726 THE STRUCTURE OF THE SPINAL CORD. 



course is the longest receive them latest. In this way he established the fol- 

 lowing systems of longitudinal tracts (Fig. 252) : 



(i) The anterior column contains adjacent to the anterior median fissure (a) 

 the direct pyramidal tract; externally to this (b) the anterior ground-bundle. 

 (a) The posterior column contains (c) the column of Goll or slender column, 

 and (d) the column of Burdach or wedge-shaped column. (3) The lateral col- 

 umn contains (e) the antero-lateral tract of Gowers, (f) the lateral ground-bundle, 

 (g) the crossed pyramidal tract, and (h) the direct cerebellar tract. 



Of these, the pyramidal tracts, direct (a) and crossed (g), contain all the con- 

 nections that pass from he central convolutions of the cerebral cortex as the 

 path for voluntary motor impulses. The direct cerebellar tract (k) connects in 

 an ascending direction the superior vermis of the cerebellum on both sides through 

 the restiform body with the columns of Stilling and Clarke. As posterior roots 

 of the same side enter the columns of Clarke, the direct cerebellar tract connects 

 the cerebellum with the posterior roots of the trunk (not of the extremities). 

 Gowers' tract (e) also terminates in the superior vermis almost entirely upon the 

 same side (b, f), and a portion of d arises from the columnar cells of the gray 

 matter and represents the short tracts connecting the reflex centers in the gray 



matter of the cord and in the medulla 

 oblongata. Sensory conduction-paths are 



,T h present also in b, e, and f. Finally, the 



columns of Goll (c) connect the posterior 

 roots with the gray nuclei of the funiculi 

 graciles of the medulla oblongata. The 

 column of Burdach (d) contains paths 

 connecting the entering posterior roots 

 with the nucleus funiculi fcuneiformis 

 and also tracts from the posterior roots 

 through the restiform body to the vermis 

 of the cerebellum. 



The direction of conduction in the 

 posterior columns (the continuations of 

 the posterior roots) is undoubtedly ascend- 

 ing, as they degenerate upward after 

 <] / destruction of the posterior roots. 



The following additional points have 



System of Conducting Tracts .in been established with regard to these 



tracts: The pyramidal tracts (Fig. a . 

 black central portion of the figure is the i and 2), the direct cerebellar tracts (3), 



gray matter; v, anterior root; hw, pos- an( i the columns of Goll (O exhibit pro- 



^dtind^^Er c'oKS'' I Strive diminution in size in cross section 



column of Goll; d, column of Burdach; from above downward. 1 hey connect 



e and f, mixed tracts of the lateral column; intracranial central parts with the groups 



h, direct cerebellar tract. Qf ganglia distributed throughout the gray 



matter of the spinal cord. The columns of 



Burdach and the anterior ground-bundle, together with the bundle of Gowers and 

 the ground-bundle of the lateral tract (6) show marked variations in the area 

 of section at different levels of the spinal cord in proportion to the size of the 

 incoming nerve-roots. It can, therefore, be concluded that these tracts contain 

 fibers that connect the gray matter at the different levels of the spinal cord and 

 finally also in the medulla, without, however, penetrating into the higher parts 

 of the brain itself. 



The trophic center for the pyramidal tracts is situated in the cerebrum; that 

 for the anterior roots of the spinal cord in the ganglia of the gray matter of the 

 cord. After division of the spinal cord the columns of Goll and the direct cere- 

 bellar tracts degenerate in an ascending direction. The trophic center for the 

 former is situated in the cells of the spinal ganglia of the posterior roots, that for 

 the latter in those of the columns of Clarke. Those fibers of the white substance, 

 finally, that do not degenerate at all after section of the cord (and of which there 

 are many in the anterior and lateral columns) are probably commissural fibers 

 of the cord, which pass from ganglion to ganglion (columnar-cell fibers) and 

 have their trophic centers in the ganglion at either extremity. 



Flechsig makes the following statements with reference to the time of forma- 

 tion of the different systems : The first to form are the paths between the periphery 

 and the central gray matter of the cord, especially, therefore, the nerve-roots. 



