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Arthur 0, Norton 








W. D. ROSS M.A. 











^^^..^.J- c^. Μ^ί^ β. 0ΐ4η^Λ 








It was the desire of the late Master of Balliol, Dr. Benjamin 
Jowett, as formulated in his will, that the proceeds from the 
sale of his works, the copyright in which he bequeathed to 
Balliol College, should be used to promote the study of Greek 
Literature, especially by the publication of new translations 
and editions of Greek authors. In a codicil to his will he ex- 
pressed the hope that the translation of Aristotle's works begun 
by his own translation of the Politics should be proceeded with 
as speedily as possible. The College resolved that the funds 
thus accruing to them should, in memory of his services to the 
College and to Greek letters, be applied to the subvention of 
a series of translations of the works of Aristotle. Through 
the co-operation, financial and other, of the Delegates of the 
University Press it has now become possible to begin the 
realization of this design. By agreement between the College 
and the Delegates of the Press the present editors were 
appointed to superintend the carrying out of the scheme. 
The series is published at the joint expense and risk of the 
College and the Delegates of the Press. 

The editors have secured the co-operation of various scholars 
in the task of translation. The translations make no claim to 
finality, but aim at being such as a scholar might construct in 
preparation for a critical edition and commentary. Wherever 
new readings are proposed the fact will be indicated, but notes 


justificatory of conjectural emendations or defensive of novel 
interpretations will, where admitted, be reduced to the smallest 

The editors, while retaining a general right of revision and 
annotation, will leave the responsibility for each translation to 
its author. 

J. A. S. 

W. D. R. 
















This translation is a revised version of one made by me 
very many years ago and published in 1883, with intro- 
ductory essays and very copious annotation. Exigencies 
of space have necessitated the omission of the former and 
a very great abridgement of the latter, while the translation 
itself has been largely altered and corrected. It still, how- 
ever, remains as before, a very free version ; for it is not 
intended to meet the linguistic requirements of the critical 
Greek scholar so much as those of the student of biological 
history, to whom a treatise that is the earliest extant 
attempt to assign its function to each several organ of the 
animal body cannot but be of great interest. Such being 
my main object, I have not hesitated to transfer clauses, 
or even an entire sentence, when by such transposition the 
argument can be made less obscure or more consecutive, 
and have ventured in no few cases to suggest new readings 
or adopt new readings suggested by others, when such 
readings are in my judgement called for by the context. 

Bekker's text has been followed as a rule, and any 
departure from it is mentioned in a note. If there be MS. 
authority for the departure the letter designating the MS. 
is added, as Omitting ψυχρόν (Ζ)'. If the new reading be 
one suggested by some other person, the name of that 
person is given, as ' For σνστάν read σννιστάν (Piatt)'. For 
other new readings I am myself responsible. 

My sincere thanks are due to Mr. W. D. Ross of Oriel 
College and to Professor Piatt of University College, Lon- 
don, for many valuable criticisms and suggestions made in 
the course of revision. 


Introductory Matter, i. i— i. 5. 
I. Concerning the method of Natural Science ... i. i. 

ii. Concerning Necessity and the Final Cause and their 

relative importance . . . . . . . i. i. 

iii. Concerning the Soul and how far it falls into the pro- 
vince of Natural Science . . . . . . i. I. 

iv. Concerning Classification, dichotomous or other, and the 

insufriciency of the former 1.2—1.4. 

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

vi. The plan of this treatise to take the parts in succession, 
and inquire 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. i. 

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

2. Hot 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 Sanguineous Animals 

ii. 10— iv. 4, and iv. 10— end of treatise. 

a. Organs of the Head ii. 10— iii. 2. 

10. Brain and organs of sense. 11, 12. Ears. 
13, 14, 15. Eyelids a)td Eyelashes. 16. Nos- 
trils, Lips. 17. Tongue. iii. i. Teeth. 

2. Horns. 

β. Organs of the Neck iii• 3. 

3. Oesophagus J- IVindpipey Epiglottis. 

γ. Visceral Organs . . . .iii, 4— iii. 15, iv. i— iv, 4. 
4. Heart. 5. Blood vessels. 6. Lung. 7. Liver, 
Spleen. 8. Bladder. 9. Kidneys. 10. Dia- 
phragm. II. Fibrous membranes. 12. Vis- 
cera 0/ different groups compared. 13. Vis- 


cera compared with flesh. 14. Stomach and 
Intestines. ,15. Rennet, iv. I. Peculiarities 
of visce7-a in ovipara. 2. Gall bladder. 
3. Omentuvi. 4. Mesentery. 

δ. External parts iv. 10— iv. 14. 

10. /;/ vivipara. 11. In reptiles. 12. In birds. 
13. In fishes and intermediate groups, 
cetacea, seals, bats. 14. In the ostrich. 

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

it. Internal parts iv. 5. 

i3. External parts iv. 6— iv. 9. 

6. /;/ insects. 7. lit testacea. 8. In crtistacea. 
9. In cephalopoda. 


I Every ^ systematic science, the humblest and the noblest 639^ 
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 5 
to form a fair off-hand judgement 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 10 
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 com- 
petence in some one branch of knowledge without having 
it in all. 

It is plain then that, as in other sciences, so in that 
which inquires into nature, there must be certain canons, 
by reference to which a hearer shall be able to criticize the 
method of a professed exposition, quite independently of 
the question whether the statements made be true or false. 
Ought we, for instance (to give an illustration of what 15 
I mean), to begin by discussing each separate species — 
man, lion, ox, and the like — taking each kind in hand 
independently of the rest, or ought we rather to deal first 

^ This treatise, known to us as 'On the Parts of Animals', is referred to 
by A. himself (C. ./i. V. 3. 782^ 21) as 'On the Causes of the Parts of 
Animals'. It is professedly (ii. i. 646=^ li) an inquiry as to how far 
the e.xistence and structure of each part are due to Necessity and how 
far to Design. Owing, however, to the giant share ascribed by A. to 
the latter cause, the treatise becomes one on the functions of the parts 
rather than on their causes, and miglit almost be styled, as was Galen's 
later work, a treatise De Usii Partiiaii. 

ΛΚ. 1..Λ. Β 


with the attributes which they have in common in virtue 
of some common element of their nature, and proceed from 
this as a basis for the consideration of them separately? 
20 For genera that are quite distinct yet oftentimes present 
many identical phenomena, sleep, for instance, respiration, 
growth, decay, death,^ and 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 deal with each 
species independently of the rest, we shall frequently be 
obliged to repeat the same statements over and over again ; 
25 for horse and dog and man present, each and all, every one 
of the phenomena just enumerated. A discussion therefore 
of the attributes of each such species separately" would 
necessarily involve frequent repetitions as to characters, 
30 themselves identical but recurring in animals specifically 
distinct. (Very possibly also there may be other characters 
639^' which, though they present specific differences, yet come 
under one and the same category. For instance, flying, 
swimming, walking, creeping, are plainly specifically dis- 
tinct, but yet are all forms of animal progression.) We 
must, then, have some clear understanding as to the manner 
5 in which our investigation is to be conducted ; whether, 
I mean, we are first to deal with the common or generic 
characters, and afterwards to take into consideration 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 uncer- 
tainty 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 pre- 
10 sented by animals, and their several parts, proceed subse- 
quently to treat of the causes and the reason why ; or 
ought he to follow some other method } And when these 

^ All of these, be it noted, as also the modes of progression men- 
tioned a few sentences later on, were made subjects of special treatises 
by A. 

* Reading τα συμβίβηκότα for τών σνμβΐβηκότων. 

BOOK I. I 639^ 

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- 15 
point, alike in the 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 perceptible to mind, in the other to 
sense, of his end — the physician of health, the builder of 
a house — and this he holds forward as the reason and 
explanation of each subsequent step that he takes, and of 
his acting in this or that way as the case may be. Now in 20 
the works of nature the good end and the final cause is 
still more dominant than in works of art such as these, nor 
is necessity a factor with the same significance in them all ; 
though almost all writers, while they try to refer their 
origin to this cause, do so without distinguishing the various 
senses in which the term necessity is used. For there is 
absolute necessity, manifested in eternal phenomena ; and 25 
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 realized, 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, 30 
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 ^ from what 640" 
they are in the theoretical sciences f of which we have 

^ We might add, 'and in art.' 

^ A. divides the sciences into three groups {Metaph. E. i). Firstly, 

the Theoretical, which are purely intellectual and not concerned with 

action. In this are comprised Metaphysics, Physics, and Mathematics. 

Secondly the Practical \ and thirdly, the Constructive or Artistic. 

IJ 2 


spoken elsewhere. For in the latter the starting-point is 
that which is ; in the former that which is to be. For it is 
5 that which is yet to be — health, let us say, or a man — that, 
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 has been generated, makes it necessary that 
health or a man is in, or shall come into, existence. Nor 
is it possible to trace back the series of necessary ante- 
cedents to a starting-point, of which you can say that, 
existing itself from eternity, it has determined their exist- 
ence as its consequent. These however, again, are matters 
lo that have been dealt with in another treatise. There too it 
was stated in what cases absolute and hypotheticahnecessity 
exist ; in what cases also the proposition expressing hypo- 
thetical necessity is simply convertible, and what cause it is 
that determines this convertibility.^ 

The Practical and the Artistic comprehend action as well as intelli- 
gence ; but differ from each other, in that the Practical have no other 
result than the action itself; whereas the Constructive or Artistic, when 
the action is over, leave as its result a substantial product. 

The contrast in the text is between the theoretical and the con- 
structive sciences ; among which latter, A. here inconsistently includes 
η φνσικη ; and the points of contrast are as follows. The theoretical 
philosopher starts from certain eternal facts or verities {το oV)— 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 
realized in the future (τ-ό ίσόμΐνον). Starting from this, he reasons 
backwards through the antecedent steps that are necessary, if the 
conception is to be realized. The realization of my conception Ξ, he 
says, requires first the realization of Z> ; if Z> is to be produced, there 
must previously be C ; C again requires Β 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 Β produces C, 
and so on, retracing his previous steps, until he reaches E, the con- 
ception of which was his starting-point, as its^ material realization is 
his end. 

^ (Cf. De G. et C. ii. 9-II.) 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. The heavenly bodies consist of this ; and they alone are 
individually eternal. The Divinity, however, wishing to give the 
things of earth as near an approach to eternity as is compatible with 
their being made of other elements than aether, caused their motions 

BOOK I. I 640» 

Another matter which must not be passed over without 
consideration is, whether the proper subject of our exposi- 
tion is that with which the ancient writers concerned them- 
selves, 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 already 
mentioned, and begin with the phenomena presented by 
each group of animals, and, when this is done, proceed 15 
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 form ; and 
because it has this and that form, therefore is its con- 
struction 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 cha- 20 
racters presented by animals were merely the results of 
incidental occurrences during their development ; for in- 
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 [G. A. iv. 10. 777'^ 16), 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 (De An. 
ii. 4. 415^^4 ; G.A. ii. i. 731^^32); 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 man. Any hypothetical proposi- 
tion 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 conversion ' A. means, then, all those in which two stages in 
the cyclical evolution of an organism are placed as antecedent and con- 
sequent. 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 con- 
struction of the world. 


stance, 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 over- 
looked the fact that propagation implies a creative ^ seed 
endowed with certain formative properties. Secondly, he 
neglected another fact, namely, that the parent animal 

25 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 holds good also for the operations of art, and 
even for those which are apparently spontaneous.^ For 
the same result as is produced by art may occur sponta- 
neously. Spontaneity, for instance, may bring about the 

30 restoration of health. The products of art, however, require 
the pre-existence of an efficient cause homogeneous with 
themselves, such as the statuary's art, which must neces- 
sarily precede the statue ; for this cannot possibly be 
produced spontaneously. Art indeed consists in the con- 
ception of the result to be produced before its realization in 
the material. As with spontaneity, so with chance ; " for 

^ For συστύν read σννιστάν (Piatt). 

2 No reason is here given as to how the desirable result of Chance 
or Spontaneity can be said to occur for the sake of such end. The 
explanation seems to be as follows : — 

In the living body there are series of concatenated motions, estab- 
lished by nature or habit, to produce each some desirable end. If 
any one of these motions be set a-going, the rest of the series follow 
automatically in due succession till the end is attained (όταν αρχή 
■γένηται κινησίως, ωστκρ iv τοίί ηυτομάτοΐί βαΰμηαι, avveipeTcu το ΐφβζήί, 
G.A. ϋ. 5• 741 '^ 8). Such a series is that which terminates in Health, 
and its final terms are Heat, Uniform bodily condition {όμαΚύτηί), 
Health. The man of Art, i. e. the physician, says, in order to restore 
Health I must obtain υμ({Κότψ ; to obtain this Heat is required ; Heat 
again will follow on Friction. Here then he has come to something 
within his power. He applies Friction, and Heat, Equable Condition, 
Health follow in due order. But Friction may be applied by mere 
Chance and set the mechanism going that ends in Health. In such 
case the result may be said to be produced i7itc>iiionally , as it is 
produced by machinery intentionally set up by nature with a view to 
that end. It is only in the case of bodies that possess such inherent 
capacity for self-motion (pla κινΐΊσβηι ίφ' αΐτης) that chance can do the 
work of Art. Results that Art produces from a purely inert material, 
e. g. a statue, are quite beyond the power of Chance. Cf. P/iys. ii. 4-6, 
Metaph. Z. 7-9. 

* Accident is called Chance— or preferably Luck— when the accidental 

BOOK I. I 640-^ 

this also produces the same result as art, and by the same 

The fittest mode, then, of treatment is to say, a man has 
such and such parts, because the conception of a man in- 
cludes their presence, and because they are necessary con- 
ditions of his existence, or, if we cannot quite say this, which 35 
would be best of all, then the next thing to it, namely, 
that it is either quite ^ impossible for him to exist without 
them, or, at any rate, that it is better for him that they 
should be there ; and their existence involves the existence 
of other antecedents. Thus we should say, because man 640^ 
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 Avith which the ancient writers, who first philo- 5 
sophized about Nature, busied themselves, was the material 
principle and the material cause. They inquired what this 
is, and what its character ; how the universe is generated 
out of it, and by what motor influence, whether, for in- 
stance, 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 10 
to be light, the latter heavy. Por 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 15 
of the nostrils ; air and water being the materials of which 

agent acts with intention, though not with the intention of producing 
the result that actually occurs. It is called Spontaneity when the 
agent has no intention at all. It is the intermixture of semi-intention 
that gives force to the line τΰχη τίχνψ earep^e κηΐ τίχνη τϋχψ. 

^ For ολωί 'ύτι read ort ολω? (Ζ). 

" Omitting οτι. 


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 
consideration not merely the ultimate substances of which 
they are made, but also flesh, bone, blood, and all the other 

20 homogeneous parts ; not only these, but also the hetero- 
geneous parts, such as face, hand, foot ; 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 or earth, is no more sufficient than would 
be a similar account in the case of 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 

25 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 
embodied in this or that matter, or such and such a matter 
with this or that form ; so that its shape and structure 
must be included in our description. For the formal nature 
is of greater importance than the material nature. 

30 Does, then, configuration and colour constitute the essence 
of the various animals and of their several parts ? For 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, seeing that he is recognizable by his shape and colour. 

35 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 constituted in any but the 
appropriate way can possibly be a hand in more than name. 
041* For like a physician in a painting, or like a flute in a sculp- 
ture, 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 hand, is 
5 really an eye or a hand. To say, then, that shape and 
colour constitute the animal is an inadequate statement, 

BOOK I. I 641^ 

and is much the same as if a vvoodcarver were to insist that 
the hand he had cut out was really a hand. Yet the physio- 
logists, when they give an account of the development 
and causes of the animal form, speak very much like 
^ch 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 10 
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 concavity, 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 15 
state what the definitive characters are that distinguish 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 soul, or part of the soul, or something 
that without 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 con- 20 
figuration, 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 con- 
cerning 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 attri- 
butes that attach to this essential character, especially as 25 
nature is spoken of in two senses, and the nature of a thing 
is either its matter or its essence : nature as essence includ- 


ing both the motor cause and the final cause. 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 

30 inquirer 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. 

What has been said suggests the question, whether it 
is the whole soul or only some part of it, the consideration 

.'.δ of which comes within the province of natural science. Now 
if it be of the whole soul that this should treat, then there 
641'^ 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 
5 include the whole universe in its province. But perhaps it 
is not the whole soul, nor all its parts collectively, that con- 
stitutes the source of motion ; but there may be one part, 
identical with that in plants, which is the source of growth, 
another, namely the sensory part, which is the source of 
change of quality, while still another, and this not the 
intellectual part, is the source of locomotion. I say not the 
intellectual part ; for other animals than man have the power 
of locomotion, but 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 

10 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 

15 of an analogous cause or principle, not external but internal, 

BOOK Ι. I 641" 

derived like the hot and the cold ^ from the environing 
universe. And that the heaven, if it had an origin, was 
evolved and is maintained by such a causcj there is there- 
fore even more reason to believe, than that mortal animals 
so originated. For order and definiteness are much more 
plainly manifest in the celestial bodies than in our own 
frame ; while change and chance are characteristic of the 20 
perishable things of earth. Yet there are some who, while 
they allow that every animal exists and was 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 2.^ 
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 
wJiat 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 these it is by nature, the offspring being at 30 
any rate that which in nature will spring from it. At 
the same time the offspring is anterior^ to the germ; for 
germ and perfected progeny are related as the develop- 
mental process and the result." Anterior, however, to both 
germ and product is the organism from which the germ 
was derived. For every germ implies 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 35 
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 same seed then is the seed both of the horse and 
of the mule, though in different ways as here set forth. 

' And the other material elements of our bodies. 

- That is to say, in the order of thought. 

^ And result is in thought anterior to evolution. 


Moreover, the seed is potentially that which will spring from 
it, and the relation of potentiality to actuality we know.^ 
642'' 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 

5 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 

10 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 bronze or iron. Now exactly 
in the same way the body, which like the axe is an instru- 
ment — for both the body as a whole and its several parts 
individually have definite operations 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. 

It is plain then that there are two modes of causation, 

15 and that both of these must, so far as possible, be taken 
into account in explaining the works of nature, or that 
at any rate an attempt must be made to include them 
both ; ^ and that those who fail in this tell us in reality 

^ We know, that is, to be that of consequent to antecedent. 

^ As A. has fully explained what he means by Hypothetical Neces- 
sity only a few pages back, it is strange that he should now deal 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 inter- 

^ 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 strorger 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 Hypotheticcl. 
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 
veiior. Schrift. d. Arist. 179. 

^ Reading et hi μι], πΐΐρΰσθαί •)£ ποιΰρ τοΰτο, brjXov. 

BOOK I. I 642'' 

nothing about nature. For primary ^ cause constitutes the 
nature of an animal much more than does its matter. 
There are indeed passages in which even Empedocles hits 
upon this, and following the guidance of fact, finds himself 
constrained to speak of the ratio (6 λόγοί) as constitut- 20 
ing 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 ratio (0 λόγος) of their 
combination.^ 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 25 
this method of treatment was, that they were not in pos- 
session of the notion of essence, nor of any definition of 
substance. The 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 inquiring into the works of nature, and 
philosophers diverted their attention to political science 30 
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 necessity, the necessity, that is, that the 
requisite antecedents shall be there, if the final end is to be 
reached ; and sometimes absolute necessity, such necessity 
as that which connects substances and their inherent pro- 
perties and characters. For the alternate discharge and re- 35 

* i. e. the final cause ; for, as said earlier in the chapter, ' that cause 
is the first which we call the final.' 

^ Both Empedocles and Aristotle can speak of the λόγος of a bone, 
but in different senses ; Empedocles meaning no more than the pro- 
portion or ratio of the several component parts of bone ; while Aris- 
totle means the reason or cause of such composition, and professes to 
believe that Empedocles meant something of the same kind. 


entrance of heat and the inflow of air are necessary if we are 
to live. Here we have at once a necessity in the former of 
642^ the two senses. But the alternation of heat and refrigeration 
produces of necessity an alternate admission and discharge 
of the outer air, and this is a necessity of the second 

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. 

5 Some - writers propose to reach the definitions of the 2 
ultimate forms of animal life by bipartite division. But 
this method is often difiicult, 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, Cleft- 
footed,^ the last term is all-expressive by itself, and to 
append the higher terms is only an idle iteration. 

10 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 
placed in a different class. The group Birds and the group 
Fishes happen to be named, while other natural groups 

15 have no popular names ; for instance^ the groups that we 
may call Sanguineous and Bloodless are not known popu- 
larly 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 
dislocation. The group of the Many-footed, for instance, 

* This passage defies all other than a paraphrastic rendering with 
some expansion, 

^ Alluding to Plato's method of dividing downwards until by suc- 
cessive bifurcations the infima species is at last reached. Examples 
of this method, abscissio infiniti, will be found in the Sophistes 
and PoliticHs. These are 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 main 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, ^ Omitting Imow. 

BOOK I. 2 642'' 

would, under this method, have to be dismembered, and 
some of its kinds distributed among land animals, others 20 
among water animals. 

3 Again, privative terms inevitably form one branch of 
dichotomous division, as we see in the proposed dicho- 
tomies. But privative terms in their character of privatives 
admit of no subdivision. For there can be no specific 
forms of a negation, of Featherless for instance or of Foot- 
less, as there are of Feathered and of Footed. Yet a 
generic differentia must be subdivisible ; for otherwise what 25 
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 Unbarbed, and feet 
into Manycleft, and Twocleft, like those of animals with 
bifid hoofs, and Uncleft or Undivided, like those of 
animals with solid hoofs. Now even with differentiae 30 
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 impossible, is it to do 
this, if we start with a dichotomy into two contradictories. 35 
(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 643^ 
present in their essence a common undifferentiated element, 
but any apparently common element must really be diffe- 
rentiated. (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 

^ P^or ί'ιναιμα read evavria. 

^ The wing of an insect was held by A. to be a feather (πτίρόΐ', not 
πτ//ίυ^), differing, however, from the feather of a bird in being without 
barbs and without shaft {ίίσχιστον and (ίκαυλον) and also in its mode of 
origin (cf. iv. 6.6821^ 18). 


this it follows that a privative term, being insusceptible 
5 of differentiation, cannot be a generic differentia ; for, if 
it were, there would be a common undifferentiated element 
in two different groups. 

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 

lo groups, then it is plain that in virtue of that common 
differentia specifically distinct animals would fall into the 
same division. It is necessary then, if the differentiae, under 
which are ranged all the ultimate and indivisible groups, are 
specific characters, that none of them 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 

15 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 

20 would equal the number of ultimate animal forms.^ 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 power 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 

25 and matter.* For no part of an animal is purely material 
or purely immaterial ; nor can a body, independently of its 
condition, constitute an animal or any of its parts, as has 
repeatedly been observed.)'' 

^ Omitting μη with Titze. 

^ And that, he impHes, is inconceivable. 

^ For τα λΐυκά read τό XevKov κα\ το μίλαν (Edit. nonnuUi). 

* Reading ev Tjj νλτ] τό udos (Υ). 

^ e.g. at i. I. 641'^ 19. 

BOOK I. 3 643^ 

Further, the differentiae must be elements of the essence, 
and not merely essential 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 30 
its essence that its angles are equal to two right angles. 

Again, the bifurcations must be opposites, 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. 

Furthermore, living beings cannot be divided ^ by the 35 
functions common to body and soul, by Flying, for instance, 
and Walking, as we see them divided in the dichotomies 
already referred to. For some groups, Ants for instance, 643' 
fall under both divisions, some ants flying while others do 
not. Similarly as regards the division into Wild and 
Tame ; for it also would involve the disruption of a species 
into different groups. For in almost all species in which 5 
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 differ- 
ences. 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 10 
to recognize 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 contrary groups 

' Reading ου fiei 8iaipelt> (Gaza). 

^ Reading OTroiaovu (Y) and διαφορά (ΕΥ). 

AP,. P. A. C 


15 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 
ultimate species. 

If, again, a new differential character be introduced at 
any stage into the division, the necessary result is that the 
continuity of the division becomes merely a unity and con- 
tinuity of agglomeration, like the unity and continuity of 
a series of sentences coupled together by conjunctive par- 
ticles. For instance, suppose we have the bifurcation 

20 Feathered and Featherless, and then divide Feathered into 
Wild and Tame, or into White and Black. Tame and 
White are not a differentiation of 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- 

25 plicity of differentiae. If we do so, privative terms will be 
available, which are unavailable to the dichotomist. 

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 con- 
siderations. It is impossible that a single differentia, either 

30 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 Cleft-footed ; in 
saying a single differentia with antecedent I mean, to give 
an instance, Many-cleft-footed preceded by Cleft-footed.^ 
The very continuity of a series of successive differentiae in 
a division is intended to show that it is their combination 
that expresses the character of the resulting unit, or ultimate 

35 group. But one is misled by the usages of language into 

imagining that it is merely the final term of the series, 

Many-cleft-footed for instance, that constitutes the whole 

differentia, and that the antecedent terms, Footed, Cleft- 

644* footed, are superfluous.^ Now it is evident that such a 

' For προς τό σχιζόπουν read προς τω σχιζόττονν (Piatt). 

^ In the text as it stands the terms of several distinct series of 
differentiae are mixed together with much confusion. If, however, 
we omit η τ6 binow, and substitute σχιζόπουν for πολνπονν, as I have 
ventured to do in the translation, the terms of only one series — 

BOOK I. 3 644^ 

series cannot consist of many terms. For if one divides 
and subdivides, one soon reaches the final differential term, 
but for all that will not have got to the ultimate division, 
that is, to the species.) No single differentia, I repeat, either 
by itself or mih its antecedents, can possibly express the 
essence of a species. Suppose, for example, Man to be the 5 
animal to be defined ; the single differentia will be Cleft- 
footed, either by itself or with its antecedents, Footed and 
Two-footed.^ Now if man was nothing more than a Cleft- 
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 10 
forms by dichotomous division. 

4 It deserves inquiry why a single name denoting a higher 
group was not invented by mankind^ as an appellation 
to comprehend the two groups of Water animals and 
Winged animals. For even these have certain attributes 15 
in common.^ 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 whose attributes are not 
identical but analogous are separated. For instance, bird 20 
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 

Footed, Cleft-footed, Many-cleft-footed— are used, and the passage 
becomes intelligible and clear. 

^ If the text be correct, which the many different readings make 
doubtful, A. is speakirg carelessly; for Many-cleft-footed clearly does 
not imply Two-footed, seeing that many quadrupeds are πολυσχιδή. 
Much alteration would be required to make the passage logically 
accurate. It might, however, be done by reading η το πολυσχώϊί μύρον 
instead of ί; τ6 σχιζόπονν μόνον, and for νπόπυνν 8ίπονν σχίζήπονν reading 
νπόπονν σχιζόπονν πολνσχιδί'ϊ ; and then ηολνσχιδί! after άνθρωπος. 

"^ Read αΰτη ή μία. 

^ Omit και Tols άλλοις. 

C 2 


in having analogous organs ; for what in the bird is feather, 
in the fish is scale. Such analogies can scarcely, however, 
serve universally as indications for the formation of groups, 
for almost all animals present analogies in their correspond- 
ing parts. 

The individuals ^ comprised within a species, such as 
Socrates and Coriscus, are the real existences ; but inas- 
much as these individuals possess one common specific 

25 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 Avill be endless reiteration, 
as has already been pointed out.- 

But as regards the larger groups — such as Birds — which 
comprehend 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 

30 practicable, to examine these ultimate species separately, 
just as we examine the species Man separately ; to ex- 
amine, that is, not the whole class Birds collectively, 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 re- 

35 peated mention of the same attribute, as the same attribute is 
644** common to many species, and so far would be somewhat 
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 sub- 
ordinate forms, whether they are groups recognized by 
5 a true instinct of mankind, such as Birds and Fishes, or 
groups not popularly known by a common appellation, but 
withal composed 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. 

^ By TO. 'ίσχατα (Ί8η, if such be the true reading, must here be meant 
'the ultimate forms', i.e. the individuals comprised in a species, as 
rendered above. This, however, seems a scarcely tenable translation 
of the words, and I prefer, as a possible emendation, that we should 
read τα eaxara without ft'S//. 

2 Cf. i. I. 639=^ 27. 

BOOK I. 4 644^ 

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, FisheSj Cephalopoda,^ and Testacea have been made 10 
to form each a separate class. For Avithin the limits of 
each such class, the parts do not differ in that they have no 
nearer resemblance than that of analogy — such as exists 
between the bone of man and the spine of fish — but differ 
merely in respect of such corporeal conditions as largeness 
smallness, softness hardness, smoothness roughness, and 
other similar oppositions, or, in one word, in respect of 15 

We have now touched upon the canons for criticizing 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 why 
dichotomy is either impracticable or inefficacious for its 
professed purposes. 

Having laid this foundation, let us pass on to our next 20 

5 Of things constituted by nature some 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 knowledge. The -'5 
evidence that might throw light on them, and on the 
problems which we long to solve respecting them, is fur- 
nished but scantily by sensation ; whereas respecting perish- 
able plants and animals we have abundant information, 
living as we do in their midst, and ample data may be 30 
collected concerning all their various kinds, if only we are 
willing to take sufificient pains. Both departments, how- 
ever, 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 

^ yV.'s μαλάκκι do not Correspond to our INIollusca, though often so 
rendered, but to the limited and well-defined group of Cephalopoda ; 
and the term is so translated in the rest of this treatise. 


35 world in which we live ; just as a half glimpse of persons 
that we love is more delightful than a leisurely view of 
645=^ other things, whatever their number and dimensions. On 
the other hand, in certitude and in completeness our know- 
ledge 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 
5 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 

10 all who can trace links of causation, and are inclined to 
philosophy. Indeed, it would be strange if mimic repre- 
sentations 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 reasons that determined 

15 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 warm- 
ing himself at the furnace in the kitchen and hesitated 

20 to go in, 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 some- 
thing 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 

25 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, 

30 and the like — without much repugnance. Moreover, when 

BOOK I. 5 645=* 

any one of the parts or structures, be it which it may, is 
under discussion, it must not be supposed that it is its 
material composition to which attention is being directed 
or which is the object of the discussion, but the relation of 
such part to the total form. Similarly, 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 35 
material elements, but their composition, and the totality 
of the form, independently of which they have no existence. 

The course of exposition must be first to state the 645^ 
attributes common to whole groups of animals, and then to 
attempt to give their explanation. Many groups, as already 
noticed,^ present common attributes, that is to say, in some 
cases absolutely identical affections, and absolutely identical 5 
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 ofiice. 
To treat of the common attributes in connexion with each 10 
individual group would involve, as already suggested, 
useless iteration. For many groups have common attributes. 
So much for this topic. 

As every instrument and every bodily member subserves 
some partial end, that is to say, some special action, so the 15 
whole body must be destined to minister to some plenary 
sphere of action. Thus the saw is made for sawing, for 
sawing is a 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 subordinate function, to which 
it is adapted. 

1 Cf. i. I. 639'^ 18 and 27. 

"^ A. divides animals into those with and those without blood, mean- 
ing exclusively red blood. This division into Sanguineous and 
Bloodless tallies closely with that into Vertebrates and Invertebrates, 
but not completely. For in Amphioxus, usually classed as vertebrate, 
the blood is colourless, while it is red in no few invertebrates, e. g. in 
Planorbis, Area, Pectunculus, Solen legumen, &;c., &c. Possibly it was 
the red blood in some worms, e. g. those common in pond-mud, that 
led A. to consider worms generally to be immature eels {G. A. iii. 11. 
762'' 26, H. A. vi. 16. 570••» is). 


20 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 

25 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 
manifestly obtains between the organs which discharge 

30 these functions ; and similarly, if one function is prior to and 
the end of another, their respective organs Avill stand to 
each other in the same relation. Thirdly, the existence of 
these parts involves that of other things as their necessary 

Instances of what I mean by functions and affections are 

35 Reproduction, Growth, Copulation, Waking, Sleep, Loco- 
motion, and other similar vital actions. Instances of what 
I mean by parts are Nose, Eye, Face, and other so-called 
646^ 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, 
5 as we have indicated, to the order of nature. 

^ Reading ά τούτων for των. The meaning is plain from other 
passages. Thus : ' we must not always expect to find such a final 
cause ; for granted the existence in the body of this or that constituent 
with such and such properties, many results must ensue as necessary 
results of these properties' (iv. 2. 677"' ly) ; and again, 'everything 
given by nature is either itself given for an end, or is the incidental 
accompaniment of something else that is so given ' (De An. iii. 
12.434^31). A.'s triple division may be illustrated by an example, 
(i) The alimentary canal, as a whole, has the elaboration of food for 
its plenary function. (2) The teeth, gullet, stomach, and intestines, 
with their several offices, are ancillary to the last. (3) The fatty 
omentum is held by A. (iv. 3. 677'^ 22) to be the necessary consequent 
of the above parts, and to have no distinct function of its own. 

^ Such appears to be the meaning of των ΰλλων ; μόρια that are not 
μ£ρη ; that is homogeneous as contrasted with heterogeneous parts. 
Cf. ii. I. 646^ 20 note. 


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 quite distinct from that dealt with in the Re- 

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 earth, air, water, 
fire. Perhaps, however, it would be more accurate to say 
composition out of the elementary forces ; ^ nor indeed out 

^ In the Hist. A/niiialiiaji (Books i.-iv. 7) the parts were described; 
their cai/ses are now to be considered— a very different subject. 

- The so-called elements, says A. elsewhere [De G. et C. ii. 2), 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 endless ways, as regards colour, taste, smell, 
&c. {Meteo}-. iv. 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 elementaiy properties, and each object possesses two of them. 
Now among four things there may be six combinations of two and two 
(fTufeL'^fii) ; but the pairing of two directly opposite properties, as of 
cold and hot, causes them both to disappear ; for they neutralize 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 corresponds to vapour ; 
fluid and cold forming water; cold and solid forming earth. 

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 ex- 
cepting 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. De 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, &c. For he is speaking 
not of abstract properties, but of concrete substances. His views 
{De G. et C. ii. i) were as follows. There is one ultimate matter, 


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 bodies ; ^ and all 
other differences are secondary to these, such differences, 
that is, as heaviness or lightness, density or rarity, roughness 
or smoothness, and any other such properties of matter as 
20 there may be. The second degree of composition is that 
by which the homogeneous ^ parts of animals, such as bone, 

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, &c. 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. 

^ The traditional rendering of iypov and ξηρόν is Wet or Moist and 
Dry. They are here rendered Fluid and Solid. For though these 
terms are, as A. says (ii. 3. 649'' 9), used in several senses, the 
definitions he gives of them {De G. et C. ii. 2. 329^' 30) are distinctly 
definitions of Fluid and Solid. He defines vyp6v (fluid) as 'that 
which has no definite boundary of its own but readily has one 
imposed upon it ', meaning, of course, by the receptacle into which it is 
poured; while ξηρόν (solid) is 'that which has a definite boundary of 
its own and resists the imposition of another'. 

"^ By compound substances A. means all substances made by com- 
binations of the elements. Every such compound, that is every 
actually existing substance, contains, says A. {Be G. et C. ii. 8), 
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 [De 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 imper- 
fection 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 affinities, nor, of course, of combination 
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. It was 
to this αοριστία τηςυλης {G. A. iv. 7. yj%^6) that A. ascribed the apparent 
imperfections in Nature's handiwork. 

^ The division into Homogeneous and Heterogeneous parts corre- 

BOOK Π. I 646^ 

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 25 
logical existence are always the inverse of each other. For 
that which is posterior in the order of development is 
antecedent in the order of nature, and that is genetically 
last which in nature is 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 sake of the house ; and the same is the 
case with the materials of other bodies. Nor is induction 
required to show this. It is included in our conception of 30 
generation. For generation is a process from a something 
to 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 form or similar end ; for 
man generates man, and plant generates plant, in each 35 
case out of the underlying material.)^ 

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 646'' 
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 

spends in a general way to the later division into Tissues and Organs; 
the former, however, including much that we should not call tissue, 
e. g. the blood, and, in short, any constituent of the body which A. held 
to be incapable of further structural analysis, being formed directly 
out of the compound, i. e. the chemical, substances. These Homo- 
geneous parts again were of two kinds, (a) simple tissues or stuffs, 
without any notion of size or shape, e. g. cartilaginous or osseous 
tissues, and [β) simple organs, that is, organs made of a single tissue 
but with definite form and size, e.g. a cartilage or a bone. In this 
sense even the heart was homogeneous, being made of a single 
tissue, viz. flesh, while it was heterogeneous as having a definite 

* The material substratum is of comparatively small importance ; 
the form is derived from the parent. 


include nor presuppose that of house-building ; and the 

5 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 

!o 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 

15 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 
substances 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, 

20 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 hetero- 
geneous 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 

25 and different property for simple prehension. For this 

' The first degree of composition was that of the compound sub- 
stances ; the second that of the homogeneous parts or tissues ; the 
third that of the heterogeneous parts or organs. The evolution, then, 
of an individual organ has reached its final term when this third slage 
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 multi- 
plicity of organs. This, however, is not the case with all organisms. 
The simpler kinds (Aristotle \vould 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. 

BOOK Π. I 646^ 

reason the active or executive parts of the body are 
compounded out of bones, sinews, flesh, and the hke, 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 30 
beginning have possibly been other than they are. For 
heterogeneous parts can be made up out of homogeneous 
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 35 
substances should be formed out of a combination of 
heterogeneous parts is clearly an impossibility. For these 647* 
causes, then, some parts of animals are simple and homo- 
geneous, while others are composite and heterogeneous ; 
and dividing the parts into the active or executive and the 
sensitive, each one of the former is, as before said, hetero- 5 
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 order of sensibles, 
and its organ must be such as to admit the action of that 
kind or order. But it is only that which is endowed with 
a property in posse that is acted on by that which has the 
like property hi esse, so that the two are the same in kind, 
and if ^ the latter is single so also is the former. Thus it is 10 
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 15 
parts. But, as might reasonably be expected, the organ of 

^ Reading και el ίκύνο ΐν. If the organ were not a simple homo- 
geneous substance it would be acted on by more than one order of 
sensibles, which is not the case. 


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 recognize more than one category of 
contrasts, heat and cold, for instance, solidity and fluidity, 
and other similar oppositions. Accordingly, the organ 

20 which deals with these varied objects is of all the sense- 
organs 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 

25 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 

30 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 

35 of its definite configuration. And the same is true of the 
other so-called viscera, which are indeed formed from the 
647^ 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 

5 blood in the vessels. And as to the heart, the very starting- 
point of the vessels, and the actual seat of the force by 

^ Cf. ii. 8. 653^ 30 note. 
^ Cf. De Soiimo, 2. 455'^ 34, 456* 5. 

* 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. 

BOOK II. I 647^' 

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. 

2 Of the homogeneous parts of animals^ some are soft and 10 
fluid, others hard and solid ; and of the former some are 
fluid permanently, others only so long as they are in the 
living body.^ Such 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 15 
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 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 in one sense are 
designated by the same term — as, for example, is the case 
with blood-vessel and bit of blood-vessel — while in another 
sense they are not ; but a portion of a heterogeneous part, 20 
such as face, in no sense has the same designation as the 

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 constructed of bones, sinews, 
flesh, and the like ; which are either essential elements in 25 
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 

' Or ' the system '. For φΰσις in this sense cf. ii. 3. 649'' 28-32. 

^ Hesh is presumably called fluid as being potentially blood (iii. 5. 
668* 27) ; a view which very possibly derived support from its cada- 
veric rigidity. 

^ Namely the simple organs. Cf. ii. I. 646^^ 21 note. Blood-vessel 
and bit of blood-vessel are both vascular tissue, but a bit of blood- 
vessel is not a blood-vessel. 


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 varia- 
30 tions, 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 com- 
pare the bloods from different parts of the same individual 
35 or the bloods of different animals. For, in the individual, 
all the differences just enumerated distinguish the blood of 

648''^ 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 differences, the 
thicker and the hotter blood is, the more conducive is it to 
strength, while in proportion to its thinness and its coldness 
5 is its suitability for sensation and intelligence. A like 
distinction exists also in the fluid which is 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 
10 time thin and clear. For such are suited alike for the 

\ development of courage and of intelligence. 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, 

^ Reading το ανύΧογον υπάρχον. 

^ It was the unquestioning belief of Aristotle 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 honour- 
able position' (iii. 4. 665 '^ 20). 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. όδό'^ 13). Man's nobility is shown by his upper part 

BOOK II. 2 648=" 

homogeneous and heterogeneous alike. For here also such 
variations as occur must be held either to be related to the 
essential constitution and mode of lii"e of the several animals, 15 
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 20 
something of a similar character, and what the nature of 
blood may be, these are matters which can only be con- 
sidered 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 25 
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, 30 
and that it is the warmth and abundance of their blood 
which causes their menstrual flow, while Empedocles main- 
tains 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 35 
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 648*^ 

being turned towards the upper part of the universe (ii. 10. 656* 11). 
The front of man is chosen in preference to the back, for the growth 
of hair (ii. 14. 658^ 23). The nictitating membrane conies from the 
canthus in front, rather than the canthus on the side (ii. 13. 6$7^ 22). 
The heart, being the noblest part, is in front and in the upper half of 
the body (iii. 4. 665^ 18), and so on. 
^ Empedocles, cf. Ve Resp. 14. 

AR. P.A. D 


statements, though in verbal contradiction with each other, 
may yet all be more or less true, [^here 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,- and that they are 
5 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 

lo 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 

15 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 sometimes 
to be a false one ; for occasionally it is the idiosyncrasy of 
the individual that causes the sensation to be painful. 
Again, of two things, that is the hotter which the more 
readily melts a fusible substance, or sets on fire an inflam- 
mable one. Again, of two masses of one and the same 
substance, the larger is said to have more heat than the 

20 smaller. 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 

25 mentioned, and perhaps in still more. Now it is impossible 
for one body to be hotter than another in all these different 
^ De G. et C. ii. 2-3, Meteor, iv. 

BOOK II. 2 648^ 

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 more rapidly and completely. For in fact fire never 30 
becomes cold ; whereas water invariably does so. Boiling 
water, again, is hotter to the touch than oil ; yet it gets cold 
and solid more rapidly than this other fluid. Blood, again, is 
hotter to the touch than either water or oil, and yet coagu- 
lates before them. Iron, again, and stones and other similar 
bodies are longer in getting heated than water, but when 
once heated burn other substances with a much greater 
intensity. Another distinction is this. In some of the 35 
bodies which are called hot the heat is derived from without, 
while in others it belongs to the bodies themselves ; and it 649=^ 
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 that musicians are hotter than 
healthy men. Of that which is hot per se and that which is 5 
hoiper 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 10 
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 15 
substratum may not itself be hot, but may be hot when 
coupled with heat as an attribute, as would be the case if 
one attached a single name to hot \vater or hot iron. 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 

^ 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. 
D 2 


influence, it is plain that cold is not a mere privation, but 
an actual existence. 

20 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, 

25 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. 

30 Now such things as are formed merely of water are soli- 
dified by cold, while such as are formed of nothing but 
earth are solidified by 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 constituent 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 

35 been dealt with more precisely in another treatise.^ 

In conclusion, then, seeing that the terms hot and hotter 
649^ are used in many different senses, and that no one sub- 
stance 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 
5 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. 

' Cf. Meteor, iv. 6-8, 10. 

BOOK II. 2 649'' 

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

3 In natural sequence we have next to treat of solid and 
fluid. These terms are used in various senses. Sometimes, 10 
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 15 
fluid, but potentially and essentially are solid. Now sepa- 
rate the constituents in such a mixture and you have 
on the one hand the watery components to which its 
fluidity was due,^ and these are both actually and poten- 
tially fluid, and on the other hand the earthy components, 
and these are in every way ^ solid ; and it is to bodies 
that are solid in this complete manner that the term ' solid ' 
is most properly and absolutely applicable. So also the 
opposite term ' fluid ' is strictly and absolutely applicable 20 
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 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 foi'm, is not hot. Blood then in a certain sense 25 
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 there- 
fore blood is essentially hot. But so far as blood becomes 
hot from some external influence, it is not hot essentially. 

^ The distinctive character of a fluid is that it is άνηπληστικόν, that is, 
that it has no shape of its own but takes that of the vessel which it fills up 
as a. mould {Be G. ct C. ii. 2.329'^ 34). To say then that a constituent of a 
mixture is (ΐναττ\ηστικήν is to say that it confers fluidity on the mixture. 

- That is, ' both potentially and actually '. "λπηντη, if the true 
reading, must be taken as adverbial and as used though 'deduobus 
tantum agitur ' (Bonitz, 571^ 51J ; but I suggest πάντως as a preferable 


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 

30 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 withdrawn 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 

35 must attribute to such substances the possession of opposite 
properties in a greater or less degree. 
650* 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 
5 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 elabora- 
tions 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, 

10 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 

^ A. looked on the heart as the main but not the excUisive seat of 
vital heat. ' The whole body and all its parts have a certain connate 
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 luv. et Sen. 4. 469'' 12). 

- The upper cavity is of course the stomach. By the lower is meant 

BOOK II. 3 650=» 

effected by the aid of natural heat. Again, just as there is 15 
a channel for the admission of the 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 manger. For plants get their food 20 
from the earth by means of their roots ; and this food is 
already elaborated when taken in, which is the reason why 
plants produce no excrement,^ the earth and its heat 
serving them in the stead of a stomach. But animals, 
with scarcely an exception, and conspicuously all such 
as are capable of locomotion, are provided with a stomachal 
sac, \vhich is as it were an internal substitute for the earth. 
They must therefore have some instrument which shall 25 
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 

the large intestine, or rather its caecal enlargement. This is some- 
times, as here, spoken of by A. as 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. 

' Π(μίττωμα, like the nutriment (G. A. i. 18. 725*4) of which it is 
the surplus, is of two kinds, the useless {ίίχρηστον) and the serviceable 
(χρήσιμοι•). The former is eliminated, mainly by the bowels and 
kidneys, and may be called the excremental residue. The latter is 
such of the nutriment reduced to blood as remains after the nobler 
parts, such as the sense-organs and flesh, have taken what they 
require {G. A. ii. 6. 744^23). This surplus is utilized in various ways. 
Some is spent on the inert parts, such as nails, hairs, sinews, bones 
(744^25); some is stored up as fat (ii. 5. 651^21) ; and some forms 
useful secretions and notably the generative (iv. 10. 689''^8-l3). All 
these products of the π(ρίττωμη are themselves called περιττώματα. The 
χρησιμον π(ρίττωμα in the blood contrasts with the σύντηγμα or product 
of body-waste [G. A.l 18. 724^^ 26 sq.) ; and when A. says of anything, 
other than excrement, that it is πίρίττωμα, he means that it derives from 
the serviceable residue, not from the effete matter. Plants, he says 
above, have no excremental residue, while their serviceable residue 
forms their fruit and seeds (ii. 10. 65 s'' 35). 


stomach, and there must necessarily be something to 
receive it in turn from this. This something is furnished 

30 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 

35 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 
650^ 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 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 pro- 
duced by touching the blood than by touching one of the 
5 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 vessels. The 
manner in which the parts grow at the expense of the 
blood, and indeed the whole question of nutrition, will find 

10 a more suitable place for exposition in the treatise on 
Generation, and in other writings.^ For our present purpose 

^ Cf. H.A.\. 16; iii. 4, 514'' 12. 

- A. often refers to a treatise which he was going to write on 
Nutrition. It has been generally supposed that the De Generatione 
Afiimalziiin, in which (ii. 4. 740^ 21-'' 12, ii. 6. 743*^8-7. 746'* 28) nutri- 
tion 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 Genera- 
tiofie itself (v. 4. 784^ 3). The present passage, moreover, speaks of 
' other writings ' besides the De Getiera/iofte. The promised treatise 
is not extant ; perhaps was never written; for no mention of such is 
to be found in Diogenes Laertius. Heitz {Die vej-lor. Schrift. d. Arist. 
61) thinks it probable that a short separate treatise was written, such 
as those massed together in the Parva Naiumlta, and that some 
portions of it have come down to us merged in the De Generatione ; 

BOOK II. 3 650^ 

all that need be said is that the blood exists for the sake 
of nutrition, that is the nutrition of the parts ; and with 
this much let us therefore content ourselves. 

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 15 
of such animals as these never coagulates. For one part of 
the blood consists mainly of water ^ and therefore docs not 
coagulate, this process occurring only in the other and 
earthy constituent, that is to say in the fibres, while the 
fluid part is evaporating. 

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 to the coldness of their blood, but 20 
rather to its thinness and purity ; neither of which qualities 
belongs to the earthy matter. For the thinner and purer 
its fluid is, the more easily affected is an animals sensi- 
bility. Thus it is that some bloodless animals, notwith- 
standing their want of blood, are yet more intelligent than 25 
some among the sanguineous kinds. Such for instance, as 
already said,^ is the case with the bee and the tribe 
of 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 prepared for the operation of this emotion. For 
water is congealed by cold. This also explains why blood- 30 
less 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 

and there is in fact in the De Sonino (3. 456'' 6) a passage which 
apparently refers to a treatise on Nutrition as already written. The 
subject is treated in De G. et C. i. 5. 2i'^i^ 32-322^33, ii. 8. 335•"* 10, 
Metccr. iv. 2. 379'' 23. 

^ Elsewhere [H.A. iii. 6. ^,1^^ 34) to these animals are added the 
Bubalis (antelope) and hare. It will be noted that all these are animals 
that are hunted : and the blood of animals hunted to death coagulates 
so imperfectly that J. Hunter was led to suppose erroneously that it did 
not coagulate at all (Hunter's IVorks, i. 234). A. {H. A. iii.6. Slo'' l) 
admits an imperfect coagulation of such blood. 

2 Omitting ^\τνχρ6ν (Ζ). s ^f^ \\^ 3. 648» 6. 


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 

35 liable to bursts of passion. For anger is productive of heat ; 

and solids, when they have been made hot, give off more heat 

651'' than fluids. The fibres therefore, being earthy and solid, are 

turned into so many hot embers in the blood, like the embers 

in a vapour-bath, and cause ebullition in the fits of passion. 

This explains why bulls and boars are so choleric and so 

passionate. For their blood is exceedingly rich in fibres,^ 

and the bull's at any rate coagulates more rapidly than 

6 that of any other animal.^ If these fibres, that is to say if 

the earthy constituents 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 

10 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 bloodless animals that remain motionless when frightened are 
beetles, moths, &c. (iv. 6. 682** 25). Those that discharge their excreta 
are various insects and cephalopods (iv. 5. 679* 6) ; and it is these 
latter that change colour (iv. 5. 679»• 13). 

^ Elsewhere {H.A. iii. 19. 521'* 5) the ass is instanced as well as the 
bull. Bovine animals (but still more swine and horses) have a larger 
proportion of fibrine in their blood than men (Andral, A7tn. de 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 evincing a disparity uniform in its reference to the classes of 
animals, yet it appears probable that a more complete examination 
would prove the crassamentiDii to bear a proportion to the siretigth 
atid ferocity of the animal, since I ne\er 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). 

^ Thackrah says {Oti 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. 

* Cf. Meteor, iv. 6-8, where A. discusses at length the Cjuestions of 
coagulation, liquefaction, &c. 

BOOK II. 4 651^ 

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 15 
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 

5 The differences between lard and suet correspond to 20 
differences of blood. ^ For both are blood concocted into these 
forms as a result " of abundant nutrition, being that surplus 
blood that is not expended on the fleshy part of the body, 
and is of an easily concocted and fatty character. This is 
shown by the unctuous aspect of these substances ; for such 
unctuous aspect in fluids is due to a combination of air and 
fire.^ It follows from what has been said that no non- 25 
sanguineous animals have either lard or suet ; for they have 
no blood. Among sanguineous animals those whose blood 

^ By the ' necessary process ' is meant the waste of the body 
(σιΊ /Tr/lis) that is constantly going on, but is increased by toil {Dc 
Soiuno, 3. 456^ 34). The efifete matter (σύντηγμα) that results from 
this necessary process, passing into the blood on its way to elimination 
by the various emunctories, is there commingled with nutritive 
material {χρησιμην π(ρίττωμα) that is on its way to repair the body- 
Λvaste. This σύντη-γμα, to use modern terms, is catabolic matter, while 
the χρησιμον π(μίττωμη is anabolic. 

^ A. calls the softer kinds of fat πιμίλη and the harder kinds στίαρ, 
terms corresponding to the Pinguedo and Sevum of later times. These 
are here rendered Lard and Suet, ' lard ' being used in want of a better 
word for any soft fat, not merely that of swine. J. Hunter made four 
divisions — Oil, Lard, Tallow, Spermaceti, also taking consistency as the 
basis of distinction. 

^ A. held that in over-fed or well-fed animals the blood was of such 
a character as favoured its conversion by further concoction into fat 
rather than into generative secretions ; just as vines in rich soil run to 
leaf rather than to fruit. G. A. i. 18. 725'' 26 sq., ii. 7. 746'^ 27 ; H. A. 
V. 14. 5468• i_ 

^ This clause seems so inconsecutive that one may suspect it to be 
an interpolation. 


is dense have suet rather than lard. For suet is of an 
30 earthy nature, that is to say, it contains but a small pro- 
portion 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 broths which contain such fibrous 
matter. Thus it is that in those horned animals that have 
no front teeth 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 this earthy element ; 
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 
35 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 
651^' 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 
5 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. 
10 For so much of their blood is used in forming fat, that they 
have but little 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 

' Cf. iv. 10. 690"^ 13 note. 

"^ i.e. Swine. Elsewhere {H.A. iii. 17. 520''^ 9) A, says correctly 
that the horse as well as the hog has soft fat. 

"" Cf. ii. 8. 653'^ 30 note. 

* Cf. ThacVcrah, On the Blood, p. 131 : ' 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 com- 
paratively small, and the quantity of blood, even when two or three 
vessels are opened, is less than flows from one vein of a lean 
person ' etc. 

BOOK II. 5 651^^ 

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 15 
nothing but concocted blood ; so that in these animals 
there is either no reproductive excretion at all, or only 
a scanty amount.^ 
6 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. 

The marrow also is of the nature of blood, and not, as 20 
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 natural, seeing 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 25 
up and ripens into maturity, the marrow changes its colour, 
just as do the external parts and the viscera."* For the 
viscera also in animals, so long as they are young, 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 unctuous and lard-like ; but when the blood is con- 
verted by concoction into suet, and does not assume the 
form ^ of lard, then the marrow also has a suety character. 30 

^ '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 sent en raison inverse I'un de I'autre ' (Bichat, Anat. Gen. 
i. 5 5). That over-fat animals are bad breeders is known to every farmer. 
So also it is well known that castrated animals grow fat. 

* Alluding to Plato, who expresses this view in the Timaeiis {y^ c). 

^ ' The bones of the foetus are void of a distinct medullary canal, and 
present merely a reddish homogeneous vascular pulp, somewhat con- 
sistent but presenting soft portions. This state continues for some 
time after birth ' (Todd, Cyclop. Anat. and P/iys. i. 60). So also Vir- 
chow's Ce/iii/arpath. 369. 

* In the foetus and infant there is less pigment in the body generally 
than in the adult. The skin, hair, eyes {G.A. v. I. 779-^ 26), and 
olfactory region, are all lighter-coloured than in later life. 

^ For ομοιυς read υμοιον (Ζ). 


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 backbone, inasmuch as 
35 this bone consists of separate vertebrae. But were the 
spinal marrow ^ either of unctuous 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 
652* 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 
5 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 de- 
veloped in it from its being thus surrounded, undergoes 
10 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 compact bones, some of these should 

' 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 '. 

2 Cf. ii. 4. 651a 14. 

^ 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 not convert blood into fat, nor digest food, nor the like. But the 
heat of the body, as the heat of the sun, says A. {G.A. ii. 3. 737* l), 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 

BOOK Π. 6 652=" 

be entirely void of marrow, while the rest contain but little 
of it ; ^ for here the nutriment is 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 they have naturally but a small amount of blood ; 
and secondly the only hollow fish-spine is that of the chine. 15 
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 con- 
necting 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 glutinous character, and at the 
same time sinewy so as to admit of stretching, ^o 

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

7 From the marrow we pass on in natural sequence to the 
brain. For there are many " who think that the brain 25 
itself consists of marrow, and that it forms the commence- 
ment 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 fat and unctuous character. Indeed this is 
the very reason why the brain and spinal marrow are con- 30 
tinuous 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 

* Reading ολίγος for υλίγοα (U). 

^ No fish has a medullary canal in its bones, though there are some, 
as the trout, in which the bony tissue is more or less penetrated by an 
oily fluid (Todd, Cyclop, of An. and Phy. iii. 958). 

^ As Plato in the Timaeiis {ji c). 


coldness of the brain is also manifest enough.^ For in 
the first place it is cold even to the touch ; and, secondly, 

35 of all the fluid parts of the body it is the driest ^ and the 
one that has the least blood ; for in fact it has no blood 
652'' at all in its proper substance. This brain is not residual 
matter, 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 con- 
tinuity with the organs of sense is plain from simple in- 
5 spection, 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 excre- 
ment. The purpose of its presence in animals is no less 
than the preservation of the whole body. For 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 

TO in some substance of a fiery character. The reason for 
this being so is that of all substances there is none so suit- 
able for ministering to the operations of the soul as that 
which is possessed of heat. For nutrition and the impart- 
ing of motion are ofiices of the soul, and it is by heat that 

^ There are three strange statements in this chapter as to the brain — 
that it is cold ; that it is bloodless ; that it is fluid, (a) The belief 
that the brain is cold lasted from the time of Hippocrates into the six- 
teenth or even the seventeenth century. For, as Dr. Payne states in 
his Harveian Oration, it was taught by Harvey in his MS. Praelectiones 
of 1616, and this though an anatomist of the preceding century is 
quoted by himself as having placed one hand on the heart and the 
other on the brain of a recently killed animal and found them equally 
hot. O) Most of the blood that goes to the brain goes to the super- 
ficial gray matter. This, differing as it does from the mass below 
in colour and general aspect, was considered by A. to be part of the 
highly vascular Pia mater, from Avhich indeed he can hardly have 
learnt to separate it mechanically. He appears to have overlooked 
the small vessels which penetrate the white mass, and which, though 
numerous, only appear as bloody puncta. (y) A. uses the term ' fluid ' 
with much latitude ; and may mean no more than that the brain is, as 
Galen calls it, ' nearly fluid.' At any rate he qualifies his statement 
very much by saying that of all the fluids it is the least fluid {αυχμ^ρά- 
Tarov), that is, the most consistent, and that it is only fluid in the 
young and becomes consolidated afterwards (G. A. ii. 6. 744=^ 17). 

^ i. e. the most consistent. 

^ Such as the vascular or osseous systems. See ii. 9. 654=^ 33. 

* Democritus {De Aft. i. 2. 403'^ 31). 

BOOK II. 7 652^^ 

these are most readily effected. To say then 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 15 
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 20 
region of the heart with its contained heat, and has given it 
to animals to moderate the latter, combining in it the 
properties of earth and water.^ For this reason it is, that 
every sanguineous animal has a brain ; whereas no blood- 
less creature has such an organ, unless indeed it be, as the 
Poulp, by analogy.^ For where there is no blood, there -5 
in consequence there is but little heat. The brain, then, 
tempers the heat and seething of the heart. In order, how- 
ever, that it may 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 30 
which surrounds the brain ; * while at the same time, in 
order to prevent any injury from the heat, these encom- 
passing vessels, instead of being few and large, are numerous 
and small, and their blood scanty and clear, instead of being 
abundant and thick. We can now understand why de- 
fluxions have their origin in the head, and occur whenever 
the parts about the brain have more than a due propor- 35 

^ And therefore causing it to be cold ; for both earth and water are 
compounds of cold matter, the former with solid, the latter with fluid 
matter. (Cf. ii. i. 646=^ 16 note.) 

^ Elsewhere (//. A. i. 16. 494'' 27) 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 as to rival the brains of vertel)rates 
in size and importance. 

^ Cf. iii. 5. 667'' 16 note. 

* i.e. the //a mater. A. (//. A. i. 16) 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 {pia mater). 
This latter is the vascular one, so often mentioned by Aristotle. This 
membrane consists in great part of a plexus of extremely numerous 
and very minute vessels, as A. says. 

AR. .'.A. Ε 


tion of coldness. For when the nutriment steams upwards 
653"^ 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 of showers. For when vapour steams up from 

5 the earth and is carried by the heat 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 

ΪΟ 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 heavi- 

15 ness in the region in which it lies (which is the reason why 
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 region that pro- 
duces complete sleep, taking away the power of standing 
upright from those animals to whom that posture is natural, 
and from the rest the power of holding up the head. 
These, however, are matters which have been separately 

20 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 

25 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 con- 
stituent, behind. 

Of all animals, man has the largest brain in proportion to 

^ As to the question whether the promised treatise on the Principles of 
Diseases was ever written, see Heitz, Die verlor. Schrift. d. Arist. p. 58. 
' De Sojnno, 2. 455^^ 28 - 3. 458* 32. I find nothing in l)e Setisu. 

BOOK Π. 7 653^ 

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 3o 
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 
any 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 35 
the last to become solidified ; so long does evaporation ^ 
continue to occur through it under the influence of heat. 
Man is the only sanguineous animal in which this takes 
place. Man, again, has more sutures in his skull than any 653^ 
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 blood, and in the other will not cool it at all ; and thus 
will cause disease, madness, and death. For the cardiac 5 
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. ^ 

^ i. e. the anterior fontanel, considered by A. to be a separate bone 

(i/.^. i. 7. 491^ 31)• 

^ The erroneous notion that the use of the sutures is to ventilate 
the brain is repeated by Galen {De Inst. Odor. 2 ; De Sanit. iuenda, 

'• J 3)• . 

° This is an error. A. was probably led to it by the fact that in 
numerous animals the sutures become more or less effaced at a very 
early age. This is notably the case with birds, fishes, and, of mammals, 
with the cetacea and elephants. 

* The sutures in the female skull are really identical with those of 
the male. Still it is not impossible that A.'s statement may have been 
founded on some single observation. For it is by no means uncommon 
for the sutures on the vertex to become more or less effaced in pregnant 
women ; so common indeed is it, that the name ' puerperal osteophyte ' 
has been given to the condition by Rokitansky {Path. Anat. iii. 208, 
Syd. Soc. TransL). 

^ A. is ridiculed by Galen for having made the brain no more than 

a spongeful of cold water. It is plain, however, that in reality he 

assigned to it an otilice scarcely less important than that he attached 

to the heart. It is true he made this latter the actual sensory centre, 

Ε 2 


The fluids which are present in the animal body at the 
time of birth have now nearly all been considered. Amongst 

10 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 

15 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 Genera- 
tion,^ 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. 

We have now to consider the remaining homogeneous 8 
20 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 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 
25 in the same way as the pupil 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 com- 

but he represented it as so directly dependent upon the brain for the 
discharge of its functions, and as so instantaneously affected by any 
change which occurs in this organ, that heart and brain came as it 
were to form one consolidated organ. 

' G.A. i. 17 - ii. 3, iv. 8. 

^ Not meaning that the other special senses are only modifications of 
touch or general sensibility. For this view, entertained by Democritus, 
is expressly repudiated by A. {De Sensu, 4. 442=* 29). 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 with- 
out any other (De Ati. iii. 13. 435^ i ; ii. 3. 415*3; H. A. i. 3. 489^* 17) ; 
and secondly, loecause it is by touch that we are able to recognize the 
four primary properties of matter {De Afi. ii. 11). 

BOOK Π. 8 653» 

bined, that is it answers to the pupil with the whole 
transparent medium attached to it. Now in the case of 
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 corporeal 
substance, or at any rate it is more corporeal than any 
other, and its medium must be corporeal like itself.^ 

It is obvious also to sense - that it is for the sake of the 30 
flesh that all the other parts exist. 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 hard- 35 
ness ; and in animals that have no bones the same office is 
fulfilled by some analogous substance, as by fish-spine in 
some fishes, and by cartilage in others. 

Now in some animals this supporting substance is situated 
within the body, while in]some of the bloodless species it is 654^* 

' A.'s statements as to the relation of the flesh to Touch are by no 
means clear. The flesh is sometimes (ii. i. 651''' 20) spoken of as the 
Sense-organ (αίσθητηριον) of Touch ; sometimes this is strenuously 
denied (ii. 10., oso'' 25) and it is said to be the medium (τι) μεηιξύ 
τοΰ άπτικού). Here it is suggested that it is medium and organ com- 
bined ; and this seems to be the view to which A. inclines, the 
outer mass of flesh being the medium and some undefined and purely 
hypothetical part of it, situated internally in close proximity to the 
heart (evBou, πρυς tjj καμ8ία), being the organ. Medium, organ, and 
heart being thus in continuity with each other, any motion of the 
medium affects organ and heart not in succession but simultaneously, 
just as a blow on a shield in immediate contact with the body affects 
shield and body together. A. held [Df G. et C. i. 7) that nothing 
could be set in motion except by an agent generically homogeneous 
with itself. In sensation the object of sense sets the medium in 
motion, and then the motion of the medium is communicated to the 
sense-organ (/> yi;/. ii. 7j. The medium then and the sense-organ 
must be generically alike. Now, wherever an animal may be, its eye 
and ear find media of corresponding nature to themselves in the 
external air or water ; but the sense-organ of Touch being a corporeal, 
that is a solid, substance requires a solid medium, and this it can 
only have if attached to itself and carried about as part of the body. 

- Besides having its right to precedence logically demonstrable, as 
stated a few sentences back. 

•* Reading τον μαλακοί•. 


placed on the outside. The latter is the case in all the 
Crustacea,^ as the Carcini {Crabs) and the Carabi {Prickly 
Lobsters) ; it is the case also in the Testacea, as for in- 
stance in the several species known by the general name ot 
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. 

5 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 arrangement in another and 
distinct tribe of animals, namely the Tortoises, including 

10 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 main bulk 
of the body consists of a soft flesh-like substance, or rather 

IS of a substance which is intermediate to flesh and sinew, 
so as not to be so readily destructible 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, this 
being the most advantageous condition, so far as strength is 
concerned. These animals have also a part inside them 

2o 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 

' Cf. iv. 8. 683'^ 25 note. ^ ς^^ };;_ c). 671» 32 note. 

"^ Cf. iii. 4. 6661^ 13 note. 

* Read τό for τά and yerof after πολι/ττόδω»/ (Piatt). 

" Cf. iv. 9. b^Y 5 note. 

BOOK Π. 8 654=^ 

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 25 
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 30 
this is to make the body of the insect less liable to get 
broken into pieces. 

9 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 thing in itself, but each is 
either a portion of what may be considered a continuous 35 
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 654^ 
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 5 
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 derived from this centre that 
hinders the blood from coagulating ; indeed the blood, 
when \vithdrawn from its influence, becomes manifestly 10 
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 holds together the whole length of 
an animal and preserves its straightness. But since it is 
necessary that the body of an animal shall bend during 

15 locomotion, this chine, while it is one in virtue of the con- 
tinuity 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, in such animals as have these 
parts, proceed, and with it they are continuous, being fastened 
together by the sinews where the limbs admit of flexure, and 

20 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 hucklebone,^ 
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 per- 
formed with great difficulty. There are some joints, again, 
in which the lower end of the one bone and the upper end 

25 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 
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 

30 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, 

35 when the parts are motionless, act as a protection. The 

' Read συνιχη irpos αυτήν τα τούτων οστά των μορίων (Ζ) ΐστίν, fj 'ίχ(ΐ 
τα κωΚα κάμψιν σ-υνδ(8ΐμίνα tois (SU) vevpois κτλ. 

^ i. e. Ball and socket joints, as of hip and shoulder. The next form, 
containing an astragalus, is the ankle joint. The third kind mentioned 
includes arthrodial joints, e. g. the sterno-clavicular, carpal, &c., but 
probably refers more especially to the knee-joint with its semilunar 

•* Cf. iv. 10. 690^ 10 note. 

BOOK II. 9 654^ 

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. 655* 
The Avails 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 part after a meal, nor, in 
females, any interference with the growth of the foetus, 
which is lodged here. 

Now the bones of viviparous animals, of such, that is, as 5 
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 10 
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, 15 
that, when struck, they give off sparks, as though they 
were stones. It may be mentioned also that the Dolphin, 
inasmuch as it is viviparous, is provided with bones and not 
with fish-spines. 

In those sanguineous animals, on the other hand, that 
are oviparous, the bones present successive'slight variations 
of character. Thus in Birds there are bones, but these are 
not so strong as the bones of the Vivipara. Then come the 
Oviparous fishes, Avhere there is no bone, but merely fish- 20 
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 

' i.e. Of the truly viviparous, not the ovo• viviparous such as the 
Selachia, whose bones are cartilaginous. Cf. iv. i. 676^ 3 note. 


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 

25 again requires the framework that supports the body to be 
made of a pliable and not of a brittle substance. Moreover, 
in these Selachia ^ nature has used all the earthy matter on 
the skin ; and she is unable to allot to many different parts 
one and the same superfluity of material.- Even in vivi- 
parous animals many of the bones are cartilaginous. This 
happens in those parts where it is to the advantage of the 

30 surrounding flesh that its solid base shall be soft and muci- 
laginous. Such, for instance, is the case with the ears and 
nostrils ; for in projecting parts, such as these, brittle sub- 
stances would soon get broken. Cartilage and bone are 
indeed fundamentally the same thing, the differences 
between them being merely matters of degree. Thus 
neither cartilage nor bone, when once cut off, grows again.^ 

35 Now the cartilages of these land animals are without 
marrow, that is without any distinctly 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 Sela- 
655^ chia 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, whether solid or cloven, horns, and the 

^ 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. 

^ 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 
Geofifroi St. Hilaire or to Goethe; the former of whom spoke of it as 
' la loi de balancement organique ', while the latter expressed it in 
these terms, ' Nature must save in one part in order to spend in 
another.' As a matter of fact, the law, whether true or false, is 
perfectly recognized by Aristotle, and is used by him over and over 
again in explanation of morphological phenomena. 

' So also Hippocrates {Aphor. vii. 28) ; where, as also in the Coacae 
Praenotiones (Kiihn i. 319), the word used is, as in this passage and 
H. A. iii. 8. 5 ιό'' 33, άποκοπ/}, i. e. excised. But διακοπή— cut through— 
is used in another Aphorism (vi. 19) and is the object of the hostile 
criticism from which Galen somewhat weakly defends Hippocrates 
(Kuhn xviii, Part i. 30). 

BOOK II. 9 655^ 

beaks of birds, all of which are intended to serve as means 
of defence. For the organs which are made out of these 5 
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 mastication 
of the food, while in others they have an additional office, 
namely to serve as weapons ; as is the case with all animals lo 
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 more developed in four-footed vivipara than in man. 
For there is always more earth in the composition of these 15 
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 inquire into the 
causes which produce them, and into the objects of their 
presence severally in the bodies of animals. For, as with 20 
the heterogeneous parts, so with these, it is from a con- 
sideration 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 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 25 
suitable place for their examination, seeing that the former 

' Cf. as to Bladder, iii. 8 ; Membrane, iii. 1 1 ; Hairs, ii. 14 ; Feathers, 
iv. 12.692'' 10 sq. ; Nails, iv. 10. 687^23 sq. ; Hoofs, iv. 10. 690!* 4; 
Horns, iii. 2; Beaks, iii. i. 662» 29 sq.; Teeth, iii. I. 661* 34 sq. 

2 G. A. i. 17-ii. 3, iv. 8. 


of the two is the very foundation of the thing generated, 
while the latter is its nourishment. 

Let us now make, as it were, a fresh beginning, and con- lo 
sider the heterogeneous parts, taking those first which are 
the first in importance. For in all animals, at least ^ in all 

30 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. Intervening ^ 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 

35 part for the discharge of waste residue. For the food 
which they absorb from the ground is already concocted, 
and they give off as its equivalent their seeds and fruits. 
6s6* 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, how- 
5 ever, that not only live but feel, present a greater multi- 
formity 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 

10 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 
the 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 

^ For και read toIs ye, 

^ This sentence is transposed from 11, 36-37. 

BOOK II. ΙΟ 656" 

the necessary consequence of what has ah-eady been stated ^ ^5 
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 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 sensa- 
tion, they say, cannot penetrate to parts that are too 
thickly covered with flesh. But neither part of this state- 
ment is true. On the contrary, Avere the region of the 20 
brain thickly covered with flesh, the very purpose for which 
animals are provided with a brain would be directly con- 
travened. For the brain would itself be heated to excess 
and so unable to cool any other part ; and, as to the other 
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 as 
head, and are unable to discern the 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 

1 Cf. ii. 7. 

^ e.g. Plato in the Tiinaeiis (75 B), who probably borrowed the 
opinion, as Galen says he did his physiology generally, from Hippo- 
crates. Democritus also had taught that the sovereign part of the 
soul was in the head ; and Diogenes of ApoUonia, more directly, had 
held that the brain was the seat of sensation, being surrounded by 
a layer of hot dry air, which was in connexion with the sense-organs 
by means of the blood-vessels, and so sympathized with their motions 
and affections (cf. Grote's Plato, i. 65). 

^ A.'s chief reasons for refusing to admit that the brain was the 
sensory centre were as follows. (l) It was insensible to touch (ii. 10. 
656* 23 ; ii. 7. 652'' 5). (2) There was no brain or analogous organ in 
any of the bloodless animals, cephalopods excepted (ii. 7. 652^ 25). 
(3) It was cold and bloodless (ii. 7. 652'^ 33). (4) It was not anatomi- 
cally connected with the sense-organs, notably with those of touch and 
taste (ii. 7. 652'' 3). 

On the other hand, the heart (l) was palpably affected in emotion or 
when pain or pleasure was felt (iii. 6. 669=^ 19) ; (2) was present, or an 
analogous organ, in all animals (iii. 4. 665•^ 10 ; G. A. iv. 4. 771^ 3) ; 
(3) was the source of heat and of the blood (iii. 5. 667^ 26) ; (4) was in 
anatomical connexion, through the blood-vessels, with all the sense- 
organs {G. A. ii. 6. 744»• 3) ; (5) was the first part to be formed in the 
embryo, the ' primum vivens, ultimum moriens ' {G. A. ii. 5. 741^^ 20) ; 
(6) was in a central position befitting the supreme organ (iii. 7. 
670» 24). 


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 

30 the sensory centre. There also it was stated that two of 
the senses, namely touch and taste, are manifestly in imme- 
diate connexion with 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 invari- 
ably the case with hearing or with smell. For fishes and 

35 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 
656^ of the brain is but what one would rationally expect. For 
the brain is fluid and cold, and vision is of the nature of 
Avater, water being of all transparent substances the one 
most easily confined. Moreover it cannot but necessarily 
be that the more precise senses will have their precision 
5 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 head, it is this head which more than any other 
part requires to be held up. But, were the head heavily 

10 laden with flesh, this would be impossible ; for nothing so 
burdened can be held upright. This is an additional proof 
that the absence of flesh from the head has no reference to 

^ Cf. De Sensii, 2. 439^ i. 

^ 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. 533^^ i), 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 (πόροι) 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. 659^ 16 note). 


BOOK II. ΙΟ 656* 

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 

In some animals hearing as well as vision is lodged in 
the region of the head. Nor is this without a rational '5 
explanation. For what is called the empty space is full 
of air, and the organ of hearing is, as we say, of the nature 
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 some one of the parts 20 
that are formed of blood. •^ 

^ An error borrowed from Hippocrates (Kiihn's edit. i. 183); but 
very possibly deriving support from examination of the brain of 
cold-blooded animals. 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 
Mammals and Birds {Phil. Zool. i. 276, Martin's edit.). In the 
tortoise, for instance, the area of a vertical section of the brain, ac- 
cording to Desmoulins (Todd, Cyclop, of An. and Phys.'x. 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 pro- 
portionate to that of the cranium itself. That A. had noticed this is 
probable from his saying {G. A. ii. 6. 744* 17) 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 
Α., and with whose so-called brain he was acquainted, the cavity in 
which the ganglia are lodged is much larger than the ganglia them- 

^ Frantzius, following Schneider, interprets these channels or τιόροι 
to mean nerves, and, were the iropoL of the eye alone in question, there 
are passages {H. A. i. 16, 495=* 11-18 ; G. A. ii. 6. 744» 9) which would 
make this view highly probable. But A. {G. A. ii. 6. 743'' 36) speaks 
of all the sense-organs as being on πόροι, and describes the ττόροι of the 
ears and nose as full of connate air, and running to the blood-vessels 
on the outside of the brain and so communicating with the heart. 
The present passage, moreover, seems to imply that the internal auditory 
πόρο? is of the same character as the external auditory meatus, that is 
to say is an air-duct. Meyer ( Thie>kutide, p. 42S) takes the ττόροι to be 
blood-vessels. It seems, however, unnecessary to assume that some one 
exclusive structure applicable to all the sense-organs is indicated. The 
nerves of the eye, the supposed air-ducts of the ears and nose, the 
blood-vessels of the organs generally, are all πόροι ; all, that is, are 
channels by which the sense-organs communicate with the heart, 
either directly or with the intermediation of the φλίβια τα π(ρ\ τον 
(-γκΐφαλορ (G. Α. ϋ. 6. 744"' 4)• 

^ The argument is this: The channels from the eyes end in the 


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 

25 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 well-ordered manner. 
The organs of hearing are so placed as to divide the circum- 
ference of the head into two equal halves ; for they have to 
hear not only sounds which are directly in a line with 

30 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 direc- 
tion it is necessary that we should see before us, in the 
direction of our motion. Lastly, the organs of smell are 
placed with good reason between the eyes. For as the 
body consists of two parts, a right half and a left, so also 

35 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 in- 
ternally.^ In the case of taste, which is merely a modifica- 
tion of touch and which is placed in the tongue, the fact 
is more apparent than in the case of touch, but still not 
657* so manifest as in the case of the other senses. However, 
even in taste it is evident enough ; for in some animals the 
tongue is plainly forked. The double character of the 
sensations is, however, more conspicuous in the other organs 
of sense. For there are two ears and two eyes, and the 
nostrils, though joined together, are also two. Were these 
5 latter otherwise disposed, and separated from each other as 

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 connexion with the interior of the cranium. 

A short sentence is here omitted, as being partly unintelligible, 
partly empty iteration. Part of it, moreover, is wanting in E, one of the 
best MSS. 

^ Cf. ii. 8. 653^' 30 note. 

BOOK II. ΙΟ esr 

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 lo 
central of the three sense-organs, setting them side by side 
on a level with each other, to avail themselves of the 
inspiratory motion. In other animals than man the arrange- 
ment of these sense-organs is also such as is adapted in 

11 each case to the special requirements. For instance, in 
quadrupeds the ears stand out freely from the head and are 
set to all appearance above the eyes. Not that they are in 15 
reality above the eyes ; but they seem to be so, because 
the animal does not stand erect, 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 movable ; for by turning themselves about 
they can the better take in sounds from every quarter. 

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 20 
have not got the proper material for the formation of ears. 
Exactly the same is the case with such oviparous quadru- 
peds as are clad with scaly plates, and the same explanation 
applies to them. There is also one of the viviparous quad- 
rupeds, 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 

13 Men, and Birds, and Quadrupeds, viviparous and ovi- 25 
parous 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 the oviparous quadrupeds, and 
the heavy-bodied birds ^ as well as some others, use only 

' That is the Gallinaceous birds (//. A. ii. 8. 613^ 6). 

AR. P.A. V 


3D the lower lid to close the eye ; ^ while birds blink by means 
of a membrane that issues from 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 

35 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, 
5gyb 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 re- 
semble 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 growth of the feathers are diverted thence, and 

10 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 

^ In birds, as a rule, as also in Chelonia, in crocodiles, and in frogs, 
the lower lid is much larger and more movable than the upper, and 
it is with it therefore that the eye is closed in sleep. There are, how- 
ever, some few exceptions, and of these the owl is one, as noticed by 
A. elsewhere {H. A. ii. 12. 504* 26). A few sentences later it is said 
that pigeons use both lids to close the eye, which is also a correct 

^ This is an unfortunate statement, borrowed however from Hippo- 
crates (Kiihn'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 the prepuce can be made to unite by proper appliances. 

BOOK Π. 13 657* 

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. i- 

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 canthus that 
is nearest to the nostrils that the membrane comes. For it 
is better to have one starting-point for nictitation than two ; 20 
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 birds, inasmuch as they have to use their eyes 25 
at long distances. This too explains why birds with talons, 
that have to search for prey by eye from aloft, and there- 
fore 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 Avhich 
imperatively requires it. 30 

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 Crustacea 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 

^ And by all other birds also (cf. N. A. ii. 12. 504•"^ 26). 

^ 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. 

^ There are exceptions among fishes, particularly in sharks. 

* Read ταχ€ΐίΐν την ^(ρμητίκην (χα f'pyaainv. 

F 2 


no eyelids and, in default of this protection, their eyes are 
35 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 sharp- 
ness of vision, nature has endowed the eyes of Insects, and 
658* still more those of Crustacea,^ with mobility (just as she 
has given some quadrupeds movable 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 consistency. For animals that move much about 
have to use their vision at considerable distances. If now 
5 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 eyelids to fishes, 
while to counterbalance the opacity of the water she has 
10 made their eyes of fluid consistency. 

All animals that have hairs on the body have lashes on 14 
the eyelids ; but birds and animals with scale-like plates, 
being hairless, have none.^ The Libyan ostrich, indeed, 
forms an exception ; for, though a bird, it is furnished with 
eyelashes. This exception, however, will be explained 
15 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 pro- 
tection to its possessor. Now, in quadrupeds, owing to 

* A.'s knowledge of Crustacea was confined, or nearly so, to 
Podophthalmata, in which the eyes are supported on movable 
peduncles. Insects have, almost invariably, sessile and motionless 
eyes ; and though in a few instances the eyes are on peduncles, these 
peduncles are not movable like those of Crustacea. 

^ Birds, as a rule, have no eyelashes. There are, however, a few 
exceptions, and of these the Ostrich is one.— Casaubon rightly 
explains the construction — ' voluit dicere et scripsisset alius, opvides fie 
ovK ΐχονσιν ovde των φολιδωτών ονδ^ν '. 

BOOK II. 14 658=» 

their inclined attitude, the under or anterior surface does 30 
not require so much protection as the back, and is therefore 
left comparatively 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 therefore 
has assigned the protective covering to the nobler of the 
two surfaces ; ^ 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 ; 25 
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 30 
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 35 
gives to one part what she subtracts from 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 tail. This, for instance, in the case with 658'' 

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 5 

^ Cf. ii. 2. 648=* 13 note. 

^ 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 [H. A. ii. 8. 502»• 31) recognized 
by Α., 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. 


greatest outgrowth. But, secondly, the thickness of the 
hah• in this part has a final cause, being intended to protect 
the head, by preserving it from 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 sub- 
stance is, the more readily does it get excessively heated or 
10 excessively chilled, while substances of an opposite character 
are less liable to such injurious affections. 

These, however, are matters which by their close con- 
nexion with eyelashes have led us to digress from our real 
topic, namely the cause to which these lashes owe their 
existence. We must therefore defer any further remarks 
we may have to make on these matters till the proper 
occasion arises and then return to their consideration. 

Both eyebrows and eyelashes exist for the protection of 15 

15 the eyes ; the former that they may shelter them, like the 

eaves of a house, from any fluids that trickle down from 

the head ; ^ the latter to act like the palisades which are 

sometimes placed in front of enclosures, and keep out any 

objects which might otherwise get in. The brows are 

placed over the junction of two bones, which is the reason 

20 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 

25 operation of nature which interferes, by diverting the 

moisture to another purpose. 

' The explanation and the comparison are borrowed from Xenophon 
{Me?)i. i. 4. 6), who puts them into the mouth of Socrates. 

^ A. knew that the blood passed from the heart to the various parts 
by the vessels, but scarcely recognized its returning. Thus when the 
blood reached the peripheral ends of the vessels, it had to be disposed 
of 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 (ii. oso'* 22 note). So also 
was it regarded by Bacon {Nal. Hist. cent, i, sect. 58) and Shake- 
speare — ' Your bedded hair, like life in excrements, 

Starts up, and stands on end ' {Hamlet iii. 4). 

BOOK Π. i6 658'' 

16 Viviparous quadrupeds, as a rule, present no great 
variety of form in 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 30 
its nostril as a hand ; this being the instrument with 65^ 
which it conveys food, fluid and solid alike, to its mouth. 
With it, too, it tears up trees, coiling it round their stems. 
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 has to 
get its food from 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 5 
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 ro 
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 pro- 15 
boscis, as already said, is a nostril. Now it would have 

' The elephant is much given to bathing : but A. appears to have 
entertained an exaggerated idea of its aquatic habits, and to have mis- 
interpreted its reasons for betaking itself to the water ; imagining that 
it went there not merely to slake its thirst or for the luxury of a cold 
bath, but because it depended, of course in its wild state, on water- 
plants for its sustenance ! 

- 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 (Tylor, Anthrop. p. 208) are said 
to be able to swim for a distance under water, so as to approach 
a flock of ducks without being seen. 

^ Cf. H. A. ix. 46. 630'' 27. The elephant does in fact use its trunk in 
the way described when crossing a deep river (cf.TennentjC^y/i^/^ii. 3 10). 


been impossible for this nostril to have the form of a pro- 
boscis, 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 

20 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 intended not merely to support 

25 the weight of the body, but to serve as hands. But in ele- 
phants, 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 

30 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 already said, made 

3.=) 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, 
659^^ 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 distinctly formed nostrils, nothing in fact which 
can be called nostrils except from a functional point of 
5 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 story comes from Herodotus (iv. 183). 

* Although the toes are not separate nor clearly defined, άσχίστονς 
και ηρ(μα διηρθρωμίνονς. (Cf. //. Α. ill. 9. 5 '7'' 32•) 

' Α. does not mean that the elephant has no joints in its legs, for 
he specially repudiates this vulgar error {H. A. ii. i. 498* 9). 

BOOK II. i6 659^ 

this makes it necessary that their head and neck shall be 
of light weight ; just as it makes it necessary that their 
breast^ shall be narrow. 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 10 
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 15 
a blow-hole, or, if they are insects, by the hypozoma ; ^ and 
how the power of smelling depends, like their motion, 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 20 
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 

^ Cf. iv. 12. 693'' 17 note. 

* Perhaps this refers to De Sfusu 5. 444^ 6 sq. 

^ By hypozoma A. designates no distinct organ or structure, but the 
indefinite mid part of the trunk, that in the human body is called the 
waist, but in other animals has no name. In insects this region is 
marked by a narrow constriction, but A. also speaks of a hypozoma in 
fishes where there is no such constriction {G. A. i. 8. 718'' l). It is 
not difficult to understand why A. located the sense of smell in or near 
this region of the insect's body. Arguing by analogy from the higher 
animals, A. believed that the organ of smell was inseparable from the 
organ of respiration, or, in the lower animals, of refrigeration. He 
accordingly located smell in the gills of fishes, in the blowpipe of 
Cetacea, and in insects, in a specially thin part of the integument, 
covering a fissure just below the hypozoma, and serving, as he thought, 
for escape of heat and production of sounds {De Resp. 9. 475^^ 1-19 ; 
H. A. iv. 9. 535^ 8). This refers to the so-called 'drums' of cicadae and 
the ' tympana ' of grasshoppers, to which A. apparently supposed there 
was something correspondent in other insects ; meaning perhaps the 
thinner integument between the successive rings of the abdomen. The 
alternate contractions and dilatations, which are visible in an insect's 
abdomen, and which are in reality respiratory, were attributed by him 
to the refrigerating motion of the 'connate spirit'. It must be by 
inadvertence that the blowpipe of Cetacea is mentioned, for A. is 
speaking of animals that have no lungs, and he well knew that 
Cetacea were not of these. 


25 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, narrowing them on 
either side and making them project forwards, supposing, 
I say, ?his to be done, we should at once have a bird-like 

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 

30 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 
of¥ice, contributing in common with other parts to man's 

35 faculty of speech. For just as nature has made man's 
tongue unlike that of other animals, and, in accordance 
660* with what I have said ^ is her not uncommon practice, has 
used it for two distinct operations, namely for the per- 
ception 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 
5 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 applica- 
tions of the tongue. But what are the differences presented 
by these and what the nature and extent of such differences, 
are questions to which answers must be sought from those 

10 who are versed in metrical science.^ It was necessary that 
the two parts which we are discussing should, in con- 
formity with the requirements, be severally adapted to 
fulfil the office mentioned above, and be of appro- 
priate character. Therefore are they made of flesh, and 
flesh is softer in man than in any other animal, the reason 

' Cf. 659=^ 21. 

^ The so-called Metrical Science had for its province everything 
relating to words considered merely as sounds, and ranged therefore 
from prosody and the laws of versification back to the elementary 
vocal sounds and the mechanism of their production. Cf. Poetics 20. 

BOOK II. i6 660-» 

for this being that of all animals man has the most delicate 
sense of touch. 

17 The tongue is placed under the vaulted roof of the 
mouth. In land animals it presents but little diversity. 15 
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 20 
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 25 
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 there are certain letters which they cannot 
pronounce. 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 30 
as have 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. All birds use 33 
their tongues to communicate with each other. But some 
do this in a greater degree than the rest ; so that in some 660^ 
cases it even seems as though actual instruction were 

^ In parrots, included by A. among the birds with talons, the tongue 
is 'epaisse, charnue et arrondie ; deux circonstances qui leur donnent 
la plus grande facilite a imiter la voix humaine' (Cuvier, Re^. An. i. 461), 

2 Cf. //. A. iv. 9. 536^ 24. 


imparted from one to another by its agency. These, 
however, are matters which have ah-eady been discussed in 
the Researches concerning Animals.^ 

As to those oviparous and sanguineous animals that h've 
5 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 
savours. 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 great 
liking for dainty food. For by this arrangement they 

lo derive a twofold 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 

15 what exists in river crocodiles. In most of these cases the 
apparent absence of the part can be rationally explained 
on some ground or other. 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 

20 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, the projection of 
this part is quite invisible. The region exposed by thus 

* Cf. H. A. ii. 12. 504^^ I ; iv. 9. 536^ 20-*^ 19 ; ix. i. 608* 17. 

■•* Cf,//. ^. ii. 13. 505*31. Many fishes have no tongue. In none is it 
protrusible, being at best an insignificant h'gamentary or cellular body, 
scarcely projecting from the glosso-hyoid. Cf. Owen {Vert. i. 41 ij, 
Cuvier {An. Comp. ii. 681), Gunther {St. of Fishes, p. 119). 

BOOK II. 17 660" 

opening the mouth is spinous ; for it is formed by the close 
apposition of the gills, which are of a spinous character. ^5 

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. For its upper and lower jaws are, as it were, 
inverted, it being the upper jaw which in other animals is 
the immovable one. The tongue, however, of this animal 
is not attached to the upper jaw, because that would 30 
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 

The roof of the mouth resembles flesh, even in many of 35 
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 661* 
tongue of fishes, however, though it exists as a separate 
part, is never formed with such distinctness as 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 5 
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, by which food produces the sensation is not 
precisely alike in all of them, but while in some it is free 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. 648'^ 11 note). 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 

'^ In the Cyprinoids the palate is cushioned with a thick soft vascular 
substance, remarkable for its great irritability. This is still commonly 
known in France as ' langue de carpe ' (Cuvier, Λ'. A/i. ii. 270). 


from attachments, in others, where it is not required for 
vocal purposes, it is adherent. 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 

15 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, and is hollow and spongy, so as to 
serve at one and the same time for the tasting and for 

20 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 the gad-flies 
and cattle-flies^ can pierce through the skin of man, and 

25 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 sting. 
In all other animals the tongue agrees with the 

30 description already given. 

' Under Purpura are probably included all the various species of 
Murex and Purpura from which purple dye was obtainable. Of these 
the most important seem to have been M. tniitadus and M. bmndaris 
(Woodward, R. &^ F. Shells, p. 106). As to the power possessed by 
P. lapillus of boring through shells by means of its armed tongue, see 
Forbes and Hanley, Brit. Mollusca, iii. 385. 

^ By Oestri and Myopes, translated vaguely as Gad-flies and Cattle- 
flies, are probably meant some species or other of Tabanus. 


I We have next to consider the teeth, and with these the 
mouth, that is the cavity which they enclose and form. 35 
The teeth have one invariable office, namely the reduction δβΐ'' 
of 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 5 
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 
office, 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 the 
dog-teeth, which, in accordance with the rule that the mean 10 
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 even of these sharp teeth have 
been mainly determined by the requirements of speech. 
For the front teeth of man contribute in many ways to the 15 
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 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 20 

* That is * broad below and sharp above ' (//. A. ii. 3. 537'' 17). 


these depend for their efficiency 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 has sharp interfitting teeth is at the same 
time furnished with tusks. For nature never makes anything 

25 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 

30 others that will occur later on. Nature allots each weapon, 
offensive and defensive alike, 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 that such parts as those just mentioned 
are found, either exclusively, as in some species, or more 
fully developed, as in others. For though females are of 

35 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 
662^ 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 
5 them, and accounts for similar facts relating to all 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 Scarus is doubtless the parrot-fish {Scams Cretensis). This 
is, however, by no means the only exception to the general statement 
that all fishes have serrated dentition. 

BOOK III. I 662=» 

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 lo 
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 a time while triturating the 
food, the water would run into their digestive cavities. 
Their teeth therefore are all sharp, being adapted only for 
cutting,^ and are numerous and set in many parts,^ that their 
abundance may serve in lieu of any grinding faculty, to 
mince the food into small bits. They are also curved, 
because these are almost the only weapons which fishes 15 

In all these ofifices 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 20 
has one universal function in all animals alike, namely its 
alimentary ofifice ; 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 con- 25 
tracted, 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 

' Reading Bmipeaiv μόνον, κηί (Ρ). 

^ 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 towards the oesophagus. 

* Namely, at ii. 16. 658^ 35, when speaking of the elephant's trunk. 
Similar statements are made (iv. 10. 688* 24, and ogo'^ 2) concerning 
the female mammae, and the tails of animals. 

■• i. e. not of necessity. 


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 

30 shall have a wide opening ; for the Avider 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 carni- 
vorous, 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. 

35 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 
662^ 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 this form renders it service- 
able 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 
5 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 crow-like habit, while in the smaller 
birds it is delicate, so as to be of use in collecting seeds 

10 and picking up minute animals. In such birds, again, 
as eat herbage, and such as live about 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 

^ i. e. the Raptores. 

^ 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. 

BOOK III. I 662' 

on roots. Moreover, in these root- eating birds and in some 15 
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 {prosopoji) being, it would seem, derived 20 
from the function of the part. For as man is the only 
animal that stands erect, he is also the only one that looks 
directly in front {proso) ; and the only one whose voice 
is emitted in that direction. 

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 25 
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 fur- 30 
nished with horns. For horns are defensive weapons, 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 other adequate 
defensive appliance. There are horns, however, in most of 35 
the cloven-hoofed animals, and in some ^ of those that have 663^ 
a solid hoof, serving them as an offensive weapon, and 
in some cases also as a defensive one. There are ho^ns 

^ 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 horns {H. A. iv. 2. 526^ 6). He alludes, however, 
more especially to the Egyptian snake (//. A. ii. i. 500^ 3) : ' Thus the 
Egyptians speak of the snakes about Thebes as horned, 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. 

"^ Under Polydactyla are included Carnivora, Rodentia, Insectivora, 
Cheiroptera, as well as man, apes, and elephants ; in fact all Mammalia 
known to A. excepting Ruminantia, Solidungula, and Cetacea. 

^ Meaning the Indian Ass. Cf. 663^ 20 note. 


also in all animals that have not been provided by nature 
v^'ith some other means of security ; such means, for instance, 
as speed, which has been given to horses ; or great size, as 
5 in camels ; for excessive bulk, such as has been given 
to these animals, and in a still greater measure to elephants, 
is sufficient in itself to protect an animal from being de- 
stroyed by others. 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 append- 
ages, have been provided by nature with some additional 

lo 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 ; 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 pugnacious. 

15 The Bonasus^ again, whose horns curve inwards towards 
each other,'' is provided with a means of protection in the 
discharge of its excrement ; and of this it avails itself when 

^ And therefore, he imphes, might be expected to have horns, Hke 
most cloven-hoofed animals. Read διχαλον 'όν. 

'^ It is somewhat astounding to find so determined a teleologist 
suddenly declaring that antlers are not merely useless but actually 
injurious to stags. A modern writer, however (Bailly, Sur Vusage des 
comes, 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, not 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. 

^ The Bubalus must not be confounded with the Buffalo {Buba/us), 
which was known to A. as the wild ox of the Arachotae [H. A. i. 2. 
4998• 4). It is probably an Antelope, perhaps the Bubaline Antelope 
of N. Africa. 

* The Bonasus {H. A. ix. 45) is universally admitted to be the 
European bison, 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 (//. A. ii. 
I. 500^ i) as living in his days in Paeonia and Medica, i.e. North 

" And are therefore of no use as weapons. 

BOOK III. 2 663^ 

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 20 
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 25 
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, whether solid or cloven, is 
of the same nature as horn ; so that the two naturally 
undergo division simultaneously and in the same animals. 30 
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 35 
to set the horns ; and i^sop's Momus ^ is beside the mark, 

^ The account of the Indian Ass with a solid hoof, and a single 
horn, was taken by A. from Ctesias, 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 (Λ*, 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 observation. 

2 Probably the Leucoryx of N. Africa. 

^ The fable of Momus, the critic God, is alluded to by Lucian 
(Nigrinus, 32), and told in full by Babrius (Sir C. Lewes's ed. 59). 
Their account of the criticism on the bull's structure is not quite the 


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, 
663^ 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 
5 increased; not only without any compensating gain whatso- 
ever, 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 

10 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 
throughout, 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. 

'.=5 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, though it grows 
out '^ of the skin, 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 

same as Aristotle's. Momus objects that the horns are so placed 
as to be in the way of the animal's sight when it has its head down to 
attack its foe. 

^ άvtμπόbιστa, in spite of its form, is here supposed to be used in an 
active sense on the authority of I3onitz (56^ 6) and of Liddell and 

- Omitting oli before πίφυκ^ν (EPYZ), cf. H. A. ii. i. 500•'' 8. For 
(Ivni read eVriV (Piatt). 

BOOK III. 2 663^ 

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 20 
such the reasons why they are present in some animals, 
absent from others. 

Let us now consider the character of the material nature 
whose necessary results have been made available by rational 
nature for a final cause. 

In the first place, then, the larger the bulk of animals, the 
greater is the proportion of corporeal and earthy matter 25 
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 specula- 
tions concerning nature, what we have to consider is the 
general rule ; for that is natural which applies either uni- 
versally or generally. And thus when \ve say that the 
largest animals have most earthy matter, we say so because 30 
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 35 
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 664* 
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 5 
this is that they, as much as the males, are naturally horn- 
bearing animals ; but they have been stripped of their 

^ ' The inverse relationship between the development of teeth and 
horns, exemphfied by the total absence of canines in the ruminants 
with persistent frontal v.'eapons, 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 
Camelidae' (Owen Veri. iii. 348). 


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 less 
of an impediment. In other animals, where this material is 
not secreted from the body in the shape of horns, it is used 
10 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. 

So much, then, of the parts which appertain to the head. 

Below the head lies the neck, in such animals as have 3 
15 one. This is the case with those only 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 
20 discharge the air. Therefore it is that, when there is no 
lung, there is also no neck. Of this condition the Fishes 
are an example. The other part, or oesophagus, 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 
25 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 — it being bipartite — the 
breath may be apportioned to their respective bronchi, and 
thence pass into the air-pipes ; and such an arrangement 

^ In some cases. 

2 The word here 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, &c., 
can only be what we call larynx. Yet the word larynx was known to 
Α., 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. 535=* 29, 32, and Aristophanes, Frogs, 57 175)» 
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 

BOOK III. 3 664* 

will be the best for giving perfection to inspiration and 
expiration. The organ then concerned in respiration must 30 
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 extension 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 35 
pass downwards, 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 664'' 
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, 5 
choking and much distress and violent fits of coughing 
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 men- 
tioned occur invariably, whenever a particle of food slips in, 
and are quite obvious. Indeed on many grounds it is 10 
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 15 

^ It would probably be truer to say that there is 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. does, 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. 

2 Cf. iii. 4. 666'^ 13 note. 

* Alluding to Plato {Twtaetis, 70C). Hippocrates mentions and 
attacks this same strange notion {De Morbis, iv. 30). 


bladder 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. 

20 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 sanguineous 
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 

25 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 

30 into the windpipe. 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 con- 
trived, however, is the movement both of the epiglottis and 
of the tongue, that, while the food is being ground to a pulp 

3.5 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. 
65ca 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. It 
would, indeed, take a longer time to shut down an epiglottis 
5 made of the peculiar flesh of these animals, and shaped 

^ For ζωοτοκοϋρτα, which is obviously wrong, read ζώα τα 'ίναιμα. 

•^ Mamnials alone have an epiglottis. In other vertebrates the 
opening into the larynx and trachea is closed simply by constrictor 

BOOK III. 3 665' 

like that of those with hairy skins, than to bring the edges 
of the windpipe itself into contact with each other. 

Thus much then as to the reason 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. 10 
That position is the result of necessity. For it is in the 
front and centre of the body that 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 15 
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 ^o 
oesophagus. For they lead to the lung and heart,^ whereas 
the oesophagus leads to the stomach. And it is a universal 
law that, as regards above and below, front and back, right 
and left, the nobler and more honourable part invariably 
is placed uppermost, in front, and on the right, rather than 
in the opposite positions, unless some more important 
object stands in the way. 25 

^ It is not necessary to infer with Frantzius from this passage, that 
A. thought that the windpipe communicated directly with the heart. 
For he supposed that air could pass without any such direct channel, 
as the following passages show. ' When the windpipe reaches the 
lung, it divides and subdivides, each division producing smaller and 
smaller branches, till the whole lung is permeated by them ' (//. yi. 
i. 16. 495^ 8). 'There are also ducts (i.e. tlie pulinonary 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 the two (ούδβίί δ' 
ΐστι Koivos πόρος). Notwithstanding this, however, air can pass from 
the former (i.e. /he bronchial lubes) into the latter (i.e. the pulmonary 
vessels), owing to the close contact in which the two lie (δια τψ σίνηψιν), 
and be transmitted to the heart ' {//. A. i. 17. 496•"* 28). This passage 
shows that A. not only had a fair knowledge of the anatomy of the lung, 
but also 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. 


We have now dealt with the neck, the oesophagus, and 4 
the windpipe, and have next to treat of the viscera. These 
are peculiar to sanguineous animals, some of which have 

30 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, that is 
to say, he fancied that the reason why none were dis- 
coverable in bloodless animals was that these animals were 
too small to allow them to be seen. For, in sanguineous 
animals, both heart and liver are visible enough when the 
body is only just formed, and while it is still extremely 

35 small. For these parts are to be seen in the egg sometimes 
as early as the third day, being then no bigger than 
665^ 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 
5 dififering in different animals. Viscera, then, are peculiar 
to sanguineous animals ; and therefore 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 pro- 
portion to the body, than at any later period of life, it 
being in the earliest stage ^ of formation that the nature 
of the material and its abundance are most conspicuous. 

10 There is a heart, then, in all sanguineous animals, and 

' A. 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. 665^ 6; iii. 10. 673^ i). As the bloodless animals have 
merely a fluid analogous to blood, so they can only have parts 
analogous to viscera. 

^ Cf. //. A. vi. 3. 561=^ II, where it is said that the 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 
functum saliois of later writers. 

^ The liver in the mature foetus forms ^^yth of the whole body ; in 
the adult it forms only gVth. The heart also is larger proportionately 
to the whole body in the young embryo (^^th) than in the mature 
foetus (ϊ -J^th), and in the foetus than in adult man (yloth). In infancy 
again the lungs are of a brightish colour, ' which might be compared 
to blood froth ; but as life advances they become darker, mottled with 
spots, patches, &c.' Cf. Ouain's Anat. 1145. 

BOOK HI. 4 665^ 

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 
apparently 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 15 
one such, when possible, rather than several. This primary 
source of the vessels is the heart. For the vessels mani- 
festly issue from it and do not go 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 20 
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 25 
not to be counted with the parts which are necessary for 
life. For life can be maintained even when they are re- 
moved ; 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 mani- 30 
festly 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 continue their course through the 
other viscera, but no vessel spreads through the heart. ^ 

' Cf. iii. 3. 665a 12. 2 See note 4. 

^ Elsewhere (//. A. iii. 3. ζΐ2,'^ lo) A. says that not only some but all 
his predecessors held this opinion. 

■• The terms δΐί;^ουσι and hiareivovai, used several times in describing 
the relation of the blood-vessels to the viscera, present much difficulty. 


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 

35 its structure. For its central part consists of a dense and 

hollow substance, and is moreover full of blood, as though 

666^ the vessels took thence their origin. It is hollow to serve 

for the reception of the blood, while its wall is dense, that 

it may serve to protect the source of heat. For here, and 

here alone in all the viscera and indeed in all the body, 

there is blood without blood-vessels, the blood elsewhere 

5 being always contained within vessels. Nor is this but 

consistent 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 

The natural interpretation of δΐί'χουσι would be that the vessels traverse 
the viscera and pass on to some other part ; and in the case of the 
liver such an interpretation is neither impossible nor improbable. 
For A. may have well supposed that the Hepatic vein after giving 
numerous small branches to the liver (//. A. iii. 4. 514^ 33) passed on 
as the vena pot'tae to the intestinal parts ; and indeed it is difficult to 
see what other explanation A. could find for the vena fortae ; if no 
vessel could originate in the liver and the course of all vessels was to 
the periphery. 

But in the case of the other viscera such an interpretation is im- 
possible ; for A. distinctly states that all the blood brought to kidneys 
and spleen is used up in the substance of those viscera (iii. 9. 671^ 13 ; 
H. A. i. 17. 497a 9 ; iii. 4. 514^^ 5), the viscera being indeed mainly in- 
tended to provide means of disposing of the surplus blood. 

It seems therefore impossible to give any other meaning to δί€χοΐ'σι, 
at any rate in the case of other viscera than the liver, than ' spread 
through the substance', making it equivalent to Siaruvovai as indeed 
it apparently is at iii. 4. oos'' 32. Similarly when it is said that no 
blood-vessel Biareipii the heart, it must be understood as meaning 
that no nutrient vessels are distributed through its substance (the 
coronary vessels being overlooked), this organ being nourished (ii. 
I. 647^ 6) by the blood in its own cavities. A. appears to have 
used διίχονσί ambiguously, applying it to the liver in a different sense 
from that in which he applies it to the other viscera and the heart. 

^ These words must not be interpreted too strictly ; for, though of 
course A. holds the main current of blood to run from the heart 
outwards, he admits some flow in the opposite direction. Indeed, 
without this the heart could have no material for elaboration. The 
food, absorbed from the stomach as vapour, is, he says, converted 
into fluid in the blood-vessels and passes on as such to the heart 
{De S. et V. 3. 456'^ 3). The blood-vessels that go to the head are 
likened by him to a narrow strait in which the current changes to and 
fro {De S. et V. 3. 456'^ 20) ; and the heart is distinctly stated [De S. 
et V. 3. 458^ 18) to receive blood both from the great vessel and from 
the aorta. 

BOOK III. 4 666'' 

dissections and from observations on the process of develop- 
ment that the truth of these statements receives its clearest 
demonstration. For the heart is the first of all the parts to lo 
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 have their source in the 
heart, and find in it their ultimate termination. This, indeed, 
reason would lead us to expect. For the source must, when- 
ever possible, be one ; and, of all places, the best suited for 
a source is the centre. For the centre is one, and is equally 15 
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, 20 
than its heart is seen in motion as though it were a living 
creature, and this before any of the other parts, it being, as 
thus shown, the starting-point of their nature 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 25 
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 its blood is in a vessel as in all the other viscera. 
The vessel, moreover, extends through it, and no vessel 30 
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 organ in 


other respects. For the definitive characteristic of an animal 
35 is the possession of sensation ; and the first sensory part is 
that which first has blood ; that is to say is the heart, v/hich 
666^ 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 compara- 
tively little flesh over the breast, whereas there is a more 
5 abundant covering of that substance on the posterior surface, 
so that the heat has in the back a sufficient amount of pro- 
tection. 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 
10 of that side. For the left side is colder in man, as compared 
with the right, than in any other animal. It has been stated 
in an earlier treatise ^ that even in fishes the heart holds the 
same position as in other animals ; and the reason has 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 

^ 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. 197), and in the mole. 

2 De Resp. 16. 478^ 3. 

^ By the apex of the heart of fishes A. plainly means the point at 
the anterior extremity of the organ, where the bulbus arteriosiis gives 
off the branchial artery. This, however, has no anatomical corre- 
spondence with the apex of the heart of other vertebrates. A. makes 
a similar statement as to the position of the fish's heart elsewhere 
{H. A. ii. 17. 507a 3 ; DeResp. 16. 478'^ 2), and accounts for it by saying 
that the head in other animals is moved in a vertical plane, from 
above downwards, 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 

*■ Under vfvpa A. included (iii. 4. 666^ 14 note) tendons, sinews, liga- 
ments, and all other fibrous parts ; with which, moreover, were con- 
founded any nerves which may have been noticed, without recognition 
of their special nature, in the course of dissection ; and this accounts 
for the statement {H.A. iii. 5. 5 is'' 20) that numbness is never produced 
in a part where there are no vevpa. The active part in muscular con- 
traction was taken not by the red tissue but by the vivpa, that is by the 

BOOK III. 4 666^ 

might reasonably be expected. For the motions of the 
body commence from the heart, and are brought about by 15 
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 

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 pro- 20 
vided with a bone as a support ; just as the bones serve as 
supports for the body generally.^ 

In animals of great size the heart has three cavities; ^ in 
smaller animals it has two ; and in all has at least one, for, 
as already stated,"* there must be some place in the heart 
to serve as a receptacle for the first blood ; Avhich, as has 
been mentioned more than once, is formed in this organ. 25 
But inasmuch ^ as the main blood-vessels *^ are two in 

tendinous fibres. The blood-vessels as they advanced became smaller 
and smaller, until at last their calibre was insufficient for the passage 
of blood, and the red muscular tissue consisted of a mass of small 
vessels thus choked up with inspissated blood (iii. 5. 668'^ i). The 
vessels themselves, however, were continued as solid fibres [H. A. iii. 
5. 515^31) to form by their aggregation the tendon {vtvpov), and it 
was to the shortening and widening of these tendinous fibres, endowed 
with transverse extensibility {H. A. iii. 5. 515"^ 15), that muscular action 
was due, the red tissue being completely inactive, and serving merely 
as the medium of Touch. 

^ iii. 4. 666^ 22. 

"^ Cf. H. A. ii. 15. 506^- 8. It is not uncommon to find in large 
mammalia, especially in Pachyderms and Ruminants, a cruciform ossifi- 
cation 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. 

^ Commentators differ widely as to these three cavities, nor do the 
several passages relating to them admit of any thoroughly consistent 
and satisfactory interpretation. I am, however, strongly of opinion that 
the three are the two ventricles and the left auricle (see ch. 5. 667^ 
16 n.). This view was promulgated by me in a lengthy note to my 
former translation. I found afterwards that Huxley had already come 
to the same conclusion, and had set it forth in an elaborate article in 
Nature (Nov. 6, 1869) ; republished in Science and Nattire (p. 180). 

^ Cf 666^ 7. 

° Put a full stop after άρψαμίν. Read Aui δί τό (ESUYZ) and put 
ίκατίρης ΐροΰμΐν in brackets with omission of yap. 

® See first note to next chapter. 

AR, I'.A. Η 


number, namely the so-called great vessel and the aorta, 
each of 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 

30 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 centre common to both sides. But 
this requires the heart to be of greater magnitude, so that 

35 it is only in the largest hearts that there are three cavities. 
667* Of these three cavities it is the right that has the most 
abundant ^ and the hottest blood, and this explains why the 
limbs also on the right side of the body are warmer than 
those on the left. 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 
5 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 

1 Cf. iii. 5. 667^^ 15. 

" In an animal, especially one killed by strangulation, as recom- 
mended by A. {H. A. iii. 3. 513=^ 13), the right side of the heart and the 
vessels connected with it would be found gorged with dark blood and 
contrasting strongly with the almost empty left side and vessels. It 
is doubtless this that makes A. say that the blood is more abundant, less 
pure, and denser (//. A. i. 17. 496^ 10) on the right side than on the left. 

^ The allusion is to the transverse and longitudinal grooves which 
mark out on the surface the limits of auricles and ventricles. A. is 
quite right in saying that the heart is not formed by the union of dis- 
tinct parts into a whole. It is at first a body with a single cavity, which 
is converted into several by the after-development of internal septa. 

BOOK III. 4 66r 

jointings are most distinct in animals of keen sensibility, and 
less so in those that are of duller feeling, in swine for lo 
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 tempera- 
ments of the animals. For in animals of low sensibility the 
heart is hard and dense in texture, 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 15 
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. 

The heart is of large size ^ in the hare, the deer, the 20 
mouse, the hyena, the ass, the leopard, the marten, and in 
pretty nearly all other animals that either are manifestly 
timorous, or 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. For just as a fire of equal size gives less 25 
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 effect than in a small one. More- 
over, all hot bodies are cooled by motions external to them- 
selves,^ and the more spacious the cavities and vessels are, 
the greater the amount of spirit they contain, and the more 
potent its action. Thus it is that no animal that has large 30 
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 affection.^ This is but what might reasonably be 

1 The heart is very large in the hare, nearly twice as heavy in pro- 
portion to the body-weight, as in man. As regards the other animals 
1 can give no accurate figures. 

^ Cf. iii. 6. 669'' 3 note. 

^ Cf. iv. 2. 677'^ 4. (Daremberg {Gaicn. i. 401) represents A. as 
H 2 


expected. For, if the primary or dominant part be diseased, 

35 there is nothing from which the other parts which depend 

667'' upon it can derive succour. A proof that the heart is thus 

unable to tolerate any morbid affection is furnished by the 

fact that in no sacrificial victim has it ever been seen to be 

affected with those diseases that are observable in the other 

viscera. For the kidneys are frequently found to be full of 

stones, and growths, and small abscesses, as also are the 

5 liver, the lung, and more than all the spleen. There are 

also many other morbid conditions 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 explana- 

10 tion. 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, and 

from affections such as are mentioned above, they are found 

on dissection to have morbid affections of the heart. 

Thus much of the heart, its nature, and the end and cause 
of its existence in such animals as have it. 

15 In due sequence we have next to discuss the blood- 5 
vessels, that is to say the great vessel and the aorta.^ For 

saying in this passage that the heart is not liable to disease, or at any 
rate less liable than other organs ; just as Galen said that it was made 
of hard flesh 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 dies 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. 16) ! 

^ The ' great vessel ', as I interpret A.'s account, consists of the upper 
and lower Venae cavae, with the right auricle, considered by Α., as by 
Galen and later anatomists, to be no part of the heart but merely the 
dilated junction of the two Venae cavae. This communicates with the 
largest cavity [right ventricle) by the wide auriculo-ventricular opening, 
and from this same cavity issues the pulmonary artery, regarded by A. 
in virtue of its connexion with the same cavity, its having a similarly 
thin wall, and being found after death (iii. 4. 667* 2 note) similarly 
gorged with dark blood, as a part of the ' great vessel ', though 
separated from its main trunk by the interposition of the right ventricle, 

BOOK III. 5 667*^ 

it is into these two that the blood first passes when it quits 
the heart ; and all the other vessels 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 20 
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 ; and this one-ness of the 
sensory soul determines a corresponding one-ness of the 
part in which it primarily abides. In sanguineous animals 25 
this one-ness is not only actual but potential, whereas in 
some bloodless animals ^ it is only actual. 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 oneness of the part in which is lodged the 
prime source of sensation and of heat is involved the one- 30 
ness of the source in which the blood originates ; and this, 

this being the cavity referred to (I/ 3. 513'^ 4) as that iv ω λιμνάζη 
TO αίμα. The middle cavity from which the aorta proceeds is the left 
ventricle, and the smallest is the left auricle. All three cavities are 
connected with the lung, but in only one {right ventricle) is the con- 
nexion distinctly visible {H.A. iii. 3. 513=* 36). Thus ' the great vessel' 
comprises ail the vessels connected with the right side cf the heart, 
and the aorta comprises all that are connected with the left, that is all 
the systemic arteries and the pulmonary veins, and each side has its 
distinct and completely separate blood (iii. 4. 666^ 29), which is much 
more abundant, denser, and less pure (iii. 4. 667'^ 2 note) on the right 
side than on the left. Lastly, the opening by which the aorta com- 
municates with the heart is much smaller {H. A. iii. 3. 513'' 5) than 
that by which 'the great vessel' so communicates, i.e. the right auri- 
culo-ventricular opening, not the aperture of the pulmonary artery, 
as stated by error in my former translation. 

^ 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 vitality ; the entire animal seemingly consisting of an aggre- 
gation 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 when 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. 


again, explains why the blood-vessels have one common 

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. 
35 Now as the front is more honourable and of higher supre- 
macy than the hinder aspect, so also and in like degree is 
668''^ 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. 
5 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 bloodless 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 source from which 

^ As all the sanguineous animals, i. e. 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. 

'^ A.'s general notions on the subject of nutrition were much as 
follows : — 

The food masticated in the mouth, but not otherwise altered (ii. 3. 
650'* 11), reaches the stomach, where it is concocted ; the heat for this 
purpose, which is not common heat but a heat with special powers 
(ii. 6. osa»• ID note), being supplied by the liver and spleen, which are hot 
organs in close contiguity with the stomach (iii. 7. 670-^ 21). The solid 
and indigestible portion passes off by the lower bowel, but the fluid 
portion, which alone can be serviceable in nutrition (ii. 2. 647^ 26), is 
absorbed by the blood-vessels of the stomach and intestine (iv. 4. 
678*• 10), over the surface of which they are spread like the roots of 
a plant (ii. 3. 650'* 25). These blood-vessels open by very minute and 
invisible pores into the intestine, pores like those in jars of unbaked 
day that let water filter through (G. A. ii. 6. 743-"^ 9). The matter thus 
absorbed passes up to the heart in the form of vapour {άναθνμιαταή, 
not as yet being blood, but only (ii. 4. 651* 17) an imperfect serum 
(Ιχωρ). In the heart and vessels [De Sonmo, 3. 456^ 4) 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. 521''* 17), the ultimate food of all the organs. The amount of blood 
thus formed is extremely small, as compared with the original materials 

BOOK III. 5 668« 

they obtain nutriment and as to the way in which they 
absorb this from the stomach, these are matters which may 
be more suitably considered and explained in the treatise 
on Generation.^ But inasmuch as the parts are, as already lo 
said, formed out of the blood, 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 about 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 15 
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 waten 
and the foundation walls in the other are built out of the 
stones. Now just after the same fashion has nature laid 20 
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 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, 25 
there is nothing left of them but their vessels. The ex- 
planation of this is that the blood, or fluid which takes its 

(G.A. i. 18.725•'^ 18). 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, 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, as bones 
and sinews, are fed on the inferior elements or leavings {ΰπολ(ίμμητα) 
of the former {G.A. ii. 6. 744** 15). This nutrition of the parts 
goes on most actively at night {Be Soinno, i. 454'^ 32). 

Thus every part of the blood that can be turned to account is 
utilized ; but such as from its quality is unfit for use, for instance any 
bitter substance, is excreted as bile, urine, sweat, etc., in company with 
the matter which results from the decay (σι-μτ^^ι?) of the parts them- 

Such surplus of nutritious matter as there may be, after all parts are 
satisfied, is either stored up in the body as fat or the like, or passes 
out to form hairs, scales, feathers, and other cutaneous appen- 

1 G.A. ii. 4.740=^ 21-'^ 12, 6. 743'' 8-7. 746=* 28. 


place, is potentially body and flesh, or substance analogous 
to flesh. Now just as in irrigation the largest dykes are 
permanent, while the smallest are soon filled up with mud 

30 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 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 

35 are invisible owing to their being clogged up, just as the 
dykes for irrigation are invisible until they have been 
cleared of mud. 
668'' As the blood-vessels advance, they become gradually 
smaller and smaller, until at last their tubes are too fine to 
admit the blood. This fluid can therefore no longer find its 
way through them, though they still give passage to the 
humour which we call sweat ; and especially so when the 
5 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 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. 

10 For, as was before said, every compound 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 

15 again may be of two kinds, either quantitative or quali- 
tative ; for all substances are not equally amenable to 

The widest passages in the body are of all parts the most 

' Cf. iii. 4. 666^ 15 note. 

^ Instances of red-coloured sweat are not unknown. Cf. Todd, 
Cycl. Aft. and Phys. iv. 844. 

BOOK III. 5 668^ 

liable to haemorrhage ; so that bleeding occurs not infre- 
quently from the nostrils, the gums, and the fundament, 
occasionally also from the mouth. ^ Such haemorrhages are 
of a passive kind, and not violent as are those from the 

The great vessel and the aorta, which above lie somewhat 20 
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 25 
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 how- 
ever of the mutual relations of the different vessels must be 
looked for in the treatises on Anatomy and the Researches 30 
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 inquiry to them. 

6 The lung,^ then, is an organ found in all the animals of 

' The mention of gums and mouth points to the existence of scurvy 
in those days. 

^ The common iUac arteries, formed by the division of the descending 
aorta, do in fact, as A. says, come forwards and he in front of the 
common iliac veins ; whereas as a general rule the veins lie in front 
of the arteries. 

' The pulmonary artery, regarded by A. as a part of the μ€γάλη φλίλ//•, 
at its origin is in front of the aorta, but when it reaches the arch sends 
its right and larger division behind the ascending aorta. It is probably 
to this that A. alludes. 

* Cf. I/.A.U17; iii. 2-4. 

" It will be noticed that A. always speaks of //le lung of an animal, 
and not as we do of the lungs. He considers the two to be merely 
subdivisions of a single organ, because they have 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 


a certain class, because they live on land. For there must 
of necessity be some means or other of tempering the heat 

35 of the body ; and in sanguineous animals, as they are of an 
especially hot nature, the cooling agency must be external, 
669** whereas in the bloodless kinds the innate spirit is sufficient 
of itself for the purpose. The external cooling agent must 
be either air or water. In fishes the agent is water. Fishes 
therefore never have a lung, but have gills in its place, as 
5 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. 

10 For many animals lie half-way 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 

15 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 col- 
lapses.^ It has been said ^ that the lung exists as a provision 

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. 507a• 19 ; p. A. iii. 7. 6691» 24. 

^ De Resp. 10. 475'' 15 sq. 

^ The mechanism of respiration is described elsewhere {De Resp. 
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 brought 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. 

^ Plato ( Zzw. 70 C) regarded the lungas a soft yielding buffer, intended 
to receive the impact of the heart, when throbbing violently in fits of 
emotion. To this A. objects that animals that are not liable to such 
fits of emotion nevertheless have lungs ; and, moreover, that the lung 
is not placed on the side of the heart where the impact occurs ; that is, 
not on the sternal aspect. 

BOOK III. 6 669^ 

to meet the jumping of the heart. But this is out of the 
question. For man is practically the only animal whose 
heart presents this phenomenon of jumping, inasmuch as 
he alone is influenced by hope and antidnalion of the 20 
future. Moreover, in most animals the lung is separated 
from the heart ^ by a considerable interval and lies above it, 
so that it can contribute nothing to mitigate any jumping. 

The lung differs much in difterent animals. For in some 
it is of large size and contains blood ; while in others it is 25 
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 30 
air, the animals known as birds.- For in all these the lung 
is spongy, and like foam. For it is membranous and col- 
lapses 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 35 
drink but sparingly, and that they are able to remain for 
a considerable time under water. For, inasmuch as they 669^ 
have but little heat, the very motion of the lung, airlike 
and void, suffices by itself to cool them for a considerable 

These animals, speaking generally, are also distinguished 
from others by their smaller bulk. For heat promotes 

^ The natural nominative to anexei, as the text stands, is ό π\(ΰμων, 
and this, as also the sense, requires that for τοϋ πλίνμονος should be 
read t?,s καρδίας ; for in no sense can the heart be said to be al'oz'e the 
lung, nor would such a position invahdate Plato's notion, whereas ' in 
most animals', that is in quadrupeds, the lung is placed above the 
heart, and away from the side where the heart's impact occurs. 

^ The lungs of birds, though smaller in proportion to the body than 
those of mammals, are highly vascular. 

^ 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 says, ' is cooled by the motions of bodies external 
to itself (iii. 4. 667'^ 28). So he supposes here 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 neighbouring parts. See also Be Resp. 9. 475^^ 14. 


growth, and abundance of blood is a sure indication of 
5 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. For no vivi- 
parous 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 in one order of animals it is bloodless 
and has the structure described above, to suit the special 
10 requirements. 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. 

Of the viscera some appear to be single, as the heart η 
and lung ; others to be double, as the kidneys : while of 
a third kind it is doubtful in which class they should be 

15 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 

In reality, however, all the organs are double. The 
reason for this is that the body itself is double, consisting 

20 of two halves, which are however combined together under 

^ Meaning the viper, which is apparently said to be less of a trog- 
lodyte than its congeners, because other snakes conceal themselves 
underground during their period of torpor, while the viper remains on 
the surface, hiding under stones. {H.A. viii. 15. 599^^ i.) 

* It seems to have been the universal opinion of the ancients that the 
spleen was the left homologue of the liver. In modern times the more 
general view is that of Miiller, that there is no such relation between 
them, each being an azygos organ. The ancient opinion is not, how- 
ever, without its modern advocates. Dr. Doellinger, for instance (6^r««^- 
riss der Naturle/tfe des menschl. Organ. 1805), supported it ; and 
more recently Dr. Sylvester {The Discov. of the Nature of the Spleeti, 
1870) has argued with much ingenuity that 'the spleen is not a blood- 
gland in the mesial line of the body, having no homologous relation- 
ship with the liver,' but that ' it is the left lateral homologue of a portion 
of the liver, the latter being a combination of a sanguiferous gland and 
a bihary apparatus,' and the spleen the homologue of the former por- 
tion of it. 

BOOK III. 7 669* 

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 25 
actually two lungs. As to the kidneys, no one can over- 
look 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 30 
plainly consists of two parts ; of which the larger tends to 
lie on the right side and the smaller on the left.^ Not but 
what there are some even of the Ovipara in which this con- 
dition 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 

* That is to say in the viviparous quadrupeds. 
^ Namely the Ovipara. 

' There is some foundation for the statement that the size of the 
spleen and the distinctness 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 spleen 
is large in ruminants and their liver at the same time presents scarcely 
any marks of lobulation. In the Ovipara the spleen is much 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 dis- 
tinctly divided into two lobes. In the remaining class, fishes, the 
spleen varies much in size; sometimes is apparently altogether absent, 
sometimes excessively small, sometimes almost as large in proportion 
to the body as that of a mammal, and the liver is sometimes multilobed, 
sometimes bilobed, sometimes unilobed. In this class, however, I can- 
not ascertain that there is any such relation as that mentioned in the 
text between the two conditions. 

* The exceptional ovipara are the Ophidia and many osseous fishes, 
where the liver is unilobed. The exceptional vivipara are the rodents, 
of which A. specially mentions the hare. Omit κακ€ΐ and ωσπίρ 'ίν 
ησι (ΕΥ). 


division are furnished by the hares of certain regions, which 
have the appearance of having two Hvers, and by the car- 

35 tilaginous and some other fishes.^ 

It is the position of the liver on the right side of the 

670* 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 

5 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 

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 

10 connexion with the body. For the vessels give off branches 
which run to the body through the outstretched structures,* 
like so many anchor-lines thrown out from a ship. The 
great vessel sends such branches to the liver and the spleen; 

15 and these viscera — the liver and spleen on either side with 
the kidneys behind — attach the great vessel to the body 
with the firmness of nails. ^ The aorta sends similar branches 
to each kidney, but none to the liver or spleen.'' 

These viscera, then, contribute in this manner to the 

20 compactness of the animal body. The liver and spleen 
assist, moreover, in the concoction of the food ; for both are 

' In cartilaginous fishes the liver consists of two distinct lobes, 
whereas in osseous fishes it is often unilobed. 

^ Reading και καθάττίρ (PZ). 

3 Assisting them in the mechanical way immediately mentioned, and 
also by providing an outlet for their surplus blood. Cf. iii. 10. 673^ I. 

* The mesentery is meant. 

^ The introduction of nails into the metaphor is so out of place, that 
the temptation is strong to substitute ΐυναί — mooring-stones — for ηΚοι. 
The metaphor would then run on all fours ; the ship being the main 
blood-vessel ; the anchor-lines its outstretching branches ; the moor- 
ing-stones the liver, spleen, kidneys. 

•^ The hepatic and splenic arteries seem to have escaped A.'s notice ; 
probably because they are not given off directly from the aorta. 

BOOK III. 7 670* 

of a hot character, owing to the blood which they contain. 
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 part or other there must be which, like a hearth, shall ^5 
hold the kindling fire ; and this part must be well protected, 
seeing that it is, as it were, the citadel of the body. 

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 30 
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 ani- 
mals as have a hot stomach. Such are the pigeon, the 
hawk, and the kite.^ It is the case also in oviparous quad- 670^ 
rupeds, 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 applied to the for- 
mation of feathers and scales. For the spleen attracts the 5 
residual humours ^ from the stomach, and owing to its 
bloodlike 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 nutriment. Often, too, when the 

^ The spleen is small in all birds, but whether specially so in these, 
or in the owl, which he adds elsewhere {H. A. ii. 15. soo•"* 13) to the 
list, I cannot say. 

^ The notion that the spleen serves to attract superfluous humours is 
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 
Morbis, iv. 9 and De Morb. Mul. i. 15). 

^ Reading πληθΐΐ for πλψη. 


spleen is affected by disease, the belly becomes hard ^ owing 
to the reflux into it of the fluid ; just as happens to those 

10 who form too much urine, for they also are liable to a simi- 
lar diversion of the fluids into the belly. But in those ani- 
mals 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. 

15 For their lung is spongy, and they drink but little, and 
such superfluous fluid as they have is applied to the growth 
of the body and the formation of scaly plates, just as in 
birds it is applied 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. 

20 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. 

25 For by their 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, 

30 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 is one of the parts 
that environ the viscera and therefore has to be considered 
with them. 

^ Also from Hippocrates (Kiihn's Ed. i. 533). 

2 A. thought that the bladder was the essential agent in forming the 
urine, the kidneys being comparatively unimportant adjuncts, though 
he also admits that when the fluid leaves these organs, it already has 
in a measure the characters of the final excretion. Cf. iii. 9. 671'' 24. 

BOOK III. 8 670'' 

8 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 671^ 
she should give this part. For the superabundance in their 
lung of its natural constituents 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 5 
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 10 
being of a spongy texture, or 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, 15 
which are comprised 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 disproportionately 

^ A. distinguishes the scales of fishes from those of reptiles by 
giving them distinct names, but nowhere discusses their differences 
excepting that he says (iv. 2. 691*^ 16) ' these plates (φολίδίς) are 
equivalent to scales (Kfni^es) but of a harder character '. But sec iv. 1 3. 
697=^ 5 note. 

^ All viviparous quadrupeds, i.e. Mammalia, have (Monotremata 
excepted) a urinary bladder. Birds have none. In many fishes the 
ureters form a small dilatation or bladder. Among reptiles, Ophidia 
and many Saurians have no bladder ; but there is one in some Saurians 
and in all Chelonia, and in these latter it is of great size. 

A. is mistaken in supposing that tortoises drmk but little. Darwin 
describes them as wearing broad and well-beaten paths to the springs 
in Chatham Island [Voyage of BeagU\ p. 383). 

AR. P. A, I 


large size.^ Moreover, inasmuch as the covering which in- 
vests them is dense and shell-like, so that the moisture 

20 cannot exhale through the porous flesh, as it does in birds 
and in snakes and other animals vi'ith 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 

25 sea-tortoise a large one, the land-tortoises an extremely 
small one.^ 

What has been said of the bladder is equally true of the 9 
kidneys. For these also are wanting in all animals that are 
clad with feathers or with scales or with scale-like plates ; 
the sea and land tortoises ^ forming the only exception. In 
some of the birds, however, there are flattened kidney-like 
30 bodies, as though the flesh allotted to the formation of the 
kidneys, unable to find one single place of sufficient size, 
had been scattered over several.^ 

^ 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 tous les visc^res' (Cuvier, Leqons^ iv. 347). They are, 
moreover, not only thus larger, but contain ' in correlation with the non- 
transpirable integument a much greater development of internal paren- 
chyma' (Rolleston, Forms of An. Life, Ix). This comparative abun- 
dance of parenchyma is more marked in marine than in other tortoises 
(Cuvier, Leqotis, iv. 324 and 332). 

^ Perrault found on repeated dissections that precisely the contrary 
was the case, and consequently inferred ' qu'il y a faute au texte par la 
transposition des mots terrestre et marine ' {Mem. pour servir a Γ hist, 
η at. des Afiimaux, 2^ par tie, p. 403). 

^ A similar statement, that no Ovipara save the tortoises have 
kidneys, is made elsewhere {H.A. ii. 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 to understand how the kidneys of other 
Ovipara 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 a priori that it was impossible for there 
to be a kidney if there was no bladder. For the essential organ in the 
formation of urine was, as he thought, not the kidney, but the bladder ; 
and the kidneys were but adjuncts to this (iii. 7.670'' 28 note). A kidney, 
then, in an animal without a bladder was to A. just as absurd a sup- 
position as would be to us a urinary bladder when there was no 
kidney. That A. was misled by this preconception is shown by the 
fact that he did see the kidneys in birds, and did recognize their 
kidney-like aspect ; but yet refused to consider them as true kidneys. 

* In birds the kidneys, almost always trilobed, are flattened against 

BOOK III. 9 671^ 

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 z=> 
lung contains blood are, as before said, provided with 
kidneys. For nature uses these organs for two separate 671^' 
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 5 
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 un- 
broken surface like the kidneys of sheep and other quadru- 
peds.^ For this reason, should the kidneys of a man be 
once attacked by disease, the malady is not easily expelled. 10 
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 
on the substance of the organ, so that there is no blood in 15 
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 

the back, and, fitting into the deep interspaces between the bones, 
retain the impressions of these successive cavities or depressions. 

^ The Emys was some freshwater tortoise (//. A. v. 33. 558-'^ 8) ; 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 Emys a soft shell. 

- Cf. iii. 7. 670-'^ 8 note. 

^ The cavity in the seal's kidney is very small. It is pictured in 
section by Bufifon {Hisi. Nai. xiii. pi. 48). The kidney consists of 
numerous distinct lobes, and in this respect resembles that of an ox. 

* This is not true of adult man, excepting as an occasional anomaly. 
But it is true of the foetus. This is one of the statements which lead 
me to think that A. may have dissected the human foetus. 

* 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. 


continuous, lead into the kidneys from the aorta.^ The 
purpose of this arrangement is to allow the superfluous 
fluid to pass from the blood-vessel into the kidney, and the 
resulting renal excretion to collect, by the percolation of the 

20 fluid through the solid substance of the organ, in its centre, 
where as a general rule 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 that have been mentioned, 
having already assumed in great degree the character of 

25 excremental residue.^ The bladder is as it were moored to 
the kidneys ; for, as already has been stated, it is attached 
to them by strong ducts. These then are the purposes for 
which the kidneys exist, and such the functions of these 

In all animals that have kidneys, that on the right is 
placed higher than that on the left.^^ For, inasmuch as 

30 motion commences from the right,* and the organs on this 
side are in consequence stronger than those on the left, they 
must all push upwards 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 

35 upwards is in all animals brought into contact with the 
liver ; for the liver lies on the right side. 
672* 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, 
5 and the final result of thorough blood-concoction is lard 
and suet. For just as a certain amount of fire is left in the 
ashes of solid substances after combustion, so also does a 
remnant of the heat that has been developed remain in 

^ The bloodless ducts are the ureters. The ducts from the aorta and 
great vessel are the renal arteries and veins respectively. 

I Cf. iii. 7. 670^ 28 note. 

' 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. 

* Cf. De Cae/o, ii. 2. 284'' 28 and Be An. Inc. 4. 705'^ 29 ; 6. 706'' 17. 

BOOK ΠΙ. 9 672« 

fluids after concoction ; and this is the reason why oily 
matter is h'ght, 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 about lo 
their external surface. It consists of lard or of suet, accord- 
ing 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 ex- 
plained, a consequence of the necessary conditions which 15 
accompany the possession of such organs. But at the same 
time the fat has a final cause, namely to ensure 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 a shield for 
the heart and neighbouring viscera, the loins, in accordance 
\vith a rule that applies to all bendings, are destitute of 
flesh ; and fat is therefore formed as a substitute for it, so 20 
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 25 
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 30 
free. The reason why sheep are the only animals that 
suffer in this manner, or suffer more than others, is that in 

' Cf. ii. 5, //.^. iii. 17. 

^ Aubert and Wimmer say this is true of rabbits. 


animals whose fat is composed of lard ^ this is of fluid con- 
sistency, 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 

35 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 
^T^"" suet, in none is the suet so dense as in the 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 moisture and the 
wind getting shut up in the kidneys, and is a malady that 
5 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. 

We have now dealt with the heart and the lung, as also 

10 with the liver, spleen, and kidneys. The latter are sepa- lo 
rated 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, all ■* of which 
have a midriff, just as they all have a heart and a liver. 

'5 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. 

20 For it was to guard against this that nature made a division, 

1 Cf. ii. 5. 651^35. 

2 A. is plainly speaking of some disease that is compatible with 
accumulation of fat, and that 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). 

^ The ox and the sheep, says John Hunter, have more fat about the 
kidneys, the loins, and within the abdomen, than most other animals 
{Micseum Cat. iii. 312). 

* Mammals alone have a perfect diaphragm, but in most vertebrates 
there is something analogous to it. The description, however, given 
further on, applies only to the perfect diaphragm, viz. that of mammals. 

BOOK III. ΙΟ 672" 

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 is pos- 
sible. 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 portion of the midriff which is near the ribs is 25 
fleshier and stronger than the rest, but the central part has 
more of a membranous character ; for this structure con- 
duces best to its strength and its extensibility. Now that 
the midriff, which is a kind of outgrowth from the sides of 
the thorax, acts as a 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 30 
a marked disturbance of intellect and of sensation. It is 
indeed because of this that the midriff is called ^ Phrencs, 
as though it had some share in the process of thinking 
{Phroncin). 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 intelli- 
gence 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 35 
of the fleshy whole which lie nearest to the ribs must neces- 
sarily be fleshier than the rest,^ yet besides this there is a 
final cause, namely to give it as small a proportion of humour 
as possible ; for, had it been made of flesh throughout, it 673* 
would have been more likely to attract and hold a large 
amount of this. That heating of it affects sensation rapidly 
and in a notable manner is shown by the phenomena of 
laughing. For when men are tickled they are quickly set 
a-laughing, because the motion quickly reaches this part, 5 

' A notion still commemorated in the anatomical terms ' phrenic 
nerves ' and ' phrenic centre '. 

- The central part of the midriff, which is tendinous, is the ' cordi- 
form tendon ' of modern anatomists. 


and heating 1 it though but sh'ghtly nevertheless manifestly 
so disturbs the mental action as to occasion movements that 
are independent of the will. That man alone is affected by 
tickling is due firstly to the delicacy of his skin, and secondly 
to his being the only animal that laughs. For to be tickled 
is to be set in laughter, the laughter being produced by such 

10 a motion as mentioned of the region of the armpit. 

It is said also that when men in battle are wounded any- 
where 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 

15 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 

20 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, ' Cercidas slew man on man.' Search 
was thereupon 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 

25 the lung. 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 

^ Reading βΐρμαΐνονσαν (PUY) for θΐρμαίνουσι, with a comma before 
it ; but the text of this passage is too corrupt for more than conjectural 

^ When the diaphragm is suddenly ruptured, instant death usually 
follows, and the face is said invariably to assume the peculiar expres- 
sion or grin, called Risus Sardoniciis. Cf. Did. d. Sci. Medic, ix. 214. 

^ Iliad X. 457 ; Odyssey xxii. 329. In both places the reading is 
φθΐγγομίνου not φθΐγγομίρη. 

* Probably meaning ' armed ' Zeus. So too there was a temple of 
Here Hoplosmia in the Peloponnesus. (Liddell and Scott.) 

BOOK III. ΙΟ 673» 

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 30 
can live, and that for a considerable time, after decapitation, 
as has been set forth and explained in other passages.^ 

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 
humour, and that of a bloody character, cannot but exude 
at these points, and it is of this, solidified and coagulated, 673'' 
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. 

11 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 5 
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 humour nor retain it, 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 10 
reason. For these are the parts which require most pro- 
tection, seeing that they are the main governing powers of 
life, and that it is to governing powers that guard is due. 

12 Some animals have all the viscera that have been enu- 
merated ; 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 15 

^ Cf. iii. 5. 677'' 27 note; De An. i. 5. 411'' 19; ii. 2. 413^ 20 ; De 
Long. Vit. Iiiv. et Sen. 6. 467•^ \^\ De Vita, 2. 468'' 25,''2 ; De Resp. 
3. 471'' 20; H. A. iv. 7. 531'' 30-532=1 5 ; De Inc. An. 7. 707» 27. 

" Cf. ii. 15.658'' 24 note. 

■' The pericardium and dura mater. 

^ Cf. iii. 4. 665=•^ 29. 


not precisely alike in all animals that have one ; nor, in fact, 
is any viscus whatsoever. 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 

20 even among those sanguineous animals that are viviparous, 
but are more marked in fishes and in the oviparous quad- 
rupeds, and this whether we compare them with each other 
or with the Vivipara. 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 

25 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 of ovi- 
parous quadrupeds and fishes inclines, as a rule, to a yellow 

30 hue,^ and there are even some of them in which it is entirely 
of this bad colour,* in accordance with the bad composition 
of their bodies generally. Such, for instance, is the case in 
the toad, the tortoise, and other 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 size has caused some part of it to extend its 

674*^ growth longitudinally, as has happened in the case of the 

^ Cf. ill. 7. 669'' 32, 35 notes. ^ Cf. iv. 2. 676'^ 26. 

^ The liver of mammals and birds is as a rule of a brown-red colour. 
In reptiles it inclines to a yellow hue ; and in fishes this yellow tint is 
often still more decided. Cf. Cuvier, Leqo7is, iv. 14-16. 

* ' Bad ' 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 unfavourable omen, the lucky tint 
being the normal mottled red, the ποικίλη ίνμορφία of Aeschylus ; 
in which case ' bad ' would correspond to the titrpia exta of Livy 
(xxvii. 26). 

° Or perhaps ' of a broad oval form ' ; στρογ^νΚοί being the term 
applied to a merchant vessel as distinguished from a ship of war. 

BOOK III. 12 674^ 

ox. On the other hand, it is elongated in all polydactylous 
animals.^ 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. 

13 The viscera differ from the flesh not only in the turgid 
aspect of their substance, but also in position ; for they lie 5 
within the body, whereas the flesh is placed on the outside. 
The explanation 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 

14 Below the midriff lies the stomach, placed at the end of 
the oesophagus when there is one, and in immediate con- 10 
tiguity with the mouth when the oesophagus 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 

^ The spleen ' is broader at one end in the cow, reindeer, and giraffe 
than in other ruminants' (Owen, Verteb. iii. 561). In the hog it is 
elongated ; so also in Carnivora generally. In the Ungulata it is of 
proportionately smaller dimensions 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. 13ut 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. 

^ A. seems to have been at a loss to classify the pig. Here he 
reckons it with the many-toed animals 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 a separate division, consisting of ' those 
that have a cloven hoof, but yet have front teeth in both jaws ' ; of 
course in contradistinction to the ruminants. In another place [H. Λ. 
ii. I. 499^' 12) he says the pig lies half-way between the cloven-hoofed 
and the solidungulates ; and, in corroboration of this, states that 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 two 
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. 

^ It is the viscera that exist 'for the sake of the vessels' (iii. 7. 
670^ 8), the flesh that 'cannot exist without them ' (iii. 5. όόδ^^ 32). 


shall receive the incoming food ; and necessary also that it 

IS shall discharge the same when its goodness is exhausted. 
This residual matter, again, must not occupy the same 
place as the yet unconcocted 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. Thus 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 

20 which will be more suitably set forth when we come to 
deal with Generation and Nutrition.^ What we have at 
present to consider are the variations presented by the 
stomach and its subsidiary parts. For neither in size nor 
in shape are 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 

25 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 

30 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 horn-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 ex- 
planation 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 constructed like that of animals without 
674^' upper front teeth^ and, its dental arrangements being such 

' G. A. ii. 4. 740^ 21-^12; 6. 743''^ 8-7. 746* 28. 

2 Cf. iii. 12. 674^ 3 note. 

^ The camel has in fact 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 of his views as to the inverse 
development of teeth and horns. Cf. iii. 2. 664* i. 

BOOK ΠΙ. 14 674^ 

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 5 
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, only imperfectly per- 
forms its office as regards the food, this multiplicity of 10 
stomachs is intended to make up for its shortcomings ; 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 bag, the manyplies, and the reed. 15 
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 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 even more completely — for birds have no teeth at all, 20 
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 oeso- 
phagus is either wide throughout - or a part of it bulges 

1 Cf. H. A. ii. 17. 507*34-!' 15• . 

- The oesophagus, as a general rule, is wide and dilatable in birds, ' in 
correspondence with the imperfection of the oral instruments as com- 
minutors of the food' (Owen). It is especially wide in the cormorant 
and other fishing birds. A. (//. A. ii. 17. 508'' 35) gives as examples 
several species of crows, with which he appears (//. A. viii. 3. 593'' iS) 
to have classed the cormorant. 


25 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,^ 
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 

30 legs and live in marshes, that have none of these provisions, 
but merely an elongated oesophagus.^ 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. 
675^^ Fishes are provided with teeth, which in almost all of 
them ■'' are of the sharp interfitting kind. For there is but 
one small section in which it is otherwise. Of these the fish 
called Scarus {Parrot-fish) is an example. And this is 
probably the reason why this fish apparently ruminates, 

^ Alluding to the /Γί>7/^«/Γ/ν;/•///ί or glandular stomach. This exists 
in all birds, but is much larger and more glandular when there is no 
crop, than when this is present. Doubtless in such cases it supplies 
the absence of the crop (Cuvier, Lei^otis, iii. 408), and acts as a store- 
house of food. 

^ The example given in the H. A. (ii. 17. 509^ 6) is a bird which 
Aubert and Wimmer identify with Falco tinminculiis. They point out 
that in all the diurnal birds of prey there is a peculiarity, thus described 
by Meckel (7>. Gen. d'Atiat. Comp. viii. 314) : ' L'estomac folliculeux 
d'une ampleur peu considerable forme subitement une saillie allongee, 
qui est separde par un dtranglement, sup^rieurement de I'oesophage, 
et infdrieurement de l'estomac musculaire.' 

^ The gizzard is strong and muscular in graminivorous birds ; but thin 
and membranous in the carnivorous species. 

■* In the Greek text, instead of oesophagus (στόμαχοι) we have crop 
(ττρόλοβοί). 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 therefore read στόμαχοι for πρόλοβος ; which is in harmony with 
the parallel passage in the Hi's/. An. (ii. 17. 509* 9), where it is said 
that these birds have a long oesophagus to match their long neck. 

In the typical waders there is no crop ; neither is the stomach fleshy, 
but has thin walls, as in piscivorous birds generally. The ' dilatation 
of the oesophagus before it enters the stomach', i. e. the provetitriculus, 
would also seem to A. to be absent ; for it forms one single cavity \vith 
the thin-walled gizzard ; at least such is the case in the heron (Cuvier, 
Leqons., iii. 410). 

^ For παστοί read' πάίτ^ r. 

BOOK III. 14 675=* 

though no other fishes do so.^ For those horned animals 5 
that have no front teeth in the upper jaw also ruminate. 

In fishes the teeth are all " sharp ; so that these animals 
can divide^ their food, though imperfectly. For it is im- 
possible 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, 10 
to facilitate the concoction of the food, some of them, as the 
Cestreus* {mullet)^ 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 putrefac- 
tion^ and concoction. There is a contrast between fishes 15 
and birds in the position of these processes. For in fishes 
they are placed 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 

^ Whether the parrot-fish ruminates I do not know ; but A. is wrong 
in saying that no other fish does so. There are several species, 
especially of the carp tribe, in which a sort of rumination occurs. Cf. 
Owen, CoDip. Anat. ii. 236. 

- For ττάντα read πάντης. 

' Cf. iii. I. 662=* 13. The sharp teeth of fishes, however, serve rather 
for the retention than for the mastication of food. 

* The Cestreus is doubtless some species of Mugil, a tribe of which 
our grey mullet is a familiar example. What species is meant is un- 
certain ; the Mediterranean containing at least five. In all these 
Mugilidae 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 ofifices of 
mastication and digestion.' — John Hunter. 

^ A. seems here to admit that digestion is in part due to putrefaction, 
a doctrine held by Pleistonicus. 

" In most osseous fishes, though not in all, there are a variable 
number of caecal 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 rightly stated by 
A. (//. A. ii. 17. 508^^22) to be without these caeca. In birds, as a rule, 
there are two caeca at the junction of small and large gut ; rarely, as 
in the heron, a single caecum. Sometimes, however, as A. notices here 
and elsewhere {H. A. ii. 17. 508'^ 14), the caeca are absent. This is the 
case, for instance, in the wryneck, woodpecker, lark, and cormorant, 
among birds known to Aristotle. 


the lower part of the gut ^ which serve the same purpose as 
that stated above. 

20 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 undergoing concoction ; and, of all, those are 
the most gluttonous that have a straight intestine. For as 
the passage of food in such cases is rapid, and the enjoy- 
ment derived from it in consequence but brief, it follows of 
necessity that the return of appetite is also speedy.- 

25 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 head- 
ings, 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 folds of 
moderate size, the purpose of which is to lengthen out the 
period of concoction ; while the stomach of the dog is of 

30 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 

^ Meaning of course the caecum and vermiform appendix. There 
is the greatest variety in the different mammalian orders as to the 
presence or absence of these. Cf. Cuvier, Legotis, iii. 465. 

^ Fishes, says Α., do not digest their food well, because they have 
a short gut ; and so they are ravenous. Similarly in the Timaeiis it is 
said that a long intestine was given to animals to prevent insatiable 
gluttony. An abnormally short gut is, in fact, a sufficient cause for 
a ravenous appetite (cf. Schiff", Sur la Digestiofi, i. 44). The normally 
short gut of a fish is, however, probably to be explained by the easy 
digestibility of their food. 

" What he stated before was that they had a single stomach, not 
a small one. The single stomach is, however, small as compared with 
the multiple stomach of the ruminants. 

* 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.A. ii. 17. 507^19. The two 
types, then, under which A. classes stomachs are the small, perfectly 
simple stomach of Carnivora, and the larger and less simple stomach 
that, beginning with the pig, culminates in the very complicated organ 
of the ruminants. Cf. Owen, A?iat. of Vert, iii. 463. 

BOOK ΠΙ. 14 675* 

others it differs in different portions. Thus in some cases it 
is wider in the neighbourhood of the stomach, and narrower 
towards the other end ; and this explains by the way why 
dogs ^ have to strain so much in discharging their excre- 
ment. But in most animals it is the upper portion that is SjS^ 
the narrower and the lower that is of greater width. 

Of greater length than in other animals, and much con- 
voluted, are the intestines of those that have horns.- These 
intestines, moreover, as also the stomach, are of ampler 
volume, in accordance with the larger size of the body. For 
animals with horns are, as a rule, animals of no small bulk, 5 
because of the thorough elaboration which their food under- 
goes. The gut, except in those animals " where it is 
straight, invariably widens out as we get farther from the 
stomach and come to what is called the colon, and to 
a kind of caecal dilatation. After this it again becomes 
narrower and convoluted.•* Then succeeds a straight portion 
which runs right on to the vent. This vent is known as the 10 
anus, and is in some animals surrounded by fat, in others 
not so. All these parts have been so contrived by nature 
as to harmonize with the various operations that relate to 
the food and its residue. For, as the residual food gets 
farther on and lower down, the space to contain it enlarges, 
allowing it to remain stationary and undergo conversion. 
Thus is it in those animals which, owing either to their large 15 
size, or to the heat of the parts concerned,^ require more 
nutriment, and con.sume more fodder than the rest. 

^ ' Dans les chiens . . . . les gros intestins n'ont gueres plus de 
diametre que les greles.' Cuvier, Leqims, iii. 485. 

- The intestines, longer in Heibivora generally than in Carnivora, attain 
the greatest length in ruminants. In the sheep, for instance, they are 
twenty-eight times as long as the body ; in the equally herbivorous but 
non-ruminating rabbit ten times ; in the carnivorous dog only five times. 

^ What animals, if any, at all comparable with ruminants, A. held to 
have a straight intestine, I cannot surmise. Here, however, he seems 
to include all non-ruminants under (.vQvivTtpa, as being comparatively 
straight-gutted. Cf. H. A. ii. 17. 507'-• 34. 

^ Referring to the spiral coil of the colon, which forms one of the 
characteristics of the Artiodactyla (cf. Owen, Vert. iii. 474). The 
colon becomes narrower where it assumes this spiral disposition. 
Later on A. calls this part the coil or helix (eXt|). The straight 
terminal part is of course the rectum. 

^ The digestive cavities. As to τόττωΐ' compare τώι/ τύπωι/ άμφοτίρων, 
676^ 2. 

AR. P.A. Κ 


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 

20 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 excremental residue 
from being discharged all at once.^ 

In all such animals, however, as have to be comparatively 
moderate in their alimentation,^ the lower stomach presents 
no wide and roomy spaces, though their gut is not straight, 

25 but has a number of convolutions. For amplitude of space 
causes desire for ample food, and straightness 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 meals at short intervals. 

Again, since the food in the upper stomach, having just 

30 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 
what is called the jejunum ;2 which is a part of the small 
gut, of the gut, that is, which comes next to the stomach. 

35 For this jejunum lies between the upper cavity which con- 
tains the yet unconcocted food and the lower cavity which 
holds the residual matter, which by the time it has got here 
has become worthless. There is a jejunum in all these 
676'"^ animals, but it is only plainly discernible in those of large 
size, and this only when they have abstained from food for 

^ Why should she do so? A. probably has in mind the Bonasus 
(iii. 2. oos^* 16). 

^ That is, the Carnivora ; whose food is only taken at comparatively 
long intervals (iv. 10. 688^ 4) and is not so bulky as that of Herbivora. 
In these the gut, though not unconvoluted, is less so than in ruminants, 
of which animals A. has up to now been speaking, and is without their 
spiral coil or their capacious caecum and colon. 

^ Jejunum (νηστις) 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, Legons, iii. 130). 

BOOK III. 14 676'' 

a certain time. For then 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 whatsoever of the upper 
intestine, but in males it comes just before the caecum and 5 
the lower stomach.^ 

15 What is known as rennet - is found in all animals that have 
a multiple stomach, and in the hare^ among animals whose 
stomach is single. In the former the rennet neither occupies 
the large paunch, nor the honeycomb bag, nor the terminal 
reed, but is found in the cavity which separates this terminal 10 
one from the two first, namely in the so-called manyplies.•* 
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 with- 
out horns does not. Rennet forms in the hare because it feeds 1 5 
on herbage that has juice like that of the fig ; ^ for juice of 
this kind coagulates the milk in the stomach of the sucklings." 
Why it is in the manyplies that rennet is formed in animals 
with multiple stomachs has been stated in the Problems.^ 

^ This strange statement has no anatomical foundation. 

* 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 used for the milk when thus 
coagulated, which, owing to the substance mixed with it, has the power 
of coagulating other milk. It is this concreted milk that A. calls rennet, 
attributing its formation to that convenient agent ' Vital heat' [G. A. 
ii. 4. 739^ 23 ; H. A. iii. 21. 522^ 7). 

■' So also Varro (De Re rustica, ii. li). 

* This is erroneous. It is the fourth stomach that gives rennet. 

^ Thethicknessof milk, as explained in//. .<4. iii. 20. 521^ 28, 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. 

" The leaves of the common Pinguicula contain a juice which has 
the power of coagulating milk, and is said by Linnaeus to be used by 
the Laplanders in the fabrication of cheese. The same property is 
possessed by Galiunt Veriini, sometimes therefore called Cheese 
Rennet. As to fig-juice cf. //. A. iii. 20. 522'' 2. 

"' "Εμβμνον seems a strange term for a suckling which not only sucks 
but grazes. Cf. Odyssey ix. 245, 

* Not in the Problems as they have come down to us. 

Κ 2 


The account which has now been given of the viscera/ I 
the stomach, and the other several parts holds equally good 
not only for the oviparous quadrupeds, but also for such 

25 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. None of these 

30 animals, excepting the tortoise, as also no fish, has a urinary 
bladder.^ For owing to the bloodlessness of their lung, they 
drink but sparingly ; and such fluid as they have is diverted 
to the scaly plates, as in birds it is diverted to the feathers, 
and thus they come to have the same white matter on the 
surface of their excrement as we see on that of birds. For ^ 
in animals that have a bladder, its excretion when voided 
throws down a deposit of earthy brine in the containing 

35 vessel.^ For the sweet and fresh elements, being light, are 
expended on the flesh. 
676^ Among the Serpents, the same peculiarity attaches to 
vipers, as among fishes attaches to Selachia. For both these 
and vipers are externally viviparous, but previously produce 
ova internally.^ 

^ The stomach is not one of the viscera in A.'s sense. Cf. ill. 4. 
oos'* 31 note. 

^ Cf. iii. 8. 671^ 15 note. ^ For bionep read διόη. 

* And this earthy brine, it is implied, must, if there is no bladder, 
be discharged by the bowel. It is, of course, discharged with the 
faecal matter from the reptilian and avian cloaca. 

•'"' A. includes under Selachia all cartilaginous fishes, among which he 
erroneously classes the Lophius (cf. iv. iS-ogs'^ 14 note). All these, he 
often says, with the exception of Lophius, are ovoviviparous : that is, 
they retain their ova Avithin the body till hatched. In some of these 
ovovivipara the embrjO throughout remains free from all anatomical 
connexion with the mother, but in some, when the nutriment supplied 
by the yelk is exhausted, the embryo forms a connexion with the 
parent's body (G. A, ii. 4. 727'^ 23 ; iii. 3. 754'' 27). The latter part of 

BOOK IV. I 676'' 

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 always 5 
happens when there is no bladder. In serpents these viscera 
are, moreover, dififerently shaped from those of other animals. 
For, a serpent's body being long and narrow, its contents 
are as it were moulded into a similar form, and thus come 
to be themselves elongated. io 

All animals that have blood possess an omentum, a 
mesentery,^ intestines with their appendages, and, moreover, 
a diaphragm and a heart ; and all, excepting fishes, a lung 
and a windpipe. 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. ^ 15 

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.^ It is in fishes that this is most 

this statement applies to certain sharks, which do in fact present a 
rudimentary placenta. The former part of his statement is too wide 
a generalization ; for the oviparous dogfishes and the rays present 
exceptions to the statement that all A.'s Selachia are, as he says, ovo- 
viviparous. Yet A. [H.A. vi. 10. 565'"^ 22) was well acquainted with the 
eggs of the dogfishes and the rays. The explanation seems to 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, Tkierkunde, p. 281. 

The osseous fishes A. states to be all oviparous. This rule, however, 
is not without exception ; e. g. the viviparous blenny. 

^ All vertebrata 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, cf, iv. 3. 677^^ 23 note ; as to 
the diaphragm, cf. iii. 10. 672^ 13 note. 

^ Cf. iii. 3. 664^ 3, where, however, the inconvenient position is 
described, but no explanation proffered. 

^ 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, Ajih. 
d. Sc. Nat. XXX. 127). A similar condition is found in some fishes 
(Owen, Led. on Co/fip. A>i. ii. 243), among others in the Lophius, the 
Swordfish, and the Muraena ; all of which are elsewhere (//. A. ii. 15. 
506^ 15) enumerated as examples of this structure. Probably this 
peculiar arrangement has reference to the long narrow shape of the 
animals, and exists for convenience of packing. 

* As to lower stomach, cf. ii. 3. 650-'^ 14 note ; iii. 14. 675^ 19. The 


20 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 enter- 
tained by some writers, that the gall exists for the sake of 
some sensory action. For they say that its use is to affect 
that part of the soul which is lodged in the neighbourhood 

25 of the liver, vexing this part when it is congealed, and re- 
storing it to cheerfulness when it again flows free. 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 of a biliary 
character. Again, there is no such organ in the seal, nor, of 
purely sea-animals, in the dolphin.* Even within the limits 

30 of the same genus, some animals appear to have and others 
to be without it.'^ Such, for instance, is the case with mice ; 

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. 

^ Fishes are very rarely without a gall-bladder, though there are 
some few exceptions, e. g. sawfish, lamprey, and basking-shark. 

^ The Amia appears to be the Scomber Sarda of Cuvier. This fish 
abounds in the Mediterranean. Like the tunny, bonito, and sundry 
other Scombridae, it is remarkable for the extreme length and slender- 
ness of its gall-bladder. Cuvier, /^e£: Anii/i. ii. 199, and Owen, 
Lecf. ii. 244. 

* This very obscure and con-upt passage is intended to summarize 
Plato's views as to the gall as given in the Timaetis 71. For σ^ιστ)/ 
read συστη. 

* A. is correct in this enumeration of animals that have no gall- 
bladder, with the exception of the seal. The Phoca vitulma has 
a gall-bladder ; but it may possibly, though improbably, be that the 
Phoca ifwnachus, which was the species best known to the ancients 
(Cuvier, Rcgne An. i. 169), is without one, as Frantzius suggests. 

-' The gall-bladder is sometimes present, sometimes absent in giraffes 
(Owen-Joly) ; in the apteryx and bittern (Owen) ; in the guinea-fowl, 
&c. It is especially variable, as A. rightly says, in the different 
species of Μ us (Cuvier, Leqo7is, iv. 36). In man a congenital absence 
of the gall-bladder has been noticed in rare instances (Rokitansky, ii. 
155 ; Phil. Trans. 1749). This, however, could not be known to Α., 
who says, moreover (//. A. i. 17. 496^' 22), that most men are without 
a gall-bladder. If, as is not impossible, A. examined aborted human 
embryos, he 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. 

BOOK IV. 2 676^ 

such also with man. For in some individuals there is a dis- 
tinct gall-bladder attached to the liver, while in others there 
is no gall-bladder 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 35 
has occurred in the case of sheep and of goats. For these 
animals usually have a gall-bladder; but, while in some 677^ 
localities it is so enormously big as to appear a monstrosity, 
as is the case in Naxos, in others it is altogether wanting, 
as is the case in a certain district belonging to the inhabi- 
tants of Chalcis in Euboea.^ Moreover, the gall-bladder in 
fishes is separated, as already mentioned,^ by a considerable 
interval from the liver.^ No less mistaken seems to be the 5 
opinion of Anaxagoras and his followers, that the gall- 
bladder is the cause of acute diseases, inasmuch as it be- 
comes over-full, and spirts out its excess on to the lung, the 
blood-vessels, and the ribs. For, almost invariably, those 
who suffer from these forms of disease are persons who 
have no gall-bladder at all, as would be quite evident were 10 
they to be dissected. Moreover, there is no kind of corre- 
spondence 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 is present in 
any other part of the body is a mere residuum or a product 
of decay, so also when it is present in the region of the 
liver it is equally excremental and has no further use ; just 
as is the case with the dejections of the stomach and 15 
intestines. For though even the residua are occasionally 
used by nature for some useful purpose, yet we must not in 
all cases expect to find such a final cause ; for granted the 
existence in the body of this or that constituent, with such 

' Cf. //. A. i. 17. 496^^ 26. 2 cf i^. 2 575b ic), 

■"■ And therefore cannot have the action these writers attribute to it. 
■* When an animal's body is opened some time after death, the parts 
near the gall-bladder are often found to be stained yellow from an 
exudation of bile. It is probably to this overflow that reference is 
made, as being excessively small in comparison with the amount of 
bile which is apparent in the human body in cases of jaundice. 


and such properties, many results must ensue merely as 
necessary consequences of these properties. All animals, 

20 then, whose liver is healthy in composition and supplied 
with none but sweet blood, are either entirely without 
a gall-bladder on this organ, or have merely small bile- 
containing vessels ; 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 

25 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 excrement is that it is the opposite of 
nutriment, and of bitter that it is the opposite of sweet ; 
and healthy blood is sweet. So that it is evident that the 
bile, which is bitter, cannot have any useful end, but must 

30 simply be a purifying excretion. It was therefore no bad 
saying of old writers that the absence of a gall-bladder gave 
long life. In so saying they had in mind deer and animals 
with solid hoofs. For such have no gall-bladder and live 
long. But besides these there are other animals that have 
no gall-bladder, though those old writers had not noticed 
the fact, such as the camel and the dolphin ; and these also 

35 are, as it happens, long-lived.^ Seeing, indeed, that the 

liver is not only useful, but a necessary and vital part in all 

677^ 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 

5 to the rest of the viscera, none excepting the liver are 

necessary parts of an animal. It is the liver therefore that 

alone has this provision. In conclusion, wherever we see 

bile we must take it to be excremental. For to suppose 

^ The camel is said by A. {H. A. viii. 9. 596-'^ 10) to live for 30 
years, and exceptionally for 100 years. Burckhardt gives it a life of 
40 years. As to the dolphin it is stated {H. A. vi. 12. 566^ 24) 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. 

BOOK IV. 2 677^ 

that it has one character in this part, another in that, would 
be as great an absurdity as to suppose mucus or the dejec- 
tions of the stomach to vary in character according to 
locality and not to be excremental wherever found. 10 

3 So much then of the gall-bladder, and of the reasons why 
some animals have one. while others have not. We have 
still to speak of the mesentery and the omentum ; for these 
are associated with the parts already described and con- 
tained in the same cavity. The omentum, then, is a mem- 15 
brane containing fat ; the fat being suet or lard, according 
as the fat of the animal generally is of the former or latter 
description. What kinds of animals are so distinguished 
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 20 
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, and this alike 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 de- 
scribed is the result of necessity. For, whenever solid and 
fluid are mixed together and heated, the surface invariably 
becomes 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 close texture 25 
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 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 de- 
velopment, then, of the omentum is simply the result of 30 
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 

' Cf. ii. 5. 657^ 35• 

"^ A similar statement is made elsewhere (iv. i. 676^ 11 ; //. A. iii. 
14). It is, however, erroneous. Mammalia alone have an omentum. 


from the middle of the stomach ; for the upper part of the 

stomach has no need of it, being assisted in concoction by 

35 the adjacent h'ver. Thus much as concerns the omentum. 

The so-called mesentery is also a membrane ; and ex- 4 
tends continuously from the long stretch of intestine to the 
678^ great vessel and the aorta. In it are numerous and close- 
packed vessels, which run from the intestines to the great 
vessel and to the aorta. The formation of this membrane 
we shall find to be the result of necessity, as is that of the 
5 other [similar] parts.^ What, however, is the final cause of 
its existence in sanguineous animals is manifest on reflection. 
P'or it is necessary that animals shall get nutriment from with- 
out ; and, again, that this shall be converted into the ulti- 
mate nutriment, which is then distributed as sustenance to the 
various parts ; this ultimate nutriment being, in sanguineous 
animals, what we call blood, and having, in bloodless ani- 

10 mals, 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 in- 
testines represent the ground from which the nutriment is 
to be taken. The mesentery, then, is an organ to contain 

15 the roots ; and these roots 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 distributed by them to ^ the various 
parts of the body,are questions which will be considered when 

20 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 se- 
quence we should next go on to the organs of generation, 
as yet undescribed, on which depend the distinctions of male 

25 and female. But, inasmuch as we shall have to deal spe- 

^ A. cannot have meant that all the parts are the necessary outcome 
of purely physical conditions, but only that membranes {G. A. ii. 4. 
739I' 27) so originate. Either τοιοντοις must be supplied before μορίοίς 
or for μορίοις may be read νμίσιν (Piatt). 

" For ταντα read πάντα. 

BOOK IV. 4 678» 

cially with generation hereafter, it will be more convenient 
to defer the consideration of these parts to that occasion. 

5 Very different from the animals we have as yet considered 
are the Cephalopoda and the Crustacea. For these have 
absolutely no viscera ^ whatsoever ; as is indeed the case 
with all bloodless animals, in which are included two other 30 
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, must be in- 
cluded in the conception which determines their respective 
essences. Moreover, in the animals we are now considering, 35 
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 6jS^ 
do they breathe ; the only part that it is necessary for them 
to have being that which is 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. The organs of nutrition are also of 5 
necessity present in them all. They differ, however, in 
character because of differences of the habitats in which 
they get their subsistence. 

In the Cephalopoda there are two teeth," enclosing what 
is called the mouth ; and inside this mouth is a flesh-like 
substance which represents a tongue and serves for the dis- 
crimination of pleasant and unpleasant food. The Crustacea 
have teeth corresponding to those of the Cephalopoda, 10 
namely their anterior teeth,'^ and also have the fleshy repre- 

' Cf. iii. 4. 665^ 31 note. 

"^ Urinary bladder and lung (iii. 8. 671* l) were to A. signs of 
abundant blood; and viscera (iii. 7. 670•'^ 8 note) were one of the 
channels by which superfluous blood was eliminated. 

^ By the teeth are meant the two halves of the parrot-like beak. 
The so-called tongue is a large organ, and its anterior part ' very soft 
in texture, beset with numerous papillae, having all the characters of 
a perfect organ of taste' (Owen). 

"* The 'anterior teeth' are the strong shear-like mandibles; which 
are called anterior to distinguish them from the stomachal teeth 
presently to be mentioned. By the tongue is meant the bifid lower lip, 
which has been called a tongue by other writers than Α., but is not 
properly comparable to such an organ. Cf. Todd, Cyd. i. 773. 


sentative 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 In- 

15 sects. For some of these, such as the Bees and the Flies, 
have, as already described, ^ their proboscis protruding from 
the mouth ; while those others that have no such instru- 
ment in front have a part which acts as a tongue inside the 
mouth." Such, for instance, is the case in the Ants and the 
like. As for teeth, some insects have them, the Bees and 
the Ants •* for instance, though in a somewhat modified 

20 form, while others that live on fluid nutriment are without 
them. For in many insects the teeth are not meant to deal 
Avith the food, but to serve as weapons. 

In some Testacea, as was said in the first treatise,^ the 
organ which is called the tongue is of considerable strength ; 
and in the Cochli {Sea-snails) there are also two teeth," just 

25 as in the Crustacea. The mouth in the Cephalopoda is 
succeeded by a long gullet. This leads to a crop,"^ like that 
of a bird, and 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 Teuthides {Calaniaries). Here, as in the other 

30 groups, there are the two stomach-like receptacles ; but the 

' The tongue or odontophore forms a very remarkable organ in the 
Gasteropoda, but there is none in the Conchifera or bivalves of 
Aristotle. 2 q^ ^_ ^_ |^,_ ^^ ^28'^ 29. 

^ The so-called ' tongue ' of insects is the upper portion of the 
labium, and is very distinct in some species. In bees and flies this 
tongue goes, with the rest of the labium, to form what A. calls their 
proboscis ; so that it is only in other insects that there is a distinct 
tongue inside the mouth. 

* Reading μνρμηκων for μνιών, the very probable emendation of 
Meyer. The 'modified teeth' are the mandibles. The insects that 
live on fluid nutriment and have no teeth are the Lepidoptera, in which 
the maxillae are converted into a long proboscis, while the mandibles 
are quite rudimentary. ^ //. A. iv. 4. 528'' ^2,. 

^' i.e. the horny jaws with which some Gasteropods are furnished. 

'' By the crop [πρόΧοβυς) and stomach of the Cephalopoda A. meant 
respectively what modern anatomists recognize as the stomach and 
the first part of the intestine ; which latter is dilated and has a diver- 
ticulum that in some species is spirally convoluted so as to be aptly 
likened by A. {H. A. iv. i. 524^ 11) to the helix of a whelk. The real 
crop, which is present only in the poulps among dibranchiate Cephalo- 
poda, was not noticed by A. 

BOOK IV. 5 678" 

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 body indeed being made of a softer 
kind of flesh. 

The object of this arrangement of the parts in question is 
the same in the Cephalopoda as in Birds ; for these also are 
all unable to masticate their food ; and therefore it is that 3.^ 
a crop precedes their stomach. 

For purposes of defence, and to enable them to escape 
from their foes, the Cephalopoda have what is called their 
ink. This is contained in a membranous pouch, which is 679^ 
attached ^ to the body and 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 Cephalopoda alike have 5 
this characteristic ink, but chief of all the Sepia, where it is 
more abundant than in the rest. When the animal is dis- 
turbed and frightened it uses this ink to make the surround- 
ing 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 lower down, against the 10 
stomach. For the Sepia has a more plentiful supply of ink 
than the rest, inasmuch as it makes 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 its long twining feet to use in its defence, and 
is, moreover, endowed with the power of changing colour.^ 
This changing of colour, like the discharge of ink, occurs as 

^ For προσπΐφνκότη read πμοσπ(φνκ6τι. 

- The mytis is identical with the mecon, which exists in all 
Crustacea {H.A. iv. 2. 526'' 32) ; is a bag containing excretory matter 
(H.A. iv. 4. 529'' 11) ; placed (680=^ 23) near the hinge in bivalves, and 
in the spiral part of the shell in Turbinata, being spiral itself, in the 
whelk for instance {H. A. iv. 4. 529*'^ 10). This can be nothing else 
than the liver ; and Kohler's notion that the glandular appendages of 
the veins are meant (Todd, Cycl. 0/ An. and Phy. i. 539) is out of the 

' In reality all these Cephalopods have the faculty of changing 
colour ; but the phenomenon is most conspicuous in the poulps (cf. 
Cuvier, A'. An. iii. 10). 


numerous. For there are those with turbinate shells, of 
which some have just been mentioned ; and, besides these, 
there are bivalves and univalves. Those with turbinate 
shells may, indeed, after a certain fashion be said to resemble 

20 bivalves. For they all from their very birth have an oper- 
culum to protect that part of their body which is exposed 
to view.^ This is the case with the Purpuras, with Whelks, 
with the Nerites, and the like. Were it not for this, the part 
which is undefended by the shell Avould be very liable to 
injury by collision with external objects. The univalves 
also are not without protection. For on their dorsal surface 
they have a shell, and by the under surface they attach 

25 themselves to the rocks, and so after a manner become bi- 
valved, 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 Turbinata by the 
operculum just mentioned, which transforms them, as it were, 
from univalves into bivalves. But of all there is none so 
perfectly protected as the sea-urchin. For here there is 
a globular shell which encloses the body completely, and 

30 which is, moreover, set with sharp spines. This peculiarity 
distinguishes the sea-urchin 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 Cephalopoda. 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 sea-urchin, how- 
ever, there is no fleshy part whatsoever. 

35 AH the Testacea then, those that have not been mentioned 

^ That all Turbinata have opercula is of course an error. In many 
genera, especially those with large apertures, it is quite rudimentary 
or obsolete (Woodward, Λ'. and F. Shells, p. 102). So also a con- 
siderable division of air-breathing gasteropods is inoperculate. 

That the operculum corresponds to the second valve of bivalves is 
a view that has been held by some modern zoologists, erroneously. 
It represents their bysstis (Woodward, R. atui F. Shells, p. 47). More- 
over, the bivalve shell is really a single shell, hardened by deposits of 
lime on the right and left, but with a central strip left uncalcified and 
soft, so as to allow the two sides to fold together. 

- I can find no passage to which this can refer. 

BOOK IV. 5 679^ 

as well as those that have, agree as stated in possessing 
a mouth with the tongue-like body, a stomach, and a vent 
for excrement, 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 con- 680* 
cerning 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 sea-urchins and the 
animals known as Tethya {Ascidians). The sea-urchins 5 
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 the stomach, 
divided into a number of separate compartments, which look 
like so many distinct stomachs ; for the cavities are separate 
and all contain abundant residual matter. They are all, 
however, connected with one and the same oesophagus, and 10 
they all end in one and the same excremental vent.* There 
is nothing besides the stomach of a fleshy character, as has 
already been stated.^ All that can be seen are the so- 

1 Cf. H. A. iv. 4. 528'^ 10 sq. 

^ This passage with others shows that the Hist. Animaliiiin and the 
lost treatises on Anatomy were illustrated. Cuvier indeed {Hist. d. 
Sc. i. 141) says the latter contained iTi^/cwr^^/ illustrations. I can find 
no authority for this statement. There is none in the twenty-eight 
passages referring to the ανατομαί collected by Heitz {Verlor. Schr. des 
A fist. p. 70). 

^ Forming what is still known as the 'lantern of Aristotle' from 
a comparison in the Hist. An. (iv. 5. 531* 5). The central fleshy 
piece is there said (iv. 5. 530'' 25) to be ' in place of a tongue'. As the 
sea-urchin has no tongue, the pharyngeal portion of the oesophagus 
must be meant. 

* The oesophagus of Echinus terminates in a much wider tube, 
λvhich 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 distinct stomachs, but 
still more from his language in Hist. An. (iv. 5. 530^ 27), where he says 
that all the loops (κόλποι) of the stomach run together to the anus ; and 
where also he makes no mention of an intestine as distinct from the 

* What he said (679'» 34) was that there was no fleshy part at all. 
Perhaps, therefore, for πσρά should be read π^ρί (with U). 


called ova/ of which there are several, contained each in 
a separate membrane, and certain black bodies which have 
no name, and which, beginning at the animal's mouth, are 
scattered round its body here and there promiscuously.^ 

15 These sea-urchins are not all of one species, but there are 
several different kinds, 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 that with which we are all 
familiar.^ A similar distinction may be made generally in 

20 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 fundus, and in bivalves is placed near the hinge, 

25 the so-called ovum lying on the right ;^ while on the opposite 

^ 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, or in males the testes. These are five in number, and arranged 
symmetrically round the upper interior of the shell, and would be called 
by fishermen ' sea-urchins' eggs '. 

^ These mysterious black Ijodies are also mentioned in the ///j/.yi;;. 
(iv. 5. 530^ 31) and are said to be bitter and uneatable. They are 
further said, in one kind at any rate (530^ 14), to start from the mouth 
and run in distinct lines that converge towards the aboral aperture of 
the test, dividing this into segments. This plainly suggests the rows 
of ambulacral vesicles ; and, though these do not appear to be black 
in any known species, there is generally a certain amount of pigment 
connected with them in E. esculenius, as I am informed by the 
Director of the Plymouth Laboratory, and this, though scanty in young 
Echini, becomes more extensive in some of the older specimens. See 
also Macbride (CciWi^. Nat. Nisi. Echinod. pp. 527-8), as to 'masses of 
pigment ' formed in these animals by certain degenerative processes. 
Admitting, however, these pigmentary deposits to be the ' black 
bodies' there still remains unexplained the further statement (//.^. iv. 5. 
530^^ Ό)) that analogous bodies, though of different colour, are present 
in Frogs, Toads, Tortoises, turbinated Testacea, and Cephalopods. 

^ Frantzius, as also Meyer {Thierkimde, p. 175), takes ί'πιπολά^οι^τα 
to mean ' floating on this surface '. But no sea-urchins do this, and 
Frantzius therefore supposes A. to be speaking of dead specimens ! 
Possibly the word may mean ' living nea?- the surface ', that is in 
shallow water, in opposition to the deep-sea species {G.A. v. 3. 783* 
21 sq.). The most probable interpretation, however, is that given above, 
meaning the common edible kind. 

* See 679^ II n. 

* So also N.A. iv. 4. 529^' 12. What A. exactly meant by the right 

BOOK IV. 5 68ο' 

side is the vent. 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 makes its appearance 
in Testacea at those seasons of the year when they are in 
good condition, namely, spring and autumn. For no Testacea 
can abide extremes of temperature, and they are therefore 
in evil plight in seasons of great cold or heat. This is 30 
clearly shown by what occurs in the case of the sea-urchins. 
For though the ova are to be found in these animals even 
directly they are born, yet they acquire a greater size 
than usual at the time of full moon; not, as some think, 
because sea-urchins 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 35 
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 680^ 
strait. There the sea-urchins 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 sea-urchins, and 
is an odd one. For there are five ova, just as there are also 
five teeth and five stomachs ; and the explanation of this is 5 
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 a so-called ovum, 
corresponding in character to that of the sea-urchins, but 
existing only on one side of their body. Now inasmuch as 

and left side of a bivalve it is impossible to say. For he had not made 
out the position of the mouth, and therefore had no guide as to what 
was the front aspect. As is not surprising, he entirely failed to make 
out the internal structure of these animals. 

^ Cicero {De Diviu. ii. 14) mentions, among other instances of some 
natural connexion existing between things apparently remote and 
incongruous, 'that oysters and other shell-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 sub- 
mersa fretis, concharum et carcere clausa, Ad lunae motum variant 
animalia corpus.' The two last quotations I borrow from Mead 
{^Iiifluence of Sun and Moon, &c., 1748, p. 65), who accepts the state- 
ment as true ; as also at the present day, as I am informed, do fisher- 
men on the Riviera. 


10 the sea-urchin 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, its ovum must 
necessarily be of a corresponding symmetry. For the spheri- 
cal shape has not the asymmetry of the disk-shaped body 
of the oysters. For in all these animals the head is central, 

15 but in the sea-urchin the so-called ovum is above [and sym- 
metrical, while in the oyster it is only on one side].^ 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 sea-urchins asymmetrical, being placed only 
on one side of the body. Owing then to this necessary dis- 
continuity of the ovum, which belongs to the sea-urchin as 
a member of the class, and owing to the spherical shape of 
its body, which is its individual peculiarity, this animal 

20 cannot possibly have an even number of ova. For were 
they an even number, they would have to be arranged 
exactly opposite to each other, in pairs, so 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 uneven, three for 

25 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 

30 number of teeth. For seeing that the ova represent each 
of them a kind of body for the animal, their disposition 

^ An attempt is made in the translation to give some kind of meaning 
to this uninteUigible passage by supposing that τοΙς δ' άλλοις eVl θάτίμα 
μόρον should be read here, having been omitted by the copyist because 
of the occurrence of similar words at the end of the next sentence. 

" Read λίαν αν ην. 

BOOK IV. 5 680" 

must conform to that of the stomach,^ seeing that it is from 
this that they derive the material for their growth. Now 
if there were only one stomach, either the ova would be too 
far off from it, or it WOuld be so big as to fill up the whole 
cavity, and the sea-urchin 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 .^5 
interval. So also, and on like grounds, there are five teeth. 
For nature is thus enabled to allot to each stomachal com- 681* 
partment and ovum its separate and similar tooth. These, 
then, are the reasons why the number of ova in the sea- 
urchin is an odd one, and why that odd number is five. In 
some sea-urchins the ova are excessively small, in others 
of considerable 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 5 
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. As evidence of this, it will be found that they always 
have something or other sticking to their spines, as though 
they moved much about ; for they use their spines as feet.^ 

The Ascidians differ but slightly from plants, and yet 10 
have more of an animal nature than the sponges, which are 
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 groups owing to their close proximity."* 

' For ζω?]ς read κοιλίας. 

^ Literally ' for which reason the uneatable varieties are more full 
of residual matter', but expanded above for clearness. Ώίρίττωμα is 
here used not for excremental matter but for unconcocted food. 

^ 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 in either Echini or Star-fishes. 

* N.A. viii. 588^' 4 sq. 


15 A sponge, then, as already said, in these respects com- 
pletely 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 Holo- 
thurias and the sea-lungs, as also sundry other sea-animals 
that resemble them. For these are free and unattached. 

20 Yet they have 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 upon other plants, or even 
entirely free. Such, for example, is the plant which is 
found on Parnassus, and which some call the Epipetrum.^ 

25 This you may hang up on a peg- 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 un- 
attached,^ but, on the other hand, inasmuch as they have 
a certain flesh-like substance, they must be supposed to 

30 possess some degree of sensibility. 

An Ascidian has a body divided by a single septum and 
with two orifices, one where it takes in the fluid matter that 
ministers to its nutrition, the other where it discharges the 
surplus of unused juice, for it has no visible residual sub- 
stance, such as have the other Testacea. This is itself 
a very strong justification for considering an Ascidian, and 
anything else there may be among animals that resembles 
it, to be of a vegetable character ; for plants also never have 
any residuum.^ Across the middle of the body of these 

35 Ascidians there runs a thin transverse partition, and here it 
is that we may reasonably suppose the part on which life 
depends to be situated. 

^ Probably a Sedum. There is an English species, S. ielephhnn, 
which has gained the popular name 'Livelong' from its persistent 
vitality after being pulled up from the ground. 

* Literally 'the pegs'; apparently referring to some constant house- 
hold fixture. Or perhaps ' the rafters '. 

^ Aristotle's Tethya, or Ascidians, are not Tunicata generally, but 
only the simple solitary Ascidians, which are always sessile. 

* Cf. ii, 3. 650=* 23 note. 

BOOK IV. 5 681^^ 

The Acalephae/ or Sea-nettles, as they are variously 
called, are not Testacea at all, but lie outside the recognized δδ!** 
groups. Their constitution, like that of the Ascidians, ap- 
proximates them on one side to plants, on the other to 
animals. For seeing that some of them can detach them- 
selves and can fasten upon their food, and that they are 
sensible of objects which come in contact with them, they 
must be considered to have an animal nature. The like con- 
clusion follows from their using the asperity of their bodies ^ 5 
as a protection against their enemies. But, on the other 
hand, they are closely allied to plants, firstly by the imper- 
fection of their structure, secondly by their being able to 
attach themselves to the rocks, which they do with great 
rapidity, and lastly by their having no visible residuum not- 
withstanding that they possess a mouth. 

Very similar again to the Acalephae are the Starfishes. 
For these also fasten on their prey, and suck out its juices^ 10 
and thus destroy a vast number of oysters. At the same 
time they present a certain resemblance to such of the 
animals we have described as the Cephalopoda and Crus- 
tacea, inasmuch as they are free and unattached. 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 15 
there must be some part or other which shall be analogous 
to what in sanguineous animals is the presiding seat of sen- 
sation. Whether an animal has or has not blood, it cannot 
possibly be without this. In the Cephalopoda this part 
consists of a fluid substance contained in a membrane, 

* //. A. iv. 6. 531'^ 32 sq. The anemones of our coasts, though 
richly furnished with nematocysts, very exceptionally cause irritation, 
when handled, to the fingers. Presumably such irritation must be 
more common with the Greek anemones, as otherwise they would 
scarcely have got the general name of Sea-nettles. In all the instances 
of such stinging by British anemones cited by Gosse (Br. Sea A/i., 
pp. 166, xxxviii) the culprit was Anthea cerens. This is common in 
the Mediterranean, and ' would probably be one of the first species of 
the whole race to become popularly known ' [op. cit., p. 162). It was 
known to Rondelet as Urtica cinerea. 

^ More definitely called slinging (//. A. ix. 37. 621"' 11) and ascribed 
to the general surface of the body. 


through which runs the gullet on its way to the stomach. 
It is attached to the body rather towards its dorsal surface, 
20 and by some is called the viytis} Just such another organ 
is found also in the Crustacea and there too is known by the 
same name. This part is at once fluid and corporeal and, 
as before said, is traversed by the gullet. For had the 
gullet been placed between the mytis and the dorsal surface 
of the animal, the hardness of the back would have inter- 
25 fered with its due dilatation in the act of deglutition. On 
the outer surface of the mytis runs the intestine ; and in con- 
tact with this latter is placed the ink-bag, so that it may be 
removed as far as possible from the mouth and its obnoxious 
fluid be kept at a distance from the nobler and sove- 
reign part. The position of the mytis shows that it corre- 
sponds to the heart of sanguineous animals ; for it occupies 
30 the self-same place. The same is shown 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 
corresponding position, but is less easily made out.^ It 
should, however, always be looked for in some midway 
position ; namely, in such Testacea as are stationary, mid- 
35 way between the part by which food is taken in and the 
channel through which either the excrement or the sper- 
matic fluid ^ is voided, and, in those species which are capable 
682* of locomotion, invariably midway* between the right and 
left sides. 

In Insects this organ, which is the seat of sensation, 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 {Millipedes), it is 

^ The myiis, which in cephalopods is traversed by the oesophagus, 
is the liver, not the heart (cf. 679^ 9 η.). The real heart of cephalopods, 
as of all other invertebrates, escaped Aristotle. 

^ A. does not profess to have seen the heart of a mollusc, but only 
to say where it is likely to be found on a priori grounas. 

^ ' or the spermatic fluid ' is probably an interpolation. For A. 
{G. A. iii. II. 761'^ 25) denied the existence of any distinct generative 
secretion in bivalves. 

* Read ϊντωμίσω (Ρ). ^ Η. Α. iv. 7. 531^ 34. 

BOOK IV. 5 682« 

made up of several parts, so that such insects continue to live 5 
after they have been cut in pieces. For the aim of nature 
is to give to each animal only one such dominant part ; and 
when she is unable to carry out this intention she causes the 
parts, though potentially many, to work together actually 
as one. This is much more clearly marked in some insects 
than in others. 

The parts concerned in nutrition are not alike in all 10 
insects, but show considerable diversity. Thus some have 
what is called a sting in the mouth, which is a kind of 
compound instrument that combines in itself the character 
of a tongue and of lips. In others that have no such in- 
strument in front there is a part inside the mouth that 
answers the same sensory purposes. Immediately after the 
mouth comes the intestine, which is never wanting in any 
insect. This runs in a straight line^ and without further 
complication to the vent ; occasionally, however, it has a 15 
spiral coil. There are, moreover, some insects in which 
a stomach succeeds to the mouth, and is itself succeeded 
by a convoluted intestine, so that the larger and more 
voracious insects may be enabled to take in a more abun- 
dant supply of food. More curious than any are the 
Cicadae. For here the mouth and the tongue are united 20 
so as to form a single part, through which, as through a 
root, the insect sucks up the fluids on which it lives.^ In- 
sects 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 requires no sustenance. In 
no insects is this so conspicuous as in these Cicadae. For 
they find enough to live on in the moisture which is depo- 25 

^ In most Myriapoda, included by A. among insects, the alimentary 
canal is a simple tube running in a straight line from mouth to anus. 
]5ut in some, e. g. Glomeris, the tube, though still simple, is convoluted. 
In true insects the canal varies much in complexity; but in many 
is a long convoluted organ divided into a varying number of distinct 

^ 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 maxillae converted into lancet-shaped 


sited from the air. So also do the Ephemera ^ that are 
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. 
30 We have now done with the internal parts of animals, 
and must therefore return to the consideration of the ex- 
ternal parts which have not yet been described. It will be 
better to change our order of exposition and begin with the 
animals we have just been describing, so that proceeding 
from these, which require less discussion, our account may 
have more time to spend on the perfect kinds of animals, 
those namely that have blood. 

35 We will begin with Insects. These animals, though they 6 
present no great multiplicity of parts, are not without 
diversities when compared with each other. They are all 
many-footed ; the object of this being to compensate their 
682'' natural slowness and frigidity, and give greater activity to 
their motions. Accordingly we find that those which, as the 
Juli {Millipedes), have long bodies, and are therefore the most 
liable to refrigeration, have also the greatest number of feet. 
Again, the body in these animals is insected^ — the reason 
for this being that they have not got one vital centre but 
many — and the number of their feet corresponds to that 
of the insections ^. 
5 Should the feet fall short of this, their deficiency is 
compensated by the power of flight. Of such flying 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 side, to support it. 
10 Such are bees and the insects akin to them. When, how- 
ever, such insects are of very small bulk, their feathers are 

1 The Ephemera of A. are presumably the insects still so named. 
They are said, however (//. A. i. 5. 490»- 34), to have only four legs, 
which is neither true of Ephemera nor of any other insects. 

- That is, are divided into segments. The Ιντομαί or insections are 
the more or less complete belts of softer and more pliable integument 
that form joints between the successive segments, being visible on the 
upper or under surface of the body or on both ; and it is to these 
('ντομηί or insections that '4ντομη or insects owe their name (//. A.\. i. 
487^ 33 : iv. I. 523'' 13)• 

^ Read κατίι ταύτης. 

BOOK IV. 6 682^ 

reduced to two, as is the case with flies. Insects with heavy ^ 
bodies and of stationary habits, though not polypterous in the 
same way as bees, yet have sheaths to their feathers to main- 
tain their efficiency.- Such are the Melolonthae " and the like. 1 5 
For their stationary habits expose their feathers to much 
greater risks than are run by those of insects that are more 
constantly in flight, and on this account they are provided 
with this protecting shield. The feather of an insect has 
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 body, as the fleshy substance grows cold. 

These animals then have their bodies insected, not only ^° 
for the reasons already assigned,*^ but also to enable them to 
curl round in such a manner as may protect them from in- 
jury " ; for such insects as have long bodies '^ can roll them- 
selves up, which would be impossible were it not for the 

' For βραχία read βηρία, and in the next line for «χα be read 'ίχ^ι 

- If the Greek text as it stands is correct, we must suppose that A. 
thought that beetles have elytra — that is shards, m addition to their 
multiple πτ^ρά. But it is scarcely credible that A. should have thought 
this to be the case. I have therefore adopted a suggestion made by 
Prof. Piatt, and read ονκ after μίλίσσηι:. This aheration not only makes 
the passage intelligible, but, moreover, gives its proper significance to 


^ Probably Cockchafers. But, if so, the statement as to their 
development (//. A. v. 19. 552''^ 16) is quite erroneous. 

* Frantzius,as also Aubert and Wimnier, renders nrepi')» when applied 
to insects as ' wing '. But this part of an insect is never termed 
πτίρνξ, by Α., but always wrepov or πτίλον ; and, moreover, is said to 
contrast with other nrepa in being ΙΊσχιστην and ίΊκηνλον, which can only 
mean ' without barbs or shaft '. It must, however, be admitted that 
A. calls bats deppourepa, in which title nrepnv can only mean ' wing'. 

^ Cf. iv. 5. 677^ 23 ; 678=* 3 note : G. A. ii. 4. 739'' 27. 

^ Or rather ' reason ', for only one niVtVi was assigned. 

■^ Liddell and .Scott (7th ed.) interpret δι' άν:άθ(ΐαν as 'without 
suffering pain ', which makes admirable sense but seems scarcely 
tenable. If the reading be correct, the words must apparently be 
taken as equivalent to προς το απαθή eivm (iii. 11. 673^ 5), διά being used 
in the sense, exceptional in Α., of ' for the sake of as in 8ui τήν Ισχνρ 
(iv. 10. 687^ 17). Conjecturally, however, the reading may be δι' 
άκινησίαν, ' curl round and derive security from remaining motionless'. 

* The Juli when alarmed coil themselves up in a spiral form, with 
the feet entirely concealed. The Glomeridns roll themselves into a 
perfect ball. Not only long-bodied insects, but some others, roll 
themselves up. For instance, the ant known as Myriii. Laireillii is 
said by Sir J. Lubbock to do so. 


insections ; and those that cannot do this can yet draw 
their segments up into the insected spaces, and so increase 

35 the hardness of their bodies. This can be feh quite plainly 
by putting the finger on one of the insects, for instance, 
known as Canthari.^ The touch frightens the insect, and 
it remains motionless, while its body becomes hard. The 
division of the body into segments is also a necessary re- 
sult of there being several supreme organs in place of one ; 
and this again is a part of the essential constitution of in- 
sects, and is a character which approximates them to plants. 
For as plants, though cut into pieces, can still live, so also 
can insects. There is, however, this difference between the 
two cases, that the portions of the divided insect live only 
for a limited time, 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 sting. In some 

30 this is in front, connected with the tongue, in others behind 
at the posterior end. For just as the organ of smell in 
elephants answers several uses, serving alike as a weapon 
683* and for purposes of nutrition, so does also the sting, when 
placed in connexion with the tongue, as 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 the mouth. 
Such of these insects as have no anterior sting are provided 
with teeth, which serve in some of them for biting the food, 
5 and in others for its prehension and conveyance to the 
mouth. Such are their uses, for instance, in ants and all the 

^ The description of the Canthari in the Hist. An. (v. 19. 552^ 17), 
where they are said to roll dung into balls, in which they deposit their 
progeny, seems to identify them with the Scarabaei of Egypt {Ateuchus 
sacer). Many beetles when touched assume attitudes more or less 
such as here described. ' The common dung-chaffer, 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,' &c., &c. 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 immovable with 
the separation of the segments scarcely visible' (Kirby and Spence). 

BOOK IV. 6 683= 

various kinds of bees.^ As for the insects that have a sting 
behind, this weapon is given them because they are of 
a fierce disposition. In some of them the sting is lodged 
inside the body, in bees, for example, and wasps. For these 
insects are made for flight, and were their sting external and 
of delicate make it would soon get spoiled ; ^ and if, on the 10 
other hand, it were of thicker build ,^ as in scorpions, its 
weight would be an incumbrance. As for scorpions that 
live on the ground and have a tail, their sting must be set 
upon this, as otherwise it would be of no use as a weapon. 
Dipterous insects never have a posterior sting. For the very 
reason of their being dipterous is that they are small and 15 
\veak, and therefore require no more than two feathers to 
support their light weight ; and the same reason which 
reduces their feathers to two causes their sting to be in 
front ; for their strength is not sufficient to allow them to 
strike efficiently with the hinder ^ part of their body. Poly- 
pterous insects, on the other hand, are of greater bulk — in- 
deed it is this which causes them to have so many feathers ; 
and their greater size makes them stronger in their hinder 
parts. The sting of such insects is therefore placed be- 
hind. Now it is better, when possible, that one and the same 20 
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 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 

^ Ants, bees, and Hymenoptera of all kinds have biting jaw? or 
mandibles. It is these that A. calls their 'modified ' teeth (iv. 5. 678*^ 
1 8 note). These mandibles, however, are not used merely or principally 
for the prehension of food, as stated in the text, but ' comme instru- 
ments de sculpture dans les travaux architecturaux de ces animaux ' 
(M. Edwards, Leqo7is, v. 520). 

^ Read (ϋφθαρτα αν ην. 

^ For άπ€'ίχίν read παχία ην (Piatt) ; and two lines down for κίντρην 
read κ^ρκον, and for fVi τηντα read iVi ταύτΐ]. 

* For ro(s 'ίμηροσθΐν read τοΊς οπιπθ(ν. 

' 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 
meme que dans I'industrie des hommes, c'est surtout par la division du 


of acting like a coppersmith who for cheapness makes 

26 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 wipe away any foreign matter 

that may lodge on the insect's eyes and obstruct its sight, 

which already is not very distinct owing to the eyes being 

30 made of a hard substance. Flies and bees and the like may 

be constantly seen thus dressing themselves with crossed 

forelegs. 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 locusts for instance, and in the various kinds of fleas.^ 

travail, que ce perfectionnement s'obtient,' and in a note he adds, ' Ce 
principe de physiologic generale qui aujourd'hui est adopte par presque 
tous les zoologistes a ete formule pour la premiere fois dans un article 
que j'ai publie en 1827 ' (M. Edwards, Leqons, i. 16). 

' This strange implement with a double purpose is also mentioned 
in the Politics (iv. 15. 1299^ 10); where A. likens it to a board of 
magistrates charged with a multitude of distinct functions. Among 
the Graeco-Roman antiquities in the British iMuseum is a lampholder, 
to which my attention was directed by Mr. Arthur Smith, and which 
I think may very probably be an actual οί^ίΚϊσκοΚνχνιον. This holder 
is a bronze rod, some sixteen inches long, formed at one end into 
a horse-shoe, within which a small detachable oil-lamp swings freely, 
so as to have its face uppermost in all positions of the holder. A little 
way from the other end is a hook, obviously for suspension ; while 
the end itself — and this is the distinctive character — is a spike, intended, 
as I conjecture, to allow the holder to be stuck in the ground when the 
lamp was used out of doors or in a tent, as by soldiers, for whose use 
it was meant (Theopomp. El ρ η ν η, quoted by Pollux, χ. 1 1 8). When 
the soldier wanted the holder for cooking purposes, he would detach it 
from the lamp and fix the meat on the spike as on a toasting-fork, 
possibly, if the piece was large, further securing it by aid of the hook. 
In the passage of Theopompus cited above the οβίλισκολύχνιον is 
coupled with ξιφομύχαιρα, sword and knife in one. So sergeants in our 
own army used to carry sword-bayonets, which served both purposes 
indicated by the name. 

'^ The anterior pair of legs are remarkably long in some insects ; 
(Kirby, Bridg. Tr. ii. 180) ; with what use it is difficult to say. Some- 
times, 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. 

' 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 

BOOK IV. 6 683^ 

For these first bend and then extend the legs, and, by doing 
so, are necessarily shot up from the ground. It is only the 35 
hind legs of locusts, and not the front ones, that resemble 
the steering oars ^ of a ship. For this requires that the joint 683^ 
shall be deflected inwards, and such is never the case with 
the anterior limbs. The whole number of legs, including 
those used in leaping, is six in all these insects. 

7 In the Testacea the body consists of but few parts, the 
reason being that these animals Hve a stationary life. For such 5 
animals as move much about must of necessity have more 
numerous parts than such as remain quiet ; for their activi- 
ties are many,^ and the more diversified the movements the 
greater the number of organs required to effect them. Some 
species of Testacea are absolutely motionless, and others 
not quite but nearly so. Nature, however, has provided 
them with a protection in the hardness of the shell with 10 
which she has invested their body. This shell, as already 
has been said,-' may have one valve, or two valves, or be 
turbinate. In the latter case it may be either spiral, as in 
whelks, or merely globular,'^ as in sea-urchins. When it has 
two valves, these may be gaping, as in scallops and mussels, 15 
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 the Solens^ {razoi'-fishes). In 
all cases alike the Testacea have, like plants, the head 
downwards.*' The reason for this is, that they take in their 

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. 

1 The resemblance of these legs to the long lateral rudder-oars of 
ancient ships includes not only position but function. ' 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, ii. 162). 

"^ For hill TO eivai read δια τόπολλάς flvm (Piatt). ^ Cf. iv. 5. 679^* 16. 

* A. reckons Echinus, though globular, with Turbinata (στρομβώ^ν)• 

^ Probably So/en 7narginatus, see Forbes and Hanley {Brit. Mol- 
lusca, i. 240). 

•"' The ordinary position of most living bivalves is not on their side 
but vertical, with the opening between the valves downwards. This 
probably led Λ. to the conclusion that the head, or what answered to 
it, was downwards, so as to take in food from below. 


20 nourishment from below, just as do 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 mem- 
brane, and through this the animal filters fluid free from 
salt and absorbs its nutriment. In all there is a head ; but 
none of the parts, excepting this recipient of food, has any 
distinctive name. 

25 All the Crustacea ^ can crawl as well as swim, and accord- 8 
ingly 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 con- 

30 siderably 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 in place of hands for seizing and holding objects ; 
and they are therefore bent in the opposite direction to the 
feet, being so twisted as to turn their convexity towards the 

35 body, while their feet turn towards it their concavity. For 
in this position the claws are best suited for laying hold of 
684^ the food and carrying it to the mouth. The distinction 
between the Carabi and the Carcini [Crabs) consists in the 
former having a tail while the latter have none. For the 
Carabi swim about and a tail is therefore of use to them, 
serving for their propulsion like the blade of an oar. But it 
would be of no use to the Crabs ; for these animals live 
5 habitually close to the shore, and creep into holes and 
corners. In such of them as live out at sea, the feet are 
much less adapted for locomotion than in the rest, because 
they are little given to moving about but depend for pro- 
tection on their shell-like covering. The Maiae ^ and the 

^ For a more detailed account of Crustacea see H. A. iv. 2. A. 
divides those known to him into four groups (i) Carcini— our Bra- 
chyura or Crabs. (2) Carabi— our Pahnuridae or Spiny Lobsters. 

(3) Astaci — comprising the Smooth Lobsters and the River Crawfish. 

(4) Carides— among which are included Prawns, Shrimps, Squills, and 
other small species. 

^ The very large [H. A. iv. 2. 525^ 4), hard-shelled {H. A. viii. 17. 

BOOK IV. 8 684" 

crabs known as Heracleotic are examples of this ; the legs 10 
in the former being very thin, in the latter very short. 

The very minute crabs that are found among the small 
fry at the bottom of the net have their hindermost feet 
flattened out into the semblance of fins or oar-blades, so as 
to help the animal in swimming.^ 

The Carides are distinguished from the Carcinoid species 15 
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. 

Of the parts on the ventral surface, those near the head 
are in some of these animals formed like gills, for the admis- 20 
sion and discharge of water ; while the parts lower down 
differ in the two sexes. For in the female Carabi these are 
more laminar than in the males,^ and in the female crabs 
the flap is furnished with hairier appendages. This gives 
ampler space for the disposal of the ova, which the females 
retain in these parts instead of letting them go free, as do 
fishes and all ^ other oviparous ■* animals. In the Carabi and 25 
in the Crabs the right claw is invariably the larger and the 
stronger.^ For it is natural to every animal in active 

601 '* 18), thin-legged Maia, with eyes placed close together near the 
central line (H. A. iv. 3. 527'' 13), is doubtless the Spiny Spider-crab 
{iM. squinado). There are no sufficient data for determining what are 
meant by the ' Heracleotic crabs '. 

^ In most crabs the four hinder pairs of feet are formed exclusively 
for running ; 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. 

- ' 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, 
Led. i. 185). Similarly Cuvier {Reg. An. iv. 28), speaking of the flap 
or tail of the Brachyura, says, ' Triangulaire dans les males et garnie 
seulement k sa base de quatre ou deux appendices, elle s'arrondit, 
s'elargit et devient bombee dans les femelles. Son dessous offre 
quatre paires de doubles filets velus, destines a porter les ceufs. 
riusieurs de ces filets existent dans les males, mais dans un etat 

^ There are exceptions. Thus some spiders, toads, and even at least 
one fish carry their ova about with them after extrusion. 

* For τ'ικτοντα read ωοτοκονντα. 

^ This is too absolute a statement ; and elsewhere (//'. A. iv. 3. 

AR, p. A. Μ 


operations to use the parts on its right side in preference 
to those on its left ; and nature, in distributing the organs, 
invariably assigns each, either exclusively or in a more per- 
30 feet condition, to such animals as can use it. So it is with 
tusks, and teeth, and horns, and spurs, and all such defen- 
sive and offensive weapons. 

In the Lobsters 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 

35 character ; but they have them in this indeterminate way, 

owing to imperfect formation and to their not using them 

684^ 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 con- 

5 cerning Animals.^ 

We come now to the Cephalopoda.^ Their internal 9 
organs have already been described * with those of other 
animals. Externally there is the trunk of the body, not 
distinctly defined, and in front of this the head sur- 
rounded by feet, which form a circle about the mouth and 
10 teeth, and are set between these and the eyes. Now in all 
other animals the feet, if there are any, are disposed in one of 
two ways ; either before and behind or along the sides, the 
latter being the plan in such of them, for instance, as are 
bloodless and have numerous feet. But in the Cephalopoda 
there is a peculiar arrangement, different from either of these. 

527^ 6) 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 chelae 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 AIa?i, i. 330). There are, however, some 
small Crustacea in which the right claw appears to be invariably the 
bigger. Such, for instance, is the case in some, but not all, species of 

^ This is apparently correct, but not so the further statement that 
lobsters use their claws only for locomotion and not for prehension. 

^ H. A. iv. 3, 3 ; V. 7. 541*' 29. 

^ For a fuller account of Cephalopoda see H. A. iv. l. 523^ 21 sq. 

* Cf. iv. 5. 678'' 24 - 679* 31. 

BOOK IV. 9 684^ 

For their feet are all placed at what may be called the fore 
end. The reason for this is that the hind part of their body 
has been drawn up close to the fore part,^ as is also the case 15 
in the turbinated Testacea. For the Testacea, while in some 
points they resemble the Crustacea, in others resemble the 
Cephalopoda. 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 Cephalopoda ; and, though this is true in a certain 20 
degree of all the Testacea, it is more especially true of those 
turbinated species that have a spiral shell.^ Of this general 
plan, common to the two,^ we will speak presently. But let us 
first consider the case of quadrupeds and of man, where the 
arrangement is that of a straight line. Let A at the upper 25 
end ** of such a line be supposed to represent the mouth, 
then Β the gullet, and C the stomach, and the intestine to 
run from this 6" to the excremental vent where D is inscribed. 
Such is the plan in sanguineous animals ; and round this 
straight line as an axis are disposed the head and so-called 
trunk ; the remaining parts, such as the anterior and posterior 
limbs, having been superadded by nature, merely to minister 30 
to these and for locomotion. 

In the Crustacea also and in Insects there is a tendency to 
a similar arrangement of the internal parts in a straight line ; 
the distinction between these groups and the sanguineous 
animals depending on differences of the external organs 

^ A similar idea concerning the cuttlefish, viz. that it is 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 Geofifroy 
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 controversy which excited Goethe more 
than the revolution of 1830 (see Lewes, Goethe, ii. 436). 

^ Excluding, that is, the Echini, which A. reckons among Turbinata, 
notwithstanding their more or less globular shell. 

^ What A. means in this passage is perfectly clear, but the tran- 
scribers have evidently misunderstood him and the text consequently 
requires very free handling. 

* The manifestly corrupt text may be conjecturally amended as 
follows : πρώτον /nef eVrt ακρω τω ανω rrjs (υθύαί κατά τυ Α τυ στόμα, 
(πάτα κατά το Β τυν στόμαχοι', τυ δί Γ την κοιλίαν, άπο δε τοίτου το 
tVTfpov (Piatt). 

Μ % 


which minister to locomotion. But the Cephalopoda and 
the turbinated Testacea have in common an arrangement 
685'' which stands in contrast with this. For here the two ex- 
tremities are brought together by a curve, as if one were to 
bend the straight line marked Ε until D came close to Λ. 
Such, then, is the disposition of the internal parts ; and 
round these, in the Cephalopoda, is placed the sac (in the 
5 Poulps alone called a head),^ and, in the Testacea, the tur- 
binate shell which corresponds to the sac. There is, in fact, 
only this difference between them, that the investing sub- 
stance of the Cephalopoda is soft while the shell of the 
Testacea is hard, nature having surrounded their fleshy part 
with this hard coating as a protection because of their 
limited power of locomotion. In both classes, owing to 
this arrangement of the internal organs, the excrement is 

10 voided near the mouth ; at a point below this orifice in the 
Cephalopoda, and in the Turbinata on one side of it.- 

Such, then, is the explanation of the position of the feet in 
the Cephalopoda, 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 

15 the Poulps, owing to the former having no other mode of 
progression than by swimming, while the latter not only 
swim but crawl. For in the former six ^ of the feet are 
above the teeth and small, the outer one on either side being 
the biggest ; while the remaining two, which make up the 
total eight, are below the mouth and are the biggest of all, 
just as the hind limbs in quadrupeds are stronger than the 

20 fore limbs. For it is these that have to support the weight,* 

^ The head and body in the Poulps 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. 

■^ In Gasteropoda the mouth and anus are near each other, but never 
in the same median plane. 

^ After ohowuiv read Ιξ μικρούς (Gaza) and for μιγίστονς τούτων read 
μβγίστους πάντων. 

* Α. 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, says Owen, this difference in 
function that explains the different conformation of iiiamis and pes. 
Cf. Owen, Nature 0/ Limbs, p. 26, and Archet. of the Skeleton, p. 167. 

BOOK IV. 9 685* 

and to take the main part in locomotion. And the outer 
two of the upper six are bigger than the pair which inter- 
vene 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 Cephalopoda, namely eight,^ their length varies in 
different kinds, being short in the Sepias and the Cala- 
maries, but greater in the Poulps. For in these latter the 
trunk of the body is of small bulk, while in the former it is 25 
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 oppo- 
site way, and has given to the growth of the body what she 
has first taken from the feet.•'' The 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 30 
of progression, being small while the bulk of the body is 
considerable. These short feet would not enable their pos- 
sessors to cling to the rocks and keep themselves from 
being torn off by the waves when these run high 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 long proboscises, by which 
it can moor itself and ride at anchor like a ship in rough 35 
weather. These same processes serve also to catch prey at 685^ 

^ There does not seem any very certain rule as to the comparative 
lengths of the different arms in Sepia and Lohgo. 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 Poulps. 
Cuvier [Reg. An. iii. 11) says that their arms are all much of the same 
length. Owen {Lcct. on Comp. Atiat. i. 344) says that in most of 
them the dorsal pair are the longest, which accords with H. A. iv, i. 
524^ 4• 

"^ A. does not reckon the two long retractile tentacles or ' probo- 
scises' of sepias and calamaries as feet ; so that he is correct in saying 
that all Cephalopoda are octopodous. 

* Cf. ii. 9. 655-*^ 28 n. '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 the two elongated retractile 
tentacles are superadded by way of compensation' (Owen, Led. i.344). 


a distance and to bring it to the mouth. They are so used 
by both the Sepias and the Calamaries. In the Poulps the 
feet are themselves able to perform these offices, and there 
are consequently no proboscises. Proboscises ^ and twining 
tentacles,^ with acetabula set upon them, act in the same 
5 way and have the same structure as those plaited instru- 
ments ^ which were used by physicians of old to reduce 
dislocations of the fingers. Like these they are made by 
the interlacing of their fibres, and * they act by pulling upon 
pieces of flesh and yielding substances. For the plaited 
fibres encircle an object in a slackened condition, and when 
they are put on the stretch they grasp and cling tightly to 
whatever it may be that is in contact with their inner sur- 
lo face. Since, then, the Cephalopoda have no other instru- 
ments with which to convey anything to themselves from 
without, than either twining tentacles,^ as in some species, 
or proboscises as in others, they are provided with these to 
serve as hands for offence and defence and other necessary 

' As the Greek text stands A. likens the entire cephalopod, and not 
merely its various tentacles with their suckers, to a πλ^γμάτιορ and, 
moreover, entirely leaves out of account the most important of the 
instruments he is discussing, namely, the ττροβοσ-κίδα of sepias and 
calamaries ; for these are not counted by him as nobes. I venture 
therefore to suggest that for όσου should be read δσαις and προβοσκίσι 
for πμόί τοΊς πήσι. 

^ The term πλεκτάναι, though sometimes used to denote the feet of 
any cephalopod without distinction, is applied more precisely to the 
long twining tentacles of the poulps, as contrasted with the compara- 
tively short tentacles of the sepias and calamaries. These ττλ^κτάνηι, 
and especially the dorsal pair (//. A. iv. i. 5243• 4), are held by A. 
to combine with their common office of feet the function of the long 
retractile tentacles (προβοσκίδας) of the sepias and calamaries, that is, 
to lay hold of prey at a distance and draw it to the mouth. 

^ These are the 'Saurae ' mentioned by Hippocrates (Kiihn's ed. iii. 
266). The ' Saura ' was a short tube of plaited palm-fibres, in size 
like the finger of a glove but open at both ends. Placing one end 
round the dislocated finger, the operator introduced his own finger into 
the other end, and, on pulling, the tube grasped both fingers tightly and 
enabled the surgeon to reduce the dislocation. A. likens the προβο- 
σκίς to a Saura ; Owen [Cjci. An. attd Phys. i. 529, fig. 215) with equal 
aptness to obstetrical forceps. * For αΓ<• (λκονσι read καί ίλκονσι. 

^ Though A. uses carelessly the general term ποσι, he plainly means 
πλΐκτάνηα. For parts special to some species of cephalopods, not 
parts common to all, are clearly indicated ; and it is the π\(κτάνίη of 
the poulps that serve like the proboscises of sepias and calamaries to 
bring objects in from without. After ΰλλην read xpelau και (Υ). 

BOOK IV. 9 685^ 

The acetabula are set in double line in all the Cephalo- 
poda excepting in one kind of poulp, where there is but 
a single row.^ The length and the slininess which is part 
of the nature of this kind of poulp explain the exception. 
For a narrow space cannot possibly admit of more than 15 
a single row. 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 contin- 
uous, as is also the case in the larger calamaries known as 
Teuthi.^ But in the smaller kind, called Teuthides, the fin 20 
is not only broader than in the Sepias and the Poulps, where 
it is very narrow, but, moreover, does not encircle the entire 
sac, but only begins in the middle of the side. 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 or so indis- 
tinct as in the Poulps." For in these the body is of small 25 
bulk and can be steered by the feet sufficiently well without 
other assistance. 

The Insects, the Crustacea, the Testacea, and the Cephalo- 
poda, have now been dealt with in turn ; and their parts 
have been described, whether internal or external. 

10 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 30 
on to the oviparous, 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 already been taken into con- 

^ The poulp with a single row of suckers is some species of Eledone 
{H. A. iv. I. 525'* 16), E. cirrhosa according to Owen. 

2 For the distinctive characters of Teuthi and Teuthides see //. A. 
iv. I. 524" 29. It is sufficient here to consider them as large and 
small calamaries without attempting precise identification, as to which 
zoologists differ greatly. 

^ The Octopodidae have in fact no body-fin at all. 

* i. e. the Mammalia. 


sideration.^ All animals that have blood have a head ; 
686* whereas in some bloodless animals, such as crabs, the part 
v\^hich represents a head is not clearly defined. 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.^ 
5 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 in an opposite region to 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 

lo suitable proportions as to ensure their tranquillity and pre- 
cision, while at the same time it can supply the brain with 
such warmth as it requires. There is yet a third con- 
stituent 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 

15 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 necessitated 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 

The head, then, exists for the sake of these three parts ; 
while the neck, again, exists for the sake of the windpipe. 

^ Cf. ii. lo-iii. 3. 

^ i. e. Fishes. Serpents, though they have a lung, have no neck. 
This exception, though not noted here, is dealt with in the next chapter. 

3 Cf. ii. 7. 652^ 17• , „ 

* Read πολΰ γαρ αν το μήκος ην (Ρ). 

^ 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. 648* 13 n.) ; 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. 664"• 23) 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 

BOOK IV. ΙΟ 686» 

For it acts as a defence to this and to the oesophagus, 
encircling them and keeping them from injury. In all 20 
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 25 
anterior limbs. in man the forelegs and forefeet 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 30 
under the burden of a heavy body, pressing down from 
above and obstructing by its weight the motions of the 
intellect and of the general 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 forefeet, and has thus con- 35 
verted the animal into a quadruped. For, as every animal 
that walks must of necessity have the two hinder feet, such 686'' 
an animal becomes a quadruped, its body inclining down- 
wards in front from the weight which its soul cannot sustain. 

^ Though there were lions in N. Greece in A.'s time they were rare 
and confined to a small iocahty (//; A. vi. 31. 579^ 6), and A. clearly was 
scantily informed about them ; for nearly all his statements about 
their structure are erroneous. Here he says that they have only one 
cervical vertebra ; a little later on he says they have but two dugs ; else- 
where that their bones are without medullary cavity, &ο. 

^ Such uses, for instance, as turning round quickly to guard the 
hinder part against a foe (iv. 11. 692=^ 5) ; picking up food from the 
bottom of the water, as do web-footed and other water-birds (iv. 12. 
693^ 8) ; or catching prey at a distance, the long neck serving as 
a fishing rod (iv. 12. 693^ 23). 

^ There are some perceptions, says Α., that are peculiar to one 
sense, e. g. colour to vision, hardness and temperature to touch, (S:c. 
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. De An. iii. I and 2 ; De 
Soin. 2 ; l)e Sens. 4. 442'' 4. 


For all animals, man alone excepted, are dwarf-like in form. 
For the dwarf-like is that in which the upper part is large, 
while that which bears the weight and is used in progression 
5 is small. This upper part is what we call the trunk,^ which 
reaches from the mouth to the vent. In man it is duly pro- 
portionate 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, Avhile the lower part is small ; so that the infant can 

lo only crawl, and is unable to walk ; nay, at first cannot even 
crawl, but remains without motion. For all children are 
dwarfs in shape, but cease to be so as they become men, 
from the growth of their lower part ; whereas in quadrupeds 
the reverse occurs, their lower parts being largest in youth, 
and advance of years bringing increased growth above, that 
is in the trunk, which extends from the rump to the 

15 head. Thus it is that colts are scarcely, if at all, below 
full-grown horses in height ; and that while still 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 

20 degree ; and therefore the greater growth of the lower parts 
as compared with the upper is also small, being proportionate 
to this smaller deficiency.^ 

Dwarf-like again is the race of birds and fishes ; and so 
in fact, as already has been said, is every animal that has 
blood. This is the reason why no other animal is so intelli- 

^ In the Greek text 'thorax' (θώραξ) ; this term not being as yet 
restricted to the cavity above the diaphragm, cf. H. A. i. 7. 491'*• 29. 

■^ Cf. H. A. ii. I. 500'^ 26 sq. This statement as to the aheration 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 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, Veri. 
p. 488). On the other hand, every one is familiar with the prepon- 
derant 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. 

BOOK IV. ΙΟ ese^" 

gent as man. For even among men themselves if we 
compare children with adults, or such adults as are of 25 
dwarf-like shape with such as are not, we find that, what- 
ever 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 further decrease occur in the elevating heat, and 
a further increase in the earthy matter, and the animals 30 
become smaller in bulk, and their feet more numerous, until 
at a later stage they become apodous, and extended full 
length on the ground. Then, by further 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 35 
head, while the seed has an opposite significance,^ for it is 687* 
produced above at the extremities of the twigs. 

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 5 
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 more rational to suppose that 
his endowment with hands is the consequence rather than 10 
the cause 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 it is a better plan to take a person who 
is already a flute-player and give him a flute, than to take 
one who possesses a flute and teach him the art of flute- 
playing. For nature adds that which is less to that which 15 

* Answers, that is to say, to the residual nutriment of animals. Cf. 
ii. 3. 650^ 20 n. 


is greater and more important, and not that which is more 
valuable and greater to that which is less. Seeing then 
that such is the better course, and seeing also that of what 
is possible nature invariably brings about 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 who would put 

20 the most organs to use ; and the hand is not to be looked 
on as one organ but as many ; for it is, as it were, an in- 
strument for further instruments.^ This instrument, there- 
fore, — 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 

Much in error, then, are they who say that the construc- 
tion of man is not only faulty, but inferior to that of all 
other animals ; seeing that he is, as they point out, bare- 

25 footed, 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 

30 their bodies, nor changing such single weapon as they may 
chance to possess. But to man numerous modes of defence 
687^ are open, and these, moreover, he may change at will ; as 
also he may adopt such weapon as he pleases, and at such 
times 2 as suit him. For the hand is talon, hoof, and horn, 
at will. So too it is spear, and sword, and whatsoever other 
5 weapon or instrument you please ; for all these can it be 
from its power of grasping and holding them all. In har- 
mony with this varied ofifice is the form which nature has 
contrived ^ for it. For it is split into several divisions, and 
these are capable of divergence. Such capacity of diver- 
gence does not prevent their again converging so as to 
form a single compact body, whereas had the hand been an 
undivided mass, divergence would have been impossible. 

^ Cf. Polit. i. 4. 1253•^ ^2)• ^ Read οπόταν for οπον ην. 

^ For σνμμίμηχηνησθαι read σνμμΐμηχάνηται and omit καί before 
rr] φνσΐΐ. 

BOOK IV. ΙΟ 687'^ 

The divisions also may be used singly or two together and 
in various combinations.^ The joints, moreover, of the lo 
fingers are well constructed for prehension and for pressure. 
One of these 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 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 15 
and hold like a tight clamp. As for the shortness of this 
digit, the object is to increase its strength, so that it may 
be able, though but one, to counterbalance its more 
numerous'•^ opponents. Moreover, were it long it would be 
of no use. This is the explanation ^ of its being sometimes 
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 a centre oar^ in a ship. 
This is rightly so ; for it is mainly by the central part of 20 
the encircling grasp that a tool must be held when put to use. 

No less skilfully contrived are the nails. For, while in 
man these serve simply as coverings to protect the tips of 
the fingers, in other animals they are also used for active 
purposes ; and their form in each case is suited to their 

The arms in man and the fore limbs in quadrupeds bend 25 
in contrary directions, this difference having reference to the 

^ If the text be correct, by hi must be meant one of the divisions 
implied in διαψΐτη, viz. one of the fingers. Not only is this a very 
strange construction, but τώρ Βακτύλων in the next sentence seems to 
mark that as the beginning of the account of the fingers. We should 
also expect πλείοσι rather than πολλαχως if fingers are meant. May it 
not be that for hu should be read μώ, the transcriber having been led 
to make this mistake by the ew that begins the preceding sentence ? 
' The hands also may be used singly or together and in various com- 

^ Transposing iW . . . πολΧοϊς to follow την Ισχύν. 

^ Transpose καΐ διά . . . uvev τούτου to come after el μακρός. 

'' For μίσον νίως read μ(:σόν(ως (Schneider). According to Dr. Warre 
(Badminton, Boating, p. 14) the midship oars in an ancient Greek 
vessel were longer and heavier than those nearer stern and prow ; 
and consequently it was these centre oars that poets put in the hands 
of heroes, see Apoll. Rhodius, Argon, i. 395-400. 


ingestion of food and to the other oiifices which belong to 
these parts. For quadrupeds must of necessity bend their 
anterior limbs inwards that they may serve in locomotion, 
for they use them as feet.^ Not but what even among 

30 quadrupeds there is at any rate a tendency for such as are 
polydactylous to use their forefeet not only for locomotion 
eSS'^ but 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 quadru- 
peds 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 
5 explains why in some of the polydactylous quadrupeds, such 
as wolves, lions, dogs, and leopards, there are actually five 
digits on each forefoot, 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 

10 animals are creepers ; and the increased number of nails 
serves to give them a tighter grip, and so enables them to 
creep up steep places with greater facility/ or even to run 
head downwards. 

In man between the arms, and in other animals between 
the forelegs, lies what is called the breast. This in man is 
broad, as one might expect ; for as the arms are set 

15 laterally on the body, they offer no impediment to such 
expansion in this part. But in quadrupeds the breast is 

^ Reading ως (Ρ) before ττοσίν, and substituting a comma for the 
colon after κώλα. 

^ Analogous is here used in the modern sense, i. e. having similar 
functions, and not as equivalent to homologous. 

^ And therefore is not vi^anted, as the hind foot has no hand-like 
office such as that of the corresponding forefeet. 

* In Canidae and Felidae, from which A.'s examples are taken, there 
are only four toes to the hind foot, while the forefeet iave each five, 
as in most Unguiculata. The smaller quadrupeds, that are described 
as having five hind toes and as creeping or even running head down- 
wards, 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. 

BOOK IV. ΙΟ 688-» 

narrow, owing to the legs having to be extended in a for- 
ward 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 20 
is ample space in this part ; moreover, the heart and neigh- 
bouring organs require protection, and for these reasons this 
part is fleshy and the mammae are placed upon it separately, 
side by side, being themselves of a fleshy substance in the 
male and therefore of use in the way just stated ; while in 
the female, nature, in accordance with what we say is her 
frequent practice, makes them minister to an additional 
function, employing them as a store-place of nutriment for 25 
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 ; while they form two separate 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 forelegs, for they would 30 
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 
region of the thighs, and are two in number,^ while in such 
as produce litters, or such as are polydactylous, the dugs 

* The upper or true ribs which are united to the sternum, in opposi- 
tion to the false ribs below. Thus there is firmness given to the 
mammae by the firm substratum. For άλληλας read αλλ>;λαί$•. 

^ As the arms are not used for locomotion, the mammae 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. 

^ Elsewhere (//. A. ii. 8. 502•'* 34), apes, as well as man, are excepted. 
Pectoral mammae 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. 

* Omit ήδη before πολλοίς. 

^ The horned 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.W. i. 499=^ 19) 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. 


are either numerous and placed laterally on the belly, as in 

35 swine and dogs, or are only two in number, being set, how- 
ever, in the centre ^ of the abdomen, as is the case in the lion.^ 
688^^ 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. 

5 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 region 
of the thighs, because they never occupy that position in 
any polydactylous animal such as this. Lastly, they are 

lo 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. Evidence 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 the dugs which 
are under the axillae. This, then, is the reason why the 

15 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 will have more young to nourish. 
Now it is impossible that these dugs should be set trans- 
versely in rows of more than two, one, that is, for each side 
of the body, the right and the left ^ ; they must therefore be 

^ In opposition to the general rule in bi-mammary animals, whose 
mammae, as said a few lines back, are set iv rols μηροΐς, that is are 
inguinal, or are pectoral as in man. 

^ The number and position of the mammae are given correctly by 
A. in the other instances ; but as usual 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 (G. A. iii. 10. 760^^ 23). 

^ The δια . . . be^u)v must refer in sense to the preceding διο, not to 
the μόνον:. There must be two in each row because of the require- 

BOOK IV. ΙΟ 688" 

placed Iength\vays, and the only place where there is 
sufficient length for this is the region between the front and 20 
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 region of the thighs.^ 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 goat, and '-5 
all other similar animals. 

The explanation is that in these animals growth takes 
place 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 
orifices for efflux, and here therefore nature has placed the 
mammae. For the place in which the nutriment is set in 
motion must also be the place whence nutriment can be de- 30 
rived by them. 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 35 
is left unenclosed by the ribs for a reason which has already 689* 
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. 

ments of bilateral symmetry (cf. 688^ 26), and not more than two, 
because of the narrow space. 

^ Omit κηί before eV τοΐς μηροΐς. 

^ 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, 
and the seat of plenty and location of the mammae is accordingly at the 
opposite or pectoral end. As to direction of growth cf. 686'^ 32 note. 

^ 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. 

* Cf. ii. 9. 655='' 2. 

AR. P.A. Ν 


At the extreme end of what is called the trunk are the 
parts concerned in the evacuation of the solid and also of 
the fluid residue. In all sanguineous animals with some 
5 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 con- 
gress, and this alike in male ^ and female. For the semen 
is a kind of fluid and residual matter.^ The proof of this 
will be given hereafter,* but for the present let it be taken 

lo for granted. (The like holds good of the menstrual fluid in 
women, and of the part where they ^ emit semen. 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 like the semen 

15 of the male are residual matter.*" Both of them, moreover, 

^ This passage is translated as it stands ; but the text cannot but be 
corrupt. For it makes A. say that all oviparous vertebrates with some 
few exceptions form urine, in contradiction of his repeated and distinct 
statement (e.g. iii. 8 and 9, iv. 13. 697'"^ 13 ; H.A. ii. 16) that none of 
them do so or have either kidneys or bladder, except tortoises. I have 
no doubt that what A. really said here was as follows : ' hi all such 
sangumeous animals as are viviparous and in some few of those that 
are oviparotis, the same part,' &c. ; the ' some few ' being the various 
tortoises, as to whose coitus see H. A. v. 3, v. 5. 541''^ 8. For 'έξω . . . 

έναίμοις, therefore, I would read iv ολίγοις τισ\ν των ωοτόκων. 

^ For των αρρένων read roh apptaiv. 

^ See note 6 and ii. 14. 658^ 23 note. 

* G. A. i. 18. 724'" 21-726^ 25. 

^ If the reading be correct, A. apparently attributes to females the 
secretion of yovi] ift addition to the καταμήνια. So also in the //. A. 
(i. 3. 489^^ 9-13) he attributes to them the secretion of σπέρμα. But 
when he considers the question more fully in the G. A.he again and 
again (e.g. 6^. ^. i. 19. 727'^ i and 28) maintains that the καταμήνια are 
themselves the female equivalent of yovn or σπέρμα. Prof. Piatt, how- 
ever, ingeniously suggests that the reading should be el προΐ^νταί τίνα 
-γονψ, ' and of the semen if so be that they emit any.' 

® Hippocrates (Kuhn ed. i. 551) had said, in partial anticipation of 
Darwin's doctrine of pangenesis, that the semen was formed by con- 
tributions 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. (G. A. i. 17, 18), who 
insists, among other arguments, that it would imply that the semen 
was a product of dissolution or decay (σύντηξις), which is clearly 
inadmissible. He argues that the semen can be nothing else in 
substance than part of that surplus or residue of sound nutriment, 
which, after conversion into blood, has not been required for the 
growth or maintenance of the bodily fabric. This, he says, explains 
why no semen is formed either when the growth is active, as in 

BOOK IV. ΙΟ 689' 

being fluid, it is only natural that the parts which serve for 
voidance of the urine should give issue to residues which 
resemble it in character.^) Of the internal structure of these 
parts, and of the differences which exist between the parts 
concerned with semen and the parts concerned with con- 
ception, 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 20 
to deal with Generation.^ As regards, however, the external 
shape of these parts, it is plain enough that they are adapted 
to their operations, as indeed of necessity they must be. 
There are, however, differences in the male organ corre- 
sponding to differences in the body generally. For all 
animals are not of an equally sinewy nature. This organ, 
again, is the only one that, independently of any morbid 
change, admits of augmentation and of diminution of bulk. 25 
The former condition is of service in copulation, while the 
other is required for the advantage of the body at large. 
For, were the organ constantly in the former condition, it 
would be an incumbrance. The organ therefore has been 
formed of such constituents as will admit of either state. 
For it is partly sinewy, partly cartilaginous,^ and thus is 3° 
enabled either to contract or to become extended, and is 
capable of admitting air.* 

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. 65 1'' 13). The 
semen, then, instead of being, as Hippocrates would have it, some- 
thing which comes from each and every part of the parent, is some- 
thing 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 {G. A. iv. 5. 774* 2), and there- 
fore retains a greater resemblance to blood. 
^ Omitting των αντων και. 

2 Η. Α. i. 13, 14) i• 17• 497''' 27, >ϋ• ι ; G. Α. i. 2-16. 

^ Elsewhere [Η. Α. ϋ. ΐ. 500^ 22) 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 conferring the power of contraction, cf. iii. 4. 666'^ 14 note. 

* Erection was attributed to air, not to blood {Probl. xxx. i. 953'' 34) ; 
as also emission (//. A. vii. 7. 586* 16). 

Ν 3 


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 only some 
few males, such as the lynx, the lion, the camel, and the 
hare.^ No quadruped with a solid hoof is retromingent. 
689^ The posterior portion of the body and the parts about 
the legs are peculiar in man as compared with quadrupeds. 
Nearly all these latter have a tail, and this whether they 
are viviparous or oviparous. For, even if the tail be of no 
5 great size, yet they have a kind of scut, as at any rate a small 
representative^ of it. But man is tail-less. He has, how- 
ever, buttocks, which exist in none of the quadrupeds. His 
legs also are fleshy (as too are his thighs and feet) ; ^ while 
the legs in all other animals that have any, whether vivi- 

10 parous or not, are fleshless, being made of sinew and bone 
and spinous substance. 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 

15 that the buttocks, the thighs, and the calves of the legs 
were all made fleshy. The character which she thus gave 
to the buttocks renders them at the same time useful in 

^ The camel, the cats, and many rodents including the hare, are 

^ For σμικρόν read σημίίον (Bonitz). 

'^ For κνήμης read πόδαϊ (Υ). 

Α. uses the term σκίΧος, as we use ' leg ', to designate not only the 
entire limb, but also that lower part of it which lies between thigh and 
foot ; but, as he shares the popular misconception which identifies the 
knee-joint of man with what is really the tarsal joint of other vertebrates, 
the tibial segment in man with its fleshy calf {κνήμη and -γαστροκνημία) 
and the scraggy metatarsal segment of quadrupeds and birds come 
to be the σκ€λη which he supposes to correspond anatomically and 
compares with each other. 

The same misconception as to the knee-joint causes him to find the 
counterpart of the human femur in the tibial segment of the other verte- 
brates ; but this leaves him in the case of these vertebrates with an extra 
limb-segment (the femur) unaccounted for. The human femur is jointed 
to the pelvic ischium, and therefore A. calls this extra segment an 
ischium, though it is a separate bone, and looks, he is bound to admit, 
when detached from its surroundings, just like a femur {H. A. ii. 12. 
503^ 35)• 

BOOK IV. ΙΟ 689" 

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, 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 20 
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 
Avhich 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. 25 
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 excrement, nature has given them a tail 3° 
of some kind or other, subtracting for the purpose some of 
the nutriment which would otherwise go to the legs. Inter- 
mediate 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 690^* 
is sometimes used by nature for by-purposes, being made 
to serve not only as a covering and protection to the 
fundament, but also for other uses and advantages of its 

There are differences in the feet of quadrupeds. For in 
some of these animals there is a solid hoof, and in others 5 
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 

^ i. e. the hind legs, //. A. ii. i. 500'' 29. 


10 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 ^ being that the presence of such a bone in the joint 
of the hind leg somewhat impedes its free motion. For 
extension and flexion can be made more rapidly in parts 
that have but one angle than in parts that have several. 
But the presence of a huckle-bone, as a connecting bolt, is 
the introduction as it were of a new limb-segment between 

15 the two ordinary ones. Such an addition adds to the 
weight of the foot, but renders the act of progression more 
secure. Thus it is that in such animals as have a huckle- 
bone, it is only in the posterior and not in the anterior limbs 
that this bone is found. 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 extensibility 

20 are what are 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 w^hich 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 

25 being deficient in the foot. As to the polydactylous quad- 
rupeds, none of them have huckle-bones. For if they had 
they would not be polydactylous, 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. 

^ Not every tarsal bone, which modern anatomists call astragalus, 
was so called by Α., but only such as in size and shape were suitable 
for the ancient game which has come down to us as the game of 
huckle-bone or knuckle-bone. Such are the astragali of the smaller 

^ Read καί before Sta ro Βυσκινητοτίραν (S U). 

^ A. probably 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. 

'' As to the supposed exceptions see //. A. ii. i. 499^* 20. 

BOOK IV. ΙΟ ego» 

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 are intended to bear all the weight of 30 
the body must be both long and broad. Equally intelli- 
gible 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 por- 
tion that the hand grasps an object. But the function of 690^ 
the feet is to enable us to stand securely, and for this ^ the 
undivided part of the foot requires to be of larger size 
than the toes. However, it is better for the extremity to be 
divided than to be undivided. For in an undivided foot 
disease of any one part would extend to the whole organ ; 5 
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 
fingers, namely because such projecting parts are weak and 10 
therefore require special protection. 

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 
II sanguineous animals as are oviparous. Of these some have 
four feet, while others have none. The latter form a single 
genus, namely the Serpents ; and why these are apodous 15 
has been already explained in the dissertation on Animal 

^ ' 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 Thomme tient a ce qu'il appuye le tarse, le metatarse et 
tous les doigts a terre, ce qu'aucun animal ne fait aussi parfaitement ' 
(Cuvier, Lemons, i. 474J. 

- For ωστΐ read π /jos be. For νομίζΐΐν read μ(ίζον (Piatt). 

^ For ΐσχισμίνων read (σχισμίνου. For σνμΙ3λάπτοιντο read av β\ά- 
πτοιντο (Piatt). 

* That is, all the Mammalia known to him, with the exception of 


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 

20 all, with the single exception 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 crocodile 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 some 
fishes, as has already been mentioned,^ there is no appear- 

25 ance whatsoever of a tongue, unless the mouth be stretched 
open very widely indeed ; while in others 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.^ 

30 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 qualities of food are 

^ De An. Inc. 8. yoS'^ 9-20. See also iv. 13. 696''^ 10, where the 
explanation is repeated. 

2 Cf. iv. 10. 686» 5-18. 

^ 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 (//. A. ii. 10. 
5038• i; P. A. ii. 17. 660'' 15). 

* Cf. ii. 17.660^ 13. 

^ 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 possibiHty of any delicate gustation. Still they 
are probably not entirely without this sense, as is elsewhere (//. A. iv. 
8. 533^^ 30) admitted ; for, as there pointed out, they manifest certain 
preferences for one food rather than another. 

BOOK IV. II 690'^ 

recognized ; and,^ in fact, the satisfaction from most solid 
edibles and dainties is derived almost entirely from the 
dilatation of the oesophagus during deglutition .^ This egi'* 
sensation, then, belongs even to animals that have no^ tongue, 
but while other animals have in addition the sensations of 
taste, tongueless animals have, we may say, 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. 

In some oviparous quadrupeds, namely in lizards, the 5 
tongue is bifid,^ as also it is in serpents,^ and its terminal 
divisions are of hair-like fineness, as has already been de- 
scribed.'^ (Seals also have a forked tongue.) This it is 
which accounts for all these animals being so fond of dainty 
food.^ The teeth in the four-footed Ovipara are of the 10 
sharp interfitting kind, like the teeth of fishes.'' The organs 
of all the senses are present and 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 

^ Transposing ^χα . . . α'ίσθησιν to after η χύρι.ς, and δίό . . . (8ω8ην to 
after ή ίτίρη. 

^ ' On which account a certain gormandizer wished that his throat 
were longer than a crane's, implying that his pleasure was derived from 
the sense of touch ' [Ethics, iii. 13. iiiS" 32). 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). 

^ For ζωοτόκα, substitute «γλωττα, as imperatively demanded by the 
context. A. did not suppose any vertebrate to be absolutely tongue- 
less, not even the crocodile (ii. 17. 660^ 25) though he calls ίΐηγλωττοί. 
In fishes, however, this part was almost rudimentary (ii. 17.660'^ 14 note) 
and their sense of taste consequently very feeble. 

* For ώστΐΐρανά read ώσπ^ρ μόνη (Υ). 

^ Cf. //. A. ii. 17. 508" 23. 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 chameleon 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. 

'■ Read και before oi οφίΐ? (Υ), 

■ Cf. ii. 17. 660'' 9. 

^ For Ισχνά read λίχνα (Karsch). 

' 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 whatsoever. 


duct, as also is the case in birds. This is due in both cases 

15 to the hardness ^ of the integument ; birds having their 
bodies covered with feathers, and these oviparous quad- 
rupeds with horny plates. These plates are equivalent to 
scales, but of a harder character. This is manifest in tor- 
toises and river crocodiles, and also in the large serpents. 
For here the plates become stronger than the bones,^ being 

20 seemingly of the same substance as these. 

These animals have no upper eyelid, but close the eye 
with the lower lid.^ In this they resemble birds, and the 
reason 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 corner. But none of the oviparous quadrupeds 

25 blink ; '^ for their eyes are harder than those of birds.^ The 
reason for this is that keen vision and far-sightedness ^ are 
of very considerable service to birds, flying as they do in 
the air, whereas they would be of comparatively small use 
to the oviparous quadrupeds, seeing that they are all of 
troglodytic habits. 

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 

30 and downwards, but also from side to side ; ^'^ while in fishes, 

^ Cf. ii. 12 ; and ii. 13. 657^ 5. 

^ All reptiles have homy epidermal scales, but not so such Amphibia 
as the frog and toad, which A. included 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, 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. 

^ Most reptiles have an upper eyelid, though they use the lower lid 
exclusively or preferentially. 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. 657^^ 32) to exist in Crustacea. 

; Cf.ii. 13.657^5. 
Not some but all, as more correctly stated, H. A. ii. 12. 504'"^ 26. 

" This is an error (cf. ii. 13. 657^ 23 note). 

'' And therefore, he implies, do not require so much protection. 

^ Reading ό^υωπία και το πόρρω wpoiSelv (U Υ). ^ Omitting ovv (Y). 

"* The Carnivora are an exception, their teeth being adapted for 

BOOK IV. II egr 

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 691'' 
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 superfluous. While in all other animals it is the lower 5 
jaw that is movable, in the river crocodile it is exception- 
ally the upper.^ This is because the feet in this creature 
are so excessively small as to be 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 that 
direction of motion which will give the greater force to 10 
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 prehen- 
sion 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 ^5 
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 also 
move 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 com- 
minution ; for such comminution and biting is the office 20 
of teeth. In crabs, then, and in such other animals as 
are able to seize their food in a leisurely manner, inasmuch 
as their mouth is not called on to perform its office while 
they are still in the water, the two functions are assigned to 

cutting and not for grinding. This exception, though not mentioned 
here, is recognized presently, when it is said that lateral motion goes 
with grinding teeth only, and therefore not with the serrated dentition 
of Carnivora. 

' This was the common behef 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 I'ont ecrit ainsi ; mais il ne se meut qu'avec la tete toute 
entiere' (A'r^. An. ii. 18). 


different parts, prehension to the hands or feet, biting and 
25 comminution of food to the mouth. But in crocodiles 
the mouth has been so framed by nature as to serve both 
purposes, the jaws being made to move in the manner just 

Another part present in these animals is a neck, this 
being the necessary consequence 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 
30 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 
692* allied to them, that they are able to turn their head back- 
wards without stirring the rest of the body. The reason of 
this is that a serpent, like an insect, has a body that admits 
5 of being curled up, its vertebrae being cartilaginous and 
easily bent.^ The faculty in question belongs then to 
■ serpents simply as a necessary consequence of this character 
of their vertebrae ; but at the same time it has a final cause, 
for it enables them to guard against attacks from behind. 
For their body, owing to its length and the absence 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 animals with which we are dealing have, moreover, 
10 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." For all such produce eggs, and the 

^ Cf. iii. 3. 664'*^ 30 note. 

^ The vertebrae 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. 

^ 'Internally viviparous' is equivalent to Mammalia, whose ovum 

BOOK IV. II 692^ 

nutriment which in Vivipara has the character of milk is in 15 
them engendered in the egg. Of all this, however, a clearer 
account will be given in the treatise on Generation.'^ As 
to the mode in which the legs- bend, a general account, in 
which all animals are considered, has already been given in 
the dissertation on Progression.^ These animals also have 
a tail, larger in some of them, smaller in others, and the 
reason for this has been stated in general terms in an earlier 20 

Of all oviparous animals that live on land there is none so 
lean as the Chamaeleon. 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 25 
aspect testify.'' But fear is a refrigeration, and results from 
deficiency of natural heat and scantiness of blood. 

We have now done with such sanguineous animals as are 692'' 
quadrupedous and also such as are apodous, and have stated 
with sufficient completeness what external parts they possess, 
and for what reasons they have them. 

12 The differences of birds compared one with another are 
differences of magnitude, and of the greater or smaller develop- 
ment of parts. Thus some have long legs, others short legs ; 5 
some have a broad tongue, others a narrow tongue ; and so 
on with the other parts. There are few of their parts that 
differ save in size,•^ taking birds by themselves. But when 
birds are compared with other animals the parts present 
differences of form also. For in some animals these are 

was unknown to Aristotle ; it excludes ovoviviparous animals, which 
A. called ' externally viviparous but internally oviparous.' 

' G. A. iii. 2. 752'' 15 sqq. ^ For καμπύλων read σκίλων (Ρ). 

3 Cf. De An. Inc. 13. 

* Cf. iv. 10. 689'' 3-690^ 4. 

^ Alluding of course to the well-known changes of colour that occur 
in this animal (cf. Owen, Verteb. i. 556), which are apparently deter- 
mined 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. 

^ The sense requires ii\r\v κατά μί•γ(θος or equivalent words after 
ά\\η\ων. The class Aves is remarkably homogeneous. ' The struc- 
tural modifications which they present are of comparatively little 
importance' (Huxley). 


hairy, in others scaly, and in others have scale-like plates, 
while birds are feathered, 

10 Birds, then, are feathered,^ and this is a character common 
lo them all and peculiar to them. Their feathers, too, are 
split and distinct in kind from the undivided feathers of 
insects ; for the bird's feather is barbed, these are not ; the 
bird's feather has a shaft, these have none.- 

15 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 
beak, which, being bony,^ serves in place of teeth and lips. 

20 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, 
ogS'"* 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 weak, and it is on their superior strength that car- 
5 nivorous birds depend for their subsistence. No bird, there- 
fore, that has talons ever has an elongated neck. In web- 
footed birds, however, and in those other birds ^ belonging 

^ Transpose πτερωτοί . . . τών ίί\\ων, placing it after the next sen- 

2 Cf. iv. 6. 682I' 17 note. ^ Cf. ii. 16. 6$^"° 33• 

* Read οστινον ov (Y). Not, however, actually bony, but resembling 
bone in being hard. Cf. ii. 9. 655^ 3. 

5 Cf ii. 12-17. 

^ Read vnevavriov av ην τό (Ρ Υ b). 

"^ Read κα\ τα δίΤ]ρημενους, and for ώί ev τω read και evT(S. The birds 
alluded to are the Grebes, Phalaropes, and Coots (the Pinnatipedes of 
Temminck), in which the toes, as described more distinctly farther on, 
are bordered with broad membranous lobes. The word in the Greek 
text (σΐσιμοψίνονς), rendered ' with flat marginal lobes ', is literally 
'snub-nosed ' ; the main stem of the toe answering to the ridge of the 
nose, and the lobes on either side to the flattened nostrils. 

BOOK IV. 12 693^ 

to the same class, whose toes though actually separate have 
flat marginal lobes, the neck is elongated, so as to be suit- 
able for collecting food from the water ; while the legs are 
short, so as to serve in swimming. 

The beaks of birds, as their feet, vary with their modes of 10 
life. For in some the beak is straight, in others crooked ; 
straight, in those who use it merely for eating ; crooked, in 
those that live on raw flesh. For a crooked beak is an 
advantage in fighting ; and these 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 15 
and are herbivorous the beak is broad and flat, 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 too is the neck, the reason for this 
being that the bird gets its food from some depth below the 
surface. For most birds of this kind, and most of those 20 
whose feet are webbed, either in their entirety or each part 
separately,^ live by preying on some of the smaller animals 
that are to be found in water, and use these parts for their 
capture, the neck acting as a fishing-rod, and 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 un- 25 
broken surface, and they have no arms^ or forelegs attached 
to it, but in their stead wings, which are a distinctive 
peculiarity of these animals ; and, as these wings are sub- 693^ 
stitutes for arms, their terminal segments 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 forelegs of 5 

^ The sense is obvious (see last note), but the true meaning doubtful. 
I suggest omitting τό with Υ and for ταντό reading tovtois, meaning 
the elongated neck and beak. 

^ Read και ('χονσι άπηρτημίνίΐί, omitting {'χουσι after προσθίων (Υ b). 

^ The scapula in birds is a simple elongated bone, not flattened out 
into a plate or blade, and so was not recognized by A. as a ' blade- 
bone ', just as he did not recognize the astragalus unless it had the 
form suiting it for use as a ' huckle-bone '. 

* Cf. //. A.'ii. I. 498" 27 ; De An. Inc. 15. 7 12'' 22 sq. A. uses two sets 


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, 

lo 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 the arms or forelegs 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 

15 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.^ The 
sharp edge is to minister to flight, for broad surfaces move 
with considerable difficulty, owing to the large quantity of 
air which they have to displace ; while the fleshy character 

of terms to describe the bendings of the hmbs : (i) Forwards and back- 
wards, (2) Inwards and outwards. A hmb is said to be bent forwards or 
backwards when its convexity is turned forwards or backwards ; e. g. 
the leg of a man is bent forwards ; so is the foreleg 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 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. Cf. H. A. ii. i. 498=^ 3-31 ; De An. Jnc. 12-1 5. 

It must be remembered that A. knows nothing of the homologies of 
the various joints. He simply takes the limbs as Avholes, and 
compares the general direction of their main curvature in different 

^ A. rightly says that no sanguineous animal has inore 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. But in the De An. Inc. 
(10. 709'' 22) he expressly repudiates such a statement. 

^ Reading σκίΧη rois be τ€τράποσι σκί\η (ΡΥ). 

^ Α. 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, and is compared by him {De An. Inc. 10. 710^ 31) to the 
sharp prow of a felucca, reminding one of the term ' Carinatae ' now 
applied to birds with a keeled sternum. By the fleshy covering is of 
course meant the mass of pectoral muscles. 

BOOK IV. 12 693^ 

acts as a protection, for the breast, owing to its form, would 
be weak, were it not amply covered. 

Below the breast lies the belly, extending, as in quad- 
rupeds and in man, to the vent and to the place where the 20 
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 umbilicus during their 
development, but, when the bird has attained to fuller 
growth, no signs of this remain visible. The cause of this 
is plainly to be seen during the process of development ; 
for in birds the umbilical cord unites with the intestine, and 25 
is not a portion of the vascular system, as is the case in 
viviparous animals.^ 

Some birds, again, are well adapted for flight, their wings 
being large and strong. Such, for instance, are those that 694=* 
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, namely, that depend on speed 5 
for security, or 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 get 

' 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 (G. A. iii. 3. 754'^ 4 ; G.A. iii. 2. 753'^ 20 sq. ; 
H. A. vi, 3. 561'^ 5) 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 {aiiantois) 
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 com- 
paratively 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 Needham discovered the umbilical vesicle of mammals, and 
recognized its correspondence to that of birds. Neither had A. ob- 
served that Amphibia in this matter resemble fishes and not reptiles, 
with which latter he grouped them. 

AR.P.A. Ο 


their living in watery places. In those that have talons the 
body, without the wings, is small ; for the nutriment is con- 
sumed in the production of these^ wings, and of the weapons 
and defensive appliances ; whereas in birds that are not 
made for flight the contrary obtains, and the body is bulky 
and so of heavy weight. In some of these heavy-bodied birds 
the legs are furnished with what are called spurs, which 
replace the wings as a means of defence. Spurs and talons 

15 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 ; 

20 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 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 
development. For the earthy matter in the body issuing " 
from it is converted into parts that are useful as weapons. 

25 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 claws upon the 
feet. 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 eiificiency. In other birds this earthy residue furnishes 
694^ the legs with the material for their elongation ; or some- 
times, in place of this, fills up the interspaces between the 

^ For ίντανθη read ds ταντας (Ο S U Ζ) ; and read και before dt τα όπλα. 

^ 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 (//. A. ix. 
32. 619'^ 7) 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. Moreover, in the Falconidae the claws are retractile, so that 
they can be elevated at pleasure, and their sharp ends kept from being 
blunted by contact with any hard body on which the bird may perch. 

^ If the strange word 'ά^ορμον be kept, we may read 'ί^ηρμον eV τοντον 
τά (Υ), and suppose the earthy matter making its way out of the body 
to be compared metaphorically to a ship making its way out of a 
harbour, but Langkavel's suggested reading ίξω ρνίν is very probable. 

BOOK IV. 12 694" 

toes. Thus it is simply a matter of necessity,^ that such 
birds as swim shall either be actually web-footed, or shall 
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 5 
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 oars of a boat, or the fins ^ of 10 
a fish ; and the destruction of the foot-web has the same 
effect as the destruction of the fins ; that is to say, it puts 
an end to all power of swimming. 

In some birds the legs arc 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 func- 
tion for the organs. It is, then, because these birds are not 15 
meant for swimming that their feet are without webs, 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, 
though all birds have the same material composition, they 
are not all made for flight ; and in these, therefore, the 
nutriment that should go to their tail-feathers is spent on 20 
the legs and used to increase their size. This is the reason 
why these birds when they fly make use of their legs as 
a tail, stretching them out behind, and so rendering them 
serviceable, whereas in any other position they would be 
simply an impediment.^ 

1 Because the earthy matter has not been used in any othermanner, 
and must be disposed of in some way or other. 
^ For τττΐρών read πτΐρν-^ων (Yb). 
^ Read καί before τά nrepvyia Tols ιχθνσιν (Υ b), 

* 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 

* ' 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' 
(Bewick's Birds, p. 11). 

Ο 3 


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 
25 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 protected, and less likely to get broken, 
should the bird fly against any obstacle.^ 
695* In all birds there is an ischium,^ but so placed and 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 
5 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 up at all.^ 
For while man stands erect, and while quadrupeds have 
their heavy bodies propped up in front by the forelegs, 
birds can neither stand erect owing to their dwarf-like 
shape, nor have anterior legs to prop them up, these legs 
10 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 she has placed the legs 
under this central point, 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 
15 flesh has also already been stated ; *' for the reasons are the 
same as in the case of quadrupeds. 

^ 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, &c., fly with the comparatively stout neck outstretched. 

"^ A. uses the term ' ischium ' in two senses ; firstly, for the fleshy 
buttocks, and it is with this meaning that he says (iv. 10. 690^ 25) that 
man alone has ischia; secondly, for the bone with which the femur in 
man, and what he mistakes for the femur in other vertebrates, is ar- 
ticulated at its upper end ; and it is with this meaning that he says 
that birds have long ischia. (Cf. iv. 10. oSg'' 7 note.) 

^ For ορθόν read όλως (Ρ Q U). 

^ Read 8ia τοΰτο, nripvyas 8( dj/r' αυτών (Υ). 

^ By σκίΧη here are plainly meant not the whole legs, but their 
tarso-metatarsal segments. " Cf. iv. 10. 689'' 7. 

BOOK IV. 12 egs"» 

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 further on.^ Of these four toes 
three are in front, while the fourth points backwards, serv- 20 
ing, as a heel, to give steadiness. In the long-legged birds 
this fourth toe is much shorter ^ than the others, as is the 
case with the Crex,^ but the number of their toes is not in- 
creased.^ The arrangement of the toes is such as has been 
described in all ^ birds with the exception of the wryneck. 
Here only two of the toes are in front,^ the other two behind ; 
and the reason for this is that the body of the wryneck is 25 
not inclined forward 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 Genera- 
tion of Animals.^ 

13 Thus then are fashioned the parts of birds. But in fishes 695^ 
a still further stunting has occurred in the external parts. 
For here, for reasons already given,^ there are neither legs 
nor hands nor wings, the whole body from head to tail pre- 
senting one unbroken surface. This tail differs in different δ 
fishes, in some approximating in character to the fins,^° while 
in others, namely in some of the flat kinds, it is spinous and 
elongated, because the material which should have gone to 

^ 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. " Cf. iv. 14. 

^ 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. 

* 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. Cf. D'Arcy Thompson, Greek Birds, p. 103. 

^ Although such increase might perhaps have been expected by way 
of compensation. 

^ Elsewhere {H.A. ii. 12. 504''' 1 1) A. says, more correctly, that there 
are several exceptions besides the wryneck. 

"^ Transpose οπ^θίν and (μπροσθίρ (Karsch). 

* G. A. i. 4. 717'' 4, i. 12. 

' I cannot say to what passage A. refers. But his explanation of 
the substitution of fins for limbs is given a little further on in this 
chapter. See 695^ 17. 

^^ After παραπλησίαν, by itself unmeaning, read toIs πτ-^/η^ύη?. 


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 

10 may be of Hke nature. In such fishes, then, the tail is 
spinous and long; while in some others it is short and 
fleshy, for the same reason which makes it spinous and long 
in the Torpedo. For to be short and fleshy comes to the 
same thing as to be long and less amply furnished with flesh. 
What has occurred in the Fishing-frog ^ is the reverse of 
what has occurred in the other instances just given. For 

15 here the anterior and broad part of the body is not of 
a fleshy character, 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 super- 
fluous or void of use. Now inasmuch as fishes are made 

20 for swimming they have fins,"* and as they are not made for 

^ The electric rays or Torpedos are found abundantly in the Medi- 
terranean, and must have been well known to Α., 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. The Trygon is doubtless the Trygon 
Pastinaca or sting-ray, which is abundant in the Mediterranean. 

^ The Fishing-frog {Lophius piscatoriiis or L. budcgassa) was 
erroneously classed by A. with Selachia, confounding it with the rays. 
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. Ail. iii. 250), and by its naked skin, rough with warts and tubercles. 
A. did not, however, fail to observe that this fish differed in many 
important points from the rest of the group ; in being, for instance, 
oviparous {G. A. iii. 3. 754* 25) ; and in having an operculum for its 
gills, which are themselves placed laterally, not ventrally as in true 
rays (//. A. ii. 13. 505» 5). 

^ For αυτό read αυτών (U). 

^ Although A. recognizes the correspondence of the paired fins (i. e. 
pectorals and ventrals) of fishes to the four limbs of other vertebrates, 
this recognition is not based on any serious anatomical grounds, as is 
plain from what he says of the Rays. For he fails to see that the 
marginal parts of the flattened bodies of these fishes are really the 
pectorals, but supposes these to have been moved back and to be 
represented by the [dorsal) fins on the tail, which in many rays are two 
in number. So also he speaks of the serpents, which have no limbs 
at all, as still resembling the other sanguineous animals, i. e. in having 
four points of motion. ' For,' says he, 'their flexures are four,' while 

BOOK IV. 13 695" 

walking they are without feet ; for feet are attached to the 
body that they may be of use in progression on land. 
Moreover, fishes cannot have feet, or any other similar 
limbs, as well as four fins ; for they are essentially san- 
guineous animals. The Cordylus,^ though it has gills, has 25 
feet, for it has no fins but merely has its tail flattened out 
and loose in texture.^ 

Fishes, unless, like the Batos and the Trygon, they are 
broad and flat, have four fins, two on the upper and two on 696^ 
the under side of the body ; and no fish ever has more 
than these. For, if it had, it would be a bloodless 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 a certain kind of Cestreus that is found in the 5 
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 Smuraena,* 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 serpents swim in water exactly 
in the same way as they glide on the ground. The reason 10 
for these serpent-like fishes being without fins is the same 
as that which causes serpents to be without feet ; and what 

in such fishes as have only two fins ' the flexures are two, to replace 
the missing pair' (cf. H. A. i. 5. 490* 30). 

^ Cf. H. A. viii. 2. 589^ 26. The Cordylus must presumably be the 
larval form of some triton or newt which retains its gills for a longer 
period than the generality of tadpoles. Such, says Prof. D'Arcy 
Thompson, are Triton alpestris and Salamandra atra. It is strange 
that A. should not have known that tadpoles are the larval forms of 
frogs and newts. * Destitute, that is, of fin-rays. 

" 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 com- 
plete, no rudiment of them appearing on dissection, e. g. in Muraena, 
Muraenophis, Gymnotus, litc. There are pectoral, but no ventral, fins 
in the eel, the conger, and the rest of the so-called Apodal Physo- 
stomatous fishes. As to the Cestreus, it is impossible to say what fish 
is here meant. It can scarcely be one of the Mugilidae, though these 
are the fishes usually called Cestreus by Aristotle. 

* The Smuraena and Muraena are probably one and the same fish, 
namely the Muraena Helena, common in the Greek seas, and still, 
according to Erhard, called Smurna or Sphurna. 


this is has been aheady stated in the dissertations on the Pro- 
gression and the Motion of Animals.^ The reason was this. 
If the points of motion were four, motion would be efiected 
under difficulties ; for either the two pairs of fins would be 
close to each other, in which case motion would scarcely be 

15 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 would convert the fishes into 
bloodless 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 ofiice 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 begin 

20 to gasp until they have been for a considerable time out of 
the water, while others, whose nature is akin to that of land- 
animals, do not even do as much as that.^ In such fishes as 
have but two fins it is the upper pair {pectorals) that is 
present, excepting when the flat broad shape of the body 
prevents this. The fins 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 

25 lengthening out in fishes of this conformation. As for the 
Bati and the like, they use the marginal part of their flat- 
tened bodies in place of fins for swimming.* 

In the Torpedo and the Fishing-frog the breadth of the 
anterior part of the body is not so great as to render loco- 
motion by fins impossible, but in consequence of it the 
upper pair {pectorals) are placed further back and the under 
pair {ventrals) are placed close to the head, while to com- 

30 pensate for this advancement they are reduced in size so as 
to be smaller than the upper ones.^ In the Torpedo the 

' Cf. De An. hic. 7. 709^ 7 sqq. There is no corresponding passage 
in the De Motu. Moreover, that treatise is universally admitted to be 
spurious. Possibly A. is merely using a longer title than usual to 
designate his treatise on Progression. ^ See 695'^ 20 note. 

^ The text here is so corrupt as only to admit of somewhat con- 
jectural rendering;. 

* The Rays swim as here described. See, however, 695^ 20 note. 

^ In the Fishing-frog the ventral fins are, as stated, in advance of 

BOOK IV. 13 6g6'' 

two upper fins [pectorals) are placed on the tail,^ and the fish 
uses the broad expansion of its body to supply their place, 
eachlateralhalf 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 set forth in 696'' 
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-spine for its formation, and 
in other fishes the skeleton is made of this substance, 5 
whereas in the Selachia it is invariably formed of cartilage. 
Again, while the motions of spinous fishes are rapid, those 
of the Selachia are sluggish, inasmuch as they have neither 
fish-spine nor sinew ; but an operculum requires rapidity of 
motion, seeing that the office of the gills is to minister as it 
were to expiration.^ For this reason in Selachia the branchial 10 
orifices themselves 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 

the pectorals and smaller than these. It is quite true that when the 
ventrals are advanced 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. Set. Nat., 1872, t. xvi. p. 93. 

^ Cf. 695^^ 20 note. 

''■ Namely, in the latter part of the second book and beginning of the 
third book. ^ Be Resp. 10. 476* i sq., and 21. 480'^ 13. 

* 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. 

^ 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. 

^ 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. 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, Scorpaena, Cottus, most Labroids, &c. 


a detailed account of all this, reference must be made to the 

15 treatises on Anatomy, and to the book of Researches con- 
cerning 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 ; ^ and numerous and double gills act with more force 

20 and rapidity than such as are few and single. Thus, too, it 
is that some fishes that have but few gills, and those of 
comparatively 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. For 

25 in some this is placed in front, at the very extremity of the 
body, while in others, as the dolphin ^ and the Selachia, it is 
placed on the under surface ; so that these fishes turn on the 
back in order to take their food. The purpose of Nature in 
this was apparently not merely to provide a means of salva- 
tion for other animals, by allowing them opportunity of 
escape during the time lost in the act of turning — for all the 

30 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 

^ Cf. H. A. ii. 13. 504^ 28-505* 20. 

^ Because the hotter an animal is, the more perfect must be the 
arrangements for its refrigeration. 

^ 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 
probably an interpolation ; and this notwithstanding the objection to 
that view taken by Meyer, namely, the fact that the same false statement 
occurs elsewhere {H. A. viii. 2. 591^ 26). The same transcriber who 
made the addition to the text in the one place may very possibly have 
made it in the other. 

* 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. 

BOOK IV. 13 696^ 

able to seize their prey more easily than they do, they 
v/ould soon have perished from over- repletion. An addi- 
tional reason is that the projecting extremity of the head in 
these fishes is round and small, and therefore cannot admit 
of a wide opening. 

Again, even when the mouth is not placed on the under 
surface, there are differences in the extent to which it can 
open. For in some cases it can gape widely, while in others 
it is set at the point of a small tapering snout ; the former 697* 
being the case in carnivorous fishes, such as those with sharp 
interfitting teeth, whose strength lies in their mouth, while 
the latter is its form in all such as are not carnivorous. 

The skin is in some fishes covered with scales (the scale 
of a fish is a thin and shiny film, and therefore easily becomes 5 
detached from the surface of the body^). In others it is 
rough, as for instance in the Rhine, the Batos -, and the like. 
Fewest of all are those whose 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 10 
indeed have no apodous animals, among which of course are 

^ This parenthesis appears to be a note introduced to point out 
the difference between the scale of a fish {XeTris) and the scale of 
a reptile {φολίς) ; the former thin and quite superficial, so as to be 
easily rubbed off, the latter thicker and set more firmly in the skin. 
It is strange that λαμπρότης should be assigned as a cause of easy 
detachment, unless 'shiny' is supposed to connote ' superficial'. Per- 
haps, however, for λαμπρότητα should be read μαλακήτψα. 

- The Batus is indisputably a Ray. The Rhine is usually identified 
with the Angel-fish {R. Squatiua), but much more probably is some 
other shark in shape like a dog-fish ; while the Angel-fish is the 
Rhinobates, said (//. A. vi. li. 566^ 28) to be in the fore part like the 
Batus and in the hind part like the Rhine, and supposed to be a cross 
between the two. It ' has a form and appearance intermediate between 
the Sharks and Rays ' (Seeley). 

^ That is to say they have no solid organ of the globular or ovoid 
shape \vhich characterizes 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 
(G.A. iii. I. 750^ 15; H. A. vi. 14. 568'^ 6). He refuses, however, to call 
these saccular organs 'testes', because of their shape and of their being 
hollow, and styles them spermatic tubes {πόροι) or roe [θορικά). He 
supposed {G. A.\. 4) that these saccular spermatic tubes or roe, as 


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, whether two- 
footed or four-footed,^ inasmuch as they have no urinary 
bladder and form no fluid excretion.^ 

15 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 pro- 
vided with a blow-hole ; for this serves them to discharge 
the sea-water which has been taken into the mouth.^ For, 
feeding as they do in the water, they cannot but let this 

20 fluid enter into their mouth, and, having let it in, they must 
of necessity let it out again. The use of gills, however, as 
has been explained in the treatise on Respiration,^ is limited 
to such animals as do not breathe ; for no animal can 
possibly possess gills and at the same time be a respiratory 
animal. In order, therefore, that these Cetacea may dis- 
charge the water, they are provided with a blow-hole. This 

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 deferetitia ; 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, Vert. p. 135). 

^ 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 notice. Thus in these 
animals the faeces 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 orifice or abdominal pore. 

^ Read και h'nroha και τετράποδα. 

^ The meaning must be : 'If there were urinary organs and external 
urinary orifice, the generative secretions would be discharged by this. 
But as there is none, these secretions are discharged by the anus.' 

* The like statement is often enough made nowadays, 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 begins 
before the animal has quite reached the surface. 

s ne Resp. 10.476» i sq. ; 21. 480^^ 13. 

BOOK IV. 13 697=» 

is placed in front of the brain ; for otherwise it would have 25 
cut off the brain from the spine.^ The reason for these 
animals having a lung and breathing, is that animals of 
large size require an excess of heat, to facilitate ^ their 
motion. 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 30 
resemble water-animals in having no feet and in deriving 
their food from the sea. So also seals lie half-way between 697^ 
land and water animals, and bats half-way between animals 
that live on the ground and animals that fly ; and so 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 ; and their teeth 5 
also are sharp and interfitting "* 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 quad- 
ruped's tail, because they are winged animals; no bird's 
tail, because they are terrestrial. This absence of tail is 10 
the result of necessity. For bats fly by means of a mem- 
brane, but no animal, unless it has barbed feathers, has the 
tail of a bird ; for a bird's tail is composed of such feathers. 

' As to continuity of brain and spinal cord, and its supposed purpose, 
cf. ii. 7. 652* 30. 

^ Heat is the instrument of the soul in motion, as in all operations. 
Cetacea, therefore, that move actively must have much heat ; and this 
again necessitates a perfect organ to regulate heat, and such is the 
lung. ^ For τπ-ίμυγας read nrepvyia. 

* H. A. ii. I. 501» 21. 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.' 

' 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. 
511^ 31 sq.), and groups them with the hare and the rat among vivi- 
parous animals with teeth in both jaws. 


As for a quadruped's tail, it would be an actual impedi- 
ment, if present among the feathers. 

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

15 characters of a quadruped. It differs from a quadruped in 
being feathered ; and from a bird in being unable to soar 
aloft, and in having feathers that resemble hair and are use- 
less for flight.•^ Again, it agrees with quadrupeds in having 

20 upper eyelashes,'"^ which are the more richly supplied with 
hairs because the parts about the head and the upper por- 
tion of the neck are bare ; ^ and it agrees with birds in being 
feathered in all the parts posterior to these. Further, 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 that of a bird. For, 

25 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 

30 sequence must next deal with the question of their genera- 

■" In the ostrich and other Ratitae 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. 

■^ Cf. ii. 14. 658a 13 note. 

^ The head and neck are naked, or covered with only a short 
downy plumage. Cf. ii. 9. 65 5^• 28 note. 

* 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 ha\^e 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. 


666^ ΙΟ note 4. Before Under vivpa read Meaning the 
Chordae teiidineae (H. A. iii. 5. 515* 25). and omit reference 
after A. included 

680^^ 15 note 3. For this surface read\)i\Q surface 
693* 20 note I. For true meaning read true reading 
In Index : under Birds, at line 5 for ib. read 92^ 
under Heart, at line 26 for ib. read 66^ 

Aristotle Translation : de Partibus Aniinaliuiii. 
March 1 9 1 1 . {^At encT) 


39"— 97^ = 639^—697'^ 

The English version clearly cannot tally line for line with the Berlin 
Greek text ; it tallies, however, pretty closely with it at the lines marked 
5, 10, 15 &.C. In the following Index, the matter intervening between two 
consecutive figures, say 10 and 15, is regarded as a section, and anything 
occurring in that section is referred to by the figure at its beginning. For 
instance, anything between 63'' 10 and 63'' 15 is referred to in the Index 
as 63^ 10. 

Abdomen, why unenclosed by ribs 
55a I, 89'^!. 

Acalephae or sea-nettles 81'* 35 ; in- 
termediate to plants and animals 
81'' I ; in what characters like 
animals ιδ. ; in what like plants 
ζί>. s ; protected by stinging sur- 
face 81'^ 5η. 

Aesop's Momus wrongly criticizes 
bull's horns 63» 35. 

Amia, its gall-bladder 76'^ 20. 

Anaxagoras, ascribed acute diseases 
to gall-bladder 77^ 5 ; man's in- 
telligence to his hands 87'"^ I. 

Ants, some apterous some not 43^ 
i; teeth 78'M5, 83'"^5_; tongue- 
like body 6 1''' 15 ; why intelligent 

Aorta and Great Vessel 67" 15η.; 
relative position at heart 68* I ; 
changed at bifurcation of legs 68'^ 
20 ; advantage of this ϊδ. 25 ; 
blood from heart first passes into 
these two 67^ 15; all other vessels 
being branches from them ζί>. ; 
both send branches to brain sur- 
face 52^25 ;to kidneys 71^^ 10, 15, 
72^ 5 ; to mesentery 78» I ; but 
only Great Vessel to liver and 
spleen 70* 10. v. Blood-vessel, 

Ape, its intermediate character 89'' 

Art, the conception of the result as 

yet unrealized in matter 40* 30. 
Ascidia, like plants always attached 

and without excrement 81* 25 ; 

but flesh-like substance implies 

some sensation ib. : two orifices 

and central septum ib. 30 ; vital 
centre presumably in this septum 
ib. 35. Grouped with Testacea 
80a I. 

Ass V. Solidungtila. 

Astragalus v. Hucklebone. 

Backbone v. Chine. 

Bat, intermediate character 97^ 5. 

Batos, fins 95^ 25 ; mode of swim- 
ming 96=* 25 ; skin 97* 5. 

Beak, variations of 62* 35 sq. 

Bear, much hair on body, therefore 
little for tail 58^ i. 

Bee, light and polypterous to suit 
mode of life 82'' 10 ; modified 
teeth and their use 78'^ 15, 838- 5 ; 
proboscis for suction 61* 20, 78'^ 
15 ; sting, why internal 83* 5. 
Why intelligent 48* 5, 50'^ 25. 

Beetle, its shards 82^ 10 n. ; be- 
haviour when frightened 82^ 25. 

Bendings of limbs, descriptive 
terms 93'' 5 n., 92' 15, 87^ 25 ; of 
insects 83^ i ; of Crustacea ib. 30. 

Bilaterality, of sense-organs 56'^ 30, 
57* I ; of viscera 69^ 15, 70* i ; 
of motor organs 63''^ 20 ; of 
horns ib. 

Bile, yellow bile becomes more fluid 
when withdrawn from body 49'' 
30 ; is always to be looked on as 
excremental ηη^ 2ζ, ηΫ' 5. v. 
Liver, Gall-bladder. 

Birds, a homogeneous class 92^ 5. 
Why generally small 97'' 25. 
Feathers, how different from 
πτίρύ (feather-wings) of insects 
ib. ID. Beak for lips and teeth 


ib. 15; its varied forms in har- 
mony with mode of life 93^^ 10. 
Neck usually varies in length 
with legs 92^' 20. Breast sharp- 
edged and fleshy 93'^ 15. Wings 
and scapula ib. i ; differences 
of wings 94* I. Legs not fleshy 
95^ 10 ; length varies with mode 
of life 94'' 10 ; long ischia <^γ• i 
n.; spurs never co-exist with talons 
94"• 10; toes four except in os- 
trich 95^ 15 ; only one points 
backwards save in wryneck ib. 
20 ; webbed in swimmers, or with 
marginal lobes 94'' i. Testes in- 
ternal 95* 25 ; no external ears 
but auditory passages 91=* 10, 57=^ 
15 ; nor nostrils, but olfactory 
passages 59'' 10. Eyes, charac- 
ter of 57=^ 30 ; in most closed by 
lower lid γ]^ lo ; and nictitating 
membrane ib. 15, 57="' 30 ; no eye- 
lashes 58^^ 10. Oesophagus 74^ 
20, 30 ; want of teeth compen- 
sated by crop or proventriculus 
or gizzard or hot stomach ib. 20. 
Liver, why of pure blood-like hue 
73^^ 20; spleen very small 70^ 30, 
70'' 10; no bladder but kidney- 
like bodies 71^ 2ζ ; white matter 
on faeces represents earthy part 
of urine 76=^ 30 ; lung small, mem- 
branous but highly distensible 
69'* 30; umbilical cord 93^ 25 ; 
navel not persistent ib. 20. Why 
birds are not erect though bipeds 
95^ 5. Can communicate vocally 
with each other 60* 35 ; those 
that can utter words have broad 
tongues ib. 30 ; small birds have 
most variety of notes ib. Birds 
luiih talons live by rapine 93^ 
10; keen sighted 57'^ 25; beak 
hooked 93=^ 10 ; neck short 92^ 
20 ; body small 94^ 5 ; powerful 
wings and abundant plumage 
ib. I ; never have spurs ib. 15 ; 
walk badly and never settle on 
rocks ib. 20 ; legs, why held 
against body in flight 94^^ 25. 
Swimming birds, long neck but 
short legs, and reason 93^ 5, 20 ; 
feet webbed or with marginally 
lobed toes 94'^ i. Maj-sh birds, 
long legs and toes 94^' 10 ; toes 
generally with extra joint ib. 15 
n. ; beak broad 93* 15 ; some- 

times elongated as is the neck ib. ; 
purpose of this ib. 20 ; legs used 
as a tail in flight 94'' 20 ; neck if 
thick stretched out, if slender 
coiled up ib. 25. Heavy bodied 
birds not made for flight 94^ 10 ; 
frugivorous and live on ground 
ib. 5 ; often have spurs ib. 10. 

Bladder urinary, only in animals 
that have full-blooded lung 70^^ 
30, and drink freely 71^5; none 
in birds, reptiles, fishes ib. 10, 70'^ 
I, except tortoises 71•'^ 15, 76'* 30; 
reasons for this 71* 15 ; urine 
formed by it, kidneys only ad- 
juncts 70'' 25 ; attached by strong 
passages to kidneys 71'^ 25. v. 

Blood, formed by concoction of ab- 
sorbed nutriment 68'' 5-10, 51=* 15 ; 
is the final nutriment ib.; material 
for all the parts ib. 10, 68'"^ 20; 
hot and fluid in the body, cold 
and solid when withdrawn 49^^ 
30; its fluidity due to heat 51* 
10, 54^^ 5 ; its heat not intrinsic 
but derived from heart 49^ 15η.; 
varies in amount and wholesome- 
ness with the food 50^35 ; varies 
in different animals, and relation 
of such difference to tempera- 
ment, intelligence, sensibility 50^ 
15» 3o> 51^ 1°) 48^ I ; varies in 
different parts of body 47'' 30 ; 
as in upper compared with lower 
48^ I ; each side has its separate 
and different blood 66''30, 67»ί ; of 
head suitable toensure tranquillity 
of sense organs 86^ 10 ; being 
purest 56'' 5 ; its serum in part 
not yet fully concocted nutriment, 
in part product of body-waste 
51^ 15 ; its fibres the part that 
coagulates 50'' 15 ; abundance of 
these causes rapid coagulation 
51^1; as in bull and in boar ib. ; 
their absence prevents it,as in deer 
50'' ion. ; so does excess of water 
until it evaporates ib. 15, 51=^ 5. 

Blood-vessels, a connected system 
of which heart is centre 54'' I, 
10; why one centre 67^20; 
start from heart oois• 5 ; not 
from head 65'' 25 ; nor from liver 
66•^ 25 ; are all branches of aorta 
and great vessel 67'^ 15η.; absorb 
nutriment from abdominal organs 


50^ 15 ; and convey it to all parts 
68^ 20 ; except heart itself όό»• 5 ; 
resemble water-courses in gar- 
den ib. 10 ; as they advance grow 
smaller till too fine for passage of 
blood 68^^ I ; still allow sweat to 
transude ib. ; then constitute 
flesh 68=^ 30 ; or viscera 47^^ i, 
ηγ• 30. V. Aorta and Great Vessel. 

Bonasus, how it protects itself 63^ 
15 ; its horns do not serve the 
purpose ib. 10. 

Bone and cartilage differ only in 
degree 55^30; neither grows 
again when cut off ib. Bones 
form a continuous system of 
which chine is centre 54^ 30 ; 
united by sinews at the joints 
54^ 20 ; with interposed car- 
tilage ib. 25 ; strongest in vivi- 
para 55* 5 ; in carnivora stronger 
than in herbivora ib. 10 ; in males 
than in females ib. ; less strong 
in birds ib. 1 5. Replaced by fish- 
spine in oviparous fishes ib. 20 ; 
and in smaller serpents ib. ; by 
cartilage in Selachia ib. ; reason 
for this ib. ; and in projecting 
parts as nose and ears ib. 30. 
Bones serve to support fleshy 
parts 54^ 30 ; or protect them ib. 
35j 53"^ 30 ; '^^'hy none round ab- 
domen 55^ I. I3one in heart of 
horse 66'^ 15 ; in cephalopods 
54^ 20. 

Brain, a peculiar organ 52^ i ; why 
present in every sanguineous ani- 
mal ib. 20 ; compounded of earth 
and water 53* 20 ; cold and fluid 
ib. 30, 52^^ 30; fatal results if 
too fluid or too solid 53'^ i ; but 
excess of cold or heat obviated 
by vessels on surface 52*^ 25 ; 
solidified when boiled 53''' 20 ; 
contrasts with spinal marrow 52* 
25 ; why continuous with it ib. 30 ; 
not formed of marrow ib. 25 ; no 
blood in its substance ib. 35 ; 
numerous small vessels in the pia 
mater 52'^ 30 ; derived both from 
aorta and great vessel ib. 25 ; no 
brain in back part of head 56'^ 10 ; 
not the organ of sensation 56'* 20 ; 
why thought to be so ib. 25 ; in- 
sensitive itself ib. 20, 52^' 5 ; not 
directly continuous with sense- 
organs ib. I ; its function to tem- 

per heat of heart ib. 20 ; neces- 
sary for preservation of the whole 
body ib. 5 ; slightest change on 
its surface immediately affects the 
heart 53'^ 5 ; how it causes sleep 
538• 10 ; how defluxions 52•^ 30 ; 
largest in man, and in males 
larger than in females 53=* 25 ; 
none in bloodless animals 52^^ 20 ; 
but analogous organ in poulps 

Breast, broad in man 88^ 10 ;narrow 
in quadrupeds z<i. 15 ; and reason 
ib. ; in man alone site of mammae 
88=^ 20 ; narrow in birds 59'^ 5 ; 
and sharp-edged and fleshy 93^ 
15 ; reason for this ib. 

Bregma, last part of man's skull to 
ossify 53^ 35. 

Bubalus, its horns no adequate de- 
fence 63'' 10 n, 

Calamary v. Cephalopoda. 

Camel, stomach as in horned ani- 
mals 74* 30 ; therefore ruminates 
74^ 5 ; hard palate for thorny 
food ib. I ; no distinct gall-bladder 
but small biliary vessels ηη^ 30 ; 
male retromingent 89'' 30 ; long- 
lived 77^ 30; its bulk a protection 


Canthari v. Beetle. 

Carabi 83^^ 25 n. v. Crustacea. 

Carides 83^ 25 n. v. Crustacea. 

Cartilage v. Bone. 

Catamenia 89^ 10. 

Celestial order constant, terrestrial 
subject to change 41^ 15 ; teires- 
trial general, not universal 63'' 
25 ; study of celestial things com- 
pared with that of terrestrial 44^ 

Cephalopoda, fleshy part outside, 
hard within 79^^ 30 ; soft part in- 
termediate to flesh and sinew 54=* 
15; softest in Teuthis 78^ 30; 
all have eight feet 85^^20; differ- 
ences in length of different pairs 
and in different kinds ib. 15 ; in 
sepias and calamaries a pair of 
proboscises in addition to feet ib. 
30; use of these ib., 85^ I ; their 
resemblance to saurae ib. 5 n. ; 
suckers on tentacles in double 
row save in one kind of poulp ib. 
10 ; fin round body, and its differ- 
ence in different species /i^. 15 ; its 


use ib. 20 ; general internal plan 
that of spiral Testacea 84^ 10, 30 ; 
teeth and tongue 78^' 5 ; gullet, 
crop, stomach, unconvoluted gut 
ib. 25 ; crop as in birds to com- 
pensate absence of mastication 
ib. ; inkbag and ink ib. 35 ; its 
use 79=^ 5 ; ink represents urine 
ib. 1 5 ; discharged with excre- 
ment by funnel 79=^ i ; in fright 
ib. 25 ; of necessity but also as a 
protection ib. 30 ; ink most abun- 
dant and bag lower down in Sepia 
ib. 5; reason for this ib. 10; an 
internal bone in Sepias and Cala- 
maries but not in poulps ib. 20, 
54^^ 20 ; reason for this ib. ; poulps 
have a part analogous to a brain 
52'' 20; and change colour in 
fright 79^ 10. Sensory centre the 
viytis 81^ 15. V. Mytis. 

Cercidas 73^^ 20. 

Cestreus, stomach fleshy like a 
bird's 75^ 10 ; one kind without 
ventral fins 96^ 5. 

Cetacea, intermediate to land and 
Avater animals <^η^ 30 ; all breathe 
air 69^ 5 ; lung and blow-hole 
97=^15; position of this explained 
ib. 25 ; organ of smell 59^ 15 n. 

Chameleon, lean and timid and 
almost bloodless 92^^ 20 ; chang- 
ing aspect ib. 25. 

Chance and Spontaneity, may pro- 
duce the same results as art 40^ 
25 ; but not all ib. 30 ; not cause 
of construction of the heavens 
41^ 20. 

Chine, centre of osseous system 54'^ 
10 ; preserves the straightness 
and extension of body ib. ; made 
of vertebrae to allow of flexure ib. 
15 ; the only bone in fishes with 
marrow 52^^ 10 ; its marrow dif- 
ferent from that of other bones ib. 
15. V. Marrow. 

Cicada, rostrum how formed 82'^ 
20 ; can live on moisture of air 
for a time ib. 25. 

Classification, by dichotomy im- 
practicable 42^ 5, 43^ 25 ; the 
natural groups formed instinc- 
tively by man 43^^ 10 ; must be 
the recognized basis ib. ; these 
not defined by a single character 
but many ib. Requisite condi- 
tions of 43^ 10. 

Cloven-hoofed and horned animals 
[Riewijtaiits) 621^35, 63^15; 
mostly of large size 75^^ 5, 63^' 25 ; 
cloven foot due to deficient 
earthy material 63=* 30 ; have no 
upper front teeth 63'^ 35 ; have 
hucklebones 90=^ 20, Stomach 
multiple 74^^ 5 ; intestines long 
and much convoluted 75'' I ; 
spleen rounded 73^ 30. Their 
fat is suet Si''• 30; as also their 
marrow 51^ 30. Have rennet 
76^ 10; their milk is thick and 
coagulates ib. v. Horns, Huckle- 
bone, Inies/ines, Rennei,Stonuuh, 

Cockchafer 82^^ 15. 

Complexity of life involves com- 
plexity of organs and vice versa 


Composition, three degrees of, 46* 
10; first ib. 15; second and 
third ib. 20. 

Concoction of food, not begun in 
mouth 50^ 10 ; efi"ected in upper 
and lower abdominal cavities ib. ; 
with aid of liver and spleen 70* 
20 ; by means of vital heat 50* 
10. Concoction of absorbed 
food in heart and vessel forms 
blood 51* 15, 68^ 5-10. Con- 
coction of blood forms fat and 
semen 51* 20 n. 

Conger, no ventral fins 96* I. 

Cordylus 95^^ 25 n. 

Crane 44* 30. 

Crex 95'^ 20. 

Crocodile, land and water animal 
combined 60^^ -^o, 90^ 20 ; upper 
jaw the movable one 60'' 25 ; 
reason for this 91'' 5 ; scarcely 
has a tongue 90^' 20 ; this adhe- 
rent to lower jaw 60^^ 30 ; has 
hard scaly plates 91* 15. 

Crustacea — usual name the soft- 
shelled, but sometimes the hard- 
skinned 57^ 30, 35 ; soft parts in- 
side, hard without 54=^ i, 79^ 30 ; 
four main divisions, each with 
numerous species 83^^ 25 ; which 
kind have claws ib. 30 ; which 
none and reason 84* 15; why 
right the larger in Carabi and 
crabs ib.i'^ ; why no fixed rule in 
lobsters ib. 30 ; claws used as 
hands and so bent differently 
from feet 83'' 30 ; feet numerous 


ib.i^ ; not well adapted for loco- 
motion in pelagic species 84* 
5 ; in small swimming species 
the hindennost like fins ib. 10. 
Some have gill-like processes 
near head ib. 15. Tail serves as 
an oar-blade ib. i ; why none in 
crabs ib. Under surface hairy 
and laminated in females for re- 
tention of ova ib. 20. General 
internal plan that of insects, not 
of Turbinata or Cephalopods 84^ 
30. Two anterior teeth 79* 30, 
78^ 5 ; gustatory organ ib. ; small 
gullet, stomach sometimes with 
second teeth, unconvoluted gut 
79^^ I ; mytis 81^ 20. Eyes hard 
without lids 57^ 30 ; but movable 
58^ I. Sensory centre the mytis 
81^ 15. V. Mytis. 
Cyprini, fleshlike palate 60^ 35. 

Deer, long-lived ηη* 30 ; blood does 
not coagulate 50'^ 15 ; alone have 
solid horns and cast them 63'' 10 ; 
their large branching horns detri- 
mental 63=^ 10 ; protected by 
speed ib. ; does hornless 62^ i, 
64^ 5 ; why so ib. 

Democritus 40'^ 30, 42''• 25, 65'*3o. 

De Partibus, its special subject the 
causes of the parts 46^ 10. 

Diaphragm ?'. Midriff. 

Dichotomy, inadequacy of 42'^ 5 
sq., 43^ 10 sq. V. Classifuation. 

Divers, instrument used by 59'* 10. 

Dog, stomach typical 75'* 25; this 
small and smooth internally ib. 
30; intestine narrower in lower 
part, and defaecation difficult ib. ; 
spleen elongated 74* I ; dugs set 
laterally on belly 88^ 35. Indian 
dogs 43'' 5. 

Dolphin, has true bones 55^ 15 ; no 
gall-bladder 76^ 25, 77=^ 30 ; posi- 
tion of mouth 96'^ 25. V. Cetacea. 

Dwarf-like, disproportionate bulk 
of upper parts 86'^ i ; all animals 
as compared with man ib. 10 ; 
man himself in infancy ib. ; 
changes in later life ib. n. ; dwarfs 
comparatively unintelligent ib.iz^. 

Ears V. Sense-organs. 
Educated man competent critic of 
method 39* 5. 

Eel, no ventral fins 96* i ; why few 
gills 96'* 20. 

Elementary forces, fluid, solid, hot, 
cold,the material of all compound 
bodies 46^ 15η.; all other differ- 
ences secondary to these ib. ; and 
comparatively unimportant 48*^ 5. 

Elements, the so-called, earth, air, 
water, fire 46* 10 ; are compounds 
of the elementary forces ib. 15 η. 

Elephant, aquatic habits 59* 30 ; 
trunk and its multiple offices 58'' 
30 sq., 61^ 25, 82'^ 35 ; fore-feet 
serve merely as supports 59^ 25 ; 
foot has toes ib. ; mammae two 
and axillary 88^ 15 ; protected by 
bulk 63a 5. 

Empedocles 40* 15,42-'^ 15, 48* 30; 
alluded to 48=* 25 n. 

Emys, why without bladder and 
kidneys 71'' 30 n. 

Ephemera, live without food for a 
day 82^^ 25. 

Epiglottis V. Windpipe. 

Epipetrum Si'^ 20. 

Exposition, course of to be adopted 
45^ I sq. 

Eyebrows, grow over junction of 
two bones 58'' 15; consequent 
growth and occasional shagginess 
in old age ib. 20 ; shelter eyes like 
eaves ib. 15; right more raised 
than left in man 71'^ 30. 

Eyelashes, in all hairy animals and 
no others, except ostrich 58^ 10 ; 
set at ends of small vessels 58^ 
20 ; and necessary result of their 
exudation ib. ; why in man alone 
on both lids 58* 15 ; act as a 
palisade 58'' 15, 

Eyelids, in men, birds, and all quad- 
rupeds 57^^ 25 ; are rolls of skin 
without flesh 57*^ I ; therefore do 
not reunite after section tb. 5 ; 
both used by vivipara to close 
eye and in blinking 57* 25 ; only 
lower by reptiles and most birds 
ib. ; cause of this 57^ 5 ; man 
blinks more than other animals 
57^* I ; this action quite involun- 
tary /<5. ; birds have a special nic- 
titating membrane 57* 30 ; reason 
for this 57^ 15 ; why fishes have 
no eyelids 58=^ 5 ; why Crustacea 
and insects 57^ -^^o. 

Fat, reckoned with fluids 47^ 10 

Γ 2 


surplus of concocted blood in 
well-fed animals 51* 20, 72=^ 5 ; 
none in bloodless animals Si'' 25 ; 
according to character of blood 
is lard or suet ib. ; in what animals 
respectively ib. yi ; in moderate 
amount beneficial ib. 35 ; in excess 
injurious 51^ I ; why fat animals 
age rapidly ib. 5 ; inverse relation 
of fat and semen ib. 10. 

Fear, associated with cold and 
watery blood 50^^ 25; and with 
large heart 67^ 20 ; bloodless 
animals more timorous than san- 
guineous 50'^ 30, 79=^ 25. Fright 
causes alvine disturbance and 
discharge of urine ib. ; and of ink 
by cuttlefish ib. 10 ; and change 
of colour ib. ; behaviour of some 
beetles when frightened 82^ 25. 

Final cause v. Necessity. 

Fire, one of the so-called elements 
46''' 10 ; perhaps due to some ex- 
ternal influence on a cold sub- 
stratum 49=* 20 ; soul is not fire 
but incorporate in a fiery sub- 
stance 52^ 5. 

Fishes, general form 95^'l ; skin scaly 
or rough and rarely smooth 97^ 5 ; 
tail inversely developed to ante- 
rior body 95'^ 5 ; limbs replaced 
by two pairs of fins ib. 15 ; upper 
pair rarely absent, under in some 
long species 96'' I ; both in still 
longer ib. 5 ; locomotion by flex- 
ures in absence of fins ib. I ; or 
by margins of flattened body 
when fins are misplaced ib. 30 ; 
position of fins in such species 
ib. 25. Gills, double or single 
96^ 10 ; their number determined 
by cardiac heat ib. 1 5 ; why some 
fishes can live for a time out of 
water 96^ 20; gill-covers in 
osseous fishes, not in Selachia 
ib. I ; reason for this ib. 5 ; how 
Selachia close the orifices ib. 10. 
Bones made of fish-spine but in 
Selachia of cartilage 55'* 20; 
reason for this ib. 25 ; no marrow 
save in chine 52^ 10. Mouth in 
some fishes terminal but in Se- 
lachia underneath body 96*^ 25 ; 
reason for this ib. ; its varied gape 
97-'• I. Teeth sharp and serrate 
except in Scarus 75^ 1 , 62^ 5 ; and 
curved ib. 10 ; often on tongue 

and palate ib. 5 ; and very nu- 
merous ib. 10 ; reason for this ib., 
ηγ• 5- Tongue poorly developed 
60^ 10 ; mainly consists of tip 
61=* I ; reason for this 60^ 15. 
Palate sometimes fleshy ib. 35. 
Oesophagus short or wanting 
75* 5. Stomach sometimes 

fleshy ib. 10 ; has certain caecal 
processes close to it ib. 15. Gall- 
bladder constant 76'^ 20, ηη^ 4 ; 
at considerable distance from 
liver ^η^ l. Liver in some fishes, 
as Selachia, much divided 69^ 30, 
73^ 20 ; inclines to yellow ib. 30. 
Spleen small 70^ 10. Food im- 
perfectly elaborated and conse- 
quent gluttony 75^ 20; provision 
against gluttony in Selachia 96*^ 
25. No testicles 97^ 10 n. ; one 
orifice for generative secretions 
and excrement ib. n. Selachia 
ovoviviparous ηθ^ i. Heart, apex 
turned towards head 66*^ 10 n. 
No external organs of smell or 
hearing t^^^ 35 n. Smell through 
gills 59^ 15 η. 

Fishing-frog, why erroneously 
classed by A. with Selachia 95** 
10 n. ; position of fins 96=^ 25. 

Flesh, reckoned among fluids 47^^ 
10; constituted by ultimate 
minute blood-vessels 68=^ 30 ; 
bleeds wherever cut ib. ; the dis- 
tinctive part of animals Si'' i; 
the basis of animal body S3^^ 20; 
all other parts exist for it ib. 30 ; 
is the medium, or organ and 
medium combined, of touch ib. 
20 ; not its primary organ 56^' 
3S ; its relative position to hard 
parts in different classes 54'* I. 

Flies, small and dipterous 82^' 10; 
have projecting proboscis 78'' IS ; 
this a hollow spongy stinglike 
instrument for taste and suction 
61=^15; no tail-sting 83^• 10; 
dress themselves with crossed 
forelegs ib. 30. Gadflies and 
cattle-flies pierce the hide of ani- 
mals 61=^20 n. 

Food, necessary for everything that 
grows so* I ; desired by all ani- 
mals as pleasant 61^ 5 ; consists 
of both solid and fluid so* i ; 
pleasure from fluid derived 
through tongue, from solid 


through oesophagus 90^ 25 ; com- 
minuted in mouth but not altered 
50'' 10 ; concocted in stomach 
and intestines by natural heat ib. ; 
absorbed by mesenteric vessels 
ib. 30. Its useless residue 74^ 15, 
75^^ 25 ; discharged at nether end 
of trunk 89•"* i ; by bowel and 
bladder 53'' 10. Food of plants 
deri\'ed from the earth, already 
elaborated 50^ 20. 

Foot 90-'^ 25 sq. ; human contrasted 
with hand ib. 30. v. Man. 

Front, superior to back 65* 20, 67^ 
35 ; therefore heart in front 65^^ 
20 ; and hair of man more abun- 
dant in front 58'""• 20 ; and great 
vessel in front of aorta 68* i. 

Function, every part has some 45^ 
15 ; soul the function of entire 
body ib. ; organ made for func- 
tion not function for organ Sy^ 10. 

Gall-bladder, present in most San- 
guinea 76•^ 15 ; from what animals 
absent ib. 25 ; not constant in 
man or in some genera as mice 
ib. 30 ; its variable position ib. 
15; in all cases an appendage of 
lower stomach ib. n. ; does not 
affect sensation as some sup- 
pose ib. 20; nor cause acute 
diseases as Anaxagoras thought 
77•'* 5 ; how far true that its ab- 
sence gives long life ib. 30. v. Bile, 

Gazelle, smallest homed animal 63^ 
25 ; its horns not of much avail 
63* 10. 

Generative orifice, same as urinary 
in animals with a bladder 89»• 
5 n. ; when no bladder same as 
faecal 97=^ 10. 

Glow-worm, winged and wingless 
42^' 30. 

Goat, gall-bladder 76^' 35 ; spleen 
73'^ 30 ; stomach 74'^ 8. 

Hair, in some Sanguinea, in others 
feathers or scales 64'' 20 ; grows 
out from skin at ends of vessels 
58'' 20 ; of head most abundant 
in man ib. i ; this a necessary 
result of his many sutures and 
fluid brain ib. ; but also protects 
brain from excess of cold or heat 
ib. 5 ; its distribution in quad- 

rupeds 58•"» 25; in them most 
abundant on back, in man the 
contrary ib. 15 ; reason for this 
ib. 20 ; hair in axillae or on pubes 
only in man ib. 25 ; correlation 
of hair with skin 57^^ 10; when 
abundant in one part scanty in 
others sS••* 35. 

Hand 87'^ i sq., 90^ 30. v. Man. 

Hard and soft parts, relative posi- 
tion of in different classes of 
animals 54^ i sq. 

Hare, has large heart βη^ 20 ; liver 
in some so divided as to seem 
two 69'^ 30 ; has rennet 76=* 5 ; 
the reason ib. 1 5. 

Hawk, hot stomach, small spleen 
70'^ I. 

Head, distinct in all Sanguinea but 
not in all bloodless animals 8 5'^ 30 ; 
exists for the sake of three parts 86* 
1 5 ; firstly to lodge the brain ib. 
5 ; which must be distant from 
the heart ib. ; secondly to lodge 
the sense-organs ib., 56* 30 ; of 
vision always ib. ; not always of 
hearing and smell ib. ; why suit- 
able place for these 56^ i, 86* 10 ; 
thirdly for the inlet of food ib. 10 ; 
its suitability for this ib. i 5. Why 
destitute of flesh 56* 15. Has 
empty space at back, connected 
with ear 56'' 15. Its sutures and 
their use 53^ i, 58^' i. Why 
hairiest in man ib. v. Hair, 
Mouth, Sense-organs, Sutures. 

Heart, at once homogeneous and 
heterogeneous 47* 25 ; it and 
liver the most necessary organs 
in Sanguinea 70*20 ; seat of sen- 
sory, motor, and nutritive faculties 
47* 25, 78'' I, 66* 10; central 
source of heat 70* 20 ; it and not 
liver centre and source of the 
vessels 66* 25 ; its dominating 
position 65^15; well protected 
like a citadel 70*25; within reach 
of all parts 66* 15 ; why in front 
of body 66*' i ; why in man in- 
clined slightly to left ib. 5 ; its 
wall dense especially towards 
apex 66'' i ; has no vessels in its 
substance 65*^ 30 n., 66* i ; 
nourished by the blood in its 
cavities 47'' 5 ; no bone except 
in horse and certain oxen 66^* 1 5 ; 
number of its cavities depends on 


size of animals ib. 20 ; three in 
none but largest ib. 35; differences 
of blood in the three t"]^ I ; the 
chordae tendineae and their use 
ib. 10 ; joint-like sutures on the 
outer surface 67^ 5 ; these not 
due to heart being formed by 
union of separate parts but to 
subdivision ib. ; relation of differ- 
ences of structure to character 
ib. 10 ; heart the first part formed 
66* 10 ; to be seen in motion in 
embryo like a living creature ib. 
20 ; visible in egg on third day 
65* 35 ; cannot stand serious 
morbid affection 67''^ 30; as shown 
by sacrificial victims 67'' i ; gives 
off Aorta and Great Vessel ib. i. 
V. Aorta, Blood-vessels, 
Heat, important difference between 
intrinsic heat and heat derived 
from without 49* i, 52=^ 10 n. ; 
all animals must have a natural 
source of heat 50=^ 5 ; its central 
seat and source the heart 70* 20 ; 
but must belong to many parts 
50^^ 5 ; for to it is due concoction 
ib.., j"]^^ 25, nutrition and motion 
52^^ 10, growth 69^^ I, and erect 
attitude of body ib. 5, 53^• 30 ; 
is greater in vivipara than in ovi- 
para 69^ 25 ; and greatest of all 
in man 53-'^ 30 ; abundant blood 
its sure indicator 69'' I ; is tem- 
pered by air in animals with 
lungs and by water in fishes 69'^ 
I. Heat induced by tickling of 
arm-pit 73^^ 5 ; or by wounds near 
midriff /A 10. Fluids after con- 
coction retain remnant of heat 
72»• 5. Solids that have been 
made hot give off more heat than 
fluids 50^ 35. Heat requires sus- 
tenance 82=* 20. Heat causes 
both solidification and melting 

49* 30• 

Heracleotic crabs 84* 5. 

Heraclitus 45* 15. 

Herodotus, account of backward- 
grazing oxen 59* 20 n. 

Hippocrates, apparent borrowings 
from, as to non-reproduction of 
excised bone or cartilage 55^* 30η.; 
empty space at back of head 56'^ 
ion.; non-reunion of eyelid or pre- 
puce after section 57^ 5 n. ; action 
of spleen 70^^ 5 η.; as to saurae 85'' 

5 n. ; his pangenetic doctrine 
opposed 89''• 15 n. 

Hog, classed with polydactyla 74* 
I n. ; but also called cloven- 
hoofed ib. 25 ; though with front 
upper teeth ib. ; snout broad, 
suitable for digging 62^ 10 ; pro- 
tected by tusks 63''• 5 ; of which 
sows have none 61^ 25; mammae 
numerous, abdominal 88^^ 30 ; 
foremost presented by sow to 
first-born 88^ 10. Stomach single 
74'"^ 25 ; and typical 75* 25 ; has 
internal folds to prolong concoc- 
tion ib. Spleen elongated 74* I. 
Grooves on heart indistinct 67* 
10; and sensibility dull ib. 

Holothuria 8ι* 15. 

Homogeneous and heterogeneous, 
the second and third stages of 
composition 46^ 20 n. ; their 
mutual relation due to necessity 
46•^ 25 ; but also has final cause ib. 
10; sense-organs homogeneous 
and why 47* 5 ; executive organs 
heterogeneous and why 46'^ 1 5 ; 
some parts homogeneous by sub- 
stance but heterogeneous by de- 
finite form 47!* 25 ; such as heart 
and viscera ib. 35 ; fluid homo- 
geneous parts instanced 47^^ 10; 
and solid ib. 15 ; causes of the 
homogeneous parts, and their 
several kinds ib. 20 ; variations 
of individual homogeneous parts, 
such as blood ib. 30 ; kinds 
severally dealt with 50^ 10-55^ 
30 ; so also heterogeneous parts 
55''3o— end of treatise, v. Synop- 

Horned animals v. Cloven-hoofed. 

Horns only in vivipara save meta- 
phorically 62^ 25 ; why none in 
polydactyla ib. 30 ; in most 
cloven-hoofed animals and some 
solidungulates ib. 35 ; in no very 
small animals 63'^ 25 ; inversely 
developed to teeth 63'' 35 ; are 
weapons of offence and defence 
63*^ I ; only in animals with no 
other means of defence ib. ; some- 
times, however, useless appen- 
dages ib. 5 ; or even detrimental 
ib. 10; in such cases other modes 
of protection provided ib. 15 ; 
usually bilateral but single and 
central in Oryx and Indian ass 


63* 20 ; relation of this to hoof 
ib. 25 ; are soHd in deer and cast 
by them 63'^ 10 ; in other animals 
hollow and dermal but fitted on 
a bony outgrowth //;. 15 ; their 
position wrongly criticized by 
Momus 63''• 35. 

Horse, some wild 43^^ 5 ; colt almost 
as tall as dam 86'' 1 5 ; bone in 
heart 66'^ 15. v. Solidungnla. 

Hot, cold, solid, fluid, terms used 
with much ambiguity 48'' i, 49'' 
5, 10 ; when used require further 
statement 49'' i ; only strictly 
applicable to things that are such 
both actually and potentially ib. 
15; different significations of 
hot 48'' 10 sq. ; cold not mere 
privation of heat 49* 15. v. Ele- 
nien/ary forces. 

Hucklebone, an additional limb- 
segment 90^ 10 ; only in hind-legs 
ib. 15 ; and in horned and cloven- 
hoofed animals ib. 20, t^l'•^ 30; 
why none in Solidungula 90* 
ion.; nor in Polydactyla ib. 25 ; 
its use ib. 20. 

Hyaena, heart large 67* 20. 

Hypozoma 59'' 15 n. 

Indian ass 63* 20. 

Innate spirit, agent of refrigeration 
in bloodless animals 69*'' I ; of 
motion and olfaction in insects 
59" 15. 

Insects, no distinction of soft and 
hard parts 54•"^ 10. Many-footed 
and why 82^^ 35 ; especially milli- 
pedes 82'^ I ; feet correspond in 
number to segments ib. ; or de- 
ficiency compensated by power 
of flight ib. 5. Feathers four in 
active fliers ib. ; or only two in 
smaller kind, as flies ib. 10 ; 
their real nature and formation 
ib. 15 ; shards of beetles and 
their use ib. 10 n. Vital centre 
usually one and thoracic 82'' i ; 
but multiple in long-bodied kind 
as millipedes 82^ i. Segmenta- 
tion due to this ib. i, 25 ; but 
also protective ib. 20 ; is reason 
why insects can live when cut in 
pieces 82* 5, 82'' 25 ; though not 
like plants permanently ib. Legs 
six in [most] insects 83''' I ; dif- 
ferences of successive pairs and 

their several uses 83^ 25. Sting 
anterior or posterior d>2^ 25 ; an- 
terior a combination of tongue 
and lips 82^^ 10; used both for 
taste and suction 83'"^ i ; when 
no anterior, food dealt with by 
teeth ib. ; posterior, if delicate, is 
internal, but stout and external in 
scorpion ib. 10; none in Diptera 
but only in Polyptera ib. 15 ; 
reason for this ib. Mouth has 
projecting proboscis for taste in 
bees and flies 78*^ 15 ; or a 
tongue as in ants ib. ; sometimes 
has modified teeth ib. ; but not 
when food is fluid ib. 20 ; these 
often serve not for food but as 
weapons ib. Intestine imme- 
diately follows mouth 82^' 10 ; 
usually unconvoluted but some- 
times with a coil ib. ; in some a 
stomach and convoluted intestine 
ib. 15. Smell by their hypozoma 
with aid of the innate spirit 59'' 
15 ; on which latter their motion 
also depends ib. ; and their re- 
frigeration 69^ I, Insects, why 
small eaters 82"• 20 ; behaviour 
when frightened 82'' 25. 

Intemperance as to drink, why dis- 
tinct from intemperance as to 
solids 91* I. 

Intestines of vivipara, sometimes 
uniform, sometimes vary in dif- 
ferent parts 75=* 30; wh£?i stomach 
is single, usually widen out in 
lower part 75'' i ; but not always 
75''"' 30 ; jejunum the part of small 
intestine in which the food parts 
with its nutritive matter 75'' 30 ; 
this quite exhausted when caecum 
is reached ib. 35 ; transit through 
jejunum rapid 76^^ i ; in what 
animals and when jejunum is 
visible ib. ; iuhe7i stomach is mul- 
tiple, are voluminous and much 
convoluted 75'' i ; widen out to 
caecum or second stomach ib. 5 ; 
here conversion of food com- 
pleted ib. 10 ; then narrower and 
with a spiral coil ib. 5, 20 ; then 
rectum and vent ib. 5. 

Ischia, used in two senses 95* I n. 

Jaws, lower the movable, save in 
crocodile 91'' 5 ; motion both 
vertical and lateral in animals 


with grinders 91*^ 30 ; only vertical 
in other animals ib. ; reasons for 
this 91^ I ; why crocodile is ex- 
ceptional 91'' 5. 

Jejunum v. Iniestiiies. 

Joints, various kinds of 54^' 20. 

Juli 82a I, 82I' I. 

Kidneys, none in birds or reptiles, 
except tortoises 71^ 25; other 
than Emys //;. 30 ; but in birds 
certain kidney-like bodies ih. 30 ; 
lobulated in ox and in man 71^^ 
5 ; which makes disease of them 
in man difficult of cure ib. 10; 
always a central cavity except in 
seal ib. i ; receives branch from 
great vessel ib. 10 ; and from 
aorta ib. 15, 70» 15; the blood 
does not run into central cavity, 
but is expended in the substance 
71'Ίο; attached to bladder by 
strong ducts ib. 15, 20; right 
higher than left and reason ib. 
25 ; are the fattest of the organs 
72^• I ; the left the fatter and why 
ib. 20; the fat superficial ib. 5 ; 
and a result of necessity ib. 10 ; 
but also has a final cause ib. 15 ; 
what this is ib. 20; fat in moderate 
amount beneficial in man, in ex- 
cess pernicious ib. 35 ; in sheep 
cause of rot 72'' i. Stone and 
other renal diseases 67^^ i. Kid- 
neys serve to keep vessels in 
place 70a IS, 71^ i ; and take 
part in secretion of urine ib. 1 5, 
20, 70•'^ 20, 72•''' 20 ; but only as 
adjuncts to bladder 70'' 25 ; and 
therefore are not necessary organs 
Jb. 20, V. Bladder. 

Kite, hot stomach, small spleen 
70a 30. 

Knowledge, scientific and general 
contrasted 39^ i. 

Larynx, sometimes called Pharynx 

64=* 15 η. V. Windpipe. 
Laughter peculiar to man 73"• 5 ; 

why produced by tickling ib. ; 

or by wounds of midriff ib. 10. 
Leopard 88^ 5 ; has large heart 

67^»' 20. 
Limbs of Sanguinea, never more 

than four 93'^ 5, 951» 20, 96^ 15 ; 

replaced by fins in fishes 95'' 15 ;' 

altogether absent in some φ^ 5 ; 

absent in serpents alone among 

reptiles 90^' 15. Anterior bend 
differently in man and quadrupeds 
87'^ 25 ; and reason ib. ; used in 
some measure as hands by Poly- 
dactyla ib. 30 ; and therefore 
have five toes SS»• 5 ; represented 
in birds by wings 93^' 10; which 
bend like the forelegs of quad- 
rupeds 93I' 5. Posterior stronger 
than fore limbs in quadrupeds 85^• 
15; firmer and more extensible 
90^- 15 ; alone have hucklebone 
ib. ; support the weight and take 
main part in locomotion 85^ 20 ; 
used by Solidungula as weapons 
88» I, 90a 20. 
Limpet, how defended 79'^ 25 ; 

position of its mecon 80^ 20. 
Lion, erroneous statements about 
86» 20 n., 88» 30, 52» I ; its mane 
58» 30 ; its hard bones 55» 15 ; 
five toes to forefoot, four to hind 
88» 5 ; male retromingent 89» 30. 
Lips, general use to guard teeth 
59^ 25 ; vary in distinctness with 
nicety of these ih. 30; none in 
birds being toothless ib. 20 ; re- 
presented in them by beak ib. ; 
in man aid also in speech 60» I ; 
and are of appropriate character 
for this ib. 10. 
Liver of Sanguinea ; it and heart 
the only two constant organs 
70» 25 ; essential as ministering 
to concoction ib. 20 ; a necessary 
and vital part 'j']^ 35 ; has more 
blood than any organ save heart 
T^ 25 ; receives branches from 
the great vessel 70» 10; but not 
from aorta ib. 15 ; and serves as 
an anchor to great vessel ib. ; 
may be regarded as correspond- 
ing on right to spleen on left 
69''. IS) 35 ; andis the main cause 
of its formation 70» i ; in some 
animals is split into several parts, 
in others undivided -j-^^ 15 ; such 
division most marked in fishes 
and oviparous quadrupeds /A 20 ; 
especially in Selachia 69^^ 35 ; 
distinctness of its division in- 
versely related to size of spleen 
69^^ 25 n. ; but with exceptions 
ib. 30. Contributes largely to 
maintain purity and healthiness 
of body T'i^' 25. Colour pure and 
blood-like in vivipara and birds 


ib. 20 ; and when there is no 
gall-bladder ηη^ 20 ; or in part 
under bladder when there is one 
ib. ; of yellow hue in fishes and 
oviparous quadrupeds 73^ 30. 
V. Gall-bladder, Bile. 

Lizard v. Oviparous Quadrupeds. 

Lobster ?'. Crustacea. 

Locust, hind legs like steering oars 

83=^ 35• 

Lung, though a single organ looks 
like two in ovipara 69'^ 20 ; in 
what animals present 69* i ; no 
common name for these 69'^ 10 ; 
the organ of respiration ib. 5 ; 
required to temper heat of body 
68'' 30 ; close to heart and round 
it 65^* 15 ; derives from this its 
motion 69^15; its alternate ex- 
pansion and collapse ib. n. ; is 
not a buffer for heart's impact ib. ; 
nor a receptacle for drink 64'' 5 ; 
large and full of blood in vivipara 
69^ 25 ; small dry but highly dis- 
tensible in ovipara //;. ; liable to 
morbid growths 67'' i ; especially 
in parts farthest from windpipe 
ib. 5 ; reason for this ib. 10. 

Lynx, retromingent 89* 30, 

Maia 84^ 5. 

Male, superior to female 48* 10; 
stronger and more choleric oi^^ 
30 ; has weapons exclusively or 
more fully developed ib. ; and 
even larger organs of nutrition 
ib. 35; harder bones 55•"* 10; 
more sutures in skull 53'' i ; his 
generative organ 89^ 20. Jeju- 
num differs in the two sexes 
76'* I. Male lion alone has mane 
58* 30 ; in male crabs under 
parts less laminated and with 
less hairy appendages 84^* 20. 
Different views as to comparative 
heat of sexes 48»• 30. 

Mammae pectoral in man 88-''' 20 ; 
why not so in quadrupeds ib. 25 ; 
two and inguinal in animals that 
produce few at a birth 88'' 20; 
why so ib. 25 ; numerous and 
abdominal in those that produce 
litters 88'*^ 30 ; reason for this 
88'' 15 ; foremost give most milk 
ib. 10; in elephant two and axil- 
lary ib. 5 ; why so ib. 10 ; but in 
lion two and abdominal ZZ^ 35 n. ; 

present in males of man but not 
of all animals 88'' 30; why pre- 
sence variable in stallions ib. ; in 
human male fleshy and protective 
88=1 20. 

Man, his godlike nature 56* 5, 86* 
25 ; in him alone upper parts 
lighter than lower 89^ 10; alone 
erect 53^ 30, so^» 10, 62'' 20, 69'' 
5, 86* 25, 87* I ; consequently 
has buttocks and fleshy thighs 
89'' 10 sq. ; and no tail ib. 20 ; 
and largest feet in proportion to 
body 90* 25 ; and arms and hands 
for fore limbs 87* 5 ; allowing 
breast to be broad 88* 10; and 
mammae to be pectoral ib. 20. 
Man wrongly said to be defence- 
less, for his hand supplies the 
place of many weapons 87^ i ; 
admirable construction of this 
hand 87'' 5 sq. ; which is not the 
cause but consequence of his 
intelligence 87* 15 ; hand and 
foot contrasted 90* 30 ; why foot 
has toes and why these are short 
90'' 5. Man has the largest brain 
53* 25 ; the softest flesh 60* \o ; 
and most delicate sense of touch 
ib. ; and of taste ib. 1 5 ; tongue 
free, soft, broad, and adapted for 
speech 60* 20 sq. ; as also are 
his lips 59''3o; andteeth6i''i5 ; be- 
sides their fitness for mastication 
ib. 5. Face 62'' 15. Heart more 
central than in other animals os'' 
20 ; why inclined towards left 
66'' 5 ; why alone subject to pal- 
pitation 69*15; spleen 74*1; 
gall-bladder 76'' 30 ; kidneys 
much divided like those of ox 
71'' 5. More hair on front surface 
than on back as in quadrupeds, 
and why 58* 15 ; hair on head 
more abundant than in other 
animals, and why 58'' 1 ; alone 
has lashes on both eyelids 58* 
15 ; and hair in axillae and on 
pubes ib. 25. Solid earthy parts 
less developed than in quadrupeds 
55'' 10. Man alone laughs and 
alone affected by tickling 73* 5. 
7'. Dwarf -I ike, and various parts. 

Marrow, not seminal 51'' 20; is 
blood concocted by heat of en- 
vironing bones 52* 20 ; and their 
nutriment ib. 5 ; of blood-like 


aspect in embryo 51^^ 25 ; absent 
or scanty in very compact bones 
ζ2^ id; as those of lion Si'' 35 ; 
in fishes none save in chine, and 
reason for this 52^ 10. Marrow 
of chine of a different character 
to. 15 ; why so /^., 51^ 35 ; is con- 
tinuous with brain 52^* 25 ; but 
hot while brain is cold /ύ. ; this 
the reason for the continuity id. 

Mastication, no action on food save 

comminution 50=* 10 ; necessarily 

rapid in fishes 75'^ 5. 7'. Tee//i. 
Material existence antecedent in 

development to logical 46''' 25 ; 

but posterior in order of nature 

ii>. 35• 

Mecon, inside stomach of Testacea 
79^ 10 ; in what part of shell 
80=* 20 ; edible only in some 
kinds ϊί>. 

Membrane, formed of necessity on 
compounds of solid and fluidwhen 
cooling 77^ 20, 78'"^ I, 82'M5 ; but 
utilized 77^ 30, 78»' 5 ; suitable 
in character for a protection 73'' 
5 ; surround each viscus t'd. i ; 
strongest round heart and brain 
to. 5. 

Mesentery, present in all Sangumea 
76^ 10; formed like all mem- 
branes of necessity, but utilized 
for an end 78^^ I sq. ; carries the 
small nutrient vessels from ab- 
dominal organs to the great vessel 
and aorta ζ'δ. i, lo. 

Method of discussion, general ques- 
tions concerning 39** lo sq. ; 
course of, to be adopted 45'' i sq. 

Metrical science 60=* 5 n. 

Mice, gall-bladder in some species, 
not in others 76^ 30 ; heart large 
67* 20. 

Midriff, in all Sanguinea, 72^ 10 n. ; 
its marginal part fleshy, central 
membranous id. 25 ; why so ι'ύ. 
35 ; a barrier between the nobler 
and less noble parts ίύ. 20 ; keep- 
ing back heat and vapour of food 
ζύ. 15; why called Phrenes in 
Greek to. 30; only affects intel- 
lect and sensation indirectly il>. ; 
how affected by heat or tickling 
73* 1 ; or by wounds ζί>. lo. 

Milk, residual nutriment 53^ 10 ; 
most abundant in foremost dugs 

88^' 10 ; thick in horned animals, 
thin in others 76^ 10 ; former 
alone coagulated by rennet id. ; 
coagulated by certain herbage 
id. 15 ; to be discussed in De 
Gen. 53I' 15, 55I' 25. 

Mouth, its various offices 62^ 15 sq. ; 
has no actual part in concoction 
50'* 10 ; its gape wide when used 
for defence, otherwise contracted 
62* 25. 7'. LiJ>s, Teeth., Tongue. 

Mule V. Solidtingiila. 

Mussel, bivalved 79•^ 25 ; gaping 
valves 83^ 15. 

Mytis, presiding seat of sensation 
in Cephalopoda 81'' 15 ; corre- 
sponding to heart ib. 25 ; is a 
bag of fluid traversed by gullet 
ih. 15; why so ib. 20; similar 
part in Crustacea ib. 

Nails, in man to protect tips of 
fingers 87^ 20 ; and of toes 90^ 5 ; 
in other animals for active pur- 
poses 87^^ 20 ; five to each hind- 
foot in smaller Polydactyla 88* 10. 

Nature makes nothing without pur- 
pose 6i''2o; or superfluous gi'^ 
5, 95^ 15 ; brings about the best 
of what is possible 58^^20, 87^ 15 ; 
gives organs to those only that 
can use them 61^ 30, 84* 25, 87* 
10 ; often utilizes the results of 
necessity 58'^ 5, 63'' 20, 7^ 30; 
spends on one part what she 
saves in another 52» 10, 55a• 25, 
57''5. 5^^^35,63^30, 64^1,74^^1, 
84* 15, 85^^ 25, 89'' 10, 20; often 
uses one organ for more than one 
office 59a• 20, 60^ I, 62^• 15, 88* 
20, 90* I ; but if possible gives 
each function its separate organ 
83* 20 ; modifies an organ com- 
mon to several animals to suit 
their several requii'ements 62* 20 ; 
places the nobler parts in the 
more honourable position 65'' 15 ; 
never gives an animal more than 
one adequate means of protection 
63* 15. 

Necessity, absolute and hypothe- 
tical 39** 20, 40* 10. 

Necessity and Final cause, the two 
causes of living things 39^ 10 ; 
must both be taken into account 
42* 15 ; the former alone con- 
sidered by former writers 40'' 5 ; 


inadequacy of this ih. 15 ; the 
final cause the first cause 39'' 10 ; 
and starting-point in art and 
nature ib. 1 5 ; and in nature more 
dominant than in art ib. 20. 
Many things in body are results 
of necessity alone 42^^ i ; or are 
necessary consequents of parts 
made with design 45'' 30 n., ']']^ 
1 5 ; such results of necessity often 
utilized for an end 63^ 20. 

Neck, defined as part between head 
and shoulders 91'' 25 ; therefore 
strictly speaking none in serpents 
ib. 30 ; only in animals with lung 
64•'^ 20, 86•'' I ; exists for sake of 
windpipe ib. 15 ; on account of 
length of this 91^' 25, 64*30; 
flexible and with several vertebrae 
So^"• 20 ; save in wolves and lions 
where there is only one ib. ; rea- 
son for this ib. 

Nerites, defended by operculum 
79^^ 20. 

Nictitating membrane v. Eyelids. 

Nutrition, A.'s views concerning 68'"* 

Oesophagus, no action on food 64'^ 
20 ; only necessitated by neck ib. 
30; satisfaction from solid food 
due to its dilatation 90^' 30; 
why soft, yielding, and dilatable 
64=» 30. 

Omentum, in all Sanguinea 76'' 10; 
a membrane containing fat 77'^ 
15 ; formed of necessity but 
utilized for an end ib. 30 ; namely 
to aid in concoction ib. ; why it 
is attached to middle of stomach 
only ib. 

Oryx, has single horn 63•'' 20. 

Ostrich, avian by feathers, which, 
however, are like hair and useless 
for flight 97^^ 15; quadrupedal 
by cloven hoof and upper eye- 
lashes ib. 20, 58•'^ 10. 

Oviparous quadrupeds, less erect 
than vivipara 69^ 5 ; integument 
with horny plates 91* 15 ; a neck 
to accommodate long windpipe 
91'' 25 ; breast but no mammae 
92* 10; a tail of variable size ib. 
15. Teeth serrate 91* 10; only 
motion of lower jaw up and down 
//;. 30 ; in crocodile the upper 
jaw the movable one 91'' 5. Lung 

membranous and small but highly 
distensible 69'' 25. Senses all 
present 91*10; eyes hard and 
without upper lid ib. 20 ; why 
closed by lower 57^ 5 ; do not 
blink nor are keensighted, and 
reason for this 91* 25 ; no exter- 
nal ears, and reason ib. 10, 15; 
tongue in all save crocodile 90*^ 
20; this bifid in lizards 91*5. 
Spleen small and like a kidney 
70^^ 10 ; no kidneys 71'"^ 25 ; nor 
bladder save in tortoises ib. 10, 
76^ 30. Can live for a time un- 
der water 69•'^ 35 ; reason for this 
69'^ I. Usually of smaller bulk 
than vivipara ib. 

Ovoviviparous, vipers and carti- 
laginous fishes 76'' I. 

Ox, some wild 43'^ 5 ; spleen in one 
part elongated 74* i ; a certain 
kind has bone ii heart 66^* 15; 
backward-grazing kind 59•'* 20 η. ; 
blood of bull rich in fibres 51* i ; 
and therefore coagulates rapidly 
ib. V. Cloven-hoofed imimals. 

Oyster, general name for various 
species 54* i ; body a disk, and 
not symmetrical 80'' 10; head 
central ib. ; ovum unilateral ib. 
5, 20; vast number destroyed by 
starfish 81'^ 10. 

Parmenides thought women hotter 
than males 48=^ 25. 

Pig V. Hog. 

Pigeon, small spleen 70^^ 30 ; use 
both lids to close eye 57^* 10. 

Plants, not much variety of organs 
56* I ; upper and lower parts in- 
verted 83'' 20, 86'^ 30 ; roots their 
mouth ib. 35 ; absorb food already 
elaborated from the ground 50* 
20, 78'^ 10 ; therefore no excreta 
55^ 30, 8i=* 30; give off their 
surplus nutriment as fruit and 
seeds 55'' 30, 86'^ 35; some live 
free, some on other plants 81=* 
20 ; some when uprooted ib. ; 
separated parts live on and attain 
perfect form 82'^ 25 ; whether 
plant or animal in some cases 
doubtful 81* 25 ; distinguished 
from animals by absence of sensa- 
tion Go^* 30. 

Plato, views alluded to ; as to dicho- 
tomy 42'' 5 ; as to marrow of 


bones 51^ 20; as to brain and 
spinal marrow 52=^ 25 ; as to 
absence of flesh from head 56^ 
15 ; as to fluid passing by wind- 
pipe 64^ 5 ; as to lung serving as 
Ijufifer to heart 6g^ 15 ; as to gall- 
bladder 76'' 20, 

Polydactylous vivipara, less dwarf- 
like than other quadrupeds 86'^ 
1 5 ; forefeet serve as hands and 
not only for locomotion 87^ 30 ; 
or for support jQ'^ 20; which is 
their only use in elephants j7>. 
25 ; are used in defence 88^ i ; 
usually five toes to each fore- 
foot, four to each hind foot 88^ 5 ; 
but in small kinds five to this 
also ιό.; reason for this ζύ. lo; 
have no horns 62^ 30 ; because 
they have claws, fangs, or other 
defensive weapons ιί>. ; why no 
hucklebones go^ 25 ; mammae 
never pectoral, and reason 88=* 1 5 ; 
their position and number to. 35 ; 
fat soft like lard 51* 35. 

Poulp V. Ceplialopoda. 

Proboscis, of elephant 58^^ 30 sq. ; 
of insects 78^^ 10; of sea-snails 
and other molluscs 79^' 5 ; of 
sepias and calamaries 85^ 30. 

Proportions of upper and lower 
parts 86^ i ; changes in later life 
ib. 10. V. Dwarf-like. 

Protection, no animal has more than 
one adequate 63^ 15 ; various 
forms of enumerated 62'^ 30 sq., 

79a 5, 7gb 25,30, 83^ 10, 82^ 20. 

V. Weapons. 
Purpura, shell turbinate 79^ 10; 
has operculum 79^ 20 ; bores 
holes through hard shells 61* 20. 

Rain, how produced 53^ 5. 

Refrigeration, heat of body requires 
tempering oS"» 30 ; in bloodless 
animals this effected by innate 
spirit 69^ I ; in sanguineous by 
external agency 68'^ 35 ; viz. water 
and gills in fishes, air and lung in 
the rest 69* i ; or by mere motion 
of lung without air 69^^ i. 

Rennet, found in third stomach of 
horned animals 76* 5 n. ; result 
of their thick milk ib. 10; also 
formed in hare ib. 5 ; because of 
the character of the herbage it 
consumes ib. 15. 

Reptiles, quadrupedal and apodal 
ovipara 90^ 10; alike save as 
regards feet ib. 15. v. Oviparous 
quadmpeds. Serpents. 

Residual substances, Avhat meant 
50^ 20 n. 

Rhine, \vhat fish meant 97'"* 5 n. ; 
skin rough ib. 

Right, superior to left 48^ 10, 65=* 
20; is hotter 67'* i, 70^' 15; 
stronger and more advanced 71^ 
30 ; more solid and better suited 
for motion 72^ 25 ; motion com- 
mences from it 71^ 30 ; naturally 
used preferentially 84^ 25. 

Roe, no gall-bladder 76^' 25 ; blood 
without fibres 50^ 10 n. ; and 
therefore does not coagulate ib. 15. 

Rot, how caused 72^ 1 ; why only 
or chiefly in sheep 72^30; why 
so rapidly fatal 72^^ 5. 

Rumination, horned animals with 
no upper front teeth ruminate 
75^ I ; as also does the camel 
though hornless 74^ 5. Among 
fishes the Scarus alone ruminates 
75'-^ I. 

Ruminants v. Cloven-hoofed. 

Sanguineous and bloodless, how 
far same as vertebrate and in- 
vertebrate 45^' 5 n. ; Sanguinea 
the more perfect 82''* 30 ; vital 
centre always single 67*^ 25 ; all 
have heart and liver 65'^ 10, 66* 
25 ; and distinct head 85^' 35, 
90^^ 15 ; alone have viscera 65 '^ 
30 ; are hotter than bloodless 68'' 
35 ; therefore have special organs 
for refrigeration by external 
agencies ib. ; are bilaterally sym- 
metrical 67'' 30 ; never have more 
than four motor points 93'' 5, 95'* 
20, 96* I, 15. Bloodless must 
have some part analogous to 
heart 81^ 15. v. Ascidia, Cepha- 
lopoda, CruslaceOf Insects. 

Scale of Nature, gradual ascent 
from inanimate things through 
plants to animals 8 1'"^ 10 ; gradual 
descent from erect man to plants 
with upper part downwards 86'^ 
30 ; life, and life of high degree 

Scale of fish and scaly plate of 

reptile, 91="• 15, 97=* 5 n. 
Scarus, teeth not serrate 62^ 5, ηγ• 


I ; this probable cause of rumi- 
nation ib. 

Sciences, classification of 40^ i n. 

Scorpion, sting why external 83^^ 

Seal, intermediate animal 97^ i ; 
has both feet and fins ib. ; no ex- 
ternal ears 57=* 20; teeth serrate 
97^ 5 ; tongue bifid 91^ S ; no 
gall-bladder ηΘ> 25 ; kidneys 
solid and lobed 71'' 5. 

Sea-lung 81* 15. 

Sea-nettles v. Acalephae. 

Sea-urchin, classed with Testacea 
80» I, 79b 30 ; well protected by 
globular spiny shell ib. 25 ; spines 
serve as feet Si-'"• 5. Teeth five 
80* 5 ; surrounding a fleshy sub- 
stance ib. ; stomach single but in 
five compartments ib. 10 n., 80^^ 
25. So-called ova also five ib. i ; 
not real ova but surplus nutri- 
ment 80» 25, 'ξ>ο^^ 5 ; why largest 
in spring and autumn ib. ; and at 
full moon ib. 30 ; not edible in 
every species 80* 15. Why all 
these several parts are five So*^ 
5 sq. Black substances in inte- 
rior without name 80^ 10 n. 

Selachia, cartilaginous fishes 55* 
20. V. Fishes. 

Semen, is residual matter 89* 10, 
50* 20 n. ; inversely related to fat 
5 1'^ ID, 5 la- 20 n. ; in animals with 
bladder has same orifice as urine 
893• 15; in others as faeces 97* 
10 ; to be discussed in the De 

Sensation, distinctive character of 
animals 66* 30 ; its central seat 
in Sanguinea the heart ^β^ 25 ; 
in Cephalopoda and Crustacea 
the mytis 81'^ 15 ; in Testacea 
situation doubtful, but in some 
median position ib. 30 ; in insects 
usually single and thoracic 82* i ; 
but in long-bodied as millipedes 
multiple ib. ; in Ascidia presuma- 
bly in central septum 81'' 35. 

Sense-organs, why homogeneous 
47* 5 ; each coupled by older 
physiologists with a separate ele- 
ment ib. 10; are bilateral 56*^30, 
57* I ; of sight always in head 
56* 30 ; of hearing and smell 
usually ib. ; why so placed 56*^ 5 ; 
local arrangements of these three 

and the reason ib. 25 sq. ; are 
connected by channels with vessels 
of pia mater ib. 15 ; or those of 
hearing with empty space at back 
of head ib. ; but not continuous 
with brain 52^^ i. Eyes, why of 
water 56'' i ; the best of fluid 
consistency and with eyelids 48^* 
15, 57* 30; why \vithout lids in 
fishes though of fluid consistency 
58^^ 5 ; hard and unprotected in 
Crustacea and insects 57*^30; 
this compensated by mobility sS'* 
I. Olfactory organ, not very di- 
verse in quadrupeds 58^^25 ; placed 
at inspiratory orifice 57^^ 5 ; with- 
out nostrils in birds and reptiles 
59^ I ; peculiar in elephant 58'' 
25 ; in Cetacea is the blowhole 
59'^ 15η.; in fishes the gills ib. ; 
in insects the hypozoma ib. 
Auditoiy organs, so placed as to 
catch sounds from all quarters 
56'^ 25 ; have no bone but carti- 
lage 55* 30; projecting in quad- 
rupeds 570• 10; and movable in 
some 58=^ I. Only auditory 
passages in birds 91^ 10, 57»• 15 ; 
and reptiles 91^^ 15 ; and seal 57* 
20; none visible in fishes 56^* 30. 
Organ of touch and taste internal 
56*^ 35 ; in direct connexion with 
the heart 56=* 30. 

Senses, touch the primary sense 
53^ 20 ; recognizes more distinct 
differences than any other 47* 
15 ; most delicate in man 60^ 10. 
Taste a form of touch 56"^ 35, 
60* 20 ; deficient in tongueless 
animals 91* i ; limited in fishes 
60^ 15 ; acute in serpents ib. 5 ; 
most delicate in man 60* 20. 
Sight, most accurate when eyes 
are of fluid consistency 48* 15 ; 
exercised in a straight line only 
56^30. Hearing, recognizes sounds 
from all quarters 56*^ 25. Media 
of senses 53'^ 25, 

Sepia v. Cephalopoda. 

Serpents, are like oviparous quadru- 
peds save in absence of feet 90^ 
15, 76*25. Viscera moulded to 
fit elongated body 76'^ 5. Integu- 
ment in large kinds has hard 
bony plates 91* 15. No neck 91'' 
30 ; yet can turn head back while 
body is at rest 92* i ; owing to 


vertebrae being cartilaginous ib. 
5. Tongue long, protrusible, bifid 
gi'* 5, 60'' 5 ; consequent fondness 
for dainty food ib. No testes 97=^ 
ID n. Oviparous except viper, 
which is ovoviviparous 76^ I. v. 
OviparoHS qriadrupeds. 

Sheep, horned 74^ 5 ; stomach 
multiple ib. ; variable character 
ofgall-bladder76''35 ; its kidneys 
without lobes 71'^ 5; has the 
densest suet 72^ l ; why alone 
liable to rot 72* 30. v. Clovefi- 
hoofed animals. 

Sinew, various fibrous structures 
included 66^ ion. 

Sleep, cause of 53'^ 10. 

Smuraena 96^ 5 n. 

Socrates, study of nature neglected 
after him 42* 25. 

Solen, valves united on both sides 

83^ 15. 

Solid and Fluid v. Hot, Cold, Solid, 

Solidification, caused both by heat 
and cold 49^^ 30 ; what substances 
so affected and the causes, dis- 
cussed elsewhere ib. 

Solidungula, much earthy constitu- 
ent in body 90^^ 5 ; why no huckle- 
bone ib. 10; repel assailants with 
hind-legs 88^ i ; mammae two and 
inguinal ib. 30 ; have mane 58^* 
30 ; stomach single 74=* 25 ; 
spleen broad in one part, long in 
another ib. i ; no gall-bladder 
ηη^ 3o ; never retromingent 89* 
30 ; single young at a birth 88'' 

Soul, how far within the province of 
natural science 41* 30 sq. ; is 
not fire but incorporate in a fiery 
substance 52^^ 5 ; heat its in- 
strument ib. 10. Is the function 
of the whole body 45^ 15. 

Speech, consists in combination of 
letter sounds 60* i ; these pro- 
duced by lips and tongue ib. 5, 
59'' 30, 61* 10 ; and front teeth 
61^ 15; man's tongue suited for 
this by softness, breadth, free- 
dom 60^ 20 ; and his lips by 
their moisture ib. 5 ; speech in- 
distinct in tongue-tied persons 
ib. 25 ; birds that can pronounce 
words have broadest tongues ib. 
30 ; all birds communicate orally 

with each other ib. 35 ; and in 
some cases instruction apparently 
so imparted όο'^ i. v. Vocal 

Spit and Lampholder in one 83'' 25 n. 

Spleen, not invariably present 70* 
30 ; nor when present necessary 
except as an inevitable concomi- 
tant ib. I ; and a counterpart to 
liver 66* 25, 69'' 35 ; its size in- 
versely related to lobulation of 
liver ib. 25η.; receives a branch 
from great vessel 70^* 10 ; but not 
from aorta ib. 15; its shape in 
different animals η•^ 30; helps 
to concoct food 70* 20 ; and 
draw off superfluous fluid from 
stomach 70^ 5 ; small when there 
is little of this as in birds and 
fishes ib. 10 ; or when it is other- 
wise expended as in reptiles ib. 
1 5 ; when present in other animals 
is of watery character ib. 1 5 ; belly 
hard when spleen is diseased 70*" 
5 ; is excessively liable to morbid 
growths 67^ 5. 

Sponge, always attached and dies 
when separated, altogether like a 
plant 8i"• 10, 15. 

Starfish, destroys many oysters 81'' 

Sting, in some Testacea tongue 
serves also as a sting 61* 15, 25. 
V. Itisects. 

Stomach of vivipara. Single when 
both jaws have front teeth 74* 
20 ; and small ']γ• 2ζ ; is of two 
types, the dog's and the pig's 
ib. ; how these differ ib. Multi- 
ple when upper jaw has no front 
teeth 74^* 30 ; so as to compensate 
for the imperfect dentition 74^^ 5 ; 
names of the successive cavities 
ib. 10 ; their several uses ib. 

Sutures of skull, ventilate the brain 
53^^ I ; most numerous in man, 
and in male more than female ib. ; 
this due to his larger brain ib. ; 
late ossification of anterior fonta- 
nel 53* 35. V. Bregma. 

Sweat, secreted from minute blood- 
vessels 68^ I ; blood-like not un- 
known ib. 5. 

Tadpole v. Cordylus. 
Tail, different forms of 90* i ; in 
most quadrupeds 89^ I ; none in 


ape lb. 30; nor in man, and why 
lb. 20 ; relation of its hairiness to 
that of the body sS»• 30; its uses 
ib. 25, 90» I ; of birds 97*^ 10; of 
fishes 95^ 5,15, 96^^ 20 ; of tad- 
pole 95*^ 25 ; used as oar by 
Carabi 84^ i . Why bat has none 
97'' 10. 

Taste, variety of touch 56'^ 35, 60* 
20. V. Senses. 

Teeth of bloodless animals v. Cepha- 
lopoda, Crusiacea, Insects, Sea- 
urchin, Testacea. 

Teeth of Sanguinea, universal 
function reduction of food 61'' i ; 
admirably suited for this in man 
ib. 5 ; grinders, dog-teeth, inci- 
sors ib. ; his front teeth aid also 
in speech ib. 1 5 ; no upper front 
teeth in horned animals 63'^ 35 ; 
and why 64* i . Teeth also serve 
as weapons, defensive, offensive, 
or both 61^ I ; viz, as tusks to 
strike with, or by serrate arrange- 
ment in biters ib. 25 ; advantage 
of serrate arrangement ib. 20. 
Serrate also in most fishes and 
curved and numerous 62'* 10 ; 
reason for this ib. 5. 

Testacea, mostly stationary, there- 
fore few parts 83^^ I ; of which 
head alone has distinctive name 
ib. 20 ; in some points like Crus- 
tacea, in others Cephalopoda 84'' 
15) 85* I) 79^30; genera and 
species numerous ib. 15 ; com- 
prise Turbinata, univalves, bi- 
valves ib. ; and sea-urchins ib. 
25 ; and ascidians 80* 5 ; various 
kinds of protective shell 83^ 10. 
Turbinata also protected by oper- 
culum 79^25 ; which makes them 
in a way bivalved ib. ; univalves 
by attachment to rock which acts 
as second valve ib. ; bivalves by 
power of closure ib. ; sea-urchins 
by spiny globular shell ib. 30. 
Head downwards as in plants, 
and why 83*^ 15 ; all have mouth, 
tongue-like organ, stomach, vent 
79^ 35; gullet and crop ib. 10; 
inside the stomach the inecon 
giving rise to intestine ib. ; posi- 
tion of this in the several genera 
80* 20 ; some have teeth 78^ 
20 n. ; position of tongue and its 
great strength in some 61^ 15,20, 

78*^ 20. Proboscis 79^ 5. So- 
called ova not ova but resemble 
fat 80* 25 ; appear when animals 
are in good condition, viz, in spring 
and autumn ib. ; where situated 
in different kinds 8θ^ 5 sq. Vital 
centre not easily made out, but 
must be looked for in a median 
position 81^ 30. v. Ascidia, Sea- 

Tethya v. Ascidia. 

Teuthi and Teuthides 85'^ 15 n. v. 

Toad 73^ 30. 

Tongue, present in all Sanguinea 60'' 
10 ; least variable in land animals 
60^ 15 ; freest, softest, broadest in 
man ib. ; and so adapted for taste 
and speech ib. 20 ; taste chiefly 
in tip 61="^ I ; in viviparous quad- 
rupeds hard, thick, and vocal use 
very limited 60* 30 ; in birds 
broadest in those that can pro- 
nounce words 60^ 30 ; in reptiles 
hard, tied down, and useless for 
vocal purposes 60^ 5 ; but forked 
in serpents and lizards ib. ; giving 
double gustatory sensation ib. 10 ; 
peculiar in crocodile ib. 25 ; in 
fishes barely developed ib. 10 ; 
not more than the tip 61* 5 ; why 
so rudimentary 60^ 15. Blood- 
less animals such as Cephalopoda 
and Crustacea have tongue-like 
body inside mouth όι'^ 10 ; Testa- 
cea also and insects, either in or 
out of mouth ib. 15; when ex- 
ternal serving for taste, suction, 
and also as a piercer or sting ib. ; 
its great strength in some of these 
ib. 20. 

Torpedo, broad body, long spinous 
tail 95^ 5 n,; altered position of fins 
96^^ 25 ; mode of swimming ib. 30. 

Tortoise, shell preserves the heat 
54^ 5 ; liver yellow owing to bad 
composition 73^ 30 ; alone of 
reptiles has bladder 76* 30, 71* 
20 ; reason for this ib. ; difference 
of bladder in land and sea species 
71=^ 25 ; and of lung ib. 15 ; both 
kinds have kidneys ib. 25. v. 
Oviparous qieadrupeds, 

Trygon 95^ 5, 25, 

Turbinata v. Testacea. 

Upper— in man alone upper turned 


to upper in universe 56* 10; upper 
is part for which rest exists 72^ 
20 ; superior to lower 65'^ 20, 48^ 
ID ; therefore heart in upper 65^ 
20 ; upper and lower reversed in 
Testacea 83^ 20; and in plants 
86'^ 30. 

Viper, ovoviviparous 76^ I. 

Viscera, at once homogeneous and 
heterogeneous 47^ 35, 47^ 5 ; none 
in bloodless animals 65* 25, 65*^ 
5, 78^^ 25 ; formed by exudation 
from ultimate blood-vessels 47'^ 
I) 73* 30; as shown by blood-like 
aspect and large size in new-born 
animals 65^ 5 ; are bilateral 69^ 
15 ; why so 70^ 5 ; each enclosed 
in membrane 73^^ i ; the abdomi- 
nal serve to anchor the main 
vessels "jo^ 5 ; and some to aid 
concoction il•. 20 ; heart and liver 
the most constant ib. 25 ; con- 
trast with flesh in position and 
aspect 74^ 5 ; differences in differ- 
ent animals 73^ 15 sq. ; small 
when there is no bladder 76'^ 5. 

Vital or Natural Heat, differs from 
ordinary 52=* ion.; belongs not 
only to heart but to many parts 
50^^ 5 n. V. Heart. 

Vocal utterance, impossible with- 
out lung and larynx 73^ 20 ; very 
limited in viviparous quadrupeds 
60* 30 ; in oviparous quadrupeds 
tongue useless for this purpose 
60^ 5 ; small birds have greatest 
variety of notes 60=* 30. v. Speech. 

Wasps, sting internal 83^ 5. 

Weapons offensive or defensive 55'' 
I ; given to those only that can 
use them 61'' 30, 84* 25, 87^*• 10; 
to males exclusively, or more per- 
fectly 62'^ 1,6 1*^30; such as stings, 
spurs, horns, tusks and the like 
ib. ; hind leg used as weapon by 
Solidungula 88'"^ i ; foreleg by 
Polydactyla ib. ; who have no 
horns but claws, fangs, or other 
defensive \veapons 62'^ 30. Man 
not unarmed 87^ 20; his hand 
represents many weapons 87^ l. 

Whale 69* 5, 97^^ 15. v. Cetacea. 

Whelk, shell turbinate 83^^ 10, 79^ 
10 ; has operculum ib. 20. 

Wild boar, blood rich in fibres ^\^ 
I ; in consequence passionate ib. 

Windpipe and larynx, why neces- 
sarily of some length 64* 30 ; car- 
tilaginous for vocal purposes ib. 
35 ; is not a passage for fluid 
64^ 10; its vicious position in re- 
lation to oesophagus ib. 1,65*10; 
why so placed ib. ; possible ill 
results 64^^ 20 ; obviated by epi- 
glottis ib., 65* 5 ; admirably 
accurate action of this 64^ 30 ; 
only exists in hairy sanguinea ib. 
20 ; in other sanguinea larynx 
effects its own closure ib. 25 ; why 
they have no epiglottis 65* I. 

Wolf, only one cervical vertebra 
86* 20. 

Wood-pecker, hard strong beak 
62^^ 5. 

Wryneck, two toes point backwards, 
and the reason 95* 20. 

Oxford : Printed at the Clarendon Press by Horace Hart, M.A. 












Μ. S. 



These translations have been made from Bekker's text 
(Berlin, 1831) with the help of the critical apparatus there 
given, of photographic facsimiles of the manuscripts Ε and Υ 
for de MotH, and of U for de Incessu, as well as the C.C.C. 
Oxon. MS. of the latter treatise (Bekker's Z). I have noted 
some readings fiOm an antiqua 7icrsio of both tracts (Ball. 
Coll. MS. CCL) of the late Xlllth century. I refer to it 
as Γ, though the text on which it is based is not the same 
for both de Motu and de Incessu, nor is the Latin by the 
same translator. The pages of the Berlin edition are given 
in the margin. 

The commentary of Michael Ephesius (Comm. in Arist. 
Graeca, xxii. 2, Hayduck, 1904) has been some help for 
the text of both treatises, occasionally for the interpretation. 
In a small measure this holds also of Alexander Aphrodisias' 
de Anima (Supp. Arist. ii. i, Bruns). Of the MSS. Ε and Ζ 
are the oldest, Γ is independent though approaching Ζ very 
closely in the last part of de Incessti, U and S are akin, Υ 
is copied from Ε and a MS. very like Z, Ρ has preserved 
some good variants. The paraphrase of de Mottt by 
Albertus Magnus (0pp. ix. 2, Borgnet, 1890), derived 
from a Greek original (' in Campania nobis iuxta Graeciam 
iter agentibus peruenit ad manus nostras libellus Aristotelis 
de motibtts anini'^K'), throws some light on the text. It is 
referred to as A.M. in the notes. I have used with profit the 
Latin translation of Nicolaus Leonicus Thomaeus (ob. A. D. 
1 533), an Aristotelian scholar who evidently made use of more 
than one MS. Isaac Casaubon speaks ill of his Aristotelian 
labours {de Enthusiasmo, ch. vi), but I venture rather to 
agree with Wyttenbach's praise of his elegance and learning 
{OpHscnla, i. 363). I have also read Bernardino Crippa's 
Latin translation and notes (a.d. 1566). St. Hilaire's 
French rendering and notes are useful for the general sense. 


Authorities differ as to the genuineness of dc Motu, the 
more modern opinion inclining to accept it. It certainly 
gives, except in one difficult passage, the exact doctrine of 
Aristotle, and I hope that the rather full references I have 
given will show this. I have defended its genuineness, 
with especial regard to the remarkable doctrine of ch. x, in 
a paper communicated to the Oxford Philological Society, 
a paper favourably received by the scholars then present. 

I have to thank Dr. Gunther, Fellow of Magdalen College, 
who kindly read my MSS., for valuable criticisms from the 
naturalist's point of view. It was difficult to resist the 
temptation to make the notes fuller in this connexion. 
Mr. W. D. Ross, Fellow of Oriel College, has done the 
same by the rendering of the actual Greek. I am very 
sensible of his patience and accuracy as well as of his 
learning. I have also had the advantage, in the critical 
estimate of the text, of one evening with the Oxford Philo- 
logical, and of two with the Oxford Aristotelian Society. 
My thanks are also given to Mrs. New and to Mr. F. J. 
Routledge of New College, who made for me transcripts of 
the Latin Version ; to my friend Monsieur R. Simeterre, 
for his generous labour in Paris; to Rev. H. M. Bannister of 
Pembroke College, who helped me in Rome ; and to 
Corpus Christi and Balliol Colleges for the loan of MSS. 
The little book is dedicated to the memory of my old 
schoolmaster. He died just as I had finished. Whiston's 
successor at Rochester, the descendant of Plutarch's trans- 
lator, by his stern judgement and nice taste first opened to 
me the Greek and Roman Classics. I could wish that this 
interpretation were exact enough to have disarmed his 
inveterate prejudice against Oxford versions. 

jftine, 191a. 




1. The source or ground of animal movement, i.e. movement in 

place (translation). Physics teaches that all movements in the 
Universe are related to an unmoved ground (primum movens). 
Experience, the handmaid of Science, confirms physical theory. 

2. Animal movement requires 

(a) points of rest (joints) in an organized body ; 
{ί>) an external resisting fulcrum (e. g. earth, air, or water). 
Illustrative experiments. 
3,4. Can the primum movens he pari of the Universe? Truth and 
error in older speculation. Equilibrium and vis inertiae. As 
the universe is eternal, the p. m. must lie outside the physical 
universe, itself immovable. Motions of inorganic bodies on 
the earth derived ultimately from animate bodies. 

5. Subordinate kinds of motion ; structural alteration, growth, 

generation and decay. 

6. Final cause of movement. How does Soul move Body? Such 

movements relate to an End. 

Animal movement belongs to the sphere of action, not specu- 
Analogy between the Universe and the animate body. 

7. Action and Speculation. Act the conclusion of the syllogism of 

action. Animal movements compared with automatic toys. 
Toys mechanical, animal change physiological. Latens pro- 

8. Minute organic changes are subconscious. Psychophysical 

mechanism. Chain of movements indicate a common centre. 
Illustrative experiment. 

9. Efficient cause of movement, the heart. Bilateral symmetry of 

the body. Anatomical confirmation. Analogy of centre of 
sense. The common original is the heart, the organ of soul. 

10. Formal and material cause of movement. Physiological changes, 

necessary to movement, depend upon place-movements of 
' connatural spirit '. Physical characters of ' spirit '. The body 
a well-ordered commonwealth. Central control, local self- 

11. Similar principles hold of involuntary and non-voluntary n.ove- 

ments. Rationale of body's structure. Irrational movements 
related to physical states. Conclusion. 



1. Variety of organs of locomotion in animals. Number and modes 

of flexion of limbs vary. 

2. General scientific principles, and accepted definitions presumed. 

3. Joints necessary to animal movement, and an external fulcrum. 

4. Dimensions of living bodies to be determined by function, not by 

spatial position. Plants compared with Animals. Dimensions 
determined by Nutrition, Sensation, and Locomotion. Superiority 
of right to left. Illustrations. Gradation of natural forms. 
Higher animals more differentiated. Man the most natural 

5. Number of limbs (generically termed 'feet ') related to dimensional 

differentiation. Bipeds more natural than Quadrupeds. 

6. Bodily structure and mechanics of movement. Principles of 

^ de Motu assumed and recapitulated. One dimensional pair 

7. Four points of normal movement. These characterize Sanguinea, 

the most natural animal order. Sanguinea true unities, Poly- 
poda really aggregates. Limbless Sanguinea no exception. 
Snakes, eels, &c. 

8. Absence of limbs in elongated Sanguinea explained. Limbs 

necessarily even. Experiments on living animals. 

9. Further inquiry into mechanism of jointed limbs. Physical and 

mathematical proofs. Flexion necessary also to limbless animals. 
Further illustrations from saltatorial animals, birds and fishes. 

10. Birds, though bipeds, use four points. Function of tail in birds 

and insects. 

11. Structure of man, the only erect animal. Comparison with birds. 

Balance of a bird's structure. The tail. Monstrous inventions 
of artists. 

12. Reasons for differences in flexions of man's limbs and quadruped's. 

13. Diagrams of limb-flexion. Principle of alternate opposition. 

14. Why a quadruped's limbs move criss-cross. The crab's peculiar 


15. Birds compared with quadrupeds. Reasons for structure and 

flexion of a bird's legs. General survey of creatures of air 
and of the water. Oblique attachment of wings and fins. 
Oviparous quadrupeds. 

16. Locomotion of non-sanguineous animals explained. Peculiarity 

of the Crab. 

17. Crabs, crayfish, flatfish, and aquatic fowl. 

18. Why birds have feet, but fish none. Homology of wings and fins. 

19. Distorted animals ; Molluscs compared with Seals and Bats. 

Zoophytes. Conclusion. 


I Elsewhere we have investigated in detail ^ the move- 698* 
ment of animals after their various kinds, the differences 
between them, and the reasons for their particular characters 
(for some animals fly, some swim, some walk, others move δ 
in various other ways) ; there remains an investigation of 
the common ground ^ of any sort of animal movement 

Now we have already determined (when we were dis- 10 
cussing^ whether eternal motion exists or not, and its 
definition, if it does exist) that the origin of all other 
motions is that which moves itself, and that the origin'* of 
this is the immovable, and that the prime mover must of 
necessity be immovable. And we must grasp this not 
only generally in theory,^ but also by reference to individuals 
in the world of sense, for with these in view we seek general 
theories, and with these we believe that general theories 
ought to harmonize.^ Now in the world of sense too it is 15 
plainly impossible for movement to be initiated if there is 
nothing at rest, and before all else in our present subject — 
animal life.'^ For if one of the parts of an animal be moved, 

^ e.g. P. A. iv. 10-14 iind de Inc. Afiim. (the latter treatise being 
a section of the former Avork and presupposed in de Mot» Anini.). 

^ The full title seems to have been nep\ της κοινής κινησΐως τώρ ζώων 
{704^ 2), cf. the last words in some MSS. of de Divinatione per 
Somnum ; or η κοινή αιτία της των ζωών κινησΐως (782* 2l),de causa ntotus 
a7ii))ialium. That is, On animal movement in general ; or The general 
ground of animal movement. (Cf. P. A. 646* 10.) Movements had been 
reduced in the Physics to a primary kind, Thrusts and Pulls, i.e. 
Translation ; this treatise discusses the origination of such primary- 
movements in the animate body; they are referred to a central original, 
the heart, and that is the organ of the soul. 

^ Cf. de Anvn. iii. 2, 9, 10 ; Physics, viii. 5 ; Metaph. xii. 7 and 8. 

* Leg. τούτον ΕΥΡΓ, Mich. Eph., Leonicus. (Zeller, Arist. Eng. 
trans, ii. 492.) Cf. Physics, 252^ l -πάντων 8e to άκίνητον : A/ei. 1072^7. 

' Ρ and Mich. om. καθόλου, but vid. G.A. 729*24. 

* Zeller finds in this an exaggeration of A.'s empirical attitude ; cf. 
however Parv. Nat. 468*23; G.A. 760'' 28, 788*» 19. Bon. Index 
177'' 45• ■' Cf. Physics, 259^ I ψανίρώς. 

V. AR. M. A. Tl 

698^ DE MOTU 

another must be at rest, and this is the purpose of their 
joints ; ^ animals use joints like a centre,^ and the whole 

20 member, in which the joint is, becomes both one and two,^ 
both straight and bent, changing potentially and actually 
by reason of the joint. And when it is bending and being 
moved one of the points in the joint is moved and one is at 
rest, just as if the points A and D of a diameter were at 
rest, and Β were moved, and DAC were generated.* How- 
ever, in the geometrical illustration, the centre is held to be 

25 altogether indivisible (for in mathematics motion is a fiction, 
as the phrase goes, no mathematical entity being really 
moved),^ whereas in the case of joints the centres become 
now one potentially and divided actually, and now one 
698*• actually and divided potentially. But still the origin ^ of 
movement, qua origin, always remains at rest when the 
lower part of a limb is moved ; for example, the elbow 
joint, when the forearm ' is moved, and the shoulder, when 
the whole arm ; the knee when the tibia is moved, and the 
5 hip when the whole leg. Accordingly it is plain that each 
animal as a whole must have within itself a point at rest, 
whence Λνίΐΐ be the origin of that which is moved, and 
supporting itself upon which ^ it will be moved both as a 
complete whole and in its members. 

' Inc. Aniin. 3 and 9. 

"^ Cf. de Anini. 433^ 26 ; P. A. 654^ I i^iva χρηται η φΰσις και ως ev\ και 
σννΐχύ, κα\ ως δυσΐ κα\ ^ιτ^ρημίνοις ηρος την κάμψιν), Avhere there is an 
account of various types of joint. 

' Cf. de Anim. 427^ 10 and injra, 702^30. 

* Leg. yivoiTo ή ΔΑΓ (Prof. J. C. Wilson). The Diagram contemplated 
is given by Mich. Eph. : 

DB, the whole arm. q 

AC, the forearm (cf. radius). '' 

DA, the humerus. 

A, the elbow. 

ε Leg. /(ΐί/είσ(9αι EYSr. Ci. Physics, 
193^ 34 ; M^^' 989^ 32, 1064* 30, 

* άρχη used for terminus a quo or origin ; source of inovement or 
original, sometimes with a suggestion of rule or command, or seat of 
government. In this treatise it is most often translated Original'. 

' βραχίων loosely for πηχνς. The Greeks did not speak of forearm, 
but lower arm. Later προπηχιον (Poll. ii. 142) was used for the ulna, 
by contrast with παραπηχιον (radius). A. here is thinking of the move- 
ment of the ulna. 

^ Cf. de Inc. 705* 5 ; Met. 1040^ 10. For the notion of something 
external against which the moving body must support itself (a notion 

ANIMALIUM 2 698»» 

But the point of rest in the animal is still quite ineffectual 
unless there be something without which is absolutely at 
rest and immovable. Now it is worth while to pause and 10 
consider what has been said, for it involves a speculation 
which extends beyond animals even to the motion and 
march of the universe.^ For just as there must be some- 
thing immovable within the animal, if it is to be moved, so 
even more must there be without it something immovable, 
by supporting itself upon which that which is moved moves. 
For were that something always to give way (as it does for 15 
mice ^ walking in grain or persons walking in sand) advance 
would be impossible, and neither would there be any walking 
unless the ground ^ were to remain still, nor any flying or 
swimming were not the air and the sea to resist. And this 
which resists must needs be different from what is moved, 
the whole of it from the whole of that, and what is thus 
immovable must be no part of what is moved ; otherwise 20 
there will be no movement.* Evidence of this lies in the 
problem why it is that a man easily moves a boat ^ from 
outside, if he push with a pole, putting it against the mast 
or some other part, but if he tried to do this ■vi'hen in the 
boat itself he would never move it, no not giant Tityus 
himself nor Boreas '^ blowing from inside the ship, if he 25 
really were blowing in the way painters represent him ; for 
they paint him sending the breath out from the boat. For 

more fully developed in de Motu than elsewhere, though accepted in 
de Inc.) we may compare A.'s general doctrines of the moving universe, 
and of sense perception (e.g. de Anim. 417^4 αν^υ τών ίξω ου ποιοΰσιν 

1 Cf. Λΐεί. ιο72^ 14. 

* Leg. οίον τοΙς μνσΧ iv τη ζ(ΐΰ η rols e'u ττ] Ι'ψμω ττορΐυομίνοις (eV rrj . . . 
Ε). Mich, had -γβ but did not understand it ; in his Commentary to 
de. hic. (p. 138. 18) he illustrates the same point by βά8ί<ης ds αλω πλήρη 

^ i.e. the ground beneath their feet; Mich, is mistaken here in 
speaking of the immobility of the Earth ; cf. de Inc. 705^• 9, where A. 
speaks of the relative stability of the ground. 

* In all this discussion A. obviously intends 'relative ' movement and 
* relative ' equilibrium. 

^ For the illustration of the boat cf. Phys. 254^30. 

" Cf. Meteor. 349^ I. Mich, says the representation of Winds in this 
way was very familiar. The point requires the wind-god to be in a 
boat. I cannot find any trace of such representation in ancient art, 
nor any other literary reference to such representation (cf. de Inc. 
711*2 note). Leg. αυτόν, with Γ viz. τοΰ πλοίου. 


698b DE MOTU 

whether one blew gently or so stoutly as to make a very 

699^ great wind, and whether what were thrown or pushed were 

wind or something else, it is necessary in the first place to 

be supported upon one of one's own members which is at 

rest and so to push, and in the second place for this member, 

5 either itself, or that of which it is a part, to remain at rest, 

fixing itself against something external to itself.^ Now the 

man who is himself in the boat, if he pushes, fixing himself 

against the boat, very naturally does not move the boat, 

because what he pushes against should properly remain at 

rest. Now what he is trying to move, and what he is fixing 

10 himself against is in his case the same. If, however, he 

pushes or pulls from outside he does move it, for the ground 

is no part of the boat. 

Here we may ask the difficult question whether if 3 
something moves the whole heavens this mover must be 
immovable,^ and moreover be no part of the heavens, nor 
in the heavens. For either it is moved itself and moves the 

15 heavens, in which case it must touch something immovable 
in order to create movement, and then this is no part of 
that which creates movement ; or if the mover is from the 
first immovable it will equally be no part of that which is 
moved. In this point at least they argue correctly who 
say ^ that as the Sphere is carried round in a circle no single 
part remains still, for then either the whole would necessarily 

30 stand still or its continuity be torn asunder ; * but they 
argue less well in supposing that the poles have a certain 
force, though conceived as having no magnitude, but as 
merely termini or points. For besides the fact that no such 
things have any substantial existence it is impossible for a 
single movement to be initiated by what is twofold ; ^ and 

^ Curiously enough he does not in this treatise give a general reason 
for this ; cf. G.A. 768^ 18 δλω? το κινούν 'ίξω Toi πρώτον άντικινΐ'ηαί τίνα 
κίνησιν, οϊον το ώθονν άντωθΐϊταί πως και άντιθλίβ€ται το ΘΧ'ιβον. 

* Leg. (ίναί Tf δίΐ άκ'ινητον και τοντο, και μηθ^ν. . . , 

' οι \tyovTes, probably some of the Physicists {Phys. 193^ 29). 
Possibly these were Pythagoreans {de Aiiiin. 405^ 32 ; de Caelo, 
293^ 33). The Sphere is that of the fixed stars {Met xii. 8 ; de 
Caelo, ii. 6). 

* Cf. de Caelo, 290» 6. 
" Cf. Phys. 259a 18. 


yet they make the poles two. From a review of these 
difficulties we may conclude that there is something so 
related to the whole of Nature, as the earth is to animals 25 
and things moved by them. 

And the mythologists with their fable of Atlas ^ setting 
his feet upon the earth appear to have based the fable upon 
intelligent grounds. They make Atlas a kind of diameter ^ 30 
twirling the heavens about the poles. Now as the earth 
remains still this would be reasonable enough, but their 
theory involves them in the position that the earth is no 
part of the universe. And further the force of that which 
initiates movement must be made equal to the force of that 
which remains at rest. For there is a definite quantity of 
force or power by dint of which that which remains at rest 35 
does so, just as there is of force by dint of which that which 
initiates movement does so ; and as there is a necessary 
proportion between opposite motions, so there is between 
absences of motion. Now equal forces are unaffected by 
one another, but are overcome by a superiority of force. 
And so in their theory Atlas, or whatever similar power 699'' 
initiates movement from within, must exert no more force 
than will exactly balance the stability of the earth— other- 
wise the earth will be moved out of her place in the centre 
of things. For as the pusher pushes so is the pushed 5 
pushed, and with equal force. But the prime mover moves 
that which is to begin with at rest, so that the power it 
exerts is greater, rather than equal and like to the power 
which produces absence of motion in that which is moved. 
And similarly^ also the power of what is moved and so 
moves must be greater than the power of that which is 
moved but does not initiate movement. Therefore the 
force of the earth in its immobility will have to be as great 
as the force of the whole heavens, and of that which moves 

' Atlas, cf. Met. 1023a• 20 (where the beHevers in Atlas are said to be 
poets and some physicists). Bacon approves A.'s ' very elegant inter- 
pretation ' of this ancient fable, de Aug. iv. 4. 

2 Diameter, rather radius. The Greeks had no word except ν ημίσίΐα 
^ιάμιτρος for radius. 

* Leg. ή τον κινουμένου (^και kivovvtos της τοΰ κινουμίρου^ μίν μη 
κινοΰντο! δε. 

699* DE MOTU 

lo the heavens. But if that is impossible,^ it follows that the 
" heavens cannot possibly be moved by any force of this kind 
inside them. 

There is a further difficulty about the motions of the parts 4 
of the heavens ^ which, as akin to what has gone before, may 
be considered next. For if one could overcome by force of 

15 motion the immobility of the earth he would clearly move 
it away from the centre. And it is plain that the power from 
which this force would originate will not be infinite, for the 
earth is not infinite ^ and therefore its weight is not. Now 
there are more senses than one of the word ' impossible '.* 
When we say il is impossible to see a sound, and when we 
say it is impossible to see the men in the moon,° we use two 

20 senses of the word ; the former is of necessity, the latter, 
though their nature is to be seen, cannot as a fact be seen 
by us. Now we suppose that the heavens are of necessity 
impossible to destroy and to dissolve,^ whereas the result of 
the present argument would be to do away with this 
necessity. For it is natural and possible for a motion to 
exist greater than the force by dint of which the earth is at 

25 rest, or than that by dint of which Fire and Aether '^ are 
moved. If then there are superior motions, these will be 
dissolved in succession by one another : and if there actually 
are not, but might possibly be (for the earth cannot be 
infinite ^ because no body can possibly be infinite), there is 
a possibility ^ of the heavens being dissolved. For what is 

^ Cf. de Caelo, 298* 19 ; Meteor. 340^ 7, 352» 27 for the small size of 
the Earth by comparison with the universe. 

" Heavens, i. e. universe ; cf. Bonitz, Index, 541^ 56. 

^ Cf. Phys. iii. 5. * Cf. Phys. 204^• 4 ; de Aftim. 422^27. 

^ The men in the moon were a belief of the Pythagoreans, and were 
connected with the fiery element. (Cf. Aet. Plac. ii. 30 ; Diels, 
Doxographi, p. 361 ; and Galen, Hist. Phil. 70.) Some Stoics thought 
the souls of the departed dwelt here, ' circa lunam (dormitio nostra) 
cum Endymionibus Stoicorum,' Tert. de Anim. 55. It is merely an 
illustration here, due perhaps to a commentator. For animals in the 
moon cf. G.A. 761^22. A.M. uses the sun's rays to illustrate the 

® Cf. Phys. viii. i et seq. ; de Caelo, i. 10-12, ii. i. 

' arw σώμα, \. e. the aether. Mich, takes it to mean ονρανό^ in the 
limited sense. Cf. de Caelo, 270^22 ; Meteor. 340^ 6; de Mundo, 392*5 ; 
G.A. 736^29. ^ Cf. Phys. iii. 5 ; de Caelo, i. 12. 

» Cf. Phys. 203^530 ; de Caelo, i. 5. 


to prevent this coming to pass, unless it be impossible ? 
And it is not impossible unless the opposite is necessary. 3° 
This difficulty, however, we will discuss elsewhere.^ 

To resume, must there be something immovable and at 
rest outside of what is moved, and no part of it, or not ? 
And must this necessarily be so also in the case of the 
universe ? Perhaps it would be thought strange were the 
origin of movement inside. And to those who so conceive 35 
it the word of Homer ^ would appear to have been well 
spoken : 

* Nay, ye would not pull Zeus, highest of all, from heaven 700* 
to the plain, no not even if ye toiled right hard ; come, all 

ye gods and goddesses ! Set hands to the chain ' ; for that 
which is entirely immovable cannot possibly be moved by 
anything. And herein lies the solution ^ of the difficulty 
stated some time back, the possibility or impossibility of 
dissolving the system of the heavens, in that it depends from . 
an original which is immovable. 

Now in the animal world there must be not only an 
immovable without, but also within* those things which move 
in place, and initiate their own movement. For one part of 
an animal must be moved, and another be at rest, and 
against this the part which is moved will support itself and 
be moved ; for example, if it move one of its parts ; for one 10 
part, as it were, supports itself against another part at rest.* 

But about things without life which are moved one might 
ask the question whether all contain in themselves both that 
which is at rest and that which initiates movement, and 
whether they also, for instance fire, earth, or any other 
inanimate thing,^ must support themselves against something 
outside which is at rest. Or is this impossible and must it 15 
not be looked for rather "^ in those primary causes by which 

1 Cf. Phys. Book N\\\, passim ; de Caelo, Book I. 

^ Iliad, viii. 21 (wrongly quoted more A. in order and words). Cf. 
Met. xii. 8 ; Theophrastus, Met. Br. 310^ 16 (Usener v^ 17). 

' Mich, records a variant δυεται for \ν(ταί, which shows that a difficulty 
was felt. 

* Viz. ultimately the central part of the heart. 
^ Cf. ch. 1, supra ; de Inc. Anim. passim. 

® For a discussion of the movement of inorganic bodies cf. Phys. 
viii. 4; de Caelo, 311a• 12. 
' Leg. αλλ* ύφ' hv ΡΓ, Mich. (Leonicus, sed). 

700*: DE ΜΟΤυ 

they are set in motion ? For all things without life are 
moved by something other, and the origin of all things so 
moved are things which move themselves. And out of 
these we have spoken ^ about animals (for they must all have 
in themselves that which is at rest, and without them that 

20 against which they are supported) ; but whether there is 
some higher and prime mover is not clear, and an origin of 
that kind involves a different discussion.^ Animals at any 
rate which move themselves are all moved supporting them- 
selves on what is outside them, even when they inspire and 
expire; for there is no essential difference between casting 

25 a great and a small weight, and this is what men do when 
they spit and cough and when they breathe in and breathe 

But is it only in that which moves itself in place that 5 
there must be a point at rest, or does this hold also of that 
which causes its own qualitative changes, and its own 
growth ? * Now the question of original generation and 
decay is different ; for if there is, as we hold, a primary 
30 movement,^ this would be the cause of generation and 
decay,'' and probably of all the secondary movements too. 
And as in the universe, so in the animal world this is the 
primary movement, when the creature attains maturity ;'' and 
therefore it is the cause of growth, when the creature 
becomes ^ the cause of its own growth, and the cause too of 
alteration. But ^ if this is not the primary movement then 

^ Mich, refers to P. Α., i.e. de Inc. ch. 3, &c. ; cf. supra, ch. 2. 

2 e. g. Met. xii. 8. 

^ For respiration as movement cf. Phys. 243^ 12 (where πτνσυ is 
held to be cognate). Marc. Antonin. Co7nm. ii. 2 {το πνίνμα) πάσης 
(upas (ζ€μονμΐνον και πάλιν ροφοΰμ^νον. 

* 1. e. does the aforesaid principle hold also of the two subordinate 

species οίκΊνησίί ? {η κατά μ€γίθος = ανξησις, and ή κατά πάθος = άλλοίωσίί). 
Cf. de Anim. 406^ 10 ; Phys. viii. 7 ; Met. 1069^ 12, 1088* 32. 

^ i. e. motion in place or translation ; cf. Phys. viii. 7 et seq. ; 
Generation and Decay are not properly motions though sometimes 
loosely termed such (cf. G. A. Ί. 4; de Anim. 406* 12). They depend 
upon primary movements. 

* Del. comma after φθοράς (with Leonicus),— [here as elsewhere the 
Berlin edition misprints the Latin version], and leg. των Άλλων δη. 

' Cf. Phys. 260^33 ; G.A. 735^13, 740*26 (with a suggestion also 
of the coming to be of the perfect creature, Phys. 261^ 17). 
^ Leg. yivfTui avTo αντω αίτιον, και . . . 
^ The suppressed argument is 'and if this be so these secondary 


the point at rest is not necessary. However, the earliest 
growth and alteration in the living creature arise through 35 
another and by other channels,^ nor can anything possibly 700^ 
be the cause of its own generation and decay, for the mover 
must exist before the moved, the begetter before the 
begotten,^ and nothing is prior to itself. 

6 Now whether the soul is moved or not, and how it is 
moved if it be moved, has been stated before in our treatise 5 
concerning it.^ And since all inorganic things are moved 
by some other thing — and * the manner of the movement of 
the first and eternally moved, and how the first mover 
moves it, has been determined before in our Metaphysics,^ 
it remains to inquire how the soul moves the body, and 10 
what is the origin of movement in a living creature. For, if 
we except the movement of the universe, things with life are 
the causes of the movement of all else, that is of all that are 
not moved by one another by mutual impact. And so all 
their motions have a term or limit, inasmuch as the move- 
ments of things with life have such. For all living things 15 
both move and are moved with some object, so that this is 
the term of all their movement, the end, that is, in view. 
Now we see that the living creature is moved by intellect, 
imagination, purpose, wish, and appetite. And all these are 
reducible to mind and desire.*^ For both imagination ^ and 
sensation are on common ground ^ with mind, since all 20 
three are faculties of judgement^ though differing according 
to distinctions stated elsewhere.^" Will, however, impulse,^^ 

movements, depending on the primary, will a fortiori require a point 
of rest '. 

^ Viz. the embryo is nourished, the child suckled by the movement of 
its parent's blood, or by her changes of position. 

"^ Cf. G.A. 735a 13 ; de Anim. 416^ 17 ; Met. 1073*3. 

3 Cf. de Anim. i. 3-5, ii. 4, iii. 9-end. 

* Leg. πΐρ\ δε του πρώτου Ε (sic) ST. 

^ Cf. Met. xii. 7. 

6 Cf. Nii. Eth. 11393• 17, ιΐ47»3ΐ. Throughout opi^i^ is translated 
by ' desire ', ΐπιθυμία by ' appetite '. 

■^ Cf. de Anim. 433=^ 9. 

^ Perhaps there is a reference also to the heart as the seat of all these 
powers (cf. Farv. A^at. 469'' i). 

9 Cf. de Anim. 426•^ 10, 432» 16. 
^" Cf. de Anim. iii. 3. " i.e. βυμό^. 

700^ DE MOTU 

aiid appetite, are all three forms of desire, while purpose ^ 
belongs both to intellect and to desire. Therefore the 
object of desire or of intellect ^ first initiates movement, not, 
that is, every object of intellect, only the end in the domain 

25 of conduct. Accordingly among goods that which moves 
is a practical end,^ not the good in its whole extent. For it 
initiates movement only so far as something else is for its 
sake, or so far as it is the object of that which is for the 
sake of something else. And we must suppose that a 
seeming * good may take the room of actual good, and so 
may the pleasant, which is itself a seeming good.^ From 

30 these considerations it is clear that in one regard that which 
is eternally moved by the eternal mover is moved in the 
same way as every living creature, in another regard 
differently, and so while it is moved ^ eternally, the move- 
ment of living creatures has a term.'^ Now the eternal 
beautiful, and the truly and primarily good (which is not at 

35 one time good, at another time not good), is too divine and 
precious to be relative ^ to anything else. The prime mover ^ 
701^ then moves, itself being unmoved, whereas desire and its 
faculty are moved and so move. But it is not necessary for 
the last in the chain of things moved to move something 
else ; ^° wherefore it is plainly reasonable that motion in 
place should be the last of what happens in the region of 
things happening, since the living creature ^^ is moved and 

» Cf. Nic. Eih. 1113^ 10 and vi. 2, 5 and 6 ; Phys. viii. 2. 
In de Ani>n. iii. 10 βούληση is used instead of προαίμίσι?. 
2 Cf. FAjs. 253a 17 ; de Anun. 4338• 18 ; Met. 1072^ 26 ; Nic. Eth. 
1 139* 34• ^ Cf. de Anim. 433* 29. 

^ Cf. de Anim. 433*28 ; Nic. Eth. 11138• 16 ; Rhet. 1369^ 18. 
® Qi. Nic. Eth. 1146^22; End. Eth. 1227*39; Rhet. 1369ΙΊ9. 
® Leg. το μίν ae\ κινύται. 
'^ ό ττρακτίκοί vois διαφβρει τοΰ θίωρητικοΰ τω reXet, de AfliDl. 433*^4• 

* προί ertpov ΡΓ., Trporepou ESY (sic Mich, who interprets ' than to 
have anything prior to itself). Perhaps Mich, had really ώστ' flvai η 
πρότΐρον. Leon. ' quam ut illo quicquam sit prius'. The point is that 
the first good has nothing beyond to move it, cf. Phys. 260* 5 ovBev 
avTo μεταβάλλον προς το κινοίιμΐνον, and Met. 1072* 26. 

TTporepov, cf. de Cae/o, i. 12. Bywater, Contributions, &c., p. 1 5. 

• i.e. the good aimed at or achieved in act. Cf. de Anim. 433'' 16, 
TO optKTOv is TO Κίνοϊιν ov κινοΰμΐνον (433^ 12), i.e. το πρακτον ά-γαβόν, here 
called το πρώτον ov κινονμΐνον κινονν. 

^^ Cf. de A?ti}n. 434^35 rb ΐσχατον ωβύται. ουκ ωσάν. 
" The last in the chain of causes and effects. 


goes forward by reason of desire or purpose,^ when some 5 
alteration has been set going on the occasion of sensation or 

7 But how is it that thought (viz. sense, imagination, and 
thought proper) is sometimes followed by action, some- 
times not ; sometimes by movement, sometimes not ? What 
happens seems parallel to the case of thinking and inferring 
about the immovable objects of science. There the end 10 
is the truth seen ^ (for, when one conceives the two premisses, 
one at once conceives and comprehends the conclusion), but 
here the two premisses result in a conclusion which is an 
action — for example, one conceives that every man ought 
to walk, one is a man oneself : straightway ^ one walks ; 15 
or that, in this case, no man should walk, one is a man : 
straightway one remains at rest. And one so acts in the 
two cases provided that there is nothing in the one case to 
compel or in the other to prevent. Again, I ought to create 
a good, a house is good : straightway I make a house. 
I need a covering, a coat is a covering: I need a coat. 
What I need I ought to make, I need a coat : I make 
a coat.* And the conclusion I must make a coat is an 20 
action. And the action goes back to the beginning^ or 
first step. If there is to be a coat, one must first have B, 
and if Β then A, so one gets A to begin with. Now that 
the action^ is the conclusion is clear. But the premisses 
of action "^ are of two kinds, of the good and of the possible.^ 

And as in some cases of speculative inquiry we suppress 25 
one premise so here the mind does not stop to consider at 
all an obvious minor premise ; for example if walking is 

^ Cf. supra, 700^ 23 and note. 

^ On the contrast between the Syllogisms of Science and of Practice 
see Nic. Eth. vii. 3. An explanation such as that before us is there 
described as φυσικώς (cf. de Ajiiin. 434* 18 ; Etui. Eik. 1227^28). 

' Cf. Nic. Eth. 1147a 24. * Leg. Ιμάτιον ττοΐίΐ Ε (sic). 

"* Cf. Nic. Eth. 1 1 12'' 23, 1113*6 ; in a different sense the άρχη is the 
major premise (I.e. 1144^ 32). 

^ It is the same in art (ττοί/^σι? proper), Met. 1032^ 6 ; Nic. Eth. 

' ποιητικοί = πρακτικοί : cf. Nic. Eth. II47* 28 ; End. Eth. 1227^ 30. 
In this matter the spheres of ποίΐΐν and πράτταν agree. 

* δυνατά 8f a di ημών yevoiT iiv, Nic. Eth. 1112^27, the possible is 
what can be brought about by our own or our friends' agency. 

701^ DE MOTU 

good for man, one does not dwell upon the minor ' I am 
a man'. And so what we do without reflection, we do 
quickly. For when a man actualizes himself in relation 
to his object either by perceiving, or imagining or con- 
30 ceiving it, what he desires he does at once.^ For the 
actualizing of desire is a substitute for inquiry or reflection. 
I want to drink, says appetite ; this is drink, says sense 
or imagination or mind : straightway I drink. In this way 
living creatures are impelled to move and to act, and 

> 35 desire is the last or immediate cause of movement, and 
desire arises after perception or after imagination and con- 
ception. And things that desire to act now create and 
now act under the influence of appetite or impulse or of 
desire or wish.^ 

701^ The movements of animals may be compared with those 
of automatic puppets,^ which are set going on the occasion 
of a tiny movement ; the levers are released, and strike 
the twisted strings against one another ; * or with the toy 

^ Del. comma after dpeyerai [sic Mich.). A good instance would be 
what is now called ideomotor action. 

^ ίίρίξΐί is the kind of which ΐπιθυμία, θυμός, and βούλησις are species. 
Cf. de Anim. 414^2. 

^ A natural illustration, much used by A. (cf. G. A. 734^ lo; ^let. 
983^^ 14) as it was later by the Stoic Emperor Marcus, and his great 
contemporary Galen (e. g. de Usii Part. K. iii. 48, 262). Plato uses the 
θαύματα differently in the famous allegory of the cave," 7?<?/. 514 Β 
(cf. Leges, 782 B, &;c.). The mechanism of strings in the simple toy 
which moved its members in answer to a pull from one governing cord 
{^de Mundo, ch. 6), the nervis alienis mobile lig7itim of the Roman poet, 
developed into the true automata which seem to have been puppets 
dancing in answer to an elaborate hidden mechanism of strings, 
weights, and rollers. The dolls may be seen in any museum, but the 
automatic machinery is nowhere fully described. We may get some 
notion of it from the figures of surgical machines in medical MSS. (vid. 
Littre, Hipp, iv, p. 305, Hipp. Ariic. 74, Apoll. Cit. (Schone) Tab. 
xvii, xviii). For other automatic toys cf. de Aniin. 416'' 18 ; Parv. 
Nat. 461^ 15 ; Pol. 1253^35 ; Plato, Euthyphro, 11 Β ; Meiio, 97 D. 

* Leg. τώκ ^υΚων και κρουόντων άλλήλαΐ! ras σ. (i7tfra ^ 9)• The sense 
οίστρίβληι is clear, they are the strings which agitated the limbs, though 
the word is not used in Hippocrates, στρφλοϋσθαι gets its sense in 
this way, and we may see a play upon the double meaning in Die 
Chrys. C/iaridemus, 303 Μ υπό τούτων κατατΐίνΐσθαι κα\ στρφ\ονσθαι. 
Philoponus (or Michael Eph.) in a gloss upon G.A. 734^4 (Conwi. in 
Arist. Graeca, xiv. 3, p. jj) explains that the ν^νροσπάστης or showman 
knocked one of the ξν\α and so released the mechanism, which then 
went off of itself, the various ^ΰλα somehow releasing one another : 
' ωσπίρ eVt των αυτομάτων θαυμάτων ό μίν θαυματοποιός κινησας τόδί τι 
ΊΤΐπαυται του κινΰν, τοΰτο Se το προσεχώς νπ αντον κινηθΐν ίκίνησΐν «λλο, 
κάκ(ΐνο €Tepov', and 'ό θαυματοποιός Kivel τόδί μΐν το ξνλον και άπίρχίται, 


wagon. For the child mounts on it and moves it straight 
forward,^ and then again it is moved in a circle owing to its 5 
wheels being of unequal diameter (the smaller acts like 
a centre on the same principle as the cylinders ^). Animals 
have parts of a similar kind, their organs, the sinewy- 
tendons to wit and the bones ; the bones are like the wooden 
levers in the automaton, and the iron ; the tendons are 
like the strings, for when these are tightened or released ^ 
movement begins. However, in the automata and the toy κ 
wagon there is no change of quality, though if the inner 
wheels became smaller and greater by turns there would 
be the same circular movement set up. In an animal the 
same part has the power of becoming now larger and now 
smaller, and changing its form,* as the parts increase by i, 
warmth and again contract by cold and change their quality. 
This change of quality is caused by imaginations and sensa- 

TOVTO 8e νπο της ΐν^οθΐίσηί αυτφ κινητικής δυνάμιως διά τίνος μηχανής Kivei 
(τΐρον, κακύνο άλλο, κάκΐΐνο το (ϊδωλον.' Ι take it that the machine 
(like a rack or surgical instrument) was of cylinders with strings wound 
round them, and with weights suspended (cf. aweipeTai in G.A. 741^ 9 
referring to the rollers strung together) ; the cylinders had pegs (ξΰλα) 
on them which in time {(φεξής) set other rollers going and so made the 
puppets dance on the table above. Aristotle alludes to the rollers, 
I think, in his laconic manner in the words καθάπΐρ iv τοις κνλίνδροις. 
The point in both this and the following simile lies in the automatism 
of the body, and the manifest outward gestures which flow from a tiny 
internal initial motion, just as the prow swings through a wide circle 
on a small movement of the helm. 

^ Leg. καΐ TO άμάξιον' ό yap οχονμΐνος αυτό Kive'i (οχούμΐνος S). The 
point is the change of motion in a straight line to circular movement 
by the automatic action of the inner wheels, as well as the slight 
impulse given by the child. I have often seen children in old days 
jumping on such little carriages in the side streets of London and then 
swinging round in a circle. (The emendation Λvas suggested indepen- 
dently by I\Ir. H. P. Richards and Mr. W. D. Ross.) 

* The reference is obscure, being apparently a brief note for 
Aristotle's own use. I take it to refer to the cylinders of the automatic 
machine. St. Hilaire illustrates from coiiical rollers which are used for 
crushing cement (but cf. Probl. 913^38 where the cone is expressly 
distinguished from the cylinder ό κ^νος ωσθάς κύκλω πΐριφίρΐται, της 
κορυφής μΐνοΰσης). Mich. speaks vaguely of toy carriages with cylin- 
drical wheels, ' which babies drag along in their games — very pretty 
playthings for the colours lavished on them by painters ' ! 

^ Leg. ώΐ' συστΐλλομίνων κα\ avif μίνων, 

* i.e. the body's motions are produced physiologically (by alteration) 
and not mechanically. A change of temperature in the heart's region 
causes an alteration in the tendons {vevpa) and these pull the bones. 
In ch. 10 A. is gravelled by the difficulty of relating this physiological 
change to φορά or translation, in his system the necessarily primary 
motion (cf. notes to ch. 10 ; and Galen, referred to in 703* 31 note). 

701^ DE MOTU 

tions and by ideas. Sensations are obviously a form of 
change of quality, and imagination and conception have the 
same effect as the objects so imagined and conceived. 

30 For in a measure the form conceived ^ be it of hot or cold 
or pleasant or fearful is like what the actual objects would 
be, and so we shudder and are frightened at a mere idea. 
Now all these affections involve changes of quality, and 
with those changes some parts of the body enlarge, others 
grow smaller. And it is not hard to see that a small 

25 change occurring at the centre ^ makes great and numerous 
changes at the circumference, just as by shifting the rudder 
a hair's breadth you get a wide deviation at the prow. 
And further,^ when by reason of heat or cold or some 
kindred affection a change is set up in the region of the 

30 heart, even in an imperceptibly small part ^ of the heart, 
it produces a vast difference in the periphery of the body, — 
blushing, let us say, or turning white, goose-skin and 
shivers and their opposites.^ 

But to return, the object we pursue or avoid in the field 8 
of action is, as has been explained, the original of move- 
35 ment, and upon the conception and imagination of this 
there necessarily ^ follows a change in the temperature of 

^ Species intelligibilis of later writers. 

^ Viz. the heart (cf. ^ 29 infra). For these small changes at or affect- 
ing the centre Αηίνι.ύ,οι^'ζι ; Η.Α.^9θ^Ζ•, G^. ^.716^ 3, 788* 1 1. 

^ Del. full stop after πάθος. 

* Cf. Hobbes, Lev. i. 16 'And altho' unstudied men doe not conceive 
any motion at all to be there, where the thing moved is invisible ; or 
the space it is moved in is (for the shortness of it) insensible ; yet that 
doth not hinder but that such motions are'; a favourite topic with 
Bacon, e.g. Λ'; O. ii. 6 'omnis actio naturalis transigitur per ilia quae 
sunt minora quam ut sensum feriant ', and with Des Cartes, e.g. Princ. 
Phil, iv, CCi ' At multas in singulis corporibus considero, quae nullo 
sensu percipiuntur : quod illi fortasse non probant, qui sensus suos pro 
mensura cognoscibilium sumunt' et seq. For ships' rudders cf. Mech. 
ch. 5 (lever principle). 

^ Homer {Iliad, Ν 279) gives a vivid description of the motions set 
up by fear. Such observations developed into the Prognostics or 
Symptoms of physicians (vid. Hipp. Progn. et Epid. Book III) ; cf. 
Prob. 902^ 37 ; the opposites are caused by θερμότης evKparos, which 
ίΐνίησί T€ TO σώμα και αΰξησιν αντω εμηοκί. (Alex, de Anim. yj. l); 'and 
their opposites ' seems a gloss, cf. Mich. 115. 22. 

^ Des Cartes' equivocal treatment of the Soul, and strong inclination 
to see automatism in bodily changes, present a remarkable contrast 
and parallel. (Vid. Traite des Passions, passim.) 


the body. For what is painful we avoid, what is pleasing 
we pursue. We are, however, unconscious of what happens 
in the minute parts ; ^ still anything painful or pleasing is 702^ 
generally speaking accompanied by a definite change of 
temperature'^ in the body. One may see this by con- 
sidering the affections. Blind courage and panic fears, 
erotic motions, and the rest of the corporeal affections, 
pleasant and painful, are all accompanied by a change of 
temperature, some in a particular member, others in the 
body generally. So, memories and anticipations,^ using 5 
as it were the reflected images* of these pleasures and 
pains, are now more and now less causes of the same 
changes of temperature. And so we see the reason of 
nature's handiwork ^ in the inward parts, and in the 
centres of movement of the organic members ; they change 
from solid to moist, and from moist to solid, from soft to 10 
hard and vice versa. And so when these are affected in 
this way, and when besides the passive and active ^ have 

^ Leon, apparently had λίαν λανθάνω, a variant not in Ε nor Υ nor 
recorded in Bekker. The passage is out of place, but the sense is clear. 
Mich., with our reading, translates de as yap. 

2 The stress on heat and cold is connected with the doctrines of the 
' hypothetical ' school of Medicine ridiculed by Hippocrates {de a7itiq. 
Med. ch. 13). In Des Cartes a purely hypothetical change in the 'vital 
spirits ' is the analogue to these temperature changes. The first germ 
of the doctrine of 'animal spirit' {^νχικον -ην^ΰμα) is contained in ch. x, 
infr-a, and in G. A. It played a disproportionate part in subsequent 
physiology (e.g. in the Stoics and in Galen). 

For the bodily effects of heat and cold vid. P. A. 600^28, 679^25, 
692* 23 ; it2fra, 703^ 15 ; G. A. 740^ 32. 

2 Cf. Parv. Nat. 449^ 27 ; Plato, Phil. 32 c ' memory of the past, 
anticipation of the future pleasures or pains' {jh μ^ν προ των ή8(ων 
(\πίζόμ(νοι> ή8ύ και θαρραΧίον, το δι προ των λυπηρών φοβΐρον κα\ 

* Viz. φαντάσματα, cf. Parv. Nat. 450^ 1 3, either images, likenesses 
{Parv. Nat. 462" 1 1 ), called Λκόν^ς {Parv. Nat. 45 1 ■'^l 5 ; Plato, Phil. 39 B), 
and ζωγραφηματα (450*27, Flaio, Pht'l. 40 a), or reflections {Pat v. Nat. 
464^9), dream phantoms being like forms reflected in more or less 
troubled water (cf. Plato, Tim. 72 B). The later Peripatetics called 
them άναζωγραφηματα. 

^ Cf. G.A. 731^24. Α., though free from the vulgar Teleology of 
Design, is fond of calling Nature a cunning artificer, especially in his 
Nat. Hist, treatises. His language becomes coloured with enthusiasm 
in such passages as P. A. 645* 9 ; de Inc. 71 1» 18 ; and G.A. 730^5 27, 
743^ 23. Cf. Galen de Usu P. passim. 

^ Cf. de Aniin. 417* I eV roij καθόλον Xoyoi'i πΐρΐ τοϋ ποιΰν κα\ πάσχ(ΐν. 
Some have thought there was a special treatise so named, and similarly 
a treatise π(ρ\ τροφής. On the interrelation of agent and patient ci. 

702* DE MOTU 

the constitution we have many times described, as often as 
it comes to pass that one is active and the other passive, 
and neither of them falls short of the elements of its 

15 essence,^ straightway one acts and the other responds. 
And on this account thinking that one ought to go and 
going are virtually simultaneous, unless there be something 
else to hinder action.^ The organic parts are suitably 
prepared by the affections, these again by desire, and desire 
by imagination.^ Imagination in its turn depends either 

20 upon conception or sense-perception. And the simultaneity 
and speed are due to the natural correspondence of the 
active and passive. 

However, that which first moves the animal organism 
must be situate in a definite original. Now we have said 
that a joint is the beginning of one part of a limb, the end 
of another.^ And so nature employs it sometimes as one, 
sometimes as two.° When movement arises from a joint, 

35 one of the extreme points must remain at rest, and the 
other be moved (for as we explained above the mover 
must support itself against a point at rest) ; accordingly, 
in the case of the elbow-joint, the last point of the forearm 
is moved but does not move anything, while, in the flexion, 
one point of the elbow, which lies in the whole forearm 

30 that is being moved, is moved,*' but there must also be 
a point which is unmoved, and this is our meaning when 
we speak of a point which is in potency one, but which 
becomes two in actual exercise. Now if the arm were 
the living animal, somewhere in its elbow-joint would be 

Parv. Nat. 465^ 15 ; Physics, iii. 3 ; Meteor, iv ; de Gen. et Corr. i. 9 ; 
G. A. 740^ 21, 768'' 23 ; Metaphysic, ix. 5 (especially de Gen. et Corr. 
324a 9 ; Met. 1047^ 35). 

^ Or ' definition '. Cf. Met. 1048» 2. ^ Cf. Met. 1048» 17. 

^ Cf. Phys. 253S• 17 ; de Anim. 433^ 28, 

* Leg. oTi του μίν ϊστιν, Υ, i.e. the elbow-joint is the end of the fore- 
arm, the beginning of the upper arm. The joint is ultimately two 
juxtaposed points (more accurately surfaces, de Anim. 433'^ 22); of 
these one is the original, the other the end of the extremity moved. In 
another sense the centre point is the middle of a line, and therefore 
both beginning and end [Phys. 220^ 12, 262^ 21, &;c.). This geometrical 
point is in potency two but in act one, the point here is potentially one, 
in act two, just because it is not a mathematical entity. Cf. de Anim. 
427» 10. ^ Cf. supra, 698^ 19. 

« ? Leg. κινύ και κινάται Γ, A.M. Cf. P. and infra 703* 14 (note). 

AN I MALI υ Μ 8 7oa* 

situate the original seat of the moving soul. Since, how- 
ever, it is possible for a lifeless thing to be so related 
to the hand as the forearm is to the upper (for example, 
when a man moves ^ a stick in his hand), it is evident that 
the soul,- the original of movement, could not lie in either 35 
of the two extreme points, neither, that is, in the last point 
of the stick which is moved, nor in the original point which 
causes movement. For the stick too has an end point and 702'' 
an originative point by reference to the hand.^ Accordingly, 
this example shows that the moving original which derives 
from the soul is not in the stick ; and if not, then not in the 
hand ; for a precisely similar relation obtains between 
the hand ^ and the wrist, as between the wrist and the 
elbow. In this matter it makes no difference whether 
the part is a continuous part of the body or not ; the stick ^ 5 
may be looked at as a detached part of the whole. It 
follows then of necessity that the original cannot lie in 
any individual origin which is the end of another member, 
even though there may lie another part outside ^ the one 
in question. For example, relatively to the end point 
of the stick the hand is the original, but the original of the 
hand's movement is in the wrist. And so if the true 
original is not in the hand, because there is still something 10 
higher up/ neither is the true original in the wrist, for once 

' Leg. κινοίη Tis βακτηρίαν, viz. by bending the wrist. A. speaks 
loosely of the wrist's function, and nowhere considers the rotation 
of the hand, just as in de hic. Aftini. he treats only implicidy of the 
ankle, ignoring its rotation in human progression. If A. studied, as 
is almost certain, only animal anatomy these movements would more 
easily escape him. 

''■ η -^υχή loosely for 17 αττό της ι\τνχης αρχή, or else the soul is carelessly 
spoken of as the original of bodily movement (cf. de Ajiim. 406'' 
24. &c.). 

^ The ' extreme ' is not the outermost end of the stick or the 
argument would fail. It is the end point where the stick meets the 
hand, the ' beginning ' or ' original ' is the point of the wrist which is 
at rest, hand being, as often, used for wrist (contrast H,A. 493'' 27). 
Mich, was puzzled and is more than usually unhappy in his explanation ; 
the confusion arises from a play upon ηρχή, most characteristic of 
Aristotle (cf. 702^17 note ; Newman, The Pol. of A. iv. 322). 

* Lit. extremity of the hand, viz. all the hand from the wrist 
(regarded as part of the hand) outwards ; a popular use in Greek. 

^ For the ' stick ' illustration cf. I'hys. viii. 5. 

• Viz. further from the centre of the organism, i. e. the heart. 

■^ Viz. higher up towards the shoulder— a local centre— and ultimately 

V. AR. M.A. C 

702" DE MOTU 

more if the elbow is at rest^ the whole part below it can be 
moved as a continuous whole. 

Now since the left and the right sides are symmetrical,'^ 9 
and these opposites are moved simultaneously,^ it cannot 
be that the left is moved by the right remaining stationary, 

15 nor vice versa; the original must always be in what lies 
above both. Therefore, the original seat of the moving 
soul must be. in that which lies in the middle, for of both 
extremes the middle is the limiting point ; * and this is 
similarly related to the movements from above [and below,] 
those that is from the head, and ^ to the bones which spring 

20 from the spinal column, in creatures that have a spinal 

And this is a reasonable arrangement. For the senso- 
rium "^ is in our opinion in the centre too ; and so, if the 
region of the original of movement is altered in structure 
through sense-perception and thus changes, it carries with 
it the parts ' that depend upon it and they too are extended 
or contracted, and in this way the movement of the creature 

25 necessarily follows. And the middle of the body must 

towards the heart. Cf. tn/ra, 702'' 15 ; and G.A. 788* 14 τοντογάρ e'an 
TO αρχήν elvai το αντην μΐν αΐτίαν elvai πολλών, ταύτηί δ' άλλο ανωθ(ν 
μηθίν. Fr. 1 49 1* Ι3• 

^ Viz. if the lower arm and hand be held rigid, like the stick in 
the illustration ; similarly the αρχή is not in the elbow, nor yet in the 

^ TO ζώον rather than ή αρχή is the implied subject. 

' Mich, violently turns 5/xa by κητα μίρος, confounding the argument. 

* Lit. ' extreme ' {(σχατον). Of both extremes the middle is the 
extreme or limit point. The paradox is very Aristotelian ; cf. de Caelo, 
312* 10 ίστι yap «ay (σχητον κα\ μίσον αμφοτέρων {iVri) το μΐταξΰ. Cf. 
P. Α. 66ι^ η ; Prob. 913^36 ; Me/. 1022^ 12; Nic. Eth. 1107*8. 

° Leg. κ£φαλής, κα\ προς τά (τά ΕΥ), και κάτω is, Ι think, a gloss. om. Γ. 

^ The ραχίί is the άρ;^)7 of the bony system (cf. //../4. 516* 10 ; P. A. 
654* 32, ^ 12 ; Alex, de Am'ma, 97 1. 27), rds (sc. κινήαας) would imply a 
knowledge of the nervous system of the spine which only arose much 
later. The heart is also centrally situate in regard to the skeletal 
system, radiating from the ρίχι^. It is thus the centre of the bony 
and vascular, of the sensory as well as of the motor organization. 

■' Cf. P. A. 647» 25, 656* 28, 665a• 10, 721» 22; Parv. Nat. 456» 4. The 
heart is the original of sense apprehension, though some of the nopoi 
αισθητικοί pass through the head. 

* Viz. τά vtvpa {chordae te7idi?ieae), the sinewy tendons that are con- 
ceived to move the limbs. The αρχαί or four local originals are the 
centres from which the limbs are moved (cf. de Inc. 704» 15). 

ANIMALIUM 9 702'' 

needs be in potency one but in action more than one ; for 
the limbs are moved simultaneously from the original seat 
of movement, and when one is at rest the other is moved. 
For example, in the line BAC,^ Β is moved, and A is the 
mover. There must, however, be a point at rest if one is to 30 
move, the other to be moved. A (AE)^ then being one 
in potency must be two in action, and so be a definite 
spatial magnitude not a mathematical point.^ Again, C 
may be moved simultaneously with B. Both the originals 
then in A must move and be moved, and so there must 
be something other than them which moves but is not 
moved. For otherwise, when the movement begins, the 
extremes, i. e. the originals, in A would rest upon one 35 
another, like two men putting themselves back to back 703® 
and so moving their legs. There must then be some one 
thing which moves both.* This something is the soul, 
distinct from the spatial magnitude just described and yet 
located therein.^ 

10 Although from the point of view of the definition of 
movement — a definition which gives the cause — desire ^ is 

* Cf. 703^ 30. The diagrams, so often mentioned 
(cf. Parv. Nat. 452^ 17; G. A. 749^8, 761* 10), are lost, 
though substitutes appear in the margins of some MSS. 
According to Mich, the figure contemplated is 

Mich, speaks of A, or AE, as μί-^ίθό^ τι, so that A.'s 
drawing may have been after the similitude of a pair 
of compasses, Ε being the actual centre. On the central 
part of the heart cf. P. A. 666^ 33. 

2 AE in Mich. ; cf. AB in S. 

^ TO άμΐρίς ουκ (ν^ίχ(τηι κινίΐσθαι, P/lJ'S. 240^8, 258^ 
25 ; ife Αηίηι. 402^ I ; De Iticessu, 705*23 (note). 

* Leg. avayKoiov tv dvai. ' necesse esse unum ' Γ, cf. 
A. M., 1. c. p. 343. 

* This unity is properly the organ of soul, like Des Cartes' pineal 
gland. He regarded this as the material centre of animal movement 
because it alone had no double in the brain (cf. de Attim. 406^ 24, 
415^ 21 οθ(ν πρώτον η κατά τόπον κίνησίΐ, ψνχη). Α. did not consider the 
body to be moved oy the soul but κατά ταντην, as fire by its levity, or 
the artist by his art. 

^ The word yfrvx^, at the end of last chapter, is used loosely for 
η όρΐκτίκη δνναμις της ^^/υχης, by reason of which organized bodies 
are moved. Desire, then, is the formal cause or ground of move- 
ment, it remains to find the material cause. (Cf. de Anim. 412^20, 
where oy\ns is ουσία οφθαλμού ή κατά τον λόγον, ό δ' οφθαλμός νλη 


703* DE MOTU 

5 the middle term or cause, and desire moves being moved,^ 
still in the material animated body there must be some 
material ^ which itself moves being moved. Now that 
which is moved, but whose nature is not to initiate move- 
ment, is capable of being passive to an external force, 
while that which initiates movement must needs possess 
a kind of force and power. Now experience shows us that 

lo animals do both possess connatural spirit ^ and derive power 
from this. (How this connatural spirit is maintained in the 
body is explained in other passages of our works.*) And 
this spirit appears to stand to the soul-centre or original in 
a relation analogous to that between the point in a joint 
which moves being moved and the unmoved.^ Now since 
this centre is for some animals in the heart, in the rest in 

15 a part analogous^ with the heart, we further see the reason 
for the connatural spirit being situate where it actually is 
found. The question whether the spirit remains always the 
same or constantly changes and is renewed, like the cognate 
question about the rest of the parts of the body, is better 
postponed.^ At all events we see that it is well disposed 

^ Cf. de Anim. 433^ 16. 

^ Cf. de Anim. 433^ 19 ω 5e κινύ όργάνω x] ope^tf, η^η τοντο σω- 

' Aristotle heroically faces the difificulty of relating άλλοίωσί? to φορά, 
since his general view of κίνησα involves the priority of translation to 
alteration. On this very obscure subject, consult among many passages 
Meteor. 366'* i ; de Anim. ii. 4 ; Parv. Nat. 474» 25 et seq. ; G.A. 728^ 28, 
ySS'^S?. 736*^37, 741^32, 781*24, 789*' 7• 

The spirit is called ΐ'μφντον πν€ΰμα in Farv. Nat. 475* 8 ; φνηκον πυρ 
in 474^12. 

* The unnecessary assumption that this is a reference to nepl 
■ηνΐνματος, a later work, has been used as an argument against the 
genuineness of De Motu. The reference is the other way about, as 
will be seen from the opening words of de Spiritu. The reference here 
is quite undetermined but we may compare de Anim. 416^' 31 ; Parv. 
iVa/. 456* 15, 474''3 ; /".yi. 647'' 5, 651* 15. Mich, refers to πβρι τροφοί, 
a work possibly contemplated by Α., but if written soon lost (cf. 
702* 1 1 note). 

* Cf. chs. I and 7 supra. The point is here called with greater 
accuracy ' moving and moved '. Cf. 702* 30 (note). 

* Cf. Parv. Nat. 474^ 2 rois αναίμοα άνώι/υμον and P. A. 68i^ i6; G.A. 
721» 21, 759^ 18. 

■^ Passages are scattered about the works on this question (vid. Bonitz, 
Index, 1041» 16). The renewing agent is the blood, which generates by 
vital heat this ' spirit ' in the heart, and then by help of the lungs and 
the cold air from without acts and reacts upon the heart's walls and so 
on the whole bodily frame. (Cf. P. A. ii. 3, iv. 4; G.A. ii. 6-7, v. 4 ; 

ANIMALIUM ίο 703* 

to excite movement and to exert power ; ^ and the functions 
of movement are thrusting and pulling.^ Accordingly, the 20 
organ of movement must be capable of expanding ^ and con- 
tracting ; and this is precisely the characteristic of spirit. 
It contracts and expands naturally,* and so is able to 
pull and to thrust from one and the same cause, ex- 
hibiting gravity compared with the fiery* element, and 
levity by comparison with the opposites of fire.^ Now that 35 
which is to initiate movement without change of structure 
must be of the kind described, for the elementary bodies "^ 

Alex, de Anim. 94. 17 ; Galen, de Usu Part. K. iii. 496, de Usu Resp. 
K. iv. 502.) 

1 φαίνΐται, a reference perhaps to holding the breath when a weight is 
lifted. A,, like gymnastic teachers to-day, supposed it gave power (of. 
de Anim. 421*3 ; Parv. Nat. 456» 15 ; G.A. 775^3). 

* Cf. de Inc. ηοί^ 23 ; for the reduction of all movements to Jatr καΐ 
fX^if, vid. Phys. 243* 16, 243'' 16. Movement, it must be remembered, 
is not contemplated in abstraction from bodies, but taken in the sense 
of movement communicated by force to body. 

' αυ^άνίσθαι in its vulgar sense, cf. P. A. 653* 31 η γαρ τοϋ θίρμον φύσις 
(Ρίσχΰονσα noiel την αυξησιν άπο του μίσον κατά την αντης φοράν. 

* Leg. άβιάστως συστΐλλομίνη (τ€ καΐ (κτανομίνη <η\ ΐλκτικη^ κα\ ώ. 
The emendation seems certain from Mich.'s words quoted below and 
from Γ * tractiua et pulsiua '. άβίαστοί is a word only found in Antoninus 
{Comm. iii. 16, &c.) and Alex. Aphr. The sense is 'naturally' (αυτο- 
φυώί in the later Peripatetics), cf. de Anim. 406^6 ωσθάη yap av βία τ6 
ζώον. For the omission of ΐκτ^ινομίνη cf. supra, 701^ 15, where σνστ(\- 
Χομίνων is omitted by EY. Mich., probably following an older com- 
mentator, says in his notes on P. A. p. 88. 35 τον iv τβ καρδία πνΐίματοί 
(κτΐΐνομΐνου και συστίΧΧομίνον ως fv ttJ nepl ζ. κινησίως δίδβικται ', cf. ρ. 1 28. ζ. 

Aristotle seems to have conceived the contraction of the spirit as giving 
a pull (ελκτική), and its expansion as loosening the sinews, whereas Des 
Cartes thought the vital spirits blew up the muscles and so shortened 
and broadened them. A. probably was thinking of such a similitude 
as that of an inflated wineskin or bladder, having in mind the familiar 
Greek mode of reducing a dislocation of the thigh by blowing up a 
wineskin ; cf. Hipp. Art. yy (Littre, iv. 310), where Ισχνς and άναγκαζΐΐν 
are used of the force so applied to the injured member. 

For the doctrine cf. de Anim. 403^31 where ορΐξις from a physicist's 
point of view is said to be ζ(σις τοΰ ntpl καρδίαν αίματος καΐ θ(ρμον ; Ρ. Α. 
653^31 ; «^"d for a parallel treatment of the mechanism of respiration, 
P. A. 666^15. We may compare also the later Stoic notions of βία 

πνίυμ<ιτική, &C. (cf. H.A. 586* I7). 

' πνρώδη, cf. G.A, 737*1 avaXoyov ονσα τώ των άστρων στοιχιίω : 
' respondens elemento stellarum,' Harvey, Treatise on Generation. 

* Called β^ρμος άήρ in G. A. 736* I ; vital heat is not ordinary heat, 
and πνίΰμα σ. is conceived as a nice balance between the fiery and the 

For its volatile nature cf. G. A. 735*' 34 ; 744» 3 ; and for the language 
Parv. Nat. 479•* 3 1 where ζΐσις is πνΐνματονμίνον τον vypov. 

'' τα φασικά σώματα, viz. Earth, Air, Fire, and Water, cf. de Caelo, 
269* 2 and 29 (κρατάν). 

703^ DE MOTU 

prevail over one another in a compound body by dint of 
disproportion ; the Hght is overcome and kept down by the 
heavier, and the heavy kept up by the hghter. 

We have now explained what the part is which is moved 
when the soul originates movement in the body, and what 

30 is the reason for this. And the animal organism must be 
conceived after the similitude of a well-governed common- 
wealth.^ When order is once established in it there is no 
more need of a sepamte monarch to preside over each 
several task. The individuals each play their assigned 
part as it is ordered, and one thing follows another in its 

35 accustomed order. So in animals there is the same order- 
liness — nature taking the place of custom — and each part 
naturally doing his own work as nature has composed them.^ 
There is no need then of a soul in each part, but she resides 
in a kind of central governing place of the body, and the 
703^ remaining parts live by continuity of natural structure, and 
play the parts Nature would have them play. 

So much then for the voluntary movements of animal H 
bodies, and the reasons for them. These bodies, however, 
5 display in certain members involuntary movements too, but 
most often non-voluntary movements.^ By involuntary I 
mean motions of the heart * and of the privy member ; ^ for 
often upon an image arising and without express mandate 
of the reason these parts are moved. By non-voluntary I 

^ Cf. Plato, Tim. 70 A ; P. A. 670* 26 where the head or heart as 
seat of government is termed ακρόπολίΓ. In Nic. Eth. 1113*8 the com- 
parison is with the Homeric monarchy, in Pol. 1254*^ 5 the relation of 
soul and body is that of master to slave {8(σποτική). The simile is 
worked out elaborately in de Mundo, 400^ 14 et seq. For the Stoic 
view vid. Seneca, Epist. Mor. 113. 23. Galen, de Usu P. K. iii. 268. 

Galen, de Placitis, vii. 4 (K. v. 61 1) states the conflicting views about 
■πνίΰμα. Does it pass through the body, or does a message go from the 
brain and produce alteration in the local nerves, or does the brain act 
by force without matter ? This last view he illustrates from the power 
of the sun, who stays in his own seat and yet warms and brightens the 

^ Leg. (καστον των ούτω (i.e. φΰσίΐ) συστάντωι/, cf. P/iys. 250^14; 
de Anim. 416* 16. 

' Cf.the division of actsinto voluntary, non- voluntary, and involuntary, 
Nic. Eth. iii. i. 

* Palpitation, cf. Parv. Nat. Δ,η& 22, 479'' 19, 480* 14 ; P. A. ββφ• 20 
[πτη^ησι^ connected with eXnls). 

' Cf. deAnim. 432^28 ; P.A. 666^17. 


mean sleep and waking and respiration,^ and other similar 
organic movements. For neither imagination nor desire is lo 
properly mistress of any of these; but since the animal body 
must undergo natural changes of quality,^ and when the 
parts are so altered some must increase and others decrease, 
the body must straightway be moved and change with the 
changes that nature makes dependent upon one another. 
Now the causes of the movements are natural changes of 15 
temperature,^ both those coming from outside * the body, 
and those taking place within it.^ So the involuntary 
movements which occur in spite of reason in the aforesaid 
parts occur when a change of quality supervenes.*' For 
conception and imagination, as we said above, produce the 
conditions necessary to affections, since they bring to bear 20 
the images or forms'' which tend to create these states. 
And the two parts aforesaid display this motion more 
conspicuously than the rest, because each is in a sense 
a separate vital organism,^ the reason being that each 
contains vital moisture.^ In the case of the heart the cause 
is plain, for ^° the heart is the seat of the senses, while an 
indication that the generative organ too is vital is that there 25 
flows from it the seminal potency, itself a kind of organism. 

^ Cf. Phys. 259^9, growth, decay, respiration. Λ. does not seem to 
contemplate here such semi-voluntary movements as winking {P. A. 
657^ I ovK €K προαφίσ€ως, and compare what is said of tickling in P. A. 

^ Mich, puts a full stop after άλλοίωσιν, but the apodosis is και <il πάρα 
τον Xoyov δη , . , 

^ For effect of heat and cold cf. P. A. 679^ 26 ; Proi/. 902^ 37. 

* ai θύραθεν, cf. Phys. 253* 15 ; p. A. 653* I. 
^ Insert comma after νπάμχονσαι. 

^ Sleep, &c., are non-voluntary movements ; we set ourselves upon 
going to sleep and then the changes occur, largely owing to heat 
}:enerated in digestion. Similarly, A. argues (like Des Cartes), the 
involuntary movements are bye-products of natural changes. Cf. 
Parv. NaL 455^28 ; P. A. 653^• 10. 

'' ra yap e't'Sr;, cf. 701^20, Stlpra. 

* I do not know any other references to this individuality of organs. 
For the heart cf. P. A. 666* 21, ^ 17 ; for the other member, Plato, Tim. 
91 Β oXov ζωοι> άνυπηκυον τον λόγου, and (of the σπέρμα) αόρατα ζωα. The 
βάνματα emphasized this individuality of the alboiop, Hdt. ii. 48 ; Luc. 
de Dea Syria, Reitz, iii. 463. 

^ Cf Parv. Nat. 466^ 18 το ζφόν ίστι φνσα vypov κηΧ θερμόν, G.A. 
74'^^ 15 ; Galen, Defin.Med. (Κ. xix. 370) <τπίρμα ίστιπνενμαΊνθΐρμον iv 
ί/γρω ί^ (αυτοί κινονμίνον et seq. 

^° Leg. ταί γαρ αρχάί (PS Γ), and insert comma after αΐτίαν. 


Again, it is a reasonable arrangement that the movements 
arise in the centre upon movements in the parts, and in the 
parts upon movements in the centre, and so reach one 
another. Conceive A to be the centre or starting-point. 
30 The movements then arrive at the centre from each letter 
in the diagram ^ we have drawn, and flow back again from 
the centre which is moved and changes, (for the centre is 
potentially "^ multiple) the movement of Β goes to B, that 
of C to C, the movement of both to both ; but from Β to C^ 
the movements * flow by dint of going from Β to A as to 
35 a centre, and then from A to C as from a centre. 

Moreover^ a movement contrary to reason sometimes 
does and sometimes does not arise in the organs on the 
occasion of the same ^ thoughts ; the reason is that some- 

704* times the matter which is passive '^ to the impressions is 
there in sufficient quantity and of the right quality and 
sometimes not. 

And so we have finished our account of the reasons ^ for 

704^ the parts of each kind of animal, of the soul, and further of 
sense-perception, of sleep, of memory,^ and of movement in 
general ; it remains to speak of animal generation. 

* Cf. supra, 702^ 29. 

^ Surdfiii— one would expect ivepyeia (702*31, &c.). The other and 
more ordinary sense of potentiality has slipped in here. 

^ Omit α^)χή a gloss on preceding words, with which Γ actually 
places it. 

* Leg. semicolon after Άμφύ, a comma after Γ, and delete hi after τώ 
[sic Ε Γ). 

° Leg. en EP for on (Mich, and Γ had on) and ου αίτιον το {ort δ' ου 
αίτιοι> οτο μ(ν Ε Sic). 

* Leg. ταυτά {τα αυτά Ρ). Cf. Bywater, Contributions, Qr'c., Ν. Ε. vi. 4• 

'' Cf. de Anim. 403* 19; Parv. Nat. 447* 16, 450'' i rotf μίν h κινψτΐΐ 
noWfj δια ττάθο! η δι' ήλικίαν ουσιν ον γίν€ται μνήμη et seq. 

* Reasons, grounds or causes— cf. supra, 698^^ 4 ; G.A. 782* 22. 

^ This was the position of the Treatise in Mich.'s MSS. and is the 
place it occupies in Ε S and P. The traditional order of the two 
treatises was for de Incessu to follow de Parti bus immediately (as it now 
follows in U Υ b), and for de Motu with de Gen. Atiim. to be interposed 
amid the treatises often called Parva Naturalia or Minuta Naturalia. 
These two followed de Div. per Somnitm (cf. Themistius, Parva Natu- 
ralia) and preceded de long, et brev. Vitae. The equivocal position of 
deMotu is explained by its subject-matter (eV to'h kowoh σώματος καΐ ψνχης 
tpyois, de Anim. 433^20). We may compare Ptolemy's list of the works, 
where it follows immediately after i/i'6'u;««f. Compare also the MS. end- 
ing of de Div. (omitted in Bekker) and the similar words in Themistius 
(p. 105 V ) and Mich. Eph. p. 103. (Vid. Note at end of de Incessu.) 



We have now to consider the parts which are useful to 4 
animals for movement in place (locomotion) ; first, why- 
each part is such as it is and to what end they possess them ; 
and second, the differences ^ between these parts both in 
one and the same creature, and again by comparison of the 
parts of creatures of different species with one another. 
First then let us lay down how many questions we have to 

The first is what are the fewest points of motion necessary 10 
to animal progression, the second why sanguineous animals 
have four points ^ and not more, but bloodless animals more 
than four, and generally why some animals are footless, 
others bipeds, others quadrupeds, others polypods, and why 
all have an even number of feet, if they have feet at all ; 
why in fine the points on which progression depends are 15 
even in number. 

Next, why are man and bird bipeds, but fish footless ; 
and why do man and bird, though both bipeds, have an 
opposite curvature of the legs. For man bends his legs 20 
convexly,^ a bird has his bent concavely ; again, man bends 

^ It should rather have been ' the reasons for the differences . . .' On 
the subject generally cf. Galen, de Usic Partium, iii. 2. 

* The four points in a quadruped (Bacon's quaternion) are the points 
of attachment of the limbs, cf. infra, 712» 19. 

^ Convexly and concavely, that is forwards and backwards {H.A. 
498*6, «Slc), or as it is sometimes expressed outwards and inwards {P. A. 
693^3 •, C.A. 728^9, where fWos is correct). The terms seem chosen 
in this treatise to avoid confusion with the fore and hind limbs and 
to be later in date than de Partibus (vid. P. A. 693*' 35). Forwards 
and backwards are clear enough, since the front of an animal is deter- 
mined by the senses, especially by vision (rois ομμασι διώρισται ro 
πρόσθιοι/, infra, 712^17, cf. 7θ5'Ί6ί. The next step is to call these 
flexions outwards and inwards [ΐξω of man's \egs,P.A. 693'' 3 €Ϊσωof a 
bird's). Man is the norm, and his knees bend away from the centre 
of his figure or outwards, that is fVi την πΐμιφίμΐίαν towards the circunv- 
ference. This somewhat equivocally is then treated as towards the 
convex, and tVt τ6 κοίλον used as its opposite. The Americans have 
coined the barbarous words cephalads and caudads, i. e. headwards and 
tailwards, for a similar purpose. 


his arms and legs in opposite directions, for he has his arms 
bent convexly, but his legs concavely. And a viviparous 
quadruped ^ bends his limbs in opposite directions to a 
man's, and in opposite directions to one another ; for he 
has his forelegs bent convexly, his hind legs concavely. 
7°4 Again, quadrupeds which are not viviparous but oviparous ^ 
have a peculiar curvature of the limbs laterally^ away from 
the body. Again, why do quadrupeds move their legs 

We have to examine the reasons for all these facts, and 
others cognate to them ; that the facts are such is clear 
10 from our Natural History,^ we have now to ask reasons for 
the facts. 

At the beginning of the inquiry we must postulate the 2 
principles ^ we are accustomed constantly to use for our 

* Except the elephant \ H.A. 498* 8 ; infra, 712* 1 1. 

* e. g. lizards. The flexion of Ovipara is said in H.A. 498* 15 to be 
forwards for both pairs of limbs, but infra, ch. 13, their flexion is con- 
sidered the same as that of Viviparous Quadrupeds except for the lateral 
inclination. A. speaks only superficially as he did not grasp the homo- 
logy of the parts of the limbs. In the case of lizards and crocodiles (as 
in frogs) the superficial appearance is that the forelegs bend backwards, 
the hind legs forwards, though in some positions both look backwards 
bent, never both forwards. The text of H.A. 498* 1 5 seems therefore 
corrupted, though the general drift shows that A. there contrasted vivi- 
parous and oviparous quadrupeds in this regard (cf. 498* 23). 

' Cf. H. A. 498^ 16 μικρόν (Is TO πλάγιον παρβγκΧίνοντα. 

* Cf. //. A. 490^ 4 lit. diagonally, i. e. the normal contrary movement 
of a trotting horse's feet, near fore with off hind (cf. infra, ch. 14). In the 
trot the pairs come down exactly together. A. considers a galop force 
to be abnormal, not progression but jumping (cf. ch. 14). In H.A. 
498^ 6 he records another kind, the amble of the camel, as normal to it 
(and to the hon !) In ch. 14 he does not seem to remember about the 
camel, which achieves what he there regards as dynamically impossible. 

"^ Ιστορία φυσική, cf. P. A. 650*32, the Original of our term Natural 
History. The reference is to the work called usually ai περί των ζωών 
ιστορίαι, vid. H.A. 490^4, 493'^ 3 seq. ; cf. P. A. 646» 9. 

^ Unfortunately A. instances only the principles of Purpose, and of 
Selection of the Best Possible (Bonitz, Index, 836'* 48) ; cf. Leibniz, 0pp. 
(ed. Erdmann) p. 106, ' Bien loin d'exclure les causes finales et la con- 
sideration d'un Etre agissant avec sagesse, c'est de Ik qu'il faut tout 
deduire en Physique.' In the following few pages A. appeals also to : 

(2) Economy or Organic Equivalents, 7 10^ 32, 7 1 6* lojcf./".^. 652*31, 
658* 34, 694^ 18 et passim, a species of Compensation, H. A. 487^ 26, 
504'' 7 et saepe. 

(3) Bilateral Symmetry, 7io''3, cf. Z•.^. 656''3i, 663*22, 669^17, 
686* 12. 

(4) Specialized Differentiation, viz. one organ for one primary pur- 
pose, 706* 18, cf. Pol. 1252*' 3, &c. 


scientific investigation of nature, that is we must take for 
granted principles of this universal character which appear 
in all Nature's work. Of these one is that Nature creates 15 
nothing without a purpose, but always the best possible in 
each kind of living creature by reference to its essential 
constitution. Accordingly if one way is better than another 
that is the way of Nature.^ Next we must take for granted 
the different species of dimensions ^ which inhere in various 
things; of these there are three pairs of two each, superior a ο 
and inferior, before and behind, to the right and to the left. 
Further we must assume that the originals of movements in 
place are thrusts and pulls.^ (These are the essential place- 
movements, it is only accidentally that what is carried by 
another is moved ; it is not thought to move itself, but to 705^ 
be moved by something else.^) 

3 After these preliminaries, we go on to the next questions 
in order. 

Now of animals which change their position some move 
with the whole body at once, for example jumping animals, 5 
others move one part^ first and then the other, for example 
walking (and running) animals. In both these changes the 
moving creature always changes its position by pressing 
against what lies below it. Accordingly if what is below 
gives way ^ too quickly for that which is moving upon it to 10 

(5) Secondary Adaptation, 714* 1 1, cf. P. A. 688^24. 

(6) Utility : (a) for preservation in environment, 710*27, 713^28, cf. 
P. A. 693*4; {ύ} of mechanical structure, 710^21, 711^32, 713^20, 
cf. P. A. 694^13. 

(7) Homology of organs and members, 709^30, 714'' 3, et passim 
{cf.P.A.Lch. i). 

(8) Serial Homology, 707^ 2. 

(9) Analogy between the parts and works of Nature, 705^^ 5. 

(10) Sovereignty, the principle of subordination running through 
Creation {Po/. 1254*31: (a) man's superiority to the rest of the animal 
kingdom, cf. P. A. 656* 7 ; (ύ) of the right to the left, of upper to lower, 
706'' 10 et seq., cf. P. A. 686*25 ; (c) the 'gradual scale' from lifeless 
things to the highest animate beings, cf. P. A. 681* 12. 

^ Leg. τά κατά φύσιν Ζ, cf. N/c. Eth. 1099^23 (Bywater). 

"^ Cf. ch. 4, inf7-a ; Topics, 142^ 34 ; Phys. 208^ 13, 2438• 16 ; de Caelo, 
284^6; Met. 1016^25 ; Plato, Leges, 817 E, &c. For the application 
to organisms cf. H. A. 493^ 17, 494* 20 ; P. A. 669'' 20. 

' Cf. de Motii, 703* 20 and note. 

* Cf. Phys. 243'' 19. ε Leg. κατά. μίρο: Ζ, cf. z>// 708* 28. 

β Cf.deAfotu, 698'^i5,&c. 


lean against it, or if it affords no resistance at all to what is 
moving, the latter can of itself effect no movement upon it. 
For an animal which jumps makes its jump both by leaning 
against its own upper part^ and also against what is 

15 beneath its feet ; for at the joints the parts do in a sense 
lean upon one another, and in general that which pushes 
down leans upon what is pushed down. That is why 
athletes jump further with weights^ in their hands than 
without, and runners run faster if they swing their arms ; 
there is in extending the arms a kind of leaning against the 
hands and wrists. In all cases then that which moves 

20 makes its change of position by the use of at least two parts 
of the body ; one part so to speak squeezes, the other is 
squeezed ; for the part that is still is squeezed as it has to 
carry the weight, the part that is lifted strains against that 
which carries the weight. It follows then that nothing 
without parts ^ can move itself in this way, for it has not in 

25 it* the distinction of the part which is passive^ and that 
which is active. 

Again, the boundaries ^ by which living beings are 4 
naturally determined are six in number, superior and 
inferior, before and behind, right and left. Of these all living 
beings have a superior and an inferior part ; for superior 
30 and inferior is in plants too, not only in animals. And this 
distinction is one of function, not merely of position 
relatively to our earth and the sky above our heads. The 

* Leg. avTo Ur Mich.; cf. If. A. 567*8, infra, 709'^ 8. It is most 
remarkable that A. nowhere refers in this treatise to the vertebrae of 
the back, though they are presupposed here and certainly in his discus- 
sion of snakes ; cf. P. A. 654^ 14 avaym] κινουμένου του ζφου κάμπτίσθαι 
το σώμα : Galen, de Usu Part. xii. 10. Prof. Piatt {J. of Phil, xxxii. 63) 
suggests τω ανω (τω S). 

''■ Pieces of wood or metal, shaped either as half disks or like our 
dumb-bells, used by Greek athletes to give the body additional 
momentum in the long-jump (cf. Prob. 881 " 3 ; Nic. Eth. 1 123'' 31). 
They are illustrated in Dubois- Villeneuve, Int. a I'Etude des Vases 
antiques, Plate xvi. 

' PSU and Mich. αμ(\ίς, viz. without limbs ; but cf. supra, line 20; 
de Motu, 702^31 (note) ; infra, 705^22. Γ read άσκίλί'ί. 

* Leg. αυτω Ζ. (sic). * Cf. de Motu, 702* 1 1 (note). 

* Cf. de Motu, 703b 18 (note), δκίστασις might almost be turned by 
' dimension ', but A. uses it only of body (a line is defined by Proclus, 
μ(γ(θος ΐ'φ' ev ^ιάστατον). Cf. de Caelo, 284^ 24, where ' up ' is the 
principle of length, ' right ' of breadth, and ' front ' of depth. 


superior is that from which flows in each kind the distribution 
of nutriment and the process of growth ; the inferior is that 7C5 
to which the process flows and in which it ends. One is a 
starting-point, the other an end, and the starting-point is 
the superior. And yet it might be thought ^ that in the 
case of plants at least the inferior is rather the appropriate 
starting-point, for in them the superior and inferior are in 
position other than in animals.^ Still they are similarly 5 
situated from the point of view of function, though not in 
their position relatively to the universe. The roots are the 
superior part ^ of a plant, for from them the nutriment * is 
distributed to the growing members, and a plant takes it 
with its roots as an animal does with its mouth.^ 

Things that are not only alive but are animals have both 
a front and a back, because they all have sense/ and front ό 
and back are distinguished by reference to sense.'^ The 
front is the part in which sense is innate, and whence each 
thing gets its sensations, the opposite parts are the back. 

All animals which partake not only in sense, but are able 
of themselves to make a change of place,^ have a further 15 
distinction of left and right besides those already enumerated; 
like the former these are distinctions of function and not of 
position. The right ^ is that from which change of position 

^ Leg. καίτηι So^fie y' av tois φντο'ΐ! U, cf. Mich. 

* Plato calls Man φντον ουκ eyyeiov αλλ' ονράνιον, plant not of earth 
but of the firmament (Tim. 90 a). Among animals Testacea are inverted 
like plants (P. A. 683^ 20); Molluscs (Cephalopods) have no superior and 
inferior (G.A. 741^33), cf. z>{/>7z, 706^ I. Linnaeus said ' Planta est 
animal inversum ' ; Bacon [N. O. ii. 27) ' homo sit tanquam planta 

3 Cf. de Anim. 416* 5 ; Parv. Nat. 468» I ; H.A. 494* 26, 500^ 28 ; 
P. A. 650*20, 656* 10. 

* Cf. de Gen. et Corr. 335* 13 ; G. A. 762^ 12. 
^ Cf. de Anhn. 412^ 3 ; P. A. 62,6^ 28. 

' a. de Anim. 413^1; Parv. Nat. 467'' 23 ; P. A. 666^34; G.A. 
731'' 4 ; Met. 980*28. 

'' Cf. de Caelo, 284^ 29 'ίμπροσθΐν εφ' δ al αΙσθήσεις, 285*^ 24 το Be [els 
το] πρόσβ(ν β'φ' δ (sc. ή κίνησίί). 

^ Sensation [de Anim. 414^3; Parv. Nat. 454^25; Z".^. 653*' 22) 
and movement in Place {Pol. 1290*" 26) are the proper characteristics 
of animals [Phys. 265*^34). Some of the Testacea (e.g. mussels) are 
almost sedentary, and are therefore akin to both plants and animals 
(H.A. 487^6; P.A. 683^ 4; G.A. 731^ 8). Cf. what is said of Sponges, 
P. A. 681* II, and of Ascidians, 68ΐ"•26. Contrast de Caelo, 284^32. 

» Cf. de Caelo, 285» 25, ^ 16. 


20 naturally begins, the opposite which naturally depends 
upon this is the left. 

This distinction (of right and left) is more articulate and 
detailed in some than in others. For animals which make 
the aforesaid change (of place) by the help of organized 
parts (I mean feet for example, or wings or similar organs) 
have the left and right distinguished in greater detail, while 

25 those which are not differentiated into such parts, but make 
the differentiation ^ in the body itself and so progress, like 
some footless animals (for example snakes and caterpillars 
after their kind, and besides what men call earth-worms'*), 
all these have the distinction spoken of, although it is not 

30 made so manifest to us. That the beginning of movement 
is on the right ^ is indicated by the fact that all men carry 
burdens on the left * shoulder ; in this way they set free the 
side which initiates movement and enable the side which 
bears the weight to be moved. And so men hop easier on 
706^ the left leg ; for the nature of the right is to initiate move- 
ment, that of the left to be moved. The burden then must 
rest on the side which is to be moved, not on that which is 
going to cause movement, and if it be set on the moving 
side, which is the original of movement, it will either not be 
5 moved at all or with more labour. Another indication 
that the right is the source of movement is the way we put 
our feet forward ; all men lead off with the leftj and after 
standing still prefer to put the left foot forward, unless 
something happens to prevent it. The reason is that their 

^ Viz. by undulations, cf. infra, 707^ 7. 

' Lit. earth-entrails. 

^ Cf. H.A. 498'' 7 ; infra, 712^25. Man is the standard, he moves 
his left leg first, the right being the original of motion (αρχή κινησ€ωί). 
It is strange that A. nowhere considers the effect of the bilateral structure 
in this connexion ; since the determining cause seems to be the develop- 
ment of the right hand and arm ; in quadrupeds it would follow naturally 
that the near hind should move first (and so in fact is the tendency in 
most horses), but infra, 7ΐ2='•25, he says that the ofiffore moves first, and 
that strictly should correspond to man's right hand. 

* Many curious observations might be made. Beginners in skating 
exhibit a painful tendency to strike off with the left (706* 5) ; fencing 
and boxing seem adverse to A.'s doctrine. In Testacea (e.g. Snails) 
A. says the spiral runs from left to right ; their movement being from 
the spiral is from right to left, accordingly they carry their shell on the 
right, contrary to the usual position of a burden (cf. infra, 706^ 13). 


movement comes from the leg they step off, not from the 
one put forward. Again, men guard themselves with their 
right. And this is the reason why the right is the same in 10 
all, for that from which motion begins is the same for all, 
and has its natural position in the same place, and for this 
reason the spiral-shaped Testaceans have their shells on the 
right,^ for they do not move in the direction of the spire, 
but all go forward in the direction opposite to the spire. 15 
Examples are the murex and the ceryx.^ As all animals 
then start movement from the right, and the right moves in 
the same direction as the whole, it is necessary for all to be 
alike right-handed. And man has the left limbs detached ^ 
more than any other animal because he is natural in a 
higher degree than the other animals ; now the right is 20 
naturally both better* than the left and separate from it, 
and so in man the right is more especially the right, more 
dextrous that is, than in other animals. The right then 
being differentiated it is only reasonable that in man the 
left should be most movable,^ and most detached.^ In 
man, too, the other starting-points ^ are found most 25 

1 Cf. H. A. 528^ 9 ; infra, 714'' 8 ; G.A. 763^ 22. 

2 The Trumpet-shell. 

' Except the elephant, cf. H. A. 497^22. 

* For the principle of Sovereignty, obtaining between each pair, cf. 
Plato, Tim. 45 ; P. A. 648*11, 665*22, 672'' 22 ; G.A. 742^16. The 
idea is of Pythagorean origin, de Caelo, 284^ 7, /r. 1513*24; the 
superior being in their view prior to the right, and to the front, 
de Caelo, 285* 21. On the physiological ground for the sovereignty of 
the right, cf. P. ^.667* 21, ^ 35 ; G.A. 765^1. 

Pliny, N. H. xviii. 24 (54) makes a suggestive remark on sowing : 
' Manus utique congruere debet cum gradu semperque cum dextro 
pede,' and this action may be seen in medals and other plastic repre- 
sentations of sowing. Some modern writers connect the Saturnian 
metre with this beat of the right foot. 

^ Leg. ίνκίνψότατη, which appears to be Z's original reading. Two 
letters are erased and α written in a later hand. Man is the only ambi- 
dextrous animal, H.A. 497^31; Nic. Eth. 1134^34. Plato held that at 
birth he was nearly ambidextrous, only dextrous by habit (Z.^^^'j•, 794 E). 
The determining influence of habit is recognized in Mag. Mor. 1 194^ 30, 
but e\'en for the ambidextrous the right is still φύσίΐ βίλτίω. Hippo- 
crates (de Acr. 17) makes some interesting remarks upon the effect of 
mutilation and habit upon the right side of Sauromatian women. 

^ The reasoning seems a priori. Feline creatures have their left 
forelimbs more detached than men; ml/. A. 497^22 the elephant is 
said to be the equal of man in this respect. 

■^ άρχίΐί, as usual, hard to render adequately. The superior, front 
and right, are said to be αρχ^αί in two senses in de Caelo, 284'' 20. 


naturally and clearly distinct, the superior part that is and 
the front. 

Animals which, like men and birds, have the superior 5 
part distinguished from the front are two-footed (biped). 
In them, of the four points of motion, two are wings in the 
one, hands and arms in the other. Animals which have the 
30 superior and the front parts ^ identically situated are four- 
footed, many-footed, or footless (quadruped, polypod, 
limbless). I use the term foot ^ for a member employed for 
movement in place ^ connected with a point on the ground, 
for the feet appear to have got their name from the ground 
under our feet. 
706* Some animals, too, have the front and back parts 
identically situated, for example Cephalopods (molluscs) 
and spiral-shaped Testaceans, and these we have discussed 
elsewhere in another connexion.* 

Now there is in place ^ a superior, an intermediate, and 
an inferior ; in respect to place bipeds have their superior 
part corresponding to the superior part of the universe ; ^ 
6 quadrupeds,'^ polypods, and footless animals to the inter- 
mediate part,^ and plants to the inferior. The reason is 
that these have no power of locomotion, and the superior 

^ Cf. P. A. 686*33 ; man is the norm, his arms are superior limbs ; 
a quadruped's forelegs are homologous with man's arms, and are 
therefore strictly 'superior', and so the superior and front are in 
quadrupeds identical. 

^ πονς ποδόί, derived άττό τον ττ/ δου ; cf. foot and pad in English, as if 
we related pad to path etymologically ; cf. P. A. 695^22 17 των ττοΒωρ 
πρόσθΐσΐί irpos την em τω πίδω κίνησιν χρήσιμος (leg. πίδω with PSU). 

^ Leg. κινητικόν (with Γ), cf. last note. 

* e.g. 77.^.523^21 ; cf. P. A. 684^14, ''34seq. (πάντας ίχονσι tovs 
πόδας ΐπΐ τυ κάΚονμ^νον ΐ'μπροσθίν' τούτον δ' αίτιον δτι σννηκται αντων το 
οπισθΐν προς το ίίμπροσθ(ν). 

^ Cf. supra, 705^ 4 (note). The passage is almost unique in doctrine. 
It would be more characteristic to consider the middle or intermediate 
to be the best, as in P. A. 666* 15 (υφυίστητος των τόπων ό μίσος (cf. Pol. 
1327^29 ; Plato, Epin. 987 D ; Theoph. Met. Br. 321). 

In this connexion A. generally uses only superior and inferior, and το 
μίσον is '('σχατον, cf. de Cae/o, 308* 23, in which treatise there is a parallel 
to our passage, 31 2*7 ol τόποι δύο, τό μίσον (the centre) κα\ τ6 (σχατον. 'ίστι 
δί δή τι κα\ [τυ] μΐταξν τούτων . . . το μΐταξν (viz. region of water and air). 

* τον δλον, cf. de A/o/u, 699* 12 for the complete term 6λος ουρανός. 
' Leg. τίι δ( (^τίτράποδα η') ποΧνποδα . . . 

* τό μεταξύ. Cf. Parv. Nat. 468* 7» and for the Universe, Meteor. 
340*5, 18 ό μίταξν γης καΐ oipavov τόπος. 


part is determined relatively to the nutriment, and their 
nutriment is from the earth. Quadrupeds, polypods, and 
footless animals again have their superior part corresponding 
to the intermediate, because they are not erect. Bipeds 
have theirs corresponding to the superior part of the 
universe because they are erect, and of bipeds, man par 
excellence ; for man is the most natural of bipeds. And it 10 
is reasonable for the starting-points to be in these parts ; 
for the starting-point ^ is honourable, and the superior is 
more honourable^ than the inferior, the front than the 
back, and the right than the left. Or we may reverse the 
argument and say quite well that these parts are more 15 
honourable than their opposites just because the starting- 
points are in them. 

6 The above discussion has made it clear that the original 
of movement is in the parts on the right. Now every 
continuous whole,^ one part of \vhich is moved while the 
other remains at rest must, in order to be able to move as 
a whole while one part stands still, have in the place * where 20 
both parts have opposed movements^ some common part 
which connects the moving parts with one another. Further 
in this common part the original of the motion (and similarly 
of the absence of motion) of each of the parts must lie. 

Clearly ^ then if any of the opposite pairs of parts (right 
and left, that is, superior and inferior, before and behind) 25 
have a movement of their own, each of them has for common 
original of its movements the juncture "^ of the parts in 

Now before and behind are not distinctions relatively to 

^ Cf. Post. An. 88» 5 ; Nic. Eth. 1102» 3. 

"^ Cf. supra, 706^ 20 and note. 

3 Cf. H.A.m.j. 

* Viz. at the joints, particularly at the four ' points ' of an organized 

^ The opposed movements are motion, and privation of motion, 
regarded as contraries by A. He does not realize that the stationary 
limb is so kept by muscular contraction, though this would chime with 
his general doctrine. 

® Leg. hr{Kov οτί (Γ) and insert comma after στάσ€ως. 

■' Or perhaps leg. κατά την των etp. ΡΓ {sic Mich.), viz. ' has a common 
original by reason of the natural interconnexion of the parts in question '. 
The common original is the joint. 

V. AR. I. A. D 


30 that which sets up its own motion,^ because in nature 
nothing has a movement backwards,^ nor has a moving 
animal any division whereby it may make a change of 
position towards its front or back ; but right and left, 
superior and inferior are so distinguished. Accordingly, all 
707^ animals which progress by the use of distinct members have 
these members distinguished not by the differences of before 
and behind, but only of the remaining two pairs ; the prior 

5 difference dividing these members into right and left (a 
difference which must appear as soon as you have division 
into two), and the other difference appearing of necessity 
where there is division into four. 

Since then these two pairs, the superior and inferior and 
the right and left, are linked to one another by the same 
common original^ (by which I mean that which controls 
their movement), and further, everything which is intended 
to make a movement in each such part properly must have 

10 the original cause of all the said movements arranged in 
a certain definite position relatively to the distances from 
it of the originals of the movements of the individual 
members (and these centres of the individual parts are in 
pairs arranged co-ordinately or diagonally,^ and the common 
centre is the original from which the animal's movements 
of right and left, and similarly of superior and inferior, 

15 start) ; each animal must have this original at a point ^ 

^ The fore and hind limbs of a quadruped are superior and inferior 
by homology with man ; there is therefore no articulation corresponding 
to the dimensions 'front' and 'behind'. Cf. H.A. 494a• 27; P. A. 
686» 34. 

^ Apparent exceptions are cephalopods and crayfish {H. A. 489^ 33, 
490* 3). The latter is correctly described as sometimes swimming back- 
wards, but A. only hesitatingly recognizes the use of the abdomen in 
that kind of progression. The crayfish also walks backwards. 

Among quadrupeds the badger and the weasel seem to trot back- 
wards quite easily and naturally. 

' Viz. the heart. 

* Co-ordinately, e. g. fore near and hind near ; diagonally, fore near, 
hind off. 

* Leg. ταντην Set €;^eii^ ΐκαστον η όμοιων η παραπλησίω: εχα προς . . . ; 
. η παραπλησίωί ev Υ. Γ preserves ομοίως, ' eodem modo aut quasi similiter.' 

ταντην δ' ΐχαν (κάστω η παραπλησίως ΐχα προς ΐκαστον των Ζ {-ην δ' (χΐΐν 
ίκάστω is written above an erasure, and above that avajKoiov ; ί'καστον has 
been altered to ίκάστην much later) and Mich. όμοΙως, p. 148. 19. 

ταντην, i. e. την αρχήν, το των κινήσεων α'ίτιον, the heart ; cf. P. Α. 666''* 1 5 
TO μίσον (the heart) tVi παν εφικτόν ομοίως ή παραπλησίως . . . 


where it is equally or nearly equally related to each of 
the centres in the four parts described. 

7 It is clear then how locomotion belongs to those animals 
only which make their changes of place by means of two 
or four points in their structure, or to such animals par 
excellence. Moreover, since this property ^ belongs almost 
peculiarly to Sanguineous animals, Ave see that no San- 20 
guineous animal can progress at more points than four,^ 
and that if it is the nature of anything so to progress at 
four points it must of necessity be Sanguineous. 

What we observe^ in the animal world is in agreement 
with the above account. For no Sanguineous animal if it 25 
be divided into more parts can live for any appreciable 
length of time, nor can it enjoy the power of locomotion 
which it possessed while it was a continuous and undivided 
whole. But some bloodless animals and polypods can live 
a long time,^ if divided, in each of the severed parts, and 
can move in the same way as before they were dismembered. 30 
Examples are what is termed the centipede^ and other 
insects that are long in shape, for even the hinder portion 707'' 
of all these goes on progressing in the same direction as 
before ^ when they are cut in two. 

The explanation of their living when thus divided is that 
each of them is constructed like a continuous body of many 
separate living beings.'^ It is plain, too, from what was said 5 
above why they are like this. Animals constructed most 
naturally are made to move at two or four points, and even 
limbless Sanguinea are no exception. They too move by 

The exception is man's heart, which is a little to the left and upwards ; 
//.^. 496 Μ 5, 507^1 ; /^.yi. 666^6. 

1 Viz, to have a common centre of movement or αρχή, lying in the 
middle, cf. infra, ^ 27. 

2 Qi.H.A. 490^27. 

^ A. appeals, as so often in his scientific treatises, to experience for 
confirmation of general theory. 

* Viz. τα ΐ'ντομα, Η. Α. 531^ 3° ! cf. de Aniin. 409=^ 9, 41 1^ 19, 413'' 20; 
Parv. Nat. 467=* 19, 468*25, 471^20; P. A. 667^27, 673*30. 

* Scolopendra, cf. H. A. 505!^ 13, 532* 5, 621a• 7. 

* Leg. κατά ταντο {και Ζ) and τω πρόσθεν. Cf. H. Α. 532^* 4? where 
the several parts are said to move either way (cf. Prof. Piatt, 1. c. p. 40). 

■' On this point and its relation to the many limbs A. seems in 
advance of Galen (cf. de Usu Partium, iii. 2). 




dint of four points, whereby they achieve progression. They 
lo go forward by means of two flexions.^ For in each of their 
flexions there is a right and a left, both before and behind 
in their flat surface,^ in the part towards the head a right 
and a left front point, and in the part towards the tail the 
two hinder points.^ They look as if they moved at two 
points only, where they touch before and behind, but that 
15 is only because they are narrow in breadth. Even in them 
the right is the sovereign part,•* and there is an alternate 
correspondence behind,^ exactly as in quadrupeds. The 
reason of their flexions is their great length, for just as tall 
men walk with their spines bellied (undulated) forward, and 
when their right shoulder is leading in a forward direction 
20 their left hip is rather inclined backwards, so that their 
middle becomes hollow and bellied^ (undulated), so we 

^ The doctrine is somewhat different from that of H.A. 490*31. 
There the snake is said to progress by means of four bends (cf. the 
same theory as to eels, 708*5 ififra). Here the philosopher seems 
to intend the theory expressed in the translation, which the diagram 
below will make clear. Had A. compared the progression of snakes 
with that of lizards his theory of four points would have been exactly 

exemplified. I am not certain 
that the snake or lizard alter- 
nates the curves, though a fish 
necessarily does so in order 
to keep straight. The point 
is not discussed in Cuvier. 
Α., though he describes their 
great number {H. A. 508^ 3), 
did not realize the function of 
the ribs of the snake which, 
with their remarkable ball 
and socket joints, make the 
snake a polypod rather than 
a quadruped, though if he had he would have doubtless referred them 
to four original points (of course the ribs are not strictly feet). He 
does not remark upon the function of the tail of fish or lizard in this 
connexion, though in H.A. 490*4 he says that the newt's tail is used 
for progression (cf. P. A. 684*3). Vid. A. M. 0pp. ix, p. 298. 
^ Leg. και (to') οττίσθιον PY. Lit. ' in the breadth '. 
' Mich, forcing the Greek takes this to describe /Oi(r flexions. 
* rjye'iTai has the pre-eminence, viz. initiates movement, not necessarily 
goes first or leads, which is ή-γΰσθαι rfj deaei, 711* 23. 

' Viz. the opposed response is made behind, i. e. motion of the left 

^ A.'s observation about tall men is just, λορδόί is opposed to κνφόί 
(7io^ 18) ; it was a medical term strictly used of the spine, viz. hollow 
backed )( hunched. Hipp, de Artie. 807 Β ; λορδωτόι/ . . . ivavriov τ~ 
κνρτω Erotiani Glossaria, p. 242 (Franzius). 




■ Β 












ought to conceive snakes as moving in concave curves 
(undulations) upon the ground. And this is evidence that 
they move themselves like the quadrupeds, for they make 
the concave in its turn convex and the convex concave. 
When in its turn the left of the forward parts is leading, the 
concavity is in its turn reversed, for the right becomes 25 
the inner. (Let the right front point be A, the left B, the 
right hind C, the left D.') 

Among land animals this is the character of the move- 
ment of snakes, and among water animals of eels, and 
conger-eels and also lampreys, in fact of all that have their 
form snakelike.2 However, some marine animals of this 30 
shape have no fin, lampreys ^ for example, but put the sea 708* 
to the same use^ as snakes do both land and water (for 
snakes swim precisely as they move on the ground).^ Others 
have t\vo fins only, for example conger-eels and eels and 
a kind of cestreus^ which breeds in the lake of Siphae. 5 
On this account too those that are accustomed to live on 
land, for example all the eels, move with fewer flexions 
in a fluid than on land,'^ while the kind of cestreus which 
has two fins, by its flexion in a fluid makes up the remaining 
8 points.^ The reason why snakes are limbless ^ is first that 
nature makes nothing without purpose, but always regards 10 
what is the best possible for each individual, preserving the 

^ Cf. 707^ 10 (note) and 702^ 29 (note). Probably Z's cyclic order is 

2 Cf. H. A. 489"^ 26; P. A. 696* 3 (and Dr. Ogle's note), and infra, 
709^ 12. 

^ Cf. H. A. 489'' 28, 5041^ 34. 

* Muraefia htiefia, cf. H.A. 489'' 29, where the lamprey and other 
similar creatures are said to use the sea as snakes do the earth, and to 
swim in the watery medium in a manner similar to the movements of 

^ Cf. P. A. 696*9. 

* Cf. H.A. 5041^33 ; P. A. 694»• 4. The features are not those of 
a mullet. Perhaps it is a fish akin to the Bichir of the Nile, and the 
Reed fish of Old Calabar. The latter has no ventral fins. 

' Eels appear to be regarded here as land fishes. The true reason 
of their fewer flexions in water is the greater ease of their progress 
there, not the fins, which are practically of no help. 

^ Leg. Tti λοιπά σημεία Ζ. I.e. inasmuch as they have two fins they 
use fewer flexions in the Avater than a snake, and thus preserve Nature's 
balance of four points of motion ; cf. //.A. 490^32 δύο {καμττάΊ} συν 
Tols nrepvyiois, and infra, 709•^ 13 (τψ Χοιπην κίνησιν). 

» Qi. P. Α. 6(^6° ΙΑ, 692*16. 


peculiar essence of each and its intended character, and 
secondly the principle we laid down above that no San- 
guineous creature can move itself at more than four points. 
Granting this it is evident that Sanguineous animals like 

15 snakes, whose length is out of proportion to the rest of their 
dimensions, cannot possibly have limbs ; for they cannot 
have more than four (or they would be bloodless), and if they 

20 had two or four they would be practically stationary ; so slow 
and unprofitable would their movement necessarily be.^ 

But every limbed animal has necessarily an even number 
of such limbs. For those which only jump and so move 
from place to place do not need limbs ^ for this movement 

36 at least, but those which not only jump but also need to 
walk, finding that movement not sufficient for their purposes, 
evidently either are better able to progress with even limbs 
or cannot otherwise progress at all,^ [for* every animal 
which has limbs must have an even number], for as this 
kind of movement is effected by part of the body at a time, 
and not by the whole at once ^ as in the movement of 

30 leaping, some of the limbs must in turn remain at rest, and 

others be moved, and the animal must act in each of these 

cases with opposite limbs, shifting the weight from the 

limbs that are being moved to those at rest. And so^ 

708^ nothing can walk on three limbs or on one ; '' in the latter 

^ Cf. P. A. 696* II, where the present passage is referred to. 

^ Viz. do not need limbs in the specific sense of locomotory organs. 

Elsewhere A. relates the movement of jumping to the abnormally 
developed hind legs (e.g. in άκρ'ώ^ς and •ν|/•ύλλαι), cf. H.A. 532*27; 
Z'.^. 683*23. 

A. nowhere recognizes the uses of the tail in leaping, nor does he 
appear to mention the Elateridae (Skipjacks). 

* Leg. brjkov OTi οΰτως μ(ν βίλτιορ rols δ' όλως άδΰνιηον {αλλωί/ 
πορΐνεσθαι. My emendation gives the necessary sense, that polypods 
though they can succeed in progressing on odd limbs (cf. in/ra, ^ 14-16) 
do so de//er on even limbs ; quadrupeds cannot walk at all on odd 
limbs. Γ seems to have read ώ? el ovros μ^ν βίλτιον τοΙς δε άΒννατον δλως. 
Necessity in the organic world manifests itself in a distribution of 
organs which is e/c τώι> ίν^ΐχομίνων βίλτιστον (best of possible arrange- 
ments) or necessary and inevitable because of some reXoy, cf. P. A. 

640* 36 17 on o\(uS advvarov άλλωί rj καλώς ye οντωί. 

* Clearly a gloss on the whole paragraph (om. PSU). 
^ Cf. supra, 705 a• 5, 

^ Viz., on account of this opposition. 

'' Leg. τρισι μΐν ovOev οϋδ' ivi, rpe'is μϊν ονθ' iv\ ovdev Z. Cf. Mlch. 
151. 27 ή δι' ivos η δια τριών, 'nullum neque uno ' Γ. 

ANIMALIUM 8 708»» 

case it has no support at all on which to rest the body's 
weight, in the former only in respect of one pair of opposites, 
and so it must necessarily fall in endeavouring so to move. 
Polypods however, like the Centipede,^ can indeed make 5 
progress on an odd number of limbs, as may be seen by 
the experiment of wounding one of their limbs ; for then 
the mutilation of one roλv of limbs is corrected by the 
number of limbs which remain on either side. Such muti- 
lated creatures, however, drag the wounded limb after them 10 
with the remainder, and do not properly speaking walk. 
Moreover, it is plain that they, too, would make the change 
of place better ^ if they had an even number, in fact if none 
were missing and they had the limbs Avhich correspond to 
one another. In this way they could ^ equalize their own 
weight, and not oscillate to one side, if they had corre- 15 
sponding supports instead of one section of the opposite 
sides ^ being unoccupied by a limb. A walking creature 
advances from each of its members alternately,^ for 
in this way it recovers the same figure that it had at 

The fact that all animals have an even number of feet, 20 
9 and the reasons for the fact have been set forth. What 
follows will explain that if there were no point at rest 
flexion and straightening would be impossible. Flexion ^ 
is a change from a right line to an arc or an angle, 
straightening a change from either of these to a right line. 
Now in all such changes the flexion or the straightening 25 
must be relative to one point.'' Moreover, without flexion 
there could not be walking or swimming or flying. For 
since limbed ^ creatures stand and take their weight alter- 
nately on one or other of the opposite legs, if one be thrust 

^ Scolopendra, vid. 707* 30 note. 

2 βελτίον, cf. supra, 708^26 note. 

^ Leg. 8ύναιτ' αν {δύναιντο PSUY, cf. 709* 12 reading of PY), 

* Om. την after χώραν PSUY. 

® He is thinking of quadrupeds as typical, and their movement κατά 

8ιάμ(τρον (cf. ch. 14 infra), ΐναλλάξ as in Euclid, i. 27 αϊ (ναλληξ γωνίαι, 

the alternate angles, the angles there being taken, like the limbs here, 
in cyclic order. 

« Cf. Meteor. 386* 2. 

^ Cf. de Moiu, ch. i ; supra, ch. 3. 

' μίν refers to bi in 709* 24. 


30 forward the other must of necessity be bent. For the 
opposite limbs are naturally of equal length, and the one 
which is under the weight must be a kind of perpendicular '^ 
at right angles to the ground. 

When then one leg is advanced it becomes the hypo- 
709°^ tenuse of a right-angled triangle. Its square then is equal 
to the square on the other side together with the square 
on the base.^ As the legs then are equal, the one at rest 
must bend either at the knee or, if there were any kneeless 
animal which walked, at some other articulation. The 
5 following experiment exhibits the fact. If a man were 
to walk parallel to a wall in sunshine,^ the line described 
(by the shadow of his head^) would be not straight but 
zigzag,^ becoming lower as he bends, and higher when he 
stands and lifts himself up. 

It is, indeed, possible to move oneself even if the leg be 
10 not bent, in the way in which children "^ crawl. This was 
the old though erroneous account of the movement of 
elephants.'' But these kinds of movements involve a flexion 
in the shoulders^ or in the hips. Nothing at any rate^ 
could walk upright continuously and securely without 
flexions at the knee, but would have to move like men in 
the wrestling schools who crawl forward through the sand 
15 on their knees. For the upper part of the upright creature 
is long so that its leg has to be correspondingly long ; in 

^ Cf. Mech. 857^ 27 avayKX] τον ΐστωτα κάθΐτον etVoi προς την •γην. 

^ The base, i. e. the line between the point where the advanced leg 
touches the ground and the stationary foot. 

' Leg. ev ανγ rj ήλιου : ev yjj PSUY : ev . . .^. . . . Ζ with ΓΗ in later 
hand (the space is for about 9 letters). Cf. Plut. Conviv. iii. i (ii. 658 F). 
It should be evening light. Γ seems to have read eV ^ίΐτονων (uicinus). 
Perhaps this belongs to the alternative in Mich. p. 155. 

* Not in the Greek. 

^ Arist., like many Greek geometers, regards a zigzag as a kind of 
line, cf. Met. 1016^ 2, 12. The line traced is νννν\Λ as Mich. says. 

® To judge from Mich.'s note some words like και ο/ ανάπηροι Xeyo- 
/xei/oi are missing here, viz. seals and bats, cf. ίηβ-α, 714^ 12. 

' It was reported (perhaps by Ctesias of Cnidos, G. A. 7368• 22) that 
the elephant had no knee-joints. A. corrects this mistake in H.A. 
498* 8, and infra, 712* 1 1. He appears to be incorrectly informed in 
P. A. 659*29, where he speaks of their legs as bending with difficulty 
{άφνΐαν της κάμ^Ιτεως), unless that means the exceptional bending. 

* Scapula, cf. H.A. 498*31 ή 8e φωκη ωσπΐρ πίπηρωμίνον . . . €νθύς 
(\ei μ(τά την ωμοπΧάτην τουί πόδα?. 

® Leg. ορθόν ye. 


consequence there must be flexion. For since a stationary- 
position is perpendicular, if that which moves cannot bend ^ 
it will either fall forward as the right angle becomes acute 
or will not be able to progress. For if one leg is at right 
angles to the ground and the other is advanced, the latter 
will be at once equal and greater. For it will be equal to 
the stationary leg and also equivalent to the hypotenuse of 20 
a right-angled triangle.^ That which goes forward there- 
fore must bend, and while bending one, extend the other 
leg simultaneously, so as to incline forward and make 
a stride and still remain above the perpendicular ; for the 
legs form an isosceles triangle, and the head sinks lower 
when it is perpendicularly above the base on which it 

Of limbless animals, some progress by undulations (and 25 
this happens in two ways, either they undulate on the 
ground, like snakes, or up and down, like caterpillars), 
and undulation is a flexion ; others by a telescopic * action, 
like what are called earthworms and leeches. These go 
forward, first one part leading and then drawing the whole 30 
of the rest of the body up to this, and so they change from 
place to place. It is plain too that if the two curves were 
not greater than the one line ^ which subtends them undu- 
lating animals could not move themselves ; when the flexure 709 
is extended they would not have moved forward at all if 

^ Inser. el (ίκαμπτον ί'σται το κινονμ^νορ Υ (cf. Ζ) ; the words do not 
seem a gloss. (Prof. Piatt agrees, I. c. p. 42.) 

' bwrjaerai, not here used in the mathematical sense as supra, 709* i, 
but in the ordinary sense. The leading leg is both equal to the back leg, 
because a man's legs are equal, and greater because (in the figure 
made necessary by the inflexibility hypothesis) it subtends the right 

^ βαίνΐΐν, as in Euclid iii, Def. 9, an angle stands on the arc below 
it (not in L. and S. or Bonitz in this sense). As the man moves, his 
head drops lower until it is the perpendicular of an isosceles 
triangle, where AB and AC are his legs. The brachy- 
logy is easier in Greek because isosceles means ' with 
equal /egs'. 

* Ιλΰσπασίί, cf. //. A. 487^ 22 ; telescopic suggests the movement 
of earthworms, which is concertina-like. L. and S. wrongly translate 
' wriggling ', which is not a worm's normal movement. A.'s account of 
the fact is characteristically accurate ; characteristically too he does not 
ask how it squares with his theory of movement. 

^ Viz. the two arcs are together greater than the chord which sub- 
tends them. 



the flexure or arc were equal to the chord subtended ; as it 
is, it reaches further when it is straightened out, and then 
this part stays still and it draws up what is left behind. 
In all the changes described that which moves now 

5 extends itself in a straight line to progress, and now is 
hooped ; it straightens itself in its leading part, and is 
hooped in what follows behind. Even jumping animals all 
make a flexion in the part of the body which is underneath/ 
and after this fashion make their leaps. So too flying 

loand swimming'^ things progress, the one straightening and 
bending their wings to fly, the other their fins to swim. 
Of the latter some have four fins,^ others which are rather 
long, for example eels, have only two. These swim by 
substituting a flexion of the rest of their body for the 
(missing) pair of fins to complete the movement, as we 

15 have said before.* Flat fish use two fins, and the flat of 
their body as a substitute for the absent pair of fins.^ 
Quite flat fish, like the Ray,^ produce their swimming 
movement with the actual fins and with the two extremes 
or semicircles of their body, bending and straightening 
themselves alternately. 

20 A difficulty might perhaps be raised about birds. How, 10 
it may be said, can they, either when they fly or when they 
walk, be said to move at four points ? Now we did not say 
that all Sanguinea move at four points, but merely at not 
more than four. Moreover, they cannot as a fact fly if 

^ Cf. supra, 705* 12. 

^ A. nowhere in this treatise recognizes the use of the tail in swim- 
ming ; he treats the tail as a rudder throughout (cf. 710* i) ; by fins 
he means the pectoral and ventral fins, and these he considers the sole 
organs of locomotion in the normal fish (cf. 709^ 9 and note). 

» Cf. 7/.^. 489^24. 

* Cf. 708^ 7 and note. 

^ A. seems to think that fish like the plaice use their flat edges for 
swimming, as the rays do. Correct about the rays, he is wrong about 
these flat fish. 

" Cf. H.A. 489^32; P. A. 696*26. A. gives there a remarkably 
accurate account of the Rays, distinguishing those that have no obvious 
fins from the Torpedo fish which has two (regarded by A. as pectorals) 
on the tail. It is this fish which uses €κατερω τω ημικνκΧίω, to supply 
the other two points of movement. This is what he is describing here, 
though he does not realize that these processes are the true pectoral 

ANIMALIUM ίο 709^ 

their legs be removed, nor walk without their wings. Even 25 
a man does not walk without moving his shoulders. Every- 
thing indeed, as we have said, makes a change of place by 
flexion and straightening, for all things progress by pressing 
upon ^ what being beneath them up to a point ^ gives 
way as it were gradually ; accordingly, even if there be no 
flexion in another member, there must be at least in the 
point whence motion begins, that is in feathered ^ (flying) 30 
insects at the base of the ' scale-wing \^ in birds at the 
base of the wing, in others at the base of the corresponding 
member, the fins, for instance, in fishes. In others, for 
example snakes, the flexion begins in the joints of the hoay. 710^ 

In winged creatures the tail ^ serves, like a ship's rudder, 
to keep the flying thing in its course. The tail then must 
like other limbs be able to bend at the point of attachment.^ 
And so flying insects, and birds (Schizoptera) whose tails are 5 
ill-adapted for the use in question, for example peacocks, 
and domestic cocks, and generally birds that hardly fly,'' can- 
not steer a straight course.^ Flying insects have absolutely 
no tail, and so drift along like a rudderless^ vessel, and 

^ άποστηριζόμ^να or a similar word must be supplied, and has perhaps 
dropped out after yap. Cf. supra, 705'^ 7 (reading of Z). 

^ Cf. 705^ 9 and de Motu 698^^ 1 5 ; up to a point, because in the 
case of \vater and air the resisting medium is not regarded as quite 
stationary like the earth. 

A. does not discuss the results upon flying and swimming creatures 
of the fact that the medium is all round them. 

' Holoptera, lit. with whole feathers (viz. what we call wings in 
Lepidoptera, &c.), in contrast with birds which have wings divided 
into feathers (Schizoptera, 710=* 5). 

* Leg. ■ητίΚον Ζ {sic), cf. infra, 713=^ lo. 

^ ovpowiiyiov (cf. H.A. 504*32; F.A. 697"^ 1 1), viz. the tail with 
the tail feathers. 

' πρόσφνσΐ!, viz. the caudal vertebrae, Avhich, as A. says, are freely 
movable, and do not anchylose like those of the trunk. 

'' Lit. that are not made for flight. 

* A. does not recognize the function of the tail in keeping the flying 
body horizontal, and in helping the bird to rise and sink. He thinks 
of it apparently only as subserving a direct course. Contrast A. M. ix. 
p. 296. 

^ A. did not detect the uses of the abdomen in an insect's flight. 
Movements to right and left are governed primarily by deflexion of the 
abdomen. The drifting flight (e. g. of butterflies) is perhaps protective, 
and in the case of the chafers, &c., is due less to the causes A. suggests 
than to the imperfect balance produced by the relatively excessive 
weight of the hind parts. We may compare the erect flight of moor- 
hens and coots, among birds, where the wings are set too far forward. 


beat against anything they happen upon ; and this applies 

10 equally to sharded ^ insects, like the scarab-beetle^ and the 
chafer,^ and to unsharded, like bees and wasps. Further, 
birds that are not made for flight have a tail that is of no 
use ; for instance the purple coot * and the heron ® and 
all water-fowl. These fly stretching out their feet ^ as 

15 a substitute for a tail, and use their legs instead of a tail 
to direct their flight. The flight of insects is slow and frail 
because the character of their feathery wings '' is not pro- 
portionate to the bulk of their body ; this is heavy, their 
wings small and frail, and so the flight they use is like 

20 a cargo boat attempting to make its voyage with oars ; 
now the frailty both of the actual wings and of the out- 
growths ^ upon them contributes in a measure to the flight 
described. Among birds, the peacock's tail is at one time 
useless because of its size, at another because it is shed.^ 
But birds are in general at the opposite pole to flying 

25 insects as regards their feathers, but especially the swiftest 
flyers among them. (These are the birds with curved 
talons,^" for swiftness of wing is useful to their mode of 
life.^^) The rest of their bodily structure is in harmony with 

30 their peculiar movement, the small head, the slight ^^ neck, 

^ Coleoptera. 

^ Cf. N. H. 552^ 17 ; P. A. 682^ 26, perhaps Scarabaeus pilularius. 
'^ Cf. TV. H. 490a 14 ; P. A. 682'^ 14. The kind is uncertain, but the 
descriptions tally with our May-bug or cockchafer. 

* Or Purple Gallinule, a bird akin to our water-hen {Porphyria 
hyacinthus or coeruleiis). This is Dr. Thompson's identification 
(Glossary of Greek Birds). Bonitz, with Aubert, thinks it may be the 
Flamingo {Phoefticoptertcs rosetes), and certainly the remark about its 
legs would then be more pointed. Why should it not be the Purple 
Heron [Ardea Purpurea) ? 

^ Gilbert White remarks {Selborne, Letter xlii) 'herons seem en- 
cumbered with too much sail for their light bodies '. 

6 Cf. P. A. 694'' 20. ■^ Cf. supra, 709'' 30. 

* Omit 17, Z. ΐκφυιτις seems here to refer to the scales which form 
the surface of the wings ; cf. P.A. 6ζ8^ S where the word is used for 
hair growing as a covering. 

* Cf. //. A. 564* 32. This so-called tail is not a true tail, the feathers 
in the οϊφοπύγιον are only about 6 in. long. 

^^ i.e. Raptores. 

" Cf. P. A. 694*2 πΧηθοί 'έχονσι πτ(ρών and δια τον βίον. 

" Leon, omits οΰ, but Α. is now speaking of birds generally, not of 
Raptores. The head and neck are relatively small and light ; cf. P. A. 
659^ 8, 692^ 20 {τ(ταμίνοί). In P. A. 694^ 26 he is speaking of 
a relatively thick neck. 

ANIMALIUM ίο 7io* 

the strong and acute breastbone (acute ^ like the prow of 
a ch'pper-built vessel, so as to be well-girt,'^ and strong by 
dint of its mass of flesh ^), in order to be able to push away 710'' 
the air that beats against it,^ and that easily and without 
exhaustion. The hind-quarters, too, are light and taper again, 
in order to conform to the movement of the front and not by 
their breadth to suck ^ the air, 

II So much then for these questions. But why an animal 5 
that is to stand erect must necessarily be not only a biped, 
but must also have the superior parts of the body lighter, 
and those that lie under these heavier, is plain. ^ Only if 
situated like this could it possibly carry itself easily. And 10 
so man, the only erect animal, has legs '' longer and stouter 
relatively to the upper parts of his body than any other 
animal with legs. What we observe in children also is 
evidence of this. Children ^ cannot walk erect because 
they are always dwarf-like, the upper parts of their bodies 
being longer and stouter than the lower. With advancing 15 

* Referring to the sternal crest or ^e/ of Carinate Birds ; cf. F. A. 
659^ 9, 693'^ 16. 

^ fVTovov, well-girt, cf. Proi. 885* 6 θίοντα ΐυτόνως. Lucian, Attach. 
R. ii. 906, κοΰφα καΐ evrova και τα αντα βαρία. (Leon. translates euVopoi/, 
ut bene viam paret.) 

' η€ριφΰσ(ί, if correct (φισα PSUY and Mich.), seems to be an 
instance of the Principle of Compensation (cf. P. A. 689^ 30, 695^ 7, 
and note to 704^ 12). 

A.'s language describes the great mass of pectoral muscles in a bird, 
but he does not realize the function of muscles, nor the use of these to 
support the wings. 

In P. A. 693^ 1 8 he gives a different explanation, 'to protect the breast- 
. bone,' just as he explains a man's breasts and pectoral muscles in that way. 

* Iv άπωθύν Βννηται, &c., depends upon both adjectives, cf. P. A. 
693^ 16 ; the intermediate words are parenthetic. 

^ This word was used by a rustic in conversation with me to 
explain the lumbering flight of a heavy bird. The Greek means 'to 
draw the air ', and is a similarly popular explanation. Cf. P. A. (loc. 
cit.) τα πλατία ποΧΰν aepa ώθοϋντη δυσκίνητα ΐστι. The first airships 
were wrongly constructed with the greatest width in the centre ; the 
later have, like a bird, a blunt forecastle from which the lines gradually 
taper to the stern. 

* Cf. the interesting discussion in P. A. iv. 10. 
' Cf. P. A. 690» 27. 

* Cf. P. A. 686'' 8, where children are contrasted with colts, calves, 
and other young, and Pari/. Nat. 453'' 6 ; H.A. 500^^ 33. Birds are said 
to be not erect because of their dwarfishness, P. A. 686'' 21, 695* 8. 

For the subject generally, and its connexion with A.'s embryology, 
vid. G.A. 741^27, 742'' 14, 779*24. 


years the lower increase disproportionately, until the children 
get their appropriate size, and then and not till then they 
succeed in walking erect. Birds are hunchbacked ^ yet 
stand on two legs because their weight is set back, after 
the principle of horses fashioned in bronze with their fore- 

20 legs prancing.'^ But their being bipeds and able to stand 
is above all due to their having the hip-bone shaped like 
a thigh, and so large that it looks as if they had two 
thighs,^ one in the leg before the knee-joint, the other joining 
this part to the fundament. Really this is not a thigh but 

25 a hip, and if it were not so large the bird could not be a 
biped. As in a man or a quadruped, the thigh and the 
rest of the leg would be attached immediately to quite 
a small hip ; consequently the whole body would be tilted 
forward. As it is, however, the hip is long and extends 
right along to the middle of the belly, so that the legs are 

30 attached at that point and carry as supports the whole 
frame. It is also evident from these considerations that 
a bird cannot possibly be erect in the sense in which man 
is. For as it holds its body now the wings are naturally 
711^ useful to it, but if it were erect they would be as useless 
as the wings of Cupids * we see in pictures. It must have 
been clear as soon as we spoke that the form of no human 
nor any similar being permits of wings ; not only because 
5 it would, though Sanguineous, be moved at more than four 

^ Leg. κνφοί Ζ (cf. 707^21 note). The spine of a bird is hunched, 
and this gives it a top-heavy appearance (dwarfish) ; in spite of this 
Nature sets the weight back like a skilful statuary. 

2 Cf. 711^2 (note). 

^ A. intends by Ισχίον the true femur, by the * other bone ' the tibia 
and fibula. Cf. H.A. ii. 12 and P. A. 694^29. In his note to the 
latter passage Dr. Ogle expresses the opinion that A. correctly identi- 
fied the Ισχίον with the elongated pelvis of a bird. This is certainly 
favoured by the language of P. Α., and in that case A. may have been 
writing with a bird's skeleton before him ; here and in H.A. he cer- 
tainly seems to take his normal view of the segments of the limb, 
a view which is incorrect. 

* The language suggests that Greek artists gave their Cupids long 
wings, like those of Love in Watts's pictures. Perhaps, however, the 
stress is merely on the incorrect anatomy of six points of movement. 
The question is part of a favourite quarrel between the natural philo- 
sopher and the artist, in which Galen takes a share (Galen, de Usu 
Part, iii, ch. i ; Aristotle, Meteor. 349^ i ; de Motu, 698'' 25). Bell's 
criticism {Bridgewater Treatise^ ed. 4, p. 324) is similarly directed to 
the relations between structure and locomotion. 


points, but also because to have wings would be useless to 
it when moving naturally. And Nature makes nothing 
contrary to her own nature. 

12 We have stated above ^ that without flexion in the legs 
or shoulders and hips no Sanguineous animal with feet 
could progress, and that flexion is impossible except some lo 
point be at rest, and that men and birds, both bipeds, bend 
their legs in opposite directions, and further that quadru- 
peds bend theirs in opposite directions, and each pair in 
the opposite way to a man's limbs. For men bend their 15 
arms backwards,'^ their legs forwards; quadrupeds their 
forelegs forwards, their back legs backwards, and in like 
manner also birds bend theirs. The reason is that Nature's 
workmanship is never purposeless, as we said above, but 
everything for the best possible in the circumstances. 
Inasmuch, therefore, as all creatures which naturally have 20 
the po\ver of changing position by the use of limbs, must 
have one leg stationary with the weight of the body on it, 
and when they move forward the leg which has the leading 
position must be unencumbered, and the progression con- 
tinuing the weight must shift and be taken off on this 
leading leg, it is evidently necessary for the back leg from 25 
being bent to become straight again,^ while the point of 
movement of the leg thrust forward and its lower part 
remain still. And so the legs must be jointed.^ And it is 
possible for this to take place and at the same time for the 
animal to go forward, if the leading leg has its articulation 
forwards, impossible if it be backwards. For, if it be for- 30 
wards, the stretching out of the leg will be while the body 
is going forwards, but, if the other way, while it is going 
backwards. And again, if the flexion were backwards, the 
placing of the foot would be made by two movements and 
those contrary to one another, one, that is, backwards and 711^ 
one forwards ; for in the bending together of the limb 

^ Cf. ch. 9, supra. 

^ Lit. ' concavely '. Cf. note on 7048• 19. 

' Om. T€ after αύθις with YZ (Mich.'s text had it), cf. 709^ 20, supra. 
* This is the suppressed conclusion, the next paragraph shows which 
way the joints must bend in order to progression. 


the lower end of the thigh would go backwards, and the 
shin would move the foot forwards away from the flexion ; 
5 Avhereas, with the flexion forwards, the progression described 
will be performed not with contrary motions, but with one 
forward motion. 

Now man, being a biped and making his change of 
position in the natural way with his two legs, bends them 
forward for the reasons set forth, but his arms bend back- 

10 wards reasonably ^ enough. If they bent the opposite way 
they would be useless for the work of the hands,^ and for 
taking food. But quadrupeds which are also viviparous 
necessarily bend their front legs forwards. For these lead 
off first ^ when they move, and are also in the fore-part of 

15 their body. The reason that they bend forward is the same 
as in the case of man, for in this respect ^ they are like 
mankind. And so quadrupeds as well as men bend these 
legs forward in the manner described. Moreover, if the 
flexion is like this, they are enabled to lift their feet high ; 

20 if they bent them in the opposite way they would only lift 
them a little way from the ground, because the whole thigh 
and the joint from which the shin-bone springs would lie 
under the belly as the beast moved forward. If, however, 
the flexion of the hind legs were forwards the lifting of 
these feet would be similar to that of the forefeet (for the 

25 hind legs, too, would in this case have only a little room 
for their lifting inasmuch as both the thigh and the knee- 
joint would fall under the position of the belly) ; but the 
flexion being backwards, as in fact it is, nothing comes in 
the way of their progression with this mode of moving the 

30 feet. Moreover, it is necessary or at least better ^ for 

^ Cf. p. A. 687*6, &c., for a remarkable discussion of the hand as 
a mark of humanity. 

^ Cf. P. A. 687^31, where A. recognizes the secondary uses of the 
forehmbs in some quadrupeds for manual purposes. 

^ Tj-yelrai ; or ' govern their movement ', because the front is superior 
to the back. 

* Viz. the forelegs play the chief part in movement (cf. a bird's 
wings, 712^27), and so are analogous in function (and in curvature) to 
man's legs. 

In truth the hind legs play the chief part in quadruped progression, 
and this is recognized in P. A. 685*20 where theory is not involved. 

^ A. shows often how a secondary purpose affects Nature's handi- 


their legs to bend thus when they are suckling their young, 
with a view to such ministrations. If the flexion were 
inwards it would be difficult to keep their young under 
them and to shelter them.^ 

13 Now there are four modes of flexion if we take the 712° 
combinations in pairs.^ Fore and hind may bend either 
both backwards, as the figures^ marked A, or in the 
opposite way both forwards, as in B, or in converse ways 5 
and not in the same direction, as in C where the fore 
bend forwards and the hind bend backwards, or as in D, 
the opposite way to C, where the convexities are turned 
towards one another * and the concavities outwards. Now 
no biped or quadruped bends his limbs like the figures 
A or B, but the quadrupeds like C, and like D only the 10 
elephant ^ among quadrupeds and man if you consider his 
arms as well as his legs. For he bends his arms concavely 
and his legs convexly. 

In man, too, the flexions of the limbs are always alter- 
nately^ opposite, for example the elbow bends back, but 

work, just as a part (in spite of the Platonic principle of specialization) 
is sometimes adapted to secondary uses. Cf. P. A. 688^ 24. 

^ A somewhat different solution is offered in P. A. (688* 15, 688* 31) 
of the problem of the position of the lacteal glands in the animal 
creation. There A. thinks that the lateral attachment of man's arms 
enables his chest to be broad, and so furnishes room to the breasts ; 
the forelegs of a quadruped, on the other hand, dictate a narrow chest 
and have no room for udders. The considerations here put forward 
would have explained very well the forward position of the elephant's 
udder (cf. H.A. 498* i, 500=^ 19) since his hind legs bend forward in 
A.'s view. A. gives a farfetched a friori explanation of the fact in 

^ Leg. κατά TOvs συνδυασμούς Ζ Γ (of. Po/, 
1290^35, 1317*1), the other reading seems \\ / \ a. 
to have arisen from the loss of τής κάμψ^εως /^ / \ / 
(cf. INIich.'s τρόπων κατά rovs σννδίσμονί). '\\ y \ 

^ Mich, gives the figures which are lacking / y \ y ^ 
in the text of our MSS. ^ ^ ^ ^ 

* The full expression is used \n H.A. . . 

498* 7 τα κοΐΚα της περιφέρεια? npos Άλληλα ^ ^ / \ ^ 

άντίστραμμίνα ; lit. are conversely related to ^o^ ^ S^ 
one another, αντιστροφή being used of geo- / / \^ y ρ 
metrical as well as of logical conversion. \ \ / \ 

° Does not the elephant bend like Β ? Cf. 
H. A. 498* 12. The MSS. are much confused. 

* Elsewhere A. explains that similarly man has his flexions alternate 
and opposite to those of an animal throughout. 

In the above diagram α and γ are alternate and opposite, and so 


15 the wrist of the hand forwards, and again the shoulder 
forwards. In like fashion, too, in the case of the legs, the 
hip backwards, the knee forwards, the ankle in the oppo- 
site way backwards. And plainly the lower limbs are 
opposed in this respect to the upper, because the first ^ 
joints are opposites, the shoulder bending forwards, the 

20 hip backwards ; wherefore also the ankle bends backwards, 
and the wrist of the hand forwards. 

This is the way then the limbs bend, and for the reasons 14 
25 given. But the hind limbs move criss-cross with the fore 
limbs ; after the off fore they move the near hind, then the 
near fore, and then the off hind. The reason is that (a) if 
they moved the forelegs together and first, the animal 
would be wrenched, and the progression would be a 
stumbling forwards with the hind parts as it were dragged 
30 after. Again, that would not be walking but jumping, 
and it is hard to make a continuous change of place, 
jumping all the time. Here is evidence of what I say ; 
even as it is, all horses that move in this way soon begin 
to refuse,'^ for example the horses in a religious procession.^ 
712'' For these reasons the fore limbs and the hind limbs move 
in this separate way.* Again, {b) if they moved both the 
right legs first the weight ^ would be outside the supporting 
limbs and they would fall. If then it is necessary to move 
in one or other of these ways or criss-cross fashion, and 
neither of these two is satisfactory, they must move criss- 
5 cross ; for moving in the way we have said they cannot 
possibly experience either of these untoward results. And 
this is why horses and such-like animals stand still with 

necessarily the remaining joints which follow in succession (cp. H.A. 
498* 24). 

^ άρχη : SO. της κινησΐωί, principle of motion. The superior joint in 
each limb is regarded as the initial point in animal progression. 

^ anayopdovai. It is remarkable that A. says nothing of hopping 
birds in this treatise. After a few hops, they have recourse to a short 

' i.e. prancing, caracoling, Xen. Equ. xi. Admirably expressed by 
the artists of the Parthenon frieze. I can find only one genuine trot 
there represented. ♦ Del. ov with ZUSYr. 

^ Lit. * they would be '. In later terminology, the centre of gravity 
would he outside the hmbs, and so produce unstable equilibrium. 


their legs put forward criss-cross, not with the right or the 
left put forward together at once. In the same fashion 
animals with more than four legs make their movements ; 10 
if you take two consecutive pairs of legs the hind move 
criss-cross with the forelegs ; you can see this if you watch 
them moving slowly. Even crabs move in this way, and 
they are polypods. They, too, always move criss-cross in 
whichever^ direction they are making progress. For in 15 
direction this animal has a movement all its own ; it is the 
only animal that moves not forwards, but obliquely.^ Yet 
since forwards is a distinction relative to the line of vision,^ 
Nature has made its eyes able to conform to its limbs, for 
its eyes can move themselves obliquely,* and therefore after 20 
a fashion crabs are no exception but in this sense move 

15 Birds bend their legs in the same way as quadrupeds.^ 
For their natural construction is broadly speaking nearly 
the same.'' That is, in birds the wings are a substitute 
for the forelegs ; "^ and so they are bent in the same way 
as the forelegs ^ of a quadruped, since when they move 25 
to progress the natural beginning^ of change is from the 
wings (as in quadrupeds from the forelegs). Flight in 
fact is their appropriate ^" movement. And so if the wings 
be cut off a bird can neither stand still nor go forwards. 

Again, the bird though a biped is not erect," and has the 30 
forward parts of the body lighter than the hind, and so it 
is necessary (or at least preferable for the standing posture) 
to have the thigh so placed below the body as it actually is, 

^ Leg. βφ' όποτερ' αν Ζ (sic). 

"^ Cf. supra, 706^ 30 and note. 

^ Cf. 705*5 12 and note (vision is here taken as the typical sense). 

* Ci.H.A. 526*10, 527^8, 529^27; a different reason is given in 
P. ^.658-^2. 

^ Viz. as quadrupeds bend their hind legs ; perhaps τα όπισθεν has 
dropped out, though the sense is made certain by the context. 

® Leg. τοΐί τίτράποσι (ΥΖ) nlyap (Ζ) a reading which may be traced 
by the side of Bekker's in Mich. (p. 166. 26). So also reads Γ. 

'' Cf. P. A. 693^ 12, 695*9. 

8 Cf. N. A. 498* 28 ; A A. 6gs^ 5. 

* Cf. supra ^ 711'' 13 and note. 
1» Cf.P.^. 693^14. 

" Cf. 7^.^.695*3. 

Ε 3 


I mean growing towards the back.^ If then it must have 
this situation the flexion of the leg must be backwards, as 
713^ in the hind legs of quadrupeds. The reasons are the same 
as those given in the case of viviparous quadrupeds. 

If now we survey generally birds and winged insects,* 
5 and animals which swim in a watery medium, all I mean 
that make their progress in water by dint of organs of 
movement, it is not difficult to see that it is better to have 
the attachment of the parts in question oblique to the frame, 
exactly as in fact we see it to be both in birds and insects. 
And this same arrangement obtains also among fishes. 

10 Among birds the wings are attached obliquely ; so are the 
fins 2 in water animals, and the feather-like wings of insects. 
In this way they divide the air or water most quickly^ and 
with most force and so effect their movement. For the 
hinder ° parts in this way would follow forwards as they 

15 are carried along in the yielding medium, fish in the water, 
birds in the air. 

Of oviparous quadrupeds all those that live in holes, like 
crocodiles, lizards, spotted lizards,^ freshwater tortoises,'^ 
and turtles,^ have their legs attached obliquely® as their 
whole body sprawls over the ground,^'' and bend them 

^ Cf. P. A. 695* II els μίσον. 

^ Holoptera. 

^ Put a comma for the full stop after πτερύγια. 

* A. nowhere grasps the mechanical purpose of the forwards-upwards, 
backwards-downwards movement of the wings. His description of the 
movements themselves is only superficial. 

° Leg. και τα όπισθεν μόρια Υ, cf. supra, 710^ 3• The MSS. are much 
confused, and the argument not satisfactory. Mich, has the Bekker 
reading, but gives a ludicrous explanation. I do not know whether 
there may not be concealed a reference to the patent fact that the 
motion of a bird's wings as of the fins of a fish is simultaneous. It is 
extraordinary that A. nowhere refers to this except sud siletttio. It was 
adverted to by the mediaeval naturalist Albertus Magnus, de motzbus 
An. ii. 2, ch. 3. 

* i.e. Lacerta maiiretanica ; the ocellated lizard or gecko (tarantula) 
of S. Europe and N. Africa. 

'' i. e. Emys lutaria. 

^ i. e. Sea tortoises. There are two kinds in the Mediterranean ; 
Dernwchelys coriacea and Thalassochelys caretta ( Tartar uga de mart, 
Sardinia ; Tartuca de mart, Sicily). 

^ Cf. H.A. 498» 15 though there the joints are diiiferently described. 
We may add the chameleon (//. A. 503^ 21). 

^^ Leg. exei, en\ rrj yjj κατατίταμίνα δλα (και om. ΥΖ, κατΐταγμένα δλα Ζ 

ordinata tota Γ). Mich, has τ^ταμίνα (p. 166. 27), the loss of κατά 

ANIMALIUM 15 .713' 

obliquely. The reason is that this is useful for ease in ao 
creeping into holes, and for sitting upon their eggs^ and 
guarding them. And as they are splayed outwards ^ they 
must of necessity tuck in^ their thighs and put them 
under them in order to achieve the lifting of the whole 
body. In view of this they cannot bend them otherwise than as 

16 We have already stated the fact* that non-sanguineous 
animals with limbs are polypods and none of them quadru- 
peds. And the reason why their legs, except the extreme 
pairs, were necessarily attached obliquely and had their 
flexions upwards, and the legs themselves were somewhat 
turned under (bandy-shape) ^ and backwards is plain.° In 30 
all such creatures the intermediate legs both lead and 
follow.' If then they lay under them, they must have 713' 
had their flexion both forwards and backwards ; on account 
of leading, forwards ; and on account of following, back- 
accounting for the καί in S and U. He explains ' let down to the 
ground ' as compared with birds' wings ! 

^ Cf. I/. A. V. 33. 

^ Not as Mich, takes it ' when they are out of their holes ', cf. infra, 
713^25. YZ add the explanatory gloss (or true reading) αντων (τον 


^ Leg.7Γpoσσreλλoι'Γα,asMich,'s words indicate, and the sense demands. 

* Supra, 704* II. 

^ There are three several characters correctly described from nature : 

(«) the intermediate legs are attached laterally, cf. H.A. 525^25 ; 
P. ^.683^33; 

{b) the principal flexion is upwards (as in a fly's legs) ; 

[c) the limbs are bent under, or bandy, cf. P. A. 683^ 35. 

In the text as it stands no explanation is offered of the upward bend- 
ing, while the phrase ' bend laterally ' is used as equivalent to ' laterally 
attached' (quite a different feature), that is the plane of the bent limb is 
oblique to the plane of progression and vision. His examples are cray- 
fish, &c., and again flying insects, not centipedes, millipedes, &c. 

^ The interpretation οίβΧαισότης is very difficult, and the various uses 
not consistent. The word means 'bandiness', and sometimes expresses 
an actual curvature of a bone or segment of a limb, sometimes the general 
he of a whole limb. For example the elbow-joint (in A.'s sense) normally 
lies further outside the line of progression than the hand or shoulder, 
and so a man's arms are bandied as they hang normally. etV to οπισθΐν 
seems to mean here that the foot is also behind a plane drawn through 
the knee at right angles to the plane or axis of progression (unless it 
could mean that the elbow is up and back, cf. H.A. 498^21). L. and 
S. seem wrongly to take βλαισότης to mean 'bent inwards at the joint", 
through misinterpretation of Hippocrates, de art. 53 (L. iv. 234). 

' Cf. H.A. 498*17 τα μβταξν των (σχάτων aeX (τταμφοτίρίζΐΐ και τ;7»' 

καμπην ΐχα tit το πλάγιον μΰλλοί'. (Not, certainly, true of centipedes.) 


wards. Now since they have to do both, for this reason 
5 their limbs are turned under ^ and bent obliquely, except 
the two extreme pairs. (These two are more natural in 
their movement, the front leading and the back following.^) 
Another reason for this kind of flexion is the number of 
their legs ; arranged in this way they would interfere less 
with one another in progression and not knock together. 

I ο But the reason that they are bandy ^ is that all of them or 
most of them live in holes, for creatures living so cannot 
possibly be high above the ground.* 

But crabs are in nature the oddest ^ of all polypods ; they 
do not progress forwards except in the sense explained 
above,^ and they are the only animals which have more 

15 than one pair of leading limbs.' The explanation of this 
is the hardness of their limbs, and the fact that they use 
them not for swimming but for walking ; they always keep 
on the ground. However, the flexion of the limbs of all 
polypods is oblique, like that' of the quadrupeds which live 
in holes — for example lizards and crocodiles and most of 

20 the oviparous quadrupeds. And the explanation is that 
some of them in their breeding periods, and some all their 
life, live in holes. 

Now the rest ^ have bandy legs because they are soft- 17 
skinned, but the crayfish is hard-skinned and its limbs are 

^ The explanation is of the oblique bending, clearly not of the 
bandiness ; of the latter an explanation is attempted in 713^^9. 

* i.e. the leading feet bend forwards, the hind backwards (with a 
slight turn outwards, H.A. 498* 16). 

^ Itifra, 1^20, this troglodyte habit is used to explain the lateral 
situation of the limbs. 

* Leg. τα ζωντα τον τρόπον τοϋτον{Ζ) as Mich. evidently read ρ, 1 68. 20, 
p. 169. 9. So also Γ reads. 

^ Leg. wepiTTOTaToi YZ, Mich. The passage looks like a dittograph 
of 24 seq. m/ra. In ^ 26 the hardness is used to explain why crabs are 
not bandy. 

* Supra, 712^20. 

'' It has four front legs, two pairs. Cf. //. A. 490^ 6. 

* The argument seems to have been that, by contrast with other 
polypods, crayfish and crabs are not bandy ; crayfish both because 
their skin is hard, and because they would swim worse if bandy ; crabs 
because of their hard skin, even though they live on the ground and 
in holes (P. A. 684» 5). I think that the true text is lost beyond 

ANIMALIUM 17 713* 

for swimming and not for walking (and so are not bandy).* 
Crabs, too, have their h'mbs bent obliquely, but not bandy * 35 
like oviparous quadrupeds and non-sanguineous polypods, 
because their limbs have a hard and shell-like skin, although 
they don't swim but live in holes ; they live in fact on the 
ground. Moreover, their shape is like a disk,^ as compared 
with the crayfish which is elongated, and they haven't 
a tail * like the crayfish ; a tail is useful to the crayfish 30 
for swimming, but the crab is not a swimming creature. 
Further, it alone has its side equivalent to a hinder part,^ 
because it has many leading feet. The explanation of this 
is that its flexions are not forward nor its legs turned in 714° 
under (bandy). We have given above the reason why its 
legs are not turned in under, that is the hardness and shell- 
like character of its integument. 

For these reasons then it must lead off with more than 
one limb,^ and move obliquely ; obliquely, because the 5 
flexion is oblique ; "^ and with more than one limb, because 
otherwise the limbs that were still would have got in the 
way of those that were moving. 

^ These words, και δια ταίτα ου βΐβλαίσωται, are necessary to the 
sense (Mich. 8ia ταϊτα ov βλαισοΰνται, p. 169. 14) and were perhaps in the 
MSS. which Mich. used. 

"^ The MSS. evidently are confused through a desire to omit οΰ; that 
the negative is correct is shown by 714* 1. Mich.'s reading was equiva- 
lent in sense though he gives an absurd explanation by which A. is 
made to mean that crabs were born bandy and do not (like soft-skinned 
creatures) bend bandy as they walk (cf. //.A. 498*21). Can the ex- 
planation be that since a crab is odd enough to walk sideways, its 
legs are not bandy as they appear to be if you take the line of 
progression to be through the eyes ? 

^ Cf. N. A. 525^ 33 where στρογγυλοί' and προμήκης are contrasted. 

* Cf. H.A. S^S^Zi ; P-A. 684^2. 

^ This obscure remark seems to mean that since a crab progresses 
ίΐί TO πλάγιοι', its hind pairs of legs lie on its πλάγια, and thus its πλάγιοι/ 
or flank is equivalent to a hinder part (cf. for πλάγιοι/ in this sense 
P. A. 657'' 21, 670*14). 

" Leg. πλειΌσι in place of the repeated πάσι {κάμ^\ης nXelov Ζ, πλειΌσι 
Υ). It leads with two pairs criss-cross with the relatively hinder pairs 
{supra, 712^ 13). The sense may have been originally that this leading 
makes it go sideways, as is the truth, I think, apart from deeper 
grounds ; or that its going sideways demands this leading, otherwise 
the legs would obstruct one another. Γ embodied both, 'pluribus 

'' This lateral bending would according to A.'s normal theory 
be explained as an arrangement to prevent obstruction (cf. supra, 
713'' 8). 


Fishes of the flat kind swim with their heads twisted, 
as one-eyed men walk ; they have their natural shape 
distorted. Web-footed birds swim with their feet ; because 

lo they breathe the air and have lungs ^ they are bipeds,^ 
but because they have their home in the water they are 
webbed ; ^ by this arrangement their feet serve them 
instead of fins.•* They have their legs too, not like the rest 
of birds in the centre of their body, but rather set back. 
Their legs are short, and being set back are serviceable for 

15 swimming. The reason for their having short legs is that 
nature ^ has added to their feet by subtracting from the 
length of their limbs ; instead of length she gives stoutness 
to the legs and breadth to the feet. Broad feet •^ are more 
useful than long for pushing away the water when they are 

30 There is reason, too, for winged creatures having feet, but 18 
fish none. The former have their home in the dry medium, 
and cannot remain always in mid air ; they must there- 
fore have feet. Fish on the contrary live in the wet medium,"' 
Ti^ and take in water, not air. Fins ^ are useful for swimming, 
but feet not. And if they had both they would be non- 
sanguineous. There is a broad similarity between birds 
and fishes in the organs of locomotion. Birds have their 
5 wings on the superior part, similarly fish have two pectoral 
fins ; again, birds have legs on their under parts and near 

^ Lit. ' respire ' ; πάντα τα αναπνίοντα 'έχει πλίνμονα, Ρ. Α. 669* 6. 

^ Because they must not have more than a quaternion of points of 
motion, cf. P. A. 693^ 5. 

« Ci. P. A. 693^ 6, 694'M. 

^ Cf.P.^. 694^10. 

^ According to the natural principle of organic equivalents, cf. P. A. 
6948-27, ^ 18 ; supra, 710*32 ; and note to 704^ 12. 

" Leg. πλατβΓϊ Ζ as the concord requires ; cf. P, A. 694*^ 5. 
' A. does not pause to ask why a fish can remain balanced in the 
watery medium whereas a bird cannot so remain in the air. He 
accepts the fact that a fish floats at any chosen point. Again, he says 
nothing of the surface presented to the water by the fish, though he 
has touched on the parallel question in respect of birds {supra, 
710^1). In P. A. 695^4 he states that he has raised this question 
elsewhere, so that perhaps it is missing here by some mischance. 

* Cf. P. A. 695'' 21. (Strictly of course these are feet, cf. ch. 5.) 

AN I MALI UM i8 714 

the wings ; ^ similarly, most ^ fish have two fins ^ on the 
under parts and near the pectorals. Birds, too, have a tail 
and fish a tail-fin. 

19 A difficulty may be suggested as to the movements of 
molluscs,^ that is, as to where that movement originates ; 
for they have no distinction of left and right. Now observa- 10 
tion shows them moving. We must, I think, treat all this 
class as mutilated,^ and as moving in the way in which 
limbed creatures do when one cuts off their legs, or as 
analogous with the seal and the bat. Both the latter are 
quadrupeds but misshapen. Now molluscs do move, but 
move in a manner contrary to nature. They are not 15 
moving things, but are moving if as sedentary creatures ^ 
they are compared with zoophytes,'^ and sedentary if classed 
with progressing animals. 

As to right and left, crabs, too, show the distinction 
poorly, still they do show it. You can see it in the claw ; 
the right ^ claw is larger and stronger, as though the right 
and left sides were trying^ to get distinguished.^'^ 

^ Leg. και rots μΐu oi nobes ev re ro'is νπτίοις και iyyvs (^των τΓΤίρύ-γων') 
Tois fie τα nrepvyia εγγΰ? των πρανών το'ις πλείστοίς (Ζ except the WOrds 
των 7ϊ-τ€ρΰγων). Ι think Ζ preserves the original words. The point is : 
(a) the external similarity of the positions of the bird's limbs and the 
fish's paired fins (by contrast with quadrupeds) ; {ύ) that wost fish have 
ventral fins, and those near the pectorals, cf. F.A. 696*3. A. might 
have added the lateral attachment of both wings and fins (supra, 
713* 10). Bacon refers to the passage with approval, Nov. Org. ii. 27. 

For a bird's legs cf. P. A. 695 -''ii ; supra, 714^ 12 ; iox τχρανων (sc. 
πτίρυγίων) cf. H.A. 514^2. Γ is mutilated but confirms Z. 

- Cf. //. A. 489'' 24, 504^ 30 ; P. A. 696» 3, 21 ; stipra, 707* 31, 708^ 3. 

^ Viz. the ventral fins. A. uses nTepvyia only for the paired fins. 

* i.e. Mollusca, excluding Cephalopoda. 

^ Cf. the discussion of Seals and Bats as intermediate and mutilated 
species in H. A. 498* 31 ; P. A. 697^ I et seq. 

* Leg. ώί μ(ν μόνιμα και προί τα π^φνκότα. SUZ have π(φυκότα. 
Mich, has ώ? μΐν τα μόνιμα κα\ πΐφνκότα, and προς τα π. κινητικά. 

"^ Lit. ' growing things ' (or if προσπ(φνκότα be kept, cf. //. A. 487^ 8, 
531* 32 ; G. A. 715^ 17. 'attached things '), of which the sponge is the 
typical species (cf. P. A. oSi'^ 16). In H.A. 548^8 φυόμβνα, usually 
equivalent to τα φυτά (plants) is by a natural extension made to include 
sponges, the lowest of animals. 

* Cf. I/. A. 527^ 5, 590^ 25 ; P. A. 684» 26, 691^ 16 ; Darwin's Descent 
of Man., i. 330. 

' βονλ(σϋ<η. A. says ' intend ' where the modem says ' tend '. 
Nature is often spoken of as trying without necessarily succeeding (cf. 
Z'. ^. 665^ 22). 

'° A.'s speculations upon the commensal habits of some of the so-called 


20 The structure of animals, both in their other parts, 
and especially in those which concern progression and 
any movement in place, is as we have now described. It 
remains, after determining these questions, to investigate 
the problems of Life and Death.^ 

lower forms of life would be very diflferent from those of a modern 
naturalist ; he would not admire such adaptations. 

^ Leg. nepl ζωής κηΐ θανάτου (πΐρ\ Ζ, in margin ζωής). In Ζ, aS 

we have it, G. A. follows ; but as the place of de Motic at least in the 
Collections of A.'s works was not seldom after the former group of 
Parva Natiiralia, and before the group known broadly as 'On Life and 
Death ', this transitional paragraph may have run ' it follows to speak of 
Life and Death ', preluding the final discussions of Parva Naturalia 
and the treatise on Reproduction {G.A.). All MSS. (except Z) and 
Mich, have ' the de An/ma is our next topic ', a remark due perhaps 
to a rearrangement followed by the antiqtia icersio (cf. reference to 
William of Brabant, Dittmeyer, Aristotle H.A. (1907), p. xviii). In 
_ all our Greek MSS. de Anima precedes Parv. Nat. Cf. Parv. Nat. 
464'' 20, 32, 480^ 21 ; and the remarks of Wendland in Comm. in A^. 
Graeca, vol. xxii. i (Preface). 

In P. A. 696^ 12 the two treatises are grouped together as Iv τοΐς nepl 
ποριίας κάΐ κίνησΐω: των ζωών, and perhaps they were arranged thus in 
the archetype of Z. 


98«•— 99b = 698^—699'' o^ etc. = 700^ etc. + refers to a series of 

remarks extending through several sections. 

In the Index, the matter contained between two consecutive figures, 
e. g. 5 and 10, is treated as a section, and each such section is referred to 
by the figure at its beginning. Anything, e. g. between 701^ 5 and 701* 10 
is referred to as 1^5. References to notes are rarely given. 

Absolute, the eternal beautiful, the 
truly and primarily good o^ 30 ; 
not relative to anything beside 

Abstinence from act like act is 
conclusion of a practical syllogism 
1=* 15. V. Actioti. 

Accidental )( by itself = moved by 
another )( self-moved 4^ 20. 

Act, last in chain of causes and 
effects \^\. V. Potency. 

Action )( Thought, practical and 
speculative syllogism i'* 10 ; 
thought sometimes followed by 
act, sometimes not i=* 5 ; minor 
premiseas in speculative syllogism 
may be suppressed, if obvious 
1^25 ; action = conclusion of syl- 
logism 1^20; action or abstinence 
maybe prevented i» 15 ; involves 
a series going back to first step 
1^20; unreflective is rapid, rea- 
son being that minor is suppressed 
1*25; suppression of reflexion or 
inquiry by action of desire i''^30 ; 
ideomotor 1^30; immediateness 
due to physiological automatism 


Active )( Passive 5^25; natural 
correspondence of 2=* 15 ; how 
related to organism 2^ lo. 

Aether, force of movement of 99^ 

Affections, related to heat and cold 
l'' 25 ; corporeal, blind courage, 
panic, erotic 2 =Ί ; cause of physio- 
logical change 1'^ 20. 

Air, serves as fulcrum for wing of 
birds 98^ 15. V. Flight. 

Alteration, a movement = change 

of quality i^ 5 ; incidental to 
movement 1^5; characteristic of 
life i^' 10 ; produced by heat and 
cold i^'iS ; in heart produces 
alteration in members 2^' 20 ; pre- 
cedes involuntary movements 
3^M 5 ; connatural spirit not sub- 
ject to γ• 2ζ. V. Movement. 

Alternate opposition of flexion of 
man's limbs 12^ 10. 

Ambidexterity, man only ambidex- 
trous animal ό'* 2o(note). 

Analogy of function, \vebbed feet 
)_( fins of fish 14=^ 10. 

Animal, parts of, compared to parts 
of automata i^ i, bones = levers, 
sinews = strings i'^ 5 ; movement 
of, difficult in sand or grain (?) 
98'' 15 ; must originate in definite 
part 2^20; kneeless animal (viz. 
seal) 9«• i. v. Movement. 

Ankle, flexion of 12^ 15. 

Apoda, include caterpillars, earth- 
worms ^^ 25 ; why limbs absent 
7^ 15 ; have superior and front 
identical 6=^ 30 ; their superior cor- 
responds with middle of universe 
6^ I ; not erect ό^^ 5 ; if Sanguine- 
ous, move at 4 points η^ 5 ; move- 
ment of, compared with tall man's 
gait η^ 20. 

Appetite v. Faculty ; how related to 
action i^ 30 + . 

Arc greater than chord 9* 30. 

Aristotle, refers to his other works : 
deAnima, 98=^ 10, o^ 5, o'^ 20, 4^ i ; 
de Caelo 99^ 30 ; de Incessu 98'* I ; 
de Partibtis 98^ I, 4^ I, 6^ I, 
14^ 20 ; G.A.i^\\ H. N. 4^ 10, 
6'' I ; Metaphysics 98=^ 10 ; Ραπ'α 

AR. M. A. I. 


Nat. 4^ I, 14^ 20 ; Physics qS'* 10, 
99^ 30, 0=* 25 ; (?) lost work de 
Ntitrimento 2* 10. 

Arms, flexion of, adapted to second- 
ary uses 11^ 10; treated ex. hyp. 
as an organism 2=^ 30. 

Art, syllogism of = Practical i^ 20 
(note), I'"• 35 ; stimulated by appe- 
tite, impulse, desire, wish i^ 35. 

Athletes, jump with dumb-bells 5^* 
1 5 ; swing arms in running 5*15; 
reasons why 5^ 15. 

Atlas, fable of, in physicists' theories 
99^ 25 ; a radius twirling the 
Heavens 99^ 30 ; stands on earth 
99^ I ; force exerted by 99^ i. 

Automata, compared with organisms 
i^'i ; strings and levers of )( sinews 
and bones i'^5; mechanism de- 
scribed i^' I ; how different from 
hving organisms i'^ 10 ; not sub- 
ject to alteration i^ 10. 

Automatism of body 2^ 15 ; chain of 
connexion, imagination — desire 
— affection — organic change 2-'^ 15. 

Back, centre of bony system 7}'' 20. 

Bandiness, related to troglodyte 
habits 13^ 10 ; crayfish not char- 
acterized by i•^ 7.o\ nor crab 13^ 

Bat, a quadruped but misshapen 
14^ 10. 

Batos V. Ray. 

Beautiful, the absolutely = prime 
good o^^ 35. 

Bees, drifting flight of ιο-"^ lo ; un- 
sharded 10^ 10. 

Beetle v. Scarabaeus. 

Before )( Behind v. Dimension. 

Beginning {αρχή) = first step in 
series of acts i ^ 20. v. Origiiial. 

Best possible v. Nature. 

Bipeds, defined by distinction of 
superior from front in movement 
6^ 25 ; superior of = superior 
part of universe 6^^ i ; are erect 
6^ 5 ; man and bird 4^^ 15 ; man 
is most natural of ό'' 5 ; birds, 
how constructed in order to be 
10'' 15 ; peculiar ischia of birds 
10^ 20. 

Birds (Schizoptera), general struc- 
ture of 10* 30; bipeds for erect 
posture 10^ 5 ; superiorlighterthan 
inferior parts 10'' 5 ; forward part 
lighter than hind 12^30; wings 

= quadruped's forelegs 12^ 20 » 
analogy with Fish 14^ 20 ; cannot 
fly without legs, nor walk without 
wings 9^ 25, 12^ 25 ; hunch- 
backed 10^ 15 ; how able to stand 
erect 10^ 15 ; not erect like man 
10^ 30 ; compared with Eques- 
trian Statue 10^ 15 ; structure 
adapted to movement through air 
10^ I ; limb flexions 11^^15; flexion 
at wing base 9^ 30 ; lateral attach- 
ment of wings 13*^ 15 ; pectoral 
muscles, explanation of 10^ i ; 
breast bone \o^ 30 ; wings dif- 
ferent from those of holoptera 
10=^ 15 ; peculiar ischia 12^ 30, 
10^ 20 ; groimd bi?'ds 10^ 10 ; fly 
badly, using legs for tail 10* 5 ; 
ill-developed tail 10* 10; Kaptores, 
strength of wing lo^ 25 ; swim- 
7?iing-birds, webbed feet, why ? 14'* 
10; have lungs 14^ 10; legs set 
back, why? 14^ 10; short legs, 
wide feet 14^ 15, v. Purple Coot, 
Herofi, Water-fowl. 

Bloodless animals, aggregates not 
single wholes like Sanguinea 7^ i ; 
can live long divided, and preserve 
power of locomotion (insects) 7* 
25. -v. Nan- Sanguineous. 

Blushing due to change of tempera- 
ture i^ 30. 

Body, none can be infinite 99^ 25. 

Boreas, artist's representation of 
981^ 25. 

Boundary v. Dimension. 

Boxing, men guard with right hand 

Breast bone of birds lo* 30. 

Breeding habits of polypods and 
oviparous quadrupeds 13^ 20. 

Burdens, why carried on left 
shoulder 5'' 30. 

Cantharus v. Scarabaeus. 
Caterpillars, treated as Apoda 5^ 

25 ; have right and left 5^^ 25 ; 

undulatory-vertical movement 9* 

Centipede, can walk on odd number 

of limbs 8^ 5 ; lives when divided 

73- 30 ; divided parts continue to 

progress 7^ 30. 
Centre, of organism = heart i^ 25 ; 

how related to parts and vice versa 

3^ 25 ; potentially multiple 3^ 30. 


Cephalopods (Mollusca) have front 
and back identical in situation 6'Ί. 

Ceryx (Trumpet-shell) 6^ 15, 

Cestreus, finless species of in lake 
of Siphae, 8=* 5. 

Chafer, drifting flight lo* 10. 

Children, why they cannot stand 
erect 10^ 10 ; growth of 10'' 15 ; 
dwarf-like lo"^ 10. 

Classification of animals according 
to Dimensions 5^ 25. 

Claw of crab, right larger 14^ 15. 

Cold V. Temperature. 

Coleoptera v. Scarabaens, Chafer. 

Combinations of various flexures 
12»• I. 

Compensation, a principle of Nature 
14a 15. 

Conception, like Imagination, pro- 
duces efifect = perceived object 


creates forms therefore 

affections 3^ 20 ; affects body's 
temperature i^ 35 ; same concep- 
tions not always issue in same 
involuntary reflexes 3^^ 35. 

Conclusion = end of syllogism = 
truth seen or act or creation i* 10. 

Congers, movement of y'" 25 ; two 
fins only 8^ i. 

Consciousness, minute changes be- 
low threshold of 2^ i. 

Contraction due to cold i^ 15. 

Convex and Concave t'. Limbs, 
Curvature of; in flexions 12^ 15. 

Coughing = moving a small weight, 
comes under general mechanical 
laws o'^ 25. 

Crab, shape disk-like is'' 25 ; oddest 
of polypods 12^ 15, 13^ 10; ob- 
lique walk of 12'' 15, 13'' 10, 14'' 
5 ; more than one pair of leaders 
13^ 10, 14^ 5 ; walks in a sense 
forwards 12^ 20 ; a pedestrian not 
a swimmer i^,"" 10, 13^ 15, 13'' 
30; reasons for quaint movements 
13^ ID, 14^ 5 ; troglodyte habit 
is'' 25 ; keeps on ground 13'' 25 ; 
absence of tail is'' 25 ; peduncu- 
lar eyes 12'' 15; distinguishes 
right from left in claws 14'' 15 ; 
side of = hinder part, why? 13'' 
20; why not bandy-legged 13'' 5, 
14^ I ; hard integument 13'' 10. 

Crawling, of children 9=* 10 ; of 
wrestlers in palaestra 9* 10. 

Crayfish, elongated in shape 13'' 25 ; 
tail used in swimming 13'' 25; 

not bandy because a swimmer 
13'' 20. 

Criss-cross movement of limbs ex- 
plained 12* 25. V. Moveme7it. 

Crocodile, oviparous 13* 15 ; trog- 
lodyte 13'' 15 ; legs set obliquely 

Crustacea τ>. Crabs., Crayfish. 

Cupid (Eros), artists falsely give 
wings to I* I. 

Custom )( Nature 3^ 35. 

Cylinders (? part of automata) i** 5. 

Definition gives cause 3^ I. 

Desire, formal cause of movement 
3* 5 ; middle term or cause 3^ 5 ; 
moves being moved i'^ i ; causes 
animal to move on occasion of 
sensation or imagination i^ 5 ; 
medium between object and ac- 
tion i^* I ; related to act and art 
impulse i* 35 ; no control over 
sleep, waking, or respiration 
3" 10. 

Dexterity, all animals dextrous 
6* 15 ; man more so than other 
animals 6* 20. v. Right. 

Diagrams used by author 2'' 25, 
3'' 30, 7'' 25, 12^ I +. 

Diameter, movement of radius about 
centre i'' 5 ; efifect of small move- 
ment at centre i'' 25. v. Atlas. 

Differentiation, of animals by dimen- 
sion 6'' I ; into parts necessary 
for animal movement 5* 20 ; 
Cephalopods and Testacea have 
front and back identical 6'' i. 

Dimensions, 3 pairs of 6'' 25 ; su- 
perior )( inferior, fore )( hind, 
right )( left 4'' 20 ; determined by 
function not spatial position 5** 
30, ό'' 15; animals classified by 
5=^ 25 ; apply to all organisms 
4'' 20 ; six in number 5^^ 25 ; 2 
pairs require common original 
to link them 7'' 5 ; life always 
involves superior and inferior ^^ 
25; sovereignty of 6'' 1 5 ; deter- 
mined by function in movement 
ό'' 15 ; superior related to nutri- 
ment, inferior = excremental 
parts S'' I, ό'' 5 ; superior that 
from which food and develop- 
ment flow S** I ; animals have 2 
pairs, superior, inferior, fore and 
hind 5'' 10 ; fore)( hind determined 
by sense perception ^^ \o, 12'' 


15 ; not distinctions relatively to 
movement 6'' 25 ; right and left 
determined by self-movement 5^ 
15; in movement right and left 
first to appear, next superior and 
inferior 7^ i ; bipeds distinct as 
to superior and fore 6=^ 25 ; of 
man dimensions more clear and 
distinct 6^ 25 ; superior and fore 
identical in quadrupeds, polypods, 
and apoda 6°• 30 ; in molluscs left 
and right not distinct 14^ 5 ; front 
and back identical in Testacea 
6^ I ; crabs distinguish right and 
left 14^ 15 ; hind in crabs = side 
1^"° 20; of plants superior the 
root 6^ 5 ; superior and inferior 
inverted z,^ I. 

Divine nature of primum movens 
oi^ 35. 

Domestic cock, tail of 10* 5 ; bad 
flier 10=^ 5. 

Dwarf-like, meaning of term lo^ 15 ; 
children so termed 10^ lo. 

Earth, difficulties concerning im- 
mobility of 99^^ I + ; problem 
postponed 99^ 30 ; finite 99^ 15 ; 
weight of 99^ 15 ; = ground, ful- 
crum for walking and jumping 
98^ 10. 

Earthworms (lit. earth - entrails), 
movement of g'* 25 ; have right 
and left 5^ 25. 

Eels, movement of 7^ 25 ; two fins 
only 8=^ I, 9^ 10. 

Elbow, a local original 2^ 10 ; joint 
2^ 25, 2^ I. 

Elements, how related in compound 
3^ 25. 

Elephant, flexion of legs 12^ 10 ; 
popular error about 9^ 10. 

End V. Li/nit. 

Erect posture, mechanics of 10^ 5 ; 
involves knee joint 9* 10+ ; 
man's upper part long, involves 
long leg 9^ 15 ; bird not truly 
erect like man 10^ 30, 12^ 30. 

Eros V. Cupid. 

Essence of living creature 4^ 15. 

Essentially )( accidentally = by 
itself 4^ 20. 

Evenness in limbs, why necessary 

8=*20 + . 

Excrement determines inferior part 

5^ I. V. Dimension. 
Expansion due to heat 1^ 15. 

Experience appealed to 3=^ 5. 
Experiment, on living animals 8^5, 

14b 10 ; on birds 9^ 25 ; shadow 

on wall 9^* 5. 

Facts )( theory based on or a priori 


Faculties, grouped under mind and 
desire o^' 15 ; purpose equivocal 
o^ 15; judgement o•^ 20; mind 
includes sensation, imagination, 
purpose o^ 15 ; desire includes 
will, impulse, appetite, purpose 
o^ 20. 

Feather wings (of flying insects) 
laterally attached 13^ 15. 

Feet V. Limbs. 

Fins,"function of 9^ 10, 14^ I ; usually 
four (viz. the paired fins) g'' 10 ; 
laterally attached 13^ 15 ; flexion 
at base 9^ 30 ; absence of, in some 
marine animals 8* i+, ()^ 10; 
eel, conger, and cestreus have 
two only 9^ 10; two only in flatfish 
9^ 10 ; analogous to wings 14^^ 20. 

Fire, force of movement of 99^ 25. 

First Philosophy = Metaphysics 
o'' 5. 

Fish, sanguineous, do not respire 
14^ I ; why apoda 14^ i ; fins 
laterally attached 13^ 15 ; flexion 
at base of fins 9^ 30 ; Flatfish use 
two fins 9'' 10 ; compensate for 
missing two 9^^ 15 ; have head on 
one side 14^ 5 ; distorted contra 
naitiram 14=^ 5. 

Flexion, defined 8^ 20 ; necessary 
to movement 11^5; mechanical 
reasons for 11^25+ ; four com- 
binations two by two 12^1 ; mini- 
mum flexion at least necessary 
to movement 9^ 25 ; undulation 
a kind of 9^ 25 ; alternate opposi- 
tion of 12^ 10 ; of limbs in man 
)( bird, man )( vivipara 11^ 10; 
hip, knee, ankle, shoulder, wrist 
12* 15 ; of legs in elephant excep- 
tional 12''^ 10; in birds 9^ 30, 12^ 
20 ; reason for flexion of birds'Iegs 
12^ 30; of oviparous troglodytes 
13* 15+ ; reasons for 13^ i+; 
in polypods oblique 13^ 25+ ; of 
extreme limbs 13^ 5 ; in flying 
insects 9^ 30 ; in apoda, a sub- 
stitute for limbs 7"^ 10 ; four 
flexions = four points of motion 
7^ 10 ; in fish 9^ 30 ; of eels fewer 


flexions in water than on shore, 
cf. snakes 8^ 5. 

Flight, air yields yet resists 12^ 15 ; 
involves flexion 9^^ 5. 

Foot, used technically as = motor 
limb 6^^ 30 ; etymology of 6^ 30. 

Force (Power), vis inertiae 99* 35 ; 
no loss of 99^ 5 ; what inoves 
Heavens must lie beyond 99^^ 10 ; 
possessed by connatural spirit 3^ 5 . 

Form, conceived represents object 
l^ 20 ; = image created by con- 
ception and imagination 3^ 20. 

Forwards, relative to line of vision 
12^ 15. 

Fulcrum, for movement relatively 
fixed 9^^ 25 ; necessary to all 
movement de Motu ch. i, de 
Incessu chs. 3 and 9, 5* 5. 

Function, determines dimensions 5^ 
5 + ; of webbed feet = fins 14=^ 10. 

Galop 123• 30. 

Gecko 13* 15. V. Spotted Lizard. 

Generation v. Movement. 

Geometry used for illustration and 
proof 9^^ I, 15, 20, 30. 

Good, absolute )( relative o^^ 35 ; 
theoretical )( practical o^ 20 ; ac- 
tual )( apparent 0^25 ; apparent 
= pleasant o^^ 25 ; in realm of 
practice is a kind of primum mo- 
vens I* I ; moves being unmoved 
i=* I ; good or possible, premiss 
of practical syllogism i^ 20. 

Goose-skin due to change of tem- 
perature in heart i^ 30. 

Grain slips under feet of mice 

98^ 15. 
Gravity )( Levity 3=^ 25. 
Growth V. Movement. 

Hand, relation to wrist and to stick 
2^ 5, 12^20; determines flexion 
of elbow 1 1*» 10. 

Head, small in birds 10'* 30. 

Heart, seat of soul but distinct from 
it 3^^ I ; centre of organism 3^^ 10 ; 
situated centrally relatively to 
sense and bony system 2^ 1 5 ; 
seat of senses ■^'^ 20 ; correspond- 
ing part in Bloodless animals 3* 
15; change of temperature in, 
related to affections 2^ i ; small 
change in, produces great effect, 
cf. rudder and prow of ship i^ 
25 ; must have a central part 3^ i; 

an individual organism 3^^ 20 ; 
contains vital moisture 3'^ 25 ; in- 
voluntary movement of 3^ 5. 

Heat V. Temperature. 

Heavens = Universe, eternity of 
99^ 20 ; destructible according to 
some theorists 99^ 20 ; mytholo- 
gical account of movement of 
99* 25 ; cannot be moved from 
inside 99^^ 10 ; Homer as witness 
to movement of o^ i. 

Heron, poor flier 10^ 10 ; uses feet 
as substitute for tail 10^ 15. 

Hip, flexion of 12* 15 ; in crawling 
9'* 10; tall men's left hip and 
right shoulder 7^ 20. 

Holoptera (flying insects), flight of 
9^ 30 ; flexion at base of scale 
wing 9^ 30. 

Homer cited as witness in physics 

0=^ I. 

Homology, of Birds, Insects, and 
Fish 13* I ; of \vings to forelegs 
12^ 20 ; of wings and fins 9^ 30 ; 
in Birds and Fish of wings )( fins 
pectoral, legs )( fins ventral, tail 
and tail fin 14^ 5. 

Hop, easier on left leg 5^ 30. 

Horse, galop 12^ 30; in religious 
processions 12^ 30. 

Hymenoptera v. Bees and Wasps. 

Idea produces change in organism 
i^ 20. 

Illustration from two men back 
to back 3^ I. 

Images, of pleasant and painful 
objects reflected in mind 2* 5 ; 
related to memory and anticipa- 
tion 23• 5. 

Imagination, grouped with Percep- 
tion and Conception in relation 
to Desire i^ 25; equivalent to 
Perception in effect 1^ 15 ; pro- 
duces effect of object imaged i'' 
15 ; like sensation produces altera- 
tion and somovement I* 5; creates 
images and therefore affections 3'^ 
20 ; by vivid presentation causes 
alteration 1^15; reflects pleasure 
and pain and so causes tempera- 
ture changes 2^ 5, i^ 35; effect 
upon heart and membrum virile 
3^ 5 ; not mistress of sleep or 
breathing 3'^ 10. v. Faculty. 

Immovable, as fulcrum not con- 
tinuous with the moved 98*^ 15. 


Impossible, necessarily )( contin- 
gently 99^ 1 5 ; to dissolve universe 

Impulse related to action and 
artistic creation I* 35. v. Faculty. 

Incubation related to structure of 
oviparous quadrupeds 13* 20. 

Inference follows immediately on 
conception of premisses i^ 10. 

Inorganic bodies, cannot move 
themselves o^ 5 ; moved by or- 
ganisms o'' 10 ; by mutual impact 
o^ 10 ; fire, earth, etc. o^ 10. 

Insects, flying (Holoptera), are tail- 
less 10* 5 ; lateral attachment of 
wings 13* 15; sharded (Coleo- 
ptera) lo'^ 10 ; frail drifting flight 
of 10^*10 + ; insects )(birds 10^ 20. 

Intellect v. Faculty. 

Intermediate in place of universe 
6^ I (and note). 

Iron used in toys or automata i'' 5. 

Isosceles triangle used to illustrate 
walking 9* 20. 

Joint, function of, in movement 98* 
15, de Incessu chs. 3 and 9 ; me- 
chanism of 2=^ 25 ; involves juxta- 
position of two material points 
98^ 20 ; one potentially, divided 
η act 98''' 25, 2^ 20 ; a beginn ng 
and end 2* 20 ; compared to 
centre of diameter 98^ 20 ; pres- 
sure exerted at 5^ 15 ; athletes 
press against 5^ 15. v. Elbow, 
Knee, Hip, Shoulder. 

Judgement o^ 20. 

Jumping, involves articulation 5*20; 
pressure against upper and lower 
5^ 10 ; a horse's galop is a jump 
12^ 30; animals need no hmbs 
8* 20 ; whole moves at once 8•'^ 
25 + . V. Movement, Animal. 

Knee, flexion of 
to walk 9a I. 

I, 12»• 15; bent 

Lampreys, move in water like snakes 
7^ 25 ; finless 8* i. 

Leech, movement of 9^ 25. 

Left V. Right, Dimension, Move- 

Legs, one or three impossible δ'' l ; 
form isosceles triangle 9^* 20. 

Levers v. Autoinata. 

Light )( Heavy, in nature 3* 25. 

Limbs (= feet, techn.), organ of 
locomotion in animals, why some 
polypods, some apoda? 4^ 10+ ; 
obliquely attached in birds, fish 
and insects 13^ 15 ; curvature of: 
man's legs conΛ'ex )( bird's con- 
cave 4* 20 ; laterally and outwards 
in oviparous quadrupeds 4* 20, 
4^ I ; fore and hind opposed in 
man 4* 20; man's )( viviparous 
quadruped's 4^ 20. v. Flexion. 

Limit (or term), necessary to organic 
movement o'' 10 ; to all inorganic 
motion ο^» lo ; = object or end 
in organic movement o^ 15. 

Lines divided into straight, curved, 
zigzag 9* 5. 

Living things, classified by Dimen- 
sions 5^ 25 +. 

Lizard, oviparous troglodyte 13^ 15 ; 
legs attached and bend obliquely 
13^ 15 ; two kinds mentioned 13* 

Long jump v. Athletes. 

Mammae, relation to leg-flexion 1 1^ 

Man, legs relatively stouter and 
longer 10^ 10 ; mechanism of legs 
and arms 11^ 5; functional ex- 
planation of elbow 11^ 10 ; flexion 
of Hmbs 11^ 15; most natural 
biped 6^ 5 ; moves shoulders when 
walking 9^^ 25 ; has left more de- 
tached, movable, and natural than 
any animal 6* 15 ; better differen- 
tiated in all motor organs and 
dimensions β'* 25 ; tall man's 
figure y'^ 1 5 ; one-eyed man's gait 
14^ 5- 

Marine animals, serpentine move- 
ment like Apoda ashore 7^ 25. 

Mathematics, illustration from 98* 
20 ; motion in, a fiction 98* 25 ; 
point has no magnitude 2^ 30. 

Means )( end 0^25. 

Mechanics of erect posture 10^ S ; 
of flight 10^ I ; of movement 8* 30, 

Membrum virile, an individual 
organism 3^ 20 ; contains mois- 
ture of life 3^ 20 ; involuntary 
motions of 3'^ 5 ; affections cause 
temperature change in 2* i. 

Memory, psychology of 2* 5. 

Mice walking in grain 98•^ 15. 

Middle, term of both ends 2^ 15. 


Minute parts, changes in, are below 
threshold of consciousness 2* i. 

Moisture, life-giving, in heart and 
other member 3^ 20. 

MoUusca, equivocal classification of, 
between sessile and progressive 
animals 14^^ 15 ; are seen to move 
14^ 20; do not differentiate right 
and left 14^ 5 ; contra iiaturafti 
14^ 15. V. Cephalopods. 

Movement, general principles of'. 
a point at rest which is ground 
or original 98* 15, ^l, 9^ 25 ; this 
without the mover and the moved 
99* 5 ; three terms, unmoved 
mover, moved mover, unmoving 
moved 99^ 5 ; of Heavens by 
primum movens 98^ 10, 99^ 25 + ; 
primum movens or supreme good 
immovable 98* 10 ; transcends 
relation o'^ 35 + ; a fiction in 
Geometry 98=* 25 ; objects of 
science immovable 1*10; illustra- 
tions 98* 20, 2^ I + , 9=* I ; single 
not initiated by twofold 99=^ 20 ; 
kinds of, are Translation, Altera- 
tion, Growth o'^ 25 ; Generation 
and Decay hypothetically treated 
as movements o* 30 ; primary 
movement is translation o* 30 ; 
of translation primary kind is 
thrust and pull 4^ 20, 3^ 20 ; of 
inorganic things depends (i) on 
primary causes o* 15, (2) on or- 
ganic bodies o^ 15 ; small central 
movement makes great movement 
at circumference, e.g. rudder and 
ship i^ I, l^ 25 ; circular, of toy- 
wagon 1^10; of automata i^ I. 

animal tnovetnent, definition of, 
and formal cause = desire 3* I, or 
purpose i* 5, 35 ; final cause 
object of desire or intellect = 
practical end o^ 20 ; good, real 
or apparent (pleasure) o'' 25, 1*^30; 
material cause = connatural spirit 

psychology of, sense, imagina- 
tion or intellect cause alteration, 
this causes desire or purpose ο** 
15, 1^5 ; involves alteration i^ 5 ; 
desire, the immediate cause i^ 35 ; 
chain of causation l^ 30 ; same 
conception not always issuing in 
action 3^ 35 ; how inhibited 4=* i ; 
definitely limited by ends o'' 10 ; 
contrast with movement of Uni- 

verse o^ 30 ; kinds of, voluntary, 
involuntary, non-voluntary 3^^ 5 ; 
illustrations 3^ 15 ; sleep, walking, 
breathing, non-voluntary by-pro- 
ducts 3^ 15 ; heart and membrum 
virile move involuntarily 3^ 5. 

psychophysical mechanism of\ 
common centre necessary 7* 10 ; 
the heart the organ of soul 3^* I ; 
series of changes 2*^ 20 ; sensation 
and alteration 2^^ 20 ; connatural 
spirit and its behaviour 3^ 5 +. 

?nechanics of, general problem 
stated 4^ 10, ξ>^ 3o, 1 1^ 20, o» 10 ; 
involves differentiation into parts 
or members, 5* 20 ; fixed point 
98^ 15 -I-, 98^10, 0*5, Ϋ-^,άεΙ^. 
chs. 3 and 9 ; an active and a 
passive 5-^ 20 ; illustration 2^ 30 ; 
flexion necessary 8^ 25 + , 9=* 15, 
9^25,98^15, ii='25 ; hence articu- 
lation 98^ 1 5 ; varieties of, knee, 
shoulder, hip, elbow, \vrist, wing- 
base, ankle, tail-base {v. Flexion) 
98*1, 8^25 + ,9=^ 1 5, 11^5 ; need of 
centre or common original (heart) 
6''20, 2'^I5 ; involves Dimensions 
(q. V.) viz. Right and Left 5^ 15 ; 
original and active = right, passive 
or moved = left 6^ i ; alternation 
S*• 15 ; quaternion or four local 
points of movement 4=^ 10, 12* 15 
et passim ; kinds of, jumping 
γ• 5, 8'*^ 20, 9^ 5 ; crawling 9^* 10 ; 
walking = alternate recovery of 
former shape 8^ 15, 5^ 5 ; in biped 
involves shoulder action, in bird 
presence of wings ψ 25 ; galop = 
a jump 12» 30 ; flight 8'^ 25, 9^ 5, 
de Inc. ch. 10, 98^ 15 ; swimming 
98•^ 15, 13* 5, 9^ 10 ; undulation 
9*25; two kinds, horizontal and 
vertical 9*25, 9'' 15; telescopic 
9^ 25 ; belongs to S.par excellence 
7=* 15 ; of Sanguinea at four points 
43- 10, 6'^ 25, 7* I, 12=^ 15 ; bipeds 
no exception 9^^ 20 ; why even 
number necessary 4^ 10, 8* 25 ; 
diagonal or criss-cross 8^ 15 +, 
4^5, 7^5 15, 123• 25+ ; of Apoda 
de Inc. chs. 7 and 8, 7^ 5 ; of 
Birds de Inc. ch. 10, 9^^ 30, 12^ 25 
(flight is proprium), tail = rudder 
lo"• I ; webbed feet 14'• 5 ; of 
Insects de Inc. ch. 10, 9^ 30 ; 
better on even limbs 8'* 30 ; more 
than four points 8'' 5 ; of Fish, 

AR. M. A. I. A. 


gb JO, y^ 5 ; four flexions, or two 
fins and two flexions, or four fins 
8* 5 ; of flatfish 9^ 15, 14=* 5 ; fins' 
function 14*^ i ; of Centipede and 
Polypods 8b 5 ; of Crab 12^ 15, 
13^^ 10; of Mollusca (proved by 
observation) 14^ 10; contrary to 
Nature 14^ 15 ; Respiration, 
Coughing, Spitting o^ 20. v. 
Dimensions, Flexion, Right and 

Moon, men in, invisible to us gg'' 15. 

Motion, eternal, of universe 98^* 10 ; 
origin of all movement 98* 10. v. 
Movement, Primum Movens. 

Mouth = root of plant 5^ 5. 

Murex (Purpura), 6* 15. 

Mutilated animals, flatfish 14^ 5 ; 
mollusca, seals, bats 14^ 10. 

Mythologists, their fable of Atlas 
99a 25. 

Natation, of snakes 8^ i ; of eels, 
lampreys, etc. 7^30. v. Swimming. 

Natural, man more than other 
animals 6=^ 20 ; man most of 
bipeds 6^ 5 ; right superior to 
left and separate from it natur- 
ally 6=^ 20 ; right naturally same 
in all creatures β'* 10 ; Sanguinea 
more than non-sanguineous 7^ 5. 
Sanguinea naturally move at four 
points 7*^ 5 ; no movement natur- 
ally backward 6^ 30. 

Nature, reasonableness of 3^ 25, 
2'» 20; purposeful 8a 10, 4^15, 1 1'^ 
15 ; Nature )( custom 3"• 35 ; an 
artificer with purpose 2^ 5 , 1 1 » 1 5 ; 
principles of, de Inc. ch. 2 (note) : 
best of possibles relatively to 
essence 4^15, 8*ιο; economy 
I oa 30, 14a 15, 1 6a 15 ; secondary 
purpose 11^30, 14^• 10 ; Bilateral 
symmetry 10^ i ; specialization 6'^ 
15 ; utility 10^ 25, lo'' 20, ii^ 30, 
13^ 25 + ; homology 9^ 30, 14^ i ; 
serial homology 7^ i ; analogy 
5^ I ; sovereignty 6'Mo ; is not 
self-contradictory Iia5; attempts 
or tends, not always successfully 
14^15; orders the parts of an 
organism 3^ i. 

Necessity and impossibility 99^ 15. 

Neck of birds loa 30. 

Non-sanguineous animals, are poly- 
pods 13" 25 ; have part analogous 
to heart 3* 15. %<. Bloodless. 

Object, if imagined or conceived 
acts like real object i*^ 15 ; reasons 

Observation )( Theory 98* 10,7*20; 
appealed to 98^ 15, lo^ 10, ^ 30, 
7a 20, 7^ 15, 14a 5, 14'J 10, &c. 

One-eyed men have head twisted 

14"^ 5• 

Organisms, a kind of commonwealth 
3a 30 ; symmetry of 2^ 10; cen- 
tralized and differentiated 3a 35 ; 
nature of, like man's custom 3a35 ; 
effect on, of mere idea i^ 20 ; how 
originally moved o^ 10 ; structure 
changed by affections l'' 20 ; 
automatism of 3'Ίο ; affected by 
active and passive elements 4a i, 
2ai5 ; alteration in, produced by 
temperature changes i'^ 30, 2a 15 ; 
change from moist to solid, hard 
to soft and vice versa 2* 10 ; cause 
motion of inorganic bodies o^ 10 ; 
illustrations of automatism of ^^ 
30, i'^ 25, i'^ 1 + . 

Original (or origin), αρχή, of move- 
ment always at rest 98^ I ; of 
movement in organic body o•^ 10 ; 
centrally situate to four points 
7a 5 + ; in a common part ϋ° 20 ; 
in superior parts ό** 10 ; of move- 
ment, the right 6'' 15 ; more 
honourable 6^ 10 ; determines 
sovereignty of dimensions 6^ 15 ; 
local originals, how related to 
true centre 7^15; in pairs diagon- 
ally and coordinately arranged 
7a 10; lie in juncture β*' 25 ; in 
birds original of movement from 
wings 12*^ 25. 

Outgrowth upon feather-wings of 
insects loa 20. 

Pain causes changes of body's 
temperature 2a i. 

Palaestra 9a 10. 

Pallor due to change of temperature 
in heart i'^ 30. 

Palpitation 3I• 5. 

Panathenaic procession 12^ 30. 

Parts, necessary division into, for 
movement 5a 20. 

Passive )( Active γ• 2$ ; relation to 
organism 4a i ; must have requi- 
site quantity and quality 4a i. 

Peacock, bad flier loa 5 ; big tail 
loa 5, 20 ; moults tail lo* 20. 

Perception, innate in front, so deter- 


mines front and back 5^^ 10 ; )( 
imagination 1^ 15 ; )( self-actua- 
lization 1*25 ; psychologically = 
imagination and conception 1* 25; 
followed by desire i'^ 35 ; effect 
on heart 2'* 20. 

Periphery, changes at, due to minute 
heart changes i^^ 25 ; blushing, 
pallor, shivers, &c. i^ 30. 

Perpendicular used to explain move- 
ment 8^ 30. 

Place, tripartite division of 6^ i. 

Plants, their superior = inferior part 
of universe 6^ 5 ; no power of 
locomotion 6'^ 5 ; their root = 
mouth of animal 5^ 25, 5^ 5 ; 
root = superior 5^ i, 6^^ 5. 

Pleasure = apparent good o^ 25 ; 
effect on body's temperature 2* I. 

Point, mathematical, has no parts 
2'^ 30 ; in a joint is a magnitude 
2* 30, 2^ 30 ; in potency one, in 
act two 2^ 30 ; in joint )( con- 
natural spirit 2* 10. 

Poles, two in number 99^ 20 ; insub- 
stantial 99* 20 ; of sphere of fixed 
stars conceived in some theories 
as mere points, resultant absurdity 
99^ 20. 

Polypods, non-sanguineous 13=* 25 ; 
have superior and front identical 
6*^ 30 ; superior of, parallel to 
middle of universe 6'' i ; not erect 
6*^ 5 ; intermediate legs attached 
obliquely, flexion upwards 13-' 25 ; 
legs more criss-cross 12^ 10 ; legs 
bandied backwards 13*25 ; flexion 
of two extreme legs 13^ 5 ; some 
always, others when breeding, 
troglodyte 13^ 20 ; can progress 
onoddnumberof]imbs8^5; expla- 
nation of flexion of limbs 13'' 20. 

Popular, error about elephant 9* 10 ; 
explanation of mechanics of flight 

ID» I. 

Possible (or good), premiss of prac- 
tical syllogism i* 20 ; best of 
possibles v. Nature. 

Potency )( Act, of heart -2!^ i<^\ of 
limbs 2=* 20 ; of joint 98* 25, 1^ 30. 

Power V. Force. 

Premiss, conclusion follows at once 
on conception of two premisses i* 
10 ; minor suppressed in action 
as in speculation i^• 25 ; of prac- 
tical syllogism may be the good 
or possible i'*20. 

Primum mobile, manner of move- 
ment o'^ 5 ; moved by primum 
movens o^^ 5. 

Primum movens, at rest and immov- 
able 98'"^ 10, 99^ 5, 99'^ 30 ; how it 
moves primum mobile explained 
in Met. 9S* 10, o^ 5 ; force of, 
greater than inertia of universe 
99^ 5 ; is it part of Heavens de 
Motti ch, 3 ; discussion of, post- 
poned o* 20 ; analogy \vith object 
of desire or practical reason i* i. 

Principles, general, in Natural 
Science v. Nature, Original ; no 
Sanguinea moved at more than 
four points 8*^ 10. 

Prior, mover to moved p^ i ; begetter 
to child o^ I ; nothing prior to 
itself o'^ I. 

Problems, of boat movement 98'' 
20 ; of wind moving boat 98'' 20 ; 
solutions 99* 5 ; of movement of 
universe de Motu chs. 3 and 4. 

Procession, horses in religious 1 2* 

Prow, swerves through wide arc )( 
extremities of organism 1^25. 

Psychology, divisions of soul, viz. 
(a) judgement, (b) desire o'^ 15. 

Pull )( Thrust v. Movement. 

Puppets V. Autonata. 

Purple Coot, bad flyer 10* 10 ; 
characteristic tail 10* 15 ; uses 
legs as rudder 10* 15. 

Purpura 6'^ 15. 

Purpose, partly intellect, partly appe- 
tite o''20 ; moves organism i* 5 ; 
connexion with sense and imagi- 
nation i*^ 5. V. Faculty. 

Pythagoras's theorem 9* I, 9^ 20. 

Quadrupeds, not erect 6^ 5 ; have 
superior and front identical 6* 30 ; 
superior of = middle of universe 
6^ I ; vi-L'iparoHs, flexions of 
limbs 4»2θ, II^IS, 11^ 10; ex- 
planation of 11^ 10 -f ; are San- 
guineous 7-* 20; movement of, com- 
pared with Apoda 7'^ 20 ; limbs 
more criss-cross 4•^ i, 12^ 25-f ; 
stand with legs criss-cross 12'^ 5 ; 
seal and bat 14'Ίο ; suckling and 
sheltering young ii*'3o; ovi- 
parous, lateral attachment of 
limbs 4'^ I, IS»• 15, 13'' 15 ; flexion 
of limbs 12* 10; bandy-legged 
13-^20; troglodytes for breeding 


and shelter 13* 1 5 + . v. Crocodile, 
Lizard, Tortoise, Turtle. 

Radius v. Diameter. 

Raptores z/. Birds. 

Ray (Batos), two fins 9^ 15 ; undula- 
tion of 9'' 15. 

Reason not involved in non-volun- 
tary and involuntary movements 
3^ 5, 3'' 15. V. Movement. 

Respiration, a non-voluntary move- 
ment 3'' 5 ; requires external 
fulcrum o* 20 ; involves move- 
ment of weight o^ 25. 

Rest, prerequisite of movement 98a• 
15 ; point at rest distinct from 
what moves or is moved 98*^ 15 ; 
rest-point in animal =joint 98''^ 1 5, 
98*^ 5, 5^ 5 ; vis inertiae balances 
opposed motion 99''^ 35. 

Right )( Left determined by function 
5'' 15 ; depends on articulation 
into two η^ 5 ; right = original of 
source of movement 5*^15 ; proved 
empirically 5^30, 6^ i + ; identical 
in all animals β»• 10 ; sovereign 
even in apoda 7'' 15 ; more de- 
tached in higher animals, viz. by 
differentiation of special motor 
organs 5^^ 20 ; distinction seen in 
crabs 14'' 15 ; absent in molluscs 
14^ 5 ; right and left symmetrical, 
and moved simultaneously 2^ lo ; 
therefore original of movement not 
in either 2^ 15. v. Dimensions. 

Roots, in plants the superior ^ 5 ; 
== mouth in animals 5'^ 5. 

Rudder, comparison of heart with 
ship's i'' 25. 

Sand, feet give way in 98'' 15. 

Sanguinea, four pomts of movement 
and no more η^ 2o, 11^ 5 ; there- 
fore cannot have wings and arms 
1 1* 5 ; apoda no exception 7^ 5 ; 
die quickly if dismembered 7^20; 
lose power of locomotion 7^ 20 ; 
unlike insects 7^20. 

Scale-wing in holoptera <^ 30. 

Schizoptera v. Birds. 

Seal, a misshapen quadruped 14^ 10. 

Sedentary )( Progressive animals 
\\^ 15. 

Semen, a potency 3'' 20; an indi- 
vidual organism 3^ 20. 

Sensations, seated in heart 2^ 15 ; 
produce alteration in body i^ 15. 

Sense v. Perception. 

Sensorium seated in heart 2^ 20. 

Ship, rudder of, compared to tail 
lo» I. 

Shivers due to change of tempera- 
ture in heart i^ 30. 

Shoulder, flexion of 12a• 15 ; in 
crawling 9^ 10 ; right forward in 
tall men 7^^ 15 ; burdens carried 
on left 5^ 30, ό^* I. 

Siphae, kind of cestreus found there 
8» 5. 

Sleep, a non-voluntary movement 

Snake, disproportionate length de- 
termines limblessness 8^ 5 + ; 
Sanguineous 8=Ί5 ; movement of, 
de Inc. chs. 7 and 8, 9^ 25 ; by 
flexion at four points 7*^ 10 ; criss- 
cross η^ 15, 9*^ 1+ ; flexion in 
joints of body 10^ i ; move in 
alternate curves, concave and 
convex η^ 2o ; have right and left 
in body '^ 25 ; mode of swimming 

Soul, distinct from yet located in 
heart 3''' i ; original cause of move- 
ment 3 Μ ; is it moved ? o'» I ; 
how it moves body o^ 10; com- 
pared to monarch in centre of his 
city 3^ 35 ; not diffused through 
members 3-'• 35. 

Sound, necessarily impossible to be 
seen 99^^ 15. 

Sovereignty, principle of, of supe- 
rior over inferior, right over left, 
front over back €° 10. v. Dimen- 

Spinal column and bony system 
related to heart 2'' 20. 

Spirit, connatural de Motu ch. 10; 
moves being moved 3^^ 5 ; related 
to soul as end point of hmb to 
original point of joint 2=* 10; active 
and passive at once 3* 5 ; heavy 
compared with fire, light with 
other elements 3^* 20 ; how main- 
tained 3=* 5 ; causes movement 
without alteration 3^ 25 ; both 
pulls and thrusts 3* 20 ; excites 
movement and exerts power 3* 
1 5 ; permanent or everchanging ? 
3^ 15 ; expands and contracts 
naturally 3^ 20. 

Spitting = moving a weight o* 25 ; 
no exception to law of movement 


Spotted Lizard (Gecko), oviparous 
troglodyte 13^15; legs attached 
laterally and bend obliquely 13* 

Stars, sphere of fixed, moves in 

circle 99^^ 15 ; continuous 99=* 15. 
Starting-point) (end S^ I. v.Original, 

Statuary, problem of prancing horses 

10'' 15. 
Sternal crest of birds 10*30. 
Stick, compared to detached mem- 
ber 2'' 5 ; mechanical illustration 

2'' I +. 
Straightening defined 8'^ 20. 
Strings, move limbs of puppets i^' I ; 

compared with tendons I^ 5. v. 

Structure, of oviparous quadrupeds 

related to breeding 13=* 20 ; of 

birds )( quadrupeds 12'^ 20. 
Superior )( Inferior v. Dimension. 
Swimming, kind of progression 98* 

5, 98'^ 15 ; water yields as well as 

resists 12" 15 

ivolves flexion 

9•^ 5 ; of apoda 8» I + ; of fish 
13a 5, 14^ I ; of flatfish 9*^5 ; of 
crayfish 13'' 30. v. Natation. 

Syllogism, practical )( speculative 
i^io ; examples of practical l^ 
15 + . V. Action. 

Symmetry of left and right sides in 
organisms 2'^ 10. 

Tail, function of lo^ i ; bends at 
point of attachment 10* l ; com- 
pared with tail fin 14^' 5 ; use of, 
to crayfish 13^' 25. 

Tall men, hollowed back of 7^ 20 ; 
peculiar gait y'' 15 ; throw back 
left hip 7*^ 15. 

Telescopic movement of earthworms 
and leeches 9* 25. 

Temperature of body, changes from 
without and from within 3*^5; 
affected by conception and imagi- 
nation i'^ 35, 2'* 5 ; related to 
pleasant and painful 2» i ; pro- 
duces alteration i'^ 15, 1'^ 25 ; 
effects blushing, shivers, &c. i '^ 30 ; 
causes non- voluntary and in- 
voluntary movements 3'^ 15. 

Testacea, spiral-shaped, have front 
and back identically situated 6^* I ; 
movement of, related to spire 6* 
15; carry shell to right 6^10; 
direction of spire 6=* 10. 

Theory )f Experience 98* 10; must 
agree with empirical data 98* 10. 

Thigh of birds ΐο^ 20, 12'' 30. 

Thought )( Action de Motu ch. 7. 
V. Action. 

Thrust )( Pull v. Movement. 

Tityus, the giant, used to illustrate 
98b 20. 

Tortoises, freshwater, legs laterally 
attached and bend obliquely, 
oviparous, troglodytes 13-'^ 15. 

Toys, child's wagon i*» i +. v. 

Translation, the primary movement 
o"• 30 ; cause of growth and altera- 
tion o^ 30 ; last in chain of causes 
and effects l-*^ i ; caused by con- 
natural spirit 3* 25. 

Troglodyte habits of oviparous 
quadrupeds 13'' 15 +, of crab 13'^ 

Trot, normal movement of horse 
12^ 30. 

Trumpet-shell (Ceryx) 6•Μ5. 

Turtles, legs laterally attached, bend 
obliquely, oviparous, troglodytes 
13'' 15• 

Undulation, mode of movement, 
explained geometrically 9'' i ; used 
by eels and ray 9'' 15 ; tall men 
7'Ί 5 ; snakes 7'^ 5 + , 9'' 25 ; cater- 
pillars 9^*25 ; water animals 7^*25 . 

Universe, movement of 98'' 10; 
eternal 0^30; from without 99*^30; 
dissolution of 99^^ 20 ; difiiculty 
resolved 0=^ 5 ; determining di- 
mension )( function s'' 5, 6^ i +. 

Vessel, clipper built (felucca), prow 
of compared to sternal crest 10=* 
30; rudderless, course of, com- 
pared to drift of insect's flight 10^ 
5 ; cargo boat using oars io=* 20. 

Vivisection 8'' 5, 9^ 25, 14'' 10. 

Wasps, drifting flight of 10^ 10 ; un- 

sharded 10* 10. 
Water, fulcrum for swimming 98'' 


Waterfowl, poor flyers, character- 
istic tail 10* 10 ; use legs as rudder 
10* 15. 

Will V. Faculty. 

Winged animals, why footed 14'* 20. 


Wings )( arms 6^ 25 ; laterally 
attached 13* IS ; )( fins 14* 20 ; 
laterally attached 13* 5; how 
used 9*• 10 ; why impossible to 
man 11^ i ; )( feather wings of 
holoptera 10=^ 15. 

Wish related to action and art 
impulse i* 35. 

Wrestlers, crawling in sand 9^ 10. 

Wrist, flexion of 12^ 15 ; relation to 
hand 2^ i, 5*^ 15 ; to elbow 2^ 10 ; 
leaned upon by running athletes 

Zigzag, kind of line 9* 5 ; shadow 

on wall 9* 5. 
Zoophytes (?), sedentary 14'' 15 ; 

compared with Molluscs 14^ 1 5• 












μίτά δ€ τριτάτοκην avaaaei 


This translation has been made from Bekker's octavo 
text, Oxford, 1837. I have also used Aubert and Wimmer's 
edition, with German translation and notes, Leipzig, 1S60, 
referred to by me as ' AW,'. I must confess to finding this 
work somewhat disappointing ; the translation often fails to 
make the connexion of thought intelligible, and the notes 
are very scanty and sometimes incorrect. Much greater is 
my debt to Dr. Ogle's Aristotle on the Parts of Animals, 
London, 1882 ; without this model before me I should never 
have ventured on so hazardous an enterprise. References 
to his Introduction are given with his name and the Roman 
numeral of the page (e. g. ' see Ogle, p. xxix '), to his notes 
with the pages and lines of the Berlin edition (e.g. 'Ogle on 
641^ 17'). References to the work of G. H. Lewes, 
named Aristotle, are given as ' Lewes ' with the sections 
of the book, which I take this opportunity of remarking 
to be full of scandalous blunders and thoroughly untrust- 
worthy, at least where Aristotle's meaning is concerned. 
The Greek medical writers are referred to by the volume 
and page of Kiihn's edition, the question of their exact 
authorship being of course left open. My endeavour has 
been throughout to represent as exactly as possible what 
Aristotle said or meant to say ; to this I have sacrificed 
all graces of style, comforted a little by knowing that the 
author himself would have been the last man in the world 
to complain. 

Whenever Bekker's reading has been deserted the reading 
preferred is given in a note ; if it has MS. authority I say 
e.g. ' reading άλλο ', if it is a conjecture by another scholar 
the name of the author is added, if it be a new conjecture 
I say ' Read ' or ' I read ' whatever it may be. 

The pleasant duty remains of thanking many friends and 
others who have assisted mc in various ways. In particular 


Professor J. P. Hill has read through the proofs and 
helped me on zoological questions, Dr. George Blacker 
made me several communications on medical points, and 
Dr. Ogle has made me still further his debtor by talking 
over some passages with me and correcting some errors. 
My obligations to others are acknowledged in the proper 
places in the notes. From the Aristotelian point of view 
Mr. W. D. Ross has gone through the translation minutely 
and caused me to improve it in many places. The Index 
has been made by Mr. A. W. Kappel. 

With regard to the information in the notes, I have been 
thankful to get it wherever I could. If some of it is not 
exactly up to date, it is all at any rate two thousand years 
later than Aristotle, and compared to that interval of time 
what are a few years more or less? And, should any man 
of science come fresh to the reading of this treatise, he will, 
I think, be amazed and delighted to see what grasp and 
insight Aristotle displays in handling questions which still 
absorb us after all that time. If we smile at some parts, 
and those very considerable parts, of the discussion, especi- 
ally at all the importance attached to ' form ' and ' matter ', 
and at the curious depreciation of the female sex, let us 
remember that most of these oddities were accepted by no 
less a man than William Harvey, and that Darwin wrote 
with generous enthusiasm concerning another of the zoologi- 
cal works : ' Linnaeus and Cuvier have been my two gods, 
though in very different ways, but they were mere school- 
boys to old Aristotle ' {Life and Letters^ vol. iii, p. 252). 


The arrangement of this treatise is somewhat confused and there is 
much repetition in it. But the following table may give the reader a 
view of the course of the discussion and of the more important subjects 

There are four main parts : — 

Part I (Books I, II down to 737'' 24J 
General view of the subject. 
Section I. The generative organs. 

II. The generative secretions, and the Aristotelian theory of 

III. Miscellaneous, partly developing questions already raised, 
partly introductory to Part II. 

Part II (Book II 737^ 25 to end of Book III) 
Detailed account of generation in the dififerent classes of animals. 

Part III (Book IV) 
Essays on various questions connected with generation. 

Part IV (Book V) 

Development after birth, and distinctions between individuals of the 
same species. 

These four parts are laid out as follows : — 


Section I 

Book I. ch. i. Introduction. 

ii. The sexes and sexual parts, 
iii. Testes and uterus in different classes of animals, 
iv-vii. Male organs in various classes of vertebrates (san- 

viii-xi. Female organs and methods of producing young in 

the vertebrata. 
xii, xiii. Further remarks on the organs of the vertebrata. 
xiv-xvi. Generative organs, sexual and spontaneous genera- 
tion, in the invertebrata. 

Section II 

Book I. χνϋ,χνϋϊ. Semen. Criticism of the Hippocratic theory of 
xix, XX. The catamenia. 
xxi, xxii. The Aristotelian theory of sexual generation, 
xxiii. Conclusion to this Section. 


Section III 

Book II. ch. i. (73i''l8) Reason for the existence of sexes. 

(732* 25) Classification of animals in relation to 

(733^23) Development of the embryo. Praeforma- 
tion and epigenesis. 
ii. The nature of semen. 

iii. * Soul' in the semen and the fertilized germ, 
iv. (737'^8) Note (misplaced .'') on various classes of 


Book II. ch. iv. (737^25) Generation in man and other vivipara. 

(739^33) Development and nutrition of the embryo. 
V. Digression on the necessity of fertilization by the 

vi. Development of the embryo continued, 
vii. (745'' 22) Nutrition of the embryo continued. 

(746* 29) Hybrids and sterility, 
viii. Mules. Birds, 
iii-v. Fish, 
vi, vii. Miscellaneous observations, 
viii. Cephalopoda, &c. 
ix. Insects. 
X. Bees. 

xi. Testacea. Note on the origin of man and quad- 


Book,ii. Causes of sex in the embryo, 
iii. (7678' 36) Heredity. 

(769^ 10) Teratology, 
iv. Teratology continued. Number of young produced 

at a birth. 
v. Superfoetation. 
vi. Varying state of development in the young at birth. 

vii. Mola uteri. 

Book IV. ch. viii. Milk. 

ix. Why animals are born head foremost. 
x. The period of gestation. 


Book V. ch. i. Distinction between characters that exist for a final 
cause and those that exist by ' Necessity '. Con- 
dition of the embryo and of the infant. Differences 
in the eye Sight, 
ii. Hearing, 
iii-v. Hair. 

vi. Colours of animals, 
vii. The voice. 
viii. Teeth, 


I We have now discussed the other parts ^ of animals, both 715* 
generally and with reference to the peculiarities of each 
kind,^ explaining how each part exists on account of such 
a cause, and I mean by this the final cause. ^ 

There are four causes underlying everything : first, the 
final cause, that for the sake of which a thing exists ; 
secondly, the formal cause, the definition of its essence (and 
these two we may regard pretty much as one and the 5 
same) ^ ; thirdly, the material ; and fourthly, the moving 
principle or efficient cause. 

We have then already discussed the other three causes, 
for the definition and the final cause are the same, and the 
material of animals is their parts — of the whole animal the 
non-homogeneous parts, of these again the homogeneous, 10 
and of these last the so-called elements of all matter.^ It 
remains to speak of those parts which contribute to the 
generation of animals and of which nothing definite has 
yet been said,^ and to explain what is the moving or 
efficient cause. To inquire into this last and to inquire into 
the generation of each animal is in a way the same thing ; 15 
and, therefore, my plan has united them together, arranging 

' i. e. the parts not concerned in generation, 

^ i. e. each kind of animals (see de Partibus, ad βη.), kind meaning 
sometimes what we should now call a species, sometimes a class of any 
wider extent. 

^ This is equal to saying : ' the final cause corresponding to each 

■* The final and formal causes are the same in an animal since its 
final cause is simply to exist in the most perfect form possible. 

^ A. assumes all parts to be homogeneous which appear such to the 
naked eye. His division into homogeneous and non-homogeneous 
corresponds to Bichat's distinction of tissues and organs. Bone e. g. is 
homogeneous ; a hand is composed of the homogeneous parts, flesh, 
sinew, bone, &c., and is thus itself heterogeneous. 

•^ Much has been said of them in H.A. however. 


the discussion of these parts last/ and the beginning of the 
question of generation next to them. 

Now some animals come into being from the union of 
male and female, i.e. all those kinds of animal which possess 

ao the two sexes. This is not the case with all of them; though 
in the sanguinea ^ with few exceptions the creature, when 
its growth is complete, is either male or female, and though 
some bloodless animals have sexes so that they generate 
offspring of the same kind, yet other bloodless animals 
generate indeed, but not offspring of the same kind ; such 
are all that come into being not from a union of the sexes, 

25 but from decaying earth and excrements. To speak gener- 
ally, if we take all animals which change their locality, 
some by swimming, others by flying, others by walking, we 
find in these the two sexes,^ not only in the sanguinea but 
also in some of the bloodless animals ; and this applies in 
the case of the latter sometimes to the whole class, as the 
715^ cephalopoda and Crustacea, but in the class of insects only 
to the majority. Of these, all which are produced by union 
of animals of the same kind generate also after their kind, 
but all which are not produced by animals, but from decay- 
5 ing matter, generate indeed, but produce another kind, and 
the offspring is neither male nor female ; such are some of 
the insects.* This is what might have been expected, for if 
those animals which are not produced by parents had 
themselves united and produced others, then their offspring 
must have been either like or unlike to themselves. If 

10 like, then their parents ought to have come into being 
in the same way ; this is only a reasonable postulate 
to make, for it is plainly the case with other animals. 
If unlike, and yet able to copulate, then there would 
have come into being again from them another kind 
of creature and again another from these, and this would 

* i.e. after the other parts, discussed in the de Incessu and de 

^ Animals with red blood. If we exclude red-blooded worms, the 
modern term vertebrates exactly corresponds to the Aristotelian class. 
See Ogle, pp. xxvi, xxvii. The ' few exceptions ' are some fishes which 
will be discussed later. 

'^ The text is corrupt ; I give what Aristotle must have meant. 

* See Ogle, pp. xxvii, xxviii, and ii. i, iii. 9 of this treatise. 

BOOK Ι. I 715* 

have gone on to infinity. But Nature flies from the infinite, 15 
for the infinite is unending or imperfect, and Nature ever 
seeks an end. 

But all those creatures which do not move, as the testacea 
and animals that live by clinging to something else/ inas- 
much as their nature resembles that of plants, have no sex 
an}^ more than plants have, but as applied to them the word 
is only used in virtue of a similarity and analogy. For 20 
there is a slight distinction of this sort, since even in plants 
we find in the same kind some trees which bear fruit and 
others which, while bearing none themselves, yet contribute 
to the ripening of the fruits of those which do, as in the 
case of the fig-tree and caprifig.^ 25 

The same holds good also in plants, some coming into 
being from seed and others, as it were, by the spontaneous 
action of Nature, arising either from decomposition of the 
earth or of some parts in other plants, for some are not 
formed by themselves separately but are produced upon 
other t;rees, as the mistletoe. Plants, however, must be 716^ 
investigated separately. 

2 Of the generation of animals we must speak as various 
questions arise in order in the case of each, and we must 
connect our account with what has been said. For, as we 
said above, the male and female principles^ may be put 5 
down first and foremost as origins of generation, the former 
as containing the efficient cause of generation,"^ the latter 
the material of it. The most conclusive proof of this is 

^ Sponges, sessile ascidians, barnacles, &c. 

"^ For the fascinating phenomena connected with ' caprification ' see 
e. g. Kerner and Oliver, Natural History of Plants^ vol. ii, pp. 160-2 ; 
for the little known or guessed about the sexes of plants before 
Camerarius (1665-1721), Sachs, History of Botany, pp. 376-85 (Eng- 
lish translation, Oxford, 1890). That the palm in particular was male 
and female was a familiar notion, though not resting on any exact 
basis ; a quaint reference to this which has escaped the notice of the 
historian is to be found in Nonnus, Dionysiaca, iii. 142 κα\ tipaeva φύλλα 
π€τάσσαί \ θηΧυτΐρω φυίνικι τιόθον πιστώσατο φοίνιξ. 

^ ' The male ' and ' the female ' are throughout in the neuter, and it 
is impossible to convey their force precisely in English. 

* Lit. ' the beginning of the movement and of the generation.' The 
female contributes the matter which is set in motion and so put into 
form by the semen of the male. 

Β 2 


drawn from considering how and whence comes the semen ; 
for there is no doubt that it is out of this that those 
creatures are formed which are produced in the ordinary 

lo course of Nature ^ ; but we must observe carefully the way 
in which this semen actually comes into being from the 
male and female. For it is just because the semen is 
secreted from the two sexes, the secretion taking place 
in them and from them, that they are first principles of 
generation. For by a male animal we mean that which 
generates in another, and by a female that which generates 

15 in itself; wherefore men apply these terms to the macro- 
cosm also, naming ^ Earth mother as being female, but 
addressing Heaven and the Sun and other like entities as 
fathers, as causing generation.^ 

Male and female differ in their essence ^ by each having 
a separate ability or faculty, and anatomically ^ by certain 

20 parts ; essentially the male is that which is able to generate 
in another, as said above ; the female is that which is able 
to generate in itself and out of which comes into being the 
offspring previously existing in the parent. And since 
they are differentiated by an ability or faculty and by their 

25 function, and since instruments or organs are needed for all 
functioning, and since the bodily parts are the instruments 
or organs to serve the faculties, it follows that certain parts 
must exist for union of parents and production of offspring. 
And these must differ from each other, so that consequently 
the male will differ from the female. (For even though we 

^ As opposed to spontaneous generation and parthenogenesis. A. 
speaks here very loosely, not having yet developed his own view. We 
shall see presently that animals are not formed ' out of the semen at 
all. If we construed σπέρμα by ' seed ' and took it to mean the 
fertilized germ, we should correct the meaning in this sentence, but only 
to wreck upon the next. 

"^ Reading όι/ομά^ουσιΐ'. 

' The influence of the Sun and other heavenly bodies was supposed 
to cause generation of plants, (Sec, in the earth. Thus the Sun generates 
in another. Earth in herself, and A. supposes that this accounts for poets 
and others calling them father and mother. 

* \oyov, their definition, which is also their final cause or raison 
d'etre, the law of their being. This is the important thing, the varia- 
tion of parts being only consequent upon it. 

® Lit. ' according to sense-perception.' The λόγο? is not visible or 
tangible, but the organ, which corresponds to it, is. 

BOOK I. 2 716^ 

speak of the animal as a whole as male or female, yet really 
it is not male or female in virtue of the whole of itself,^ but 
only in virtue of a certain faculty and a certain part — just 30 
as with the part used for sight or locomotion — which part is 
also plain to sense-perception.) 

Now as a matter of fact such parts are in the female the 
so-called uterus, in the male the testes and the penis,'^ in all 
the sanguinea ; for some of them have testes and others the 
corresponding passages. There are corresponding differences 
of male and female in all the bloodless animals also which 716^ 
have this division into opposite sexes. But if in the 
sanguinea it is the parts concerned in copulation that differ 
primarily in their forms, we must observe that a small change 
in a first principle is often attended by changes in other 
things depending on it.^ This is plain in the case of castrated 5 
animals, for, though only the generative part is disabled, 
yet pretty well the whole form of the animal changes in 
consequence so much that it seems to be female or not far 
short of it, and thus it is clear that an animal is not male or 
female in virtue of an isolated part or an isolated faculty. 
Clearly, then, the distinction of sex is a first principle ; at 10 
any rate, when that which distinguishes male and female 
suffers change, many other changes accompany it, as would 
be the case if a first principle is changed."* 

3 The sanguinea are not all alike as regards testes and 
uterus. Taking the former first, we find that some of them 

^ The text is corrupt. Qu. κητα πάν ye το αντον (σώμα) for κατίι παν 
ye το αντό ? 

^ πίριΊ'ίοί. Liddell and Scott need correction on this word. 

^ Lit. 'a small principle being changed, many of the things after 
the principle are wont to change with it.' We see here stated 
clearly enough the distinction between primary and secondary sexual 

* Turning Aristotle's phraseology about ' first principles ' into 
modern language, we should say that the phenomenon of secondary 
sex-characteristics varying in consequence of injury to the primary 
proves that the primary sex-distinction is deeply rooted in the 
organism, and that the secondary characteristics have been acquired 
later in consequence of and in connexion with it. The physical cause 
of the secondary characteristics is probably certain chemical substances 
called ' hormones ' which are secreted by the testes and getting into the 
blood act as a stimulus upon the other parts concerned, making the 
beard to grow, &c. 


15 have not testes at all, as the classes of fish and of serpents, 
but only two spermatic ducts. ^ Others have testes indeed, 
but internally by the loin in the region of the kidneys, and 
from each of these a duct, as in the case of those animals 

20 which have no testes at all ; these ducts unite also as with 
those animals ; this applies (among animals breathing air 
and having a lung) to all birds and oviparous quadrupeds.^ 
For all these have their testes internal near the loin, and 
two ducts from these in the same way as serpents ; I mean 

25 the lizards and tortoises and all the scaly reptiles. But all 
the vivipara have their testes in front ^ ; some of them inside 
at the end of the abdomen, as the dolphin,* not with ducts 
but with a penis projecting externally from them ^ ; others 

30 outside, either pendent as in man or towards the fundament 
as in swine.•^ They have been discriminated more accu- 
rately in the Enquiries about A7iiinals? 

The uterus ^ is always double, just as the testes are always 

two in the male. It is situated either near the pudendum 

(as in women, and all those animals which bring forth alive 

717^ not only externally but also internally, and all fish that 

^ These spermatic ducts or tubes {nopQC) really are testes, but A, 
refuses to call them so, ' because of their shape and their being hollow,' 
see Ogle, note on de Partibus, iv. 697^ 9. And cf. next chapter of this 
work. It is clear, however, that A. knew nothing of the testes of 
the cartilaginous fish, which are not simple hollow tubes but oval firm 

^ By oviparous quadrupeds are meant Reptilia and Amphibia, which 
A. does not separate from each other. (It is a curious thing, however, 
that in this work he never says a word which suggests any reference to 
amphibia, though he must surely have known that frog's eggs are 
altogether different from those of reptiles ; in this respect (as in 
others) the amphibia must be classed with the fishes. Of the ovi- 
parous monotremes, duck-bill and echidna, he was naturally ignorant.) 

^ i.e. they would be in front if the creature stood up like a man. 

^ ' lis restent constamment dans I'abdomen, places a cot^ des reins, 
dans . . . les Cetaces.' Cuvier, Legofis^ xxxiii, ari. i. B. 

^ I omit the corrupt or interpolated words καθάπΐρ ol βάΐς. 

^ ' lis sont serres sous la peau du perinee . . . chez les Pachy- 
dermes '. Cuvier, ibid. 

' H. A. iii. I. 

* This term in A. includes the oviducts. He is wrong in regarding 
either oviduct or true uterus as analogous to the testes, and of the 
ovaries he knew nothing. The uterus (in the modern sense) is single 
in the higher mammalia and in some of the Edentates, but as the 
oviducts are included in the Aristotelian conception of the word the 
statement in the text is verbally correct. 

BOOK Ι. 3 717^ 

lay eggs externally) or up towards the hypozoma ^ (as in 
all birds and in viviparous fishes). The uterus is also 
double in the Crustacea and the cephalopoda, for the mem- 
branes which include their so-called eggs are of the nature 5 
of a uterus. It is particularly hard to distinguish in the 
case of the poulps, so that it seems to be single, but the 
reason of this is that the bulk of the body is everywhere 
similar.^ 10 

It is double also in the larger insects ; in the smaller the 
question is uncertain owing to the small size of the body. 

Such is the description of the aforesaid parts of animals. 

4 With regard to the difference ^ of the spermatic organs 
in males, if we are to investigate the causes of their exist- 
ence, we must first grasp the final cause of the testes.* 15 
Now if Nature makes everything either because it is neces- 
sary or because it is better so, this part also must be for 
one of these two reasons. But that it is not necessary for 
generation is plain ; else had it been possessed by all 

^ The hypozoma is the division between the thorax and the abdomen, 
equivalent to the diaphragm in the mammalia, its analogue in other 
vertebrates, the waist of insects, and so on. In fish, however, it would 
be only an imaginary line. 

"^ Cf. de Pariibus, ii. 654* 1 3, ' the mass of the body consists of a soft 
flesh-like substance.' A. means that the parts are difficult to make 
out, because the whole body is comparatively homogeneous. The 
cephalopoda have only one ovary, but the poulps (octopods) and some 
calamaries have two oviducts ; the sepia and common calamary have, 
however, only one oviduct. For their eggs ' on sait que les oeufs du 
poulpe et du calmar sont rassemblos en petits boudins, par une matiere 
gelatineuse, et ceux de la seiche en grosses grappes comparables k 
celles des raisins, par une matiere ductile'. Cuvier, Lei^ons, xxxvi, 
art. i. 

^ This means the difference observed between males of various kinds, 
especially in that some have testes and others not. 

* Lit. 'of the systasis of the testes,' which I think is only a 
periphrasis. Lewes (§ 425) sneeringly remarks of this that * Aristotle's 
anatomical knowledge was imperfect ; this imperfection stimulated his 
readiness to explain phenomena by final causes '. A. is so far 
absolutely right, and as Lewes published five years after the Origin of 
Species there is really no excuse for him. It is true that A. is 
amusingly wrong in this case ; I have seen his theory ascribed to 
Hippocrates, but have failed to find any reference to it in him ; Lewes 
says it comes from Plato's Ti»iaeus, which it does not ; Galen (vol. iv, 
p. 564) attributes it entirely to Aristotle himself. Harvey told Boyle 
that he was led to his discovery of the circulation by considering the 
final cause of the valves in the veins. 


creatures that generate, but as it is neither serpents have 
testes nor have fish ; for ^ they have been seen uniting and 

20 with their ducts full of milt.^ It remains then that it must 
be because it is somehow better so. Now it is true that 
the business of most animals is, you may say, nothing else 
than to produce young,^ as the business of a plant is to 
produce seed and fruit. But still as,* in the case of nutri- 
ment, animals with straight intestines are more violent in 
their desire for food,"^ so those which have not testes but only 

25 ducts, or which have them indeed but internally, are all 
quicker in accomplishing copulation. But those which 
are to be more temperate " in the one case have not 
straight intestines, and in the other have their ducts 
twisted to prevent their desire being too violent and hasty. 

30 It is for this that the testes are contrived ; for they make 
the movement of the spermatic secretion steadier, preserv- 
ing the folding back of the passages^ in the vivipara, as 
horses and the like, and in man. (For details see the 
Enquiries about Animals?) For the testes are no part of 

35 the ducts but are only attached to them, as women fasten 

stones to the loom when weaving " ; if they are removed 

717'' the ducts are drawn up internally, so that castrated animals 

are unable to generate ; if they were not drawn up they 

would be able, and before now a bull mounting immedi- 

^ The connexion of thought is : ' nor have fish, and fish άυ generate 
sexually (though some deny this), for,' &c. 

^ These ducts are the testes ; see above on chap. 3, and for the 
serpent, on chap. 7. On the alleged copulation of all fishes see note 
on chap. 6. 

^ So says Harvey : ' The egg is the terminus from which all fowls 
have sprung and to which all their lives tend— it is the result which 
nature has proposed to herself in their being.' 

* The connexion is : ' still it is advisable that there should be some 
check upon this process, and as,' &c. 

^ This is true (Ogle, pp. 215, 216), but the analogy is hardly 

^ That A. should ascribe ' temperance ' to an animal is startling, but 
on the virtues of animals see //. A. i, i, nd β?ι., a passage clearly 
written with Plato's Laches xxv in mind. And cf. de Faftibus, 
iii. 675^ 22. 

^ i.e. they keep the duct down in a bent and twisted state, thus 
retarding the passage of semen. Cf Galen, vol. iv, p. 575. The ducts 
are the epididymis and vasa deferentia. 

* H.A. iii, I, which was illustrated by A. with a diagram. 
^ In order to keep the warp steady. 

BOOK I. 4 7n 

ately after castration has caused conception in the cow^ 
because the ducts had not yet been drawn up. In birds 
and oviparous quadrupeds the testes receive the spermatic 5 
secretion, so that its expulsion is slower than in fishes. 
This is clear in the case of birds, for their testes are much 
enlarged at the time of copulation, and all those which pair 
at one season of the year have them so small when this 
time is past that they are almost indiscernible, but during lo 
the season they are very large.^ When the testes are in- 
ternal the act of copulation is quicker than when they are 
external, for even in the latter case the semen is not emitted 
before the testes are drawn up. 

5 Besides, quadrupeds have the organ of copulation, since 
it is possible for them to have it,^ but for birds and the foot- 15 
less animals it is not possible,* because the former have their 
legs under the middle of the abdomen and the latter have 
no legs at all ; now the penis depends from that region 
and is situated there. (Wherefore also the legs are strained 
in intercourse, both the penis and the legs being sinewy.) 20 
So that, since it is not possible for them to have this organ, 
they must necessarily either have no testes also, or at any 
rate not have them there, as those animals that have both 
penis and testes have them in the same situation. 

Further, with those animals at any rate that have ex- 
ternal testes, the semen is collected together before emission, 
and emission is due to the penis being heated by its move- 
ment ; it is not ready for emission at immediate contact as 25 
in fishes.^ 

' This is perfectly possible for a week or two after castration, as 
Prof. Starling tells me. Was it not this unlucky observation which 
led A. to deny the testes their true function? 

^ e.g. 'chez le moineau, son diametre longitudinal est douze fois 
aussi grand h. I'epoque du rut qu'avant cette epoque.' Cuvier, 
Legons, xxiii, ar/. i. c. 

^ And Nature always provides means to an end if it is possible. 

•* This is wrong; some birds have a penis, e.g. the goose, and on 
serpents see chapter 7. A. himself had correctly ascribed a penis 
to the goose in //. A. iii. 509^^ 30, but apparently had either forgotten 
about it or changed his mind. 

^ Apparently A. means that it is an advantage for some reason 
to have the semen collected first, and that this is another final cause 


All the vivipara have their testes in front, internally or 
externally, except the hedgehog ; he alone has them near 
the loin. This is for the same reason as with birds, because 
their union must be quick, for the hedgehog does not, like 
30 the other quadrupeds, mount upon the back of the female, 
but they conjugate standing upright because of their spines.^ 
So much for the reasons why those animals have testes 
which have them, and why they are sometimes external 
and sometimes internal. 

All those animals which have no testes are deficient in 6 

this part, as has been said, not because it is better to be so 

but simply because of necessity,^ and secondly because it 

is necessary that their copulation should be speedy. Such 

718^ is the nature of fish and serpents. Fish copulate throwing 

themselves alongside of the females and separating again 

quickly.^ For as men and all such creatures * must hold 

their breath before emitting the semen, so fish at such 

5 times must cease taking in the sea-water, and then they 

perish easily. Therefore they must not mature the semen 

during copulation, as viviparous land-animals do, but they 

have it all matured together before the time,° so as not to 

be maturing if while in contact but to emit it ready 

10 matured. So they have no testes, and the ducts are 

of the existence of testes. The theory that emission is due to heat 
and the movement of the body is Hippocratic (vol. i, p. 321), A. held 
wrongly that fish copulate by throwing themselves alongside of one 
another. See chap. 6. 

^ It is true that the testes of a hedgehog, as of several other 
insectivora, which have no spines, are ' near the loin.' I do not know 
whether the statement about the hedgehog's attitude is true ; from 
Dobson's Monograph of the Inseciivora it appears that nobody 
knows very much about their breeding ; Professor Hill, however, tells 
me that the spiny echidna is believed to copulate ventre ά ventre, 
and it seems probable that this is true also of the hedgehog. Cf. 
H.A.v. 2. See Addenda. 

^ Referring to the first argument in chap. 5. 

^ A. often repeats this, but it is of course totally untrue of the great 
majority of fish, in which the female deposits the eggs unfertilized and 
the male fertilizes them afterwards by shedding his milt upon them. 
A. knew of this latter process, but regarded it as merely supplementary 
to the supposed original copulation. 

^ i. e. air-breathers. 

^ Qu. αλλά προ της ωρης for αλλ' νπο rrjs a>pas ? 

* Reading πίτταν for noulv (AW.). 

BOOK I. 6 718' 

straight and simple. There is a small part similar to this 
connected with the testes in the system of quadrupeds, for 
part of the reflected duct is sanguineous and part is not ; 
the fluid is already semen when it is received by and 
passes through this latter part, so that once it has arrived 
there it is soon emitted in these quadrupeds also.^ Now 
in fishes the whole passage resembles the last section of the 15 
reflected part of the duct in man and similar animals. 

7 Serpents copulate twining round one another, and, as 
said above, have neither testes nor penis,'^ the latter because 
they have no legs, the former because of their length,^ but 
they have ducts like fish ; for on account of their ex- 20 
treme length the seminal fluid would take too long in its 
passage and be cooled if it were further delayed by testes. 
(This happens also if the penis is large ; such men are less 
fertile than when it is smaller because the semen, if cold, is 
not generative, and that which is carried too far is cooled.) 25 
So much for the reason why some animals have testes and 
others not. Serpents intertwine because of their inaptitude 
to cast themselves alongside of one another. For they are 
too long to unite closely with so small a part and have no 
organs of attachment, so they make use of the suppleness 30 
of their bodies, intertwining. Wherefore also they seem to 
be slower in copulation than fish, not only on account of 
the length of the ducts but also of this elaborate arrange- 
ment in uniting. 

8 It is not easy to state the facts about the uterus in 35 
female animals, for there are many points of difference. 
The vivipara are not all alike in this part ; women and all 

^ This is more clearly expressed in H.A. iii. i ' The liquid is still 
sanguineous in the duct adhering to the testis, though less so than in 
the passages above from the aorta, but in the ducts reflected into the 
channel of the penis the liquid is white.' 

^ So far from having none, they have two. Cuvier, Legofts, 
xxxiv, seci. 3, art. i. Treviranus took them to be urinary vessels 
in the chamaeleon ; perhaps A. made some similar mistake. 

^ The testis of course is elongated along with the rest of the body, 
and, as it was just because of this elongation that A. refused to 
recognize it as a testis, his statement is in a sort of way correct. 


the vivipara with feet have the uterus low down by the 
yiS'' pudendum, but the cartilaginous viviparous fish have it 
higher up near the hypozoma. In the ovipara, again, it is 
low in fish (as in women and the viviparous quadrupeds), 
high in birds and all oviparous quadrupeds.^ Yet even 
5 these differences are on a principle. To begin with the 
ovipara, they differ in the manner of laying their eggs, 
for some produce them imperfect, as fishes whose eggs 
increase and are finally developed outside of them.^ The 
reason is that they produce many young, and this is their 

lo function as it is with plants. If then they perfected the 
egg in themselves they must needs be few in number, but 
as it is, they have so many that each uterus seems to be an 
egg, at any rate in the small fishes•^ For these are the 
most productive, just as with the other animals and plants 

15 whose nature is analogous to theirs,^ for the increase of 
size turns with them to seed.^ 

But the eggs of birds and the quadrupedal ovipara ^ are 
perfect when produced. In order that these may be pre- 
served they must have a hard covering (for their envelope 
is soft so long as they are increasing in size), and the shell 
is made by heat squeezing out the moisture from the earthy 

20 material ; consequently the place must be hot in which this 
is to happen. But the part about the hypozoma is hot, as 
is shown by that being the part which concocts the food. 
If then the eggs must be within the uterus, then the uterus 
must be near the hypozoma in those creatures which pro- 
duce their eggs in a perfect form. Similarly it must be low 
down in those which produce them imperfect, for it is 
profitable that it should be so. And it is more natural for 

25 the uterus to be low down than high up, when Nature has 

•^ //z'^/t and /o7t> in A. generally mean towards the head and away 
from it. 

^ The eggs do increase after oviposition, but it is only due to 
imbibition of water. 

^ i. e. each oviduct is so filled with roe that it seems a solid mass. 

* This means 'small compared with other members of the same 
class'. Cp. iv. 771'^ 25. 

* i. e. that which goes to increase the bulk of the larger is diverted to 
producing seed in the smaller. An instance of the so-called ' law of 
organic equivalents ' ; see Ogle, p. xvi. 

" True of Reptilia. As usual A. ignores Amphibia. 

BOOK I. 8 718" 

no other business in hand to hinder it ; for its end is low 
down, and where is the end, there is the function, and the 
uterus itself is naturally where the function is.^ 

9 We find differences in the vivipara also as compared with 
one another. Some produce their young alive, not only 
externally, but also internally,^ as men, horses, dogs, and all 30 
those which have hair,^ and among aquatic animals, dol- 
phins, whales, and such cetacea.'' 

10 But the cartilaginous fish and the vipers produce their 
young alive externally, but first produce eggs internally. 
The egg is perfect,^ for so only can an animal be generated 
from an egg, and nothing comes from an imperfect one. 
It is because they are of a cold nature, not hot as some 35 
assert,*^ that they do not lay their eggs externally. 

II At least they certainly produce their eggs in a soft 
envelope, the reason being that they have but little heat 
and so their nature does not complete the process of drying 

^ i. e. the function of the uterus is to give birth to young, but this 
function is performed low down in the body ; therefore naturally the 
uterus is low. But if Nature finds it desirable to cover the egg with 
a hard shell, she moves the uterus or oviducts higher up to secure the 
heat required for this purpose. Therefore the uterus of fish may 
remain low in its natural position, but with birds and reptiles it must 
go higher up. 

* End,' ne'pas. Does A. mean ' end ' in a physical sense or does 
he mean ' aim and object ' ? He appears to be quibbling on both 

* This odd phrase is often used to denote animals which are 
viviparous without first producing an egg internally. 

^ i. e. all mammalia except the cetacea. 

* δίλφίι/ί? T€ Koi φάλαιναι και τα τοιαύτα κήτη. Cf. Η. Α. vi. 566^ 2. The 

exact meaning is uncertain ; the obvious thing is to suppose that 
όνλφΐνίί is a generic term for the smaller, φαΚαινσι for the larger 
cetaceans ; but then what are the others, τα τοιαύτα ? As a specific 
term, it is ag^'eed that δΐ'λφίς is Delphinus delphis, but φάλαινα is 
supposed by AW. to be Delfhitius tiirsiops, by Ogle the sperm-whale, 
while Sundevall declines to decide on anything definite. 
^ i. e. does not increase after oviposition. 

* No doubt somebody had said the cartilaginous fishes (sharks and 
rays) were hot because they were viviparous. A. liked to test theory 
by fact, though he may leave much to be desired himself. His own 
views on the heat and cold of various animals are excessively strange ; 
see Ogle, pp. xxii seqq. 


the egg-shell. Because, then, they are cold they produce 
719^ soft-shelled eggs, and because the eggs are soft they do not 
produce them externally ; for that would have caused their 

The process is for the most part the same as in birds, for 
the egg descends and the young is hatched from it near the 
vagina, where the young is produced in those animals which 

5 are viviparous from the beginning.^ Therefore in such 
animals the uterus is dissimilar to that of both the vivipara 
and ovipara, because they participate in both classes ; for it 
is at once near the hypozoma and also stretching along 
downwards in all the cartilaginous fishes. But the facts 
about this and the other kinds of uterus must be gathered 

10 from inspection of the drawings of dissections and from the 
Enquiries.^ Thus, because they are oviparous, laying 
perfect eggs, they have the uterus placed high, but, as being 
viviparous, low, participating in both classes. 

Animals that are viviparous from the beginning all have 
it low, Nature here having no other business to interfere 
with her, and their production having no double character. 
Besides this, it is impossible for animals to be produced 

15 alive near the hypozoma, for the foetus must needs be heavy 
and move, and that region in the mother is vital and would 
not be able to bear the weight and the movement. Thirdly, 
parturition would be difficult because of the length of the 
passage to be traversed ; even as it is there is difficulty 
with women if they draw up the uterus in parturition by 

20 yawning or anything of the kind, and even when empty it 
causes a feeling of suffiDcation if moved upwards. For if 
a uterus is to hold a living animal it must be stronger than 
in ovipara, and therefore in all the vivipara it is fleshy, 
whereas when the uterus is near the hypozoma it is mem- 

25 branous. And this is clear also in the case of the animals 
which produce young by the mixed method, for their eggs 
are high up and sideways, but the living young are produced 
in the lower part of the uterus. 

^ i.e. which produce young without any &gg at all. A. of course 
knew nothing of the mammalian ovum. 

"^ H.A, iii. I, where we are again referred to the drawing. 

BOOK I. II 719^ 

So much for the reason why differences are found in the 
uterus of various animals, and generally why it is low in 
some and high in others near the hypozoma. 30 

12 Why is the uterus always internal, but the testes some- 
times internal, sometimes external ? The reason for the 
uterus always being internal is that in this is contained the 
egg or foetus,^ which needs guarding, shelter, and matura- 
tion by concoction, while the outer surface of the body is 
easily injured and cold. The testes vary in position ^ because 
they also need shelter and a covering to preserve them and 719^ 
to mature the semen ; for it would be impossible for them, 
if chilled and stiffened, to be drawn up and discharge it. 
Therefore, whenever the testes are visible, they have a cuti- 
cular covering known as the scrotum. If the nature of the 5 
skin is opposed to this, being too hard to be adapted for 
enclosing them or for being soft like a true ' skin ', as with 
the scaly integument of fish and reptiles, then the testes 
must needs be internal. Therefore they are so in dolphins 
and all the cetacea which have them,^ and in the oviparous 10 
quadrupeds among the scaly animals. The skin of birds 
also is hard so that it will not conform to the size of 
anything and enclose it neatly. (This is another reason 
with all these animals for their testes being internal besides 
those previously mentioned ^ as arising necessarily from the 
details of copulation.) For the same reason they are 15 
internal in the elephant and hedgehog, for the skin of these, 
too, is not well suited to keep the protective part separate.^ 
[The position '^ of the uterus differs in animals viviparous 
within themselves and those externally oviparous, and in 
the latter class again it differs in those which have the 
uterus low and those which have it near the hypozoma, as 20 

^ TO γινόμ^ρον, lit, ' the thing that is coming into being *. 

^ Supply ' but if external are specially provided for '. 

' A. seems not to be certain whether all cetacea have testes ; 
perhaps he only knew of them in the dolphin and thought it unsafe to 

* See chap. 5 of this book. 

^ Another reason has been already given for the hedgehog, chap. 5. 

® This paragraph is an incorrect reminiscence of preceding chapters, 
and should be ejected. 


in fishes compared with birds and oviparous quadrupeds. 
And it is different again in those which produce young in 
both ways, being oviparous internally and viviparous ex- 
ternally. For those which are viviparous both internally 
25 and externally have the uterus placed on the abdomen, as 
men, cattle, dogs, and the like, since it is expedient for the 
safety and growth of the foetus that no weight should be 
upon the uterus.] 

The passages also are different through which the solid I3 

?,o and liquid excreta pass out in all the vivipara. Wherefore 

both males and females in this class all have a part whereby 

the urine is voided, and this serves also for the issue of the 

semen in males, of the offspring in females. This passage is 

situated above ^ and in front of the passage of the solid 

720^ excreta.2 The passage is the same as that of the solid 

nutriment ^ in all those animals that have no penis, in all 

5 the ovipara, even those of them that have a bladder, as the 

tortoises.^ For it is for the sake of generation, not for the 

evacuation of the urine, that the passages are double ; but 

because the semen is naturally liquid, the liquid excretion 

also shares the same passage.^ This is clear from the fact 

^ Perhaps this means that the bladder is nearer the head than is the 
anus. But I suspect confusion of the text in all this passage. 

* Reading (τον) της ξηρά: τροφής with the Aldine (AW.). Here 
follows in the MSS. another interpolation connected with that at the 
end of chap. 12. ' Ovipara laying imperfect eggs, as the oviparous 
fishes, have the uterus not under the abdomen but near the loin. For 
the growth of the egg does not hinder this, because the growing 
creature is perfected and develops externally.' 

^ Omitting και and reading τω (AW.). 

* A. held wrongly that no animals have a bladder except mammals 
and tortoises. Therefore he would expect the tortoises to have a 
separate urinary passage, like the mammals, and is surprised that they 
have not. 

^ See Flower and Lydekker, Mammals^ p. 118. 'The canal,' of 
the penis in the monotremata or lowest mammalia, ' is open at the 
base and brought only temporarily in contact with the termination of 
the vasa deferentia, so as to form a seminal urethra when required ; 
but it never transmits the nrifiary secretion. This condition is a 
distinct advance on that of the Sauropsida ' (birds and reptiles) ' in the 
direction of the more complex development of these parts in most of 
the other mammalia', i. e. the penis has been developed 'for the sake 
of generation ' and only took on the transmission of the urine as an 
afterthought. Though the reason A. gives for his statement in the 

BOOK I. 13 720» 

that all animals produce semen/ but all do not void liquid 10 
excrement. Now the spermatic passages of the male must 
be fixed and must not wander, and the same applies to the 
uterus of the female, and this fixing must take place at either 
the front or the back of the body. To take the uterus first, it 
is in the front of the body in vivipara because of the foetus, 15 
but at the loin and the back in ovipara. All animals which 
are internally oviparous and externally viviparous are in 
an intermediate condition because they participate in both 
classes, being at once oviparous and viviparous. For the 
upper part of the uterus, where the eggs are produced, is »o 
under the hypozoma by the loin and the back, but as it 
advances is low at the abdomen ; ^ for it is in that part that 
the animal is viviparous. In these also the passage for solid 
excrement and for copulation is the same, for none of these, 
as has been said already, has a separate pudendum. 

The same applies to the passages in the male, whether 25 
they have testes or no, as to the uterus of the ovipara. For 
in all of them, not only in the ovipara, the ducts adhere to 
the back and the region of the spine. For they must not 
wander but be settled, and that is the character of the 
region of the back, which gives continuity and stability. 30 
Now in those which have internal testes, the ducts are 
fixed from the first, and they are fixed in like manner ^ if 
the testes are external ; * then they meet together towards 
the region of the penis. 

The like applies to the ducts in the dolphins, but they 
have their testes hidden under the abdominal cavity. 35 

We have now discussed the situation of the parts con- 
tributing to generation, and the causes thereof. 720'' 

14 The bloodless animals do not agree either with the 
sanguinea or with each other in the fashion of the parts 

next sentence is quaint enough, yet how astonishing that he should 
have hit upon the truth ! 

^ A. is here thinking of the higher animals. 

'^ The text appears corrupt. Qu. προϊούσα or προϊόντων for προϊούσης ? 

^ Only not from the first. 

* By omitting Άμα toIs πόροις I hope I have restored sense to 
Aristotle ; to combine Greek and sense in the received text would 
puzzle Diels himself. 


contributing to generation. There are four classes still left 
5 to deal with, first the Crustacea, secondly the cephalopoda, 
thirdly the insects, and fourthly the testacea. We cannot 
be certain about all of them, but that most of them copu- 
late ^ is plain ; in what manner they unite must be stated 

lo The Crustacea copulate like the retromingent quadrupeds,^ 
fitting their tails to one another, the one supine and the 
other prone. For the flaps attached to the sides of the tail ^ 
being long prevent them from uniting with the belly against 
the back. The males have fine spermatic ducts, the females 

15 a membranous uterus alongside the intestine, cloven on 
each side, in which the egg is produced.^ 

The cephalopoda entwine together at the mouth, pushing 15 
against one another and enfolding their arms. This atti- 
tude is necessary, because Nature has bent backwards the 
end of the intestine and brought it round near the mouth, 

20 as has been said before in the treatise on the parts of 
animals.^ The female has a part corresponding to the 
uterus, plainly to be seen in each of these animals, for it 
contains an egg which is at first indivisible to the eye ^ but 
afterwards splits up into many ; each of these eggs is im- 
perfect when deposited, as with the oviparous fishes. In 

25 the cephalopoda (as also in the Crustacea) the same passage 
serves to void the excrement and leads to the part like a 
uterus, for the male discharges the seminal fluid through 
this passage. "^ And it is on the lower surface of the body, 
where the mantle is open and the sea-water enters the 

^ Reading on συνδυάζεται. 

^ Cf. //.A. vi. 31, 33. But the statement there made about retro- 
mingent quadrupeds is neither true nor, if it were, does it illustrate the 
Crustacea. For A. did not hold that one of these quadrupeds is 
supine and the other prone. 

^ i. e. in the female. Cf. de Pa7'tibus, iv. 684^^ 20. 

* This description applies only to the macrurous Crustacea ; of the 
crabs a separate account is given in H. A. v. 7. 

^ de Partibus, iv. 9. 

^ The eggs of the poulps and calamaries are compacted together 
in the ovary so that they look like a homogeneous mass (J. P. Hill). 
Similarly A. speaks elsewhere of the roe of a fish as an egg. 

^ Reading provisionally το γαρ cippev τον θορον άφίησι δια τοΰ πόρου 
τούτον, (στ\ δ' (AW.). 

BOOK I. 15 72< 

cavity. Hence the union of the male with the female 
takes place at this point, for it is necessary, if the male dis- 30 
charges either semen or a part of himself or any other 
force, that he should unite with her at the uterine passage. 
But the insertion, in the case of the poulps, of the arm of 
the male into the funnel of the female, by which arm the 
fishermen say the male copulates with her, is only for the 
sake of attachment, and it is not an organ useful for genera- 35 
tion, for it is outside the passage in the male and indeed 
outside the body of the male altogether.^ 

^ This passage refers to one of the most astonishing phenomena in 
zoology, the so-called * hectocotylization ' of the di-branchiate cephalo- 
poda. The fishermen were right and Aristotle is wrong. The male has 
one arm modified to form a generative organ, which is charged with 
spennatophores and thrust into the funnel of the female ; in three 
genera of the Octopodidae (poulps) it actually comes off from the male 
altogether and remains within the mantle of the female. See Lewes, 
pp. 197-201 ; Cambridge Natural History, \Q)\. iii, pp. 137-40. Lewes 
has an easy task in demolishing the moderns \vho asserted that A. 
knew all about the hectocotylus, but he knew nothing of this decisive 
passage in which A. definitely says the fishermen are wrong. The 
Cambridge Nat. Hist, is also misleading on this point. 

Aristotle's argument against the fishermen, however, is apparently 
conclusive, and he seems justified on the evidence before him. To this 
day it is not known how the spermatophores ever get into the arm 
(Arnold Lang, Textbook of Cotuparaiive Anatomy, Eng. ed. , Pt, ii, 
p. 242). A. saw the apparent impossibility involved ; the arm does not 
connect with the vasa deferentia or with the funnel of the male through 
which the generative product must pass, and it is no wonder that he 
thought this decisive against the theory of the fishermen. He only 
deserves credit for doing so. 

It will be seen that several important words have to be supplied in 
the last sentence of the translation. The obvious meaning would be 
that the arm is outside the 'uterine passage' or body of the female. 
But A. does not deny that it is thrust into the funnel of the 
female ; he knows that it is but thinks this is only to attach the 
male to the female. His position is this : the male and female 
unite by embracing mouth to mouth ; in this position the funnels 
of both come in contact and the generative fluid passes from 
the vasa deferentia through the funnel of the male into that of 
the female and then into her oviducts. But the hectocotylus 
arm is outside this passage altogether, it does not connect with the 
funnel of the male, and therefore though it is thrust into the funnel of 
the female it cannot convey the fluid into it, because, as he means to 
say, it is not in the funnel or passage of the 7nale nor in the male body 
at all but only an outgrowth from the head. 

The words ' or a part of himself certainly seem to imply the actual 
detachment of the hectocotylized arm, the ' peculiar marvel ' which 
Lewes denies that A. had ever heard of. The loss of the arm accounts 
for the fact that ancient representations of octopods sometimes have 
only seven arms. 

C 2 


Sometimes also cephalopoda unite by the male mounting 
721^ on the back of the female, but whether for generation or 
some other cause has not yet been observed. 

Some insects copulate and the offspring are produced l6 
from animals of the same name, just as with the san- 
5 guinea ; such are the locusts, cicadae, spiders,^ wasps, and 
ants. Others unite indeed and generate ; but the result is 
not a creature of the same kind, but only a scolex,^ and 
these insects do not come into being from animals but from 
putrefying matter, liquid or solid ; such are fleas, flies, and 
cantharides. Others again are neither produced from ani- 

10 mals nor unite with each other ; such are gnats, ' conopes ',^ 
and many similar kinds. In most of those which unite 
the female is larger than the male. The males do not 
appear to have spermatic passages. In most cases the 
male does not insert any part into the female, but the 
female from below upwards into the male ; this has 

15 been observed in many cases* (as also that the male 
mounts the female), the opposite in few cases ; but 
observations are not yet comprehensive enough to enable 
us to make a distinction of classes. And generally it is 
the rule with most of the oviparous fish and oviparous 
quadrupeds that the female is larger than the male because 

20 this is expedient in view of the increase of bulk in con- 
ception by reason of the eggs. In the female the part 
analogous to the uterus is cleft and extends along the 
intestine, as with the other animals ; in this are produced 
the results of conception.. This is clear in locusts and all 

25 other large insects whose nature it is to unite ; most insects 
are too small to be observed in this respect. 

Such is the character of the generative organs in animals 

^ Spiders were included among insects until the time of Lamarck 

'^ See iii. 9 and notes. 

' ϊμπίδΐς re καΐ κωνωπΐί. One cannot say exactly what insects are 

* Though A. often insists on this, it is scarcely necessary to say that 
there is not a word of truth in it, any more than in the statements 
about spontaneous generation of insects. All insects copulate in the 
usual way, and the males have * spermatic passages ' which A. could not 
make out. 

BOOK I. i6 721^ 

which were not spoken of before.^ It remains now to speak 
of the homogeneous parts concerned, the seminal fluid and 
milk. We λνϋΐ take the former first, and treat of milk 

17 Some animals manifestly emit semen, as all the san- 30 
guinea, but whether the insects and cephalopoda do so is 
uncertain. Therefore this is a question to be considered, 
whether all males do so, or not all ; and if not all, why 
some do and some not ; and whether the female also con- 
tributes any semen or not ; and, if not semen, whether she 721'' 
does not contribute anything else either, or whether she 
contributes something else which is not semen. We must 
also inquire what those animals which emit semen con- 
tribute by means of it to generation, and generally Avhat is 
the nature of semen, and of the so-called catamenia in all 5 
animals which discharge this liquid. 

Now it is thought that all animals are generated out of 
semen, and that the semen comes from the parents. Where- 
fore it is part of the same inquiry to ask whether both 
male and female produce it or only one of them, and to ask 
whether it comes from the whole of the body ^ or not from 
the whole ; for if the latter is true it is reasonable to sup- 10 
pose that it does not come from both parents either.^ 

M.e. in the de Partibus. ^ iv. 8. 

^ This was the Hippocratic view, held also by Democritus, and very 
similar to Darwin's famous ' pangenesis '. (See his Vanaiwn, chap. 27, 
especially note 42 in the second edition.) It is particularly interesting 
to observe that Hippocrates like Darwin accounted by this theory for 
the supposed inheritance of acquired characteristics. (Hipp., vol. i, 

p• 551)•. 

■* This does not follow rigorously, but as the Hippocratic view com- 
bines two distinct theories, of which A. accepts neither the one nor the 
other, he thinks that if he can overset the one it will afford a presump- 
tion that the other is wrong also. 

His arguments against pangenesis, if we may adopt the Darwinian 
term for the similar though not identical theory, are of varying validity, 
but he is certainly right in the main ; see e.g. Wilson, Cell in Develop- 
ment and In/ieHtante, chap. 9 ; Poulton, Essays on Evohetion, p. 1 27. 
On the other hand, when A. denies that the female contributes semen, 
though he may be right in a certain sense, he is in truth fundamentally 
wrong, for his position is that the mother does not contribute anything 
resembling the semen of the male, whereas the ovum is just as 
important as the spermatozoon and carries inheritance equally with it. 


Accordingly, since some say that it comes from the whole 
of the body, we must investigate this question first. 

The proofs from which it can be argued that the semen 
comes from each and every part of the body may be 

15 reduced to four. First, the intensity of the pleasure of 
coition ; for the same state of feeling is more pleasant if 
multiplied, and that which affects all the parts is multiplied 
as compared with that which affects only one or a few. 
Secondly, the alleged fact that mutilations are inherited, 
for they argue that since the parent is deficient in this part 
the semen does not come from thence, and the result is 

20 that the corresponding part is not formed in the offspring. 
Thirdly, the resemblances to the parents, for the young are 
born like them part for part as well as in the whole body ; 
if then the coming of the semen from the whole body is 
cause of the resemblance of the whole, so the parts would 
be like because it comes from each of the parts. Fourthly, 

25 it would seem to be reasonable to say that as there is some 
first thing from which the whole arises, so it is also with 
each of the parts, and therefore if semen or seed is cause of 
the whole so each of the parts would have a seed peculiar 
to itself. And these opinions are plausibly supported by 
such evidence as that children are born with a likeness to 

30 their parents^ not only in congenital but also in acquired 
characteristics ; ^ for before now, when the parents have 
had scars, the children have been born with a mark in the 
form of the scar in the same place, and there was a case at 
Chalcedon where the father had a brand on his arm and 
the letter was marked on the child, only confused and not 
clearly articulated.^ That is pretty much the evidence on 
722^ which some believe that the semen comes from all the 

' Lest I should be suspected of modernizing the language unduly, I 
give the Greek words : ov μόιον τα σύμφυτα ιτμασίοικότΐί . . . άλλα καΙ τα 
(ττίκτητα. The distinction between congenital and acquired characters 
was evidently perfectly familiar to A. 

"^ Legends of this sort have always been popular; Mrs. Harris's 
husband's brother was ' marked with a mad bull in Wellington boots 
upon his left arm on account of his precious mother havin' been 
worrited by one into a shoemaker's shop ' {Martin Chuzzlewit , chap, 
xlvi). Hippocrates, however, held such inheritance to come direct 
from the father. 

BOOK I. i8 722* 

18 On examining the question, however, the opposite appears 
more likely, for it is not hard to refute the above arguments 
and the view involves impossibilities. First, then, the re- 
semblance of children to parents is no proof that the semen 
comes from the, whole body, because the resemblance is 5 
found also in voice, nails, hair, and way of moving, from 
which nothing comes.^ And men generate before they yet 
have certain characters, such as a beard or grey hair. 
Further, children are like their more remote ancestors from 
whom nothing has come, for the resemblances recur at an 
interval of many generations, as in the case of the woman 
inEliswhohad intercourse with the Aethiop ; her daughter 10 
was not an Aethiop but the son of that daughter was.'^ 
The same thing applies also to plants, for it is clear that if 
this theory were true the seed would come from all parts of 
plants also ; but often a plant does not possess one part, 
and another part may be removed, and a third grows after- 
wards.^ Besides, the seed does not come from the pericarp,^ 15 
and yet this also comes into being with the same form as 
in the parent plant. 

We may also ask whether the semen comes from each of 
the homogeneous parts only, such as flesh and bone and 
sinew, or also from the heterogeneous, such as face and 
hands. For if (i) from the former only, we object that the 
resemblance exists rather in the heterogeneous parts, such 20 
as face and hands and feet ; if then it is not because of the 

' A. assumes this for hair and nails because they have no blood- 
vessels, I suppose. 

"^ It is possible that this story may be true ; see Lawrence, Lectures on 
Physiology, &^c., 1822, pp. 260, 261. In the absence of details we can- 
not even say exactly what is ineant here ; the daughter, for instance, 
might have been an albino and her son a quadroon, which would be 
enough to start the story, and then there would be nothing remarkable 
about it. But such tales are recklessly invented in America to this day. 

Granting it to be true in its obvious and strongest meaning, it would 
not be a case of Mendelism. For if black were the dominant character, 
how could the daughter be white .'' And if white were dominant how 
could her son be black ? (It is obvious that A. supposes the daughter 
mated with a white man, and it would be askmg too much of the 
goddess of probabilities to postulate a black ' allelomorph ' in him also.) 

Plutarch's similar story {de sera miniinis vindicta, cap. 21) seems to 
be another version of this of Aristotle's. 

* And yet the new plant is like its parent in all these parts. 

* i.e. the material of the pericarp contributes nothing to the seed. 


semen coming from all parts that children resemble their 
parents in tJiese, what is there to stop the homogeneous parts 
also from being like for some other reason than this ? If 
(2) the semen comes from the heterogeneous alone, then it 
does not come from all parts ; but it is more fitting that it 

25 should come from the homogeneous parts,for they are prior 
to the heterogeneous which are composed of them ; and as 
children are born like their parents in face and hands, so 
they are, necessarily, in flesh and nails.^ If (3) the semen 
comes from both, what would be the manner of generation? 
For the heterogeneous parts are composed of the homo- 

30 geneous, so that to come from the former would be to come 
from the latter and from their composition. To make this 
clearer by an illustration, take a written name ; if anything 
came from the whole of it, it would be from each of the syl- 
lables, and if from these, from the letters ^ and their composi- 
tion. So that if really flesh and bones are composed of fire 
and the like elements, the semen would come rather from the 
elements than anything else, for how can it come from their 
722^ composition ? Yet without this composition there would 
be no resemblance. If again something creates this com- 
position later, it would be this that would be the cause of 
the resemblance, not the coming of the semen from every 
part of the body.^ 

Further, if the parts of the future animal are separated 
in the semen, how do they live ? and if they are connected, 
they would form a small animal.^ 

5 And what about the generative parts ? For that which 
comes from the male is not similar to what comes from the 

^ Since face and hands are composed of flesh and nails and other 
homogeneous parts. 

^ The word for letter and element is the same in the Greek. 

^ This something which creates the composition of the elements so 
as to cause the resemblance remains as great a mystery now as it was 
then. But how profound is Aristotle's analysis ! 

* Which is absurd. It is true that we call the carrier of the genera- 
tive element in the semen the spermatozoon, but the spermatozoon of a 
rhinoceros is not a little rhinoceros. 

■'' This objection means, I think, that we can understand how germs 
from the hand or foot of both mother and father (being alike) may 
combine to form the hand or foot of the child, but that we cannot 

BOOK I. i8 72i 

Again, if the semen comes from all parts of both parents 
alike, the result is iivo animals, for the offspring will have 
all the parts of both. Wherefore Empedocles seems to say 
what agrees pretty well with this view (if we are to adopt 
it),^ to a certain extent at any rate, but to be wrong ifio 
we think otherwise. What he says agrees with it when 
he declares that there is a sort of tally in the male and 
female, and that the whole offspring does not come from 
either, ' but sundered is the fashion of limbs, some in 
man's . . .' - For why does not the female generate from 
herself if the semen comes from all parts alike and she has 
a receptacle ready in the uterus? But, it seems, either it 15 
does not come from all the parts, or if it does it is in the 
way Empedocles says, not the same parts coming from each 
parent, which is why they need intercourse with each other. 

Yet this also is impossible, just as much as it is impossible 
for the parts when full grown to survive and have life in 
them when torn apart, as Empedocles accounts for the 
creation of animals ; in the time of his ' Reign of Love ', 
says he, ' many heads sprang up without necks,' and later 20 
on these isolated parts combined into animals. Now that 
this is impossible is plain, for neither would the separate 
parts be able to survive without having any soul or life in 
them, nor if they were living things, so to say, could several 
of them combine so as to become one animal again. Yet 
those who say that semen comes from the whole of the 
body really have to talk in that way, and as it happened 25 
then in the earth during the ' Reign of Love ', so it happens 
according to them in the body. Now it is impossible that 

understand how germs from the generative parts of both parents (being 
unlike) can combine to form a part which is only male or only female. 
The pangenesists would have answered that there is a conflict and one 
or other sex prevails. 

^ i. e. if we are to say that semen comes from all parts, and that is 
why e. g. the hand of a son is like his father's, we must understand it to 
mean that each part in the offspring comes from a corresponding part 
in either male or female parent. Your hand may come from the 
father, your foot from the mother, or vice versa. But we must not say 
that all parts come from both parents, or we shall get a double animal 
with two pairs of hands and feet, &c. 

* Empedocles said something like ' some in the semen of the man, 
some in that of the woman.' And so Diels restores the fragment. 


the parts should be united together when they come into 
being• and should come from different parts of the parent, 
meeting together in one place.^ Then how can the upper 
and lower, right and left, front and back parts have been 

30 ' sundered ' ? All these points are unintelligible. Further, 
some parts are distinguished by possessing a faculty, 
others by being in certain states or conditions ; the hetero- 
geneous, as tongue and hand, by the faculty of doing 
something, the homogeneous by hardness and softness and 
the other similar states. Blood, then, will not be blood, nor 
flesh flesh, in any and every state.^ It is clear, then, that 
that which comes from any part, as blood from blood or 
723^ flesh from flesh, will not be identical with that part. But 
if it is something different from which the blood of the 
offspring comes, the coming of the semen from all the parts 
will not be the cause of the resemblance, as is held by the 
supporters of this theory. For if blood is formed from 
5 something which is not blood, it is enough that the semen 
come from one part only, for why should not all the other 
parts of the offspring as well as blood be formed from one 
part of the parent ? Indeed, this theory seems to be the 
same as that of Anaxagoras, that none of the homogeneous 
parts come into being, except that these theorists assume, 
in the case of the generation of animals, what he assumed 
of the universe.^ 

Then, again, how will these parts that came from all the 

10 body of the parent be increased or grow ? It is true that 
Anaxagoras plausibly says that particles of flesh out of the 
food are added to the flesh.* But if we do not say this 

^ This seems to mean that we cannot suppose as an alternative that 
the separate parts are somehow united, before they come together, in 
the semen of each parent. 

^ Because they, being homogeneous substances, are defined by a 
particular state. And that particular state does not exist in the 

^ Anaxagoras postulated an infinite number of particles homogeneous 
in themselves, atoms of flesh, blood, &c., which by their combination 
make the things we see. These particles do not ' come into being ' 
because they exist eternally. Aristotle evidently is not serioits in this 

* So if we accepted this theory we might say that once the foetus 
is formed it will grow by addition of such particles without the added 
matter undergoing any change. 

BOOK I. i8 723" 

(while saying that semen comes from all parts of the body), 
how will the foetus become greater by the addition of some- 
thing else if that which is added remain unchanged ? But 
if that which is added can change/ then why not say that 15 
the semen from the very first is of such a kind that blood 
and flesh can be made out of it,^ instead of saying that it 
itself is blood and flesh ? Nor is there any other alterna- 
tive, for surely we cannot say that it is increased later by 
a process of mixing, as wine when water is poured into it. 
For in that case each element of the mixture would be 
itself at first while still unmixed, but the fact rather is that 20 
flesh and bone and each of the other parts is such later. 
And to say that some part of the semen is sinew and bone 
is quite above us, as the saying is. 

Besides all this there is a difficulty if the sex is deter- 
mined in conception (as Empedocles says : 'it is shed 
in clean vessels ; some wax female, if they fall in with 23 
cold').^ Anyhow, it is plain that both men and women 
change not only from infertile to fertile, but also from 
bearing female to bearing male offspring, which looks as if 
the cause does not lie in the semen coming from all the 
parent or not, but in the mutual proportion or disproportion 
of that which comes from the woman and the man, or in 30 
something of this kind. It is clear, then, if we are to put 
this down as being so, that the female sex is not determined 
by the semen coming from any particular part, and conse- 
quently neither is the special sexual part so determined (if 
really the same semen can become either a male or female 
child, which shows that the sexual part does not exist in 
the semen). Why, then, should we assert this of this part 
any more than of the others ? For if semen does not come 72 
from this part, the uterus, the same account may be given 
of the others. 

Again, some creatures come into being neither from 

^ As the pangenesists, unlike Anaxagoras, hold that it can. 

"^ Just as they are made out of the food later on. 

' According to Empedocles, if the embryo began developing on the 
left or cold side of the uterus it became female, if on the right or hot 
side male. Parmenides held the same view. See Emp. frag. 67 
(Diels), and my note on iv. 765'* 19. 


parents of the same kind nor from parents of a different 
kind,^ as flies and the various kinds of what are called 
5 fleas ; ^ from these are produced animals indeed, but not 
in this case of similar nature, but a kind of scolex. It 
is plain in this case that the young of a different kind are 
not produced by semen coming from all parts of the parent, 
for they would then resemble them, if indeed resemblance 
is a sign of its coming from all parts. 

Further, even among animals some produce many young 

lo from a single coition (and something like this is universal 
among plants, for it is plain that they bear all the fruit of 
a whole season from a single movement ^). And yet how 
would this be possible if the semen were secreted from all 
the body ? For from a single coition and a single segrega- 
tion of the semen scattered throughout the body must needs 
follow only a single secretion. Nor is it possible for it 
to be separated in the uterus, for this would no longer be 

15 a mere separation of semen, but, as it were, a severance 
from a new plant or animal.* 

Again, the cuttings from a plant bear seed ; clearly, 
therefore, even before they were cut from the parent plant, 
they bore their fruit from their own mass alone,^ and the 
seed did not come from all the plant. 

But the greatest proof of all is derived from observations 

20 we have sufficiently established on insects.^ For, if not in 
all, at least in most of these, the female in the act of copu- 
lation inserts a part of herself into the male. This, as we 
said before, is the way they copulate, for the females mani- 
festly insert this from below into the males above, not in all 

25 cases, but in most of those observed. Hence it seems clear 
that, when the males do emit semen, then also the cause of 
the generation''^ is not its coming from all the body, but 

^ But by spontaneous generation. ^ Reading \^νλλών. 

^ A. does not mean that one plant is fertilized by another as a single 
act, for he knew nothing about their fertilization. He can only mean 
that the plant as a whole produces fruit all over itself in consequence 
of a single impulse at its heart, so to say. 

* This argument is repeated in chap. 20, where see note. 

^ Lit. * from the same size'. " See above on chap. 16. 

'' Sic ; but what have we to do in this argument with the cause of 
generation ? Should it not be the cause of the I'&semblance ? 

BOOK I. i8 723'' 

something else which must be investigated hereafter. For 
even if it were true that it comes from all the body^ as 
they say, they ought not to claim that it comes from 
all parts of it, but only from the creative part — from the 30 
workman, so to say, not the material he works in. Instead 
of that, they talk as if one were to say that the semen 
comes from the shoes, for, generally speaking, if a son is 
like his father, the shoes he wears are like his father's 

As to the vehemence of pleasure in sexual intercourse, it 
is not because the semen comes from all the body, but 
because there is a strong friction (wherefore if this inter- 
course is often repeated the pleasure is diminished in the 724^ 
persons concerned). Moreover, the pleasure is at the end 
of the act, but it ought, on the theory, to be in each of the 
parts, and not at the same time, but sooner in some and 
later in others.^ 

If mutilated young are born of mutilated parents,^ it is 
for the same reason as that for which they are like them. 
And the young of mutilated parents are not always muti- 5 
lated, just as they are not always like their parents ; the 
cause of this must be inquired into later, for this problem is 
the same as that. 

Again, if the female does not produce semen, it is reason- 
able to suppose it does not come from all the body of the 
male either.* Conversely, if it does not come from all 
the male it is not unreasonable to suppose that it does not 
come from the female,^ but that the female is cause of the 10 
generation in some other way. Into this we must next 
inquire, since it is plain that the semen is not secreted from 
all the parts. 

In this investigation and those which follow from it, the 

^ In modern language, the germ-cell creates the body which it wears. 
This body clothes the germ-cells, as shoes again clothe the body. A.'s 
insight in all this passage is miraculous. 

^ Because the semen would have further to travel from some than 
from others. 

^ Modern science simply denies the fact in toto. 

* Because the young resemble the mother as well as the father. 

^ I do not follow this argument. 


15 first thing to do is to understand what semen is, for then it 
will be easier to inquire into its operations and the phe- 
nomena connected with it. Now the object of semen is to 
be of such a nature that from it as their origin come into 
being those things which are naturally formed, not because 
there is any agent which makes them from it as . . . but 

20 simply because this is the semen.^ Now we speak of one 
thing coming frofn another in many senses ; it is one thing 
when we say that night comes from day or a man becomes 
man from boy, meaning that A follows Β ; it is another if 
we say that a statue is made from bronze and a bed from 
wood, and so on in all the other cases where we say that 

25 the thing made is made/r<?;yi a material, meaning that the 
whole is formed from something pre-existing which is only 
put into shape. In a third sense a man becomes unmusical 
from being musical, sick from being well, and generally in 
this sense contraries arise from contraries. Fourthly, as in 
the * climax ' of Epicharmus ; ^ thus from slander comes 

30 railing dmafrom this fighting, and all these Q.refrom some- 
thing in the sense that it is the efficient cause. '^ In this last 
class sometimes the efficient cause is in the things them- 
selves, as in the last mentioned (for the slander is a part of 
the whole trouble), and sometimes external, as the art is 
external to the work of art or the torch to the burning 

35 house.^ 

Now the offspring comes from the semen, and it is plainly 
in one of the two following senses that it does so — either 
the semen is the material from which it is made, or it is the 
724^ first efficient cause. For assuredly it is not in the sense of 
A being after B, as the voyage^ comes from, i.e. after, the 
Panathenaea ; nor yet as contraries come from contraries, 
for then one of the two contraries ceases to be, and a third 
substance must exist as an immediate underlying basis from 

' A corrupt passage, αλλ' is printed before δη τοντό Ιστι το σττίρμα in 
the Basle edition. 

^ See Lorenz's Epicharimis, p, 271, 

^ Read 'ίκ τιιό? 17 αρχή. 

^ The work of art comes from the art which makes it, and the 
burning house /r^?;;; the torch which sets it afire. 

^ Of the sacred ship to Delos. 

BOOK I. i8 7! 

which the new thing comes into being.^ We must discover, 5 
then, in which of the two other classes the semen is to be put, 
whether it is to be regarded as matter, and therefore acted 
upon by something else, or as a form, and therefore acting 
upon something else,^ or as both at once. For perhaps at 
the same time we shall see clearly also how all the products 
of semen come into being from contraries, since coming 
into being from contraries is also a natural process, for 
some animals do so, i.e. from male and female, others from 10 
only one parent, as is the case with plants and all those 
animals in which male and female are not separately dif- 
ferentiated. Now that which comes from ^ the generating 
parent is called the seminal fluid, being that which first has 
in it a principle of generation, in the case of all animals 
whose nature it is to unite ; semen is that which has in it 
the principles from both united parents,* as the first mixture 15 
which arises from the union of male and female, be it 
a foetus or an ovum,•^ for these already have in them that 
which comes from both. (Semen, or seed, and grain differ 
only in the one being earlier and the other later, grain in 
that it comes from something else, i. e. the seed, and seed 20 
in that something else, the grain, comes from //, for both 
are really the same thing.) ^ 

^ e.g. the unmusical man comes into being from the musical. Then 
the musical man as such ceases to exist. But for the unmusical man 
to come into being there must exist the substratum 7nan, of which 
musical and utwmsical are attributes. So, if the offspring came into 
being from the semen as opposite from opposite, the semen would 
cease to exist. What then would the offspring come from ? We shall 
have to assume some third substance. 

^ Matter is inert and incapable by itself, it is acted upon by the 
efficient or the formal cause, which are often identified as here. But 
A. goes rather far when he speaks of semen as merely * form ', even 
though qualified by the word rt. 

^ Reading a-now. 

* After this come in the MSS. the words olov τά re των φυτών κηΐ 

(νιων ζώων, iv ois μη κ^χώρισται το θτ]λν και το appev, a repetition from 
above in almost identical words and here utterly out of place. 

° Read ωόν. Observe that A. here defines the semen as what 
we should now call the fertilized ovum, though generally he means by 
it the same as we do. Lewes, § 443, remarks that the ' moderns call 
both the impregnated and unimpregnated egg an ovtim ' in like manner. 
' Foetus or ovum ', because A. was naturally unacquainted with the 
mammalian ovum. 

^ This sentence is exceedingly irrelevant and probably interpolated. 


We must again take up the question what the primary 
nature of what is called semen is. Needs must everything 
which we find in the body either be (i) one of the natural 
25 parts, whether homogeneous or heterogeneous, or (2) an 
unnatural part such as a growth, or (3) a secretion or 
excretion,^ or (4) waste-product,^ or (5) nutriment. (By 
secretion or excretion I mean the residue of the nutriment, 
by waste-product that which is given off from the tissues ^ 
by an unnatural decomposition.) 

Now that semen cannot be a part of the body is plain, 
for it is homogeneous, and from the homogeneous nothing 
30 is composed, e.g. from only sinew or only flesh ; nor is it 
separated as are all the other parts. But neither is it con- 
trary to Nature nor a defect, for it exists in all alike, and 
the development of the young animal comes from it. 
Nutriment, again, is obviously introduced from without. 

It remains, then, that it must be either a waste-product 
35 or a secretion or excretion. Now the ancients * seem to 
think that it is a waste-product, for when they say that it 
comes from all the body by reason of the heat of the move- 
725^ ment of the body in copulation, they imply that it is a kind 
of waste-product. But these are contrary to Nature, and 
from such arises nothing according to Nature. So then it 
must be a secretion or excretion. 

But, to go further into it, every secretion or excretion is 
5 either of useless or useful nutriment ; by * useless ' I mean 
that from which nothing further is contributed to natural 
growth, but which is particularly mischievous to the body 
if too much of it is consumed ; by ' useful ' I mean the 
opposite. Now it is evident that it cannot be of the former 
character, for such is most abundant in persons of the 
worst condition of body through age or sickness ; semen, 
on the contrary, is least abundant in them, for either they 
10 have none at all or it is not fertile, because a useless and 
morbid secretion is mingled with it. 

Semen, then, is part of a useful secretion. But the most 

^ περίττωμα, a word which will have to be translated in many ways. 

" σΰντη-^μα. See Addenda. 

' αυξημητος, ' den zum Wachsthum aufgenommenen Stoffen,' AW. 

* See Hippocrates, vol. i, p. 371. 

BOOK I. i8 725^ 

useful is the last and that from which finally is formed each 
of the parts of the body. For secretions are either earlier 
or later ; ^ of the nutriment in the first stage the secretion 
is phlegm- and the like, for phlegm also is a secretion of 15 
the useful nutriment, an indication of this being that if it 
is mixed with pure nutriment it is nourishing,^ and that 
it is used up in cases of illness. The final secretion is 
the smallest in proportion to the quantity of nutriment. 
But we must reflect that the daily nutriment by which 
animals and plants grow is but small, for if a very little be 20 
added continually to the same thing the size of it will 
become excessive.'^ 

So we must say the opposite of what the ancients said. 
For whereas they said that semen is that which comts from 
all the body, τνε shall say it is that whose nature is to go to 
all of it,^ and what they thought a waste-product seems rather 
to be a secretion. For it is more reasonable to suppose 
that the last extract of the nutriment which goes to all 25 
parts resembles that which is left over from it, just as part of 
a painter's colour is often left over resembling that which he 
has used up. Waste-products, on the contrary, are always 
due to corruption or decay and to a departure from Nature. 

A further proof that it is not a waste-product, but rather 
a secretion, is the fact that the large animals have few 
young, the small many. For the large must have more 3° 
waste and less secretion, since the great size of the body 
causes most of the nutriment to be used up, so that the 
residue or secretion is small. 

Again, no place has been set apart by Nature for waste- 
products but they flow wherever they can find an easy 

' In the digestive process. 

'^ Phlegm is to be understood here as the second of the four famous 
' humours ' of Hippocrates. 

^ ' All the phlegm that is carried in the veins, being useful, needs not 
to be evacuated. We must recognize the fact that some phlegm in 
animals is useful and according to Nature, some useless and contrary 
to Nature.' Galen, vol. xv, p. 326. 

* I read τω κη& ημίραν' παμμικροϋ yap au προστιθ(μΐνου τψ αντω 

ΰτΓίρβάλλοι, partly from conjectures by A\V. and myself. 

° Because semen is derived from the nutriment which is conveyed by 
the blood-vessels /<? every part of the body. Though it does not itself 
go to every part it is a sort of quintessence of that which does. 

AR. G. A. D 


passage in the body, but a place has been set apart for all 
725'' the natural secretions ; thus the lower intestine serves for the 
excretion of the solid nutriment, the bladder for that of 
the liquid ; for the useful part of the nutriment we have the 
upper intestine, for the spermatic secretions the uterus and 
pudenda and breasts,^ for it is collected and flows together 
into them. 

And the resulting phenomena are evidence that semen is 

5 what we have said, and these result because such is the 
nature of the secretion. For the exhaustion consequent on 
the loss of even a very little of the semen is conspicuous 
because the body is deprived of the ultimate gain drawn 
from the nutriment. With some few persons, it is true, 
during a short time in the flower of their youth the loss of 

10 it, if it be excessive in quantity, is an alleviation (just as in 
the case of the nutriment in its first stage, if too much have 
been taken, since getting rid of this also makes the body 
more comfortable), and so it may be also when other 
secretions come away with it, for in that case it is not only 
semen that is lost but also other influences come away 

15 mingled with it,^ and these are morbid. Wherefore, with 
some men at least, that which comes from them proves 
sometimes incapable of procreation because the seminal 
element in it is so small. But still in most men and as 
a general rule the result of intercourse is exhaustion and 
weakness rather than relief, for the reason given. Moreover, 
semen does not exist in them either in childhood or in old 

20 age or in sickness — in the last case because of weakness, 
in old age because they do not sufficiently concoct their 
food, and in childhood because they are growing and so all 
the nutriment is used up too soon, for in about five years, 
in the case of human beings at any rate, the body seems 

35 to gain half the height that is gained in all the rest of life.^ 

In many animals and plants we find a difference in this 

connexion not only between kinds as compared with kinds, 

^ For milk is a spermatic secretion, iv. ηηη^ 3-15. 

^ Read τούτω. 

' Sic; of course A. means in the whole of life. AW. refer to 
Quetelet to show that as a matter of fact half the adult height is 
reached in the third ytax. 

BOOK I. i8 725" 

but also between similar individuals of the same kind as 
compared with each other, e. g. man with man or vine with 
vine. Some have much semen, others little, others again 
none at all, not through weakness but the contrary, at any 30 
rate in some cases. This is because the nutriment is used 
up to form the body, as with some human beings, who, 
being in good condition and developing much flesh ^ or 
getting rather too fat,'^ produce less semen and are less 
desirous of intercourse. Like this is what happens with 
those vines which 'play the goat', that is, luxuriate wan- 
tonly through too much nutrition, for he-goats when fat 726^ 
are less inclined to mount the female ; for which reason they 
thin them before breeding from them, and say that the 
vines 'play the goat', so calling it from the condition of 
the goats. And fat people, women as well as men, appear 
to be less fertile than others from the fact that the secretion 
when in process of concoction turns to fat ^ with those who 5 
are too well-nourished. For fat also is a healthy secretion 
due to good living.* 

In some cases no semen is produced at all, as by the 
willow and poplar.^ This condition is due to each^ of 
the two causes, weakness and strength ; the former prevents 
concoction of the nutriment, the latter causes it to be all 
consumed, as said above. In like manner other animals 10 
produce much semen "^ through weakness as well as through 

^ i. e. muscle. 

' For μάλλον with comparatives in A. see Cope on Rhetoric ii. 11. 

' A. distinguishes between πιμΑη and arenp in de Partibiis, ii. 5, 
but a comparison of that chapter will show that he uses πιμ^λη here in 
a general sense. 

* ' That over-fat animals are bad breeders is known to every farmer. 
So also 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 sont en raison inverse I'un de Tautre."* 
Ogle on de Pariibus, ii. 5 ad fin. 

* A popular delusion among the ancients. This is why the trees 
are connected with the dead — tVtai ώλΐσίκαρποι, Odyssey x. 510. 

* Reading «Kiirfpai (AW.). 

'' (cat ιτολνγοά eVrt και ΐτολνσπίρμα. Elsewhere πολνχοα means pro/ific, 
but that plainly cannot be the meaning here ; apparently it = πολϋ 
σπίρμα χίοντα. But another reading is πολυχρόνια and possibly the 
word is corrupt. 

D 2 


strength, when a great quantity of a useless secretion is 
mixed with it ; this sometimes results in actual disease 
when a passage is not found to carry off the impurity, and 
though some recover of this, others actually die of it. For 

15 corrupt humours collect here as in the urine, which also has 
been known to cause disease. 

[Further, the same passage serves for urine and semen ; 
and whatever animals have both kinds of excrement, that 
of liquid and that of solid nutriment, discharge the semen 
by the same passage as the liquid excrement (for it is 
a secretion of a liquid, since the nutriment of all animals 

20 is rather liquid than solid), but those which have no liquid 
excrement discharge it at the passage of the solid residua. 
Moreover, waste-products are always morbid, but the removal 
of the secretion is useful ; now the discharge of the semen 
participates in both characteristics because it takes up 
some of the non-useful nutriment. But if it were a waste- 

25 product it would be always harmful ; as it is, it is not so.^] 
From what has been said, it is clear that semen is a secre- 
tion of useful nutriment, and that in its last stage, whether 
it is produced by all ^ or no. 

After this we must distinguish of what sort of nutriment 19 
it is a secretion, and must discuss the catamenia which occur 
30 in certain of the vivipara. For thus we shall make it clear 
( I ) whether the female also produces semen like the male 
and the foetus is a single mixture of two semens, or whether 
no semen is secreted by the female, and, (a) if not, whether 
she contributes nothing else either to generation but only 
provides a receptacle, or whether she does contribute some- 
726*' thing, and, if so, how and in what manner she does so. 

We have previously stated that the final nutriment is 
the blood in the sanguinea and the analogous fluid in the 
other animals. Since the semen is also a secretion of the 
nutriment, and that in its final stage, it follows that it will 

^ This incoherent and disorderly paragraph has no connexion of 
any sort with the context ; it is a fricassee of reminiscences from what 
has been said before, and should be rejected from the text. 

"^ ' All ' here seems to mean iofA sexes. 

BOOK I. 19 726'' 

be either (1) blood or that which is analogous to blood, or 
(2) something formed from this. But since it is from the 5 
blood, when concocted and somehow divided up, that each 
part of the body is made, and since the semen if properly- 
concocted is quite of a different character from the blood 
when it is separated from it, but if not properly concocted 
has been known in some cases to issue in a bloody condition 
if one forces oneself too often to coition,^ therefore it is • 
plain that semen will be a secretion of the nutriment when 10 
reduced to blood, being that which is finally distributed to 
the parts of the body. And this is the reason why it has so 
great power,^ for the loss of the pure and healthy blood is 
an exhausting thing ; for this reason also it is natural that 
the offspring should resemble the parents, for that which goes 
to all the parts of the body ^ resembles that which is left 15 
over.* So that the semen which is to form the hand or the 
face or the whole animal is already the hand or face or whole 
animal undifferentiated, and what each of them is actually 
such is the semen potentially, either in virtue of its own 
mass or because it has a certain power in itself. I mention 
these alternatives here because we have not yet made it 
clear from the distinctions drawn hitherto whether it is the 30 
matter of the semen that is the cause of generation, or 
whether it has in it some faculty and efficient cause thereof, 
for the hand also or any other bodily part is not hand 
or other part in a true sense if it be without soul or some 
other power, but is only called by the same name as the 
living hand."* 

* Hippocrates (vol. ii, p. 512) mentions λάγνίυμη νφαιμον νποπίλώνον 
as a symptom of an internal disease. Dr. Blacker tells me that * un- 
doubtedly excessive coitus may lead to bleeding from the prostate gland 
and so the semen may contain blood.' 

^ As is shown by the exhaustion consequent upon coition. 

^ i. e. the blood. * i. e. the semen. 

^ Soul {"^υχη) is the truth and reality of an organism according to 
Α., and a dead hand, or a hand of stone, is only called hand by a 
sort of analogy. The essence of a hand is that it shall be able to 
grasp, which the dead hand cannot do, and it is able to grasp because 
it has "^υχη (or we should say life) in it. 

The i\i SS. proceed with a passage which AW. have bracketed as 
out of place, but which to me is totally unintelligible anywhere. The 
literal translation runs thus : 

And it is plain that in all cases where a spermatic humour occurs 


30 On this subject, then, so much may be laid down.^ But 

since it is necessary (i) that the weaker animal also should 

have a secretion greater in quantity and less concocted, 

and (2) that being of such a nature it should be a mass of 

sanguineous liquid,^ and (3) since that which Nature endows 

with a smaller portion of heat is weaker, and (4) since it 

has already been stated that such is the character of the 

female 2 — putting all these considerations together we see 

that the sanguineous matter discharged by the female is 

727^ also a secretion. And such is the discharge of the so-called 


It is plain, then, that the catamenia are a secretion, and 

that they are analogous in females to the semen in males. 

The circumstances connected with them are evidence that 

5 this view is correct. For the semen begins to appear 

this also is a secretion. This happens when it is dissolved into that 
which has come to it, just as when the coating falls away at once from 
stucco; for that luhich has cotne away is the satne as that which was 
applied first. In the same way also the last secretion is the same as 
the first humour. 

' And we can now proceed to consider the question of what is 
contributed to generation by the female. 

^ The final concoction of the blood is semen, which does not appear 
sanguineous, but if the concoction is less thorough, as in women, it will 
naturally be sanguineous. For the same reason it will be greater in 
quantity, the weaker animal being less able to reduce it to a small and 
perfect form. 

^ A. held that vital heat \vas a sign of superiority and that man was 
hotter than woman. To put his argument here in a simpler form : 
Woman has less vital heat than man. 
.•. woman is inferior to man. 
.•. the concoction is less thorough in woman. 
.•. the secretion will be still sanguineous. 

But we do find such a sanguineous discharge in the female. 

.•. we may conclude that the catamenia are a secretion. 

For A. is very anxious to prove that both the male and female 
discharges are secretions, not waste-products. 

* ' True menstruation is only found in women and certain monkeys. 
There is, however, a slight discharge corresponding to it in other 
mammals at the rutting period ' (G. Blacker). Blundell expresses 
his surprise that A. should have attempted 'to explain what is 
common to all animals by a circumstance peculiar to one class' 
{Midwifery, 1840, p. 903), and certainly A. made a hazardous leap 
when he argued from Avomen to all vertebrata. But he several times 
observes that women alone have any superfluous catamenia, and 
his great mistake was rather in taking this attendant phenomenon for 
the important essential in generation ; in assuming that the ' material 
contributed ' by all female vertebrates was analogous he was right, but 
he should have called it an ovum. (In de Somno, 455'' 33, he lays down 
the principle that we should argue from man to other animals.) 

BOOK Ι. 19 727' 

in males and to be emitted at the same time of life that the 
catamenia begin to flow in females, and that they change 
their voice and their breasts begin to develop. So, too, in 
the decline of life the generative power fails in the one sex 
and the catamenia in the other. lo 

The following signs also indicate that this discharge in 
females is a secretion. Generally speaking women suffer 
neither from haemorrhoids nor bleeding at the nose nor 
anything else of the sort except Avhen the catamenia are 
ceasing,^ and if anything of the kind occurs the flow is 
interfered with because the discharge is diverted to it.^ 15 

Further, the blood-vessels of women stand out less than 
those of men, and women are rounder and smoother because 
the secretion which in men goes to these vessels is drained 
away with the catamenia. We must suppose, too, that the 
same cause accounts for the fact that the bulk of the body 
is smaller in females than in males among the vivipara, 20 
since this is the only class in which the catamenia are dis- 
charged from the body.^ And in this class the fact is 
clearest in women, for the discharge is greater in women 
than in the other animals. Wherefore her pallor and the 

^ Ισταμίνων is the medical word ; cf. Luke, Evang. viii, 44 ΐστη 
ή ρνσΐί, Harnack, Luke the Physician, p. 186. We should have expected 
at first sight the aorist here, but A. has in mind the aphorism of 
Hippocrates (vol. iii, p. 743) • ywaiKi των καταμηνίων ΐκΚΐΐπόντων αίμα 

(Κ των ρινών ρνήναι αγαθόν. And the present must be explained by say- 
ing that A. does not mean to say that such bleeding does not also occur at 
other times but only that it does not occur a/ong wiih the catamenia 
except when they are ceasing. 

I believe that alpoppotdes means haemorrhoids here, not haemorrhages 
in general ; cf. Hippocrates, vol. i, p. 325. Indeed, the wording of this 
passage is enough to show this. As to the fact, Dr. Blacker informs 
me that it is ' no doubt to some extent true. Women do not as a rule 
suffer from nose-bleeding &c. at their periods '. 

' Reading μΐθισταμίνψ. 

^ The explanation is ingenious though wrong. The facts are correct 
indeed, for the rule in the animal kingdom is that the male is smaller 
than the female, often as in spiders, rotifers, cirrhipedes, &c., 
ridiculously so, and the mammalia form the only exception. But this 
is due to the fighting of the males of mammals with one another for 
the females, in which the bigger and stronger prevail. The male of 
some of the eared seals may be six times as big as the female. 

The pallor of women, as compared with men, was much more con- 
spicuous among the Greeks than among us, as the women stayed at 
home mostly, while the men were sunburnt by constant exposure in the 


absence of prominent blood-vessels is most conspicuous, 
25 and the deficient development of her body compared with 
a man's is obvious. 

Now since this is what corresponds in the female to the 
semen in the male, and since it is not possible that two 
such discharges should be found together,^ it is plain that 
the female does not contribute semen to the generation 
of the offspring. For if she had semen she would not have 
the catamenia ; but, as it is, because she has the latter she 
30 has not the former. 

It has been stated then that the catamenia are a secretion 

as the semen is, and confirmation of this view may be 

drawn from some of the phenomena of animals. For fat 

creatures produce less semen than lean ones, as observed 

before. The reason is that fat also, like semen, is a secre- 

35 tion, is in fact concocted blood, only not concocted in 

the same way as the semen. Thus, if the secretion is 

727^^ consumed to form fat the semen is naturally deficient. 

And so among the bloodless animals the cephalopoda 

and Crustacea are in best condition about the time of 

producing eggs, for, because they are bloodless and no 

fat is formed in them, that which is analogous in them 

5 to fat is at that season drawn off to form the spermatic 


And a proof that the female does not emit similar semen 
to the male, and that the offspring is not formed by a 
mixture of both, as some say, is that often the female 
conceives without the sensation of pleasure in intercourse, 
and if again the pleasure is experienced by her no less 

^ Why is this * not possible ' ? Because A. had found that every- 
where Nature is economical, and does not use superfluous methods ; it 
is in fact the 'law of the physiological division of labour'. And if the 
catamenia really were analogous to the semen it really would follow that 
the female did not produce semen also. The truth, however, is that 
the catamenia are a discharge connected with the maturation and 
liberation of the ovum from the Graafian vesicle. The ovum is the 
important factor in generation, and this does correspond to the 
semen ; to that limited extent, therefore, A.'s doctrine is correct. 
Whether we are to say that the female produces semen or not depends 
simply on the verbal question whether we are to call the ovum semen 
or not. Nobody ever did, but it would not be absurd to do so, con- 
sidering that the word σπίρμα means any kind of ' seed ', and the 
ovum might as well come under that head as the semen does. 

BOOK I. 19 727 

than by the male and the two sexes reach their goal 10 
together/ yet often no conception takes place unless the 
liquid of the so-called catamenia is present in a right pro- 
portion. Hence the female does not produce young if 
the catamenia are absent altogether, nor often when, they 
being present, the efiflux still continues ; but she does so 
after the purgation. For in the one case she has not the 
nutriment or material from which the foetus can be framed 15 
by the power coming from the male and inherent in the 
semen, and in the other it is washed away with the cata- 
menia because of their abundance. But when after their 
occurrence the greater part has been evacuated, the re- 
mainder is formed into a foetus. Cases of conception 
when the catamenia do not occur at all, or of conception 
during their discharge instead of after it, are due to the 
fact that in the former instance there is only so much 20 
liquid to begin with as remains behind after the discharge 
in fertile women,^ and no greater quantity is secreted 
so as to come away from the body, while in the latter 
instance the mouth of the uterus closes after the discharge. 
When, therefore, the quantity already expelled from the 
body is great but the discharge still continues, only not 
on such a scale as to wash away the semen, then it is that 25 
conception accompanies coition. ^ Nor is it at all strange 
that the catamenia should still continue after conception 
(for even after it they recur to some extent, but are scanty 
and do not last during all the period of gestation ; this, how- 
ever, is a morbid phenomenon, wherefore it is found only 
in a few cases and then seldom, whereas it is that which 
happens as a regular thing that is according to Nature). 30 

It is clear then that the female contributes the material 
for generation, and that this is in the substance of the 
catamenia, and that they are a secretion. 

^ Omit τΓπρά after ισοδρομί^σάιτωΐ'. Cf. Ovid, Ars Am. ii. 727. 

" Sic, but the context shows that A. means ordinary women who 
have catamenia, for he is not opposing barren to fertile, but the rare 
case of conception without catamenia to the ordinary case of conception 
with them. 

* Omitting πά\ιν, which possibly should go somewhere in the next 


Some think that the female contributes semen in coition 20 
35 because the pleasure she experiences is sometimes similar 
to that of the male, and also is attended by a liquid dis- 
charge. But this discharge is not seminal ; it is merely 
728^ proper to the part concerned in each case, for there is 
a discharge from the uterus^ which occurs in some women 
but not in others. It is found in those who are fair-skinned 
and of a feminine type generally, but not in those who 
are dark and of a masculine appearance. The amount 
of this discharge, when it occurs, is sometimes on a different 
5 scale from the emission of semen and far exceeds it. 
Moreover, different kinds of food cause a great difference 
in the quantity of such discharges ; for instance some 
pungently-flavoured foods cause them to be conspicuously 
increased. And as to the pleasure which accompanies 
10 coition it is due to emission not only of semen, but also 
of a spiritus,^ the coming together of which precedes the 
emission. This is plain in the case of boys who are not 
yet able to emit semen, but are near the proper age, and of 
men who are impotent, for all these are capable of pleasure 
by attrition. And those who have been injured in the 
15 generative organs ^ sometimes suffer from diarrhoea because 
the secretion, which they are not able to concoct and turn 
into semen, is diverted into the intestine.* Now a boy is 
like a woman ^ in form, and the woman is as it were an 

' It seems clear that A. here refers to the vulvo-vaginal discharge 
(Playfair, Midwifery^, vol. i, p. 28). This however, as its name 
denotes, does not take place 'from the uterus'. In ii. 7Z<)^2>7 A. says 
more correctly * the region in front of the uterus '. 

A. goes on however to say that this discharge may be very large ; 
Dr. Blacker tells me that this is never true of the vulvo-vaginal secre- 
tion, but that it suggests ' leucorrhoea or whites, which at times is 
present in very large amount '. This also suits the statement about 
brunettes and blondes to some extent, as Blacker suggests, because 
leucorrhoea ' is present in greater quantity in anaemic women '. But 
again A. elsewhere speaks of leucorrhoea (738^ 25) in quite a distinct 
manner. On the whole I am driven to conclude that there is some 
confusion in this passage between the two discharges. 

^ ττνΐϋμα. See ii. 3. That the semen is expelled by a πνΐϋμα is a 
Hippocratic doctrine (Hipp., vol. iii, p. 748.) 

^ ^κφθαρμίνοίς την yivtaiv, 

* The secretion which is turned into semen is blood. Consequently 
by ' diarrhoea' here A. means a flow of blood. 
^ Reading ywaiKi παις. 

BOOK I. 20 728* 

impotent male, for it is through a certain incapacity that 
the female is female, being incapable of concocting the 
nutriment in its last stage into semen (and this is either 20 
blood or that which is analogous to it in animals which 
are bloodless owing to the coldness of their nature). As 
then diarrhoea is caused in the bowels by the insufficient 
concoction of the blood, so are caused in the blood-vessels 
all discharges of blood, including that of the catamenia, for 
this also is such a discharge, only it is natural whereas the 
others are morbid. 

Thus it is clear that it is reasonable to suppose that 25 
generation comes from this.^ For the catamenia are semen 
not in a pure state but in need of working up, just as in 
the formation of fruits the nutriment is present, when it 
is not yet sifted thoroughly,^ but needs working up to purify 
it. Thus the catamenia cause generation by mixture with 
the semen, as this impure nutriment in plants is nutritious 30 
when mixed with pure nutriment. 

And a sign that the female does not emit semen is the 
fact that the pleasure of intercourse is caused by touch in 
the same region of the female as of the male ; and yet 
is it not from thence that this flow proceeds. Further, 
it is not all females that have it at all, but only the 35 
sanguinea, and not all even of these, but only those whose 
uterus is not near the hypozoma and which do not lay 
eggs ; it is not found in the animals which have no blood 728'' 
but only the analogous fluid (for what is blood in the 
former^ is represented by another fluid in the latter). 
The reason why neither the latter nor those sanguinea 
mentioned (i. e. those whose uterus is low and which do 
not lay eggs) have this effluxion is the dryness of their 5 
bodies ; this allows but little matter to be secreted, only 
enough for generation but not enough to be discharged 
from the body. All animals that are viviparous without 
producing eggs first (such are man and all quadrupeds 

^ i.e. that the catamenia contain the element contributed to 
generation by the female. 

^ Reading διηττημίνη. The meaning is that all the material is present 
in an unripe fruit before it is sweetened. 

^ Read fV ΐκύνοις for eViotr or eV ivioit. 


which bend their hind-legs outwards,^ for all these are 

lo viviparous without producing eggs) — all these have the 
catamenia, unless they are defective in development as the 
mule, only the efflux is not abundant as in women. Details 
of the facts in each animal have been given in the Enquiries 
concerning animals? 

The catamenia are more abundant in women than in the 

15 other animals,•'^ and men emit the most semen in proportion 
to their size. The reason is that the composition of their 
bodies is liquid and hot compared to others, for more 
matter must be secreted in such a case. Further, man 
has no such parts in his body as those to which the super- 

20 fluous matter is diverted in the other animals ; for he has 
no great quantity of hair in proportion to his body, nor 
outgrowths of bones, horns, and teeth. 

There is evidence that the semen is in the catamenia,* 
for, as said before^, this secretion appears in the male at the 
same time of life as the catamenia in the female ; this indi- 

25 cates that the parts destined to receive each of these 
secretions are differentiated at the same time in both 
sexes ; and as the neighbouring parts in both become 
swollen the hair of puberty springs forth in both alike. 
As the parts in question are on the point of differentiating 
they are distended by the spiritus ; this is clearer in males 

30 in the testes, but appears also about the breasts ; in 
females it is more marked in the breasts, for it is when 
they have risen two fingers' breadth that the catamenia 
generally begin. 

Now, in all living things in which the male and female 
are not separated the semen (or seed) is a sort of embryo ; 
by embryo I mean the first mixture of male and female ; ^ 

35 hence, from one semen comes one body, — for example, one 
stalk of wheat from one grain, as one animal from one egg 

^ Reading cktos (=eVi τό κοΐΚον^ de Iiicessu, 704^4 &c.). The 
quadrupedal mammalia are meant. 

* See H. A. vi. 18, where, however, only a few animals are men- 

^ See note on 727^ 2. 

* Sic, but if A. wrote this he only means that the material in question 
is semen not ' purified '. 

° i. e. in the generation of the higher animals. 

BOOK Ι. 20 729' 

(for twin eggs are really two eggs). But in whatever kinds 
the sexes are distinguished, in these many animals may 
come from one emission of semen, showing that the semen 
differs in its nature in plants and animals. A proof of this 
is that animals which can bear more than one young one 5 
at a time do so in consequence of only one coition. 
Whereby, too, it is plain that the semen does not come 
from the whole of the body ; for neither would the dif- 
ferent parts of the semen already be separated as soon 
as discharged from' the same part, nor could they be 
separated in the uterus if they had once entered it all 
together ; ^ but what does happen is just what one would 
expect, since what the male contributes to generation is 10 
the form and the efficient cause,^ while the female con- 
tributes the material. In fact, as in the coagulation of 
milk, the milk being the material, the fig-juice or ^ 
rennet is that which contains the curdling principle, so acts 
the secretion of the male, being divided into parts in the 
female. Why it is sometimes divided into more or fewer 
parts, and sometimes not divided at all, will be the subject 15 
of another discussion.* But because it does not differ in 
kind at any rate this does not matter, but what does 
matter is only that each part should correspond to the 
material, being neither too little to concoct it and fix it 

^ This is a very difficult argument to follow and it is with diffidence 
that I propose this explanation. On the Hippocratic theory of 
pangenesis the resemblance of e. g. the nose of the son to the nose of 
his father is due to part of the semen being drawn from the father's 
nose. But suppose an animal to produce a litter of six in consequence 
of a single impregnation ; then it follows that six different 'nose-germs' 
(or whatever they might be called) have found their way to the six 
different embryos. How could they be sorted out in this way ? They 
could not, says Α., all be kept separate in the semen when emitted by 
the male (six different bundles each carrying countless germs corre- 
sponding to each separate part), because the semen is all discharged in 
one mass from one and the same part and so is all mixed up together. 
Nor can they be afterwards sorted out when once in the uterus, 
because (according to chap. 18) that would be like splitting up a single 
animal into several. 

The latter argument is terribly inconclusive, and I imagine that 
the pangenesists could have held their own against A. without very 
great ingenuity being required. Darwin's 'gemmules' certainly 

* Or ' principle of motion '. 

' Reading η η. * See book iv. 771''. 


into form, nor too much so as to dry it up ; it then gene- 
rates a number of offspring. But from this first formative 

20 semen, if it remains one, and is not divided, only one young 
one comes into being. 

That, then, the female does not contribute semen to 
generation, but does contribute something, and that this 
is the matter of the catamenia, or that which is analogous 
to it in bloodless animals, is clear from what has been said, 
and also from a general and abstract survey of the question. 

25 For there must needs be that which generates and that 
from which it generates ; even if these be one,' still they 
must be distinct in form and their essence must be different ; 
and in those animals that have these powers separate in 
two sexes the body and nature of the active and the 
passive sex must also differ. If, then, the male stands for 
the effective and active, and the female, considered as 

30 female, for the passive, it follows that what the female 
would contribute to the semen of the male would not be 
semen but material for the semen to work upon. This 
is just 'what we find to be the case, for the catamenia 
have in their nature an affinity to the prirnitive matter. 

So much for the discussion of this question. At the 21 
same time the answer to the next question we have to 
investigate is clear from these considerations, I mean how 
729*• it is that the male contributes to generation and how it is 
that the semen from the male is the cause of the offspring. 
Does it exist in the body of the embryo as a part of it 
from the first, mingling with the material which comes 
5 from the female ? Or does the semen communicate nothing 
to the material body of the embryo but only to the power 
and movement in it? For this power is that which acts 
and makes, while that which is made and receives the 
form is the residue of the secretion in the female.^ Now 
the latter alternative appears to be the right one both 
a priori and in view of the facts. For, if we consider the 
question on general grounds, we find that, whenever one 

' i. e. if they are united in the satne animal. 

"^ i. e, as much of the catamenia as is not discharged. 

BOOK I. 21 72ί 

thing is made from two of which one is active and the lo 
other passive, the active agent does not exist in that which 
is made ; ^ and, still more generally, the same applies when 
one thing moves and another is moved ; the moving thing 
does not exist in that which is moved. But the female, 
as female, is passive, and the male, as male, is active, and 
the principle of the movement comes from him. There- 
fore, if we take the highest genera under which they each 
fall,^ the one being active and motive and the other passive 15 
and moved, that one thing which is produced comes from 
them only in the sense in which a bed comes into being 
from the carpenter and the wood, or in w^hich a ball comes 
into being from the wax and the form. It is plain then 
that it is not necessary that anything at all should come 
away from the male, and if anything does come away it 
does not follow that this gives rise to the embryo as being 
in the embryo, but only as that which imparts the motion 20 
and as the form ; so the medical art cures the patient. 

This a priori argument is confirmed by the facts. For 
it is for this reason that some males which unite with the 
female do not, it appears, insert any part of themselves into 
the female, but on the contrary the female inserts a part 
of herself into the male ; this occurs in some insects.^ For 25 
the effect produced by the semen in the female (in the 
case of those animals whose males do insert a part) is 
produced in the case of these insects by the heat * and 
power in the male animal itself when the female inserts 
that part of herself which receives the secretion. And 
therefore such animals remain united a long time, and 
when they are separated the young are produced quickly. 30 
For ^ the union lasts until that which is analogous to the 
semen has done its work,^ and when they separate the 
female produces the embryo quickly ; for the young is 

^ e. g. a man, the active agent, makes a boat out of wood, the passive 
material ; the man does not exist in the boat as a part of it. 

^ τα ίίκρα (κατίρων. Aciive and passive are wider and more 
important categories than jnale 2^6, female. 

^ See on chap. 16. 

^ Reading θίμμότης. ^' Reading avvbeSCaarai yap. 

^ Lit. 'until it puts together, as the semen.' 


imperfect inasmuch as all such creatures give birth to 

What occurs in birds and oviparous fishes is the greatest 
proof that neither does the semen come from all parts 
730^ of the male nor does he emit anything of such a nature 
as to exist within that which is generated, as part of the 
material embryo, but that he only makes a living creature 
by the power which resides in the semen (as we said in 
the case of those insects whose females insert a part of 
themselves into the male). For if a hen-bird is in process 
5 of producing wind-eggs and is then trodden by the cock 
before the egg has begun to whiten and while it is all still 
yellow,^ then they become fertile instead of being wind- 
eggs. And if while it is still yellow she be trodden by 
another cock, the whole brood of chicks turn out like the 
second cock. Hence some of those who are anxious to 

10 rear fine birds act thus ; they change the cocks for the 
first and second treading, not as if they thought that the 
semen is mingled with the egg or exists in it, or that it 
comes from all parts of the cock ; for if it did it would 
have come from both cocks, so that the chick would have 
all its parts doubled. But it is by its force that the semen 

15 of the male gives a certain quality to the material and the 
nutriment in the female, for the second semen added to 
the first can produce this effect by heat and concoction, as 
the egg acquires nutriment so long as it is growing.^ 

The same conclusion is to be drawn from the generation 
of oviparous fishes. When the female has laid her eggs, 

20 the male sprinkles the milt over them, and those eggs are 
fertilized which it reaches, but not the others ; this shows 
that the male does not contribute anything to the quantity 
but only to the quality of the embryo. 

^ i. e. while the egg consists merely of the yolk in the vitelline 
membrane, when it first begins its passage through the oviduct. The 
* white of egg ' is deposited round it as it gets further on in the . 

* And this acquired nutriment is benefited by the semen of the 
second cock. 

Of course the chickens can only take after the second cock if the 
first has failed to fertilize the ova. A. can hardly be mistaken about 
the habits of Greek breeders, and such people have strange fancies, 
but it is a very astonishing statement. Cf. //. A. vi. 2. 

BOOK I. 21 730* 

From what has been said it is plain that the semen does 
not come from the whole of the body of the male in those 25 
animals which emit it, and that the contribution of the 
female to the generative product is not the same as that 
of the male, but the male contributes the principle of 
movement and the female the material. This is why the 
female does not produce offspring by herself, for she needs 
a principle, i. e. something to begin the movement in the 
embryo and to define the form it is to assume. Yet in 30 
some animals, as birds, the nature of the female unassisted 
can generate to a certain extent, for they do form some- 
thing, only it is incomplete ; I mean the so-called wind- 

22 For the same reason the development of the embryo 
takes place in the female ; neither the male himself nor the 
female emits semen into the male,^ but the' female receives 
within herself the share contributed by both, because in the 730'' 
female is the material from which is made the resulting 
product. Not only must the mass of material exist there 
from which the embryo is formed in the first instance, but 
further material must constantly ^ be added that it may 
increase in size. Therefore the birth must take place in 5 
the female. For the carpenter must keep in close connexion 
with his timber and the potter with his clay, and generally 
all workmanship and the ultimate movement imparted to 
matter must be connected with the material concerned, as, 
for instance, architecture is in the buildings it makes. 

From these considerations we may also gather how it is 
that the male contributes to generation. The male does 10 
not emit semen at all in some animals, and where he does 
this is no part of the resulting embryo ; just so no material 
part comes from the carpenter to the material, i. e. the wood 
in which he works, nor does any part of the carpenter's art 
exist within what he makes, but the shape and the form 
are imparted from him to the material by means of the 15 
motion he sets up. It is his hands that move his tools, his 

^ Reading αλλ' ουκ els το clppev οΰτ αντο το appev (Didot's ed.) 
^ Reading del της νΧης. 

AR. G. A, Ε 


tools that move ^ the material ; it is his knowledge of his 
art, and his soul, in which is the form,^ that move his hands 
or any other part of him with a motion of some definite 
kind, a motion varying with the varying nature of the object 
made. In like manner, in the male of those animals which 

3o emit semen, Nature ^ uses the semen as a tool and as pos- 
sessing motion in actuality, just as tools are used in the 
products of any art, for in them lies in a certain sense 
the motion of the art. Such, then, is the way in which 
these males contribute to generation. But when the male 

25 does not emit semen, but the female inserts some part of 
herself into the male, this is parallel to a case in which 
a man should carry the material to the workman. For by 
reason of weakness in such males Nature is not able to do 
anything by any secondary means, but the movements 
imparted to the material are scarcely strong enough when 
Nature herself watches over them.^ Thus here she re- 

30 sembles a modeller in clay rather than a carpenter, for she 
does not touch the work she is forming by means of tools, 
but, as it were, with her own hands.^ 

In all animals which can move about, the sexes are 23 
separated, one individual being male and one female, though 
731* both are the same in species, as with man and horse.^ But 
in plants these powers are mingled, female not being 
separated from male. Wherefore they generate out of 
themselves, and do not emit semen but produce an embryo, 
what is called the seed.'' Empedocles puts this well in the 
line : ' and thus the tall trees oviposit ; first olives . . .' 
5 For as the egg is an embryo, a certain part of it giving rise 

' Reading ai 8e Xtipts τα opynva και τα όργανα την ΰλην. 

* For soul is the ' place of forms ', containing them potentially (de 
Anima, iii. 4). The carpenter's mind contains the form of the chair, 
into which form he seeks to bring the material wood. 

^ Reading ή φύσις (v τώ appevi. 

* This is shown by the length of time required in such copulation. 
^' Lit. ' herself with the parts of herself.' 

* Reading ανθρωττος η Ιππος. 

'' An embryo is the ' first mixture of male and female ' where the 
sexes are differentiated. Plants, having no sexes according to Α., 
produce a germ capable of developing without fertilization by any 
other principle, and thus a sort of embryo ready made. 

BOOK I. 23 731^ 

to the animal and the rest being nutriment, so also from 
a part of the seed ^ springs the growing plant, and the rest 
is nutriment for the shoot and the first root. 

In a certain sense the same thing ^ happens also in those 
animals which have the sexes separate. For when there is 10 
need for them to generate the sexes are no longer separated 
any more than in plants, their nature desiring that they 
shall become one ; and this is plain to view when they 
copulate and are united, that one animal is made out of 

It is the nature of those creatures which do not emit 15 
semen to remain united a long time until the male element 
has formed the embryo, as with those insects which copu- 
late. The others so remain only until the male has dis- 
charged from the parts of himself introduced something 
which will form the embryo in a longer time, as among the 
sanguinea. For the former remain paired some part of 
a day, while the semen forms the embryo in several days. 20 
And after emitting this ^ they cease their union. 

And animals seem literally to be like divided plants, as 
though one should separate and divide them, when they 
bear seed, into the male and female existing in them. 

In all this Nature acts like an intelligent workman. For 
to the essence of plants belongs no other function or busi- 25 
ness than the production of seed ; since, then, this is brought 
about by the union of male and female, Nature has mixed 
these and set them together in plants, so that the sexes are 
not divided in them. Plants, however, have been inves- 
tigated elsewhere. But the function of the animal is not 30 
only to generate (which is common to all living things), but 
they all of them participate also in a kind of knowledge,* 
some more and some less, and some very little indeed. 
For they have sense-perception, and this is a kind of know- 
ledge. (If we consider the value of this we find that it is 
of great importance compared with the class of lifeless 
objects, but of little compared with the use of the intellect. 

^ Reading κηΐ ϊκ τον σπίρματος μίρηνς. Modern botanists talk of the 
' egg ' of a plant. 

^ Reading ταυτό (AW.) ^ Qu. προ4μ(να ? 

* γι-ώσίωΓ, lit. * getting to know.' 

Ε 2 

73i" Di: (;ι•;νι•:κλίί()νι•: animalium 

ϊ'ον afiiiinst the latter the mere participiition in touch and 
taste seems to be practically nothinj^r^ but beside absolute 
iiisetisibility it seems most excellent ; for it would seem 
a treasure to pain even this kind of knovvledj^e rather than 
to lie in a state of death and non-existence.) Now it is by 
scnsc-perce[)tion that an animal differs from those organisms 

δ which have only life. Ikit since, if it is a living animal, it 
must also live ; ' therefore, when it is necessary for it to 
accomplish the fuiution of that which has life,'•^ it unites 
and coi)ulates, becoming like a plant, as we said before. 

Testaceous animals, being intermediate between animals 
and plants, perform the function of neither class as bclong- 

10 ing to both. As plants they have no sexes, and one does 
not generate in another ; as animals they do not bear fruit 
from themselves like plants ; but they are formed and 
generated from a licjuid and earthy concretion. However, 
we must speak later of the generation of these animals.•' 

' i.e. Ii;ivc (lie simple• vit;il piiiuiplc as will as sense. 
' i.e. lo puKliue sceil, as staled above. 
" iii. 1 1. 

1Κ)()Κ II 

I ΊΊΐΛΊ' the in.iki aiul female are ihe piineiples of generation 731*^ 
has been previously slated, as also what is their power and 
their essence. But why is it that one thin^' becomes and is ^o 
male, another female? It is the business of our discussion 
as it proceeds to try and point out (1) that the sexes arise 
from Necessity and the fn-st efficient cause, (3) from what 
sort of material they are formed. That (3) they exist 
because it is better and on account of the final cause, 
takes us back to a princi[)le still further remote. 

Now (i) some existing thin[j;s are eternal and divine 
whilst others admit of both existence and non-existence. 25 
But (2) that which is noble and divine is always, in virtue 
of its own nature, the cause of tiie better in such things as 
admit of being better or worse, and what is not eternal does 
admit of existence and non-existence,' and can partake in 
the better and the worse. And (3) soul is better than body, 
and the living, having soul, is thereby better than the life- :\o 
less which has none, and being is better than not being, 
living than not living. These, then, are the reasons of the 
generation of animals. ¥ov since it is im[)ossible that such 
a class of things as animals should be of an eternal nature, 
therefore that which comes into being is eternal in the only 
way possible. Now it is impossible for it to be eternal as 
an individual (though of course the real essence of things 
is in the individual) — were it such it would be eternal but 
it is possible for it as a species.'- This is why there is 

l\c;id «li'dt Kill μι) tiviti, 
"^ Cf. </ί• j'lui)n<i, ii. 415'' 3 7, willioul wliich this pass.iKc: would baffli; 
interiJietution. I have concclcd Jkkkcr's j)iin( tualion. Tlic paren- 
thesis, tlie explanation of which I owe to Dr. Jackson, is a liit at 


always a class of men and animals and plants.^ But since 
the male and female essences are the first principles of 
these, they will exist in the existing individuals for the sake 
of generation. Again, as the first efficient or moving cause, 
to which belong the definition and the form, is better and 
more divine in its nature than the material on which it 

5 works, it is better that the superior principle should be 
separated from the inferior. Therefore, wherever it is 
possible and so far as it is possible, the male is separated 
from the female. For the first principle of the movement, 
or efficient cause, whereby that which comes into being is 
male, is better and more divine than the material whereby 

10 it is female.^ The male, however, comes together and 
mingles with the female for the work of generation, because 
this is common to both. 

A thing lives, then, in virtue of participating in the male 
and female principles, wherefore even plants have some 
kind of life ; but the class of animals exists in virtue of 
sense-perception. The sexes are divided in nearly all 

15 of these that can move about, for the reasons already stated,^ 
and some of them, as said before,^ emit semen in copulation, 
others not. The reason of this is that the higher animals 
are more independent in their nature, so that they have 
greater size, and this cannot exist without vital heat ; ^ for 

20 the greater body requires more force to move it, and heat 
is a motive force. Therefore, taking a general view, we 
may say that sanguinea are of greater size than bloodless 
animals, and those which move about than those which 
remain fixed. And these are just the animals which emit 
semen on account of their heat and size. 

So much for the cause of the existence of the two sexes. 

25 Some animals bring to perfection and produce into the 
world a creature like themselves, as all those which bring 
their young into the world alive ; ^ others produce some- 
^ Not one individual of each species. 

^ I read provisionally η τ6 nppev νπάρχΐΐ ro'is -γινομίνοις η η ΰ\η rj το θήλυ 
for ή appev νπάρχΐΐ tols γινομ€νοΐ!• νλη b( το ή θήλν, partly ΟΠ the 
suggestion of Mr. Ross. 

^ I do not know where these reasons have been given or what they are. 

* i. 17. ^ See Ogle, pp. xxii-xxiv. 

^ The vivipara, including the cartilaginous fishes. 

BOOK II. I 732^ 

thing undeveloped which has not yet acquired its own 
form ; in this latter division the sanguinea ^ lay eggs, the 
bloodless animals either lay an egg or give birth to a scolex.^ 
The difference between egg and scolex is this : an egg is 
that from a part of which the young comes into being, the 30 
rest being nutriment for it ; but the whole of a scolex is 
developed into the whole of the young animal.^ Of the 
vivipara, which bring into the world an animal like them- 
selves, some are internally viviparous (as men, horses, cattle, 
and of marine animals dolphins and the other cetacea) ; 
others first lay eggs within themselves, and only after this 
are externally viviparous (as the cartilaginous fishes). 732^ 
Among the ovipara some produce the egg in a perfect con- 
dition (as birds and all oviparous quadrupeds and footless 
animals, e.g. lizards and tortoises and most snakes;^ for 
the eggs of all these do not increase when once laid). The 5 
eggs of others are imperfect ; such are those of fishes, 
crustaceans, and cephalopods, for their eggs increase after 
being produced.^ 

All the vivipara^ are sanguineous, and the sanguinea 
are either viviparous or oviparous, except those which are 
altogether infertile.'^ Among bloodless animals the insects 10 
produce a scolex, alike those that are generated by copula- 
tion and those that copulate themselves though not so 
generated. For there are some insects of this sort, which 
though they come into being by spontaneous generation 
are yet male and female ; from their union something is 
produced, only it is imperfect ; the reason of this has been 
previously stated. 

* Birds and reptiles. 

'^ Read τα δ' ηναιμη (j) ωοτοκΰ ή) σκωληκοτοκΐΐ, ΟΓ something of the 
sort. Α. could not have said, or at least could not have meant, that 
αϊ/ invertebrates produce a scolex ; over and over again he speaks of 
the eggs of Crustacea and cephalopoda. 

^ Cf. the modern distinction between meroblastic and holoblastic 

* The exception among the snakes is the viper. 

' The increase in size is however only due to imbibition of water ; 
there is no further development of the egg (AW.). 

^ Omit the words η ωοτοκοΰντα which are false to fact and to 
Aristotle himself. 

■^ Mules. 


15 These classes admit of much cross-division. Not all 
bipeds are viviparous (for birds are oviparous), nor are 
they all oviparous (for man is viviparous), nor are all 
quadrupeds oviparous (for horses, cattle, and countless 
others are viviparous), nor are they all viviparous (for 

20 lizards, crocodiles, and many others lay eggs). Nor does 
the presence or absence of feet make the difference between 
them, for not only are some footless animals viviparous, 
as vipers and the cartilaginous fishes, while others are ovi- 
parous, as the other fishes and serpents, but also among 
those which have feet many are oviparous and many vivi- 
parous, as the quadrupeds above mentioned. And some 

25 which have feet, as man, and some which have not, as the 
whale and dolphin, are internally viviparous. By this 
character then it is not possible to divide them,^ nor is 
any of the locomotive organs the cause of this difference, 
but it is those animals which are more perfect in their 
nature and participate in a purer element ^ which are vivi- 

30 parous, for nothing is internally viviparous unless it receive 
and breathe out air. But the more perfect are those which 
are hotter in their nature and have more moisture and are 
not earthy in their composition. And the measure of 
natural heat is the lung when it has blood in it, for gene- 
rally those animals which have a lung are hotter than 
those which have not, and in the former class again those 
whose lung is not spongy nor solid nor containing only 
733^ a little blood, but soft and full of blood. And as the 
animal is perfect but the egg and the scolex are imperfect, 
so the perfect is naturally produced from the more perfect. 
If animals are hotter as shown by their possessing a lung ^ 
but drier in their nature, or are colder but have more 

^ A hit at Plato's ' dichotomy ' of animals which was based on this 
character. Aristotle's own test, the condition in which the young are 
produced, is of course vastly superior, foreshadowing the doctrine that 
embryology affords the most important evidence of affinities. And he 
refuses to consider even that as the sole test. Cf. Ogle, p. xxv. 

'^ άρχψ. The internally viviparous animals, including the cetacea, 
are air-breathers ; the cartilaginous or elasmobranch fishes are only 
externally viviparous, laying eggs first within themselves. 

^ Lit. 'hotter on account of having a lung', but this means what is 
said in the text. The business of the lung is to cool, not to heat, 
according to A. 

BOOK II. I 733' 

moisture, then they either lay a perfect egg or are vivi- 5 
parous after laying an egg within themselves. For birds 
and scaly reptiles because of their heat produce a perfect 
egg, but because of their dryness it is only an egg ; the 
cartilaginous fishes have less heat than these but more 
moisture, so that they are intermediate, for they are both 
oviparous and viviparous within themselves,^ the former 10 
because they are cold, the latter because of their moisture ; 
for moisture is vivifying, whereas dryness is furthest removed 
from what has life. Since they have neither feathers nor 
scales such as either reptiles or other fishes have, all which 
are signs rather of a dry and earthy nature, the egg they 
produce is soft ; for the earthy matter does not come to 15 
the surface in their eggs any more than in themselves. 
This is why they lay eggs in themselves, for if the egg 
were laid externally it would be destroyed, having no 

Animals that are cold and rather dry than moist also 
lay eggs, but the egg is imperfect ; at the same time, 
because they are of an earthy nature and the egg they 
produce is imperfect, therefore it has a hard integument 
that it may be preserved by the protection of the shell- 
like covering. Hence fishes, because they are scaly, and 20 
Crustacea, because they are of an earthy nature,^ lay eggs 
with a hard integument. 

The cephalopods, having themselves bodies of a sticky 
nature, preserve in the same way the imperfect eggs they 
lay, for they deposit a quantity of sticky material about 
the embryo.^ 

All insects produce a scolex. Now all the insects are 25 
bloodless, wherefore all creatures that produce a scolex 
from themselves are so.* But we cannot say simply that 

^ From comparison of i. 8 it seems that this should mean ' oviparous 
internally and viviparous externally '. 

* oi ιχθύα here means what are now called the teleosteans, the 
vast majority of fish, opposed to the cartilaginous elasmobranchs. 
The latter have no scales like those of the teleosteans. The Crustacea 
are ' earthy ', as shown by their exo-skeletons. But ' the eggs of all 
teleosteans are soft-shelled' (Giinther, Study of Fishes, p. l6oj. 

* i.e. about their eggs. 

* Reading και τα σκωληκοτοκοΐντα. 


all bloodless animals produce a scolex, for the classes 
overlap one another, (i) the insects, (2) the animals that 
produce a scolex,^ (3) those that lay their egg imperfect, as 
the scaly fishes, the Crustacea, and the cephalopoda.'^ I say 
30 that these form a gradation, for the eggs of these latter 
resemble a scolex, in that they increase after oviposition, 
and the scolex of insects again as it develops resembles an 
egg ; how so we shall explain later.^ 

We must observe how rightly Nature orders generation 
733*• in regular gradation. The more perfect and hotter animals 
produce their young perfect in respect of quality (in respect 
of quantity this is so with no animal, for the young always 
increase in size after birth), and these generate living 
animals within themselves from the first. The second 
5 class do not generate perfect animals within themselves 
from the first (for they are only viviparous after first 
laying eggs), but still they are externally viviparous. The 
third class do not produce a perfect animal, but an egg, 
and this egg is perfect. Those whose nature is still colder 
than these produce an egg, but an imperfect one, which 
is perfected outside the body, as the class of scaly fishes, 
10 the Crustacea, and the cephalopods. The fifth and coldest 
class does not even lay an egg from itself;* but so far as 
the young ever attain to this condition at all, it is outside 
the body of the parent, as has been said already.^ For 

' Inserting και ra σκωΚηκοκοΰντα. 

^ The classes are (A) vertebrates, (B) invertebrates, (X) laying 
imperfect eggs, (Y) producing a scolex. All Υ are B, but we cannot 
convert and say all Β are Y, because many Β are X. The scaly fishes 
take us up again into another class, being both X and A. 

With his usual idea of a graduated scale of Nature in his mind, 
Aristotle then proceeds to point out how the imperfect egg is a sort of 
intermediate step between scolex and perfect egg. Nature approxi- 
mates to the parallel arrangement : 

1. Insects. Scolex. 

2. Higher Invertebrates. Imperfect egg. 

3. Lower Vertebrates. Perfect egg. 

4. Higher Vertebrates. Perfect animal. 

But unluckily the overlapping of the classes forbids our making this 
neat scheme absolute. ^ iii. 9. 

* 'From itself, because the scolex does later develop into an egg, 
i. e. the pupa, according to Α., but the parent does not lay this pupa 

e'^ αΰτοΰ. 

' The reference seems to be to 733* 31. τον τοιούτον in the Berlin 
edition is a misprint for to τοιοίτοι^. 

BOOK II. I 73ί 

insects produce a scolex first ; the scolex after developing 
becomes egg-like (for the so-called chrysalis or pupa is 
equivalent to an egg) ; then from this it is that a perfect 15 
animal comes into being, reaching the end of its develop- 
ment in the second change.^ 

Some animals then, as said before, do not come into 
being from semen, but all the sanguinea do so which are 
generated by copulation, the male emitting semen into 
the female ; when this has entered into her the young 20 
are formed and assume their peculiar character, some 
within the animals themselves when they are viviparous, 
others in eggs.^ 

There is a considerable difficulty in understanding how 
the plant is formed out of the seed or any animal out 
of the semen.2 Everything that comes into being or is 25 
made must (i) be made out of something, (2) be made 
by the agency of something, and (3) must become some- 
thing. Now that out of which it is made is the material ; 
this some animals have in its first form within themselves, 
taking it from the female parent, as all those which are 
not born alive but produced as a scolex or an egg ; * others 
receive it from the mother for a long time by sucking, as 
the young of all those which are not only externally but 30 

^ In the f/iird change, literally, according to the Greek way of 

^ I omit the words καΙ σττίρμασι και τοιανταις αλλαις άποκρίσίσιν. 
They are obviously unintelligible Avhen the question is only of 
vertebrates. Either they are a senseless addition or else something 
considerable has dropped out before them. 

^ The discussion which follows extorted the admiration of even the 
malignant Lewes (§§ 457-63). The battle is between 'preformation' 
and ' epigenesis ' ; the advocates of the former maintained that the 
young animal already existed complete in the germ and grew out of it 
by what was called ' evolution ' ; the advocates of the latter maintained 
that the separate parts were added one after another as Aristotle says. 
Harvey declared for epigenesis, but Haller himself subsequently went 
wrong. The preformationists were reduced to the absurdity of saying 
that every germ contained packed away within itself not only one 
perfect animal but all that animal's descendants as well, and Aristotle 
finally triumphed all along the line. 

The controversy has, however, recently arisen again in a new and 
very different form (Wilson, T/ie Cell in Development and Inheritance, 
2nd ed., p. 432). 

* The egg has in it nourishment derived from the female parent, 
to wit, the yolk ; for the scolex see iii. 758'' 36. 


also internally viviparous.^ Such, then, is the material out 
of which things come into being, but we now are inquiring 
not out of what the parts of an animal are made, but by 
what agency. Either it is something external which makes 
them, or else something existing in the seminal fluid and 
734^ the semen ; and this must either be soul or a part of soul, 
or something containing soul.'^ 

Now it would appear irrational to suppose that any of 
either the internal organs or the other parts is made by 
something external, since one thing cannot set up a motion 
in another without touching it. nor can a thing be affected 
in any way by another if it does not set up a motion in 
5 it. Something then of the sort we require exists in the 
embryo itself, being either a part of it or separate from it. 
To suppose that it should be something else separate from 
it is irrational. For after the animal has been produced 
does this something perish or does it remain in it ? But 
nothing of the kind appears to be in it, nothing which is 
not a part of the whole plant or animal. Yet, on the other 
hand, it is absurd to say that it perishes after making either 

10 all the parts or only some of them. If it makes some of 
the parts and then perishes, what is to make the rest 
of them ? Suppose this something makes the heart and 
then perishes, and the heart makes another organ, by the 
same argument either all the parts must perish or all must 
remain.^ Therefore it is preserved and does not perish. 
Therefore it is a part of the embryo itself which exists in 
the semen from the beginning ; and if indeed there is no part 

15 of the soul which does not exist in some part of the body, 
it would also be a part containing soul in it from the 

How, then, does it make the other parts ? Either all the 
parts, as heart, lung, liver, eye, and all the rest, come into 
being together or in succession, as is said in the verse 
ascribed to Orpheus, for there he says that an animal 

^ i. e. the mammalia suckle, but the cartilaginous fish do not. 

''■ For soul is the form of body, and it is this form which the semen 

^ For why should not the heart perish in its turn, and so with the 
rest ? 

BOOK Π. I 734^ 

comes into being in the same way as the knitting of 20 
a net.^ That the former is not the fact is plain even to 
the senses, for some of the parts are clearly visible 
as already existing in the embryo while others are not ; 
that it is not because of their being too small that they 
are not visible is clear, for the lung is of greater size than 
the heart, and yet appears later than the heart in the 
original development. Since, then, one is earlier and 25 
another later, does the one make the other, and does the 
later part exist on account of the part which is next to 
it, or rather does the one come into being only after the 
other ? I mean, for instance, that it is not the fact that 
the heart, having come into being first, then makes the 
liver, and the liver again another organ, but that the liver 
only comes into being after the heart, and not by the 
agency of the heart, as a man becomes a man after being 
a boy, not by his agency.^ An explanation of this is that, 
in all the productions of Nature or of art, what already 30 
exists potentially is brought into being only by what exists 
actually ; therefore if one organ formed another the form 
and the character of the later organ would have to exist 
in the earlier^ e. g. the form of the liver in the heart. And 
otherwise also the theory is strange and fictitious. 

Yet again, if the whole animal or plant is formed from 
semen or seed, it is impossible that any part of it should 35 
exist ready made in the semen or seed, whether that part 
be able to make the other parts or no. For it is plain that, 
if it exists in it from the first, it was made by that which 
made the semen. But semen must be made first, and that 734'' 
is the function of the generating parent. So, then, it is not 
possible that any part should exist in it, and therefore it 
has not within itself that which makes the parts.^ 

^ This metaphor of the net occurs repeatedly in modern works on 
the subject. 

^ That is to say that one organ is formed later in time than another, 
by epigenesis in modern language ; A. cannot and does not mean that 
one organ grows into another as a boy becomes a man, but the 
illustration is very unluckily and badly chosen, and I trust the words 
ωσπ€ρ μΐτα το παϊς άνηρ γΐνίται may be an interpolation. 

^ If all the parts are made 6y the semen, it is evident that no part 
can exist in it from the first. 


But neither can this agent be external,^ and yet it must 
needs be one or other of the two. We must try, then, to 

5 solve this difficulty, for perhaps some one of the statements 
made cannot be made without qualification, e. g. the state- 
ment that the parts cannot be made by what is external 
to the semen. For if in a certain sense they cannot, yet in 
another sense they can. (Now it makes no difference 
whether we say ' the semen ' or ' that from which the semen 
comes ', in so far as the semen has in itself the movement 
initiated by the other.) It is possible, then, that A should 
move B, and Β move C ; that, in fact, the case should be 

lo the same as with the automatic machines shown as curiosi- 
ties. For the parts of such machines while at rest have 
a sort of potentiality of motion in them, and when any ex- 
ternal force puts the first of them in motion, immediately the 
next is moved ^ in actuality. As, then, in these automatic 
machines the external force moves the parts in a certain 
sense (not by touching any part at the moment, but by 
having touched one previously), in like manner also that from 

15 which the semen comes, or in other words that which made 
the semen, sets up the movement in the embryo and makes 
the parts of it by having first touched something though 
not continuing to touch it.^ In a way it is the innate 
motion that does this, as the act of building builds the 
house. Plainly, then, while there is something which 
makes the parts, this does not exist as a definite object, 
nor does it exist in the semen at the first as a complete 

30 But how is each part formed ? We must answer this by 
starting in the first instance from the principle that, in all 

^ As we proved before. 

^ Lit, ' comes to exist in actuality.' 

^ i. e. the male parent makes the semen and somehow imparts to 
it a potentiality of setting up movements in the embryo ; this power 
given to the semen is like the impulse given to a piece of clock-work 
by pushing a wheel. Father = watch-maker, first wheel = semen, 
other wheels moved by the first = the parts developed by the semen. 
We cannot solve the riddle any better at the present day ; we can only 
say that no sooner has the spermatozoon penetrated the ovum than 
there is set up in the latter a series of movements which differentiate 
it and develop the parts one after another. The whole of this 
passage sounds amazingly modern ; cf. e. g. the language of the 
Presidential address to the British Association, κρΖ, passim. 

BOOK Π. I 734'' 

products of Nature or art, a thing is made by something 
actually existing out of that which is potentially such as 
the finished product. Now the semen is of such a nature, 
and has in it such a principle of motion, that when the 
motion is ceasing ^ each of the parts comes into being, and 
that as a part having life or soul. For there is no such 
thing as face or flesh without life or soul in it; it is only 25 
equivocally that they will be called face or flesh if the life 
has gone out of them,^ just as if they had been made of 
stone or wood. And the homogeneous parts and the 
organic come into being together. And just as we should 
not say that an axe or other instrument or organ was 
made by the fire alone, so neither shall we say that foot or 
hand were made by heat alone.^ The same applies also 30 
to flesh, for this too has a function. While, then, we may 
allow that hardness and softness, stickiness and brittleness, 
and whatever other qualities are found in the parts that 
have life and soul, may be caused by mere heat and cold, 
yet, when we come to the principle '* in virtue of which flesh 
is flesh and bone is bone, that is no longer so ; what makes 
them is the movement set up by the male parent, who is 35 
in actuality what that out of which the offspring is made 
is in potentiality.^ This is what we find in the products 
of art ; heat and cold may make the iron soft and hard, 
but what makes a sword is the movement of the tools 735^ 
employed; this movement containing the principle of the 
art. For the art is the starting-point and form of the 
product ; only it exists in something else,^ whereas the move- 
ment of Nature exists in the product itself, issuing from 
another nature "^ which has the form in actuality. 

Has the semen soul, or not ? The same argument applies 5 

^ πανομΐνψ, but is the text sound ? Qu. λνομίνης, ' when the motion 
is resolving ' ; cf. iv. 3 passim, where the ' motions ' which cause 
resemblance to a parent are said to be often 'resolved' into other 
motions causing resemblance to grandparents, &c. 

^ Lit. ' being spoilt ', φθαι^ίντα. The essence of e. g. a hand is to 
grasp ; a dead hand or a stone hand cannot grasp, and therefore is 
not a hand at all, strictly speaking, though still called a hand. 

' As certain early philosophers asserted. 

* λόγος. ■"' Omitting ή after ^ννύμα. 

^ i. e. in the mind of the artist, and that potentially. 

'' i.e. the parent. 


here as in the question concerning the parts. As no part, 
if it participate not in soul, will be a part except in an 
equivocal sense (as the eye of a dead man is still called 
an * eye '), so no soul will exist in anything except that 
of which it is soul ; it is plain therefore that semen both 
has soul, and is soul, potentially.^ 

But a thing existing potentially may be nearer or further 

10 from its realization in actuality, as e. g. a mathematician 
when asleep is further from his realization in actuality as 
engaged in mathematics than when he is awake, and when 
awake again but not studying mathematics he is further 
removed than when he is so studying. Accordingly it 
is not any part that is the cause of the soul's coming 
into being, but it is the first moving cause from outside. 
(For nothing generates itself, though when it has come 
into being it thenceforward increases itself.) Hence it is 

15 that only one part comes into being first and not all of 
them together. But that must first come into being which 
has a principle of increase (for this nutritive power exists 
in all alike, whether animals or plants, and this is the same 
as the power that enables an animal or plant to generate 
another like itself, that being the function of them all 
if naturally perfect). And this is necessary for the reason 

20 that whenever a living thing is produced it must grow. 
It is produced, then, by something else of the same name, 
as e.g. man is produced by man, but it is increased by 
means of itself. There is, then, something which increases 
it.2 If this is a single part,^ this must come into being 
first.* Therefore if the heart is first made in some animals, 
and what is analogous to the heart in the others which 

^ The argument is this. Every part being alive must have soul, 
and all the parts are formed by the semen, and that in a living state. 
The life or soul imparted to them must therefore come from the semen. 
But that soul cannot exist m the semen unless it is the soul 0/ the 
semen, for ' no soul can exist in anything of which it is not the soul '. 
.•. the semen has soul, at least potentially. It is not itself actually 
possessed of soul, because it is not a living animal. Modern science of 
course says that the spermatozoa in the semen are living matter. 

^ And that something must be within it. Reading Ίσην upa ο αΰξίΐ. 

^ Omitting πρώτον. 

* And conversely that which comes into being first must be able to 
increase the embryo. 

BOOK II. I 735^ 

have no heart, it is from this or its analogue that the first 35 
principle of movement would arise. 

We have thus discussed the difficulties previously raised 
on the question what is the efficient cause of generation 
in each case, as the first moving and formative power. 

2 The next question to be mooted concerns the nature 
of semen. For whereas when it issues from the animal 3° 
it is thick and white, yet on cooling it becomes liquid as 
water, and its colour is that of water. This would appear 
strange, for water is not thickened by heat ; yet semen 
is thick when it issues from within the animal's body which 
is hot, and becomes liquid on cooling. Again, watery fluids 
freeze, but semen, if exposed in frosts to the open air, does 35 
not freeze but liquefies, as if it was thickened by the 
opposite of cold. Yet it is unreasonable, again, to suppose 
that it is thickened by heat. For it is only substances 
having a predominance of earth in their composition that 735** 
coagulate and thicken on boiling, e. g. milk. It ought then 
to solidify on cooling, but as a matter of fact it does not 
become solid in any part but the whole of it goes like 

This then is the difficulty. If it is water, water evidently 
does not thicken through heat, whereas the semen is thick 5 
and both it and the body whence it issues are hot. If 
it is made of earth or a mixture of earth and water, it 
ought not to liquefy entirely and turn to water. 

Perhaps, however, we have not discriminated all the 
possibilities. It is not only the liquids composed of water 
and earthy matter that thicken, but also those composed 
of water and air; foam, for instance, becomes thicker and 10 
white, and the smaller and less visible the bubbles in it, 
the whiter and firmer does the mass appear. The same 
thing happens also with oil ; on mixing with air it thickens, 
wherefore that which is whitening becomes thicker, the 15 
watery part in it being separated off by the heat and turning 
to air.^ And if oxide of lead is mixed with water or even 

^ From this passage it appears that the Greeks made their oil 
whiter by heating it ; at least A. states the fact as if that was their 


with oil, the mass increases greatly and changes from liquid 
and dark to firm and white, the reason being that air 

2 is mixed in with it which increases the mass and makes 
the white shine through, as in foam and snow (for snow 
is foam}.^ And water itself on mingling with oil becomes 
thick and white, because air is entangled in it by the act 
of pounding them together, and oil itself has much air in 

25 it (for shininess is a property of air, not of earth or water). 
This too is why it floats on the surface of the water, for the 
air contained in it as in a vessel bears it up and makes 
it float, being the cause of its lightness. So too oil is 
thickened without freezing in cold weather and frosts ^ ; 
it does not freeze because of its heat (for the air is hot 

30 and will not freeze), but because the air is forced together 
and compressed, as . . .,^ by the cold, the oil becomes 
thicker. These are the reasons why semen is firm and 
white when it issues from within the animal ; it has 
a quantity of hot air in it because of the internal heat ; 

35 afterwards, when the heat has evaporated and the air has 
cooled, it turns liquid and dark ; for the water, and any 
small quantity of earthy matter there may be, remain in 
semen as it dries, as they do in phlegm. 
736^ Semen, then, is a compound of spirit {ττνβνμα) and water, 
and the former is hot air (άηρ) ; hence semen is liquid in 
its nature because it is made of water. What Ctesias the 
Cnidian has asserted of the semen of elephants is mani- 
festly untrue ; he says that it hardens so much in drying 

object. Sir W. Ramsay tells me that oil is whitened by exposure to 
sunlight and air being blown through it, and that the same effect would 
follow from simple exposure to sunlight, but would take longer owing 
to the slowness of oxidation. 

' AW. deny this flatly, but A. is perfectly right. Snow is white, the 
chemists tell me, because it is mixed with air ; indeed Professor Collie 
says: 'Snow t's frozen foam.' The first chapter of the ntpl Χρωμάτων 
shows that μ^λαν may include any dark colour, and that XevKOf means 
transparent as well as ^vhite. ' Air is naturally white,' and this 
' shines through ' when air is mixed with water, &c., but A. seems to 
confound the two notions. 

* ' Olive-oil coagulates some seven degrees above the freezing-point 
of water, fish-oil remains fluid at a temperature considerably below ' 
this. Ogle on de Partibus, ii. 648'' 32. A. seems, then, to be here 
thinking of the latter. 

^ The MSS. variations seem to point to some loss after ώσττερ (which 
is bracketed by AW., though they mark a lacuna in their translation). 

BOOK II. 2 736= 

that it becomes like amber.^ But this does not happen, 5 
though it is true that one semen must be more earthy than 
another, and especially so with animals that have much 
earthy matter in them because of the bulk of their bodies. 
And it is thick and white because it is mixed with spirit, 
for it is also an invariable rule that it is white, and Hero- 'o 
dotus does not report the truth when he says that the 
semen of the Aethiopians is black, as if everything must 
needs be black in those who have a black skin, and that 
too when he saw their teeth were white. The reason of 
the whiteness of semen is that it is a foam, and foam is 
white, especially that which is composed of the smallest 15 
parts, small in the sense that each bubble is invisible, 
which is what happens when water and oil are mixed and 
shaken together, as said before. (Even the ancients seem 
to have noticed that semen is of the nature of foam ; at 
least it was from this they named the goddess who presides 20 
over union.^) 

This then is the explanation of the problem proposed, 
and it is plain too that this is why semen does not freeze ; 
for air will not freeze. 

3 The next question to raise and to answer is this. If, in 
the case of those animals which emit semen into the female, 25 
that which enters makes no part of the resulting embryo, 
where is the material part of it diverted if (as we have seen) 
it acts by means of the pow er residing in it ? It is not 
only necessary to decide whether what is forming in the 
female receives anything material, or not, from that which 
has entered her, but also concerning the soul in virtue of 
which an animal is so called (and this is in virtue of the 30 
sensitive part of the soul) — does this exist originally in 
the semen and in the unfertilized embryo ^ or not, and if it 
does whence does it come ? For * nobody would put down 

^ Ambergris is an internal product of a huge animal, the sperm- 
whale ; can this be at the bottom of the statement of Ctesias .? 

^ Aphrodite, the foam-born ! Cf. Galen, vol. iv, p. 531. 

2 κνημα throughout this passage must mean the unfertilized embryo 
or germ, not as usual the ' first mixture of male and female '. 

* The connexion of thought is : ' I raise this question about the 
F 2 


the unfertilized embryo as soulless or in every sense bereft of 
life (since both the semen and the embryo of an animal have 

35 every bit as much life as a plant), and it is productive up 
to a certain point.'^ That then they possess the nutritive 
soul is plain (and plain is it from the discussions elsewhere 
736* about soul why this soul must be acquired first ^). As they 
develop they also acquire the sensitive soul in virtue of 
which an animal is an animal. For '^ e. g. an animal does 
not become at the same time an animal and a man or 
a horse or any other particular animal. For the end is 
developed last, and the peculiar character of the species is 
5 the end of the generation in each individual.^ Hence arises 
a question of the greatest difficulty, which we must strive 
to solve to the best of our ability and as far as possible. 
When and how and whence is a share in reason acquired 
by those animals that participate in this principle ? It is 
plain that the semen and the unfertilized embryo, while 
still separate from each other, must be assumed to have 

JO the nutritive soul potentially, but not actually, except that 
(like those unfertilized embryos that are separated from the 
mother) it absorbs nourishment and performs the function 
of the nutritive soul.^ For at first all such embryos seem 
to live the life of a plant. And it is clear that we must be 
guided by this in speaking of the sensitive and the rational 

sensitive soul because the vegetative (or nutritive) is certainly in the 
embryo even before impregnation. For, &c.' 

^ Referring to wind-eggs of fowls. " de Anima, ii. 4. 

3 The connexion of thought is : ' This is in accordance with the law 
of development, the more general appearing first, the particular later. 
For, &c.' 

* This passage states clearly the famous law generally attributed to 
von Baer, the law that in development the character, e. g., of the class, 
is assumed before that of the genus, of the genus before that of the 
species. Aristotle's example may be otherwise stated thus : the 
embryo assumes the character which marks it out as an animal, not a 
plant, before it assumes the character which marks it out as a man or 
horse, not some other animal. And therefore it must acquire the 
sensitive soul before it is specialized as a member of a sub-kingdom of 

^ Read 'όντα χωριστά for τα χωριστά, and ττΚψ el for ■ιτρ\ν η (πλην ή 
seems not to be used by Α.). The parenthesis refers to wind-eggs, the 
only ' unfertilized embryos ' which are ' separated from the mother ' 
(or laid as eggs), within Aristotle's cognizance, by animals possessing 
distinction of sex. This is the best I can make of this excessively 
difficult passage. 

BOOK II. 3 736^ 

soul. For all three kinds of soul, not only the nutritive, 15 
must be possessed potentially before they are possessed in 
actuality. And it is necessary either (i) that they should all 
come into being in the embryo without existing previously 
outside it, or (2) that they should all exist previously, or 
(3) that some should so exist and others not. Again, it is 
necessary that they should either (i) come into being 
in the material supplied by the female without entering 
with the semen of the male, or (2) come from the male and 
be imparted to the material in the female. If the latter, 
then either all of them, or none, or some must come into 20 
being in the male from outside. 

Now that it is impossible for them all to pre-exist is clear 
from this consideration. Plainly those principles whose 
activity is bodily cannot exist without a body, e.g. walking 
cannot exist without feet. For the same reason also they 
cannot enter from outside. For neither is it possible for 25 
them to enter by themselves, being inseparable from a body, 
nor yet in a body, for the semen is only a secretion of the 
nutriment in process of change.^ It remains, then,^ for the 
reason alone so to enter and alone to be divine, for no 
bodily activity has any connexion with the activity of 
reason. ^ 

Now it is true that the faculty of all kinds of soul seems 30 
to have a connexion with a matter different from and more 
divine than the so-called elements ; but as one soul differs 
from another in honour and dishonour, so differs also the 
nature of the corresponding matter. All have in their 
semen that which causes it to be productive ; I mean what 
is called vital heat. This is not fire nor any such force, but 35 
it is the spiritus included in the semen and the foam-like,* 
and the natural principle in the spiritus, being analogous to 
the element of the stars.^ Hence, whereas fire generates 737^ 
no animal and we do not find any living thing forming in 
either solids or liquids under the influence of fire, the heat 

^ Therefore the nutritive and sensitive souls, which require bodily 
organs, do not enter from outside. '^ Read 8η for oe. 

^ The function of the brain being to cool the blood. 
* For this spiritus is found in all water or liquid matter ; see iii. 1 1. 
^ The ether, or fifth element, in which the stars move. 


of the sun and that of animals does generate them. Not only 
is this true of the heat that works through the semen, but 
whatever other residuum of the animal nature there may 
be, this also has still a vital principle in it.^ From such 
5 considerations it is clear that the heat in animals neither is 
fire nor derives its origin from fire.^ 

Let us return to the material of the semen, in and with 
which comes away from the male the spiritus ^ conveying 
the principle of soul. Of this principle there are two kinds ; 
the one is not connected with matter, and belongs to those 

to animals in which is included something* divine (to wit, 
what is called the reason), while the other is inseparable 
from matter. This material ^ of the semen dissolves and 
evaporates because it has a liquid and watery nature. 
Therefore we ought not to expect it always to come out 
again from the female or to form any part of the embryo 
that has taken shape from it ; the case resembles that of 

i5 the fig-juice which curdles milk, for this too changes 
without becoming any part of the curdling masses. 

It has been settled, then, in what sense the embryo and 
the semen have soul, and in what sense they have not ; they 
have it potentially but not actually.'^ 

Now semen is a secretion and is moved with the same 
movement as that in virtue of which the body increases 

20 (this increase being due to subdivision of the nutriment in 
its last stage). When it has entered the uterus it puts into 
form the corresponding secretion of the female and moves it 
with the same movement wherewith it is moved itself. For 
the female's contribution also is a secretion, and has all the 

^ This appears e. g. from the generation of worms in manure heaps. 

^ There seems to be here a considerable lacuna. We know now that 
all three kinds of soul have vital heat, and we expect to hear of some 
higher material element corresponding to the higher kinds of soul. 
For the rest, we have now settled, more or less, how the three kinds of 
soul arise in the embryo, and we return abruptly to the question raised 
in the first words of the chapter : what happens to the material part 
of the semen ? 

On the development of the soul, compare the most masterly resume 
of this discussion in Dante, Purgatorio, xxv. 

■* I read πνεύμα for σπίρμα. 

* Reading τι. The animals are man and perhaps bees (iv, 10, ad fin). 

'" Reading σώμα for σπίρμα (AW.). 

" This sentence is misplaced, but one cannot say where it should go. 

BOOK II. 3 737^ 

parts in it potentially though none of them actually ; it has 
in it potentially even those parts which differentiate the 25 
female from the male, for just as the young of mutilated 
parents are sometimes born mutilated and sometimes not, 
so also the young born of a female are sometimes female 
and sometimes male instead. For the female is, as it were, 
a mutilated male, and the catamenia are semen, only not 
pure ^ ; for there is only one thing they have not in them, 
the principle of soul. For this reason, whenever a wind-egg 30 
is produced by any animal, the egg so forming has in it the 
parts of both sexes potentially, but has not the principle in 
question, so that it does not develop into a living creature, 
for this is introduced by the semen of the male. When 
such a principle has been imparted to the secretion of the 
female it becomes an embryo. 

Liquid but corporeal substances become surrounded by 35 
some kind of covering on heating, like the solid scum which 
forms on boiled foods when cooling. All bodies are held 737^ 
together by the glutinous ; this quality, as the embryo 
develops and increases in size, is acquired by the sinewy 
substance, which holds together the parts of animals, being 
actual sinew in some and its analogue in others. To the 
same class belong also skin, blood-vessels, membranes, and 5 
the like, for these differ in being more or less glutinous and 
generally in excess and deficiency.- 

4 In those animals whose nature is comparatively im- 
perfect, when a perfect embryo (which, however, is not yet 
a perfect animal) has been formed, it is cast out from the 10 
mother, for reasons previously stated.^ An embryo is 
then complete w hen it is either male or female,"* in the case 

^ See i. 20. 

^ This paragraph is obviously misplaced, but there is no other place 
in G. A. to which it belongs (AW.). 

^ Chap. I of this book. 

* From recent researches it appears that ' the male or female 
character is already fully developed in the fertilized egg ' from the very 
beginning (Lock, Variation, Heredity, aiid Evolution, p. 259). 'Sex 
is predetermined in the fertilized ovum ' (Poulton, Essays on Evolu- 
tion, p. 133). Indeed it is probable that both ova and spermatozoa are 
themselves both male and female, at least in the higher animals. For 


of those animals who possess this distinction, for some 
(i. e. all those which are not themselves produced from 
a male or female parent nor from a union of the two) 
produce an offspring which is neither male nor female. 

15 Of the generation of these we shall speak later. 

The perfect animals, those internally viviparous, keep 
the developing embryo within themselves and in close 
connexion until they give birth to a complete animal and 
bring it to light. 

A third class is externally viviparous but first internally 
oviparous ; they develop the egg into a perfect condition, 

20 and then in some cases the egg is set free as with creatures 
externally oviparous, and the animal is produced from the 
egg within the mother's body ; in other cases, when the 
nutriment from the egg is consumed, development is com- 
pleted by connexion with the uterus, and therefore the egg 
is not set free from the uterus. This character marks the 

25 cartilaginous fish, of which we must speak later by them- 

Here we must make our first start from the first class ; 
these are the perfect or viviparous animals, and of these 
the first is man. Now the secretion of the semen takes 
place in all of them just as does that of any other residual 
matter. For each is conveyed to its proper place without 

30 any force from the breath or compulsion of any other 
cause, as some assert, saying that the generative parts 
attract the semen like cupping-gla.sses, aided by the force 
of the breath, as if it were possible for either this secretion 
or ^ the residue of the solid and liquid nutriment to go 
anywhere else than they do without the exertion of such 
a force. Their reason is that the discharge of both is 

35 attended by holding the breath, but this is a common 

feature of all cases when it is necessary to move anything, 

738^ because strength arises through holding the breath. Why, 

even without this force the secretions or excretions are 

discharged in sleep if the parts concerned are full of them 

evidence, however, against this in some lower animals see e. g. Wilson, 
T/ie Cell in Development a7id hilieritance''•, p. 144. 
' iii. 3. ^ Reading r\ ταΰτψ . . . . ή την. 

BOOK Π. 4 738' 

and are relaxed. One might as well say that it is by the 
breath that the seeds of plants are always segregated to 5 
the places where they are wont to bear fruit. No, the real 
cause, as has been stated already, is that there are special 
parts for receiving all the secretions, alike the useless (as 
the residues of the liquid and solid nutriment), and the 
blood, which has the so-called blood-vessels. 

To consider now the region of the uterus in the female — 
the two blood-vessels, the great vessel and the aorta, divide ro 
higher up, and many fine vessels from them terminate in 
the uterus.^ These become over-filled from the nourish- 
ment they convey, nor is the female nature able to con- 
coct it, because it is colder than man's ; so the blood is 
excreted through very fine vessels into the uterus,^ these 
being unable on account of their narrowness to receive the 15 
excessive quantity, and the result is a sort of haemorrhage. 
The period is not accurately defined in women, but tends 
to return during the waning of the moon.^ This we 
should expect, for the bodies of animals are colder when 
the environment happens to become so,^ and the time of 20 
change from one month to another is cold because of the 
absence of the moon, whence also it results that this time 
is stormier than the middle of the month. When then the 
residue of the nourishment has changed into blood, the 
catamenia tend to occur at the above-mentioned period, 
but when it is not concocted a little matter at a time 25 
is always coming away, and this is why ' whites ' appear in 

^ By the great vessel A. means the vena cava and the whole venous 
system, by the aorta he means the aorta and the whole arterial system. 
He does not distinguish between their functions, holding that both 
alike nourish the body by carrying the blood to all parts of it. The 
fine vessels are the smallest veins and arteries visible to the naked eye, 
7iot the capillaries, which were unknown even to Harvey. 

^ This was the theory of Coste, that ' the blood transudes through 
the capillaries '. But the precise nature of the process seems to be 
still uncertain ; see Playfair, Midwifery'^, vol. i, p. 74. 

^ This of course is quite untrue, but the notion that the moon has 
something to do with it has been renewed in modern times. ' Dr. 
Mead was, I fancy, disposed to be a little merry, when he gravely 
ascribed the tides and the catamenia equally to the influence of the 
moon' (Blundell, Mid%vz/ery, 1840, p. 632). Yet probably there really 
is a connexion between them ; see Darwin, Descent of Ala/i, chap, vi, 
note 32. Life of Huxley, vol. i, p. 359. 

* This again is untrue of the temperature of warm-blooded animals. 


females while still small, in fact mere children. If both these 
discharges of the secretions are moderate, the body remains 
in good health, for they act as a purification of the secre- 
tions which are the causes of a morbid state of body ; if 

?,o they do not occur at all or if they are excessive, they are 
injurious, either causing illness or pulling down the patient ; 
hence whites, if continuous and excessive, prevent girls 
from growing. This secretion then is necessarily discharged 
by females for the reasons given ; for, the female nature 

35 being unable to concoct the nourishment thoroughly, 
there must not only be left a residue of the useless nutri- 
ment, but also there must be a residue in the blood-vessels, 
and this filling ^ the channels of the finest vessels must 
738'' overflow. Then Nature, aiming at the best and the end, 
uses it up in this place ^ for the sake of generation, that 
another creature may come into being of the same kind 
as the former was going to be, for the menstrual blood 
is already potentially such as the body from which it is 
5 In all females, then, there must necessarily be such a 
secretion, more indeed in those that have blood and of 
these most of all in man, but in the others also some 
matter must be collected in the uterine region. The reason 
why there is more in those that have blood and most in 
man has been already given, but why, if all females have 

10 such a secretion, have not all males one to correspond ? 
For some of them do not emit semen but, just as those 
which do emit it^ fashion by the movement in the semen 
the mass forming from the material supplied by the female, 
so do the animals in question bring the same to pass and 
exert the same formative power by the movement ^ within 
themselves in that part from whence the semen is secreted.^ 

15 This is the region about the diaphragm in all those animals 
which have one,^ for the heart or its analogue is the first 
principle of a natural body, while the lower part is a mere 

' Reading πληθνοντα. ^ The uterus. 

" Reading πμοιψ^ρα. * Omitting f'v (AW.). 

^ The reference is to certain insects ; see i. 16. 

' Or the corresponding region in those which have not. 

BOOK II. 4 738* 

addition for the sake of it.^ Now the reason why it is not 
all males that have a generative secretion, while all females 
do, is that the animal is a body with soul or life ; the female 20 
always provides the material, the male that which fashions 
it, for this is the power that we say they each possess, and 
this is what is meant by calling them male and female. 
Thus while it is necessary for the female to provide a body 
and a material mass, it is not necessary for the male, 
because it is not within the work of art or the embryo that 25 
the tools or the maker must exist. While the body is from 
the female, it is the soul that is from the male,^ for the 
soul is the reality of a particular body.^ For this reason 
if animals of a different kind are crossed (and this is 
possible when the periods of gestation are equal and con- 
ception takes place nearly at the same season and there is 
no great difference in the size of the animals), the first cross 30 
has a common resemblance to both parents, as the hybrid 
between fox and dog, partridge and domestic fowl, but as 
time goes on and one generation springs from another, the 
final result resembles the female in form, just as foreign 
seeds produce plants varying in accordance with the 
country in which they are sown.* For it is the soil that 35 
gives to the seeds the material and the body of the plant. 
And hence the part of the female which receives the semen 
is not a mere passage, but the uterus has a considerable 

^ The truth is the other way about in the order of evokition, for 
some of the lowest animals have a digestive canal without a heart, but 
from A.'s point of view the heart as the seat of life is the end to which 
everything else is subordinate ; besides it is visible to the eye before 
the canal in the embryo of higher animals. 

^ And it is this which gives reality to the body. 

^ A body which is not alive is not strictly speaking a body at all, 
any more than a statue is really one. Hence soul makes a body really 
to be one in the strict sense. 

* e. g. if seed of a mountain plant is sown in a fertile plain it will 
grow more luxuriantly. Despite AW. the astonishing statements 
about dog and fox, partridge and fowl are totally wrong ; the experi- 
ments of Flourens, to which they refer, only show that if you cross two 
species and keep on crossing the hybrids with otie of the iwo orighiul 
species the result will in a few generations be indistinguishable 
irom it. 

A. thought that the Laconian hounds were descended from a cross 
between dog and fox. 


width, whereas the males that emit semen have only 
passages for this purpose, and these are bloodless.^ 

Each of the secretions becomes such at the moment 
when it is in its proper place ; before that there is nothing 
of the sort unless with much violence and contrary to 
5 We have thus stated the reason for which the generative 
secretions are formed in animals. But when the semen 
from the male (in those animals which emit semen) has 
entered, it puts into form the purest part of the female 
secretion (for the greater part of the catamenia also is 
useless and fluid, as is the most fluid part of the male 

10 secretion, i. e. in a single emission, the earlier discharge 
being in most cases apt to be infertile rather than the 
later, having less vital heat through want of concoction, 
whereas that which is concocted is thick and of a more 
material nature). 

If there is no external discharge, either in women or 
other animals, on account of there not being much useless 

15 and superfluous matter in the secretion, then the quantity 
forming within the female altogether is as much as what 
is retained within those animals which have an external 
discharge ; this is put into form by the power of the male 
residing in the semen secreted by him, or, as is clearly 
seen to happen in some insects, by the part in the female 
analogous to the uterus being inserted into the male. 

20 It has been previously stated that the discharge accom- 
panying sexual pleasure in the female contributes nothing 
to the embryo. The chief argument for the opposite view 
is that what are called bad dreams occur by night with 
women as with men ; but this is no proof, for the same 
thing happens to young men also who do not yet emit 

25 semen, and to those who do emit semen but whose semen 
is infertile. 

It is impossible to conceive without the emission of the 

^ See i. 6, ad βη. Stress is laid upon the bloodlessness of the ducts 
because this contrasts with the material of the female. 

^ e. g. the blood remains blood so long as it is in the blood-vessels, 
but when it enters the testes semen is secreted from it, and not before 

BOOK Π. 4 739^ 

male in union and without the secretion of the correspond- 
ing female material, whether it be discharged externally or 
whether there is only enough within the body. Women 
conceive, however, without experiencing the pleasure usual 
in such intercourse, if the part chance to be in heat and 30 
the uterus to have descended.^ But generally speaking 
the opposite is the case, because the os uteri is not closed 
when the discharge takes place which is usually accom- 
panied by pleasure in women as well as men, and when 
this is so there is a readier way for the semen of the male 
to be drawn into the uterus. ^. 

The actual discharge does not take place within the 
uterus as some think, the os uteri being too narrow, but 
it is in the region in front of this, where the female dis- 
charges the moisture found in some cases, that the male 739'' 
emits the semen.^ Sometimes it remains in this place ; ^ 
at other tim