CHAPTER VII 



TEMPERATURE AND HUMIDITY 



Preliminary— High atmospheric temperatures — Conclusions — References. 



PRELIMINARY. 



Having finished with the introductory portion of our task, we 

 enter upon the second part of this book, which is devoted to the 

 causation of disease, and is therefore essentially pathological. This 

 subject is divided into three sections, embracing the physical, 

 chemical, and parasitic causes of tropical diseases. 



HIGH ATMOSPHERIC TEMPERATURES. 



The present short chapter is confined to a brief consideration of 

 the pathological effects of high atmospheric temperatures, which 

 are the most important physical causes of disease in the tropics, 

 and are only markedly evident when there is a definite amount of 

 atmospheric humidity; and therefore we have entitled this chapter 

 Temperature and Humidity. 



To exemplify what we mean we will quote a concrete example. 

 In a certain tropical locality there were the usual high air tempera- 

 tures with relatively low humidity and cool nights until about the 

 middle of a month, when the temperature rose to ii6° F., the humi- 

 dity increased, the sky became cloudy, and for twenty-four hours 

 there was little breeze. During this period about fifty laboratory 

 animals died, though well protected from the sun by living in large 

 brick houses. They showed post-mortem the typical signs of heat- 

 stroke — viz., the congestion of the meninges and brain, and the 

 marked congestion of the lungs, which were almost black with 

 stagnated blood. During this period there were a few deaths in 

 the population of the place from the same cause. 



Clinical experience has shown that there are two different pictures 

 associated with the pathological effects of high air temperatures. 

 The first picture is that of extremely high fever, and is called heat- 

 stroke ; while the second is depicted by collapse and low bodily 

 temperatures, and is named heat-syncope. 



We have investigated these two conditions experimentally. It 

 was our practice in our journeys from Ceylon to Europe to test the 

 effects of high air temperatures upon ourselves, and such of our 



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