~Metabolism of Body Tissues.~--The constant breaking down and building up of the tissues of the body and the evolution of heat as a by-product of the energy expended may be summed up in the term "metabolism." The metabolism of the body is normally supported by the food ingested. However, it is a known fact that were no food eaten the processes would continue just the same, the difference only being the use of the body structure instead of food materials. According to Sherman, the chemical changes and energy transformations are of course inseparable. It has become customary to speak of the metabolism of matter and the metabolism of energy, and to regard the extent of the metabolism of any material substance as measured by the amount of its end products eliminated, and the extent of the energy metabolism as measured by the amount of heat or of heat and external muscular work which the body gives off. * * * * * In summarizing the important factors in the utilization of food by the body several distinct points are made evident: 1. The composition of the body, and the composition of food, are practically the same. 2. Food must make good the losses resulting from metabolic processes and physical activity. 3. Utilization of food by the body necessitates: (a) Transformation through a series of processes: (1) Digestion. (2) Absorption. (3) Metabolism. (4) Elimination. (b) Factors influencing use of food: (1) Stimulation of secretory cells through appetite juice (stomach); hormone secretin (intestines). (2) Factors retarding use of food:--Fear, worry, anger, nervous excitement, fatty foods and alkaline carbonates (bacterial action causing fermentation and putrefaction). PROBLEMS (a) Outline the processes through which a slice of bread and butter must pass, from the time it is eaten until it reaches the blood stream. (b) Outline with a diagram the manner in which the foodstuffs are utilized in the body. (c) Show in the form of a table the effect of the enzymes on proteins, on fats, on carbohydrates. FOOTNOTES: [51] "Chemistry of Food and Nutrition," by Henry Sherman. [52] "Chemistry of Food and Nutrition," by Sherman. [53] "Chemistry of Food and Nutrition," by Henry Sherman. [54] Compiled from "Textbook of Physiology," by Howell, and "Chemistry of Food and Nutrition," by Sherman. [55] "Chemistry of Food and Nutrition," by Henry Sherman. [56] This scheme applies to the protein, fat and carbohydrates with quantitative variations only. Courtesy of Dr. A. R. Taylor, Leland Stanford University. [57] "Chemistry of Food and Nutrition," by Sherman. [58] Herter's "Bacterial Infections of the Digestive Tract" (1907). [59] "Chemistry of Food and Nutrition," by Sherman. [60] "Chemistry of Food and Nutrition," by Sherman.