Duane E. Haines, PhD, FAAAS, FAAA, Professor of Neurobiology and Anatomy, and Professor of Neurology, Wake Forest School of Medicine, Winston-Salem, North Carolina; Professor Emeritus, Department of Neurobiology and Anatomical Sciences, and Professor of Neurology and of Neurosurgery, The University of Mississippi Medical Center, Jackson, Mississippi and Gregory A. Mihailoff, PhD, Professor Emeritus, Department of Anatomy, Arizona College of Osteopathic Medicine, Midwestern University, Glendale, Arizona