624 GENERAL DISCUSSION 



C. S. Bachofer (University of Notre Dame, South Bend, Indiana): As one who 

 has been radiating B and C fibers for some time I know that the work is not 

 finished, but I would like to ask Sister Mary Albert if she would make a comment 

 as to the relative sensitivity of B and C fibers to radiation. 



Sister Mary Albert (Notre Dame): The B and C fibers which I have been 

 irradiating are the sympathetic fibers, and I get just about the same results that 

 Father Bachofer reported as far as enhancement is concerned. I also find that C 

 fibers are more resistant as Dr. Gasteigcr pointed out with the vagus. It would 

 seem that the parasympathetic and sympathetic have somehing in common. 



C. T. Gaffey (University of California, Berkeley, California): Dr. Noell, I 

 was wondering what the minimal dose was that knocked out the ERG? 



Werner K. Noell (University of Buffalo, Buffalo, New York): That must 

 depend on the quality of the irradiation, but 2,000 kvp, 4,000 rad . . . 



C. S. Bachofer: If you wait, it goes down, you say, but how long after 4,000 

 rads does it go out? It does not go out immediately, does it? 



Werner K. Noell: It drops out somewhere within 2 hours after radiation. 



C. S. Bachofer: A lower dose would knock it out if you waited a longer period 

 of time, would it not? 



Werner K. Noell: No. These are all acute effects. 



C. S. Bachofer: A higher dose would be required if you tried to knock it out 

 sooner than 2 hours, is that correct? 



Werner K. Noell: Yes, up to a certain time level. 



C. S. Bachofer: Would you care to say what time? 



Werner K. Noell: Five minutes after the minimal dose is given. 



C. S. Bachofer: And the minimal dose you would set at what? 



Werner K. Noell: The minimal dose for a knock out of it is 4,000 rads. 



C. S. Bachofer: Would you qualify it and say at 2 hours time? 



Werner K. Noell: Yes. 



C. S. Bachofer: I presume it is going down up to 2 hours time, is that correct? 



Werner K. Noell: No. The ERG effect is a thing which occurs in minutes. It 

 is a sharp decline. Then it continues down for another IJ^ hours. These are acute 

 effects, and if these acute effects do not occur, then we have not reached the mini- 

 mal dose. 



C. S. Bachofer: We have been watching the ERG response after irradiation for 

 a couple of years, and there are two things we found. A heavy dose will knock out 

 the ERG momentarily, but it will usually come back. The other aspect is the 

 ERG after a dose of radiation will continue to decline over a long time and it 

 will go down faster with a high dose and slower with a low dose. So the time and 

 dosage together are important, I think. 



Leo E. Lipetz (Ohio State University, Columbus, Ohio): In regard to the paper 

 by Dr. Sato, Dr. Stahl, and Dr. Austin, I would like to say that I had hoped the 

 question of whether the cell body of the neuron is more sensitive than the axon 

 would be settled, but after seeing the slides I have great reservations that this 

 question has been answered at all. 



