THE GENERATIVE ORGANS. 2OI 



structure are accounted for by the fact that certain 

 of the follicles are mature or approaching maturity, 

 while others are still undergoing development. 



We will first consider the structure of those which 

 are mature, or nearly so. The interstitial tissue of 

 the ovary arranges itself, in the immediate vicinity 

 of the follicle, in the form of a tolerably well-defined 

 wall, called the thcca folliculi, consisting of an ex- 

 ternal denser layer and an internal layer very richly 

 supplied with cells, and containing an abundant 

 capillary net-work. Within the theca folliculi is a 

 layer, usually several cells deep, of larger and 

 smaller spheroidal, or, in the periphery, cuboidal 

 epithelium, called follicular epithelium, and consti- 

 tuting the so-called membrana granulosa. At one 

 or other side the follicular epithelium is heaped up 

 into a larger or smaller mass, which projects into 

 the cavity of the follicle and contains the ovum; 

 this accumulation of cells is called cumulus proliger us 

 or germ-hill. The remainder of the follicular cav- 

 ity is filled with a colorless fluid, in which not 

 infrequently fine granules are suspended. This fluid 

 increases in quantity as the follicle approaches ma- 

 turity, and the pressure occasioned by its accumu- 

 lation probably conduces in no slight degree to 

 the final rupture of the follicle. The follicular 

 epithelium immediately surrounding the ovum is 

 cylindrical and arranged radially about it. 



In the ovum itself, which is a cell of the most 



