2/5/13 - breathing and our mysterious sense of smell

In today's selection -- breathing and our mysterious sense of smell:

"Each day, we breathe about 23,040 times and move around 438 cubic feet of air. It takes us about five seconds to breathe -- two seconds to inhale and three seconds to exhale -- and, in that time, molecules of odor flood through our systems. Inhaling and exhaling, we smell odors. ...  

"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). ... 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, 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. ...

"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. ... 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."


Diane Ackerman


A Natural History of the Senses




Copyright 1990 by Diane Ackerman


6-7, 11-13
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