Galen: Ancient Medical Professor

Galen was one of the most famous anatomists and physiologists of the ancient world, and he is often called the founder of experimental physiology. He was also an outstanding physician. Galen was the first to diagnose subjects by the pulse, associating the pulse rate with health, and he discovered that arteries contained blood and not air, as had been previously thought.

Galen was the first person to distinguish between sensory nerves, which carry impulses to the brain, and motor nerves, which transmit impulses from the brain to the muscles. Galen also identified many muscles, particularly those that function in breathing.

After the dissection of human corpses was outlawed in the Roman Empire in the second century AD, Galen's knowledge of anatomy and physiology was based primarily on dissections of dogs, apes, pigs, and other animals. As a result, many of his conclusions with regard to human anatomy were wrong. Galen's findings were also influenced by his religious views, and he sometimes interpreted his observations to make them agree with his own fixed opinions.

His descriptions of parts of the skeleton and the muscles were quite accurate and he gave authoritative accounts of diseases such as malaria and bronchitis. However, his theory that disease was caused by secretion of 'humours' inside the body (four fluids that influenced character) which interacted with factors like the weather was to delay medical progress for some time.

Galen was a monotheist, though not a Christian, and he opposed the empirical school of medicine. This enhanced the appeal of his works to the Arabs who were instrumental in taking them to Europe, thereby introducing the first knowledge of Greek medicine to the Western world.

He adopted the 'teleological' doctrine which stated that every organ had its own specific function that could be determined. In line with this idea he postulated that blood contained a 'life spirit' (pneuma) which gave it its red colour. He also believed that the heart contained a porous dividing wall through which the blood could pass. Such ideas held sway for centuries and therefore were significant even if incorrect.

Despite such errors, most of Galen's ideas were based on observation and reasoning and they dominated the study of anatomy and physiology for more than 1,300 years. It was not until the 16th century, when his theories were challenged by the Flemish anatomist Andreas Vesalius, that scientists again began to base their findings on their own observations, not on earlier, mistaken beliefs.

It is believed that there were approximately 500 treatises written by Galen, of which just over 100 survive. He died in Pergamum in about 200 A.D.