THE CERVICAL NERVES 



921 





in one of the sympathetic plexuses. In all cases they end by forming synapses around other nerve 

 cells. From the cells of the ganglia of the sympathetic trunk other fibers, postganglionic fibers, 

 take origin; some of these run through the gray rami communicantes to join the spinal nerves, along 

 which they are carried to the bloodvessels of the trunk and limbs, while others pass to the viscera, 

 either directly or after interruption in one of the distal ganglia. The afferent fibers are derived 

 partly from the unipolar cells and partly from the multipolar cells of the spinal ganglia. Their per- 

 ipheral processes are carred through the white rami communicantes, and after passing through one 

 or more sympathetic ganglia (but always without interruption in them) finally end in the tissues of 

 the viscera. The central processes of the unipolar cells enter the medulla spinalis through the 

 posterior nerve root and form synapses around either somatic or sympathetic efferent neurons, thus 

 completing reflex arcs. The dendrites of the multipolar nerve cells form synapses around the cells 

 of type II (cells of Dogiel) in the spinal ganglia, and by this path the original impulse is transferred 

 from the sympathetic to the somatic system, through which it is conveyed to the sensorium. 



Divisions. After emerging from the intervertebral foramen, each spinal nerve 

 gives off a small meningeal branch which Centers the vertebral canal through the 

 intervertebral foramen and supplies the vertebrae and their ligaments, and the 

 bloodvessels of the medulla spinalis and its membranes. The spinal nerve then 

 splits into a posterior or dorsal, and an anterior or ventral division, each receiving 

 fibres from both nerve roots. 



POSTERIOR DIVISIONS OF THE SPINAL NERVES (RAMI POSTERIORES). 



The posterior divisions are as a rule smaller than the anterior. They are directed 

 backward, and, with the exceptions of those of the first cervical, the fourth and 

 fifth sacral, and the coccygeal, divide into medial and lateral branches for the supply 

 of the muscles and skin (Figs. 800, 801, 802) of the posterior part of the trunk. 



GREAT OCCIPI- 

 TAL NERVE 



RECTUS CAP1TIS 

 LATERALIS 



ANTERIOR PRIMARY DIVI- 

 SION OF FIRST CERVICAL 



POSTERIOR PRIMARY DIVI- 

 SION OF FIRST CERVICAL 



OBLIQUUS 

 SUPERIOR 



ANCH TO COMPLEXUS OUT 

 VERTEBRAL ARTERY 

 POSTERIOR PRIMARY DIVISION 

 OF FIRST CERVICAL 

 ANASTOMOTIC BRANCH 



ANASTOMOTIC 

 THIRD CERVICAL 



OBLIQUUS 

 INFTRIOR 



Fio. 800. Posterior primary divisions of the upper three cervical nerves. (Testut.) 



The Cervical Nerves (Nn. Cervicales). 



The posterior division of the first cervical or suboccipital nerve is larger than 

 the anterior division, and emerges above the posterior arch of the atlas and beneath 

 the vertebral artery. It enters the suboccipital triangle and supplies the muscles 

 which bound this triangle, viz., the Rectus capitis posterior major, and the Obliqui 

 superior and inferior; it gives branches also to the Rectus capitis posterior minor 





