THE OVARIES 



685 



bryonic ovary is covered with short columnar cells, or the so-called germinal 

 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. , Certain cells of the 

 germinal epithelium enlarge, and form ova; and the formation 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. 



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



Downgrowths of epith^Hum 

 Germinal epithelium 



Ovum with its investing cells 



Stratum grajmlosom 



epithelial cells Ovarian strorna 



Graafian follicle 



Ovum 



uorfolliculi 

 Discus proligerus 



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

 Arise During the Development of the Ovary. B, Diagram Illustrating the Structure of a Ripe 

 Graafian Follicle. (Cunningham.) 



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 Graafian 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 Graafian 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 Graafian vesicles 

 is more abundant, the size and degree of development attained by them are 

 greater, and the ova are capable of being fertilized. 



