TWENTY years have now elapsed since I had the honour and pleasure of addressing Anderson's College Medical School at the opening of its winter session of 1903. This is, indeed, only a short interval in cosmic time; for-to use a figure which will exhibit the rapidity of scientific advance nowadays-all these years amount only to twenty vibrations of the electron which we call the earth round its nucleus the sun, in this atom which we name the solar system ! However, for us it has been a considerable period. Many of those who faced me twenty years ago as students are now placed in the seats of the mighty, and will, I hope, support what I have to say to-day. Alas ! two of the faces with which I was then familiar are missing- Prof. R. S. Thomson, dean of the Medical Faculty, and Sir James Marwick; some of the distinguished men who were helping us-Dr. Laveran, Dr. Robert Koch, Sir Patrick Manson, Sir William Osier, Lord Lister, Sir Alfred Jones, Sir Rubert Boyce-are no more; and, above all, I must mourn that great pupil of the School, a ruler of many Colonies, and my own master, friend, and supporter, Sir William MacGregor.