324 OF THE GROWTH, &c. 



cllately confined by the amnios, which is the in- 

 ternal membrane : It is thin and tranfparent, 

 and folds itfelf round the umbilical cord, at its 

 infertion into the placenta, and continues to co- 

 ver it the whole way to the navel of the foetus. 

 The chorion is the external menibrane ; it is 

 thick, fpcngy, and interfperfed with blood- vef- 

 fels. It confifts of feveral coats, the outermoll 

 of which covers the convex furface of the pla- 

 centa. It fends off duplicatures to cover the 

 papillae, which are inferted into the cavities at 

 the fundus of the uterus, called lacunae. Thefe 

 infertions connect the foetus to the uterus. 



Som.e anatomlUs have maintained, tliat the 

 human foetus, like thofe of certain quadrupeds, 

 was furnilhed with an ailantois, a membrane 

 deftined for the reception of the urine ; and they 

 have pretended to have difcovered it between 

 the chorion and amnios, or in the middle of the 

 placenta, at the root of the umbilical cord, un- 

 der the form of a pretty large bladder ; and that 

 it received the urine by means of a long tube, 

 which made a part of the cord, and which open- 

 ed at one end into the bladder, and, at the other, 

 into the ailantois, anfwering the fame purpofes 

 as the urachus in other animals. They acknow- 

 ledge, however, that the urachus of the human 

 foetus is not near fo large as in quadrupeds ; 

 but they afiert that it is divided into a number 

 of fmall tubes, and that the urine paffes into 



their cavities. 



To 



