Gulp: Adventures on the Alimentary Canal

by Mary Roach

  Van Vliet wants to start me out with the basics of crispy-crunchy. We begin with nature’s version, a fresh apple or carrot. “It’s all bubbles and beams,” he says, sketching networks of water-filled cells and cell walls on a sheet of my notepad paper. When you bite into an apple, the flesh deforms, and at a certain moment the cell walls burst. And there is your crunch. (Ditto crispy snack foods, but here the bubbles are filled with air.) “This is why fresh fruit is crisp, and also why it is a little bit juicy,” says van Vliet. His voice is reedy and high-pitched, with a musical cadence.

  As a piece of produce begins to decay, the cell walls break down and water leaks out. Now nothing bursts. Your fruit is no longer crisp. It is mealy or limp or mushy. The same thing happens with a snack food degraded by moisture: cell walls dissolve, air leaks out.

  The staler the chip, the quieter. For a food to make an audible noise when it breaks, there must be what’s called a brittle fracture—a sudden, high-speed crack. “Like this.” Van Vliet is drawing graphs again. As you bite down on a chip, energy builds and is stored. In a millisecond, the chip gives way and the stored energy is released, all at once. Crack is a superb onomatopoeia; the word sounds like the noise, and the noise is the fracture. (Crumbly foods, by contrast, break apart quietly because the energy isn’t released all at once.)

  Van Vliet reaches for a bag of puffed cassava chips René bought for us to use as props. He snaps one in two. “To get this noise, you need crack speeds of 300 meters per second.” The speed of sound. The crunch of a chip is a tiny sonic boom inside your mouth. Van Vliet rubs his palms together to brush off the crumbs. This too makes a sound, dry like papers being shuffled. The Dutch winter is a brutal desiccant, to borrow from the language of snack foods.

  René and I have been working our way through the props. He tilts the bag toward van Vliet, who waves it off. “I don’t like chips and things.”

  René and I exchange a glance: Get out!

  “I like beschuit . . .” He turns to me. “It’s a Dutch toast that is round. We serve it when babies are born.”

  René wears an expression that FaceReader will have no trouble decoding. “Are you kidding me? It is so dry. I mean, you cannot move your tongue anymore! Really, I am hoping no more babies are born.”

  “It’s very nice,” insists van Vliet. “You have to put butter on it, and then honey on it.”

  I get up to look for some, but the restaurant has none.

  Van Vliet juts his jaw. “Then that is not a good restaurant.”

  René leans in close to van Vliet, laughing. “It’s a very good restaurant that takes care of its customers.”

  Moving along, van Vliet provides the answer I was looking for. Crispness and crunch appeal to us because they signal freshness. Old, rotting, mushy produce can make you ill. At the very least, it has lost much of its nutritional vim. So it makes sense that humans evolved a preference for crisp and crunchy foods.

  To a certain extent we eat with our ears. The sound made by biting off a piece of carrot—more so than its taste or smell—communicates freshness. René told me about an experiment in which subjects ate potato chips while a researcher digitally altered the sounds of their chewing. If they muted the crunch or masked the higher frequencies, people no longer sensed the crispness. “They rated the chips as old even though the texture had not changed.”

  Van Vliet is nodding. “People eat physics. You eat physical properties with a little bit of taste and aroma. And if the physics is not good, then you don’t eat it.”

  Crispness and crunch are the body’s shorthand for “healthy.” The snack-food empires have cashed in on this fact, producing crisp, crunchable foods that appeal to us but fail to deliver in terms of health and survival.

  A good amount of thought appears to have gone into designing optimal crunch. “People like it most when it is around 90 to 100 decibels,” says van Vliet. To achieve that, you need about a hundred bubbles bursting in rapid succession. “An avalanche of cracks in your mouth! To the ear it sounds like one sound, but in fact it is made up of more than one hundred sound bursts.” This is achieved by messing around with the bubbles and beams—their size, their brittleness.

  It’s a marvel: such sophisticated physics in the service of junk food. I ask van Vliet which crispy-crunchy snack foods he has helped design. He wears a look that conveys both amusement and something dimmer. “Oh, the food companies are not using this science. They just make a product, give it to somebody, and say, ‘How do you like it?’”

  René confirms this. “They are so low-tech. They have no clue.” It takes five to ten years for the discoveries of food physics to find their way into industry.

  What is the point, then? For van Vliet anyway, the point is physics. Earlier, when I’d complained that the food-texture journals were “just a lot of physics,” van Vliet seemed taken aback. “But physics is so nice!” It was as though I’d insulted a friend of his.

  René cranes his neck toward the steam tables. “Can you stay for lunch, Ton?” It’s 12:30 and all we’ve had are cassava chips. With his tongue, René works some free from a molar.*

  Van Vliet considers this. “Well, I would have to tell my wife. You see I’m a good Dutch man, I go home for lunch every day! On my bicycle.” In his eight years at Wageningen University, he adds, he has never tried the food in Restaurant of the Future. We are unable to tell if this is a yes or a no. René asks him whether he has a cell phone, to call his wife.

  “Yes, we have one at home.”

  We let it drop. Later, walking to the parking lot, we glimpse van Vliet on a campus bike path, pedaling into the slanting snow.

  * * *

  * Fingerprints come in three types: loop (65 percent), whorl (30 percent), and arch (5 percent). Oral processing styles for semisolid foods come in four: simple (50 percent), taster (20 percent), manipulator (17 percent), and tonguer (13 percent). Thus the millions of variations that make you the unique and delightful custard-eater and fingerprint-leaver that you are.

  * I nominate Rhode Island.

  * Assuming equal terrain and baggage count, about as fast as a tortoise—.22 miles per hour.

  * Its full medical name, and my pen name should I ever branch out and write romance novels, is palatine uvula.

  * Technical term: toothpack.

  8

  Big Gulp

  HOW TO SURVIVE BEING SWALLOWED ALIVE

  IN THE COLOR plate that illustrates the Jonah story in my mother’s Bible, the fisherman is halfway in the mouth of an indeterminate species of baleen whale. He wears a sleeveless red robe, and his hair, just starting to recede around the temples, is slicked back with seawater. One arm is outstretched in an effort to swim free. Baleen whales are strainer feeders. They close their mouth on a large gulp of ocean and use their tongue to push it forward through the vast comb of baleen, expelling the seawater and retaining small fish, krill, anything solid. It is a gentle, perhaps even survivable, way to be eaten. The prey is rarely much larger than a man’s foot, however, and the whales are built accordingly.

  “Baleen whales have very small gullets,” says Phillip Clapham, a whale biologist with the National Oceanic and Atmospheric Administration. “They could not possibly swallow a hapless victim of God’s wrath.” But a sperm whale could. Its gullet is wide enough, and though it has teeth, it doesn’t, as a matter of course, chew its food. Sperm whales feed by suction. Evidently quite powerful suction: in 1955, a 405-pound giant squid—six foot six minus the tentacles—was recovered intact from the stomach of a sperm whale caught off the Azores.

  And then there is James Bartley. On November 22, 1896, the New York Times picked up the story of a sailor on the whaling ship Star of the East who disappeared in the waters off the Falkland Islands after a harpooned sperm whale, “apparently in its death agonies,” capsized his whaleboat. Assuming Bartley had drowned, the rest of the crew set to work flensing the whale, which had by then finished up its agonies. “The workmen were startled . . . to discover somethi
ng doubled up in [the stomach] that gave spasmodic signs of life. The vast pouch was hoisted to the deck and cut open and inside was found the missing sailor, . . . unconscious” but alive—after thirty-six hours inside the whale.*

  Bible literalists seized upon the Bartley story. For decades, it turned up in religious tracts and fundamentalist sermons. In 1990, professor and historian Edward B. Davis, then at Messiah College in Grantham, Pennsylvania, did some fact-checking. His paper runs to nineteen pages and encompasses research that took him from the newspaper archives of the British Library to the history room of the Great Yarmouth public library. Short version: The Star of the East was not a whaler, and there was no whaling going on in the Falklands at that time. No one named James Bartley had been on the ship, and the captain’s wife was certain no crew had ever been lost overboard.

  Placing history aside, let’s look at the digestive realities of the Bartley situation. If survival in the stomach were a simple matter of the size of the accommodations, any one of us could manage just fine. The forestomach of a killer whale, a far smaller creature, has been measured, unstretched, at five feet by seven feet—about as big as a room in a Tokyo capsule hotel, with a similar dearth of amenities. Figure 154 of Whales, by esteemed whale biologist E. J. Slijper, is a scale drawing of a twenty-four-foot killer whale and the fourteen seals and thirteen porpoises recovered from its stomach. The prey are drawn in a vertical lineup beneath the whale’s belly, like whimsically shaped bombs dropping from a plane.

  While a seaman might survive the suction and swallow, his arrival in a sperm whale’s stomach would seem to present a new set of problems.* “Bartley’s skin, where it was exposed to the action of the gastric juices, underwent a striking change. His face and hands were bleached to a deadly whiteness and the skin was wrinkled, giving the man the appearance of having been parboiled.” Hideous. And, it turns out, bogus. The whale’s forestomach secretes no digestive fluids. Hydrochloric acid and digestive enzymes are secreted only in the second, or main, stomach, and the passage between first and second is too small to admit a human.

  While the absence of acid in the sperm whale forestomach shoots another hole in the Bartley tale, it lends some credence to the Jonah parable. Let’s say the whale swallowed some air as it surfaced in pursuit of Jonah. Or let’s fast-forward a few centuries and give him a scuba tank of oxygen. Might the whale stomach under these circumstances be a survivable environment?

  It might, if not for this: “Whales ‘chew’ their food with their stomachs,” writes Slijper. Since sperm whales swallow prey whole, they need some other way to reduce it to smaller, more easily digestible pieces. The muscular wall of the forestomach measures up to three inches thick in some species. Slijper compares the cetacean forestomach to the gizzard in birds—an anatomical meat grinder that stands in for molars.

  Would a man in a whale forestomach be crushed or merely tumbled? Is the force lethal or just uncomfortable? No one to my knowledge has measured the contraction strength of the sperm whale forestomach, but someone has measured gizzard squeeze. The work was done in the 1600s, to settle an argument between a pair of Italian experimenters, Giovanni Borelli and Antonio Vallisneri, over the main mechanism of digestion. Borelli claimed it was purely mechanical: that birds’ gizzards exerted a thousand pounds of force, and with that kind of grinding going on there was no call for chemical dissolution. “Vallisneri, on the contrary,” wrote author Stephen Paget in a 1906 chronicle of early animal experimentation, “having had occasion to open the stomach of an ostrich, had found there a fluid* which seemed to act on bodies immersed in it.”

  In 1752, a French naturalist devised a way to resolve the debate—and, unintentionally, address the inane whale-stomach-survival query of an American author two and a half centuries into the future. René Réaumur owned—or anyway, had access to—a small raptor called a kite. Like most carnivorous birds, the kite regurgitates a pellet of fur and feathers once it has finished with the digestible portions of its prey. This gave Réaumur an idea. He could hide in the kite’s food a small tube carrying meat. The tube would keep the meat from being crushed by the gizzard, and mesh grates at either end would allow stomach solvents, if they existed, to enter and digest it. The kite’s gizzard, taking the tube to be an unusually large, hard bone, would conveniently return it to daylight. If the meat in the regurgitated tube was dissolved, it meant some sort of fluid had done the work of digestion. Réaumur would eventually try this with a variety of barnyard birds. For our purposes, we are more interested in the fate of the tubes than that of the food. Those made from glass were smashed by the contractions of the gizzards, as were the tin tubes that replaced them. Réaumur had to use lead tubes that would withstand close to 500 pounds of pressure before they emerged from a gizzard uncrushed.

  To get a sense of what that would feel like—what it would be like inside a gizzard or, by extension, a sperm whale stomach—I did a Google search on “500 pounds of pressure.” That is, among other things, the maximum pressure exerted by the beak of a Moluccan Cockatoo, a bird that can bite off a man’s finger. It’s the force exerted by the footfall of a 130-pound person, which means that being inside a gizzard feels like me stepping on you, perhaps in my haste to escape your cockatoo. And, finally, the American Automobile Association tells us that 500 pounds is the force with which an unrestrained ten-pound dog will hit the windshield in a fifty-mile-per-hour head-on.

  And a sperm whale’s forestomach muscles are presumably more powerful than those of a turkey gizzard. I’d say your chances of surviving in a sperm whale stomach are slender. I’d say you’re better off with the Chihuahua in the crashing pickup truck.

  The biblical account of Jonah’s travails does not actually use the word whale. It says “big fish.” University of California, Santa Cruz, biologist Terrie Williams once had occasion, as they say, to open the stomach of a sixteen-foot tiger shark. It happened while she was working in Hawaii. A woman had been killed while swimming, not far from where the shark had been caught, and Williams was called in to see if pieces of her might be found inside it. Instead, Williams found three full-grown, manhole cover–sized, intact green turtles, all facing forward. “They never saw it coming. All they knew was like, ‘I’m swimming around and it’s blue, it’s Hawaii, how great is this . . .’ And the next thing they see is this huge mouth shutting.” And shark stomachs, unlike sperm whale forestomachs, secrete gastric acids and enzymes. Williams thought that the turtles, withdrawn into their protective shells and able to store oxygen in their muscles, might have survived a half day or so.

  What about a scuba diver in a wetsuit with a tank of oxygen? How long could he survive in a tiger shark? Christiananswers.net puts forth an intriguing digestive loophole that, were it true, would have worked in his—or for that matter, Jonah’s—favor: “As long as the animal . . . swallowed is still alive, digestive activity will not begin.”

  THIS PERSISTENT BIT of digestive bunk can be traced to eighteenth-century Scottish anatomist John Hunter, an otherwise estimable scientist who more or less invented modern surgery. In the course of hundreds of dissections, Hunter would come across cadavers with mysterious lesions in the stomach wall. He first assumed, reasonably enough, that the lesions had been the cause of death. But the condition was turning up even in vigorous young men killed in brawls, including one man done in by a blow to the head with an iron poker. In this case, too, the man’s stomach was dissolved clear through, Hunter noting that the contents of his supper—cheese, bread, cold meat, and ale—had spilled into the body cavity. There are several things one might take away from this case: that pub fare has changed little in two hundred years; that the owners of drinking establishments would do well to keep the fireplace tools behind the bar. Hunter came away with the realization that the inexplicable lesions he’d been seeing were not disease but auto-digestion. The stomach tissue, he noted, was damaged in the same way the digested cold cuts were. In other words, the stomach, at death, begins to digest itself.

 
This raised the question, What keeps it from doing so while the person is alive? Hunter’s explanation—and the source of the Christiananswers.net piffle—was that living tissue exudes some sort of vital force field that protects it. “Animals . . . possessed of the living principle, when taken into the stomach, are not the least affected by the powers of that viscus . . . ,” stated Hunter in a 1772 text. Ditto humans taken in: “If one conceive a man to put his hand into the stomach of a lion, and hold it there,” wrote Hunter in a separate text, “. . . the hand would not in the least be digested.” A small and temporary consolation, it must be said.

  French physiologist Claude Bernard didn’t buy it. Bernard took some animals into the stomach. The year was 1855. The stomach belonged to a live dog and had been given a fistulous opening similar to the one that had enabled William Beaumont to spy on the digestive activities of Alexis St. Martin a few decades (and chapters) earlier. Bernard restrained the dog and then “introduced,” through the fistula, the hindquarters of a frog. After forty-five minutes, the frog’s legs were “largely digested”—nothing new to a Frenchman, except that here the frog was still alive. The experiment, concluded Bernard, “shows that life is not an obstacle to the actions of gastric juices.” And that cruelty was not an obstacle to the actions of Claude Bernard.*

  In 1863, English physiologist Frederick W. Pavy extended Bernard’s findings to mammals. In keeping with the French market-day theme, Pavy selected a rabbit. He inserted one of its ears into the stomach of yet another fistulated dog while it was digesting a meal. Four hours later, a half inch of the tip was “almost completely removed, the small fragment only being left attached by a narrow shred to the remainder of the ear.” Again, digestion had proceeded unthwarted by the “living principle” or any sense of decency.