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It is said that nearly all the caffeine now made is obtained from tea. For years past it has been asserted, and commonly accepted as the fact, that this alkaloid was identical with that derived from either coffee, cocoa, Paraguay tea, guarana or kola. Latterly, however, this opinion has been unsettled, since the separate study of the alkaloids, derived from these different sources, has shown that a marked difference in the therapeutic effects of some of them can be demonstrated. The production of palpitations of the heart, a peculiarity of theine, may be accounted for in that class of cases that have greatly puzzled some recent observers, when the fact becomes known to them that the tea plant has been substituted for the coffee-berry, as a source of their caffeine. A recent paper by Dr. T. Cranstoun Charles, in the British Medical Journal, contains an interesting study of the physiological
SOURCES OF CAFFEINE.. JAMA. 1890;XV(19):689. doi:10.1001/jama.1890.02410450025006