164 Irving Hardesty 



membrane is entirely coextensive with the organ of Corti. The basilar 

 membrane as such is not entirely coextensive. 



(c) From its specific gravity, its evident lateral elasticity and from 

 its most remarkable transverse flexibility and sensitiveness to agitations 

 in a fluid surrounding it, the tectorial membrane appears to be far 

 more admirably qualified to serve as the vibrating mechanism than does 

 the basilar membrane. 



(d) From the evidence that the tectorial membrane is attached along 

 but one of its sides; from the fact that, even if it were attached along 

 both sides, none of its fibers are coextensive with its width; from the 

 fact that it is so constructed that relatively very few of the fibers, even 

 if vibrating, can in any way come in contact with the hairs of the hair 

 cells, and from the fact that the great majority of its fibers are evidently 

 attached at neither of their ends, it is very improbable that the mem- 

 brane is capable of acting as a sympathetic resonator, 



(e) , In addition to its suggestive consistency and structure, the tec- 

 torial membrane is so shaped and proportioned as to suggest that it may 

 act with reference to vibrations in the endolymph in a way by which 

 the peripheral components of the phenomena of hearing may be ex- 

 plained; namely, the membrane may be acted upon as a whole, the 

 extent, region, amplitude and quality of its vibrations depending upon 

 the force, frequency, amplitude and quality of the vibrations acting 

 upon it. 



From the various pathological phenomena, observation of which have 

 been followed by post-mortem examinations of the cochlea, it is quite 

 generally accepted that sensations of the higher pitches are mediated 

 by the structures of the basal coil of the cochlea, and from this it has 

 been assumed, naturally, that the sensations of lower pitch are mediated 

 by the apical coil. 



The tectorial membrane is narrowest and thinnest in the basal coil 

 and gradually increases in both width and thickness to acquire its 

 greatest proportions in its apical end. Being attached along its inner 

 edge throughout, it must be affected by sound waves in the endolymph 

 very much as a very flexible ribbon so attached would be by agitations 

 running parallel with its length in a fluid in which it floats. 



The extent to which the tectorial membrane can be agitated must 

 depend (1) upon the energy of the wave motion, or upon the extent 

 and point at which the wave motion in the endolymph is neutralized by 

 overcoming the inertia of the fluid and by the resistance offered by the 



