A Natural History of the Senses

by Diane Ackerman

  *Novelists have written about the smell of fear, and researchers working with rats have found that stressed rats give off a special odor. Other unstressed rats detect the odor and have a physical, analgesic response, so that they will be prepared for pain.

  *Butterflies often give off an aroma to attract a mate, and may smell like roses, sweetbriar, heliotrope, and other flowers.

  *Among the curious diseases recognizable by smell is maple syrup urine disease, which afflicts infants. Doctors aren’t sure what produces the odor. The smell of acetone on a patient’s breath often signals diabetes. “Menses breath” (some women develop an oniony smell) comes from a change in sulfur compounds in the body during a woman’s menstrual cycle.

  Touch

  They are excessively warm hands, that continually want to cool themselves and involuntarily lay themselves on any cold object, outspread, with air between the fingers. Into those hands the blood could shoot, as it mounts to a persons head, and when clenched, they were indeed like the heads of madmen, raging with fancies.

  Rainer Maria Rilke,

  The Notebooks of Malte Laurids Brigge

  THE FEELING BUBBLE

  Our skin is a kind of space suit in which we maneuver through an atmosphere of harsh gases, cosmic rays, radiation from the sun, and obstacles of all sorts. Years ago, I read about a boy who had to live in a bubble (designed by NASA) because of the weakness of his immune system and his susceptibility to disease. We are all that boy. The bubble is our skin. But the skin is also alive, breathing and excreting, shielding us from harmful rays and microbial attack, metabolizing vitamin D, insulating us from heat and cold, repairing itself when necessary, regulating blood flow, acting as a frame for our sense of touch, aiding us in sexual attraction, defining our individuality, holding all the thick red jams and jellies inside us where they belong. Not only do we have unique fingerprints, we have unique pore patterns. According to Catholic belief, there is somewhere, protected in a secret vault, the relic foreskin of Christ. Since he ascended to heaven, his foreskin is the only mortal part of him that remains. We like to decorate our skin whenever we get the chance, and that is made easier by skin being portable, washable, and sloughy. Psychiatrist David Hellerstein’s description of skin in Science Digest (September 1985) offers a simple, convenient picture of it in cross section:

  Skin is basically a two-layered membrane. The lower, thick spongey dermis, one to two millimeters thick, is primarily connective tissue, rich in the protein collagen; it protects and cushions the body and houses hair follicles, nerve endings and sweat glands, blood and lymph vessels. The upper layer, the epidermis, is 0.07 to 0.12 millimeter thick. It is primarily composed of squamous, or scalelike, epithelial cells, which begin their lives round and plump at the boundary of the dermis and over a 15-to-30-day period are pushed upward, toward the surface, by new cells produced below. As they rise, they become flattened, platelike, lifeless ghosts, full of protein called keratin, and finally they reach the surface, where they are ingloriously sloughed off into oblivion.

  Our skin is what stands between us and the world. If you think about it, no other part of us makes contact with something not us but the skin. It imprisons us, but it also gives us individual shape, protects us from invaders, cools us down or heats us up as need be, produces vitamin D, holds in our body fluids. Most amazing, perhaps, is that it can mend itself when necessary, and it is constantly renewing itself. Weighing from six to ten pounds, it’s the largest organ of the body, and the key organ of sexual attraction. Skin can take a startling variety of shapes: claws, spines, hooves, feathers, scales, hair. It’s waterproof, washable, and elastic. Although it may cascade or roam as we grow older, it lasts surprisingly well. For most cultures, it’s the ideal canvas to decorate with paints, tattoos, and jewelry. But, most of all, it harbors the sense of touch.

  The fingertips and tongue are much more sensitive than the back. Some parts of the body are ticklish, and others respond when we itch, shiver, or get gooseflesh. The hairiest parts of the body are generally the most sensitive to pressure, because there are many sense receptors at the base of each hair. In animals, from mice to lions, the whiskers around the mouth are extraordinarily sensitive; our body hairs are sensitive, too, but to a lesser degree. The skin is also thinnest where there’s hair. Feeling doesn’t take place in the topmost layer of skin, but in the second layer. The top layer of skin is dead, sloughs off easily, and contributes to that ring around the bathtub. This is why safecrackers are sometimes shown sandpapering their fingertips, making the top layer of skin thinner so that the touch receptors will be closer to the surface. A carpenter looking for rough patches may run a thumb over the plank of wood he has just planed. A cook may roll a bit of dough between a thumb and forefinger to test its consistency. Without having to look at the spot, we know at once where we cut ourself shaving, or where a stocking is starting to run. It’s entirely possible to feel wet, even though we may not be wet (when washing dishes with plastic gloves on, say), which suggests the complex sensations that constitute touch. The reason it’s easier to get our feet wet first when we brave an icy ocean is that there aren’t as many cold receptors in the feet as there are on, for example, the tip of the nose.

  In the Middle Ages, so-called witches and others who lived on the outskirts of the law, piety, or convention were burned at the stake. Mimicking the fire and brimstone of hell, it was the ultimate horror. Death would happen cell by cell, receptor by receptor; each of life’s minute sensations would be torched. Today people who have somehow survived accidental burning come to the burn units of metropolitan hospitals to be re-dressed. If their burns are too deep for the body to repair by itself, they receive temporary coverings (cadaver skin, pigskin, lubricated gauze) until doctors can begin grafting skin from other body parts. Our skin makes up about 16 percent of our body weight (about six pounds), and stretches two square yards, but if too much of the body is burned, there isn’t enough skin to graft.

  In 1983, a Harvard Medical School team led by Dr. Howard Green found a revolutionary way to repair burned skin. Two small boys, Jamie and Glen Selby, were removing paint from their naked bodies when the solvent accidentally caught fire. Only five and six years old, the boys had burned themselves horrendously, one over 97 percent of his body, the other 98 percent. At the Shriners Burn Institute in Boston, doctors covered the boys with cadaver skin and artificial membrane, removed small squares of skin from their armpits and cultured them into large sheets of skin, which they grafted on gradually over a five-month period. They were able to repair half of the burned areas on each boy’s body, and a little over a year later the boys went home to Casper, Wyoming. Although the boys didn’t have any sweat glands or hair follicles on this skin, it was pliable and protective, and they were able to return to school. The doctors had been able to grow large quantities of new skin.

  Here is how it is done: In a Harvard laboratory, doctors cut up a small patch of skin donated by a patient, treat it with enzymes, then spread it thinly onto a culture medium. After only ten days, colonies of skin cells begin linking up into sheets, which can then be chopped up and used to make further sheets. In twenty-four days, enough skin will be produced to cover an entire human body. The new skin is attached to gauze that has been saturated in Vaseline, then, gauze side up, sutured to the body. About ten days later, the gauze is removed, and the skin soon grows into a surface much smoother and more natural-looking than the rough one a normal skin graft usually leaves. As revolutionary as skin-growing is, other methods are equally intriguing. At New York Hospital—Cornell Medical Center, doctors have been experimenting with cadaver skin, which they grow in large quantities and store in a skin bank. At MIT, researchers have developed a high-speed technique that uses a quarter-sized patch of skin from the burn patient to manufacture a large amount of skin in under two hours. A graft can be made right away, without a three-week wait. In two weeks, the burn will be covered with fresh new skin. Again, the skin will lack hair follicles, sweat glands,
and pigment, but it will protect and function like normal skin. Such techniques are not for minor burns or even small serious burns; they’re useful only in patients who are severely burned over large areas and therefore have too little skin left for grafting. None of the techniques is without risk—delay; rejection; possible infection—but the very fact of being able to grow an organ, indeed the largest organ in the body, makes one pause to think about growing other organs or at least parts of them—eyes, ears, hearts—in a farm whose fields are pans and whose silos are test tubes.

  SPEAKING OF TOUCH

  Language is steeped in metaphors of touch. We call our emotions feelings, and we care most deeply when something “touches” us. Problems can be thorny, ticklish, sticky, or need to be handled with kid gloves. Touchy people, especially if they’re coarse, really get on our nerves. Noli me tangere, legal Latin for “don’t meddle or interfere,” translates literally as “Don’t touch me,” and it was what Christ said to Mary Magdalen after the Resurrection. But it’s also one term for the disease lupus, presumably because of the disfiguring skin ulcerations characteristic of that illness. A toccata in music is a composition for organ or other keyboard instrument in a free style. It was originally a piece intended to show touch technique, and the word comes from the feminine past participle of toccare, to touch. Music teachers often chide students for having “no sense of touch,” by which they mean an indefinable delicacy of execution. In fencing, saying touché means that you have been touched by the foil and are conceding to your opponent, although, of course, we also say it when we think we have been foiled because someone’s argumentative point is well made. A touchstone is a standard. Originally, touchstones were hard black stones like jasper or basalt, used to test the quality of gold or silver by comparing the streaks they left on the stone with those of an alloy. “The touchstone of an art is its precision,” Ezra Pound once said. D. H. Lawrence’s use of the word touch isn’t epidermal but a profound penetration into the core of someone’s being. So much of twentieth-century popular dancing is simultaneous solo gyration that when people returned to dancing closely with partners again a couple of years ago, we had to call it something different—“touch dancing.” “For a while there, it was touch and go,” we say of a crisis or precarious situation, not realizing that the expression goes back to horse-and-carriage days, when the wheels of two coaches glanced off each other as they passed, but didn’t snag; a modern version would be when two swerving cars brush fenders. What seems real we call “tangible,” as if it were a fruit whose rind we could feel. When we die, loved ones swaddle us in heavily padded coffins, making us infants again, lying in our mother’s arms before returning to the womb of the earth, ceremonially unborn. As Frederick Sachs writes in The Sciences, “The first sense to ignite, touch is often the last to burn out: long after our eyes betray us, our hands remain faithful to the world.… in describing such final departures, we often talk of losing touch.”

  FIRST TOUCHES

  Although I am not a portly middle-aged gentleman with nothing else to do, I am massaging a tiny baby in a hospital in Miami. Often male retirees volunteer to enter preemie wards late at night, when other people have families to tend or a nine-to-five job to sleep toward. The babies don’t care about the gender of those who cosset and cuddle them. They soak it up like the manna it is in their wilderness of uncertainty. This baby’s arms feel limp, like vinyl. Still too weak to roll over by itself, it can flail and fuss so well the nurses have laid soft bolsters on its bed, to keep it from accidentally wriggling into a corner. Its torso looks as small as a deck of cards. That this is a baby boy lying on his tummy, who will one day play basketball in the summer Olympics, or raise children of his own, or become a heliarc welder, or book passage on a low-orbital plane to Japan for a business meeting, is barely believable. The small life form with a big head, on which veins stand out like river systems, looks so fragile, feels so temporary. Lying in his incubator, or “Isolette,” as it’s called, emphasizing the isolation of his life, he wears a plumage of wires—electrodes to chart his progress and sound an alarm if need be. Reaching carefully scrubbed, disinfected, warmed hands through the portholes of the incubator with pangs of protectiveness, I touch him; it is like reaching into a chrysalis. First I stroke his head and face very slowly, six times for ten seconds each time, then his neck and shoulders six times. I slide my hands down his back and massage it in long sweeping motions six times, and caress his arms and legs six times. The touching can’t be light, or it will tickle him, nor rough, or it will agitate him, but firm and steady, as if one were smoothing a crease from heavy fabric. On a nearby monitor, two turquoise EKG and breath waves flutter across a radiant screen, one of them short and saw-toothed, the other leaping high and dropping low in its own improvisatory dance. His heartbeat reads 153, aerobic peak during a stiff workout for me, but calm for him, because babies have higher normal heart rates than adults. We turn him over on his back and, though asleep, he scrunches up his face in displeasure. In less than a minute, he runs a parade of expressions by us, all of them perfectly readable thanks to the semaphore of the eyebrows, the twisted code of the forehead, the eloquent India rubber of the mouth and chin: irritation, calm, puzzled, happy, mad.… Then his face goes slack and his eyelids twitch as he drifts into REM sleep, the blackboard of dreams. Some nurses refer to the tiny preemies, sleeping their sleep of the womb, as fetuses on the outside. What does a fetus dream? Gently, I move his limbs in a mini-exercise routine, stretching out an arm and bending the elbow tight, opening the legs and bending the knees to the chest. Peaceful but alert; he seems to be enjoying it. We turn him onto his tummy once more, and again I begin caressing his head and shoulders. This is the first of three daily touch sessions for him—it may seem a shame to interrupt his thick, druglike sleep, but just by stroking him I am performing a life-giving act.

  Massaged babies gain weight as much as 50 percent faster than unmassaged babies. They’re more active, alert, and responsive, more aware of their surroundings, better able to tolerate noise, and they orient themselves faster and are emotionally more in control. “Less likely to cry one minute, then fall asleep the next minute,” as a psychologist, detailing the results of one experiment, explained in Science News in 1985, they’re “better able to calm and console themselves.” In a follow-up examination, eight months later, the massaged preemies were found to be bigger in general, with larger heads and fewer physical problems. Some doctors in California have even been putting preterms on small waterbeds that sway gently, and this experiment has produced infants who are less irritable, sleep better, and have fewer apneas. The touched infants, in these studies and in others, cried less, had better temperaments, and so were more appealing to their parents, which is important because the 7 percent of babies born prematurely figure disproportionately among those who are victims of child abuse. Children who are difficult to raise get abused more often. And people who aren’t touched much as children don’t touch much as adults, so the cycle continues.

  A 1988 New York Times article on the critical role of touch in child development reported “psychological and physical stunting of infants deprived of physical contact, although otherwise fed and cared for …,” which was revealed by one researcher working with primates and others working with World War II orphans. “Premature infants who were massaged for 15 minutes three times a day gained weight 47 percent faster than others who were left alone in their incubators … the massaged infants also showed signs that the nervous system was maturing more rapidly: they became more active … and more responsive to such things as a face or a rattle … infants who were massaged were discharged from the hospital an average of six days earlier.” Eight months later, the massaged infants did better in tests of mental and motor ability than the ones who were not.

  At the University of Miami Medical School, Dr. Tiffany Field, a child psychologist, has been studying a group of babies admitted to the intensive care unit of its hospital for various reasons. With 13,000 to 15
,000 births a year at the hospital, she never lacks for a steady supply of babies. Some are receiving caffeine for bradycardia and apnea problems, one is hydroencephalic, some are the children of diabetic mothers who must be carefully monitored. At one Isolette, a young mother sits on a black kitchen chair by her baby, reaches a hand in and gently strokes, whispering motherly nothings into its ear. Inside another Isolette, a baby girl wearing a white nightie with pink hearts bursts into a classic textbook wail that rises and pulses and sets off the alarm on her monitor. Across the room, a male doctor sits quietly beside a preemie, holding a two-pronged plastic stopper close to her nostrils, trying to teach her to breathe. Next to him, a nurse turns a baby girl onto her tummy and begins a “stim,” as they call the massage, shorthand for stimulation. They use the word interchangeably as a verb or a noun. What old faces the preemies have! Changing expressions as they sleep, they seem to be rehearsing emotions. The nurse follows her massage schedule, stroking each part of the preemie six times for ten seconds. The stimulation hasn’t changed the baby’s sleep patterns, but she’s been gaining thirty grams more a day and will soon be going home, almost a week ahead of what one would expect. “There’s nothing extra going into the babies,” Field explains, “yet they’re more active, gain weight faster; and they become more efficient. It’s amazing,” she continues, “how much information is communicable in a touch. Every other sense has an organ you can focus on, but touch is everywhere.”

  Saul Schanberg, a neurologist who experiments with rats at Duke University, has found that licking and grooming by the mother rat actually produced chemical changes in the pup; when the pup was taken away from the mother, its growth hormones decreased. ODC (the “now” enzyme that signals it is time for certain chemical changes to begin) dropped in every cell in the body, and protein synthesis fell. Growth began again only when the pup was returned to the mother. When experimenters tried to reverse the bad effects without the mother, they discovered that gentle stroking wouldn’t work, only very heavy stroking with a paintbrush that simulated the mother’s tongue; after that the pup developed normally. Regardless of whether the deprived rats were returned to their mothers or stroked with paintbrushes by experimenters, they overreacted and required a great deal of touching, far more than they usually do, to respond normally.