FCETAL MEMBRANES. 



585 



From their relation to the ovum and to the uterus, the deciduse (by which is 

 meant the uterine mucosa of pregnancy) have been divided into the decidua 

 parietalis or decidua vera t the decidua basalis or serotina, and the decidua cap - 

 sularis or reflexa. 



t3 ,_ iL-,^-----, ^- 



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cap., Capillary; cyt., cellular layer (cyto-trophoderm); ep., uterine epithelium; g/., uterine gland ; 

 n. z., necrotic zone of decidua (uterine mucosa); P. e., point of entrance of the ovum; tro., 

 syncytium (plasmodium, plasmodi-trophoderm); tro. 1 , masses of vacuolating syncytium 

 invading capillaries. The cavity of the blastodermic vesicle is completely filled by meso- 

 derm, and embedded therein are the amniotic. and entodermic (yolk) vesicles. The 

 natural proportions of the several parts have been observed. 



The decidua parietalis is the changed mucosa of the entire uterus with the 

 exception of that portion to which the ovum is attached. The decidua basalis 

 is that portion of the mucosa to which the ovum is attached and which later 

 becomes the maternal part of the placenta. The decidua reflexa is either the 



