This section is from the "A Practical Treatise On Materia Medica And Therapeutics" book, by Roberts Bartholow. Also available from Amazon: A Practical Treatise On Materia Medica And Therapeutics
The dried leaves of Camellia Thea; th'e, Fr.; Thee, Ger.
The constituents of tea are very much the same as those of coffee: theine; an aromatic oil; sugar and gum, and a peculiar form of tannic acid.
Tea is only used in the form of infusion. The character and quality of the beverage vary greatly with the kind of tea used in the preparation of the infusion. It will suffice to state that green tea is more astringent than the other varieties, partly because it contains more tannin, and partly because it is sophisticated to adapt it to a peculiar taste.