350 ON GENERATION. 



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 



