356 HISTOLOGY 



In distinction from the solid primary follicles, those with cavities are 

 known as vesicular follicles (Graafian follicles). They increase in diameter 

 from 0.5 to 12.0 mm., and are then ready to discharge the contained oocyte. 

 Occasionally a single follicle has two oocytes, and rarely more. Arnold 

 (Anat. Rec., 1912, vol. 6, pp. 413-422) describes the ovaries of a negress, 

 in which he found forty-three follicles containing four oocytes or more, 

 including one which contained eleven. It cannot be stated whether the 

 additional oocytes develop by division of the oogonium within a primary 

 follicle, or by the failure of a group of primitive sexual cells to become 

 separated from one another. 



Theca 

 folliculi. 



Tunica externa. 



Tunica interna. 



Stratum granulosum 



Cumulus ofiphorus. 



Egg cell with zona 

 pellucida, nucleus 

 and nucleolus. 



FIG. 359- SECTION OF A LARGE VESICULAR FOLLICLE OF A CHILD EIGHT YEARS OLD. X 90. 

 The clear space within the follicle contains the liquor folliculi. 



Owlation and the Corpus Luieum. Around the mature vesicular 

 follicle, the tunica interna becomes very thick and cellular, forming eleva- 

 tions toward the stratum granulosum. At this stage the follicle is large, 

 being about half an inch in diameter, and one surface of it is so close to the 

 ovarial epithelium as to cause it to bulge and then to rupture. Through the 

 opening thus made the liquor folliculi escapes, together with the oocyte. 

 The latter is said to become detached by the formation of fluid-filled spaces 

 between the cells of the cumulus; it generally carries with it more or less 

 of the innermost layer of the cumulus, and these cells, because of their 

 radial arrangement, are termed the corona radiata. As the oocyte leaves 

 the follicle there is apparently a chance for it to become lost in the abdom- 

 inal cavity, but the fimbriated orifice of the tube is near at hand, and the 

 stroke of its cilia produces a current toward its entrance. In a guinea-pig 



