A Natural History of the Senses Read Online Free PDF Page A

that everything else we call “flavor” is really “odor.” And many of the foods we think we can smell we can only taste. Sugar isn’t volatile, so we don’t smell it, even though we taste it intensely. If we have a mouthful of something delicious, which we want to savor and contemplate, we exhale; this drives the air in our mouths across our olfactory receptors, so we can smell it better.
    But how does the brain manage to recognize and catalogue somany smells? One theory of smell, J. E. Amoore’s “stereochemical” theory, maps the connections between the geometric shapes of molecules and the odor sensations they produce. When a molecule of the right shape happens along, it fits into its neuron niche and then triggers a nerve impulse to the brain. Musky odors have disc-shaped molecules that fit into an elliptical, bowl-like site on the neuron. Pepperminty odors have a wedge-shaped molecule that fits into a V-shaped site. Camphoraceous odors have a spherical molecule that fits an elliptical site, but is smaller than that of musk. Ethereal odors have a rod-shaped molecule that fits a trough-shaped site. Floral odors have a disc-shaped molecule with a tail, which fits a bowl-and-trough site. Putrid odors have a negative charge that is attracted to a positively charged site. And pungent odors have a positive charge that fits a negatively charged site. Some odors fit a couple of sites at once and give a bouquet or blend effect. Amoore offered his theory in 1949, but it was also proposed in 60 B.C. by the wide-spirited poet Lucretius in his caravansary of knowledge and thought,
On the Nature of Things
. A lock-and-key metaphor seems increasingly to explain many facets of nature, as if the world were a drawing room with many locked doors. Or it may simply be that a lock and key is familiar imagery, one of the few ways in which human beings can make sense of the world around them (language and mathematics being two others). As Abram Maslow once said: If a man’s only tool is a key, he will imagine every problem to be a lock.
    Some smells are fabulous when they’re diluted, truly repulsive when they’re not. The fecal odor of straight civet would turn one’s stomach, but in small doses it converts perfume into an aphrodisiac. Just a little of some smells—camphor, ether, oil of cloves for example—is too much, dulling the nose and making further smelling almost impossible. Some substances smell like other substances they seem remote from, in the nasal equivalent of referred pain (bitter almonds smell like cyanide; rotten eggs smell like sulfur). Many normal people have “blind spots,” especially to some musks, and others can detect smells that are faint and fleeting. When we think of what’s normal for human beings to sense, we tend to underimagine.One surprising thing about smell is the vast range of response one finds along the curve we call normal.
BUCKETS OF LIGHT
    Much of life becomes background, but it is the province of art to throw buckets of light into the shadows and make life new again. Many writers have been gloriously attuned to smells: Proust’s lime-flower tea and madeleines; Colette’s flowers, which carried her back to childhood gardens and her mother, Sido; Virginia Woolf’s parade of city smells; Joyce’s memories of baby urine and oilcloth, holiness and sin; Kipling’s rain-damp acacia, which reminded him of home, and the complex barracks smells of military life (“one whiff … is all Arabia”); Dostoevsky’s “Petersburg stench”; Coleridge’s notebooks, in which he recalled that “a dunghill at a distance smells like musk, and a dead dog like elder flowers”; Flaubert’s rhapsodic accounts of smelling his lover’s slippers and mittens, which he kept in his desk drawer; Thoreau’s moonlight walks through the fields when the tassels of corn smelled dry, the huckleberry bushes oozed mustiness, and the berries of the wax myrtle smelled “like small confectionery”;