He would push aside the little flap of skin and put into the stomach any kind of food that he pleased, and then watch to see what happened to it. In this way, he learned a great deal and wrote it down, so that other people might know, too. In other ways, also, which it would take too long to tell you here, doctors have learned how these magical food-bags take care of our food. WHY DOES THE FOOD NEED TO BE CHANGED? Your mamma tells you sometimes at breakfast that you must eat oat-meal and milk to make you grow into a big man or woman. Did you ever wonder what part of you is made of oat-meal, or what part of milk? That stout little arm does not look like oat-meal; those rosy cheeks do not look like milk. If our food is to make stout arms and rosy cheeks, strong bodies and busy brains, it must first be changed into a form in which it can get to each part and feed it. When the food in the stomach is mixed and prepared, it is ready to be sent through the body; some is carried to the bones, some to the muscles, some to the nerves and brain, some to the skin, and some even to the finger nails, the hair, and the eyes. Each part needs to be fed in order to grow. WHY DO PEOPLE WHO ARE NOT GROWING NEED FOOD? Children need each day to make larger and larger bones, larger muscles, and a larger skin to cover the larger body. Every day, each part is also wearing out a little, and needing to be mended by some new food. People who have grown up, need their food for this work of mending. CARE OF THE STOMACH. One way to take care of the stomach is to give it only its own work to do. The teeth must first do their work faithfully. The stomach must have rest, too. I have seen some children who want to make their poor stomachs work all the time. They are always eating apples, or candy, or something, so that their stomachs have no chance to rest. If the stomach does not rest, it will wear out the same as a machine would. The stomach can not work well, unless it is quite warm. If a person pours ice-water into his stomach as he eats, just as the food is beginning to change into the gray fluid of which you have learned, the work stops until the stomach gets warm again. ALCOHOL AND THE STOMACH. You remember about the man who had the little door to his stomach. Sometimes, the doctor put in wine, cider, brandy, or some drink that contained alcohol, to see what it would do. It was carried away very quickly; but during the little time it stayed, it did nothing but harm. It injured the gastric juice, so that it could not mix with the food. If the doctor had put in more alcohol, day after day, as one does who drinks liquor, sores would perhaps have come on the delicate lining of the stomach. Sometimes the stomach is so hurt by alcohol, that the drinker dies. If the stomach can not do its work well, the whole body must suffer from want of the good food it needs.[C] TOBACCO AND THE MOUTH.