Why do cats purr? Why do Cheshire cats grin?

Dear Cecil:

Why do cats purr? And while we're on the subject, what is the pedigree of the Cheshire cat?

Cecil replies:

Cats don’t purr just when they’re feeling chipper — they also purr when they’re frightened or badly hurt. Purring doesn’t have any specific emotional connotation; rather it seems to be a kind of homing device. Cats learn the signal in the first few days of kittenhood, when they can’t see, hear, or smell very well. The mother cat purrs to call the kittens to nurse — unable to hear the sound, the kitten can feel the vibrations.

There are two schools of thought on exactly how a cat purrs. One theory traces the vibrations to a set of “false vocal cords,” a bundle of membranes that lies above the genuine vocal chords and seems to have no other clear function. The other opinion locates the purr in the vibrations of the hyoid apparatus, a series of small bones connecting the skull and the larynx that nominally serves to support the tongue. Since it’s difficult to induce a cat to purr while you’re examining his hyoid apparatus, the truth may never be known.

As for the Cheshire cat — well, kids, there ain’t no such thing. The Cheshire cat in Alice in Wonderland is Lewis Carroll’s play on a popular expression — “to grin like a Cheshire cat” — of obscure origin. Cheshire is a dairy county in western England famous for its cheese — cheese that once, according to legend, came molded in the shape of a grinning cat. A rival theory finds the Cheshire cat in the coat of arms of the area’s Grosvenor family. What started out as a lion on the crest came to resemble, in the bumbling hands of the Cheshire sign painters, an inebriated alley cat. The phrase first appears in print in Peter Pindar’s “Pair of Lyric Epistles” in 1795: “Lo, like a Cheshire cat our court will grin.”

Send questions to Cecil via cecil@straightdope.com.

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