UC-NRLF 
 
 T BOOK 
 
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 DEF 
 
 Gift 
 
 No. 
 
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LIPPINCOTT'S PHTSIQLOGiES 
 
 THE FIRST BOOK 
 
 OF 
 
 ANATOMY, PHYSIOLOGY 
 
 AND 
 
 HYGIENE 
 
 OF THE HUMAN BODY 
 
 FOR PUPILS IN THE LOWER GRADES 
 BY 
 
 J. A. CULLER, PH.D. 
 
 PROFESSOR OF PHYSICS IN MIAMI UNIVERSITY, OXFORD, OHIO 
 
 PHILADELPHIA AND LONDON 
 
 J. B. LIPPINCOTT COMPANY 
 
. 
 
 C$4 
 
 COPYRIGHT, 1904 
 
 BY 
 
 J. B. LIPPINCOTT COMPANY 
 
 Electrotyped and Printed by 
 J. B. Lippincott Company, Philadelphia, U.S.A. 
 
PREFACE 
 
 WHAT to present and how to present it is 
 the chief concern of the teacher of physiology 
 in the lower grades. Without a book, the 
 work in this subject is apt to be neglected or 
 only fragmentary. 
 
 As soon as a pupil has learned to read 
 fairly well, he can profitably use a primary 
 book in physiology. Such a book should 
 make the study of the subject interesting, 
 definite, and systematic. 
 
 The aim of this book is to supply such a 
 need. The language and manner of expres- 
 sion are such as children can understand. The 
 simple facts only are presented, much being 
 left unsaid, and yet definite and direct infor- 
 mation is given as far as it goes. The ability 
 of children to understand a subject such as 
 this is often underestimated. 
 
4 PREFACE 
 
 Boys and girls are always more interested 
 when they are given something to do along 
 with the study of the book. In several places 
 in this book directions and suggestions are 
 made to this end, and we suggest that the 
 teacher add to the list as time and opportu- 
 nity permit. 
 
 One aim in this book is to get the pupil to 
 feel that he is studying about himself. If he 
 can be made to realize, as far as a child can, 
 how wonderfully and delicately his body is 
 made, so that he begins to wonder and admire, 
 then the great aim of this early study is 
 accomplished. This counts for much more 
 than nomenclature. 
 
 The effect of alcohol and narcotics is given 
 along with the study of the various parts and 
 organs of the body. The evils of intemper- 
 ance are a proper study in public schools that 
 seek to train up citizens who will be strong 
 mentally, morally, and physically, and there 
 is no excuse for its neglect in connection 
 with this subject. 
 
 Several stories based on facts of history 
 
PREFACE 5 
 
 or experience are given to fix the statements 
 that have just preceded. While story-telling 
 may easily be overdone, yet the right kind 
 of a story at the right time is a most efficient 
 means of education. 
 
 We acknowledge our indebtedness to Ginn 
 & Co. for Figs. 24 and 30 from Dr. Blaisdell's 
 " Physiology," and also to the J. B. Lippincott 
 Company for Figs. 15 and 25 from Cutter's 
 " Physiology." Also to all others who contri- 
 buted in any way to the preparation of this 
 book. 
 
 J. A. C. 
 
CONTENTS 
 
 
 
 CHAPTER PAGB 
 
 I. WHY WE STUDY PHYSIOLOGY . . .11 
 
 II. BONES . 17 
 
 III. MUSCLES 29 
 
 IV. FOOD 40 
 
 V. DIGESTION .48 
 
 VI. BLOOD 64 
 
 VII. BREATHING 75 
 
 VIII. THE SKIN 95 
 
 IX. EXCRETION . . . . . .107 
 
 X. THE BRAIN, SPINAL CORD, AND NERVES . in 
 XI. THE SENSES 131 
 
PAGE 
 
 ILLUSTRATIONS 
 
 
 
 FIG. 
 
 1. A healthy body . . . . . .12 
 
 2. Two pots of flowers . . . . .12 
 
 3. The framework . . . . . 17 
 
 4. Bones of hand and arm . . . .18 
 
 5. The femur . . . . . . 19 
 
 6. Bones of a boy's hand ..... 22 
 
 7. Bones of a man's hand . . . . 23 
 
 8. Bone tied in a knot . . . . 25 
 
 9. Cross-section of bone ..... 26 
 
 10. Tendons of hand . . . . 32 
 
 11. Muscle .... 34 
 
 12. An old well ... -45 
 
 13. Section of front tooth 49 
 
 14. A girl laughing . . 50 
 
 15. Stomach and intestines . . 53 
 
 16. Section of intestine . . . . 56 
 
 17. Villi of intestine . . . . . -57 
 
 18. The heart 65 
 
 19. Counting the pulse 68 
 
 20. Veins in the arm ...... 70 
 
io ILLUSTRATIONS 
 
 FIG. PAGE 
 
 21. Red corpuscles . . . . . .71 
 
 22. Fine silk . . . . . . .72 
 
 23. Candle flame ...... 76 
 
 24. Air-tubes ... ... 78 
 
 25. Lungs . .... 79 
 
 26. Breath and candle flame . . . .84 
 
 27. A soap-bubble ...... 88 
 
 28. Water-jug 91 
 
 29. Bee sting ....... 98 
 
 30. The skin .... . . 100 
 
 3 1 . The brain . . . . . .112 
 
 32. A vertebra . ... . 113 
 
 33. A skull . . . . .118 
 
 34. Before and after long practice . . .121 
 
 35. Demosthenes . . . . . .124 
 
 36. The eyes 132 
 
 37. Section of eye ...... 132 
 
 38. The ear 135 
 
FIRST BOOK OF PHYSIOLOGY 
 
 CHAPTER I 
 
 WHY WE STUDY PHYSIOLOGY 
 
 This book should be very interesting, for it 
 is all about ourselves. 
 
 We ought to know something about our 
 bodies, so that we may be able to take care of 
 them. 
 
 Every boy and girl wants to grow up strong 
 and healthy. 
 
 There are some things that are good for us, 
 and we ought to know what they are ; then 
 there are other things that will make us weak 
 and sickly, and we must know how to avoid 
 them. 
 
 Here is the picture of a young man who 
 has always taken good care of his health. 
 
 You can see that he is strong. 
 
 He can do a great deal of work without 
 getting very tired, and he is always in good 
 humor and is happy. 
 
 People like to do business with him. 
 
 ii 
 
12 
 
 FIRST BOOK OF PHYSIOLOGY 
 
 He is,, getting along better in the world than 
 some others who had an equal chance, but did 
 
 I. A healthy body. 
 
 not care for their health when they were 
 younger. 
 
 2. Two pots of flowers. 
 
 In the second picture you see two sets of 
 plants. One of them is far ahead of the other, 
 and yet they had an equal start. For a while 
 
WHY WE STUDY PHYSIOLOGY 13 
 
 at first we could not see any difference be- 
 tween them. 
 
 The larger bunch grew in rich ground and 
 had good air and sunshine. 
 
 The other one was planted in poor ground 
 and so it could not get enough food, and it 
 was in a place where it could not get the right 
 amount of light. 
 
 It is no fault of these small plants that they 
 are not as strong and large as the others, for 
 they could not help themselves. But it is 
 often the fault of boys and girls and men and 
 women when they are not healthy, for either 
 they did not know what they ought to do or 
 else they did not do it. 
 
 Most people who are not healthy have no- 
 body but themselves to blame. 
 
 The doctor may be able to help us when we 
 are sick, but he cannot keep us well. We 
 must do that ourselves. 
 
 When you know what a wonderful body 
 you have and how nicely it works, you will 
 surely do all you can to help it and nothing 
 to hinder it. 
 
 There are three things that we will study in 
 this book. 
 
 First, we will try to learn what the different 
 parts of the body are and what they are like. 
 
14 FIRST BOOK OF PHYSIOLOGY 
 
 Second, what these different parts will do 
 for us. 
 
 Third, how to care for all the parts of the 
 body that they may do their work well. 
 
 You have all at some time taken a ride on 
 a railroad train. You noticed that the train 
 was pulled along by a great engine in front. 
 
 Up in the engine sat a man who was called 
 the engineer. Now, what kind of a man do 
 you think would make the best engineer? I 
 think you would all say it would be the man 
 who knew all the parts of the engine and what 
 each part should do. But, most important of 
 all, he should know how to manage and care 
 for his engine so that it will pull the train 
 swiftly and safely from town to town until it 
 reaches the end of its journey. 
 
 These engineers go to school and study 
 hard to learn how to manage their engines. 
 Certainly we should be willing to learn the 
 best way to use and care for our bodies so that 
 they may do their work well. 
 
 The different parts of our bodies do different 
 kinds of work. 
 
 No doubt you have all seen a printing-press 
 at work. Maybe it was printing one of the 
 papers that the boys sell on the streets. You 
 
WHY WE STUDY PHYSIOLOGY 15 
 
 saw that there was a strong frame of iron to 
 hold all the parts of the press in their proper 
 places. One part of the machine drew in a 
 large sheet of white paper. Another part 
 spread the ink on the type. Then a large 
 steel roller pressed the paper down on the 
 metal letters. Then another part of the ma- 
 chine-took the printed paper and folded it up 
 ready for the boy to take under his arm and 
 run out into the street to sell. 
 
 You noticed that there was a great number 
 of wheels and levers and rollers. 
 
 Each one had its own work to do, and all 
 these parts had to work together to make one 
 complete machine called the printing-press. 
 
 If any one part failed to do its work, then 
 the whole machine would have to stop till this 
 part could be fixed. 
 
 In the same way our bodies are made up 
 of many different parts, and each part has its 
 own kind of work to do. We have a strong 
 framework made of bone, and this holds the 
 other parts of our bodies in their proper 
 places. 
 
 The heart has nothing to do but make 
 the blood go around and around through the 
 body. The lungs only breathe in the air 
 which we need. Our muscles move us about 
 
1 6 FIRST BOOK OF PHYSIOLOGY 
 
 from place to place. Our minds think. Our 
 eyes can do nothing" but see. Our ears can 
 do nothing but hear. 
 
 There are a great number of parts in the 
 human body, and when they all work together 
 and each part does what it ought to do, then 
 the body is in good health. 
 
 The man who owns the printing-press that 
 we just talked about takes good care of it, so 
 that it may last a long time. Every boy and 
 girl should know how to take care of their 
 bodies, so that they, too, will be strong and 
 will last a long time. 
 
 In the next lessons we will try to learn some 
 interesting things about this body of ours. 
 
 Questions. 
 
 1. Why can a man get along better when his health is 
 good ? 
 
 2. Tell about the two pots of plants. 
 
 3. How is physiology a useful study ? 
 
 4. What three things are to be studied in this book ? 
 
 5. Tell about the engineer on a railroad train. How did 
 he learn to manage his engine ? 
 
 6. Tell how a printing-press works. 
 
 7. How are our bodies like a printing-press ? 
 
 8. When is the body in good health ? 
 
 9. Name some things which you think are good for the 
 health. 
 
 10. Name some things that do the body harm. 
 
CHAPTER II 
 
 THE BONES 
 
 EVERY animal has some kind of a frame- 
 work to hold its body in shape and to make it 
 strong. Some have this framework on the 
 outside and some on the inside. A crab has 
 no bones on the inside of its body, but it is 
 covered by a hard crust. An oyster has a 
 strong, hard shell on the outside of its body. 
 A turtle has a strong shell on the outside and 
 also bones on the inside. 
 
 A man and all the larger animals have their 
 framework on the inside. 
 
 3. The framework. 
 
 You see in the picture the framework of a 
 monkey. The monkey is a very lively crea- 
 
i8 FIRST BOOK OF PHYSIOLOGY 
 
 ture, and can climb a tree or jump a long way 
 from limb to limb ; but if he did not have tiis 
 framework of bone he would be nearly as 
 slow as a snail. 
 
 We have inside of our bodies a framework 
 of bone much like that of the monkey, only 
 our bones are larger and stronger and we 
 stand up straight. 
 
 Let us try to find some of the bones of our 
 body. How many bones have you in each 
 
 4. Bones of hand and arm. 
 
 finger ? How many in the fingers and thumbs 
 of both hands? Can you feel any bones in 
 your wrist? Try. You see in the picture 
 that you have two bones above the wrist and 
 these run all the way to the elbow. 
 
 Feel for them in your own arm. Count the 
 bones of the wrist as you see them in the 
 picture. 
 
 Feel for a bone in your arm above the elbow. 
 
THE BONES 19 
 
 There is only one bone here, but it is a long 
 and stronor one. 
 
 o 
 
 Try to find your collar-bone and your 
 shoulder-blade. You can easily find your ribs, 
 for they are near the outside and extend from 
 the backbone around the body to the breast- 
 bone in front. 
 
 In the leg is the largest and strongest bone in 
 the body. It is between the hip and the knee. 
 
 5. The femur. 
 
 In the picture you can see how it looks. 
 This bone needs to be strong, for it has to 
 hold up the weight of the body, and also any 
 other weight that a man may carry in his arms 
 or on his shoulder. 
 
20 FIRST BOOK OF PHYSIOLOGY 
 
 From the knee down to the ankle there are 
 two bones again, just as we found two in the 
 arm lying side by side. 
 
 The bones of the ankle and foot are about 
 like those of the wrist and hand. 
 
 Kinds of bones. 
 
 There are about two hundred different 
 bones in the human body. Some of them are 
 called long bones, and this is the kind you 
 have in your arms and legs. Some are called 
 short bones. You have these in your wrist 
 and ankle. Others are the flat bones, such as 
 are found in the skull and the shoulder-blade. 
 The irregular bones form a fourth kind. 
 These are such as the jaw-bone and backbone. 
 
 Bones are made in a great many different 
 sizes and shapes so that they may fit in where 
 they belong and may be most useful to us. 
 
 Joints. 
 
 You can see that it would not do to have 
 only one long bone in the arm or leg, for then 
 we could not bend the arm at the elbow or the 
 leg at the knee. 
 
 You have counted and found that there are 
 many bones in the hand, and so there can be 
 many joints. Our hands are very useful to 
 
THE BONES 21 
 
 us because they have so many joints and so 
 can bend in so many different ways. 
 
 Bend your arm at the elbow. You find 
 that you can bend the arm in and out, but you 
 cannot bend it sideways. The elbow-joint 
 acts much like the hinge on a door, and so it 
 is called a hinge-joint. The knee is the same 
 kind of joint. 
 
 Now swing your right arm about, using the 
 joint at the shoulder. Feel with your other 
 hand and see if you can tell how this joint 
 works. Try this at home where you can take 
 off your clothes. This is called a ball-and- 
 socket joint. The same kind of joint is found 
 in the hips. In picture 5 you can see the ball 
 at the upper end of the bone. 
 
 Our backbones are made up of thirty-three 
 different bones placed one on top of the other. 
 This allows us to bend the body forward and 
 backward or sideways. 
 
 How would you have to act if the backbone 
 were one long, solid bone ? 
 
 How the joints are made. 
 
 Where the bones come together at the ends 
 they are bound by very strong bands to keep 
 them together and in their right place. Some- 
 times a bone is pushed out of place by acci- 
 
22 
 
 FIRST BOOK OF PHYSIOLOGY 
 
 dent, and then the doctor has to be called in 
 to set it right. 
 
 In children a very soft cushion is found be- 
 tween the ends of the bones at all the joints. 
 This is called cartilage. 
 
 In older persons this cushion of cartilage is 
 not nearly so thick, but the bones never come 
 close together. 
 
 6. Bones of a boy's hand. 
 
 This is a picture of the hand of a boy who is 
 ten years old. You see there is a wide space 
 between the bones in the wrist and at the joints 
 of the fingers. These spaces are filled with 
 soft, tough cartilage. Some of the cartilage 
 is turning to bone, as you can tell by the thin 
 buttons of bone which you see in each joint. 
 
THE BONES 23 
 
 By the time the boy is about fifteen years 
 of age these buttons will grow thicker, and 
 will fasten themselves to the end of the bones, 
 and then the hand will be as you see it in pic- 
 ture 7. 
 
 7. Bones of a man's hand. 
 
 Between the many bones of the backbone 
 there are soft cushions of this sort. They act 
 like the springs under a buggy, and prevent 
 any sudden jolting of the body and head when 
 we walk or run or jump. 
 
 What bone is made of. 
 
 If you will try you can find a large bone out 
 in a field or in a boneyard. Look at it closely. 
 You will find that it is very hard and is hollow. 
 
24 FIRST BOOK OF PHYSIOLOGY 
 
 When it was alive it was filled with a fatty 
 substance called marrow. 
 
 Also, get a piece of fresh bone from your 
 butcher. Try to cut it with your knife. You 
 find it very hard, but it has soft matter mixed 
 with it which makes it tough. In all very 
 young animals, as well as in boys and girls, 
 there is more soft matter than hard. As we 
 grow older the bones get harder and harder. 
 
 The substance that makes the bone hard 
 is lime. The bones of small children are soft 
 because there is not much lime in them. The 
 ear is just like bone, but it has no lime in it, and 
 so you can bend your ear without breaking it. 
 
 One tribe of Indians had a very foolish 
 notion that it was nice to have the tops of 
 their heads flat. So when their children were 
 very young they would press a board down 
 on the tops of their heads and tie it there till 
 the bones of the skull would get lime into 
 them and then they would stay flat. 
 
 You can see that you ought to be very care- 
 ful how you stand and sit and dress while you 
 are young. After a while the bones get hard 
 and then you cannot change them. Boys and 
 girls should stand straight and sit up straight 
 and keep their shoulders up. It looks much 
 better, and it is better for the health. 
 
THE BONES 25 
 
 Something for you to do. 
 
 The next time you have chicken for dinner 
 save the long bone of the chicken's leg and 
 put it into a bottle. Pour in enough water to 
 cover the bone. Then pour in about three 
 tablespoonfuls of muriatic acid. Leave it 
 there for one day. Now take the bone out 
 and you will find it so soft that you can tie it 
 into a knot. 
 
 The acid has eaten away all the lime and 
 left all the soft part. Try it. In the picture 
 you see the rib of a lamb that was treated 
 that way and then tied into a knot. 
 
 8. Bone tied in a knot. 
 
 Now get a bone that has been used in mak- 
 ing soup. Put it into the stove with the hot 
 coals and leave it there for a few hours. Then 
 take it out and you will find that all the soft 
 part has been burned away and only the lime 
 is left. Try it. 
 
 Broken bones. 
 
 The bones of grown people are hard and 
 strong, and yet they will bend a little. In 
 children they will bend a great deal, but are 
 
26 FIRST BOOK OF PHYSIOLOGY 
 
 often broken. Bones are often broken by a 
 fall down-stairs or from a tree, o'r by slipping 
 and falling on a leg or arm. When this hap- 
 pens a surgeon must be called in to set the 
 bones in place again. You must then keep 
 the broken part very quiet for three or four 
 weeks or more until the broken ends grow 
 together. 
 
 If you have good health and are careful the 
 ends will grow together again, but the bone 
 will never be quite so good as it was before. 
 
 
 How bones grow. 
 
 The bone is alive just like flesh and other 
 parts of the body. The picture shows how a 
 thin slice of bone looks in a microscope. 
 
THE BONES 27 
 
 The slice was cut across the bone. You 
 see that it is full of small holes. Blood-tubes 
 pass through these holes and carry blood to 
 all parts of the bone. That is the way the 
 bone gets its food. 
 
 Now you can see that the blood should 
 have in it what the bone needs. If the bones 
 cannot get from the blood the kind of food 
 they need, they will not grow and make a 
 strong framework for our bodies. 
 
 Things that harm the bones. 
 
 You have just seen that the bone is alive, 
 and so of course it can become diseased. The 
 doctors all tell us that tobacco has a very bad 
 effect on the bones of a growing boy. The 
 boy who uses tobacco will never be as large 
 and strong as he would have been without it. 
 His bones will not grow well because he is 
 feeding them poison instead of pure blood. 
 In this way many boys are stunting their 
 growth by the use of cigarettes. 
 
 Any drink, too, that has alcohol in it is a 
 poison to the blood. One who uses such a 
 drink cannot be healthy. 
 
28 FIRST BOOK OF PHYSIOLOGY 
 
 Questions. 
 
 1. What kind of framework has a crab ? An oyster ? A 
 turtle ? 
 
 2. What kind of framework does a monkey have ? Of 
 what use is it ? 
 
 3. What kind of framework is in the human body ? 
 
 4. How many bones in the whole hand ? 
 
 5. Where is the largest and strongest bone in the body ? 
 Why is it so strong ? 
 
 6. How many bones in the whole body ? 
 
 7. Name four kinds of bones. 
 
 8. W 7 hat is the use of joints ? 
 
 9. Name two kinds of joints and give an example of each 
 kind. 
 
 10. How do the joints in the boy's hand differ from those 
 in the hand of the man ? 
 
 11. What makes bone hard ? 
 
 12. Why are the bones of young children soft ? 
 
 13. Have you tried to tie a bone in a knot ? 
 
 14. What should be done when a bone is broken ? 
 
 15. What does a cross-section of a bone look like under 
 a microscope ? What are the holes for ? 
 
 1 6. What are some things that harm bones ? 
 
 17. Could you throw a ball if there were no bones in your 
 arm ? 
 
CHAPTER III 
 
 MUSCLES 
 
 IN the last lesson we learned that the bones 
 are the framework of the body. They keep 
 the body in shape. They make it strong. 
 They protect some parts of the body from 
 harm. They help us to make swift motions. 
 But the bones cannot move themselves, and a 
 man would not be of much use if he could 
 not move about. You know that you can 
 move your body in all sorts of ways. How 
 do you do this ? We will try to tell you in 
 this lesson. 
 
 Now look again at the first picture in this 
 book. You cannot see this man's bones be- 
 cause they are all covered up with muscles. 
 On his arm you see a large bundle of muscles. 
 They make his arm strong. 
 
 Let us try to find some muscles on our own 
 bodies. Put your hands on your cheeks and 
 close your teeth together. Bite the teeth to- 
 gether several times while you feel for the 
 muscles in the cheeks. Keep on doing this 
 
 till you know just about where the muscles are, 
 
 29 
 
30 FIRST BOOK OF PHYSIOLOGY 
 
 and how strong they are. The upper ends of 
 these muscles are fastened to the skull, and :he 
 lower ends to the lower jaw-bone. When we 
 make them shorter they pull the jaw up. In 
 this way you can bite off your food and chew it. 
 
 There are other muscles around the mouth 
 so that you can pull your lips back and show 
 your teeth, or you can draw your lips to a small 
 round hole as boys do when they whistle. 
 
 Then there is another muscle which is fas- 
 tened to each corner of the mouth, and we 
 use it when we laugh or smile. 
 
 There are a great number of muscles in 
 the face, and we can use them just as we like. 
 Boys and girls can make their faces look 
 happy and cheerful, and then people will like 
 to be with them, or they can draw the muscles 
 so that the face will look sour and cross, and 
 then people will want to shun them. 
 
 We must be careful about this while we are 
 young, for when we get older our faces will 
 stay the way we have trained them. 
 
 Now hold out the right arm. Place the 
 left hand upon it above the elbow. Bring the 
 right hand up towards the head, and you can 
 feel a large muscle which gets harder and 
 shorter. This is the one that bends the arm 
 in at the elbow. 
 
MUSCLES 31 
 
 Put the left hand below the elbow and close 
 the fingers of the ri^ht hand. You can easily 
 
 o o J 
 
 find the muscles that do this work. 
 
 Now grasp the back of the leg below the 
 knee and raise yourself upon your toes. You 
 find here a large muscle which pulls hard 
 enough on your heel to raise your whole 
 weight. Every movement of the body is 
 made by a muscle. If we could not use them 
 we would be perfectly still and helpless. 
 
 What the muscles are. 
 
 Most of the meat which we eat is muscle. 
 Beefsteak was the muscle of the ox. Lean 
 pork was the muscle ot the hog. When these 
 animals were alive they used these muscles to 
 move themselves about. 
 
 When you get a piece of beefsteak at the 
 butcher shop its color is pink, and it cannot 
 be easily pulled apart. After it is boiled till 
 it is tender, you can divide it into threads 
 so fine that you can hardly, see them. A 
 muscle is a bundle of such fine threads of 
 lean meat tightly bound together. 
 
 How the muscles are fastened to the bones. 
 
 Most of the muscles are fastened at each 
 end to a bone. When they get shorter they 
 
3 2 
 
 FIRST BOOK OF PHYSIOLOGY 
 
 pull on the bones, and in that way we make 
 most of our movements. 
 
 Many of the muscles taper at the ends into 
 a white cord, and this cord is fastened to the 
 
 10. Tendons of hand. 
 
 bone. Rub the fingers over the back of the 
 hand and you can feel the cords that pull the 
 fingers out straight. Try it. 
 
 It would not do to have large muscles down 
 
MUSCLES 33 
 
 in the fingers or wrist, for that would make 
 them too large and clumsy. The muscles 
 that close and open the fingers are put on 
 the arm below the elbow, and only these 
 tough, slender cords run down to the fingers. 
 In this way the hand can be very strong and 
 yet be small. 
 
 Feel across the inner side of the wrist. 
 These cords pull the fingers shut. You can 
 see them in picture 10. 
 
 All such cords are called tendons. They are 
 used in a number of places in the body. You 
 can easily find the strong tendons at the elbow 
 or back of the knee or back of the ankle above 
 the heel. 
 
 How we make our muscles work. 
 
 The muscles cannot move themselves any 
 more than the bones can. 
 
 How, then, can you throw a ball or run or 
 jump? You have just learned that all the 
 motions of the body are made by the mus- 
 cles. You can sit or stand whenever you 
 wish to do so. You can bend your arm or 
 knee whenever your mind tells that muscle 
 to go to work. 
 
 The mind must be joined to the muscle in 
 some way. 
 
 3 
 
34 FIRST BOOK OF PHYSIOLOGY 
 
 We find that there is a cord called a nerve 
 which runs from the brain out to the muscles. 
 
 When the mind wants a muscle to work, it 
 sends word down along the nerve and the 
 muscles act when they receive this order. 
 
 We will learn more about this wonderful 
 arrangement when we get farther on in the 
 book. 
 
 In picture 1 1 you see a bundle of muscle. 
 The upper part shows how it looks when it 
 
 ii. Muscle. 
 
 is resting. When the mind orders it to go to 
 work, it draws up till it looks like the lower 
 part of the picture. By doing this it gets 
 much shorter and pulls hard on anything that 
 is fastened to the end of it. 
 
 We have some muscles that do their work 
 without our thinking about them. Our hearts 
 work all day and at night while we are asleep. 
 
MUSCLES 35 
 
 The muscles that make us breathe keep on 
 working while we are thinking about other 
 things. If we had to think of our heart and 
 lungs to keep them going, we would not have 
 time to do anything else. 
 
 How to make muscle strong and healthy. 
 
 Muscles get strong by using them. If you 
 use your right arm more than the left one, the 
 right arm will be stronger. When a muscle 
 works hard more blood will flow to it, and it 
 will keep getting larger and stronger. 
 
 It is good that boys and girls like to run 
 and jump and play when they are out of 
 doors. This gives them good exercise and 
 makes them grow. Play is not the only exer- 
 cise that will make children healthy. Useful 
 work will do it just as well. Work in the 
 garden and about the house is very good 
 exercise. Any outdoor work that children 
 do cheerfully is good for their health. 
 
 Boys sometimes go to the extreme, and try 
 to do more than they are able to do. Such 
 exercise does more harm than good. You 
 cannot make the muscle strong by working 
 very hard for a few days. Good exercise 
 every day for a long time is needed. When 
 you are very tired that means that your 
 
36 FIRST BOOK OF PHYSIOLOGY 
 
 muscles need rest. Good air, good food, 
 good exercise, and the proper amount of sle<ip 
 and rest will give you healthy and strong 
 muscles. 
 
 Effect of cigarettes and tobacco on the 
 muscles. 
 
 It is certain that cigarettes do a great deal 
 of harm to the muscles as well as to the whole 
 body. 
 
 A boy who has been smoking cigarettes for 
 some time, can generally be picked out in 
 school. He smells bad, to begin with ; but that 
 is not the worst part of it. You can tell from 
 the way he acts that there is something wrong 
 with both his mind and his body. 
 
 It has been found in many schools that the 
 boys who smoke cigarettes are a year or more 
 behind the other boys who do not smoke. 
 
 Tobacco is a poison to the blood. When 
 the blood is bad no part of the body can be 
 healthy. 
 
 At first a boy gets very sick when he tries 
 to use tobacco. All tobacco contains a deadly 
 poison called nicotine. It is this poison that 
 makes him sick. After a while he gets used 
 to the poison and it will not make him sick, 
 but the poison harms him just as much. 
 
MUSCLES 37 
 
 You can often tell that a boy uses tobacco 
 by the way he works. His muscles have 
 been poisoned by nicotine or have been starved 
 by bad blood. After such a boy works for 
 a little while he gets very tired. A healthy 
 man would call him lazy, but he does get 
 tired, because his weak, poisoned muscle does 
 not have the power to do much work. 
 
 You have learned that the muscles are all 
 controlled by nerves. Nicotine also poisons 
 the brain and nerves so that they cannot send 
 the proper order down to the muscles. Such 
 a person gets awkward and his hand shakes. 
 The nerves cannot bring the right kind of 
 an order to the muscles, and the muscles do 
 not have the strength to do their work. 
 
 Effect of alcohol on the muscles. 
 
 There are some drinks that are very bad 
 for the muscles. They are such as beer, 
 whiskey, wine, and hard cider. 
 
 These drinks are not good for us because 
 they all contain alcohol. Alcohol is a poison 
 to the body. 
 
 People used to think that alcohol made the 
 muscles stronger. They thought they could 
 do more work when they drank whiskey and 
 beer. We know now that this is not true. It 
 
38 FIRST BOOK OF PHYSIOLOGY 
 
 has been tried many times, and it is always 
 found that the men who drink whiskey aild 
 beer and wine will get tired and give out 
 sooner than those who do not. 
 
 The young men who are trained for hard 
 games, like boat-racing, foot-ball, wrestling, 
 and the like, are not allowed to use any alco- 
 hol or tobacco. The muscle cannot be trained 
 to work hard for a long time if it has any 
 nicotine or alcohol in it. 
 
 Some people think they can make them- 
 selves healthy by drinking beer, because beer 
 makes them fat. They think they are healthy 
 when the body is fat. This is a great mistake. 
 They get more fat, but less muscle. They 
 get weak instead of strong. Our strength is 
 in our muscles, and not in our fat. 
 
 You can plainly see why men and boys who 
 drink alcohol and smoke cigarettes are not 
 wanted in the stores, or in the shops, or on the 
 railroads. They are not worth as much as 
 are those with strong, healthy bodies. 
 
 The only safe way is to let tobacco and 
 strong drink alone. 
 
 Your body is doing its best all the time to 
 keep you in good health. You ought to help 
 it, and not hinder it. 
 
MUSCLES 39 
 
 Questions. 
 
 1. Name four uses of bones. 
 
 2. How can the bones be made to move ? 
 
 3. Find the muscle you use when you bring your hand to 
 your mouth. 
 
 4. What is a muscle ? 
 
 5. How are muscles fastened to bones ? 
 
 6. What are tendons ? Where can you find some of 
 them? 
 
 7. How can the mind make the muscle work ? 
 
 8. How can a muscle move a bone ? 
 
 9. Name some muscles that keep working all the time. 
 
 10. What will exercise do for the muscles ? 
 
 1 1 . What are some of the bad effects of smoking ciga- 
 rettes ? 
 
 12. Why is a cigarette smoker not wanted in the big stores 
 and shops ? 
 
 13. What are some of the bad results of drinking alcohol ? 
 
 14. What is the best drink ? 
 
CHAPTER-IV 
 
 FOOD 
 
 Appetite. 
 
 THE growing boy or girl gets hungry very 
 often. This is the way our bodies tell us that 
 we need more food. 
 
 If you are healthy and do not spoil your 
 appetite, it will tell you just what you ought 
 to eat. Sometimes it tells us to eat some- 
 thing sour. At other times it tells us to eat 
 something sweet. Sometimes it will call for 
 vegetables, and at other times for meat. 
 
 When we are sick our appetites often call 
 for things that are not good for us. At such 
 times we must eat only what the doctor tells 
 us to eat. 
 
 Some boys spoil their appetites by doing 
 things that make the body unhealthy. The 
 boy who uses tobacco will get an appetite for 
 it that will grow stronger and stronger. It is 
 not safe for him then to follow his appetite 
 in anything. 
 
 People who drink whiskey or beer or any 
 
 strong drink that has alcohol in it will get a 
 40 
 
FOOD 41 
 
 very strong appetite for such drinks. The 
 more they drink the stronger the appetite 
 becomes. 
 
 After a while the appetite gets stronger 
 than the man, and he cannot quit even when 
 he wants to do so. 
 
 A good appetite will always want the 
 things that are good for us. 
 
 Sometimes even young boys and girls lose 
 their appetites. They come to the table at 
 meal-time, but cannot find anything there that 
 they like. This means that something is 
 wrong. Maybe they have been eating too 
 much candy or other things between meals. 
 Maybe they ate too much at the last meal or 
 have not had enough exercise. 
 
 Here is a good recipe for keeping up a 
 healthy appetite. It was written by Alice 
 
 Gary. 
 
 " My lad, who sits at breakfast 
 With forehead in a frown 
 Because the chop is under-done 
 And the fritter over-brown, 
 
 Just leave your dainty mincing 
 And take, to mend your fare, 
 
 A slice of golden sunshine 
 And a cup of morning air. 
 
42 FIRST BOOK OF PHYSIOLOGY 
 
 ' ' And when you have eat and drunken, 
 
 If you want a little fun, 
 Throw by your jacket of broadcloth 
 And take an up-hill run. 
 
 " And with the one and the other 
 You will be so strong and gay 
 That work will be only a pleasure 
 Through all the rest of the day. 
 
 " And when it is time for supper 
 Your bread and milk will be 
 As sweet as a comb of honey. 
 Will you try -my recipe ?' ' 
 
 Why we eat. 
 
 Our food does three things for us. It 
 makes us grow. It makes us warm. It makes 
 us strong, so that we can work. 
 
 We can say that a steam-engine eats coal. 
 The engine will run as long as the engineer 
 keeps up a good fire and keeps water in the 
 boiler. When he lets the fire go down the 
 engine will stop. Then we can say that the 
 engine is hungry and must have some more 
 of its kind of food before it will run again. 
 
 When you get tired and hungry, you know 
 that you must eat again before you can do 
 much more work. We eat for nearly the 
 same reason the engine does, but we cannot 
 use coal for our food. 
 
FOOD 43 
 
 The proper kinds of food for us. 
 
 We need five different kinds of food. 
 
 The first kind is proteid. We get it from 
 such food as eggs, meat, vegetables, and 
 milk. 
 
 The second kind is starch. We get it from 
 such food as flour, rice, potatoes, and fruit. 
 
 The third kind \sfat. We get it from such 
 food as butter, cream, and fat meat. 
 
 The fourth kind is water. 
 
 The fifth kind is the minerals. 
 
 No one of these kinds of food would sat- 
 isfy us. We must have some of each kind. 
 Milk is nearly a perfect food, for it has all 
 the different kinds mixed together. 
 
 Tea and coffee are not foods at all. Chil- 
 dren will always be in better health if they 
 drink only milk and water. They should 
 never drink tea and coffee. 
 
 Enough of all the minerals, except one, is 
 already in the other kinds of food. That one 
 is salt. So we add salt to our food when we 
 cook it or while we are eating. 
 
 Water. 
 
 A large part of the body is water. 
 
 We cannot live long without it. All of our 
 
44 FIRST BOOK OF PHYSIOLOGY 
 
 foods contain water, but we need to drink a 
 great deal besides. 
 
 Water is a food because our^bodies need it 
 and cannot be healthy without it. 
 
 It is our natural drink, and when we are 
 real thirsty nothing is so good. 
 
 It is a blessing that water is so plentiful. 
 Some places are a desert because there is no 
 water there, but we have great lakes and 
 rivers of it. We can drill a hole down into 
 the ground and are almost sure to strike a 
 vein of good, fresh water. Sometimes it 
 comes up itself to the top of the ground in a 
 cool spring. 
 
 The water that comes from springs or from 
 deep wells is nearly always good to drink. 
 The water from a shallow well or from a river 
 near a town or city may be very bad. A 
 great deal of sickness and death is caused by 
 drinking impure water. If you think the 
 water you have to drink is not good, you 
 should boil it before you drink it. 
 
 Never drink the water from a shallow well 
 if you can avoid it. Here you see the top of 
 a well which is almost sure to contain bad 
 water. The well is walled up with loose 
 stones and is only about fifteen feet deep. 
 When a heavy rain falls, the water will carry 
 
FOOD 45 
 
 into this well any poison or filth that may be 
 near. The well may look clean and neat on 
 top and yet hold very bad water. Whole 
 families often get typhoid fever or other kinds 
 of disease by drinking from such a well. 
 
 12. An old well. 
 
 The ice which is used in the summer-time 
 should never be put into the drinking-water. 
 The ice is not pure when it is taken off of 
 water that was impure. Then, too, the ice in 
 the water makes it too cold to drink. It is 
 
46 FIRST BOOK OF PHYSIOLOGY 
 
 much better to drink the water just as it 
 comes from the hydrant or spring or dt&p 
 well. 
 
 Manners at the table. 
 
 There is a right and a wrong way to act 
 while you are at the table. It is easy to tell 
 how boys and girls have been trained by see- 
 ing how they eat. 
 
 Everything that is done at the table should 
 be refined and polite. 
 
 We cannot tell you here all the things you 
 should do or should not do at the table, but 
 here are a few rules which you must try to 
 observe. 
 
 Be sure you never use a knife to carry the 
 food to your mouth. You must use your 
 fork or spoon for that purpose and must 
 learn the right way to hold them. 
 
 Be careful not to make any noise with your 
 mouth when you eat or drink. 
 
 Do not let your knife or fork rattle on your 
 plate. 
 
 Do not lounge or rest your elbows upon 
 the table. 
 
 Do not rise in your chair to reach for any- 
 thing. Ask for it in a polite way. 
 
 While we eat we should be cheerful and 
 
FOOD 47 
 
 happy. This will not only give us a pleas- 
 ant time, but our food will do us more 
 good. 
 
 There are many rules of this kind, and you 
 can soon learn them if you will try. 
 
 Your teacher will tell you about them, and 
 you can notice how polite people eat. 
 
 Every one will be much better pleased with 
 you when you eat in the right way, and you 
 will not need to be ashamed to eat with polite 
 people when you are older. 
 
 Questions. 
 
 1 . What does the appetite tell us ? 
 
 2. How may the appetite be spoiled? 
 
 3. Repeat Alice Gary's recipe for an appetite. 
 
 4. Why do we eat ? 
 
 5. What three things will food do for us ? 
 
 6. What kinds of food do we need ? 
 
 7. What are the best drinks ? 
 
 8. Where can pure water be found ? 
 
 9. Why do shallow wells often contain impure water ? 
 
 10. Why is it wrong to drink ice-water ? 
 
 11. Why should we be cheerful and happy at the table ? 
 
 12. Tell all you can about good and bad table manners. 
 
CHAPTER V 
 
 DIGESTION 
 
 The teeth. 
 
 After the food is taken into the mouth it 
 must be chewed. This is done by the teeth. 
 You had no teeth till you were a little over 
 a year old, and then your first set came 
 through the gums. Then you had only ten 
 upper teeth and ten lower ones. 
 
 When you were six or seven years old 
 your first teeth came out and new ones came 
 in their places. Count your teeth and see 
 how many you have now. 
 
 These are the only teeth you will ever have, 
 and if you take good care of them they will 
 last a longf time. 
 
 o 
 
 How a tooth looks on the inside. 
 
 Picture 13 shows you how a tooth looks 
 when it is cut in two lengthwise. A tooth is 
 alive and grows like other parts of the body. 
 It gets its food from the blood. At the lower 
 end of the tooth you can see how the blood- 
 tubes enter and carry blood up through the 
 
 centre. 
 4 8 
 
DIGESTION 49 
 
 In the picture you see that in this tooth 
 eight lines enter in at the bottom. Six of 
 them stand for blood-tubes and two of them 
 for nerves. These nerves also run to all parts 
 of this central part of the tooth. Even a very 
 small opening in to where the nerves are will 
 give us a severe toothache. 
 
 13. Section of front tooth. 
 
 The outside rim at the top of the tooth is 
 called enamel. It is the hardest substance in 
 the whole body. When the enamel is kept 
 clean it is a beautiful white, and needs to be 
 very hard, for we use it to grind our food. 
 
 Care of teeth. 
 
 The teeth are not only useful for chewing 
 our food, but we look much better when we 
 have sound white teeth. 
 
 4 
 
5 o FIRST BOOK OF PHYSIOLOGY 
 
 The girl in the picture is enjoying a hearty 
 laugh. It does any one good to have a hearty 
 laugh when something very amusing happens. 
 At such times a set of sound white teeth, 
 
 14. A girl laughing. 
 
 such as this girl has, adds very much to the 
 personal appearance. 
 
 The best way to have good teeth is to be- 
 gin to take care of them when we first get 
 them. 
 
 Here are a few rules that you ought to 
 follow. 
 
 Never pick your teeth with a pin or any 
 other hard substance. Use a toothpick. 
 
DIGESTION 
 
 5 1 
 
 Do not bite on anything that is hard. 
 
 Do not allow any bits of food or candy to 
 remain between the teeth. 
 
 Wash the teeth often with a tooth-brush. 
 
 Do not take any very hot or very cold 
 liquid into the mouth. Either may crack the 
 enamel. 
 
 Have the dentist look over your teeth once 
 in a while to see if they are sound. A small 
 cavity can be filled with gold and the tooth 
 will be almost as good as new. 
 
 Saliva. 
 
 When you think of something real good to 
 eat you say it makes your mouth water. This 
 fluid is called saliva. While we are grinding 
 our food between our teeth a great deal of 
 saliva pours into the mouth. It wets the food 
 and changes some of the bread and potatoes 
 and other kinds of starch into sugar. 
 
 When the food has been ground up fine 
 and mixed with the saliva the tongue pushes 
 it into the back part of the mouth. 
 
 Swallowing. 
 
 The food is now ready to be swallowed. It 
 enters the top of a tube called the gullet or 
 oesophagus. The gullet is just back of the 
 
52 FIRST BOOK OF PHYSIOLOGY 
 
 windpipe. The muscles of this tube squeeze 
 the food down farther and farther till it reaches 
 the stomach. This is done every time we 
 swallow. 
 
 If we attempt to swallow food that has not 
 been well chewed and mixed with saliva it will 
 stick in the gullet. The same thing will hap- 
 pen if we try to swallow too large a mouthful. 
 Some animals have been choked to death in 
 this way. 
 
 The large lump of food that is stuck in the 
 gullet will press on the back part of the wind- 
 pipe and shut off our breath. 
 
 The stomach. 
 
 The stomach is a bag that looks very much 
 like what you see at the top of this picture. 
 A man's stomach will hold about three pints. 
 The gullet pushes the food in at the top. 
 Then the muscles of the stomach begin to 
 roll the food about and mix it thoroughly. 
 
 At the same time the stomach pours out on 
 the food a sour liquid called the gastric juice. 
 This juice will digest nearly all of the first kind 
 of foods that we told you about on page 43. 
 It changes such food to a liquid form. 
 
 You can now see why the food should be 
 cooked till it is tender and then chewed real 
 
DIGESTION 53 
 
 fine before it is swallowed. The stomach can 
 then easily mix it with the gastric juice. 
 
 As soon as any of the food is digested and 
 changed to a liquid it passes out at the other 
 end of the stomach. 
 
 15. Stomach and intestines. 
 
 After a hearty meal it will be two or three 
 hours before the stomach is empty again. If 
 the stomach is not healthy or the food is very 
 hard to digest it may take four hours or more. 
 
54 FIRST BOOK OF PHYSIOLOGY 
 
 After the stomach has been hard at wor-k 
 with one meal, it should be allowed to rest for 
 a while. It is a bad practice to eat between 
 meals. Wait till the next regular meal, and 
 then the stomach will be greedy to get it and 
 digest it for you. 
 
 Many people eat too much. They keep on 
 eating even after they know they have enough. 
 They fill the stomach so full that it cannot 
 work well. There is not enough gastric juice 
 to digest so much food at once. This is not 
 so bad when we are eating simple food like 
 corn bread or potatoes or oat-meal, but it 
 is very bad for us when we eat too much 
 of the strong foods like pork and beef and 
 eggs. 
 
 You should quit eating just as soon as you 
 begin to feel satisfied. It is not the amount 
 we eat that does us good, but the amount we 
 can digest and use. 
 
 Any food more than this is only a burden 
 to the body, and is sure to produce poisons 
 that will make us sick. 
 
 The intestines. 
 
 When the food leaves the stomach it passes 
 into a long tube called the intestines. In the 
 picture 15 you see them below the stomach. 
 
DIGESTION 55 
 
 They are often called the bowels. You see 
 there are two kinds. The small intestines are 
 in the centre and the large ones are around 
 them. This tube is very soft and is folded 
 back and forth many times. If it were 
 stretched out into a straight tube it would 
 reach a distance of nearly twenty feet. 
 
 When the food gets into the small intestine 
 two more juices are poured out upon it. 
 
 Bile. 
 
 One of these juices is called bile. The bile 
 is made by the liver, which is on your right 
 side just under the lowest ribs. The liver 
 stores the bile in a little bag called the gall- 
 bladder. When the food comes along, this 
 juice pours out onto it and helps a great deal 
 in digestion. 
 
 Pancreatic juice. 
 
 The other juice is called the pancreatic juice. 
 It is gathered up by the pancreas, which lies 
 right below the stomach, and is not nearly so 
 large as the liver. This juice is poured out 
 onto the food along with the bile, and the two 
 work together to digest the food in the intes- 
 tines. 
 
56 FIRST BOOK OF PHYSIOLOGY 
 
 How the food gets into the blood. 
 
 The bile and the pancreatic juice digest the 
 food that was not digested before. No food 
 can get into the blood or do us any good until 
 it is first changed to a liquid. The muscles 
 of the intestines keep mixing the food with 
 these juices till it is all in a liquid form. Then 
 it soaks through the sides of the intestines and 
 
 1 6. Section of small intestine. 
 
 is carried away in the blood-tubes. In picture 
 1 6 you see a very thin slice across the small 
 intestine of a cat. It is enlarged here so you 
 can see it more plainly. Ours are made in the 
 same way. You see the tube is not smooth 
 on the inside, but is much like the nap on 
 velvet. Each little tuft has blood-tubes in it, 
 
DIGESTION 
 
 57 
 
 and when the food comes along it is easily 
 soaked up and carried away in the blood. 
 
 Picture 1 7 shows you how some of these 
 same tufts look when we see them through a 
 
 17. Villi of small intestine. 
 
 strong microscope. You can see the blood- 
 tubes running down into each one and coming 
 close to the food. 
 
 The work of the liver. 
 
 After the food gets out of the intestine and 
 into the blood-tubes it is not yet ready to be 
 sent out over the body.. It is not good blood 
 yet. Nearly all of it must now go through 
 the liver. The liver, as we have learned, 
 takes bile out of it. It also takes out other 
 things that would poison us if they would ever 
 
58 FIRST BOOK OF PHYSIOLOGY 
 
 get to the heart. It changes the food, too, in 
 some other ways. 
 
 After the liver has done its part, the liquid 
 food is now ready to be carried up to the 
 heart. 
 
 A good liver is our most faithful friend. If 
 it gets out of order, everything goes wrong, 
 and we become very sick. 
 
 Review of the work of digestion. 
 
 After you swallowed your food you did not 
 have to give it any further attention. 
 
 The stomach took whatever you gave it, 
 and poured upon it the sour gastric juice and 
 mixed all well together. This digested part 
 of the food and it began to flow out of the 
 other end of the stomach into the small in- 
 testine. In three or four hours the stomach 
 was empty. 
 
 In the intestines two more juices were 
 poured upon the food. They are called the 
 bile and the pancreatic juice. The bile is 
 made by the liver and the pancreatic juice is 
 made by the pancreas. The intestines mixed 
 the food with these juices and digested all 
 that was not digested in the stomach. 
 
 Now the food was all in a liquid form, and 
 soaked through the sides of the intestine and 
 
DIGESTION 59 
 
 was carried away in blood-tubes to the liver. 
 The liver purified it and made it into the 
 right kind of blood for the body, and then it 
 was sent on to the heart. 
 
 This is all wonderful, and you will learn 
 many more interesting things about it in the 
 larger books. 
 
 Care of stomach and intestines. 
 
 Every boy and girl wants to have a healthy 
 stomach and intestines. 
 
 People who have stomach trouble are very 
 miserable, and are of little use in any kind of 
 work until they get well again. If your stom- 
 ach and intestines will not do their work, it is 
 no use for you to eat. The food cannot do 
 you any good, for it cannot be digested and 
 get into the blood. 
 
 The way to keep anything in good order is 
 to take good care of it. Learn to do this 
 while you are young, and you will be sure to 
 have better health and will be much happier 
 when you are older. 
 
 Here are some things that you should do 
 and some things you should not do. Follow 
 all of these rules, and you will never be 
 troubled with bad digestion : 
 
 Eat only good food. 
 
60 FIRST BOOK OF PHYSIOLOGY 
 
 Eat food that is well cooked. 
 
 Chew the food thoroughly till it is in fine 
 pieces. 
 
 Drink only milk and water. 
 
 Eat only three times a day. The stomach 
 must have some rest. 
 
 Stop eating before the stomach is too full. 
 Overeating is the cause of a great deal of 
 trouble. 
 
 Eat but little candy, and have it pure. 
 
 Never drink ice-water. The water may be 
 cool, but ice-cold water is always bad for the 
 stomach. If you want to cool off, plunge your 
 hands into cold water, but do not drink it. 
 
 Be cheerful and happy while you eat. 
 Good cheer will help digestion. 
 
 Never drink anything that has alcohol in it, 
 for alcohol spoils the gastric juice and makes 
 the food hard to digest. 
 
 Do not drink anything while the mouth is 
 full of food. Keep on chewing the food till 
 the saliva has had time to wet it. Food 
 digests better when it is well mixed with 
 saliva. 
 
 Eat more of the simple, coarse foods and 
 less of the strong meats. A good soup made 
 of beef-broth and vegetables is an excellent 
 food. 
 
DIGESTION 61 
 
 A story. 
 
 A long time ago there was a great king 
 whose name was Nebuchadnezzar. He lived 
 in a grand palace and had an army of ser- 
 vants about him to do his bidding. One day 
 he told his chief servant to search through his 
 kingdom for the best boys he could find and 
 bring them to the palace. 
 
 The king told him to get only those boys 
 who had good health and a pleasing face 
 and who were quick to learn. The servant 
 hunted all around and brought in a large 
 number of the best boys. 
 
 Then the king told him to take good care 
 of them and train them for three years. At 
 the end of that time the king said he would 
 call the boys before him, so that he could see 
 how they looked and what they could do. 
 
 Now the king had told his servant to give 
 the boys all the rich food they could eat. 
 They could have all the meats and dainties 
 they wanted and all the wine they could 
 drink. Their table was to be just as rich as 
 that of the king himself. He thought he was 
 doing the best thing for the boys. 
 
 The most of them ate and drank what the 
 servant gave them, and thought it was very 
 good ; but four of them did not like this rich 
 
62 FIRST BOOK OF PHYSIOLOGY 
 
 food, and asked the servant to let them have 
 just simple vegetable soup, and instead of 
 wine they asked for pure water. 
 
 Then the servant said that he had to do just 
 as the king told him, and he feared his master 
 would be angry unless they did just as they 
 were ordered to do. 
 
 The four boys then asked him to try them 
 just for ten days to see how they would get 
 along, and not tell the king anything about 
 it. They knew that they were right. 
 
 The servant liked these boys, and so he let 
 them try it. When the ten days were up, they 
 looked so healthy and were so bright that the 
 servant let them eat this kind of food all the 
 time. 
 
 At the end of the three years the king- sent 
 for all the boys. He looked at them closely 
 and examined them to see what they could do. 
 Then he picked out these four boys because 
 they had the best health and the brightest 
 minds, and he kept them in his palace. 
 
 They were a great help to the king, and 
 grew up to be very famous men. We often 
 talk and read about them even to the present 
 day. 
 
DIGESTION 63 
 
 Questions. 
 
 1. How many teeth have you in each jaw ? 
 
 2. What causes tooth-ache ? 
 
 3. Why is the enamel on a tooth so hard ? 
 
 4. Why should we take care of our teeth ? 
 
 5. How can we care for our teeth ? 
 
 6. What is saliva, and of what use is it ? 
 
 7. Tell what you know about swallowing. 
 
 8. Describe the stomach. 
 
 9. What does the stomach do with the food ? 
 
 10. Why is it wrong to eat too much or to eat between 
 meals ? 
 
 11. What two juices act on the food in the small intestine ? 
 
 12. Tell about bile. 
 
 13. Tell about pancreatic juice. 
 
 14. Why must food be digested ? 
 
 15. How does the food get into the blood ? 
 
 1 6. Tell what you can about the work of the liver. 
 
 17. Give a short account of the whole work of digestion. 
 
 1 8. Give some rules for eating and drinking. 
 
 19. Tell the story of the four boys. 
 
 20. What were the names of these boys ? 
 
CHAPTER VI 
 
 THE BLOOD 
 
 THE blood goes to every part of the body. 
 It makes its way even into the hard bone and 
 the teeth. If you push a fine needle through 
 the skin at any place on the body, some blood 
 will run out. The skin looks pink and the 
 cheeks red because the red blood is just under 
 the skin. 
 
 There is enough blood in your body to fill 
 a tincup six or eight times. Of course, there 
 is more blood in a large body. A large man 
 has about eight quarts of blood. 
 
 About one-thirteenth of the weight of the 
 body is blood. If your weight is one hundred 
 and thirty pounds, then your blood by itself 
 would weigh ten pounds. Divide your weight 
 in pounds by thirteen, and the answer will be 
 about the number of pounds of blood you 
 have. 
 
 The heart. 
 
 The blood is never still. It is moving 
 around and around through the body all the 
 6 4 
 
THE BLOOD 65 
 
 time. What makes it move? You say the 
 heart does it, and that is correct. 
 
 In the picture you see how the heart looks. 
 It is about as large as the fist and is made of 
 strong muscles. The heart is double. There 
 is the right heart and the left heart. These 
 two are tightly fastened together. The left 
 heart is stronger than the right one because 
 it has harder work to do. Each half of the 
 
 1 8. The heart. 
 
 heart has two tubes at the top of it. One 
 tube carries the blood in and the other carries 
 it out. The blood first goes into the right 
 heart, and when it is full it squeezes upon the 
 blood and forces it out through the other tube 
 and sends it to the lungs. 
 
 When it comes back from the lungs it goes 
 into the left heart, and when it is full the 
 strong muscles on that side squeeze the blood 
 
 5 
 
66 FIRST BOOK OF PHYSIOLOGY 
 
 out through another tube and send it out 
 on its trip through the whole body. 
 
 Care of the heart. 
 
 You all know where your heart is, but may- 
 be you have not thought how faithful it is to 
 you. It beats all day and all night. The only 
 rest it ever gets is the short time between the 
 beats. If your heart would get badly out of 
 order or would stop for just one minute you 
 would die. 
 
 Some people take very poor care of the 
 heart. Boys and men often have what the 
 doctor calls "tobacco heart." Such a heart 
 will flutter. At times it beats very rapidly 
 and at other times slowly. 
 
 This bad condition is often caused by 
 smoking cigarettes or by using tobacco in any 
 way. If the heart does not beat as it should, 
 then the body cannot get the blood it needs. 
 You cannot be healthy without a good heart. 
 Your heart will do good work for you if you 
 do not hinder it. 
 
 Beer is bad for the heart, for beer makes 
 fat. The heart must be made of strong mus- 
 cles. Beer changes some of the muscles of 
 the heart to fat. This makes the heart weak, 
 and it is not able to send out a strong current 
 
THE BLOOD 67 
 
 of blood through the body. People often die 
 because they keep on drinking beer till the 
 heart is so fat and weak that it cannot work 
 any longer. 
 
 The arteries. 
 
 The blood is forced out by the heart 
 through strong tubes called arteries. They 
 spread out all over the body. They divide 
 into a great many branches, and get smaller 
 and smaller till they are finer than a hair. 
 When an artery is cut the blood will spurt 
 out in a stream. If the artery is a large one, 
 the person would soon bleed to death unless 
 he knew what to do at once. If such an acci- 
 dent should ever happen to you or to one of 
 your friends, press the cut tight together with 
 both hands. Do not be afraid of the blood. 
 No time must be lost. 
 
 Also, if you can have some one to help, tie 
 a handkerchief or strong cord around the leg 
 or arm above the cut. Draw the cord as tight 
 as you can to press the artery shut, so the 
 blood cannot get down to the cut. As soon 
 as the doctor comes he will know what to do. 
 
 The pulse. 
 
 The arteries are put deep down under the 
 skin, but in a few places they come very 
 
68 FIRST BOOK OF PHYSIOLOGY 
 
 close to the surface. At such places we can 
 plainly feel the pressure on the blood when- 
 ever the heart beats. This pressure or throb- 
 bing in an artery is called the pulse. 
 
 The pulse can be felt most plainly at the 
 wrist. 
 
 The girl in the picture is counting her 
 pulse. If she does it correctly, she will know 
 how fast her heart is beating. You try it. 
 
 19. Counting the pulse. 
 
 Look at the second-hand of a watch and 
 count till it goes once around. This tells you 
 how often your heart beats in one minute. 
 
 I have just tried, and I find that my heart is 
 beating eighty times in one minute. 
 
THE BLOOD 69 
 
 How fast does yours beat ? 
 
 Now exercise for a few minutes and then 
 count again. See how much faster the heart 
 is beating. When we work we need more 
 blood. The heart tries to give it to us. 
 What a faithful old heart we have ! 
 
 Capillaries. 
 
 At the ends of the arteries is a network of 
 very fine tubes called capillaries. 
 
 The blood is now pushed on from the ar- 
 teries into these small tubes. Here is where 
 the blood feeds the body and takes away any 
 waste matter. The capillaries are very small, 
 short tubes ; but there are so many of them 
 that if you push the finest needle through the 
 skin at any place you are sure to run the 
 needle through some of them and to let some 
 blood out. 
 
 The blood keeps flowing on through them 
 in a steady stream. 
 
 Veins. 
 
 The heart sent the blood out through the 
 arteries and then through the capillaries. 
 
 Now the blood goes into another kind of 
 tube called a vein. The veins carry the 
 blood back to the heart again. 
 
70 FIRST BOOK OF PHYSIOLOGY 
 
 Pull up your sleeve and grasp your arm 
 with the other hand. You see that the veins 
 will fill up with blood. This blood was mov- 
 ing up the arm, but your hand stopped it. 
 As soon as you let go it will move on back to 
 
 20. Veins in the arm. 
 
 the heart. Many of the veins are close to 
 the surface of the body, and you can see that 
 it would not be right to wear any tight bands 
 or tight clothing on any part of the body, for 
 that would stop the flow of blood in the veins. 
 
 Red corpuscles. 
 
 The blood looks red, but it is not all red. 
 I drew a little blood from my thumb and 
 looked at it with a microscope. 
 
 In picture 21 you can see how it looked. 
 
 The little round bodies are called red cor- 
 puscles. 
 
 They are the only part of the blood that is 
 red. There are so many of them that they 
 make all the blood look red. 
 
THE BLOOD 71 
 
 The red corpuscles are so small that you 
 cannot see them unless you look through 
 a strong microscope. The same microscope 
 that made the blood look like picture 2 1 made 
 the finest kind of silk look like picture 22. 
 
 Old people do not have as many red cor- 
 puscles in their blood as do young people, 
 and so they are always pale. 
 
 2 1 . Red blood-corpuscles. 
 
 The work of the red corpuscle is to carry 
 oxygen from the lungs out to all parts of the 
 body. 
 
 White corpuscles. 
 
 There are also many white corpuscles float- 
 ing along in the blood with the red ones, but 
 not nearly so many of them. They are al- 
 ways on the lookout for any substance that 
 
72 FIRST BOOK OF PHYSIOLOGY 
 
 may harm the body. They try to keep us 
 from getting sick. If we do get sick, they do 
 their best to make us well again. When any 
 of the little germs of disease get into the 
 body, they try to kill them off. If the white 
 corpuscles are good and strong, they nearly 
 always succeed. 
 
 When you cut your finger, a great number 
 
 22. Fine silk. 
 
 of them will hurry to that spot and will try 
 to heal it. The white matter that you often 
 see in a sore is made of the white cor- 
 puscles. 
 
 They are our body's best friends, and we 
 ought to do all we can to keep them strong 
 and in good health. Alcohol has a very bad 
 effect on them. They do not seem to care 
 
THE BLOOD 73 
 
 whether they work or not when alcohol gets 
 into the blood. This is one of the reasons 
 a hard drinker will catch a disease much 
 quicker than other persons. The nicotine of 
 tobacco is also a poison to them. 
 
 A man who drinks whiskey and smokes 
 cigarettes is more likely to get sick than a 
 man who does not use them, and then it 
 takes a longer time for him to get well. 
 
 The liquid part of blood. 
 
 The corpuscles are carried along in a 
 liquid. The liquid is composed of water and 
 the liquid foods. You learned a little while 
 ago that the meat and potatoes and other 
 foods were changed into a liquid when they 
 were digested in the stomach and intestines. 
 Now we find this food in the blood, and the 
 heart keeps pushing it out through the ar- 
 teries to the capillaries. In that way every 
 part of the body gets the food it needs. 
 
 Blood-clot. 
 
 As long as the blood is moving about in 
 the body it is a very thin liquid, but it will 
 soon form into a clot when it is taken out of 
 the body. When you cut your finger or any 
 part of the body the cut will soon fill up with 
 
74 FIRST BOOK OF PHYSIOLOGY 
 
 a thick clot of blood. If it is not a very bad 
 cut, the clot will soon stop the bleeding. It is 
 good for us that this is so, for a very little cut 
 might bleed us to death if it did not have a 
 way of stopping itself. When a large artery 
 is cut the clot cannot stop the blood, and we 
 have to hold the blood in till a doctor comes 
 and ties the end of the artery. 
 
 Questions. 
 
 1. How much blood is in your body ? 
 
 2. Describe the heart. 
 
 3. What causes tobacco heart ? 
 
 4. What effect does beer have on the heart ? 
 
 5. Describe the arteries. 
 
 6. What can you do when an artery is cut ? 
 
 7. How many times does your pulse beat in one minute ? 
 
 8. Tell about the capillaries. 
 
 9. What is the use of the veins ? 
 
 10. What makes the blood red ? 
 
 1 1 . What work do the red corpuscles have to do ? 
 
 12. Of what use are the white corpuscles ? 
 
 13. What is the liquid part of the blood ? 
 
 14. What is the use of a blood-clot ? 
 
CHAPTER VII 
 
 BREATHING 
 
 Why we breathe. 
 
 THE food of a steam-engine is coal, but the 
 coal alone will not make a fire. There must 
 be a strong draft of air. When we have 
 good coal and a good draft, then we can have 
 a good fire and can get up steam, and the 
 engine will do work. 
 
 A man's body is a little like the engine. 
 Food alone will not keep us alive, but we 
 must breathe in the air. Then the food and 
 the air together will make us warm and en- 
 able us to work. 
 
 Something for you to do. 
 
 Place a lamp-chimney over a lighted candle. 
 Let the chimney rest on two pencils, as you 
 see in picture 23. The candle-flame will be 
 even brighter than before. A little smoke 
 will show that the air is rushing in at the bot- 
 tom of the chimney. Now take the pencils 
 away and let the chimney sit down on the 
 box or paper. The flame will soon die out 
 
 75 
 
76 FIRST BOOK OF PHYSIOLOGY 
 
 because it cannot get fresh air. This shows 
 you that the candle alone cannot burn. It 
 takes the two together to make a fire. The 
 
 23. Candle-flame. 
 
 part of the air that the flame wants is oxygen. 
 Everything that is alive, even the trees and 
 the grass, must have oxygen that they may 
 live. 
 
BREATHING 77 
 
 The reason we breathe, then, is that we 
 may get oxygen to combine with our food. 
 This is what keeps us alive and makes us 
 able to think and work. 
 
 The nostrils. 
 
 Air should be breathed in through the nose 
 and not through the mouth. The nostrils 
 warm the air before it gets to the lungs, and 
 also strain out the dust and the dirt. Even 
 when you run or work hard you should 
 breathe through the nose. Before going to 
 sleep be careful to have your mouth closed, 
 and lie in such a way that the mouth will not 
 drop open during the night. 
 
 The windpipe. 
 
 A large tube called the windpipe conducts 
 the air down to the lungs. Grasp your throat 
 with your fingers and you can feel that this 
 pipe is made of rings. You can also see them 
 in picture 24. They are not hard bone, but 
 are so stiff that the windpipe stands open all 
 the time. On the top of the windpipe is a 
 lid that can open and shut. When we breathe 
 it is open ; but when we swallow food the lid 
 closes down, and the food passes over it and 
 down another tube called the gullet. 
 
78 FIRST BOOK OF PHYSIOLOGY 
 
 When we are not careful, some food gets 
 under the lid and into the windpipe, and we 
 have to cough hard to get it out. 
 
 The lungs. 
 
 Each of us has a pair of lungs. If you 
 could look into your chest, you would see 
 your lungs and heart about as they are placed 
 in picture 25. 
 
 24. Air- tubes. 
 
 The lungs are not firm like the muscle in 
 your arm, but are soft and spongy. When 
 you fill your lungs with air, they swell up and 
 get much larger. 
 
 Look again at picture 24, and you see that 
 the windpipe divides at its lower end into 
 two branches. One branch goes to each lung. 
 Then these divide again and again until the 
 
BREATHING 79 
 
 tubes are as fine as a hair and reach every 
 part of the lung. At the end of each one of 
 the fine air-tubes is a thin little air-sac. When 
 you take a deep breath, it is like blowing up a 
 million little balloons all at once. 
 
 25. The lungs. 
 
 Just outside the little air-sacs are fine tubes 
 that carry blood. We will now try to learn 
 what all this is for. 
 
 What the lungs do. 
 
 Awhile ago we learned that when the blood 
 went out through the body, it gave up its food, 
 and the red corpuscles gave up their oxygen. 
 The blood then came back through the veins. 
 Much of the waste matter that the body did 
 not want any more came back with it, The 
 
8o FIRST BOOK OF PHYSIOLOGY 
 
 corpuscles are not red any more, for they have 
 lost their oxygen and are now purple in color. 
 Such blood is impure. It would not do for 
 the heart to send this kind of blood out again. 
 It must be made pure. 
 
 The right heart first sends it into the lungs. 
 There the blood gets ricl of the waste matter 
 in it, and the corpuscles load up with oxygen 
 and turn bright red. Now it comes back to 
 the heart, and the left heart takes it and sends 
 it out over the body again. 
 
 Do not think that this happens to all the 
 blood at one time. While some of the blood 
 is in the heart and lungs, the rest of it is out 
 on its trip. Some is in the head, some in the 
 arms or legs, and some in all other parts of 
 the body. After awhile this blood, too, will 
 come back to the heart and lungs. 
 
 So it keeps going around and around. It 
 takes about twenty seconds for a drop of 
 blood to make a trip from the left heart back 
 to the left heart again. 
 
 How the lungs purify the blood. 
 
 The air which we breathe out is impure. It 
 was changed in the lungs. 
 
 You just learned that each air-sac in the 
 lungs is surrounded by tiny tubes full of blood. 
 
BREATHING 81 
 
 When you take a breath, the oxygen of the 
 air will go right through the sides of the air- 
 sac and get to the red corpuscles of the blood. 
 The gas that makes the blood impure is called 
 carbon dioxide. This gas, along with some 
 other waste, comes from the blood over into 
 the air-sac and then we breathe it out. 
 
 Then we take another fresh breath, and the 
 same thing happens again. We will have to 
 keep on doing this as long as we live. Breath- 
 ing is one of the most important things we 
 have to do ; and we will now tell you some- 
 thing about pure air and how to breathe. 
 
 Cigarette smoke. 
 
 Any boy can now see why the smoke of the 
 cigarette does so much harm. 
 
 The cigarette smoker does not only draw 
 the smoke into his mouth and blow it out 
 again. That would be bad enough, but he 
 inhales it. He takes it down into all the little 
 air-sacs, where it gets real close to the blood. 
 The lungs are trying to make the blood pure, 
 but they cannot do so unless we give them 
 pure air. Cigarette smoke contains a deadly 
 poison called nicotine. This poison goes from 
 the air-sacs into the blood, and so is carried 
 out into the whole body. 
 
82 FIRST BOOK OF PHYSIOLOGY 
 
 Is it any wonder that cigarette smoke so 
 quickly ruins the health of the body and of thje 
 mind ? 
 
 Pure air. 
 
 The air in the country is nearly always pure. 
 That is the reason you should play out in the 
 park or take a romp in the open fields or work 
 in the garden. Exercise will do you no good 
 unless you can get good air at the same time. 
 
 In the crowded city the air often gets very 
 bad, even in streets. The worst air is often 
 found in the rooms where we live and where 
 we sleep. We cannot always tell that the air 
 is bad by the way it smells. The little germs 
 of disease are so small that we cannot see 
 them, and yet if they get into the blood they 
 can make us very sick. They like to live in 
 damp, dark rooms, but the sunlight Avill kill 
 them. Every room should often be aired out, 
 and the sunlight should be allowed to pour 
 right into the room for a part of the day. 
 
 Sick people get along much better when 
 they can lie in a room where the air is dry and 
 there is plenty of sunlight. 
 
 We cannot help breathing some of these 
 little germs into our lungs every day ; but if 
 our lungs are good and sound, we will breathe 
 
BREATHING 83 
 
 them right out again, and they can do us no 
 harm. 
 
 How the breath makes air impure. 
 
 The air may be very pure when we take it 
 into the lungs, but it is not pure when it 
 comes out. We take some of the oxygen 
 out of the air every time we fill the lungs, and 
 in its place we breathe out bad air. When 
 you stay long in a small room that is closed 
 up tight you get sleepy and do not feel well. 
 This is because the air is getting bad and you 
 are breathing some of the old breath over 
 again. If you let in fresh air, you will soon get 
 wide awake again and will be as lively as ever. 
 
 In the summer-time most people can have 
 plenty of fresh air, for then the windows and 
 doors can be open. 
 
 In winter the coal-stove or grate will take 
 out a great deal of bad air ; but if there are 
 many people in the room, the window should 
 be let down just a little at the top so fresh air 
 can be coming in all the time. 
 
 Something for you to do. 
 
 Take a short piece of a candle and fasten 
 it to a wire, as you see in the picture. Light 
 the candle and let it down into the fruit-jar. 
 
8 4 
 
 FIRST BOOK OF PHYSIOLOGY 
 
 It still burns brightly. Now lift the candle 
 out. Put your mouth close down onto the 
 mouth of the jar and breathe out slowly a 
 long breath from your lungs. Let the candle 
 down into the jar again and it will burn very 
 dimly or go clear out. Try it. 
 
 26. Breath and candle flame. 
 
 The candle needs oxygen just as we do. 
 When the air will not keep a candle burning 
 very brightly, it is certainly not fit for us to 
 breathe. If we keep on breathing bad air our 
 life will grow dim or will go out just like that 
 candle light. 
 
 If a mouse be put into a jar of that impure 
 air he will jump about for a short time and 
 
BREATHING 85 
 
 then fall over on his side. He is not dead, 
 but has only fainted. If you shake him out 
 onto the table where he can get fresh air he 
 will soon revive and run off. If he is left 
 in the jar very long, he will die because he 
 cannot get oxygen. 
 
 Good air while we sleep. 
 
 We should be very careful to have good air 
 in the bedroom, because we go on breathing 
 all night. Before you go to sleep, be sure 
 there is some way for fresh air to get into the 
 room. Open a window a little from the top, 
 no matter how cold it is on the outside. Some 
 people sleep in summer-time on the top of 
 their houses, so they can be sure to have 
 plenty of fresh air. They have the bed inside 
 a cage that is covered only with a thin net to 
 keep out the mosquitoes and other insects. 
 Some sleep in tents out in the yard, and it 
 always gives them better health. This shows 
 how important it is for all of us to breathe 
 only good air. 
 
 Because some boys and girls are afraid in 
 the dark, they cover themselves up, face and 
 all, under the blankets. Then they have to 
 breathe the bad air from their lungs over and 
 over again. This is a very bad thing to do. 
 
86 FIRST BOOK OF PHYSIOLOGY 
 
 Some children have become very sickly and 
 have suffered from bad diseases because the/ 
 slept in this way. 
 
 If you will think of how the candle acted 
 in bad air, you will not go to sleep again with 
 your head under the covers. 
 
 How often we should breathe. 
 
 I have just counted and found myself taking 
 fifteen breaths in a minute. Then I stood up 
 and took some rapid exercise and then counted 
 again, and found I was breathing thirty times 
 in a minute. You try it. 
 
 When we do hard work of any kind the 
 blood must go around faster. The heart 
 beats faster, and so we must breathe faster to 
 make the blood pure. 
 
 When boys run a long race they breathe 
 very rapidly. Some cannot run very far till 
 they are out of breath. If they would practise 
 running every day, and would learn to take in 
 deep breath only through the nostrils, they 
 would not get short of breath for a long 
 time. 
 
 It is found that a cigarette smoker soon 
 gets out of breath. His lungs will not hold 
 as much air as they should. The tobacco 
 has spoiled a part of the air-sacs, hence the 
 
BREATHING 87 
 
 rest of them have to be filled oftener to get 
 the right amount of oxygen to the blood. 
 
 When young men are trained for athletic 
 games, like foot-ball, wrestling, running, and 
 boxing, they are not allowed to use any to- 
 bacco or drink any beer or whiskey. They 
 tire out and lose their breath much sooner 
 when they smoke or drink, and are almost 
 sure to lose the game. 
 
 Men who drink alcohol sometimes get so 
 short of breath that they cannot lie down. 
 They have to sit up all the time for fear they 
 may smother to death. 
 
 Taking a deep breath. 
 
 A man's lungs will hold about 330 cubic 
 inches of air. That is a little more than 
 one and one-half gallons. When he fills his 
 lungs full he can then breathe out 230 cubic 
 inches of air, which is almost exactly one gal- 
 lon. Some air always remains in the lungs. 
 Blowing soap-bubbles is a good practice in 
 breathing. If you can blow a bubble five or 
 six inches across, with one breath, you are 
 doing very well. It is good for the health to 
 take fresh air deep down into the lungs every 
 once in a while. 
 
 We should learn to sit and walk with the 
 
88 FIRST BOOK OF PHYSIOLOGY 
 
 chest forward and the shoulders back. This 
 gives the lungs room, and then it is easy tc 
 fill them with air. 
 
 Some girls have a very bad fashion of 
 fastening the dress very tight about the 
 waist. This cramps the lungs. Such a girl 
 cannot take a full breath. She tries to make 
 up for it by breathing faster, but she will 
 
 27. A soap-bubble. 
 
 be sure to have poor blood and poor health. 
 The lungs must get enough air so that each 
 red corpuscle can get its load of oxygen, and 
 also the poison in the bad blood must get out 
 into the air. This can never be done well 
 when the lungs are squeezed out of shape. 
 
 It is very good for any one to go to an 
 open window or out onto the porch and take 
 five or six deep breaths every day, winter and 
 
BREATHING 89 
 
 summer. Fill the lungs full and hold it there 
 for a while. Then breathe out and fill them 
 again. 
 
 If you will practise this and make sure that 
 you always get plenty of good air to the lungs, 
 it is quite likely you will never catch a cold. 
 
 How the body is kept warm. 
 
 When coal is burning in a stove, you know 
 that, if it can get a good draft of air, it will 
 make the stove very hot. If you want the coal 
 to quit burning, you close the damper so the 
 air cannot get in. 
 
 The oxygen of the air which you breathe is 
 carried by the red corpuscles out even to the 
 tips of the fingers and toes. When it unites 
 with the food, it makes heat just as it did with 
 the coal in the stove. There is no blaze of 
 fire in the body like the one in the stove, but 
 the food is slowly burned, and that keeps our 
 bodies warm. 
 
 Just warm enough. 
 
 Our bodies must not get too warm nor too 
 cold. Look at the thermometer in your house 
 or school-room. It ought to show a tempera- 
 ture of 70 degrees. Your body on the inside 
 
90 FIRST BOOK OF PHYSIOLOGY 
 
 is 28 degrees warmer than that. That would 
 make your temperature 98 degrees. 
 
 It will be almost exactly 98 as long as you 
 are not sick. If you get a fever, your tem- 
 perature may go up to 103 or 104 degrees. 
 Then the doctor says you are very sick. 
 
 No part of our body can do its best work 
 unless its temperature is 98 degrees or very 
 close to it. 
 
 In winter-time we wear heavy clothes to 
 keep the heat in our bodies from getting away, 
 and we live in warm rooms for the same 
 reason. 
 
 Another good way to keep warm is by exer- 
 cise. When we make our muscles work, the 
 food is burned up faster, and that makes us 
 warmer. Good exercise in the cool fresh air 
 is a much better way to get warm than to sit 
 all day by a warm stove. 
 
 We can nearly always manage to keep our 
 bodies from getting too cold, but there is often 
 danger that they may get too hot. The body 
 has a very nice way of keeping itself from 
 getting too warm, and we will study that next. 
 
 How sweat cools us. 
 
 When the body gets too warm, the sweat 
 begins to pour out all over the surface of the 
 
BREATHING 91 
 
 skin. As soon as the sweat gets to the air, it 
 begins to dry up, and that takes heat from the 
 body. This is a way nature has to keep us 
 from getting too hot. 
 
 Put a drop of gasoline on the back of your 
 hand, and it will feel very cool because it 
 dries up so quickly. 
 
 28. A water- jug. 
 
 Dip one of your hands into warm water, 
 and then hold both hands up where the wind 
 is blowing. The wet hand will feel much 
 cooler than the dry one, even if the water is 
 very warm. 
 
 In some warm countries they make their 
 water-jugs out of clay that is much like our 
 flower-pots. The water will soak through the 
 
92 FIRST BOOK OF PHYSIOLOGY 
 
 sides of the jug and keep it wet on the out- 
 side. Then they hang the jug up where the 
 wind is blowing, and after a while the water is 
 nice and cool. Sweat cools our bodies in just 
 the same way. 
 
 The picture shows you a water-jug of this 
 kind. This one was used by a boy in Cuba. 
 
 Will alcohol warm the body. 
 
 Some men think that if they take a drink 
 of whiskey or beer on a cold day it will keep 
 them warm. 
 
 It has been found out that this is a mistaken 
 notion. Alcohol will soon make the body 
 colder. When a man drinks whiskey, a great 
 deal of the warm blood will come to the sur- 
 face of the body just under the skin. The 
 heat can then easily get away. He will lose 
 more heat than the alcohol can give him. 
 Then, too, his food will not burn as well as it 
 did before. The alcohol smothers out his fire. 
 A man who uses strong drinks will freeze to 
 death sooner than those who do not. 
 
 The very best way to keep warm is to eat 
 a hearty meal, take full breaths of fresh 
 air, and keep the blood in rapid motion by 
 exercise. 
 
BREATHING 93 
 
 A story. 
 
 One very cold day six men started out on 
 a long trip. They had food enough with 
 them to last for three days. After they had 
 travelled for two days it grew bitter cold, and 
 they lost their way. Soon it began to get 
 dark. They could make no fire, for they 
 could find no wood to burn. They thought 
 they would all surely freeze to death before 
 morning. Their leader told them all to eat 
 heartily of the food they had with them, for 
 he knew that was the only way they had to 
 keep warm. 
 
 Then they ran about and took all sorts of 
 exercise to get warm, but they were not able 
 to do this all night. 
 
 So they spread a blanket on the ground, 
 and all lay down very close together and cov- 
 ered themselves as best they could. Just 
 before this three of the men took a large 
 drink of strong whiskey. They thought it 
 would help to keep them warm. The other 
 three believed they could get along better 
 without it. They were all so tired that they 
 went to sleep. The next day they were 
 found there, but the three men who drank 
 the whiskey were frozen to death. The other 
 three had suffered very much with the cold, 
 
94 FIRST BOOK OF PHYSIOLOGY 
 
 but not even their little toes were frozen. 
 Their food and breath kept making heat all 
 night and kept them from freezing. 
 
 Questions. 
 
 1 . What two things make fire burn ? 
 
 2. Tell about the experiments with the candle and lamp- 
 chimney. Have you tried it ? 
 
 3. Why should we breathe through the nose ? 
 
 4. Describe the windpipe. 
 
 5. Tell about the air-tubes and air-sacs in the lungs. 
 
 6. Why is the blood sent through the lungs ? 
 
 7. How is the blood purified in the lungs ? 
 
 8. Why is cigarette smoke so harmful ? 
 
 9. Tell all you can about pure and impure air. 
 
 10. What makes the air in a room impure ? 
 
 1 1. Show the effects of breath on a candle flame. 
 
 12. How can we have fresh air while we sleep ? 
 
 13. How often do you breathe ? 
 
 14. How much air will the lungs hold ? 
 
 15. What keeps the body warm ? How warm should it be ? 
 
 1 6. How do clothes keep us warm ? 
 
 17. How does sweat cool the body ? 
 
 1 8. Tell the story of the six men. 
 
CHAPTER VIII 
 
 THE SKIN 
 
 What the skin is. 
 
 THE skin is a thin covering stretched all 
 over the outside of the body. There are two 
 layers of skin. The outside one is called the 
 scarf-skin, and right under it is a second layer 
 called the true skin. The scarf-skin is thin, 
 but it may grow quite thick. A man who 
 works every day with a shovel or pick will 
 have a hard, thick scarf-skin on the palms of 
 his hands. Corns on the feet are caused in 
 the same way by the rubbing of the shoes. 
 You see how the body tries to protect itself 
 by making the skin hard and tough wherever 
 it is needed. A little cut or scratch in the 
 skin will soon show us how useful the skin is 
 as a protection to the tender parts under it. 
 
 This outside skin is a great deal like the 
 outside bark of a tree. The bark may be 
 called the skin of the tree. In the centre of 
 the tree is the hard wood. Around it is a 
 tender bark, which is a little like our true 
 skin. Outside of all is the rough bark, which 
 
 95 
 
96 FIRST BOOK OF PHYSIOLOGY 
 
 is like our scarf-skin. You can cut away the 
 bark without hurting the tree if you do no; 
 cut too deep. 
 
 Nails. 
 
 The scarf-skin is not the same all over the 
 body. On the tops of the fingers and toes 
 it changes to a harder substance, called 
 finger-nails and toe-nails. The nails keep 
 growing out all the time, and we have to pare 
 them off. They need care, and should be 
 cleaned every day. Some boys and girls 
 have a bad habit of biting their finger-nails, so 
 they always look rough and ragged. Such a 
 hand never looks well. 
 
 Hair. 
 
 On the head is a heavy growth of hair. 
 This also is a part of the scarf-skin. The 
 hair is alive but it cannot feel, and so it does 
 not hurt to cut it. In picture 30 you can see 
 the root of a hair. It is deep down in the 
 skin. A tiny blood-tube runs into the bottom 
 of each hair and brings it its food. On each 
 side of it you see a little sac, which holds a 
 kind of oil. This is poured onto the hair and 
 keeps it soft and glossy. 
 
THE SKIN 97 
 
 Care of the hair. 
 
 A fine head of hair makes one look a great 
 deal better. It also protects the head and 
 keeps one from catching cold easily. We 
 must take proper care of the hair if we want 
 it to be in good condition. The scalp and 
 hair will get dirty, and must be washed once 
 in a while, but not too often. It is not good 
 to wet the hair every time you wash your 
 face, for that will make it lose its gloss and 
 become brittle. Comb the hair dry, and every 
 few days brush the scalp briskly with a hair- 
 brush. It does no good to put oil on the hair. 
 If the scalp is healthy, it will give the hair all 
 the oil that it needs. 
 
 How the scarf-skin protects us. 
 
 If you have ever tried to pick a splinter 
 from your hand or foot, you know that the 
 skin is very tough. 
 
 The butcher always saves the skin of a 
 calf or ox because it can be used in making 
 boots and shoes. It is hard to get through 
 the skin to the tender parts under it. The 
 little germs of disease would like to get in 
 where the blood and tender flesh are, but the 
 skin acts like the walls of a castle and keeps 
 
 7 
 
98 FIRST BOOK OF PHYSIOLOGY 
 
 these enemies out. You can even take 
 poison into your hand, and it cannot easily 
 get to the blood unless the skin is cut or 
 scratched. 
 
 It hurts when you are stung by a bee, 
 because he makes sure to put his poison 
 
 29. A bee-sting. 
 
 under the scarf-skin. You can see in this 
 picture a bee-sting as it looks under a mi- 
 croscope. The point is finer than the sharp- 
 est needle, so that he may be sure to push 
 it through the tough skin when he stings 
 us. 
 
THE SKIN 99 
 
 The color of the skin. 
 
 Between the scarf-skin and the true skin 
 are little grains of coloring matter. 
 
 These are the cause of the difference in the 
 color of the skin of different people. 
 
 The grains are very numerous and black in 
 the Negro. In some people they are yellow. 
 In white people they are of a light color, but 
 when the sun shines upon the skin, they get 
 darker, and then we say the skin is tanned. 
 In many people these grains are collected in 
 spots, and when the sun makes these spots 
 darker, we call them freckles. 
 
 A few people have no coloring matter in 
 the skin at all. This is unfortunate. They 
 look very pale ; and even their eyes and hair 
 are not colored as they are in other people. 
 Such persons are called Albinoes. 
 
 A study of the picture. 
 
 The picture 30 shows you about how the 
 skin would appear if you could look down 
 into it and see everything very much en- 
 larged. 
 
 At the top is the layer of scarf-skin, which 
 is also called the epidermis. Below it is the 
 thicker layer called the true skin. 
 
100 
 
 FIRST BOOK OF PHYSIOLOGY 
 
 At the top of the true skin you see ridges 
 and points. These are called papillae. The;ye 
 are the ends of the nerves of feeling. 
 
 Running down through both layers of the 
 skin are tubes, which you can see are coiled 
 
 30. The skin. 
 
 up at the lower ends. These are the sweat- 
 tubes. The picture also shows one hair and 
 its oil sacs. These sacs are called sebaceous 
 glands. -The fat in the skin makes it smooth 
 and plump. 
 
THE SKIN 
 
 Nerves of feeling. 
 
 The nerves of feeling are just below the 
 scarf-skin all over the body. When the least 
 thing touches the body, these nerves report it 
 to the mind. If it were not for this, we might 
 often be severely hurt without knowing it. 
 
 These nerves of feeling are very numerous 
 on the ends of the fingers, but there are only 
 a few on our backs. Can you tell why this is 
 so? 
 
 Sweat-pores. 
 
 The surface of the skin is full of little open- 
 ings called pores. They are the ends of the 
 sweat-tubes. There are a great number of 
 them. Nearly 20,000 of them are on the palm 
 of the hand alone. 
 
 The sweat-tubes bring water and waste 
 matter from the blood out through the pores. 
 When the pores are stopped up in any way, 
 the poison and water cannot get out. If all 
 or most of your pores are stopped, you will 
 get very sick. 
 
 Bathing. 
 
 You can now see plainly why we ought to 
 keep the body clean. There are several good 
 reasons for bathing. The sweat often pours 
 
io2, FIRST BOOK OF PHYSIOLOGY 
 
 out on the skin, where it gets mixed with dust 
 and dirt that dries and closes the pores. 
 
 The skin is also kept oily so it will not 
 break or crack. This oil also gathers dirt. 
 
 Then the scarf-skin is growing out all the 
 time, and its loose scales need to be rubbed 
 off. Bathing keeps the pores of the skin 
 open so the sweat-tubes can do their work. 
 At least once every week the body should be 
 washed all over. In summer we need a bath 
 oftener than in winter. 
 
 If you have a bath-tub in your home, so 
 much the better ; but you can keep the skin 
 clean without it. 
 
 A large basin of soft water, a sponge or 
 wash-rag, some good mild soap, and one or 
 two large towels, are all that is needed for a 
 good bath. After bathing you must be sure 
 to rub with the towels until the skin is pink 
 and real dry. 
 
 If you will be careful about the rubbing, 
 there will be little danger of catching a cold 
 after a bath. 
 
 Clean clothing. 
 
 The clothing next to the skin will soon get 
 dirty. Even when it looks white, it may hold 
 a great deal of waste matter that has come 
 
THE SKIN 103 
 
 out of the pores of the skin. Such clothing 
 must be often washed, not only for the sake 
 of our own health, but to make ourselves 
 agreeable to other people. 
 
 When you go to bed, all the clothes you 
 wore in the daytime should be taken off, and 
 only a night-dress should be worn while you 
 sleep. 
 
 A good bath, a clean night-dress, and clean 
 bedclothes will help you to sleep soundly. 
 
 How to have a clear skin. 
 
 People who have good health always have a 
 nice clear skin. The best way to have a good 
 complexion is to take good care of the health 
 of the whole body. When we eat too much 
 or do not eat the kind of food that is good for 
 us, the skin will often get coarse and will break 
 out in pimples. 
 
 Simple, coarse food will make the best com- 
 plexion. You remember the story of the four 
 boys who would not eat the king's meat, but 
 wanted only their simple kind of food. When 
 they came before the king, he said they were 
 fair to look upon. 
 
 If the skin is not healthy, it will do no good 
 to put any kind of wash or powder upon it. 
 
io 4 FIRST BOOK OF PHYSIOLOGY 
 
 Nothing but good health will make a good 
 complexion. 
 
 Effect of alcohol on the skin. 
 
 The true skin is full of fine blood-tubes. 
 Alcohol makes these tubes larger, and then 
 too much blood is found in the skin. After a 
 while, if a man keeps on drinking, these tubes 
 will stay larger all the time. This makes the 
 face red. You can tell an old drinker by the 
 appearance of his nose. It is swollen and 
 very red. His eyes are blood-shot for the 
 same reason. 
 
 The man who drinks whiskey or beer or any 
 strong drink soon gets so he does not care 
 about his health. He allows his skin to get 
 very dirty, and then it will not do its share of 
 throwing off the waste and poisons of the 
 body. Alcohol puts so much poison into the 
 body that even a healthy person could not get 
 rid of it all. 
 
 When the body is not in good health, it is 
 much easier to catch any disease that comes 
 along. The drunkard is the first to catch 
 diseases and is much more apt to die when he 
 gets them. He is not strong enough to fight 
 them off. This is the reason a doctor does 
 
THE SKIN 105 
 
 not have much hope for a drinker when he 
 gets real sick. 
 
 The surgeon does not like to cut through 
 the skin and operate on an old drinker be- 
 cause he knows his patient is apt to die in the 
 operation, and if he does live, it will take a 
 long time for the cut to heal. 
 
 Effect of tobacco on the skin. 
 
 The evil effects of tobacco can be seen in 
 the skin as well as in the rest of the body, 
 When a man takes a strong poison like nico- 
 tine, every part of his body must suffer. It 
 does most harm to boys under twenty-one 
 years of age. 
 
 The skin tries to throw off the tobacco 
 poison, but it has enough to do without that. 
 When you give it too much extra work it can 
 do nothing well. 
 
 When a tobacco user comes out of the 
 bath you can often smell the tobacco in the 
 water. 
 
 The skin of a boy who smokes cigarettes 
 becomes sallow and has an unhealthy look. 
 This cannot be cured by bathing and rubbing 
 the skin. The only way is to let tobacco alone, 
 and then the body will cure itself. 
 
io6 FIRST BOOK OF PHYSIOLOGY 
 
 Questions. 
 
 1 . Tell about the two layers of skin. 
 
 2. Tell all you can about the nails. 
 
 3. Describe a hair. 
 
 4. How can the hair be cared for ? 
 
 5. Why is the scarf-skin made so tough ? 
 
 6. What gives the skin its color ? 
 
 7. Tell about the parts you can see in picture 30. 
 
 8. What is the use of the nerves of feeling in the skin ? 
 
 9. What is the use of the sweat-pores ? 
 
 10. Why should we bathe ? 
 
 1 1 . What is the best way to have a good complexion ? 
 
 1 2. What bad effects does alcohol have on the skin ? 
 
 13. What bad effects does tobacco have on the skin ? 
 
CHAPTER IX 
 
 EXCRETION 
 
 How the body gets rid of poisons and waste. 
 
 THIS is a short chapter, but a very important 
 one. Our good health and our very life de- 
 pend on how well we can get rid of poisons 
 and waste. Poisons are often taken into the 
 body with the food and drink. Poisons are 
 made inside of the body itself, and there is 
 always a great deal of waste matter that must 
 be thrown out. 
 
 The most of this kind of work is done by 
 the lungs, the liver, the skin, the kidneys, and 
 the intestines. 
 
 The lungs. 
 
 We have learned that the air that comes 
 from the lungs is impure because it is loaded 
 with a waste called carbon dioxide. It got this 
 from the blood in the lungs. Besides this a 
 great deal of water comes out with the breath. 
 The carbon dioxide is a gas, and so we cannot 
 
 see it, but you can show that it is there by 
 
 107 
 
io8 FIRST BOOK OF PHYSIOLOGY 
 
 trying the experiment we told you about on 
 page 76 of this book. 
 
 You can easily find the water in your breath 
 by breathing against a cold window-pane. 
 The water will collect on the glass. On a 
 cold day you say you can see your breath. 
 This is only water taken from the blood, and 
 when it strikes the cold air it forms into very 
 small drops like fog. 
 
 The breath works for us both when it goes 
 in and when it comes out. When it goes in it 
 carries oxygen to the blood and when it comes 
 out it brings waste and poisons from the blood. 
 
 The liver. 
 
 The liver is a very important part of the 
 body. We told you something about it on 
 pages 55 and 57. Read that again. 
 
 If your liver would cease to work for only 
 a short time you would get sick and die. 
 
 It gathers up many poisonous substances 
 from the liquid food and the blood. It takes 
 out the bile and turns it to good use in diges- 
 tion. A healthy liver will always do its work 
 well if we do not give it too much to do. 
 
 o 
 
 If we eat too much, or eat food that is not 
 good for us, we may give the liver more work 
 than it is able to do. Then some bad blood 
 
EXCRETION 109 
 
 gets past it and we get sick. When a man 
 drinks alcohol he always overloads his liver. 
 Alcohol is a poison, and the liver tries to keep 
 it out of the blood. While it is doing this, it 
 cannot do its other work in the right way. 
 
 Alcohol also spoils the digestion of the food, 
 and that throws more work onto the liver. An 
 old drinker's liver gets weaker and smaller, 
 and so you can see that alcohol gives the liver 
 more to do and then makes it weaker so that 
 it cannot do it. 
 
 The kidneys. 
 
 There are two kidneys in the human body, 
 one on each side of the backbone at the small 
 of the back. Each kidney has the shape of 
 a bean, and is about four inches long, two and 
 one-half inches broad, and one inch thick. 
 
 Their work is to take water and several 
 kinds of poisons and minerals out of the blood. 
 When they do not work right, we soon know 
 that something is going wrong with us. 
 
 The water washes away the poisons that the 
 kidneys gather up. We should drink plenty 
 of water. The skin and lungs are throwing 
 off water all the time, and the kidneys take 
 out about three pints every day, and the body 
 needs a great deal all the time. 
 
no FIRST BOOK OF PHYSIOLOGY 
 
 It will do no harm to drink good water even 
 when you are not thirsty. If you get toe 
 much the kidneys and skin will soon take it 
 away, and it will carry poisons and waste out 
 with it. 
 
 A man can live a long time without other 
 foods, but he would hardly get through a single 
 day without water. 
 
 We have already told you about the work 
 done by the skin and the intestines, and so 
 we end this chapter here. 
 
 Questions. 
 
 1. How do poisons get into the body ? 
 
 2. How are the wastes and poisons taken out of the body ? 
 
 3. Tell what the lungs do. 
 
 4. Tell what the liver does. 
 
 5. Describe the kidneys. 
 
 6. What work is done by the kidneys ? 
 
 7. Why should we drink plenty of good water ? 
 
 8. What two things does breathing do for us ? 
 
CHAPTER X 
 
 THE BRAIN, SPINAL CORD, AND NERVES 
 
 How the body is governed. 
 
 THE brain is the ruler of the body. The 
 muscles may be strong, but they will not move 
 till the brain sends out an order to them. 
 Everything the body does is governed by the 
 brain. The muscles are like an army of sol- 
 diers, and the brain is like their general. All 
 the messages of the soldiers are sent in to the 
 general, and then his orders are sent out to 
 the soldiers. If the army is well trained, it 
 will do only what it is ordered to do, and will 
 not move until it gets orders from the general. 
 In the same way, if our muscles are well 
 trained, they will carry out the orders of the 
 brain. 
 
 What the brain is. 
 
 The brain is made of a soft, delicate sub- 
 stance. It is very easily harmed, and so it is 
 enclosed in a hard, bony case called the skull. 
 The brain weighs about three pounds. It is 
 
 gray on the outside and white on the inside. 
 
 in 
 
ii2 FIRST BOOK OF PHYSIOLOGY 
 
 If you could see the top of your brain, it 
 would look like what you see in picture 31; 
 
 31. The brain. 
 
 It is not smooth on the surface, but lies in 
 folds or ridges. 
 
 The spinal cord. 
 
 The spinal cord of a man is about eighteen 
 inches long and about as thick as the little 
 finger. At its upper end it is connected with 
 the brain and runs down through the back- 
 bone. 
 
 You have learned that the backbone is 
 made up of a number of bones placed one on 
 top of the other. Each one has a hole through 
 
BRAIN, SPINAL CORD, AND NERVES 113 
 
 it, as you can see in picture 32. Altogether 
 these holes make a long tube and in it the 
 spinal cord is placed. This makes a strong 
 covering for it. It is very tender, like the 
 brain, and so it can be easily hurt. 
 
 32. A vertebra. 
 
 You can easily see how the spinal cord is 
 placed inside the bones if you will examine the 
 neck of a chicken. The next time you have 
 chicken for dinner pull apart the bones of the 
 neck and you will find the spinal cord inside. 
 
 Nerves. 
 
 The nerves are fine white threads that run 
 out from the brain and spinal cord to every 
 part of the body. The brain could not send 
 
ii4 FIRST BOOK OF PHYSIOLOGY 
 
 an order to the hand or foot unless it had a 
 nerve to send the message on. 
 
 There are many telephones in a town, and a 
 wire runs from each one to a central telephone 
 office. Messages are going back and forth 
 over some of the wires all the time, so that 
 the central office is kept very busy. Your 
 telephone would be of no use to you without 
 the wires. In the same way the brain cannot 
 control the body without the nerves. One 
 pair of nerves comes from the brain out to the 
 eye and we use it to see. If these nerves 
 were cut in two we would be entirely blind, no 
 matter how good the eyes might be. Another 
 pair goes to the ear and we use them to hear. 
 Another pair runs to the nose and still another 
 to the mouth, and we use them to smell and 
 taste. 
 
 A great number of nerves run from the 
 brain down through the backbone. These 
 are tied up into a bundle which we have called 
 the spinal cord. 
 
 At a number of places along the backbone 
 we find holes in the sides of the bones. Nerves 
 branch off from the spinal cord and come out 
 through these holes to all parts of the body. 
 
 A large nerve is only a bundle of a great 
 many smaller ones. It is like one of the large 
 
BRAIN, SPINAL CORD, AND NERVES 115 
 
 cables which you see on the telephone poles 
 near the central office. Two or three hundred 
 wires are often put inside a lead tube and each 
 wire covered so it cannot touch the others. 
 A large nerve is made up a great deal like 
 that. It keeps branching off and getting 
 smaller and smaller till it is so fine you cannot 
 see it without a strong microscope. 
 
 What the brain does. 
 
 The brain, the spinal cord, and the nerves are 
 together called a nervous system. We have 
 just learned something about what the parts 
 of this system are and where they are. Let 
 us now try to find out what they do. 
 
 The brain is the most important part of our 
 bodies. We use the brain when we think. If 
 the brain is good and healthy, we can get good 
 lessons and can think well. We use the brain 
 to work out examples in arithmetic or to pre- 
 pare lessons in geography and language and 
 spelling. When a boy or girl does not have 
 good lessons, we think that he either does not 
 have a good brain or he is not making good 
 use of it. 
 
 We make our brains stronger by using 
 them. The more we think the better we can 
 think. One thing you learned about the mus- 
 
n6 FIRST BOOK OF PHYSIOLOGY 
 
 cles was that they would grow strong by use. 
 It is the same with the brain. A lazy boy will 
 never have a strong body or brain because he 
 will not use them. 
 
 What the nerves do. 
 
 There are two kinds of nerves. One kind 
 carries messages to the brain and the other 
 carries messages from the brain out to the 
 body. Ends of nerves are found under the 
 skin all over the surface of the body. When- 
 ever the skin is touched even by a feather, a 
 report is sent in at once to the brain. In this 
 way the mind is warned at once of any danger 
 that might come to the body. If it were not 
 for these nerves, you could put your hand into 
 the fire or cut off a finger and it would not 
 hurt. I fear we would not take very good 
 care of our bodies if it did not pain when we 
 are scratched or cut or bruised or burned. 
 These nerves have other uses too, but we will 
 tell you about that in the next chapter. 
 
 The other nerves are used to carry mes- 
 sages from the brain out to the muscles. 
 When I want to move my big toe, the brain 
 sends an order all the way down to a muscle 
 there and the toe is moved. We cannot feel 
 anything going along the nerve, but we know 
 
BRAIN, SPINAL CORD, AND NERVES 117 
 
 that if this nerve were cut in two we could not 
 make the toe move, no matter how hard the 
 mind would try. 
 
 What the spinal cord does. 
 
 The spinal cord carries messages back and 
 forth between the body and the brain ; but it 
 does more than that. It often takes part of 
 the work of the brain upon itself and sends 
 out orders to the muscles without telling the 
 brain anything about it. If you put your hand 
 on a hot stove, the nerves send in a message 
 to the spinal cord, and right away an order is 
 sent back to the muscles of the arm to pull 
 the hand away. When you make up your 
 mind to take a walk, the brain sends an order 
 to the muscles of the legs to begin work ; but 
 after you are started, the spinal cord will look 
 after the walking, and the mind can be free to 
 think of other things. 
 
 The upper part of the spinal cord is thicker 
 than the rest of it. This thick part is just in- 
 side the skull. In picture 33 you can see the 
 hole where the spinal cord enters the base of 
 the skull. This part of the cord is very im- 
 portant. It looks after our breathing and the 
 beating of our hearts. We may stop breath- 
 ing for a little while, but it will soon start 
 
n8 FIRST BOOK OF PHYSIOLOGY 
 
 again in spite of all we can do. The mind 
 cannot stop the heart at any time. 
 
 If any serious accident should happen to 
 this part of the spinal cord death would follow 
 at once, for the heart and lungs would stop 
 their work. 
 
 You see that the whole spinal cord is very 
 useful to us. It watches over our bodies all 
 
 33. A skull. 
 
 day and night. It is always on guard to keep 
 us from getting hurt. It leaves the mind free 
 to study and think. No wonder it is so well 
 protected inside a strong, bony tube. 
 
 Sleep. 
 
 All healthy boys and girls are all the time 
 doing something. Their minds are at work 
 
BRAIN, SPINAL CORD, AND NERVES 119 
 
 all day and their bodies are active in work or 
 play. The brain and the whole body must 
 have rest or they will soon break down. We 
 cannot get complete rest while we are awake. 
 When we are in sound sleep the brain is not 
 doing anything, and the body is doing only 
 enough to keep us alive till we get awake 
 again. The heart beats slower and we do not 
 breathe so often when we are asleep. 
 
 You must have plenty of sleep during the 
 night or you will not be able to do good work 
 the next day. You cannot even play well un- 
 less you have had a good sleep. Most people 
 need about eight hours of sleep every night. 
 Children should sleep nine or ten hours out 
 of every twenty-four. 
 
 Night is the proper time for sleep. Babes 
 and young children need to sleep some in day- 
 time, but the boys and girls who read this 
 book should get enough of good sound sleep 
 in the night so that they can be wide awake all 
 day. A sleepy boy is not of much account in 
 school or in any other place. 
 
 Habit. 
 
 Most things are hard to do the first time we 
 try. After we have done them several times 
 they become much easier, and by and by the 
 
120 FIRST BOOK OF PHYSIOLOGY 
 
 way we do things and the way we act become 
 fixed habits. You can now tie your shoe-* 
 strings without thinking about it, but it was a 
 task for you at first. It has become a habit. 
 The way a man ties his necktie is a habit with 
 him, and it is hard for him to tie it in any other 
 way. 
 
 You can get into a habit of always being 
 neat and clean ; of having good lessons every 
 day ; of always being pleasant and polite ; of 
 always being on time. There are many habits 
 of this kind that every boy and girl should try 
 to form. If you will try them till they become 
 easy then they will be a habit with you, and 
 you would rather follow them than do any 
 other way. 
 
 It is easy to get into bad habits, and then it 
 will be hard to get away from them. A boy 
 can get into a bad habit of smoking cigarettes, 
 and then he gets an appetite for it. Then the 
 two together are stronger than the boy, and 
 he will not quit even when he knows his bad 
 habit is killing him. 
 
 Men and boys get into the habit of going 
 " down town" in the evenings. Every evening 
 they are almost sure to go again. They get 
 into a bad habit of drinking, and keep on 
 going from bad to worse. 
 
BRAIN, SPINAL CORD, AND NERVES 121 
 
 Every boy and girl should try to have many 
 habits, but they should all be good ones. 
 
 It is easy to fall into bad habits, but very 
 hard to get out of them. 
 
 Skill. 
 
 We all want to have strong muscles, but we 
 want them to be well trained, too. 
 
 When the muscle will do just what the mind 
 wants done, it is a trained muscle. Boys and 
 girls should try hard every day to train their 
 muscles to do things well. If you do not 
 train them they will always be awkward. You 
 
 34- Before and after long practice. 
 
 want to be a good writer. Then you must 
 practise every day to get the muscles of your 
 arm and fingers trained. The last page in 
 your copybook should be much better than 
 the first one. If it is not, then you are not 
 getting any good out of your practice in 
 writing. Try again, and think all the time 
 that you are trying to get your muscle to obey 
 
122 FIRST BOOK OF PHYSIOLOGY 
 
 the mind. It will be sure to do so if you will 
 try your best every day. 
 
 The writing in this upper line was done by 
 a little girl several years ago. You can see it 
 was hard for her to make the pen go right. 
 She went right on doing her best, and to-day 
 she can write like that in the second line. 
 
 It is the same way with drawing. You 
 know what a poor picture you made when you 
 first tried to draw. You can do much better 
 now, and if you keep on trying, your mind 
 and hand will work nicely together. 
 
 You must also train the muscles of the 
 mouth if you want to speak well. It is hard 
 for little children to learn to talk. They have 
 to try for a long time before they can get the 
 tongue and lips to move just right to make 
 the words. Maybe there are some words you 
 do not say very well yet. Some boys and 
 girls mumble their words so that you can 
 hardly tell what they are trying to say. They 
 are not trying, and they will never do any 
 better till they do try. 
 
 A story. 
 
 More than two thousand years ago there 
 lived in the city of Athens a boy whose name 
 was Demosthenes. He was not as bright as 
 
BRAIN, SPINAL CORD, AND NERVES 123 
 
 some of the other boys. He had to study 
 very hard when he wanted to learn anything. 
 He could not speak his words plainly and he 
 stammered. He was awkward in his motions, 
 and people laughed at him. 
 
 One day, after he had grown older, he went 
 to hear a famous speaker in Athens. There 
 he saw what wonderful power there was in a 
 great speech by a great orator. 
 
 He thought if he could only speak like that 
 how much good he could do and what a great 
 man he would be. So he made up his mind 
 that he would be a great speaker. He went 
 to work with all his might, and one day he got 
 up before a large audience to make his first 
 speech. He did not speak well, and the people 
 laughed at him and hissed him. 
 
 Many young men would have given up and 
 not tried any more. Demosthenes only said 
 that he would try all the harder, and now he 
 went to work in dead earnest to make his mus- 
 cles obey his mind in just the way he wished. 
 
 Part of the time he stood before a mirror 
 while he practised speaking. There he could 
 see for himself how he looked. If he did not 
 stand in the right manner or if he moved his 
 hands or arms in an awkward way, he could 
 see it in the mirror and would correct it. 
 
124 FIRST BOOK OF PHYSIOLOGY 
 
 He had a bad habit of holding one shoulder 
 higher than the other. To correct this, he 
 would stand with this shoulder just under the 
 point of a sharp sword while he was speaking. 
 
 35. Demosthenes. 
 
 Sometimes he would shut himself up for 
 several weeks in a cave, and there he would 
 practise speaking. 
 
 At another time he would go down to the 
 seashore and fill his mouth with pebbles and 
 then speak. If he could learn to talk well 
 with pebbles in his mouth, then surely he could 
 do much better when he took them out. 
 
 The above picture shows him at this prac- 
 tice. 
 
BRAIN, SPINAL CORD, AND NERVES 125 
 
 At last Demosthenes became the most 
 famous speaker in the world. 
 
 Boys and girls who are willing to go through 
 the long practice that is needed to get the 
 body to obey the mind may also be famous in 
 one way or another. 
 
 Effect of alcohol on the brain and nerves. 
 
 You must use your brain when you think. 
 You can do good thinking only when your 
 brain is in good working order. You have 
 learned that a muscle must have food that it 
 may do work. It is the same way with the 
 brain. Every time the heart beats, a part of 
 the blood is sent to the head to feed the brain. 
 Press the ends of your fingers against either 
 side of your neck and you can feel the pulse 
 of the blood as it goes up through a large 
 artery to the head. This blood must be good 
 and pure, and there must be plenty of it. Un- 
 less this is so, we cannot do good thinking. 
 Anything that will poison the blood or weaken 
 it will have a bad effect on the brain. 
 
 When alcohol gets into the blood some of 
 it is carried at once to the head. The brain 
 is excited by it, and for a while seems to be 
 brighter than ever. Very soon the poison of 
 the alcohol is sure to have its bad effect. The 
 
126 FIRST BOOK OF PHYSIOLOGY 
 
 brain gets stupid and will not work again till 
 the body sends it good blood. 
 
 The alcohol has also been spoiling the work 
 of the stomach and lungs and liver and kid- 
 neys so they cannot make good blood. In 
 this way, too, the brain is both starved and 
 poisoned. 
 
 A man may seem to get over the bad effects 
 of a few drinks of alcohol, but he is getting 
 weaker in body and mind all the time. If he 
 keeps on drinking, it will soon be plain that he 
 cannot think about anything as well as he did 
 before. 
 
 Alcohol makes the nerves lose their power 
 over the muscles. The hand trembles and 
 loses its skill. Such a person can not write as 
 well as he did before. He cannot even raise 
 a glass of water to his mouth without showing 
 how weak and unsteady he is. Alcohol has 
 made him awkward and clumsy. He is not 
 wanted any more to do fine work in the shops 
 and offices, and so his wages go down. People 
 do not trust him, and he cannot get a good 
 position. 
 
 When the brain becomes very weak or un- 
 healthy, it will think very strange things and 
 will imagine many things that do not exist. 
 Such a person is called insane, and has to be 
 
BRAIN, SPINAL CORD, AND NERVES 127 
 
 locked up to keep him from harming 1 other 
 people. Alcohol makes many men insane. 
 
 The children of drunkards are often weak 
 and diseased. It is no fault of the children, 
 but they have to suffer for the alcohol which 
 their father drank. 
 
 Not many boys who now read this book 
 ever drank any whiskey or beer or wine, but 
 we want you to know how much evil it is 
 doing to many older people. Now is the best 
 time for you to begin to be an able and healthy 
 man. Our bodies are not of much use to us 
 without a good brain, spinal cord, and nerves, 
 and we know that alcohol has the worst kind 
 of an effect upon the whole nervous system. 
 
 Effect of cigarettes on the brain and nerves. 
 
 Many boys who would not think of drinking 
 whiskey are doing their brains and nerves 
 great harm by smoking cigarettes. We have 
 shown you how tobacco will poison the blood. 
 It is this kind of blood, then, that must feed the 
 brain. A cigarette smoker cannot sleep well 
 at night. When he gets up in the morning he 
 does not feel fresh and strong. He comes to 
 school sleepy. He cannot make his brain 
 work, for it is poisoned and weak. Of course, 
 he cannot keep up in his school-work. 
 
128 FIRST BOOK OF PHYSIOLOGY 
 
 A story. 
 
 In one of the schools of a Western towit 
 was a bright boy eleven years of age. He had 
 started to school when he was six, and was 
 promoted every time with high grades. His 
 teachers aH praised him for his good deport- 
 ment and good lessons. The boys and girls 
 all liked him because he was smart and was 
 good at running, jumping, and playing ball. 
 He was now about half-way through the fifth 
 grade when something began to go wrong. 
 Neither the teachers nor the scholars could 
 guess what the matter was. The boy began 
 to be careless about himself. He would go 
 about with his hat pulled down over his eyes 
 and would not look square at you when you 
 would speak to him. His clothes and shoes 
 were not brushed, and he walked in a slouchy 
 manner. 
 
 In the school-room he did not give attention, 
 but spent much of his 'time looking about or 
 just staring without looking at anything. At 
 other times he would start some mischief that 
 would annoy the other scholars, and when the 
 teacher would try to correct him he would 
 only grunt out some impolite reply and then 
 sulk in his seat. 
 
 What in the world had gone wrong ! 
 
BRAIN, SPINAL CbRD, AND NERVES 129 
 
 The boy would try sometimes to master 
 himself. He would try to force himself to 
 study and act as he used to do, but he could 
 not keep it up. 
 
 After this had gone on for several weeks, 
 he stayed one evening after school of his own 
 accord. When all the children had gone, he 
 came up to the teacher and said that he 
 wanted to tell her something. He told her 
 that he once smoked a few cigarettes just to 
 see what it was like, and after he had learned, 
 he wanted to smoke them all the time. He 
 said he could see that if he did not stop, they 
 would ruin him, and he wanted to quit. 
 
 His teacher always liked to do anything for 
 the good of her scholars, and she was very 
 glad when the boy came right out and told 
 her all about it. He promised that he would 
 come to her every day for one month and tell 
 her that he had not used tobacco in any way. 
 
 He was a manly little fellow and kept his 
 word. He now thinks that this changed his 
 whole life. If he had gone on with cigarettes, 
 it is almost certain that he would soon have 
 quit school, and would have gone with bad 
 company and become a drunkard at last. 
 
 This all happened a number of years ago. 
 The boy passed on through every grade in 
 
130 FIRST BOOK OF PHYSIOLOGY 
 
 school and then graduated from college. He 
 is now a useful and successful man, but hfe 
 never forgets that evening in school when he 
 had the courage to quit smoking cigarettes. 
 
 Questions. 
 
 1 . Describe the brain. 
 
 2. Tell about the spinal cord. 
 
 3. What is the use of nerves ? 
 
 4. How are nerves like telephone wires ? 
 
 5. What does the brain do ? How can it be made 
 strong ? 
 
 6. What are the two kinds of nerves and what does each 
 do? 
 
 7. What does the spinal cord do ? 
 
 8. Why do we need sleep ? How much sleep should we 
 have ? 
 
 9. Tell all you can about habit. 
 
 10. How can you learn to write and draw and speak well ? 
 
 1 1 . Tell the story of Demosthenes. 
 
 12. How does alcohol harm the brain and nerves ? 
 
 13. How does tobacco harm the brain and nerves ? 
 
 14. Tell the story of the boy who smoked cigarettes. 
 
CHAPTER XI 
 
 THE SENSES. 
 
 WE have five senses. They are seeing, 
 hearing, feeling, tasting, and smelling. 
 
 The mind uses these senses to find out about 
 things it wants to know. If you would lose 
 all your senses, you could not tell whether you 
 were alive or not. When I hand you some- 
 thing and ask you to tell me all you can find 
 out about it, you look at it, then maybe you 
 tap it and listen to the sound, then you feel it 
 or taste and smell it. This is all we can do 
 with the senses, but all that we know was first 
 learned in this way. 
 
 The eyes. 
 
 The eye is the shape of a ball. It is set in 
 a bony socket on a bed of fat. It is covered 
 with a tough coat called the white of the eye. 
 In front it is as clear as glass, so the light can 
 get in. A little farther back is a curtain, 
 which in some people is black and in others 
 blue or gray. 
 
 In the centre of the curtain is a round hole, 
 
I 3 2 
 
 FIRST BOOK OF PHYSIOLOGY 
 
 that gets large when the light is dim and small 
 when the light is bright. Look into a mirror ! 
 
 
 30. The eyes. 
 
 and see how the curtain works when you sud- 
 denly make the light bright and then dim. 
 The light goes through this hole and then 
 
 37. Section of eye. 
 
 on through a lens that you can see in picture 
 37. This lens acts just like the glass in 
 
THE SENSES 133 
 
 your microscope and makes a picture on the 
 back part of the eye. The nerve then carries 
 it to the brain, and in that way we see. 
 
 How we move the eyes. 
 
 Muscles are fastened to the eyeball on the 
 top and bottom and at the sides. When they 
 pull, they roll the eye up or down or sideways. 
 This is a great help to us when we want to 
 look around. You can see the whole side of 
 a room without moving your head. 
 
 How the eye is protected. 
 
 The eyes are very delicate and can be easily 
 harmed. Curtains called eyelids are made to 
 close over the front of the eye, and we wink 
 whenever there is danger of dust or dirt get- 
 ting into the eye. 
 
 The eyebrows also protect the eyes by 
 keeping sweat from running down into 
 them. 
 
 Just above the eyes are little sacs that gather 
 from the bloocl a liquid called tears. A little 
 of this liquid keeps running out over the eyes 
 all the time to keep them moist and wash 
 away any specks of dust. At the inner cor- 
 ner of the eye is a small tube that carries the 
 tears into the nose. When you laugh real 
 
134 FIRST BOOK OF PHYSIOLOGY 
 
 hard or cry, the tears come so fast that the 
 tube cannot carry them off, and they run over 
 on the cheeks. 
 
 Care of the eyes. 
 
 Most people say they would not give up 
 their eyes for the world, and yet they use them 
 so badly that we would think they did not care 
 for them. 
 
 You should never look at the sun or any 
 bright light. Do not try to read out in the 
 bright sunlight. When you use a light that is 
 too strong, the sight will get dim. 
 
 It is just as bad to read when the light is too 
 weak. Do not try to read in the dusk of the 
 evening or in the dark corner of a room or 
 by any weak, flickering light. 
 
 Do not sit facing the light when you read, 
 but let it fall down over your shoulders upon 
 the book. 
 
 Do not read while you are lying down. 
 People have made themselves blind by reading 
 in this way. 
 
 Alcohol and tobacco have a very bad effect on 
 the eyes. Alcohol affects the nerve, so it can- 
 not carry a true picture back to the brain, and 
 it weakens the other delicate parts of the eye. 
 Cigarettes have had such a bad effect on the 
 
THE SENSES 135 
 
 eyes of boys that the doctor told them he 
 could not keep them from going blind unless 
 they would quit smoking. 
 
 If you have good eyes and take care of 
 them, they will be good for nearly all your 
 lifetime. 
 
 The ear. 
 
 We would lose a great deal in this world if 
 we had no eyes, but it would be about as bad 
 
 38. The ear. 
 
 if we had our eyes, but had no ears. If you 
 had to give up your eyes or your ears, which 
 would you let go ? Think carefully before you 
 answer. 
 
 The part of the ear outside the head catches 
 sound and sends it into the ear. People who 
 
136 FIRST BOOK OF PHYSIOLOGY 
 
 cannot hear very well put their hands back of 
 the ears to catch more sound. 
 
 The rest of the ear is just the size and shape 
 that you see in picture 38. One of these is 
 on each side of the head in the bone of the 
 skull. 
 
 Waves of sound come in where you see the 
 arrow in the picture. These waves shake the 
 ends of the nerves at the other end of the ear, 
 and the nerves then carry the sound back to 
 the brain. 
 
 The ear and throat. 
 
 In the picture, on the right of it, you can 
 see the tube that connects the ear with the 
 throat. We cannot hear well unless this tube 
 is kept open. Often, when you have a cold, it 
 gets stopped up, and then you have earache 
 or a roaring sound in the ear. You can often 
 open the tube by swallowing, and then the 
 roaring stops. 
 
 Care of the ears. 
 
 The ear tries to protect itself, but often we 
 have to help it. The tube that leads into the 
 ear is lined with hairs and wax. These keep 
 out insects and dirt. Sometimes, though, a 
 bee or bug will creep away into the ear and 
 
THE SENSES 137 
 
 cause a great deal of pain and fright ; but the 
 doctor can soon pull it out. 
 
 The ear should not be filled tight with 
 cotton. If any cotton is used, it should be 
 very loose and only at the entrance of the ear. 
 
 Very loud sounds injure the ear and often 
 make people deaf. When you are expecting 
 a very loud sound, it is a good plan to hold 
 the mouth wide open or close the mouth and 
 put your fingers in your ears. 
 
 It is wrong to pick the ear with an ear-spoon 
 or with anything else, or to put any kind of a 
 liquid into it unless it is the order of the 
 doctor. The ear, like the eye, is too valuable 
 and delicate to be tampered with. 
 
 Feeling. 
 
 We can learn a great deal about things by 
 the sense of touch. You will find it an in- 
 teresting game if you will blindfold one of 
 your playmates and then put different things 
 into his hands and see if he can tell what they 
 are. He can tell that it is an egg, or a stone, 
 or a pencil, or a marble, and do it all by feeling. 
 Once in a while he will make a bad mistake, 
 and that is where the fun comes in. 
 
 Blind children learn to read with the fingers. 
 On the pages of their books the letters are 
 
138 FIRST BOOK OF PHYSIOLOGY 
 
 raised, and by running their fingers over them 
 they can tell what the words are. One girl, 
 whose name is Helen Kellar, can neither see 
 nor hear, and yet she can tell what you are 
 saying by holding her fingers on your lips 
 while you are talking. 
 
 Taste and smell. 
 
 The nerves of taste are in the tongue, and 
 the nerves of smell are in the nose. 
 
 These two senses do not tell us so much as 
 any one of the other three, but they are very 
 useful. 
 
 They guard the gateways to the stomach 
 and the lungs. They warn us against bad 
 food and bad air. When food is spoiled, our 
 nerves of taste and smell will tell us not to 
 eat it. When we come in out of fresh air, 
 our nerves of smell will tell us if the air in 
 the room is bad. 
 
 These two senses are also very useful in 
 other ways. Salt may look just like sugar^ 
 but the taste will soon tell us which it is. 
 
 These nerves are often spoiled by misuse. 
 Alcohol and tobacco will make them so blunt 
 that they will be of no use, and then they 
 cannot give any warning against bad food and 
 impure air. 
 
THE SENSES 139 
 
 Questions. 
 
 1 . What are the five senses ? 
 
 2. Describe the eye. 
 
 3. How can we move our eyes ? 
 
 4. How is the eye protected ? 
 
 5. What are some things that injure the eyes ? 
 
 6. How do we hear ? 
 
 7. How is the ear joined to the throat ? 
 
 8. How can we care for our ears ? 
 
 9. Which one of the senses do blind children use when 
 they read ? 
 
 10. What can we find out by the sense of taste and smell ? 
 
INDEX 
 
 A 
 
 PAGE 
 
 Air 82 
 
 Air-sacs 79 
 
 Albinoes 99 
 
 Alcohol : 
 
 Appetite for 41 
 
 Effect on muscle 37 
 
 Effect on heart 66 
 
 Effect on white corpuscles 73 
 
 Effect on warmth of body 92 
 
 Effect on skin 104 
 
 Effect on liver 109 
 
 Effect on brain and nerves 125 
 
 Effect on eyes 134 
 
 Appetite : 
 
 Use of 40 
 
 Recipe for 41 
 
 Arteries 67 
 
 B 
 
 Bathing 101 
 
 Beer '. 38 
 
 Effect on heart 66 
 
 Bee-sting -. 98 
 
 Bile 55,57 
 
 Bleeding 67, 73 
 
 141 
 
142 INDEX 
 
 Change in lungs .................................. 79 > 
 
 Clot of ............................................ 73 
 
 Effect of deep breathing on ....................... 88 
 
 In bones .......................................... 27 
 
 Liquid part of .................................... 73 
 
 Quantity of ....................................... 64 
 
 Bones : 
 
 Broken .......................................... 25 
 
 Care of .......................................... 27 
 
 Change in shape .................................. 24 
 
 Composition of ................................... 24 
 
 Experiment with .................................. 25 
 
 Growth of ............... : ........................ 26 
 
 Kinds of ......................................... 20 
 
 Largest in body .................................. 19 
 
 Of hand ......................................... 18 
 
 Brain ................................................ 1 1 1 
 
 Work of ...................................... in, 115 
 
 Breathing ......................................... 75, 107 
 
 Effect of tight dressing on ........................ 88 
 
 Frequency of ..................................... 86 
 
 Of pure air ....................................... 83 
 
 Use of .......................................... 75, 77 
 
 C 
 
 Candle : 
 
 Experiment with 75, 84 
 
 Capillaries : 
 
 Number of 69 
 
 Use of 69 
 
 Carbon dioxide 81, 107 
 
INDEX 143 
 
 PAGE 
 
 Cartilage 22 
 
 Cigarettes 36 
 
 And athletics 87 
 
 Effect on brain and nerves 127 
 
 Effect on eyes 134 
 
 Effect on heart 66 
 
 Effect on lungs 81, 86 
 
 Clean clothing 102 
 
 Clear skin 103 
 
 Corns 95 
 
 Corpuscles : 
 
 Red 70 
 
 White . ... 71 
 
 D 
 
 Deep breathing 88 
 
 Digestion : 
 
 In intestines 55 
 
 In stomach 53 
 
 E 
 
 Ear 135 
 
 Care of 136 
 
 Eating : 
 
 Manner of 60 
 
 Enamel on teeth 49 
 
 Epidermis 99 
 
 Excretion 107 
 
 Eyes 131 
 
 Care of 134 
 
144 INDEX 
 
 PAGE 
 
 Fat 43 
 
 Feeling 137 
 
 Femur 19 
 
 Food: 
 
 Five kinds 43 
 
 In blood 73 
 
 Its three uses 42 
 
 Plain 61, 103 
 
 Warmth from 72 
 
 Framework : 
 
 Advantage of 18 
 
 Kinds of 17 
 
 Of monkey 17 
 
 G 
 
 Gall-bladder 55 
 
 Gastric j uice 52, 58 
 
 Germs of disease 82 
 
 Gullet 51 
 
 H 
 
 Habit 119 
 
 Hair 96 
 
 Care of 97 
 
 Health : 
 
 Advantage when good 12, 16, 38 
 
 When good 16 
 
 Heart 64 
 
 Care of 66 
 
 Structure of 65 
 
 Work of.. 65 
 
INDEX 145 
 
 I PAGE 
 
 Intestines 54 
 
 Description of 55 
 
 Juices in 55 
 
 Section of 56 
 
 Two kinds : 55 
 
 Joints : j 
 
 How made 21 
 
 Kinds 21 
 
 Use of 20 
 
 K 
 Kidneys 109 
 
 L 
 
 Lime in bone 24 
 
 Liver : 
 
 Work of 57, 109 
 
 Lungs 78, 107 
 
 Air-tubes in 78 
 
 Capacity of 87 
 
 Work of 79, 80 
 
 Manners : M 
 
 At table 46 
 
 Movements of eyes 133 
 
 Muscles : 
 
 About the mouth 30 
 
 Care of 35, 37 
 
 How caused to move 34 
 
 How cause movement 32, 34 
 
 10 
 
146 INDEX 
 
 Muscles : PAGB 
 
 In the arm 3 :. 
 
 Nature of 31 
 
 Of eye 133 
 
 Use of 29, 31 
 
 N 
 
 Nails 96 
 
 Nerves 101, 1 13, 1 14, 1 15 
 
 Of feeling 101 
 
 Use of 1 16 
 
 Nicotine 36, 81 
 
 
 
 (Esophagus 51 
 
 Oxygen 76, 89 
 
 P 
 
 Pancreas 55 
 
 Pancreatic juice 55, 56 
 
 Physiology : 
 
 Why studied 1 1 
 
 Its three parts 13 
 
 Protection of eyes 133 
 
 Proteid 43 
 
 Pulse 67 
 
 Counting the 68 
 
 Effects of exercise on 69 
 
 Pure air 82 
 
 1 
 
 Red corpuscles 70 
 
 Size and shape 71 
 
 Use of 71 
 
INDEX 147 
 
 S 
 Saliva : PAGK 
 
 Its use 51 
 
 Scarf-skin 95, 96, 99 
 
 Sebaceous glands 100 
 
 Shallow wells 44 
 
 Skill 121 
 
 Skin 95 
 
 As a protection 97 
 
 Color of 99 
 
 Section of 100 
 
 Two layers of 95 
 
 Sleep 118 
 
 Smell 138 
 
 Soap-bubbles 87 
 
 Special senses 131 
 
 Spinal cord 112 
 
 Use of 117 
 
 Starch 43 
 
 Stomach : 
 
 Care of 54 
 
 Change of food in 52 
 
 Description of tj2 
 
 Stories : 
 
 Of a boy 128 
 
 Of Demosthenes 122 
 
 Of four boys : 61 
 
 Of six men 93 
 
 Swallowing 5! 
 
 Sweat 90, 91 
 
 Sweat-pores . 101 
 
148 INDEX 
 
 T PAGE 
 
 Taste I3*i| 
 
 Teeth : 
 
 Care of 50 
 
 Number of 48 
 
 Structure of 49 
 
 Use of 48 
 
 Temperature of body 89, 90 
 
 Tendons 32 
 
 Tobacco 36 
 
 Effect on heart 66 
 
 Effect on skin 105 
 
 Tobacco heart 66 
 
 True skin 95, 99 
 
 Typhoid fever 45 
 
 V 
 
 Veins 69 
 
 Location and use 70 
 
 Ventilation 83 
 
 During sleep 85 
 
 W 
 
 Warmth of body 89 
 
 Water 43 
 
 Abundance of 44 
 
 Hydrant 46 
 
 Ice in 45 
 
 In breath 108 
 
 In wells 44 
 
 Water-j ug 91 
 
 Wells 44, 45 
 
 White corpuscles 71 
 
 Windpipe 77 
 

 A 
 
 f C . V^tyP ( 
 
 UNIVERSITY OF CALIFORNIA LIBRARY