THE OVARIES 



721 



epithelium. The cells of this layer undergo proliferation so as to form several 

 strata, and grow into the ovarian stroma as longer or shorter columns or 

 tubes. By degrees these tubes become cut off from the surface epithelium, 

 and form cell nests, small if near the surface, larger if in the depth of the 

 stroma. The nests increase in size from multiplication of their cells. Cer- 

 tain cells of the germinal epithelium enlarge and form ova; and the forma- 

 tion of ova takes place in the nests within the stroma. The small cells 

 of a nest surround the ova, and form their membrana granulosa, and the 

 stroma growing up separates the surrounded ova into so many Graafian 

 follicles. 



Downgrowths of epithelium 

 ininal epithelium 



Ovum with its investing cells 



Stratum granulosum 



epithelial cells Ovarian strorna 



Graah'an follicle 



Ovum 



Liquor folliculi 

 Discus proligerus 



FIG. 494. A, Diagrammatic Representation of the Manner in which the Vesicular 

 Ovarian Follicles Arise During the Development of the Ovary. B, Diagram Illustrating 

 the Structure of a Ripe Vesicular Ovarian Follicle. (Cunningham.) 



The smallest follicles are formed at the surface, and make up the cortical 

 layer. It is said by some that the superficial follicles as they ripen become 

 more deeply placed in the ovarian stroma; and, again, that as they increase 

 in size they make their way toward the surface. 



When the vesicular ovarian follicles mature, they form little prominences 

 on the exterior of the ovary covered only by a thin layer of condensed fibrous 

 tissue and epithelium. From the earliest infancy, and through the whole 

 fruitful period of life, there appears to be a constant formation, development, 

 and maturation of ovarian vesicles, with their contained ova. Until the 

 period of puberty, however, the process is comparatively inactive. But, 

 coincident with the other changes which occur in the body at the time of 

 puberty, the ovaries enlarge and become very vascular, the formation of 

 ovarian vesicles is more abundant, the size and degree of development 

 attained by them are greater, and the ova are capable of being fertilized. 

 4 6 



