376 GENERATION. 



goes development into the maternal portion of the placenta. 

 The rest of the decidua vera becomes extended, loses its ves- 

 sels and glands, and is reduced to the condition of a simple 

 membrane. 



According to Robin, the cylindrical epithelial cells of the 

 mucous membrane of the body of the uterus, soon after fe- 

 cundation, become gradually exfoliated, and their place is 

 supplied by flattened epithelial scales, of the pavement-va- 

 riety. This change is effected at from the sixth to the eighth 

 week, and the pavement-cells are then found covering both 

 the decidua vera and the reflexa. The epithelium of the cer- 

 vix retains its cylindrical character, but most of the cells lose 

 their cilia. 1 



During the first periods of utero-gestation, the two layers 

 of decidua are separated by a small amount of an albuminous 

 and sometimes a sanguinolent fluid; but this disappears at 

 about the end of the fourth month, and the membranes then 

 come in contact with each other. 2 They soon become so 

 closely adherent as to form a single membrane, which is in 

 contact with the chorion. Sometimes, at full term, the mem- 

 branes of the foetus can be separated from the decidua ; but 

 frequently all of the different layers are closely adherent to 

 each other. 



The changes we have just described are not participated 

 in by the mucous membrane of the neck of the uterus. The 

 glands in this situation secrete a semisolid, transparent, viscid 

 mucus, which closes the os, and is sometimes called the uter- 

 ine plug. 



Toward the fourth month, a very delicate, soft, homo- 

 geneous layer appears over the muscular fibres of the uterus, 

 beneath the decidua vera, which is the beginning of a new 

 mucous membrane. This is developed very gradually, and 



1 ROBIN, Memoire sur quelques points de Vanatomie et de la physiologic de la 

 muqwuse et de T epithelium uterins pendant la grossesse, Journal de la physiolo- 

 gie, Paris, 1858, tome i., pp. 60, 61. 



2 LONGET, Traite de physiologic, Paris, 1869, tome iii., p. 868. 



