Among the "highest compliments a dog can pay its food," Mary Roach writes in her latest book, Gulp: Adventures on the Alimentary Canal, "is to vomit."
Apparently, when Fido catches a whiff of something really tasty, he'll "wolf down too much too fast" and then send it right back up. "No consumer likes that," a pet food expert tells Roach, "but it's the best indication that the dog just loved it."
It's also a good indication, figuratively speaking, that a reader loved Gulp. I inhaled this terrific, offbeat book in a couple of sittings, and have been gleefully regurgitating its fascinating insights and astonishing, delightfully repulsive anecdotes.
Gulp is all about the tube — Roach prefers to describe it as a "railroad flat: a long structure, one room opening onto the next" — that extends from your pie hole to your, um, other hole. Gulp is insatiably curious, ably written and wildly entertaining. It's also, Roach claims, the first book of its kind.
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"Authors have profiled the brain, the heart, the eyes, the skin, the penis and the female geography, even the hair," she writes in the introduction, "but never the gut."
That might well be due to the topic's unremitting ickiness. Follow food down the hatch, and you're going to get dirty. Even your point of entry, the act of eating, is fundamentally unappealing. "In a restaurant setting, conviviality distracts us from the biological reality of nutrient intake and oral processing," Roach points out. "But a man alone with a sandwich appears as what he is: an organism satisfying a need."
Parts of Gulp are indeed hard to stomach. You'll hear about the nightmarish giant kidney worm, "a parasite that bores out the entire organ and then exits the body through the urethra."
You'll meet a 19th-century French physiologist who tested whether gastric acid would consume living organisms by callously feeding an eel up to its head through a hole in a dog's stomach. (The eel and the dog were alive at the beginning of the experiment.) You'll turn up your nose at the Liverpudlian who ruptured her stomach after eating, among 19 total pounds of food, "two pounds of kidneys, one and a third pounds of liver, a half pound of steak."
But beyond its spectacular grossness, this book reminds us that the human apparatus for dealing with food is "at least as interesting as the photogenic arrangements we push through it."
Take, for example, the "neuromuscular elements of chewing." By certain measures, your jaw muscles are the most powerful in your body. To prevent them from reducing your molars to rubble, they've developed an unbelievably precise braking system. "The faster and more recklessly you close your mouth," Roach writes, "the less force the muscles are willing to apply — without your giving it a conscious thought."
Gulp also is filled with fabulous trivia. A puffed cassava chip, for instance, has a crack speed of 300 meters per second, the speed of sound. This means you get "a tiny sonic boom inside your mouth" whenever you bite into one.
And despite popular belief, Roach claims, it's not the drinking from a sniffly person's glass that gives you a cold: "One person's finger leaves virus particles on the glass; the next person's picks them up and transfers them to the respiratory tract via an eye-rub or a nose-pick."
Perhaps the book's most incredible detail is its theory on the origin of mythic fire-breathing serpents.
Decomposing rats inside the digestive tracts of pythons have been observed to release hydrogen. So imagine you're a caveman sitting around the fire with your catch of the day, a python that had been digesting a gazelle ("Neanderthal turducken"). One of your kids falls on the snake's tail, forcing gas out of its mouth. Which ignites. "There's your fire-breathing serpent," one of Roach's sources says. "Imagine the stories that would generate."
Dubbed "America's funniest science writer" by The Washington Post, Roach's enthusiasm and wit are infectious. Here she is looking, for instance, at a photo of herself elbow deep in a live cow rumen (part of the stomach) by way of a fistula in its side: "The cow appears unmoved," she writes. "I look like I've seen God."
Later, Roach visits a prison to learn about rectal smuggling. "A few inmates glance over as we cross the prison yard, but most ignore us," she observes. "I am really, I think to myself, getting old."
Early in the book, Roach explains that part of the reason we don't like consuming organs, despite their high nutritional value, is because they're too familiar. "In the same way a corpse spawns thoughts of mortality, tongues and tripe send an unwelcome message," she writes, "you too are an organism, a chewing, digesting sack of guts."
There's no arguing that point. But Gulp shows us just how marvelous that "sack of guts" is.
'Gulp: Adventures on the Alimentary Canal'
By Mary Roach
Norton. 348 pp. $26.95.