Interesting claim! My delving suggests that this might be a fine line between truth and woo. First, the woo. I have strong suspicions about the following quotes from your provided source, The Cat's Purr for Healing:
Since cats purr when they are severely injured or dying, it has to be survival-related.
Not really. See some reasons cats might purr on Wikipedia. Note that I said might. It doesn't seem that we really know. Self-healing is speculated, but I followed Wiki's link for that suggestion to Scientific American and was sorely disappointed. No sources, no specifics cited... it reads like an editorial opinion piece based simply on intuition and speculation.
The type of frequencies that are found in the cat's purr are good for healing muscle, tendon, and ligament injuries, as well as for muscle strengthening and toning. They are good for any type of joint injury, wound healing, reduction of infection and swelling, pain relief, and relief of chronic pulmonary disease.
Wow. Huge claim and one would think that we'd have heard about it by now if it had such wide effects. My honest thought when reading this is that the same could be said of certain shades of purple quartz — but only certain shades. Again, no sources whatsoever about how such effects were determined as "good" for such illnesses.
Some stats for cat vs. dog lameness and other sicknesses are given (cats come out ahead — surprise), followed up by this:
This basically says that cats are in fact healthier than dogs are. People like to say, "Oh, that's just coincidence," but it can't be. The odds of its being coincidence are like three billion to one.
No idea where the statistics are coming from. By this reasoning, if we take any species and compare illness rates to another species, should we conclude that all instances in which one does better than another simply cannot be a coincidence? Re. the claim that cat bones heal faster; I could find no such evidence in my searching. Every search phrase returns that site or a copy-cat of it, though.
Animals have so much more than we have. As humans we are limited by what we're able to see, hear, and smell. Our senses are nowhere near as keen as those of a dog or a cat. You may have seen your own cat at times looking at something you cannot even sense, much less see. Most humans presume that their cats are just staring into space, but they are tracking something.
Again, we have no idea. A cat literally might be spacing out. We anthropomorphize and pattern-seek out a "contemplative look" on their faces and thus assume they must actually be contemplating. Until we rig up some better inter-species communication or analysis techniques for lower animals, we just won't know what a cat/dog is "thinking."
Now, onto the potential truth. First of all, I think this area has been clouded with woo. Note the results for the google phrase, "using sound waves for healing". Lots of hinting at "deeper levels," spiritual refreshment, the bringing about of "oneness" and the like. See The Power of Sound for an example of what I'm talking about.
I did find some references that indicate that audio frequencies may be beneficial for bone growth.
So... what to make of this? It seems that low intensity ultrasound has definite evidence going for it in terms of bone growth stimulation. Also, acoustic shockwaves from the patent are also cited, but my skim showed them referring to frequencies in the ultrasonic range as well (I could have missed something, though). However, a cat purr is not going to use their supplied method of causing bone bleeding.
I could find no evidence for the claims that I think would be required to support what you're asking about, thought. Namely, nothing supporting:
- cat purrs themselves for healing bones, various illnesses and/or other bodily damage
- acoustic waves themselves in the range of 50-150 Hz (the range of purring frequencies) for healing
For one last thought... we are quite ignorant of all the variables involved the body's healing. One's outlook, the placebo effect, stress levels, etc. I wouldn't doubt that one's psychological disposition due to the presence of a beloved pet really could have an effect — I just don't think there's anything particularly amazing about the "power of a purr" at this particular moment :)