APPENDIX 275 



diseases. In the tropics death-rates are high, but bad 

 sanitary conditions and lack of medical attendance account 

 to some extent for mortality among the natives, while an 

 irrational mode of life explains many deaths among persons 

 coming from cooler climates. Generally speaking, malarial 

 and yellow fever are only endemic on coasts and in the 

 neighbourhood of waterways, and only then when the air 

 temperature is 75 F. or over and the earth sodden. In 

 such case there would be an upper earth-stratum of un- 

 usually low resistance, and the air-charge might be at its 

 minimum, with consequent loss of part of its value as a 

 vitalising agent. Stations more than a few hundred or 

 thousand feet above the sea-level are free from yellow 

 fever, probably because of their lower temperatures 

 increased earth-resistance, and higher air-potential. 

 Yellow fever has only very rarely occurred at an altitude 

 of 4,000 ft. above sea-level, and the same remarks appear 

 to apply to dysentery and diarrhceal disorders, as well as to 

 many other diseases of which the predisposing cause is 

 lowered vitality. 



Dengue fever is distinctly a disease of warm climates, 

 and is always checked by cold weather ; it follows coast- 

 lines, deltas, and large river-valleys. In beri-beri high 

 temperature and dampness are controlling factors, as is the 

 case in sleeping sickness and yaws. In the tropics " the 

 drier districts are to be preferred to the moister, the higher 

 altitudes to the lowlands." (Ward, 1908.) 



Temperate zones may be said to be intermediate 

 between the equatorial and polar zones. Here we have 

 variations of temperature and moisture which, so far as 

 their influence upon health is concerned, are beyond our 

 purview, inasmuch as there are many conflicting theories 

 and no really conclusive evidence, apart from the broad 

 fact that in tuberculosis and other and similar diseases 

 the dry, pure air and abundant sunshine of many of the 



