Regenerative Capacity of Ovarian Tissue 33 



certain observations reported by Simpson and van Wagenen 

 (1953), and in which purified FSH was administered to im- 

 mature rhesus monkeys. Histological preparations of the 

 ovaries gave the impression that this treatment stimulated 

 oogenesis in all its phases, and that "small ovocytes" were 

 formed in the germinal cords. Subsequent counts showed, 

 however, that the total number of oocytes present after 

 treatment was much the same as in the ovaries of normal 

 monkeys of comparable age. In a further set of experiments, 

 in which FSH was administered to unilaterally-ovariecto- 

 mized immature monkeys, it was found that the numbers of 

 oocytes in the hormone-stimulated ovary was of the same 

 order as in the ovary that was removed before treatment 

 began. 



3. The number of oocytes does not increase in successful 

 autografts of ovarian tissue, reimplanted after freezing at 

 very low temperatures (— 190° C) or after having been kept 

 at normal room temperature (Green, Smith and Zuckerman, 

 1956). 



To the best of my knowledge, this study is the only one so 

 far carried out in which the numbers of oocytes were counted 

 in ovarian grafts. The conclusion to which it points is in line 

 with what is said below about fragments of ovarian tissue left 

 in the body in situ. 



4. Oocytes can survive for 2 J months in ovarian homo- 

 grafts in rats, and for a year or more in autografts in monkeys, 

 in the absence of the germinal epithelium (Breward and Zuck- 

 erman, 1949; Mandl and Zuckerman, 1949). 



Here, our observations merely confirm a number of earlier 

 ones made by other workers (e.g. Herlitzka, 1900; Marshall 

 and Jolly, 1907; Pettinari, 1928). The indication is that 

 oocytes may have a very long life. 



5. The total number of oocytes in the one ovary of rats from 

 which all traces of germinal epithelium had been removed by 

 means of the application of corrosive fluids was not significantly 

 different, over a period of nearly 1 J years, from that in the un- 

 treated normal ovaries of the same animals. Correspondingly, 



AGEING VOL. 2 3 



