~Effect of Bacterial Activity in the Body.~--In summarizing the effects of bacterial action in the body it is found that with the exception of oxalic acid, which is exceedingly injurious, and which, according to Herter, results from the eating of large quantities of meat and sugar, the products of fermentation are simply irritating in character, while those resulting from putrefaction are distinctly toxic. Among the substances deserving mention under this head we have indol, skatol, cresol, and phenol. These substances are very soluble and upon absorption combine with the sulphuric acid formed in the body and are excreted by way of the kidneys where they appear in the urine as "conjugated sulphates," the chief of which is indican. The amount of indican in the urine is taken as a measure of the intensity of the putrefaction taking place in the body. ~Metabolism.~--Under the term metabolism we understand the series of processes through the foodstuffs and carried (a) in the conservation of the tissues of the body and (b) in the maintenance of body temperature and physical work (Taylor). The processes concerned in metabolism are chiefly those of building up, "anabolism," and breaking down, "catabolism." In the processes of anabolism the products absorbed are built into the tissues and cells of the body. In catabolism, the worn particles from the cells, and the dead cells no longer useful are broken up and thrown out of the body. According to Taylor, "side by side with these processes are the reactions of combustion, whereby the temperature necessary for the life of the cells is maintained, and the energy needed for external work furnished." ~Behavior of Carbohydrates in Metabolism.~--As Sherman[59] has said: "At least two kinds of enzymes are believed to be involved in the combustion of glucose in the tissue cells, (1) cleavage enzymes, which split the molecule into fragments more easily oxidized, and (2) oxidizing enzymes or oxidases which stimulate the oxidation of the cleavage products. Both kinds of enzymes are widely distributed through the body and are believed to be normal constituents of all active cells." ~Production of Energy.~--It has been proved that the energy for external and internal work is produced largely from the glucose brought by the blood and oxidized in the muscles. When a surplus amount of carbohydrate food is eaten, over and above the immediate needs of the body for fuel, it is stored in the liver and muscles as glycogen, which can be readily reconverted into glucose. When the supply of carbohydrate food is greatly in excess of the body's needs, that is when the liver and muscles cease to store glycogen, it is built up into adipose tissue and furnishes a readily available source of emergency fuel.