GREEK BIOLOGY AND MEDICINE 



parts, is fashioned by its final cause through a 

 process of generation. Even when mature, it 

 is not a static being, but still a vital process, 

 living its life, its full life which it had not 

 attained as an embryo. The embryo has the 

 nutritive soul or life, but not the sensitive 

 and motor soul which comes at birth, and still 

 less the rational soul which comes to man 

 alone. 



" For nobody would put down the unfertil- 

 ized embryo as soulless or in every sense bereft 

 of life (since both the semen and the embryo 

 of an animal have every bit as much life as a 

 plant). . . . That then they possess the nutri- 

 tive soul is plain. ... As they develop, they 

 also acquire the sensitive soul, in virtue of 

 which an animal is an animal. ... An animal 

 does not become at the same time an animal 

 and a man and a horse or any other particular 

 animal. For the end is developed last, and the 

 peculiar character of the species is the end of 

 the generation of each individual." * 6 This 

 passage states a fundamental principle of em- 

 bryology, that the general characters belong- 

 ing to the class or genus are first displayed by 

 the embryo, and afterwards the distinguishing 

 characters of the species to which it belongs.* 1 



[70] 



