THE GENITAL GLANDS AND DUCTS OVARY 



223 



mass are transformed into young ova, the process extending from the rete ovarii 

 peripherally (Fig. 221). (3) In embryos of from 80 to 180 mm. length the ovary 

 grows rapidly, owing to the formation of a new peripheral zone of cells, derived 

 in part from the epithelium. At the end of this period the epithelial cells beneath 

 the epithelium are gradually replaced by a fibrous stroma, the anlage of the tunica 

 albuginea. \ Hereafter, although folds of the epithelium are formed, these do not 

 penetrate beyond the tunica albuginea, and all cells derived from this source 

 subsequently degenerate. In late fetal life, according to Felix, the so-called 

 "germinal epithelium" does not give rise to primitive ova. 



s ^^r ^-i^4^f it 



S^*r : ^3^>' //;: 



S-vsassrh -5~ <\(\ ( 

 V^SiiSfe^ ^ 



f* &&& ! * R w < 5> , - - AM - Theca 



fe^i^Sj W folliculi 



S) .-^Wl Membrana 



^^pfy , ,)//. granulosa 



'A ' / ;' ' J 



rimordial Vitelline J 



follicle mem - ^ 



A B 



FIG. 222. Primordial ova and early stages in the development of the Graafian follicle (De Lee's 



Obstetrics). 



Coincident with the origin of a new zone of cells at the periphery of the ovary 

 goes the degeneration of young ova in the medulla. By the ingrowth into this 

 region of connective tissue septa, the ova are separated into clusters or cords, the 

 genital cells of which all degenerate, leaving in the medulla only a stroma of con- 

 nective tissue. Late in fetal life the indifferent cells, by surrounding young ova, 

 produce primordial follicles (Fig. 222 A). During the first year after birth the 

 primitive follicles are transformed into the vesicular Graafian follicles. By cell 

 division the follicle cells form a zone many layers deep about the young ovum 

 (Fig. 222 B). Next a cavity appears in the sphere of follicle cells, enlarges and 

 produces a vesicle filled with fluid (Fig. 223). The ovum is now eccentrically 



