ART, LIFE, AND EXPERIMENT
PHYSICS has been the cutting edge of science since Galileo, and its mathematicization in dynamics was, therefore, the crucial act in the scientific revolution. But modern science is a complex enterprise, compact of elements both intellectual and social. The strands which the genius of the seventeenth century twisted together, it drew from diverse areas of the Renaissance. Naturalism, for one, had expressed itself in art long before it became an essential element of the scientific outlook. Empiricism, secondly, may be more explicitly exemplified in the life sciences than in physics, and there it was early coupled with a half-heroic, half-petulant, and wholly self-conscious revolt against authority. Thirdly, the technological achievements of Renaissance navigator, engineer, and artisan were realities behind the Baconian philosophy, which makes science an inductive systematization of observations or experiments performed upon nature rather than of concepts, and which holds up as the reward for understanding nature the power to control its forces.
For Leonardo da Vinci, as for many a Renaissance humanist, there was a whole world in man. In his eyes science and art were both illumination—the reality of the great world suffusing the consciousness of the little in the act of perception. This was not to be, of course. The two modes of grasping nature are different, the one particular and concrete, the other general and abstract. Nevertheless, in Leonardo’s infinite capacity to see and draw the structure in things, he presaged all unwittingly that acceptance of the innocence of nature which takes it as the morally passive object of inquiry.
To the mind sensitive to cultural pathos, there is nothing more moving in the history of our technical tradition than the pencil of Leonardo forever pinning nature to the page. What are we to make of him? Of those notebooks teeming with designs of devices yet unborn, submarines and armored cars, machine guns and planned cities? Of the aphorisms that seem to foretell organizing concepts like inertia and evolution in all branches of science, from astronomy through mechanics and geology to biology? Of the clear assumption that to illustrate the structure of a bat’s wing is to understand the dynamics of flight preparatory to flying—that to see is to know is to act? The historian must answer that he can make nothing of them, and that no one else could. Leonardo’s science remains the marvelous jottings of a unique spirit. Nor were the contents of his notebooks known until the end of the eighteenth century, when they were carried back to Paris by the cultural raiders sent to Italy by the French Republic in the wake of Napoleon’s armies.
It is true that Leonardo’s studies of draperies and anatomies, of horses stamping and rearing, of weapons and fortifications, of architecture and the strength of materials, express a mind which perceived geometric form in nature. But his geometry was palpable, not abstract. His was the mind of an engineer addressing itself to mechanisms which are identical with their specifications, which fit themselves utterly. His conception of mathematics was what the subject would be if those plaster and string models which illustrate curves in space and figures of solid geometry, were themselves solid geometry.
It is tantalizing, but it did not lead to science in general. Leonardo’s humanism and naturalism did, however, lead into one particular science, the anatomy of the human body. In an early stage, the descriptive sciences had to presuppose that things are what they seem to observation. Accordingly, the artistic technique of recording three-dimensional observations on a plane surface was an essential instrument. That technique was an application of the geometry of perspective. An attempt to imagine a scientific anatomy illustrated by a medieval artist will suggest its importance. And on the other hand, the study of anatomy was stimulated by the artist’s need to master the subject in order to achieve the natural representation demanded by the taste of the High Renaissance. Leonardo warns the student of the difficulties:
Though possessed of an interest in the subject you may perhaps be deterred by natural repugnance, or, if this does not restrain you, then perhaps by the fear of passing the night hours in the company of these corpses, quartered and flayed and horrible to behold; and if this does not deter you then perhaps you may lack the skill in drawing essential for such representation; and even if you possess this skill it may not be combined with a knowledge of perspective, while, if it is so combined, you may not be versed in the methods of geometrical demonstration or the method of estimating the forces and strength of muscles, or perhaps you may be found wanting in patience so that you will not be diligent.
SO FAR AS IS KNOWN, Andreas Vesalius, who distinguished himself above all other Renaissance anatomists, had never read Leonardo’s precepts nor ever seen Leonardo’s practice in anatomical drawing. But his work looks as if he had been acting on that inspiration, which is only to say that Leonardo epitomized but did not cause the crossing of art and science in naturalism. The year 1543 saw one of those publishing coincidences which serve the history of ideas as chronological pegs. It was the date both of Copernicus’s On the Revolutions of the Celestial Orbs and Vesalius’s On the Fabric of the Human Body. But how different is the anatomical treatise, not only in subject matter but in manner and appearance. The reader’s eye is not repelled by the crabbed computations of astronomy, but is invited by the bold clear typeface of Italian printing. The evidence is presented, not in forbidding trigonometrical tabulations, but in stunning woodcuts of the human body, which are so clearly the work of an old master that they have been attributed (though most tendentiously) to Titian. And if the sheets on which the great muscular figures posture gracefully are placed side by side, it is apparent that they are displaying the physical structure of man against a continuous Renaissance landscape. This has even been identified. It lies in the countryside of Petrarch, near Abano Terme, not far southwest of Padua, where Vesalius worked and taught. There he had access to Venice, and to the workshop of Titian, if not to Titian himself. Like the style of the Venetian school, the culture of the Renaissance was already a little full blown by 1543. But under the encroaching shadow of the baroque, the work of Vesalius established a permanent residence for naturalism in science, just as at the very last moment of the Renaissance, and as its final triumph, the work of Galileo was to embody Platonism in physics.
The sciences of life, therefore, find their place in the scheme of a scientific revolution. The impression is difficult to avoid, however, that it was a subordinate place. Despite the very evident appeal of Vesalius’s subject, or perhaps because of it, his achievements were of a lower intellectual order than those of Copernicus or Galileo. His were not the ideas which changed man’s conception of the world, or even of himself. Nor did those of any biological scientist before Darwin. Generally, the deepening of theory in the physical sciences preceded the widening of fact, whereas the sciences of life developed in the reverse order. When the transformation of biology did come in the nineteenth century—not till then!—it took the form, bound to be something less than revolutionary, of an assimilation of biology to the objective posture of physics.
The disadvantageous comparison of the science of living nature to physics must not be pushed too far, for the material, if not more difficult, was at any rate more incoherent. Nor were generalizations lacking. The movement of thought from Vesalius’s anatomy to Harvey’s demonstration of the circulation of the blood is as interesting for the evolutionary structure of theory as any episode in the history of physics. The limitation of Harvey’s achievement was in its scope, not its merit. In the theory of gravity Newton could unite Kepler’s planetary laws with Galileo’s mechanics in a mathematical science of matter in motion that encompassed all of physics. But the circulation of the blood united only anatomy and physiology. This was as near as biology could come in generality to physics, and it left innumerable fragments of information and superstition strewn across the vast wastelands of medicine and natural history, unorganized by any objective concepts.
It is, indeed, indicative of the inchoate nature of these subjects that the word “biology” had to await the nineteenth century to be coined. In the sixteenth and seventeenth centuries the subjects it was to embrace scarcely had an independent existence. Anatomy and physiology were rather aspects of medicine than science, and medicine was oriented more toward art and therapy than knowledge. Although human anatomy was studied more by analogy to animals than from cadavers, this practice was the source rather of error than of comparative anatomy, which does not antedate the eighteenth century. Natural history, for its part, was pursued rather in the spirit of the bird-watcher or the moralist than the investigator. Etymologically, the term means simple description of nature. Zoology was the source of fables, botany of medicinal herbs, and mineralogy of ores. Nor was the mineral as distinct from the animal and vegetable kingdoms as might be supposed, for minerals were thought of as bred in the womb of the earth to be ranged by species in categories of form.
In all fields the attitude to Aristotle and antiquity was ambivalent. There was criticism in detail, and a kind of ritual resentment of authority. In part this was a wholesome striving for originality, an assertion of the imperative of seeing for oneself. But mingled with this was the less worthy element of jealousy that those unsure of themselves feel, less for the mistakes of authority, than for the superiority which earns it. There was, as a consequence, no such clean break with antiquity as is represented by the law of falling bodies, but only a girding against it. For part of the difficulty in biology was that Aristotle’s methods really did suit its problems for a very long time. Taxonomy, the classification of organisms, had to be the first step in ordering the millions of forms of life. Considerations of purpose, the teleological analysis of function, dominated biology right down to Darwin. The attempt to answer the question why? carried the biologist much further into his science than it did the physicist; or perhaps one should say that it became an obstacle much later. For all these reasons, therefore, biology was the less radical of the two great branches of science, and so it is, perhaps, that throughout history biologists have been more likely to be men of humane temper than have their mathematical colleagues, whose minds dwell on the abstract and the exact rather than on life and the flesh.
Vesalius lived a somewhat puzzling life. What the spirit of his career actually was is less clear than in the case of anyone of comparable stature in the history of science. He was born in Brussels in 1514 into a family which had originated in the Rhenish town of Wesel (hence the surname) and which had a long medical tradition. He studied first at Louvain and then at Paris, where he hated his teachers. Indeed, he always expressed that violent scorn for his professors which is likely to seem (at least in the eyes of their alarmed successors) one of the less attractive Renaissance conventions. He went back to Louvain to submit his doctoral dissertation and on to Padua to complete his studies. There the degree of M.D. was awarded him in 1537, and on the very next day he was named professor of surgery by the Venetian Senate. He was then 23 years old. He taught for five or six years only, and published his course in 1543. Then, his great book in print and his reputation assured, he abandoned anatomy and teaching to accept appointment as court physician to the Emperor Charles V and to spend the rest of his life tending the ailments of that powerful and unhealthy monarch, who felt more secure in ignoring medical advice when Vesalius was by him to deal with the consequences. Whether Vesalius is to be counted a scholarly inquirer, therefore, or a careerist, is a question as difficult to avoid as to answer.
He was, at any rate, a great success as a teacher. In those six years he worked out and put into practice the tactics of anatomical demonstration. Since his time the subject has been corrected in many details and subordinated to a scientific biology. But in its substance it has not changed essentially. Vesalius’s book was not a work of ideas. Perhaps, therefore, there was no point in his continuing to teach once it was printed, for it put the anatomical theater between covers. To the squeamish, indeed, that might even seem the best place for it. The tourist may still visit the old anatomical theater in the University of Padua, built only fifty years after Vesalius taught there. It is much as it was then. But the term “theater” is misleadingly spacious. For the room is a tiny, airless pit, oval in form and scarcely thirty feet across. Around the sides run shallow galleries in which one can barely stand. What must the atmosphere have been when these were packed with scores of sweating students, some of whom would surely faint or vomit, all jostling and craning to see down on the slab in their midst where the professor was dissecting the putrefying cadaver of some thief or beggar who would have been notably unsavory even when alive.
The success of Vesalius’s course and of the book which embodied it was compounded of three elements: the authority of its information, the method of exposition, and the systematic approach. None of these was wholly novel, and Vesalius’s essential contribution was the comprehensive skill with which he wove them into a corpus of anatomical practice rather than originality in any single detail or method. Vesalius himself made a great point of learning anatomy from bodies rather than books. And it is true that Greek humanism in antiquity and Christian teaching in the Middle Ages had created a powerful repugnance for opening the human body even in death. Nevertheless, Vesalius was far from having been the first anatomist to look inside his subject. Queen Elizabeth allowed the medical school at Cambridge three criminals a year. At the University of Bologna there was a standing rule in the fourteenth century that the medical students might procure cadavers for dissection, provided they did not belong to people who lived within thirty miles of Bologna. Indeed, the problem of the inadequate supply of bodies, like that of their rapid decomposition, was a handicap but not an absolute obstacle to research.
More obstructive was the spirit in which dissections were performed, for it was less one of inquiry than of demonstration—intended to show the artist or the student how the body is made rather than to subject it to functional analysis. Far from being nonexistent, dissection was almost routine by Vesalius’s time, and he criticized his predecessors’ lectures not for omitting demonstrations, but for confiding them to an assistant. Traditionally, the professor of medicine would stand up to his lectern droning out some text from Galen on the heart while the ignorant menial down below would grapple in the body laid out at his feet and hold up the liver by way of illustration. The frontispiece to De Humani Corporis Fabrica points the moral by representing Vesalius descended from his chair discoursing and demonstrating directly from the corpse, while the nobility and men of note look on. Two laboratory assistants have been demoted and are seen beneath the table scuffling squalidly, while a monkey at the left is both a symbol of medicine and a criticism of the source of too much anatomical misinformation. Vesalius’s innovation, then, is the method of actual demonstration which has become the technique of much teaching of natural knowledge. It is no accident, but a conscious philosophy of communication. Vesalius evidently worked very closely with the artist in order to assure integration of the text and plates and to perpetuate the graphic realism of his method in print. His book is no casual commentary but a work of reference and a manual of technique. For he had that fine hand of the surgeon in which the probe or scalpel becomes like an outgrowth of sense.
De Fabrica, finally, is a highly systematic work in which the system is no arbitrary scheme but the Vesalian analysis of the body itself. The structure of the object gives structure to the study. Skin and muscle are flayed away layer after layer to reveal each level of organization: the muscular system itself, the vascular system, the nervous system, the respiratory organs, the abdominal tract, the architecture of the skeleton, and the articulation of the joints. Particular organs, the heart and lungs, the brain, the genitalia, are dismounted and dismembered and depicted, mistakenly on occasion (the uterus looks like some Freudian nightmare), but generally with an accuracy and precision never before seen. The plates combine the scientist’s eye for detail with the artist’s eye for effect. The importance of the work, therefore, derived from its influence as a whole. Not only is it a model anatomical treatise, it was the first treatise in the history of any science in which all the relevant facts were put down in order and from nature. There were no new theories, but here were all the facts. Here was a technique, laborious and detailed, but available for mastery. One knew what one had to do to become an anatomist. Here was a body of information which irresistibly invited comparison with the traditional account of the subject. And so, even though Vesalius was a Galenist in physiology, the effect of his work was to ruin the composure of the old science, to teach the lesson that the whole corpus of anatomy must be reformed by meticulous observation, and eventually by that independent manner of thought of which Vesalius, its founder, was not himself quite capable.
Anatomy necessarily moves from description to function, and despite Vesalius’s contempt for second-hand observation, Galen remained the lawgiver of physiology. No one could conceive of the body alive and working in the objective mood of science. There is no physician of classical antiquity of whom we know more, and none of any time whose influence so touched every detail. The legacy of Hippocrates, his master, was that of a school, not a man, and of a naturalistic philosophy of medicine, not a body of medical art. Galen’s place in the history of medical science was altogether comparable, indeed, to Aristotle’s in physics. If possible, he went beyond Aristotle in his commitment to teleology as the path to understanding. His was a teleology which compounded Aristotle’s rational interest in the purpose of objects with Plato’s mystique about the divinity of perfect plans. It is often said that posterity looked at the body with Galen’s eyes. It was not that simple—Vesalius certainly looked with his own—but it is easier to look than to see differently, and there was no alternative to the illusion of understanding created by explanations like that which makes the humble heel as perfectly adapted for its role in the human body as is the sun for giving life to the body of the world.
The function of the heart is crucial for any physiological theory which would discern the mechanism of the body. But Galen followed Plato on the sovereignty of the liver. His admiration for the rich capacities of that organ echoes certain strange and difficult passages in the Timaeus. In Galen the liver mediates between the three major involuntary processes of life: digestion, respiration, and the beating heart. From the stomach it draws through the intestinal veins the “white chyle,” the product of the digestive “coction” or cooking of food. By a second coction the liver makes blood of chyle, and of this blood a large part is sucked up the vena cava by the expanding stroke or diastole of the heart into the right auricle. Then the heart contracts. Some blood is pushed out the pulmonary artery to irrigate the lungs, and the rest is extruded right through the central wall of the heart, the septum, to the left side. There it mixes with vital spirits of the air piped directly from the lungs down the pulmonary vein, which in Galen is a pneumatic tube, not a blood vessel. Hence, there are two kinds of blood. That which had been transmuted by vital spirits—further quickened, according to some accounts, by animal spirits issuing from the brain—was a life-giving fluid, bright red and foaming with spirit, which surged up and down the body through the arterial vessels in a cyclic ebb and flow like the rhythm of the lungs or the tides. At the same time, the venous blood from the liver carried dark nutriment more sluggishly about the body. In neither case was there a circulation.
Here was a complex and consistent explanation of the body. Like Aristotle’s physics it made sense of its subject, it was wrong, and it was not refutable by the techniques of which anatomy disposed. But like the question of what moves the projectile, there were certain little difficulties, certain handles to dissent waiting to be grasped, which would turn out to have such an unexpected leverage as would overset the entire structure. There was, first, the statement that the main action of the heart is suction, whereas anyone who had ever opened the chest cavity of a laboratory animal could see that diastole is a relaxation of muscle and systole, a tensing. There was, secondly, the direct passage of air from lungs to heart, whereas dissection frequently showed these vessels, not only to be full of blood, but to be structurally identical with blood vessels and very unlike bronchial tubes. Galenists might and did say that such phenomena were accidents of dissection, derangements produced by the shock of incision or of death. Nor were they specious in these views, but only faithful to that assumption of order in their subject which is one of the preconditions of science. For science had yet to develop that assurance which takes each occasion to modify or rearrange the elements of order as a widening or deepening of confidence rather than a weakening.
Their faith was tested most shrewdly by the routing of blood right through the central wall of the heart. That it passed the test for centuries is the most notable testimony to the ordering power of the Galenic system. For the septum is a thick, tough piece of muscle. Vesalius investigated the pits himself and could find no passages: “None of these pits penetrate from the right ventricle to the left; … therefore, indeed, I was compelled to marvel at the activity of the Creator of things, in that blood should sweat from right ventricle to the left through passages escaping the sight.” And what is interesting in retrospect is how investigators refrained from finding the answer, which is that if blood cannot pass directly from one side of the heart to the other, it must go round through the lungs. When one reads the memoirs, it almost seems to shriek at them from their own discoveries. But they went on fitting those findings into Galen’s pattern right up to publication of William Harvey’s theory of the circulation in 1628. (The chronological span from Vesalius to Harvey, it will be noticed, is exactly the same as that from Copernicus to Galileo.)
The conservatism created by the illusion of understanding may be illustrated by the failure to exploit two major discoveries of that interval, by either of which a bold mind might have anticipated Harvey. The lesser circulation of the blood, that is to say its transit from right ventricle to left auricle by way of the lungs, was described in print in a very curious book of 1553. Its author was a Spaniard, Miguel Serveto, one of the more implausible figures in the history of science. He had studied law at Toulouse, where he had also developed an interest in theology, particularly in natural theology, and his book dealt with that subject under the title Christianismi Restitutio. It argues in favor of penetrating beyond the vanities and corruptions perpetrated by the theologians of all centuries to the simple word of God which may be read in nature. Even Moses does not escape Serveto’s censure. This was heresy, of course, and Serveto was burnt at the stake by order of the responsible theologians—not in this case Catholic theologians, but John Calvin and the elders of Geneva, which righteous city was no host to blasphemy.
Serveto’s description of the passage of the blood from the heart through the lungs and back to the heart occurs in a page and a half of Restoration of Christianity. This passage was his chief scientific writing. It is possible that he knew an Arabic description of the lesser circulation, contained in the writings of Ibn al-Nafis. Serveto had studied anatomy at Paris. A discussion of the Holy Spirit in the Trinity led him to write of the three spirits of the blood, which conveys soul throughout the body. There is, he said, no communication through the septum. Instead, “the subtle blood, by a great artifice, passes along a duct through the lungs; prepared by the lungs, it is made bright and transfused from the pulmonary artery to the pulmonary vein. Then in that vein it is mixed with air during inspiration, and purged of impurity on expiration.” What with the notoriety attendant on his burning, Serveto’s book was often read, and even accepted, though not widely. But it never served, apparently, to suggest to anyone influential the possibility that all the blood circulates. All it did was to substitute a pulmonary detour for sweating through the septum as a means of getting blood from one side of the heart to the other and burnished by vital spirits in the transit.
A second discovery might have been even more suggestive. One of Vesalius’s successors in the chair of anatomy at Padua was Fabrici d’Acquapendente, a supporter years later of Galileo. In 1603 he published an anatomical work describing certain valves he had discovered in the veins. Vesalius had never noticed them, but they are not, in fact, difficult to observe even with quite simple techniques. Their significance now seems absolutely obvious, for they permit venous blood to flow in one direction only, toward the heart. But Fabrici had learned his anatomy well. Their purpose, he said, is that of microcosmic floodgates. They check the flow away from the heart and restrain the outward ebb so as to prevent all the blood from collecting in the feet or hands. By his time, therefore, anatomists had all the information needed to get the dynamics of the body right. They had even tried ligaturing veins, and had observed the accumulation of blood on the side away from the heart, a phenomenon explained by pointing out that the blood took alarm and pressed off in the wrong direction. The subject, therefore, was in a state where it needed, not new facts, but a new approach.
THE ANSWER was born of the first faithful marriage on equal terms of inquiry and empiricism. William Harvey’s On the Motion of the Heart is a classic of inductive science. Galileo, to make a contrast, conducted most of his experiments in his head and on paper. They are beautiful examples of models in physical thought, but not of experimental science. When he did perform one, it was usually to demonstrate properties of the behavior of bodies which he had already deduced in good Archimedean fashion from geometric consideration of motion or equilibrium. In Harvey, too, scientific creation was the elegant expression of a temper combining imagination with impatience, and what provoked impatience in both minds was error, not the discipline of systematic thought. But Harvey was the first to use observation and experiment to find out something fundamental instead of to demonstrate it. In his work experience and its artificial reproduction in the laboratory were first instrument of inquiry, and then arbiter of theory.
Harvey’s family were minor gentry in Kent. He was educated first in Canterbury, then at Cambridge, and in 1599 went on to Padua as a medical student. Both Galileo and Fabricius were teaching then, and we know he studied under Fabricius. There was always something both grave and imperative about his writing and his bearing—qualities intensified, perhaps, by Paduan manners. He was back in London in 1602, where (it is said) he always carried the little dagger affected by Paduan students in their dress. His practice was a success. He was appointed to Saint Bartholomew’s Hospital in 1609 and served as physician extraordinary to James I and Charles I. In 1615 the Royal College of Physicians of London appointed him Lumleiian lecturer, on which foundation he was to discourse annually of anatomy and surgery. He combined research with practice, and published his book in 1628. He had then, he wrote, been developing his views for years in his lectures. The subject was involved in much confusion: “Those persons do wrong who while wishing, as all anatomists do, to describe, demonstrate, and study the parts of animals, content themselves with looking inside one animal only, namely man—and that one dead.” And it would appear that Harvey had been dissatisfied with the physiological doctrine of Padua and had been studying the heart ever since, through ever wider and more meticulous inquiry involving frequent examinations of the insides of many different living animals and the collation of many observations.
His book is a truly beautiful argument. Absolutely appropriate facts are arranged with perfect art. It would be almost as difficult to withhold assent from his demonstrations as from a geometric theorem. “All true and fruitful Natural Philosophy,” wrote Francis Bacon, “has a double scale or ladder, ascendant and descendant, ascending from experiments to axioms and descending from axioms to the invention of new experiments.” Harvey was a scientist rather than a methodologist and meant his book to convey the correct physiology of the heart. But in retrospect it may be more instructive to read it as an object lesson in inductive reasoning. Each chapter makes a simple point illustrated by multiple instances. First it is shown from vivisection of cold-blooded animals (chosen for their slow heart-beat) that the contraction of the heart muscle is a pumping stroke. Then it is demonstrated how the pulsation, first of the auricles, afterward of the arteries, synchronizes with the rising thrust of the ventricles which lifts the heart against the chest wall. Now we are ready to agree to the local action of the heart. This in turn prepares us to draw more out of the induction than the instances that went into it. It leads to consideration of the pulmonary circulation which must be a function of the structure of the heart, for animals without lungs exhibit hearts with only one ventricle. Moreover, in the mammalian embryo the two ventricles act as one since the lungs are not yet in use. Occasionally Harvey betrays the authentic intolerance of science for stupid error. The pulmonary circulation is still denied by anatomists who make blood seep through the septum: “But damme there are no pores and it is not possible to show such.”
Having shown the heart transferring the blood from the veins to the arteries by filtering it through the lungs, Harvey is ready to state his thesis in its most general form. He postulates the completion of the circuit from arteries to veins in the major circulation throughout the body.
The remaining matters, however (namely, the amount and source of the blood which so courses through from the veins into the arteries), though well worthy of consideration are so novel and hitherto unmentioned that, in speaking of them, I not only fear that I may suffer from the illwill of a few, but dread lest all men turn against me. To such an extent is it virtually second nature for all to follow accepted usage and teaching, which, since its first implanting, has become deep-rooted; to such extent are men swayed by a pardonable respect for the ancient authors. However, the die has now been cast, and my hope lies in the love of truth and the clear-sightedness of the trained mind.
In substance, Harvey’s arguments are quantitative and anatomical. The decisive one turns on the amount of blood. From the capacity and rate of the heart and its beat, he calculates that in one hour the heart pumps a weight of blood greater than that of a man—far more blood than could possibly be created out of any amount of food one could eat, be the liver never so active. It is impossible to say where it came from or where it went except on his theory.
Harvey now starts his descent of the ladder of induction, which verifies by the prediction of consequences. In form he presents his demonstrations as suppositions imposed by the hypothesis. In being confirmed by experiment, these then serve to validate the hypothesis, promoting it (as some might say) to the rank of theory. So the arteries are made as blood vessels, not air tubes, and observations of the valves in the veins and appropriate ligatures in both sets of vessels establish the direction of flow. Therefore,
Since calculations and visual demonstrations have confirmed all my suppositions, to wit, that the blood is passed through the lungs and the heart by the pulsation of the ventricles, is forcibly ejected to all parts of the body, therein steals into the veins and porosities of the flesh, flows back everywhere through those very veins from the circumference to the centre, from small veins into larger ones, and thence comes at last into the vena cava and to the auricle of the heart; all this, too, in such amount with so large a flux and reflux—from the heart out to the periphery, and back from the periphery to the heart—that it cannot be supplied from the ingesta, and is also in much greater bulk than would suffice for nutrition.
I am obliged to conclude that in animals the blood is driven round a circuit with an unceasing, circular sort of motion, that this is an activity of the heart which it carries out by virtue of its pulsation, and that in sum it constitutes the sole reason for that heart’s pulsatile movement.
But even now Harvey is not finished. He draws attention to still further consequences of a lower order of generality—the distribution of certain pathological conditions by the blood stream, the consonance between the development and tone of the heart and other muscles in particular subjects. These gave his theory its maximum extension. Only one link was missing. How does the blood pass from the finest arteries to the finest veins? For the capillaries are invisible, and the microscope was not yet at hand. Nevertheless, Harvey posited their existence, and when that instrument did come into use, his prediction was verified—by Malpighi, who in 1661 identified capillary structures in the lungs of a frog.
There are writers who would make Harvey a heart-worshiper as Copernicus was a sun-worshiper. And indeed there are a few echoes of the debate between Plato and Aristotle over the relative excellence of the liver or the heart:
We must equally agree with Aristotle’s view about the pre-eminence of the heart, and refrain from asking if it receives movement and sensation from the brain and blood from the liver…. For those who attempt to refute Aristotle with such questions disregard or do not appreciate the chief point, namely, that the heart is the first part to exist, and that it was the seat of blood, life, sensation and movement before either the brain or the liver had been created, or had appeared clearly, or at least had been able to perform any function. With its special organs designed for movement the heart, like some inner animal, was in place earlier. Then, with the heart created first, Nature wished the animal as a whole to be created, nourished, preserved and perfected by that organ, to be in effect its work and its dwelling place. Just as the king has the first and highest authority in the state, so the heart governs the whole body.
But Harvey is here writing with reference to embryology, not to mysticism, and the admiration he often expresses for Aristotle is no more than the reverence which any honest biologist who has truly studied the classics must feel.
Indeed, it distorts the import of Harvey’s approach to assimilate his outlook to anything like the world alive. Its place in the history of physiology is obvious and central. The phenomena ordered by Harvey could not reach beyond that science. Nevertheless, his work was the first, if partial, breach opened by the scientific revolution in the life sciences. His subject is not the ineffability of life. It is a problem in fluid mechanics. The heart is a pump, “a piece of machinery in which though one wheel gives motion to another, yet all the wheels seem to move simultaneously.” The veins and arteries are pipes. The blood, so far as the problem is concerned, is simply a liquid, a lubricant to be passed periodically through the air filter of the lungs. No vital spirit, no principles of nourishment intrude into the analysis.
However different his subject from Galileo’s, and however different their methods, Harvey’s work portended the same conception of science. In him a new science which makes objective measurements superseded an old science which found qualities, humors, purposes, and tendencies indwelling. On yet another front, personality was displaced as a category of scientific thinking and as the model for order. Galileo had excluded the biological metaphor from physics. Harvey went further and introduced mechanistic thinking into organic studies. And by a simple though systematic extension, Descartes would find a machine in man. Dim fears stirred at all these vaguely sensed implications. Harvey’s views were not generally accepted in the thirty years or more before Malpighi’s discovery forced assent. As Harvey foresaw, he had against him more than force of habit. For his hydraulics of the blood stream destroyed a whole philosophy of the body in order to establish a single phenomenon of nature.
THE misunderstandings between Harvey and Francis Bacon make an ironical commentary on the relationships between those who do science and those who write of its methods. De Motu Cordis might be taken as the purest and best Baconianism. In fact, Harvey dismissed Bacon as one who “writes philosophy like a Lord Chancellor,” and Bacon in one of his less fortunate pronouncements denied the circulation of the blood. Not only so, but Bacon also rejected Gilbert on magnetism, Copernicus on the sun, and Kepler on the planets. Nor did he understand Galileo. These misjudgments might seem to cast some doubt upon the right that Bacon claimed at great and eloquent length to speak as the philosopher of the new science. Nevertheless, that right has been very generally accorded him. Bacon created no science. But his prophecy—he was nothing if not a prophet—of a world perfected by a reformed science created an image of scientific progress which has been vastly more popular than science itself can ever think to be. With all his scorn for the scholastics, he founded a new school, a new orthodoxy which organizes knowledge, not for understanding, but for use. With all his facile contempt for Aristotelians, he made himself the Aristotle of the philosophical bourgeoisie and held out his method as a royal road to science for the middle-brow mind. For the shadows of the Middle Ages lingered, and Bacon’s dream of progress was not altogether glad and confident. He did not rightly know whether modern times are the morning or the evening of history, but he did not suppose that modern man could attain the stature of the ancients. We must, therefore, make the most of our smaller forces: “The course I propose for the discovery of the sciences is such as leaves but little to the acuteness and strength of wits, but places all wits and understandings nearly on a level.”
This is comfortable democratic doctrine, and it is obvious why Baconianism has always held a special appeal as the way of science in societies which develop a vocation for the betterment of man’s estate, and which confide not in aristocracies, whether of birth or brains, but in a wisdom to be elicited from common pursuits—in seventeenth-century England, in eighteenth-century France, in nineteenth-century America, amongst Marxists of all countries. Nevertheless, it would be simply snobbish to deplore Bacon’s influence. His was the philosophy that inspired science as an activity, a movement carried on in public and of concern to the public. This aspect of science scarcely existed before the seventeenth century. Since then it has accompanied and at times enveloped intellectual effort. There is bound to be a certain tension in affairs which associate the expert with the layman. The scientist wants of his subject an intellectual adventure which can only remain private. The public wants advantage for itself, and though it does not wish to pay the mental price of understanding, may all too humanly resent exclusion. But tensions bind while they distort, and science and public welfare are not likely to separate out of the complex fashioned by Bacon.
There was more than a gibe in Harvey’s remarks, for Bacon was a lawyer and politician. His career is difficult to admire. As defence against the charge of accepting bribes while in high judicial office, he pleaded that he had not allowed them to influence his decisions. This reasoning failed to placate, and he ended in disgrace: “The rising unto Place is laborious; and by pains men come to greater pains; and it is sometimes base; and by indignities men come to dignities. The standing is slippery, and the regress is either a downfall, or at least an eclipse, which is a melancholy thing.” Such was the lawyer-like worldliness which invested science with a civic dimension.
The subject matter of Bacon’s writings falls into three categories: demonstration of the worth and dignity of learning; analysis of the obstacles which kept it languishing in futility; and prescriptions for its reformation and advancement. It is not, perhaps, necessary to insist much on the first point—indeed, it was not so necessary in the early seventeenth century as Bacon would imply. His pleas for learning generally took the form of a rather scornful repudiation of all that passed for such. As for the hindrances, it was trite enough to blame the sterile habit of reliance on authority and the circularity of scholastic logic. But though no student of science, Bacon was an extremely acute student of human beings, and in his discussion of the obstacles raised by the intellect against itself, he showed his mettle. There is that in the very constitution of our understanding which renders the mind a pesky instrument for innovation. “Idols,” Bacon called these innate blinders. The “Idols of the Tribe” are distortions which arise from our common nature: “The human understanding is no dry light, but receives an infusion from the will and affections; whence proceed sciences which may be called ‘sciences as one would.’ For what a man had rather were true he more readily believes.” The “Idols of the Cave” compound this common tendency to error with the favorite prejudices or enthusiasms of the individual man, each of whom “has a cave or den of his own, which refracts and discolours the light of nature.”
Third, are “Idols formed by the intercourse and association of men with each other, which I call Idols of the Market-Place on account of the commerce and consort of men there. For it is by discourse that men associate, and words are imposed according to the apprehension of the vulgar. And therefore the ill and unfit choice of words wonderfully obstructs the understanding.” This was perhaps the most penetrating and valuable of Bacon’s observations. Not much can be done about human nature, after all, any more than about gravity or inertia, even when its disadvantages are recognized. But identification of the error that lurks in words was the first step to correction. The attempt to put precision into scientific language has never since been relaxed. Humanists may complain of the jargon of the specialties, sometimes with justice. But no science can flourish until it has its own language in which words denote things or conditions and not qualities, all loaded with vague residues of human experience.
Finally, Bacon held up to suspicion the “idols of the theater,” by which he meant the systematic dogmas of philosophies, “because in my judgement all the received systems are but so many stage plays, representing worlds of their own creation after an unreal and scenic fashion.” Many gratuitous suppositions of the ancient philosophies—the perfection of circles, for example, or the notion of purpose in nature—go far to justify this indictment of great flights of system. Nothing, as Descartes was to observe a few years later, is so absurd that it has not been said by one of the philosophers. And this proscription of system, coupled with analysis of language, was to become one of the main motifs of science in the eighteenth-century Enlightenment. But though it brought much sanity, it developed the drawback of too sane an outlook—it discountenanced imagination. Reinforced by a misunderstanding of Newton’s famous “I frame no hypothesis,” it discouraged theory in favor of accumulation of detail, abstract generalization in favor of natural history. In Baconian science the bird-watcher comes into his own while genius, ever theorizing in far places, is suspect. And this is why Bacon would have none of Kepler or Copernicus or Gilbert or anyone who would extend a few ideas or calculations into a system of the world. But reason had its revenge on Bacon’s dogmatic empiricism in the manner of his death: he took a chill while stuffing a chicken with snow, the most famous experiment he is known to have performed.
So radically inane, in Bacon’s view, was the corpus of received philosophy that it must simply be jettisoned. “It is idle to expect any great advancement in science from the super-inducing and grafting of new things upon old. We begin anew from the very foundations, unless we would revolve forever in a circle, with mean and contemptible progress.” There must be a New Learning, then, with Bacon as its guide. And the goal? In a word, Progress—progress as it has been understood everywhere in the West since the seventeenth century, progress through technology and the domination of nature. “The true and lawful goal of the sciences is none other than this: that human life be endowed with new discoveries and power.” Thus will be turned the last of the barriers to knowledge, at once the most obstructive and the most unnecessary, left standing through the failure to demand practical results from learning. Natural philosophers had been allowed to enter on speculations, not with a view to applying their results, but to please their own vanity, or out of idle curiosity. There is, therefore, no choice to be made in Bacon’s philosophy between basic and applied science. On the contrary, applied science is by definition basic: it is the object of the search.
The positive side of Bacon’s program for building an infinity of better mousetraps into a better world envisioned three related stages: application of the inductive method, creation of a universal natural history, and the public organization of science. Induction will redress the empty rationalism of science and start anew by reversing its procedures. Scholastic science, thought Bacon, began with the principle and deduced the consequence. He would begin with the particular fact, with all relevant facts, and rise by successive steps to the general principle. Not that he was quite so uncritical as this might seem. He placed great emphasis on comparative analysis and the exclusion of facts or possibilities which do not carry the mind toward general laws. Suppose, for example, one is studying heat. Metals can be heated without producing light. The moon gives light, but no heat. Therefore, in distinguishing the laws of heat, the phenomena of light are to be excluded. This principle of elimination is obviously important in scientific investigation. It is doubtful, however, that it needed Bacon to become established. It is implicit, after all, in Galileo’s resolution of motions, explicit in Harvey, and inherent in all workable science.
More important, Bacon’s emphasis on experiment did shape the style of science. So strongly did it do so that the term “experimental science” has become practically a synonym for “modern science,” and nothing so clearly differentiates post-seventeenth-century science from that of the Renaissance, or of Greece, as the role of experiment. Where is Bacon’s new scientist to find the facts from which he will draw out inductions? He will look to observations of nature, of course, but preferably to that artificial reproduction of nature which is experiment. Experimentation practices the principle of elimination of the irrelevant. It puts the inquirer in control of the inquiry. It reveals more than passive observation: “Nature when vexed takes off her mask and reveals her struggles.”
The prospects for examining nature by the inductive process obviously depended on having a vast collection of particulars from which to begin. Like any philosopher who mistrusts abstraction, like Aristotle, for example, Bacon was driven back on classification as an instrument for ordering the world—an instance, by the way, of the relationship of “frères-ennemis”—obtaining between Bacon and his largest target. A “natural and experimental history” was, therefore, prerequisite to progress. In The Dignity and Advancement of Learning (1623) he classified all knowledge as history, poesy, philosophy, and theology, and divided history into the two categories of civil and natural. This is the beginning, perhaps, of the separation of science and philosophy at the higher level, and of science and the humanities at the lower. For civil history embraces human affairs and natural history the facts of nature. Nor was Bacon modest. He meant his natural history to range into place nothing less than all the facts. They were to be gathered everywhere, even from accounts of sorcery, witchcraft, and magic, if there be facts therein. But it was to the mechanical arts, to industry, trade, cookery, agriculture, seafaring, in a word to the practical man, that Bacon looked with fondest confidence. In this emphasis he struck a note which resounds very far back in western history, spoke indeed as an echo of his namesake, that other technological seer, friar Roger Bacon, who equally impatient of scholastic subtleties, and even guiltier of them, sought in the thirteenth century to define knowledge as what men can do rather than what definitions they can look up. There is both good sense and a constant flirtation with vulgarity in that practical western instinct which holds that the blacksmith knows metals and the metallurgist only books, that in real life an Edison outweighs an Einstein, and a businessman a scholar. And nothing has so flattered the audience that always welcomes Bacon’s philosophy as this central imperative which would send errant philosophy back to the school of industry to learn what’s what by experience.
Bacon did not expect to complete the natural history himself. The collection and encyclopaedic ticketing of all the facts would be an enterprise of considerable magnitude, requiring cooperation and subsidy. But it was a finite venture. In principle (again as in Aristotle) a completed science is perfectly feasible. “I take it that all these things are to be held possible and performable, which may be done by some persons, though not by one alone; and which may be done in the succession of the ages; though not in one man’s life; and lastly, which may be done by public designation and expense, though not by private means and endeavours.” Since science will benefit humanity, it is up to the state to support and organize science. Nowadays, it is even so, of course—except that the work no longer seems likely to be finished. Science has in fact become a cooperative enterprise. There are indeed vast numbers of technicians, worker-bees in the Baconian hive, passing information up through computers to the master theorists. In his last book, The New Atlantis, Bacon clothed his dream in that favorite device of the man with a message, a Utopia. He even situates it on a remnant of that lost continent which in the cosmological allegory of the Timaeus had carried Plato’s final evocation of philosopher-kings down to oblivion. There the shipwrecked Europeans find a land in perfect order, full of untroubled knowledge, empty of discord or jealousy. The explanation, it emerges, lies in the nature of the sovereign, which is no king nor any tyrant, but a community of sages, living apart and devoted to learning and guidance of the land. The very model of a wise government, then, is a society of scientists with leisure to accumulate knowledge and power to apply it to the public weal, and the catalogue of wonders they have wrought reads like one of the crasser paeans to the American standard of living.
After Galileo, science could no longer be humane in the deep, internal sense of its forerunner in classical antiquity. Instead, Bacon dressed it out as humanitarianism. The reasons for his popularity are obvious, therefore. He makes science what it has become in part, and what the public tends to wish it were in its entirety: an innocuous instrument of human betterment which requires of him who would master it, not difficult abstract thought, but only patience and right method. It is less obvious why Baconianism has often enjoyed popularity among scientists themselves. No discovery has ever been made by following his method. Scientific thought itself is bound to be far more abstract, elegant, and intellectually aristocratic than Bacon foresaw or would have approved. But scientists are likely to be humane men who wish to do good and like to be told that they do. And an appreciation—like Pascal’s, for example—of the poignancy of science is fairly rare among them: that is to say that the act of understanding is an act of alienation. Pascal took the contemporary attitude to authority wryly, as a commentary on the perversity of human nature. In science, he pointed out, men are so respectful of authority and fearful of innovation that they disbelieve in the vacuum on the word of Aristotle, whereas in theology, where they ought to depend on authority, they go running after novelty. But the wringing of hands has never been an influential posture in western history, and it is the materialistic commitment of a Bacon, at once tough-minded and humanitarian, rather than the delicacy of mind of a Pascal, which has shaped the technical tradition. The public soon grows bored with the man behind the tragic mask.