All of these contain more or less carbohydrates, and the principal amount of carbohydrates of our diet is obtained from them.

1. Foods Rich In Proteids

Leguminous foods (peas, beans, lentils, etc.) contain a nitrogenous substance called legumin, which is allied to albumin, in the proportion of twenty-five per cent. They form a chief source of the nitrogen of the food of vegetarians.

2. Foods Rich In Carbohydrates. (A) Cereals

Bread made from the ground grain obtained from various so-called cereals, namely, wheat, rye, maize, barley, rice, oats, etc., is the direct form in which the carbohydrate is supplied in an ordinary diet. Besides starch it contains gluten, a nitrogenous body, and a small amount of fat. White bread is easier to digest than brown bread. Various articles are made from flour: sago, macaroni, biscuits.

(B) Vegetables (Rice, Potatoes)

They contain chiefly starch and sugar.

(C) Green Vegetables

Green Vegetables (cauliflower, asparagus, turnips, cabbage, carrots, spinach, string beans) are especially rich in salts.

Almost all vegetables are not eaten in their raw state, but after being cooked. The cooking produces the necessary effect of rendering them softer so that they can be more readily broken up in the mouth. It also causes the starch grains to swell up and burst and so aids the digestive fluids in penetrating into their substance. The albuminous matter is coagulated and the gummy, saccharine, and saline matters are removed. The conversion of flour into dough is effected by mixing it with water and adding a little salt and a certain amount of yeast. It is by the growth of the yeast which lives upon the sugar produced from the starch of the flour that a quantity of carbonic-acid gas and alcohol is formed. By means of the former the dough rises. By the action of heat during baking the dough continues to expand, and the gluten being coagulated, the bread sets as a permanently vesiculated mass.

(D) Fruit (Pears, Apples, Etc.)

They all contain sugar and organic acids like tartaric, malic, citric, and others.