Our interest in experimental lobectomy and pneumectomy was aroused by the discovery of a safe and reliable method of permanently closing large bronchi.1 A review of the literature on this subject reveals the appalling mortality of these operations to be due primarily to either pleural infection or reopening of the bronchial stump (or both) subsequent to the operation. The idea at once presented itself that these postoperative complications would be obviated by "closing the stump" before removal of the pulmonary tissue. The results of the experimental investigation of this report bear out this hypothesis. Pneumectomy was first performed by Rolandus2 (1492) for the cure of diaphragmatic hernia. However, little attention was given to this field of surgery at that time. At the beginning of the sixteenth century, Schenk3 aroused interest in thoracic surgery which subsequently has been kindled by the introduction of apparatus and procedures pertaining to