THE SYMPATHETIC NERVE SYSTEM. 217 



from the tenth and eleventh ganglia, and is distributed to the celiac 

 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 system, are 

 situated by the side of the celiac 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 vertebra ; they give off branches, which unite to form the 

 aortic himbar 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. Division 

 of the sympathetic nerve in the neck is followed by a vascular con- 

 gestion of the parts above the section on the corresponding side, 

 attended by an increase in the temperature ; not only is there an 

 increase in the amount of blood, but the rapidity of the blood current 

 is very much accelerated and the blood in the veins becomes of a 

 brighter color. Galvanization of the upper end of the divided nerve 

 causes all the preceding phenomena to disappear; the congestion 

 decreases, the temperature falls, and the venous blood becomes 

 dark again. 



The sympathetic exerts a similar influence upon the circulation 

 of the limbs and the glandular organs ; destruction of the first thoracic 

 ganglion and division of the nerves forming the lumbar and sacral 

 plexuses are followed by a dilatation of the vessels, an increased 

 rapidity of the circulation, and an elevation of temperature in the 

 anterior and posterior limbs ; galvanization of the peripheral ends 

 of these nerves causes all of these phenomena to disappear. Division 

 of the splanchnic nerve causes a dilatation of the blood-vessels of 

 the intestine. 



These phenomena of the sympathetic nervous system are dependent 

 upon the presence of vaso-motor nerves, which, under normal cir- 

 cumstances, exert a tonic influence upon the blood-vessels. These 



