PEXETEATIOX OF DECIDUA BY THE VILLI. 



717 



From what has been previously stated, it will be seen that there is at 

 first a general union or interpenet ration of the villi of the chorion with 

 the vascular decidna, the more extended part of this union taking place 

 in the decidua reflexa, and the remainder in that portion of the decidua 

 which is interposed between the ovum and the uterus, and which has 

 been already referred to as decidua serotina, but which might from its 

 relation to the formation of the placenta with propriety be named 

 decidua ^jJaccnicdls. Already in the latter half of the second month of 

 pregnancy, the villi on the uterine side of the chorion become larger 

 and more ramified than those which run into the decidua reflexa ; and 



Fi.-. 52L 



Fig. 521. — View of the Dissection of the Pregxant Uterus op Forty Days after 

 Conception (from Leisliman after Coste). 



a, the embryo sho-OTi within the amnion ; c, the chorion opened, the umbilical vesicle 

 seen lying between it and the amnion ; d, deep surface of decidua reflexa where it has 

 been turned back from the ovum ; r, r, remainder of the decidua i-eflexa projecting from 

 the uterine surface ; v, decidua vera, of which the glandular structure is shown in the 

 cut edges ; x x , openings of the Fallopian tubes seen within the uterus. In the 

 uterine wall the distinction is sho-rtai between the outer muscular part with the wide 

 uterine vessels, and the glandular and decidual internal parts. 



