ENVIKONMENT AMONG MEN 343 



conduce, it cannot be said that any important conclusions have 

 been attained. . . . But though we may not be able to indicate 

 precisely the way in which our bodies are physiologically affected 

 by extremes of atmospheric temperature, especially prolonged 

 high temperature, our sensations, the loss of physical and mental 

 energy, the modification of physical characteristics undergone by 

 white races when placed for several generations in tropical 

 conditions, and the dark skins of all tropical races indicate that 

 the white races on first arrival are not in all respects adapted 

 for tropical conditions, that they are somehow prejudicially 

 affected thereby, and that while living in tropical countries they 

 are more open to certain pathological risks than are the natives' 

 of those countries.' ^ Since the year in which Sir Patrick Manson 

 wrote further information has been obtained on this subject. 

 Our knowledge is, however, still scanty. With regard to actual 

 facts it is known that the pulse, rate of breathing, and temperature 

 of the body do not vary when measured in Europe and when 

 measured among white men under tropical conditions. The 

 number of red blood-corpuscles and the amount of haemoglobin 

 in the blood is the same and metabolism is not less intense. 

 On the other hand the rate by which a nervous impulse travels 

 along a nerve decreases in Europeans the longer they live in 

 the tropics. The muscles and the connective tissue become 

 more elastic. The well-known pallor of Europeans living in the 

 tropics is due to a thickening and softening of the epidermis, 

 which becomes opaque.^ 



It is very difficult to arrive at any conclusions as to what the 

 effects of a tropical climate upon Europeans really are. It is 

 necessary to discount the effect of tropical diseases and of the 

 habits and customs of Europeans living in the tropics. On the 

 whole it is probable that the popular notion of the considerable 

 and generally injurious nature of the modifications undergone 

 by Europeans living in the tropics is exaggerated. It is said 

 that, for example, in Java, when sanitary conditions are good 

 and reasonable habits adopted, the death-rate among European 

 children is less than in Europe. Nevertheless a tropical climate 

 does have an injurious effect upon Europeans. There is no doubt 

 that Europeans in the tropics are more irritable and in general 



1 System of Medicitie, edited by Allbutt and Rolleston, vol. ii, part ii, p. 2. 

 2 See Kohlbrugge, ' Influence of a Tropical Climate on Europeans ', Eug. Eev., 

 vol. iii. 



