Some foods, especially vegetables of the leguminous class, appear to be provocative of excessive intestinal fermentation. Flatulence and even toxic poisoning may be the result of great bacterial activity in the digestive tract. It is hardly possible to check this by administering septics, but purging is of value by removing the fermentative material. Particular foods, especially soured milk and kephir, have been shown to have a preventive action on putrefaction. _Influence of Food on Secretion._—The more recent investigations reveal the fact that the kind of food has an influence not only on the abundance, but also on the kind of digestive secretions; this is most important because an abundant supply of digestive juices is necessary for good digestion. Broths, meat extracts, and milk stimulate the secretion of the gastric juice, which makes rational the taking of soup or bouillon as the first course at dinner, or the eating of toast or zwieback by persons with weak digestions. Fats, on the other hand, tend to inhibit gastric secretion, so that an excessive proportion of fat in the meat might hinder digestion in the stomach. Food may exert an indirect influence on the pancreatic secretion. The acid in the chyme stimulates the flow of pancreatic juice. One is almost inclined to speak of the physiologic education of the digestive glands, and to conceive them as being trained for fat, protein, or carbohydrate digestion. =Metabolism.=—Life consists, so far as material phenomena are concerned, in the transformation of matter into energy. To these transformations the term _metabolism_ is applied. In the metabolism of matter the changes are chemical; in energy the changes are physical. It is commonly assumed that the laws of conservation of matter and energy are conformed to or obeyed in animal bodies. The body converts potential into kinetic energy by metabolism in the body. The potential energy of food is transformed into the actual energy of heat and mechanical labor. In this respect the only difference between man and other vertebrates is the nervous and intellectual processes, which are not yet understood.