A snake eating its own tail has been a symbol of infinity since ancient times. But seeing an illustration of this concept is nothing like witnessing the real-life horror. On rare occasions, mostly cataloged in captivity, a snake really can swallow its own tail. As the reptile guzzles back more and more of its body, the emblem of eternity quickly becomes a spiral of death. If the snake's owner does not intervene, its digestive fluids may start breaking down its own body. Some captive snakes that make a habit of eating themselves show damage on their scales from their acidic...