502 



Mr. K. Lucas. 



[June 6, 



B. The Electric Response. 



We turn now to the second stage of our analysis, the problem how the 

 propagated disturbance is related to the electric response. The starting point 

 of this problem is the work of Bernstein * which showed that the electric 

 response keeps time with the propagated disturbance in its passage along 

 a nerve or muscle. The fact actually shown was that the time-interval 

 between the culmination of the electromotive force of the electric response 

 at two points on the length of a nerve or muscle agrees with the interval 

 between the passage of the propagated disturbance under those two points, 

 as calculated from the mean rate of travel of the latter. This work 

 established the proposition that the electric response is a normal accompani- 

 ment of the propagated disturbance, but does not resolve our doubt com- 

 pletely. We have to enquire further if the association is a necessary one. 

 This point must be fundamental to any hypothesis of the propagated 

 disturbance, because any hypothesis must give an account of the electric 

 response and must know whether to include it as the central feature of 

 propagation or to regard it as a mere accessory. 



From time to time physiologists have brought experimental evidence to 

 show that the two phenomena can be dissociated, that there can be an 

 electric response when there is no propagated disturbance or a propagated 

 disturbance with no electrical accompaniment. The most careful experiments 

 of this sort are those of G-otch and Burch.f They observed that when two 

 stimuli separated by a suitable interval of time were applied to a cooled 

 portion of a nerve, the electrometer connected to this part of the nerve 

 showed only a single electric response, whereas in a warmer portion of the 

 nerve more distant from the seat of stimulation the electrometer showed 

 clearly that two separate electric responses were present. They concluded 

 that the second propagated disturbance must have passed along the cooled 

 part of the nerve unaccompanied by such differences of potential as 

 constitute the familiar index of the electrical response, and that the absence 

 of any perceptible electric response does not necessarily imply the absence 

 of the propagated excitatory disturbance. LaterJ Gotch brought evidence 

 that within a short distance of a recent injury a propagated disturbance 

 might pass without any perceptible electric change, a fact in which he saw 



* Bernstein, ' Untersuchungen iiber d. Erregungsvorgang im Nerven- u. Muskel- 

 systeme,' Heidelberg, 1871. 



t Gotch and Burch, ' Proc. Physiol. Soc.'; 'Journ. Physiol.,' January, 1899, vol. 23, 

 p. xxii ; 1 Journ. Physiol.,' 1899, vol. 24, p. 422. 



X Gotch, ' Journ. Physiol.,' 1902, vol. 28, p. 50. 



