What is the function of a cat's whiskers?
The most perfect organs of touch are the vibrissce or whiskers of the cat, which act as long levers in communicating...

There is an old belief that a cat uses its whiskers to determine whether it can squeeze through a small hole or opening. According to this notion, the whiskers are exactly the same width as the animal's body and if they touch the sides of the hole the cat will not attempt to enter. Although not strictly true, there is a grain of truth in the belief. The large facial hairs, known scientifically as vibrissce, serve as feelers or organs of touch and they contribute materially to the cat's ability to move about in the dark. These hairs themselves, of course, are not sensitive, but the roots are provided with sensitive nerve-endings.

The most perfect organs of touch are the vibrissce or whiskers of the cat, which act as long levers in communicating impulses to the nerve fibers that terminate in clusters about the dermal sacs in which they are inserted. These cat-whiskers are merely specialized forms of such hairs as those which cover the bodies of most mammals, and which remain upon the human skin imbedded in minute sacs. Facial hairs of this type are particularly well developed, both in number and size, in those predatory species which hunt chiefly in jungles and other thick undergrowth. In the vegetable-eating bears the whiskers are few in number, small in size and apparently without any function. There may be a relationship between a cat's whiskers and its sense of sight. A naturalist found that cats with their whiskers cut short were unable to judge distances accurately. In experiments cats without whiskers would repeatedly miss their prey when springing for it. The investigator concluded that the facial hairs aid the animal to fix its eyes on its prey and that it is undoubtedly injurious to remove the whiskers from a cat which must hunt for a living.