566 ANNUAL REPORT SMITHSONIAN INSTITUTION, 193 



The strain of residence in tropical climates seems to react distinctly 

 unfavorably upon the nervous system of the majority of persons 

 from colder climates, and, in the opinion of many medical authori- 

 ties, it is just here that the greatest obstacle in the way of white 

 colonization may be found. The muggy, oppressive " hothouse"" air 

 is not only uncomfortable and difficult to endure, but it has a dis- 

 tinctly enervating effect, which is more or less widespread among all 

 white residents in the Tropics, and especially among women and chil- 

 dren. Energetic physical and mental action are difficult, even 

 impossible. " A depression of bodily and mental activity follows — 

 enervation, indifference, disinclination to exertion, a general, ill- 

 defined condition of debility." There is lessened power to do work, 

 greater fatigue from work, lowered vitality. Dr. James Horton, an 

 English physician, who was for some time stationed on the west 

 coast of tropical Africa, reported that every continued mental effort 

 in that climate was almost immediately accompanied by extreme 

 fatigue and headache. While in England he could be actively at 

 work 15 hours a day, he found that immediately on his return to the 

 Tropics six hours was his extreme limit of continued activity and 

 intellectual effort if he wished to avoid serious mental fatigue. An 

 anemic condition is widespread in the moist Tropics. All this 

 renders the body less able to resist disease. It is already weakened, 

 and then the microorganism of some specific disease finds a fertile 

 field for its ravages. The individual has largely lost his powers of 

 resistance. 



The monotony of tropical heat, together with a high degree of 

 humidity, may produce the condition of neurasthenia so widespread 

 among the white population of the Tropics, " a complex of symptoms 

 produced by nerve exhaustion and often associated with, if not caus- 

 ing, an alteration in bodily nutrition." " It is this terrible nerve 

 exhaustion," writes Dr. Havelock Charles, president of the Medical 

 Board of India, " which has, in the past, been the most important 

 factor in preventing the northern races from settling and procreating 

 their line with a full share of the nerve vigor which the parental 

 stock possessed." Tropical neurasthenia is not directly fatal, but 

 it tends to create an emotional state of depression and to undermine 

 a vigorous and healthy constitution. It prevents the development 

 and maintenance of the viens sana in corpore sano. 



The problem of acclimatization is not a question of climate alone. 

 It is tremendously complicated by the controls exercised by race, diet, 

 occupations, habits of life, and the like. The Chinese, for example, 

 succeed where other people have failed. Indeed, so well do they 

 thrive that there may, in the distant future, be more in " the Yellow 

 Peril " than most people are willing to believe. The southern Eu- 

 ropean is more successful than the northern European; the Latin 



