CHAPTER XIV. HOW TO KEEP THE LUNGS HEALTHY.--What is the thing most necessary to preserve life? Name some of the ways in which the blood becomes impure. Why is bad-smelling air dangerous to health? What are germs? Why are some diseases "catching"? Name some such diseases. What should be done with a person who has a "catching" disease? What is the effect of the breath upon the air? How much air is poisoned and made unfit to breathe by each breath? How much air do we spoil every minute? every hour? How much pure air does each person need every minute? every hour? How do we get fresh air into our houses? Why are windows and doors not good means of ventilating in cold weather? How should a room be ventilated? How should we use the lungs in breathing? What about the clothing in reference to the lungs? Why is it injurious to breathe habitually through the mouth? What is the effect of alcohol upon the lungs? What is the effect of tobacco-using upon the throat and nose? CHAPTER XV. THE SKIN AND WHAT IT DOES.--How many layers in the skin? What is each called? To what is the color of the skin due? What glands are found in the true skin? What are the nails and what is their purpose? How does the hair grow? Name the different uses of the skin? CHAPTER XVI. HOW TO TAKE CARE OF THE SKIN.--What happened to the little boy who was covered with gold leaf? Why did he die? What is the effect of neglecting to keep the skin clean? What is the effect of wearing too much clothing and living in rooms which are too warm? How should the hair be cared for? the nails? What is the effect of alcohol, tobacco, and other narcotics upon the skin? CHAPTER XVII. THE KIDNEYS AND THEIR WORK.--What is the work of the kidneys? How may we keep these organs healthy? What is the effect of alcohol upon the kidneys? CHAPTER XVIII. OUR BONES AND THEIR USES.--How many bones in the body? What are the bones called when taken all together? Name the principal parts of the skeleton. Name the bones of the trunk, of the arms, of the legs. What are the uses of the bones? What is a joint? What is cartilage? By what are the bones held together? Of what are the bones largely composed? CHAPTER XIX. HOW TO KEEP THE BONES HEALTHY.--What sort of bread is best for the bones? Why? If a child tries to walk too early why are its legs likely to become crooked? What are the effects of sitting or lying in bad positions? Of wearing tight or poorly-fitting clothing? Of tight or high-heeled shoes? What injuries are likely to happen to the bones and joints by accident or rough play? CHAPTER XX. THE MUSCLES AND HOW WE USE THEM.--How many muscles in the body? Of what are the muscles composed? How are many of the muscles connected to the bones? To what are all bodily movements due? How do the muscles act? What causes the muscles to act? Do all muscles act only when we will to have them act?