21 8 ANATOMY AND PHYSIOLOGY FOR NURSES 



the medulla oblongata, and runs to the upper border of the 

 first or the second lumbar vertebra, where it divides into 

 a bundle of nerves, called the cauda equina, which supply 

 the lower limbs. 



The cord is cylindric in form, and slightly flattened 

 from before backward. On its anterior and posterior 

 surfaces it presents fissures; laterally it is provided with 

 two grooves on each side, from which the spinal nerves 



FIG. in. Lumbar section of spinal cord, showing main tracts of white 

 substance and location of principal groups of nerve cells in gray matter :-a, 

 Anterior median fissure ; b, posterior median fissure ; c, anterior horn of 

 gray matter ; d, posterior horn of gray matter ; e, central canal ; f, anterior 

 white commissure ; g, posterior white commissure ; h, i, anterior and pos- 

 terior gray commissures ; /, anterior median column ; K, lateral column ; 

 L, posterior column; m, column of Clarke; n, inner group of nerve cells; 

 o, anterior group ; f, anterolateral group ; q, posterolateral group ; r, lateral 

 horn (Leroy). 



emerge. It is divided into three columns anterior, pos- 

 terior, and lateral; the fibers of the anterior are motor, the 

 posterior sensitive, while those of the lateral are of both 

 varieties. 



In making a transverse section of the cord it will be 

 observed (see Fig. in) that the interior contains gray 

 matter, which resembles two crescents placed one in each 

 half, and connected across the center by a band called the 



