Proteins

in the study of food, a large class of compounds containing nitrogen. According to Snyder the proteins as a class contain "about sixteen per cent of nitrogen, fifty-two per cent of carbon, from six to seven per cent of hydrogen, and less than two per cent of sulphur." Protoplasm is composed mainly of protein. A food supplying nitrogenous elements may be called a proteid. Peas, beans, the gluten of wheat and other cereals, milk, lean meat, eggs, and cheese supply nitrogen. Proteins are found in the fluids of the body, as the blood, chyme, chyle, and the digestive fluids. Starch, sugar, and fat are valuable foods; but proteins are needed to build muscle and to make good the wear and tear of the body. The food of a working man should be rich in proteins.