Nourishing the sick is not always an easy problem, but its importance can hardly be overestimated. Indeed, proper feeding in many illnesses makes the difference between life and death. The actual amount of nourishment needed in sickness is often less than in health, but it may be just as great, or even greater if the illness causes increased tissue waste. Yet the digestive process of a sick person must be rendered as little laborious as possible, all foods ordinarily difficult to digest must be eliminated, certain others must be withheld or restricted according to the nature of the sickness, and in addition one may have to deal with an appetite that is capricious, diminished, or totally absent. Diet for the sick is often a part of medical treatment; in such cases the doctor will prescribe special diets and his orders must be carefully carried out. Except for special diets, food for the sick is generally divided into four classes: first, liquid or fluid diet; second, semi-solid diet; third, light or convalescent diet; and lastly, full diet. These diets are not very sharply distinguished. LIQUID DIET generally includes milk, eggnog, albumen water, broths, soup, beef juice, thin gruel, and beverages. Liquid diet makes least demand upon the digestive powers, because it consists of food already dissolved and therefore nearer the condition in which it can be absorbed. Moreover, it is less likely than other foods to contain excess of fat, improperly cooked starches, and other indigestible material. Liquids must be given at regular intervals and at shorter intervals than solid foods; 6 to 8 ounces every two or three hours is not too much if the patient can take it. The doctor usually specifies the amount and the interval. Some patients will take more nourishment at one time if the interval is slightly increased. SEMI-SOLID DIET includes all fluids and in addition soft milk toast, soft cooked eggs, well cooked cereal, custards, ice cream and ices, junket, and gelatine jellies. Liquid or semi-solid diet is commonly given in acute fevers because digestive juices and other fluids of the body are then diminished, and also because their digestion places a minimum of work upon a system already burdened with bacterial poisons. LIGHT OR CONVALESCENT DIET generally means a simple mixed diet. In addition to the articles in the two preceding diets it includes oysters, chicken, baked potatoes, most fruits except bananas, simple desserts, white fish, and other meats and vegetables added judiciously until full diet is reached. Fried foods should not be included.