Ribs and vertebral bodies have been resected bilaterally between the second and ninth thoracic levels. The periosteum (6) which covered the inner surfaces of the ribs has been preserved in most areas. The anterior longitudinal ligament (23), with remnants of the intervertebral discs attached,has also been retained in part. The lungs have been inflated and are visible through the intact costal pleura. The proximal parts of the III-VII thoracic nerves have been positioned on the pleura in such a way that their dorsal and ventral roots, dorsal rami and communications with the sympathetic trunk are visible. These components are labeled for the left seventh thoracic nerve (8,9,10). The intercostal arteries and veins have been cut off in various ways.