Experiments have shown that a small amount of sugar assists in the normal chemical changes that go on in the body, and it is, therefore, obvious that nature intends us to take a certain quantity of it. Moreover it is true that sugars while being burned in the body give off much energy--mainly manifested in muscular power; where then we are taking active physical exercise foods of this kind are peculiarly appropriate. It would, therefore, not be wise for us to leave this food entirely out of the dietetic list, but to use it only in small amounts--particularly where we lead sedentary lives. Sugar and alcohol play a more or less similar role in the animal economy. It is well known that those who do not use alcohol are peculiarly prone to consume considerable quantities of sugar; and it is equally a matter of common observation that those who habitually take alcohol rarely eat sweets to any extent. When sugar is properly assimilated, as seems to be done most easily by children, it is an excellent food, but where sweets are over-eaten, and not properly digested, they give rise to a great accumulation of gas in the intestine, and produce in many persons a marked acidity of the stomach, frequently accompanied by severe insomnia. Nothing so quickly relieves such sleeplessness, caused by a "sour stomach," as allowing ten or fifteen grains of ordinary cooking-soda to slowly dissolve in the mouth and swallowing the saliva rendered alkaline in this way. _Milk._--Milk may be looked upon as an ideal food, it being composed of water carrying in solution the three great natural foods--albumins in the form of casein, carbohydrates as milk-sugar or lactose, and fat. Mixed in the proportion in which they here occur, they are most admirably adapted to the delicate digestive apparatus of the infant--the relative proportion of the different substances even gradually changing as the assimilative powers of the youthful organism increase; it is thus seen that milk itself is not of constant composition, even in the same animal, and that it alters in such a manner as to meet best the needs of the delicate being depending upon it for proper sustenance. It is also the case that the composition of milk varies in different animals--showing again how admirably nature exerts its powers in meeting desired ends. The lesson of practicable importance that we learn from this is that the milk of one of the lower animals is not in its natural state quite suited to the delicate stomach of the growing infant, and that if it be substituted for the mother's milk it must be more or less altered, depending upon the age of the child. It is particularly important that sweet milk be taken slowly, as otherwise large curds, difficult of digestion, form as soon as it gets into the stomach. CHAPTER VIII FOOD-VALUE OF VEGETABLES