*Social Custom and the Caffeine Habit.*—By suitable processes a white, crystalline solid, easily soluble in water, can be separated from the leaves of tea, and from the berry of the coffee plant. This is the drug caffeine, the substance which gives to tea and coffee their stimulating properties, but not their agreeable flavors. Less injurious, on the whole, than either alcohol or tobacco, caffeine has come into general use in much the same way as these substances. In a sense, however, caffeine is more deceptive than either alcohol or nicotine, because the usual mode of preparing tea and coffee gives them the appearance of real foods. The housewife who would feel condemned in purchasing caffeine put up as a drug somehow feels justified when she extracts it from plant products in the regular preparation of the meal. *Counts against Caffeine.*—People of vigorous constitutions and of active outdoor habits are injured but slightly, if at all, by either tea or coffee when these are used in moderation. As already stated (pages 56, 167, 326, 329), they do harm when used to excess and, in special cases, in very small amounts, in one of the following ways:— 1. By stimulating the nervous system, thereby causing nervousness and insomnia and interfering with vital organs. 2. By introducing a waste which forms uric acid into the body, thereby throwing an extra burden upon the organs of elimination. In this connection it may also be stated that there appears to be little, if any, real advantage to the healthy body from the use of either tea or coffee, beyond that of temporary stimulation and the gratification of an appetite artificially acquired. Hence the large sums of money expended for these substances in this country yield no adequate returns. *Caffeine Restrictions Necessary.*—Though with many the cup of tea or coffee at breakfast does no harm, but gives an added pleasure to the meal, there is no question but that the use of caffeine beverages should be greatly curtailed. Children should not be permitted to drink either tea or coffee. Brain workers and indoor dwellers generally should use these substances very sparingly, and people having a tendency to indigestion, nervousness, constipation, rheumatism, or diseases of the heart, kidneys, or liver frequently find it best to omit them altogether.