GENERAL DISCUSSION 319 



James Lott (North Texas State College): Since Dr. Gaffey's results seem to 

 not coincide with Dr. Bachofer's and mine, working with peripheral nerves in the 

 rat, I would like to ask him about some of his techniques. I would like to know 

 how often he stimulated the nerve during the control period, how long after he 

 removed the nerve did he begin his recordings, how often he stimulated the nerve 

 during irradiation, when he was taking his recordings, and whether he has ever 

 seen an increase in the action potential due to alpha or deuteron irradiation. 



C. T. Gaffey: The stimulation period of the frog was short. About half a 

 minute to a minute. Once every 2 hours the nerve was monitored. So, essentially 

 there would be no change in the nerve due to the stimulation effect. It is known 

 that stimulations at low frequency, compared to high frequency, will change the 

 magnitude of the potential of the compound A fibers. These stimuli that were 

 given were maximal for a response. Enhancement of neural output is demonstrated, 

 but there is some confusion in the season of the year in which the enhancement 

 is shown. In winter frogs, enhancement is strongest. In summer and fall frogs, 

 enhancement is minor. It would appear that the potassium gradients across the 

 fibers are seasonal and reflect the degree of enhancement shown in any par- 

 ticular experiment. 



Orville T. B.mley (University of Illinois): The pathology of radiation in the 

 central nervous system leads to a series of questions which are very difficult to 

 separate and on which we have conflicting opinions which may be related to 

 extraneous factors. In regard to the long latent period, I am perhaps somewhat 

 influenced by experiences with radiation changes in skin. Experience with these 

 makes this long latent period more understandable. One patient seen over many 

 years with repeated biopsies was an eminent scientist who, as late as 35 years 

 after he stopped using x-ray, was not only developing new carcinomas but was 

 developing patches of typical x-ray dermatitis in previously normal skin. The 

 participation of allergic responses in the pathology of radiation is an open ques- 

 tion. Similar end results do not necessarily mean similar pathogenesis. Because the 

 reconstituted vessels in repair have the same appearance when these processes 

 are finished that they have an allergic arteritis does not necessarily mean that all 

 the stages or that the pathogenesis is the same. Finally, one of the strongest argu- 

 ments for differential effects of radiation on the various types of cells in the central 

 nervous system is the alteration in the sequences of histologic repair. 



