A Natural History of the Senses

by Diane Ackerman

  THE SHAPE OF SMELL

  All smells fall into a few basic categories, almost like primary colors: minty (peppermint), floral (roses), ethereal (pears), musky (musk), resinous (camphor), foul (rotten eggs), and acrid (vinegar). This is why perfume manufacturers have had such success in concocting floral bouquets or just the right threshold of muskiness or fruitness. Natural substances are no longer required; perfumes can be made on the molecular level in laboratories. One of the first perfumes based on a completely synthetic smell (an aldehyde)* was Chanel No. 5, which was created in 1922 and has remained a classic of sensual femininity. It has led to classic comments, too. When Marilyn Monroe was asked by a reporter what she wore to bed, she answered coyly, “Chanel No. 5.” Its top note—the one you smell first—is the aldehyde, then your nose detects the middle note of jasmine, rose, lily of the valley, orris, and ylang-ylang, and finally the base note, which carries the perfume and makes it linger: vetiver, sandalwood, cedar, vanilla, amber, civet, and musk. Base notes are almost always of animal origin, ancient emissaries of smell that transport us across woodlands and savannas.

  For centuries, people tormented and sometimes slaughtered animals to obtain four glandular secretions: ambergris (the oily fluid a sperm whale uses to protect its stomach from the sharp backbone of the cuttlefish and the sharp beak of the squid on which it feeds), castoreum (found in the abdominal sacs of Canadian and Russian beavers, and used by them to mark territories), civet (a honeylike secretion from the genital area of the nocturnal, carnivorous Ethiopian cat), and musk (a red, jellylike secretion from the gut of an East Asian deer). How did people first discover that the anal sacs of some animals held fragrance? Bestiality was common among shepherds in some of these regions, and it can’t be ignored as one possibility. Because animal musk is so close to human testosterone, we can smell it in portions of as little as 0.000000000000032 of an ounce. Fortunately, chemists have now designed twenty synthetic musks, in part because the animals are endangered, and in part to ensure a consistency of odor difficult to achieve with natural substances. An obvious question is why secretions from the scent glands of deer, boar, cats, and other animals should arouse sexual desire in humans. The answer seems to be that they assume the same chemical shape as a steroid, and when we smell them we may respond as we would to human pheromones. In fact, in one experiment conducted at International Flavors and Fragrances, women who sniffed musk developed shorter menstrual cycles, ovulated more often, and found it easier to conceive. Does perfume matter—isn’t it all packaging? Not necessarily. Can smells influence us biologically? Absolutely. Musk produces a hormonal change in the woman who smells it. As to why floral smells should excite us, well, flowers have a robust and energetic sex life: A flower’s fragrance declares to all the world that it is fertile, available, and desirable, its sex organs oozing with nectar. Its smell reminds us in vestigial ways of fertility, vigor, life-force, all the optimism, expectancy, and passionate bloom of youth. We inhale its ardent aroma and, no matter what our ages, we feel young and nubile in a world aflame with desire.

  Sunlight bleaches some of the smell from things, which anyone who has hung musty bedclothes on a clothesline in the sun will tell you. Even so, what remains might still smell stale and uninviting. We need only eight molecules of a substance to trigger an impulse in a nerve ending, but forty nerve endings must be aroused before we smell something. Not everything has a smell: only substances volatile enough to spray microscopic particles into the air. Many things we encounter each day—including stone, glass, steel, and ivory—don’t evaporate when they stand at room temperature, so we don’t smell them. If you heat cabbage, it becomes more volatile (some of its particles evaporate into the air) and it suddenly smells stronger. Weightlessness makes astronauts lose taste and smell in space. In the absence of gravity, molecules cannot be volatile, so few of them get into our noses deeply enough to register as odors. This is a problem for nutritionists designing space food. Much of the taste of food depends on its smell; some chemists have gone so far as to claim that wine is simply a tasteless liquid that is deeply fragrant. Drink wine with a head cold, and you’ll taste water, they say. Before something can be tasted, it has to be dissolved in liquid (for example, hard candy has to melt in saliva); and before something can be smelled, it has to be airborne. We taste only four flavors: sweet, sour, salt, and bitter. That means 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 so many 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”; Baudelaire’s plunge
s into smell until his “soul soars upon perfume as the souls of other men soar upon music”; Milton’s description of the odors God finds pleasing to His divine nostrils and those preferred by Satan, an ace sniffer-out of carrion (“Of carnage, prey innumerable … scent of living carcasses”); Robert Herrick’s fetishistic and intimate sniffing of his sweetheart, whose “breast, lips, hands, thighs, legs … are all/ richly aromatical,” indeed “All the spices of the East/ Are circumfused there”; Walt Whitman’s praise of sweat’s “aroma finer than prayer”; François Mauriac’s La Robe Prétexte, which is adolescence remembered through its smells; Chaucer’s “The Miller’s Tale,” where we find one of the first mentions in literature of breath deodorants; Shakespeare’s miraculously delicate flower similes (to the violet he says: “Sweet thief, whence didst thou steal the sweet, if not from my love’s breath?”); Czeslaw Milosz’s linen closet, “filled with the mute tumult of memories”; Joris-Karl Huysmans’s obsession with nasal hallucinations, and the smell of liqueurs and women’s sweat that fills his lush, almost unimaginably decadent, hedonistic novel, A Rebours. About one character, Huysmans explained that she was “an ill-balanced, nerve-ridden woman, who loved to have her nipples macerated in scents, but who really experienced a genuine and overmastering ecstasy when her head was tickled with a comb and she could, in the act of being caressed by a lover, breathe the smell of the chimney soot, of wet from a house building in rainy weather, or of dust of a summer storm.”

  The most scent-drenched poem of all time, “The Song of Solomon,” avoids talk of body or even natural odors, and yet weaves a luscious love story around perfumes and unguents. In the story’s arid lands, where water was rare, people perfumed themselves often and well, and this betrothed couple, whose marriage day approaches, in the meantime converse amorously in poetry, sweetly dueling with compliments lavish and ingenious. When he dines at her table he is “a bundle of myrrh” or “a cluster of camphire in the vineyards of En-ge-di,” or muscular and sleek as a “young gazelle.” To him, her robust virginity is a secret “garden … a spring shut up, a fountain sealed.” Her lips “drop as the honeycomb: honey and milk are under thy tongue; and the smell of thy garments is like the smell of Lebanon.” He tells her that on their wedding night he will enter her garden, and he catalogues all the fruits and spices he knows he’ll find there: frankincense, myrrh, saffron, camphire, pomegranates, aloes, cinnamon, calamus, and other treasures. She will weave a fabric of love around him, and fill his senses until they brim with oceanic extravagance. So stirred is she by this loving tribute and so wild with desire that she replies yes, she will throw open the gates of her garden to him: “Awake, O north wind; and come, thou south; blow upon my garden, that the spices thereof may flow out. Let my beloved come into his garden, and eat his pleasant fruits.”

  In the macabre contemporary novel Perfume, by Patrick Süskind, the hero, who lives in Paris in the eighteenth century, is a man born without any personal scent whatsoever, although he develops prodigious powers of smell: “Soon he was no longer smelling mere wood, but kinds of wood: maple wood, oak wood, pinewood, elm wood, pearwood, old, young, rotting, moldering, mossy wood, down to single logs, chips, and splinters—and could clearly differentiate them as objects in a way that other people could not have done by sight.” When he drinks a glass of milk each day, he can smell the mood of the cow it has come from; out walking, he can easily identify the origin of any smoke. His lack of human scent frightens people, who treat him badly, and this warps his personality. He ultimately creates personal odors for himself that other people aren’t aware of per se, but which make him appear more normal, including such delicacies as “an odor of inconspicuousness, a mousey, workaday outfit of odors with the sour, cheesy smell of humankind still present.” In time, he becomes a murderer-perfumer, who seeks to distill the fragrant essence from certain people as if they were flowers.

  Many writers have written of how smells trigger flights of comprehensive remembrance. In Swann’s Way, Proust, that great blazer of scent trails through the wilderness of luxury and memory, describes a momentary whirlwind in his day:

  I would turn to and fro between the prayer-desk and the stamped velvet armchairs, each one always draped in its crocheted antimacassar, while the fire, baking like a pie the appetizing smells with which the air of the room was thickly clotted, which the dewy and sunny freshness of the morning had already “raised” and started to “set,” puffed them and glazed them and fluted them and swelled them into an invisible though not impalpable country cake, an immense puff-pastry, in which, barely waiting to savor the crustier, more delicate, more respectable, but also drier smells of the cupboard, the chest-of-drawers, and the patterned wall-paper I always returned with an unconfessed gluttony to bury myself in the nondescript, resinous, dull, indigestible, and fruity smell of the flowered quilt.

  Throughout his adult life, Charles Dickens claimed that a mere whiff of the type of paste used to fasten labels to bottles would bring back with unbearable force all the anguish of his earliest years, when bankruptcy had driven his father to abandon him in a hellish warehouse where they made such bottles. In the tenth century, in Japan, a glitteringly talented court lady, Lady Murasaki Shikibu, wrote the first real novel, The Tale of Genji, a love story woven into a vast historical and social tapestry, the cast of which includes perfumer-alchemists, who concoct scents based on an individual’s aura and destiny. One of the real tests of writers, especially poets, is how well they write about smells. If they can’t describe the scent of sanctity in a church, can you trust them to describe the suburbs of the heart?

  THE WINTER PALACE OF MONARCHS

  We each have our own aromatic memories. One of my most vivid involves an odor that was as much vapor as scent. One Christmas, I traveled along the coast of California with the Los Angeles Museum’s Monarch Project, locating and tagging great numbers of overwintering monarch butterflies. They prefer to winter in eucalyptus groves, which are deeply fragrant. The first time I stepped into one, and every time thereafter, they filled me with sudden tender memories of mentholated rub and childhood colds. First we reached high into the trees, where the butterflies hung in fluttering gold garlands, and caught a group of them with telescoping nets. Then we sat on the ground, which was densely covered with the South African ice plant, a type of succulent, and one of the very few plants that can tolerate the heavy oils that drop from the trees. The oils kept crawling insects away, too, and, except for the occasional Pacific tree frog croaking like someone working the tumblers of a safe, or a foolish blue jay trying to feed on the butterflies (whose wings contain a digitalis-like poison), the sunlit forests were serene, otherworldly, and immense with quiet. Because of the eucalyptus vapor, I not only smelled the scent, I felt it in my nose and throat. The loudest noise was the occasional sound of a door creaking open, the sound of eucalyptus bark peeling off the trees and falling to the ground, where it would soon roll up like papyrus. Everywhere I looked, there seemed to be proclamations left by some ancient scribe. Yet, to my nose, it was Illinois in the 1950s. It was a school day; I was tucked in bed, safe and cosseted, feeling my mother massage my chest with Vicks VapoRub. That scent and memory brought an added serenity to the hours of sitting quietly in the forest and handling the exquisite butterflies, gentle creatures full of life and beauty who stalk nothing and live on nectar, like the gods of old. What made this recall doubly sweet was the way it became layered in my senses. Though at first tagging butterflies triggered memories of childhood, afterward the butterfly-tagging itself became a scent-triggerable memory, and, what’s more, it replaced the original one: In Manhattan one day, I stopped at a flower-seller’s on the street, as I always do when I travel, to choose a few flowers for the hotel room. Two tubs held branches of round, silver-dollar-shaped eucalyptus, the leaves of which were still fresh—bluish-green with a chalky surface; a few of them had broken, and released their thick, pungent vapor into the air. Despite the noise of Third Avenue traffic, the drilling of the City Wor
ks Department, the dust blowing up off the streets and the clotted gray of the sky, I was instantly transported to a particularly beautiful eucalyptus grove near Santa Barbara. A cloud of butterflies flew along a dried-up riverbed. I sat serenely on the ground, lifting yet another gold-and-black monarch butterfly from my net, carefully tagging it and tossing it back into the air, then watching for a moment to make sure it flew safely away with its new tag pasted like a tiny epaulet on one wing. The peace of that moment crested over me like a breaking wave and saturated my senses. A young Vietnamese man arranging his stock looked hard at me, and I realized that my eyes had suddenly teared. The whole episode could not have taken more than a few seconds, but the combined scent memories endowed eucalyptus with an almost savage power to move me. That afternoon, I went to one of my favorite shops, a boutique in the Village, where they will compound a bath oil for you, using a base of sweet almond oil, or make up shampoos or body lotions from other fragrant ingredients. Hanging from my bathtub’s shower attachment is a blue net bag of the sort Frenchwomen use when they do their daily grocery shopping; I keep in it a wide variety of bath potions, and eucalyptus is one of the most calming. How is it possible that Dickens’s chance encounter with a few molecules of glue, or mine with eucalyptus, can transport us back to an otherwise inaccessible world?