FOEMATION OF THE DECIDUA. 



713 



OS internum, and the openings of the Fallopian tubes, the tlnckening- 

 gradually decreases, and the membrane assumes the unaltered condition 

 which is maintained in these passages. 

 By the fifth or sixth week, when the ovum has reached a diameter of 



Fig. 519. 



Fig. 519.— View of the Interior of the Human Gravid Uterus at the 

 Twenty-fifth Day (from Farre after Coste). 



?t,_ uterine wall ; o, villi of the chorion of the ovnm : dv, decidua vera and enlarged 

 iitenne glands ; dr, decidua reflexa, di\-ided round the margin of the ovum, and turned 

 down so as to expose its pitted surface, which has been removed from the ovum. The 

 right ovary is divided, and shows in section the plicated condition of the earlv conius 

 luteum. "^ '■ 



