252 



PLACENTA OF THE UNGULATA. 



the surface of the chorion cover a broad zone, leaving only the two poles 

 free ; their arrangement differs therefore from that in a zonary placenta 

 in the greater breadth of the zone covered by them. The villi have the 

 form of simple papillae, arranged on a series of ridges, which are highly 



FIG. 154. PORTION OF THE INJECTED CHORION OF A PIG, SLIGHTLY MAGNIFIED. 



(From Turner.) 



The figure shews a minute circular spot (b) (enclosed by a vascular ring) from 

 which villous ridges (r) radiate. 



vascular as compared with the intervening valleys. If an injected chorion is 

 examined (fig. 154^ certain clear non-vascular spots are to be seen (b], from 

 which the ridges of villi radiate. The surface of the uterus adapts itself 

 exactly to the elevations of the chorion ; and the furrows which receive the 



FIG. 155. SURFACE-VIEW OF THE INJECTED UTERINE MUCOSA OF A GRAVID PIG. 



(From Turner.) 



The fig. shews a circular non-vascular spot where a gland opens (g) surrounded by 

 numerous vascular crypts (cr). 



