246 



NORMAL HISTOLOGY. 



stance'' (Stohr) of the ovary. The follicles are in different stages of devel- 

 opment, but, for the most part, are small, inconspicuous and immature. Cor- 

 responding with their development, the egg-sacs are divided into primary ', 

 grounng and maturing follicles. In general, the youngest and least devel- 

 oped lie nearest the surface, the more advanced deep and towards the medulla, 

 while those approaching full development appear as huge vesicles that may 



Surface 

 epithelium 



Stratum 

 granuiosum 



FIG. 295. Section of cortex of ovary of young woman, showing primary and growing follicles within the 



ovarian stroma. X 190. 



occupy not only the entire thickness of the cortex, but produce marked eleva- 

 tion of the surface. The entire number of ova, as estimated from the ovaries 

 of a seventeen-year-old subject, is approximately 35,000 for both ovaries. 



The immature primary follicles are microscopic in size (40-60 /*) and, in the 

 ovaries of young adults, form an incomplete and scattered single, or at most double 

 layer. Each follicle includes the centrally situated young egg or ovulum, surrounded 

 by a single row of flattened epithelial or mantle cells, which are directly lodged within 

 the interstices of the stroma-tissue. The ova and the mantle cells are derived from 

 the proliferation of the germinal epithelium, the modified mesothelium covering the 

 germinal ridge on the median surface of the Wolffian body. Very early certain cells 

 are distinguished by their exceptional size and large clear nuclei. These are the 

 primary ova, around which the small descendants of the germinal epithelium become 

 arranged as the mantle cells. Soon an active intergrowth occurs between the prolife- 

 rating epithelium and the invading vascular connective tissue of the Wolffian body that 

 becomes the ovarian stroma. The latter increases so rapidly that the primary follicles, 

 single or in small groups, become separated by augmenting tracts of stroma-tissue. 



The primary ova, approximately spherical and 40-50 // in diameter, may remain 

 for years, sometimes from early infancy to advanced age, practically unchanged, until 

 they undergo either atrophy, as do most of them, or further growth leading, under 



