If tannin is injurious, it should be observed that its proportion in the leaf of green teas is very much larger than in Black teas. An analysis by Mulder gave as the percentage of tannin in a Black tea, 12.85 per cent., and in a green tea as 17.80 per cent. But another analysis made by Y. Kazai, of the Imperial College of Agriculture of Japan, made the per centage of tannin (gallo- tannic acid) in a Green tea 10.64, and in a Black tea from the same leaf 4.89. In the green leaf from which these teas were derived he found 12.91 per cent. of tannin. This analysis indicates also that a portion of the tannin disappears in manufacturing Green tea, but a still larger, proportion is lost or changed in the manufacture of Black tea. Tannic acid taken into the human stomach in large quantity produces, according to the U.S. Dispensatory, "only a mild gastro-intestinal irritation." Passing over the phosphoric acid, the gluten, and other interesting constituents of the tea leaf, we proceed to the observed effects of tea upon the human system. Professor Johnston (before quoted) says that tea "exhilarates without sensibly intoxicating. It excites the brain to increased activity and produces wakefulness; hence its usefulness to hard students, to those who have vigils to keep, and to persons who labor much with the head. It soothes, on the contrary, and stills the vascular system, (arteries, veins, capillaries, etc.), and hence its use in inflammatory diseases, and as a cure for headaches. Green tea, when strong, acts very powerfully on some constitutions, producing nervous tremblings and other distressing symptoms, acting as a narcotic, and in inferior animals even producing paralysis. Its exciting effect upon the nerves makes it useful in counteracting the effects of fermented liquors, and the stupor sometimes induced by fever." And again, tea "lessens waste," and diminishes the quantity of food required; "saves food; stands to a certain extent in the place of food, while at the same time it soothes the body and enlivens the mind." Professor A. H. Church, of Oxon, England, in one of his often quoted books on Food, says that "the infusion of tea has little nutritive value, but it increases respiratory action, and excites the brain to greater activity." J.C. Hutchinson, M.D., (late President Medical Society of State of New York), remarks that caffein, which he regards as identical with theine, "is a gentle stimulant, without any injurious reaction. It produces a restful feeling after exhausting efforts of mind or body; it tranquilizes but does not disqualify for labor, and therefore it is highly esteemed by persons of literary pursuits. The excessive use of either tea or coffee will cause wakefulness." Dr. Kane, the Artic Explorer, speaking of the diet of his men while sojourning in the Artic ice fields, said that his men preferred coffee in the mornings, but at night, "tea soothed them after a hard day's labor, and better enabled them to sleep."