Adam Smith - William Harvey’s Methodological Legacy

Adam Smith STS.002, Fall 2004, Professor David Kaiser Paper 3 William Harvey’s Methodological Legacy “I profess to learn and teach anatomy not from books but from dissections, not from the tenets of Philosophers but from the fabric of Nature.” - William Harvey1

The mainstream use of the experimental method in biology, brought about by William Harvey, marked the beginning of modern medicine and biology. This paper discusses the events surrounding William Harvey’s contribution, and attempts to distill a summary of the current beliefs held by most historians. I do not claim to have a new discovery to share with historians. Instead, I will attempt to bring clarity to the reader amongst the many disparate writings which can be hard to piece together without a sharp eye and extensive reading. Unfortunately, to summarize a large body of knowledge, some of the details must be left out. This is the problem that faces all historians; Steven Shapin states in his The Scientific Revolution, “selection is a necessary feature of any historical story, and there can be no such thing as definitive or exhaustive history.”2 Thus, this paper leaves out some historical information. I hope to provide the information necessary to obtain a firm understanding of this important historical event, and I also hope that the interested reader will find the bibliography sufficient to investigate further. If there is a bias in this paper, it is towards the methodology side of

William Harvey, The Circulation of the Blood, and other Writings, translated by Kenneth J. Franklin (London: J. M. Dent, 1990 [1649]), 6. 2 Steven Shapin, The Scientific Revolution (Chicago: University of Chicago Press, 1996). 1

the story. Although we will discuss, specifically, the discovery of the circulation of blood in the body, most of that discussion will be given to set up the scene for highlighting the general methodologies. This paper unfolds in roughly chronological order. First, we will consider the methodologies in use before William Harvey’s works. Next, we will consider Harvey’s works, beginning with his specific discoveries, then generalizing about his methodology and evaluating his predecessors’ impact on his works. We will conclude with a discussion of how he impacted the future of modern science, and we will find that he spearheaded the widespread use of experimental methods in biology.

Methodology before Harvey Though Aristotle used his mind to reason about the world, his reasoning did not lack real-world observations. He did not put himself in a dark room, disconnect his senses from the world, and then ponder about logic. Certainly he did think about logic as abstracted from the wider world (e.g. syllogisms), but that was not the totality of his studies. The observations he used can be called experiences; they are what every person living at the time might agree to be true. Shapin states: “Take, for example, the experience – cited by Aristotle and his followers as evidence that the earth did not move – that an arrow shot straight up in the air landed about where it started. Or take the experience that heavy bodies fall, or that the sun sets in the west.”3

This is an important point, worth repeating. Aristotle used observations from the world. However his observations were restricted to passive, every day experiences; he did not perform experiments, which can be defined as actively manipulating nature in an 3

Shapin, Revolution, pp. 81

attempt to glean information. Bayon agrees, and describes how experiences were turned into conclusions: “the ancient sages learnt and then speculated ‘why’ things happened, relying on existing lore, for which purpose they employed an intellectual method whose use is not yet superfluous: Logic.”4 In today’s modern world, scientists also use experience and logic to reason about things; these methods are not flawed. Instead, these methods were simply not the limit of human capabilities. Aristotle did not utilize experimentation. We will see how Harvey brought about the widespread use of experimentation in biology, but he was not the first person to employ the method. Although Galen performed dissections and other forms of experimentation, his conclusions were sometimes correct and other times incorrect. As Bayon states, Galen’s experimental methodology might not have caught on because of his interpretational errors. “It remains unclear why experimentation was neglected during so many centuries; even after that Galen had shown the way in several sound tests, some of them in relation to the flow of the blood; though it must be admitted that in these his interpretation was erroneous and performance must have been faulty.”5

For whatever reason, scientists after Galen did not begin to employ experiments. Even famous scientists around Harvey’s time did not perform active experiments, even though the method was gaining attention, such as Bacon. “Francis Bacon (1561 – 1629) who pleaded so engagingly for the merits of ‘Experiments of Light’ had no conception how to carry out any demonstrative test.”6

H. P. Bayon, “The Significance of the Demonstration of the Harveyan Circulation by Experimental Tests,” Isis 33 (Dec., 1941): 452. 5 Bayon, “Significance,” 450. 6 Bayon, “Significance,” 450. 4

Certainly the experimental approach, as an improvement over the experience observation approach, was brewing. However it did not come to fruition until William Harvey’s works, as we will now discuss.

Harvey’s Discoveries and Methods Harvey makes many contributions to the study of circulation and respiration in his work The Circulation of the Blood.7 He discusses pulmonary circulation, proves that veins and arteries only carry blood, and debunks the notion of transport of blood between the heart’s ventricles. Most importantly, however, he discovers that blood circulates around the body and through the heart, opposing the previously held notion that blood is transmitted from the heart to tissues in the body, where it is absorbed. For clarity and succinctness our discussion of Harvey’s discoveries and methods will focus on the circulation of the blood. 8 The opening paragraph to the section on circulation communicates the magnitude of the jump in scientific knowledge that Harvey is making. “The remaining matters,” Harvey states, “are so novel and hitherto unmentioned that, in speaking of them, I not only fear that I may suffer from the ill-will of a few, but dread lest all men turn against me.”9 Harvey then proceeds to set up his argument. He first lays out three pieces of experimental observations as his evidence:

Harvey, Circulation Circulation of the blood can refer to two different concepts. The physical circulation of blood in the body refers to the cycling nature of the physical liquid. The chemical circulation refers to the cyclic oxygenation of the blood in the lungs and de-oxygenation at the tissues. Harvey was concerned with the former. 9 Harvey, Circulation, pp. 45. 7 8

1.

He observes “the symmetry and size of the ventricles of the heart and of the vessels which enter and leave them (since Nature, who does nothing in vain, would not purposelessly have given these vessels such relatively large size).”10

2.

Furthermore, he points out “the elegant and carefully contrived valves and fibres and other structural artistry of the heart.”11

3.

Finally, he notices “the amount, i.e. of transmitted blood, and the very short time it took for its transfer, and I also noticed that the juice of the ingested food could not supply this amount without our having the veins.”12 When he states that the blood takes a short time to transfer to the parts of the body, he is implicitly deducing its high speed and thus its large volume of flux through the heart.

With these pieces of evidence in mind, he deduces his conclusion that blood must move around the body in a circular way: “I then began to wonder whether it had a movement, as it were, in a circle.”13 Bayon re-states Harvey’s reasoning succinctly: “Harvey enforced his reasoning most acutely by calculating the amount of blood that would pass through the heart in an hour; thus obtaining the conviction that, since the blood could only flow in one direction – on account of the valves – it must necessarily retrace its course, because such a large quantity could not possibly disappear into the tissues.”14

Harvey’s discovery is well accepted and widely celebrated. One author boasts of Harvey, “if you desire to follow the bloud all along every steppe, in its progress from the

Harvey, Circulation, pp. 45. Harvey, Circulation, pp. 45. 12 Harvey, Circulation, pp. 45. 13 Harvey, Circulation, pp. 46 14 Bayon, “Significance,” 444. 10 11

hart round about the body, till it return backe againe to its center, Doctory Haruey who most acutely teacheth this doctrine must be your guide.”15 One modern historian concludes that if Harvey never existed, then his discoveries would have still been made within another fifty years.16 The acceptance of Harvey’s methodology had more important implications for biology and all of science. His method of gleaning evidence from experiments and employing logic to manipulate that evidence into valuable conclusions was of utmost importance. Harvey showcases his experimental method in his writing, saying “I thought particularly long and hard about the results of my experimental animal dissections and opening the veins, an enquiry that took various forms.”17 Bayon discusses the implications of Harvey’s method: “Because Harvey’s De motu cordis was the first published record of the solution of a biological problem by demonstrative tests, it […] announced the beginning of the development of medicine from a period of philosophical speculation to one of clinical observation, anatomical investigation, and application of biological experimentation”18

Harvey’s discovery was the origin of the revolution in biology; his thought process marked a huge leap in scientific capabilities. We will discuss the implications and lasting effects in the last section of this paper.

Harvey’s Predecessors Harvey had an explicit strategy for learning from those who came before him. He used his predecessors’ conclusions as starting points for his studies, and then used his experimental method to confirm or correct those conclusions. He explains this in the first Sir Kenelm Digby, Two Treatises, (Paris: G. Blaizot, 1644), 238. George Kimball Plochmann, “William Harvey and His Methods,” Studies in the Renaissance 10 (1963): 192-196. 17 Harvey, Circulation, pp. 45. 18 Bayon, “Significance,” 449. 15 16

paragraph of his introduction: “It profits one […] to read what his predecessors have written […]. For by so doing he can confirm their correct statements, and through anatomical dissection, manifold experiments, and persistent careful observation emend their wrong ones.”19 This approach closely resembles the scientific processes employed today for evolving knowledge. Historians widely hold three people as Harvey’s main influences: Aristotle, Galen, and Realdo Colombo. We will discuss each of these people and their influence on Harvey. Walter Pagel claims that “Harvey […] was a staunch Aristotelian.”20 Indeed, Harvey says in another one of his works that “The authority of Aristotle has always [held] such weight with me that I never think of differing from him inconsiderately.”21 These statements are coincident with Harvey’s stated high level strategy; he employs Aristotle when it is not contradicted by experimentation. Recall, from above, that Aristotle used experience observations and logic to reach conclusions. Harvey’s approach, then, accepts these experience observations and their logical conclusions except when more active tests or experiments contradict them.22 Harvey also looks to Aristotle’s works for inspiration. After devising the circulation of the blood, he makes an analogy: “We have as much right to call this movement of the blood circular as Aristotle had to say that the air and rain emulate the circular movement of the heavenly bodies.”23

Harvey, Circulation, pp. 7. Walter Pagel, “William Harvey and the Purpose of Circulation,” Isis 42 (Apr., 1951): 28. 21 William Harvey, On Generation, translated by Robert Willis (New York: Johnson Reprint, 1965 [1651]), pp. 87. 22 An example of a contradiction, and Harvey’s subsequent disagreement with Aristotle, is given in Harvey, Circulation, pp. 47. 23 Harvey, Circulation, pp. 46. 19 20

There is more disagreement about Galen’s role in influencing Harvey. As discussed earlier, many of Galen’s conclusions were wrong. Some historians claim that Galen’s errors slowed the discovery of truth,24 while other historians assert that Galen aided Harvey’s studies.25 Both groups are correct. If Galen had not made the errors he did, then he would have seen that the veins and arteries carry only blood26 and might have also discovered the circulatory system. However, the correct discoveries that Galen made, namely the one-way valves that we will discuss shortly, were important to Harvey’s reasoning. So, while Galen made mistakes that set back biology, he also made contributions that helped. When asked what brought him to hypothesize about circulation, Harvey said the valves restricting the flow of blood to one direction were the catalyst. Robert Boyle recalls this: “And I remember, that when I asked our famous Harvey … what were the things, that induced him to think of a circulation of the blood? he answered me, that when he took notice, that the valves in the veins of so many parts of the body were so placed, that they gave free passage to the blood towards the heart, but opposed the passage of venal blood the contrary way; …[the blood] should be sent through the arteries, and return through the veins, whose valves did not oppose its course that way.”27

Galen discovered the valves that Harvey mentions. Therefore, Fleming concludes, “The real tribute paid by Harvey to Galen would then consist in acknowledgement that Galen by his description of the cardiac valves […] had afforded conclusive evidence of such a circulation for those who cared to see.”28 Fleming then Plochmann takes up this perspective in Plochmann, “Methods,” 194-200. Fleming adopts this perspective, and fervently defends it throughout Donald Fleming, “William Harvey and the Pulmonary Circulation,” Isis 46 (Dec., 1955): 319-327. 26 Bayon, “Significance,” 450. 27 Robert Boyle, A Disquisition about the Final Causes of Natural Things, in Works, ed. Thomas Circh, 2nd ed. (London: 1772), vol. 5, 427. 28 Fleming, “Pulmonary Circulation,” 321-322. 24 25

defends Galen’s mistakes, claiming that they did not hurt Harvey’s progress. “Galen’s conception of what happened to the blood in the heart and lungs did not obstruct Harvey’s work.”29 This latter statement is true; Harvey’s work did come to be, and was therefore not obstructed. However, Galen’s errors probably slowed Harvey’s progress, and might have prevented further discoveries aside from the circulation. In the end it is impossible to determine what would have happened if Galen’s work had been any more right or any more wrong than it was; these points are all speculation. What is not speculation, however, is that Harvey used some of Galen’s conclusions to make new discoveries. In this way, Galen helped Harvey in at least one instance. It is fruitful to consider the impacts that Aristotle and Galen had on Harvey, relative to one-another. As described above, Harvey inherited from Aristotle a tradition of logical thinking and experience observation. Harvey gained an example of experimentation from Galen, albeit many of Galen’s conclusions were wrong. These two sets of lessons learned are orthogonal, and came together nicely for Harvey to form a very solid base of knowledge and methods to work from. Plochmann expresses this, and attributes the greater contribution to Aristotle. He says, “Harvey’s debts to Galen and to men of the Renaissance in matters of observation were no doubt greater, indeed could hardly help being so; yet the treasure he lifted from Aristotelian methodology was incomparably more important to the success of his inquiry and his demonstration”30

Although Plochmann seems convicted that Aristotle’s contributions to Harvey’s success were greater than those of Galen, once again it is an impossible point to settle. 29 30

Fleming, “Pulmonary Circulation,” 322. Plochmann, “Methods,” 193.

Even if Harvey offered a first-hand opinion on this (he does not), Harvey could be wrong. For a more elaborated discussion of both sides of the debate, see Plochmann24 and Fleming25. Realdo Colombo was one of Harvey’s contemporaries. Colombo studied under Vesalius, even though Bayon characterizes Colombo as “a vain boaster, addicted to plagiarism, and he quarreled with Vesalius.”31 Nevertheless, Colombo had significant achievements. According to Bayon: “[Colombo] was the first to combine the results of clinical observation, anatomical dissections, and experimental tests on dogs, so as to deduce a correct interpretation of the heart-through-the lung-to-heart circuit. […] For this reason Colombo may be considered a true precursor of Harvey.”32

Harvey, as with Aristotle and Galen, evaluated Colombo’s studies and absorbed what he could from them. Harvey highlights errors made in some of Colombo’s conclusions,33 but also acknowledges Colombo’s correct ideas.34 There were others who claimed to have discovered circulation before Harvey, but all of these have been adequately disputed.35 In conclusion of this section, Harvey draws from the works of many scientists who preceded him. However, he only uses those works as starting points in his studies; he used experiments to arrive at his ultimate conclusions. Thus, standing on the shoulders of those giants gave him an enormous head start, but his methodology allowed him to rely on the right conclusions and make progress in the right direction.

Bayon, “Significance,” 446. Bayon, “Significance,” 446. 33 Harvey, Circulation, pp. 9. 34 Harvey, Circulation, pp. 12. 35 For more discussion on these cases, see Bayon, “Significance,” 446-448. 31 32

Harvey’s Legacy - Scientific Effects Contrary to what we might have hoped for, Harvey’s methodology of combined experimentation and logical argumentation did not spread immediately to other scientists. Initial results were mixed. Bayon highlights how two scientists responded to Harvey’s work differently. “Digby repeated some of Harvey’s tests with excised hearts and did obtain a clear conception of the circulation,” Bayon explains, “while Descartes in his Discours (1637) approved without really comprehending.”36 During the state of transition that follow Harvey’s work, the scientists who had an open mind tended to catch on to the methodology and its power quickly. Inversely, some scientists did not pay attention, did not agree, or agreed but did not change. Sarton relates this well: “Not only did the new method open the path to untold and unimaginable discoveries, but it put an end to unprofitable quests and idle discussions; it broke the vicious circles wherein philosophers had been obstinately turning for more than a thousand years. It was simple enough in itself, but could not be understood as long as a series of intellectual prejudices obscured man’s vision.”37

Those who did adopt the new methodology, however, found it rewarding. The next major achievement in the study of the circulatory system was the discovery that blood undergoes a change while passing through the lungs. This discovery was fueled directly by Harvey’s experimental approach. Its originator described, “When venous blood is received into a vessel, the surface and uppermost part of it takes on this scarlet colour through exposure to the air.”38

Bayon, “Significance,” 451. George Sarton, The History of Science and the New Humanism (Cambridge: Harvard University Press, 1937), 101. 38 Richard Lower, Tractatus de corde item de motu et colore sanguinis et chili in eum transitu, translated by Kenneth J. Franklin (Oxford: R. T. Gunther, 1935 [1669]). Vol 11, 168. 36 37

In the long term, Harvey’s method did become wide-spread in the study of biology. Walter Pagel summarizes, “the scientific demonstration of blood circulation by Harvey between 1615 and 1619 marks the foundation of modern scientific medicine.”39

Conclusion We have described the scientific methodologies used before William Harvey’s time, Harvey’s discoveries, the methodology he used to make those discoveries, the people he inherited wisdom from, and his scientific legacy in biology. It was found that Harvey was the first person to use experimental and logical methods to correctly induce a significant discovery in biology. Furthermore, it was found that the method he used was slowly adopted and is now widely used in medicine and biology.

Bibliography Bayon, H. P., 1941. “The Significance of the Demonstration of the Harveyan Circulation by Experimental Tests.” Isis 33: 3-15, 45-47. Boyle, Robert. 1772. A Disquisition about the Final Causes of Natural Things. In Works, ed. Thomas Circh, 2nd ed. London: 1772. Digby, Sir Kenelm. 1644. Two Treatises. Paris: G. Blaizot. Fleming, Donald. 1955. “William Harvey and the Pulmonary Circulation.” Isis 46: 319327. Harvey, William. Translated by Robert Willis. 1965 [1651]. On Generation. New York: Johnson Reprint. Harvey, William. Translated by Kenneth J. Franklin. 1990 [1649]. The Circulation of the Blood, and other Writings. London: J. M. Dent. Lower, Richard. Translated by Kenneth J. Franklin. 1935 [1669]. Tractatus de corde item de motu et colore sanguinis et chili in eum transitu. Oxford: R. T. Gunther. Pagel, Walter. 1951. “William Harvey and the Purpose of Circulation.” Isis 42: 22-38. Plochmann, George Kimball. 1963. “William Harvey and His Methods.” Studies in the Renaissance 10: 192-210. Sarton, George. 1937. The History of Science and the New Humanism. Cambridge: Harvard University Press. 39

Pagel, “Purpose of Circulation,” 22.

Shapin, Steven. 1996. The Scientific Revolution. Chicago: University of Chicago Press.