Deformities that limit the motion of the spine and hold it in unnatural positions, particularly in the thoracic spine, are far more serious for the general health of the patient than are deformities occurring in the extremities. When the spine is stiffened by arthritis, proper functioning of the thoracic and abdominal viscera is not possible,1because the position such patients habitually assume is one of forward flexion of the spine. The chest becomes flattened, and the ribs droop and gradually are fixed with the chest in the position of expiration (fig. 1). Normally there is a moderate excursion of the chest in ordinary respiration, with about 1½ to 2 inches increase in chest circumference. In arthritis of the dorsal spine there is often no measurable expansion of the chest in respiration. Usually the costal angle is 70 degrees or less, and there is often no palpable space between the