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diff --git a/32251.txt b/32251.txt new file mode 100644 index 0000000..1e6ca33 --- /dev/null +++ b/32251.txt @@ -0,0 +1,4161 @@ +The Project Gutenberg eBook, Applied Physiology, by Frank Overton + + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + + + + +Title: Applied Physiology + Including the Effects of Alcohol and Narcotics + + +Author: Frank Overton + + + +Release Date: May 4, 2010 [eBook #32251] + +Language: English + +Character set encoding: ISO-646-US (US-ASCII) + + +***START OF THE PROJECT GUTENBERG EBOOK APPLIED PHYSIOLOGY*** + + +E-text prepared by Larry B. Harrison and the Project Gutenberg Online +Distributed Proofreading Team (http://www.pgdp.net) + + + +Note: Project Gutenberg also has an HTML version of this + file which includes the original illustrations. + See 32251-h.htm or 32251-h.zip: + (http://www.gutenberg.org/files/32251/32251-h/32251-h.htm) + or + (http://www.gutenberg.org/files/32251/32251-h.zip) + + +Transcriber's note: + + Text enclosed between equal signs was in bold face + in the original (=bold=). + + + + + +APPLIED PHYSIOLOGY + +Including the Effects of Alcohol and Narcotics + +by + +FRANK OVERTON, A.M., M.D. + +Late House Surgeon to the City Hospital, New York + +Primary Grade + + + + + + + +New York Cincinnati Chicago +American Book Company + +Copyright, 1898, 1910, by +Frank Overton + +OV. PHYSIOL. (PRIM.) +E-P 42 + + + + +PREFACE + + +This primary text-book of applied physiology follows a natural order +of treatment. In each subject elementary anatomical facts are +presented in a manner which impresses function rather than form, and +from the form described derives the function. The facts and principles +are then applied to everyday life. Anatomy and pure physiology make +clear and fix hygienic points, while applied physiology lends interest +to the otherwise dry facts of physiology and anatomy. From the great +range of the science there are included only those subjects which are +directly concerned in the growth and development of children. + +The value of a primary book depends largely upon the language used. In +bringing the truths within the comprehension of children, the author +has made sparing use of the complex sentence. He has made the +sentences short and simple in form, and logical in arrangement. + +A child grasps new ideas mainly as they appeal directly to the senses. +For this reason, physiological demonstrations are indispensable. +Subjects for demonstrations are not given, because they cannot be +performed by the children; but the teacher should make free use of the +series given in the author's advanced physiology. + +Cuts and diagrams are inserted where they are needed to explain the +text. They are taken from the author's _Applied Physiology, +Intermediate Grade_. Each was chosen, not for artistic effect, but +because of its fitness to illustrate a point. Most of the cuts are +adapted for reproduction on the blackboard. + +The effects of alcohol and other narcotics are treated with special +fulness. The subject is given a fair and judicial discussion, and +those conclusions are presented which are universally accepted by the +medical profession. But while this most important form of intemperance +is singled out, it should be remembered that the breaking of any of +nature's laws is also a form of intemperance, and that the whole study +of applied physiology is to encourage a more healthy and a more noble +and self-denying mode of life. + + + + +CONTENTS + + + CHAPTER PAGE + + I. CELLS 7 + + II. OF WHAT CELLS ARE MADE 10 + + III. DIGESTION OF FOOD IN THE MOUTH 13 + + IV. DIGESTION OF FOOD IN THE STOMACH 17 + + V. FOODS 23 + + VI. TOBACCO 31 + + VII. FERMENTATION 37 + + VIII. KINDS OF STRONG DRINK 42 + + IX. THE BLOOD 49 + + X. BREATHING, HEAT, AND CLOTHING 59 + + XI. THE SKIN AND KIDNEYS 75 + + XII. THE NERVES, SPINAL CORD, AND BRAIN 84 + + XIII. THE SENSES 100 + + XIV. BONES AND JOINTS 109 + + XV. MUSCLES 115 + + XVI. DISEASE GERMS 123 + + XVII. PREVENTING SICKNESS 132 + + INDEX 139 + + + + +APPLIED PHYSIOLOGY + + + + +CHAPTER I + +CELLS + + +Our body is made of many parts. Its head thinks. Its legs carry it, +and its arms and hands take hold of things. The leg cannot do the work +of the arm, nor the head do the work of the hand; but each part does +only its own work. + +=1. The simplest animal.=--Some animals have parts like a man's; but +these parts are fewer. No animal has arms or hands like a man. A fish +has little fins in place of legs and arms, while a worm has not even a +head, but only a body, and yet it moves. An oyster has only a body and +cannot move. The simplest of all animals is very small. A thousand of +them would not reach an inch. Yet each is a complete animal. It is +called the _ameba_. It is only a lump of jelly. It can put out any part +of its body like an arm and take a lump of food. This same arm can eat +the food, too. It can also put out any part of its body like a leg and +move by rolling the rest of its body into the leg. It can do some things +better than a man can do them, for any part of its body can do all kinds +of work. So the ameba grows and moves and does as it likes. + +[Illustration: =Different forms of an ameba (x400).=] + +[Illustration: =Cells from the human body (x200).= + + _a_ A colored cell from the eye. + _b_ A white blood cell. + _c_ A connective tissue cell. + _d_ A cell from the lining of the mouth. + _e_ Liver cells. + _f_ A muscle cell from the intestine.] + +=2. Cells.=--A man's finger moves and grows something like a separate +animal, but it must keep with the rest of the body. A little piece of +a finger moves and grows, too. If you should look at a finger, or any +other part of your body, through a microscope, you would see that it +is composed of little lumps of jelly. Each little lump looks like an +ameba. We call each lump a cell. The cells make up the finger. + +=3. What cells do.=--Each cell acts much as an ameba does. From the +blood it gets food and air and takes them in through any part of its +body. It also grows and moves. But the cells are not free to do as +they wish, for they are all tied together in armies by very fine +strings. We call these strings _connective tissue_. One army of cells +makes the skin, and other armies make the bones and flesh. Some armies +make the fingers, and some the legs. Every part of our body is made up +of armies of separate cells. + +=4. The mind.=--The body is a home for the mind. The cells obey the +mind. The mind pays the cells by feeding them and taking good care +of them. When an army of cells is hurt, the body feels sick, and +then the mind tells the whole body to rest until the cells are well +again. When we study about a man's body, we learn about the separate +cells in his body. + + +WHAT WE HAVE LEARNED + + 1. Our body is made up of many small parts. + + 2. The smallest parts are each like a little animal, and are + called _cells_. + + 3. Each cell eats and grows. + + 4. One army of cells makes a finger and another a leg, and so on + through the body. + + 5. The mind lives in the body. + + 6. The mind takes care of the cells. + + + + +CHAPTER II + +OF WHAT CELLS ARE MADE + + +The cells of our body are made of five common things. You would know +all these things if you should see them. + +=5. Water.=--The first thing in the cells is _water_. Water is +everywhere in the body. Even the teeth have water. Most of our flesh +is water. Without water we should soon shrink up. Our flesh would be +stiff like bone and no one could live. + +[Illustration: =The body is made of these five things.=] + +[Illustration: =Fat tissue (x100).= The liquid fat is stored in living +pockets.] + +=6. Albumin.=--_Second_, next to water, something like the white of an +egg makes the most of the body. The white of an egg is _albumin_. +When dried it is like gelatine or glue. Albumin makes the most of the +solid part of each cell. Lean meat and cheese are nearly all albumin. +When it is heated it becomes harder and turns white. The word albumin +means white. Dry albumin is hard and tough, but in the living cells it +is dissolved in water and is soft like meat. It is the only living +substance in the body, and it alone gives it strength. + +=7. Fat.=--_Third_, next to albumin, the most of the body is fat. Fat +does not grow inside the cells of the body, but it fills little +pockets between the cells. Fat does not give strength. It makes the +body round and handsome. It also makes the cells warm and keeps them +from getting hurt. + +=8. Sugar.=--_Fourth_, sugar also is found in the body. Sugar is made +out of starch. When we eat starch it changes to sugar. Starch and sugar +are much alike. We eat a great deal of starch and sugar, but they are +soon used in warming the body. Only a little is in the body at once. + +=9. Minerals.=--_Fifth_, there are also some minerals in the body. +When flesh is burned they are left as _ashes_. Salt, lime, iron, soda, +and potash are all found in the body. + +[Illustration: =Starch grains (x400).= + + _a_, of potato. + _b_, of corn.] + +Everything in the body is either water, albumin, fat, sugar, or +minerals. These things are also our food. We eat them mixed together +in bread, meat, eggs, milk, and other foods. + +=10. Life.=--Our food is not alive, but after we eat it the body makes +it alive. We do not know how it does it. When the body dies we cannot +put life into it again. There is life in each cell. + + +WHAT WE HAVE LEARNED + + 1. The body is made of five things: water, albumin, fat, sugar, + and minerals. + + 2. Water is mixed with all parts of the body. + + 3. Albumin makes the living part of each cell. + + 4. Fat is in pockets between the cells. It warms the cells and + keeps them from being hurt. + + 5. Sugar is made from starch. It warms the body. + + 6. The minerals in the body are salt, lime, iron, soda, and potash. + + + + +CHAPTER III + +DIGESTION OF FOOD IN THE MOUTH + + +=11. Food of the cells.=--All the cells of the body work and wear out. +They must eat and keep growing. The food of the cells is the blood. +Water, albumin, fat, sugar, and minerals are in the blood. The cells +eat these things and grow. All food must be one or more of these five +things. Before they reach the blood, they must all be changed to a +liquid. A few cells of the body are set aside to do this work of +changing them. Changing food into blood is digestion. + +=12. Cooking.=--Cooking begins digestion. It softens and dissolves +food. It makes food taste better. Most food is unfit for use until it +is cooked. Poor cooking often makes food still worse for use. Food +should always be soft and taste good after cooking. Softening food by +cooking saves the mouth and stomach a great deal of work. The good +taste of the food makes it pleasant for them to digest it. We must cut +our food into small pieces before we eat it. If we eat only a small +piece at a time we shall not eat too fast. If we cut our food fine we +can find any bones and other hard things, and can keep them from +getting inside the body. + +=13. Chewing.=--Digestion goes on in the mouth. The mouth does three +things to food. _First_, it mixes and grinds it between the teeth. + +_Second_, it pours water over the food through fine tubes. The water of +the mouth is called the saliva. The saliva makes the food a thin paste. + +_Third_, the saliva changes some of the starch to sugar. Starch must +be all changed to sugar before it can feed the cells. + +=14. Too fast eating.=--Some boys fill their mouths with food. Then +they cannot chew their food and cannot mix saliva with it. They +swallow their food whole, and then their stomachs have to grind it. +The saliva cannot mix with the food and so it is too dry in the +stomach. Then their stomachs ache, and they are sick. Eating too fast +and too much makes children sick oftener than anything else. + +Birds swallow their food whole, for they have no teeth. Instead, a +strong gizzard inside grinds the food. We have no gizzards, and so we +must grind our food with our teeth. + +=15. Teeth.=--We have two kinds of teeth. The front teeth are sharp +and cut the food; the back teeth are flat and rough and grind it. If +you bite nuts or other hard things you may break off a little piece of +a tooth. Then the tooth may decay and ache. + +After you eat, some food will sometimes stick to the teeth. Then it +may decay and make your breath smell bad. After each meal always pick +the teeth with a wooden toothpick. Your teeth will also get dirty and +become stained unless you clean them. Always brush your teeth with +water every morning. This will also keep them from decaying. + +[Illustration: =Digestive organs of a bird.= + + _a_ esophagus or swallowing tube. + _b_ crop or bag for carrying food. + _c_ stomach. + _d_ intestine. + _e_ gizzard or food grinder.] + +=16. Swallowing.=--When food has been chewed and mixed with saliva +until it is a paste, it is ready to be swallowed. The tongue pushes +the food into a bag just back of the mouth. We call the bag the +_pharynx_. Then the pharynx squeezes it down a long tube and into the +stomach. The nose and windpipe also open into this bag, but both are +closed by little doors while we swallow. We cannot breathe while we +swallow. If the doors are not shut tightly, some food gets into the +windpipe and chokes us. + + +WHAT WE HAVE LEARNED + + 1. We eat to feed the cells of the body. + + 2. All food must be made into blood. + + 3. Changing food to blood is digestion. + + 4. Cooking softens food and makes it taste good. + + 5. Food is ground fine in the mouth, and mixed with saliva to + form a paste. Some of its starch is changed to sugar. + + 6. If food is only half chewed the stomach has to grind it. + + 7. When we swallow, the tongue pushes the food into a bag back of + the mouth and the bag squeezes it down a long tube to the + stomach. + + + + +CHAPTER IV + +DIGESTION IN THE STOMACH + + +=17. The stomach.=--When food is swallowed it goes to the stomach. The +stomach is a thin bag. In a man it holds about three pints. Like the +mouth, it does three things to the food. + +[Illustration: =Gastric glands in the stomach (x200).= + +The cells _a_ and _b_, form the juice. The fibers _c_, bind the tubes +in place.] + +_First_, the stomach gently stirs and mixes the food. + +_Second_, it pours a fluid over the food. This fluid is called the +_gastric juice_. The gastric juice is sour and bitter. + +_Third_, the gastric juice changes some of the albumin of food to a +liquid form. + +If the mouth has done its work well, the stomach does its work easily +and we do not know it. But if the mouth has eaten food too fast and +has not chewed it well, then the stomach must do the work of the mouth +too. In that case it gets tired and aches. + +=18. The intestine.=--The food stays in the stomach only a little +while. All the time a little keeps trickling into a long coil of tube. +This tube is called the _intestine_ or the _bowels_. Three or four +hours after a hearty meal the stomach is empty. Some of the food has +been changed to a liquid, but most of it has only been ground to +smaller pieces, and mixed with a great deal of water. Now it all must +be changed to a liquid. + +=19. What the intestine does.=--Like the mouth and stomach, the +intestine does three things. + +_First_, it mixes the food and makes it pass down the tube. + +_Second_, two sets of cells behind the stomach make two liquids and +pour them into the intestine. One set of cells is the _sweetbread_, or +_pancreas_, and its liquid is the _pancreatic juice_. The other is the +_liver_ and its fluid is the _bile_. + +_Third_, the pancreatic juice makes three changes in food. _First_, +like the mouth, it changes starch to sugar. _Second_, like the +stomach, it makes albumin a liquid. _Third_, it divides fat into fine +drops. These drops then mix with water and do not float on its top. + +=20. Bile.=--The bile is yellow and bitter. It helps the pancreatic +juice do its work. It also helps to keep the inside of the intestine +clean. + +=21. Digestion of water and minerals.=--Water and the mineral parts of +food do not need to be changed at all, but can become part of the +blood just as they are. Seeds and husks and tough strings of flesh all +pass the length of the intestine and are not changed. + +=22. How food gets into the blood.=--By the time food is half way down +the intestine it is mostly liquid and ready to become part of the +blood. This liquid soaks through the sides of the intestine and into +the blood tubes. At last the food reaches the end of the intestine. +Most of its liquid has then soaked into the blood tubes and only some +solid waste is left. + +=23. Work of the liver.=--The food is now in the blood, but has not +become a part of it. It is carried to the liver. There the liver changes +the food to good blood, and then the blood hurries on and feeds the +cells of the body. Spoiled food may be swallowed and taken into the +blood with the good food. The liver takes out the poisons and sends them +back again with the bile. The liver keeps us from getting poisoned. + +=24. Bad food.=--Sometimes the stomach and intestine cannot digest the +food. They cannot digest green apples, but they try hard to do so. +They stir the apples faster and faster until there is a great pain. +Sometimes the stomach throws up the food and then the pain and +sickness stop. Spoiled food makes us sick in the same way. + +=25. Too fast eating.=--When the food stays too long in the stomach or +intestine it sours, or decays, just as it does outside of the body. +This makes us very sick. When we eat too much, or when we do not chew +the food to small pieces, the stomach may be a long time in digesting +the food. Then it may become sour and make us sick. + +=26. Biliousness.=--When the food is poor or becomes sour, it is +poorly digested. Then the liver has more work to do, and does not +change the food to blood as it should. It also lets some of the sour +poisons pass by it. These poison the whole body and make the head +ache. We call this _biliousness_. The tongue is then covered with a +white or yellow coat and the mouth tastes bad. These are signs of +sickness. The stomach and liver are out of order. + +=27. Rules for eating.=--If we eat as we should, our stomach will +digest its food. We must follow three rules. + +_First_, we must chew the food in the mouth until all the lumps are +fine. Then the food will be ready for the stomach. + +_Second_, we must eat slowly. If we eat fast we cannot chew the food +well. The stomach cannot take care of food if it comes too fast. We +must swallow all of one mouthful before we put another into the mouth. + +_Third_, we must eat only at meal times. The stomach needs a rest. +Even a little candy, or apples, or nuts will keep the stomach at work, +and tire it out. A child needs to eat more often than his father. So, +besides his meals, he should have something to eat in the middle of +the morning and some more in the afternoon. But he should not be +eating at all hours. He ought not to eat little bits just before +dinner, for that spoils his meal. + + +WHAT WE HAVE LEARNED + + 1. The stomach and intestine stir and rub the food, and mix it + with juices. + + 2. The juices change albumin to a liquid, and starch to sugar. + They also change fat to the form of tiny drops. + + 3. The digested food soaks through the sides of the intestine + into the blood tubes. + + 4. The blood carries the food to the liver. + + 5. The liver changes food to blood. + + 6. Blood goes to all parts of the body and feeds the cells. + + 7. The liver keeps poisons from getting into the blood. + + 8. Water and minerals become a part of the blood without being + digested. + + 9. When food is not well digested, the liver cannot make it into + good blood. This makes us bilious. + + 10. If food is not soon digested it sours and decays. This makes + us sick. + + 11. We can make food digest quickly by chewing it well and eating + slowly. + + + + +CHAPTER V + +FOODS + + +=28. Kinds of food.=--The cells of the body need water, albumin, fat, +sugar, and minerals for food. We sometimes eat sugar alone, and we +drink pure water. But most of our food is a mixture of all five kinds +of food. Food comes from animals and plants. + +=29. Milk=.--Milk is the best food known. It contains just enough +water, albumin, fat, sugar, and minerals. Babies and young mammals +live on milk alone. A man can live upon four quarts of milk a day. In +sickness, milk is the very best food for men, as well as for babies. + +The albumin of milk becomes hard when the milk sours. This makes +_cheese_. The fat of milk rises to the top. We call it _cream_. When +cream is churned, the pure fat comes together in a lump. Pure fat of +milk is called _butter_. Cheese and butter are both good foods. + +=30. Eggs.=--Eggs are also good food. The white of an egg is almost pure +albumin. The yolk is albumin and fat. Eggs have no starch or sugar. +They are not a perfect food, for some sugar must be eaten. But they can +be quickly digested and they produce a great deal of strength. + +=31. Meat.=--Meat contains albumin and fat, but no sugar. Fish, +oysters, and clams are like meat. They all make good food. Boys and +girls should eat milk, eggs, and meat. These foods are the best to +give strength to the body. Nearly all food from animals is more +quickly digested and gives more strength than food from plants. + +=32. Bread.=--White bread is a food made from wheat. The wheat is +ground to flour. Flour is mixed with water, and yeast is added. The +yeast makes a gas, and the gas puffs up the wet flour and makes it +full of holes. The holes make the bread _light_. Then bread is baked. +Rye or corn meal makes good bread. Cake, biscuit, and pancakes are +much like bread. Sometimes in place of yeast, baking powder is used to +make the bread or cake light. + +=33. Meal.=--Oatmeal, corn meal, and cracked wheat and rice are +sometimes boiled, and eaten with milk. Bread, biscuit, oatmeal, and +corn meal are made from grain. All are very much alike. The cooking +makes them look and taste different, but yet they are nearly the same. + +=34. Why we need grain food.=--All kinds of grain have much albumin, +but only a little fat. But all have a great deal of starch. By +digestion the starch becomes sugar. Grain is a good food because it +has starch or sugar. Animal foods have no sugar, so we eat grain food +with them. The two together make the most nourishing food. Potatoes +have a great deal of starch and only a little albumin. They also are +good food with meat. + +[Illustration: =A healthy man needs as much food as this every day.=] + +A person cannot live well upon plant food alone, for it has too much +starch and sugar, and too little albumin and fat. We need nearly equal +parts of albumin, fat, and sugar. A mixture of bread, meat, eggs, +vegetables, and milk makes the best food. + +=35. Fruit.=--Fruit, like apples, peaches, and plums all have sugar. +They taste good, and give us an appetite for other kinds of food. +They have little albumin or fat. + +=36. Salt.=--There is enough mineral matter in all food, and we do not +have to eat iron or lime or soda. But we do need some more salt. Even +animals need salt. Salt makes food taste good, and helps its digestion. + +[Illustration: =People are made sick by drinking water from such a +well.=] + +=37. Water.=--Water is also a food, for it forms the most of our +bodies. All food has water. Even dry crackers contain it. + +=38. Pure water.=--Water in a well runs through the dirty earth, and +yet is clear and pure. This is because sand holds back the dirt. But +sometimes slops from the house, and water from the barn yard, soak +through the soil until the sand is full. Then the well water will be +dirty and poisonous. People are often made sick by drinking such +water. In cities the dirt fills all the soil and spoils the water. So +the water must be brought from the country in large pipes. + +Water in lead pipes takes up some of the lead. Lead is a poison. You +should let the water run off from a pipe a little while before you use +it. Good water is clear and has no smell or taste. Dirty or yellow +water, or water with a taste or smell, is not fit for use. + +=39. Tea and coffee.=--Tea and coffee are steeped in water and used as a +drink. The drink is the water. The tea and coffee are neither food nor +drink. They cause the cells of the body to do more work, and at the same +time they take away the feeling of being tired. They do not give +strength to the body, but are like a whip and make the body work harder. + +=40. The appetite.=--When we have so many kinds of food, what kind is +best for us? The taste of food tells us the kind of food to eat. Bread +and meat, and such plain foods, always taste good, and we never get +tired of them. Sugar tastes good until we get enough. Any more makes us +sick. More than enough sugar or starch is found in bread and potatoes. + +[Illustration: =One kind of intemperance.=] + +If we can eat food day after day, without getting tired of it, the +food is good for us. If we get tired of its taste, either the food is +not good for us or we are eating too much. Bad tasting or bad smelling +food is always dangerous. + +We can tell how much food to eat by our _hunger_ or _appetite_. We can +always feel when we have enough. Then is the time to stop. + +Sometimes we eat plain bread and meat until we have enough, and then +sweet cake or pie is brought in. Then we have a false appetite for +sweet things. If the sweet things had not made a false hunger, we +should have had enough to eat. But the false appetite makes us want +more, and so we eat too much, and sometimes get sick from it. + +=41. Intemperance.=--Eating for the sake of a false appetite is +_intemperance_. Drinking strong drink for the sake of its taste is a +common form of intemperance. But eating too much preserves, pie, and +candy is intemperance too, and can do a great deal of harm. A little +pie, or pudding, or candy, is good, because we can eat our sugar as +well that way as in bread. But we should eat only a little. + +=42. Food and Diseases.=--If our food is dirty or is handled with +dirty hands, or is put into dirty dishes, there may be disease germs +in it. Our food should always be clean, and we should have our hands +clean when we handle it or eat it. + +Storekeepers sometimes keep fruit and vegetables out of doors where +street dust may blow upon it. This dust is often full of disease +germs. Flies may also bring disease germs to the food. If food is +kept where dust and flies can get at it, we ought not to buy it. + + +WHAT WE HAVE LEARNED + + 1. Food is a mixture of water, albumin, fat, starch or sugar, and + minerals. + + 2. Animal foods, like milk, eggs, and meat, have albumin and fat + in the best form. + + 3. Plant food has albumin and fat, but it has very much starch or + sugar. So, taken together with animal food, it makes a + complete food. + + 4. Lime, iron, soda, and salt are found in all foods, but we must + add a little more salt to food. + + 5. Water is found in all food, but we must drink some besides. + + 6. Dirty water, or water with a taste or smell, is not fit for use. + + 7. Taste tells us what kind of food to use. + + 8. Hunger, or the appetite, tells us how much food to use. + + 9. There can be a false hunger for sweet things. This may lead us + to eat too much. + + 10. Eating too much of sweet things is one form of intemperance. + + + + +CHAPTER VI + +TOBACCO + + +=43. Harmful eating.=--Men often eat for the fun of eating, and +sometimes they eat harmful things. They chew tobacco and drink strong +drinks, because they like their taste, just as a child eats candy. + +=44. Tobacco.=--Men have always drunk strong drink. Within the last +four hundred years, men have learned another way to please a wrong +taste. When Columbus discovered America, the Indians were using +tobacco. They taught the Spaniards how to smoke it, and since then +almost the whole world has used it. + +Tobacco is the leaf of a tall plant. It needs a better soil than any +other crop. It takes the richness from the ground, and spoils it for +other crops. + +=45. Nicotine.=--About 1/30 of each tobacco leaf is a strong poison. +This poison is called _nicotine_. A drop or two of it, or as much of +it as is in a strong cigar, will kill a man. It gives the tobacco its +smell and taste. Men use tobacco for the sake of a poison. + +=46. Why men use tobacco.=--Men give queer reasons for using tobacco. +One smokes for its company, another because he is with company. One +smokes to make his brain think better, and another to keep himself +from thinking. Some use tobacco to help digest their food, and others +use it to keep themselves from eating so much. Boys smoke to make +themselves look like men. The real reason for using tobacco is that +men learn to like its taste, and do not care if it harms them. + +=47. Spitting.=--Tobacco in any form makes the saliva flow. Men do not +dare swallow it, for it makes them sick. So they spit it out. No one +likes to see this. It is a dirty and filthy habit. Besides, the saliva +is lost, and cannot help digest food. + +Tobacco stains the teeth brown. You can always tell a tobacco chewer +by his teeth. His breath will smell of tobacco, and even his clothes +are offensive to the nose. + +=48. Tobacco lessens strength.=--Tobacco always makes a person sick at +the stomach, at first. After a while, he becomes used to it, and an +ordinary chew or smoke does not make him sick. But a large chew or +smoke will always make him sick again. When a person is sick from +tobacco he is very weak. Even if he is not sick, the tobacco poisons +his muscles and makes his strength less. When a man trains for a hard +race he never uses tobacco. + +=49. Tobacco hinders digestion.=--Tobacco and its smoke both have a +burning taste. This makes the throat sore, and causes a cough. Tobacco +does not help the stomach to digest food. Smokers and chewers often +have headaches and coated tongues. These are signs of a poor digestion. + +=50. Effect upon the young.=--Tobacco is more harmful to boys than to +men. If boys smoke they cannot run fast or long. They cannot work hard +with their brains or hands. They do not grow fast, and are liable to +have weak hearts. + +=51. Tobacco harms others.=--Many persons do not like the smell of +tobacco, and no one likes the spit. No one should use it in the +presence of others. The tobacco user's pleasure should not spoil the +comfort and happiness of others. + +=52. Snuff.=--Powdered tobacco is called snuff. Snuff causes sneezing. +No one should harm the nose and the whole body for the pleasure of a +sneeze. Years ago snuff was used much more than it is now. + +=53. Chewing.=--Chewing tobacco is the most poisonous way of using it, +for it keeps most of the nicotine in the mouth. Chewing will make any +one very sick, unless he spits out all the saliva. + +=54. Smoking.=--Men smoke pipes, cigars, and cigarettes. The smoke has +nicotine, and is poisonous. Pipe stems get dirty and full of nicotine. +After a while they smell bad and are very poisonous. An old smoker's +pipe will make a young smoker sick. + +=55. Cigarettes.=--Cigars are not so poisonous as a pipe, for more of +the nicotine is burned up. Cigarettes are often made of weak tobacco. +A cigarette does not contain so much tobacco as a cigar. Hence a +cigarette does not cost much. It can be smoked in a hurry. It does not +make a boy so sick as cigars do. Boys and men use a great many +cigarettes where they would not touch a cigar. This makes the use of +cigarettes the most dangerous form of smoking. Selling cigarettes to +young boys is forbidden by law. + +=56. Habit.=--When men have used tobacco for some time, they like it +and feel bad without it. So they get into the habit of using it, and +find it hard to stop. The tobacco seems to help them, but it does not +do so. It cheats men, and they do not know it. + +=57. Chewing gum.=--Chewing gum is made from pitch or paraffin, for +these substances will not dissolve in the mouth. The gum is flavored +with sugar and spices. The gum and its flavors are not harmful in +themselves, and yet chewing them is harmful. Chewing makes a great +deal of saliva flow. All this saliva is wasted, and when we eat our +meals we may have too little. Then our food will not digest well, but +we shall have dyspepsia and headaches. + +By pulling and handling the gum while chewing it, you may get some +poisonous dirt into your mouth, and make yourself very sick. + +Even if your gum should not harm you, there is a good reason for +letting it alone. When you are chewing gum, you look as if you were +chewing tobacco. No one likes to see a boy or girl even appearing to +chew tobacco. If you form a habit of chewing gum you will be more +likely to chew tobacco when you are grown. + + +WHAT WE HAVE LEARNED + + 1. Men use tobacco for the sake of its nicotine. Nicotine is a + very strong poison. + + 2. Tobacco causes a man to waste his saliva. + + 3. Tobacco makes the mouth dry. + + 4. Tobacco hinders digestion. + + 5. Tobacco stains the teeth, and makes the breath smell bad. + + 6. Tobacco makes a person sick at the stomach. + + 7. Tobacco weakens the muscles. + + 8. Tobacco is more harmful to the young than to grown persons. + + 9. Chewing is the worst form of using tobacco. + + 10. Smoking cigarettes is the worst form of smoking. + + + + +CHAPTER VII + +FERMENTATION + + +=58. Souring of fruit.=--When a little fruit is set away in a warm +place for a day or two it sours or ferments. Anything sweet will do +the same thing. Little bubbles rise up through the juice and a foam +comes on top. Then the juice has a sharp taste or is sour. Canned and +preserved fruit becomes sour soon after the jar is opened, and cider +soon turns to vinegar. All fruit juice does this even in cold weather. +But in cold weather it keeps for a longer time. + +[Illustration: =Fermentation in a jar of cherries.=] + +=59. Preserving fruit.=--If your mother wishes to keep fruit all winter +she boils it and at once puts it into tight jars. This shuts out the air +and then the fruit keeps good all winter. Boiling kills all living +things, and no more can get in through the tight jars. Does a living +thing have anything to do with making the fruit juice turn sour? + +=60. Yeast.=--Yeast will make all sweet things ferment. Bakers make +yeast grow in bread sponge. Yeast is alive. It is made of millions of +tiny round cells. New cells sprout out from the side of the old cells +like young lilies on an old lily bulb. Soon each new cell breaks off +and lives all by itself. In a single night enough new cells will form +to fill the whole loaf of bread. + +[Illustration: =Yeast plant cells (x500).=] + +=61. How yeast makes alcohol.=--Yeast will grow only where sugar is. +When it has grown for some time there is no more sugar, and instead of +a sweet taste there is a sharp or sour taste. The yeast has changed +the sugar to alcohol. All alcohol is made from sugar by yeast. + +The seeds of the yeast plant are everywhere in the air. Some are on +the skins of fruit and so are found in the juice when it is squeezed +out. There they begin to grow at once and soon change the sugar to +alcohol. They do this by taking a gas away from the sugar. The gas +rises in little bubbles, and makes a froth upon the top of the juice. +Boiling kills the yeast plant. If the juice is at once put into tight +jars no new yeast plants can get in, and so the juice keeps. + +=62. Vinegar.=--Sometimes fruit juice turns sour. The sourness is due +to vinegar. Besides yeast, other little living plants fall into the +juice and turn the sugar to vinegar. But if there is much alcohol in +the juice, the vinegar plants will not grow. + +=63. Yeast in bread.=--Growing yeast plants always make alcohol. They +change some of the sugar of bread dough to alcohol and a gas. The gas +bubbles through the bread and makes it light. When bread is baked, the +heat of the oven drives off the alcohol, and so we do not eat any in +bread. + +=64. Alcohol.=--Alcohol is a clear liquid and looks like water. It has +a sharp taste and smell. It burns very easily and makes a very hot +flame. Its smoke cannot be seen, and its flame will not make anything +black, as a match flame will do. + +=65. Use of alcohol.=--Alcohol will dissolve more things than water +will dissolve. It is used to dissolve drugs, varnishes, perfumery, and +many other things. It will dissolve even oil and fat. Tailors clean +grease spots from clothes with it. It takes water away from flesh and +makes it dry, hard, and tough. It will keep anything from rotting. In +museums we pour alcohol over pieces of flesh or plants in glass jars. +Then they will keep and we can look at them at any time. Thus alcohol +is a very useful thing, and we could hardly do without it. + +=66. Strong drink.=--Some men use alcohol in a wrong way. They swallow +it as a drink. But men cannot drink pure alcohol, for it would burn +their mouths. They always drink it mixed with some water. Alcohol in +water is called _strong drink_. + +=67. Why men use strong drink.=--Some men take strong drink to make +themselves warm, and some to make themselves cool. Some drink to keep +themselves awake, and some to make themselves sleep. Some drink to +keep themselves still, and some to make themselves stir around faster. +Men use strong drink really because it seems to make them feel strong +for a while. It does not make them stronger, but it harms the body and +the mind. Its alcohol does the harm. + + +WHAT WE HAVE LEARNED + + 1. Sugar in fruit or in water turns to alcohol or vinegar, and a + gas. + + 2. The change to alcohol is caused by the cells of the yeast plant. + + 3. The change to vinegar is caused by another small plant. + + 4. Boiling fruit juice kills the yeast plants and then the juice + will keep without change. + + 5. Alcohol looks like water. It has a sharp and burning taste. + + 6. Alcohol takes water from flesh and hardens it. + + 7. Alcohol burns with a great heat and no smoke. + + 8. Alcohol is used to dissolve things, and to keep things from + spoiling. + + 9. Alcohol in water forms _strong drink_. + + + + +CHAPTER VIII + +KINDS OF STRONG DRINK + + +=68. Wine.=--All strong drink is alcohol and water. There may be other +things to give it taste, but alcohol and water are always in it. No +strong drink is over one half alcohol. + +[Illustration: =A glass of wine contains so much alcohol.=] + +In olden times wine was the only strong drink. Men used to crush out +the juice of grapes and let it ferment. This made wine. But very often +they used the juice before it fermented. Then it had no alcohol and +could do no harm, but was a good food. We read of wine in the Bible. +Some of it was fresh fruit juice. + +In wine, the sugar is changed to alcohol. The rest of the juice stays +the same. All wine is made by the yeast plant growing in fruit juice. +No yeast is put in, for there is always enough on the outside of the +fruit. Wine is about one tenth alcohol. + +=69. Homemade wine.=--Cider is a kind of wine. It is made from apple +juice. It has alcohol a day or two after it is made. All homemade +wines have alcohol. Any of them can make a person drunk. Using weak +homemade wine and cider often makes an appetite for stronger drinks. +The alcohol in any of them is enough to harm the body. + +[Illustration: =A glass of beer contains so much alcohol.=] + +=70. Beer.=--After man had made wine for a long time, some one found +out how to cultivate yeast. Then men could make sugar and water +ferment whenever they wanted to. So men boiled grain to take out its +sugar. Then they poured off the liquor and added yeast and let it +ferment. This made beer and ale. Now millions of bushels of grain are +used every year in making beer. Men call beer a _light_ drink. But it +has alcohol and is a strong drink, and can make men drunk. + +=71. Root beer.=--Some persons boil roots and herbs, and add molasses +and yeast. Then the liquid ferments and becomes _root beer_. They say +"it has no alcohol, for we made it." But it does have alcohol, for +yeast always makes alcohol. Some ginger ale is made by putting yeast +in sweetened ginger water. It has alcohol, too. + +=72. Distillation.=--Boiling water turns to vapor or steam and goes +off in the air. When the vapor is cooled, you can see the water again. +It often cools on the window and makes little streams of water. You +can catch the steam in a tube. If you keep the tube cool, the steam +will turn to water in the tube. This process is called _distillation_. + +[Illustration: =A glass of whisky contains so much alcohol.=] + +Boiling alcohol also passes off into the air as vapor. When the vapor +is cooled, it becomes liquid again. Alcohol boils with less heat than +water. When alcohol in water is heated, the alcohol boils first. So +the vapor has more alcohol than the water. When the vapor is cooled, +the liquid has more alcohol than it had at first. When the liquid is +distilled again it has more alcohol yet. Pure alcohol can be made in +this way. + +=73. Whisky.=--Distilling wine or strong beer makes _whisky_ and +_brandy_. Whisky is one half alcohol. It is more harmful than wine or +beer. + +=74. Habit.=--Some strong drinks have only a little alcohol and some +have a great deal. No one begins to drink the strong liquors. He +begins with wine or beer. When he has once learned, he has a hard time +to stop drinking. It is dangerous to drink even weak drinks. + +=75. Strong drink and thirst.=--When a man is thirsty, water will +satisfy him but strong drink will not. Sometimes the mouth is dry and +dirty and then a man feels thirsty. Rinsing the mouth with water, and +rubbing the tongue and teeth clean will help the dryness and stop the +thirst. At any rate, strong drink will only make the mouth dryer. + +Some men drink only when they are tired. Then a cup of strong and hot +tea or coffee will make them feel much better than a glass of strong +drink, and will not harm them so much. + +When strong drink is swallowed, its alcohol takes water from the +mouth. When your mouth is dry, you feel thirsty. Strong drink makes +the mouth dry, and so a drink makes a man more thirsty. The alcohol +also makes the mouth smart. Men need another drink to cool the mouth +after the first one. So one drink leads to another. All the while a +person drinks water with the alcohol until he has too much water. But +his mouth is dry and he feels as thirsty as ever. + +=76. Effect of alcohol upon the stomach.=--When strong drink is +swallowed it makes the stomach smart just as it does the mouth. So the +stomach feels warm, but it is really no warmer. This harms the stomach +and keeps it from working well. + +Alcohol also keeps the gastric juice from changing albumin to a +liquid. Alcohol keeps flesh from decaying in a museum. In the same way +it may hinder the digestion of food in the stomach. + +When alcohol is used for only a short time, the stomach can get well; +but if it is used for months and years, the stomach will stay weak. +Then the drinker can hardly eat at all. + +=77. What becomes of alcohol.=--In the stomach a great deal of gastric +juice is mixed with the alcohol. So it is very weak when it reaches +the intestine. Alcohol needs only a little digesting. It soon soaks +into the blood from the intestine along with the other food. The blood +flows fast and washes the alcohol away as soon as it leaves the +intestine. Too little gets into the blood at once to harm it much. + +Alcohol goes to the liver, and is there destroyed; but it still does +great harm. The liver has to attend to the alcohol, and so it does not +change the food to good blood, and it does not take all the poisons +out of the blood. Then the whole body becomes weak and sick. Alcohol +hurts the liver first, and more than other parts of the body. On this +account, drinkers often have bilious attacks and stomach troubles. + +=78. Bitters.=--Many medicines are made by dissolving drugs in +alcohol. In taking a strong medicine, we use only a few drops, and so +do not get much alcohol. Some kinds of medicines must be taken in +large doses. Bitters are weak medicines, and must be taken by the +tablespoonful. A tablespoonful of the medicine has more alcohol than a +large drink of whisky. The bitters seem to make a person feel well, +but it is because he is taking a large amount of strong drink. + +Jamaica Ginger is only common ginger dissolved in alcohol. It, too, is +a form of strong drink. + +=79. Strong drink as medicine.=--People sometimes keep whisky or +brandy in the house to give for colds or other slight forms of +sickness. A drink of hot coffee does more good than the strong drink, +and has none of its dangers. + +By using whisky or brandy for medicine, children learn to believe in +strong drink, and so they will be likely to use it when they grow up. +This reason alone ought to keep any one from giving it to a child. + +=80. Alcohol in cooking.=--In making bread, alcohol is formed in the +dough by the yeast. When the bread is baked, all the alcohol is driven +off by the heat, and so we do not eat any. + +Sometimes brandy or wine is put into desserts. If it is put in after +the dessert is cooked, we shall get as much alcohol as if we had drunk +it. If the liquor is put in before cooking, the heat will drive off +the alcohol but the flavor of the liquor will remain. The flavor will +do no harm in itself, but people will learn its taste, and from it +may learn to like the strong drink itself. The alcohol in bread has no +special flavor and does not leave any taste behind. So we cannot learn +to like strong drink by eating bread. + + +WHAT WE HAVE LEARNED + + 1. Fruit juice makes wine or cider. + + 2. All kinds of wine contain alcohol. + + 3. When the liquid from boiled grain has fermented, it becomes + beer, or ale. + + 4. By boiling wine or beer, and cooling the vapor, distilled + drinks like whisky are made. They are one half alcohol. + + 5. Water will satisfy a real thirst. Strong drink will not. + + 6. Alcohol keeps the stomach from digesting food. + + 7. Alcohol soaks into the blood tubes and goes to the liver. + + 8. The liver destroys the alcohol, but is hurt in doing it. + + + + +CHAPTER IX + +THE BLOOD + + +=81. Blood.=--After food becomes blood, it goes to every part of the +body to feed the cells. Even a pin prick anywhere in the body draws +blood. The blood makes the skin pink. There are five or six quarts of +blood in a man's body. This is about 1/13 of his body. + +[Illustration: =Blood corpuscles (x400).= + + _a_ a pile of red blood cells. + _b_ red blood cells seen flatwise. + _c_ red blood cells seen edgewise. + _d_ white blood cells.] + +Blood looks like a red liquid. But if you look at it through a strong +microscope, it looks like water, and millions of little red cells. +These cells carry air through the body. They make the blood look red. +There are also a smaller number of white cells. Blood is made of red +cells, white cells, and a liquid. + +=82. The liquid in blood.=--The liquid part of the blood is albumin, +and water, with a little fat, sugar, and minerals. It is food and +drink for the cells of the body. When blood is drawn from the body it +soon becomes like jelly. We call the jelly a _clot_. When you cut your +finger, a clot forms in the cut and plugs up the bleeding place. If +it did not, the blood would all run out of the body and we should die. + +[Illustration: =Diagram of the heart while it is beating.= + + _a_ vein entering the auricle. + _b_ auricle. + _c_ closed valve to keep blood from flowing back into the auricle. + _d_ ventricle. + _e_ artery. + _f_ valve to keep blood from returning to the ventricle.] + +=83. The heart.=--The blood is held in tubes. A pump inside the body +keeps it always moving. This pump is called the _heart_. The heart is +a bag of muscle with thick sides. It is about as large as your fist. +When it is full, it has the power to make itself smaller, and so it +squeezes the blood out through a tube. We can feel each squeeze as a +heart-beat. You can find the heart-beat just to the left of the middle +of the body about two hand-breadths below the neck. + +=84. The heart-beat.=--A man's heart beats about seventy times each +minute. Boys' and girls' hearts beat much faster. Running or hard work +of any kind makes the heart beat faster yet. Your heart will keep on +beating until you die. It does not seem to rest at all, yet it works +only while you feel it beat. Between each beat it rests while the +blood is filling it again. So it really rests one half of the time. + +=85. Arteries.=--The heart pumps the blood through a single tube. This +tube opens into smaller tubes. These open into still smaller ones. You +must use a strong microscope to see the finest blood tubes. The tubes +reach every part of the body, and carry blood to its cells. They are +called _arteries_. At each heart-beat a wave of blood can be felt in +an artery. This wave is the _pulse_. It can be felt in the wrist, +temples, and other places. By the pulse we can tell how often and how +strongly the heart is beating. + +[Illustration: =Arrangement of capillaries.= + + _a_ smallest artery. + _b_ smallest vein. + _c_ network of capillaries.] + +=86. Capillaries.=--The smallest arteries divide into a fine network +of small tubes. These tubes are the _capillaries_. They lie around +every cell of the body. Their sides are very thin. As the blood flows +through them, some of it soaks through the sides of the tubes. Blood +contains all kinds of food for the cells. Each cell is always wet with +food and can eat it at any time. The cells are like the tiny animal, +the ameba, and can take in the food by any part of their bodies. The +cells are better off than the ameba, for their food is brought to +them. They pay the body for their food by working for it. + +=87. Veins.=--The capillaries come together again to form large tubes. +These tubes are called _veins_. Only a little of the blood goes through +the sides of a capillary. The rest flows on into the veins. The veins +unite to form two large tubes. These two tubes open into the heart. + +=88. How the blood flows.=--The blood is pumped out of the heart, +through the arteries to the capillaries. There some goes out to the +cells. The rest flows into the veins and goes back to the heart. All +the blood in the body passes through the heart every two minutes. It +takes only twenty seconds for a drop of blood to go from the heart to +the toes and back again. The arteries are deep in the flesh, but some +of the large veins can be seen upon the back of the hands. + +=89. Bleeding.=--If a large artery or vein is cut there is a great +deal of bleeding. You can always stop a cut from bleeding by holding +it fast between the hands. Do not be afraid of the blood when you see +any one bleeding, but hold the sides of the cut tightly with both of +your hands. This will stop any bleeding until help comes. You may keep +a person from bleeding to death by doing this when other persons are +afraid of the blood. + +=90. Healing cuts.=--When your flesh is cut it soon grows together +again. The work of the little white cells in the blood is to help heal +cuts and wounds and bruises. These cells are like little amebas in the +blood. They keep moving around with the blood, and now and then burrow +outside the capillaries to see if all is well. If they find a cut, +hundreds and thousands rush to the spot at once. Some eat up any +specks of dirt on the cut. Others fit themselves into the sides of the +cut and grow long and slender, like strings, and so bind the two edges +of the cut together. In this way all cuts are healed. + +[Illustration: =Bacteria growing in a kidney and producing an abscess +(x300).= + + _a_ kidney tube. + _b_ white blood cell attacking bacteria. + _c_ bacteria. + _d_ blood vessel of the kidney.] + +=91. The white blood cells kill disease germs.=--There are tiny living +beings everywhere in the air, and soil, and water. Some of them can grow +inside a man and make him sick. These tiny things are called _disease +germs_. One kind gives a man typhoid fever, and another diphtheria. +Another kind grows on cuts, and sometimes makes them very sore. The +white cells of the blood are always watching for these enemies, like a +cat hunting mice, and when they find them they at once try to kill them. +But sometimes the white blood cells get killed. Then they look like +cream in the cut. We call this creamy liquid _matter_ or _pus_, and say +"We have caught cold in the cut." In most pricks and cuts the white +cells of the blood can kill all these enemies and also heal the cut. + +=92. Catching cold.=--Sometimes the cold air blows on our head and +hurts the cells of the nose. If there are disease germs in the air, +they may grow in the injured part of the nose and make us have a "cold +in the head." Then the white blood cells gather at the spot so as to +kill the disease germs. Also the arteries bring a great deal of blood +to the nose so as to heal the injured parts. Some of the white blood +cells and the liquid from the blood run out, and we have to blow the +nose. The white blood cells help to make us well whenever we catch a +cold or other kind of sickness. + +=93. Red blood cells.=--The red blood cells are like tiny flat plates. +They float in the liquid part of the blood and make the blood look +red. They carry air from the lungs to the cells of every part of the +body, and thus help all the cells to breathe. + +=94. Why the heart beats hard when we run.=--When we work hard, the +cells of our bodies need a great deal of food. So the heart beats much +harder, and sends them much more blood. We can feel our heart beat +when we run hard. + +When the cells work they get more blood in another way. The arteries +become larger and hold more blood. Then the part looks red and feels +warm. Thus your face gets red when you run hard. This is because your +heart and arteries bring more blood to feed the working cells. + +=95. Need of a strong heart.=--The heart must keep sending blood to +feed the cells. If it should stop for only a little while, the cells +would starve to death and we should die. We need strong hearts. When +we work very hard for a long time, the heart gets tired. Then the +cells do not get enough food and we feel weak all over. Boys ought not +to run and lift till they are tired out, for this hurts their hearts. + +=96. What alcohol does to the blood.=--Alcohol hinders the digestion +of food. Then too little food will reach the blood, and so the cells +of the body will get too little. Alcohol does not add strength to the +body, but it takes it away. It seems to make men stronger, for it +takes away their tired feelings. But it makes them really weaker, for +it harms the blood. + +=97. How alcohol affects the heart.=--Alcohol at first makes the heart +beat more strongly and quickly, but it tires it out and makes it +weaker. Then the heart pumps too little blood to the rest of the body, +and a man is weaker all over. + +If a drinker tries to run or work hard, his heart may not pump enough +food to the working cells of his arms and legs. Strong drink takes +away a man's strength and makes him less able to endure a long strain. + +=98. How alcohol harms the arteries.=--Alcohol causes the arteries to +become larger and to carry more blood. Then the face will be red and +the skin will become warm. This makes a person feel well, and he seems +to be helped. His blood seems to be flowing faster because his face is +red. But really it is flowing slower. + +When the arteries have been made large very often, they stay large all +the time. A drinker's nose is often red from this cause. + +Alcohol sometimes causes the arteries to become hard, and even to +change to a kind of bone. Then they cannot change their size to carry +just so much blood as each part needs. + +=99. How tobacco affects the heart.=--Tobacco weakens all the body, +but it harms the heart more than the rest. It often makes the heart +beat slowly at one time and fast at another. It weakens the heart and +keeps it from working harder when the working cells need more food. A +smoker gets out of breath quickly. He cannot run far or work very +hard. Chewing is a still more harmful form of using tobacco. When men +train for a game or a race they never use tobacco. + +Boys are not so strong as men, and so tobacco is more hurtful to them. +Boys are harmed by tobacco far more than men. Cigarette smoke harms +their stomachs and keeps food from their blood. If boys smoke, they +become pale and weak. The poisonous smoke weakens the heart, and they +cannot run or work so hard as they should. Even if a father uses +tobacco, he should not allow his boys to use it. + + +WHAT WE HAVE LEARNED + + 1. Blood is a liquid. It contains many round red cells and a few + white cells. + + 2. Blood contains all kinds of food for the cells of the body. + + 3. The blood is kept moving by the heart. + + 4. The heart pumps or beats about seventy times a minute. + + 5. The blood flows through arteries to all parts of the body. + + 6. The arteries open into the capillaries. Capillaries make a + network around each cell of the body. + + 7. Some of the liquid parts of the blood go out through the sides + of the capillaries and become food for the cells of the + body. + + 8. From the capillaries the blood flows into the veins and back + to the heart. + + 9. Bleeding can be stopped by holding the cut tightly between the + hands. + + 10. The white blood cells grow into the sides of cuts, and so + heal them. They also guard the body against the seeds of + many diseases. + + 11. The red blood cells carry air to the cells of the body. + + 12. Alcohol weakens the heart and arteries. + + 13. Tobacco harms the heart. + + + + +CHAPTER X + +BREATHING, HEAT, AND CLOTHING + + +=100. The lungs.=--Our food becomes blood and feeds the cells of our +body, but we grow only a little heavier. What becomes of the food? + +[Illustration: =The air tubes and lung.= + + _a_ larynx or voice box. + _b_ trachea or windpipe. + _d_ air sacs, each like a tiny frog's lung.] + +Besides food, air is always getting into our bodies. In breathing, air +passes through the nose into a tube in the neck. This tube is called +the _windpipe_. You can feel it as a pile of hard rings in the front +part of the neck. The windpipe divides into many branches. At the end +of its smallest branches are little bags or sacs. The branches and +the sacs make the two lungs. So a lung is a soft and spongy piece of +flesh, and can be blown up like a rubber bag. A frog's lung is a +single, thin bag, about half an inch across it. Each little sac of a +man's lung is like a tiny frog's lung. + +[Illustration: =A frog's lung (x4).=] + +=101. The diaphragm.=--The lungs fill the upper part of the body just +below the neck. They are covered by the bony ribs, and rest upon a +broad muscle. This muscle is called the _diaphragm_. It divides the +inside of the body into two parts. The upper part is the _chest_, and +holds the heart and lungs. The lower part is the _abdomen_, and holds +the stomach, intestine, and liver, and a few other parts. + +[Illustration: =The parts inside the body.= + + _a_ lungs. + _b_ heart. + _c_ diaphragm. + _d_ stomach. + _e_ liver. + _f_ intestine.] + +=102. Breathing.=--When the diaphragm lowers itself, or the ribs are +raised, the chest is made larger. Then the air rushes through the +nose and swells out the lungs to the size of the chest. This is taking +a breath. Then the chest becomes smaller again, and blows the air out. +A man breathes about eighteen times a minute. He does not seem to rest +in breathing, but as he works only when he takes in breath, he rests +one half of the time. + +=103. How air gets into the blood.=--After the blood has been around the +body through the arteries and capillaries and veins, the heart sends +every drop to the lungs before it sends it out to feed the cells again. +The blood flows through little capillaries upon the sides of the air +sacs. There the red blood cells take up some of the air, and carry it +with them. When they have a load of air, they become of a brighter red +color. The blood in the arteries on its way to the cells is bright red. + +=104. How the cells get air.=--When the blood reaches the capillaries +around the cells of the body, the red blood cells give up some of the +air to the cells. Thus each cell of the body gets some air, and so it +breathes. The cells cannot reach the air themselves, and so the red +blood cells bring it to them. We breathe so as to supply the cells +with air. + +=105. What burning is.=--When meat is put into a hot stove it quickly +burns, and passes off in smoke, and leaves only a little ashes. The +ashes are the mineral parts of the meat. If the fire is very hot, you +cannot see the smoke. The burning of the meat makes heat. Heat in a +steam engine makes the machine do work. + +Every fire must have plenty of air. If air is shut off, the fire goes +out. When meat burns, the air unites with the meat and makes smoke, and +ashes, and gives out heat. Air unites with something in every fire. + +=106. Burning inside the body.=--In every part of a man's body a very +slow fire is always burning. The blood brings to the cells food from +the intestine, and air from the lungs. The food and air join in a +burning. The smoke goes back to the blood and is carried to the lungs, +and breathed out with the breath. The ashes, also, go back to the +blood, and are carried away by the skin and kidneys. The burning makes +no flame or light for it goes on very slowly. You cannot see the +smoke, but you can feel the warmth of the burning. Some of the heat is +turned to power, and gives the body strength to do work. The body is +like a steam engine. It burns up all its food. + +=107. How the body is warmed.=--The body is warmed by the slow burning +in the cells. This burning keeps the body always at the same warmth. +On a hot summer's day you feel warmer than on a cold snowy morning. +But your body is no warmer. Only your skin is warmer. + +If the skin is warm, the whole body feels warm, but if the skin is +cold, the whole body feels cold. On a hot summer's day the heat is +kept in the skin, and we feel warm. On a cold winter's day a great +deal of heat passes off from the skin, and we feel cold. Yet our +bodies have the same warmth in winter as in summer. + +=108. How the sweat keeps us cool.=--When your hands or feet are wet, +they are cold. On a hot summer's day, your body becomes wet with +sweat. This cools the body as if water were poured over it. So +sweating keeps you from getting too warm, and from being sunstruck. + +We are sweating all the time, but the sweat usually dries as fast as +it forms. When we are too warm it comes out faster than it dries. On a +winter's day we sweat only a little, and so we save the heat. But more +heat passes off from the skin into the cold air, and we do not grow +warmer. + +=109. Clothes.=--We wear clothes to keep the heat in the body. They do +not make heat, but they keep it from going off. Wool and flannel +clothes keep the heat in better than cotton. We wear woolen in the +winter, and cotton in the summer. + +Fur keeps in heat the best of all. In very cold lands only fur is worn. + +Linen lets heat out easily. It makes good summer clothes. + +=110. Where to wear the most clothes.=--The face and hands are kept +warm by the blood and we do not cover them except in the coldest +weather. Our feet are more tender and need to be covered enough to +keep them warm. We ought to wear thick-soled shoes or rubbers in damp +weather so as to keep the feet dry and warm. We ought to dry the +stockings every night, for they will get wet with sweat. + +The trunk of the body needs the most clothes. The legs ought to be +kept warm, too. If the dress reaches only to the knee, thick +underclothing is needed for the lower part of the leg. + +Do not keep one part of the body warm while another part remains cold. +It is wrong to bundle the neck or wear too much clothing over any part +of the body. It is also wrong to wear too little and be cold. + +When you are moving about, you need less clothing than when you are +sitting still. When you have worked until you are very warm, it is +wrong to stop to cool off. When you stop, you ought to put on a thick +coat or else go into the house. If you do not, you may be chilled and +made weak so that you can easily catch cold or some other disease. + +=111. Heating houses.=--In winter our bodies cannot make heat fast +enough to keep us warm unless we put on a great deal of clothing. So +we warm our houses. Our grandfathers used fireplaces, but these did +not give out much heat. People now use stoves, but some use a furnace +in the cellar, or heat the rooms by steam. Some use kerosene stoves, +but they are not so good, for they make the air bad. A room should +feel neither too warm nor too cold. It is of the right warmth when we +do not notice either heat or cold. + +=112. Change of air.=--After air has been breathed it is no longer fit +for use. In an hour or two you would breathe all the air of a small room +once if it were not changed. When the air is partly used, you feel dull +and short of breath, and your head aches. As soon as you get out of +doors, you feel better. Foul air of houses and meeting places often +contains disease germs. It is necessary to change the air of all rooms +often. You can do this by opening a door or window. It is a good plan to +sleep with your bedroom window open, so as to get good air all night. + +Air passes in and out of every crack in the windows and doors. If +only one person is in a room, this may make enough change of air. If +many persons are in a room, you will need to change the air in other +ways. You can do this by opening a door or window. Do not let the cold +air blow upon any one, for it may help to make him catch cold, if the +air of the room is impure. If we lower a window from the top, warm +impure air may pass out above it without making a draft. + +[Illustration: =Diagram of the natural ventilation of a room.= + +The arrows show the direction of the air currents.] + +You need fresh air at night as much as in the daytime. You need not be +afraid of the night air, for it is good and pure like the day air. You +ought to sleep with your window open a little. You ought to open the +windows wide every morning and air your bed well. At night you ought +to take off all your clothes and put on a night-dress. Then hang your +clothes up to air and dry. + +=113. When to air a room.=--When you first enter a room full of bad +air it smells musty and unpleasant. But after you have been in the +room a while, you get used to it. If, however, you go out of doors a +minute and then come back, you will smell the bad air again. If the +air smells bad, open a door or window until it is sweet again. + +=114. How to breathe.=--When you run hard, the cells of your body use +up all the air, and then you feel short of breath. While you run, +burning goes on faster, and you feel warmer. You can work harder and +longer if you can breathe in a great deal of air. You will also feel +better and stronger for it. Then if you are sick, you will be able to +get well more quickly. You ought to know how to breathe right. + +_First_, you ought to breathe through your nose. Even when you run, +you ought to keep your mouth closed. + +_Second_, you should try to breathe deeply. You should take a very +deep breath often, and hold it as long as you can. By practice you can +learn to hold it a full minute. + +_Third_, you ought to run, or do some hard work, every day. When you +get short of breath, you will have to breathe more deeply. After a +while you may be able to run a half mile, or even a mile, without +getting out of breath. But do not get tired out in your run, for this +will harm you. + +_Fourth_, you must sit and stand with your shoulders back, and your +chest thrown forward. A round-shouldered boy cannot have large lungs +or be long winded. + +By breathing right, you can make your lungs very much larger and +stronger. + +=115. The voice.=--We talk by means of the breath. At the upper part +of the windpipe is a small box. Its front corner can be felt in the +neck, just under the chin, and is called the _Adam's apple_. Two thin, +strong covers slide across the top of the box, and can be made to meet +in the middle. The covers have sharp edges. When they are near +together, and air is breathed out between them, a sound is made. This +sound is the _voice_. The tongue and lips change it to form _words_. + +=116. Care of the voice.=--The voice shows our feelings, even if we +do not tell them in words. We can form a habit of speaking in a loud +and harsh tone, as if we were always angry, or we can speak gently and +kindly. We shall be more pleasant company to others if we are careful +always to speak in gentle but distinct tones. + +[Illustration: =Top view of the larynx, with the vocal cords closed, +as in speaking.= + + _a_ epiglottis. + _b_ vocal cords.] + +[Illustration: =Top view of the larynx, with the vocal cords open, as +in breathing.= + + _a_ epiglottis. + _b_ vocal cords.] + +Shouting strains the voice and spoils its tone for singing. Reading +until the throat is tired makes the voice weak. Singing or shouting in +a cold or damp air is also bad for the voice. Breathing through the +mouth is the worst of all for the voice. + +=117. What becomes of alcohol in the body.=--When alcohol is taken up +by the blood, it is carried to the liver. The liver tries to get rid +of it by taking some air from the blood and burning it up, just as it +burns the real food of the body. But this takes some air from the +cells of the body. Then they do not burn as they should. + +When a stove gets too little air through its draft, it makes an +unpleasant smoke, and cools off. Just so, when the cells of the body +do not burn as they should, they produce the wrong kind of smoke and +ashes. This poisons the body and makes men sick. The most of the +poisoning of alcohol is due to these new poisons. + +When alcohol takes air from the cells of the body, they do not get +enough air. Then they are like a short-winded boy, and do not do their +work well. In this way alcohol makes the body weak. + +Alcohol does not cease to be harmful because it is burned up in the +body. It is harmful just because it burns so quickly. Using alcohol in +the body is like trying to burn kerosene in a coal stove. The body is +not made to burn alcohol any more than a coal stove is made to burn +kerosene. You can burn a little kerosene in a coal stove if you are +very careful. Just so, men can burn alcohol in their bodies. But +kerosene will always smoke and clog up the stove, and may explode and +kill some one. So alcohol in the body burns quickly and forms poisons. +It always harms the body and may destroy life at once. + +=118. Alcohol and the lungs.=--If you run a long race, your lungs will +need a great deal of air. If you take strong drink, the alcohol will +use up much of the air, and you will not have enough to use on your +run. So you will feel short of breath, and will surely lose the race. +You cannot drink and be long-winded. + +Two drinks of whisky will use up as much air as the body uses in an +hour. It would be easy to smother a person with strong drink. Drunken +persons are really smothered; they often die because of the failure of +their breathing, even while their heart is able to beat well. + +Alcohol often causes the lungs to become thickened. Then air cannot +easily pass through their sides, and a person suffers from shortness +of breath. Sometimes these persons cannot lie down at all, but must +sit up to catch their breath. + +=119. Drinking and taking cold.=--A strong, healthy man can stand a +great deal of cold and wet. If he breathes deeply in his work, all the +cells of his body get plenty of air, and if he eats good food, the +cells get plenty to eat. Then it will take a great deal to harm them. +But alcohol hinders the digestion of their food, and also takes away +their air. So the cells are both starved and smothered, and are easily +hurt. Then a little cold and wet may do great harm to his body, for a +drinker cannot stand bad weather or hard work so well as he could if +he should leave drink alone. + +Men often drink to keep themselves from taking cold. The alcohol +really makes them more liable to take cold. It causes the blood to +flow near the surface of the skin; there it is easily cooled, and the +drinker soon becomes chilled; then he feels colder than ever. The cold +harms the cells of his body, and then the white blood cells cannot +easily fight disease germs. For this reason a drinker easily takes +cold and other diseases. + +=120. Alcohol lessens the warmth of the body.=--Alcohol causes the +blood tubes in the skin to become larger. Then more blood will touch +the cool air, and the body will become cooler. But because more warm +blood flows through the skin, a man feels warmer. But he is really +colder. Alcohol makes men less able to stand the cold. Travelers in +cold lands know this and do not use it. + +=121. How tobacco affects breathing.=--We would not live in a room +with a smoking stove. But tobacco smoke is more harmful than smoke +from a stove, for it has nicotine in it. Tobacco smoke in a room may +make a child sick. + +Cigarette smoking is very harmful to the lungs, for the smoke is drawn +deeply into them, and more of the poison is likely to stay in the +body. The smoke of tobacco burns the throat and causes a cough. This +harms the voice. + + +WHAT WE HAVE LEARNED + + 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. + + + + +CHAPTER XI + +THE SKIN AND KIDNEYS + + +=122. Waste matters.=--The food is burned in the cells. As this +burning goes on, the _smoke_ goes off by the lungs and the unburned +substances, the _ashes_, 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. + +[Illustration: =The skin (x100).= + + _a_, _b_ and _c_ epidermis. + _d_ and _g_ tough and thick part of skin. + _e_ sweat gland. + _f_ blood tubes. + _h_ fat 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 scales are called _epithelium_, or _epidermis_. +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 a _hair_. Fine short hair grows on almost every part +of the body. On the top of 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. + +[Illustration: =A hair (x200).= + + _a_ the surface of the skin. + _b_ a hair. + _c_ an oil gland. + _d_ a muscle to make the hair stand on end. + _e_ and _g_, the growing cells of the hair. + _f_ fat 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 the _sweat_, or +_perspiration_, 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 Sec. 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. We should 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 or +cholera 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 called _sewers_. 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 kidneys have 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. + + +WHAT WE HAVE LEARNED + + 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. + + + + +CHAPTER XII + +THE NERVES, SPINAL CORD, AND BRAIN + + +=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 a _nerve_. The mind and the +cells signal to each other over the nerves. By means of the nerves the +mind makes the cells work together. + +[Illustration: =A nerve thread (x400).= + + _a_ central conducting fiber. + _b_ covering of fat.] + +[Illustration: =A thin slice for the end of a cut nerve (x200).= + + _a_ nerve thread. + _b_ connective tissue binding the threads 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. + +[Illustration: =A thin slice from the spinal cord with the cells and +nerves magnified 200 diameters.= + + _a_ cells in the gray matter. + _b_ fibers in the gray matter. + _c_ nerve 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 +the _spinal 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. + +[Illustration: =Regions of the head and action of the different parts +of 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 the different 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 called _memories_. 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 hear and 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 we think. 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. Then it 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 called _nervous_. + +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. When a 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 frightened by 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 again +_habit_. 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 not feel 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 called _delirium 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 +has made 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. + + +WHAT WE HAVE LEARNED + + 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. + + + + +CHAPTER XIII + +THE SENSES + + +=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 +a _touch_. 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 a _pain_. 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 feel _heat_ and _cold_. 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. + +[Illustration: =The human eye.= + + _a_ bony case of the eye. + _b_ muscle to move the eye. + _c_ and _d_ coverings of the eye. + _e_ lining or seeing part of the eye. + _f_ eyelid. + _g_ colored curtain or iris. + _h_ and _i_ clear windows of the 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 called +_tears_. + +=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. Tobacco= causes 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. + +[Illustration: =Diagram of the ear.= + + _a_ outer ear. + _b_ drum head. + _c_ _d_ and _e_ bones to carry sound to inner ear. + _f_ _g_ and _h_ inner ear. + _i_ tube to the mouth. + _j_ middle 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. + +_Alcohol_ and _tobacco_ burn the mouth and harm the taste. Food does +not taste so good and we may eat spoiled food and not know it. + + +WHAT WE HAVE LEARNED + + 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. + +[Illustration: =The Human Skeleton, showing position of bones.=] + + + + +CHAPTER XIV + +BONES AND JOINTS + + +=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 to feed 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 a +_joint_. 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. + +[Illustration: =Hinge joint of the elbow.= + + 1 humerus + 2 ulna] + +The shoulders and hips can be moved in every direction. The upper ends +of the arm and leg bones are round like half a ball. They fit into cups +on the shoulder and hip bones. They are very smooth, and are oiled like +the hinge joints. The joints are made to work very smoothly and easily. + +=184. Bones out of joint.=--When the ends of bones are torn away from +each other, the bone is out of joint. Then the bone cannot be moved +without great pain. It should be put back in place at once and kept +there by splints and bandages. A person is less liable to have his +joints out of place than he is to have his bones broken. + +=185. Sprains.=--Sometimes a joint is turned too much. This stretches +the flesh around the joint, and makes it very tender and painful. This +is a _sprain_. When you sprain a joint, you should put it in hot water +for an hour or two. Then keep it still for a few days. + +=186. Why bones and joints grow wrong.=--While bones and joints are +growing they can be made to take any shape we please. They cannot be +bent all at once, but if we hold them in one way much of the time, +they will keep that shape. Some boys and girls sit with their backs +bent forward and lean against the desk as if they were too lazy to sit +up. When they grow up, they will be bent and round-shouldered. You +should sit and stand straight. Then you will grow tall and straight +and strong. A soldier has square shoulders and walks erect because he +is drilled until his bones and joints grow in the proper shape. As you +stand straight with your feet together, your two big toes, your two +ankles, and your two knees should touch each other. + +If you wear tight shoes and press the toes out of shape, they will +soon grow so. Nearly every one's feet are out of shape from wearing +short, pointed shoes. Your toes should be straight and not cramped by +the shoe. If you wear narrow shoes, you may harm your feet. It is +better to have one's feet useful, even if they are large, than to make +them small and useless. + + +WHAT WE HAVE LEARNED + + 1. Bones make the body stiff, and give it form. + + 2. Some bones are long, some round, and some flat. All are hard + and springy. + + 3. Some bones are hinged together. The hinge is a joint. + + 4. The ends of bones in joints are rounded and smooth, and are + oiled with a liquid like the white of an egg. + + 5. Some bones are bound together by springy pads, as in the + backbone. + + 6. Bones can be broken. They will grow together again themselves. + + 7. Joints can be put out of place; then we must put them back. + + 8. If joints or bones are kept in wrong positions they will grow + into bad shapes. Tight shoes deform the feet. + +[Illustration: =The muscular system.=] + + + + +CHAPTER XV + +MUSCLES + + +=187. Shape of muscles.=--Bones are covered with muscles. Muscles give +shape to the body, and move it about. One half of the body consists of +muscles. These are arranged in bundles, and each causes a bone to make +one motion. There are over four hundred separate bundles of muscle in +the body. + +One end of a muscle is large and round and is fast to a bone. The +other end tapers to a strong string or tendon. The tendon passes over +a joint, and becomes fast to another bone. You can easily feel the +tendons in the wrist and behind the knee. + +[Illustration: =Muscle cells, cut across (x200).= + + _a_ muscle cell. + _b_ connective tissue binding the cells together.] + +A muscle is made of tiny strings. You can pick them apart until they +are too fine to be seen with the eye. Each string is a living muscle +cell. It is the largest kind of cell in the body. You can see the fine +strings in cooked meat. + +[Illustration: =A thin slice of a voluntary muscle, cut lengthwise +(x100).= + + _a_ muscle cell. + _b_ capillaries surrounding the cells. + _c_ connective tissue binding the cells together.] + +=188. How muscles act.=--A nerve runs from the brain, and touches +every cell of the muscle. When we wish to move, the brain sends an +order down the nerve. Then each muscle cell makes itself thicker and +shorter. This pulls its ends together, and bends the joint. We can +make muscle cells move when we wish to, but we cannot make any other +kind of cell move. We make all our movements by means of our muscles. + +=189. Where you can see muscles.=--In a butcher's shop you can see lean +meat. This is the animal's muscle. White and tough flesh divides the +tender red meat into bundles. Each red bundle is a muscle. You will see +how the muscle tapers to a string or tendon. The butcher often hangs up +the meat by the tendons. You can see the muscles and tendons in a +chicken's leg or wing when it is being dressed for dinner. + +Roll up your sleeve to see your own muscles. Shut your hand tight. You +will see little rolls under your skin, just below the elbow. Each roll +is a muscle. You can feel them get hard when you shut your hand. You +can feel their tendons as they cross the wrist. + +Open your hand wide. You can see and feel the tendons of the fingers +upon the back of the hand. These tendons come from muscles on the back +of the arm. You can feel the bundles of these muscles when they open +the fingers. There are no muscles in the fingers, but all are in the +hand or arm. You cannot open your hand so strongly as you can close it. + +=190. Strength of muscle.=--By using a muscle you can make it grow +larger and stronger. If you do not use your muscles they will be small +and weak. Children ought to use their muscles in some way, but if they +use them too much, they will be tired out. Then they will grow weaker +instead of stronger. Lifting heavy weights, or running long distances, +tires out the muscles, and makes them weaker. Small boys sometimes try +to lift as much as the big boys. This may do their muscles great harm. + +=191. Round shoulders.=--The muscles hold up the back and head, and +keep us straight when we sit or stand. A lazy boy will not use his +muscles to hold himself up, but will lean against something. He will +let his shoulders fall, and will sit down in a heap. Sometimes he is +made to wear shoulder braces to keep his shoulders back. This gives +the muscles nothing to do, and so they grow weaker than ever. The best +thing to do for round shoulders is to make the boy sit and stand +straight, like a soldier. Then he will use his muscles until they are +strong enough to hold his shoulders back. + +=192. How exercise makes the body healthy.=--When you use your +muscles, you become warmer. Your face will be red, for the heart sends +more blood to the working muscle cells. You will be short of breath, +for the cells need more air. You will eat more, for your food is used +up. Your muscles are like an engine. They get their power from burning +food in their own cells. When they work they need to use more food and +air. So working a muscle makes us eat more and breathe deeper. The +blood flows faster, and we feel better all over. The muscle itself +grows much larger and stronger. + +If we sit still all day, the fires in our bodies burn low and get +clogged with ashes. We feel dull and sleepy. If we run about for a few +minutes, we shall breathe deeply. The fires will burn brighter. Our +brains will be clearer, and we shall feel like work again. Boys and +girls need to use their muscles when they go to school. Games and play +will make you get your lessons sooner. + +=193. How to use the muscles.=--You should use your muscles to make +yourself healthy, and not for the sake of growing strong. Some very +strong men are not well, and some men with small muscles are very +healthy. Some boys have strong muscles because their fathers had +strong muscles before them. Strength of muscle does not make a man. + +You ought to have healthy muscles. Then your whole bodies will be +healthy, and you can do a great deal of work. You ought to learn how +to use your muscles rather than how to make them strong. An awkward +and bashful boy may be very strong, but he cannot use his muscles. A +boy is graceful because he can use them. + +The best way to use your muscles is in doing something useful. You can +help your mother in the house and your father at the barn. You can run +errands. You can learn to use carpenter's tools or to plant a garden. +Then you will get exercise and not know it. You will also be learning +something useful. + +Play is also needed. Work gets tiresome, and you will not want to use +your muscles. Play is bad when it takes you from your work or when you +hurt yourself trying to beat somebody. + +=194. Alcohol and the muscles.=--Men use alcohol to make themselves +strong. It dulls their weak feelings, and then they think themselves +strong. They are really weaker. The alcohol hinders digestion and +keeps food from the cells. Then the fires in the body burn low, and +there is little strength. + +Alcohol sometimes causes muscle cells to change to fat. This weakens +the muscles. + +Men sometimes have to do hard work in cold countries; and at other +times they must make long marches across hot deserts. Neither the +Eskimos in the cold north, nor the Arabs in the hot desert, use strong +drink. Alcohol does not help a man in either place. It really weakens +the body. The government used to give out liquor to its soldiers; but +soldiers can do more work and have better health without liquor and it +is no longer given out. + +A few years ago men were ashamed to refuse to drink. Even when a new +church building was raised, rum was bought by the church and given to +the workmen. Farmers used to give their men a jug of rum when they +went to work. Farm hands would not work without it. + +Now all this has changed. Men do not want drinkers to work for them. A +railroad company will discharge a man at once if he is known to drink +at all. A man can now refuse to drink anywhere and men will not think +any less of him. + +=195. Tobacco= poisons the muscle cells and makes them weak. At first +it makes boys too sick to move. It always poisons the cells even if +they do not feel sick. + +=196. A long life.=--A man's body is built to last eighty years, but +only a few live so long. If you are careful in your eating and +drinking, if you breathe pure air, and if you use your muscles, your +body will be healthy and will last the eighty years and more. All +through your life you will be strong and able to do good work. + + +WHAT WE HAVE LEARNED + + 1. Muscles cover the bones and move the body. + + 2. Muscle is lean meat. It is made of bundles of cells like + strings. Nerves from the brain touch each cell. + + 3. Each muscle is fast to a bone. It becomes a small string or + tendon at the other end. The tendon crosses a joint and is + fast to another bone. + + 4. When we wish to move, the brain sends an order to the muscle + cells to make themselves thicker and shorter and so bend the + joint. + + 5. You can feel the muscles and tendons in the arm and wrist. + + 6. Muscle work makes us breathe deeper, and eat more food. It + makes the blood flow faster. So it makes our whole bodies + more healthy. + + 7. Every one ought to use his muscles some part of the day. + + 8. Alcohol and tobacco lessen the strength of the muscles. + + + + +CHAPTER XVI + +DISEASE GERMS + + +=197. Catching diseases.=--Our body may get out of order like a +machine. Some parts of it may be cut, or broken, or worn out, or hurt +in other ways. Then we are sick until it is made whole again. Sickness +always means that a part of the body is out of order. + +Some kinds of sickness are like a fire. A small bit of something from +a sick person may start a sickness in us, just as a spark may set a +house on fire. Then we may give the sickness to others, just as a fire +may spread to other houses. If a person has measles, we may catch the +measles if we go near him; but if a person has a toothache, we cannot +catch the toothache from him. So we may catch some kinds of diseases, +but we cannot catch other kinds. + +=198. Bacteria and germs.=--Every kind of catching sickness is caused +by tiny living things growing in our flesh and blood. Some of them are +tiny animals. Most of them are plants, and are called _bacteria_ or +_microbes_. A common name for all of them is _germs_. + +The word germ means nearly the same as the word seed. Bacteria are so +small that we cannot see them unless we look at them through a strong +microscope. Then they look like little dots and lines (p. 54). A +million of them could lie on a pin point; but if they have a chance, +they may grow in numbers, so that in two days they would fill a pint +measure. + +Very many kinds of bacteria and other germs are found nearly +everywhere. They are in the soil and in water, and some float in the +air as dust. When they fall on dead things, they cause _decay_ or +_rotting_. When we can fruit, we kill the germs by boiling the fruit +and the cans. Then we close the cans tightly so that no new germs can +get into them. The fruit will then keep fresh for years. + +Decay is nearly always a good thing, for by it dead bodies and waste +substances are destroyed and given back to the ground, where plants +feed upon them. Many plants would not grow if they could not feed upon +decaying things. So most bacteria and other germs are useful to us. +But some kinds of germs will grow only in our bodies, and these kinds +are the cause of most of our sickness. + +=199. Germs of sickness.=--We catch a sickness by taking a few of the +germs of the sickness into our flesh. There they grow quickly, like +weed seeds in the ground, and form crops of new germs within a few +hours. After a few days the germs become millions in number, and crowd +the cells of our flesh, just as weeds may crowd a potato plant (p. 54). + +Disease germs in the body also form poisons, just as some weeds in a +field form poisons. The poisons make us sick, just as if we had +swallowed the leaves of a poisonous weed. + +=200. Fever.=--If a sickness is caused by disease germs, the body is +nearly always too warm. Then we say that the sick person has a +_fever_. Almost the only cause for a fever is disease germs growing in +the body. We can make a person have any kind of fever by planting a +few of the germs of the fever in the right part of his body. + +We are made sick by the germs of fevers more often than by all other +causes put together. Here is a list of common diseases caused by fever +germs:--colds and sore throats, most stomach aches, blood poisoning in +wounds, boils and pimples, tuberculosis, whooping cough, measles, +chicken pox, diphtheria, scarlet fever, typhoid fever, smallpox, and +malaria. + +Which of these kinds of sickness have you had? What sickness have you +had besides these? + +=201. Sickness and Dirt.=--Disease germs leave the body of a sick person +in three ways: first, through the skin, second, through the kidneys and +intestines, and third, through the nose and throat. In these same ways +our body gives off its waste matters. If we did not take anything from +another person's body into our own body we should not catch fevers. + +Whatever a feverish person soils may contain disease germs. When a +person has only a slight fever he often keeps at work, and then he may +scatter disease germs wherever he goes. So disease germs are likely to +be found wherever there is dirt or filth. Cleanliness means good +health as well as good looks. + +=202. Disease germs in the skin.=--Disease germs may often be found in +sores and pimples on the skin, but they will not leave anybody's flesh +and blood through sound and healthy skin. If our skin is smooth and +fair, there will be few disease germs on it unless we rub against +something dirty. A dirty skin nearly always contains disease germs. +Washing and bathing our body will take disease germs from our skin and +help us to keep well. + +=203. Disease germs in slops.=--A great many disease germs leave the +body through the intestine and kidneys, and may be found in the slops +and waste water of our houses. Slops are dangerous to health, for they +may run into a well, or spring, or river, and so carry disease germs +into our drinking water (p. 27). Also, house flies may light on the +pails or puddles and carry the germs to our food. In these ways we +catch typhoid fever, stomach aches, and other diseases of the +intestines. All slops and waste matters from the body should be put +where they cannot reach our drinking water, and where flies cannot +crawl over them (p. 80). + +=204. Disease germs from the nose and throat.=--If a person is sick with +a fever, many of the germs are likely to be found in his nose and +throat. Thousands of them are driven out with every drop of saliva and +phlegm when he blows his nose, or spits, coughs, or sneezes, or talks. +If he puts anything into his mouth, it will be covered with germs. More +diseases are spread from the nose and mouth than in any other way, for +we are always doing something to spread bits of saliva and phlegm. + +=205. Spitting.=--Colds and consumption and other forms of sickness +are often spread by sick persons spitting on the floor or pavement. +The germs become dried and are blown away as dust. For this reason +dust from the streets of cities and in crowded halls is often the +cause of sickness. In many places spitting on a floor or pavement is +strictly forbidden by law. + +=206. Putting things in the mouth.=--Many persons have the habit of +sucking their fingers, or of touching a pencil to the tongue when they +write or think, or of wetting their fingers with their lips when they +turn the leaves of a book. In all these ways we may give a disease to +others or may take a disease from some one else. + +=207. Public drinking cup.=--When you touch your lips to a cup, you +leave some saliva and cells from your mouth on the cup. If a cup is +used by a number of persons, some one is almost sure to leave germs of +sickness on it, and others are likely to take them into their own +mouths when they drink. So a public drinking cup is a dangerous thing. +Each school child should have his own cup. Public drinking fountains +should be so made that we may drink by putting our lips to a stream of +running water. + +[Illustration: =A safe drinking fountain.= + +A stream of water gushes up from the middle of the cup.] + +[Illustration: =An unsafe drinking place.= + +Photograph taken in the basement of a schoolhouse.] + +=208. Sweeping.=--Dusty air in a room is dangerous to health, for +disease germs are likely to be found in it. We can get rid of dust by +keeping our floors swept clean. After sweeping we should wipe the dust +from the tables and furniture. A feather duster or dry cloth will only +stir up the dust and make it float in the air again. We should use +either a damp cloth, or a dry duster made of tufts of wool, so that +the dust will stick to the duster. + +[Illustration: =House fly, magnified.= + +The hairs on its body and legs catch dirt and disease germs.] + +=209. Foul air.=--If we live in a closed room, the air soon becomes +foul and dusty, and is likely to have disease germs in it. Foul air is +one of the greatest of the causes of sickness. We should change the +air of a room often so as to keep it fresh and free from dust and +disease germs (pp. 65-67). + +=210. House flies.=--House flies come from garbage heaps and filth of +all sorts. So they carry disease germs on their bodies. They light on +our food and on our faces, and so they often make us sick. They are +often the cause of typhoid fever, stomach aches, and stomach sickness +in babies. + +[Illustration: =Life history of house flies.=] + +Flies are hatched in manure piles and garbage heaps. At first they +look like white worms, and are called _maggots_. Every maggot is a +young fly. We can get rid of flies by cleaning up every garbage heap +and manure pile. + +[Illustration: =Young mosquitoes hanging head downward in water.=] + +=211. Mosquitoes.=--Mosquitoes carry malaria and yellow fever from +sick persons to the well. If there were no mosquitoes, there would be +no malaria or yellow fever. + +Mosquitoes are hatched in water, and the young are called _wigglers_. +We may often see them in rain barrels. We may get rid of mosquitoes by +emptying all rain barrels and pails and cans of dirty water, at least +once a week, and by drying up swamps and marshes. + + +WHAT WE HAVE LEARNED + + 1. We catch a fever by taking disease germs into the body. + + 2. Disease germs cannot be seen without a strong microscope. + + 3. The germs may be found in dust and dirt. + + 4. Slops from our houses are often full of the germs. + + 5. You may take germs into your body by putting pencils and other + things into your mouth, and by drinking from a public + drinking cup. + + 6. Spitting on the floor or pavement may scatter disease germs. + + 7. House flies and mosquitoes often spread diseases. + + + + +CHAPTER XVII + +PREVENTING SICKNESS + + +=212. How our body kills disease germs.=--We take disease germs into +the body in three ways: first, through the mouth, second, through the +nose, and third, through the skin. So we should watch the purity of +our food, drink, and air, and should be careful about putting things +into the mouth, and about the cleanliness of the skin. We often take a +few disease germs into the body without catching a disease. This is +because the white cells of our blood fight the germs and kill them (p. +53). If the body is hurt or weakened, the white blood cells may also +be weakened so that they cannot kill the germs. We should take good +care of the body so that every part of it may do its work well. We +need not be able to run fast, or to lift heavy weights, but the best +sign that every part of the body is in good order is to feel bright +and wide-awake. Then our white blood cells will also be in good order +and able to fight disease germs. + +=213. Catching cold.=--When we catch a disease, we often say that we +have caught cold. We used to think that cold air and dampness were +almost the only causes of taking cold, and this is the reason why we +called many kinds of sickness by the name of colds. Now we know that +we catch cold by taking disease germs into the body. The germs will +not be able to grow unless the body is weakened in some way, as by +cold and dampness. Yet if we are wet and cold, we shall not catch cold +unless we take disease germs into the body. We do not get the germs +from the outdoor air, for very few germs are there. We get them from +the foul air of our houses when we come in to warm and dry ourselves. +If the air of our houses were always as clean and pure as the outdoor +air, we should hardly ever have colds. + +We can safely let the cold air blow on us if we are out of doors, but +if we sit in a house, a small draft sometimes seems to make us take +cold. This is because there are likely to be many disease germs in the +house and few out of doors. + +Other things besides cold air and dampness may weaken the body, and so +help us to take cold. If germs of colds are in a warm room, we may sit +there and take cold even if we are not wet or chilled at all. The body +may be weakened by poor food, wrong eating, or overwork, so that +disease germs will easily grow in it. We take as many colds from these +causes as from cold air and dampness. + +=214. Kinds of colds.=--A person takes most of the germs of colds +through his nose and mouth. If they grow only in his nose, we say that +he has a cold in his head. If they grow in his throat, he has a sore +throat, or tonsillitis. If they reach as far as the upper part of his +windpipe, he is hoarse, or has a cough, or the croup. If the germs are +planted in his lungs, he may have bronchitis or pneumonia. All these +kinds of sickness often spread from one person to another. If one person +in a family has a cold, others in the family often catch cold from him. + +=215. Diseases like colds.=--Diphtheria, tuberculosis, whooping cough, +and measles all begin like a common cold and often look like a cold +during the whole sickness. Colds do not turn into any of these +diseases, for each of them comes from its own germ, just as corn comes +only from seed corn. + +=216. Curing a cold.=--If you have a cold, you ought to stay at home +and rest, or lie in bed. Then your white blood cells can gain strength +to fight the disease germs. You ought to have plenty of fresh air in +your room. You ought not to eat much food for a few days, so that your +stomach and intestine and liver can use all their strength in throwing +off the poisons of the germs. But you ought to drink plenty of water, +so as to help wash away the poisons from your body. + +=217. Keeping colds from spreading.=--You should keep away from other +persons while you have a cold, or other catching disease, so as to +keep from spreading the sickness. You ought not to go visiting, or go +to school, or to church, or to other meeting places. When you cough or +sneeze, you should hold a handkerchief to your mouth, so as to keep +from blowing disease germs from your throat and nose. You ought to +sleep in a bed by yourself, so that no one may take the disease germs +from your bedclothes. No one else should use your towel, or +handkerchief, or knife, or fork, or spoon, or dish, until they have +been washed in hot water, so as to kill the disease germs on them. + +=218. Keeping from catching cold.=--You can keep yourself from +catching cold by keeping your body strong and in good order. You +should keep your clothes dry, eat good food, breathe pure air, get +good rest and sleep, and keep your body, your clothes, and your house +clean. You should also keep disease germs out of your body. You should +not form a habit of putting your fingers or a pencil to your mouth (p. +127). You should keep your nose, your throat, and your mouth clean. + +=219. Cleanliness of the nose.=--The inside of the nose is wet with a +slippery liquid. If you have a cold, the liquid is thick and stops +your nose, and is called _phlegm_. The liquid catches and holds dust +and disease germs, and keeps them from going into the windpipe. It +also kills many of the disease germs. + +You should always carry a handkerchief and use it so as to blow the +germs out of your nose. You should have a clean handkerchief every day. + +[Illustration: =Photograph of model of the nose and throat.= + +_A._ tonsil; _B._ adenoids; _C._ opening of Eustachian tube.] + +=220. Adenoids and large tonsils.=--Sometimes children have large +tonsils growing in the back of the throat, or soft bunches of flesh +called _adenoids_ back of the nose. These children cannot breathe well +through the nose, but must breathe through the mouth. Then they take +dust and disease germs deep into the body, and so take colds and other +sickness easily. If a child has adenoids or large tonsils, an +operation should be done to take them out. + +=221. Cleanliness of the mouth.=--We often breathe dust and disease +germs into the mouth or snuff them into the throat from the nose. Then +they are caught between the teeth and in the folds of the cheeks and +throat. There they may grow, and finally go deeper into the body and +make us sick. A dirty mouth is very often the cause of colds and other +sickness. + +We should keep our mouths clean by brushing our teeth with a +toothbrush two or three times a day. We should also rub the toothbrush +over the tongue and around the back part of the throat so as to clean +the germs from every part of the mouth. Each child should have a +toothbrush of his own, and should use it every day. + +=222. Contagious diseases.=--Diphtheria, whooping cough, measles, +scarlet fever, and smallpox are all dangerous kinds of sickness, and +spread with great ease. The germs may float in the air, and we may +take them into our bodies if we go into a room where any one has the +sickness. So we call these diseases _contagious_. If a person has one +of these diseases, he should be made to stay in a house or room by +himself until he is well. Keeping the sick away from well persons is +called _quarantine_. When the sickness is cured, the sick room and +everything in it should be cleaned and washed so as to kill the germs. + +=223. Board of health.=--There is a board of health in every city and +town. The men on the board show persons how to keep diseases from +spreading, and make them obey the rules of health. Everybody in a town +should help the board of health in every possible way. + + +WHAT WE HAVE LEARNED + + 1. The white blood cells of our body kill disease germs. + + 2. We catch cold by taking disease germs into our body. + + 3. The germs of colds are not often found in the air out of + doors. They are often found in the foul air of houses. + + 4. If a person has a cold, he should keep away from other + persons, so as to keep from spreading the sickness. + + 5. Cleansing the nose helps us to keep from catching cold. + + 6. Cleansing the teeth and the inside of the mouth removes many + disease germs. + + 7. Adenoids and large tonsils should be taken from the throat by + an operation. + + 8. If a person has a dangerous contagious disease, he should be + quarantined. + + 9. Boards of health have charge of the prevention of contagious + diseases. + + + + +INDEX + + + Abdomen, 60. + + Adam's apple, 68. + + Adenoids, 136. + + Air, 59, 65, 129. + + Albumin, 10, 17, 18, 49. + + Alcohol, 38. + + Alcohol and arteries, 56. + biliousness, 46. + bitters, 46. + blood, 55. + brain, 95. + breathing, 70. + burning, 69. + catching cold, 71. + character, 97. + cooking, 47. + delirium tremens, 96. + digestion, 46. + eyes, 103. + feeling, 95. + habit, 44. + heart, 56. + heat, 72. + heredity, 96. + insanity, 96. + Jamaica ginger, 47. + kidneys, 81. + liver, 46. + lungs, 70. + medicine, 47. + money waste, 97. + motion, 95. + muscles, 119. + sickness, 82. + skin, 81. + stomach, 45. + strength, 56, 120. + strong drink, 40. + suffering, 97. + taste, 107. + thirst, 44. + thought, 95. + + Alcohol, use of, 39. + + Ameba, 7, 52. + + Appetite, 27. + + Arteries, 51, 55. + + Ashes, 12, 62, 78. + + + B + + Bacteria, 123. + + Bathing, 78, 126. + + Beer, 43. + + Bile, 18. + + Biliousness, 20. + + Bitters, 46. + + Bleeding, 49, 52. + + Blood, 13, 19, 49, 61. + + Board of Health, 137. + + Bones, 109. + + Bowels, 18. + + Bowlegs, 110. + + Brain, 88. + + Brandy, 44. + + Bread, 24, 38. + + Breathing, 59, 60, 67. + + Broken bones, 110. + + Burning, 61, 118. + + Butter, 23. + + + C + + Cake, 24, 29. + + Candy, 29. + + Canning fruit, 37, 124. + + Capillaries, 51, 61. + + Catching cold, 54, 65, 72, 125, 132. + + Cells, 8. + + Cells, blood tubes of, 51. + breathing of, 61. + burning of, 62. + composition of, 11. + food of, 13, 55. + messages of, 85, 100. + + Cells of blood, 49, 132. + bone, 109. + brain, 88. + epithelium, 76. + muscle, 115. + skin, 75. + spinal cord, 86. + yeast plant, 38. + + Cheese, 23. + + Chest, 60. + + Chewing, 14. + + Chewing gum, 34. + + Chewing tobacco, 33. + + Cider, 42. + + Cigarettes, 34. + + Cigars, 34. + + Clams, 24. + + Clot, 49. + + Clothes, 63. + + Coated tongue, 20. + + Coffee, 27. + + Cold, feelings of, 101. + + Colds, 54, 65, 72, 125, 132. + + Connective tissue, 9. + + Contagious diseases, 137. + + Cooking, 13. + + Cotton, 63. + + Cream, 23. + + Cross-eyes, 102. + + Cuts, 53. + + + D + + Deafness, 105. + + Decay, 124. + + Delirium tremens, 96. + + Diaphragm, 60. + + Digestion, 13. + + Diphtheria, 53, 134, 137. + + Dirt, 126. + + Dirt in eye, 102. + + Disease germs, 29, 53, 65, 72, 81, 123. + + Distillation, 43. + + Drinking cup, 128. + + + E + + Ear, 104. + + Ear wax, 104. + + Eating, 20. + + Egg, 23. + + Epidermis, 76. + + Epithelium, 75. + + Eustachian tube, 105, 136. + + Exercise, 118. + + Eye, 101. + + Eyeball, 101. + + Eyelids, 102. + + + F + + Far sight, 103. + + Fat, 11, 18, 25, 49, 92. + + Fear, 92. + + Feeling, 100. + + Fermentation, 37. + + Fever, 125. + + Fire drill, 93. + + Fish, 24. + + Flannel, 63. + + Flies, 130. + + Food, 12, 13, 19, 23. + + Fresh air, 67, 129. + + Fruit, 25. + + Fur, 64. + + + G + + Gastric juice, 17. + + Gelatine, 11. + + Germs, 29, 53, 65, 72, 81, 123. + + Gizzard, 14. + + Good habits, 94. + + Grain, 24. + + + H + + Habit, 94, 127. + + Hair, 76. + + Hair dyes, 77. + + Hair oil, 77. + + Handkerchief, 135, 136. + + Healing, 53. + + Hearing, 104. + + Heart, 50. + + Heart beat, 50, 55. + + Heat, 62, 101. + + Heating houses, 65. + + House flies, 129. + + Hunger, 29. + + + I + + Intemperance, 29. + + Intestine, 18. + + Iron, 12. + + + J + + Jamaica ginger, 47. + + Joints, 110. + + + K + + Kidneys, 62, 78. + + Knowledge, 89. + + + L + + Lead, 27. + + Life, 12. + + Lime, 12. + + Linen, 64. + + Liver, 18, 19. + + Lungs, 60. + + + M + + Maggots, 130. + + Malaria, 130. + + Matter, 54. + + Meal, 24. + + Measles, 134, 137. + + Meat, 24, 116. + + Memory, 89. + + Microbes, 123. + + Microscope, 8. + + Milk, 23. + + Mind, 9, 84, 88. + + Minerals, 11, 19, 49. + + Mosquitoes, 130. + + Motion, 88. + + Motor nerves, 85. + + Mouth, 14, 127, 137. + + Muscles, 115. + + + N + + Nails, 76. + + Near sight, 103. + + Nerve messages, 85. + + Nerves, 84, 116. + + Nervousness, 92. + + Nicotine, 31. + + Night air, 67. + + Nose, 127, 135. + + + O + + Oatmeal, 24. + + Oysters, 24. + + + P + + Pain, 100. + + Pancakes, 24. + + Pancreatic juice, 18. + + Pencils, 127, 135. + + Perspiration, 78. + + Pie, 29. + + Pneumonia, 134. + + Poisons, 19. + + Potash, 12. + + Potatoes, 25. + + Public drinking cup, 128. + + Pulse, 51. + + Pus, 54. + + + Q + + Quarantine, 137. + + + R + + Red blood cells, 49, 54, 61. + + Reflex action, 86. + + Root beer, 43. + + Round shoulders, 112, 117. + + Rubbers, 64. + + + S + + Saliva, 14. + + Salt, 12, 26. + + Scarlet fever, 137. + + Senses, 88, 100. + + Sensory nerves, 85. + + Sewers, 81. + + Sick room, 66. + + Sight, 101. + + Skin, 63, 75, 126. + + Sleep, 90. + + Slops, 80, 126. + + Smallpox, 137. + + Smell, 106. + + Smoke, 62. + + Smoking, 34. + + Snuff, 33. + + Soda, 12. + + Spinal cord, 86. + + Spitting, 32, 127. + + Sprains, 112. + + Starch, 11, 14, 18, 25. + + Steam engine, 62. + + Stockings, 64. + + Stomach, 17. + + Strength, 117. + + Strong drink, 40. + + Sugar, 11, 14, 18, 25, 28, 38, 42, 49. + + Swallowing, 15. + + Sweat, 63, 78. + + Sweeping, 129. + + Sweetbread, 18. + + + T + + Taste, 28, 106. + + Tea, 27. + + Tears, 102. + + Teeth, 14, 137. + + Tendon, 115. + + Thinking, 89. + + Tight shoes, 112. + + Tobacco, 31. + + Tobacco and brain, 98. + breathing, 72. + chewing, 33. + children, 33. + digestion, 33. + eyes, 104. + habit, 34. + heart, 57. + muscle, 121. + strength, 32. + taste, 107. + teeth, 32. + + Tongue, 15. + + Tonsils, 134, 136. + + Toothpick, 15. + + Touch, 100. + + Tuberculosis, 134. + + Typhoid fever, 53, 127. + + + V + + Vegetables, 25. + + Veins, 52. + + Ventilation, 65, 129. + + Vinegar, 39. + + Voice, 68. + + + W + + Warmth, feeling of, 63. + + Washing clothes, 80. + + Waste of body, 75, 78. + + Water, 10, 19, 26, 49, 127. + + Wells, 26, 81. + + Whisky, 44, 71. + + White blood cells, 49, 53, 132. + + Whooping cough, 134, 137. + + Wigglers, 131. + + Windpipe, 15, 59. + + Wine, 42. + + Wool, 63. + + Words, 68. + + Working of fruit, 37. + + Worry, 91. + + + Y + + Yeast, 24, 38, 42. + + + + + * * * * * * + + + + +Transcriber's note: + + Pg 137 Added period after "223" in "223 Board of health". + + Pg 141 Replaced a comma with a period after "101" in "Eye, 101". + + + +***END OF THE PROJECT GUTENBERG EBOOK APPLIED PHYSIOLOGY*** + + +******* This file should be named 32251.txt or 32251.zip ******* + + +This and all associated files of various formats will be found in: +http://www.gutenberg.org/dirs/3/2/2/5/32251 + + + +Updated editions will replace the previous one--the old editions +will be renamed. + +Creating the works from public domain print editions means that no +one owns a United States copyright in these works, so the Foundation +(and you!) can copy and distribute it in the United States without +permission and without paying copyright royalties. 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