ciation of Physicians. He is an editor for several basic and clinical science journals, a former member of the executive committee of the American Society for Cell Biology, and a past president of the Society for Developmental Biology.

PHILIPPE DE WALS, M.D., Ph.D., is professor in the Department of Community Health Sciences at the Faculty of Medicine, University of Sherbrooke, Québec, Canada, and has been a visiting professor at the Department of Maternal and Child Health, School of Public Health, University of North Carolina at Chapel Hill. He was born and educated in Belgium and received his degrees from the Catholic University of Louvain. Dr. De Wals’s research is focused on the epidemiology of adverse reproductive outcomes and on the evaluation of health services and public health programs. He has authored over 60 peer-reviewed publications and book chapters. He is a consultant in public health policy for the Regional Health Board of Monteregie, the Ministry of Health of Québec and Health Canada. In 1990 he was awarded the Jean Van Beneden Prize for distinguished achievement in public health research.

RALPH GREEN, M.D., is professor and chair of the Department of Pathology at the University of California at Davis and pathologistin chief at the University of California at Davis Medical Center. He received his medical degree and dissertational doctorate at the University of the Witwatersrand in Johannesburg, South Africa. Dr. Green’s research interests span several aspects of nutrition as applied to the blood and the nervous system. In particular, his work has focused on vitamin B₁₂, folate, and iron metabolism. He has developed improved methods for diagnosing deficiency of these nutrients. He has also been involved in population-based programs for food folate fortification in an economically deprived rural community. Recently, he has been studying the role of disturbance in homocysteine metabolism caused by vitamin deficiencies and genetic defects and how they may relate to vascular occlusive disease. Dr. Green has served on expert panels and advisory groups convened by the Food and Drug Administration, the Centers for Disease Control and Prevention, and the Life Sciences Research Office of the Federation of American Societies for Experimental Biology to assess folate nutritional status with particular reference to fortification of the U.S. diet with folate.

DONALD B.McCORMICK, Ph.D., is a professor of biochemistry at Emory University School of Medicine, Atlanta. He received his