Mind

The modern study of the body's functions began with the work of the English physician William Harvey (1578–1657). Harvey trained at the University of Padua, where he learned Aristotle's methods of comparative zoology and functional anatomy. He returned to England and eventually became a royal physician to James I and Charles I, during which time he discovered the circulation of the blood.

As important as this discovery was, however, Harvey's methods were even more significant. He did not rely solely on Galen (129–c. 199 C.E.) or some other ancient source. Rather, he searched for confirmation of his hypothesis in comparative studies on animals and through experiments. By the 1650s, young natural philosophers were emulating Harvey, not Aristotle, as they studied the liver, lungs, and other organs of the body. And in the early 1660s, a group of Harvey's disciples applied his methods to the brain.

These natural philosophers were led by an Oxford physician named Thomas Willis (1621–1675). A royalist soldier during the English Civil War, Willis had been rewarded at the Restoration with an appointment as professor of natural philosophy at Oxford. He used the new position to embark on a bold project—to seek out the hiding place of the mind. Based on a decade of previous research, including dissections, chemical experiments, and medical observations, Willis decided that the most promising way to study the mind was to make a careful study of the brain.

Willis enlisted a number of colleagues, including his junior medical partner Richard Lower (1631–1691) and his young friend Christopher Wren (1632–1723). They dissected brains of humans, dogs, sheep, and other animals, and Willis recorded their work in his 1664 book The Anatomy of the Brain, the first major work on the brain ever written. Over the next eight years he would rely on both his anatomical discoveries and his careful bedside observations to write Pathologiae Cerebri (Cerebral pathology), a book on convulsive disorders, and Two Discourses Concerning the Soul of Brutes, on neurological and psychological disorders.

Together, this trilogy stands as a defining moment in neuroscience. (Indeed, Willis even coined the word neurology.) Willis dismissed Descartes's notions of the pineal gland and ventricles, demonstrating that these chambers could not possibly house the spirits. The brain itself was the site of mental functions, Willis argued, and he carried out experiments to show that different functions were localized in different regions. Instead of Descartes's speculative sketch of involuntary movements, he offered a far more accurate account of reflexes.

Willis also added chemistry to Descartes's mechanical nervous system. As a young physician, Willis had been strongly influenced by the work of alchemist-physicians such as Paracelsus (1493–1541) and Jan Baptista Van Helmont; he also worked with the Irish chemist Robert Boyle (1627–1691) in 1650s Oxford. Willis envisioned the brain as an alembic (an apparatus alchemists used to distill substances), and he conceived of the brain's disorders as disorders of chemistry. He saw epilepsy, for example, not as demonic possession, but as uncontrolled explosive reactions in the brain and nerves.

In the decades around the turn of the twenty-first century, neuroscientists looked back at Willis's work with growing admiration. He has even been called the Harvey of the nervous system. Not only did Willis create a masterful theory of the brain, but in his writings scientists can see the first clinical descriptions of a wide range of neurological conditions, ranging from myasthenia gravis to narcolepsy. By the late seventeenth century, the work of Willis and continental anatomists such as Nicolaus Steno (1638–1686) and Franciscus dele Bo Sylvius (1614–1672) had led most physicians to accept the basic tenets of neurology.