FCETAL NUTRITION: THE PLACENTA 455 



by the plasmodiblast, and is replaced by foetal elements. In the 

 ripe placenta the only maternal constituent is blood, except a 



Cr. 



Fig. 116. — Uterus and embryo of Sorex (Hubrecht). 



a.T. , allantoidean trophoblast with knobs entering the epithelial crypts (Cr.) ; 

 am,, amnion ; aU., free knob'projecting into the extra-embryonio ccelom 

 (-S.ee.) ; a.v., area vasoulosa ; an', embryonic cells which grow downwards 

 from the upper rim of the trophoblastic annulus (tr.an.), and adhere 

 against the maternal tissue; n/p.T., non-placental trophoblast ; Gl., 

 glands ; M., mesometrium. 



thin discoid sheet of nuclear remnants next the muscularis. The 

 glands are not penetrated by vascular viUi. In the early stages 

 they are plugged by syncytium and later disappear. 



