Harvey’s liber aureus is certainly his “Exercitatio anatomica de motu cordis et sanguinis in animalibus.” [An Anatomical Treatise on the Movement of the Heart and Blood in Animals, by William Harvey, the Englishman, Physician to the King and Professor of Anatomy in the London College of Physicians.] The work was issued from the press of William Fitzer, of Frankfort, in the year 1621. Harvey chose Frankfort as the place of publication for his book because the annual book fair held in the town enabled a knowledge of his work to be more rapidly spread than if it had been issued in England.

The book contains the matured account of the circulation of the blood, of which somewhat more than the germ had appeared in the notes of the Lumleian visceral lecture for 1616. It is a small quarto, containing seventy-two pages and a page and half of errata, for Harvey wrote a villainous hand, and communication between Germany and England was too slow, expensive, and uncertain to allow an author to correct his book sheet by sheet as it issued from the press.

The Treatise opens with a dedication to Charles I. couched in fitting emblematical language, and signed “Your Most August Majesty’s Most Devoted Servant, William Harvey.” The dedication is followed by a preface addressed to “Dr. Argent [then President of the College of Physicians, and one of Harvey’s intimate friends] as well as to the other learned physicians, his most esteemed colleagues.” In this preface he excuses himself for the book, saying that he had already and repeatedly presented to them his new views of the movement and function of the heart in his anatomical lectures. And that he had now for nine years and more confirmed these views by multiplied demonstrations in their presence. He had illustrated them by arguments and he had freed them from objections of the most learned and skilful Anatomists. He then proceeds so modestly that it is difficult to realise how great an innovation he was really making when he says, “I profess both to learn and to teach anatomy, not from books but from dissections, not from the positions of philosophers but from the fabric of nature.”

Such a statement is now a mere truism, because every one who starts upon a subject of original research follows the method adopted by Harvey. He learns thoroughly what is known already; he frames a working hypothesis and puts it to the test of experiment. He then combines his À priori reasoning with a logical deduction from the facts he observes. A feeble mind is sometimes overmastered by its working hypothesis, and may be led to consider it proved when a better trained observer would dismiss it for a more promising theory. Harvey’s hypothesis—tested by experiment, by observation, and by reasoning—was no longer an hypothesis but a proved fact fertile beyond measure, for it rendered possible a coherent and experimental physiology and a new medicine and surgery.

The anatomical treatise gives in seventeen short chapters a perfectly clear and connected account of the action of the heart and of the movement of the blood round the body in a circle. A movement which had been foreshadowed by some of the earlier anatomists and had been clearly indicated by Harvey himself as early as 1616. But it is here laid down with a precision of detail, with a logical exactness, and with a wealth of illustration which is marvellous even to us who read of the circulation as an established and fundamental principle upon which the whole body of physic rests. Harvey’s proof fell short of complete demonstration, for he had no means of showing how the smallest arteries are connected with the smallest veins. He worked, indeed, with a simple lens, but its magnifying power was too feeble to show him the arterioles and the venules, whilst the idea of an injection does not seem to have occurred to him. It was not until after the invention of the compound microscope that Leeuwenhoek, in 1675, described the blood corpuscles and the circulation in the capillary blood vessels, though they had already been seen by Malpighi.

The first chapter of the Treatise is introductory. It is a review of the chief theories which had been held as to the uses of the heart and lungs. It had been maintained that the heart was the great centre for the production of heat. The blood was driven alternately to and from the heart, being sucked into it during the diastole and driven from it during the systole. The use of the arteries was to fan and cool the blood, as the lungs fanned and cooled the heart, for the pulse was due to an active dilatation and contraction of the arteries. During their dilatation the arteries sucked in air, and during their contraction they discharged murky vapours through pores in the flesh and skin. In the heart, as well as in the arteries, the dilatation was of greater importance than the contraction. The whole of this tissue of falsehood seems to have been founded upon an incorrect apprehension of the nature of heat. It was looked upon as a fundamental principle or entity, and until chemistry and physics reached the stage of experimental sciences it was impossible to give a correct explanation of the phenomena it presents. Even Harvey sometimes lost himself in mysticism when he had to deal with the subject of animal heat, though he was struggling hard to find a firm foothold when he said, “We are too much in the habit of worshipping names to the neglect of things. The word Blood has nothing of grandiloquence about it, for it signifies a substance which we have before our eyes and can touch; but before such titles as Spirit and Calidum Innatum [or inherent heat] we stand agape.”

Harvey begins his Treatise on the movement of the Heart and Blood with the clear statement that the heart must be examined whilst it is alive; but he says, “I found the task so truly arduous and so full of difficulties that I was almost tempted to think with Fracastorius that the movement of the heart was only to be comprehended by God. For I could neither rightly perceive at first when the systole[10] and when the diastole took place, nor when and where dilatation and contraction occurred, by reason of the rapidity of the movement, which in many animals is accomplished in the twinkling of an eye, coming and going like a flash of lightning.

“At length by using greater and daily diligence and investigation, making frequent inspection of many and various animals and collating numerous observations, I thought that I had attained to the truth ... and that I had discovered what I so much desired—both the movement and the use of the heart and arteries. From that time I have not hesitated to expose my views upon these subjects, not only in private to my friends, but also in public in my anatomical lectures, after the manner of the Academy of old.

“These views, as usual, pleased some more, others less: some chid and calumniated me and laid it to me as a crime that I had dared to depart from the precepts and opinion of all anatomists: others desired further explanations of the novelties, which they said were both worthy of consideration, and might perchance be found of signal use.”

The results of his experiments soon made it plain to Harvey that the heart’s movements could be studied more readily in the colder animals, such as toads, frogs, serpents, small fishes, crabs, shrimps, snails, and shell-fish, than in warm-blooded animals. The movements of the heart became more distinct even in warm-blooded animals, such as the dog and hog, if the organ was attentively noted when it began to flag. The movements then became slower, the pauses longer, so that it was then much more easy to perceive and unravel what the movements really were and how often they were performed.

Careful observation and handling the heart made it clear that the organ was muscular, and that its systole was in every way comparable with the contraction which occurs in the muscles of the forearm when the fingers are moved. “The contraction of the heart is therefore of greater importance than its relaxation. During its contraction the heart becomes erect, hard, and diminished in size, so that the ventricles become smaller and are so made more apt to expel their charge of blood. Indeed, if the ventricle be pierced the blood will be projected forcibly outwards at each pulsation when the heart is tense.”

After thus disproving the erroneous views of the heart’s action, Harvey next proceeds to discuss the movements in the arteries as they are seen in the dissection of living animals. He shows that the pulsation of the arteries depends directly upon the contraction of the left ventricle and is due to it, whilst the contraction of the right ventricle propels its charge of blood into the pulmonary artery which is distended simultaneously with the other arteries of the body. When an artery is divided or punctured the blood is forcibly expelled from the wound at the instant when the left ventricle contracts, and when the pulmonary artery is wounded the blood spurts forth with violence when the right ventricle contracts. So also in fish, if the vessel leading from the heart to the gills be divided the blood flows out forcibly when the heart becomes tense and contracted.

These facts enabled Harvey to disprove the current theory that the heart’s systole corresponded with the contraction of the arteries which then became filled with blood by a process of active dilatation, as bellows are filled with air. He illustrated this by a homely method which he had been accustomed to use in his lectures for years. He says that “the pulses of the arteries are due to the impulses of the blood from the left ventricle may be illustrated by blowing into a glove, when the whole of the fingers will be found to become distended at one and the same time and in their tension to bear some resemblance to the pulse.”

The broad points in connection with the vascular system being thus settled, Harvey turned his attention more particularly to the mechanism of the heart’s action. He shows that the two auricles move synchronously and that the two ventricles also contract at the same time. Hitherto it had been supposed that each cavity of the heart moved independently, so that every cardiac cycle consisted of four distinct movements. To prove that the movement of the heart was double he examined the eel, several fish, and some of the higher animals. He noticed that the ventricles would pulsate without the auricles, and that if the heart were cut into several pieces “the several parts may still be seen contracting and relaxing.” The minute accuracy of Harvey’s observation is shown by his record of what is in reality a perfusion experiment. He says: “Experimenting with a pigeon upon one occasion after the heart had wholly ceased to pulsate and the auricles too had become motionless, I kept my finger wetted with saliva and warm for a short time upon the heart and noticed that under the influence of this fomentation it recovered new strength and life, so that both ventricles and auricles pulsated, contracting and relaxing alternately, recalled as it were from death to life.” We now know that this was due to the warmth, to the moisture, and to the alkalinity of Harvey’s saliva, so that he performed crudely, and no doubt by accident, one of the most modern experiments to show that the heart, under suitable conditions, has the power of recovering from fatigue.

This portion of the treatise affords an insight into the enormous amount of labour which Harvey had expended in its production, for he says: “I have also observed that nearly all animals have truly a heart, not the larger creatures only and those that have red blood, but the smaller and pale-blooded ones also, such as slugs, snails, scallops, shrimps, crabs, crayfish, and many others; nay, even in wasps, hornets, and flies I have, with the aid of a magnifying glass and at the upper part of what is called the tail, both seen the heart pulsating and shown it to many others.” That this was the result of a careful study of the animals mentioned and not a simple observation is shown by the following sentences: “In winter and the colder season, pale-blooded animals such as the snail show no pulsations: they seem rather to live after the manner of vegetables or of those other productions which are therefore designated plant animals.... We have a small shrimp in these countries, which is taken in the Thames and in the sea, the whole of whose body is transparent: this creature, placed in a little water, has frequently afforded myself and particular friends an opportunity of observing the movements of the heart with the greatest distinctness, the external parts of the body presenting no obstacle to our view, but the heart being perceived as though it had been seen through a window.

“I have also observed the first rudiments of the chick in the course of the fourth or fifth day of the incubation, in the guise of a little cloud, the shell having been removed and the egg immersed in clear, tepid water. In the midst of the cloudlet in question there was a bloody point so small that it disappeared during the contraction and escaped the sight, but in the relaxation it reappeared again red and like the point of a pin.”

Harvey formulates in his fifth chapter the conclusions to which he had been led about the movement, action, and use of the heart. His results appear to be absolutely correct by the light of our present knowledge, and they show how much can be done by a careful observer, even though he be unassisted by any instrument of precision.

“First of all the auricle contracts, and in the course of its contraction forces the blood (which it contains in ample quantity as the head of the veins, the storehouse and cistern of the blood) into the ventricle which, being filled, the heart raises itself straightway, makes all its fibres tense, contracts the ventricles and performs a beat, by which beat it immediately sends the blood supplied to it by the auricle into the arteries. The right ventricle sends its charge into the lungs by the vessel which is called the vena arteriosa [pulmonary artery], but which in structure and function and all other respects is an artery. The left ventricle sends its charge into the aorta and through this by the arteries to the body at large.

“These two movements, one of the ventricles, the other of the auricles, take place consecutively, but in such a manner that there is a kind of harmony or rhythm preserved between them, the two concurring in such wise that but one movement is apparent, especially in the warmer blooded animals in which the movements in question are rapid. Nor is this for any other reason than it is in a piece of machinery in which, though one wheel gives movement to another, yet all the wheels seem to move simultaneously; or in that mechanical contrivance which is adapted to firearms, where the trigger being touched, down comes the flint, strikes against the wheel, produces a spark, which falling among the powder, ignites it, upon which the flame extends, enters the barrel, causes the explosion, propels the ball, and the mark is attained—all of which incidents by reason of the celerity with which they happen, seem to take place in the twinkling of an eye.... Even so does it come to pass with the movements and action of the heart.... Whether or not the heart besides propelling the blood, giving it movement locally and distributing it to the body, adds anything else to it—heat, spirit, perfection—must be inquired into by and by, and decided upon other grounds. So much may suffice at this time, when it is shown that by the action of the heart the blood is transfused through the ventricles from the veins to the arteries and is distributed by them to all parts of the body.

“The above indeed is admitted by all, both from the structure of the heart and the arrangement and action of its valves. But still they are like persons, purblind or groping in the dark, for they give utterance to various contradictory and incoherent sentiments, delivering many things upon conjecture.... The great cause of doubt and error in this subject appears to me to have been the intimate connection between the heart and the lungs. When men saw both the pulmonary artery and the pulmonary veins losing themselves in the lungs, of course it became a puzzle to them to know how or by what means the right ventricle should distribute the blood to the body or the left draw it from the venae cavae....

“Since the intimate connection of the heart with the lungs, which is apparent in the human subject, has been the probable cause of the errors that have been committed on this point, they plainly do amiss who, pretending to speak of the parts of animals generally, as Anatomists for the most part do, confine their researches to the human body alone, and that when it is dead. They obviously do not act otherwise than he who, having studied the forms of a single commonwealth, should set about the composition of a general system of polity: or who, having taken cognisance of the nature of a single field, should imagine that he had mastered the science of agriculture; or who, upon the ground of one particular proposition, should proceed to draw general conclusions.

“Had Anatomists only been as conversant with the dissection of the lower animals as they are with that of the human body, the matters that have hitherto kept them in a perplexity of doubt would, in my opinion, have met them freed from every kind of difficulty.”

After this plea for the employment of comparative anatomy to elucidate human anatomy, Harvey proceeds to deal in a most logical manner with the various difficulties in following the course taken by the blood in passing from the vena cava to the arteries, or from the right to the left side of the heart. He begins with fish, in which the heart consists of a single ventricle, for there are no lungs. He then discusses the relationship of the parts in the embryo, and arrives at the conclusion that “in embryos, whilst the lungs are in a state of inaction, performing no function, subject to no movement any more than if they had not been present, Nature uses the two ventricles of the heart as if they formed but one for the transmission of the blood.” He therefore concludes that the condition of the embryos of those animals which have lungs, whilst these organs are yet in abeyance or not employed, is the same as that of the animals which have no lungs. From this he wishes it to be understood that the blood passes by obvious and open passages from the vena cava into the aorta through the cavities of the ventricles. A statement which was in direct opposition to the generally received tradition of the time that the blood passed from the right into the left ventricle by concealed pores in the septum which separates the two cavities in the heart.

Thus far Harvey’s teaching has been excellent, but now, leaving the highway of fact, he plunges into theory and is at once involved in error. He proceeds, “And now the discussion is brought to this point, that they who inquire into the ways by which the blood reaches the left ventricle of the heart and pulmonary veins from the vena cava will pursue the wisest course if they seek by dissection to discover why, in the larger and more perfect animals of mature age, Nature has rather chosen to make the blood percolate the parenchyma of the lungs, than as in other instances chosen a direct and obvious course—for I assume no other path or mode of transit can be entertained. It must be because the larger and more perfect animals are warmer, and when adult their heat greater, ignited I might say, and requiring to be damped or mitigated, that the blood is sent through the lungs, in order that it may be tempered by the air that is inspired, and prevented from boiling up and so becoming extinguished or something else of the sort. But to determine these matters and explain them satisfactorily were to enter upon a speculation in regard to the office of the lungs and the ends for which they exist. Upon such a subject, as well as upon what pertains to respiration, to the necessity and use of the air, &c., as also to the variety and diversity of organs that exist in the bodies of animals in connection with these matters, although I have made a vast number of observations, I shall not speak till I can more conveniently set them forth in a treatise apart.”

The next chapter is devoted to the description of the manner in which the blood passes through the substance of the lungs from the right ventricle of the heart into the pulmonary veins. It is followed by the glorious eighth chapter, in which Harvey’s style, always impressive and solid, rises into real eloquence, for a great occasion justifies the use of repetitions, of antitheses and an abundance of metaphors. He now quits the method of demonstration and experiment for that of indirect but irrefragable argument. He deals with the quantity of blood passing through the heart from the veins to the arteries, and again brings together all his threads to a nodal point. “Thus far I have spoken of the passage of the blood from the veins into the arteries, and of the manner in which it is transmitted and distributed by the action of the heart; points to which some, moved either by the authority of Galen or Columbus, or the reasonings of others, will give their adhesion. But what remains to be said upon the quantity and source of the blood which thus passes is of a character so novel and unheard of that I not only fear injury to myself from the envy of a few, but I tremble lest I have mankind at large for my enemies, so much doth wont and custom become a second nature. Doctrine once sown strikes deeply its root, and respect for antiquity influences all men. Still the die is cast, and my trust is in my love of truth and the candour of cultivated minds. And sooth to say when I surveyed my mass of evidence, whether derived from vivisections and my various reflections on them, or from the study of the ventricles of the heart and the vessels that enter into and issue from them, the symmetry and the size of these conduits, for Nature doing nothing in vain, would never have given them so large a relative size without a purpose—or from observing the arrangement and intimate structure of the valves in particular and of the other parts of the heart in general, with many things besides, I frequently and seriously bethought me and long revolved in my mind, what might be the quantity of blood which was transmitted, in how short a time its passage might be effected and the like. But not finding it possible that this could be supplied by the juices of the ingested aliment without the veins on the one hand becoming drained, and the arteries on the other getting ruptured through the excessive charge of blood, unless the blood should somehow find its way from the arteries into the veins and so return to the right side of the heart; I began to think whether there might not be a movement, as it were, in a circle. Now this I afterwards found to be true, and I finally saw that the blood, forced by the action of the left ventricle into the arteries, was distributed to the body at large and in several parts in the same manner as it is sent through the lungs impelled by the right ventricle into the pulmonary artery, and that it then passed through the veins and along the vena cava and so round to the left ventricle in the manner already indicated. This movement we may be allowed to call circular.”

Harvey’s great discovery is here formulated in his own words. The lesser or pulmonary circulation was already tolerably well known, owing to the work of Realdus Columbus, the successor of Vesalius in the anatomical chair at Padua, though he had been anticipated by Servetus, who published it at Lyons in 1543 in the “Christianismi Restitutio,” a theological work, containing doctrines for which Calvin caused him to be burnt. But it is more than doubtful whether Harvey knew of this work, as not more than three or four copies of it have escaped the flames which consumed the book and its writer.

Harvey continues his treatise by laying down three propositions to confirm his main point that the blood circulates.

First, that the blood is incessantly transmitted by the action of the heart from the vena cava to the arteries.

Secondly, that 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 is sufficient for nutrition or than the whole mass of fluids could supply.

Thirdly, that the veins return this blood incessantly to the heart. “These points being proved, I conceive it will be manifest that the blood circulates, revolves, is propelled, and then returning from the heart to the extremities, from the extremities to the heart, and thus that it performs a kind of circular movement.”

These propositions Harvey proves to demonstration and in a most masterly manner. He says of the first: “Let us assume either arbitrarily or by experiment, that the quantity of the blood which the left ventricle of the heart will contain when distended to be, say two ounces, three ounces, or one ounce and a half—in the dead body I have found it to hold upwards of two ounces. Let us assume further how much less the heart will hold in the contracted than in the dilated state, and how much blood it will project into the aorta upon each contraction, and all the world allows that with the systole something is always projected ... and let us suppose as approaching the truth that the fourth, or fifth, or sixth, or even but the eighth part of its charge is thrown into the artery at each contraction, this would give either half an ounce, or three drachms, or one drachm of blood as propelled by the heart at each pulse into the aorta, which quantity by reason of the valves at the root of the vessel can by no means return into the ventricle. Now in the course of half an hour the heart will have made more than one thousand beats, in some as many as two, three, or even four thousand. Multiplying the number of drachms by the number of pulses we shall have either one thousand half ounces, or one thousand times three drachms, or a like proportional quantity of blood, according to the amount we assume as propelled with each stroke of the heart, sent from this organ into the artery: a larger quantity in every case than is contained in the whole body. In the same way in the sheep or dog, say that but a single scruple of blood passes with each stroke of the heart, in one half hour we should have one thousand scruples, or about three pounds and a half of blood injected into the aorta, but the body of neither animal contains more than four pounds of blood, a fact which I have myself ascertained in the case of the sheep.”

This is one of the highest efforts of Harvey’s genius. The facts are simple and they are easily ascertained. But the reasoning was absolutely new and the conclusion must remain sound until the end of time, for it is true. It shows too the minute care taken by Harvey not to overstate his case, for he deliberately takes a measurement of the capacity of the ventricles which he knew to be well under the average.

This part of his argument is ended with an appeal to practical experience. “The truth, indeed, presents itself obviously before us when we consider what happens in the dissection of living animals: the great artery need not be divided, but a very small branch only (as Galen even proves in regard to man), to have the whole of the blood in the body, as well that of the veins as of the arteries, drained away in the course of no long time—some half hour or less. Butchers are well aware of the fact and can bear witness to it; for, cutting the throat of an ox and so dividing the vessels of the neck, in less than a quarter of an hour they have all the vessels bloodless—the whole mass of blood has escaped. The same thing also occasionally occurs with great rapidity in performing amputations and removing tumours in the human subject.... Moreover it appears ... that the more frequently or forcibly the arteries pulsate, the more speedily will the body be exhausted of its blood during hÆmorrhage. Hence also it happens that in fainting fits and in states of alarm when the heart beats more languidly and less forcibly, hÆmorrhages are diminished and arrested.

“Still further, it is from this, that after death, when the heart has ceased to beat, it is impossible by dividing either the jugular or the femoral veins and arteries by any effort to force out more than one-half of the whole mass of the blood. Neither could the butcher ever bleed the carcass effectually did he neglect to cut the throat of the ox which he has knocked on the head and stunned before the heart had ceased beating.”

Harvey continues to push his argument to a logical conclusion in the succeeding chapters of his Treatise partly by argument and partly by adducing fresh experimental evidence. But if any one shall here object that a large quantity may pass through (the heart) and yet no necessity be found for a circulation, that all may come from the meat and drink consumed, and quote as an illustration the abundant supply of milk in the mammÆ—for a cow will give three, four, and even seven gallons a day, and a woman two or three pints whilst nursing a child or twins, which must manifestly be derived from the food consumed; it may be answered, that the heart by computation does as much and more in the course of an hour or two.

“And if not yet convinced he shall still insist, that when an artery is divided, a preternatural route is, as it were, opened, and that so the blood escapes in torrents, but that the same thing does not happen in the healthy and uninjured body when no outlet is made ... it may be answered, that ... in serpents and several fish by tying the veins some way below the heart, you will perceive a space between the ligature and the heart speedily to become empty, so that unless you would deny the evidence of your senses, you must needs admit the return of the blood to the heart.... If, on the contrary, the artery instead of the vein be compressed or tied, you will observe the part between the obstacle and the heart and the heart itself to become inordinately distended, to assume a deep purple or even livid colour, and at length to be so much oppressed with blood that you will believe it about to be choked; but the obstacle removed, all things immediately return to their natural state in colour, size, and impulse.”

Harvey next proceeds to demonstrate his second proposition. He shows that the blood enters a limb by the arteries and leaves it by the veins; that the arteries are the vessels carrying the blood from the heart, and the veins the returning channels of the blood to the heart; that in the limbs and the extreme parts of the body the blood passes either immediately by anastomosis or mediately by the pores of the flesh.

Harvey is here hampered by the conditions of the age in which he lived, yet it is here that he shows himself far superior to his contemporaries as well as to the most enlightened of his predecessors. His lens was not sufficiently powerful to show him the capillary blood-vessels, and he had therefore no real knowledge of the way by which the blood passed from the arterioles into the venules. On the other hand, he did not repeat the mistake made by Aristotle, and reiterated by Cesalpino in 1571 that the blood passed from the smallest arteries into “capillamenta,” the ?e??a of Aristotle.

Later commentators have given to Cesalpino the credit due to Harvey by translating “capillamenta” into our term capillaries. But this process of “reading into” the writings of man what he never knew is one of the commonest pitfalls of defective scholarship.

Harvey attempted to solve the problem of the capillary circulation by an appeal to clinical evidence, which soon led him into inaccuracies, as when he says that the fainting often seen in cases of blood-letting is due to the “cold blood rising upwards to the heart, for fainting often supervenes in robust subjects, and mostly at the moment of undoing the fillet, as the vulgar say from the ‘turning of the blood.’”

This Chapter XI. is an important one. Harvey takes the operation of bleeding as one which is familiar to every class of his readers, and he uses the various phenomena which attend the application of a ligature to the arm to clinch his arguments as to the existence of the circulation of the blood. He introduces incidentally his surgical and pathological knowledge, quoting, amongst other instances, the fact that if the blood supply to a tumour or organ be stopped, “the tissues deprived of nutriment and heat dwindle, die, and finally drop off.” He also introduces some pathological results from personal experience, for he says:—“Thrown from a carriage upon one occasion, I struck my forehead a blow upon the place where a twig of the artery advances from the temple, and immediately, within the time when twenty beats could have been made, I felt a tumour the size of an egg developed, without either heat or any great pain; the near vicinity of the artery had caused the blood to be effused into the bruised part with unusual force and velocity.”

This passage shows one of the minor difficulties that Harvey and all observers in his age had to contend with in the fact that no method existed by which small fractions of time could be measured.[11] The ordinary watch had only a single hand marking the hours, so that neither minutes nor seconds could be registered by them.

The difficulty was one of old standing, and Dr. Norman Moore alluded to it, when he says in regard to Mirfeld’s “Breviarium Bartholomei:” “The mixture of prayers with pharmacy seems odd to us; but let it be remembered that Mirfeld wrote in a religious house, that clocks were scarce, and that in that age and place time might not inappropriately be measured by the minutes required for the repetition of so many verses of Scripture or so many prayers. Thus Mirfeld recommends that chronic rheumatism should be treated by rubbing the part with olive oil. This was to be prepared with ceremony. It was to be put into a clean vessel while the preparer made the sign of the cross and said the Lord’s Prayer and an Ave Maria. When the vessel was put to the fire the Psalm ‘Why do the heathen rage’ was to be said as far as the verse, ‘Desire of Me, and I shall give thee the heathen for thine inheritance.’ The Gloria, Pater Noster, and Ave Maria are to be said, and the whole gone through seven times. Which done let that oil be kept. The time occupied I have tried, and found to be a quarter of an hour.”

In the succeeding chapters Harvey continues his observations on phlebotomy, and draws a conclusion so striking in its simplicity that it appears hard to understand why it had not already occurred to others. He says: “And now, too, we understand why in phlebotomy we apply one ligature above the part that is punctured, not below it: did the flow come from above, the constriction in this case would not only be of no service but would prove a positive hindrance. It would have to be applied below the orifice in order to have the flow more free did the blood descend by the veins from the superior to inferior parts.”

Harvey next returns to the question whether the blood does or does not flow in a continuous stream through the heart—a subject upon which his contemporaries had the wildest notions, for even Cesalpino says: “That whilst we are awake there is a great afflux of blood and spirit to the arteries whence the passage is to the nerves and whilst we are asleep the same heat returns to the heart by the veins, not by the arteries, for the natural ingress to the heart is by the vena cava, not by the artery ... so that the undulating flow of blood to the superior parts, and its ebb to the inferior parts—like Euripus—is manifest in sleeping and waking.” Harvey combats this theory in exactly the same manner as we should do if it were propounded at the present day. He first brings forth his mathematical proof of the circulation, and then continues his surgical observations upon the operation of bleeding. “It is still further to be observed that in practising phlebotomy the truths contended for are sometimes confirmed in another way, for having tied up the arm properly and made the puncture duly, still, if from alarm or any other causes, a state of faintness supervenes, in which the heart always pulsates more languidly, the blood does not flow freely, but distils by drops only. The reason is that with the somewhat greater than usual resistance offered to the transit of the blood by the bandage, coupled with the weaker action of the heart and its diminished impelling power, the stream cannot make its way under the ligature; and further, owing to the weak and languishing state of the heart, the blood is not transferred in such quantity from the veins to the arteries through the sinuses of that organ.... And now a contrary state of things occurring, the patient getting rid of his fear and recovering his courage, the pulse strength is increased, the arteries begin again to beat with greater force, and to drive the blood even into the part that is bound, so that the blood now springs from the puncture in the vein, and flows in a continuous stream....” Thus far, he proceeds, “we have spoken of the quantity of blood passing through the heart and the lungs in the centre of the body, and in like manner from the arteries into the veins in the peripheral parts, and in the body at large. We have yet to explain, however, in what manner the blood finds its way back to the heart from the extremities by the veins, and how and in what way these are the only vessels that convey the blood from the external to the central parts; which done, I conceive that the three fundamental propositions laid down for the circulation of the blood will be so plain, so well established, so obviously true, that they may claim general credence. Now the remaining proposition will be made sufficiently clear from the valves which are found in the cavities of the veins themselves, from the uses of these, and from experiments cognisable by the senses.”

Harvey returns again to his anatomical demonstrations to prove his point. He explains the true uses of the valves in the veins, whose existence, he says, were known to his old teacher “Hieronymus Fabricius, of Aquapendente, a most skilful anatomist and venerable old man.... The discoverer of these valves did not rightly understand their use, nor have succeeding anatomists added anything to our knowledge; for their office is by no means explained when we are told that it is to hinder the blood by its weight from all flowing into the inferior part; for the edges of the valves in the jugular veins hang downwards, and are so contrived that they prevent the blood from rising upwards; the valves, in a word, do not invariably look upwards, but always towards the trunks of the veins, invariably towards the seat of the heart. Let it be added that there are no valves in the arteries, and that dogs, oxen, &c., have invariably valves at the divisions of their crural veins, in the veins that meet towards the top of the os sacrum, and in those branches which come from the haunches, in which no such effect of gravity from the erect position was to be apprehended.”

“The valves are solely made and instituted lest the blood should pass from the greater into the lesser veins, and either rupture them or cause them to become varicose.... The delicate valves, whilst they readily open in the right direction, entirely prevent all contrary movement.... And this I have frequently experienced in my dissections of the veins: if I attempted to pass a probe from the trunk of the veins into one of the smaller branches, whatever care I took, I found it impossible to introduce it far any way, by reason of the valves; whilst, on the contrary, it was most easy to push it along in the opposite direction from without inwards, or from the branches towards the trunks and roots.” He concludes his argument by again pointing out that the uses of the valves can be clearly shown in an arm which has been tied up for phlebotomy, and that the valves are best seen in labouring people.

The fourteenth chapter is devoted to the “Conclusion of the Demonstration of the Circulation.” It runs thus:—

“And now I may be allowed to give in brief my view of the circulation of the blood, and to propose it for general adoption.

“Since all things, both argument and ocular demonstration show that the blood passes through the lungs and heart by the force of the ventricles, and is sent for distribution to all parts of the body, where it makes its way into the veins and pores of the flesh, and then flows by the veins from the circumference on every side to the centre from the lesser to the greater veins, and is by them finally discharged into the vena cava and right auricle of the heart, and this in such quantity or in such afflux and reflux, thither by the arteries, hither by the veins, as cannot possibly be supplied by the ingesta, and is much greater than can be required for mere purposes of nutrition; it is absolutely necessary to conclude that the blood in the animal body is impelled in a circle, and is in a state of ceaseless movement; that this is the act or function which the heart performs by means of its pulse, and that it is the sole and only end of the movement and contraction of the heart.”

Harvey concludes his treatise with a series of reasons which he rightly considers to be of a less satisfactory nature than those he has already adduced. The seventeenth chapter contains much comparative anatomy. It opens with the statement that “I do not find the heart as a distinct and separate part in all animals; some, indeed, such as the zoophytes, have no heart.... Amongst the number I may instance grubs and earth-worms, and those that are engendered of putrefaction and do not preserve their species. These have no heart, as not requiring any impeller of nourishment into the extreme parts.... Oysters, mussels, sponges, and the whole genus of zoophytes or plant-animals have no heart, for the whole body is used as a heart, or the whole animal is heart. In a great number of animals, almost the whole tribe of insects, we cannot see distinctly by reason of the smallness of the body; still, in bees, flies, hornets, and the like we can perceive something pulsating with the help of a magnifying glass; in pediculi also the same thing may be seen, and as the body is transparent, the passage of the food through the intestines, like a black spot or stain, may be perceived by the aid of the same magnifying glass.

“But in some of the pale-blooded and colder animals, as in snails, whelks, shrimps, and shell-fish, there is a part which pulsates—a kind of vesicule or auricle without a heart—slowly, indeed, and not to be perceived except in the warmer season of the year.... In fishes, serpents, lizards, tortoises, frogs, and others of the same kind there is a heart present, furnished with both an auricle and a ventricle.... And then in regard to animals that are yet larger and warmer and more perfect,... these require a larger, stronger, and more fleshy heart.... Every animal that has lungs has two ventricles to its heart, one right, the other left, and whenever there is a right there is a left ventricle, but the contrary does not hold good; where there is a left there is not always a right ventricle.... It is to be observed, however, that all this is otherwise in the embryo where there is not such a difference between the two ventricles.... Both ventricles also have the same office to perform, whence their equality of constitution. It is only when the lungs come to be used ... that the difference in point of strength and other things between the two ventricles becomes apparent. In the altered circumstances the right has only to drive the blood through the lungs, whilst the left has to propel it through the whole body.”

This concludes Harvey’s Demonstration of the Circulation of the Blood in 1628, but he continued to work at the subject throughout his life. In two letters or anatomical disquisitions, addressed to the younger Riolanus of Paris, and dated from Cambridge in 1649, Harvey gives his latest reflections upon the subject of the Circulation of the Blood. These disquisitions differ very greatly from the original treatise. They are less clear and concise, and dwell more upon points of dispute which had arisen in connection with the controversy, which raged for many years round Harvey’s discovery.

The first disquisition is devoted more especially to the question of the anastomosis which takes place between the arteries and the veins, whilst the second disquisition illustrates more fully a number of details connected with the nature and quantity of the blood and its mode of progression. Harvey says incorrectly of the anastomosis, “Neither in the liver, spleen, lungs, kidneys, nor any other viscus, is such a thing as an anastomosis to be seen, and by boiling I have rendered the whole parenchyma of these organs so friable that it could be shaken like dust from the fibres or picked away with a needle, until I could trace the fibres or every sub-division, and see every capillary filament distinctly. I can, therefore, boldly affirm that there is neither any anastomosis of the vena portÆ with the cava, of the arteries with the veins, or of the capillary ramifications of the biliary ducts, which can be traced through the entire liver, with the veins.”

The second disquisition opens with Harvey’s view of the contemporary criticism upon his treatise. “But scarce a day, scarce an hour has passed since the birthday of the Circulation of the blood that I have not heard something, for good or for evil, said of this, my discovery. Some abuse it as a feeble infant, and yet unworthy to have seen the light; others again think the bantling deserves to be cherished and cared for. These oppose it with much ado, those patronise it with abundant commendation. One party holds that I have completely demonstrated the circulation of the blood by experiment, observation, and ocular inspection against all force and array of argument; another thinks it scarcely sufficiently illustrated—not yet cleared of all objections. There are some, too, who say that I have shown a vainglorious love of vivisections, and who scoff at and deride the introduction of frogs and serpents, flies, and other of the lower animals upon the scene, as a piece of puerile levity, not even refraining from opprobrious epithets.

“To return evil speaking with evil speaking, however, I hold to be unworthy in a philosopher and searcher after truth. I believe that I shall do better and more advisedly if I meet so many indications of ill breeding with the light of faithful and conclusive observation. It cannot be helped that dogs bark and vomit their foul stomachs, or that cynics should be numbered among philosophers; but care can be taken that they do not bite or inoculate their mad humours, or with their dogs’ teeth gnaw the bones and foundations of truth.

“Detractors, mummers, and writers defiled with abuse, as I resolved with myself never to read them, satisfied that nothing solid or excellent, nothing but foul terms was to be expected from them, so have I held them still less worthy of an answer. Let them consume on their own ill-nature. They will scarcely find many well-disposed readers, I imagine, nor does God give that which is most excellent, and chiefly to be desired—wisdom—to the wicked. Let them go on railing, I say, until they are weary, if not ashamed.”

Amidst a mass of unprofitable speculation, the second Disquisition contains one or two gems of pathological observation, illustrating physiological conclusions. Desiring to set in a clear light “that the pulsific power does not proceed from the heart by the coats of the vessels, I beg here to refer to a portion of the descending aorta, about a span long in length, with its division into two crural trunks, which I removed from the body of a nobleman, and which is converted into a bony tube: by this hollow tube nevertheless, did the arterial blood reach the lower extremities of this nobleman during his life, and cause the arteries in these to beat.... Where it was converted into bone it could neither dilate nor contract like bellows, nor transmit the pulsific power from the heart to the inferior vessels: it could not convey a force which it was incapable of receiving through the solid matter of the bone. In spite of all, however, I well remember to have frequently noticed the pulse in the legs and feet of this patient whilst he lived, for I was myself his most attentive physician, and he my very particular friend. The arteries in the inferior extremities of this nobleman must, therefore, and of necessity, have been dilated by the impulse of the bloodlike flaccid sacs, and not have expanded in the manner of bellows through the action of their tunics.

“I have several times opened the breast and pericardium of a man within two hours after his execution by hanging, and before the colour had totally left his face, and in presence of many witnesses, have demonstrated the right auricle of the heart and the lungs distended with blood: the auricle in particular of the size of a large man’s fist, and so full of blood that it looked as if it would burst. This great distension, however, had disappeared next day, the body having stiffened and become cold, and the blood having made its escape through various channels.

“I add another observation. A noble knight, Sir Robert Darcy, an ancestor of that celebrated physician and most learned man, my very dear friend, Dr. Argent, when he had reached to about the middle period of life, made frequent complaint of a certain distressing pain in the chest, especially in the night season, so that dreading at one time syncope, at another suffocation in his attacks, he led an unquiet and anxious life. He tried many remedies in vain, having had the advice of almost every medical man. The disease going on from bad to worse, he by and by became cachectic and dropsical, and finally grievously distressed, he died in one of his paroxysms. In the body of this gentleman, at the inspection of which there were present Dr. Argent, the President of the College of Physicians, and Dr. Gorge, a distinguished theologian and preacher, who was pastor of the parish, we found the wall of the left ventricle of the heart ruptured, having a rent in it of size sufficient to admit any of my fingers, although the wall itself appeared sufficiently thick and strong. This laceration had apparently been caused by an impediment to the passage of the blood from the left ventricle into the arteries.

“I was acquainted with another strong man, who, having received an injury and affront from one more powerful than himself, and upon whom he could not have his revenge, was so overcome with hatred and spite and passion, which he yet communicated to no one, that at last he fell into a strange distemper, suffering from extreme oppression and pain of the heart and breast, and the prescriptions of none of the very best physicians proving of any avail, he fell in the course of a few years into a scorbutic and cachectic state, became tabid, and died. This patient only received some little relief when the whole of his chest was pummelled or kneaded by a strong man, as a baker kneads dough. His friends thought him poisoned by some maleficent influence or possessed with an evil spirit. His jugular arteries enlarged to the size of a thumb, looked like the aorta itself, or they were as large as the descending aorta: they had pulsated violently and appeared like two long aneurysms. These symptoms had led to trying the affects of arteriotomy in the temples, but with no relief. In the dead body I found the heart and aorta so much gorged and distended with blood that the cavities of the ventricles equalled those of a bullock’s heart in size. Such is the force of the blood pent up, and such are the effects of its impulse.”

His letters show that Harvey was employed almost to the end of his life in devising fresh experiments in proof of the circulation of the blood. Thus, in a letter addressed to Paul Marquard Slegel, and dated London, this 26th of March, 1651, Harvey writes: “It may be well here to relate an experiment which I lately tried in the presence of several of my colleagues.... Having tied the pulmonary artery, the pulmonary veins, and the aorta, in the body of a man who had been hanged, and then opened the left ventricle of the heart, we passed a tube through the vena cava into the right ventricle of the heart, and having at the same time attached an ox’s bladder to the tube, in the same way as a clyster-bag is usually made, we filled it nearly full of warm water and forcibly injected the fluid into the heart, so that the greater part of a pound of water was thrown into the right auricle and ventricle. The result was that the right ventricle and auricle were enormously distended, but not a drop of water or of blood made its escape through the orifice in the left ventricle. The ligatures having been undone, the same tube was passed into the pulmonary artery and a tight ligature having been put round it to prevent any reflux into the right ventricle, the water in the bladder was now pushed towards the lungs, upon which a torrent of the fluid, mixed with a quantity of blood, immediately gushed forth from the perforation in the left ventricle: so that a quantity of water, equal to that which was pressed from the bladder into the lungs at each effort, instantly escaped by the perforation mentioned. You may try this experiment as often as you please: the result you will still find to be as I have stated it.”

The exact teaching of Harvey’s contemporaries in London is easily accessible. One of his distinguished colleagues at the College of Physicians was Alexander Reid, son of the first minister of Banchory, near Aberdeen, brother of Thomas Reid, Secretary for Latin and Greek to King James I. Reid was born about 1586, learnt Surgery in France, was admitted a Fellow of the College of Physicians in 1624, and was appointed Lecturer on Anatomy at the Barber Surgeons’ Hall December 28, 1628, in succession to Dr. Andrewes, Harvey’s assistant. Reid, eight years younger than Harvey, lectured at an annual stipend of £20 on every Tuesday throughout the year from 1628 to 1634, when he published a tiny Manual of Anatomy containing the substance of his lectures. For some reason Harvey’s doctrines did not recommend themselves to Reid, and the Manual therefore contains the following traditional account of the heart.

“As for the heart, the substance of it is compact and firm, and full of fibres of all sorts. The upper part is called Basis or Caput: the lower part Conus, Mucro or Apex Cordis. When the heart contracteth itself it is longer, and so the point is drawn from the head of it. But when it dilateth itself it becometh rounder, the conus being drawn to the basis. About the basis the fat is. It is covered with a skin which hardly can be separat[ed]. In moist and cowardly creatures, it is biggest.... Of all parts of the body it is hottest, for it is the wellspring of life, and by arteries communicateth it to the rest of the body. The heart hath two motions, Diastole and Systole. In Diastole, or dilatation of the heart, the conus is drawn from the basis to draw blood by the cava to the right ventricle, and air by the arteria venosa [pulmonary vein] to the left ventricle. In Systole or contraction the conus is drawn to the basis.

“First, that the vital spirit may be thrust from the left ventricle of the heart into the aorta.

“Secondly, that the arterial blood may be thrust into the lungs by arteria venalis [the left auricle].

“Thirdly, that the blood may be pressed to the lungs, in the right ventricle by vena arterialis [right auricle].

“The septum so called because it separateth the right ventricle from the left, is that thick and fleshy substance set between the two cavities.

“Riolan will have it the matter of the vital blood to pass through the holes or porosities of it from the right to the left ventricle, but that hardly any instrument can show them. First, because they go not straight, but wreathed. Secondly, because they are exceeding narrow in the end. He affirmeth that they are more easily discerned in an ox-heart boiled.”

It is difficult to realise how any reasonable man could teach such a farrago of nonsense when he must have heard Harvey’s perfectly simple and clear demonstration of the structure and uses of the heart. Harvey was lecturing on Tuesdays, Wednesdays, and Thursdays; Reid only lectured on Tuesdays, and Harvey had especially set himself to controvert the very errors that Reid was promulgating. But Reid was perfectly impenitent, for his Manual was reprinted in 1637, in 1638; and after his death it appeared again in 1642, 1650, 1653, and 1658, yet there is no alteration in his text. He was not even sure of the broad features of the anatomy of the heart, for he writes: “The first vessel in the chest is the vena cava or magna. The second vessel in the breast is vena arterialis. It is a vein from its office, for it carrieth natural blood to the lungs by the right side of the windpipe. It is called an artery because the coat of it is double, not single. It doth spring from the upper part of the right ventricle of the heart, and is implanted into the substance of the lungs by the right side of the windpipe.”

It seems obvious that this is a perverted description of the right auricle, and that Reid had no idea of the pulmonary artery as a distinct structure.

“The third vessel is arteria venalis. It is called an artery because it carrieth arterial blood, but a vein because it hath a single coat as a vein. It ariseth from the upper part of the left ventricle of the heart, and is implanted into the substance of the lungs by the left side of the windpipe.”

This in like manner appears to be the left auricle and the pulmonary veins.

“The vena arterialis hath three valves called sigmoides from the figure of the great sigma, which answereth the Latin S, the figure is this, C. They look from within outwards, to let out the blood but to hinder the return of the same.

“The arteria venalis hath two valves called mitrales, because they are like a bishop’s mitre. They look from without inward to let in blood carried from the vena arterialis. They are bigger than those of vena cava and have longer filaments and to strengthen them many fleshy snippets are joined together.

“It hath two valves only that the fuliginous vapours might the more readily be discharged.”

Reid, like all his contemporaries, had a glimmering of the lesser circulation, for he says: “First the blood is carried by vena arterialis and from hence to arteria venalis by sundry anastomoses, and from hence to the left ventricle of the heart. Where being made spirituous it is sent by the aorta to impart life to the whole body.

“One thing is to be noted that no air in its proper substance is carried to the heart; for the blood contained in these two vessels is sufficiently cooled by the bronchia passing between them.... One thing is to be noted, that in arteria venosa a little below the valves there is found a little valve ever open. It being removed, there appeareth a hole by the which the blood passeth freely from the vena cava to it and returneth by reason of this anastomosis that the blood in the veins may be animate.” This is a description of the foramen ovale and its use.

Such a comparison with the work of a contemporary teacher in the same town shows how immeasurable was the advance made by Harvey. It only remains to show what has been done since his death to perfect our knowledge of the heart and of the circulation. The use of the microscope by Malpighi in 1661 gave an insight into the true nature of the porosities by which the blood passed from the terminal arteries to the commencing veins in the lungs and proved them to be vessels. The capillary circulation was still further investigated by Leeuwenhoek in 1674 who described it as it is seen in the web of a frog’s foot, and in other transparent membranes; Blankaart in 1676, William Cowper in 1697, and afterwards Ruysch, studied the arrangement of the capillaries by means of injection. In 1664 Stenson demonstrated that the heart was a purely muscular organ.

The various histological details being thus settled there came a long interval until chemistry was sufficiently advanced to enable definite statements to be made about the aËration of the blood.

The work of Black in 1757 and of Priestley and others in 1774 and 1775 at last allowed the process of respiration and the true function of the lungs to be explained upon scientific grounds. But the interval between the discovery of the capillaries and the explanation of the act of respiration was not wholly barren; for in 1732 Archdeacon Hales, by means of experiments, obtained an important insight into the hydraulics of the circulation. During the present century our knowledge of the physics of the heart and circulation has been reduced almost to an exact science by the labours of the German, French, and Cambridge schools of physiology under the guidance respectively of Ludwig, of Chauveau, and of Foster; whilst the nervous mechanism of the heart and of the arteries has been thoroughly investigated by Gaskell and others.