FUNCTIONS OF THE NERVOUS SYSTEM 303 



a bicycle, the movements at first slow and toilsome become 

 rapid and unconscious as well as more accurate by prac- 

 tice, which places them under the direction of the spinal 

 cord instead of the brain. They become, as we say, 

 " automatic," instead of voluntary. 



441. Advantages of Reflex Action. By this provision for 

 independent action in the spinal nerve centers the brain is 

 relieved of a great amount of labor, and so given leisure 

 for the more important energies of life. Then, as the 

 spinal cord can act more promptly than the brain, it is 

 better able to protect us from sudden injury. If we had 

 to wait till the brain ordered the muscles of the arm to 

 pull the hand out of the fire, we might often be seriously 

 burned. 



A thorough education of the spinal cord in respect to 

 a wide variety of reflex movements greatly extends a 

 man's useful and enjoyable activities. 



442. Voluntary Control of Reflex Action. Although 

 what are called reflex actions take place largely without 

 the interference of the will, it does not follow that any 

 distinct arbitrary line of demarkation can be drawn 

 between reflex and voluntary acts. In playing the 

 piano, for instance, the rapid and complex movements 

 required are to a certain extent voluntary as well as 

 reflex, though the cells of the nerve centers discharge 

 without waiting for the reception of orders from the 

 brain. In respect to a large number of reflex acts the 

 will is able to exercise a restraining influence if not entire 

 inhibition, and such overruling power constitutes self- 

 control. A child may, by reflex action, utter piercing 

 screams at sight of what he judges to be a dangerous 

 object, and may even be thrown into convulsions by terror ; 

 but when he has become a man if he has received proper 



