A Johns Hopkins urology intern in 1923 when Traumatic Shock4 was published, Alfred Blalock failed to secure a permanent position in the surgical residency there and left for Nashville, Tennessee, to join the Vanderbilt University training program. There, Blalock set about organizing laboratory studies with his good friend Tinsley Harrison (whose textbook of medicine remains popular today).6 They became interested in derangements of cardiac output. Using the Fick principle and the Van Slyke device that determines the oxygen content of blood, they reported on changes in cardiac output in anemia, hemorrhage, anoxia, anesthesia, and thyroid disease. By 1927, Blalock had developed great facility in measurement of oxygen content and thus blood flow. In his initial report on shock's effect on cardiac output, Blalock cited Cannon, noting that the latter “did not mention diminished minute cardiac output”7(p792) despite observations of his contemporaries.