THE SPINAL CORD. 



307 



posterior median and lateral columns of the cord. It is 

 continuous with the restiform body of the medulla. The 

 posterior median column is a narrow tract of white fibres 

 continuous with the posterior pyramid of the medulla. 



FIG. 138. HALF SECTION THROUGH THE LUMBAR CORD. 



1, posterior root; 2, inner portion of posterior root; 3. posterior commissure; 4, central 

 canal ; 5, fibres of anterior commissure ; 6, fibres of anterior root. 



The gray or vesicular substance of the cord is in the 

 interior, invested by the white, fibrous structure. It con- 

 sists of two crescents connected by commissural fibres. 

 The anterior segment of the gray crescent is called the 



