William Harvey (1578-1657)


An Anatomical Study on the Motion of the Heart and the Blood in Animals

William Harvey received his B.A. from Cambridge, where he studied with John Caius, once a pupil of Vesalius. Like Caius before him, Harvey chose Padua for his medical education, and after completing his degree in 1602, he returned to England to set up a private practice. In 1609, Harvey was appointed physician at St. Bartholomew’s Hospital and began to consider a problem that had as yet been barely formulated: How is it that blood moves through the body’? An anatomist by training, Harvey focused his attention on the heart, dissecting hundreds of animals from nearly eighty different species. Although Galen had speculated that blood flows from the heart’s right side to the left through pores in the septum, Harvey could not find them. In watching the heart, he noted that it contracted seventy-two times per minute, forcing blood into the arteries with every movement. Harvey’s next question was inspired: How much blood does the heart pump every hour? Calculating that it ejects two fluid ounces per beat, seventy-two times per minute (72 x 60 x 2), he came up with the astounding figure of 8,640 ounces per hour. Finding it impossible to believe that the heart could make such a quantity of blood every hour, Harvey was forced to conclude that the heart does not continually produce new blood but rather circulates or "recycles" it. The path of return to the heart could only be the veins, and Harvey was able to demonstrate this by applying pressure to the veins of the forearm. Although most of Harvey’s discoveries were in place by the time he was appointed physician to James I in 1618, he delayed publishing them until 1628, in anticipation of the storm of controversy that would follow his "reinvention" of the body. Few readers would fail to grasp the fact that De Motu Cordis had leveled the old qualitative model of form and function, and that in its place, Harvey had erected a new physiology based on measurement and mathematics, and on the ceaseless dynamic of ordered motion.


To The Most Illustrious and Indomitable Prince CHARLES, KING of


Most Illustrious Prince!

The heart of animals is the foundation of their life, the sovereign of everything within them, the sun of their microcosm, that upon which all growth depends, from which

[From Exercitatio Anatornica De Motu Con/is et Sanguinis in Anirnalibus, trans. Chauncey D. Leake, 4th ed. (Springfield. 11].: Charles C.. Thomas, 1958). Used by permission of Blackwell Scientific Publications Ltd.]

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all power proceeds. The King, in like manner, is the foundation of his kingdom, the sun of the world around him, the heart of the republic, the fountain whence all power, all grace doth flow. What I have here written of the motions of the heart I am the more emboldened to present to your Majesty, according to the custom of the present age, because almost all things human are done after human examples, and many things in a King are after the pattern of the heart. The knowledge of his heart, therefore, will not be useless to a Prince, as embracing a kind of Divine example of his functions,—and it has still been usual with men to compare small things with great. Here, at all events, best of Princes, placed as you are on the pinnacle of human affairs, you may at once contemplate the prime mover in the body of man, and the emblem of your own sovereign power. Accept, therefore, with your wonted clemency, I most humbly beseech you, illustrious Prince, this, my new Treatise on the Heart; you, who are yourself the new light of this age, and, indeed, its very heart; a Prince abounding in virtue and in grace, and to whom we gladly refer all the blessings which England enjoys, all the pleasure we have in our lives.

Your Majesty’s most devoted servant,


(London.... 1628.)

To His Very Dear Friend


the excellent and accomplished PRESIDENT of THE ROYAL COLLEGE of

PHYSICIANs, and to other learned PHYSICIANS, his esteemed COLLEAGUES.


I have already and repeatedly presented you, my learned friends, with my new views of the motion and function of the heart, in my anatomical lectures; but having now for nine years and more confirmed these views by multiplied demonstrations in your presence, illustrated them by arguments, and freed them from the objections of the most learned and skilful anatomists, I at length yield to the requests, I might say entreaties, of many, and here present them for general consideration in this treatise.

Were not the work indeed presented through you, my learned friends, I should scarce hope that it could come out scatheless and complete; for you have in general been the faithful witnesses of almost all the instances from which I have either collected the truth or confuted error; you have seen my dissections, and at my demonstrations of all that I maintain to be objects of sense, you have been accustomed to stand by and bear me out with your testimony. And as this book alone declares the blood to course and revolve by a new route, very different from the ancient and beaten pathway trodden for so many ages, and illustrated by such a host of learned and distinguished men, I was greatly afraid lest I might be charged with presumption did I lay my work before the public at home, or send it beyond seas for impression, unless I had first proposed its subject to you, had confirmed its conclusions by ocular demonstrations in your presence, had replied to your doubts and objections, and secured the assent and support of our distinguished President. For I was most intimately persuaded, that if I could make good my proposition before you and our College, illustrious by its numerous body of learned individuals, I had less to fear from others;

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I even ventured to hope that I should have the comfort of finding all that you had granted me in your sheer love of truth, conceded by others who were philosophers like yourselves. For true philosophers, who are only eager for truth and knowledge, never regard themselves as already so thoroughly informed, but that they welcome further information from whomsoever and from whencesoever it may come; nor are they so narrow-minded as to imagine any of the arts or sciences transmitted to us by the ancients, in such a state of forwardness or completeness, that nothing is left for the ingenuity and industry of others; very many, on the contrary, maintain that all we know is still infinitely less than all that still remains unknown; nor do philosophers pin their faith to others’ precepts in such wise that they lose their liberty, and cease to give credence to the conclusions of their proper senses. Neither do they swear such fealty to their mistress Antiquity, that they openly, and in sight of all, deny and desert their friend Truth. But even as they see that the credulous and vain are disposed at the first blush to accept and to believe everything that is proposed to them, so do they observe that the dull and unintellectual are indisposed to see what lies before their eyes, and even to deny the light of the noonday sun. They teach us in our course of philosophy as sedulously to avoid the fables of the poets and the fancies of the vulgar, as the false conclusions of the sceptics. And then the studious, and good, and true, never suffer their minds to be warped by the passions of hatred and envy, which unfit men duly to weigh the arguments that are advanced in behalf of truth, or to appreciate the proposition that is even fairly demonstrated; neither do they think it unworthy of them to change their opinion if truth and undoubted demonstration require them so to do; nor do they esteem it discreditable to desert error, though sanctioned by the highest antiquity; for they know full well that to err, to be deceived, is human; that many things are discovered by accident, and that many may be learned indifferently from any quarter, by an old man from a youth, by a person of understanding from one of inferior capacity.



In discussing the movements and functions of the heart and arteries, we should first consider what others have said on these matters, and what the common and traditional viewpoint is. Then by anatomical study, repeated experiment, and careful observation, we may confirm what is correctly stated, but what is false make right.

Nearly all anatomists, physicians, and philosophers up to now have thought with Galen that the pulse has the same function as respiration, differing only in one respect, the former arising from an animal, the latter a vital faculty, but from the standpoint of function or movement behaving alike. Thus one finds, as in the recent book on Respiration by Hieronymus Fabricius of Aquapendente, that since the pulsation of the heart and arteries is not sufficient for the aeration and cooling of the blood, Nature has placed the lungs around the heart. So it seems that whatever has been said prior to this about the systole and diastole of the heart and arteries has been proposed with special reference to the lungs.

Since the movements and structure of the heart differ from those of the lungs,

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as those of the arteries from those of the chest, separate functions or purposes are likely. The pulsings and uses of the heart as well as of the arteries are distinct from those of the chest and lungs. If the pulse and respiration have the same purpose, if the arteries in diastole draw air into their cavities (as commonly said) and in systole give off waste vapors by the same pores in flesh and skin, and if also in the time between systole and diastole they contain air, in fact containing at all times either air, spirits, or sooty vapors, what may be answered to Galen? He declared that the arteries by nature contain blood and blood alone, neither air nor spirits, as may easily be determined by experiments and explanations found in his report.

It is not to be supposed that the function of the pulse is the same as that of respiration because the respiration is made more frequent and powerful, as Galen says, by the same causes as running, bathing or any other heating agent. Not only is experience opposed to this (though Galen strives to get around it), when by immoderate gorging the pulse becomes great and the respiration less, but in children the pulse is rapid when respiration is slow. Likewise in fear, trouble, or worry, in many fevers, of course, the pulse is very fast, the respiration slower than usual.

If one repeats Galen’s experiment of opening the trachea of a living dog, forcing air into the lungs by a bellows, and then firmly tying off the trachea, a great abundance of air even out to the pleurae will be found in the lungs on opening the chest. No air, however, will be found in the pulmonary vein or in the left ventricle of the heart. It certainly should be if the heart drew in air from the lungs, or if the lungs transmitted air to the heart, in the living dog. On inflating the lungs of a cadaver in an anatomical demonstration, who doubts the air could be seen going this way if such a passage exists? This function of the pulmonary vein, the transmission of air from the lungs to the heart, is considered so significant that Hieronymus Fabncius of Aquapendente insists the lungs were made for the sake of this vessel and that it is their most important structure.

Even less tolerable is the opinion which supposes two materials, air and blood, necessary for the formation of vital spirits. The blood is supposed to ooze through tiny pores in the septum of the heart from the right to the left ventricle, while the air is drawn from the lungs by the large pulmonary vein. According to this many little openings exist in the septum of the heart suited to the passage of blood. But, damn it, no such pores exist, nor can they be demonstrated!

The septum of the heart is of denser and more compact material than any part of the body except bones and tendons. Even so, supposing the pores are there, how could the left ventricle draw blood from the right when both ventricles contract and dilate at the same time? Why not rather believe that the right ventricle draws spirits through these pores from the left instead of the left ventricle drawing blood from the right? It is surely miraculous and incongruous that plenty of blood should be drawn through obscure invisible openings in the same time as air through wide open ones. Why require invisible pores and obscure uncertain channels to get the blood to the left ventricle when there is such a wide open passage through the pulmonary vein?




7. Diagram illustrating William Harvey s experiments on the valves of the veins (1628); after a drawing by S. Gooden for the Nonesuch edition of De Motu Cordis (London, 1928). Wellcome Institute Library, London. This diagram illustrates the simple exercise Harvey designed to demonstrate the fact that the veins carry blood back to the heart. While his subject grasped a staff Harvey pressed a finger on the veins of the forearm and, through a sequence of movements, was able to show that the valves in the veins are arranged in such a way that blood passing through them can flow only toward the heart.











73 Harvey, Motion of the Heart and the Blood


When I first tried animal experimentation for the purpose of discovering the motions and functions of the heart by actual inspection and not by other people’s books, I found it so truly difficult that I almost believed with Fracastorius, that the motion of the heart was to be understood by God alone. I could not really tell when systole or diastole took place, or when and where dilatation or constriction occurred, because of the quickness of the movement. In many animals this takes place in the twinkling of an eye, like a flash of lightning. Systole seemed at one time here, diastole there, then all reversed, varied and confused. So I could reach no decision, neither about what I might conclude myself nor believe from others.

Finally, using greater care every day, with very frequent experimentation, observing a variety of animals, and comparing many observations, I felt my way out of this labyrinth, and gained accurate information, which I desired, of the motions and functions of the heart and arteries. From that time I have not hesitated to declare my thoughts on this matter, not only in private to friends, but even publicly in my anatomical lectures, as in the ancient Academy.




Briefly let me now sum up and propose generally my idea of the circulation of the blood.

It has been shown by reason and experiment that blood by the beat of the ventricles flows through the lungs and heart and is pumped to the whole body. There it passes through pores in the flesh into the veins through which it returns from the periphery everywhere to the center, from the smaller veins into the larger ones, finally coming to the vena cava and right auricle. This occurs in such an amount, with such an outflow through the arteries, and such a reflux through the veins, that it cannot be supplied by the food consumed. It is also much more than is needed for nutrition. It must therefore be concluded that the blood in the animal body moves around in a circle continuously, and that the action or function of the heart is to accomplish this by pumping. This is the only reason for the motion and beat of the heart.





It will not be irrelevant here to point out further that even according to common ideas, the circulation is both convenient and necessary. In the first place, since death is a dissolution resulting from lack of heat, all living things being warm, all dying things cold (Aristotle, De Respir., lib. 2 & 3, De Part. Animal., etc.), there must be a place of origin for this heat. On this hearth, as it were, the original native fire, the warming power of nature, is preserved. From this heat and life may flow everywhere in the body, nourishment may come from it, and on it all vegetative energy may depend.


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That the heart is this place and source of life, in the manner just described I hope no one will deny.

The blood, then, must move, and in such a way that it is brought back to the heart, for otherwise it would become thick and immobile, as Aristotle says (Dc Part. Animal., lib. 2), in the periphery of the body, far from its source.

Hence as long as the heart is uninjured, life and health can be restored to the body generally, but if it is exhausted or harmed by any severe affliction, the whole body must stiffer and be injured. The heart alone is so situated and constructed as a reservoir and fountain that blood may be apportioned from it and distributed by its beat to all regions according to the size of the artery serving them.

Moreover, force and effort, such as given by the heart, is needed to distribute and move the blood this way. Blood easily concentrates toward the interior, as drops of water spilled on a table tend to run together, from such slight causes as cold, fear, or horror. It also tends to move from the tiny veins to the intermediate branches and then to the larger veins because of the movements of the extremities and the compression of muscles. So it is more inclined to move from the periphery toward the interior, even though valves offered no opposition to the contrary. Therefore, blood requires force and impulse to be moved from its origin against its inclination into more narrow and cooler channels. Only the heart can furnish this.



I do not find the heart a separate and distinct organ in all animals. Some, called plant-animals, have no heart at all. These animals are colder, have little bulk, are softer, and of uniform structure, such as grubs, worms, and many which come from decayed material and do not preserve their species. These need no heart to impel nourishment to their extremities, for their bodies are uniform and they have no separate members. By the contraction and relaxation of the whole body they take up and move, expel and remove aliment. Oysters, mussels, sponges and the whole genus of zoophytes or plant-animals have no heart, for the whole body functions as a heart, and the animal itself is a heart.

The auricles exist as the initial motive power of the blood. Especially the right auricle, the first to live and the last to die, ... They are necessary in order to cast the blood conveniently into the ventricles. These, continually contracting, throw out more fully and forcibly the blood already in motion, just as a ball-player can send a ball harder and farther by striking it on a rebound than if he simply throws it.

It is noteworthy that the auricles are disproportionately large in the fetus, because they are present before the rest of the heart is made or can take up its function, so that.. . they assume the duty of the whole heart.

While the fetus is still soft like a worm, or as is said, in the milk, there is a single bloody spot, or pulsating sac, as if a part of the umbilical vein were dilated at its base or origin. After a while when the fetus is outlined and the body begins to be

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more substantial, this vesicle becomes more fleshy and stronger, and its constitution changing, it turns into the auricles. From these the bulk of the heart begins to sprout, although as yet it has no function. When the fetus is really developed, with bones separated from fresh, when the body is perfected and has motion, then the heart actually beats and, as I said, pumps blood by both ventricles from the vena cava to the artefles. Thus divine Nature making nothing in vain, neither gives a heart to an animal where it is not needed, nor makes one before it can be used. By the same steps in the development of every animal, passing through the structural stages, I might say, of egg, worm, and fetus, it obtains perfection in each. These points are confirmed elsewhere Ld by many observations on the formation of the fetus.

[The heart] is the first to exist, and contains in itself blood, vitality, sensation and motion before the brain or liver are formed, or can be clearly distinguished, or at least before they can assume any function. Being finished first, Nature wished the rest of the body to be made, nourished, preserved, and perfected by it, as its work and home. The heart is like the head of a state, holding supreme power, ruling everywhere. So in the animal body power is entirely dependent on and derived from this source and foundation.