630 



THE NEUROGLIA AND BLOOD-VESSELS OF THE CORD. 



in tbejroterior column of the opposite side. Other fibres (the lateral bundle) pass into the 

 11 



Fig. 448. 



Fig. f 447. Longitudinal section of the human spinal cord, a, anterior, c, posterior, d, lateral 



' white columns ; b, anterior, c, posterior nerve-roots ; /, horizontal (pyramidal) fibres passing 



to m, cells of anterior cornu ; n, oblique fibres of posterior root. Fig. 448. Multipolar 



nerve-cell, from the anterior horn of the spinal cord, z, axis-cylinder process ; y, branched 



processes. 



lateral column of the same side, and ascend in it as far as the decussation of the pyramids, 



ii i3 where they cross in the medulla to the other 



side. The fibres of the posterior root enter the 

 posterior horn, and, after dividing, terminate 

 in the nervous protoplasmic network of the 

 grey matter. By means of this network they 

 are connected indirectly with the ganglionic 

 cells of the posterior horn, which are said not 

 to have an axial cylinder process. The grey 

 network, which connects the ganglia of the 

 anterior and posterior horns with each other, 

 also sends fibres, which pass to the other side 

 of the cord in front of and behind the central 

 canal. They then take a backward course, to 

 ascend partly in the posterior horns and partly 

 in the lateral columns. 



[The anterior root enters in several bundles 

 of coarse fibres which diverge before they reach 

 the grey matter. Most, or perhaps all, the 

 fibres end in the large motor nerve-cells in the 

 anterior cornu or its lateral process (fig. 449, 

 a, b, c, d, e). But the fibres diverge in all 

 directions, some of the fibres of the bundle 

 nearest the middle line (3) end in the laterally 

 placed cells (c) ; a part (4) crosses the anterior 

 commissure to end in cells on the opposite side 

 (d). Some of them (6) run upwards to become 

 connected with motor cells lying further up 

 the cord.] 



[The posterior root enters as a single bundle, 

 composed of finer fibres with bundles of 

 Scheme of the course of the fibres in the spinal ^ch* on f s - * * n *. fib 8 ' which are usu- 

 cord. The longitudinal fibres are indicated by all J r P^ ed most ^terally 7), or outer radi- 

 small circles ; while the nerve-cells are black. cuI * r >> curve " lto the longitudinal fibres, 



so that they are cut across in a transverse sec- 

 tion, but they again take a horizontal course and enter the substantia gelatinosa. The remainder 



