During the 19th century the treatment of non-union of fractures in the United States progressed from the insertion of a seton (first performed in 1802) and either externally or internally applied caustics or other irritants designed to stimulate the formation of callus, to the modern treatment using bone grafts at the end of the century. Successful ambulatory treatment wearing a brace or "artificial limb"—the forerunner of the cast-brace—was described in 1855.