Part Seven of The Renaissance Brain Mini-Series.
Part Six can be found here:http://www.examiner.com/science-news-in-allentown/cerebrum-renatus-the-renaissance-brain-vi-willis
Rene Descartes (1596-1650)associated the origin of the ‘animal spirits’ to the pineal gland. The pineal gland, to Descartes, was associated with movement and sensation. He believed that within the nerves of the body are tiny ‘valvules’ that operated to control the flow of the spirits into and out of the nerves (Finger, 1994). He thought that this idea of the ‘valvules’ would explain involuntary movement—stimuli would present themselves on the skin, which would in turn pull on the strands connecting to the valvules, which then in turn control the release of animal spirits, which would cause some muscular activity. However, for voluntary movement, Descartes implicated that the pineal gland’s movements caused muscular movements by controlling the rate at which spirits were sent out to the nerves. This pineal-gland theory for movement made sense to Descartes because this part of the brain is surrounded by cerebrospinal fluid, in which, Descartes believed, the animal spirits were housed. This theory, however, was not widely accepted by Descartes’ contemporaries. Overall, though, Descartes viewed the human body as a mechanical device, created by the hand of God, but still purely mechanical, a machine, different from the beasts only because of a God-given intellect.
Finger, Stanley. Origins of Neuroscience: A History of Explorations into Brain Functions. New York, USA: Oxford University Press: 1994.
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