214 SoMERS H. Sturgis 



the first place, the interstitial tissue of the mature ovary is gradually built up 

 by the theca of atretic follicles, and the fibrous organization of their remains. 

 It seems likely that such an increase in bulk of interstitial tissue may be 

 necessary before any one follicle in the ovary is enabled to achieve full 

 maturation at or after puberty. The second, and perhaps much more signifi- 

 cant aspect of the dissolution of eggs and follicles in mature life probably 

 relates to the limitation of offspring to that which is typical for each species. 

 At least in the monkey where the steps of atresia of the ovarian follicle have 

 been studied in detail, it is apparent that this process wipes out all follicles 

 of second rank in each cycle, the ones that ordinarily would be most likely next 

 to mature and ovulate. Perhaps the most dramatic feature of nature's own 

 control of ovulation in the monkey, and probably the human, is the induction 

 of atresia in all but one of the ripening follicles each month. 



Clearly this is not a local phenomenon such as one due to mounting 

 intraovarian pressure associated with the rapid spurt of growth of the 

 maturing follicle, because second rank follicles are wiped out equally just 

 prior to ovulation in the contralateral ovary as well. Although atresia of 

 lesser follicles continues unabated at all times of the cycle, yet this is a wave 

 of dissolution that is significantly present during the ovulation phase. 



It is important, then, to review the stages of atresia as seen in the monkey 

 ovary in an attempt to fit these processes into what is known of gonadotropin 

 stimulation and steroid response. The examples to be shown are from the 

 beautiful collection of monkey ovaries in the Carnegie Institute of Embryology 

 where a study was made through the courtesy of Dr. George W. Corner (2). 

 Figure 1 shows the egg and surrounding cumulus on day 13 just before 

 ovulation. The egg shows the first maturation spindle. The granulosa cells 

 of the cumulus are beginning to separate with edema fluid. The theca interna 

 layer is thin and delicate and hard to demonstrate. The diameter of this 

 follicle was seven thousand microns. It was judged to be within 24 hr of ovula- 

 tion. At the same time, in the same monkey, Fig. 2 indicates two follicles of 

 second rank. These could be found by tracing down serial sections to measure 

 in largest diameter nine hundred to twelve hundred micra. The striking 

 features are first, the dissolution of the granulosa indicating the first sign of 

 impending atresia, and second the dramatic thickening of the theca interna 

 layer. To make the comparison of this theca hypertrophy with that of the 

 maturing follicle more obvious, Fig. 3 shows the thin undeveloped theca 

 layer of the maturing follicle and Fig. 4 shows in higher power the thick, 

 juicy apparently secretory theca interna layer of the follicles going into 

 atresia. 



Within the next two or three days, these large follicles collapse rapidly and 

 here in another specimen (Fig. 5) is seen, with Mallory's connective tissue 

 stain, a follicle undergoing atresia with the egg already amorphous and 

 degenerate. One can see the condensation of fibers between the cells of the 



