306 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



forms at first a single layer of cells. These remain 

 small and multiply rapidly, forming two layers of 

 cells between which, at one side of the follicle, a 

 cavity appears. As the follicle grows larger this cav- 

 ity, which is eccentric in position, becomes filled 

 with a fluid called the follicular fluid. The ovum 

 remains attached to the side of the follicle and be- 

 comes surrounded by several layers of cells called 

 the discus proligerus. The outer layer also multi- 



Theca. 



Follicular cavity. 



Stratum granu- 

 losum. 



Discus proligerus. 



Ovum. 

 Fig. 222. Ripe Graafian follicle. 



plies, forming eight to twelve layers of cells and is 

 then called the stratum granulosum, to which the 

 discus proligerus is attached. External to the 

 stratum granulosum a connective-tissue envelope 

 forms, called a theca. This theca develops from the 

 ovarian stroma and consists of two layers, an ex- 

 ternal, the theca fibrosa, and an internal, the theca 

 vasculosa, the latter being supplied with a fine 

 plexus of lymph- and blood-vessels. The mature 



