Purring does not always mean happiness. Purring could mean a cat is in terrible pain such as during childbirth. The catnip plant contains an oil called hepetalactone which does for cats what marijuana does to some people. Not all cats react to catnip(mj); those that do appear to enter a trance-like state. Most cats had short hair until about 100 years ago, when it became fashionable to own cats and experiment with breeding. Purring is a process of inhaling and exhaling, usually performed while the mouth is closed. Cats have AB blood groups just like people. Cats are North America's most popular pets: there are 73 million cats compared to 63 million dogs. Over 30% of households in North America own a cat. The Egyptian Mau is probably the oldest breed of cat. In fact, the breed is so ancient that its name is the Egyptian word for cat. Isaac Newton invented the cat flap. Spithead, his cat, kept opening the door and wrecking his experiment. The cat flap kept both Newton and Spithead happy. The Turkish Van is one cat that likes swimming. Bred in central Asia, its coat has a unique texture that makes it water resistant. People who are allergic to cats are actually allergic to cat saliva or to cat dander. If the cat is bathed regularly the allergic people tolerate it better. [spoiler]My brother is sending me automated cat fact texts, one every two hours for a total of 180. They started last week T-T[/spoiler]