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A brief history of physiology

Hippocrates is considered by many to be the "father of medicine. "The study of physiology traces its roots back to ancient India and Egypt. As a medical discipline, it goes back at least as far as the time of Hippocrates, the famous "father of medicine" - around 420 BC. Hippocrates coined the theory of the four humors, stating that the body contains four distinct bodily fluids: black bile, phlegm, blood, and yellow bile. Any disturbance in their ratios, as the theory goes, causes ill health. Claudius Galenus (c.130-200 AD), also known as Galen, modified Hippocrates' theory and was the first to use experimentation to derive information about the systems of the body. He is widely referred to as the founder of experimental physiology. It was Jean Fernel (1497-1558), a French physician, who first introduced the term "physiology," from Ancient Greek, meaning "study of nature, origins." Fernel was also the first to describe the spinal canal (the space in the spine where the spinal cord passes through). He has a crater on the moon named after him for his efforts - it is called Fernelius. Another leap forward in physiological knowledge came with the publication of William Harvey's book titled An Anatomical Dissertation Upon the Movement of the Heart and Blood in Animals in 1628. Harvey was the first to describe systemic circulation and blood's journey through the brain and body, propelled by the heart. Perhaps surprisingly, much medical practice was based on the four humors until well into the 1800s (bloodletting, for instance). In 1838, a shift in thought occurred when the cell theory of Matthias Schleiden and Theodor Schwann arrived on the scene, theorizing that the body was made up of minute individual cells. From here on in, the field of physiology opened up and advancement was swift:

Joseph Lister, 1858 - initially studied coagulation and inflammation following injury, he went on to discover and utilize lifesaving antiseptics
Ivan Pavlov, 1891 - conditioned physiological responses in dogs
August Krogh, 1910 - won the Nobel Prize for discovering how blood flow is regulated in capillaries
Andrew Huxley and Alan Hodgkin, 1952 - discovered the ionic mechanism by which nerve impulses are transmitted
Andrew Huxley and Hugh Huxley, 1954 - made advances in the study of muscles with the discovery of sliding filaments in skeletal muscle
Hippocrates is considered by many to be the "father of medicine."