Nature's call for water is usually early and imperative, and no one doubts its great value. The amount of water necessary for different individuals varies greatly, but many, especially women, drink too sparingly. The practice of taking water at meals has long been frowned upon, and on account of the weak stomach muscles in many patients it should not be overdone in those suffering from pulmonary tuberculosis. If, however, the stomach is not displaced and the muscles strong, water at meals is excellent. One rule, however, should be absolutely followed if water is taken at meals. It should be drunk only after the food is swallowed and not used to wash down food incompletely mixed with saliva. Water is of great help in many instances of constipation. Pure spring or tap water is just as valuable for this purpose as many of the bottled waters on the market. There is, however, one great difference. Tap water is free; we all have an unlimited supply of it. For this reason we regard it as of little value. Bottle it, give it a fancy name and charge for it by the gallon and we drink it with marked benefit. Great is the power of suggestion!

Inorganic salts comprise combinations of sodium, potassium, calcium, magnesium, iron, iodin and probably others, in combination with chlorine, phosphorus, sulphur, carbon and other elements. The most familiar of these is sodium chloride, or common table salt. The larger the

part vegetables play in the diet the more salt is necessary. Iron is contained in comparatively large quantities in spinach, yolk of eggs, asparagus, beef, cabbage (green leaves) and apples, and it is well known that anemic persons should take iron. Many today are aware of the value of lime salts (calcium) in the coagulation of the blood and the curdling of milk, but that animals fed on a liberal diet free from these compounds die more quickly than those without any food is not so fully known. These salts then are very important, but luckily we usually find most of what we need in our ordinary diet.

Anybody can tell that a cow is an animal, and a cabbage a plant, but when both animal and plant have such simple structures that they strongly resemble one another the problem is different. Now one of the fundamental differences between an animal and a plant is the fact that the plant can use nitrogen in the form of a simple chemical compound to build up its cells, whereas the animal requires the nitrogen to be in a very complex state or, in fact, in the final stage in which it is found in the plant. These highly complex bodies are called "proteins," and occur in considerable amounts in lean meats, eggs and milk, and in smaller quantities in certain vegetables, such as peas, beans, rice, potatoes, wheat and corn, and in gelatin. These protein substances are absolutely necessary for life and can be replaced by no others. Recent

studies have shown that they fall into three or four classes, according to their ability to maintain life for a time or continuously, to maintain weight or to aid in growth. It is only necessary to add that the proteins in meat, milk, rice and potato belong to the last or the highest and most important group.

The group of albuminoids is best represented by gelatin which is good food in that it spares or saves the proteins for other uses. By itself it cannot form any new body substances which contain nitrogen.

The carbohydrates are represented in our food chiefly by the starches (bread, rice, potatoes, etc.), and to a certain extent by the sugars. Most of these are changed to grape-sugar by digestion and as such are absorbed into our bodies. We have seen that food might be looked upon as fuel for the human machine and have learned that the protein food is necessary for the repair and growth of the body. These carbohydrates really carry out much more closely the analogy of fuel. In the body they (as sugars) are burnt (oxidized) in the muscles during work (muscular contraction) and probably even during rest, for the muscles are rarely, if ever, absolutely relaxed. In this way they supply a large part of the heat of the body. It can easily be inferred from what has been said that the carbohydrates also supply a large amount of the energy of the body, possibly all the energy

of the muscles. These are the main uses of this class of foodstuffs, but like the albuminoids they can also "spare" the proteins, i. e., when the supply of starch and sugar is abundant less protein food is required. If this supply is in excess of the needs of the body it may be changed into fat and stored up as such.

The fats of the food really require no definition. Fat is found not only in meat, but also in the many oils found in fish and in vegetables (cod-liver oil, olive oil, cottonseed oil, peanut oil, etc.). The fats also furnish energy to the body, and, weight for weight, much more energy than the carbohydrates. We store fat in many nooks and crannies of the body, which when we fall ill and cannot eat, we draw upon to supply the energy to keep the necessary physiologic activities in action (the beat of the heart, the movements of breathing, etc.). So whenever our intake falls below our daily requirement of food we use or consume more and more of our body fat. When this has reached an advanced stage in tuberculosis, the disease is popularly called "consumption."

This brings us to consider briefly the fuel value of the foodstuffs. This has been studied outside and inside the body and the results expressed in heat units called calories, one of which represents heat enough to raise 1.056 quarts of water from 32° F. to 33.8° F. The fuel value of fat is greater than that of carbohydrates or of protein

as ordinarily used in the body. For this reason fat and carbohydrates might be called the "fuelfoods." It is impossible for the body to make use of as much fat as carbohydrates, and consequently, as has been stated, the carbohydrates (starches and sugars) are the chief heat- and energy-producing foodstuffs. The body of an adult man produces and gives off to the surrounding air about 2400 calories of heat in twentyfour hours. Now when the various foods are analyzed in regard to the various foodstuffs they contain, it is not difficult to determine how many calories or how much heat they are capable of supplying to the body. Many tables have been compiled, and it is of interest to note a few facts regarding them. One glass of milk contains twice as many heat units (150) as one raw egg. A tablespoonful of fairly thick cream or a butter ball is equivalent to an egg, or to a cubic inch of many cheeses. Skimmed milk or buttermilk has half the caloric value of whole milk, whey about one-third. Twenty ounces (forty tablespoonfuls, about three tumblers) of beef-juice equal one glass of milk. A good slice of roast beef equals four and one-half to five raw eggs, if the fat and all are eaten; if the roast is very lean, it is equivalent to only one and one-half eggs. Lamb chops, turkey and roast ham have a higher value than chicken, while veal is much lower. Two heaping tablespoonfuls of calf's-foot jelly equal about one egg.