A famous case is the early study of stomach physiology by the American military surgeon William Beaumont.(8) In the 1820s, Alexis St. Martin, a young Canadian trapper, received a gunshot wound in the abdomen and thus came under Beaumont's care. Although the wounded man eventually recovered, he was left with a gastric fistula and through this artificial opening Beaumont was able to observe the walls of his patient's stomach and obtain pure gastric juice. For two years the patient and surgeon became partners in a valuable piece of physiological research with Beaumont making almost daily observations and experiments. Chemical analysis showed that the gastric juice contained free hydrochloric acid and was only secreted when food entered the stomach. Beaumont demonstrated the action of gastric juice both within the body and in the test tube, and carefully noted the changes in stomach physiology as a result of fear and anger, feverish symptoms and excessive alcohol intake. Ultimately, Dr Beaumont worked out over 50 positive conclusions and according to Sir Arthur Hurst,(9) Senior Physician to Guy's Hospital in London, his research "…laid the foundation of our knowledge of gastric digestion."
Another example is the study of brain function. Although many researchers rely on animals with deliberately induced brain damage, neurologists Antonio and Hanna Damasio at the University of Iowa College of Medicine observe patients with brain injuries and relate changes in their behavior to the damaged part of the brain.10 The Damasios have studied brain lesions in 1500 patients, often locating injuries in living subjects with the use of imaging techniques. The impetus to such studies, and the realization that different activities are located in different parts of the brain, stemmed from the clinical observations of Paul Broca during the 1860s when he identified the speech center.(4,11) Broca found that patients with left frontal lesions of the brain also suffered speech impairments. More recently, it was clinical investigation of patients with amnesia that pinpointed the hippocampus as the crucial brain structure involved in memory.(10)
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