Food is used to repair the waste and worn-out elements of the body. The occupation to a very great extent influences the character of these needed elements, and though the food we eat should be determined first by the normal appetite, a diet rich in the elements mostly needed to perform the daily work should always be supplied. One who works hard at manual labor all day will require far more of the muscle-making, and also of the heating foods than a brain worker. The heating foods are the source of all power in the body, just the same as fire is the source of power in an engine, and the nitrogenous, muscle-making foods repair the waste of the muscles which furnish the means by which these heating foods produce their results. Neither would be capable of accomplishing anything without the aid of the other, no more than would an engine if not influenced by heat under its boiler. One would starve to death with just as much certainty and just as speedily, and in some cases more speedily, if furnished exclusively with foods containing only one of these elements, as he would if totally fasting.

If no food is taken the body feeds upon itself until the skeleton condition is produced and the elements are supplied in proper proportion, but Nature has made no provision for properly nourishing a body fed on a partial food, for the reason that there are no partial foods in Nature. Partial foods are all man-made. Though the chemical constituents of foods furnished by Nature vary quite widely, there are none that do not contain a certain amount of every necessary element, enough at least to sustain life if such a necessity occurred. If being fed on a partial food the body does not seem able to find within itself the element not furnished in the food, and in many cases under such conditions death would ensue as quickly as when totally fasting.

One eminent authority maintains that a brain worker needs more food than the muscle worker or manual laborer. Such conclusions would be difficult to verify. It is well known that laborers eat and can digest far more than the brain worker, and in consideration of the fact that a manual worker keeps in active use the three-fourths of his body represented by his muscular system, while the brain worker uses only that small portion represented by his brains, it is difficult to see how the brain worker would call for as much energy or break down as much tissue as the muscle worker.

The brain worker's principal needs are fattening foods to keep up the heat of the body, and to furnish the needed mental energy, and muscle-making nitrogenous foods to repair or replace the worn-out brain cells and furnish the digestive fluid. The manual worker's principal needs are fattening foods to maintain the heat of the body and to furnish the needed muscular energy, and a large amount of muscle-making foods to repair the waste of the active muscular system and to furnish the digestive fluids. Therefore it can be readily seen that the manual worker's food should contain a larger percentage of muscle-making foods than that of the brain worker, and as he is undoubtedly exerting more energy than the brain worker he consequently requires a larger supply of fattening foods though the appetite is the only guide as to quantity. In fact the appetite of both the brain and manual worker, if made normal, will always clearly indicate which foods are mostly needed to nourish the body.

It is the deficiency of certain elements in the fluids of the body that create an appetite and the foods that supply these elements the most liberally are naturally enjoyed the most, if the normal appetite has not been dulled by poisonous liquors or gourmandizing.

Such foods as peas, beans, lentils and lean meats would furnish the muscle worker with the elements needed to nourish his body and repair the waste. While rice, potatoes, whole wheat bread and foods of like nature would be more applicable to the brain worker's needs.

Though a long list of tables might easily be used here to illustrate quality and character of foods needed by different individuals under different circumstances, they would be of but slight and perhaps of no value to the average reader in determining his own daily needs.

As stated before, in a previous chapter, food is of no value, regardless of how nourishing it may be, unless it can he eaten with appetite. Therefore the normal appetite is the guide that can be depended upon in all the varying conditions, both as to elements and as to the quantity needed.

Each reader should carefully study the chemical analysis of various foods and should see that his table is supplied with a variety of those foods which he likes and which contain a liberal supply of the elements that are needed to nourish his body.

If this duty is performed his appetite "will do the rest." He can then simply eat what he likes best, and can eat until this appetite is satisfied - not all he can.

If the appetite is not normal, if it does not dictate clearly as to character and quality of food needed, there is but one remedy and that is to fast until it designates by an unmistakable desire just exactly what is needed. That is the only infallible means of developing a normal appetite, and after having taken the trouble to develop this normal appetite, you should keep it normal by abstaining from liquors and other stimulants, and also avoid overeating, or eating without appetite as you would a poison.