Blood Circulation and De Motu Cordis, 1628

A model assembled from the works of the second-century physician Galen was highly influential in medieval and Renaissance learned medicine. In simplified form, it held that food was transformed into venous blood in the liver and distributed for nourishment. Some blood supposedly crossed unseen pores in the interventricular septum, mixed with inhaled pneuma or spirit on the left side, and entered the arterial system. “Spirit” here is a historical physiological category, not a modern substance. Galenic writing was extensive and later practice was diverse; it is misleading to make one scheme stand for all ancient medicine (Nutton, 2005).

In the 1240s, the Damascus-born physician Ibn al-Nafis, then working in Cairo, rejected a porous cardiac septum in his Commentary on Anatomy in Avicenna's Canon. He argued that blood from the right ventricle reached the left through the lungs and proposed small communications between the pulmonary vessels. This was a scholarly commentary within Arabic medicine, not an account of the complete systemic circuit. Its relevant manuscript passages became widely known to twentieth-century historians only after Muhyo al-Din al-Tatawi studied a Berlin manuscript in 1924. Similarity does not prove transmission: surviving evidence has not established that Harvey knew this work (West, 2008).

In Europe, Michael Servetus placed a pulmonary-transit account inside the theological Christianismi restitutio (1553), a work suppressed as heretical. Realdo Colombo presented pulmonary transit in the anatomical De re anatomica (1559), and Harvey acknowledged Colombo's view. These cases had different purposes and audiences, and priority between some sixteenth-century accounts remains debated. They explain part of the route through the lungs; they do not by themselves state Harvey's repeated circulation through the entire body (Boyle, 2013).

Venous valves also had a history before Harvey. Charles Estienne and other sixteenth-century anatomists described folds in veins before Harvey's Paduan teacher Girolamo Fabrici published the richly illustrated De venarum ostiolis (1603). Fabrici interpreted their purpose differently; Harvey made their orientation evidence for flow towards the heart. This is another reason to avoid awarding the valves themselves to one discoverer (Scultetus et al., 2001).

Harvey took his medical degree at Padua in 1602, after studying in an unusually prominent university culture of anatomy and natural philosophy. The city's anatomy theatre made dissection a formal teaching performance, while teachers such as Fabrici asked not only what structures looked like but what actions and purposes they served. Harvey returned to England, became physician to St Bartholomew's Hospital in 1609, and was appointed Lumleian lecturer at the College of Physicians in 1615. His surviving lecture notes begin in 1616; in the 1628 preface, he said that he had demonstrated the subject at the College for more than nine years (RCP Museum).

The printed argument proceeds through bodies and interventions. By observing animals whose hearts beat slowly, Harvey tried to establish that systole—contraction—expelled blood. Tying an artery on the side nearer the heart and tying a vein on the opposite side showed different patterns of swelling. On a person's forearm, a moderate ligature made veins and their valves visible; pressing blood along a vein demonstrated that the valves obstructed movement away from the heart. These were demonstrations for anatomists, not clinical tests for patients.

Harvey also reasoned from abundance. Even cautious assumptions about the amount expelled at each beat produced, after multiplication, more blood than continual manufacture from food could plausibly supply. The result made return and reuse necessary. Yet historians have challenged the tidy story that calculation—or Fabrici's valves—single-handedly triggered the discovery. Don Bates's close reading shows that Harvey's account emerged from a longer interaction of anatomical structure, observed cardiac action, vivisection, severed arteries, and reasoning about flow (Bates, 1992).

Much of this knowledge was materially obtained from dissected and living animals, alongside observations of human bodies and arms. Harvey worked centuries before modern systems of consent and animal-research oversight. Naming vivisection is important both because it supplied crucial evidence and because celebratory retellings can hide who or what was made available for anatomical knowledge. A digitized 1894 facsimile and translation lets readers inspect the argument, but its Victorian title and language are themselves later editorial framing (Harvey, 1628/1894).

Readers could dispute the motion of the heart, the quantity of blood, or the unseen passage from arteries to veins while accepting other parts of Harvey's case. Harvey's influential Parisian critic Jean Riolan did not merely choose “tradition” over “experiment”; he proposed modified forms of blood movement and pressed problems the 1628 book had not visually solved. Harvey answered him in two Latin exercises published at Cambridge in 1649. The exchange shows circulation being tested and revised within a European republic of letters, not accepted everywhere at once (NLM catalogue record).

Nor was Harvey simply a modern mechanist confronting ancient authority. His anatomy remained shaped by Aristotle, questions of purpose, learned textual argument, and the professional world of the College of Physicians. Supporters could accept circulation while explaining the heart differently. Roger French's intellectual history reconstructs those categories instead of treating De Motu Cordis as a modern laboratory report (French, 1994).

Harvey inferred that blood passed from the smallest arterial branches to veins, but he could not see the connection. In 1661, four years after Harvey's death, Marcello Malpighi published two letters to Giovanni Alfonso Borelli as De pulmonibus. With magnification and the thin, translucent lungs of frogs, Malpighi described a fine vascular network joining arterial and venous branches. The observation supplied important visible evidence for pulmonary microcirculation; it did not by itself explain oxygen exchange or every capillary bed (West, 2013; Malpighi, 1661).

Harvey's lasting contribution was to make circulation a coherent research framework: heart and vessels could be investigated through direction, sequence, obstruction, volume, and repeated motion. That framework proved portable across anatomy, natural philosophy, microscopy, and later work on injection and transfusion. Its clinical consequences accumulated over time rather than appearing fully formed in 1628.

The heroic phrase “discovery of the circulation” therefore needs care. Harvey supplied the most consequential early modern argument for the complete circuit, but he depended on inherited questions, Paduan training, previous descriptions of pulmonary transit and valves, animals and human bodies used as evidence, printers, readers, critics, and later microscopy. Recognizing that collective chronology does not diminish De Motu Cordis; it explains why the book changed physiology and why no single date contains the whole history.