In Gulp: Adventures on the Alimentary Canal, Mary Roach blurs the line between the repugnant and the mesmerizing.

Why the digestive tract?

I am fascinated by the intersection of science and eating. We should be so grateful that the amazing ring of anal muscles and nerves can distinguish between gases and solids, for obvious reasons. Saliva is also amazing—if saliva didn’t lower the pH [of our mouths], we would have no teeth due to mouth acids. And a few people who didn’t cleanse properly—leaving gas inside—really did blow up during colonoscopies, back when polyps were burned off.

Your prose is often surprisingly poetic, as when you enumerate the sensory impressions that compose the scent of a particular wine (“tobacco, dark things, smoking jackets”). Did you set out to become a poet before you became a science writer?

Thank you, no—although the first thing I published was a limerick I wrote in fifth grade. It was about a fellow named Bruce and his mechanical moose.

While serving as a science writing judge in 2011, you said that a reporter’s writing was memorable less for the science than for the way he enlivened it with on-site detail. Does this assessment apply to your own work?

I’ve read plenty of amazing science pieces where the writers don’t hang out in labs. I just have fun doing it. And I get rewarded for it; I get gushy, especially when kids tell me they expected to be bored by my books, but weren’t. That stuff about kids today having no attention spans is not true. They are excited and sweet, whether claiming your books were the first they ever really read, or reporting, “Hey, man, the maggots in your book were cool.”

You’ve praised the way some science writers “impart urgency without sowing despair.” Do you try to do that in your own writing?

I don’t write on topics that require a lot of urgency. But in Stiff, I wanted to change people’s hearts about organ donation. Whenever I get a chance, I try to talk about that.

In Packing for Mars, I tried to convey the importance of getting young people interested in science. And while readers may start Gulp thinking, “yuck,” I hope they end it thinking our guts are somewhat miraculous. For that is what they are.