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Physician to Roman emperors and early author of works on anatomy and physiology.

Galen, the last and most influential of the great ancient medical practitioners, was born in Pergamum, Asia Minor. His father, the architect Nicon, is supposed to have prepared Galen for a career in medicine following the instructions given him in a dream by the god of medicine, Asclepius. Accordingly, Galen studied philosophy, mathematics, and logic in his youth and then began his medical training at age sixteen at the medical school of Pergamum attached to the local shrine of Asclepius. At age twenty, Galen embarked on extensive travels, broadening his medical knowledge with studies at Smyrna, Corinth, and Alexandria. At Alexandria, the preeminent research and teaching center of the time, Galen was able to study skeletons (although not actual bodies).

Returning to Pergamum at age twenty-eight, Galen became physician to the gladiators, which gave him great opportunities for observations about human anatomy and physiology. In 161 A.D., Galen moved to Rome and quickly established a successful practice after curing several eminent people, including the philosopher Eudemus. Galen also conducted public lectures and demonstrations, began writing some of his major works on anatomy and physiology, and frequently engaged in polemics with fellow physicians. In 174 A.D., Galen was summoned to treat Marcus Aurelius and became the emperor's personal physician.

Galen once again returned to Pergamum in 166 A.D., perhaps to escape the quarreling, perhaps to avoid an outbreak of plague in Rome. After a few years, Galen was summoned back to Rome by Marcus Aurelius. He became physician to two subsequent emperors, Commodus and Septimius Severvs, and seems to have stayed in Rome for the rest of his career, probably dying there in about 200 A.D.

Galen (Archive Photos, Inc. Reproduced with permission.)

Galen was an astonishingly prolific writer, producing hundreds of works, of which about 120 have survived. His most important contributions were in anatomy. Galen expertly dissected and accurately observed all kinds of animals, but sometimes mistakenly—because human dissection was forbidden—applied what he saw to the human body. Nevertheless, his descriptions of bones and muscle were notable; he was the first to observe that muscles work in contracting pairs. He described the heart valves and the structural differences between arteries and veins. He used experiments to demonstrate paralysis resulting from spinal cord severing, control of the larynx through the laryngeal nerve, and passage of urine from kidneys to bladder. An excellent clinician, Galen pioneered diagnostic use of the pulse rate and described cardiac arrhythmias. Galen also collected therapeutic plants in his extensive travels and explained their uses.

In his observations about the heart and blood vessels, however, Galen made critical errors that remained virtually unchallenged for 1,400 years. He correctly recognized that blood passes from the right to the left side of the heart, but decided this was accomplished through minute pores in the septum, rather than through the pulmonary circulation. Like Erasistratus, Galen believed that blood formed in the liver and was circulated from there throughout the body in the veins. He did show that arteries contain blood, but thought they also contained and distributed pneuma, a vital spirit. In a related idea, Galen believed that the brain generated and transmitted another vital spirit through the (hollow) nerves to the muscles, allowing movement and sensation.

After Galen, experimental physiology and anatomical research ceased for many centuries. Galen's teachings became the ultimate medical authority, approved by the newly ascendant Christian church because of Galen's belief in a divine purpose for all things, even the structure and functioning of the human body. The medical world moved on from Galenism only with the appearance of Andreas Vesalius 's work on anatomy in 1543 and William Harvey's work on blood circulation in 1628.

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