CHAPTER V 

 WORK AND FATIGUE 



While it is true, as shown in the last chapter, that ca- 

 pacity for work is one of the principal characteristics of the 

 human body, no experience of daily life is more familiar 

 than that work is followed by fatigue. This is true both 

 of individual organs and of the organism as a whole ; for 

 fatigue may be either local, as when some one muscle is 

 tired from hard work, or general, as when weariness affects 

 all organs those which have been resting as well as those 

 which have been working. 



We use the word "fatigue" in two different senses, and it 

 is important that a distinction be clearly made between them. 

 In the one sense the word means the diminution of working 

 capacity due to work. In testing one's strength of grip or of 

 back a second test, if made immediately, shows less work done 

 than at the first test, and this is true whether or not we 

 are conscious of fatigue or of diminished working power. If, 

 however, a certain time be allowed for rest, the second test 

 will give as good results as the first. 



In the other sense the word refers to the feeling of fatigue 

 which frequently, though not always, accompanies the dimi- 

 nution of working power. We may " feel tired " when we 

 have been doing nothing, and conversely, under the influence 

 of excitement or other causes we may experience no feeling 

 of fatigue even when we are near the limit of our working 

 power. Often in an exciting game the players do not know 

 at the time that they are tired or even that their working 

 power is lessened; and stories are told of soldiers in hasty 



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