CHAPTER XVII 



CARE AND TRAINING OF THE NERVOUS SYSTEM 



163. Food and Air. The spinal cord and the brain 

 are sometimes called the master organs, because the 

 growth and activity of every cell in the body are under 

 their direct control. Glands and muscles act only 

 when stimulated by nerves. Hence the nervous system 

 is carefully protected against injury, and has a large 

 proportion of the blood carried to it. The brain is 

 about one forty-fifth of the weight of the entire body, 

 but it receives about one eighth of the whole quantity of 

 blood. 



It requires a large amount of food to keep the deli- 

 cate brain cells in a good working condition. The 

 health of the brain and the kind and amount of work it 

 can do depend upon the quantity and quality of the 

 blood sent to it. The boy or girl who eats only coffee 

 and rolls for breakfast, and attempts to do hard school 

 work all forenoon on that scanty and unhygienic meal, 

 must not be surprised if he becomes exhausted and 

 suffers from headache in the latter part of the morning 

 exercise. A schoolboy needs a good supply of nutri- 

 tious and easily digested food three times a day, and a 

 light lunch in the middle of the forenoon, if he wishes 

 to do the best kind of mental work. 



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