of his own good health ; but he is not familiar with medicine in the same respect as he has worked his own cure ; it happens simply that the man who here recovers his health is a physi- cian. It therefore occasionally happens, that these two things are distinct and separate. But it is not otherwise with every- thing besides that is of art : none of these has in itself a principle of performance or action, though some of them have such a principle in other things and beyond themselves, such as a house, and aught else that is made with hands ; and some have even such a principle inherent, but not per se and independently: everything, for example, may by accident become a cause to it- self. Nature is therefore, as stated [that which has an inhe- rent principle of motion] ; and those things have nature within them which possess this principle. Now all such are substances; for nature is always some subject, and inheres in the subject."
These things I have spoken of at length, and even quoted the words of the writers appealed to, that it might thence appear first, that all I attribute to the egg is actually there, viz. : matter, organ, efficient cause, place, and everything else requi- site to the generation of the chick; and next and more especially, that the truth in regard to the following very difficult ques- tions might be made clearly to appear, viz.: Which and what principle is it whence motion and generation proceed? By what virtue does the semen act, according to Aristotle ? What is it that renders the semen itself fruitful ? (for the philosopher will have it that nature in all natural bodies is the innate prin- ciple of motion and of rest, and not any second accident.) Whether is that which in the egg is cause, artificer, and principle of generation and of all the vital and vegetative operations conservation, nutrition, growth innate or superadded ? and whether does it inhere primarily, of itself, and as a kind of nature, or intervene by accident, as the physician in curing dis- eases ? Whether is that which transforms the egg into a pullet inherent or acquired, or is it already conceived in the ovary, and does it nourish, augment, and perfect the egg there ?
What is it besides that preserves the egg sweet after it is laid? What is it that renders an egg fruitful is it to be called soul, or a portion of the soul, or something belonging to the soul, or some- thing having a soul, or is it intelligence, or, finally, is it Divinity? seeing that it acts to a definite end, and orders all with in-
