 section 5 of fathers of biology this is a LibriVox recording all LibriVox recordings are in the public domain for more information or to volunteer please visit LibriVox.org fathers of biology by Charles McCrae chapter 5 Harvey the importance of Harvey's discovery of the circulation of blood can only be properly estimated by bearing in mind what was done by his predecessors in the same field of inquiry. Aristotle had taught that in man and in the higher brutes the blood was elaborated from the food in the liver conveyed to the heart and then distributed by it through the veins to the whole body. Erassus Stratus and Herophilus held that while the veins carried blood from the heart to the members the arteries carried a subtle kind of air or spirit Galen discovered that the arteries were not merely air pipes but that they contained blood as well as vital air or spirit Sylveus the teacher of Vassilius was aware of the presence of valves in the veins and Fabricius Harvey's teacher at Padua described them much more accurately than Sylveus had done but neither of these men had a true idea of the significance of the structures of which they wrote Servetus the friend and contemporary of Vassilius writing in 1533 correctly described the course of the lesser circulation in the following words quote this communication that is between the right and left sides of the heart does not take place through the partition of the heart as is generally believed but by another admirable contrivance whereby from the right ventricle the subtle blood is agitated in a lengthened course through the lungs where in prepared it becomes of a crimson color and from the venous arterialis pulmonary artery is transferred into the arterial vinalis pulmonary vein mingled with the inspired air in the arterial vinalis freed by respiration from phalingenous matter and become a suitable home of the vital spirit it is attracted at length into the left ventricle of the heart by the diastole of the organ end quote but when Servetus comes to speak of the systemic circulation what he has to say is as old as Galen the opinions therefore on the subject of blood and its distribution which were prevalent at the end of the 16th century prove one that although the blood was not regarded as stagnant yet its circulation such as is nowadays recognized was unknown two that one kind of blood was thought to flow from the liver to the right ventricle and then to the lungs and general system by the veins while another kind flowed from the left ventricle to the lungs and general system by the arteries three that the septum of the heart was regarded as admitting of the passage of blood directly from the right to the left side for that there was no conception of the functions of the heart as the motor power of the movement of the blood for biologists of that day doubted whether the substance of the heart were really muscular they supposed the pulsations to be due to expansion of the spirits it contained they believe the only dynamic effect which it had on the blood to be that of sucking it in during its active diastole and they supposed the chief use of its constant movements to be the do mixture of blood and spirits this was the state of knowledge before Harvey's time by his great work he established one that the blood flows continuously in a circuit through the whole body the force propelling it in this unwirried round being the rhythmical contractions of the muscular walls of the heart to that a portion only of the blood is expended in nutrition each time that it circulates three that the blood conveyed in the systemic arteries communicates heat as well as nourishment throughout the body instead of exerting a cooling influence as was vulgarly supposed and four that the pulse is not produced by the arteries enlarging and so filling but by the arteries being filled with blood and so enlarging we can now consider the method by which Harvey arrived at these results the work to Motu Cordes is sanguine after giving an account of the views of a preceding physiologist ancient and modern commences with a description of the heart as seen in a living animal when the chest has been laid open and the pericardium removed three circumstances are noted a the heart becomes erect strikes the chest and gives a beat be it is constricted in every direction see grasped by the hand it is felt to become harder during the contraction from these circumstances it is inferred one that the action of the heart is essentially of the same nature as that of voluntary muscles which become hard and condensed when they act to that as the effect of this the capacity of the cavities is diminished and the blood is expelled three that the intrinsic motion of the heart is the systole and not the diastole as previously imagined the motions of the arteries are next shown to be dependent upon the action of the heart because the arteries are descended by the wave of blood that is thrown into them being filled like sacks or bladders and not expanding like bellows these conclusions are confirmed by the jerking way in which blood flows from a cut artery in the heart itself two distinct motions are observed first of the oracles and then of the ventricles these alternate contractions and dilations can have but one result namely to force the blood from the oracle to the ventricle and from the ventricle on the right side by the pulmonary artery to the lungs and on the left side by the order to the system these considerations suggest to the mind of Harvey the idea of the circulation I begin to think he says whether there might not be emotion as it were in a circle this is next established by proving the three following propositions one the blood is incessantly transmitted by the action of the heart from the vena cava to the arteries in such quantity that it cannot be supplied from the ingesta and in such wise that the whole mass must very quickly pass through the organ to the blood under the influence of the arterial pulse enters and is impelled in a continuous, equitable and incessant stream through every part and member of the body in much larger quantity than were sufficient for nutrition or than the whole mass of fluids could supply three the veins in like manner return this blood incessantly to the heart from all parts and members of the body as to the first proposition Harvey says quote did the heart eject but two dracoms of blood on each contraction and the beats in half an hour were a thousand the quantity expelled in that time would amount to twenty pounds and ten ounces and where the quantity announced it would be as much as eighty pounds and four ounces such quantities it is certain could not be supplied by any possible amount of meat and drink consumed within the time specified it is the same blood consequently that is now flowing out by the arteries now returning by the veins and it is simply matter of necessity that the blood should reform a circuit or return to the place from whence it went forth unquote demonstration of the second proposition that the blood enters a limb by the arteries and returns from it by the veins is afforded by the effects of a ligature for if the upper part of the arm be tightly bound the arteries below will not pulsate while those above will throb violently the hand under such circumstances will retain its natural color and appearance although if the bandage be kept on for a minute or two it will begin to look livid and to fall in temperature but if the bandage be now slackened a little the hand and the arm will immediately become suffused and the superficial veins show themselves tumid and knotted the pulse at the wrist in the same instant beginning to beat as it did before the application of the bandage the tight bandage not only compresses the veins but the arteries also so that blood cannot flow through either the slacker ligature obstructs the veins only for the arteries lie deeper and have firmer coats seeing then says Harvey that the moderately tight ligature renders the veins turgid and the whole hand full of blood I ask whence is this does the blood accumulate below the ligature coming through the veins or through the arteries are passing by certain secret pores through the veins it cannot come still less can it come by any system of invisible pores it must needs then arrive by the arteries the third position to be proved is that the veins return the blood to the heart from all parts of the body that such is the case might be inferred from the presence and disposition of the valves in the veins for the office of the valves is by no means explained by the theory that they are to hinder the blood from flowing into inferior parts by gravitation since the valves do not always look upwards but always towards the trunks of the veins invariably towards the seat of the heart the action of the valves is then demonstrated experimentally on the arm bound as for bloodletting the point of a finger being kept on a vein the blood from the space above may be streaked upwards till it passes the valve when that portion of the vein between the valve and the point of pressure will not only be emptied of its contents but will remain empty as long as the pressure is continued if the pressure be now removed the empty part of the vein will fill instantly and look as turgid as before other confirmatory evidence is then added for example the absorption of animal poisons and of medicines applied externally the muscular structure of the heart and the necessary working of its valves William Harvey the illustrious physiologist anatomist and physician to whom this discovery is due was the eldest son of a kentish yeoman and was born in April 1578 at the age of 10 he entered the canterbury grammar school where he appears to have remained for some years at 16 he passed the chaos gonville college Cambridge and three years afterwards took his BA degree and quitted the university like most students of medicine of that day he found it necessary to seek the principal part of his professional education abroad he traveled to Italy selected Padua as his place of study and there continued to reside for four years having as one of his teachers the famous Fabricius of aqua pendente on his return to England in 1602 he took his doctor's degree at Cambridge and entered on the practice of his profession in 1604 he joined the College of Physicians and three years later was elected a fellow of that learned body two years afterwards he applied for the post of physician to Saint Bartholomew's hospital and his application being supported by letters of recommendation to the governor from the king and from the president of the College of Physicians he was duly elected to the office in the same year as soon as the vacancy occurred in 1615 when 37 years of age Harvey was chosen to deliver the lectures on surgery and anatomy to the College of Physicians and it is possible that at this time he gave an exposition of his views on the circulation he continued to lecture on the same subject for many years afterwards although he did not publish his views until 1628 when they appeared in the work to Motu Cordes some few years after his appointment as lecturer to the college he was chosen one of the physician's extraordinary to King James I and about five or six years after the accession of Charles I he became physician in ordinary to that unfortunate monarch the physiologists investigations seem to have interested King Charles for he had several exhibitions made of the punctum saliens in the embryo chick and also witnessed dissections from time to time when in 1630 the young Duke of Lenox made a journey on the continent Harvey was chosen to travel with him and probably remained abroad about two years during this time Harvey most likely visited Venice of this tour the doctor speaks in the following terms in a letter written at that time quote I can only complain that by the way we could scarcely see a dog crow kite raven or any bird or anything to anatomize only some few miserable people their relics of the war and the plague where famine had made anatomies before I came six years after this in April 1636 he accompanied the Earl of Arundel in his embassy to the emperor having to visit the principal cities of Germany he was thus afforded an opportunity of meeting the leading biologist of the time and at Nuremberg he probably met Casper Hoffman and made that public demonstration of the circulation of the blood which he had promised in his letter dated from that city and which convinced everyone present except Hoffman himself holler the artist informs us that Harvey's enthusiasm in his search for specimens often led him into danger and cause grave anxiety to the Earl of Arundel quote for he would still be making of excursions into the woods making observations of strange trees plants earths etc and sometimes like to be lost so that my lord ambassador would be really angry with him for there was not only danger of wild beasts but of thieves end quote soon after his return to England as court physician his movements became seriously restricted by the forges of the king Aubrey says when King Charles I by reason of the tummelt left London Harvey attended him and was at the fight of Edge Hill with him and during the fight the prince and the Duke of York were committed to his care he told me that he withdrew with them under a hedge and took out of his pocket a book in red but he had not read very long before a bullet of a great gun grazed on the ground near him which made him remove his station I first saw him at Oxford sixteen forty two after Edge Hill fight but was then too young to be acquainted with so great a doctor I remember he came several times to our college Trinity to George Bathurst B.D. who had a hen to hatch eggs in his chamber which they daily open to see the progress and way of generation in sixteen forty five Charles after the execution of Archbishop Lord took upon himself the functions of visitor of Merton College and having removed Sir Nathaniel Brent from the office of Warden for having joined the rebels now in armies against him he directed the fellows to take the necessary steps for the election of a successor this course consisted in giving in three names to the visitor in order that one of the three the one named first probably should be appointed Harvey was so named by five out of the seven fellows voting and was accordingly duly elected a couple of days after his admission he summoned the fellows into the hall and made a speech to them in which he pointed out that it was likely enough that some of his predecessors had sought the office in order to enrich themselves but that his intentions were quite of another kind wishing as he did to increase the wealth and prosperity of the college and he finished by exhorting them to cherish mutual concord and amity after the surrender of Oxford July sixteen forty six Harvey retired from the court he was in his sixty ninth year and doubtless found the hardships and inconveniences which the miserable war entailed far from conducive to health the rest and seclusion to be had at the residence of one or other of his brothers offered him the much needed opportunity of renewing his inquiries into the subject of generation and it is of this time that Dr. Ent speaks in the preface to the published work on that subject which appeared in sixteen fifty one quote harassed with anxious and in the end not much availing cares about Christmas last I sought to rid my spirit of the cloud that oppressed it by a visit to that great man the chief honor and ornament of our college Dr. William Harvey then dwelling not far from the city I found him Democratist like busy with the study of natural things his countenance cheerful his mind serene embracing all within its sphere I forthwith saluted him and asked if all were well with him how can it said he lost the commonwealth is full of distractions and I myself am still in the open sea and truly he continued did I not find solace in my studies and a balm for my spirit in the memory of my observations of former years I should feel little desire for longer life but so it has been that this life of obscurity this vacation from public business which causes tedium and disgust to so many has proved a sovereign remedy to me unquote Harvey died in June sixteen fifty seven Aubrey his contemporary says quote on the morning of his death about 10 o'clock he went to speak and found he had the dead palsy in his tongue then he saw what was to become of him he knew there was then no hopes of his recovery so presently sends for his young nephews to come up to him to whom he gives one his watch to another another remembrance etc and made signed to Sam broke his apothecary to let him blood in the tongue which did little or no good and so he ended his days the palsy did give him an easy passport he lies buried in a vault at hemstead in Essex which is brother Eliab Harvey built he is lapped in lead and on his breast in great letters dr. William Harvey I was at his funeral and helped to carry him into the vault end quote the publication of Harvey's views on the movement of the blood excited great surprise and opposition the theory of a complete circulation was at any rate novel but novelty was far from being a recommendation in those days according to Aubrey the author was thought to be crack-brained and lost much of his practice and consequence he himself complains that Contamelius epithets were leveled at the doctrine and its author it was not until after many years had elapsed and the facts had become familiar that men were struck with the simplicity of the theory and tried to prove that the idea was not new after all and that it was to be found in Hippocrates or in Galen or in Severitus or in Cecil Pinus anywhere in fact except where alone it existed namely in the work to Motu Cordes Isanguinis no one seems to have denied while Harvey lived that he was the discoverer of the circulation of the blood indeed Hobbes of Malisbury his contemporary said of him quote he is the only man perhaps that ever lived to see his own doctrine established in his lifetime unquote in one important respect Harvey's account of the circulation was incomplete he knew nothing of the vessels which we now speak of as capillaries writing to Paul Marcard's legal of Hamburg in 1651 he says quote when I perceive that the blood is transferred from the veins into the arteries through the medium of the heart by a grand mechanism and exquisite apparatus of valves I judge that in like manner wherever transportation does not take place through the pores of the flesh the blood is returned from the arteries to the veins not without some other admirable artifice unquote non-seen artificial quantum admirably it was this artificium admirable of which Harvey was unable to give a description on account of the minuteness of their structure the capillaries were beyond his sight aided as it was by a magnifying glass merely he indeed demonstrated physiologically the existence of some such passages but it remained for a later observer with improved appliances to verify the fact this was done by Mal Piggy in 1661 who saw in the lung of a frog which was so mounted in a frame as to be viewed by transmitted light the network of capillaries which connect the last ramifications of the arteries with the radicals of the veins Harvey rightly denied that the arteries possessed any pulsific power of their own and maintained that their pulse is owing solely to the sudden distention of their walls by the blood thrown into them at each contraction of the ventricles but the remission which exceeds the pulse was regarded by him as close simply by collapse of the walls of the arteries due to elastic reaction knowing nothing of the muscular coat of the arteries he was unaware of the fact that the elastic reaction of the arteries after their distention is aided by the tonic contractility of their walls the two forces physical and vital acting in concert with each other the former converting the intermittent flow from the heart into an even stream in the capillaries and veins the latter through the vasomotor system regulating the flow of blood to particular parts in order to meet changing requirements it is somewhat surprising to find that such an accurate observer as Harvey should have failed to recognize the significance and importance of the system of lactial vessels but such was the case eustaceous in the 16th century had discovered the thoracic duct in the horse although he seems to have thought that it was peculiar to that animal a silly while dissecting the body of a dog in 1622 accidentally discovered the lactials and thought at first that they were nerves but upon puncturing one of them and seeing the milky fluid which escaped found them to be vessels he however failed to trace them to the thoracic duct and believe them to terminate in the liver Pequett of Dieppe followed them from the intestines to the mesenteric glands and from these into a common sac or reservoir which he designated receptaculum chile and then stood their entry by a single slender conduit into the venous system at the junction of the jugular and subclavian veins the existence of the lactials had not entirely escaped Harvey however he had himself noticed them in the course of his dissections before a selly's book was published but for various reasons could not bring himself to believe that they contained Kyle the smallest of the thoracic duct seemed to him a difficulty and as it was a demonstrated fact that the gastric veins were largely absorptive the lactials appeared to him superfluous he is not obstinately wedded to his own opinion and does not doubt but that many things now hidden in the well of democratists will by and by be drawn up into day by the ceaseless industry of a coming age late in the author's life as we have seen the work on the generation of animals appeared but neither physiological nor microscopical science was sufficiently advanced to admit of the production of an enduring work on a subject necessarily so abstruse as that of generation it was impossible however for so shrewd enable an investigator as Harvey to work at a subject even as difficult as this without leaving the impress of his original genius he first announced the general truth omna animal x ovo and clearly proved that the essential part of the egg that in which the reproductive processes begin was not the chalazee but the cicatricula this for bryceus had looked upon as a blemish a scar left by a broken pet uncle harvey described this little cicatricula as expanding under the influence of incubation into a wider structure which he called the eye of the egg and at the same time separating into a clear and transparent part in which later on according to him there appeared as the first rudiment of the embryo the heart or punctum saliens together with the blood vessels he was clearly of opinion that the embryo arose by successive formation of parts out of the homogeneous and nearly liquid mass this was the doctrine of epigenesis which notwithstanding its temporary overthrow by the erroneous theory of evolution is with modifications the doctrine now held footnote according to the theory of evolution the egg contained from the first an excessively minute but complete animal and the changes which took place during incubation consisted not in a formation of parts but in a growth that is in an expansion of the already existing embryo and a footnote of harvey scholarship and culture we are not left in ignorance bishop piercen writing about seven years after the doctor's death and or bry have told us of his appreciation of the works of Aristotle and in his own writings he refers more frequently to the stagerite than to any other individual sir william temple has also put it on record that the famous doctor harvey was a great admirer of virgil whose works were frequently in his hands his store of individual knowledge must have been great and he seems never to have flagged in his anxiety to learn more he made himself master of oak treads clavis mathematically in his old age according to aubrie who found him perusing it and working problems not long before he died nor should it be forgotten that this illustrious physiologist and scholar was also the first english comparative anatomist of his knowledge of the lower animals he makes frequent use and he says in his work on the heart quote had anatomist only been as conversant with the dissection of the lower animals as they are without of the human body many matters that have hitherto kept them in a perplexity of doubt would in my opinion have met them freed from every kind of difficulty aubrie says that harvey often told him quote that of all the losses he sustained no grief was so crucifying to him as the loss of his papers containing notes of his dissections of the frog toad and other animals which together with his goods in his lodgings at white hall were plundered at the beginning of the rebellion unquote and of chapter five and of fathers of biology by charles mccray