50 



eye./ Sec 



.AAA/WWWWl AAA/WWWW\ 



50 

 eye./ 



SCO. 



Fig. i8. Extracellular recordings obtained by Hodgkin from a single 

 motor axon of a crab in response to constant current steps of loo 

 milliseconds' duration. The numbers beneath index letters indicate 

 relative current strengths. Except at very high current intensities 

 (e.g. H) successive impulse intervals are all identical with that 

 interval of time between the onset of the stimulating current and the 

 appearance of the first spike. (From Hodgkin, ^^ Fig. i.) 



46 



