Discussion 57 



continuous "oestrus" within about forty days after treatment. Phases 

 of oestrus occurred intermittently in the preceding period. Animals 

 which were not in continuous oestrus forty days after irradiation usually 

 turned out to be incompletely sterilized. Having moved into a state of 

 continuous vaginal cornification, the animals remained in that con- 

 dition for from two to fourteen weeks, and then became anoestrous. The 

 weight of the uterus, however, was higher than that in spayed litter- 

 mate controls, even 26 weeks after treatment. A small amount of 

 oestrogen was clearly being produced throughout the period of observa- 

 tion (as judged by the weight of the uterus) even though it was insuffi- 

 cient to cause cornification in smears, except in the earlier part of the 

 experiment. The vaginal mucosa showed some degree of oestrogenic 

 stimulation, and consisted of more than four layers of cells. Approxi- 

 mately the same results have been obtained on the mouse. 



Parkes: That interests me very much because of the work I did years 

 ago with Brambell on irradiation of the mouse ovary. At that time we 

 were concerned entirely with finding out whether or not cyclic activity 

 would persist after the destruction of the follicular apparatus ; and it 

 did persist. We were not interested then in trying to find out how 

 long endocrine activity would persist, but endocrine activity survived 

 certainly for some months after destruction of the follicular apparatus. 

 It so happened that, talking to Prof. Zuckerman recently, I discovered 

 that he was doing these irradiation experiments and he discovered that 

 I was doing not very dissimilar ones — irradiating rat ovarian tissues in 

 vitro before making a graft. Our work is in an early stage but the results 

 we have obtained so far are at least compatible with his, though we do 

 not know for certain what happens to a graft which has been irradiated 

 in vitro. 



Zuckerman: Both what Dr. Parkes has just said, and our own findings, 

 suggest that there may be some relation between the secretory capacity 

 of the ovary and the follicular system, in the sense that the elimination 

 of the latter eventually affects the former. But exactly what the relation 

 is, I do not yet know. 



Parkes: Then there is a further point; that if you put up the dose 

 of the X-rays too high you destroy the whole ovary in the same way as 

 a smaller dose destroys the oocytes only. 



Krohn: But of course, in the menopausal ovary you have no oocytes 

 left and no hormone production apparently. The two do go hand in 

 hand there. 



Dempsey: In these experiments in which you produce continuous 

 oestrus after irradiation, will the animals mate ? 



Zuckerman: No. In spite of a completely cornified smear they will not 

 mate. 



Dempsey: And have you tried interrupting their continuous oestrus 

 either by giving gonadotrophins or progesterone ? 



Zuckerman: Neither. 



Dempsey: There is a phenomenon in the rat in which continuous 

 oestrus is produced by constant illumination and in which as long as the 

 animal is maintained under lights, the vaginal smear will be in a cornified 



