highly interconnected via fiber pathways to the entire body (Fig. 2.10).
There were fibers connecting the brain with the sensory organs: the
eyes, ears, nose, and tongue. There were fibers connecting the brain
with the heart, and lungs, and digestive system. And there were fibers
connecting the spinal cord—which was contiguous with the brain
—with muscles throughout the body. It seemed likely that extensive
communication of some sort was taking place between the brain and
all parts of the body.
One of the early thinkers on signaling in the nervous system was René
Descartes (1596-1650). Born in France and living much of his adult
life in the Netherlands, he was a key figure in the history of Western
philosophy and science. Descartes was interested in how the human
body worked, how we are able to perceive the world, and how the
actions of the body are related to the subjective mental experiences
of mind. Among his early writings, when he was in his thirties, were
essays on the world (Le Monde) and on man (L’Homme). These were
published only after he had died. Some say he was worried about pub-
lication in part because these essays addressed big questions about the
nature of reality, perception, and mind. Descartes was aware that at
the very time he was writing his pieces (the 1630s), elsewhere on the
European continent Galileo Galilei (1564-1642) was being tried and
sentenced by the Catholic Inquisition for heresy as a result of his writ-
ings on related topics of grand scope.