Subject No. 17 January 2, 1906 256 Subject No. 17 February 27, 1906 256 Subject No. 17 April 24, 1906 252 Subject No. 17 June 27, 1906 252 THE NUTRITION OF MAN CHAPTER I FOODS AND THEIR DIGESTION TOPICS: The purpose of nutrition. The food of man. Proteid foods. Carbohydrate foods. Fats. Food as fuel. Composition of foodstuffs. Availability of foods. Food as source of energy. Various factors in the nourishment of the body. Processes of digestion. Secretion of saliva. Function of saliva. Enzymes. Reversible action of enzymes. Specificity of enzymes. Mastication. Gastric secretion. Components of gastric juice. Action of gastric juice. Muscular movements of stomach. Time foods remain in stomach. Importance of stomach digestion. Processes of the small intestine. Secretion of pancreatic juice. Chemical changes in small intestine. Destruction of proteid food. Significance of the breaking down of proteid. Change of fatty foods and carbohydrates in intestine. Digestion practically complete at end of small intestine. Putrefaction held in check. Digestion a prelude to utilization of food. One of the great mysteries of life is the power of growth, that harmonious development of composite organs and tissues from simple protoplasmic cells, with the ultimate formation of a complex organism with its orderly adjustment of structure and function. Equally mysterious is that wonderful power of rehabilitation by which the cells of the body are able to renew their living substance and to maintain their ceaseless activity through a period, it may be of fourscore years, before succumbing to the inevitable fate that awaits all organic structures. This bodily activity, visible and invisible, is the result of a third mysterious process, more or less continuous as long as life endures, of chemical disintegration, decomposition, and oxidation, by which arises the evolution of energy to maintain the heat of the body and the power for mental and physical work.