A Little History of Science: Uncovering the Human Body

The following is an excerpt from A Little History of Science.

If you want to really understand how something is made, it is often a good idea to take it apart, piece by piece. With some things, like watches and cars, it helps if you also know how to put them back together again. If what you want to understand is a human or an animal body, it has to be dead before you start, but the goal is the same.

Galen, as we know, dissected – took apart – many animals, because he couldn’t dissect any humans. He assumed that the anatomy of pigs or monkeys was pretty much like that of human beings, and in some ways he was right, but there are differences, too. The dissection of human bodies started to be done occasion­ally around 1300, when medical schools began to teach anatomy. At first, when people noticed any differences between what they saw in the human body and what Galen had said, they assumed that human beings had simply changed, not that Galen had been wrong! But as they began to look more closely, anatomists discovered more and more small differences. It became obvious that there was more to uncover about the human body.

The man who did the uncovering was an anatomist and surgeon known to us as Andreas Vesalius (1514–64). His full name was Andreas Wytinck van Wesel. He was born in Brussels, in modern-day Belgium, where his father was a medical man employed by the German Emperor Charles V. A clever child, he was sent to the University of Louvain to study arts subjects, but decided to change to medicine. Clearly ambitious, he then went to Paris where some of the best teachers were. They all followed Galen, and during his three years there he impressed them. He also showed his abilities in Greek and Latin, and his fascination with dissection. A war between the German Empire and France forced him to leave Paris, but he reintroduced human dissection to the medical faculty at Louvain before travelling, in 1537, to what at the time was the best medical school in the world, at the University of Padua in Italy. He took his exams, passed with the highest distinction, and the next day was appointed as a lecturer in surgery and anatomy. At Padua they knew when they were on to a good thing: Vesalius taught anatomy through his own dissections, the students loved him, and the very next year he published a series of beautiful anatomical illustrations of parts of the human body. They were so good that doctors all over Europe began copying these pictures for their own use, much to Vesalius’s annoyance, since they were actually stealing his work.

Andreas Vesalius' De Humani Corporis Fabrica, p. 559

Cutting open a dead body is not a particularly pleasant thing to do. After death, the body quickly begins to decay and smell and, in Vesalius’s time, there was no way to stop it from rotting. This meant that the dissection had to be done quickly, and in an order that made it possible to get it done before the smells became over­powering. The belly was done first, since the intestines are the first to rot. This was followed by the head and brain, then the heart, lungs, and other organs in the chest cavity. The arms and legs were saved to the end: they lasted the best. The whole thing had to be done in two or three days, and anatomy was generally taught in winter, when the colder weather at least delayed the decay and gave the doctors a little more time.

Means of preserving bodies were discovered in the 1700s, and this made it easier to take more time to dissect and examine the whole body. When I was a medical student, I took eight months to dissect a body, and on dissection days my clothes and fingernails smelled not of the rotting body but of the preserving chemical. I worked on the body of an old man and I became very familiar with him during those months. The order we did things was pretty much the same as it was in Vesalius’s time, except we saved the brain for last, since it is such a complicated organ and we were supposed to be better at carefully cutting out and exposing the different parts of the body by then. The old man had donated his body to science. He certainly taught me a lot.

Despite the speed needed, and the smells he confronted, dissec­tion was Vesalius’s great passion in life. We cannot know how many bodies he carefully cut apart, but it must have been many, for he came to know more about the parts of the human body than anyone then alive. The five and a half years between the time Vesalius became a teacher in Padua and the publication of his great book, in 1543, were very busy. Vesalius’s book is enormous, forty centime­tres high and weighing nearly two kilograms – not exactly a paper­back you could slip in your pocket for holiday reading. It was called De Humani coporis fabrica (‘On the structure of the human body’), and it is still known as De Fabrica. It was beautifully and intricately illustrated. Vesalius travelled to Basel, in Switzerland, to supervise the printing of the text and the making of the illustrations.

We live in a world where illustrations are everywhere. Digital cameras make it easy to send pictures to our friends, and maga­zines and newspapers have pictures on every page. It was not like that in Vesalius’s day. The printing press had been invented less than a hundred years before, and pictures had to be made from carefully carved blocks of wood, copied from a drawing. Like a rubber stamp, these blocks were then inked and pressed on a piece of paper.

Detail from De Fabrica: Vesalius publicly dissecting a female corpse.

The pictures in Vesalius’s book are staggering: never before had the human body been depicted so accurately, or in such detail. Even the title page tells us that something special is happening. It shows the dissection of a woman, in public, with hundreds of people crowding around. Vesalius stands in the middle, by the woman’s body, and he is the only person looking out at the reader. The rest of the audience is either fascinated by the dissection or gossiping with each other. On the left of the picture is a monkey, on the right a dog, reminders that Galen had had to use animals for his anatomical work. In his own book, Vesalius is talking about human anatomy, from human bodies, and doing the dissecting himself. It was a wonderfully daring thing for a young man of not yet thirty.

But, then, Vesalius had every reason to be confident. He knew that he had seen further into the human body than anyone. Among the magnificent pictures in his book are those showing the muscles of the body, front and back, with the muscles nearer the surface dissected away to expose the deeper ones. These ‘muscle men’ are posed against landscapes, and the buildings, trees, rocks and hill­sides in the pictures all join up. One of Vesalius’s muscle men is being hanged by the neck, a reminder that Vesalius often used criminals for his dissections. Indeed, he once found a criminal who had been hanged and his body had been picked clean by birds, leaving only his skeleton. Vesalius smuggled the bones back to his room one by one, in order to study in private.

Vesalius had a very skilled artist to work with him, although we don’t know his name for sure. Science was closely linked with art during this period, which we call the Renaissance, ‘re-birth’. Many Renaissance artists – Leonardo da Vinci (1452–1519), Michelangelo (1475–1564), and others – dissected bodies in order to learn how to paint them better. Doctors weren’t the only ones who wanted to know about the structure of the human body.

Vesalius was fascinated by the structure (anatomy) of the body, but dead bodies do not carry out functions (physiology) like breathing, digesting and moving, as living ones do. So the long written part of Vesalius’s book was a mix of old and new ideas. He often pointed out how Galen had described some organ or muscle incorrectly and he set it right. For instance, when Galen described the liver, he was talking about the pig’s liver, which has five distinct ‘lobes’, or sections. The human liver has four, which are not so clearly defined. Several muscles in human hands and feet are different from those of even our close kin, monkeys and apes. Galen’s theory of how the blood moves required a little of it to move from the right side of the heart to the left; he had it seeping through tiny pores in the wall between the two big chambers (ventricles) of the heart. Vesalius dissected many human hearts and could not find these pores. His knowledge would be very important a few decades later when William Harvey began to think in more detail about what the heart and blood do. Yet Vesalius’s discussion of how the living body works still used many of Galen’s ideas. This is perhaps why Vesalius’s pictures were so much more valued than his writing: the pictures were soon copied and used throughout Europe, and made Vesalius famous (even if they did not earn him much money).

Although he lived for another twenty years, the publication of his great book was the highlight of Vesalius’s career. He did produce a second edition of the book, with a few corrections, but soon after the first edition was published, he went off to be a court doctor. He spent his time taking care of the rich and powerful. Perhaps he thought he had said everything he had to say.

He had said and done enough to make sure that he was remem­bered. De Fabrica remains one of the great books of all time: a combination of art, anatomy and printing that is still admired today. And with it Vesalius left us two permanent gifts. First, he encouraged other doctors to continue his minute descriptions of the structure of the human body. Later anatomists discovered other parts of the body that Vesalius had missed, or corrected errors that he had made. The mix of artistic presentation and careful dissection that he had started encouraged others to produce books that illustrated the body on the page. Vesalius’s book was the first in which the pictures were more important than the writing, but it was not the last. Doctors needed to be taught how to see what was before them, and pictures were essential to help them learn.

Second, Vesalius stood up to Galen. He wasn’t rude about him, like Paracelsus, but he quietly showed that one could know more than Galen had. He showed that knowledge can grow from genera­tion to generation. He helped begin a debate that lasted for more than a hundred years. The question was simple: Can we know more than the Ancients? In the thousand years before Vesalius, the answer had been No. After Vesalius, the answer began gradually to change. People started to think: ‘If everything worth knowing has already been discovered, what’s the point of bothering? But if I look for myself, maybe I can see something that no one else has seen.’ Vesalius encouraged doctors and scientists to start bothering.