ANATOMICAL DESCRIPTION 



281 



surface of the cord. The gray matter consists largely of 

 nerve cells with many branching processes, but there are 

 also many delicate nerve fibers, together with the support- 

 ing neuroglia. The cord is divided into symmetrical 

 halves by fissures before and behind, the posterior fissure 

 being the deeper, and the anterior wider and more 

 distinct. Neither of the fissures cuts quite through the 

 white matter to the gray in the center. 



416. Spinal Nerves. From the grooves nearest the ante- 

 rior fissure spring, by many fine rootlets, the anterior roots 



Fig. 128. Diagrammatic cross section of the spinal cord, showing the 

 origin and the chief divisions of a spinal nerve. 



A anterior column of white matter. 

 D posterior branch of nerve trunk. 

 Ga ganglion on the posterior root of the nerve, containing the cells from which 



arise most of the fibers of the sensory root (<S). 

 Gr gray matter of the cord. 

 L lateral column of white matter. 

 M anterior or motor root of the nerve. 

 Me motor cells from which arise the motor nerve fibers. 

 N main trunk of the nerve. 

 P posterior column of white matter. 

 S posterior or sensory root of the nerve. 

 Sy ganglion of the sympathetic system which communicates with the spinal 



nerve. 

 V anterior branch of nerve trunk. 



of the spinal nerves, while the posterior roots of the same 

 nerves appear to rise near the other groove on the same 

 side (Fig. 128). The two roots soon unite; but before 



