Thus does the great English discoverer bring the pulmonary transit and the circulation of the blood to the rescue of the Aristotelian heart, despite Galen and the tricuspid valve! Between Harvey and the school that refused to the heart more than a fraction of the blood, there could be no peace. It is the Galenists whose system he attacked and shattered so thoroughly; and those who long and bitterly opposed the acceptance of the Harveian circulation were of the Galenic school. In a private letter written twenty-three years after the publication of his discovery, Harvey excuses the French physician Riolanus for having slighted the circulation not long before, saying, among other things:—
"It was proper that the dean of the College of Paris should keep the medicine of Galen in repair; and should admit no novelties into his school without the utmost winnowing."[154]
We have found the discoverer of the circulation an admirer and defender of Aristotle; but we shall leave him far less Aristotelian than we found him. Before he died, he had transferred to the blood itself that physiological primacy which Aristotle had given to the heart; Harvey having come to regard the blood even as the very seat of the soul, harking back to a Greek doctrine older than Aristotle and expressly discountenanced by him.[155] This final view of Harvey was not simply an outcome of his old age, though he develops and formally declares and insists upon the doctrine of the primacy of the blood in the writings which he published when beyond the age of seventy, more than twenty years after the publication of his treatise of 1628. We have seen that in this his most famous work he adheres impressively to the Aristotelian doctrine of the primacy of the heart; though even this work contains utterances of Harvey which do not well accord with that doctrine. More than eleven years earlier, when making notes for his lectures of 1616, he asked himself in striking terms, whether the circulation do not exist in order that the blood may be heated by the heart.[156] Yet there are passages in those very same notes which show that, beside vaguer conjectures,[157] the doctrine of the primacy of the blood was present clearly to Harvey's mind even so early as in his thirty-seventh year. In his lecture notes four passages are especially significant as to this doctrine. Of these the first is as follows:—
"Yf I could shew what I hav seene, y^t weare att an end between physicians et philosophers."
After these words in English Harvey falls into his usual Latin, which may be translated thus:—
In a second passage of his note-book Harvey says, speaking of the heart:—
"It is most exceeding full of contained blood, as no other viscus is. Wherefore Aristotle [holds] against the physicians that the origin of the blood is not in the liver but in the heart, because in the liver there is no blood outside the veins. Rather is the blood the origin of both, as I have seen."[161]
In a third passage Harvey says of the heart that its
"temperature is exceeding hot, inasmuch as it is exceeding full of blood."[162]
In a fourth passage of the lecture notes which bears upon the primacy of the blood we may read:—
"1. [The heart] is the most principal part of all, not because of itself,[163] for its flesh is more fibrous and harder and colder than the liver, but because of the abundance of blood and spirits in the ventricles.
"1. Whence the fount of the entire heat.
"Whence the auricles pulsate, after removal of the heart, because of the multitudinous blood.[164]
"2. Nor is [the heart] the principal part because of its origin: for I believe that the ventricles (which in the fœtus are both united as in fishes) are made out of a drop of blood which is in the egg; and that the heart, together with the rest [of the parts] all sprout[165] simultaneously, as [occurs] in an ear of corn, from an imperceptible size. Is there only a drop of blood in the auricles whence bestowing heat upon all parts, receiving from none, it is the citadel and domicile of the heat, the household shrine[166] of that edifice, fowntayn conduit hed."[167]
More than eleven years after the making of his lecture notes Harvey, at the age of fifty, published his treatise of 1628; and later, after keeping silence for more than twenty years, he published together the two Exercises addressed to Riolanus. During these twenty years and more the blood must have been rising and the heart declining, in Harvey's esteem, as ruling powers in the body; for at the end of that time more than thirty-two years after the jotting down of the statements and varied conjectures of his lecture notes, he formally throws over Aristotle's primacy of the heart, in a passage near the close of the second Exercise to Riolanus. Of this passage the following is a part. Referring to certain opinions, mainly Aristotelian, regarding the heart and blood, Harvey says:—
"To speak openly, I do not believe that those things are so in the sense commonly received; and my opinion is inclined in the direction aforesaid by much which is visible in the generation of the parts, but which is not convenient to set down here. Soon, perhaps, I shall make public things even more wonderful and destined to cast even greater light upon natural philosophy.
"For the present I will only say and set forth without demonstration—by good leave of the learned and with due respect to the ancients—that the heart, as the beginning, author, source, and origin of everything in the body and the first cause of life, should be held to include the veins and all the arteries and also the contained blood; just as the brain, including all its nerves and sensory organs and spinal marrow, is the one adequate organ of sensation, as the phrase is. If by the word 'heart,' however, only the body of the heart be meant with its ventricles and auricles, I do not believe that it is the manufacturer of the blood; nor that the blood possesses vigor, faculty, reason,[168] motion, or heat, as the gift of the heart."[169]
In the second year after that of the Exercises to Riolanus Harvey's final publication, his treatise On Generation with appended essays, was given to the world, not long before his seventy-third birthday. During how many years this work had been in preparation we do not know; but it is avowedly based upon the views of Aristotle, whom Harvey styles his "dux"—his leader—as regards the subject of this treatise.[170] In it, to be sure, the ancient master is often weighed in the balance and found wanting by Harvey, who even questions whether Aristotle had seen for himself what he "narrates as to the generation of the chick," or "had accepted it from some expert."[171] Nevertheless, it is with the doctrines of Aristotle that Harvey incessantly compares the results of observation. Here the veteran records anew his denial of the Aristotelian primacy of the heart, and records as well his final emphatic assertion of the primacy of the blood. In regard to these matters it is interesting to note the various grades of expression which appear to mirror in this single work the various phases of Harvey's thought.
In the following florid passage doubt of the primacy of the heart seems hardly even hinted at. Harvey says:—
"Certain of the parts themselves are said to be generative, such as the heart, from which Aristotle declares that the rest of the parts derive their origin; as is also clear from the history which I have given. The heart, I say—or at least its first beginning, to wit, the vesicle and leaping point—constructs the rest of the body to be its future abode; enters this when once built up, and hides in it, vivifies and governs it; fortifies it with ribs and sternum super-imposed as a bulwark; and is a kind of household shrine, as it were, the first seat of the soul, the first receptacle and perennial soul-endowed[172] hearth of the innate heat, the source and origin of all the faculties, and their sole relief in calamity."[173]
Divergence from Aristotle in the matter of the heart is plainly marked, however, in the following passage of the same treatise, where Harvey says:—
"We find the blood formed before anything else in the egg and in the product of conception;[174] and almost at the same time the receptacles of the blood, the veins and the pulsating vesicle, become plainly visible. Wherefore, if the leaping point together with the veins and blood, which are all conspicuous as one single organ at the first beginning of the embryo, be accepted as the heart (the parenchyma of which is superadded to the vesicle later in the formation of the embryo), it is manifest that, accepted in this sense, that is, as an organ composed of parenchyma, ventricles, auricles, and blood, the heart in animals is in very truth, as Aristotle would have it, the principal and first generated part of the body; of which part, however, the first and foremost part is the blood, both by nature and in the order of generation."[175]
In the following third passage of the same treatise no reconciling interpretations of the master's words are to be found; flat disagreement with Aristotle is declared; and the "Sun of the Microcosm"[176] declines nearly to its simple modern status of a living pump! Harvey says:—
"Nor can I agree with Aristotle himself, who maintained that the heart is the primary generative part and that it is endowed with soul; for, truly, I believe the blood alone to be entitled to these distinctions, since the blood it is which first appears in generation; and that such is the case not only in the egg but also in every fœtus and very early animal embryo, shall at once be made plain.[177]
"At the beginning, I say, there appear the red leaping point, the pulsating vesicle, and filaments, derived thence, which contain blood in their interior. And, so far as can be discerned by accurate inspection, the blood is made before the leaping point is formed, and the blood is endowed with vital heat before it is set in motion by pulsation; and, further, as pulsation is begun in and by the blood, so at last it ends in the blood at the final instant of death. Indeed, by numerous experiments done upon the egg and otherwise I have made sure that it is the blood in which the power of returning to life persists, so long as the vital heat has not wholly vanished. And since the pulsating vesicle and the sanguineous filaments derived from it are seen before anything else, it stands to reason in my belief that the blood is prior to its receptacles—the contained, that is, to its container—since the latter is made for the use of the former. Therefore, it is probable that the filaments and the veins and then the vesicle and at length the heart, having organs destined to receive and retain the blood, are made for the sole purpose of transmitting and distributing it, and that the blood is the principal part of the body....
"Therefore, relying with certainty upon what I have observed in the egg and in the dissection of living animals, I maintain against Aristotle that the blood is the primary generative part; and that the heart is its organ, destined to send it on a circuit. Surely the function of the heart is the propulsion of the blood, as is admirably clear in all animals that have blood; and in the generation of the chick the same duty falls to the pulsating vesicle, which in the very early embryos of animals[178] no less than in the egg I have often exhibited to view as something more minute than a spark, beating and when in action contracting itself and at the same time pressing out the blood contained in it, and in its relaxation receiving the same afresh."[179]
Whether in studying the foregoing passages we read Harvey's earlier jottings in his private note-book or the deliberate statements published in his old age, it is evident that to his mind the question of the primacy of the blood versus the primacy of the heart depends for answer upon the further question whether in the development of the embryo the blood be made before the heart, or the heart before the blood. In no other part than one of these two can the primacy inhere, for him; and whichever of these two has the priority must be, to Harvey's mind, the origin of the other and of the remaining parts and must continue to be the "principal part" of the body throughout life. The matter of the primacy thus resolves itself into one of well-devised and accurate observation; and the discoverer is once more upon the ground where his undying laurels grew. He, therefore, deals no longer "without demonstration," as in the second Exercise to Riolanus, but makes report of actual observations and so gives ocular evidence in support of his views, remembering, it may be, that he had said to Riolanus: "Soon, perhaps, I shall make public things even more wonderful and destined to cast even greater light on natural philosophy."[180] Harvey's contemporary Milton said to Parliament: "Truth is compar'd in Scripture to a streaming fountain; if her waters flow not in a perpetuall progression, they sick'n into a muddy pool of conformity and tradition."[181] These words seem timely as we note the great discoverer, magnifying glass in hand, searching in incubated eggs for an answer to the question, now wholly obsolete, whether the primacy of the heart should not give way to the primacy of the blood.
"Surely," says Harvey, "this investigation is one of great moment, to wit: whether or no the blood be present before the pulse; and is the point[182] derived from the veins or the veins from the point? So far as I have been able to observe, the blood appears to exist before the pulse; and I will show cause for this opinion as follows: On a Wednesday evening I put three eggs under a hen; and having come back on the Saturday, a little before the same hour, I found these eggs cold as though deserted by the hen. I opened one of them, nevertheless, and came upon the beginning of a chick, namely, a red sanguineous line at the circumference,[183] but at the centre instead of the leaping point a point which was white and bloodless. By this sign I perceived that the hen had left off sitting not long before. So I caught her, shut her up in a box, and kept her there the entire night; that is, after I had put under her the two remaining eggs together with other fresh ones. What was the result? Next day in the very early morning both eggs had revived; and at the centre the beating point itself was visible, much smaller than the white point; out of which, that is, out of the white one, it made its appearance in diastole only, like a spark leaping forth from a cloud: so that the red point seemed to me to flash out of the white point; the leaping point being generated in the latter, in one way or another; and the blood to be already in existence, when the leaping point is brought into existence or at least into motion. Indeed, I have very often found that even when the leaping point lies still and devoid of all motion as though quite dead, it recovers motion and pulsation again if warmed afresh. From the foregoing I judge that in the order of generation the point and the blood come into existence first; but that pulsation does not come on till afterward. Certainly this is settled, viz.: that of the future embryo nothing at all appears on this day[184] except the sanguineous lines and the leaping point and also those veins which grow all from one trunk (as this grows from the leaping point) and are dispersed throughout the entire colliquative[185] region in very many ramified filaments....
"Toward the end of the fourth day and the beginning of the fifth the sanguineous point is already increased in size and is seen to be turned into a small and very delicate vesicle containing blood within itself; which blood it drives out at every contraction, and receives afresh when its diastole takes place.
"Up to this stage I have found it impossible to discriminate between the vessels; for the arteries are not to be distinguished from the veins either by their coats or by the pulse; and so I think it best to style all the vessels, indiscriminately, veins or, with Aristotle,[186] venous canals....[187]
"On the sixth day ... the parenchyma of the heart grows on to the pulsating vesicle; and shortly afterward the rudiments of the liver and of the lungs are discernible."[188]
It is clear that Harvey's hens did not very often take such well-timed steps against Aristotle; for in another passage of his treatise on generation, in summing up its events and their order, he frankly states the difficulties which render uncertain the question of priority between the blood and the heart. He speaks of "the first generated and generative part; that is to say, the blood together with its receptacles or, if you prefer, the heart with its veins."[189] A few lines further on he says:—
"In the generation of this first part (which is accomplished in the egg on the fourth day) although I have not been able to observe any order, because all portions of the part aforesaid (namely, the blood, the veins and the pulsating vesicle) appear at the same time; nevertheless, my belief would be, as I have said, that the blood is present before the pulse; and that, therefore, in obedience to a law of nature the blood is prior to its receptacles, that is, to the veins."[190]
In Harvey's first publication, of 1628, we have read:—
"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."[191]
In his last publication, of 1651, we have read:—
"So far as can be discerned by accurate inspection, the blood is made before the leaping point is formed, and the blood is endowed with vital heat before it is set in motion by pulsation; and further, as pulsation is begun in and by the blood, so at last it ends in the blood at the final instant of death."[192]
Harvey's own words in the foregoing two passages effectively sum up both the nature of his doctrine that the blood is the first part of the body to live, and the nature of his evidence. But the words of the second passage foreshadow a closely related doctrine, advanced and held by him on the evidence of observation, viz.: that the blood, being the first part to live, is also the last part of the body to die. That the first part to live is always the last to die, is a doctrine set forth by Aristotle. This, Harvey seems to accept without question and to apply upon proper evidence to the blood; as he accepts and warmly upholds the ancient master's doctrine that there is a primacy of the body. The results of observation have forced Harvey to transfer this primacy from the heart to the blood, but it is the Aristotelian primacy still. Presently he shall show us that the blood is not only the first part to live, but the last to die. Before he does so, however, let Aristotle speak for himself, saying briefly:—
"The point[193] of origin [of the rest of the body] is the first thing generated. The point of origin in the animals which possess blood is the heart; in the rest, the analogue thereof, as I have often said. Moreover, the fact that the heart is the first thing generated is evident, not only to the senses, but from its death.[194] For therein life ceases the last; and in all cases the last generated is the first to make an end, the first generated, the last to make an end; nature, as it were, doubling back and returning upon her point of origin whence she came.[195] For generation is the change from not being to being; destruction is the reverse change, from being to not being."[196]
Aristotle does not tell us why "in all cases ... the first generated" is "the last to make an end," and vice versa. Let it suffice that Harvey accepts this sweeping doctrine. Now let him complete his evidence in favor of the primacy of the blood by showing that the blood is not only the first part to live and to live tenaciously, but the last part to die.
In a passage of the treatise On the Motion of the Heart and Blood, we have already read Harvey's promise to publish observations
"on the formation of the fœtus, where numerous problems of the following order can find a place: Why should this part 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]
That Harvey should have printed this passage in 1628, in the same work with his repeated eulogies of the Aristotelian heart, shows that the idea of the possible primacy of the blood must have been in his mind early. It was, indeed, so from the jotting down of his private notes of 1616, to the publication of the Exercises to Riolanus in 1649 and the treatise On Generation in 1651. The same mental attitude is revealed, perhaps more strongly, in the following passage of an earlier chapter of Harvey's treatise of 1628. Here we come upon the thought that it may be the blood, and neither ventricle nor auricle, which is the last to die. Harvey says:—
"Besides this, however, I have occasionally observed, after the heart and even its right auricle[197] had ceased their pulsations as though in the act of dying, that an obscure motion and flow and a sort of palpitation manifestly remained in the blood itself contained in the right auricle, so long, that is, as the blood appeared to be imbued with heat and spirits. Something of the sort is very plainly to be seen at the beginning of the generation of an animal, in the hen's egg within the first seven days of incubation. There is present, first and before all else, a drop of blood which palpitates (as Aristotle also noted); from which, when growth has taken place and the chick has been formed to some extent, the auricles of the heart are made; and in these, which pulsate perpetually, life inheres....
"Whoever, therefore, shall choose to investigate more closely will say that the heart is not the first to live and the last to die, but that the auricles, and the part which answers thereto in serpents, fishes, and such animals, are alive sooner than the heart itself and also die later than the heart. Whether even earlier the blood itself, or the spirit, have not an obscure palpitation of its own, which it has seemed to me to retain after death, may well be questioned; and whether we should not speak of life as beginning with palpitation."[198]
It is plain that fibrillar contractions of cardiac muscle misled Harvey into thinking and writing of "an obscure motion and flow," of "an obscure palpitation," of the blood itself within the dying auricle. It is plain that when he wrote his most famous treatise he was loath, even under Aristotle's leadership, to reach out so far beyond the evidence of the senses as to attribute the palpitation of the visible drop of blood in the very early embryo to anything but the hot blood itself. Later, in his treatise On Generation, he published a passage which in some ways runs parallel with the foregoing. In the earlier passage the results of observation are brought forward as food for thought; in the later one, as proofs of a theory, fully, clearly, and emphatically stated by a thinker who is near the end of life and is imparting his final judgment. This later passage is as follows:—
"In whatsoever part of the body heat and motion have their beginning, in that same part life also first arises and therein is extinguished last; nor may it be doubted that there, too, life has its innermost home, that there the soul itself has fixed its seat.
"The life then inheres in the blood (as we read also in Holy Writ[199]), because therein the life and the soul are manifest first and fail last. For, as I have said, in the dissection of living animals I have found repeatedly that, though the animal be dying and breathe no longer, nevertheless, the heart pulsates for some time and keeps the life in it. Moreover, when the heart is quieted you may see movement surviving in the auricles, and latest in the right auricle; and at length all pulsation ceasing there, you may find in the blood itself a kind of undulation and obscure agitation or palpitation, the last indication of life. And anyone can perceive that the blood retains in itself to the last the heat which is the author of pulsation and life; if this heat is once wholly extinguished and the blood now is blood no more, but cruor, so there is left no hope of a return to life again. Nevertheless, after all pulsation has disappeared, both in the egg, as I have said, and in dying animals, if you will make a gentle warm application, in the former case to the leaping point, in the latter to the right auricle of the heart, you shall see movement, pulsation, and life, renewed immediately by the blood; provided it have not utterly lost all its innate heat and vital spirits."[200]
How readily heat from without can revive the cool leaping point, is strikingly set forth by Harvey in another chapter of this treatise On Generation. He says:—
"Moreover, if an egg be exposed too long to a colder atmosphere, its leaping point pulsates less often and stirs more languidly; but if a warm finger be applied to it, or any other bland source of warmth, straightway it recovers strength and vigor. Indeed, when such a point has become gradually weak and though full of blood ceases to move at all and gives no sign of life, seeming utterly to have succumbed to death, if my lukewarm finger be placed over it for the space of twenty pulsations of my artery, behold! the little heart revives once more, becomes erect, and renews its pristine dance as though come back from Hades. This I myself and others, too, have brought about again and again by means of gentle warmth of any kind, such as that of a fire or of tepid water; thus at our pleasure being able to give over the poor little soul to death, or call it back to the light."[201]
As in the embryo the leaping point may be revived by external warmth, so may the heart in the full-grown bird. In his treatise of 1628 Harvey says:—
"In the pigeon, at any rate, at an actual experiment, after the heart had wholly ceased to move and even the auricles had left off moving, I placed my finger, wetted with saliva and warm, upon the heart and kept it there for a while; as the result of which fomentation the heart, as though restored to strength and life again, and its auricles with it, were seen to move and contract and relax themselves and, as it were, to be recalled from death."[202]
In his treatise On Generation, Harvey confirms the doctrine of the primacy of the blood by citing observations made upon sluggish or hibernating animals and also certain morbid phenomena in man, as follows:—
"This, too, clearly follows from many observations; especially the cases of certain animals which possess blood yet live a long time without a pulse; and of some which lie hidden the whole winter and, nevertheless, continue alive, although meanwhile all movement of the heart has ceased and their lungs enjoy a rest from breathing, like people who lie half dead and pulseless in syncope or faintness or hysterical affections."[203]
So Harvey convinced himself, by observation, that the first part of the developing embryo to appear is the blood of the "sanguineous lines"; after this the blood which seems to palpitate of itself at the leaping point, which later develops into a pulsating vesicle wherein blood is contained within a contractile wall; to this being superadded still later the contractile parenchyma of the heart. Also, by observation, he convinced himself that in a dying animal the blood within the right auricle may palpitate of itself after the palpitations due to contractions of the auricular wall have ceased. Thus was Harvey led to believe that the blood and not the heart is the first part to live and the last to die, the principal part of the body, the generator of the heart and of all the rest. In spite of his appeal to observation, his impressive primacy of the blood is now as completely forgotten in its turn as is Aristotle's impressive primacy of the heart, which Harvey felt called upon to supersede. Naturally in this matter the great discoverer used true methods of investigation; and doubtless his imperfect conclusions were due in large part to the weakness of his magnifying glasses and to the deficient technique of his day. Harvey said of himself, speaking generally, that he trusted much to the plain use of his senses.[204] That he did so, was well for him and for all mankind; yet because of this very trust he did not always escape the pitfalls dug by what we now call "naked-eye" appearances.
The primacy of the blood was no isolated fact for Harvey, but one linked with the very existence of the circulation. This primacy depended largely upon the blood being the primal abode of the innate heat. Palpitation produced by the innate heat in the blood itself, he held to be the first sign of life in the embryo and the last sign of life in the dying creature; and a swelling produced by the innate heat, he held to take place throughout life, localized in the blood just outside of the entrance to the heart. This local swelling of the blood was, to him, the exciting cause of the heart-beat and, therefore, of the circulation. We have heard him deny that the blood possesses motion "as the gift of the heart."[205] We can now grasp the probable meaning of this denial. He would not have been illogical had he said also that the heart possesses motion as the gift of the blood. This view of the cause of the heart-beat was first set forth by Harvey in 1649 in the Exercises to Riolanus, and in immediate connection with declarations in favor of the primacy of the blood, which also was first formally advocated in those Exercises. As we know, the question of this primacy had given Harvey food for thought long before. But his view of the cause of the heart-beat is not to be found in his lecture notes, nor in the treatise of 1628, and may well have been a later outgrowth from the larger doctrine of the primacy of the blood.
Let us now turn to the Exercises and to Harvey's own account of the cause of the heart-beat. The first passage to be quoted begins with a few sentences which have been introduced previously, but which form a necessary cue for the statement we are to study. Harvey says to Riolanus:—
"For the present I will only say and set forth without demonstration—by good leave of the learned and with due respect to the ancients—that the heart, as the beginning, author, source, and origin of everything in the body and the first cause of life, should be held to include the veins and all the arteries and also the contained blood; just as the brain, including all its nerves and sensory organs and spinal marrow, is the one adequate organ of sensation, as the phrase is. If by the word 'heart,' however, only the body of the heart be meant with its ventricles and auricles, I do not believe that it is the manufacturer of the blood; nor that the blood possesses vigor, faculty, reason,[168] motion, or heat, as the gift of the heart. Moreover, I judge the cause of diastole and expansion not to be the same as that of systole and contraction, either in the arteries, or in the auricles or the ventricles of the heart; but that part of the pulse which is called diastole has another cause, different from the systole, and always and everywhere must precede every systole; I judge the first cause of expansion to be the innate heat and expansion to occur first in the blood itself, gradually thinned and swelling up like matters in fermentation, and to be extinguished last in the same; and I accept Aristotle's parallel with pottage or milk with this proviso, that the rising or falling of the blood is not brought about by vapors, or exhalations, or spirits, excited into some vaporous or aërial form, and is caused, not by an external agent, but by an internal principle, and is regulated by nature.
"Nor is the heart (like a hot kettle), as some imagine, the origin of the heat and of the blood in the same sense as a hot coal or a fire-place. The blood rather imparts heat to the heart, as to all other parts, than receives heat from it, for the blood is, of all things within the body, the hottest; and so the heart is provided with coronary arteries and veins for the same purpose as that of the arteries and veins of other parts, viz.: to secure an influx of heat which shall foster and preserve. Hence it is to use convertible terms to say that all the hotter parts contain more blood and that the richer they are in blood, the hotter they are. It is in this sense that the heart, so remarkable for its cavities, should be reckoned a workshop, source, perpetual fire-place; it is like a hot kettle by virtue, not of its body, but of its contained blood, in the same sense in which the liver, the spleen, the lungs, and other parts are reckoned hot; because they contain many veins or vessels containing blood. In this way also I maintain that the native heat, or innate warmth, being the common instrument of all the functions, is likewise the prime efficient cause of the pulse. This I do not now assert positively, but only propose as a thesis. Whatever may be brought forward to the contrary by learned and upright men without scurrilous language, clamor, or contumely, I shall be glad to know, and whoever shall do that will earn my gratitude."[206]
Harvey has thus transferred to the blood the primacy of the body, making the blood in place of the Aristotelian heart the primal abode of the innate heat, "the common instrument of all the functions." Nevertheless, the blood of the Harveian circulation cannot perform the duties of the primacy without the aid of Aristotle.
If we turn from the Exercises to the treatise On Generation, published about two years later, we find the author saying:—
"The primacy of the blood is evident from this also, that the pulse has its origin in the blood. For since a pulsation consists of two parts, to wit: an expansion and a contraction, or a diastole and systole, and since the prior of these movements is the expansion, it is plain that this action is due to the blood, but that the contraction is set a-going in the egg by the pulsating vesicle, as by the heart in the chick, by means of its own fibres as though by an instrument devised for that purpose. It is certain also that the aforesaid vesicle and, at a later time, the cardiac auricle from which pulsation starts, is excited by the blood, which expands to the motion which constricts. The diastole, I say, is produced by the blood which swells up as if with interior spirits; and so Aristotle's opinion as to the heart's pulsation—namely, that it is produced after the manner of ebullition—is in some measure true. For the same thing which we see every day in milk heated over the fire and in the fermentation of our beer, comes into play also in the pulsation of the heart, in which the blood swells as from some fermentation, is expanded, and subsides; and what is brought about in the cases aforesaid by accident and by an external agent, to wit, by adventitious heat from somewhere, is effected in the blood by the internal heat or innate spirits, and is also regulated by the soul in conformity to nature, and is kept up for the health of living things. Pulsation, therefore, is accomplished by a double agency: that is to say, the expansion or dilatation is accomplished by the blood, but the contraction or systole is accomplished in the egg by the membrane of the vesicle, in the fœtus after birth by the auricles and ventricles of the heart; and these alternate and mutually associated efforts once begun, the blood is impelled through the whole body, and thus the life of animals is perpetuated."[207]
Nearly two thousand years before Harvey's time Aristotle had said:—
Moreover, Aristotle, as Harvey says, had likened to "ebullition"[211] what Aristotle himself described as "the pulsation which occurs at the heart, at which the heart is always to be seen incessantly at work." "For," says Aristotle, "ebullition takes place when liquid is vaporized[212] by heat; for it rises up owing to its bulk becoming greater."[213] He continues:—
"In the heart the swelling up from heat of the liquid which is always arriving from the food produces pulsation, for the swelling rises against the outer tunic[214] of the heart; and this process is always and incessantly going on, for the liquid is always and incessantly flowing in, out of which the nature of the blood arises; for the blood is first worked up in the heart. The thing is plain in generation from the beginning; for before the vessels have been marked out the heart is to be seen containing blood. Hence, too, it pulsates more in the young than in the old; for the vapor[215] arises more abundantly in the young.
"All the vessels also pulsate and do so simultaneously one with another, because they are dependent upon the heart.[216] This is always moving, so that they, too, are always moving, and simultaneously one with another, when[217] the heart moves. Leaping [of the heart],[218] then, is the reaction which takes place against the condensation produced by cold, and pulsation is the vaporization[219] of heated liquid."[220]
In another treatise Aristotle says: "In all animals the blood pulsates in the vessels everywhere at the same time."[221] It is interesting, in a negative way, that his sweeping and faulty references to the pulsation of the vessels put into words no physiological idea except the vague one of "dependence" on the heart.
One may be tempted to see in the seething of the heart's blood the source of some of those spirits within the body elsewhere than in and about the heart, of which one gets brief ill-defined glimpses here and there in the genuine works of Aristotle. But no words of his can be adduced to confirm such a conjecture.
Evidently, however, the seething of the nascent blood suffices, in Aristotle's eyes, to explain both the phases of the heart-beat; for both the rising and the falling of the wall of the hot central laboratory of the blood are movements as passive apparently as those of the lid of a boiling pot. One may be excused for wondering at the crudity of such a conception; nor is one's wonder lessened by recalling that elsewhere in Aristotle's works he places at the heart the central origin of the bodily movements. But when it is recalled, as well, that Aristotle was totally ignorant of the function of muscle and, therefore, even of the mode of working of the limbs, his doctrine of the heart-beat may seem less amazing.
There are indications that the function of muscle, though unknown to Aristotle, was known not long after his time,[222] and in Galen's time that function was entirely familiar, he styling the muscles "the organs of voluntary movement," and calling their contraction their "systole," a term which has survived only in connection with the heart and arteries.[223] For Harvey, born more than thirteen centuries after Galen's death, the function of muscle was a portion of ancient knowledge; and in his treatise On the Motion of the Heart and Blood, he expressly states that the heart, including the auricles, is muscular both in structure and in function. The opinions of Harvey's day rendered these statements by no means superfluous.[224] Naturally, therefore, in accepting the aid of the Aristotelian seething of the blood in connection with the heart-beat Harvey utilized only the force of expansion thus generated, and obtained from muscle the force of contraction which he required. Indeed, the conception of the auricles and ventricles as muscular force-pumps was fundamental to his doctrine of the circulation. Moreover, we have found Harvey careful to limit and mitigate the expansion of the blood, he saying to Riolanus:—
"I accept Aristotle's parallel with pottage or milk with this proviso, that the rising or falling of the blood is not brought about by vapors, or exhalations, or spirits, excited into some vaporous or aërial form, and is caused, not by an external agent, but by an internal principle, and is regulated by nature."[225]
Long before, indeed, he had jotted down a terse statement among his lecture notes which is fatal to any extreme development of the Aristotelian idea. In dealing with the action of the heart he had written:—
"To what end? Aristotle: To none, but a passive process, as in boiling pottage. But when wounded it gives out not wind, but blood."[226]
Harvey, therefore, could do no less than criticize adversely his famous contemporary, the philosopher Descartes, for accepting in its entirety Aristotle's doctrine of the heart-beat. Referring to Descartes he says:—
"Nor in the matter of the pulse am I satisfied with the efficient cause thereof which he, following Aristotle, has laid down as the same at the systole as at the diastole, to wit: an effervescence of the blood like that produced in boiling. For the movements aforesaid are sudden strokes and swift beats; while in fermentation or ebullition nothing rises up and collapses thus, as it were in the twinkling of an eye, but there is a slow swelling with a sufficient subsidence. By means of dissection, moreover, one can discern for oneself that the ventricles of the heart are expanded as well as filled by the constriction of the auricles and are increased in size proportionately, according as they are filled more or less; and that the expansion of the heart is a movement of a certain violence, produced by impulsion, not by attraction[227] of some sort."[228]
In a letter written four years after the publication of the Exercises to Riolanus and two years after that of the treatise On Generation, Harvey sets forth anew, with admirable clearness and brevity, his doctrine as to the nature and cause of the systole of the ventricles. In this he stands upon purely modern ground as an observer, and his words are free from all Aristotelian tinge. Referring to another physiologist he says:—
"I could wish, however, that he had observed this one thing, namely, that the motion which the heart enjoys is of a threefold kind, to wit: a systole, in which the heart contracts itself and drives out the blood contained in it; and then a certain relaxation, of a character contrary to the foregoing motion, a relaxation in which the fibres of the heart which make for motion are slackened. The two motions aforesaid are inherent in the very substance of the heart, just as in all other muscles. Finally, there takes place a diastole, in which the heart is expanded by blood impelled into its ventricles out of the auricles; and the heart is incited to its own contraction by this filling and expansion of the ventricles; and the motion aforesaid always precedes the systole, which follows at once."[229]
Harvey materially clarifies his doctrine of the nature and cause of the heart-beat in the following admirable summary. In the second Exercise to Riolanus he says:—
"Since I see that many are embarrassed and doubt the circulation, and that some attack it, because they have not understood me thoroughly; for their sake I will recapitulate briefly what I meant to say in my little book on the motion of the heart and blood. The blood contained in the veins, where its deeps are, as it were, where it is most abundant, that is, in the vena cava close to the base of the heart and to the right auricle, gradually grows warm and thin by reason of its own internal heat, and swells and rises up like matters in fermentation; whereby the auricle is dilated, contracts itself by reason of its own pulsific faculty, and propels the blood promptly and frequently into the right ventricle of the heart. This, when filled, frees itself of blood at its succeeding systole by the impulsion thereof and, as the tricuspid valve is a bar to the egress of the blood, drives it where an open door is offered, into the arterial vein, and thereby brings about the expansion of the latter. The blood within the arterial vessels cannot now go back in opposition to the sigmoid valve, while at the same time the lungs are widened and enlarged and then narrowed by inspiration and expiration—and with the lungs their vessels also—and offer to the blood aforesaid a path and transit into the venous artery. The left auricle accomplishes its movement, its rhythm, its order [of events], its function, at the same time and in the same way as the right auricle, and in like manner sends on into the left ventricle out of the vessels aforesaid the same blood which the right auricle had sent on into the right ventricle. As a result the left ventricle, at the same time and in the same way as the right, impels the blood into the cavity of the aorta and consequently into all the branches of the artery, the return of the blood whence it had come being prevented in the same way as before by the barrier of an opposing valve. The arteries are filled by this sudden impulsion and, as they cannot unload themselves as suddenly, are expanded, receive an impulse, and undergo their diastole."[230]
Harvey seems to have attributed more importance to the auricular systoles than do the physiologists of to-day, he making the ventricles depend very greatly for their charge of blood upon the systole of the auricles. This view appears in three passages already quoted; and is tersely put by Harvey when he says elsewhere that the heart "is dilated by the auricle, contracts of itself";[231] that "the auricles are prime movers of the blood."[232] The unduly high value set by him upon the auricular systole agrees well with the polemical vigor with which Harvey exalted impulsion and rejected suction,[233] in his general physiology as well as in the physiology of the heart. In the heart especially the force of suction had played for centuries a part which Harvey rejected more completely than the physiologists of to-day feel warranted in doing. Again he shall speak for himself, saying tersely:—
"Hence it is made plain how the blood enters the ventricles; not by reason of being drawn in, or of the heart expanding, but because sent in by the pulse of the auricles."[234]
"The expansion of the heart," he has told us already, "is a movement of a certain violence, produced by impulsion, not by attraction of some sort." He says that he maintains these views
"against the commonly received opinion; because neither the heart nor anything else can so expand itself that it can draw anything into itself in its diastole, unless as a sponge does which has first been forcibly compressed and is returning to its natural state."[235]
But, one may ask oneself, how does that modified seething in the vena cava which produces the diastole of the right auricle produce the diastole, the simultaneous diastole, of the left auricle? In his lecture notes Harvey had stated, as Columbus had before him, that the venous artery does not pulsate—at least, he means, not in the same sense as the auricle, or ventricle, or artery.[236] Obviously regarding the left auricle there could be available, for Harvey, no explanation parallel to that of to-day, viz.: the swift conduction of a stimulus from point to point of the texture of a wall which is common to both auricles. He is careful to state that corresponding auricular events occur simultaneously and in the same way in the two auricles; and incidentally but frankly he confesses ignorance of the reasons why, in the following passage:—
"From those who declare the causes and reasons of all things in such a smattering way, I would be glad to learn how it is that both eyes move together hither and thither and in every direction when they look; how it is that this eye does not turn by itself in that direction, that eye in this; likewise, both auricles of the heart; and so forth."[237]
The circulation of the blood, then, according to the final view of its discoverer, is maintained by a self-regulating mechanism worked by causes operating within the blood itself, the "principal part" of the body. The systolic muscular contractions of the walls of the ventricles are caused by direct mechanical stimulation (in modern language) due to diastolic distension by blood of the relaxed muscular walls of these chambers. The blood which distends the ventricles is driven forcibly into them by the auricular systole, the muscular walls of the auricles having been stimulated to contract by diastolic distention due likewise to blood.
So much of Harvey's doctrine of the heart-beat, although not that of to-day, is very effective as physiology, and has advanced with modern swiftness far beyond that of his predecessors. It seems strange, therefore, even to one familiar with the movement of the Renaissance, to be swept back nearly two thousand years under Harvey's guidance to reach the underlying cause of the phenomena. According to him the distention which stimulates the right auricle to contract is produced by an expansion of the blood of the great veins, due to the innate heat. The Harveian heart-beat is caused and initiated by an Aristotelian swelling up of the hot blood. Both this expansion and the fiery central hearth at which it is produced have been expelled by Harvey from within the fully developed heart; and the primal abode of the innate heat has been transferred to the blood, with which that heat has been intimately incorporated by him. Just without the heart, moreover, Harvey has established anew the Aristotelian seething; making this the result of what we to-day may style a localized automatism of the conjoined heat and blood. He has localized this automatism of the hot blood "in the vena cava, close to the base of the heart and to the right auricle," i.e., close to that region at and between the mouths of the two venæ cavæ of our present terminology, where the physiology of to-day places, not within the blood but in the texture of the walls which contain it, the seat of what is prepotent in determining the rhythm of the mammalian heart-beat.
Observation shows that from seemingly pulseless peripheral veins the blood continuously enters the venæ cavæ, which pulsate visibly in the region of Harvey's swelling of the blood. Yet in his lecture notes, in dealing with the significance of the thick resistent walls of the arterial vein and the aorta, he wrote: "Neither the vena cava nor the venous artery is of such construction, because they do not pulsate but, rather, are attracted."[238] On a neighboring page he had written:—
"At the same time [that] the pulse of the artery is perceived by touch, the vena cava is attracted, as it were."[239]
We will not now search for what he meant by saying that "the vena cava is attracted, as it were." Clearly, however, in denying that it pulsates, he meant not to deny that its wall moves rhythmically, but to deny only that this movement is of the nature of what he styles pulsation in the case of the auricles or the ventricles, or the arteries, or the arterial vein.
We know not what influence the rhythmic movements of the wall of the vena cava may have had upon Harvey's transfer to its cavity of the Aristotelian seething of the blood. To this was referable the palpitation seen by him in the blood itself as the first sign of life in the embryo and the last sign of life in the dying animal; and in this same familiar seething he found ready to his hand a life-long cause for the visible sharp expansion of the auricle in its diastole, for which expansion he could find no such obvious muscular cause as for the corresponding expansion of the ventricle or the arteries. The seething of the blood, however, was carefully kept by him below the point of vaporization and adapted to maintain the circulation by keeping the muscular cardiac pump at work.
Connected with Harvey's doctrine of the cause of the heart-beat there is a point which a student of his thought may find knotty, despite the aid of a well-developed historical sense. Harvey made the systolic contraction of auricle or ventricle dependent on the mechanical stimulus of its next preceding diastolic distension. It is not quite easy to see how he found this process compatible with the orderly recurrence of all the systolic contractions in the beating of a nearly empty heart. It is well known that the heart may beat for a while when cut out of the body, when, therefore, the heart is nearly drained of blood. In the treatise of 1628 Harvey himself speaks of studying the ventricular systole of "the heart of an eel, taken out and laid upon the table or the hand"; and says that the phenomena seen in this are seen likewise "in the hearts of little fishes, and in those colder animals in which the heart is conical or elongated."[240] In his lecture notes he says, we remember, that "the auricles pulsate after removal of the heart, because of the multitudinous blood."[241] But this jotting, written only as a brief reminder for himself, is obscure to others. By the word "heart" Harvey means sometimes the ventricular mass without the auricles and sometimes the ventricular mass and the auricles taken together. Hence it is uncertain whether the above reference be to auricles left attached to the body or removed with the ventricular mass. In neither case is it easy to imagine effective distention produced by the seething even of "the multitudinous blood." However, in the same lecture notes a few pages farther on Harvey says: "Nevertheless, the heart pulsates, cut away from the auricles;"[242] and in the treatise of 1628 he says:—
"The heart of the eel and of some fishes, and of animals even, when taken out, pulsates without auricles; indeed, if you cut it in pieces you shall see its divided parts contracting and relaxing separately; so that in these creatures the body of the heart pulsates and palpitates after the auricles have ceased to move. Is this, however, peculiar to the animals which are more tenacious of life, whose radical moisture is more glutinous, or rich, and sticky,[243] and not so readily dissolved? For in eels the thing is apparent even in their flesh, which retains the power of motion after they have been skinned, drawn, and cut in pieces."[244]
At this point we may recall the following words of our author:—
"I affirm also that in this way the native heat or innate warmth, being the common instrument of all the functions, is likewise the prime efficient cause of the pulse."[245]
Should we hazard the improbable guess that Harvey meant his cause of the heart-beat to be effective only in warm-blooded animals, we must remind ourselves that it certainly was well known to him as to all the other physicians of his day that the heart of the mammal beats after excision. If few had made experiments, all had studied Galen; and Galen cites the beating of the heart after excision as evidence that its beat does not depend upon the nervous system, the context making it obvious that he refers to the heart-beat of the mammal. Moreover, he makes it evident that the striking phenomenon in question must have been seen by the ancients at the altar, as an incident of sacrificial rites.[246] This fact makes it easy to understand how it happened that earlier still, at least two centuries before Galen's time, the layman Cicero, one of Harvey's favorite authors, should have made a stoic say:—
"It has often been observed that, when the heart of some animal has been torn out, it palpitates with a mobility which imitates the swiftness of fire."[247]
Moreover, thirty-five years before Harvey was born, even the beating of the excised human heart had been seen by Vesalius, and referred to in his celebrated treatise on anatomy, as an incident of one of the barbarous executions of the sixteenth century.[248]