206 ELECTRO-PHYSIOLOGY CHAP. 



It is obvious that we cannot speak of any regular passage 

 of current in a given direction in the terminal apparatus of the 

 auditory nerve. Brenner (27), to whom we owe the most 

 extensive researches in this subject, placed one (the indifferent) 

 electrode at any part as far removed as possible from the ear 

 (back of head, chest, hand), while the other, with which he 

 experimented, was introduced as a fine wire into the auditory 

 meatus, after filling this with water, or applied as a small knob 

 covered with moist flannel to the skin near the ineatus. 



If the kathode is used for the exploring electrode, a sound 

 will be heard on closing a constant current of medium strength, 

 which gradually dies away during closure ; opening the circuit 

 gives no auditory sensation. On the other hand, if the anode 

 is applied to the ear there is no effect at closure, while the 

 opening is accompanied by a sensation of sound, which is usually 

 weaker than that at closure of the opposite current. On reversal 

 from anode to kathode, auditory sensations are produced with 

 an intensity of current at which a simple kathodic closure 

 gives no reaction (voltaic alternative). Oscillations of current, 

 starting not from zero, but from any finite value, produce the 

 same auditory sensations. 



In character the galvanic auditory sensation is for the most 

 part in successful experiments, with not too strong currents, a 

 true musical sound. Kiesselbach (49) determined its pitch as 

 that of the intrinsic tone of his ear. Since this is also the 

 pitch of the subjective sound heard with the so-called singing 

 in the ear, Kosenthal (I.e.) assumes that " on simultaneously 

 exciting all the auditory fibres with a weak stimulus, the 

 resulting tone is always that to which the subject is, as it were, 

 most accustomed." 



As regards electrical stimulation of cutaneous sensory nerves 

 many opinions have prevailed from the time of Eitter, the most 

 prominent fact being that an ascending current produces warmth 

 during its closure, while a descending current gives a cold 

 sensation. With a zinc -copper pile of 150 couples, the poles 

 of which terminated in beakers of salt solution into which the 

 hands dipped, du Bois-Eeymond experienced " waves of heat, and 

 cold shudders, alternately, running up the arms to the shoulders." 

 He was unable to convince himself that one arm felt heat and 

 the other cold. Goldscheider (49), on the other hand, with even 



