228 



NORMAL HISTOLOGY. 



FIG. 269. 



seventy thousand. In view of the unquestionably large number of 

 follicles in very young ovaries, and the relatively small proportion of 

 ova which reach maturity, the degeneration of many follicles, 

 after attaining a certain development, seems certain; the atrophic 

 remains of such degenerating Graafian vesicles, continually encoun- 

 tered, point conclusively to the fate of a large contingent. 



The medulla contrasts with the cortex by its looser structure and 

 the number and the size of its vascular canals. The stroma of this 

 portion of the ovary more nearly resembles ordinary connective 



tissue, the peculiar spindle-cells occur- 

 ring much less abundantly, while the 

 fibrous tissue forms an important con- 

 stituent of the supporting matrix. A 

 considerable amount of involuntary 

 muscle is mixed throughout the fibrous 

 bundles separating and surrounding the 

 numerous blood-vessels. The latter 

 are largely venous, the large sinus- 

 like veins being very conspicuous 

 objects in the medulla. 



In addition to the elements already 

 described, groups of polygonal inter- 

 stitial cells occur between the bun- 

 dles of stroma-tissue, especially in the medulla, but also within the 

 cortex. These cells are epithelial in character, and represent the 

 remains of the cylindrical cell-masses which grow from the Wolffian 

 body into the tissue of the primitive ovary. In some animals the 

 interstitial cells are much more numerous than in the human ovary ; 

 in the rabbit these cells constitute an important part of the stroma 

 of the organ. 



On the escape of the ovum, the ruptured and partly-collapsed 

 follicle becomes filled with the blood poured out from the torn vessels 

 of the walls of the vesicle ; subsequent changes lead to the conver- 

 sion of the follicle into a corpus luteum. The production of these 

 characteristic bodies depends principally upon the proliferation of 

 the walls of the follicle, in some cases the interstitial cells being in- 

 volved; the process results in the plication of the remains of the 

 envelope, as well as in the gradual formation of a mass of polyhedral 

 cells, between which the capillaries derived from the vessels of the 

 follicle extend ; the enclosed area corresponds to the remains of the 

 cavity of the follicle, and is for a time occupied with the yellowish 

 mass composed of the degenerating blood-clot and the membrana 

 granulosa ; these tissues are replaced by a shrunken fibrous area, 

 which is later invaded by the proliferating peripheral cells. When 



Section of medulla of human ovary : 

 v, vascular canals surrounded by the 

 stroma-cells and the connective tissue; 

 w, group of interstitial cells derived 

 from Wolffian tubules. 



