Regenerative Capacity of Ovarian Tissue 47 



is still persisting within the substance of the ovary. What we 

 need to know is whether any thesis other than that a finite 

 stock of oocytes is involved can be reconciled with such plain 

 numerical propositions as "the total number of oocytes does 

 not increase in an ovary undergoing compensatory hyper- 

 trophy"; or "the relative rate of loss of oocytes increases 

 inversely with the amount of ovarian tissue left in the body". 

 To some extent Aron et al. appreciate this point, and their way 

 of dealing with it is to suggest, in effect, that the smaller the 

 amount of ovarian tissue left in the body, the more the work 

 it has to do in satisfying the body's need for oocytes, and con- 

 sequently, the more rapid the decline in the oogenetic potency 

 of its germinal epithelium. The difficulty with this hypothesis 

 is not that it is arbitrary; it is un verifiable. The only tangible 

 measure of oogenetic potency which one can conceive of 

 would be the numbers of oocytes produced in the ovary at 

 any given time. As I have tried to show, any realistic analysis 

 of the differences which occur in the numbers of oocytes in 

 different experimental conditions, or as between different 

 normal physiological states, leads inevitably to a conclusion 

 which implies a primary stock of oocytes. The other possi- 

 bility is that oocytes are transitory structures, and that the 

 actual ones that are seen, and which could be counted under 

 the microscope at any given moment, would have been re- 

 placed by another set of oocytes had the ovary been examined 

 on a later occasion (e.g. that the number counted on one 

 occasion was the measure of a given oogenetic potency at that 

 moment ; and a lesser number counted in another set of com- 

 parable ovaries on a physiologically later occasion was a 

 measure of a lesser oogenetic potency). This, in fact, is what 

 is implied by Aron's suggestion. If it were accepted, no more 

 would be demanded of one's credulity than would be from a 

 man who counted the apples on a tree on successive days, 

 and who held that each day he was counting a set of apples 

 which had miraculously replaced those that were there the 

 day before — and just as miraculously disappeared (there 

 being no fallen apples to account for the new ones that had 



