Everybody has admired a whiskered head of cat one day. Countrymen think: the longer cat whiskers the better it chases mice. And there's a grain of truth here, because whiskers not only decorate a cat (dog, rabbit, rat...) muzzle but are the sense organs as well. Special long hairs - vibrissae (from Latin, vibrae - vibrate) - are situated on pads around mouth, above eyes, on "moles" on cheeks.
The base of a vibrissa lies in a skin sack - follicle, where special cells that percept displacement and pressure, - strain-receptors, winded with nerve fibers are situated. The tremble of a vibrissa is provided by a muscular filament, which forms a loop around sack. Any alteration in position of a hair stimulates a signal that passes through the nerve fiber in central nervous system. In central nervous system a signal comes to a cerebral hemispheres cortex. In cerebral cortex both animals and humans the "map of body" exists, which represents a total surface of body, different parts of which are represented unequally by their size. The most sensitive parts of body, tips of fingers, face, the area of mouth and tongue, for instance, occupy the biggest square on the brain "map of body"; the smallest part corresponds to a skin on a back and limbs. Every out of 33 long and many short vibrissae, situated on muzzle of an animal have its' own representation on the "map of body" as a complex of nerve cells, which is called "keg". If one to move away all vibrissae of a newborn kitten, nerve cells of corresponding kegs will perish and cells of adjacent kegs, the vibrissae of which are intact will occupy a vacant place. The map of body will change but will correspond to a real surface of a kitten muzzle.
Scientists investigated biochemical processes in brain by means of substances, marked with radioactive ions. It was found that vibrissae ablation of an adult cat (trimming) causes biochemical disturbances in kegs and alters animal behavior for some time and oppresses its' mind. Rough jerks by vibrissae causes unpleasant feelings in animal and breaks the glucose assimilation by cells of keg for several hours.
One can study the work of nerve cells registering electrical signals of these cells by special apparatus. Scientists determined that nerve cells of keg alter the frequency of discharges in accordance with change in speed, range and direction of movement of vibrissae. The processing of information, coming into central nervous system from vibrissae allows animals to find their bearings in darkness, narrow burrows and passages.
Scientists have invented a complicated experiment to study the work of vibrissae. First, they taught rats to wear opaque glasses. Then they taught these animals to differ surfaces of two paths leading to food with the help of vibrissae. One surface was smooth, other - shaggy. The roughness of path was due to small hollows. A rat blind owing to opaque glasses came close to a path and directed its' vibrissae towards its' surface. Some rats were fed at the end of a smooth path, and others - at the end of shaggy path. After examining of both paths by vibrissae a rat chose that one that always led it to food. During the experiment rats were shot by camera. The analysis of video record of rat during examination of paths showed that its' vibrissae touched the surface by its' bent part (not the tip), making very quick movements (trembling) towards a surface and back up to 20 times a second. These movements and touches are enough to define surface characteristic. Rats by means of vibrissae may distinguish even the emery paper of different size.
Vibrissae are the substitute of fingertips by which men and monkeys examine surface and shape of objects.
Taking into account scientific knowledge about the role of vibrissae in behavior, one should apparently change some models of dog haircuts and leave whiskers (for example, for poodles) not only for the sake of beauty, but to preserve mentality healthy. So should one damage an outstanding sense organ for the sake of fashion?
Translated by Tatiana Karpova (Moscow)
(MSU, Biology faculture, Dep. zoology and ecology).