410 HUMAN PHYSIOLOGY 



of it may be. If he keep faithfully busy each hour of the work- 

 ing day, he may safely leave the final result to itself. He can with 

 perfect certainty count on waking up some fine morning, to find 

 himself one of the competent ones of his generation, in whatever 

 pursuit he may have singled out." — James, Psychology. 



Necessity of Food, Fresh Air, and Rest. — The nerve cells, like all 

 other cells in the body, are continually wasting away and being 

 rebuilt. Oxidation of food material is more rapid when we do 

 mental work. The cells of the brain, like muscle cells, are not 

 only capable of fatigue, but show this in changes of form and of 

 contents. Food brought to them in the blood, plenty of fresh 

 air, especially when engaged in active brain work, and rest at 

 proper times, are essential in keeping the nervous system in con- 

 dition. One of the best methods of resting the brain cells is a 

 change of occupation. Tennis, golf, baseball, and other outdoor 

 sports combine muscular exercise with brain activity of a different 

 sort from that of business or school work. 



Necessity of Sleep. — Sleep is an essential factor in the health of 

 the brain, especialh' for growing children. Most brain cells attain 

 their growth early in life. Changes occur, however, until some 

 time after the school age. Ten hours of sleep should be allowed 

 for a child, and at least eight hours for an adult. At this time, 

 only, do the brain cells have opportunity to rest and store food and 

 energ}^ for their working period. 



Effects of Alcohol. — Alcohol has the effect of temporarily para- 

 lyzing the nerve centers. The first effect is that of exhilaration. 

 This, however, is a false feeling, the alcohol having paralyzed the 

 sense of fatigue. A man may do more work for a time under the 

 influence of this false feeling of exhilaration, but it is of short 

 duration and is invariably followed by a period of depression and 

 inertia. In this latter state, a man will do less work than before. 

 He frequently takes more alcohol to renew the feeling of buoyancy, 

 and. in this way the alcohol habit may be formed. In larger 

 quantities, alcohol has the effect of completely paralyzing the 

 nerve centers. This is seen in the case of a man ''dead drunk." 

 He falls in a stupor because all of the centers governing speech, 

 sight, locomotion, etc., have been temporarily paralyzed. If a 



