434 



Our Surroundings 



for other work. Skill in any art can be acquired only by the 

 aid of reflex action. 



The Sympathetic System. The sympathetic system consists 

 of two chains of ganglia, or collections of nerves, running along 



each side of the spinal column. 

 There are twenty- four ganglia in 

 each chain. These have branches 

 connecting them with the vital 

 organs of the body, the heart, 

 lungs, stomach, liver, intestines 

 and kidneys. The action of the 

 sympathetic system is under the 

 control of the spinal cord, from 

 which impulses are sent to the 

 ganglia whose functions are to 

 regulate the dilation of the ar- 

 teries, the peristalsis of the intes- 

 tine, the secretions of the various 

 glands and other unconscious ac- 

 tivities of the body. Whenever 

 one organ of the body is affected 

 by some unfavorable condition, 

 all the other organs seem to be 

 more or less influenced. This ex- 

 plains why this collection of 

 nerves is known as the sympa- 

 thetic system. 



Hygiene of the Nervous 

 System. The conditions neces- 

 sary for the keeping of the nerv- 

 ous system in a normal state, so 

 that it can perform all its func- 

 tions well, are the same as those essential to the healthy activity of 

 the other parts of the body, namely good food, fresh air, exercise 

 and rest. Like all living cells of the body, nerve cells must have 

 food for growth and repair, and oxygen to unite with the food 

 for the production of energy. Exercise is necessary to insure 



THE NERVOUS SYSTEM 



The telephone system of the body. 



