In 1616, the year Shakespeare died, Harvey probably began in his classes to teach that doctrine which has immortalised his name. He began to show his pupils, and whoever else desired to be present, from dissections of the human body and of animals, and by experiment when necessary, the true office of the heart, the true course of the movement of the blood in the body. This he continued to do for more than ten years, listening patiently to objections, indeed inviting criticisms so that the complete truth might be discovered free from any falsities or misconceptions. At last, upon the earnest entreaties of his most distinguished medical friends, he was persuaded to publish his discovery to the world. These facts are of interest in throwing some light on Harvey’s character. A discoverer who waits years before publishing what he is firmly convinced in his own mind is a new idea, not to say a great discovery, must be possessed of that calmness of mind and abnegation of self which we associate with the true philosopher. A discoverer who employs so long an interval to give opportunity for criticism, and to deal with objections, must indeed be wedded to truth. This devotion to truth, however, had its reward, for it resulted in one of the most remarkable scientific treatises ever written. When, in 1628, Harvey published at Frankfort-on-Main, his book on “The Movement of the Heart and Blood,” he gave his reasons for believing the blood to circulate, and explained the use of the heart in language so simple, so clear, so exact, that now, nearly three hundred years afterwards, the most accomplished physiologist can hardly improve on it. This assuredly is a fact almost unique in the history of science.