GENERATION OF ANIMALS, I. xx. 



cause a great difference in the amount of this dis- 

 charge which is produced : e.g., some pungent foods 

 cause a noticeable increase in the amount. 



The pleasure which accompanies copulation is due 

 to the fact that not only semen but also pneuma " is 

 emitted : it is from this pneuma as it collects together 

 that the emission of the semen results. This is plain 

 in the ease of boys who cannot yet emit semen, 

 though they are not far from the age for it, and in 

 infertile men, because all of them derive pleasure 

 from attrition. Indeed, men whose generative organs 

 have been destroyed sometimes suffer from looseness 

 of the bowels caused by residue which cannot be 

 concocted and converted into semen being secreted 

 into the intestine. 



Further, a boy actually resembles a woman in 

 physique, and a woman is as it were an infertile male ; 

 the female, in fact, is female on account of inabiUt}'** 

 of a sort, \\z., it lacks the power to concoct semen 

 out of the final state of the nourishment (this is 

 either blood, or its counterpart in bloodless animals) 

 because of the coldness of its nature. Thus, just as 

 lack of concoction produces in the bowels diarrhoea, 

 so in the blood-vessels it produces discharges of blood 

 of various sorts, and especially the menstrual dis- 

 charge (which has to be classed as a discharge of 

 blood, though it is a natural discharge, and the rest 

 are morbid ones). 



Hence, plainly, it is reasonable to hold that genera- 

 tion takes place from this process ; for, as we see, the 

 menstrual fluid is semen, not indeed semen in a pure 

 condition, but needing still to be acted upon. It 



<• See 718 a 4, 738 a 1, etc. 

 * Cf. 765 b 9. 



103 



