The carbohydrates are our chief source of heat and energy, and as previously stated, furnish sixty to sixty-five per cent of the total fuel value of our food. Each ounce of pure carbohydrate yields one hundred sixteen calories of heat when burned. In caloric yield, they are equal to the proteins gram for gram, but yield less than one half that of the fats. If two thousand five hundred calories are again taken as our standard, then sixty per cent would make one thousand five hundred calories to be furnished by the carbohydrates. At one hundred sixteen calories an ounce, we find that it would require thirteen ounces of pure carbohydrate a day to balance this part of our diet. _Other Essential Elements_ The inorganic salts or ash of food are just as essential to the body as the other groups of food elements. These essential salts consist of the most common chemical elements, such as soda, potash, lime, magnesia, iron, phosphorus, sulphur, etc. One might expect to find some rare elements in a piece of mechanism as complicated as the human body, but such is not the case. The body salts are of the most common kinds. These salts are found in proper amounts in foods as produced by nature. We cannot take these salts as they are found in the chemical laboratory and use them to good advantage, but we should make sure that we are taking foods that will supply them in the proper amounts. Our best sources of supply are the grains, the fruits, and the vegetables. It is interesting to note that these mineral elements are generally found most abundantly, in the grains at least, in or near the outer coating, and that our high-grade flours are partially robbed of them when the bran and the middlings are removed. The same seems to be true of potatoes. In peeling, a large part of these salts is removed, and thus the real value of this splendid food product is lessened. This is one of the strong arguments for the use of whole wheat flours and other whole grain products. These inorganic salts are needed in the body to keep the various tissues up to their normal in composition. For example, the blood constantly needs some iron to build the red cells. Though the actual amount needed is very small, yet that small amount is exceedingly important to have at hand. As some of these salts are constantly being eliminated from the body, there must be a constant supply to keep the tissues in equilibrium. _Vitamines_ Vitamines are elsewhere considered in this booklet, hence only a very brief summary here. The chemistry of these products is very little understood at present. They were so named by Funk because of their nitrogen content and similarity to ammonia, the name really meaning _vital ammonias_. The term "vital" carries with it the idea of their importance to life. Some persons have questioned this name; but up to the present, it seems to be the best suggested.