The most important invention in the past two thousand years is
anesthesia. Have you ever had surgery? If so, either a) part of
your body was temporarily "deadened" by "local" anesthesia, or
b) you "went to sleep" with general anesthesia. Can you imagine
having surgery, or needing surgery, or even possibly needing
surgery without the prospect of anesthesia? And beyond the
agony-sparing factor is an extra added feature — understanding
the mechanism of anesthesia is our best path to understanding
consciousness. Anesthesia grew from humble beginnings. Inca
shamans performing trephinations (drilling holes in patients'
skulls to let out evil humors) chewed coca leaves and spat into
the wound, effecting local anesthesia. The systemic effects of
cocaine were studied by Sigmund Freud, but cocaine's use as a
local anesthetic in surgery is credited to Austrian
ophthalmologist Karl Koller who in 1884 used liquid cocaine to
temporarily numb the eye. Since then dozens of local anesthetic
compounds have been developed and u