THE NERVOUS SYSTEM. 815 



the lumbar region, sections of the cord in this region show certain quite 

 well-defined areas of degeneration. The zone of Lissauer early shows 

 marked degenerative changes. This zone extends across the entering 

 fibres of the posterior root which divide the zone into two parts. The de- 

 generation of the outer part has been wrongly described by some writers 



FIG. 532. TABES DORSALIS. 

 Cervical region, showing an early stage of the lesion. 



as a lateral -column degeneration. It will be remembered that these 

 fibres are short fibres which have entered the cord in the nearest posterior 

 root. Degeneration usually appears early in that part of the column of 

 Burdach which borders the posterior horn. The column of Goll varies 

 as to the extent of involvement. In many cases it is only slightly af- 

 fected, in others the degeneration is marked. As the fibres of this col- 

 umn come mainly from the last lumbar and first two sacral segments, it 

 is seen that its condition depends entirely upon the integrity of these 

 roots. The fibres of the posterior columns have two sources: (1) enter- 

 ing fibres of the posterior roots; (2) fibres from cells in the gray matter 

 of the cord. The latter are situated mainly in a narrow strip behind the 

 posterior commissure and in the median oval area of Flechsig. These 

 fibres are unaffected in tabes. 



The appearances of cross sections in the dorsal and cervical regions 

 in lumbar tabes are dependent upon an ascending degeneration of the 

 fibres affected below. The columns of Goll are thus usually affected, 

 while the columns of Burdach are often only slightly involved. If at 

 any level of the cord degenerated root fibres enter the cord, there results 

 a degeneration in the zone of Lissauer and in the baud of fibres lying 

 along the posterior horn at that level. 



Earely the tabetic process begins in the cervical region. In these 

 cases section of the cervical cord shows not only normal endogenous 

 fibres, but a normal condition of the column of Goll and of such part of 

 the column of Burdach as originated below the level of the lesion. Some- 

 times the dorsal roots are affected with the cervical. In cervical tabes 



