ACTION OF THE TECTORIAL MEMBRANE 509 



conclusion that all these suggestions might have been due to lack 

 of uniformity in construction of the model or faults in arrangement 

 of parts. Certainly the model showed no evidence of resonance 

 in the definite way advanced by the theory of Helmholtz as 

 applied to an assumed structure of the basilar membrane. 

 Altogether, with the suggestions so far obtained, the question 

 may be revived as to whether analysis of sound is not accom- 

 plished in the interpretations of the stimuli by the central nerv- 

 ous organ. It may be a question whether any actual analysis 

 is accomplished by the cochlea at all other than to such extent 

 as can be possible in the indications that, dependent upon the 

 vibration frequencies and amplitudes of the sound waves ap- 

 plied, varying lengths of the tectorial membrane are thrown 

 into efficient vibration, the lengths beginning at the basal end. 

 Instead of its different regions manifesting selective resonance, 

 the membrane may lie limply passive, agitated by given wave 

 motions only in so far as the resistance offered by itself and the 

 perilymph and endolymph will permit, and, just as in the sense 

 of touch for example, differences in qualities, intensities and 

 frequencies of the stimuli are interpreted by the central nervous 

 system as qualities, intensities and pitch of sounds. A number 

 of different stimuli applied to the unit area of the skin give rise, 

 within the peculiar possibilities of skin innervation, to an inter- 

 pretation different from one stimulus applied to that area, and 

 stimuli involving varying extents of skin, above certain limits, 

 are interpreted differently. The same may be urged in general 

 for the other sense organs, within the variations of their special 

 differentiation. Gray ('00) in applying a modification of the 

 resonance theory to the basilar membrane, notes, among others, 

 that a mixture of tones of closely approximate vibration fre- 

 quencies cannot be analysed by the auditory apparatus. If 

 of varying amplitude or intensity, that of the maximum intens- 

 ity in the mixture alone is perceived. Such a mixture of notes 

 must all involve so nearly the same extent of the vibratory 

 mechanism and hair cells and with so nearly the same frequency 

 of impingement upon the unit area that the different components 

 are not separately interpreted, just as when two or more points 



THE AMERICAN JOURNAL OF ANATOMY, VOL. IS, NO. .3 



