Recently, a fascinating story about Hadrian’s Wall went viral on Twitter. While today we think of Hadrian’s Wall as, well, Hadrian’s, already by Late Antiquity, many Romans did not remember who had originally built the wall, and over time rumor had started that it was actually Septimius Severus who had done it. And so, for about millennium and a half the wall was known as Severus’ wall, with such luminaries as the Venerable Bede continuing to perpetuate false information. Some scholars questioned the Severan attribution in the 1500s, but were wary of overthrowing over a thousand years’ worth of tradition on the matter. And so, it was not until 1840, that John Hodgson, a little-known clergyman, published his findings, confirming that it was Hadrian’s wall.
This cautionary tale is a sobering reminder that sometimes, by relying on iconic authorities who provided erroneous information, historians and other practitioners can unintentionally perpetuate false information, giving it yet more weight and authority with age. No one wants to be the squeaky wheel that flips accepted wisdom of millennia on its head. Besides, no one will believe that squeaky wheel anyway, at least at first. While the book under review has nothing to do with walls, it deals with this very same dilemma of the difficulty of challenging established authorities on a topic. But in this case, the story resides in the field of medicine.
At its most basic, Dhun Sethna’s fascinating and highly readable book is a well-researched intellectual history of views on blood circulation from Antiquity to the modern world. He summarizes his intentions at the outset: “This book is the biography of an idea, the idea that blood circulates around the body. It may seem a common, even obvious notion. Yet that familiar concept that the heart is an organ that pumps blood and oxygen through the arteries, with the “waste” returning by way of the veins, took over two thousand years to develop” (xi). Blood circulation as we know it today was the discovery of English physician William Harvey, who first published his theory in 1628. In the process, he proved completely wrong the previous theories of blood, “the wine-dark sea within” of the title, and its work in the human body, going back to Aristotle and Galen:
“Harvey’s own work encompassed two simultaneous paradigm shifts: the mechanism of contraction of the heart, and then the circulation of blood. The correct analysis of the heart’s motion as a mechanical pump, and only as a pump, that ejected blood into the vessels at each contraction was a central innovation essential to his scheme. Before Harvey, the accepted process of heart function, which came from Aristotle, was a heat-driven ‘fermentation’ of blood within the heart that caused that organ to expand and, like ‘boiling milk spilling over,’ caused an overflowing of blood into the aorta” (xv).
The book is divided into seven sections, marking different stages that Sethna identifies in historical thinking about the role of blood in the human body. The first of these begins with the earliest medical texts and their description of blood, ranging from Egypt to China to Greece. And one of the Greeks’ earliest notable discoveries in this area included identifying, at least, that blood moved within the body’s vessels and arteries. They also “identified the heart as a vital organ and correctly described the function of the heart valves” (44). Aristotle is this first section’s greatest hero and greatest villain at once. He was the first Greek to recognize the importance of the heart in the body, but he was also responsible for many errors and misunderstandings that would continue well into the modern era. For instance, he believed the heart had three cavities, rather than four. He also came up with a complicated (and utterly wrong) idea of a heating/cooling system within the arteries, which was responsible for blood circulating along the model of overboiling milk.
The second section examines in greater detail Greek discoveries on blood, beginning with Erasistratus, who “was among the first to recognize that the function of the four heart valves was to coordinate blood flow in a single direction” (47). But this section’s greatest hero-cum-villain is Galen. While Galen correctly determined that arteries contained blood, and not just pneuma—that hypothetical breath or air that some earlier philosophers, including Aristotle, had posited there—he “declared that each independent vascular scheme with its unique blood must have its own distinctive origin” (60). Sethna holds Galen responsible, as a result, for the regression that effectively shut the door for fifteen centuries on even considering the idea of blood circulating throughout the body.
The third section begins with Leonardo da Vinci’s contribution to this debate, as he devoted much of his life to studying both human and animal anatomy, and drew many internal organs in detail. But, “in his physiology, Leonardo was Galenic” (78). Sethna moves next to consider the anatomical research of Vesalius and Massa. Vesalius, in particular, is the real hero in this section, as the first to challenge Galen’s theories. Unfortunately, Galen’s views by the sixteenth century had acquired a status that was not just almost but literally considered sacred: “in the fear and confusion of Luther’s Reformation, there was utmost pressure upon scientific innovators to avoid direct conflict with classical doctrine or the Catholic Church. The church determined what was to be counted as knowledge; natural philosophy, of which anatomy was part, was still a religious business. The battle for and against Galen was as much the battle for and against the Catholic Church” (92).
In the fourth section, Sethna turns to the works of Michael Servetus, a polymath with a heretical streak—rejecting the Trinity, he articulated a view of Unitarianism. But his theologically unorthodox views were inextricably connected also to his rejection of Galenic theories of blood. This section also examines the experiments of several other European researchers throughout the first part of the sixteenth century, showing the slowly mounting resistance to Galenic views of blood circulation from a variety of quarters.
Section five finally brings us to the hero of the book—William Harvey, physician to James I and Charles I. Taking advantage of royal resources—in particular, access to all the deer he could ever want to dissect—Harvey studied blood circulation and the role of the heart in the process, and built on the work of predecessors, especially Fabricius, to reach the revolutionary (and correct) conclusion that “blood flowed in the body as a unidirectional circulation!” (157). But after making his initial discovery, it took him years more to publish it, and the conclusions that others reached in the wake of his discovery were not immediately the most helpful for patients. In particular, Sethna discusses the blood transfusion craze in late 1600s Europe. But after the success of the initial transfusion of sheep’s blood into a fifteen-year old boy who recovered from the experience, subsequent transfusions proved to have much higher mortality than recovery rates, and the practice was quickly abandoned.
Section six digs deeper into the impact of Harvey’s findings, and tracks their dissemination already in his lifetime, as well as the controversy that they unsurprisingly inspired. One reader who appreciated Harvey’s findings, and had possibly already reached the same conclusions even before reading them, was none other than Descartes. But wider acceptance of Harvey’s findings, despite a number of strong endorsements, was slower to come, because no one wanted to contradict Galen so spectacularly. When the question was raised in the Sorbonne in 1645 “whether Galen’s account of blood flow should be formally revised,” the dean of the Faculty of Medicine, Jean Riolan, wasn’t prepared to go quite that far. Instead, he published polemics attacking Harvey’s findings and defending Galen. Still, acceptance of Harvey’s views kept steadily growing in his lifetime, the result of his able responses to critics, so that by the time Harvey died in 1657, Galen had finally been dethroned.
In the seventh and final section of the book, Sethna considers how the study of circulation led to increased understanding of breathing. The hero of this section is Antoine Lavoisier, who built on Harvey’s discovery of blood circulation to formulate his own theory of respiration.
Overall, in this history of views on blood, leading up to the difficult debunking of Aristotle and Galen’s theories, which proved so transformational for modern medicine, lies the parallel between this book and the story of the correct re-attribution of Hadrian’s wall to Hadrian. In the case of this book too, we are dealing with a modern scientific discovery that challenged something that was incorrect, but was accepted as fact for millennia. And so, Sethna’s book is more than just a history of the idea of blood circulation. It is also a story that witnesses to the difficulty of challenging accepted paradigms in any field. It reminds us that crowning some experts as kings whose views are not to be challenged is a problem. But it also shows the value of scholarly communities over time, as Harvey would not have been able to make his own discoveries, had it not been for many other researchers whose work led up to his own. Many of these predecessors (Sethna reminds us) did not realize the value or full implications of their discoveries.
It is worth noting that Sethna is not a Classicist. He is, rather, an accomplished cardiologist. This means that in evaluating the different incorrect arguments about blood and the heart, he is drawing on his own medical expertise. But he does so in a way that is remarkably accessible, never condescending. As he notes, furthermore, his book does not claim to uncover new knowledge. Rather, it is “a work of synthesis, not of original scholarship” (313). And yet, by presenting the story of an idea that we take for granted, but that had such a complex road, in an engaging and readable way, he has done a service to both intellectual historians of medicine and Classics and to more popular audiences, whether those be doctors or their sometime patients, including college students in history of medicine courses.