ON GENERATION. 351 



not the ' adequate ' cause of generation ; that the hen comes 

 in here as something. In this place, therefore, we are princi- 

 pally to inquire how the semen of the cock fecundates the egg 

 otherwise unprolific, and secures the engenderment of a chick 

 from it? 



But let us hear Fabricius : l " Those things differ/' he ob- 

 serves, "that are produced from eggs, from those that origi- 

 nate from semen, in this, that oviparous animals have the 

 matter from which the embryo is incorporated distinct and sepa- 

 rate from the agent ; whilst viviparous animals have the effi- 

 cient cause and the matter associate and con corporate. For 

 the ( agent ' in the oviparous animal is the semen of the male, 

 in the fowl the semen of the cock, which neither is nor can be 

 in the egg ; the ' matter/ again, is the chalazae from which 

 the foetus is incorporated. These two differ widely from one 

 another ; for the chalazse are added after the vitellus is formed, 

 whilst it is passing through the second uterus, and are an ac- 

 cession to the internal egg ; the semen galli, on the contrary, 

 is stored near the fundament, is separated from the chalazse by 

 a great interval, and nevertheless by its irradiating faculty, 

 fecundates both the whole egg and the uterus. Now in the 

 viviparous animal, the semen is both ' matter ' and ' agent/ 

 the two consisting and being conjoined in the same body/' 



Our author appears to have introduced this distinction be- 

 tween oviparous and viviparous animals, that he might spare, 

 or at all events, that he might not directly shock or upset the 

 notions of medical writers on the generation of man, they 

 teaching that the seminal fluids of either sex, projected to- 

 gether in intercourse, are mingled ; that as one or other pre- 

 ponderates, this becomes the ' efficient/ that stands in lieu of 

 the ' matter ; ' and that the two together, tending to the 

 same end, amalgamate into the ' conception* of the viviparous 

 animal. 



But when he finds that neither in the egg nor uterus of the 

 fowl is there any semen or blood, and avows his belief that 

 nothing is emitted by the male in intercourse, that can by 

 possibility reach the uterus of the female, nor in the egg dis- 

 covers a trace of aught supplied by the male, he is compelled 



1 Op. cit. p. 38. 



