CLASSIFICATION OF FOODS.
Proteids
Organic
Protein
Fats.
Albumen, white of egg.
Myosin, lean of meat.
Albuminoids Casein, of milk.
Gluten, of wheat.
Legumen, of peas.
Collagen of skin and tendons.
Gelatinoids
Ossein of bones.
Extractives of meat.
Extractives of vegetables (amides).
Inorganic
Starches.
Carbohydrates
Cellulose.
Sugars.
Mineral matter.
Water.
The chief office of proteids is to build and repair tissues and they only can do this work. They also furnish heat and energy, and in cases of emergency are capable of supplying fat. The chemical elements found in proteid foods are carbon, hydrogen, oxygen, nitrogen, sulphur, and generally phosphorus and iron. They differ from the other food principles inasmuch as they contain nitrogen and nitrogen is essential to life.
The principal animal proteids are meat, fish, eggs, and cheese; the principal vegetable proteids are cereals, peas, beans, and lentils. The proteids obtained from animal foods are more easily digested and more completely absorbed than those obtained from vegetable foods. This is due in part to the presence of the large quantity of cellulose in vegetables. During the oxidation of proteids ammonia is set free, which neutralizes the acids constantly being formed.
The waste products of proteids are excreted by the urine in the form of urea. While a well-balanced dietary
