A 19th-century physiologist modelled the body on Adam Smith's factory
In the 1820s Henri Milne-Edwards borrowed economics to explain life. Organs, he wrote, are like workers in a factory, each labouring nonstop at its own task. That notion of a physiological division of labour let scientists study living things almost as machines, and it helped shape the science of how bodies work.
Physiology, from Greek words for nature and study, examines how organisms, organs, cells and molecules carry out their chemical and physical functions. Its core themes are biophysical and biochemical processes, communication between cells and homeostasis, the regulation that keeps the internal environment steady. It leans on anatomy, since structure and function shape each other, and on biochemistry, biophysics, genetics and evolutionary biology. Branches can be sorted by organism, from human to plant to microbe, or by level, from molecules to whole ecosystems.
Medical physiology began in classical Greece around the time of Hippocrates in the late 5th century BC, with comparable early traditions in China and India. Hippocrates linked four elements to four humours, including blood and black bile, ideas Galen later extended. The French physician Jean Fernel coined the word physiology in the 16th century. Galen, Ibn al-Nafis, William Harvey and others advanced understanding of circulation, and in the 1610s Santorio Santorio measured pulse with a device called the pulsilogium.
Discoveries accelerated. Luigi Galvani showed in 1791 that electricity drives frog nerves; Legallois located the breathing centre in the medulla oblongata in 1811; Bell and Magendie worked out the distinct roles of spinal nerve roots. The 1838 cell theory of Schleiden and Schwann declared all organisms built of cells. Claude Bernard's idea of a milieu intérieur was championed by Walter B. Cannon in 1929 as homeostasis. Joseph Lister's study of inflammation led him to antiseptic surgery, sharply cutting deaths, and in 1891 Ivan Pavlov studied dogs salivating in response to a bell.
Professional bodies followed: London's Physiological Society began as a dining club in 1876, the American society in 1887. The Nobel Prize in Physiology or Medicine honoured August Krogh in 1920 for explaining how capillaries regulate blood flow. In 1954 Andrew Huxley and Hugh Huxley described the sliding filaments of muscle. Much human physiology rests on animal experiments, and in the 20th century comparative physiology and ecophysiology widened attention to other species.
Source: Physiology
