1 1 94 THE EAR. 



of the two generating tones. Such tones are, according to him, entirely 

 subjective. On the other hand, when two notes are sounded, a new series 

 of tones appear, as was previously pointed out by Konig. Thus, suppose 

 two tones of 5 : 8 are sounded, then there are heard (a) 8-5=3 (tone 

 corresponding to 3) ; also (/?) 5 x 2 - 8 = 2 (tone corresponding to 2) ; and 

 also (y) 5x3 8x2 = 1 (tone corresponding to 1), and so on. Such occurs 

 even when the generators have no overtones, and their intensities depend on 

 the varying strengths of the two primary tones. 



Thus Max Mayer agrees with Hurst in imagining a series of waves being 

 transmitted along the scalae, instead of the scalae forming part of one wave. 

 The two differ in respect that Max Mayer supposes, on physical grounds, that 

 the amplitude must diminish from base to apex of the cochlea, while Hurst 

 argues, also from the physical point of view, that the amplitude must increase. 

 Mayer's theory wholly rests on the supposition of diminished amplitude. I 

 would urge two objections to both theories : (1) it is impossible to conceive 

 of minute waves following each other in rapid succession in the minute tubes 

 forming the scalae ; and (2) neither theory takes into account the remarkable 

 differentiation of structure found in the epithelium of the organ of Corti. 

 Further, each push out and in of the base of the stapes must cause a 

 movement of the fluid in the scalae as a whole. It appears to me, therefore, 

 that the theory of sympathetic resonance gives a more satisfactory explanation 

 of the facts. 



THE SEMICIRCULAR CANALS. 



These organs, regarding the functions of which there are still differ- 

 ences of opinion, are anatomically in close connection with the internal 

 ear, and indeed form an integral part of it. The membranous tubes, 

 with their ampullae, communicate freely with the cavity of the utricle, 

 just as the saccule opens into the ductus cochlearis. In the ampullae 

 the adherent portion of the membranous structure projects into the 

 cavity of the ampulla as a transverse septum or sharp ridge, which partially 

 divides the ampulla into two. On the summit of this ridge we find a 

 highly specialised epithelium, forming the crista acustica ampullae, and 

 which presents characters similar to those shown by the maculae in the 

 utricle and saccule. These general anatomical facts support the supposi- 

 tion that the canals and ampullae are connected with the sense of hearing. 



On the other hand, there is a suggestion that they and the structures 

 lying in the vestibule have functions different from that of the cochlea, 

 in the fact that the cochlear and vestibular nerves pursue a somewhat 

 different course when they reach the brain, and apparently have different 

 centres. 1 Too much weight, however, must not be given to this state- 

 ment, as the nerve to the posterior semicircular canal passes along the 

 cochlear branch, while those to the two remaining canals accompany 

 the vestibular branch. Further, while one can understand that the 

 structures in the utricle, on receiving impulses from the base of the 

 stapes, may act as peripheral organs for the perception of sounds, with- 

 out reference to pitch or character, it has as yet been found impossible 

 to suggest any rational view as to the action of the canals and ampullae 

 with regard to auditory impressions. Helmholtz 2 thought that in 

 the ampullae eddies of fluid pressure might follow the pushes inwards 

 and outwards of the base of the stapes, thus causing currents or 

 pressures to pass transversely across the bristles on the hair cells in the 



1 Flatau, " Atlas of the Human Brain," 1894, p. 17, plate i. fig. 13. 



2 Op. tit., p. 217. 



