CHAPTEE XI. 



DEVELOPMENT OF THE DECIDUAL MEMBRANE, 

 AND ATTACHMENT OF THE EGG TO THE UTERUS. 



IN the human species, where the development of the embryo is com- 

 pleted within the cavity of the uterus, the egg depends for its nutrition 

 and growth upon materials derived from the organism of the female 

 parent. The immediate source of supply for this purpose is the mucous 

 membrane of the uterus, which becomes unusually developed and in- 

 creased in functional activity during the period of gestation. The 

 uterine mucous membrane, when thus modified in structure, is known 

 as the decidual membrane, or the decidua. It has received this name 

 because it is exfoliated and discharged at the same time that the egg 

 itself is expelled from the uterus. 



The mucous membrane of the body of the uterus, in the unimpreg- 

 nated condition, is thin and delicate, and presents a smooth internal 

 surface. There is no distinct layer of connective tissue between it and 

 the muscular substance of the uterus ; so that the mucous membrane 

 cannot here, as in most other 



organs, be readily separated Fig. 264. 



by dissection from the subja- 

 cent parts. The structure of 

 the mucous membrane, how- 

 ever, is sufficiently well 

 marked. It consists, through- 

 Fig. 263. 





UTERINE Mucous MEM- 

 BRANE, from the unimpregnated 

 uterus, in vertical section, a. Free 

 surface, b. Attached surface. Mag- 

 nified about 10 diameters. 



UTERINE TUBULES, from the mucous mem- 

 brane of an unimpregnated human uterus. Mag- 

 nified 125 diameters. 



out, of tubular follicles, ranged side by side, and running perpendicu- 

 larly to its free surface. Near this surface, they are nearly straight ; but 

 toward the deeper part of the mucous membrane, where they terminate 

 in blind extremities, they become more or less wavy or spiral in their 

 ( T50 ) 



