In the text I take the opportunity of expressing my thanks to many of my colleagues in the medical profession, and others who so generously helped me in the different countries that I visited. Here I wish to tender respectfully my thanks to His Excellency Sir Arthur Young, K.C.M.G., Governor of the Straits Settlements and High Commissioner of the Federated Malay States, for the credentials with which he provided me; to His Excellency Sir Walter Egerton, K.C.M.G., who invited me to make my headquarters at Government House, and in other ways assisted me in British Guiana; and to Colonel Goethals, Governor of the Isthmian Canal Zone, and Colonel Gorgas, for their assistance in connection with my visit to the Panama Canal. And finally, for revising the proofs of this work and for seeing it through the press, I am indebted to George S. Middleton, M.D., LL.D., late Senior Physician to the Glasgow Royal Infirmary. To find myself again associated in work with a beloved Teacher and inspiring “Chief” brings back the breath and bloom of the happy years spent in the G.R.I.