350 l*rot'. A. M. MaN'cr's Expcrlincitts on t/ie t<uj»j/i».i<( 



with the theorem ol" Fourier, reasoned that there must be ii 

 cause for it in the very dyuainie 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 llehnholiz that these were suitable bodies to effect the 

 decomposition of a composite sonorous wave by their covibratini; 

 witii its simi)le haimonic elements. This supposed function of 

 the Corti organ gave a rational explanation of the theorem of 

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

 holtz to the discoveries contained in his renowned work Die 

 Lehre von den Tonempjindungen-^ . 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 niav perhaps never be possible to bring Ileliuholtz's hypo- 

 tliesis 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 ])arts of 

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

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

 a view is obtained of the organ of Corti, its parts are rarely 

 in situ, and often they have already had their natural structure 

 altered by the acid with which the bone has been saturated to 

 render it soft enough for dissection and for the cutting of sec- 

 tions for the uiicroscojje. 



As we descend in the scale of development from the higher 

 vertebrates, we observe the parts of the outer and middle ear 

 disappearing, while at the same time we sec the inner ear 

 gradually advancing toward the surface of the head. The 

 externarear, the auditory canal, the tympanic membrane, and 

 with the latter the now useless ossicles, have disappeared in 

 the lower vertebrates, and there remains but a rudiinentary 

 labyrinth. 



• Accordin{» to Waldeyer, there are 6500 inuer aud 4500 outer pillars in 

 the organ ot Corti. 



t " 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 

 extraordinarv ilegiee. 



".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 aud of resultant sounds."— Ilelm- 

 iioltz, TontinpfinduiKjen, p. '■SA"2. 



