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The Ear

Category: THE LOOKOUT DEPARTMENT
Source: A Handbook Of Health

Structure of the Ear. Next after sight, hearing is our most important
sense; without it, speaking, and consequently reading and writing, would
be impossible. Man learned to speak by hearing the sounds made by other
people and things, and then by listening to his own voice and practicing
until he could imitate them. Children who are unfortunate enough to be
born deaf also become dumb, not because there is anything the matter
with their voice organs, but simply because, as they cannot hear the
sounds they make, they do not form them by practice into words and
sentences. By proper training, deaf mutes can now be taught to speak,
though their voices sound flat and tinny, like a phonograph.

As in the nose and the eye, the important part of the ear is the nerve
spot that can feel the air waves that we call sound, just as the
retina feels light. It is from this sensitive spot that the auditory
nerve carries the sound to the brain. This spot has grown into quite an
elaborate structure, buried, for safety, deeply in the bones of the
skull, close to the base of the brain. It is made up of a long row of
tiny little nerve rods, laid side by side like the keys of a piano, only
there are about three thousand of them. Each one of these is supposed to
respond, or vibrate, to a particular tone, or sound. This keyboard,
from the fact that, to save space, it is coiled upon itself like a
sea-shell, instead of running straight, is called the cochlea (Greek
for snail-shell); it is also called, because it is the deepest, or
innermost, part of the hearing apparatus, the internal ear.

Just as the retina has a lens and a vitreous humor in front of it to act
upon the light, so the internal ear has an apparatus in front of it to
act upon the sound waves. This is called the drum (tympanum). It
consists of a fold of thin, delicate skin stretched tightly across the
bottom of the outer ear canal, as parchment is stretched across the head
of a drum. If you should take a hand-mirror--best a hollow, or concave,
one--and throw a bright ray of light deep into some one's ear, you would
be able, after a little trying, to see this drum-skin stretched across
the bottom of it and about an inch and a quarter in from the surface of
the head.



When the sound waves go into the ear canal and strike upon this tiny
drum, which is about two-thirds the size of a silver dime and really
more like a tambourine or the disk of a telephone or phonograph than a
drum, they start it thrilling, or vibrating, just as a guitar string
vibrates when you thrum it. These little vibrations are carried across
the hollow behind the drum by a chain of tiny bones, known as the
ear-bones (called from their shapes, the hammer, the anvil, and
the stirrup), and passed on to the keyboard of the cochlea.

Here comes in one of the most curious things about this ingenious
hearing-apparatus. This little hollow behind the drum-skin has to be
kept full of air in order to let the drum vibrate properly, and this is
arranged for by a little tube (the Eustachian tube) which runs down from
the bottom of it and opens into the back of the throat just behind the
nasal passages, and above the soft palate. When you blow your nose very
hard, you will sometimes feel one of your ears go pop; and that means
that you have blown a bubble of air out through this tube into your drum
cavity.

If your nose and throat become inflamed, then the mouth of this little
tube may become blocked up; the drum can no longer thrill, or vibrate,
properly; and, for the time being, you are deaf. This tube is of great
importance, because nearly all the diseases that attack the ear start in
at the throat and travel up the tube until they reach the drum cavity.
This is why one so often has earache after an attack of the grip or
after a bad cold. The drum cavity, with its chain of bones and its tube
down to the throat, is called, from its position, the middle ear.

The outer, or external, ear, though far the largest of the three
parts, and quite imposing in appearance, is really of little use or
importance. It is simply a sort of receiving trumpet for catching
sounds, with a very wide and curiously curved and crumpled mouth, or
bell. The large, expanded mouth of the trumpet, called the concha
(conch shell), was at one time capable of being pricked up and
turned in the direction of sounds, just as horses' or dogs' ears are
now; and in our own ears there are still for this purpose three pairs of
tiny unused muscles running from them to the side of the head. But the
concha is now motionless and almost useless, except for its beauty; and
it is very troublesome to wash.

The Care of the Ear. The tube of the trumpet leading down from the
surface of the ear to the drum is lined with skin; and this skin is
supplied with glands, which pour out a sticky, yellowish fluid called
ear wax, which catches the bits of dust or insects that get into the
ear and, flowing slowly outward, carries them with it. If it is let
alone, it will keep the ear canal clean and healthy; but some people
imagine that, because it looks yellowish, it must be dirt; and
consequently, from mistaken ideas of cleanliness, they work at it with
the end of the finger, the corner of a towel, or even with a hairpin, an
ear-spoon, or an ear-pick, and in this way stop the proper flow of the
wax and make it dry and block up the ear.

Remember, you should not wash too deeply into your ears; (as the old
German proverb puts it, Never pick your ear with anything smaller than
your elbow). And if you don't, you will seldom have trouble with wax in
the ear. Scarcely one case of deafness in a hundred is caused by wax.
When your ear does become blocked up with wax, it is best to go to a
doctor and let him syringe it out. Picking at it, or even syringing too
hard, may do serious damage to the ear.

If an earache is neglected, the inflammation may spread into some
air-cells in the bony lump behind the ear (the mastoid) and thus cause
mastoid disease, which may spread to, and attack, the brain if not
cured by a surgical operation.





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