Cat's purring – one of the reasons for which people get these animals. The fluffy lump which was curtailed on a lap and making rhythmical sounds is capable to calm nerves, to remove stress after unlucky day and to lighten the mood.
The popular English writer Terry Pratchett in the book "Cat without Fools" best of all described cat's essence: "Call at least one more animal who is fed not for the fact that it brings benefit, protects the house or loudly chirps but because, having gorged on, it goes happy and hums".
Why cats purr
Purring – one of ways of communication of cats. It is given them practically since the birth. The two-day kittens who are not able to mew yet can already purr. So they communicate with mom during sucking of milk, giving her signals of the good health. It is often possible to hear reciprocal purring from a cat.
With age the circle of the reasons for which animals make such sounds extends. Cats purr when they want to show the satisfaction. For example, if are glad to see the owner after long separation. If the animal is strongly frightened, it can also make similar sounds. Thus it calms itself just as people sing to themselves under a nose cheerful songs in a stressful situation. The cat who went to the relatives can purr, showing the benevolent spirit.
Cases when fatally sick cats understanding that they needed to live not for long purr meet. These are the finishing sounds which can indicate nervousness of an animal or, on the contrary, euphoria.
As cats purr
An initiator of purring is the central nervous system of a cat. The animal does not make efforts for it, everything occurs spontaneously. During the first experiments it was revealed that the nervous impulse causes vibration of vocal chords, and the diaphragm in turn pushes through them air. As a result in a throat of a cat the purring sound is formed. However the reliability of the conducted researches did not manage to be proved, animals were immobilized at this time. More exact results were shown by scientists from the USA. They made experiments under natural conditions, using hypersensibility microphones. They managed to prove that during a breath and an exhalation of a cat air passes through two folds located in a throat. They are called still false vocal chords. Vibration of these folds also causes purring. The person is not able to repeat the similar mechanism of communication. Unlike cats, people are capable to make sounds only on an exhalation. On a breath the vocal chords are densely closed.