THE FIVE BEST DOCTORS 135 GLOSSARY 136 KEEP-WELL STORIES FOR LITTLE FOLKS [Illustration] A WONDERFUL ENGINE We all have seen a steam engine, have we not? There are engines that pull trains on the railroad, and there are engines that make factories, gins, and saw-mills work. Then there are engines that run great ships on the water. How many know what must be done to one of these engines before it can do all this work? "It must have coal, or wood, or gasoline put into it." That is right. Now this coal or wood or gasoline, when it is used in an engine to make it work, is called fuel. Would we put rotten or green wood into the engine? No. We must always put in the kind of thing that will burn best, and make the most heat and do the most work. Let us see how this wood or coal we call fuel makes the engine work. First, we must burn the fuel. Second, when the fuel burns, it heats the water in the boiler. Third, the water changes into steam, and this steam gives the engine the power to work. Now we see how an engine is made to move and do work, such as hauling great trains of cars, and pulling great ships across the wide ocean. But we must remember that the engine will not do this work unless there is a man near-by to put the fuel into the engine. I want to tell you of another engine that is very like the steam engine. It too must have fuel before it can run or work. It is unlike the steam engine in as much as it grows all the time, and it does not need to have an extra man to put the fuel into it. You must think of your body as an engine and remember that it needs fuel to run it. The fuel that makes the body-engine move and work is the food you eat. You have learned that you must put into the steam engine the fuel that will burn best and make the most heat and work. The same thing is true of your body-engine. You must put in the fuel that will best make heat and the power to work. Have you sometimes eaten something which made you sick? It must have been that that was the wrong kind of fuel for the little body-engine. This is the reason our mothers are so very careful in preparing our food. They want the little engines to have the right kind of fuel so that they will not run off the track. Now what fuel must you use in your body-engine? In the first place you must put in fuel that will make the engine grow so that it can do a great deal of work. This fuel you get when you eat lean meat, eggs, milk, and many other things. If you want your engine to keep warm, you must use fuel that will make heat. You get this fuel by eating plenty of fats, such as nice butter and some sweet things. Potatoes, rice and syrup help to run your engine.