In taking up the study of dietetics, the student is introduced to some of the fundamental principles governing the health and well-being of a people, since dietetics includes a study of food and its relation to the body. The relationship between right food and good health is very close; how close is being demonstrated constantly in experimental fields of scientific research. To be able to judge whether the food one eats daily is giving the best possible value from a physiological and economic standpoint, requires a definite knowledge of food, its source, composition and nutrient value, as well as its relation to the body in health and disease. No one is capable of giving constructive advice upon matters pertaining to diet, unless he has acquired this knowledge through training. A nurse should obtain this training during her course in the hospital, through the class room, the wards and the diet kitchen. The dividing line between health and disease is frequently almost imperceptible, and without a knowledge of the normal body, it is, at times, impossible to tell where the normal leaves off and the abnormal begins. For this reason a nurse must understand normal nutrition, that is, the behavior of food in the healthy body, before undertaking the task of ministering to the body attacked by disease. In a text of this kind, it is impossible to cover all phases of the subject, especially since day by day new discoveries are being made with relation to food and its uses in the body. But with careful attention to the principles set forth, a nurse should be able to carry out the dietary orders given her by the physician and dietitian in the hospital. And, when her course of training is finished, she should find herself equipped to assist in raising the standard of health through her knowledge of dietetics. With this brief summary of the aims and object of the study of dietetics, we will begin the actual work with a study of Food. ~Food Materials.~--Food is the name given to any substance which, taken into the body, is capable of performing one or more of the following functions: 1. Building and repairing tissue, maintenance, growth, and development of the muscles, bones, nerves, and the blood. 2. Furnishing the energy for the internal and external work of the body. 3. Regulating the body processes, maintaining the proper alkalinity and acidity of the various fluids throughout the body, regulating the proper degree of temperature, and determining the osmotic pressure, etc. For the convenience of study scientists have arranged the foodstuffs in groups: 1. According to type; 2. According to their chemical composition; 3. According to the function they perform in the body.