The reason why : $b a careful collection of many hundreds of reasons for things which, though generally believed, are imperfectly understood. A book of condensed scientific knowledge for the million
John Stuart Mill · en
The insect called the _earwig_ is popularly supposed to be so
named from its tendency to get into the human ear, and cause pain
and madness by penetrating to the brain. An earwig, however, is no
more likely to get into the ear than any other insect whose habit
it is to penetrate the corollas of flowers; and should an insect
enter the ear, it could get no further than the _membrane of the
tympanum_, which spreads all over the auditory passage, just as
the parchment of a drum spreads over the entire circumference of
that instrument. The fact is, that the wing of the insect, when
spread, _resembles the external ear_ in shape. It is similar to
the wing of the stag beetle (_see_ illustration), and this fancied
resemblance of the wing of the insect to the ear of man may have
given rise to the name of _ear-wing_, which became corrupted to
_earwig_.
[Verse: "Doth not the ear try words? and the mouth taste his
meat."--JOB XII.]
987. _Why is wax secreted at the entrance of the ear?_
Because, by the peculiar resinous property which it possesses, _it
improves the sound-conducting power_ of the auditory canal through
which it prevails.
[Illustration: Fig. 65.--THE STRUCTURE OF THE EAR.]
A A. Glands which secrete wax in the walls of the tube of the ear.
B. The membrane of the _tympanum_, or drum of the ear, formed in
the shape of a funnel.
C C. Bones which act as a sort of sounding-board to the ear,
giving strength to the vibrations.
D. The Eustachian tube, which opens into the root of the mouth,
and which serves to preserve an equilibrium in the density of the
air occupying the tubes of the ear.
E and F. The _labrynth_ of the ear, consisting of folds of
membraneous tubes, filled with fluid, which serves to undulate
with the vibrations of the _tympanum_, and thus gives clearness
and precision to the sounds.
The _auditory nerves_ are distributed in the tubes above described
(the _vestibule_ and the _cochlea_ E F), and the nerves receive
their impressions from the undulations of the fluid.
988. _Why do we sometimes hear singing noises in the ear?_
Because the ear is liable to inflammation from various causes, and
when the blood flows unduly through the vessels of the ear it _produces
a slight sound_.
[Verse: "Apply thine heart unto instruction, and thine ears to the
words of knowledge."--PROVERBS XXIII.]
989. _Why do people become deaf?_
Because the ear may be injured in various ways: the tympanum may be
impaired, the fluid of the ear dried up, or the nerves be pressed upon
by swellings in the surrounding parts. When, therefore, the _mechanism
of hearing_ is impaired, the sense of hearing becomes weakened, or
altogether lost.
990. _Why do persons accustomed to loud noises feel no inconvenience
from them?_