Thomas and Blalock did groundbreaking research into the causes of hemorrhagic[14] and traumatic shock.[15] This work later evolved into research on crush syndrome[16] and saved the lives of thousands of soldiers on the battlefields of World War II.[16] In hundreds of experiments, the two disproved traditional theories which held that shock was caused by toxins in the blood.[17] Blalock, a highly original scientific thinker and something of an iconoclast, had theorized that shock resulted from fluid loss outside the vascular bed and that the condition could be effectively treated by fluid replacement.[17] Assisted by Thomas, he was able to provide incontrovertible proof of this theory, and in so doing, he gained wide recognition in the medical community by the mid-1930s. At this same time, Blalock and Thomas began experimental work in vascular and cardiac surgery,[14] defying medical taboos against operating upon the heart. It was this work that laid the foundation for the revolutionary lifesaving surgery they were to perform at Johns Hopkins a decade later.