A STUDY OF THE NERVOUS SYSTEM 



267 



from the base of the skull to the coccyx, 

 the stomach is a large mass 

 of nerves and ganglia known 

 as the solar plexus, and still 

 other masses of this gray nerve 

 tissue are found near the vari- 

 ous organs in the chest and 

 abdomen. Branches from the 

 spinal nerves connect the 

 sympathetic ganglia with the 

 gray matter of the cord and 

 brain, and from the ganglia 

 there pass off a great number 

 of nerve fibers that supply the 

 organs of digestion, respira- 

 tion, and circulation. 



Physiology. The vital or- 

 gans just mentioned carry on 

 their work without any con- 

 scious direction on our part. 

 When the stomach receives 

 food from the mouth, the pan- 

 creas begins to secrete more 

 rapidly the juice that will be 

 needed to act upon this food in 

 the intestines ; during diges- 

 tion the muscles of the abdomi- 

 nal arteries relax, thus allow- 

 ing a greater blood supply in 

 the walls of the alimentary 

 canal; violent exercise quick- 

 ens the action of the heart, 

 these and many other activi- 

 ties of the body are controlled 

 either directly by the sym- 

 pathetic ganglia or indirectly 



In the region of 



. 124. Diagram of Sympathetic 

 System on One Side of Body. 



1 = ganglia and nerve sup- 



plying heart = car- 

 diac plexus. 



2 = solar plexus (for stom- 



ach and other organs 

 of ahdomen). 



3 = hypogastric plexus (for 



organs of pelvic re- 

 gion). 



4, 5, 6, 7 = row of ganglia near 

 spinal column. 



