In my novel, “The King’s Anatomist,” the Greek physician Galen serves as a foil for the triumph of Andreas Vesalius; it was Galen’s anatomical findings that Vesalius overturned thirteen centuries after Galen’s death. But don’t be left with the impression that Galen was a clueless scribbler undeserving of his fame; in his day he was a renowned physician, a sophisticated medical investigator, and a learned philosopher. In his prolific writings, much of which has survived to the modern era, we find a worldly, educated guy with keen powers of observation – and an ego to match.

Galen was born into a prominent family in Pergamon, in present-day Turkey, one of the great cities of the Roman world and a center of Greek culture. Galen’s early medical education was from a series of mentors, there being no medical schools; when Galen’s architect father died, making him independently wealthy, he took to the road. After a few years learning his craft in legendary Alexandria, he returned to his home city of Pergamon, where his reputation grew as a gladiatorial surgeon. His career in Pergamon seemed secure, but the ambitious physician set out for Rome where he secured his legacy as the supreme authority in medicine.

The medical scene in Rome, while vibrant, was intensely competitive in ways hard to fathom today. Physicians would compete publicly through debates and surgical demonstrations before crowds that would gather to watch, and even wager, on the outcome. Galen turned out to be a master self-promoter and braggart. He attracted a wealthy clientele, including emperors. Of course he did not endear himself to his physician colleagues, but his reputation and real skills overwhelmed them.

He wrote extensively on many aspects of medicine, and certainly anatomy, where he recorded his dissection methods and his careful observations. But there was a hitch: human dissection was forbidden in Rome; Galen’s only chance to see inside a human body was a fast look within a gladiator’s wound or finding a skeleton picked clean by birds or dogs. His anatomy, therefore, relied mainly on animals such as Barbary apes, pigs, and goats.

Many findings in animals translated fairly well to humans; many did not. But such was his standing that his anatomical were accepted uncritically until the 16th century, when the brash genius Andreas Vesalius exposed Galen’s shortcomings. Even as he shook the earth under Galen’s feet, Vesalius did so with great respect for the Greek master on whose shoulders he stood.