OF THE FOETUS. 345 



blood, and that the adlion of this blood upon 

 the uterus, during every periodic revolution, is 

 the reafon why the human foetus is excluded at 

 fo many different terms ? It is natural to i- 

 magine, that, if the females of viviparous ani- 

 mals had menfes like women, their deliveries 

 would be follow^ed by an effufion of blood, and 

 be equally various in their terms. The foetufes 

 of animals are brought forth covered with their 

 membranes ; and it is feldom that the mem- 

 branes are broken, or the waters flow before 

 delivery. But the birth of a child, with its 

 membranes entire, is a rare phaenomenon. This 

 circumfhance feems to evince, that human foe- 

 tufes make greater efforts to efcape from their 

 prifon than thofe of other animals, or that the 

 uterus of a woman affords not fo free a paffage 

 to the child ; for it is by the ftruggles of the 

 foetus againft the rcfiftance it meets with at the 

 orilice of the uterus, that the membranes are 

 torn. 



R E C A P I- 



