THE CENTRAL NERVOUS SYSTEM. 



28 5 



These furrows marking the anterior and the posterior roots, to- 

 gether with the penetrating processes from the pia, divide the white 

 matter of each half of the cord into definite areas or tracts. The 

 anterior median fissure penetrates a little more than one-third of the 

 diameter of the cord, and does not quite reach the bridge of gray 

 substance, but leaves an intervening band which connects the white 

 matter of the two halves ; this constitutes the white commissure in- 

 cluded between the gray bridge behind and the anterior median fissure 

 in front. 



The part of the cord embraced between the anterior median fis- 



FIG. 318. 



-w 



Section of spinal cord from cervical region of child : a, anterior "median fissure ; b, posterior median 

 septum ; c, d, anterior and posterior horns ot gray matter ; e, f, anterior and posterior nerve-roots ; 

 f, lateral reticulum of gray substance into white matter ; k, median and antero-lateral groups of 

 ganglion-cells ; 2, central canal ; k, /, gray and white commissures ; A, Z,, /*, anterior, lateral, and 

 posterior columns ; G, column of Goll ; B, column of Burdach. 



sure and the anterior root is the anterior column ; the large area 

 bounded by the anterior root, the gray matter, and the posterior 

 root forms the lateral column ; while the field included between 

 the posterior root and the posterior median septum corresponds to 

 the posterior column. Since the first two divisions are very 

 closely associated both as to their position and as to their constit- 

 uents, they are very frequently regarded as a single column, the 

 antero-lateral. Each of these principal segments is subdivided 

 into secondary tracts, distinguished by names indicating the gen- 

 eral course or the destination of the component nerve-fibres. 



