62 



P. C. Williams 



progressively decreases and there is a reduction in the size of 

 the largest follicle. 



I have recently studied some of this old material from 

 the point of view of follicular degeneration. Some interesting 

 points arose. The normal immature rat ovary contains about 

 40-50 follicles more than 200 [i in diameter and of these about 

 half are in the early stages of atresia. My impression is that 



Table II 



Effect of Stilboestrol Implantation at Operation on the Histology 

 of the Ovaries in Immature, Hypophysectomized Rats 



this process is a very rapid one; certainly almost all the 

 follicles in the later stages of atresia are smaller than this, and 

 so are not included in the counts. These is little change in the 

 total count during the first five days after operation but the 

 proportion of atretic follicles is greatly increased. Only 6-10 

 of the follicles are normal at this time and 20-30 are atretic. 

 The proportion of atretic follicles has increased from 40-50 

 per cent to 60-80 per cent. 



At this point we have to reckon with the observation of 

 Aron and his colleagues (Firket, Petrovich, Marescaux and 



