The Greek Physician Galen

The Greek physician Galen (c. 129-c. 200) was probably the most influential writer of all time on medical subjects. For nearly fifteen hundred years his works were the unimpeachable authority on medicine in many different lands. A bitter polemicist yet broad in view, Galen was both a careful, accurate observer and an uncritical believer, a dogmatic authoritarian and an original thinker.

Born in Pergamum to a father of wealth, position, and education, Galen received tender but intensive instruction from this parent, whom he called a man of “justice, modesty, and goodness.” At the age of fourteen, he was further trained in philosophy, mathematics, and natural science by philosophers who exposed him to the importance of anatomy, empiricism, and the doctrines of Hippocrates. Galen reported that his father guided him in the direction of medicine on advice from Asclepios in a dream.

At the time, the city of Pergamum (Gr. Pergamon) was a great cultural center in Roman Asia Minor where Galen’s medical studies could have continued with profit, but after his father’s death Galen traveled widely. Wherever he went, he found anatomy repeatedly emphasized; in Smyrna, Corinth, and Alexandria he came under the influence of several famous teachers of anatomy. He found pharmacologic information about plants and minerals also widely available in each new region. Furthermore, Galen was able to observe many kinds of illness, treatments, and medical philosophies, especially in Alexandria where physicians from all over the Roman world gathered to study, teach, and practice. There he also had opportunities for direct clinical experience by participating in the care of patients.

When he returned to Pergamum after years of voyaging, he had already gained some renown from a few writings on anatomy and physiology and from displays of clinical acumen. Possibly because of his reputation and his family’s standing, the chief of the local gladiatorial games appointed Galen physician to the gladiators. The need to keep these performers fit taught him the importance of hygienic regimens and preventive measures. Treating the severe injuries which were part of a gladiator’s existence enabled him to observe living human anatomy, particularly of bones, joints, and muscles, and to develop skill in treating fractures as well as brutal chest and abdominal wounds.

When he again left Pergamum, to go to Rome for the first time, he was an experienced, skillful physician. Although he gave up surgical activities in Rome (the social pressures to avoid operations may have been too strong) his former association with surgery formed the basis for his extensive, detailed, and brilliant discussions of surgical treatment.

He left Rome but had the good fortune of being recalled by the emperor himself, Marcus Aurelius. He was evidently the most prestigious and successful practitioner in Rome, and royal favor added unmistakable luster to his star. Yet, he was not content to repose at the pinnacle; he mocked and ridiculed opinions and methods contrary to his own—whether contemporary or earlier.

In the midst of traveling, studying, practicing, dissecting, experimenting, debating, demonstrating, and absorbing all the medical knowledge of the time, Galen wrote voluminously in Greek, his native tongue and the language of science. Anatomy, physiology, pharmacology, pathology, therapy, hygiene, dietetics, and philosophy were all subjects for his keen mind and ceaseless pen.

Inherent in the entire body of his work are teleological explanations for everything. A view that the purpose of everything was predetermined sometimes deluded him into distorting what he saw or into presuming a function for an organ because Nature must have given it a clear purpose. These preconceptions (which led him on a path of error from today’s vantage point) were the very characteristics in his teachings that were attractive to medieval Christian minds. Aristotle had said, “Nature does nothing without a purpose.” Galen insisted that he could perceive the purpose.

A second characteristic was his use of the humoral theory inherited from early Greek times. The four fundamental humors (phlegm, blood, yellow bile, and black bile) were responsible for health and illness, and Galen elaborated this conception in classifying all personalities into four types: phlegmatic, sanguine, choleric, and melancholic, terms still used to characterize dispositions.

Another attribute of Galen’s works is the concentration on anatomical details. Some of his studies were pioneering. For instance, he showed that veins are connected to the heart but that nerves arise from the central nervous system. He described the nerve to the voice box, the anatomy of the spinal cord, the ureters, the bones and their muscle attachments. Since direct dissection of the human body, which had earlier been the principle in Alexandria, was no longer practiced, Galen and other anatomists had to seek information in other ways: observing the chance exposure of organs in an injury; discovering fortuitously an abandoned corpse; dissecting animals and assuming their similarity to humans.

Because his knowledge was derived for the most part from animal (principally the Barbary ape) rather than human dissection, Galen made many mistakes, especially concerning the internal organs. For example, he incorrectly assumed that the rete mirabile, a plexus of blood vessels at the base of the brain of ungulate animals, was also present in humans. In addition, he sometimes postulated the presence of structures not there in order to fit his theories. Although normally there are no direct connections between the left and right heart chambers, Galen “found” openings in the dividing septum to fit his theoretical system in which blood had to pass from one side to the other.

In spite of Galen’s mistakes and misconceptions, one is astonished at the wealth of accurate detail in his writings. Scholars of later centuries swallowed his descriptions whole—correct and incorrect—not even subjecting them to the scrutiny called for in Galen’s principle of discovery by experiment. In actually testing animals he differentiated sensory and motor nerves, elucidated the effects of transection of the spinal cord, examined the physiological actions of the chest cavity, and proved that the heart could continue to beat without nerves. In stopping the squealing of a pig by cutting a particular nerve in the neck he demonstrated its function. He showed for the first time that arteries contained blood not air. Of course some of his contributions may have had antecedents which did not survive, but he has been referred to as the first experimentalist.

As a clinical observer, Galen was probably unequaled in his time. One has to say “probably,” because most information about contemporary medical practice is obtained from Galen’s own writings. Unlike Hippocrates, who reported good and bad results without bias or boast, Galen recounted mostly successes, often accompanied by expressions of self-satisfaction. But he did display great acumen. When the physicians of Marcus Aurelius concluded that the emperor’s symptoms were the beginning of a severe febrile illness, Galen diagnosed a milder ailment (an “upset stomach”), from which the patient quickly recovered. The treatment, which consisted of applying to the abdomen wool soaked in medicaments, probably had little to do with the course of the sickness—a common circumstance in the practice of medicine in all times. He paid considerable attention to the pulse and developed a complicated lexicon of descriptive terms. In addition, Galen understood the uncertainties and fears of the sick, as well as the interrelations of emotions and bodily symptoms. Although he used bloodletting often on a basis related to the theory of the four humors, he advised caution in the amount of blood to be removed. Despite his recourse to purgings and cuppings, much of his treatment was in the tradition of Hippocrates—helping nature by gentle methods such as diet, rest, and exercise. Prevention of illness through hygienic regimens was also of special concern to him.

A particular characteristic attached to the name of Galen was the large-scale use of medications. He gathered medicinal plants and prepared his own prescriptions—out of mistrust for the rhizotomists and drug sellers. The many ingredients which he put together in a single preparation have sometimes been referred to as “Galenicals,” but the term has no precise meaning. He carried polypharmacy to an extreme, mixing and blending agents whose properties he classified according to the humors and their qualities of hot, cold, dry, and moist. For example, an illness categorized as hot required a drug which was in the cold category—a classification system founded on speculative doctrines.

One extraordinary pharmaceutical combination which Galen elaborated even further was theriac. This ancient multi-ingredient preparation originated as an antidote against snakebite and eventually was used to combat all poisons and even pestilences. The legend is that Mithridates VI, King of Pontus (132-63 B.C.), experimented on slaves to find antidotes to poisons, of which he had a fanatical fear. His final combination was called mithridatium. In the first century A.D., after viper’s flesh was added to the formula by Nero’s physician Andromachus, the preparation was designated theriac, a word derived from the Greek for “wild beast.”

More and more items were added to theriac over the years. Galen increased its ingredients beyond seventy, and in the Middle Ages the number exceeded a hundred. This universal antidote, after a production process lasting months, was supposed to be aged for years like vintage wine before use, although it appears to have been more solid than liquid. So important was theriac in medical practice and thinking that its use persisted throughout the Middle Ages and Renaissance into recent centuries. The most important and effective criticism of it came in the eighteenth century from William Heberden, but even then it took decades before it was dropped in England. Indeed pharmacopoeias in France, Spain, and Germany were still listing theriac in the last quarter of the nineteenth century.

The educated and ignorant, the sensible and foolish, all seemed to rely on theriac (“treacle” comes from the same root) to prevent illness, to treat inflammations, to ward off the Black Death, to cure venomous bites of all kinds—including that of humans (the exceptional danger of which was recognized by Celsus, Pliny, Galen, and others). At least some of its popularity may have been due to the presence of opium among its many elements. Galen, like others of his day, thought so highly of theriac that he compounded it personally for the several emperors he served.

The many studies of Galen’s investigative, clinical, and pharmacologic activities have sometimes obscured his talents and incisive observations on surgical practice. “All the operations in surgery fall under two heads, separation and approximation. Approximation has to do with the reduction and dressing of fractures, reduction of dislocation of the joints, reductions of prolapsed intestines, uterus, or rectum, suture of the abdomen and restoration of tissue deficiencies, as in the nose, lips, and ears. Division is concerned with simple incisions, circumcisions, elevations of skin, scalping, excision of veins, amputation, cauterization, scraping, smoothing, excisions with the saw.”

He gave sensible suggestions on the use of instruments, of which the Romans had a wide variety, including knives of different sizes, scissors, forceps, splints, and retractors to hold operative incisions open. His advice on placing incisions and closing them, on the management of the open abdominal cavity, and on the draining of abscesses was astute. He boldly excised tumors and infected bone but was not reckless. Even allowing for his tendency to boast, he wrote descriptions which reflect a surgeon of skill and pragmatism.

In summing up the complexities of Galen’s writings, one is prompted to ask why his works were so durable, exercising a profound influence virtually unchallenged for fifteen hundred years. In the first place, the unsettled conditions of the Middle Ages produced a longing for certainty and authority, an attitude prevalent in the Muslim East as well as the Christian West. Galen’s dogmatic, didactic, even pedantic style met the desire for absolutes, and Galen left no questions unanswered. Furthermore, his repeated insertions of teleological reasoning made his ideas easy for the Christian Church to embrace. Also, his encyclopedic codifications which integrated all earlier knowledge made them ready sources of medical information. Indeed, an important reason for their influence lay in the fact that of his five hundred known works eighty-three medical treatises survived. Finally, the early compilers and commentators after him enshrined his name. Oribasius, Aetius, Alexander of Tralles, Paul of Aegina, themselves authorities in high repute, spoke of Galen as the fountainhead of all medical knowledge.

No one equaled him or challenged him effectively until the sixteenth century, when Vesalius, anatomist of the Renaissance, shook the foundations of authority.


  1. Sally Thai Reply
    July 23, 2009 at 1:42 am

    That was nothing that I wanted because the only thing that was there was his work and not were he lived or were he was born and were he lived so that was really poor.

  2. Diane Reply
    December 11, 2011 at 10:48 am

    I was looking for the earliest reference I could find on animal experimentation. Think I've found it. Thanks!

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