PHYSIOL OGICAL EFFECTS OF HO T CLIMA TES. 39 



while we lay opposite Guayaquil. But the sense of 

 oppressive closeness was more or less felt by every 

 one, and, whatever may be the cause, it seems safe to 

 conclude that the notoriety of this city as one of the 

 most unhealthy in South America is intimately con- 

 nected with it. 



There is, no doubt, much yet to be learned as to 

 the effects of climate on the human constitution, but 

 a few points seem to be sufficiently ascertained. To 

 those whose constitution has been hereditarily adapted 

 to a temperate or cold climate, the enfeebling effect 

 of hot countries depends much more on the constant 

 continuance of a high temperature than on its amount. 

 A place with a mean temperature of 80° Fahr., which 

 varies little above or below that point, is far more 

 injurious to a European than one where intervals of 

 great heat alternate with periods of cooler weather. 

 Still more important, perhaps, is the effect of a hot 

 climate in places where the air is habitually nearly 

 saturated with aqueous vapour. When the tempera- 

 ture of the skin is not much greater than that of the 

 surrounding air, if this be near the point of saturation 

 but little evaporation can take place from the surface. 

 The action of the absorbent vessels is thus checked, 

 and the activity of all the functions is consequently 

 lowered. As it usually happens that the two agencies 

 here discussed act together in tropical countries, the 

 places having a uniform temperature being also for 

 the most part those having an atmosphere heavily 

 charged with vapour, it is easy to understand that 

 Europeans whose vitality is already depressed are 

 especially exposed to suffer from whatever causes 



