216 
THE EAR AND HEARING. 
and scala media. These shakes are transmitted to the endo- 
lympli through the membranous envelope, and by the aid of 
the otoconia (or otolithes) and fibres of Corti are finally 
converted into impulses, which act as irritants of the ends of 
the vestibular and cochlear terminations of the auditorv 
IS 
nerve. 
The labyrinthine fluids are, it would seem, also in a 
measure agitated by sound waves travelling through all parts 
of the skull (though most of these are, doubtless, so dissipated 
as to produce no appreciable effect). As examples of sounds 
transmitted through the skull we may quote the well-known 
case of applying the stem of a vibrating tuning fork to the 
teeth, &c., and the production of “ big bells” by the kitchen 
poker, suspended from a string, held at each end by the index 
finger closing the entrance to either ear. An eminent 
London Aurist also quotes, as an illustration, the opening of 
the mouth in cases of rapt attention to a discourse, music, 
&c. He considers that in this state hearing is assisted by 
sound waves being able to reach the tympanic cavity through 
the eustachian tube, and thus compares it to the cetacean 
“backward” hearing, noted above. I should also consider 
this as an example in point, although, in common with the 
relaxation of other members in states of rapt attention, &c., 
it may also be explained by reference to the effects of 
absorbing object regards, and is noticed in cases of concen¬ 
trated attention generallv,—but, as the pharyugeal end of 
the Eustachian tube is almost closed by its projecting lips, 
except during swallowing, and the soft palate offers an 
obstacle to the passage of sound waves. I should be more 
inclined to attribute any improvement in hearing in this case 
to the transmission of saund vibrations through the teeth. 
The character of sound sensations of course depends 
greatly upon the nature of the originating vibrations, 
whether rapid or slow, intense or delicate. 
The three physical peculiarities of sonorous impressions 
are :— 
I. Intensity and Quantity —loudness or feebleness, and 
volume of sound. 
II. Pitch —or note sounded. 
III. Quality, timbre, or klany —the difference between 
sounds of the same pitch proceeding from dif¬ 
ferent sources. 
I. Intensity, supposed to be discriminated by the parts of 
the labyrinth other than the rods of Corti, depends directly 
upon the degree of stimulation. Above a given point the 
effect becomes pungent, like the action of ammonia on the 
