While it is true that the vegetable albumens furnish all that is really needed for the bodily health, animal food of some kind is an economical and useful addition to the diet. Races of men who endure prolonged physical exertion have discovered for themselves, without the teaching of science, the great value of meat. Hence the common custom of eating meat with bread and vegetables is a sound one. It is undoubtedly true that the people of this country, as a rule, eat meat too often and too much at a time. The judicious admixture of different classes of foods greatly aids their digestibility. The great abundance and variety of food in this country, permit this principle to be put into practice. A variety of mixed foods, as milk, eggs, bread, and meat, are almost invariably associated to a greater or less extent at every meal. Oftentimes where there is of necessity a sameness of diet, there arises a craving for special articles of food. Thus on long voyages, and during long campaigns in war, there is an almost universal craving for onions, raw potatoes, and other vegetables. 166. Hints about Meals. On an average, three meals each day, from five to six hours apart, is the proper number for adults. Five hours is by no means too long a time to intervene between consecutive meals, for it is not desirable to introduce new food into the stomach, until the gastric digestion of the preceding meal has been completed, and until the stomach has had time to rest, and is in condition to receive fresh material. The stomach, like other organs, does its work best at regular periods.[25] Eating out of mealtimes should be strictly avoided, for it robs the stomach of its needed rest. Food eaten when the body and mind are wearied is not well digested. Rest, even for a few minutes, should be taken before eating a full meal. It is well to lie down, or sit quietly and read, fifteen minutes before eating, and directly afterwards, if possible. Severe exercise and hard study just after a full meal, are very apt to delay or actually arrest digestion, for after eating heartily, the vital forces of the body are called upon to help the stomach digest its food. If our bodily energies are compelled, in addition to this, to help the muscles or brain, digestion is retarded, and a feeling of dullness and heaviness follows. Fermentative changes, instead of the normal digestive changes, are apt to take place in the food. 167. Practical Points about Eating. We should not eat for at least two or three hours before going to bed. When we are asleep, the vital forces are at a low ebb, the process of digestion is for the time nearly suspended, and the retention of incompletely digested food in the stomach may cause bad dreams and troubled sleep. But in many cases of sleeplessness, a trifle of some simple food, especially if the stomach seems to feel exhausted, often appears to promote sleep and rest.