602 REPRODUCTION. 



The vesicular membrane is lined throughout by a layer of granular 

 cells, which form for it a kind of epithelium. This layer is termed 

 the membrana granulosa. It adheres but slightly to the vesicular mem- 

 brane, and may easily be detached by manipulation before the follicle 

 is opened, when it appears mingled, in the form of light flakes and 

 shreds, with the serous fluid of the follicle. 



At the most superficial part of the Graafian follicle the membrana 

 granulosa is thicker than elsewhere. Its cells are here accumulated, in 

 a kind of mound or " heap," which has received the name of the cumu- 

 lus proligerus. It is also called the discus proligerus, because the- 

 thickened mass, when viewed from above, has a circular or disk-like 

 form. In the centre of the discus proligerus the egg is imbedded. It 

 is accordingly always situated at the most superficial portion of the 

 follicle, nearest the surface of the ovary. 



As the period approaches for the discharge of the egg, the Graafian 

 follicle becomes more vascular, and enlarges by an increased exudation 

 into its cavity. It then begins to project from the surface of the ovary, 

 still covered by the albugineous tunic and its peritoneal investment. 

 (Fig. 167.) The accumulation of fluid exerts such a pressure from 

 within, that the albugineous tunic and peritoneum gradually yield 



FIG. 167. 



GRAAFIAN FOLLICLE, near the period of rupture. a. Vesicular membrane. 6. Membrana granu- 

 losa. c. Cavity of follicle, d. Egg. e. Peritoneal surface. /. Tunica albuginea. g, g. Tissue of 

 the ovary. 



before it ; until the Graafian follicle protrudes from the ovary as a 

 tense, rounded, translucent vesicle, in which fluctuation can be perceived 

 on applying the fingers to its surface. Finally, the process of effusion 

 and distention still going on, the wall of the follicle gives way at its 

 most prominent portion, and the contained fluid is expelled by the 

 elastic reaction of the ovarian tissue, carrying with it the egg, entangled 

 in a portion of the membrana granulosa. 



The rupture of the Graafian follicle is accompanied, in some instances, 

 by hemorrhage from its inner surface, by which it is filled with blood. 

 This occurs in the human species, in the pig, and to some extent in 

 several other animals. Sometimes, as in the cow, where there is no 

 immediate hemorrhage, the Graafian follicle collapses at the time of 



