So that the median lines are the shared pathway of the EMF that is controllably shunted out of the chemical reaction to allow the flexible shifts in efficiency needed to prevent
uncontrolled runaway feedback or disease processes that cause death.
One of the things that people (particularly from an engineering background) have trouble with is the idea that the
feedback from a small amount of warming can give rise to a much larger amount of warming, and this seems, from an «enginering perspective» on the meaning of «
feedback», to result in an
uncontrolled «
runaway» response.