THE ROOTS OF THE PERIPHERAL NERVES, ETC. 165 



fibres. To these subdivisions we have given the general name 

 of columnar systems. In the anterior columns the anterior 

 direct pyramidal tract ; in the lateral columns the lateral crossed 

 pyramidal tract, and the direct cerebellar tract ; in the posterior 

 columns the ground-bundles and the funiculi graciles. 



If you will look at Fig. 100 you will observe, aside from 

 the above-named, two areas in the section which have been left 

 white. They are marked 1 and 3, and are situated in the 

 anterior and lateral columns. They are probably a region which 

 is only traversed by the anterior roots, and have received the 

 name of remnant of the antero-lateral column. The part lying 

 in the anterior column is also called the anterior ground-bundle 

 (1, in figure). The part lying in the lateral column has received 

 the name of anterior mixed zone of the lateral column (3, in 

 the figure). The fibres of the remnant of the antero-lateral 

 column arise in part in the anterior roots and in part in the 

 gray matter. They come principally from the centripetal pro- 

 cesses of the sensory tract. The field marked 4 in Fig. 100 

 (lateral limiting layer of the gray matter) contains the direct 

 continuations of the nerve-roots which, after passing transversely 

 through the posterior horn (see Fig. 98), ascend in this layer. 



Let us, now that we have learned the i> - eneral arrangement 



7 O o 



of the structures of the spinal cord, see what becomes of the 

 entering root-fibres, the examination of which we abandoned 

 for a time. Let us see how far their course within the central 

 organ has been investigated. We are no longer considering the 

 form and arrangement of the different parts of the central 

 nervous system ; that which now demands our attention is the 

 intimate connection between its constituent elements, the relation 

 of fibre to fibre and of fibre to cell. 



The fasciculi of the anterior roots pass in a gentle ascent 

 through the midst of the antero-lateral columns. Each fasciculus 

 is spread out over a large extent of the white substance. For 

 this reason any injury to the column must involve a certain 

 number of the anterior root-fibres, and it is therefore impossible 



