by John Rendle-Short, M.A., M.D. (Cantab.), M.R.C.P., D.C.H., Professor of Child Health, University of Queensland and O.P. Gray, M.B., Ch.B., M.R.C.P., D.C.H., Senior Lecturer, Department of Child Health, Welsh National School of Medicine, Cardiff Honorary Consultant Pediatrician, United Cardiff Hospitals.