The cereal grains are composed largely of starchy foods, and so are certain tubers, such as the potato, cassava, etc. Of the common cereals rice contains more starch than any other and oats the least. Sugars are intimately related to starch and are included under the term starchy food or carbohydrate food. The carbohydrate matter in the flesh mentioned above, namely glycogen, is of the nature of a sugar. Among the typical sugar foods are beets, melons, and fruits, some of which contain large percentages of sugar. All fruits contain greater or less quantities of sugar, and that is true, also, of all vegetables. Of the plants which produce the sugar of commerce there may be mentioned the sugar-cane, the sugar-beet, the maple, and palm trees. The principal sources of the sugar of commerce are the sugar-cane and the sugar-beet. Of the condimental foods may be mentioned spices, including pepper, mustard, cinnamon, allspice, and other foods of this class. Common salt occupies a unique position in food products. It is the only mineral substance which has any value as a condiment in human food. But it also has a more important function than its condimental character, namely, it furnishes the supply of hydrochloric acid without which digestion in the stomach could not take place. For this reason common salt must be regarded as an essential food product as well as a condiment. EXPLANATION OF CHEMICAL TERMS. Inasmuch as this manual is not solely intended for expert chemists and physiologists but also for the general public, a simple explanation of the use of the terms used in analytical data and tables is advisable. Under the term =moisture= is included all the water which is present in a free state, that is, not combined in any way with the ingredients of the material, and other substances volatile at the temperature of drying. The water is determined by drying to a constant weight at the temperature of boiling water or slightly above. In bodies which are easily oxidized this drying takes place in a vacuum or in an inert gas like hydrogen or carbon dioxid. =Protein.=--Under this term is included all the nitrogenous compounds in a food product which contain in their composition sulfur, nitrogen, carbon, hydrogen, and oxygen, forming that class of tissues represented by the gluten in wheat, the white of an egg, muscular and tendinous fibers, etc. =Ether Extract.=--Under this term is included the fats and oils, the term fat being applied to animal fat and the term oil to vegetable products. These bodies are all soluble in ether and therefore are grouped together under the term “ether extract.” There are some fats both in animal and vegetable substances insoluble in ether, but they exist in minute quantities and therefore are not separated from the extracts, but the whole matter is given together and represents practically the fats and oils in food.