A Handbook of Health

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THE EAR

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.

[Illustration: THE APPARATUS OF HEARING

A cross-section diagram from the outer ear to the lobes of the brain.]

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.

OUR SPIRIT-LEVELS

The Sixth Sense. Though we usually speak of having five
senses,--sight, smell, hearing, touch, and taste,--we really have also a
sixth--the sense of direction, or of balance. The "machine" of this
sense is comparatively simple, being made up of three tiny curved tubes,
which, from their shape, are called the _semi-circular canals_. These
are buried in the same bone of the skull as the internal ear, and
so close to it that they were at one time described as part of it.
These little canals are three in number, one for each of the
dimensions--length, breadth, and thickness,--so that whichever way the
head or body is moved,--backward and forward, up and down, or from side
to side,--the fluid with which they are filled will change its level in
one of them, just as the "bead" does in the carpenter's spirit-level
that you can find in any tool shop. The delicate nerve twigs that run
out into the fluid in these tiny canals are gathered together into a
bundle, or nerve-cable, which runs back to the part of the brain known
as the _cerebellum_ or hind-brain, which has most to do with controlling
the balance and movements of our bodies.

It is the disturbance set up in these spirit-level canals by the
pitching and rolling of a ship, which makes us seasick. Neither the
stomach, nor anything that we may have eaten, has anything to do with
it. In the same way we sometimes become sick and dizzy from swinging too
long or too high, or from riding on the cars.

FOOTNOTES:

[28] To show in how many different ways nature may carry out the same
purpose, the smelling organs in insects, lobsters, and crabs are on the
ends and sides of tiny feelers, which they wave about; and the eyes in
lobsters, crawfish, and snails, are on the ends of stalks, which they
thrust about in all directions as a burglar handles a bull's-eye
lantern. Snakes "hear," or catch the sound-waves, with their flickering,
forked tongues; and grasshoppers and locusts have "ear-drums" on the
sides of their chests.

[29] These are called the _recti_ or "straight" muscles, upper, lower,
inner, and outer, according to their position. Then, to roll the eye
round and round, there are two little muscles, one above and one below,
which run "crosswise" of the orbit, called the upper and lower _oblique_
muscles.

[30] The retina is chiefly made up of a great number of fine little
nerve cells called, from their shape, the _rods_ and _cones_. These are
kept soaked in a colored fluid called the _retinal purple_, which
changes under the influence of light, somewhat in the same way that the
film on a photographic plate does, thus forming pictures, which are
translated by the rods and cones and telegraphed along the fibres of the
optic nerve to the brain. Naturally, all parts of the retina are not
equally sensitive to light; its centre, which is directly opposite the
pupil of the eye, is far the most so, while those around the rim of the
cup are dull. This is why, when you are looking, say at some one's face
across the room, only the face and a few inches around it are seen
perfectly clear and sharp, while the rest of the room is seen only
vaguely.

[31] As the inside of the eye is dark, or comparatively so, the pupil,
or little opening in the centre of the iris, looks black, and was at one
time supposed to be a solid body instead of a hole. You can easily watch
the pupil changing in size, according to the brightness of the light,
from a mere pin-point in very bright sunlight or gaslight, up to the
size of the butt-end of a lead pencil in the dark or in a dim light.

This change in size is very simply but ingeniously carried out by two
sets of tiny muscles. One set of these muscles runs in a ring right
around the pupil; and when they shorten, the opening is contracted or
narrowed. The other set runs outward through the iris like the spokes of
a wheel; and when they shorten, they pull the pupil open. If anyone has
had "drops" (_atropin_) put into his eyes in order to have them fitted
with glasses, he will know what a disagreeably dazzling thing it is to
have the pupil permanently enlarged, so that it cannot _contract_ in a
bright light.

CHAPTER XXIV

THE SPEECH ORGANS

The Voice, a Waste Product. It is one of the most curious things in
this body of ours that what we regard as its most wonderful power and
gift, the voice, is, in one sense, a waste product. So ingenious is
nature that she has actually made that marvelous musical instrument--the
human voice--with its range, its flexibility, and its powers of
expression, out of spent breath, or used-up air, which has done its work
in the lungs and is being driven off to get rid of it. It is like using
the waste from a kitchen sink to turn a mill.

The organs that make the human voice were never built for that purpose
in the first place. Unlike the eye and the ear, nature built no special
organ for the voice alone, but simply utilized the windpipe and
lung-bellows, the swallowing parts of the food passage (tongue, lips,
and palate) and the nose, for that purpose, long after they had taken
their own particular shapes for their own special ends.

The important point about this is that a good voice requires not merely
a large and well-developed "music box" in the windpipe, but good lungs,
a well-shaped healthy throat, properly arched jaws,--which mean good,
sound teeth,--clear and healthy nasal passages, and a flexible elastic
tongue. Of course, the blood and the nerves supplying all these
structures must be in good condition, as well. So practically, a good
voice requires that the whole body should be healthy; and whatever we do
to improve the condition of our nose, our teeth, our throat, our lungs,
our digestion, and our circulation will help to improve the
possibilities of our voice. There are, of course, many exceptions; but
you will generally find that great singers have not only splendid lungs
and large vocal cords, but good hearts, vigorous constitutions, and
bodies above the average in both stature and strength.

How the Voice is Produced. The chief parts of the breathing machine
that nature has made over for talking purposes are the windpipe, or air
tube, and the muscles in its walls. In the neck, about three inches
above the collar bone, four or five of the rings of cartilage, or
gristle,--which, you remember, give stiffening to the windpipe,--have
grown together and enlarged to form a voice box, or _larynx_.

[Illustration: THE VOCAL CORDS

Looked at from above: position _A_, in quiet inspiration; _B_, in
singing a low tone; _C_, in singing a high tone.]

The upper edge of this voice box forms the projection in the front of
the throat known by the rather absurd name of the "Adam's apple." This
grows larger in proportion to the heaviness of the sounds to be made,
and hence is larger in men than in women and boys. When the boy's voice
box begins to grow to the man's in shape and size, his voice is likely
to "break"; for it is changing from the high, clear boy's voice to the
heavy, deep voice of the man.

Inside of this voice box, one of the rings of muscle that run around the
windpipe has stretched into a pair of straight, elastic bands, or
strings, one on each side of the air pipe, known as the _vocal cords_,
or voice bands. These are so arranged that they can be stretched and
relaxed by little muscles; and, when thrown into vibration by the air
rushing through the voice box, they produce the sounds that we call
talking or singing. The more tightly they are stretched, the higher and
shriller are the tones they produce; and the more they are slackened, or
relaxed, the deeper and more rumbling are the tones.

This is why, when you try to sing a high note, you can feel something
tightening and straining in your throat, until finally you can stretch
it no tighter, and your voice "breaks," as you say, into a scream or
cry.

All musical instruments that have strings, are played, or produce their
sounds, upon this same principle. The thinner and shorter the string, or
the more tightly it is stretched, the higher the note; the heavier and
longer the string, the lower the note. But no musical instrument ever
yet invented can equal the human voice in the music of its tones, in its
range, in the different variety and quality of tones it can produce, and
in its wonderful power of expression. The human voice is a combination
of reed organ, pipe organ, trumpet, and violin; and can produce in its
tiny music box--only about two inches long by one inch wide--all the
tones and qualities of tones that can be produced on all these
instruments, except that it cannot go quite so high or so low.

All the musical instruments in the world, from the penny whistle to the
grand piano, are but poor imitations of the human music box. The
bellows, of course, of the human pipe organ are the lungs; while the
tongue furnishes the stops; and the throat, mouth, and nose, the
resonance, or sounding, chambers.

Just as a violin, or guitar, has two main parts,--a string, which
vibrates and makes the sound; and a box, or hollow body, which catches
that sound and enlarges it and gives it sweetness and vibration and
quality,--so the human voice has two similar parts--the vocal bands,
which make the sound; and a sound box, or rather series of three
resonance boxes,--the throat, the mouth, and the nasal passages,--which
enlarge and soften it and improve its quality.

You would naturally think that the strings, or cords, were the most
important part both of the voice and of a musical instrument; and in one
sense they are, as it could make no noise at all without them. But in
another sense, far more important are the sounding boxes, or resonance
chambers. The whole quality and value, for instance, of a
Stradivarius[32] violin, which will make it readily bring ten thousand
dollars in the open market, are due to the skill with which the body, or
sound box, was made; the quality of the wood used; and, odd as it may
seem, even the varnish used on it--the strings are the same as on any
five-dollar fiddle. This is almost equally true of the human voice.
While its size, or volume, is determined by the voice box and vocal
bands, and its power largely by the lungs and chest, its musical
quality, its color, and its expression are given almost entirely by the
throat, mouth (including the lips), and nose. The proper management of
these parts is two-thirds of voice training, and all these are largely
under our control.

How a Good Voice may be Developed. If the nasal passages, for
instance, are blocked by a bad cold or a catarrh or adenoids, then
nearly half the body of your violin is blocked up and deadened; half
your resonance chamber is destroyed, and the voice sounds flat and dead
and nasal. If, on the other hand, your throat be swollen, or blocked, as
by enlarged tonsils or chronic sore throat, then this part of the
resonance chamber is muffled and spoiled, and your voice will be either
entirely gone or hoarse; though perhaps by driving it very hard you may
be able to make a clear tone.

If you have an attack of inflammation or cold further down, and the
vocal bands swell, or the mucous membrane lining the voice box becomes
inflamed and thickened, then the voice is lost entirely, just as the
tone of a violin would be if a wet cloth were thrown across the strings.
But disturbances in the voice box, or larynx, cause only a very small
percentage of husky, poor, or unmusical voices.

A far commoner cause, indeed probably the commonest single cause of a
poor, squeaky, or drawling, unmusical voice is careless and improper
management of the mouth and lips. In the first place, you can easily
show that such marked differences in sound as those of the different
vowels are all produced by the mouth and lips. If you will prepare to
say the vowels--_a, e, i, o, u_--aloud, and begin with _a_, and then
hold your mouth and lips firmly in the same position, you will find that
all the other vowels also come out as _a_. If, on the other hand, you
begin with your mouth and lips in the rounded and somewhat thrust-out
position necessary to say _o_, and try to repeat the rest of the vowels,
you will find that you cannot say them at all, but only different forms
of _o_. When you have convinced yourself of this, repeat the vowels
loudly and clearly without stopping to think about the position of the
mouth, and notice how your lips, the tip and base of your tongue, and
your soft palate and throat all change their positions for each
successive vowel.

If you will try to sing the scale, beginning with a comfortable note
about the middle of your voice range, and letting your mouth take the
shape for that note unconsciously, you will find that, as you sing up
the scale, you change the shape of your mouth, lips, and tongue at every
note, thrusting the lips and mouth further forward as if to whistle,
narrowing the opening and closing up the back of your throat for the
high notes.

On the other hand, as you sing down, you tend to open the mouth and
lips more widely, to drop the bottom of your mouth--that is, the base of
your tongue--toward your throat, and your chin down toward your chest.
Again you will find, just as in the case of the different vowels, that
you can sing any tone clearly and musically after putting the mouth in
precisely the shape that best fits that tone; and learning how to do
this is a most important part of vocal training.

What we call words are simply breath sounds and voice-box sounds chopped
into convenient lengths by the movements of the tongue and lips and
throat. So when we come to the question of clear and pleasant speaking,
or, as we term it, _articulation_, the lips and tongue have almost
everything to do with making the difference between a clear, musical,
and refined enunciation, which is so easy to understand that it is a
pleasure to listen to it, and a slurred, drawling, squeaky, nasal kind
of speech, which is as hard to understand as it is unpleasant to listen
to.

Few of us can ever hope to develop a really great singing voice; but
anyone who will take the pains can acquire a clear, distinct, and
pleasing speaking voice; and perhaps half of us can learn to sing fairly
well. But to do this, we must first have good, healthy, well-developed
lungs and elastic chest walls, which can come only from plenty of
vigorous exercise in the open air, combined with good food and
well-ventilated rooms. We must have a healthy stomach, which will not
fill up with gas and keep our diaphragms from going down and enlarging
our chests properly; we must have clear nasal passages, good teeth,
well-shaped mouths and flexible lips, which we are willing to use
vigorously in articulating, or cutting up our voice sounds; and we must
have good hearing and a well-trained ear. In short, the best way to get
a clear, strong, pleasant voice is to have a vigorous, well-grown,
healthy body.

FOOTNOTES:

[32] A famous violin-maker who lived about 200 years ago in Cremona,
Italy. Fifty thousand dollars has been asked for an unusually choice
"Strad."

CHAPTER XXV

THE TEETH, THE IVORY KEEPERS OF THE GATE

Why the Teeth are Important. The teeth are a very important part of
our body and deserve far more attention and better care than they
usually get. They are the first and most active part of our digestive
system, cutting up and grinding foods that the stomach would be unable
to melt without their help. In all animals except those that have horns
or fists, the teeth are their most important weapons of attack and
defense. So important are they in all animals, including ourselves, and
so closely do they fit their different methods of food-getting and of
attack and defense, that when scientists wish to decide what class, or
group, a particular animal belongs to, they look first and longest at
its teeth.

The shape and position of the teeth literally make the lower half of the
face and give it half its expression. A properly grown and developed set
of teeth not only is necessary to health and comfort, but helps greatly
to make the face and expression attractive or unattractive. Few faces
with bright eyes, clear skin, and white, regular, well-kept teeth are
unpleasing to look at. Beauty and health are closely related, and we
ought to try to have both. In fact, nine times out of ten, what we call
beauty is the outward and visible sign of inward health. The healthier
you are, the handsomer you'll be.

It is particularly important to understand the natural growth and proper
care of the teeth because there are few organs in the body for which we
are able to do so much by direct personal attention. Our stomachs, our
livers, and our kidneys, for instance, are entirely out of sight, and
more or less out of reach; but our teeth are both easily got at and in
full view; and, to a large degree, upon the care that we give them while
they are young, will depend not only their regularity and whiteness, but
also the length of their life and the vigor and comfort of our digestion
all our lives.

[Illustration: TEETH--A QUESTION OF CARE]

The first thing to be remembered about the teeth is that, hard and shiny
and different from almost everything else in the body as they look, they
are simply a part of the skin lining the mouth, hardened and shaped for
their special work of biting and chewing. Much of the care needed to
prevent decay should be given, not to the teeth themselves directly, but
to the gums and the mucous membrane of the whole mouth. The gums and the
mouth literally _grew_ the teeth in the first place; and when they
become diseased, they secrete acids which slowly eat away the crowns and
roots of the teeth. Their diseases come chiefly from irritation by
decaying scraps of food, or from the blocking of the nose so that air is
breathed in through the mouth, drying and cracking the soft mucous
membrane. After the acids from the diseased gums have attacked the
teeth, the poisons of the germs that breed in the warmth and moisture of
the mouth cause the teeth to decay. Eight times out of ten, if you take
care of the gums the teeth will take care of themselves.

Structure of the Teeth. The upper half of the tooth, which pushes
through and stands up above the jaw and the gum, we call the _crown_;
and this is the portion that is covered with _enamel_, or "living
glass." The body of the tooth under the enamel is formed of a hard kind
of bone called _dentine_. The lower half of the tooth, which still is
buried in the jaw, we call the _root_. Wrenching the lower or root part
of the tooth loose from its socket in the jaw is what hurts so when a
tooth is pulled. The crown of the tooth is hollow, and this hollow is
filled with a soft, sensitive pulp, in which we feel toothache. Tiny
blood vessels and nerve-twigs run up from the jaw to supply this pulp
through canals in the roots of the tooth.

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