568 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 



properly been more concerned with the study of specific causes of 

 tropical diseases than with the general physiological eifects of tropi- 

 cal climates. 



The acclimatization of the white race in the Tropics is a question 

 of vast importance. Upon it depend the future settlement, control, 

 government and utilization of the Tropics. It is becoming more im- 

 portant with the passing of the years. The increasing pressure of 

 population in Europe demands an outlet. The need of an additional 

 food supply in the not far distant future is turning our attention 

 more and more toward the hot belt of the world. Tropical products, 

 like coffee, rubber, quinine, spices, fruits, and lumber are desired in 

 ever-increasing quantity. The land areas within the Tropics are to 

 a large extent under the control of extra-tropical nations, as colonies, 

 or protectorates, or possessions of one sort or another. The future 

 more and more looks toward the Tropics. And what becomes of the 

 Tropics is for the white man to decide. 



This problem is of concern to many. It interests the statesman, 

 whose responsibilities include relations with tropical countries; the 

 economist, who concerns himself with laws of population and with 

 food supply; the medical man, whose business it is to fight disease 

 and to improve conditions of health all over the world; the clima- 

 tologist, whose intimate study of tropical climates is essential to any 

 thorough understanding of tropical problems ; the "engineer, geolo- 

 gist, or business man whose livelihood is to be gained in tropical 

 countries. 



The literature is already very extended. We Americans are apt 

 to forget that people of our own blood, of the British Isles, have had 

 many long years of intimate contact with the Tropics, and have made 

 many important studies of the experience of their troops and of their 

 civilians in hot countries. France has had her own dealings with 

 the Tropics, in Africa and in the Far East. Germany, also, more re- 

 cently, chiefly in Africa, accumulated information along the same 

 lines. 



One of the very natural misconceptions of a layman is that the 

 climates of the whole tropical zone are in all respects alike. This is 

 by no means the case. There are, in reality, three logical subdivisions 

 of that zone : The equatorial belt, the trade wind belts, and the mon- 

 soon belts. In each of these there are modifications due to oceanic 

 and to continental influences. Further, the effect of altitude is so 

 important that another subdivision should be added to include moun- 

 tain climates. All parts of the hot zone are not equally disagreeable 

 or hostile, so far as occupation by the white race is concerned. 



The tropical zone includes extended deserts over the continental 

 areas in the latitudes of the trade winds ; immense expanses of damp 

 forests and jungles and swamp land in the vicinity of the equator; 



