1882.] Influence of the Galvanic Current, Sfc, 



353 



III. " On the Influence of the Galvanic Current on the Excita- 

 bility of the Motor Nerves of Man." By Augustus Waller, 

 M.D., and A. de Watteville, M.A., B.Sc. Communicated 

 by J. S. Burdon Sanderson, M.D., F.R.S. Received 

 February 2, 1882. 



(Abstract.) 



The object of the experiments described in this paper is to demon- 

 strate on the living nerves of man, alterations of excitability during 

 and after the passage of a galvanic current, and to determine how far 

 such alterations concord with the results obtained by Pfluger and 

 other physiologists on the exsected frog's nerve. 



In order to subject the nerve to the influence of a " polarising " 

 current, and to test its excitability by means of induction currents, the 

 secondary coil is introduced into the galvanic circuit, so that the 

 points of entrance and exit of the two currents (galvanic and in- 

 duced) coincide at the two electrodes. One electrode, N, is applied 

 over the nerve, the other, F, to any distant part of the body. 



The density of the current which passes in the nerve is much 

 greater in the " polar " region (that is, immediately under the 

 electrode N) than in the adjacent region, which may be termed the 

 " peri-polar " zone, and the authors' experiments go to prove that 

 these two regions are to be physiologically distinguished by the fact 

 that their electrotonic states are opposed. 



The authors observe that the excitatory effect of an induction 

 current is increased during the passage of a galvanic current in the 

 same direction, diminished during its passage in an opposite direction, 

 that the increase is greater when both currents are directed from F 

 to N than when both are directed from N to F, and that the diminution 

 is greater when the induction current is from F to N and the galvanic 

 current from N to F than when these two currents flow in the reverse 

 direction. 



These results admit of a complete explanation, for which the 

 grounds are stated in the paper. During the passage of the galvanic 

 current from F to N katelectrotonus is set up in the polar region 

 and anelectrotonus in the peri-polar region ; during the passage 

 of a galvanic current from 1ST to F the polar region is in anelectrotonus, 

 the peri-polar in katelectrotonus. At the passage of the induction 

 current from F to N excitation is made in the polar region, at its 

 passage from N to F in the peri-polar region. 



Some subsidiary phenomena are discussed, and an experimental 

 proof is given of the physiological reality of the above changes. 



In addition to the induction current the authors have used the 



VOL. xxxiii. 2 c 



