1. Air is always being breathed into little sacs inside the body. The sacs form the lungs.2. The red blood cells pass through the lungs, and take little loads of air. They then carry the air through the arteries to the capillaries.3. In the capillaries the air leaves the red blood cells, and goes to the cells of the body.4. The air unites with the cells, and slowly burns them to smoke and ashes.5. The smoke goes back to the blood, and is carried to the lungs and given off by the breath. The ashes go back to the blood and pass off through the skin and the kidneys.6. The burning in the cells makes heat.7. Some of the heat is changed to power, as it is in a steam engine.8. The heat also warms the body. It keeps it at the same warmth on a cold day as on a hot day.9. We wear clothes to keep the heat in, and so to keep us warm.10. The air of a room needs to be changed often. It is made stuffy by our breath.11. The voice is made by the breath in a box in the neck.12. Alcohol uses air belonging to the cells of the body.13. Tobacco smoke has the same poisons as tobacco. It can poison the whole body through the lungs.
1. Air is always being breathed into little sacs inside the body. The sacs form the lungs.
2. The red blood cells pass through the lungs, and take little loads of air. They then carry the air through the arteries to the capillaries.
3. In the capillaries the air leaves the red blood cells, and goes to the cells of the body.
4. The air unites with the cells, and slowly burns them to smoke and ashes.
5. The smoke goes back to the blood, and is carried to the lungs and given off by the breath. The ashes go back to the blood and pass off through the skin and the kidneys.
6. The burning in the cells makes heat.
7. Some of the heat is changed to power, as it is in a steam engine.
8. The heat also warms the body. It keeps it at the same warmth on a cold day as on a hot day.
9. We wear clothes to keep the heat in, and so to keep us warm.
10. The air of a room needs to be changed often. It is made stuffy by our breath.
11. The voice is made by the breath in a box in the neck.
12. Alcohol uses air belonging to the cells of the body.
13. Tobacco smoke has the same poisons as tobacco. It can poison the whole body through the lungs.
122. Waste matters.—The food is burned in the cells. As this burning goes on, thesmokegoes off by the lungs and the unburned substances, theashes, go off by the skin and kidneys. The ashes are mostly the minerals of the cells, but there are also some from the burned albumin. All these go back to the blood and are carried to the skin and kidneys.
SkinThe skin (×100).a,bandcepidermis.dandgtough and thick part of skin.esweat gland.fblood tubes.hfat pockets.
The skin (×100).a,bandcepidermis.dandgtough and thick part of skin.esweat gland.fblood tubes.hfat pockets.
123. The skin.—The skin covers the whole body. It is strong and keeps the body from being hurt.
124. The epithelium.—The skin is covered with a thin layer of cells like fine scales. These scalesare calledepithelium, orepidermis. They have no blood tubes or nerves and so have no feeling. You can run a pin under them without feeling pain. They are always growing on their under side and wearing off on their upper side. They keep the nerves and blood tubes of the skin from being hurt.
125. The nails.—The top scales of epithelium at the ends of the fingers become matted together to make the nails. The nails keep the ends of the fingers from being hurt. They can also be used to hold or cut small things. The new parts of the nails form under the skin and push down the older parts. So the nail grows farther than the end of the finger and needs to be cut off. Biting the nails leaves their ends rough. Then they may catch in the clothes and tear into the tender flesh. We ought to keep the nails cut even with the ends of the fingers.
The nails are not poisonous, but the dirt under them may be. We ought to keep them clean. Clean nails are one mark of a careful boy or girl.
126. Hair.—Some of the scales of epithelium over some parts of the body dip into tiny holes in the skin. In each hole they become matted together to form ahair. Fine short hair grows on almost every part of the body. On the topof the head it grows long and thick. When boys become men, it also grows long upon their faces. The skin pours out a kind of oil to keep the hair soft and glossy.
HairA hair (×200).athe surface of the skin.ba hair.can oil gland.da muscle to make the hair stand on end.eandg, the growing cells of the hair.ffat in the skin.
A hair (×200).athe surface of the skin.ba hair.can oil gland.da muscle to make the hair stand on end.eandg, the growing cells of the hair.ffat in the skin.
127. Care of the hair.—The hair may become dirty like any other part of the body. Brushing it takes out a great deal of dirt, but you should also wash it once a week.
The oil in the skin ought to be enough for the hair. Hair oils do not do the hair any good. If you wet the hair too often, you may make it stiff and take away its gloss. It is best to comb the hair dry. Brush it so as to spread the oil of the skin. Hair dyes are poisonous, and ought not to be used.
128. The sweat or perspiration.—The scales of epithelium dip into the skin and there line tiny tubes. The tubes form thesweat, orperspiration, out of the blood. The tubes are too fine to be seen, but they are upon almost every part of the body. They take the ashes or other waste matter or poisons from the blood and wash them out of the tubes with the perspiration. So the perspiration has two uses. First, it takes heat away from the body (see §108). Second, it gets rid of the waste matters or ashes of the body. It has very little of these at any one time, but in a day it gets rid of a great deal.
129. The kidneys.—The kidneys are close to the backbone, below the heart. They are made of tiny tubes much like the sweat tubes in the skin. The tubes take ashes and other waste matters from the blood, also a great deal of water. They also take away poisons and disease germs when we are sick. The kidneys take away about as much water as the skin, but they get rid of very much more poisons and waste matters than the skin does. If our kidneys should stop their work, we should soon die.
130. Need of bathing.—When the perspiration dries from the skin, it leaves the waste and poisons behind. We cannot always see the dried matters, but they always have an unpleasant odor. Weshould bathe often enough to keep our body from having an unpleasant smell. We should wash the whole body with soap and hot water at least once a week in winter and more often than that in summer.
Another reason for bathing is to wash disease germs from the body. Most dirt has disease germs in it. Disease germs also float in the dust of the air and stick to our skin when we go into a dusty room. If our skin is dirty, some of the germs may be carried into our flesh when our skin is pricked, or scratched, or cut. We sometimes catch boils, or erysipelas, or lockjaw, from very little wounds in a dirty skin. Cleanliness of our skin helps to keep us from catching diseases.
131. Cold baths.—Sometimes we bathe when we are clean so as to get refreshed. If we bathe in cold water, we feel cold at first. In a little while we feel warm again. Then we feel stronger, and refreshed for work. If we stay in the bath too long, we become cold again and feel weak. When boys go in swimming, they ought to come out before they begin to feel cold.
It is a good plan to take a cold bath every morning when you get up, even if you use only a wash-bowl with a little water. It will take only a few minutes, but will keep you clean and make you feel more like doing your day's work.
132. A fair skin.—We must wash often, to make the skin fair and smooth. Use enough good soap to keep the skin clean.
If you eat as you should, and digest the food well, your skin will have the least amount of waste to give off. Then it will look well. A bad looking skin is due to bad food and to bad digestion. If you do not digest your food well, you cannot have a fair skin.
Face paint and powder make the skin look worse, for they hinder perspiration. Nothing of that sort will do the skin any good. You must eat as you should, and you must keep clean. Then your skin will be clear.
133. Washing clothes.—Our clothes rub off a great deal of the perspiration and waste. They become soiled. A great deal of dirt also gets upon the sheets of our beds. Our clothes need to be washed as well as our bodies when they are soiled. Air and the sun as well as water destroy the waste of the body. Our clothes need to be aired at night, and the bed and bedroom should be aired through the day.
134. Slops.—After water has been used to wash our body or our clothes it is dirty and is not fit to be used again. It must not be thrown where it can run into a well. If a person has typhoid fever orcholera or other catching disease, the water may carry germs of the disease to the well, and so other persons may get it. Slops from the house should not be poured out at the back door, but they should be carried away from the house. In cities the slops are poured into large pipes and tunnels underground. These pipes are calledsewers. They empty outside the city.
135. Alcohol and the skin.—Alcohol interferes with digestion and causes biliousness. This makes the skin rough and pimply. A drinker seldom has a clear skin.
Alcohol causes the arteries of the face to become enlarged. Then the face is red. A red nose is one of the signs of drinking. When a person uses strong drink he is often uncleanly. He does not care for the bad looks of his clothes and skin, and so he lets them stay dirty. This harms the skin and makes it look bad. The dirt also poisons the skin and may itself be a cause of sickness.
Because alcohol poisons the whole body and often produces kidney diseases, the drinker is apt to catch other diseases. Drinkers are the first to catch such diseases as smallpox and yellow fever. Where there are great numbers of cases, the drinkers are the first and often the only persons to die. This is because their skin and kidneyshave been harmed by the alcohol and cannot throw off the poisons of the disease. Any kind of sickness will be worse in a drinker. Surgeons do not like to operate on drinkers, for their wounds do not heal so quickly as in other people.
When there is too little air, a fire burns slower, and makes a blacker smoke and more ashes. Alcohol takes some air from the cells of the body. So they burn with smoke and ashes of the wrong kind. The skin has to work harder to get rid of these, and sometimes it cannot do it well. Then the body is poisoned. The alcohol is burned and cannot poison the body any more. But it causes the body to make poisons, and so it is to blame. The poisons do great harm to the skin and kidneys. Alcohol causes more kidney disease than all other things put together.
1. Little tubes in the skin are always giving off ashes and waste matters in the perspiration.2. Perspiration dries on the skin. So the skin must be washed often.3. The kidneys get rid of more water and waste matter than the skin does.4. Perspiration also gets upon the clothes and bed sheets. These must be washed too.5. Dirty water from washing should be thrown out where it cannot run into a well.6. The skin is thick and strong and keeps the body from being hurt.7. The skin is covered with a layer of scales. The scales have no feeling.8. The scales form the nails on the ends of the fingers.9. The scales also form the hair.
1. Little tubes in the skin are always giving off ashes and waste matters in the perspiration.
2. Perspiration dries on the skin. So the skin must be washed often.
3. The kidneys get rid of more water and waste matter than the skin does.
4. Perspiration also gets upon the clothes and bed sheets. These must be washed too.
5. Dirty water from washing should be thrown out where it cannot run into a well.
6. The skin is thick and strong and keeps the body from being hurt.
7. The skin is covered with a layer of scales. The scales have no feeling.
8. The scales form the nails on the ends of the fingers.
9. The scales also form the hair.
136. Need of nerves.—The cells of the mouth, stomach, and intestine digest food; the cells of the liver change the food to blood; the cells of the heart pump the blood to feed all the cells of the body; the red blood cells carry air for the cells to breathe; and the cells of the skin and kidneys carry away the waste of the rest of the cells. Each set of cells works for all the rest. If the cells of the body were only tied together, each one would do as it pleased, and no two would work together. But something tells each cell of the body to work with the others. The cells all obey the mind. A tiny thread goes to each cell of the body. Each thread is anerve. The mind and the cells signal to each other over the nerves. By means of the nerves the mind makes the cells work together.
A nerveA nerve thread (×400).acentral conducting fiber.bcovering of fat.
A nerve thread (×400).acentral conducting fiber.bcovering of fat.
A sliced nerveA thin slice for the end of a cutnerve (×200).anerve thread.bconnective tissue binding thethreads into a cord.
A thin slice for the end of a cutnerve (×200).anerve thread.bconnective tissue binding thethreads into a cord.
137. Nerve messages.—The nerve threads run in bundles and form nerves large enough to be seen. The mind uses the nerves to tell the cells to do work. It tells the muscles to move the arms and legs. It tells the heart to beat and stomach to pour out gastric juice; and it tells each of the cells to eat.
The cells also send word over the nerves to the mind. They tell the mind when they are touching anything, and whether it is hard, or smooth, or hot, and many other things about it. The cells also tell the mind if they need more food, or are tired.
The nerves are always carrying messages to and from the cells. The cells depend upon these messages to tell them when and how to work. If the nerve of any part of the body is hurt or cut, we cannot feel with the part or move it, and its cells do not act in the right way. We do not feel the nerves while they are carrying the messages. We wish the cells of the arm to work, and they work, but we do not feel the message as it goes from the mind to the cells of the arm.
The spinal cordA thin slice from the spinal cord with thecells and nerves magnified 200 diameters.acells in the gray matter.bfibers in the gray matter.cnerve threads in the white matter.
A thin slice from the spinal cord with thecells and nerves magnified 200 diameters.acells in the gray matter.bfibers in the gray matter.cnerve threads in the white matter.
138. The spinal cord.—The nerves start inside the backbone. The backbone is hollow. It has a soft, white cord inside, as thick as the little finger. Part of the mind lives in this cord. The cord is called thespinal cord. Some of the nerves start from cells of the spinal cord. These cells send word to the muscles to move and to all the cells of the body to eat and grow. They also send word to the arteries to carry the right amount of blood to the cells.
From the nerves the spinal cord gets word when something hurts any part of the body. You may put your finger on a sharp pin. The spinal cord feels the prick, and quickly sends word to snatch the finger away. So the finger is taken away before you really feel the prick. When some one sticks a pin into you, you cannot help jumping. This is because the spinal cord sends word for you to jump away from the pin before it can harm you much. Thus the spinal cord keeps the body from being hurt. It acts while we are asleep as well as when we are awake.
139. Need of a spinal cord.—We do not feel the spinal cord acting, and we cannot keep it from acting. It tells the cells when to eat and grow, and it tells the heart and arteries how much blood to send to each cell. If we had to think about feeding an arm or a leg, we should sometimes forget it, but the spinal cord keeps doing it without our thinking of it. We put food into the body, and the spinal cord tells the cells to use it. If it stops acting for an instant, the cells stop work and we die. We cannot change its action by any amount of thinking.
The human headRegions of the head and action of the different partsof the brain.
Regions of the head and action of the different partsof the brain.
140. The brain.—The nerves of the body go to the brain as well as to the spinal cord. The brain lies in the top of the head. A hard cover of bone keeps it from getting hurt. It is a soft white mass, and weighs about three pounds. Its outside is made of cells, while its inside is the very beginning of the nerves of the body.
141. The mind.—The mind is the real man. It is the thinking part of himself. It lives in the body and works by means of the cells of the brain. If these cells are hurt or killed, the body seems to have no mind, but yet it may keep on living. If all the mind leaves the body, the body is dead.
By means of the mind we feel, and know, and think. The mind uses each part of the brain for only one kind of work.
142. The senses.—The cells of the body send word to the brain over the nerves. The eye tells of sight, the ear of sounds, the nose of odors, the mouth of tastes, and the skin of feelings. All these messages go to the back part of the brain. They tell the mind of the news outside of the body. We get all our knowledge in this way. The cells also tell of their need of food and drink by means of the feelings of hunger and thirst.
143. Motion.—The mind in the cells of the top part of the head sends the orders for moving thedifferent parts of the body. When we wish to run, the mind in the top of our head sends an order over our nerves to our legs, and they carry the body where we wish. If the top part of your brain is hurt, as by a blow, it cannot send orders to move, but you will lie stunned.
144. Memory.—The mind lays away all its messages, and often looks them over again. These old messages are calledmemories. They always stay with the brain, and the mind can call them up at any time. Our memories make our knowledge.
Every act of the mind leaves some mark on the memory. We may not be able to bring it back when we want to, but it will come back some time. Every bad word and evil deed will tend to come back and make us bad again. Every good work and word will leave its memory and make us better. We ought to fill our minds with good memories.
145. Thinking.—The brain also thinks. Thinking is different from feeling and from moving, but we can think about our feelings and about our movements. The brain just back of the forehead does all our thinking. A dog has only a little forehead, and cannot think much. But the rest of its brain is large, for it can see and hear and run as well as a man. A baby can see and hearand move, but it cannot think until it is taught how. Boys and girls go to school to learn to think. Thinking is work, just as truly as running is work. At school, no one can learn to think without working. Looking at things and hearing some one talk about them will not make you a strong-minded man, but thinking about these things will. Boys and girls should study and think, as well as look around and listen.
146. How thought rules the body.—We are always feeling and moving. We often do these things without trying, but we must make ourselves think. We can make our bodies move, or keep still, and we can keep from too much feeling. Our thoughts direct our natural desires to move and feel. In an animal, the feelings and movements direct the thoughts. When men let their feelings rule their thoughts, they are like animals. When the thoughts control the feelings and acts, we are men. If you get angry and cry, when you hurt your finger, then you are like an animal; but if you think about it and control your feelings, you are behaving like a strong and noble man. The thought part of the brain ought to rule all the rest.
147. Sleep.—Most of the brain does its work without our knowing it, but we know when wethink. The thinking part of the brain gets tired, like any other part of the body. When it stops work, we are asleep.
We must give the brain a rest in sleep, just as we must rest an arm or a leg. We ought to give it regular rest. Every night we ought to go to bed early. Then we shall be ready to get up early and shall feel like working. Boys and girls need nine or ten hours' sleep each day. When they are grown, they need seven or eight hours' sleep each day.
The spinal cord and some parts of the brain must always stay awake to make the cells of the body eat and grow. When we are asleep, they must be wide awake, and must repair the worn-out parts. They do not seem to rest at all. If they rested for any length of time, then the lungs, heart, stomach and all other parts of the body would stop work, and we should die. But they really rest a part of the time. Like the heart, they act for a second, and then stop for a second. They seem to act all the time, but in all they rest half the time.
148. Worry.—The mind can do a great deal of work, if it gets good sleep. If a person gets enough sleep and rest, he cannot harm his mind by hard work. Sometimes the mind is troubled and worried over a danger or a loss. Thenit cannot rest, but soon wears itself out. Worry is far more tiresome than hard work. By an effort, we can keep from worrying. It never does us good to worry, and we ought to keep from it.
149. Nervousness.—The thoughts are able to rule all the rest of the mind. They can keep us from feeling ill-tempered when we cannot have our own way. Sometimes a little unpleasant feeling makes us very unhappy, and keeps us from thinking about our work. A little noise or pain keeps some children from study, while others can bear a great deal without being disturbed by it. Some persons jump at a little noise, and are afraid of a tiny bug or mouse. This is because their feelings rule their thoughts. Such persons are callednervous.
A nervous person is very uncomfortable and makes others so too. Yet any one can get over the habit of being nervous, if he will try. You ought not to laugh at a nervous person if he is afraid of some little thing while you are not. You should help him to get over his nervousness and to become brave.
150. Fear.—Some persons are always brave. In danger they calmly stop to think, and then know how to save themselves. A timid person does not think, but rushes where his feelings lead. Whena crowd is in danger, all will rush to do one thing. All will run for a door, and perhaps tread on one another. Then some one will surely be hurt. At a fire, or in any other danger, you should always stop to think how to act. If you rush with the crowd, you may be hurt. You will be more likely to be safe, if you stay away from them. Then, if help comes, you will be able to receive it. Besides, if you are cool and brave, you will help others around you to be brave too.
151. Fire drill.—In schools the children are taught how to go out of the building when there is a fire. A bell is struck when the children do not expect it. Then every child must leave his seat at once and march out of the building. The bell is struck every few days. Then, when the bell really sounds for a fire, the children know how to march out quickly, and so they learn to be brave.
By training we can learn to be brave at all times. We fear many harmless things, and in many cases do not fear real dangers. We are liable to be hurt at any time. We are more liable to be hurt by a horse when we are out driving than we are by the dark. Yet we do not fear the horse, while some do fear the dark. We ought to learn to think, so as to control our fear.
Some are afraid of the dark, some are frightenedby ghost stories, and others expect to see a wild animal jump from behind every bush. No one fears these things unless he has been told about them. We ought to be careful not to tell children of these things. We ought to teach them to control their fear.
152. Habit.—After we have thought about a thing a few times, its hold on our memory becomes strong, and leads us to think about it often. When we have done a thing a few times, we are likely to do it again without knowing it. We call this doing things over againhabit. When we once form a habit, we find it very hard to break. We can form habits of doing right or of doing wrong. We can get into the habit of swearing or of drinking by doing these things a few times. Then we shall do these things when we do not want to. When a drinker begins, he does not expect to keep on drinking. But his habit makes him drink, and he cannot help it. We should be careful not to do bad things, for we easily form the habit of doing them.
153. Good habits.—We can form habits of doing right. We can speak kindly and be generous. Then we shall do these things as easily as others get cross. After a person has tried to do good a few times, he will find it much easier to do good.Then he will speak kindly and give generously just as easily as others get angry and keep their good things to themselves.
154. Alcohol takes away thought.—Alcohol affects and weakens the cells of the brain sooner than it does those of any other part of the body. It first makes the thought cells weak. Then a person does not think how he acts. He lights his pipe in the barn and throws the match in the hay. He drives his horse on a run through a crowded street. He swears and uses bad language. He gets angry at little things and wants to fight. He seems to think of himself, and of no one else. He is happy, for he does not think of the bad effects of the drink. He has a good time, and does not care for its cost. He likes to drink, because it makes him feel happy.
155. Alcohol spoils motion.—Some cells of the brain cause the arms and legs, and all other parts of the body, to move. Alcohol next makes these weak. Then a person cannot move his legs right, but he staggers when he walks. He cannot carry a full cup to his lips. His hands tremble, and he cannot take care of himself. He is now really drunk.
156. Alcohol takes away feeling.—After a man is drunk, he loses the sense of feeling. He does notfeel cuts and blows. Because he does not feel tired, he feels very strong. He often sees two things for one, and hears strange noises. The whole brain at last gets weak, and cannot act. Then the drinker lies down in a drunken sleep, and cannot be waked up. Some die in this state.
157. Insanity.—When the brain is misused by alcohol for some time, it cannot get over it. Then the person becomes insane. Drink sends more persons to the insane asylum than all other causes put together.
158. Delirium tremens.—If a drinker gets hurt, or becomes sick, he sometimes has terrible dreams. In them he sees dirty and savage animals coming to harm him. These dreams seem very real to him, and he cries out in his fright. This is calleddelirium tremens. A person is liable to die from it.
159. Alcohol harms a drinker's children.—The children of drinkers are apt to be weak in body and mind. A drinker hurts his children even more than he hurts himself. They are liable to catch diseases, and are often cross and nervous, or weak-minded. It is a terrible thing for a man to make his children weak and nervous.
160. Other bad things about drink.—There are many other terrible things about drink, besides the harm it does a man's body. Many a man hasmade himself drunk so as to steal or kill. No man can drink long without becoming a worse man for it. Men will not trust him, and he loses the respect of his friends.
Making strong drink takes thousands of men away from good work. They might work at building houses, or raising grain, or teaching school. As it is, their work is wasted.
A great deal of money is wasted on strong drink. All the mines of the world cannot produce enough gold and silver to pay the drink bill. The people of the United States pay more for strong drink than for bread.
The price of two or three drinks a day would amount to enough, in ten years, to buy a small home.
The cost of strong drink is made much greater if we count the cost of jails and insane asylums. Over one half of all crimes and cases of insanity are caused by strong drink.
We must also add the misery and suffering of most children of drunken fathers. This loss cannot be counted in money. Numbers of children become truants from school and learn theft and falsehoods from lack of a father's care. When all the cost is counted, nothing will be found so expensive as strong drink.
On the other hand, what do people get for their money and suffering? They get only a little pleasure, and then they are ashamed of it. Men use strong drink only because they like it more than they dislike its bad effects.
Since drink does a great deal of harm, with no good to any one, it is right to make laws to control its sale.
161. How tobacco affects the brain.—Some men smoke to make themselves think, and some to keep themselves from thinking. Now, smoking cannot do both things. It really makes the brain less able to think, for it weakens the whole body. A school-boy's brain will surely be harmed if he uses tobacco at all.
1. The mind makes all the cells of the body work together.2. Tiny nerve threads carry messages from the mind to the cells.3. Most of the nerves begin at the spinal cord in the backbone.4. The mind in the spinal cord tells the cells to eat and grow. It tells the arteries how much blood to carry to the cells.5. The cells tell the spinal cord if they need food,or if something suddenly hurts them. The spinal cord sends word to snatch the part from danger.6. Nerves carry to the brain news of sight, sound, odor, taste, and touch.7. The brain sends word to the muscles to move the arms, the legs, and the rest of the body.8. The brain thinks.9. The brain stores up all its messages; these make memory and knowledge.10. The thought part of the brain can control the feelings and the movements of the body.11. Alcohol is more harmful to the brain than to any other part of the body.
1. The mind makes all the cells of the body work together.
2. Tiny nerve threads carry messages from the mind to the cells.
3. Most of the nerves begin at the spinal cord in the backbone.
4. The mind in the spinal cord tells the cells to eat and grow. It tells the arteries how much blood to carry to the cells.
5. The cells tell the spinal cord if they need food,or if something suddenly hurts them. The spinal cord sends word to snatch the part from danger.
6. Nerves carry to the brain news of sight, sound, odor, taste, and touch.
7. The brain sends word to the muscles to move the arms, the legs, and the rest of the body.
8. The brain thinks.
9. The brain stores up all its messages; these make memory and knowledge.
10. The thought part of the brain can control the feelings and the movements of the body.
11. Alcohol is more harmful to the brain than to any other part of the body.
162.A man has five ways of knowing about things outside of the body. He can feel, see, hear, smell, and taste.
163. Feeling.—Nerves go to nearly every cell in the body. They carry news to the brain when anything touches them. The news produces a feeling. Feelings are of three kinds:—
First, when anything touches the cells without harming them, we feel atouch. We feel a touch by nerves in the skin. Those in the ends of the fingers and tongue can feel the best. Those upon the back give but little feeling.
Touch tells whether anything is hard, or rough, or round, or square, or has other qualities and shapes.
Second, when anything touches the bare nerves or hurts the cells, we feel apain. We can feel a pain anywhere in the body. Pain tells us if we are being harmed. If we had no feeling of pain, we might be killed before we could know of our danger. Pain warns us away from danger.
Third, we can feelheatandcold. Anything very hot or very cold, however, makes only a pain and gives no feeling either of cold or of heat.
164. Sight.—We see with our eyes. An eye is a hollow ball. In its front is a clear window. Behind the window is a round curtain with a round hole in its middle. When we speak of the color of the eye, we mean the color of this curtain. Light passes through the hole in the curtain and falls upon some nerves in the back of the eyeballs. There it forms a picture like a photograph. The nerves carry this picture to the brain, and we see it.
An eyeThe human eye.abony case of the eye.elining or seeing part of the eye.bmuscle to move the eye.feyelid.gcolored curtain or iris.canddcoverings of the eye.handiclear windows of the eye.
The human eye.
165. Movements of the eyes.—We can turn our eyes so as to look in any direction. Sometimes a person has one eye turned sidewise. Such a person is cross-eyed, and sees well out of only one eye at a time. Glasses may help the eyes, but sometimes a surgeon has to cut a tiny muscle.
166. Coverings of the eyes.—The eyeballs lie in a bony case, upon a soft bed of fat. In front each is covered with two lids. We can shut the lids to keep out dust and insects. When we are sleepy, they come together and cover the eyes. Little hairs at their edges help to keep out the dust.
Sometimes a little dirt gets under the lids. Then the eye smarts or itches, and we want to rub it; but this may grind the dirt in deeper. Then you should get some one else to lift your eyelid and pick out the dust with a soft handkerchief. If you cannot get help, lift the lid by the eyelashes; blow your nose hard, and the tears may wash the dirt away.
Dust and disease germs may get into our eyes and make them sore and red. You should bathe your eyes well every time you wash your face. You should use a clean towel, for a dirty one may carry disease germs to your eyes. Some forms of sore eyes are catching. If any one has sore eyes, no one else should use his towels or handkerchiefs.
167. Tears.—Clear salt water is always running over the eyes and down a tube into the nose. The use of this water is to bathe the eyes and keep them clean. It sometimes runs over the lids in drops calledtears.
168. How to use the eyes.—If using your eyes makes them painful or gives you a headache, you are straining your eyes. Facing a bright light strains the eyes. Shade your eyes while you study. A cap may be used as a shade if you cannot get anything else. Never try to look at the sun or a very bright light. You should have the light at one side or behind you. The light should be steady. Reading in a dim light will harm the eyes.
169. Near sight.—If you cannot read without holding your book less than a foot from your eyes, you are nearsighted, and should wear glasses all the time. If you do this, your eyes may be strong, and you may be able to see well.
170. Far sight.—If you cannot read without holding your book at arm's length, you are farsighted and need glasses. Most old persons are farsighted.
171. Alcohol and the eyes.—Alcohol makes the eyes red. It weakens the eyes and may produce blindness. A drunken person often sees double.
172. Tobaccocauses dimness of sight and sometimes produces blindness.
173. Hearing.—We hear with the ears. Sound is made by waves in the air. The part of the ear on the outside of the head catches the air waves and throws them inside the ear. These air waves strike against a little drum. Three little bones then carry the waves on to nerves farther inside the head. Animals can turn their ears and catch sound from any direction.
An earDiagram of the ear.aouter ear.fgandhinner ear.bdrum head.itube to the mouth.cdandebones to carry sound to inner ear.jmiddle ear.
Diagram of the ear.
174. Ear wax.—Wax is formed just inside the ear. It keeps flies and insects from crawling into the ear. Boys in swimming sometimes get cold water into their ears. This may make them have an earache.
175. How the throat affects the ear.—An air tube runs from the inside of the ear to the mouth. Sometimes when you blow your nose, you blow air into the ear. This makes you partly deaf and you hear a roaring in your ears.
Sometimes when you have a cold in your throat, this little tube is stopped. Then your ear may ache and may even discharge matter. This may make you somewhat deaf. Earache and deafness are most often due to a cold in the throat and a stoppage of this tube.
Many little boys and girls are deaf and do not know it. They cannot hear the teacher well, and sometimes the teacher thinks they are bad or careless because they do not answer.
176. Care of the ears.—Very loud noises may harm the ear and make you deaf. When you expect a very loud noise, put your fingers in your ears to shut out the sound.
Boxing the ears may break their tiny drums and make you deaf.
Do not get cold water in your ear. This may cause an earache and make you deaf. If you get water in your ear while you are in swimming, turn your head to one side and shake it. This will get the water out.
Do not put cotton or anything else into your ears.
177. Smell.—We smell with the nose. Some things give out a vapor to the air. When we draw the air into the nose, this vapor touches the nerves, and we perceive a smell. The nerves are high up in the nose. In order to perceive smell clearly, we sniff the air far up the nose.
178. Use of smell.—Bad air and spoiled food smell bad. A bad smell is the sign of something spoiled. The sense of smell tells us when food or air is unfit for use. Some people try to hide a bad smell with perfumery. To do this only makes the danger greater, for then the smell does not tell us of the danger of food or air.
Some animals can smell much better than a man. A dog will smell the track of a wild animal hours after it is made. Savages can smell much better than civilized men.
179. Taste.—We taste with the tongue. Dry food has no taste, but it must first dissolve in the mouth. Spoiled food tastes bad. Bad-tasting food is not fit to eat. Taste tells us whether food is good or bad.
We can learn to like the taste of harmful things. At first no one likes tobacco or strong drink, but the liking is formed the more one uses these. We ought to be careful not to begin to use such things.
Alcoholandtobaccoburn the mouth and harm the taste. Food does not taste so good and we may eat spoiled food and not know it.
1. We can feel in every part of the body, but mostly in the ends of the fingers.2. Light makes a picture upon the nerves inside of the eye.3. If the eyes ache, the light should be softened or the position of the book or work changed, or else the eyes should be rested.4. Sound in the air goes into the ear and strikes against a drum. Bones then carry the sound to the ear nerves.5. Air snuffed up the nose gives the sense of smell. Smell tells us if the air or food is fit for use.6. Taste tells us whether food is fit for use. Men can learn to like the taste of wrong things like tobacco or alcohol.
1. We can feel in every part of the body, but mostly in the ends of the fingers.
2. Light makes a picture upon the nerves inside of the eye.
3. If the eyes ache, the light should be softened or the position of the book or work changed, or else the eyes should be rested.
4. Sound in the air goes into the ear and strikes against a drum. Bones then carry the sound to the ear nerves.
5. Air snuffed up the nose gives the sense of smell. Smell tells us if the air or food is fit for use.
6. Taste tells us whether food is fit for use. Men can learn to like the taste of wrong things like tobacco or alcohol.
A human skeletonThe Human Skeleton, showing position of bones.
The Human Skeleton, showing position of bones.
180.Bones make the body stiff and strong, and give it shape. Long bones reach through the arms and legs, and little bones reach down the fingers and toes. Rounded plates of bone form the head, and a pile of bony rings makes up the backbone. Each bone is built to fit exactly into its own place and to do its own work. In all there are over two hundred bones in the body. They form one seventh of its weight.
181. Form of bones.—A bone is not like a solid piece of timber, but is hollow like the frame of a bicycle. This makes it strong and light. At its ends a bone is like a hard sponge covered with a firm shell. This makes it too strong to be easily crushed, and keeps it light.
A bone grows like any other part of the body. It is made of living cells like woven threads. Lime is mixed among the cells, and makes them stiff like starch among the threads of a linen collar. Blood tubes go through every part of the bone so as tofeed the cells. The living cells form one third of the bone, while the lime forms two thirds.
182. Broken bones.—Bones are very hard, and yet they can bend a little without breaking. Most of them are curved a little, and so they will spring instead of breaking when they are pressed hard. But sometimes they break. Then a person must wear a splint and bandage to keep the bones in place until they grow together again. The living cells will mend a bone in about a month.
An old person's bones are more tender than a child's, and will not spring much without breaking. An old man is afraid of falling and breaking his bones, while a child falls a dozen times a day without danger.
The bones of some children bend too easily. When they stand, the bones of their legs bend a little. After a while they grow in the crooked shape, and the child is bow-legged.
183. Joints.—Some bones are hinged upon each other. A bone hinge is ajoint. The rings of the backbone are held together by very tough pads of flesh. Each pad lets the backbone bend only a little, but altogether they let us bend our backs in any direction. These pads are like rubber springs in a wagon, and keep our bodies from being jarred too much.
The finger and toe joints, the wrists and ankles, the elbows and the knees, bend back and forth like a hinge. Tough bands of flesh bind the bones together. The ends of the bones are rounded and smooth. They fit together and make perfect hinges. The joints are oiled by a fluid like the white of an egg. In old people this fluid sometimes dries up. Then the joints become stiff, and creak like a squeaking hinge.