246 THE PHYSIOLOGY OF MUSCULAR WORK 



In addition to the above data may be given the results of 

 observations upon soldiers after marching : l 



In observations upon the temperature of the body it is necessary 

 to determine both the deep and surface temperature, for there is 

 no doubt that the greatest discomfort arises when the temperature 

 of the skin is abnormal. It is in the skin that the sensations of 

 heat and cold arise. A rise in both the deep and surface tem- 

 perature shows that the body is warmed in all its parts, and dis- 

 comfort is then experienced : if, on the other hand, the skin be 

 kept cool by sweating or exposure, no discomfort and no bad 

 effects are experienced by a healthy man whose internal tempera- 

 ture has been raised a degree or two degrees by hard work. After 

 exercise the temperature of the body falls, and the reaction is 

 generally seen in a temperature below the normal for a day 

 of rest. 



All men know that it is easier to work hard if the clothing be 

 sufficiently light and loose to allow of the free evaporation of 

 sweat. Work can only be performed efficiently under such con- 

 ditions on a warm and damp day. When a labourer keeps on 

 his coat he does not mean to do a fair day's work, and there 

 is very little doubt that he is being paid by the day and not 

 by the piece. 



A man who is not forced to work finds in his sensations of 

 heat a safeguard against overwork and heat-stroke ; he works 

 more slowly when he feels too hot, or, if he -wishes to continue to 

 work hard, he increases his loss of heat by the removal of his 

 coat or waistcoat and by turning up his sleeves. The evapora- 

 tion of sweat is thus facilitated, as shown by the following 

 comparative observations 2 upon soldiers after a march of seven 

 miles : 



1 Committee on Physiological Effects of Food, Training, and Clothing on the 

 Soldier, Second Report, 1908. 

 * Ibid., Fourth Report, 1908. 



