chap, xxxii.] FEMALE GENITAL ORGANS. 263 



follicles, of which the ovum has been impregnated, 

 grows to a much larger size than under other condi- 

 tions, the granulosa becoming by overgrowth much 

 folded. 



351. Development of the ovary and Graa- 

 fhiii follicles* The germinal epithelium of the 

 surface of the foetal ovary at an early stage undergoes 

 rapid multiplication, in consequence of which the epi- 

 thelium becomes greatly thickened. The vascular 

 stroma of the ovary at the same time increases, and 

 permeates the thickened germinal epithelium. The 

 two tissues in fact undergo mutual ingrowth, as is the 

 case in the development of all glands viz., the epithe- 

 lial or glandular part suffers mutual ingrowth with 

 the vascular connective tissue stroma. 



In the case of the ovary, larger and smaller 

 islands or nests (Balfour) of epithelial cells are thus 

 gradually differentiated off from the superficial epithe- 

 lium. These nests are largest in the depth, and smallest 

 near the surface. They remain in connection with 

 one another and with the surface for a considerable 

 period. Even some time after birth some of the 

 superficial nests are still connected with the surface 

 epithelium, and with one another (Fig. 143A). These 

 correspond to the ovarial tubes (Pfliiger). While in 

 the rabbit these nests are solid collections, in the dog 

 they soon assume the character of tubular structures 

 (Pfliiger, Schafer). The cells constituting the nests 

 undergo multiplication (by karyokinesis), in conse- 

 quence of which the nests increase in size, and even 

 new nests may be constricted off from old ones (see 

 also above). 



352. At the earliest stages we notice in the 

 germinal epithelium some of the cells becoming en- 

 larged in their cell-body, and especially their nu- 

 cleus ; these represent the primitive ova. When the 

 germinal epithelium undergoes the thickening above 



