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- 



Follicular cavity. 



Discus proligerus. 



I ?< 



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 



