Harvey??™s Circulation of Blood
Before the seventeenth century, scientific concepts were mostly based on ancient philosophical and theological explanations (Lubitz SA.). By the early 17th century, with the invention of different kinds of new devices, experimental and observational methods had been used to turn most of the traditional theoretical concepts upside down.
One of the most astonishing announcements was made by Johannes Kepler. He described planetary orbits as elliptically revolving around the Sun at one focus, which was in conflict to the wide-spread Platonic idea of circular motion. Kepler worked as Tycho Brahe??™s assistant in order to assess the accuracy of Brahe??™s data in his observations, which were collected over a period of some 25 years. However, Brahe kept his original data from Kepler. Until after Brahe died, Kepler immediately took the data from Brahe??™s property in secret in order to perform calculations to establish his theories based on Brahe??™s data (Steven C. Frautschi).
Kepler was assigned to establish the orbit of Mars. He was one of Copernicus??™ proponents and originally believed in that planets were moving around the sun in perfect circular motion (Brian S. Baigrie). Brahe??™s data allowed Kepler to determine twelve points on the orbit of Mars. However, these points didn??™t perfectly fit into a circular motion for Mars (Steven C. Frautschi). Instead, Kepler made a model with elliptical orbit for Mars combining Brahe??™s data and his mathematical method. The data fitted quite well into the model (Steven C. Frautschi). Kepler was then forced to accept the fact that the planets were orbiting in an elliptical shape. From Kepler, in his astronomical book of ???Astronomia Nova???: “I was almost driven to madness in considering and calculating the matter. I could not find out why the planet (Mars) would rather go on an elliptical orbit…. With reasoning derived from physical principles agreeing with experience, there is no figure left for the orbit of the planet except for a perfect ellipse…. The truth of Nature, which I had rejected and chased away, returned by stealth through the back door, disguising itself to be accepted….I thought and searched, until I went nearly mad, for a reason why the planet preferred an elliptical orbit.”. Kepler had chosen the side of experimentation, and broke down the traditional thought of the circular motion of the planets (Steven C. Frautschi). Even though he could not visually inspect the elliptical orbit of Mars, his mathematical model was quite convincing.
Experimentation has become a legitimate component of scientific investigation. Analogical to Kepler, William Harvey was another great revolutionary scientist who turned the long-lasting traditional theories upside-down. Harvey??™s reported work was based on purely on his experiments and observation, which he thought was the only correct way to draw correct conclusions (Lubitz SA.).
William Harvey (1st April 1578 ??“ 3rd June 1657) announced a concept on the circulation of blood inside the body in his work Exercitatio anatomica de motu cordis et sanguinis in animalibus (1628: Anatomical Treatise on the Movement of the Heart and Blood in Animals) (Brian S. Baigrie). He was considered as the first person who correctly described the systemic circulation and properties of blood in the circulation system (W1).
There were several scientists who have ventured into the work of the circulation of blood before Harvey??™s discoveries. Some of these scientists were Ibn al-Nafis, Renaldus Columbus, Michael Servetus and Andrea Cesalpino (W1). Renaldus Columbus??™ discovery of pulmonary circuit paved a way for Harvey??™s theory of circulation a few years later. Colombo found that only blood, and not air, travelled in the pulmonary vein in his experiment of vivisections of dogs and other animals (W1). In Colombo??™s model, venous blood travelled from the heart to the lungs where it was mixed with air and then returned to the heart, which was an important idea for supporting Harvey??™s third theory of the circulation of the blood (W1). Hieronymus Fabricius (1537-1619) was one of the influential figures is Harvey??™s career (Lubitz SA). William Harvey was one of Fabricius??™ students in his anatomy class. Fabricius was the first person to describe the valves in the interior of the veins (John Ridington Young). Fabricius described the functions of these valves were to allow the blood evenly distribute to the various parts of the body; also, the valves can reinforce the wall of the veins and prevent the stretching of the blood vessels (W3). Fabricius reported his observations in the treatise De venarum ostiolis (On the Valves in the Veins) in 1574 (W3). Later, this treatise was studied by Harvey which started his work on the circulation of blood (W3).
Long before the appearance of Harvey??™s theory, Galenic theory of blood had been considered as the authorized anatomical knowledge. And his theory has been chosen as basic educational material in schools (Lubitz SA).
Claudius Galenus (c.129 ??“ c.199), was a prominent Roman physician, surgeon and philosopher. Galen??™s contributed to numerous scientific disciplines including anatomy, pathology, physiology, pharmacology, neurology, philosophy, logic, and so on (Baigrie??™s Note). Galenus was well known as ???the Founder of anatomy??? from his great contribution on anatomy (Baigrie??™s Note). Galen acquired most of his knowledge on anatomy through dissecting animals (Baigrie??™s Note). During his period in Rome, it was forbidden to dissect a human body (Lubitz SA). He constructed a tripartite system that accounted for the circulation system in animals. The liver, heart, and brain each inject into the body three different spirits ??“ natural, vital, and animal, which travel through the body via the venous, arterial, and nervous channels respectively (Baigrie??™s note). In Galen??™s point of view, blood was made in the liver and used food as ingredients. The blood is then used by the blood by travelling around the body (Brian S. Baigrie). This conventional belief lasted more than 1400 years (Jackie DiGiovanni). Some of the blood passed along the vena cava to the right side of the heart and to the left side of the heart directly. Galen??™s theory of blood included (Baigrie??™s note):
1. The septum of the heart is pervious and allows blood to pass from the right to the left side.
2. The heart is not a pump but expands simply due to expansion of the spirits that it contains. The only dynamic effect of the heart is sucking in the blood during systole or the contraction of heart.
3. One kind of blood flowed from the liver to the right ventricle of the heart and from there to the lungs and to the general system by the veins; and another kind of blood flowed from the left ventricle to the lungs and to the general system by the arteries.
Harvey made a simple calculation based on the assumption that the liver produced blood without circulating back. He found that the liver needed to produce large amounts of blood every day in order for the body to function (Baigrie??™s Note). Harvey then started an idea of the circulation of blood to replace the conventional thought which liver was a production factory of blood. He performed experiments on animals and the bodies of executed criminals ( Lubitz SA). He found out that the heart acted as a pump that pushed the blood throughout the body (Brian S. Baigrie). He also saw that the valves in the veins, which were discovered by Fabrici, helped the push the blood in one direction but not going back (Lubitz SA). For instance, Harvey performed experiments showing that the blood in the veins in the arm and lower parts of the body preferred go upward; and the blood in the neck preferred to down toward the direction of heart (W1). Harvey??™s arterial and venous system precisely stated that the heart pumped the blood into the arteries, which would pass into the veins back to the heart, but not the other way around (Baigrie??™s Note). This can be easily proven by the experiments with ligatures. The flaw in this system was that Harvey could not observe and prove the thin capillaries that connected the arteries and veins (Baigrie??™s Note). Hence, blood was able to go around in a full cycle and return to the heart for reuse. When the blood was in the heart, Harvey??™s description is completely different from Galen??™s point of view, who thought blood passes from the right ventricle to the left ventricle of the heart, as stated in Galen??™s first theory (Brian S. Baigrie). Harvey described that the blood went from the right side to the left side of the heart via the lung, but not through the septum between the right and left sides ( Brian S. Baigrie). This was not a new idea. Before that, other scientists like Renaldus Columbus and Michael Servetus had already proposed similar idea on the concept of pulmonary circuit (W1).
Harvey??™s final complete work was published in de motu cordis in 1628 (John Ridington Young). His theory had received both positive and negative comments. The proponents of this theory were largely agreed with the logical method performed in Harvey??™s experiment (Lubitz SA). The opposition was from the proponents of Galenic theory or other religious and conventional philosophical belief and from the lack of proof the existence of capillaries (Lubitz SA).
Marcello Malpighi (1628-1694) was able to prove that capillaries were existed under the microscope (J.M.S. Pearce). Malpighi observed that blood passed through a network of small tubes on the surface of the lung of a frog in 1661(J.M.S. Pearce). He kept working on these small tubes and discovered that they connected the arteries and veins, and allowed the blood flow back to the heart (J.M.S. Pearce). Malpighi??™s work allowed the completion of Harvey??™s theory of circulation of blood.
Many corrections are made to the conventional belief and theory due to logic and quantitative experimentation. Galileo had broken down few Aristotle??™s theories with the help of telescope. For example, Galileo described that celestial bodies were not perfect by the observation of moon (Baigrie??™s Note). Descartes??™ law of motion was also a revolutionary idea. Descartes proposed that moving and resting were two primary states of an object (Baigrie??™s Note). They were opposed to but parallel to each other (Baigrie??™s Note). He also came up with the idea of relative motion, which served as an important basis for solving many later dynamic problems. These were scientists like Kepler and Harvey; they did not come up with a theory from nothing, but instead, they performed series of experiments and combined the knowledge of predecessors and what they had experienced.
J.M.S. Pearce (2007), ???Malpighi and the Discovery of Capillaries???, European Neurology, Vol. 58:253-255
Steven C. Frautschi, Richard P. Olenick, Tom. M. Apostol, David L. Goodstein (1986), ???The Mechanical Universe? ???Cambridge University Press, pp. 431-435
Lubitz SA. (2004) Internal Medicine, The Mount Sinai Hospital, ???Early reactions to Harveys circulation theory: the impact on medicine???, Vol. 71(4):274-80
John Ridington Young (2003), ???Poetical Allusions to the Circulation of Blood up to the End of the Seventeenth Century???, Vesalius, Vol. 9, 3-8
Scientific Revolutions, Primary tests in the history of Science, by Brian S. Baigrie
Baigrie??™s Note: Scientific Revolution (2007)
(W3)Encyclopedia of the Scientific Revolution from Copernicus to Newton: http://www.bookrags.com/tandf/fabrici-girolamo-tf/