The altered hemodynamics of the pulmonary circulation in response to an increase in the volume flow of blood have been subjected to experimental observation through several different methods. The most direct studies have been made with a Starling heart-lung preparation1 or a modification thereof.2 In these preparations the lung is a surviving organ isolated from any possible control by the central nervous system, and deductions as to the state of affairs in the intact organism are to be drawn with caution. Ligation of one branch of the pulmonary artery has been employed as a device to increase the volume flow in the contralateral lung,3 but this method also has its obvious limitations. Wiggers4 augmented the venous return to the heart by the intravenous injection of saline solution, again a method that is at variance with normal physiologic occurrences.
In the experiments herewith reported the venous return