508 



Mr. K. Lucas. 



[June 6, 



' I must now turn away from this dark question of the part played by the 

 electric phenomena in propagation, and must trace the remaining steps of the 

 analysis. It must be confessed with regret that just on that point which 

 seems most fundamental to any hypothesis of the propagated disturbance the 

 analytical evidence is the most obscure. 



G. The Refractory State. 

 The refractory state is the last of the phenomena found in nerve whose 

 position in the chain of processes must be examined. I am using the term 

 refractory state in perhaps too wide a sense, meaning to include all those 

 phenomena of impaired functional activity which are associated with 

 recovery from the excited state. These include not merely the actual 

 impaired excitability which shows itself as the complete inefficacy of a 

 stimulus of any strength for a short time, and then as the need for a stimulus 

 stronger than the normal by an amount diminishing as recovery proceeds. 

 There are also the phenomena which seem at first sight to affect the 

 propagated disturbance more directly, namely the fact that the electric 

 response to the second of two stimuli occurs with abnormally long delay, a 

 phenomenon which Gotch* was the first to attribute to a slowing of the rate of 

 propagation, and the fact that the second of two propagated disturbances is 

 of abnormally small intensity if it follows a predecessor closely, f All these 

 phenomena pass away gradually as the time increases since the previous 

 activity of the tissue, and it seems not improbable that they are all expressions 

 of a single process of recovery. The problem of the present analysis is the - 

 relation of this recovery to the propagated disturbance. The phenomena all 

 follow the passage of an effective stimulus, and might therefore represent the 

 recovery either from some change associated with the propagated disturbance 

 or from some local change produced by the exciting current at the seat of 

 excitation only. 



The evidence on this point may best be taken for each of the phenomena 

 separately. For the actual refractory period TschagowetzJ has given 

 expression to the latter view by including that phenomenon in his hypothesis 

 of the nature of the local excitatory process. Gotch § noticed, however, that 

 the refractory period appeared to be little affected if the second stimulus, 

 instead of falling on the same point as the first, fell on a part of the nerve 



* Gotch, ' Journ. Physiol., 1 1910, vol. 40, p. 250. 



t Boycott, 'Journ. Physiol.,' 1899, vol. 24, p. 144 ; Adrian and Keith Lucas, 'Journ. 

 Physiol.,' 1912, vol. 44, p. 93. 



% Tschagowetz, 'Arch. f. d. ges. Physiol.,' 1908, vol. 125, p. 401. 

 § Gotch, 'Journ. Physiol.,' 1910, vol. 40, p. 267. 



