166 



PHYSIOLOGY 



CHAP. 



and new formation of the follicles, with a progressive prevalence 

 of the first over the second process, which becomes less than ever 

 at the critical period. The primary ovarian follicles are to be 

 distinguished from the vesicular or Graafian. The first are little 

 spherical bodies which proceed from a stratum of cells called the 

 follicular epithelium surrounding a large cell of 35 to 48 p, which 

 is the ovum with a cell-nucleus known as the germinal vesicle. 

 The follicles increase progressively in size, and undergo modifica- 

 tions of form in regard to the follicular walls as well as to the 

 ovum (as is seen in Figs. 47, 48, 49, 50). At a given period of 

 their development, at one or more points of the follicular wall, 



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FIG. 52. Ovarian follicle, from ovary of rabbit, in a more advanced stage of growth than in the 

 preceding figure. Magnified 190 diameters. (Chiarugi.) u, ovum ; v, germinal vesicle ; z, zona 

 pellueida ; e, follicular epithelium ; c, first sign of formation of follicular cavity ; tl, theca 

 interna ; te, theca externa. 



is formed a space for the reception of a liquid which increases 

 constantly until the follicle becomes vesicular. The follicular 

 liquid is yellowish, slightly alkaline, and contains protein sub- 

 stances ; it is a product of secretion accompanied by destruction 

 of the epithelial cells of the follicle (Figs. 52, 53). The mature 

 vesicular follicle is known as a Graaftan follicle. It consists 

 of an investing membrane with two layers, due to modifications 

 undergone by the stroma of the perifollicular connective tissue, 

 called the theca or wall of the follicle ; of the cumulus oophorus, 

 formed by a mass of cells of the stratum granulosum, with which 

 it is in communication at a peripheral point, situated generally 

 towards the deep pole of the follicle ; of the ovum (contained within 



