A text-book of physiology for medical students and physicians . ved by thecochlea is not explained satisfactorily by the theoryof resonators. Other theories of the function of thecochlea have been proposed to avoid such , Ewald f suggests a view according to which thebasilar membrane vibrates throughout its length foreach note. He has shown that a rubber membrane ofthe dimensions of the basilar membrane will be setinto such vibrations throughout its length and whenexamined under the microscope presents such a pic-ture as is represented in Fig. 178, in which the crestsof the wa
A text-book of physiology for medical students and physicians . ved by thecochlea is not explained satisfactorily by the theoryof resonators. Other theories of the function of thecochlea have been proposed to avoid such , Ewald f suggests a view according to which thebasilar membrane vibrates throughout its length foreach note. He has shown that a rubber membrane ofthe dimensions of the basilar membrane will be setinto such vibrations throughout its length and whenexamined under the microscope presents such a pic-ture as is represented in Fig. 178, in which the crestsof the waves are at a fixed interval for each tone. Ifat these intervals the corresponding hair cells andnerve fibers are supposed to be stimulated, then ourconsciousness would recognize each note by its appro-priate interval. For the application of this theory to musical harmony—combinational tones and beats—reference must be made to the original. * Baginsky, Virchows Archiv f. pathol. Anat., 94, 65, Ewald. Archiv f. d. gesammte Physiologie, 76, 147, Fig. 178— To il-lustrate the idea ofa fixed sound wave.—(Ewald.) The illus-tration shows a fun-damental note and itsfirst overtone. EAR AS AN ORGAN FOR SOUND SENSATIONS. 395 Sensations of Harmony and Discord.—The combination ofnotes to produce various harmonies or intentional discords is a partof the theory of music, but attention may be called briefly to thephysiological explanation offered by Helmholtz to account for thefact that certain notes when combined give us a disagreeable sen-sation, appear rough and unpleasant; while others, on the contrary,produce pleasant sensations. Discord or dissonance is due, accord-ing to Helmholtz, to the beats produced when two dissonant notesare sounded together. On the physical side the beat,—that is, arhythmical variation in the intensity of the sound,—is due to thephenomenon of interference. If the rates of vibration of two notesare such that at certain intervals the cres
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