O F T H E F O E T U S. 293 



tion, as much exterrial heat as is fufhcient for its 

 expanfion. This heat communicates motion to 

 the fluids ; it gives play to all the organs ; and 

 the hlood is formed in the placenta, and in the 

 body of the foetus, folely by the motion excited 

 by the heat. We might even maintain, that the 

 formation of the blood in a child is as indepen- 

 dent of the mother, as that which arifes in the 

 egg is independent of the hen that covers it, or 



of the furnace which heats it. 



Jt is certain that the foetus, the membranes, 

 and the placenta, are all nouriihed and expanded 

 -by abforption ; for, at lirft, the lac that con- 

 tains the whole produd: of generation does not 

 adhere to the uterus : And we have feen, from 

 the experiments of De Graaff upon female rab- 

 bits, that he made the globules which contained 

 the foetufes roll about in the uterus. They 

 could receive no nourifliment, therefore, but by 

 abforbing the fluids that conftantly bedew the 

 uterus, to which they afterwards begin to ad- 

 here by means of a mucilage that gradually gives 

 origin to fmall blood vefTels, as ihall afterwards 

 be more fully explained. 



But, to return to the formation of the foetus, 

 concerning which we have to make feveral re- 

 marks, both as to its fituation, and to the difl'er- 

 ent clrcumflances that may prevent or alter ihe 

 mode of its-produdtion. 



In the liuman fpccics, the femen of the male 

 enters into the ureru?, the cavity of which i' 



T 3 confiderubl'.' , 



