BOOK TWO

 [p. 133]it would remain inoperative and would not turn into a nature. Therefore, in order that it may not perish, but may become a nature in place of semen, there must be an afflux to it of a little blood- or, rather, one should not say a little, but a quantity commensurate with that of the semen. What is it then that measures the quantity of this afflux? What prevents more from coming? What ensures against a deficiency? What is this third overseer of animal generation that we are to look for, which will furnish the semen with a due amount of blood? What would Erasistratus have said if he had been alive, and had been asked this question? Obviously, the semen itself. This, in fact, is the artificer analogous with Phidias, whilst the blood corresponds to the statuary's wax.

Now, it is not for the wax to discover for itself how much of it is required; that is the business of Phidias. Accordingly the artificer will draw to itself as much blood as it needs. Here, however, we must pay attention and take care not unwittingly to credit the semen with reason and intelligence; if we were to do this, we would be making neither semen nor a nature, but an actual living animal.

i.e. we should be talking psychology, not biology; cf. stomach, p. 307, note 3.

And if we retain these two principles- that of proportionate attraction,

Attraction now described not merely as qualitative but also as quantitative. cf. p. 85, note 3.

and that of the non-participation of intelligence- we shall ascribe to the semen a faculty for attracting blood similar to that possessed by the lodestone for iron.

He still tends either to biologize physics, or to physicize biology - whichever way we prefer to look at it. cf. Book I., chap. xiv.

Here, then, again, in the case of the semen, as in so many previous instances, we have been compelled to acknowledge some kind of attractive faculty.