73 



TROPICAL CLIMATOLOGY 



temperature so that with high air temperatures it still remains within the 

 normal limits, if the atmospheric humidity is low, and these experiments have 

 been well borne out by life in the tropics. 



It is, however, quite otherwise when the atmospheric humidity is high: 

 as far back as 1775 Blagden and Fordyce noted that in a damp room with a 

 temperature of 123-9° F. (54*4° C.) their bodily temperature rose to 100° F. 

 (37*8° C). Haldane observed that there was no abnormal rise of the bodily 

 temperature until the wet bulb thermometer indicated 88° F. (31° C), pro- 

 vided that the experimenters were stripped to the waist or clad in light flannel. 

 If, however, the wet bulb exceeded this temperature by even one degree, then 

 the bodily temperature rose hour by houi in proportion to the rise of the wet 

 bulb thermometer above 88° F., but the bodily temperature increased more 

 rapidly when high wet bulb temperatures were reached than when they were 

 relatively low. With the abnormal rise of bodily temperature was associated 

 increase of the pulse-rate by about twenty beats per minute for each degree 

 Fahrenheit and thirty-six for each degree Centigrade. All these bodily 

 temperatures were taken in the rectum and with the patient standing. When 

 this rectal temperature reached 102° F. hyperpnoea was observed, while other 

 symptoms associated with the rise of the bodily temperature were profuse 

 sweating and a general feeling of exhaustion and discomfort. 



It was observations like these that caused Tyler to attempt to 

 correlate personal sensations with meteorological data, and to 

 formulate his ' hyther ' degrees, by which he meant the degree 

 of discomfort caused by high air temperatures associated with high 

 relative humidity. 



Haldane's experiments have often been repeated by ourselves 

 on normal people by placing them alongside the condensers in the 

 engine-room of steamers in the Red Sea during very hot months. 

 Near the condensers one can usually find a comer where there is no 

 obvious movement of the air, which is nearly saturated with aqueous 

 vapour, and where there is a high atmospheric temperature. Placed 

 in such a corner and clad only in loose pyjamas, the skin of the body 

 flushes and burns, the perspiration rolls downwards in streams, 

 and the temperature after a short pause commences to rise and goes 

 on rising until the experiment is broken off, usually about 103° F. 



This is not a pathological rise, though associated with throbbing 

 vessels, etc., but is simply due to atmospheric conditions acting 

 upon a normal man, and all symptoms disappear rapidly after 

 removal to cooler air. 



If such a climate existed no human being could live therein, 

 but no such place is known, and although conditions of high atmo- 

 spheric temperatures may produce fever, yet these are pathological 

 and not physiological, and depend upon factors which will be dis- 

 cussed later. 



From the time of Davy in 1839, observations have been made 

 into the temperature of healthy men during the passage from the 

 temperate to the tropical zone, during their residence in the tropics, 

 and during the passage from the warm to temperate climates. 

 In previous editions of this work we gave the known data, and any- 

 one who cares to look at the pages from 91 to 97 in the second 

 edition of this book will observe how confusing and contradictory 

 are the results, while they will be struck with the relative paucity 

 of these results. The truth is that the earlier observers omitted 



