Great discoveries bring lasting fame – if not always fortune. But in the days before patents or articles in learned journals established who did what first, credit didn’t always go to the right person. Before books beccame commonplace, new ideas travelled slowly. And those that did filter out were often ignored: in the great European medical schools, scholars clung to the teachings of classical authors for more than a thousand years, despite growing evidence that much of what they taught was nonsense. Some ideas flickered briefly and disappeared. Others were suppressed because they came from the wrong sort of person or the wrong part of the world.
The story of the “lesser circulation” – the passge of blood from the right side of the heart round the lungs and back to the heart’s left chamber – is a perfect example of discovery made several time over several centuries. So who really does deserve credit for being first?
IN THE early days of medicine, the heart was a bit of a puzzle. Blood clearly travelled from the right side to the left. But how did it do it? To us the answer is perfectly plain: it travels in a loop, via the lungs. Living after William Harvey, we know that blood circulates all the time.
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But at the dawn of medicine these things were far from obvious. Galen, the colossus of ancient medicine who lived in Rome in the 2nd century AD, envisaged the movement of the blood through the body in terms of a “tidal motion”, starting from the liver, where he believed it was made. Having no inkling of circulation-which Harvey didn’t describe until 1628-he proposed that blood passed directly from the right to the left chamber of the heart. He was anatomist enough to be aware of the solid septum that divides the two. To overcome that difficulty, he suggested that the blood “sweated” its way imperceptibly through the fleshy partition. As with everything else, what the great dictator of classical medicine said about the heart carried authority for centuries.
But Galen’s ideas didn’t wash with Andreas Vesalius, the great dissector of the Renaissance. In his book On the Fabric of the Human Body, published in 1543, Vesalius scoffed at the notion of a septum dotted with little perforations: “We are driven to wonder at the handiwork of the Almighty,” he mocked, “by means of which the blood sweats from the right into the left ventricle through passages which escape the human vision.” Then, 12 years later, he spelled out exactly why the septum couldn’t be full of holes.
This proved a turning point, for it led fellow anatomists such as the Italian Realdo Colombo to advance the idea of the “pulmonary” transit. Animal experiments taught Colombo that blood flowed from the right side of the heart through the lungs to the left. Blood was mixed with air not in the left ventricle, as Galen thought, but in the lungs, where it acquired the bright red hue of arterial blood. For Harvey, a couple of generations later, this “lesser” circulation served as confirmatory evidence for the “greater” circulation of the blood as a whole.
So, writing in the late 1550s, Colombo made the crucial breakthrough in our understanding of the circulation of the blood. Or did he? Unlikely though it might seem, a Spanish theologian, Michael Servetus, was a few years ahead of him.
Servetus initially studied medicine in Paris. Sickened by the corruption of the Church of Rome, however, he took a religious stand, denying the idea of the Holy Trinity and the divinity of Christ, earning the hatred of Catholics and Protestants alike. In 1553 he brought out his major work, the 700-page The Restoration of Christianity.
It was in that book, published anonymously six years before Colombo’s, that Servetus described the transport of the blood through the lungs-in the form of an unorthodox account of how the Holy Spirit entered man. The Bible taught that the blood was the seat of the soul and that the soul was breathed into man by God: so there had to be a contact point between air and blood. This meant that blood could not seep through the septum, insisted Servetus. Instead, he proposed a path from the right side of the heart to the left through the lungs. It was there, in the lungs, that blood mixed with the atmosphere-that is, the Holy Spirit.
Unlike Colombo’s ideas, however, Servetus’s views had no influence on the progress of anatomy-not least because almost all copies of his book were burnt at the stake, along with their author. In any case, nearly three hundred years before these Renaissance anatomists there lived the man who rightly deserves recognition as the discoverer of the lesser circulation. He is the 13th-century Arab physician “Ala” al-Din Ibn al-Nafis.
Born in 1200 and growing up in Damascus in Syria, Ibn al-Nafis studied medicine at the city’s famous Nuri hospital. Typically for an Islamic physician, his interests were wide, and embraced logic and theology. He also wrote numerous commentaries on the work of earlier physicians, including his illustrious predecessor Ibn Sina, known in Europe as Avicenna. It was in one of these commentaries that Ibn al-Nafis described the lesser circulation. Challenging Galen’s assertion that blood travelled through “invisible pores”, Ibn al-Nafis contended that no blood could possibly pass through the septum and must therefore pass through the lungs. He unequivocally proposed the pulmonary circuit, stating:
“When the blood in this cavity [the right] has become thin, it must be transferred into the left cavity, where the spirit is generated. But there is no passage between these two cavities, and the substance of the heart there seems impermeable . . . It must, therefore, be that when the blood has become thin, it is passed into the pulmonary artery to the lung, in order to be dispersed inside the substance of the lung, and to mix with the air. The finest parts of the blood are then strained, passing into the pulmonary vein reaching the left of the two cavities of the heart.”
Just how Ibn al-Nafis reached his conclusions remains uncertain, since Arab culture did not permit human dissection. In any case, his views passed into utter oblivion. His manuscript was forgotten and the work wasn’t published until the 20th century.
The crucial question is whether Servetus and Colombo knew of Ibn al-Nafis’s findings. Islamic scholars hold that Western anatomists had access to Ibn al-Nafis’s writings through translations of his manuscript circulating in Italy-and that the Europeans suppressed all mention of this borrowing so they could claim the credit for themselves. Western historians, predictably, counter that Servetus and Colombo made their discoveries independently. One Spanish scholar has even declared that Ibn al-Nafis never existed.
Where does the truth lie? It’s impossible to be sure. What can be said for certain is that for patients suffering cardiovascular diseases, the delay in the uptake of new ideas cannot have made one jot of difference to the treatment they received. Indeed, the new teachings, when they finally arrived, seem to have frightened patients off. “I have heard him say,” the gossipy biographer John Aubrey reported of William Harvey “that, when his book on blood circulation came out, his practice suffered and people called him mad”.