Concerning the Origin and Nature of Osteoblasts.

Three specimens are described which illustrate the formation of true bone in laparotomy wounds of the epigastric region of the abdomen. The literature dealing with their occurrence is surveyed and it is found that the majority of instances (34 out of 36) occur n laparotomy wounds made in or near the supra-umbilical part of the linea alba. Specimens in the R.C.S. Museum are enumerated illustrating heterotopic formation of bone in organs and parts which have no direct connexion with the skeletal system. An attempt is made to explain their occurrence on the traditional conception of bone-growth, namely, that it is the work of a specialized cell normally confined to the skeletal system. It is concluded that the heterotopic formation of bone cannot be explained unless it be accepted, as is now advocated by Professor Leriche, of Strassburg, that under certain states cells of tissues other than the skeletal can become osteoblastic in nature and in action-a view supported by the results of many recent experimental investigations. The view advocated here, not a novel one, is that "new" osteoblasts arise from the capillary system-especially from buds thrown out by that system when a neighbouring substance or body has to be absorbed. Certain necessary conditions are mentioned, but it is admitted that a full and satisfactory explanation of why supra-umbilical scars are more frequently the site of heterotopic bone formation than laparotomy scars in other parts of the abdomen has not been reached.