1. From Department of Anatomy and Cell Biology (S.N.W., N.A.B., G.C., D.F.C.), University of Western Ontario, London, Canada; Department of Anatomy & Neurobiology (G.V.A.), Faculty of Medicine, Sir Charles Tupper Medical Building, Dalhousie University, Halifax, Nova Scotia; Faculty of Medicine and Dentistry (V.C.H.), University of Western Ontario, London, Canada.