58 Discussion 



state. Here, however, the continuous oestrus may be interrupted by 

 a variety of devices, by mating or by administration of gonadotrophin 

 or progesterone, in which case the animal will run a cycle or two and 

 then go back into continuous oestrus again. I was wondering if perhaps 

 part of the phenomenon of your animals ceasing ultimately to be in 

 oestrus was not merely a matter of exhaustion. After all, fourteen weeks 

 of continuous oestrogenic secretion in the life of a rat is a long period. 



Parkes: In our experience, rats in which cyclic corniflcation is passing 

 into persistent corniflcation will quite often mate, and they will certainly 

 mate under conditions where the ovarian tissue they possess does not 

 have any follicular system. 



Zuckerman: We specifically tested the animal's readiness to mate, but 

 failed to observe it on any occasion. I do not know why the intermittent 

 corniflcation in the immediate post-irradiation period fades into con- 

 tinuous corniflcation, and then into the anoestrous type of smear. 



Williams: May it not be something to do with the adrenal? 



Zuckerman: No. We have removed the adrenals, keeping the animals 

 on saline and that does not interrupt it. 



Williams: Do I understand that if you adrenalectomize the animals, 

 you do not interfere with the cyclic phase? I was thinking that you 

 might get hypertrophy or overactivity of the adrenal later and this might 

 account for the loss of corniflcation. 



Zuckerman: The experiments on the removal of the adrenals were 

 done when we knew the animals were so many days in continuous 

 oestrus, and from previous experience, could predict they would con- 

 tinue until corniflcation faded out altogether. 



Huggett: What is your index of oestrus? 



Zuckerman: We do not call it "oestrus"; we refer to vaginal 

 corniflcation. I should like to ask Dr. Parkes whether he believes there is 

 any difference between the likelihood of obtaining a successful graft of 

 testicular as compared with ovarian tissue. 



Parkes: For the gametogenic property or the endocrine one? 



Zuckerman: Gametogenic, although I do not imply the complete 

 formation of spermatozoa. 



Parkes: Well, the situation is quite different because unless the testis 

 graft is put in a position where it would normally have a chance of 

 showing spermatogenesis you won't get it, of course. 



Zuckerman: I do not mean complete gametogenesis ; I mean the 

 multiplication of spermatogonia, and not necessarily spermatocytic 

 differentiation. I was under the impression that it is easier to make a 

 successful graft of testicular than of ovarian tissue, as judged by the 

 continuation of the earlier stages of gametogenesis. 



