These officers first ask all the doctors in the town to report to this Central Health Office, or Board of Health, every case of a patient with an infectious disease. Then, when the case has been reported, that office sends some one with a card on which the name of the disease is printed in large letters, and he tacks the card upon the front of the house or upon the fence around the lot, so that everyone who goes near the house may know that there is danger, and keep away from it. Then, sometimes, a messenger from the Board of Health goes into the house and talks to the family, and tells them how they can keep the patient in a room by himself, so as to prevent the rest of the family from catching the disease; and how they can best take care of the patient, and keep from carrying the infection through clothing or food or anything else. [Illustration: ONE WAY IN WHICH THE BOARD OF HEALTH PROTECTS US] Then, because anyone who has been sick with an infectious disease will still be shedding the germs of the disease and spitting or coughing, not only as long as he is sick, but for two or three weeks after he is beginning to feel better, the messenger will tell the family that the patient must stay either in his own room or within his own house or yard, for so many days or weeks. This is called keeping _quarantine_. The word comes from the Italian word _quaranta_, "forty"; because in the early days when the practice was first begun, the patients used to be kept by themselves in this way for forty days. While sometimes this is very inconvenient and hard and troublesome, it is really the only safe way of stopping the spread of these diseases; and I am sure anyone of you would be willing to take this extra trouble sooner than let any of your friends catch a disease from you, and perhaps die of it. Quarantine is also the best and safest thing for the patient, because it keeps him quiet and at rest until he has completely recovered, and until all danger that the poison of the disease will attack his lungs or heart or kidneys is over. In some of the best schools now there is an examination of all the children every morning, by a visiting doctor sent by the Board of Health. If the doctor finds any child that has red and watery eyes, or is running at the nose, or sneezing, or coughing, or has a sore throat, he usually sends him home at once, so that the other children will not catch the infection. The school doctor is not thinking only about what seems to be a cold, although, as you know, it is very important that anyone with a cold should take good care of himself and should not let others catch it from him. The doctor sends the child home because this is just the way in which several other infectious diseases may begin--_measles_, _scarlet fever_, _chicken pox_, _whooping cough_, and _diphtheria_. For most infectious diseases, as you will remember, are caught from germs floating in the air and breathed into the nose and throat.