would have known that not everything which is taken for food under the pressure of outward necessity turns out to be suitable nourishment for the animal, but that some things no sooner come into contact with the plicatures of the stomach than they are wont to be corrupted, and are vomited or voided, or disposed of in some other way, so that not even for a little time do they undergo the first and natural digestion, much less become incorporated with that which is to be nourished; as also, that not even everything which has been digested in the stomach and received the first change actually arrives at the parts to be nourished, since some of it loses its nutritive power even in the stomach, and some during the second change, and the digestion that takes place in the liver is separated and passes into something else which is destitute of the power to nourish; nay, that the change which takes place in the liver does not all issue in nourishment to men, but the matter changed is separated as refuse according to its natural purpose; and that the nourishment which is left in the members and parts themselves that have to be nourished sometimes changes to something else, according as that predominates which is present in greater or less[1] abundance, and is apt to corrupt or to turn into itself that which comes near it.
Chap. vi.—Everything that is useless or hurtful is rejected.
Since, therefore, great difference of nature obtains in all animals, and the very nourishment which is accordant with nature is varied to suit each kind of animal, and the body which is nourished; and as in the nourishment of every animal there is a threefold cleansing and separation, it follows that whatever is alien from the nourishment of the animal must be wholly destroyed and carried off to its natural place, or change into something else, since it cannot coalesce with it; that the power of the nourishing body must be suitable to the nature of the animal to be nourished, and accordant; with its powers; and that this, when it has passed through the strainers appointed for the purpose, and been
- ↑ The common reading is "excessive."
