A Handbook of Health

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[Illustration: A TOOTH

(Lengthwise section.)

_E_, enamel; _D_, dentine; _P_, pulp cavity; _C_, cement; _B_, blood
vessels; _N_, nerve.]

Kinds of Teeth. If you look at your own teeth in a mirror, the first
thing that strikes you is your broad, white, shiny front teeth, four
above and four below, shaped like the blade of a rather blunt chisel.
Their shape tells what they are used for. Like chisels, they cut, or
bite, the food into appropriate sizes and lengths for chewing between
the back teeth; and from this use they are called the _incisors_, or
"cutters." From having been used for so many generations upon the kind
of food we live on, they have grown broader than the _canines_, the
teeth next to them, and almost as long.

The canines are of a cone-like shape, although it is a pretty blunt
cone, or peg. Those in the upper jaw lie almost directly under the
centre of each eye, and are called the "eye-teeth"; though their proper
name, from the fact that they are the most prominent teeth in the dog,
is the canine teeth. These are our oldest and least changed teeth; and
as you might guess from their shape, like a heavy, blunt spear-head,
were originally the fighting and tearing teeth, and still have the
longest and heaviest roots of any teeth in our jaws. If you slip your
finger up under your upper lip, you can feel the great ridge of this
root, standing out from the surface of the gum.

Lastly, looking farther back into our mouths, we see behind our canines
a long row of broad, flat-topped, square-looking teeth, which fill up
the largest part of our jaws. Again their shape tells what they are used
for. They are not sharp enough to cut with, or pointed enough to tear
with, but are just suited for crushing and grinding into a pulp, between
their broad, flat tops, any food that may be placed between them; and
from this grinding they are called the _molars_, or "mill" teeth. If you
will look closely at the back ones, you will see that each of them has
four corners, or _cusps_, with a cross-shaped, sunken furrow in the
centre, where they come together. After they have been used in grinding
food for some years and rubbing against each other, these little corner
projections become worn away, and their tops become almost flat. Those
in the upper jaw have three roots, and those in the lower jaw have two,
so that they are solidly anchored for their heavy, grinding work. The
first two molars in each jaw, behind the canines, are smaller than the
others and made up of only two pieces instead of four, and hence are
called the _bicuspids_, or "two-cusped" teeth.

As we are what the scientists call an omnivorous, or "all-devouring,"
animal, able to eat and live upon practically every kind of food that
any animal on earth can deal with,--animal and vegetable, soft and hard,
wet and dry; fruits, nuts, crabs, roots, seaweeds, insects, anything
that we can get our teeth into,--we have kept in working condition some
of every kind of teeth possessed by any living animal; and the most
important rule for keeping our teeth in health is to give all these
kinds something to do.

Just as in other animals the teeth appear when needed, and grow into the
shape required, so they grow in our own mouths when they are wanted, and
of the size and shape required at the time. We are born without any
teeth at all; and it is only when we begin to need a little solid food
added to our milk diet,--when we are about seven months old,--that our
first teeth appear; and these are incisors, first of all in the lower
jaw. Then, at average intervals of about three months, the other
incisors and the canines appear and, last of all, the molars, so that at
about two years of age we have a complete set of twenty teeth. These are
called the _milk teeth_.

Most animals (_mammals_) have formed the habit of growing two sets of
teeth--a smaller, slighter set for use during the first few months or
years of life, and a larger, heavier set to come in and take their place
after the jaws have grown to somewhat more nearly their permanent size.
In our mouths, at about seven years of age, a larger, heavier tooth
pushes up behind the last milk tooth,--called the "seventh year
molar,"--the milk teeth begin to loosen and fall out, and their places
are taken by other new teeth budding up out of the jaw just as the first
set did. These take a still longer time to grow, so that the last four
of the full set of thirty-two do not come through the gums until
somewhere between our eighteenth and twentieth years. These last four
teeth, for the rather absurd reason that they do not appear until we are
old enough to be wise, are known as the "wisdom teeth." Instead of
being, as one might expect, the hardest and longest-lived of all our
teeth, they are the smallest and worst built of our molars and among the
first of our permanent teeth to break down and disappear. Not only so,
but our jaws are so much shorter than they were in the days when man
fought with his teeth and knew nothing about cooking and had no tools or
utensils with which to grind and prepare his food, that there is
scarcely room in them for these last teeth to come through. They often
cause a great deal of pain in the process, and may even break through at
the side of the jaw and cause abscesses and other troubles.

[Illustration: THE REPLACING OF THE MILK TEETH

The "second teeth" are shown fully formed in the gums, ready to push out
the milk teeth. The wisdom teeth, which appear later, cannot be shown at
this stage.--After Gray.]

Care of the Teeth. The most important thing for the health of any
organ in the body is to give it plenty of exercise, and this is
especially true of our teeth. This exercise can be secured by thoroughly
chewing, or _masticating_, all our food, of whatever sort, especially
breads, biscuits, and cereals. Thorough chewing not only gives valuable
exercise to the teeth, but, by grinding up these foods thoroughly, makes
them easier for the stomach to digest; and, by mixing them well with the
saliva, enables it to change the starch into sugar. Meats, fish, eggs,
cheese, etc., do not need to be mixed with the saliva, nor to be ground
so fine for easy digestion in the stomach, and hence do not require such
thorough chewing, though it is better to make a rule of chewing all
food well. We can exercise our teeth also by eating plenty of foods that
require a good deal of chewing, especially the crusts of bread, and
vegetables such as corn, celery, lettuce, nuts, parched grains, and
popcorn.

It is most important to keep the nasal passages clear and free, and the
teeth sound and regular by proper dental attention, so that the jaws
will grow properly, and each tooth will strike squarely against its
fellow in the opposite jaw, and both jaws fit snugly and closely to each
other, making the bite firm and clean, and the grinding close and
vigorous. If we are mouth-breathers, our jaws will grow out of shape, so
that our teeth are crowded and irregular and do not meet each other
properly in chewing. Pressure upon the roots of the teeth, from meeting
their fellows of the opposite jaw in firm, vigorous mastication, is one
of the most important means of keeping them sound and healthy. Whenever
a tooth becomes idle and useless, from failing to meet its fellow tooth
in the jaw above or below properly, or from having no fellow tooth to
meet, it is very likely to begin to decay.

The next important thing in keeping the teeth healthy is to keep them
thoroughly clean. The greatest enemies of our teeth are the acids that
form in the scraps of food that are left between them after eating.
Meats are not so dangerous in this regard as starches and sugars,
because the fluids resulting from their decay are alkaline instead of
acid; but it is best to keep the teeth clear of scraps of all kinds.
This can best be done by the moderate and gentle use of a quill, or
_rolled_ wooden tooth-pick, followed by a thorough brushing after each
meal with a rather stiff, firm brush. Then use floss-silk, or linen or
rubber threads to "saw" out such pieces as have lodged between the
teeth.

This brushing should be given, not merely to the teeth, but to the
entire surface of the gums as well; for, as we have seen, it is the gums
that make or spoil the health of the teeth, and they, like all other
parts of the body, require plenty of exercise and pressure in order to
keep them healthy. In the early days of man, when he had no knives and
gnawed his meat directly off the bones, and when he cracked nuts and
ground all his grain with his teeth, the gums got an abundance of
pressure and friction and were kept firm and healthy and red; but now
that we take out the bones of the meat and stew or hash it, have all our
grain ground, and strip off all the husks of our vegetables and skins of
our fruits, though we have made our food much more digestible, we have
robbed our gums of a great deal of valuable friction and exercise. The
most practical way to make up for this is by vigorous massage and
scrubbing with a tooth-brush for five minutes at least three times a
day. It will hurt and even make the gums bleed at first; but you will
be surprised how quickly they will get used to it, so that it will
become positively enjoyable.

[Illustration: A TOOTH-BRUSH DRILL

A school in which the children are taught the importance of using the
tooth brush, are supplied with brushes at cost, and required to report
both on their care of their teeth and on the condition of the brushes.]

It is good to use some cleansing alkaline powder upon the brush. The
old-fashioned precipitated chalk, which makes the bulk of most tooth
powders, is very good; but an equally good and much cheaper and simpler
one is ordinary baking soda, or saleratus, though this will make the
gums smart a little at first. Any powder that contains pumice-stone,
cuttle-fish bone, charcoal, or gritty substances of any sort, as many
unfortunately do, is injurious, because these scratch the enamel of the
teeth and give the acids in the mouth a chink through which they may
begin to attack the softer dentine underneath the "glaze" of enamel.

Antiseptic powders and washes, while widely advertised, are not of much
practical value, except for temporary use when you have an abscess in
your gums, or your teeth are in very bad condition. It is almost
impossible to get them strong enough to have any real effect in checking
putrefaction of the food or diseases of the gums, without making them
too irritating or poisonous. If you keep the gums and teeth well brushed
and healthy, you will need no antiseptics.

Not only should the teeth be kept thoroughly clean and sweet for their
own sake, but also for the sake of the stomach and the health of the
blood and the whole body. The mouth, being continually moist and warm
and full of chinks and pockets, furnishes an ideal breeding ground for
all kinds of germs; and the average, uncleansed human mouth will be
found to contain regularly more than thirty different species of germs,
each numbering its millions! Among them may sometimes be found the germs
of serious diseases such as pneumonia, diphtheria, and blood-poisoning,
just waiting, as it were, their opportunity to attack the body. In fact,
a dirty, neglected mouth is one of the commonest causes of disease.

CHAPTER XXVI

INFECTIONS, AND HOW TO AVOID THEM

What Causes Disease. The commonest and most dangerous accident that is
likely to happen to you is to catch some disease. Fortunately, however,
this is an accident that is as preventable as it is common. Indeed, if
everybody would help the Board of Health in its fight against the spread
of the common "catchable" diseases, these diseases could soon be wiped
out of existence. Every one of them is due to dirt of some sort; and
absolute cleanness would do away with them altogether.

Diseases that are "catching," or will spread from one person to another,
are called _infections_; and all of them, as might be supposed from
their power of spreading, are due to tiny living particles, called
_germs_--so tiny that they cannot be seen except under a powerful
microscope. Nine-tenths of these disease germs are little plants of the
same class as the moulds that grow upon cheese or stale bread, and are
called bacteria, or bacilli. The different kinds of bacteria, or
bacilli, are usually named after the diseases they produce, or else
after the scientists who discovered them. For instance, the germ that
causes typhoid fever is called the _bacillus typhosus_; that which
causes tuberculosis is called the bacillus tuberculosis; while the germ
of diphtheria known as the _Klebs-Loeffler bacillus_, after the two men
who discovered it.

A few kinds of disease germs belong to the animal kingdom, though all
germs are so tiny that you would have to have a very powerful microscope
to tell the difference between the animal germs and the bacilli, or
little plants. Most of these animal germs are called _protozoa_ and
cause diseases found in, or near, the tropics, like malaria and the
terrible "sleeping sickness" of Africa. Smallpox, yellow fever, and
hydrophobia--the disease that results from the bite of a mad dog--are
also probably due to animal germs.

So far as prevention is concerned, however, it makes practically little
difference whether infectious diseases are due to an animal or a
vegetable germ, or to one bacillus or another. They all have two things
in common: they can be spread only by the touch of an infected person,
and "touch" includes breath,--indeed "by touch" is the meaning of both
infectious and contagious; and they can all be prevented by the
strictest cleanness, or killed by various poisons known as germicides
("germ-killers"), or disinfectants. Most of these germicides are,
unfortunately, poisonous to us as well; for, as you will remember, our
bodies are made up of masses of tiny animal cells, not unlike the animal
germs. Most of the germicides, therefore, have to be used against germs
while they are outside of our bodies.

Scripture says that "a man's foes shall be they of his own household,"
and this is true of disease germs. They grow and flourish--and, so far
as history tells us, the diseases they cause seem to have started--only
where people are crowded together in huts or houses, breathing one
another's breaths and one another's perspiration, and drinking one
another's waste substances in the well water. This fact has, however,
its encouraging side; for, since this habit of crowding together, which
we call civilization, or "citification," has caused and keeps causing
these diseases, it can also cure them and prevent their spread if all
the people will fight them in dead earnest. No amount of money, or of
time, that a town or a county can spend in stamping out these infectious
diseases would be wasted. Indeed, every penny of it would be a good
investment; for, taken together, they cause at least half, and probably
nearly two-thirds, of all deaths. Not only so, but most of the so-called
chronic diseases of the heart, kidneys, lungs, bones, and brain are due
to the after-effects of their toxins, or poisons.

How Disease Germs Grow and Spread. But perhaps you will ask, "If these
bacteria and protozoa are so tiny that we have to use a microscope, and
one of the most powerful made, in order even to see them, how is it that
they can overrun our whole body and produce such dangerous fevers and so
many deaths?" The answer is simply, "Because there are so many millions
of them; and because they breed, or multiply, at such a tremendously
rapid rate." When one of these little bacilli breeds, it doesn't take
time to form buds and flowers and seeds, like other plants, or even the
trouble to lay eggs like an insect or a bird, but simply stretches
itself out a little longer, pinches itself in two, and makes of each
half a new bacillus.

This is known as _fission_ or "splitting," and is of interest because
this is the way in which the little cells that make up our own bodies
increase in number; as, for instance, when a muscle is growing and
enlarging under exercise, or when more of the white blood cells are
needed to fight some disease. Remember that we and the disease germs are
both cells; and that, if they are numbered by millions, we are by
billions; and that we are made up of far the older and the tougher cells
of the two. Except in a few of the most virulent and deadly of fevers,
like the famous "Black Death," or _bubonic plague_, and lock-jaw, or
_tetanus_, ninety-five times out of a hundred when disease germs get
into our bodies, it is our bodies that eat up the germs instead of the
germs our bodies. Keep away from disease germs all that you reasonably
and possibly can; but don't forget that the best protection against
infectious diseases, in the long run, is a strong, vigorous, healthy
body that can literally "eat them alive."

Grow that kind of body, keep it perfectly clean inside and out, and you
have little need to fear fevers, or indeed any other kind of disease;
for you will live until you are old enough to die--and then you'll want
to, just as you want to go to sleep when you are tired. Remember that
this fight against the fevers is a winning fight, this study of disease
germs a cheering and encouraging one, because it will end in our
conquering them, not merely nine times out of ten, but ninety-nine times
out of a hundred.

We are not making this fight just to escape death; what we are fighting
for is to live out a full, useful, and happy life. And we already have
five chances to one of gaining this, and the chances are improving every
year; for science has already raised the average length of life from
barely twenty years to over forty. Broadly speaking, if you will keep
away from every one whom you know to have an infectious disease; wash
your hands always before you eat, or put anything into your mouth; keep
your fingers, pencils, pennies, and pins out of your mouth,--where they
_don't_ belong; live and play in the open air as much as possible and
keep your windows well open day and night, you will avoid nine-tenths of
the risks from germs and the dangers that they bring in their wake.

Children's Diseases. We have already studied two of the greatest and
most dangerous diseases, and the way to conquer them--tuberculosis, or
consumption, in the chapter on the lungs; and typhoid fever, in the
chapter on our drink. One of the next most important groups of
"catching" diseases--important because, though very mild, they are so
exceedingly common,--is that known as the "diseases of childhood," or
"diseases of infancy" because they are most likely to occur in
childhood. So common are they that you know their names almost as well
as you know your own--measles, mumps, whooping cough, scarlet fever, and
chicken-pox. Though they are in no way related to one another, so far as
we know (indeed, the precise germs that cause two of them--measles and
scarlet fever--have not yet positively been determined), yet they can be
practically taken together, because they are all spread in much the same
way, they all begin with much the same sort of sneezing and inflammation
of the nose and throat, they can all be prevented by the same means,
and, if properly taken care of, they result in complete recovery
ninety-five times out of a hundred.

[Illustration: THE WINNING FIGHT

Statistics for the population of the old City of New York. The chart
shows a decrease from 95 out of every 1,000 in 1891-92 to 48 out of
every 1,000 in 1909. This is due very largely to the careful methods of
prevention enforced by the Board of Health, especially the inspection of
milk.]

Any child who has sneezing, running at the nose or eyes, sore throat, or
cough, especially with headache or backache, a flushed face and
feverishness, ought to be kept at home from school and placed in a
well-ventilated, well-lighted room by himself for a day or two, until it
can be seen whether he has one of these children's diseases, or only a
common cold. If it turns out to be measles, scarlet fever, or whooping
cough, he should then be kept entirely away from other children in a
separate room, or, where that is impossible, in a special hospital or
ward for the purpose; he should be kept in bed and given such remedies
as the doctor may advise. Then no one else will catch the disease from
him; and within from two to five weeks, he will be well again. The most
important thing is not to let him get up and begin to run about, or
expose himself, too soon; five times as many deaths are caused by taking
cold, or becoming over-tired, or by injudicious eating, during recovery
after measles, scarlet fever, and whooping cough, as by the disease
itself. This one caution will serve two purposes; for, as a sick child's
breath, and the scales from his skin, and what he coughs out from his
mouth and nose are full of germs, and will give the disease to other
children from two to four weeks after the fever has left him, he ought
to be kept by himself--"in quarantine," as we say--for this length of
time, which is just about the period needed to protect him from the
dangers of relapse or taking cold. Boards of Health fix this period of
quarantine by law and put a colored placard on the house to warn others
of the danger of infection.

[Illustration: DEATH-RATE FROM MEASLES

Note that, after the quarantining of measles in 1896, the death-rate
dropped at once. Statistics for the old City of New York.]

Colds and Sore Throats. A milder and even more common kind of
infection is that known as common colds. These, as shown by their name,
were once supposed to be due to exposure to cold air, or drafts, or to
becoming wet or chilled. But, while a few of them are so caused, at
least eight, and probably nine, out of ten are due to germs caught from
somebody else. They are never caught in the open air and very seldom in
cold, pure fresh air of any sort, but almost always in the hot, foul,
stuffy, twice-breathed air of bedrooms, schoolrooms, churches, theatres,
halls, sleeping cars, etc. The colds, for instance, that you catch when
traveling, are usually due not to drafts or damp sheets, but to the crop
of cold germs left behind by the last victim.

You have probably known of colds that have run through a family or a
school or a shop. It is well worth trying to keep away from the
infection of colds, because not only is their coughing and sore throat
and hoarseness and running at the nose very disagreeable and
uncomfortable, but they may cause almost as many different kinds of
serious troubles in heart, kidneys, and nervous system as any of the
other infections. In fact, they probably cause more than any other,
because they are at least ten times as common and frequent. For
instance, many cases of rheumatism, or rheumatic fever, come after
attacks in the nose and throat, which cannot be distinguished from a
common cold or ordinary tonsilitis. Indeed, it is more than probable
that one of the ten or a dozen different germs that may get into your
nose or throat and give you a cold, is the germ that causes rheumatism.
At all events, it would be fairly safe to say, "No colds, no
rheumatism."

Whenever you have a cold, keep away from everybody that you possibly can
and stay at home from school or business for a day or two. You will do
no good to yourself or others, working in that condition; and you may
infect a dozen others. If you find anyone in your class or room or shop,
sneezing or coughing or running at the nose, report him to your teacher
or foreman; and if he won't send him home, keep away from him as much as
possible.

Diphtheria. Another common and serious disease, until quite recently
very fatal, is diphtheria. This is caused by getting into your mouth or
nose the germs from another case of the disease. This disease also is
most likely to occur in childhood, though it may attack a person of any
age, and is always serious. It may be prevented from spreading by
keeping children who have it shut up in rooms, or wards, by themselves
and keeping all other children away from them, or from their nurses or
those who have anything to do with them. Up to about thirty years ago,
it was one of the deadliest and most terrible diseases that we had
anything to do with. We knew absolutely nothing that would cure it, or
even check its course; and nearly half of the children attacked by it
died.

About that time, however, two scientists, Klebs and Loeffler, discovered
that, by taking some of the membrane, or tough growth that forms in the
throat in this disease, and by rubbing it over a plate of gelatin jelly,
they could grow on that gelatin a particular kind of germ. This germ, or
bacillus, they then put into the throats of guinea pigs, and found that
it would give them diphtheria.

This is the way disease germs are discovered, or, as we say, identified;
but of course this did not give at once any remedy for the disease.
Scientists soon found, however, that, if a very small number of these
bacilli were put into a guinea pig's throat, it would have diphtheria,
but in a very mild form. If, when it had recovered, it was again
infected, it would stand a much larger dose of the bacilli without harm.
This made them suspect that some substance had been formed in the
guinea-pig's blood that killed the bacillus or worked against its toxin,
or poison; and soon, to their delight, they succeeded in finding this
substance, which they called _antitoxin_ (meaning "against poison").
Then came the idea that if they could only get enough of this antitoxin,
and inject it into the blood of a child who had diphtheria, it might
cure the disease. A guinea pig is such a tiny animal that the amount of
antitoxin which it could form would be far too small to cure a man, or
even a child. So larger animals were taken; and it was finally found
that the largest and strongest of our domestic animals, the horse,
would, if the diphtheria germs were injected into its blood, make such
large amounts of antitoxin that merely by drawing a quart or two of the
blood--and closing up the vein again--enough antitoxin could be got to
cure fifty or a hundred children of diphtheria. This treatment has not
the slightest harmful effect upon the horse. The pain of injecting is
only like sticking a pin through the skin, while the pain of bleeding is
no greater than cutting your finger. There are now at our great
manufacturing laboratories whole stables full of horses, for the
production of this wonderful remedy.

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