1*5 msec. 



1*0 msec 



Fig. 6 (B) 



Fig. 6. (A) Oscillograph traces representing the responses of a single 

 crustacean nerve fiber to single, brief cathodal and anodal electric 

 stimuli. The responses to increasing strengths of cathodal stimulus 

 are shown as upward deflections of the oscillograph trace. They mirror 

 the responses to corresponding strengths of anodal current when they 

 are of sub-threshold value. At threshold, cathodal shocks evoke pro- 

 longed local membrane responses which can trigger action potentials, 

 three of which are shown (truncated). (B) Local membrane response 

 (a) obtained by subtraction of passive residual potential (dotted line) 

 from the potential record obtained in response to a barely threshold 

 cathodal stimulus. An anodal stimulus of identical intensity (downward 

 deflection) generates only a passive decay of potential, due to recharging 

 of the membrane capacitance. (From Hodgkin,^" Figs. 7 and 8.) 



20 



