Some of the most inspiring achievements in history have been accomplished not on battlefields or corridors of courtly power, but by the patient persistence and steady resolve of learned men. Masculine energy is best expressed in focused effort, breaking through barriers, and bursting through boundaries. The slow amassing of expertise in a field, the careful collection of data, the intense study of such data, and the sudden flash of inspiration that can move mountains and change the paradigm: is there any drama more compelling?

One such example is the discovery of the circulation of the blood by William Harvey in the seventeenth century. Although we take anatomical knowledge today for granted, it is important to remind ourselves that this knowledge took centuries to acquire; and each step forward was made by men guided by persistence, intuition, and hard labor.


After his education at Cambridge and then Italy, Harvey returned to England to practice medicine in London. He secured appointment as personal physician to James I and Charles I. Like Vesalius—whom I have discussed previously here at Return of Kings—he carried out laborious and painstaking examination of cadavers to wean himself away from reliance on Galen, who for two thousand years had held the medical profession in his grip.

A great genius in his time, Galen’s texts had begun to show their age by the early seventeenth century. Galen had believed that the liver, as well as the heart, helped to convey blood throughout the body, and confused the proper function of the veins, arteries, and the heart’s septum and ventricles. Physicians before Harvey had cast doubt on Galen’s theories:  Vesalius and Fabrizio had showed, by careful study, that the veins and arteries could not function as Galen believed. In the 1550s, Servetus and Realdo Colombo had discovered the pulmonary circulation of the blood.

And here we see another characteristic feature of a great man: the ability to build on the work of those who came before him, without slavishly adhering to the theories of predecessors. Even great men like Harvey have to stand on the shoulders of those who came before: rarely in science is discovery accomplished in a total vacuum. Harvey’s forebearers made major steps forward, but what was needed was one man to tie it all together in a comprehensive explanation of how the blood circulated throughout the body.

What I find interesting about scientific discoveries is the process of how the discoverer begins his journey. Harvey made the chance observation that the amount of blood expelled from the heart by each contraction was about half an ounce. It followed, then, that in an hour the heart should pump into the blood vessels over 1000 ounces. But this was a larger amount of fluid than the body contained. Clearly, the blood in the body was not being continuously generated by the tissues, but was being circulated to and from the heart by some continuous cycle of ingress and egress.  But how, precisely, was this happening?  No one could answer this question.

Obsessed with this problem, his exhaustive experimentation finally demonstrated that venous blood (blood carried by the veins) was being carried toward the heart, and that arterial blood was being carried away from it. He imagined the motion of the blood throughout the body as “a motion as it were in a circle.” For its day, such an assertion was revolutionary. It directly contradicted Galen and the legacy of medieval medicine.  Islamic medicine, far ahead of Europe in the Middle Ages, had conspicuously missed this fact as well. Harvey arrived at his theory by 1615, but hesitated to publish it straight away.

His book Anatomical Explanation of the Action of the Heart and Blood in Animals found print in Frankfurt, Germany in 1628. It probably seemed safer to Harvey to release his bombshell on continental Europe first, rather than in his backyard in England. It has been called “the first and greatest classic of English medicine.” He predicted no one would believe him, and he was right. The publication of the work temporarily blackened his reputation, and he found his medical practice suffer grievously. However, like so many theories which are ahead of their time, Harvey’s explanation of the circulation of the blood was confirmed beyond doubt by another physician in 1660, who demonstrated how capillaries carry blood from the arteries to the veins.  It was a moment of vindication and triumph.


Like many men of great ability, he found it difficult to hold his tongue and suffer fools. He was brusque, prickly, and curt to those he deemed unworthy of his patience; but this was the defense mechanism of a man who had been mocked and ridiculed by lesser intellects for years. He was what he had to be. His pugnacity earned him many enemies, but he found in Charles I a loyal advocate.

He continued to work and discover well into his old age. In a treatise published in 1651, he attacked the commonly-held view of the “spontaneous generation” of animals, and postulated that all animals ultimately evolved from eggs. It is a view held by biologists today. He had the true scholar’s humility and awe of the physical universe. “All that we know”, he said, “is still infinitely less than all that remains unknown.”

Although William Harvey may seem a minor figure today, greater appreciation of his achievement is realized when we recall that in his day the only tools available to a physician were his eyes, hands, and surgical instruments that had hardly changed since antiquity. The human body, as Vesalius showed, is a complex and mysterious machine. How all the parts worked together was not at all obvious. It is one thing to map and describe the internal organs, as Vesalius did, but quite another to demonstrate by experimentation precisely how these organs operate. And is there anything more inspiring than the sight of a great man incrementally and patiently working towards that noblest of goals, the advancement of learning?

Read More:  The Greatest Physician In History