FOLLICLES OF THE OVARY. 



289 



mary follicles, each being a single egg cell surrounded by a simple layer 

 of flat cells derived from the peritonaeum. Sometimes a follicle contains 

 two or more egg cells, all but one of which may atrophy; or the egg cell 

 may have two nuclei the significance of which is obscure. The number 

 of t follicles in an ovary has been estimated to be from 8,000 to 16,000. Some 

 consider that no new ones 

 are formed after birth, but 

 others believe that they 

 may be produced in the 

 adult. At all events only 



Egg cells in 

 an island. 



Germinal 

 epithelium. Egg cell. 



Egg cell. ^_. iSsC-;*-." ; 



" ^*\^ . ' ' 



Nucleus. 4-^S !>-) ; &/'",'^'-- ^^3J/ 



V' ~^ * t '* V ' jf". *, 



Protoplasm. ""'-'' - 



about 200 of them become 



mature; the others degene- I Foiiicuiar ceils. 



rate af varirmc; <;tao-p< of HP FlG " 33o. FROM A SECTION OF THE OVARY OF A CHILD 



Tdie d,l VdilOUb bldgeb OI Cie- FOUR WEEKS OLD. X 240. 



velopment. 



With further growth the follicular cells become columnar and then 

 stratified (Fig. 331); the egg cells enlarge as their protoplasm becomes 

 charged with nutritive material (yolk granules or deutoplasm). The 

 connective tissue around the follicle is compressed to form a distinct layer, 

 the theca folliculi. Later the theca is divisible into a dense fibrous tunica 

 externa, and a vascular tunica interna containing many cells with abun- 



A degenerating 

 follicle. 



Follicular cells. 



Nucleus. 



Nucleolus. Protoplasm. Zona pellucida. 



FIG. 331. FROM A SECTION OP A RABBIT'S OVARY. X 240. 



dant protoplasm (Fig. 332). A delicate membrana propria is found 

 between it and the follicular cells. After the follicles have attained a 

 certain size a crescentic cleft appears among their stratified cells. By 

 distention of the cleft and enlargement of the follicle the condition shown 

 in Fig. 332 is produced. These vesicular follicles [Graafian follicles] vary 

 in diameter from 0.5 to 12.0 mm. Besides the theca, the follicle includes 



