444 OUTLINES OF CHORDATE DEVELOPMENT 



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FIG. 182. Diagrammatic section through the gravid human uterus and the 

 embryo at the seventh or eighth week. From Quain's Anatomy, after Allen 

 Thomson, al, Allantois; am, amnion; c, c, openings of the oviducts (Fallopian 

 tubes) into the uterine cavity; c', cervix filled with mucous plug (the reference 

 letters c,c,c', are placed in the cavity of the uterus; ch, chorion with vascular 

 villi growing into the decidua capsularis and decidua basalis; in the decidua cap- 

 sularis the villi are becoming atrophied (chorion laeve) ; dr, decidua capsularis; 

 ds, decidua basalis; dv, decidua vera; i, embryo; u, umbilical cord; y, yolk-sac; 

 y' ', yolk-stalk; 



