STRUCTURE OF THE NERVOUS SYSTEM 



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Nature of the Nervous System. The nervous system 

 represents the sum total of the neurons in the body. In 

 some respects it may be compared to the modern telephone 

 system. The neurons, like the electric wires, connect dif- 

 ferent places with a central station (the brain and spinal 

 cord), and through the central station connections are 

 established between the different places in the system. 

 As the separate wires are massed together to form cables, 

 the neurons are massed to form the gross structures of 

 the nervous system. The nervous system, however, is so 

 radically different from anything found outside of the ani- 

 mal body that no comparison can give an adequate idea of 

 it. We now pass to a study of the gross structures ob- 

 served in the nerve skeleton. 



Divisions of the Nervous System. While all of the 

 nervous structures are very closely blended, forming one 

 complete system for the entire body, this system presents 

 different divisions which may, for convenience, be studied 

 separately. As physiologists have become better ac- 

 quainted with the human nervous system, different schemes 

 of classification have been proposed. The following out- 

 line, based upon the location of the different parts, presents 

 perhaps the simplest view of the entire group of nervous 



structures : 



(Forebrain Cerebrum 

 Midbrain 

 TPons 

 _ Hindbrain - Cerebellum 



(Bulb 



Spinal cord 

 Nervous System r Dorsal-root ganglia 



Brain 



Peripheral 



in * ' (Sympathetic ganglia 



(Cranial nerves 

 Nerves J Spinal nerves 



I Sympathetic nerves 



