The legumes are the seeds of peas, beans, lentils, and peanuts. These seeds differ from the cereal seeds in containing a very much larger proportion of protein, as is shown by the accompanying table, which sets forth the chemical composition. Because of their richness in proteins, the legumes may be used in the dietary as a source of protein food next in importance to eggs and meat. In all dietaries which are vegetarian or ovo-lacto-vegetarian in character, it is customary to make very frequent use of the legumes to replace the meat of the ordinary mixed diet. A sandwich of peanut butter spread upon thin slices of bread would be quite as nourishing as a ham or tongue sandwich, and chemical analysis would show it to contain about the same amount of protein. Baked beans may well be used as a substitute for the meat of a dinner menu. The protein of the legumes is in the form of legumin, which is so much like the casein of milk that it has been called vegetable casein. This protein of the legumes is less easily digestible than meat protein.

The very thorough cooking of legumes is even more important than the thorough cooking of other foods. This prolonged cooking is necessary, owing to the fact that the nutrients are inclosed within the walls of the plant cells, which makes them inaccessible to the digestive juices until the cell walls are broken down by cooking and mastication. The grinding of dried legumes into meal greatly facilitates the cooking and the mastication, and therefore in turn the digestibility. Owing to the fact that dried legumes, such as the navy beans and the dried peas of the market, are rather difficult of digestion, they are less adapted for general use in the dietaries of people of sedentary occupation than for those who are engaged in active out-of-door pursuits. In the dietary of the lumberman, boiled or baked beans appear as almost a daily ration throughout the winter season.

Table VI. - Legumes

Besides the large proportion of protein, the legumes show a very high percentage of carbohydrates, mostly starch, but only a trace of fat, excepting the peanuts, which are very rich in fat and show only a moderate amount of carbohydrates. Because of the small proportion of fat in beans, peas, and lentils, that food should be added in the preparation. A common method of adding the required fat is to bake or boil fat meat with the legumes, as in the case of boiled or baked pork and beans. When fat has been thus added, the combination is a complete food, having the three organic foods in a proportion which would sustain life for an indefinite period. In the preparation of dried legumes, as dried peas and beans, one should avoid the use of hard water, as the mineral salts in hard water tend to form a combination with the legumin which makes the seeds hard and almost indigestible. The use of soft water, or even distilled water, will avoid such a result. Even the salt used in seasoning should be added as late as possible in the process of cooking. If soft water is not to be obtained a little baking soda may be added to the water, in the proportion of half a teaspoonful to two quarts. This softens the shells and overcomes in a large measure the influence of any calcium and magnesium salts present.

Green beans and peas have been mentioned above under green vegetables. Green beans, string beans, or snap beans appear in the market in early summer, and it is the whole bean pod with the contained young bean that is used. The crisp succulent pod is tender and luscious after brief boiling, and may be served as a side dish with butter or a cream dressing. At a later stage in their development the beans are greatly increased in size at the expense of the pod, the latter becoming thin and leathery. When the beans have reached this stage of their development they should be shelled; the shelled green beans may be prepared and served like green peas. At a somewhat later stage in their development they may be baked. These moist ripening beans from the garden bake very easily as compared with the dried beans of the winter market, and possess all of the nourishing qualities of the dried beans, besides being more easily digested.

Green peas are never eaten with the pod, but are shelled, and like the beans they may be used at various stages of their development. When too mature to serve as green peas, they may by longer boiling be made into a delicious puree by removing the tough skin of the seed and passing them, when thoroughly cooked, through a sieve.

Lentils are used in the menu like dried peas. They are not in common use in this country, and are seen only in the metropolitan markets.