Gulp: Adventures on the Alimentary Canal

by Mary Roach

sand or grit ten microns in diameter. A micron is 1/25,000 of an inch. If you shrank a Coke can until it was the diameter of a human hair, the letter O in the product name would be about ten microns across. “If there’s

Tom Little, an Irish American laborer who ate his meals by chewing food and spitting it into a funnel that fed into his stomach. When he was nine years old, in 1895, Tom swallowed a draught of clam chowder without letting it cool. The burn healed with strictures that fused the walls of his esophagus. Surgeons created a fistulous opening to his stomach so he could eat—or “feed,” as Tom now referred to the act of taking in sustenance. It was an undiminishing source of embarrassment. (Interestingly, his doctor noted in a book about the case, Tom “blushed both in his face and his gastric mucosa.”) He told no one, and took his meals alone or with his mother.

He summed up the soldiers’ take on potted meat: “We could undoubtedly survive on these rations a lot longer than we’d care to live.” (NASA went ahead and tested an all-milkshake meal plan on groups of college students living in a simulated space capsule at Wright-Patterson Air Force Base in 1964. A significant portion of it ended up beneath the floorboards.)

Crack is a superb onomatopoeia; the word sounds like the noise, and the noise is

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.

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.”

“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.

If you must spend time in a digestive organ, I recommend the penguin stomach. Penguins can shut down digestion by lowering the temperature inside their stomach to the point where the gastric juices are no longer active. The stomach becomes a kind of cooler to carry home the fish they’ve caught for their young. Penguins’ hunting grounds may be several days’ journey from the nest.

1896 was a banner year for human-swallowing, or yellow journalism. Two weeks after the Bartley story broke, the Times ran a follow-up item about a sailor buried at sea. An axe and a grindstone, among other things, were placed in the body bag to sink the parcel. The man’s son, frantic with grief, plunged overboard. The next day, the crew hauled aboard a huge shark with an odd sound issuing from within. Inside the stomach, they found both the father and the son alive, one turning the grindstone while the other sharpened the axe, “preparatory to cutting their way out.” The father, the story explains, “had only been in a trance.” As had, apparently, the Times editorial staff.

As so often is the case with apocryphal tales like this, finding someone who knows someone who’s seen it is easy.

That appears to be what was depicted in a photograph that went viral in 2005, of a dead python in a Florida swamp with the tail and hind legs of an alligator sticking out of its side.

“That’s what everyone was saying: that the alligator kicked its way out,” Stephen Secor told me. Secor had been flown out to the scene by a National Geographic television production team, who had hired him as an on-camera expert for a one-hour special spawned by the chimerical remains. Secor knew before he arrived that the dinner-kicking-its-way-out scenario was extremely

unlikely. Pythons kill their prey before eating it.* “And there’s no way stuff can mov...

There was in fact a weak spot. Secor pointed to a printout of the photograph I’d brought with me when I visited his lab in late 2010. Two-thirds of the way down the python’s exterior is a patch of black (dead) tissue—a poorly healed wound from some earlier incident. The rupture of this wound, Secor thinks, was caused by an alligator, let’s call him alligator B, who attacked the python while he was digesting alligator A. The python broke open at the poorly healed wound, and A popped out. So ...

THE OTHER THEORY Stephen Secor debunked for the National Geographic program was that the alligator dinner was so enormous the python simply burst. “That,” he said, pointing to the meal in the famous photograph, “is nothing.” The python is built to accommodate prey many times wider and bulkier...

bubble gum. Secor went over to his computer and pulled up a slide of a python engulfing the head, neck, and shoulders of an adult kangaroo. This was followed by a shot of a python with three-quarters of a gazelle “down in,” with only the hips and rear legs remaining al fresco. Pythons use their muscular coils to pull the prey apart, like taffy, so it’s narrower and easier to get down. And they don’t swallow in a single peristaltic wave of muscle contraction, as we do. They do what’s called a “ptergoid walk.” They inch their jaws along on the prey like marines on their bellies, moving forward by the elbows, left, right, left. The other reason Secor could dismiss the bursting-stomach theory is that he knows exactly how much pressure that would take. “We sealed off the cloaca of a dead python and inserted an air line down the esophagus.” Probably much like you at this moment, Secor was “sick of listening to people talk about pythons bu...

“The predator has a very compliant stomach,” says David Metz, a gastroenterologist with the Hospital of the University of Pennsylvania who has studied people who compete in eating contests. “Think of the lion

after the big meal, with its huge, distended belly. They can lie in the sun for the next few days, letting it all slowly get digested.” When you occupy the top spot on the food chain, you are free to lounge around with little concern over someone larger and stronger jumping you and eating you. The lion falls prey only to humans, in the form of

hunters—and the occasional Mesopotamian v...

Those of you who swallow oysters without chewing them may be curious as to the fate of your appetizers. Mollusk scientist Steve Geiger surmised that a cleanly shucked oyster could likely survive a matter of minutes inside the stomach. Oysters can “switch over to anaerobic” and get by without oxygen, but the temperature in a stomach is far too warm. I asked Geiger, who works for the Florida Fish and Wildlife Research Institute, about the oyster’s emotional state during its final moments inside a person. He replied that the oyster, from his understanding, is “pretty low on the scale.” While a scallop, by comparison, has eyes and a primitive neural network at its disposal, the adult oyster makes do with a few ganglia. And mercifully, it is likely to go into shock almost immediately because of the low pH of the stomach. Researchers who need to sedate crustaceans use seltzer water because of its low pH. Geiger imagined it would have a similar effect on bivalves. But you might like to chew them nonetheless, because they’re tastier that way.

addition to the social side effects, chronic

belching splashes the esophagus with an excess of gastric acid, which sloshes out of the stomach along with the gas. If this happens too much or too often, the acid burns the esophagus. Now you have another reason to visit Dr. Jones: heartburn. How much acid exposure is “too much”? More than about an hour a day, according to research by David Metz, the University of Pennsylvania gastroenterologist we met in the previous chapter. That’s the cumulative time each day that the normal esophagus is exposed to gastric acid. (People with gastric reflux spend far more time bathing their pipes in acid; in their case the sphincter may be leaky.)

A WOMAN’S abdomen is stretched so far that her belly button is inside out, it is usually safe to assume she is pregnant. The woman wheeled into the emergency room of the Royal Liverpool Hospital at 4 A.M. on an unspecified date in 1984 was an exception. She turned out to be carrying a meal. As dinners go, this was triplets: two pounds of kidneys, one and a third pounds of liver, a half pound of steak, two eggs, a pound of cheese, a half pound of mushrooms, two pounds of carrots, a head of cauliflower, two large slices of bread, ten peaches, four pears, two apples, four bananas, two pounds each of plums and grapes, and two glasses of milk. Nineteen pounds of food. Though her stomach eventually ruptured and she died of sepsis, the organ heroically held out for several hours.

Had Parks’s team not gotten to the bag first, the plugs would have been “keistered” by convicts into the prison yard, two or three and occasionally six at a time, and then laid like the eggs the men spend their days

The slang for the rectum is “prison wallet,” but it could be “Radio Shack.”

The defecation reflex causes the rectal wall muscles to contract—that is, squeeze—at the same time the anal sphincter muscles relax. To the conscious mind this registers as urgency—somewhere between “Hello” and “Drop what you’re doing.” The larger or more liquid the load, the more pressing the urge and the tougher it is to hold back. Water will leak out a very small opening. As one gut expert put it, “Not even the sphincter of Hercules can hold back water.” Take this to its end point and you have the simple saline enema—and an urgency that is not easily, if at all, overridden.

“Follow each call to the stool.” Or, in the words of a British physician quoted in Inner Hygiene, James

Whorton’s

Crump says a rectal bomb wouldn’t bring down a plane either. “At most, you’d blow the seat apart.” I showed him a Fox News piece that quoted unnamed explosives experts saying that a body bomb containing as little as five ounces of PETN could “blow a considerable hole” in an airline’s skin, causing it to crash. “Total codswallop,” said Crump. As fans of the TV program MythBusters

know, even blowing out a window in flight won’t create explosive decompression. The cabin will depressurize, but as long as the oxygen masks drop, people are likely to survive. “Remember that Southwest 737?” asks Crump. “The roof panel ripped partway off and they were fine. As long as you’ve got the pilots at the controls, and the plane’s got wings and a tail, it will still fly.”

This was comforting, but only for a moment. “Really, why bother with all that?” Crump said. “With a bit of prior observation, I can generally figure out a way to avoid going through a body scanner at most international airports.”

Anal tissue is among the most densely innervated on the human body. It has to be. It requires a lot

information to do its job. The anus has to be able to tell what’s knocking at its door: Is it solid, liquid, or gas? And then selectively release either all of it or one part of it. The consequences of a misread are dire. As Mike Jones put it, “You don’t want to choose poorly.” People who understand anatomy are often cowed by the feats of the lowly anus. “Think of it,” said Robert Rosenbluth, a physician whose acquaintance I made at the start of this book. “No engineer could design something as multifunctional and fine-tuned as an anus. To call someone an asshole is really bragging him up.”

* Other red flags for customs agents include the unique breath odor created by gastric acid dissolving latex, and airline passengers who don’t eat. For years, Avianca cabin crew would take note of international passengers who refused meals, and report the names to customs personnel upon landing.

The flammability of methane and hydrogen is part of the reason for the seeming overkill of protracted bowel-cleansing that precedes a colonoscopy. When gastroenterologists find a polyp during a screening, they will usually remove it while they’re in there, using a snare with an electrocoagulating option to staunch the bleeding. They do not want to worry about

igniting a rogue pocket of combustible gas—as happened in France, in the summer of 1977, to fatal effect.

At a university hospital in Nancy, a sixty-nine-year-old man arrived at the Services des Maladies de l’Appareil Digestif (French for “Gastroenterology Department”). With the current set to 4, the doctor began a simple polypectomy. Eight seconds into it, an explosion was heard. “The patient jerked upwards off the endoscopy table,” reads the case report, and the colonoscope was “completely ejected” (French for “launched from the rectum like a torpedo”). What was strange was that the Frenchman had followed his colonoscopy prep instructions to the letter. The culprit, in this case, had been the laxative. The staff had prescribed a solution of mannitol, a sugar alcohol similar to sorbit...

enough hydrogen to set the stage for an internal Hindenburg scenario. A study done five years later found potentially explosive concentrations of hydrogen or methane, or both, i...

This is no excuse for putting off your colonoscopy. Mannitol is no longer used, and doctors routinely blow air or nonflammable carbon dioxide into the colon as they work, which dilutes any pockets of hydrogen or methane. (Inflating the colon also helps them see what they’re doing. And creates the magn...

On whether they expel it with gusto or try to hold it in, letting it out in many tiny squeakers and falsely upping their flatographic tally. Len pointed out a related shortcoming to the breath hydrogen test. When people, stereotypically women, hold in their gas, they absorb more of it into their bloodstream, “so it comes out in the breath.” This artificially raises their breath hydrogen numbers and may serve to explain the occasional highly counterintuitive finding that women are more flatulent than men. “Right, Alan?” Kligerman stirred his chili. “I don’t know, Len. I don’t know what the ultimate fate of a suppressed fart is.”

What amazed me about Magendie, aside from his zest for gore, was this: using instruments available in 1814, he was able to detect hydrogen sulfide, a gas that typically makes up one-ten-thousandth of the gas produced in the human colon. It’s possible the instrument Magendie used was, in fact, his nose. The human olfactory system detects the rotten-egg smell of hydrogen sulfide at the practically nonexistent rate of .02 parts per million. Though present in no more than trace amounts, hydrogen sulfide is, in the words of Michael Levitt, “the most important determinant of flatus odor.” He would know.

Devrom “internal deodorant” pills.

Less time in the colon means less water is absorbed. The runnier the waste, the more surface area is exposed to the air and the more volatiles escape to reach the nose.

Hydrogen sulfide is as lethal, molecule for molecule, as cyanide. This may explain why humans evolved such exquisite sensitivity to its smell. Repellent odors are unpleasant but often helpful in terms of not dying. As with any poison, dosage makes the killer. The concentration of hydrogen sulfide in offensive human flatus is around 1 to 3 parts per million. Harmless. Ramp it up to 1,000 parts per million—as can exist in manure pits and sewage tanks—and a couple breaths can cause respiratory paralysis and

suffocation.

Workers die this way often enough that a pair of physicians, ...

journal, coined a name for it...

It is fitting that the Devil is said to smell of sulfur. Hydrogen sulfide is a diabolical killer. Its telltale rotten-egg smell, screamingly obvious at 10 parts per million, disappears at concentrations above 150 parts per million; the olfactory nerves become paralyzed. Without the odor to warn them, coworkers and family members may rush into a manure pit to rescue the fallen. Whole families have been taken out in a catastrophic “chain of death.” One case report included a police photo taken after the victims had been pulled from the mire and laid on the ground. It was a wrenching play on the family portrait, the four adults arranged in a row in matching knee-high muck boots, black bars over their eyes. The farmer had

gone in to unclog a pipe. Both he and the worker who tried to rescue him collapsed and died. The farmer’s mother found the two, hurried down the ladder and also succumbed. Then the son came along. And on it went, all the way to a team of pathologists nearly overcome in a poorly ventilated autopsy room.