The jSTature of the Tectorial Membrane 155 



rations, indicating that they do not lie in direct contact and probably 

 adhere to each other, and such an arrangement must tend to interfere 

 with sensitive resonant vibration. 



(3) Assuming that any or all parts of the basilar membrane proper 

 consist of independent fibers, the question may be asked whether the 

 membrane is capable of being thrown into vibration at all by sound 

 waves. Ewald, '99, constructed a model in which he was able to so 

 stretch a very thin rubber membrane that he succeeded in getting pieces 

 as small as 0.5 mm. broad to vibrate when suspended in water by sound 

 waves in the air. The recent measurements of the assumed vibratory 

 width of the basilar membrane by Kolmer, '07, show this width to vary 

 from only about 0.2 mm. (168 microns) in the basal turns to only 

 0.3 mm. (304 microns) in the apical turns. Shambaugh, '07, thinks 

 that Ewald's model falls far short of proving that the basilar membrane, 

 which he describes as being "much shorter, thicker and more rigid" than 

 Ewald's rubber membrane, vibrates in response to sound waves transferred 

 to the endolymph, and he mentions the fact that Helmholtz himself 

 appreciated the doubt as to whether fibers so short as the width of the 

 basilar membrane can be thrown into vibration by sound waves. Cer- 

 tainly its relative width and thickness, coupled with objections 1 and 

 2 above, make its vibration reasonably doubtful. Shambaugh describes 

 the basilar membrane, in his preparations of the cochlea of the pig, as 

 becoming so thick arid rigid in the basal coil, "a considerable distance" 

 from its basal termination, as to preclude the idea of its being a vibra- 

 tory structure. In one specimen he found complete absence of the 

 basilar membrane in the basal end of the coil, but instead the perfectly 

 formed organ of Corti, with its tectorial membrane, rested upon a direct 

 junction of the crista of the spiral ligament with the labium tympanicum 

 of the spiral limbus. In another specimen, he found the perfectly 

 formed organ of Corti resting upon a solid bony plate bridging the 

 width between the lamina spiralis ossea and the outer wall of the 

 cochlea. Such absences of the basilar membrane under a completely 

 formed organ of Corti, suggest that it is not essential to the sense of 

 hearing either as a structure vibrating in accordance with the resonance 

 theory or in accordance with the telephone theory. 



(4) To the above anatomical objections to the resonance theory may 

 be added evidence that the basilar membrane is not composed of indi- 

 vidual and independent fibers at all. The idea of resonant vibration 

 as implied in the theory demands the existence of such. Some of the 



