purpose in the present chapter to inquire whether such wrecking of the army was inevitable, and if not, why it was allowed to happen. A review of the history of campaigns in tropical countries seems to show that Northern armies in such regions have always suffered more from disease than from battle; but it does not by any means show that the virtual destruction of a Northern army by disease in a tropical country is inevitable _now_. When the British army under the Earl of Albemarle landed on the Cuban coast and attacked Havana in 1762, it lost nearly one half its efficiency, as a result of sickness, in about four weeks; but at that time the fact that nine tenths of all tropical diseases are caused by microscopic germs, and are therefore preventable, was not known. The progress made in sanitary science in the present century renders unnecessary and inexcusable in 1898 a rate of sickness and mortality that was perhaps inevitable in 1762. Northern soldiers, if properly equipped and cared for, can live and maintain their health now under conditions which would have been absolutely and inevitably fatal to them a century ago. In April last there was an interesting and instructive discussion of this subject, or of a subject very closely connected with this, at a meeting held in the rooms of the Royal Geographical Society, London, and attended by many of the best-known authorities on tropical pathology in Great Britain. Most of the gentlemen who took part in the debate were of opinion that there is no reason whatever why the white man should not be able to adapt himself to the new conditions of life in the tropics, and protect himself against the diseases that prevail in those regions. The popular belief that the white man cannot successfully colonize the tropics is disproved by the fact that he has done so. It is undoubtedly true that many Northerners who go to equatorial regions contract disease there and die; but in the majority of such cases the man is the victim of his obstinate unwillingness to change his habits in respect to eating, drinking, and clothing, and to conform his life to the new conditions.