ee degrees of composition,
viz.:--

(1) "Composition out of what some call the elements, such as air,
earth, water, and fire," or "out of the elementary forces, hot
and cold, solid and fluid, which form the material of all
compound substances."

(2) Composition out of these primary substances of the homogeneous
parts of animals, e.g. blood, fat, marrow, brain, flesh, and
bone.

(3) Composition into the heterogeneous parts or organs. These parts he
describes in detail, considering those belonging to sanguineous
animals first and most fully.

These divisions correspond roughly to the threefold study of structure
which we nowadays recognize as chemical, histological, and anatomical.

As examples of Aristotle's method of treatment, his descriptions of
blood, the brain, the heart, and the lung may be considered.

Of the _blood_ he says, "What are called fibres are found in the blood
of some animals, but not of all. There are none, for instance, in the
blood of deer and of roes, and for this reason the blood of such
animals as these never coagulates.... Too great an excess of water makes
animals timorous.... Such animals, on the other hand, as have thick and
abundant fibres in their blood are of a more choleric temperament, and
liable to bursts of passion.... Bulls and boars are choleric, 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 are taken out of the blood, the fluid that remains will no longer
coagulate."

From these quotations it will be noted that Aristotle attributed the
coagulum to the presence of fibres, and in this he anticipated
Malpighi's discovery made in the seventeenth century. His remarks on the
proportion of coagulum and serum in different animals, which is enlarged
upon in the "History of Animals,"[5] harmonize with modern observations.
In another of his works[6] he remarks that the blood in certain diseased
conditions will not coagulate. This is known to be the case in cholera,
certain fevers, asphyxia, etc.; and the fact was probably obtained from
Hippocrates. Although Aristotle speaks here of entire absence of
coagulation in the blood of the deer and the roe, in the "History of
Animals" he admits an imperfect coagulation, for he says, "so that their
blood does not coagulate like that of other animals." The animals named
are commonly hunted, a