SPINAL NERVES. 



607 



lumbar, five sacral, and one coccygeal. Each nerve arises from the spinal cord by an 

 anterior (motor) and a posterior (sensory) root ; the posterior roots being the larger, and 

 each having a ganglion. Immediately beyond the ganglion, the two roots unite into a 

 single mixed nerve, which passes out of the spinal canal by the intervertebral foramen. 

 The nerve thus constituted is endowed with both motor and sensory properties. It 

 divides outside of the spinal canal into two branches, anterior and posterior, both con- 

 taining motor and sensory filaments, which are distributed respectively to the anterior 

 and the posterior parts of the body. The anterior branches are the larger, and they sup- 

 ply the limbs and all parts in front of the spinal column. 



FIG. 192. Cervical portion of FIG. 193. Dorsal portion of FIG. 194. Inferior portion of 



the spinal cord. (Hirsch- the spinal cord. (Hirsch- the spinal cord, and caii- 



feld.) feld). da equinti. (Hirschfeld.) 



1, antero-inferior wall of the fourth ventricle; 2, superior peduncle of the cerebellum; 3, middle peduncle of the 

 cerebellum ; 4, inferior peduncle of the cerebellum ; 5. inferior portion of the posterior median columns of the 

 cord ; 6, glosso-pharyngeal nerve; 7, pneumogastric ; 8, spinal accessory nerve; 9, 9, 9, 9, dentated ligament; 10, 

 10, 10, 10, posterior roots of the spinal nerves; 11, 11, 11, 11, posterior lateral groove; 12, 12, 12, 12, ganglia 

 of the posterior roots of the nerves; 18, 13, anterior roots of the nerves ; 14, division of the nerves into two 

 branches ; 15, lower extremity of the cord; 16, 16, coccygeal ligament; 17, 17, cauda equi'na; I VIII, cervical 

 nerves; I, II, III, IV XII, dorsal nerves; I, II V, lumbar nerves; I V, sacral nerves. 



The anterior branches of the four upper cervical nerves form the cervical plexus, and 

 the four inferior cervical nerves, with the first dorsal, form the brachial plexus. The 

 anterior branches of the dorsal nerves, with the exception of the first, supply the walls 

 of the chest and abdomen. These nerves go directly to their distribution, and do not 

 first form a plexus, like most of the other spinal nerves. The anterior branches of the 

 four upper lumbar nerves form the lumbar plexus. The anterior branch of the fifth 

 lumbar nerve and a branch from the fourth unite with the anterior branch of the first 

 sacral, forming the lumbo-sacral nerve, and enter into the sacral plexus. The three 

 upper anterior sacral nerves with a branch from the fourth form the sacral plexus. The 

 greatest portion of the fourth anterior sacral is distributed to the pelvic viscera and the 



