FUNCTIONS OF THE SPINAL COED. 



797 



covered with myelin at different periods of development, those receiving 

 their myelin last which had the longest course. On the data obtained by 

 this method Flechsig mapped out the following system (Landois) : 



1. In the anterior column lie the (a) uncrossed, or direct pyramidal 

 tract (a in Fig. 338), and, external to it, (6) the anterior ground-bundle, 

 or anterior radicular zone. 



2. In the posterior column he distinguishes (c) (roll's column, or the 

 postero-median column, and (d) Burdach's funiculiis cuneatus, the pos- 

 terior radicular zone, or the postero-external column. 



3. In the lateral columns are 

 (e) the anterior and (/) the lateral - 



mixed paths, (g) the lateral or Mlllllill!!llll'===^^^ ,. <z* 



crossed pyramidal tract, and (h) the 

 direct cerebellar tract. The rela- 

 tions of these fibres in the cervical 

 region are shown in Fig. 339. 



FIG. 338. SCHEME OF THE CONDUCTING 

 PATHS IN THE SPINAL AT THE THIRD 

 DORSAL NERVE, AFTER FLECHSIG. 

 (Landois.) 



The 



posterior 



*, anterior column ground-bundle; c, Go'll's column; 

 postero-external column ; e and /, mixed lateral paths ; 

 h, direct cerebellar tracts. 



e black part is the gray matter, v, anterior, hw, 

 or roots ; a, direct, and g, crossed pyramidal tracts ; 



FIG. 339. SECTION OF THE CERVICAL, POR- 

 TION OF THE SPINAL, CORD, SHOWING 

 BY DIFFERENCES OF SHADING THE 

 WHITE TRACTS SUPPOSED TO BE 

 FUNCTIONALLY DISTINCT. (Yeo.) 



A, anterior, P, posterior median fissures : dp, direct 

 pyramidal, cp, crossed pyramidal tracts ; dc, direct cere- 

 bellar, pm, posterior median column (Goll) ; az, anterior, 

 pz, posterior root-zones. 



Of these columns, as we shall find directly, the pyramidal tracts may 

 be traced to the anterior pyramids of the medulla oblongata, where each 

 lateral pyramidal tract crosses to the opposite side, through the pons to 

 the middle third of the crusta, thence to the internal capsule, where 

 they diverge like the rays of a fan through the white matter of the 

 cerebrum to the central convolutions. 



The direct cerebellar fibres may be traced to the cerebellum, reaching 

 it through the restiform body from Clarke's column of gray cells, thus 

 directly connecting part of the fibres of the posterior roots with the 

 cerebellum. 



