Galen
With his new medical degree he returned to his home town to look for work and landed a job sewing up wounded gladiators, but, after four years of this, he headed for Rome and the bright lights of the eternal city. Now about thirty-one years old he quickly established a reputation for himself with a knife and frequently gave public demonstrations of his surgical skill. Even Emperors came to him for attention. Not that he had much competition. Roman medicine was at its lowest point in history and Galen made no friends for himself in the medical community by pointing out all the ignorance, corruption, sloppy workmanship, and outright charlatanism that was then passing as medical practice.
As they still do, the doctors of Rome closed ranks against someone smarter and more honest, and they drove him out of the city in 168 A.D. So he went home to think, read and write. But not for long. Within a year the Emperor Marcus Aurelius wanted to take him on an expedition against the Germans - an offer he politely turned down - but did accept the responsibility of training the young prince Commodus.
As quick with a pen as with a knife, Galen did a lot of writing, much of which is still in existence and can still be read. Although not recognized in his time, this body of work survived and was a steady source of inspiration as Greek medicine spread along with Greek culture through out Syria and the new counties of Islam. Caliphs Harun-al-Rashid and Abdul-Rahman III were avid followers.
Galenism spread from Mohammedan countries to the West in about the 11th century, where, during the Middle Ages it was given the rank of 'supreme authority' in the Schools of Salerno and the Universities of Naples and Montpellier.
Reading Galen, even today, one is struck by his 'common sense' approach, and his ability to cut through all the mumbo-jumbo and superstition of his times with icy logic and devastating dismissal of any other explanation. He more or less invented the diagnostic arts of palpation, pulse taking and the analysis of body fluids, especially urine. He brought together a synthesis of medicine based on Hippocraties, Plato, and Aristotle. You can still detect in Galen's writing his admiration of Aristotle's love of practical investigation, and what we would call scientific logic.
But it was anatomy where he made some of his greatest contributions. He constantly dissected bodies and, using animals, performed a series of experiments on the spinal cord to find out what it was doing. This was typical of his 'hands on, logical approach, which established his reputation for the next 1,700 years. He was good, and he knew it.