In many ways the body is like a machine, with food as its source of motive energy. In the furnace fuel is burned quickly, in the body, slowly; but the final results are the same. The body differs from the machine, however, in that the food or fuel assists in building up as well as in supplying energy. Further, if more fuel is taken into the body than is necessary, it can be stored as reserve material, usually in the form of fat.

Foods are classified according to their uses in the following manner:

Protein - forms tissue; yields energy.

White of egg

Curd of milk

Lean meat

Gluten of grain

Old peas, beans, lentils Fats - stored as fat; yield energy.

Fat of meat

Butter

Olive oil

Oils of nuts and grains

Carbohydrates - transformed into fat: yield energy. Starch Sugar

Mineral Matters - form bone; assist in digestion. Phosphates of lime, potash, soda, etc.

A Model Kitchen

The kitchen cabinet, convenient sink and glass-top table facilitate work, and the sanitary wall-covering, which can be washed from floor to ceiling like ordinary oil-cloth, makes the room an unusually clean and attractive place.

In general it may be said that the different nutrients can to a greater or less extent do one another's work, one being burned as fuel in place of another; but while protein can be burned in the place of fats and carbohydrates, neither of these can do the work of the protein in building or repairing tissue. Care should therefore be taken to preserve the proper balance of foods in every daily menu. The wise housekeeper will not plan a meal in which all starchy or all fatty foods predominate, and she will see to it that protein in some form is provided. (See chapter on "Menus," page 481.) The protein she will find in cheese, meat, eggs, fish, dried legumes, etc., using one or another at practically every meal, and being guided in her choice by the market value at different seasons and by the tastes of her family. If she is skilful in preparing the various foodstuffs in appetizing ways, the daily menu may be both adequate and pleasing.