Last week, with the help of Mary Roach's fascinating book Gulp, I tackled a question surely on the back of everybody's mind: Can you eat via your anus?

This week, again guided by Gulp, I do the disgusting and flip the question. Ladies and gentlemen, restrain your gag reflexes.

Can you poop via your mouth?

Sketchy websites, questionable YouTube videos, and a hilarious episode of South Park all present evidence pointing to "yes." What's more, the American Heritage Medical Dictionary defines a condition dubbed fecal vomiting: "The vomiting of fecal matter that has been drawn into the stomach from the intestine by spasmodic contractions of the gastric muscles." The term is even used various times in the medical literature.

The answer to the question, however, seems to be a nuanced "no."

Indeed, fecal vomiting is a genuine condition, rarely occurring in cases of severe constipation in which the colon is completely full of feces. The vomit, however, doesn't actually contain what we recognize as poop, which comes from the colon. It contains liquid from the small intestine, ejected in with the help of powerful, reverse contractions of muscles in the small intestine and esophagus.

"A well-formed stool does not exit the upper end of the colon," Roach writes.

To the few unfortunates afflicted with fecal vomiting, the difference may seem borderline semantic. After all, liquid from the small intestine can be darker in color and doesn't exactly smell like roses.

Strangely enough, there are a couple dozen reports of actual feces being expelled from the mouth, however all of them come from the early days of modern medicine and are highly dubious. The reports prompted one skeptical physician, Dr. Gustav Langmann, to put a claimant to the test. In 1889, he undertook the care of a female patient who witnesses reported had passed stools via the mouth. At some point during the woman's hospital stay, nurses discovered "some hard feces, wrapped in paper" under her pillow. Ewwww. Case closed.

Source: Gulp: Adventures on the Alimentary Canal, Mary Roach, 2013

(Image: South Park Studios)