612 



STRUCTURE OF THE SPINAL CORD. [CH. XLII. 



the medulla oblongata. When we become acquainted with the 

 structure of the medulla oblongata, we shall be able to trace 

 these fibres further (see fig. 484). 



In general terms the anterior root-fibres pass out of the grey 

 matter of the anterior horns, and after a short course leave the 

 spinal cord in the anterior spinal nerve-roots. The posterior roots 

 on the other hand do not pass to any great extent into the grey 

 matter immediately, but into the white matter on the inner side 

 of the posterior horn ; in other words they go into the column of 

 Burdach (fig. 452, 2) ; they pass up in this column but gradually 

 approach the middle line, and are continued upwards to the 

 medulla in the column of Goll ; but as they go up they become 

 less numerous, as some terminate in the grey matter of the cord 



Fig. 454. Degeneration in column of Goll after section of posterior nerve-roots. 



on the way in the manner described. A few fibres of the posterior 

 root, however, travel for a short distance in a small tract on the 

 outer side of the posterior horn ; this is called the tract of Lis- 

 sauer (4 in fig. 452); the comma tract (3 in fig. 452) has been 

 already explained. 



Suppose now one cuts through several posterior roots between 

 the spinal ganglia and the cord, so that the course of degenera- 

 tion may be more readily traced. Immediately below the points 

 of entrance of these nerve-roots, the comma tract will be found 

 degenerated; immediately above, the degenerated fibres will be 

 found in the column of Burdach ; higher up in the cord they will 

 be less numerous, and have approached the middle line ; the fibres 

 which enter the cord lowest get ultimately nearest the middle 

 line, so that the greater part of the column of Goll is made up of 

 sensory fibres from the legs ; the fibres which enter the cord last, 



