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The Felid Purr:A healing mechanism?

Animal Voice is a non profit organisation and relies solely on donations & sponsorship. With your support we can accomplish so much more Caring Classrooms provides a trove of resources for teachers, learners and parents! Resources include, books, games, posters, puppets, teaching guides and more. Animal Voice - One of the main things that make this life worth living, is to help alleviate and end the suffering of innocente beings, no matter in what shape and form they came to express their soul on this planet. Animal Voice - One of the main things that make this life worth living, is to help alleviate and end the suffering of innocente beings, no matter in what shape and form they came to express their soul on this planet. Dec 07, 2012 Human beings have a 'descended' larynx, a voice box that lies down in the throat. In men, this shows as the 'Adam's apple.' The only other land animals to have this feature are elk and red deer. Not only do these deer have Adam's apples, but they can actually lower their voice boxes even further, all the way into their chests!

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**Notice to readers. The following is layman'sversion of a speculative research paper. It is a hypothesis. The definition of hypothesis is 'a tentative suggestion'and science would not occur without them. Since we have only just begun thisstudy, and as yet nothing has been proven (except for referencedresearch and the frequency range of the cat's purrs), this paper is notdesigned to give veterinary or medical advice.**

All smaller felids, including the domesticcat, caracal, serval, puma, ocelot, and even some large cats such as lions andcheetah purr. Since the1970's no one has pursued research into the 3000 year old question, 'Why docats purr?' Perhaps it is because, one, we didn't have the knowledge wehave now, and two, it was simply easier to assume that cats purr when they arecontent, which cannot be argued-they do purr when they are content. The contentment hypothesis, however, clearlycannot be the only reason cats purr:.

(1) A vocalization is used to display a particular emotionor physiological state. This enables an individual in society or pack to be ableto express themselves. As any cat owner knows well, there are different'meows' for different emotions. A cat owner knows the differencebetween their cat's 'fearful hiss' and 'foodmeow'. This cannot be applied to the purr however. Cats purr even when they give birth and when severelyinjured in a barren cage at the veterinarian's. There are cases of cats purringwhen they are in grave physiological or psychological stress, as well as whenthey sit on your lap. Therefore, purring really cannot be considered avocalization, as the purr is produced under differing emotions or physiologicalstates. As an example, a cat hissing when he/she was happy and when he/she wasscared, would confuse the rest of the cat's companions and probably would leadto him/her being ostracized.

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(2) Natural selection insures that a particular trait beadvantageous to an animal. Admittedly, there is some benefit to be obtained frompurring to one's self or to kittens, (a sort of kitty lullaby if you wish). Yet,there does not appear to be a strong 'survival' advantage to this behavior,unless, of course, you wish to constantly display submission. For the purrto exist in different cat species over time, therewould likely have to be something very important (survival mechanism) about thepurr. There is also a very good reason for energy expenditure (in this casecreation of the purr), when one is physically stressed or ill. It wouldhave to be somehow involved in their survival.

Old wives' tales usually have a grain of truth behindthem, and most people have heard of a cat's 'nine lives.' There is also an old veterinaryadage still repeated in veterinaryschools which states, 'If you put a cat and a bunch of broken bones in the sameroom, the bones will heal.' Any veterinary orthopedic surgeon willtell you how relatively easy it is to mend broken cat bones compared with dog boneswhich take much moreeffort to fix, and take longer to heal. There is excellent documentation of thecats' quick recovery from such things as high-rise syndrome. First mentioned by Dr. Gordon Robinson in 1976, high-rise syndrome was laterstudied by Whitney, W., and Mehlhaff, C., (1987) the Journal of the AmericanVeterinary Medical Association. They documented 132 cases of cats plummeting many stories from high riseapartments, (average 5.5 stories) some suffering severe injuries. Interestingly, 90%of these cats survived. The record for survival from heights is 45 stories, however most cats suffer from falls of 7 stories ormore and manage to live.

There has been someresearch which that suggests that domestic cats are in general less prone topostoperative complications following elective surgeries. Using computerrecords, Pollari and Bennet, (1996) state that complications following surgery for dogs undergoing castration to be averaged at 9.8%. The samesurgery for catslists the rate of complications to be 1.2%. Dogs undergoing overiohysterectomies(OHE) had complications 17.4% of the time and cats 8.4%. In another study by thesame authors comparing paper records with computerized documentation, dogsundergoing castration complications varied from 2.4% to 22%, in cats 0.0% to6.3%. With OHE complications varied from 6.5% to 17.7% in dogs and 3.6% to 16.%in cats. Lund et al. (1999) the records of 31,484 dogs and 15,226 cats at 52veterinary practices to determine the most common disorders. Arthritis in dogswas listed as 2.4% of the population and was not listed as being reported in thecat. The prevalence of lameness in dogs occurred 3.1% of the time, in cats it isnot mentioned as being reported. Healthy dogs were listed as 6.8% of the dogpopulation, healthy cats 9.5%.

Bone and muscles/ligaments

Although it is impossible to standardize the healing time for dogs and cats in clinically occurring fractures, due to the type of fracture, amount of trauma to soft tissues, the type of treatment, the standard evaluation time or the after care, some general statements can be made, (Johnson, 2001). Cats do not have near the prevalenceof orthopedic disease or ligament and muscle traumas as dogs do. Additionally, Toombs et al. (1985) suggests that non-union of fractures in cats is rare.

Osteo diseases that are rarely found in cats but can be found in all breeds and sexes of dogs include; Osteochondritis dissecans of the proximal humerous, scapulohumeral joint luxations, hip dysplasia. Osteo diseases in which cats are completely unaffected include fragmented coronoid process, ununited anconeal preoceese, traumatic elbow luxation, elbow subluxation, and legg-perenes. Osteosarcoma occurs much less frequently in the cat then in the dog. Johnson, 1999. Osteoarthritis and CPPd have only been found in large cats that were raised in zoological parks. The frequency of effected cats in the wild is apparently so low, that they are infrequently effected by these diseases in the wild. (Rothschild et al., 1998)

Myeloma is a tumor of plasma cells originating in the bone marrow. Only eightcats with multiple myeloma have been reported to have osteolytic bone lesions.56% of all dogs reported with this condition involve bone. The metastaticbehavioral differences between dogs and cats is that tumors in the dog involvethe whole body, whereas in the cat it involves the distal ends of theextremities.In Lameness

With regard to the prevalence of ligament and muscle injuriesand disease, those that are seen regularly in dogs but not in cats include,cranial crutiate ligament ruptures, meniscal injuries (torn ligaments), musclecontusions and strains, muscle contracture and fibrose, quadricepts contractorand inialsinatus, bicipital tenosynovitis, medial patellar luxation, lateralpatellar luxation, osteochronditis dissecans of the stifle, and ligamentousinjury of the tarsus. Johnson

One explanation for the lack of trauma or disease found incat bone and muscle/ligaments is that cats are more sedentary then dogs, howeverthis is a supposition and is not documented.

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There have been studies that indicate that purring can aid indyspnea as Cook in 1972 suggests. Kidd et al. in 2000 found in a study with 11cats and 17 dogs with acute and subacute myocardial necrosis, none of the catsin the study had dyspnea, although all the dogs did. The overall incidence ofprimary lung tumors in the dog is 1.24%, and in the cat, .38% (Miles, 1988)


Free skin grafting is often used for the treatment of large skin defects on thedistal limbs of dogs and cats. However while using this technique in dogs,the overlapped skin edges of the graft usually become necrotic by 3 dayspostoperatively, and need to be debrided. In cats, the grafts are usually viableeven after six days.


Unfortunately, there has been no research that hasattempted to explain the extraordinary ability cats have for healingthemselves.

Just two years ago, Dr. Clinton Rubinand his associates made a fantastic discovery. They found that exposure tofrequencies between 20-50 Hz (at low dB) creates the robust striations of increased bonedensity, Clinton Rubin,(1999), Strain mediated augmentation of bone mass andmorphology: Is it possible to harness the anabolic potential of mechanicalstimuli without necessarily requiring exercise?, Wellcome Trust. In one study chickens were placed on a vibrating plate every day for 20 minutes,and grew stronger bone,NationalGeographic, January 2001, p. 11. Thisdiscovery of anabolicfrequencies between 20- 50 Hz (at low dB), is a tremendous breakthrough.Astronauts in space loose bone density in zero gravity, and this method couldhelp them maintain healthy bones. Dr. Rubin's group has begun research trialswith humans, designed to test whether thisnon-invasive method halts osteoporosis and perhaps even renews bone growth inpost-metapausal women; J. Zhi,and M. Hadjrargyrou, (1999) The expression of a novel and a knowngene, unregulated by disuse is down regulated by anabolic mechanical stimulation,American Society of Bone and Mineral Research. This method is not yet FDA approved, although it is hoped itwill be soon. Additionally, Chen (1994) The effects of frequency of mechanicalvibration on experimental fracture healing, Zhonghua Wai Ke Za Zhi, in hiswork with rabbits, foundthat frequencies of 25 and 50 hertz promote bone strength by 20%, and stimulateboth the healing of fractures, and the speed at which the fractures heal.

There is also documentation that lowfrequencies, at low dB are helpful with regard to pain relief, and the healingof tendons and muscles. Vibrational stimulation between 50-150 Hz has been foundto relieve suffering in 82% of persons suffering from acute and chronic pain (Lundeberg,1983). In 1999, M. Falempin and S.F. In-Albon discovered that mechanicalvibration at 120 Hz counteracted atrophy in tendons after hind-limb muscleloading. Biomechanicalstimulation which uses mechanical vibration of standardized frequencies from 18- 35 Hz is used in Russian sports medicine. This technique improves therelaxation of strained muscle structures and increases the stretching ability ofcapsules and tendons. Lake in 1992, found that biomechanicalstimulation prevents a decrease in muscle strength and muscle mass and theoxidative capacity of thigh muscles, following knee immobilization after sports injuries. Theuse of low frequency therapy also applies to tendon healing. It can increase the mobility of upper ankle jointsby 16- 19 %, Klysczt et. al, 1997, Biomechanical stimulation therapy asphysical treatment of arthrogenic venous insufficiency, Hautarzt. Exposure to frequencies between 2-100 Hz results in in the reduction of musclespasms and more pronounced reduction of the spasms occurs the longer thetreatment is applied, (D. Ardic, A. Buljina, 2000). After ten days of shortperiods of biomechanical stimulation, upper mobility of ankle joints improved by16 and 19 degrees and was accompanied by the healing of venous ulcerations afterskin flap transplantation, (Klysch, T. et al., 1997). It is interesting to notethat Biomechanical stimulation is also used in public gyms and work-out centersto increase muscle mass. A web search will bring up many manufactures ofsuch equipment.

It has also been found that in- phase chestwall vibration at 100 Hz, is known to decrease dysponea in patients with chronicobstructive pulmonary disease while at rest (Cristiano and Schwartzstein 1997;Nakayama, et al., 1998; Sibuya, 1994).

In Summery: Vibrations between 20-140 Hz are therapeutic forbone growth/fracture healing, pain relief/swelling reduction, wound healing,muscle growth and repair/tendon repair, mobility of joints and the relief ofdyspnea.

We think that this research could help explain why cats purr,and here is why:

Fauna Communications has recorded manycats' purrs, at a non-profit facility and the Cincinnati Zoo , includingthe cheetah, puma, serval, ocelot and the domestic house cat. After analysisof the data, we discovered that cat purrs create frequencies that fall directly in the range that is anabolic forbone growth.

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  • The dominant and fundamental frequency for three species of cats' purrs isexactly 25 Hz, or 50 Hz the best frequencies for bone growth and fracturehealing. All of the cats purrs all fall wellwithin the 20 - 50 Hz anabolic range, and extend up to 140 Hz. All thecats, except the cheetah have a dominant or strong harmonic at 50 Hz.

  • The harmonics of three cat species fall exactly on or within 2 points of 120 Hzwhich has been found to repair tendons. One species within 3 Hz and one within 7Hz.
  • Eighteen to thirty-five Hz is used in therapeutic biomechanical stimulationfor joint mobility. Considering the small size of many of these cats, especiallythe domestic cats, it is interesting to note that that all of the individualcats, have dominant frequencies within this range. In fact, some of thecats, have 2-3 harmonics in this range.
  • The frequencies for therapeutic pain relief are from 50-150 Hz. All of theindividual cats have al least 5 sets of strong harmonics in this range.
  • Therapeutic frequencies for the generation of muscle strength lie between2-100 Hz. All of the individual cats have al least 4 sets of strong harmonics inthis range.
  • Therapy for COPD uses 100 Hz, all of the individual cats have a dominant frequerncy of exactly 100 Hz.

There is another cluefound in a study performed by Dr. T. F.Cook, (1973) The relief of dyspnoea in cats by purring, New ZealandVeterinary Journal. A dying cat who could not breath (they were consideringeuthanasia), was found to breath normally once it began purring. The purringopened up the cat's airway, and improvementwas 'remarkable and the next day commenced to eat..' Threespecies of cats have a strong harmonic at exactly 100 Hz, the vibrationalfrequency found to relieve dyspnea. One species within 2 Hz and one species within7 Hz of 100 Hz. It could be that the cat's purr decreases the breathlessness byvibratory stimulation.

Is it possible that evolution hasprovided the felines of this world with a natural healing mechanism for bonesand other organs?Researchers at Fauna Communications believe so.

Being able to produce frequencies that have been proven toimprove healing time, strength and mobility could explain the purr's naturalselection. In the wild when food is plentiful, the felids are relativelysedentary. They will spend a large portion of the day and night lounging intrees or on the ground. Consistent exercise is one of the greatest contributorsto bone, (Karlsson et al, 2001), and muscle (Roth et al, 2000; Tracy et al1999), and tendon and ligament strength (Simoson et al, 1995; Tipton et al1975). If a cats exercise is sporadic it would be advantageous for them tostimulate bone growth while at rest. Digicom speed test online. As well, following injury, immediateexercise can rebreak one and re-tear healing muscle and tendon (Montgomery,1989). Inactivity decreases the strength of muscles (Tipton et al, 1975).Therefore, having an internal vibrational therapeutic system to stimulatehealing would be advantageous, and would also reduce edema and provide a measureof pain relief during the healing process.

Unfortunately there isno easy way totest this hypothesis.Strangely, after speaking with several of the foremost specialists on animalbones, it was discovered that there has apparently never been a study on any small cat bones, not serval, caracal, puma, ocelot, or domestic. Only cheetah andtiger bones have been studied, and tigers do not purr. Cheetahs do purr, butthey are one of the most unique and specialized forms of the felid family.The cheetah's bones were found to have dense remodeling (growth), whichapparently is found in carnivores and in humans.

Purring-cat physiology would have to becompared to non-purring cat physiology to test this theory. The study would have tobe entirely non-invasive.

There are inherent difficulties indiscovering whether purring aids in healing, as purring-cat physiology wouldhave to be compared to non-purring cat physiology. The dilemma is that most allcats purr, even under duress. They are even capable of producing a purrfollowing a laryngectomy (Hardie et al, 1981), due to vibration of the diaphragm(Stogdale and Delack, 1985). A naturally occurring, non-purring cat is veryrare, and this effect is usually associated with a physical problem. Cats thathave physical problems related to purring cannot be admitted to the studybecause of the possible variables presented by the physical disability.Therefore, any research would have to be non-invasive and observation based.

Given the data on anabolic frequencies,fracture and healing research, the exact match of the frequencies and amplitudesof thecat's purrs to vibrational therapy research, time proven adages, biomechanical therapy,studies on tendon and muscle repair andDr. Cook's study, it is certainly not a leap of faith to speculate that thecat's purr is a healing mechanism. Having a natural way toincrease strength, and decrease healing time, would indeed be very advantageousand would explain the purr's development.

It is suggested that purring bestimulated as much as possible when cats are ill or under duress. If purring is a healing mechanism, it may just help them to recover faster, andperhaps could even save their life.

We are currentlygathering veterinarian case studies and beginning a study to test the cats'purr-healing theory.No cats will, or have been harmed in this study. All of Fauna Communication'sstudies are non-invasive. We need your help for this research. We thank you foryour support!

Please send your tax-deductibledonations to:

Fauna CommunicationsResearch Institute

P.O. Box 1126, Hillsborough,N.C. 27278

****Please note, before submitting your e-mail to our site we e-mail you and request yourpermission. We will not mention your name or e-mail address,unless you request it. Alsobefore you e-mail us on this topic, weare not attempting to disprove the contentment theory, we are merelysupplying an additional hypothesis as to what the purr may do.Additionally, this research is not designed to determine how thepurr is created.

For more information: E-MAILor United States (919) 732-1322

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The scientific version of this paper has been submittedfor review.

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Many thanks to Shelley Adams, Dr. JohnCurrey, Dr. Clinton Rubin, Dr. Terry Cook, Dr. Margerie Lindeke, JacquiRoddick, Cincinnati Zoo, and all the other professionals and helpful people we contactedabout this topic.

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Copyright (2001) Fauna Communications ResearchInstitute