Care of the Teeth. The most important thing for the health of any organ in the body is to give it plenty of exercise, and this is especially true of our teeth. This exercise can be secured by thoroughly chewing, or _masticating_, all our food, of whatever sort, especially breads, biscuits, and cereals. Thorough chewing not only gives valuable exercise to the teeth, but, by grinding up these foods thoroughly, makes them easier for the stomach to digest; and, by mixing them well with the saliva, enables it to change the starch into sugar. Meats, fish, eggs, cheese, etc., do not need to be mixed with the saliva, nor to be ground so fine for easy digestion in the stomach, and hence do not require such thorough chewing, though it is better to make a rule of chewing all food well. We can exercise our teeth also by eating plenty of foods that require a good deal of chewing, especially the crusts of bread, and vegetables such as corn, celery, lettuce, nuts, parched grains, and popcorn. It is most important to keep the nasal passages clear and free, and the teeth sound and regular by proper dental attention, so that the jaws will grow properly, and each tooth will strike squarely against its fellow in the opposite jaw, and both jaws fit snugly and closely to each other, making the bite firm and clean, and the grinding close and vigorous. If we are mouth-breathers, our jaws will grow out of shape, so that our teeth are crowded and irregular and do not meet each other properly in chewing. Pressure upon the roots of the teeth, from meeting their fellows of the opposite jaw in firm, vigorous mastication, is one of the most important means of keeping them sound and healthy. Whenever a tooth becomes idle and useless, from failing to meet its fellow tooth in the jaw above or below properly, or from having no fellow tooth to meet, it is very likely to begin to decay. The next important thing in keeping the teeth healthy is to keep them thoroughly clean. The greatest enemies of our teeth are the acids that form in the scraps of food that are left between them after eating. Meats are not so dangerous in this regard as starches and sugars, because the fluids resulting from their decay are alkaline instead of acid; but it is best to keep the teeth clear of scraps of all kinds. This can best be done by the moderate and gentle use of a quill, or _rolled_ wooden tooth-pick, followed by a thorough brushing after each meal with a rather stiff, firm brush. Then use floss-silk, or linen or rubber threads to "saw" out such pieces as have lodged between the teeth.