318 GENERAL DISCUSSION 



By comparing the wet and dry weights of the cerebral hemispheres, brain stem, 

 and cerebeUum, we see that the accumulation of water is localized to the cere- 

 bellum and that the cerebral hemispheres, operative or inoperative side, are such 

 that the brain cell shows practically no swelling. With this prolonged time it 

 becomes obvious that in the cerebellum the granular cells go much further than 

 we had thought in the normal guinea pig. After 5 days, there is karyorrhexis, as 

 well as pyknosis, but there is no evidence of reversibility. I would ask Dr. Vogel 

 if his remarkable, almost inconceivable, recovery of the monkey at 72 hours might 

 not be a reflection of the individual variation in sensitivity of monkeys to irradia- 

 tion near the threshold level, probably around 10,000 r and that the monkey that 

 showed no change at 72 hours really didn't show any 48 hours earlier. 



F. Stephen Vogel (Cornell Medical Center): The graph that was shown with 

 the spectrum of changes was from a group that were all exposed to 10,000 r. It 

 was felt that this dose was capable of regularly producing pyknotic changes in the 

 granular cells. Someone could postulate that any animal sacrificed at one time or 

 another had either shown this change or would show it at the time of sacrifice. 

 The pairs of animals were killed so that we had not one animal at 72 hours, but 

 four animals. I think similar findings have been seen in the rabbit in our labora- 

 tory and elsewhere, coupled with the fact that there was no evidence of inflamma- 

 tion or karyorrhexis later nor evidence of pyknosis or decrease in number of cells. 

 I think one is justified in suspecting that these four animals showed the same type 

 of change as the much larger group of about 20 animals that were killed earlier. 

 With the observation that in tissue culture this change appears to be transitory, 

 we feel that this is a difference in sensitivity. I think one would have to increase 

 the dose above 30,000 r, perhaps, before one reached the stage where you could 

 destroy the granular cells of the monkey. 



L. M. H. Larramendi (University of Illinois): In using the sciatic nerve of the 

 bullfrog, I assume the action potentials that Dr. Gaffey showed were of the A 

 fibers. I would like to know if he has tried the same experiment to the B and C 

 fibers. Anatomically they are different. And I think Dr. Grashchenkov mentioned 

 that the autonomic nervous system is more sensitive, and the B and C fibers are 

 related to the autonomic system. Concerning previous comments by several persons 

 about the granular layer of the cerebellum, they were referring continuously to 

 the granules of the granular layer of the cerebellum. The implication I think was 

 that all the granular cells were within the granular layer of the cerebellum and 

 that they are neurons. This is not the case. 



C. T. Gaffey (Donner Laboratory, University of California, Berkeley, Cal- 

 ifornia): Concerning the species of frog, the Rana catesbeiana is the bullfrog, and 

 the Rana pipiens is the grasshopper frog. A question was raised concerning the 

 sensitivity of A, B, and C fibers. It is my understanding that the Rana catesbeiana 

 does not have B fibers from a histologic point of view. Gerstner has studied 

 sensitivity to x-irradiation within the A fibers (American Journal of Physiology, 

 1956). I believe the A-gamma fibers have essentially the same sensitivity, but 

 the B fibers are more resistant. Most of the changes are rather minor between 

 these fiber types in the A group. He also thought the C fibers were too thin and 

 delicate. 



