448 MAN BECOMES THE CONQUEROR OF THE WORLD 



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rested, 

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tired 

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Sleep is one way in which all the cells in the body, and par- 

 ticularly those of the nervous system, get their rest. The nervous 



system, by far the most delicate 

 and hardest-worked set of tissues 

 in the body, needs rest more than 

 do other tissues, for much of its 

 work of directing the body ends 

 only with sleep or unconscious- 

 ness. The afternoon nap, snatched 

 by the brain worker, gives him re- 

 newed energy for his evening's 

 work. It is not hard application 

 to a task that wearies the brain ; it 

 is continuous work without rest. 



Health habits for the sense or- 

 gans. Overstimulation of any of 

 the sense organs is a bad thing. 

 The ear may be overstimulated 

 by loud noises; the eye by too 

 bright light; the olfactory cells 

 by too heavy odors, the taste cells by too highly seasoned food. 

 The most frequent habits of abuse of the eyes are using them for 

 reading in a dull or flickering light or in too bright a light which 

 makes a glare on the page. We should avoid looking directly into 

 the source of any light. 



The eyes are also subject to infection and injury from dust, cin- 

 ders, flying bits of metal, etc. Certain trades in the past have 

 taken a high toll of eye injuries, although now workers are pro- 

 tected by proper goggles. In case of soreness or irritation place a 

 drop of newly prepared weak solution of argyrol in each eye. This 

 may prevent serious eye trouble. 



Many eyes are imperfect because the curvature of the lens is not 

 normal. Such defects are a cause of headaches, and should be 

 remedied by having an oculist prescribe corrective glasses. 



Practical Exercise 9. Make two lists — one of habits practiced by you 

 that are detrimental to health and the other one of habits that promote good 

 health. What can you do to improve your health? Show what habits would 

 result in the protection of your eyes. 



The effect of fatigue on a nerve cell. 

 What has happened to the dark granules 

 characteristic of a normal cell ? 



