The influence of fermentation theory on Newton's hypothetical neurophysiology
Newton published statements in later editions of both of his major works which advanced a quasi-electrical hypothesis of nervous transmission. In these passages, Newton described the nerves as "solid, pellucid and uniform capillamenta" permeated with a subtle aether. He proposed that vibrations in the aether are transmitted along the capillamenta just as light is transmitted through transparent glass, and they cause muscular contraction by altering the density of aether in the muscle. Newton arrived at this hypothesis through the influence of Willis, who in his treatise De cerebri anatome (1664), proposed all of the principal ingredients of Newton's hypothesis: solid nerves, a vibratory mechanism of transmission, and a luminous or light-like nervous fluid. Both models hinge on a vibratory transmission mechanism, which was made possible by a fermentation-based mechanism of muscular contraction. If the muscle contracts due to ebullition produced by fermentation, then the nerve need only deliver a tiny droplet of fluid in order to cause contraction. This frees the nerve to transmit commands by vibation, a much faster method than direct inflation of the muscle with a spirit, as was supposed by the Cartesians. Newton's use of fermentation concepts indicates that his theory of nervous transmission was indebted to the nascent science of iatrochemistry, a borderline discipline whose conceptual foundation was quite foreign to that of Renaissance anatomy or physics.
Session II -- Medieval to 18th Century
Providence, Rhode Island, USA