This section is from the book "Materia Medica And Therapeutics: An Introduction to the National Treatment of Disease", by John Mitchell Bruce. Also available from Amazon: The pharmacology and therapeutics of the materia medica.
Tea. (Not Officinal.) - The dried leaves of Thea sinensis,
Composition. - Tea contains an alkaloid, thein, C8H10N4O2, identical with caffein; a volatile oil, most abundant in green tea, and tannin. The relations of the alkaloid, as well as its Action And Uses, are described fully under Caffein, page 271.