The bones have more diseases than the muscles, but really comparatively few, considering their great number and size, and the constant strain to which they are subjected in supporting the body, and driving it forward and doing its work under the handling and leverage of the muscles. Most of their diseases are, like those of the muscles, the after-effects of general diseases, particularly the infections and fevers, which begin elsewhere in the body; and the best treatment of such bone diseases is the cure and removal of the disease that caused them.

Repair of Broken Bones. If bones are broken by a fall, or blow, they display a remarkable power of repair. The "skin" covering them (periosteum) pours out a quantity of living lime-cement, or animal-mortar, around the two broken ends, which solders them together, much as a plumber will make a joint between the ends of two pipes. This repair substance is called callus. The most remarkable thing about the process is that, when it has held the two broken ends together long enough for them to "knit" firmly—that is, to connect their blood vessels and marrow cavities properly—this handful of lime-cement, which has piled up around the break, gradually melts away and disappears; so that, if the ends of the bone have been brought accurately together, you can hardly tell where the break was, except by a slight ridge or thickening.

TROUBLES OF THE NERVOUS SYSTEM

The Nervous System is not easily Damaged. The nervous system is subject to a good many more diseases than are either the muscles or the bones; but, considering how complex it is, it is not nearly so easily damaged or thrown out of balance as we usually imagine, and has astonishing powers of repair. Instead of being one of the first parts of the body to be attacked by a disease, such as an infection or a fever, it is one of the very last to feel the effects of disease, except in the sense that it often gives early that invaluable danger signal, pain.

Headache. Next after fatigue the most valuable danger signal given us by our nerves is that commonest of all pains, headache. Indeed, it is not too much to say that headache is the most useful pain in the world. It has little to do with the condition of the brain, but occurs in the head chiefly because the nerves of the head and face are the most sensitive of all those in the body, and the first ones, therefore, to "cry out" when hurt.

Headache has been described as the cry of a poisoned or starved or over-worked nerve, and is simply nature's signal that something is going wrong. Toxins, or poisons, formed anywhere in the body, from any cause, get into the blood, are carried to the sensitive nerves of the head and face, and irritate them so that they ache. It is foolish to try to do anything to the head itself for the relief of headache, although cold cloths, or a hot-water bottle, may be soothing in mild cases. The thing to do is to clear the poison out of the blood, and the only way is to find what has caused it.

Nearly all the things that cause headache do so by poisoning the blood. A very common cause of headache, for instance, is getting over-tired, especially if at the same time you do not get enough sleep; and, as you already know, tiredness, or fatigue, is a form of self-poisoning. Another very common cause of headache is bad air—sitting or sleeping in hot, stuffy rooms with the windows shut tight. If you do this, not only are you not getting oxygen enough into your blood to burn up the waste poisons that your own cells are making all the time, but also you are breathing in the waste poisons from other people's lungs, and the germs that are always in bad air.

Another very common cause of headache is eye-strain. Whenever you find that, when you try to read, the letters begin to dance before your eyes, and your head soon begins to ache, it is a sign that you need to have your eyes examined and perhaps a pair of glasses fitted to enable you to see properly.

Constipation and disturbances of digestion also very often cause headache by poisoning the blood; and, as you know, the first sign of a bad cold, or the beginning of a fever, or other illness, will often be a bad headache.

In short, a headache always means that something is going wrong; and the thing to do is to set to work at once to see if you can find out what has caused it, and then to remove the cause. If you cannot find out the cause, then go to a doctor and ask him to tell you what it is, and what to do to get rid of it.

Above all things, don't swallow a dose of some kind of headache medicine, and go on with your work, or your bad habits of eating, or using your eyes; because, even though it may relieve the pain, it doesn't do anything whatever to remove the cause and leaves you just as badly off as you were before you took it. Besides, most of these headache medicines, which for a time will relieve the pain of a headache, are narcotics, or pain-deadeners; and in more than very moderate doses they are poisons, and often dangerous ones. Those in commonest use, known as the "coal tar" remedies, because the chemists make them out of coal tar,[27] are likely to have a weakening effect upon the heart; and, while not very dangerous in small doses, they are very bad things to get into the habit of using.

The Exaggerated Claims of Patent Medicines. The same thing must be said of the habit of dosing yourself every time you feel a pain or an ache, with some sort of medicine, whether obtained at some previous time from a doctor, or bought at a drug store. A large majority of the medicines that are most widely advertised to cure all sorts of pains and aches contain some form of narcotic—most commonly either alcohol or opium. The reason for this is that no one medicine can possibly be a cure for all sorts of diseases; and the only kind of medicine that will make almost every one who takes it feel a little bit better for the time being is a narcotic, because it has the power of deadening the nerves to pain or discomfort.

Careful analyses by boards of health and government chemists of a great number of advertised medicines have shown that three-fourths of the so-called tonics and "bitters" and "bracers" of all sorts contain alcohol—some of them in such large amounts as to be stronger and more intoxicating than whiskey. The same investigations have found that a large majority of the "colic cures," "pain relievers," nearly all the "soothing syrups" and "teething syrups," and most of the cough mixtures, cough cures, and consumption cures contain opium, often in quite dangerous amounts. The widely-advertised medicines and remedies guaranteed to cure all sorts of diseases in a very short time are almost certain to be one of two things: either out-and-out frauds, costing about four cents a bottle and selling for fifty cents or a dollar, or else dangerous poisons. All patent pain relievers are safe things to let entirely alone.

Another risk in taking medicines wholesale, especially those that are known as patent medicines, is that you never can be quite sure what you are taking, as their composition is usually kept a strict secret. It may happen to be something very good for your disease, it may be entirely useless, and it may be something very harmful. There is no one drug, or medicine, known to the medical profession, that will cure more than one or two diseases, or relieve more than four or five disturbed and uncomfortable conditions. As you not only do not know what you are taking, but are not always quite sure what is the matter with you, the chances of your getting the right remedy for your disease are not much more than one in a hundred. If it isn't the right thing, you are certainly wasting your money, and may be doing yourself a serious injury.

We should not pour drugs of which we know little into a body of which we know less. Doctors give scarcely a fourth as much medicine now as they did fifty years ago. The best cures are food, exercise, sleep, and fresh air.

The Effects of Disease. In the case of nearly all infectious diseases, the effects on the nervous system are among the last to appear, and may not occur until weeks, months, or even years after the main fever or attack of sickness. This is one of the reasons why, when they do occur, they are often hard to cure; the whole system has become saturated with the poisons before they reach the nerves at all. So it happens that the idea has grown up that nervous diseases are very hard to cure. When, however, we know that two-thirds of them are a late result of some of the preventable infectious diseases and fevers, we can realize that it is perfectly possible to prevent them, and that prevention is the best cure.

The poisons that attack the brain and nervous system may be formed in the body by disease germs or brought in from without, as are alcohol, tobacco, lead, or arsenic. Even such mild infections as measles, scarlet fever, and influenza may poison certain nerves supplying the muscles of an arm or a leg, causing temporary paralysis, or even permanent laming; or they may attack the nerve of sight or of hearing and produce blindness or deafness.

A great many of the cases of paralysis and insanity are caused by alcohol. Alcohol in excess may attack the nerves supplying the arms and legs, producing severe pain and partial paralysis. It may also, after long-continued use, affect the cells of the brain itself, producing the horrible condition known as delirium tremens—a form of acute insanity with distressing delusions, in which the patient imagines that he sees rats, snakes, and other reptiles and vermin crawling over him, or in his room. Even in those who never use it to such excess as this, or indeed in those who may never become intoxicated, the long-continued use of alcohol may produce a slow poisoning and general breaking-down of the whole nervous system, causing in time the hand to tremble, the eye to become bleared and dim, the gait weak and unsteady, the memory uncertain, and the judgment poor.

Are Nervous Diseases Increasing? The direct use of the brain and nervous system has much less to do with the production of its diseases or even its serious disturbances than is usually believed. Most of these, as we have seen, are due either to the poisons of disease or alcohol, or to the fatigue-poisons, or other poisons, produced in the stomach, the liver, the muscles, or other parts of the body. The worst results of brain-work are due to the extent to which it deprives us of proper exercise and fresh air. Good, vigorous mental activity,—hard brain work, in fact,—when you are in good condition, is, if not overdone, as healthful and almost as invigorating as physical exercise or hearty play. We often hear it said that the rush and hurry of our modern strenuous life is increasing the number of mental diseases and nervous breakdowns. But there is no evidence that the strain of civilization upon our brains and nervous systems is damaging them, or that either nervous diseases or insanity are more frequent now than they used to be one hundred or five hundred years ago. In fact, all the evidence that we have points in exactly the opposite direction; for, as we have seen, most of these brain and nerve diseases are due to infectious diseases, bad food, and bad living conditions generally, all of which the progress of modern civilization is rapidly lessening and preventing.

We are collecting our insane in modern hospitals and comfortable homes, instead of letting them wander in rags about the country, and this makes them live longer and seem more numerous. But the poorest and least highly civilized classes and races have much more insanity among them than those who live under more favorable conditions.

CHAPTER XXII

In muscular training, a series of light, quick movements, none of which are fatiguing, repeated fifteen, twenty, or a hundred times, will do much more to build up muscle and increase strength, than three or four violent, heaving strains that tax all your strength. Real athletes and skilled trainers, for instance, use half-or three-quarter-pound dumb-bells and one-or two-pound Indian clubs, instead of the five-pound dumb-bells and ten-pound clubs with which would-be athletes delight to decorate their rooms. A thoroughbred race-horse is trained on the same principle: he is never allowed to gallop until tired, or to put out his full speed before he is well grown. In fact, the best methods of all forms of exercising and training always stop just short of fatigue. Education and study ought to be planned on the same principle. Exercise of either our muscles or our minds after they have begun to poison themselves through fatigue never does them any good, even if it does not do them serious harm; and, where the exercise is for the sake of building us up and developing our powers, it is best to stop for a little while, or change the task, as soon as we begin to feel distinctly tired, and then to try it again when we are rested.

This is one of the secrets of the healthfulness and value of play and games for children, and for older persons as well. When you get tired, you can stop and rest; and then start in again when you feel rested—that is to say, when your heart has washed the poisons out of your muscles and nerves. In fact, if you will notice, you will find that nearly all play and games are arranged on this plan—a period of activity followed by a period of rest. Some games have regular "innings," with alternate activity and rest for the players; or each player takes his turn at doing the hard work; or the players are constantly changing from one thing to another—for instance, throwing or striking the ball one minute; running to first base the next; and standing on base the next. Every muscle, every sense, every part of you is exercised at once, or in rapid succession, and no part has time to become seriously fatigued; so that you can play hard all the afternoon and never once be uncomfortably tired, though your muscles have done a tremendous lot of work, measured in foot-pounds or "boy-power," in that time.

The good school imitates nature in this respect. The recitation periods are short, and recesses frequent; a heavy subject is followed by a lighter one; songs, drawing, calisthenics, and marching are mixed in with the lessons, so as to give every part of the mind and body plenty to do, and yet not over-tire any part.

All-Round Training from Work and Play. Every game that is worth playing, every kind of work that accomplishes anything worth while, trains and develops not merely the muscles and the heart, but the sight, hearing, touch, and sense of balance, and the powers of judgment, memory, and reason, as well.

If you are healthy, you know that you don't need to be told to play, or even how, or what, to play; for you would rather play than eat. You have as strong and natural an appetite for play as you have for food when you are hungry, or for water when you are thirsty, or for sleep when you are tired. It is just as right to follow the one instinct as the others, though any one may be carried to extremes.

Some of the most important part of your training and fitting for life is given by plays and games. Not only do they put you in better condition to study and enjoy your work in school, but they also teach you many valuable lessons as well. Our favorite national game, base-ball, for instance, not only develops the muscles of your arms and shoulders in throwing the ball and in striking and catching it, and your lungs and heart in rushing to catch a fly or in running the bases, but also develops quickness of sight and hearing,—requires, as we say, "a good eye" for distance,—makes you learn to calculate something of the speed at which a ball is coming toward you or flying up into the air, requires you to judge correctly how far it is to the next base and how few seconds it will take to get there and whether you or the baseman can get there first.

More important yet, like all team games, it teaches you to work with others, to obey orders promptly, to give up your own way and do, not what you like best, but what will help the team most; to keep your temper, to bend every energy to win, but to play fair. It also teaches you that you must begin at the beginning, take the lowest place, and gradually work yourself up; and that only by hard work and patience and determination can you make yourself worth anything to the team, to say nothing of becoming a "star" player.

If you will just go at your studies the way you do at base-ball, you will make a success of them. Make up your mind to gain a little at a time, to learn something new every day, and you will be astonished how your knowledge will mount up at the end of the year. When you first start in a new study, it looks, as you say, "like Greek" to you. You feel quite sure that you never will be able to understand those hard words or solve those problems "clear over in the back of the book." But remember how you started in on the diamond as a "green player," with fumbling fingers that missed half the balls thrown to you, with soft hands that stung every time you tried to stop a "hot" ball; how you ducked and flinched when a fast ball came at you, and how you fumbled half your flies and, even when you fielded them, were likely to send them in six feet over the baseman's head. But by quietly sticking to it—watching how the good players did it, and playing an hour or two every day during the season—you gradually grew into the game, until, almost without knowing how it happened, you had trained your muscles, your nerve cells, and your brain and found yourself a good batsman and a sure catcher.

So it will be in your school work. Just stick quietly to it, taking your work a lesson at a time; give yourself plenty of sleep and plenty of fresh air, and eat plenty of good food three times a day, and your mind will grow in strength and skill as gradually, as naturally, and as happily as your body does.

Every season of the year has its special games suited to the weather and the condition of the ground. If you take pride in playing all of them in their turn, hard and thoroughly, and making as good a record in them as you can, you will find that it will not only keep you healthy and make you grow, but will help you in your school work as well, by keeping your wits bright and your head clear. There is a fine group of running games, for instance, such as Prisoner's Base, or Dare Base, Hide-and-Seek, or I Spy, and the different kinds of tag,—Fox-and-Geese, Duck-on-Rock,—which are not only capital exercise for leg muscles, lungs, and heart, but fine training in quickness of sight, quickness and accuracy of judgment, and quickness of ear in catching the slightest rustle on either side, or behind you, so that you can rush back to the base, or "home," first.

Then with the winter comes skating, with hockey and Prisoner's Base on the ice, and coasting and sledding and snow-balling, to say nothing of forts and snowmen. You should try to be out of doors as many hours a day in the winter-time as in the summer, so far as possible. If you play and romp hard, you will find that you don't mind the cold at all, and that, instead of taking more colds and chills, you will have fewer of these than you had when you cooped yourself up indoors beside the warm stove.

It is just as important for girls to play all these games as it is for boys; and girls enjoy them just as much and can play them almost, if not quite, as well, if they are only allowed to begin when they are small and do just as they please. There is no reason whatever why a girl should not be just as quick of eye and ear, and as fast on the run, and as well able to throw or catch or bat a ball, as a boy. Up to fifteen years of age boys and girls alike ought to be dressed in clothes that will allow them to play easily and vigorously at any good game that happens to be in season. Girls like base-ball as well as boys do, if they are only shown how to play it.

In summer, of course, the whole wide world outdoors turns into one great playground; and it is largely because we turn out into this playground that we have so much less sickness, and so many fewer cases of the serious diseases like tuberculosis, pneumonia, and rheumatism in summer than in winter.

Boys and girls ought to know how to swim and how to handle a boat before they are twelve years old; for these are not only excellent forms of exercise and most healthful and enjoyable amusements in themselves, but they may be the means of saving lives—one's own life or the lives of others.

As a form of exercise and education combined, nothing is better than walks in the country or, where this is impossible, in parks and public gardens. An acquaintance with trees, flowers, plants, birds, and wild animals, is one of the greatest sources of enjoyment and good health that any one can have all his life through.

Last, but not by any means least, comes that delightful combination of work and play known as gardening, and the lighter forms of farming. Every child naturally delights in having a little patch of ground of his own in which he can dig and rake and weed and plant seeds and watch the plants grow. In our large cities, where most of the houses have not sufficient space about them to allow children to have gardens of their own at home, land is being bought near school-houses and laid out as school gardens, and the work done in them is counted as part of the school work. Indeed, so important is this work considered as a part of school education, that some large cities are actually building their schools out in the open country, so that they can have plenty of space for playgrounds and gardens and shops, and carrying the children from the central parts of the city out to them by trolley or train in the morning and back at night.

Wherever you happen to live, you should engage in healthy happy, vigorous play in the open air at least two to four hours a day all the year round. If you live in a town, while it will not be quite so easy to reach the woods and the fields and the swimming holes and the skating ponds, yet you will have a large number of playmates of your own age, and have good opportunity to play the games calling for half a dozen or more players; and there will be plenty of vacant lots and open spaces, or little-traveled streets, in which to play base-ball and foot-ball and Prisoner's Base and tag. And although you may not be within reach of the best zoological garden ever made,—a barnyard,—yet you can make occasional trips to the city "Zoo," or the botanical gardens, or to parks.

Healthful Methods of Study. In the growth and training of the highest, most valuable, and most wonderful part of the body—the brain—the same methods followed in our outdoor games will give the best results. We do not create intelligence by study, nor manufacture a brain for ourselves, in school. We simply develop and strengthen and improve the brains and the mental power that we were born with.

Our minds grow as our bodies do, by healthful exercise—little at a time, with plenty of rest and change of occupation between the periods of work. That is why our school studies are arranged as they are: instead of one subject being studied all the morning, or all day, four or five subjects are studied for twenty or thirty minutes each, and a change is made to another before our minds become over-tired and begin poisoning themselves with fatigue toxins. A subject that is rather hard for us is followed by one that is easier; and the hardest subjects in the course are usually taken up early in the morning session, or after recess, or early in the afternoon, when we are well-rested and feeling fresh and ready for work.

We should try to keep our bodies and our brains and our sight and hearing in the very best possible condition for our work, so as to come up to each task that we have to master keen and fresh and clear-headed, rather than to take pride in spending so many hours a day studying in a half-tired, half-hearted, listless kind of way. You will find that you will be able to master a lesson and see through a problem in half the time if you get plenty of sleep in a room with the windows open, play a great deal out-of-doors, and do not hurry through your meals for either school or play.

Study just as you play ball when you are trying to make a place on the team. Bend every energy that you have to that one thing, and forget everything else, until you have finished it. You can do more work in fifteen minutes in this way than you can in forty minutes of sitting and looking out of the window and wondering how much longer the study period is to last, and what the next chapter is about in the story that you are reading at home, or what you are going to wear to the party next week.

Keep yourself in good condition, and then buckle down to your work as if that were the only thing there was in the world for the time being, and you will be surprised to find, not only how much more easily and quickly you will do your work, but how much better you will remember it afterwards. Do not set out to accomplish too much at a time; but when you undertake a task, don't let go until you have finished it. If you will train yourself in this way, you will soon find that it will seldom take you longer to master a lesson than it will to recite it. It is becoming more and more the custom in the best schools to plan to do all the school work in school hours, alternating periods of recitation and play with periods of study, so that no school-books need be taken home at night. This cannot always be done; but it is well to come as near to it as possible, in order, first, to learn to do work quickly and thoroughly and to drop it when it is finished, and, secondly, to give time to playing and resting and forming the priceless habit of reading. You will leave school some day, but you may still be a student in the great University of Books; and the pleasure of widening your knowledge and kindling your imagination will never fail you or pall on you as long as you live. An evening spent with newspapers and magazines, with books of travel and adventure, with good stories and poetry, with enjoyable and sensible parlor games such as authors, checkers, chess, charades, and with music and singing, will help you more with your lessons next day than two hours of listless yawning over text-books.

If you take your school work in this spirit, you will find that you will enjoy it quite as well as any other form of exercise—even play itself. The harder and more intelligently you play, the better you will be able to work in the schoolroom; and the harder and more intelligently you study, the more you will enjoy your play.

CHAPTER XXIII

These three sets of organs have gradually and slowly grown into the shape in which we now find them, in order to do the particular kind of smelling, seeing, and hearing that will be most useful to us. Every kind of animal has a slightly different shape and arrangement of eye, of ear, and of nose to fit his particular "business"; but in all animals they are built upon the same simple, general plan.

THE NOSE

How the Nose is Made. The nose began as a pair of little puckers, or dimples, just above the mouth, containing cells that were particularly good smellers, in order to test the food before it was eaten. All smells rise, so these cells were right on the spot for their particular "business."

The original way of breathing, before the nose-dimples or pits opened through into the throat, was through the mouth; and that is one reason why it is so easy to fall into the bad habit of mouth-breathing whenever the nose gets blocked by adenoids or catarrh. Some creatures—fishes, for instance,—breathe through their mouths entirely; if you watch one in an aquarium or a clear stream, you will easily see that it is going "gulp, gulp, gulp" constantly. The saying "to drink like a fish" is a slander upon an innocent creature; for what it is really doing is breathing, not drinking. Even a frog, which has nostrils opening into its throat, still has to swallow its air in gulps, as you can see by watching its throat when it is sitting quietly. And, strange as it may seem, if you prop its mouth open, it will suffocate, because it can no longer gulp down air.[28]

Our noses are nine-tenths for breathing, and only about one-tenth for smelling; so that by far the greater part of the nose is built on breathing lines. But the smelling part of it, though small, is very important, because it now has to decide, not merely upon the goodness or badness of the food, but also upon the purity or foulness of the air we breathe. The nostrils lie, as you can see, side by side, separated from each other by a thin, straight plate of gristle and bone known as the septum. This should be perfectly straight and flat; but very often when the nose does not grow properly in childhood, it becomes crumpled upon itself, or bulged over to one side or the other, and so blocks up one of the nostrils. This is a very common cause of catarrh, and requires, for its cure, a slight operation, a cutting away of the bulging or projecting part of the septum. The rims of the openings of the nose, known as the wings, have little muscles fastened to them which pull them upward and backward, thus widening the air openings or, as we say, dilating the nostrils. If you will watch any one who has been running fast, or a horse that has been galloping, you will see that his nostrils enlarge with every breath; and these same movements occur in sick people who are suffering from disease of the lungs or the heart, which makes it difficult for them to get breath enough.

Each nostril opens into a short and rather narrow, but high, passage, known as the nasal passage, through which the air pours into the back of the throat, or pharynx, and so down into the windpipe and lungs. Instead of having smooth walls, however, the passage is divided into three almost separate tubes, by little shelves of bone that stick out from the outer wall. These are covered with thick coils of tiny blood vessels, through which hot blood is being constantly pumped, like steam through the coils of a radiator, so that the air, as it is being drawn into the lungs, is warmed and moistened. The passage is lined with a soft, moist "skin," called mucous membrane, very much like that which lines the stomach and bowels, except that it is covered with tiny little microscopic hairs, called cilia, and that its glands pour out a thin, sticky mucus, instead of a digestive juice. This thick network of blood vessels just under the thin mucous "skin" is easily scratched into or broken, and then we have "nose-bleed."

The purpose of this mucus is to catch and hold, just as flypaper catches flies, all specks of dust, lint, or germs that may be floating in the air we breathe, and to keep them from going on into the lungs. As these are caught upon the lining of the nose, they are washed down by the flow of mucus or wafted by the movement of the tiny hairs back into the throat, and swallowed into the stomach, where they are digested. Or, if they are very irritating, they are blown out of the nostrils, or sneezed out, and in that way got rid of.

If the dust is too irritating, or the air is foul and contains disease germs, these set up an inflammation in the nose, and we "catch cold," as we say. If we keep on breathing bad or dusty air, the walls of the nasal passages become permanently thickened and swollen; the mucus, instead of being thin and clear, becomes thick and sticky and yellowish, and we have a catarrh.

Catarrh is the result of a succession of neglected "bad colds," caused, not by fresh, cold air, but by hot, stuffy, foul air containing dust and germs. The best and only sure way to avoid catarrh is by breathing nothing but fresh, pure air, day and night, keeping your skin clean and vigorous by cool bathing every day, and taking plenty of play in the open air.

So perfect is this heating, warming, and dust-cleansing apparatus in the nose, that by the time quite cold air has passed through the nostrils, and got down into the back of the throat, it has been warmed almost to the temperature of the body, or blood-heat, and has been moistened and purified of three-fourths of its dust or disease germs. When you go out of doors on a cold, frosty morning, your nose is very likely to block up, because so much hot blood is pumped into these little steam-coils of blood vessels, in order to warm the air properly, that they swell until they almost block up the nostrils.

The Sense of Smell. The lower three-fourths of the nasal passages have nothing whatever to do with the sense of smell; this is found only in the highest, or third, division of the passages, right up under the root of the nose, where odors can readily rise to it. Here can be found a little patch of mucous membrane of a deep yellowish color, which is very sensitive to smells, and from which a number of tiny little nerve twigs run up to form the nerve of smell (olfactory nerve), which goes directly to the brain. The position of the smell area at the highest and narrowest part of the nose passage explains why when you have a very bad cold, you almost lose your sense of smell; the lining of the lower part of the nose has become so inflamed and swollen as to block up the way to the highest part where the smelling is done.

Adenoids. If colds are neglected and allowed to run on, the inflammation spreads through the nose back into the upper part of the throat, or pharynx. Here it attacks a spongy group of glands, like a third tonsil, which swells up until it almost blocks up the nose and makes you breathe through your mouth. These swollen glands are called adenoids, and cause not only mouth-breathing, but deafness, loss of appetite, indigestion, headache, and a stupid, tired condition; so that children that are mouth-breathers are often two or more grades behind in school, poor students, and even stunted and undersized. You can often tell them at sight by their open mouths and vacant, stupid look. A very simple and harmless scraping operation will remove these adenoids entirely, and what a wonderful improvement the mouth-breather will make! He will often catch up two grades, and gain two inches in height and ten pounds in weight within a year.

Adenoids not only cause deafness by blocking up the tube (Eustachian) that runs from the throat to the ear,—the tube through which the air passes when your ear "goes pop,"—but are also the commonest cause of ear-ache and gatherings in the ear, which may burst the drum.

THE TONGUE

The Tongue is not Used chiefly for Tasting. If you will notice the next time that you have a bad cold, you will find that you have almost lost your sense of taste, as well as of smell, so that everything tastes "flat" to you. This illustrates what scientists have known for a long time, but which seems very hard to believe, that two-thirds of what we call taste is really smell. If you carefully block up your nostrils with cotton or wax, so that no air can possibly reach the smell region at the top of them, and blindfold your eyes, and have some one cut a raw potato, an apple, and a raw onion into little pieces of the same size and shape, and put them into your mouth one after the other, you will find that it is difficult to tell which is which.

The only tastes that are really perceived in the mouth are bitter, sweet, sour, and salty; and even these are perceived quite as much by the roof and back of the mouth, especially the soft palate, as they are by the tongue. All the delicate flavors of our food, such as those of coffee or of roast meat or of freshly baked bread, are really smells.

The tongue, which is usually described as the organ of taste, is really a sort of fingerless hand grown up from the floor of the mouth—to help suck in or lap up water or milk, push the food in between the teeth for chewing, and, when it has been chewed, roll it into a ball and push it backward down the throat. It is not even the chief organ of speech; for people who have had their tongues removed on account of cancer, or some other disease, can talk fairly well, although not so clearly as with the whole tongue.

The tongue is simply a "tongue-shaped" bundle of muscles, covered with a thick, tough skin of mucous membrane, dotted all over with little knob-like processes called papillæ, which are of various shapes, but of no particular utility, except to roughen the surface of the tongue and give it a good grip on the food. If the mucous "skin" covering the tongue does not shed off properly, the dead cells on its surface become thickened and whitish, and the germs of the mouth begin to breed and grow in them, forming a sort of mat over the surface. Then we say that the tongue is badly coated. This coating is in part due to unhealthy conditions of the stomach and bowels, and in part to lack of proper cleaning of the mouth and teeth.

The Sense of Taste can usually be Trusted. Since the nose and the tongue have had about five million years' experience in picking out what is good and refusing what is bad, their judgment is pretty reliable, and their opinion entitled to the greatest respect. As a general thing, those things that taste good are wholesome and nutritious; the finest and most enjoyable flavors known are those of our commonest and most wholesome foods, such as good bread, fresh butter, roast meats, apples, cheese, sugar, fruit, etc.; while, on the other hand, those things that taste bad or bitter or salty or sour, or that we have to learn to like, like beer or pickles or strong cheese or tea or coffee, are more often unwholesome or have little nutritive value. Very few real foods taste bad when we first try them. If we used our noses to test every piece of food that went into our mouths, and refused to eat it if it "smelt bad," we should avoid many an attack of indigestion and ptomaine poisoning. It is really a great pity that it is not considered polite to "sniff" at the table.

THE EYE

How the Eye is Made. Next in importance after the smell and the taste of our food comes the appearance of it; hence, our need of eyes to help us in choosing what to eat, as well as how to avoid the dangers about us.

The eyes began as little sensitive spots on the surface of the head. Like the nose pits, as they became more sensitive, they too sank in beneath the surface; but with this difference, that, instead of remaining open, the rims or edges of the eye-pit grew together and became transparent, forming a cover, or eye-glass, which became the clear part of the eye, called the cornea. At the same time, the little sensitive spot at the bottom of the eye-pit spread out into the shape of the bottom of a cup, called the retina; and then the hollow of that cup between the retina and the cornea filled up with a clear, soft, animal jelly called the vitreous humor, and we have the eye as it is in our heads to-day.

The sensitive retina, spreading out, as it does, to form the back of the eyeball, is the nerve-coat of the eye; and from its centre a thick round bundle of nerve fibres, known as the optic nerve, runs back to the brain.