THE SYMPATHETIC SYSTEM 299 



Arrangement. There is on each side of the spinal column, 

 extending from the lenticular ganglion above to the gang- 

 lion impar below, a chain of ganglia all of which are united 

 to each other and to the ganglia of the opposite chain by 

 commissural fibers. From these ganglia go fibers to form 

 numerous plexuses and to be distributed to the various parts. 

 In the skull there are four of these ganglia, the otic, oph- 

 thalmic, submaxillary and spheno-palatine or Meckel's; in 

 the cervical region there are three; in the dorsal twelve; in 

 the lumbar four ; in the sacral four or five ; and in front of 

 the coccyx the single ganglion impar. 



Connections between the cranial nerves and cranial sym- 

 pathetic ganglia have already been noted. 



The cervical ganglia are of special interest as furnishing 

 the chief sympathetic supply to the heart. 



The thoracic or dorsal ganglia give rise to the sympa- 

 thetic supply for the great abdominal viscera. From the 

 sixth, seventh, eighth and ninth springs the great splanchnic 

 nerve, which passes through the diaphragm to the semilunar 

 ganglion. This is the largest of the sympathetic ganglion, 

 and is sometimes called the abdominal brain. It has been in- 

 accurately called the center of the sympathetic system. The 

 two ganglia occupy positions on opposite sides of the celiac 

 axis, and give rise to fibers which supply most of the abdom- 

 inal viscera. The tenth and eleventh thoracic ganglia give 

 rise to the lesser splanchnic nerve. From the last thoracic 

 springs the renal splanchnic nerve. The radiating fibers 

 from the semilunar ganglia form the solar plexuses for the 

 two sides. 



The lumbar ganglia give off fibers to form the aortic lum- 

 bar and hypogastric plexuses. 



The sacral and coccygeal ganglia supply the pelvic vessels. 



Properties. The ganglia and nerves are slightly sensitive. 

 Contraction of involuntary muscular tissue follows stimula- 

 tion not immediately, but after a considerable interval, and 

 the subsequent relaxation is tardy. Some of the ganglia are 



