632 



DISCHARGE OF THE OVUM. 



the middle and latter periods of gestation, it presents itself as a 

 small, flattened, and shrivelled vesicle, situated underneath the 

 amnion, at a variable distance from the insertion of the umbilical 

 cord. A minute bloodvessel is often seen running to it from the 

 cord, and ramifying upon its surface. 



Fig. 231. 



GRAVID HUMAN UTERUS AND CONTENTS, showing the relations of the cord, placenta, mem. 

 branes, &c., about the end of the seventh month. 1. Decidua vera. 2.. Decidua reflexa. 3. Choriou. 

 4. Amnion. 



The decidua reflexa, during the latter months of pregnancy, is 

 constantly distended and pushed back by the increasing size of the 

 egg ; so that it is finally pressed closely against the opposite surface 

 of the decidua vera, which still lines the greater part of the uterine 

 cavity. By the end of the seventh month, the opposite surfaces 

 of the decidua vera and reflexa are in complete contact with each 

 other, though still distinct and capable of being separated without 

 difficulty. After that time, they fuse together and become con- 

 founded with each other ; the two at last forming only a single, 

 thin, friable, semi-opaque layer, in which no trace of their original 

 glandular structure can be discovered. 



This is the condition of things at the termination of pregnancy. 

 Then, the time having arrived for parturition to take place, the 

 hypertrophied muscular walls of the uterus contract forcibly upon 

 its contents, and the egg is discharged, together with the whole of 

 the decidual uterine mucous membrane. 



