By Matthew Megill (email)
Why was the great Greek physician Galen unable to figure out that the heart circulated blood throughout the body? And even more to the point, does Galen's failure to discern the heart's true function hold any lessons for the scientists of today?
Throughout the ages, the heart has been portrayed in poetry and on Valentine's Day cards as an organ of the emotions. It wasn't until the 17th century that scientists fully understood the heart's role in the circulatory system.
Yet this physiological puzzle might have been solved as early as the 2nd century, by the Greek physician Galen, had he not been such a staunch advocate of Plato's conception of the soul. For despite Galen's eminence and erudition, his philosophical beliefs appear to have clouded his scientific judgment. But his fallibility is not a matter for modern- day smugness: the story of his research into the heart contains a caution that is still pertinent nearly 2,000 years later.
Galen was probably the most respected Greek doctor after Hippocrates, who codified medicine's precepts in the Hippocratic Oath in the 5th century b.c. Galen knew a great deal about the heart, as evidenced by his extant writingsmost notably On the Doctrines of Hippocrates and Plato.
Given Galen's intellectual accomplishments, many scholars of more recent centuries have wondered how he failed to recognize the heart's true role in circulating the blood. From a strictly scientific perspective, he could haveperhaps even should havediscovered the process of circulation. He had all the required pieces of the puzzle and could have easily conducted any of the observations and experiments that William Harvey used to fi- nally describe the circulatory system in 1628.
Nevertheless, Galen failed to pursue the concept of circulation or to try the simple calculations that brought Harvey such success many centuries later. What was it that prevented this brilliant scholar from making the logical leap to seeing blood as a reusable vehicle that transports oxygen to the cells of the body? Why did he continue to hew to the idea of blood as a consumable fuellike the wood used to stoke a fire or the water used to irrigate a field?
Many scholars feel that Galen had a philosophical bias that deterred him from understanding the heart's role in circulation. He was a devoted follower of Plato and disagreed vehemently with the opposing Stoics over the nature of the soul. Indeed, his advocacy for the Platonic view led him to disregard many experimentally verifiable facts that might have enabled him to conceive of the heart's circulatory function.
Pieces of the puzzle
Charles Harris, a professor of the medical humanities, in his 1973 book The Heart and the Vascular System in Ancient Greek Medicine, examines the pieces of the puzzle that Galen held: Galen knew that the heart was associated with the pulsing of the arteries. He knew that the arteries and the veins ran parallel to each other and were connected. And he knew that both contained blood, though blood of different types. Harris concludes that this information could have led Galen to an accurate understanding of the heart.
It is also worth noting that Galen was familiar with Erasistratus's description of a pumping heart. Erasistratus, a 3rd-century b.c. Alexandrian, had accurately described the heartright down to the critical role of the valves in allowing blood to flow in only one direction through the heart's chambers. But Erasistratus failed to discover circulation because he believed that the arteries contained pneuma, or air. Galen, on the other hand, decisively refuted that belief in his On Blood in the arteries. In the process, he showed that he had a more than passing familiarity with Erasistratus's writings. So it seems clear that Galen not only was familiar with the pump theory but embraced it himself.
If Galen understood this critical concept, he was barely a heartbeat away from Harvey's most convincing piece of evidence for circulation. Harvey wrote that he first considered the circulation of the blood when he noted how much blood is expelled by the heart with each contraction. Over the course of a day, he concluded, the amount totaled more than the body's daily intake of food by weight. With the aid of some rough calculations, Harvey proved beyond doubt that the blood must be reused. From there, conceiving of the process of circulation was but a short step. Yet Galen failed to perform this simple calculation and continued to view blood as a consumable fuel for the body.
Harvey's other major points serve to further implicate Galen's bias. In his seminal publication, De motu cordis et sanguinis in animalibus (On the movement of the heart and blood in living creatures), Harvey described how he could push a rod up a vein but was unable to push it down a vein because of the one-way nature of the valves. Another of his experiments was equally simple and elegant. "Now let anyone make an experiment upon the arm of a man," he wrote. "Let a ligament be thrown about the extremity and drawn as tightly as can be borne. . . . It will first be perceived that beyond the ligament, neither in the wrist nor anywhere else, do the arteries pulse." On the basis of these observations, Harvey concluded, correctly, that blood flows out from the heart through the arteries and back toward the heart through the veins.
Nevertheless, Galen failed to pursue the concept of circulation. What prevented this brilliant scholar from making the logical leap to seeing blood as a reusable vehicle that transports oxygen to the cells of the body?
The 2nd-century physician Galenpictured abovewas a brilliant scholar but had a blind spot where the heart was concerned. He was not alone, however. Even the great 16th-century anatomist Vesalius didn't figure out the concept of circulation. Note Vesalius's illustrations of the veins (left, top) and arteries (left, bottom) of the forearm; the absence of detail in the latter betrays his lack of understanding about how the circulatory system worked.
Harvey also demonstrated that the heart's pumping action will spit blood from a cut artery. In addition, he noted that while a cut in an artery will quickly clear the whole arterial system of blood, there is no such effect with a cut vein. All of these observations could have been made just as readily in the 2nd century as in the 17th.
To conclude that Galen was intellectually incapable of realizing the significance of these observations seems absurd, given his general erudition. In many of his other anatomical explorations, experimental evidence led Galen to think quite creatively. For example, he suggested that unseen nerve channels allowed the brain to send message pneuma to the muscles. But in his investigations of the heart, Galen apparently ignored any observations that did not support his theory.
What was it about Galen's theory of the heart that he held so dear? The answer to that question fairly leaps off the pages of On the Doctrines of Hippocrates and Plato, which contains much of Galen's analysis of the heart. From the book's introduction through the last of its surviving sections, Galen's polemical objective is clear: he wants to discredit the Stoics and their view of the soul, while upholding his own Platonic conception of the tripartite soul.
Harvey's other major points further implicate Galen's bias. In his seminal publication, he described how he could push a rod up a vein but was unable to push it down a vein because of the valves' one-way nature.
William Harveypictured abovefinally riddled out the puzzle of circulation in 1628. But the simple calculations and experiments that he used to prove the concept could have been accomplished just as easily in Galen's time. One of them is depicted in the illustration at left from Harvey's seminal book, De Motu Cordis. Dartmouth owns a very rare first edition of De Motu Cordisone of just 43 known copies of the book.
The theory of the tripartite soul had been proposed by Plato in the 4th century b.c. as an explanation for inner psychological disagreement and conflict. Plato fully expounded the concept in Book IV of his famous Republic and embellished the idea from a biological standpoint in the Timaeus. In the latter book, he opined that the heart acts as a sort of emotional guard-chamber, passing the commands and the spirit for applying reason on to the limbs of the body. Galen seems not only to have accepted these ideas but also to have augmented themclaiming that they were anticipated by Hippocrates. Galen's respect for both Plato and Hippocrates in this, as in other issues, is a hallmark of his style.
On the other hand, Galen saw the Stoics as a bunch of self-promoting, sophistical rabble-rousers. They had proposed some radical new theories: denying that emotions were legitimate, or that any part of the soul was located outside the heart, while affirming that reason made up the undivided soul. Their arguments were based on irrelevant poetry and etymology and on inaccurate, even deceptive, science. They hoped to supplant the theories of the ancients, such as Plato.
Galen felt that the Stoics' conception of an undivided soul offered no explanation for mental con- flict, and so he aimed to prove their view wrong. Indeed, much of Galen's research was directed against the Stoics. Christopher Gill, a British classicist, describes Galen as "highly partisan and misleading" in single-mindedly defending Platonism.
Yet in taking this stance, Galen was merely re- flecting the Zeitgeist of his time. He lived in the Second Sophistic era, a period characterized by much polemical public oratory. Heinreich Von Staden, a classicist at Yale, agrees that Galen's rhetorical methods and even his goals were influenced heavily by the combative spirit of his time. And, like many other partisans of the period, Galen attacked not only the Stoics' ideas but also the leading proponent of the Stoic view, Chrysippus.
Galen's philosophical framework was also heavily influenced by science (or, one might argue, vice versa). Dutch historian Teun Tieleman, in his 1996 book Galen and Chrysippus on the Soul, explains that Galen viewed scientific facts as test cases for philosophical ideas. Therefore, Galen believed, if he could bring science to bear on the Stoic view of the monistic heart, he would win his point. His own words highlight his devotion to the Platonic view of the soul's location: "Now where will proof of this be found? Where else but from dissections?"
Building his case
Galen tried to make his case by proving that the whole soul could not possibly be located in the heart, as the Stoics contended. Instead, he tried to show that the three powers of the Platonic soul - the rational, the spirited, and the desiderative - were each matched by a corresponding organ system. For just as every body part had to have a specific function, in Galen's mind every function had to have a corresponding organ. He desperately wanted to identify three parallel organ systems running throughout the body in order to combat the Stoic theories that he found so pernicious.
Accordingly, when he observed three systems that extended throughout the whole body - the veins, the arteries, and the nerves - he seems never to have considered that the arteries and the veins might be an interconnected loop. Instead, he labeled the brain as the seat of reason and the liver as the seat of desire, which left the heart to be the seat of emotion. To conceive of the heart's arteries as transferring blood to the liver's veins would have undermined this concept and thus weakened his attack on the Stoics.
The way Galen saw it, the existence of these three systems provided clear evidence that his preconception was correct, and he was satisfied with relatively few experiments proving that each system distributed the power he had assigned to it.
Incidentally, Galen failed to acknowledge in his writings the views of those who considered the brain to be the center of emotion and reason. This was a strange oversight, because Chrysippus wrote about this view even though he did not espouse it. It was also an unfortunate oversight, because if Galen had disassociated the emotions from his heart, he might have been able to see its true function. For although he held the more progressive position - that reason emanates from the brain, not from the heart - his staunch opposition to the Stoics' view of the heart prevented him from thinking further about its true role. Once he thought he'd proved one anti-Platonic theory wrong, he proceeded no further.
Galen's preoccupation with the dialectic mindset of his era may be understandable, but it was detrimental scientifically. Instead of studying all the data in order to form a hypothesis, Galen commenced his investigations with a clear objective in mind. He thus used his mental resources to determine whether the heart was an emotional center, and whether it controlled reason, instead of exploring larger questions that might have revealed its true function. Of course, Galen did find some evidence suggestive of his tripartite theory. But he would have benefited from the advice of Claude Bernard, a 19th-century French physiologist who pointed out that researchers must be extremely careful not to find what they are looking for. "It is what we think we know already that prevents us from learning," wrote Bernard. "We must never make experiments to confirm our ideas, but simply to control them."
A pertinent precaution
Bernard's precaution, like the lesson to be drawn from Galen's exploration of the heart, remains pertinent today. Medical historians point out that one of the reasons for studying ancient medicine is to see how early doctors came to be misled, for it is not impossible that their failures are like our own. The story of Galen and the heart is a case in point. He had a goal, and even though his observations did not always support this end, he persisted in holding to the Platonic view of the heart as an emotional organ, ignoring all the evidence pointing him toward an understanding of circulation.
"Though he sees the truth, he does not use it": So said Galen of Chrysippus. Yet history must say the same of Galen.
Have a heart!
For centuries, the heart has served for lovers and warriors, for parsons and poets, as a shorthand way of describing emotion from passion and courage to grief and despair. Even long after the heart's true physiological function was understood, the fist-sized organ has continued to serve a symbolic role. Here's a selection of references to the heart by poets through the ages.
For May wol have no slogardie anyght.
The sesoun priketh every gentil herte,
And maketh hym out of his slep to sterte.
Geoffrey Chaucer (1343-1400)
To fret thy soule with crosses and with cares;
To eate thy heart through comfortlesse dispaires.
Edmund Spenser (1553-1599)
And make my seated heart knock at my ribs,
Against the use of nature. Present fears
Are less than horrible imaginings.
William Shakespeare (1564-1616)
The heart of man is the place the Devil's in:
I feel sometimes a hell within myself.
Sir Thomas Browne (1605-1682)
Grief tears his heart, and drives him to and fro
In all the raging impotence of woe.
Alexander Pope (1688-1744)
Forever, Fortune, wilt thou prove
An unrelenting foe to love;
And when we meet a mutual heart,
Come in between and bid us part?
James Thomson (1700-1748)
And what shoulder, and what art,
Could twist the sinews of thy heart?
William Blake (1757-1827)
The music in my heart I bore
Long after it was heard no more.
William Wordsworth (1770-1850)
Oh, many a shaft at random sent
Finds mark the archer little meant!
And many a word at random spoken
May soothe, or wound, a heart that's broken!
Sir Walter Scott (1771-1832)
From every place below the skies
The grateful song, the fervent prayer
The incense of the heartmay rise
To heaven, and find acceptance there.
John Pierpont (1785-1866)
The heart bowed down by weight of woe
To weakest hope will cling.
Alfred Bunn (1790-1860)
Love works at the centre,
Forth speed the strong pulses
To the borders of day.
Ralph Waldo Emerson (1803-1882)
I have you fast in my fortress,
And will not let you depart,
But put you down into the dungeon
In the round-tower of my heart.
Henry W. Longfellow (1807-1882)
But for the unquiet heart and brain
A use in measured language lies;
The sad mechanic exercise
Like dull narcotics numbing pain.
Alfred Tennyson (1809-1892)
Only I discern
Infinite passion, and the pain
Of finite hearts that yearn.
Robert Browning (1812-1890)
The Land reposed in peace below;
The children in their glee
Were folded to the exulting heart
Of young Maternity.
Herman Melville (1819-1891)
It is not wisdom to be only wise,
And on the inward vision close the eyes,
But it is wisdom to believe the heart.
George Santayana (1863-1952)
They change their skies above them,
But not their hearts that roam.
Rudyard Kipling (1865-1936)
I will arise and go now, for always night and day
I hear lake water lapping with low sounds by the shore;
While I stand on the roadway, or on the pavements grey,
I hear it in the deep heart's core.
William Butler Yeats (1865-1939)
Ah, when to the heart of man
Was it ever less than a treason
To go with the drift of things,
To yield with a grace to reason.
Robert Frost (1874-1963)
There is nothing to save, now all is lost,
but a tiny core of stillness in the heart
like the eye of a violet.
D.H. Lawrence (1885-1930)
I know I am but summer to your heart,
And not the full four seasons of the year.
Edna St. Vincent Millay (1892-1950)
My heart will laugh a little yet, if I
May win of Thee this grace, Lord: on this high
And sacrificial hill 'twixt earth and sky,
To dream still pure all that I loved, and die.
Countee Cullen (1903-1946)
In the deserts of the heart
Let the healing fountain start.
W.H. Auden (1907-1973)
Light breaks where no sun shines;
Where no sea runs, the waters of the heart
Push in their tides.
Dylan Thomas (1914-1953)
In our crowded hearts
Our steaming bathrooms, kitchens full of
Things to be done, the
Denise Levertov (1923-)
Megill, who graduated from Dartmouth College with the Class of 2000, received his degree with honors in classics. This article is adapted from his senior thesis, which won both the Classical Association of New England's undergraduate prize and the Bronze Chalice Award of AbleMedia's Web-based Classics Technology Center. It is published here with permission from AbleMedia.