48 The Physiology of Sense Organs 



have examined the operation of these independent factors, which 

 tend to lessen the steady response of the neural membrane, in the 

 eccentric cells of the Limulus compound eye. They have shown 

 that prolonged depolarizations, induced by passing outward 

 current across the neural membrane, produce impulse trains 



Tir-T^ 



1^ 



-h — 50 — sh — tSt 



80 



* 100 



Fig. 20. Data from two experiments on single isolated crab nerve 

 fibers showing the increasing discrepancy at high stimulus-strengths 

 between the interval between first and second spikes of a train (filled 

 circles) and the interval between current onset and the first spike (open 

 circles). The ordinate is relative current strength. (From Hodgkin,^^ 

 Fig. 3.) 



