This has been already treated of, in reference to its effects on the system generally (i. 561). As a rubefacient it has considerable energy, and is sometimes though rarely employed; the liquid preparations above mentioned being preferred. it may be mixed with three or four parts of simple ointment or lard, and rubbed upon rheumatic joints; or, incorporated with extract of belladonna, in the proportion of one part to three of the extract, may be applied, by means of suitable dressings, in the pains of rheumatism and neuralgia.

Potassa

A solution, containing two drachms of hydrate of potassa in four fluidounces of water, was employed by the late Dr. Hartshorne, of Philadelphia, as a powerful rubefacient, in tetanus, rubbed along the whole length of the spine; care being taken not to produce cauterization. This practice has been imitated by many American physicians.