This wonderful stream carries all these things from one country to the other, exchanges the produce of one country for the produce of another--so to speak. The little freight boats on this stream cannot do the work they were intended to do, the Dreadnoughts cannot overcome and disable the germs that get on their decks, if they are not kept in the very best condition. The only way in which we can keep them "fit" is by living according to the rules of hygiene. Eat wholesome food. Take outdoor exercise. Sleep with the windows open. Drink pure water. Bathe the body frequently. QUESTIONS 1. What are the little round boats? 2. What do they carry? 3. What are the Dreadnoughts? 4. What are the muscle men? 5. What is the stream, and what is the force pump that forces the stream on? 6. What are the rules for keeping the little freight boats, and the great Dreadnoughts on this wonderful stream in the best working condition? TWO MILLS Come, children, listen to the story Uncle Ned told to me. It was the story of a long time ago when Uncle Ned was a little boy. One day his mother took him on her knee and said, "Ned, do you know that your mouth is like a little mill?" It is. The mill grinds corn. Your teeth grind your food. Look in the mirror. Are your teeth all alike? Some of the teeth in your mouth are to bite the food into bits, and others are to grind it fine so that it will not hurt your stomach. You have twenty now because you are a little boy and do not need any more. When you have grown to be a man you will have thirty-two teeth. You will have more grinders in your mouth when you are a man than you have now. The jaw teeth are called grinders, because they grind the food you put into your mouth, just as the big mill stones grind the corn into meal down at Grandpa's mill. You wear clothes to keep your bodies warm, so the teeth need some covering to keep out the cold. The enamel, a hard outer covering on the teeth, keeps them from feeling the cold. Down in the middle of the tooth is a place for the nerves of the tooth. When you break the covering on the tooth the cold and hot things that you sometimes put into your mouth will make the nerves ache. Sometimes things that are very sweet or very sour hurt the covering on the teeth. To use the teeth to crack nuts or ice will harm them, for it often breaks the outer covering, and it will not grow again. Your teeth should last you all your life if you will take care of them. Grandpa's mill would not grind the corn well, nor would the mill last long, if he did not take care of it and keep the big stone grinders clean and free from grit and dirt. Your teeth must have just as good care as the stones in the mill if you wish them to last you a long time, and if you want them to grind your food fine.