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For cat owners, the greatest pleasure is in that feeling of contentment
cats share with us. We feel calmer and more peaceful when that
purring bundle of warm fur climbs into our lap. We may not always
hear the purring – a soft vibrating rumble – but we can feel it.
Ever since the Egyptians started worshipping the cat, philosophers,
scientists and cat lovers worldwide have wondered why cats purr.
It is commonly believed that cats purr when content. However,
cats also purr when they are severely injured, frightened or giving
birth. So if cats were purring solely out of happiness they would
not purr when injured, especially as the generation of the purr
requires energy, and an injured animal will generally not expend
precious energy needed for healing on an activity not directly
connected with their survival. Since the purr has lasted through
hundreds of generations of cats, there must be a survival mechanism
behind its continued existence.
A kitten is able to purr by the second day of life, and although
he can’t meow and nurse at the same time, he can purr and nurse.
And the mother cat often purrs back, probably to reassure the
kitty.
There are many theories to explain how the purr is generated.
One study determined that purring involves activation of nerves
within the voice box. These nerve signals cause vibration of the
vocal cords while the diaphragm serves as a piston pump, pushing
air in and out of the vibrating cords, thus creating a musical
hum.
Domestic cats and some wild cats, like pumas and mountain lions
(almost any big cat that cannot roar), are all able to purr. A
scientific research study recorded the purrs of five species of
cats - cheetah, puma, serval, ocelot and the domestic cat. The
purring of the subject cats was recorded to be at a frequency
between 25 and 150 Hertz. Medical investigators have shown that
sound frequencies in this range can improve bone density and promote
healing in humans as well as other animals.
The durability of the cat has facilitated the notion that cats
have "nine lives." Purring may provide a basis for this
feline mythology. Cats do not display as many muscle and bone
abnormalities as their more strongly selected carnivore relative,
the domestic dog. Perhaps cats' purring helps alleviate the dysplasia
or osteoporotic conditions that are more common in their canid
cousins.
After a day or night of hunting, purring could be likened to
an internal vibrational therapeutic system, a sort of "kitty
massage" that would keep muscles and ligaments in prime condition
and less prone to injury. Additionally, the purr could strengthen
bone, and prevent osteodiseases. Following injury, the purr vibrations
would help heal the wound or bone associated with the injury,
reduce swelling, and provide a measure of pain relief during the
healing process.
Cats are often used as "therapy animals" in convalescent
hospitals, or in retirement residences. It is an accepted fact
that cat owners have lower blood pressure, especially in older
people.
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