This is of some importance, e. g., the saline cathartics act most rapidly after a period of fasting, so are usually administered before breakfast. Irritant drugs, as arsenic or iron or digitalis, are best given after meals, when they become well diluted with the stomach contents, and come very little in contact with the stomach-wall to irritate it. Quinine sulphate is given after meals not only because it is irritant, but so that it may be dissolved by the acid gastric juice; otherwise its absorption is retarded or may not take place at all. Sleep producers are most effective at the natural time of sleeping, and when the surroundings are favorable to sleep; they may have no effect at all if the patient is up and about. Sodium bicarbonate given on an empty stomach, i. e., before a meal, is absorbed as sodium bicarbonate, and furnishes alkali directly to the blood; but if it is given during the digestive period, it neutralizes the hydrochloric acid of the gastric juice, is changed to sodium chloride, and sets free carbon dioxide. Appetizers must be given just preceding the meal.