592 



C. S. BACHOFER 



AIIAIIDV 3AllV13iJ 



Fig. 16. Effect of UV irradiation on refractory period of single median giant nerve 

 fibers of earthworm. Relative activity is the ratio of the refractory period in milliseconds 

 at the beginning of irradiation to the refractory period in milliseconds at any desig- 

 nated time. This ratio is plotted as a function of time after the beginning of irradiation. 

 Enhancement of activity precedes deterioration and ultimate block. Mean values are 

 plotted together with standard deviations. 



