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Or 
Or 
George E. Shambaugh 
3. The stimulation of the hair cells is effected only through the 
medium of their projecting hair. 
4. The hypothesis that each hair cell acts as its own agent in selecting 
its stimulus from the impulses passing through the endolymph is shown 
to be untenable for a number of reasons, chiefly, however, because the 
relation existing normally between the hair cells and membrana tectoria 
will not permit of these impulses coming in direct contact with the hair 
cells. I have shown conclusively that the hairs of the hair cells project 
normally into the under surface of the membrana tectoria. 
5. The stimulation of the hair cells is accomplished only through an 
interaction between the hairs of the hair cells and the membrana tectoria. 
6. The hypothesis of Helmholtz that this stimulation is brought about 
through the vibration of the fibers of the membrana basilaris is untenable 
especially for the following reasons: In tracing the membrana basilaris 
toward the beginning of the basal coil in the vestibule this structure is 
found, at a considerable distance from the lower end of the coil and 
where a perfectly formed organ of Corti is still present to become so stiff 
and rigid as to render it incapable of vibrating. Even a complete absence 
of a basilar membrane in this locality is sometimes noted. The logical 
conclusion is that since the stimulation of the hair cells in this locality is 
accomplished without the intervention of a vibrating membrana basilaris, 
therefore, the stimulation of the hair cells throughout the cochlea is not 
dependent on the vibration of this membrane. 
7. The logical conclusion is that the stimulation of the hair cells is 
accomplished through vibrations of the membrana tectoria transmitted to 
it by impulses passing through the endolymph. 
8. The membrana tectoria is shown to be so constituted anatomically 
as to be capable of responding to the most delicate impulses passing 
through the endolymph. Furthermore, the great variation in size of this 
membrane from one end of the cochlea to the other, together with its 
lamellar structure, suggest the probable physical basis which renders it 
capable of acting the part of resonator by responding in one part to im- 
pulses of a certain pitch and in another part to impulses of another pitch. 
9. The phenomenon of “ beats” is more readily accounted for than by 
the Helmholtz hypothesis; moreover, all the scientific observations by 
Helmholtz and his followers supporting a resonator hypothesis apply 
more readily and with greater force to my theory, viz., that the delicate 
membrana tectoria acts as resonator. 
10. Finally, the pathological phenomena of “tone islands,” “ dipla- 
