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. 



np.T 



FIG. 116. Uterus and embryo of Sorex (Hubrecht). 



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

 am., amnion ; all., free knob projecting into the extra- embryonic ccelom 

 (E.ec.) ; a.v., area vasculosa ; an', embryonic cells which grow downwards 

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

 against the maternal tissue; np.T., non-placental trophoblast; Gl. t 

 glands ; M., mesometrium. 



thin discoid sheet of nuclear remnants next the muscularis. The 

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

 they are plugged by syncytium and later disappear. 



