On The Parts Of Animals   

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 bloodless animals are, as a general rule,
more timorous than such as have blood, so that they remain motionless,
when frightened, and discharge their excretions, and in some instances
change colour. Such animals, on the other hand, as have thick and
abundant fibres in their blood are of a more earthy nature, and of a
choleric temperament, and liable to bursts of passion. For anger is
productive of heat; and solids, when they have been made hot, give off
more heat than fluids. The fibres therefore, being earthy and solid,
are turned into so many hot embers in the blood, like the embers in a
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 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 cold, the fluid, as has been already
stated, passes off with it by evaporation, and the residue is dried up
and solidified, not by heat but by cold. So long, however, as the
blood is in the body, it is kept fluid by animal heat.
The character of the blood affects both the temperament and the
sensory faculties of animals in many ways. This is indeed what might
reasonably be expected, seeing that the blood is the material of which
the whole body is made. For nutriment supplies the material, and the
blood is the ultimate nutriment. It makes then a considerable
difference whether the blood be hot or cold, thin or thick, turbid or
clear.
The watery part of the blood is serum; and it is watery, either owing
to its not being yet concocted, or owing to its having become
corrupted; so that one part of the serum is the resultant of a
necessary process, while another part is material intended to serve
for the formation of the blood.
Part 5
The differences between lard and suet correspond to 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-sanguineous
animals have either lard or suet; for they have no blood. Among
sanguineous animals those whose blood is dense have suet rather than
lard. For suet is of an earthy nature, that is to say, it contains but
a small proportion of water and is chiefly composed of earth; and this
it is that makes it coagulate, just as the fibrous matter of blood
coagulates, or 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 toes, there is no suet, but
in its place lard; and this, not being of an earthy character, neither
coagulates nor dries up into a friable mass.
Both lard and suet when present in moderate amount are beneficial; for
they contribute to health and strength, while they are no hindrance to
sensation. But when they are present in great excess, they are
injurious and destructive. For were the whole body formed of them it
would perish. For an animal is an animal in virtue of its sensory