506 IRVING HARDESTY 



character but so high as to be damped out by the other structures 

 of the auditory apparatus to an extent rendering them unable 

 to produce effective stimulation of any of the hair cells at all. 

 It is stated that the auditory apparatuses of certain individuals 

 are capable of appreciating higher pitches (vibration frequencies) 

 than others and that certain species of animals have an auditor^' 

 range including high pitches not heard at all by other species. 

 It is suggested by the model that the lower vibration frequencies 

 may affect all auditory apparatuses. The range of the model 

 extended no higher than the note / above 'middle C. Con- 

 sidering its relatively enormous size and coarseness of constuc- 

 tion, it is interesting that it had a range so high, even though 

 the end of the horn was inserted directly into the external meatus. 



The quality of a note is supposed to depend upon the form of 

 the wave-motion producing it. The peculiar form of a vibration 

 must be represented in its transmission to the endolymph as well 

 as its amplitude and frequency, and the consequent fonn of the 

 undulations of the tectorial membrane while striking the hairs 

 of the hair cells must give rise to interpretations of quality by 

 the central nervous system. Sensations of pitch must be de- 

 termined by the number of stimuU appHed in a unit of time upon 

 a unit area of sensory surface, that is, by frequency of vibration. 

 Also, among the higher frequencies, it may depend somewhat 

 upon the extent of the sensory surface involved by a given sound : 

 the greater the extent, the lower the note. Intensity of sensation 

 must depend upon the force of the impingement of the hairs of 

 the hair cells (amplitude) and also upon the extent of the sensory 

 surface involved. Of two sounds of the same vibration frequency , 

 that of the greater intensity involves the greater extent of the 

 tectorial membrane. It is suggested that sensations of intensity 

 and quality of sound are produced in ways entirely comparable 

 with those recognized for the other organs of special sense, namely, 

 in all the interpretation of the sensations is correlated with the 

 number, quality and intensity of the stimuli and the area of 

 sensory surface involved. 



(8) As to the question of resonance, very little could be 

 determined with the model. The suggestion that, within the 



