282 



C. T. GAFFEY 



2 4 6 8 10 12 14 16 



Hours after alpha particle irradiation 



Fig. 3. The percent of the initial spike potential is plotted against postirradiation 

 time for a nerve exposed to 72 krad of alpha particles and for its pair control. The 

 oscillograms in Fig. 2 provided the data for the construction of Fig. 3. 



140 



_ 120 

 g 



Sioo- 



o 



Q. 



« 80 

 '5. 



r 60 



Pre-irrodiotion 



20- 339 krad 



2 4 6 8 10 12 



Hours after alpha particle irradiation 



Fig. 4. Percent of initial spike potential plotted against the time after irradiation 

 by 910 Mev alpha particles for doses between 2 and 339 krad. 



The relative inhibitory effects of alpha particle and deuteron irradiation 

 on excitability are exemplified in Fig. 7. The time for the complete extinction 

 of spike amplitude is a logarithmic function of the absorbed dose within cer- 

 tain limits. Below 30 krad for alpha particles and 60 krad for deuterons, no 

 demonstrable suppression of the spike potential of sciatic nerve due to irradi- 

 ation can be reported. Irradiated nerves after more than 24 hours showed 



