CH. XLII.] 



WHITE MATTER OF THE SPINAL CORD 



609 



nerve-fibres, but with more neuroglia, which gives the grey aspect to 

 this commissure (fig. 446, B). Each half of the spinal cord is marked 

 on the sides (obscurely at the lower part, but distinctly!above) by 



FIG. 446. Different views of a portion of the spinal cord from the cervical region, with the roots of the 

 nerves (slightly enlarged). In A, the anterior surface of the specimen is shown ; the anterior nerve- 

 root of its right side is divided ; in B, a view of the right side is given ; in c, the upper surface is 

 shown ; in D, the nerve-roots and ganglion are shown from below. 1, the anterior median fissure ; 

 2, posterior median fissure ; 3, anterior lateral depression, from which the anterior nerve-roots are 

 seen to issue ; 4, posterior lateral groove, into which the posterior roots are seen to sink ; 5, 

 anterior roots passing the ganglion ; 5', in A, the anterior root divided ; 6, the posterior roots, the 

 libres of which pass into the ganglion 6' ; 7, the united or compound nerve ; 7', the posterior primary 

 branch, seen in A and D to be derived in part from the anterior and in part from the posterior root. 

 (Allen Thomson.) 



two longitudinal furrows, which divide it into three portions, columns, 

 or tracts, an anterior, lateral, and posterior. From the groove between 

 the anterior and lateral columns spring the anterior roots of the 

 spinal nerves (fig. 446, B and c, 5) ; and just in front of the groove 

 between the lateral and posterior column the posterior roots enter 

 (B, 6) : a pair of roots on each side corresponds to each vertebra. 



White matter. The white matter of the cord is made up of 

 medullated nerve-fibres, of different sizes, arranged longitudinally, 

 and of a supporting material of two kinds, viz. : (a) ordinary fibrous 

 connective-tissue with elastic fibres, which is connected with septa 

 from the pia mater which pass into the cord to carry the blood- 

 vessels, (b) Neuroglia; the processes of the neuroglia-cells are 

 arranged so as to support the nerve-fibres which are without the 

 usual neurilemmal nerve-sheaths. 



2 Q 



