GENERATION OF ANIMALS, I. xi.-xii. 



function that prevents this, nor do they produce their 

 young by the two-stage process." Besides, it is 

 impossible for young animals to be formed near the 

 diaphragm ; embryos are bound to be hea\y and to 

 move about, and that part of the body is a vital spot 

 and would not be able to put up vvith such things. 

 Further, (if the uterus were placed high,) parturition 

 would of necessity be difficult on account of the 

 distance to be covered, since even as it is, in the case 

 of women, if they draw up the uterus at the time of 

 parturition by yav\-ning or by doing something of the 

 sort, difficulty in delivery is the result. Even when 

 empty the uterus produces a stifling sensation if ' 



pushed upwards. Besides, a uterus which is destined 

 to contain (not an egg but) an actual animal must of 

 necessity be a stronger thing ; that is why the uterus 

 of all viviparous animals is fleshy, whereas in those 

 cases where it is near the diaphragm the uterus is 

 membranous. This is clearly to be seen in the case 

 of those animals which produce their young by the 

 two-stage process : the eggs are carried high up and 

 towards one side, whereas the young creatures are 

 carried in the lower part of the uterus. 



We have now explained the reason why contrary 

 arrangements of the uterus are found in certain 

 animals, and in general why in some the uterus is 

 placed low down and in others high up by the dia- 

 phragm. 



We have seen too that while all animals have their XII 

 uterus inside, some have their testes inside and others re^n^rkf*^ 

 outside. The reason whv the uterus is alwavs inside 

 is that it is the container for the voung creature while 

 it is being formed, and this needs protection, shelter, 

 and concoction,^ which the outer part of the body 



35 



