THE SPINAL CORD. 



465 



abolished on the corresponding side below the injury ^This would 

 seem to prove that the fibers of the posterior roots which enter and 

 cross the column of Burdach and ascend in the column of Goll are 

 derived mainly from the muscles^,. It is, however, believed by some 

 investigators that those 

 fibers which subserve the" 

 sense of touch do not 

 decussate at once, but 

 ascend in the column of 

 Goll as far as the medulla 

 oblongata, where they, 

 in common with the 

 fibers coming from the 

 muscles, arborize around 

 the nerve-cells in the 

 gracile and cuneate nu- 

 clei. The afferent path 

 is then continued by 

 new nerve-fibers which 

 emerge from these cells, 

 and which, after crossing 

 the median plane and de- 

 cussating with the fibers 

 coming from the oppo- 

 site side, join the afferent 

 path from the spinal cord. 

 These fibers are known 

 as the internal arcuate 

 fibers and assist in the 

 formation of the lemnis- 

 cus or fillet. (Fig. 210.) 

 The sensor pathway de- 

 cussates in part at differ- 

 ent levels of the spinal 

 cord and in part at the 

 level of the gracile and 

 cuneate nuclei. The 

 former is often termed 

 the lower, the latter the 

 upper sensor decussation. 

 The pathways for the 



impulses that give rise to the different sensation have been variously 

 located by different observers, e. g., in the gray matter, in the limiting 

 layer, and in the antero-lateral tract of Gowers ; the pathway for the 

 impulses that give rise to temperature sensations has been located 



3 



FIG. 210. DIAGRAM OF THE SENSOR PATHWAYS IN 

 THE SPINAL CORD AUGMENTED ABOVE BY 

 FIBERS OP THE SENSOR CRANIAL NERVES AND 

 NERVES OP SPECIAL SENSE. V. The trifacial 

 Nerve. VIII. The vestibular branch of the 

 acoustic nerve. IX. The glosso-pharyngeal 

 nerve. X. The pneumogas trie nerve. (Van 

 Gehitchten.) 



