Botanical Source.—This plant, called in England Cursed thistle, has a perennial, creeping, very long root, extremely tenacious of life, with a stem 3 or 4 feet in height, having a ranching panicle at the top. The leaves are alternate, oblong or lanceolate, sessile, smooth, or slightly woolly beneath, sinuate-pinnatifid, and prickly margined. The heads are rather small, numerous, and imperfectly dioecious. The flowers are rose-purple. The involucre round or ovate, with minute spin and the scales close pressed, and ovate-lanceolate (W.—G.).
History.—Canada thistle grows in various sections of the United States, in cultivated fields and pastures, roadsides, and waste places, flowering from June to August. It is an extremely troublesome plant to the farmer, requiring his utmost vigilance to extirpate it from his fields. The involucre is the only part of the plant that can be handled with safety. The root is the part employed, which yields its properties to water. Herman J. Pierce has made a chemical analysis and found a volatile alkaloidal principle difficult to obtain crystalline, of narcotic odor, soluble in ether, chloroform and alcohol; an organic acid, resin, etc., while starch, tannins and glucosids were absent (Amer. Jour. Pharm., 1896, p. 529).
Action, Medical Uses, and Dosage.—Tonic and astringent. Used principally, boiled with milk, in diarrhoea and dysentery; some recommend the addition of dried codfish skin to the decoction. Also, used as a local application to some cutaneous diseases, ulcers, and in leucorrhoea.
King's American Dispensatory, 1898, was written by Harvey Wickes Felter, M.D., and John Uri Lloyd, Phr. M., Ph. D.