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."
Dr. Edward Smith, an English Physiologist, in an address before the Royal Medical and Chirurgical Society, remarked that "tea increased waste in the body, excited every function, and was well fitted to cases where there was a superfluity of material in the system;—but is injurious to the under-fed, or where there is greater waste than supply." Dr. Smith recommended tea as a preventive of heat-appoplexy, and in cases of suspended animation, as from partial drowning.
We have selected these expressions of opinion from among a large number of diverse character, for the purpose of illustrating the uncertainty of knowledge concerning tea. To recapitulate:—
Professor Johnston finds that tea exhilarates; excites to activity, produces wakefulness; yet it sooths, and it tranquilizes the vascular system; it lessens waste and saves food.
Dr. Smith found tea to increase waste, and to be injurious where food is deficient; says tea excites every function,—which must include the vascular system.
Dr. Hutchinson and Dr. Kane agree in the main.
What is the meaning of such radical differences of view? We think they arise from three causes: First, tea affects different persons very differently; secondly, the subject has not received that careful study which it merits, and thirdly, there is a careless confounding of at least three classes of effects, and a confusion of terms in describing them.