THE HISTORY of the pulmonary circulation provides a measure of man's thinking about himself and his place in the universe. For centuries before De Motu Cordis in 1628,1 the blood vessels of the lungs were incorporated into an elaborate scheme that explained the origin and distribution of spirits that animated and sustained the human being. Only after the circulation was described could the speculative natural philosophy of ancient times give way to the observations and interpretations that we now take for granted.
THE GROWTH OF IDEAS
The thinking of the ancients was dominated by the views of Aristotle as updated by Galen in the second century AD.2 According to Galen, the body was governed by a hierarchy of three principal organs: the liver, the heart, and the brain. According to this schema, the liver was the source of "natural spirits" that the veins distributed throughout the body. These
Fishman AP. The Pulmonary Circulation. JAMA. 1978;239(13):1299–1301. doi:10.1001/jama.1978.03280400039017