238 PHYSIOLOGY 



to perceive single tones or groups of neighbouring tones, while 

 they preserve the perception of other notes of the scale, which 

 form, as it were, auditory islands contiguous to the lacunae. This 

 can he readily explained by the resonance theory, assuming 

 circumscribed and disseminated lesions in the organ of Corti, 

 owing to which the function of certain elements on which depend 

 the perception of certain separate notes or groups of notes is 

 abolished. 



It is more ditlicult to explain by Hehnholt/' theory the clinical 

 cases of continuous, subjective sensations of special tones (Stuuipf), 

 and cases of what is known as double disharmonic hearing 

 (Jacobson). In the latter affection patients have a wrong JI.T- 

 ception of certain notes in the affected ear, or of a more or less 

 extensive portion of the musical scale, so that combined hearing 

 with the healthy and the diseased ear gives rise to disagreeable 

 dissonances. 



Hehnholtz' theory that the perception of the highest tones 

 depends on the first convolution of the cochlea, i.e. the part of the 

 organ of Corti that lies nearest the fenestra ovalis, where the 

 stapes is inserted, and of the deepest tones upon the apical spiral, 

 i.e. nearer the helicotrema, is partially supported by anatomical 

 observations in certain clinical cases. Moos and Steinbrligge, 

 for instance, in sections from a patient who had lost the perception 

 of high notes, found atrophy of nerve filaments in the first con- 

 volution of the cochlea. Other otologists, from their observations, 

 arrived at conclusions contradictory to those of Helmholtz 

 (Stepanow). Baginsky tried to solve the question experimentally, 

 on dogs, by destroying the whole of the cochlea on one side, and 

 its apex or base alone on the other. In the first case he found 

 deafness to deep tones, as shown by their reactions, but in the 

 second he was never able to prove deafness to high tones. These 

 results were afterwards confirmed by E. Ewald. But they only 

 partially agree with Helmholtz' theory, and may, as we shall 

 see, be adequately explained by a perfectly different theory. 



In conclusion it may be said that in proportion as the analysis 

 of auditory phenomena becomes more complete, arguments 

 accumulate which tend to disprove rather than to confirm the 

 resonance theory. Hermann, Mach, Konig and others have all 

 declared against it. 



In 1886 Eutherford proposed a different theory of hearing, 

 which is the logical development of a conception already put 

 forward by Einne (1865) and Voltolini (1885). According to 

 Eutherford the mechanism by which the cochlear apparatus is 

 excited is comparable with that of the telephone. The vibrations 

 transmitted to the fluid in the scala tympani through Eeissner's 

 membrane impress the tectorial membrane and hairlets of the 

 hair-eells. The hairlets are all excited simultaneously, and again 



