“The chief constituent of the coffee berry, the alkaloid _caffeine_——in chemical analysis recognized as identical with that of the tea plant, _theine_——when separated from the other constituents, ... so as to be seen in its perfect purity, appears in snow-white, silky, filiform crystals, flexible and fragile, without odor, but having a mildly bitter taste.... But it remains an important consideration that this crystallized constituent ... is built on the chemical type of the alkaloid, a class of bodies which nature forms in plants, but not in food-plants——bodies that include narcotics, stimulants, hypnotics, deliriants, poisons, tonics; some of them affecting the whole nervous system, one to excite and another to depress; and others influencing only parts of the nervous system, for special functions of the body.”[85] [Footnote 84: This paper first appeared in the Boston _Journal of Chemistry_ and _Popular Science Review_, May and June, 1882.] [Footnote 85: Professor Albert B. Prescott, in _Popular Science Monthly_, Jan., 1882, “Chemistry of Tea and Coffee.”] “Medically speaking, this theine has a totally distinctive action from the infusions of which it forms a part. In the form of an infusion of tea or coffee, we have to deal with a large proportion of astringent matter, in the form of tannic acid, and with the presence of the essential oil, which is an excitant to the nervous system, and is the substance to which must be ascribed disorders of the nervous system which result from tea and coffee drinking, such as palpitation of the heart and sleeplessness. The theine, upon the other hand, of which there is about one-tenth of a grain in an ordinary cup of tea, is the restorative agent to the nervous system, and is opposed, in its therapeutic properties, to the action of the essential oil. The infusion, therefore, of tea or coffee may induce palpitation in a heart liable to excessive or incoordinate action; but theine, on the contrary, may be looked to, therapeutically, to quiet palpitation. The infusion, by being an excitant, may prevent sleep. Theine, by being a restorative and an indirect sustainer and regulator of the circulation, may induce sleep. Individual medical investigators have, more than this, attempted, from time to time, to show that the action of theine is allied to that of quinine.”[86] [Footnote 86: “Tea and Coffee as Nervines,” by Dr. Lewis Shapter, in _British Medical Journal_.] It can not be questioned that the administration of coffee, in the form of an infusion or otherwise, is entirely in accord with the theory and practice of medicine at the present day. It is, however, a fact well known to practitioners, and indeed generally to “laymen,” that the constant and long-continued use of any medicine transforms its “remedial” influence into one promotive of disease that may perhaps demand the curative aid of some other drug.