230 STUDIES IN ELECTRO-PHYSIOLOGY: 



modification of consciousness which we call the sensation 

 of sound." (Thornton.) 



Landois and Stirling say : " Normal hearing takes 

 place through the external auditory meatus. The enor- 

 mous vibrations of air first set the tympanic membrane in 

 vibration ; this moves the malleus (Fig. 123), whose 

 long process is inserted into it ; the malleus moves the 

 incus (a), and this the stapes (s), which transfers the move- 

 ments of its plate to the perilymph of the labyrinth." 



All this, up to and including the movements of the 

 stapes, is perfectly consistent and indeed almost identical 

 with a telephone receiver and microphone attachment, 

 but when it becomes a' question of transfer of mechanical 

 vibrations to nerve-filaments, or to the wires of a closed 

 circuit, I would point out that there is no evidence that the 

 true function of a nerve is to convey mechanical impulses. 

 The physiological theory is that the nerve impulse is 

 chemical. My contention is that it is neuro- electrical. It 

 is difficult to understand how mechanical vibrations can 

 be transformed into chemical impulses, but not at all 

 difficult to conceive them being neuro-electrically trans- 

 mitted over a closed telephone circuit. 



Thornton remarks : " The whole subject of the 

 mechanism of hearing is far from being satisfactorily 

 settled. . . . For hearing the stimulus is of a mechanical 

 nature." I venture to think that the utmost that can be 

 said in favour of this hypothesis is that mechanical 

 stimulus extends from the external meatus, by the endo- 

 lymph, to the auditory nerve. It is the nerve, not the 

 endolymph, which conveys the stimuli to the brain. 



I can offer one very convincing proof that in this case 

 at least the impulse is neuro-electrical. In purely nerve 

 deafness the measure of nervous energy, as shown by the 

 hand-to-hand galvanometric deflection, is not more than 

 30 or 40 mm. ; deflections from the back of the cartilage 



