240 



THE NERVOUS SYSTEM 



The divisions of the cord already referred to are purely 

 anatomical. Physiological and pathological researches war- 

 rant the further division of the white substance of the cord 

 into eight columns for each side. The course of all the fibers 

 in the white matter of the cord is by no means certain. The 

 division here given may not be strictly correct, but it prob- 



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

 roots. (Kirkes.) 



ably receives as little adverse criticism as any of the others. 

 Classified according 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 col- 

 umn of Goll, and (b) the direct cerebellar tract; (III) de- 

 generating 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 lat- 

 eral 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 un- 



