CHAPTER XXII 



THE SYMPATHETIC DIVISION OF THE NERVE 

 SYSTEM 



We have thus far considered those nerve actions which are 

 associated with consciousness, Although some may be performed 

 in a purely reflex manner, all may be exercised voluntarily. 



The Sympathetic Division is concerned with involuntary 

 processes only. Nerve stimulus between the central nerve system 

 and internal organs, and to all involuntary muscle fibers, is con- 

 veyed through sympathetic nerves. 



The nerve tissues of this division are mostly gray, a large 

 majority of the fibers being non-medullated, that is, they have no 

 white sheath. This division of the nerve system consists of many 

 ganglia connected together with nerve trunks, and of nerves which 

 connect the ganglia with various organs. 



About twenty- two pairs of sym- 

 pathetic ganglia are arranged in two 

 chains situated at the sides of the 

 vertebrae, and connected below in 

 front of the coccyx. These are the 

 FIG. 203. TERMINATIONS OF vertebral or central ganglia (Fig. 204). 

 NERVE-FIBRES IN THE GLAND- The pre-vertebral ganglia are situ- 



A. Cells of the parotid gland of ated in tne cavities of the body 



a rabbit. B Cells of the mam- thoracic, abdominal and pelvic; these 

 mary gland of a cat in gestation. 



(Doyon and Morat.} are intimately connected with the 



viscera. 



The vertebral ganglia are named according to their location. 

 They are cervical, thoracic, lumbar, sacral and coccygeal. They 

 all receive communicating branches from spinal nerves, and send 

 gray fibers to join spinal nerves and enter the spinal cord. (Gray 

 and white communicating branches or rami communicantes .) 



The branches or nerves belonging to these various ganglia in- 

 terlace in close networks, forming plexuses which follow the course 

 of arteries, supplying their walls and the viscera to which they 

 run. They also supply the cells of glands. 



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