Regenerative Capacity of Ovarian Tissue 43 



"activity" of the germinal epithelium. This conclusion is 

 hardly borne out by the data that are published, since these, 

 in fact, show that the total number of primordial oocytes was 

 smaller in treated animals than in controls of the same weight- 

 groups. Results of experiments in which rats were fed the 

 highly toxic drug Myleran are also taken by Burkl and Kellner 

 (1954a, b) to support the thesis that oogenesis is a process 

 which continues into adult life. Some of the animals used in 

 this experiment died as a result of the treatment, and only 

 one normal and three experimental rats were left to provide 

 what in effect proved to be the basic thesis of the study, that 

 Myleran acts only on follicles whose oocytes exceed 38 (x in 

 diameter. This figure is used in a series of calculations de- 

 signed to determine the daily maturation rate of follicles, by 

 which is meant the number of oocytes over 38 fx in diameter 

 divided by the period of the experiment. By successive and 

 increasingly unconvincing transformations and comparisons, 

 the conclusion is then reached that some 25 oocytes degenerate 

 in each cycle. Since the stock of oocytes at the onset of sexual 

 maturity is asumed to be 3500, it is concluded that neoforma- 

 tion of oocytes must occur if the ovary is not to be depleted of 

 oocytes too soon. Quite apart from various theoretical and 

 mathematical defects of the argument, the design of the whole 

 experiment is totally inadequate to sustain any such conclu- 

 sion. It is worth noting, too, that the average number of 

 oocytes at puberty in the Birmingham strain of albino rats is 

 6000, and that a stock of oocytes of this size would be sufficient 

 to sustain the rate of loss of oocytes calculated by Burkl and 

 co-workers without assuming that oogenesis continues after 

 sexual maturity had been reached. 



In a later paper, Burkl (1955) again concludes, but on this 

 occasion without resorting to oocyte counts or a study of 

 nuclear changes, that oogenesis occurs in the mature ovary of 

 the dog. This he does merely on the basis of the topographical 

 relation of oocytes to cords of epithelial cells which had 

 presumably been derived from the germinal epithelium. And 

 in a paper which follows (Burkl and Kellner, 1955), he 



