An Anatomical Disquisition on the Motion of the Heart & Blood in Animals

The discovery made by Harvey was this: That the blood passed from the heart into the arteries, thence to the veins, by which it was brought back to the heart again; that the blood moved more or less in a circle, coming back eventually to the point from which it started.

In a phrase, there was a Circulation of the Blood. Moreover, this circulation was of a double nature—one circle being from the right side of the heart to the left through the lungs, hence called the Pulmonary or Lesser Circulation; the other from the left side of the heart to the right, through the rest of the body, known as the Systemic or Greater Circulation. Further, that it was the peculiar office of the heart to maintain this circulation by its continuous rhythmic beating as long as life lasts.