History and Fate of Redundant Follicles 65 



stimulates the proliferation of the membrana granulosa, but 

 even in the continued presence of oestrogen the degenera- 

 tion of this tissue is not prevented — it is only delayed for at 

 most several days. I think that there is evidence too that 

 the degeneration may be hastened by gonadotrophin, perhaps 

 acting by the liberation of ovarian androgen. Apart from this, 

 the ageing process in the membrana granulosa is completely 

 obscure. Histochemistry has revealed some interesting facts 

 about the degeneration process once it has started but no-one 

 can yet tell whether a follicle is proceeding to ovulation or will 

 undergo atresia until the degeneration starts. 



Postscript 



The observation recorded by Professor Zuckerman in his 

 communication suggests to me that all the ovarian tissues are 

 transient. He has certainly convinced me that oogenesis is no 

 longer a function of the ovary in adult life. The transience of 

 the membrana granulosa I have just discussed, and that of 

 the corpus luteum is well established. 



Professor Zuckerman' s findings in rats with X-irradiated 

 ovaries suggest that the thecal tissue and its successor, the 

 interstitial tissue, are transient too. He has confirmed Dr. 

 Parkes's earlier observation that cyclic vaginal cornification 

 may continue in the complete absence of oocytes and fol- 

 licles and has extended this finding by observing that such 

 vaginal cycles do not continue indefinitely. After a number of 

 weeks the vagina reverts to a continuous di-oestrous condition. 

 This suggests that the function of the interstitial tissue is 

 limited in time unless the tissue is continually renewed from 

 the thecal cells of degenerating follicles and corpora lutea. 

 Such a hypothesis would explain the lack of cyclic activity 

 in the postmenopausal woman, in whom, as Professor Krohn 

 pointed out, lack of cyclic ovarian activity is not accompanied 

 by persistence of cyclic vaginal changes. 



Acknowledgement. 



I am very grateful to Dr. D. J. Trevan, Mr. E. V. Willmott, F.R.P.S., 

 and Mr. G. D. Leach for preparing the photomicrographs. 



AGEING VOL. 2 4 



