According to the U. S. Pharmacopoeia, this is made by digesting cantharides in oil of turpentine. it is a powerfully stimulating and also vesicating lotion, which was first prepared by the late Dr. Joseph Harts-horne, of Philadelphia, who used it in very low states of typhus fever. it is applicable only to conditions of great prostration, in which a rapid and at the same time sustained impression is required. it may be applied as a lotion to the inside of the thighs. Care must be taken, in using it, not to produce too extensive a vesication. When this effect is not wanted, it has little or no advantage over the oil of turpentine itself. When considered too strong, in any particular case, it may be diluted with olive oil. in the British preparation the virtues of the flies are extracted by means of acetic acid and ether, instead of the oil of turpentine.