THE BLOOD THE SEAT OF THE SOUL
No doctrine of Harvey sounds stranger to a biologist of to-day than his doctrine that the blood is the seat of the soul; nor does any other belief of the great discoverer reveal him more clearly to be a link between the old and the new; not simply an innovator who fixed a gulf between them. We have heard him explicitly deny in his old age the Aristotelian doctrine that the heart "is endowed with soul." We have seen that thirty-five years earlier he had jotted down in his note-book these words: "The soul is in the blood."[271] Let us study him now as he lays stress, not merely on the primacy of the blood, but on its psychological endowments.
Thirteen years before the date of Harvey's note-book Shakspere's play of "Hamlet" had appeared in print; in which the prince speaks thus of following his father's ghost:—
"Why, what should be the fear?
I do not set my life at a pin's fee;
And, for my soul, what can it do to that,
Being a thing immortal as itself?"[272]
It has been foreshadowed that for Harvey, the graduate of Cambridge and of Padua, the physician of the Renaissance, the word "anima"—"soul"—did not simply mean the immortal part of man, as for Hamlet, but was equivalent to the "psyche" of ancient philosophy. In order, therefore, readily to follow Harvey's thought at this juncture, we must first, like him, go to the fountain head; for only sayings of Aristotle can give us a sufficient clue to what he, and after him Harvey, meant by "soul."
Aristotle says in his treatise On Soul:—
"Some natural bodies have life and some have not. By life we mean the being nourished, and growing, and decaying, of oneself."
In the same treatise he says further:—
"The soul is that by which primarily we are alive, and display sensation and intellect; ... but it is not matter and substratum."
Again he says:—
"Were the eye an animal, vision would be the soul thereof; for reason indicates that vision is the essence of the eye.[273] The eye in its turn is the material [basis] of vision; which latter failing, the eye is not an eye except in name, like an eye of stone or in a drawing."
The doctrines of the foregoing three passages are developed and made more explicit in the following, still from the treatise On Soul:—
"It is the presence of life, we say, which makes the difference between that which has soul and that which has not. To amplify regarding life: we call anything alive which possesses even a single one of the following: intellect, sensation, motion and rest in space, and also the motion[274] involved in nutrition, and both decay and growth. Therefore, even all the plants are held to be alive."
A few lines further on Aristotle says, speaking of the power or faculty[275] of taking nourishment:—
"This can exist without the others, but not the other faculties without this, in mortal beings. The aforesaid is clear in the case of plants; for they possess no other faculty of the soul. To this faculty then life owes its origin in living things; but the being an animal owes its origin primarily to sensation; for beings that neither move nor change their place but yet possess sensation, we call animals and not merely living things. The primary sense, which exists in all, is touch; and just as the nutritive faculty can exist without touch or sensation of any kind, so can touch exist without the other senses. The "nutritive" is our term for such part of the soul as is shared even by plants, all animals, however, evidently possessing the sense of touch. The cause of the presence of each of the two aforesaid shall be told later. Now let us only go so far as to say that the soul is the source of the [faculties] aforesaid, and is defined by means of them, to wit: the nutritive, the sensory, the intellectual, the motor.[276] As to whether each of these is a soul or is a part of the soul; and if a part, whether in the sense that it is only separable by reasoning,[277] or locally as well—as to some of these points, it is not hard to see our way, but some present difficulties."[278]
If we turn to Aristotle's treatise On Generation we find him dealing with the relations of the body to the nutritive soul, in virtue whereof the body is alive; with its relations to the sensory soul, in virtue whereof it is an animal body; and, finally, in man with its relations to the intellectual soul. Of these three kinds of soul or parts of the soul, he concludes, the mind "is alone divine; for in the working thereof no bodily working is involved."[279] Only soul of this divine quality does he admit to be separable from body.[280]
The master has spoken. Now let the great pupil speak. In the last Exercise but one of his treatise On Generation, Harvey says, referring to the blood:—
"It assuredly contains the soul first and foremost, not only the nutritive, but the sensory soul as well, and the motor. The blood penetrates in all directions and is present everywhere; if it be taken away, the soul itself is made away with also and at once; so that the blood would seem to be wholly indistinguishable from the soul or, at least, should be reckoned the substance of which the soul is the activity. The soul I aver to be such that neither is it body at all, nor yet entirely without body, but comes in part from without, in part is born on the premises,[281] and in a manner is part of the body; in a manner, however, is the origin and cause of everything within the body of an animal, certainly of nutrition, sense, and motion, and hence, in like manner, of life and death; for whatsoever is nourished, that same is living, and vice versa. So, likewise, whatsoever is nourished abundantly, increases; but whatsoever too sparingly, dwindles; and whatsoever is nourished perfectly, keeps its health; whatsoever otherwise, lapses into disease. Therefore, as is the soul, so also is the blood to be reckoned the cause and author of youth and old age, of sleep and of waking, and even of respiration also—especially in view of this, that in the things of nature the first instrument contains within itself an internal moving cause. Therefore, it comes to the same whether one say that the soul and the blood, or the blood together with the soul, or, if preferred, the soul together with the blood, bring everything within an animal to pass."[282]
Only two years before these words were published the aged Harvey had said the following:—
"Nor does the blood possess vigor, faculty, reason, motion, or heat, as the gift of the heart."[283]
A comparison of the foregoing passages from Harvey with the preceding passages from Aristotle makes it clear that, for Harvey, although the soul dwells no longer in its Aristotelian seat, it is no other than the Aristotelian soul which pervades the "principal part" of the body, the living blood of the Harveian circulation.
What proofs does Harvey offer that the soul is in the blood? He has offered already one weighty piece of evidence noted by many from of old in the chase, in butchery, in sacrifice, in battle—the evidence from fatal hæmorrhage. This had been set forth nineteen centuries before him by one of his Hippocratic predecessors, who had referred to the reasoning
"used by those who say that the blood is the man; for, seeing men slaughtered and the blood running out of the body, they conclude that the blood is the soul of man."[284]
Presently Harvey himself shall tell us that in placing the soul in the blood he is consciously reaffirming one of the most ancient of beliefs; but he is far from basing his adhesion to it merely on such immemorial evidence, known to all, as the result of loss of blood, for he also adduces once more his own observations of the early embryo of the fowl, to prove not only the primacy of the blood but the presence of the soul therein. His testimony follows, and in reading it one must bear carefully in mind that in Harvey's time no clear scientific distinction had yet been worked out between movements which imply sensation, and movements, whether reflex or not, which do not depend upon consciousness. In his treatise On Generation Harvey says:—
"For my own part I am sure from numerous experiments that not only motion is inherent in the leaping point,—which no one denies—but sensation also. For you will see this point thrown into varied commotion and, as it were, irritated, at any touch whatever, even the slightest, just as sensitive bodies in general usually give evidence of sensation by movements proper to themselves. Moreover, if the injury be repeated often, the leaping point becomes excited and the rhythm and order of its pulsations disturbed. In like manner do we infer the presence of sensation in the so-called sensitive plant and in zoöphytes, from the fact that when they are touched they draw themselves together as though taking it ill.... So there is no doubt that the leaping point lives, moves, and feels like an animal."[285]
In a later part of the same treatise he says:—
"It is manifest that all motion and sensation do not proceed from the brain, since we plainly perceive the presence of motion and sensation before the brain has come into existence; what I have related proves that clearly sensation and motion dawn forthwith in the first droplet of blood in the egg, before a vestige of the body has been formed. Moreover, in that first state of the structure or constitution of the body which I have called the mucilaginous, before any members are discernible and when the brain is nothing but limpid water, if the body be only lightly pricked it moves, contracts, and twists itself obscurely like a worm or caterpillar; so that it gives clear evidence of sensation."[286]
In another Exercise of the same treatise he says:—
"It is evident also from the generation of the chick, that whatever the source of its life or the vegetative first cause of it may be, this had a prior existence in the heart. Wherefore, if the said first cause be itself the soul of the chick, it stands proved likewise that this had a prior existence in the leaping point and the blood; seeing that we observe therein motion and sensation; for it moves and leaps like an animal. If, then, there exist in the leaping point the soul, which (as I have taught in my account) constructs for itself the rest of the body, nourishes and increases it, certainly from the heart as from a fount the soul flows out[287] into the entire body.
"So, likewise, if the egg be prolific because there is a soul in it, or (as Aristotle would have it) the vegetative part of the soul, it is clearly proved that the leaping point, in other words the generative part endowed with soul, springs from the soul of the egg, for nothing is the author of itself, and that the soul is transferred from the egg to the leaping point, next to the heart, and then to the chick."[288]
In still another chapter of his treatise On Generation Harvey says:—
"Nor does the blood deserve to be called the original[289] part and the principal part, merely because in it and by it motion and pulsation are originated, but also because in the blood the psychical heat first comes into existence, the vital spirits are generated, and the soul itself inheres. For wherever the immediate and principal instrument of the vegetative faculty is first found, there probably the soul also is first present and takes its origin thence; since the soul is inseparable from the spirits and the innate heat....[290]
"The life then inheres in the blood (as we read also in Holy Writ),[291] because therein the life and the soul are manifest first and fail last....[292]
"It stands clearly proved that the blood is a generative part, the source of life, the first to live and the last to die, the primary seat of the soul; that in the blood, as in its source, the heat first and chiefly abounds and flourishes; and that by and from the blood all the other parts of the whole body are fostered and obtain their life by means of the influx of heat. Indeed, the heat which accompanies the blood floods, fosters, and preserves the entire body, as I have demonstrated already in my book on the motion of the blood."[293]
Harvey's proof that the blood is "the first to live and the last to die," we have scanned already in an earlier chapter of this paper. In the next chapter of his treatise On Generation he says:—
"No heat is to be found, either innate or inflowing, other than the blood, to be the soul's immediate instrument."[294]
On the next page, after briefly making certain suppositions, he says further:—
"Why should we not affirm with equal reason that there is soul in the blood; and also, since the blood is the first thing generated, nourished, and moved, that out of the blood the soul is first evoked and kindled? Certainly it is the blood in which vegetative and sensitive workings first come to light; in which heat, the primary and immediate instrument of the soul, is innate; it is the blood which is the common bond of body and soul, and in which as a vehicle soul flows into all parts of the whole body."[295]
But no matter how far on high the blood may have been exalted by Harvey the physician and psychologist, it is still subject to the lancet of Harvey the clinician, the heir of Hippocrates; for in his treatise On Generation, in the same Exercise with the foregoing passage, occurs the following:—
"While I assert that the seat of the soul is in the blood, first and foremost, I would not have the false conclusion drawn from this that all blood-letting is dangerous or hurtful; nor have it believed, as the multitude believes, that just to the degree that the blood is taken away does the life pass away at the same time, because holy scripture has placed the life in the blood. For it is known from everyday experience that the taking of blood is a wholesome aid against very many diseases and is chief among the universal remedies; seeing that depravity of the blood, or excess thereof, is at the bottom of a very great host of diseases; and that the timely evacuation of blood often brings exemption from most dangerous diseases and even from death itself. For just to the degree that the blood is taken away as our art prescribes, is an addition made to life and health. This very thing has been taught us by Nature, whom physicians set themselves to imitate; for Nature often makes away with the gravest affections by means of a large and critical evacuation by the nares, by menstruation, or by hæmorrhoids."[296]
Not only does Harvey affirm that "the soul is in the blood" and, as we have seen, appeal to observation and experiment in support of this doctrine; but he refers to those who had believed it before him, and maintains it against Aristotle's express denial. We have heard him testify as an observer; now let us hear him deal historically and polemically with the doctrine in question. Quite simply, in the final work of his old age, does the veteran tell of the wide acclaim which at last has greeted his discovery of the circulation—the most modern and revolutionary achievement of his time. The contrast is startling when, in the same breath, with equal simplicity he proceeds formally to identify his own latest view of the significance of the circulating blood with a doctrine which had been ancient in ancient times; a doctrine not only found in the Old Testament, but held by Greek thinkers who were historic figures even in the eyes of Aristotle. In his treatise On Generation Harvey says:—
"I see that the admirable circulation of the blood which I discovered long ago has proved satisfactory to nearly all, and that so far no one has made any objection to it which greatly calls for answer. Therefore, if I shall add the causes and uses of the circulation and reveal other secrets of the blood, showing how much it conduces to mortal happiness and to the welfare of soul as well as body, that the blood be kept pure and sweet by a right regimen, I truly believe that I shall do a work as useful and grateful to philosophers and physicians as it will be new; and that the following view will seem to nobody so improbable and absurd as it formerly seemed to Aristotle, viz.: that the blood, a domestic deity as it were, is the very soul within the body, as Critias and others thought of old; they 'believing that capacity for sensation is the most special attribute of the soul, and exists because of the nature of the blood.' By others again that which derives from its own nature the power of causing motion was held to be the soul; as Thales, Diogenes, Heraclitus, Alcmæon, and others believed.[297] It is made plain, however, by very numerous signs that both sensation and motion inhere in the blood in spite of Aristotle's[298] denial."[299]
We have noted with Harvey the doctrine of Leviticus, which still rules the procedure of the Jewish butcher; and as we look backward to Athens across the centuries, we find Plato putting this question into the mouth of Socrates: "Whether it be the blood with which we think, or air, or fire, or none of these."[300] In Hellas this doctrine had been well known before Plato, Socrates, or the Hippocratic writers, one of whom we have found referring to it. The Sicilian Greek Empedocles, a philosopher and physician born at Acragas about 495 B.C., is said to have held, long before Aristotle, that the heart is the part formed first in the embryo;[301] and in a line of verse which has come down to us Empedocles said: "In the blood about man's heart is his understanding."[302] Empedocles is reported to have held to this because in the blood "are most perfectly blended the elements of the parts,"[303] that is, earth, water, air, and fire.
The accomplished and wicked Athenian Critias, to whom Harvey refers, was that chief of the Thirty Tyrants who was slain in 403 B.C., four years before Socrates drank the hemlock and nineteen years before the birth of Aristotle. With the opinion of "Critias and others" Harvey, as we have seen, identifies his own view that the soul is in the blood. They held capacity for sensation to be the mark of soul and to be due to the nature of the blood; and Harvey's statement of these views is a literal quotation from the second chapter of the first book of Aristotle's treatise On Soul, which Harvey cites. This chapter is also the source of his summary and not quite exact reference to those other ancients who, as he avers, held spontaneous motor power to be the mark of soul—a power which Harvey unites in the blood with capacity for sensation.[304]
In the aforesaid chapter of Aristotle's work On Soul this philosopher had curtly reckoned among the "cruder" thinkers those of his predecessors who, "like Critias," had held the soul to be blood. Harvey notes the master's condemnation, but, as we have seen, stoutly ranges himself with the condemned ancients and affirms that sensation is inherent in the blood despite the master's denial. It is strange to note how the London physician seems less modern, for the moment, than the ancient philosopher of Athens. Aristotle, like a man of to-day, treats the blood simply as the immediate food of the tissues, noting expressly that it has "no feeling when touched in any animal, just as the excrement in the belly has no feeling."[305] Harvey deals as follows with this obvious truth in dealing with the question whether the blood can properly be reckoned a part of the body in the technical sense. He says:—
"At this time I will only say this: Even if we concede that the blood does not feel, nevertheless, it does not follow that it is not a part of a sensitive body and the principal part at that."[306]
We do not know that Aristotle ever saw or noted in the dying auricle the "undulation" by which Harvey was so much impressed; but we have seen that, like Harvey, Aristotle treated of the development of the early embryo within the hen's egg and that, like Harvey, he laid special stress upon the red "leaping point." Aristotle concluded that the heart is the first generated living part, that it makes and will make throughout life the blood which it contains and distributes. In the heart he fixed the focus of the innate heat and, knowing nothing of the nervous system, he fixed in the heart the seat of the soul also. Harvey came to the conclusion that the blood is the first generated living part; that it has made the heart which contains it and which keeps it circulating and which it will nourish throughout life, as it will the other parts. In the blood itself he placed the innate heat and, though he knew the nervous system, he placed in the circulating blood the seat of the soul, which animates every part.
"We conclude," he says, "that the blood lives and is nourished of itself and in no wise depends upon any other bodily part either prior to or more excellent than itself."[307]
Thus the rigorously proved and demonstrated circulation of the blood was linked by its discoverer with the speculations of remote antiquity.
As we have seen, the use of the circulation became to Harvey a life-long subject of speculation, because this discovery had raised questions which no man could answer before the finding of oxygen. How obscure a problem Harvey found the functions of the blood to be, is nowhere better indicated than where he says in his old age:—
"So with better right one might maintain that the blood is equally the material of the body and its preserver, but not merely its food. For it is well known that in animals that perish of hunger, and also in men who waste away and die, there is abundance of blood to be found in the vessels, even after death."[308]
Is it the least part of Harvey's glory that his mind had cloven its way through long-lived beliefs to a truth which he could demonstrate but could not explain, and which seemed to other eminent men to be no truth, because too senseless to be true?[309] When he finally broke with the ancient master, Harvey could not be content with sheer ignorance; and the same observations and experiments which led him out of Aristotelian error misled him into error quite as grave. As to the venerable doctrine regarding the seat of the soul, which he at last embraced upon grounds now seen to be too slender, was not this doctrine one with which the Harveian circulation could harmonize well and which in turn could greatly glorify the circulation? Let us pause, think, and read further.