228 SPECIAL SENSES. 



possible application of physical laws to the supposed vibra- 

 tion of the rods. 1 



Viewing the question from its anatomical aspect, it is by 

 no means certain that the rods of Corti are so attached and 

 stretched that they are capable of separate and individual 

 vibrations. It has not been demonstrated that certain of 

 these rods vibrate under the influence of certain tones, or are 

 tuned in accord with certain tones. Hensen, who has writ- 

 ten elaborately upon the very question under consideration, 

 denies the accuracy of the theory of Helmhgltz, basing his 

 opinion upon the anatomical arrangement of the rods of 

 Corti, and assumes that it is a physical impossibility for the 

 different rods to vibrate individually, and that it is not cer- 



1 It is a curious historical fact that Du Verney, in a work first published in 

 French, in 1683, and afterward translated into Latin, stated that the filaments 

 of those auditory nerVes distributed upon the lamina spiralis were so arranged as 

 to receive the various impressions made by different musical tones. (Du VER- 

 NEY, Tradatus de Organo Auditus, Lugd. Batav., 1730, pp. 28, 29.) Le Cat, 

 the first edition of whose work on the Senses was published in 1739, also ad- 

 vanced the theory that the cochlea was the only portion of the auditory apparatus 

 capable of appreciating musical tones. After speaking of the vestibule and 

 the semicircular canals as the parts affected by irregular sonorous vibrations, he 

 states that the cochlea has a more delicate function : 



" The design of this construction is of the most perfect mechanism. The 

 essential office of an organ of sense is proportionate to its object, and, for the 

 organ of hearing, it is the capacity of being in unison with the different vibra- 

 tions of the air ; these vibrations have infinite differences ; their progression is 

 susceptible of infinitely small degrees. An organ, then, is necessary, which is 

 made in unison with all these vibrations, and, in order to receive them dis- 

 tinctly, should be composed of parts, the elasticity of which follows this same 

 progression, insensible, or infinitely small. The spiral hi mechanics is the only 

 apparatus adapted to give this insensible gradation." 



Farther on, Le Cat states that, " whatever division may be conceived of in 

 tones, there is none which does not meet, in points of this spiral, with its unison, 

 or its equal vibration, thus there is no tone which cannot distinctly impart its 

 vibration to this spiral ; and in this consists the grand design of the cochlea. 

 This is why I regard the cochlea as the sanctuary of audition, as the special 

 organ of harmony, or of the most distinct and the most delicate sensation of 

 this kind." (LE CAT, Traite des sensations, etc., Paris, 1767, tome ii., pp. 281, 

 282.) The above is simply the theory of Helmholtz, wanting the exact ana- 

 tomical and physical details developed by modern researches and experiments. 



