F. Macfarlane Burnet I have been an interested onlooker for many years at research on the biology of trace elements, particularly in its bearing on the pas- toral and agricultural importance of copper, zinc, cobalt, and mo- lybdenum deficiencies in the soil of various parts of Australia. More recently I have developed a rather more specific interest in the role of zinc, particularly in relation to the dominance of zinc metalloenzymes in the processes...