A STUDY OF THE NERVOUS SYSTEM 285 



bicycle riding, or general athletics, for these sports, when 

 properly regulated, besides developing strong lungs and 

 vigorous muscles, are important means of educating the 

 nerve cells and fibers. 



Not only in youth, but throughout life, must the student, 

 the business man, or the laborer, at the end of a day's 

 employment, find relaxation in other forms of activity. If 

 he fails to do this, not only will he become weary of his 

 work, but also he will finally come to lose the power of 

 enjoying the pleasures he has been neglecting. In the 

 later years of his life, the great naturalist, Charles Darwin, 

 wrote as follows : " My mind seems to have become a kind 

 of machine for grinding general laws out of large collections 

 of facts. ... If I were to live my life again, I would 

 have made a rule to read some poetry and listen to some 

 music at least once every week; for perhaps the parts of 

 my brain now atrophied would thus have been kept alive 

 through use. The loss of these tastes is a loss of happiness, 

 and may possibly be injurious to the intellect, and more 

 probably to the moral character, by enfeebling the emo- 

 tional part of our nature." 



Rest. Experiments with animals show a striking dif- 

 ference in the appearance of nerve cells before and after 

 vigorous exercise. In the nerve cells of a bird that has 

 been flying all day, the protoplasm has a distinctly granular 

 appearance, which is not seen in a specimen killed before 

 exercise. The tired nerve cells can be restored by rest 

 alone. Experience, too, tells us that sleep is the best 

 remedy for most of our ills. In childhood and youth an 

 abundance of sleep is absolutely essential for healthy de- 

 velopment. Late hours of evening entertainment or of study 

 must never be alloived to keep growing boys or girls from having 

 at least nine hours of dreamless sleep. 



Effect of Alcohol on the Nervous System. " The effect of 

 alcohol appears to be, as it were, to shave off the nervous 

 system, layer by layer, attacking first the highest-developed 



