GENERATION OF ANIMALS, II. iv. 



on the one hand, the result of necessity, and the 

 reasons have been given : The female system cannot 

 effect concoction, and therefore of necessity residue 

 must be formed not only from the useless nourish- 

 ment, but also " in the blood-vessels, and when there 

 is a full complement of it in those very fine blood- 

 vessels, it must overflow. On the other hand, in 

 order to serve the better purpose, the End, Nature 

 diverts it to this place and employs it there for the 

 sake of generation, in order that it mav become 

 another creature of the same kind as it would ha^e 

 become, since even as it is, it is poteniiallt/ the same in 

 character as the body whose secretion it is. 



In all female animals, then, some residue must of 

 necessitv be formed : a greater amount of it in the 

 blooded ones, and the greatest of all in human beings, 

 though some substance must of necessity collect in 

 the region of the uterus in the other animals too. 

 The reason why a larger amount is produced in the 

 blooded animals, and the largest amount of all in 

 human beings, has already been stated." 



But although a residue of this sort occurs in all 

 females, it does not occur in all males. Why is tills r '^ 

 Some males do not emit semen, but, just as the ones 

 which emit semen fashion the creature that is taking 

 shape out of the material supplied by the female by 

 the agency of the movement resident in the semen, 

 so these fashion it into shape by the agencv of the 

 movement which resides in that part of themselves 

 whence the semen is secreted ; thev produce this 

 same effect of causing the material to set."^ (The 

 part to which I refer is the region around the dia- 

 phragm in all those animals which have one, because 



** Cf. above, 736 a 27 and references there given. 



183 



