Abstract
Isolated hearts of dogs have been preserved in a viable condition for 72 hours with hypothermic perfusion (5 degrees C.) at normal atmospheric pressure. On removal and connexion to the femoral artery and vein of another dog these hearts beat strongly and without failing until removed after six hours. In mechanical function and histological appearance they were virtually identical with control hearts. The most useful criterion of viability of the quiescent myocardium during storage was the change in coronary resistance with time of perfusion.