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ations through which blood could mix between the two sides of the heart. The experiment led to the truth, the reasoning without fact led to error. The fallacies engendered by the fertile imagination of a learned philosopher were only dispelled by the direct observations of those who followed, and especially by the untiring labours of Harvey. The opponents of research by experiment on living animals would have left us in the darkness and ignorance of Galenic times, for the dawn of light and scientific truth were due to experiment and not to mere reasoning.
Vesalius, in 1512, rebelled against the assertions of the older fathers in physic, and he set at nought the mere authority of Galen. He first shewed, that the blood passed through the vessels of the lungs from the right to the left side of the heart, and that the blood was modified in its transit. Servetus, about the same time published the same truth of a pulmonary circulation, but he still held, that the venous blood derived from the liver was for nourishment, and that the blood in
