197. Catching diseases.—Our body may get out of order like a machine. Some parts of it may be cut, or broken, or worn out, or hurt in other ways. Then we are sick until it is made whole again. Sickness always means that a part of the body is out of order.

Some kinds of sickness are like a fire. A small bit of something from a sick person may start a sickness in us, just as a spark may set a house on fire. Then we may give the sickness to others, just as a fire may spread to other houses. If a person has measles, we may catch the measles if we go near him; but if a person has a toothache, we cannot catch the toothache from him. So we may catch some kinds of diseases, but we cannot catch other kinds.

198. Bacteria and germs.—Every kind of catching sickness is caused by tiny living things growing in our flesh and blood. Some of them are tiny animals. Most of them are plants, and are called bacteria or microbes. A common name for all of them is germs. The word germ means nearly the same as the word seed. Bacteria are so small that we cannot see them unless we look at them through a strong microscope. Then they look like little dots and lines (p. 54). A million of them could lie on a pin point; but if they have a chance, they may grow in numbers, so that in two days they would fill a pint measure.

Very many kinds of bacteria and other germs are found nearly everywhere. They are in the soil and in water, and some float in the air as dust. When they fall on dead things, they cause decay or rotting. When we can fruit, we kill the germs by boiling the fruit and the cans. Then we close the cans tightly so that no new germs can get into them. The fruit will then keep fresh for years.

Decay is nearly always a good thing, for by it dead bodies and waste substances are destroyed and given back to the ground, where plants feed upon them. Many plants would not grow if they could not feed upon decaying things. So most bacteria and other germs are useful to us. But some kinds of germs will grow only in our bodies, and these kinds are the cause of most of our sickness.

199. Germs of sickness.—We catch a sickness by taking a few of the germs of the sickness into our flesh. There they grow quickly, like weed seeds in the ground, and form crops of new germs within a few hours. After a few days the germs become millions in number, and crowd the cells of our flesh, just as weeds may crowd a potato plant (p. 54).

Disease germs in the body also form poisons, just as some weeds in a field form poisons. The poisons make us sick, just as if we had swallowed the leaves of a poisonous weed.

200. Fever.—If a sickness is caused by disease germs, the body is nearly always too warm. Then we say that the sick person has a fever. Almost the only cause for a fever is disease germs growing in the body. We can make a person have any kind of fever by planting a few of the germs of the fever in the right part of his body.

We are made sick by the germs of fevers more often than by all other causes put together. Here is a list of common diseases caused by fever germs:—colds and sore throats, most stomach aches, blood poisoning in wounds, boils and pimples, tuberculosis, whooping cough, measles, chicken pox, diphtheria, scarlet fever, typhoid fever, smallpox, and malaria.

Which of these kinds of sickness have you had? What sickness have you had besides these?

201. Sickness and Dirt.—Disease germs leave the body of a sick person in three ways: first, through the skin, second, through the kidneys and intestines, and third, through the nose and throat. In these same ways our body gives off its waste matters. If we did not take anything from another person's body into our own body we should not catch fevers.

Whatever a feverish person soils may contain disease germs. When a person has only a slight fever he often keeps at work, and then he may scatter disease germs wherever he goes. So disease germs are likely to be found wherever there is dirt or filth. Cleanliness means good health as well as good looks.

202. Disease germs in the skin.—Disease germs may often be found in sores and pimples on the skin, but they will not leave anybody's flesh and blood through sound and healthy skin. If our skin is smooth and fair, there will be few disease germs on it unless we rub against something dirty. A dirty skin nearly always contains disease germs. Washing and bathing our body will take disease germs from our skin and help us to keep well.

203. Disease germs in slops.—A great many disease germs leave the body through the intestine and kidneys, and may be found in the slops and waste water of our houses. Slops are dangerous to health, for they may run into a well, or spring, or river, and so carry disease germs into our drinking water (p. 27). Also, house flies may light on the pails or puddles and carry the germs to our food. In these ways we catch typhoid fever, stomach aches, and other diseases of the intestines. All slops and waste matters from the body should be put where they cannot reach our drinking water, and where flies cannot crawl over them (p. 80).

204. Disease germs from the nose and throat.—If a person is sick with a fever, many of the germs are likely to be found in his nose and throat. Thousands of them are driven out with every drop of saliva and phlegm when he blows his nose, or spits, coughs, or sneezes, or talks. If he puts anything into his mouth, it will be covered with germs. More diseases are spread from the nose and mouth than in any other way, for we are always doing something to spread bits of saliva and phlegm.

205. Spitting.—Colds and consumption and other forms of sickness are often spread by sick persons spitting on the floor or pavement. The germs become dried and are blown away as dust. For this reason dust from the streets of cities and in crowded halls is often the cause of sickness. In many places spitting on a floor or pavement is strictly forbidden by law.

206. Putting things in the mouth.—Many persons have the habit of sucking their fingers, or of touching a pencil to the tongue when they write or think, or of wetting their fingers with their lips when they turn the leaves of a book. In all these ways we may give a disease to others or may take a disease from some one else.

207. Public drinking cup.—When you touch your lips to a cup, you leave some saliva and cells from your mouth on the cup. If a cup is used by a number of persons, some one is almost sure to leave germs of sickness on it, and others are likely to take them into their own mouths when they drink. So a public drinking cup is a dangerous thing. Each school child should have his own cup. Public drinking fountains should be so made that we may drink by putting our lips to a stream of running water.

208. Sweeping.—Dusty air in a room is dangerous to health, for disease germs are likely to be found in it. We can get rid of dust by keeping our floors swept clean. After sweeping we should wipe the dust from the tables and furniture. A feather duster or dry cloth will only stir up the dust and make it float in the air again. We should use either a damp cloth, or a dry duster made of tufts of wool, so that the dust will stick to the duster.

209. Foul air.—If we live in a closed room, the air soon becomes foul and dusty, and is likely to have disease germs in it. Foul air is one of the greatest of the causes of sickness. We should change the air of a room often so as to keep it fresh and free from dust and disease germs (pp. 65–67).

210. House flies.—House flies come from garbage heaps and filth of all sorts. So they carry disease germs on their bodies. They light on our food and on our faces, and so they often make us sick. They are often the cause of typhoid fever, stomach aches, and stomach sickness in babies.

Flies are hatched in manure piles and garbage heaps. At first they look like white worms, and are called maggots. Every maggot is a young fly. We can get rid of flies by cleaning up every garbage heap and manure pile.

211. Mosquitoes.—Mosquitoes carry malaria and yellow fever from sick persons to the well. If there were no mosquitoes, there would be no malaria or yellow fever. Mosquitoes are hatched in water, and the young are called wigglers. We may often see them in rain barrels. We may get rid of mosquitoes by emptying all rain barrels and pails and cans of dirty water, at least once a week, and by drying up swamps and marshes.

WHAT WE HAVE LEARNED