By _foodstuff_ is meant the chemical elements, appropriated by the animal for the use of the body, as described above. By _foods_ is meant those articles of diet found in the market which contain the chemical elements used by the body in various combinations. Bread, for example, contains all of the foodstuffs and has been called the staff of life, because it sustains life. Foods may contain elements, not foodstuffs, and not used by the body, but cast out as waste, while certain foods, such as sugar, cornstarch, olive oil, and egg albumen, contain only one foodstuff, as will be noted in the following classification of foods and foodstuffs—grouped according to the body uses. There are many classifications but the following tables, as compiled by a leading dietitian[2] for his practical work in classes, are clear and concise. Carbonaceous foods: Sugars Starches Root and tuberous vegetables Green vegetables Fruits Fats Nitrogenous foods: Lean meat Eggs Gluten Carbo-nitrogenous foods: Cereals Legumes Nuts Milk The above classifications are made because of the preponderance of certain elements in them, not because they do not contain other substances; e.g. vegetables are mixtures of sugars and starches; fruits are mixtures of sugars, vegetable acids, and salts; milk, legumes, cereals, and nuts contain a more equal division of sugars, fats and proteins and are therefore represented as carbo-nitrogenous; lean meats, with the exception of shell fish, contain no starch, but all meats contain fat, protein, and water, and all, except liver, contain ash. In the table below, examples are given of foodstuffs in which the chemical elements are almost pure representatives of their classes. Cornstarch, sago, and tapioca are almost pure starch, containing very little of any other element; glucose, cane sugar, syrups, and honey are almost pure sugar; butter, lard, and olive oil are nearly all pure fat; egg albumen, gluten, and lean meat are almost pure protein. { { Water { Corn Starch { Inorganic { Salts { Starches { Sago { { { Tapioca { { { { Carbonaceous { { Glucose { { (producing { Sugars { Cane Sugar { { heat & energy){ { Syrups Foodstuffs { { { { Honey { { { { { { { Lard { Organic { { Fats { Olive Oil { { { Butter { { { { { Egg Albumen { { Nitrogenous—Proteins { Gluten { { (growth and { Lean Meat { { repair)