Machine Metaphors in Biology III: A Dialectical Synthesis
“To control the production of a chemical and rely on the diffusion rate of a chemical is to employ a much more sophisticated analog procedure than we ever use in analog computing machines. The most important loops in the human system are of this nature. A system of nervous stimuli goes through a complicated network of nerves and then controls the operation of what is essentially a chemical factory. The chemicals are distributed by a very complicated hydrodynamical system, which is completely analog. These chemicals produce nervous stimuli which travel in a digital manner through the nervous system. There are loops where this change from digital to analog occurs several times. So the human organism is essentially a mixed system.” —John von Neumann.