288 LAMINA SPIRALIS OF THE COCHLEA. 



as alone, among all the others, to act or vibrate, when the 

 note or harmonic chord, for which that single rod, or that 

 group of rods, had been provided, passes through the cochlea 

 in the form of sonant vibrations of a correspondent physical 

 value. If this be the case, we can understand how, by the 

 instrumentality of a cochlea, the physical value of each tone, 

 or harmonic combination of tones, may be detected by the ear, 

 and impressions of correspondent value transmitted along the 

 nerve-filaments to the seat of sonant sensation in the brain. 

 It must be borne in mind, however, that the aesthetic percep- 

 tion of the sensations produced by the instrumentality of the 

 cochlea, its nerves, and the sentient centre, is a psychical 

 function, and a result of the pre-established harmony between 

 the mental and corporeal elements of the animal constitution 

 on the one hand, and external nature on the other. 



