THE ELEMENTS OF FOOD
Although there may be thousands of different dishes, and combinations of foodstuffs, fundamentally they are all closely akin, and can be all resolved into a few quite simple elements: Proteid, Carbohydrate, Fat or Mineral Salts, or combinations of these; the Proteid class having many subdivisions, and the Carbohydrates being made up of the various sugars and starches.
We also know definitely just what use the body makes of these various substances. The Proteid is the up-builder of tissue, the essential foodstuff without which life cannot exist. If we compare the human body to an engine, as nearly all physiologists seem bound to do, we may say that Proteid is like the brass, or other metal, of which the structure is composed. The various Carbohydrates and the Fats are the fuels from which are derived the energy which animates and operates the mechanism. The Mineral Salts are used to supply various important bodily needs, such as elements required by the bones, or the delicate tissue in the eyes, the enamel for the teeth, and so forth.