Harvey's Views on the Use of the Circulation of the Blood

by John Green Curtis

"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:—