GENERAL DISCUSSION 317 



to several months. During this so-called latent period of sensitization, the animals 

 show a mosaic of neurologic symptoms. Some who are sacrificed or die during 

 the acute phases showed edema and vascular changes of the necrobiotic or in- 

 flammatory coverings around the veins. Of particular interest to me was the reac- 

 tion which Professor Scholz showed in the H and E preparations and with the 

 elastic stain. He emphasized the fact of so-called plasmodic or fibroid material 

 which has involved the vascular material as well as necrosis. We have observed 

 similar changes during the early phases of the allergic reaction in experimental 

 encephalomyelitis. It occurs to me that possibly the x-ray effects on the tissue 

 produce a necrobiotic phenomena; and this phenomena, which requires a certain 

 period of sensitization, initiates a chain of reactions with particular involvement 

 of the blood vessels. I would like to suggest the possibility that delayed reactions 

 could be produced by a necrobiotic process, induced by irradiation. 



J. R. Innes (Brookhaven National Laboratory): I am pleased to hear Dr. 

 Arnold mention that he thought the monkey was the ideal animal for radiation; 

 however, although they don't suffer the legion of disorders which affect the ner\'ous 

 system of man, Van Bogaert, Schair, and others, show that they do suffer a 

 remarkable variety of neurologic diseases, some of them unique. Curiously, some 

 show lesions like the ones I showed and Dr. Scholz showed in his rabbits, which 

 are specific in monkeys, except the gorilla and chimpanzee. In any work involved 

 with monkeys where they are kept a long time, you must be alert to neuroparalysis, 

 palsy, blindness, and leucoencephalomyelosis, which although uncommon is a well 

 recognized condition. In this disease, brain as well as spinal lesions appear scat- 

 tered, spotty, and more denominational. Concerning the specific effect of irradia- 

 tion on the myelin system, I think this effect on the neuron is specifically on white 

 matter and far more than on the axis cylinder. In the cord it seems to affect the 

 ventrolateral more than the dorsal. Let us remember that there is such a thing as 

 a conducting cylinder, the myelin system. 



Percival Bailey: It is true that monkeys have diseases of the brain, like other 

 animals. But on our animals we never saw anything of the kind. Furthermore, it is 

 not possible that any such disturbance could have occurred in them, because we 

 used a beam produced by the betatron which makes a constant lesion without any 

 scatter, and in one hemisphere using the opposite hemisphere for the same animal 

 as a control. 



Webb Haymaker: We would like to hear from Dr. Alvord because of his 

 sensitivity studies with the granular layer of the cerebellum under different 

 physiologic conditions. 



E. C. Alvord (Seattle, Washington): The answers we get usually depend on 

 the methods we use. I would like to develop the idea that there is specificity within 

 the nervous system in its susceptibility to the effects of radiation and to bring up 

 for comment the irreversibility or reversibility of some of these changes and the 

 site of swelling or edema. When a large part of one cerebral hemisphere has been 

 removed and a guinea pig is given 7,500 r in the head, the normal guinea pig 

 will die in 24 hours. If you provide internal decompression by surgery, it can 

 live 4 to 6 days. Those sacrificed 4 hours after irradiation look reasonably normal. 

 The others show swelling of the entire brain, with cerebellar consular herniation. 



