[ 371 ] 



LI. Researches in Acoustics. — No. V. 

 By Alfred M. Mayer. 



[Continued from p. 274.] 



3. Experiments on the supposed Auditory Apparatus of the 

 Culex mosquito. 



OHM states in his proposition that the ear experiences a 

 simple sound only when it receives a pendulum-vibration, 

 and that it decomposes any other periodic motion of the air into a 

 series of pendulum-vibrations, to each of which corresponds the 

 sensation of a simple sound. Helmholtz, fully persuaded of the 

 truth of this proposition, and seeing its intimate connexion 

 with the theorem of Fourier, reasoned that there must be a 

 cause for it in the very dynamic constitution of the ear ; and 

 the previous discovery by the Marquis of Corti of several 

 thousand* rods of graded sizes in the ductus cochlearis, indi- 

 cated to Helmholtz that these were suitable bodies to effect the 

 decomposition of a composite sonorous wave by their covibrating 

 with its simple harmonic elements. This supposed function of 

 the Corti organ gave a rational explanation of the theorem of 

 Ohm, and furnished " a leading-thread " which conducted Helm- 

 holtz to the discoveries contained in his renowned work Die 

 Lehre von den Tonemp findung en f. In this book he first gave 

 the true explanation of timbre, and revealed the hidden cause 

 of musical harmony, which, since the days of Pythagoras, 

 had remained a mystery to musicians and a problem to philo- 

 sophers. 



It may perhaps never be possible to bring HelmhohVs hypo- 

 thesis of the mode of audition in the higher vertebrates to the 

 test of direct observation, from the apparent hopelessness of 

 ever being able to experiment on the functions of the parts of 

 the inner ear of mammalia. The cochlea, tunnelled in the hard 

 temporal bone, is necessarily difficult to dissect ; and even when 



* According to Waldeyer, there are 6500 inner and 4500 outer pillars in 

 the organ of Corti. 



f " But all of the propositions on which we have based the theory of 

 consonance and dissonance rest solely on a minute analysis of the sensa- 

 tions of the ear. This analysis could have been made by any cultivated 

 ear without the aid of theory ; but the leading-thread of theory and the 

 employment of appropriate means of observation have facilitated it in an 

 extraordinary degree. 



"Above all things I beg the reader to remark that the hypothesis on the 

 covibration of the organs of Corti has no immediate relation with the ex- 

 planation of consonance and dissonance, which rests solely on the facts of 

 observation, on the beats of harmonics and of resultant sounds." — Helm- 

 holtz, Tonempfindungen, p. 342. 



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