amount of waste matter in the air exhaled from the lungs is markedly increased. Tea, then, acts as a food principally by hastening the oxidation or burning of other substances in the body. It creates a blast which burns up the half charred débris of the system, and from the burning or oxidation we receive increased energy. From what has been said, it will be evident that the only time when tea should be used is late in the day, after the heaviest meals have been taken. For the weak and debilitated it is not suitable, or should be used very sparingly. Its tendency to produce sleeplessness may also restrict its use. So far as its chemical composition is concerned, tea contains but little of nutritive value. The high place of tea among foods is solely due to its effect upon the nervous system. In the market there are two kinds of tea,-green and black. Until recently it was supposed that these were products of different species, or at least of varieties, of the tea plant; but it is now known that the two kinds arise from different methods of curing the leaves. In preparing green tea, the leaves are dried immediately; while in the other, the leaves are thrown into heaps, and a certain degree of fermentation or decomposition is allowed to take place before the drying is perfected. The chief constituents of tea are its active principle called theine, which is identical with the active principle of coffee, a volatile oil, tannic acid, and a small amount of ordinary food substances. Theine forms from 2 to 3 per cent. of tea. In making tea, as is ordinarily done, the greater part of the theine is dissolved out of the leaves,— tea yielding its active principle to water more readily than coffee. From equal weights, three times as much theine is obtained from tea as from coffee. According to the investigations of Mr. Fellows, 224 five-ounce cups of tea beverage are made from one pound of tea, and 45 eight-ounce cups from a pound of coffee. This makes the cost of an ordinary cup of tea, when the leaf sells at 75 cents per pound, about one third of a cent; and of a cup of coffee, when the berry sells at 27 cents per pound, about three fifths of a cent. In this estimation the sugar and milk added to these beverages are not considered. The volatile oil of tea is the special stimulant, and the market value of a tea depends more upon this than any other constituent. The amount and quality of this substance present are judged by the odor as well as by the taste of the hot beverage. Large tea houses have experts who are called "tea-tasters," and whose duties consist of deciding as to the value of different samples by the odor and taste. By virtue of the volatile oil, tea increases the flow of perspiration, and thus, although taken hot, may act as a cooling agent. The volatile oil is more abundant in green than in black tea. Tannin is also more abundant in green than in black tea. The object in making tea should be to dissolve as little of the tannin as possible, and at the same time extract as much as possible of the theine and volatile oil. To accomplish this, tea should be steeped five or ten minutes, by no means longer than ten minutes; but the water should be kept warm after that until the beverage is drawn for drinking. Mr. Fellows found the amount of tannin extracted from the best Japan tea, after steeping for five minutes, to be 0.10 per cent.; after ten minutes, 0.98 per cent.; after thirty minutes, 3.09 per cent. It is to the tannin that the astringent properties of tea are due, and when tea has been boiled, it is so astringent that it is well-nigh unfit for use, and indeed may cause derangements of the digestive organs. Tea contains small amounts of albuminous and starchy substances, but, as has been stated, these are present in such small amounts that they are not worthy of consideration. Tea is subject to the following adulterations, which, fortunately, are not largely used at present: (1) "Spent" leaves, those which have been once used for making tea, are dried, and mixed with fresh leaves. This adulteration is not practised extensively in this country. (2) The poorer varieties are mixed with the better, and the whole sold as of first quality. (3) Green tea is sometime tinted with indigo and gypsum Prussian blue is said also to be used, but the writer has failed to detect it after examining many samples. Black tea is also tinted with graphite. This is not used in large amounts, and, as used, is not detrimental to health, but is a pecuniary fraud. (4) Other leaves, notably those of the willow, elder, and beech, are added to the tea leaves. None of these are exactly like the tea leaf, and the adulteration may be detected by close inspection, even without a microscope. The border of the tea leaf is serrated nearly, but not quite, to the stalk. The primary veins run from the midrib nearly to the border, and turn in so that there is a distinct space left between their terminations and the border. Tea dust, which consists of broken leaves and sweepings of tea storage houses, is a legitimate article of commerce, yielding an average of 1.27 per cent. of theine. COFFEE. It is unnecessary to go into detail concerning coffee, since it resembles tea in so many of its properties. The active principle of coffee, called caffeine, is identical in chemical composition and physiological effects with theine of tea. The per cent. of this substance in the raw coffee berry is about one, and this is not given up so readily to water as that in tea. There is no volatile oil, corresponding to that of tea, in raw coffee; but one or more such oils are generated by roasting. The physiological action is not the same, however, as that of tea. It is not so stimulating, nor does it increase the perspiration to so great an extent. Tannin is present in a much smaller amount than in tea, and for this reason the steeping of coffee may be carried on longer than ten minutes. The unground coffee cannot be adulterated to any extent; but the ground coffee put in packages and boxes is almost universally adulterated. Often it contains no coffee at all. A student of the writer examined all the specimens that could be obtained in the market. The first, known as Java coffee, put up by the "Centennial Coffee Company," of New York, contained, besides some coffee, chickory, pease, wheat, acorns, and corn. The second, "Gillies Gold Medal Java," contained very little coffee, being composed principally of wheat, much of it unground chickory, corn, and pease. The remaining samples were ground coffee, sold in bulk, and in every case adulterated. CHOCOLATE. Chocolate is prepared from the ground seeds of the fruit of the cocoa palm. Cocoa nibs consist of these seeds, which are about the size of almonds, roughly broken, while chocolate contains a substance,-theobromine,—very similar, but not identical with theine or caffeine; its other constituents give it a very different position in the class of foods. The cocoa seeds contain from 45 to 49 per cent. of fat, and from 14 to 18 per cent. of nitrogenous matter. It will be seen from this that these seeds may be classed among the most nutritious foods. Chocolate always contains sugar, which has been mixed with the ground seeds. Chocolate does not stimulate the nervous system to anything like the extent that tea and coffee do; but for travellers and others who cannot obtain milk, chocolate may be used instead of that, the most nutritious of liquid food. Chocolate is often adulterated by the addition of too much sugar, or with starch. |