The explanation for insensitivity to smell seems to be that brain finds it 14 to keep all smell receptors working all the time but can 15 new receptors if necessary. This may 16 explain why we are not usually sensitive to our own smells we simply do not need to be. We are not 17 of the usual smell of our own house but we 18 new smells when we visit someone else's. The brain finds it best to keep smell receptors 19 for unfamiliar and emergency signals 20 the smell of smoke, which might indicate the danger of fire.
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