GENITAL ORGANS OF THE FEMALE. 635 



a fluid, liquor folliculi, formed by a secretion of the cells and by 

 the destruction of some of them. 



Graafian follicles continue to be formed in the ovary for a 

 short time after birth, and have been estimated to number, in 

 both ovaries, more than 70,000 ; but a small proportion of these, 

 however, become mature, the rest undergoing degeneration. 



During the development of Graafian follicles the ova which 

 they contain also become developed in the following manner 

 (Nagel, Bohm and DavidofF). In the early period of the develop- 

 ment of the ovary the germinal epithelium pushes into the sub- 

 jacent connective tissue in solid projections (Fig. 416); these form 

 the primary egg-tubes of Pflvger, some of the cells of which become 

 ova, while others become Graafian follicles. The differentiation 



f-- 



FIG. 420. Mature ovum of rabbit : a, cells from the discus proligerus (epithe- 

 lium of ovum) ; b, zona pellucida ; c, vitellus ; d, germinal vesicle ; e, germinal 

 spot ; /, large globules with dull luster in the germinal vesicle. 



of the cells of the germinal epithelium into ova and follicles may 

 occur in the epithelium itself, in which case the larger cells con- 

 stitute primitive or primordial ova. " In the further development 

 of the ovarian cortex the primitive egg-tubes are penetrated 

 throughout by connective tissue, so that each egg-tube is separated 

 into a number of irregular divisions. In this way a number of 

 distinct epithelial nests are formed, which lose their continuity 

 with the germinal epithelium and finally lie embedded in the con- 

 nective tissue. According to the shape and other characteristics of 

 these epithelial nests, we may distinguish several different groups : 

 (1) The primitive egg-tubes of Pfliiger ; (2) the typical primitive 

 follicles i. e., those which contain only a single egg-cell (present in 

 the twenty-eighth week of fetal life) ; (3) the atypical follicles i. e., 



