614 



PLACENTA 



CHAP. 



which represents the point of connection between the 

 foetus and the placenta. The intra-abdominal portion 



mi 



mk 



va 



aa 



ny 



ys 



F T G, 1 68. A transverse section across the uterus and the contained embryo of a 

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

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

 alia ntoic stalk, (x af.) 



A, dorsal aorta ; aa. allantoic artery ; a.x. cavity of amnion, between the inner or 

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

 the amnion ; gu. uterine glands ; h. endoderm of upper or vascular wall oi 

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

 circular muscles of wall of uterus ; mm. mesentery 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 ; pr. inter-placental groove ; pw. 

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

 the allantois (see Fig. 166) ; ts. 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 

 abeorbed ; ys. cavity of yolk-sac, continuous with the uterine cavity owing to 

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



