On The Parts Of Animals   

pre-existence of an efficient cause homogeneous with themselves, such
as the statuary's art, which must necessarily precede the statue; for
this cannot possibly be produced spontaneously. Art indeed consists in
the conception of the result to be produced before its realization in
the material. As with spontaneity, so with chance; for this also
produces the same result as art, and by the same process.
The fittest mode, then, of treatment is to say, a man has such and
such parts, because the conception of a man includes their presence,
and because they are necessary conditions of his existence, or, if we
cannot quite say this, which 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 is an animal with such
and such characters, therefore is the process of his development
necessarily such as it is; and therefore is it accomplished in such
and such an order, this part being formed first, that next, and so on
in succession; and after a like fashion should we explain the
evolution of all other works of nature.
Now that with which the ancient writers, who first philosophized 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 instance, by antagonism or friendship, whether by intelligence or
spontaneous action, the substratum of matter being assumed to have
certain inseparable properties; fire, for instance, to have a hot
nature, earth a cold one; the former to be light, the latter heavy.
For even the genesis of the universe is thus explained by them. After
a like fashion do they deal also with the development of plants and of
animals. They say, for instance, that the water contained in the body
causes by its currents the formation of the stomach and the other
receptacles of food or of excretion; and that the breath by its
passage breaks open the outlets of the nostrils; air and water being
the materials of which bodies are made; for all represent nature as
composed of such or similar substances.
But if men and animals and their several parts are natural phenomena,
then the natural philosopher must take into consideration not merely
the ultimate substances of which they are made, but also flesh, bone,
blood, and all other homogeneous parts; not only these, but also the
heterogeneous 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 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.
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. 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. For like a physician in a painting, or like
a flute in a sculpture, in spite of its name it will be unable to do
the office which that name implies. Precisely in the same way no part