CHAPTER 1 2
Nose and Smell
You walk along a street in an unfamiliar neighborhood, looking for
a place to enjoy a small lunch. A savory aroma attracts you intoa
small restaurant to investigate the menu. Perhaps it is a smell of basil
and thyme, or of cumin and coriander, depending on the cuisine.
Our sense of smell—our capacity to detect and respond to airborne
molecules in the environment—is the human analogue of what a
bacterium does when it detects and responds to chemicals in its
environment.
It is sometimes said humans don’t have a very sophisticated sense
of smell and that the ability to smell is not very important to us. On
the contrary, there are plenty of reasons to believe that the sense of
smell in humans is quite refined and that smells—odors and aromas
—play important roles in human life. People respond intensely to
smells, being strongly attracted or repulsed. Perfumery was one of the
early applications of alchemy.
Olfactory sensory perception begins when odorants—airborne
volatile molecules (Latin volare = to fly)—enter the nasal passages,
via the constant streams of air inhaled and exhaled through the nose.