20 The Philippine Journal of Science im 



with. Man can so select and arrange his clothing that it will 

 interfere little with the escape of heat from the body, while 

 at the same time it will shield the body from the heat rays 

 coming from the sun. Moreover man is acquainted with a 

 larger variety of foods. This enables him to avoid the useless 

 production of heat and toxins in the body. By taking at each 

 meal only enough of each food to furnish the quantity of each 

 element and each compound needed by the body at the time, 

 he avoids for his body the necessity of burning an excess of 

 any one food in order to get a sufficient quantity of some one 

 of its contituents; he also avoids leaving a large or dangerous 

 residue in the intestine, thus avoiding or diminishing the elabora- 

 tion of poison in the intestine by bacteria. 



Experimental acclimatization of the white man to the tropics. — 

 The foregoing observations by me on the acclimatization of the 

 monkey to the injurious combinations of climatic factors that 

 may arise in the tropics led me to institute some experiments 

 on the white man to see whether or not the inference in regard 

 to man could be experimentally justified. The experiments were 

 begun upon me — a blonde American — and have already contin- 

 ued for a period of six months. As far as the experiments 

 have gone, they have justified in every particular the inference 

 drawn. I now frequently walk at a rapid, forced pace, bare- 

 headed in the Manila sun at midday for more than an hour at 

 a time, without causing more serious symptoms than a moder- 

 ately abundant perspiration. At no time were more serious 

 symptoms observed than a mild erythema solare, resulting in 

 moderate desquamation of epidermis and some increase in tan. 

 At no time was there any sign of a deficiency in sweating, nor 

 was there ever any indication that the necessary amount of 

 sweating was at all exhausting. 



It was noted, however, that changes in diet produced marked 

 changes in the power of resistance. Since diet has such a marked 

 influence and since the white man sweats much more readily than 

 the monkey, it seems that the major factor in the acclimatiza- 

 tion of the white man is not the development of his capacity 

 for sweating, but rather the proper regulation of diet. There 

 are other factors of more or less importance for the white man, 

 for instance, the development of tan on the portions of the body 

 exposed to the sun. 



Duration of this immunity acquired hxj monkeys. — A few ex- 

 periments seemed to indicate that acclimatized monkeys lose their 

 resistance if they are kept in the shade for a few days. 



