This Classic article is a translation by M.O. Heller, W. R. Taylor, N. Aslanidis, and Georg N. Duda of the original work by Julius Wolff, Zur Lehre von der Fracturenheilung (supplemental materials are available with the online version of CORR). An accompanying biographical sketch on Julius Wolff is available at DOI 10.1007/s11999-010-1258-z. A second Classic article is available at DOI 10.1007/s11999-010-1239-2. An accompanying Editorial is available at DOI 10.1007/s11999-0101238-3. The Classic Article is (C) 1873 and is reprinted from Wolff J. Zur Lehre von der Fracturenheilung. Langenbeck's Archives of Surgery. 1873; 2. (C) The Association of Bone and Joint Surgeons (R) 2010