APPENDAGES OF THE FtETrs. 



77 



arranirement closely resembles that of vegetables, each ceil containing 

 a distinct nucleus ; the villi have the same texture, but tlieir cells are 

 tilled with a granular matter. Tiie strength of the membrane is greatest 

 in the early ovum ; it is formed by the zona jicllucida, which is lined by 

 the external layer of the blastoderm. It is thought that the primitive 

 chorion disappears by resorption, and that this blastodermic layer 

 becomes the definitive chorion ; also that when the allantois lias spread 



Fig. 47. 



F(KTAL MrMBRANKS OK THK (Jo.AT AT Fri.I, Tl.MK: TwiNS. 



A, Cervix of the I'teruM ; B, Ltft Cornu ; C, Kiirht Cornu ; J), Allantois of 

 one of the K.i'tuses ; K, Amni-.n „f ditto ; F, Portion of the I'terine Wall 

 left at the middle of its Body, where the Fa-tUHes come in contact ; G, I'nion 

 of the Two Chorions at the Cervix Uteri. 



itself between the amnion and the external envelope, carrying outward 

 the umbilical vessels, this detinitive chorion becomes vascular, and 

 furnished with its numerous villosities. 



Differences. 



liuminants. 

 In Ruminants, the chorion corresponds to the internal face of the 

 uterus, whose form it repeats, and with whose surface it is more or less 



