This section is from the book "Botanic Drugs Their Materia Medica, Pharmacology and Therapeutics", by Thomas S. Blair. Also available from Amazon: Botanic Drugs, Their Materia Medica, Pharmacology and Therapeutics.
Costmary, Tanacetum balsamita, is official in Spain, and is used as an aromatic bitter. Our common Tansy, Tanacetum vulgare, is official only in Belgium. In small doses tansy is an aromatic bitter; in large doses it is an irritant narcotic. Its common use to stimulate menstruation, and the use of the oil to produce abortion, is to be unqualifiedly condemned. Numerous fatal cases are on record. See "Helonias" for a discussion of the alleged abortifacient and emmenagogue oils. Tansy is also used as a vermifuge, but is dangerous; it should never be employed in this direction, as we have better and safer agents. See "Gentian" for a discussion of the bitters. Tansy is a drug very properly going out of use, even as a bitter. If one cares to use a similar agent that is safe, and yet is a tonic and mild emmenagogue, let him use a related member of the Compositae, Yarrow, Achillea millefolium, in warm infusion. Also see "Artemesia," another one of the Compositae with a dangerous oil. Gentlemen who condemn the Compositae generally as inert, should remember tansy and wormwood, and then revise their theories.