follows:—Mix six ounces of tincture of Peruvian bark with half an ounce of sal-ammoniac. Shake these well for a few moments every time before the tincture is used. The method of using it is, to take a spoonful and hold it near the teeth, then with a finger dipped in, rubbing the gums and teeth, which are afterwards to be washed with warm water. Another method of preserving the teeth is to wash out the mouth with water after every meal, especially if animal food has been eaten; by these means the particles of food lodging about the teeth and gums are dislodged, which, when allowed to remain and accumulate, prove excessively injurious. Much harm is frequently done to the teeth by cleaning them with too hard a brush or deleterious dentifrices, in either case the enamel being scratched and otherwise injured. As a matter of course, the preservation of the teeth is greatly influenced by what is eaten and drunk. All things that are either very hot or very cold are extremely bad; acids are especially injurious, as are also sweets. _The decaying of teeth_ is partly due to chemical decomposition of the food lodged between the teeth in eating. When there is joined to this an unhealthy or weak condition of the ivory, which is thus rendered incapable of resisting the action of external causes, and also the continual pressure of the adjacent teeth, when too close together, then decay is almost sure to take place in some part or other of the crown. When it occurs in the sides of the necks, just below the enamel, the cause always is in the food, and generally so when in the middle of the crown of the molars; but sometimes decay takes place beneath the enamel, and long before the slightest fissure in this part can be detected by any ordinary observation, or, at all events, while there is no opening large enough to admit the food. Besides these causes, another exists in the uncovered state of the roots, or fangs, or on these being covered by tartar instead of gum, both of which circumstances tend to produce decomposition and decay, and should be cautiously guarded against. When a cavity is actually developed, the sooner it is filled the better. When it is small and has not opened into the natural cavity of the tooth gold leaf is the best material, the dentist previously cutting away the decayed matter and pressing in the gold with great force. When, however, this cavity is exposed, gold is useless under ordinary circumstances. The following are some of the best methods of filling teeth when beginning to decay:—1. Mix thirteen parts of pure finely powdered caustic lime with twelve parts of anhydrous phosphoric acid. This powder is moist during the mixing, and while in that state is to be introduced into the decayed tooth. The place in the tooth is to be made dry before receiving the mixture. This kind of filling must be used two or three minutes after being prepared. Soon after it is lodged in the decayed cavity, it becomes very solid. 2.