by Peter Watson
That attitudes to the body were changing is shown from the drawings of Leonardo da Vinci, mostly executed around 1510, or three decades before Vesalius. There is a memorandum of the artist which shows that he had conceived a book on the ‘human body’ as early as 1489 (though this, like much else of his, was never completed).49 What seems clear from the memorandum, and from Leonardo’s drawings, is that he had studied anatomy professionally even before he joined forces with the anatomist Antonio della Torre, and that Leonardo continued to make dissections long after their relations were severed about 1506. The artist made more than seven hundred sketches showing the architecture of the heart and the layout of the vascular system, bones drawn from different aspects, the muscles and their attachments, cross-sections of the leg at different levels, and of the brain and nerves. The detail was sufficient not just for artists, but for medical students as well.50 According to one source, by 1510 Leonardo had dissected no fewer than thirty human cadavers, of both sexes.
Born in Brussels on New Year’s Eve 1514, Andreas Vesalius came from a family of physicians but was given a wide-ranging education. As a young man, he published a translation from the Greek of a medical book by Rhazes. Vesalius went from Brussels to the Universities of Louvain and Paris, returning home to become a military surgeon, serving in Belgium’s wars. Finally, he moved to Padua, drawn by the relatively free access to bodies. In 1537, when he was still only twenty-three, he was placed in charge of anatomy teaching, and it was there, in the course of repeated dissections, that he began to see where Galen had gone wrong. This soon led him to reject Galen entirely and Vesalius began to teach only what he himself had uncovered. This proved enormously popular and students flocked to his lectures, five hundred at a time according to some accounts.51
After five years in Padua and while he was still barely twenty-eight, he produced The Structure of the Human Body, with a dedication to Charles V. Published in Basle, it contained many plates and woodcuts.52 (The illustrations were drawn by his fellow countryman John Stephen de Calcar, a pupil of Titian.) To the modern eye, de Calcar’s images are bizarre: in an attempt to soften the sheer rawness of what he was depicting, the artist put his skeletons in lifelike poses, and arrayed them, for example, in picturesque landscapes. Bizarre or not, no drawings of such vivid detail had been seen before and the impact was immense and immediate. ‘Vesalius corrected more than two hundred anatomical errors of Galen.’53 Many contemporaries denounced him for this, but Vesalius had done the work and nothing they said could trump that. For example, he showed that the jawbone in man is a single bone, not divided as it is in the dog and other lower mammals. He proved that the thigh bone is straight, not curved as it is in the dog. He proved that the sternum is made up of three bones, not eight, as was thought. There were some who tried to argue that human anatomy had developed since Galen’s day, or that ‘the fashion for narrow trousers had caused man’s leg bones to straighten’. Theologians also remained unconvinced. ‘It was a widely accepted dogma that man had one less rib on one side, because from the scriptural account Eve was formed from one of Adam’s ribs. Vesalius, however, found an equal number of ribs on each side.’54 But this was the mid-sixteenth century, the Reformation and Counter-Reformation were under way and the church was implacable. The attacks on Vesalius got so bad that he resigned his professorship in Padua and accepted a position as court physician to the emperor Charles V, then living in Spain.
‘But what Vesalius had begun, nothing could stop.’55 The main figure to follow him was the Englishman William Harvey. Born at Folkestone in 1578, he studied for five years at King’s School Canterbury, and then went up to Cambridge at the age of sixteen. Like Newton he did not shine early on (he was very young) and he studied mainly Latin and Greek, and an elementary level of physics. However, after graduation at nineteen, he immediately set out for Italy, and for Padua, showing he must have had some interest in medicine. There he studied under Fabricius, a famous teacher of the day.56 Sixty-one when Harvey arrived, Fabricius was just then refining his understanding of the valves of the veins, though he also showed that the pupils of the eye responded to light. Fabricius’ own knowledge was dated but he did stimulate in Harvey a great enthusiasm for medicine, which he took back home in 1602, having gained his doctorate. He went back to Cambridge, this time to earn an MD, which was necessary if he wanted to practise in Britain. He opened up shop in London and, within barely a decade, was appointed a lecturer at the Royal College of Physicians.57 There is written evidence–the written evidence of his own spindly hand–that he was teaching the doctrine of the circulation of the blood within a year of his arrival at the Royal College, in 1616. But he was rather less forward than Vesalius who–remember–had published his anatomical observations when he was just twenty-eight. Harvey, we now know, had been lecturing on the circulation of the blood for a good twelve years before he committed himself to print. When his great classic, The Movement of the Heart and the Blood, appeared in 1628, Harvey was already fifty.
His observations were nothing if not thorough. In De motu cordis et sanguinis, to give the book its Latin title, he refers to forty animals in which he had seen the heart beating. These animals included fish, reptiles, birds, mammals and several invertebrates.58 At one point he confides as follows: ‘I have also observed that almost all animals have truly a heart, not only (as Aristotle says) the larger red-blooded creatures, but also the higher pale-blooded crustacea and shell fish, such as slugs, snails, mussels, shrimps, crabs, crayfish and many others; nay, even in wasps, hornets and flies, with the aid of magnifying glasses (perspicilli), and at the upper part of what is called the tail, I have seen the heart pulsating myself, and have shown it to many others.’59 The book is only seventy-eight pages long, is much more clearly written than either Newton’s or Copernicus’ masterpieces, and its argument is plain enough for even the layman to grasp: all the blood in the body moves in a circuit and the propelling force is supplied by the beating of the heart.60 In order to make his breakthrough and conceive the circulation of the blood, Harvey must have deduced that something very like capillaries existed, connecting the arteries and veins. But he himself never observed a capillary network. He saw very clearly that the blood passes from arteries to veins ‘and moves in a kind of circle’. But he preferred the idea that arterial blood filtered through the tissues in reaching the veins. It was only in 1660 that Marcello Malpighi, using lenses, observed the movement of the blood through the capillaries in transparent animal tissues.
Harvey’s discovery of the circulation of the blood was the fruit of a clear mind and some beautiful observation. He used ligatures to show the direction of the blood currents–towards the heart in veins and away from the heart in arteries. And he calculated the volume of the blood being carried, to show that the heart was capable of the role he assigned to it. Observing the heart carefully, he demonstrated that its contraction expels blood into the arteries and creates the pulse. In particular, he showed that the amount of blood which leaves the left side of the heart must return, since in just under half-an-hour the heart, by successive beats, delivers into the arterial system more than the total volume of blood in the body.61 It was because of Harvey, and his experiments, that people came to realise that, in fact, it was the blood which played the prime role in physiology. This change in perspective created modern medicine. Without it we would have no understanding of respiration, gland secretion (as with hormones) or chemical changes in tissues.
In the 1840s the English archaeologist Austen Layard discovered a lens-shaped rock crystal in the ruins of the palace at Nineveh in what is now Iraq. For some, this was ‘a quartz lens of great antiquity’, dating from 720–700 BC.62 Few people believe this any longer–more likely it was a ‘burning glass’, to create fire, which we know was used in antiquity. In Seneca’s Natural Questions (AD 63) he says: ‘I may now add that every object much exceeds its natural size when seen through water. Letters however small and dim are comparatively large when seen through a glass
globe filled with water.’ Even this, which does show a reference to magnification, is no longer taken as evidence that magnifying appliances were used in ancient times.63 The first accepted reference comes in the writing of Alhazen, the Arab physician, in a manuscript of 1052. The subject of the manuscript is not only the human eye and optical principles, but he also refers to globules of glass or crystals, by means of which he observes that objects are enlarged. Roger Bacon (1214–1294) in his Opus majus (1267) says much the same, but there is no evidence that Bacon ever made either a telescope or a microscope.
This situation had changed by the end of the sixteenth century. We know that spectacle makers were common at the time in the Netherlands, Italy and Germany and it did not take long for people to happen upon a combination of lenses inserted into tubes. The Englishman, Leonard Digges (1571), and the Dutchman, Zacharias Jansen (1590), both flirted with telescopes, but it was very possibly Galileo who first used the telescope and the compound microscope fruitfully.64 Following his first telescope in 1608, which has already been mentioned, a year later he made microscopical observations on tiny objects. In 1637, when Descartes published his Discourse on Method, it contained an appendix with printed pictures of microscopes.
This was all prologue. The first clear descriptions of minute living organisms were published by Athanasius Kircher in his Ars magna lucis et umbrae, released in 1646. There, he says that with the aid of two convex lenses, held together in a tube, he observed ‘minute “worms” in all decaying substances’–in milk, in the blood of persons stricken with fever, and in the spittle ‘of an old man who had lived soberly’.65 In this way Kircher anticipated the germ theory of disease. He was followed by the Dutchman Antony van Leeuwenhoek of Delft, who in the course of his life made several hundred microscopes, some of which, it was said, could achieve magnification of up to 270 times.66 At his death Leeuwenhoek left a couple of dozen of his instruments to the Royal Society of London, which had published a good deal of his work, and where he was elected a Fellow.67 These microscopes account for his great success as an observer. Beginning in 1673, when Leeuwenhoek was forty-one years of age, and throughout his career, he sent 375 letters to the Royal Society.68 Out of these, William Locy tells us, three in particular stand out. ‘These are his discovery of protozoa, of bacteria, and his observation on the circulation of the blood.’ ‘In the year 1675,’ Leeuwenhoek wrote, ‘I discover’d living creatures in Rain water, which had stood but a few days in a new earthern pot, glazed blew within. This invited me to view the water with great attention, especially those little animals appearing to me ten thousand times less than those represented by Mons. Swammerdam, and by him called Water-fleas or Water-lice, which may be perceived in water with the naked eye…The first sorte by me discover’d in the said water, I divers times observed to consist of 5, 6, 7, or 8 clear globules, without being able to discern any film that held them together, or contained them. When these animalcula or living Atoms did move, they put forth two little horns, continually moving themselves…’ Regarding size, Leeuwenhoek said that some of the ‘animalcula’ in question were ‘more than 25 times less than a globul of blood’. One philosophical implication of this was that it seemed to supply the long looked-for bridge between visible organisms and inanimate nature.69 Other observers soon followed and, by 1693, the world was given the first drawings of protozoa. For quite some time, little distinction was made between protozoa, bacteria and rotifers and even in the eighteenth century Linnaeus, who did not use the microscope, completely misconceived micro-organisms, placing them together in a single group which he called ‘Chaos’.70
But in 1683, Leeuwenhoek discovered an even smaller form of life–bacteria. He had first observed them two years before but made careful drawings before he dared publish his discovery. (These too appeared in the Philosophical Transactions of the Royal Society.) The drawings were essential because they make it clear that he had indeed observed the chief forms of bacteria–round, rod-shaped and spiral forms.71 Here are some details from his letter: ‘Tho my teeth are kept usually very clean, nevertheless when I view them with a Magnifying Glass, I find growing between them a little white matter as thick as a wetted flower: in this substance tho I could not perceive any motion, I judge there might probably be living Creatures. I therefore took some of this flower and mixt it either with pure rain water wherein were no animals; or else with some of my Spittle (having no Air bubbles to cause a motion in it) and then to my great surprise perceived that the aforesaid matter contained very many small living Animals, which moved themselves very extravagantly.’72
Leeuwenhoek’s final triumph was his visual confirmation of the circulation of the blood. (Harvey, remember, had never actually seen the circulation of the blood through the capillaries. He had attempted to fit the final piece of the jigsaw–via the comb of a young cock, for example, the ears of a rabbit, the membranous wing of a bat. But that final observation had always eluded him.73) Then, in 1688, Leeuwenhoek trained his microscope on the transparent tail of the tadpole. ‘A sight presented itself more delightful than any mine eyes had ever beheld; for here I discovered more than fifty circulations of the blood in different places, while the animal lay quiet in the water, and I could bring it before my microscope to my wish. For I saw that not only in many places the blood was conveyed through exceedingly minute vessels, from the middle of the tail toward the edges, but that each of the vessels had a curve or turning, and carried the blood back toward the middle of the tail, in order to be again conveyed to the heart.’74 Nor should we overlook Leeuwenhoek’s discovery, in 1677, of spermatozoa, though it would be another century before their true role was identified. Leeuwenhoek was the first person to make biologists aware of the vast realms of microscopic life.75
In biology, the seventeenth century proved to be as fertile as it was in physics. In 1688 Francesco Redi showed that insects were not the result of spontaneous generation, as had been thought, but developed from eggs laid by fertilised females. As early as 1672 Nehemiah Grew had speculated on the role of pollen as an agent in fertilisation in plants but it was not until 1694 that Rudolf Jakob Camerarius demonstrated, in his De sexu plantarum epistola, that anthers are the male sex organs in plants, and confirmed through experimentation that pollen (and very often wind) was needed for fertilisation. Camerarius showed himself well aware that sexual reproduction in plants was just the same in principle as in animals.76
Francis Bacon (1561–1626) and René Descartes (1596–1650) are both intermediary figures, in the sense that they lived their entire lives between the publication of Copernicus’ De revolutionibus and Newton’s Principia Mathematica. But they were not intermediate in any other sense: both were radical thinkers who used the scientific findings of their own day to move philosophy forward to accommodate the recent discoveries, and in so doing anticipated much of the world that Newton finally identified.
As Richard Tarnas, among others, has pointed out, there have been three great epochs in Western philosophy. During the classical era, philosophy–though influenced by the science and religion of the day–was a largely autonomous activity, mainly as a definer and judge of all other modes of activity. Then, with the advent of Christianity, theology assumed a pre-eminent role and philosophy became subordinate to that. With the coming of science, however, philosophy transferred its allegiance from theology–and this is still more or less where we are today.77 Bacon and Descartes were the main figures in bringing about this latest phase.
Francis Bacon wrote a number of works in which, in effect, he proposed a society of scientists, exploring the world together by experiment and showing no especial concern for theory (and none at all for traditional theory). Chief among these books were the Advancement of Learning (1605) (dedicated to James I), the Novum Organum (1620), and the New Atlantis (1626). Socrates had equated knowledge with virtue but for Bacon, a man of the world as well as a philosopher, it was to be associated with power–he had a very practical view of knowledge and this in itself changed
beliefs about and attitudes to philosophy. For Bacon, science in itself became an almost religious obligation and, since his view was that history is not cyclical but progressive, he looked forward to a new, scientific civilisation. This was his concept of ‘The Great Instauration’, the Great Renovation, ‘a total reconstruction of the sciences, arts, and all human knowledge, raised upon the proper foundations’.78 Bacon shared the view of many contemporaries, that knowledge could only be built up by the observation of nature (rather than through intuition or ‘revealed’ knowledge), starting from concrete data rather than abstractions that had just occurred to someone. This was his main criticism of both the ancients and the schoolmen and what he most wanted to jettison before moving on. ‘To discover nature’s true order, the mind must be purified of all its internal obstacles.’79 But Bacon also thought that the understanding of the High Middle Ages and of the Renaissance–that the study of nature would reveal God, by disclosing the parallels between man’s mind and God’s–was wrong. Matters of faith, he felt, were appropriate to theology but matters of nature were different, with their own set of rules. Philosophy, therefore, had to dispense with theology and go back to basics, examining the detailed findings of science and using those as the basis for further reasoning. This ‘marriage’, between the human mind and nature, was the basis of the modern philosophical approach. Bacon’s view had a major influence on the fledgling Royal Society. ‘It has been estimated that nearly 60 per cent of the problems handled by the Royal Society in its first thirty years were prompted by practical needs of public use, and only 40 per cent were problems in pure science.’80
