Book 2
3
For there is not a single animal which could live or endure for the shortest time if, possessing within itself so many different parts, it did not employ faculties which were attractive of what is appropriate, eliminative of what is foreign, and alterative of what is destined for nutrition. On the other hand, if we have these faculties, we no longer need channels, little or big, resting on an unproven hypothesis, for explaining the secretion of urine and bile, and the conception of some favourable situation (in which point alone Erasistratus shows some common sense, since he does regard all the parts of the body as having been well and truly placed and shaped by Nature).
