Why Do Cats Purr?

We’ve shown before that cats don’t always purr when they’re happy, but the mystery goes way deeper than that. There is no purring organ in the throat of a cat, and even though extensive research has been done on the function itself, the exact origin of the function in the anatomy of cats is still unknown.

 

It’s theorized that they might do it by the constriction and dilation of the larynx, but no evidence has ever been provided to prove or disprove that theory. It was, however, found that the frequency of a cat’s purr falls somewhere in the range required to accelerate bone regeneration and healing, so it might just be a healing superpower that we had no idea even existed in the animal kingdom. That might also explain why we take it to be a happy sound, as the frequency is not just beneficial for the cat—it tends to make us happier as well.

http://listverse.com/2014/06/30/10-easy-questions-we-still-dont-know-the-answer-to/