THE NERVOUS SYSTEM 



379 



and to many other organs. This autonomic system is most evident in the 

 chain of sympathetic ganglia which lie along the dorsal aorta from the 

 neck to the sacrum. These, however, are only a portion of the autonomic 

 system, which is distinguished by functional rather than anatomical 

 characteristics, for the cerebro-spinal system is so intimately connected 

 with autonomic nerve fibers that the two systems cannot be separated 



SKIN 



SOMATIC, <^v.,-H 

 MOTOR 

 GANGLION 

 CELLS 



tLSOMATlC 

 ^ MUSCLE 



SYMPATHETIC GANGLION 



VISCERAL MOTOR ^,<^. 

 FIBERS ^^' 



Fig. 336. — A diagram of neurons of the spinal cord and spinal nerves shown in their 

 relations to one another and to their end-organs. Sjmatic sensory fibers are shown by 

 continuous lines, somatic motor fibers by fine dots. Visceral sensory fibers are indi- 

 cated by short broken lines, visceral motor by long broken lines. (Redrawn after 

 Plate.) 



anatomically. The vagus nerve, for example, which seems to be a part 

 of the cerebro-spinal system, contains many autonomic fibers connected 

 with the nervous plexuses of the viscera. Moreover, each sympathetic 

 ganglion of the trunk has fiber connexions with a spinal nerve and with 

 the plexuses of the intestine. (Figs. 335, 336, 337) 



Autonomic nerves are connected not only with the digestive and 

 circulatory systems but also with respiratory and urogenital systems, 



