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

by John Green Curtis

THE INNATE HEAT NOT DERIVED FROM ELEMENTAL FIRE

So Harvey denies the doctrine falsely based upon Aristotle's words, the doctrine of the ethereal nature of the innate heat; but he affirms and adopts as his own the Aristotelian distinction between the heat which is sterile and the heat which gives life. This weighty affirmation obliges us who study Harvey to examine this impressive distinction further.[381]

Aristotle says, we remember: "The heat in animals is not fire and does not take its origin from fire." We remember also that Harvey says: "I, too, would say the same, for my part, of the innate heat and the blood, to wit: that it is not fire and does not take its origin from fire." This doctrine is based by both Aristotle and Harvey upon observation; and Aristotle's argument is contained in the passage which Harvey quotes, a passage obscure in the Latin and rugged in the Greek. Briefly, Aristotle's argument is this: Observation shows that fire is sterile, but that the heat of the sun is generative and the heat of animals likewise; therefore, the heat of animals is not fire. Harvey declares that this same conclusion "is taught excellently well" by his observations also—by which he does not expressly say. That Aristotle, in drawing the distinction aforesaid between the heat of fire and the heat of the sun, was playing at hide and seek with a great truth of biology, would soon be apparent to whosoever should take a flourishing green plant from a window warmed by sunshine and try to make the same plant flourish in a dark room warmed by a hidden fire.

At this point let us scan further the words of Aristotle which Harvey has quoted.[337] Aristotle says:[318]—

"For there exists in the semen of all [animals] that which makes their semen generative, the so-called heat. Yet this is not fire, nor any such power, but the spirits[319] included in the semen and in foaminess, and in the spirits the nature which is analogous to the element of the stars.[320] Wherefore fire generates no animal, nor does anything [animal] appear in process of formation in that, whether moist or dry, which is undergoing the action of fire;[321] whereas the heat of the sun and that of animals—not only that [which acts] through the semen,[322] but also, should there occur some excretion of a different nature[323]—even this, too, possesses a life-giving principle. It is patent, then, from such [facts] as these that the heat in animals is not fire and does not take its origin from fire."[324]

In this passage a forcible presentment is made of the sterilizing power of fire, and elsewhere we are told by Aristotle that "only in earth and in water are there animals; there are none in air and in fire."[382] That by the word "fire" we are to understand elemental heat of greater or less intensity is sufficiently shown perhaps by the context. But no doubt will linger if we glance at two lines from another treatise in which, referring expressly to the four elements, Aristotle speaks of earth, water, air, and "what as a matter of custom we call 'fire' but it is not fire; for fire is an excess, a boiling, as it were, of heat."[383]

Harvey, looking askance as he did at the four ancient elements and even bluntly questioning the elementary constitution of matter, felt himself free to reduce the analogue of the ether to a pious epithet, and yet to accept with emphasis the Aristotelian doctrine that the heat of animals "is not fire." At the end of his Exercise On the Primitive Moisture he says: "Nor, lastly, do we find that anything is naturally generated out of fire, as out of something capable of mixture, and the thing is perhaps impossible." Here, however, he is not dealing merely with the generation of living beings, but with a subject deeper yet, the possibility of fire acting as an element at all.[384]

The drift of those sentences which Harvey quotes is lighted up, better perhaps than by any modern commentary, by a passage of Cicero's treatise On the Nature of the Gods, a treatise mentioned by Harvey in his lecture notes,[385] as we have seen. In the orator's lucid Latin we may read what purports to be a quotation from the Greek philosopher Cleanthes, who was a child when Aristotle died in 322 B.C., and who became the second head of the Stoic school, the powerful younger rival of the school of Aristotle. Let us listen to the Roman stoic of 45 or 44 B.C., who is set up by Cicero to quote and expound Cleanthes as follows:—

"Cleanthes says: 'Since the sun is fiery and is nourished by the humors of Ocean (seeing that no fire can last without some kind of food), therefore, the sun must needs be similar either to the fire which we use and apply in our daily life, or to that fire which is contained in the bodies of animate beings. But this fire of ours, which is requisite for the uses of life, is the destroyer and consumer of all things, and wheresoever it has made its way disturbs and dissipates everything; whereas that fire of the body is vital and salutary and by it everything is preserved, nourished, increased, sustained, and endowed with sense.' Cleanthes denies, therefore, that it is doubtful to which of these two fires the sun is similar, seeing that the sun likewise makes all things flourish and ripen, each after its kind. Wherefore, since the sun's fire is similar to those fires which exist in the bodies of animate beings, the sun, too, must be an animate being and, indeed, the rest of the stars that arise in the celestial ardor which is named ether or heaven."[386]

Unlike Aristotle, Cicero's stoic admits that the sun and even the heavenly ether are fire. But we see him to be no less impressed than Aristotle by the difference between the killing heat of flame and the life-giving heat of heaven and of living things. It is interesting to find this difference expressly given as a reason for believing the heavenly bodies to be alive; and one wonders whether this difference may not have had some share in convincing Aristotle that the ether is an element distinct from fire and the other three elements, and more exalted than they. It must be said, however, that Aristotle's habitual use of language about "the heat contained in animals" prepares us ill for the momentous distinction drawn by him between this and elemental heat.

We have found him speaking of "the soul being, as it were, afire" within the heart;[387] and he says also that "the concoction through which nutrition takes place in animals does not go on either in the absence of soul or in the absence of heat, seeing that everything is done by fire."[388] Moreover, there is in his treatise On Soul a passage deserving immediate quotation, no less as a picture of the nascent stage of biological thought, than as showing a phase of Aristotelian doctrine contrasting with the doctrine of the analogue of the ether. He says:—

"By some the nature of fire is held to be quite simply the cause of nutrition and growth; for fire alone among bodies or elements is seen being nourished and growing; wherefore one might assume it to be that which does the work both in plants and in animals. It is, in a way, the contributing cause[389] but not the cause in the simple sense, the soul rather being that; for the growth of fire is limitless, so long as there are combustibles, but in the case of all natural organisms[390] there is a limit to size and growth, and a rationale[391] thereof; these things depending upon the soul, not upon fire, and upon reason rather than upon matter."[392]

Nevertheless, in spite of seeming inconsistencies, we find Aristotle declaring that the heat of fire sterilizes, but the heat of the sun and of animals gives life. Moreover, when he tells us in the passage quoted by Harvey[393] that not only the heat of the sun and of semen, but also the heat of other animal excretions possesses a "life-giving principle," the words appear to suggest not merely generation without sex, but the spontaneous generation either of parasites within the animal body, or of living things in matters cast off from it. We seem to be confronted with the far-reaching thought that there is in the world a life-giving principle by which, when associated with soul, matter is quickened in ways of which sexual generation is only one; and that this principle is generative heat, streaming from the sun or transmitted by the male in coition, and, thereafter, innate in the resulting creature and shared by the humors thereof. The fact must always have been recognized that in some way the existence of living things on earth depends upon the sun. On the other hand, no modern methods fortified Aristotle's intelligence against spontaneous generation, which he accepted as a matter of course and called "automatic generation," even asserting that eels and some other fishes originate in this way.[394] Further statements of his own shall show us now that the sun in its orbit dominates the changes upon and above the earth and is the giver of life, whether imparted by sexual intercourse or otherwise. Then Harvey shall repeat the lesson and thus help us to understand his declaration regarding the innate heat and the blood, to wit: that it "is not fire and does not take its origin from fire."

Aristotle refers to a region beneath the celestial spheres, which region he calls "the first in proximity to the earth," or "the region common to water and air." He says of the events therein:—

"Of these the efficient[395] cause and ruler and first origin is the circle of the sun's course, which, it is evident, produces separation and combination by its approach or withdrawal and is the cause of generation and corruption."[396]

These last words are used in a large sense to mean the formation and disintegration of whatever is composed of the four elements.

But the annual circuit of the sun does more than bring to pass the rhythmic changes of the seasons with their effects upon man's environment. To the sun's circuit man owes his life. Aristotle has said to us already: "Man and the sun generate man," in words which have no biological context.[338] He does better when he enumerates among the "causes" of a man these three: his father, the sun, and "the oblique circle," i.e., the ecliptic. These he styles "efficient[397] causes" of man,[398] as we have heard him style "the circle of the sun's course" the "efficient cause" of the mighty changes in inanimate things. We learn in what sense a father is the "efficient cause" of his offspring when Aristotle says: "The female always provides the matter, while the male provides that which fashions it";[399] and when we are told that this matter provided by the female "is quickened by the principle derived from the male, which thus perfects the animal";[400] "the animal" meaning the product of conception. "The body," says Aristotle further, "is from the female, but the soul from the male."[401] For although he says elsewhere that "Genesis is the first obtaining in heat of a share of nutritive soul, and life is the tarrying thereof";[402] although he concedes a share of this lowest kind of soul to wind-eggs, to plants, and to the humblest things which live; nevertheless, he holds that, where the sexes are divided, the indispensable "sensory soul" which distinguishes the animal from the plant is derived from the male parent only.[403] So the seminal fluid and the solar rays are coupled together as "efficient causes" of man; and thus the moving sun is made responsible, by what chain of causation we are not told expressly, for the results of sexual generation.

From this we may turn now to other forms of generation in the light of the following prodigious analogy. Aristotle says:—

"We call 'male' an animal which engenders within another, and 'female' one which engenders within itself; and, therefore, in the case of the universe the earth's nature is held to be female and maternal, while heaven and the sun and other such are called engenderers and fathers."[404]

Next, after these sweeping generalities, let us peruse Aristotle's account of spontaneous generation. He says:—

"Animals and plants arise in earth and in moisture, because in earth there is water and in water there is air,[319] and in all air there is psychical heat; so that in a certain sense all things are full of soul. Therefore, when once inclusion of this[405] has taken place, an individual is quickly formed.[406] Inclusion takes place and a kind of foam-bubble arises, produced by the heating of moisture which has body[407] of its own."[408]

The last expression in this passage evidently means moisture which is charged with earthy matter in solution; for Aristotle says in the same treatise that seawater "has much more body" than drinking-water.[409] Still speaking of spontaneous generation he says a little further on:—

"Whoever would inquire aright should ask: What product in such cases answers to that material principle which in the female is a certain animal excretion,[410] potentially similar to what it came from? That excretion is quickened by the principle derived from the male, which thus perfects the animal. In the present case what should be likened to that excretion, and whence and what is the quickening principle which answers to the principle from the male? Now we must assume that, even in animals which procreate, the heat within the animal[411] separates and concocts, and thus makes out of the nourishment which enters the animal the excretion which is the beginning of the embryo. Such is the case with plants likewise; although in these and in some animals there is no need of the principle imparted by the male, for this they have within and mingled with themselves; whereas in most animals the excretion aforesaid stands in need of that principle. The nourishment of some is water and earth, that of others is derived from water and earth; so that what the heat in animals[412] prepares out of their nourishment, the heat of the season in the circumambient air combines by concoction out of the sea and the earth, and puts together.[413] But so much of the psychical principle as is included or separated within the air[319] constructs and quickens[414] the embryo. In like manner are put together such plants as arise by spontaneous generation."[415]

The doctrine that in sexual generation the semen furnishes soul and generative heat but none of the matter[416] of which the embryo consists, renders logical the view, which Aristotle would seem to hold, that it is soul from the air and generative heat from the sun which in spontaneous generation represent the derivatives from the male.[417] The presence about us of "the psychical principle," thus diffused, may well seem startling to a modern biologist; but we may remind ourselves that in ancient times many believed the soul to be conveyed by the air into even the higher animals; even into man himself, even man's "understanding" reaching him thus.[418] Indeed, not only the words "pneuma" and "spiritus," as we have learned, but also the Greek and Latin words for "soul," viz.: "psyche" and "anima," meant originally simply "breath." Let us recall the words of scripture, which seem so vivid to one who watches the change in a new-born child as the first breath is taken: "And the Lord God formed man of the dust of the ground, and breathed into his nostrils the breath of life; and man became a living soul."[419]

That the soul enters with the breath is, however, expressly denied by Aristotle. Conceding a share of soul to every living thing he points out quite simply that there are animals which do not breathe at all, to say nothing of plants.[420] Clearly, the doctrine which he rejects would be hard to reconcile with his theory of sexual generation, according to which theory the sensory soul, and in man even the divine intellectual soul, is potential in the semen and imparted thereby to the product of conception.[421] Indeed, there is a chapter of Aristotle's treatise On Soul in which he even seems to argue against the presence of soul in the air, in a polemic directed against those who believe the soul to be "composed of the elements."[422] In this polemic he is the subtle philosopher; but in his statements about generation he seems more the biologist; for in these his thought, if not more ripe, appears to be less concerned with disputation than with phenomena and the interpretation thereof.

The generation of living things is but generation still, whether it be sexual or spontaneous; and the modern student of general physiology may trace further parallels of thought in Aristotle's account of spontaneous generation and in those words of his about the semen which Harvey quotes and we have studied. That living rudiment, spontaneously generated, which consists of a foam-bubble whose film of earth and water was formed by the heat of the sun and includes air charged with generative heat associated with soul—surely that reminds one of the foamy semen, and of "the spirits included in the semen and in foaminess," and of that within the spirits "which makes semen generative, the so-called heat," the "nature which is analogous to the element of the stars," which nature is derived from the male parent and is associated with the soul potential in the semen. In the Greek text of Aristotle one and the same word, "pneuma" is used to express both the air in the foam-bubbles of spontaneous generation, and the vapor in the foam-bubbles of the semen. In translation "pneuma" must be rendered "spirits" in the case of the semen, and the verbal identity is lost which, by reason of the very vagueness of the Greek word, helps to mark the parallelism of thought. It is with pneuma, spirits, that the testicles and breasts are swollen at the advent of puberty,[423] according to Aristotle; and with the presence of pneuma he connects the pleasure of the sexual act.[424] We have found him laying stress upon the fact that "the nature of semen is foamy"—that its "generative medium ἡ γονή is foam": and he tells of the spontaneous generation of certain shellfish in a place where there is "foamy mud."[425] When he obscurely says that in the semen "the pneuma included in the semen and in foaminess"[426] is the vehicle of the generative heat, does not the turn of phrase indicate that Aristotle's thought is ranging far, that he is thinking not only of the foam of the semen but of other widely different kinds of prolific foam as well? Does he not seem to think that, in general, the power of bringing matter to life as a new individual dwells typically in a bubble representing earth, water, and air, and charged with soul and with generative heat, for the presence of which the sun is responsible, heat other than that of elemental fire?[320] It is not fanciful—for Aristotle himself, we remember, has done so incidentally—to connect such speculation with the ancient myth of Aphrodite, the goddess of love, who sprang from the foam which had risen upon the sea, about the immortal genitals of Uranus, which had been severed and cast therein; Uranus being the heavens personified.[427]

Before the time of Aristotle important thinkers had held the heavenly bodies, and even the heavens themselves, to be fire;[428] and we have seen that after his time Cleanthes did the same, simply setting apart the generative fire from the destructive. Aristotle denied that the sun is fire, though he could not have denied that its radiant generative heat produces no different sensation from that of sterile fire kindled upon earth. He did not identify the sun's heat with ether, the "body on high," though he styled the heat of the semen a "body" analogous to the ether. How then did Aristotle obtain heat from the ethereal sun? The point is crucial and he met it; but in so doing he revealed a very weak place in his towering fabric of speculation. In his treatise On Heaven, speaking of the heavenly bodies, he says:—

"The heat and light from these arise from the friction which the air undergoes by reason of their course. For it is the nature of motion to fire even wood and stone and steel."

He then speaks of projectiles, and says:—

"These, then, are heated because borne onward in air which becomes fire from the shock of the motion. But each of the bodies on high is borne onward in its sphere, so that they are not fired; while the air, being beneath the sphere of the circling body,[429] is heated of necessity as this [body] is borne onward, and mainly where the sun is set in place. Therefore, when the sun approaches and rises and is above us, heat is generated. Be it said, then, of the heavenly bodies, that neither are they fiery nor are they borne on in fire."[430]

In his Meteorology Aristotle boldly says: "The sun, which is held to be especially hot, appears white, but not to be like fire."[431]

Hardy thinker as he is, however, Aristotle nowhere undertakes to tell how the heat of friction between the air and the circling "first element" on high becomes generative, as opposed to the heat of friction between the air and a projectile composed of the lower elements. As to this the Aristotle who deals with the heavens does not strike hands with Aristotle the biologist; nor is light thrown by its author on the Aristotelian passage quoted by Harvey, in which alone does the generative heat of animals figure as "the nature which is analogous to the elements of the stars";[432] nor yet does the Aristotelian dictum that "Man and the sun generate man"[338] remain other than a great truth which awaits elucidation.

More than nineteen centuries after Aristotle's death Harvey published the following, in his treatise On Generation:—

"Thus the sun and man, that is, the sun through man as an instrument, generate. In the same way the Father of all and the cock generate the egg and the chick derived from the egg; namely, by means of the perpetual approach and withdrawal of the sun, which by the will of divine authority, or by fate if you choose, serves for the generation of all things.

"Our conclusion, then, is that the male, although a prior and more important efficient cause than the female, is only an instrumental efficient cause; that he, no less than the female, receives his fecundity or generative power from the approaching sun; and that, accordingly, the art and providence which we discern in his works proceed not from himself but from God."[433]

Two pages farther on Harvey says, again:—

"In fact, what the cock confers upon the egg to make it no longer a wind-egg but prolific, is the same that is bestowed by the summer fervor of the sun upon vegetable fruits, that they may reach maturity, and their seeds, fecundity; and the same that imparts fecundity to beings that arise spontaneously[434] and that produces caterpillars out of worms, chrysalides out of caterpillars, out of chrysalides, butterflies, flies, bees, and the rest."[435]

In a later Exercise of the same treatise Harvey says:—

"As I have said, the product of conception in viviparous creatures is analogous to the seed and fruit of plants; as also is the egg in the ovipara; in creatures which come into existence spontaneously, the worm;[436] or some bubble of confined moisture[437] pregnant with vital heat. In all of the foregoing exists that which is the same in all, that in virtue of which they are called with truth seeds; that, namely, out of which and by which, preëxisting as matter, artificer, and instrument, every animal is in the first instance made and comes into existence."[438]

Despite emphatic denials of Aristotelian doctrine which Harvey freely makes in his treatise On Generation, the Aristotelian flavor of the foregoing passages is obvious. It is not easy to make out from Harvey's writings the exact nature of his views as to spontaneous generation. He sometimes seems to assume the truth thereof; but it is by no means certain that he believed in it in the same simple sense in which it had been accepted by Aristotle.[439] Nothing, however, can be clearer than this: that, though for Harvey the "innate heat" is not ethereal spirits nor even an analogue of the ether, but is simply identical with the living blood; nevertheless, for him as emphatically as for Aristotle the "heat in animals" which "is not fire and does not take its origin from fire," derives its origin from the solar ray.

To Harvey, the lifelong thinker upon the meaning of the circulation, the prodigious history of generation was but continued in the history of the blood, with which he had identified the "innate heat" and which he saw appear and live, before all other parts, in the minute first rudiment of the embryo. We have seen him pondering the cycle wherein unending life is transmitted from egg to fowl and from fowl to egg beneath the sun's life-giving rays. So now shall we see him pondering a cycle of life wherein, from generation to generation, the circulating blood takes over and exercises the generative powers of the semen from which it is derived, and transmits them in turn to the semen evolved out of itself. He says:—

"Further, since we have just seen the study of the semen to be so difficult; that is to say, the way in which the structure of the body is built up by the semen with foresight, art, and divine intelligence; why should we not equally admire the excellent nature of the blood, and make the same reflections upon it as upon the semen? Especially since the semen itself is made of blood,[440] as is proved in the case of the egg; and since the whole body is seen not only to take origin from the blood as from a generative part, but also to owe its preservation to the same."[441]

To this same theme Harvey returns in his Exercise On the Innate Heat near the end of his treatise On Generation, saying:—

"The blood, too, acts in like manner above the powers of the elements, because, when it has come into existence as the first generated part and the innate heat, as is brought to pass in the semen and spirits, the blood constructs the remaining parts of the whole body in order; and does so with the highest foresight and understanding,[442] acting to a certain end and as though by some use of reason.[443] Surely the blood does not accomplish these things because it is composed of elements and draws its origin from fire, but because by the grace of plastic power and vegetative soul it is made the first generated heat and the immediate and fitting instrument of life."[444]

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