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Galen (129 — 201 AD), also known as Aelius Galenus, Claudius Galenus, and Galen of Pergamon, is one of the most influential physicians in the history of medicine. He was born in Greece, studied medicine in Egypt and became the most celebrated physician of his time. Galen gained fame as a surgeon to the gladiators of Pergamos and eventually was summoned to Rome to be physician to the Emperor. He spent the rest of his life at court writing medical works until his death in 201 AD. His name in Greek is Γαληνός or Galēnos which comes from the adjective "γαληνός" or "calm". Galen underlined the importance of philosophy in medicine, and wrote about it in That the Best Physician is also a Philosopher.
Galen performed human dissections, and stressed their importance to medical students. He recommended they practice dissection especially of the muscles, spinal cord, heart and urinary system; and, he proved that the arteries are full of blood. However, he believed blood originated in the liver, and sloshed back and forth through the body, passing through the heart, where it combined with air through pores in the septum. Galen introduced a system of spirits, consisting of the natural spirit or "pneuma" (air he thought was in the veins), vital spirit (blood mixed with air he felt was in the arteries), and animal spirit (found in the nervous system). In On the Natural Facilities, Galen describes his experimentation on a living dog to investigate the bladder and flow of urine. It was Galen who first introduced the notion of experimentation to medicine.
Galen believed everything in nature had a purpose, and that nature used a single object for more than one purpose. He believed "the best doctor is also a philosopher" and advocated for the study of philosophy, logic, physics and ethics. Galen's theories dominated Western medical thinking for more than more than (15) centuries after his death, and he remained an authority in medicine until Andreas Vesalius in the sixteenth century. Many of Galen's views on human anatomy, however, were incorrect as he had formed them from dissecting pigs, Barbary apes and dogs. Galen thought that humans had a five-lobed liver (which dogs do) and that the heart had two chambers (it has four).
The field of anatomy, one of the most ancient sciences, began in Ancient Egypt. From the Early Dynastic Period (3100 BC) until Galen, Egypt was the centre of knowledge about anatomy. Knowledge of neuroanatomy became so important that rituals were performed by embalmers during mummification. It was also later a science to be studied by wise men at the temple of Memphis. As religious conflict took root, study of the human body became forbidden. Myths began to replace scientific research, and exploration of the human body stalled until Alexander the Great founded the city of Alexandria. This period witnessed a revolution in the study of anatomy and functional anatomy. Herophilus of Chalcedon, Erasistratus of Chios, Rufus of Ephesus, and Galen were prominent physicians who studied at Alexandria and contributed to knowledge about human anatomy. After the Library of Alexandria was burned and laws were passed prohibiting human dissection based on religious and cultural factors, knowledge of human anatomy plateaued for 1500 years.
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