Having determined how many meals to serve in the day and what their hours shall be, the next question is how to choose and distribute the constituents of the day's ration so as to promote digestibility and satisfaction. A meal of pure protein, or fat, or carbohydrate would not be relished, and would have some physiological disadvantages. Digestion is likely to be more complete on a mixed diet. A meal of carbohydrate alone leaves the stomach more quickly than any other kind, and one would feel hungry before the next meal, though one might have had plenty of fuel; a meal of fat alone would leave the stomach very slowly, and one would not have so good an appetite for the next meal; a meal of pure protein would stimulate heat production without any particular advantages, except possibly in very cold weather : it would be decidedly undesir-able in hot weather. For these and other reasons it is best to have the different foodstuffs represented in each meal, and to see that no one contains an excess of fat, which tends to retard all digestion. This is what is usually meant by a balanced meal, but it may also include care that about the same proportion of fuel is served at the same meal each day. A meal does not need to be "balanced " in quite the same sense as a day's ration. The latter must have a definite amount of fuel, a suitable proportion of protein, ash well represented, some food for bulk, the whole selected with regard for the physical condition, tastes, habits, and pocket-books of those to be fed.
Food taken at a stated time constitutes a meal. It may consist of a single food material, as bread, or a single dish, as soup; or it may contain many kinds of food and many dishes. When the day's ration consists of a single food, there is no trouble in arranging the bill of fare, for all meals are alike. But as soon as we have two foods, we may consider whether they will digest better if eaten together or separately, and which way they will please the palate better. Balanced diets do not necessarily afford attractive menus. Macaroni and oatmeal would make a fairly well balanced meal except as regards ash constituents, but no one would call such a combination pleasing. By the substitution of a little cheese and an orange for the oatmeal, a meal containing about the same fuel value and proportion of protein could be arranged, and it would certainly appeal more to the appetite, and furnish better proportions of ash constituents.
In the construction of the menu for the day or meal, we must consider not only food values and time of day and combinations which shall be digestible, but flavor, color, texture, and temperature of our foods. The study of digestible combinations belongs to the science of nutrition. The harmoni-ous blending of tastes, odors, colors, and the like is an art. Just as there are pleasing combinations of sound, so there are harmonies of flavor; certain dishes seem naturally to "go together." Habit has a great deal to do with food combinations. A Chinaman would not eat sugar on rice; a Japanese would not cook beans with molasses as the Bos-tonian does. It is interesting to experiment with new combinations, and study to find out why old ones are pleasing. Why do we like crackers with soup? Butter on bread? Toast with eggs? Peas with lamb chops?