Circulating The Truth: Harvey vs. Galen & Rush.

Posted on | November 10, 2025 | 9 Comments

Galen’s Circulation

Mike Magee

“I have found bleeding to be useful, not only in cases where the pulse was full and quick, but where it was slow and tense.” That was the sage advise Benjamin Rush offered to fellow clinicians in the middle of the Yellow fever epidemic in Philadelphia in 1796.

Rush’s ignorance on first glance is both historic and incomprehensible in that he was relying on the teachings of Galen (Aelius Galens/129 AD -216 AD), who himself had incorporated the biases of Hippocrates and Aristotle based on their belief that circulation involved the four bodily fluids –  blood, phlegm, yellow bile and black bile. All of the above they believed could overwhelm the body by offering “too much blood.”.

To make matters worse, Rush had had 165 years to absorb the incontrovertible findings of William Harvey and his 1628 landmark publication Exercitatio Anatomica de Motu Cordis et Sanquinis in Animalibus (Anatomic Exercises on the Motion of the Heart and Blood in Animals) which exposed Galen’s classic assertions as wrong on multiple counts.

Galen was born in Pergamum, Asia Minor (present day Turkey) when the Roman Empire was in full swing. He began studying medicine at age 16, and 12 years later was awarded with the active post of “Surgeon to the Gladiators.” At age 33, he was “Physician to the Emperor.”

He was fascinated by human anatomy but legally prohibited from human cadaver studies. Instead he focused on dead and living animals. At the core, Galen was obsessed with nutrition, or more specifically how the food one ingested was distributed to the human flesh. He believed food was transformed to blood, and then somehow transformed via the liver into flesh.

Galen spent a great deal of time observing species in varying distress, and deduced:

1. The heart beat.
2. Breathing was essential for life.
3. A warm body was good. A dead body went cold.
4. Hearts had valves.
5. Thick arteries and thinner veins connected to the heart and carried different color blood.

All true. But then he got the circulatory system wrong. He described two disconnected tracks. The first path connected liver, veins and right heart, and delivered processed food to various parts of the body. The second path connected left heart, lung, and arteries and delivered cooling air.

The Roman Empire lasted another quarter century after Galen’s death and then collapsed giving way to the century-long Dark Ages (lasting till 1400). In the Latin West, the Church controlled everything and embedded Galen’s beliefs in their scripture. But the Islamic and Byzantium worlds continued to explore and experiment and move forward. For example, in 1240, an Arab polymath from Damascus, Ibn al‐Nafis, described with accuracy the form and function of pulmonary circulation. 

Three hundred years later, in 1547, that Arab publication was translated into Latin. By then, the Renaissance was underway in Italy, led by the likes of Leonardo da Vinci who correctly noted that “the heart is a vessel made of thick muscle, vivified and nourished by artery and vein as are other muscles.” Others piled on proving that the heart valves allowed blood flow in only one direction; that blue blood was pumped from the right ventricle into the lungs and returned to the left heart bright red; and that the “invisible pores” that Galen theorized connected right and left ventricles providing lively and spirited air didn’t exist.

All of the above was available to 19-year old William Harvey when he graduated in 1547 from university at Padua, Italy. At the time, Galileo occupied the chair of mathematics at the university. Harvey taught and continued his studies there before returning to England to become Assistant Physician at St. Bartholomew’s Hospital in 1604. A decade later, he received a lifetime appointment as Lecturer at the Royal College of Physicians in 1615. And thirteen years after that, he set Galen straight in his monumental 72-page de Motu Cordis publication.

Where Galen saw straight lines, Harvey saw “circular motions” which preserved and carried blood in perpetuity. “One action of the heart is the transmission of the blood and its distribution, by means of the arteries, to the very extremities of the body,” he wrote.

Harvey had access to human cadavers. After calculating the volume of blood ejected by the left ventricle, and the number of beats, he proved that “it is matter of necessity that the blood perform a circuit, that it return to whence it set out.” That was because, by his calculations, unless blood recirculated, you would need to create 540 pounds of blood per hour to keep the system full

Harvey loved ligatures and applied them liberally to arteries and veins in fish, snakes, dogs, men and more. He also probed venous valves and realized that blood was only able to flow one way in veins. From these and other observations, he saw the heart as mirroring industrial force pumps that were common in his day, and systole as the driver of circulation. 

The venous system carried blood back to the right heart which delivered its goods to the lungs for (still not understood) oxygenation. That refreshed blood was then delivered to the left heart for forceful arterial distribution – thus a virtuous cycle. The remaining mystery of peripheral blood transport from tiny distal arterial branches to venous counterparts was resolved when Marcello Malpighi discovered and described capillaries in frog lungs in 1661, four years after Harvey’s death.

Harvey was prepared and anxious to challenge a centuries old status-quo. Two decades after publishing de Motu, his 1649 fighting words read, “For the concept of a circuit of the blood does not destroy, but rather advances traditional medicine.” Rene Descartes, the philosopher apparently agreed. He saw Harvey’s idea of the heart as a pump as valid, drawing comparisons to new combustion engines which were both “mechanistic and vitalistic” sources of life and energy.

And yet 250 years later, Benjamin Rush was pushing not only blood letting and cathartics in moribund patients, but babbling on about “the four humors – blood, phlegm, yellow bile, and black bile” – Galen’s four best friends. So why did it take so long for Harvey’s vision to overtake Galen’s? 

Three reasons: 1. Galen’s explanation of circulation was internally consistent, providing a role and purpose for what was visible at the time, and invisible. 2. Galen was careful not to challenge Aristotle or Hippocrates, agreeing that “the heat of the body is innate and inexorably linked to life and the soul.” 3. In largely endorsing Galen’s views, the Church made it a sacrilege to challenge the doctrine. Direct examination of human cadavers, in opposition to church doctrine, lent permission to challenge accepted scientific doctrine.

Comments

"Available Everywhere Now"
"Code Blue INDEX online"

 

  Ralph Snyderman
Prospective Health Blog
BIOGRAPHY   Meredith Magee Donnelly
Homegrown Friends
BIOGRAPHY   Eric Dishman
NIH Precision Medicine
BIOGRAPHY   Barbara Ficarra
Health in 30
BIOGRAPHY   William L. (Larry) Minnix, Jr.
Larry's Letters
BIOGRAPHY     Eric Dishman
Precision Medicine, Euthanasia, Abortion, Communism, Trillions of Dollars, Losing Freedom, and Town Hall Mobs BIOGRAPHY   Michael Millenson
Yearning for Universal Coverage Is Not Universal
BIOGRAPHY