MECHANICS OF THE INNER EAR 137 



ample, parrots, are able to imitate human speech sounds. 

 Speech sounds are characterized, according to the present state 

 of phonetics, by particular groupings of tones in both simul- 

 taneity and succession. It is not certain that the rough imi- 

 tation of human speech sounds by parrots is more than an 

 imitation of the successive groupings of tones. Granted even 

 that the birds possess the ability to perceive more than one 

 tone simultaneously, the anatomical facts would make it prob- 

 able that this ability is very limited in comparison with the 

 human ear which perceives the most varied combinations of 

 tones in speech sounds and in harmonic music. 



Let us now briefly look back upon what we have done. 

 We have regarded the organ of hearing as a long and narrow 

 tube, filled with a practically incompress- 

 The need of ^'^^^ ^*^'*^ ^^^ divided lengthwise by an im- 



experimental perfectly elastic partition which is the seat 



data of the auditory nerve ends. We have found 



that the problem of determining exactly, 

 for each given form of stirrup movement, the mechanical pro- 

 cesses taking place in the tube is from the mathematical side 

 an almost hopelessly complex one, made still more difficult 

 by the lack of data concerning the mere facts of hearing as 

 well as the elastic and other physical properties of the parti- 

 tion. In order to overcome the intrinsic and accidental diffi- 

 culties standing in our way, we have introduced six simpli- 

 fying provisional assumptions ; not using all six in every case, 

 but now some of them, now others, according as the purpose 

 of the moment seems to warrant. We have thus obtained a 

 superficial, but for a beginning satisfactory, insight into the 

 wonderful machinery by which we analyze the complicated 

 sound waves with a result which — for example, with respect 

 to the hearing of difiference tones — is most surprizing to one 

 who knows nothing of the mechanics of the inner ear. 



