Diphtheria is one of the most common of all the preventable diseases. It causes more deaths than any of the other diseases that can be prevented, except tuberculosis. The great prevalence of diphtheria is due to lack of care on the part of those who have this disease and of those who come in contact with them. [Sidenote: Where the diphtheria germ comes from] The germ that causes diphtheria always comes from some person or animal that has diphtheria. It never "just happens." If you went into your yard in the morning and found some beets growing in your flower bed, you would know positively that beet seeds had got into your flower bed in some way. You would not say that the beets just happened to grow there. So diphtheria will not "just happen." Diphtheria is always caused by germs that come from some one who has diphtheria. They may have come in a letter that was written in the room with the sick person. They may have come from the library in a book that had been used by some one ill with diphtheria. They may have come on some toy that had been played with by a child that had the disease. There are a thousand ways by which the germs may be brought to you without your knowing where they come from. [Sidenote: How to confine diphtheria germs] The public health officers try hard to keep these germs from being brought to you. In order to do this, they have to shut away from other people those who have diphtheria germs; that is, they make the sick ones stay at home until they are free from the germs of the disease. We call this _quarantine_. Quarantine means that you must stay away from other people when you are sick with a communicable disease, and that other people must stay away from you. People are not put in quarantine because they are sick, but because they are dangerous, and because we are trying to prevent other people from getting the same disease. Do not think the health officers unreasonable when they tell you that you must stay at home and that no one can come in to see you. This is done to protect other people and to keep them from getting the same disease that you have. If you ever have diphtheria, or any other communicable disease, you must remember that if any of your playmates come in to see you, they may get the same disease. [Illustration: FIG. 53. Disease germs are as deadly as guns.] [Sidenote: Seriousness of breaking quarantine]