When in 1940 the air blitz on London started, we expected to see patients with "shock," a mysterious condition with as many definitions as there are writers on it, something that could be produced by natural processes such as burning, bleeding and bruising, as well as by such unnatural practices as injecting histamine, ground up muscle tissue and snake venom, and roentgen irradiation. The patients that we saw were suffering from the consequences of aerial bombardment. Most of them were only frightened—pale, rather cold, often described as "shocked." But the blood pressure was often rather above normal, and all they needed was rest and reassurance. Others we saw had severe lacerations; their pallor, coldness and sweating were accompanied by a low blood pressure and by a gradual hemodilution such as could be explained by the severe hemorrhage they had had. This surely was nothing mysterious but a reaction to blood