The tansy, or Tanacetum vulgare, is an herbaceous perennial, indigenous in Europe, but introduced into the United States, where it grows wild, and is cultivated in gardens. The whole herbaceous part is used. It has a strong, peculiar odour, which is much diminished by drying, and a warm, bitter, sub-acrid, aromatic taste. Its activity, which is imparted to water and alcohol, depends on a bitter ingredient, and a volatile oil. There is also a little tannic acid, but insufficient materially to influence the operation of the medicine. The oil is greenish-yellow, and has the characteristic odour of the plant.

Tansy has been known as a medicine for at least one thousand years. It is a stimulating tonic, and supposed also to possess anthelmintic and emmenagogue properties. In large quantities, it is probably somewhat narcotic; at least, so we may infer from the operation of the volatile oil. From its supposed possession of the power of causing abortion, this oil has been repeatedly taken in large doses; and three cases of death from it, in this country, have been recorded; one resulting from a single fluidrachm of the oil, a second from half a fluidounce, and the third from an ounce. The symptoms were violent convulsions, coma, and great prostration, which speedily ended in death. The fatal issue was too rapid to be owing to any irritant operation on the stomach, and in one case, which was examined after death, no inflammation was found.

The medicine has been given in dyspeptic affections, intermittent fever, to prevent the paroxysms of gout, in hysteria, amenorrhoea, and worms in the bowels. At present, its use is confined mainly to the two latter affections, and in these it is employed much more in popular than regular practice. The seeds are thought to be more powerful, as a vermifuge, than the oil.

The dose of the powder is from thirty grains to a drachm; that of an infusion, made with an ounce of the herb to a pint of water, two or three fluidounces, two or three times a day. A drop or two of the oil may be added to each dose of the infusion.