256 EMBRYOLOGY. 



They are Ulso found in the spongy layer, but in the cords and septa 

 they are more elongated and spindle-shaped. 



In the second stage, Jrom the sixth month forward, in which the 

 decidua vera becomes much thinner, and under the pressure of the 

 growing foetus gradually diminishes from 1 cm. to 2 mm. in thickness, 

 many regressive processes take place in the individual parts that have 

 just been described (fig. 147). 



The mouths of the glands, which caused the sieve-like condition of 

 the inner surface of the decidua, become more and more difficult to 

 see and finally disappear altogether. 



The inner compact layer (C) assumes a uniform, compact, lamellar 

 condition, since by the pressure the cavities of the glands occupying 

 it become wholly obliterated, and then by disappearance of the epithe- 

 lium their walls become fused. 



In the spongy layer (Sp) the cavities of the glands (dh) persist,, 

 but, in consequence of the pressure, are converted into fissures, which 

 are parallel to the wall of the uterus, and are separated by partitions- 

 which in comparison to earlier months of pregnancy have become 

 very much thinner. The glandular cavities which are adjacent to 

 the compact layer have lost their epithelium or exhibit cellular debris 

 (de), swollen bodies, and a slimy mass permeated with fine granules ; 

 toward the uterine musculature, on the contrary, they possess a well- 

 preserved epithelium of short cylindrical or cubical cells. 



(2) The decidua refiexa (fig. 148 Dr) exhibits close agreement in its 

 structure with the decidua vera. That it has arisen from the latter 

 by a process of folding may be inferred, as KUNDRAT has rightly 

 maintained, especially from the circumstance that during the first 

 months of pregnancy the mouths of uterine glands (glu), at least 

 at the place of transition to the vera, are found upon both its sur- 

 faces. The mouths lead into fissures (glu) which are parallel to the 

 surface of the refiexa and are lined with cuboidal epithelium. In 

 the inter-glandular tissue there appear the Fame large, round decidual 

 cells as in the vera. 



From the fifth month forward the space between vera and reflexa 

 begins to disappear ; both membranes now, after loss of their epithe- 

 lium, become firmly pressed together, and finally completely fused 

 with each other (fig. 147). By this process the refiexa, from which 

 the glandular spaces disappear except in the transitional region, 

 becomes so extraordinarily thinned that it constitutes [in sections] 

 only a narrow band, occasionally ^ mm. broad. 



A separation of the two membranes at the close of pregnancy 



