History has a way of repeating itself — even the history of science. Today we are
witnessing a revolution in neuroscience, as researchers chart the circuitry of memory,
cognition, and emotion, offering the promise of a chemically based medicine of the mind
). But these same words would have been just as apt over 300 years ago, when
neurology first emerged as an experimental science (
). In the mid-1600s, humanity's
understanding of the brain changed no less profoundly than it is changing today.
Medieval concepts of the soul and spirits rapidly disappeared, replaced with a vision of
the brain based on anatomy, chemistry, and physics.
Gazing into this distant mirror, we can see how many of the themes of modern
neuroscience can actually be traced back to a time long before the luxuries of
electroencephalograms (EEG) or magnetic resonanice imaging (MRI) existed. We can
admire the brilliance of the minds that created a science of the mind itself. But not
everything we see in this mirror is beautiful. The first neurologists did not hesitate to leap
from scant evidence to wild speculation. They believed that the biology of the brain
justified the social divide between the powerful and the powerless. And although they
promised that neurology would usher in new treatments for madness and other mental
disorders, they did nothing of the kind: In the late 1600s, neurology often served as a new
bottle for ancient wines.
It is difficult to appreciate just how unimportant the brain was considered to be before the
scientific revolution. Medieval and Renaissance physicians sought to understand the
mind with a mix of Christian theology and Greek philosophy. The body was believed to
be divided into three anatomical regions, each designed for its own soul. The vegetative
soul in the liver was responsible for desires and appetites. The heart housed the vital soul,
which produced passions and action. The rational soul was immaterial and immortal and,
hence, could not reside in one specific place in the body. But its faculties — such as
reason, memory, and imagination — were carried out by the body's invisible spirits.
These spirits were believed to swirl in three hollow chambers in the head known as the
Anatomy, then, was the study of the houses of the souls. But anatomy alone was not
enough to account for the life of the mind. Physicians also had to understand the fluids
that coursed through the body. The four humors — black bile, yellow bile, blood, and
phlegm — needed to be balanced for good health. Humors also gave each individual his
or her temperament, be it the sad detachment of melancholy or the swift rage of choler. If
the humors became corrupted or moved to the wrong place in the body, they could cause
epilepsy or alter the temperament, even lead to madness. Physicians sought to cure many
psychological disorders by bringing the humors back in balance, typically with bleeding
and purging or by applying herbs.
During the Renaissance, the theories of souls and humors were vigorously debated. Some