and motions, for illustrations ; at another time to an ' anima ' in the egg, and in the seed of the male. Moreover, when he seems positively and definitively to determine what it is in each seed, whether of plants or animals, which render the same fer- tile, he repudiates heat and fire as improper agents ; nor does he admit any faculty of a similar quality ; nor can he find any- thing in the seed which should be fit for that office ; but he is driven to acknowledge something incorporeal, and coming from foreign sources, which he supposes (like art, or the mind) to form the foetus with intelligence and foresight, and to in- stitute and ordain all its parts for its welfare. He takes refuge, I say, in a thing which is obscure and not recognizable by us; namely, in a spirit contained in the seed, and in a frothy body, and in the nature in that spirit, corresponding in proportion to the elements of the stars. But what that is, he has nowhere informed us.
EXERCISE THE FORTY-EIGHTH.
The opinion of Fabricius on the efficient cause of the chick is refuted.
As I have chosen Aristotle, the most eminent among the an- cient philosophers, and Fabricius of Aquapendente, one of the foremost anatomists of modern times, as my especial guides and sources of information on the subject of animal generation, when I find that I can make nothing of Aristotle upon a particular topic, I straightway turn to Fabricius ; and now I desire to know what he thought of the efficient cause of generation.
I find that he endeavours to satisfy three doubts or diffi- culties involved in this subject : First, What is the ' efficient ' of the chick ? This he answers, by saying, the semen of the male. Secondly, How does this appear in the egg, and in what way does the semen of the cock fecundate the egg ? Thirdly and lastly, In what order are the parts of the chick engendered ?
As to the first query, it appears from our observations, that the cock and his seminal fluid are verily the ( efficient/ but
