Theory of Audition subjected to Experiments. 167 



responders would prove adequate to account for the known 

 facts of the case. 



It would appear from the experiments thus made and their 

 accompanying photographic records, that about twelve re- 

 sponders to the octave or a total of about one hundred in all r 

 if of suitable damping, would probably suffice to account for 

 some of the chief facts of audition. 



And this number is only about one thirtieth of the number 

 of Corti arches present in the human ear. Accordingly on this 

 view the resonance theory would not make the demand for so 

 large a number of structures with separate nerves as its 

 adherents have usually supposed. On the contrary, it leaves 

 a liberal allowance for the possibility of the number of nerve- 

 fibres being much smaller than the number of Corti arches. 

 So that if a single nerve-fibre is distributed to a number of 

 arch segments (as found by Held), this would not necessarily 

 invalidate the resonance theory. 



Fundamental Facts of Audition. — We may now review 

 some of the basal facts of audition, so as to set up a standard 

 such that the success or failure of the resonance theory to 

 account for these facts would afford a confirmation or disproof 

 of the hypothesis. 



For those whose hearing is normal the following may be 

 taken as fairly representative of the fundamental facts with 

 which we are now concerned. 



1. When two different notes at a considerable interval are 

 sounded together, we can hear both notes and estimate their 

 interval, but do not mistake them for a single note of inter- 

 mediate pitch. Thus C and G sounded together are recognized 

 as forming the interval of the fifth and are not mistaken for 

 a single note of pitch E or E\}. (This is the direct contrary 

 of the case with colour vision in some parts of the spectrum.. 

 For, when beams of red and green light are converged on to 

 the same white screen, the impression received is that of yellow,, 

 and the unassisted eye furnishes no hint of the dual nature of 

 this composite light which might be a monochromatic yellow 

 for aught we are able to perceive.) 



2. When two near notes are sounded successively the 

 small interval between them can be perceived by a specially 

 keen ear down to something of the order of two vibra- 

 tions in a thousand or one twentieth of an equal-tempered 

 semitone. 



3. When two very near notes of almost equal intensities 

 are sounded simultaneously, the difference of their frequen- 

 cies can be recognized by anyone as the number of beats 

 per second. And this may serve to discriminate an interval 



