128 



A. GLiJCKSMANN 



exposure to X-rays or by exposure of the pelvic region only. The results for 

 both types of exposure were essentially the same and only those for pelvic 

 exposure are given. In intact animals the pelvic and whole-body radiation 

 shortened the induction period for vulval carcinomas, but decreased the 

 incidence of sarcomas to about the same level as for castration. In castrate 

 rats, on the other hand, pelvic Hke whole-body exposure to X-rays strikingly 

 shortened the induction period for vulval carcinomas and for vaginal sarcomas 



80 



o 



E 



60 



0) 

 en 

 O 



Intact 

 Castrate 

 Intact 

 Castrate 



Carcinoma of vulva 

 Sarcoma of vagina 



E 



40 



20 



400 



Time (days) 



Fig. 9. The effect of irradiation on the induction of vulval carcinomas and vaginal sarcomas 

 by weekly DMBA paintings in castrate and intact rats. The irradiation was given at 200 kVp 

 in whole-body exposures (five times 400 rads in sixteen weeks) or pelvic exposures with shielding 

 of the body (six times 400 rads in twenty weeks). 



and also significantly increased the yield of vaginal sarcomas in castrate 

 animals. Since the effects of whole-body and pelvic radiation are the same in 

 this instance too, it is unhkely that a mere lowering of the immune response 

 is responsible for rapid tumour formation and the fact that the vulva and 

 vagina of intact rats behave differently under radiation supports this view. 

 Thus hormonal and other, as yet undefined, systemic factors enter even into 

 the local induction of tumours by the application of carcinogens. 



This example brings us back to the intricate problem of the mteraction of 

 hormonal and other factors in the induction of tumours by whole-body 

 irradiation. We quoted the example of the induction of ovarian tumours in 

 mice in the beginning and pointed out that irradiation of the ovaries is one 



