Chap. VII.] 



THE NERVOUS SYSTEM. 



79 



stomach, and other viscera in the trunk ; they also enter the 

 cranium, send branches to the organs of special sense, and, 

 in particular, influence 

 the pupil of the eye. 

 Their most important 

 distribution, however, 

 is in connection with 

 the blood-vessels. 

 They form plexuses 

 around the vessels, 

 especially the arteries, 

 and send fibres to ter- 

 minate in the involun- 

 tary muscular tissue 

 of which the walls of 

 these tubes are largely 

 composed. The nerves 

 thus distributed are 

 called " vaso-motor " 

 nerves. 



In the sympathetic 

 ganglia the relation of 

 the neurones is such 

 that each nerve-fibre, 

 arriving at the gan- 

 glion from the spinal 

 cord, is brought into 

 contact with several 

 other neurones which 

 lie wholly in the sym- 

 pathetic system. Thus 

 an efferent impulse, 

 passing along an axone 

 from the cord, may 

 pass to the dendrones 

 of several sympathetic 

 cells, and then by their Fig. 67. — General View of the Sympathetic 



axonps to thp -smnrifli System. 1, 2, 3, cervical ganglia ; 4, 1st thoracic 

 axones to ine smootn ganglion; 5, Ist lumbar ganglion; 6, 7, sacral gan- 

 muscles of the viscera, glion ; 9, 9, cardiac nerves ; 13, branch of pneumo- 

 , • •! T gastric nerve ending in seini-lunar ganglion; 14, 



or to sinnlar endings, epigastric plexus. 



