AUDITORY SENSATIONS. 609 



The explanation of our wonderful appreciation of the delicate 

 shades of quality of tones is more difficult. Even persons with 

 indifferently good ears, as musicians say, and no special musical 

 education, can at once distinguish between the quality of the same 

 note when sounded on a violin, a piano, and a flute. In examin- 

 ing the resound from a piano when a note is sung against its 

 strings it becomes obvious that with ever so pure a tone a great 

 number of strings are set vibrating. It will be found that not 

 only the string which sounds the note vibrates, but also all those 

 strings that have a certain simple numerical relation to its number 

 of vibrations. In fact, all its over-tones or harmonics are also 

 sounded. Now, in the cochlea we suppose the same takes place 

 with the fibres of the basilar membrane. Not only does the one 

 fibre whose proper tone is sounded vibrate in response, but also 

 all those fibres which represent the many and varied over-tones 

 or harmonics of the fundamental tone that reach the ear. It has 

 already been pointed out that quality of a note depends on the 

 relative number, force, and arrangement of the harmonics which 

 invariably accompany any musical note possessing a definite char- 

 acter. 



When such a note, then, arrives at the auditory nerve-terminals, 

 one of these is strongly stimulated by the wave of the funda- 

 mental tone, and many others are stimulated by the different 

 over-tones. Thus, a complexity of impulses, corresponding to a 

 mixture of tones of varying intricacy, is transmitted to the brain- 

 cells, where it gives rise to the impression of the quality which we 

 by experience associate with that of a violin, flute or piano, as 

 the case may be. 



With regard to the judgment of the distance of sounds, it need 

 only be remarked that they chiefly depend on former experience 

 of the habitual quality and intensity of the sounds. A faint sound 

 with the same quality that we familiarly attribute to loud sounds 

 seems to us to be far away. Thus, sounds reaching our labyrinths 

 by the cranial bones appear distant, and ventriloquists deceive 

 us by imitating the character of distant sounds. 



In man the direction from which sounds come is chiefly judged 



51 



