Long-continued suppuration of large cavities in open pneumothorax is followed by a deviation of the spine to the healthy side. During the last two years, I have had an unusual opportunity to study this type of case.1 As a result of these observations, I believe it has been demonstrated that the cause of the scoliosis in these cases is pressure, due to the ribs on the diseased side, proof of which is afforded by the effect of extensive thoracotomy in correcting the deformity. When the lung is firmly held in a collapsed state by the dense enveloping membrane, which develops in long standing cases of large empyema cavities, nature attempts to obliterate the dead space by approximating the chest wall to the fixed lung. The anterior extremities of the ribs fall, making their horizontal direction more vertical; the intercostal spaces become obliterated, and in very long standing cases, such