Claude Bernard (1813-1878), a French physiologist noted for his fundamental contributions to our understanding of human energetics. Bernard showed that the pancreas produces substances that break down molecules of fat. He also discovered that nerves control the blood supply to the organs such that, in cold weather, the nerves restrict the supply of blood to conserve heat, while in hot weather they allow the blood vessels to expand and encourage heat loss through the skin. Bernard found that the human body has control mechanisms that produce hormones to maintain body temperature, nutrient levels, and waste products. This process would later be known as homeostasis.

Source

• Cleveland, Cutler (Lead Author); Tom Lawrence (Topic Editor). 2006. "Bernard, Claude." In: Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). [First published in the Encyclopedia of Earth June 16, 2006; Last revised December 5, 2006; Retrieved August 4, 2009]. <http://www.eoearth.org/article/Bernard,_Claude>