CHAPTER I. 



THE NERVOUS SYSTEM OF MAN. 



The nervous system of man, and indeed of all ver- 

 tebrates, may be divided into two subsystems, viz., the 

 cerebro-spinal and the ganglionic. Their relations to one 

 another are shown in a subsequent figure (Fig. 38, 

 page 68). We put aside for the present the ganglionic 

 system. 



THE CEREBRO-SPINAL SYSTEM. 



General Plan. — The general plan of structure of 

 this system in man, and indeed in all 

 vertebrates, is simply expressed as a 

 continuous tract or axis of gray matter 

 extending nearly the whole length of 

 the body, from which run off in pairs 

 bundles of fibers (nerves) going to every 

 part of the body, as shown in the dia- 

 gram (Fig. 14). In the lower verte- 

 brates there is very little more than this, 

 but in the higher vertebrates, and espe- 

 cially in man, this simple plan is ob- 

 scured by the enormous development of 

 the anterior part as a brain, as shown 

 in the dotted outline. This continuous 

 tract is called the cerebro-spinal axis. 



The cerebro-spinal axis may be 

 again subdivided into the brain and the 

 spinal cord; so that the subject of the 



Fig. 14. — Diagram 

 showing the gen- 

 eral plan of struc- 

 ture of the verte- 

 brate nervous sys- 

 tem. 



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