Diane Ackerman begins her A Natural History of the Senses with this assertion: "Nothing is more memorable than a smell."
Well, thanks, Diane.
I have no sense of smell. My affliction is called anosmia, and it is rare enough not to have a common name. Ackerman suggests "smumb," a blend of smell and dumb ("There goes Chet. He's smumb.").
I haven't a clue why my nose doesn't work. I was born that way.
There are something like 100 million olfactory receptors in the nose -- bare nerve endings that somehow detect specific molecules in the air and trigger the appropriate scent sensation in the brain. My problem seems to reside at the cerebral end of the circuits.
Naturalist recently drew our attention to a relatively new theory of smell. The biochemist Luca Turin thinks he has evidence that nerve endings in the nose are sensitive to the vibrational frequencies of molecules; according to this theory, each molecule of scent is like a little turning fork the nose interprets as a smell.
Most neuroscientists are skeptical.
The standard theory of smell assumes the triggering mechanism is lock-and-key. Molecules of a certain shape fit the nooks and crannies on nerve-cell proteins, causing the nerves to shoot a message down the line -- pine, bacon, aftershave, dirty diaper.
However it works, all sensation is chemical. Molecules are the messengers that connect the world "out there" to the imaginary worlds we build in our heads. What a miracle, when you think about it. Our wonderfully rich interior lives, our dreams, memories, loves and lusts are mediated by chemistry. The "heady succulence of life," as Ackerman calls it, is molecules.
I mentioned in Comments a gorgeously sensuous novel by Patrick Suskind called Perfume that is about as close as I have ever come to imagining smell. It is about a man born without a personal scent but with an unnaturally acute sense of smell, who apprentices himself to a perfumer in 18th-century France and masters the craft of distilling aromas. Orange, lime, clove, musk, jasmine, bergamot, attar of roses, ambergris, civet, sandalwood: Of these and a thousand other scents, our protagonoist mixes aromas "capable of creating a whole world, a magical, rich world, and in an instant you forgot all the loathsomeness around you and felt so rich, so at ease, so free, so fine . . ." His quest for the ultimate scent that will give him irresistible power over others leads him at last to murder -- and to an unspeakably horrible end. Suskind's talent is to portray the outer and inner worlds of smell in words so vivid that it almost lets me feel those lock-and-key molecules -- or is it tiny tuning forks? -- tickling my nose.