the exploits of conquering heroes, and yet pass almost unnoticed the achievements of men of science. Few persons are at all acquainted with the history of when and how, through a series of successive revelations, this truly wonderful function came to be thoroughly understood. It is a long and delightful story if followed through all its details, which I shall, however, endeavor to cut short in relating it to persons outside of the medical profession. We are obliged to glance back through several centuries and make the acquaintance of nearly a score of anatomical celebrities, who have each contributed some observation or discovery leading to the final comprehension and complete interpretation of God's beautiful but simple method of circulating the vital fluid and keeping it ever replenished and pure.
The pathway to the climax of this discovery was not only long but rugged, hedged in by deeply-rooted errors, and obscured by rank prejudices ancient and wide-spread. The errors must be destroyed, the clouds dispelled, parts carefully observed; the explorers must work slowly and cautiously, and what is discovered must be explained. Thus it came to pass that anatomists discovered one thing after another, and little by little the light of truth dawned upon their minds, wherewith they saw and gave the world sensible ideas of the uses of parts, when eventually "the immortal Harvey," the crowning light, the clear-headed philosopher, the Newton of physiology, drew the simple chart of the double circulation. This event took place two hundred and fifty-seven years ago, for it was in 1619 that Harvey completed the discovery. He made no haste to tell the world what he had done, except what the individuals of his classes learned from his lectures, for he taught his discoveries ten full years before he published his modest but wonderful little book "Concerning the Motion of the Heart and Blood in Living Creatures," printed in Latin at Frankfort-on-the-Main, in a thin quarto of only seventy-two pages, in the year of grace 1628.
I propose to give a brief account of the antecedent errors and discoveries to the time of Harvey—that of Erasistratus, who taught that the arteries were air-vessels; of Galen, who demonstrated that they are blood-vessels as well as the veins; of Vesalius, who convinced the world that Galen erred in declaring that holes existed in the partition between the two sides of the heart; of Servetus, Columbus, and Cæsalpinus, who, quite independently of each other, discovered the circulation through the lungs; of Fabricius, who discovered the valves in the veins; of Harvey, who first comprehended the entire circulation; of Asellius, who discovered the lacteals; Pecquet, the receptacle of the chyle; Rudbeck, the lymphatics of the liver; and, lastly, of Thomas Bartholin, who discovered the lymphatics of the whole body.
Erasistratus (300-260 b. c.), a Greek physician and anatomist, of Iulis (the modern Zea), in the island of Ceos, was the grandson of the