NERVOUS SYSTEM 71 



SYMPATHETIC SYSTEM. 



The Sympathetic Nervous System consists, first, of 

 a delicate, double chain of ganglia, extending 

 along the ventral side of the spinal column from 

 the head to the tail, and, secondly, of numerous 

 branches and ganglia throughout the body. The 

 branches of both divisions are distributed to the 

 viscera and blood-vessels. In the head they com- 

 municate w^ith many of the cranial nerves, and in 

 the trunk w^ith the spinal nerves. 



In the thorax the tw^o sympathetic cords may 

 be seen lying along the line of the heads of the 

 ribs, between the pleura and intercostal blood- 

 vessels. In the lumbar region the cords lie 

 nearer together on the bodies of the vertebrae, 

 at the inner margins of the psoas muscles. In 

 the sacral region the cords unite in a single gan- 

 glion. 



There are three plexuses of nerves and ganglia 

 connected with the sympathetic system : 



1. The Cardiac Plexus lies at the base of the 

 heart on the aorta and pulmonary artery. It re- 

 ceives branches from the vagus and cervical sym- 

 pathetic ganglion, and innervates the heart. 



2. The Solar Plexus lies between the adrenal 

 bodies, stomach, aorta, and crura of the diaphragm. 

 It receives branches from the vagus, cardiac plex- 

 us, and sympathetic cords, and sends nerves to the 

 abdominal viscera. 



