Chapter 5

To the work on the "Fabric of the Human Body" we have already alluded, as well as to the causes which led to its being written. More than half of this great treatise is occupied with a minute description of the build of the human body--its bones, cartilages, ligaments, and muscles. It may have been owing to the thorough acquaintance which Vesalius showed with these parts that his detractors pretended afterwards that he only understood superficial injuries. But other branches of anatomy are fully dealt with. The veins and arteries are described in the third book, and the nerves in the fourth; the organs of nutrition and reproduction are treated of in the next; while the remaining two books are devoted to descriptions of the heart and brain.

Vesalius gives a good account of the sphenoid bone, with its large and small wings and its pterygoid processes; and he accurately describes the vestibule in the interior of the temporal bone. He shows the sternum to consist, in the adult, of three parts and the sacrum of five or six. He discovered the valve which guards the _foramen ovale_ in the f[oe]tus; and he not only verified the observation of Etienne as to the valve-like fold guarding the entrance of each hepatic vein into the inferior vena cava, but he also fully described the _vena azygos_. He observed, too, the canal which passes in the f[oe]tus between the umbilical vein and vena cava, and which has since been known as the _ductus venosus_. He was the first to study and describe the mediastinum, correcting the error of the ancients, who believed that this duplicature of the pleura contained a portion of the lungs. He described the omentum and its connections with the stomach, the spleen, and the colon; and he enunciated the first correct views of the structure of the pylorus, noticing at the same time the small size of the caecal appendix in man. His account of the anatomy of the brain is fuller than that of any of his predecessors, but he does not appear to have well understood the inferior recesses, and his description of the nerves is confused by regarding the optic as the first pair, the third as the fifth, and the fifth as the seventh. The ancients believed the optic nerve to be hollow for the conveyance of the visual spirit, but Vesalius showed that no such tube existed. He observed the elevation and depression of the brain during respiration, but being ignorant of the circulation of the blood, he wrongly explained the phenomenon.

Exclusively an anatomist, he makes but brief references in his great work to the functions of the organs which he describes. Where he differs from Galen on these matters he does so apologetically. He follows him in regarding the heart as the seat of the emotions and passions--the hottest of all the viscera and source of heat of the whole body; although he does not, as Aristotle did, look upon the heart as giving rise to the nerves. He considers the heart to be in ceaseless motion, alternately dilating and contracting, but the diastole is in his opinion the influential act of the organ. He knows that eminences or projections are present in the veins, and indeed speaks of them as being analogous to the valves of the heart, but he denies to them the office of valves. To him the motion of the blood was of a to-and-fro kind, and valves in the veins acting as such would have interfered with anything of the sort. He expresses clearly the idea, that was entertained in the old physiology, of the attractions exerted by the various parts of the body for the blood; and especially that of the veins and heart for the blood itself. "The right sinus of the heart," he says, "attracts blood from the vena cava, and the left attracts air from the lungs through the _arteria venalis_ (pulmonary vein), the blood itself being attracted by the veins in general, the vital spirit by the arteries." Again, he speaks of the blood filtering through the septum between the ventricles as if through a sieve, although he knows perfectly well from his dissection that the septum is quite impervious.

It will thus be seen that the physiological teaching of Galen was left undisturbed by Vesalius.

FOOTNOTES:

[19] See Professor Morley's article on "Anatomy in Long Clothes," in _Fraser's Magazine_, 1853, from which most of the facts in this sketch have been taken.

HARVEY.

_HARVEY._

The importance of Harvey's discovery of the circulation of the 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 thence distributed by it through the veins to the whole body. Erasistratus 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. Sylvius, the teacher of Vesalius, was aware of the presence of valves in the veins; and Fabricius, Harvey's teacher at Padua, described them much more accurately than Sylvius 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 Vesalius, writing in 1533, correctly described the course of the lesser circulation in the following words: "This communication (_i.e._ 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, wherein prepared, it becomes of a crimson colour, and from the vena arterialis (pulmonary artery) is transferred into the arteria venalis (pulmonary vein). Mingled with the inspired air in the arteria venalis, freed by respiration from fuliginous 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." 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 the blood and its distribution which were prevalent at the end of the sixteenth century prove--

(1) That although the blood was not regarded as stagnant, yet its circulation, such as is nowadays recognized, was unknown;

(2) That one kind of blood was thought to flow from the liver to the right ventricle, and thence 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;

(3) That the septum of the heart was regarded as admitting of the passage of blood directly from the right to the left side;

(4) 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 believed 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 due mixture of blood and spirits.

This was the state of knowledge before Harvey's time. By his great work he established--

(1) That the blood flows continuously in a circuit through the whole body, the force propelling it in this unwearied round being the rhythmical contractions of the muscular walls of the heart;

(2) That a portion only of the blood is expended in nutrition each time that it circulates;

(3) 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

(4) 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, "De Motu Cordis et Sanguinis," after giving an account of the views of preceding physiologists, 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;

(_b_) It is constricted in every direction;

(_c_) Grasped by the hand, it is felt to become harder during the contraction.

From these circumstances it is inferred--

(1) 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;

(2) That, as the effect of this, the capacity of the cavities is diminished, and the blood is expelled;

(3) 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 distended by the wave of blood that is thrown into them, being filled like sacs 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 auricles, and then of the ventricles. These alternate contractions and dilatations can have but one result, namely, to force the blood from the auricle 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 aorta to the system.

These considerations suggest to the mind of Harvey the idea of the circulation. "I began to think," he says, "whether there might not be a motion, as it were, in a circle." This is next established by proving the three following propositions:--

(1) 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;

(2) The blood, under the influence of the arterial pulse, enters, and is impelled in a continuous, equable, 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;

(3) 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, "Did the heart eject but two drachms 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 were the quantity an ounce, 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 perform a circuit, or return to the place from whence it went forth."

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 colour 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, or 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 blood-letting. 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, e.g. 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 ten he entered the Canterbury Grammar School, where he appears to have remained for some years. At sixteen he passed to Caius-Gonvil College, Cambridge, and three years afterwards took his B.A. 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 travelled 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 Aquapendente. 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 St. 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 a vacancy occurred.

In 1615, when thirty-seven 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 "De Motu Cordis."

Some few years after his appointment as lecturer to the college, he was chosen one of the physicians 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 physiologist's 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 Lennox 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 the time: "I can only complayne that by the waye we could scarce see a dogg, crow, kite, raven, or any bird or any thing to anatomise; only sum few miserable poeple the reliques of the war and the plauge, 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 biologists of the time, and at Nuremberg he probably met Caspar Hoffmann, 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 every one present except Hoffmann himself. Hollar, the artist, informs us that Harvey's enthusiasm in his search for specimens often led him into danger, and caused grave anxiety to the Earl of Arundel. "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."

Soon after his return to England, as court physician, his movements became seriously restricted by the fortunes of the king. Aubrey says, "When King Charles I., by reason of the tumults, left London, Harvey attended him, and was at the fight of Edgehill 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 tooke out of his pockett a booke and read; but he had not read very long before a bullet of a great gun grazed on the ground neare him, which made him remove his station.... I first sawe him at Oxford, 1642, after Edgehill fight, but was then too young to be acquainted with so great a doctor. I remember he came severall times to our Coll. (Trin.) to George Bathurst, B.D., who had a hen to hatch egges in his chamber, which they dayly opened to see the progress and way of generation."

In 1645, Charles, after the execution of Archbishop Laud, 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 Rebells now in armes 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, 1646, 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 1651. "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 honour and ornament of our college, Dr. William Harvey, then dwelling not far from the city. I found him, Democritus-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, 'whilst 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.'"

Harvey died in June, 1657. Aubrey, his contemporary, says, "On the morning of his death, about ten o'clock, he went to speake, and found he had the dead palsey in his tongue; then he sawe 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.; made sign to Sambroke his Apothecary to lett him blood in the tongue, which did little or no good, and so he ended his dayes.... The palsey did give him an easie passeport.... He lies buried in a vault at Hempsted in Essex, which his brother Eliab Harvey built; he is lapt in lead, and on his brest, in great letters, 'Dr. William Harvey.' I was at his Funerall, and helpt to carry him into the vault."

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 crackbrained, and lost much of his practice in consequence. He himself complains that contumelious epithets were levelled 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 Servetus, or in Caesalpinus--anywhere, in fact, except where alone it existed, namely, in the work, "De Motu Cordis et Sanguinis." No one seems to have denied, while Harvey lived, that he was the discoverer of the circulation of the blood; indeed, Hobbes of Malmesbury, his contemporary, said of him, "He is the only man, perhaps, that ever lived to see his own doctrine established in his lifetime."