354 PHYSIOLOGY CHAP. 



in varying conditions rest, walking, work in the shade. He re- 

 corded the external temperature (which varied from 3 9 '4 to 17 

 C.), the moisture, and wind all the experiments being carried on 

 in the open air, and between January and April, the hottest months 

 in those regions. The results of the experiments partly confirmed 

 and partly contradicted existing ideas. He found that the loss 

 of water by the skin through evaporation, whilst in direct pro- 

 portion to the outer temperature, depends not only on this factor, 

 but also on the dampness of the air. If the temperature remains 

 unchanged, but the relative humidity of the air is diminished, 

 the loss of water by the body will of course increase. The same 

 thing happens when the air is 'stirred by wind, hence a strong, 

 cold, dry wind causes a notable increase in the amount of heat 

 lost by the body, which can only be met by an increase in its 

 metabolism. 



He confirms another fact already noted, namely, the great 

 increase in pulmonary ventilation when the external temperature 

 rises. Osborne ascribes this thermic hyperpnoea or polypnoea to 

 the heating of the carotid blood in its passage to the head. 



In contradiction to the way in which homothermic animals 

 react, he remarked that the quantity of carbon dioxide exhaled 

 was in direct, not inverse, proportion to the outer temperature. 

 This agrees with the results arrived at already by Yoit and 

 Rubner, and is in all probability partly due to the increased work 

 performed by the respiratory muscles. v 



In conclusion, it would appear that with the increase of the 

 external temperature the respiratory quotient increases also and 

 approaches unity. This harmonises with the results obtained by 

 H. Sutton in his laboratory researches in 1908, which led him to 

 conclude that this special reaction of the inhabitants of tropical 

 countries depended upon the preponderance of carbohydrates in 

 the diet of these peoples. 



W. P. Chamberlain, who, in 1911, studied the influence of the 

 climate of the Philippine Islands on a large number of both white 

 and coloured soldiers, came to the conclusion that it is impossible 

 to establish any invariable difference in the health of the two 

 types. He considers it extremely doubtful whether the action 

 of the solar rays is a factor to which the injurious influence of 

 tropical climates can be ascribed. 



Another question in close connection with the exchange of 

 material is that of dress. It might logically be supposed that its 

 adoption first began when man left his original habitations, which 

 were probably in some warm country, and took up his abode in 

 colder climates, where the necessity of lessening the loss of heat 

 as far as possible made him cover himself with garments or furs. 



This supposition is undoubtedly a very plausible one; 

 ethnologists have, however, pointed out that by no means all races 





