REPRODUCTION IN MAN 



1367 



(v. p. 1361). The first stage in the growth of the follicle is a proliferation 

 of the follicular epithelium, the cells of which become cubical and are 

 arranged in several layers round the ovum. At one point in the mass 

 of cells surrounding the ovum a cavity appears filled with fluid, 

 the liquor folliculi. The epithelium thus becomes separated into 



FIG. 559. Graafian follicle of mammalian ovary. (PRENANT and BOUIN.) 



ov, ovum ; dp, discus proligerus ; Iq.f, liquor folliculi ; ch, theca ; 

 gr, membrana granulosa. 



two parts, i.e. the membrana granulosa, several layers thick, lining 

 the whole follicle, and the discus proligerus, a mass of cells attached to 

 one side of the follicle, in which is embedded the ovum (Fig. 559). 

 Round the growing follicle the stroma assumes a concentric arrange- 

 ment and forms a capsule, of which the internal layer consists chiefly of 

 spindle-shaped cells richly supplied with blood-vessels, while the outer 

 layer the theca externa is made up of a tough fibrous tissue. With the 

 growth of the follicle the ovum also becomes larger and surrounds itself 

 with a distinct membrane, known as the zona pellucida. This membrane 



