A New Model for the Mind
Galvani and Volta
The Field Advances
Tools of the Trade
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"Animus idem eadem idem materia"
The soul is the same thing as matter
In the last decade of the 18th century, the world was poised for revolution, in society as well as in science. The study of the brain and of the mind was no exception. A new paradigm was in the make: electricity was substituting mechanics for good as the main physical explanation for the function of the nervous system.
Until that time, the main model of brain function was based on the ideas of René Descartes (1596-1650), one of the greatest philosophers of all times. Analyzing simple phenomena, such as the sudden involuntary jerk of a limb which happens when someone burns his hand or foot in a fire, Descartes proposed the idea of the reflex arc, and correctly identified its components: the sensation of pain, the nerves leading to the central nervous system, the motor nerves exiting from it, and finally, the muscles which are responsible for the action. He also recognized the importance of a mental representation of the external world in the brain. He said: "The flame that burns the hand is transmitted along the nervous system to the brain as a stimulus, where it torments man as a small flame. "
However, on proposing a mechanism for this sequence, Descartes was limited by the Medieval concept of the nervous system as a set of hydraulic pipes. Influenced by Aristotle and Galen (129-199 BC), they thought that brain matter was less important than its ventricles, which were imagined as being a kind of reservoir of fluids and the seat of the rational mind. According to author Stephen Jones (The Brain Project), Galen expanded on the Greek theory of humors and combined it with the Aristotelian model of the soul, proposing that "the brain was the seat of the rational soul. It received vital spirit from the heart, mixed into the 'sanguine' humour (blood). The brain then separates the animal spirit out and stores it in the ventricles, distributing it throughout the body via the nerves. This fluid travelled, via the nerves, to muscles and organs to control all the bodies activities. The rational soul was considered responsible for imagination, reason and memory".
Descartes proposed that nerves conducted the stimulus to the brain thanks to a wave of propulsion of the fluid in its hollow interior. Pumped full of this fluid, the muscles would expand, leading to contraction. He wrote in his book, Traite de l'Homme (1664): "And truly one can well compare the nerves of the machine that I am describing to the tubes of the mechanisms of these fountains, its muscles and tendons to diverse other engines and springs which serve to move these mechanisms, its animal spirits to the water which drives them, of which the heart is the source and the brain's cavities the water main."
Since Descartes was a philosopher, not an experimental scientist, he didn't bother to check whether all this was true! However, experimentalists, such as the English anatomist, Thomas Willis (1621-1675), also believed in the hydraulic model, because they could dissect the brain in high detail, but could not see or measure its function. He speculated, for instance, that if the brain ceased to receive blood from the heart pump, then the "nerve function ceased because vital spirits could not reach the ventricles for conversion into the essential animal spirits."
The theoretical existence of an energetic organic "fluid" different from water was speculated by many natural philosophers at the time (17th century). The great scientific genius Sir Isaac Newton wrote in the Principia Mathematica (1687) of "a certain most subtle spirit which pervades and lies hid in all gross bodies," and that "all sensation is excited, and the members of animal bodies move at the command of the will, namely, by the vibrations of this spirit, mutually propagated along the solid filaments of the nerves, from the outward organs of sense to the brain, and from the brain into the muscles." Electricity was not the subject of much scientific interest at the time!
Albrecht von Haller (1708-1777), professor of anatomy and medicine at Göttingen, Germany also speculated on "the nervous fluid" and whether "electrical matter" was present in the "animal spirits". But all this was not science, and only in the last decade of the 18th century that an experimental approach was feasible. The pioneers were to be two great Italian scientists, neighbours and friends, Luigi Galvani and Alessandro Volta.
Prof. Renato M.E. Sabbatini, PhD is a neuroscientist and a specialist in medical
informatics, holding a doctoral degree in neurophysiology by the University of São Paulo, Brazil, and a
post-doctoral fellowship at the Max Planck Institute for Psychiatry, in Munich, Germany. He is the director of
the Center for Biomedical Informatics and associate professor and chairman of medical informatics at the Faculty
of Medical Sciences, both at the State University of Campinas, Brazil. Email: firstname.lastname@example.org