Galen, the last and most influential of the great ancient medical practitioners, was born in Pergamum, Asia Minor. His father, the architect Nicon, is supposed to have prepared Galen for a career in medicine following the instructions given him in a dream by the god of medicine, Asclepius. Accordingly, Galen studied philosophy, mathematics, and logic in his youth and then began his medical training at age sixteen at the medical school of Pergamum attached to the local shrine of Asclepius. At age twenty, Galen embarked on extensive travels, broadening his medical knowledge with studies at Smyrna, Corinth, and Alexandria. At Alexandria, the preeminent research and teaching center of the time, Galen was able to study skeletons (although not actual bodies).

Returning to Pergamum at age twenty-eight, Galen became physician to the gladiators, which gave him great opportunities for observations about human anatomy and physiology. In 161 a.d., Galen...