The Ear


Categories: THE LOOKOUT DEPARTMENT
Sources: 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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