CHAPTER XVI 



THE NERVOUS SYSTEM 



153. Plan of the Nervous System. We shall now 

 learn something about the system that regulates, con- 

 trols, and harmonizes the activities of all the cells and 

 organs of the body, and makes us aware of the world 

 about us and of our relation to it. 



The great central organs of the nervous system are 

 the brain and the spinal cord. There are nerves going 

 from the brain to the millions of cells in all parts of the 

 body. Nerves come to the brain from every part of 

 the body. The nerves going to the brain carry stimuli 

 to this central organ. It is because of these stimuli 

 that we see, hear, taste, smell, feel, and know what is 

 going on around and within us. The brain receives 

 these stimuli and sends messages out over the nerves 

 that go from it, which tell the muscles, glands, and other 

 tissues what to do in order that the various activities 

 and interests of the body as a whole may be properly 

 and harmoniously carried on. It is the brain that con- 

 trols the nutrition and function of every cell and makes 

 it work at the right time and in the right way. 



The brain with its incoming and outgoing nerves 

 may be compared to the central railroad station with its 



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