748 GENERAL DISCUSSION 



previous studies (Clemente and Hoist, 1954), it was found that, even though we 

 shielded the body of monkeys sustaining head radiation with a Ys in. lead shield, 

 0.5% of our head radiation dose was scattered and absorbed by the bodies of the 

 animals. These were doses that were calculated for us by the physicists and seemed 

 reliable, and I wonder whether or not Dr. Arnold took the trouble to measure 

 the scatter to the bodies in his rats and whether this is the reason that a generalized 

 radiation sickness was observed. In this regard I would also like to ask Dr. Riopelle 

 whether the monkeys which sustained brain radiation in his series showed symp- 

 toms of diarrhea, blood cellular changes, or gastrointestinal pathology, such as 

 intestinal hemorrhages, usually described as indicative of the generalized radiation 

 sickness syndrome. 



Arthur J. Riopelle (Yerkes Laboratories, Orange Park, Florida): No. Our 

 head irradiated monkeys die from a variety of things. Temperature control went 

 out in the laboratory one night, and we lost a few animals a week or two after 

 that. Autopsy showed a variety of ailments scattered throughout the body, as one 

 would anticipate, from infections. Chins were necrotic. They sloughed off. There 

 was also sloughing of the lips. Infection via that route certainly appeared. But 

 we did not see the usual radiation sickness syndrome. 



William J. Arnold (University of Nebraska, Lincoln, Nebraska) : I did not say 

 that I thought head irradiation alone would produce a total pattern of radiation 

 sickness exactly comparable to that of total body irradiation. I feel sure that if 

 someone checked carefully, there would be differences. With respect to the back 

 scatter, we did not check the amount which seeped through or scattered from 

 the radiation site. I believe it would be small. We did radiate the hind legs of 

 animals using a comparable area and dosage with all conditions the same as for 

 the brain area irradiation. We noted no evidence of radiation sickness from our 

 general observations or from careful measurement of weight loss or food intake. 

 We observed no evidence of radiation sickness in those animals. 



T. J. Haley (University of California, Los Angeles, California): In confirma- 

 tion of what Dr. Harlow and Dr. Riopelle stated about conditioned avoidance, 

 we have studied rats under this situation using sound as our conditional stimulus 

 and in doses of 300, 600, and 900 r we could detect no statistically significant dif- 

 ference between the control period prior to irradiation and the results obtained 

 afterwards. In fact, with animals at the 900 r level, where they live only 6 or 7 

 days, we actually saw animals on the grid perk up their ears at the sound, make 

 one last lunge for the pole, and drop dead. I would also like to comment on this 

 controversy on the LD/50 in the monkeys. It seems as though we need a definition 

 of terms. As I understand it. Dr. Harlow is working with pure x-rays or gamma 

 rays. Dr. Lynn Brown is working with gamma rays and neutrons. The LD/50 

 will not be the same under those two conditions. We should always define the 

 conditions of our experiments implicitly so that no one will get the wrong 

 impression. 



Marcel Monnier (Basel, Switzerland): I would like to ask Dr. Ruch if he 

 thinks it is possible to discriminate two mechanisms for the high percentage of 

 errors in monkeys, one type related to hyperdistractibility with motor hyperactivity, 

 and the other type related to an abnormal passivity. Our observations point on one 



