Thorax: first published as 10.1136/thx.33.5.555 on 1 October 1978. Downloaded from Thorax, 1978, 33, 555-564 The thorax in history 5 Discovery of the pulmonary transit R K FRENCH From the Wellcome Unit for the History of Medicine, University of Cambridge The discovery that blood passes from the heart to in the belief that the Arabs had merely corrupted the lungs and from the lungs back again to the the true spirit of Greek medicine. Moreover, the heart was the first major development in physi- Arabic texts in Latin guise contained ugly, barbaric ology since the early days of the Alexandrian words that did not decline properly and which school more than a thousand years before. It obscured the meaning of the purer Greek. followed shortly after the rediscovery of the The dispute about where to let blood was not ancient writings, particularly those of Galen and merely an academic one, for it had immediate Aristotle. The scholarly evaluation of these texts practical significance. The humanists found that showed that on certain fundamental issues, in our the Greek texts of Hippocrates and Galen in- case the structure and function of the heart and structed the physician to let blood from a vein on lungs, Aristotle's opinion could not be reconciled the same side of the body as the diseased part, with that of Galen. The same texts provided a while the traditionalists believed the vein should model of scientific procedure including a con- be on the opposite side. Everyone agreed in general sidered evaluation of scientific "fact" derived from that blood was one of the four cardinal humours, historical sources. Finally, medieval human dis- and that disease was dyscrasia, or unequal mixture section provided the means whereby this scientific of humours; but when the disease was localised in method could be put into practice and used to the body it was obviously of great importance to http://thorax.bmj.com/ discover which, if any, of the ancient writers had know from where the physician was subtracting been right in their descriptions of anatomy and blood. The difference between "revulsive" (distant physiology. Broadly, the natural philosophers fol- from the disorder) and "derivative" (close) bleed- lowed Aristotle, and the medical men accepted ing was exactly this-that is, the traditionalists and Galen; everyone tried to follow Hippocrates, and the humanists had to employ exactly opposite tech- the occasional zealot like Vesalius attempted to niques to achieve the same end. The dispute waged restore anatomy to its pristine Alexandrian glory, furiously in the earlier middle years of the six- had been corrupted by described some whence, he claimed, it teenth century, and although by on October 1, 2021 by guest. Protected copyright. Galen's dissections of apes. historians' as futile, it was an essential component of medical thinking of the time and in fact Where to let blood? prompted medical progress. The story was rehearsed in antiquity, in Galen's commentary on The comparatively rapid arrival of renaissance the Hippocratic Regimen in Acute Diseases,2 where medical humanism at universities like Paris (where the Hippocratic author is discussing letting blood Vesalius spent some three years) sharpened the from the arm for pains of the thorax. Galen had distinctions mentioned above and added another: much more anatomical knowledge than the Hippo- that between traditionalists and moderns. "Tradi- cratic writer, and Galen felt it his duty to put the tionalist" now meant someone who admitted any advice of the revered "Hippocrates" on a sound value to the medieval and in particular the Arabic rational basis by explaining the underlying anat- medical texts. Barengario da Carpi was such a man, omy. This meant giving a description of the who accepted, read, carefully considered, and azygos vein, literally the single, or asymmetrical pronounced judgement on almost every anatomical vein, and the Galenic rationale behind the Hippo- text that was available, whether Arabic, Greek, or cratic treatment was that the azygos, serving the Latin in origin. The medical humanists of the six- lower eight ribs, joins the vena cava close to where teenth century, a generation younger than da the vena cava itself joins the heart, and not far Carpi, preferred to forget about the Arabic texts from the junction of the vena cava with the sub- 555 Thorax: first published as 10.1136/thx.33.5.555 on 1 October 1978. Downloaded from 556 R K French clavian veins.3 Bearing in mind that the direction therapeutic technique. Vesalius found himself at of venous bloodflow in Galenic physiology was odds with Galen on various aspects of the question, centrifugal, we can see that letting blood from the and published his ideas in 1539 in the "Venesection vena basilica, cephalica, or communis, branches of letter"8 (see fig 1). Vesalius's later criticism of what we call the subclavian vein, could be said to Galen was central to the anatomical revolution of have some effect on the veins serving the ribs, the the sixteenth century, and it has been said that site of the pain. "The emancipation of Vesalius begins with the The medical writers of the renaissance were in venesection letter."9 a position similar to that of Galen, inheriting a time-honoured therapeutic device from a respected teacher of antiquity, and anxious to put it on a "rational"-that is, modern-basis. Both Massa and Vesalius were aware of Galen's commentary on the Hippocratic text. It had been clear to anat- omists like Barengario da Carpi that observation of the dissected body was the final arbiter between the conflicting accounts of the ancients, and the prin- ciple was much more readily applicable to the dis- putes between modern medical men. Would not all the difficulties of the modern physicians disappear, asked Niccolo Massa, if only they would devote themselves to the anatomia sensata of the veins? "To the anatomy of which, God willing, I intended to devote a separate book".4 In fact Massa's anat- omia sensata of the azygos was less than successful; disagreeing both with modern anatomy and with Galen he said that it arises from the vena cava at some distance from the heart (perhaps the result of his dissecting a dog)5 and that it served the lower ten ribs. He actually described the vein as http://thorax.bmj.com/ double, and so was either confused by the hemi- azygos or by the paired azygos of the pig. Never- theless, Massa's purpose in investigating the structure of the vein was to give a structural basis for the practice of phlebotomy, and he was led by close scrutiny of the (animal) body into disagreeing with Galen, an attitude that by now was essential to anatomical progress. on October 1, 2021 by guest. Protected copyright. Massa's book was published in 1536, and practi- cally his only predecessor as a critic of Galen was Fig 1 Vesalius's drawing of the vena azygos, from Barengario da Carpi. Three years later Vesalius the venesection letter. was teaching anatomy at Padua. He too had strong ideas about the correct way to let blood, and the Nevertheless Vesalius was far from freeing him- anatomical reasons behind it, and his reaction to self from Galenic doctrine when he published the the dispute between the traditionalists and the venesection letter and the Tabulae. His drawing of humanists was to take up his chalk or charcoal the aortic arch is almost certainly a reconstruction while teaching6 and sketch out the course of the in pictorial form of Galen's words in his short veins, including the azygos. (His physiology re- guide to the anatomy of the blood vessels,10 a book mained Galenic7 and so the azygos was important Vesalius was probably already preparing for the in bloodletting). These sketches proved to be Junta edition of the collected works of Galen of popular, and a set of them illustrating the systems 1541-2. Consequently Vesalius illustrates only of the body was published as the Tabulae Sex. The two branches from the aorta, the left subclavian importance of the development of the graphic artery and a common trunk giving rise to the in- method in anatomical progress can hardly be nominate and the right subclavian. Contemporary overemphasised, and again we see that the spur to anatomists-da Carpi, Estienne, and Dryander- progress was the contemporary dispute over a depended instead on Galen's De Usu Partium and Thorax: first published as 10.1136/thx.33.5.555 on 1 October 1978. Downloaded from The thorax in history S Discovery of the pulmonary transit 557 so drew a single common trunk arising from the the heart. In fact the function of these valves was aorta and branching to form the other arteries. taken to be to slow down the centrifugal flow of This description was probably derived from un- venous blood. In a sense discussion about the gulates; Galen refers simply to "animals." In the valves in the veins was the most important step to short guide to the anatomy of the blood vessels he the discovery of the circulation of the blood. gives us simian or perhaps feline anatomy, and During the sixteenth and early seventeenth cen- features from these three groups of animals turn turies these structures were investigated by dis- up again in Vesalius's account of the heart and its section as anatomical novelties, and their function veins. debated. The terminology did not become fixed until the early seventeenth century, after a search The valves of the veins through the anatomical literature and a review of similar structures elsewhere had suggested valva We have seen, then, that because of its importance or valvula on the basis of an analogy with sluice in bleeding for disorders of the thorax like and lock-gates.