282 
THE EAR AND HEARING. 
Dr. Wollaston considers that the degree of tension of the 
tympanic membrane affects our sensibility to pitch, and he 
thus explains the functions of the tympanic muscles. The 
Tensor tympani, which is inserted in the upper part of the 
handle of the malleus, by its contraction tightens the 
membrane ; the Laxator tympani, inserted in the processus 
gracilis of the malleus, is supposed by some to assist in 
relaxing the membrane upon the remission of the action of 
the tensor ; and the Stapedius, attached to a loop in the neck 
of the stapes, is supposed to govern the contact of this bone 
with the membrane of the oval foramen,—the tensor tympani 
concurring with it to tighten the membrane. From his experi¬ 
ments upon the effects of tension of the tympanic mem¬ 
brane, Dr. Wollaston concludes that a tense state of the 
membrane deadens its susceptibility to the effect of intense 
and grave sounds, as the firing of cannon, the rumbling of 
carriages over a bridge, &c., whilst it increases susceptibility 
to shrill sounds. The action of the muscles would seem to 
be in a measure voluntary, coming into play in the acts of 
listening and of preparing the ear to resist loud sounds,—in 
which condition I fancy I can myself detect a feeling of 
tension in my ear—though they must be largely reflex, called 
into action by the intensity of the sound itself. 
One may render tense his own tympanic membrane by a 
strong continued effort of expiration or inspiration, keeping 
the mouth and nostrils closed—in the one case forcing air 
into the tympanum, tending to make the membrane convex 
towards the external meatus, and in the other case extracting 
air and making it convex towards the interior—in either case 
producing temporary dulness of hearing. 
The gravest sound audible to the human ear is (according to 
Helmholtz) produced by 1G vibrations a second, the highest 
audible sound corresponding to 88,000, or, according to some, 
50,000 vibrations a second—one of the deepest tones in 
use on orchestra instruments is the E of the double bass, 
giving 41J vibrations a second, and the highest, the D of the 
piccolo flute, is 4,752. The practical range is thus about seven 
octaves; at the upper limit of hearing persons differ as much 
as two octaves ; the squeak of a bat and the sound of a cricket 
are unheard by some ears. 
A sound of uniform pitch is a musical note, the fact of 
uniform continuance inducing a pleasure of the nature of 
harmony. 
The pleasurable and other effects of music open out a 
field much too wide for our present consideration. Spencer 
holds that the characteristic depth and vagueness of the 
