A special thanks to my very patient and supportive wife, Angela. To our son, Mark Jr., who gave me lots of much needed breaks by running into my office while working on this book. To Dr. Jason Schneider, for his research assistance on the first two chapters of the book. To my talented editor Arden—thanks for the great work. Mel Schoenberger for his great cartoon drawings. To my patients, from whom I learn every day.