Soul searching

It is perhaps surprising, given the contemporary eminence of neuroscience within biological research, that it was not appreciated until the 17th century that the brain might have an important function. A compelling new book by Carl Zimmer surveys the scientific, conceptual and political upheavals in England at this time as a backdrop to the major experimental work carried out by a little-known doctor, Thomas Willis in Oxford, who was key to unravelling the beginnings of our modern view of the brain. Aristotle dominated ‘natural philosophy’ for 2,000 years, but he had little interest in the kind of theories you could test. He explained the world by the ends not the means which did not teach one to look closely at the detail. The Greeks, for example, had a horror of dissecting people. This didn’t prevent them from offering an account of human biology in which the heart served as the seat of reason, and the brain simply ‘temper[ed] the heat and seething of the heart’. ‘Aristotle’s rational soul was both nowhere and everywhere in the human body. Yet Aristotle also believed that specific parts of the body carry out its faculties. He scoffed at the idea that the brain could be such a place, since he saw from his dissections that many animals had no visible brain at all but could still perceive the world and give rise to actions... without freezers or formaldehyde to halt its decay, a brain quickly takes on the look and feel of custard hardly the stuff of reason and will,’ writes Zimmer. The second-century physician Galen mapped the body by dissecting animals and looking at the open wounds of gladiators. When, in 1537, Andreas Vesalius, a lecturer in anatomy at the University of Padua, began to sketch his dissections of human cadavers, he found that people were not made from the animal organs described by Galen. Nonetheless the heart held conceptual sway as a key to the source of thoughts and feelings. But in 1600, the young English doctor William Harvey studied at Padua. His eventually discovery that the ‘heart sends blood through the body in a loop’ and functioned basically as a pump sent out philosophical shockwaves. Harvey later served as a physician to the English king, Charles I, who introduced him to Viscount Montgomery. Montgomery had fallen from a horse when he was a boy, leaving a gap in his ribs, subsequently covered by a metal plate, which he was able to remove for Harvey. ‘I immediately saw a vast hole,’ Harvey wrote, and he was able just to observe the beating heart. I was almost tempted to think... that the motion of the heart was only to be comprehended by God.’ It is understandable, then, that Harvey had trouble persuading his peers of his breakthrough. As civil war loomed, Harvey followed Charles I to Oxford as loyalists and puritans grouped around their centres of support before the battles ahead. Harvey began teaching his theories to some of the students, including a young man named Thomas Willis, who had recently decided to pursue a career in medicine rather than the Church. Harvey now had his disciples, determined not only to trace the course of blood through the body but to follow his experimental methods. Willis eventually tracked the flow of blood to the brain. In attempting to understand its function there, he gave the first account of the network of nerves and blood vessels on which our understanding of that organ is based. By comparing the brains of humans and animals, he found that the brain of a fish or a cow had the same basic architecture as a human’s a medulla, Soul searching