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The first brain wave

SOUL MADE FLESH: The Discovery of the Brain _ and How It Changed the World

By Carl Zimmer

Free Press, $26, 384 pp

Reviewed by TOM VALEO

Most historians adopt the Great Man approach to history. They assume history is propelled by a few exceptional people who guide the destiny of the human race.

The opposite is true, of course _ historical forces drive the lives of every human, including those who make it into the history books. The people we deem great may possess exceptional talents, but they get carried along by the waves of change just like everyone else. Their accomplishments usually depend as much on luck as on skill.

In Soul Made Flesh: The Discovery of the Brain _ and How It Changed the World, Carl Zimmer shows how historical forces affected the destiny of Thomas Willis, the 17th century English physician who essentially invented the study of the brain. Instead of presenting a close-up of Willis, however, Zimmer places him within a panoramic history of England during a period of political upheaval, civil war, religious ferment, plague and assorted other stresses. Zimmer provides so much historical context that at times Soul Made Flesh resembles Where's Waldo? with Willis, like the title character of those children's books, appearing as one small figure among the teeming masses.

Historical forces altered the arc of Willis' life at every stage. He attended Oxford University, for example, but ended up guarding the city walls against Parliamentary armies during the Civil War. The war also disrupted the traditional curriculum, freeing Willis from Aristotle and other ancient authorities on the natural world. The restoration of the monarchy provided Willis _ a loyal Royalist who always supported the king _ with the political protection needed to publish works that some religious zealots considered scandalous. And the creation of the Royal Society for Promoting Natural Knowledge in 1660, just as Willis was achieving his greatest insights into the brain, extended the influence of his work.

What influenced Willis even more, however, were the exceptional people who crossed his path.

One of his teachers at Oxford was William Harvey, who discovered that the heart pumped blood through the body in a loop. A good friend, William Petty, introduced Willis to dissection, which aroused the enthusiasm of an artist friend named Christopher Wren, who went on to become England's greatest architect. (Willis used Wren's beautiful drawings of the brain to illustrate The Anatomy of the Brain and Nerves, and Zimmer reproduces a Wren drawing at the front of each chapter.) Robert Boyle, fascinated by alchemy, brought the wonders of chemistry to Willis and the circle of friends they assembled at Oxford.

These friends generated a synergy that pushed Willis toward a modern approach to science based on the logical inferences he drew while dissecting corpses. He noticed, for example, that four arteries converged at the base of the brain, forming what has become known as the Circle of Willis. To test his hypothesis that this circle enabled the four arteries to share blood, he tied off three of the four arteries in a dog, which not only recovered from the operation but behaved normally, with only one artery supplying blood to its brain.

Willis wanted to explain the human body "without recourse to occult qualities, sympathy, or other refuges of ignorance," as he put it. Yet, despite his modern approach to scientific discovery, Willis did not completely transcend the conventional wisdom of his time. To treat lesions caused by the plague, for example, he recommended that "live frogs be apply'd and renew'd as oft as they die."

Such bizarre advice shows that Willis remained firmly rooted in his epoch, but by allowing his curiosity to roam freely _ and by receiving a few lucky breaks from the forces of history _ he managed to launch an investigation into the brain that neurologists carry on to this day.

Tom Valeo is a freelance writer who divides his time between Chicago and St. Petersburg.