148 CARL R. MOORE 



writer applies the term 'interstitial cell,' and it is such cells of 

 the ovary that are at least involved in the reduction of osmic- 

 acid preparations. 



Since the graft material was all preserved in Bouin's fluid, 

 recourse has been had to very young normal ovaries for a demon- 

 stration of the property of reducing osmic acid by the interstitial 

 cells. Histologically and developmentally, such interstitial cells 

 of a young ovary are identical with the same type of cell in the 

 grafts, and inasmuch as atretic follicles are abundant in both 

 instances it will throw some light on the changes taking place 

 in the grafts to examine the young ovary. Reference to figure 

 12 will remind one of the atresia that is going on in such an 

 immature ovary and the relative number of these follicles to 

 normal ones. Moreover, it will show that the stratum granu- 

 losum of the follicles remains intact during the atretic changes, 

 for in these abnormal follicles the discus proligerus is undergoing 

 dissolution while the granulosa cells are present, but also under- 

 going the characteristic changes of the cells as they acquire their 

 lipoid content. In the osmic preparations the gradual steps 

 in these changes are well represented. Figures 9 and 10 have 

 for comparison in each case a normal follicle and one beginning 

 atresia. Follicle A is the normal follicle and the granulosa cells 

 possess but little osmic-blackened material, while follicle B in 

 each case has begun to degenerate (in fig. 9, B, a small fragment 

 of the contained ovum is visible in the section). In comparing 

 follicle A with follicle B in each figure one can readily see that 

 the blackened material in the granulosa cells is much more apparent 

 in the degenerating follicle, and (using other follicles) as this 

 atresia progresses the intracellular lipoid material is still more 

 pronounced, until finally such masses of cells as are shown at C 

 (fig. 9) represent the original follicle; these masses are situated 

 between the follicles, some may contain a very small represent- 

 ative of the original follicular cavity, and in this characteristic 

 position, and behaving as they do after osmic fixation they are 

 spoken of as the interstitial cells of the ovary. 



This origin of this type of cell can be followed in practically 

 every graft of the series, and with but one possible exception the 



