Knowledge of the manner in which healing proceeds in clean perforating injuries of the labyrinth, such as fractures or surgical procedures, is limited. This limitation is in large part due to the paucity of histopathologic material available for study, both of the human and of the experimental animal, and to the complicating element of infection, which is so often superimposed on the initial injury. In 1926 Ulrich1 summarized the histopathologic material reported to date and, with his 2 cases, showed that but 18 specimens of the human temporal bone were extant in which a sufficient time had elapsed between injury and death to permit observation of the process of healing. Since that time but a few more specimens have become available for study.2 In general the study of the available human material shows that in the first eleven days no evidence of healing can be made out; a fibrous tissue