Dry whiskey, Divine herb, Devil's root, Medicine of God, Peyote: for some people, to use it is to hear colors and see sounds. For many Native Americans, it brings an ability to reach out of their physical lives, to communicate with the spirits, and to become complete. For chemists, pharmacologists, and psychiatrists, the plant is fascinating in its complexity and in the ways its chemicals work upon the human mind. What is it in peyote that causes...