HELMHOLTZ IN BONN 



tain not only the gist of the matter, but be full of 

 suggestions for coming observers. 



We shall now endeavour to give a short account 

 of the contributions of Helmholtz to the theory of 

 hearing, and in doing so it will be more convenient 

 and intelligible if we make the attempt, not in the 

 chronological order of Helmholtz's papers, but in 

 connection with the physiological mechanism of the 

 ear itself. Sound waves are collected by the external 

 ear and transmitted by the external canal or meatus 

 to the drumhead. The drumhead is subjected to 

 periodic pressures corresponding to the individual 

 waves of sound, and thus it moves inwards with each 

 pressure and outwards by its elasticity. These move- 

 ments of the drumhead are transmitted across the 

 middle ear or tympanum to the internal ear by a chain 

 of bones, the malleus, incus and stapes. Lastly, the 

 internal ear consists of a very complicated arrange- 

 ment of sacs, in which lie the nerve endings immersed 

 in fluid, and the nerve endings receive, in their turn, 

 the pressures communicated by the chain of bones, 

 ending in the base of the stapes, which fits into 

 the oval window. How these nerve endings are so 

 affected by these pressures as to stimulate the fibres 

 of the auditory nerve is the ultimate problem of 

 hearing. How do we become conscious of pitch, 

 of loudness or intensity, and especially of the timbre, 

 quality or klangfarbe of a tone, so that we at once 

 recognise the instrument producing it, whether it be 

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