GENERATION OF ANIMALS, IV. viii. 



sufficient independent supply of nourishment and be 

 able to go about from place to place.) It is from 

 here, too, that the seminal residue is drawn : the 

 reason is given in the earlier chapters of our discus- 

 sion." Both the residue in males and the menstrual 

 fluid in females are of a bloodlike nature ; now the 

 source of the blood and of the blood-vessels is the 

 heart, which is situated in these ^ parts : therefore of 

 necessity it is here that the change which this sort of 

 residue undergoes must be first of all apparent. For 

 this reason the voice of both male and female under- 

 goes a change when they begin to produce semen, 

 because the source of the voice is there, '^ and the voice 

 changes its quality when that which provides its 

 movement does so ; and further, the parts around the 

 breasts rise up plainly in males as well as in females, 

 though more so in the latter, since, as there is a 

 plentiful excretion of matter downwards in females, 

 the region of the breasts becomes empty and spongy ; 

 and similarly in the case of those animals whose 

 breasts are down below. Of course, this change in 

 the voice and in the region of the breasts makes itself 

 evident in the other animals as well — to those who 

 have experience of each particular kind ; but the 

 change is greatest in human beings. The reason is 

 that women produce more residue than any other 

 female animal, and so do men than other male 

 animals, in proportion to their size [this refers to the 

 excretion of menstrua] fluid and of semen respect- 

 ively]. Thus, when the embryo no longer absorbs 



' The heart, which is the apxri of the organism, is also in 

 particular the source of all physical sexual characteristics ; 

 see 766 a 30 ff., and note on 763 b 27. Cf. 787 b 15 et 

 preced. See also App. B § 31. 



471 



