A research trail over half a century.

The author describes his major research activities from the time of his PhD thesis work (1937-1940) on properties of erythrocyte membranes to the present. His involvement in research on circulatory shock during World War II led to a continuing interest in the physiology and pharmacology of smooth muscle and cardiac muscle. From 1956 to 1978, his main areas of research were photorelaxation of blood vessels, factors influencing contractility of cardiac muscle, peripheral adrenergic mechanisms, and receptor theory. The major findings of his and his collaborators in these areas are described. He then recounts how an accidental finding in an experiment in 1978 on preparations of rabbit aorta eventually led to the discovery of endothelium dependent relaxation and the endothelium-derived relaxing factor (EDRF); and how additional findings led him to propose in 1986 that EDRF is nitric oxide.