WHEN ALFRED Blalock joined the faculty at the Vanderbilt University School of Medicine, Nashville, Tenn, in 1925, he rapidly became interested in the pathogenesis of shock. In that era the status of shock was in total disarray. He was later to write in his well-known monograph entitled Principles of Surgical Care: Shock and Other Problems that there had been many theories advanced to explain shock, including suprarenal hyperactivity and hypoactivity, acidosis, acapnia, basal motor exhaustion, vasoconstriction, loss of blood and fluids, nociceptive nervous stimuli, and toxemia. Since there was little agreement, Blalock began a series of thoughtful and well-planned experiments designed to determine the causes of shock. He conducted laboratory experiments to demonstrate the experimental production of shock and to document the hemodynamic and metabolic changes that occurred. The early experiments were described in an article entitled "Shock Following Hemorrhage" in 1927, which was the first of a series published