242 



EMBRYOLOGY. 



(blastula) no longer lies free in the cavity of the uterus, but is 

 enclosed in a special capsule produced by the growth of the mucous 

 membrane. Hitherto no one has had the opportunity to make 

 observations concerning the formation of this capsule. Following 

 an hypothesis of SHARPEY, which has been somewhat modified by 



PftCIS) 



Tig. 139. Diagrammatic section through the gnvid human uterus, from WIKDEKSHEIM. 



U, Uterus ; UH, cavity of the same ; Tb, Fallopian tube ; Dv, decidua vera ; Dr, decidua v 



Pit, placenta uterina (decidua seroiina) ; Pf. p'.acenta fu'talis <>r elion,,:i fion,lo,um (Cii.t ) ; 

 Chi, chorion laeve ; A (on black background), .-axity of the .-minion tilled with amniotie 

 fluid ; D, yolk- (unibilical) vesicle ; in the embryo one sees the umbilii-al vessels (Al) ; t the 

 liver traversed by the vera mnhilie.ali> ; 11. the heart; A, the aorta; ci and r, the \>-t;a 

 cava inferior and superior ; p, vena ix>rtarum. 



KEICHERT, it is now gem-mlly ns-uincd tliat the ovum upon its 

 entrance into the uterus imbeds itself in a depression of the inm-ous 

 membrane, which is tin-own into ridp-> and is in process of brin*,' 

 nie(aniorp]:<^fd into tlu^ decidua. Tlie m.-ii-giiis of the depression 

 goon grow around the hlastula on all sides, and fuse together tdt'orm 

 i'u-tal cai Mile. The fusion lakes place at a point diametrically 



