There is great difficulty in finding a novel theme as the subject of an address to the members of an Association which rejoices in the maturity of its eighty-third year of existence. Still greater is the difficulty in finding a subject of common interest having regard to the varied branches of work covered by their labours, ranging as they do from the busy routine of a crowded day to the silent special research in the laboratory. And the greatest difficulty of all lies in the fact that in each of these fields of work there are many present who have had vastly wider opportunities than I have had, and who could treat their chosen subject with infinitely more skill in thought and language than I can command. Since, however, you have been good enough to give me the opportunity of addressing you I feel you will be no less generous in pardoning my shortcomings on this occasion.