Authors: Hugh Aldersey-Williams
Now, to the mystery. Bone exhibits a curious effect known as piezoelectricity. This means that it generates a small electric field when a force is applied to it. This is what happens around the tiny cracks that form when a bone is stressed. Although the details remain unclear, it seems that this effect must be the key to the ability of bones to remodel themselves. New bone cells are created by precursors known as osteoblasts, which carry a positive electric charge owing to the bone-building calcium ions they bring with them. Stress placed on existing bone during exercise generates a negative charge by means of the piezoelectric effect, which then automatically draws these osteoblasts to the site where they are most needed. It is a detail that would have delighted William Paley.
Like Paley, perhaps, we are apt to think of the skeleton as the perfect architectural frame, and so with minor variations it is for most of us. To get a sense of what a wild ride it is to grow a proper skeleton, it is necessary to visit an anatomical collection, such as the one kept at the Royal College of Surgeons in London, which holds the skeleton of a victim of a rare genetic condition called fibrodysplasia ossificans progressiva, in which muscle tissue turns to bone, producing massive calcareous overgrowths that accrete over years, leading to complete immobility. I am forced to acknowledge that the skeleton is not a rock-hard armature like the steel frame of a building, but an entirely organic florescence, subject to shaping by chemicals and external forces.
The ability to grow bone tissue in laboratory conditions is now an attraction to artists. In 2005, for example, Tobie Kerridge, then at the Royal College of Art in London, sought out couples who were interested in a new kind of love token – rings made from the bone tissue of their partner. Potential participants in his Biojewellery Project had to be people who were both due to have their wisdom teeth removed. From small fragments of bone removed during the normal procedure of the tooth extraction, Kerridge was able to culture new bone tissue, which grew and hardened on a ring-shaped scaffold over a period of several weeks, fed by suitable nutrients. Each romantic partner was then able to wear a ring that is a ‘part’ of the other. ‘I cannot imagine anything more intimate, anything more symbolic of our bond, as two individuals, to each other,’ wrote one applicant for the project. The couples have various motives for taking part. One pair are materials scientists, another are protesting at the diamond trade, while a third are body piercers taking that art to inner depths. The rings were designed with the participation of the wearers, and carved and decorated in ways that inevitably evoke the 30,000-year human history of working and wearing bones for tools and decoration.
It is the background details in the magnificent illustrations to Vesalius’s seven volumes of human anatomy that tell his own story. Engraved on pear wood by an unknown Venetian artist, possibly a pupil of Titian, more than 200 drawings show the body and its parts in all stages of dissection. Vesalius’s detailed accompanying text discusses the appearance and functions of these parts, mingling his own discoveries with the respected opinions of Classical scholars and autobiographical anecdotes. When it came out in 1543,
De Humani Corporis Fabrica
became, as its author intended, the most scientifically accurate and complete encyclopedia of the human body ever published – or that would be published for a very long time. The principal subject matter is delineated in a bold and clear manner that is well matched to Vesalius’s objective, namely to instruct and enlighten. But there is drama and pathos in the pictures, too. In drawings showing the muscles, for example, flayed skin remains hanging from the body like the drooping clocks of Salvador Dalí. In diagrams of the internal organs, opened torsos have their limbs sharply cut off like the statues of Classical antiquity. The organs heave with visceral realism, but the stumps of these arms and legs are shaded to suggest they are made of sculptor’s marble rather than flesh and bone. These illustrations are a perfect fusion of art and science.
The only portrait of Vesalius known to be authentic is contained in one of these woodcuts. It shows him holding a dissected forearm upon which he is demonstrating the working of the hand. (It is certain that both Tulp and Rembrandt were familiar with this likeness.) He is compact and dark-complexioned with wiry, close-cropped hair and an immaculately trimmed beard. His head seems too large for his body, which is certainly diminutive compared with the cadaver he is working on. He turns towards us out of the page and fixes us with a direct glance that has more than a little impishness in it. His attitude chimes with the grim humour in some of the other drawings. In one, a muscled body stands knife in hand, triumphantly holding aloft his own excoriated skin. In another, a skeleton man leans nonchalantly on his spade having apparently effected his own disinterment. He gestures with his free arm as if to say, ‘Well, what of it?’
But, as I say, it is the little details that are revealing about the man. Hills in the background of this illustration have been identified as those close to Padua, where, in 1537, at the exceptionally young age of twenty-three, Vesalius acceded to the chair of surgery and set about making anatomy central to the curriculum of the most important medical school in Europe. Roman ruins appear in many of the illustrations, perhaps symbolizing Vesalius’s demolition of the work of Galen, the Greek physician and anatomist active in Rome during the second century
, whose writings had dominated medical understanding for nearly 1,400 years.
One engraving is organized so as to present a skeleton in side view. This is the illustration that contains the Hamlet pose, with the skeleton resting its right hand on a skull, which in turn rests on a tomb. The tomb bears the inscription ‘VIVITUR INGENIO CAETERA MORTIS ERUNT’, an old Latin aphorism which can be taken impersonally to mean ‘Genius survives, the rest belongs to death’, but might be taken to refer to Vesalius’s immodest hope that
genius might outlive his rivals’. Behind the skeleton, the stump of a bush is sprigging, indicating that life is both cut off and renewed, a motif that appears in quite a few of the engravings.
In the first illustration of the volume of the
devoted to the muscles, two putti appear around a decorated initial capital letter in the text. If you look closely, you notice they are no angels, but in fact body-snatchers. Just for fun, it seems, a subsequent illustration chooses to suspend its anatomical subject by a rope, as if it has been hanged, although the rope passes not around the neck but through the eye sockets in such a way as to pull back the head in order to expose the muscles of the throat to the viewer’s gaze. The pictures are a reminder not only of the roughness of the times but of the methods to which Vesalius had to resort in order to obtain his research materials. He tells the story of how he stole the remains of a criminal from the gibbet outside Leuven, the Flemish university city where he studied before moving on to Paris and Padua. One day, he goes for a walk ‘where the executed criminals are usually placed along the country roads – to the advantage of the students’. He comes across a dried cadaver, its flesh picked away by birds. ‘Consequently the bones were entirely bare and held together only by the ligaments so that merely the origins and insertions of the muscles had been preserved.’ With the help of a physician friend, he climbs up the post and pulls the thigh bone away from the hip, takes down the shoulder blades with arms and hands attached and brings the parts home ‘surreptitiously’, making several trips. He leaves behind the head and trunk, which are secured to the gibbet by a chain. But one night soon after, he allows himself to be shut out of the city so that he has time to liberate the rest of the body undisturbed while it is dark. ‘So great was my desire to possess those bones that in the middle of the night, alone and in the midst of all those corpses, I climbed the stake with considerable effort and did not hesitate to snatch away that which I so desired.’ He conceals the retrieved bones on the ground, and then ‘bit by bit’ takes them home as well, so that he is able to reassemble the complete skeleton in his bedroom, making up its few missing parts – a hand, a foot and both kneecaps – from other miscellaneous body remains.
Andries van Wesel, his name Latinized as Andreas Vesalius, was born in 1514 in Brussels, the son of an apothecary, and trained in medicine at the University of Paris. Through direct observation, Vesalius largely reinvented the study of human anatomy, modernizing the understanding of Galen, the greatest medical thinker of the Classical period. Galen had brought from Greece the ideas of Aristotle and Hippocrates, the latter still regarded today as the founder of scientific medicine thanks in no small part to Galen’s championing of him, and rose in Rome to become the personal physician of the emperor Marcus Aurelius. Galen’s concept of the body, formulated in ancient Greece and persisting throughout the Roman Empire and the rise of Christianity, was one of significant parts – chief among them the brain, heart and liver, which respectively governed the bodily compartments of the head, thorax and abdomen. These parts were bound together by the four humours (blood, phlegm, black bile and yellow bile) and a thinner fluid, the spirit, which accounted for the existence of the soul. It was what we might call today a holistic view.
Galen’s works had been rediscovered and published in Paris shortly before Vesalius arrived there as a medical student. Vesalius supported this revival, building on it with his own dissections, but also uniquely dared to refute Galen when the evidence of his own eyes did not correspond with the Classical view. An anatomical feature called the
– the ‘wonderful net’ – illustrates the shift in understanding. The
is a mesh of veins and arteries found wrapped around the brain in species as varied as sheep and apes. Galen and others believed it was a conduit for the spirit, and Christians subsequently accepted it as the interface between body and soul. Vesalius’s early dissections of animals gave him no reason to dispute this, but when he came to perform human dissections while preparing the
in Padua, he could not find the
, and boldly denied its existence in humans. Vesalius’s questioning of Galen was a signal moment not only in the study of anatomy, but also in modern science, implanting the thought that while the Greeks provided a valuable foundation, their ancient knowledge was not unsurpassable. Vesalius was nevertheless careful at first not to alienate his Galenist peers and elders, and it was only in the second edition of the
, which appeared in 1555, that he finally pointed out the error.
We can hardly wonder that medicine made little progress while so many of its ideas of anatomy were based on dissections of animal rather than human parts. Vesalius criticized Galen for this, but was not unknown to take similar shortcuts himself. His plan for the
was to verify everything by reference to the human body, but the shortage of cadavers occasionally drove him to rely on previous published sources or on animal dissections. Although he was the first to describe the prostate gland, Vesalius was generally weak on the reproductive system. His anatomy of the uterus, apparently based on a ‘monk’s mistress whose body was acquired by dubious means’, was reliable enough, but his section on the pregnant anatomy was poor, owing to the paucity of human specimens, pregnant women tending to be healthy women, and his illustration of a human foetus was disgracefully accompanied by a drawing of a canine placenta.
revealed the body’s interior as a terra incognita ripe for exploration. Anatomical voyagers now set sail to claim its territories, naming body parts like new channels and islands as they went. Vesalius’s pupil Falloppio made up for his master’s shortcomings by charting the female reproductive system; as we have seen already, the tubes between the uterus and the ovaries, though actually described long before, are now named after him. Eustachi did the same for the ear. Even Nicolaes Tulp got in on the act: Tulp’s valve is the puckered portal between the small and large intestines that regulates the passage of digested food waste.
The X-marks-the-spot approach to human anatomy makes a number of dangerous assumptions. It assumes, for example, that identified parts have a distinctive composition or function. This is only sometimes true. It also creates a sense of dividedness, where interconnection may be what matters. Major organs may seem to have a distinct nature and yet are multiply integrated with other parts of the body. ‘Bits in between’, meanwhile, such as the diaphragm, say, which separates the organs of the chest from those in the abdomen, may be unfairly neglected because they are not seen as forming suitable discrete units.
Carving the body up into parts does have some important advantages. A reductionist approach was essential in order for scientific progress to begin properly to understand the true functions and overturn the old symbolic model of the organs, for example. But it also introduced some troublesome new thoughts. The idea of the human body as a kind of kit that can be taken apart disturbs us because it finds, when all the parts are laid out, that the all-important soul which once seemed to inhabit the body has somehow disappeared. Disassembly also sets up the possibility that a body might be
– Victor Frankenstein created his monster from body parts (presumably both human and animal) stolen from ‘charnel-houses . . . dissecting room and the slaughter-house’. Mary Shelley describes the ‘miserable monster’ very sparingly. ‘His limbs were in proportion, and I had selected his features as beautiful,’ she has Frankenstein recount. But of course, when it comes to ‘bestowing animation’, those beautiful parts join to make a horrible, soulless whole.
To investigate how the body actually worked, it was natural to start with the heart, the most dynamic of all the organs, full of moving parts driven by powerful muscles. Body function was fortunately an area where comparison with animals was on safer ground than anatomizing. Vivisection became an important tool. Human vivisection, once practised in ancient Alexandria, was ruled out by the teachings of the Christian church, but there was no restriction on experiments using living animals. If the same organ was observed to respond in a similar way in enough animals of different kinds then this could be taken to be general behaviour that would be found in humans too.
In the mid 1540s, Realdo Colombo, Vesalius’s successor in the chair at Padua, gave the first detailed description of pulmonary circulation, the passage of blood via the lungs from one chamber of the heart to the other. (Much later it was learned that Ibn al-Nafis of Damascus had discovered this more than 300 years before.) Vesalius and others had accepted the Galenic belief that blood must pass directly through pores in the muscle wall that separates these chambers, although nobody had observed these pores. Colombo’s vivisections showed that spent blood in fact leaves the right chamber of the heart altogether, and travels via an artery to each lung, while veins from the lungs bring fresh blood into the left chamber. Apart from anything else, Colombo’s discovery offers a dramatic illustration of the gains that can be made when organs are not regarded as entirely self-contained. Aristotle had held that the blood in the left chamber is cold and that in the right is warm. Colombo was able to correct this. Blood entering the left chamber of the heart is warmer because, as we now know, it has been replenished with oxygen whose reaction with haemoglobin releases heat. He was also able to show that the most important action of the heart is the vigorous contraction that squeezes out the blood and not its subsequent expansion.