The Fetal Membraties 



63 



gers are obviated in part by the formation of the placenta. 

 The placenta consists of two complementary parts — one 

 due to a special development of the whole or certain areas 

 of the uterine mucosa, or endometrium, of the mother, and 

 the other to an analogous development from the chorion of 

 the fetus. The embryo or embryos early become arrested 

 and detained for the rest of intra-uterine life in a definite 

 and comparatively fixed location. In unipara the rule is 



Fig. 31 — Chorionic Placenta of Ewe. 

 The right hand figure includes a portion of the Chorion. 



that the embryo becomes located partly within the cavity 

 of the uterine body, with the remainder of its body lying in 

 that horn of the uterus from the corresponding ovary of 

 which the ovum was derived. Pathologically, the fetus of a 

 sohped, instead of growing into the uterine body, may ex- 

 tend across the ovarian end of the uterine body cavity into 

 the opposite horn, to constitute bicornual pregnancy. In 

 multipara the embryos become halted at approximately 



