212. How our body kills disease germs.—We take disease germs into the body in three ways: first, through the mouth, second, through the nose, and third, through the skin. So we should watch the purity of our food, drink, and air, and should be careful about putting things into the mouth, and about the cleanliness of the skin. We often take a few disease germs into the body without catching a disease. This is because the white cells of our blood fight the germs and kill them (p. 53). If the body is hurt or weakened, the white blood cells may also be weakened so that they cannot kill the germs. We should take good care of the body so that every part of it may do its work well. We need not be able to run fast, or to lift heavy weights, but the best sign that every part of the body is in good order is to feel bright and wide-awake. Then our white blood cells will also be in good order and able to fight disease germs.

213. Catching cold.—When we catch a disease, we often say that we have caught cold. We used to think that cold air and dampness were almost the only causes of taking cold, and this is the reason why we called many kinds of sickness by the name of colds. Now we know that we catch cold by taking disease germs into the body. The germs will not be able to grow unless the body is weakened in some way, as by cold and dampness. Yet if we are wet and cold, we shall not catch cold unless we take disease germs into the body. We do not get the germs from the outdoor air, for very few germs are there. We get them from the foul air of our houses when we come in to warm and dry ourselves. If the air of our houses were always as clean and pure as the outdoor air, we should hardly ever have colds.

We can safely let the cold air blow on us if we are out of doors, but if we sit in a house, a small draft sometimes seems to make us take cold. This is because there are likely to be many disease germs in the house and few out of doors.

Other things besides cold air and dampness may weaken the body, and so help us to take cold. If germs of colds are in a warm room, we may sit there and take cold even if we are not wet or chilled at all. The body may be weakened by poor food, wrong eating, or overwork, so that disease germs will easily grow in it. We take as many colds from these causes as from cold air and dampness. 214. Kinds of colds.—A person takes most of the germs of colds through his nose and mouth. If they grow only in his nose, we say that he has a cold in his head. If they grow in his throat, he has a sore throat, or tonsillitis. If they reach as far as the upper part of his windpipe, he is hoarse, or has a cough, or the croup. If the germs are planted in his lungs, he may have bronchitis or pneumonia. All these kinds of sickness often spread from one person to another. If one person in a family has a cold, others in the family often catch cold from him.

215. Diseases like colds.—Diphtheria, tuberculosis, whooping cough, and measles all begin like a common cold and often look like a cold during the whole sickness. Colds do not turn into any of these diseases, for each of them comes from its own germ, just as corn comes only from seed corn.

216. Curing a cold.—If you have a cold, you ought to stay at home and rest, or lie in bed. Then your white blood cells can gain strength to fight the disease germs. You ought to have plenty of fresh air in your room. You ought not to eat much food for a few days, so that your stomach and intestine and liver can use all their strength in throwing off the poisons of the germs. But you ought to drink plenty of water, so as to help wash away the poisons from your body. 217. Keeping colds from spreading.—You should keep away from other persons while you have a cold, or other catching disease, so as to keep from spreading the sickness. You ought not to go visiting, or go to school, or to church, or to other meeting places. When you cough or sneeze, you should hold a handkerchief to your mouth, so as to keep from blowing disease germs from your throat and nose. You ought to sleep in a bed by yourself, so that no one may take the disease germs from your bedclothes. No one else should use your towel, or handkerchief, or knife, or fork, or spoon, or dish, until they have been washed in hot water, so as to kill the disease germs on them.

218. Keeping from catching cold.—You can keep yourself from catching cold by keeping your body strong and in good order. You should keep your clothes dry, eat good food, breathe pure air, get good rest and sleep, and keep your body, your clothes, and your house clean. You should also keep disease germs out of your body. You should not form a habit of putting your fingers or a pencil to your mouth (p. 127). You should keep your nose, your throat, and your mouth clean.

219. Cleanliness of the nose.—The inside of the nose is wet with a slippery liquid. If you have a cold, the liquid is thick and stops your nose, and is called phlegm. The liquid catches and holds dust and disease germs, and keeps them from going into the windpipe. It also kills many of the disease germs.

You should always carry a handkerchief and use it so as to blow the germs out of your nose. You should have a clean handkerchief every day.

220. Adenoids and large tonsils.—Sometimes children have large tonsils growing in the back of the throat, or soft bunches of flesh called adenoids back of the nose. These children cannot breathe well through the nose, but must breathe through the mouth. Then they take dust and disease germs deep into the body, and so take colds and other sickness easily. If a child has adenoids or large tonsils, an operation should be done to take them out. 221. Cleanliness of the mouth.—We often breathe dust and disease germs into the mouth or snuff them into the throat from the nose. Then they are caught between the teeth and in the folds of the cheeks and throat. There they may grow, and finally go deeper into the body and make us sick. A dirty mouth is very often the cause of colds and other sickness.

We should keep our mouths clean by brushing our teeth with a toothbrush two or three times a day. We should also rub the toothbrush over the tongue and around the back part of the throat so as to clean the germs from every part of the mouth. Each child should have a toothbrush of his own, and should use it every day.

222. Contagious diseases.—Diphtheria, whooping cough, measles, scarlet fever, and smallpox are all dangerous kinds of sickness, and spread with great ease. The germs may float in the air, and we may take them into our bodies if we go into a room where any one has the sickness. So we call these diseases contagious. If a person has one of these diseases, he should be made to stay in a house or room by himself until he is well. Keeping the sick away from well persons is called quarantine. When the sickness is cured, the sick room and everything in it should be cleaned and washed so as to kill the germs.

223. Board of health.—There is a board of health in every city and town. The men on the board show persons how to keep diseases from spreading, and make them obey the rules of health. Everybody in a town should help the board of health in every possible way.

WHAT WE HAVE LEARNED