GENITAL ORGANS OF THE FEMALE. 637 



those containing two or three egg-cells ; (4) the so-called nests of 

 follicles, in which a large number of follicles possess only a single 

 connective-tissue envelope ; (5) follicles of the last-named type, 

 which may assume the form of an elongated tube, and which are 

 then known as the constricted tubes of Pfliiger. The fourth, fifth, 

 and possibly the third types are further divided by connective- 

 tissue septa, until they finally form distinct and typical follicles 

 (Schottlander). 



" In the adult ovary true egg-tubes are no longer developed. 

 Isolated invaginations of the germinal epithelium sometimes 

 occur, but apparently lead merely to the formation of epithelial 

 cysts (Schottlander). The theories as to when the formation of 

 new epithelial nests or follicles ceases are, however, very conflict- 

 ing, some authors believing that cessation takes place at birth, 

 others that it continues into childhood and even into middle 

 age. 



" The ova of the primitive or primordial follicles attain a size 

 (in fresh tissue teased in normal salt solution) varying from 48 fj. 

 to 69 p. They possess a nucleus varying in size from 20 // to 32 /*, 

 presenting a doubly contoured nuclear membrane, and containing 

 a distinct chromatin network with a nucleolus and several accessory 

 nucleoli. The protoplasm shows a distinct spongioplastic network 

 containing a clear hyaloplasm. The primitive ova, until they 

 undergo development, retain this size and structure, irrespective 

 of the age of the individual. They are numerous in embryonic 

 life and early childhood, always found during the ovulation period, 

 but not observed in the ovaries of the aged. Changes in the size 

 and structure of the ova accompany the proliferation of the 

 follicular cells in the growing follicles. As soon as the follicular 

 cells of a primitive follicle proliferate, as above described, the 

 ovum of the follicle increases in size until it has attained the size 

 of a fully developed ovurn. The zona pellucida now makes its 

 appearance, and after this has reached a certain thickness, yolk 

 granules (deutoplastic granules) develop in the protoplasm of the 

 ovum. In a fully developed Graafian follicle the ovum presents 

 an outer clearer protoplasmic zone and an inner fine granular zone 

 containing yolk-granules ; in the former lies the germinal vesicle. 

 Between the protoplasm of the ovum and the zona pellucida is 

 found a narrow space known as the perivitelline space. The 

 germinal vesicle (nucleus), which is usually of spherical shape, 

 possesses a doubly contoured membrane and a large germinal spot 

 (nucleolus), which shows ameboid movements. 



"The origin of the zona pellucida has not as yet been fully 

 determined. It probably represents a product of the egg-epithe- 

 lium, and may be regarded in general as a cuticular formation of 

 these cells. At all events it contains numerous small canals or 

 pores into which the processes of the cells composing the corona 



