THE CENTRAL NERVOUS SYSTEM 



675 



and smaller than those of the anterior horn. Throughout 

 the whole cord, however, two small groups of cells may be 

 distinguished, one on the lateral side of the horn, about its, 

 middle, and the other on the mesial side, a little in front of 

 (i.e., ventral to) the edges of the substance of Rplando, 

 Both of these groups are broken up by the passage through 

 them of bundles of fibres which form a network, and they are 

 therefore called respectively the group of the lateral and the 

 group of the posterior reticidar formation. 

 The white matter of the cord is anatomically divided by 



Antero-lateral 



ground-bundle 



FIRST CERVICAL. 



SIXTH CERVICAL. 



Direct pyramidal 



Antero-lateral ascend- 

 ing 



Crossed pyramidal 

 Direct cerebellar 



Postero-external (Burdach's) 

 Postero-median (Coil's) 



SIXTH DORSAL. FJKTH LUMBAR. 



FIG. 239. DIAGRAMMATIC SECTIONS OF THE SPINAL CORD TO snow THE 

 TRACTS OF WHITE MATTER AT DIFFERENT LEVELS. 



the position of the nerve-roots and the anterior and posterior 

 fissures into three columns on each side : the anterior, lateral, 

 and posterior columns (Plate V., 3). The first two are often 

 grouped together as the antero-lateral column. In the 

 cervical region it may be seen with the microscope that 

 the posterior white column is almost bisected by a septum 

 running in from the pia mater towards the grey commissure. 

 The inner half is called the postero-median column, or 



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