[Illustration: FIG. 62.--A dish of beef broth jelly left open two minutes in a room being swept. Each spot is a city of thousands of germs which grew from one germ dropping on the jelly. By counting the spots you can tell how many germs fell from the dust on this dish three inches in diameter.] _Dust is the partner of disease._ It contains germs. Avoid dust. Wipe up the rooms with a damp cloth; never use a feather duster. Avoid dry sweeping. Use a suction cleaner or have rugs which can be cleaned out of doors. Give the lungs fresh air and deep breathing and the body good food and plenty of sleep to make it so strong that germs cannot overcome it when they enter. [Illustration: FIG. 63.--Photograph of consumption germs, the tiny rods which often grow and cause tuberculosis in bodies weakened by beer or whisky. Much enlarged.] =Alcoholic Drink and the Lungs.=--The most common disease of the lungs is _tuberculosis_. Nearly all bartenders who sell strong drink take some themselves. Lately it has been learned in Germany that tuberculosis causes one half of all the deaths among bartenders. Alcohol was once thought to be a good medicine for lung troubles, but it has been clearly proven that beer and whisky weaken the lungs and make them ready for the germs of disease. The body already weakened by the poison of the alcohol is then easily overcome by the disease. =Tobacco and the Lungs.=--The occasional use of tobacco does not seem to hurt the lungs when fully grown. A study of many young persons has shown that the chest of smokers grows much more slowly than in those who do not use tobacco. As the lungs cannot grow any faster than the chest, they must grow slowly in boys using much tobacco. Tobacco is a common cause of sore throat. Many smokers have been compelled to quit the habit because of throat troubles. PRACTICAL QUESTIONS 1. Where are the lungs located? 2. What do the tubes in the lungs carry? 3. What part of the air do we use in the body? 4. Tell how the air gets into the lungs. 5. What passes from the blood into the air sacs? 6. Why should we breathe through the nose? 7. Why should you keep the fingers away from the nose? 8. What are the vocal cords? 9. Give two reasons why no one should spit on the floor. 10. Tell how alcohol harms the lungs. CHAPTER XV FRESH AIR AND HEALTH =How much Air we Breathe.=--At every breath we take in about one pint of air. We breathe eighteen times each minute. Nine quarts of air therefore pass in and out of the lungs every minute. Air once breathed is not fit to breathe again. It contains waste and carbon dioxide which weaken the body. If you breathe three full breaths into a wide-mouthed jar or bottle, it will contain so much of the carbon dioxide that a lighted candle or splinter will at once go out when thrust into the jar. A cat shut in a tight box two feet square and one foot high will die in less than a half hour.