Churches, theaters, and ten-cent shows are often very poorly ventilated. You can always tell a poorly ventilated room by the foul odor when you go into it from the fresh air, and it is not wise to stay in such a room. You are killing the cells in your body when you do so, and you will very probably come out of it with a bad cold. When the fresh air strikes you, you feel chilly and you may think you are taking cold then, but in reality you took cold in that room full of foul air. [Sidenote: Ventilation of workshops] Workshops are often poorly ventilated. No person should ever work in a badly ventilated place. The labor unions frequently strike for higher wages, but until recently a strike for better ventilation was rarely heard of. Better ventilation would be practically equal to an increase in wages, because there would be fewer doctors' bills to pay, and less likelihood of losing work through illness. Always have plenty of pure, fresh air wherever you are--in school, in bed, at work, or at play. [Sidenote: Why we should breathe through the nose] The cells in the skin of the nose secrete a watery fluid, and this fluid serves to moisten the air as it passes through the nose. Dry air irritates the mucous membrane which lines the nose, throat, and lungs, and it is very important that the air be moistened before it reaches the throat. Air is also warmed as it passes through the nose. Cold air is irritating to the throat and lungs. The small hairs in the nose catch the dust and dirt in the air and prevent it from going into the lungs. The nose was made to breathe through, and all the air that goes into your lungs should pass through your nose, in order that it may be moistened, warmed, and cleansed. [Illustration: FIG. 28. Showing position of adenoids and tonsils in the throat.] [Sidenote: Why some children breathe through the mouth] Frequently we see boys and girls breathing through the mouth. They do this because there is something in the nose that prevents the air from passing freely through it. If there were nothing in the way, the child would breathe through the nose instead of the mouth, because the natural way of breathing is through the nose. The most common reason for mouth-breathing is the growth of small lumps in the throat just behind the nose. These little lumps are called adenoids. They are not natural, and should be taken out. We do not know why they grow in some children and not in others, but we do know that they should be taken out so that the child can breathe easily through the nose. Large tonsils also cause boys and girls to breathe through the mouth. Tonsils that are large enough to cause the child to breathe through the mouth ought always to be taken out. Large tonsils and adenoids are often found in the same child. [Sidenote: Effects of mouth-breathing]