SYMPATHETIC NERVOUS SYSTEM. 149 



join the glosso-pharyngeal and pneumogastric, to form the pharyngeal 

 plexus. 



The Middle cervical ganglion, the smallest of the three, is occasionally 

 wanting; it is situated opposite the 5th cervical vertebra; sends branches 

 to the superior and inferior cervical ganglion, and to the thyroid artery. 



The Inferior cervical ganglion, irregular in form, is situated opposite the 

 last cervical vertebra ; it is frequently fused with the first thoracic ganglion. 



The superior, middle and inferior cardiac nerves, arising from these 

 cervical ganglia, pass downward and forward to form the deep and super- 

 ficial cardiac plexuses located at the bifurcation of the trachea, from which 

 branches are distributed to the heart, coronary arteries, etc. 



The Thoracic Ganglia are usually twelve in number, placed against 

 the heads of the ribs behind the pleura ; they are small in size and gray in 

 color; they communicate with the cerebro spinal nerves by two filaments, 

 one of which is white, the other gray. 



The great splanchnic nerve is formed by the union of branches from the 

 sixth, seventh, eighth and ninth ganglia ; it passes through the diaphragm 

 to the semilunar ganglion. 



The lesser splanchnic nerve is formed by the union of filaments from the 

 tenth and eleventh ganglia, and is distributed to the cceliac plexus. 



The renal splanchnic nerve arises from the last thoracic ganglion and 

 terminates in the renal plexus. 



The semilunar ganglia, the largest of the sympathetic, are situated by 

 the side of the coeliac axis; they send radiating branches to form the solar 

 plexus; from the various plexuses, nerves follow the gastric, splenic, 

 hepatic, renal, etc., arteries, into the different abdominal viscera. 



The Lumbar Ganglia, four in number, are placed upon the bodies of 

 the vertebrae; they give off branches which unite to form the aortic lumbar 

 plexus and the hypogastric plexus, and follow the blood vessels to their 

 terminations. 



The Sacral and Coccygeal Ganglia send filaments of distribution to 

 all the blood vessels of the pelvic viscera. 



Properties and Functions. The sympathetic nerve possesses both 

 sensibility and the power of exciting motion, but these properties are much 

 less decided than in the cerebro -spinal system. Irritation of the ganglia 

 does not produce any evidence of pain until some time has elapsed. If 

 caustic soda be applied to the semilunar ganglia, or a galvanic current be 

 passed through the splanchnic nerves, no instantaneous effect is noticed, as 

 in the case of the cerebro-spinal nerves ; but in the course of a few seconds 



