DE CID UA SER O TINA AT SE VEN MONTHS. 



335 



D' , and compact layers, D" , are very clearly separated; the mucosa is sharply 

 marked off from the muscularis, although scattered decidual cells have pene- 

 trated between the muscular fibers. The muscularis is about lo mm. thick and 

 is characterized by the presence of quite large and numerous venous thrombi, 

 especially in the part toward the decidua. The decidua itself contains jew blood- 

 vessels. Upon the surface of the decidua can be distinguished a special layer of 

 denser decidual tissue, which in many places is interrupted by the ends of the 

 chorionic villi which have penetrated it, as is well shown in the accompanying 



D'< 



Fig. 194. — The Human Decidua Serotina at Seven Months. The Section is Taken from near 



THE Margin of the Placenta. 

 Vi, Chorionic villi ; the intervillous spaces were filled writh maternal blood, which is not represented in the 

 figure. D', Cavernous layer of the decidua. D'\ Compact layer of the decidua. mc, Muscularis. 



figure. The gland cavities of the spongy layer, D' , are long and slit-like; they 

 are filled for the most part with fine granular matter, which stains light blue with 

 hematoxylin ; they also contain a little blood, and sometimes a few decidual cells. 

 There also occur in them hyaloid concretions, — oval bodies several times larger 

 than any of the decidual cells, and presenting a vacuolated appearance. In 

 uteri over two months pregnant they are probably invariably present. In many 

 places the glandular epithelium is perfectly distinct; its cells vary greatly in 



