Saturday, October 15, 2011

William Harvey's Discovery of Blood Flow

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Pronunciation fi-zE-รค-l&-jE

Function noun

Etymology Latin physiologia natural science, from Greek, from physi- + -logia -logy

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Date 157

1 a branch of biology that deals with the functions and activities of life or of living matter (as organs, tissues, or cells) and of the physical and chemical phenomena involved

the organic processes and phenomena of an organism or any of its parts or of a particular bodily process

Through his fundamental discoveries within the disciplines of circulation and cardiology, William Harvey laid the foundations for modern physiology and the aided in the development of Medicine as an applied science. Not only did he found a branch of modern science, he also made it possible to apply this branch to other sciences, in particular medicine. In addition to explaining the major discrepancies in the work of others, Harvey also accomplished it in the face of adversity. At the time of Harvey’s experimentation regarding the circulation of the blood, the views and theories of a second century anatomist, Galen, had rarely been questioned. Thus, after Harvey’s work was published, and was clearly accurate, Harvey was criticized with regards to his research. Not only was it a bold move to question the works of an accepted source of knowledge, it was also inevitable that Harvey would face harsh condemnation because of it. Others preceded Harvey’s published work such as Realdus Columbus, Andreas Vesalius and Hieronymus Fabricius, all of who were afflilated with Harvey as anatomy lecturers. Harvey utilized their work to further develop the thoughts and theories that these scientists before him had initially introduced. His reliance on experimentation, not books, guided him to new theories. Simple experimentation, both with and without incisions and dissections, allowed Harvey to gain his ideas and prove that insightful observation was vital.

By all accounts, William Harvey led a charmed life. Harvey, oldest of seven children, was born in 1578 in Kent, England, at the halfway point of the reign of Queen Elizabeth I. He was a voracious student, earning his bachelors degree in 157 from Cambridge University at the age of 1. He continued his schooling at the University of Padua, the foremost medical school of the time. Here, Harvey’s interest into the circulation of the blood began.

This is also where Harvey learned of the teachings of Galen, and later questioned them. Until the time that Harvey’s work was published, Galen had never been directly questioned throughout history, as no one placed any explicit doubt in his work and theories. Obviously, Galen’s work in the areas of anatomy and therapeutics had lasted the test of time. A simple analogy of the criticism of Galen’s work in anatomy at that time to modern times would be a situation in which Bill Gates’ work in software development was criticized now- it is widely accepted by the public, considered to be “the way” and few other theories have been put forth to differ.

Galen contested that all blood originated from the Liver. He also stated that all food passed into the stomach and intestines, before undergoing concoction. According to Galen, from here the food mixture is separated off to the portal vein, where it undergoes further concoction and becomes venous blood. This blood, which is endowed with “natural spirit,” is delivered to all parts of the body. Specifically, the nutrients from the food are delivered to all parts of the body via the blood, which is then returned to the liver to be replenished.

According to Galen, one of the areas of the body that the venous blood is delivered to is the right ventricle of the heart. Here, some of the blood is expelled to the lungs for nourishment purposes. The remainder of the blood passes through the porosities of the septum, before entering the left ventricle.

Once in the left ventricle, the blood is nurtured with air from the pulmonary vein. According to Galen, this air has the “basic principle of life” in it. The venous blood is then concocted further to produce arteriole blood. After sufficient concoction, the arteriole blood leaves via the aorta, and distributed to the rest of the body. Any vapours produced from the concoction process are breathed out of the body.

Galen also has a theory regarding the relation of blood to air within the heart during the actions of diastole and systole. During diastole, air comes into the body through the pulmonary vein and enters the left ventricle. Venous blood enters the right ventricle. During systole, vapours are expelled through the pulmonary vein; venous blood goes to the lungs via the pulmonary artery. Arteriole blood is also expelled to the body via the aorta at this time. Furthermore, Galen believed that the heart struck the chest wall during the time of diastole.

One of the first anatomists to produce an opinion contrary to the works of Galen was Andres Vescellius. Vescellius was a professor at Padova during the time that Harvey was a student there. Within a publication that was published in 154, Vescellius implicitly pointed out Galen’s errors. He did not, however challenge Galen’s opinion. Vescellius clearly stated that he could not find any pours that penetrated through the septum from one ventricle to the other, but at the same time did not deny their existence.

Vescellius’ successor, Realdus Columbus also pointed out some of Galen’s errors. In particular, he stated that the timing of the apex of the heartbeat against the chest wall was actually during systole. In addition, Columbus denied the existence of pours within the septum dividing the two ventricles and the breeding of vapours in the left ventricle.

Columbus maintained that blood left the right ventricle to the lungs via the pulmonary artery. He also maintained that from this point, the blood returned to the left ventricle of the heart via the pulmonary vein. This hypothesis was based on the competence of the valves within the heart. Columbus tested his hypothesis by opening the pulmonary vein to see whether it contained air or blood.

The works of Vescellius and Columbus encouraged the work of another famous anatomist, Hieronymus Fabricius. Harvey had the privilege of studying under the esteemed scientist and surgeon. Fabricius was a lecturer of surgery, a good teacher and was popular with the students. He did not challenge the works of Galen, and did not believe the truth of Columbus.

Fabricius observed the one-way valves in veins, but had not figured out exactly what their role was. The popular belief of the day held that a sort of pulsing action of the arteries circulated blood. He believed that blood left the heart through veins and that valves were placed in veins to prevent the back flow. To help prove his hypothesis, Fabricius did experiments on human arms to observe the prevention of back flow of blood. Using pressure to compress one end of a vein, Fabricius repeatedly tried to allow the blood to travel in the opposite direction of the flow. The blood would travel to a point � then simply stop. This was a direct indication to Fabricius that a physical barrier existed that allowed the flow of the blood in only one direction within the veins.

Harvey’s interest into the circulation of the blood stems from the works of all three of the above fore mentioned anatomists. Fabricuis, because he was Harvey’s “master,” had the most influence over him. He was the first to give Harvey the idea that blood circulated throughout the body.

Harvey returned to England in 160 and married Elizabeth Browne, who was the daughter of one of the Queens physicians. In 1615, Harvey himself obtained a fellowship at the Royal College of Physicians. He was given the prestigious position of Lumley lecturer in surgery and anatomy. In 1616, he gave his first public lecture in anatomy. The notes from this lecture give the idea of Harvey’s new hypothesis. He agreed with Columbus that Galen’s relationship between the systole and diastole in relation to the apex of the heartbeat was wrong. Moreover, at this point he had no idea about the function of veins. His reputation grew, as in 1618 Harvey was appointed as a physician to the court of James I.

His research into the circulatory system and other anatomical interests were generously sponsored and encouraged by James Is successor, King Charles I, to whom Harvey was later appointed personal physician. By studying animals given to him by his regal employer, Harvey eventually developed an accurate theory of how the heart and circulatory system operated. Using the animals given to him, Harvey utilized a new concept working from dissections. Instead of learning from old textbooks, Harvey had the luxury of dissecting mammals that were physiologically similar to humans.

Through his explorations of the hearts and circulatory systems of other animals, Harvey observed many features of both the heart and circulatory system. First, he noticed that the heart moves in a pattern. Harvey observed that the heart sometimes moves, and other times rests. In addition, he also noticed that, contrary to popular belief, the systole is harder, and during contraction, the apex is felt.

The second major area that Harvey made observations was the nature of the relationship between the flow of the blood within the heart and contractions. He saw that the action of the heart pumped the blood from the atria, into the ventricles, then to the arteries. He also noticed that in some animals, the ventricle was completely filled before contraction to the arteries. Through his dissections, Harvey noticed that blood enters the ventricles via the atria, and not otherwise. In one particular experiment, Harvey cut the end of a ventricle and noticed the pattern of flow out of the hole with every contraction of the atria.

Harvey’s next accomplishment was his explanation of how blood travelled from one side of the heart to the other. Harvey denied the existence of any pours within the septum of the heart. He also stated that the pulmonary artery has three valves that prevented the reflux of blood, and in particular, blood from returning to the heart. He also suggested that the structure, function and placement of the valves indicated that the blood flows from the pulmonary artery, to the lungs and to the pulmonary vein. These observations on Harvey’s behalf helped confirm the work of Columbus.

Harvey’s theories regarding the movement of the heart, contraction of the heart, flow of blood within the heart and the structure and function of the valves within the heart were published in168. This publication is Harvey’s famous book Anatomical Studies on the Motion of the Heart and Blood or De Motu Cordis, which made him notorious throughout Europe.

Although Harvey’s publication described the role of the valves within the heart, it did not outline an experiment for which the solid nature of septum could be confirmed. That is, Harvey’s theory regarding the absence of pours in the septum of the heart could not be confirmed. It was not until years later, 1651, that he devised an experiment which proved that the septum was solid, and without pours.

To prove this, Harvey continued to use the animals that were provided to him. Harvey tied the pulmonary artery, pulmonary vein and the aorta of a live animal. After tying these three major blood vessels, he opened the left ventricle of the heart. Next, he passed a tube through the vena ceva, and into the right ventricle. After ensuring that the tube lead directed into the right ventricle, Harvey injected water into the tube. At this point he observed that no water flowed out of the hole of the left ventricle. He also saw that the right atrium and ventricle grew in size. Upon untying the pulmonary artery, pulmonary vein and aorta, Harvey placed the tube with water flowing from it into the pulmonary artery and tied the artery behind the tube. At this point, water gushed from the hole in the left ventricle. From this series of experiments, Harvey correctly deduced that the blood flowed to the lungs from the heart and back, via the pulmonary artery and pulmonary vein. Thus, he determined that this was the mechanism that transferred blood from the right side of the heart to the left. This proved that blood did not flow through the ventricles and denied the existence of any pours that would enable such flow.

Harvey’s next conclusion was that the flow of blood was in a circle. His interest into this subject stemmed from his observations of the great abundance of blood that flows through the heart. He observed that an incredibly large amount of blood flowed through the heart and began reasoning that after a short period of time, the body would simply run out of space before any fluids were removed by other means. Thus, Harvey constructed a quantitative experiment to prove his thoughts. Harvey measured that approximately ounces of blood is in the left ventricle when full. After each contraction, he measured how much residual blood remained in the left ventricle. The difference between each measurement was the amount of blood that entered the aorta. Harvey found that the average amount of blood that entered the aorta was approximately one gram. After observing that 1000 pulses occurred every one half-hour, Harvey calculated that the volume of the blood pumped through the aorta would quickly reach an amount greater than the whole body. Thus, Harvey concluded that blood flowed in a circular motion, eventually returning to the heart.

Harvey next wanted to prove that arteries receive blood from the veins through the heart. Once again, Harvey created a qualitative experiment. First, he plugged the vena cava, which stopped blood from returning to the heart. Shortly after doing this, he noticed that the heart began to pump slower, lose some of its colour and shrink in size. Upon releasing the plug, the normal speed, colour and size returned to the heart. The change in speed, colour and size of the heart confirmed to Harvey that the vena cava was the principle vein that returned blood to the heart, and allowed the blood to be passed through the heart and onto the arteries. To further prove his point, Harvey completed another experiment on an artery leaving the heart, similar to the experiment in which the vena cava was plugged. As he expected, Harvey observed a swelling of the ventricle from which the artery in question stemmed from. Thus, if the pulmonary artery was plugged, a swell was to be seen in the right ventricle, while if the aorta was plugged, a swell was to be seen in the left ventricle. In addition, the ventricle in question would also gain a purple colour. This colour, combined with the swelling, made the ventricle look as if it was suffocating. Once the plugs were removed, the ventricles returned to a normal colour and size. In addition, blood did not leave the heart via the veins that entered the atria. Through these experiments, Harvey was able to assume that blood entered the heart via a specific path, and left the heart in an equally specific path.

Harvey now had the task of “completing the circle.” Through his experimentation, observation and reasoning with plugging of the veins and arteries that enter and leave the heart, Harvey had proved that blood enters and leaves the heart via specific pathways. Through his quantitative analysis of the large amounts of blood that leave the heart over a period of time, Harvey reasoned that blood must circulate the body and return to the heart.

How did the blood return to the heart? At what point does an artery become a vein? Although the technology was not available to facilitate the viewing of capillary beds, Harvey rationalized that there was a tissue connection between the two types of blood vessels. Once again, Harvey created an experiment that would lead him to another theory.

First, he tied a tight knot with a strand of cloth directly above the elbow of a lean man. After the pulsation from one of the arteries just below the elbow stops, the veins in the elbow swell up, as blood is fed into them. Due to the fact that the knot is tight, the blood within these veins cannot leave the forearm. Thus, after the knot is applied, the arteries empty the blood into the tissues. From this point, the blood is taken from the tissues into the veins. These veins continue to grow in size until all the blood that has emptied from the arteries. Clearly, this blood cannot leave the forearm if the knot is still applied.

Harvey realized that no blood was entering the arm below the knot, and no blood was leaving the forearm via the veins. Thus, as one type of blood vessel was emptying, another was filling. At this point, Harvey had made the connection that the blood was diffusing from the arteries to the veins via the tissues.

Another aspect of the heart and circulation that intrigued Harvey was the direction of flow of blood within the body. By cutting particular blood vessels and observing which end of the cut the blood flowed out of, Harvey easily determined the direction of flow within arteries and veins. For example, when a vein is cut, the side of the cut closer to the heart does not have any blood flow, while the side of the cut further from the heart poured abundantly. Conversely, when an artery is cut, only very little blood flows from the end of the cut further from the heart. The end of the cut closer to the heart provides a forceful stream of blood that pulsates with every beat of the heart. This flow is similar to that of an ancient fire extinguisher apparatus- the force of the flow increases with every pulsation of the heart, just as the flow of water from a hose would increase with every action of the pump. Thus, Harvey concluded that not only did arteries carry blood away from the heart; they also were under intense pressure. The beating of the heart provided this high-pressure environment of the arteries. He also concluded that the veins were a flow system- instead of operating with mechanical action, they simply aided the blood back to the heart as they filled.

But William Harvey was not satisfied with being the foremost anatomist of his day. He was intrigued by everything about the body, and at some point turned his attention to reproduction. He speculated that humans and other mammals must reproduce through the joining of an egg and sperm. No other theory made sense. It was 00 years before a mammalian egg was finally observed, but Harveys theory was so compelling and so well thought out that the world assumed he was right long before the discovery was finally made.

Harvey remained a physician at St. Bartholomews until 164. He maintained his college lectureship until 1656, the year before his death, missing by a moment the dismantling of the monarchy that had supported his research throughout his life.

Harvey’s conclusions in De Motu Cordis caused many to revisit Galen’s anatomical theories that had been widely accepted to this point. Before Harvey’s time and continuing until today, there are three stages in the history of every medical discovery. First, when it is announced people say that it is not true. Second, when its truth has been borne in on them, so that it can no longer be denied, they say it is not important. Third, after that if its importance becomes sufficiently obvious, they say that anyhow it is not new. The truth of this sequence of events is well borne out by the reception of Harvey’s discovery, with the proviso that the three phases overlapped.

Harvey’s experimental methods, observation and visual inspection enabled his hypothesises to be plausible, and perhaps correct. Many believed that this was the case. However, other scientists of the time did not think the same. Some anatomists believed that his experiments were poorly illustrated within the publication, thus could not be easily replicated. Harvey acknowledges the contrasting views held on his publication, and described the first stage of the receiveal by other anatomists and scientists of his medical discovery. Having mentioned that he seemed to hear comment on the circulation every day he notices how, “One party holds that I have completely demonstrated the circulation of the blood by experiment, observation and ocular inspection, against all force and array of argument; another thinks it scarcely yet sufficiently illustrated. There are some too, who say that I have shown a vainglorious love of vivisections, and who scoff at and deride the introduction of frogs and serpents, flies, and other of the lower animals upon the scene, as a piece of puerile levity, not even refraining from opprobrious epithets.” Between the universities of Oxford and Cambridge and individual scientists from mainland Europe, the reactions to Harvey’s anatomical research varied greatly.

For the extension of the influence of Harvey’s discoveries beyond a handful of cognoscenti anatomists, it was necessary for his fame to spread into the “hatcheries” of the English intelligentsia, the two ancient universities. John Aubrey, an English antiquary and miscellaneous writer of Harvey’s time, said that Harvey’s theory on the circulation of the blood would “with much adoe at last, in about 0 or 0 years time, it was received in all the Universities in the world.” What was true of the world was true of Oxford and Cambridge.

Francis Glisson, as Regius Professor of Medicine at Cambridge from 166 to 1677, was most instrumental in introducing Harvey’s work into their home university. Glisson has fifteen fat volumes of manuscripts to his name in the British Library. Among these fifteen volumes, there are over 400 separate orations, lectures and disputations on anatomy, physiology, and medicine, the great bulk of which seem to be ascribable to his teaching duties at the university. Most of the lectures were on clinical subjects, but scattered among these are a large number on anatomy and physiology, including items on the heart, lungs, arteries and veins. Clinical topics, such as rickets, fever and liver disorders were Glisson’s specialty.

Many of Glisson’s anatomy lectures were straight from Harvey’s work. Lectures titled “On the Circuit of the Blood” and “The Arteries Are Moved According to the Motion of the Heart;” as well as a number of untitled lectures were administered by Glisson to the medical school students at Cambridge. Glisson also expanded on Harvey’s work through his lectures on how “There are No Vital Spirits Separable from the Blood”, among others.

Due to the fact that this newly discovered information was being delivered to the students by a credible source such as Glisson, the same innovative spirit may be seen in the topics disputed by students at Cambridge. Glisson frequently supervised the medical school students’ disputations regarding various topics on anatomy and physiology. Before Glisson began using Harvey’s material in his lectures, these disputations by students under Glisson were understandably on such clinical topics as fevers, phlebotomy, purgation, diet and medication. By the 1650s, a significant portion of the students answered on topics in the new anatomy and physiology. For example, one young doctor recapitulated how “The Blood is Moved in a Circle.”

One student in particular, is an interesting example of Harveian influences exerted at a distance. During the 1640s Henry Power followed the advise of a friend to learn anatomy by autopsia, and most especially to make himself master of Harvey’s De Motu Cordis. By 165 his reading and dissections on a large number of animals, led Power to compose a small tract, Circulatio sanguinis. The manuscript brought forward over fifty experiments, both dissectional and vivisectional (including one later published by Glisson), to support “our Reverend and Worthy Dr. Harvey,” and “that incomparable Invention of his, the Circulation of the Blood”- a sentiment that seems to have been shared by Power’s fellow students at Cambridge in the 1650s. In 1654, Henry Power debated the complementary thesis that “The Liver is Not the Organ of Sanguification,” as the Galenic tradition mentioned earlier had held. Thus, not only did the students of Cambridge accept the works of Harvey as valid and valuable, they also refuted the principles of Galen that were directly contested by Harvey’s research. Henry Glisson’s active proliferation of Harvey’s works facilitated the acceptance of these works by the students of Cambridge, who later became physicians. Once physicians, these young doctors that had been educated with Harvey’s work employed their knowledge to others, thus assisting the acceptance of Harvey’s theory.

Oxford, though it lacked a Glisson to put forward Harvey’s cause, had had the physiologist himself, if only briefly, in 164-1646. One Oxford professor that did encourage the studying of the works of Harvey was William Petty. When he arrived in Oxford in 164, he was already well disposed to Harveianism; he had studied with Jan van der Wale and Cornelius can Hooghelande in the Netherlands, and had carried out anatomical research of his own at Paris and London in the late 1640s. Before departing in the late 165 for more remuneratice adventures in Ireland, Petty had organized a club of local experimental philosophers to meet at his lodgings. One of their exploits, the resuscitation of a hanged woman destined for the anatomical table, gained for Petty the university’s Tomlins Readership in Anatomy. He used these Oxford lectures to preach the mix of Harveian physiology and Cartesian philosophy he had learned in the Netherlands. For example, Petty began his public lecture at the Act in 1651 be reciting a poem in praise of Harvey and his work. His anatomical lectures similarly slighted the statutory injunction to teach descriptive anatomy in the Galenic mold, and concentrated instead on theories concerning the motion of the heart, the function of respiration, and the origin of the blood. Soon, this group comprised of Petty and local philosophers proliferated the teachings of Harvey onto the students of Oxford.

Perhaps because of Petty’s teachings, even at the beginning of their careers, Oxford medical students learned anatomy with a Harveian bent. During the 1650s the head of Hart Hall, Philip Stevens, taught tutorial groups from Johannes Vesling’s Syntagma anatomicum, a popular introductory text. More importantly, Vesling was a correspondent of Harvey, and his book was one of the few student manuals that accepted the circulation. Vesling described the motions of the heart, the structure its valves, and explained that since the heart continuously sent out blood to the periphery to replenish the vital heat and spirits of the parts, it must necessarily return to the heart in a perpetual circular motion. Thus, although opportunities were available for the Oxford medical school students to be taught in Galenic terms, from the 1650s onward, they were not.

Evidence of Harvey’s acceptance was evident everywhere in the university town. Most literary critics of the time praised the work of Harvey on circulation and anatomy, but pointed out that one could not expect such advances in the theory of medicine to change the day-to-day practise of medicine radically. This is true, but did not stop the biggest Oxford bookstores from carrying all of Harvey’s works, both in Latin and English, as well as those of his English followers, including Glisson. In addition, many of the libraries of dons, especially those connected to he Oxford “Clubb” of experimental philosophers, had Harvey’s works.

In sum, many separate lines of evidence suggest that by the late 1640s and early 1650s, Harvey’s discoveries were well known to both teachers and students at the English universities, and were rapidly becoming the mold for a recasting of the basic medical sciences of anatomy and physiology, a task of a magnitude unsurpassed since Galen. The discrepancy of approximately twenty years between the year of publication of De Motu Cortis and its general acceptance may be due to the later explanations that Harvey provided with regards to the structure of the septum of the heart.

Although it had taken almost twenty years from the time of the publication of De Motu Cortis to the proliferation of the its acceptance at Oxford and Cambridge, the thesis faired no better among the scientists of mainland Europe. Many European anatomists criticized Harvey because they emphasized the all-sufficiency of Galen’s principles for practical purposes. One critic’s attitude to Harvey is illustrated best by his comment; “Thou hast observed a sort of pulsatile heart in slugs, flies, bees, and even squill-fish. We congratulate thee upon thy zeal. May God preserve thee in such perspicacious ways…those who mark in thy writings the names of so many and diverse animals will take thee to be an oracle seated upon the tripod and dictating thy decisions.” Rarely can such angry words contain so much truth. One critic in particular, Jean Riolan, was particularly stubborn in accepting the validity of Harvey’s work.

The fiercest attack on Harvey came from an ultra-conservative, Jean Riolan the Younger (1580-1657), the leading Galenist in the Paris faculty. Riolan had studied medicine under his distinguished father, and became Dean of the Paris faculty just as his father did. He grasped that Harvey’s doctrine of the circulation had the potential to explode Galenic physiology. It would mean, for instance, that that liver was no longer the blood-making organ, and once the liver’s function was questioned, what else would not be questioned? Even Galenic therapeutics would be challenged, because the rationale for bleeding had been undermined what price all the old rules about the correct places to bleed if the same blood were streaming round the body?

In his second publication, Opuscula anatomica, 164, Riolan fired salvoes while offering a few concessions the blood still followed the old Galenic pathways and did not generally circulate, but he conceded a minor circulation in the aorta and vena cava. Riolan’s attack reiterated the old arguments; for example, “Harvey is very learned, but when he says that the blood passes through the lungs, he is going against Nature.”

Riolan also felt that when experimental findings contradicted Galen there must be something wrong with the new findings. Experiments might also create experimental injury that would destroy the physiological conditions and prevent accurate observation. Other possibilities included a deterioration of the Galenic texts; minor errors of Galen owing to his lack of human cadavers; and changes in human physiology since Galen’s time due to the influence of climate, soil, and diet. He felt that there was some circulation of the blood going on, but not as Harvey saw it. “I assert,” he wrote, “that the use of the circulation lies in the uninterrupted generation of vital blood and the maintenance of a continual heart beat.” One of his major objections was that if Harvey was right, the liver lost its central position as the source of the blood.

In addition, what made Riolan’s objections so worrisome was his high standing in the world of medicine; his skill as an anatomist was celebrated throughout Europe. In fact, anatomy students still read today of Riolan’s arch (in the colon), Riolan’s bone (a small bone at the back of the head), Riolan’s nosegay (a small group of muscles in the same region of the head), and Riolan’s muscle (in the eyelids). Riolan hoped by the strength of both his reputation and his “arguments” to finally put Harvey’s nasty theory out to pasture. What must have been particularly galling to Harvey was that he had actually cited “the learned Riolanus” in the introduction to De Motu Cortis. Through all of the preceding two decades Harvey had shown enormous self-restraint, hoping that his colleagues would step in to counter the continuing tirades. Unfortunately, there was precious little of such support.

Some of Harvey’s reticence had to do with his own reluctance to engage in controversy, and some to the continuing problems that plagued the England of his era. Part of the time he spent in exile with the king; in the early 1640s the Parliamentarians ransacked his apartment and made off with some of his notes and manuscripts. As a member of the College of Physicians, he also had to deal with opposition from two other groups looking to assert their independence and authority the apothecaries and the surgeons. Thus, it is obvious that Harvey was reluctant to engage his opponents in print.

Finally, Harvey could stand no more and, in 164, he issued the only published response he ever made to criticisms of De Motu Cordis. More than two decades had passed, an astonishing example of self-control. He penned two essays in the form of letters to Riolan, a fairly common form of scientific communication.

In published form, his essays/letters are generally known as De Circulatione. The first letter, probably written in 1648 or 164, presents a set of detailed answers to Riolan’s objections. The first three paragraphs and the closing paragraph of the second letter also direct answers to Riolan. But the rest answers many of the objections made by one and all in the years leading up to this point, and includes a description of four new experiments he had performed since publication of De Motu Cordis.

Like the interchanges mentioned earlier, the second letter starts off with some courteous, even courtly, language. But it also includes some honest venting of feelings long pent up against “those who cry out that I have striven after the empty glory of vivisections, and [who] disparage and ridicule with childish levity the frogs, snakes, flies, and other lower animals which I have brought on to my stage. Nor do they abstain from scurrilous language.” Harvey writes that he refuses to “return scurrility with scurrility.”

Nevertheless, he adds, “It is unavoidable that dogs bark and vomit their surfeit . . . but one must take care that they do not bite, or kill with their savage madness, or gnaw with a canine tooth the very bones and foundations of truth.” Finally, “Let them enjoy their evil nature. . . Let them continue with their scurrility until it irks if it does not shame them, and finally tires them out.” The goal of Harvey’s letters to Riolan was to insist that Riolan’s position made observational nonsense, for the blood in all the arteries moved with considerable force and in great quantities, which pointed clearly to the circulation.

It is clear that informed medical opinion in Europe had great difficulty in accepting the consequences of Harvey’s new thesis; and the more informed the opinion the more difficult these were to accept; to do so meant eventually completely abandoning much that they had learned. Unfortunately for Harvey, the most influential physicians and anatomists were the most informed. This asks a lot of any generation of physicians; even those of the twentieth century have had great difficulty in so doing.

As the founder of modern physiology, Harvey did eventually gain acceptance from the entire scientific community in Europe. Harvey’s supporters at the two major British medical schools assisted in the spreading of his theories. Gilsson at Cambridge and Petty at Oxford used Harvey in their teachings. Moreover, the criticism from Harvey’s fiercest rivals, such as Riolan, made his work all the more spectacular. For every logical (and in some cases illogical) argument that Riolan placed forward, Harvey had an equally logical explanation. One cannot help imagine what would happen today if such an incidence occurred. For example, what if an individual attempted to convince the entire scientific community that the photosynthetic reaction does not require light, or that Bill Gate’s software programming is in error. Surely, there would be resistance. Thus, it is understandable that great anatomists and physicians of the day, such as Riolan, had difficulty in accepting Harvey’s profound discovery. What cannot be denied are the qualitative and quantitative experiments that Harvey conducted on his way to the production of De Motu Cordis. These experiments, combined with the works of other anatomists before him at Padova, directed Harvey to the production of a medical revolution.


Figure 1 The anatomy theatre Figure Galen’s theory of blood formation

of Fabricius in the liver

Figure Harvey’s theory of blood circulation


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8. Pagel, Walter; New Light on William Harvey; 176; S. Karger; 1-0.

. Poore, George Vivian; The Harveian Oration; 18; Adlard and Son; 5-0.

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