THE SYMPATHETIC SYSTEM 



1031 



especially true for the fibres passing from the second, third, and fourth sacral nerves. In the cer- 

 vical region white rami are not in evidence, a fact probably explicable as due to an arrangement 

 by which at least most of the visceral efferent fibres arising in the cervical segments of the spinal 

 cord pass downward in these segments and join the sympathetic through the white rami of the 

 upper thoracic nerves; others may enter the cervical portion of the gangliated cord through the 

 spinal accessory or eleventh cranial nerve, rather than through individual white rami, while 

 others pass into the nerves of the brachial plexus to terminate in the minute ganglia of the plex- 

 uses upon the blood-vessels of the limb. All the spinal nerves are joined by grey rami communi- 

 cantes from the sympathetic trunk. 



Vaso-motor fibres to the meninges and intrinsic blood-vessels of the spinal 

 cord pass to the spinal nerves by way of the grey rami. Thence they may reach 

 the meninges by one of three ways: — (1) through the delicate recurrent or 

 meningeal branch of the spinal nerve (fig. 785) ; (2) through the trunk and ventral 



Fig. 786. 



Spinal ganglion 



Posterior primary {. 

 division 



Anterior pnmary 

 division 



Vaso-motor, pilo- J. 



motor and secre- 

 tory fibres 



-Diagram suggesting the Origin, Course and Connections op 

 Sympathetic Nerve-fibres. 



Meningeal vaso-motor (recurrent) fibre in dorsal root of 

 spinal nerve (probably rare) 



-• Sympathetic trunk 



Sympathetic ganglion 



Peripheral associative ramus 



Grey ramus communicans 



White ramus communicans 



White ramus communicans 

 Grey ramus communicans 



Sympathetic trunk 



Peripheral associative 

 ramus 



Intermediate 

 ganglion and 

 plexus 



Terminal ganglion and plexus in ___ 

 peripheral organ ~~~ 



root of the spinal nerve; (3) probably more rarely, through the trunk and dorsal 

 root of the spinal nerve (fig. 786) . 



Corresponding communications exist between the cranial nerves and the sympathetic, 

 but the corresponding rami usually extend further toward the periphery and in not so regular a 

 manner as the communications between the spinal nerves and the sympathetic system. The 

 mesencephalon, for example, is chiefly connected with the cihary ganghon of the sympathetic 

 by fibres which are sent through the oculo-motor nerve and which enter this ganghon by way 

 of its short root and terminate about its cells. Visceral efferent fibres frorn the rhombencephalon 

 pass outward to the sympathetic in the roots of the facial, glosso-palatine, glosso-pharyngeal, 



