Certain figures and tables and portions of the text in the chapter by Dr. Clifford L. Mitchell on pages 41 to 64 are copyrighted by the New York Academy of Sciences. All figures and tables and portions of the text in the chapter by Drs. Jack H. Mendelson, Nancy K. Mello, and Barbara W. Lex on pages 117 to 141 are copyrighted by Williams and Wilkins.