EFFECTS ON BIOELECTRIC ACTIVITY OF NERVES 



583 



failure of the nerves z?? situ to maintain the increased ampUtude as long as 

 those in vitro and a somewhat later increase in conduction velocity on the 

 part of the nerves irradiated in situ. 



X-irradiation of giant fibers of earthworm. Since a stable, predictable 

 response on which to superimpose the efTects of x-irradiation was necessary, 

 20 controls were observed for 10 hours for spike amplitude, sensitivity, 

 conduction velocity, and relative refractory period ( Fig. 7 ) . Zero time cor- 

 responded to the beginning of x-irradiation, 90 minutes after the nerve 

 cords were placed on the recording electrodes. The time at which x-irradi- 



© © Conduction Velocity 



A A Sensitivity 



o o Spike Amplitude 



• — • (Relative Refractory Period)'^ 



^9^j 



50 



100 



150 



200 



250 



600 



t^lNUTES 



Fig. 7. Relative activities of giant nerve fibers of earthworm, plotted as a function 

 of time. Curves represent mean values of 20 nonirradiated controls. Arrow at 90 

 minutes indicates time at which, in subsequent experiments, x-irradiation was begun. 

 Second arrow indicates average time at which x-irradiation was terminated. Values 

 plotted represent ratios of activities as designated times relative to the activity at 90 

 minutes. In most experiments involving UV irradiation, the right arrow would be 

 moved to approximately 210 minutes. 



