The clinical features of obstruction of the superior vena cava have been discussed by Ehrlich, Ballon and Graham.1 As a review of the literature revealed no references to experimental studies of this condition in laboratory animals, a series of experiments were undertaken in which the superior vena cava was obstructed above, below or including the azygos vein. The object of the experiments was, primarily, to determine the tolerance of animals to occlusion of the superior vena cava, to measure the effects on venous pressures and to trace the paths of collateral circulation. Additional observations were made to determine the immediate effects of obstruction of the superior vena cava on the arterial blood pressure.
EXPERIMENTAL METHOD
Dogs were anesthetized with ether, positive pressure with the intratracheal technic being employed. An intercostal incision was made aseptically on the right side of the chest, usually through the fourth intercostal space. The superior