Dear Cecil: What is it about smoking a cigarette that will sometimes send me to the bathroom for a number two? C.B.M., Washington

Cecil replies:

During my foolish youth this is the kind of question I would kiss off with some totally uncalled-for if hilarious remark. Now that I am mature, however, I know that behind many seemingly inane queries there lie deep scientific truths. It is even so in the present case. The reason smoking makes you feel like heading for the john is that your body has been specially programmed to respond to the products of the R.J. Reynolds company. No fooling. Your guts are crammed with “nicotinic receptors,” which are part of the parasympathetic nervous system, which controls your digestion, among other things. When you use tobacco, these receptors are stimulated and your innards commence to churning. If you were pretty full already, you may well feel the need to visit the john.

Some people become dependent on this odd phenomenon. Cecil has heard of a case involving an old coot who used to spend every waking moment with a chaw of tobacco between cheek and gum. One time he had to go into the hospital for prostate surgery. While he was stretched out in the recovery room, a nurse noticed that his abdomen was swelling up. The attending physicians feared that they had pierced his intestine during the operation and infected him. But then another doctor strolled in and remarked, “Hey, that’s the first time I’ve ever seen old Charlie without his wad.” Remembering the nicotinic receptors, the physicians immediately guessed that old Charlie had become so accustomed to tobacco that his intestines wouldn’t work without it. His abdomen was swelling because his bowels were filling up with air like a balloon, an event known as an ileus. They promptly sent out for a family-size can of Red Man and administered a double dose. (I presume they woke Charlie up first.) The swelling soon subsided. Another triumph for modern pharmaceutical technology, and a damn good reason to think twice about abandoning your bad habits.

Cecil Adams

Send questions to Cecil via cecil@straightdope.com.