THE SYMPATHETIC NERVE SYSTEM 



1067 



SPINAL 

 ACCESSORY 



In the neck the ganglia are situated in front of the transverse processes of the 

 vertebra?; in the thoracic region, in front of the heads of the ribs: in the lumbar region, 

 on the sides of the bodies of the 

 vertebrae; and in the sacral 

 region, in front of the sacrum. 



Connections with the Spinal 

 Nerves. Communications are 

 established between the sym- 

 pathetic and spinal nerves 

 through what are known as 

 gray and white rami communi- 

 cantes (Fig. 779), the gray rami 

 conveying sympathetic fibres 

 into the spinal nerves, and the 

 white rami transmitting afferent 

 and efferent fibres to the sym- 

 pathetic . Each spinal nerve 

 receives a gray ramus com- 



municans from the gangliated 

 cord of the sympathetic,, but 

 white rami are not supplied by 

 all the spinal nerves. The 

 white rami are derived from the 

 first thoracic to the first lum- 

 bar, inclusive, while the visceral 

 branches which run from the 

 second, third and fourth sacral 

 nerves directly to the pelvic plex- 

 uses of the sympathetic belong 

 to this category. The majority 

 of the fibres which spring from 

 the sympathetic ganglia are 

 amyelinic (fibres of Remak}; the 

 fibres which reach the sympa- 

 thetic through the white ramus 

 communicans are myelinated. 



The branches of distribution, 

 or sympathetic nerves, derived 

 from the gangliated cords, from 

 the pre vertebral plexuses, and 

 also from the smaller ganglia, 

 are principally destined for the 

 bloodvessels and thoracic and 

 abdominal viscera, supplying 

 the involuntary muscle fibres 

 of the coats of the vessels and 

 the hollow viscera, and the se- 

 creting cells, as well as the 

 muscular coats of the vessels in 

 the glandular viscera. They 

 consist of efferent and afferent 

 fibres, for the origin and course of which see pages 1017 and 1018. 



The three great gangliated plexuses (collateral ganglia) are situated in front of 

 the spine in the thoracic, abdominal, and pelvic regions, and are named, respec- 



LUMBAR GANGLIA 



COCCYGEA 

 PLEXUS 



FIG. 779. Anterior surface of the spinal cord, showing 



th 



the 



spinal nerves and their connections with the sympathetic trunk on 

 one side. (Testut.) 



