Since the original experiments of Duhamel, a voluminous literature on the regeneration of bone has accumulated. It has dealt chiefly with the nature of the process, the elements of normal bone from which the new is formed and the bearing of these questions on the problems encountered by the orthopedic surgeon. Because of the nature of these problems, interest has been centered on means of assuring regeneration after operation, of stimulating it after fractures, and explaining why it does not occur in some cases. The occasions in which its prevention has been desirable have been few or none. In thoracic surgery, however, in which the bony ribs are encountered chiefly as a hindrance to exposure and collapse, the prevention of their regrowth is frequently desirable. This is the case in drainage operations (empyema and abscess of the lung), in operations performed in stages, and in cardiolysis and the operation for