The solid crystal of the sulphate is a good stimulant to indolent ulcers, and a good caustic for exuberant granulations. Dissolved and used as an injection it is of service in various forms of ulceration affecting the rectum, especially, according to Mr. C. Heath's experience, in the later syphilitic forms, when the dorsal surface, or sometimes the whole circumference of the bowel within two inches of the anus, is affected, and there is much muco-purulent discharge. For such cases Mr. Heath recommends an injection containing about 10 gr. of sulphate to the pint, a fourth part to be used at one time, and retained for ten minutes: this has an excellent astringent effect, and should be combined with the use of mercurial ointments locally, and iodides internally (Lancet, i., 1873).