421 
The Effect of some Local Anesthetics on Nerve. 
By W. L. Symes and V. H. VELEY, F.R.S. 
(Received December 10, 1910,—Read February 9, 1911.) 
(From the Physiological Laboratory of the University of London.) 
CONTENTS. 
PAGE 
SPOR UOC OCLLON. (ects such soi stivaicieas ccc beige eer scclrons desir Creek Se cee onan coenonaes Genie 421 
mie RoC Od! OL EX PELIMCM be; 5.05 s0isy.a1sasacetaneesadoascasesacsecaseacsaradeauem\ouss 422 
III. Conditions which Influence the Anesthetic Block...........cccccceceseseese 423 
mVelttects:o£ the Individual Drags... ......0.0..csdvcenssnececcecuccsseseessedesate 424 
WG eEMOTal CONSIGETAGIONS! © sis. cclscoscasesascececsesseccepesedddstesaececiacseecesicees 428 
VI. Conclusions....... eRe Rectan tt aialctes Hele acdueauiees ating sadam eaeauhiine 432 
I, INTRODUCTION. 
The employment of stovaine, in clinical practice, to produce local 
anesthesia by direct application of the drug to nerve (lumbar anesthesia) 
suggested comparison of this substance with its homologues,* as also with 
cocaine, on a similar plan. Afferent nerves, however, were not chosen for 
the purpose, as their use would have involved the ambiguities inseparable 
from quantitative examination of reflex action. Hence motor nerves, with 
their simpler index of activity (muscular contraction), were taken in 
preference. 
In principle, the plan adopted was identical with that used by Griinhagenf 
and others in studying the effect of gases and vapours on the conductivity of 
nerve, viz., applying the agent under examination to the nerve between the 
stimulating electrodes and the muscle. Wedenski,t on the same lines, has 
investigated the effect of painting solutions of cocaine (and of other drugs) 
on a motor nerve trunk, and more recently Dixon,§ and Tait and Gunn 
have respectively tested cocaine and yohimbine by analogous methods. 
This method is advantageous in that it entails no disturbance of the 
stimulated portion of the nerve, and enables study of the modes of onset 
and of subsidence of the anesthetic block under constant excitation. It 
was found possible, with as many as six excitations per minute, to observe 
these two processes, on the same nerve-muscle preparation, within times 
sufficiently short to exclude fatigue. 
* The physical properties of these bodies and their effect on skeletal muscle, on 
respiration, and on circulation are dealt with in the preceding paper, p. 413. 
+ Griinhagen, ‘ Arch. f. d. ges. Physiol.,’ 1876, vol. 6, p. 180. 
{ Wedenski, zbid., 1900, vol. 82, p. 134; and 1903, vol. 100, p. 1. 
§ Dixon, ‘J. Physiol.,’ Cambridge, 1905, vol. 32, p. 87. 
|| Tait and Gunn, ‘Quart. Journ. Exp. Physiol., London,’ 1908, vol. 1, p. 191. 
