156 Irving Hardesty 



older papers illustrate the fibers as separately distinct, and even counts 

 of them are claimed, varying from 15,000 to 25,000. And measurements 

 of their thickness have been given, varying from 1.5 to 2.3 microns. One 

 of the most recent modifications of the theory, that of Hensen, is 

 founded wholly upon the existence of separate fibers. 



After becoming convinced by micro-chemical tests that the basilar 

 membrane consists of white fibrous connective tissue, some horizontal 

 sections of pig cochlea were prepared here and stained by Mallory's 

 method for white fibrous tissue. The sections were necessarily cut quite 

 thin in order to get areas containing the basilar membrane alone, 

 exclusive of its coverings, so that its actual construction might be 

 studied. Fig. 11 is an attempt to show the appearance of fiat sections 

 of the membrane as brought out by Mallory's method. From these 

 preparations, and afterwards even from the pieces obtained from the 

 teased cochleae stained with fuchsin, it became evident that the basilar 

 membrane is nothing more nor less than a thin flat tendon, and that its 

 so-called "fibers" correspond exactly to the well known fiber-bundles in 

 tendon fasciculi, being by no means independent of each other even as 

 bundles. Each bimdle is, of course, composed of multitudes of fibers so 

 fine that, even under oil immersion, one can never separate them with 

 certainty as to the divisional units of the structure, much less measure 

 them. The bundles (fibers of the basilar membrane), just as the bundles 

 in a tendon fasciculus, are abundantly connected or continuous with each 

 other by myriads of fine, silver-like collateral fibers inserted at all con- 

 ceivable angles, the majority slanting in the direction of the bundles. 

 In other words, the basilar membrane, instead of being formed of inde- 

 pendent fibers, is a sort of a feltwork or modified reticulum of inter- 

 woven fibers, the general direction of most of which is radial to the axis 

 of the cochlea, but withal, the resulting structure is such as to wholly 

 preclude the idea of the independent vibration of adjacent fibers. True, 

 in itself, it does not preclude the telephone theory of hearing. This 

 radial or parallel tendency is no doubt due to the fact that, as the 

 cochlea grows, the basilar membrane is developed from the mesenchyme 

 under tension, just as tendons are, and thus it becomes stretched taut 

 as the fioor of the ductus cochlearis and merely serves for the support of 

 the neuro-epithelium in the position for its functioning. The membrane 

 differs from an ordinary flat tendon in the distribution of its nuclei. 

 These, instead of being arranged throughout in the varying columns of 

 tendon cells, are absent under the region of the organ of Corti. As 



