Over a period of 40 years, Dr. Bull, through his individual research and his association with other workers has made an outstanding contribution to the field of comparative pathology, bacteriology and parasitology. In particular may be cited his studies on infection by, and resistance to Corynebacterial ovis in sheep, his studies on bovine and mastitis (from which have largely arisen the now accepted methods of control of infection by Streptococcus agalactiae), the foundation work on myxomatosis and the causal organism (Myxomatosis cuniculi), and his contribution to the understanding of copper and molybdenum metabolism in sheep in relation to the problems of chronic copper poisoning and the toxicity of Heliotropium Europeum. Dr. Bull has made an outstanding contribution to the science and to the well-being of livestock industries of the Commonwealth.