Page:Popular Science Monthly Volume 17.djvu/874

854 part of it is extracted in the beverage as usually prepared, both of tea and coffee. A pound of tea usually furnishes from three to five times as many pints of beverage as are obtained from a pound of coffee, but the ways of preparing and the estimates are so different that nothing exact can be determined on this point. As a whole, the proportions for given volumes of beverage can not be declared habitually much larger in the one than in the other; if there is any difference, the coffee-beverage is likely to be the stronger. The tannins are tannic acid in both substances—boheic and gallic acid in tea, and caffeic acid in coffee, all astringents. Tea contains, according to the analyses relied upon by Dr. Prescott, from six to twenty per cent., an average of twelve per cent, of tannins; some other estimates make the percentage very much larger. This large amount is, however, by no means all dissolved in the ordinary preparation of tea as a beverage. No tannin was dissolved in steeping for five minutes six out of eleven specimens of different qualities of tea at the Michigan University, and the percentage of the other five specimens was not large, the average percentage of the whole being only 0·08. After thirty minutes' steeping, the quantity of tannin dissolved varied from 1·09 to 4·50 per cent., the average being 2·49, and was in no case equal to half the amount contained in the tea. A larger quantity of tannin was extracted in other experiments in which the tea had been macerated at ordinary temperature before boiling. The tannin in coffee-berry, by all reports, is not more than one third the quantity of that in tea-leaves, and may be considerably less. Six specimens of coffee were steeped for five minutes without yielding any tannin; two of them showed a trace of tannin after ten minutes' steeping; after twenty minutes', five of the specimens showed from 0·01 to 0·25; after thirty minutes', the proportion of tannin given up varied from 0·09 to 1·80, the average being 0·83. Other analyses show that tea contains an average of 0·206 grains, coffee 0·055 grains, of tannin to the fluid ounce of the beverage in use. These results leave no doubt that the tea we drink contains at least four or five times as much tannin as the coffee we drink, and that the tea yields only a small proportion of its large quantity of tannin, after from five to ten minutes of steeping. If tea or coffee is to be administered, as in any case of poisoning by alkaloids, tea, well steeped, is to be chosen as the better antidote for the precipitation of alkaloids, and equally potent as a stimulant. The essential oil of tea is a very small but distinct constituent, the most important factor in determining its market value. It is conjectured to be an organic stimulant, and may promote perspiration. Coffee, in the unroasted berry, has no volatile oil; but, in roasting, an agreeable essential oil is developed, the effects of which are not known, but which may cause the digestive disturbance sometimes ascribed to coffee-drinking. Of nutrient substances, tea contains pectin, gum, legumine, and indeterminate matters, yielding, in all, to boiling water about thirty-two per cent, of its weight. Coffee contains, after roasting, from one to two per cent, of glucose, ten to twelve per cent, of fat, nearly as much legumine, and a little gum, and yields thirty-five per cent, to water. "It is not unlikely," Dr. Prescott concludes, "that these food-substances, as modified by roasting, disagree with the digestion of many persons. This is, let me submit, a not improbable explanation of the class of injurious effects of coffee-drinking, when the substitution of tea-drinking gives relief. The powerful nerve-stimulant, caffeine, as we have seen, is obtained in about as large doses from tea as from coffee. The caffeine of both these beverages undoubtedly produces injury to the nervous system in many cases; but, when coffee causes palpitation, sleeplessness, etc., not resulting from tea, let me suggest that some attention be paid to the digestive organs."

Water in Disease.—Dr. S. G. Webber, in the "Archives of Medicine" for August, attributes a considerable value to water as a preventive and a remedy of disease, and opposes the abstinence from drinking at meals, advocated by many, as injurious. Among patients who have come under Dr. Webber's care affected with "symptoms of an undefined character, a vague unrest and disquiet showing itself by discomfort or even pain, sometimes in one place, sometimes in another," with constipation and an unhealthy