate matter, something which, whether deliberative or not,
acts as would an intelligent agent, selecting the best end, and reaching
it by the most appropriate means. "Invariably, however, when there
is plainly some final end to which a motion tends, should nothing stand
in the way, we say that such final end is the aim or purpose of the
motion."^ In other words, in the works of Nature, as in those of Art,
it is the desirability of the end, which in some way or other determines
the antecedent processes that lead to it. But you say, that what I call

' Phys. ii, 8, 13. ^ -q p_ i ^ ^^ 3 p^yg. jj. g, 4. * Phys. ii. 8, 13.

» D. G. V. 8, 4. « Phys. ii. 8, 15. ' Phys. ii. 8, 9. e d. P. i. i, 37.

INTRODUCTION. Vll

Nature occasionally produces deformities and monstrosities. Does the
artist, your builder, let us say, or your shipwright, never make a
blunder?^ Do such blunders make you infer that the artist had no
definite end in view ? Monstrosities are Nature's mistakes ; or, rather,
they are her failures ; for they are due not to any imperfection or
uncertainty in her action, which is invariable and faultless, but to the]
.uncertainty of her materials. The substances in which she works are
of indefinite composition, and her work cannot therefore possibly be
uniform. The monstrosity is not Nature's work; it is the victory of
matter over Nature.* Thus it is that though there is nothing of hap-
hazard or of chance in Nature herself. Nature being invariably the
source of order,' yet her operations appear to be liable to exceptions,
and her rules to be of general rather than of universal application.
"In all our speculations, therefore, concerning Nature, what we have"^
to consider is the genejal rule. For that is natural which holds good^
either universally or generally." *

There is an apparent difficulty here which requires a moment's con-
sideration. Aristotle held the properties of the elementary forms of
matter to be fixed and immutable. How, then, could he explain
Nature's occasional miscarriages by the indefinite character of the
materials ? Clearly, if the properties of the elementary bodies are
fixed, when once an organism has been formed from them with a
certain degree of perfection, any failure thereafter to attain at any rate
to an equal degree must be attributable not to the necessary properties I
of matter, but to the faulty selection of material. For the properties
of matter manifestly cannot be inconsistent with such perfection as
has actually once been realised. Nature, therefore, must have been
held by Aristotle either to have been an influence acting with limited
intelligence, or to have been in some way or other hindered in her I
qhoice of materials ; to have had, that is, her freedom narrowed by I
something more than the ultimate properties of elementary matter. The
latter was, undoubtedly, Aristotle's view; and the limitation consisted
in the materials with which Nature had to deal not being the ultimate
elements themselves with their immutable properties, but those com-
pound substances which were in reality the simplest actually producible
bodies in existence, the pure elements themselves never being actually
presentable as such, in a condition, that is, of isolation.^ Had Nature
been able, as a modern chemist, to take so much of each or any of
the elementary substances as she pleased, and to form from them
compounds of fixed composition, and therefore of fixed properties, her

' Phys. ii. 8, II. ^ D. G. iv. 4, 11, and iv. 10, 10,

^ De Crelo, ii. 8, 2; Pliys. viiL i, 16 ; De CJen. iii. 10, 18, etc.
* D. P. iii, 2, 16. ^ Cf. ii. l, note 3.

Vlll INTRODUCTION. .

operations would have had a fixed basis, and her invariable purposes
have been carried out with invariable precision. But, in making earthly
organisms, she had to deal with materials as they actually exist on
iearth ; and such were of in^temiinate composition,^ and therefore of
indeterminate properties. For it must be borne in mind that though
Aristotle distinguished chemical union from mere mechanical inter-
mixture,'^ he had of course no notion either of combination in definite
proportions, or even of preferential affinities. There was no such thing
as definite composition, or definite compound substances. One piece
of compound matter might more or less nearly resemble another, but
that it should be identical with it in composition, and therefore in
properties, was in the infinity of possibilities not to be dreamed of.
Every sample of material would differ more or less from every other ; and
organisms made from such materials could never be precisely alike. The
heavenly bodies being formed of a single pure uncombined elementary
substance were free from such variability, and their phenomena were
therefore absolutely fixed and eternal. But earthly substances were all
compound, and therefore all indeterminate. Their compound character
introduced an element of chance, which often thwarted Nature's efforts,
the faulty matter refusing to take the form she would impress upon it.

There is a question to which one would gladly find an answer, but
to which no sure answer is forthcoming. Did Aristotle suppose that there
stood anything in the background behind this mysterious organising
force which he personified as Nature ? And, if so, what was it ? That
the force which constrained the material of each individual organism
to develop into the form most suited to the requirements was the same
force which, acting on a larger scale, brought the fishes of the sea, the
fowls of the air, the plants of the earth, and in short all forms of life,
more or less completely into harmonious relations with each other,'
and established an ascending scale of inletdepeadejice, in which plants
should minister to animals, and animals to man,* may be fairly assumed.
But this is only to remove the question one stage back. Whence did
this universal Nature (j; toO oXov (pvaa) derive its principle of harmony
and excellence.? Was it a something self-existing, or something, Hike
the orderly discipline of an army, which, though apparently inherent,

' D. G. iv. 10, 10. 2 Cf. ii. I, note 4.

* Met. xi. (xii.) 10, 2. The passage is worth quoting, if only for the "noblesse oblige"
simile. '* The universe is not so constituted that there is no interdependence between
one thing and another. Such relation does in truth exist. For all things have been
ordered together as part of one whole ; and all things, the fowls of the air, the fishes of
the sea, and the plants of the earth, have been in some wise brought into harmony with
each other, though not all in equal degree. It is as in a household ; where the masters
are by no means at liberty to act by chance, but in all or most of their doings are guided
by fixed rules ; while the slaves and animals do some little for the common weal, but for
the most part act by chance, and follow the dictates of their individual natures."

*Polit. i. 8, II.

INTRODUCTION. IX

is in reality dependent on a general in the background ? Aristotle
himself asks ^ the question, but gives no answer. This much, however,
seems clear. The general, if general there. were, could not be the
extra-cosmic God whose existence is postulated in the Metaphysics,
the " Unmoved that causes motion as an object of desire ; " for his
life was an undisturbed ecstacy of self-contemplation. But whether
there were other divine essences of less serene attributes, answering to
the inferior gods who in the Timaeus are interposed between the
Demiurgus and mortal beings, of whose intelligent activity Nature was
but the expression, is a question which, whatever surmise we may form
from a few stray and hazy passages, admits of no definite solution.
In the biological treatises there is no reference whatsoever to the re-
lation in which, if in any. Nature stands to God. In these Aristotle
limits himself to the teachings, or supposed teachings, of the senses.
These revealed to him the phenomena of animal life, and he wrote of
them. They showed him also, or seemed to show him, as plainly as
his eyes showed him the existence of colour, that these phenomena
were not explicable by reference to the ordinary properties of inanimate
matter, but implied the action of some other and co-ordinating force.
They told him also something of the conditions and limitations under
which this force acted, and with these, also, he deals. But they told
him nothing of the origin of this force, and, whatever may have been
his ideas as a metaphysician, as a biologist he was silent.

Having in the first book of this treatise laid down his general position,
Aristotle proceeds in the rest of the work to deal with the application
of his views to particulars. With this purpose he takes the various
parts of the body, both tissues and organs, one after the other, into*
consideration, and praises to examine in e^i case how far the struc- j
ture is the outcome oF^gceaai^, how far ^-^PPt^iF"^ ^'^^Ifir"- Such, I
say, is his profession. His actual practice is merely to see if it be
possible to find any ^use. real or imaginary, for a given structure, and
if such can be devised, at once to claim that structure, without further
argument, for design. Seeing how fertile was his fancy in generating
final causes, it will be readily understood how scanty a margin remained
after this process as the share of necessity. One set of structures indeed
there was which seems to have caused him much difficulty. These were
the organs which we now-a-days know as rudimentary parts. The inutility
of these was too striking to escape notice, and seemed to exclude them
from the predesigned plan of Nature, that " makes nothing without a
purpose." Were they then the offspring of mere necessity } To this
question Aristotle never gives a definite answer. He speaks in many

1 Met. xi. (xii.) lo, I.

X INTRODUCTION.

places as though Nature worked under some kind of restraint, the
obligation of which is never clearly defined, whether, that is, it is self-
imposed or dictated from without. This restraint consists in the
existence of certain definite types or patterns, in more or less close
accordance with which each organism must be made. Nature, for
instance, can fashion this or that bird to fit the exact mode of life
/ which is pre-ordained for its species ; but in so fashioning it she must
I not transgress certain limits. Each and all birds, through all their
varieties, must present in form and composition ^ the essential characters
of the ideal bird which constitutes the avian type. If any part in this
type be useless to the special animal created, nay, even if its presence
be actually prejudicial,^ yet it must still be there in some shape or other,
" by way of token " (arjfjLeiov ')(apiv)- The most that Nature in such a
case can do is to reduce its size ; and, inasmuch as the ultimate com-
position of all the animals in a given class is precisely, or almost pre-
cisely,' alike, she can only do this by diverting the material which should
have gone to the full formation of the useless or prejudicial part into
some other organ where it may be of use, or at any rate not equally
injurious. So that, in fact, the organisation of an individual species
of animals is not always the best conceivable, but the best of which
the essential type of the class to which that species belongs admits.^
Aristotle, as I have said, never expresses himself clearly on this matter.
Did Nature herself make these types, and adhere to them in her after-
work with the obstinacy of a prejudiced inventor ; or, was there some
external necessity coercing her, and driving her against her own better
judgment to make her products in part futile ? I take it that Aristotle
was not himself clear as to his own views on the matter ; that his
opponents, or his own mind, had pointed out the impossibility of
^ preconciling the existence of rudimentarv organs with the strictly teleo-

yl logical position, "^and that he met the difficulty with a phrase, " by way
of token," leaving it really unexplained.

The giant share which Aristotle allots to final causes, and the almost
complete exclusion of necessity from consideration, make the main
portion of his treatise to consist of little more than an attempt to assign
to each part of the animal body a definite use ; so that the work
becomes rather one on the functions of parts than on the causes of
their existence, and might almost have been styled, as was Galen's
later work, a treatise "De Usu partium." Very possibly it was on this
account that the designation by which Aristotle himself* refers to the
work, " On the Causes of the Parts of Animals," was in time superseded
by the vaguer title " De Partibus," which it has ever since borne.

» D. r. iv. 12, 28. 2 D. p^ iii_ 2, 5. 3 De incessu. 2, i, and 8, r. * D. G. v. 3, 6.

INTRODUCTION.

XI

We have now to enquire how it fared with Aristotle in his search
after final causes, in his attempt, that is, to assign to each organ its
proper function.

It must be confessed that his success, as measured by what has been
attained in modem times, was but small. In dealing, indeed, with the
external parts he was more happy. His account, for instance, of the
adaptation of the visible parts of birds to the varied modes of life in
this class of animals is admirable, and reads like a chapter from Cuvier,
whose unstinted praise was lavished on it. But with the internal organs
it was otherwise. The most that can be said is that he devised an
ingenious system, which included in its range pretty fairly all such
facts as were known to him, but which in its conclusions was far wide
of the truth as now ascertained. This was indeed inevitable. He was
trying to solve the complex problems of biology, while the ancillary/
sciences were yet unknown. Anatomy was still in its first infancy, physics
embryonic, and chemistry hardly as yet conceived. What possibility
was there that digestion or respiration should, under these conditions,
find an adequate interpretation } This explanation of Aristotle's failure!
to assign to the several internal parts their several functions seems tol
me a sufficient and a true one. It is more usual, )rowever, to account
for it on other grounds, and to attwLute it to hil]<iarelessness in the
observation of individual facts, hisJbastiness in geaeralisation. and the
3^mperfection of his method. A few words on each of these alleged
causes of defeat ; and, first, as to his supposed inaccuracy of observa-
tion. I cannot but think that this has been, to say the least, enormously
exaggerated. Were we indeed to suppose that Aristotle had committed
all the extravagant blunders which critics have laid to his charge, the
accusation would have to be admitted as just. But a very large pro-
portion, at any rate, of his supposed mistakes have no other ground
than the careless mode in which his writings have been studied. They
are not mistakes of Aristotle, but mistakes of his critics. To give a few
examples. It is laid to his charge that he represented the arteries as
void of blood and containing nothing but air ; the aorta as springing
from the right ventricle ; the heart as beating in man and in no other
animal, and as not liable to disease ; the gall-bladder as situated in
some animals on or close to the tail ; reptiles as having no blood \^
and so on, till the list might be swollen with almost every conceivable
absurdity. In reality not one of the errors here enumerated was made
by him. Still I am far from denying that there are strange misstate-
ments of simple facts to be found in his works. That there is but a
single bone in the neck of the lion and of the wolf; that there are
more teeth in male than in female animals ; that the mouth of the
dolphin is placed, as in rays and sharks, on the under surface of the

(3>

'^ rl'

XU INTRODUCTION.

body; these and the like are strange blunders, however they originated.
This much, however, seems to me beyond question : these were not
the personal observations of the same man who had noted the heart
beating in the embryonic chick as a " punctum saliens " on the third
1^ day of incubation ; who haif^distinguished the allantoidean development
A \of birds ^nd reptiles from the non-allantoidean development of fishes ;
'who had"unravelled with fair accuracy the arrangement of the bronchial
tubes and^their relation to the pulmonary blood-vessels ; and who had
jnot only-^ven zoological and anatomical details concerning the cepha-
lopods, which both Cuvier and Owen regard as " truly astonishing," but
had described nine species of them " with so much precision and happy
a selection of their distinctive characters as to enable modern naturalists
to identify pretty nearly all."^

Is it possible to believe that the same eye that had distinguished
the cetacea from the fishes, that had detected their hidden mammse,
discovered their lungs, and recognised the distinct character of their
bones, should have been so blind as to fancy that the mouth of these
animals was on the under surface of the body? Although a statement
to this effect occurs twice over in the Greek text, yet it is to me as
incredible that it should have been actually made by Aristotle, as it
would be that Professor Huxley should make a similarly palpable mis-
statement about an animal with which he was perfectly familiar. If it
Tbe asked how we can account for the presence of the erroneous state-
Vment in the text, we have not to go far for, at any rate, a very possible
explanation. We have only to remember the strange vicissitudes to which
the original manuscripts of Aristotle's treatises are said to have been sub-
jected. Hidden underground in the little town of Scepsis, to save them
from the hands of the kings of Pergamus, who were then collecting books
to form their famous library, and who, in so doing, apparently paid but
little regard to the rights of individual owners, they were left for the
better part of two centuries to moulder in the damp, "blattarum et
tinearum epulae ; " and when they were at last again brought to light,
fell into the hands of Apellicon of Teos, a man who, as Strabo says,
was a lover of books rather than a philosopher, and who felt no scruples
in correcting what had become worm-eaten, and supplying what was
defective or illegible.'' To what extent this corruption of the very
fountain head took place, we have now absolutely no means whatsoever
of ascertaining. We are, however, I think, justified in assuming with
i much confidence that such palpable absurdi^ties. is the one which has
f^ I just been mentioned were due to this Bacrilegious interference with the
I text, and should be put not to the account of Aristotle, but to that of
the incompetent Apellicon, or his fellow transcribers and emendators.
' Todd's Cyclop, i. 561. - Grote's Aiist. i. 51.

INTRODUCTION. Xlil

Similarly would I explain another blunder already mentioned, namely, ^
the statement which occurs in the Historia Animalium, that in certain
species of animals, namely men goats sheep and swine, the teeth are j jyjpf
more numerous in the males than in the females, a blunder which has i ' (j
been quoted, with others, by Mr. Lewes, as an instance of Aristotle's J^/fAW^
carelessness^ in observation. That this statement is due to interpolation /v/i^tAA^
or correction of the original manuscript I feel the more assured, because a

in other passages, in the De Partibus, when the distinctions between (

males and females as regards their horns, teeth, and their offensive and
defensive weapons generally, are discussed/ no such erroneous state-
ment is to be found. It is said, and said correctly, that horns and
tusks are often larger in the male than in the female, and horns fre-
quently wanting in the latter when present in the former ; but as to
any difference in the number of the teeth, there is not a single word.
We can readily conceive how an incompetent editor, finding in the
manuscript a half legible passage relating to the teeth of male and
female animals, may have so filled up the gap as to convert a difference
of size into a difference of number." Some of the more striking blunders
in Aristotle's treatises, especially such as occur only in single instances,
may, I think, be fairly thus explained. As to others, we must remember '

that Aristotle, like every writer on a vast subject, had to rely in great j /
measure on the statements as to matters of facts "Iftflr ^y ^thprc and "* ^

this the more implicitly as the opportunities of verifying these state-
ments were but rare, neither menageries nor museums of anatomy
having as yet come into existence.

There is indeed a tale that Alexander supplied Aristotle with animals
from all the countries into which his expeditions led him ; but this
story is so plainly fabulous that it might be passed over entirely without
notice, had it not received the sanction of the great Cuvier. " On voit
en effet," says he,' "par 1' exactitude avec laquelle Aristote d^crit
plusieurs animaux de I'lnde et de la Perse, qu'il a eu sous les yeux les
objets eux-memes." Five animals are mentioned* as examples of this
statement, the elephant, the camel, the hippelaphus, the hippardium,
the buffalo. As regards the first two of these, the description given
by Aristotle is fairly complete ; and inasmuch as these animals, being
tamed, would present no difficulty in transportation, it is not impossible
that Aristotle may actually have seen them. I can, however, find no
evidence that he had done so, there being nothing in the description

» D. P. iii. r.

" There are, it may be noted, some species in which the males have more teeth than the
females ; in the sense that teeth which are more or less highly developed in the males are,
if not absent, yet rudimentary in the females. The narwhal is a well-known instance, the
horse is another.

3 Hist. d. Sc. Nat. i. 137. * Ibid. p. 154.

XXV INTRODUCTION.

which might not easily have been communicated by others, while some
remarks are made which seem to me much more compatible with the
latter view than with the former. As regards the other three animals, it is
astonishing how Cuvier can speak of their being so accurately described
as to imply actual examination. They are only mentioned once,
all together, in a few clauses (H. A. ii. i, 20, 21, 22); just as they
might be if Aristotle were citing a passage of a letter from his pupil
Callisthenes, who accompanied Alexander, and with whom Cuvier him-
self supposes Aristotle to have kept up a continuous correspondence.^
The hippelaphus may be identified with much probability, though no
actual certainty, with the nylghau, and the wild oxen are undoubtedly
buffaloes. But the details given in this passage are quite insufficient to
determine what animal is meant by the pardium or hippardium ; and to
prove this it is enough to say that Cuvier, who must have been speaking
at second-hand, and relying upon some utterly untrustworthy authority,
actually identifies it with the "tigre chasseur," or cheetah, whereas
it is said by Aristotle to have a cloven hoof and horns, in this re-
sembling the hippelaphus, and has been supposed by some to cor-
respond to the giraffe ! Cuvier the historian of science is, as I
have often found, an authority of very different value from Cuvier the
biologist.

/ Whether Ptolemy Philadelphus, not very many years after Aristotle's

''death, instituted a museum with a zoological garden attached to it, more

richly supplied with animals than any that has since existed, as is stated,'

may be doubtful ; but that no such collection was open to Aristotle is,

I think, indisputably shown by the utter absence of any allusion to it

in his treatises. Thus Aristotle, in all probability, had. never, had the

rppportunity of personally examining any of the larger carnivora, either

Lalive or dead. The stories of hunters, always prone to exaggeration,

/ /were the only source of information as to the habits of these animals

^».in life ; and if a chance skin, hung up in a temple to commemorate

an escape from a perilous encounter, may perhaps have sometimes

given a more direct notion of their external aspect, yet the internal

parts — spirits of wine or other preservatives of organic structures not

having as yet been discovered — must have been entirely beyond the

reach of investigation. A hunter, noticing the thick and solid neck

of the lion and the wolf, jumped to the conclusion that it contained

but a single bone, and did not hesitate to report as an actual anatomical

' I do not know on what authority Cuvier makes this probable statement. I presume,
however, that he relied on a passage in Simplicius, where it is stated that CaUisthenes
fonvarded certain ancient astronomical observations to Aristotle from Babylon. Cf.
Simpl. Comment, ex recens. Karstenii, p, 226.

» Hist. d. Sc. Nat. i. 174.

INTRODUCTION. XV

observation what was in reality a mere supposition.^ Nor does it imply

any great credulity on the part of Aristotle, that he should unhesitatingly

have accepted such a report. For it is not the actual falseness of a

statement, but its inconsistency with our previous experience, which

makes the ready acceptance of it to be an act of credulity. A modern

naturalist knows from an examination of a vast number of species that,

as a rule to which there is scarcely an exception, the mammalian neck

contains seven vertebrae, and that in no known instance are there less

than six. Possessing this knowledge, he would show great credulity

were he to accept without further question any account of a mammal

with but one cervical bone. But to Aristotle, who had not this previous \

knowledge, there would seem nothing strange in such an account ; arid

as there was nothing in it to rouse his suspicions, he would accept it

without question. In no instance do we find similar outrageous errors,

when Aristotle, as he often does, states a fact to have been derived from

his own observation. So far, indeed, as I can judge, he seems to have]

been anything rather than a careless and inaccurate observer. It cannot,

of course, be maintained that he was able to observe with the precision

of a modern man of science. His substratum was insufiicient for this.

To observe, unless the phenomena be of the very simplest, it is not

enough to keep the eyes open and to watch with honest intention for

what may turn up. To be effectual, observation requires a stock of previous | ^fe— **

knowledge. He that has most of this will see best and most. Tell

me, said even the long-experienced Faraday, when asked to be witness

of an intended experiment, tell me what you expect me to see, that I

may be able to see it.

A second source of Aristotle's failure is found in his habit of has^ty yenf^- l.^
ralisatinn,- That he was constantly generalising on a very scanty basis of
facts cannot be denied. The stage to^vhich biology had then attained
made this a matter of necessity. ThejArst stage in every new science
is the simple accumulationofjjacts. The next, if it may be called next,
LVseeing that it must go hand in hand witji the first, is the rough sorting
of these facts and the reduction of their chaos to some kind of order.
This is effected by tQmgorary generalisations, which, though they may
be very far from the ultimate truth, yet serve for the time the necessary
purpose of enabling the observer to manage his otherwise unwieldy
material. All that can fairly be demanded at this period is that there
shall be diligence in the collection of facts, and that the temporary
generalisations shall not be obviously untrue. As regards Aristotle's

' Possibly, however, not a mere supposition, but a hasty generalisation from some single
example, in which the cervical vertebrae had been affected as they are occasionally in the
hyaena, and become anchylosed. And this is the more possible, inasmuch as the anchy-
losis has actually given rise to a similar belief concerning the hyaena, namely, that it has
but one bone in the neck. Cf. Regne Animal, i. i6o.

a

XVI INTRODUCTION.

diligence there can be no doubt. Every chapter in his treatises bears
testimony to it. What proportion, indeed, of the huge array of facts
there stored was due to his own personal observations, to his dissec-'
tions, vivisections, and occasional experimentations, what was borrowed
from others, it is impossible to say with any exactness, P'or the works
of his predecessors and contemporaries have perished almost completely;
and the laudable custom of citing the authority on which a statement
is made had not yet been established. As yet there was no mistrust of

Tother observers, because as yet it was not known how easy it is for an
jpbserver to be misled. Aristotle does indeed occasionally mention a
name, but it is the name of some one whose statement he rejects, and very
rarely, if ever, the name of one whose statement he borrows.^ Nor
must it be supposed that Aristotle's generalisations, though often false,
were utterly puerile. Among them are not a few that, with little or no
modification, have stood the test of time ; and some even that, restated
by moderns in ignorance of his writings, have been cksmed by them-
selves or their admirers as deserving high credit. TtU^law of organic
Ie^quivalents, for instance, the general statement, that is, that Nature
must save in one part if she spends in another, be it true or false, has
been claimed for Goethe and for Geoifroy St.-Hilaire. Yet it had
been stated in unmistakable ternis^over and over again in this treatise
of Aristotle's.* The advantage ((f^hysiological division of labour "was
first set forth," says Milne-Edwards,' " by myself in 1827 ;" yet Aristotle
had said repeatedly that it is preferable when possible to have a separate
organ for a separate office ; and that Nature never, if she can help it,
makes one organ answer two purposes, as a cheap artist makes " spit
and candlestick " in one.* That the position of an organism in the
kingdom to which it belongs is not to be settled by a single differentia,

(but by a consideration of its aggregate characters ; " that the complexity
of life varies with the complexity of the organisation ; ' that the struc-
tural differences of the alimentary organs are correlated with differences
of the animal's alimentation ; ^ that no animal is endowed with more
than one adequate means of defence against its enemies ; ^ that there
is an inverse relation between the development of horns and of teeth ; •

* Thus, when A. borrows the account of the hippopotamus (H. A. ii. 7) almost verbatim
from Herodotus, he makes no mention of his authority ; neither does he when he takes
from the same source the account of a skull without sutures (H. A. iii. 7, 3) ; but on three
occasions, when he contradicts him, he mentions in so doing his name (H. A. iii. 22, i,
D. G. ii. 2, II, and iii. 5, 15). From Ctesias he takes without acknowledgment the
account of the parrot, and very probably of the elephant ; but whenever he mentions
Ctesias by name, it is to contradict him flatly. His treatment of Plato is exceptional.
For though he frequently, in the De Partibus, alludes to statements in the Timaeus to
reject them, he always forbears in so doing to mention his former teacher's name.

* Cf. ii. 9, note 9. ^ Lemons sur la Phys. i. 16. * Cf iv. 6, note 15.
» D. P. i. 3, 14. 6 D. P. iv. 7, I. ' D. P. iii. 14.

* Cf. iii. 2, note 9. ' Cf. iii. 2, note 19.

INTRODUCTION. xvil

that no dipterous insect has a sting ; ^ that there is an inverse relation
between growth and generation ; * that the embryo is evolved by a suc-
cession of gradual changes from a homogeneous mass into a complex
organism,' and that the development of an organism is a progress from
a general to a special form ; * these and numerous others are instances
of generalisations made by Aristotle, and which have lasted, with but
slight modifications of his terms, to the present day.

There remains yet the faulty method. Mr. Lewes, in an interesting
chapter, traces Aristotle's failure to the ahcpnrp nf vp;]-jfiratmn from ^
his method of enquiry. Again, however, I would say that verification
does not find its proper sphere in the early condition of a nascent
science, when the generalisations are merely provisional, and though
false yet necessary precursors of more accurate ones. How far,
indeed, Aristotle himself recognised the true character of his biolo-
gical work, may be a matter of doubt. Few men care to look on J
the results of their hard toil as provisional and ephemeral. I can,
however, find no passage in which he betrays any confidence in the
finality or permanence of his conclusions. In the absence of such it
seems but simple justice to credit him with at least the same degree
of modesty as he evinced when speaking of his much more successful ^
labours in another branch of science. " I found," he says, " no basis^
prepared ; no models to copy .... Mine is the first step, and there- \
fore a small one, though worked out with much thought and hard \
labour. It must be looked at as a first step, and judged with indul- I
gence. You, my readers or hearers of my lectures, if you think I have I
done as much as can fairly be required for an jpitiatory start, compared |
with other more advanced departments of theory, will acknowledge what ' I
I have achieved, and pardon what I have left for others to accomplish."']

So far the comparison has been between Aristotle and his successors
in modern times ; for it is only in contrast with their achievements that
we can speak of his results as failures. Such a comparison might serve
in estimating their claims, but not in estimating his. For it is the gap
that separates a man from his predecessors, not that which lies between
him and his successors, that gives the true measure of his position. Let*
any one then compare Aristotle's physiology with that of the Timseus,
which Plato, as Galen tells us,^ borrowed from Hippocrates, and which
we may therefore fairly take to represent the general views of the most
prominent authorities immediately antecedent to Aristotle.

In passing, then, from the Timaeus to Aristotle's treatises, one is

^ Cf. iv. 6, note 13. 2 D. G. iv. 4, 20 ; i. 8, 4. » D. G. ii. ch. 4, 5, and 6.

' The embryo of man or horse or other animal is not at first man or horse or other
animal, but only assumes the specific form at a final stage," being first living thing, then
animal, then special kind of animal. D. G. ii. 3, 4 ; ii. 6, 29 ; iii. 9, 2.

* Soph. El. xxxiv., as rendered by Grote, ii. 133. * De Usu Part. i. 8.

it

XVlll

INTRODUCTION.

M*M

conscious of passing into an entirely new order of things. In the former
.we have airy and fanciful constructions, in which imagination along
'supplies the foundation, and in which facts, if introduced at all, are
introduced merely as ornamental additions, in no wise essential to the
fabric. In the latter the positions have been inverted. What was the
ornament has become the foundation ; what was foundation has been
converted into ornament. It may, indeed, be that sometimes these new
foundations are but slight and weak in comparison with the structure
they are made to support, but they are at any rate substantial, and of
the right material. "Jamais," says Cuvier,' speaking of his great pre-
decessor, "jamais il ne pose une r^gle d priori;" and even if we allow,
as perhaps we must, that exceptional cases may be found in which this
too general statement hardly holds good, and in which Aristotle seems
to lapse into the faulty methods of earlier writers, yet it must at the
same time be conceded that these occasions are at most but rare ; and
that when they do occur, it is because, as with other men so with
Aristotle, practice falls somewhat short of principle. Neither should
we forget that in most minds there exists an aesthetic craving after
/completeness, or, when this is not to be had, after its semblance, a
j craving which leads men almost irresistibly to fill up the gaps in their
^stems with such makeshifts as come to hand ; and this weakness may
be forgiven them, if only they are ready to pull down their stop-gaps
and cart them to the rubbish-heap, so soon as better materials can be
obtained. That Aristotle, who manifestly felt this desire most acutely,
and who in those early days of science had but scanty means of giving
it legitimate satisfaction, should occasionally have had recourse to this
palliative, can scarcely be a matter of surprise. But how ready he was
to abandon it for better things the following passage, amongst others,
shows. " Such," he says, after speaking of the reproduction of bees,
" such is the conclusion to which we are led d priori, and facts appa-
rently support it. I say apparently, for the actual facts are not yet
sufficiently made out. Should future research ever discover them, we
must surrender ourselves to their guidance, rather than to that of theory;
and theories must be abandoned unless their teachings tally with the
indisputable results of observation" (De Gener. iii. 10,25). It was by
/thus altering the basis of enquiry, and substituting facts for theories,
'^' more than by actual observations, that Aristotle made a huge step in
advance of his biological predecessors. And if, some two thousand
years later, Bacon gained for himself an immortal name by insisting
still more peremptorily upon the value of induction, it must be remem-

' "Toutes les propositions generales, qu'il exprime, sont des inductions, resultant de
I'observation et de la comparaison des fails particuliers ; jamais il ne pose une regie
i priffri."—IiisL d. Sc. Nat. i. 143.

INTRODUCTION. xix

bered that the instniment in his own hands was at any rate not more
successful than in those of Aristotle. By the skilful use of scientific
method to discover new tmths is a noble achievement ; but far noblen
is it to discover the rn^^yj^jjjgj£^ by which alone such achievementa^c:
are made possible ; and to have done this is Aristotle's glory. Thar
the method as left by him was not perfect, that there were flaws which
the fuller experience of after-ages detected, and gradually remedied,
may be allowed. Seldom, if ever, does a great invention come fuU^
armed from the brain of its first_auti)or. Weak points there invariably
are, which trial alone will reveal. ^ To detect and strengthen these is
to confer a benefit on mankind ; but is a service which can never be
put on a par with that rendered by the original conception. "MnvenO
tions," to quote from a treatise ^ already once cited, " are either the |
final shapings of what has been partly elaborated by others, or they are J
original discoveries, and but roughly shaped. The latter are the mosH
important. The first step, according to the proverb, is the grand thing
and the most^ifficult ; for first^ beginnings are as small and incon-
spicuous as they are potent. When they are once accomplished, the
remainder is easily added or developed."

' Arist. on Fallacies. Poste's transl., p. 95.

THE MAIN GROUPS OF ANIMALS.

Aristotle has left us no systematic classification of animals. It will
nevertheless be convenient to arrange the chief groups recognised by
him in a tabular form ; and the form which seems most consistent with
his views is that in which these groups are placed in linear series,
according to their supposed degrees of excellence.

Before, however, doing this, it will be well to consider very briefly
what Aristotle means when he speaks, as he so often does, of one animal
being superior to or more noble than another ; and also to enquire what
were the external characters by which he thought such superiority could
be recognised. When we have done this, we can proceed to apply
Aristotle's tests of comparative excellence to his various groups with the
fair expectation of being able to arrange them in much the same order
as he would himself have done.

(i). The basis of all excellence is the presence of a soul, that is, the
possession of life. " Anything nobler or better than the soul cannot
possibly exist ;"^ and again, "to be is better than not to be ; to live
than not to live ; things with a soul than things without ; the soul itself
than the body." ^ As things that live are superior to things that are*
lifeless, so also things with much life are superior to things with little^
" Souls differ from each other in their degrees of honour ; " ^ and the
difference is thus set forth. " The faculties of the soul are many ; and
though everything that lives has a soul, yet have not all souls all these
faculties. In some souls there is but one faculty, in others several, in
some all. The faculties are the Nutritive, the Sensitive, the Appetitive,
the Motor, the Intellectual. In plants there is no other faculty than the
Nutritive, but in all animals there is not only this, but the Sensitive, and,
as a necessary consequence, the Appetitive as well. Some animals there
are, again, that possess also the Motor faculty ; and a few, such as man
and any other creature, if such there be, that equals or surpasses him in

' De Anima, i. 5, 15. ^ De Gen. ii. i, 2. ^ De Gen. ii. 3, 11.

XXll THE MAIN GROUPS OF ANIMALS.

honour, in whose soul there is still further the Intellectual faculty and
Reason." ' In proportion as the soul includes more or fewer of these
successive faculties will its possessor's place be higher or lower in the
scale of excellence. At the bottom will come organisms whose life is
■confined to nutrition ; next, those that are also endowed with' sensation ;
jthen, such as besides feeling are also capable oMocomotion ; and, lastly,
jthose who add to these endowments the possession of^ reason. The
few groups thus obtained will again be divisible into smaller groups,
according to the degree in which each successive faculty is developed.
There are degrees of Nutritive power, of Sensibility, of Motility, of
Intelligence ; and the question next to be considered is, what were the
external characters by which Aristotle thought that he could determine
these degrees.

(2). The Nutritive soul manifests itself, of course, in growth and
reproduction ; and the tests of its power are the bulk of the body,'' and
the duration of life, which is usually proportionate to the bulk. " For,
as a rule, big animals are long lived, though not invariably."' The
number of the progeny is not so good a measure as might be expected,
because the requirements of a large body on the nutritive material may
prevent an animal of great size from being prolific* The sensitive soul
is of course certainly present, if the organism have external organs of
sense. But a doubt may arise when, as in the sponge,* there are none
such. The test in such a case is to see whether the organism shrinks
when irritated. The degrees of ' sensibility must be judged of by the
number and perfection of the organs of sense, and especially of those
senses from which are* derived the perceptions, which conduce most to
knowledge.

As to the Motor soul, and the Intellectual, the tests are self-evident ;
and may therefore be passed over.

But besides these special tests, applicable to the several parts of the
soul, Aristotle had other more general ones, by which he gauged the
. . excellence of the soul as a whole. Foremost among these was the
temperature of the body. For though Aristotle would not allow,* with
Democritus, that heat was identical with the soul, that is, with life, yet
he admitted that heat was its necessary agent, so that the two were
inseparably conjoined, and the degree of the one became a measure of
the degree of the other. " The nobler an animal is, the greater is the
amount of heat it possesses. For with greater heat there must of neces-
sity be combined a nobler soul." ^ But how was the temperature to be
measured .'' As Aristotle had no thermometer, he could only form a

' De An, ii. 3, i. "^ De Gen. ii. i, 7. ^ De Long, vitas 4, 3 ; De Gen. iv. 10, i.

* De Gen. iv. 4, 20, and i, 8, 4. ' H. A. L i, 18. « D. P. ii. 7, 5.

» De Resp. 13, 2.

THE MAIN GROUPS OF ANIMALS. xxiii

notion of the relative temperatures of different animals either directly

by touch, or indirectly by inference from structure. On touch, though

sometimes used by him, he apparently placed but little reliance. For,

as he says,* it could not tell whether the heat was intrinsTc, or whether I

it was merely accidental and derived from without. Moreover, even

supposing that touch were a sufficient measure of ordinary heat, it by no

means would necessarily follow that it would be an equally good test

of " vital heat," which was something in Aristotle's opinion quite distinct

in its efficacy from common heat,'^ and would require to be measured by

its own appropriate standards. He relied therefore mainly on inference q

from structure. The presence or absence of blood, and its relative / ; /r AO'W^

abundance, gave him indications^ in which he had absolute confidence.

No less certain was the evidence given by the presence or absence of a ^ aIm^K^

lung, and by its degree of development. For, by his theory of respira- ^ ^

tlon," the whole purpose of a lung was to temper the excess of heat. ''

" Those animals," he says, " are the more perfect that have the greatetj

amount of heat ; and in animals that have blood the measure of natural]

heat is the lung. For those that have a lung are invariably hotter than

those that are without one ; and among such as possess one, those in

whom it is richly supplied with blood and soft in texture are hotter than

those in whoni it is bladdery or hard, or contains but little blood." * r </•

Besides thepblood and theviung, Aristotle had a third structural "~" "

measure of temperature in thO^brain^ which shared, as he thought, with C . t-^y^^
the lung the office of reducing excess of heat. The close connection,
however, of the brain with the higher sense organs, and its delicate
sympathy ' with the heart, made its presence and size a measure of the
intellectual faculty rather than of the excellence of the soul as a whole.

A fourth measure of animal heat, on which Aristotle placed great • DAfmdyiiA
reliance, was the condition of the embryo when liberated from the
mother's body.* Impressed by the manifest action of heat in effecting
the development of the eggs of birds and reptiles, he erroneously though
not unnaturally inferred that the more mature condition of the mamma-
lian embryo at the time of birth was mainly due to its having been
subjected to a higher temperature in its mother's womb ; and similarly
that all other ovipara must be colder than birds and reptiles, inasmuch
as their eggs were, as he thought, deposited in a still less advanced state.
This, however, we shall have to consider at greater length hereafter.

There remains yet a fifth among Aristotle's thermometers, which,
almost childish as it now appears, yet requires a moment's notice. One
of the primary axioms upon which all his notions of the material world

» D. P. ii. 2, 20. ' Cf. ii. 6, note 7, and D. G. ii. 3, 13. ^ D. P. iii. 6, 9.

* D. G. ii. I, 16. * Cf. ii. 7, note 27. " D. G. ii. 1, 17, etc.

U>^

XXIV THE MAIN GROUPS OF ANIMALS.

were built was that it was the inherent_£ropertj of heat, and therefore
\ of everything possessing heat, to motint upwa_rd&. He fancied that
varying indications of such a tendency were to be traced in the ordinary
attitudes of animals. At the bottom of the scale came those humble
creatures in whom there was so little elevating heat that their bodies
lay prostrate on the ground/ or were even, like plants, actually attached
to it ; while at the other end came man of all animals alone erect and
of all the one with most heat; while between these two extremes came
animals in intervening gradations of heat and corresponding differences
) of bodily attiliide.

Such were Aristotle's tests of vital heat. The relative warmth of
animals was not, however, his only, though his main, guide in judging
of the soul's excellence. Another, to which he not unfrequently refers,
was the djggree of complexity of the organism. The nobler the soul
the more varied its activities, and the more numerous the instruments
it requires. " For when the functions are but few, few also are the
organs required to effect them. For this reason animals present a
greater complexity of structure than plants ; and this complexity is
again more marked in some animals than in others, being most varied
in those to whose share has fallen not mere life but life of high degree."'
Nature might, of course, use one organ for many purposes, and so
endow a simple organism with complex activities. Sometimes, indeed,
she does so.^ But as in handicrafts so in the body ; it is better to have
special instruments for special operations, than single instruments for
multiple uses. Nature never, therefore, when she can help it, acts like
\ the artisan, who for cheapness makes "a spit and lamp-holder" in
ikone.* In the more perfect animals, then, there are numerous organs,
V V reach with its separate office; whereas in less perfect ones such division
of labour is much less complete, and in some is so slight that, when
the body is cut into bits, each separate fragment can continue to live
independently for a short time ; there being scarcely more unity between
them than if the animal had been a plant or an aggregation of distinct
animals into a single mass.* " But in animals of the most perfect con-
formation no such phenomena as these are observable, because their
nature has attained to the highest possible degree of unity." ^ Thus
^ - centralisation of vitality^ becomes a test of excellence as well as com-

plexity of structure, the one like the other implying division of labour.

(3). These tesls we may now proceed to apply. But it is important
to bear in mind that no one of them was supposed by Aristotle to be
sufficient by itself. The true nature of any group is not to be defined

' D. P. iv. 10, 16, and iii. 6, 9. ' D. P. ii. lo, 3. » D. P. iii. i, 11, and ii. 16, 6.

* D. P. iv. 6, 13. » De Resp. 17, 4 ; D. P. iii. 5, 3. ^ De Juvent. 2.

THE MAIN GROUPS OF ANIMALS.

XXV

by a single differentia, but requires many.^ That is to say, its position |
in regard to other groups must be determined by a consideration not/
of one but of all its characters, and by striking a balance between those
points in which it excels and those in which it shows inferiority. How
inadequate a single test may be, and into what confusion it may lead,
Aristotle points out in the De Generatione (ii. i, 15), selecting the
apparent degree in which the instruments of the motor soul are deve-
loped as an example. So also he admits that the test on which he
chiefly relies in that treatise in judging of the heat of animals,^ namely,
the condition in which the young are produced, is not a perfectly sure
one ; other conditions, such as moisture.^ having some influence, and
even caid itself sometimes producing indirectly the same result as heat.*'

But though Aristotle thus refused to accept any one test of excellence
as sufficient, yet it is clear that he held some of his tests to be much
more trustworthy than others. What was wanted was a test that should
gauge the soul. But the soul is incorporate in matter, and such is the
uncertain character of matter that the bodily organs do not always
correspond with perfect strictness to the soul within. This makes it
" impossible to classify by functions common to body and soul." ' As
we can only judge of the soul through the body, every one of the tests
has this failing. This is partly obviated by taking many tests in place
of one, and by selecting those which give most direct information about
the soul, that is to say, with the least implication of matter.

Aristotle divides all terrestrial things into three great primary groups:
|^5)^i''^&s without a soul, i.e. the Inorganic kingdom lYp^things with\ >
a purely nutritive soul, i.e. the Vegetable kingdom ; /Tt/ things with a I
soul that is not only nutritive but sensitive, i.e. the^tnimal kingdom^
These three groups, he says, are not separated from each other by deep-
cut lines of demarcation ; but Nature passes from one to the other so
gradually and imperceptibly that it is sometimes difficult to say under
which heading a given object should be classed.* What group it was
with such dim vestiges of life as to bridge over the interval which
divided plants from the inorganic world, Aristotle does not say. We
may, however, fairly suppose that he had in his mind the Lichens and
the Mosses, of which latter Lord Bacon spoke as interposed between
corruption and life.'' But as to the transition from Plants to Animals he
is more explicit ; placing between them the indiscriminate collection or
organisms, which in after-times were confused together as zoophytes,

' D. P. i. 3, 14. « D. G. ii. I, 23. 3 D G. ii. I, 18. * D. G. i. 10, and i. 11, i.

* D. P. i. 3, 12. « H. An. viii. 1,5; D. P. iv. 5, 42.

' Nov. Organ, xxx. "Moss, which holds a place between putrescence and a plant."
And in another passage, "Moss, which is but a rudiment between putrefaction and
a herb."

XXVI THE MAIN GROUPS OF ANIMALS.

but for which Aristotle had no common name. This group, then, in
which he included Sponges, Sea-anemones, Jelly-fishes, Holothurias,
and Star-fishes, stood at the bottom of his scale of animal life. Their
inferiority was shown by even their common sensibility being so scantily
developed as to become sometimes of doubtful presence, while in none
of them were there any organs whatsoever of higher sense.' None
of them, moreover, possessed organs for active locomotion. Such of
them as changed place at all did so ajt the mercy of the waves and
currents, floating passively about " like plants detached from the soil " ;
to which the rest were more or less permanently fixed. As to the re-
production of these animals Aristotle says but little. He supposed them
to be developed spontaneously,'^ and to be altogether without organs
of generation, a character which, with the absence of a vent and their
simple structure generally, approximated them closely to plants.

From this intermediate group we pass insensibly to true animals, that
is, to organisms whose sensibility is indisputable. These form two ^eat
groups, those that haVjel- blood, and those whose nutritive fluid iS'not
true blood but something '^ analogous to it ; a division which coincides
with the modern one, introduced by Lamarck, into Vertebrata and Inver-
tebrata. To this division of animals, into those with blood and those
without, it is objected that the one group has but a negative character.
The objection is drawn from Aristotle's own quiver, and is equally fatal
to Lamarck's Invertebrata. Aristotle's division may, however, be so
expressed as to avoid this criticism. Animals whose nutritive fluid is
jred, and animals whose nutritive fluid is white or colourless. But to this
again it is objected that some worms have coloured blood, and it may
be added that there is a fish whose blood is colourless. Similarly we
might object to Lamarck's division that there are fishes whose chorda
dorsalis is never replaced by vertebrae. Nomenclature is after all to a
great extent a matter of simple convenience ; and, when a convenient
name has been found for an undoubtedly natural group, exceptional
cases to which it scarcely applies, though they require to be noted, yet
hardly suffice for its displacement. "Vertebrata " will probably be retained
in spite of the exception to its accuracy given above ; nor are we likely to
discard the familiar " Reptilia," though the Pterodactyle flew and though
the Turtles swim. I am by no means sure then that Aristotle would have
abandoned his group-names even had he known of the exceptions to
their accuracy. But did he know of them ? Of the fish with colourless
blood, it need scarcely be said, he was ignorant. But earth-worms can
hardly have escaped his notice. It is strange, however, that he never
makes definite mention of them. It may be, nay probably is, the case,

1 D. P. iv. 5, 43, etc. ^ H. A. v, 15, 21. ' D. G. iv. i. 30 ; D. P. ii. 3, 12.

THE MAIN GROUPS OF ANIMALS. XXVll

that the animals he once ^ alludes to as popularly called " entrails of the
earth " are earth-worms. If so, we have another explanation of his
division. For, sad to say, he thought that these were embryonic forms
of eels, that is, of animals with red blood.

The Bloodless animals are in every respect less perfect than the
Sanguineous, and inferior to them. They are, as a rule, of smaller* size,
and live for a shorter time.' They are colder, as is shown not only by
their want of blood,* but also by the almost universal absence of any
special provision for refrigeration, such as gills and lungs and brain ;
the simple bathing of the surface with_airj)r water sufficing, as a rule,)
to temper their small heat.' Another proof of this cold nature is furnished
by the immature condition in which they produce their young. None
of them deposits a perfect ovum, an ovum, that is, which has attained
its full growth ; but if they produce an ovum at all, it is at best an
imperfect one, an ovum, that is, that increases in size after it is
deposited ; and though this is true of some of the least perfect among
the Sanguineous animals, namely, the scaly fishes, it is true of all the
Bloodless kinds.^

It should be said in explanation of this latter ground of distinction,
that the ova of fishes and mollusca, and other animals that lay their
eggs in water or damp situations, sometimes increase considerably in
size after being deposited. This increase was supposed by Aristotle to
be due to actual growth,'' whereas it is in reality attributable to mere
imbibition of water. This explanation applies to most of his classes
of Bloodless animals, but not to Insects. These he thought produced
something even less mature than the imperfect ovum of the water ,
animal, and to it he gave the name of Scolex. The scolex was distin-
guished from the ovum not only by being less mature, but by being
metamorphosed as a whole into the perfect animal ; and not, as the
true ovum, serving partly for the nourishment of the embryo, partly
for its development. It has been supposed from this that Aristotle had
in some extraordinary way overlooked the eggs of insects, and fancied
that these animals produce primarily grubs or maggots. This, however,
was not so. He says that there are two kinds of scolex, one capable of
motion, in other words a grub or maggot, the other incapable of motion,
and so excessively like an ovum in shape, size, and consistency, as
to be indistinguishable from it, excepting by considering its ulterior
changes.® The insects which produce the moving scolex or grub are

^ D. G. ill. II, 24. Aratus also uses the term "entrails of the earth," apparently in
reference to earth-worms.

- H. A. i. 5, 13 ; De Gen. ii. i, 7. ^ pg Long. V. 4, 2. * D. P. ii. 7, 8.

* Cf. iii. 6, note 3. ' D. G. ii. I, 17, etc.

' So also Pliny, ix. 74 : " piscium ova in mari crescunt, quredam summa celeritate."

* D. G. iii. 9, 5.

XXVIU THE MAIN GROUrS OF ANIMALS.

those viviparous species, in which, as in the flesh-fly, the ovum is
hatched into a grub before being extruded from the parent's body ;
while the ordinary oviparous insects and spiders are those which produce '
the motionless egg-like scolex. Why, however, it will be asked, should
Aristotle have considered the scolex, whether in shape of egg or of
grub, to be more immature than an ovum ? Simply because the con-
dition of scolex was antecedent to and preparatory of the condition of
chrysalis or pupa; and the chrysalis or pupa which neither ate nor
grew, and was the motionless form which immediately gave rise to the
perfect animal,' was supposed by him to correspond to the true ovum
of other animals.^ Though, however, it corresponded to an ovum, it
diff'ered from one because the whole of it was converted by metamor-
phosis into the perfect animal. Still less mature than the scolex was
the generative product of certain T^itacs^. This consisted at most of
a slimy fluid produced asexually, and scarcely diff"ering from the inorganic
mud, which could itself generate these animals spontaneously, though
its power of so doing was somewhat increased by the addition of this
excretion.' The slimy substances to which Aristotle alludes are the
agglutinated egg-masses of Gasteropodous molluscs. Although he failed
to see that these masses consist of a multitude of distinct ova, and are
not a simple homogeneous slime, yet in recognising them as the gene-
rative products of Testacea, he was in advance of the naturalists of the
eighteenth century, who described these egg-masses as distinct species
of animals, and gave them separate names.*

The ova of other Testacea completely escaped Aristotle's observation ;
and he supposed these animals to be generated either spontaneously,
or by budding® from the parent; which is actually true of some of the
animals included by him in the group, but which he also supposed to
be true of the bivalved molluscs, such as Oysters and Mussels, which
live in large communities and are often found adhering to each other's
valves in masses, as though they had budded from each other.*

There was thus a regular' series of gradations in the degree of maturity
reached by the generative product of diff"erent animals at the time of
birth, corresponding generally with similar gradations in the natural

» D. G. iii. 9, 8, 9.

* D. G. ii. I, 25. "The scolex after a time assumes the form of an epg ; for the so-
called chrysalis is equivalent to an egg." And again, iii. 9, 6. "The scolex as it becomes
matured and of larger size invariably at last assumes the condition of an ovum ; for
its outside hardens into a shell, and at this period it becomes motionless. This is readily
seen in the case of bees and wasps, and of caterpillars. The explanation lies herein ; that
the nature of these animals is imperfect, and that their eggs are consequently produced
before the due time, the scolex being as it were an ovum, still soft and in process of growth."

' H. A. V. 15, 3 ; D. G. iii. 11, 12. etc. * Cf. M. Edwards, Le9ons s. 1. Phys. ix. 367.

* D. G. iii. II, 12.

•The spat of oysters was apparently first observed in the time of Pliny. "Nuper
compertum in ostreariis humorem iis fetificum lactis modo effluere." — N. H. ix. 74.
' D. G. ii. I, 23.

THE MAIN GROUPS OF ANIMALS. XXlX

heat of the parents. In only one instance did the two series fail to
coincide, namely, in the case of the ovoviviparous fishes, which exception
is elsewhere explained. Omitting these, the series runs: (i) the fully
developed foetus of Vivipara, i.e. of Mammalia; (2) the perfect ovum of
Birds and Reptiles ; (3) the imperfect ovum of bony Fishes, of Cepha-
lopods, and of Crustacea; (4) the scolex of Insects ; (5) the generative
slime of certain Testacea ; (6) the bud, as in Bivalves, Ascidians, etc. ;
(7) the absence of all generative product and consequently spontaneous
generation, as in all lower groups ; and even occasionally in the higher,
up to Fishes.

The Bloodless aaimals are dijwded by Aristotle »jto four great groups,
thq.'J'^stacea, theilssecta, the vjrustacea, and th^TCIqllusca ' (jidkaKia).
This last group corresponds to the modern Cephalopoda, and in the
following pages will be called by that name, to avoid the confusion into
which we should be led by retaining Aristotle's name Mollusca, this title
having acquired a different significance in modern times. At the bottom
stand the Testacea, in which are included all the modern Mollusca
excepting the Cephalopods, and also the Ascidians and the Echini.
Their inferiority to the rest is shown by their being completely or
almost completely incapable of locomotion ; by their having, that is,
no motor soul, or only dim traces of it ; so that they are repeatedly
spoken of as Sedentary (fiovifia), in opposition to all other true animals,
which are Locomotive (kivtjtiko.)' In this respect they resemble plants
rather than animals, as also they do in many other points, such as the
absence of sexual distinction,^ there being only one species, namely, the
Snails, in which there are any grounds for believing such distinction to
exist ; ' and in their mode of origin. For, like plants, they are generated
either spontaneously, or by budding, or from an excretion produced, like
the vegetable seed, asexually.* So nearly in fact do they resemble plants,
that they seem intended by Nature to occupy in the sea the place which
these occupy on the earth ; so that they may almost be spoken of as
sea-plants, while plants may be similarly looked on as land testacea.*
They graduate insensibly into plants through the Zoophytes ; the Echini
and Ascidians, which are usually reckoned by Aristotle as Testacea in
virtue of their external covering, being sometimes apparently included
by him in the group of Zoophytes. Still further signs of the inferiority

' Aristotle having called these animals Mollusca, because their body consists of an
uniformly soft substance, tries also to define and name the three other groups according to
their consistence. The Ostracoderma [shell-skinned'), or Testacea, were soft within, and
hard without. The Malacostraca {soft- shelled), or Crustacea, were also soft within and
hard without ; but the hardness was that of a crusta, not of a testa. There remained the
Insecta. These, says Aristotle boldly, are uniformly hard throughout. But the statement
is so manifestly untenable, that he does not again insist upon it, nor attempt to give the
group a name expressing so false a notion.

2 D. G. i. 23, 10. 3 D, Q, iii_ 11^ i8_ 4 D Q, iii_ 11^ II, 5 D. g. iii. 11, 5.

XXX

THE MAIN GROUPS OF ANIMALS.

^^

of the Testacea, as compared with animals capable of greater locomo-
tion, are furnished by the simplicity of their structure,* which accords
with the simplicity of their life, and by the absence, or at any rate the
doubtful presence, of the higher_senses, hearing and sight.'^

Next above the Testacea come the segmented animals ot Insecta^^
in which group Aristotle included not only Insecta, Myriapoda, and
Arachnida, but also intestinal parasites, and in fact all such Annulosa
as were known to him, with the exception of Crustacea.

These were suoerior to the Testacea ; in the first place, because they
were capable or tgcomotion ; secondly, because they had afl ^ the five
§fiases ; and thirdly, because they presented generally, though not * in-
variably, distinctions of sex, and reproduced their species by congress.
They were inferior^'EcTTtie' other two groups of bloodless animals in
being occasionally sexless and spontaneously developed ; and in pro-
ducing, when sexual, a less perfect generative product, viz. the Scolex.
They are therefore distinctly stated by Aristotle to be the coldest of all
animals * that give off generative products, that is, of all animals excepting
the Testacea. Their low position in the scale was also shown by their
want of vital centralisation : for after they have been cut into pieces,
each segment continues to live independently for a space, as though
the animal were a plant, or an aggregation of distinct animals united
into a mass. The only reason, says Aristotle, that such a piece does
not live still longer, is that it has not got the necessary organs of
nutrition, such as mouth and the like.® _-*

QLthe two remaining groups of Bloodless animals, the* Crustacea and
thcxTephalopods, it is not so easy to decide which was held by Aristotle
to be the more perfect. In most respects they were on a par ; for in
both the sexes were always distinct, and in both the generative product
was an equally immature ovum. Probably, however, the first place must
be assigned to the Cephalopods, in virtue of the great size to which
they occasionally'' attain, and still more in virtue of their having a
brain,* a mark of superiority distinguishing them from all other bloodless
animals.

We come now to Aristotle's second group, the Sanguineous animals,
the Vertebrata of Lamarck and his successors. These doubtless from
time immemorial have been popularly divided into Beasts, Birds, Reptiles,
and Fishes. Aristotle adopted the popular ' division, in the formation
of which men had been guided by a happy instinct ; and in so doing
he has been followed by all zoologists, until almost in our own day the
Amphibia have been separated from the Reptiles, and made to form a

» D. P. iv. 7, I.
* H. A. iv. II, 4.
' H. A. i. 5, 13.

' H. A. iv. 8, 32.
0 D. G. ii. I, 25.
8 D. P. ii. 7, note 9.

» H. A. iv. 8, 25.

* D. Juvent. 2, 6, etc.

» D. P. i. 3, 14.

THE MAIN GROUPS OF ANIMALS. XXXI

fifth class. First, however, he divided his Sanguineous group into two
subdivisions, the v ivipara and the Ovipara. Of these the Vivipara,
including the biped Man, the quadrupedous Beasts, and the apodous

I Cetacea, were manifestly superior to the Ovipara ; for their more perfect

organs of respiration, and the more mature condition of their young
at birth testified indisputably to their greater heat.

The Ovipara include the Birds, the Reptiles, and the Fishes. Of
these the Fishes were clearly at the bottom. The stunted character of
their external form,' the absence of lungs and the substitution for them

I of an inferior organ of refrigeration, were unmistakable signs of inferiority.

But more than all was this shown by their ovum being deposited in an
imperfect condition. It was true that in one great subdivision of Fishes
the ovum was not so deposited. These fishes were ovoviviparous, that is,
the ovum was hatched inside the body, and in some cases the embryo
even formed a kind of '^ placental attachment to the mother. But, says
Aristotle, such ovoviviparity is not to be taken like viviparity for a sign
of heat. On the contrary, it is a sign of cold. These fishes are of
so cold ^ a nature, that they have not enough heat to harden the outside
of their ovum into a shell. Their egg remains soft ; and if extruded in
this condition would soon be destroyed. It is therefore retained in the
parent's body for security. »,

There remain the Reptiles and the Birds. It is not easy to decide | .
off"hand which of these was held by Aristotle to be the higher in the !
scale. One would have thought that the manifest warmth of the one to
the touch, and equally manifest coldness of the other, would at once
have decided the matter. But, strange as it seems, there is no passage,
so far as I can ascertain, in which Aristotle recognizes this difference.
Yet he had most certainly laid his hand on a living chameleon, and on a
living tortoise, for he describes* their vivisection ; and it is impossible
to imagine that he had never touched a living bird. The explanation, I
think, is to be found in the fact, already stated, that Aristotle drew a wide
distinction between ordinary heat and vital heat; and would not allow that
touch was any measure of the latter. Tried by his main vital standards the
two groups were on a par. Each had red blood ; each breathed b.y a lung,
and in each this lung was of a bladdery and therefore an inferior character.*
In each the sexes were invariably separate. Each was oviparous, and in
each the ovum was a perfect one, that is, had attained its full size at the
time of deposition. The similarity between the ova went moreover still
farther. For in each it consisted of a white part and a yellow part ;

1 D. P. iv. 13, 1.

' D. G. iii. 3, 9. This statement of Aristotle regarding the smooth galeus (Mustelus
Isevis) has been shown by Miiller to be true.

' D. G. i. 10 and 11. * H. A. ii. 11, 11 ; D. Resp. 17, 4.

* Aristotle mistook the bladder-like air-sacs of Birds for their lungs, cf. iii. 6, note 10.

xxxii THE MAIN GROUPS OF ANIMALS.

and in each the embryo was provided not only with an umbilical vesicle,
but also with an allantois.^ In all these characters Birds and Reptiles
resembled each other, and differed from Fishes.'^ The two groups then
were on a par in all their main characters. Still.we may, I think, fairly
assupie that the greaterviy^city of Birds, theiiAapid locomotion, their
mori^ varjed life, and theigcomparatively erect position, as contrasted
with the grovelling attitude of Reptiles, cannot but have led Aristotle
to assign to the former the place of honour. And this accords with
a passage' where he classes animals by the degrees in which the
parental instinct is developed. The purpose of Nature, he says, is to
give such an instinct to all animals. But in the lowest kinds the
instinct ceases to act with the deposition of the eggs. This applies to
the Bloodless animals, and as a rule to Fishes. In the next group the
instinct lasts till the eggs are hatched, and then ceases. This applies
to the Reptiles, whom he describes as laying their eggs on the ground
to be hatched by the heat of the soil, and coming backwards and
forwards at intervals to see that no mischief happens to them. A step
farther and we have animals of higher intelligence, that continue their
care until their young have not only been hatched, but have attained
full growth. Such are the Birds ; and most Mammals. While lastly
come man and some few animals of high intelligence, who retain their
affection for their young throughout life.

Such were the main groups recognised by Aristotle, and such the
order in which he apparently placed them. It would, I think, not be
impossible, nor even very difficult, to apply the same tests to his minor
groups, and arrange these also pretty much in the order in which he
would himself have placed them. The zoophytes, for instance, would
have been classified by him, it may almost be said were * classified by him,
according to their apparent degrees of sensibility, their freedom from
attachment, and generally their less or greater resemblance to plants ;
the fixed sponges with their doubtful signs of feeling being at the
bottom, and the free and more manifestly sensitive star-fishes at the top,
while between them came groups less freely motor than the latter, and
yet more clearly sensitive than the former, which were " in fact virtually
plants, and nothing more"; namely the Holothuriae and Sealungs, which,
though not actually fixed, yet floated at the mercy of the waves like
"detached plants," and were as insensible as sponges, and the Acalephae,
which, though usually attached to the rocks, could, some or all, detach
themselves at will. Of the Testacea, again, we can hardly be wrong in
supposing that Aristotle would have placed the motor, and occasionally

' Cf. iv. 12, note 15. " D. G. iii. I, iii. 2 ; iii. 3.

=» D. G. iii. 2, 14. * D. P. iv. 5.

THE MAIN GROUPS OF ANIMALS. xxxiii

sexual, Turbinata at the top, and the ^ sedentary and asexual Bivalves at
the bottom, while the Univalves or limpets, usually fixed but capable of
locomotipii, would have held the middle place. Xlje greater or less
power of^'ocomotion, the presence or absence of the^'Xiigher senses, the
degrees of vital '^en.trali2ation, of which the number of legs formed a
criterion, and the^ position of.the bady in regard to its elevation above_
the ground, would have given to the subdivisions of his Insecta the
following order : Intestinal worms ; Myriapoda ; Spiders ; Hexapodous
Insects. So we might go on with the other groups. But it is hardly
worth while to do so, seeing what space the necessary collection of
passages would occupy, and how much conjecture after all would have
to be allowed. It will be as well therefore to limit ourselves to the
main groups ; and these may now be presented in the following
tabular form : —

i. Sanguineous Animals [Vertebrata\.

A. Vivipara {Mammalia]. i. Man.

2. Quadrupeds.

3. Cetacea.

B. Ovipara.

a. With perfect ovum. 4. Birds.

5 . Quadrupeds and Apoda {Reptiles and
Amphibia.']
^. With imperfect ovum. 6. Fishes,
ii. Bloodless Animals [Invertebrata].

a. With imperfect ovum. 7. Malacia \Cephalopodf].

8. Malacostraca {Crustacea].
^. With scolex. 9. Insecta {Remaining Arthropoda and

some Vermes^]
7. With generative \

slime ; buds ; f 10. Ostracoderma or Testacea {Mol-
or spontaneous i lusca excepting Cephalopods].

generation. j

S. With spontaneous) r-T- ^i ^ t

generation only.) ^'- l^oophytes.]

^ Or rather "the usually sedentary Bivalves" ; for Aristotle was acquainted with the
peculiar motion of the Scallop, cf. H. A. iv. 4, 8.

XXXV

SYNOPSIS.

Introductory Matter, i. i— i. 5.

i. Scientific methods a part of general education i. i,

ii. The method of biology and questions relating thereto.

a. Whether generic or specific characters should be first considered.

/8. Whether phenomena or their causes should be first considered.

7. The materialistic view of previous writers, and the several meanings

of "necessity."
5. The relative importance of the material and final causes, and the

propriety of taking both into account.
e. The insufficiency of Dichotomy or division by a single diflFerentia,

and the advantages of the natural method or classification by

many differentiae i. 2 — i. 4.

iii. A defence of the study of animal structure, as not ignoble i. 5.

iv. The plan of this treatise to take the parts in succession, and enquire what
share Necessity and the Final Cause respectively have in their formation.

The Three Degrees of Composition ii. i — end of treatise.

i. The mutual relations of the three ii. 1.

ii. The first degree. Physical substances ii. 2 — ii. 3.

2. I/oi and cold. 3. Solid and fluid.

iii. The second degree. Homogeneous parts or tissues ii. 4 — ii. 9.

4. Blood. 5. Fat. 6. Marrow. 7. Brain. 8. Flesh. 9. Bone.

iv. The third degree. Heterogeneous parts or organs ii. 10 — end of treatise.

A. In Sangoineons Animals ii, 10 — iv. 4, and iv. 10 — end of treatise.

a. Organs of the Head ii. lo — iii. 2.

10. Brain and organs of sense. II, 12. Ears. 13, 14, 15. Eye'
lids and Eyelashes. i6. Nostrils, Lips, 1 7. Tongue.
iii. I. Teeth. 2. Horns.

$. Organs of the Neck iii. 3.

3. (Esophagus; Trachea; Epiglottis.

y. Visceral Organs iii. 4 — iii. 13, iv. i — iv. 4.

4. Heart. 5. Blood vessels. 6. Lung. 7. Liver, Spleen.
8. Bladder. 9. Kidneys, 10. Diaphragm. II. Fibrous
membranes. 12. Viscera of different groups compared.
13. Viscera compared -with flesh, iv. i. Peculiarities of
viscera in ovipara, 2. Gall bladder, 3. Omentum.
4. Mesentery.

5. External parts iv. ID — iv. 14.

ID. Invivipara. II, In reptiles. 12. In birds. 13. In flshes
and intermediate groups, cetacea, seals, bats. 14. In the
ostrich,

B. In Bloodless Animals iv, 5 — iv. 9.

a. Internal parts iv. 5.

/3, External parts iv. 6 — iv, 9.

6. In insects. 7. In testacea. 8. In Crustacea, 9. In
cephalopods.

1. I

BOOK I.

(CJi. I.) Every systematic science, the humblest and the noblest
alike, seems to admit of two distinct kinds of proficiency ; one of
which may be properly called scientific knowledge of the subject,
while the other is a kind of ^educational acquaintance with it.
For an educated man should be able to form a fair offhand
judgment as to the goodness or badness of the method used by
a professor in his exposition. To be educated is in fact to be
able to do this ; and even the man of universal education we
deem to be such in virtue of his having this ability. It will,
however, of course, be understood that we only ascribe universal
education to one who in his own individual person is thus critical
in all or nearly all branches of knowledge, and not to one who
has a like ability merely in some special subject. For it is possible
for a man to have this competence in some one branch of know-
ledge without having it in all.^

It is plain then that, as in other sciences, so in that which enquires
into nature, there must be certain canons, by reference to which
a hearer shall be able to criticise the method of a professed expo-
sition, quite independently of the question whether the state-
ments made be true or false. Ought we, for instance, to give an
illustration of what I mean, to begin by discussing the specific
characters of each kind of animal — man, lion, ox, and the like —
and by describing separately the distinctive features of each, or
ought we rather to deal first with the characters which all these
animals have in common, and thus form a basis for the considera-
tion of them separately? For genera ^ that are quite distinct yet
oftentimes resemble each other in many of their phenomena ; in
sleep, for instance, in respiration, in growth, in decay, in death,
639 a. j^

2 1. I.

and in other similar affections and conditions, which may be passed
over for the present, as we are not yet prepared to treat of them
with clearness and precision. Now it is plain that if we discuss
each kind of animal separately, we shall frequently be obliged to
repeat the same statements over and over again ; for horse and dog
and man present, each and all, every one of the phenomena just
enumerated. A discussion therefore of these several animals
separately would necessarily involve frequent repetitions as to
characters, themselves identical, but recurring in animals speci-
fically distinct. (Very possibly also there may be other characters
which, though they present specific differences, yet come under
one and the same category. For instance, flying, walking, swim-
ming, creeping, are plainly specifically distinct, but yet are all
forms of animal progression.) We must, then, have some clear
understanding as to the manner in which our investigation is to
be conducted ; whether, I mean, we are first to deal with the
common or generical characters, and afterwards to take into con-
sideration special peculiarities ; or whether we are to start straight
off with the ultimate species. For as yet no definite rule has been
laid down in this matter. So also there is a like uncertainty as
to another point now to be mentioned. Ought the writer who
deals with the works of nature to follow the plan adopted by
the mathematicians in their astronomical demonstrations, and
after considering the phenomena presented by animals, and their
several parts, proceed subsequently to treat of the causes and the
reason why ; or ought he to follow some other method ? And
when these questions are answered, there yet remains another.
The causes concerned in the generation of the works of nature
are, as we see, more than one. There is the final cause and there
is the motor cause. Now we must decide which of these two
causes ^ comes first, which second. Plainly, however, that cause
is the first which we call the final one. For this is the Reason,
and the Reason forms the starting-point, alike in works of art
and in works of nature. For consider how the physician or how
the builder sets about his work. He starts by forming for himself
a definite picture, in the one case mental, in the other actual, of
his end — the physician of health, the builder of a house — and
this he holds forward as the reason and explanation of each sub-
sequent step that he takes, and of his acting in this or that way
as the case may be. Now in the works of nature the good end
630 b.

1. I. 3

and the final cause is still more dominant than in works of art,
such as these, and necessity is a much less constant factor in their
production ; though it is to this that almost all writers would
seek to refer their origin, though they do not distinguish the
various senses in which the term necessity is used. For there is
absolute necessity, manifested in eternal phenomena ; and there
is hypothetical necessity, manifested in everything that is
generated by nature as in everything that is produced by art,
be it a house or what it may. For if a house or other such
final object is to be realised, it is necessary that such and such
material shall exist ; and it is necessary that first this and then
that shall be produced, and first this and then that set in motion,
and so on in continuous succession, until the end and final result
is reached, for the sake of which each prior thing is produced and
exists. As with these productions of art, so also is it with the
productions of nature. The mode of necessity, however, and the
mode of ratiocination are different in natural science [and in art]
from what they are in the theoretical sciences ;* of which we have
spoken elsewhere. For in the latter the starting-point is that
which is ; in the former that which is to be. For it is that which
is yet to be — health, let us say, or a man — which, owing to its
being of such and such characters, necessitates the pre-existence
or previous production of this and that antecedent ; and not this
or that antecedent which, because it exists or is generated, makes
it necessary that health or a man shall come into existence. Nor
is it possible to trace back the series of necessary antecedents to
a starting-point, of which you can say that, existing itself from
eternity, it has determined their existence as its consequent.
These, however, again are matters that have been dealt with in
another treatise. There too it was stated in what cases absolute
and hypothetical necessity exist ; in what cases also the propo-
sition expressing hypothetical necessity is simply convertible, and
what cause it is that determines this convertibility.^

Another matter which must not be passed over without con-
sideration is, whether the proper subject of our exposition is that
with which the ancient writers concerned themselves, namely, what
is the process of formation of each animal; or whether it is not
rather, what are the characters of a given creature when formed.
For there is no small difference between these two views.^ The
best course appears to be that we should follow the method
640 a.

4 1. I.

already mentioned, and begin with the phenomena presented by-
each group of animals, and, when this is done, proceed afterwards
to state the causes of those phenomena, and to deal with their
evolution. For elsewhere, as for instance in house building, this
is the true sequence. The plan of the house, or the house, has
this and that features ; and because it has this and that features,
therefore is its construction carried out in this or that manner.
For the process of evolution is for the sake of the thing finally
evolved, and not this for the sake of the process. Empedocles,
then, was in error when he said that many of the characters pre-
sented by animals were merely the results of incidental occurrences
during their development ; for instance, that the backbone was
divided as it is into vertebrae, because it happened to be broken
owing to the contorted position of the foetus in the womb.^ In
so saying he overlooked the fact that propagation implies a creative
seed endowed with certain formative properties. Secondly, he
neglected another fact, namely, that the parent animal pre-exists,
not only in idea, but actually in time. For man is generated from
man ; and thus it is the possession of certain characters by the
parent that determines the development of like characters in the
child. The same statement^ [namely, that the process of pro-
duction occurs for the sake of the thing produced] holds good
also for the operations of art, and even for those which are appa-
rently spontaneous. For the same result as is commonly produced
only by art may sometimes occur spontaneously. Spontaneity,
for instance, may do the work of the physician and bring about
the restoration of health. As a general rule, however, the pro-
ducts of art are such as cannot possibly be produced spontaneously;
for they require the pre-existence of an efficient cause homogeneous
with themselves, such as the statuary's art which must necessarily
precede the statue ; art indeed consisting in the conception of
the result to be produced before its realisation in the material.
%\s with spontaneity,^ so with chance ; for this also occasionally
produces the same result as art, and by the same process of
evolution.

The fittest mode, then, of treatment is to say, a man has such
and such parts, because the conception of a man includes their
presence, and because they are necessary conditions of his exist-
ence, or at any rate of his perfection ; and these conditions in
their turn imply other prior conditions. Thus we should say,
640 b.

i. I. 5

because man is an animal with such and such characters, therefore
is the process of his development necessarily such as it is ; and
therefore is it accomplished in such and such an order, this part
being formed first, that next, and so on in succession ; and after
a like fashion should we explain the evolution of all other works
of nature.

Now that with which the ancient writers, who first philosophised
about Nature, busied themselves, was the material principle and
the material cause. They enquired what this is, and what its
character ; how the universe is generated out of it, and by what
motor influence, whether, for instance, by antagonism or friendship,
whether by intelligence or spontaneous action,'*' the substratum of
matter being assumed to have certain inseparable properties ;
fire, for instance, to have a hot nature, earth a cold one ; the former
to be light, the latter heavy. For even the genesis of the universe
is thus explained by them. After a like fashion do they deal also
with the development of plants and of animals. They say, for
instance, that the water contained in the body causes by its
currents '^ the formation of the stomach and the other receptacles
of food or of excretion ; and that the breath by its passage breaks
open the outlets of the nostrils ; air and water being the materials
of which bodies are made ; for all represent nature as composed
of such or similar substances.

But if men and animals and their several parts are natural
phenomena, then the natural philosopher must take into con-
sideration [not merely the ultimate substances of which they are
made, but also] flesh, blood, bone, and all the other homogeneous
parts ; '^ nor only these, but also the heterogeneous parts, such as
face, hand, foot, and the like ; and must examine how each of these
comes' to be what it is, and in virtue of what force. For to say
what are the ultimate substances out of which an animal is formed,
to state, for instance, that it is made of fire and water, is no more
sufficient, than would be a similar account in the case of an
inanimate object, such as a couch or the like. For we should not
be content with saying that the couch was made of bronze or'
wood or whatever it might be, but should try to describe its
design or mode of composition in preference to the material ; or,
if we did deal with the material, it would at any rate be with
the concretion of material and form. For a couch is such and
such a form of this or that matter, or such and such a matter
640 b.

O 1. I.

with this or that form ; so that its shape and structure must be
included in our description. For the formal nature is of much
greater importance than the material nature.

Does, then, configuration and colour constitute the essence of
the various animals and of their several parts ? P^or if so, what
Democritus says will be strictly correct. For such appears to
have been his notion. At any rate he says that it is evident to
every one what form it is that makes the man ; as if man were
constituted by a certain recognisable shape and colour. And yet
a dead body has exactly the same configuration as a living one ;
but for all that is not a man. So also no hand of bronze or wood
or of any but the appropriate materials can possibly be a hand
in more than name. For like a physician in a painting, or like
a flute in a sculpture, in spite of its name, it will be unable to do
the office which that name implies. Precisely in the same way
no part of a dead body, such I mean as its eye or its foot, is
really an eye or a foot. To say, then, that shape and colour
constitute the animal is an inadequate statement, and is much
the same as if a woodcarver were to insist that the hand he
had cut out was really a hand. Yet the physiologists, when
they give an account of the development and causes of the
animal form, speak very much like such a craftsman. What,
however, I would ask, are the forces by which the hand or the
body was fashioned into its shape ? The woodcarver will perhaps
say, by the axe or the auger ; the physiologist, by air and by
earth. Of these two answers the artificer's is the better, but it
is nevertheless insufficient.^^ For it is not enough for him to say
that by the stroke of his tool this part was formed into a con-
cavity, that into a flat surface ; but he must state the reasons
why he struck his blow in such a way as to effect this, and what
his final object was; namely, that the piece of wood should develop
eventually into this or that shape. It is plain, then, that the
teaching of the old physiologists is inadequate, and that the
true method is to state what the definitive characters are that dis-
tinguish the animal as a whole ; to explain what it is both in
substance and in form, and to deal after the same fashion with
its several organs ; in fact, to proceed in exactly the same way
as we should do, were we giving a complete description of a couch.

If now this something that constitutes the form of the living
being be the souV* or part of the soul, or something that without
641a.

1. I. ' 7

the soul cannot exist; as would seem to be the case, seeing at
any rate that when the soul departs, what is left is no longer a
living animal, and that none of the parts remain what they were
before, excepting in mere configuration, like the animals that in
the fable are turned into stone ; if, I say, this be so, then it will
come within the province of the natural philosopher to inform
himself concerning the soul, and to treat of it, either in its entirety,
or, at any rate, of that part of it which constitutes the essential
character of an animal ; and it will be his duty to say what this
soul or this part of a soul is ; and to discuss the attributes that
attach to this essential character. Again, nature is spoken of in
two senses, and the nature of a thing is either its matter or its
essence ; nature as essence including both the motor cause and
the final cause.i'^ Now it is in the latter of these two senses that
either the whole soul or some part of it constitutes the nature of
an animal ; and inasmuch as it is the presence of the soul that
enables matter to constitute the animal nature, much more than
it is the presence of matter which so enables the soul, the enquirer
into nature is bound on every ground to treat of the soul rather
than of the matter. For though the wood of which they are made
constitutes the couch and the tripod, it only does so because it is
capable of receiving such and such a form.

So far as has yet been said it remains a debatable question,
whether it is the whole soul or only some part of it, the considera-
tion of which comes within the province of natural science. Now
if it be of the whole soul that this should treat, then there is no
place for any other philosophy beside it. For as it belongs in all
cases to one and the same science to deal with correlated subjects
— one and the same science, for instance, deals with sensation and
with the objects of sense — and as therefore the intelligent soul
and the objects of intellect, being correlated, must belong to one
and the same science, it follows that natural science will have to
include the whole universe in its province. But perhaps it is not
the whole soul, nor all its parts collectively, that constitutes the
source of motion ; but there may be one part, identical with that
in plants, which is the source of [change of quantity or] growth,
another which is the source of feeling or change of quality, while
still another, and this not the intellectual part, is the source of
[change of place or] locomotion.^^ I say not the intellectual part ;
for other animals than man have the power of locomotion, but
641b.

« 1. I.

in none but him is there intellect. Thus then it is plain that it
is not of the whole soul that we have to treat. For it is not the
whole soul that constitutes the animal nature, but only some part
or parts of it.^' Moreover, it is impossible that any abstraction^®
can form a subject of natural science, seeing that everything that
Nature makes is means to an end. For just as human creations
are the products of art, so living objects are manifestly the products
of an analogous cause or principle, not external but internal,^^
derived like the hot and the cold [and the other material elements
of our bodies] from the environing universe.^" And that the heaven,
if it had an origin,^^ was evolved by such a cause, there is even
more reason to believe, than that mortal animals so originated.
For order and arrangement and constancy are much more plainly
manifest in the celestial bodies than in our own frame ; while
change and chance are characteristic of the perishable things of
earth. Yet there are some who, while they allow that animals
were all generated by nature, nevertheless hold that the heaven
was constructed to be what it is by chance and spontaneity ; the
heaven, in which not the faintest sign of hap-hazard or of disorder
is discernible ! ^^ Again, whenever there is plainly some final end,
to which a motion tends, should nothing stand in the way, we
always say that such final end is the aim or purpose of the motion ;
and from this it is evident that there must be a something or
other really existing, corresponding to what we call by the name
of Nature. For a given germ does not give rise to any chance
living being, nor spring from any chance one ; but each germ
springs from a definite parent and gives rise to a definite progeny.
And thus it is the germ that is the ruling influence and fabricator
of the offspring ; for the offspring is that which in the course of
nature will spring from it. At the same time [in the order of
thought] the offspring is anterior to the germ ; for germ and
perfected progeny are related as the developmental process and
the result, [and result is in thought anterior to evolution]. An-
terior, however, to both germ and product is the organism from
which the germ was derived. For every germ connotes two
organisms, the parent and the progeny. For germ or seed is
both the seed of the organism from which it came, of the horse,
for instance, from which it was derived, and the seed of the
organism that will eventually arise from it, of the mule, for
example, which is developed from the seed of the horse. The
641b.

1. I.

same seed then is the seed both of the horse and of the mule,
though in different ways. Moreover, the seed is potentially that
which will spring from it, and the relation of potentiality to
actuality we know [to be that of consequent to antecedent].^^

There are then two causes, namely, necessity and the final end.
For many things are produced, simply as the results of necessity.
It may, however, be asked, of what mode of necessity ^* are we
speaking when we say this. For it can be of neither of those
two modes which are set forth in the philosophical treatises.-'^
There is, however, the third mode, in such things at any rate as are
generated. For instance, we say that food is necessary ; because
an animal cannot possibly do without it. This third mode is what
may be called hypothetical necessity. Here is another example
of it. If a piece of wood is to be split with an axe, the axe must
of necessity be hard ; and, if hard, must of necessity be made of
iron, or bronze, or the like. Now exactly in the same way the
body, which like the axe is an instrument — for both the body
as a whole and its several parts individually have definite opera-
tions for which they are made — ^just in the same way, I say, the
body, if it is to do its work, must of necessity be of such and
such a character, and made of such and such materials.

There are then, as before said, two modes of causation, and both
of these must, so far as possible, be taken into account in explain-
ing the works of nature.^^ At any rate it is plain that an attempt
must be made to include them both ; and that those who fail in
this tell us in reality nothing about nature. For the main factor
in the nature of an animal is much more the final cause than
the necessary material. There are indeed passages in which even
Empedocles hits upon this, and following the guidance of fact,
finds himself constrained to speak of the final cause as constituting
the essence and real nature of things. Such, for instance, is the
case when he explains what is a bone. For he does not merely
describe its material, and say it is this one element, or those two
or three elements, or a compound of all the elements, but states the
law or plan of their combination, and takes this to constitute the
bone. As with a bone, so manifestly is it with the flesh and all
other similar parts.

The reason why our predecessors failed in hitting upon this
method of treatment was, that they were not in possession of the
notion of formal cause, nor of any definition of essence.^''' The
642 a.

10 1. I — i. 2.

first who came near it was Democritus, and he was far from
adopting- it as a necessary method in natural science, but was
merely brought to it, spite of himself, by constraint of facts. In
the time of Socrates a nearer approach was made to the method.
But at this period men gave up enquiring into the works of
nature, and philosophers diverted their attention to political
science and to the virtues which benefit mankind.

Of the method itself the following is an example. In dealing
with respiration we must show 'that it takes place for such or
such a final object ; and we must also show that this and that
part of the process is necessitated by this and that other stage
of it. By necessity we shall sometimes mean hypothetical neces-
sity, the necessity, that is, that the requisite antecedents shall be
there, if the final end is to be reached ; and sometimes abso-
lute necessity, such necessity as that between substances and their
inherent properties and characters. Thus it is necessary [if we
are to live] that there shall be alternating discharges and returns
of heat from and to the body, and a necessary condition for this
is the inflow of air. Here at once we have a necessity [in the
former of the two senses]. But the reduction of the internal heat by
refrigeration produces [as a necessary result] the outflow of the
air, while vice versd the reduction of the cold by the internal
heat produces an inflow. [This is a necessity in the second of
the two senses.] ^^

In the foregoing we have an example of the method which we
must adopt, and also an example of the kind of phenomena, the
causes of which we have to investigate.

(Ch. 2.) Some ^ writers propose to reach the definitions of the
ultimate forms of animal life by bipartite division. But this
method is often difficult, and often impracticable.

Sometimes the final differentia of the subdivision is sufficient
by itself and the antecedent differentiae are mere surplusage.
Thus in the series Footed, Two-footed, Cloven-footed,^ the last
term is all-expressive by itself, and to append the higher terms
is only an idle iteration.

Again it is not permissible to break up a natural group, Birds
for instance, by putting its members under different bifurcations,
as is done in the published dichotomies, where some birds are
ranked with Animals of the water, and others with Animals of the
air. The group Birds and the group Fishes happen to be named,
642b.

i. 2—1. 3. 1 1

while other natural groups have no popular names ; for instance
the groups that we may call Sanguineous and Exsanguineous are
not known popularly by any designations. If such natural groups
are not to be broken up, the method of Dichotomy cannot be
employed, for it necessarily involves such breaking up and disloca-
tion. The group of the Many-footed, for instance, would, under
this method, have to be dismembered, and some of its kinds
distributed among land animals, others among water animals.^

(Ch. 3.J Again privative terms inevitably form one branch of
dichotomous division, as we see in the proposed dichotomies. But
privative terms in their character of privatives admit of no
subdivision. For there can be no specific forms of what is non-
existent, of Featherless for instance or of Footless, as there are
of Feathered and of Footed. Yet a generic differentia must be
subdivisible ; for otherwise what is there that makes it generic
rather than specific ? There are to be found generic, that
is specifically subdivisible, differentiae ; Feathered for instance
and Footed. For feathers are divisible into Barbed and Un-
barbed, and feet into Many cleft, like those of a bird, or Two-
cleft, like those of an ox, or Uncloven and Undivided, like those
of a horse. Now even with differentiae capable of this specific
subdivision it is difficult enough so to make the classification, as
that each animal shall be comprehended in some one subdivision
and in not more than one ; but far more difficult, nay impos-
sible, is it to do this, if we start with a dichotomy into two
contradictories. (Suppose for instance we start with the two
contradictories. Feathered and Unfeathered ;^ we shall find that
the ant, the glow-worm and some other animals fall under both
divisions.) For each differentia must be presented by some
species. There must be some species, therefore, under the privative
heading. Now specifically distinct animals cannot present in their
essence a common undifferentiated element, but any apparently
common element must really be differentiated. (Bird and Man
for instance are both Two-footed, but their two-footedness is
diverse and differentiated. So any two sanguineous groups must
have some difference in their blood, if their blood is part of
their essence.) From this it follows that a privative term, being
insusceptible of differentiation, cannot be a generic differentia ;
for, if it were, there would be a common undifferentiated element

in two different groups.^
643 a.

12 1. 3.

Again, if the species are ultimate indivisible groups, that is,
are groups with indivisible differentiae, and if no differentia be
common to several groups, the number of differentiae must be
equal to the number of species. If a differentia though not
divisible could yet be common to several groups, then it is
plain that in virtue of that common differentia specifically dis-
tinct animals would fall into the same division. It is necessary
then that none of the differentiae that belong to the ultimate or
indivisible groups shall be common ; for otherwise, as already
said, specifically distinct animals will come into one and the
same division. But this would violate one of the requisite
conditions, which are as follows. No ultimate group must be
included in more than a single division ; different groups must
not be included in the same division ; and every group must be
found in some division. It is plain then that we cannot get at
the ultimate specific forms of the animal, or any other, kingdom
by bifurcate division. If we could, the number of ultimate
differentiae would equal the number of ultimate animal forms,
[which is inconceivable]. For assume an order of beings whose
prime differentiae are White and Black, Each of these branches
will bifurcate, and their branches again, and so on till we reach
the ultimate differentiae, whose number will be four or some
other multiple of two, and will also be the number of the
ultimate species comprehended in the order.

(A species is constituted by the combination of differentia and
matter. For no animal, nor portion of an animal, is purely
material or purely immaterial, in other words purely corporeal or
purely incorporeal, as repeatedly observed.)

Further the differentiae must be elements of the essence, and
not merely properties or attributes. Thus if Figure is the
term to be divided, it must not be divided into figures whose
angles are equal to two right angles, and figures whose angles
are together greater than two right angles. For it is only an
attribute of a triangle and not part of its essence that its angles
are equal to two right angles.

Again the bifurcations must be contradictories, like White and
Black, Straight and Bent ; and if we characterize one branch by
either term, we must characterize the other by its opposite, and
not, for example, characterize one branch by a colour, the other
by a mode of progression, swimming for instance.
643 a.

Furthermore living beings [cannot be divided] by the functions
common to body and soul, by Flying, for instance, and Walking,
as we see them divided in the current dichotomies. For some
groups, Ants for instance, fall under both divisions, some ants
flying while others do not. Similarly the division into Wild and
Tame [must be rejected] ; as it also would involve the disruption
of a species into different groups. For in almost all species in
which some members are tame, there are other members that
are wild. Such for example is the case with Men, Horses,
Oxen, Dogs in India,' Pigs, Goats, Sheep ; groups which, if
double, ought to have what they have not, namely, different
appellations ; and which, if single, prove that Wildness and
Tameness do not amount to specific differences. And whatever
single element we take as a basis of division the same difficulty
will occur.

The method then that we must adopt is to attempt to recog-
nise the natural groups, following the indications afforded by the
instincts of mankind, which led them for instance to form the
class of Birds and the class of Fishes, each of which groups
combines a multitude of differentiae, and is not defined by a
single one as in dichotomy. The method of dichotomy is either
impossible (for it would put a single group under different
divisions or dissimilar groups under the same division) ; or it
only furnishes a single ultimate differentia for each species, which
either alone or with its series of antecedents has to constitute
the whole essence.

If, again, a new differential character be introduced at any
stage into the division, the necessary result is that the unity of
the whole, and the continuity of the division, become merely a
unity and continuity of agglomeration, like the unity and con-
tinuity of a series of sentences coupled together by conjunc-
tive particles. For instance, suppose we have the bifurcation
Feathered and Featherless, and then divide Feathered into Wild
and Tame, or into White and Black. Tame and White have no
essential relation to Feathered, but are the commencement of
an independent bifurcation, and are foreign to the series at the
end of which they are introduced.

As we said then, we must define at the outset by a multi-
plicity of differentiae. If we do so, privative terms will be
available, which are unavailable to the dichotomist.
643 b.

14 1. 3—1- 4-

The impossibility of reaching the definition of any of the
ultimate forms by dichotomy of the larger group, as some '
propose, is manifest also from the following considerations. It
is impossible that a single differentia, either by itself or with its
antecedents, shall express the whole essence of a species. (In
saying a single differentia by itself I mean such an isolated
differentia as Cloven-footed ; in saying a single differentia with
its antecedents I mean such a series as Footed, Two-footed,
Cloven-footed. The very continuity of such a series of succes-
sive differentiae in a division is intended to show that it is their
combination that expresses the character of the resulting unit,
or ultimate group. But one is misled by the usages of language
into imagining that it is merely the final term of the series,
Cloven-footed for instance, that constitutes the whole differentia,
and that the antecedent terms, Footed, Two-footed, are super-
fluous. Now it is evident that such a series cannot consist of
many terms. For if one divides and subdivides, one soon reaches
the final differential term ; but for all that, one* has not got to
the ultimate division, that is, to the species.) No single dif-
ferentia, I repeat, either by itself or with its antecedents, can
possibly express the essence of a species. Suppose, for example,
Man to be the animal to be defined ; the single differentia will be
Cloven-footed, either by itself or with its antecedents, Footed and
Two-footed. Now if man was nothing more than a Cloven-footed
animal, this single differentia would duly represent his essence.
But seeing that this is not the case, more differentiae than this
one will necessarily be required to define him ; and these cannot
come under one division ; for each single branch of a dichotomy
ends in a single differentia, and cannot possibly include several
differentiae belonging to one and the same animal.

It is impossible then to reach any of the ultimate animal
forms by dichotomous division.

(Ch. 4.) It deserves inquiry why a single name denoting a single
group was not invented by mankind, as an appellation to com-
prehend the two groups of Water animals and Winged animals.
For there are certain attributes common to the two ^ and
[differentiating them from] the rest of the animal kingdom.
However, the present nomenclature is just. Groups that only
differ in degree, and in the more or less of an identical element
that they possess, are aggregated under a single class ; groups
644 a.

1.4. 15

whose attributes are not identical but analogous are separated.
For instance bird differs from bird by gradation, or by excess
and defect ; some birds have long feathers, others short ones,
but all are feathered. Bird and Fish are more remote and only
agree in having analogous organs ; for what in the bird is
feather, in the fish is scale. Such analogies can scarcely how-
ever serve universally as indications for the formation of groups,
for almost all animals present analogies in their corresponding
parts.

The individuals comprised within a species, such as Socrates
and Coriscus, are the real existences ; but inasmuch as these
individuals possess one common specific form, it will suffice to
state the universal attributes of the species, that is, the attributes
common to all its individuals, once for all, as otherwise there will
be endless reiteration, as has already been pointed out.

But as regards the larger groups — such as Birds — which com-
prehend many species, there may be a question. For on the one
hand it may be urged that as the ultimate species represent the
real existences, it will be well, if practicable, to examine these
ultimate species separately, just as we examine the species Man
separately; to examine, that is, not the whole class Birds col-
lectively, but the Ostrich, the Crane, and the other indivisible
groups or species belonging to the class.

On the other hand, however, this course would involve repeated
mention of the same attribute, as the same attribute is common
to many species, and so far would be irrational and tedious.
Perhaps, then, it will be best to treat generically the universal
attributes of the groups that have a common nature and contain
closely allied subordinate forms, whether they are groups recognised
by a true instinct of mankind, such as Birds and Fishes, or groups
not popularly known by a common appellation, but withal com-
posed of closely allied subordinate groups ; and only to deal
individually with the attributes of a single species, when such
species — man, for instance, and any other such, if such there be —
stands apart from others, and does not constitute with them a
larger natural group.

It is generally similarity in the shape of particular organs, or of

the whole body, that has determined the formation of the larger

groups. It is in virtue of such a similarity that Birds, Fishes,

Cephalopoda, and Testacea have been made to form each a

644 b.

i6 i. 4— i. 5.

separate class. In their respective subdivisions the organs are not
merely analogous, as the bone of man and the spine of fish, but •
are identical, with the exception of certain corporeal differentiations
in respect of largeness smallness, hardness softness, smoothness
roughness, and other oppositions of this kind, and, in one word, in
respect of degree.

We have now touched upon the canons for criticising the method
of natural science, and have considered what is the most systematic
and easy course of investigation ; we have also dealt with division,
and the mode of conducting it so as best to attain the ends of
science, and have shown how dichotomy is either impracticable or
inefficacious for its professed purposes.

Having laid this foundation, we proceed to the next topic, and
by way of introduction we observe, that (Ch. 5J some members
of the universe are ungenerated, imperishable, and eternal, while
others are subject to generation and decay. The former are
excellent beyond compare and divine, but less accessible to know-
ledge. The evidence that might throw light on them, and on
the problems which we long to solve respecting them, is furnished
but scantily by sensation ; whereas respecting perishable plants
and animals we have abundant information, living as we do in
their midst, and ample data may be collected concerning all
their various kinds, if only we are willing to take sufficient pains.
Both departments, however, have their special charm. The scanty
conceptions to which we can attain of celestial things give us,
from their excellence, more pleasure than all our knowledge of
the world in which we live ; just as a half glimpse of persons that
we love is more delightful than a leisurely view of other things,
whatever their number and dimensions. On the other hand, in
certitude and in completeness our knowledge of terrestrial things
has the advantage. Moreover, their greater nearness and affinity
to us balances somewhat the loftier interest of the heavenly things
that are the objects of the higher philosophy. Having already
treated of the celestial world, as far as our conjectures could reach,
we proceed to treat of animals, without omitting, to the best of our
ability, any member of the kingdom, however ignoble. For if some
have no graces to charm the sense, yet even these, by disclosing to
intellectual perception the artistic spirit that designed them, give
immense pleasure to all who can trace links of causation, and are
inclined to philosophy. Indeed, it would be strange if mimic
645 a.

1. 5. 17

representations of them were attractive, because they disclose the
mimetic skill of the painter or sculptor, and the original realities
themselves were not more interesting, to all at any rate who have
eyes to discern the reason that presided over their formation.
We therefore must not recoil with childish aversion from the
examination of the humbler animals. Every realm of nature is
marvellous : and as Heraclitus, when the strangers who came to
visit him found him warming himself at the furnace in the kitchen,
is reported to have bidden them not to be afraid to enter, as even
in that kitchen divinities were present, so we should venture on the
study of every kind of animal without distaste ; for each and all will
reveal to us something natural and something beautiful. Absence
of hap-hazard and conduciveness of everything to an end are to be
found in Nature's works in the highest degree, and the resultant
end of her generations and combinations is a form of the beautiful.

If any person thinks the examination of the rest of the animal
kingdom an unworthy task, he must hold in like disesteem the
study of man. For no one can look at the primordia of the
human frame — blood, flesh, bones, vessels, and the like — without
much repugnance.^ Moreover, in every inquiry, the examination
of material elements and instruments is not to be regarded as
final, but as ancillary to the conception of the total form. Thus
the true object of architecture is not bricks mortar or timber,
but the house ; and so the principal object of natural philosophy
is not the material elements, but their composition, and the totality
of the form to which they are subservient, and independently of
which they have no existence.

The course of exposition must be first to state the attributes
common to whole groups of animals, and then to attempt to
give their explanation. Many groups, as already noticed, present
absolutely common attributes, that is to say, absolutely identical
affections, and absolutely identical organs, feet, feathers, scales, and
the like ; while in other groups the affections and organs are
only so far identical as that they are analogous. For instance,
some groups have lungs, others have no lung, but an organ
analogous to a lung in its place ; some have blood, others have
no blood, but a fluid analogous to blood, and with the same
office. To treat of the common attributes in connexion with each
individual group would involve, as already suggested, useless
iteration. So much for this topic.

645 b. 2

i8 i. 5.

As every instrument and every bodily member subserves some
partial end, that is to say, some special action, so the whole body
must be destined to minister to some plenary sphere of action.
Thus the saw is made for sawing, for this is its function, and not
sawing for the saw. Similarly the body too must somehow or
other be made for the soul, and each part of it for some sub-
ordinate function, to which it is adapted.

We have, then, first to describe the common functions, common,
that is, to the whole animal kingdom, or to certain large groups,
or to the members of a species. In other words, we have to
describe the attributes common to all animals, or to assemblages,
like the class of Birds, of closely allied groups differentiated by
gradation, or to groups like Man not differentiated into subordinate
groups. In the first case the common attributes may be called
analogous, in the second generic, in the third specific.

When a function is ancillary to another, a like relation mani-
festly obtains between the organs which discharge these functions ;
and similarly if one function is the end of another, their respective
organs will stand to each other in the same relation. Other
phenomena there are that are [neither ancillary to higher ones,
nor the end of lower ones, but] the inevitable results of the
existing conditions [under which the animal is living].

Instances of what I mean by functions and affections are Re-
production, Growth, Copulation, Waking, Sleep, Locomotion, and
other similar vital actions. Instances of what I mean by parts are
Nose, Eye, Face, and other so-called members or limbs, and also
the more elementary parts of which these are made. So much
for the method to be pursued. Let us now try to set forth the
causes of all vital phenomena, whether universal or particular, and
in so doing let us follow that order of exposition, which conforms,
as we have indicated, to the order of nature.

646 a.

ii. I. 19

BOOK II.

(Ch. I.) The nature and the number of the parts of which
animals are severally composed are matters which have already
been set forth in detail in the book of Researches about Animals.^
We have now to inquire what are the causes that in each case
have determined this composition ; a subject reserved by us for
separate consideration.

Now there are three degrees of composition ; and of these the
first in order, as all will allow, is composition out of what some
call the elements, such ^ as air, earth, water, fire. Perhaps however
it would be more accurate to say composition out of the elementary
forces ; ' nor indeed out of all of these, but out of a limited number
of them, as defined in previous treatises. For fluid and solid, hot
and cold, form the material of all composite substances ; * and all
other differences are secondary to these, such differences, that is,
as heaviness or lightness, density or rarity, roughness or smooth-
ness, and any other such properties of matter as there may be.
The second degree of composition is that by which the homo-
geneous parts of animals, such as bone, flesh, and the like, are
constituted out of the primary substances. The third and last
stage is the composition which forms the heterogeneous parts, such
as face, hand, and the rest.^

Now the order of actual development and the order of logical
existence are always the inverse of each other. For that which
is antecedent in the true order of nature is posterior in the order
of development, and that is genetically last which is logically first.
(That this is so is manifest by induction. For a house does not
exist for the sake of bricks and stones, but these materials for the
646 a.

20 ii. I.

sake of the house ; and the same is the case with the materials
of other bodies. For generation is a process from a something t6
a something ; that which is generated having a cause in which it
originates and a cause in which it ends. The originating cause is
the primary efficient cause, which is something already endowed
with tangible existence, while the final cause is some definite [and
predictable] form ; for man generates man, and plant generates
plant, and in each case out of the material which environs both.)^
In order of time then the material and the generative process
must necessarily be anterior to the being that is generated ; but
in logical order the definitive character and form of each being
precedes the material. This is evident if one only tries to define
the process of formation. For the definition of house-building
includes and presupposes that of the house ; but the definition of
the house does not include nor presuppose that of house-building ;
and the same is true of all other productions. So that it must
necessarily be that the elementary material exists for the sake
of the homogeneous parts, seeing that these are genetically
posterior to it, just as the heterogeneous parts are posterior
genetically to them.'' For these heterogeneous parts have reached
the end and goal, having the third degree of composition, in
which degree generation or development often attains its final
term.^

Animals then are composed of homogeneous parts, and are also
composed of heterogeneous parts. The former however exist for
the sake of the latter.^ For the active functions and operations
of the body are carried on by these ; that is, by the heterogeneous
parts, such as the eye, the nostril, the whole face, the fingers, the
hand, and the whole arm. But inasmuch as there is a great
variety in the functions and motions not only of aggregate animals
but also of the individual organs, it is necessary that the sub-
stances out of which these are composed shall present a diversity
of properties. For some purposes softness is advantageous, for
others hardness ; some parts must be capable of extension, others
of flexion. Such properties then are distributed separately to the
different homogeneous parts, one being soft another hard, one
fluid another solid, one viscous another brittle ; whereas each of
the heterogeneous parts presents a combination of multifarious
properties. For the hand, to take an example, requires one
property to enable it to effect pressure, and another and different
646 b.

11. I. 21

property for simple prehension.^o For this reason the active or
executive parts of the body are compounded out of bones, sinews,
flesh, and the like, but not these latter out of the former.

So far, then, as has yet been stated, the relations between these
two orders of parts are determined by a final cause. We have
however to inquire whether necessity may not also have a share
in the matter ; and it must be admitted that these mutual relations
could not from the very beginning have possibly been other than
they are. For heterogeneous parts can be made up out of homo-
geneous parts, either from a plurality of them, or from a single
one, as is the case with some of the viscera, which varying in
configuration are yet, to speak broadly, formed from a single
homogeneous substance ; but that homogeneous substances should
be formed out of a combination of heterogeneous parts is clearly
an impossibility. For these causes, then, some parts of animals are
simple and homogeneous, while others are composite and hetero-
geneous ; and dividing the parts into the active or executive
and the sensitive, each one of the former is, as before said, hetero-
geneous, and each one of the latter homogeneous. For it is in
homogeneous parts alone that sensation can occur, as the following
considerations show.

Each sense is confined to a single kind or order of sensibles,
and its organ must therefore be such as to admit the action of
that kind, and [of no other. It must therefore have the properties
of that kind and of no other ; for] that which is endowed with
a property in posse is acted upon by that which has the like
property in esse}^ The one-ness of its sensibles implies then the
one-ness or homogeneity of the sense-organ. Thus it is that while
no physiologists ever dream of saying of the hand or face or other
such part that one is earth, another water, another fire, they couple
each separate sense-organ with a separate element, asserting this
one to be air and that other to be fire.'^

Sensation then is confined to the simple or homogeneous parts.
But, as might reasonably be expected, the organ of touch, though
still homogeneous, is yet the least simple of all the sense-organs.
For touch more than any other sense appears to be correlated to
several distinct kinds of objects, and to recognise more than one
category of contrasts, heat and cold, for instance, solidity and
fluidity, and other similar oppositions.^^ Accordingly the organ
which deals with these varied objects is of all the sense-organs
647 a.

22 11. I. — 11. 2

the most corporeal,'* being either the flesh, or the substance which
in some animals takes the place of flesh.

Now as there cannot possibly be an animal without sensation,
it follows as a necessary consequence that every animal must have
some homogeneous parts ; for these alone are capable of sensation,
the heterogeneous parts serving for the active functions. Again
as the sensory faculty, the motor faculty, and the nutritive faculty,
are all lodged in one and the same part of the body, as was stated
in a former treatise,'-'' it is necessary that the part which is the
primary seat of these principles shall on the one hand, in its
character of general sensory recipient, be one of the simple parts ;
and on the other hand shall, in its motor and active character, be
one of the heterogeneous parts. For this reason it is the heart
which in sanguineous animals constitutes this central part, and in
bloodless animals it is that which takes the place of a heart. For
the heart, like the other viscera, is one of the homogeneous parts ;
for, if cut up, its pieces are homogeneous in substance with each
other. But it is at the same time heterogeneous in virtue of its
definite configuration.'^ And the same is true of the other so-
called viscera, which are indeed formed from the same material
as the heart. For all these viscera have a sanguineous character
owing to their being situated upon vascular ducts and branches.
For just as a stream of water deposits mud, so the various
viscera, the heart excepted,'"' are, as it were, deposits from the
stream of blood in the vessels. And as to the heart, the very
starting-point of the vessels, and the actual seat of the force by
which the blood is first fabricated, it is but what one would
naturally expect, that out of the selfsame nutriment of which it
is the recipient its own proper substance shall be formed.'^ Such
then are the reasons why the viscera are of sanguineous aspect ;
and why in one point of view they are homogeneous, in another
heterogeneous.

(Ch. 2.) Of the homogeneous parts of animals, some are soft
and fluid, others hard and solid ; and of the former some are fluid
permanently, others only so long as they are in the living body.

Among the fluids ' are blood, serum, lard, suet, marrow, semen,
bile, milk when present, flesh, and their various analogues. For
the parts enumerated are not to be found in all animals, some
animals only having parts analogous to them. Of the hard and
solid homogeneous parts bone, fish-spine,^ sinew, blood-vessel, are
647 b.

ii. 2. 23

examples. The last of these points to a sub-division that may
be made in the class of homogeneous parts.^ For in some of them
the whole and a portion of the whole are synonymous. Thus a
portion of vessel is still called vessel. While in others there is
not this identity of name ; and so far these parts agree with the
heterogeneous parts ; for a portion of a face is never called face.

The first question to be asked is what are the causes to which
these homogeneous parts owe their existence ? The causes are
various ; and this whether the parts be solid or fluid. Thus one
set of homogeneous parts represent the material out of which the
heterogeneous parts are formed ; for each separate organ is con-
structed of bones, sinews, flesh, and the like ; which are either
essential elements in its formation, or contribute to the proper
discharge of its function. A second set are the nutriment of the
first, and are invariably fluid, for all growth occurs at the expense
of fluid matter ; * while a third set are the residue of the second.
Such for instance are the faeces and, in animals that have a bladder,
the urine ; the former being the dregs of the solid nutriment,
the latter of the fluid.

Even the individual homogeneous parts present variations,
which are intended in each case to render them more serviceable
for their purpose. The variations of the blood may be selected
to illustrate this. For different bloods differ in their degrees
of thinness or thickness, of clearness or turbidity, of coldness
or heat ; and this whether we compare the bloods from different
parts of the same individual or the bloods of different animals.
For, in the individual, all the differences just enumerated dis-
tinguish the blood of the upper and of the lower halves of the
body ; and, dealing with classes, one section of animals is
sanguineous, while the other has no blood, but only something
resembling it in its place. As regards the results of such dif-
ferences, the thicker and the hotter blood is, the more con-
ducive is it to strength, while in proportion to its thinness and
its coldness is its suitability for sensation and intelligence. A
like distinction exists also in the fluids which are analogous to
blood. This explains how it is that bees^ and other similar
creatures are of a more intelligent nature than many sanguineous
animals ; and that, of sanguineous animals, those are the most
intelligent whose blood is thin and cold. Noblest of all are those
whose blood is hot, and at the same time thin and clear. For
648 a.

24 11. 2.

such are suited alike for the development of courage and of
wisdom. Accordingly the upper parts are superior in these respects
to the lower, the male superior to the female, and the right side
to the left.^ As with the blood so also with the other parts,
homogeneous and heterogeneous alike. For here also such varia-
tions as occur must be held either to be related to the essential
constitution and mode of life of the several animals, or, in other
cases, to be merely matters of slightly better or slightly worse.
Two animals for instance may have eyes. But in one these eyes
may be of fluid consistency, while in the other they are hard ;
and in one there may be eyelids, in the other no such appendages.
In such a case, the fluid consistency and the presence of eyelids,
which are intended to add to the accuracy of vision, are differences
of degree.'

As to why all animals must of necessity have blood or some-
thing of a similar character, and what the nature of blood may be,
these are matters which can only be considered, when we have
first discussed hot and cold. For the natural properties of many
substances are referable to these two elementary principles ; and
it is a matter of frequent dispute what animals or what parts of
animals are hot and what cold. For some maintain that water
animals are hotter than such as live on land,® asserting that their
natural heat counterbalances the coldness of their medium ; and
again that bloodless animals are hotter than those with blood,
and females than males. Parmenides, for instance, and some others
declare that women are hotter than men,^ and that it is the
warmth and abundance of their blood which causes their menstrual
flow, while Empedocles maintains the opposite opinion. Again,
comparing the blood and the bile, some speak of the former as
hot and of the latter as cold, while others invert the description.
If there be this endless disputing about hot and cold, which of
all things that affect our senses are the most distinct, what are
we to think as to our other sensory impressions ?

The explanation of the difficulty appears to be that the term
" hotter " is used in several senses ; so that different statements,
though in verbal contradiction with each other, may yet all be more
or less true. There ought then to be some clear understanding
as to the sense in which natural substances are to be termed
hot or cold, solid or fluid. For it appears manifest, that these are
properties on which even life and death '" are largely dependent,
648 b.

ii. 2. 25

and that they are moreover the causes of sleep and waking, of
maturity and old age, of health and disease ; while no similar
influence belongs to roughness and smoothness, to heaviness and
lightness, nor in short to any other such properties of matter. That
this should be so is but in accordance with rational expectation.
For hot and cold, solid and fluid, as was stated in a former
treatise," are the foundations of the physical elements.

Is then the term hot used in one sense or in many ? To answer
this we must ascertain what special effect is attributed to a hotter
substance, and if there be several such, how many these may be.
A body then is in one sense said to be hotter than another, if
it impart a greater amount of heat to an object in contact with
it. In a second sense, that is said to be hotter which causes the
keener sensation when touched, and especially if the sensation be
attended with pain. This criterion however would seem some-
times to be a false one ; . for occasionally it is the idiosyncracy
of the individual that causes the sensation to be painful.^^ Again,
of two masses of one and the same substance, the larger is said
to have more heat than the smaller. Again, of two things, that
is the hotter, which the more readily melts a fusible substance,
or sets on fire an inflammable one. Again, of two bodies, that is
said to be the hotter which takes the longer time in cooling, as
also we call that which is rapidly heated hotter than that which
is long about it ; as though the rapidity implied proximity and
this again similarity of nature, while the want of rapidity implied
distance and this again dissimilarity of nature. The term hotter
is used then in all the various senses that have been mentioned,
and perhaps in still more. Now it is impossible for one body
to be hotter than another in all these different fashions. Boiling
water for instance, though it is more scalding than flame,
yet has no power of burning or melting combustible or fusible
matter, while flame has. So again this boiling water is hotter
than a small fire, and yet gets cold much more rapidly and
completely. For in fact fire never becomes cold ; whereas water
invariably does so. Boiling water again is hotter to the touch
than oil ; yet it gets cold and coagulates more rapidly than this
other fluid.'^ Blood again is hotter to the touch than either
water or oil, and yet coagulates before them. Iron again and
stones and other similar bodies are much longer in getting heated
than water, but when once heated burn other substances with
648 b.

26 ii. 2.

a much greater intensity. Another distinction is this. In some
of the bodies which are called hot the heat is derived from
without, while in others it belongs to the bodies themselves ;
and it makes a most important difference, whether the heat has
the former or the latter origin. For to call that one of two
bodies the hotter, which is possessed of heat, we may almost say,
accidentally and not of its own essence, is very much the same
thing as if, finding that some man in a fever was a musician,
one were to say musicians are hotter than healthy men. Of that
which is hot per se and that which is hot per accidens, the former
is the slower to cool, while not rarely the latter is the hotter to
the touch. The former again is the more burning of the two —
flame for instance as compared with boiling water — while the
latter, as the boiling water, which is hot per accidens, is the more
heating to the touch. From all this it is clear that it is no
simple matter to decide which of two bodies is the hotter. For
the first may be the hotter in one sense, the second the hotter
in another. Indeed in some of these cases it is impossible to
say simply even whether a thing is hot or not. For the actual
substratum may not itself be hot, but may be receptive of heat
as an attribute ; as, supposing hot water or hot iron had single
names, would be the case with the substratum of the substances
denoted by such names. It is after this manner that blood is
hot.'* In such cases, in those, that is, in which the substratum
owes its heat to an external influence, it is plain that cold is
not a mere privation, but an actual existence.'^

There is no knowing but that even fire may be another of these
cases. For the substratum of fire may be smoke or charcoal, and,
though the former of these is always hot, smoke being an uprising
vapour, yet the latter becomes cold when its flame is extinguished,
as also would oil and pinewood under similar circumstances. But
even substances that have been burnt nearly all possess some heat,
cinders, for example, and ashes, the dejections also of animals,
and, among the excretions, bile ; because some residue of heat
has been left in them after their combustion. It is in another
sense that pinewood and fat substances are hot ; namely, because
they rapidly assume the actuality of fire.

Heat appears to cause both coagulation and melting.'^ Now
such things as are formed merely of water are solidified by cold,
while such as are formed of nothing but earth are solidified by
649 a.

ii. 2 — 11. 3. , 2"]

fire. Hot substances again are solidified by cold, and, when they
consist chiefly of earth, the process of solidification is rapid, and
the resulting substance is insoluble ; but, when their main con-
stituent is water, the solid matter is again soluble. What kinds
of substances however admit of being solidified, and what are
the causes of solidification, are questions that have already been
dealt with more precisely in another treatise.*""

In conclusion, then, seeing that the terms hot and hotter are
used in many different senses, and that no one substance can be
hotter than others in all these senses, we must, when we attribute
this character to an object, add such further statements as that
this substance is hotter per se, though that other is often hotter
per accidens ; or again that this substance is potentially hot,
that other actually so ; or again, that this substance is hotter
in the sense of causing a greater feeling of heat when touched,
while that other is hotter in the sense of producing flame and
burning. The term hot being used in all these various senses,
it plainly follows that the term cold will also be used with like
ambiguity.

So much then as to the signification of the terms hot and cold,
hotter and colder.^^

(Ch. 3.y) In natural sequence we have next to treat of solid
and fluid. These terms are used in various senses. Sometimes
for instance they denote things that are potentially, at other
times things that are actually, solid or fluid. Ice for example,
or any other solidified fluid, is spoken of as being actually and
accidentally solid, while potentially and essentially it is fluid.
Similarly earth and ashes and the like, when mixed with water,
are actually and accidentally fluid, but potentially and essentially
are solid. Now separate the two constituents in this last instance ;
and you have on the one hand the watery part, capable of passing
by imbibition into other substances, and this is both potentially
and actually fluid ; and on the other hand you have the earthy
part, and this is both potentially and actually solid. It is to
bodies that are solid in this double manner that the term " solid "
is most properly and absolutely applicable. So also the opposite
term "fluid" is strictly and absolutely applicable to that only
which is both potentially and actually fluid. The same remark
applies also to hot bodies and to cold.

These distinctions, then, being laid down, it is plain that blood
649b.

28 ii. 3.

is essentially hot in so far as that heat is connoted in its name ;
just as if boiling water were denoted by a single term, boiling
would be connoted in that term. But the substratum of blood,
that which it is [in substance] while it is blood [in form] is not
hot. Blood then in a certain sense is essentially hot, and in
another sense is not so. For heat is included in the definition
of blood, just as whiteness is included in the definition of a white
man, and so far therefore blood is essentially hot. But so far as
blood becomes hot from some external influence, it is not hot
essentially.^

As with hot and cold, so also is it with solid and fluid. We
can therefore understand how some substances are hot and fluid
so long as they remain in the living body, but become perceptibly
cold and coagulate so soon as they are separated from it ; while
others are hot and consistent while in the body, but when with-
drawn undergo a change to the opposite condition, and become
cold and fluid. Of the former blood is an example ; of the
latter bile ; for while blood solidifies when thus separated, yellow
bile under the same circumstances becomes more fluid.^ We
must attribute to such substances the possession of opposite
properties in a greater or less degree.

In what sense, then, the blood is hot and in what sense fluid,
and how far it partakes of the opposite properties, has now been
fairly explained. Now since everything that grows must take
nourishment, and nutriment in all cases consists of fluid and
solid substances, and since it is by the force of heat that these
are concocted^ and changed, it follows that all living things,
animals and plants alike, must on this account if on no other
have a natural source of heat. This natural heat moreover must
belong to many parts,* seeing that the organs by which the
various elaborations of the food are effected are many in number.
For first of all there is the mouth and the parts inside the mouth,
on which the first share in the duty clearly devolves, in such
animals at least as live on food which requires disintegration.
The mouth, however, does not actually concoct the food, but
merely facilitates concoction ; ^ for the subdivision of the food
into small bits facilitates the action of heat upon it. After the
mouth come the upper and the lower abdominal cavities,^ and
here it is that concoction is effected by the aid of natural heat.
Again, just as there is a channel for the admission of the
650 a.

11. 3- 29

unconcocted food into the stomach, namely the mouth, and in
some animals the so-called oesophagus, which is continuous with
the mouth and reaches to the stomach, so must there also be
other and more numerous channels by which the concocted food
or nutriment shall pass out of the stomach and intestines into
the body at large, and to which these cavities shall serve as a
kind of mangerJ For plants get their food from the earth by
means of their roots ; and this food is already elaborated when
taken in, which is the reason that plants produce no excrement,*
the earth and its heat serving them in the stead of a stomach.
But animals, with scarcely an exception, and notably all such
animals as are capable of locomotion, are provided with a
stomachal sac,^ which is as it were an internal substitute for the
earth. They must therefore have some instrument which shall
correspond to the roots of plants,^" with which they may absorb
their food from this sac, so that the proper end of the successive
stages of concoction may at last be attained. The mouth then,
its duty done, passes over the food to the stomach, and there
must necessarily be something to receive it in turn from this.
This something is furnished by the blood-vessels,^^ which run
throughout the whole extent of the mesentery from its lowest
part right up to the stomach. A description of these will be
found in the treatises on Anatomy and Natural History.^^ Now
as there is a receptacle for the entire matter taken as food, and
also a receptacle for its excremental residue, and again a third
receptacle, namely the vessels, which serve as such for the blood,
it is plain that this blood must be the final nutritive material
in such animals as have it ; while in bloodless animals the same
is the case with the fluid which represents the blood. '^ This
explains why the blood diminishes in quantity when no food is
taken, and increases when much is consumed,^* and also why it
becomes healthy and unhealthy according as the food is of the
one or the other character. These facts, then, and others of a
like kind, make it quite plain that the purpose of the blood in
sanguineous animals is to subserve the nutrition of the body.
They also explain why no more sensation is produced by touching
the blood, than by touching one of the excretions or the food,
whereas when the flesh is touched sensation is produced. For
the blood is not continuous nor united by growth with the flesh,
but simply lies loose in its receptacle, that is in the heart and
650b.

30 ii. 3— ii. 4.

vessels.^5 The manner in which the parts grow at the expense
of the blood, and indeed the whole question of nutrition, will find
a more suitable place for exposition in the treatise on generation
and development, and in other writings.'^ For our present purpose
all that need be said is that the blood exists for the sake of nutri-
tion, that is the nutrition of the parts ; and with this much let us
therefore content ourselves.

(Ch. 4.) What are called fibres^ are found in the blood of some
animals but not of all. There are none for instance in the blood
of deer and of roes ; and for this reason the blood of such animals
as these never coagulates.^ For that portion of the blood which
consists mainly of water is not liable to coagulation, this process
occurring only in the earthy part, that is in the fibres, during
the evaporation of the moisture.

Some' at any rate of the animals with watery blood have a
keener intellect than those whose blood is of an earthier nature.
This is due not so much to the coldness of their blood as to
its thinness and purity ; neither of which qualities belongs to
the earthy matter. For the thinner and purer its fluid is, the
more active is an animal's sensibility. Thus it is that some ex-
sanguineous animals, notwithstanding their want of blood, are
yet more intelligent than some among the sanguineous kinds.
Such for instance, as already said, is the case with bees ^ and
ants, and whatever other animals there may be of a like nature.
At the same time too great an excess of water makes animals
timorous.* For fear chills the body; so that in animals whose
heart contains so watery a mixture the way is, as it were,
prepared for the operation of this emotion. For water is con-
gealed by cold. This also explains why bloodless animals are,
as a general rule, more timorous than such as have blood, so
that they remain motionless, when frightened, and discharge their
excretions, and in some instances change colour.^ Such animals
on the other hand as have thick and abundant fibres in their
blood are of a more earthy nature, and of a choleric temperament,
and liable to bursts of passion. For anger is productive of heat ;
and solids when they have been made hot give off more heat
than fluids. The fibres therefore, being earthy and solid,^ are
turned into so many hot embers in the blood, like the embers
in a vapor-bath, and cause ebullition in the fits of passion.'''

This explains why bulls and boars are so choleric and so
651a.

ii. 4— ii. 5- 3i

passionate. For their blood is exceedingly rich in fibres;^ and
the bull's at any rate coagulates more rapidly than that of any
other animal.^ If these fibres, that is to say if the earthy con-
stituents of which we are speaking, are taken out of the blood,
the fluid that remains behind will no longer coagulate ; just as
the watery residue of mud will not coagulate after removal of
the earth. But if the fibres are left the fluid coagulates, as also
does mud, under the influence of cold. For when the heat is
expelled by the cold, the fluid, as has been already stated, passes
off with it by evaporation, and the residue is dried up and
solidified, not by heat but by cold.'" So long however as the
blood is in the body, it is kept fluid by animal heat.

The character of the blood affects both the temperament and
the sensory faculties of animals in many ways. This is indeed
what might reasonably be expected, seeing that the blood is
the material of which the whole body is made. For nutriment
supplies the material, and the blood is the ultimate nutriment.
It makes then a considerable difference whether the blood be
hot or cold, thin or thick, turbid or clear.

The watery part of the blood is serum ; and it is watery,
either owing to its not being yet concocted, or owing to its
having become corrupted ; so that one part of the serum is the
resultant of a necessary process, while another part is material
intended to serve for the formation of the blood.^^

(Ch. ^.) The differences between lard and suet correspond to
differences of blood.^ For both are concocted blood ; being that
surplus of it, which, though well concocted and highly nutritious,
has not been expended in forming the fleshy substance of the
animal, but remains over owing to the superabundance of food.
That such is the composition of these substances is evident from
their sheeny appearance. For a sheeny look in fluids comes from
their being compounded of air and of fire.^ It follows from what
has been said that no ex-sanguineous animals have either lard
or suet ; for they have no blood.* Among sanguineous animals
those whose blood is dense are likely to have suet rather than
lard. For suet is of an earthy nature, that is to say, it contains
but a small proportion of water and is chiefly composed of earth ;
and this it is that makes it coagulate, just as the fibrous matter
of blood coagulates, or broth? which contain such fibrous matter.*
Thus it is that in those horned animals that have no front teeth
651a.

32 ii. 5 — ii. 6.

in the upper jaw the fat consists of suet. For the very fact that
they have horns and huckle-bones ^ shows that their composition
is rich in earthy matter ; for all such appurtenances are solid
and earthy in character. On the other hand in those hornless
animals that have front teeth in both jaws, and whose feet are
divided into toes, there is no suet, but in its place lard ; ^ and
this, not being of an earthy character, neither coagulates nor
dries up into a friable mass.

Both lard and suet when present in moderate amount' are
beneficial ; for they contribute to health and strength, while
they are no hindrance to sensation. But when they are present
in great excess, they are injurious and destructive. For were
the whole body formed of them it would perish. For an animal
is an animal in virtue of its sensory part, that is in virtue of its
flesh, or of the substance analogous to flesh.''' But the blood, as
before stated, is not sensitive ; as therefore is neither lard nor
suet, seeing that they are nothing but concocted blood. Were
then the whole body composed of these substances, it would be
utterly without sensation. Such animals, again, as are excessively
fat age rapidly. For their blood is used up in forming fat, and
so they have but little of it left; and when there is but little
blood the way is already open for decay.^ For decay may be
said to be deficiency of blood, the scantiness of which renders
it liable, like all bodies of small bulk, to be injuriously affected
by any chance excess of heat or cold. For the same reason fat
animals are less prolific than others. For that part of the blood
which should go to form semen and seed, is used up in the
production of lard and suet, which are nothing but concocted
blood ; so that in these animals there is either no reproductive
excretion at all, or only a scanty amount.^

So much then of blood and serum, and of lard and suet.
Each of these has been described, and the purposes told for
which they severally exist.

(Ck. 6.) The marrow also is of the nature of blood, and
not as some^ think the germinal force of the semen. That
this is the case is quite evident in very young animals. For
in the embryo the marrow of the bones has a blood-like
appearance, which is but consistent with the fact that the parts
are all constructed out of blood, and that it is on blood that
the embryo is nourished.^ But, as the young animal grows up
651b.

ii. 6. 33

and ripens into maturity, the marrow changes its colour, just
as do the external parts and the viscera.^ For the viscera also
in very young animals have each and all a blood-like look,
owing to the large amount of this fluid which they contain.

The consistency of the marrow agrees with that of the fat. For
when the fat consists of lard, then the marrow also is oily and
lard-like ; but when the concocted blood is converted into suet,
and does not assume the form of lard, then the marrow also
has a suety character. In those animals, therefore, that have
horns and are without upper front teeth, the marrow has the
character of suet ; while it takes the form of lard in those that
have front teeth in both jaws, and that also have the foot divided
into toes. What has been said hardly applies to the spinal
marrow. For it is necessary that this shall be continuous and
extend without break through the whole back-bone, inasmuch
as this bone consists of separate vertebrae. But were the spinal
marrow either of soft fat or of suet, it could not hold together
in such a continuous mass as it does, but would either be too
fluid or too frangible.* •

There are some animals that can hardly be said to have
any marrow. These are those whose bones are strong and
solid, as is the case with the lion. For in this animal the
marrow is so utterly insignificant, that the bones look as though
they had none at all.^ However, as it is necessary that animals
shall have bones or something analogous to them, such as the
fish-spines of water-animals,^ it is also a matter of necessity that
some of these bones shall contain marrow ; for the substance
contained within the bones is the nutriment out of which
these are formed. Now the universal nutriment, as already
stated, is blood ; and the blood within the bone, owing to the
heat which is developed in it from its being thus surrounded,
undergoes concoction, and self-concocted ''' blood is suet or lard ;
so that it is perfectly intelligible how the marrow within the
bone comes to have the character of these substances. So also
it is easy to understand, why, in those animals that have strong
and solid bones, some of these should be entirely void of marrow,
while the rest contain but little of it ; for here the nutriment is
all spent in forming the bones.

Those animals that have fish-spines in place of bones have
no other marrow than that of the chine.^ For in the first place
652 a, 3

34 ii- 6— ii. 7.

they have naturally but a small amount of blood ; and secondly
the only hollow fish-spine is that of the chine. In this then
marrow is formed ; this being the only spine in which there is
space for it, and moreover being the only one which owing to
its division into parts requires a connecting bond. This too is
the reason why the marrow of the chine, as already mentioned,
is somewhat different from that of other bones. For, having to
act the part of a clasp, it must be of glue-like tenacity, and at
the same time sinewy^ so as to admit of stretching.

Such then are the reasons for the existence of marrow, in those
animals that have any, and such its nature. It is the surplus
of the sanguineous nutriment apportioned to the bones and fish-
spines, which has undergone concoction owing to its being enclosed
within them.

(Ch. y.) From the marrow we pass on in natural sequence to
the brain. For there are some^ who think that the brain itself
consists of marrow, and that it forms the commencement of that
substance, because they see that the spinal marrow is continuous
with it. In reality the two may be said to be utterly opposite
to each other in character. For of all the parts of the body there
is none so cold as the brain ; whereas the marrow is of a hot
nature, as is plainly shown by its sheeny appearance,^ and by
its fatness. Indeed this is the very reason why the brain and
spinal marrow are continuous with each other. For, wherever
the action of any part is in excess, nature so contrives as to
set by it another part with an excess of contrary action, so that
the excesses of the two may counterbalance each other. Now
that the marrow is hot is clearly shown by many indications.
The coldness of the brain is also manifest enough. For in the
first place it is cold even to the touch ; and, secondly, of all the
fluids of the body it is the one that has the least blood ; for
in fact it has no blood at all in its proper substance.^ This
makes it the most consistent of all the fluids.^ This brain is
not an excretion, nor yet is it one of the parts which are
anatomically continuous with each other ; but it has a character
peculiar to itself, as might indeed be expected. That it has no
continuity with the organs of sense is plain from simple inspection,
and is still more clearly shown by. the fact, that, when it is touched,
no sensation is produced;'^ in which respect it resembles the
blood of animals and their excrement.^ The purpose of its
652 b.

ii- 7- 35

presence in animals is no less than the preservation of the whole
body. How it effects this will be seen from what follows. Some
writers assert that the soul is fire or some such force.''' This
however is but a rough and inaccurate assertion ; and it would
perhaps be better to say that the soul is incorporate in some
substance of a fiery character. The reason for this being so is
that of all substances there is none so suitable for ministering
to the operations of the soul as that which is possessed of heat.
For the functions of the soul are nutrition and motion, and it
is by heat that these are most readily effected. To say however
that the soul is fire is much the same thing as to confound the
auger or the saw with the carpenter or his craft, simply because
the work is wrought by the two in conjunction. So far then
this much is plain, that all animals must necessarily have a
certain amount of heat. But as all influences require to be
counterbalanced, so that they may be reduced to moderation and
brought to the mean (for in the mean, and not in either extreme,
lies the true and rational position), nature has contrived the brain
as a counterpoise to the region of the heart with its contained
heat, and has given it to animals to moderate the latter, com-
pounding it of earth and water.^ For this reason it is, that
every sanguineous animal has a brain ; whereas no bloodless
creature has such an organ, unless indeed it be, as the Poulp,
by analogy.^ For where there is no blood, there in consequence
there is but little heat. The brain then tempers the heat and
Seething of the heart. In order, however, that it rnay not itself
be absolutely without heat, but may have a moderate amount,
branches run from both blood-vessels, that is to say from the
great vessel and from what is called the aorta,"' and end in the
membrane which surrounds the brain ;^^ while at the same time,
in order to prevent any injury from the heat, these encompassing
vessels, instead" of being few and large, are numerous and small,
and their blood scanty and clear, instead of being abundant and
thick.^2 We can now understand why defluxions have their origin
in the head, and occur whenever the parts about the brain have
more than a due proportion of coldness. For when the nutriment
steams upwards through the blood-vessels, its refuse portion is
chilled by the influence of this region, and forms defluxions of
phlegm and serum. We must suppose, to compare small things
with great, that the like happens here as occurs in the production
653 a.

36 ii. 7-

of showers. For when vapor steams up from the earth under the
influence of heat and is carried into the upper regions, so soon,
as it reaches the cold air that is above the earth, it condenses
again into water owing to the refrigeration, and falls back
to the earth as rain.'^ These however are matters which may
be suitably considered in the Principles of Diseases, so far as
natural philosophy has anything to say to them.^*

It is the brain again, — or, in animals that have no brain, the
part analogous to it, — which is the cause of sleep. For either
by chilling the blood that streams upwards after food, or by
some other similar influences, it produces heaviness in the region
in which it lies (which is the reason that drowsy persons hang
the head), and causes the heat to escape downwards in company
with the blood. It is the accumulation of this in excess in the
lower part that produces complete sleep, taking away the power
of standing upright from such animals as are able to assume
that posture ; and from the rest the power of holding up the
head. These however are matters which have been separately
considered in the treatises on Sensation and on Sleep.^^

That the brain is a compound of earth and water ^^ is shown
by what occurs when it is boiled. For, when so treated, it turns
hard and solid, inasmuch as the water is evaporated by the heat,
and leaves the earthy part behind.^''^ Just the same occurs when
pulse and other fruits are boiled. For these also are hardened by
the process, because the water which enters into their composition
is driven off" and leaves the earth, which is their main constituent,
behind.

Of all animals, man has the largest brain in proportion to
his size ; and it is larger in men than in women.^* This is
because the region of the heart and of the lung is hotter and
richer in blood in man than in any other animal ; and in men
than in women. '^ This again explains why man, alone of animals,
stands erect. For the heat, overcoming ahy opposite inclination,
makes growth take its own line of direction, which is from the
centre of the body upwards.^'' It is then as a counterpoise to
his excessive heat that in man's brain there is this superabundant
fluidity and coldness ; and ,it is again owing to this superabundance
that the cranial bone which some call the Bregma ^^ is the last
to become solidified ; ^^ so long does evaporation continue to
occur through it under the influence of heat.^^ Man is the only
653 a.

11. 7—11. 8 37

sanguineous animal in which this takes place.-* Man, again, has
more sutures in his skull than any other animal,^^ and the male
more than the female.^^ The explanation is again to be found
in the greater size of the brain, which demands free ventilation,
proportionate to its bulk. For if the brain be either too fluid or
too solid, it will not perform its office, but in the one case will
freeze the body, and in the other will not cool it at all ; and
thus will cause disease, madness, and death. For the cardiac heat
and the centre of life is most delicate in its sympathies, and is
immediately sensitive to the slightest change or affection of the
blood on the outer surface of the brain.^'

The fluids which are present in the animal body at the time
of birth have now nearly all been considered. Amongst those
that appear only at a later period are the residua of the food,
which include the deposits of the belly and also those of the
bladder. Besides these there is the semen and the milk, one or
the other of which makes its appearance in appropriate animals.
Of these fluids, the excremental residua of the food may be
suitably discussed by themselves, when we come to examine and
consider the subject of nutrition.-® Then will be the proper time
to explain in what animals they are found, and what are the
reasons for their presence. Similarly all questions concerning
the semen and the milk may be dealt with in the treatise on
generation,^^ for the former of these fluids is the very starting-
point of the generative process, and the latter has no other
ground of existence than generative purposes.

(Ch. 8.j We have now to consider the remaining homogeneous
parts, and will begin with flesh, and with the substance that, in
animals that have no flesh, takes its place. The reason for so
beginning is that flesh forms the very basis of animals, and is the
essential constituent of their body. Its right to this precedence
can also be demonstrated logically. For an animal is by our
definition something that has sensibility, and chief of all that
has the primary sensibility, which is that of Touch ; ^ and it is
the flesh, or analogous substance, which is the organ of this
sense. And it is the organ, either in the same way as the eye
is the organ of sight, that is it constitutes the primary organ of
the sense ; or it is the organ and the medium through which
the object acts combined, that is it answers to the eye with some
or other transparent medium attached to it.^ Now in the case of
653b.

38 ii. 8.

the other senses it was impossible for nature to unite the medium
with the sense-organ, nor would such a junction have served-
any purpose ; but in the case of touch she was compelled by-
necessity to do so. For of all the sense-organs that of touch
is the only one that has a corporeal medium, or at any rate
its medium is more corporeal than any other.

Regarding then the flesh in its sensory character, it is plain
that all the other parts exist on its account. By the other parts
I mean the bones, the skin, the sinews, and the blood-vessels,
and, again, the hair and the various kinds of nails, and anything
else there may be of a like character. Thus the bones are a
contrivance to give security to the soft parts, to which purpose
they are adapted by their hardness ; and in animals that have
no bones the same office is fulfilled by some analogous substance,
as by cartilage in some fishes, and by fish-spine in others.

Now in some animals this supporting substance is situated
within the body, while in some of the bloodless species it is
placed on the outside. The latter is the case in all the Crustacea,^
as the Carcini and the Carabi ; it is the case also in the Testacea,
as for instance in the several species known by the general
name of oysters. For in all these animals the fleshy substance
is within, and the earthy matter, which holds the soft parts
together and keeps them from injury, is on the outside. For
the shell not only enables the soft parts to hold together, but
also, as the animal is bloodless and so has but little natural
warmth, surrounds it, as a chaufferette does the embers, and keeps
in the smouldering heat. Similar to this seems to be the arrange-
ment in another and distinct genus of animal, namely in the
Tortoises, including the Chelone and the several kinds of Emys.*
But in Insects and in Cephalopods the plan is entirely different,
there being moreover a contrast between these two themselves.
For in neither of these does there appear to be any bony or
earthy part, worthy of notice, distinctly separated from the rest
of the body. Thus in the Cephalopods the mass of the body
consists of a soft flesh-like substance, or rather of a substance
which is intermediate to flesh and sinew, and not so readily destruc-
tible as actual flesh. I call this substance intermediate to flesh
and sinew, because it is soft like the former, while it admits of
stretching like the latter.^ Its cleavage however is such that
it splits not longitudinally, like sinew, but into circular segments,
664 a.

ii. 8— ii. 9. 39

this being the most advantageous condition, so far as strength
is concerned. These animals have also a part inside them
corresponding to the spinous bones of fishes. For instance in
the Cuttle-fishes there is what is known as the os sepiae, and in
the Calamaries there is the so-called gladius. In the Poulps
on the other hand there is no such internal part, because the
body or, as it is termed in them, the head,^ forms but a short
sac, whereas it is of considerable length in the other two ; and
it was this length which led nature to assign to them their
hard support, so as to ensure their straightness and inflexibility ;
just as she has assigned to sanguineous animals their bones or
their fish-spines as the case may be. To come now to Insects.
In these the arrangement is quite different from that of the.
Cephalopods ; quite different also from that which obtains in
sanguineous animals, as indeed has been already stated. For
in an insect there is no distinction into soft and hard parts,
but the whole body is hard, the hardness however being of
such a character as to be more flesh-like than bone, and more
earthy and bone-like than flesh. The purpose of this is to
make the body of the insect less liable to get broken into
pieces.'

(Ch. g.) There is a resemblance between the osseous and the
vascular systems ; for each has a central part in which it begins,
and each forms a continuous whole. For no bone in the body
exists as a separate individuality in itself, but each is either a
portion of what may be considered a continuous whole, or at
any rate is linked with the rest by contact and by attachments ;
so that nature may use adjoining bones either as though they
were actually continuous and formed a single bone, or, for purposes
of flexure, as though they were two and distinct. And similarly
no blood-vessel has in itself a separate individuality; but they
all form parts of one whole. For an isolated bone, if such there
were, would in the first place be unable to perform the office,
for the sake of which bones exist ; for, were it discontinuous
and separated from the rest by a gap, it would be perfectly
unable to produce either flexure or extension ; nor only so, but
it would actually be injurious, acting like a thorn or an arrow
lodged in the flesh. Similarly if a vessel were isolated, and not
continuous with the vascular centre, it would be unable to retain
the blood within it in a proper state. For it is the warmth
654b.

40 1!. 9-

derived from this centre that hinders the blood from coagulating ; ^
indeed the blood, when withdrawn from its influence, actually
becomes putrid. Now the centre or origin of the blood-vessels
is the heart, and the centre or origin of the bones, in all animals
that have bones, is what is called the chine. With this all the
other bones of the body are in continuity ; for it is the chine
that keeps the body extended and straight But since it is
absolutely necessary that the body of an animal shall bend
during locomotion, this chine, while it is one in virtue of the
continuity of its parts, yet by its division into vertebrae is
made to consist of many segments. It is from this chine that the
bones of the limbs proceed, and with it they are continuous, in
•those animals that have limbs ; and these bones form joints at
the place where the limbs admit of flexure ; being fastened
together by sinews, and having their extremities adapted to each
other, either by the one being hollowed and the other rounded,^
or by both being hollowed and including between them a huckle-
bone, as a connecting bolt, so as to allow of flexure and extension.
For without some such arrangement these movements would be
utterly impossible, or at any rate would be performed with great
difficulty. There are some joints, again, in which the lower end
of the one bone and the upper end of the other are alike in
shape. In these cases the bones are bound together by sinews,
and cartilaginous pieces are interposed in the joint, to serve as
a kind of padding, and to prevent the two extremities from
grating against each other.

Round about the bones, and attached to them by thin fibrous
bands, grow the fleshy parts, for the sake of which the bones
themselves exist. For just as an artist, when he is moulding an
animal out of clay or other soft substance, takes first some solid
body as a basis, and round this moulds the clay ; so also has
nature acted in fashioning the animal body out of flesh. Thus we
find all the fleshy parts, with one exception, supported by bones,
which serve, when the parts are organs of motion, to facilitate
flexure, and, when the parts are motionless, act as a protection.
The ribs, for example, which enclose the chest are intended to
ensure the safety of the heart and neighbouring viscera. The
exception of which mention was made is the belly. The walls of
this are in all animals devoid of bones ; in order that there may
be no hindrance to the expansion which necessarily occurs in this
655 a.

11. 9- 41

part after a meal, nor, in females, any interference with the growth
of the embryo, which is lodged here.^

Now the bones of viviparous animals, of such that is as are not
merely externally but also internally viviparous,* vary but very
little from each other in point of strength, which in all of them is
considerable. For the vivipara in their bodily proportions are far
above other animals, and many of them occasionally grow to an
enormous size, as is the case in Libya and in hot and dry countries
generally. But the greater the bulk of an animal, the stronger, the
bigger, and the harder, are the supports which it requires; and
comparing the big animals with each other, this requirement will
be most marked in those that live a life of rapine. Thus it is that
the bones of males are harder than those of females ; and the
bones of flesh-eaters, that get their food by fighting, are harder
than those of herbivora. Of this the Lion is an example ; for so
hard are its bones, that, when struck, they give off sparks, as
though they were flints. It may be mentioned also that the
Dolphin, inasmuch as it is viviparous, is provided with bones and
not merely with fish-spines.^

In those sanguineous animals, on the other hand, that are
oviparous, the bones present successive slight variations of charac-
ter. Thus in Birds there are bones, but these are not so strong
as the bones of the Vivipara.^ Then come the Oviparous fishes,
where there is no bone, but merely fish-spine. In the Serpents
too the bones have the character of fish-spine, excepting in the
very large species,''' where the solid foundation of the body requires
to be stronger, in order that the animal itself may be strong, the
same reason prevailing as in the case of the Vivipara, Lastly in
the Selachia, as they are called, the fish-spines are replaced by
cartilage. For it is necessary that the movements of these animals
shall be of an undulating character ; and this again requires the
solid framework of the body to be pliable, and not rigid in its
motions. Moreover in these Selachia ^ nature has used all the
earthy matter on the skin ; and she is unable to distribute to
many different parts one and the same superfluity of material.^
Even in viviparous animals many of the bones are cartilaginous.
This happens in those parts where it is to the advantage of the
surrounding flesh that its solid base shall be soft and mucilaginous.
Such, for instance, is the case with the ears and nostrils ; for in
projecting parts, such as these, rigid substances would soon get
655 a.

42 11. 9-

broken. Cartilage and bone are indeed fundamentally the same
thing, the differences between them being merely matters of
degree.^'' This is manifested in the fact that neither cartilage nor
bone, when once cut off, grows again.^^ Now the cartilages of
these land animals are without marrow, that is without any dis-
tinctly separate marrow. For the marrow, which in bones is
distinctly separate, is here mixed up with the whole mass, and
gives a soft and mucilaginous consistence to the cartilage. But
in the Selachia the chine, though it is cartilaginous, yet contains
marrow ; for here it stands in the stead of a bone.

Very nearly resembling the bones to the touch ^^ are such
parts as nails, hoofs, claws, horns, and the beaks of birds, all of
which are intended to serve as means of defence. For the
organs which are made out of these substances, and which are
called by the same names as the substances themselves, the
organ hoof for instance and the organ horn, are contrivances to
ensure the preservation of the animals to which they severally
belong. In this class too must be reckoned the teeth, which
in some animals have but a single function, namely the mastica-
tion of the food, while in others they have an additional office,
namely to serve as instruments of offence ; as is the case with
all animals that have sharp interfitting teeth or that have tusks.
All these parts are necessarily of a solid and earthy character ;
for the value of a weapon depends on such properties. Their
earthy character explains how it is that all such parts are much
more developed in viviparous quadrupeds than in man. For
there is always more earth in the composition of these animals
than in that of the human body. However, not only all these
parts but such others as are nearly connected with them, skin for
instance, bladder, membrane, hairs, feathers, and their analogues,
and any other similar parts that there may be, will be considered
farther on with the heterogeneous parts. There we shall examine
into the causes which produce them, and into the objects of their
presence severally in the bodies of animals. For, as with the
heterogeneous parts, so with these ; it is from a consideration of
their functions that alone we can derive any knowledge of them.
The reason for dealing with them at all in this part of the treatise,
and classifying them with the homogeneous parts, is that under
one and the same name are confounded the entire organs and the
substances of which they are composed.^^ But of all these
655 b.

li. 9—11. 10. 43

substances flesh and bone form the basis. Semen and milk were
also passed over, when we were considering the homogeneous
fluids. For the treatise on generation will afford a more suitable
place for their examination, seeing that the former of the two
is the very foundation of the thing generated, while the latter is
its nourishment.

(Ch. \o.) Let us now^ make, as it were, a fresh beginning,
and consider the heterogeneous parts, taking those first which
are the first in importance.^ For in all animals, at least in all
the perfect kinds,^ there are two parts more essential than the
rest, namely the part which serves for the ingestion of food,
and the part which serves for the discharge of its residue.^ For
without food growth and even existence is impossible. Interven-
ing again between these two parts there is invariably a third,
in which is lodged the vital principle. As for plants, though
they also are included by us among things that have life, yet
are they without any part for the discharge of residue.* For
the food which they absorb from the ground is already concocted,
and they give off as its equivalent their seeds and fruits. Plants,
again, inasmuch as they are without locomotion, present no
great variety in their heterogeneous parts. For, where the
functions are but few, few also are the organs required to effect
them.^ The configuration of plants is a matter then for separate
consideration. Animals, however, that not only live but feel,
present a much greater multiformity of parts, and this diversity
is greater in some animals than in others, being most varied
in those, to whose share has fallen not mere life but life of
high degree. Now such an animal is man. For of all living beings
with which we are acquainted man alone partakes of the divine,
or at any rate partakes of it in a fuller measure than the rest.**
For this reason, then, and also because his external parts and
their forms are more familiar to us than those of other animals,
we must speak of man first ; and this the more fitly, because
in him alone do the natural parts hold their natural position ;
his upper part' being turned towards that which is upper in the
universe. For, of all animals, man alone stands erect.'''

In man, then, the head is destitute of flesh ; this being the

necessary consequence of what has already been stated concerning

the brain. There are, indeed, some ^ who hold that the life of

man would be longer than it is, were his head more abundantly

656 a.

44 ii- 10.

furnished with flesh ; and they account for the absence of this
substance by saying that it is intended to add to the perfection
of sensation. For the brain they assert to be the organ of
sensation ; and sensation, they say, cannot penetrate to parts
that are too thickly covered with flesh. But neither part of this
statement is true. On the contrary, were the region of the
brain thickly covered with flesh, the very purpose for which
animals are provided with a brain would be directly contravened.
For the brain would itself be heated to excess and so quite
unable to cool any other part ; and, as to the latter half of
their statement, the brain cannot be the cause of any of the
sensations, seeing that it is itself as utterly without feeling as
any one of the excretions. These writers see that certain of the
senses are located in the head, and are unable to discern any
reason for this ; they see also that the brain is the most peculiar
of all the animal organs ; and out of these facts they form an
argument, by which they link sensation and brain together.^ It
has however already been clearly set forth in the treatise on
Sensation, that it is the region of the heart that constitutes the
sensory centre. There also it was stated that two of the
senses, namely touch and taste, are manifestly directly dependent
on the heart ; ^" and that as regards the other three, namely
hearing, sight, and the centrally placed sense of smell, it is the
character of their sense-organs '^ which causes them to be
lodged as a rule in the head. Vision is so placed in all animals.^^
But such is not invariably the case with hearing or with smell.
For fishes and the like hear and smell, and yet have no visible
organs for these senses in the head ; ^^ a fact which demonstrates
the accuracy of the opinion here maintained. Now that vision,
whenever it exists, should be in the neighbourhood of the brain is
but what one would rationally expect. For the brain is fluid ^*
and cold, and vision is of the character of water,'^ water being of
all transparent substances the one most easily confined.'^ More-
over it cannot but necessarily be that the more precise senses
will have their precision rendered still greater if ministered to
by parts that have the purest ^^ blood. For the motion of the
heat of blood destroys sensory activity. For these reasons
the organs of the precise senses are lodged in the head.

It is not only the fore part of the head that is destitute of
flesh, but the hind part also. For, in all animals that have a
fi66b.

ii. 10. 45

head, it is this head which more than any other part requires
to be held up. But, were the head heavily laden with flesh,
this would be impossible ; for nothing so burdened can be held
upright. This fact is an additional proof that the absence of
flesh from the head has no reference to brain sensation. For
there is no brain in the hinder part of the head,^^ and yet this
is as much without flesh as is the front.

In some animals hearing as well as vision is lodged in the
region of the head. Nor is this without a rational explanation.
For what is called the empty space is full of air, and the organ
of hearing is, as we say, formed of air. Now there are channels ^^
which lead from the eyes to the blood-vessels that surround
the brain ; and similarly there is a channel which leads back
again from each ear and connects it with the hinder part of
the head. But no part that is without blood is endowed with
sensation, as neither is the blood itself, but only certain parts
formed of blood.^^ So that none of the bloodless parts of
sanguineous animals are endowed with sensation, nor their blood
itself ; for no such part is sensitive in any animal.

The brain in all animals that have one is placed in the front
part of the head ; because the direction in which sensation acts
is in front ; and because the heart, from which sensation proceeds,
is in the front part of the body ; and lastly because the instruments
of sensation are the blood-containing parts, and the cavity in the
posterior part of the skull is destitute of blood-vessels.

As to the position of the sense-organs, they have been arranged
by nature in the following suitable manner. The organs of
hearing are so placed as to divide the circumference of the head
into two equal halves ; for they have to hear not only sounds
which are directly in a line with themselves, but sounds from all
quarters. The organs of vision are placed in front, because sight
is exercised only in a straight line, and moving as we do in a
forward direction it is necessary that we should see before us,
in the direction of our motion. Lastly, the organs of srriell are
placed with good reason between the eyes. For as the body
consists of two parts, a right half and a left, so also each organ
of sense is double. In the case of touch this is not apparent,
the reason being that the primary organ of this sense is not the
flesh or analogous part, but lies internally .^^ In the case of
taste, which is merely a modification of touch ^^ and which
656 b.

46 ii. 10 — ii. 13.

IS placed in the tongue, the fact is more apparent than in
the case of touch, but still not so manifest as in the case of
the other senses. However even in taste the fact is evident
enough ; for in some animals the tongue is plainly forked.^'
The double character of the sensations is however much more
conspicuous in the other organs of sense. For there are two
ears and two eyes, and the nostrils, though combined together,
are also two. Were these latter otherwise disposed and separated
from each other as are the ears, neither they nor the nose in
which they are placed would be able to perform their office.
For in such animals as have nostrils olfaction is effected by
means of inspiration,^* and the organ of inspiration is placed in
front and in the middle line. This is the reason why nature has
brought the two nostrils together and placed them as the central
of the three sense-organs, setting them symmetrically on either
side of a perpendicular line, where they benefit by the inspiratory
motion.^^ In other animals than man the arrangement of these
sense-organs is also such as is adapted in each case to the
special requirements. (Ch. \\.) For instance in quadrupeds the
ears project from the head and are set to all appearance above
the eyes. Not that they are in reality above the eyes ; but they
seem to be so, because the animal does not stand upright, but
has its head hung downwards. This being the usual attitude
of the animal when in motion, it is of advantage that its ears
shall be high up and very moveable.^ For they can then be
turned in all directions, and readily take in sounds from all
quarters. (Ch. 12.) In birds, on the other hand, there are no
ears, but only the auditory passages.^ This is because their skin
is hard and because they have feathers instead of hairs, so that
they have not got the proper material for the formation of ears.^
Exactly the same is the case with such oviparous quadrupeds as
are clad with scaly plates, and the same explanation applies to
them. There is also one of the viviparous quadrupeds, namely
the seal, that has no ears but only the auditory passages.^ The
explanation of this is that the seal though a quadruped is a
quadruped of stunted formation.*

(C/t. 13.^ Men, and Birds, and Quadrupeds, viviparous and

oviparous alike, have their eyes protected by lids. In the vivipara

there are two of these ; and both are used by these animals not

only in closing the eye, but also in the act of blinking ; whereas

667 a.

"• 13- 47

the oviparous quadrupeds, and ^ the heavy-bodied birds as well
as some others, use only the lower lid to close the eye;^ while
birds blink by means of a membrane connected with the canthus.
The reason for the eyes being thus protected is that nature has
made them of fluid consistency, in order to ensure keenness of
vision. For had they been covered with hard skin, they would, it
is true, have been less liable to get injured by anything falling
into them from without, but they would not have been sharp-
sighted. It is then to ensure keenness of vision that the skin
over the pupil is fine and delicate ; while the lids are superadded
as a protection from injury. It is as a still further safeguard,
that all these animals blink, and man most of all ; this action
(which is not performed from deliberate intention but from a
natural instinct)^ serving to keep objects from falling into the
eyes ; and being more frequent in man than in the rest of these
animals, because of the greater delicacy of his skin. These lids
are made of a roll of skin ; and it is because they are made of
skin and contain no flesh that neither they, nor the similarly
constructed prepuce, unite again when once cut.*

As to the oviparous quadrupeds, and such birds as resemble
them in closing the eye with the lower lid, it is the hardness of
the skin of their heads which makes them do so.^ For such
birds as have heavy bodies are not made for flight ; and so the
materials which would otherwise have gone to increase the size
of the feathers are diverted thence, and used to augment the
thickness of the skin.^ Birds therefore of this kind close the
eye with the lower lid ; whereas pigeons and the like use both
upper and lower lids for the purpose. As birds are covered
with feathers, so oviparous quadrupeds are covered with scaly
plates ; and these in all their forms are harder than hairs, so that
the skin''^ also to which they belong is harder than the skin of
hairy animals. In these animals, then, the skin on the head
is hard, and so does not allow of the formation of an upper
eyelid,^ whereas lower down the integument is of a flesh-like
character, so that the lower lid can be thin and extensible.

The act of blinking is performed by the heavy-bodied birds'
by means of the membrane already mentioned, and not by this
lower lid. For in blinking rapid motion is required, and such
is the motion of this membrane, whereas that of the lower lid is
slow. It is from the inner canthus, that is from the one nearest
657 b.

48 ii. 13 — ii. 14.

to the nostrils, that the membrane comes. For it is better to
have one starting-point for nictitation than two ; and in these
birds this starting-point is the junction of eye and nostrils,
an anterior starting-point being preferable to a lateral one.'"
Oviparous quadrupeds do not blink in like manner as the birds ;
for, living as they do on the ground, they are free from the
necessity of having eyes of fluid consistency and of keen sight,
whereas these are essential requisites for such birds as have to
use their eyes at long distances. This too explains why birds
with talons, that have to search for prey by eye from aloft, and
therefore soar to greater heights than other birds, are sharp-
sighted ; while common fowls and the like, that live on the
ground and are not made for flight, have no such keenness of
vision. For there is nothing in their mode of life which
imperatively requires it.

Fishes and Insects and the hard-skinned Crustacea present
certain differences in their eyes, but so far resemble each other as
that none of them have eyelids.'^ As for the hard-skinned Crus-
tacea it is utterly out of the question that they should have any ;
for an eyelid, to be of use, requires the action of the skin to be
rapid. These animals then have no eyelids and, in default of
this protection, their eyes are hard, just as though the lid were
attached to the surface of the eye, and the animal saw through
it. Inasmuch however as such hardness must necessarily blunt
the sharpness of vision, nature has endowed the eyes of Insects,
and still more those of Crustacea,'^ with great mobility (just as
she has given some quadrupeds very moveable ears), in order
that they may be able to turn to the light and catch its rays, and
so see more plainly. Fishes however have eyes of a fluid con-
sistency. For all animals that move much about have to use
their vision at considerable distances. If now they live on land,
the air in which they move is transparent enough. But the water
in which fishes live is a hindrance to sharp sight, though it has
this advantage over the air, that it does not contain so many
objects to knock against the eyes. The risk of collision being
thus small, nature, who makes nothing in vain, has given no eye-
lids to fishes, while to counterbalance the opacity of the water she
has made their eyes of fluid consistency.

(Ch. 14.^ All animals that have hairs on the body have lashes
on the eyelids ; but birds and animals with scale-like plates, being
658 a

11. 14. 49

hairless, have none. The Libyan ostrich, indeed, forms an excep-
tion ; for, though a bird, it is furnished with eyelashes.^ This
exception, however, will be explained hereafter. Of hairy animals,
man alone has lashes on both lids. For in quadrupeds there is
a greater abundance of hair on the back than on the under side of
the body ; whereas in man the contrary is the case, and the hair
is more abundant on the front surface than on the back. The
reason for this is that hair is intended to serve as a protection
to its possessor. Now, in quadrupeds, owing to their inclined
attitude, the under or anterior surface does not require so much
protection as the back, and is therefore left bald, in spite of its
being the nobler of the two sides. But in man, owing to his
upright attitude, the anterior and posterior surfaces of the body
are on an equality as regards need of protection. Nature there-
fore has assigned the protective covering to the nobler of the two
surfaces ;2 for invariably she brings about the best arrangement
of such as are possible. This then is the reason that there is no
lower eyelash in any quadruped ; though in some a few scattered
hairs sprout out under the lower lid,^ This also is the reason
that they never have hair in the axillae, nor on the pubes, as man
has. Their hair, then, instead of being collected in these parts,
is either thickly set over the whole dorsal surface, as is the case
for instance in dogs, or, sometimes, forms a mane, as in horses
and the like, or as in the male lion, where the mane is still more
flowing and ample. So, again, whenever there is a tail of any
length, nature decks it with hair, with long hair if the stem of the
tail be short, as in horses, with short hair if the stem be long,
regard also being had to the condition of the rest of the body.*
For nature invariably distributes her material, by subtracting
from one part and giving to another. Thus when she has covered
the general surface of an animal's body with an excess of hair,
she leaves a deficiency in the region of the back. This for instance
is the case with bears.'^

No animal has so much hair on the head as man. This in
the first place is the necessary result of the fluid character of
his brain, and of the presence of so many sutures in his skull.
For wherever there is the most fluid and the most heat,
there also must necessarily occur the greatest outgrowth.^
But, secondly, the thickness of the hair in this part has a final
cause, being intended to protect the head, by preserving it from
658b. 4

50 ii. 14 — ii. 16.

excess of either heat or cold. And as the brain of man is larger
and more fluid than that of any other animal, it requires a
proportionately greater amount of protection. For the more
fluid a substance is, the more readily does it get excessively
heated or excessively chilled, while substances of an opposite
character are less liable to such injurious affections.

This however is a digression, into which we have been led
by the close connection of hair and eyelashes ; the causes
to which these latter owe their existence being the real matter
in hand. We must therefore put off all further details
concerning the hair till the proper occasions arrive and then
return to the full consideration of the subject.'*'

(Ch. 15.^ Both eyebrows and eyelashes exist for the pro-
tection of the eyes ; the former that they may shelter them,
like the eaves of a house, from any fluids that trickle down
the head ; ^ the latter to act like the palisades which are
sometimes placed in front of enclosures, and to keep out any
objects which might otherwise get in. The brows are placed
over the junction of two bones,^ which is the reason that in
old age they often become so bushy * as to require cutting.
The lashes are set at the terminations of small blood-vessels.
For the vessels come to an end where the skin itself
terminates ; and, in all places where these endings occur,
the exudation of moisture of a corporeal character necessitates
the growth of hairs,* unless there be some operation of nature
which interferes, by diverting the moisture to another purpose.^

(Ch. 16.) In the generality of viviparous quadrupeds, there is
no great variety in the forms of the organ of smell. In those
of them however whose jaws project forwards and taper to a
narrow end, so as to form what is called a snout, the nostrils
are placed in this projection, there being no other available plan ;
while, in the rest, there is a more definite demarcation between
nostrils and jaws. But in no animal is this part so peculiar
as in the elephant, where it attains an extraordinary size and
strength. For the elephant uses its nostril as a hand ; this being
the instrument with which it conveys food, fluid and solid alike,
to its mouth. With it, too, it tears up trees,^ coiling it round
their trunks. In fact it applies it generally to the purposes of
a hand. For the elephant has the double character of a land
animal, and of one that lives in swamps. Seeing then that it
659 a.

ii. i6. 51

has to get food In the water,^ and yet must necessarily breathe,
inasmuch as it is a land animal and has blood ; seeing, also,
that its excessive weight prevents it from passing rapidly from
water to land, as some other sanguineous vivipara that breathe
can do, it becomes necessary that it shall be suited alike for life
in the water and for life on dry land. Just then as divers are
sometimes provided with instruments for respiration, through
which they can draw air from above the water, and thus may
remain for a long time under the sea,^ so also have elephants
been furnished by nature with their lengthened nostril ; and,
whenever they have to traverse the water, they lift this up above
the surface and breathe through it. For the elephant's proboscis,
as already said, is a nostril. Now it would have been impossible
for this nostril to have the form of a proboscis, had it been hard
and incapable of bending. For its very length would then have
prevented the animal from supplying itself with food, being as
great an impediment as the horns of certain oxen, that are said *
to be obliged to walk backwards while they are grazing. It is
therefore soft and flexible, and, being such, is made, in addition
to its own proper functions, to serve the office of the fore-feet;
nature in this following her wonted plan of using one and the
same part for several purposes.^ For in polydactylous quadrupeds
the fore-feet are not intended merely to support the body, but
also to serve as hands. But in elephants, though they must
be reckoned polydactylous, as their foot has neither cloven nor
solid hoof,^ the fore-feet, owing to the great size and weight of
the body, are reduced to the condition of mere supports ; and
indeed their slow motion and''' unfitness for bending make them
useless for any other purpose. A nostril, then, is given to the
elephant for respiration, as to every other animal that has a lung,
and is lengthened out and endowed with its power of coiling,
because the animal has to remain for considerable periods of
time in the water, and is unable to pass thence to dry ground
with any rapidity. But as the feet are shorn of their full office,
this same part is also, as before said, made by nature to supply
their place, and give such help as otherwise would be rendered
by them.

As to other sanguineous animals, the Birds, the Serpents and
the oviparous quadrupeds, in all of them there are the nostril-
holes, placed in front of the mouth ; but in none are there any
659 b.

52 ii. i6.

distinctly formed nostrils, nothing in fact which can be called
nostrils except from a functional point of view. A bird at any.
rate has nothing which can properly be called a nose. For its
so-called beak is a substitute for jaws. The reason for this
is to be found in the natural conformation of birds. For they
are winged bipeds ; and this makes it necessary that their head
and neck shall be of light weight ; just as it makes it necessary
that their breast-bone shall be narrowed. The beak therefore
with which they are provided is formed of a bone-like substance,
in order that it may serve as a weapon as well as for nutritive
purposes, but is made of narrow dimensions to suit the small
size of the head. In this beak are placed the olfactory passages.
But there are no nostrils ; for such could not possibly be placed
there.

As for those animals that have no respiration,^ it has already
been explained why it is that they are without nostrils, and
perceive odours either through gills, or through a blow-hole,^
or, if they are insects, by the hypozoma ; ^^ and how their power
of smelling depends, like their motions, upon the innate spirit '^
of their bodies, which in all of them is implanted by nature
and not introduced from without.

Under the nostrils are the lips, in such sanguineous animals,
that is, as have teeth. For in birds, as already has been said,
the purposes of nutrition and defence are fulfilled by a bone-
like beak, which forms a compound substitute for teeth and lips.
For supposing that one were to cut off a man's lips, unite his
upper teeth together, and similarly his under ones, and then
were to lengthen out the two separate pieces thus formed, flat-
tening them on either side and making them project forwards,
supposing I say this to be done, we should at once have a bird-
like beak.

The use of the lips in all animals except man is to preserve
and guard the teeth ; and thus it is that the distinctness with
which the lips are formed is in direct proportion to the degree
of nicety and perfection with which the teeth are fashioned. In
man the lips are soft and flesh-like and capable of separating
from each other. Their purpose, as in other animals, is to guard
the teeth, but they are more especially intended to serve a higher
office, contributing in common with other parts to man's faculty
of speech. For just as nature has made man's tongue unlike
650 b.

ii. i6— ii. 17 53

that of other animals, and, in accordance with what I have said
is her not uncommon practice,^^ has used it for two distinct
operations, namely for the perception of savours and for speech,
so also has she acted with regard to the lips, and made them
serve both for speech and for the protection of the teeth. For
vocal speech consists of combinations of the letters, and most of
these it would be impossible to pronounce, were the lips not moist,
nor the tongue such as it is. For some letters are formed by
closures of the lips and others by applications of the tongue.
But the differences of these movements, their nature and their
number, are questions, the discussion of which belongs to the
writers on articulation. It was necessary however for us to follow
up the several parts in question at once to the function now
assigned to them, and to show that they are of a character well
suited for its performance. Therefore it is then that they are
made of flesh. And the flesh of man is softer than that of any
other animal, the reason ^^ for this being, that of all animals man
has the most delicate sense of touch.'*

(Ch. ly.) The tongue is placed under the vaulted roof of the
mouth. In land animals it presents but little diversity. But
in other' animals it is variable, and this whether we compare
them as a class with such as live on land, or compare their
several species with each other. It is in man that the tongue
attains its greatest degree of freedom, of softness, and of breadth ;
the object of this being to render it suitable for its double function.
For its softness fits it for the perception of savours, a sense which
is more delicate in man than in any other animal, softness being
most impressionable by touch, of which sense taste is but a
variety.^ This same softness again, together with its breadth,
adapts it for the articulation of letters and for speech. For these
qualities, combined with its freedom from attachment, are those
which suit it best for advancing and retiring in every direction.
That this is so is plain, if we consider the case of those who are
tongue-tied in however slight a degree. For their speech is
indistinct and lisping; that is to say they have not got the full
power of uttering letters. In being broad is comprised the
possibility of becoming narrow ; for in the great the small is
included, but not the great in the small.

What has been said explains why, even among birds, those
that are most capable of pronouncing letters are such as have
660 a.

54 11- 17-

the broadest tongues ;^ and why the viviparous and sanguineous
quadrupeds, where the tongue is hard and thick and not free in
its motions, have a very limited vocal articulation. Some birds
have a considerable variety of notes. These are the smaller
kinds.* But it is the birds with talons that have the broader
tongues and consequently the greater aptitude for speech. All
birds use their tongues to communicate with each other. But
some do this in a greater degree than the rest ; so that in some
cases it even seems as though actual instruction were imparted
from one to another by its agency.^ These however are matters
which have already been discussed in the Researches concerning
Animals.^

As to those oviparous and sanguineous animals that live not
in the air but on the earth, their tongue in most cases is tied
down and hard, and is therefore useless for vocal purposes ; in
the serpents however and in the lizards it is long and forked, so
as to be suited for the perception of savoursJ So long indeed
is this part in serpents, that though small while in the mouth it
can be protruded to a great distance. In these same animals it
is forked and has a fine and hair-like extremity, because of their
extreme liking for dainty food. For by this arrangement they
derive a two-fold pleasure from savours, their gustatory sensation
being as it were doubled.

Even some bloodless animals have an organ that serves for
the perception of savours ; and in sanguineous animals . such an
organ is invariably present. For even in such of these as would
seem to an ordinary observer to have nothing of the kind, some
of the fishes for example, there is a kind of shabby representative
of a tongue,® much like what exists in river crocodiles. In most
of these cases the apparent absence of the part can be rationally
explained on some or other ground. For in the first place the
interior of the mouth in animals of this character is invariably
spinous. Secondly in water animals there is but short space of
time for the perception of savours, and as the use of this sense
is thus of short duration, shortened also is the separate part
which subserves it. The reason for their food being so rapidly
transmitted to the stomach is that they cannot possibly spend
any time in sucking out the juices ; for were they to attempt
to do so, the water would make its way in during the process.
Unless therefore one pulls their mouth very widely open indeed,
660 b.

"• I/- 55

the projection of this part is quite invisible. The region exposed
by thus opening the mouth is spinous ; for it is formed by the
close apposition of the gills, which are of a spinous character.

In crocodiles the immobility of the lower jaw also contributes
in some measure to stunt the development of the tongue.
For the crocodile's tongue is adherent to the lower jaw;^ and
its upper and lower jaws are as it were inverted, for in other
animals it is the upper jaw which is the immoveable one. The
tongue, then, of this animal does not adhere to the upper jaw,
because that would interfere with the ingestion of food, but
adheres to the lower jaw, because this is, as it were, the upper
one which has changed its place.^'' Moreover it is the crocodile's
lot though a land animal to live the life of a fish, and this
again necessarily involves an indistinct formation of the part in
question.^^

The roof of the mouth resembles flesh, even in many of the
fishes ; and in some of the river species, as for instance in the
fishes known as Cyprini,^^ is so very flesh-like and soft as to be
taken by careless observers for a tongue. The tongue of fishes,
however, though it exists as a separate part, is never distinctly
visible like this, as has been already explained. Again, as the
gustatory sensibility is intended to serve animals in the selection
of food, it is not diffused equally over the whole surface of the
tongue-like organ, but is placed chiefly in the tip ; ^' and for
this reason it is the tip which is the only part of the tongue
separated in fishes from the rest of the mouth. As all animals
are sensible to the pleasure derivable from food, they all feel a
desire for it. For the object of desire is the pleasant. The part
however in which food produces the sensation is not precisely alike
in all of them, but while in some it is free from attachments, in
others, where it is not required for vocal purposes, it is united with
the base of the mouth ; in some again it is hard, in others soft
or flesh-like. Thus even the Crustacea,^* the Carabi for instance
and the like, and the Cephalopods, such as the Sepias and the
Poulps, have some such part inside the mouth. As for the
Insects, some of them have the part which serves as tongue
inside the mouth, as is the case with ants, and as is also the
case with many Testacea, while in others it is placed externally.
In this latter case it resembles a sting or piercer, and is
hollow and spongy, so as to serve at one and the same time for
661a.

56 ii. 17.

the tasting and for the sucking up of nutriment. This is plainly
to be seen in flies and bees and all such animals, and likewise
in some of the Testacea. In the Purpurae,^^ for instance, so
strong is this part that it enables them to bore holes through
the hard covering of shell-fish, of the spiral snails, for example,
that are used as bait to catch them. So also gad-flies and
cattle-flies ^^ can pierce through the skin of man, and some of
them even through the skins of other animals. Such, then, in
these animals is the nature of the tongue, which is thus as it
were the counterpart of the elephant's nostril. For as in the
elephant the nostril is used as a weapon, so in these animals
the tongue serves as a piercer or sting.*'

In all other animals the tongue agrees with the description
already given.

661a.

iii. I. 57

BOOK III.

(Ch. I J We have next to consider the teeth, and with these
the mouth, that is the cavity which they enclose and form. The
teeth have one invariable office, namely the reduction of the food ;
but besides this general function they have other special ones,
and these differ in different groups. Thus in some animals the
teeth serve as weapons ; but this with a distinction. For there
are offensive weapons and there are defensive weapons ; and while
in some animals, as the wild carnivora, the teeth answer both
purposes, in many others, both wild and domesticated, they serve
only for defence.^ In man the teeth are admirably constructed
for their general function, the front ones being sharp, so as to cut
the food into bits, and the hinder ones broad and flat, so as to
grind it to a pulp ; while between these and separating them
are^^he dog-teeth, which, in accordance with the rule that the
mean partakes of both extremes, share in the characters of those
on either side, being broad in one part but sharp in another.^
Similar distinctions of shape are presented by the teeth of other
animals, with the exception of those whose teeth are one and
all of the sharp kind. In man, however, the number and the
character of the teeth have been mainly determined by the require-
ments of speech. For the front teeth of man contribute in many
ways to the formation of letter-sounds.

In some animals, however, the teeth, as already said, serve
merely for the reduction of food. When, besides this, they serve
as offensive and defensive weapons, they may either be formed
into tusks, as for instance is the case in swine, or may be sharp-
pointed and interlock with those of the opposite jaw, in which
661b.

58 iii. I.

case the animal is said to be saw-toothed. The explanation of
this latter arrangement is as follows. The strength of such an
animal is in its teeth, and the efficacy of these depends on their
sharpness. In order, then, to prevent their getting blunted by
mutual friction, such of them as serve for weapons fit into each
other's interspaces, and are so kept in proper condition. No
animal that is saw-toothed is at the same time furnished with
tusks.3 For nature never makes anything superfluous or in vain.
She gives, therefore, tusks to such animals as strike in fighting,
and serrated teeth to such as bite. Sows, for instance, have no
tusks, and accordingly sows bite instead of striking.

A general principle must here be noted, which will be found
applicable not only in this instance but in many others that will
occur later on. Nature allots each weapon, offensive or defensive,
to those animals alone that- can use it; or, if not to them alone,
to them in a more marked degree ; and she allots it in its most
perfect state to those that can use it best ; and this whether it
be a sting, or a spur, or horns, or tusks, or what it may of a like
kind.

Thus as males are stronger and more choleric than females,
It is in males alone that such parts as those just mentioned are
found, or at any rate it is in males that they are found in the
highest degree of perfection.* For though females are of course
provided with such parts as are no less necessary to them than
to males, the parts for instance which subserve nutrition, they
have even these in an inferior degree,^ and the parts which answer
no such necessary purpose they do not possess at all. This
explains why stags have horns, while does have none ; why the
horns of cows are different from those of bulls, and, similarly,
the horns of ewes from those of rams. It explains also why the
females are often without spurs in species where the males are
provided with them, and accounts for similar facts relating to
other such parts.^

All fishes have teeth of the serrated form, with the single
exception of the fish known as the Scarus.' In many of them
there are teeth even on the tongue and on the roof of the mouth.^
The reason for this is that, living as they do in the water, they
cannot but allow this fluid to pass into the mouth with the food.
The fluid, thus admitted, they must necessarily discharge again
without delay. For were they not to do so, but to retain it for
662 a.

111. I. 59

a time while triturating the food, the water would run into their
digestive cavities. Their teeth therefore are all of the sharp kind,
so as to serve for comminution of their food, and at the same
time are numerous, and set in many parts, that by their very
abundance, in the absence of any grinding faculty, they may
mince the food into small bits.^ Their teeth are also curved,
because these are almost the only weapons which they possess.^^

In all these offices of the teeth the mouth also takes its part ; but
besides these functions it is subservient to respiration, in all such
animals as breathe and are cooled by external agency. For
nature, as already said,^^ uses the parts which are common to all
animals for many special purposes, and this of her own accord.^^
Thus the mouth has one universal function in all animals alike,
namely its alimentary office ; but in some, besides this, the special
duty of serving as a weapon is attached to it ; in others that of
ministering to speech ; and again in many, though not in all, the
office of respiration. All these functions are thrown by nature
upon one single organ, the construction of which she varies
so as to suit the variations of office. Therefore it is that in some
animals the mouth is contracted, while in others it is of wide
dimensions. The contracted form belongs to such animals as use
the mouth merely for nutritive, respiratory, and vocal purposes ;
whereas in such as use it as a means of defence it has a wide
gape. This is its invariable form in such animals as are saw-
toothed. For seeing that their mode of warfare consists in biting,
it is advantageous to them that their mouth shall have a wide
opening ; for the wider it opens, the greater will be the extent of
the bite, and the more numerous will be the teeth called into play.

What has just been said applies to fishes as well as to other
animals ; and thus in such of them as are carnivorous, and made
for biting, the mouth has a wide gape ; whereas in the rest it is
small, being placed at the extremity of a tapering snout. For
this form is suited for their purposes, while the other would be
useless.

In birds the mouth consists of what is called the beak, which in
them is a substitute for lips and teeth. This beak presents
variations in harmony with the functions and protective purposes
which it serves. Thus in those birds that are called Crooked-
clawed^^ it is invariably hooked, inasmuch as these birds are
carnivorous, and eat no kind of vegetable food whatsoever. For
662b.

6o iii. I — iii. 2.

this form renders it serviceable to them in obtaining the mastery
over their prey, and is better suited for deeds of violence than any
other. Moreover, as their weapons of offence consist of this beak
and of their claws, these latter also are more crooked in them than
in the generality of birds. Similarly in each other kind of bird
the beak is suited to the mode of life. Thus, in woodpeckers^*
it is hard and strong, as also in crows and birds of crowlike habit,
while in the smaller birds it is delicate, so as to be of use in
collecting seeds and picking up minute animals. In such birds,
again, as eat herbage, and such as live on the edges of marshes —
those, for example, that swim and have webbed feet — the bill is
broad, or adapted in some other way to the mode of life. For
a broad bill enables a bird to dig into the ground with ease, just
as, among quadrupeds, does the broad snout of the pig, an animal
which, like the birds in question, lives on roots. Moreover, in
these root-eating birds and in some others of like habits of life,
the tips of the bill end in hard points, which gives them additional
facility in dealing with herbaceous food.

The several parts which are set on the head have now, pretty
nearly all, been considered. In man, however, the part which lies
between the head and the neck is called the face, this name (in
Greek prosopoii) being, it would seem, derived from the function
of the part. For as man is the only animal that stands upright,
he is also the only one that looks directly in front (in Greek proso) ;
and the only one whose voice is emitted in that direction.^^

(Ch. 2.) We have now to treat of horns ; for these also, when
present, are appendages of the head. They exist in none but
viviparous animals ; though in some ovipara certain parts are
metaphorically spoken of as horns, in virtue of a certain
resemblance.^ To none of such parts however does the proper
office of a horn belong ; for they are never used, as are the horns
of vivipara, for purposes which require strength, whether it be
in self-protection or in offensive strife. So also no polydactylous
animal"^ is furnished with horns. For horns are weapons of
strife, and these polydactylous animals possess other means of
security. For to some of them nature has given claws, to others
teeth suited for combat, and to the rest some or other adequate
defensive appliance. There are horns, however, in most of the
cloven-hoofed animals, and in some^ of those that have a solid
hoof, serving them as an offensive weapon, and in some cases
663 a.

iii. 2. 6i

also as a defensive one. There are horns also in all animals that
have not been provided by nature with some other means of
security ; such means for instance as speed, which has been
given to horses ; or excessive bulk of body, which is sufficient
in itself to protect an animal from being destroyed by others
and which has been given to camels, and in a still greater measure
to elephants. Other animals again are protected by the possession
of tusks ; and among these are the swine, though they have a
cloven hoof.*

All animals again whose horns are but useless appendages have
been provided by nature with some additional means of security.
Thus deer are endowed with speed ; for the large size and great
branching of their horns makes these a source of detriment rather
than of profit to their possessors.-'' Similarly endowed are the
Bubalus ^ and gazelle -p for though these animals will stand up
against some enemies and defend themselves with their horns,
yet they run away from such as are fierce and valiant. The
Bonasus again, whose horns curve inwards towards each other
[and are therefore of no use as weapons], is provided with a
means of protection in the discharge of its excrement ; and of
this it avails itself when frightened. There are some other
animals besides the Bonasus that have a similar mode of defence.^
In no case however does nature ever give more than one adequate
means of protection to one and the same animal.^

Most of the animals that have horns are cloven-hoofed ; but
the Indian ass, as they call it, is also reported to be horned, though
its hoof is solid. ^'^

Again as the body, so far as regards its organs of motion,^^
consists of two distinct parts, the right and the left, so also and
for like reasons the horns of animals are, in the great majority of
cases, two in number. Still there are some that have but a single
horn ; the Oryx '^ for instance, and the so-called Indian ass ; in the
former of which the hoof is cloven, while in the latter it is solid.
In such animals the horn is set in the centre of the head ; for as
the middle belongs equally to both extremes, this arrangement is
the one that comes nearest to each side having its own horn.

Again, it would appear consistent with reason that the single

horn should go with the solid rather than with the cloven hoof

For hoof, as also claw, is of the same nature as horn ; so that

the two naturally undergo division simultaneously and in the

663 a.

62 iii. 2.

same animals. Again, since the division of the cloven hoof
depends on deficiency of material, it is but rationally consistent,
that nature when she gave an animal an excess of material for
the hoofs, which thus became solid, should have taken away
something from the upper parts and so made the animal to have
but one horn.^^

Rightly too did she act when she chose the head whereon to set
the horns. And ^sop's Momus^* is beside the mark, when he finds
fault with the bull for not having its horns upon its shoulders.
For from this position, says he, they would have delivered their
blow with the greatest force, whereas on the head they occupy the
weakest part of the whole body. Momus was but dull-sighted in
making this hostile criticism. For had the horns been set on the
shoulders, or had they been set on any other part than they are,-
the encumbrance of their weight would have been increased, not
only without any compensating gain whatsoever, but with the
disadvantage of impeding many bodily operations. For the point
whence the blows could be delivered with the greatest force was
not the only matter to be considered, but the point also whence
they could be delivered with the widest range. But as the bull
has no hands and cannot possibly have its horns on its feet or on
its knees, where they would prevent flexion, there remains no other
site for them but the head ; and this therefore they necessarily
occupy. In this position, moreover, they are much less in the way
of the movements of the body than they would be elsewhere.

Deer are the only animals in which the horns are solid through-
out, and are also the only animals that cast them.^^ This casting
is not simply advantageous to the deer from the increased lightness
which it produces, but, seeing how heavy the horns are, is a matter
of actual necessity.

In all other animals the horns are hollow for a certain distance,
and the end alone is solid, this being the part of use in a blow. At
the same time, to prevent even the hollow part from being weak,
the horn does not grow out of the skin, but has a solid piece from
the bones fitted into its cavity. For this arrangement is not only
that which makes the horns of the greatest service in fighting, but
that which causes them to be as little of an impediment as possible
in the other actions of life.

Such then are the reasons for which horns exist ; and such the
reasons why they are present in some animals, absent from others.
663b.

iii. 2 — iii. 3. 63

Let us now consider how the necessary results of the material
nature are made available by rational nature for a final cause.'^

In the first place, then, the larger the bulk of animals, the greater
is the amount of corporeal and earthy matter which they contain.
Thus no very small animal is known to have horns, the smallest
horned animal that we are acquainted with being the gazelle.^''^
But in all our speculations concerning nature, what we have to
consider is the general rule ; for that is natural which applies
either universally or generally.'^ And thus when we say that
the largest animals have most earthy matter, we say so because
such is the general rule. Now this earthy matter is used in the
animal body to form bone. But in the larger animals there is an
excess of it, and this excess is turned by nature to useful account,
being converted into weapons of defence. Part of it necessarily
flows to the upper portion of the body, and this is allotted by her
in some cases to the formation of tusks and teeth, in others to the
formation of horns. Thus it is that no animal that has horns
has also front teeth in both jaws, those in the upper jaw being
deficient.'^ For nature by subtracting from the teeth adds to
the horns ; the nutriment which in most animals goes to the
former being here spent on the augmentation of the latter. Does,
it is true, have no horns and yet are equally deficient with the
males as regards the teeth. The reason, however, for this is that
they, as much as the males, are naturally horn-bearing animals ;
but they have been stripped of their horns, because these would
not only be useless to them but actually baneful ;^ whereas the
greater strength of the males causes these organs, though equally
useless, to be much less of an impediment. In other animals,
where this material is not secreted from the body in the shape
of horns, it is used to increase the size of the teeth ; in some cases
of all the teeth, in others merely of the tusks, which thus become
so long as to resemble horns projecting from the jaws.^^

(Ch. 3.J So much, then, of the parts which appertain to the
head. Below the head lies the neck, in such animals as have one.
This is the case only with those that have the parts to which a
neck is subservient. These parts are the larynx^ and what is
called the oesophagus. Of these the former, or larynx, exists
for the sake of respiration, being the instrument by which such
animals as breathe inhale and discharge the air. Therefore it is
that, when there is no lung, there is also no neck. Of this
664 a.

64 iii. 3-

condition the Fishes are an example. The other part, or
CESophagus, is the channel through which food is conveyed .to
the stomach ; so that all animals that are without a neck are
also without a distinct oesophagus. ^ Such a part is in fact not
required of necessity for nutritive purposes ; for it has no action
whatsoever on the food. Indeed there is nothing to prevent
the stomach from being placed directly after the mouth. This
however is quite impossible in the case of the lung. For there
must be some sort of tube common to the two divisions of the
lung, by which the breath may be apportioned to their respective
bronchi, and thence pass into the air pipes ; and such an arrange-
ment will be the best for giving perfection to inspiration and
respiration. The organ then concerned in respiration must of
necessity be of some length ; and this again necessitates there
being an oesophagus to unite mouth and stomach.^ This
oesophagus is of a flesh-like character, and yet admits of exten-
sion like a sinew. ^ This latter property is given to it, that it
may stretch when food is introduced ; while the flesh-like
character is intended to make it soft and yielding, and to
prevent it from being rasped by particles as they pass down-
wards, and so suffering damage. On the other hand the windpipe
and the so-called larynx are constructed out of a cartilaginous
substance. For they have to serve not only for respiration,
but also for vocal purposes ; and an instrument that is to
produce sounds must necessarily be not only smooth but firm.
The windpipe lies in front of the oesophagus, although this position
causes it to be some hindrance to the latter in the act of
deglutition.^ For if a morsel of food, fluid or solid, slips into
it by accident, choking and difficult breathing and violent cough
ensue. This must be a matter of astonishment to any of those
who assert that it is by the windpipe that an animal imbibes
fluid. ^ For the consequences just mentioned occur invariably,
whenever a particle of food slips in, and are quite obvious.
Indeed on many grounds it is ridiculous to say that this is the
channel through which animals imbibe fluid. For there is no
passage leading from the lung to the stomach, such as the
oesophagus which we see leading thither from the mouth.
Moreover, when any cause produces sickness and vomiting, it is
plain enough whence the fluid is discharged. It is manifest also
that fluid, when swallowed, does not pass directly into the bladder
664b.

iii. 3. 65

and collect there, but goes first into the stomach. For, when red
wine is taken, the dejections of the stomach are seen to be
coloured by its dregs ; and such discoloration has been even
seen on many occasions inside the stomach itself, in cases where
there have been wounds opening into that organ. However it
is perhaps silly to be minutely particular in dealing with silly
statements such as this.

The windpipe then, owing to its position in front of the
oesophagus, is exposed, as we have said, to annoyance from the
food. To obviate this, however, nature has contrived the epiglottis.
This part is not found in all viviparous animals, but only in such
of them as have a lung; nor in all of these, but only in such
as at the same time have their skin covered with hairs, and not
either with scaly plates or with feathers. In such scaly and
feathered animals there is no epiglottis, but its office is supplied
by the larynx,''' which closes and opens, just as in the other
case the epiglottis falls down and rises up ; rising up during
the ingress or egress of breath, and falling down during the
ingestion of food, so as to prevent any particle from slipping
into the trachea. Should there be the slightest want of accuracy
in this movement, or should an inspiration be made during the
ingestion of food, choking and coughing ensue, as already has
been noticed. So admirably contrived, however, is the movement
both of the epiglottis and of the tongue, that, while the food
is being ground to a pulp in the mouth, the tongue very rarely
gets caught between the teeth ; and, while the food is passing
over the epiglottis, seldom does a particle of it slip into the
windpipe.

The animals which have been mentioned as having no epiglottis
owe this deficiency to the dryness of their flesh and to the hardness
of their skin. For an epiglottis made of such materials would not
admit of easy motion.^ In fact it would take a longer time to shut
down an epiglottis made of the peculiar flesh of these animals, and
shaped like that of those with hairy skins, than to bring the edges
of the trachea itself into contact with each other.

Thus much then as to the reasons why some animals have an
epiglottis while others have none, and thus much also as to its use.
It is a contrivance of nature to remedy the vicious position of the
windpipe in front of the oesophagus. That position is the result
of necessity. For it is in the front and centre of the body that
665a. 5

66 iii. 3 — iii. 4.

the heart Is situated, in which we say is the principle of life and
the source of all motion and sensation. (For sensation and motion-
are exercised in the direction which we term forwards, and it is on
this very relation that the distinction of before and behind is
founded.) But where the heart is, there and surrounding it is the
lung. Now inspiration, which occurs for the sake of the lung and
for the sake of the principle which has its seat in the heart, is
effected through the windpipe. Since then the heart must of
necessity lie in the very front place of all, it follows that the
larynx also and the windpipe must of necessity lie in front of the
oesophagus. For they lead to the lung and heart,^ whereas the
oesophagus leads to the stomach. And it is an universal law
that, as regards above and below, front and back, right and left,
the nobler and more honourable part invariably is placed upper-
most, in front, and on the right, rather than in the opposite
positions, unless some more important object stands in the way.^''
(CA. 4.) We have now dealt with the neck, the oesophagus, and
the windpipe, and have next to treat of the viscera. These are
peculiar to sanguineous animals, some of which have all of them,
others only a part, while no bloodless animals have any at all.^
Democritus then seems to have been mistaken in the notion he
formed of the viscera, if he fancied that the reason why none
were discoverable in bloodless animals was that these animals were
too small to allow them to be seen. For, in sanguineous animals,
the heart and liver are visible enough when the body is only just
formed, and while it is still extremely small. For these parts are
to be seen in the egg sometimes as early as the third day, being
then no bigger than a point ; ^ and are visible also in aborted *
embryos, while still excessively minute. Moreover, as the external
organs are not precisely alike in all animals, but each creature is
provided with such as are suited to its special mode of life and
motion, so is it with the internal parts, these also differing in
different animals. Viscera, then, are peculiar to sanguineous
animals ; and this accords with the fact that the viscera are each
and all formed from sanguineous material, as is plainly to be seen
in the new-born young of these animals. For in such the viscera
are more sanguineous, and of greater bulk in proportion to the
body, than at any later period of life, because the nature of the
material and its abundance are most distinctly marked in objects
at the period of their first formation.* There is a heart, then, in
665 b.

iii. 4. 6^

all sanguineous animals, and the reason for this has already been
given. For that sanguineous animals must necessarily have blood
is self-evident. And, as the blood is fluid, it is also a matter of
necessity that there shall be a receptacle for it ; and it is clearly
to meet this requirement that nature has devised the blood-vessels.
These, again, must necessarily have one primary source. For it
is preferable that there shall be one such, when possible, rather
than several. This primary source of the vessels is the heart.^
For the vessels clearly are from it, and not through it.^ Moreover,
being as it is homogeneous, it has the character of a blood-vessel.
Again its position is that of a primary or dominating part. For
nature, when no other more important purpose stands in her way,
places the more honourable part in the more honourable position ;'
and the heart lies about the centre of the body, but rather in its
upper than its lower half, and also more in front than behind.
This is most evident in the case of man, but even in other animals
there is a tendency in the heart to assume a similar position, in
the centre of the necessary part of the body, that is to say of the
part which terminates in the vent for excrement. For the limbs
vary in position in different animals, and are not to be counted
with the parts which are necessary for life. For life can be
maintained even when they are removed ; while it is self-evident
that the addition of them to an animal is not destructive of it.

There are some^ who say that the vessels commence in the
head. In this they are clearly mistaken. For in the first place,
according to their representation, there would be many sources
for the vessels, and these scattered ; and secondly these sources
would be in a region that is manifestly cold, as is shown by its
intolerance of chill, whereas the region of the heart is as manifestly
hot.' Again, as already said, the vessels extend through all the
other viscera, but no vessel extends through the heart.^" From
this it is quite evident that the heart is a part of the Vessels and
their origin ; and for this it is well suited by its structure. For its
centraPi part consists of a thick and hollow body, and is more-
over full of blood, as though the vessels took thence their origin.
It is hollow to serve for the reception of the blood, while its wall
is thick, that it may serve to protect the source of heat. For
here, and here alone in all the viscera and in fact in all the
body, there is blood without blood-vessels, the blood elsewhere
being always contained within vessels.' ^ Nor is this but con-
666 a.

68

111. 4.

sistent with reason. For the blood is conveyed into the vessels
from the heart, but none passes into the heart from without.
For in itself it constitutes the origin and fountain, or primary-
receptacle, of the blood. It is, however, from dissections and
from observations on the process of development that the truth
of these statements receives its clearest demonstration. For the
heart is the first of all the parts to be formed ; and no sooner
is it formed than it contains blood. Moreover the motions of
pain and pleasure,^^ and generally of all sensation, plainly start
from the heart, and find in it their ultimate termination. This,
indeed, reason would lead us to expect. For the starting-point
must, whenever possible, be one ; and, of all places, the best
suited for a starting-point is the centre. For the centre is one,
and is equally or almost equally within reach of every part.
Again, as neither the blood itself, nor yet any part which is
bloodless, is endowed with sensation, it is plain that that part
which first has blood, and which holds it as it were in a receptacle,
must be the primary source of sensation.'* And that this part is
the heart is not only a rational inference, but is also evident to
the senses. For no sooner is the embryo formed, than its heart
is seen in motion like a living creature, and this before any
of the other parts, as though it constituted the starting-point
of life in all animals that have blood. A further evidence of
the truth of what has been stated is the fact that no sanguineous
animal is without a heart. For the primary source of blood must
of necessity be present in them all. It is true that sanguineous
animals not only have a heart but also invariably have a liver.
But no one could ever deem the liver to be the primary organ
either of the whole body or of the blood.''' For the position in
which it is placed is far from being that of a primary or dominating
part ; and moreover in the most perfectly finished animals there
is another part, the spleen, which as it were counterbalances it.'^
Still further, the liver contains no spacious receptacle in its
substance, as does the heart, but has its blood in a vessel like
all the other viscera. The vessel moreover extends through it, and
no vessel whatsoever originates in it ; for it is from the heart
that all the vessels take their rise. Since then one or other of
these two parts must be the central source, and since it is not
the liver which is such, it follows of necessity that it is the
heart which is the source of the blood, as also the primary
666 a.

iii. 4. 69

organ in other respects. For the definitive characteristic of an
animal is the possession of sensation ; and the first sensory part
is that which first has blood ; that is to say is the heart, which
is the source of blood and the first of the parts to contain it.

The apex of the heart is pointed and more solid than the rest
of the organ. It lies against the breast, and entirely in the
anterior part of the body, in order to prevent that region from
getting chilled. For in all animals there is comparatively but
little flesh over the breast, whereas there is a more abundant
covering of that substance on the posterior surface, so that the
heat has in the back a sufficient amount of protection. In all
animals but man the heart is placed in the centre of the pectoral
region ; but in man ^^ it inclines a little towards the left, so that
it may counterbalance the chilliness of that side. For the left
side is colder in man, as compared with the right, than in any
other animal. ^^ It has already been stated that even in fishes
the heart holds the same position as in other animals ; and the
reasons have been given why it appears not to do so. The
apex of the heart, it is true, is in them turned towards the
head, but this in fishes is the front aspect, for it is the direction
in which their motion occurs. ^^

The heart again is abundantly supplied with sinews,-" as might
reasonably be expected. For the motions of the body commence
from the heart, and are brought about by traction and relaxation.
The heart therefore, which, as already said, is as it were a living
creature inside its possessor, requires some such subservient and
strengthening parts.

In no animals does the heart contain a bone, certainly in none
of those that we have ourselves inspected, '-^^ with the exception of
the horse and a certain kind of ox. In these exceptional cases
the heart, owing to its large bulk, is provided with a bone as a
support ; just as the bones serve as supports for the body
generally. 23

In animals of great size the heart ^^ has three cavities ; in
smaller animals it has two ; and in all has at least one. The
reason for this, as already stated, is that there must be some
place in the heart to serve as a receptacle for the first blood ;
which, as has been mentioned more than once, is formed in this
organ. But inasmuch as the main blood-vessels are two in
number,^* namely the so-called great vessel and the aorta, each of
666b.

70 ^ lii. 4.

which is the origin of other vessels ; inasmuch, moreover, as these
two vessels present differences, hereafter to be discussed, when"
compared with each other, it is of advantage that they also shall
themselves have distinct origins. This advantage will be obtained
if each side have its own blood, and the blood of one side be
kept separate from that of the other.^^ For this reason the heart,
whenever it is possible, has two receptacles. And this possibility-
exists in the case of large animals, for in them the heart, as the
body generally, is of large size. Again it is still better that there
shall be three cavities, so that the middle and odd one may serve
as a common origin for both sides.^^ But this requires the heart
to be of greater magnitude, so that it is only in the largest animals
that the heart has three cavities.

Of these three cavities it is the right which has the most
abundant and the hottest blood,^''' and this explains why the limbs
on the right side of the body are also warmer than those on the
left.2^ The left cavity has the least blood of all, and the coldest ;
while in the middle cavity the blood, as regards quantity and
heat, is intermediate to the other two, being however of purer
quality than either. For it behoves the supreme part to be as
tranquil as possible, and this tranquillity can be ensured by the
blood being pure, and of moderate amount and warmth.^^

In the heart of animals there is also a kind of joint-like division,
something like the sutures of the skull.^" This is not however
attributable to the heart being formed by the union of several
parts into a compound whole, but is rather, as already said, the
result of a joint-like division. These jointings are most distinct
in animals of keen sensibility, and less so in those that are of
duller feeling, in swine for instance. Different hearts differ also
from each other in their sizes, and in their degrees of firmness ;
and these differences somehow extend their influence to the
temperaments of the animals. For in animals of low sensibility
the heart is hard and solid, while it is softer in such as are
endowed with keener feeling. So also when the heart is of large
size the animal is timorous, while it is more courageous if the
organ be smaller and of moderate bulk. For in the former the
bodily affection which results from terror already pre-exists ; ^^ for
the bulk of the heart is out of all proportion to the animal's heat,
which being small is reduced to insignificance in the large space,
and thus the blood is made colder than it would otherwise be.
667 a.

111. 4—111. 5. 71

The heart is of large size^'^ in the hare, the deer, the mouse,
the hyaena, the ass, the leopard, the marten, and in pretty nearly
all other animals that are either manifestly timorous, or that
betray their cowardice by their spitefulness.

What has been said of the heart as a whole is no less true of its
cavities and of the blood-vessels ; these also if of large size being
cold.^3 For just as a fire of equal size gives less heat in a large
room than in a small one, so also does the heat in a large cavity
or a large blood-vessel, that is in a large receptacle, have less
influence than in a small one. The more spacious, moreover, these
cavities and vessels are, the greater is the amount of spirit ^ which
they contain, and the greater its effect, for all hot substances are
cooled by the motion of external objects,^^ Thus it is that no
animal that has large cavities in its heart, or large blood-vessels,
is ever fat, the vessels being indistinct and the cavities small in
all or most fat animals.^^

The heart again is the only one of the viscera, and indeed the
only part of the body, that is unable to tolerate any serious affec-
tion.^''' This is but what might reasonably be expected. For, if
the primary or dominant part be diseased, there is nothing from
which the other parts which depend upon it can derive succour.
A proof, that the heart is thus unable to tolerate any morbid
affection, is furnished by the fact that never has it been seen
diseased in a sacrificial victim, though this is not the case with
the other viscera. For the kidneys are frequently found to be
full of stones, and growths, and small abscesses, as also is 'the
liver, the lung, and more than all the spleen.^^ There are also
many other affections which are seen to occur in these parts, those
which are least liable to such being the portion of the lung which
is close to the windpipe, and the portion of the liver which lies
about the junction with the great blood-vessel. This again admits
of a rational explanation. For it is in these parts that the lung
and liver are most closely in communion with the heart. On the
other hand when animals die not by sacrifice but from disease,
they are found on dissection to have morbid affections of the heart.

(Ch. 5. J Thus much of the heart, its nature, and the end and
cause of its existence in such animals as have it. In due sequence
we have next to discuss the blood-vessels, that is to say the great
vessel and the aorta. For it is into these two^ that the blood
first passes when it quits the heart; and all the other vessels
667 b.

72 iii. 5.

are but offshoots from them. Now that these vessels exist on
account of the blood has already been stated. For every fluid"
requires a receptacle, and in the case of the blood the vessels
are that receptacle. Let us now explain why these vessels are
two, and why they spring from one single source, and extend
throughout the whole body.

The reason, then, why these two vessels coalesce into one
centre, and spring from one source, is that the sensory soul is
in all animals actually one ; (in sanguineous animals one not
only actually but potentially, but in some bloodless animals
one actually only and not potentially ;2) and this one-ness of
the sensory soul determines a corresponding one-ness of the
part in which it primarily abides. Where, however, the sensory
soul is lodged, there also and in the self-same place must
necessarily be the source of heat ;* and, again, where this is
there also must be the source of the blood, seeing that it
thence derives its warmth and fluidity. Thus, then, in the one-
ness of the part in which is lodged the prime source of sensation
and of heat is involved the one-ness of the source in which the
blood originates ; and this, again, explains why the blood-vessels
have one common starting-point.

The vessels, again, are two, because the body of every sanguineous
animal that is capable of locomotion * is bilateral ; for in all such
animals there is a distinguishable before and behind, a right and
left, an above and below. Now as the front is more honourable
and of higher supremacy than the hinder aspect, so also and in
like degree is the great vessel superior to the aorta. For the
great vessel is placed in front, while the aorta is behind ; the
former again is plainly visible in all sanguineous animals, while
the latter is in some indistinct and in some not discernible at all.

Lastly, the reason for the vessels being distributed throughout
the entire body is that in them, or in parts analogous to them,
is contained the blood, or the fluid which in ex-sanguineous
animals takes the place of blood, and that the blood or analogous
fluid is the material from which the whole body is made. Now
as to the manner in which animals are nourished,^ and as to the
ways and means by which they absorb nutriment from the stomach,
these are matters which will be more suitably considered and
explained in the treatise on Generation and Development. But
inasmuch as the parts are, as already said, formed out of the blood,
668a.

iii- 5- 73

it is but rational that the flow of the blood should extend, as it does,
throughout the whole of the body. For since each part is formed
of blood, each must have blood through and in its substance.

To give an illustration of this. The water-courses ^ in gardens
are so constructed as to distribute water from one single source
or fount into numerous channels, which divide and subdivide so
as to convey it to all parts ; and, again, in house-building stones
are thrown down along the whole ground-plan of the foundation
walls ; because the garden-plants in the one case grow at the
expense of the water, and the foundation walls in the other are
built out of the stones. Now just after the same fashion has nature
laid down channels for the conveyance of the blood throughout
the whole body, because this blood is the material out of which
the whole fabric is made. This fact becomes very evident in
bodies that have undergone great emaciation. For in such there
is nothing to be seen but the blood-vessels ; just as when fig-
leaves or vine-leaves or the like have dried up, there is nothing
left of them but their vessels. The explanation of these facts is
that the blood, or fluid which takes its place, is potentially body
and flesh, or substance analogous to flesh. Now just as in
irrigation the larger dykes are permanent, while the smaller ones
are soon filled up with mud and disappear, again to become
visible when the deposit of mud ceases ; so also do the largest
blood-vessels remain permanently open, while the smallest ones
are converted actually into flesh, though potentially they are no
whit less vessels than before.''' This too explains why, so long as
the flesh of an animal is in its integrity, blood will flow from any
part of it whatsoever that is cut, though no vessel, however small,
be visible in it. Yet there can be no blood, unless there be a
blood-vessel. The vessels then are there, but are invisible
owing to their being clogged up, just as the dykes for irrigation
are invisible until they have been cleared of mud.

As the blood-vessels advance, they become gradually smaller
and smaller, until at last their tubes are too fine to admit the
thick blood. This fluid can therefore no longer find its way
through them, though they still give passage to the moisture
which we call sweat ; and especially so when the body is heated,
and the mouths of the small vessels are dilated. Instances,
indeed, are not unknown of persons who in consequence of a
cachectic state have secreted sweat that resembled blood,^ their
668 b.

74 iii. 5— iii- 6.

body having become loose and flabby, and their blood watery,
owing to the heat in the small vessels^ having been too scanty
for its concoction. For, as was before said, every mixture of earth
and water — and both nutriment and blood are such — becomes
thicker from concoction-^"^ The inability of the heat to effect
concoction may be due either to its being absolutely small in
amount, or to its being small in proportion to the quantity of food,
when this has been taken in excess. This excess again may be
of two kinds, either quantitative or qualitative ; for all substances
are not equally amenable to concoction.

The larger the channels, the more easily does the blood flow
through them. Thus it is that when haemorrhages occur from
the nostrils and gums and fundament, and sometimes also from
the mouth, they are of a passive kind, and not violent as are
those from the windpipe. ^^

The great vessel and the aorta, which above lie somewhat
apart, lower down exchange positions, and by so doing give
compactness to the body. For when they reach the point where
the legs diverge, they each split into two, and the great vessel
passes from the front to the rear, and the aorta from the rear
to the front. By this they contribute to the unity of the whole
fabric. For as in plaited work the parts hold more firmly
together because of the interweaving, so also by the interchange
of position between the blood-vessels are the anterior and
posterior parts of the body more closely knit together. A
similar exchange of position occurs also in the upper part of
the body, between the vessels that have issued from the heart.^^
The details however of the mutual relations of the different
vessels must be looked for in the treatises on Anatomy and
the Researches concerning Animals.

So much, then, as concerns the heart and the blood-vessels.
We must now pass on to the other viscera and apply the same
method of enquiry to them.

(Ch. 6.) The lung,^ then, is an organ found in all the animals
of a certain class, because they live on land. For there must
of necessity be some or other means of cooling down the heat
of the body ; and in sanguineous animals, as they are of an
especially hot nature, the cooling agency must be an external
one ; whereas in the bloodless kinds the innate spirit is sufficient .
of itself for the purpose. ^ The external cooling agent must be
669 a.

iii. 6. 75

either air or water. In fishes the agent is water. Fishes there-
fore never have a lung, but have gills in its place, as was stated
in the treatise on Respiration. But animals that breathe are
cooled by air. These therefore are all provided with a lung.^

All land animals breathe, and even some water animals, such
as the whale,* the dolphin, and all the spouting Cetacea. For
many animals lie halfway ^ between terrestrial and aquatic ; some
that are terrestrial and that inspire air being nevertheless of such
a bodily constitution that they abide for the most time in the
water ; and some that are aquatic partaking so largely of the
land character, that respiration constitutes for them the main
condition of life.

The organ of respiration is the lung. This derives its motion
from the heart ; but it is its own large size and spongy texture
that affords amplitude of space for the entrance of the breath.
For when the lung rises up the breath streams in, and is again
expelled when the lung contracts.^ It has been stated, but
incorrectly, that it is to the lung that the beating of the heart
is due. That this is not so is shown by the phenomenon of
palpitation occurring, so to speak, in man alone ; inasmuch as
man alone is influenced by hope and expectation.' Again in
most animals the heart is at a distance from the lung and
placed above it;^ so that its beating can in no degree be
brought about by this latter.

The lung differs much in different animals. For in some it is
of large size and contains blood ; while in others it is smaller and
of spongy texture. In the vivipara it is large and rich in blood,
because^ of their natural heat ; while in the ovipara it is small
and dry but capable of expanding to a vast extent when inflated.
Among terrestrial animals, the oviparous quadrupeds, such as
lizards, tortoises, and the like, have this kind of lung ; and,
among inhabitants of the air, the animals known as birds.'" For
in all these the lung is spongy, and like foam. For it is bladdery
and collapses from a large bulk to a small one, as does foam when
it runs together. In this too lies the explanation of the fact that
these animals are little liable to thirst and ^^ drink but sparingly,
and that they are able to remain for a considerable time under
water,^^ For, inasmuch as they have but little heat,^' the very
motion of the lung, airlike and void, suffices by itself to cool
them for a considerable period.^*
669 b.

^6 iii, 6 — iii. 7.

These animals, speaking generally, are also distinguished from
others by their smaller bulk.^^ For heat promotes growth, and'
abundance of blood is a sure indication of heat. Heat again
tends to make the body erect ; and thus it is that man is the
most erect of animals, and the vivipara more erect than other
quadrupeds.^6 For no viviparous animal, be it apodous '^'^ or be it
possessed of feet, is so given to creep into holes as are the ovipara.

The lung then exists for respiration ; and this is its universal
office. But the amount of blood it contains, and its structure
generally, varies with the requirements of different groups of
animals.^^ There is however no one term to denote all animals
that have a lung, no designation, that is, like the term Bird,
applicable to the whole of a certain class. Yet the possession of
a lung is a part of their essence, just as much as the presence of
certain characters constitutes the essence of a bird.

(Ch. y.) Of the viscera some appear to be single, as the heart
and lung ; others to be double, as the kidneys ; while of a third
kind it is doubtful in which class they should be reckoned. For
the liver and the spleen would seem to lie half-way between
the single and the double organs. For they may be regarded
either as constituting each a single organ, or as a pair of organs
resembling each other in character.^

In reality however all the organs are double.^ The reason for
this is that the body itself is double, consisting of two halves,
which are however combined together under one supreme centre.
For there is an upper and a lower half, a front and a rear, a
right side and a left.

This explains why it is that even the brain and the several
organs of sense tend in all animals to consist of two parts ;
and the same explanation applies to the heart with its cavities.
The lung again in ovipara is divided to such an extent, that
these animals look as though they had actually two lungs. ^ As
to the kidneys no one can overlook their double character. But
when we come to the liver and the spleen, any one might
fairly be in doubt. The reason of this is, that, in animals that
necessarily have a spleen,* this organ is such that it might be
taken for a kind of bastard liver ; while in those, in which a
spleen is not an actual necessity but is merely present, as it
were, by way of token, in an extremely minute form, the liver
plainly consists of two parts ; of which the larger tends to lie
669 b.

111. 7. 77

on the right side and the smaller on the left. Not but what
there are some ovipara in which this condition is comparatively
indistinctly marked ; while on the other hand there are some
vivipara in which the liver is manifestly divided into two parts.^
Examples of such division are furnished by the hares of certain
regions that have the appearance of having two livers, and by
some fishes, especially the cartilaginous kinds.^

It is the position of the liver on the right side of the body
that is the main cause for the formation of the spleen ; the
existence of which thus becomes to a certain extent a matter
of necessity in all animals, though not of very stringent necessity.

The reason, then, why the viscera are bilateral is, as we have
said, that there are two sides to the body, a right and a left.'''
For each of these sides aims at similarity with the other, and
so likewise do their several viscera ; and as the sides, though
dual, are knit together into unity, so also do the viscera tend to
be bilateral and yet one by unity of constitution.

Those viscera which lie below the diaphragm exist one and all
on account of the blood-vessels \^ serving as a bond, by which
these vessels, while floating freely, are yet held in connection with
the body. For the vessels give off branches which run to the
body through the out-stretched structures,^ like so many anchor-
lines thrown out from a ship. The great vessel sends such
branches to the liver, the spleen, and the kidneys ; and these
viscera — the liver and spleen on either side and the kidneys
behind — attach the great vessel ^° immoveably to the body. The
aorta sends similar branches to the kidneys, but none to the liver
nor to the spleen.^^

These viscera, then, contribute in this manner to the compact-
ness of the animal body. The liver and spleen assist moreover
in the concoction of the food ; for both are rich in blood,^^ and
therefore of a hot character. The kidneys on the other hand
take part in the separation of the excretion which flows into
the bladder.^^

The heart then and the liver are essential constituents of every
animal ; the liver that it may effect concoction, the heart that
it may lodge the central source of heat. For some or other part
there must be which like a hearth shall hold the kindling fire ;
and this part must be well protected, seeing that it is, as it were,
the citadel of the body.
670 a.

78 iii. 7.

All sanguineous animals, then, need these two parts ; and this
explains why these two viscera, and these two alone, are invariably
found in them all. In such of them, however, as breathe, there
is also as invariably a third, namely the lung. The spleen on
the other hand is not invariably present ; and, in those animals
that have it, is only present of necessity in the same sense as
the excretions of the belly and of the bladder are necessary, in
the sense that is of being an inevitable concomitant. Therefore
it is that in some animals the spleen is but scantily developed
as regards size. This for instance is the case in such feathered
animals as have a hot stomach. Such are the pigeon, the hawk,
and the kite.^* It is the case also in oviparous quadrupeds, where
the spleen is excessively minute, and in many of the scaly fishes.
These same animals are also without a bladder, because the loose
texture of their flesh allows the residual fluid to pass through and
to be converted into feathers and scales. For the spleen attracts
the residual humours from the stomach, and owing to its blood-
like character is enabled to assist in their concoction.^^ Should
however this residual fluid be too abundant, or the heat of the
spleen be too scanty, the body becomes sickly from over-repletion
with food. Often too, when the spleen is affected by disease, the
belly becomes hard ^^ owing to the reflux into it of the fluid ;
just as happens to those who form too much urine, for they also
are liable to a similar diversion of the fluids into the belly. But
in those animals that have but little superfluous fluid to excrete,
such as birds and fishes, the spleen is never large, and in some
exists no more than by way of token. So also in the oviparous
quadrupeds it is small, compact, and like a kidney. For their
lung is spongy, ^^ and they drink but little, and such superfluous
fluid as they have is diverted to the formation of feathers.

On the other hand in such animals as have a bladder, and
whose lung contains blood, the spleen is watery, both for the
reason already mentioned, and also because the left side of the
body is more watery and colder than the right. For each of two
contraries has been so placed as to go together with that which
is akin to it in another pair of contraries. Thus right and left,
hot and cold, are pairs of contraries; and right is conjoined with
hot, after the manner described, and left with cold.

The kidneys when they are present exist not of actual necessity,
but as matters of greater finish and perfection. For by their
670 b.

111. 7 — 111. 8. 79

special character they are suited to serve in the excretion of the
fluid which collects in the bladder. In animals therefore where
this fluid is very abundantly formed, their presence enables the
bladder to perform its proper office with greater perfection.^^

Since then both kidneys and bladder exist in animals for one
and the same function, we must next treat of the bladder,
though in so doing we disregard the due order of succession ^^
in which the parts should be enumerated. For not a word has
yet been said of the midriff", which, though not one of the viscera,
is yet one of the parts that environ them, and has to be considered
with them.

(Ch. Z.) It is not every animal that has a bladder ; those
only being apparently intended by nature to have one, whose
lung contains blood. ^ To such it was but reasonable that she
should give this part. For the character of their lung with its
abundant blood causes them to be the thirstiest of animals,
and makes them require a more than ordinary quantity not
merely of solid but also of liquid nutriment. This increased
consumption necessarily entails the production of an increased
amount of residue ; which thus becomes too abundant to be
concocted by the stomach and excreted with its own residual
matter. The residual fluid must therefore of necessity have a
receptacle of its own ; and thus it comes to pass that all animals
whose lung contains blood are provided with a bladder. Those
animals on the other hand that are without a lung of this
character, and that either drink but sparingly owing to their
lung being of a spongy texture, or that never imbibe fluid at all
for drinking's sake but only as nutriment, insects for instance
and fishes, and that are moreover clad with feathers or scales
or scaly plates ^ — all these animals, owing to the small amount
of fluid which they imbibe, and owing also to such residue as
there may be being converted into feathers and the like, are
invariably without a bladder.^ The Tortoises,* which are com-
prised among animals with scaly plates, form the only exception ;
and this is merely due to the imperfect development of their
natural conformation ; the explanation of the matter being that
in the sea-tortoises the lung is flesh-like and contains blood,
resembling the lung of the ox, and that in the land-tortoises
it is of larger size in comparison with the bulk of the body
than in other animals of the same class.^ Moreover, inasmuch
671a.

8o iii. 8 — ill. 9.

as the covering which invests them is dense and shell-Hke, so
that the moisture cannot exhale through the porous flesh, as it
does in birds and in snakes and other animals with scaly plates,
such an amount of secretion is formed that some special part
is required to receive and hold it. This then is the reason why
these animals, alone of their kind, have a bladder, the sea-
tortoises a large one, the land-tortoises an extremely small onc.^

(Ch. g.) What has been said of the bladder is equally true
of the kidneys. For these also are wanting in all animals that
are clad with feathers or with scales or with plates ; the sea and
land tortoises^ forming the only exception. In some of the birds,
however, there are flattened kidney-like bodies, as though the flesh
allotted to the formation of the kidneys, unable to find one single
place of sufficient size, had been distributed over several regions.^

The Emys^ has neither bladder nor kidneys. For the softness
of its shell allows of the ready transpiration of fluid ; and for this
reason neither of the organs mentioned exists in this animal. All
other animals, however, whose lung contains blood are, as before
said, provided with kidneys. For nature uses these organs for two
separate purposes, namely for the excretion of the residual fluid,
and to subserve the blood-vessels,* a channel leading to them from
the great vessel.

In the centre of the kidney is a cavity of variable size. This is
the case in all animals, excepting the seal.^ The kidneys of this
animal are more solid than those of any other, and in form
resemble the kidneys of the ox. The human kidneys are of
similar shape ; being as it were made up of numerous small
kidneys,^ and not presenting one unbroken surface like the
kidneys of sheep and other quadrupeds.''' For this reason,
should the kidneys of a man be once attacked by disease, the
malady is not easily expelled. For it is as though many kidneys
were diseased and not merely one ; which naturally enhances the
difficulties of a cure.

The duct which runs to the kidney from the great vessel does
not terminate in the central cavity, but is expended in the
substance of the organ, so that there is no blood in the cavity,
nor is any coagulum found there after death. A pair of stout ducts,
void of blood, run, one from the cavity of each kidney, to the
bladder; and other ducts, strong and continuous, lead into the
kidneys from the aorta.^ The purpose of this arrangement is to
671b.

111. 9. 81

allow the superfluous fluid to pass from the blood-vessel into the
kidney, and the resulting renal excretion to collect, by the perco-
lation of the fluid through the solid substance of the organ, in its
centre, where as a general Tule there is a cavity. (This by the way
explains why the kidney is the most ill-savoured of all the viscera.)
From the central cavity the fluid is discharged into the bladder by
the ducts just mentioned, having already assumed in great degree
the character of residuum.^ The bladder is as it were moored^" to
the kidneys ; for, as already has been mentioned, it is attached to
them by strong ducts. These then are the purposes for which the
kidneys exist, and such the functions of these organs.

In all animals that have kidneys, that on the right is placed
higher than that on the left.*^ For, inasmuch as motion commences
from the right, the organs on this side become stronger than those
on the left, and must all push forward in advance of their opposite
fellows ; as may be seen in the fact that men even raise the right
eyebrow more than the left, and that the former is more arched
than the latter.^^ The right kidney being thus drawn upwards is
brought into contact with the liver ; for the liver in all animals lies
on the right side.

Of all the viscera the kidneys are those that have the most
fat.^^ This is in the first place the result of necessity, because
the kidneys are the parts through which the residual matters
percolate. For the blood which is left behind after this excretion,
being of pure quality, is of easy concoction, and the final result
of thorough blood-concoction is lard and suet. For just as a
certain amount of heat is left in the ashes of. solid substances,
such as wood, after combustion, so also does a remnant of the
heat that has been developed remain in fluids after concoction ;
and this is the reason why oily matter is light, and floats on
the surface of other fluids.^* The fat is not formed in the
kidneys themselves, the density of their substance forbidding
this, but is deposited on their external surface. It consists
of lard or of suet, according as the animal's fat is of the
former or latter character. The difference between these two
kinds of fat has already been set forth in other passages.^^
The formation, then, of fat in the kidneys is the result of
necessity ; being, as explained, . a consequence of the necessary
conditions which accompany the possession of such organs. But
at the same time the fat has a final cause, namely to ensure
672 a. 6

82 iii. 9 — iii, lo.

the safety of the kidneys, and to maintain their natural heat.
For placed, as these organs are, close to the surface, they require
a greater supply of heat than other parts. For while the 'back,
is thickly covered with flesh, so as to form ^ shield for the heart
and neighbouring viscera, the loins, in accordance with a rule
that applies to all joints, are destitute of flesh ;^^ and fat is
therefore formed as a substitute for it, so that the kidneys may
not be without protection. The kidneys, moreover, by being
fat are the better enabled to secrete and concoct their fluid ; for
fat is hot, and it is heat that effects concoction.

Such then are the reasons why the kidneys are fat. But in
all animals the right kidney is less fat than its fellow.^''' The
reason for this is, that the parts on the right side are naturally
more solid and more suited for motion than those on the left.
But motion is antagonistic to . fat, for it tends to melt it.

Animals then, as a general rule, derive advantage from their
kidneys being fat; and the fat is often very abundant and extends
over the whole of these organs. But, should the like occur in the
sheep, death ensues. Be its kidneys however as fat as they may,
they are never so fat but that some part, if not in both at any
rate .in the right one, is left free.'^ The reason why sheep are
the only animals that suffer in this manner, or suffer more than
others, is that their fat is harder 'and more abundant than that
of other animals. For the soft lard, of which the fat of some
animals is composed, is of fluid consistence, so that there is not
the same chance in their case of wind getting shut in and causing
mischief • But it is to such an enclosure of wind that rot ^^ is
due. And thus even in men, though it is beneficial to them to
have fat kidneys, yet should these organs become over-fat and
diseased, deadly pains ensue. As to those animals whose fat
consists of suet, their suet is not so dense as that of sheep,
neither is it nearly so abundant ; for of all animals there is
none in which the kidneys become so soon gorged with fat as
in the sheep.^" Rot then is produced by the m'oisture and the
wind getting shut up in the .kidneys, and is a malady that
carries off sheep with great rapidity. For the disease forthwith
reaches the heart, passing thither by the aorta and the great
vessel, the ducts which connect these with the kidneys being
of unbroken continuity.

(Ch. \o.) We have now dealt with the heart and the lung,
672b. #

iii. 10. ^ 83

as also with the liver, spleen, and kidneys. The latter are
"separated from the former by the midriff or, as some call it, the
Phrenes. This divides off the heart and lung, and as already
said ^is called Phrenes in sanguineous animals, alP of which
have a midriff, just as they all have a heart and a liver. For
they require a midriff to divide the region of the heart from
the region * of the stomach, so that the centre wherein abides
the sensory soul may be undisturbed, and not be overwhelmed,
directly food is taken, by its up-steaming vapour ^ and by the
abundance of heat then superinduced.^ For it was to guard
against this that nature made a division, constructing the midriff
as a kind of partition-wall and fence, and so separated the nobler
from the less noble parts, in all cases where a separation of
upper from lower was possible.* For the upper part is the
more^ honourable, and is that for the sake of which the rest
exists ; while the lower part exists for the sake of the upper
and constitutes the necessary element in the body, inasmuch as
it is the recipient of the food.

That part of the midriff which is near the ribs is somewhat
fleshy and thick ; but the central part has more of a membranous
character, for this structure gives it strength and capability of
extension. Now that the midriff is as it were a curtain or
screen to prevent heat mounting up from below, is shown by
what happens, should it, owing to its proximity to the stomach,
attract thence the hot and residual fluid. For when this occurs
there ensueS forthwith a marked disturbance of intellect and of
sensation. It is indeed because of this that the midriff is called^
Phrenes, as though it. had some share in the process of thinking,
for which the Greek term is PJironein. In reality however it
has no part whatsoever itself in the matter, but, lying in close
proximity to organs that have, it brings about the manifest
changes of intelligence in question by acting upon them. This
too explains why its central part is thin. For though this is in
some measure the result of necessity, inasmuch, as those portions
of the fleshy whole which lie nearest to the ribs must necessarily
be fleshier than the rest,'' yet besides this there is a final cause,
namely to give it as small a proportion of moisture as possible ;
for, had it been made of flesh throughout, it would have been
more likely to attract and hold a large amount of fluid. That
rapid heating of it affects sensation in a notable manner is
673 a.

84 iii. 10. ■

shown by the phenomena of laughing. For when men are
tickled they are quickly set a laughing, because the motion
quickly reaches this region. And, even when the heating is
more slowly applied, there is still a manifest affection and
motion of the intellect in opposition to the will. That man
alone is affected by tickling,^ is due firstly to the delicacy of
his skin, and secondly to the fact that he is the only animal
that laughs. For to be tickled is to be set in laughter, the
laughter being produced by such a motion as mentioned of the
region of the armpit.

It is said also that when men in battle are wounded anywhere
near the midriff, they are seen to laugh, owing to the heat
produced by the wound.^ This may possibly be the case. At
any rate it is a statement made by much more credible persons
than those who tell the story of the human head, how it speaks
after it is cut off. For so some assert, and even call in Homer
to support them, representing him as alluding to. this when he
wrote,'" " His head still speaking rolled into the dust," instead of
"The head of the speaker." So fully was the possibility of. such
an occurrence -accepted in Caria, that one of that country was
actually brought to trial under the following circumstances. The
priest of Zeus Hoplosmios '^ had been murdered ; but as yet it
had not been ascertained who was the assassin ; when certain
persons asserted that they had heard the murdered man's head,
which had been severed from the body, repeat several times the
words, " It was Cercidas that killed the man." Search was there-
upon made and a man of those parts who bore the name of
Cercidas hunted out and put upon his trial. But it is impossible
that any one should utter a word when the windpipe is severed
and no motion any longer derived from the lungs. Moreover
among the Barbarians, where heads are chopped off with great
rapidity, nothing of the kind has ever yet occurred. Why again
does not the like occur in the case of other animals than man ?
For that none of them should laugh, when their midriff is
wounded, is but what one would expect ; for no animal but man
ever laughs. So too there is nothing irrational in supposing
that the trunk may run forwards to a certain distance after the
head has been cut off; seeing that bloodless animals at any
rate can live, and that for a considerable time, after decapitation,
as has been set forth and explained in other passages.'^
673 a.

iii. 10 — iii. I2. 85

The purposes then for which the viscera severally exist have
now been stated. It is of necessity upon the inner terminations
of the vessels that they are developed ; for moisture, and that
of a bloody character, cannot but exude at these points, and it
is of this, solidified and coagulated, that the substance of the
viscera is formed.^^ Thus they are of a bloody character, and
in substance resemble each other while they differ from other parts.

(Ch. \\.) The viscera are enclosed each in a membrane. For
they require some covering to. protect them from injury, and
require moreover that this covering shall be light. To such
requirements membrane is well adapted ; for it is close in texture
so as to form a good protection, destitute of flesh so as neither
to attract nor hold moisture, and thin so as to be light and not
add to the weight of the body. Of the membranes those are
the stoutest and strongest, which invest the heart and the brain ; ^
as is but consistent with reason. For these are the parts which
require most protection, seeing that they are the main governing
powers of life,^ and that it is to governing powers that guard is due.

(Ch. \2.) Some animals have all the viscera that have been
enumerated ; others have only some of them. In what kind 'of
animals this latter is the case, and what is the explanation, has
already been stated. Moreover the self-same viscera present
differences in different possessors. For the heart is not precisely
alike in all animals that have one ; nor in fact is any yiscus what-
soever. Thus the liver is in some animals split into several parts,
while in others it is comparatively undivided.^ Such differences
in its form present themselves even among the viviparous quad-
rupeds, but are more marked in fishes and in the oviparous
quadrupeds, and this whether we compare them with each other
or with the vivip'ara. As for birds, their liver very nearly resembles
that of the vivipara ; for in them, as in these, it is of a pure and
blood-like colour. The reason of this is that the body in both
these classes of animals admits of the freest exhalation, so that
the amount of foul residual matter within is but small. Hence
it is that some of the vivipara are without any gall-bladder ^ at
all. For the liver takes a large share in maintaining the purity
of composition and the healthiness of the body. For these are
conditions that depend finally and in the main upon the blood,
and there is more blood in the liver than in any of the other
viscera, the heart only excepted.' On the other hand the liver
673b.

86 iii. 12 — iii. 14. ,

of oviparous quadrupeds and of fishes is, 'as a rule, of a pale
yellow,* and there are even some in which its colour is utterly-
foul,-^ so as to match the foul composition of their bodies. Such,
for instance, is the case in the toad, the tortoise, and otlier similar
animals.

The spleen, again, varies in different animals. For in those
that have horns and cloven hoofs, such as the goat, the sheep,
and the like, it is of a rounded form ;^ excepting when increased
growth and size has caused some part of it to be lengthened out,
as has happened in the case of the ox."" In all polydactylous
animals on the other hand it is elongated. Such for instance, is
the case in the pig,^ in man, and in the dog. While in animals
with • solid hoofs it is of a form intermediate to these two, being'
broad in one part, narrow in another. Such for example is its
shape in the horse, the mule, and the ass.

(Ch. 13.^ The viscera differ from the flesh not only in the turgid
aspect of their substance, but also in position ; for they lie within
the body, whereas the flesh is placed on the outside. The expla-
nation of this is that these parts partake of the character of blood-
vessels, and that while the former exist for the sake of the vessels,
the latter cannot exist without them.^

(Ch. i/!if.) Below the mid-line of the body lies the stomach,
placed at the end of the oesophagus, when there is one, and in
immediate contiguity with the mouth, when the CESophagus is
wanting.^ Continuous with this stomach is what is called the
gut. These parts are present in all animals, for reasons that are
self-evident. For it is a matter of necessity that an animal shall
receive the incoming food ; and necessary also that it shall dis-
charge the same when its goodness is exhausted. This residual
matter, again, must not occupy the same place as the yet uncon-
cocted nutriment. For as the ingress of food and the discharge
of the residue occur at distinct periods, so also must they
necessarily occur in distinct places. TJius there must be one
receptacle for the ingoing food and another for the" useless
residue, and between these, therefore, a part in which the
change from one condition to the other may be effected. These
however are matters which will be more suitably set forth, when
we come to deal with Development and Nutrition.

We must now consider the variations presented by the stomach
and its subsidiary parts. For neither in size nor in shape are
674a.

* • iii. 14- ' 87

these parts uniformly alike in all animals. Thus the stomach
is single in all such sanguineous and viviparous animals as have
teeth in front of both jaws. It is single therefore in all the
polydactylous kinds, such as man, dog, lion, and the rest ; in all
the solid-hoofed animals also, such as horse, mule, ass ; and in
all those which like the pig, though their hoof is cloven, yet
have front teeth in both jaws.^ . When, however, an animal is of
large size, and feeds on substances of so thorny and ligneous a
character as to be difficult of concoction, it may in consequence
have several stomachs, as for instance is the case with the camel.
A similar multiplicity of stomachs exists also in 'the horned
animals ; the reason being that horrt-bearing animals have no
front teeth in. the upper jaw. The camel also, though it. has
no horns, is yet without upper front teeth.^ The explanation
of this is that it is more essential for the camel to have a
multiple stomach than to have these teeth. Its stomach, then,
is shaped like that of animals without upper front teeth, and,
its dental arrangements being such as to match its stomach,
the teeth in question are wanting.* They would indeed be of
no service. Its food, moreover, being of a thorny character,
and its tongue necessarily made of a fleshy substance,^ nature
uses the earthy matter which is saved from the teeth to give
hardness to the palate.^ The camel ruminates like the horned
animals, because its multiple stomach resembles theirs. For all
animals that have horns, the sheep for instance, the ox, the
goat, the deer, and the like, have several stomachs. For since
the mouth, owing to its " lack of teeth, fails to perform- its due
office as regards the food, this multiplicity of stomachs is intended
to supply its place ; the several cavities receiving the food one
from the other in succession ; the first taking the unreduced
substances, the second the same when somewhat reduced, the
third when reduction is complete, and the fourth when the
whole has become a smooth pulp. Such is the reason why
there is this multiplicity of parts and cavities in animals with
such dentition. The names given to the several cavities are
the paunch, the honey-comb, the manyplies and the reed. How
these parts are related to each other, in position and in shape,
must be looked . for in the treatises on Anatomy and the
Researches concerning Animals.""

Birds also present variations in the part which acts as a recipient
674b.

«8 ill. 14. •

of the food ; and the reason for these variations is the same as
in the animals just mentioned. For here again it is because the
mouth fails to perform its office and fails ev«n more completely; —
for birds have no teeth at all, nor any instrument whatsoever with
which to comminute or grind down their food^it is, I say, because
of this, that in some of them ^ what is called the crop precedes
the stomach and does the work of the mouth ; while in others
the oesophagus either is dilated throughout,^ or expands just
before it enters the stomach, so as to form a preparatory store-
house for the unreduced food ; ^^ or the stomach itself has a
protuberance in some part,^^ or is strong and fleshy ,^2 so as to be
able to store up the food for a considerable period and to concoct
it, in spite of its not having been ground into a pulp. For nature
retrieves the inefficiency of the mouth by increasing the efficiency
and heat of the stomach. Other birds there are, such, namely,
as have long legs and live in marshes, that have none of these
provisions, but merely an elongated cesophagus.^^ The explanation
of this is to be found in the moist character of their food. For
all these birds feed on substances easy of reduction, and their
food being moist and not requiring much concoction, their digestive
cavities are of a corresponding character.^*

Fish are provided with tepth, which are almost invariably of the
serrated kind. For there is but one small section in which it is
otherwise. Of these the fish called Scarus is an example. And
this is^^ probably the reason why this fish apparently ruminates,
though no other fishes do so. For those horned animals that
have no front teeth in the upper jaw also ruminate.

In all fishes the teeth are sharp ; ^^ so that these animals can
divide their food, though imperfectly. For it is impossible for
a fish to linger or spend time in the act of mastication, ^' and
therefore they have no teeth that are flat or suitable for grinding;
for such teeth would be to no purpose. The oesophagus again
in some fishes is entirely wanting, and in the rest is but short.^^
In order however to facilitate the concoction of the food, some
of them, as the Cestreus, have a fleshy stomach resembling
that of a bird ; *^ while most of them have numerous processes
close against, the stomach, to serve as a sort of antechamber in
which the food may be stored up and undergo putrefaction 2°
and concoction. There is a contrast between fishes and birds
in the position of these processes. For in fishes they are placed
675a.

iii. 14. 89

close to the stomach ; while in birds, if present at all, they are
lower down-, near the end of the gut?^ Some of the vivipara
also have processes connected with the lower part of the gut
which serve the same purpose as that stated above. ^^

The whole tribe of fishes is of gluttonous appetite, owing to the
arrangements for the reduction of their food being very imperfect,
and much of it, consequently passing through them without under-
going concoction; and, of all, those are the most gluttonous "that
have a straight intestine. For as the passage of food in siich
cases is rapid, and the enjoyment derived from it in consequence
but brief, it follows of necessity that the return of appetite is
also speedy.2^

It has already been mentioned that in animals with front teeth
in both jaws the stomach is of small size.^* It may be classed
pretty nearly always under one or other of two headings, namely
as resembling the stomach of the dog, or as resembling the
stomach of the pig. In the pig the stomach is larger than in
the dog, and presents certain flat projections of moderate size,
the purpose of whidh is to lengthen out the period of concoction ;
while the stomach of the dog is of small size, not much larger
in calibre than the gut, and smooth on the internal surface.^

Not much larger, I say, than the gut ; for in all animals after
the stomach comes the gut. This, like the stomach, presents
numerous modifications. For in some animals it is uniform,
when uncoiled, and alike throughout, while in others it differs
in different portions. Thus in some cases it is wider in the neigh-
bourhood of the stomach, and narrower at the other .end. This
is the case in dogs, and explains why they have to strain so
much in discharging their excrement. While in other animals,
and these the majority, it is the upper portion that is the narrower
and the lower that is of greater width.^^

Of larger size than in any of these animals, and much con-
voluted, are the intestines of those that have horns.^' The
bulgings moreover both of their stomach and of their intestines
are more prominent, in accordance with the larger bulk of their
bodies generally. For the horned anirnals are, as a rule, of large
bulk, because of the thorough elaboration which their food under-
goes.2^ The gut, excepting in those animals where it runs in a
straight line, invariably widens out as we get farther from the
stomach and come to what is called the colon and to a kind of
675b.

90 iii. 14. •

caecal dilatation. After this it again becomes narrower and con-
voluted.^'^ Then succeeds a straight portion which r.uns right on
to the vent; This vent is known as the fundament, and is in
some animals surrounded by fat, in others not so. All these
varying parts have been so contrived by nature as to harmonize
with the various operations that concern the food and the residue.
For, as the residue gets farther on and lower down, the space to
contain it becomes ampler. This is suited to the wants of those
animals that, owing either to their large size or to the heat of
their digestive cavities,^^ require more nutriment and consume
more fodder than the rest ; for it allows the food to remain
stationary and undergo conversion.

Neither is it without a purpose that, just as a narrower gut
succeeds to the upper stomach, so also does the residual food,
when its goodness is thoroughly exhausted, pass from the colon
and the ample space of the lower stomach ^^ into a narrower
channel and into the spiral coil. For so nature can regulate
her expenditure and prevent the residual substances from being
discharged all at once.^^

Now in all such animals as it behoves to be more temperate ^^
in the consumption of food than those we have been considering
the lower stomach presents no wide and roomy spaces, neither
is their gut ever straight, but hals numerous convolutions. For
amplitude of space causes desire for ample food, and straight-,
ness of the intestine causes quick return of appetite.^^ And thus
it is that all animals whose food receptacles are -either simple or
spacious are of gluttonous habits, the latter eating enormously
at a meal, the former making many meals at short intervals.

Again, since the food in the upper stomach, having just been
swallowed, must of necessity' be quite fresh, while that which
has reached the lower* stomach must have had its. juices exhausted
and resemble dung, it follows of necessity that there must also
be some intermediate part, in which the change may be- effected,
and where the food will be neither perfectly fresh nor yet dung.
And thus it is that, in all such animals as we are now considering,
there is found <vhat is called the jejunum f^ which is a part of
the small » gut, of the gut, that is, which comes next to the
stomach. For this jejunum lies between the upper cavity which
contains the • yet unconcocted food and the lower cavity which
holds the residual matter, which by the time it has got here is
675 b.

111. 14 — 111. 15. 91

quite worthless. . There is a jejunum in all animals, but it is only
plainly, visible in those of larger bulk, and in these only when
they have abstained from food for a certain time. For thus
alone can one hit on the exact period when the food lies half-
way between the upper and lower cavities ; a period which is
.very short, for the time occupied in the transition of food is
but brief In females this jejunum may occupy any part what-
soever of the upper intestine, but in males it comes just before
the caecum and the lower stomach.^^

(Ch. 15.;) The substance called rennet^ is found in all animals
that have a multiple stomach, but only in the hare'^ among
animals \yhose stomach is single. In the former the rennet
nefther occupies the large paunch, nor yet the reticulum, nor the
terminal abomasus, but is found in the cavity which separates
this terminal one from- the two first, namely in the so-called
psalterium,' It is the thick character of their milk which causes
all these animals to have rennet ; whereas in animals with a
single stomach the milk is thin, and consequently no rennet is
formed. It is this difference in thickness^ which makes the
milk of horned animals coagulate, while that of animals without
horns does not. Rennet forms in the hare because it feeds on^
herbage that has juice like that of the fig. For juice of this
kind coagulates the milk in the stomach of the young animal.
Why it is in the psalterium that rennet is formed in animals
with multiple stomachs has been stated in the Problems.^

676 a.

92 iv. I,

BOOK IV.

(Ch. \.) The account which has now been given of the viscera,*
the stomach, and. the other several parts of the vivipara, holds
equally good for the oviparous quadrupeds, and also for such
apodous animals as the Serpents. These two classes of animals
are indeed nearly akin, a serpent resembling a lizard which has
been lengthened out and deprived of its feet. Fishes again
resemble these two groups in all their parts, excepting that,
while these, being land animals, have a lung, fishes have no lung,
but gills in its place. Of all these animals, including the Fishes,
none excepting the tortoise has an urinary bladder.^ For, owing
to the bloodlessness of their lung, they drink but little ; and such
moisture as they have is converted into scales, as in birds it is
converted into feathers ; ^ and so they come to have the same
white matter on the surface of their excretions as we see on
those of birds. For even in animals that have a bladder, if the
excretion when voided be placed in a vessel, it will throw down
a deposit of earthy brine.* ' For the sweet and fresh elements,
being light, are expended on the flesh.

Among the Serpents, the same peculiarity attaches to vipers,
as among the fishes attaches to the Selachia. For both these
and vipers are externally viviparous, but previously produce ova
internally.^

The stomach in all these animals is single, just as it is single
in all other* animals^ that have teeth in front of both jaws ; and
their viscera are excessively small, as alwiays happens when there
is no bladder. In serpents these viscera are, moreover, differently
shaped from what they are in other animals. For, a serpent's
676b.

IV. I — IV. 2. '93

body being long and narrow, its contents are as it were moulded
into a similar form, and thus come to be themselves elongatedJ

All animals that have blood possess an omentum, a mesentery,^
an intestine with its appendages, and, moreover, a diaphragm
and a heart ; and all, excepting fishes, a lung and a trachea. The
relative positions, moreover, of the windpipe and the oesophagus
are precisely similar in them all ; and the reason is the same as
has already been. given.^

(Ch. 2.) Almost all sanguineous animals have a gall-bladder.
In some this is attached to the liver, in others separated from
that organ ^ and attached to the intestines, being apparently in
the latter case no less than in the former an appendage of the
lower stomach.2 It is in fishes that this is most clearly seen.
For all fishes-^ have a gall-bladder ; and in most of them it is
attached to the intestine, being in some, as in the * Amia, united
with this, like a border, along its whole length. It is similarly
placed in most serpents. There are therefore^ no good grounds
for the view entertained by some writers, that the use of the
gall-bladder is to give rise to certain sensations. They say
that its final cause is to affect that part of the soul which is
lodged in the neighbourhood of the liver, and that it induces
a gloomy or a cheerful disposition,' according as it irritates this
or leaves' it alone. But this cannot be. For in some animals
there is absolutely no" gall-bladder at all, in the horse for instance,
the mule, the ass, the deer, and the roe ; and in others, as the
camel, there is no distinct bladder," but merely small vessels
that bear some resemblance to one.^ Again there is no such
organ in the seal, nor, of sea-animals, in the dolphin.' Even
within the limits of the same genus, some animals appear to
have and others to be without it.^ Such for instance is the
case with mice ; such also with man. For in some individuals
there is apparently a gall-bladder attached to the liver, and in
others none at all. This explains how the existence of this
part in the whole genus has been a matter of dispute. For
each observer, according as he has found it present or absent
in the individual cases he has examined, has supposed it to be
present or absent in the whole genus. The same has occurred
in the. casie of sheep and of goats. For these animals usually
have a gall-bladder ; but, while in some it is so enormously big as
to appear a monstrosity, as is the case in Naxos, in other instances
677a.

94 IV. 2.

it is altogether wanting, as is the case in a certain district of
Chalcis in Euboea.^ Another fact, which shows that the opinion
of these writers is erroneous, is that the gall-bladder in fishes
is separated, as already mentioned, by a considerable interval
from the liver. No less mistaken seems to be the opinion of
Anaxagoras and his followers, that the gall-bladder is the cause
of acute diseases, inasmuch as it becomes over-full, and spirts
out its excess into the lung, the blood-vessels, and the thest
For, almost invariably, those who suffer froni these acute forms
of disease are persons who have no gall-bladder at all, and,
were they to be dissected, this fact would be quite evident.^^
Moreover there is no kind of correspondence between the
amount of bile which is ' present in these diseases and the
amount which is exuded.'^ The most probable opinion is that,
as 'the bile when it exists in any other part of the body is a
mere residuum or a product of decay, so also when it exists in
the region of the liver it is equally excremental and has no
further use ; jtist as is the case with 'the dejections of the
stomach and intestines. For though even the residua are occa-
sionally used ^^ by nature for some useful purpose, ye^- we must
not in all cases expect to find such a final cause ; for granted
the existence in the body of this oi« that constituent, with such
and such properties, many results must ensue merely as necessary
consequences of these properties.^^ All animals, then, whose liver
is healthy in composition and supplied with none but sweet
blood, are either entirely without a gall-bladder, or have merely ^*
bile-containing ducts ; or are some with and some without such
parts. Thus it is that the liver in animals that have no gall-
bladder is, as a rule, of good colour and sweet ; and that, when
there is a gall-bladder, that part of the liver is sweetest, which
lies immediately underneath it. But, when animals are formed
of blood less pure in composition, the bile serves for the excretion
of its impure residue. For the very meaning of residuum is that
it is the opposite of nutriment, and of bitter that it is the opposite
of sweet ; and sweet blood it is which alone is nutritious,^^ So
that it is evident that the bile, which is bitter, cannot have any
useful end, but must simply be a purifying excretion.^^ It was
therefore no bad saying of old writers that the aUsence of a
gall-bladder gave long life. In so saying they had in mind
deer and animals with uncloven hoofs. For such have no
677a.

IV, 2 — ly. 3. 95

gall-bladder and' live long. But besides these there are other
animals that have no gall-bladder, though those old writers
were not aware of the fact, such as the carriel and the dolphin ;^''^
and these also are, as it happens, long-lived. Seeing, indeed,
that the liver is not only useful, but absolutely necessary, to all
animals that have blood, it is but reasonable that on its character
should depend the length or the shortness of life. Nor less
reasonable is it that this organ and none other should have
such an excretion as the bile. For the heart, unable as it is to
stand any violent affection,'^ would be utterly intolerant of the
proximity of such a fluid ; and, as to the rest of the viscera, none
excepting the liver are necessary parts of an animal.'^ In con-
clusion, wherever we see bile we must take it to be residual or
excremental. For to suppose that it has . one character in this
part, another in that, would be as great an absurdity as to
suppose mucus or the dejections of the stomach to vary in
character according to locality and not to be excremental wherever
found.

(Ch. 3.J So much then of the gaJl-bladder, and of the reasons
why some animals have one, while others have nbt.^ We have
next to speak of the mesentery and the omentum ; for these are
contained in the same cavity»as the parts already described. The
omentum, then, is a membrane containing fat ; the fat being suet
or lard according as the fat of the animaj generally is of the
former or latter description. What kinds of animals are so dis-
tinguished has been already set forth in an earlier part of this
treatise.^ This membrane, alike in animals that have a single and
in those that have a multiple stomach, grows from the middle of
that organ, along a line which is marked on it like a seam. Thus
attached, it covers the rest of the stomach and the greater part
of the bowels. It is found in all sanguineous animals whether
they live on land .or in water.^ Now the development of this
part into such a form as has been described is the result of
necessity. For, whenever solid and fluid are mixed together and
heated, the surface invariably becofnes membranous and skin-like.*
But the region in which the omentum lies is full of nutriment of
such a mixed character. Moreover, in consequence of the thick-
ness of the membrane, that portion of the sanguineous nutriment
will alone filter into it which is of a greasy character ; for this
portion is composed of the finest particles ; and when it has so
677b.

96 iv. 3 — iv. 4.

filtered in, it will be concocted by the heat of the part, and will
be converted into suet or lard, and will not acquire a flesh-like or
sanguineous constitution. The development, then, of the omentum
is simply the result of necessity. But when once formed, it is
used by nature for an end, namely, to facilitate and to hasten the
concoction of food.^ For all that is hot aids concoction ; and fat
is hot, and the omentum is fat. .This too explains why it hangs
from the middle of the stomach ; for the upper part of the stomach
has no need of it, being assisted in concoction by the neighbouring
liver. Thus much as concerns the omentum.

(Ch. 4.) The so-called mesentery is also a membrane ; and
stretches from the intestines, in their whole extent, to the great
vessel and the aorta. In it are numerous and close-packed vessels,
which run from the intestines into the great vessel and into the
aorta. The formation of this mertibrane we shall find to be the
result of necessity, as is that of the other parts.^ What however
is the final cause of its existence in sanguineous animals is
manifest on reflection. For it is necessary that animals shall
get nutriment from without ; and, again, that this shall be con-
verted into the ultimate nutriment, which is then distributed as
sustenance to the various parts ; this ultimate nutriment being,
in sanguineous animals, what we caJl blood, and having, in ex-
sanguineous animals, no definite name. . This being so, there
must be channels through which the nutriment shall pass, as it
were through roots,^ from the stomach into the blood-vessels.
Now the roots of plants are in the ground ; for thence their
nutriment is derived. But in animals the stomach and intestines
represent the ground, from which the nutriment is to be taken.
The mesentery, then, is an organ to contain the roots ; and these
rpots are the vessels that traverse it. This then is the final
cause of its existence. But how it absorbs nutriment, and how
that portion of the food which enters into the vessels is dis-
tributed by them to the various parts of the body, are. questions
which will be considered when we come to deal with the generation
and nutrition of animals.'

The constitution of sanguineous animals, so far as the parts as
yet mentioned are concerned, and the reasons for such constitution,
have now been set forth. In natural sequence we should next
go on to the organs of generation, as yet undescribed, on which
depend the distinctions of male and female. But, inasmuch as
678 a.

iv. 4— iv. 5. 97

we shall have to deal specially with generation and development
hereafter, it will be more convenient to defer the consideration
of these parts to that occasion.

(Ch. <f.) Very different from the animals we have as yet con-
sidered are the Cephalopods, and the Crustacea. For these have
absolutely no viscera ^ whatsoever ; as indeed is the case with all
ex-sanguineous animals, in which are included two other genera,
namely the Testacea and the Insects. For in none of them does
the material out of which viscera are formed exist. None of
them, that is, have blood. The cause of this lies in their essential
constitution. For the presence of blood in some animals, its
absence from others, will be included in the conception which
determines their respective essences.^ Moreover, in the animals
we are now considering, none of those final causes will be found
to exist, which, in sanguineous animals, determine the presence
of viscera. For ' they have no blood-vessels nor urinary bladder,
nor do they breathe. All, in fact, that it is necessary for them
to have is some organ which shall be analogous to a heart ; for
in all animals there must be some central and commanding part
of the body, to lodge the sensory portion of the soul and the
source of life. They must of course also all have the organs of
nutrition ; and a diversity of character exists among them,
depending on differences of these receptacles of food.

In the Cephalopods there are two teeth,* enclosing what is called
the mouth ; and inside this mouth is a fleshy substance, which
represents a tongue and serves for the discrimination of pleasant
and unpleasant food. The Crustacea have teeth corresponding to
those of the Cephalopods, namely their anterior teeth,^ and also
have the fleshy representative of a tongue. This latter part is
found, moreover, in all Testacea,^ and serves, as in sanguineous
animals, for gustatory sensations. Similarly provided also are the
Insects. For some of these, such as the Bees and the Flies, have,
as already described, a proboscis protruding from the mouth;'''
while others, that have no such piercing instrument in front,
have a part which acts as a tongue inside the mbuth.^ Such for
instance is the case in the Ants and the like. As for teeth, some
insects have them, the Bees and the Flies for instance, though
in a somewhat modified form, while others, that live on fluid
nutriment, are without them. For in many insects the teeth are
not organs of mastication, but weapons of defence.

678b. 7

98 • . iv, 5.

In some Testacea, as was said in the ^ first treatise, the organ
which is called the tongue is of considerable strength ; and In
one kind, namely the Sea-snails, in addition to the tongue there
are two teeth,'" resembling those of the Crustacea. The mouth
in the Cephalopods ^^ is succeeded by a long gullet. This leads
to a crop, like that of a bird. Directly continuous with this is
the stomach, from which a gut runs without windings to the
vent. The Sepias and the Poulps resemble each other completely,
so far as regards the shape and consistency of these parts. But
not so the Calamaries. Here, as in the other groups, there are
two stomach-like receptacles ; but the first of these cavities has
less resemblance to a crop, and in neither is the form or the
consistency the same as in the other kinds, the whole animal
indeed being made of a softer kind of flesh.

The object of this arrangenient of the parts in question is the
same in the Cephalopods as in Birds. For in neither of these
groups is the* mouth suited for mastication ; and therefore it is
that a crop precedes their stomach.

For purposes of defence, and to enable them to escape from
their foes, the Cephalopods have what is called an ink-bag
attached to their body. This is a membranous pouch, which
is provided with a terminal outlet just at the point where what
is termed the funnel gives issue to the residua of the stomach.
This funnel is placed on the ventral surface of the animal. All
Cephalopods alike have this characteristic ink-bag, but chief of
all the sepia, where it is of greater size than in the rest.'^ When
the animal is disturbed and frightened it uses the ink to make
the surrounding water black and turbid, and so, as it were, puts
a shield in front of its body.

In the Calamaries and the Poulps the ink-bag is placed in
the upper part of the body, in close proximity to the mytis}^
whereas in the sepia it is much lower down, against the stomach.
For the sepia has a larger ink-bag than the rest, owing to its
making more use of it. The reasons for this are, firstly, that it
lives near the shore, and, secondly, that it has no other means
of protection ; whereas the poulp has twining feet ^* that it can
use in its defence, and is moreover endowed with the power of
changing its colour.'^ This changing of colour, like the discharge
of ink, occurs as the result of fright. As to the calamary, it
lives far out at sea, being the only one of the Cephalopods that
679 a.

iv. 5. 99

does so ; and this gives it protection.'^ These then are the
reasons why the ink-bag is much larger in the sepia than in
the other Cephalopods; and its larger size again explains its
lower position. For though this position removes it farther from
the funnel, yet the larger size .of the bag gives increased force,
and so allows the ink to be ejected wfth ease even from a distance.
The ink itself is of an earthy character, in this resembling the
white deposit on the surface of a bird's excrement. And the
explanation in both cases is the same, namely the absence of an
urinary bladder.^'' For, in default of this, it is the ink that serves
for the excretion of the earthy matter. And this is more
especially the case in the sepia ; because there is a greater
proportion of earth in its composition than in that of the other
Cephalopods. The earthy character of its bone is a clear proof
of this. For in the poulp there is no bone at all, and in the
calamary it is small and merely cartilaginous.'^ Why this bone
should be present in some Cephalopods, and wanting in others,
and how its character varies in those that have it, has now been
set forth.

These animals, having no blood, are in consequence cold and
of a timid character.'^ Now, in some animals, fear causes an
evacuation from the bowels, and, in. others, a flow of urine from
the bladder.20 Similarly in these it produces a discharge of ink,
and though this ink, like the urine, is residual matter, and though
its ejection in fright is merely the result of necessity, yet it is used
by nature for a purpose,^' namely the protection and safety of the
animal that excretes it.

The Crustacea also, both the Caraboid forms and the Crabs,''^
are provided with teeth, namely the two so-called anterior teeth ;
and between these they also present the tongue-like piece of flesh,
as has indeed been already mentioned.^^ Directly after their
mouth comes a gullet, which is very small considering the size of
the whole body ; and then a stomach, which in the Carabi and
some of the Crabs is furnished with a second set of teeth, the
anterior set being insufficient for mastication. From the stomach
an unconvoluted gut runs in a direct line to the vent.^*

The parts described are to be found also in all the various

Testacea.25 The degree of distinctness, however, with which they

are formed varies much in the different kinds, and the larger the

size of the animal the more easily distinguishable are all these parts

679 b.

100 IV. 5.

severally. In the Sea-snails, for example, we find teeth, hard and.
sharp, as before mentioned,^^ and between them a fleshy substance
like the tongue of Crustacea and Cephalopods, and again a
proboscis which has already been described as something between
a piercing instrument and a tongue." Directly after the niouth
comes a kind of bird-like crop,^® then a gullet, and continuous
with this a stomach, in which is the mecon^ as it is styled ; and this
mecon in turn gives rise to an intestine, starting directly from it.^^
It is the excretion of this mecon, which appears in all the Testacea
to form the most palatable morsel. Purpurae,^° and whelks, and
all other Testacea that have turbinated shells, in structure
resemble the sea-snail.

The genera and species of Testacea are very numerous. There
are those with turbinated shells, of which some have just been
mentioned ; and, besides these, there are bivalves and univalves.
Those with turbinated shells may indeed after a certain fashion be
said to resemble bivalves. For they all, from their very birth,
have a covering to protect that part of their body which would
otherwise be exposed.^^ This is the case with the Purpurae, with
whelks, with the Nerites,^^ and all the like. Were it not for this,
the part which is undefended by the shell would be very liable to
injury from without. The Univalves also are not without pro-
tection. For on their dorsal surface they have a shell, and by
the under surface they attach themselves to the rocks, and so after
a manner may be said to become bivalved, the rock representing
the second valve. Of these the animals known as limpets are an
example. The Bivalves, scallops and mussels for instance, are
protected by the power they have of closing their valves ; and the
turbinated genera by the operculum just mentioned, which trans-
forms them, as it were, from univalves into bivalves. But of all
there is none so perfectly protected as the Echinus. For here
there is a globular shell which encloses the body completely,
and which is moreover set with sharp spines. This peculiarity
distinguishes the Echinus from all other Testacea, as has already
been mentioned.

The structure of the Testacea and of the Crustacea is exactly the
reverse of that of the Cephalopods. For in the latter the fleshy
substance is on the outside and the earthy substance within, whereas
in the former the soft parts are inside and the hard part without.
In the Echinus, however, there is no fleshy part whatsoever.
679b.

iv. 5. lOi

All the Testacea, then, those that have not been mentioned as
well as those that have, agree as stated in possessing a mouth ^^
with the tongue-like body, a stomach, and a vent ; but they differ
from each other in the positions and proportions of these parts.
The details, however, of these differences must be looked for in
the Researches concerning Animals and the treatises on Anatomy.
For while there are some points which can be made clear by
verbal description there are others which are more suited for
ocular demonstration.^*

Peculiar among the Testacea are the Echini and the animals
known as Ascidians.^ The Echini have five teeth,^ and in the
centre of these the fleshy body,'"'^ which is common to all the
animals we have been discussing. Immediately after this comes
a gullet, and then a stomach, divided into a number of separate
compartments, which look like so many distinct stomachs ; for
the cavities are separate, and each contains residual matter. They
are all however connected with one and the same oesophagus, and
they all end in one and the same vent.^ There is nothing, with
the exception of the stomach, of a fleshy character, as has already
been stated. All that can be seen are the so-called ova,^^ of which
there are several, contained each in a separate membrane, and
certain black bodies which have got no name, and which, beginning
at the animal's mouth, are scattered round its body here and there
profusely.*" Of these Echini there are many different species, and
in all of them the parts mentioned are to be found. It is not
however in every kind that the so-called ova are edible. Neither
do these attain to any size in any other species than those which
are found in shallow water.*' A similar distinction may be made
generally in the case of all Testacea. For there is a great
difference in the edible qualities of the flesh of different kinds;
and in some, moreover, the residual substance known as the mecon*^
is good for food, while in others it is uneatable. This mecon in
the turbinated genera is lodged in the spiral part of the shell,
while in univalves, such as limpets, it occupies the apex, and
in bivalves is placed near the hinge. In these bivalves the so-
called ovum lies on the right ; while on the opposite side is the
vent.*3 The former is incorrectly termed ovum,** for it merely
corresponds to what in well-fed sanguineous animals is fat ; and
thus it is that it only makes its appearance in Testacea at those
seasons of the year when they are in good condition, namely spring
680 a.

102 iv. 5-

and autumn. For no Testacea can abide extremes of temperature,
and they are therefore in evil plight in winter and in summer.
This is clearly shown by what occurs in the case of the Echini.
For though the ova are to be found in these animals even directly
they are born, yet they acquire a much greater size than usual at
the time of full moon ; • not, as some think, because the Echini eat
more at that season, but because the nights are then warmer, owing
to the moonlight.*^ For these creatures are bloodless, and so are
unable to stand cold and require warmth. Therefore it is that
they are found in better condition in summer than at any other
season ; and this all over the world excepting in the Pyrrhean
tidal strait. There the Echini flourish as well in winter as in
summer. But the reason for this is that they have a greater
abundance of food in the winter, because the fish desert the strait
at that season.*^

The number of the ova is the same in all Echini, and is an odd
one. There are in fact five ova, just as there are also five teeth
and five stomachs ; and the explanation of this is to be found in
the fact that the so-called ova are not really ova, but merely, as
was said before, the result of the animal's well-fed condition.
Oysters also have an ovum, corresponding in character to that of
the Echini, but existing only on one side of their body.^^ .Now
inasmuch as the Echinus is of a spherical form, and not merely
a single disk like the oyster, and in virtue of its spherical shape
is the same from whatever side it be examined, it follows as a
necessary consequence that its ovum must be of a corresponding
symmetry. For the spherical shape has not the asymmetry of
the disk-shaped body of the Oysters. For though the head in
all of these is central, yet their ovum is on one side, namely the
upper."*® Now the necessary symmetry would be observed, were
the ovum to form a continuous ring. But this may not be. For
it would be in opposition to what prevails in the whole tribe of
Testacea ;^^ for in all the ovum is discontinuous, and in all,
excepting .the Echini, asymmetrical, being placed only on one
side of the body. Owing, then, to this necessary discontinuity
of the ovum, which belongs to the Echinus as a member of the
class, and owing to the spherical shape of the body, which is its
individual peculiarity, this animal cannot possibly have an even
number of ova. For were they in even number, they would
have to be arranged exactly opposite to each other, in pairs,. so
680b.

iv. 5. 103

as to keep the necessary symmetry ; one ovum of each pair being
placed at one end, the other ovum at the other end, of a transverse
diameter. This again would violate the universal provision in
Testacea. For both in the Oysters and in the Scallops we find the
ovum only on one side of the circumference. The number then
of the ova must be an uneven one, three for instance or five. But
if there were only three, they would be much too far apart ; while
if there were more than five, they would come to form a continuous
mass. The former arrangement would be disadvantageous to the
animal, the latter an impossibility. There can, therefore, be
neither more nor less than five. For the same reason the stomach
is divided into five parts, and there is a corresponding number
of teeth. For seeing that the ova represent each of them a kind
of body for the animal, from which the materials for growth are
derived, there must be a conformity between them and the general
configuration of the vital organs. Now, if there were only one
stomach, this conformity would be wanting. For either the ova
would be too far off from the stomach, or the stomach would be
so big as to fill up the whole cavity, and the Echinus would have
great difficulty in moving about, and finding due nourishment for
its repletion. As then there are five intervals between the five
ova, so are there of necessity five divisions of the stomach, one
for each interval. So also and on like grounds there are five
teeth. For by this arrangement nature is enabled to allot to
each stomachal compartment and ovum its separate and similar
tooth. These then are the reasons why the number of ova in
the Echinus is an odd one, and why that odd number is five.
In some Echini the ova are excessively small, in others of con-
siderable size, the explanation being that the latter are of a
warmer constitution, and so are able to concoct their food more
thoroughly ; while in the former concoction is less perfect, so
that the stomach is found full of residual matter, while the ova
are small and uneatable.^ Those of a warmer constitution are,
moreover, in virtue of their warmth more given to motion, so that
they make expeditions in search of food, instead of remaining
stationary like the rest. In proof of this, it will be found that
they always have something or other sticking to their spines,
which they use as feet in their frequent ramblings.^^

The Ascidians differ but slightly from plants and yet have
more of an animal nature than the Sponges, which are in
681a. ■,

104 IV. 5-

fact virtually plants and nothing more. For nature passes from
lifeless objects to animals in such unbroken sequence, interposing
between them beings which live and yet are not animals, that
scarcely any difference seems to exist between two neighbouring
classes owing to their close proximity.^^

A sponge ^^ then, as already said, in these respects completely
resembles a plant, that throughout its life it is attached to a
rock, and that when separated from this it dies. Slightly different
from the Sponges are the so-called Holothuriae and the Sea-
lungs,^ as also sundry other sea-animals that resemble them.
For these are free and unattached. Yet have they no feeling,^
and their life is simply that of a*plant, separated from the ground.
For even among land-plants there are some that are independent
of the soil, and that spring up and grow, either parasitically upon
other plants,-"*^ or even entirely free. Such for example is the
plant which is found on Parnassus, and which some call the
Epipetrum.-''^ This you may take up and hang from the rafters,
and it will yet live for a considerable time. Sometimes it is a
matter of doubt whether a given organism should be classed with
plants or with animals. The Ascidians, for instance, and the
like so far resemble plants as that they never live free and
unattached,^ but, on the other hand, inasmuch as they have a
certain flesh-like substance, they must be supposed to possess
some degree of sensibility.^^

In the Ascidians there are two orifices and a single septum,
which latter separates the part into which the animal takes the
fluid that ministers to its nutrition from the part by which it
again discharges the superfluity of moisture. For it appears
to have no distinct residual matter, such as have the other
Testacea. This is itself a very strong justification for con-
sidering an Ascidian, and any thing else there may be among
animals that resembles it, to be of a vegetable character ; for
plants also never have any residuum.^" Finally there runs across
tht middle of the body of these Ascidians a thin partition, and
here it is that we may reasonably suppose the part on which
life depends to be situated.

The animals which some call Sea-nettles and others Acalephae ^^

are not Testacea at all nor included in their divisions. Their

constitution approximates them on the one side to plants, on

the other to animals. For seeing that some of them can detach

681b.

iv. 5. 105

themselves and can seize hold of their food, and that they are
sensible of objects which come in contact with tljem, they must
be considered to have an animal nature. The • like conclusion
follows from their using the roughness of their bodies ^^ as a
protection against their enemies. But on the other hand they
are closely allied to plants, firstly by the imperfection of their
structure, secondly by their being able to attach themselves to the
rocks with great rapidity, and lastly by their having no visible
residuum, notwithstanding that they possess a mouth.

Very similar again to the Acalephae, are the Starfishes. For
these also seize hold of their prey, and suck out its juices, and
thus destroy a vast number of oysters.^' At "the same time
they present a certain resemblance to such animals as the
Cephalopods and Crustacea, inasmuch as they are free and un-
attached. The same may also be said of the Testacea.

Such then is the structure of the parts that minister to nutrition,
and which every animal must necessarily possess. But besides
these organs it is quite plain that in every animal there must be
some part or other which shall be analogous to what in sanguineous
animals is the presiding seat of sensation. Whether an animal
has or has not blood, it cannot possibly be without this. In the
Cephalopods this part consists of a membrane, containing fluid,
through which runs the gullet on its way to the stomach. It
lies rather towards the dorsal surface of the animal, and is by
some called the mytis.^ Just such another organ is found in
the Crustacea, and is known in them also by the same name.
This part is formed by a combination of fluid and solid, and
is, as before said, traversed by the gullet. For had the gullet
been placed farther back, between the mytis and the dorsal
surface of the animal, the hardness of the back would have
interfered with its due dilatation in the act of deglutition. On
the outer surface of the mytis runs the intestine ; and in contact
with this latter is the ink-bag, which is thus removed as far as
possible from the mouth, while a considerable interval divides
its irritating fluid from the nobler and sovereign parts.^ The
position of the myiis shows that it corresponds to the heart
of sanguineous animals ; for it occupies the self-same place.
The same is proved by the sweetness of its fluid, which has the
character of concocted matter and resembles blood.^^

In the Testacea the presiding seat of sensation is in a cor-
681b.

io6 iv. 5.

responding position, but is less easily made out.®"' It should,
however, always be looked for in the following situations. In such
Testacea as are stationary, between the gullet and the channel
through which either the excrement or the spermatic fluid ^ is
voided ; but, in those species which are capable of locomotion,
invariably in the centre, midway that is between the right and
left sides.

In Insects this important organ lies, as was stated in the first
treatise,®^ between the head and the cavity which contains the
stomach. In most of them it consists of a single part ; but in
•others, for instance in such as have long bodies and resemble the
Juli,™ it is made up of several parts, so that such insects continue
to live after they have been cut into pieces.'''^ For the aim of
nature is to give each animal only one such governing part ; and
when she is unable to carry out this intention she causes the parts,
though potentially many, to work together actually as one.''^ The
phenomenon referred to is much more clearly marked in some
insects than in others.

The parts concerned in nutrition are not alike in all insects,
but show a considerable diversity. Thus some have what is called
a piercer in their mouths, which is a kind of compound instrument
that combines in itself the character of a tongue and of lips.''''
In others, that have not got this anterior piercer, there is an
organ inside the mouth that answers the same sensory purposes.
After the mouth comes the intestine, which is never wanting in
any insect. This runs in a straight line and without further com-
plication to the vent ; occasionally, however, it has a spiral coil.
There are, moreover, some insects in which a stomach succeeds
to the mouth, and is itself succeeded by a convoluted intestine.'''*
By this arrangement the larger and more voracious insects are
enabled to take in a more abundant supply of food.''''^ More
curious than any are the Cicadae. For here the mouth and the
tongue are united so as to form a single part, through which, as
through a root, the fluids on which the creature lives are sucked
up.''^ Insects are always small eaters, not so much because of
their diminutive size as because of their cold temperament. For
it is heat which requires sustenance; just as it is heat which
speedily concocts it,"''^ But cold neither requires sustenance nor
concocts it. In no insects is this more evident than in these
Cicadae. For they find enough to live on in the moisture which
682 a.

iv. 5 — iv. 6. 107

is deposited from the air.'^^ So also do the Ephemera found
about the Black Sea."^ But while these latter only live for a
single day, the Cicadae subsist on such food for several days,
though still not many.

We have now done with the internal parts of animals, and must
return to the consideration of such external parts as have not
yet been described. It will be better to begin with the animals
we have just been describing, that is with the bloodless animals,
so that we may not be hampered with them hereafter, but may
be free to deal leisurely with the more perfect kinds of animals,
those namely that have blood.

(Ch. 6.) We will begin with Insects.^ These animals, though
they consist of but few parts, are yet not without diversities when
compared with each other. They are all many-footed ; the object
of this being to compensate their natural slowness and frigidity,
and give greater activity to their motions. Accordingly we find
that those which, as the^ Juli, have long bodies, and are there-
fore the most liable to refrigeration, have also the greatest number
of feet. Again in all insects the body is made up of segments —
the reason for this being that in these animals there is no one
supreme and sovereign part^ but several — and the number of
feet corresponds to the number of segments. Should the feet
fall short of this, their deficiency is supplied by the presence of
feathers. Of such feathered insects some live a wandering life
and are forced to make long expeditions in search of food.
These have a body of light weight, and four feathers, two on
either sidcj to support it. Such are bees and other insects
akin to them. When, however, such insects are of very small
bulk, their feathers are reduced to two, as is the case with
flies.* Even insects of squarer build and of stationary habits of
life yet come to have as many feathers in all as have bees ; for
they have shards, which protect the acting feathers from injury.
Such are the Melalonthae^ and the like. For their stationary
habits expose them to much greater risks than are run by those
insects that are more constantly in flight, and on this account
they are provided with this protecting shield. The feather of an
insect h-as neither barbs nor shaft.^ For, though it is called a
feather, it is no feather at all, but merely a skin-like membrane
that, owing to its dryness, necessarily becomes detached from the
surface of the fleshy body.
682b.

io8 iv. 6.

The body of an insect is made of segments, npt only for the
reasons already assigned, but also to enable it to bend in sucK
a manner as may protect it from injury. For such insects as
have long bodies can roll themselves up,''' which would have been
impossible, had they not been formed of segments ; and even
those which cannot do this can yet draw their segments closer
together, and so increase the hardness of their bodies. This can
be feltjquite plainly by putting the finger on any of the insects
known as Canthari.^ ' The touch frightens the insect, 'and it
remains perfectly motionless, while its body is felt to become
harder than before. The division, then, of the body into segments
has this final cause ; but it is also a necessary result of there being
several supreme organs in place of one ; and this again is a part
of the essential constitution of insects, and is a character, which
approximates them to plants. For as plants, though cut into
pieces, still live, so also do insects. There is however this differ-
ence between the two cases, that the portions of the divided insect
live for "a very short space, whereas the portions of the plant live
on and attain the perfect form of the whole, so that from one
single plant you may obtain two or more.^

Some insects are also provided with another means of protection
against their enemies, namely a piercer or sting. In some this
is in front, connected with the tongue, in others behind and
connected with the tail. For just as the organ of smell in
elephants ^^ answers several uses, serving alike for purposes of
nutrition and for purposes of defence, so also does the lingual
arrangement in some insects answer more than one end. For
it is the instrument through which they derive their sensations
of food, as well as that with which they suck it up and bring
it to their mouths ; and, when no such anterior piercer or sting
exists, the mouth is furnished with teeth, which so far supply its
place as to serve either for the mastication of food or for its
prehension and conveyance to the mouth. They serve this latter
use for instance in ants and in all the various kinds of bees.^^

As for a tail-sting, nature has given it to such insects as are
of a fierce disposition, and to no others. Sometimes this instru-
ment is lodged inside the body, as in bees and wasps. This is
a necessary consequence of their being made for flight. For,
were their piercer or sting external and of delicate make, it
would very easily get spoiled. If on the other hand, still being
683a.

iv. 6. 109

external, it were of stouter build, as in scorpions, its weight
would interfere with flight. As for scorpions, they never rise
from the ground, and their piercer or sting must therefore
be arranged in the way it is, as otherwise it would be of no
use as a weapon.^^ The Diptera never have a tail-sting. ^^ For
the very reason of their being dipterous is that they are small
and weak, and therefore require no rnore than two feathers to
support their light weight. And the same reason which reduces
their feathers to two causes their piercer or sting to be in
front ; for their strength is not sufficient to allow them to strike
efficiently with the hinder part ^* of their body. Polypterous
insects on the other hand are of greater bulk — indeed it is this
which causes them to have so many feathers — and their greater
size makes them much stronger in their hinder parts. These
insects therefore have tail-stings. For it is better, when possible,
that one and the same instrument shall not be made to serve
several dissimilar uses ; but that there shall be one organ to
serve as a weapon, which can then be very sharp, and a second
distinct one to serve as a tongue, which can then be of spongy
texture and fit to absorb nutriment. Whenever, therefore, nature
is able to provide two separate instruments for two separate
uses, without the one hampering "the other, she does so, instead
of acting like a coppersmith, who for cheapness makes a spit
and lampholder in one. It is only when this is impossible, that
she uses one organ for several functions.^^

The anterior legs are in some cases longer'^ than the others,
that they may serve to clean off the dust or other matter which
may fall into the insect's eyes and obstruct its sight, which already
is not very distinct owing to the eyes being made of a hard
substance. Flies and bees and the like may be constantly seen
thus dressing themselves with crossed fore-legs. Of the other
legs, the hinder are bigger than the middle pair, both to aid in
running and also that the insect, when it takes flight, may spring
more easily from the ground. This difference is still more marked
in such insects as leap, in grasshoppers for instance and in the
various kinds of fleas.^^ For these first bend and then extend
the legs, and, by so doing, are necessarily sl^ot up from the
ground. It is only the hind legs of grasshoppers, and never
the front ones, that resemble the two long stern oars by which
a ship is steered.^^ For it is essential that the joint shall be
683 b.

I lO iv. 6 — iv. 8.

bent inwards, and this never occurs in the anterior limbs.^^ The
whole number of legs, including those used in leaping, is six, iri
all these insects.

(Ch. y.) In the Testacea^ the body consists of but few parts,
the reason being that these animals lead a stationary life. For
such animals as move much about must of necessity have more
numerous parts than such as remain quiet ; for, the more diversified
the movements, the greater the number of organs required to effect
them.2 Some species of Testacea are absolutely motionless, and
others very nearly so. They would thus fall an easy prey to their
enemies, were it not for the hardness of the shell with which
nature has invested their body as a means of protection. This
shell, as already has been said, may have one valve, or two
valves, or be turbinated. In the latter case it may either be
spiral as in whelks, or merely globular, as in the Echini.^ When
it has two valves, these may be gaping, as in scallops and
mussels, where the valves are united together on one side only,
so as to open and shut on the other, or they may be united
together on both sides, as in razor-fishes,* In all cases alike
these Testacea have, like plants, their head downwards. The
reason for. this is that they imbibe their nourishment from below,
just as dok plants with their roots.^ Thus the under parts come
in them to be above, and the upper parts to be below. The body
is enclosed in a membrane, and through this the animal filters
suitable fluid and absorbs nutriment. In all there is a head;^ but
none of the other parts, excepting the receptacle for food, has any
distinctive name.

(Ch. Z.) All the Crustacea ^ can crawl as well as swim, and
accordingly they are provided with numerous feet. There are
four main genera, viz. the Carabi, as they are called, the Astaci,
the Carides, and the Carcini. In each of these genera, again,
there are numerous species, which differ from each other not only
as regards shape, but also very considerably as regards size. For,
while in some species the individuals are large, in others they
are excessively minute. The Carcinoid and Caraboid Crustacea
resemble each other in possessing claws. These claws are not
for locomotion, but to serve as hands for seizing and holding
objects ; and they are therefore bent in exactly the opposite
direction to the feet, being so twi-sted as to turn their convexity
towards the body, while the feet turn towards it their concavity
683b.

. iv. 8. Ill

For by this position the claws are best suited for laying hold of
food and carrying it to the 'mouth. The distinction between the
Carabi and Carcini consists in the former having a tail while the
latter have none. For the Carabi swim about, and a tail is there-
fore of use to them, serving for their propulsion like the blade of
an oar. But it would be of no good to the Carcini ; for these
animals as a rule live close to shore, and creep into holes and
corners. In such of them as live out at sea, the feet are much
less adapted for crawling than in the rest, because they make but
little use of them for this purpose and depend for protection on
their shell-like covering. The Maiae and the crabs known as
Heracleotic are examples of this ; the legs- in the former being
very thin, in the latter very short.^

The very minute crabs, that are found at the bottom of the
net mixed with small fishes, have their posterior legs expanded
into the resemblance of fins or oar-blades, so as to help the animal
in swimming.^ The Carides are distinguished from the Carcinoid
species by the presence of a tail ; and from the Caraboids by the
absence of claws. This is explained by their large number of
feet, on which has been expended the material for the growth
of claws.* Their feet again are numerous to suit their mode of
progression, which is mainly by swimming.^

The parts on the ventral surface and near the head are in some
of these animals formed like gills, for the admission and discharge
of water. The parts lower down differ in the different sexes. For
in the female Carabi the parts are more laminar than in the males,^
and in the female Crabs the flap is furnished with hairier appen-
dages. This gives ampler space for the disposal of the ova, which
the females retain in these parts instead of letting them go free,
like fishes and other animals, as soon as they are brought forth.

In the Carabi and in the Carcini the right claw is invariably
the larger and the stronger.''^ For it is natural^ to every animal
to use its right side in preference to its left ; and nature, in dis-
tributing the organs, invariably assigns each, either exclusively
or in a more perfect condition, to such animals as can use it. So
is it with tusks, and teeth, and horns, and spurs, and all such
offensive and defensive weapons.^

In the Astaci alone it is a matter of chance which claw is the
larger, and this in either sex.^'' Claws they must have, because
they belong to a genus in which this is a constant character ;^^
684 a.

112 iv, 8 — iv. 9.

but they have them in this irregular way, owing to imperfect
formation and to their not using them for their natural purpose,
but for locomotion.

For a detailed account of the several parts of these animals, of
their position, and their differences, those parts being also included
which distinguish the sexes, reference must be made to the
treatises on Anatomy and to the Researches concerning Animals.

(Ch. g.) We come now to the Cephalopods.^ Their internal
organs have been already described with those of other animals. ^
Externally there is an uniform sac inclosing the body ; and in
front of this sac a head surrounded by feet, which form a circle
about the mouth and teeth, and are set between these and the
eyes. Now in all other animals the feet, if there are any, are
placed in one of two ways ; either before and behind, or along
the sides, the latter being the method adopted in those bloodless
animals whose feet are numerous. But in the Cephalopods there
is a peculiar arrangement, distinct from either of these. For their
feet are all placed at what may be called the fore end. The reason
for this is that the hind and fore parts of their body have been
drawn up close to each other, ^ as is also the case in the turbinated
Testacea. For these latter, while in some points they resemble
the Crustacea, in others resemble the Cephalopods. Their earthy
matter is on the outside, and their fleshy substance within. So
far they are like the Crustacea. But the general plan of their
body is that of the Cephalopods ; and, though this is true in a
certain degree of all the Testacea, it is more especially true of
those turbinated species, that have a spiral shell.* This general
plan, common to the two, is as follows. Let us first consider
the case of quadrupeds and of man, where the arrangement is
that of a straight line. At the upper end of this line, A represents
the mouth, then B the gullet, and C the stomach. After this
comes the intestine reaching to the vent, which is marked by DJ^
Such is. the plan in sanguineous animals ; and round this straight
line as an axis are disposed the head and trunk ; the remaining
parts, such as the anterior and posterior limbs, having been super-
added by nature, merely to minister to these and for locomotion.

Now in Crustacea and in Insects there is a tendency to a similar
arrangement of the internal parts in a straight line ; the distinc-
tions between these groups and the sanguineous animals depending
on differences of the external organs which minister to locomotion.
684b.

IV. 9- 113

But the Cephalopods and the turbinated Testacea have in common
an arrangement which stands in contrast with this. For here the
two extremities are brought together by a curve, as if one were
to berid the straight line marked E until D came close to A.
Such, then, is the disposition of the internal parts ; and round
these, in the Cephalopods, is placed the sac (in the Poulps alone
called a head),^ and, in the Testacea, the turbinated shell which
corresponds to the sac. There is, in fact, only this difference
between them, that the sac of the Cephalopods is soft while the
shell of the Testacea is hard, nature having invested the fleshy
parts with this hard coating as a protection to the animal, which
from its limited power of locomotion is exposed to considerable
risk. In both classes, owing to this arrangement of the internal
organs, the excrement is voided near the mouth ; at a point below
this orifice in the Cephalopods, and in the Turbinata somewhat
on ohe side of it.''^

Such then is the explanation of the position of the feet in the
Cephalopods, and of the contrast they present to other animals
in this matter. The arrangement, however, in the Sepias and the
Calamaries is not precisely the same as in the Poulps, owing to
the former having no other mode of progression than by swimming,
while the latter not only swim but crawl.^ Thus the former have
six of their feet above the teeth, and of these six the two outer
ones are the biggest ; while the remaining two, which make up
the total eight, are below the mouth and are much the biggest
of all, just as the hind limbs in quadrupeds are stronger than the
fore Hmbs. For it is these lower feet and these ^ hind legs
that have to support the weight, and to take the main part in
locomotion. And the outer pair of the upper six are bigger than
the pair which intervene between them and the uppermost of all,
because they have to assist the lowermost pair in their office.
In the Poulps, on the other hand, the four central feet are the
biggest.^" Again, though the number of feet is the same in all
the Cephalopods, namely eight,^^ their length varies in different
kinds, being short in the Sepias and the Calamaries, but greater
in the Poulps. For in these latter the body with its sac is of
small bulk, while in the former it is of considerable size ; and so
in the one case nature has used the materials subtracted from
the body to give, length to the feet, while in the other she has
acted in precisely the opposite way, and has given to the growth
685 a. 8

I H IV. 9.

of the body what she has first taken from the feet.^^ jhe Poulps,
then, owing to the length of their feet, can not only swim but
crawl, whereas in the other genera the feet are useless for the
latter mode of progression, being small while the bulk of thfe body
is considerable. These short feet would not enable their possessors
to cling to the rocks and keep themselves from being torn off by
the waves in times of storm ; neither would they serve to lay
hold of objects at all remote and bring them in ; but, to supply
these defects, the animal is furnished with two ^' proboscides, by
which it can moor itself and ride at anchor like a ship in rough
weather.^* The same processes serve also to catch prey even at
some distance and to bring it to the mouth. They are so used
both by the Sepias and the Caletmaries. In the Poulps the feet
are themselves able to perform these offices, and there are con-
sequently no proboscides. In all the Cephalopods that have
suckers on their feet and ^^ twining tentacles, these act in the
same way, and have indeed the same structure, as those plaited
instruments which were used of old by physicians to reduce
dislocations of the fingers.^^ The tentacles, like these, consist
of plaited fibreSj which act by pulling upon portions of flesh or
any substance of a yielding nature. The physician places his
instrument in a slackened condition round the finger ; and, when
it is put on the stretch, it grasps and clings tightly to whatever
may be in contact with its inner surface. The tentacles act in the
same manner, serving in place of hands for offensive or defensive
purposes, the Cephalopods having indeed no other instrument than
either feet or proboscides with which to lay hold on anything and
bring it to the mouth.

The suckers are set in double line in all the Cephalopods
excepting in one kind of poulp, where there is but a single row.^'
The length and the slimness which is part of the nature of this
kind of poulp explains the exception. For a narrow space
cannot possibly admit of more than a single line of suckers. This
exceptional character, then, belongs to them, not because it is the
.most advantageous arrangement, but because it is the necessary
consequence of their essential specific constitution.^®

In all these animals there is a fin, encircling the sac. In the

Poulps and the Sepias this fin is unbroken and continuous, as is

also the case in the larger calamaries. But in the smaller kind,

called Teuthides, the fin is not only broader than in the Sepias

685b.

iv. 9 — iv. lo. 115

and the Poulps, where it is very narrow, but moreover only begins
in the middle of the side, and does hot encircle the entire sac.
The use of this fin is to enable the animal to swim, and also to
direct its course. It acts, that is, like the rump-feathers in birds,
or the tail-fin in fishes. In none is it so small as in the Poulps ;
where it is difficult to make it out.^^ ' For in these the body is of
small bulk and can be steered by the feet sufficiently well without
other assistance.'

All the bloodless animals, namely the Insects, the Crustacea,
the Testacea, and the Cephalopoda, have now been dealt with in
turn; and the parts of .all have been described, whether internal
or external.

(Ch. \o.) We must now go back to the animals that have
blood, and consider such of their parts, already enumerated,
as were before passed over. We will take the^ viviparous animals
first, and, when we have done with these, will pass on to the
ovipara, and treat of them in like manner.

The parts that border on the head, and on what is known as
the neck and throat, have been already taken into consideration.
As for the head- itself, such a part is found in all animals that
have blood ; whereas in some bloodless animals, in crabs for
instance, there is no head distinctly separable from the trunk.
As to the neck, it is present in all the vivipara, but only in some
of the ovipara ; for while those that have a lung also have a neck,
those that do not inhale the outer air have none.^

The head exists mainly for the sake of the brain. For every
animal that has blood must of necessity have a brain ; and must,
moreover, for reasons already given, have it placed as far as
possible from the heart.-^ But the head has also been chosen
by nature as the part in which to set some of the senses ; because
its blood is mixed in such suitable proportions as to ensure quiet
and precision to the sensations, while at the same time it can
supply the brain with such warmth as it requires.* There is yet
a third constituent superadded . to the head, namely the part
which ministers to the ingestion of food. This has been . placed
here by nature, because such a situation accords best with the
general configuration of the body. For the stomach could not
possibly be placed above the heart, seeing that this is the sovereign
organ ; and if placed below, as in fact it is, then the mouth could
not possibly be placed there also. For this would have neces-
686a.

Il6 iv, 10.

sitated a great increase in the length of the body ; and the
stomach moreover would have been removed too far from the
source of motion and of concoctiort^ The head, then, exists for
the sake of these three parts.

The neck, again, exists for the sake of the windpipe. For it
acts as a defence to this and to the oesophagus, encircling them
and keeping them from injury. In all -other animals this neck
is flexible and contains several vertebrae ; but in wolves and lions
it contains only a single bone.^ For the object of nature was to
give these animals- an organ which should be serviceable in the
way of strength, rather than one that should be useful- for any
of the other purposes to which necks are subservient.'''

Continuous with the head and neck is the trunk with the
anterior limbs. In man the fore-legs and fore-feet are replaced
by arms and by what we call hands. For of all animals man
alone stands erect, in accordance with his god-like nature and
essence. For it is the function of the god-like to 'think and to
be wise ; and no easy task were this under the burden of a heavy
body, pressing down from above and obstructing by its weight
the motions of the intellect and of the common sense. ^ When,
moreover, the weight and corporeal substance become excessive,
the body must of necessity incline towards the ground. In such
cases therefore nature, in order to give support to the body, has
replaced the arms and hands by fore-feet, and has thus converted
the animal into a quadruped. For, as every animal that walks must
of necessity have the two hinder feet, such an animal becomes a
quadruped, its body inclining downwards in front from the weight
which its soul cannot sustain. For all animals, man alone excepted,
are dwarf-like in form. For, as in a dwarf, their upper part is
large, while that which bears the weight and is used in walking
is comparatively small. ^ This upper part is what we call the
trunk, and reaches, from the mouth to the vent. In man it -is
duly proportionate to the part below, and diminishes much in its
comparative size as the man attains to full growth. But in his
infancy the contrary obtains, and the upper parts are large, the
lower small ; so that the infant can only crawl, and is unable to
walk ; nay, at first cannot even crawl, but remains without motion.
In fact all children are dwarfs in shape:, but cease to be so as they
become men, from the growth of their lower portion ; whereas
in quadrupeds the reverse occurs, their lower parts being larges,^
686 b.

iv. lo. 117

in youth, and advance of years bringing increased growth above,
that is in the trunk, which extends from the buttocks to the head.
•Thus it is that colts are scarcely, if at all, below full-grown horses
in height ; and that while quite young they can touch their heads
with the hind legs, though this is no, longer possible when they
are older. Such then is the form of animals that have either
•a solid or a cloven hoof But such as are polydactylous and
without horns; though they too are of dwarf-like shape, are so
in a less degree ; nor is the original disproportion between their
upper and lower parts increased by aftergrowth.^''

Dwarf-like again is the race of birds and of fishes ; and so in
■fact, as already has been said, is every animal that has blood.
This ig the reason that no other animal is so intelligent as man.
For even among men themselves if we compare children with
adults, or such adults as are of dwarf-like shape with such as
are not, we find that, whatever other superiority the former may
possess, they are at any rate deficient as compared with the latter
in intelligence. The explanation, as already stated, is that their
psychical principle is corporeal, and much impeded in its motions.
Let now a still further decrease occur in the ^^ elevating heat,
and a still further increase in the earthy matter, and the animals
become smaller in bulk, and their feet more numerous, until at
a later stage they become apodous, and extended full length on
the ground. Thus, by gradual small successions of change, they
come to have their principal organ below ; and at last their
cephalic part becomes motionless and destitute of sensation. Thus
the animal becomes a plant, that has its upper parts downwards
and its lower parts above. ^^ For in plants the roots are the
equivalents of mouth and head, while the seed, which is pro-
duced above at the extremities of the twigs, has an opposite
significance.'^

The reasons have now been stated why some animals have many
feet, some only two, and others none ; why, also, some living things
are plants and others animals ; and, lastly, why man alone of all
animals stands erect. Standing thus erect, man has no need of
legs in front, and in their stead has been endowed by nature with
arms and hands. Now it is the opinion of Anaxagoras, that the
possession of these hands is the cause of man being of all animals
the most intelligent. But it is rational to suppose that the
possession of hands is the consequence rather than the cause
687 a.

Ii8 • iv. 10.

of his superior intelligence. For the hands are instruments or.
organs, and the invariable plan of nature in distributing the organs
is to give each to such animal as can make use of it; nature
acting in this matter as any prudent man would do. For to
such an one it would seem much more appropriate to take a
person who was already a flute-player and give him a .flute, than
to take one who possessed a flute and teach him the art of
flute-playing. For by the former plan something comparatively
insignificant would be added to something of much greater
importance; while by the latter the more valuable and the more
important element would be superadded to the less yaluable one.
Seeing then that it is a better plan to assign an instrument" to
a workman than to assign a workman to an instrument, and
seeing also that of all available plans nature invariably adopts
the best, we must conclude that man does not owe his superior
intelligence to his hands, but his hands to his superior intelligence.'*
For the most intelligent of animals is the one which would put
the most organs to the best use; and the hand is apparently
not a single organ but many in one ; for it is an organ that can
serve in the place of many. This instrument, then, — the hand —
of all instruments the most variously serviceable; has been given
by nature to man, the animal of all animals the most capable of
acquiring the most varied handicrafts.

Much in error then are they, who say that the construction of
man is not only faulty, but inferior to that of all other animals;
seeing that he is, as they point out, barefooted, naked, and without
weapon of which to. avail himself For other animals have each
but one mode of defence, and this they can never change; so that
they must perform all the offices of life and even, so to speak,
sleep with sandals on, never laying aside whatever serves as
a protection to their bodies, nor changing such single weapon as
they may chance to possess. But to man numerous modes of
defence are open, and these moreover he may .change at will ;
as also he may adopt such weapon as he pleases, and at such
times as suit him. For the hand is talon, hoof, and horn, at will.
So too is it spear, and sword, and whatsoever other weapon or
instrument you please ; for all these can it be from its power of
grasping and holding them all.^^ In harmony with this varied
office is the form which nature has contrived for it. For it is
split into several divisions, and these are capable of divergence.
687b.

IV. 10. 119

Such capacity of divergence does not prevent their again con-
verging so as to form a single compact body, whereas had the
hand been an undivided mass, divergence would have been
impossible. Again these parts may be used singly or together,
and in various combinations. The joints, moreover, of the fingers
are well constructed for prehension and for pressure. One of the
digits also, and this not long like the rest but short and thick, is
placed laterally. For were it not so placed all prehension would
be as impossible, as were there no hand at all. For the pressure
of this lateral digit is applied from below upwards, while the rest
act from above downwards ; an arrangement which is essential,
if the grasp is to be firm and hold like a tight clamp. As for
the shortness of this lateral digit, the object is to increase its
strength, so that it may be able, though but one, to counter-
balance its more numerous opponents. Indeed were it long it
would be of no use. This is the explanation of its being some-
times called the great digit, in spite of its small size ; for without
it all the rest would be practically useless. The finger which
stands at the other end of the row is small, while the central
one. of all is long, like the centre oar in a ship. This is rightly
so; for in grasping an object,- as a workman grasps his tool, it
is the central part of the encircling hold which is of the most
importance. .

No less skilfully contrived are the nails. For, while in man
these serve simply as coverings to protect the ends of the fingers,
in other animals they are also i}sed for active purposes ; [and
their form in each case is suited to their office.] ^^

The arms in man and the fore limbs in quadrupeds bend in
precisely ^^ contrary directions, this difference having reference to
the ingestion of food ^^ and to the other offices which belong to
these parts. For -quadrupeds use their anterior limbs as feet in
progression, and must therefore have them bent inwards. In such
of the quadrupeds indeed as are polydactylous, these fore limbs
are at any rate intended not only to serve in locomotion, but also
to act as hands. And they are in fact so used, as any one may
see. For these animals seize hold of objects, and also repel
assailants, with their anterior limbs ; whereas quadrupeds with
solid hoofs use their hind legs for this latter purpose.*^ For their
fore limbs are not analogous to the arms and hands of man.^"

It is this hand-like office of the anterior limbs which explains
688a.

126 i V. I o.

why in some of the polydactylous quadrupeds, such as wolves,
lions, dogs, and leopards, there are five digits on each fore-foot,
though there are only four on each hind one. For the fifth
digit of the foot corresponds to the fifth digit of the hand,
and like it is called the big one. It is true that in the smaller
polydactylous " quadrupeds the hind feet • also have each five
toes. But this is because these animals are creepers ; and the
mcreased number of nails serves to give them a tighter grip of
the ground, and so enables them to creep up steep places, or
even to run overhead, with greater facility .^^

In man between the arms, and in other animals between the'
fore legs, lies what is called the breast. This in man is broad,
as one might expect. For as the arms are set laterally on the
body, they offer no impediment to the expansion of this part.
But .in quadrupeds the breast is narrow, owing to the legs
having to be extended in a forward direction in progression and
locomotion.

Owing to this narrowness the mammae of quadrupeds are
never placed on the breast. But in the human body there is
ample space in this part ; moreover the heart and neighbouring
organs require such protection as would be afforded by a fleshy
covering ; and for these reasons the mammae in man are placed
on the breast, side by side. In the male these mammae are
of a fleshy substance and are therefore of use in the way just
stated ; but, in the female, nature, in accordance ^^ with what
we say is her frequent practice, makes these organs minister
to an additional function, employing them as a store-place of
nutriment for the offspring. The human mammae are two in
number, in accordance with the division of the body into two
halves, a right and a left. They are somewhat firmer than they
would otherwise be, because the. ribs ^' in this region are joined
together ; and they form two distinct masses, because their
presence is in no wise burdensome.^* In other animals ^^ than
man, it is impossible for the mammae to be placed on the breast
between the fore legs, for they would interfere with locomotion ;
they are therefore disposed of otherwise, and in a variety of
ways. Thus in such animals as produce but few at a birth,
whether horned quadrupeds or those with solid hoofs, the mammae
are placed in the groins, and are two in. .number,^^ while in such
as produce litters, or such as are polydactylous, the dugs are
e88a.

IV. lO. 121

either numerous and placed laterally on the belly, as in swine
and dogs, or are only two in number and placed in the centre
of the abdomen, as is the case in the lion." The explanation
of this latter condition is not that the lion produces few at a
birth, for sometimes it has more than two cubs at a time, but
is to be found in the fact that this animal has no plentiful
supply of milk. For, being a flesh-eater, it gets food at but
rare intervals, and such nourishment as it obtains is all expended
on the growth of its body.

In the elephant also there are but^ two mammae, which are

placed under the axillae of the fore limbs. The mammae are

not more than two, because this animal has only a single young

one at a birth ; and they are not placed in the groins, because

they never occupy that position in any polydactylous animal

such as this.^ Lastly they are placed above close to- the axillae,

because this is the position of the foremost dugs in all animals

whose dugs are numerous, and the dugs .so placed give the most

milk. A proof of this is furnished by the sow. For she always

presents these foremost dugs to the first-born of her litter.

A single young one is of course a first-born ; and so such

animals as only produce a single young one must have these

anterior dugs to present to it ; that is they must have dugs

close to the axillae. This, then, is the reason why the elephant

has but two mammae, and why they are so placed. But, in

such animals as have litters of young, the dugs are disposed

about the belly ; the reason being that more dugs are required

by those that have more young to nourish. Now as there

are but two sides to the body, the right and the left, it is

impossible that these dugs should be sfet transversely in* rows

of more than two. They must therefore be placed lengthways,

and the only place where there is sufficient length for this is

the region between the ' front and hind legs. As to the animals

that are not polydactylous but produce few at a birth, or have

horns, their dugs are placed in the groins. The horse, the ass,

the camel are examples ; all of which bear but a single young

one at a time, and of which the two former have solid hoofs,

while in the last the hoof is cloven. As still further examples,

may be mentioned the ' deer, the ox, the gpat, and all other

similar animals.

The explanation is that in these animals growth takes place
688b.

122 IV. lO.

in an upward direction ;^^ so that there must be an abundant
collection -of residual matter and of blood in the lower region,
that is to say in the neighbourhood of the excremental orifices.
Here therefore nature hag placed the mammae. For the part
whence they can most easily derive nutriment will clearly be
that part in which the nutriment is set in motion. In man
there are mammae in the male as well as in the female; but
some of the males of other animals are without them. Such
for instance is the case with horses, some stallions being destitute
of these parts, while others that resemble their dams have
them.^ Thus much then concerning the mammae.

Next after the breast comes the region of the belly, which
is left unenclosed by the ribs for a reason which has already
been given ; ^^ namely that there may be no impediment to
the swelling which necessarily occurs in the food as it gets
heated, nor to the expansion of the womb in pregnancy.

At the extreme end pf what is called the trunk are the parts
concerned in the evacuation of the solid and also of the fluid
residues. In all sanguineous animals with some few exceptions,^^
and in all vivipara without any exception at all, the same part
which serves for the evacuation of the fluid residue is also made
by nature to serve in sexual congress, and this alike in male and
female. For the semen is a kind of fluid and a residue. The
proof of this will be given hefeifter, but for the present let it be
taken for granted. The like holds good of the menstrual fluid in
women, and of the part by which they give issue to it. This
also, however, is a matter of which a more accurate account will
be given hereafter. For the present let it be simply stated "as
a fact, that the catamenia of the female as also the semen of the
male are residual matter.^^ The catamenia, then, and the semen
are both fluid, and thus it is only reasonable that the same parts
which serve for voidance of the urine should give issue to these
residues, which have identical or similar characters. Of'.the internal
structure of these parts, and of the differences which exist between
the parts concerned with semen and the parts concerned with *
conception, a clear account is given in the book of Researches
concerning Animals and in the treatises on Anatomy. Moreover
I shall have to speak of them again when I come to deal with
Generation and Development. As regards, however,- the external
shapes of the parts, it is plain enough that they are adapted to their
689a.

IV. 10. 123

operations, as indeed of necessity they must be. There are, how-
ever, differences in the male organ corresponding to. differences
in the body generally. For it is not of an equally sinewy
character in all animals. This organ, again, is the only one that,
independently of any .morbid change, admits of augmentation
and of diminution of bulk. The former change is of service in
copulation, while the other is required for the advantage of the
body at large. For, were the organ constantly in a state of
erection, it would be an incumbrance. The organ therefore has-
been formed of such constituents, as will admit of either condition.
For it is partly sinewy, partly cartilaginous,^* and thus is enabled
either to contract or to become extended, and is capable of
admitting air.^*

All female quadrupeds void their urine backwards, because
the position of the parts which this implies is useful to them
in the act of copulation. This is the case with very few males,
though there are some exceptions, as the lynx, the lion, the
camel, and the hare.^^ No quadruped with a solid hoof is
retromingent.

The posterior portion of the body and the parts about the
legs are different in man from what they are in quadrupeds.
Nearly all these latter have a tail, and this whether they are
viviparous or oviparous. For, even if the tail be of no great
size, yet they have a kind of scut; as at any rate a small repre-
sentative of it. But man is tail-less. He has however buttocks,
which exist in none of the quadrupeds. His legs also, calves
and thighs alike, are fleshy ; while in all other animals that
have legs, viviparous or not, they are fleshless, being made of
sinew and bone and a substance resembling fish-spine.^^ For
all these differences there is, so to say, one common explanation,
and this is that of all animals man alone stands erect. It was
to facilitate the maintenance of this position that nature made
his upper parts light, taking away some of their corporeal
substance, and using it to increase the weight of the parts
below, so that the buttocks, the thighs, and the calves of the
legs, all became fleshy. The character which she thus gave
to the buttocks renders them at the same time useful in resting
the body. For standing causes no fatigue to quadrupeds, and
even the long continuance of this posture produces in them no
weariness ; for they are supported the whole time by four props,
689b.

124 iv. 10.

which is much as though they were lying down.'^ But to man
it is no easy task to remain for any length of time on his
feet, his body demanding rest in a sitting position. This, then,
is the reason why man has buttocks and fleshy legs; and the
presence of these fleshy parts explains why he has no tail. For
the nutriment which would otherwise go to the tail is used up
in the production of these parts,^^ while at the same time the
existence of buttocks does away with the necessity of a tail.
But in quadrupeds and other animals the reverse obtains. For
they are of dwarf-like form, so that all the pressure of their
weight and corporeal substance is on their upper part; and is
withdrawn from the parts below.^'' On this account they are
without buttocks and have hard legs. In order however to cover
and protect that part which serves for the evacuation of excre-
ment, nature has given them a tail or brush, subtracting for
the purpose some of the nutriment which would otherwise go
to the legs. Half-way in shape between man and quadrupeds
is the ape,^^ belonging therefore to, neither or to both, and having
on this account neither tail nor buttocks ; no tail in its character
of biped, no buttocks in its character of quadruped. There is a
great diversity of so-called tails; and this organ like others*^ is
sometimes used by nature for bye-purposes, being made to serve
not only as a covering and protection to the fundament, but also
for other uses and advantages of its possessor.*^

There are differences in the feet of quadrupeds. For in sorne
of these animals there is a solid hoof, and in others a hoof cloven
into two, and again in others a foot divided into many parts.

The hoof is solid when the body is large and the earthy matter
present in great abundance ; in which case the earth, instead of
forming teeth and horns, is separated in the character of a
nail, and being very abundant forms one continuous- nail, that
is a hoof, in place . of several. ^ This consumption of the earthy
matter on the hoof explains why these animals, as a rule, have
no ^* huckle-bones ; a second reason, however, being that the
presence of such a bone in the joint of the hind leg somewhat
impedes its free motion. For ex;tension and flexion can be made
more rapidly in parts that have but one angle than in parts that
have many. But the presence of a huckle-bone, as a connecting
bolt, is the introduction as it were of a new limb-segment between
the two ordinary ones. Such an addition adds to the weight of
690a.

iv. 10, 125

the foot, but renders the act of progression more secure. Thus
it is that even in such animals as have a huckle-bone, it "is only
in the posterior limbs and never in the anterior ones that this
bone is foundn For the anterior limbs, moving as they do in
advance of the others, require' to be light and capable of ready
flexion, whereas firmness and extension are what is wanted in the
hind limbs. Moreover a huckle-bone adds weight to the blow
of a limb, and so renders it a .suitable weapon of defence; 'and
these animals all use their hind legs to protect themselves, kicking
out with their heels against anything, which annoys them. In the
cloven-hoofed quadrupeds the lighter character of the hind legs
admits of there being a huckle-bone ; and the presence of the
huckle-bone prevents them from having a solid hoof, the bony
substance remaining in the joint, and therefore being deficient
in the foot. As to the polydactylous quadrupeds, none of them
have huckle-bones. For if they had they would not be poly-
dactylous, but the divisions of the foot would only extend to that
amount of its breadth which was covered by the huckle-bone.*^
Thus it is that most of the animals that have huckle-bones are
cloven-hoofed.

Of all animals man has the largest foot in proportion to the
size of the body.*^ This is only what might be expected. For
seeing that he is the only animal that stands erect, the two feet
which have to bear all the weight of the body must be both long
and broad. Equally intelligible is it that the proportion between
the size of the fingers and that' of the whole hand should be
inverted in the case of the toes and feet. ' For the function of
the hands is to take hold of objects and retain them by pressure ;
so that the fingers require to be long. For it is by its flexed
portion that the hand grasps an object. But the function of the
feet is to enable us to walk with security ; so that here the
undivided part is to be looked on as of most importance. How-
ever it is better for an extremity to be divided than to be un-
divided. For in an undivided foot disease of any one part would
affect by sympathy the whole ; whereas, if the foot be divided
into separate digits, there is not an equal liability to such an
occurrence.*'' The digits, again, by being short would be less
liable to injury. For these reasons the feet in man are many-
toed, while the separate digits are of no great length. The toes,
finally, are furnished with nails for the same reason as are the
690b.

126 IV. 10 — iv. II.

fingers, namely because such projecting parts are weak and there-
fore require especial protection.

(Ch. w.) We have now done with such sanguineous animals as
live on land and bring forth their young alive ; ^ and, having
dealt with all their main kinds, we may pass on to such sanguineous
animals as are oviparous. Of these some ha.ve four feet, while
others have none. The latter form a single genus, n9.mely the
Serpents ; and why these are apodous has been already explained
in the dissertatipn on Animal Progression.^ Irrespective of this,
absence of feet, serpents resemble the oviparous quadrupeds in
their conformation.^

In all these animals there is a head with its component parts ;
its presence being determined by the same causes * as obtain in the
case of other sanguineous animals ; and in all, with the single ex-
ception of the river crocodile, there is a tongue inside the mouth.*
In this one exception there would seem to be no actual tongue,
but merely a space left vacant for it. The reason is that a croco-
dile is in a way a land-animal and a water-animal combined. In
its character of land-animal it has a space for a tongue ; but
in its character of water-animal it is without the tongue itself.
For in fishes, as has already been mentioned, there is either no
appearance of a tongue at all, unless the mouth be stretched open
very widely indeed ; or, if there be a tongue, it is indistinctly
separated from the rest of the mouth.^ The reason for this is
that a tongue would be of but little service to such animals, seeing
that they are unable to chew their food or to taste it before
swallowing, the pleasurable sensations they derive from it being
limited to the act of deglutition.''' For it is in their passage down
the gullet that solid edibles cause enjoyment, while it is by the
tongue that the savour of fluids is perceived. Thus it is during
deglutition that the oiliness, the heat, and other such qualifies of
food, are recognised ; and in fact the satisfaction from solid
edibles and dainties in general is derived almost exclusively
from the dilatation of the oesophagus during deglutition.^ This
pleasurable sensation, then, belongs to all sanguineous animals,
viviparous or not, alike ; but, while the rest have in addition the
sensations of taste, tongueless animals have no other satisfaction
than it. What has now been said explains why intemperance as
regards drinks and savoury fluids does not go hand in hand with
intemperance as regards eating and solid relishes.^
691a.

iv. II. 127

In some oviparous quadrupeds, namely in lizards, the tongue
is bifid, as also it is in serpents, and its terminal divisions
are of hair-like fineness, as has already been* described.^''
(Seals also have a forked tongue.) This it is which accounts
for all these animals being so fond of dainty food.'^ The teeth
in these oviparous quadrupeds are of the sharp interfitting kind,
as also are the teeth of fishes.*^ The organs of all the senses
are present; and these resemble those of other animals! Thus
there are nostrils for smell, eyes for vision, and ears for hearing.
The latter organs, however, do not project from the sides of
the head, but consist simply of the duct, as also is- the case in
birds. This is due in both cases to the hardness ^^ of the
integument ; birds having their bodies covered with feathers,
and these oviparous quadrupeds with horny plates. These
plates are equivalent to scales, but of a harder character. This
is very manifest in tortoises and river crocodiles, and also in
the large serpents: For so hard are they in these animals, as
to become even stronger than the bones.^* * .

These animals have no upper eyelid, but close the eye with the
lower lid.'^ In this they resemble birds, and the reason of the
peculiarity, is the same as was assigned in their case.^^ Among
birds there are some that can not only thus close the eye, but
can also blink by means of a membrane which comes from its
inner corner. But none of the oviparous quadrupeds blink in this
manner." For their eyes are harder than those of birds.^^ The
reason for this is that sharpsightedness is of very considerable
service to birds, flying as they do in the air, whereas it would be
of comparatively small use to the oviparous qiiadrupeds, seeing
that they all live in holes.

Of the two separate portions which constitute the head, namely
the upper part and the lower jaw, the latter in man and in the
viviparous quadrupeds moves not only upwards and downwards,
but also from side to side ; ^^ while in fishes, and birds, and
oviparous quadrupeds, the only movement is up and down. The
reason is that this latter movement is the one required in biting
and dividing food, while the lateral movement serves to reduce
substances to a pulp. To such animals, therefore, as have grinder-
teeth this lateral motion is of service ; but to those animals that
have no grinders it would be quite useless, and they are therefore
invariably without it. For nature never makes anything that is
691b. .

128

IV. II.

superfluous. While in all other animals it is the lower jaw that
is moveable, in the river crocpdile it is exceptionally the upper
one.^" This is because the feet in this creature are so excessively
sijiall as to be perfectly useless for seizing and holding prey ; ' on
which account nature has given it a mouth that can serve for
these purposes in their stead. For clearly that direction of motion,
which will give the greater force to a blow, will be the more
serviceable one in holding or in seizing prey; and a blow from
above is always more forcible than one from below. Seeing, then,
that both the prehension and the mastication of food are offices
of the mouth, and that the former of these two is the more
essential in an animal that has neither hands nor suitably formed
feet, these crocodiles will derive greater benefit from a motion of
the upper jaw downwards than from a motion of the lower jaw
upwards. The same considerations explain why crabs move only
the upper division of each claw and not the lower. For their
claws are substitutes for hands, and so require to be suitable for
the prehension of food, and not for its comminution ; for such
comminution and mastication is the ofiice of teeth. In crabs,
then, and in such other animals as are able to seize their food
in a leisurely manner, and are not forced by being constantly in
the water to perform this office with the mouth,^^ the two functions
are assigned to different parts, prehension to the hands or feet, the
division or mastication of food to the mouth. But in crocodiles
the mouth has been so franied by nature as to serve both purposes,
the jaws being made to move in the manner just described.

All these animals have a neck, which is the necessary con-
sequence of their having a lung. For the windpipe by which the
air is admitted to the lung is of some length.^^ If however the
definition of a neck be correct, which calls it the portion between
the head and the shoulders, a serpent can scarcely be said with
the same right as the rest of these animals to have a neck, but
only to have something analogous to that part of the body. It
• is a peculiarity of serpents, as compared with other animals allied
to them, that they are able to turn their head backwards without
stirring the rest of the body. The reason of this is that a serpent,
like an insect, has a body that admits of being curled up, its
vertebrae being cartilaginous and easily bent.^^ The faculty in
question belongs then to serpents simply as a necessary con-
sequence of this character of their vertebrae ; but at the same
692 a.

IV. II — IV. 12. 129

time it has a final cause, for it tells to their advantage by-
enabling them to guard against attacks from behind. For their
body, owing to its length and its want of feet, is ill-suited for
turning round and protecting the hinder parts ; and merely to
lift the head, without the power of turning it round, would be
of no use whatsoever.

The ovipara with which we are dealing have, moreover, a part
which corresponds to the breast ; but neither here nor elsewhere
in their body have they any mammae, as neither has any bird
or fish. This is a consequence of their having no milk ; for
a mamma is a receptacle for milk and, as it were, a vessel to
contain it. This absence of milk is not peculiar to these animals,
but is common to all such as are not internally viviparous. 2*
For all such produce eggs, and the nutriment which corresponds
to the milk is in them formed in the egg. Of all this, however,
a clearer account will be given in the treatise on Generation and
Development.^^ As to the mode in which the joints bend,
a general account, in which all animals are considered, has
already been given in the dissertation on Progression. So also
the reasons for the presence or absence of a tail have been already
stated at large.^^ It suffices therefore to say that these animals
always have a tail of some sort, though the size which it attains
varies considerably.

Of all the ovipara that live on land there is none so lean as
the Chartiaeleon.2'' For there is none that has so little blood.
The explanation of this is to be found in the psychical-
temperament of the creature. For it is of a timid nature, as
the frequent changes it undergoes in its outward aspect testify.^
But fear is a refrigeration, and results from deficiency of natural
heat and scantiness of blood.^^

We have now done with the sanguineous animals, both such
as are quadrupedous and such as are apodous, and have stated
with sufficient completeness what external parts they possess, and
for what reasons they have them.

(C/i. 12.^ The differences of birds ^ compared one with another
are differences of magnitude, and of the greater or smaller
development of parts. Thus some have long legs, others short
legs ; some have a broad tongue, others a narrow tongue ; and
so on with the other parts. There are very few of their parts
that present any greater differences than these, taking birds by
692 b. 9

130 iv. 12.

themselves,^ But, when we compare birds with other animals, we
find the parts differing not merely in relative size but in form.
Thus birds are invariably feathered, and this is a peculiarity
which is characteristic of them. For while other animals are
some hairy, some scaly, some covered with scaly plates, birds
alone are feathered. Insects it is true are also feathered, but
the feathers of a bird are split and different in kind from the
undivided feathers of an insect ; for the bird's feather is barbed,
while the insect's is not ; the bird's feather has a shaft, the
insect's has none.^

A second strange peculiarity which distinguishes birds from
all other animals is their beak. For as in* elephants * the nostril
serves in place of hands, and as in some insects ^ the tongue
serves in place of mouth, so in birds there is a bony^ beak which
serves in place of teeth and lips. Their organs of sense have
already been considered.

All birds have a neck extending from the body ; and the
purpose of this neck is the same as in such other animals as
have one.' This neck in some birds is long, in others short ; its
length as a general rule being pretty nearly determined by that
of the legs. For long-legged birds have a long neck, short-legged
birds a short one, to which rule, however, the web-footed birds
form an exception. For to a bird perched up on long legs a
short neck would be of no use whatsoever in collecting food
from the ground ; and equally useless would be a long neck,
if the legs were short. Such birds, again, as are carnivorous
would find length in this part interfere greatly with their habits
of life. For a long neck is a weak one, and it is on their superior
strength that carnivorous birds depend for their subsistence. No
bird, therefore, that has talons ever has an elongated neck.
In web-footed birds, however, and in those other birds that seem
to belong to the same genus, inasmuch as their toes though
actually separate are yet flattened and expanded into lobes,^
the neck is elongated, so as to be suitable for collecting food
from the water ; while at the same time the legs are short, so
as to serve in swimming.

The beaks of birds, as their feet, vary with their modes of life.

For in some the beak is straight, in others crooked ; straight,

in those whose food requires that form ; crooked, in those that

live on flesh. For a crooked beak is an advantage in fighting ;

603 a.

IV. 12. 131

and carnivorous birds must of course get their food from the
bodies of other animals, and in most cases by violence. In such
birds, again, as live in marshes and are herbivorous the beak
is broad, this form being best suited for digging and cropping,
and for pulling up plants. In some of these marsh birds,
however, the beak is elongated, as also is the neck, the reason
for this being that the bird gets its food from some depth below
the surface. For most birds that have this conformation, and
most of those that are either actually web-footed or web-footed
in the partial way already mentioned, live by preying on some
of the small animals that are to be found in water. In these
the neck acts the part of a fishing-rod, the beak representing
the line and hook.

The upper and under sides of the body, that is of what in
quadrupeds is called the trunk, present in birds one unbroken
surface. For there are no arms nor fore legs attached to it, but
in their stead wings, which are a distinctive peculiarity of birds;
and, as these wings are substitutes for arms, their terminal seg-
ments lie on the back in the place of a shoulder-blade.^

The legs are two in number, as in man ; not however, as in
man, bent outwards, but bent inwards like the hind legs of a
quadruped.^" The wings are bent like the fore legs of a quadruped,
having their convexity turned outwards. That the feet should be
two in number is a matter of necessity. For a bird is essentially
a sanguineous animal, and at the same time essentially a winged
animal ; and no sanguineous animal has more than four points
for motion." In birds, then, as in those other sanguineous animals
that live and move upon the ground,^^ the limbs attached to the
trunk are four in number. But, while in all the rest these four
limbs consist of a pair of arms and a pair of legs, or of four legs
as in quadrupeds, in birds alone the arms or fore legs are replaced
by a pair of wings, and this is their distinctive character. For
it is of the essence of a bird that it shall be able to fly ; and it
is by the extension of wings that this is made possible. Of all
arrangements, then, the only possible, and so the necessary, one
is that birds shall have two feet ; for this with the wings will
give them four points for motion. The breast in all birds is sharp-
edged, and fleshy.^3 -p^e sharp edge is of advantage in flight ;
for broad surfaces move with considerable difficulty, owing to
the large quantity of air which they have to displace. The fleshy
693 b.

132 IV, 12.

character acts as a protection to the breast, which owing to its
form would be very weak, were it not amply covered.^*

Below the breast lies the belly, extending, as in quadrupeds
and in man, to the vent and to the place where the legs are jointed
to the trunk.

Such, then, are the parts which lie between the wings and the
legs. Birds like all other animals, whether produced viviparously
or from eggs, have an umbilical cord during their development,
but, when the bird has attained to fuller growth, no signs of this
remain visible. The explanation of this will be set forth in the
treatise on Generation and Development, but amounts to this,
that in birds the umbilical cord unites with the intestine, and is
not a portion of the vascular system, as is the case in the vivipara.'^

Some birds, again, are well adapted for flight, their wings being
large and strong. Such, for instance, are those that have talons
and live on flesh. For their mode of life renders the power of
flight a necessity, and it is on this account that their feathers are
so abundant and their wings so large. Besides these, however,
there are also other genera of birds that can fly well ; all those,
for example, that depend on speed for security, and all those
again that are of migratory habits. On the other hand some
kinds of birds have heavy bodies and are not constructed for
flight. These are birds that are frugivorous and live on the
ground, or that are able to swim and gain their livelihood in
watery places. In those that have talons the body, when stripped
of [its feathers and] wings, is small ; for the nutriment is con-
sumed ^^ in the production of these weapons and defensive ap-
pliances; whereas in birds that do not fly the contrary obtains,
and the body is bulky and so of heavy weight. In some of these
heavy birds the legs are furnished with what are called spurs,
which replace the wings as a means of defence. Spurs and
talons never co-exist in the same bird. For nature never makes
anything superfluous ; and if a bird can fly, and has talons, it
has no use for spurs ; for these are weapons for fighting on the
ground, and on this account are an appanage of certain heavy-
bodied birds. These latter, again, would find the possession of
talons not only useless but actually injurious ; for the claws
would stick into the ground and interfere with progression. This
is the reason why all birds with talons walk so badly, and why
694 a.

IV. 12. 133

they never settle upon rocks.^''' For the character of their claws
is ill-suited for either action.

All this is the necessary consequence of the process of develop-
ment. For the earthy matter in the body issues from it and is
converted into some or other useful kind of weapon. That which
flows upwards gives hardness or size to the beak ; and, should
any flow downwards, it either forms spurs upon the legs or gives
size and strength to the talons. But it does not at one and the
same time produce both these results, one in the legs, the other
in the claws ; for such a dispersion of this residual matter would
destroy all its efiicacy. In other birds this earthy residue furnishes
the legs with the material for their elongation ; or sometimes,, in
place of this, fills up the interspaces between the toes. Thus it
is simply a matter of necessity,'® that such birds as swim shall
either be actually web-footed, or, if not so, shall at any rate have
a kind of broad blade-like margin running along the whole length
of each distinct toe.*^ The forms, then, of these feet are simply
the necessary results of the causes that have been mentioned.
Yet at the same time they are intended for the animal's advantage.
For they are in harmony with the mode of life of these birds,
who, living on the water, where their wings are useless, require
that their feet shall be such as to serve in swimming. For these
feet are so developed as to resemble the broad-bladed oars of
a boat, or the fins of a fish ; and the destruction of the foot-web
has precisely the same effect as the destruction of the fin ; that
is to say, it puts an end to all power of swimming.^**

In some birds the legs are very long, the cause of this being
that they inhabit - marshes. I say the cause, because nature makes
the organs for the function, and not the function for the organs.^^
It is, then, because these birds are not meant for swimming that
their feet are unwebbed, and it is because they live on ground that
gives way under the foot that their legs and toes are elongated,
and that these latter in most of them have an extra number of
joints.^ Again, seeing that all birds are made of the same
substance,^ and yet are not all constructed alike to fly, the
materials which in some are expended on organs of flight can
in others be diverted to different purposes ; and in these birds
the nutriment which would otherwise go to form the tail-feathers
is used in increasing the dimensions of the legs. This is the
reason why these birds when they fly make use of their legs
694b.

134 iv. 12.

as a tail, stretching them out behind, and so rendering them
serviceable, whereas in any other position they would be simply
in the way.^*

In other birds, where the legs are short, these are held close
against the belly during flight. In some cases this is merely
to keep the feet out of the way, but in birds that have talons
the position has a further purpose, being the one best suited for
rapine.^-'' Birds that have a long and a thick neck, keep it
stretched out during flight ; but those whose neck though long
is slender fly with it coiled up. For in this position it is pro-
tected, and less likely to get broken, should the bird fly against
any obstaclc^^

In all birds there is an ischium, but of such length that it
would scarcely be taken for an ischium, but rather for a second
thigh-bone ; for it extends as far as to the middle of the belly.^^
The reason for this is that the bird is a biped, and yet is unable
to stand erect. For if its ischium extended but a short way
from the fundament, and then immediately came the leg, as is
the case in man and in quadrupeds, the bird would be unable
to stand upright at all. For while man stands erect, and while
quadrupeds have their heavy bodies propped up in front by the
fore legs, birds can neither stand erect owing to their dwarf-like ^^
shape, nor have anterior legs to prop them up, these legs being
replaced by wings. As a remedy for this nature has given them
a long ischium, and brought it to the centre of the body, fixing
it firmly ; and under this central point she has placed the legs,
that the weight on either side may be equally balanced, and
standing or progression rendered possible. Such then is the reason
why a bird, though it is a biped, does not stand erect. Why its
legs are destitute of flesh has also already been stated ; for the
reasons are the same as in the case of quadrupeds.^^

In all birds alike, whether web-footed or not, the number of toes "
in each foot is four.^" For the Libyan ostrich may be disregarded
for the present, and its cloven hoof and other discrepancies of
structure as compared with the tribe of birds will be considered
farther on. Of these four toes three are in front, while the fourth
points backwards, serving, as a heel, to give steadiness. In the
long-legged birds this fourth toe is much shorter ^^ than the others,
as is the case also with the Crex.^^ In no bird is the number
of toes more than four. The arrangement of the toes is such
695a.

IV. 12 — IV. 13- 135

as has been described, in all birds with one exception. This
exception is the wryneck.^ Here two of the toes are in front,
the other two behind ; and the reason for this is that the body
of the wryneck is not inclined forwards so much as that of other
birds. All birds have testicles ; but they are inside the body.
The reason for this will be given in the treatise on the Generation
and Development of Animals.'*

(Ch. 13.J Thus then are fashioned the parts of birds. But in
fishes^ a still further stunting has occurred in the external parts.
For here, for reasons already given,^ there are neither arms nor
legs nor wings, the whole body from head to tail presenting one
unbroken surface. This tail differs in different fishes, in some
having a consistency similar to that of the body, while in others,
namely in some of the flat kinds, it is spinous and elongated,
because the material which should have gone to the tail has been
diverted thence and used to increase the breadth of the body.
Such for instance is the case with the Torpedos,' the Trygons,* and
whatever other Selachia there may be of like nature. In such
fishes, then, the tail is spinous and long ; while in some others
it is short and fleshy, for the very same reason which makes it
spinous and long in the Torpedo. For to be short and fleshy
comes to exactly the same thing as to be long and less amply
furnished with flesh.

What has occurred in the Fishing-frog,^ is exactly the reverse
of what has occurred in the other instances just given. For here
the anterior and broad part of the body is destitute of flesh, and
so all the fleshy substance which has been thence diverted has
been placed by nature in the tail and hinder portion of the body.

In fishes there are no limbs attached to the body. For in
accordance with their essential constitution they are swimming
animals ; and nature never makes anything superfluous or void of
use. Now, seeing that fishes are essentially sanguineous animals,
they must have four points of motion ; and, seeing that they are
meant for swimming, these must be fin& and not feet; for feet
are attached to the body that they may be of use in walking on
dry ground.^ Moreover it is impossible for fishes, that are san-
guineous animals, to have four fins and also at the same time, to
have feet or in fact any other kind of limb. Tadpoles,' it is
true, though they have gills, have feet; but then they have no
fins, but merely have their tail flattened out and loose in texture.*
695 b.

136 iv. 13.

Fishes, unless, like the Batos^ and the Trygon, they are broad
and flat, have four fins, two on the upper and two on the under
aspect of the body ; and no fish ever has more than these. For,
if it had, it would be an ex-sanguineous animal.

The upper pair of fins is present in nearly all fishes, but not so
the under pair; for these are wanting in some of those fishes
that have long thick bodies, such as the eel, the conger, and the
Cestreus which is found in the lake at Siphae.^" When the body
is still more elongated, and resembles that of a serpent rather than
that of a fish, as is the case in the Smyraena,^^ there are absolutely
no fins at all; and locomotion ^^ is effected by the flexures of the
body, the water being put to the same use by these fishes as is
the ground by serpents. For in fact serpents swim in water
exactly in the same way as they glide on the ground. The reason
for these serpent-like fishes being without fins is precisely the
same as that which causes serpents to be without feet ; and what
this is has been already stated in the dissertation on the Pro-
gression and the Motion of Animals.'^ The reason was this. If
the points of motion were four,^* motion would be effected under
difficulties. For either the two pairs of fins would be near each
other, in which case motion would scarcely be possible, or they
would be at a very considerable distance apart, in which case the
long interval between them would be just as great an evil. On the
other hand, to have more than four such motor points is out of
the question. For that would convert the fishes into ex-sanguineous
animals.^^ A similar explanation applies to the case of those
fishes that have only two fins. For here again the body is of
great length and like that of a serpent, and its undulations do
the office of the two missing fins. It is owing to this that such
fishes can even crawl on dry ground, and can live there for a
considerable time; and do not, like other fishes, begin to gasp
the moment they are taken out of the water ; and the less so, the
nearer their nature conforms to that of land-animals. In such
fishes as have but two fins it is the upper pair that is present, ^^
excepting when the flat broad shape of the body prevents this.
These fins, moreover, in such cases are placed at the head, because
in. this region there is no elongation, which might serve in the
absence of fins as a means of locomotion ; whereas in the
direction of the tail there is a considerable lengthening out in
fishes of this conformation. As for the Bati and the like, they
696 a.

IV. 13- 137

use the marginal parts of their flattened bodies in place of fins
for swimming.^'^

In the Torpedo and the Fishing-frog the breadth and flatness
of the anterior part of the body is not so great as to render
locomotion by fins impossible. It necessitates, however, the dis-
placement of the upper pair to a point further back, and the
advancement of the under pair to the head. At the same time
to compensate for this advancement these lower fins are reduced
in size so as to be smaller than the upper ones.'* In the Torpedo
the two upper fins are placed on the tail, and the fish uses the
broad expansion of its body to supply their place, each lateral
half of its circumference serving the office of a fin.*^

The head, with its several parts, as also the organs of sense,
have already come under consideration.^"

There is one peculiarity which distinguishes fishes from all
other sanguineous animals, namely, the possession of gills. Why
they have these organs has been explained in the treatise on
Respiration.'-^' These gills are in most fishes covered by opercula,
but in the Selachia, owing to the skeleton being cartilaginous,
there are no such coverings. For an operculum requires fish-bone
for its formation, and in other fishes the skeleton is made of this
substance, whereas in the Selachia it is invariably formed of car-
tilage. Again, while the motions of bony fishes are rapid, those
of the Selachia are but sluggish, owing to the absence of bone
and of sinew. But an operculum requires rapidity of motion,
seeing that the office of the gills is to minister as it were to expira-
tion.'^^ For this reason in Selachia the branchial orifices them-
selves effect their own closure, and thus there is no need for an
operculum to ensure its taking place with due rapidity .^^ In some
fishes the gills are numerous, in others few in number ; in some
again they are double, in others single. The last gill in most cases
is single.^* For a detailed account of all this, reference must be
made to that part of the treatises on Anatomy which relates to
fishes, and to the book of Researches concerning Animals.^^

It is the abundance or the deficiency of the cardiac heat which
determines the numerical abundance or deficiency of the gills.
For, the greater an animal's heat, the more rapid and the more
forcible does it require the branchial movement to be ;2^ and
numerous and double gills act with more force and rapidity than
few and single ones, Thus too it is that some fishes that have
696b.

138 iv. 13.

but few gills, and those of corhparatively small efficacy, can live
out of water for a considerable time ; for in them there is no great
demand for refrigeration. Such, for example, are the eel and all
other fishes of serpent-like form.^^

Fishes also present diversities as regards the mouth. In some
this is placed in front, at the very extremity of the body, while
in others, as the dolphin ^s and such fishes as resemble the Selachia,
it is placed on the under surface ; so that these fishes have to turn
on their backs in order to take their food. The purpose of nature
in this was apparently not merely to provide a means of salvation
for other animals, by allowing them opportunity of escape during
the time lost in the act of turning — for all the fishes with this kind
of mouth prey on living animals — but also to prevent these fishes
from giving way too much to their gluttonous ravening after food.^^
For had they been able to seize their prey more easily than they
do, they would soon have perished from over-repletion. An
additional reason for placing their mouth on the. under surface
is that the projecting extremity of the head is round and small,
so that a mouth, if placed there, could not possibly open widely.
In such fishes as have the mouth placed at the anterior extremity
there are differences in the extent to which that orifice can open.
In those that are carnivorous, such as the fishes ^° with sharp inter-
fitting teeth, whose strength lies in their mouth, this orifice can
gape widely, whereas it is placed at the point of a small tapering
snout in all such as are not carnivorous.

The skin is in some fishes covered with scales, a scale being a
shiny film which owing to its thinness becomes detached from the
surface of the body. In others it is rough, as for instance in the
Rhine,^^ the Batos, and the like. In others again, but in very few,
the skin is smooth.^^ The Selachia have no scales, but a rough
skin. This is explained by their cartilaginous skeleton. For the
earthy material which has been thence diverted is expended by
nature upon the skin.^^

No fish has testicles^* either externally or internally ; as indeed
have no apodous animals, among which of course are included
the serpents.^^ One and the same orifice serves both for the
excrement and for the generative secretions,^^ as is the case also
in all other oviparous animals, the quadrupeds as well as the
rest, inasmuch as they have no urinary, bladder and form no fluid
excretion.^^
697a.

IV. 13— IV. 14- 139

Such then are the characters which distinguish fishes from all
other animals. But dolphins and whales and all such Cetacea^®
are without gills ; and, having a lung, are provided with a blow-
hole. By this they discharge the sea-water which has been taken
into the mouth.^^ For, feeding as they do in the water, they
cannot but let this fluid enter into their mouth, and, having let
it in, they must of necessity let it out again. This they cannot
do by the aid of gills ; for the use of gills, as has been explained
in the treatise on Respiration, is limited to such animals as do
not breathe ; so that no animal can possibly possess gills and
at the same time be a respiratory animal.^** In order, therefore,
that these Cetacea may discharge the water, they are provided
with a blow-hole. This is placed in front of the brain ; for, if
placed behind, it would have cut off the brain from the spine.'*^
The reason for these animals having a lung and breathing, is
that their large size demands an excess of heat, to render motion
possible.'*^ A lung, therefore, is placed within their body, and is
fully supplied with blood-heat. These creatures are after a fashion
land and water animals in one. For so far as they are inhalers
of air they resemble land-animals, while they resemble water-
animals in having no feet and in deriving their food from the
sea. So also seals *^ lie half-way between land and water animals,
and bats half-way between animals that live on the ground and
animals that fly ; and so may be said to belong to both kinds
or to neither. For seals, if looked on as water-animals, are yet
found to have feet ; and, if looked on as land-animals, are yet
found to have fins. For their hind feet are exactly like the fins
of fishes. Their teeth also are all of the sharp and interfitting
kind, as in fishes.'** Bats again, if regarded as winged animals,
have feet ; and, if regarded as quadrupeds, are without them.'*^
So also they have neither the tail of a quadruped nor the tail of
a bird ; no quadruped's tail, because they are winged animals ;
no bird's tail, because they live on the ground. This absence
of tail is the result of necessity. For bats fly by means of a
membrane, not by means of barbed feathers ; and no animal
unless it has barbed feathers has the tail of a bird ; for a bird's
tail is composed of such barbed feathers. As for a quadruped's
tail, it would be an impediment to an animal that flies.

(Ch. 14.J Much the same may be said also of the Libyan ostrich.
For it has some of the characters of a bird, some of the characters
697b.

140 IV. 14.

of a quadruped. It differs from a quadruped, in possessing wings ;
from a bird in being unable to soar aloft, and in having feathers
that resemble hair and are useless for flight.^ On the other
hand it agrees with quadrupeds in having upper eyelashes,^
which are the more richly supplied with hairs because the parts
about the head and the upper portion of the neck are bare ; ^
and it agrees with birds in being feathered in all the parts
posterior to these. Again it resembles a bird in being a biped,
and a quadruped in having a cloven hoof. For it has hoofs
and not toes.* The explanation of these peculiarities is to be
found in its bulk, which is that of a quadruped rather than of
a bird. For, speaking generally, a bird must necessarily be
of very small size. For a body of heavy bulk can with difficulty
be raised into the air.

Thus much then as regards the parts of animals. We have
discussed them all, and set forth the cause why each exists ;
and in so doing we have severally considered each group of
animals. We must now pass on, and in due sequence must next
deal with the question of their generation and development.

6G7b.

Notes, i. I. 141

NOTES.

BOOK I.

(Ch. 1.) 1. A similar view of education, as embracing a knowledge of the methods of
sciences, and making its possessor a competent judge of the performance of scientific
professors as regards method and the degree of precision which may be expected from
• them in each science, is to be found in several passages [e.g. Pol. iii. i r ; N'. Eth. i. i). In
the former of these passages three degrees or kinds of knowledge seem to be recognised in
each science. In medicine, for instance, there is the knowledge of {practice, which
belongs to the empiric ; the knowledge of theory or method, which belongs to the
man of education ; and the knowledge of practice and of theory combined, which
belongs to the scientific physician. Besides this distinction as to the quality of knowledge,
there is further a distinction as to its extent ; for it may be limited to one science or
embrace them all.

2. A. employs only two formal terms of classification, species («l5oj) and genus {-yhoi).
Of these the former is practically defined by him {H. A. i. I, 4) as "an assemblage of
individuals in which not only the whole form of any one resembles in all essential points
the whole form of any other, but each separate part, internal and external, similarly
resembles the corresponding part in any other." This definition scarcely differs from that
of Cuvier : " Chaque corps organise, outre les qualites communes de son tissu, a une
forme propre, non seulement en general et \ I'exterieur, mais jusque dans le detail de la
structure de chacune de ses parties " {Regne An. i. 14) ; and " tous les etres appar-
tenants k I'une de ces formes constituent ce que I'on appelle une espece" {do. p. 16). A.'s
fiSos may then as a rule be fairly translated species. The other term (^eVos) is used
much more vaguely. It is described by him as " an assemblage of individuals, all of
which bear an obvious resemblance to each other, but which do not belong to one and
the same species, inasmuch as their corresponding parts are not precisely similar, but
differ usually in colour, shape, or proportion. Sometimes even one has some parts that
are not represented in another. Thus Birds and Fishes each form a genus, containing
numerous species" {H. A. i. i, 5 — 8). Again, "there are other groups of animals, in
which the difference between the corresponding parts is still greater ; the only resem-
blance being that of analogy, as between a scale and a feather ; a scale being to a fish
what a feather is to a bird " (^ff. A. i. I, 9). Such groups are too wide asunder to be
united into one genus (Z>. P. i. 4, 2). Putting these several passages together, we have
a tolerably clear definition of genus ; and, judging from the examples, it may mean any
natural group of animals larger than a species and not larger than a class. The class

142 Notes, i. I.

•'Birds" for instance or the class "Fishes" is a genus, but the larger division or sub-
kingdom ♦' Sanguineous animals," i.e. Vertebrata, is not a genus. But in fact A. is very
far from adhering strictly to this definition of genus. He uses the term in the most lax
manner to express any group however large and however small. Thus we have "the
genus of plants," "the genus of animals," where genus equals kingdom. "There
are many genera of bees," where it is equivalent to species ; and yet in another place
"the genus of bees." So again "one genus of oxen has a bone in the heart," where
genus answers to variety. This vague use of the term makes it impossible to translate
it invariably by the same English word. I have therefore rendered it variously —
genus— order— tribe— class— natural group — kind, etc., as seemed most convenient in
each separate case. «

3. Aristotle recognised four causes, or necessary conditions of existence ; the Material,
Formal, Efficient, and Final. Everything that is made is made of matter ; has a definite
form ; is brought into being by some agency ; and brought into being for a purpose
[^Phys. ii. 3). Take a statue for example. Its material cause is marble ; its formal
cause the shape into which that marble is fashioned ; its efficient or motor cause the
sculptor's art ; its final cause the realisation of the artist's idea. In the text, however,
A. speaks as it there were but two causes. For, as he says elsewhere {Phys. ii. 7, 2),
the fbrmal, efficient, and final causes are often one and the same. This is the case
with living beings. The body constitutes their material cause ; the soul the remaining
three {D.A. ii. 4, 5). The soul is the formal cause ; for just as the addition of the
impression to wax forms the seal, or as the addition of sphericity to the metal forms the
copper globe, so is it the addition of the soul to the body that forms the living organism.
The soul is the efficient cause ; because it is the soul which, imparted in the generative
fluid of the father, effects the development of the inert matter furnished by the mother,
and is the motor agent in its after activities. Lastly the soul is the final cause of the
organism, for the activity of the soul is the purpose aimed at by nature in its construction
{D. P. i. s, 12).

4. A. divides the sciences into three groups {Metaph. v. i). Firstly the Theoretical,
•which are purely intellectual and not concerned with action. In this are comprised
Metaphysics, Pliysics, and Mathematics. Secondly the Practical ; and thirdly the
Constructive or Artistic. The Practical and the Artistic comprehend action as well
as intelligence ; but differ from each other, in that the Practical have no other result
than the action itself; whereas the Constructive or Artistic, where the action is over,
leave as its result a substantial product.

The contrast in the text (from which I omit the rt) is between the theoretical and
the constructive sciences ; and the points of contrast are as follows. The theoretical
philosopher starts from certain eternal facts or verities (rb iv) — the mathematician for
instance from his axioms — and proceeds to deduce from these those consequences which
are linked to them by absolute necessity. The artist, on the other hand, or nature,
the chief of artists, starts from an ideal conception, not yet existent in matter, but to
be realised in the future (tJ> ialt^iivov). Starting from this, he reasons backwards
through the antecedent steps that are necessary, if the conception is to be realised.
The realisation of my conception E, he says, requires first the realisation of D ;
if Z> is to be produced, there must previously be C; C again requires B for its
production ; and so farther and farther back, until he reaches a link in the chain of
antecedents, let us say A, the material production of which is within his power. Here
the ratiocination ceases, and construction begins. He produces A ; then by means of A
produces B, from B produces C, and so on, retracing his previous steps, until he

Notes, i. I. 143

reaches E, the conception of which was his starting-point, as its material realisation
is his end.

6. (Cf. D.G. et C. ii. 9 and 10.) The following is a brief abstract of A.'s views. The
only motion capable of being eternal is motion in a circle ; and the only element
endowed with a rotatory motion is the celestial aether (cf. ii. I, Note 2). The heavenly
bodies consist of this ; and they alone are individually eternal. The Divinity, how-
ever, wishing to give the things of earth as near an approach to eternity as is com-
patible with their being made of other elements than aether, caused their motions to
be so affected by that of the celestial bodies as to simulate rotation in the only way
possible, namely by a cyclical arrangement of their serial phenomena. Not only is
this manifested in the periodicity of many phenomena (Z>. G. iv. 10) ; but still more in
the successive stages of the evolution of organisms, these stages being so arranged as
to form a circle. Germ, foetus, infant, man, and then germ again, and so on in eternal
succession. Thus a simulacrum of eternity is impressed on even perishable things in
the only way possible for them {D.A. ii. 4, 4 ; D.G. ii, I, 3); an eternity however
which differs from, that of the celestial bodies, in that it does not attach to the individual
but to the species. For in the cycle — germ, foetus, man, germ — it is not the same
germ, but only a similar one, in which the circle is completed. Each term in such a
cycle is at once the antecedent and the consequent of all the rest. Man necessarily
presupposes germ, and germ as necessarily presupposes m^n. Any hypothetical pro-
position then that states the necessary relation of any two of the terms —e.g. if there
is to be a man there must necessarily be a germ — is capable of simple conversion
—viz. if there is to be a germ there must necessarily be a man.

By the " propositions expressing hypothetical necessity and capable of simple con-
version" A. means, then, all those in which two stages in the cyclical evolution
of an organism are placed as antecedent and consequent. By the "cause which
determines this " he may mean either the action of the heavenly bodies upon terrestrial
bodies ; or possibly, going a stage farther back, the purpose of the Divinity in the
construction of the world.

6. The older physiologists held that the characters of an animal are determined by
the physical causes that bring about its evolution, while A. holds that the characters
determine the mode of evolution. The older writers therefore placed the evolution in
the foreground, while A. places there the characters (cf. i. i, Note 27).

7. Very similar to this is the explanation proposed by H. Spencer {Biol. ii. ch. 15), in
which he attributes the segmentation of the vertebral column to the alternate pressures
and tensions which would necessarily be produced by the lateral undulations of an
animal with an originally uniform notochord.

8. The text is doubtless corrupt in this passage, and the exact meaning difficult to
determine. So far as I can decipher it by the light of other passages {Phys. ii. 4 — 6.
Metaph. vi. 7 — 9) the general drift is as follows. The teleological position — this is
made as intelligent design would have made it, and therefore "was made by such — would
clearly be untenable, could it be shown that a similar object was undoubtedly at times
produced simply as the result of accident or chance. Now Aristotle admits that such
is sometimes the case, and gives the restoration of health as an example.

How is this difficulty to be met ? In the first place, says Aristotle, such an occurrence
is quite exceptional. No chance could possibly produce a statue, or, to take Paley's
instance, a watch. All those results of art, that are produced from a purely inert
material, a material that is without any capacity for self-motion (ofe KiveTadai v<p' avT^s\
are quite beyond the power of chance. It is only in the case of such bodies as possess

144 Notes, i. i.

certain inherent motor possibilities that chance can do the work of art. We may
suppose for instance a mechanical automaton, so constructed that on touching a spring
and starting the action, a series of connected motions shall ensue, leading to some pre-
arranged result. Now chance could never make such an automaton as this ; but when
such has been made by art, we can readily understand how chance might occasionally
touch the spring, and the series of motions ensue with their fixed result : irav ipxh
yfVTjTM Kivf)(rfUi, &ffirfp iv toIs avrondrois daifiatri, ffvyfiperai rh f<pe^7js {D. G. ii. 5» 9).
Now in every living organism analogous sequences of concatenated motions are present ;
established either by nature or by habit (De Mem. 2, i6), which is but a second nature, in
order to ensure certain desirable ends. Such for instance is the sequence of phenomena
which constitute the evolution of an organism from the germ (Z>. G. ii. 5, 9). This series
of consecutive motions can only be set going by fecundation. This and this alone
possesses the key of the mechanism. Another sequence is that by which the organism
is maintained in a state of health ; a sequence of which the final terms are health,
uniform bodily condition (i/uoXfJrijj), heat. Each link in this chain must be in constant
activity, if the final effect — health — is to be constantly maintained. Should the chain be
interrupted, by any cause whatsoever, at any point, the further dependent motions cease ;
health vanishes, and disease, which is no more than privation of health, makes its
appearance. In such a case what is wanted to restore health is that the series of move-
ments that terminate in it shall be again set going. To do this it will be enough to
reproduce any one of the antecedent links ; for they are all indissolubly connected with
each other. The man of art then, i.e. the physician, hunts about for a link in the chain
which may be within his range of action. Health, he says, is dependent on uniformity
of bodily condition, this again upon due warmth ; but heat can be produced by friction
of the body. Here, then, he has come to a link over which he has power. He
applies friction, and heat, uniformity, health, follow. Art, then, in such a case restores
health by using the machinery of nature, and using it moreover with the intention of
producing nature's result. But pure accident can plainly set the same sequence in
motion, acting blindly and without any intention whatsoever. By pure accident the
ailing body may be subjected to friction, and the whole chain of consequents will result
as before, and health be restored. The difference is that the physician acted with
definite intention, accident without such. The presence or absence however of intention
in the immediate agent is a matter of no importance. Both art and accident make
use of machinery constructed by nature with intention ; nor could they have brought
about the result without so doing. In all cases alike then there was intention, though
not in all cases intention on the part of the immediate agent. In all cases alike then
it is true that the process of production occurred for the sake of the thing produced.

9. A. uses the term Spontaneity in two senses. In a limited sense, as opposed to
Chance ; and in a wider sense as including both of these (Phys. ii. 4 — 6). The
different ultimate forms of matter are endowed with different inherent properties. When
such different kinds of matter are jumbled together indiscriminately, and not so arranged,
as in nature's works, as to make their activities converge to one predesigned end, the
interaction of their conflicting properties will habitually result in incoordinate random
motions, quite beyond human calculation. Such motions are accidental, or spontaneous
in its wider sense.

Sometimes however such accidental motions produce results, such as intelligence or
nature would have produced, and produce them by the same steps. In such a case
accident is either called chance, or is called spontaneity in its limited sense. It is called
chance when the accidental agent is an intelligent being acting with intention, though

Notes. \. r. • 145

not with the intention of producing the result which actually occurs. It is called
spontaneity when the accidental agent has no intention at all. No inanimate thing
therefore, no beast, no child, can possibly be the agent of chance, for they are incapable
of intention, though they are often the agents of spontaneity.

Aristotle's Spontaneity does not then imply the absence of external agency, but merely
the absence of intention in the agent, and would perhaps be more fitly represented, were
such permissible, by the word chance ; while Aristotle's Chance, which implies an agent
acting with a certain intention, though not the intention of producing the result that
actually occurs, would find a better though still inadequate representative in our word
luck. It is this intermixture of semi-intention that gives force to the line
Ti/x^ TtxyTjc eoTfpfe koX rtx^V fvxhv-

10. Empedocles attributed the development and destruction of all bodies to the action
of two alternate forces. Friendship and Enmity, upon the particles of the four ultimate
elements ; while Anaxagoras attributed the phenomena to Intelligence or vovs (cf.
Metaph. i. 3—4, and Grate's Flato, i. ch. l).

11. Cornpare H. Spencer's account of the formatioii of the vessels (/';-. of Biol.

§300)-

12. "If asked what is the material cause of any object, we must state what are the
proximate and special substances, not what are the ultimate substances such as fire or
earth" {^Metaph. vii. 4, 5). As to homogeneoife and heterogeneous parts, cf. ii. i,
Note 5.

13. " Works of art are said to be made by the artist's tools ; but it is truer to say that
they are made by the motion of these tools, supplied and directed by art. Just in the
same way the growth of a plant or animal is said to be due to heat and cold ; but it is
only due to them in the sense that these are the instruments of which the nutritive soul
makes use in its operations " {D. G. ii. 4, 43).

14. In rendering "i^vxM ^oul I have adhered to common usage, though Soul is far from
being an equivalent term. But I know of no term that is. Vital principle has been
proposed and includes much of A.'s conception which Soul omits ; but on the other hand
it omits as muc^ ..at 6<7«/ includes. For "ifvxM is the principle to which are due all the
phenomena of life, from the highest intellectual procesg down to the growth of a
microscopic fungus. The former is excluded by Vital Principle, the latter by Soul, which
has moreover the further inadequacy that a religious element enters into the ordinary
conception of it. The following abridged passage {D. A. ii. 2 — 3) will serve to give A.'s
idea pretty fairly. "The faculties of the soul are many; but, though all living things
have a soul, all the psychical faculties are not present in every soul. In the soul of
some living things only one faculty is present, in that of others several, and in others
again all. The faculties are the Nutritive, the Sensory, the Appetitive, the Locomotor,
the Intellectual. In the soul of plants the Nutritive faculty alone is present ; in the
soul of animals not only this but the Sensory, or at least the Tactile, faculty and with
this as a necessary consequence the Appetitive. This is the case in all animals ; but
only in some of them is there in addition the Locomotor faculty. The number is still
smaller in whose soul there is yet further the Intellectual faculty, as in man, and" in
any other being, if such there be, that equals or even surpasses him in honour." The
soul then is the principle of vitality ; and each main mode in which vitality manifests
itself, that is each main group of functions, is ascribed to a different faculty of this soul.

How is this soul engendered in the body ? asks A. [D. G. ii. 3). Is it derived from
the mother? or from the father? or from neither, but from without? The mother
furnishes the material for the formation of the body. But the unfecundated' germ never

10

146 • Notes, i. I.

ripens into maturity. It never acquires a sensory faculty ; never, that is, develops into
an animal. Still it is capable of growth up to a certain point, as the wind-eggs of birds
testify, so that some share in the nutritive faculty must be allowed to come from the
mother (Z>. G. ii. 5, 3). Such an egg then, if regarded as the conception of a plant,
is perfect; but, if regarded as the conception of an animal, is imperfect [D. G. iii. 7, 8).
The other faculties than the nutritive only appear in the fecundated germ. They are
imparted, then, to the germ m the fertilising fluid of the male parent. But how does this
fecundating fluid come to possess them ? Does it get them from the male organism, from
which it issues itself, or from some external source ? As regards the Sensory, the Motor,
and all other faculties than the Intellectual, they must necessarily come from the father ;
for they are inseparable from bodily "matter, there being no such thing as Sensation and
Motion without sensory and motor organs, and the matter of the fecundating fluid is
evidently all derived from the father's body. But as regards the higher faculty, or
Intellect, the case is otherwise^ This requires no bodily substance in which to be
incorporate. It exists independently of tangible matter ; and so may, and in fact does,
come into the fecundating fluid not from the father's body but from wlthou^> viz. from
the divine soul of the Cosmos. Thus the mother furnishes the material of the body
and, in some degree at least, the Nutritive faculty. The father contributes the Sensory
and the Motor faculties. While the Intellect comes from the soul of the Cosmos, and
is only transmitted by the father interrnediately.

15. Cf, Note 3.

16. The Soul is the source of vital motion, and the several psychical modes correspond,
though not always as the active source, to the several modes of motion. Of these there
are three (Phys. v. 2, 8). Firstly motion leading to change of bulk, i.e. growth and decay
(o<;{7/(r/s and <pdlffis) ; with this is associated the Nutritive and Genetic faculty, as the
active cause. Secondly motion with change of quality (ctAAJiojo-iy), of which sensation is
a form {D. A. ii. 4, 8) ; with this is associated the Sensory faculty, no longer however as
the active source, but as the passive recipient of the motion which starts from the objects
of sense. Thirdly motion with change of place {ipopi.) ; with this is associated the
Motor faculty of the 'soul, here again not passive but active.

17. Cf. Metaph. v. i, 7. "The natural philosopher has to deal with the soul, so far
as it is inseparably united with matter," i.e. with all the soul, excepting the active
intellect, which is independent of the body and separable from it {D. G. ii. 3, 10 ;
D. A. ii. 2, 10). The consideration of this element of the soul belongs to "the first
philosophy " or metaphysics. It is, I presume, of the separable intellect that A. speaks,
when he compares the relation of soul and body to that of rower and boat (£>.A. ii. I, 12);
and of the inseparable faculties, when he takes for his simile the relation of vision to the
eye, or of the impression to wax (D. A, ii. i, 7 — ^9).

18. The argument seems to be as follows: "Moreover that part of the soul which is
independent of matter cannot come within the province of natural science ; for this deals
only with the works of nature, and these are not abstractions but actual bodies,
concretions of form and matter, for" by such alone can the ends of nature, viz. the
activities of life, be fulfilled. [Natural Science then is concerned with that soul only
which is incorporate in matter.] For that there is such a soul, or nature, informing the
body, and that to it, and not to blind chance, are due the evolution and activities of
organisms, is shown by the constancy of the phenomena they present and by the fact
that the result of their evolutional processes is predictable with certainty."

19. Both art and nature are concerned with concrete bodies in which form and matter
are combined ; but in the case of art the form is impressed on the matter from without.

Notes, i. I. 147

while in the natural object the moulding principle is within; for the soul or principle
of life informs the body not as an external independent force, but as an indwelling
inseparable influence. It is comparable, not to a physician acting upon another person,
but to a physician curing himself {P/iys. ii. 8, 15). As to hot and cold, cf ii. I, Note 3.

20.^ Compare this with the poetical account of the creation in the Timaeus. The
secondary Gods are there represented as borrowing portions of the body of the Cosmos
to form the bodies of men and animals ; while the Demiurgus gives the surplus of what
had formed the cosmical soul to form their intellectual soul.

21. 'The question whether the Heavens were or were not generated is discussed else- .
where and answered in the negative {De Cash, i. io, ii. l).

22. Cf. Fhys. ii. 4 for a similar passage.

23. Potentiality and Actuality are discussed in the Metaphysics (viii. 6 — 8). The
distinction between them, says A., will be better set forth by giving examples than
definitions. What, then, an animal awake is to an animal asleep ; what an animal
gazing is to an animal with its eyes shut ; what the perfected work is to the raw material ;
what the \t'rought is to the unwrought, that is Actuality to Potentiality ; the relation
being sometimes that of a body in motion to the same body at rest, sometimes that of
form to matter. In the order of thought Actuality is anterior to Potentiality > for we
cannot understand nor define the Potential without first understanding and defining
the Actual. That which is "able to build" or that which is "capable of sight"
presupposes for its comprehension and definition that which does build and that which
does see. In order of time or material existence Actuality is in one sense posterior to
Potentiality, in another anterior to it. It is posterior, if we only regard the individual ;
for before an individual man can actually exist in matter, the potential germ must exist,
that is to give rise to him. It is however anterior, if we regard not the individual
but the species ; for before the germ, that is the Potential, came into being, there must
have been an actual man, similar to though not identical with the man that is to be
produced, to give origin to the germ.

24. As A. has fully explained what he means by Hypothetical Necessity only a few
pages back, it is strange that he should now deaj with it again in terms that seem to
imply that he is stating something quite new. Very possibly the whole of this long
paragraph is an interpolation.

25. Elsewhere {Metaph. iv. 5) A. speaks of three kinds of necessity, Absolute necessity,
Necessity of coercion, as when a weaker agent is constrained by a stronger one, and
Hypothetical necessity. There is also another passage {^Phys. ii. 9) in which he deals
with necessity, and distinguishes, as in the text, two kinds^ Absolute and Hypothetical.
Plainly, however, it can be to neither of these passages that he is now referring. The
passage wherever it is, or was, must have been one in which the two modes of necessity
distinguished from each other were Absolute and Coercive necessity. It may perhaps
have been contained in the lost dialogue on Philosophy ; concerning which see Heitz,
Die verier. Schrift. d. Arist. 179.

f6. " The natural philosopher must deal with both causes; and more especially with
thQ final cause. For this is the cause of the material, and not the material the cause
of it" {^Phys. ii. 9, 5). So also Plato {JaweWs Tr. ii. 540, S41) ; "Now the lover of
intellect and knowledge ought to explore causes of intelligent nature first of all ; and
secondly those which are moved of others and of necessity move others. And this
is what we also must do. Both kinds of causes should be considered by us, but a
separation should be made of those which are endowed with mind, and are the workers
of things fair and good, and those which are deprived of intelligence and accomplish

148 Notes, i. 1—3.

their several works by chance and without order Creation is mixed, and is the

result of an union of necessity and mind."

27. "For, as was said on an earlier occasion, each thing made by nature has certain
fixed and definite characters ; and these it has not because it is developed with them,
but rather it is developed with them because it has them ; for the essence precedes ^nd
determines the development, not the development the essence. Physiologists of old
held a contrary view. For they did not perceive how many causes there are ; but
recognised only the material and the motor causes, and even these confusedly, while
the formal and the final cause entirely escaped their notice " [D. G. v. i, 5).

28. As to Aristotle's notions of the mechanism and use of respiration, cf. iii. 6, Notes 3, 6.
(Ch. 2.) 1. Alluding to Plato's method of dividing downwards until by successive

bifurcations the infima species is at last reached. Examples of this method, abscissio
infiniti, will be fo.und in the Sophistes and Politicus. These ai;e apparently the
"published dichotomies" of which A. speaks; and it is to them that his criticisms
in this and the two next chapters have immediate reference. The great interest of
these chapters to the biologist lies in the evidence they give that the idea of natural
classification had occurred to Aristotle, their whole drift indeed being to uphold the
claims of natural as opposed to artificial systems.

2, Not a well-chosen example. For Cloven-footed does not necessarily imply Two-
footed, as many quadrupeds have free toes. But A. is probably thinking only of Birds,
which he subdivides into Web;footed and 'Cloven-footed ; using the latter term as it is
used in the following passage : " Great variety of water- fowl, both whole and cloven-
footed, frequent the waters " {^Ray on Creation). '

3. By the water-animals with many feet are meant the Cephalopoda and certain
Annelida confounded by A. with Myriapoda. Cf. iv. 5, Note 70.

(Ch. 3.) 1. What we call the wing of an insect, A. called the feather, which he
distinguished from the feather of a bird by its being undivided into barbs (iv. 6, Note 6).

2. The argument is this. If we start with such a dichotomy as A and Not A, there
must be subdivisions of each of these. Let us say B and C are the subdivisions of A,
while D and E are the subdivisions of Not A. A then is a differentia common to
B and C, but though common to them it applies really to each in a different manner.
Not A '\% z. differentia common to D and E, and as there are no possible diversities
of Not Af it belongs to D and to Em exactly the same sense. In other words the
groups D and E have a common undifferentiated element, something therefore which
cannot be part of their essence.

3. The wild dogs of India were supposed by A. to be a cross between the Dog and
the Tiger. Cf. II. A. viii. 28, 14 ; D. G. ii. 7, 9.

4. The following appear to be the chief rules recognised by A. in the classification of
animals.

a. The groups must be formed by consideration of the sum of the characters, not by a
single character arbitrarily selected.

/3. Those characters are the most important which have guided mankind in generaf in
forming groups, to each of which they have given a popular name : in other words the
external characters.

7. There are however natural groups, which are founded on other characters, and
which have been confounded popularly with alien groups owing to their external similarity,
e.g. Cetacea.

8. When the individuals in a group are precisely alike in all theiV parts, the group is a
species (i. I, Note 2). A number of species may resemble each other in all their parts

Notes, i. 3 — 5. 149

excepting in matters of degree ; such species together constitute a larger natural group
(yeVoy), still as a rule with a popular name. Some species, however, as man, stand
isolated, and cannot be so combined with other species (see next chapter).

e. These larger natural groups, and these isolated species, may be arranged in still
larger groups. But the basis of such arrangement will be merely analogy or distant
resemblances of the parts, not identity with differences of degree. And such groups will
have no popular names (see next chapter).

f. The natural groups may be arranged in a linear series according to the degree of
animality they possess ; the series extending from those animals which most nearly
resemble plants to those which, as man, are most remote from them. Cf. iv. 10, Note 12.

(Oh. 4.) 1. The similarity is in the media in which the two live, the fish in the liquid
water, the bird in the liquid air. So in the Sophistes {Jrweti's Transl. ii. 479) we read :
" Of swimming animals one class live on the wing and another in the water." The close
resemblance of flight to natation is shown in the fact that there are both birds and insects
that use their wings for swimming, while on the other hand there are fishes that can
support themselves for a short time in the air.

(Ch. 5.) 1. This passage seems to imply that A. had, in some degree at any rate,
studied the flesh, bones, and vessels, of the human body. But it does not necessarily imply
that he had dissected them. For his observation may have been limited to such parts as
were exposed in operations by the surgeon's knife, or in wounds received accidentally or
in battle. When in fact we remember how excessively strong was the religious feeling of
the Greeks as to the sanctity of the human body, and when we also See how ignorant A.
was of its internal anatomy, an ignorance he fully admits {H. A. i. 16, l), and which is
betrayed in numerous statements, we may feel certain that his scalpel had never touched
a human subject, or at any rate an adult one. For I am by no means so certain that A.
may not have sought to gratify his curiosity by dissection of the human foetus. In the
.first place it is quite easy to conceive that the religious feeling which peremptorily forbad
all meddling with the body of the adult may have disregarded the aborted embryo ; and
in fact there is some reason to believe [Cuvier, Hist, d. Sc. Nat. i. 39) that in the time of
Galen, when the religious obstacle was as strong as in the time of Aristotle, some such
distinction between the sanctity of adult and foetus was actually recognised. Secondly,
such a supposition would explain several difficulties. Thus A. says that the heart is
visible in the aborted embryo while it is still quite small {D. P. iii. 4, 2). He does not
actually say in the human abortion; but, seeing that he was able to procure the embryos
of other animals without waiting for the occasional accident of abortion, and in fact did
procure them (Z>. G. iv, i, 10 : v. i, 12), it is most natural to suppose that it is of the
human embryo that he is speaking. Again he says that the human kidney is lobulated,
like that of the ox ; and this is true of the foetus, not of the adult. Again he says that
the heart in man lies diagonally, with the point inclined to the left, and the right ventricle
above the rest (iii. 4, Note 17). It is difficult to see how he can have known this without
inspection. That in man there is often, though not invariably, no gall-bladder, is, again,
a statement which we can understand, if founded on examination of embryos. For the
gall-bladder is not developed till the liver is already so large as almost to fill the abdomen.
If, again, the description of the heart and vessels (iii. 4, Note 23) be intended for those
parts in man, as would seem to follow from the statement that the right ventricle is upper-
most, tlien this description can only have been got by examination of tiie foetus, for it
includes, as I believe, the ductus arteriosus. The brain, again, in an aborted foetus would
almost certainly be found in a diffluent condition ; and thus would be explained the state-
ment (ii. 7, Note 4) that the human brain is more fluid than that of any other animal.

I50 Notes, ii. i.

BOOK IL

(Ch. 1.) 1. That is, the treatise which by a mistranslation of its title is usually known
as the Natural History of Animals ; a mistranslation to which our popular term ' ' natural
history " is due. The ordinary title is so sanctioned by use, that I have elsewhere occa-
sionally retained it.

2.. It will be noticed that A. says "such as air earth fire and water," implying
apparently that there are more elements than these. In fact he held that there was aT
fifth, the quintessence of later writers ; this fifth however, the aether, not entering into the
composition of strictly terrestrial objects, but forming the sole substance of the heavenly
bodies. To this belief he was led by his views as to motion. He held that all visible motion
could be reduced on analysis to three elements, (i) motion round the centre, or circular
motion; (2) rectilinear motion from the centre towards the periphery, or upwards; (3)
rectilinear motion from the periphery towards the centre, or downwards. Now there is no
such thing as motion without a moving body. There must therefore be elementary bodies
corresponding to these elementary motions. To the motion upwards fire and, in a lesser
degree, air correspond; to the motion downwards earth and, in a lesser degree, water.
There is apparently nothing left to correspond to circular motion, which is yet the most
perfect motion of all, seeing that a circle is a perfect line, which a straight, line is not.
•' From this it is evident that there is in nature some essence of body besides the elements
which we have, here, more divine than these and superior to them. For "it is absurd to
suppose that motion in a circle can possibly be an unnatural motion, seeing that every-
thing which is unnatural quickly perishes, whereas this motion, alone of all, is continuous
and eternal. So that from all this we infer with perfect confidence, that besides the
elements which we have here and about us there is another removed far off, and the
more excellent in proportion to its distance from the things of earth " [^De Ccelo, i. 2 ;

iii. 3. 5)-

3. The so-called elements, says A, elsewhere {D. G. el C. ii. 2-3-5), are not simple
bodies but compounds, being produced by combinations of the primary forces or active
properties of matter. Tangible objects differ from each other in endle'ss ways, as
regards colour, taste, smell, etc. {Meteor, 'w'. 10) ; but they are all either fluid or solid, and
all either hot or cold. Everything tangible presents two of these properties ; it is either
solid or fluid, and either hot or cold. There are then four main elementary properties,
and each object possesses two of them. Now among four- things there may be six com-
binations of two and two (eruC**^!*") '> but the pairing of two directly opposite properties,
as of cold and hot, causes them both to disappear ; for they neutralise each other. Thus
only four combinations remain, and these correspond to the four apparently simple bodies,
fire, air, water, earth ; solid and hot forming fire ; hot and fluid forming air, for air cor-
responds to vapour ; fluid and cold forming water ; cold and solid forming earth.

EARTH

Solid

WATER - - - - { ""rr"' \ FIRE

Hot
AIR

Notes, ii. i. 151

It is evident then why A. holds it more accurate to say composition from the elementary
forces rather than from the elements, the former being the components of the latter.
It is plain also that when he says "nor out of all of them," he means to exclude all
other properties excepting the four main ones, two of which belong to every tangible object.
From these four primary properties, he says, all others are derived, and in contrast to
them may be called" secondary. As to the mode in which .the secondary properties are
deducible from the primary ones, cf. D. G. et C. ii. 2.

It will be noticed that A. uses the adjectival forms, hot, cold, solid, fluid, and not
the substantives, heat, fluidity, etc. For he is speaking not of abstract properties,
but concrete substances. His views [D. G. et C. ii. i) were as follows. There is one
ultimate matter, which forms the universal substratum of all terrestrial things. This
matter however has no existence in a condition of isolation, but is invariably combined
with some or other of the primary properties, heat, fluidity, etc. Thus we have fluid
matter, hot matter, solid matter, cold matter ;. but there is no such thing as simple matter
by itself, any more than there is such a thing as fluidity by itself. By hot, cold, solid,
fluid, A. means then the universal substratum ' in a state of heat, coldness, solidity, or
fluidity.

Even hot matter, solid matter, etc., are however not forthcoming as actual existing
bodies; for matter, as already explained, is always combined with more than one. of
the four primary properties.* The simplest producible substances would therefore be
those formed by matter in combination with two properties, that is the elementary
substances, earth, air, fire, water. But even these are nob actually forthcoming in
absolute purity ; for the substances we know as earth, air, water, fire, are not the pure
elements themselves, but compounds of all four, in which one element so preponderates
as to give its general character and name to the whole. (See next note.)

It is usual to render \rff6v and i,-r\p6v as wet and dry, and not, as I have rendered them,
fluid and solid. But A. can never have supposed wetness to be one of the primary
properties of matter. The definitions, moreover, given by him {D.G. et C. ii. 2) are
conclusive. " Wet (StepJ*') is that which has extraneous liquid on its surface ; Soaked
(ffefipfyixivov) is that which has it in its substance. Fluid (iiyp6i/) is that which has
no form of its own, but readily accepts one. Solid (|?7/>(J»') is that which has a distinct
form of its own, and resists the imposition of a fresh one. "

We know, at the present day, that the physical condition of a substance is distinct
from its chemical composition ; a substance may be hot or cold, solid, fluid, or gaseous,
while all the time its deeper-lying chemical composition remains unchanged. But A.
knew of no such distinction. Physical and chemical qualities were to him one and
the same thing ; substances differed from each other in their composition, because of
the diff"erent proportions in which the fundamental physical properties were intermixed
to constitute them. Water, for instance, in its ordinary fluid condition, consisted of
cold ma^tter and fluid matter. When such water became vapour, it changed not
merely its physical condition but its composition, hot matter being added to the former
constituents ; and similarly its composition was altered by another addition when it
became ice.

4. By compound substances A. means all substances made by combinations of the
elements. " Some substances are simple, others compounds of these. By simple
substances I mean those that have natural motions, such as fire, earth, and the like,
and their several fornjs " [De Ccelo, i. 2, 4). In one sense indeed even the elements are
compound (see last note) ; but it is of compounds out of the elements that A. is here
speaking. Every suph compound, that is every actually existing substance, contains, says

152 Notes, ii. I.

A. (Z>. G. et C. ii. 8, l), some proportion of every one of the four elementary substances.
The differences between substances depended therefore not on differences in the elements,
of which they were made, but on differences in the ever-varying proportions in which
these were combined to form them.

A. distinguished clearly enough between chemical combination and mere mixture.
In the former, he says (Z>. G. et C. i. 10), the combining substances disappear with their
properties, and a new substance with new properties arises from their unification. In
the latter the mixed substances remain with all their properties, and it is merely the
imperfection of our vision which prevents us from seeing the particles of each lying side
by side and separate. Had we the eyes of Lynceus we should do so, however intimate
the mixture might be. But though A. thus distinguished chemical combination from
mechanical mixture, he had no notion of preferential aflSnities, nor of course of com-
bination in definite proportions. The elementary bodies combined with each other with
perfect indifference, and in any chance proportions. There was thus no such thing as
definite composition, and consequently no such thing as definite properties in substances.
One piece of matter might resemble another more or less, but that it should be identical
with it in composition and therefore in properties was, in the infinity of possibilities, so
improbable as to be out of the question.

The compound substances then are formed by combinations of the four elementary
substances, and this is A.'s first degree of composition ; the study of which has developed,
as Frantzius remarks, into modern Chemistry. From these compounds the homogeneous
parts or tissues are formed. This is the second degree of composition, and its study
corresponds to our Histology. Lastly from the tissues are formed the heterogeneous parts
or organs, which are dealt with by Descriptive Anatomy. It is strange that A. should *
not allude here to the higher grade of composition, namely the formation of the
whole body from the organs. Presumably he omits it, as being a stage not reached by
all organisms. Cf. ii. I, Note 8.

5. The division of the parts into Homogeneous and Heterogeneous, which A. puts
forward so prominently in this book, corresponds to the more modern division into Tissues
and Organs ; the main difference being that A. includes among his homogeneous parts
not only the tissues but even the secretions. It was the revival of A.'s doctrine in a
more perfect form that first made the name of Bichat illustrious.

The heterogeneous parts or organs are formed from the homogeneous parts or tissues.
From what are the tissues formed? A. said, directly from the compound substances.
Modern histologists as a rule say from cells, fibres and the like, which they interpose
between the tissue and its constituent chemical substances. A. knew of nothing answering
to these "morphological units," the tissue being to him the last term in the structural
analysis. In fact before the microscope was invented the existence of the cell could not
be suspected. Theophrastus however, the pupil of A., seems to have tried to resolve the
tissue into simpler elements, though still more complex ones than its physical or, as we
should now say, its chemical constituents. "Other parts there are," he says, speaking
of the organs of plants, "from which these are formed, such as bark, pith, wood, all of
which are homogeneous. There are parts again anterior even to these, and from which
these are made. Such are juice, fibre, vessel, flesh. These are the primary constituents ;
there being nothing anterior to them, unless one reckons in the elementary properties of
matter, which are the common basis of all substances " {HUt. Plant, i. 2).

6. The fact that, with similar material to select from, man generates man and plant
plant, shows that it is not the material that determines the process, but the process that
determines the material.

Notes, ii. i. 155

7. The final cause must exist in conception before the stractures which are made with
a view to it. The whole organism therefore exists ideally before the orgfans, and these
again before the tissues, and these latter before their physical constituents. But actually
or materially the order is reversed. The physical constituents are the first to be produced ;
then from these are generated the tissues, and lastly from these the organs. And similar
sequences, ideal and actual, occur in the development of other than animal bodies, in
plants for instance, in works of art, etc. If, therefore, we have before us the order of
genesis, that is of actual evolution, we have merely to invert it to get the order of final
causes. The fact, then, that the tissues ar;2 evolved after their component substances
shows that the latter exist for the sake of the former, and the fact that the organs are
evolved after the tissues shows that the tissues are for the sake of the organs.

8. The first degree of composition was that of the compound substances ; the second
that of the tissues ; the third that of the organs. The evolution, then, of an individual
organ has reached its final term when this third stage is attained. But in an animal or
a plant, as a rule, there is yet a fourth degree of composition. For the entire organism
is made up of a multiplicity of organs. This, however, is not the case with all organisms.
The simpler kinds (Aristotle would probably have instanced the Sponge, the Actinia,
the Medusa and, among plants. Lichens and Fungi) present no such distinction of parts,
as allows us to say that they are made up of organs. They are constructed not of
organs, but directly out of tissues. Their evolution, therefore, as that of a single organ,
ends with the third degree of composition. They are aggregates of the third not of the
fourth degree.

'9. Having distinguished the homogeneous parts or tissues from the heterogeneous parts
or organs, A. proceeds to enquire why these latter are made out of the former, and ascribes
it partly to necessity, partly to a final cause. In the first place no other arrangement is
possible. The heterogeneous can only result from a combination of homogeneous
parts ; while the homogeneous cannot possibly be constructed from the heterogeneous.
Secondly, an organ is often used for several distinct offices ; and therefore requires distinct
properties. But its properties are those of the tissues which compose it, and therefore
it requires to be made of several tissues, seeing that each tissue has but one main
property. A. apparently confuses the properties of an organ with its functions. The
properties of an organ are doubtless the resultant of the properties of its component
tissues ; but the functions of an organ depend on more than this, namely on the relations
and structural connections of the organ as a whole with other parts. The properties of
a muscle, for instance, are' doubtless the resultant of the properties of the various tissues
that enter, into the composition of a muscle. The chief of these being muscular tissue,
and the main property of this being contractility, the main property of the whole
muscle is contractility ; and this property attaches to it whatever be its situation. But
the function of the muscle is to produce a certain definite motion of some part of the
body, and for this are required not merely the property of contractility but certain definite
attachments to the bones or other parts that are to be moved.

10. A. had not the slightest suspicion of the contractility of muscle or, as he called it,
flesh ; the main purpose of this substance being in his opinion to serve as a medium for
the sense of touch (cf. ii. 8, Note 2 ; ii. lo, Note lo). Still less therefore could he have
any notion that a limb is. flexed or extended, accordingly as this or that part of the fleshy
mass about it contracts. He therefore apparently attributes extension and flexion to the
presence in the limb of diff'erent properties, one extensibility, the other flexibility ; these
properties being derived by the part, each from a different tissue. But he does not
attempt to state what these tissues may be. .

154 Notes, ii. i.

11. It was a disputed questiqn whether the passive agent must be s'imilar or dissimilar
to the active agent ; the former being the opinion of Democritus, the latter the general .
view. Aristotle says both opinions are partly true, partly false. "The active and the
passive agents cannot be absolutely similar ; for if so each object would move itself, and
everything would bain perpetual motion. Neither can they be utterly dissimilai; For
how can two such essentially distinct things as whiteness and a line affect each other ?
Whiteness indeed and a coloured line can affect each other ; but this is in virtue of their
generical resemblance, both having colour. So also a savour cannot affect a colour, nor
a colour a savour; but -one savour aff'ects another savour, one colour another colour.
The result then is that the passive and the active agents are generically one, but
specifically distinct " (Z>. G. et C. i. 7).

12, The ancients agreed in assigning each separate sense to a separate element, but
differed from each other in their distribution, some, as Plato, coupling vision with fire,
others, as Democritus, with water. '' It is plain that we must attach each one of the
sense-organs to one of the elements. The optical part of the eye we must take to
be of water. The part of the ear which is sensitive to sound we must take to be of
air. Smell we must take to be of fire ; for a smell is a kind of smokelike ascent of
vapour, and such comes from fire. The organ which is sensitive to touch we must take
to be of earth, and taste is but a variety of touch " {De Sensu, 2, 18).

From the passage paraphrased in the last note it appears that A, held that nothing
could be set in motion excepting by a motor agent homogeneous with itself. Now in
sensation " the object of sense sets the medium in motion, and then the motion of the
medium is communicated to the sense organ " {D. A. ii, 7). In order then for this
communication to be possible the medium and the sense organ must be homogeneous
with each other, " The medium of sound is clearly air ; the ear then must be of this
element. The eye must be of water, because to water animals the medium of sight is
water, and though to land animals air is the medium, it is so not in its character of air,
but in its character of transparent substance. The organ of touch, which lies in or close
to the heart, must be of earth, because the flesh which is earthy is the medium of touch
(ii. 8, Note 2), and taste goes with touch, being only a variety^ of it (ii. 10, Note 22).
The organ of smell must be of fire," partly because this is the only remaining element,
and also "because the medium of smell seems to be of fire, a smell being a kind of smoke-
like exhalation which occurs in a fiery medium " {De Sensu, 2). There is plainly in
the above a difficulty as regards eye and vision. The element air has already been
assigned to the ear, and the hypothesis requires each sense organ to be coupled with
a distinct element. It is necessary therefore to say the eye is of water, although air is
the usual medium of sight ; and doubtless the presence of so much fluid in the eye,
and the case of water animals, seemed to corroborate this view. But clearly the
explanation that air acts as well as water not in its character of element but of transparent
substance is inconsistent with the original hypothesis.

The foregoing will serve to show what the ancients meant in connecting each sense
with a separate element. But it seems at least doubtful whether A. himself held
this doctrine. In the text he speaks only of others holding it, not of himself. It is
true the passage quoted above from the De Sensu expressly adopts the doctrine. But
there are sti-ong grounds for believing that passage to have been interpolated ; seeing
that in it smell is said to be "a smokelike exhalation from fire," while very shortly
afterwards in the same treatise A. says that this view is held by some but is an error,
which he proceeds to refute. His own opinion as to the media, so far as can be gathered
from the scanty data- forthcoming, seems to have been as follows. Air and water form

Notes, ii. i. ^55

the medium for sight sound and smell alike, but not in virtue of the same qualities.
In sight it is the Transparent (Sm^aye's) which is effectual. In smell it is a nameless
something, which like the Transparent is common to both elements. And similarly
there is another nameless something in them both which serves as the medium of sound.
These nameless qualities were afterwards called the Trans-olent \^[o(j\t.ov) and Trans-
sonant (SiTjxe's). Cf Torstrik's notes to De Animd, ii. 7. Of these several hypothetical
media, the sole survivor is the luminiferous aether of modem physicists.

13. "Each sense seems to recognise but one pair of contraries. Vision, for instance,
recognizes white and black ; hearing, treble and bass ; taste, bitter and sweet ; (smell ?).
But in the tangible object there are many contraries, hot and cold, solid and fluid, hard
and soft, and other such oppositions" {D. A. ii. il). This leads A. to enquire whether
there may not be several different senses included under touch, and confounded together
because they have a common medium, viz. the flesh, which hides from sight their really
distinct sense organs, which are placed internally, somewhere in the neighbourhood
of the heart. . To this question, however, he gives no decided answer. Many modem
physiologists hold, as at least probable, that tactile impressions, impressions of pain,
and impressions of • temperature, though usually referred in common to touch, have in
reality their own distinct organs, central and peripheral.

14. And therefore, he intends to imply, the least simple. As to the flesh, cf. ii. 10,
Note 10 ; ii. 8, Note 2.

15. Cf. Dejfu. et Sen. I.

16. What A. means is this. '* Most organs are constructed out of several homo-
geneous parts or tissues ; but some, as the heart, of only one. Yet in such a case the
organ may be considered one of the heterogeneous parts, in virtue of its definite shape."
Thus a cartilage or a horn is made of one tissue, cartilaginous or homy tissue, and
yet is- an organ as much as if it were made of several- tissues, because it has a definite
shape and size, which suit it to its function. The difference is the same as between
silvef and a half-crown. The latter has a definite size and form, which makes it
equivalent to an organ; the former is simply material, into the conception of wljich
neither size nor form in any way. enter, and answers to the tissue. The one is
tVX'JMa'rfff/nei'oj', the other kcrx'hf'-^T^'f'^ov.

In short A. divides the parts into three classes, as follows :
a. Parts purely homogeneous, i.e. tissues.
)8. Parts purely heterogeneous, i.e. compound organs.

7. Parts homogeneous in substance, but heterogeneous as Tiaving a definite shape,
i.e. simple organs.
In the last of these classes A. includes the heart, which he erroneously supposes to be
made of a single tissue ; and says it is capable of being the sensory centre in virtue of
its homogeneous substance, and capable of being the motor centre in virtue of its
heterogeneous form.

17. The heart is excepted, because A. thought that it was formed earlier than the blood,
which is true if by blood be meant a red fluid. As to the other viscera, cf. iii. 8, Note 2.

18. A. often {e.g. iii. 4 ; H. A. iii. 3, 8) contrasts the heart with the other viscera in
respect to the relation they severally bear to the vessels. The heart, he says, is like an
expanded portion of the vessels, in which the blood is stored as in a reservoir or lake
(so Dante, " n^l lago del cor"") ; while in the vessels the blood forms a stream. Moreover
in the heart no vessel breaks up into branches," whereas in the other viscera this is
invariably the case, the vessel sometimes disappearing in the substance of the viscus, as
in the kidney (D. P. iii. 9, 5), at other times, as in the liver, passing through. It would

15^ Notes, ii. i — 2.

thus appear that A. entirely overlooked the coronary vessels, and so imagined, as stated '
here, that the nutrition of the heart was effected directly by the blood in its-cavities.

(Ch. 2.) 1. That fat is fluid, while in the living body, is often stated even in modem
books. But the statement would seem to be inaccurate, except in the case of fishes and
amphibia {Todd's Cycl. i. 58 ; ii. 232). The heat of the body in man, and in mammalia
generally, only suffices to keep the fat in a softish condition.

Why does A. call flesh a fluid? Probably because he thought flesh was a form of
blood (iii. 5, Note 7), and so attributed to it the fluidity and coagulability of the latter ;
wiiich view would have derived support from what he cannot but have noticed, namely
the rigidity of the muscles after death. As to the bile, see ii. 3, Note 2 ; as to serum,
ii. '4, Note 6.

2. Cf. ii. 6, Note 6 ; and, as to sinew, iii. 4, Note 20.

3. The distinction is the same as in last chapter (Note 16), viz. into parts purely
homogeneous, i.e. tissues, and parts homogeneous in substance but possessed of definite
shape. Of the former a piece is synonymous with the whole ; for a bit of horny tissue
is still horny tissue, a bit of cartilage is still cartilage. Of the latter a bit is not
synonymous with the whole ; a bit of a heart is not called a heart ; because it has not
got the size or shape which enters into the conception of a heart. In this respect, then,
the latter resembles the compound organs, such as the face, hand, etc.

So far A.'s meaning is clear. But he has chosen so bad an example, in blood-vessel,
as to disguise his meaning. For he has carelessly made blood-vessel an instance of the
first class of parts, the tissues ; whereas it should have been classed by him with simple
organs {l<rxi]i^o.riayi.(:va. not d(rx'?M«^Tto-To), for the tubular shape is essential to its con-
ception ; and it is quite possible to cut a vessel into bits which will no longer be called
vessels, if only the bits be such as are no longer tubular.

4. "The food of all animals Is mainly fluid ; and, even when it is not so originally, it
becomes fluid by the excretion of the solid portion" (Z>. G. i. 18, 62).

5. "Bees have a divine element in them, which wasps have not" {D. G. iii. 10, 27) ;
that is they have an intelligent soul, incorporate in pure aether. It is to this that Virgil's
lines refer :

" His quidem signis, atque hsec exempla secuti,
Esse apibus partem divinse mentis et haustus
^therios dixere." — Georg, iv. 219.

Elsewhere A. gives a less flattering account of their intellect, in a passage which may
be thus paraphrased : " All animals have sensations ; but only some have memory of
these. Such are Bees. These therefore have images of the past to guide their life. But,
as they cannot hear, their experience is but personal and scanty, for they can neither
learn nor teach others ; whereas in man the faculty of speech aggregates the memories
of many into one common experience, which is the foundation of his art and science.
Intermediate to man and bees are those animals that can hear, and that, though
speechless, can in some measure communicate with each other by sounds " {Meiap/i. i. i ).

6. A. held, as also did Plato {jfowett's Trans7. ii. 538), that the right was in nature
superior to the left, the upper to the lower, the front to the back. He also held that
" Nature, when no more important purpose stands in the way, places the more honourable
part in the more honourable position " (iii. 4, 6). This dogma he uses as an axiom
beyond dispute, and has recourse to . it on numerous occasions in explanation of the
relative positions of organs and other phenomena. • The stomach, for instance, is placed
where it is and not nearer the mouth because otherwise it would be above the heart,
a nobler organ than itself (iv. 10, Note 5). Man's nobility is shown by his upper part

Notes, ii. 2. • 157

being turned towards the upper part of the universe (ii. 10, 5). The front of man is
chosen in preference to the back, for the growth of hair (ii. 14, 3). The nictitating
membrane comes from the canthus in front, rather than the canthus on the side (ii. 13, 7).
The heart, being the noblest part, is in front and in the upper half of the body (iii. 4, 6),
and so on.

It is almost entirely as a deduction from this mischievous dogma that he infers that the
blood of the upper parts and of the right side is hotter than, or in some way or other
superior to, that of the lower parts and left side. I say "almost entirely," because even
here A. doubtless thought that his a priori statement was confirmed by some actually
observed facts. Thus he saw the vena cava and the aorta running side by side down the
trunk of the body, both containing blood. The vena cava he noticed was larger than
the aorta and lay in its general course on the right of the latter ; he also noticed that
the blood in the two differed in aspect (iii. 4, Note 24), as also did that of the right
and left ventricles. He supposed that the vena cava nourished the right side of the
body, on which it was placed, and the aorta the left side. Hence his statement that the
blood of the two sides differed in quantity and quality. He found, again, in some animals
the blood of the head of a brighter hue than that of the rest of the body (ii. 7, Note 12).
Here was evidence of the superiority of the upper parts to the lower. Another observa-
tion can hardly have failed to have been made by him, and to have confirmed his previous
opinion. When a limb is much exercised, not only is the general temperature of the
body raised, but that of the limb itself rises higher than that of the unused parts. The
right arm, being the one used preferentially by most men in any action requiring great
muscular force, is often so much hotter than the left that the difference is readily percep-
tible to the touch without any instruments. This may easily have led A. to believe that
the blood of the right side was hotter than that of the left, as his previous observations
bad led him to believe it was more abimdant. Still it is not to be denied, that the
statement was in the main a priori ; and that it had, as such dogmas invariably have,
the mischievous effect of blinding its acceptor's eyes to facts palpably inconsistent
with it.

7. No greater differences that is than occur within the range of a genus (cf i. i,
Note 2).

8. This was the opinion of Empedocles ; it is discussed at length in De Resp. 14.
The coldness of water-animals is at any rate in part due to the rapid loss of heat to
which they' are subjected by aquatic life ; and thus their temperature often rises when
they are taken out of the water and kept in the air, where the conduction is much less
rapid. This was observed by Spallanzani to be the case with many fishes, and more
recently by Valentin with Aplysise.

9. Cf. ii. 7, Note 19. The question whether the catamenia are an . indication of
greater heat in the female is discussed in De Gen. iv. i, and answered in the negative.

10. A. has left special treatises on Sleeping and Waking, Youth and Old Age, Life and
Death ; but the treatise on Health and Disease, if ever written, is lost. His general
views however, as may be gathered from the first section of the Problemata, were as
follows. The characteristics of a living body are that it is hot and contains fluid* matter ;
of the dead body that it is cold and without fluid. The coldness is perceptible to
the touch, and the want of fluid to the eye; for not only do the fluids coagulate,
but the whole body turns to dust. The heat and moisture of the body are at their
maximum in youth. For there is a constant exhalation of fluid and heat going on
during life, so that the body gradually becomes colder and its fluid less abundant. The
older therefore the body, the more easily is its heat extinguished by any chance cause

15^ Notes, ii. 2 — 3.

of refrigeration, just as a small fire is more easily extinguished than a large one. In
other words disease, which consists in an abnormal increase or decrease of the bodily
heat and moisture, is the more dangerous the older the body is. Should no disease
intervene, the bodily heat and moisture grow less and less by gradual exhalation, until
at last they are expended ; but so gradual is the process that the departure of the soul
occurs imperceptibly and without pain,

11. Z). G. et C. ii. 2 and 3 ; cf. ii. I, Note 3.

12. It is a matter of familiar observation that degrees of heat 'and cold which affect
some persons agreeably are distressing to others ; and in disease one sometimes finds
a striking contrast in this respect even between different parts of the same person.
Thus I once had a patient who presented the following curious phenomenon. A
moderately hot substance applied to his right foot caused an agreeable sensj,tion of
warmth ; but the application of the same to the left foot made him yell, ^nd he said
that the sensation he experienced was not of heat but of simple pain.

13. Olive oil can scarcely be meant, as Frantzius supposes ; for it coagulates some
seven degrees above the freezing-point of water. "EAojoj' is often used generally for any
oil,.as {H. A. vii. 3, 2) for oil of cedar. Possibly A. is here sJDeaking of fish-oil, with
which he was (ZT. A. iii. 17, 3) well acquainted, and which remains fluid at a temperature
considerably below the. freezing-point of water.

14. Because in A.'s opinion it derives its heat from the heart, or from the celestial heat
which has its main seat in the heart.

15. The more obvious phenomena of heat and cold can.be explained equally well
either by supposing both of these to be actual existences with opposite characters, or
by supposing one of them to be merely the absence or privation of the other. Which
of these two views was the right one was the subject of early and often-renewed dispute.
Plutarch {fie primo frigido) discusses the question and answers it in the same sense as
Aristotle. In stating however the opposite opinion Plutarch incidentally touches on
what would I fancy be given by modem physicists as the reason for holding cold to
be no more than privation of heat. "Is there," he asks, in beginning his treatise,
•'such a thing actually existing as cold ? or is cold nothing more than privation of heat,
as darkness is privation of light and immobility privation of motion ? For in fact cold
appears to be quiescent, and heat to be a source of motion " (^Tret koI rb xpvxpov ^oiKe ardtriixoy
flfai, Kivi\riKov 5e rh Oepfiov).

16. "Limus ut hie durescit, et hsec ut cera liquescit, *

Uno eodemque igne." — Virgil.

17. Cf. ii. 4, Note 10.

18. Had A. possessed the thermometer or similar instrument he would have seen that
in some of his instances the difference is only one of degree. That boiling water for
instance acts differently from red-hot iron, because its temperature is enormously inferior.
It is worth noticing how well A. has here escaped the popular error, according to which,
in all bodies which are ordinarily designated by a common adjective, there must be one
common elementary property corresponding to this common title. From this tyranny
of an adjective, as Whewell calls it, even Bacon was not free. Among his "instantiae
convenientes in naturam calidi " we find nasturtium which is hot to the tongue, acids
which hotly burn the skin, fur and other hot coverings, spirits of wine which, as hot
bodies, coagulate white of egg, and so on ; the mere verbal link serving to bind together
most diverse phenomena.

(Ch. 3.) 1. The external influence is the heat of the heart, to which A. attributes
that of the blood (cf. ii. 2, Note 14).

Notes, ii. 3. I59

2. Bile obtained from the gall-bladder is usually very viscid, owing to the admixture
of mucus, derived from the walls of that receptacle, with the slightly alkaline fluid.
When* this viscid bile is left to stand, the mucus rapidly decomposes, and the fluid
becomes acid. This disappearance of the mucus restores to the bile the greater degree
of fluidity, which it had before entering the gall-bladder.

3. The opinion that digestion is due to heat appears to have origitiated with
Hippocrates, and was adopted by A. and also by Galen. Digestion according to this
view was a process of cooking (see however ii. 6, Note 7), and in Greek the same word
(ire'ifjs) stands for both cooking and digestion. Our words "dyspepsia" and "pepsine"
are records of the old. belief, which was prevalent for ages after A.'s time, the action
of the heat being still called "concoction." The various opinions as to the cause of
digestion are thus enumerated by Celsus : " Duce, alii, Erasistrato atteri cibum in ventre
contendunt ; alii, Pleistonico Praxagorse discipulo, piitrescere ; alii credunt Hippocrati,
per calorem cibos concoqui ; acceduntque Asclepiadis aemuli qui omnia ista vana fet
supervacua proponunt ; nihil enim concoqui, sed crudam materiam, sicut assumpta est,
in corpus omne diduci." Although we have now learnt that digestion is due to the
action of gastric and other juices, yet it is- no less certain that heat is not without
considerable influence on the process, A temperature of from 106° to 96° F. is in fact
necessary in order to keep up the chemical process, and each successive fall below
this standard produces successive retardations of the action ; which is completely
suspended when the ordinary atmospheric temperature is reached. On the other hand
a rise of temperature to about "140" F. causes a decomposition of the gastric juice, and
entirely destroys its power.

4. A. looked on the heart as the main but not the exclusive seat of vital heat. "The
whole body and all its parts have a certain innate natural heat. But in sanguineous
animals the main seat of this heat must be- the heart. For, though the other parts by their
natural heat ,can effect the concoction of the food, yet chief and foremost in this office
is the heart. The rest of the body then may become cold, and yet life continue ; but
should the heart cease to be hot, all life is at an end ; for no longer does there remain
a source whence the rest of the body may derive heat " {De yuv. et Sen. 4, 3).

6. A. knew nothing of the salivary glands, or of their action upon starch. He
therefore limits the part played by the mouth to mastication, which he truly says is not
actually a digestive process, though essential for easy digestion.

6. The upper cavity is of course the stomach. By the lower is meant the large
intestine, or rather its csecal enlargement (cf. iii. 14, Note 35). This is sometimes, as
here, spoken of by A. ds a seat of digestion, that is as a second stomach, and sometimes
merely as a receptacle of residual matter, as though all digestion were over before this
part was reached. We may fairly suppose that A. in the different passages is speaking
of different animals ; for while the caecum in sOme animals, as in the horse, really acts
as a second stomach, in others, as in man, its contents are almost entirely faecal.

7. The same simile occurs in the Timseus {Jinveti's Tr. ii. 564).

8. One term (ircptTTcojuo) served A. to express several things, viz. (i) The indigestible
residue of food, i.e. the excreta. This is often distinguished as the "useless residuum"
^i. 10, 2 ; Z>. G. i. 18, 2). (2) Such part of the food as, though nutritious, is not
consumed for the direct benefit of the individual, but for that of the species, as milk,
semen, and generally the generative secretions (iv. 10, 47). (3) The parts of the
blood which remain after the nobler organs have been supplied, and which are used
for the inferior parts, such as sinews, bones, etc. (iii. 5, Note 5). (4) Such inferior
parts themselves, e.g. hairs (ii. 15, Note 4). (s) Such surplus materials as are not used

i6o Notes, ii. 3 — 4.

immediately, but are stored up in the body, as fat {D. G. i. 18, 59). It is in the first
sense that plants are said to have no excrement ; in the second that seeds are sometimes
(iv. 10, 17) regarded as representing the residual matter. .

9. A. means sponges. There are numerous microscopical animals capable of active
locomotion, and yet without intestinal cavities ; but such were of course unknown to
Aristotle. ' . •

10. The comparison occurs again in iv. 4, 4. Elsewhere A. compares the roots of
plants to the mouth of an animal, "being the channel by which they take food from the
ground" {De Juv. et Sen. I, 7), and yet again (Z>. G. ii. 7, i) to the vessels of the
umbilical cord.

11. Cf. iii. 5, Note 5. A. knew nothing of the lacteals. But not long after his time,
Erasistratus, his pupil, opening a sucking kid (cf. Galen, An Sanguis in art. ch. 5), saw
many small white vessels in the mesentery. He noticed that these did not, like the
blood-vessels, pass to the liver, and also that they were in connection with certain
glandular bodies, the mesenteric glands. He supposed rightly enough that the contents
of these white vessels were derived from the milk swallowed by the kid ; that is he
recognised their absorbent character. But Galen {De Usu part. iv. 19) held that their
office was to nourish the intestines. Erasistratus's observation seems to have led to no
further result, and to have been quite forgotten. Thus the discovery had to be made
again nearly 2000 years later (a.d. 1622) by Aselli of Cremona.

12. H. A. i. 16, iii. 4.

13. The argument is as follows. The entire food, digestible or not, has a receptacle,
viz. the stomach ; and the indigestible part of it also has a receptacle, viz. the lower
abdominal cavity or large gut ; the digestible portion must therefore also have a
receptacle, inasmuch as it is separated from the indigestible part. But there is no other
receptacle than the blood-vessels ; which must therefore be the receptacle of the nutritious
portion. And as these blood-vessels are seen to contain nothing but blood, the blood and
the nutritious matter must be one and the same thing.

14. After a meal the amount of blood is even as much as doubled according to
Bernard {Lemons, 1859, i. 419).

15. The argument is to the following effect. Neither is the entire food sensitive ; nor
the excremental part of the food ; nor yet the nutritious part of it, even after it has been
converted into blood. It is only when the blood has been farther converted into flesh,
that it becomes sensitive. Up to that time it is insensible ; for though it is in immediate
contact with the flesh, yet it has therewith no anatomical continuity whatsoever.

16. A. often refers to a treatise which he was going to write on Nutrition. It has been
generally supposed that the De Generatione, in which nutrition is handled to a certain
extent, is the treatise thus promised. But this view seems incompatible with the fact
that a similar reference to a future treatise "on growth and nutrition" is made in the De
Generatione itself (v. 4, 4), in a passage which appears to have been overlooked. The
present passage moreover speaks of "other writings" besides the De Generatione. The
promised treatise is not extant ; perhaps was never written ; for no mention of such is
to be found in Diogenes I-aertius. Heitz {Die verlor. Schrift. d. Arist. 61) thinks it
probable that a shott separate treatise was written, such as those massed together in the
Parva Naturalia ; and that some portions of it have come down to us merged in the De
Generatione. And thei-e is in fact in the De Somno (3, 4) a passage which apparently
refers to a treatise on Nutrition as already written.

(Ch. 4.) 1. The coagulation of the blood is considered in two other passages {H. A.
iii. 6; iii. 19). In all of these places A. speaks distinctly of the coagulum as being

Notes, ii. 4. i6i

formed of fibrous matter ; thus anticipating the discovery usually said to have been
made by Malpighi (cf. M. Edwards, Lemons, i. 1 15). What A. did not discover and what
Malpighi did, was that by washing the coagulum tHe red colour could be discharged,
and the fibres shown to be white.

That A. paid much attention to the coagulation of the blood is plain. It \vill be
seen, that several of his remarks on the proportion of coagulum .and serum in different
animals harmonize with modern observations. Elsewhere, moreover, he notices [^Meteor.
iv. 7, 1 1 ) that the blood in certain diseased conditions will not coagulate. .This is known
to be the case in cholera, certain fevers, asphyxia, etc. This fact was probably got
from Hippocrates, who bled largely.

2. Elsewhere {H. A. iii. 6, 2), besides the deer and roe, the bubalis (antelope) and
hare are mentioned as having blood that does not coagulate so fully as that of other
animals. All these are animals that are hunted; and it is well known that John
Hunter, finding the blood fluid, or only slightly thickened, in two deer that had been '
hunted to death {Hunter's Works, i. 239), formed the opinion that the blqod under such
circurnstances completely loses its power of coagulation. Mr. Gulliver \HewsorCs Works,
p. 25). shows by instances that this is not the case; coagulation sometimes at any rate
occurring, though imperfectly. We may fairly suppose that the animals examined by
A. had been hunted to death ; and though he speaks in this passage of an entire
absence of coagulation, in the Hist. An. he admits an imperfect degree of it. "In the
blood of most animals there are fibres ; but none in that of deer, roes, antelopes and
some others ; so that their blood does not coagulate similarly to that of other animals.
The blood of deer however coagulates in about the same measure as that of hares. In
both of these coagulation occurs, but the coagulum is not firm as in other animals, '
but flabby, like the clot in milk when no rennet is used. The blood of the antelope
coagulates rather more completely, indeed only a little less fully than that of sheep."
In the last clause of this paragraph I followed the MS. in my College library which
omits ^l/vxp^y-

3. Cf. ii. 2, Note 5.

4. Fear and a "blood-frozen heart" have been everlastingly coupjed together by
writers of all ages. See Hamlet, i. 4 ; Faery Queen, i. ix. 25 ; Virgil, Ain. 3, 40, etc.
The notion is of course founded on the fact that many of the external signs of fear,
as pallor, shivering, erection of hair, are identical with the signs of intense cold. There
is an apparent confusion in the passage in the text as to which is cause, and which effect ;
fear being first said to chill the blood,- and then chilled blood to lead to fear. The
contradiction 'is only on the surface. In every emotion, says A. (Z>. ^. i. l), there are
two factors, one bodily the other psychical. These two factors are so closely associated
with each other, that, when either is in asiy way evoked, it immediately evokes its
fellow, and the emotion is complete. Thus the psychical factor of fear, if excited, will
determine the bodily factor, viz. chilling of the blood, etc. ; while chilled blood, however
produced, will similarly give rise to the psychical factor. Each factor that is may be
either cause or consequent of the other.

5. The bloodless animals that remain motiopless when frightened are beetles, irioths,
etc. (iv. 6, Note 8) ; but the same phenomenon is really obsei-vable in some sanguineous
animals, e.g. in the landrail ( YarrelCs Birds, iii. 95). . Those that discharge their
excreta are various insects and cuttle-fishes. Here again however examples can be
found among sanguineous animals; snakes fOr instance ( W^/izV/j Selborne, xxv.),
hedgehogs, the aurochs as described by Aristotle (iii. 2, 5), and many other animals

i62 . * Noks. ii. 4.

(iv. 5, Note 20). Those that change colour are the cephalopods (iv. 5, Note 15);
but the sanguineous chamaeleon does so as well (iv. Ii, Note 28).

6. Though from some of A.'s language it might be supposed that he looked on the
whole blood as being fluid while in the living body, and so anticipated Borelli,' this
passage shows that he really considered the fibrine to exist in the solid form even during
life; as also did Plato «(y^w//'j- Tr. ii. 578).

7. The hot vapour-bath to which A. alludes was made by getting under an air-tight
cloth and throwing aromatic substaiices upon hot embers. Cf. Herodot. iv. 75.

8. Elsewhere \H. A. iii. 19,' 6) the ass is instanced as well as the bull. Bovine
animals (but still more swine and horsps) have a larger proportion of fibrine in their
blood than man {Andral, Ann. du Chimie, 1842, p. 306); and from such scanty •
observations as exist it would seem that the blood of bulls is richer in fibrine than that
of cows or oxen {ibid. p. 307). Thackrah seems 'to have arrived at much the same
general conclusion as Aristotle. " Although my experiments are far from e^'ipcing a
disparity uniform in its reference to the classes' of animals,, yet it appears probable that
a more complete examination would prove the crassamentum to bear a proportion to tl.ie
strength and ferocity of the animal, since I never found the serum in such quantity as in
the timid sheep, nor the crassamentum so abundant as in the predatory dog" {On the
Blood, 1834, p. 154). .

That abundant fibrine goes with strength and ferocity appears to be a popularly

accepted notion. . . ' .

" Come you spirits

That tendon mortal thoughts, unsex me here

And fill me from the crown to the toe, tqp-full

Of direst cruelty ! * Make thick my blood. "■ — Macbeth, i. 5.

9. I cannot find any exact observations as to the period of coagulation of bull's blood-
It differs in composition from that of the ox (see last note) and may therefore differ
from it in this point also. The blood of an ox, however, commenced coagulating, in
Thackrah's experiments, on an average in 6 minutes ; the minimum being 2 and the
maximum 10 ; whereas that of the sheep, hog, and rabbit commenced in from ^ to 2
minutes; that of a duck in from i to 2 minutes; and that of a mouse, according. to
Haller, "in a moment." Thackrah says {On the Blood, p. 154) that "from my
observations the general inference may be drawn that coagulation commences sooner in
small and weak animals than in large and strong." This seems in contradiction with
A. 's statement.

10. Cf. Meteor, iv. ch. 6, 7, 8, where A. discusses at length the questions of coagula-
tion, liquefaction, etc. "Compounds of earth 'and water," he says, "such, for instance,
as blood, in order that they may retain their fluid condition, require a certain amount
of water and a certain amount of heat. They can therefore be solidified either by
excessive heat or by CQld. By heat because it directly causes evaporation 6f the water.
By cold because in the first place it expels the heat, and secondly because the heat in
passing off carries with it much of the water in the shape of vapour. Blood when
withdrawn from the warm body and exposed to the cold air coagulates owing to tfie
second cause." . ' ' ■

11. A*, considers the fibrine, or rather the clot, i.e. the -fibrine with the corpuscles, to be
the part of the blood which is ready to serve for nutrition. Besides this, he says, there
are in the serum materials derived, from the food which after concoction will be converted
into this nutritious form (so also' Z;^. A. iii. 19, 9— 12), and others again whiph are
derived from the waste of the body. This accords with the view of those who hold that

Notes, ii. 4 — 5. 1 63

• fibrine is a higher elaboration of the albumen of the serum, necessary before this can
be put to use ; and with the undoubted fact that the blood is not only the channel for
nutrimMit, but also the channel by which such waste as arises from decay is carried off
to the excretory organs. That "the necessary process" means the waste of the body
caused by its own activity is shown by De Soiiino (3, 10) : " Toil produces wasting ; and
the product of this waste, unless it be cold, is similar to unconcoGted nutriment."

(Ch. 6.) 1. A. calls the softeir kinds of fat Lard, the harder kinds Suet. This
answers to the division .of later writers into Pinguedo and Sevum. J. Hunter made four
divisions. Oil, Lard, Tallow, Spermaceti, also taking consistency as the basis of
distinction.

2. We have here an example of the manner in which the ancient philosophers judged
of the composition of a substance. They simply inferred it from a comparison of the
superficial qualities with those of the four elements. Oil is shining; so is fire. Oil
is more or less transparent ; so is air. Oil then contains fire and air. There was no
attempt to reduce bodies to their supposed constituents by actual analysis. " The
supposed analysis was, in short," says Whewell, "a decomposition of the b.ody into
adjectives not into substances."

3. This is an error, ,'ln caterpillars, for instance, there is abundance of fat, ^ A.
himself later on (iv. 5, 30) speaks of the Echini as having something like fat, mistaking
the nature of their ovaries. He would say, however, that these substances are not true
fat, but ortly something analogous to fat (Z>, G. i. 19, 18), just as he says that the
ex-sanguineous animals have no true blood, but only something analogous to blood.

4. The coagulation of broth, is due to gelatine and not to fibrine. These substances,
however, were of course not distinguished by Aristotle. This may perhaps account in
part for his supposing that the fluidity of the- blood was due to heat, and its coagula-
tion, when withdrawn fronT the body, to cold ; for gelatine is thus affected by heat and
cold.

. 5, Cf. iv. 16, Note 44. ■ , .

6. The fat of Ruminants and Rodents is harder than that of man ; the fat of
Carnivora and Pachyderms softer. A.'s statement is therefore correct, excepting, as
regards the Rodents, which he did not distinguish from the Carnivora. Though he .
makes no mention of Pachyderms in this place, elsewhere {,H. A. iii. 17, i) he correctly
says that the horse and the hog have soft fat.

7. Gf. ii. 3, Note 15 ; ii. 10, Note 10. ^

8. Cf. Thackrah, " On the Blood" p. 131 : " The state of the general system as to
Fatness or Leanness seems to affect the quantity and character of the blood. Fat
animals have I believe considerably less blood in proportion to their weight . than lean
ones ; and in the fat human subject venesection shows the veins to be comparatively small,
and the quantity of blood, even when two Dr three vessels are opened, is less than flows
from one vein of a lean person, etc." So also Ijippocrates {Aph. i. 44) : "Those who are
naturally very fat are likely to die earlier than those who are. slender ;" which Galen
explains by saying that fat men have smaller vessels than lean ones, and so are less
plentifully supplied with vital spirit (irj/cC/ia). Cf. Celsus, ii. l ; Hippocr. Kukri's ed.
iii- 434-

9. Cf. D. G. i. i8, 59. That over-fat animals are bad breeders is known to every farmer.
So tilso it is well known that castrated animals grow fat. These and similar facts led
Bichat {Anat. Gen. i. 55) to express an opinion much the same as that 'of Aristotle.
" On dirait qu'il y a un rapport constant et rigoureux entre la secretion de la semence et
I'exhalation de la graisse ; que ces deux fluides son! en raison inverse I'un de I'autre."

164 ■ Notes, ii. 6. . ■

(Ch. 6.) 1. Alluding to Plato, who expresses this view in the Timseus {JoTvelfs
Transl. ii. 571).

2. "The bones of the foetus are void of a distinct medullary canal, and present
merely a reddish homogeneous vascular pulp, somewhat consistent but presenting soft
portions. This state continues for some time after birth" {Todd's Cyclop. Anat. i. 60).
So also VirchoTv's Cellularpath. 369,

3. In the foetus and infant there' is less pigment in the body generally than in the adult.
The skin, hair, eye's (Z?. G. v. i, 16), and olfactory region, are all lighter-coloured than
in later life. I have tried to show elsewhere {Med. Chir. Trans. 1870) that this develop-
ment of pigment after birth coincides with, and is a necessary condition of, an increased
sensory acuteness.

4. That the spinal cord is the marrow of the vertebrae is an error, the memory of which
is still preserved in the popular term "spinal marrow." Although A. observed that the
cord was in substance quite iinlike any other marrow, having indeed no other resem-
blances to this substa^ice, than its position in a bone cavity and its Hght colour, and
though he knew that it was directly continuous with .the brain, which latter he
knew was not marrow (see next chapter), yet he held fast to the popular notion,
because his theory required the cord to be made of some hot substance, such as he took
fat to be. The uses assigned by A. to the spinal cord were, firstly, the mechanical
office of holding the vertebrae together, and, secondly, that of tempering the heat of
the brain.

•5. Cf. H. A. iii. 7, 9 : "Sgme animals, the lion for instance, appear to have no mar-
row in their bones, because the marrow is excessively small and only present in a few of
the bones, as in those of the thighs and fore-legs." "Whether the lion (iv. 10, Note 6) has
or has not smaller medullary cavities than weaker animals, I cannot say ; but it would
appear to have bones of more than ordinary density. For the per-centage of hard matter in
its bones is 72*3, that of man 68-9, of the ox 69, of the porpoise (i\'\ (Oweii's Verteb. i.
20). So hard are the lion's bones, says Aristotle (ii. <^ ; H. A. iii. 7, 9), that they give
out sparks when struck. ^

6. A. distinguishes the substance of which fish-bones are made from that which
composes ordinary bone. The difference consists in there being a much srftaller amount
of heavy inorganic matter in the former than in the latter. . It may fairly be supposed
that this is of use to the fish by diminishing the specific gravity of its body ; and it is in
harmony with this view that»thfe proportion of inorganic matter is much higher in the bones
of sea-fishes than of such as live in fresh water, the former swimming in a denser medium.
The porpoise, though a mammal, has bones iri this respect- like those of a sea-fish (Owen's
Verteb. i. 20) ; and as A. in this place speaks not merely of fishes, but of aquatic animals
generally, we might suppose him to mean to include this animal, were it not that
elsewhere (ii. 9, 11, and H. A. iii. 7, 9) he expressly says, as others had sai'd before
Jiim {Herod, iv. 53), that the dolphin has true bones, and not fish-spines.

7. This passage is of importance ; for it indicates the answer to the obvious objection,
that many of the phenomena attributed by A. to heat are manifestly not so producible.
For, in using the term "self-concoction," A. means to draw a distinction between
ordinary heat, and the heat of the blood or body. Mere cooking with fire of course does
nof convert blood into fat, nor digest food, nor the like. But the heat of the body, as
the heat of the sun, says A. {D. G. ii. 3, 13), is something very different from this. . It
has a vivifying influence, which simple fire has not, and produces effects far beyond the
power of this element. Cf. Introd. p. xxiii.

8. No fish has a medullary canal in its bones, though there are some, as the trout, in

Notes, ii. 6 — 7. 165'

which the bony tissue is more or less penetrated by an oily fluid ( Todd's Cyclop, iii, 958).
The same is true of the bones of Cetacea and of seals {Cuvier, Anat. Comp-. i. 1 10).
• 9. Cf..iii. 4, Nqte 20.

(Ch. 7.) I. As Plato in the Timaeus {JoweWs Transl. ii. 567).

2. Cf. ii. 5, Note 2.

3. "In its proper substance" as opposed to the vascular membranes that surround it.
As to the supposed bloodlessness and coldness of the brain, cf. ii. 10, Note 18.

■ 4. A. uses the term fluid with much latitude. Jhus he calls the faeces fluid. This
however might be defended,, as they sometimes are so, especially in bovine animals.
Here he calls the brain fluid, and Galen also calls it " almost fluid." It is true A. says
it is the most consistent of all the animal fluids, and also (Z>. G. ii. 6, 35) that it is only
actually fluid in the very young, and afterwards gradually becomes more consolidated.
But even with' these limitations the term gives an exaggerated idea of the softness of
the part. -Probably A. thought the brain was more fluid during life than after death, •
reckoning it, with fat and marrow, among the substances which are fluid only so long as
they are in the living body (ii. 2, Note ij. It may be objected to this that A. had at
any rate seen the brain of the chamaeleon during the animal's life {H. A. ii. 7), and that
he must have known that this was not fluid but solid. But it must be remembered that
according to A. 's views the colder the nature of an animal the less fluid should its
brain be ; for in his opinion it is on the fluidity of the brain that its coldness depends,
and this must be proportioned to the animal's heat, which it has to temper. But
the chanigeleon is cold-blooded ; so that the firmness of its brain would be only what
A. would expect, and would in no wise lead him to look for like firmness in the brain of
a warm-blooded animal.

It will be noticed that the human brain is said to be more fluid than that of any other
aninial. This is not the case. Doubtless A. had never seen an adult human brain.
But I think it not unlikely (i. 5, Note l) that he may have examined the brain of an
aborted foetus, in which case he would most probably have found the brain diffluent,
aind that his statement was founded on this.

5. This fact may have been learnt from Hippocrates, or some other surgeon who had
exposed the brain in an operation, and noticed its apparent insensibility to mechanical
irritation. Or it may have been noticed by A. himself in his vivisection of the chamseleon
i^H. A. ii. 11). Very possibly it may have been an observation made on that same
occasion that led him to the hasty generalization that the brain was always cold.

6. I take the meaning to be as follows : "The excrements have of course no anatomical
connection "wjth the body, but are isolated substances. The brain, though not an
excremental substance, yet so far resembles one that it also is without anatomical con-

. nection with the rest of the body, excepting as already stated with the spinal marrow.
In this it differs from the other organs, none of which is ever isolated. Thus (ii. 9, l)
every bone is connected with others so as to fonn an osseous system, and similarly
every blood-vessel is connected with the rest so as to form a vascular" system. But
the brain is isolated. For it is not true as some say that it is anatomically con-

• nected with the organs of sense, so as to form with them a sensory system." As to
the continuity of brain with sense-organs, cf. ii. 10, Note 9.

7. Democritus {D. A. i, 2).

8. And therefore causing it to be cold ; for both earth and water are copipounds of
cold matter, the former with solid, the latter with fluid matter (cf. ii. i, Note 3).

9. Elsewhere {H. A. i. 16, -2), A. speaks of Cephalopods in general, and not only
of the poulp, as having a brain. The cephalic ganglia in these animals are so large

i66 • ■ Notes, ii. 7. .

as to rival the brains of vertebrates in size and importance. Thus A. , who had made a
special study of Cephalopdds, could not help seeing their ganglia, vv'hereas those of
other invertebrates are so small that, with his want of instruments, it is no wonder they
should have escaped his notice.

10. Cf. iii. 4, Note 24. .

11. i.e. the //a mater. A. {H. A. i. i6) describes the brain as having two membranes,
an outer and stronger one next to the bone {dura mater), and an inner one in contact
with the brain itself (/«■« wa/^r). This latter is the vascular onCj so often mentioned by,
Aristotle. This membrane consists in great part of a plexus of extremely numerous and
very minute vessels, as A. says. The same statement is to be. found in De Somno, 3, 26 :
"The small si^e and narrowness of the vessels on the brain assists in producing'
refrigeration and in preventing the easy access of the ascending vapour of nulriment."
The real use of the peculiar and extreme subdivision of the arteries before they are
distributed to the brain seems to be to make the blood-pressure and blood-supply as
uniform and equable as possible in all parts of this sensitive organ.

12. Not only in the fcetal mammal, but in the adult batrachian and reptile there are
special contrivances by which the head is supplied with purer blood than goes to the rest
of the body. The anatomical arrangements by which this is brought about were of course
quite unknown to A.; but it is not improbable that he may have noticed the different
colour of the blood going to the head and of that going elsewhere, in his vivisections of
the tortoise {De Resp. 17, 4) and of the chameleon {H. A. ii. 11); . What wasi true of
some animals, he supppsed to be true of all, because the conclusion chimed in with his
^/wW views (cf. ii. 2, Note 6). • ■

13. The same comparison is to be found in De Somno, ch. 3.

14r. "As to the causes of health and of disease, these are matters which come not only
into the province of the physician, but also to a certain extent into that of the natural
philosopher. The two however regard the subject from diiTerent poinjts of view, as must
not be forgotten. Still it is plain enough that there is no very broad line of demarcation
between them. For such physicians) as are boastful and officious, are given to talk of the
phenohiena of nature, and profess to derive from natural philosophy their principles of
practice; while the most accomplished among the natural philosophers rarely fail
eventually to touch on the principles of the art of healing" {De Long, et £r. Vita, 2).
As to the question whether the promised treatise' on the Principles of Disease was ever
written, see Heitz, Die verlor. Schrift. d. Arist. p. 58.

15. A similar account of sleep is given in the special treatise De Somno. A. argues
that as the main feature of sleep is the abeyance of all the senses, sleep must clearly be
due to some condition of the sensorium commune, i.e. the heart ; and as sleep is notably
, consequent on a heavy meal, on severe exercise, and, the like, it must be due to some
effect producible by such influences on the heart. After a meal the dissolved food
passes into the blood-vessels, as also after severe exercise does the waste matter resulting
from such exercise, and ascends through them in form of vapour. When this reaches
the head, it is condensed by the cold brain and falls back to the heart as a cold fluid,
consistir>g after a meal of the coarse and fine elements of the food, and after exercise of
coarse matter only. It is this accumulation of cold; coarse, thick fluid In the sensorium
commune that suspends its activity. After a time this fluid undergoes concoction, and
then the sensorium is relieved and wakens into activity. What happens in sleep, says A.,
happens also in an epileptic attack, so that sleep is a kind of epilepsy ; and in confirma-
tion of this view he cites, the perfectly accurate facts, that the night is the most usual
time for these fits, and that in most cases the earliest attacks occur during sleep. It is

■ Notes: ii. 7. 167

easy to ridicule A.'s view, and ridicule has not been spared. But to me A.'s theory,
erroneous as it was, seems an honest and ingenious attempt to colligate hypothetically
and in a presentable form such facts and supposed facts as Were known to him or
accepted by him. We now know that the brain and not the heart is the sensorium
commune ; allowing for this fundamental error the view of A. agrees with the modern
views, in attributing sleep to an alteration, quantitative and qualitative, in the blood-
supply of the sensorium, and in finding a similarity between sleep and epilepsy. A. held
that the amount of blood in the sensorium was increased, and until quite recently, when
Mr. Durham and others showed by actual inspection that this Was not so, but that in
reality there was diminished vascularity, physiologists as a rule were of the same opinion.
A. thought the qualitative change was due to additional impurity, modem conjecture
points to exhausted oxygen. As regards the relation of sleep to epilepsy, ** nous pouvons
meme dire," says Brown Sequard,'*' que chez beaucovp de personnes lion dpileptiques le
sommeil ressemble a une legere attaque d'epilepsie " {Le(ons sur les nerfs vasomoteurs,
p. 121). . . •

16. Cf. Note 8.

17. Cfv ii, 4, Note 10 ; ii. 10, Note 18.

18. That man's brain is heavier than that of other animals in proportion to his weight
is- true with very few exceptions, which are. furnished by certain species of small birds,
monkeys, and rodents, whose body is lean and therefore light {Cuvier, An. Comp. ii. 419).
Leuret gives the following general results ; in fishes the brain is to body as I to 5668 ; in
reptiles as I to 1321,. in birds as I to 212, in mammals as I to 186. But in man the brain
forms from t'ir to ^ of the whole weight. . ' '

Whether man or woman has the larger brain in proportion to- the body is a question not
satisfactorily settled ; for observers have arrived at different results. Thus Dr. Peacock
in one set of observations ^Monthly Joiirn. Med. Sc. vii. 1847) found the encephalon in
• women in the proportion to the body of i : 33'5 ; that of man I : 37 "2 ; that is he found
the female braiii the heavier in proportion to the whole weight. In another set however
{Path. Tr. xii. ) he found the proportions I : 3273 in the male, and'i : 39 in the female.

The actual weight of ths brain of womenis, on an average, about 5 ounces less than
that of men,

19. The slight differences of temperature betweeii one warm-blooded animal and.
another cannot be estimated by touch ; and as A. had no thermometer his statements in
the text are but guesses, and unlucky guesses.- (See however ii. 6, Note 7, and Introd.
p. xxiii.) For all or most birds, and not a few mammals, are hotter than man, Neither
again is man hotter than woman : the differences in this respect being apparently
independent of sex ; or the ballnce being in favour of woman. Thus in a long series
of observations made by me on a man and woman, the temperature of the latter was
notably higher than that of the former {Diurnal variations of the tempirature of the
huvian body in health, St. Georgis Hospital Reports, i.). Wunderlich also concludes from
such insufficient observations as exist that the temperature in adult women is slightly
higher than that of man {Eigenwiirme, etc. 2nd.ed. p. 104).

The reasons why A. considers the male to be hotter than the female are set forth in De
Gen. iv. i, 27. ' •

20. The meaning- is : heat promotes growth ; and as heat mounts upwards from its
source, i.e. the heart, growth will be promoted in the upward direction in preference to
any other. Cf. iv. 10, Note il. That heat mounts upwards is of course A.'s mode of
viewing such facts as the ascent of hot air, and the upward pointing of flame, etc. Cf. ii.
I, Note 2.

i68 . Notes, ii. 7. ' • •

21. Elsewhere (//. A.m. 7) A. says there are si)( bones in the skulj. Of these (//.^.
i. 7) the anterior is the Bregma, which alone covers the brain and is, on this account, •
the last to ossify. By this he clearly means the anterior fontenelle, which he considers
to be a separate bone. The posterior bone, covering the empty space, he calls Inium ;
clearly meaning the Occipital. Two others are placed above the ears, and are smaller
than the rest. By these he doubtless means the Temporals. The other two he does
not describe ; but they can be nothing else tlian the Parietals. The Frontal {-npiffui-Kov)
A. reckons as a bone of the face.

22. This is the case with the superior races of man ; such as alone would have fallen
under A.'s observation. In them the posterior sutures close before the anterior, and
both close late. But in the inferior races, according to Gratiolet, the ahterior close
before the posterior, and both cloge early {Soc. Anthropol. 1861, p. 180).

23. The erroneous notion that the use" of the sutures is to ventilate the brain is
repeated by Galen {Organ of Smell, 2; De Sanit. tuehdA, i. 13). Their real use is to
allow of the growth of the.encephalon, which can no longer increase in bulk when the
sutures are once closed. The greater development of the anterior lobes in civilized races
as compared with the posterior explains the facts given in the last note.

24. I cannot' ascertain whether this be so, or not.

25. This is an error. Doubtless.A. was led to it by the fact that in numerous animals
the sutures become more or less effaced it a very early age.. This is notably the case
with birds, fishes, and, of mammals, with the cetacea and elephants.

26. "■ In woman the suture is circular; while in man there are three sutures on the.
t6p of the head which run together, in three-cornered fashion. A man's skull has
indeed been observed without any suture at all" {^H. A. iii. 7, 3). The latter statement is
borrowed from Herodotus, ix. 83. The three sutures meant are the Sagittal and the two
divisions of the Lambdoid, which run together and form three angles. The Coronal
suture would riot, be a suture of the cranium in A.'s view, because he makes the frontal
bone a bone of the face (cf. Note 21). The account then of the male skull is intelligible
.enough. Doubtless battle-fields would furnish from time to time specimens for observa-
tion, as in the case taken by A. from Herodotus. But it is difficult to account for
the statement as to the female skull. The sutures are really identical with those of the
male. Of course the opportunities of seeing a female skull would be much fewer than
of seeing a male skull ; for battle-fields would no longer be of service. Still it is not
impossible that A.'s statement may have been founded on some 'single observatiori. For
it is by r\o means uncommon for the sutures on the vertex to become more or less effaced
in pregnant women; so common indeed is it, that the naijie "puerperal osteophyte"
has been given to the condition by Rokitansky {Path. Anat.'iu. 208, Syd. Soc. Transl.).
A woman's skull may have been observed in which the Sagittal suture had thus
disappeared ; when the Lambdoid, with the lateral sutures, and the Coronal, might
fairly be described as forming together a circular suture. It must not be forgotten what
great difficulty there was in A.'s time in getting a sight of human bones. Even much
later Galen, it is said, went all the way to Egypt for the purpose of seeing merely a
bronze representation of the human skeleton {Ctevier, Hist. d. Sc. i. 59). A well-known-
story is told of Democritus, how he was in the habit of wandering about among tombs
and was therefore supposed by his fellow-citizens to be mad ; and how the great
Hippocrates was sent to see him, and, having heard his account, pronounced him not
only to be sane, but the sanest of men. Cuvier explains this strange habit of Democritus,
by supposing that his object was -to find "quelques pieces osteologiques " !

27. A. is ridiculed by Galen for having made the brain 110 more than a spongeful of

.Notes, ii'. 7 — 8, 169

cold water. It is plain, however, that in reality he assigned to it an office scarcely less
important than that he attached to the heart. It is tnie he made this latter the actual
sensory centre, but he represented it as so directly dependent upon the brain for. the
discharge of its functions, and as so instantaneously aflfected by any change which occurs
in this organ, that heart and brain came as it were to form one consolidated organ.
Seeing that it was impossible for A, to admit the doctrine which made the brain the
sensory centre (ii. lo, Note 9), it was necessary for him to devise some other account
of the matter ; and the ingenious hypothesis he put forth had at least this merit that it
apparently covered all the anatomical, physiological, and pathological facts, actual or
supposed, with which he was acquainted. It seemed for instance to explain : (i). The
supposed absence of any anatomical connection between brain and sense-organs (ii. 10,
Not.e 9). (2). The presence of connecting links between these organs and the heart.
For A. imagined that the heart itself was the sense-organ of touch and taste (ii. 10,
Note 10), and that the other sense-organs, ear, eye, nostril, were connected by certain
ducts or passages (ii. 10, Note 19) with the blood-vessels, and through these of course with
the heart (Z>. G. ii. 6, 32). (3). The apparent insensibility of the brain when touched
(ii. 7, Note 5). (4). The fact that keenness of sensibility is diminished or annulled in
anaemic • parts, increased in hyperaemic ; and that parts naturally without blood are not
sensitive (ii. 10, 14). (5). The supposed bloodlessness of the brain-substance (ii. 10,
Note 18). (6), The fact that the heart is the centre of the vascular system. (7). That
the heart is the firet part to enter. into activity and the last to stop work, ^^ primuni vivens,
ultimum martens" (Z>. G^. ii. 5, 11), and therefore probably the seat of the essential
characteristic of animal life, viz. sensibility. (8). The augmentation or, diminution of the
heart's action when intense pleasure or pain is experienced. (9). The loss of sensibility from
loss of blood {H. A. iii; 19, §). (10). The loss of sensibility and other psychical effects
of brain lesion, as explained in the text. (11). The position of the heart in the centre of
the body (ii. 2, . Note 6), a dignified and safe position, as of an acropolis (iii. 7, iij,
worthy of so high an office. One of the main difficulties .which led A. astray in.thisj
_ matter was the apparent want of anatomical connection between brain and sense-organs.^
A very few years later Erasistratus and Herophilus (whose name still lives in the ,
torcular Herophili) showed that such a connection did exist, in the nerves, which they
were among the first to separate from tendons, ligaments and. the like. Since that i
day the doctrine which A. repudiated has been universally recognised as true. The
unscientific world, however, feeling the heart throb or slacken in joy or grief, still makes j
this organ the centre of their emotional feelings ; and the scientific world still recognises, '
as an undoubted fact, the intimate- connection and rapid sympathy between heart and
brain, which A. first pointed out. " En resume," says Claude Bernard, " chez Thomme
le coeur est le plus sensible des organes de la vie vegetative ; il re9oit le premier de tous
I'influence nerveuse cerebrale. Le cerveau est le plus sensible des organes de la vie
animale ; il re9oit le premier de tous I'influence de la circulation du sang. De la resulte
que ces deux organes culminants de la machine vivante soient dans des rapports incessans
d'action et de reaction. Le coeur et le cerveau se trouvent des lors dans une solidarite
d'actions reciproques des jJus intimes, "qui se multiplient et,se resseryent d'autant plus
que I'organisme devient plus developpe et plus delicat" {Revue d. deux Mondes, 1865,
t. Ivi. p. 250).

28.. Cf. ii. 3, Note 16.
. .29. D. G. i. 17, etc. '

(Ch. 8.) 1. What does A. mean by saying that Touch is the primary sense ? One is
tempted at first to attribute to him the view held by modern physiologists, that the higher

170 Notes, ii. 8—9.

sensibilities have been evolved by gradual differentiations of parts, originally endowed in
common with the rest of the .body with sensibility to resistance and to temperature, ■
both of which are included by A. under Touch ; in other words, that the remaining
special senses are but modifications of Touch or general sensibility. But in the treatise
on Sensafion (ch. 4) this view, which was held by Democritus, is expressly repudiated.
Touch is to A. the primary sense ; firstly, because it is the most universally distributed
of the senses ; no animals being without it, though they may be without any other
{D.A. iii. 13, 4 ; ii. 3, 8 ; H.A. i. 3, 3) ; and, secondly, because it is by touch that we
are able to recognise the four primary properties of matter (ii. i, Note 3; and D.A. ii. II).
"Touch," says John Hunter, "is the first sense, because no animal that ha.s a sense (as
far as I know) is without it, while there are many animals without the others." And
again, "Touch I call the first sense; it is the simplest mode of receiving impressions;
for all the other senses have this of touch in common with the peculiar or specific ; and
most probably there is not any part of the body, but what is, susceptible of simple feeling
or touch" {^Museum Cat. iii. 53, 51).

2. This passage seems to have baffled Frantzius, and with him Mr. Lewes. Yet its
meaning, is clear enough, especiaiUy if one compares it with such other passages as tlrose
quoted in ch. 10, Note 10, The flesh, A. there argues, is not the organ of touch, in
the sense that the eye is the organ of sight, or the ear of hearing,, but is simply the
medium through which the object affects the sense-organ ; and answers therefore to
the transparent medium, air or water, through which the • visible object acts on the
eye, or to the air through which sound acts upon the ear. In the present passage A.
says that inasmuch as there is air or water about an animal wherever it may move itself,
the requisite medium for sight or for hearing is always at hand, and there is no reason
why nature, even if she were able, should so attach the medium of these senses to the
sense-organ, as to make it an actual part of the body. But, in the case of touch, a solid
medium is required for the action of the object upon the sense-organ, and this can
only be always at hand, if it be permanently attached to the organ, and carried about
by the animal as part of its own body.

3. Cf. iv. 8, Note i ; as to Testacea, cf. iv. 5, Note 25.

4. Cf. iii. 9, Note 3 ; as to Insects, cf. iv. 6, Note i ; as to Cephajopods, iv. 9, Note i.

5. Cf.'iii. 4, Note 20.

6. Cf. iv. 9, Note 6.

7. Cf. Introd. p. xxix. Note i. "
(Ch. 9.) 1. What prevents the blood' from coagulating in the living vessels is still

unknown ; but certainly it is not rnere heat, as A. assumes. For moderate heat really
favours coagulation, and a temperature about that of the body is found to' be most
favourable to the process (cC HausorCs tVoris, Syd. Soc. p. 4).

2. i.e. Ball and socket joints, as of hip and shoulder. The next form, containing an
astragalus (cf. iv. 10, Note 44), -is the ancle joint. The third kind mentioned includes
arthrodial joints, e.g. the sterno-clavicular, carpal, etc., but probably refers more*
especially to the knee-joint with its semilunar cartilages.

■3. So also iv. 10, 44. To these advantages derived from the absence of abdominal
ribs might be added the facility afforded for the motion of the diaphragm during
respiration.

4. i.e. Of the truly viviparous, not the ovo-viparous such as the Selachia, whose bones
are cartilaginous. Cf. iv. i, Note 5.

6. Cf. ii. 6, Notes 5 and 6. '

G. The bon6s of birds contain a larger proportion of inorganic matter than do those

• Notes, ii. 9. 171

of other vertebrata. * This makes them more brittle, which is what A. must mean by
calling them weaker.

7. Here A. speaks of the bones of the smaller serpents as made of fish-spine ; else-
where (i v. II, 17) he says they are cartilaginous. In reality however the proportion of
inorganic matter in a snake's bones is very high, nearly as high as in the bones of birds ;
and this it is which gives so beautiful a whiteness and compact a look to a snake's
skeleton. I can find no confirmation of A. 's statement that there is a difference between
the bones of small and of large serpents. The only large ophidian he can possibly
have seen was the Coluber elaphis, which sometimes attains a length of six feet. His
information as to other large serpents was simply derived from Such "traveller's tales"
as that given at H. A. viii. 28, 10,

8. Cf. iv. 13, Notes i and 33. The skin of the fishes called Selachia by A. is studded
with numerous tubercles, granules, or spines, of bony matter ; a peculiarity designated
as " placoid " by modern ichthyologists. ' •

9. . It has been a matter of question, whether the credit of being the first to put forth
the law "of organic equivalents should be assigned to Geoffrey St. Hilaire or to Goethe ;
the former of whom spoke of it as " la Iqi de balancenlent organique," while tl^^ latter
expressed it in these terms, "Nature must save in one part in ordei: to spend in another." .
As a matter of fact, the law, whfether true or false, is perfectly recognised by Aristotle,
and is used by him over and over again in explanation of morphological phenomena.
We have" already had in this book one instance of this, when the inverse relation of fat
and the generative secretions was mentioned (cf. ii. 5, Note 9), and we shall come to
numerous others. Thus, for instance, is explained (ii. 14, Note 4) the coincidence of
long hair and short fail; thus also (iii. 2, Note 19) the want of upper front teeth in
horned animals ; thus again (iv. 9, Note 12) the great length of the arms in cephalopods
with a short body, and their comparative shortness when the body is long, etc. , etc.

10, Seeing how much attention A. gave to development, it is strange that he should
not have noticed that the osseous is preceded by a cartilaginous framework. Had he
done so, he would certainly have cited th© fact here, in support of his statement of the
essential identity of the two substances.

11. See also Hippocrates (Kilhn's ed. i. 319). When cartilage is fractured, •reunion
may be effected by fibrous or by calcareous tissue, but never by true cartitage ; whereas
when bone is fractured, reunion is effected by true osseous tissue. Frantzius and Lewes
find in this grounds for attacking the statement in the text. But in reality A. says
nothing about reunion of broken parts, and neither he nor Hippocrates can have been
ignorant of the common facts of the mending of a broken bone. • What is said is that
a piece of cartilage or of bone, if once excised, is never regenerated ; and though this
is not actually true, it is what every physiologist believed to be so till comparatively
a short time ago. The statement is founded partly on surgical experience, partly on
observations of mutilated animals. When a portion of bone is removed by the surgeon,
It is not regenerated unless the periosteum be left. This was unknown till Duhamel's
time, though Hippocrates was near it when he said, "An extensive fracturfc is less

■formidable if the periosteum be sound" (iii. 369), and A. also when he said, "A bone
becomes necrosed, if stripped bare of its membrane" {H. A. iiL 13, 2). No effort being
made by the ancients to preserve the periosteum, removal of bone was never followed
by regeneration. That excised cartilage is never replaced is still the general belief ; but
Legros and Peyraud" have recently showTi that regeneration can occur also in this tissue
if the perichondrium be preserved {ViixJumfs Jahresb. 1869, -p. 143). As to mutilated'
animals, it was known to A. i^H. A. ii. 17, 24) that when a lizard's tail is cut off, the

r

172 Notes, ii. 9 — 10. .

part in time is regenerated. It was believed until very recently that in this case the
restoration though externally complete did not extend to the lost vertebrse. . But Legros-
{Gaz. Midic. 1869, p. 75) has shown that even these bones are replaced after several
years' interval. More rapid restoration of bone had moreover already been observed by
Spallanzani to occur after the rem6val of the limbs of water-newts, and great was the
astonishment of physiologists when he announced this fact.

• 12. It will be noted that A. only likens nails, horns, hoofs, etc., to bone in their
tactile properties. In other passages {D. G. ii. 6, 50 ; H. A. iii. 9, 2) he says that the
former are all developed from the skin, and follow its changes of colour ; and he
distinguishes the group of dermal parts thus formed from the bones and the teeth ;
which latter he imagines are not dermal but osseous, because they remain white when the
skin is black.

13. Aft organ or heterogeneous part made from a single tissue .or homogeneous part
(to eVx»7/iaTf(r|U6ca) wrll have the same name as the tissue. Hoof, nail, cartilage is the
name of both organ and tissue. These might therefore be dealt with either among the
tissues, or among the organs. The latter plan, says A., is the better ; for it is only by
studying the purposes subserved " by the organ hoof or nail, that we can learn fhe nature
of the tissue hoof or nail, Cf. ii. I, Note 16.

(Ch. 10.) . 1. The discussion of the homogeneous parts, or tissues, is now finished, and
A. proceeds to consider the heterogeneous parts or organs.

■ 2, Strangely enough, A. after all does not follow the order here indicated, but begins
vvith the brain and other parts of the head, and then proceeds to the neck, thorax, and
abdomen, in succession ; following the simple plan of beginning at the top and goirig
downwards.

3. This limitation is introduced because some of the lower animals are without digestive
cavities at all (ii. 3, Note 9), and others {H. A. i. 2, 2) without excremental orifice.
By the latter A. probably meg-ns Acalephre, which have, he says (Z>. P. iv. 5, 49), no
visible excretion; though it must be admitted that elsewhere {H. Ai viii. 2, 15) he
speaks of them as having an excremental orifice.

4. Cf. ii. 3, Note 8.

5. A similar recognition of the truth, that simplicity of life and simplicity of structure
go hand in hand, will be found at iv. 7, i.

6. Cf. ii. 2, Note 5, and iv. 10, 8. ' •

7. That man alone is erect is repeatedly mentioned by A. as a proof of his superiority
to other animals. Doubtless the erect position, leaving as it does tjie upper extremities
free for skilful manual operations, is an important element in man's structure. But
this position is not the exclusive privilege of man ; some birds, as the penguin, and some
mammals, as the kangaroo, having a vertical attitude.

8. e.g. Plato in the Timaeus {Jowetfs Trans, ii. 568), who probably borrowed the
opinion, as Galen says he did his physiology generally, from Hippocrates. Democritus
also had taught that the sovereign part of the squI was in .the head ; and Diogenes of
ApoUonia, mofe directly, had held that the brain was the seat of sensation, being
surrounded by a layer of hot dry air, which was in connection with the sense-organs by
means of the blood-vessels, and so sympathised with their motions and affections (cf.
Grate's Plato, i. 65).

9. Hpw came A. to reject this view of the brain's office in favour of his own apparently
less plausible one ? The reasons seem to be as follows :

a. Firstly, as he says here, and repeats oftentimes (ii. 7, Note 5 ; //. A. iii. 19, 2),
the brain is insensible to external mechanical stimulation. If the brain of a living

\

. ' Notes, ii. lO. 173

ariimal be laid bare, as in A.'s vivisection of the chamseleon {H. A^ ii. 11), the hemispheres
may be cut witliout any signs of pain whatsoever, and without any struggling on the
part of the animal. This difficulty was insuperable to Aristotle. i3. He could find no
brain, nor anything apparently analogous to a brain, in any of the invertebrata, excepting
in the Cephalopods ; the cephalic ganglia in other animals having, owing to their
minute size, escaped his unaided vision.' Yet sensation was the special characteristic of
an. animal. The absence of a brain, then-, from numerous sentient creatures was quite
imcompatible with the notion that the brain was the sole organ of sensation. 7. The
brain he erroneously thought (cf. Note 18) to be bloodless, as also did Hippocrates ; and
all experience taught him that those parts alone were sensitive that contained blood
(cf. Note 20). 5, "It is manifest," he says (ii. 7, 4), "on inspection, that there is no
anatomical connection between brain and sense-organs." It has indeed been supposed
that he knew of the optic, auditory, and olfactory nerves (cf. Note 19). If he really
knew of them, he did not know that they united the sense-organs to the brain itself,
but thought that they led to the vascular membrane round it, or to the supposed empty
space behind it. They would thus be in connection with the blood, and so with the
heart, but not with the actual brain. It is true that in his account of the vivisection
of the chamseleon {H. A. ii. 11, 9) he says that the eyes are "continuous with the
brain," and elsewhere {De Sensu, 2, 20) that the eyes are "made out of the. brain";
but these, passages must be read in connection with others, such as D. G. ii. 6, 33, where
he says that "the purest part of the fluid which is about the brain is separated from it,
and passes to the eyes by the channels {ir6poi) which visibly connect them with the
membrane that surrounds the brain." «. Lastly, he believed that he had good grounds
for supposing another part, viz. the heart, to be the sensory centre (cf. ii. 7, Note 27).

10. The heart, according to A., is the sensorium commune ; but while three of the
five senses have also external organs, viz. the eyes, ears and nostrils, the remaining two,
viz. touch and its variety taste, have no such external organs, but are lodged in or close
to the heart itself, which is thus their first and also their final organ. "The question,"
says A., " whether the sense-organ lies internally or not, being on the latter supposition
the flesh itself, is not to be answered off-hand by adducing the fact that a sensation is felt
the moment the body is touched. For even if one were to stretch a piece of membrane
tightly over the surface of the body, a touch would equally call forth immediate signs
of sensation ; and yet it is plain that the membrane is not the sense-organ. Indeed
the fact adduced proves the contrary, for "the direct contact of an object with an organ
of sense in no case produces a sensation. Thus if a white body be placed in contact
with the eye, there is no sensation of whiteness. This shows plainly that the sense-
organ of touch lies deeper than the flesh. For the same must occur in the 'organ of
touch as in the organs of other senses. That is to say it must be, as they are, insensible
to objects in direct contact with it. The fact, then, that objects are felt when in contact
with the flesh shows that the flesh must be the medium which separates the sense-object
from the sense-organ ; the flesh and the tongue standing to touch and taste apparently
in the same relation as do air and water to sight and .hearing" {D. A. ii. il). So, again,
' ' If the coloured body be placed in direct contact with the eye, the eye will not see it.
There must be a transparent medium, such' as air, which is set in motion by the colour,
and which in turn sets in motion the sense-organ, with which it is in continuity. For
Democritus was mistaken in supposing that, if the interval* between the eye and the
object were a vacuum, vision would be so distinct, that we should be able to discern
even an ant though it were at the distance of the heaven. ... In reality, with a
vacuum for a medium, there would be no vision at all. The same is true in the case

174 *. Notes, ii. lo. • .

of hearing or of smellgig. A smell or a sound sets the medium in motion, and this
in turn sets the organ of sense in motion. But .when the substance from which .the sound
or smell proceeds is placed directly upon the sense-organ, it produces no sensation. .The
same is true of touch, though it is not so evident for reasons to be given hereafter.
The medium in the case of sound is air ; in the case of smell it has no designation.
For smell is an affection alike of air and of water. Just as any transparent substance
is a medium for colour, so smell can occur in either water or air. For even water
animals appear to have this sense " {JD. A. ii. 7).

11. Cf. De Sensu, 2. The eye is placed near the brain, because the eye is developed
from it (Z>. G. ii. 6, 33) ; the ear, because it requires to be near the space in the occiput'
which is full of air ; the organ of smell, because smell is of a hot character and so can
temper the coldness of the brain {De Sensu, 5, 18). All three senses, moreover, derive
advantage, as stated further on in thjs chapter (-see also iv. 10, 4), from being- in a part
where the blood is pure, and heat moderate. Can A. possibly have felt satisfied v/ith
this explanation?

12. Not so. In some Annulosa there are ocelli on the gills, on each segment, or
even on the tail. Scallops, ag^in, have eye-specks on the edge of the mantle ; and
star-fishes at the ends of their rays. A. thought that scallops could see {H. A. iv. 8, 32),
though he had not made out their eye-specks.

13. One might suppose from this passage that the excavations near the anterior part
of the snout, which constitute in fishes the external organs of smell, had entirely
escaped A.'s notice. But this was not so, as appears from a passage {H. A. iv. 8, 9),
where he mentions these recesses, and says that some Consider them to be organs of
sense. This, however, he will not admit, because " the passages (iropoi) do not appear
to lead .to the brain, but are either blind or lead to the gills. " His notion was that in
fishes the gills were the external •organs of smell (cf. ii. 16, Note 10) ; and his reason
for so thinking appears to have been this. In man the' nostrils serve for the admission
of air, and at the same time for olfaction. In fishes the gills serve for the admission of
water, and so correspond to the nostrils, the water in fishes and the air in man serving
one and the same purpose, viz. refrigeration. Finding this correspondence in one point
between gills and nostrils, A. assumed that they corresponded in other matters, and so
assigned to the gills the olfactory duties of the nostrils. Similarly he supposed that
CetAcea smell by the blow-hole, though he did not apparently recognise the fact that
this corresponds anatomically to the nostrils ; and, 'again, that in insects the same part
.served for smell as for cooling the body. That fishes can smell A. inferred from their
refusing as a rule to .take stinking bait ; and that they can hear, from th6 care which
fishermen have to take to avoid making a noise with oars or nets when they approach
a shoal {ff. A. iv. 8, 15). There is no communication in fishes between the internal
ear and the outer surface ; and the existence of the internal ear entirely escaped
Aristotle's notice. He nowhere says how he supposes fishes to hear.

14. Cf. ii. 7, Note 4. ' '

15. Cf. ii. I, Note 12,

• 16. " The fapulty of sight does not belong to the eye, because it is of water, but
because it is transparent, a quality which exists in air no less than in water. But water
is less elastic, and more easily kept in place than air, and on this, account the eye is
made of it That the eye is made of it, is manifest from the fact, that water runs
out of it when it is ruptured" {£>e Sensu, ch. 2, 12). '

17". Cf. ii. 7, Note 12. . . <

18. There are in this chapter, as in other passages, three very strange statements

'Notes, ii. ip. 175

as to the brain : firstly, that it only occupies the front portion of the skull, there
being an. empty space behind it ; secondly, that it is entirely destitute of blood-
vessels ; and, 'thirdly, that it is cold to the touch. For the two first of these
it is perhaps unfair to hold A. as directly responsible, seeing they are both to be
found in Hippocrates [Kiihn^s edit. i. 683, iii. 349), and may have been accepted by A.
on his authority without personal examination into the matter. Still A. did. undoubtedly
himself examine the brains of some animals, and we have to consider how a man who
was certainly no utterly mean observer can have reconciled what he learnt from authority
with what he saw himself. I suspect that the explanation is to be found in his having
only examined, and that imperfectly, the brains of fishes, tortoises, and other cold-
blooded animals. For while it is certain" that he did examine the brains of such animals,
there is no clear sign of his having examined the brains of any warm-blooded animal,
at any rate in a fresh conditionj though he inay very possibly havo examined them after
cooking, a process to- which he seemingly had resort (cf. ii. 7, 16), with the idea
of hardening them. Admitting this supposition to be correct, we can see how his
errors may have originated. For in Fishes and Reptiles the brain is not large enough
to fill the cranial cavity, a character to which Lamarck attached great importance in
distinguishing these groups from Mammails and Birds '(/'>4?7. Zool. i. z'jiy. Martinis edit.).
In the tortoise, for instance, the area- of a vertical section of the b'rain, according to
Desmoulins {Todd's Cycl. i. 724), is nearly a third less than the area of the cavity.
So also the brain completely fills the brain-case in embryonic fishes, but in the adult
only occupies a. small part of it, as its growth is by no means proportionate to that of
the cranium itself. That A. had noticed this is highly probable from his saying (Z?. G.
ii- 6, 35) that the brain of animals is at first of large size, but afterwards falls in and
becomes of smaller dimensions. So also in Cephalopods, animals specially studied by
A., and with whose so-called brain he was acquainted, the cavity in which the ganglia
arQ lodged is much larger than the ganglia themselves.

So much for the first error. Now for the second. The brain does as a' matter of
fact receive a very large amount of blood ; but by far the greatest part of this goes to
the superficial gray matter.. All this superficial blood A. reckoned as belonging to the
Pia mater, which he describes sis highly vascular. Either he did not see that the small
vessels were prolonged from this into the superficial brain-substance, or more probably
he considered this superficial substanc^, differing as it does from the mass below in
colour and. general aspect, to be part of the Pia mater itself, from which in fact he can
hardly have learnt to separate it mechanically. That this was really the view of the
Pia mater entertained by the ancients of his time is, I think, confirmed by the fact,
that when the nerves had afterwards been distinguished from' other white structures,
Erasistratus still maintained for many years that they ended in the Pia mater. It
seems inconceivable that lie can have so thought, unless he included in the Pia mater
the superficies of the brain itself. There are, however, numerous small vessels in that
white mass, which A. regarded as exclusively the brain. These are so «mall that on
section they appear only as bloody puncta, and are so barely visible in the brains of
fishes and tortoises, that they might easily escape notice. In the brain of a mammal
they are more apparent ; but if we imagine, as I have suggested, that A. only examined
sucji brains when cooked, they would have been quite invisible to him. Even had he
seen them, I do not think that, considering their minuteness and the general bloodlessness
of the part when compared with other organs, he would have attributed any importance
to their presence. The contrast in amount in the two cases would have seemed sufficient
to warrant him in speaking of the one organ as full of blood, and of the other as having

1/6 • Notes, ii. lo.

none at all. Similarly, though he knew there was some blood' in the lung of oviparous
vertebrates, he often speaks of it as bloodless, because the amount was insignificant, as
he thought, when compared with that in the lung of a mammal (iii. 6, Note lo).

So also I would explain the third error, that the brain is cold to the touch. He
very possibly found the basis for this Jiotion, which was essential for his interpretation
of the brain's function, in the brain of a fish or tortoise ; for it is extremely unlikely
that he even examined the brain of a warm-blooded animal while the warmth of life
was still in it. We must remember that the art of dissection was in its infancy, and
that even much later, in Galen's time, the mechanical difficulty of removing the calvaria
was such, that Galen recommends his readers, because of the imperfection of their
yistruments, to get from the butcher a head in which the brain was already exposed.
Nor must we neglect to make full allowance for the constant results of preconceived
theories. Every experimental physiologist must be painfully conscious how they thwart
his most honest intentions, and put a film between his eyes and his object. Aristotle
would have been more than human to have escaped this source of error.

19. What A. precisely meant by the passages, or channels, or pores (irSpoi) upon
which the sense-organs are placed, is very problematical. Meyer {T/iier/mnde; p. 42S)
takes him to mean the blood-vessels, .mainly because" this accords with the statement
{D. G.-v. 2, 2) that all these irSpoi pass to the heart. There is no doubt that vSpoi
is often used by A. to designate blood-vessels ; but I think it plain, that A. is here
speaking of something which is more distinctive of the sense-organs than the presence of
vessels, which they share with the rest of the body. Frantzius, following Schneider,
has no doubt that nerves are meant, and thus A. would have to be credited with the ana-
tomical discovery of the nerves of sense, or at any rate of the optic, auditory, and olfactory
nerves. ' I have little doubt that on several occasions where A. uses the term irSpos,
the thing he is speaking of is a nerve, as in Z>. G. ii. 6, 33, where he speaks of either
the optic nerve, or of some other nerve going to the eyfe, under this title. And agaiij in
this passage : " Cases have occurred, when men have been wounded in battle in the head,
in such a way that the irSpoi of the eye have been severed ; a sudden darkness has then
come over them, as though a lamp were extinguished, etc." (De Sensu, 2, 17); and
perhaps, though I am very doubtful, in the obscure passage in the Hist. An. (i. 16, 6).
Moreover, that he had seen the optic nerve is certain from his statement {H. A. ii. Ii, 9)
that the eye of the chamseleon is continuous* with the brain. Were he then only
speaking of the eye, it might fairly be admitted that its v6poi were its nerves ; and it
may be noted that in after-times Tr6poi was the term specially applied by Herophilus to
the nerves of the eye {Galen, De Usu part. iii. 12). But A. uses the same expression for
the other sense-organs. "All the sense-organs have it6poi connecting them with the
heart" (Z>. G. v. 2, 2). Now it seems to me exceedingly improbable that A. knew of the
olfactory or auditory nerves. He clearly looks on the nerve of the eye as something very
peculiar, and explains its presence by the eye being made of the same substance as the
brain, and therefore requiring a communicating passage by which the cold fluid of this
latter may pass into it (Z?. G. ii. 6, 33). This is quite incompatible with the notion that
he had seen similar leipoi. with similar substance going to the very dissimilar ear and nose.
Indeed, he expressly says that the ■n6po\. of these two sense-organs are full of " innate spirit,"
that is, of something physically like air (ii. 16, Note 11), and that they communicate with
the air outside the body. The way moreover in which he speaks of the auditory irfipos
in the text shows that he means something of the same character as the external meatus.
"There is a idpoi which leads back again from the ear to the hinder part of the head."
The same notion is apparent in what he says of the olfactory organs of fishes (cf. Note 13).

Notes. \\. lo. . 177

He refuses to admit that the nasal passages in these animals are organs of smell because
they end blindly, and do not lead to the brain. Clearly he knew nothing then of the
olfactory nerves of these animals. What he looked for in a sense-organ of sight, hearing,
or smell, was not a nerve, but an opening of some kind leading to the inside of the skull.

On the whole I think it most probable that by it6pot. in this place A. means no more
than openings or foramina by which the sense-organs are in communication with the
interior of the skull ; in the eye, the optic and other fissures or foramina of the orbit ;
in the ear, the external and internal meatus ; and in the nose, the anterior nares and
possibly the ethmoidal foramina, which he may have noticed, small as they are, in a
dog's skull ; though I am by no means sure he may not have thought the communication
was completed by the Eustachian tube, with which he was acquainted. {^. A. i. II, 2),
a view which would explain his statement that the olfactory itipoi, no less than the
auditory, are full of hot air.

The various foramina or passages place the sense-organ in communication with the
vascular membrane that surrounds the brain, and the connection with the heart is
completed by means of the blood-vessels that run to it from this membrane. So I
interpret the words, "These vipoi lead into the small vessels which extend from the
heart to the brain and surround this latter " (Z>. G. ii. 6, 32).

The difficulty of interpreting A.'s exact meaning is probably due to the fact that he
was himself not quite certain as to the channels by which he supposed the ear and
nostrils to communicate with the inside the skull. For his account of the auditory
■jTtJpos differs in each of the three main treatises. In the Hist. An. (i. II, 2) it is positively
asserted that there is no vipos leading to the brain from the inner ear, there being
however a blood-vessel which connects the two, and a ttlpos (the Eustachian tube)
running to the mouth. Here in the De Partibus he speaks of a iro'poy running from the
ear to the empty space in the occiput ; while in the Z>^ Generaiione (ii. 6, 32) he says
that it runs to the vessels on the surface of the brain,

20. The argument is this : The channels from the eyes end in the blood-vessels
outside the brain, and blood itself is insensible. The channels from the ears end in
the void space, where there are no blood-vessels ; and no part without blood-vessels
is sensitive. Neither the sensibility of the eyes nor that of the ears can therefore be
explained simply by their connection with the interior of the cranium.

The last sentence in this paragraph with its empty repetition is, I doubt not, an
interpolation.

21.' Gf. Note 10, and ii. 8, Note 2.

22. The sense of taste "appears to have a greater analogy to touch .than any of the
others, and appears to be as universal, few animals being endowed with touch, but
what are most probably also endowed with taste " (y. Hunter). The close connection
of touch and taste is shown in the fact that, while the nerves that minister to the
other special senses are exclusively channels of their respective special sensations,
those which minister to taste are at the same time nerves of ordinary tactile sensibility.
This was of course unknown to A., who rests his statement of the similarity of the
two senses on the fact that they both require actual contact of the object with the
body, whereas the other three senses are affected by distant objects (cf. D. A. H. 10, l).

23. Alluding to snakes and seals, cf. iv. II, Note 10.

24. A. explains (/). A. ii. 9, 12) the manner in which respiration is essential to
smell, in such animals^ as have lungs, as follows : " Some animals have their eyes bare,
and thus see what occurs in the transparent medium directly. Others have their eyes
covered with lids, which protect them as the shards protect a beetle's wings, and these

12

178 Notes, ii. 10 — 13.

animals only see wTien this covering is drawn back. So also is it with the organ of
smell. In some animals this lies bare and exposed. But in those that have lungs it
is covered, and the covering is removed by the act of inspiration ; for this dilates the
channels and vessels." See also De Sensu, 5, 24. By saying that there is a covering
he probably only means that there is something analogous to the covering of the eye ;
this something being the contracted condition of the nasal passages, which are dilated
when air enters.

25. A. accounts for the nostrils being where they are by the necessity of their
coinciding with the organs for admission of air ; but gives no reason why these organs
should be central.

(Ch. 11.) 1. '"Man is the only animal with ears that are incapable of motion"
[^H. A. i. 1 1, 2). As to the use of a large concha, cf. D. G. v. 2, 8.

(Ch. 12.) 1. Birds have no concha, neither have Reptiles. But in some birds "which
enjoy the locomotive or visual faculties in a less perfect degree than the rest of the
class, there is found a peculiar arrangement of the feathers round the external meatus,
which serves in some degree the office of an external ear. The Ostrich and Bustard
are so provided, and these birds can raise the auditory circle of plumes to catch
distinctly any distant sound that may alarm them. The Owls again are furnished with
a large crescentic flap, or valve " {Todd's Cycl. i. 308).

2. Because ears made of hard skin would not be readily moveable. See what he
says in the next chapter as to moveable eyelids.

3. Elsewhere (Z). G. v. 2, 10) it is said that external ears would not only be useless
but prejudicial to seals, as they would allow of the entrance of water. The true
teleological explanation of the absence of external ears from these animals, as also
from cetacea and birds, is apparently, as Hunter pointed out, that they would be a
hindrance to progressive motion,

4. " The seal is as it were a stunted quadruped. For it has feet immediately after
its shoulder-blade, and these feet are like hands, just as in the bear. For each foot
has five digits, and each digit has three joints and a small nail. The hind-feet also
have each five digits, and joints and nails, like the fore-feet, but in shape they resemble
the tail of a fish " {H. A. ii. i, 14). Thus it appears that A. thought that the seal
had IK) humerus nor ulna, their shortness disguising their presence in the undissected
animal.

(Ch. 13.) 1. The "heavy-bodied" birds are described in various passages as living
on the ground, being unsuited for flight, liking to roll in the dust, not constructing
regular nests, and frequently having spurs. Partridges, quails, pheasants, common
fowls, are mentioned as belonging to the group, which clearly corresponds generally
to our Gallinacese.

2. In birds, aS a rule, as also in chelonia, in crocodiles, and in frogs, the lower lid
is much larger and more moveable than the upper one, and it is with it therefore that
the eye is closed in sleep. There are, however, some few exceptions. Thus in the
.nightjar and in the owls the upper lid is the more moveable of the two. Tliis latter
exception is noticed by A. elsewhere {H. A. ii. 12, 7). In many parrots also the two
lids are equally mobile. This is not noticed by A., who probably never saw a living
parrot (cf. ii. 17, Note 3). He does, however, a few sentences later, say that pigeons
use both lids to close the eye, which also is a correct observation. A. both here and
elsewhere speaks erroneously of a nictitating membrane as peculiar to birds. For,
though it is especially well developed in birds, yet it is to be found in numerous
reptiles, amphibia, and sharks, not to mention some mammals.

Notes, ii. 13 — 14. 179

3. That is to say, it is an involuntary reflex action.

4. This is an unfortunate statement, borrowed however from Hippocrates [Kuhn^s ed.
i. 319 ; iii. 752). Firstly, the presence of flesh, i.e. of muscular tissue, is not essential
for reunion after section ; secondly, the eyelid does contain muscular tissue ; and,
lastly, cuts both in it and in the prepuce can be made to unite bytproper appliances.
It is true, however, as Frantzius points outs, that owing to the looseness of the
subcutaneous tissue in these .parts, the inflammatory swelling after a wound is very
considerable, and keeps the edges of the wound widely apart, so that it requires •
careful attention to produce reunion. Still such can be brought about wheij desirable ;
but in the case of the prepuce it is usually the object of the surgeon to prevent reunion.

6. Because a hard skin, as stated farther on, cannot move with due rapidity. Compare
what he says (iii. 3, Note 8) as to the motion of the epiglottis, and (ii. 12, Note 2) of
the ears. The mobility of the lid does really stand in direct relation with the delicacy
of the' integument which forms it. Thus the skin of the lower lid {Todd''s Cycl. iii. 94)
is naked and finer than that of the upper lid in birds and chelonia, and as already
noted (Note 2) is the more moveable one.

6. Cf. ii. 9, Note 9.

7. " Upon thick skins, the hair is generally harsh and thick, .... and the case
is similar in those animals that are covered with scales or scutes " {^H. A. iii. 10, 2).
The character of the hair seems really to tvary with the thickness of the skin, cf. Low,
Domest. Anim. p. 368.

8. Or rather, of a moveable upper eyelid.

9. And by all other birds also (cf. H. A. ii. 12, 7).

10. Cf. ii.2, Note 6.

1 1 . There are exceptions among fishes, particularly in sharks.

12. A. 's knowledge of Crustacea was confined, or nearly so, to Podophthalmata, in
which the eyes are supported on moveable peduncles. Insects have, almost invariably,
sessile and motionless eyes ; and though in a few instances the eyes are on peduncles,
these peduncles are not moveable like those of Crustacea. The mobility of the eyes of
Crustacea, as compared with Insecta, is to be looked on as an atonement for the smaller
mobility of their heads, which are fused with the thorax.

(Ch. 14.) 1. Birds as a rule have no eyelashes. There are however a few exceptions ;
the ostrich, as here mentioned, and the rhea ; some parrots also, owls, and hombills.
But in these "they are rather feathers with short barbs than true eyelashes" (Otven).
As to the ostrich, cf. iv. 14, Note 2.

2. Cf. ii. 2, Note 6.

3. So far as I can ascertain it is true that man is the only mammal with a distinct
marginal lower eyelash, with the exception of some monkeys, an exception elsewhere
(J7. A. ii. 8, 4) recognised by A., and some few antelopes. In very many mammals,
especially the smaller kinds, there are no eyelashes at all. In the larger kinds, as a rule,
the upper lash is well developed and marginal, while the lower lash is represented, as
A. rightly says, by some long straggling hairs set below the lid, not on its margin.

4. In the horse the stump is short and furnished with long hair ; while in the ass it
is long, and the hair short except at the extremity. It is, however, evident that the rule
which A. lays down is far from being of universal application. Still the idea is not
so utterly absurd as it appears at first sight. For the tail of an animal, consisting in
great part of tegumentary tissues, is in reality liable to vary with . other tegumentary
structures, such as hair, teeth, horns. The variations however which occur simultaneously
in this group of structures are not always such as can be explained by the law of organic

i8o Notes, ii. 14 — 16.

equivalents, according to which excess in one part should be balanced by deficiency in
another. This does sometimes occur, as when animals with unusually redundant hair
are, as not rarely, deficiently supplied with teeth. Many instances of such an occurrence
in the human species are given in The Field of Feb. 14, 1874. But more commonly
the variations in tl»e allied parts occur in the same direction, excess or deficiency in the
one attending excess or deficiency in the other. Thus the well-known Julia Pastrana to
a monstrous excess of hair added a doubled set of teeth ; and Mr. Darwin quotes an
agriculturist as asserting that "pigs' with little hair on their bodies are most liable to
lose their tails, showing a weakness of the tegumental structure. It may be prevented
by crossing with a more hairy breed " {Dom. An. and Plattis, ii. 327).

6. Cf. ii. 9, Note 9. The tail in the typical bears is remarkably short, and the body
usually covered with very long shaggy hair.

6. The moisture of the brain and the heat of the blood on its surface escape, according
to A., by the sutures (cf. ii. 7, Note 23). As to fluidity of brain, cf. ii. 7, Note 4.

7. The subject is discussed 'at length in D. G. v. 3.

(Ch. 15. ) 1. The explanation and the comparison are borrowed from Xenophon {Mem.
i. 4, 6), who puts them into the mouth of Socrates. Somewhat similarly we have
"my penthouse eyebrows" in Dryden, and "his penthouse lid" in Shakespeare.

2. Cf. ii. 14, Note 6.
. 3. Ci. H.A. iii. 11, 11.

4. In truth the hypertrophy which follows an increased blood-supply is more distinctly
marked in the case of hair than of other parts. It is well known that long hairs are
developed in the hyperaemic circle round old sores, ulcers, etc. I have several times
seen the hair on the hypersemic ear of a young rabbit, after sectioa of the cervical
sympathetic, become longer than that on the opposite side.

It will be remembered that A. was ignorant of the circulation of the blood. He
supposed that the blood passed from the heart to the various parts by the vessels, but
knew nothing of its returning. Thus when the blood reached the peripheral ends of
the vessels, it had to pass out in some form or other ; that which escaped internally
formed the viscera, that which escaped externally formed hair and the like. Thus the
hair was . in a certain sense an excretion (cf. ii. 3, Note 8). So also was it regarded
by Bacon {Nat. Hist. cent. I, sect. 58) : "Living creatures put forth (after ;;heir period
of growth) nothing that is young, but hair and nails, which are excrements and no parts."
So also Shakespeare :

"Your bedded hair, like life in excrements,

Start up and stand on end " (Hamlet, iii. 4).
Very similar is the view expressed by Sir J. Paget {Swg. Pathol. Led. z).

5. Such purposes as the growth of feathers, scales, and the like (cf iii. 7, Note 2).
(Ch. 16.) 1. Cf. Tennenfs Ceylon, ii. 388.

2. The elephant is very fond of bathing, and often frequents marshy ground. But
Aristotle appears to have imagined its habits of life to be much more aquatic than they
really are. Elsewhere however {^H. A. ix. 46, 2) it is said that the elephant lives not in
rivers but on their banks; and is unable to swim on account of its heavy weight.

3. From this curious passage it would appear that the ancients were already acquainted
with some form of diving apparatus corresponding to the submarine helmet and tubes in
use at the present time. It may, however, have been some very simple instrument, such
as the reed, by means of which Australian natives are said to be able to swim for a
distance under water, so as to approach a flock of ducks without being seen. There
is another passage in Aristotle which shows that the diving bell also was known

Kotes. ii. i6. i8i

in his time : " Divers breathe by letting down a metallic vessel. For this does not get
filled with water, but retains the air within it" {Probl. xxxii.).

The elephant does in fact use its trunk in the way described when crossing a deep
river (cf. Tennenfs Ceylon^ ii. 310).

4. This story comes from Herodotus (iv. 183). It is there stated that in a certain
part of Africa, inhabited by the Garamantes, there are oxen that walk backwards while
grazing, "for their horns are so bent as to render it impossible for them to move
forwards while grazing, as the horns would stick into the ground in front of them.
These oxen differ in no other respects than this from ordinary oxen, excepting that their
hides are thicker and harder." This has been copied by Pliny (A^. Hist. viii. 45) and
others. Heeren finds a foundation for the story in the fact that the horns of cattle
among the nomad tribes of Africa are not uncommonly so bent by the herdsmen that one
projects forwards, the other backwards ; and cattle of this kind are, he says, to be found
represented on Nubian monuments.

There is an Egyptian wall-painting in the British Museum (No. 169) which I suppose
to be such a , representation as Heeren alludes to. One horn is there made to project
straight forwards and the other backwards. I attribute the appearance to the artist's
inability to deal properly with perspective. Still such a painting may have been the
source of the strange account.

5. It is of course true that one single part is often used for several separate
purposes, but it is no less true that such an accumulation of functions is a mark of
inferiority of organisation, as indeed is fully recognised elsewhere by Aristotle. See
for instance iv. 6, Note 15, where he says that nature when it is possible provides separate
organs for separate offices, instead of acting like a coppersmith, who for cheapness
makes "a spit and lamp-holder " all in one.

6. The foot of the elephant is furnished with five flat hoofs, which correspond to the
five toes ; these latter being distinct enough in the skeleton, but, in the living animal,
concealed "within the thick skin, though indicated externally by the divisions of the hoof.
A. thus describes it elsewhere: "All animals that have toes have nails, excepting
the elephant. For in this animal the toes are not separated nor clearly distinct,
and there are no nails whatsoever " {H. A. iii. 9, 6). I do not think that A. ever
saw an elephant. Had he himself examined the animal, he would hardly have said it
had no nails whatsoever, nails of course including hoofs. (Cf. next note, and Introd.,
pp. xiii-xiv.)

7. It was the general belief of the ancients that the elephant had no joints in its legs
and was therefore unable to lie down, but slept leaning against a tree (iv. 10, Note 38).
This notion. Sir T. Browne complains (Fu/gar Errors, iii. l), was still in his time "alive
and epidemicall in England and Italy, although we have had the advantage in England
not many years past of an elephant shown in many parts thereof, not only in the
posture of standing but kneeling and lying down, whereby although the opinion at
present be well suppressed, yet from some strings of tradition and fruitful recurrence
of error, it may revive in the next generation again, this being not the first that hath
been seen in England." Sir T. Browne's anticipation was realised, and almost up to
the present day traces of the old eyror are to be- found in our literature. Aristotle
however escaped the mistake ; though the inaccuracy of his own account renders it
probable that he had never himself seen an elephant, but described it at second-hand.
"The elephant," he say's, "is not made as some would have it, but is able to bend
its legs so as to rest on the ground. Its great weight however renders it impossible
for it to bend tli« legs on both sides at once. It sinks down therefore on one side

1 82 Notes, ii. i6.

or the other, right or left as Ihe case may be, and sleeps in that position. Its hind
legs it bends in the same way as a man" (Z^. A. iL i, 9). The reader will find an-
interesting discussion explaining the probable source of the ancient belief in this
matter in TennettCs Ceylon.

8. In the present day the term " respiration " is commonly used to designate the
process by which a gaseous interchange is effected between the blood and the medium,
be the organs in which the process is wrought what they may. But A. uses it exclusively
for the act of inspiring and expiring air from lungs. The purpose of this was, he
thought, to produce cooling. But, though a similar result was obtained by the water
acting on the gills, he did not apply the term respiration to this latter process, not
crediting the existence of air in water. This was known to Galen, who supposed
{De Usu part. vi. 9) that the air got into the gills through little holes, which, though
large enough to admit air, were yet too small to admit water. As to the reasons why
A. supposed fishes to smell by the gills) cf. Note 10.

9. It is of course of the Cetacea that A. is speaking. It must be an accidental slip
that makes him include them here amongst animals that do not breathe ; for he
frequently mentions the fact that they have lungs. The blowhole corresponds
anatomically to the nostrils. It is however very doubtful whether any of the
Cetacea can smell. Dolphins and porpoises at any rate must bfe unable to do so ;
for they have no olfactory nerves.

10. Frantzius gives up the hypozoma as unintelligible. There is however no doubt
what A. means by it. It is the waist or border-line between thorax and abdomen ;
which in insects is especially distinct. Nor is there any difficulty in understanding why
A. located the sense of smell in this part of an insect's body. He says that the part
below this hypozoma is that which in insects functionally corresponds to the lungs or
gills of higher animals ; that is, is the organ through which cooling is produced. This
is brought about by there being in this region a portion with a membranous covering,
much thinner than the rest of the integument, so as to allow of the escape of heat.
The cooling is effected not by the external air, but by the fanning motions of the internal
"innate spirit." The motions are visible in the alternate rise and fall of the part of
the body in question. Not only is this thin membranous part the organ of refrigeration ;
but it also corresponds to the lung in another way. It is the organ of sound ; and thus
it is that there is a special cleft in this part in those Cicadae that are said to sing, but no
such special cleft in those that do not sing (ZT. A. iv. 9, 3 ; De Som. 2, 17).

It is plain that A. is speaking of the so-called drums of the Cicadae, which are placed
on the first segment of the abdomen, that is directly below the hypozoma, and which are,
as he rightly says, the organs by which these insects produce sounds. Though he
describes these rightly as specially belonging to the Cicadae, yet he seems to think there
is something of the same sort in all insects that make buzzing sounds, as bees, wasps,
and the like, probably alluding to the thinner portions of integument which lie between
the successive segments of the abdomen. That these " drums", serve as the equivalent
of the respiratory organs of higher animals is incorrect ; yet the notion was by no means
an unnatural one. The motions of the abdomen to which A. refers are of course the
alternate contractions and dilatations by which air is exjielled and inhaled, from and
into the tracheal system.

We can now see why A. supposed the olfactory sense of insects to be located in the
hypozoma or rather in the part below it. It was the same reason as that which made
him believe that the gills of fishes (cf. ii. 10, Note, 13) and the blowhole of Cetacea were
organs of smell ; the reason being that gills, blowhole, hypozoma, corresponded to the

Notes, ii. i6. 183

nostrils in one respect, viz. as regards the refrigerating process, and therefore probably
corresponded to them in others.

That insects perceive odours is unquestionable. But it is still uncertain where their
olfactory organs are situated. It is supposed by some writers at any rate that the
stigmata which admit air, and which are mostly "below \hQ- hypozoma" are also the
parts which admit olfactory stimulants, " the ultimate ramifications of the tracheae forming
one extensive nose." This view (erroneous as I believe) coincides very fairly with that
of Aristotle.

II. A. often speaks of the innate spirit [ijxipvTov irvevna), and distinguishes it from the
spirit or breath that is introduced from without (irveC/ua Heiaaicrov). It is however far
from clear what his conception of this innate spirit really was.

There is indeed a special treatise De Spiritu, but this is .most undoubtedly spurious.
One sufficient proof of this is that whereas A. in his genuine works gives the same name
(<f Ae'jSej) to both arteries and veins, and states positively that they both in life contain
blood, the author of this treatise has already learnt to apply the term "arteries" to the
former, reserving the term <p\(0es for the latter ; and moreover asserts that the arteries
contain air, not blood. The term apr-tjpia in Aristotle always means trachea, or its
larger divisions the right and left bronchus, and is never used for any blood-vessel. So
again while A. expressly states, in the passage to which this is a note, that the innate
spirit is not introduced from without, the author of the De Spiritu says that it varies in
amount at different times, and discusses the question whether the increased amount is
derived from the food or from the inspired air. Neglecting then this spurious treatise,
and putting together the genuine 'passages in which A. speaks, or seems to speak, of the
innate spirit, the following seems to me to be his view.

The " vital heat" which is the immediate agent of the soul in its operations (Z?. G. ii.
4, 43) is not common heat, but something with much greater efficacy. The heat of fire
cannot effect digestion, cannot convert blood into fat or the like (ii. 6, Note 7), nor cause
the development of the embryo (Z>. G. ii. 3, 13). It is only the vital heat, or the celestial
heat of the sun, that can do this. Of this heat, derived from the heavenly bodies, there
is a store in the air or spirit which is contained in every fluid ; and as everything
contains water, "everything is in a sense full of soul " or life (Z>. G. iii. ii, i6).
This air or spirit with its stored-up celestial heat is imparted to the embryo in the
sperm, of which it forms the active principle; so that "man is produced by man
and by the sun" {Pkys. ii. 2, 11), or, in animals generated spontaneously, is imparted
in the fluid from which they originate. Thus in all animals it is innate ; and it is
on the proportion of this vitalized air or innate spirit that enters into their composition
that the greater or less nobility of all animals depends {D. G. ii. 3, 1 1 ). This innate
spirit with its vitalizing heat is comparable to, if not identical with, the heavenly aether
of which celestial bodies are made (Z>. G. ii. 3, 12), and becomes the agent of the
soul in its operations. Its central seat is the heart, and because it is there, this organ
becomes the centre of sensation, motion, and vitality generally.

In short, the innate spirit is the material in which the soul is incorporate, a material
akin to, or identical with, the celestial sether.

A.'s views as to the innate spirit, or innate heat, prevailed for many centuries, and
are discussed in Harvey's work on Generation [Exei'cit. Ixxi).

As regards the mode in which the innate spirit ministers to the soul, the following
seems to have been A.'s view. The innate spirit is a suitable agent of the nutritive soul
in virtue of its special heat, the use of heat in concoction, growth, development,
being evident. It is also a suitable substance to act as the agent of the soul in sensation,

1 84 Notes, ii. i6. 17.

because it has physically the character of hot air, and therefore, as air, is capable of
receiving the motions, or as we should say the vibrations, of the medium, which are
communicated to it through the agency of the several sense-organs ; these sense-organs
either lying directly in contiguity with the heart, that is with the central seat of the
spirit, (as in the case of touch and taste), or communicating with it or its accessory blood-
vessels by means of ducts, themselves filled with innate spirit, as in the case of hearing
and of smell (Z>. G. ii. 6, 32). So also the innate spirit is a suitable agent for the
production of motion. For, as air, it has the faculty of expansion and of contraction
by means of changes in its heat ; and the motion of parts, which is either a being
thrust forward or a being pulled back, can only be brought about by an agent that
itself- expands and contracts {De Mot. An. 10).

A. seems to have pictured to himself the motions of the body as produced in the
following way. The spirit in the heart by its changes of bulk acts on the numerous
tendinous cords inside that organ (iii. 4, Note 20), and these, being continuous with
the sinews which are attached to the various bones, in turn act upon them.

12. Cf. Note 5.

13. Most would say that man has the more delicate sense because he has the more
delicate organ. But A. usually inverts the statement ; for he insists that nature does
not take a man who chances to have a flute and teach him to play on it, but takes
a man who can play and gives him a flute (iv. 10, 20). There is however a passage
in a later treatise in which A. says that " In each case nature gives organ and
function simultaneously ; for such is the best plan. The parts in which secretions
occur are formed simultaneously with the function of secretion, and with its matter.
There is no such thing as vision without an eye, nor perfect eye without vision, etc."
{D. G. iv. I, 32).

14. That man is superior to other animals in touch, but inferior to them in the
other senses, is often stated by A. {De Sensu. 4, 2 ; D. A. ii. % l; H. A. \. 15,14).
Compare Bichat {Anat. Gin. i. 117) and Cuvier {Anat. Cotnp. ii. 538). Elsewhere
(D. G. V. 2, 8) A. explains that man's inferiority consists merely in his not seeing,
hearing, or smelling, objects at so great a distance as other animals, while he surpasses
them all in his power of nice discrimination. This however apparently was not the
view held by him when he wrote the De Animd, at any rate so far as regards smell.
"Man," he says there (ii. 9), "can distinguish pleasant odours from unpleasant ones,
and this is all. Here his power of discrimination ends. Just in the same way it is
probable that animals with hard eyes (i.e. Crustacea, and insects) are unable to
discriminate between different colours, excepting so far as that some colours excite
terror in them while others do not. . . . The objects that are perceptible by
smell seem to be analogous to those that are perceptible by taste ; but our sense of
taste is more delicate than our sense of smejl, inasmuch as taste is a variety of touch,
which in man is most acute. For whereas man is far behind other animals in his
other senses, in touch he is far superior to them. And this it is that makes him the
most intelligent of animals."

(Ch. 17.) 1. That is, in aerial atid in aquatic animals.

2. Cf. ii. 10, Note 22.

3. Meaning parrots. In these the tongue is "epaisse, charnue, et arrondie ; deux
circonstances qui leur donnent la plus grande facilite k imiter la voix humaine " ( Cuvier,
/?. An. i. 461). It will be noticed that A. includes parrots among the birds with talons,
i.e. Raptores. He did not know of the peculiarity of their toes; for he speaks of tlie
Avryneck (iv. 12, Note 2>})) ^s the only bird that has two of its toes turned backwards.

Notes, ii. 17. 185

In all probability he had never seen a living parrot ; for even as to the fact alluded to
in this passage, viz. the peculiar topgue, he plainly {H. A. viii. I2, 13) is speaking
at second-hand.

4. " Small birds have a greater variety of notes and are more loquacious than
large birds" i^H. A. iv. 9, 14). "It is remarkable that only small birds properly
sing. The Australian genus Menura, however, must be excepted ; for the Menura
Albert!, which is about the size of a half-grown turkey, not only mocks other birds,
but its own whistle is exceedingly beautiful and varied" {^Darwin, Descent of Man,

"• 55)-

5. " With birds the voice serves to express various emotions, such as distress, fear, anger,
triumph, or mere happiness. It is apparently sometimes used to excite terror. . . . The
common domestic cock clucks to the hen, and the hen to the chickens, when a dainty
morsel is found. The hen when she has laid an egg repeats the same note very often,
and concludes with the sixth above, which she holds for a longer time, and thus expresses
her joy. Some social birds apparently call to each other for aid, and as they flit from
tree to tree, the flock is kept together by chirp answering chirp. During the nocturnal
migrations of geese and other water-fowl, sonorous clangs from the van may be heard
in the darkness over-head, answered by clangs in the rear. Certain cries serve as
danger-signals, which, as the sportsman knows to his cost, are well understood by the
same species and by others. The domestic cock crows, and the humming-bird chirps,
in triumph over a defeated rival. The true song however of most birds and various
strange cries are chiefly uttered during the breeding season, and serve as a charm, or
merely as a call-note to the other sex" (Darwin, Descent of Man, ii. 51). Whether
the voice of bitds, besides expressing emotions and serving to give signals, can also be
used by them for the communication of more complex intellectual ideas, is still an
open question. "J'incline a croire," however says M. Edwards [Lecons sur la
Phys. xiv. 118), "que chez quelques-uns de ces animaux, les Hirondelles par exemple,
une sorte de conversation pent s'etablir entre les differents individus d'une meme troupe."
In the Hist. An. (ix. 31, 2) it is stated that when a battle had occurred in a far-off
country, all the crows disappeared from Attica and the Peloponnese, as though informa-
tion of the banquet had been passed on from crow to crow.

6. Cf. H. A. iv. 9.

7. The tongue is not protrusible in Chelonia nor in crocodiles, but highly so in
serpents and in lizards. In serpents it is slit into two at the end, and deeply so in
lizards. It appears however to be an organ of exploration rather than of taste, for " les
serpents, tout en etant fort delicats sur la choix de leur nourriture, ne paraissent pas
avoir le sens du gout tres developpe ; car lorsque ces reptiles ont commence a ingurgiter
leur proie, on pent leur faire avaler d'autres aliments, sans qu'ils s'aper9oivent du
changement. II suffit d'attacher ces corps entre les pattes posterieures de I'animal qu'ils
sont en train d'avaler ; c'est une operation que Ton pratique souvent dans les menageries
erpetologiques par un motif d'economie " {^M. Edtvards, xi. 451)'

8. "There is no tongue in this rudimentary fish [lancelet). ' That organ is often absent
or very small in the typical members of the class ; its basis, the glossohyal, when it
projects at all into the mouth, is rarely covered by integument so organised as to suggest
their being endowed with the sense of taste" {Owen, Vert. i. 411). See also Cuvier,
An. Comp. ii. 681.

9. The tongue of the crocodile scarcely projects from the hning membrane in the floor
of the mouth. For a drawing of it, see R. Jones, An. Kingdom, p. 686. As to the jaw,
cf. iv. II, Note 20.

1 86 Notes, ii. 17 — iii. i.

10. The exact, drift of this passage is not very evident. I take it that A. thinks it
necessary to explain why the tongue, if it adheres to one jaw, does not adhere to that-
which in his view is the nobler, namely the upper (ii. 2, Note 6). His explanation is
that in reality the tongue does adhere to the upper jaw ; but that the upper jaw has
been brought into the position of the lower one, as its immobility testifies, lest the
adherence of the tongue to it should interfere with deglutition.

11. Cf. iv. u. Notes 6, 7.

12. In the Cyprinoids the palate is cushioned wjth a thick soft vascular substance,
•remarkable for its great irritability. , This is still commonly known in France as "langue
de carpe" [Cuvier, R. An. ii. 270).

13. This is true.

. 14. As to the tongue of Crustacea, Cephalopods, Gasteropods, etc., cf. iv. 5, Notes
4, 6, 8.

15. What species of Gasteropod corresponds to Aristotle's Purpura is a matter of doubt.
All that we learn from the various passages in which it is mentioned is that it had a
spiral shell, an operculum, and a strong tongue, which enabled it to prey on other
shell-fish ; . that it deposited its eggs in honey-like masses ; furnished a dye ; and that
there were numerous species of it, some large, some small. Probably the term includes
all the various species of Murex, Buccinum, and Purpura, from which purple dye was
obtainable. Of these the more important seem to have been Murex trunculus. and
M. brandaris. M. Boblaye found numerous heaps of shells of M. brandaris on the coast
of the Morea, close to the ruins of ancient dyeworks. Similar evidence was obtained by
Wilde on the Tyrian coast for M. trunculus (cf. Woodward, Mollusca, p. 106 ; Meyer,
Tkierkunde, p. 183). As to the power possessed by the Purpura lapillus of perforating
shells by means of its armed tongue, see Forbes and Hanley, Brit. Mollusca, iii. 385.

16. The words I have translated vaguely as gad-flies and cattle-flies are in the text ^stri
and Myopes. There are not sufficient data to determine what exact species of Diptera
are meant. The general statements made about them in various passages seem to point
clearly to some or other species of Tabanus such as T. bovinus, and Chrysops caecutiens
(Aubert and IVimmer); but the account given of the development of ^strus {H. A. v. 19)
is inconsistent with this identification.

17. The similarity consists in the accumulation of distinct functions in one and the
same part.

BOOK III.

(Ch. 1.) 1. As a rule the same organs which serve as weapons of defence serve also
in offensive warfare ; such for example is the case with the long horns of the Or}'x.
But, as A. says, this is not always the case. Thus the upper branches of the horns are
used by some kinds of deer chiefly or exclusively for defence, while the brow antlers
are used in attack. In wild boars the skin over the shoulder is specially modified
to form a shield, which, like the mane of a lion, is exclusively a weapon of defence.
Similar distinctions may be noticed with regard to the teeth. In such camivora as
the lion they serve indifferently for protection and attack ; but in the Babirusa pig
the lower tusks alone are used for offence, the upper ones being useless except for
protection. In the common wild boar exactly the reverse is the case ; the upper tusks

Notes, iii. i. . 187

being here the offensive, and the lower the defensive, weapons. Cf. Darwin, D. of Man,
ii. ch. 17. .

2. That is, " broad below and sharp above " {^H. A. ii. 3, i).

3. "Tusks and horns never co-exist in the same animal ; nor does any animal that is
saw-toothed ever have either of these parts" {H. A. ii. I, 52). Cf. iii. 2, Notes 9 and 19.

4. That the males in any armed species are almost invariably furnished with more
formidable weapons than the females is a conspicuous fact, as also is their more pugna-
cious temperament. The temperament is according to A.'s views the antecedent of the
weapons. But it is more probable that both weapons and temperament are attributable
to one common cause ; and what that cause is Darwin has shown in his work on sexual
selection. The males contend with each other for the females, and such males as chance
variation has endowed with a slightly stronger weapon or slightly stouter heart will as
a rule prevail in the straggle ; and, obtaining preferential possession of the females,
will leave offspring in greater numbers than their less favoured competitors. Of this
offspring some will inherit the physical and moral advantages of their sires. Of these
again the best-armed and the most valiant will be most successful in 'propagating their
kind ; and so on, generation after generation, the comparatively weakly and cowardly
being eliminated at each stage of improvement

5. The only grounds for saying that the organs of vegetative life are smaller pro-
portionately in females than in males are, so far as I am aware, the smaller size of the
gills in female fishes {Yarrell, Fishes, i. xxi), and of the respiratory organs in the females
of the higher vertebrates , and the alleged smaller proportions of the female heart [M.
Edwards, Lefons, iii, 483). Berhaps however A. merely means that all the organs of
females are smaller than the corresponding parts in males. If so, he must be speaking
only of Mammals. For while he recognises the greater size of the males in this group,
he also recognizes the contrary in other groups {H. A. iv. 11, 9 ; v. 5, 3 ; Z>. 6^. i. 16, 2).

6. It will be noticed how carefully and accurately A. expresses himself in this passage.
As he was of course ignorant of the reindeer, his statement that the female deer are
without horns is quite correct. As to sheep and cattle he merely says that the horns
differ in the two sexes, being stronger in the male {H. A. iv. II, 15). This is also
correct. For "in all the wild species of sheep and goats the horns are larger in the
male than in the female, and are sometimes quite absent in the latter, as is also the
case in several domestic breeds. In most wild bovine animals the buU has longer and
thicker horns than the cow. While in the domestic races of cattle, the horns of the
bull though thicker than those of the cow are shorter " [Dai-imn, Des. of Man. ii. 245).
So also he is correct' in simply saying that female birds are often without spurs when
the males have them. For in some species of Gallinacese the hens are without any
vestige of spurs ; in most they possess them in a rudimentary condition ; while in a few
exceptional cases they have them fully formed.

Elsewhere {H. A. ix. 49, 2) it is remarked that in some pugnacious hens small spurs
rise up on the legs ; and mention is made {H. A. iv. 2, 9) of a crustacean in which the
male has much larger spur-like appendages than the female.

7. The Scarus is doubtless the parrot-fish {Scarus Cretensis) of the Archipelago. The
beak-like jaws of these fishes have a dense covering of four-sided prismatic denticles.
With this strong apparatus they scoop off the calcareous lithophytes from the bottom
of the sea, on which they browse just as the ruminants crop the herbage of the fields.
See Owen's Vert. i. 378, for a representation of this dentition. The parrot-fish is by no
means the only exception to the general statement that all fishes have serrated dentition.
In the wolf-fish .for instance most of the teeth are powerful crushers, as in many other

l88 Notes, iii. i — 2.

genera that live on Testacea and Crustacea. The rays, again, and skates have the
mouth paved with flat teeth, and A. was familiar with these fishes. He speaks moiie
guardedly elsewhere (iv. 13, Note 30).

8. "In the sharks and rays the teeth are supported by the upper and lower jaw ; but
many other fishes have teeth growing firom the roof of the mouth, from the surface of
the- tongue, from the bony hoops supporting the gills, and some have them developed
from the base of the nose and base of the skull " [Owen).

9. The mouth in many fishes, e.g. the pike, is beset with a countless number of sharp
teeth which project from all parts of the internal surface. The object of this is not so
much the comminution of the food, as A. supposes, as to enable the fish to retain
hold of its slippery prey. Similarly the recurved form of the teeth, noticeable in many
predatory species, serves to prevent the prey when once in the mouth from escaping,
the points being all directed towar3s the oesophagus.

10. The other weapons are the dorsal fin, armed with rigid spines and highly developed
for defence in such a fish as the perch, where the dentition is "en fin velours" (cf.
Rolleston, Forms of Animal Life, p. 43) ; and the still stronger spines on the back of
dog-fishes, and the skin of rays, etc.

11. Namely, at ii. 16, 6, when speaking of the elephant's trunk. Similar statements
are made (Z?. P. iv. 10, 33, and 58) concerning the female mammae, and the tails of
animals.

12. That is to say without any compulsion from the necessary laws of matter. As to
the general statement, cf. M. Edwards (Lefons de Phys. Comp. i. 21), "En effet, lorsq'une
propriete physiologique commence a se localiser dans un§ serie d'animaux de plus en plus
parfaits, elle s'exerce d'abord a I'aide d'une partie qui existait deja dans I'organisme des
especes inferieures et qui est seulement modifiee dans sa structure pour s'approprier a des
fonctions speciales. Tantot c'est, pour ainsi dire, un fbnds commun qui fournit aux
diverses facultes leurs premiers instruments particuliers ; d'autres fois c'est a un appareil
deja destine k des usages speciaux que la fonction nouvelle emprunte ses organes, et c'est
seulement apres avoir epuise les ressources de ce genre, que la puissance creatrice introduit
dans la constitution des etres a organisation plus parfaite un element nouveau."

13. i.e. the Raptores, cf. iy. 12, Note i.

14. The example is well chosen. For in woodpeckers, especially in the larger species,
the beak acquires the density of ivory (cf. Owen, Vert. ii. 146). In the raven also,
which is the bird usually meant by A. when he speaks of crows, the beak is hard and
strong.

15. A. does not make 'the mistake committed by many other writers, of basing man's
supremacy on his power of gazing upwards ; on the contrary he rightly describes him
as looking in front. The error he escaped is ridiculed by Galen {De Usu part. iii. 3),
who says it can only be entertained by those who had never seen a flat fish, and that
every donkey can bend back his neck and look upwards as easily as can man. But
that man alone of animals is erect, is repeatedly mentioned by A. as a proof of his
superiority. Doubtless the erect position leaving as it does the upper extremities free
for skilful manual operations is an important element in man's structure. But this
position is not the exclusive privilege of man ; some birds, as the penguin, having a
vertical attitude, and even some mammals, as the kangaroo. Cf. Lewes, Arist. p. 309.

(Ch. 2.) 1. For instance in some male fishes, lizards, and many beetles, where the
horns are not weapons but mere ornaments. So A. calls the antennae of Crustacea
horn? (// A. iv. 2, 10). He alludes however more especially to the Egyptian snake
(//. A. ii. I, 36) : "Thus the Egyptians speak of the snakes about Thebes as horned.

Notes, iii. 2. ■ ■ . 189

because they have a kind of projection which as it were simulates a horn." This is
a reference to Herodot. ii, 74, and the snake in question was doubtless the Cerastes of
Egypt.

2. i.e. Carnivora, Rodentia, Insectivora, Cheiroptera, as well as man, apes, and
elephants ; in fact all Mammalia known to A. excepting Ruminantia, Solidungula, and
Cetacea.

3. Meaning the Indian Ass. Cf. Note 10.

4. And therefore, he implies, might be expected to have horns, like most cloven-hoofed
animals.

5. It is somewhat astounding to find so determined a teleologist suddenly declaring
that antlers are not merely useless but actually injurious to stags. A modem writer
however {Bailly, Sur Pusage des cornes, Ann. d. Sc. Nat. ii. 371) has come to the
same conclusion: "Quant aux bois du cerf, du renne, de I'elan, on sait qu'ils sont plus
nuisibles qu'utiles." The horns are however riot so utterly useless as is here supposed,
the upper antlers serving in defence, the brow antlers in attack {Desc. of Man,
ii. 253). Still, as Darwin points out, the large branching horns do present a difficulty.
For a straight point would inflict a much more serious wound than several diverging
ones. Their great size and branching serve however as ornaments, and so give an
advantage in the sexual struggle.

6. The Bubalus must not be confounded with the Bos Bubalus or Buffalo, which was
known to A. under the name of the wild ox of the Arachotse {H. A. i. 21). His Bubalus
or Bubalis, as he elsewhere calls it, is always mentioned by him in company with deer,
antelopes, and the like. It is mentioned in like association by Herodotus (iv. 192), who
enumerates it among the animals of Libya ; and by Pliny it is said to be something like
a calf or deer [^Nat. Hist. viii. 15). From these insufficient data it is taken to be the
Antelope bubalis, or hartbeeste of Africa.

The Dorcas that had horns like those of the Hippelaphus or nylghau {H. A. ii. i, 22),
that was the smallest known animal with horns, and that was an inhabitant of Africa
{Herod, iv. 192), is probably the gazelle, and I have so rendered it. The gazelles are by
no means cowardly. They fly of course from lions and panthers, of which they form
the chief prey, but "the flock when brought to bay defend themselves with courage and
obstinacy, uniting in a close circle with the females and fawns in the centre, and pra-
senjting their horns at all points to the enemy."

7. The Bonasus {H. A. ix. 45) is universally admitted to be the aurochs or European
bison, the Bison jubatus of Pliny, which in the present day is almost extinct, existing

• only in Lithuania and in the Caucasus, but which in ancient times abounded in the
forests of Europe generally. A. speaks of it {H. A. ii. I, 35) as living in his days in
Pseonia and Medica, i.e. North Macedonia. There is a fine specimen in the British
Museum. The story of the use to which the Bonasus puts its dung is given with more
detail elsewhere (//. A. ix. 45, 6). The only conjecture I can make as to the foundation
of the statement is that it may have been derived from the aurochs, in its flight,

' kicking up stones and dirt into the face of its pursuers, just as the giraffe is said to do
(cf. Dallas, Animal Kingd. p. 712), and the ostrich.

8. For instance snakes, hedgehogs, skunks, and, of invertebrata, cuttle-fishes and the
beetles known from their habits as Bombardiers. See the account of Brachyurus crepitans
given by Kirby and Spence. Mr. Tristram {The Great Sahara, p. 64) describes the
houbara or bustard as employing a similar singular mode of defence when hunted with
falcons : "As the hawk approaches, the houbara ejects both from the mouth and vent a
slimy fluid. A well-trained bird eludes this shower by repeated feints, until the quarry's

IQO Notes, ill. 2.

supply of moisture is exhausted. An impatient one rushes in and gets his whole
plumage so bedaubed that his flight is materially impeded, and his swoop when made
is irresolute."

9. This statement, so often made by A., has much truth in it. . For example many
insects are protected by the dull tints of their colouring, or their resemblance to vegetable
or inanimate objects, rendering them practically invisible to birds. But when they are
endowed with some more special means of defence, their colouring is often such as to
render them very conspicuous. The stinging Hymenoptera, for instance, are as a rule
showy and brilliant, and in no single instance are protected by mimicry of vegetable or
inanimate objects. The Chrysididas again, though stingless, can roll themselves into a
ball as hard and polished as if of metal, and these are most gorgeously coloured. So also
the foetid Hemiptera, and the ladybirds that emit fluids which are highly distasteful to
birds, are in large proportion gay-coloured and conspicuous (cf. Wallace, Natural Selection,
2nd ed. p. 69). Facts of similar significance are observable in mammalia. "Very few
male quadrupeds," says Darwin {Descent of Man, ii. 257), have weapons of two distinct
kinds specially adapted for fighting with rival males," a statement which he proceeds to
support by the inverse relation which obtains as a rule between the development of horns
and of canine teeth.

10. The account of the Indian Ass with a solid hoof, and a single horn, was taken by
A. from Gtesias, who apparently did not profess himself to have seen more of the animal
than its astragalus. It has been plausibly conjectured that the Indian Rhinoceros {R.
unicornis) is the animal meant. For, though this animal has three toes, they are so
indistinctly separated, that the real character of the foot might easily escape a casual
observer, to whom the animal would moreover probably not give much leisure for ob-
servation. I may, however, observe that on the obelisk of Nimroud, made long before
the time of Ctesias, and very possibly seen by him, there is represented a rhinoceros, with
feet distinctly divided into toes. An argument oa the side of the supposed identification is
furnished by the fact that the horn of the Indian Ass was supposed to have certain
magical powers, so that a* cup made of it gave the drinker immunity from poison, as is
related by Philostratus in his life of Apollonius j while similar virtues are assigned in the
East to rhinoceros horn, even in the present day. Siipposing the one-homed ass of India

•to be the Rhinoceros unicornis, may it not be that "the asses with horns" {pi ovoi -rh.
Kfpea e'xoj'Tes) which Herodotus (iv. 191) enumerates among the animals of Libya are the
two-horned rhinocerotes of Africa ?

11. An apparent recognition of the fact so much insisted on by Bichat, namely the
greater symmetry of the organs of animal life, as compared with the organs of vegetative *
life. Cf. iii. 5, Note 4.

12. The Oryx is probably the Leucoryx of North Africa, which is often represented on
Egyptian and Nubian monuments. It is supposed that some individual that had lost a
horn in fighting had been seen, and taken for a member of a normally one-horned species.
I do not think it necessaiy to suppose this ; for the Oryx, when seen in profile, has
wonderfully the look of having a single horn, and I once actually heard some ladies at the
Zoological Gardens when they came to it, cry out, ' ' Why, it has only got one horn " !
The explanation of the appearance is that the horns run straight back from their origin
without diverging, save in the very smallest degree, to right and left. Thus when the
animal is seen in profile, one horn concealing the other parallel one, the appearance is
as though there were a single central horn. When the horns diverge widely from each
other, as for instance in the common ox, no such appearance is produced by a side view.
So long as 2000 years after Aristotle, we find Sir T. Browne asserting, in opposition

Notes, iii. 2. 19 1

to those who held that the unicorn was a fabulous animal, that there are no less
than five kinds ; among which he reckons the Oryx and the Indian ass. Cf. Vulgar
Errors, iii. 23. '

13. Cf. ii. 9, I^fote 9.

14. The fable of Momus, the critic God, is alluded to by Lucian {Nigrinus, 32), and
told in full by Babius (.$"?> C. Lewes' s ed. 59). Their account of the criticism on the
bull's structure is not quite the same as Aristotle's. Momus objects that the horns are ia
placed as to be in the way of the animal's sight when it has its head down to attack its
foe.

15. A. knew nothing of the giraffe, except perhaps by name, if the Hippardium, as
some think, be that animaL So that he is correct in saying that deer alone have solid
horns ; and that they alone^ cast them. The rest of the horned ruminants are all
sheath-homed— cavicomia. That is to say, their horns consist each of a conical process of
bone, which is covered by a sheath of horny matter, and is not cast periodically like the
solid horn of the stag, excepting by the Prong-homed Antelope of North America.

16. Cf. Introduction, p. iv.

17. The gazelle, though small, is by no means the smallest of the homed ruminants ;
sundry other species of antelope, such as the guevi and the kleenebock, being much
more diminutive. Indeed one variety of guevi is said by Adanson to be not much
larger than a good-sized Norway rat.

18. Cf. Introd. p. vii.

19. "The inverse relationship between the development of teeth and homs, exemplified
by the total absence of canines in the ruminants with persistent frontal weapons, by
their first appearance in the periodically hornless deer, and by their larger size in the
absolutely hornless musks, is further illustrated by the presence not only of canines but
of a pair of laniariform incisors in the upper jaw of Camelidse " {Owen, Vert. iii. 348),
and to this statement may be added the recently acquired fact that the water-deer of
China has no antlers, like other true deer, but has two long projecting canine teeth to
serve in their place for defence. It is however very doubtful whether these facts are
to be explained as in the text by the law of organic equivalents (ii. 9, Note 9).
Still the amount of Organic matter consumed in the development of homs is so great,
that it is by no means impossible that their presence may necessitate a greater economy
in the rest of the body ; and this economy will be practised in those parts which are
the least necessary, such as the canine teeth which are no longer required as weapons
of strife. "Tusks and horns," says Darwin (Desc. of Man, ii. 258), " are manifestly of
high importance to their possessors, for their development consumes much organised
matter. A single tusk of the Asiatic elephant, one of the extinct woolly species, and
of an African elephant, have been known to weigh 150, 160, and 180 pounds, and even
greater weights have been assigned by some authors. With deer in which the homs are
periodically renewed, the drain on the constitution must be greater : the homs for
instance of the moose weigh from 50 to 60 pounds, and those of the extinct Irish elk
from 60 to 70 pounds, the skull of the latter weighing on an average only ^\ pounds.
With sheep, although the horns are not periodically renewed, yet their development, in
the opinion of many agriculturists, entails a sensible loss to the breeder." That such
may be the case we may readily suppose when we consider that homs weighing 72 lbs.
have been developed in deer in ten weeks (cf. Huxley, Verteb. 385).

20. Cf. Note 5.

21. Thus in the Babimssa pig the tipper tusks "more nearly resemble horns than
teeth."

192 Notes, ill. 3.

(Ch. 3.) 1. The word I have rendered larynx is in the Greek pharynx. It is quite
clear however that the part which is made of cartilage, serves for vocal and respiratory
purposes, lies in front, of the oesophagus, etc., can only be what we call larynx, and I
have therefore so translated it. Yet the word larynx was known to A., and occasionally
used by him as. by us. It would seem that the two words pharynx and larynx had not
in his day been clearly differentiated from each other, but were used indifferently for one
and the same part {H. A. iv. 9, i and 2), namely the larynx. What we call pharynx
had for A. no distinct name, being nothing more than the first part of the oesophagus ;
which latter he says, later on in this chapter, is directly continuous with the mouth.
This can hardly be called confounding pharynx and larynx, with which Mr. Lewes
charges Aristotle. Galen sometimes uses pharynx as equivalent to larynx ; sometimes
in the modem sense, as the common meeting-place of gullet and windpipe (cf. Darem-
derg^s Galen, i. S^l).

2. "In some fishes there is no oesophagus at all; in the rest it is of short length"
{D. P. iii. 14, 12). As a rule the oesophagus is indistinct in fishes, being scarcely
differentiated from the stomach and. intestine. In some fishes however, as the rays, it is
distinct enough.

3. It would probably be truer to say that there js a long trachea in order that there
may be a long neck, so as to facilitate the motions of the head, than to say, as A. dofes,
that there must be a long neck, in order to provide space for a long trachea. Still
the length of the trachea is not without use ; for the air in its passage down the long
canal is filtered of its dust, moistened, and warmed. In some animals the trachea is
still further lengthened by being formed into a coil.

4. Cf. iii. 4, Note 20.

5. It is indeed impossible to explain teleologically the strange position occupied by
the orifice of the trachea. A supposed explanation has been found in the homologies of
the part. The lungs and trachea correspond anatomically to the swim-bladder and
pneunaatic duct of fishes, and have probably been developed as modifications of these
latter organs, whose place they occupy {Danvin, Or. of Species, p. 191). But the duct
in fishes as a general rule opens on the dorsal, and very exceptionally on the ventral,
aspect of the oesophagus ; a fact which scarcely harmonizes with this explanation.

6. Alluding to Plato (ymveWs Transl. ii. 584). Hippocrates mentions and attacks this
same strange notion {De Morbis, iv. 30).

7. Mammals alone have an epiglottis. In other vertebrata the opening into the larynx
and trachea is closed simply by constrictor muscles.

8. Cf. ii. 13, Note $.

9. Frantzius, as I think erroneously, infers from this passage that A. supposed the
trachea to communicate directly with the heart. Had A. so imagined, he would not
have said, as in the text, "leads to the lung and the heart," but merely''*to the heart";
for the fact of its also leading to the lung would have had nothing to do with the matter.
But, as the trachea only leads to the lung, he is qbliged to mention this organ as well
as the heart; his argument being as follows. "The heart is in front; but, where the
heart is, there and surrounding it must be the lung, in order to perform its due office
to the heart. The lung, then, must also be in front ; and therefore the windpipe also,
which leads to it." There is indeed one vague passage (^H. A. i. 16, 14) which would
at first sight seem to establish Frantzius's view. "The heart also is connected with the

windpipe by fatty, cartilaginous, and fibrinous bands When the windpipe is inflated,

in some animals there is no sign pf the air getting into it, but in some of the large
animals it plainly does." Allowing that by "it" is meant the heart, which is not

Notes, ill. 3 — 4. • 193

certain, for it may only mean the trachea, the passage still by no means necessarily
in>plies that A. thought there was any communicating channel between trachea and heart.
It merely states that the two are connected by bands, and that a passage of air from
the windpipe to the heart is somehow possible in some large animals. In order, however,
^ for this to occur, A. by no jneans supposed it necessary that a direct communicating
channel should exist, as is sufficiently shown in his description of the lungs : "When the
windpipe," he says, "reaches the lung, it divides and subdivides, each division producing
smaller anismaller branches, till the whole lung is. permeated by them" (^H. A. i. 16, 13).
"There are also ducts (i.e. the pulmonary blood-vessels) which lead from the heart to the
lung ; and these also divide and* subdivide, their branches accompanying the branches
from the windpipe. But there* is no communication between thd two (ouSeh 5€ iarX Koivbi
' ir6pos). Notwithstanding this, however, air can pass from the former (i.e. l/te bronchial
tubes) into th*e latter (i.e. ths pulmonary vessels), owing to the close contact in which the
two lie (5jd t^v avvaci^iv), and be transmitted to the heart" {H. A. i. 17, 5). This
passage shows that A. not only had a fair knowledge of the anatomy of the lung, but also
that he believed the air to pass from the air-passages into the blood-vessels through
their unbroken walls, just as we hold the oxygen to do. The trachea then was not-
supposed by him to lead directly to the heart, but merely to the lung. As to his state-
ment, if it be his statement, that mechanical inflation of the trachea sometimes sends air
visibly into the heart, it can only be explained by his having ruptured the parts in his
experimental manipulations.
10. Cf. ii. 2,, Note 6;

(Ch. 4.) 1. It" must not be supposed that A. means that the bloodless animjds have
none of what we call viscera. For he often mentions the stomach, intestines, and other
internal organs of cephalopods, insects, etc. He limits the term viscera to such internal
parts as are so coloured as to resemble blood, of which^in fact he- supposes them to be
formed (iii. 4, 3 ; iii. 10, 13). As the bloodless animals have merely a fluid analogous to
. blood, so they can only have parts analogous to viscera. It is however to be noted that
once A. admits of .an exception to this, viz. the liver or mytis of the Cephalopods (iv. 5>
Note 13). This he regards as. a viscus, doubtless on account of its dull-red or violet hufe.

2. Cf. H. A. yi. 3, 2, where it is said that thc.heart in the bird's egg at its first
appearance looks like a bloody spot, and palpitates as though endowed with life;. a
description which is the origin of the "punctum saliens" of later writers. These
minute observations as to the heart in ovum and embryo were made, as we. learn from
atiother passage [De Juv. 3, 4), by A. himself, and are sufficient to establish .his fame
as an original oliserver. The hfeart is not actually the first part to appear in the embryo,
but it is the first to enter actively into its functions, contracting in the bird so early as
the second day of incubation, and becoming a few hours later rhythmical in its motions.

3. Cf. i. 5, Note I. . •

4. The liver in the mature foetus forms -j^th of the vyhole body ; in the adult it forms
only ^th. The heart also is larger proportionately to the whole body in the young
embryo (yb-th) than in the mature foetus (T2ijth), and in the foetus than in adult
man (ilijth). In infancy again the lungs are .of a brightish colour, "which might.be
compared to Hood froth ; but as life advances they become darker, mottled with spots,
patches, etc." <Zl. Quain's Anat. Wi,^.

5. In calling the heart the origin or centre of the vessels, A. implies two distinct
things : firstly, that it is the place where the blood is made ; and, secondly, the place
whence the blood, when thus made, is propelled into the vessels, blood going from it,
but none returning to it.

13

194 Notes. \\\. 4.

His predecessors (//. A. iii. 3,. 5) had said that the origin of the vessels was in the
head ; but it does not appear clearly what they meant by origin, or whether they used
the term in the same sense as did Aristotle. This much, however, geems certain : that
they regarded the heart as no ' essential part, if part at all,, of the vascular system.
Neither Syennesis nor Polybus, who was son-in-law of Hippocrates, so much as mention
the heart iji their accounts of the vascular system ; and though Diogenes speaks of it as
receiving two large branches, he clearly regards these branches as of no more importance
than the branches to other organs or parts (/T. A. iii. 2; iii. 3). A. had therefore to
show not only that the heart was the centre of the vascular system, but firstly that it was
part at all of that system.

His arguments are somewhat confusedly given, but may be thus arranged.

That the heart is part of the vascular system is shown in the first place by dissection ;
for, when exposed,- it is seen in most direct and evident communication with the large
vessels. Secondly, the heart resembles the rest of the vascular system in structure ; for
' it is hpniogeneous in substance, like the blood-vessels (cf. ii. I^ ■ Note 16). Thirdly,
the heart has no nutrient vessels, which can only be explained on the view that it is
nourished by blood, of which it .is the receptacle (cf. ii. i. Note 18). The solidarity,
of heart and vessels is still further shown by the fact that throbbing occurs sipiultaneously
in them all {De Resp. 20, 7). The heart then is part of the vascular system. That it
is the centre of the system is shown, firstly, by dissection, for the ■ large vessels seem to
radiate from it. Secondly, the heart rs the first 'part formed in the embryo {D. G. ii. 4,
33>' 36), and, no sooner is it formed, than it is found -to contain blood, at a time when
there are no blood-vessels as yet to be seen (Z><? Resp. 20,' 6) ; that is to say the heart
contains blood, at a period when there is no other organ than itself in which the blood
can possibly have been fabricated. Thirdly, the seat of fhe blood formation must be
some part where there is much heat, and whence heat cannot readily escape. The
region of the heart is such ; for the trunk is sensibly hottef than the extremities ; and
comparing the heart with th^ rest of the vascular system, its wall, though of similar
material, is found to be thicker, so as to keep in the heat. • Fourthly, it is probable, and
preferable on practical as well as metaphysical, gi'ounds, that the source of the blood
shall be an unpaired and central organ, so as to be in .as equal reach as possible of all
parts of the body; and, moreover, seeing of what vital importance such an organ is,
that it shall be in some well- protected position. It must also evidently be some part
present in all animals that have blood. The heart alone fulfils all these conditions, or
fulfils them better than any other organ. Lastly, the heart is shown by independent
considerations to be the centre of sensation ; and the intimate relation of sensation with
blood-supply renders it highly probable that the sensory centre will also be the blood-
centre. M . Edwards. {Lemons sui' la Phys. iii. 5) says that A. was the first to show that
'the blood-vessels communicate with tlie heart, or arise from it. It must however be
noted that Plato in the Timceus {§ 45) incidentally speaks of the heart as the meeting-point
or kilot (fiM^a) of the vessels, and the fountain of the blood.

6. Cf. Note 10.

7. Cf. ii. 2, Note 6.

8. Elsewhere [H. A. iii. 3, 5) A. says that not only some, but all his predecessors held
this opinion. ' ' ^ ■ ' .

9. The temperature of the body sensibly declines, th^ farther one goes from the centre
towards the extremities.

10. The most natural interpretation of this passage and some others would doubtless
be that the bipod-vessels pass right through the viscera, and come out again on the other

■Nates, ill. 4. . . ' " • 195

side ; in which case A, would have to be credited with the opinion that artery and vein
■were in direct peripheral communication with each other, and that the surplus' blood from
a viscus passed away by one or other vessel, and came back in a circle to the heart. But,
in spite of the wording of the passages, I cannot believe that this was A.'s opinion. I have
no doubt that he thought that the vessels ended in the viscera, and indeed (D. P. iii. 9,, 5)
he expressly says that this is the case in the kidneys. How then is the wor^ Ziexovcrt,
which I have rendered, "extend through," to be understood? I think it must mean
."spread throughout the substance " ; the contrast between heart and viscera being that
. in the latter the vessel breaks .up into nutrient branches which retain the character of
vessels, while in the heart there is' no such breaking up, but the vessels expand into a.
reservoir, and lose altogether the character of vessels, while the heart is nourished at the
expense of th^ blood in its own cavities (ii. ij Note 18). At the same time there are
certainly passages in which Siexovffi has the other sense. Such, for instasce, is the
passage {//. A. i. 17, 12) referred to' in Note; 15. That passige I interpret as meaning
th&t the hepatic vein, when it reaches the portal eminences of the liver, sends branches into
it, which terminate in the substance of that organ, while the rest passes on {Vend porta)
and terminates on the walls of the intestine.

11. I|y the central part is meant, as I take it, the main bulk of the heart in opposition
to the apical part, which later on is described as being solid. Possibly, however, the
whole of what we call heart may be meant, and be called central, because the pericardium
is included in the heart by Aristotle.

12. Cf ii. I, Note 18. ' .

13. Alluding to the throbbing of the heart on any strong. emotion, whether pleasant or
painful.

14. Cf. ii. 7, Note 27. Neither the blood, nor yet parts without blood, are sensitive ;
but only parts which contain blood, and of these that which first contains bl6od will first
be sensitive, that is will be the primary source of sensation.

15. Galen, however, did sUppose that the liver was the origin of the vessels, in the sense
of being the organ in which the blood was formed. Galen founded his opinion upon a more
correct view of the vena portas than that entertained by Aristotle. A. apparently thought
{H. A. i. 17, 12) -that the vena portse was simply the continuation on the far side of the
liver of the hepatic vein, conveying blood Sxora. the heart past the liver to the intestinal
parts. The absorbed food passed, as he thought, up the portal veiminto the hepatic"' vein,
and so oh to the heart without pause in the liver.- Galen recognised the fact that the
absorbed food was converted into blood on its passage, in the liver.

, 16. And therefore it is not a single organ, such as a dominating part should be. Cf iii.
7, Note I.

17. This correct description of the position of the human heart, though it renders it
probable that A. had seen the organ in situ, does not actually prove such to have been
the case. For, as Lewas says, A. may have been led to his conclusion by merely feeling
the impulse of the heart on the left side ; and Galen in fact {De Usu part. vi. 2) says
that the heart is central^ but erroneously supposed to be on the left because the impulse
is felt there. There is however, I think, another ground for suspecting that A. spoke
from actual inspection of the human heart. He describes the right ventricle as being not
only on the right side, but above the rest of the heart, that is anterior to it {H. A. iii. 3, 10).
This is true of the human . heart, which is so tilted round as. to bring the right ventricle
to the front, but is not the case in other animals {cf. Todcfs Cycl. ii. 578).

It is not quite true that man is the only animal in which. the heart inclines to the left.
A like obliquity exists in the higher quadrumana {Cuvier, Anat. Comp: iv. I97)> and in
the mole.

196 ' . Notes, ill. .4.

. 18. The probable reason why -A. supposed the right side^to be hotter than the left is
pointed out at ii. 2, Note 6 ; and that reason would only apply in the case of man.

19. By the apex of the heart of fishes A. plainly means the point at the anterior
extremity of the organ, where the bulbus arteriosus gives off the branchial artery.
This however has no anatomical correspondence with the apex of the heart of other
vertebrates.

A. makes a similar statement as to the position of the fish's heart elsewhere (Z^. A. ii.
17, 1 ; De Resp. 16, 3), and accounts for it by saying that the head in other animals is. moved
in a vertical plane, from above ddwnwards, whereas in fishes it has no such motion. ,
Forwards then in a fish is in the line from tail to mouth, while in other animals it is in the
line from above downwards, that is from the back to the sternum. Strange as this explan-
ation is, it is stUl stranger when one considers .that, in order to supply it, A. had to
abandon his usual definition of forwards, as the direction in which sight and sense
generally is exercised, and to give a new and inconsistent one.

• 20. It is important to have a clear understanding of what A. meant by vivpa. (sinews),
as it is one of the words which have led commentators astray. The chief passage
concerning the vivpa. is the following {H. A. iii. 5) : "The sinews. (j'eCpa) like the blood-
vessels have their origin in the heart. For in the largest of the heart's cavities (i.e. right
ventricle) are found sinews (i.e. chordcB ttndinece') ; and the aorta, as it is called, is a
sinewy blood-vessel. Its ultimate branches are indeed completely sinews. For they are
solid, and have the same kind of extensibility as those sinews which terminate about
the joints (i.e. the ligaments). The sinews how^yer do hot, like the vessels, form a
continuous whole. For the vessels, as in anatomical outlines, give the configuration of
the whole body, and this so perfectly, that in very emaciated individuals the whole bulk
of the frame appears to consist of one mass of small vessels ; for the very same part which
in fat persons is flesh is turned into small vessels when they become thin. The sinews
"on the other hand form no such continuous system, but are placed separately from each
other about the joints and bendings of the bones. For, did they form a continuous
whole, their continuity would be apparent inemaciated bodies. . The chief sinews are that
connected with the hollow of the knee, which is the part of main importance in leaping,
the double sinew called the tendon {Achillis ?), the Epitonus, and the shdulder sinew,
•which two latter are used in acts requiring great strength. Others there are without
name^ about the joiuts. For all the bones are connected together by sinews (i.e.
ligaments) at their points of contact, with the exception of the skull bones, which are
connected by sutures. Sinew can be split lengthways ; transversely however it cannot
be so split, but admits of considerable extension. The sinews are surrounded by a
slimy fluid, which is white and sticky {synovial Jluid?). If a sinew be cut in two, it
never reunites. No numbness ever occurs in a part which is "without sinews, etc."
From this it is quite plain that what A. meant by vivpov was sinew, ligament, and fibrous
tissue generally ; though it is highly probable that he confounded with these such nerves
as" he may have seen, owing to their white colour. In fact the last clause in the above
quotation shows pretty plainly that such was the case. S*till it is absuM to say as did
Galen, and even in modern time Milne Edwards (Lefons, iii. 5), that A. held that the
small arteries were , converted into nerves ! This is simply a mistranslation of vtvpov.
What A. meant was that they were converted into tendinous fibres, and into this error
he was led by his limited mieans of observation rendering it impossible for him to detect
the minute cavity in a small arterial branch, which is indeed reduced- to nothing by post-
mortem contraction. ■

'We have now to consider in what manner these fibrous parts came to be, in A.'s

.'. Notes, iii. 4. . 197

scheme, the main instruments of motion. Of the contractility of muscular tissue he knew
nothing ; though it is impossible to suppose that he did not know that what we call
a muscle swelled up, becoming shorter and broader, during action. The changes of
shape for instance in the Biceps, perfectly well known to every painter and sculptor,
cannot possibly have escaped his notice. Such a muscle however he considered to have
two constituents ; firstly flesh, that is the true red muscular tissue, which' he supposed
to be nothing more than an aggregate of small vessels clogged up with inspissated blood
(iii. 5, Note 7) ; and, secondly, tendinous fibres and other fibrous elements such as the
muscular sheath, etc., which he supposed to be the ultimate " terminations of the arteries,
converted into solid strings. The action of the muscle he attributed not to the former of
these elements, the red muscular tissue, but to the latter, the really inactive tendinous
fibres, which have, he says, a transverse extensibility, that is to say can become broader
and shorter.

His idea of the" mode in which these tendinous parts were called into play seems to
have been as follows. The heart, as it is the centre of the nutritive 'and the sensory
principles, ^ so also is the centre of voluntary motion. By its independent (cf. ii. 16,
Note 11) contractions and relaxations (for it is as it were a distinct living being within
its possessor) it acts upon the chordae tendinese, and either directly or through these upon
the fibrous aorta. This in turn acts upon- the tendinous fibres of the muscles, which
are in fact its terminal branches, and these fibres become transversely extended, and
consequently longitudinally shortened ; these again act in turn upon the true tendons
and ligaments, by which the bones are set in motion.

The want of continuity in the tendinous system of which A. speaks is the gap between
the chordae tendinese and the true tendons attached to tlie bones, a gap which he fills up
by the tendinous aorta and its branches.

Such I take to be A.'s inadequate conception of the mechanism of motion. That he
himself felt how unsatisfactory it was, we may infer from his saying so vary little on
the subject, notwithstanding its importance. We must remember, moreover, that, while
nerves were still undiscovered, no explanation of voluntary motion was possible. A. had
to find some anatomical machinery connecting the tendons, which were clearly the
immediate agents that acted on the bones, with the volitional centre, which he took as
we know to be the heart and not the brain. He could find no other continuous substance
between these two, than somri or other kind of fibrous tissue, in the form either of
tendinous fibre or of arterial wall. This therefore he assumed to be Ihe intermediate
agent, no other being apparently forthcoming.

1\. This is one of many passages showing that A. himself practised dissection.
.22. .Cf. H. A. ii. 15, 6. It is "not uncommon to find in large mammalia, especially, in
Pachyderms and Ruminants, a cruciform ossificarion in the heart, below the origin of the
aorta. In • the ox this is a normal formation, as also in the stag. But in Pachyderms,
or at any rate in the horse, it is only found in old individuals, and appears to be the
result of pathological degeneration. Galen, in his manual of dissections, tells a curious
story * of the triumph • he obtained over the assembled physicians of Rome by his
demonstrating the presence of a bone in the heart of an elephant when they had failed to
find it. See also De Usu part. vi. 19. •

23. A full description of the heart is given in the Hist. An. (i. 17, and iii. 3). . There,
as here, it is stated that it Jias only three cavities. Aubert and Wimmer (i. 238) suppose
that A., took the two auricles to form one cavity, viz. that which he terms, the right
cavity. Frantiius supposes that the left auricle was overlooked. Both commentators
thus make the- second and third of A.'s cavities correspond to the right ajid left ventricles

198 Notes, iii. 4, . *.

respectively. Any one who reads A.'s description will see that this view of the matter
is utterly untenable, and would turn every sentence in the description into nonsense.
There can, I think, be no possible doubt that the three cavities are the right ventricle,
the left ventricle, and the left auricle. Why it may be asked did A. omit the right
auricle ? Simply because he looked on it as a venous sinus, being'a part_ not of the heart but
of the great vein (/.^. superior and inferior venae cavse). That he so regarded it, is plain
from his always speaking pf the superior and inferior venae cavae as forming a single
vessel, not as two distinct ones, and he even says in one place {H. A. iii. 3, 8) that the heart
appears very much like a part of the great vein, being interposed between*its upper and •
lower divisions. Galen held a precisely similar view of the right auricle. " Galien,"'says
Daremberg (i. 387), "considere la veine cave syperieure comme une continuation directe
de la veine cave inferieure, I'oreillette droite h'etant qu'un diverticulum ou un . lieu de
passage." Such a vi.ew was quite natural ; for the right auricle " semble formee par fa
reunion des veines caves qui s'ouvrent aux deux extrenlites superieure et inferieure de
cette oreillette" (CMZz/^r, Z^pjwj, iv. 199). This being understood, A.'s description of
the heart becomes fairly intelligible. Here are the main parts of it, as I interpret
them. " The heart has three cavities. The largest is placed on the right (right ventricle);
the smallest on the left {left auricle) ; and the one of middle size {left -Ventricle) lies in the
middle. All these cavities — even the two smaller ones — have openings in them which
lead to the lung {pulmonary artery; pulmonary veins ; and, for the left vlntricle, the fcetal
ductus arteriosus), but it is'only in one of them {right ventricle) that the communication
with the lung is conspicuous {pulmonary artery). The largest cavity {right ventricle) is
connected with the great blood-vessel {right auricle which is simply dilated junction of
■ vetue cava) ; and thq middle cavity {left ventricle) is connected with the aorta. Moreover
passages {pulmonary artery and veins) lead from the heart to the lungs, and divide after
the same pattern as the windpipe, their branches accompanying the branches of this latter
throughout the whole lung, and the former being placed above the latter,-- There is no
communicating passage between these two systems of branches, but those which come from
the heart receive the breath from the others, in consequence of their close contact with
them, and transmit it to the heart. For one of the passages {pulmonary artery) leads to the
right cavity {right ventricle) and the other {pulmonary veins) to the left cavity {left auricle) "
{H. A. i. 17). And again, "The heart in the largest animals has three cavities. The
largest of these {right ventricle) is on the right, and is above the rest ; the smallest
{left auricle) is on the left ; and the middle one in size {left ventricle) is also the middle
one in position. Each of the two latter cavities is much smaller than the largest one
{right ventricle). All three have openings which lead to the lungs ; but these openings
are so small as to be scarcely visible, excepting in- one ciyity {right ventricle). . Thq, great
blopd-vessel {right auricle and 'venm cavce) is connected With the largest cavity {right
yentricle), and after passing through the centre of the cavity issues from it again in the
form of a blood-vessel {pulmonary artery), as though the cavity were a part of the vessel, in
which the blood collected as in a reservoir. The aorta issues from the middle cavity {left
ventricle), having however a much narrower tube [than the pulmonary artery]. * The
great vessel {veme cavce'plus right auricle) passes through the heart, and after issuing from
it {cu pulmonary arlery) extends into the aorta {by the ductus arteriosus). [Th^ great vessel
is membranous and skin-like ; but the aorta, which is smaller than the great vessel, is very
tendinous, and, as it extends upwards tovvards the head and downwards towards the
lower parts, gets narrower, and assumes altogether the character of sinew (cf. Npte 20).
The great vessel sends first a branch upwards above the heart, to the lung and the
junction with the aorta {pulvionqry artery and ductus arteriosus), this branch forming a

Notes, iir. 4. 199

large and unbranching vessel. There are indeed two branches from the great vessel, the
one which goes to the lung {Jmlmonary artery), and one which goes to' the backbone and
last cervical vertebra {azygos vein). The one which goes to the lung (pulmonary artery"^
divides into two, as the lung itself consists of two parts," and sends branches which

accompany each air-pipe the branches of the vessel being above the branches

of the wind-pipe. The vessel which goes to the cervical vertebra and backbone
(z*. azygos) runs back along the backbone, and gives off branches to each rib and vertebra,
'ultimately dividing into two, opposite the vertebra next above the kidney {thi left and
right azygos veins which in man unite somewhat higher up, but also are often united by a
cross branch about this point. See Ofay's Anai. f. 241). ' Such are the divisions of these
branches of the great vessel. The main trunk of the great vessel, in the part which extends
from the heart above these'branches [vena cava superior above point where azygos joins it),

splits in two directions {vencE innbminata:) Such is the distribution of the vessels

above the heart. But the part of the great vessel which is below the heart {;vena cava

.inferior) passes down from above through the diaphragift The branches of the

smaller vessel which is called tJie aorta are distributed exactly in the same way as those of
the great vessel (venous system)^ and its branches accompany those of the latter, being
hoWever much smaller, etc." (H.A. iii. 3).

These passages leave no possible doubt as to what A. meant by his three cavities. If
any further prctof were wanting that the largest cavity is not meant to designate the right
auricle but the right vefttricle, it is furnished by the following passage: "There are
sinews (i.e. chordce tendine^B) inside the largest cavity of the heart"; for there are such
in the ventricle, but not in the auricle.

It is almost superfluous to say that the size of an animal does not in any way determine
the number of cavities in its heart. Galen (De JJsu part. vi. 19) points out A.'s mistake,
and says that the horse has nomore than the sparrow, the ox than the mouse. It is not
impossible that the blunder may have arisen from observation,- though of very imperfect
kind. The largest arrtmals knbwn were of course mammals, with four cavities. The huge
crocodile, again, has four, while the other and smaller reptiles have but three. Cetacea
again, though A. knew them to be really mammals, were classed by the vulgar with
fishes, and have four cavities, while the smaller aquatic animals with .which they
were usually confounded have two. . •

24. The passages quoted in the last note show what is meant by the great vessel and
the aorta. The former corresponds to the venous system, including the two venje cavse,
the right auricle, which was considered to be the dilated junction of these, and the
pulmonary artery, which is described as a continuation of the great vessel on the other
side of the heart. The aorta and its branches are of course the arterial system. The
differences noted by A. between the two are that the arteries have much thicker and
firmer, walls than the veins (H. A. iii. 3, 13) ; that the foxmer are of smaller calibre than
the latter (ZT. A, iii. 4, i), and as a rule lie in front of them ; and lastly that the two
contain different kinds of blood, that in the aorta and the- middle cavity of the heart
being purer th^n that in the great vessel and its cavity, the right ventricle. The difference
in purity was shown by difference in colour. "Blood is red; but that which is of
inferior quality, either naturally or from disease, is of a darker tint" (^H. A. iii. 19, 3).

25..' Frantzius translates,. "If the blood be of, two kinds and each kind be kept
separate,"' and considers the passage of importance as- showing that A. recognized
differences between arterial and venous blood. That A. did recognise such differences is
certain, but I do not think he alludes to them here.- For Zi(^vi\%.'\s never used- in this
treatise to express "zweifacher natur^" but is invariably applied to organs of similar

200 Notes, iii. 4.

nature placed on opposite sides of the body, e.g. the kidneys. A. appears to have thought
that the great vessel nourished the right side of the body, the aorta the left. Cf. Note 28.

26. A. does not explain in what way the middle cavity is common to the two sides ;
nor is the statement consistent with the description quoted in Note 23. A similarly
unintelligible and even more inconsistent statement is made in the De Somno (t,, 28).
It is there stated that when food is absorbed it is carried up as a vapour to 'the head,
where.it is condensed, and falls back, pure and thick materials alike, to the right and
left cavities of the heart, reaching the former by the great vessel, the latter by the aorta.
The separation of the pure material from the thick is then effected by the central cavity.
Thus A. either makes the aorta* arise from the left .auricle, or he interposes the auricle
between the two ventricles ; neither of which blunders occurs in his detailed description
of the heart and vessels. Either there has been some tampering with the text, or the
passage in the De Sonino was written before A. had made out the structure of the heart
as described in the Hist. Animalium. The latter hypothesis, however, would still leave
the passage, to which this is a note, unexplained.

27. According to Bernard, though the correctness of his statement is not universally
accepted, the blood in the left cavities is really somewhat colder .than that in the right.
But, even if it be so, A. can only be right by accident ; for he had no possible means of
measuring the difference, which is but a fraction of a degree. Moreover^ he dlso says
that the blood of the left- auricle is hotter than that of the left ventricle, which is not
the. case. His statement then seems to be purely h priori, and noticeable as such,
seeing that almost invariably his statements are based upon observed facts, though often
very insufficient ones. . Cf. Introd. p. xviii.

28. Because, as he supposed, the vense cavse nourished the right side of the body, and
the aorta, which in its general course lies somewhat to the left of the ven^e cavse, nourished
the left side. As to temperature of right and left sides, .cf. ii. 2, Note 6.

29. It would thus appear that A. regarded the left ventricle as the supreme part.

: 30. The allusion is to the transverse and longitudinal grooves which mark out on the
surface tlie limits of auricles and ventricles. A. is quite right in saying that the heart is
not formed by the union of distinct parts into a whole. It is at first a body vvith a
■ single cavity ; which cavity is converted into several by the after-development of internal
septa.

31.' Cf. ii. 4, Note 4. " ' .

32. The heart is. very large in. \he hare, nearly twice as heavy in proportion to the
body weight as in man. As regards the other animals I can give no accurate figures.

The Pardalis from the description given elsewhere {P/iysiog. 5, n) is supposed to be
the leopard, and I have so rendered it.

Prof. RoUeston (Journal of Anat. 1868) identifies the 7a\^ of the ancients, whith
among the Greeks -filled the place of the domestic cat, with the Mustela Foina, or white-
breasted marten. The wild species, or Ikt/i, also mentioned by A., he identifies with
the yellow-breasted marten or pine-weasel.

33. A. must mean when the cavities of one heart are compared with those of another
heart, not when different jcavities of one and the same heart are put in comparison. For
he has already said that the right cavities and vessels are larger and yet hotter than those
on the left. •

34. Cf. ii, 16, Note 11,

35. Cf. iii. 6, Note 2.

36. Cf. u. 5, Note 8. *

37. Cf. iv. 2. Note 18. Daremberg (Ca//V«, i. 401) represents A. as saying in this

Notes, iii. 4 — 5. 201

passage that the heart is riot liable to disease, or at any rate less liable than other organs ;
just as Galen said that it was made of hard fle.sh which could not easily be injured.
But in fact A. says nothing of the kind, but merely states what is fairly true, viz. that
diseases of the heart are more certainly fatal, and less consistent with apparently good
health, than diseases of other parts; so that when a victim, i.e. an animal supposed to be
of sound health, is sacrificed, its heart is never found diseased, though such is frequently
the case when an animal djes of a malady. What would A. have thought of the bull
sacrificed by Caesar, which the soothsayers asserted to have no heart at all! {Cicero,
De Div. ii. i6). ' • .

38. The spleen is liable to tubercle, and is indeed, with the lymphatic glands, its
favourite seat in children {Rokitansky).' If is also extremely liable to embolism; and
enlarges in malarious diseases, which were probably very common in A. 's time and
country.

(Ch. 5.) 1. Cf. iii. 4, Note 24. It is strange that even up to the present day it
should be universally stated by writers on the history of physiology that up to the time
of Galen all philosophers supposed that the arteries contained nothing but air. Even
Cuvier, the great admirer of Aristotle, attributes to him this erroneous notion. Milne
Edwards actually considers why it was that Galen attacked Erasistratus rather than
Aristotle for holding this doctrine. Nothing can be plainer than that A. knew perfectly
well that the arteries contained blood, and this chapter is sufficient by itself to show that
he did so. The mistake has, I imagine, arisen, from two causes. Firstly, that writers
have got into confusion by translating ^\€i|( into vein ; Whereas it nxeans blood-vessel, ih.z.\.
is artery or vein alike ; and by still more absurdly translating ipr-fipia into artery,
whereas it means trachea. Secondly, that the treatise De Spiritu has been trusted, 4^
a. genuine work of Aristotle ; whereas it is shown not only by its language but by its
statements to be most certainly spurious, and is in flagrant contradiction with the
genuine treatises. Cf. ii. i6, Note ii.

2. Cf. iv. 5, Note 71. Alluding to such Invertebrata as insects, myriapods, and
annelids, which he frequently mentions as capable of living for a short time when cut
into segments ; which shoWs that each segment must have its own centre of animality ;
the entire animal seemingly consisting of an aggregation of many animals, each with
a certain individuality, which ordinarily is merged in the life of the aggregate, but is
capable of asserting its existence \yhen the segment is isolated ; the only reason, in fact,
why such an isolated segment does not live more than a, short time, being that it has not
got the necessary organs of nutrition. One cannot but be struck with the similarity of
this view to that set forth by Herbert Spencer {Princ. of Biol. ii. ch. 4 and 5), who
considers the Articulata to be "tertiary aggregates." The following passage expresses
A.'s view: "Many insects oanlive when cut into pieces, in this respect resembling
plants. This necessarily implies that their nutritive soul, though actually one, is
potentially many ; and, in the case of the animals, the same must be true of the
sensory soul ; for each segment plainly retains some- sensibility. Such an animal resembles
a number of separate animals united by growth into a single mass. There is this
difference between such an animal and a plant. The segments of a plant can live
for in indefinite time, and each segment can grow into the form of the entire plant
of which it was a portion. But . the segments of the animal only live for a very
short time. This is because they have not got the organs that are necessary for their
maintenance, some of the segments having no mouth, some no stomach, some neither
mouth nor stomach, and so on. In animals of the most perfect conformation, no such
phenomena as these are observable ; because their nature has reached the highest possible

202 Notes, ill. 5. " •

degree of unity. Still even in these some portions of the whole, when isolated, seem to
retain a certain small degree of sensibility, that is show the presence of a soul. Tortoises,
for example, can still move, when the .heart has been removed " {De Ju. et Sen. 2 ;
De Resp. 17, 4). , .

3. Because heat, though, not the soul itself, is the necessary agent of the soul in all its '
operations. Cf. iv: 10, Note 11 ; i. i, Note 13. •

4. As all sanguineous animals, i.e. all vertebrates, are capable of locomotion, these
words might seem surplusage. But they are not so. For A. holds that the bilateral
symmetry of animals belongs to them primarily in virtue of their locomotor organs ;
and that the symmetrical disposition of these determines an imperfect degree of bilateral
symmetry in the organs of vegetative life. ,Cf. iii. 2, Note il.

5. A.'s general notions on the subject of nutrition were much as follows. • Food, being
the material for the formation of the body, must contain the same substances as those of
which the body itself is composed {De G. et C. ii-. 8, 4); and therefore, as the body is
complex, so must th^ food be {De Sensu; 5, 30)." No one substance therefore forms a
sufficient food for any living thing. Even plants which seem to live on water really live
on water and earth, as farmers who use manure know. The most nutritive substances
are those which are sweet {De Sensu, 4, 14), and in all nutritive substances it is the sweet
element which is really nutritivef, though the sweetness may be disguised by the inter-
mixture of bitter, etc. , into the flavour. With sweet substances must be reckoned fat, .
which is nearly allied to them {De Longit. Vita, 5, il).

The food masticated in the mouth, but not otherwise altered (ii. 3, Note 5)., reaches
the stomach, where it is concoctfed ; the heat for this purpose, which is not common heat
l^ a heat with special powers (ii. 6, Note 7), being supplied by the liver and spleen,
which are hot organs in close contiguity with the 'stomach {D. P. iii. 7, 10). .The solid
and indigestible portion passes off by the lower bowel, but the fluid portion, which alone
can be serviceable in nutrition (cf. ii. 2, Note 4), is absorbed- by the blood-vessels of the
stomach and intestine {D. /". iv. 4, 3 ; ii. 3, 11), over the surface of ivhich they are
spread like the roots of a plant. These blood-vessels open by very minute and invisible
pores into the intestine, pores like those in' jars of unbaked olay that let water filter
through {D. G. ii. 6, 19). The matter thus absorbed passes up to the heart; irf the
form of vapour \a.vaQv}i.iaTa.C), not as yet being blood, but only (ii. 4, Note il) an
imperfect serum Jlfx^'P) • In the heart and vessels {De Somno, 3, 3] it undergoes a second _
■ concoction, these being the hottest parts 'of the body, and by this second concoction
the serum is converted into blood {H. A. iii. 19, 9), the ultimate food of all the organs.
The amount of blood thus formed is extremely small, as compared with the original •
materials ; for were it not so, the body would grow to an enormous bulk {D. G. i. 18,
46). The blood when made passes from the heart by the vessels (arteries and veins
alike), being mingled with air inhaled by the lungs and thence conveyed to the heart
(iii. -6, Note 3), and is carried to all parts of the body. Each organ selects from the
common stock those materials which it requires. The nobler parts, such as the flesh
and the Organs of sense, take the choicer elements, while the inferior parts, a,s bones and
sinews, are fed on the inferior elements or leavii^gs (uiroAefju/xaTo) of the former (Z>. G.
ii. 6, 41). This nutrition of the parts goes on most actively at night {De Sainno, i, 15).

Xhus every part of the blood that can be turned to account is utilised ; but such as
from its qualify is unfit for use, for instance any bitter substance, is excreted as bile,
urine, sweat, etc., in company' with the matter which results fromi the decay {avvrt\\i%)
of the parts themselves.

Such surplus of nutritious matter as there may be, after all parts are satisfied) is either

Notes, iii. 5 — 6. 203

converted into fat, or into generative secretionsj or escapes at the extremities of the
vessels, forming internally the. viscera and flesh, and externally the scales, hairs, feathers,
etc. Cf. iii. 8, Note 2. • '

6. The simile is borrovfed from the Timaus {jfowett, ii. 570), and is also used at
/I. A. iii. 4, 15. Galen used a simile not unlike it {De Nat. Fac. iii, 15).

7. This passage, with that quoted iii. 4, Note 20, shows clearly what was A.'^ idea
of the nature of flesh, or muscular tissue. He traced veins and airteries into the muscle,
found their branches getting smaller and smaller, until at last he lost sight of most
of them. This, he thought, was owing to the small veins being choked up by the thick
blood; the thus obstructed tubes -constituting the muscular substance. At the same time
the small arteries ceased to be tubular' and were solidified into tendinous fibres, which
being continuous on the one hand with the heart by the aorta and on the other with the
tendons and bones were the instruments of motion. •. .

8. Voigtel states that he observed blood to sweat from under the arm of a young man
after violent exertion. Such perspiration is llso said to have been observed in scurvy

, and low forms of fever. Landerer observed a red-coloured sweat in the axilla of a
patient suffering from fever. Cf. Todd^s Cycl. iv. 844.

9. The formatioii of blood w^as supposed by A. to go on mainly in the heart, but also"
■partially in the blood-vessels. Cf. De Somno, 3, 3.

10. Cf.- ii. 4, Note 10.

11„ If this passage be genuine, the meaning must be that the windpipe being of smaller
calibre than the other channels mentioned does not allow blood to flow through it so
easily as they do ; and. therefore that when blood gets into it, it is Qxpelled with force.
But I strongly suspect that the whole passage is an interpolation, written »t a later dat *
when oLfyrripla had. acquired the meaning of artery ; and that the passage (here without
meaning) had reference to the distinction between passive hoemorrhages from veins and
active haemorrhages from arteries. That the writer in fact mieant to say this: "The
veins are larger than the arteries ; and so the blood flows more easily thrgugh them than
through these. Thus,*when bleeding occurs from the. veins, the haemorrhage is passive,
as we see in the ordinary bleedings of the nose, etc.; whereas, when bleeding occurs
from an artery, the blood is ejected with force and the haemorrhage is active."

12. The common iliac arteries, formed by the division of the descending aorta, do in
fact, as A. says, come forwards and lie in front of the common iliac v.einj ; whereas ais a
general rule the veins lie in front of the arteries.

What however is meant by saying that a similar interchange of position occurs between
veins and arteries above the heart it is difficult to understand. I can but conjecture that
the reference is to the pulmonary artery (considered by A. to be a vein ; see iii. 4, Notes
23 — .24), wliich at its origin is in front of the aorta, and then runs upwards and backwards
under the aortic arch, sending, moreover its right and larger division behind the ascending
aorta. A" somewhat similar, but much vaguer, passage occurs in the Timceus {yowett,
ii- 571)-

(Ch. 6.) 1. It will be noticed that A. always speaks oithe lung of an animal, and not
as we do of the lungs. H© considers the two to be merely subdivisions of a single organ,
because they ha.ve one common outlet, viz. the trachea. When the right and left bronchi
which lead from this to either lung are of more than ordinary length, as in birds, he
admits that the lung has the outward appearance of- being a double organ, but still
considers it really to be a single one for the above reason ; though " any one might think
that there were two because the ducts from the two divisions unite at a considerable
distance from them" {H. A. ii. 17, 4; D. P. iii. 7; 3). So again \H. A. i. 16, 11),

204 Notes, iii. 6. •

"The lung, i^ all animals that have one, has a tendency to consist of two parts. But
the division is not so apparent in the vivipara as in the ovipara, and is least apparent in
man. But in the ovipara, that is in the birds and the oviparqus quadrupeds, the two
parts are so widely separate that there appear to be two lungs." As to the Ophidia,
where often only one lung is developed, he specially • mentions (ZT. A. ii. 17, 22) that their
lung is simple, i.e. undivided.

2. Cf. ii. 16, Notes 10 and 11. It is noticeable that, though' A. considers the "innate
spirit " to be of a hot nature, he several times speaks of it as producing refrigeration ; not,
however, by its direct but by its indirect action, in causing fanning motions in the body. •
See iii. 6, Note 14. •

3. A.*s theory of respiration, as expressed in the separate treatise on the subject, is as
follows. He rejects the opinion that the purpose of respiration is to keep up the internal
heat of the body {De Resp. 5, 6, and 4, 8), and holds that it has exactly the .contrary
object. Heat is being perpetually produced in the heart, and would accumulate in excess,
were there no means of reducing it when necessary {De Resp. 8, 6). The bloodless
animals produce so little heat, that no special arrangements are required to cool them ;
the simple bathing of their surface with air or water being sufficient as a rule for the
purpose {fie Resp. 9, i). Yet even in some of these, as in certain insects, there is a
provision, in the Hypozoma (ii. 16, Note 10), for the better reduction of the heat. In
sanguineous animals, however, that are of a hotter nature, there is always some special
provision for keeping the heat within bounds.- In fishes the reduction is effected by the.
water, which bathes the gills into which blood is conveyed from the heart {De Resp. 21, 6).
It is,, says A., the water itself and not, as some would have it, the air contained in the
water, which is the ageni of refrigeration. In support of this statement he urges several
arguments {De Resp, 3, 3), of which the chief is that no bubbles are given off by fishes
under water, as there would be were air inspired and expired. In other sanguineous
animals the internal heat is greater, and refrigeration is effected by the, more perfect
agency of air {De Resp.' 1% 2) inspired into a lung, air being a more perfect agent than
water because it cAn permeate the body mpre rapidly. The lung itself differs in different
animals, being more perfect the nobler, that is to say the hotter, the animal is. Thus it
is dry and bladder-like in ovipara (cf. Note 10) that are comparatively cool; and full
of blood in the vivipara that are of a hotter character {H. A. i. 17, 7.; De Resp. 3, 2).
The cold air, djawn into the lung, reaches the bronchial tubes (o-iJpcyyes), and as the
vessels containing hot blood run alongside these tubes and in immediate contact with
them {De Reip. 21, 4 ; II. A. iii. 3, 15), the air cools it, and carries off the Superfluous
heat ; as is shown by the fact that the air expired is much hotter than the air' inspired
{De Resp. 5, 6). Some of the air which enters the lun^ gets from the bronchial tubes
into the blood-vessels, although there is no direct communication between themj simply
owing to the close contiguity in which tubes and vessels lie (iii. 3, Note. 9). The air
permeates the body rapidly and cools the blood in the vessels, throughout the body, as
the air in the lung cools the greater heat in the heart.

It appears then that lung and gills have the same function, and, says A., they conse-
quently never co-exist. No animal that has a lung ever has gills. "For it is best to
have a single organ for a single purpose ; and one method of refrigeration is enough for
any animal " {De Resp. 10, 6). As regards this last passage, we may remark that A.
was of course in complete ignorance of the perennibranchiate amphibia, so that^his.
erroneous statement that gills and lungs never co-exist may be passed over. • One cannot,
however, but ask, as did Galen, how he reconciles ^is present statement with his having
in fact attributed one and the ^ame function to lung and to brain. He nowhere explains

Notes, iii. 6. 205

this seeming inconsistency. I imagine, however, that what he would have said was this.
The lung provides for the general refrigeration of the heart and body at large. But in
order to ensure the perfection of the sense-organs (Z>. P. ii. .10, 11), it is necessary that
there shall be a part where the refrigeration shall be much more intense,- and this part is
the brain.

4. Cf. iv. 13, Note 38.

5. " Of all animals the strangest are the dolphins and those other Cetacea, such as the
whale, that have a blow-hole. For one cannot easily class them either simply as water-
animals, or simply as land-animals, if we define land-animals as those that- take in air,
and water-animals as those which take in water. For these animals do partly one, partly
.the other. For they take in sea- water and discharge it by the blow-hole, and they also
have a lung and with it take in air, etc." {H. A. viiu 2, 4). From this and similar
passages it is plain that A. made a distinct division of Cetacea, separating them on the
one hand from the viviparous quadrupeds owing to their living entirely in the "water and '
having no distinct limbs, and on Jhe other hand from the fishes, owing to their having
a lung, true bones, and mammae.

6. The mechanism of respiration is described elsewhere {;De J?esp. 21). ' The lung is
compared, aptly enough, to a pair of forge bellows. When the lung is expanded, air
rushes in ; when it is Contracted, the air is again expelled. The expansion is brt)ught
about by the heat derived from the heart ; heat always causing expansion in the parts to
which it extends. ■ The lung then, heated by the heart, expands ; and with it .the cavity
of the thorax. Cold air rushes in to fill the void, and the heat is reduced. This causes
the lung and thorax to collapse, and the air is expelled.

7. The argument seems -to be this. If the motion of the heart depended on the lung,
then that motion should be precisely similar in all animals that have a lung. But this is
not the case ; for in man alone, or nearly so, does palpitation occur. A; guards himself
somewhat by the words ^^ so to sfeak," which is a usual form with him for ^^witk some
exceptions." Otherwise he is in error in saying that man is the only animal whose heart
is set in violent palpitation by mental emotion, as every experimental physiologist knows.
"In a frightened horse," says Darwin, " I have felt through the saddle the beating of the .
heart so plainly that I could have counted the beats" [On Expression of Eviotions, p.
77). The distinction between jumping palpitation (ir^STja-ty) and ordinary heart action
(fiXffjs and atpvynos) is elaborated in £>e Resp. 20, A. 's explanation of the heart's action
and of the pulse, as there given, .was as follows : The food, he says, is without intermission
pouring into the heart ; here it is heated ; and this heating causes it to swell, just as water
swells and bubbles .up when boiled. The dilatation of the heart is due to this, as also
(see last note) is the expansion of the lung and thorax, which leads to the admission of
cold air into that cavity. The entrance of air cools pot only the lung but also the heart,
and in consequence they both contract.- This alternate expansion and contraction of {he
heart extends to the blood-vessels (i.e. arteries and veins), as they are continuous with the
heart, and the blood within them is affected by the changes of heat in thie same way as
that in the heart. Thus the blood-vessels throb simultaneously with the heart, and aU'at
the same moment. The internal heat is greater in youth than in after-life (ii. 2, Note
10) ; consequently the whole process described, which is due to this heat, takes place
more rapidly at that period *of life;. and this explains why the pulse is more rapid in
youth than in after-life. Aristotle also- compares the beating of the heart to the throbbing
felt in a swelling while puS is yet being formed, this throbbing like the pulsation being
due to concoction ; for, as soon as the pus is concocfed and fully formed, the throbbing

.ceases.

206 • Notes, iii. 6—^.

8. In saying that in most animals-the heart lies above the lungs,, A. means, I imagine,
that -in birds and reptiles the lung extends far down below the site of the heart ; which
is in fact the case, if we allow, as A, did, that the air-sacs form "part of the bird's lung.
Cf. Note lo. . ■

9. Their "heat is great, and therefore they require a large lung to temper it.

10. A.'s account suits very well to the lungs of amphibians and reptiles, but as regards
birds can only be explained by admitting that the true lungs, owing to. their comparatively
small size and their being confined to the back of the thorax, had escaped his notice, and*
that he took the much larger air-sacs for them, or at any rate included these in the lupg.
A. thought that a bladder-like Fung was an inferior organ, because.it had but a small
amount of blood. It is an inferior organ, because of the small surface for the exposure
of blood to the air. ' .

11. "Birds with talons may be said, speakirig generally, never to drink at all. Other
birds drink, but sparingly" {H. A. viii. i8, 3). As to reptiles, cf. iii. 8, Note 4.

12. The real reason why a reptile or amphibian can remain under water for a long
time is that its tissues produce, for equal weights, less carbonic acid in a given time than
those of _other animals, so that there, is less rapid need fof respiration (cf. Bert. Lemons mr
la Resp.). As to such birds, as the duck, etc., it is the large amount of blood in
their body, which, f9rming a store of oxygen, enables them to remain so long without
breathing.

13. A. always regards birds as cold animals, though their great heat is readily percep-
tible to touch, and cannot have been unknown to htm. It is, however, in vital heat, not
in ordinary heat, that he Jiolds them deficient. Cf. introd. p. xxxi.

14. A. seems to have had some strange notion that a fan cools a body not merely by
bringing a continuous current of cold air into contact with it, but directly by its own
motion, that is independently of the air. " Every hot body," he say's, " is cooled by the
motions of bodies external to itself" (D. P. iii. 4, 30). 80 he supposes fiere that
when an animal is under water, its lung will continue -in motion, and that, though no air
is admitted, yet the motion will itself produce a certain amount of cooling in the neigh-
bouring parts. See also De Resp. 9, 6. " • .

15. Cf. ii. 9, 9.

16. " Erect " seems to be used here, not in its ordinary sense of standing on the hind
legs, but as having the body removed from the ground, so as to apply to "quadrupeds as
well as to men. ' . •

17. Alluding to the viper, • . .

18. Plato thought that the lung in all animals was bloodless (cf. Joweifs Tr. ii. 564).
A. holds that the lung of mammals is the Organ which of all is most richly supplied with

. blood, but that the lung of ovipara is " bladder-like and contains but little blood." He
alludes elsewhere (ZT. A. i. 17, 7) to Plato's erroneous statement, without naming him.
■ (Ch. 7.) 1. It seems to have been the universal opinion of the ancients that the
spleen was the left homologue of the liver. In modem times the more general view is
that of Miifler, that there is no such relation between them, each being an azygos organ.
The ancient opinion is not, however, without its modern advocates. Dr. Doellinger for
instance (firundriss der Naturlehre des menschl. Organ. 1805) supported it ; and still
more recently Dr. Sylvester {The Discov. of the -Nature of the Spleen, 1870) has argued
with much ingenuity that *' the spleen is not a blood-gland in the mesial line of the body,
having no homologous relationship with the liver," but that "it is the left lateral homo-

. logue of a portion of the liver, the letter being a combination of a sanguiferous gland and
a biliary apparatus, " and the spleen the homologue of the form'er portion of it.

• Notes, iii.- 7. 207

2. On the question of the bilateral symmetry of the organs, and especially of the
abdominal organs, where alone there is any difficulty, cf. Sylvester, Disc, of Nature of
Spleen, p. 12,
. 3. Cf. iii. 6, Note i, '

4. By animals that necessarily have a spleen are meant, as will presently appear, , the
viviparous quadrupeds, or mammals ; by those that have it merely " by way of token "
are meant the oviparous vertebrates, i.e. birds, reptiles, amphibia and fishes.' The spleen
is in fact notably larger in the former than in the latter.

There is some foundation for the statement that the size of the spleen and the distinct-
ness with which the liver is divided into lobes are inversely related to each other. Thus
it is in Mammalia that the spleen is largest in proportion to the body, and in them also
that the liver is least distinctly lobulated. Among Mammalia it is the rodents that have
the smallest spleen, and in these also it is that the liver reaches its maximum' of sub-
division. On the other hand, the splfcen is large in ruminants and their liver at the same
time presents scarcely any marks of lobulation. In the Ovipara the spleen is ijnuch
smaller than in Mammalia, and the liver, as a general though not universal rule, is much
more decidedly cleft into distinct 'lobes. . In all birds, in all batrachians, and in all reptiles,
excepting Ophidia, the liver is distinctly divided into two lobes. In the remaining class,
fishes, the spleen varies much in size ; sometimes is apparently altogether absent, some -
times, excessively gmall, sometimes almost as large in proportion to the body as thaf of a
mammal, and the liver is sometimes multilobed, sometimes bilobed, sometimes unilobed.
In this class, however, I cannot ascertain that there is any such relation as that mentioned
in the text between the two conditions.

6. The exceptional ovipara are the Ophidia and many osseous fishes, where the liver is
unilobed. The exceptional vivipara are the rodents (see last Note), of which A. specially
mentions the hare. "Near the lake Bolbe, and in other parts, a species of hare is
found, that might be taken to have two livers, because the ducts unite at a consider-
ably distance from the organ, just as is the case with [the bronchi from the two divisions
of].the bird's lung" (ZT. ^. ii. 17, 4). \ '

6; In cartilaginous fishes th# liver consists of two distinct lobes, whereas in osseous
fishes it is ofteh unilobed.

7. Cf. iii. 5, Note' 4.

8. Assisting them va the mechanical way immediately mentioned, and also by providing
an outlet for their surplus blood. Cf. iii. 13, Note i ; iii. 8, Note 2.

9. The mesentery is meant. " ■ "

10. What I have translated "immoveably" is literally "like nails." The introduction
of nails into the" metaphor is however so out of place, that I am strongly tempted to
suggest that A. wrote ^vvi.i not ^\oi. Y.yvi.t are the large round stones to which anchor-
lines were fastened in old times. The metaphor would th'en run onfall fours. . The ship
is the main blood-vessel ; the anchor-lines are the putstretching branches ; the round
anchor-stories are the rounded liver, spleen, kidneys.

11. The hepatic and splenic arteries seem to have escaped A.'s notice ; probably because
they are not given off directly from ihe aorta.

12. Plato described the spleen as made of bloodless substance. Cf. yowett's. Trans.
ii. 566. ^ •

■ 13. Cf. Note 18.
14. The spleen is small in all birdsj but whether specially so in these, or in'the owl,
which he adds elsewhere ^H. A. ii. 15, 7) to the list, I -cannot say. The stomach, argues
A., is so hot in these birds as to be able to concoct food, without the aid of a spleen.

208 Notes, iii. 7—8.

15. A. assigns two main functions to the spleen ; one, to assist by its heat in the
concoction. of the food ; the other, to withdraw superfluous humours from the stomach.
When these offices can be adequately performed without the aid of a spleen, then this
organ is of small size. Thus in birds the stomach is hot enough to effect concoction by
itself, and there is an adequate outlet in the skin for the superfluous humours. In birds
then the spleen is^mall. So also with other ovipara. In fact in these animals the spleen
exists for no actual use ; but simply to fulfil the law of symmetrical development, which
requires some counterpart to the liver.

Such was A.'s idea of the spleen. The notion of its serving to attract superfluous
hiamours was taken from Hippocrates, who thus expresses himself, " I say that, when a
man drinks a more than- ordinary amount of .fluid, both the body and the spleen attract to
themselves the water from the stomach " (De Mortis, iv. 9). And again, " When a person
has fever and violent thirst, and drinks copiously without vomiting, a part of the fluid
passes into the bladder and is expelled as urine ; but the rest is taken by the spleen,
which attracts it from the stomach, being of a porous and spongy texture, and lying cloee
to the stomach " {De Morb. Mul. i. 15).

This notion was actually revived by Sir E. Home, who .imagined that when fluid was
drunk much of it passed from the cardiac end of the stomach by some unknown channel
directly to the spleen. This view, however, he afterwards abandoned. See Phil.
Tram. 181 1.

16. " In those that drink marsh- water the spleen always becomes enlarged, and the
belly hard." — Hippocrates.

17. A bladder-like lung is to A., owing to the small amount of fluid it contains, an
indication of scanty fluid in the body generally. See next chapfer.

18. A. thought that the bladder was the essential agent in forming the urine, and the
kidneys m«re adjuncts, though he also admits that when the fluid leaves- the kidney, it
already has in a measure the characters of an excretion. Cf. iii. 9, 7. A.'s 'error was
corrected by the time of Galen i^De Usu part. 5, 5).

19. Namely from above downwards ; an upper position implying 'generally superiority
in other respects. Cf. iL 2, Note 6.

(Ch. 8.) 1. i.e. the Mammalia (cf iii. 6,' Note 9). As a matter of fact birds have no
bladder, and yet highly vascular lungs ; but their real lungs escaped A.'s notice. Cf. iii. 6,
NotQ 10.

2. A. distinguishes the scales of fishes from those of reptiles by giving them distinct
names, but nowhere discusses their differences ; excepting that he says, " these plates are
equivalent to scales, but of a harder character." Cf iv. 11, Note 14.

As regards the formation of scales, and similar parts, his notion was this. The blood
passes from the heart to all parts of the body by the vessels. At last it reaches their
ultimate twigs. As none of it returns to the heart, it must here be disposed of in some
way or other. That in the internal vessels is converted into the substance of the viscera
(cf iii. 7, Note 8) ; that in. the external vessels oozes out as sweat, or is converted into
various integumental structures, nails, hairs, scales, feathers. But when there is loo
much blood for its excess to be thus got rid of, or when the integument is such as not to
allow of transpiration, some other means of disposal are required, and these are furnished
by the presence of urinary organs. Bacon (A'a/. Hist. § 680) expresses a similar opinion.

3. !Both here and in other passages it is stated that Mammalia alone have an urinary
bladder, with the exception of tortoises. The facts are these. AIL Mammalia have a
true bladder developed from the allantois, directly continuous with the ureters (Mono-
tiemata excepted), and serving for the reception of urine and for this alone.

Notes, iii. 8^9. 209

In tirds there is no bladder whatsoever.
•. Of reptile's, the Ophidia are Without a bladder. So are lizards, crocodiles, and some
other Saurians. Bot maiiy Saurians knd all Chel6nia (as also Amphibia) have a bladder
which appears to be the.remains of the allantois, and which if it be .so is the homologue
of the mammalian .bladder. But this bladder is not in direct continuity with the ureters,
but opens out from the anterior wall of the cloaca, while the ureters open into the cloaca
posteriorly. This bladder, in spite of its position, is supposed to serve as a receptacle
of urine, and urinary salts are said to be found in the fluid it contains. Probably,
however, its chief function is to serve as a store-house of fluid for the animal's use in
times of divDught (cf. Todd's Cycl. i. 104; Darwin, Beagle, p. 383). This bladder
acquires its greatest development in the Chelonia-, where it is of very large size. .Thus
is explained the statement in the text. . .

In fishes there is nothing homologous to . the mammalian bladder ; nothing that is
developed from an allantois, so far as is known. But in most if hot all osseous fishes,
and in some cartilaginous fishes, the ureters either before or after their junction form a
dilatation, which is called a, bladder, and doubtless serves as an urinary reservoir. This
dilatation is small, and lies behind the intestine, whereas an allantoidean bladder is
always in front ; so that it is no wonder it should have escaped A.'s notice. Its presence
•hfis indeed escaped some distinguished modem anatomists (cf. M. Edwards, Lemons,
vii. 326). In no invertebrate is there a bladder.

4. A. is mistaken in supposing thaP tortoises drink but little. ' On the contrary, they
are very fond of water. Darwin describes them as wearing broad and well-beaten paths
to the springs in Chatham Island, and adds: *' Near the springs it was a curious
spectacle to behold many of these huge creatures, one set .eagerly travelling onwards with
outstretched necks, and another set returning after having drunk their fill. When the
tortoise arrives at the spring, quite regardless of any spectator, he buries his head in the
water above the eyes, and greedily swallows great mouthfuls at the rate of about ten
a minute " ( Voyage of Beagle, p. 383). Had A. known this, he would most certainly
have accounted for the tortoise's bladder by its tl^irsty habits.

6. The lungs of Chelonia are of much greater size than those of most Saurians and
Amphibia, and "s'etendent le long du dos jusqu'au bassin au-dessus de tons les visceres "
{Cuvier, Zefons, iv. 347). They are moreover not only thus larger; but contain "in
correlation with the non-transpirable integument a much greater development of internal
parenchyma" {Rolleston, , Forms of An. Life, Ix. ). This comparative abundance of
parenchyma is more marked in marine than in other tortoises {Cuvier, Lemons, iv. 324 and
332). There can then be no doubt that A. had carefully examined the lungs of
tortoises and other reptiles. It is however an exaggeration on his part to say that the
lung of a sea-tortoise resembles that of an o:f. The amount of parenchyma is by no
means so great. Probably he was led to make the comparison by his having already
found a* likeness between the kidney of the ox and that of the sea-tortoise, in its great
subdivision. Cf. next chapter. Note i. ' .

6. According to Perrault exactly the reverse is the case ; the bladder being usually
much larger in the land-tortoises than in the sea-tortoises. Cf. M, Edwards, Lemons,
vii. 344. .

(Ch. 9.) 1. A similar statement, that no Ovipara save the tortoises hare kidneys, is
made elsewhere {H. A. \\. 16); where also it is said that the kidney of the tortoise
consists, like that of the ox, of numerous smaller parts. The chelonian kidney is in fact
extremely subdivided on the outer surface ; so that there can be no doubt that A.
had examined it. But it is difficult tp understand how the kidneys of other Ovipara

14 . •

2IO ' Notes, iii. 9. " . •

escaped his notice. It is true they are so differently shaped from those of a mammal,
or even of a tortoise, that they might appear to a careless observer to be totally different
organs. But the probable explanation is that A. argued h priori that it was impossible
for there to be a kidney ..if there were no bladder. For the essential organ in the
formation of urine was, as he thought, hot the kidney, but. the bladder ; and the kidneys
were but adjuncts to this (iii. 7, Note 18). A kidney then in an animal without a
bladder was to A. just as absurd a supposition as would be to us an urinary bladder
when there was no kidn6y. That A. was misled by this preconception is shown by the
fact that he did see the Icidneys in birds, and did recognize their kidney-like aspect ;*
but yet refused to consider them as true kidneys.

2. In birds' the kidneys, almost always trilobed.are flattened against the back, and,
fitting into the deep interspaces between the bones, retain the impressions of these
successive cavities or depressions. •

3. The Emys was some freshwater tortoise {^H. A. v. 33, 3) ; but what species is
uncertain, as there are several in Greece. None is without a bladder, but this is equally
true of all known Chelonia. Neither has any animal now known as Emyi a soft shell.
The Sphargis coriacea or leathery turtle has a soft shell, and is consequently supposed
by Frantzius to be the species meant. But' the Sphargis is a marine species. Possibly
Emys may have been a name common to both freshwater tortoises and to th5 marine .
Sphargis. ■ .

4. Cf iii. 7, Note 8. • " . *

6. The cavity in the seal's kidney is very small. It is pictured in section by Buffon
{^Hist. Nat.yixa.. pi. 48). The kidney consists of numerous distinct lobes, and in this
respect resembles that of an ox. ,

6. This is not true of adult man, excepting as an occasional anomaly. But it is true
of the foetus. This is one of the state'm'ents which lead me to fancy that A. may have
dissected the human foetus. Cf. i. 5, Note i. •

7. Not all quadrupeds other than the ox have non-lobulated kidneys, though such is
the general rule. The elephant, bear, otter, all have lobulated kidneys. It is a curious
fact, not yet explained, that the kidneys are of. this character in nearly all water
Mammalia. •

8. The bloodless ducts are the ureters. The ducts from the aorta and great vessel are
the renal arferies and veins • respectively. The reason why A. introduces the word

. " continuous " appears from the last sentence in this chapter.

9. Cf. iii. 7, Note 18, ' , ' ' '

10. The same fanciful nietaphor was used before. Cf. iii. 7, Note 10.

11. This is the general but not universal rule. One of the exceptions is man, where
the right kidney is usually slightly lower than the left.

12. As it was an axiom with A. that the right side .was naturally superior to the left
(cf ii. 2, Note 6), so also was it another axiom that all locomotion began from the right
{De Casio, ii. 2, 4). In fact, his definition of right is the part from which locomotion
begins. In the treatise De An. Incessu (4, 7; 6, i) evidence is adduced in support of this
axiom. That motion begins on the right is shown, it is said, by men preferentially
carrying bjirdens on the left shoulder, so as to leave the motor gjde free ; as also by
their standing on the left leg more easily than on the right, with the same object ; by
the attitude assumed in fighting, when the left limbs are advanced and the right kept
back, so as to serve for motion and defence ; and, lastly, by the fact that spiral shells
are dextral, that is to say, that the opening whence the motor organ is protruded is on
the animal's right. ,

Notes, iii. 9—10. 211

Whether men carry burdens preferentially on the left .shoulder, so as to bring the
■right and stronger hand into play, or whether they rest . preferentially on the left leg,
I cannot say. But parrots, as I have shown elsewhere {Royal Med. Chir. Trans.
1871), stand as a rule on the right leg. Spiral shells are as a rule dextral. . •

As to the remark in the text concerning the raising of the eyebrows, the Greeks appear
to have had much more mobile features, and to have studied facial expression more
closely than ourselves ; so that very possibly the statement taiay be a true one. The only
evidence I can find is furnished by a photograph by Duchenne of a young man simulating
grief ^nd arching his brows (reproduced in Darwin on Express, pi. ii, 2). The right
brbw is in this case very much more arched than the left.

13. The kidneys of Mammals are imbedded in a tunica adiposa.

14. The argument seems to be this. That fat is the result of concoction is sliown by
the fact that it float* on .water, this upward tendency being a proof of the presence of
heat in it ; and this heat cap only be accounted for by supposing it to be that residue of
heat which is always left in a fluid after concoction. ' Cf- ii. 2, 24.

16. Cf. ii. 5, Note i.

16, "So again the Creator placed only a small quantity of flesh in the joints'' of the
bones, that it might not interfere with the flexion of our bodies." — Timceus.
■ 17. Auber and Wimmer say that this is true of rabbits; whether it is also true of
other animals! cannot say.

18. ■ The layer of fat is not equally* spread -over all the surface of the kidney, at any rate
in man, but is accumulated especially upon the outer and inner borders.
^19. A. is plainly speaking of some disease that is compatible with accumulation of fat,
and thit also is, at any rate sometimes, rapidly fatal. Such seems to be the case with
rot., "In this disease there is no loss of condition, but quite the contrary. For the
sheep in the early stages of rot has a great propensity to fatten " ( Youatt, Book of Farm,
ii. 386). Again the rot is sometimes "rapid in its course, and this season a large
number of sheep have been killed very quickly by it " {Gamgee, Pr. Counc. Rep. v. 240).
I need hardly say that A. 's view of the pathology of the rot is erroneous. He was
probably led to attribute the disease to the kidneys, from dropsical collections being a
common accompaniment of it. • ' ' . •

. 20. The ox and the sheep, says John Hunter, hav6 more fat about the kidneys, the
loins, and within the abdomen, than most other animals {MUseum Cat.m. ^12).

(Ch.lO. ) 1. Mammals alone have a perfect diaphragm- "Most of the Vertebrata,
however, exhibit something analogous to the diaphragm. Thus in fishes the muscular
septum dividing the cavity of the branchial apparatus from the abdomen bears a certain
resemblance to a diaphragm" {Todd's Cycl. ii. i). . In birds there is an imperfect diaphragm,
most fully developed in the ostrich. In reptiles also there is "a rudjmentary form of
diaphragm which arises as a broader thinner muscle than in birds from the vertebral
column and carapace, and is interposed between peritoneum and pleura, without however
meeting its fellow in the middle line from the opposite side " {Carus, Comp. An. 149),

A.'s statement is then iii a certain sense true. The description, however, given farther
• on applies, only to the perfect diaphragm, viz. that of mammals,

•2. The absprbed food was suppose'd to pass upwards from the intestine .through the
vessels in the form of a vapour. Cf. iii. 5, Note 5. '

3. "For the motion of the heat in blood destroys the sensory activity ".(ii. 10, ii).

4. A. has plainly in his mind the views expressed in t"he Timceus. Plato held that man
had a triple soul • an intellectual soul, seated in the head ; a soul endowed with cpurage
and the nobler passions,. which had its seat in the thorax; and a third soul, to which

212 Notes, ill, 10 — 12. ■ '

belonged desire and.the grosser passions, which was located, in the belly. The diaphragm
served as a barrier to preserve the thoracic soul from the inroads of the "ravening beast"
below. ', .

6. Cf. ii. 2, Note 6.

6. A notion still commemorated in the anatomical terms "phrenic nerves" and
"phrenic centre."

7. The qentral part of the midriff, which is tendinous, is the "cordiform tendon" of
modem anatomists. It is not easy to see why A. should say that the parts nearest the
ribs must of necessity be fleshier than the centre. I suppose he must mean, 'that, as the
flesh or muscle lies generally on the external aspect of the trunk, the part of the midriff
which comes nearest the outside will partake most of the character of that surface ; and
so be the most muscular.

8. The anthropoid apes are sensitive to tickling, especially about the arm-pits, and may
be said to laugh. I have myself witnessed the fact in the case of the chimpanzee.

9. When the diaphragm is suddenly ruptured, instant death usually follows, and the
fate is said invariably to assume the peculiar expression or grin, called Risus Sardonicus.
Cf. Did. d. Sci. Medic, ix. 214. .

10. Iliad X. 557 ; Odygsey xxii. 329. In both places the reading is ^Beyyofxevov not
(pdeYyofievr). The works of Homer appear to have assumed in ancient times almost the
position of sacred books, and to have been quoted not merely as poetry, but as authori-
tative in matters of history and science. Lucian is pferpetually making fun of this absurdity.

11. Prpbably meaning " armed " Zeus. So there was a temple of Here Hoplosmia
in the Feloponnesus (cf. Lidde/i and Scoii). ' ^ • .

12. Cf. iii. 5, Note 2. ■'

13. Cf. iii. 7, Note 8. .

(Ch. 11.) 1. The pericardium and dura mater.

2. This shows how far A. was from regarding the brain as an organ of no importance,
a mere spongeful of water, as Galen says. Cf. ii. 7> Note 27.
(Ch. 12.) 1. Cf. iii. 7,' Note 4.

2. Cf. iv. 2, Notes 7, 8 ; iv. 3, Note i.

3. And, in mammals, the lung {jFf. An. i.' 17, 7).

4. The liver of mammals and birds is as a rule of a brown-ted colour. In reptiles it
inclines to a y^low hue ; and in fishes this yellow tint is often still more decided. Cf-
Cuvier, Le^ms, iv. 14. ,

5. " Foul," because the degree of yellowness is to A. a measure of the impurity which
the liver has to separate from the blood. Perhaps also with some reference to the views
of the soothsayers, who seem to have considered a pale liver to be an unfavouiable omen,
the lucky tint being the normal mottled red, the voikI\7\ tvfxop(pla of ^Eschylus ; in which
case "foul" would correspond to the " turpia exta" of Livy (xxvii. 26).

6. Or perhaps " of a broad aval form;" ffTpoyyv\oi being the term applied to a
merchant vessel as distinguished from a ship of \var. '

7. The spleen * ' is broader at one end in the cow, reindeer, and giraffe than in other
fuminants" (Owen, Verteb. iii. 561). In thehbgit is elongated; so also in Carnivora
generally. In the Ungulata it is of proportionately smaller dimensioiis than in the
Carnivora, and in the horse is "elongated, flattened, broadest at the -upper end." A.'s
account so. far therefore fairly tallies with the facts. But as regards man his statement is
erroneous. For though the human spleen is very variable in shape as in size, yet it cannot
be said to be elongated in comparison. with that of other mammalia. I am. however by
no means certain that it is not more elongated in the foetus ihan in the adult. It appears

Notes, iii. 12 — 14. 213

to be so in the drawings in Crisp on the Spleen. If so, this would be another argument in
support of the view that A. had dissected the foetus. Cf. i. 5, Note I. '■

8. A. seems to have been at a loss how to classify the pig. Here he reckons it with
the many- toed animal? in opposition to the animals with solid or cloven hoofs. In the
next chapter he separates . it from the many-toed, and puts it into \ separate division,
consisting of "those that have a cloven hoof, but yet have front teeth in both jaws," of
course in contradisfinction to the ruminants. In another place {H. An. ii, i, 3i)he says
the pig lies half-way between the cloven-hoofed and the solidungulates ; and in corrobora-
tion of this, states thai there are sometimes pigs with a solid hoof; an anomaly of which
instances do in fact occur not very rarely.*

The foot of the pig has in reality four toes ;. but of these the tvo middle ones are much
longer and stouter than the others, and form a cloven hoof which is used by the animal in
walking.. The two lateral toes are also furnished with hoofs,, but are placed at some
distance above the ground, so as not to touch it.

.(Ch. 13.) 1. I take the meaning to be this. '• Wherever there are blood-yessels there
must necessarily be either viscera or flesh ; for these are the means by which the blood
gets rid of its surplus material (cf. iii. 8, Note 2). As there are vessels both inside and
outside the trunk, so iTiere must be viscera or flesh inside and outside it ; and, the flesh
being without, the viscera are within.

It is the viscera that exist " for the sake of the. vessels "" (cf. iii. 7,. Note 8) ; the flesh
that "cannot exist without them." Cf. iii. 5, Note 7.

(Ch. 14.)" 1. i.e. in fishes. Cf. iii. 3, Note 2.

2. Cf iii. 12, Note 8. .. '

3. The camel has in feet two incisor teeth in the upper jaw. But these are placed?
laterally close against the canines, so as to leave. a considerable vacant space in the front
of the mouth. Had A. known of the existence of these upper incisors, he' would not
have failed to find in their presence a striking confirmation pf his views as to the inverse
development of teeth and horns. Cf. iii. 2, 'Note 19.

4. TJie argument is this. The presence of a multiple stomach and the absence of
upper incisors are inseparably united by correlation ; this being apparently one of those

. laws of type (Cf. Introd. p. x) to which nature is obliged to conform her action. Nature
then, when she gave a multiple stomach to the camel, as the best instrument for the
digestion of hard food, was forced to take away the upper incisors, although the absence
of horns left sufficient matter for their production. The earthy matter, thus hot disposed
'of, was utilisec^ by her in the' formation of a hard palate, which to a great extent acts as ,
substitute for the wanting teeth.

5. Because flesh is the medium of tas'te. Cf ii. 10, Note .10.

6. Not only in camels but in all ruminants the place of the upper incisors is supplied
by a hardened gum, against which the lower teeth bite ; and, in addition to this,

. numerous hard papillae are developed from the buccal membrane. Along the roof of the
mouth, these run in parallel lines, being flattened and furnished with retroverted toothed
margins. They are very conspicuous in the camel. Cf. Owen, Vert. iii. 392.

7. Cf. H. An. ii. 17, 8, and iv. 5, Note 34.

8. Elsewhere {H. An. ii. 17, 28) fowls, doves, pigeons, and partridges are enumerated
. as having a crop. That the crop does in fact in part supply the place of a masticating

mouth by softening the food is well known to bird-fanciers. If a pigeon be allowed to
swallow a number of peas, they will swell inside the crop to such an extent as almost t«
suffocate the bird.

9. The oesophagus as a general rule is wide and dilatable in birds, " in correspondence

.214 Notes, ill. 14.

with the imperfection of the oral instruments as comminutors of the food " (Owen). It is
especially wide in the cormorant and other fishing birds, A. {//. A,, ii. 17, 30) gives as '
examples several species of crows, with which he appears (//. A. viii. 3, 15) to have
classed thfe cormorant. . ' •

10. Alluding to the prmentriculus or glandular stomach. This exists in all birds, but
is much larger and more glandular when there is no crop, than when such is present.
Doubtless in such cases it supplies the absence of the crop {Cuvier, Lemons, ■ iii. 408), and .
acts as a storehouse of food. •

11.' The example given in the H. A. (ii. 17, 31) is a bird which Aubert and Wimmer
identify with Falcq tinmmculus. They point out that in all the diurnal birds of prey
there is a peculiarity, thus described by Meckel (7>. Gen, (TAnat. Comp. viii. 314) :.
"L'estomac folHculeux d'une ampleur peu considerable forme subitement une saillie*
allongee, qui est separee par une etranglement, superieurement de I'oesophage, et
inferieurement de I'estomac musculaire; "

12. The gizzard is strong and muscular in graminivorous. birds.; but thin and mem-
jbranous in the carnivorous species. • •

13. In the Greek text, instead of oesophagus .(trTiJ^uaxos) we have crop (irp6\ofiof). This
must be an error ; for the presence of a crop is one of the very provisions which A. has
just enumerated, and which he says are wanting in the long-legged marsh-birds, i.e. the
Grallatores. I'have therefore substituted oesophagus for crop ; which is in harmony with
the parallel passage in the Hisi. An. (ii. 17, 32)^ vi-here it is said th9,t these birds have
a long oesophagus to match their long neck. .

In the typical waders there is fto crop ; neither is the stomach fleshy, but has thin
walls, as ir> piscivorous birds generally. The "dilatation of the oesophagus before it
enters the stomach," i.e. the froventriculus, would also seem to A. to be absent ; for
it forms one single cavity with the thin-walled gizzard ; at least such is the case in the
heron {Cuvier, Lefons, iii. 410).

• 14. As A, here points out the direct correspondence between the nature of the food
and the structure of the digestive organs in the case of birds, 9p also does he elsewhere
('^- 5> 59) point it out in the case of insects.

15. Cf. iii. I, Note 7. Rumination is regarded- by A% as an atonement for deficient
mastication owing to want of teeth. Whether the pa*-rot-fish ruminates I do not know ;
but A. is wrong, in saying that ho other. fish does so. There are several species, especially
of the carp tribe, in which a sort of rumination occurs. Cf. Owen, Comp. Anat. ii. 236.

• 16. Cf. iii, I, Note«9. ' ' ,

17. Because, as he says elsewhere (iii. i, 10), the water constantly required for their
gill function enters in at the mouth, and would interfere with the process.

18. Cf. iii. 3, Note 2. .

19. The Cestreus is doubtless some species of Mugil, a tribe of which our grey mullet

• is a familiar example. What species is meant is uncertain ; the Mediterranean containing
at least five. In all these Mugilidse the stomach has much the character of a true
muscular gizzard. " Of all the fish I have seen the mullet is the most complete instance

. .of this (the grinding) structure'; its strong muscular stomach being evidently adapted,
like the gizzard, of birds, to the two offices of mastication and digestiori." — John Hutiier.

20. A. seems here to admit that digestion' is in part due to putrefaction, a doctrine
held by Pleistonicus. Cf. ii.' 2,- Note 3.

21. In most .osseous fishes, though not in all, there are a variable number of coecal
appendages close behind the pylorus, which have been erroneously held to be the
homologues of the pancreas. Their use is not known with certainty. The Selachia are

Notes, iii. 14. . . 215

rightly stated by A. {H. A. ii, 17, 27) to be without these cffica. In birds, as a rule,
there are two cceca at. the junction of small and large gut ; rarely, as in the heron, a
single ccecum. Sometimes, however, as A. notices here and elsewhere (^. A. ii. 17, 26),.
the coeca: are absent. T.his is the case for instance in the wryneck, woodpecker, lark, and
cormorant, among birds known to Aristotle.

. 22. Meaning- of course the coecum and vermiform appendix. There is the greatest'
variety in the different mammalian orders as to the presence or absence of these. Cf.
Cuvier, Lefons, iii. 465. *

23. Fishes, says A., do not digest their food well, because they have a short gut ; and
so they are ravenous. Similarly in the Timaus it is said that a long intestine was given
to animals to prevent insatiable gluttony. An abnormally short gyt is in fact a sufficient
cause for a ravenous appetite (cf. Schiff, Sur la Digestion, i. 44). The normally short gut
of a fish is, however, probably to be explained by the easy digestibility of their food.
Still there are some grounds for believing that the length of a fish's gut is not so great as
it might be with advantage. For if we compare one class of vertebrates with another, and
in so doing confine our attention to such species as live on similar food, e.g. the carnivorous
kinds, we find that the length of the gut in proportion to that of the body is less in fishes
than in batrachians or reptiles ; less again in these than in birds, and in birds than in
mammals. There is thus a gradual increase in the length of the gut, independently of

'the character of the food, as we. get higher in the animal scale (cf. M. Edwards, Le(ons,
vi. 3S6)..

24. What he stated before was that they had a single stomach, not a small one. The
single stomach is, however, small as compared with th? multiple stomach of the ruminants.

25. The stomach of the. dog, as of Carnivora generally, is of small size, somewhat
elongated, and perfectly smooth within. That of the pig is of larger dimensions owing to
the very ample cardiac, cul-de-sac, is of globular shape, and presents on its internal surface
two transverse folds on either side of the cardia. Cf. H. An. iii. 17, 13,

26. As a rule the intestine of mammalia is divisible into two parts, a smaH gut following
the stomach, and 'a. large gut succeeding to this. But in thosfe that are without a ccecum
there is no such distinction of size, the whole intestine being of nearly uniform diameter,.
or occasionally even becoming somewhat narrower as it advances towards the anus

( Cuvier, Lemons, iii. 467), Though the dog is not one of these animals without a coecum, •
yrt its large intestine is exceptionally of scarcely larger calibre than its small gut {ibid. p.
485). The straining efforts of a dog in defecation are however scarcely attributable to this.
They are more pVobably due to the hard and earthy character of the fseces.

27. The intestines, longer in Herbivora generally than in Carnivora, attain the greatest
length in ruminants. In the sheep, for instance, they are 28 times as long as the body ;
in the equally herbivorous but non-ruminating rabbit ten times ; in the carnivorous dog
only five times.

28. " Few homed animals are small and none very small," says A. \H. A. ii. 17, 15 ;
but cf. iii. 2, Note 17^. Having a complex-stomach, their digestion, A. supposes, is more
thorough, and the material for, growth consequently more abundant ; and thus they grow
to large size. But this is scarcely in accordance with his former statement, namely,
that the complexity of the digestive apparatus is merely an atonement for their imperfect
mastication, and for the comparatively indigestible character of their food.

29. Referring to the spiral coil of the colon, which- forms one of the characteris'tics of
the Artiodactyla (cf. Owen. VA-t. iii. 474). ' The colon becomes nalrower where it assumes
this spiral disposition. Later on A. calls this part the coil or helix (eA.(|). The straight
terminal part is of course the rectum. . •

2i6 Notes, iii. 14. — 15.

30. Cf. iv. 5, 60 ; where it is said that h^t requires nutriment and that consequently
animals of cold nature take but little food. 1

31. By "lower stomach" is meant the coecum and first part of the colon, which
precedes the spiral coil (t'At|) of the Artiodactyla (see Note 29). This does-undoubtedly
serve as a second stomach in some animals, and "is sometimes {f.g. in the hare) many times
as large as the true or upper stomach.

32. But if the residue be useless, why should nature be so economical ? A. has in his ■
mind those cases in which he has described the residue as not without some use ; as for
instance in the aurochs. Cf. iii. 2, Notes 7 and 8, and iv. 5, Note 21. ■

33. That is to say the Camivora, who, as compared with herbivorous animals, only get
food at rare intervals. In the Camivora the ccecum and colon are not nearly so capacious
as in Herbivora. Their intestine also, though still convoluted, is much shorter.

34. Partly because a short gut causes imperfect digestion, so that much food is wasted
(see Note 23), and partly because A. assumes that the satisfaction felt fron^ food is due t6
contact with the surface of the intestinal tube (iv. 11, Note 8), as in a small degree would
appear to be the case. For it is possible by swallowing clay or other indigestible Sub-
stances to allay temporarily the sensation of hunger. But such relief is only of very brief
duration. No adequate satisfaction is experienced, until the food is absorbed, aitd carried
.to the various organs that need it foi; their vital activities.

35. A little way back the colon and coecum, or second stomach, was said to "be the
place in which the conversion of food occurs ; now that part is spoken of as merely a'
receptacle for the residue, and the metamorphosis is located in the jejunum. We may,
however, fairly suppose the different passages to relate to different animals ; the former to
those that have a largely developed coecum, as ruminants, rodents, etc. ; the latter to such as
have either no coecum or a small one, as most of the Camivora. In the latter digestion,
begun in the stomach, is over by the time the food reaches the coecum, having been com-
pleted in the small intestine j the middle section of which— ;or jejunum — may therefore be
fairly enough called the place of change. While, in the former, digestion i^ continued for
a length of time after the ccecum is reached. This therefore, with the next succeeding part
of the colon,, must be in the place of metamorphosis.

36. The jejunum (I'ljo'Tts) is the name given to the middle section of the small intestine,
because it is usually found empty after death. The passage of the contained food through
it takes place with great rapidity (cf. M. Edwards, Lefons, iii. 130). There is, so far as I
know, no ground for the statement that the arrangement of the intestine differs in male
and female.

(Ch. 15.) 1. By rennet is usually meant the wall of the fourth stomach of a sucking
ruminant, which contains a substance that has the property of coagulating milk ; but the
term is also occasionally used for the milk when thus coagulated, which, owing tO' the
substance mixed with it, has the power of coagulating other milk. It is .in this latter
sense that A. uses the word. "Rennet is milk endowed with vital heat" (Z>. G. ii.

4, 29)- , . • ' •

2. Moses reckoned the hare among "those that chew the cud." A. did not make'
this mistake ; and it is "said that on this account the Septuagint translators introduced
boldly the word "not" before "chews thfe cud" into their version {Stanley, Led. on
Jewish Church, iii. 261). But A. considered the hare as so far allied to animals that
ruminate, as that it is the only other anifnal besides them that forms rennet. Varro also
{De Re rusticA, ii. 11) speaks of the rennet of the hare as highly efficacious. Whether
there be any foundation for the asserted superiority of this animal's rennet I do. not know ;
but all mammals fucnish rennet, and not only mminant^ and the hare.

Notes, iii. I5^iv. I. 217

3. This is erroneous. It is the fourth stomach that gives rennet.

4. The thickness of milk, as explained va. H. A. iii, 20, 6, depends on the proportion
of cheese it contains as compared with the whey. The milk of ruminants is rightly
stated to contain much more cheese, i.e. caseine, than that of other animals.

5. Hares "preferent les plantes, dont la seve est laiteuse." — Buffon. The leaves of the.
common Pinguecula contain a juice which has the power of coagulating milk, and is said
by Linn^^us to be used by the Laplanders in the fabrication of cheese. The juice of the
fig-tree is often mentioned as having this property, e.g. Iliad, v. 902 ; Columella, .vii. 8.

6. There is no passage in the Problemata suiting this reference '; and the same may be
said of sundry other references made by A. to that treatise. The Problems,' if indeed
they be the genuine work of A. at all, have plainly dome down to us in a v6ry'mutilated
condition, Cf, Heitz, Die Verlor. Schri/t. d. Arist. p. 103.'

BOOK IV.

(Ch. 1,) 1, The stomach is not one of the viscera in A.'s sense. Cf. iii. 4^ Note I.

2. Cf. iii. 8, Note 3.

3. Cf. iii. 8, Note 2.

4. Cf. iv. 5, Note 17. The argument is this. In animals that have urinary organs,
the urine is the channel through which not only superfluous water but earthy matter is
excreted, as is shown by the deposits which occuf in urine after standing. When there
is no urine, as in birds, the earthy matter is voided with the faeces, and forms the white
superficial substance seen on theip. I suspect that the last clause in the paragraph is an
interpolation.

5. A. includes under Selachia all cartilaginous fishes, among which he erroneously
classes the Lophius (cf. iv. 13; Note '.5), All» these, he often says, with the exception of
Lophius, are ovoviviparous ; that' is, they retain their ova within the body, till hatched.

. In some of these ovovivipara the embryo throughout remains free from all anatomical
connection with the mother, but in some, when'th'e nutriment supplied by the yelk is
exhausted, the embryo forms a connection with the parent's body(Z). G. ii, 4, 4; iii, 3, 9),
The latter part of this statement ' applies to certain sharks, which do in fact present
a rudimentary placenta. The former part of his statement is too wide a generalisation ;
for the oviparous dog-fishes and the rays present exceptions to the statement that all
A.'s Selachia are, as he says, ovoviviparous. Yet A. (/^ An, vi. 10, 9) was well
acquainted with the- eggs of the dog-fishes and the rays. The explanationseemsto.be
that he imagined that the young fish was fully developed in the ovum at the time when
this was first laid. It is however very doubtful whether this is the case, unless as an
exception. Cf. Meyer, Thierkundi, p. 281,

The osseous fishes A. states to be all oviparous. This rule, however, is not without
exception ; e.g. the viviparous blenny.

6. The multiple stomachs of ruminants were supposed by Aristotle to atone for the
deficient mastication due to the want of upper incisors. Cf. iii. 14,7.

7. This is perfectly true; As regards the kidneys, cf. kymer Jones, An. Kingd. p.
709 : as regards the liver and lung, cf. M. Edwards, Lemons, vi. 427 ; ii. 309.

2i8 Nctes. iv. I — 2.

♦

8. All yertebrata have a mesentery, with the exception of the lamprey, the carp, and
some other fishes, and even these have it in their embryonic stage. As to the omentum;
of. iv. 3, Note 3 ; as to diaphragm^ cf. iii. 10, Note I.

9. Cf. iii. 3, Note 5. ^

(Ch. 2.) r. In certain Ophidia the gall-bladder is in fact completely separated from the
liver and lies close to the pylorus. This is so in all the serpents that have the tongue
enclosed in a sheath {Duvernoy,.Ann. d. Sc. Nat. xxx. 12;/). A similar condition is found
in some fishes {Owen, Led. on Comp. An. ii. 243), among others in the Lophius, the
Swordfish and the Muraena ; all of whicn are elsewhere [,H. A. ii. 15, 14) enumerated as
ej^amples of this structure. Probably this peculiar arrangement, has reference to the
long narrow shape of the animals, and exists for convenience of packing. *

2. As to lower stomach, cf. ii. 3, Note 6 ; iii. 14, Note 31. The exact meaning of this
passage is doubtful. I understand, however, A. to mean that the bile is in all cases

. discharged into the intestine at a point below the upper or true stomach.

3. Fishes are very rarely without a gall-bladder, though there are some few exceptions,
e.g. sawfish, lamprey, and basking-shark.

.4. The Amia appears to be the Scomber Sarda af Cuvier. This fish abounds in the
Mediterranean. Like *the tunny, bonito, and sundry other Scombridse, it is remarkable
for the extreme length and slenderness of its gall-bladder. Cuvier, Reg. Anim. ii. 199,
and Owen, Lect. ii. 244.

5. " Therefore," i.e. inasmuch as the bile is always discharged into the intestine as an
excrement. The writer alluded to is Plato in the TimcBus. Cf. Joaveifs Transl. ii. 564.

6. Elsewhere {H. A, ii. 15, 11) the elephant is said to present this structure; and
correctly so stated (cf. Owen, Vert. iii. 480). Whether a similar structure exists in the
camel I do not know. It has, . however, no gall-bladder ; and the under surface of its
liver is marked by numerous irregular and intersecting fissures {Floiuer's Lect., Med. Times,
1872, p. 371). Possibly it may have been these fissures that were taken by Aristotle, or
his informant, to be dilated bile-vessels. •

7. A. is correct in this enumeration of animals that have no gall-bladder, with- the
exception of the seal. The Phoca vitulina has a gall-bladder ; but it may possibly,
though improbably, be that the Phoca irtbnachus, which was the species best known
to the ancients (Cuvier, Regne An. i. 169)^ is without one, as Frantzius suggests.

8. The gall-bladder is sometimes present, sometimes absent in giraffes {Owen, Joly) \
in the apteryx and bittern {Owen); in the guinea-fowl, etc. It is especially variable,
as A. rightly says, in the different species of Mus [Cuvier, Lemons, iv. 36). In man a
congenital absence of the gall-bladder hixs been noticed in rare instances {Rokitansky, ii. .
155 ; Phil. Trans. 1749). This however could not be known to A., who says moreover
{H. A. i. 17, 10) that most men are without a gall-bladder. 'If, as I have suggested
(i. 5, Note l), A. examined aborted human embryos, h^ might easily have been led to this
erroneous opinion. For the gall-bladder is not developed at all until the third month,
at a time when the liver almost entirely fills the abdominal cavity.

9. A similar statement is made in the Hist. An. (i. 17, 11) ; where also we learn that
the knowledge of the facts was obtained by observation of sacrificial victiriis, a source of
anatomical information elsewhere referred to (cf. iii. 4, Note 37). Chalcis was, it may be
noted, the place to which A. retired when he quitted Athens, and where he finished
his life.

10. This clearly professes to be no more than an h Jiriori notion, and not to be
founded on actual dissection. .

11. When an animal's body is opened some time after death, the parts near the gall-

• Notes, iv. 2 — 5. .'219

bladder are ' often found to be stained yellow from an exudation of bile. It is, I
imagine, to this overflow that reference is made, as being excessively sftiall in comparison
with the amount of bile which is apparent in the human body in cases of jaundice.

•12. Residua include for A. not only excretions, but sundry useful secretions (cf. ii. 3,
Note 8). But some excretions are also utilised ; as in the case of the aurochs (iii. 2, •
Note 7), the cuttlefish (iv. 5, Note '21) ; and other animals (iii. 2, Note 8).

13. Cf. Introd. p. iv. .* '

14. Cf. Note 6. . . • .

15. Nutritious substances are always sweet, and never bitter (cf. iii. 5, Note 5).

16. There are good reasons for believing that the bile does subserve an useful encf, by
facilitating the a,bsorption of fat.

17. The camel is said by A. {H. A. viii. 9, 2) to live for 30 years, and exceptionally
for 100 years. Burckhart gives it a life of 40 years. As to the dolphin it is stated
{h. a. vi. 12, 6) that some had been marked by fishermen and let go ; and that by their
recapture it had been ascertained that they live at least 30 years. There are, I believe,
no modern observations on the matter. Horses are said {H. A. vi. 22, 8) to live, as
a rule from 18 to 20 years, and occasionally, if well tended, for 50 years ; mares being
somewhat longer-lixffed than stallions. Modern authorities give much the Same figures.
Stags are said by Flourons to live 30 — 40 years. It is strange that A. should here speak
of stags as long-lived ; for elsewhere (H. A. vi. 29, 4) he rejects the statements as to
their length of life as being mere fable, and says that the gestation and grovfth of a young
stag indicate the contrary.

18. Cf. iii. 4, Note 37.

19. Cf. iii. 7. '

(Ch. 3.) 1. His explanation is given in iii. 12. "Why some animals have a gall-bladder,
while others have none, is still unexplained in any satisfactory manner. It is rarely
wanting in Carnivora, very often wanting in Herbivora.. Still there are so many exceptions
to the general rule that it cannot be said that there is any direct relation -between the
presence or absence of this organ and the nature of the food. -Otherwise we might have
accepted the explanation {Buvernoy, Ann. des Sc. Nat. xxx, 127) that Carnivora have a
^all-bladder because they eat at comparatively long intervals, and so require the bile to be
stored up for those occasions ; and that it is wanting in Herbivora, because they eat almost
continually, and so require a continuous flow of bile into the intestine. S. v. der Kolk
thinks that in animals without • a gall-bladder .the deficiency is compensated, as in the
elephant, by the greater width of the bile ducts (cf; Med. Chir. Revirw, 1862, p. 113).

2. Cf. ii. 5, Note 6.-

3. A similar statement is made elsewhere (iv. \,(>;,H. A. iii. 14). It is, however,
erroneous. Mammalia alone have an omentum.

4. A. is apparently thinking of the formation of scum on the surface of boiled milk and
■ the like.

5. Cf. Introd. p. iv. .

(Ch.. 4.) 1. That is of Hypothetical, not of Absolute, necessity: Cf. Introd. p. iii.

2. Cf. ii. 3, Note 10 ; iii. ,5, Note 5. ,

3. Cf. ii. 3, Note 16.

(Ch. 5.) 1.' Cf. iii. 4, Note I. '

2. Here, as often {e.g. iv. 9, 15 ; .iv. 10, 38), A. seems to speak of nature as being
in some way or other constrained to construct' her works in conformity with set types.
Cf. IntYod. p. X, and iii. 14, Note 4. • '

3, Urinary bladder and lung (iii. 8, i) were to A. signs of abundant blood ; and

. 220- Notes, iv. 5. '. •

viscera (iii. 7, Note 8) were one of the channels by which superfluous blood was
feliniinated. . .

4. By the teeth are meant the two halves of the parrot-like beak ; by the tongue is
meant the odontopbore, of which the anterior part is free from spines and soft, and
probably serves as an organ of taste..

5. The "anterior teeth" are the strong shear-like mandibles ; which are called anterior
to distinguish them from the stomachal teeth preseittly to be mentioned. 'By the tongue
is meant the bifid lower lip, which has-been called a tongue by other writers than A., but
is not properly comparable to such an organ. Cf. Todd, Cycl. \: 773.

6.* The tongue or odontophore forms a very remarkable organ in the Gasteropoda, but
there is none in the Conchifera or bivalves of Aristotle.

7. Though, there is a "proboscis" in bees and flies alike, yet it has not exactly the
same origin in the two cases. In bees it is a development of the labium and maxillae, the
mandibles and upper lip taking no part in the formation and the formeir serving as biting
instruments. But in the Diptera it is a development ' of the labium, the remaining oral
elements being converted into setae, lancets, etc. These latter are the ^^ modified teeth''''
of flies, as the mandibles are " the modified teeth " of bees. The insects that live on fluid
nutriment and have no teeth are the Lepidoptera,. in which the maxill?e-are converted into
a long proboscis, while the mandibles are quite rudimentary.

8. The so-called "tongue" of insects 'is the upper portion of the labium, and is very
distinct in some species. In bees and flies the labium with this tongue goes to form
what A. calls their proboscis ; so that it is only in other insects, that have no such
proboscis,. that there is a tongue inside the mouth, corresponding to that instrument.

It is evident that A. must have examined with much care the oral arrangements of
. insects ; and when we consider how difficult it is. without magnifying glasses to make
them out, we cannot but be struck with admiration at his considerable success in the
matter. •

9. The words I have rendered "first treatise " are rendered "first book" by Frantzius.
He thinks that A. refers to a passage in what is usually reckoned as the secpnd book of
the De Partibus (ii. 17, 16), and argues from this that that second book is' really the
first, the book ordinarily called the first being misplaced and transplanted from thf
Historia Animalium. I cannot but think, however, that this view is erroneous, and that
A. is referring here to the Historia Animalium (iv. 4, 15), which is called the first treatise,
as forming the initial portion of his three great connected works on Biology. For
A. uses a similar expression later on in this chapter. (cf. Note 69), where the reference
can only be to the Historia, inasmuch as there is no passage in the second book of the
De Partibus bearing on the matter of which he is then speaking, viz. the position of the
mainspring of life in insects.

Perhaps "our earh6r, or our initial discussions " wo^ild have been a better rendering
thkn " first treatise." For it is impossible to say with certainty whether these biological
treatises were regaj-ded by A. himself as distinct treatises, or whether they were not
considered by him merely as successive parts of a single work.

10. i.e. tl^e homy jaws. I imagine that " Cochli " is used as a general term for most
marine gasteropods with spiral shells, and I have therefore rendered it by the vague
term "sea-snails." Some have thought that Planorbis and Limnaeus are meant. But
it is expressly stated (/T. A. iv. 4, 2J that Cochli are marine, not freshwater, animals.

• IL A.'s account of the anatomy and habits of the Cephalopods has received a tribute
of 'praise from many writers. "Respecting the-living habits of the Cephalopods," says ■
Owen, ** Aristotle is more tich in details than any other zoological author, and Cuvier

^ Notes, iv. 5. 221

has justly observed that his knowledge of this class, both zoological and anatomical,
is truly astonishing."

As to the various species known to him, see iv. 9, Note i ; and, as to their external
parts, consult the other notes to that chapter. Here we are concerned only with their
internal parts. The digestive organs are thus described {H. A. iv. i) : "After the
mouth there is a long and narrow oesophagus. Continuous with this is a large round
crop resembling that of a bird. Then comes the stomach like a rennet. The form of
this is spiral, like the shell of a whelk. Froni this a thin intestine runs back towards
the mouth ; the intestine is however thicker than the Stomach."

It is I think clear that A. did not mean by the crop (iyoA({)3oy) What moderns call the
crop, which is found in rio, other dibranchiate cephalopod than the poulp ; for he
expressly says that the poulp and the sepia are precisely aljke so far as these parts
are concerned. The crop of the poulp, had escaped his observation. The crop of which
A. speaks is what we call the stornach. This is, as he says, of softer consistency
in the calamary than in the sepia or the poulp, where it is more muscular. What
A. calls the stomach is what we look on as the commencement of the gut, which
communicates with a membranous dilatation or sac, that is mo^e or less spirally
twisted, and is found in calamary, sepia, and poulp alike,^ though more developed in the
first of the three, where it may be not inaptly compared to the spiral body of the whelk.
The oesophagus is, as he justly says, long and narrow. Thus his description is accurate,
with the excejftion, that he does not notice the crop of the poulp; while he gives
different names to the cavities from those we use.

12. The accotint of the ink-bag, and of the differences of size and position it presents
in the different speciesj is accurate ; it being of course understood that the tetrabranchiate,
cephalopods, that have no ink-bag, were unknown to Aristotle.

13. The mytis is identical with the mecon, which exists in all Crustacea {ff. A. iv.
2, 22) ; is a bag containing excretory ^natter (JI. A. i\. 4, 24) ; placed near the hinge
in bivalves, and in the spiral part of the shell in Turbinata {H. A. iv. 4,. 22), being spiral
itself, in the whelk for instance {H. A. iv. 4, 18). This can be nothing else than the
liver ; and Kohler's notion that the glandular appendages of the veins are meant
{Todd^s Cycl. i, 539) is out "of the. question. Though A. often states that bloodless
animals have no proper viscera, he makes ari exception in the case of the mytis [H. A.
iv. I, 19). It was doubtless the dull red or violet colour of this organ which gained
it this distinction ; the viscera being, as he supposed, formed of coagulated blood
(cf. iii. 8, Note 2). In fact he speaks latef on in this chapter of the mytis as "resembling
blood," and believed it to rep;-esent the heart.

14. That is to say, have longer tentacles or arms than the rest (cf. iv. 9, Note 15).

15. In reality all these Cephalopods have the faculty of changing colour ; but the
phenomenon is most conspicuous in the poulps (cf. Cuvier, R. ^«, iii. 10).

16. The Sepiadse, and still more the calamaries, are pelagic ; the poulps are littoral.

17. Cf. iv. I, Note 4.

18. The internal shell of the sepia consists of a broad spongy calcareous plate, the
well-known cuttlefish-bone, of the shops. That of the calamary is a thin horny plate,
called, from its shape, " the pen.'' In the poulp there is no internal shell at all,

19. Cf. ii. 4, "Note 4. . . .

20. That fear does thus affect the bowels and the bladder is a fact well known to
physiologists. To the examples given at ii. 4, Note 5, may be added not only men, but
cattle, dogs, cats, and monkeys j in all of which Mr.- Darwin has noticed the phenomenon
{Expr. of Emot. p. 77). • . • .

222 Notes, iv. 5.

21. Cf. iii. 2, Notes 7 and 8 ; iii. 14, Note 32.

.22. Cf. iv. 8, Note I. ' • .

23. Cf.NoteS.

24. The oesophagus in Crastacea is, as stated in the text, very short. The stomach-
teeth are present in all Decapoda, and not only "in the Carabi and some of the crabs."-
The intestine is remarkably straight.

25. A.'s Ostracodernia,- or Testacea, ificlude all such bloodless* animals as have their
soft parts within, and their hard part without ; the hard part being brittle, and not
flexible as in Crustacea {H. A. iv. I, 4). Of their internal structure A. had made out
little or nothing. He divides the group, as do modern naturalists, by the character of
the. shell. . •

I. Those witR a single spiral shell, the-Turbinata.
• 2. Those with a single non-spiral shell, or the Univalves, e.g. limpets.
. 3. Those with a double shell, the Bivalves; which are again subdivided into those
whose valves can open, as the mussels, and those wjiose valves -are always
closed, as the razor-fishes. '.

4. Those that are completely enclosed in a* hard globular shell, i.e. the Echini. »
, 5. Those that are completely enclosed in a shell, of the consistency of leather, i.e.
the Ascidians (cf. Note 35). , To this group, though included amon^ Testacea,
the general definition of the Testacea, that they have a brittle and not a flexible
shell, is inapplicable. . •

26. Bronn {Malacozoa, part ii. 950), and Lebert {Miiiler's Archiv. 1846, p. 463),
believe that A. means the lingual teeth. But these are almost too small to be seen with •
the naked eye. So Lebert boldly asserts that A. must have used a lens of glass or
crystal, or some magnifying instrument ! Clearly, however, the jaws are meant, not
the lingual teeth : for they are said to be only two in num"ber. Cf. Note 10.

27. In many ■ gasteropods, e.g. the whelk, there is a long retractile proboscis.
Aristotle gives a much fuller account of the anatomy of the Mollusca in the H. A. i\. 4.
Neither there nor here, however, is it possible to identify with certainty the various
organs which he describes ; because there are considerable differences betw^een different
species ; and we do not know which species was taken by A. as the basis of his account.
Probably, however, he had examined the whelk, as he so frequently mentions it.

281 The crop, wrhich comes directly after the mouth, is probably the " buccal mass " ;
for the dilatation which we call crop in many gasteropods {e.g. Dolium, Cypraea,
Voluta) is as a rule removed from the mouth by half the length of the oesophagus,
though exceptionally (e.g. Turbo) it may be much nearer, Cf. Bronn, Malacozoa,
part ii. 954. •

29. The mecon (cf. Note 13) is the liver, which in all Gasteropoda is of great size,
and fills a large portion of the visceral cavity. It is of a dark brown colour, as also
is poppy-juice ; which fact is supposed to explain its name ; mecon being the Greek
word for that juice. Meconium is still the name given to the bile accumulated in the
intestine of the new-bom child. •

The stomach is here said to . contain the mecon, and the gut to siart not from the
stomach, but from this latter. A. seems to have taken the thin membrane which encloses
the visceral mass for the stomach. Inside this membrane is the liver, hiding the true
stomach, and appearing to give origin to the gut which issues from it.

30. Cf. ii. 17, Note 15. • .

31. That all Turbinata have opercula is of course an error. In mahy genera, especially
those with larger apertures, it is quite' rudimentary or obsolete ( Woodward^ s Manual,

Notes, iv. 5. 223

102). So also a considerable division of air-breathing gasteropods is inoperculate.
The land-snails, however, close their aperture during hybernation by a layer of hardened
mucus soinetimes strengthened by carbonate of lime. This A. had noticed. For he
speaks {H. A. viii, 13, 15) of the land-snails as having a superficial operculum during
hybernation. The op'erculum when present is so "from the very birth," and the use
of the expression shows that A. had attendedto the development of the gasteropods.

The operculum of a gasteropod can scarcely be considered to be the homologue of.
the second valve of ' a . lamellibranchiate mollusc, for it is developed from the foot, hot
from the mantle. Adanson, however., and more recently Mr. Gray, thought such to be
the cage' {Woodward's Manual, p. 47). Though not homologous, to the valve, it is
however analogous to it j that is, it serves the same purpose, namely, to protect the
animal when retracted into the shell.

32. There does not seem sufficient evidence to decide what molluscs exactly are meant.
'This is the short description given {,H. A. iv. 4) : " The Nerites has a large smooth
round shell, in form like that of the whelk. * But its mecon is red, not black as is that of
thewhelk.T * .

36. The Bivalves in reality have no odontophore or tongue.

34. This passage with others shows that the Hist. Animalium and the lost treatises on
Anatomy were illustrated. • Cuvier indeed {Hist. d. Sc. 1. 141) says the latter contained
coloured illustrations. I can find no authority for this statement. There is none in
the 28 passages referring to the i.vaTOfiai collected by Heitz ( Verlor. ^chr. des Arist. p. 70).

36. By Tethya are undoubtedly meant Ascidians, as the description Jiere . and in the
Hist. .<4«. (iv. 6) shows, and I have therefore so rendered it. A. includes both Echini
and Ascidia among the Testacea ; though they are, as he says, very different from the
three main groups of these animals. That he should so have classed Echini was but
natural.; for they would appear to him^ to have all . the characters which distinguish his
Testacea, viz. a hard brittle covering "(which however is not really external), a mouth
turned downwards, a stomach, intestine, vent, mecon, and so forth. But that he should
have so classed 'the Ascidians, that have no hard shell, is more remarkable. He had,
however, perceived that the extfemal covering of the Ascidians is in reality a. shell.
*' Their whole body, he says, is hidden in a shell. This shell is something intermediate
between skin and shell proper, so that it cuts like hard* leather." In the Museum
Catalogue (CoU. of Surg. i. 266) it is said that, " Mr. Hunter, who perceived the relations
subsisting between Ascidia and Salpa, and knew the true analogy of their external
covering, proposed to distinguish them as a distinct group of Mollusks under the term
'soft-shelled,' which more truly accords with their real nature than 'shell-less,' as they
have subsequently been designated by Cuvier."

36. The jaws of Echinus vdth the five teeth form a conical mass, which is still described
by writers as "the lantern of Aristotle," in reference to a comparison mjcde va. H.A. iv.'
5, 8. . . • . '

37. The flesh-like piece is said in the Hist. An. (iv. 5, 5,) to be. in place of a
tongue, and to occupy the centre, df the cavity formed by the teeth. As the Echin.us has.
no tongue, the pharyngeal portion of the oesophagus must be meant.

38. The oesophagus of Echinus terminates in a much wider tube, which is continued to
the anus without any distinct separation into stomach and intestine. This gastro-intestinal
tube is attached, by what may be called a mesentery, to the inner surface of the shell,
in such a manner as to form loops or festoons, five in each of its two coils ; and it is to
this appearance of subdivision that A. alludes. This is" plain not only from the careful
way in which he here guards himself from saying that there are actually a number of

224 • ' . Notes, ■•iv. 5.

distinct stomachs, but still more from his language in Hist. An. (iv. 5, 6,), where
he says that all the loops (kSKitoi) of the stomach run together to the anus ; and where also
he makes no mention of an intestiile as distinct from the stomach.

39. The "so-called ova" which A. thought to be masses of fat, or of something
analogous to the fat of sanguineous animals, are the ovaries, which are five in number,
and arranged symmetrically' round the upper interior of the shell. These vary in size in
proportion to the maturity of the ova within thenr, ind thus are much larger at some
seasons of the year than others. It is when the ova are mature that "die roe of the
sea-egg" is used for food along the coasts of the Mediterranean, divers being employed
to collect these animals. They may be seen in. abundance in the market at Marseilles.
According to Pennant they are also eaten by the poor in many parts of England.

40. These black bodies are also mentioned at //. A. iv. .5, 7, and are there said to
be bitter, uneatable, and connected with the origin of the teeth.' They are also said to
converge towards the aperture of the test, though separate from each other, and to divide
this into segments. The best conjecture I can offer is that A. alludes to the rows of
ambulacral vesides,' though I do not know of any species in which, these are black.
The wor^ "profusely" would accord with this conjecture; for the vesicles are present
in hundreds. But less consistent is the Statement that similar bodies, though of different
colour, are found in Batrachia, Chelonia, and Turbinata. '

41. Frantzius and also Meyer {Thierkunde, p. 175) translate l-KmoXa^ovTo. "floating on
the surface." But no Echini float; and seeing that the large esculent species were
common articles of diet, A . could scarcely have been so ignorant of their habits as to
suppose them to do so. I have little doubt that A. means " that live in shallow water " ;
and this view is confirmed by a passage {De Gen. v. 3, 21) in which he says that those
Echini that live in deep water have big spines but small- bodiesi so that they would not
be suitable for eating.

42. Cf. Note 13. . • • ■• ■

43. Cf. H. A. iv. 4. What A. meant by the right and left of a bivalve.I cannot say ;
certainly, however, not what we mean. The bivalve which he seems to have chosen
for examination was the scallop, because of its large size (^H. A. iv. 4, 24) ; and he is
correct in saying that the " ovum " is on one side, and the vent on the opposite side
of the circumference of the dislc-shaped body. The "ovum " is on the anterior convexity,
the vent on the posterior convexity; and for some reason or other the anterior is
considered by A. to be the right side. Can it be that he had made out the foot,'
which is also anterior? If so his notion that motion specially attaches to the right
side (cf. iii. 9, Note 12) would make him identify the anterior aspect with the right side.
■ 44. That the ovary of Testacea was miscalled, A. seems to have thought was shown
by its having no orifice. "The so-called ovum. (^'^a'^') never has a duct, and is merely
a swollen part of the flesh" {H. .,4. iv. 4, 25). He believed that Bivalves were
developed spontaneously or by gemmation.

45. Cicero (^De Divin. 2, 14) mentions, among other instances of some natural
.connection existing between things apparently remote and incongruous, " that oysters

and other sl\ell-fish increase and decrease with the growth and waning of the moon."
So also Lucilius says, " Luna alit ostrea et implet echinos ; " and again Manilius, " Si
submersa fretis, concharum et carcere clausa. Ad lunse motum variant animalia corpus. "
The two la,st quotations I borrow from Mead {Influence of Sun and Moon, etc. 1 748, .
. P- 65), who accepts the statement as true. '

46. So that the Echini have no competitors for the food.

47. The ovary of Bivalves is really bilateral. But it is not bilateral in A. 's sense

Notes, iv. 5. 225

(cf. Note 43) ; for it is on one side only of the circumference, when the body is viewed
from above as it lies in either valve.

48. This passage is unintelligible, and the text probably corrupt. As it stands, we
should have to suppose that A. took the central muscular mass of the oyster to be
a head. This is very improbable, and has no support from other passages. It is
true that in ch. 7 it is said that all Testacea have a head, and that in the Hist. An.
(iv. 4, 21) A., lumping univalves with bivalves, says they all have a head, as also
horns and mouth, without specifying its position. But he adds that some of their parts
can only be seen " in living specimens, and whilst they are in motion ; " that is to
say, he could not find a head in the oyster, which is motionless, though he found one
in the locomotive univalves, as the limpet. Probably, as he only says that "some of
these parts " are not to be found in the motionless kinds, he may have found the
mouth of the bivalves, and perhaps may have taken the labial tentacles for horns.
This view is confirmed by a passage {H. A. viii. 2, 16) where, after describing the
headless sea-anemone as having a mouth, he says it resembles an oyster taken out of
its shell. The ovary in this passage is said to be on the upper side ; a little farther
back it was said to be on the right side ; an inconsistency, which also seems to point
to some corruption of the text.

49. Cf. Note 2.

50. The Echini with small ova are those that live in deep water ; the species with large
ova are those that live in shallower places. Cf. Note 41.

51. The spines are really instruments of locomotion, and Agassiz said were the only
ones ; but their main function is probably protective, the chief organs of locomotion
being the tube-feet, which A. had not noticed either in Echini or star-fishes.

52. The same idea is elaborated more fully in an admirable passage in the Hist. An
(viii. i),

53. Having considered the Testacea, A. now passes on to those animals that are inter-
mediate between these and plants, to such that is as in aftertime were termed zoophytes.
In these, he says, locomotion is feeble at best, and often absent, some of them being
actually rooted in the soil. Sensibility is also dull, and sometimes scarce a sign of it is
detectable. In both of these characters, as also in the absence of any distinct excretory
organs, these animals are closely akin to plants. In this group A. reckons Sponges,
Holothurias, Sea-lungs, Acalephae, Star-fishes, and " other similar marine creatures."
These latter are probably those mentioned in the Hist. An. (iv. 7, 14) ; of which he says
he had gathered an imperfect account from fishermen. Among these is one which
naturalists have supposed, not improbably, to correspond with Pinnatula ; and another
which I take most probably to be Holothuria tremula, which abounds in the Mediterranean.

At the bottom of the group are the sponges. Ever since A.'s time it has been a
disputed question whether these should be reckoned as belonging to the animal or the
vegetable kingdom. Physiologists now admit their claim to be considered animals ; but
they would reject the evidence which led A. to the same conclusion. " The sponge
exhibits some signs of sensation ; for they say there is considerable difficulty in detaching
it from the rocks, unless the attempt is made stealthily" {H. A. i. i, 18), and again, " It
is said that the sponge possesses sensation. This is a proof of it ; it contracts if it
perceives any intention of pulling it off from the rocks, and so renders the task more
difficult. It does the same, if the wind and waves are violent, in order that it may not
lose its attachment. There are some persons who doubt this, as the natives of Torona "
{H. A. V. 16, 5). Modern naturalists seem to be of the same opinion as these natives of
Torona.

15

226 Notes, iv. 5.

64. There are not sufficient data to determine with certainty what animals correspond
to the Holothurias and Sea-lungs of Aristotle. They are above the sponges, inasmuch
as they are unattached to the ground ; but resemble them in the want of locomotion
{^H. A. i. i) and of sensibility. Very probably, however, A.'s Holothurias are some of
the animals still so named. The only difficulty in accepting this is that the Holothurias
are most manifestly sensitive ; for when irritated they actually often eject their viscera,
or fall into pieces ; neither are they incapable of locomotion. We may, however,
suppose that A. was only acquainted with such dead specimens as fishermen brought to
him, or as he found stranded on the shore.

Pliny is so servile a follower of Aristotle, that there can, I think, be no doubt that
\as, pulmones marini are the latter's Sea-lungs. Probably some of the larger kinds of
Medusae are meant, the smaller kinds being included with Actiniae under the name
Acalephse (cf. Note 61). There are a very large number of species of Medusae in the
Mediterranean. I cannot understand why S track should take the Sea-lung to be the
Sea-hare [Aplysia depilajts). That Medusae of some kind are meant is rendered probable
by the name Sea-lung, which is an apposite title for animals that move by alternate
expansions and contractions of the body ; a mode of progression still known as
Pulmonigrade, and applied to these animals. Secondly, the Medusae not only float
on the surface of the sea, but are often phosphorescent, especially when irritated, and
these are characters assigned by Pliny to the Pulmones {^Nat. Hist, xxxii. 52).

55. If they have absolutely no feeling why does A. not only consider them to be animals
but even put them above the sponges, to which he ascribes a rudimentary sensibility ? I
take it that he does not mean that they are absolutely without feeling ; but that they have
very little of it.

56. A. thought that parasitical plants, such as mistletoe (Z>. G. i. i, 11), were engendered
out of the decay of some part of the tree on which they grew. Bacon {^Nat. Hist. § 656, 643)
held a very similar opinion. Mistletoe, he says, is an exudation of something **that the
tree doth excern and cannot assimilate."

67. Very probably some kind of Sedum ; and, according to Fraas, Sedum rupestre
or amplexicaule. There is an English species, S. Telephium, which has gained the
popular name " Livelong " from its persistent vitality after being pulled up from the
ground.

68. Aristotle's Tethya, or Ascidians, are not Tunicata generally, but only the simple
solitary Ascidians, which are always sessile.

69. A. seems here half inclined to remove the Ascidians, which he had before classed
with the Echini as peculiar kinds of Testacea, from these latter, and to place them with
the Zoophytes, leaving the Echini behind and making them form part of the Turbinata.
Similarly he says later on: "Of the Turbinata some have a spiral shell, as the whelks,
and some are simply spherical, as the Echini" (iv. 7, 2). A somewhat fuller account
of the double-walled sac, with its two orifices, which forms the covering of the Ascidian,
is given elsewhere (/^ A. iv. 6).

By the " septum " I understand the perforated wall that intervenes between the cavity
of the pharynx and the atrium ; by the "median partition" I understand the reflection
of the lining membrane, or atrial tunic, over the viscera. A. supposes the heart to be here,
because the heart should be in a central position (iii. 4, 13), but he does not profess
to have made it out by dissection. The " flesh-like substance " is the real body of
the animal. As to the statement that the presence of this substance implies sensibility,
of. ii. 8, Note 2 ; ii. 10, Note 10. A. was so convinced that the heart, or whatever
corresponded to the heart as the centre of life, must be in a central position, that he

Notes, iv. 5. 227

attempted to make out a similar condition in plants : " In all seeds there are two valves,
and the development starts from the centre, that is from the point where the valves unite,
a point which is common to the two sides. For thence grows the stem and thence
grows the root, and the principhim vita (A/'X'j) is between these two" (De Juvent. 3, i).

60. The residuum of plants, that is their superfluous food, is, says A. elsewhere,
represented by their seeds. Cf. ii. 3, Note 8.

61. Schneider, Strack, Camus, Frantzius, (cf. Meyer, Thierk. p. 165) all agree in
taking A.'s sea- nettles or Acalephse to mean exclusively the Actiniae or sea-anemones ;
and there can be no doubt that the description given here, as also the more detailed
one in the Hist. An. (iv. 6), is the description of an Actinia. At the same time I
cannot but think that A. also included some of the modem Acalephse in the same
group, confounding them with the sea-anemones and imagining them to be free-living
species of these latter (/T. A. v. 16, -i). For though the sea-anemones do in fact
possess urticating organs, yet their power of stinging is insufficient, unless in very
exceptional cases, to cause any irritation to the fingers, even when the skin has been
previously softened by soaking in water {Proc. Royal Soc. ix. 723). On the other hand
the power of stinging is such a prominent fact in the Medusae that their name in almost
all languages is founded upon it.

62. That is their power of stinging which belongs "to all the surface of their bodies"
(^ A. ix. 37, 8).

63. "Star-fishes are not unfrequently found feeding on shell-fish. In such cases they
enfold their prey within their arms, and seem to suck it out of its shell with their mouths,
pouting out the lobes of the stomach " (Forbes, Brit. Star-fishes, p. 86). The damage done
to oyster-beds by these animals has always been, and still is, a matter of complaint by
fishermen. " Bishop Sprat infonns us, in his history of the Royal Society, that great
penalties are laid by the Admiralty Court upon those engaged in the oyster-fishery who
do not tread under their feet or throw upon the shore a fish which they call a Five-
finger, resembling a spur-rowel, because that fish gets into the oysters when they gape
and sucks them out" {Todd^s Cycl. ii. 38).

64. The mytis, which in cephalopods is traversed by the oesophagus, is the liver (cf.
Note 13), not the heart. The real heart of cephalopods, as of all other Invertebrata,
escaped Aristotle.

65. Cf. iv. 2, 13.

66. Cf Note 13.

67. A. does not profess to have seen the heart of Mollusca, but only to say where it is
likely to be found on ^ /riijr/ grounds. Cf. Note 59.

68. I suspect that the words " or the spermatic fluid " are an interpolation. For A.
{D. G. iii. II, 11) denied the existence of any generative secretions in bivalves. See
Introd. p. xxviii, foot-note 6.

69. H. A. iv. 7. Cf. Note 9. The heart is represented in insects by the dorsal vessel.
A. failed to make it out, and concluded on purely a priori grounds that it was in the
middle of the body (cf. Note 59).

70. A. elsewhere (ZT. A. iv. I, 6) speaks of Julus and Scolopendra as wingless insects ;
and (iv. 6, i) as having many feet. There can be no doubt that, speaking generally,
they correspond to our Myriapoda. But A. gives no accurate account of the differences
between Julus and Scolopendra ; so that we have no actual certainty that the two
divisions of Myriapoda to which these names are now given were those meant by him.
Probably, however, such was the case. As, however, A. divides (H. A. ii. 14, 2) the
Scolopendras into land species and water species, we must suppose that he confounded

228 Notes, iv. 5 — 6.

some or other Annelid with Scolopendra ; very probably, a Nereis or Aphrodite, as
Miiller suggests, an animal still called sea-centipede from its external resemblance to
the Myriapoda.

71. Cf. iii. 5, Note 2. "They stir," says Lord Verulam, "a good while after their
heads are off, or that they be cut in pieces ; which is caused also for that their vital
spirits are more diffused throughout all their parts and less confined to organs than in
perfect creatures " (Sylv. Sylvarum, Cent. vii. § 697).

72. There seems here an inkling of the truth that vegetative repetition is a mark of
inferiority.

73. Cf. Note 8.

74. A. includes the Myriapoda among Insecta. In most of these the alimentary canal
is a simple intestiniform tube, running in a straight line from mouth to anus. But
in some {e.g. Glomeris) the tube, though still simple, is convoluted. In many insects
the canal is a long convoluted organ, thick and muscular, and divided into a varying
number of distinct compartments.

75. The stomach is very minute in such insects as the butterflies, that scarcely eat at
all ; but in those that live on coarse and indigestible materials it is proportionately
elongated and capacious {Rymer Jones, An. Kingd. p. 363). As to the intestine, its
length and convolutions are greatest in those insects that have a thick and largely
developed abdomen, especially if they are herbivorous (do. p. 362).

76. Alluding to the so-called " rostrum " of Hemipterous insects. This is a suctorial
tube formed by the upper and lower lips, within which are the mandibles and maxilUe
converted into lancet-shaped needles.

77. Most of our food does in fact go to maintain the heat of the body.

78. The Cicadse really live on the juices of plants. But A. adopts the general belief of
the ancients. So Virgil, " Dumque thymo pascentur apes, dum rore cicadas." See also
Anacreon, Ode ^2) > Theocr. 4, 16 ; Pliny, xi. 32.

79. The Ephemera of A. are usually supposed to be the insects still so named. There
are however no data for the determination. They are said {H. A. i. 5, 16) to have only
four legs, which is neither true of Ephemera nor of any other insects. Neither does the
account of their development {H. A. v. 19, 26) altogether suit the modern Ephemera.

(Ch. 6.) 1. The following are the characters A. ascribes to his Insecta. i. They are
bloodless. 2. They show segmentation either on the dorsal or ventral surface or on both
{^H. A. i. I, 16). 3. They have a distinct head, thorax, and abdomen ; the thorax
however being in some {Myriapoda) formed of a number of separate segments, not fused
together {H. A. iv. 7, 3). 4. Their legs are numerous and in number proportionate to
the segments, excepting when the insect has wings (iv. 6, 2). 5. They present no distinct
differentiation of their substance into bonelike and fleshlike parts, but consist throughout
of an uniformly hard substance intermediate to bone and flesh (//. A. iv. I, 5). 6. They
are either without special organs for refrigeration, or have such below the junction of
thorax and abdomen (iii. 6, Note 4). 7. They are almost invariably land animals,
though with some exceptions ; and some are aquatic, when young, but terrestrial, when
adult {H. A. i. I, 17). 8. The females are larger than the males {H. A. iv. II, 9).
9. Their primary generative product is not an ovum but a scolex {Introd. p. xxvii).

The 5th, 6th, and' 7th characters exclude Crustacea; for these have the soft parts
within and a harder part without, are aquatic, and sometimes have gill-like apparatus
for refrigeration in the thoracic or cephalic region (iv. 8, 7). Although A. thus distinctly
separated Crustacea from Insecta, the two were confounded again by after writers. Even
Lamarck at first included both under Insecta ; though later on (in 1 799) he separated

Notes, iv. 6. 229

them. Crustacea, then, are outside the group. It includes, however, not only insects
proper, which are A.'s Hexapodous insects, but also Myriapoda, which are his Poly-
podous and Wingless insects (iv. 5, Note 70). The third of the above-named characters
should exclude the spiders, scorpions, etc. But nevertheless these also are included in
the group by A., as indeed they were by modem naturalists until Lamarck separated
them in 1800. The fourth character, again, should exclude the parasitic worms. Yet A.
includes in the group both the flat and the round parasites (i¥. A. v. 19, 3), which he
calls by the general name of Helminthes. In fact, the only character on which he practi-
cally insists is the presence of segmentation ; and he even in one place {H. A. i. i, 16)
thus expresses himself: "I call all those animals insects, that show segmentation either
on the dorsal or the ventral surface, or on both." This passage must of course be read
with the limitations introduced in other places. Still it shows that segmentation was the
main character of the group in A.'s estimation. Probably therefore he included Annelida
in the group, led to this not only by their manifest segmentation, but by their retention
of life when cut into pieces, a character often mentioned by him as specially belonging
to insects. Some water annelids were certainly so included by him, being confounded
with Myriapoda. Cf. iv. 5, Note 70,

2. Cf. iv. 5, Note 70.

3. Cf. iv. 5, Note 71, and iii. 5, Note 2.

4. The Diptera are as a rule of small size. Still the direct relation here stated to obtain
between the bulk of an insect and the number of the wings can hardly be said to exist.
There is however some relation between the size of the wings and the weight of the body.
"There are three classes of flies in this order {Diptera), the form of whose bodies, as
well as the shape and circumstances of their wings, is different. First are the slender
flies— the gnats, gnatlike flies, and craneflies. The bodies of these are light, their wings
narrow, and their legs long, and they have no winglets. Next are those whose bodies,
though slender, are more weighty — the Asilidae, etc ; these have larger wings, shorter
legs, and very minute and sometimes even obsolete winglets. Lastly come the flies,
Muscidse, etc., whose bodies, being short, thick, and often very heavy, are furnished not
only with proportionate wings, and shorter legs, but also with conspicuous winglets "
{Kirby andSpence, 7th ed. p. 476). So also there is a connection between the weight
of the body and the presence of wings. For while in most insects the tracheae dilate
into air-vesicles *' which are subservient to the diminution of the weight of the insect, in
the Apterous insects, and especially in the Myriapoda, there is no trace of these " {Owen's
Lectures, i. 225).

5. The Melolontha of A. is certainly not the beetle now known by that name, viz. the
cockchaffer. For A. describes it {H. A. v. 19, 18) as coming from a worm that lives
in the dung of cattle and of asses. Very probably some such beetles as the Geotrupidse
are meant. These are stationary during the day ; and though they fly in the evening
" rasent la terre d'un vol court, lourd et sinueux."

6. Frantzius translates thus : " Their wings also are not divided. For it is not a wing
at all, etc." But the word which A. uses for the wing of an insect {TrTfp6v) is the word
used for the feather of a bird, not for its wing (irTepiryl); and the comparison is not
between the wings of an insect and the wings of a bird, which A. knew to be perfectly
distinct parts though analogous in function, but between the wings of an insect and the
feathers of a bird, which do so far anatomically correspond to each other, as that both
are derivations from the common integument. (Cf. iv. 12, 3.) When, then, A. calls
insects dipterous and tetrapterous he has an eye to homologies ; when we call them two-
winged or four-winged we are thinking of analogies.

230 Notes, iv. 6.

7. The Juli when alarmed coil themselves up in a spiral form, with the feet entirely
concealed. The Glomeridas roll themselves into a perfect ball. Not only long-bodied
insects, but some others, roll themselves up. For instance, the ant known as Myrm.
Latreillii is said by Sir J. Lubbock to do so.

8. The description of the Canthari in the Hist. An. (v. 19, 18), where they are said
to roll dung into balls, in which they deposit their progeny, seems to identify them with
the sacred Scarabei of Egypt {Ateuchus sacer). Many beetles when touched assume
attitudes more or less such as here described. '* The common dungchaffer, when touched
or in fear, sets out its legs as stiff as if they were made of iron wire ; which is their
posture when dead ; and, remaining perfectly motionless, thus deceives," etc., etc
The pill-beetles " pack their legs so close to the body, and lie so entirely without motion
when alarmed, that they look like a dead body." Still nearer to A.'s description is the
action of certain caterpillars. " The body is kept stiff and immoveable with the
separation of the segments scarcely visible" {Kirby and Spence).

9. Cf. iii. S, Note 2,

10. Cf. ii. 16, 5 ; iv. 12, 4.

11. Ants, bees, and Hymenoptera of all kinds, have biting jaws or mandibles. It
is these that A. calls their "modified" teeth (iv. 5, Note 7). These mandibles,
however, are not used merely or principally for the prehension of food, as stated in
the text, but "comme instruments de sculpture dans les travaux architecturaux de ces
animaux" {M. Edwards, Lefons, v. 520).

12. The terminal segment of the scorpion is so shaped as to form a sharp uncinated
sting, under which are orifices giving issue to the secretion of a poison-gland. The
scorpion runs swiftly, arching its tail over its back, and turning it in all directions.

13. This generalisation especially excited the admiration of Cuvier, who says that
it implies " un examen presque universel de toutes les especes." Mr. Lewes is more
sober in his estimate, and thinks that, though the generalisation is true, it was made
after examination of but few species, and that A. was thus right almost by accident.
That A. examined the greater number of species of Diptera, or indeed any considerable
part of them, is hardly consistent with his only mentioning in all his writings five kinds,
and giving such scanty account of these, that naturalists are unable to identify them
with certainty.

14. The text gives Tory ffiirpoirdiv, i.e. "with the front part." The sense seems,
however, to require roiy 6vi(t0(v, and I have ventured so to alter it. If this
alteration be thought inadmissible, the passage must be rendered, "Weak as they are,
they have little power of striking even with the front part," implying that they would
have still less power to strike from behind.

15. Here we have a distinct statement of the advantage of division of labour in the
animal body; a truth which Milne Edwards thought he was the first to enunciate.
*' Dans les creations de la Nature, de m6me que dans I'industrie des hommes, c'est
surtout par la division du travail, que ce perfectionnement s'obtient," and in a note he
adds, " Ce principe de physiologie generale qui aujourd'hui est adopte par presque
tous les zoologistes a ete formule pour la premiere fois dans un article que j'ai public
en 1827 " {M. Edtuards, Lemons, 1. 16).

"Spit and lampholder in one," or, as perhaps it would better have been rendered,
"spit and candlestick in one," is in the Greek a single word, and so more forcible.
This strange implement with a double purpose is also mentioned in the Politics (iv.
^5> 8), where A. likens to it a board of magistrates, chained with a multitude of
distinct functions ; such a body as our Boards of Guardians, with their poor-law.

Notes, iv. 6 — 8. 231

sanitary, educational, and other functions. A. has another term of comparison for such
a body, viz. "the Delphian knife" {Polit. i. 2, 3), an implement apparently used for
many distinct purposes in the sacrificial rite.

16. The anterior pair of legs are remarkably long in some insects (ICirby, Bridg, Tr.
ii. 180) ; with what use it is difficult to say. Sometimes at any rate it seems to be
a provision to enable the male to secure the female, the peculiarity being confined to,
or most marked in, the former sex. The explanation given by A. can hardly be the
correct one; for the anterior pair are not specially elongated in ants or bees, though
these are insects that use their legs to dress themselves.

17. In such insects as are slow walkers all the legs are, as a rule, of much the same
length ; in those that run quickly all the legs are elongated, the hinder pair being the
largest ; in swimming insects, and still more in leapers, the hind legs are much longer
than the rest. In fleas the difference is not so marked as in grasshoppers ; nor do fleas
jump, like the latter, exclusively from the hind legs, for, having placed one in a glass
tube under a microscope, I have seen it hop with the anterior legs.

18. Literally " resemble a rudder," but I have slightly paraphrased the expression to
render it intelligible to those who may not know how a Greek ship was steered. In place
of a single rudder, as in a modern ship, there were usually two, one on either side of
the stern, resembling large oars, and moved in the same way as the other oars. The
size and position of these rudder-oars render, therefore, the comparison to the posterior
legs of the locust or grasshopper a very apt one. The resemblance, moreover, extends
to the functions. "Whoever," says Kirby, "has seen any grasshopper take flight or
leap from the ground will find that they stretch out their legs, and like certain birds use
them as a rudder " {Bridg. Treat. iL 162).

19. Cf. iv. 12, Note 10. A.'s meaning is expressed more intelligibly elsewhere {H. A.
iv. 7> 9)> "In some jumping insects the hind legs are simply larger than the rest, while
in others they resemble rudder-oars, being bent backwards like the [hind] legs of
quadrupeds."

(Ch. 7.) 1. Cf. iv. 5, Note 25.

2. Cf. ii. 10, Note 5.

3. Cf. iv. 5, 22-41.

4. "Aristotle in his Hist, of Animals mentions more than once a shell-fish under the
name of Solen in such expressive terms that we can scarcely doubt its identity with the
razor-fish, in all probability the Solen marginatus. He states that it buries itself in the
sand, perpendicularly, even to the depth of two feet, and can rise and sink in it, but does not
leave its hole ; that it does not spin a byssus like other Testacea ; that it is alarmed by
noise, and buries itself rapidly when frightened ; that the valves of the shell are connected
together at both sides, and that their surface is smooth. Such an enumeration of
characters indicates how carefully the great philosopher studied razor-fishes, and with
what interest he watched their doings and chronicled their fears " {Forbes and Haiiley,
Brit. Mollusca, i. 240).

5. The ordinary position of most living bivalves is not on their side but vertical, with
the opening between the valves downwards. This probably led A. to the conclusion
that the head, or what answered to it, was downwards, so as to take in food from below.
As to roots of plants, cf. ii. 3, Note 10.

6. Cf. iv. 5, Note 48.

(Ch. 8.) 1. The Crustacea are called by A. Malacostraca, ue. soft-shelled, or
sometimes Scleroderma, i.e. hard-skinned, and are defined by him as bloodless animals
that have their hard matter on the outside and their soft parts within ; the hard part,

232 Notes, iv. 8.

moreover, though readily bruised or crushed, not being brittle like that of Testacea
{H. A. iv. I, 3 ; iv. 2). There are, he says, four main genera : I, Carcini ; 2. Carabi ; ,
3. Astaci ; 4. Carides. The first three are decapodous ; the Carcini having no tail but
a flap, while the remaining two have long tails. This identifies the Carcini with our
Brachyura, or crabs. The Astaci are said to have the anterior pair of feet converted
into strong claws, of unequal size and differently toothed ; the second and third pairs
of feet being also chelate. Their shell is smooth, and some of them live in freshwater.
There is no difficulty in recognising in this description the lobster {Asfacus tnarinus) and
the river crayfish (Astacus fluviatilis). The Carabi differ from the Astaci in having
a rougher shell, larger eyes, longer and stouter antennae, a narrower thorax, and a harder
and less fleshy body. They differ also in the character of the first pair of feet. In the
Astaci these are chelate in both sexes ; but in the Carabi only in the female. On this
last point, however, A.'s language is not always quite consistent. For in the text he
speaks of the Carabi as always having claws like the crabs. This description leaves no
doubt that the animals meant are the spiny lobsters {Palinurus vulgaris). Although
the anterior feet of these animals never form such perfect claws as those of Astacus,
yet the terminal joint bends over and meets a process from the penultimate joint, so as
to make a nipper. This process is developed in very different degrees of perfection in
different individuals, as I have myself noticed, and thus it is easy to understand how
at one time they might be described as having claws, at another as without them.
Whether there is any difference in this respect dependent upon sex, I do not know.
There remain the Carides. These are said to have a tail, like that of the Carabi, no
claws, and more than five pairs of feet. The name would thus appear to designate
some of the Amphipoda, and Stomapoda. A. describes two kinds ; his account in
one case suiting the sea-mantis {Squilla mantis), but in the other being insufficient for
positive identification. As to the separation of Crustacea from Insecta, see iv. 6, Note I.

2. The Maia is said (H. A. iv. 2, 3) to be the largest of the cral:>s, the next in size being
the Paguri and the Heracleotic crabs, and to have a hard shell (^. A. viii. 17, 11).
Again (ff. A. iv. 3, 3) the Maia and the Heracleotic crabs are said to have their eyes
placed close together, near the median line. Here we are told that the Maiee have thin
legs, the Heracleotic crabs short ones, and that both live out at sea. From these passages
Cuvier and most writers have concluded with great probability that the Maia answers
to the Maia Squinado or spiny spider-crab, the largest of the crabs common in the
Mediterranean. There are no data to determine what are meant by the " Heracleotic
crabs."

3. In most crabs the four hinder pairs of feet are formed exclusively for nmning ; but
in some few they are flattened out so as to serve in swimming. These swimming crabs
are all small. Rondelet mentions several species as found in the Mediterranean.

4. Cf. ii. 9, Note 9.

5. A. does not explain why an animal that swims should want more legs than one that
has any other mode of progression ; and the statement that it does so is somewhat in
opposition with his previous remarks about Myriapoda. Probably he has in his eye the
image of a ship with its numerous oars on either side.

6. "In the Podophthalma, the lamelliform ciliated appendages of the abdominal
segments include similar marsupial or incubatory recesses for the ova. The female lobster
and other Macrura are distinguished from the male by the greater development of these
appendages" {^Owen's Led. i. 185). Similarly Cuvier {Reg. An. iv. 28), speaking of the
flap or tail of the Brachyura, says, " Triangulaire dans les males et gamie seulement
a sa base de quatre ou deux appendices, elle s'arrondit, s'elargit et devient bombee

Notes, iv. 8 — 9. 233

dans les femelles. Son dessoits offre quatre paires de doubles filets veins, destines a porter
les oeufs. Plusieurs de ces filets existent dans les males, mais dans un etat rudimentaire. "
7. This is too absolute a statement; and elsewhere (Zf. ^. iv. 3, 2) A. speaking more
carefully says that the rule is general but not universal. There are some grounds for his
statement. " In many species (of the higher Crustacea) the chelas on the opposite sides
of the body are of unequal size, the right-handed one being, as I am informed by Mr. C.
Spence Bate, generally though not invariably the largest. This inequality is often much
greater in the male than in the female" {Darwin^ Desc. of Man, i. 330). There are
however some small Crustacea in which the right claw appears to be invariably the
bigger. Thus I found no exception to this rule in loo common hermit crabs that I
examined in succession. In Alpheus villosus also the right claw is always the
larger ; and in Nika the right anterior foot is chelate, but not so the left.

8. Cf. iii. 9, 14, and ii. 3, Note 6.

9. Cf. iii. I, 7.

10. It has been stated recently {Land and Water, Aug. 20, 1870) that in lobsters the
right claw is the larger in one sex, the left in the other. This however was afterwards
contradicted by Mr. H. Lee ; and I have myself found it to be erroneous on examination.
So far then the statement in the text is correct. But there is no ground for the
further statement that the Astaci use their claws only for locomotion and not for
prehension.

11. Cf. iv. 5, Note 2, and Introd. p. x.

(Ch. 9.) 1. The Cephalopods are called by A. Malacia, i.e. Mollusca or soft animals,
and are defined by him (//". A. iv. i, 2) as bloodless animals that have their fleshy
parts outside, and their hard part, when there is any, within. They all have eight
legs, with suckers on them, in front of the head. The head itself is provided with two
jaws or teeth, large eyes, and a small brain enclosed in cartilage. These, and the
presence of an ink-bag, are the chief characters assigned to them by A., who mentions,
however, two other notable peculiarities, namely the adherence of the yelk-bag to the
head of the embryo (Z). G. iii. 8, 7) and the modification of one of the feet in the male
poulp to form an instrument of generation {H. ^. v. 6, 3 ; v. 12, 3 ; D. G.'\. \<„ 4).
The latter statement, repeated by Pliny {jSfat, Hist. ix. 74), refers of course to the
now re-discovered Hectocotylus,

Aristotle divides his Malacia into two groups, (i.) Those that have a short body
and long feet, no "proboscides," and no internal bones; a division corresponding to
our Octopoda. (ii.) Those that have a long body and short feet, but in addition
have two long "proboscides," with suckers on them. They also have an internal
bonelike support. These are our Decapoda.

Of the first gi-oup {Octopoda) there are, he says, numerous genera, (a) Those that have
a shell {ArgonautidcB). Of these he mentions two species ; the Nautilus, doubtless
Argonauta argo ; and another not determinable. (/3) Those that are without a shell
{Octopodidce). Of these he mentions the Poulps ; the Eledone, and the Bolitaena. (Cf.
Note 17.)

Of the second group {Decapoda) he mentions three kinds. The Sepias, the Teuthides,
and the Teuthi. The Sepia has a broad and strong "os sepiae," of a texture between
bone and fish-spine, and spongy within. Its body is broad rather than long, though of
good length in comparison with the feet. It has a narrow fin encircling the whole
body. Its ink-bag is large and placed low down in the body cavity. This can only be
the modem Sepia ; probably Sepia officinalis, and perhaps some others, as A. speaks
of "the genus of Sepias" (//. A. iv. i, 2). The Teuthi and the Teuthides have a larger

234 Notes, iv. 9.

body than Sepia ; a smaller ink-bag, placed higher up ; and a cartilaginous internal
support, shaped like a sword. The modem Teuthidae, comprising the calamaries or.
squids, are thus clearly indicated. It is doubtful, however, what species answer to
Teuthi and Teuthides respectively. The Teuthi are said to be bigger than Teuthides ;
to have a blunter apex ; and to be encircled by a continuous fin ; whereas the fin only
partially encircles the body in the Teuthides. The Teuthus is ordinarily supposed to be
Loligo vulgaris, and Teuthis to be Loligo media : a view accepted by Owen ( Todd^s
Cycl. i. 561) • The description of the fins, however, hardly tallies with this opinion (^M.
Edwards^ Mollusca, pi. vii. f. i). Frantzius is confident that by Teuthis is meant Sepiola
or Rossia. This would suit the account given of the fin. But on the other hand the
apex of the body is remarkably obtuse in Sepiola or Rossia {M. Edwards, Moll. pi. viii.
f. 3) ; whereas A. says that the apex of Teuthis is sharper pointed than that of Teuthus.
We must, I think, be content to speak of Teuthi and Teuthides as large and small
calamaries without affecting further precision.

2. Cf. iv. 5.

3. A similar idea concerning the cuttlefish, viz. that it was comparable to a vertebrate
animal bent double, with the approximated arms and legs extending forwards, was
advanced in a paper read before the Academy of Sciences in 1830. This paper was
referred to Geoffroy St.-Hilaire and Latreille ; was reported on most favourably, and its
position in fact almost entirely adopted, by them. This was the starting-point in the
famous controversy between G. St.-Hilaire and Cuvier as to unity of type ; the con-
troversy which excited Goethe more than the revolution of 1830 (seeZ^wj' Goethe, ii. 436).

4. Excluding, that is, the Echini, which he reckons among the Turbinata, notwith-
standing that they have no spiral shell.

5. It thus appears that this treatise was illustrated, as also were those on Anatomy.
Cf. iv. S, Note 33 ; cf. ii. 8, 8.

6. The head and body in the Octopodidse are connected by a broad cervical band.
This, and the comparatively small size of the body, doubtless caused the entire mass
to be looked on as a head by the vulgar.

7. In Gasteropoda the mouth and anus are near each other, but never in the same
median plane.

8. The ordinary mode of progression of Octopodidse is by crawling.

9. A. is not quite correct in his view of the part taken by the posterior limbs, at
least in Mammalia. For though these take the chief part in the propulsion of the body,
it is on the fore limbs that devolves the greater share in its support ; and it is this
difference in function that explains the different conformation of mantis and pes. Cf.
Owen, Nature of Limbs, p. 26, and Archet. of the Skeleton, p. 167.

10. There does not seem any very certain rule as to the comparative lengths of the
different arms in Sepia and Loligo. The general rule, however, is that there is a
gradual increase in length from the dorsal to the ventral pair ; and the statement in the
text that the ventral pair are the biggest, and the third pair the next in size, accords
with this. Neither does there seem to be any certain rule in this matter in Octopodidae.
Cuvier {Reg. An. iii. 11) says that their arms are all much of the same length. Owen
{Lect. on Comp. Anat. i. 344) says that in most of them the dorsal pair are the longest.

11. A. does not reckon the two retractile tentacles or " proboscides " as feet ; so that
he is correct in saying that all Cephalopoda are octopodous.

12. Cf. ii. 9, Note 9. "The development of the eight external arms bears an
inverse proportion to that of the body ; they are therefore longer in the short round-
bodied Octopi, and shortest in the lengthened Calamaries and Cuttlefishes, in which

Notes, iv. 9 — lo. 235

the two elongated retractile tentacles are superadded by way of compensation " [Owen,
Led. i. 344).

13. As A. speaks of the retractile tentacles of the Decapoda as " proboscides, " so
Owen [Led. i. 319) calls the proboscis of the elephant a * ' brobdignagian tentacle,"
and states that the mechanical arrangement is very similar in the two cases.

14. The Sepias in the Crystal Palace Aquarium have never been seen by Mr. Lloyd
{Field, Sept. i, 1876) to anchor themselves in the way described by Aristotle and by most
later naturalists. They use their " proboscides " to catch distant prey, darting them
out with great rapidity and precision,

15. The "twining tentacles" are the long snake-like arms of the poulp ; not the
retractile tentacles of the Decapoda. C£ iv, 5, Note 14.

16. These plaited instruments are mentioned by Hippocrates in his treatise on joints
{Kiihn^s ed. iii. 266). They are called " Saurse " by him; are said to be plaited
from some portions of the palm-tree ; and are recommended for use in dislocations of
the fingers. It was this same "Saura" that made its appearance in London a few
years back, and was sold as a toy under the name of the Siamese link.

17. The poulp with a single row of suckers is some species of Eledone ; E. moschata
according to Frantzius, E. cirrhosa according to Owen, who takes the Bolitasna to be
the E. moschata on the ground that it is also called Ozolis by Aristotle {^H. A. iv. i, 27),
which name seems to allude to its strong odour. The poulps with double rows of
suckers include the Octopus vulgaris, which is excessively abundant in the Mediterranean.
This is the species which A. speaks of {^H. A. iv. I, 26) as the largest and the most
littoral. Besides it he speaks of other smaller spotted kinds, which are not edible,
without giving enough data for their identification.

18. Cf. iv. 5, Note 5 ; Introd. p. x.

19. The Octopodidse have in fact no body-fin at all.

(Ch. 10.) 1. The viviparous animals, with blood, are of course our Mammalia. The
main characters noted by A. as belonging to them were these. They are sanguineous
animals, that produce their young viviparously, and without a previous internal ovum ;
the sexes are always distinct, and the offspring is attached to the inside of the mother
until its birth (/?<? Gen. ii. 4, 2), and afterwards is suckled by her {De Gen. ii. I, 28).
The male parent has testes, which are sometimes internal, sometimes external {De Gen.
i. 3, 4). They breathe air by a lung, the entrance to which is guarded by an epiglottis
(iii. 3, 10). They have neither feathers nor scales, nor scaly plates, but hairs in their
place {H, A.\\. i, 17).

The groups recognised by A. appear to have been these :

1. Bipeds, i.e. man.

2. Animals intermediate to man and quadrupeds, i.e. apes {H. A. ii, 8, i).

3. Quadrupeds ; again divisible into sub-groups.

a. Fissipedous animals with teeth in front of both jaws, i.e. Camivora, Rodentia,
Insectivora, which are not distinguished by Aristotle ; Dermoptera, or bats,
which are sometimes spoken of by him as a distinct group, intermediate to
these and birds; elephants (ii. 1 6, 7); and seals, which are "stunted
quadrupeds " (ii. 12).

/3. Cloven-hoofed animals, without upper front teeth, and with horns, i.e. Rumi-
nantia, in general.

7. Cloven-hoofed animals, without either upper front teeth or horns, i.e. camels.

5. Cloven-hoofed animals, with upper front teeth, and tusks, i.e. swine and
hippopotamus ; which latter animal Aristotle, who doubtless had never seen

236 Notes, iv. 10.

it, erroneously supposed, on the authority of Herodotus (of. Introd. p. xvi,
foot-note I ), to have only two hoofed toes to its foot.
6. Solid-hoofed animals, i.e. Solidungula.
4. Apoda, i.e. Cetacea.

2. i.e. Fishes. Cf. iii. 2. Serpents, though they have a lung, have no neck. This
exception, though not noted here, is dealt vi^ith in the next chapter.

3. Cf. ii. 7, 7.

4. Cf. ii. 10, Note 11. The brain requires (ii. 7, 9) a moderate degree of warmth,
as do all living parts ; but this must not be more than moderate, for ' ' the motion of the
heat of blood destroys sensory activity."

5. The argument is this. " The stomach cannot be placed above the heart, for such
a position would be inconsistent with the dignity of the chief organ (cf. ii. 2, Note 6) ;
it must therefore be placed below it. But if the mouth were also placed below the
heart, the stomach, owing to the length of the oesophagus, would be removed so far
from the heart, that digestion, which is due to heat derived from the heart, would
not be possible." A. forgets that elsewhere (iii. 3, 2) he has said that the oesophagus
is only necessary, because there is a neck, and that, but for this, the stomach might
come immediately after the mouth.

6. Cf. Intr. pp. xiv, xv. It is plain that A. was not himself acquainted with the lion ;
for nearly all his statements about its structure are erroneous. Here he says that it has
but one cervical vertebra ; a little later on he says it has but two dugs ; elsewhere that
its bones are without medullary cavity, etc. Moreover in one place {^H. A. ii. i, 33)
he uses the expression "the lion, as he is represented." Yet there were lions in his day
in Macedonia and North Greece, as we learn from Xenophon {De Venat. ch. xi. ), and
also from Herodotus (vii. 124-6). They were, however, rare {H. A. vi. 31, 2), and
confined to a small locality, so that the capture of one formed a notable event, as would
appear from the following passage : " The lame lion that was caught had many of its
teeth broken, from which some persons inferred that a lion lives for many years "
(H. A. ix. 44, 6) ; where it would seem that the writer is referring to some occurrence
so remarkable, that every one would understand his allusion. It will be observed,
however, that the author does not speak as though he had himself seen the captured
lion. Probably A. got such facts as he gives about lions from himters by hearsay.
Such clearly was the source of the account in the Hist. An. (ix. *14). As to the question
of the existence of lions in Greece in old times, see papers by Sir G. C. Lewis in
Notes and Queries, vol. viii.

7. Such uses, for instance, as turning round quickly to guard the hinder part against
a foe (iv. 11, 18); picking up food from the bottom of the water, as do web-footed and
other water birds (iv. 12, 8) ; or catching prey at a distance, the long neck serving as
a fishing rod (iv. 12, ll).

8. There are some perceptions, says A., that are peculiar to one sense, e.g. colour
to vision, hardness and temperature to touch, etc. But there are others not peculiar to
one sense, but appreciable by several, or at any rate by vision and by touch. Such are
motion, rest, number, figure, magnitude. These, then, are common sensibles, and that
which perceives them is the one common or general sense, of which the five senses are
special forms. Cf. D. A. iii. I and 2 ; De Som. 2 ; De Sens. 4, 20.

9. Cf. iv. 9, Note 9.

10. Cf. H. A. ii. I, 47-49. This statement as to the alteration that occurs in the
human body in the relative proportions of the upper and lower parts is correct. " After
birth, the proportions of the body alter in consequence of the legs growing faster than the

Notes, iv. 10. 237

rest of the body. In consequence the middle point of the height of the body— which at
birth is situated about the umbilicus — becomes gradually lower until, in the adult male,
it is as low as the symphysis pubis" (Huxley's Verteb. p. 488). On the other hand,
every one is familiar with the preponderate length of a colt's legs as compared with that
of its body. Lastly, if one compares a kitten with a cat, one finds no such contrast of
proportions.

11. Two of the mundane elements, earth and water, tend to fall downwards, the
remaining two, air and fire, to mount upwards. Cf. ii. i, Note i. Taking the passage
in the text by itself, it might be inferred that A. supposed the soul or vital principle to be
identical with heat, as did Democritus. But it was not so. Heat is elsewhere (ii. 7, 6)
said to be necessary for the operations of the soul, as its chief instrument, but not to be
the soul itself. So also fire (Z>. A. ii. 4, 12) is said not to be the true cause of growth
or nutrition, but only an assistant cause. Cf. i. I, Note 13, and ii. 6, Note 7.

12. A. here takes man as the starting-point, and descends from him to inferior creatures
by a succession of small degradations. Elsewhere, however (iv. 5, and H. A. viii. i),
he follows the other course, and starting from the simplest organisms mounts upwards,
until a succession of superadded improvements brings him to man. In the absence of
any notion of the evolution of the more complex from the simpler species, one mode of
viewing the series was as good as the other. Lamarck, however, is not quite accurate
in stating {Phil. Zool. i. 8) that his predecessors, including Aristotle, had invariably in
their serial classifications inverted what he insisted was the natural order.

13. Answers, that is to say, to the excretions of animals. Cf. ii. 3, Note 8 ; iv. 5,
Note 60.

14. Cf. ii. 16, Note 13. That the function is superadded to the organ is A.'s usual
statement. Somewhat inconsistently, however, he says in one place (Z>. A. ii. 9, 3),
" Man has a far more accurate sense of touch than other animals. For which reason
he is also far more intelligent than they." Lastly, in another passage (Z?. G. iv. i, 32)
he adopts the more tenable position that organ and function are given together.

15. The seeming impotence of man as compared with other animals has always been
a favourite topic. See for instance Shaftesbury, Moralists, 2, 4. The following passage
quoted by Sir C. Bell {Bridgewater Treat, p. 106) from Ray, is clearly an imitation of
Aristotle : "Some animals have horns, some hoofs, some teeth, some talons, some claws,
some spurs and beaks. Man hath none of these, but is weak and feeble and sent unarmed
into the world. Why, a hand with reason to use it supplies the use of all these."

16. I have introduced the short clause in brackets to give logical sequence. Plato
represents the nails as useless to man, but as given to him by the Creator, because he
foresaw that human beings would be degraded into beasts, to whom nails would be of use.
Galen (De Usu part. i. 8) rejects both Plato's and Aristotle's explanations ; and, in answer
to A.'s view, objects, that the nails in men are clearly incapable of affording any
protection either against changes of temperature or against injuries. His own opinion
was that the nails were designed to support the yielding tips of the fingers and to render
them more serviceable in the prehension of small objects, which would otherwise slip
from them. The modern view is either somewhat similar to this, namely, that they
serve by their solidity to give a certain degree of firmness to the tips of the fingers, and
so enable them to perceive slight degrees of pressure more perfectly, so far agreeing in
function with the phalangeal bones and the tactile corpuscles (Kolliker, Hum. Micr. Anat.
p. 85) ; or is something hke the view of Plato, inverted, namely that man has them in a
rudimentary condition, because he has inherited them from predecessors in byegone ages,
to whom they were of use.

238 Notes, iv. 10.

17. Cf. iv. 12, Note 10.

18. "L'homme porte les aliments i la bouclie au moyen du membra siiperieur. Les
diverses pieces dont se compose ce membre sont disposees de telle sorte, que leur mouve-
ment de flexion dirige naturellement la main vers la bouche " (Beclard, F/iys. p. 42).

19. Horses, when fighting together, use their fore-legs for striking, much more than
they do their hind-legs for kicking backwards. Cf. Darwin, Exp. of Emot. p. 112.
The main statement in the text is, however, correct. The anterior limbs in Ungulata
are quite useless for prehension, and only subserve locomotion. Hence the absence of
clavicles. Whereas in Unguiculate animals, speaking generally, the anterior limbs serve
more or less as prehensile organs, and are furnished as a rule with more or less perfect
clavicles.

20. Analogous is here used in the modem sense, i.e. having similar functions, and not
as equivalent to homologous. For A. has already said that the fore-limbs of quadrupeds
correspond anatomically to the arms of man.

21. In Canidse and Felidae, from which A.'s examples are taken, there are only four
toes to the hind-foot, while the fore-feet have each five, as in most Unguiculata.
The smaller quadrupeds, that are described as having five hind-toes and as creeping or
even running over -head, are such animals as rats, squirrels, moles, martens, weasels.
It is, however, not only small quadrupeds and creepers that have five hind-toes ; for the
same is the case with elephants and bears.

22. Cf. ii. 16, Note 5. " Is not this one of the most admirable things in the works
of nature, that she should take some part that has been developed in an animal for some
special function, and utilise it for some additional office ? " {Galen, De U. part. vii. 22).
Cf. iii. I, Note 12.

23. The upper or true ribs which are united to the sternum, in opposition to the
false ribs below. Thus there is firmness given to the mammae by the firm substratum.

24. As the arms are not used for locomotion, the mammas are not in the way, and
so there is no disadvantage in there being two of them ; otherwise they would be made
to form a single mass.

25. Elsewhere (//. A. ii. 8, 4), apes, as well as man, are excepted. Pectoral mamm^
are by no means confined, however, to man and apes. In bats, for instance, the two
mammae are pectoral ; so also in elephants, as indeed is presently mentioned.

26. The homed animals which produce few at a birth and have only two mammae are
sheep and goats. For in other horned animals, e.g. the cow, there are four, as A.
elsewhere {H. A. ii. i, 40) mentions. Even in sheep and goats there are really four ;
but two of these are usually rudimentary. The Solidungula have, as correctly stated,
only two mammae and these inguinal.

There is, as stated in the text, a very close correspondence between the number of
mammae and the number of young produced at a time. The larger uniparous mammals
have but two mammae, e.g. elephant, rhinoceros, hippopotamus, horse, etc. The
Ruminantia often produce two, and some of the larger Camivora two or more, at a birth ;
and these have as a rule four mammae. Most smaller Camivora, Insectivora, Rodentia
are multiparous, and also have numerous mammae. Thus the cat has three to six young
at a time and eight mammae. The dog has litters of four to nine, and seven to ten
mammae. The hedgehog has six to seven young and ten mammas. Rabbits, hares,
marmots, black rats, all multiparous, have each ten or more mammae.- So far then A. 's
statement is correct. But he seems to fancy that there is also some relation between the
number of mammas and the number of toes. Of course no such direct relation exists.
Still it is true that the one-toed Solipedes have but two mammae ; the cloven-hoofed

Notes, iv. 10. 239

Ruminants four ; and a very large proportion of the polydactylous quadrupeds, as
already mentioned, numerous mammae.

27. The number and position of the mammas are given correctly by A. in the other
instances ; but as usual (cf. Note 6) he is in error as regards the lion ; for though its
mammae are, as stated, abdominal, they are four, not two, in number. The lion
produces not unfrequently four, and occasionally even five or six, at a birth (cf. D. G.
iii. 10, 24).

28. Cf. iv. 5, Note 2.

29. i.e. in the direction from tail to head. This upward growth implies, he says, the
accumulation of nutriment in the part from which the growth proceeds, for otherwise
there would be no material for the growth ; and it is in this land of plenty that
the mammae are placed. In the human body the growth takes place in the contrary
direction (cf. Note 10); and the seat of plenty and location of the mammae is accordingly
at the opposite or pectoral end.

30. Linnaeus counted the horse among those exceptional quadrupeds in which the
male has no teats ; but John Hunter discovered vestiges of them in the stallion. Possibly
what A. says may be true, and thus the discrepancy between these two modern
authorities explained.

31. Cf. ii. 9, Note 3.

32. Frantzius supposes that the exceptions meant are those groups of fishes, such as
the Teleostei, in which alone among vertebrates the external urinary and generative
apertures are perfectly distinct. I also suppose these to be the exceptions. I would,
however, point out, that it cannot be to the distinctness of these two apertures that A.
refers. For he expressly and repeatedly denies the existence of urinary organs, and
of course of urinary apertures, in fishes, and indeed in all ovipara excepting tortoises
(iii. 8, Note 3 ; iii. 9, Note i ; and iv. 13, Note 36). The whole passage is written
carelessly, and must be corrected by the light of other passages, such as the following :
"The generative fluid is discharged by the same opening as the residual matter ; when
an animal has residua of both kinds, fluid as well as solid, by the opening which gives
issue to the fluid kind ; for the semen is itself a fluid residuum ; but when there is no
fluid residue, by the opening which gives issue to the solid residue" (Z>. G. i. 18, 62).
See also the passage in iv. 13, Note 37. The exceptional condition, then, in these
fishes, to which I understand A. to refer, is the distinctness of the generative and anal
apertures. And I would take the passage to be as follows : "In all animals, with the
exception of the bony fishes, the generative fluid is discharged by the same aperture as
the fluid or the solid excrement ; in the vivipara by the aperture for fluid excrement ;
in the ovipara, where there is no fluid excrement, by the anus. "

33. Hippocrates {KiihrCs ed. i. 551) had said, in partial anticipation of Darwin's
doctrine of pangenesis, that the semen was formed by contributions from all parts of the
parent's body ; and he explained on this hypothesis the resemblance of the offspring
to the parent, which extended occasionally even to accidental or acquired peculiarities
of structure. This opinion is combated by A. (Z?. G. i. 17-18), who insists, among
other arguments, that it would imply that the semen was a product of dissolution or
decay ((rhvf(\\is), which is clearly inadmissible. He argues that the semen can be
nothing else in substance than the surplus or residue of sound nutriment, which, after
conversion into blood, has not been required for growth. This, he says, explains
why no semen is formed either when the growth is active, as in childhood, or when
the power of concocting nutriment is small, as in old age or sickness ; and also why
those animals, whose surplus nutriment is turned into fat, are not prolific (ii. 5, Note 9).

240 Notes, iv. lO.

The semen, then, instead of being, as Hippocrates would have it, something which comes
from each and every part of the parent, is something which might have gone to each
and every part of the parent.

To the semen of the male corresponds the menstrual discharge of the female ; but, in
accordance with the colder nature of females, their generative secretion is less concocted
(Z>, G. iv. 5, 8), and therefore retains a greater resemblance to blood.

34. Elsewhere {H. A. ii. I, 46) sundry Carnivora are correctly stated to have a bone in
the penis ; the camel and stag to have no such bone, but a sinewy organ, also correctly ;
and man to have cartilage in the part, which chances to be true of some negroes. In no
other case however does the penis contain cartilage. As to the presence of sinew con-
ferring the power of contraction, cf. iii. 4, Note 20.

35. A. erroneously held erection to be due to air, and not to blood {Probl. xxx. I, 13).
To air also was due the force of emission, '* for nothing can be thrown to a distance
without pneumatic force" {^H. A. vii. 7, l).

36. The camel, the cats, and many rodents including the hare, are retromingent.

37. Alluding probably, as Frantzius suggests, to the ossified tendons that occur in old
specimens of gallinaceous birds.

38. True of all quadrupeds, this is especially true of elephants. "The structure of
his legs affords such support in a standing position, that reclining scarcely adds to his
enjoyment of repose; and elephants in. a state of captivity have been known for months
together to sleep without lying down. . . . Captain Dawson shot an elephant on the
banks of the Kalany Ganga. It remained on its feet, but so motionless, that after
discharging a few more balls he was induced to go close to it, and found it dead "
{ Tennent, Ceylon, p. 106). Hence in all probability the erroneous belief that the
elephant could not lie down, but rested by leaning against a tree (ii. 16, Note 7).

39. Cf. ii. 9, Note 8.

40. The parts below mean here the hind-legs.

41. A good description of the general characters of monkeys is given in the Hist. An.
(ii. 8). Three kinds are there distinguished : (l) the Pithecus, which has no tail, or only
a rudimentary one ; (2) the Cebus, which only differs from the Pithecus in having a tail ;
(3) the Cynocephalus, which is a larger, stronger, and more ferocious, species, with bigger
teeth and a face like that of a dog. These data are insufficient for exact identification.
Aubert and Wimmer however conjecture that the three species meant are Simla sylvanus;
some or other Cercopithecus ; and Cynocephalus Hamadryas ; all inhabitants of North
Africa.

42. Cf. ii. 16, Note 5.

43. For instance as an organ of prehension, as in monkeys ; a fly-flapper, as in cattle ;
an aid in turning, as in dogs ; "though the aid must be slight, for the hare, with hardly
any tail, can double quickly enough" [Darwin, Or. of Sp. p. 196),

44. The bone by which the leg articulates with the ancle is known as the astragalus.
This varies much in shape in different animals. In the ruminants it is symmetrical and
biconvex, whereas in other animals it is of irregular form and convex only at the upper
end. It was only when it had the symmetrical biconvex shape that it was suitable for
use as a die ; and then only that A., who knew nothing of its homologies, recognised it
as an astragalus, just as it is only then that boys recognise it as a hucklebone.

In the British Museum are several ancient Greek dice, or astragali. They are all
astragali of ruminants, either the bone itself or copies of the bone in various stones. So
in the marble group called " Astragalizontes " it is with the astragali of some ruminant
that the boy is playing. Amongst the Greek vases again is one representing the astragalus

Azotes, iv. 10 — 1 1;^ 241

of a ruminant. The astragali of sheep furnish the hucklebones with which children play
at the present day. " There is a game also," says an old writer, " that is played with the
pasteme bone in the hynder foote of a sheepe, oxe, gote, fallowe or redde dere, which in
Latin is called Talus" {Brand, Pop. Ant. ii. 288). A. describes the astragalus as a short
biconvex bone adapted to the concavities of the bones above and below, found only in
the hind-leg ; and this only of animals with cloven hoofs, with the exception of the
Indian ass, the hippopotamus, the lynx, and, according to some, the lion. The bone, he
says, stands upright in the joint, and has certain projections above. Of the four faces
marked in dice with figures, the face which takes the highest figure is turned inwards,
so as to front the corresponding face in the other astragalus, while that marked ace is
turned outwards. Cf. H. A. ii. i, 34.

45. I suppose he means that, if there were an astragalus, there would be much earthy
matter ; and, if much earthy matter, then the hoof would be a solid mass ; excepting in
that part of its breadth, where the earthy matter was used up in making the astragalus.

46. " L'homme a les pieds plus larges, et il peut les ecarter I'un de I'autre plus que les
autres animaux .... La grandeur de la surface du pied de l'homme tient a ce qu'il
appuye le tarse, le metatarse et tons les doigts a terre, ce qu'aucun animal ne fait aussi
parfaitement " {Cuvier, Lefons, i. 474).

47. Cf. iii. 9, 4, where the same is said as to kidne3rs.

(Ch. 11.) L That is all the Mammalia known to him, with the exception of Cetacea.

2. De Anim. Incessu, 8, I. See also iv. 13, 10, where the explanation is repeated.

3. Reptiles and Amphibia are comprised by A. in one group. The main characters
ascribed by him to them are these. They are sanguineous animals, and, with the
exception of the apodous serpents, four-footed and polydactylous {H. A. ii. 10, 2) ;
they are also oviparous, with the exception of the viper, which is ovoviviparous {H. A.
iii. I, 28). In virtue of these characters they are called "oviparous quadrupeds."

The sexes are always separate. The ovum is perfect, i.e. does not increase in size after
deposition (Z). G. ii. I, 18 ; iii. 5, 6 ; Introd. p. xxvii), and has distinct yelk and white
(Z>. G. iii. 2, 12). The embryo has two foetal appendages (iv. 12, Note 15), viz. umbilical
vesicle and dlantois. The testes, when present, are internal, but are absent in the
apodous kinds {H. A.w. $, T ; D. G. i. 3, 2). The generative outlet is one with the
anus {H. A. v. 5, 8). The females are usually larger than the males {D. G. i. 16, 3).
Refrigeration is effected by a lung, of bladder-like character (iii. 5, 6), the entrance to
which is not guarded by an epiglottis (iii. 3, 10). In all these characters they resemble
birds.

The body is neither feathered nor hairy, but covered with scales, which are harder than
those of fishes (iv. 1 1, 7). A tongue is always present (see Note 5) and often is bifid.
The teeth are always of the serrate form (iv. 11, 6). The stomach is single (iv. i, 4).

Such exceptions as the absence of scales from frogs and other Amphibia, or of teeth
from Chelonia, etc., though not mentioned by A., can hardly have been unknown to
him. The only distinct subdivision of the group recognised by him appears to be into
Tetrapoda and Apoda.

4. Cf. iv. 10, 3-5.

6. There are, as a matter of fact, some oviparous quadrupeds without a tongue ; but
these are species which were unknown to Aristotle, such as the Carinthian Proteus, the
Surinam Pipa, and the Dactylethra of South Africa. The crocodile really has a tongue ;
but it is flat, destitute of papillae, and united by its whole extent to the floor of the
mouth. This seems to be recognized in other passages {H. A. ii. lo, 2 ; D. P. ii. 17, 7).
Cf. ii. 17, Note 9.

16

242 Notes. I'v. II.

6. Cf. ii. 17, 7. So also in speaking of fishes elsewhere (//. A. ii. 13, 11) A. says,
"They have a hard and spinous tongue, which is so attached to the other parts, that
sometimes its presence would not be suspected."

7. That the sense of taste must be very dull in fishes is admitted by all naturalists
(cf. Yarrell, Brit. Fishes, i. xvii) ; for, as A. justly observes, they do not chew their food,
and thus the juices, which alone can excite true taste, are not expressed. Moreover the
inside of the mouth is being constantly washed over with water, which must of itself
interfere with the possibility of any delicate gustation. Still they are probably not
entirely without this sense, as is elsewhere (H. A. iv. 8, 8) admitted ; for, as there
pointed out, they manifest certain preferences for one food rather than another.

8. '* On which account a certain gourmandiser wished that his throat were longer
than a crane's, implying that his pleasure was derived from the sense of touch " {Ethics,
iii. 13, 10). The same notion led Spenser, in describing Gluttony, to say, "And like
a crane, his neck was long and fyne " {Faery Queen, i. 4, 21).

A. did not fail to observe a fact which some later writers have passed over, viz. that
many sensations called Tastes are in reality compound sensations. True tastes have for
their almost exclusive organ the tongue, and are only produced by fluids. So far A.
is accurate. But into most so-called Tastes enters a tactile element. By touch, which
is not limited to the mouth and tongue, but extends to the gullet, we recognise the
temperature, the hardness, the oiliness, etc., of substances. So far also A. is fairly
correct ; though the distension of the oesophagus, of which he speaks, would be rather
a muscular than a tactile sensation (compare iii. 14, Note 34). But in most so-called
Tastes there is still a larger part due to smell, as any one will find if he roll a high-
flavoured wine in his mouth while his nose is held closed. This part of the compound
taste A., like many modern writers, does not distinguish from true simple taste, which
is limited to the perception of acid, sweet, salt, bitter. Still the interlacing of Smell
with Taste, in the popular acceptation of the term, could not, and as a matter of fact did
not, escape his notice. The same savoury substances, he says {De Sensu, 5, 10), which,
when dissolved in fluid and applied to the tongue, cause taste, will, when they act upon
the nose through a nameless something (ii. i. Note 12) that is common to air and water,
cause smell. Moreover, he recognises the fact {De Sensu, 5, 14) that a smell and a taste,
when often experienced simultaneously, become so blended by habitual association that
the dual sensation becomes, a single one. For a discussion of the relations of Taste with
Smell, see a paper contributed by me to the Royal Med. Chir. Transact. 1870.

9. That drunkards are small eaters is a well-known fact. The explanation is however
more probably injured digestion than deficient sensibility to flavour. The statement is
taken from Hippocrates {KUhn^s ed. i. 528).

10. Cf. H. A. ii. 17, 21. The tongue in Ophidia is bifid, as also it is in one great
division of Sauria (hence called Fissilinguia or Leptiglossa), but not in all ; not, for
instance, in the chamaeleon nor in the wall gecko, or scarcely so, among species
known to Aristotle. In the seal the tongue is deeply notched. See Buffon, Nat. Hist.
xiii. pi. 50.

11. Cf. ii. 17, Note 7.

12. Cf. iii. I, Note 7. The teeth of Saurian reptiles are usually acutely conical and
slightly hooked. In some cases they are blade-like, and occasionally dentated on the
edges. Rarely, as in Cyclodus, they have broad crushing crowns. In Chelonia there
are no teeth at all.

13. Cf. ii. 12, Note 2 ; and ii. 13, Note 5.

14. All reptiles have horny epidermal scales, but not so such Amphibia as the frog and

Notes, iv. II — 12. 243

toad, which A. induded in the same group. In the Chelonia and the crocodiles these scales
are combined with bony scutes, and these animals are therefore known as Loricata.
But nothing of the kind occurs in the large serpents, none of which were actually known
to Aristotle (ii. 9, Note 7), but of which he had probably heard fabulous accounts from
some of Alexander's companions ; from Nearchus, for instance, whose statement as to
the existence of monstrous serpents in the East is quoted by Arrian in his Indica.

15. Most reptiles have an upper eyelid, though they use the lower lid exclusively or
preferentially (cf. ii. 13, Note 2). In Ophidia, however, and some Lacertilia, there are
no lids at all, or rather the two lids are transparent and continuous with each other in
front of the eye ; a condition of things which A. supposed (ii. 13, 10) to exist in Crustacea.

16. Cf. ii. 13, Note 5.

17. This is an error (cf. ii. 13, Note 2).

18. And therefore, he implies, do not require so much protection.

19. The Camivora are an exception, their teeth being adapted for cutting and not for
grinding. This exception, though not mentioned here, is recognised presently, when it
is said that lateral motion goes with grinding teeth only, and therefore not with the
serrated dentition of Camivora.

20. This was the common belief of the ancients (cf. Herodotus, ii. 68). Cuvier thus
accounts for the error: "Les machoires inferieures se prolongeant derriere le crane, il
semble que la superieure soit mobile, et les anciens Tont ecrit ainsi ; mais il ne se meut
qu'avec la tete toute entiere" {Reg. An. \\. 18).

21. I suppose A. means that when an animal takes its prey in the water it must
generally do so with its mouth, because the anterior limbs are occupied in the act of
swimming.

22. Cf. iii. 3, Note 3.

23. The vertebras of Ophidia are not cartilaginous but osseous. The great flexibility of
the spine is due to its division into excessively numerous segments, and to the existence
of a perfect ball and socket joint between each of these and that which precedes and
follows it.

21. " Internally viviparous " is equivalent to Mammalia, whose ovum was unknown to
Aristotle ; it excludes ovoviparous animals, which A. called " externally viviparous but
internally oviparous." Cf. iv. i. Note 5.

25. Cf. D. G. iii. 2, 9.

26. Cf. iv. 10, Note 43.

27. There is an admirable account of the chamseleon in the Hist. An. (ii. 11), and in it
occurs a passage of great interest, as showing that A. made vivisections. The chamseleon,
though found in Spain, is not found in Greece. It is, however, easy of transport alive ;
and may have come into A.'s hands either from Africa or Asia Minor. It is, I believe,
the only foreign animal, concerning which there is satisfactory evidence that it was
seen alive by Aristotle (cf. Introd. p. xiii) .

28. Alluding of course to the well-known changes of colour which occur in this animal
(cf. Owen, Verteb. i. 556), and which are apparently determined not only by variations in
the temperature, the amount of light, and the tints of surrounding objects, but also by
emotions, as fear, anger, and the like.

29. Cf. ii. 4, Note 4.

(Ch. 12.) 1. The main characters noted by A. as belonging to birds are as follows.
They are sanguineous ovipara, resembling reptiles (iv. 11, Note 3) in having the sexes
separate ; in having a perfect ovum, and an embryo with two umbilical appendages ; a
lung so deeply divided as to appear double, of bladderhke character, poor in blood,

244 Notes, iv. 12.

and without epiglottis ; a common orifice for excrement and for generative products ;
and lastly in closing the eye, with some few exceptions, with the lower lid (ii. 13, l),
the lids being without lashes excepting in the ostrich (ii. 14, i).

On the other hand, they differ from reptiles and from all other sanguineous animals in
having feathers in place of hairs or scales, a beak in place of lips and teeth, and wings in
place of arms or fore-legs. The "ischium" is extremely long (Note 27) ; the legs turn
their convexity backwards (Note 10 ; De Inc. 15 ; H. A. ii. I, 13) ; the toes, excepting in
the ostrich (iv. 14, Note 4), are four in number (Note 30). The bones are brittle (ii. 9,
Note 6), and the breast-bone sharp-edged and thickly covered with flesh, especially in
birds of rapid flight {^De Inc. 10, 9). The testes are internal. There is no bladder, though
there are flat kidney-like organs (iii. 9, Notes i and 2). There is invariably a tongue
{H. A. ii. 12, 9) ; there are no teeth, their office being discharged by variable arrange-
ments of the stomach and intestines (iii. 14, 9-10) ; there is always a gall-bladder
(^H. A. ii, 15, 12) ; and usually there are one or two ca;cal appendages to the gut low
down {H. A. ii. 17, 34). The ears and nostrils are represented by simple orifices.
The eyes are provided with a nictitating membrane (ii. 13, Note 2).

A. makes no exhaustive division of birds. The following groups are, however, distinctly
recognised by him.

(rt) Birds of prey, with talons and hooked beak, fleshy breast and stout thighs {H. A.
ii. 12, 3), small bodies, powerful wings, abundant feathers, keen sight {De Inc.
10, 8-10). These are clearly our Raptores ; with which, however, A. also
classes the parrot (ii. 17, Note 3).
{b) Heavy-bodied birds, ill-suited for flight, of terrestrial habits, fond of dusting
themselves, often with spurs (cf. ii. 13, Note i). These answer generally to
our Gallinacese,
{c) Dovelike birds, laying two white eggs, etc. ; clearly Columbid?e.
{d) Swimming birds, wholly or partially webfooted (Note 8), with long neck, short

legs and tail ; our Natatores.
(e) Marsh birds, with long legs and neck, the front toes elongated, the hind toe short ;

our Grallatores.
(_/^ The ostrich, which stands alone (iv, 14% represents our Ratitse or Cursores.

These are the only groups distinctly recognised by Aristotle ; for such
terms as "insect-eaters," "grub-eaters," "thistle-eaters," etc, are hardly meant
to represent definite subdivisions.

2. The class A ves is remarkably homogeneous. "The structural modifications which
they present are of comparatively little importance " {Huxley),

3. Cf. iv. 6, Note 6.

4. Cf. ii. 16, Note 5.
6. Cf. iv. 5, Note 8.

6. Not actually bony, but resembling bone in being hard. Cf. ii. 9. 16.

7. Cf. iii. 3, Note 3, and iv. 10, Note 7.

8. The birds alluded to are the Grebes, the Phalaropes, the Coots, in which the toes
are bordered with broad membranous lobes, which led Temminck to arrange them in
one order to which he gave the name of Pinnatipedes. A. describes this arrangement
in more distinct language farther on in the chapter. The word which he uses here
to describe the toes, and which I have rendered "flattened and expanded into lobes,"
is literally " snubnosed." Liddell and Scott, referring to this passage, interpret the
term as "with turned-up feet, like some waders." But clearly it is not the tumed-up
character of a snubnose, but its flat and broad aspect which forms the ground of the

Notes, iv. 12. 245

comparison ; the main stem of the toe answering to the ridge of the nose, the lobes on
either side to the flattened nostrils.

9. The scapula in birds is a simple elongated bone, not flattened out into a plate or
blade, and so was not recognised by A. as a " blade-bone," just as he did not recognise
the astragalus unless it had the form suiting it for use as a " hucklebone." Cf. iv. 10,
Note 44.

10. A. uses two sets of terms to describe the bandings of the limbs (i) Forwards and
backwards, {2) Inwards and outwards. A limb is said to be bent fonvards or backwards,
when its convexity is turned forwards or backwards ; e.g. the leg of a man is bent
forwards ; so is the fore-leg of a horse. But the hind-leg of a horse is bent backwards ;
the arm of a man is bent backwards with a slight inclination to the side. A limb is
bent inwards, when its concavity is turned in the direction in which the main bulk of
the body lies ; outwards when the concavity is turned away from this. Thus both the
fore and the hind legs of a horse are bent inwards. So also the leg of a bird is bent
inwards ; but the leg of a man is bent outwards.

It must be remembered that A. knows nothing of the homologies of the various joints.
He simply takes the limbs as wholes, and compares the general direction of their main ^
curvature in different animals.

11. A. rightly says that no sanguineous animal has more than four organs of
locomotion, that is, more than four limbs. There are passages from which it might be
inferred that he imagined, less correctly, that they never have less than four (cf. iv. 13.
Note 6). But in the De Incessu (10, l) he expressly repudiates such a statement.

12. That is not, as whales and fishes, in the water ; nor, as birds, in the air.

13. A. had clearly neither dissected, nor seen the skeleton of, an ostrich. In all other
birds known to him the sternum is provided with a keel, which he compares ^De Incessu,
10, 9) to the sharp prow of a felucca, reminding one of the term " Carinatae " now given
to birds with a keeled sternum.

14. The mass of muscles that move the wings is of course meant. It must be
remembered that A. knew nothing of muscular contraction (cf. iii. 4, Note 20).

15. It might be supposed from this passage that A. imagined a bird to be developed
without an allantois and merely with an umbilical vesicle. But from other passages
(Z?. G. iii. 3, 4 ; D. G. iii. 2, 22 — 28 ; H. A. vi. 3, 8) it is plain that this was not the
case. He describes the foetal bird and reptile as differing from fishes in having two
umbilical appendages, one going to the membrane surrounding the yelk, and serving to
introduce the nutriment thence derived, the other (allantois) to the membranous expansion
which lines the inner surface of the shell. This latter appendage, he says, collapses as
the embryonic bird enlarges ; while the former with the yelk is drawn back into the
abdominal cavity, the walls of which unite together behind it. He had not observed
the umbilical vesicle of mammals, which is comparatively small, and shrivels up at an
early period of foetal life, and erroneously supposed their allantois to correspond to the
umbilical vesicle of birds and reptiles. This error was not corrected till 1667, when
Needhara discovered the umbilical vesicle of mammals, and recognized its correspondence
to that of birds. Neither had A. observed that Amphibia in this matter resemble fishes
and not reptiles, with which latter he grouped them.

16. Cf. ii. 9, Note 9.

17. Birds of prey are awkward movers on the ground or other flat surface, because of
their talons, and help themselves along by flapping their wings. But the statement made
here and elsewhere {H. A. ix, 32, 12) that they very seldom or never settle on rocks is
erroneous ; they often do so, and indeed rocks are the usual resting-place of many.

246 Notes, iv. 12.

A writer in the Penny Cycl. (x. 163) makes the following remarks, how far accm-ately
I cannot say, concerning the Falconidse. "The nails or claws to be available must be
sharp ; and in order that they may be kept in this state and fit for duty, there is a
provision to enable the bird to prevent them from coming in contact with the ground
or other foreign hard bodies. For the claws are retractile, not indeed in the same
manner as those of the cats, which have the power of withdrawing or sheathing theirs
within the integuments, but by a conformation which gives the bird of prey the power
of elevating its claws at pleasure. The claws of falcons, when sitting on stones or large
branches of trees, have often a cramped appearance. But this arises in most instances
from the care of the bird so to arrange its talons that their points may not be blunted
against the perch."

18. Because the earthy matter has not been used in any other manner, and must be
disposed of in some way or other.

19. Cf. Note 8.

20. Cf. iv. 13, Note 12.

21. Cf. iv. 10, Note 14.

22. This is erroneous. The number of phalanges is the same in the several toes of
Waders as in other birds, though the toes are as a rule longer.

23. Cf. Introd. p. x.

24. " These water birds fly with their legs stretched out behind, using them in place
of a tail to steer their course." In the heron, for instance, the tail is short, and the long
legs, stretched out in flight, " seem, like the longer tails of some birds, to serve as a
rudder" {BewicKs Birds, p. 11).

25. Any one who has watched a hawk swoop down on a pigeon will recognise the
truth of this description of the position in which it holds its legs.

26. The heron in flight rests its very slender neck and head on the back, so that the
bill appears to issue from the chest; while the stork, the ibis, the goose, etc., fly with
the comparatively stout neck outstretched.

27. The term "ischia" is used by A. sometimes for the fleshy part of the buttocks,
sometimes for the bones which we know as "ossa innominata." It is owing to this
double meaning that in some places he speaks of birds as having no ischia, i.e. no
buttocks ; while in others, as here, he says that they have peculiarly long ischia, i.e.
pelvic bones. The pelvis of a bird is remarkable for its great elongation, both anteriorly
and posteriorly. It is thus described elsewhere {H. A. ii. 12, 2) : "Birds, moreover,
have an ischium which is long and resembles a thigh-bone, and is united {^mth the
vertebral column) as far as the middle of the belly, so that when it is separated from
its connections it looks like a thigh-bone." See also De Incessu, xi. $.

28. Cf. iv. 10, 10—15.

29. Cf. iv. 10, S3.

30. This is a general but not universal rule. In some birds, as the great bustard, the
Otis of Aristotle, the toes are reduced to three by suppression of the hallux, as in the
ostrich they are reduced to two by suppression of both hallux and second digit.

31. The hind toe varies very much in its development in Waders. Usually it is short,
as A. correctly says, but sometimes it is as long as, or even longer than, the others.

32. The Crex was doubtless some bird that derived its name, as does our corn-crake,
from its note. But it is uncertain what exact species was thus designated. It was a
pugnacious bird {H. A. ix. 17, l), much of the same size as the Ibis {Herod, ii. 76); with
a sharp and notched beak [Schol. to Aristoph. Aves, 1060); and, as this passage shows,
it had a stunted hind toe.

Notes, iv. 12 — 13. • 247

33. Although A. speaks here of the wryneck ( Yunx torquilld) as the only bird that
turns two toes backwards, elsewhere {,H. A. ii. 12, 4) he says there are several in which
this is the case. Probably he there refers to cuckoos or woodpeckers or owls, which
latter, as also the osprey, can turn the outer toe backwards at will ; for he had apparently
never himself seen a parrot. (Cf. ii. 17, Note 3.)

34. D. G. i. 12.

(Ch. 13.) 1. The main characters assigned by A. to Fishes were as follows. They
are sanguineous ovipara, with sexes almost, though not quite, invariably distinct (Z>. G. ii.
5, 7); producing either a perfect ovum (selackia), which is hatched internally, the embryo
in such case becoming exceptionally {mustclus) attached to its mother's uterus (D. G. iii.
3, 10), or an imperfect ovum, one that is that grows after deposition (D. G. iii. 5, 6 ;
Introd. p. xxvii). In either case the ovum differs from that of Birds and Reptiles in
presenting no distinction of white and yelk (Z>. G, iii. 3, 8-1 1), and in giving rise to an
embryo with only one umbilical appendage (Z>. G. iii. 3, 4 ; /T. A. vi. 10, 3). The
skeleton is formed not of true bone, but of a spinous substance or of cartilage, and small
spinous bones are to be found isolated in the flesh \H. A. iii. 7, ll). There are usually,
though not always, scales externally, never hairs nor feathers. The place of limbs is
supplied by fins, of which the ventral pair are often missing, and occasionally both pairs
(Notes 10, 1 1). There are gills in place of lung ; no bladder nor kidneys. The seminal
organs are hollow tubes, and there are no solid ovoid bodies like the testes of Viviparous
Quadrupeds and Birds (cf. Note 34). The generative outlet is one with the foecal (cf.
Note 36), with apparently some exceptions (cf. iv. 10, Note 32). The teeth are sharp,
but not adapted for mastication ; the oesophagus is absent or short ; processes, often
numerous, are usually given off from the intestine close to the stomach (iii. 14, 14 ; H. A.
ii. 17, 26) ; there is always a gall-bladder (iv. 2, i).

They are divided into two great groups: (l). Those with a cartilaginous skeleton;
which with one exception (cf. Note 5) are ovoviparous. This group is subdivided into
the Elongated species, i.e. sharks and dog-fishes, and the Flattened species, i.e. rays
and skates, with which A. classes the oviparous fishing-frog (cf. Note 5). (2). Those with
a spinous skeleton, and oviparous.

The former group he calls Selachia ; to the latter he gives no special name.

2. I cannot say to what passage A. refers. But his explanation of the substitution of
fins for limbs is given a little farther on in this chapter.

3. The electric rays or Torpedos are found abundantly in the Mediterranean, and must
have been well known to A., who frequently speaks of them. Yet in these the tail is
far from being spinous and elongated, as compared, that is, with other rays. Frantzius
suggests therefore that some error has got into the text, and that perhaps Batos should
be read instead of Torpedo. A similar correction would have to be made a few lines
farther on,

4. The Trygon is doubtless the Trygon Pastinaca or sting-ray, which is abundant in
the Mediterranean.

5. The Batrachus or fishing-frog is the Lophius piscatorius, often mentioned by A.,
and erroneously classed by him with Selachia. Into this error he was doubtless led by
the somewhat ray-like form of this fish, by the semi-cartilaginous character of its skeleton
{Cuvier, R. An. ii. 250), and by its naked skin, rough with warts and tubercles. A. did
not fail to observe that the Batrachus differed in many important points from the rest of
the group; in being, for instance, oviparous ^De Gen. iii. 3, i); and in having an
operculum for its gills, and the gills themselves placed laterally (//. A. ii, 13, 7). A.
had clearly examined the fish with some care ; for he notices (cf. iv. 2, Note l) the

248 Notes, iv. 13.

exceptional position of its gall-bladder ; but probably he had not examined it often,
for he speaks of it as being rare (//. A. vi. 17, 9).

6. Cf. iv. 12, Note 11. At first one is struck with admiration at the prescience of A.
in identifying the pectoral and ventral fins with the anterior and posterior limbs of other
Vertebrata ; and one is inclined to credit him with a much more accurate conception of
homologies than he really possessed. Not a single word, however, is said of any
anatomical correspondence of fin and limb. The identification is based on similarity of
function, not on similarity of formation ; that is to say, it is founded on analogies, and.
not on homologies. It is true that the other fins, which are not homologous to limbs,
are passed over by A. notwithstanding their analogous office ; but this is only owing
to the fact that they are single, that is unpaired. How little comparative anatomy had
to do with A.'s statement is shown by his overlooking the real pectorals in the rays, and
imagining their dorsals, which are merely cutaneous appendages, to be the pectorals
misplaced. So also he speaks of the serpents, which have no limbs at all, as still
reseml;ling the other sanguineous animals, i.e. in having four points of motion. " For,"
says he, "their flexures are four," while in such fishes as have only two fins "the
flexures are two, to replace the missing pair" (cf. H. A. i. 5, 15).

7. It is strange and yet, as it appears to me, indisputably true, that A. was perfectly
ignorant of the fact that tadpoles are the larval forms of frogs and newts. For it is
impossible that he can have known it, and yet made no mention of what would have
seemed to him, as indeed it is, a most extraordinary phenomenon. He appears to have
looked on tadpoles as aberrant kinds of fishes, and on frogs of course as reptiles.

8. Destitute, that is, of fin-rays, such as exist in the caudal fin of fishes. Elsewhere
{H. A. i, 5, 10) A. compares the tadpole's tail to that of Silurus glanis, referring, as I
suppose, to the fact that in Silurus the anal fin is of great length, extending along the
whole belly, and joins, or nearly joins, with the caudal fin, so as to resemble the ventral
part of the continuous fin of the tadpole.

9. The Batos is described as a flat cartilaginous fish, with rough skin, and long rough
tail {H. A. vi. 10, 17) ; as hiding itself under the sand and then, by means of certain
oral processes, attracting small fishes on which it preys (^H. A. ix. 37, 5). Lastly, it is
said to copulate with a different species of fish, called Rhine, and thus to give origin to a
mongrel, the Rhinobatus {H. A. vi. 11, 7).

The Rhine is said to be a cartilaginous fish, whether flat or elongated is not expressly
stated, with a thick tail ; producing young twice a year {^H. A. v. 10, i), and resembling
the Batos in hiding under sand and in its method of attracting prey by means of its
oral processes {/T. A. ix. 37, 5). It has moreover the power of changing its colour, in
adaptation to the stones, etc., about it ; and is the only fish that can do this {^H. A.
ix. 37, 22).

These data are insufilcient for exact determination of the species meant. It is usual,
however, to identify Rhine with the angel-fish, and Batos with some or other ray.
Numerous rays, as also the angel-fish, hide themselves as described under sand or stones.
The angel-fish has also some small processes in front, which might be those which A.
supposes to be used to allure small fishes {YarrelPs Fishes, ii. 407). But I know of
nothing similar in a ray, to suit the statement as to Batos. As regards the power of
changing colour, the angel-fish, says Yarrell, "is probably liable to some variation in
colour depending on the nature of the ground in the locality in which it is found." This
tallies well with A.'s account of Rhine. But it must be remembered that a similar
faculty of adapting the colour of the skin to that of the ground belongs to many other
fishes. I have frequently, for instance, watched its operation in the plaice j which fish
changes its hue very completely and very quickly.

A'otcs. iv. 13. 249

10. The pectoral fins are, as rightly stated in the text, much more constant than the
ventral pair. Even in those elongated eels in which no pectorals are visible externally,
rudiments of them are to be found on dissection ; whereas not only are the ventral fins
more often externally wanting than the pectorals, but their absence is often complete,
no rudiment of them appearing on dissection, e.g. in Mursena, Muraenophis, Gymnotus,
etc. There are pectoral, but no ventral, fins in the eel, the conger, and the rest of the
so-called Apodal Physostomatous fishes. As to the Cestreus, it is impossible to say what
fish is here meant. Certainly it is not one of the Mugilidse, though these are the
fishes usually called Cestreus by Aristotle.

11. The Smursena and the Mursena of A. are in all probability one and the same fish.
It is described as elongated ; without either ventral or pectoral fins (see last note) ;
marked with different colours ; having its branchiae less distinct than most fishes ;
depositing numerous ova ; living on flesh ; hiding itself under the ground in cold
weather ; occasionally leaving the water. It is moreover often mentioned in association
with the eel and conger. It seems most probable that the Muraena Helena is the species
meant. This is very common in the Greek seas, where, according to Erhard, it still
bears the name Smuma or Sphurna.

12. The pectoral and ventral fins are not, as a rule, such important agents in the
propulsion of the fish as A. seems to think. Their chief uses are to give direction to the
motion generated by the lateral strokes of the tail, to check the progress when required,
to enable the fish to maintain its equilibrium and to keep itself at any level in the water.
They have also secondary uses as organs of touch, etc.

In the elongated fishes the undulations of the body take a part in locomotion, but the
chief part still devolves, as in other fish, on the lateral strokes of the tail. These,
however, were apparently considered by A. as part of the undulatory movement.

13. a. De Incessu, 8, l. The treatise on the Motion of Animals is unquestionably
spurious. Either therefore the words "and the motion" have been introduced by some
after-writer into the text ; or Aristotle uses a longer title than usual to designate his
treatise " on the progression of animals."

At ii. 16, Note 11, the treatise on the Motion of Animals has been inadvertently quoted
as genuine.

14. In the Hist. Anim. (i. 5, 15) it is said that serpents and finless fishes are yet
moved by four points of motion like other sanguineous animals, for "their flexures
are four." The only basis for this seems to have been the desire to bring all sanguineous
animals under one general law.

15. That sanguineous animals can never have more than four motor organs is stated
over and over again by Aristotle. If it be asked why, the answer is that it is one of
those laws of type to which nature for some reason or other is bound to adhere. Cf.
Introd. p. X.

16. See Note 10.

17. A. correctly enough describes the manner of swimming of the rays ; but clearly
he had not the faintest suspicion that the lateral expansions which serve the office of
propulsion are in reality the pectoral fins themselves. Had his notion of the correspond-
ence of fins and limbs been founded on anatomical knowledge derived from dissection,
he would scarcely have made this oversight. As it is, not recognising the true pectorals,
he imagines that the dorsal fins, which in many rays are two in number and placed on
the tail, are the pectorals, placed far behind their normal position.

18. In the fishing- frog the ventral fins are as stated in advance of the pectorals, and
are much smaller than the latter. It is quite true that when the ventral fins are advanced

250 Notes, iv. 13.

forwards, so as to become jugular, they are as a rule, if not invariably, reduced in size ;
and they are also, as a rule, modified in such a way as to serve new purposes, to
act for instance as instruments of touch. Cf. Ann. d. Sci. Nat., 1872, t. xvi. p. 93.

19. Cf. Note 17.

20. Namely, in the latter part of the second book and beginning of the third book.

21. De Resp. ch. 4.

22. A. says, minister "as it were" to expiration ; for expiration is limited by him to
the expulsion of air from a lung after inspiration. The expulsion of water through gills
is analogous to this, but not the same thing. Cf. ii. 16, Note 8.

23. In these cartilaginous fishes there is no gill-cover ; the gills being placed in a
series of distinct sacs or pouches, each of which has its own separate slit-like aperture,
which is closed during inhalation by its own muscular sphincter. Compare what is said
about the epiglottis (iii. 3, 14 ; ii. 13, Note 5).

24. In the Elasmobranchii or cartilaginous fishes there are five, and in osseous fishes
four, gills on either side, as a rule. But the number is subject to some variations. For
instance in Lophius, Cotylis, Diodon, there are but three pairs ; and in Cuchia only two,
one being almost rudimentary. On the other hand in some fishes there is a kind of
accessory gill, as in Sturgeon, Chimaera ; and in many there is a small vascular apparatus,
something like a gill, though without its function, at the top of the respiratory chamber.
Each gill consists as a rule of a double row of leaflets. But it is by no means uncommon
for the last, that is the fourth, gill in an osseous fish to be, as A. says, furnished with only
a single row, e.g. Scarus, Scorpsena, Cottus, most Labroids, etc. So far then the statement
in the text is perfectly intelligible. But A. also speaks of the other gills, besides this
last one, as being sometimes uniserial. The eel for instance has, he says {^H. A. ii. 13, 8),
four uniserial gills ; as also the sturgeon {iWoip) and sundry other fishes. The explana-
tion of this statement is, I imagine, as follows. In some fishes the two series of leaflets
that constitute a single gill are quite distinct and free from each other throughout.
But in most they are united together at their basal ends for a smaller or larger proportion
of their depth. In the eel, for instance, this fusion extends one-third of the whole
depth ; in the sturgeon two-thirds or more of the whole depth ; in the salmon one-
half, and so on. When the opposite rows of leaflets are thus partially united for a
considerable proportion of their depth, so as to form a single bifurcated plate, they are
considered by A. to form only a single row or an uniserial gill ; just as he considers
the two lungs to be really one bifid organ, because they coalesce into a single trachea.
Cf. iii. 6, Note i.

25. Cf. If. A. ii. 13, 7—9.

26. Because the hotter an animal is, the more perfect must be the arrangements for its
refrigeration.

27. Why can eels and some other fishes live so long out of water? It is usually said
that it is owing to the small size of their branchial apertures, which hinders the drying
up of their gills. But Bert has shown that this is not the true cause ; the real
explanation being that these fishes produce, in a given time, ounce for ounce of body
weight, less carbonic acid and therefore require less oxygen than other species.

28. Seeing that dolphins abound in the Mediterranean, and that the main points in
their structure, and their habits of life, are accurately enough described by Aristotle, it
seems to me quite impossible either that he can have imagined their mouth to be
underneath their body, or, as has been suggested, confounded them with the larger
sharks. I agree therefore with Frantzius that the word dolphins in the text is an inter-
polation ; and this notwithstanding the objection to that view taken by Meyer, namely,

Notes, iv. 13. 251

the fact that the same false statement occurs elsewhere {H. A. viii. 2, 32). The same
ignorant transcriber who made the addition to the text in the one place may very
probably have made it in the other. Cf. Introd. pp. xii— xiii.

29. This is, so far as I know, the only place where A. speaks of the structure of an
animal as intended for the advantage of other animals than itself. Elsewhere he always
speaks of the organs as given to animals to be of service to themselves. "Nature never
gives an organ to an animal except when it is able to make use of it." Even here he
considers the habit in question to be of use to its possessor, and only speaks doubtfully
of its being intended as a means of salvation to others.

30. Sometimes A. speaks of all fishes as having this kind of dentition (cf. iii. I,
Note 7). Here he more correctly limits the statement considerably.

31. Cf. Note 9. Rhine in Greek means " file." The skin of the monk-fish or angel-
fish is still used for polishing cabinwork, furnishing a fine sort of shagreen.

32. Cf. H. A. ii. 13, 10, where the same statement is made, and certain Selachia, eels,
and tunnies mentioned as smooth fishes. The Selachian referred to is doubtless the
Mustelus Isevis, of which he speaks (Z>. G. iii. 3, 10) as the smooth galeus, and which
is still known as the smooth-hound from the comparative softness of its skin. In the
eels the scales are so deeply sunk in the skin as to be scarcely apparent, and the smooth
and slippery character of these fishes is proverbial.

33. Cf. ii. 9, Notes 8, 9.

34. That is to say they have no solid organs of the globular or ovoid shape which
characterises the testes of Mammalia, birds, and most reptiles. This is all that A. can mean ;
for he was perfectly aware that the milt was an organ from which the male fish secreted
sperm ; and he states, in opposition to those who held that there were no males among
osseous fishes, that the ova of the female fish come to nothing unless the male voids the
secretion of this milt upon them (Z). G. iii. I, 20; H. A. vi. 14, 6). He refuses however
to call these saccular organs " testes," because of their shape and of their being hollow,
and styles them spermatic tubes {jc6poC) or roe (OopiKck). He supposed {Z>. G. i. 4) that
these saccular spermatic tubes or roe, as also the elongated testes of serpents, corresponded
not to the solid globular or ovoid organs of birds, reptiles, and mammals, but to the
tubular vasa dejerentia ; and it was to these latter that he erroneously ascribed the seminal
secretion. The ovoid or globular bodies he thought were merely parts superadded, when
the secreting spermatic tubes became very long and complicated, for certain mechanical
purposes, which are set forth by him. His account of the seminal organs of fishes
seems to have been taken from osseous fishes ; for in the rays and sharks, that is to say
in his Selachia, the testes are compact oval bodies (cf. Huxley's Vert. p. 135). Even,
however, if A. had noticed this, it would not have led him to abandon his view, that such
bodies were merely mechanical additions, required when the ducts became very long and
complicated. For in these fishes the vas deferens is very much contorted and provided
with an epididymis.

35. In the Ophidia the testes are excessively elongated and narrow, differing alto-
gether in form from the ovoid organs of such other reptiles as the Chelonia. The
form, however, is determined not by the absence of feet, but by the elongation of
the whole body ; a cause which elsewhere is cited by A. himself as an explanation of the
elongation of the internal organs. It must, however, be remembered that elongation of
the body and absence of limbs are according to A. correlated conditions (cf. iv. Ii,
Note 2).

36. In birds, reptiles, amphibians, there is a cloaca, i.e. a common chamber into which
open the rectum and the genital organs, as also the urinary, though the latter escaped A.'s

252 Notes, iv. 13.

notice. Thus in these animals the feces and the generative products are voided by one and
the same orifice. There is also a cloaca in the Plagiostomous fishes, or Selachia of
Aristotle. But though the statement in the text so far is true, it is erroneous as regards
other fishes. For in these the anus is distinct from the generative opening ; and this
fact is, I think, elsewhere recognised by A. (cf. iv. lo. Note 32).

37. The meaning must be : "If there were urinary organs and an external urinary
orifice, the genital secretions would be discharged by this. But as there is none, these
secretions are discharged by the anus." As to absence of bladder, cf. iii. 8, Note 3.

38. The term " cete " was used prior to Aristotle for any sea-animals of large size,
whales, dolphins, sharks, tunnies, etc., and was merely equivalent to " sea-monsters."
But A. confines it to the spouting Cetacea. These are made by him to form a distinct
group, intermediate between the viviparous quadrupeds and the fishes. They are, he
says {^H. A. viii. 2, 4), the strangest of animals, and it is difficult to determine how they
should be classified (cf. iii. 6, Note 5). It is one of A.'s triumphs as a zoologist to have
separated the Cetacea from fishes. Here he tells us that they have lungs ; elsewhere
{H. A. i. 5, i) that they are viviparous, have mammae, the concealed position of which he
accurately describes {H. A, ii. 13, 2), and suckle their young. He states also (Z>. G. i.
12, 4) that they have testes, which no fish had in his sense of the word (cf Note 34); and
lastly he points out (ii. 9, 1 1) that they have true bones and not merely fish-spines —
a fact which possibly was known to Herodotus, but not so certainly as was assumed at
ii. 6, Note 6. A. mentions only four kinds, Delphisj Phocsena, Phalasna, Mysticetus.
Of these the first is supposed to be Delphinus Delphis, the common dolphin, which is
abundant in the Mediterranean. The Phocasna {^H. A. vi. 12, 3) is doubtless the Phocsena
communis or common porpoise. The Phalsena can hardly be anything else than the
sperm-whale or Physeter ; for in the sperm-whales the blow-hole is placed much more
forwards than in the dolphin, which accords with the only special character mentioned by
A. {H. A.\.^, 2), and Physeters moreover are found not uncommonly in the Mediterranean.
The Mysticetus, described {H. A. iii. 12, 5) as having bristles in the mouth in place of
teeth, is the only true whale mentioned. This is probably the Balasnopterus musculus
or wrinkle-throated whale of the Mediterranean {Cuvier, R. An. i. 297).

The Greeks in Aristotle's time could not have been very familiar with spouting whales ;
for an amusing story is told, in Arrian's Res Indices, by Nearchus, Alexander's Admiral,
of the fright caused to his sailors by the spectacle of a shoal of them. Afterwards he
came across one thrown up on the shore and found it measured 50 cubits.

39. The like statement is often enough made now-a-days, but is incorrect. The sea-
water taken into the mouth has no access to the respiratory passages and blow-hole, owing
to the peculiar arrangement by which the elongated trachea and larynx are continuous
with the tubular prolongation of the nasal passage formed by the soft palate. The
"spouting" is due to the sudden condensation of expired vapour, and to spray driven
up by the force of the expiration, when this commences before the animal has quite
reached the surface.

40. A. knew nothing of the characters of Amphibia as distinct from Reptilia. "Of
animals that have feet the only one we have ever seen that has a gill is the animal
known as the tadpole. No animal has ever yet been seen possessing at once a lung
and gills. The reason is this. The purpose of the lung is to produce refrigeration by
means of air j and the purpose of the gills is to produce refrigeration by means of water.
But a single organ for a single purpose is the best arrangement, and a single mode of
refrigeration is in every case sufficient " {De Resp. lo, 6). As to the limitation of the
term " i-espiration, " cf. ii. 16, Note 8.

Notes, iv, 13 — 14. 253

41. As to continuity of brain and spinal cord, and its supposed purpose, of. ii. 7, 1 1.

42. Heat is the instrument of the soul in motion, as in all operations (i. I, Note 13).
Cetacea therefore that move actively must have much heat ; and this again necessitates
a perfect organ to regulate heat, and such is the lung.

43. Cf ii. 12, Note 4.

44. Cf. iii. I. Note "] ; H. A. ii. I, 52. In the seals, says Owen {Odontog. i. 506),
"the coadaptation of the crowns of the upper and lower teeth is more completely
alternate than in any of the terrestrial Carnivora, the lower teeth always passing into the
interspace anterior to its fellow in the upper jaw."

45. A. means that the anterior limbs of bats though they are wings yet have claws,
and so resemble feet and are unlike the wings of a bird ; but at the same time they
do not so closely resemble the fore-limbs of a quadruped as to make the bat strictly
quadrupedous. A. knew that bats are viviparous and suckle their young ; for he speaks
of these animals as having cotyledons in their uterus {H. A. iii. i, 31), and groups
them with the hare and the rat among viviparous animals with teeth in both jaws.

(Ch. 14.) 1. In the ostrich and other Ratitse the barbs of the feathers are dis-
connected, so that they come to resemble long hairs, and, owing to their want of firmness,
are useless for flight.

2. Cf. ii. 14, Note i.

3. The head and neck are naked, or covered with only a short downy plumage.
Cf. ii. 9, Note 9.

4. The foot of the ostrich has two stout toes, connected at the base by a strong
membrane. Of these toes the internal is much the larger, and is furnished with a
thick hoof-like claw, but the external and smaller toe is clawless. Aristotle had
probably never himself seen an ostrich ; for, had he done so, he would scarcely have
spoken of its foot as having two hoofs. That the ostrich is a kind of link, uniting birds
with mammals, is not a fancy confined to Aristotle. The vulgar opinion in Arabia still
makes it the product of a camel and a bird, as in the days when it got the name,
already used for it by Pliny, of Struthio-camelus. The height of the bird, its long neck,
its bifid foot, its frequentation of the desert, its patient endurance of thirst, and
possibly the comparative complexity of its digestive organs, were doubtless the grounds
of this strange notion.

254

ERRATA.

Page 142 — i. I, Note 4, last line but one ; for " where " read "when."

Page 176 — line 7 ; for " even " read "ever."

Page 177 — ii. 10, Note 19, third line of last paragraph ; for "inside the skull ''
read "inside of the skull."

Page 237 — iv. 10, Note 14, first Vm.^;for "the function is superadded to the
organ" read "the organ is superadded to the function."

255

INDEX TO NOTES.

Note. — The References in this Index are to Book, Chapter^ and Note.

A priori statements, iii. 4. 25.
Abdomen, why without ribs, ii. 9. 3.
Absorption, A.'s account of, iii. 5. 5.
Acalephoe, what animals meant, iv. 5. 61 ;

no excretions, ii. 10. 3.
Accident, i. 1.9.
Actinite, iv. 5- 61.
Active and passive, ii. I. II.
Actuality and potentiality, i. i. 23.
yEther, i. 1.6, ii, i. 2.
AUantois, iv. 12. 15.
Amia, iv. 2. 4.
Amphibia, confounded with reptiles, iv.

13. 40 ; development unknown, iv.

13- 7-

Anatomy, A.'s ignorance of human, i. 5.
I ; treatise on, iv. 5. 34.

Anaxagoras, i. i. 10.

Angel-fish, iv. 13. 9.

Annelida, confused with myriapoda, i. 2.
2 ; classed with insects, iv. 5. 20, iv. 6. I.

Aorta and great vessel, iii. 4. 24.

Art, and nature, i. 1.8, i. I. 19 ; its instru-
ments, i. I, 13.

Arteries and Veins, differences of, iii. 4. 24 ;
terminations, iii. 4. 20, iii. 5, 7 ; relative
positions, iii. 5. 12 ; parts nourished by
each, iii. 4. 25, iii. 4. 28; known both
to contain blood, iii. 5. i : small in fat
animals, ii. 5. 8 ; hepatic and splenic,
iii. 7. II ; renal, iii. 9. 8 ; pulmonary,
iii. 4, 23 and 24 ; iliac, iii. 5. 12 ;
formation of, i. I. 11 ; relation to viscera,
iii. 4. 10.

Ascidians, iv. 5. 35 ; structure and classi-
fication, iv. 5. 59.

Aselli, rediscovered lacteals, ii. 3. 11.

Astaci, iv. 8. i; claws, iv. 8. 10.

Astragalus, iv. 10. 44.

Aurochs, iii. 2. 7 ; how it protects itself,
ii. 4- 5-

Balancement organique, ii. 9. 8.

Batos, iv. 13. 9.

Bats, iv. 13. 45.

Bees, intelligence of, ii. 2. 5.

Bile, its fluidity, ii. 3. 2; its use, iv. 2. 16;
exudation of, iv. 2. 11.

Bilateral symmetry, iii. 5. 4, iii. 7. 2.

Birds, characters and divisions, iv. 12. i;
a homogeneous group, iv. 12. 2; cold
animals, iii. 6. 13 ; their development,
iv. 12. 15; power of intercommunication,
ii. 17-5; small are best songsters, ii. 17.
4; drink but little, iii. 6. ii; the heavy-
bodied kinds, ii. 13. i; pinnatipede, iv.
12. 8; of prey, settling on rocks, iv. 12.
17 ; position of legs in flight, iv. 12. 24
and 25; neck in flight, iv. 12. 26 ; beak,
iii. I. 14; bones, ii. 9. 6; scapula, iv.
12. 9 ; sternum, iv. 12. 13 ; ischia, iv.
12. 27 ; pectoral muscles, iv. 12. 14 ;
excreta, iv. i. 4; ear, ii. 12. i; eyelids,
ii. 13. 2; eyelashes, ii. 14. I ; spurs, iii.
I. 6 ; number of toes, ii. 17. 3, iv. 12.
30; direction of toes, iv. 12. 33 ;
phalanges of toes, iv. 12. 22; hind toe
of waders, iv. 12. 31 ; oesophagus, iii.
14. 9, iii. 14. 13 ; crop, iii. 14. 8 ;
proventriculus, iii. 14. 10 ; gizzard, iii.
14. 12 ; caeca, iii. 14. 21 ; cloaca, iv.
13' 36} liver and spleen, iii. 7. 4,
iii. 7. 14, iii. 7. 15 ; kidneys, iii. 9.
I and 2 J lung and airsacs, iii. 6. 10.

Bivalves, structure, iv. 5. 43 and 48 ;
mouth, iv. 5. 33 ; ovary, iv. 5. 47 ;
generation, iv. 5. 68; second valve, iv.
5. 31 ; position, iv. 7. 5. See Testacea.

Bladder, iii. 8. 3 ; of ovipara, iii. 9. i ; of
tortoises, iii. 8. 6 ; use, iii. 7. 18.

Blood, how formed, iii. 5.5; where formed,
iii. 5- 9 ; formed after heart, ii. i. 17 ;
increased after food, ii. 3. 14 ; is the

256

Index to Notes.

nutritious part of the food, ii. 3. 13 ; its
fibres the nutritive part, ii. 4. Ii ; nature
of its serum, ii. 4. il ; how far fluid in
life, ii. 4. 6, iii. 5. 7 ; its coagulation
ii. 4. I ; cause of its coagulation, ii 4.
10 ; coagulation more rapid in some
animals than others, ii. 4. 9 ; coagulation
imperfect in hunted animals, ii. 4. 2 ;
relation of coagulum to strength and
ferocity of animal, ii. 4. 8 ; arterial and
venous, iii. 4. 25 ; that of head of
brighter tint, ii. 7. 12 ; is not essentially
hot, ii. 2. 14, ii. 3. I ; hotter in right
cavities than in left, iii. 4. 27 ; hotter
on right side, ii. 2. 6 ; cold blood goes
with fear, ii. 4. 4; is insensible, ii. 3. 15 ;
its relation to heart and viscera, ii. i. 18 ;
its relation to the flesh, iii. 5. 7 ; its
relation to integumental structures, iii.
8. 2.

Blood vessels. See Arteries and Veins.

Bonasus. See Aurochs.

Bones, regeneration of, ii. 9. Ii ; and
cartilage, ii. 9. 10 ; of lion, ii. 6. 5 ; of
fishes, ii. 6. 6 ; of birds, ii. 9. 6 ; of
serpents, ii. 9. 7 ; of skull, ii. 7. 21 ; in
heart, iii. 4. 22.

Brain, is fluid, ii. 7. 4 ; is made of cold
elements, ii. 7. 8 ; its supposed bloodless-
ness, ii. 10. 18, ii. 7. 3 ; its blood, ii. 7.
12 ; its blood-vessels and membranes, ii.
7. 1 1 ; its insensibility, ii. 7. 5 ; its isola-
tion from other parts, ii. 7. 6 ; is not
connected with sense organs, ii. 10. 9 ;
erroneous notions concerning it, ii. 10.
18 ; its supposed use and its importance,
ii. 7. 27, iii. II. 2; its action similar to that
of lungs, iii. 6. 3; reasons for A.'s view,
ii. 7. 27 ; of man, the heaviest, ii. 7. 18;
of cephalopods, ii. 7. 9.

Bubalus, and buffalo, iii. 2. 6.

Bustard, mode of defence, iii. 2. 8.

Caeca, of birds and fishes, iii. 14. 21.

Caecum, called lower stomach, iii. 14. 31 ;
use of, iii. 14. 35, ii. 3. 6 ; of mammals,
iii. 14. 22; of carnivora, iii. 14. 33.

Canthari, iv. 6. 8.

Camel, mouth, iii. 14. 6 ; stomach and
palate, iii. 14. 4 ; teeth, iii. 14. 3 ; bile-
vessels, iv. 2. 6 ; length of life, iv. 2. 17;
retromingent, iv. 10. 36.

Carabi, Carides, Carcini, iv. 8. I.

Cartilage, and bone, ii. 9. 10 ; regeneration
of, ii. 9. II.

Catamenia, iv. 10. 33 ; supposed indication
of heat, ii. 2. 9.

Causes, the four, i. I. 3 ; relative import-
ance of material and final, i. I. 26.

Celestial bodies, influence on terrestrial, i.

^- 5-
Celsus, as to digestion, ii. 3-3; as to fat

persons, ii. 5. 8.
Cestreus, iii. 14. 19.
Cephalopods, characters and divisions, iv.

9. I ; internal structure, iv. 5. 1 1 ;

internal shell, iv. 5. 18 ; brain, ii. 7, 9,
ii. 10. 18 ; teeth, iv. 5. 4 ; liver, iv. 5.
64 ; ink-bag, iv. 5. 12 ; external form,
iv- 9- 3 ; length of tentacles, iv. 9. 10,
II and 12; action of tentacles, iv. 9. 16;
change of colour, iv. 5.15, ii. 4. 5.
Cetacea, characters and species, iv. 13. 38;
their intermediate nature, iii. 6. 5 » have
lungs, iv. 13. 42 ; their blowhole, ii. 16.
9 and 10, ii. 10. 13; their spouting, iv.

13- 39-

Chamgeleon, changing colour, iv. Ii. 28,
ii. 4. 5 ; vivisected by A., iv. 11. 27, ii.

7. 4 and 5.

Chance, relation to design, i. 1.8; and to

spontaneity, i. i. 9.
Chemical combination, A.'s notion of, ii. I.

4 ; not distinguished from physical con-
dition, ii. I. 3.

Chordae tendineae, iii. 4. 20.

Cicadae, drums, ii. 16. 10 ; food, iv. 5. 78.

Classification, terms used by A., i. i. 2;
order adopted by A , iv. 10. 12; chief
rules recognised by A., i. 3. 4; natural
system partly recognised, i. 2. i.

Cloaca, of ovipara, iv. 13. 36.

Coagulation, causes of, ii. 4. 10 ; of oil, ii.
2. 13 ; of blood, .r^^ Blood.

Cold, whether more than privation of heat,
ii. 2. 15.

Composition, three degrees of, ii. i . 8 ;
chemical, ii. i. 4.

Concoction. See Digestion.

Constructive sciences, i. 1.4.

Coot, foot of, iv. 12. 8.

Crabs, iv. 8. 2 ; legs, iv. 8, 3 ; tail, iv.

8. 6.

Crex, iv. 12. 32.

Crocodile, jaws, iv. 11. 20 ; tongue, ii. 17.

7, 9 and 10, iv. 11. 5.
Crustacea, characters and divisions, iv. 8.

I ; claws, iv. 8. 7 and 10 ; tail, iv. 8. 6;

eyes, ii. 13. 12 ; teeth and tongue, iv. 5.

5 ; digestive organs, iv. 5- 24.
Ctesias, iii. 2. 10.
Cyprinoids, palate, ii. 17. 12.

De Spiritu, not genuine treatise, ii. 16. 11,

iii. 5. I.
De Partibus, treatise vi^as illustrated, iv.

9-5-
Decapoda, tentacles, iv. 9. 13 ; compared

to Saurae, iv. 9. 16 ; how used, iv. 9. 14.
Deer, duration of life, iv. 2. 17.
Delphian knife, iv. 6. 15.
Design, relation to chance, i. I. 8.
Democritus, coupled vision with water, ii.

I. 12 ; said soul was fire, ii. 7. 7, iv, 10.

II ; placed soul in head, ii. 10. 8 ; said

other special senses were developed from

touch, ii. 8. I.
Diaphragm, iii. lo. I; structure, iii. 10. 7;

rupture, iii. 10. 9 ; why called phrenes,

iii. 10. 6 ; use according to Plato, iii.

10. 4.
Dichotomy, i. 2. i.

Index to Notes.

257

Digestion, ancient explanations of, ii. 3. 3 ;

attributed partly to putrefaction, iii. 14.

20 ; not due to ordinary heat, ii. 6. 7 ;

its organs correspond to food, iii. 14. 14.
Diogenes, located sensation in brain, ii.

10. 8.
Diptera, size, iv. 6. 4 ; no sting, iv. 6. 13.
Disease, nature of, ii. 2. 10.
Dislocation, ancient instrument for reducing,

iv. 9. 16.
Dissection, practised by A., iii. 4. 21 ;

whether human practised by him, i. 5. i.
Diving apparatus, known to ancients, ii,

16. 3.
Dogs of India, i. 3. 3.
Dolphin, mouth, iv. 12. 28 ; duration of

life, iv. 2. 17.
Drunkards, small eaters, iv. 11. 9.
Duck, power of remaining under water, iii.

6. 12.

Ear, of man, ii. 11. i ; of birds, ii. 12. i
and 2 ; of seal, ii. 12. 3.

Earthworms, iv. 6. i.

Echini, classed with Testacea, iv. 5. 35 ;
with Turbinata, iv. 9. 4 ; teeth, iv. 5.
36 ; mouth, iv. 5. 37 ; digestive organs,
iv. 5. 38 ; ovaries, iv. 5. 39 ; Ijlack
bodies, iv. 5. 40 ; shallow and deep-
water species, iv. 5. 41 ; use of spines,
iv. 5. 51.

Education, should embrace knowledge of
methods, i. i. i.

Eels, living out of water, iv. 13. 27 ; gills,
iv. 13. 24; fins, iv. 13. 10 ; scales, iv.

13- 32-
Electric rays, iv. 13. 3.
Eledone, iv. 9. 17.

Elementary, forces, ii. i. 3; motions, ii. i. 2.
Elements, number of, ii. I. 2; their com-
pound nature, ii. i. 3.
Elephant, whether seen by A., ii. 16. 6 ;

ancient errors concerning it, ii. 16. 7 ;

trunk, ii. 16. 3 ; tusks, iii. 2. 19 ; liver,

iv. 2. 6 ; foot, ii. 16. 6 ; heart, iii. 4. 22 ;

aquatic habits, ii. 16. 2 ; rests in standing

position, iv. lo. 38.
Emotion, physical accompaniments of, ii.

4. 4 ; iii. 6. 7.
Empedocles, i. I. 10, ii. 2. 8.
Emys, iii. 9. 3.
Ephemera, iv. 5. 79.
Epiglottis, iii. 3. 7.
Epilepsy, relation to sleep, ii. 7. 15.
Erasistratus, views as to digestion, ii. 3. 3;

as to arteries, iii. 5. i ; as to nerves, ii.

10. 18 ; discovered lacteals, ii. 3. 11.
Erect position, of man, iii. i. 15 ; different

meanings of, iii. 6. 16.
Erection, iv. 10. 35.
Eternal motion, i. 1.5.
Evolution, and characters, how related, i. I.

6, i. I. 27.
Eyes, why of water, ii. 10. 16 ; connection

with brain, ii. 10. 9; their- nerves, ii. 10.

19; of invertebrates, ii. 10. 12.
Eyebrows, use, ii. 15. i.

Eyelashes, of birds, ii. 14. i ; of mammals,
ii. 14. 3.

Eyelids, comparative mobility of upper and
lower, ii. 13. 2 and 5 ; involuntary move-
ment, ii. 13. 3 ; of reptiles, iv. 11. 15.

Excretions, ii. 3. 8 ; discharged in fright,
ii. 4. 5, iv. 5. 20; used in defence, iii. 2.
7 and 8, iii. 14. 32.

Fanning, production of cold by, iii. 6. 14.
Fat, fluidity of, ii. 2. i ; various kinds, ii.

5. I ; of different animals, ii. 5. 6 ; of
bloodless animals, ii. 5. 3 ; result of
concoction, iii. 9. 14 ; inversely related
to semen, ii. 5. 9 ; abundance of fat goes
with small vessels, ii. 5. 8 ; absent from
joints, iii. 9. 16 ; of kidneys, iii. 9. 18.
19 and 20.

Father, share in generation of soul, i. I. 14.

Fear, external symptoms, ii. 4. 4 ; physical
effects, ii. 4. 5.

Feathers,!. 3. i, iv. 6. 6 ; of ostrich, iv.
14. I.

Female, size as compared with male, iii.
I. 5; comparative heat, ii. 2. 9 ; often
unarmed, iii. i. 6.

Fibres of blood, ii. 4. i ; thought to be solid
during life, ii. 4. 6 ; thought to be the
nutritive part, ii. 4. 1 1 ; not distinguished
from gelatine, ii. 5. 4 ; more abundant
in some animals than others, ii. 4. 8.

Fins, homologies of, iv. 13. 6 and 17; uses
of, iv. 13. 12 ; greater constancy of
pectoral, iv. 13. 10 ; modification of
jugular, iv. 13. 18; of tadpole, iv. 13.8.

Fishermen, information from, iv. 5. 53.

Fishes, characters and divisions, iv. 13. i ;
development, iv. 12. 15 ; how protected,
iii. I. 10 ; cannot chew food, iii. 14. 17 ;
sense of taste, iv. 11. 7; sense of smell and
hearing, ii. 10. 13 ; changing colour, iv.
13. 9; living out of water, iv. 13. 27; rumi-
nating, iii. 14. 15; oviparous and ovovivi-
parous, iv. 1.5; scales, iii. 8. 2, iv. 13.
32 ; fins, iv. 13. 6, 10, 12, 17 and 18 ;
olfactory organs, ii. 10. 13 ; bones, ii.

6. 6 ; no medullary canals, ii. 6. 8 ;
dentition, iii. i. 7, 8 and 9, iv. 13. 30;
tongue, ii. 17. 8, iv. 11. 6 ; palate, ii. 17.
12 ; CESophagus, iii. 3. 2 ; pyloric caeca,
iii. 14. 21 ; short intestine, iii. 14. 23 ;
liver, iii. 7. 6 ; gall-bladder, iv. 2. i and
3 ; spleen, iii. 7. 4 ; heart, iii. 4. 19 ;
brain, ii. lo. 18 ; gills, iv. 13. 23 and 24,
ii. 10. 13 ; respiration, ii. 16. 8, iii. 6. 3,
iv. 13. 22 ; gill-cover, iv. 13. 23; bladder,
iii. 8. 3 ; roe, iv. 13. 34 ; generative
outlet, iv. 10. 32, iv. 13. 36; temperature,
ii. 2. 8.

Fishing-frog. See Lophius.

Flesh, nature of, iii. 4. 20, iii. 5, 7 ; called
fluid, ii. 2. I ; the medium of touch and
taste, ii. 8. 2, ii. 10. 10 ; its contractility
not known to A., ii. i. 10, iii. 4. 20.

Flexures, of limbs, iv. 12. 10 ; of arm, iv.
10. 18.

Fluid, and solid, definitions of, ii. i. 3.

17

258

Index to Notes.

P'luids, of body, ii. 7. 4, ii. 2. I.

Flying, resemblance to swimming, i. 4. I.

Foetus, perhaps dissected by A., i. 5* ^ 5
heart visible on third day, iii.4. 2 ; viscera,
iii. 4. 4 ; marrow, ii. 6. 2 ; brain, ii. 7.
4 ; deficient pigment, ii. 6. 3.

Functions, and properties, ii. i. 9 ; have
separate organs when possible, iv. 6. 15 ;
sometimes accumulated in single organ,
ii. 16. 5 and 12 ; precede organs, ii. 16.

13, iv. 10. 14.

Food, iii. 5. 5; is fluid, ii. 2, 4.
Foot, large in man, iv. 10. 46.

Galen, as to lacteals, ii. 3. 1 1 ; calls brain
almost fluid, ii. 7. 4 ; says vessels are
small in fat men, ii. 5. 8 ; ridicules A.'s
view of the brain, iii. 6. 3 ; and of sinews,
iii. 4. 20 ; and of the heart's cavities, iii.
4. 23 ; on heart of elephant, iii. 4. 22 ;
on gills of fishes, ii. 16. 8 ; on position
of heart, iii. 4. I7 ; on its hard flesh, iii.

4. 37 ; on sutures of skull, ii. 7. 23 ;
locates blood formation in liver, iii. 4.
15 ; said to have visited Egypt, ii. 7. 26.

Gall-bladder, wanting in some animals,
iv. 2. 7 ; variable, iv. 2. 8 ; reasons for
absence, iv. 3. i ; of serpents, iv. 2. I ;
of fishes, iv. 2. 3 and 4 ; of seal, iv. 2. 7 ;
of sheep in Naxos, iv. 2. 9.

Gallinacese, ii. 13- I.

Gasteropods, position of mouth and anus,
iv. 9. 7 ; proboscis, iv. 5. 27 ; crop, iv.

5. 28 ; liver, iv. 5. 29 ; operculum, iv.
5.31. 6Vif Testacea.

Gazelle, iii. 2. 6 and 17.

General sense, iv. 10. 8.

Genus, and species, i. I. 2.

Gills, do not co-exist with lung, iv. 13. 40.

See Fishes.
Giraff"e, not known to A., iii. 2. 15.
Grasshopper, legs of, iv. 6. 18.
Great vessel, iii. 4. 24.
Grebe, foot of, iv. 12. 8.

Haemorrhage, active and passive, iii. 5. Ii.
Hair, how formed, ii. 15. 4 ; of head, ii.

14. 6 ; correlated with teeth, etc., ii. 14.
4 ; correlated with skin, ii. 13. 7.

Hand, in place of many organs, iv. 10. 15.
Hare, its rennet, iii. 15. 2; its food, iii.

'5- 5- ... ^

Hartbeeste, ni. 2. o.

Hawk, legs in flight, iv. 12. 25.

Health, and Disease, how far part of
natural philosophy, ii. 7. 14 ; causes of,
ii. 2. 10.

Hearing, medium of, ii. i. 12, ii. 10. 10.

Heart, is homogeneous and also hetero-
geneous, ii. I. 16 ; how nourished, ii. i.
18 ; early formation of, iii. 4. 2 ; formed
before blood, ii. i. 17 ; its cavities and
anatomy, iii. 4. 23 ; inconsistent state-
ments about, iii. 4. 26 ; at first unilocular,
iii. 4. 30 ; left ventricle the supreme
part, iii. 4. 29 ; its chordae tendineae, iii.
4. 20 ; bone in, iii. 4. 22 ; position of

in man, iii. 4. 17 ; of hare, iii. 4. 32 ; of
fishes, iii. 4. 19 ; of testacea, iv. 5. 67 ;
of insects, iv. 5. 69; its central position;
iv. 5. 59 ; relation to lung and wind-
pipe, iii. 3. 9 ; disease of, iii. 4. 37 ; its
action, iii. '6. 7 ; is centre of vascular
system and seat of blood formation, iii.
4. 5 ; main but not sole seat of vital
heat, ii. 3. 4 ; the .source of motion, iii.
4. 20 ; why held to be the sensorium
commune, ii. 7. 27 ; connection with
sense-organs, ii. 10. 19, ii. 10 9 ; special
relation to touch and taste, ii. 10. 10 ;
sympathy with brain, ii. 7. 27; throbs in
emotion, iii. 4. 13; ignored by A.'s pre-
decessors, iii. 4. 5.

Heat, and cold, ii. 2. 15 ; vital distinct
from ordinary, ii. 6. 7 ; vital is chiefly
in heart, ii. 3. 4 ; mounts upwards, ii.
7. 20 ; of male and female, ii. 2. 9, ii.
7. 19; affects different persons differently,
ii. 2. 12 ; is instrument of soul, i. I. 13,
iii. 5. 3, iv. 10; II ; is cause of digestion,
"• 3- 3 ; promotes growth, ii. 7. 20 ; is
cause of blood's fluidity, ii. 9. i ; how
regulated, iii. 6. 3.

Heavens, not generated, i. I. 21.

Hemiptera, rostrum of, iv. 5. 76.

Hepatic vessels, iii. 7. Ii.

Heracleotic crabs, iv. 8. 2.

Herodotus, ii. 6. 6, ii. 7. 26, ii. 16. 4,
iii. 2. I.

Heron, tail, iv. 12. 24 ; neck, iv. 12. 26.

Hippardium, iii. 2. 15.

Hippocrates, source of Plato's physiology,
ii. 10. 8 ; on digestion, ii. 3. 3 ; on
brain, ii. 10. 18 ; on periosteum, ii. 9.
II; on use of spleen, iii. 7. 15; on
duration of life in fat persons, ii. 5. 8 ;
on small appetite of dmnkards, iv. il.
9 ; on trachea, iii. 3. 6 ; on prepuce, ii.
13.4; on semen, iv. 10.33; on "saurae,"
iv. 9. 16.

Historia animalium, its title, ii. i. I; called
first treatise, iv. 5. 9 and 69 ; was illus-
trated, iv. 5. 34, iv. 9. 5.

Holothuriae, iv. 5. 53 and 54.

Homogeneous and Heterogeneous, distinc-
tion of, ii. I. 5, ii. 2. 3, ii. 9, 13 ;
mutual relations, ii. l. 9.

Homer, respect for his authority, iii. 10. 10,

Homology, of fins and limbs, iv. 13. 6
and 17 ; of limbs, iv. 12. 10.

Hoofs, are integumental structures, ii 9. 12.

Horns, are integumental structures, ii. 9.
12 ; not coexistent with tusks, iii. I. 3;
inversely related to teeth, iii. 2. 19; diff'er
in males and females, iii. I. 6; wanting
in polydactylous animals, iii. 2. 2 ; of
Indian ass, iii. 2. 10 ; of oryx, iii. 2. 12,
iii. I. I; of ruminants, iii. 2. 15; of
bull, iii. 2. 14; for defence or offence, iii.
I. I; sometimes an encumbrance, ii. 16.
4, iii. 2. 5 ; simulated in some animals,
iii. 2. I.

Horse, duration of life, iv. 2. 17 ; mode of
fighting, iv. 10. 19 ; mammae of male,
iv. 10. ^o.

Index to Notes.

259

Hot, various meanings of, ii. 2. 18.

Hucklebone, iv. 10. 44.

Human body, whether dissected by A., i.

5. I; proportions of, iv. lO. lO; erect
attitude of, iii. i. 15.

Hunger, allayed by contact of food, iii.

14- 34-
Hymenoptera, their oral instruments, iv.

6. II.
Hypozoma, ii. 16. 10.

Indian, dogs, i. 3- 3 ; ass, iii. 2. 10.

Innate Spirit, ii. i6. ir, iii. 6. 2.

Insects, characters and divisions, iv. 6. i ;
their wings called feather?, iv. 6. 6, i. 3.
I ; bulk and wings, iv. 6. 4 ; oral
organs, iv. 5. 7, iv. 6. II ; tongue, iv. 5.
8 ; digestive organs, iv. 5. 74 and 75 ;
eyes, ii. 13. 12 ; olfactory organs, ii. 16.
10 ; heart, iv. 5. 69 ; hypozoma, ii. 16.
10 ; anterior legs, iv. 6. 16 ; hinder legs,
iv. 6. 17, 18 and 19 ; live when cut in
pieces, iii. 5. 2, iv. 5. 71 ; how protected,
iii. 2. 9, iv. 6. 8 ; defend themselves by
excretions, ii. 4. 5, iii. 2. 8 ; feign death,
iv. 6. 8 ; roll themselves up, iv. 6. 7.

Integumental structures, ii. 9. 12.

Intellectual faculty, separable from matter,
i. I. 14 and 17 ; outside province of
natural science, i. i. 18.

Intestinal canal, of mammalia, iii. 4. 26 ;
of herbivora, iii. 14. 27 ; of carnivora, iii.
14- 33; of artiodactyla, iii. 14. 29;
effects of shortness, iii. 14. 23 and 34.

Ischia, iv. 12. 27.

Jaw, motion of in carnivora, iv. Ii. 19 ; in

crocodile, iv. 11. 20.
Jejunum, iii. 14. 36.
Joints, kinds of, ii. 9. 2.
Juli, iv. 5. 70, iv. 6, 7.

Kidneys, use of, iii. 7. 18, iii. 9. i ; their
vessels, iii. 9. 8 ; lobulation, iii. 9. 6 and
7 ; position of right and left, iii. 9. 1 1 ;
tunica adiposa, iii. 9. 13 ; right not so
fat as left, iii. 9. 17 ; fat not equably
disposed, iii. 9. i8 ; especially fat in
sheep and ox, iii. 9. 20 ; of man and
foetus, iii. 9. 6 ; of seal, iii. 9. 5 ; of
birds, iii. 9. 2 ; of chelonia, iii. 9. i.

Lacteals, discovery of, ii. 3. 11.

Lard, and suet, ii. 5. i . See Fat.

Larynx, called pharynx, iii. 3. i.

Leopard, iii. 4. 32.

Ligaments, iii. 4. 20.

Limbs, number of, iv. 12. 11, iv. 13. 15 ;

flexures of, iv. 12. lO, iv. 10. 18 ; part

taken by posterior, iv. 9. 9.
Lion, not seen by A., iv. 10. 6 ; bones and

marrow, ii. 6. 5 ; mammae, iv. 10. 27 ;

errors concerning it, iv. 10. 6.

Liver, variable colour, iii. 12. 4 and 5 ;
lobulation of, iii. 7. 4, 5 and 6 ; relation
to spleen, iii. 7. i and 4.

Lizards, tongue of, ii. 17. 7.

Lobster, claws of. iv. 8. 10.

Locomotion, begins from right, iii. 9. 12.

Lophius, iv. 1.5; errors concerning, iv.
^3- 5 ; gall-bladder, iv. 2. i ; fins, iv.
13. 18.

Lung, its air-passages and blood-vessels,
iii. 3. 9 ; why called single by A., iii. 6.
1 ; its action, iii. 6. 6 ; not source of
heart's action, iii. 6. 7 ; variable amount
of blood, iii. 6. 18 ; bladder-like kind
inferior, iii. 6. 3 and 10, iii. 7. 17 ; of
birds and reptiles, iii. 6. 8, 10 and 18 ;
of chelonia, iii. 8. 5 and 6.

Maia, iv. 8. 2.
Malacia. See Cephalopods.
Malacostraca. See Crustacea.
Male, hotter than female, ii. 7. 19 ; better
armed than female, iii. i. 4 and 6 ; size
of organs compared with those of females,
iii. I. 5 ; mammae of, iv. 10. 30.

Mammse, position of, iv. 10, 23, 24, 25
and 29 ; number of, iv. 10. 26 and 27 ;
of males, iv. 10. 30 ; of lion, iv. 10. 27.

Mammalia, characters and divisions, iv. 10.
I ; equivalent to "internally viviparous,"
iv. II. 24 ; umbilical vesicle, iv. 12. 15.

Man, erect position, ii. 10. 7, iii. i. 15 ;
bodily proportions, iv. 10. 10 ; senses
compared with those of other animals,
ii. 16. 14 ; impotence as compared with
other animals, iv. 10. 15 ; brain, ii. 7.
18 ; skull, ii. 7. 21 ; sutures, ii. 7. 26 ;
ears, ii. 11. i ; eye-lashes, ii. 14. 3;
kidneys, iii. 9. 6 and 1 1 ; spleen, iii. 12.7^
gall-bladder, iv. 2. 8 ; foot, iv. 10. 46 ;
. hand, iv. 10. 15 ; nails, iv. 10. 16 ; place
in serial classification, iv. 10. 12.

Marrow, not seminal, ii. 6. i ; not in all
bones, nor all animals, ii. 6. 5 and 8 ;
and spinal cord, ii. 6. 4 ; of foetus, ii.
6. 2.

Marten, iii. 4. 32.

Mastication, ii. 3. 5-

Mecon. See Mytis.

Medicine, how far a branch of natural
philosophy, ii. 7. 14.

Media, of senses, il 1. 12, ii. 10. 10.

Medusae, iv. 5. 54.

Melolontha, iv. 6. 5.

Memory, not possessed by all animals,
ii. 2. 5.

Mesentery, iv. i. 8.

Methods, of science, part of education, i.
I. I.

Milk, its composition, iii. 15.4; its coagu-
lation, iii. 15. I and 5.

Mollusca. See Testacea.

Momus, fable of, iii. 2. 14.

Monkeys, kinds recognised by A., iv. 10. 41 .

Monk-fish. See Rhine.

Moon, supposed influence on animals, iv.
5- 45-

26o

Index to Notes.

Mother, her share in generation of soul,

i. I. 14.
Motion, modes of, i. I. 16 ; elementary

forms of, ii. I. 2; rotatory and eternal,

i. I. 5 ; cooling action of, iii. 6. 14 ;

mechanism of in animals, iii. 4. 20, ii.

16. II ; spurious treatise on, iv. 13. 13.
Mullet, stomach of, iii. 14. 19.
MurDsna, iv. 13. 11.
Muscle. See Flesh.
Mustelus, its placenta known to A., iv.

13. I.
Myriapoda, iv. 5. 70, i. 2. 3 ; intestinal

canal of, iv. 5. 74.
Mytis, iv. 5. 13, 29 and 64, iii. 4. I.

Nails, part of skin, ii. 9. 12 ; use of, iv.
10. 16.

Natural philosophy, how far concerned
with the soul, i. i. 17 and 18; should
deal with final rather than material cause,
i. I. 26 ; may deal with principles of
medicine, ii. 7. 14.

Nature, and art, i. i. 8 and 19 ; her order
general, not universal, iii. 2. 18 ; acts
under some constraint, iv. 5. 2 ; avails
herself of necessary conditions, iii. 2.
16 ; usually gives separate organs for
separate functions, iv. 6. 15 ; sometimes
uses one organ for several functions, iii.
1. II and 12, iv. 10. 22 ; saves in one
part to spend in another, ii. 9. 9 ; gives
animals a structure useful to themselves,
iv. 13. 29.

Necessity, various kinds of, i. i. 23, 24
and 25.

Neck, uses of, iv. 10. 7 ; use of long one,

iii- 3- 3-
Nereis, confounded with centipede, iv. 5. 70.
Nerites, iv. 5. 32.
Nerves, confounded with sinews, iii. 4. 20 ;

whether any were known to A., ii. 10.

9 and 19.
Nictitating membrane, ii. 13. 2, iv. 11. 17.
Nostrils, position of, ii. 10. 25.
Nutrition, A.'s account of, iii. 5. 5 ; treatise

on, ii. 3. 16.
Nylghau, iii. 2. 15.

Occiput, empty space in, ii. 10. 18.
Octopoda, species of, iv. 9- 17 ; shape, iv.

9. 6 ; mode of progression, iv. 9. 8 ;

littoral habits, iv. 5. 16 ; absence of fins,

iv. 9. 19.
Oesophagus, whether necessary, iv. 10. 5 ;

of fishes, iii. 3. 2 ; relation to taste, iv.

II. 8.
Oestrus, ii. 17. 16.
Oils, coagulation of, ii. 2. 13.
Omentum, iv. 3. 3.
Operculum, of gasteropods, iv. 5. 31.
Ophidia, iv. 11. 3; tongue, ii. 17. 7;

elongated viscera, iv. I. 7 ; gall-bladder,

iv. 2. I ; scales, iv. 11. 14 ; bones, ii. 9.

7; vertebra?, iv. II. 23; testes, iv. 13.

35; absence of eyelids, iv. Ii. 15;

locomotion, iv. 13. 6 and 14; horned
species, iii. 2. i.

Organic equivalents, law of, ii. 9. 9, ii. 14:
4, iii. 2. 13 and 19, iv. 12. 18.

Organs, relation to tissues, ii. I. 5, 7, 8
and 9 ; functions and properties, ii. 1.9;
simple and compound, ii. i. 16 ; separate
for separate functions, iv. 6. 15 ; some-
times one for diverse functions, iii. I. 11,
ii. 16. 5, ii. 17. 17 ; whether prior or
posterior to functions, ii.' 16. 13, iv. lo.
14 ; pre-existing are modified for new
functions, iii. I. 12, iv. 10. 22 ; of animal
life are symmetrical, iii. 2. 11.

Oryx, iii. 2. 12, iii. i. i.

Ostracoderma. See Testacea.

Ostrich, not seen by A., iv. 14. 4 ; nor its
skeleton, iv. 12. 13; imperfectdiaphragm,
iii. 10. I ; eyelashes, ii. 14. i ; feathers,
iv. 14. I ; naked head and neck, iv. 14.
3 ; foot, iv. 14. 4.

Oviparous quadrupeds. See Reptiles.

Ovo-vivipara, iv. II. 24, iv. I. 5-

Ovum, perfect in birds and reptiles, iv. 11.
3, iv. 12. I ; perfect in selachia, not in
other fishes, iv. 13. i ; of mammalia
unknown to A., iv. 11. 24; of echini, iv.
S- 39> iv- 5- 50 ; of testacea, iv. 5. 44.

Oysters, discovery of generative fluids, iv.
5-68.

Oxen, grazing backwards, ii. 16. 4.

Palate, of Cyprinoids, ii. 17. 12.

Palpitation, distinct from normal heart's
action, iii. 6. 7.

Pangenesis, partly anticipated by Hippo-
crates, iv. 10. 33.

Pardalis, iii. 4. 32.

Parrot, probably never seen by A., ii. 17.
3, ii. 13. 2 ; tongue, ii. 17. 3.

Parrot-fish. See Scarus.

Parts, homogeneous and heterogeneous, ii.
I. 5 and 9 ; division of, ii. i. 16, ii. 2. 3.

Passive, and active, ii. i. Ii.

Penis, bone in, iv. 10. 34 ; erection, iv.

lo- 35- . , - ,

Periodicity, due to influence of celestial

bodies, i. i. 5-

Pharynx, and larynx, iii. 3. i.

Pia mater, ii. 10. 18.

Pig, its classification, iii. 12. 8.

Pigment, deficient in foetus, ii. 6. 3.

Pinnalipedes, iv. 12. 8.

Placental fishes, iv. i. 5.

Plants, no excretions, ii. 3. 8 ; seeds their
residue, iv. 5. 60, iv. 10. 13 ; their roots,
ii. 3. 10 ; their vital centre, iv. 5. 59 ;
parasitical kinds, iv, 5. 56 ; some coagu-
late milk, iii. 15. 5.

Plato, system of dichotomy, i. 2. I ; took
his physiology from Hippocrates, ii. 10.
8; coupled vision with fire, ii. I. 12;
thought right superior to left, ii. 2. 6 ;
thought blood fibres were solid during
life, ii. 4. 6 ; thought marrow was
generative, ii. 6. 1 ; thought spinal cord
and brain were identical in substance, ii.

Index to Notes.

261

7. I ; thought fluid passed by windpipe,
iii. 3. 6 ; said heart was meeting point
of vessels, iii. 4. 5. ; thought lung was
bloodless, iii. 6. 18 ; described spleen as
bloodless, iii. "J. xz ; on the triple soul,
iii. 10. 4 ; compared stomach to manger,
i'- 3- 7 > on use of bile, iv. 2. 5 5 on
use of long intestine, iii. 14. 23 ; on use
of diaphragm, iii. 10. 4 ; on use of
nails, iv. 10. 16 ; as to absence of fat
from joints, iii. 9. 16.

Plutarch, on cold, ii. 2. 15.

Porpoise, bones, ii. 6. 6 ; deficient marrow,
ii. 6. 8. See Cetacea.

Portal vein, how regarded by A. and Galen,
iii. 4. 15.

Potentiality, 1. i. 23.

Poulp. See Octopoda.

Prepuce, ii. 13. 4.

Problemata, iii. 15. 6.

Proboscis, of insects, iv. 5. 7 ; of elephant,
ii. 16. 3.

Proportions, of body change with age, iv.
10. 10.

Pulse, A.'s explanation of, iii. 6. 7.

Punctum saliens, iii. 4. 2.

Purpura, ii. 17. 15.

Pus, formation of, iii. 6. 7.

Rain, how formed, ii. 7. 13.

Rays, species and habits, iv. 13. 9 ; teeth,
iii. I. 7 ; fins and manner of swimming,
iv. 13. 7 ; testes, iv. 13. 34 ; skin, iv.

13- 33-
Razor-fish, iv. 7. 4.
Refrigeration, the end of respiration, iii.

6- 3 ; organs of, iii. 6. 3 ; how effected

in insects, ii. 16. lo; produced by fanning

motion, iii. 6. 14 ; due to innate spirit,

iii. 6. 2.
Regeneration, of bone and cartilage, ii.

9. II.
Rennet, iii. 15. i ; of hare, iii. 15. 2.
Reptiles, characters and divisions, iv. 11.

3; scales, iv. 11. 14; eyelids, iv. 11.

15 ; nictitating membrane, iv. II. 17,

ii. 13. 2 ; bladder, iii. 8. 3 ; lung, iii.

8. 5 ; tongue, iv. 11. 5 and 10; teeth,

iv. II. 12; cloaca, iv. 13. 36; can live

without air for long time, iii. 6. 12.
Residuum, various senses of term, ii. 3. 8 ;

turned to account sometimes, iv. 2. 12,

iii. 14. 32, iii. 2. 7 and 8.
Respiration, restricted meaning of term, ii.

16. 8, iv. 13. 22 ; A.'s theory of, iii. 6.

3 ; mechanism of, iii. 6. 6.
Retromingent animals, iv. lO. 36.
Rhine, and rhinobatus, iv. 1 3. 9 ; its skin,

iv. 13. 31.
Rhinoceros, iii. 2. 10.
Ribs, true and false, iv. lO. 23 ; absence of

abdominal, ii. 9. 3.
Right, nobler than left, ii. 2. 6 ; motion

commences from it, iii. 9. 12 ; hotter

than left, iii. 4. 28, ii. 2. 6 ; nourished

by aorta, iii. 4. 28.
Roots, of plants, ii. 3. 10.

Rot, in sheep, iii. 9. 19.

Ruminants, oral cavity, iii. 14. 6 ; multiple

stomach, iv. i. 6.
Rumination, use of, iii. 14. 15.

Sacrificial victims, source of anatomical
knowledge, iv. 2. 9.

Salivary glands, unknown to A., ii. 3. 5.

Saurse, the instruments so named, iv. 9.
16.

Saw-toothed animals, have no tusks nor
horns, iii. i. 3.

Scales, formation of, iii. 8. 2 ; of reptiles,
iv. II. 14 ; of fishes and reptiles, iii. 8. 2.

Scapula, of birds, iv. 12. 9.

Scarus, teeth, iii. I. 7 ; said to ruminate,
iii. 14. 15.

Sciences, how classified, i. I. 4 ; their
methods a part of education, i. i. i.

Scolopendra, iv. 5. 70.

Scorpion, iv. 6. 12.

Sea-anemone, iv. 5. 61.

Sea-lung, iv. 5. 54.

Seal, a stunted quadruped, ii. 12. 4 ; why
without external ears, ii. 12. 3 ; gall-
bladder, iv, 2. 7 ; kidneys, ) iii. 9. 5 ;
tongue, iv. 11. 10 ; dentition, iv. 13. 44,

Sedum, vitality of, iv. 5. 57.

Selachia, iv. i. 5 ; skin, ii. 9. 8 ; gills, iv.
13, 23 and 24 ; testes, iv. 13. 34 ; cloaca,
iv. 13. 36.

Semen, nature of, iv. 10. 33 ; inversely
related to fat, ii. 5. 9.

Senses, general and special, iv. 10. 8 ;
media of, ii. i. 12, ii. 10. 10 ; each
limited to one class of sensibles, ii. i. 13;
each ascribed to a separate element, ii.
I. 12 ; connection of their external organs
with sensorium, ii. 10. 19 ; their external
organs not connected with brain, ii. 10.
9 ; why their external organs are near
brain, ii. 10. 1 1 ; soul the passive
recipient of sensory motions, i. i. 16.

Sensorium Commune, heart not brain, ii.
7. 27, ii. 10. 10.

Sepia, description of, iv. 9. I ; retractile
tentacles, iv. 9. 11 and 13; how tentacles
are used, iv. 9. 14.

Serpents. See Ophidia.

Serum, its nature, ii. 4. 11.

Silurus, anal fin, iv. 13. 8.

Simplicity, of structure correlated with
simplicity of life, ii. 10. 5.

Sinew, iii. 4. 20.

Skin, parts developed from it, ii. 9. 12 ;
its character determines that of the hair,
ii. 13. 7 ; when hard is unsuitable for
certain uses, ii. 12. 2, ii. 13. 5.

Skull, bones, ii. 7. 21 ; use of sutures, ii.
7. 23, ii. 14. 6 ; supposed fdifference of
sutures in man and woman, ii. 7. 26 ;
closure of sutures, ii. 7. 22 ; sutures said
to be more numerous in man than in
other animals, ii. 7. 25.

Sleep, A.'s account of, ii. 7. 15.

Smell, medium of, ii. i. 12, ii. 10. 10 ;
how dependent on respiration, ii. 10.

262

Index to Notes.

24 ; central position of organ, ii. 10. 25 ;
how related to taste, iv. 11. 8 ; this sense
less developed in man than other animals,
ii. 16. 14 ; in insects, ii. 16. 10 ; in
cetacea, ii. 16. 9 ; in fishes, ii. 10. 13.

Smurasna, iv. 13. 11.

Solen, iv. 7. 4.

Solid, definition of, ii. I. 3.

Soul, its nature and genesis, 1. I. 14 ; how
related to several modes of vital motion,
i. I. 16 ; how far within the province of
natural science, i. I. 17 and 18 ; heat
only its instrument, 1. i. 13, ii. 7. 7,
iv. 10. 1 1 J Plato's account of it, iii.
10. 4.

Spallanzani, as to temperature of fishes,
ii. 2. 8.

Species, i. i. 2.

Speech, foundation of human excellence,
ii. 2. 5.

Spinal cord, confounded with marrow,
ii. 6. 4.

Spit and candlestick, in one, iv. 6. 15.

Spleen, and liver, iii. 7. i and 4 ; shape in
different animals, iii. 12. 6 and 7 ; its
uses, iii. 7. 15 ; very liable to disease,
iii. 4. 38 ; enlarged in marshy districts,
iii. 7. 16 ; size in different animals, iii.
7. 4 and 14 ; said by Plato to be blood-
less, iii. 7. 12.

Sponges, sensibility of, iv. 5. 53 ; no intes-
tinal cavity, ii. 3. 9.
. Spontaneity, i. 1.9.

Spouting, of whales, iv. 13. 39,

Spurs, of birds, iii. I. 6.

Starfish, iv. 5. 53 ; mischief done by, iv.
5- 63-

Stmg-ray, iv. 1 3. 4.

Stomach, upper and lower, ii. 3. 6, iii. 14.

31 ; is multiple in ruminants to atone for

want of teeth, iii. 14. 4 and 15, iv. 1.6;

types of shape, iii. 14. 25 ; of birds,

iii. 14. 10, II and 12; of mullet, iii.

14. 19.
Suet, and lard, ii. 5. i. &(f Fat.
Sweat, bloody occasionally, iii. 5. 8.
Swimming, resemblance to flight, i. 4. I.
Symmetry, of organs bilateral, iii. 7. 2 ;

more perfect in organs of animal than of

vegetable life, iii. 5. 4.

Tadpole, the only footed animal that has
gills, iv. 13. 40; not recognised as
larval form, iv. 13. 7 ; its tail, iv. 13. 8.

Tail, various uses, iv. 10. 43 ; how used by
birds, iv. 12. 24; supposed correlation
with other parts, li. 14. 4 and 5.

Taste, relation to touch, ii. 10. 22 ; relation
to touch and to smell, iv. 11. 8; its
organ and medium, ii. 10. 10 ; acute in
man, ii. 16. 14; dull in fishes, iv. 11. 7.

Teeth, inverse relation to horns, iii. 2. 19 ;
resembling horns, iii. 2. 21 ; of carni-
vora, iv. 1 1. 19; of seals, iv. 13.44;
of camel, iii. 14. 3 ; of reptiles, iv. 11.
12 ; of fislies, iii. i. 7 and 9, iv. 13. 30 ;
of sharks, iii. 1.8; of cephalopods, iv.

5.4; of Crustacea, iv. 5. 5 ; of snails,

iv. 5. 10 and 26 ; how represented in

insects, iv. 5. 7.
Temperature, no measure of, ii. 2. 18 ; of

different animals, ii. 17. 19 ; maintained

by food, iv. 5. 77.
Tendons, iii. 4. 20.
Testacea, characters and subdivisions, iv.

5. 25 ; tongue, iv. 5. 6 ; teeth, iv. 5. 26 ;

proboscis, iv. 5. 27 ; crop, iv. 5. 28 ;

operculum, iv. 5. 31 ; liver and stomach,

iv. 5. 29 ; heart, iv. 5. 67 ; ovary, iv. 5.

44 and 47 ; without generative secretions,

iv. 5. 68.
Testes, A.'s notion of, iv. 13. 34; of

ophidia, iv. I3-.35-
Tethya. See Ascidia.
Teuthi, iv. 9. i.

Theoretical, and other sciences, i. 1.4.
Tickling, iii. 10. 8.
Tissues, relation to organs, ii. i. 5. 7, 8

and 9, ii. 2. 3 ; attempt of Theophrastus

to resolve them into simpler elements,

ii. I. 5.
Toes, number of in various groups, iv. 10.

21 ; number supposed to be related to
number of mammae, iv. 10. 26 ; of pig,
iii. 12. 8 ; of elephant, ii. 16. 6 ; of
birds, iv. 12. 30 ; of waders, iv. 12.

22 ami 31 ; of grebes, iv. 12. 8 ; of birds
of prey, iv. 12. 17 j of scansorial birds,
iv. 12. 33.

Tongue, of seal, iv. 11. 10 ; of parrot,

ii. 17. 3; of reptiles, iv. Ii. 5; of

serpents and lizards, ii. 17. 7, iv. 11.

10 ; of crocodile, ii. 17. 9 and 10 ; of

cephalopods, iv. 5. 4 ; of Crustacea, iv.

5. 5 ; of testacea, iv. 5. 6; of insects, iv.

5. 8 ; of echini, iv. 5. 37.
Torpedo, iv. 13. 3.
Tortoise, habits, iii. 8. 4 ; lung, iii. 8. 5 ;

bladder, iii. 8. 3, iii. 9. 3 ; kidneys, iii.

9. I.
Touch, whether one sense or many, ii. r.

13 ; why the primary sense, ii. 8. I ;

fle.sh its medium, ii. 8. 2, ii. 10. 10 ; its

close relation to taste, ii. 10. 22, iv. 11.

8 ; acute in man, ii. 16. 14.
Trachea, position of orifice, iii. 3 5 ; use

of length, iii. 3. 8 ; relation to heart,

iii. 3. 9 ; of birds, iii. 6. i.
Trans-olent, and trans-sonant, ii. I. 12.
Treatises, on Health and Disease, ii. 2. 10,

ii. 7. 14 ; on Natural History, ii. i. i ;

on Nutrition, ii. 3. 16 ; on Motion of

Animals, iv. 13. 13 ; were illustrated,

iv. 5- 34, iv. 9- 5-
Trygon, iv. 13. 4.

Turbinata. See Gasteropoda and Testacea.
Tusk.s, not present in homed animals, iii.

I. 3 ; weapons of defence or offence, iii.

I. I ; of elephants, iii. 2. 19; of

Babirussa pig, iii. i. I, iii. 2. 21.
Type, laws of, iv. 13. 15.

Umbilical, vesicle, iv. 12. 15 ; cord, ii.
3. 10.

Index to Notes.

263

Unicorn, iii. 2. 10. and 12.

Upper, why supeiior to lower, ii. 2. 6.
Ureters, iii. 9. 8.

Urine, where formed, iii. 7. 8, iii. 9. I ;
contains earthy matter, iv. i. 4.

Vapor-bath, of ancients, ii. 4. 7.

Vasa deferentia, thought to be seat of

seminal secretion, iv. 13. 34.
Vegetative repetition, a sign of inferiority,

iy. 5. 72.
Veins. See Arteries.
Vertebrata, number of limbs, iv. 12. Ii,

iv. 13, 15 ; how spinal column came to

be segmented, i. i. 7.
Viscera, what meant, iii. 4. I ; relation to

vessels, iii. 4. 10, iii. 8. 2, iii. 13. i ;

use of, iii. 7. 8 and 10 ; of new-born

animals, iii. 4. 4.
Vision, medium of, ii. 10. 10. See Eyes.
Vital, principle, i. I. 14; motions, i. i. 16 ;

heat distinct from common heat, ii. 6. 7,

ii. 16. II.

Viviparous, and sanguineous animals, iee
Mammalia; and ovo-viviparous, iv. I. 5»
iv. II. 24.

Vivisection, of chamseleon, ii. 7. 4 and 5,
ii. 10. 9 ; of tortoise, ii. 7. 12.

Water-animals, temperature of, ii. 2. 8.
Weapons, offensive and defensive, iii. i. i ;

larger in males than in females, iii. 1.

4 and 6 ; no animal as a rule has more

than one, iii. 2. 9 ; of fishes, iii. I. lo.
Wet, definition of, ii. i. 3.
Wliales, iv. 13. 38. See Cetacea.
Wing, and feather, iv. 6. 6 ; of insects,

i. 3. I ; of bat, iv. 13. 45.
Woodpecker, beak, iii. i. 14; toes, iv.

12. 33-
Worms, iv. 6. i, iv. 5. 70.
Wryneck, iv. 12. 33.

Xenophon, simile boiTOwed from, ii, 15. i .

Zoophytes, characters of, iv. 5. 53.

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BERKELEY -

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This book is DUE on the last date stamped below.

a@ii(g)gy

OCT 2 7 mn

JAN 2 «51

Held at Biology Ubiarf

NOV.

NOV 2^0 1952

jfMI A 1930

LD 21-100ni-ll,'49(B71468l

JUL 2^ 135]
JUL 2 7 1961

DEC 11196;

JAN'4 "IPSZ
APR 1 7 '^€2

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^^>^^ 6 1963

6)476

MAY 1 19GA
De2'65TS

DEC 29 1969
DEC 2 3 1369 9

L ::o end c
Subject ,

, APR 1- '74-^ ■

Lue ena of FALL quarter
Subject to recail^er —

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