When, more than four years ago, I asked you to allow me to dedicate this volume to you, it was as a purely personal token of gratitude for the help I had received from what you have printed, and from what you have written to me privately. Since then much has happened: the debt is greater, and no longer purely personal. We in this country can never forget what we owe to your people. And the self-denial which led them voluntarily to stint themselves of food, that we in Europe might be fed, is one of many things about which it is not easy to speak. Our heart must indeed have been hardened if we had not considered the miracle Of those loaves. But I fear that to refer to that great debt in the dedication to this little book may draw on me the ridicule incurred by the poor man who dedicated his book to the Universe. Nevertheless, as a fellow of that College which has just received from an American donor the greatest benefaction for medical research which has ever been made in this country Of ours, I may rejoice that the co-operation between our nations is being continued in that warfare against ignorance and disease which some day will become the only warfare waged among men.