From across the room from where Finnegan lays, it can be heard--a low rumble that has been debated and speculated on for years. It's a sound that most people associate with a cat's happiness. Finny is purring.
Why do cats purr? This question is usually answered: because they are content. That is not the only reason cat's purr, however. Studies now show that cats also purr when they are in pain or distress.
All cats (besides a few large cats like Lions, Leopards, Jaguars, and Tigers) learn to purr from their mothers when they are still kittens. The purring continues as the kittens grow up into cats and indicates both comfort and discomfort.
When cats are injured, they purr to heal faster. Purring is a very low frequency vibration that aids in healing. According to to research section on the Library of Congress' website, Dr. Elizabeth Von Muggenthaler reported that "Purring may be linked to the strengthening and repairing of bones, relief of pain, and wound healing."
Just because a cat is purring, it doesn't mean he is happy. In fact, he might be in pain and using his purring as massage therapy. Even so, the most common reason for a cat to purr is to show everyone that he is happy--just like when he first learned to purr while close to his mother.