The somewhat neglected subject of Old Age has a very pertinent connexion with the most essential aim of medicine as a whole, namely, the prevention of disease. For when the ideal of the prophylaxis of infection and of other causes of morbid action is attained, a healthy old age and physiological death without attendant disabilities and horrors should be the common lot of man instead of being somewhat exceptional in the case of the first and extremely rare as regards the final act. The conditions favouring longevity and _mens sana in corpore sano_ are those necessary to make the future of the human race a happy and beneficent prospect instead of a problem inspiring doubt if not pessimism; or in Descartes’ words, “we might be free of an infinity of maladies both of body and mind, and even of the infirmities of old age, if we had sufficient knowledges of their causes and remedies.” But in addition to this broad ground of interest there are reasons why a discussion of this subject has a special claim for consideration in Cambridge. The objects of a University include the preparation of its alumni for life in its fullest and best sense, and from this point of view the permanent ornaments of the community ever set an unobtrusive example of the way to deserve and enjoy a healthy, happy, and useful old age, namely, activity of mind and body and moderation in all things; such a life of 75 years (that of Professor G. D. Liveing) in the University must be in your recollection as described by the Public Orator as _tam honesta, tam utilis_. Further, as in private duty bound, I cannot forget that Sir George Humphry, to whom this great medical school owes so much, greatly interested himself in the subject of old age and published the results of an elaborate collective investigation. Lastly, it is desirable that the problems of old age should be attacked by young and active minds in the laboratories of the University and not left as a semi-personal field of enquiry and observation to those whose “way of life is fall’n into the sere, the yellow leaf,” and who hear old age’s stealthy footsteps catching them up in the race; for in the past most of the writers on geriatrics have written with at least some personal qualification and interest, such as Cornaro, Sir John Sinclair, Sir Anthony Carlisle, Charcot, Sir George Humphry, Sir Hermann Weber, R. Saundby, Metchnikoff, Stanley Hall. As an exception, however, we may point to Dr. John Smith,[8] who, in his thirty-fifth year, was the author of _King Solomon’s Portraicture of Old Age_, which paraphrases in 266 pages the “six former” verses of the 12th Chapter of Ecclesiastes containing 205 words. II DURATION OF LIFE