248 



NORMAL HISTOLOGY. 



The wall of the ripe follicle consists of a well-developed capsule or theca, a 

 delicate membrana propria, against whose inner surface lie the follicular cells, known 

 as the stratum granulosum, surrounding the space filled with the liquor folliculi. Oppo- 



Surface at^m 



epithelium 



Primary 



follicle's 



Theca folliculi. 



_ 



Stratum .i. 1 ' 1 

 granulosum " "; " 

 '.jV 



..:!. : 



Cumulus -:..>.. 



Zona pellucida 



Ovum Cavity filled with liquor folliculi 



FIG. 297. Section of ovary, showing partially developed Graafian follicles. X 90. 



site the point where rupture takes place, the stratum granulosum is prolonged into a 

 pedunculated spherical mass of epithelial cells that projects into the cavity. This 



mass, the cumulus, encloses the 

 ovum and on section appears 

 as an epithelial ring, the corona 

 radiata, that encircles the zona 

 pellucida and the ovum and 

 consists of two or three layers 

 of radially disposed cells. The 

 membranous zona pellucida is 

 the product of the follicular cells 

 and, therefore, not a part of the 

 ovum proper. It sometimes ex- 

 hibits a radial striation, hence 

 is often called zona radiata, 

 probably due to penetrating 

 processes from the superim- 

 posed epithelial cells. 



The human ovum 

 when about to be liberated 

 from the Graafian or egg- 

 follicle possesses a diameter 

 of about . 25 mm. Its cy- 

 toplasm, the vitellus of the 

 older writers, exhibits differ- 

 entiation into a peripheral 

 ooplasmic and a central deu- 

 toplasmic zone, the latter being dark and conspicuous on account of the 

 irregular refraction of the enclosed yolk-particles. The presence of a distinct 

 cell-wall, or egg-membrane, in the human ovum is doubtful, although 



FIG. 298. Almost mature human ovum taken from fresh ovary. 

 Ovum, with germinal vesicle and spot, is encircled by clear zona 

 pellucida, which is surrounded by follicular epithelium. X 250. 

 ( Waldeyer.) 



