Walter B. Cannon (1871-1945, APS 1908) was a physiologist and medical educator. He was widely noted for his trailblazing research in gastrointestinal physiology. He was the first to use the technology of X-rays to study gastrointestinal processes. He was a pioneer in studying the influence of emotional states on bodily functions and in "the understanding of nerve transmission and hormonal regulation of the body" (Lederer, p.340) and developed the concept of homeostasis. As a Harvard medical professor, he was the first to apply the case method to teaching systematic medicine. In his position as chairman of the American Medical Association's Defense Committee in Support of Medical Research, he led the fight against the Antivivisectionist movement. His major works include The Mechanical Factors of Digestion (1911), Traumatic Shock (1923), the Wisdom of the Body (1932) and Autonomic Neuro-Effector Systems (1937).

Canon was born on October 19, 1871 at Prairie du Chien, Wisconsin. He was the only son of Colbert Hanchett Canon, a railroad worker and Sarah Wilma Denio, a school teacher. He attended primary schools in Milwaukee, Wisconsin and St. Paul, Minnesota. At fourteen, when his father was disappointed at the boy's lack of diligence in school, he sent him to work in a railroad office for two years. After he returned to high school, he finished the four-year curriculum in three years, graduating as valedictorian of his class. He took an extra postgraduate year to prepare for college examinations. His English literature teacher Ms. M.J. Newson convinced Cannon to apply to Harvard College and helped to obtain financial aid for him. As a Harvard undergraduate he studied biology and zoology under Charles B. Davenport (1866-1944, APS 1907). He graduated summa cum laude in 1896 and received an M.A. degree from Harvard in 1897. Although he would have preferred to study medicine at Johns Hopkins, his letter to Hopkins's Dean William H. Welch, requesting financial aid went unanswered. Consequently, Cannon remained at Harvard for his medical training, entering the Medical School in the fall of 1896.

During his first year of medical school at Harvard, he followed the suggestion of physiology professor Henry P. Bowditch (1840-1911, APS 1904) that he join a second-year student Albert Moser in an investigation of the phenomena of swallowing and the visceral movements in animals using the recently developed technology of x-rays. Using an x-ray apparatus provided by Dr. Ernest Amory Codman of Massachsetts General Hospital, the two students examined the esophagus of a dog during the process of swallowing or deglutition. An initial demonstration, using pearl buttons revealed nothing. However, recalling the observation of Wilhelm Röntgen, who discovered x-rays a year earlier, that salts of heavy metals obstructed the passage of x-rays, they tried the same experiment, using gelatin capsules filled with bismuth subnitrate in a frog and a goose. This time the experiment succeeded, since bismuth subnitrate is opaque to x-rays. At a Boston meeting of the American Physiological Society in late December they repeated the experiment in a goose, using Röntgen's rays. This was the first public demonstration of the movement of the alimentary canal by use of x-ray technology. Cannon's continued investigation into the digestive system would later result in his first monograph, Mechanical Factors of Digestion (1911). In it, he noted with great interest the correlation between emotional disturbances and the digestive process in animal subjects.

While in medical school Cannon also showed himself an educational innovator. Envious of the educational experiences of his roommate, a Harvard law student, who reported that he and his classmates discussed actual legal cases and their implications for practice in class, Cannon suggested a similar pedagogy in a 1900 paper published in the Boston Medical and Surgical Journal. The article, entitled "Case Method of Teaching Systematic Medicine," suggested employing real case histories and hospital data in active classroom discussions instead of the "dreary and benumbing process" of passively listening to lectures and reading texts. The young instructor's new teaching technique was quickly adopted by several departments at the Harvard Medical School and even incorporated by a number of medical texts.

In his last year of medical school Cannon was already working as a zoology instructor at Harvard College, where he taught comparative vertebrate anatomy. After he graduated from medical school in 1900, professor William Townsend Porter encouraged Harvard President Charles W. Eliot (1834-1926, APS 1871) to make Cannon an instructor of physiology. The following year on June 25, 1901 he married a longtime friend Cornelia James, who would later become a best-selling author. In 1902 Cannon advanced to the rank of assistant professor, again with Porter's backing. In 1906, when Cornell Medical School tried to recruit him, President Eliot decided to have Cannon, whose teaching ability made him popular with students, succeed the retiring professor Bowditch as George Higginson Professor of Physiology and department chairman (rather than Porter). Porter was made Professor of comparative physiology. Altogether Cannon would spend four decades on the physiology faculty of the Harvard Medical School, retiring in 1942. His tenure at Harvard was interrupted only by service with the Army Medical Corps during the First World War, when he was stationed in France and England in 1917-1918.

Cannon's growing engagement in physiological research had political, as well as professional implications for him. Following strong antivivisectionist assaults on the new Rockefeller Institute for Medical Research and legislative attempts in New York and elsewhere to curb the use of animals in medical experiments, Cannon joined the struggle against antivivisection. In 1908, in response to these antivivisectionist initiatives, the American Medical Association created a special Defense Committee in Support of Medical Research. Because of his prominence as an experimental physiologist, the thirty-seven year old Cannon was asked to head the committee, placing him in the forefront of the struggle. In this position he would be the A.M.A.'s chief strategist for the next eighteen years. He firmly defended the rights of medical researchers, declaring that "the imagined horrors of medical research do not exist . . . . [Furthermore] that their critics are ignorant—ignorant of the conditions of medical research and ignorant of the complex relations of the medical sciences to medical and surgical practice and . . . that these critics in their ignorance are endeavoring to stop that experimental study of physiology and pathology." Cannon and his retired colleague Philadelphia surgeon William W. Keen (1837-1932, APS 1884) monitored antivivisectionist activity, mobilized the medical profession, lobbied politicians, testified in public hearings, and wrote tirelessly in defense of animal experimentation.

During the first World War, Cannon worked on the treatment of trauma and wound shock. Even before the entry of the United States into the war, in the fall of 1916 the National Research Council recruited him for its Committee on Traumatic Shock. Later he joined the Harvard University Hospital Unit, and on his way to France in May 1917 stopped in London to join the Medical Research Committee, a group of physicians and surgeons from the British Expeditionary Forces, treating shock cases at the Casualty Clearing State at Béthune. The following summer, after the Medical Research Committee formed a Shock Committee, Cannon was named a member. Later, he was appointed director of the surgical research laboratory of the American Expeditionary Forces's Central Medical Department. Although Cannon and his colleagues initially focused their efforts on treating the acidosis that accompanies shock, they soon realized that acidosis was simply a secondary occurrence, the result of inadequate tissue perfusion. Cannon later summarized the conclusions of his wartime experiences in his work on Traumatic Shock (1923).

In the years preceding and immediately following World War I, he devoted much energy to research into the sympathetic nervous system and functions of the suprarenal medulla, such as the secretion of the adrenaline during stress, the "fight or flight" mechanism. The studies he started with M.A. McIver and S.W. Bliss on the sympathetic and adrenal mechanism for mobilizing sugar in hypoglycemia caused by insulin (1923) might have provided the original context for his notion of homeostatis. He coined the term in a 1926 paper titled "Physiological Regulation of Normal States." Canon published an extensive analysis of the problem of homeostatis in 1929. The article, which appeared in Physiological Reviews, discussed the homeostatic regulation of water, sodium chloride balance, glucose, protein, fat and calcium, but also examined the part played by the autonomic nervous system in homeostatis and the homeostatic functions of hunger, thirst, and uniform temperature. Cannon popularized the concept of homeostatis in a 1932 book entitled the Wisdom of the Body.

Beginning in the 1930's Cannon and his colleagues Z.M. Bacq and Arturo Rosenbluth focused their research chemical transmission of nerve impulses. An early synthesis of their work was entitled Autonomic Neuro-Effective Systems (1937), that hypothesized the existence of two "sympathins," one excitatory and one inhibitory. Although it drew critical reviews, the work bore some resemblance to the research e carried out later by Nobel laureates Otto Loewi (1936) and Ulf von Euler (1970).

In addition to his strong commitments to medical education and scientific research, Cannon cherished the deep conviction that as a citizen, a scientist is obligated to defend freedom, which is indispensable for productive scholarship. His beliefs in the family of humankind and the universality of science led to his involvement with the American-Soviet Medical Society and the American Bureau for Medical Aid to China. He was also increasingly concerned about the growing threat that fascist and authoritarian governments posed to the scientific community. After meeting Spanish physiologist Juan Negrin (later premier of the Spanish Republic), Cannon began to follow political developments in Spain very closely. In 1937 he became chair of the Medical Bureau to Aid Spanish Democracy. He also developed a friendship with Russian physiologist Ivan Pavlov (1848-1936, APS 1932), who had similar research interests, but he also had a general (albeit not uncritical) interest in the Soviet Union and it support for science. In all of these international endeavors Cannon was motivated by two concerns: the advancement of science and humanitarian support for the weak and oppressed.

Cannon was active in a number of scholarly and professional organizations, including the American Medical Association, the American Association for the Advancement of Science, and the American Physiological Society. He was elected to the American Philosophical Society in 1908. In addition to his research articles and monographs, he was author of a several popular books that found a wide audience. These works included Bodily Changes in Pain, Hunger, Fear and Rage (1915) and The Wisdom of the Body (1932), and his autobiography, The Way of an Investigator: A Scientist's Experiences in Medical Research (1945).

Cannon retired from the Harvard Medical School in 1942. Although he was a visiting professor at the New York University Medical School in 1944 and did research with Arturo Rosenbluth in Mexico City in 1945, Cannon's health was failing. The ill health he had endured for decades and the cancerous condition he developed in later life are probably the result of his experiments with x-rays during the early days of his research. Cannon died in Franklin, New Hampshire on October 1, 1945. He was survived by his wife Cornelia, his son Bradford and daughter Marian.

Throughout his adult life, Cannon steadfastly maintained that science held the key to the betterment of the human condition, and that science was synonymous with "truth" and "knowledge". To Cannon, the sanctity of science should not be curtailed or tarnished by arbitrary limitations or falsehood. Scientists should be afforded maximum freedom in their research. In fact, it is the scientist's duty to maximize his freedom by educating the public and promoting a borderless ethic in scientific discourse. These convictions led Cannon to do battle with the antivivisection movement, to assist Jewish doctors from Nazi-controlled Europe, to bring medical relief to the Spanish Republic and to support the formation of scientific ties with the Soviet Union. Consequently, Cannon viewed his opposition to antivivsection as a fundamentally "moral" proposition. Convinced that animal experimentation was essential to medical progress, he considered antivivisectionists' efforts to throw roadblocks in the way of scientific progress as "immoral," and he fulminated over what he perceived as their use of distortions, fabrications, and mistatements, or their sheer, unadulterated ignorance.