Cannon, Walter B. (Bradford)(1871–1945) physiologist; born in Prairie du Chien, Wis. As a medical student at Harvard (1896–1900), he devised the use of radiopaque chemicals for X-ray diagnosis of the gastrointestinal system (1897). He joined Harvard's faculty (1900–42), and investigated the physiology of digestion until 1911. Inquiries into the physiological effect of emotions (1911–17), including studies of surgical trauma during World War I, led him to postulate that the adrenals' action on the sympathetic nervous system is responsible for an animal's "fight or flight" response. He coined the term "homeostasis" (1926) to describe an organism's tendency to maintain physiological stability; he expounded this concept in his book, The Wisdom of the Body (1932). In the 1930s, he began his pioneering work on chemical neurotransmission; his "sympathins 1 and 2" are now known as epinephrine and norepinephrine. A visiting professor at numerous institutions and a member of many international societies, he was an antitotalitarian activist who believed that a scientist should also be a world citizen.