vin FUNCTION OF COCHLEA 386 



has its own proper note. Now, a tuning-fork will be set 

 vibrating if its own particular note be sounded in its 

 neighbourhood, but not if other notes be sounded. Hence, 

 when a pure niusicHl note is sounded close to a number of 

 tuning-forks of different pitch, only that tuning-fork the 

 pitch of wliich is the same as tliat of the note sounded is 

 set vibrating ; the others remain motionless. When an 

 ordinary musical sound, such as a note sung by the human 

 voice, is produced among such a group of tuning-forks, 

 several are set vibrating ; one of these corresponds to the 

 fundamental tone, and the others to the various overtones 

 of the sound. Similarly, if the top of a piano be lifted up 

 or removed, and any one sings into the wires with sufficient 

 loudness, a note, such as the tenor c, a number of the wires 

 will be set vibrating, one corresponding to the fundamental 

 tone, and the others to the overtones. 



If we were to imagine an immense number of tuning- 

 forks, each vibrating at different periods, so arranged that 

 each fork, when vibrating, in some way or other stimulated 

 or excited a minute delicate nerve-filament attached to it, 

 it is obvious that a musical sound uttered near these 

 tuning-forks would set a certain number of them into 

 vibration, some more forcibly than others, and that in 

 consequence a certain number, and a certain number only, 

 of the delicate nerve-filaments would be excited, and that 

 to various degrees ; and thus a particular series of nervous 

 impulses, the counterpart as it were of the musical sound 

 with its fundamental tone and overtones, would be trans- 

 mitted along the nerve filaments to the brain. 



And it is suggested that the basilar membrane of 

 the cochlea, consisting as it does of thousands of fibres 

 stretching across from the inside to the outside (from left 

 to right in Fig. 121), with its thousands of epithelial cells 

 and rods of Corti lying upon it, represents, as it were, an 

 assemblage of thousands of tuning-forks, of various rates 

 of vibration, with a separate nerve filament attached to 

 each. So that, when a number of vibrations of diflFerent 



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