38 ELEMENTARY PHYSIOLOGY. 



sion which starts from the cord a message for the 

 repetition of these muscular movements. Even 

 when it seems to have settled down quietly, if you 

 touch its body the movements will be renewed. 



s m athetic ^ e ^ ave seen ^ ow the sympathetic 

 nerves connect important organs with 



each other and each with the brain. So 

 if one organ suffers, the others suffer more or less 

 with it. When the stomach is distressed, the head 

 aches. When the heart's action is excited, the 

 stomach is affected. When the brain is impressed 

 with the mind's sense of shame or modesty, the little 

 blood-vessels in the skin of the cheeks swell out and 

 are more than usually filled with blood, and we call 

 this delicate expression of their sympathy, blushing. 

 Health of ^ e wou ^ naturally suppose that organs 

 the Nervous so delicately constructed, and yet so 



prominent in the operations of the body 

 as those of the nervous system, would need the most 

 proper care to prevent their derangement or injury. 

 And so it is. The brain needs especial care. It 

 needs rest at proper intervals ; not only from severe 

 application, but the complete rest of sleep. An 

 overworked brain is a diseased brain. On the other 

 hand, the brain must have a proper amount of exer- 

 cise to keep it in vigor. Besides healthy and varied 

 exercise, the brain needs pure blood regularly and in 

 proper quantities. Too much or too little blood will 

 paralyze it. Hence its dependence on the proper 

 action of the blood-circulating system. Impure 



