590 



GENERATION AND DEVELOPMENT. 



small round orifices, lined with epithelium and set closely to- 

 gether. 



On the internal surface of the mucous membrane may be 

 seen the circular orifices of the glands, many of which are, in 



FIG. 226. 



Section of the lining membrane of a human uterus at the period of commencing 

 pregnancy, showing the arrangement and other peculiarities of the glands, d, d, d, 

 with their orifices, a, a, a, on the internal surface of the organ. Twice the natural 

 size. 



the early period of pregnancy, surrounded by a whitish ring, 

 formed of the epithelium which lines the follicles (Fig. 228). 



FIG. 227. 



FIG. 228. 



FIG. 227. A vertical section of the mucous membrane, showing uterine glands of 

 the bitch, magnified twelve diameters; 1, 1, simple glands; 2, 2, compound ditto 

 (from Sharpey). 



FIG. 228. Two thin segments of human decidua after recent impregnation, viewed 

 on a dark ground : they show the openings on the surface of the membrane. A is 

 magnified six diameters, and B twelve diameters. At 1, the lining of epithelium is 

 seen within the orifices, at 2 it has escaped (from Sharpey). 



Coincidently with the increasing size of the follicles, the 

 quantity of their secretion is augmented, the vessels of the 

 mucous membrane become larger and more numerous, while a 

 substance composed chiefly of nucleated cells fills up the inter- 



