CHAPTER XXIII 

 THE NERVOUS SYSTEM 



We have seen that the movement of a part of our body 

 is due to the contraction of muscle. But muscles contract 

 because of a stimulus which they receive through a nerve. 

 Without nervous impulses to initiate and direct movements 

 the muscles would be inactive and useless. The nervous 

 system is one which controls and regulates to a large degree 

 the activities of the organs of the body, and to this end 

 its nerve fibers extend into practically all parts of the 

 organism. This system affords also the medium through 

 which we feel various sensations. Almost all parts of 

 our body are sensitive in one way or another, and, when 

 we feel, it is due to the fact that some of our nerve fibers 

 carry an impulse to the brain. The nervous system, and 

 especially the brain, is very closely associated with the 

 mind. It is only through this system that the mind is 

 affected by influences acting on the body, or is able to 

 produce bodily movement. When I burn my finger the 

 impulse set up in the nerves supplying this organ passes 

 to the spinal cord and thence to the brain. In consequence 

 of this impulse I feel a very unpleasant sensation. When 

 I pull away my hand, as I am pretty sure to do under the 

 circumstances, there is an impulse sent out in the reverse 

 direction, which is carried by a nerve to the muscles of 

 the arm causing them to contract. Our nerve fibers 

 perform functions very similar to those of telegraph and 

 telephone wires which carry messages to and from a 

 central station. The mind like the central operator 



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