316 GENERAL DISCUSSION 



providing I have given a dose rate of 200 r or more. If I reduce the dose rate to 

 50 r then the effect is one-half or one-third as much. I think the factor of dose 

 is important in responsiveness in the nervous system, and the total over-all effect 

 depends on the dose as well as the dose rate. Dr. Innes brought out a feature that 

 I thought was probably the highlight of the whole program, the problem of control. 

 He showed in the rat that some of the animals, after a period of time, can develop 

 neurolytic lesions in the field of demyelinization which probably are due to a virus. 

 I have seen the same thing in rabbits and dogs, and would emphasize that, if you 

 have to do a great deal of radiation studies, stay away from these animals. I have 

 followed monkeys for as long as 8 or 9 years and have never seen such demyelinating 

 disorders, which points to the monkey as the ideal animal for radiation studies 

 on the nervous system. There seems to be a dilTerence in opinion as to whether 

 we are dealing with direct or indirect effects and as to whether there is a total 

 over-all effect from a massive dose; but I firmly believe there is a differential 

 particularly when you are dealing with the glial cells and, through numerous 

 studies on tumors, we know that there can be a differential response in a tumor 

 cell. One would say that this is a different problem than the over-all nervous 

 system; but there appears to be, in the adult nervous .system in the well developed 

 animal, differences in responses between the types of glial cells as compared to, 

 for example, the vessel structure. I have noticed that glial cells responded earlier 

 than the vessels, and yet we have also noted that in time some of the late delayed 

 necrotic effects arc obviously vascular, but the myelin changes may be related to 

 all of those. 



Webb Haymaker: Professor Grashchenkov alluded to these delayed lesions, 

 and he made a distinction between the vasomotor theory and another theory. 

 Would you mind elaborating a little on that matter of the delayed radionecrosis? 

 N. J. Grashchenkov (Moscow, U.S.S.R.) : It is not my personal investigation, 

 but from my view, you have serious destruction of certain cells of the nervous 

 system, like those of the subthalamus and hypothalamus. Some lesions were con- 

 nected with other signs of destruction such as the spinal effects, caused by damage 

 to cells of the spinal cord. Mainly, however, the damage is located in the thalamic 

 tissue. 



Webb Haymaker: One point that Professor Schummelfeder brought out with 

 respect to these late lesions was that in the literature it was suggested that they 

 may represent a sensitive reaction in the vessels. I wonder if Dr. Leon Roizir 

 would comment on, from what he has seen this morning of Professor Scholz's 

 presentation, whether he sees anything in these vessels in relation to his studies 

 on sensitivity reaction. 



Leon Roizin (New York State Psychiatric Institute): Orville Bailey has em- 

 phasized the time factor in relation to delayed reactions, particularly as they were 

 affecting blood vessels. He said the character of the lesions increased with time. 

 Professor Scholz also emphasized the fact of certain delayed reactions. We have 

 studied for several years in connection with experimental vascular encephalomyelitis 

 by using as the main antigen total brain or brain fractions. The technique consists 

 of brain or brain fraction suspensions emulsified in antigens and injected sub- 

 cutancously or intramuscularly. After the injection there is a delay of from 3 weeks 



