Overview

Physiology—the study of how the body works—had its start nearly 2,000 years ago in the studies of Galen, a Greek physician. Galen (also known as Claudius Galenus) studied the writings of the ancient scholars and learned from some of the major scientists of the day, but also brought along his own ideas together with an enthusiastic search for new knowledge. He gained much of his understanding of body organs and systems through the many dissections he performed, particularly during the earlier part of his career. Over the years his work led him to see the benefit of the pulse as a diagnostic tool, to examine the blood and determine that it flowed through the veins and arteries, and to develop hypotheses about the roles of the heart, liver and brain. Galen is...