Nose & brain

tivol at tivol at
Mon Jul 4 17:11:29 EST 1994

Dear Bill,
	You ask about the phenomenon whereby you become insensitive to odors
after a while.  In general, constant stimuli become unnoticable after a time
(you cannot, for example, feel your clothing or watch, etc.).  This fatigue
keeps us from becomming overwhelmed by irrelevant stimuli to the point where
we might miss an essential stimulus, e.g. a predator who thinks of us as
lunch.  I am not sure if this fatigue is due to lessening of response at the
olfactory gland or if it occurs further up the processing chain--I think the
former.  This phenomenon was first called to my attention with regard to H2S;
my freshman chem lab instructor came into the room, almost gagged, and threw
open all the windows.  He had no trouble smelling the H2S--which, btw, is
more toxic than HCN--whereas none of us in the lab could smell a thing!  In
this case, however, there is, I believe, a specific anesthetic effect of H2S
which accounts for the loss of odor perception.


					Bill Tivol

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