[319] ON the coming First of April, three hundred years will have elapsed, since the birth of William Harvey, who is popularly known as the discoverer of the circulation of the blood.

Many opinions have been held respecting the exact nature and value of Harvey's contributions to the elucidation of the fundamental problem of the physiology of the higher animals; from those which deny him any merit at all–indeed, roundly charge him with the demerit of plagiarism–to those which enthrone him in a position of supreme honour among great discoverers in science. Nor has there been less controversy as to the method by which Harvey obtained the results which have made his name famous. I think it is desirable that no obscurity should hang around these questions ; and I add my mite to the store of disquisitions on Harvey which this year is likely to bring forth, in the hope that it may help to throw light upon several points about which darkness has accumulated, partly by accident and partly by design.

Every one knows that the pulsation which can be felt or seen between the fifth and sixth ribs, on the left side of a living man, is caused by the beating of the heart; and that, in some way or other, the ceaseless activity of this organ is essential to life. Let it be arrested, and, instantaneously, intellect, volition, even sensation, are abolished, and the most vigorous frame collapses, a pallid image of death.

Every one, again, is familiar with those other pulsations which may be felt or seen, at the wrist, behind the inner ankle, or on the [320] temples; and which coincide in number and are nearly simultaneous with those of the heart. In the region of the temples it is easy, especially in old people, to observe that the pulsation depends on the change of form of a kind of compressible branched structure which lies beneath the skin, and is termed an artery. Moreover, the least observant person must have noticed, running beneath the skin of various parts of the body, notably the hands and arms, certain other bluish-looking bands which do not pulsate, and which mark the position of structures somewhat like the arteries, which are called veins.

Finally, accidental wounds have demonstrated to all of us that the body contains an abundance of a warm red fluid–the blood. If the wound has traversed a vein, the blood flows in torrents from its interior, in an even stream ; if it has involved an artery, the flow takes place by jerks, which correspond in interval with the pulsations of the artery itself and with those of the heart.

These are facts which must have been known ever since the time when men first began to attend to and reflect. upon the every-day course of nature, of which we form a part. I doubt not, also, that butchers, and those who studied the entrails of animals for purposes of divination, must very early have noticed that both the arteries and the veins are disposed in the fashion of a tree, the trunk of which is close to the heart and connected with it, while the branches ramify all over the body. Moreover, they could not fail to observe that the heart contains cavities, and that some of these communicate with the stem of the arteries and some with the stem of the veins. Again, the regular rhythmical changes of form, which constitute the beating of the heart, are so striking in recently killed animals, and in criminals subjected to modes of punishment which once were common, that the demonstration that the heart is a contractile organ must have been very early obtained, and have thus afforded an unintentional experimental explanation of the cause of the pulsation felt between the ribs.

These facts constitute the foundation of our knowledge of the structure and functions of the heart and blood-vessels of the human and other higher animal bodies. They are to be regarded as parts of common knowledge, of that information which is forced upon us whether we desire to possess it or not; they have not been won by that process of seeking out the exact nature and the causal connection of phenomena, to the results of which the term science may properly be restricted.

Scientific investigation began when men went further, and, [321] impelled by the thirst for knowledge, sought to make out the exact structure of all these parts, and to comprehend the mechanical effects of their arrangement and of their activity.

The Greek mind had long entered upon this scientific stage, so far back as the fourth century before the commencement of our era. For, in the works attributed to Aristotle, which constitute a sort of encyclopedia of the knowledge of that time, there is evidence that the writer knows as much as has been mentioned, and he refers to the views of his predecessors. Two thousand two hundred years ago the sciences of anatomy and physiology existed, though they were as yet young and their steps tottered.

Aristotle's description of the heart is often cited as an example of his ignorance, but I think unjustly. However this may be, it is certain that, not long after his time, great additions were made to anatomical and physiological science. The Greek anatomists, exploring the structure of the heart, found that it contained two principal cavities, which we now call the ventricles, separated by a longitudinal partition, or septum: the one ventricle is on its left, the other on its right side. It was to the fleshy body which contains the ventricles that the ancients restricted the title of "heart." Moreover, there is another respect in which their terminology was so different from that of the moderns, that, unless we recollect that the facts may be just as accurately stated in their fashion as in ours, we are liable to fall into the mistake of supposing that they are blundering.¹ What they speak of as the auricles of the heart, we term the appendices of the auricles; and what we call the auricles are, for the ancients, on the right side, a part of the great vein or vena cava, and, on the left side, a part of the arterial system–the root, in fact, of what they termed the arteria venosa. Thus they speak of the auricles as mere appendages, or dilatations, situated upon the arterial and venous trunks respectively, close to the heart; and they always say that the vena cava and the arteria venosa open into the right and left ventricles respectively. And this was the basis of their classification of the vessels, for they held all those vessels which, in this sense, open into the right ventricle to be veins, and all those which open into the left ventricle to be arteries. But here a difficulty arose. They observed that the aorta, or stem of the arteries, and all the con[322]spicuous branches which proceed from it to the body in general are very different from the veins; that they have much thicker walls and stand open when they are cut, while the thin-walled veins collapse. But the "vein" which connected the right ventricle and the lungs had the thick coat of an artery, while the "artery" which connected the left ventricle and the lungs had the thin coat of a vein. Hence they called the former the vena arteriosa, or artery-like vein, and the latter, the arteria venosa, or vein-like artery.

The vena arteriosa is what we call the pulmonary artery, the arteria venosa is our pulmonary vein; but in trying to understand the old anatomists it is essential to forget our nomenclature and to. adopt theirs. With this precaution, and with the facts before our mind's eye, their statements will be found to be, in the main, exceedingly accurate.

About the year 300 B.C. a great discovery, that of the valves, of the heart, was made by Erasistratus. This anatomist found around the opening by which the vena cava communicates with the right ventricle, three triangular membranous folds, disposed in such a manner as to allow any fluid contained in the vein to pass into the ventricle, but not back again. The opening of the vena arteriosa into the right ventricle is quite distinct from that. of the vena cava; and Erasistratus observed that it is provided with three pouch-like, half-moon-shaped valves; the arrangement of which is such that a fluid can pass out of the ventricle into, the vena arteriosa, but not back again. Three similar valves were found at the opening of the aorta into the left ventricle. The arteria venosa had a distinct opening into the same ventricle, and this was provided with triangular membranous valves, like those on the right side, but only two in number. Thus the ventricles had four openings, two for each; and there were altogether eleven valves, disposed in such a manner as to permit fluids to enter the ventricles from the vena cava and the arteria venosa respectively, and to pass out of the ventricles by the vena arteriosa and the aorta. respectively, but not to go the other way.

It followed from this capital discovery, that, if the contents of the heart are fluid, and if they move at all, they can only move in one way; namely, from the vena cava, through the ventricle and towards, the lungs, by the vena arteriosa, on the right side; and, from the lungs, by way of the arteria venosa, through the ventricle, and out by the aorta for distribution in the body, on the left side.

Erasistratus thus, in a manner, laid the foundations of the theory of the motion of the blood. But it was not given to him to get any [323] further. What the contents of the heart were, and whether they moved or not, was a point which could be determined only by experiment. And, for want of sufficiently careful experimentation, Erasistratus strayed into a hopelessly misleading path. Observing that the arteries are usually empty of blood after death, he adopted the unlucky hypothesis that this is their normal condition, and that during life, also, they are filled with air. And, it will be observed, that it is not improbable that Erasistratus' discovery of the valves of the heart and of their mechanical action strengthened him in this view. For, as the arteria venosa branches out in the lungs, what more likely than that its ultimate ramifications absorb the air which is inspired; and that this air, passing into the left ventricle, is then pumped all over the body through the aorta, in order to supply the vivifying principle which evidently resides in the air; or, it may be, of cooling the too great heat of the blood? How easy to explain the elastic bounding feel of a pulsating artery by the hypothesis that it is full of air! Had Erasistratus only been acquainted with the structure of insects, the analogy of their tracheal system would have been a tower of strength to him. There was no prima facie absurdity in his hypothesis–and experiment was the sole means of demonstrating its truth or falsity.

More than four hundred years elapsed before the theory of the motion of the blood returned once more to the strait road which leads truthwards; and it was brought back by the only possible method, that of experiment. A man of extraordinary genius, Claudius Galenus, of Pergamos, was trained to anatomical and physiological investigation in the great schools of Alexandria, and spent a long life in incessant research, teaching, and medical practice.² More than one hundred and fifty treatises from his pen, on philosophical, literary, scientific, and practical topics, are extant; and there is reason to believe that they constitute not more than a third of his works. No former anatomist had reached his excellence, while he may be regarded as the founder of experimental physiology. And, it is precisely because he was a master of the experimental method, that he was able to learn more about the motions of the heart and of the blood than any of his predecessors; and to leave to posterity a legacy of knowledge, which was not substantially increased for more than thirteen hundred years.

The conceptions of the structure of the heart and vessels, of their actions, and of the motion of the blood in them, which Galen entertained, are not stated in a complete shape in any one of his [324] numerous works. But a careful collation of the various passages in which these conceptions are expressed, leaves no doubt upon my mind that Galen's views respecting the structure of the organs concerned were, for the most part, as accurate as the means of anatomical analysis at his command permitted; and that he had exact and consistent, though by no means equally just, notions of the actions of these organs, and of the movements of the blood.

Starting from the fundamental facts established by Erasistratus respecting the structure of the heart and the working of its valves, Galen's great service was the proof, by the only evidence which could possess demonstrative value, namely, by that derived from experiments upon living animals, that the arteries are as much full of blood during life as the veins are, and that the left cavity of the heart, like the right, is also filled with blood.

Galen, moreover, correctly asserted, though the means of investigation at his disposition did not allow him to prove the fact, that the ramifications of the vena arteriosa in the substance of the lungs communicate with those of the arteria venosa, by direct, though invisible, passages, which he terms anastomoses; and that, by means of these communications, a certain portion of the blood of the right ventricle of the heart passes through the lungs into the left ventricle. In fact, Galen is quite clear as to the existence of a current of blood through the lungs, though not of such a current as we now know traverses them. For, while he believed that a part of the blood of the right ventricle passes through the lungs, and even, as I shall show, described at length the mechanical arrangements by which he supposes this passage to be effected, he considered that the greater part of the blood in the right ventricle passes directly, through certain pores in the septum, into the left ventricle. And this was where Galen got upon his wrong track, without which divergence a man of his scientific insight must infallibly have discovered the true character of the pulmonary current, and not improbably have been led to anticipate Harvey.

But, even in propounding this erroneous hypothesis of the porosity of the septum, it is interesting to observe with what care Galen distinguishes between observation and speculation. He expressly says that he has never seen the openings which he supposes to exist, and that he imagines them to be invisible, by reason of their small size and their closure by the refrigeration of the heart, after death. Nevertheless, he cannot doubt their existence, partly because the septum presents a great number of pits which obviously lead into its substance as they narrow, and, as he is so fond of saying, "Nature [325] makes nothing in vain and, partly because the vena cava is so large in comparison with the vena arteriosa, that he does not see how all the blood poured into the ventricle could be got rid of if the latter were its only channel.

Thus, for Galen, the course of the blood through the heart was on the right side, in by the vena cava, out by the vena arteriosa and the pores of the septum; on the left side, in by the pores of the septum and by the arteria venosa, out by the aorta. What now becomes of the blood which, filling the vena arteriosa, reaches the lungs? Galen's views are perfectly definite about this point. The vena arteriosa communicates with the arteria venosa in the lungs by numerous connecting channels. During expiration, the blood which is in the lungs, being compressed, tends to flow back into the heart by way of the vena arteriosa; but it is prevented from doing so, in consequence of the closure of the semilunar valves. Hence, a portion of it is forced the other way, through the anastomoses into the arteria venosa; and then, mixed with "pneuma," it is carried to the left ventricle, whence it is propelled, through the aorta and its branches, all over the body.

Galen not only took great pains to obtain experimental proof that, during life, all the arteries contain blood and not air, as Erasistratus suppose ; but he distinctly affirms that the blood in the left ventricle and in the arteria venosa is different from that in the right ventricle and in the veins, including the vena arteriosa; and that the difference between the two lies in colour heat, and the greater quantity of "pneuma" contained in arterial blood. Now this "pneuma" is something acquired by the blood in the lungs. The air which is inspired into these organs is a kind of aliment. It is not taken bodily into the venosa arteria and thence carried to the left ventricle to fill the arterial system, as Erasistratus thought. On the contrary, Galen repeatedly argues that this cannot be the case, and often refers to his experimental proofs that the whole arterial system is full of blood during life. But the air supplies a material kindred to the "pneuma," out of which and the blood the "pneuma" is concocted. Hence, the contents of the arteria venosa are. largely composed of "pneuma," and it is out of the mixture of this with the blood which filters through the septum, that the bright "pneumatic" blood found in the arteries, and by them distributed over the body, is formed. The arteria venosa is a channel by which "pneuma" reaches the heart, but this is not its exclusive function; for it has at the same time, to allow of the passage of certain fuliginous and impure matters which the blood contains, in the opposite [326] direction ; and, it is for this reason, that there are only two valves where the arteria venosa enters the ventricle. These not fitting quite tightly, allow of the exit of the fuliginous matters in question.

Modern commentators are fond of pouring scorn upon Galen, because he holds that the heart is not a muscle. But if what he says on this subject is studied with care and impartiality, and with a due recollection of the fact that Galen was not obliged to use the terminology of the nineteenth century, it will be seen that he by no means deserves blame, but rather praise, for his critical discrimination of things which are really unlike.

All that Galen affirms is that the heart is totally unlike one of the ordinary muscles of the body, not only in structure, but in being independent of the control of the will; and, so far from doubting that the walls of the heart are made up of active fibres, he expressly describes these fibres and what he supposes to be their arrangement and their mode of action. The fibres are of three kinds, longitudinal, transverse, and oblique. The action of the longitudinal fibres is to draw in, that of the circular fibres to expel, and that of the oblique fibres to retain, the contents of the heart. How Galen supposed the oblique fibres could execute the function ascribed to them, I do not know; but it is clear that he thought that the activity of the circular fibres increased, and that of the longitudinal fibres diminished, the size of the cavities which they surrounded. Nowadays we term an active fibre muscular; Galen did not, unless, in addition, it possessed the characters of voluntary muscle.

According to Galen, the arteries have a systole and diastole (that is, a state of contraction and a state of dilatation), which alternate with those of the ventricles, and depend upon active contractions and dilatations of their walls. This active faculty of the arteries is inherent in them, because they are, as it were, productions of the substance of the ventricles which possess these faculties; and it is destroyed when the vital continuity of the arteries with the heart is destroyed by section or ligature. The arteries fill, therefore, as bellows fill, not as bags are blown full.

The ultimate ramifications of the arteries open by anastomoses into those of the veins, all over the body ; and the vivifying arterial blood thus communicates its properties to the great mass of blood in the veins. Under certain conditions, however, the blood may flow from the veins to the arteries, in proof of which Galen adduces the fact that the whole vascular system may be emptied by opening an artery.

[327] The two ventricles, the auricles, the pulmonary vessels, and the aorta with its branches, arc conceived by the Greek anatomist to be an apparatus superadded to the veins, which he regards as the essential foundation and the most important part of the whole vascular system. No portion of Galen's doctrines has been more sharply criticised than his persistent refusal to admit that the veins, like the arteries, take their origin in the heart, and his advocacy of the view that the fons et origro of the whole venous system is to be sought in the liver. Here, however, I must remark, that it is only those who are practically ignorant of the facts who can fail to see that Galen's way of stating the matter is not only anatomically justifiable, but that, until the true nature of the circulation was understood and physiological considerations overrode those based upon mere structure, there was much more to be said for it than for the opposite fashion.

Remembering that what we call the right auricle was, for Galen, a mere part of the vena cava, it is impossible not to be struck by the justice of his striking comparison of the vena cava to the trunk of a tree, the roots of which enter the liver as their soil, while the branches spread all over the body. Galen remarks that the existence of the vena portæ, which gathers blood from the alimentary canal, and then distributes it to the liver, without coming near the heart, is a fatal objection to the view of his opponents, that all the veins take their rise in the heart; and the argument is unanswerable, so far as the mere anatomical facts are concerned.

Nothing could have appeared more obvious to the early anatomists than that the store of nutriment carried by the vena portæ to the liver was there elaborated into blood; and then, being absorbed by the roots of the venous system, was conveyed by its branches all over the body. The veins were thus the great distributors of the blood; the heart and arteries were a superadded apparatus for the dispersion of a "pneumatized," or vivified portion of the blood through the arteries; and this addition of "pneuma," or vivification, took place in the gills of water-breathing animals and in the lungs of air-breathers. But, in the latter case, the mechanism of respiration involved the addition of a new apparatus, the right ventricle, to insure the constant flow of blood through these organs of "pneumatization."

Every statement in the preceding paragraphs can be justified by citations from Galen's works; and, therefore, it must be admitted that he had a wonderfully correct conception of the structure and disposition of the heart and vessels, and of the mode in which the [328] ultimate ramifications of the latter communicate, both in the body generally and in the lungs; that his general view of the functions of the heart was just; and that he knew that blood passes from the right side of the heart, through the lungs, to the left side, and undergoes a great change in quality, brought about by its relation with the air in the lungs, in its course. It is unquestionable, therefore, that Galen, so far, divined the existence of a "pulmonary circulation," and that he came near to a just conception of the process of respiration; but he had no inkling even of the systemic circulation; he was quite wrong about the perforation of the septum; and his theory of the mechanical causes of the systole and diastole of the heart and arteries was erroneous. Nevertheless, for more than thirteen centuries, Galen was immeasurably in advance of all other anatomist ; and some of his notions, such as that about the active dilatation of the walls of the vessels, have been debated by physiologists of the. present generation.

No one can read Galen's works without being impressed by the marvellous extent and diversity of his knowledge, and by his clear grasp of those experimental methods by which, alone, physiology can be advanced. It is pathetic to watch the gropings of a great mind like his around some cardinal truth, which he failed to apprehend simply because he had not in his possession the means of investigation, which, at this time, are in the hands of every student. I have seen learned disquisitions on the theme, Why did the ancients fail in their scientific inquiries? I know not what may be the opinion of those who are competent to judge of the labours of. Euclid, or of Hipparchus, or of Archimedes; but I think that the question which will rise to the lips of the biological student, fresh from the study of the works of Galen, is rather, How did these men, with their imperfect appliances, attain so vast a measure of success? In truth, it is in the Greek world that we must seek, not only the predecessors, but the spiritual progenitors, of modern men of science. The slumbering aptitude of Western Europe for physical investigation was awakened by the importation of Greek knowledge and of Greek method; and modern anatomists and physiologists are but the heirs of Galen, who have turned to good account the patrimony bequeathed by him to the civilized world.

The student of the works of the anatomists and physiologists of modern Europe in the fifteenth and the beginning of the sixteenth centuries, will find that they were chiefly occupied in learning of their own knowledge what Galen knew. It is not strange, therefore, that they were overpowered by so vast a genius, and that [329] they allowed themselves to be enslaved by his authority, in a manner which he would have been the first to reprove. Versalius, the great reformer of anatomy, had a bitter struggle to carry on Galen's work, by showing where he had erred in expounding the structure of the human body, on the faith of observations made on the lower animals–but it was not till the middle of the sixteenth century, that anything was done to improve on Galen's physiology, and especially to amend his doctrines concerning the movements of the heart and of the blood.

The first step in this direction is very generally ascribed to Michael Servetus, the unhappy man whose judicial murder by slow fire was compassed by John Calvin; he being instigated thereto by theological antagonism, intensified by personal hatred; and aided and abetted in his iniquity by the Protestant Churches of Switzerland. The whole story has recently been clearly and fully told by Dr. Willis,³ and I refer to it only for the purpose of remarking, that the name and fame of Calvin's victim would probably have been as completely obliterated as his persecutor intended they should be, had it not happened that one or two copies of the 'Christianismi Restitutio,' the attempted publication of which was the immediate cause of Servetus's death, were saved from destruction.

Servetus was undoubtedly well acquainted with anatomy, inasmuch as he was demonstrator to Johannes Guinterus in the, School of Paris, where he had Vesalius for his colleague; and, in his later years, he practised as a physician. Hence it is not wonderful to find that the 'Christianismi Restitutio,' although essentially a farrago of scatterbrained theological speculations, contains much physiological matter. And it is in developing his conception of the relations between God and man, that Servetus wrote the well-known passages on which many have asserted his claim to the discovery of the course of the blood from the heart, through the lungs, and back to the heart; or what is now termed the pulmonary circulation.

I have studied the passages in question with great care, and with every desire to give Servetus his due, but I confess I cannot see that he made much advance upon Galen.⁴ As we have seen, Galen said [330] that some blood goes to the left side of the heart from the right side through the lungs, but that the greater part traverses the septum. Servetus appears, at first, to declare that all the blood of the right side goes through the lungs to the left side, and that the septum is imperforate. But he qualifies his assertion by admitting that some of the blood of the right ventricle may transude through the septum, and thus the question between him and Galen becomes merely one of degree. Servetus cites neither observation nor experiment in favour,of the imperviousness of the septum; and the impression upon my mind is that he really knew no more than Versalius had already published, but that the tendency to headlong speculation, which is so characteristic of the man, led him to rush in where his more thoughtful colleague held back. .

Whatever may be thought of the moral claim of Servetus to be regarded as the discover of the pulmonary circulation, there is no reason to believe that he had any influence on the actual progress of science.⁵ For Calvin dealt with all the packages of the edition of the 'Christianismi Restitutio' he could lay hands on as he had served their author, and it is believed that only a few copies escaped the flames. One of these, in the National Library of France, is the very book used by the counsel for the prosecution, whom Calvin prompted, at Geneva; another is in Vienna. The public had no access to the work until it was reprinted, more than two centuries afterwards.

The first author who declared, without any qualification, that the septum of the ventricles is imperforate, and that all the blood of the right ventricle traverses the lungs and (except so much as may be retained for the nutrition of these organs) passes to the left ventricle, was Realdus Columbus, professor of anatomy in the famous school of Padua. The remarkable treatise, 'De Re Anatomica,' of this able anatomist, was published in 1559, or only six years after the death of Servetus, of whose notions there is no evidence that Columbus had any cognisance. Moreover, Columbus, as able an experimenter as he was a skilful dissector, deals with the question in a very different way from Servetus; so that, from his time, the existence of the pulmonary circulation, in the modern sense, may be said to have become established. Ambrose Paré, the great surgeon, writing in 1579,⁶ refers to the course of the blood through the lungs as notoriously the discovery of Columbus. And I think not only that Realdus [331] is entitled to the whole credit of this very considerable advance upon Galen's views; but that he is the only physiologist, between the time of Galen and that of Harvey, who made any important addition to the theory of the circulation.

The claim which is put forward on behalf of the celebrated botanist, Cæsalpinus, appears to me to be devoid of any foundation.⁷ Many years after the publication of the work of Realdus Columbus, who was professor at the most famous and most frequented anatomical school of the time, and who assuredly was the last man to hide his light under a bushel, Cæsalpinus incidentally describes the pulmonary circulation in terms which simply embody a statement of Columbus's doctrine; adding nothing, and, to his credit be it said, claiming nothing. Like all the rest of the world since venesection was invented, Cæsalpinus noticed that the vein swells on the side of the ligature away from the heart; and he observes that this is inconsistent with the received views of the motion of the blood in the veins. If he had followed up the suggestion thus made to him by the needful experimental investigation, he might have anticipated Harvey; but he did not.

Again, Cannani discovered the existence of valves in some of the veins, in 1547; and Fabricius rediscovered them, and prominently drew attention to their mechanism, in 1574. Nevertheless, this discovery, important as it was, and widely as it became known, had absolutely no effect in leading either the discoverers or their contemporaries to a correct view of the general circulation. In common with all the anatomists of the sixteenth century, Fabricius believed that the blood proceeded from the main trunk, or vena cava, outwards to the smallest ramifications of the veins, in order to subserve the nutrition of the parts in which they are distributed; and instead of being led by the mechanical action of the valves to reverse his theory of the course of the venous blood, he was led by the dominant theory of the course of the blood to interpret the meaning of the valvular mechanism. Fabricius, in fact, considered that the office of the valves [332] was to break the impetus of the venous blood, and to prevent its congestion in the organs to which it was sent; and, until the true course of the blood was demonstrated, this was as likely an hypothesis as any other.

The best evidence of the state of knowledge respecting the motions of the heart and blood in Harvey's time is afforded by those works of his contemporaries which immediately preceded the publication of the 'Exercitatio Anatomica,' in 1628.⁸ And none can be more fitly cited for this purpose than the 'De Humani Corporis Fabrica, Libri decem,' of Adrian vati den Spieghel, who, like Harvey, was a pupil of Fabricius of Aquapendente, and was of such distinguished ability and learning that he succeeded his master in the chair of anatomy of Padua.

Van den Spieghel, or Spigelius, as he called himself, in accordance with the fashion of those days, died comparatively young in 1625, and his work was edited by his friend Daniel Bucretius, whose preface is dated 1627. The accounts of the heart and vessels, and of the motion of the blood, which it contains, are still and clear; but, beyond matters of detail, they go beyond Galen in only two points; and with respect to one of these, Spigelius was in error.

The first point is the "pulmonary circulation," which is taught as Columbus taught it nearly eighty years before. The second point is, so far as I know, peculiar to Spigelius himself. He thinks that the pulsation of the arteries has an effect in promoting the motion of the blood contained in the veins which accompany them. Of the true course of the blood as a whole, Spigelius has no more suspicion than had any other physiologist of that age, except William Harvey; no rumour of whose lectures at the College of Physicians, commenced six years before Spieghel's death, was likely in those days of slow communication and in the absence of periodical publications to have reached Italy.

Now let any one familiar with the pages of Spigelius take up Harvey's treatise and mark the contrast.

The main object of the 'Exercitatio' is to put forth and demonstrate, by direct experimental and other accessory evidence, a pro[333]position which is far from being even hinted at, either by Spigelius, or by any of his contemporaries or predecessors; and which is in diametrical contradiction to the views respecting the course of the blood in the veins which are expounded in their works.

From Galen to Spigelius, they one and all believed that the blood in the vena cava and its branches flows from the main trunk towards the smallest ramifications. There is a similar consensus in the doctrine, that the greater part, if not the whole, of the blood thus distributed by the veins is derived from the liver; in which organ it is generated out of the materials brought from the alimentary canal by means of the vena portæ. And all Harvey's predecessors further agree in the belief that only a small fraction of the total mass of the venous blood is conveyed by the vena arteriosa to the lungs and passes by the arteria venosa to the left ventricle, thence to be distributed over the body by the arteries. Whether some portion of the refined and "pneumatic" arterial blood traversed the anastomotic channels, the existence of which was assumed, and so reached the systemic veins or whether, on the contrary, some portion of the venous blood made its entrance by the same passages into the arteries, depended upon circumstances. Sometimes the current might set one way, sometimes the other.

In direct opposition to these universally received views, Harvey asserts that the natural course of the blood in the veins is from the peripheral ramifications towards the main trunk; that the mass of the blood to be found in the veins at any moment was, a short time before, contained in the arteries, and has simply flowed out of the latter into the veins; and finally that the stream of blood which runs from the arteries into the veins is constant, continuous, and rapid.

According to the view of Harvey's predecessors⁹the veins may be compared to larger and smaller canals, fed by a spring which trickles into the chief canals whence the water flows to the rest. The heart and lungs represent an engine set up in the principal canal to aërate some of the water and scatter it all over the garden. Whether any of this identical water came back to the engine or not would be a matter of chance, and it would certainly have no sensible effect on the motion of the water in the canals. In Harvey's conception of the matter, on the other hand, the garden is watered by, channels so arranged as to form a circle, two points of which are occupied by propulsive engines. The water is kept moving in a continual round [334] within its channels, as much entering the engines on one side, as leaves them on the other; and the motion of the water is entirely due to the engines.

It is in conceiving the motion of the blood, as a whole, to be circular, and in ascribing that circular motion simply and solely to the contractions of the walls of the heart, that Harvey is so completely original. Before him, no one, that I can discover, had ever so much as dreamed that a given portion of blood contained, for example, in the right ventricle of the heart, may, by the mere mechanical operation of the working of that organ, be made to return to the very place from which it started, after a long journey through the lungs and through the body generally. And, it should be remembered, that it is to this complete circuit of the blood, alone, that the term "circulation", can, in strictness, be applied. It is of the essence of a circular motion that that which moves returns to the place from whence it started. Hence, the discovery of the course of the blood from the right ventricle, through the lungs, to the left ventricle was in nowise an anticipation of the discovery of the circulation of the blood. For the blood which traverses this part of its course no more describes a circle, than the dweller in a street who goes out of his own house and enters his next-door neighbour's does so. Although there may be nothing but a party wall between him and the room he has just left, it constitutes an efficient difense de circuler. Thus, whatever they may have known of the so-called pulmonary circulation, to say that Servetus, or Columbus, or Cæsalpinus deserves any share of the credit which attaches to Harvey appears to me to be to mistake the question at issue.

It must further be borne in mind, that the determination of the true course taken by the whole mass of the blood is only the most conspicuous of the discoveries of Harvey; and that his analysis of the mechanism by which the circulation is brought about is far in advance of anything which had previously been published. For the first time, it is shown that the walls of the heart are active only during its systole or contraction, and that the dilatation of the heart, in the diastole, is purely passive. Whence it follows, that the impulse by which the blood is propelled is a vis à tergo, and that the blood is not drawn into the heart by any such inhalent or suctorial action, as not only the predecessors, but many of the successors of Harvey imagined it to possess.

Harvey is no less original in his view of the cause of the arterial pulse. In contravention of Galen and of all other anatomists up to his own time, he affirms that the stretching of the arteries which gives [335] rise to the pulse is not due to the active dilatation of their walls, but to their passive distension by the blood which is forced into them at each beat of the heart; reversing Galen's dictum, he says that they dilate as bags and not as bellows. This point of fundamental, practical as well as theoretical, importance is most admirably demonstrated, not only by experiment, but by pathological illustrations.

One of the weightiest arguments in Harvey's demonstration of the circulation is based upon the comparison of the quantity of blood driven out of the heart, at each beat, with the total quantity of blood in the body. This, so far as I know, is the first time that quantitative considerations are taken into account in the discussion of a. physiological problem. But one of the most striking differences between ancient and modern physiological science, and one of the chief reasons of the rapid progress of physiology in the last half-century, lies in the introduction of exact quantitative determinations into physiological experimentation and observation. The moderns use means of accurate measurement, which their forefathers neither possessed nor could conceive, inasmuch as they are products of mechanical skill of the last hundred years, and of the advance of branches of science which hardly existed, even in germ, in the seventeenth century.

Having attained to a knowledge of the circulation of' the blood, and of the conditions on which its motion depends, Harvey had a. ready deductive solution for problems which had puzzled the older physiologists. Thus the true significance of the valves in the veins became at once apparent. Of no importance while the blood is flowing in its normal course towards the heart, they at once oppose any accidental reversal of its current, which may arise from the pressure of adjacent muscles, or the like. And, in like manner, the swelling of the veins on the further side of the ligature, which so, much troubled Cæsalpinus, became at once intelligible, as the natural result of the damming up of the returning current.

In addition to the great positive results which are contained in the treatise which Harvey modestly calls an 'Exercise'; and which is, in truth, not so long as many a pamphlet about some wholly insignificant affair; its pages are characterized by such precision and simplicity of statement, such force of reasoning, and such a clear comprehension of the methods of inquiry and of the logic of physical science, that it holds a unique rank among physiological monographs. Under this aspect, I think I may fairly say that it has rarely been. equalled and never surpassed.

[336] Such being the state of knowledge among his contemporaries, and such the immense progress effected by Harvey, it is not wonderful that the publication of the 'Exercitatio' produced a profound sensation. And the best indirect evidence of the originality of its author, and of the revolutionary character of his views, is to be found in the multiplicity and the virulence of the attacks to which they were at once subjected.

Riolan, of Paris, had the greatest reputation of any anatomist of those days, and he followed the course which is usually adopted by the men of temporary notoriety towards those of enduring fame. According to Riolan, Harvey's. theory of the circulation was not true; and besides that, it was not new; and, furthermore, he invented a mongrel doctrine of his own, composed of the old views with as much of Harvey's as it was safe to borrow, and tried therewith to fish credit for himself out of the business. In fact, in wading through these forgotten controversies, I felt myself quite at home. Substitute the name of Darwin for that of Harvey, and the truth that history repeats itself will come home to the dullest apprehension. It was said of the doctrine of the circulation of the blood that nobody over forty could be got to adopt it ; and I think I remember a passage in the 'Origin of Species,' to the effect that its author expects to convert only young and flexible minds.

There is another curious point of resemblance in the fact, that even those who gave Harvey their general approbation and support sometimes failed to apprehend the value of some of those parts of his doctrine, which are, indeed, merely auxiliary to the theory of the circulation, but are only a little less important than it. Harvey's great friend and champion, Sir George Ent, is in this case; and I am sorry to be obliged to admit that Descartes falls under the same reprehension.

This great philosopher,. mathematician, and physiologist, whose conception of the phenomena of life as the results of mechanism is now playing as great a part in physiological science as Harvey's own discovery, never fails to speak with admiration, as Harvey gratefully acknowledges, of the new theory of the circulation. And it is astonishing, I had almost said humiliating, to find that even he is. unable to grasp Harvey's profoundly true view of the nature of the systole and the diastole, or to see the force of the quantitative argument He adduces experimental evidence against the former position, and is even further from the truth than Galen was, in his ideas of the physical cause of the circulation.

Yet one more and a last parallel. In spite of all opposition, the [337] doctrine of the circulation propounded by Harvey was, in its essential features, universally adopted within thirty years of the time of its publication. Harvey's friend, Thomas Hobbes, remarked that he was the only man, in his experience, who had the good fortune to live long enough to see a new doctrine accepted by the world at large. Mr. Darwin has been even more fortunate, for not twenty years have yet elapsed since the publication of the 'Origin of Species'; and yet there is no denying the fact that the doctrine of evolution, ignored, or derided, and vilified in 1859, is now accepted, in one shape or other, by the leaders of scientific thought in every region of the civilised world.

I proposed at the outset of this essay to say something about the method of inquiry which Harvey pursued, and which guided him throughout his successful career of discovery.

It is, 1 believe, a cherished belief of Englishmen, that Francis Bacon, Viscount St. Albans, and sometime Lord Chancellor of England, invented that "Inductive Philosophy" of which they speak with almost as much respect as they do of Church and State; and that, if it had not been for this "Baconian induction," science would never have extricated itself from the miserable condition in which it was left by a set of hair-splitting folk, known as the ancient Greek philosophers. To be accused of departing from the canons of the Baconian philosophy is almost as bad as to be charged with forgetting your aspirates; it is understood as a polite way of saying that you are an entirely absurd speculator.

Now the 'Novum Organon' was published in 1620, while Harvey began to teach the doctrine of the circulation in his public lectures, in 1619. Acquaintance with the "Baconian induction," therefore, could not have had much to do with Harvey's investigations. The 'Exercitatio,' however, was not published till 1628. Do we find in it any trace of the influence of the 'Novum Organon'? Absolutely none. So far from indulging in the short-sighted and profoundly unscientific depreciation of the ancients in which Bacon indulges, Harvey invariably speaks of them with that respect, which the faithful and intelligent study of the fragments of their labours that remain to us, must inspire in every one who is practically acquainted with the difficulties with which they had to contend, and which they so often mastered. And, as to method, Harvey's method is the method of Galen, the method of Realdus Columbus, the method of Galileo, the method of every genuine worker in science either in the past or the present. On the other hand, judged strictly by the standard of his [338] own time, Bacon's ignorance of the progress which science had up to that time

made, is only to be equalled by his insolence towards men in comparison with whom he was the merest sciolist. Even when he has some hearsay knowledge of what has been done, his want of acquaintance with the facts and his abnormal deficiency in what I may call the scientific sense, prevent him from divining its importance. Bacon could see nothing remarkable in the chief contributions to science of Copernicus, or of Kepler, or of Galileo. Gilbert, his fellow countryman, is the subject of a sneer; while Galen is bespattered with a shower of impertinences, which reach their climax in the epithets "puppy" and "plague."¹⁰

I venture to think that if Francis Bacon, instead of spending his time in fabricating fine phrases about the advancement of learning, in order to play, with due pomp, the part which he assigned to himself of "trumpeter" of science, had put himself under Harvey's instruction, and had applied his quick wit to discover and methodise the logical process which underlaid the work of that consummate investigator, he would have employed his time to better purpose; and, at any rate, would not have deserved the just but sharp judgment which follows: "that his [Bacon's] method is impracticable cannot I think be denied, if we reflect, not only that it never has produced any result, but also that the process by which scientific truths have been established cannot be so presented as even to appear to be in accordance with it." I quote from one of Mr. Ellis's contributions to the great work of Bacon's most learned, competent, and impartial biographer, Mr. Spedding.¹¹

Few of Harvey's sayings are recorded, but Aubrey¹² tells us that some one having enlarged upon the merits of the Baconian philosophy in his presence, "Yes," said Harvey, "he writes philosophy like a Chancellor." On which pithy reply diverse persons will put diverse interpretations. The illumination of experience may possibly tempt a modern follower of Harvey to expound the dark saying thus: "So [339] this servile courtier, this intriguing politician, this unscrupulous lawyer, this witty master of phrases, proposes to teach me my business in the intervals of his. I have borne with Riolan, let me also be patient with him;" at any rate, I have no better reading to offer.

In the latter half of the sixteenth and the beginning of the seventeenth centuries, the future of physical science was safe enough in the hands of Gilbert, Galileo, Harvey, Descartes, and the noble army of investigators who flocked to their standard, and followed up the advance of their leaders. I do not believe that their wonderfully rapid progress would have been one whit retarded if the 'Novum Organon' had never seen the light: while, if Harvey's little 'Exercise' had been lost, physiology would have stood still until another Harvey was born into the world.

There is another point in reference to method on which I desire to contribute my mite towards the dissipation of a widespread popular delusion. On the faith of a conversation reported by Robert Boyle, Harvey is said to have declared that he discovered the circulation of the blood by reasoning deductively from the disposition of the valves of the veins. On this I may remark, firstly, that the words imputed to Harvey by no means warrant this conclusion; secondly, that if they did, the statement could not be true, because we have Harvey's own evidence to the contrary; and thirdly, that if the conclusion were warranted by the words reported, and were not contradicted by Harvey himself, it would still be worthless, because it is impossible to prove the circulation of the blood from any such data. What Robert Boyle says is this:–"And I remember that when I asked our famous Harvey in the only discourse I had with him (which was but a while before he died), what were the things that induced him to think of a circulation of the blood? he answered me, that when he took notice that the valves in the veins of so many parts of the body were so placed, that they gave free passage to the blood towards the heart, but opposed the passage of the venal blood the contrary way: he was invited to imagine that so provident a cause as nature had not so placed so many valves without design; and no design seemed more probable, than that since the blood could not well, because of the interposing valves, be sent by the veins to the limbs, it should be sent through the arteries and return through the veins, whose valves did not oppose its course that way."¹³

I have no doubt that it may be quite true, that Harvey was [340] "induced" to "think of a circulation of the blood" by considering the disposition of the valves of the veins; just as Cæsalpinus might have been led to the same thought; and then might have found out the true state of the case, if he had taken the hints which Nature gave him, and had used the proper means of investigation in order to discover whether those hints were valuable or worthless. Harvey must have learned the views of his master Fabricius; and it is likely enough that to his acute mind Fabricius's explanation of the functions of the valves seemed rather lame. But, as a matter of fact, Harvey did not reason out the circulation from the datum of the valves. On this point his own words, in the passage which contains the fullest account of the considerations which led him to the doctrine of the circulation, leave no doubt whatever:–

In all this very full and interesting account of the course of Harvey's inquiry, it will be observed that not one word is said about the valves of the veins. The valves of which he speaks are those of the heart, which had been known, as I have pointed out, ever since the days of Erasistratus.

Finally, I venture to affirm that Harvey did not deduce the circulation from the disposition of the valves of the veins, because it is logically impossible that any such conclusion should be deduced from such premisses. The only conclusion which is warranted by the presence of valves in the veins is, that such valves will tend to place a certain amount of obstacle in the way of a liquid flowing in a direction opposite to that in which the valves arc inclined. The amount of obstacle, from mere impediment to absolute barring of the way, will depend upon the form and disposition of the valves; upon their inertia, or stiffness of motion, in relation to the force of the current of liquid; and, above all, upon the firmness or yieldingness of the walls of the tube to which they are attached. The valve which hermetically closes the passage through an iron pipe may be of no use in an india-rubber tube. Therefore, unless the action of such valves as exist in the veins were carefully tested by experiment on the living animal, any conclusions that might .be based upon their presence would be of doubtful value, and might be interpreted either in the sense of Fabricius, or in that of Harvey.

Moreover, supposing that it could be proved that, in those veins in which valves exist, the blood can move only in one way, what is to be said about the numerous veins which have no valves? And, unless we already know upon experimental grounds that the walls of the cavities of the heart contract in a certain definite order; that the arteries are full of blood and not of air; and a number of other important facts which can only be experimentally determine; what good is it to know that there are valves in the veins? There are [342] valves in the lymphatics as well as in the veins, and yet aliy one who concluded therefrom that the lymph circulates after the manner of the blood would make a woeftil mistake.

The fact is that neither in this, nor in any, physiological problem can mere deductive reasoning from dead structure tell us what part that structure plays, when it is a living component of a living body. Physiology attempts to discover the laws of vital activity, and these laws are obviously ascertainable only by observation and experiment upon living things.

In the case of the circulation of the blood, as in that of all other great physiological doctrines, take away the truths which have been learned by observation and experiment on living structures, and the whole fabric crumbles away. Galen, Columbus, Harvey, were all great vivisectors. And the final ocular demonstration of the circulation of the blood by Malpighi, seven years after Harvey's death–the keystone of the fabric he raised–involved an experiment on a living frog.

This experiment can be performed on a demonstrably insensible animal. Nevertheless, any English subject who repeats it, in these days, may be subjected to fine or imprisonment, as a common malefactor, whenever the chances of political strife give the Home Office to some minister of less knowledge, less justice, and, above all, less firmness in resisting open and underhand pressure, than the present Secretary of State for the Home Department.

I do not think the present is a fitting occasion for the discussion of the burning question of vivisection. My opinions on the subject have been formed and expressed under a due sense of responsibility, and they have not been, and are not likely to be, affected by the preposterous misrepresentations and unseemly abuse which they have evoked. The good Harvey, in one of his fits of choler, I suppose, said that "man was but a great mischievous baboon,"¹⁶ and yet, for twenty years, he kept silence, and, at the end, answered Riolan with quite angelic mildness. I can imitate his silence, if not his mildness; and therefore I have nothing further to offer on this subject. It may be that those are right who say, perish the human race, rather than let a dog suffer. It may be that those are right who think that a man is worth a wilderness of apes, and that he who will not save human life when he could do so, by sacrificing a hecatomb of animals, is an accomplice in murder.

But without touching upon this debatable ground, I may be of some use in cleansing the ground of mere rubbish. I submit two [343] points for your consideration. The one of these is the unquestionable fact that physiology is based upon experiment and can only grow by experiment; and that the discovery of the true motion of the blood, which is one of the cardinal doctrines of that science, and a doctrine the truth of which is implied in the diagnosis and the treatment of nine diseases out of ten, has been made in no other way than by reasoning on the data supplied by repeated and multiplied vivisections.

The other is a mere suggestion, which, perhaps, may be dictated by a want of power on the part of a man who is growing old, to adjust himself to a changing world. The great mark of senility, I believe, is to be a "laudator temporis acti." But, as Harvey says, "the die is cast, and I put my faith in the candour of the lovers of truth and of learned minds."

I have had occasion to remark that the science of former days was not so despicable as some think; and that, however foolish undue respect for the wisdom of the ancients may be, undue disrespect for it may be still more reprehensible. Now I fancy that a candid mind will admit it to be within the limits of possibility, that the like may apply to the public opinion and the moral sense of former ages.

Harvey was the favoured friend of his sovereign, the honoured Nestor of his profession, the pride of his countrymen. If he lived now, and were guilty of serving mankind to the same extent and in the same way, so far from any such marks of favour reaching him, he would find himself to be a mark of a different kind–a mark I mean, for immeasurable calumny and scandalous vituperation; and. though his professional brethren would surely pay him all honour, so far from being the pride of his countrymen, a goodly number of them, of all grades in the social scale, would be spending a world of energy in the endeavour to give him the legal status of a burglar.

I venture to ask you to consider seriously whether, under these circumstances, it is quite so certain, as some seem to believe, that the public opinion of the England of Harvey's day–that time when Englishmen could hurl back a world arrayed in arms against them, because they feared neither to suffer, nor to inflict pain and death in a good cause; that age within which Shakespeare and Milton, Hobbes and Locke, Harvey and Newton, Drake and Raleigh, Cromwell and Strafford, embodied the powers of our race for good and evil in a fashion which has had no parallel before or since–was absolutely contemptible when set against that of this present enlightened and softly nurtured, not to say sentimental, age.

[344] Maybe it is; possibly the world is entering upon a phase in which the recognised whole duty of man will be to avoid the endurance, or the infliction, of physical pain, whatever future alleviation of misery may be its consequence, however great the positive benefit to mankind which may flow thereupon. If so, "Finis Physiologiæ." When that time arrives, there will be an end to all progress in our knowledge of the laws of life, to all advance towards rational medicine. And, if 1 do not greatly err, these are not the only things which the logical outcome of such premisses will have abolished. Crime must go unpunished–for what justification is there for "torturing" a poor thief or murderer except the general good of society? The "voice of the slugard" will not "be heard to complain," for no one will dare to torture him by disturbing his slumbers." There will be no means of transport, and nothing to ride, except steam-engines, and bicycles, for the "torture" involved in the training and in the labour of beasts of draught and burden will be insufferable. No man will think of eating meat, though it may be proper for him to serve as meat to other creatures; for what right can men have to "torture" fleas by the administration of insecticide powder, merely for the benefit of mankind? Sport, I need not say, will have been abolished, and war will have followed it; not so much because war is fraught with evil for men but because of the awful "torture" which it inflicts directly upon horses and mules, to say nothing of the indirect dyspeptic sufferings of the vultures and wolves, which are tempted by our wickedness to overeat themselves.

As 1 have confessed, I find myself to be regrettably out of harmony with many worthy and enthusiastic people among my contemporaries; and perhaps the prospect of the coming of the New Era, in which these things shall be, does not affect others as it does me. To say truth, I am rather glad to think that the species can hardly be perfected thus far, in my time. 1 must distinctly admit that 1 should be loath to be obliged to exist in a world, in which my notions of what men should be and do will have no application. As the old Norseman said, when the choice between Heaven with the new generation, and Hell with the old, was offered him, 'I prefer to be with my ancestors."

¹ We say that the heart, in man and the higher animals, consists of two auricles and two ventricles ; and that each auricle has an appendix in the form of a pouch. We term the vessel which arises from the right ventricle the pulmonary artery, because it supplies the lungs with blood. Those vessels which bring away the blood from the lungs to the left auricle, we call the pulmonary veins.

PREVIEW TABLE of CONTENTS BIBLIOGRAPHIES 1.   THH Publications 2.   Victorian Commentary 3.   20th Century Commentary INDICES 1.   Letter Index 2.   Illustration Index TIMELINE FAMILY TREE Gratitude and Permissions C. Blinderman & D. Joyce Clark University 1998

THE HUXLEY FILE

GUIDES § 1. THH: His Mark § 2. Voyage of the Rattlesnake § 3. A Sort of Firm § 4. Darwin's Bulldog § 5. Hidden Bond: Evolution § 6. Frankensteinosaurus § 7. Bobbing Angels: Human Evolution § 8. Matter of Life: Protoplasm § 9. Medusa § 10. Liberal Education § 11. Scientific Education § 12. Unity in Diversity § 13. Agnosticism § 14. New Reformation § 15. Verbal Delusions: The Bible § 16. Miltonic Hypothesis: Genesis § 17. Extremely Wonderful Events: Resurrection and Demons § 18. Emancipation: Gender and Race § 19. Aryans et al.: Ethnology § 20. The Good of Mankind § 21.  Jungle Versus Garden