FUNCTIONS OP THE SPINAL CORD. 



799 



different bundles : 1. The median bundle, represented by the black line 

 in the figure (Pig. 340), partly enters into direct union with the cells of 

 the anterior horn, while part passes through the gray matter to enter the 

 anterior commissure and pass to the opposite side of the cord, to termi- 

 nate, in part, in the cells of the anterior horn on this side and partly to 

 pass directly into the anterior white columns. 2. The central bundle of 

 motor fibres passes in part through the anterior horn without forming 

 any connection with its cells, to be lost in the posterior horn, where, in 

 all probability, through union with ganglionic cells it is in communica- 

 tion with the fibres of the posterior roots ; the other part of this bundle 

 directly unites with the cells 

 of the anterior horn. 3. The 

 lateral bundle is likewise 

 partly in direct communica- 

 tion with the gray matter of 

 the anterior horn and partly 

 runs up in the lateral columns 

 of the cord (Fig. 341). 



Further examinations of 

 sections of the cord (right 

 half of above figure) show 

 that the direct and croxsed 

 pyramidal tracts of opposite 

 sides of the cord are in com- 

 munication by means of fibres 

 passing through the gray sub- 

 stance into the anterior com- 

 missure, and that the direct 

 cerebellar column communi- 

 cates with Clarke's gray col- 

 umn and the latter with the 

 column of Goll on the same 

 side of the cord. 



Some of the fibres of the posterior roots pass upward in the posterior 

 column. They thus form longitudinal commissures between the different 

 ganglia and make up the greater part of the posterior columns. These 

 commissural fibres are evidently concerned in upward conduction of sen- 

 sations, for when the cord is divided they undergo ascending degeneration. 



The lateral fibres from the posterior root ascend obliquely and divide 

 in the posterior horn, with whose cells they, in all probability, communi- 

 cate, though part of these fibres may be traced as far as the anterior 

 horns. The inner bundle has been traced to the posterior commissure ; 

 its further course or termination is unknown. 



Fig. 341.— Diagram illustrating the Paths 

 probably taken by the fibres of the 

 Nerve-Roots on Entering the Spinal 

 Cord, after Schafek. (J'no.) 



a.m./, anterior median fissure ; p.m./, posterior median fissure ; 

 r.r. central canal ; SR, substantia gelatinosa of Rolando ; a a, fu- 

 niculi of anterior root of a nerve ; p, funiculus of posterior root of a 

 nerve. By following the fibres 1, 2, 3, etc., their course through the 

 gray matter of the spinal cord may be traced. 



