With assists from Madonna, Britney Spears and Lenny Kravitz, body piercing made its way into mainstream America during the last decade. It's now common for high school girls from middle-class backgrounds to have pierced navels, metal bars running through the cartilage of their upper ears, and piercings in spots their parents don't care to imagine. That, among many factors - aesthetic, spiritual and sexual - has led devotees of body modification to move on to new extremes such as scarification by cutting or branding, and decorative objects implanted under skin, or even in the whites of eyes.The growing interest in...