ON GENERATION. 297 



species, but in so far as this man and that woman in these bones 

 and muscles constitute human forms, of both of which, if So- 

 crates be a certain mixture, a compound of both, that by which 

 he is made must needs be a mixed univocal compound of the 

 two ; i. e. a mixed efficient of a mixed effect. And therefore it 

 is that the male and female by themselves, and separately, are 

 not genetic, but become so united in coitu, and made one animal 

 as it were; whence, from the two as one, is produced and educed 

 that which is the true efficient proximate cause of conception. 



The medical writers also, in directing their attention to the 

 particulars of human generation alone, come to conclusions on 

 generation at large; and the spermatic fluid proceeding from 

 the parents in coitu has in all probability been taken by them 

 for true seed, analogous to the seeds of plants. It is not without 

 reason, therefore, that they imagine the mixed efficient cause of 

 the future offspring to be constituted by a mixture of the 

 seminal matters of each parent. And then they go on to assert 

 that the mixture proceeding immediately from intercourse is de- 

 posited in the uterus and forms the rudiments of the conception. 

 That things are very different, however, is made manifest by 

 our preceding history of the egg, which is a true conception. 



EXERCISE THE THIRTY-FOURTH. 



Of the matter of the egg, in opposition to the Aristotelians and 

 the medical writers. 



The position taken up by the medical writers against the 

 Aristotelians, viz., that the blood is not the first element in a con- 

 ception, is clearly shown from the generation of the egg to be 

 well chosen : neither during intercourse, nor before nor after it, 

 is there a drop of blood contained in the uterus of the fowl; nei- 

 ther are the rudiments of eggs red, but white. Many animals 

 also conceive in whose uteri, if they be suddenly laid open after 

 intercourse, no blood can be demonstrated. 



But when they contend that the maternal blood is the food 

 of the foetus in utero, especially of its more sanguineous parts, 



