William Harvey and the Discovery of the Circulation of the Blood
2019; Lippincott Williams & Wilkins; Volume: 124; Issue: 9 Linguagem: Inglês
10.1161/circresaha.119.314977
ISSN1524-4571
Autores Tópico(s)Cardiovascular Health and Risk Factors
ResumoHomeCirculation ResearchVol. 124, No. 9William Harvey and the Discovery of the Circulation of the Blood Free AccessResearch ArticlePDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessResearch ArticlePDF/EPUBWilliam Harvey and the Discovery of the Circulation of the BloodPart II Roberto Bolli Roberto BolliRoberto Bolli Correspondence to Roberto Bolli, MD, Institute of Molecular Cardiology, University of Louisville, Louisville, KY 40292. Email E-mail Address: [email protected] From the Institute of Molecular Cardiology, University of Louisville, KY. Originally published25 Apr 2019https://doi.org/10.1161/CIRCRESAHA.119.314977Circulation Research. 2019;124:1300–1302These 3 articles on William Harvey (which are published in 3 consecutive issues of the journal) are an edited version of 3 President’s Letters that I wrote about 10 years ago for Heart News and Views, the news bulletin of the International Society for Heart Research (the source articles can be found in volume 17, numbers 1, 2, and 3, 2009–2010 of the newsletter). Three books have been used to provide specific information and quotes: Doctors:The Biography of Medicine, by Sherwin B. Nuland, Alfred A. Knopf, New York, 1988; The Personality of William Harvey, by Geoffrey Keynes, Cambridge University Press, 1949; and Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus by William Harvey, translated by Chauncey D. Leake, Charles C. Thomas, Springfield, IL, 1970.Herewith is the second part of my account of William Harvey’s life and work.Part III must admit that my interest in William Harvey stems in part from the fact that he was a scholar of classics. He was fluent in Greek and Latin. He studied classical literature and was a passionate reader of Greek and Roman authors. Both of his books, De Motu Cordis and De Generatione Animalium, were written in Latin. I love classics. I remember that the principal of my middle school used to say that the best engineers and scientists come from humanistic schools that emphasize classical subjects. He was absolutely right, because classical studies teach one how to think and how to express oneself.For all practical purposes, physiology was born in the 17th century, and Harvey was one of its fathers. Experimental medicine started with him. He was a revolutionary. He was the first scholar who dared question traditional beliefs about the heart and the circulation that dated back to Galen, 1500 years earlier. He rejected the common approach used at his time and throughout the Middle Ages, which was to rely blindly on Aristotle and Galen, accepting their theories without questions (principle of authority). This principle was summarized in the mantra “ipse dixit” (“he himself [Aristotle or Galen] said it”) (and so it must be true). Theories were accepted as valid just because Aristotle and Galen said so, not because they were verified empirically. Harvey, however, refused to believe uncritically what he was taught and insisted on relying not on the words of Galen, but on his own experimental observations, following his reason to its logical conclusions. This approach, which seems so obvious today, was truly revolutionary in the 17th century. Promoting critical thinking and experimental testing of ideas was, in my judgment, Harvey’s greatest contribution to science.In 1628, when Harvey published De Motu Cordis, the medical world was still under the pervasive (and nefarious) influence of Galen, who lived in the second century AD. It is both astounding and befuddling to realize that one man controlled medical knowledge for one-and-a-half millennia. Galen was the personal physician of the Emperor Marcus Aurelius and the most prolific writer of antiquity. He was to medicine what Ptolemy was to astronomy. His theories, which were widely accepted and taught in all universities as irrefutable truths up to the 17th century, postulated that blood was made in the liver from digested food. Blood—Galen said—leaked continuously from the liver, like water coming down from a fountain, and then went to the periphery through the veins and nourished all tissues. (So, according to Galen, blood flows in the veins centrifugally, not centripetally.) Galen also asserted that the tissues absorb and use all blood, so that the liver has to replenish it continuously; thus, there is no circulation, no recycling of blood. According to Galen, the function of the right heart is just to nourish the lungs; it is but a different kind of “vein.” Galen further asserted that some of the venous blood finds its way from the right to the left side of the interventricular septum, through what he called “pores” (these pores were never seen, but everybody believed for 1500 years that they existed because Galen had said so). Once the venous blood is in the left ventricle, Galen asserted, it mixes with the “pneuma,” a spiritual essence inhaled from the air in the lungs. The function of the lungs is to bring in the pneuma, which mixes with the blood and makes it become arterial; the blood is then warmed up by the innate heat of the heart, and this mixture is pushed into the arteries to the body. Again, as there is no recirculation, blood must be continually produced in the liver.To us, free thinkers of the 21st century, it is astounding that these extravagant ideas were not challenged for one-and-a-half millennia. It would have been easy to test them experimentally, but no one dreamed of doing that for 1500 years—a great demonstration of the power of the principle of authority, which was the mindset that dominated the Middle Ages.These ancient Galenic myths were demolished by Harvey in his book, De Motu Cordis (the full title of the book is Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus) [Anatomical Exercise About the Movement of the Heart and Blood in Animals]). This small (72 pages; 5×7 inches) monograph is one of the most important books ever written, possibly the most important book in the history of medicine (certainly, it is so for a cardiovascular scientist). It has changed the history of mankind. De Motu Cordis did for physiology what Vesalius’ “Fabrica” had done for anatomy in 1543—that is, it debunked Galenism. In De Motu Cordis, you can see the experimental spirit. You can see the beginning of a new way of looking at medicine, of using your own senses and experience and your own reason, rather than relying on the words of Galen or Aristotle. It was written in Latin, which at that time was the language of the erudite. It was published in Frankfurt, Germany, because Harvey hoped to avoid troubles at home by publishing his findings abroad. Figure 1 shows the cover of the original edition of De Motu Cordis. There are only very few original items left.Download figureDownload PowerPointFigure 1. Title page of the original edition of De Motu Cordis, 1628.In the first part of the book, Harvey studied the movement of the heart. He showed that the heart fills passively and contracts actively, and that during contraction, it expels blood. Then he showed that the expansion of the arteries (the pulse) is synchronous with, and is caused by, the contraction of the heart and by the force of the blood pushed by the heart. This seems quite obvious to us but was not understood until Harvey. Incredible though it may seem, for 1500 years, it was thought that the pulse is caused by active expansion of the arteries, or according to the Greeks, by expansion of the pneuma that Galen had postulated to be present in the arterial blood. So, Harvey’s observations were a breakthrough at the time. By dissecting animals (particularly reptiles, where the heart rate is very slow), Harvey also showed that the atria “arouse a somnolent heart.” He also pointed out that the pulmonic and aortic valves keep blood from going back into the right and left ventricle, respectively, and the mitral and tricuspid valves keep blood from going back into the atria. In defense of descriptive science, up to this point, all of Harvey’s discoveries were based on his dissections of animals and description of phenomena, not on real experiments. These were what nowadays we would call descriptive studies (had he submitted his findings to today’s top-tier journals, he probably would have had a tough time!)Harvey started doing experiments when he addressed the second part of the problem: how does blood go from the heart to the tissues and, then, how does it return to the heart? That’s when, for the first time, he used measurements—or quantitative evidence. The introduction of quantitative evidence in physiology was one of Harvey’s fundamental contributions to medicine. He was the first person to actually use measurements in studies of physiology. He asked himself: “If Galen is right—if the blood is being continuously made from food by the liver—how much blood does the liver need to make?” It is astounding that nobody actually thought to address this obvious question before. Because of his privileged position as the king’s personal physician, he was allowed to study the king’s deer. By looking at the hearts of animals, he estimated that each time the heart beats, it squeezes 2 ounces of blood during systole (not a bad estimate). Because the heart beats on average 72 times per minute, he calculated that 8640 ounces (or 540 pounds) of blood should be pumped per hour, which was 4 times the weight of an average human being at Harvey’s time (though only 3 times today, given the current epidemic of obesity). Obviously, it was impossible for the liver to make that much blood in 1 hour. These calculations led Harvey to refute the 1500-year-old Galenic idea that blood is continuously produced in the liver.He also showed that, in the veins, the blood travels centripetally. This is another thing that now seems so obvious; one cannot help but wonder why it took 1500 years to figure out that the blood in the veins flows toward the heart, not away from it as Galen had said. Harvey’s teacher, Fabricius, had described the presence of valves in the veins but had no idea what they were for. So Harvey did the obvious experiment (Figure 2). (He used muscular farm workers, who had big veins.) He put a tourniquet around the arm and tried to empty the veins with his finger. He noticed that the veins would always fill from the distal to the proximal part of the arm—not vice versa, indicating that blood flows from the hand toward the shoulder. When he did the same experiment in the neck, he noticed the opposite: the blood never went from the chest to the head but, rather, from the head to the chest. He thus concluded that the blood in the veins always flowed toward the heart (To be continued…).Download figureDownload PowerPointFigure 2. A figure from De Motu Cordis illustrating the method used by Harvey to determine the direction of blood flow in the veins of the forearm. At Harvey’s time, the Galenic theory that venous blood flows centrifugally (toward the periphery) was still predominant. By conducting the experiments illustrated in this figure (he studied farm workers because they had large veins), Harvey demonstrated that venous blood flows centripetally (toward the heart). The figure further shows how valves in the veins of a human arm allow the blood to flow towards the heart, but not away from it.DisclosuresNone.FootnotesThe opinions expressed in this article are not necessarily those of the editors or of the American Heart Association.Correspondence to Roberto Bolli, MD, Institute of Molecular Cardiology, University of Louisville, Louisville, KY 40292. Email [email protected]edu Previous Back to top Next FiguresReferencesRelatedDetailsCited By Doroudian M and Gailer J (2022) Integrative Metallomics Studies of Toxic Metal(loid) Substances at the Blood Plasma–Red Blood Cell–Organ/Tumor Nexus, Inorganics, 10.3390/inorganics10110200, 10:11, (200) Nóbrega C, Aires Pereira M, Coelho C, Brás I, Cristina Mega A, Santos C, Esteves F, Cruz R, I. Faustino-Rocha A, A. Oliveira P, Mesquita J and Vala H (2022) Virtual Physiology: A Tool for the 21st Century Updates on Veterinary Anatomy and Physiology, 10.5772/intechopen.99671 Mackie H, Suami H, Thompson B, Ngo Q, Heydon-White A, Blackwell R and Koelmeyer L (2022) Retrograde lymph flow in the lymphatic vessels in limb lymphedema, Journal of Vascular Surgery: Venous and Lymphatic Disorders, 10.1016/j.jvsv.2022.04.017, 10:5, (1101-1106), Online publication date: 1-Sep-2022. Ghosh S (2021) The evolution of epistemological methodologies in anatomy: From antiquity to modern times, The Anatomical Record, 10.1002/ar.24781, 305:4, (803-817), Online publication date: 1-Apr-2022. Shabtai R (2022) Jewish Perspectives on Death by Neurologic Criteria Death Determination by Neurologic Criteria, 10.1007/978-3-031-15947-3_27, (381-393), . Hrčková G (2021) Rare diseases and the Orphanet, Neurologie pro praxi, 10.36290/neu.2021.029, 22:2, (93-99), Online publication date: 30-Apr-2021. Wright M, Okeagu C, Broussard A, Delaune K, Patel S, Cornett E and Kaye A (2021) Prehospital Transfusions by First Providers Essentials of Blood Product Management in Anesthesia Practice, 10.1007/978-3-030-59295-0_36, (357-368), . Recio-Mayoral A (2019) Disfunción ventricular derecha: ¿qué opciones tenemos?, Revista Española de Cardiología Suplementos, 10.1016/S1131-3587(20)30009-1, 18, (46-54), . April 26, 2019Vol 124, Issue 9 Advertisement Article InformationMetrics © 2019 American Heart Association, Inc.https://doi.org/10.1161/CIRCRESAHA.119.314977PMID: 31021729 Originally publishedApril 25, 2019 Keywordsbiomedical researchcirculationinventorspersonalitybiologyPDF download Advertisement SubjectsBasic Science ResearchHemodynamicsPathophysiology
Referência(s)