PRIMARY DEGENERATIONS OF THE CORD. 431 

 FIG. 202. 



Sections of the spinal cord at the cervical (Fig. 200), dorsal (Fig. 201), lumbar (Fig. 

 202), levels showing ascending degeneration, unilateral, in the posterior column 

 after a gumma involving the second and third lumbar nerve-roots. The relative 

 extent of the degenerated fibres at the different levels is shown in the sections 

 (Starr). 



tion. In addition, microscopically, there is noted a reduction 

 in the number of nerve-fibres, and sometimes a new formation 

 of connective tissue. 



A descending degeneration affecting the pyramidal tracts 

 occurs as the result of hemorrhage or other lesion in the brain, 

 interrupting the course of the motor fibres (Fig. 198). 



Ascending degenerations occur after destruction of the cord 

 or posterior spinal nerve-roots, or from any cause interrupting 

 the course of the ascending sensory fibres of the cord, involv- 

 ing the column of Goll, direct cerebellar, and antero-lateral 

 tracts (Figs. 199-202). 



Primary Degenerations. 



Sclerosis of the posterior columns, or locomotor ataxia, is the 

 most important form of primary degeneration of the cord. 

 Though the macroscopic and microscopic changes are marked, 

 and have been carefully studied, the true nature of these 



