Children's Diseases. We have already studied two of the greatest and most dangerous diseases, and the way to conquer them--tuberculosis, or consumption, in the chapter on the lungs; and typhoid fever, in the chapter on our drink. One of the next most important groups of "catching" diseases--important because, though very mild, they are so exceedingly common,--is that known as the "diseases of childhood," or "diseases of infancy" because they are most likely to occur in childhood. So common are they that you know their names almost as well as you know your own--measles, mumps, whooping cough, scarlet fever, and chicken-pox. Though they are in no way related to one another, so far as we know (indeed, the precise germs that cause two of them--measles and scarlet fever--have not yet positively been determined), yet they can be practically taken together, because they are all spread in much the same way, they all begin with much the same sort of sneezing and inflammation of the nose and throat, they can all be prevented by the same means, and, if properly taken care of, they result in complete recovery ninety-five times out of a hundred. [Illustration: THE WINNING FIGHT Statistics for the population of the old City of New York. The chart shows a decrease from 95 out of every 1,000 in 1891-92 to 48 out of every 1,000 in 1909. This is due very largely to the careful methods of prevention enforced by the Board of Health, especially the inspection of milk.] Any child who has sneezing, running at the nose or eyes, sore throat, or cough, especially with headache or backache, a flushed face and feverishness, ought to be kept at home from school and placed in a well-ventilated, well-lighted room by himself for a day or two, until it can be seen whether he has one of these children's diseases, or only a common cold. If it turns out to be measles, scarlet fever, or whooping cough, he should then be kept entirely away from other children in a separate room, or, where that is impossible, in a special hospital or ward for the purpose; he should be kept in bed and given such remedies as the doctor may advise. Then no one else will catch the disease from him; and within from two to five weeks, he will be well again. The most important thing is not to let him get up and begin to run about, or expose himself, too soon; five times as many deaths are caused by taking cold, or becoming over-tired, or by injudicious eating, during recovery after measles, scarlet fever, and whooping cough, as by the disease itself. This one caution will serve two purposes; for, as a sick child's breath, and the scales from his skin, and what he coughs out from his mouth and nose are full of germs, and will give the disease to other children from two to four weeks after the fever has left him, he ought to be kept by himself--"in quarantine," as we say--for this length of time, which is just about the period needed to protect him from the dangers of relapse or taking cold.