Our Nervous System 435 



the full performance of their normal functions, as unused cells 

 fail to develop. Rest after exercise is necessary to restore vigor. 

 Sleep is absolutely essential to the health of the nervous system 

 since it is during this period of rest that the brain cells recuper- 

 ate. Most adults require eight or nine hours of sleep each day. 

 It is well understood that children require more sleep than adults. 

 Those under six should have from eleven to twelve hours of sleep 

 daily, and those between -six and eleven years need at least ten 

 hours. Insomnia, or sleeplessness, on account of its disastrous 

 effect on the nervous system, should be relieved as soon as 

 possible. 



Nervousness. Nervousness is a lack of self-control. A per- 

 son whose nervous system responds too readily to slight stimuli is 

 said to be "nervous." This condition may be due to inheritance, 

 to the use of a drug, to overwork, to eye strain or to other causes. 

 If due to inheritance it can be partially overcome by the exercise 

 of will power. If due to other causes it can be remedied by the 

 removal of the cause. Cases have been known where relief came 

 with the use of glasses properly fitted to the eyes, and other 

 cases where cure was brought about by simply ceasing to over- 

 work. If caused by the use of a drug or other bad habit, relief 

 becomes a matter of self-control by the individual in overcoming 

 the habit. 



Conservation of Nerve Force. Nervous force is a form 

 of energy generated by oxidation of the food in the nerve cells. 

 It is necessary for the accomplishment of work of every kind; 

 hence the need of saving it for doing the things most essential to 

 well being. Unfortunately, with the majority of people there is 

 a tendency to waste nerve force by various forms of activity that 

 serve no useful purpose, such as worry over trivial affairs, undue 

 excitement, excessive indulgence in pleasure and loss of temper. 

 All these are harmful and tend towards a state of health known 

 as nervous exhaustion. 



Effect of Alcohol on the Nervous System. We have 

 already learned how alcohol affects different parts of the body. 

 Its most dangerous effect is on the nervous system. In fact 

 it is through action on this system that all other parts of the 



