proper heat of an object perfects the corresponding passive qualities,
which are the proper matter of any given object. For when concoction
has taken place we say that a thing has been perfected and has come to
be itself. It is the proper heat of a thing that sets up this
perfecting, though external influences may contribute in some
degrees to its fulfilment. Baths, for instance, and other things of
the kind contribute to the digestion of food, but the primary cause is
the proper heat of the body. In some cases of concoction the end of
the process is the nature of the thing-nature, that is, in the sense
of the formal cause and essence. In other cases it leads to some
presupposed state which is attained when the moisture has acquired
certain properties or a certain magnitude in the process of being
broiled or boiled or of putrefying, or however else it is being
heated. This state is the end, for when it has been reached the
thing has some use and we say that concoction has taken place. Must is
an instance of this, and the matter in boils when it becomes purulent,
and tears when they become rheum, and so with the rest.
Concoction ensues whenever the matter, the moisture, is
mastered. For the matter is what is determined by the heat
connatural to the object, and as long as the ratio between them exists
in it a thing maintains its nature. Hence things like the liquid and
solid excreta and ejecta in general are signs of health, and
concoction is said to have taken place in them, for they show that the
proper heat has got the better of the indeterminate matter.
Things that undergo a process of concoction necessarily become
thicker and hotter, for the action of heat is to make things more
compact, thicker, and drier.
This then is the nature of concoction: but inconcoction is an
imperfect state due to lack of proper heat, that is, to cold. That
of which the imperfect state is, is the corresponding passive
qualities which are the natural matter of anything.
So much for the definition of concoction and inconcoction.