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 form, is not hot. Blood then in a
certain sense 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 therefore
blood is essentially hot. But so far as blood becomes hot from some
external influence, it is not hot essentially.
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 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hot and consistent while in the body, but when withdrawn under a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 must attribute to such substances
the possession of opposite properties in a greater or less degree.
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