Tracy James knew the drug she'd just swallowed was working when her old injuries from high school started twitching with new life. Pressure throbbed from a forgotten busted knee. Her ankle tingled. The fingers she'd sprained roller-skating decades back began to ache. Whatever the 37-year-old had just taken, it shot feeling back into the long-gone ailments. "When I did vomit, it was one of the most amazing moments of my life." For the past 45 minutes, the hut had been dark and silent, the air dripping with jungle moisture. James and nearly 20 others were sitting cross-legged on ornate rugs....