This book is an outgrowth of the George Fisher Baker Lecture series presented by one of us (.) at Cornell University in the fall of 1992. This author is tremendously grateful to all those at Cornell who made this occasion truly memorable, personally, and most pro- ductive, intellectually. Included especially are Jean Fréchet, Barbara Baird, John Clardy, Jerrold Meinwald, Fred McLafferty, Benjamin Widom, David Usher, and Quentin Gibson, among many others. He also wants to express great thanks to Rick Bourke, who, several times provided extraordinary help, without which lectures would have been missed or required rescheduling
