This has been already treated of in reference to all other uses, except simply those of an escharotic. (See vol. i. page 412, and II. 480.) in the latter capacity, attention has been called to it by Prof. Simpson, of Edinburgh. in the United States it has long been used, mixed with corrosive sublimate, as an excellent caustic application in onychia maligna. This use of it was referred to in the first edition of the U. S. Dispensatory, published in 1833, in the article upon corrosive sublimate (p. 854), and was highly recommended, from my own experience, in the first edition of this Treatise. I have also been in the habit, for thirty years or more, of recommending the use of a strong solution of it, as the most effectual application in the ulcerous affections of the mouth known as cancrum oris, and in other ill-conditioned ulcers of the mouth and fauces. But I am not aware that any one has anticipated Professor Simpson, in the separate use of it, in the form of powder, as a caustic agent.

Prof. Simpson employs it, deprived of its water of crystallization, and reduced by levigation to the state of fine powder. in this condition, though it will not act when the cuticle is sound, he considers it, when applied to ulcerous surfaces, as one of the most powerful and easily managed of the escharotics. it may be applied in the state of powder, or formed into a paste with a drachm of glycerin, or into an ointment with two drachms of lard, to the ounce. The depth of the eschar produced is proportioned to the thickness of the caustic layer. The death of the part takes place rapidly, and the slough, which is white, usually separates on the fifth or sixth day, leaving a red granulating surface, which quickly cicatrizes. The salt, like the chloride of zinc, acts as an antiseptic agent, and prevents putrefaction of the part destroyed. in the extirpation of malignant tumours, the application must be renewed as soon as the slough separates, whenever an unhealthy-looking surface is left.

The special recommendations of this escharotic are considered by Dr. Simpson to be, 1. its power, 2. its rapidity, 3. its simplicity of management and facility of application, 4. its indisposition to deliquesce and spread, and 5. its entire safety. Besides destroying with it organic malignant growths and deposits, he has used it successfully in the treatment of indurated ulcers of the cervix uteri, and of lupus and other eroding ulcers of the face and other parts of the surface of the body; for the removal of the small red tumours at the orifice of the female urethra and neighbouring parts; and in destroying " ulcerated condylomata and warty excrescences." (Med. Times and Gaz., Jan. 17th, 1857.)

Dr. Watson, of Glasgow, has used the powdered sulphate of zinc satisfactorily in old, indolent, callous ulcers of the legs, such as are very commonly to be seen in hospitals. He states, too, that the salt, fused and run into moulds, had been found by Dr. McGhie to act as a good escharotic, though very painful. (Bost. Med. and Surg. Journ., from Glasgow Med. Journ.)