What Goes Down

For years, science writer Mary Roach has been writing books about how science deals with uncomfortable subjects, the sort of subjects you are supposed to avoid in polite company. In Stiff, she explores the world of cadavers; in Spooked she follows the scientific search for the soul; in Bonk she dives into science and sex (recommended for mature adults only, not because of the raciness of the subject matter but because it will rob the young of all the mystery, romanticism and power they associate with the subject). Her next book, Gulp: Adventures on the Alimentary Canal, carries on the tradition, tagging along on science's trek through the digestive system.

There are really two ways to approach such uncomfortable subjects. One is to get extremely clinical. If you've ever had an especially embarrassing malady--and I'll spare you any descriptions of mine--your doctor and the workers in the medical lab may have used this approach, explaining things using Latin terms and refusing to crack a smile. The other approach is to glory in everything that makes you squeamish. There's a certain thrill in being grossed out. This is well understood by the makers of horror films and by ten year-olds the world over. It's also well understood by Mary Roach.

Roach, for instance, dedicates an entire chapter to the relationship of William Beaumont and Alexis St. Martin. After a hunting accident left a hole in St. Martin's skin and into his stomach, Beaumont, St. Martin's surgeon, preserved the hole and began using it as a window into the mysteries of the human digestive system. Beaumont would tie foods to string and dangle them down inside St. Martin's stomach. The surgeon would sometimes extract gastric juices from Beaumont's exposed innards, using them in further experiments that sometimes included, wait for it, tasting them.

Ok, if that little tidbit is too much for you, you may want to avoid Gulp, unless you're looking to lose a few pounds and need inspiration. But if you're at least as fascinated as you are repelled, you're not going to be able to resist the rest of the story. Not all of it is quite so disgusting. Roach, for example, explores cultural digestive obsession that led to Fletcherizing, a technique involving chewing food so long that it becomes liquefied before swallowing. Fletcherizing was supposed to allow practitioners to extract twice the nutritional value from food--a claim that turned out to be bogus. She answers timeless digestive questions like Could you survive in a whale's stomach? (Spoiler: no.) and Why doesn't the stomach digest itself? (Spoiler: it does, just not fast enough.) But there's ultimately no getting away from the repulsive stuff. There's plenty on vomiting, and of course there's the tail end of the alimentary canal. No way to make that pleasant.

Also, there are a lot of unusual (at least from our cultural perspective) dietary choices discussed. For instance, consider how the world's most expensive coffee beans are made. On second thought, I won't go into details. You can look it up. You might be glad in the end, that you can't afford them.