Many of the germs of "catching" diseases--most of them, in fact--are carried in the air, in scales that have rubbed off the skin of the persons sick with them, or in spray that they have coughed into the air, or in saliva that they have spit upon the floor. There is one sickness of this kind that I ought to tell you about, because it kills so many thousand people here in our own country every year. We sometimes call it the "Great White Plague." Its common name is _consumption_, and the doctors call it _tuberculosis_. I dare say you have heard of it and wondered what it meant. A few years ago people thought it could not be cured. They thought that children had it because their parents had had it before them. But now, the cheering thing about it is that we have found that Mother Nature herself can cure it with fresh air and sunshine and wholesome food. We have found, too, that people catch it from others who are sick with it, and need not have it just because their parents did. [Illustration: FRESH AIR AND SUNLIGHT ARE GOOD DOCTORS] This means, then, that thousands of people who have it need not die, but can be cured simply by living and sleeping out of doors and eating plenty of milk, eggs, and meat, nuts and fruit. There are camps for them in almost every state in the Union now. The fresh air gives them such a big appetite that they can eat more than most healthy people, and they soon get strong and well. If all the people who now have consumption were taken out into the country and cured, there would be no one left for the rest of us to catch it from, and the disease would soon die. Some day our Boards of Health will decide to do this, and then consumption will become as rare as smallpox is now, and will kill only a few hundred people a year in the United States instead of 150,000 every year, as it does now. People and governments are giving great sums of money, not only to cure the people who now have consumption, but to do something towards stopping the disease by keeping things so clean and people so strong that no one will ever have it. Even little children can help to fight and kill this "Great White Plague," and I'll tell you how.