338 



ANATOMY OF THE CENTEAL XERVOUS SYSTEM. 



the cord are not the same. Especially does the gray matter predominate 

 from the upper lumbar region downward. Pig. 217 gives cross-sections of 

 different levels of the cord. Beside the varying proportions of gray and 

 white matter, one sees also that the lateral portion of the ventral horn in the 

 lower cervical and upper dorsal cord becomes more and more prominent and 

 finally (Fig. 217, D^ and D^) becomes distinct as the lateral horn, or tractus 

 intermedio-lateralis. In the lower dorsal cord it is lost again. In Pig. 216 

 it is indicated by o. 



In the entire cervical and upper dorsal cord, the gray matter between 

 the tractus intermedio-lateralis and the ventral horn is not sharply defined. 



Fig. 216, — Half-schematic transverse section of the spinal cord, a, Ante- 

 rior and &, posterior longitudinal fissure, c, Anterior eolumn. d, Lateral column. 

 e, Posterior column, f, Funiculus gracilis, g, Funiculus cuneatus. h. Anterior, 

 and i, Posterior roots. A', Central canal. I, Sulcus intermedialis posterior, m, 

 Anterior horn, n, Posterior horn, o, Tractus intermedio-lateralis. p, Processus 

 reticularis, g, Anterior white commissure, r, Posterior gray commissure, s, 

 Clarke's column, or coJmnna resicularis. (After Erb.) 



but presents a net-work of gray bands and fibers, which pushes out into the 

 white substance. It is called processus reticularis. 



In the conus terminalis the gray matter is inclosed in a very thin layer 

 of white fibers {Co in Fig. 217). 



The root-fibers of the motor nerves pass the spinal ganglia and enter 

 the cord, penetrating its white substance to join the ventral horns. All of 

 the axis-cylinders contained in them join, as shown in Fig. 218, each with 



