What exactly is a fart? from the straight dope archive...

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What exactly is a fart?

18-Jun-1982

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Dear Cecil:

With all your scatological insight, what exactly is a fart? Is it, as some surmise, a burp gone wrong? Is it a relative of the hiccup? The sneeze? And is it not healthier to vent oneself than to squelch? --Phillip S., Chicago

Dear Phillip:

Your question comes at an opportune moment--I've just been reading up on the subject in the Harvard Medical School Health Letter. Harvard is a veritable gold mine when it comes to flatulence.

Intestinal gas, we learn, is made up mostly of five gases: nitrogen, oxygen, carbon dioxide, hydrogen, and methane. The first two you get from swallowing air during eating, while the last three are generated in the large intestine. From this we may deduce that burps and belches, which emanate from the stomach, consist mostly of air. Hiccups and sneezes, of course, are wholly unrelated.

Hydrogen and carbon dioxide are produced by bacteria nibbling on undigested food in the colon. The noble bean, for instance, contains complex sugars that cannot be broken down by the body's digestive juices. Upon arriving in the colon, these sugars are set upon vigorously by the resident microbes, and the resultant fermentation produces the cheerful calliope effect celebrated in such cinematic masterworks as Blazing Saddles.

Methane, another digestive byproduct, is responsible for the unique blue flame that has absorbed the attentions of college freshmen for generations. It is recommended, incidentally, that persons contemplating experiments in this line wear fireproof undies when doing so. Unca Cecil speaks from experience.

I might further mention that a friend of mine, who has reason to worry, has inquired whether there are any cases on record of persons who have exploded as a result of smoking in bed after a hearty bean barbecue. To date I have not been able to find any. However, internal detonations supposedly have resulted from the incautious use of an electrocautery device inside the bowel. The eating of beans before surgery, therefore, is definitely contraindicated.

Interestingly, the characteristic fragrance of the fart is produced not by any of the aforementioned gases but by "minute amounts of volatile chemicals formed by bacterial metabolism of residual protein and fat," we read here. Persons whose flatulence is especially memorable in this regard may be suffering from dietary maladjustment. For example, people with lactase deficiency who drink a lot of milk are said to be able to produce a gas of near-lethal impact.

Other foods that may produce farts of unusual pungency include broccoli, onions, cauliflower, cabbage, radishes, and raw apples. Don't those seem like the ideal salad ingredients for an eventful sorority lunch?

--CECIL ADAMS