346 



THE NERVOUS SYSTEM 



the cerebrospinal ganglia and terminate in the viscera. The statements con- 

 tained in this paragraph should not be applied without qualification to the ter- 



Spinal ganglion 

 Dorsal root 



Pacinian corpuscle ' 



Motor ending on smooth 

 muscle' 



Ventral root 

 Splanchnic nerve 



Collateral ganglion 



Blood-vessel-s? 





^- Ganglion of sympathetic trunk 



Jfr^Tji Gray ramus 



"" White ramus 



Sympathetic trunk 



Dorsal ramus 



Ventral ramus 



f$ Gland 

 '^'^^-^ Blood-vessel 



*~ White ramus 

 _ x Gray ramus 



Ganglion of sympathetic trunk 



Sympathetic trunk 



Sensory ending 



Fig. 256. Diagram showing the composition of sympathetic nerves. Black lines, visceral 

 afferent fibers; unbroken red lines, preganglionic visceral efferent fibers; dotted red lines, post- 

 ganglionic visceral efferent fibers. 



minal ganglia and plexuses, since it is probable that these contain additional 

 elements either in the nature of sensory neurons or of a nerve net. 



ARCHITECTURE OF THE SYMPATHETIC NERVOUS SYSTEM 



The sympathetic trunks are two ganglionated cords, each of which consists 

 of a series of more or less segmentally arranged ganglia, bound together by as- 

 cending and descending nerve-fibers and extending from the level of the second 

 cervical vertebra to the coccyx (Figs. 248, 257). The two trunks are symmetrically 

 placed along the anterolateral aspects of the bodies of the vertebrae. There are 

 21 or 22 ganglia in each chain; and of these, 3 are associated with the cervical 

 spinal nerves, 10 or 11 with the thoracic, 4 with the lumbar, and 4 with the sacral 

 spinal nerves. The sympathetic trunks are connected with each of the spinal 

 nerves by one or more delicate nerve strands, called rami communicantes (Figs. 



