Galen (born 129ce, Pergamum, Mysia,Anatolia [now Bergama, Turkey]—diedc. 216) was a Greek physician, writer, and philosopher who exercised a dominant influence onmedical theory and practice in Europe from theMiddle Ages until the mid-17th century. His authority in theByzantine world and the MuslimMiddle East was similarly long-lived.

Early life and training

The son of a wealthy architect, Galen was educated as a philosopher and man of letters. His hometown,Pergamum, was the site of a magnificent shrine of the healing god,Asclepius, that was visited by many distinguished figures of the Roman Empire for cures. When Galen was 16, he changed his career to that ofmedicine, which he studied at Pergamum, at Smyrna (modernİzmir, Turkey), and finally atAlexandria in Egypt, which was the greatest medical centre of the ancient world. After more than a decade of study, he returned in 157ce to Pergamum, where he served as chief physician to the troop ofgladiators maintained by the high priest of Asia.

In 162 the ambitious Galen moved toRome. There he quickly rose in the medical profession owing to his public demonstrations ofanatomy, his successes with rich and influential patients whom other doctors had pronounced incurable, his enormous learning, and therhetorical skills he displayed in public debates. Galen’s wealthy background, social contacts, and a friendship with his oldphilosophy teacherEudemus furtherenhanced his reputation as a philosopher and physician.

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Galen abruptly ended his sojourn in the capital in 166. Although he claimed that the intolerable envy of his colleagues prompted his return to Pergamum, an impendingplague in Rome was probably a more compelling reason. In 168–169, however, he was called by the joint emperorsLucius Verus andMarcus Aurelius to accompany them on a military campaign in northern Italy. After Verus’ sudden death in 169, Galen returned to Rome, where he served Marcus Aurelius and the later emperorsCommodus andSeptimius Severus as a physician. Galen’s final works were written after 207, which suggests that his Arab biographers were correct in their claim that he died at age 87, in 216/217.

Anatomical and medical studies

Galen regardedanatomy as the foundation of medical knowledge, and he frequently dissected and experimented on such lower animals as theBarbary ape (or African monkey), pigs, sheep, and goats. Galen’sadvocacy of dissection, both to improve surgical skills and for research purposes, formed part of his self-promotion, but there is no doubt that he was an accurate observer. He distinguished seven pairs ofcranial nerves, described the valves of the heart, and observed the structural differences betweenarteries andveins. One of his most important demonstrations was that the arteries carryblood, not air, as had been taught for 400 years. Notable also were hisvivisection experiments, such as tying off the recurrent laryngeal nerve to show that the brain controls the voice, performing a series of transections of thespinal cord to establish the functions of the spinal nerves, and tying off theureters to demonstratekidney andbladder functions. Galen was seriously hampered by the prevailing social taboo against dissecting human corpses, however, and theinferences he made about human anatomy based on his dissections of animals often led him into errors. His anatomy of theuterus, for example, is largely that of the dog’s.

Galen’sphysiology was a mixture of ideas taken from the philosophersPlato andAristotle as well as from the physicianHippocrates, whom Galen revered as the fount of all medical learning. Galen viewed the body as consisting of three connected systems: thebrain and nerves, which are responsible for sensation and thought; theheart and arteries, responsible for life-giving energy; and theliver and veins, responsible for nutrition and growth. According to Galen, blood is formed in the liver and is then carried by the veins to all parts of the body, where it is used up as nutriment or is transformed into flesh and other substances. A small amount of blood seeps through the lungs between the pulmonaryartery and pulmonary veins, thereby becoming mixed with air, and then seeps from the right to the left ventricle of the heart through minute pores in the wall separating the two chambers. A small proportion of this blood is further refined in a network of nerves at the base of the skull (in reality found only inungulates) and the brain to make psychicpneuma, a subtle material that is the vehicle of sensation. Galen’s physiological theory proved extremely seductive, and few possessed the skills needed to challenge it in succeeding centuries.

Building on earlier Hippocraticconceptions, Galen believed that human health requires anequilibrium between the four main bodily fluids, orhumours—blood, yellow bile, black bile, and phlegm. Each of the humours is built up from the four elements and displays two of the four primary qualities: hot, cold, wet, and dry. Unlike Hippocrates, Galen argued that humoral imbalances can be located in specific organs, as well as in the body as a whole. This modification of the theory allowed doctors to make more precisediagnoses and to prescribe specific remedies to restore the body’s balance. As a continuation of earlier Hippocratic conceptions, Galenic physiology became a powerful influence in medicine for the next 1,400 years.

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Galen was both a universal genius and aprolific writer: about 300 titles of works by him are known, of which about 150 survive wholly or in part. He was perpetually inquisitive, even in areas remote from medicine, such as linguistics, and he was an important logician who wrote major studies ofscientific method. Galen was also a skilled polemicist and anincorrigible publicist of his own genius, and these traits, combined with the enormous range of his writings, help to explain his subsequent fame and influence.

Influence

Galen’s writings achieved widecirculation during his lifetime, and copies of some of his works survive that were written within a generation of his death. By 500ce his works were being taught and summarized at Alexandria, and his theories were already crowding out those of others in the medical handbooks of the Byzantine world. Greek manuscripts began to be collected and translated byenlightened Arabs in the 9th century, and about 850Ḥunayn ibn Isḥāq, an Arab physician at the court of Baghdad, prepared anannotated list of 129 works of Galen that he and his followers had translated from Greek into Arabic or Syriac. Learned medicine in the Arabic world thus became heavily based upon the commentary, exposition, and understanding of Galen.

Galen’s influence was initially almost negligible in western Europe except for drug recipes, but from the late 11th century Ḥunayn’s translations, commentaries on them by Arab physicians, and sometimes the original Greek writings themselves were translated intoLatin. These Latin versions came to form the basis ofmedical education in the newmedieval universities. From about 1490, Italian humanists felt the need to prepare new Latin versions of Galen directly from Greek manuscripts in order to free his texts from medieval preconceptions and misunderstandings. Galen’s works were first printed in Greek in their entirety in 1525, and printings in Latin swiftly followed. These texts offered a different picture from that of the Middle Ages, one that emphasized Galen as a clinician, a diagnostician, and above all, an anatomist. His new followers stressed hismethodical techniques of identifying and curing illness, his independent judgment, and his cautiousempiricism. Galen’s injunctions to investigate the body were eagerly followed, since physicians wished to repeat the experiments and observations that he had recorded. Paradoxically, this soon led to the overthrow of Galen’s authority as an anatomist. In 1543 the Flemish physicianAndreas Vesalius showed that Galen’s anatomy of the body was more animal than human in some of its aspects, and it became clear that Galen and his medieval followers had made many errors. Galen’s notions of physiology, by contrast, lasted for a further century, until the English physicianWilliam Harvey correctly explained thecirculation of the blood. The renewal and then the overthrow of the Galenic tradition in theRenaissance had been an important element in the rise of modernscience, however.