OF THE FOETUS. 327 



It has been imagined by fome, that the blood 

 of the mother paflesinto the body of the foetus, 

 by means of the placenta and umbilical cord : 

 They fuppofed, that the blood-veffels of the u- 

 rerus opened into the lacunae, and thofe of the 

 placenta into the papillae, and that they inofcu- 

 lated with one another. But this opinion is 

 contradided by experiment. When the arteries 

 of the umbilical cord are injedted, the liquor re- 

 turns by the veins, without any of it efcaping 

 externally. Befides, the»papillae can be drawn 

 out of the lacunae in which they are lodged, 

 without any extravafation of blood either from 

 the uterus or placenta ; from both there oozes 

 out a milky matter, which, we have already re- 

 marked, ferves for the nourifhment of the foe- 

 tus. It is probable that this liquor enters the 

 veins of the placenta in the fame manner as the 

 chyle enters the fubclavian vein ; and the pla- 

 centa, perhaps, performs the ofEce of the lungs 

 in maturating the blood. One thing is certain, 

 that the blood appears much fooner in the pla- 

 centa than in the foetus ; and I have often ob- 

 ferved, in eggs which had been fat upon for a 

 day or two, that the blood appeared lirft in the 

 membranes, and that their blood-velTels are nu- 

 merous and large, while the whole body of the 

 foetus, except the point where thefe blood- 

 veffels terminate, is only a white tranfparent 

 matter, in wlilch there is not the lealt veftige 

 of blood. 



It 



