240 



THE NERVOUS SYSTEM 



matter of the cord is by no means certain. The division here 

 given may not be strictly correct, but it probably receives as 

 little adverse criticism as any of the others. Classified accord- 

 ing to the direction in which their fibers degenerate after section 

 the paths are: (i) Degenerating downward, (a) the column of 

 Turck and (b) the crossed pyramidal tract; (II) degenerating 

 upward, (a) the column of Goll and (b) the direct cerebellar 



FIG. 74. Diagram to illustrate wallerian degeneration of nerve-roots. 



(Kirkes.) 



tract; (III) degenerating in neither direction, (a) the anterior 

 fundamental fasciculus, (b) the anterior radicular zone, (c) the 

 mixed lateral column and (d) the column of Burdach. 



I. (a) The column of Turck occupies a position just lateral to 

 the anterior median fissure and extends downward to the lower 

 dorsal region. Its fibers decussate high up in the cord. This 

 column is sometimes called the direct, or uncrossed, pyramidal 

 tract, as distinguishing it from the other descending column. 

 (b) The crossed pyramidal tract is external to the posterior cornu 

 of gray matter and internal to the direct cerebellar tract. Its 



