FUNCTIONS OF THE SPINAL COED. 



787 



Between the origins of the anterior and posterior nerve-roots are 

 found tlie lateral columns, while the posterior columns are found between 

 the origin of the posterior nerve-roots and the posterior fissure, which is 

 deeper than the anterior, extending completely down to the gray matter, 

 and filled up by an inner layer of pia mater (Fig. 332). 



In certain regions of the cord each posterior column may be subdi- 

 vided into an inner part lying next the fissure, the postero-median, or 

 column of Goll, and a larger part next the posterior nerve-roots, the 

 postero-external or column of Burdach. 



/— ' 



Fig. 333.— Transverse Section of the Spinal Coed in the Cervical 

 Region, after Bevan Lewis. ( Yeo.) 

 A, anterior gray column ; a, anterior white column ; I, lateral white column; ac, anterior commis- 

 sure ; ar, anterior roots ; i\l\ anterior median fissure ; il. intermedio-lateral gray column ; v c, vesicular 

 column of Clarke ; P, posterior gray column ; p. posterior white column: pm, posterior median column ; 

 ]>c, posterior commissure ; cc, central canal ; pr, posterior roots ; pf, posterior median fissure ; ae and ai, 

 external and internal anterior vesicular columns ; ng, substantia gelatinosa. 



The white matter of the spinal cord is composed of medullated fibres, 

 in which the sheath of Schwann is absent, arranged for the most part 

 longitudinally. The nerve-fibres of the nerve-roots have an oblique 

 course, passing from the gray matter through the columns to form spinal 

 nerves; transverse fibres, also, are found, which unite the different col- 

 umns of the spinal cord and connect the gray matter with the columns 

 of the cord. 



The gray matter is composed of collections of nerve-cells arranged 

 in the form of two crescents, the convex surfaces of which are united by 

 the gray commissure. In the centre of the gray commissure runs the 



