Galen of Pergamon (129 CE- c. 200 CE) was a Greek physician. During the 2nd century C.E., he was a physician to gladiators in the Coliseum in Rome. However, he was also one of the early pioneers in animal dissection which led to a basic understanding of human anatomy that wasn't updated until the Renaissance and also did research into physiology, pharmacology, pathology and neurology.
Among his breakthroughs that are still accepted today were the distinction between arteries and veins, the role of the larynx in the voice and the difference between motor and sensory nerves. He was a pioneering surgeon who developed effective treatments for cataracts which laid the basis for the operation performed today. He also laid down the original theory that specialized body parts, organs, performed specialized functions, and also was the first to suggest that there was no distinction between the mind and the body.