The mysteries of the Purr.
Most felines, from the domestic cat to the lion and the panther can emit a deep and caracteristic vibration, the purr. This purring starts when the cat is very young and continues well into old age. We still don't know the exact mechanism.
For a long time it was thought to be a vibration from the folds of the larynx but felines having undergone a laryngectomy, (Hardie and Co-1981) continue to purr.. The diaphragm has been invoked (Stogdale1985) but current opinion suggests that purring is the result of blood flow in the vena cava: this vein narrows to pass into the liver and the diaphragm. In certain neurovegetative states the blood will form ripples in this bottleneck which then provoke vibrations in the body all the way up to the cranial cavities of the sinus by way of the windpipe..
In fact everything vibrates and the cat takes on a caracteristic relaxed (laid back) attitude. This relaxed state was for a long time associated with contentment, however cats that are in pain or distress also purr. The phenomenon of resonance: this is a physical phenomenon that touches all media in all frequencies. When one element of a medium starts to vibrate, the whole medium vibrates to the same frequence reinforcing the original sound. The violin is a good analogy: when the bow is drawn across a chord, the whole violin vibrates to produce a harmonious sound. When a cat purrs the same effect occurs in the body and everything vibrates.
The enigma of frequence 25/50 hertz.
If we analyse the sound spectrum of a cat's purr we see mainly deep sounds ranging in frequence between 25/50 hertz. These are "bass" sounds, well known to music composers for they provoke emotions and therefore have a direct influence on an organism. Can such an action be measured ?
The organisation for animal protection Animal Voice, that studies many forms of animal communication has carried out research on the subject.
Orthopedic doctors have used these frequencies to consolidate fractures and successfully treat degenerative osteoarthritis. The published results show an acceleration of the healing process and the creation of new tissue. In short these bass frequencies have an anabolic action.
At the same time, the researchers at Animal Voice have found statistics in veterinary universities showing that for the same lesion and with the same surgical treatment cats have five times fewer after effects and recuperate three times more quickly....
Hence the hypothesis of an anabolic recovery: purring has a real therapeutic effect !
Happiness or distress..... Recovery time.
Whilst treating cats in distress, veterinary surgeons have noticed that suffering animals still find the force to purr. Here we are far from the image of the contented cat purring in the arms of it's master....
All the same, in both cases purring is associated with the recovery process.
With a contented cat, sleep and happiness are well known to be anabolic states. It is whilst we sleep that we grow, build tissues and structure the memories of the days events.
With a cat in distress we can interpret purring as a desperate reaction of the organism to resist the disease. This phase of recovery and consolidation is controlled by the brain through the autonomic nervous system.
The Autonomic nervous system.
Permanently and to the best of our knowledge, the nervous system surveys the body and regulates our organs. The heartbeat, the muscles of the iris, retention of the bladder, all the major involuntary activities of the body are controlled by bundles of nerve fibres: the autonomic nervous system.
These fibres function independantly of our control and effect all the organs of the body. They control the passage of food through the gut, the inhalation and exhalation of air in the lungs, blood circulation etc. They also activate the glands and therefore control the production of hormones. ..
This autonomic nervous system, whose main function is to maintain the body in a stable state, is composed of two opposing and complementary parts, the sympathetic system and the parasympathetic system.
The Sympathetic system , whose nerve fibres are activated by the production of noradrenalin, prepares the body for an emergency by mobilising all defenses, increasing heartbeat, raising blood sugar level, constricting arteries. Fight or flight.....
It is the sympathetic nervous system that keeps the body alert and controls our degree of agressivity by the production of dopamine.
When the sympathetic system is called into action the body works very hard and rapidly consumes it's reserves, all the cell membranes depolarise.
Inversely the parasympathetic nervous system stimulates the production of serotonin (the sleeping hormone).
Serotonin is produced during the day and stored in certain parts of the brain ( pre-optic cavities). It gradually overrides an alert state and sleep can ensue. Whilst an organism is sleeping it can build up it's forces. It is often upon waking in the morning that one feels cured of a viral or bacteriological infection. .
The hypothesis of endorphines: endorphines are endogenous morphines secreted by nerve tissue, either to combat pain, or paradoxically to accompany a feeling of happiness and fulfilment. It is in these two cases that a cat begins to purr. Researchers think that purring produces endorphines that allow the animal to ease it's own pain and also to achieve visible serenity. ..
