A photograph of boys and girls holding hands and running down the sidewalkAN EARLY RUN IS A GOOD PREPARATION FOR THE DAY’S WORK
AN EARLY RUN IS A GOOD PREPARATION FOR THE DAY’S WORK
Of course you have seen a pump? Perhaps some of you have to pump water every day at home. You take the handle in your hands, lift it up, then press it down, and out pours the water through the spout; and, as you keep pumping, the water spurts out every time you press thehandle down. It is hard work, and your arms are soon tired; but, as you cannot drink the water while it is down in the well, you must pump to bring it up where you can reach it.
Anatomical drawing of a heart.THE HEART-PUMPThe big tubes are the arteries and veins.
THE HEART-PUMP
The big tubes are the arteries and veins.
Just so the heart pumps to keep the blood flowing round and round, through the muscles and all over the body. If you put your finger on your wrist, or on the side of your neck, you can feel a little throb, orpulse, for every spurt from your heart-pump; and that means for every heart-beat.
This heart-pump is made of muscle, and is about the size of your clenched fist. And just as you can squeeze water from a sponge or out of a bulb-syringe, by opening and shutting your hand around it, so the big heart muscle squeezes the blood out of the heart. It squeezes it out from one side of the heart; and then, when it lets go, the blood comes rushing in from the other side to fill the heartagain. So the heart goes on squeezing out and sucking in the blood, all day and all night as long as we live.
When the blood comes to the muscles, it is a beautiful bright red; but after the muscles have taken what they want of it for food to burn, and warm you up, the “ashes” and the “smoke” go back into the blood and dirty its color from red to purple. Then the blood is carried to the lungs, where the fresh air you breathe in blows away the “smoke” and makes the blood red again.
The blood is pumped all over the body through tubes or pipes, calledblood vessels. Those that carry the red blood out from the heart, we callarteries. They are deep down under the skin, and we cannot see them. The pipes that carry the purple blood from the muscles and other parts back to the heart again, we callveins; and some of these are so close to the surface that we can easily see them through the skin. Let your hand hang down a minute or two, then you can see the veins on the inside of your wrist, or on the back of your hand, if it is not too fat.
A photograph of children playing in the snow outside of school.IT IS GOOD TO PLAY OUT OF DOORS TILL THE BELL RINGS—EVEN IN WINTER
IT IS GOOD TO PLAY OUT OF DOORS TILL THE BELL RINGS—EVEN IN WINTER
The muscles, the brain, the skin, and other parts of the body get liquid food from the blood by “sucking” it through the walls of the smallestof the blood vessels, for these walls are very thin. In the same way, when waste passes from the muscles or the skin into the blood, it, too, soaks through the thin walls of the tiniest blood tubes, calledcapillaries.
Your heart beats or throbs about seventy-five times in a minute when you are well. Look at the second hand of a watch, while you count the beats in your wrist or in your neck.
Does your heart ever become tired? Not while you keep well, unless you over-drive it by running or wrestling too hard. It can rest between the beats. But the heart muscle, like any other muscle, must have plenty of good red blood to feed on. You put food into the blood by eating good breakfasts and dinners. The more you run and jump and play, the more work the heart has to do and the stronger it grows; and a good morning romp before school will send the blood flowing so merrily round from top to toe that you will feel fresher and brighter all the day.
The heart is not the only thing that goes faster and harder when you run about in the morning and play hard. You are breathing faster and deeper as well, as if there were somethingin the air outside that you needed in your body as much as food.
But, of course, you know that air is not good to eat. It has no strength in it, as food has; it isn’t even a liquid like milk or coffee or tea. It is so thin and light that we call it agas. Indeed, I suppose it is pretty hard for you to believe that air is a real thing at all. But all outdoors is full of the gas called air, and everything that seems to be empty, like a room or an empty box, is full of it.
You cannot even smell it, as you can that other gas which comes through pipes into our houses and burns at the gas jets; nor can you see it like the gas that comes out of a boiling kettle or from the whistle of a locomotive, and which we callsteam. This is simply because air is so pure that it has no smell, and is so perfectly clear that we can see right through it. Almost the only way that we can recognize it is by feeling it when it is moving. But it is a very real thing for all that; and, like sunshine and food, is one of the most important things in the world for us.
What is it that air does in the body? We must need it very much, for we die quickly when we cannot get it: it takes us only about three minutes to suffocate, or choke to death, if we can’t get it.
You remember that the blood is pumped out from the heart, all through the body. Everywhere it goes,—to the feet and the hands and the head,—it is carrying two things: food that it has sucked up from the food tube, and hundreds and hundreds of tiny red sponges called redcorpuscles. These little sponges are full of air which they sucked up as the blood passed through the lungs. When we stop breathing,—that is, taking in air,—the little red sponges of course can’t get any air to carry to the different parts of the body.
The body is made up of millions of tiny, tiny animals, calledcells,—so tiny that they can be seen only under a microscope. Each of these cells must have food and air, just like any other animal. They eat the food the blood brings to them, and they take the air from the red corpuscles in the blood. With the air as a “draft,” they burn up the waste scraps, as we burn scraps from the kitchen, in the back of the stove.
Suppose you light a candle and place it under a glass jar and watch what will happen. The flame will become weaker and weaker, and at last it will quite go out. You might think at first that the wind blew it out; but how could the wind get through or under the jar? No, the glass keeps allthe outside air away from the flame; and that is just the reason why it does go out. Unless it has fresh air, it cannot burn. There is something—a gas—in the air that makes the flame burn, and when it has used up all this gas inside the glass, and can’t get any more, it stops burning.
Now you will want to know what this gas in the air is. When we write about it, we use its nickname, the large capital letterO; but its whole name isOxygen.
Just as the candle flame must have oxygen to keep it burning, so our cells must have oxygen to burn their impurities, or waste; and if they don’t get the oxygen, and can’t burn their impurities, they are poisoned by them and “go out,” or die.
You can see the flame when the candle is burning, but you can’t see the fires that burn in our bodies; there are no real flames at all. I know it is hard for you to believe that there can be any burning when our bodies are so wet and damp. But if you can’t see it, you can easily feel it. Blow on your hand. How warm your breath is! Touch your hand to your cheek. It is quite warm, too. If you run or play hard, you sometimes become so hot that you want to take off your coat. That is because your fires are burningfaster. The muscles are using more food and making more scraps to be burned. You breathe faster and faster till at last you are “out of breath” and feel as if you would smother or choke. The blood has hard work to bring oxygen enough to keep the fires going.
After the cells have burned the food scraps, they turn the “ashes” and “smoke” back into the blood-stream that is always flowing past them. If the cells did not do this, they would soon smother to death, just as you could not possibly live in a house without chimneys to carry off the smoke. And, of course, the blood wants to get rid of this waste just as quickly as possible.
Part of the waste in the body is liquid, like water, and can flow away through the blood pipes without needing to be burned. Some of this watery waste comes out through the skin and stands in beads or drops upon it. That is the part we call perspiration, or sweat. The rest of it goes in the blood to another strainer called thekidneys, passes through this asurine, and is carried away from the body as the waste water from the bathtub and the sink is carried away from a house.
For the “smoke” Mother Nature has stillanother beautiful plan. She sends the blood-stream flowing through thelungs, where it can send off its “smoke” and then get fresh air to carry to the cells in the muscles. When you breathe out, you are sending out the “smoke”; and when you breathe in, you are taking in fresh air.
Our body “smoke” is not brown or blue, like the smoke from a fire; it is a clear, odorless gas, calledcarbon dioxid. This is the same gas that makes the choke-damp of coal mines, which suffocates the miners if the mine is not well ventilated; and the same gas that sometimes gathers at the bottom of a well, making it dangerous for anyone to go down into the well to clean it. And this gas is poisonous in our bodies just as it is in the mine or the well.
You see, then, how important it is that we should live much of our lives in the clear pure air out of doors, and should bring the fresh air into our houses and schools and shops. “Fill up” with it all you can on your way to school, for the best of air indoors is never half so good as the free-blowing breezes outside.
When you are running and breathing hard, and even when you are sitting still and breathing quietly, air is going into your lungs and then coming out, going in and coming out, many times every minute. How does the air get in and out of the lungs? It will not run in of itself; for it is light and floats about, you know. Here, again, Mother Nature has planned it all out. She has made us an air bellows, or air pump, to suck it into the lungs. First we’ll see what shape this pump is, and then how it works.
Diagram of the chest cavity.THE CHEST THAT HOLDS THE LUNGSBack of the lungs is the heart; its position is shown by the broken line. The black line across the chest shows how high the diaphragm rises when we breathe out quietly.
THE CHEST THAT HOLDS THE LUNGS
Back of the lungs is the heart; its position is shown by the broken line. The black line across the chest shows how high the diaphragm rises when we breathe out quietly.
Stiff rings of bone calledribsrun round your body, just like the hoops in an old hoop skirt, or like the metal rings round a barrel. Here is a picture of the bones of the chest. Perhaps your teacher can show you the skeletonof some animal. You will notice how the rings, or ribs, slant and are joined by hinges behind to the backbone and in front to the breastbone. It looks somewhat like a cage, doesn’t it? Put your hands on the sides of your chest and you can feel your own ribs. Do they slant upward or downward?
This chest-cage is our breathing-machine. Before I tell you how it pumps, I want you to get a pair of bellows and see how they work. When you lift up the handle of the bellows, you make the bag of the bellows larger so that it sucks in air; and when you press the handle down again, the air puffs out through the nozzle.
Our air machine, though it is somewhat different from the bellows in shape, works in exactly the same way. You remember that you found that the ribs slant down and can be moved on hinges. Suppose, now, you place your hands against your ribs and feel the ribs lift as you draw in a long breath. The air will be sucked into your nose just as it was into the bellows when you raised the handle. By lifting your ribs, you have made the chest-cage larger; and the air has rushed into your nose, down your windpipe, and filled your lungs. If you breathe very deeply, you will find that your stomach, too,swells out. This shows that the muscular bottom of the cage, called thediaphragm, has been pulled down, making the cage larger still.
In this chest-cage are millions of tiny air bags that make up the lungs; and every time you take a breath, the air bags are puffed out with the fresh air that comes rushing in. By the time you let your ribs sink again, the air has given its oxygen to the blood, and the blood has poured its carbon-dioxid smoke into the air bags for you to breathe out. Nature, with the same bellows, pumps in the oxygen and pumps out the “smoke.”
Now, we breathe into our lung-bellows whatever air happens to be around us. So we should take care that the air around us is fresh air.
Unless the air were kept in motion by the heat of the sun, causing breezes and winds, it would become stale and wouldn’t do at all for our lung-bellows to use. The air we breathe must be kept moving and fresh if it is to make us feel bright and strong and happy. Mother Nature has given us miles upon miles and oceans upon oceans of this clear, fresh air to breathe—“all outdoors,” in fact, as far as we can see around us and for miles above our heads. She sends the winds to move the air about and blow away the dust and dirt; and the sunshine, you remember, not onlyto warm the air and keep it moving, but to burn right through it and kill the poisons. But this brings us to something else.
You have learned that the air we breathe out would soon smother us, just as smoke would; and now we will see why. If you blow against the window pane on a cold day, the glass is no longer clear; and when you look at it closely, you see that it is covered with tiny drops of water. This is part of the breath you have just blown out. If the room is cold enough, you can see your breath in the air; that is, the steam in your breath becomes cold and appears as tiny water-drops. You have seen how in the same way, the steam, an inch or so from the spout of the teakettle, cools, making little water-drops that float in the air like clouds. Part of the breath, then, is water; but most of it is a gas, and you can’t see it at all as it floats away into the air about you.
If your teacher has a glass of limewater, and will let you breathe into it through a tube, you will see that your breath soon makes the water look milky. This shows that the gas in your breath is not like the air about you; because air was all over the top of the limewater, yet did not change it at all. The milky look is causedby carbon dioxid, one of the poisons in your breath.
When some people come close to you, you want to turn away your head, because you do not like the smell of their breath. Even when one is quite well, the breath has a queer “mousey” odor, so that we never like to breathe the breath of another person. This disagreeable odor comes not only from the lungs but from the teeth.
We are always breathing out poisons into the air. One of these you can see in the milky limewater, and others you can smell when you happen to come close to anyone else.
A girl blows through a straw into a glass of water.PROVING THAT THE BREATH IS NOT LIKE THE AIR
PROVING THAT THE BREATH IS NOT LIKE THE AIR
If you blow on your fingers, you feel that your breath is much warmer than the air. If people are crowded together in rooms with doors and windows shut, their breath soon heats and poisons the air, until they begin to have headache, and to feel dull and drowsy and uncomfortable. If they should be shut in too long, without any opening to let in the fresh air, as in a prison cell, or in the hold of a ship during a storm, the air would become so poisonous as to make themill, and would even suffocate them and kill them outright. Even the bees found this out thousands of years ago; and in their hives in hot weather they station lines of worker-bees, one just behind another from the door right down each of the main passages, whose business it is to do nothing but keep their wings whirring rapidly, so that they fan a steady current of fresh air into every part of the hive.
A girl dusts with a feather duster, and clouds of dust are everywhere.Breathing Dust.A girl dusts with a cloth. No clouds ensue.Catching the dust in a cloth.DUSTING—HOW SHALL WE DO IT?
A girl dusts with a feather duster, and clouds of dust are everywhere.Breathing Dust.
Breathing Dust.
A girl dusts with a cloth. No clouds ensue.Catching the dust in a cloth.
Catching the dust in a cloth.
DUSTING—HOW SHALL WE DO IT?
How does Mother Nature get rid of these poisons from our breath? Of course, you say, “She uses the wind and the sunshine.” Yes, the winds can whisk up the poison and blow it away so fast, and the sunshine can burn up the horridsmell so quickly, that even the air above big cities, and in their streets, is quite clean enough for us to breathe, except where the people are very closely crowded together and very dirty. Mother Nature wants all of us to help in keeping the air clean. This we can do by keeping ourselves and our houses clean, and by being careful not to leave scraps of waste, or dirty things, in the streets and cars and parks and other public places. And you children ought to be very careful about your school yard and the halls and the classrooms, where you spend so much of your time.
The only place where air is absolutely sure to be fresh is out of doors. There, as we have seen, the sun and the winds keep it so all the time. But, unluckily, we cannot spend all our time outdoors, either when we are little or after we have grown up. So we must try in every way that we can to bring the outdoors indoors—to get plenty of fresh air and light into the houses that we live in, especially the bedrooms we sleep in and the schoolrooms we study in when we are children, and the offices or shops we work in when we are grown up.
After you have your lungs and your blood well filled with air, either by walking briskly to school or by chasing one another about the school playground, you will suddenly hear the bell ring, and you march indoors and sit down at your desks. Here, of course, the air cannot blow about freely from every direction, because the walls and doors and windows are shutting you in on every side. The room, to be sure, is full of air; but if the doors and windows are shut, this air has no wayof getting outside, nor can the fresh, pure air out of doors—even though it be moving quite fast, as a wind or a breeze—get inside.
A photograph of a classroom.A CLASSROOM ALMOST AS GOOD AS THE OUT-OF-DOORSNotice the windows open top and bottom, and the high windows under the roof. Why are these good?
A CLASSROOM ALMOST AS GOOD AS THE OUT-OF-DOORS
Notice the windows open top and bottom, and the high windows under the roof. Why are these good?
We must let the fresh air come in and the stale air go out. This is one of the things that windows are for; and this is why they are hung upon pulleys and made to slide up and down easily. Of course, even when the windows are not open, they are letting in light, which, you remember, is a deadly enemy to germs and poisons.
Bright sunlight is best for purifying the air of a room, but even ordinary daylight has a good deal of germ-killing power. Therefore, a room that is well lighted is not only much pleasanter to live in, but much healthier, than one that is dull and gloomy. You see why we need plenty of windows and doors: we must let in the breezes and the sunshine, and let out the poisons and the dirt. Then, too, we must make the air in the building move about in order to keep it fresh; for if the air is not fresh, we soon grow tired and sleepy and have headaches. That is why your teacher keeps the windows open at the top a foot or so. You can easily see that when there are twenty or thirty of you breathing out poisons, and each one of you needing about four bushels of fresh air every minute, the old air ought to be going out and the fresh air coming in all the time.
A candle at the bottom of an open window has the flame pointing in, while one at the top has a flame pointing out.VENTILATIONWatch the candle flames. Which way is the air moving, and why?
VENTILATION
Watch the candle flames. Which way is the air moving, and why?
That is also why your teacher gives you a recess, so that you can run out of doors and get some fresh air. Then she can throw open all the windows and doors and have the air in the roomclean and fresh when you come back again. So when recess comes, don’t hang about in the hallways or on the stairs or in the basement, but run right out of doors into the playground and shout and throw your arms about and run races to fill your lungs full of fresh, sweet air and stretch all your muscles, after the confinement and sitting still. Don’t saunter about and whisper secrets or tell stories, but get up some lively game that doesn’t take long to play, such as tag or steal-sticks or soak-ball, or duck-on-a-rock or skipping or hopscotch. These will blow all the “smoke” out of your lungs and send the hot blood flying all over your body and make you as “fresh as a daisy” for your next lesson.
When you come back into the schoolroom after recess, the air will seem quite fresh and pure; but unless you keep the windows open, it will not be long before your head begins to be hot, and your eyes heavy, and you feel like yawning and stretching, and begin to wonder why the lessons are so long and tiresome. Then, if your teacher will throw open all the windows and have you stand up, or, better still, march around the room singing or go through some drill or calisthenic exercises, you will soon feel quite fresh and rested again.
In the mild weather of the spring or early fall, all you need to do to keep the air fresh in the schoolroom is to keep the windows well open at the top. But in the winter, the air outdoors is so cold that it has to be heated before it is brought in; and this, in any modern and properly built schoolhouse, is usually arranged for. The fresh air is drawn in through an opening in the basement and is either heated, so that it rises, or is blown by fans all over the building. This sort of fresh air, however, is never quite so good as that which comes directly from outdoors; so it is generally best to keep at least two or three windows in each room opened at the top as well, and never to depend entirely upon the air that comes through the heating system.
Sometimes this may mean a little draft, or current of uncomfortably cool air, for one or two of you who sit nearest the windows; but your teacher will always allow you to change your seat if this proves very unpleasant. If you have plenty of warmth in the room you sit in, unless the air outside is very cold, this “breeze” won’t do you any harm at all; on the contrary, it will be good for you. Instead of catching cold from a draft like this, it is from foul, stuffy, poisonous air, loaded with other people’s breaths andthe germs contained in them, that you catch cold.
A photograph of a boy planting in a gardenGARDENS TAKE US OUT OF DOORS
GARDENS TAKE US OUT OF DOORS
In fact, staying indoors is usually the reason why people are sick. They don’t go out into the clean fresh air for fear they’ll be too cold! It seems a pity we can’t just live out of doors all the time. Perhaps we shall some day; for doctors are finding out that fresh outdoor air and good food are the very best medicines known, and the only “Sure Cures.” They are pleasant to take, too. Many cities are providing outdoor schools for children who have weak lungs or are not strong in other ways. Perhaps some day all school children will be allowed to study in the open air at least part of every school day.
Now you are all ready to go to work. What are you going to work with? Books? pencils? paper? Yes, but you have something better than those and all ready for use. It is that little kit of tools that are sometimes called our “Five Senses.” You remember that we have already talked about one of them, the sense of touch in the skin. Now which one are you going to use first this morning? If your teacher talks to you, I hope it will be the one we call the sense of hearing. Suppose we try to find out something about this sense of hearing, and begin with a little experiment.
Take a piece of cork in your hand and lift it up high and then let it drop into a large basin or tub of water. What happens? The cork strikes and then goes bob-bob-bobbing up and down on its own waves. Now watch the little waves all around the cork. Where do they stop? They don’t stop until they touch the edge of the pan; and no matter how big the pan is, the waves go on and on until they reach the edge.
We can see these waves of water, and so we easily believe that they are there. Now there are, just as truly, waves of air all around us. We cannot see the waves, because they are too smalland roll too quickly. But some of these, when they roll against our ears, make us hear. They make what we callsound. You have heard about sending messages through the air, without telegraph wires. Wireless messages are often sent to ships out in the middle of the ocean. This is done by starting tiny electric waves, which travel through the air much as the waves of water are traveling across the ocean beneath. Of course there must be a machine, called areceiver, to catch the waves and “hear” the message.
Mother Nature has given each of you two very delicate little receivers to catch the sound waves and carry them to your brain. You know what they are—you can name them. But how are these wonderful little machines made?
You have never seen the whole of your ear. The part on the outside of the head, of course, you can easily see and feel. Sometimes you notice a deaf person put his hand behind his ear and press it forward so as to catch the sound waves better. These waves roll in at the little hole you can see, and travel along a short passage till they come to a rounddrum, a piece of very thin skin stretched tight like a drumhead.
Have you ever beaten a drum with a stick? You felt the drumhead quiver under the blow,did you not? Well, when the sound waves beat against the drum in the ear, it quivers and starts little waves inside the ear. Each little wave in turn beats against a little bone called thehammer; the hammer beats against another called theanvil, and this against a third called thestirrup; and the quiver of the stirrup is passed on to a little window, opening into a little room with a spiral key-board; and from this, the wave travels along a nerve to the brain. As the waves reach the brain, the brain hears. In this way we hear all sorts of sounds, from the tick of a watch to the whistle of a train.
A diagram of the structure of the ear.THE WAY BY WHICH SOUND WAVES REACH THE BRAINA section through the right ear.
THE WAY BY WHICH SOUND WAVES REACH THE BRAIN
A section through the right ear.
There is a sensible old saying, “Never put anything smaller than your elbow into the inner part of your ear.” Now, of course, you can’t put your elbow into such a tiny hole! So the old saying means, never put anything in. The eardrum is very thin and can easily be broken. Even a slap on the ear, or a loud sound too close to it,might crack and spoil the drum and make one deaf.
The outside ear needs careful washing; there are so many little creases that gather dirt and dust. The deep crease behind the ear, too, will become sore if it is not kept clean.
Besides cleaning your ears, you must train them to listen. Some boys and girls hear just a word or two of what is said, and then guess at the rest and think they are listening, or else ask to have it repeated. We should try to hear exactly what is said; and if we listen carefully, it will soon be much easier to understand at once.
Of course, if you really cannot hear, the doctor can tell you what is the matter, and usually can help you very much. Sometimes people become deaf simply because the throat is swollen. Indeed, most deafness comes from colds and catarrhs and other inflammations of the nose and throat. These spread to the ear through a little tube that runs up to the drum cavity from the back of the throat. Sometimes, when you are blowing your nose, you may feel your ear go “pop”; and that means that you have blown air up into the ear through this little tube. Be sure to see a doctor if you don’t hear well; and be sure, too, to tell your teacher, so that shemay know why it is you do not hear what she says, and ask her to give you a seat near her, so that you can hear.
Then, too, you should learn to notice outdoor sounds—the songs of the birds, the noises that the animals make, the wind in the trees, and the patter of the rain. The old Norsemen have a story that their god Heimdall had such keen ears that he could hear the grass growing in the meadow and the wool growing on the backs of the sheep! Your ears can never be so keen as that; but there are many, many happy outdoor sounds that you should listen for. They will help to make you happy, too.
Careful listening may sometime save your life. You can hear the car or the train coming, and you can learn to tell from which direction a sound comes. You can learn to tell one sound from another in the midst of many sounds. In more ways than you can think of now, this habit of listening will protect you from danger.
The Germans have a proverb, “Hear much and say little.” What does it mean?
A group of children with their teacher stand in the forest and stare at a tree.“DO YOU HEAR IT? CAN YOU SEE IT?”
“DO YOU HEAR IT? CAN YOU SEE IT?”
You can learn a great deal through your ears, but think how much more you can learn throughyour eyes. Just count over all the things that you have had to get your eyes to tell you to-day, and then shut your eyes for a minute and think what it would mean never to be able to see. Don’t you think you ought to take very good care of your eyes? You are going to keep them very busy all your life, and they deserve the very best care you can give them.
A girl reads with her back to a window.THE LIGHT ON THE PAGE, NOT IN THE EYES
THE LIGHT ON THE PAGE, NOT IN THE EYES
Just as soon as lessons begin, you get out your books; and a good share of the day in school you have a book before you, reading it or studying it or copying from it. It makes a great difference to your eyes how you hold the book and how the light falls. In reading, you should always hold your book so that the light falls upon the page from behind you, or from over one of your shoulders. In this way, the brightest light that comes into your eyes is not from the window, but from the page of your book.
If the light comes from a window in front of you, or if you sit in the evening with your face toward the lamp when you read, the light coming straight from the lamp or the window, as well as the light coming up from the pages of the book, pours into your eyes; and this dazzles and confuses your eyes, so that you can’t see plainly and comfortably and are very likely after a while to find that your head aches. At home, of course, you can seat yourself with your back to the light when you read; and usually at school your seats are so arranged that the light falls from behind you or from one side. If not, by turning a little in your seat, you can get the light from over your shoulder.
Notice how the light falls upon the blackboard. When the light comes from the windows behind you, or from one side, you can see what is written there quite plainly. But if the blackboard happens to be between two windows, and especially if this is the lightest side of the room, you will find that the light dazzles you so that you cannot see the writing clearly.
You must have noticed, too, that if, after you have been reading from the blackboard you look down again suddenly to the page of your book, for an instant you will not see the letters plainly.Then, almost before you have time to notice it, you feel a little change take place inside your eyes, and the print upon the page of your book becomes quite plain. This is because your eye has to change the shape of one of the parts inside it, called thelens, before you can see clearly the things that are near you. This change, which is calledaccommodation, is made by a little muscle of the eye; and if you keep your eyes working at close work, like reading or writing or fancy-work, too long at a time, or if your eyes need glasses to make them see clearly, and you haven’t them on, this little muscle becomes tired. Then the print of your book, or your writing, or the stitches you have taken begin to blur before your eyes. Your eyes begin to feel tired, and your head begins to ache. This is what we calleye strain.
Sometimes this eye strain upsets your appetite or your digestion and makes you sleepless and worried. The trouble may be caused by your own carelessness: you may have been reading too long, or in a poor light, or with the light shining right in your face instead of coming over your shoulder. But sometimes it is caused by the fact that your eyes are not just the right shape; and then the only way to relieve it is to have properglasses, or spectacles, fitted, which will make up for this too flat or too round shape, or too large or too small size, of your eyes.
If you cannot see clearly what is written on the blackboard when the light falls upon it from behind you, or above; or if, in a good light, you cannot read the words in your book quite easily, without straining at all, when you hold the book either at arm’s length or a foot from your face; or if your head aches or your eyes begin to feel tired or uncomfortable, or the letters begin to blur, after you have read steadily—say, for half an hour,—it is a pretty sure sign that there is some trouble with your eyes. Then you had better have them examined at once by your family doctor or by the school doctor. In many schools now there are doctors to test the children’s eyes, and ears, too, so that each child may have a chance to see and hear everything that the other children can see and hear.
Not very many years ago people thought that glasses were only for old people, but now we know that many children’s eyes need glasses, too. I knew a little girl whose sight was so poor that when she was standing and looked down at the grass, she couldn’t see the green blades. She thought that the grass looked like a green blurto everyone, just as it did to her; and so she never said anything about it. She was twelve or thirteen years old before she found out that she couldn’t see clearly. Of course, trying hard to see things gave her a headache and made her tired and cross. So some one took her to a doctor, and he saw at once what was the matter and fitted her with glasses. Soon she was quite well and strong; and how glad she was to see the leaves and a hundred other things she had not seen before!
A diagram of an eye.THE EYEBALL IN ITS SOCKETThe muscle from M to M, which helps to turn the eyeball, has been cut away to show the optic nerve.
THE EYEBALL IN ITS SOCKET
The muscle from M to M, which helps to turn the eyeball, has been cut away to show the optic nerve.
Here we have a picture of theeyeball, as we call it. The little bands fastened to it are the bands of muscle; and as soon as I saymuscleyou know what they are for—to move the eyeball about, up and down and from side to side. There are muscles outside the eye as well as inside. Coming out from the back of the eyeball is a pearly white cord quite different from the muscle bands. This is what we call anerve. This nerve in your eye carries to yourbrain, orthinking machine, picture-messages of whatever you look at.
The nerve in your eye gets messages of light much as the nerve deep in your ear gets its messages of sound—from tiny waves in the air. The light waves are smaller and faster even than the sound waves, and the eye nerve is the only nerve that can get pictures of them. You know that, for wireless messages, the receiving machines are not all alike and cannot all take the same messages, if the messages are sent with different sorts of electric waves; and neither can our receiving machines. Some get messages of sight, and some of sound, and some of touch, or taste, or smell.
Now shut your eyes as quickly as you can. How long did it take you? A minute? No, not a quarter of a second. It is about the quickest thing you can think of—“the twinkling of an eye.” You shut your eyes “quick as a wink” whenever anything seems likely to fly or splash into them, and this is what the eyelids are for. If anything gets into the eye before the lids can shut, the eye “waters,” andtearspour out of it. These are made by a gland-sponge up under the upper lid, so as to wash any dust or sand or other harmful speck out of the eye before it can hurt the sensitive eyeball.
Now look at some one’s eyeball. It is like the picture, isn’t it?—bright white around the edge and then a ring of color, brown or blue or gray; and inside the color-ring, oriris, a little round black hole that we call thepupil. Watch the little hole change as you turn the face toward the window. It becomes ever so much smaller. Now turn the face away from the window, back again into the shadow. How did the pupil change this time?
A cat in shadow and a cat in light.EYES PROTECT THEMSELVES AGAINST THE LIGHT
EYES PROTECT THEMSELVES AGAINST THE LIGHT
The iris, or color-ring, acts like a curtain, like the ring-shutter of a camera, and closes up the hole, or pupil, when the light is too bright and would dazzle or burn the inside of the eye; but when the light is dim, the iris opens again, so as to let in light enough with which to see. Look at the little window in your kitten’s eyes. It is not the same shape as yours; but when you carry her to the light, you see how the iris closes in and leaves just a little black slit or line.
You remember the blind children? Isn’t it wonderful how they can play games and study, too, even though they are blind! They have to make their senses of touch and hearing tell them many things that you learn through your sense of sight. Many of these childrenneed not have been blind, if the nurse who first took care of them when they were born had known enough to wash their eyes properly, not with soap and water, of course, but with just one or two drops of a kind of medicine—anantiseptic, as we call it—that makes the eye perfectly clean.
But you children who have good eyes that can see, do you really see things when you look at them? You can train your eyes just as you can train your ears. You can teach them to read quickly down a page, and to find things in pictures, and, better still, to see things out of doors, in the garden and the woods and on the seashore. We hear a great deal about “sharp eyes,” but most of us see very little of all we might see. Our eyes are on the lookout, too, to protect us from dangers that may come; with our skin and nose and ears, they are constantly on the watch; so the better we see the safer we are.
Even if your eyes are perfect now, you will need to take good care of them to keep themstrong. Don’t let any story, no matter how interesting it is, tempt you to read in a dim light or a light that is too strong. And if you can’t see the blackboard easily, or can’t read big print, like the school calendar, across the room, tell your mother or your teacher, so that she can ask the doctor to find out what the matter is.
It is astonishing what thirsty work studying is! Scarcely is the second recitation over before your throat begins to feel dry, and up goes your hand—“May I get a drink?”
If anyone even says the word “water,” it makes you thirsty. It is so good that just the thought of it makes you want some. I should like you to notice how much water you drink every day. Perhaps a glass in the morning when you get up, and one at night before you go to bed, and three or four in between.
Why do we need so much water? Well, how much do you weigh? Perhaps you will find it hard to believe, but more than half of that weight is water; and because we are always giving off water from the skin and from the body, we need plenty more to take its place.
No living thing can grow without water. Takea bean, for instance, and put it in an empty glass on the window sill; and even if the sun shines full upon it, nothing will happen, except that after a few days it will shrivel and dry up. But fill the glass with water, and in a few hours the bean will begin to swell; and in a few days it will burst, and a little shoot will grow out of one end of it and a tiny root at the other. The water and the warmth together have made it sprout and grow.
A sheet of paper folded into a cone.A DRINKING-CUP EASILY MADE
A DRINKING-CUP EASILY MADE
Children at school and people on trains should have their own private cups, for serious diseases may be caught from the mouths of other people. You can get a metal pocket folding cup for ten or fifteen cents, or paper ones for a few cents adozen. If you don’t have your own cup, I hope you will get one and carry it. Here is a pattern for a paper cup that you can easily make for yourselves. Try it and see. When you have once learned how, you can make it very quickly and have a fresh cup every time you want one; but of course you should be sure first that the paper itself is clean.
If you drink milk, this takes the place of some of the water and gives you food as well. It is both drink and food; and a very good food for children it is, too. You know, babies can live on it because it has everything in it to make them grow.
Do you know why it is that people are so careful nowadays about having milk and drinking-water very clean? It is because they have found that the tiny plants, called germs, that make people sick are often carried about in these drinks. A disease calledtyphoid feveris carried in this way.
Fifty years ago, cities and towns used to be very careless about where they got their water supply, and would often take it out of streams into which other cities emptied their sewage. Now, however, they are much more particular; and the health officers, or Boards of Health, are insisting that public water supply, such as isbrought into our houses in pipes, shall be taken either from some spring or deep-flowing well, or from a stream or lake up in the hills, into which no drainage from houses or farmyards, and no dirty water from factories, empties.