Response of Nerve investigated with Electrometer. 309 



From the foregoing description it will be evident that when the 

 proximal electrometer contact is relatively positive to the distal one, 

 whether owing to the extrapolar changes due to the passage of a 

 polarising current, or to the presence, in the case of a recent cross- 

 section, of the resting demarcation difference, the electrical response 

 evoked by a single stimulus has certain definite characteristics ; the 

 most conspicuous of these are the increased magnitude of the initial 

 movement forming the ascending limb of the spike and the presence 

 of a more prolonged change of similar sign to this. On the other 

 hand when the contact proximal to the seat of the stimulus is rela- 

 tively negative to the distal one and this latter therefore relatively 

 positive, other characteristics of the response are accentuated ; the 

 initial movement forming the ascending limb of the spike is quickly 

 checked and succeeded by one of opposite character, whilst the 

 prolonged change disappears. 



It would be beyond the scope of the present communication to 

 enter upon any discussion as to the physiological meaning of the 

 changes here referred to. It may, however, be pointed out that the 

 results fully support the conclusions arrived at by Hermann from 

 rheotome observations, viz., that those portions of the extrapolar 

 region nearer the anode are during polarisation capable of a more 

 pronounced excitatory electrical change than those more remote, 

 whilst those portions of the cathodic region nearer the cathode are 

 susceptible of a less pronounced change than those more remote.* 

 New features are, however, brought to light by the present research 

 as indicated in the preceding paragraphs. 



The Electromotive Force of the Changes. 



The records allow of the calculation of the E.M.F. of the potential 

 difference between the contacts. The table appended to this com- 

 munication gives five examples of the results of the method of 

 analysis introduced by one of us f (G. J. B.) The five examples 

 selected are the analyses of excursions such as are figured in curves 

 (i), (ii), (iii), (vii), and (viii) of fig. 1. In addition to the intrinsic 

 interest which attaches to the estimation of the E.M.F. of the electrical 

 response to a single stimulus, the analyses present certain features 

 which may be briefly alluded to. 



The maximum E.M.F. ifc will be observed may reach as much as 

 O032 volt (Table IY), a suggestive fact in relation to the view held 

 by us as to the nervous origin of the E.M.F. of the response in the 

 electrical organ of fishes. % This maximum is attained very rapidly 



* See Hermann, ' Fandbuch der Physiologic,' vol. 2 (i), p. 167. 



f Pmrch, ' Phil, Trans.,' A, vol. 183 (1892), pp. 81105. 



J Gotch and Enroll, ' Phil. Trans.,' B, vol. 187 (1896), p. 382. 



