How do we expend the energy? By the common wear-and-tear incident upon all voluntary motion, all work and recreation, carrying on the internal movements of digestion and respiration, by thinking, by loss of temperature, by indulgence of any of our functions, and by any wrong indulgence especially. Excessive use, voluntary or otherwise, will of course diminish our total capital and cut short our lives. Could we always maintain the right balance we need never die. The importance of what has been said must now be clearly apparent. We ought to be wisely interested in choosing the proper foods for our daily needs and in having them properly prepared; we ought to know how much carbohydrates we need, how much proteids, and regulate our diet accordingly. The foods which contain nitrogen are chiefly the following: flesh of all animals, milk, eggs, leguminous fruits (peas, beans, lentils); those which contain carbohydrates chiefly are bread, starch, vegetables and especially potatoes, rice, etc.; foods supplying fat are butter, lard, fat of meat, etc. Salts are furnished in almost all other substances, but especially in green vegetables and fruits. Liquid food is obtained by water, too often neglected, and tea, coffee, beer, cider, etc. Alcohol has no power to form tissue or to repair waste and cannot be regarded as a true food. Tea and coffee are almost entirely stimulant, not nutritious, and should be taken sparingly or not at all. The common mistakes in diet are over-feeding or taking too much of one kind of food, and of the latter class perhaps an excess of starchy food is the most mischievous. If taken in excess, especially by the young, the starchy foods are not digested and what does not digest must putrefy: the result is a bowel distended with harmful gases. Many people eat too much nitrogenous food, with resulting plethora or gout. A great deal of vigorous exercise in the open air is required to use up such a diet. CHAPTER XXVIII. SELECTION AND PREPARATION OF FOOD. The requirements for normal digestion, assimilation and elimination are: (1) An intestinal canal clean and sound from mouth to anus; (2) nutritious food properly prepared; (3) regularity and moderation in eating; (4) free use of pure water, sufficient to forward the emulsification and assimilation of the food and the elimination of waste--whether that waste be of the residual portion of the food or of detritus of tissue; (5) a seasonably clad body, free from fatigue or loss of sleep; (6) a cheerful mind. Every sensible person will grant that a good digestion of vegetable or animal food furnishes sufficient steam and stimulus for the physical man; that a good digestion of intellectual food (ideas) furnishes the corresponding requisites for the mental man; and that exalted sentiments are the pabulum of the spiritual.