INDUSTRIAL PROBLEMS OF HEALTH 385 



is supposed to result from the by-products of cell metabolism 

 and is not the same as exhaustion from lack of nourishment. 



This view is borne out by two sets of facts, illustrated by these ex- 

 periments : (i) A dog that has had plenty of rest has injected into his 

 veins some blood from another dog that has been kept running until he 

 has become tired. The first dog at once shows all the signs of fatigue. 

 (2) A muscle taken from the hind leg of a frog is kept working until it 

 fails to respond to further stimulation. The muscle is then washed in 

 salt water (which would remove certain classes of poison from the 

 cells), and it is at once restored to its original vigor. 



One of the important things about fatigue is the pace. If 

 one works too fast, the fatigue poisons cannot be carried off by 

 the blood as fast as they are formed in the cells. By working 

 more slowly one can continue to work indefinitely without 

 fatigue, although one may need to stop for other reasons. 



Since all working cells may become fatigued, a man or a 

 woman engaged at some task may show signs of fatigue out of 

 proportion to the apparent exertion or performance. One is 

 worried, for example, or eager to make a record, or anxious 

 about earning enough money. He then uses up a large amount of 

 energy for ''work"' that does not show in the product, and he 

 also accumulates fatigue poisons. In factories the machinery 

 often controls the pace, and high speed becomes a serious 

 matter, especially if connected with long hours. 



The dangers from getting too tired day after day are 



1. The tired worker causes more accidents. 



2, The tired worker, having no time to catch up between 

 one day's work and the next, falls steadily behind physiologi- 

 cally, and so becomes less capable of resisting injury or infec- 

 tion, less capable of enjoying his leisure, and less able to take 

 part in his duties as citizen or as member of a family. 



Fatigue poisons affect the gland cells as well as the nerve and 

 muscle cells ; hence the frequent indigestion following meals 

 eaten when the body is fatigued. Fatigue poisons also affect the 

 white corpuscles, and the chemical activity of the cells gen- 

 erally, so that a person when fatigued is more likely to catch 



