CH. LIX.] 



THE GRAAFIAN FOLLICLES 



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cells, which, in the early stages, were intermingled with the cells of 

 the germinal epithelium. There are also numerous vesicles of differ- 

 ent sizes which are called Grraafian follicles. The smallest follicles 

 are near the surface, the largest are deeply placed, but as they ex- 

 pand they again approach the surface, and ultimately rupture upon it. 

 A Grraafian follicle has an external wall formed by the stroma ; 

 this is lined internally by a layer of cells, derived from the germinal 

 epithelium, which surrounds the oocyte. At a later stage there are 

 two layers of cells, one lining the cavity, and the other surrounding 



Fia. 557. Corpus luteum of mouse, showing its formation completed. The central cavity is occupied 

 by jelly-like connective tissue; the converging trabeculae anastomose with one another so as 

 somewhat to break up the columnar arrangement of the luteal cells. (Sobotta.) (From Schafer's 

 Text-look of Microscopic Anatomy.) 



the oocyte, but the two are close together. A viscid fluid collects 

 between the two, and as the follicle grows, separates them. 



The cells in each layer multiply, and are eventually arranged in 

 several strata. The lining epithelium of the follicle is then called 

 the membrana granulosa, and the heaped mass of cells around the 

 oocyte, the discus proligerus. The fluid increases in quantity, the 

 follicle becomes tenser, and finally it reaches the surface of the organ 

 and bursts ; the oocyte or ovarian ovum is thus set free ; it enters 

 the fringed end of the Fallopian tube and thence passes to the 

 uterus. This process is called ovulation, and in the human female 

 the ripening of an ovum occurs about once every four weeks. 



