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THE EVOLUTION OF MAN. 



deciduous membrane ; these parts may be called the outer, 

 the inner, and the placental deciduous membrane. The 

 outer or true membrane (d. externa or vera, Fig. 198, dv, 

 Fig. 200, g), is that portion of the uterine mucous membrane 

 which coats the internal surface of the uterus wherever the 



FIG. 200. Human embryo, twelve weeks old, with its coverings; natural 

 size. The navel cord passes from the navel to the placenta : b, anmion ; 

 c, chorion ; d, placenta ; d', remains of tufts on the smooth chorion ; /, de- 

 cidua reflexa (inner) ; g, decidua vera (outer). (After Bernhard Schultze.) 



latter is not attached to the placenta. The placental or 

 spongy deciduous membrane (d. placentalis or serotina, 

 Fig. 198, plu, Fig. 200, d) is simply the maternal placenta 



