Despite its undoubted toxicity, arsenic is a much-used element, finding applications in agriculture, industry, and medicine. Arsenic as a poison has a prominent role in plays and novels as well as in real life. In medicine, arsenic was so widely used in the 19th century as a cure-all that it has been termed a therapeutic mule. Some arsenic compounds are still used in the treatment of parasitic disease. Moreover, in a striking development for a material regarded as a carcinogen, arsenous trioxide (brand name, Trisenox) was recently approved for treatment of leukemia. Arsenic has had a profound overall impact on human lives.