On The Parts Of Animals   

four-footed vivipara than in man. For there is always more earth in
the composition of these animals than in that of the human body.
However, not only all these parts but such others as are nearly
connected with them, skin for instance, bladder, membrane, hairs,
feathers, and their analogues, and any other similar parts that there
may be, will be considered farther on with the heterogeneous parts.
There we shall inquire into the causes which produce them, and into
the objects of their presence severally in the bodies of animals. For,
as with the heterogeneous parts, so with these, it is from a
consideration of their functions that alone we can derive any
knowledge of them. The reason for dealing with them at all in this
part of the treatise, and classifying them with the homogeneous parts,
is that under one and the same name are confounded the entire organs
and the substances of which they are composed. But of all these
substances flesh and bone form the basis. Semen and milk were also
passed over when we were considering the homogeneous fluids. For the
treatise on Generation will afford a more suitable place for their
examination, seeing that the former of the two is the very foundation
of the thing generated, while the latter is its nourishment.
Part 10
Let us now make, as it were, a fresh beginning, and consider the
heterogeneous parts, taking those first which are the first in
importance. For in all animals, at least in all the perfect kinds,
there are two parts more essential than the rest, namely the part
which serves for the ingestion of food, and the part which serves for
the discharge of its residue. For without food growth and even
existence is impossible. 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 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.
Plants, again, inasmuch as they are without locomotion, present no
great variety in their heterogeneous parts. For, where the functions
are but few, few also are the organs required to effect them. The
configuration of plants is a matter then for separate consideration.
Animals, however, that not only live but feel, present a greater
multiformity of parts, and this diversity is greater in some animals
than in others, being most varied in those to whose share has fallen
not mere life but life of high degree. Now such an animal is man. For
of all living beings with which we are acquainted man alone partakes
of the divine, or at any rate partakes of it in a fuller measure than
the rest. For this reason, then, and also because his external parts
and their forms are more familiar to us than those of other animals,
we must speak of man first; and this the more fitly, because in him
alone do the natural parts hold 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 the necessary
consequence of what has already been stated concerning the brain.
There are, indeed, some who hold that the life of man-would be longer
than it is, were his head more abundantly furnished with flesh; and
they account for the absence of this substance by saying that it is
intended to add to the perfection of sensation. For the brain they
assert to be the organ of sensation; and sensation, they say, cannot
penetrate to parts that are too thickly covered with flesh. But
neither part of this statement is true. On the contrary, were the
region of the brain thickly covered with flesh, the very purpose for
which animals are provided with a brain would be directly contravened.
For the brain would itself be heated to excess and so 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 head, and