THE CIRCULATION AND THE ARISTOTELIAN PRIMACY OF THE HEART
It has been stated already that the first announcement of the circulation is to be found in Harvey's lecture notes. The following is the text of the memorable passage in question, which I have translated from Harvey's Latin. He says:—
"It is proved by the structure of the heart that the blood is perpetually transferred through the lungs into the aorta, as by two clacks of a water-bellows to rayse water. It is proved by the ligature that there is a transit of the blood from the arteries to the veins; whereby it is demonstrated that a perpetual movement of the blood in a circle is brought about by the beat of the heart. Is this for the sake of nutrition, or of the better preservation of the blood and members by infusion of heat, the blood in turn being cooled by heating the members and heated by the heart?"[106]
The words "as by two clacks of a water-bellows to rayse water" are Harvey's own racy English, embedded in his Latin text. The "ligature" is the flat band which is tied about the upper arm when bleeding from a vein is to be practised at the bend of the elbow. The Hippocratic physicians called this band a "taenia,"[107] and even in their day it was known to hasten the flow of blood from the opened vein when applied as above stated, but yet to check the flow if tied too tight. This clinical observation had awaited a rational explanation for more than nineteen centuries.[108]
Page 80, right, of William Harvey's Prelectiones Anatomiæ Universalis, or Lecture Notes of 1616. The passage contains the first recorded mention of the movement of the blood in a circle.
WH constat per fabricam cordis sanguinem
per pulmones in Aortam perpetuo
transferri, as by two clacks of a
water bellows to rayse water
constat per ligaturam transitum sanguinis
ab arterijs ad venas
vnde Δ perpetuum sanguinis motum
in circulo fieri pulsu cordis
An? hoc gratia Nutritionis
an magis Conservationis sanguinis
et Membrorum per Infusionem calidam
vicissimque sanguis Calefaciens
membra frigifactum a Corde
Calefit
Transcript of the preceding page.
Our most immediate interest in the foregoing passage lies in this: that on the very same page, with the few clear simple words which tell for the first time of Harvey's facts and proofs, he has briefly written down conjectures as to the meaning of the circulation. These are as strikingly put as certain jottings are obscure which deal on a neighboring page with some possible meanings of the heart-beat.[109] In neither group of conjectures do the functions of the lungs play a part; but the discoverer asks himself whether it be not to revisit the heat of the heart that the whole mass of the blood circles back to the chest in its Harveian course! More than thirty-two years after the date of Harvey's note-book Harvey wrote to Riolanus:—
"There are some who consider that as no impulsion of nutriment is required for the nutrition of plants, their particles attracting little by little whatever they need to replace what they have lost, so in animals there is no need of any impulsion, the vegetative faculty in both working alike. But there is a difference. In animals a perpetual flow of warmth is required to cherish the members, to keep them alive by the aid of vivifying heat, and to restore parts injured from without. It is not merely nutrition that needs to be provided for."[110]
In the first Exercise to Riolanus Harvey had touched also upon the use of the circulation, interweaving this doctrine of heat with the doctrine of respiration as he then held it, in a passage the last part of which I have quoted already. Quoted more fully he says:—
"And this, indeed, is the principal use and end of the circulation, for which the blood revolves with perpetual influence in its ceaseless course and is driven along its circuit: namely, that all the parts in dependence upon the blood may be kept alive by the primary innate heat and in their state of vital and vegetative being, and may perform all their functions; whilst, to use the language of physiologists, they are sustained and actuated by the inflowing heat and vital spirits. Thus by the aid of two extremes, viz.: cold and heat, is the temperature of the animal body retained at its mean. For as the air inspired tempers the too great heat of the blood in the lungs and center of the body and effects the expulsion of suffocating fumes, so in its turn does the hot blood, thrown through the arteries into the entire body, cherish and nourish and keep alive all the extremities, preventing extinction due to the power of external cold."[111]
"The innate fire is not in the right ventricle," a Hippocratic author had written, who had written also that the wall of the left ventricle is dense, to guard the strength of the heat.[112] Aristotle, too, had placed in the heart the "origin" of the "natural innate heat";[113] had likened the heart to "the hearth on which shall lie the natural kindling, well protected also, as being the acropolis of the body."[114] At a later day Galen had affirmed the same doctrine.[115]
Let us turn now to the famous treatise of 1628, published twelve years after the note-book had been written. In the chapter in which Harvey says "I tremble lest I have mankind at large for my enemies" and then publishes and names the circulation,—in this chapter, before passing to his proofs, he published the following words which resound in a way very different from the simplicity of the note-book:—
"So probably it may come to pass in the body through the movement of the blood that all the parts are nourished, cherished, quickened, by the hotter, perfected, vaporous, spirituous, and, so to speak, alimentive blood; that the blood, on the other hand, is cooled, coagulated, and rendered, as it were, effete in the parts; whence it returns to its origin, namely, the heart, as to its fountain, or the hearth of the body, to regain perfection. There by the potent and fervid natural heat, a treasury of life, as it were, the blood is liquefied anew and becomes pregnant with spirits and, so to speak, with balsam. Thence the blood is distributed again; and all this depends upon the motion and pulsation of the heart.
"The heart, therefore, is the origin of life and the sun of the microcosm, even as the sun in his turn might well be called the heart of the world; by the vigor and pulsation of the heart the blood is moved, perfected, quickened, and delivered from corruption and thickening; and the function of nourishing, cherishing, quickening the entire body is performed by that intimate hearth, the heart, the foundation of life, the author of all. But of these matters more conveniently when I shall speculate as to the final cause of motion such as this."[116]
Upon this florid passage follow the classic six chapters which bring forward with such power and calm the proofs of the circulation. These are succeeded in their turn by words which echo their sobriety, as follows:—
"It will not be beside the question to show also from certain familiar reasonings, that the circulation is both convenient and necessary. In the first place, since death is corruption from deficiency of heat[117] and since all living things are warm, all dying things cold, the heat requires a seat and origin, a home and hearth, as it were, in which the tinder of nature, the first beginning of the innate fire, may be contained and preserved; a place from which, as from their origin, heat and life may flow out into all the parts, whence nutriment may come and upon which concoction and nutrition and all quickening may depend. That this place is the heart, that this is the origin of life as aforesaid, I should hope that none would doubt.
"Hence the blood has need of motion, of motion such that it may return to the heart; for, if sent to the outer parts of the body, far from its source,[118] and left unmoved, it would become coagulated. Heat and spirits are seen to be generated and preserved in all by motion, to vanish if quiet supervene. Therefore, the blood, thickened or stiffened by the cold of the extremities and of the ambient [air] and destitute of spirits, as in the dead, must needs return to its source and origin in order to keep itself whole, to seek thence and repair again its heat and spirits."...[119]
"Moreover," Harvey says, a page farther on, "since all animals live by nutriment concocted in their interior, it is necessary that the concoction and distribution thereof be perfect; and, further, that a place and receptacle exist where the nutriment may be perfected and whence it may be led off to the several members. Now this place is the heart, for it alone of all the parts contains blood for the public use in its cavities, the auricles and ventricles, as in cisterns and storehouse; not merely blood for its private use in the coronary vein and artery."[120]
In the next chapter we obtain glimpses of the pathological relations of this physiology. Harvey brings forward tertian fever as a case in point, explaining that the febrile paroxysm is produced when
"the preternatural heat which has been kindled in the heart is diffused throughout the entire body by way of the arteries, together with the morbific matter which thus is evaporated and dissolved by nature."[121]
As a student of the Greek science reads the foregoing passages, he clearly sees that the new wine of the circulating blood is poured into the old bottles of the Aristotelian physiology; and Harvey tells us so himself, in the last chapter of his most famous treatise. He says:—
"No less should we agree with Aristotle as to the sovereignty of the heart, in dealing with the following and similar questions: Does it receive motion and sensation from the brain, blood from the liver; or is it the origin of the veins and of the blood? For they who try to refute him leave out, or do not grasp, the main argument, which is that the heart is the first part to exist and has in it blood, life, sensation, motion, before the brain or the liver has been made or is clearly to be distinguished, or at least before either can perform any function. So the heart with its own proper organs constructed for motion—as it were, an internal animal—is the earlier formed; and, this being the first made part, it is the will of nature that thereafter the entire animal be made, nourished, preserved, perfected by the heart to be its achievement and abode. The heart is governor everywhere, like the chief in a commonwealth with whom is lodged the first and highest authority. In an animal all power is derived from and depends upon the heart as its origin and foundation."[122]
The main argument, which is that the heart is the first part to exist, is simply the argument from the development of the embryo in the hen's egg. The study of this development day by day had been recommended by one of the Hippocratic writers,[123] and Aristotle had laid stress upon the changes in the embryo during incubation.[124] Harvey, in his turn, had studied them carefully. The ancients could have made their observations only with the naked eye, but Harvey had the aid of a simple lens, though of nothing approaching in power to a microscope.[125] In the treatise of 1628 he speaks as follows of what he thus observed:—
"If you turn to the formation of the chick in the egg, the first thing to exist therein, as I have said, is a mere vesicle, or auricle, or pulsating drop of blood. Afterward, when growth has gone on, the heart is completed.... In a hen's egg after four or five days of incubation I have shown the visible presence of the rudiment of the chick in the form of a little cloud; in an egg, that is, which had been immersed in clear tepid water after removal of the shell. In the middle of the aforesaid little cloud there was a palpitating bloody point, so fine that in contracting it disappeared and became invisible, but reappeared on its relaxation, looking like the point of a needle, and of a ruddy color; so that being now visible and now invisible, as though now existent and now non-existent, it evinced palpitation and the beginning of life."[126]
In the same treatise Harvey promises to publish more observations
"on the formation of the fœtus, where numerous problems of the following order can find a place: Why should this point be made or perfected earlier, that later? As regards the dominance of the members: Which part is the cause of the other? There are very many problems connected with the heart, such as: Why should it be the first thing (as Aristotle says in his third book on the parts of animals)[127] to acquire consistency, and be seen possessed of life, motion, and sensation, before anything has been perfected in the rest of the body? And in like manner regarding the blood: Why is it before all, and how possessed of the beginnings[128] of life and of the animal, and of the craving to move and be impelled hither and thither, to which end the heart would seem to have been made?"[129]
In Harvey's celebrated treatise, despite various frank questionings by the way, such as that just quoted about the blood, he so frankly follows in the footsteps of "the master of them that know" that Aristotle need not be cited at length to prove the fact. To Aristotle are largely due Harvey's references to the heart as the central source of indispensable vital heat; his references to aliment perfected in the heart; his blending of psychological doctrines with the doctrine of the movement of the blood. Therefore, a brief account of how this became possible will be germane.
When an ancient observer looked with the naked eye at the very early embryo of the fowl, he distinguished at first only a blood-red point, which pulsated, or "leapt." This Aristotle judged to be the heart, containing blood before any blood-vessel had shown itself and before blood was visible in any other part. Very soon, however, two vessels containing blood were seen, according to him, to extend from the rudimentary heart toward the periphery. From these and other considerations Aristotle inferred that both the blood and all its containing vessels owe their first origin to the heart; and that throughout life the liquid made elsewhere from the food enters the heart, there to be perfected into blood by the action of the vital innate heat, of which, as we have seen, he held the fiery central hearth to be within the heart. Naturally, therefore, he believed the blood not to be hot of itself, but to acquire its vivifying heat at the heart, the pulsation of which he held to be caused directly by the seething of the blood within. When thus perfected and charged with heat the blood, according to him, is distributed from the heart through the vena cava as well as the aorta. These great vessels and their subdivisions Aristotle distinguished anatomically; but he made no serious physiological distinction between what we call the veins and the arteries, and, himself, applied the word "artery" to the windpipe only. As to the cavities and contents of the heart, even as to the number of its cavities, he had obscure, complex, and erroneous ideas, and of the valves he knew nothing. He recognized no essential differences between the matters distributed by way of the vena cava and by way of the aorta, all being, alike, one thing, blood; though the blood was hotter or cooler, thinner or thicker, purer or cruder, in different regions or parts of the body, in different sets of vessels, in different cavities of the heart, or at different times in the same place.
We have seen already that, in the genuine works of Aristotle, there is no sign that what we call the tissues of the adult require or receive a derivative of the air, whether crudely mingled with the blood in the earlier Hippocratic way, or separate in Erasistratean fashion, or in the form of such "spirituous blood" as Galen afterward accepted. We have seen that the air which Aristotle believed to enter the heart for cooling purposes, cannot be traced beyond it; that whatever spirits may exist in the body for him, would seem to be either of the nature of vapor produced within the body itself, or of a nature quite indeterminate.[130]
The living egg of the hen has had a vast deal to do with the history of psychology as well as of physiology. It is partly owing to what Aristotle believed to go on in the egg that we speak to-day of good hearts and bad hearts—even of sweethearts. Aristotle knew nothing of the nerves, and, therefore, could reasonably fail to find conclusive evidence that the brain and spinal cord had to do with what we call nervous functions. So he fell back upon a doctrine at least as old as the Iliad,[131] and made a psychological center of the heart. This being proved, for Aristotle, largely by its demeanor in the early embryo, to be the life-long source of the nutritive blood; and being, for him, the central hearth of the heat by means of which the blood is perfected and warmed; he held it a matter of necessity that in the heart should dwell the so-called "nutritive soul"; that is, the faculty which uses as its most immediate instrument the "innate," "natural," "vital," "psychical," heat, to bring about nutrition, growth, and generation. He says:—
"It is impossible that the other faculties of the soul should exist without the nutritive, or these without the natural fire; for in this has nature set that faculty aglow."[132]
Dealing with these other faculties, he sees that there must be an organ where the results of sight, hearing, and the other senses, are compared; and deliberately discussing and rejecting the claims made for the brain he makes the heart this "common sense-organ of all the sense-organs," as he styles it. He says:—
"If in all the creatures the seat of life is in this part, it is clear that here also must the origin of sensation be; for we say that the body has life because it is an animal, but we say that it is animal because it has sensation."[133]
Less hollow rings the argument in the modern ear, when the ancient thinker bases it on conclusions drawn from observation. We learn from him that only those parts are sensitive which contain blood, as opposed to hair and nails, or even to the blood, if taken by itself. We learn, therefore, that as the heart of the embryo is the first part to contain blood, it is the first part to be sensitive and hence is the central source of sensation. Moreover, Aristotle, like Plato,[134] knowing nothing of the nerves, judges the blood-vessels to be sensory paths; and blood-vessels connect, not only the sensitive flesh, but all the more special sense-organs with the heart. Such is the outline of the reasons why Aristotle held the heart to be the lifelong seat, not only of the "nutritive soul," but of the "sensory soul" as well.
Pain, pleasure, and desire would naturally dwell beside sensation in the heart, which Aristotle held to be obviously the seat of the emotions, as proved by its palpitation when they are stirred. Moreover, it is desire, seated in the heart, which incites to action, to motion, movement thus resulting from sensation; and, in general, "the movements" of every sense both begin and end at the heart; the word here translated "movement"[135] being used, in the technical diction of Aristotle, to include not only the "molar motion" of modern parlance, but also subtle forms of change of state. Further, in the early embryo the heart itself is plainly the first part which possesses motion; it visibly taking the lead in this, moving "as though itself an animal." The pulsating movements of the heart are the direct effects of the seething and vaporization within it; while, in the respiratory movements, the chest wall is pushed out by an expansion due to the vital heat, whose cardiac hearth the lungs inclose, and then follows inward a contraction due to the cooling air which has been drawn into the expanding lungs. As the bodily movements, in general, are "brought about by drawing and slackening" and originate at the heart, it is appropriate that the heart contains tendinous structures[136] within itself; "for it needs the service and strength" of such.[137] It is too, in a sense, the origin of the discontinuous tendinous and ligamentous structures of the body. Aristotle's doctrine of the heart as the source of motion seems especially vague. But, hardy thinker though he was, he scarcely could be definite on this subject, even in speculation. He knew that heat expands and cold contracts; he recognized the force which, as he believed, confined or compressed vapor exerts in living bodies, not only in health but in disease; and he knew the strength imparted to bodily effort by holding the breath. His genuine writings, however, bring forward no modus operandi, except in the case of respiration and of the movements of the heart itself. We are given no inkling as to how the tendons are normally drawn and slackened in obedience to the will, for the true function of muscle was unknown to Aristotle (Harvey to the contrary notwithstanding),[138] and the blood-vessels were the only continuous special paths between center and periphery which Aristotle could make out. In his time, as we have seen, the nerves had not been distinguished, even anatomically, from the bands and cords of the ligaments and tendons.
So, for Aristotle, the nutritive, sensory, and motor faculties, the desires and emotions, in short all the souls or parts of the soul (to use the ancient phraseology) that are not the most exalted, dwell in fire within the heart, suitably and honorably placed at the central "acropolis." To the divine mind of man, on the other hand, he does not assign a definite special dwelling-place within the body.
Harvey differed often and widely from Aristotle. Yet even in his old age he wrote: "The authority of Aristotle has always such weight with me that I never think of differing from him inconsiderately."[139] Cannot one fancy, may not one conjecture, that in the eyes of the discoverer of the circulation his great discovery, fundamental, new, and original, as he rightly claimed it to be, may at times have seemed to constitute a thorough correcting and filling in of a rough sketch dashed off at the Lyceum? Let us see.
Aristotle had no conception of anything resembling a circulation of the blood, nor any definite mechanical ideas as to its movement. While the vena cava as well as the aorta received blood from his valveless heart and yielded it to the body at large, blood ebbed back to the heart during sleep, and the warm nutrient liquid which the vena cava and the aorta yielded to the tissues had previously entered the heart continuously but in an imperfect state through both of these great vessels, to go forth again through both, perfected into blood and heated, with no perplexing differences of color noted between that in the great vein and that in the aorta. The relations between the food, the blood, the heart, and the body at large, though recognized to be complex, may well have presented themselves to Aristotle with something of the vagueness with which the relations between the food, the liquids, the contractile vacuole, and the living substance of a protozoön, present themselves to us. If the heart, retaining its Aristotelian powers, were found to receive the blood imperfect or impaired, but to receive it by the veins only, and to send it out, but only by the arteries, warmed and perfected or restored to perfection at its Aristotelian source; what have we but the systemic part of the circulation, as it may have pictured itself sometimes to Harvey?[140]