26 IRVING HARDESTY 



thought to further support the suggestion that the tectorial is 

 far more adapted as a vibrator^^ mechanism in the auditory 

 apparatus than is the basilar membrane. Whether in accord 

 with the Helmholtz theory, which involves sympathetic reso- 

 nance, or with a modified telephone theory, the much greater 

 variation of the tectorial membrane allows for it a much greater 

 scale of activity than seems possible in the basilar membrane. 

 Measurements of the assumed vibratory width of the basilar 

 membrane, for example those by Kolmer ('07), show that its 

 width (length of its supposedly existing vibrating fibers) at the 

 apical end of the spiral organ is only about 1.8 times its width 

 in the basal end. Averages of measurements here made in 

 cochleae of adult hogs, taken from the line at which the audi- 

 tory nerve fibers {AF, fig. 2) disappear into the spiral organ to 

 the outer angle of the scala tympani, give the basilar membrane 

 a width of 257.9 fi at the apical end and a width of 184.8 ^ . at the 

 basal end (fig. 4), thus showing it to be about 1.4 wider at the 

 apical than at the basal end. When the measurements were 

 taken at the level of the floor of the spiral sulcus (about at the 

 line AF, fig. 1), the width of the thus questionabh^ vibrating 

 part of the spiral lamina was found to be only about 1.9 wider 

 at the apex than at the base. It may be noted in the figures 

 that this latter measurement includes in the basal coils some of 

 the bony spiral lamina. As seen above, the width of the assumed 

 vibratory part of the tectorial membrane, its outspanning zone, 

 is 6.8 times greater at the apical than at the basal end. The 

 basilar membrane does not consist of independent fibers and 

 thus of fibers capable of resonant activity. Ayers ('91) described 

 it as consisting of four layers of fibers, one of which runs at right 

 angles to the other three. In my former paper, the main or 

 radially arranged part of the basilar membrane was shown to 

 be of the nature of a flat tendon, the tendon fasciculi (fibers of 

 the earlier descriptions) being abundantly connected with each 

 other by smaller collateral bundles. Vasticar ('12) said that it 

 consists of six layers. He, however, included the layer of epithe- 

 lioidal tissue, or syncytical mesenchyme, on the basal surface 

 of the basilar membrane proper and the endothelium lining the 



