70 



TROPICAL CLIMATOLOGY 



This evaporation is very markedly diminished by humidity, as is shown 

 in the following table : — 



Temperature in 



5 i5o 8 per Cent. 



8i to 89 p&y Cent. 



Centigrade. 



Humidity. 



Humidity. 



i5-o° 



36-3 



9-0 



20-4° 



54-1 



15-3 



25-3° 



75-5 



23-9 



28-9° 



i05'0 





It is also diminished by a moderately strong wind, but is increased by the 

 sun's rays and by work in a hot climate. 



To determine accurately the temperature of a man in the tropics is not the 

 eas}^ matter which most people consider it to be, and the principles applying 

 thereto should be understood even by those not likely to be deceived by an air 

 temperature so high that a maximum thermometer rises and keeps above normal 

 without any reference to the patient, a fact which we have seen lead to curious 

 mistakes. Under such conditions, the thermometer must be kept and 

 examined in cold water. 



The temperature of man, being the resultant between the heat produced 

 and the heat lost, must vary considerably under many circumstances, and 

 there is no doubt that it varies in different individuals. 



In investigating the temperature of the body, one ought to seek that which 

 most nearly represents the temperature of the iDlood, for though the different 

 organs of the body manufacture or lose heat in different proportions, the circu- 

 lation of the blood tends to bring about a mean internal temperature for the 

 whole body. 



The possible methods of investigating the temperature of the body are by 

 placing the thermometer — 



1 . In the axilla, 



2. In the mouth, 



3. In the rectum, 



to which might be added placing the thermometer in the stream of issuing 

 urine; but this method is only open to limited application, and there may be 

 considerable loss from evaporation and radiation, and, therefore, though it is 

 an excellent method when used with care, will not be further considered. 



If the thermometer is placed in a dry, well-closed axilla, and kept there 

 long enough, the result will be not unlike that in the mouth; but if it is thought 

 that any resemblance to the internal temperature of the body is to be obtained 

 by placing a thermometer in a perspiring axilla for half to one minute, then 

 the greatest mistakes as to the real temperature of the patient are possible. 

 In our experience it has not been unusual in the tropics to find several degrees 

 of difference between the axilla and the mouth. 



As a rule, it may be stated that the axilla is not a good place in which to 

 take thermometric observations which are meant to indicate the true tempera- 

 ture of the body. 



With regard to the mouth temperature there has been a great deal of dis- 

 cussion, but the most careful observations are those of Pembrey and Nicol, 

 who have shown that the mouth temperature is apt to vary considerably, 

 and that it is not a reliable indicator of the internal temperature of the body 

 in cold weather or after exercise. Haldane, in his valuable experiments to be 

 quoted presently, finds that it varies greatly with the individual. 



In warm and moist air, however, the mouth temperature approaches the 

 rectal temperature. 



The reason why the mouth temperature is apt to be lower than the rectal 

 and the real temperature of the body is apparently the cooling owing to the 



