502 IRVING HARDESTY 



(positions indicated in figure 5). It was found that all notes 

 with vibration frequencies below that of the note a (concert 

 pitch, 220 vibrations per second) resulted in constant vibration 

 of all regions of the tectorial membrane sufficiently strong to 

 make and break the current. This suggests that within the lower 

 range of the natural auditory scale, all sound waves affect the 

 entire spiral organ. 



(6) The extent of the tectorial membrane that could be thrown 

 into vibration by certain notes depended upon the intensity or 

 amplitude of vibration with which the note was sounded. For 

 example, the note g (196 vibrations per second), the next whole 

 note below a, when sounded faintly into the external meatus, 

 failed to result in vibrations of the apical end (region 6) of the 

 membrane sufficient to make and break the current, while if 

 sounded forcibly, this note caused vibrations in all regions. All 

 sounds and notes with vibration frequencies below that of g 

 resulted in vibration of the entire membrane, regardless of the 

 amplitude that could be employed. Ewald ('99) applied a modi- 

 fication of the telephone theory to the basilar membrane. He 

 constructed an arrangement in which narrow strips of thin sheet- 

 rubber were adjusted under water and observed with the micro- 

 scope the behavior of these strips when sound vibrations were 

 imparted to the water. His narrowest strips was 0.5 mm. broad. 

 From the behavior of these strips he suggested that the basilar 

 membrane vibrates throughout its entire length in response to 

 every note applied. The above observation suggesting the 

 action of the tectorial membrane, and the one following, do not 

 fully support Ewald's conclusion for the basilar membrane 

 as based upon the action of his rubber bands. His bands did 

 not vary in thickness, or load carried, along their length. Meyer 

 ('98) constructed an apparatus by which he applied the telephone 

 theory to the basilar membrane. His apparatus was designed to 

 indicate the results of varying amplitudes of vibration rather than 

 varying pitch, using electrical contact and electric lamps as indi- 

 cators. No attempt was made to imitate the basilar membrane 

 or any other structures of the auditory apparatus. His results led 

 him to conclude that the greater the amplitude of the vibration, 



