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Monday, October 1, 2012

Claude Bernard

Claude Bernard did not get off to a promising start. Born in 1813 in Saint-Julien, France, this son of poor vineyard workers attended a simple village school and originally dreamed of becoming a writer. At 21, he'd already writtenseveral plays and set off to Paris, France, to show them around. A well-knownliterary critic, however, strongly suggested he try a different career and,after some thought, Bernard took the man's advice. He entered the Faculty ofMedicine, finished almost at the bottom of his class, but managed to obtain amedical degree in 1843. Four years later, the young man's fortune changed. He became an assistant to Fran├žois Magendie, one of France's most prominent--and controversial--physiologists.
Unlike most of his contemporaries, Magendie firmly believed that researcherscould study the body's reactions in the same way that they studied the reactions of inorganic material. Bernard agreed, learned a great deal about experimental physiology from his mentor, and then went on to design a number of experimental projects of his own. In 1855, when Magendie died, Bernard took his place as Professor of Experimental Medicine at the College de France. And, because Bernard tended to be more disciplined and organized than Magendie had been, he began attracting more and more scientific attention to the comparatively new discipline.
Many of Bernard's experiments centered around the digestive process. Inspiredby William Beaumont--who had spent several years peering into the stomach ofa patient with an accidentally caused opening (or fistula) in his side--Bernard decided to create artificial fistulas in live animals. Although his experiments infuriated antivivisectionists (including his own wife and daughters),Bernard made a number of discoveries. Among other things, he found that thestomach was not the sole digestive organ, as was then widely believed. Whilethe stomach began the digestive process, much more digestion took place throughout the small intestine, Bernard reported. He also demonstrated the importance of the pancreas, whose secretions were clearly necessary to break down fat molecules, and later went on to identify the various nerves that control gastric secretion.
In 1857, Bernard isolated a starch-like substance in the liver of animals, asubstance he named glycogen. Glycogen, Bernard showed, was a large molecule built up out of numerous tiny molecules of sugar taken from the blood stream.Its primary role was to serve as the body's reserve supply of carbohydrates.When the level of sugar in the blood became low, the stored glycogen broke down again into its components and released more simple sugars back into the blood stream. This continuing process, Bernard pointed out, indicated that theanimal's body did not (as was then believed) merely break large molecules down into smaller ones, the way plants did. The animal's body could also take simple molecules and build them up into larger, more complex ones.
In 1851, Bernard devoted some of his attention to the portion of the nervoussystem which governs blood circulation (called the vasomotor system) and discovered that certain specific nerves governed the dilation and constriction ofblood vessels. But why did the blood vessels need to keep widening and narrowing? Bernard theorized that, by doing so, the body was better able to control its distribution of heat. On hot days, he suggested, people looked flushedbecause the skin's blood vessels widened in order to release more excess heatfrom the body. On cold days, people looked pale because the skin's blood vessels narrowed in order to prevent body heat from escaping. While studying thevasomotor system, Bernard also discovered that the blood's red corpuscles carry oxygen from the lungs to body tissues.
Each of Bernard's findings convinced him that the body is constantly strivingto maintain a stable, well-balanced internal environment, one that is not overly affected by outside influences. He therefore concluded that the body must be under the control of one strong and central regulating force. Bernard'stheory, although widely accepted today, appeared quite radical in his own time, when most scientists believed that the body's various organs acted quite independently of each other.
Bernard's work brought him worldwide recognition. In 1865, he published the highly influential textbook, An Introduction to the Study of Experimental Medicine, which won him election to the prestigious French Academy in 1869. He even served in the French senate under Napoleon III (1808-1873) and, when he died in 1878, Bernard became the first scientist to be given a nationalfuneral, an honor usually reserved for political and military leaders.