No. I.] THE VERTEBRATE EAR. 273 



As is well known, sound waves falling on a telephone plate 

 cause it to vibrate. An electric current is propagated to the 

 distant plate and causes it to repeat the vibrations of the first 

 plate. There is no analysis of sound waves by the second 

 plate. With these fundamental facts of the action of the elec- 

 tric telephone in mind, Rutherford (1886, 246) invented what he 

 terms his "Telephone Theory of Hearing." I give below the 

 gist of his statement of the theory. 



The hairs of the cochlea do not vibrate sympathetically, but 

 they, all of them, vibrate to every tone which enters the coch- 

 lear canal, as does the tympanum. There is no analysis of tone 

 produced by complex vibration, either in the cochlea or the part 

 of the external ear. The hair cells transform sound vibration 

 into nerve vibration similar in frequency and amplitude to sound 

 vibrations, and these simple and compound vibrations of nerve 

 energy arrive in the sensory cells of the brain and there pro- 

 duce not sound again, of course, but sensations of sound, the 

 nature of which depends not on the stimulation of different 

 sensory cells, but on the frequency, amplitude, and form of the 

 vibrations coming into the cells, probably through all the fibres 

 of the auditory nerve. 



This theory carries the physical cause of discord and harmony 

 into the brain, and the mathematical principles of acoustics find 

 entrance into the obscure region of consciousness. 



Now if nerve energy were only electricity, we might accept 

 this theory at once, but nerve energy is very sluggish as com- 

 pared with electricity. Rutherford tells us that he kept back 

 his theory for five years because he thought there was no pos- 

 sibility of sending a rapid series of vibrations along a nerve. 



If we give to a motor nerve of a Frog 10 electrical shocks 

 per second, there will be produced 10 contractions in the muscle 

 per second ; if 40 shocks, not 40 contractions, but one contimi- 

 ons conti'action, on account of the fusion of the several contrac- 

 tions. 



Now if we listen to such a muscle, we hear a musical note 

 having the pitch of 40 vibrations per second. Each sound 

 vibration results from the sudden shock of a chemical discharge, 

 due to the arrival of each nerve impulse in the muscular sub- 

 stance. If we stimulate with a rapidity of 200 times per second 

 (by means of a tuning-fork apparatus) the pitch of the muscle 



