HARVEY, WILLIAM, was born at Folkstone on the 1st of April 1578, and after having been some years at the grammar-school of Canterbury, was admitted at Cahn College, Cambridge, in being then in his sixteenth year. Having devoted himself to the study of logic and natural philosophy for six years in that university, he removed to Padua, at that time a celebrated school of medicine, where he attended the lectures of Fahricius ab Aquapeudente on anatomy, of Minadous on pharmacy, and of Casserius on surgery. He was admitted doctor of medicine there, and returned home at the ago of twenty-four. At thirty he was elected Fellow of the College of Physicians, and shortly after appointed physician to St. Bartholomew'a lioapitaL On the 4th of August 1615, ho was chosen by the college to deliver the Lumleian lectures on anatomy and aurgery, and upon this occasion he is supposed to have first brought forward his views upon the circu lation of the blood, which he afterwards more fully established, and published in 1628.
The importance of this great discovery was such, that it will be necessary to investigate from the writings of the author the atepa by which it was attained. We are informed by Boyle in his Treatise ou Final Causes,' that in the only conversation which he ever had with Harvey, he was told by hint that the idea of the circulation was suggested to him by the consideration of the obvious use of the valves of the veins, which are so constructed as to impede tho courier of the blood from the heart through those vessels, while they permit it to pass through them to the heart. Before the time of Harvey the opinions ou the circulation were numerous and inconsistent. The blood was supposed to be distributed to the various parts of the body by means of the veins, and that intended for the nutrition of the lunge by the action of the right side of the heart. According to the same doctrines the arteries were destined for the conveyance of the vital spirits, which were formed in the left side of the heart from the air and blood derived from the lungs. These vital spirits were supposed to be taken in by the arteries during their diastole, and distributed by them during their systole, whilst the vapours or fuligines, as they are called by Harvey, were returned to the lungs by the action of the left ventricle. Opinions did not agree upon the mode in which the blood found its way to the left side of the heart, for whilst some sup posed that it was conveyed with the air from the lungs, others maintained that it transuded by certain imaginary pores in the septum between the ventricles. These opinions, it is evident, rested
more upon imagination than any careful observation of facts. Those of Harvey, on the contrary, were drawn from the moat accurate dis sections of dead and living animals, and supported by arguments depending entirely upon the anatomical structure and obvious uses of the parts. The result of these observations is thus stated by him. The heart has periods of action and of rest, but in warm-blooded animals its motions are so rapid, that the different steps of them can not be distinguished. In cold-blooded animals they are more slow, and in warm-blooded also after the examination of its action, by opening the chest in a living animal, has been continued some time. During its action the heart is raised, and its point tilted forward so as to strike against the parietes of the chest. It contracts in every direc tion, but more especially on its sides ; it also becomes harder, as other muscles do during their contraction. In fishes and cold-blooded animals the heart may be observed to become paler during its systole, and assume a darker colour during its diastole. If a wound be made in the ventricle, the blood is ejected from it during its contraction. From these facts Harvey concluded that the essential action of the heart is its systole, and not its diastole, as was supposed by physicians before his time, and that the result of this contraction is the expul sion of the blood into the pulmonary artery and aorta. The diastole of the arteries or pulse is synchrouous with and caused by the pro pulsion of the blood during the systole of the ventricle, and is a passive, and not, as was previously supposed, an active operation of the vessels. If the motions of the heart be carefully observed for some minute*, it will be seen first that the two auricles contract simultaneously, and force the blood contained in them into the ventricles; and secondly, that the ventricles in their turn assume the same action, and propel most of the blood into the pulmonary artery and aorta, from which it is prevented from returniug by the valves situated at the entraoce of those vessels.. The author next proceeds to describe the manner in which the blood passee from the right to the left side of the heart.