It is of great importance you should clearly understand these teachings of Galen, because, as I said just now, they sum up all that anybody knew until the revival of learning; and they come to this—that the blood having passed from the stomach and intestines through the liver, and having entered the great veins, was by them distributed to every part of the body; that part of the blood, thus distributed, entered the arterial system by the 'anastomoses', as Galen called them, in the lungs; that a very small portion of it entered the arteries by the 'anastomoses' in the body generally; but that the greater part of it passed through the septum of the heart, and so entered the left side and mingled with the pneumatised blood, which had been subjected to the air in the lungs, and was then distributed by the arteries, and eventually mixed with the currents of blood, coming the other way, through the veins.

Yet one other point about the views of Galen. He thought that both the contractions and dilatations of the heart—what we call the 'systole' or contraction of the heart, and the 'diastole' or dilatation—Galen thought that these were both active movements; that the heart actively dilated, so that it had a sort of sucking power upon the fluids which had access to it. And again, with respect to the movements of the pulse, which anybody can feel at the wrist and elsewhere, Galen was of opinion that the walls of the arteries partook of that which he supposed to be the nature of the walls of the heart, and that they had the power of alternately actively contracting and actively dilating, so that he is careful to say that the nature of the pulse is comparable, not to the movement of a bag, which we fill by blowing into it, and which we empty by drawing the air out of it, but to the action of a bellows, which is actively dilated and actively compressed.

(FIGURE 3.—The course of the blood from the right to the left side of the heart (Realdus Columbus, 1559).)

After Galen's time came the collapse of the Roman Empire, the extinction of physical knowledge, and the repression of every kind of scientific inquiry, by its powerful and consistent enemy, the Church; and that state of things lasted until the latter part of the Middle Ages saw the revival of learning. That revival of learning, so far as anatomy and physiology are concerned, is due to the renewed influence of the philosophers of ancient Greece, and indeed, of Galen. Arabic commentators had translated Galen, and portions of his works had got into the language of the learned in the Middle Ages, in that way; but, by the study of the classical languages, the original text became accessible to the men who were then endeavouring to learn for themselves something about the facts of nature. It was a century or more before these men, finding themselves in the presence of a master—finding that all their lives were occupied in attempting to ascertain for themselves that which was familiar to him—I say it took the best part of a hundred years before they could fairly see that their business was not to follow him, but to follow his example—namely, to look into the facts of nature for themselves, and to carry on, in his spirit, the work he had begun. That was first done by Vesalius, one of the greatest anatomists who ever lived; but his work does not specially bear upon the question we are now concerned with. So far as regards the motions of the heart and the course of the blood, the first man in the Middle Ages, and indeed the only man who did anything which was of real importance, was one Realdus Columbus, who was professor at Padua in the year 1559, and published a great anatomical treatise. What Realdus Columbus did was this; once more resorting to the method of Galen, turning to the living animal, experimenting, he came upon new facts, and one of these new facts was that there was not merely a subordinate communication between the blood of the right side of the heart and that of the left side of the heart, through the lungs, but that there was a constant steady current of blood, setting through the pulmonary artery on the right side, through the lungs, and back by the pulmonary veins to the left side of the heart (Figure 3). Such was the capital discovery and demonstration of Realdus Columbus. He is the man who discovered what is loosely called the 'pulmonary circulation'; and it really is quite absurd, in the face of the fact, that twenty years afterwards we find Ambrose Pare, the great French surgeon, ascribing this discovery to him as a matter of common notoriety, to find that attempts are made to give the credit of it to other people. So far as I know, this discovery of the course of the blood through the lungs, which is called the pulmonary circulation, is the one step in real advance that was made between the time of Galen and the time of Harvey. And I would beg you to note that the word "circulation" is improperly employed when it is applied to the course of the blood through the lungs. The blood from the right side of the heart, in getting to the left side of the heart, only performs a half-circle—it does not perform a whole circle—it does not return to the place from whence it started; and hence the discovery of the so-called "pulmonary circulation" has nothing whatever to do with that greater discovery which I shall point out to you by-and-by was made by Harvey, and which is alone really entitled to the name of the circulation of the blood.

If anybody wants to understand what Harvey's great desert really was, I would suggest to him that he devote himself to a course of reading, which I cannot promise shall be very entertaining, but which, in this respect at any rate, will be highly instructive—namely, the works of the anatomists of the latter part of the 16th century and the beginning of the 17th century. If anybody will take the trouble to do that which I have thought it my business to do, he will find that the doctrines respecting the action of the heart and the motion of the blood which were taught in every university in Europe, whether in Padua or in Paris, were essentially those put forward by Galen, 'plus' the discovery of the pulmonary course of the blood which had been made by Realdus Columbus. In every chair of anatomy and physiology (which studies were not then separated) in Europe, it was taught that the blood brought to the liver by the portal vein, and carried out of the liver to the 'vena cava' by the hepatic vein, is distributed from the right side of the heart, through the other veins, to all parts of the body; that the blood of the arteries takes a like course from the heart towards the periphery; and that it is there, by means of the 'anastomoses', more or less mixed up with the venous blood. It so happens, by a curious chance, that up to the year 1625 there was at Padua, which was Harvey's own university, a very distinguished professor, Spigelius, whose work is extant, and who teaches exactly what I am now telling you. It is perfectly true that, some time before, Harvey's master, Fabricius, had not only re-discovered, but had drawn much attention to certain pouch-like structures, which are called the valves of the veins, found in the muscular parts of the body, all of which are directed towards the heart, and consequently impede the flow of the blood in the opposite direction. And you will find it stated by people who have not thought much about the matter, that it was this discovery of the valves of the veins which led Harvey to imagine the course of the circulation of the blood. Now it did not lead Harvey to imagine anything of the kind. He had heard all about it from his master, Fabricius, who made a great point of these valves in the veins, and he had heard the theories which Fabricius entertained upon the subject, whose impression as to the use of the valves was simply this—that they tended to take off any excess of pressure of the blood in passing from the heart to the extremities; for Fabricius believed, with the rest of the world, that the blood in the veins flowed from the heart towards the extremities. This, under the circumstances, was as good a theory as any other, because the action of the valves depends altogether upon the form and nature of the walls of the structures in which they are attached; and without accurate experiment, it was impossible to say whether the theory of Fabricius was right or wrong. But we not only have the evidence of the facts themselves that these could tell Harvey nothing about the circulation, but we have his own distinct declaration as to the considerations which led him to the true theory of the circulation of the blood, and amongst these the valves of the veins are not mentioned.

(FIGURE 4.—The circulation of the blood as demonstrated by Harvey (A.D. 1628).)

Now then we may come to Harvey himself. When you read Harvey's treatise, which is one of the most remarkable scientific monographs with which I am acquainted—it occupies between 50 and 60 pages of a small quarto in Latin, and is as terse and concise as it possibly can be—when you come to look at Harvey's work, you will find that he had long struggled with the difficulties of the accepted doctrine of the circulation. He had received from Fabricius, and from all the great authorities of the day, the current view of the circulation of the blood. But he was a man with that rarest of all qualities—intellectual honesty; and by dint of cultivating that great faculty, which is more moral than intellectual, it had become impossible for him to say he believed anything which he did not clearly believe. This is a most uncomfortable peculiarity—for it gets you into all sorts of difficulties with all sorts of people—but, for scientific purposes, it is absolutely invaluable. Harvey possessed this peculiarity in the highest degree, and so it was impossible for him to accept what all the authorities told him, and he looked into the matter for himself. But he was not hasty. He worked at his new views, and he lectured about them at the College of Physicians for nine years; he did not print them until he was a man of fifty years of age; and when he did print them he accompanied them with a demonstration which has never been shaken, and which will stand till the end of time. What Harvey proved, in short, was this (see Figure 4)—that everybody had made a mistake, for want of sufficiently accurate experimentation as to the actual existence of the fact which everybody assumed. To anybody who looks at the blood-vessels with an unprejudiced eye it seems so natural that the blood should all come out of the liver, and be distributed by the veins to the different parts of the body, that nothing can seem simpler or more plain; and consequently no one could make up his mind to dispute this apparently obvious assumption. But Harvey did dispute it; and when he came to investigate the matter he discovered that it was a profound mistake, and that, all this time, the blood had been moving in just the opposite direction, namely, from the small ramifications of the veins towards the right side of the heart. Harvey further found that, in the arteries, the blood, as had previously been known, was travelling from the greater trunks towards the ramifications. Moreover, referring to the ideas of Columbus and of Galen (for he was a great student of literature, and did justice to all his predecessors), Harvey accepts and strengthens their view of the course of the blood through the lungs, and he shows how it fitted into his general scheme. If you will follow the course of the arrows in Figure 4 you will see at once that—in accordance with the views of Columbus—the blood passes from the right side of the heart, through the lungs, to the left side. Then, adds Harvey, with abundant proof, it passes through the arteries to all parts of the body; and then, at the extremities of their branches in the different parts of the body, it passes (in what way he could not tell, for his means of investigation did not allow him to say) into the roots of the vents—then from the roots of the veins it goes into the trunk and veins—then to the right side of the heart—and then to the lungs, and so on. That, you will observe, makes a complete circuit; and it was precisely here that the originality of Harvey lay. There never yet has been produced, and I do not believe there can be produced, a tittle of evidence to show that, before his time, any one had the slightest suspicion that a single drop of blood, starting in the left ventricle of the heart, passes through the whole arterial system, comes back through the venous system, goes through the lungs, and comes back to the place whence it started. But that is the circulation of the blood, and it was exactly this which Harvey was the first man to suspect, to discover, and to demonstrate.

But this was by no means the only thing Harvey did. He was the first who discovered and who demonstrated the true mechanism of the heart's action. No one, before his time, conceived that the movement of the blood was entirely due to the mechanical action of the heart as a pump. There were all sorts of speculations about the matter, but nobody had formed this conception, and nobody understood that the so-called systole of the heart is a state of active contraction, and the so-called diastole is a mere passive dilatation. Even within our own age that matter had been discussed. Harvey is as clear as possible about it. He says the movement of the blood is entirely due to the contractions of the walls of the heart—that it is the propelling apparatus—and all recent investigation tends to show that he was perfectly right. And from this followed the true theory of the pulse. Galen said, as I pointed out just now, that the arteries dilate as bellows, which have an active power of dilatation and contraction, and not as bags which are blown out and collapse. Harvey said it was exactly the contrary—the arteries dilate as bags simply because the stroke of the heart propels the blood into them; and, when they relax again, they relax as bags which are no longer stretched, simply because the force of the blow of the heart is spent. Harvey has been demonstrated to be absolutely right in this statement of his; and yet, so slow is the progress of truth, that, within my time, the question of the active dilatation of the arteries has been discussed.

Thus Harvey's contributions to physiology may be summed up as follows: In the first place, he was the first person who ever imagined, and still more who demonstrated, the true course of the circulation of the blood in the body; in the second place, he was the first person who ever understood the mechanism of the heart, and comprehended that its contraction was the cause of the motion of the blood; and thirdly, he was the first person who took a just view of the nature of the pulse. These are the three great contributions which he made to the science of physiology; and I shall not err in saying—I speak in the presence of distinguished physiologists, but I am perfectly certain that they will endorse what I say—that upon that foundation the whole of our knowledge of the human body, with the exception of the motor apparatus and the sense organs, has been gradually built up, and that upon that foundation the whole rests. And not only does scientific physiology rest upon it, but everything like scientific medicine also rests upon it. As you know—I hope it is now a matter of popular knowledge—it is the foundation of all rational speculation about morbid processes; it is the only key to the rational interpretation of that commonest of all indications of disease, the state of the pulse; so that, both theoretically and practically, this discovery, this demonstration of Harvey's, has had an effect which is absolutely incalculable, and the consequences of which will accumulate from age to age until they result in a complete body of physiological science.

(FIGURE 5.—The junction of the arteries and veins by capillary tubes, discovered by Malpighi (A.D. 1664).)

I regret that I am unable to pursue this subject much further; but there is one point I should mention. In Harvey's time, the microscope was hardly invented. It is quite true that in some of his embryological researches he speaks of having made use of a hand glass; but that was the most that he seems to have known anything about, or that was accessible to him at that day. And so it came about, that, although he examined the course of the blood in many of the lower animals—watched the pulsation of the heart in shrimps, and animals of that kind—he never could put the final coping-stone on his edifice. He did not know to the day of his death, although quite clear about the fact that the arteries and the veins do communicate, how it is that they communicate—how it was that the blood of the arteries passed into the veins. One is grieved to think that the grand old man should have gone down to his tomb without the vast satisfaction it would have given to him to see what the Italian naturalist Malpighi showed only seven years later, in 1664, when he demonstrated, in a living frog, the actual passage of the blood from the ultimate ramifications of the arteries into the veins. But that absolute ocular demonstration of the truth of the views he had maintained throughout his life it was not granted to Harvey to see. What he did experience was this: that on the publication of his doctrines, they were met with the greatest possible opposition; and I have no doubt savage things were uttered in those old controversies, and that a great many people said that these new-fangled doctrines, reducing living processes to mere mechanism, would sap the foundations of religion and morality. I do not know for certain that they did, but they said things very like it. The first point was to show that Harvey's views were absolutely untrue; and not being able to succeed in that, opponents said they were not new; and not being able to succeed in that, that they didn't matter. That is the usual course with all new discoveries. But Harvey troubled himself very little about these things. He remained perfectly quiet; for although reputed a hot-tempered man, he never would have anything to do with controversy if he could help it; and he only replied to one of his antagonists after twenty years' interval, and then in the most charming spirit of candour and moderation. But he had the great satisfaction of living to see his doctrine accepted upon all sides. At the time of his death, there was not an anatomical school in Europe in which the doctrine of the circulation of the blood was not taught in the way in which Harvey had laid it down. In that respect he had a happiness which is granted to very few men.

I have said that the other great investigation of Harvey is not one which can be dealt with to a general audience. It is very complex, and therefore I must ask you to take my word for it that, although not so fortunate an investigation, not so entirely accordant with later results as the doctrine of the circulation; yet that still, this little treatise of Harvey's has in many directions exerted an influence hardly less remarkable than that exerted by the Essay upon the Circulation of the Blood.

And now let me ask your attention to two or three closing remarks.

If you look back upon that period of about 100 years which commences with Harvey's birth—I mean from the year 1578 to 1680 or thereabouts—I think you will agree with me, that it constitutes one of the most remarkable epochs in the whole of that thousand years which we may roughly reckon as constituting the history of Britain. In the commencement of that period, we may see, if not the setting, at any rate the declension of that system of personal rule which had existed under previous sovereigns, and which, after a brief and spasmodic revival in the time of George the Third, has now sunk, let us hope, into the limbo of forgotten things. The latter part of that 100 years saw the dawn of that system of free government which has grown and flourished, and which, if the men of the present day be the worthy descendants of Eliott and Pym, and Hampden and Milton, will go on growing as long as this realm lasts. Within that time, one of the strangest phenomena which I think I may say any nation has ever manifested arose to its height and fell—I mean that strange and altogether marvellous phenomenon, English Puritanism. Within that time, England had to show statesmen like Burleigh, Strafford, and Cromwell—I mean men who were real statesmen, and not intriguers, seeking to make a reputation at the expense of the nation. In the course of that time, the nation had begun to throw off those swarms of hardy colonists which, to the benefit of the world—and as I fancy, in the long run, to the benefit of England herself—have now become the United States of America; and, during the same epoch, the first foundations were laid of that Indian Empire which, it may be, future generations will not look upon as so happy a product of English enterprise and ingenuity. In that time we had poets such as Spenser, Shakespere, and Milton; we had a great philosopher, in Hobbes; and we had a clever talker about philosophy, in Bacon. In the beginning of the period, Harvey revolutionized the biological sciences, and at the end of it, Newton was preparing the revolution of the physical sciences. I know not any period of our history—I doubt if there be any period of the history of any nation—which has precisely such a record as this to show for a hundred years. But I do not recall these facts to your recollection for a mere vainglorious purpose. I myself am of opinion that the memory of the great men of a nation is one of its most precious possessions—not because we have any right to plume ourselves upon their having existed as a matter of national vanity, but because we have a just and rational ground of expectation that the race which has brought forth such products as these may, in good time and under fortunate circumstances, produce the like again. I am one of those people who do not believe in the natural decay of nations. I believe, to speak frankly, though perhaps not quite so politely as I could wish—but I am getting near the end of my lecture—that the whole theory is a speculation invented by cowards to excuse knaves. My belief is, that so far as this old English stock is concerned it has in it as much sap and vitality and power as it had two centuries ago; and that, with due pruning of rotten branches, and due hoeing up of weeds, which will grow about the roots, the like products will be yielded again. The "weeds" to which I refer are mainly three: the first of them is dishonesty, the second is sentimentality, and the third is luxury. If William Harvey had been a dishonest man—I mean in the high sense of the word—a man who failed in the ideal of honesty—he would have believed what it was easiest to believe—that which he received on the authority of his predecessors. He would not have felt that his highest duty was to know of his own knowledge that that which he said he believed was true, and we should never have had those investigations, pursued through good report and evil report, which ended in discoveries so fraught with magnificent results for science and for man. If Harvey had been a sentimentalist—by which I mean a person of false pity, a person who has not imagination enough to see that great, distant evils may be much worse than those which we can picture to ourselves, because they happen to be immediate and near (for that, I take it, is the essence of sentimentalism)—if Harvey had been a person of that kind, he, being one of the kindest men living, would never have pursued those researches which, as he tells us over and over again, he was obliged to pursue in order to the ascertainment of those facts which have turned out to be of such inestimable value to the human race; and I say, if on such grounds he had failed to do so, he would have failed in his duty to the human race. The third point is that Harvey was devoid of care either for wealth, or for riches, or for ambition. The man found a higher ideal than any of these things in the pursuit of truth and the benefit of his fellow-men. If we all go and do likewise, I think there is no fear for the decadence of England. I think that our children and our successors will find themselves in a commonwealth, different it may be from that for which Eliott, and Pym, and Hampden struggled, but one which will be identical in the substance of its aims—great, worthy, and well to live in.

THE END