OVARY 



355 



ular cells become columnar and then stratified (Fig. 358). A crescentic 

 cleft filled with fluid appears in the midst of the stratified epithelium on 

 one side of the follicle, and by the accumulation of fluid, or liquor folliculi, 

 this cleft becomes a spherical cavity (Fig. 359). The fluid is regarded by 

 some as a transudate from the blood vessels, which are abundant in the 

 stroma outside of the follicle. Others consider that it is actively secreted 

 by the cells of the follicle, 

 certain of which undergo 

 liquefaction. Spaces con- 

 taining a stainable fluid, 

 differing from that in the 

 main cavity, may appear 



Follicular cells. 



Egg cells in 

 an island. 



Egg cell. 



^ 



FIG. 357. FROM A SECTION OF THE OVARY OF A CHILD FOUR 

 WEEKS OLD. X 240. 



in the epithelium (Call- 

 Exner bodies), around 

 which the cells are radially 



arranged. By the development of the main cavity, the stratified epi- 

 thelium becomes a relatively thin layer, the stratum granulosum, which 

 decreases in width as the follicle enlarges. The oocyte is on one side of 

 the follicle, contained in a heap of cells known as cumulus oophorus (for- 

 merly the discus proligerus) . This is connected with the wall of the follicle, 

 but in certain sections it may appear completely detached (e.g., in a sec- 



Germinal 

 epithelium. 



Tunica 

 albuginea. 



Primary 

 follicle. 



A degenerating 

 follicle. 



Follicular cells. 



Nucleus. 



Xucleolus. Protoplasm. Zona pellucida. 



FIG. 358. FROM A SECTION OF A RABBIT'S OVARY. X 240. 



don at right angles with the plane of the page, near the top of the cumulus 

 in Fig. 359). 



Surrounding the follicle, even in early stages, there is a connective 

 tissue sheath, the theca folliculi (Fig. 358). This later becomes differen- 

 tiated into a vascular tunica interna, and a fibrous tunica externa (Fig. 359). 

 The tunica interna contains many cells with abundant protoplasm. It is 

 separated from the epithelium of the follicle by a delicate membrana 

 propria. 



