On the 4th of August, 1615, he was appointed Reader of Anatomy and Surgery to the College of Physicians. From some scattered hints in his writings it appears that his doctrine of the circulation was first advanced in his lectures at the college about four years afterwards; and a note-book in his own handwriting is still preserved at the British Museum, in which the principal arguments by which it is substantiated are briefly set down, as if for reference in the lecture-room. Yet with the characteristic caution and modesty of true genius, he continued for nine years longer to reason and experimentalize upon what is now considered one of the simplest, as it is undoubtedly the most important, known law of animal nature; and it was not till the year 1628, the fifty-first of his life, that he consented to publish his discovery to the world. In that year the ‘Exercitatio Anatomica de Motu Cordis et Sanguinis’ was published at Frankfort. This masterly treatise begins with a short outline and refutation of the opinions of former anatomists on the movement of the animal fluids and the function of the heart; the author discriminating with care, and anxiously acknowledging the glimpses of the truth to be met with in their writings; as if he had not only kept in mind the justice due to previous discoveries, and the prudence of softening the novelty and veiling the extent of his own, but had foreseen the preposterous imputation of plagiarism, which, with other inconsistent charges, was afterwards brought forward against him. This short sketch is followed by a plain exposition of the anatomy of the circulation, and a detail of the results of numerous experiments; and the new theory is finally maintained in a strain of close and powerful reasoning, and followed into some of its most important consequences. The whole argument is conducted in simple and unpretending language, with great perspicuity, and scrupulous attention to logical form. The doctrine announced by Harvey may be briefly stated thus:—