614 



PLACENTA 



CHAP. 



which represents the point of connection between the 

 foetus and the placenta. The intra-abdominal portion 



pr 



uc 



mk 



ns 



ys 



FIG. 168. A transverse section across the uterus and the contained embryo of a 

 Rabbit at the end of the nineteenth day. The embryo is rut transversely about 

 the middle of the body, the section passing through the " yolk-stalk " and 

 allantoic stalk. ( .:,.) 



A, dorsal aorta ; CM. allantoic artery ; ..v. cavity of amnioii, between the inner or 

 true umnion and the embryo ; ex. space between the inner and outer layers of 

 the umnion ; gu. uteriiu- Clauds ; /;. endodenn of upper or vascular wall of 

 " yolk-sac " (umbilical vesicle) ; mi, ink. outer or longitudinal, and inner or 

 circular muscles of wall of uterus ; mm. mrsrntrry of uterus ; ns. spinal cord ; 

 ny. sympathetic nerve-cord ; ph. lobule of placenta ; po. region along which 

 the separation of the placenta occurs at birth ; fir. inter-plaraital groove ; pa,'. 

 sub-placental cavity ; si. circular marginal vessel of yolk-sac ; la. cavity of 

 the allantois (sec Fig. !<><>) ; Is. stomach; uc. dilated uterine capillary, with 

 thick perivascular wall ; up. uterine or maternal sinuses of placenta ; uv. blood- 

 vessels of uterus ; va. allantoic vein ; w. liver ; yk. stalk of yolk-sac ; yl. dotted 

 line representing the lower or non-vascular wall of the yolk-sac, now completely 

 absorbed ; vs. cavity of yolk-sac, continuous with the uterine cavity owing to 

 absorption of the lower wall of the yolk-sac. (From Marshall.) 



