ELECTRICAL EXCITATION OF NERVE 153 



In the older literature of galvanism there is only one often- 

 quoted communication by Eitter (1802), with reference to altera- 

 tions of excitability in human nerve under the influence of the 

 electrical current. On dipping both hands into two vessels of 

 water connected with the poles of a strong battery, Eitter found 

 after a certain time (he remained half an hour in connection with 

 the battery) that mobility was perceptibly increased in the arm 

 through which current was ascending, while it was correspond- 

 ingly diminished in the arm traversed in the descending direc- 

 tion. These modifications continued for a short time after 

 opening the circuit. Pfliiger saw in this experiment an entire 

 confirmation of his conclusions from the frog-preparation. If a 

 battery is closed through both arms, " the nerves of the arm are 

 traversed by currents of different density from the brachial 

 plexus, or the spinal cord with its motor-nerve roots, because 

 the cross-section of the path of the current is here so large that 

 current density may, generally speaking, be regarded as minimal. 

 For this reason the arm traversed in a descending direction may 

 be pictured as if the positive electrode was applied to the 

 shoulder, the negative to the hand. That traversed in the 

 descending sense must correspond with the opposite distribu- 

 tion." Now since stimuli above a descending current discharge 

 twitches weaker than the normal, those above an ascending cur- 

 rent on the contrary being stronger, the conformity with the 

 laws of electrotonus would seem to be complete, when it is 

 remembered that " the sensorium itself here takes on the business 

 of excitation above, in the one case, the positive, and, in the other, 

 the negative electrode." At a much later period Tick (27) again 

 endeavoured to estimate the electrotonic alterations of excitability 

 in man. He tried to polarise the ulnar nerve at the posterior 

 side of the internal condyle, in order to test the anelectrotonus, 

 but without success. " At an almost unbearable strength of 

 current (1014 Bunsen) no trace of inhibition was visible in the 

 muscles supplied by the ulnar nerve." Pick ascribed his failure 

 to the impossibility of applying sufficiently strong currents, which 

 is the more improbable, since electrotonic alterations of excitability 

 appear with extremely weak currents. 



This was followed by the investigations of Eulenburg (27), 

 Erb (27), Samt (27), and others, which partly confirmed and 

 partly contradicted the conclusions of Pfliiger. Eulenburg agreed 



