lissauer's tract 543 



REGENERATION OF THE SPINAL NERVE ROOTS 



In only one case was the distal part of the proximal stump of 

 a divided ventral root included in the sections. In this case 24 

 days after the operation the ventral root near its cut end showed 

 a great prohferation of axons similar to that seen in the distal 

 end of the proxmial stump of a divided peripheral nerve. Great 

 numbers of fine new-fomied axons occupied the interstices be- 

 tween the medullated fibers and in many places bundles of these 

 new-formed axons filled the spaces formerly occupied by medul- 

 lated fibers. 



In Cats I and II, 24 days after the roots had been tied, one 

 finds a moderate number of fine axons in the dorsal roots. These 

 differed from the noniial non-medullated fibers chiefly in their 

 irregular course and grouping. Some were branched, but the 

 end bulbs typical of regenerating fibers were not seen. These 

 fibers were much more abundant near the cut end of the root 

 than at the end next the cord. But some were present at the 

 proximal end and a few could be seen in the root as it entered 

 the cord. In Cat IV, 74 days after division of the roots, the dor- 

 sal roots were crowded with fine axons which resembled normal 

 fibers. These were present in great numbers up to the point 

 where neuroglia takes the place of connective tissue just before 

 the root enters the cord and where the abrupt change in the 

 character of the degeneration was seen. Up to this point the de- 

 generated roots were crowded with new-fonned axons, but beyond 

 it only a few fine axons extended through the entering root into 

 the cord. Similar observations were made in Cat VI and Cat X, 

 respectively 70 and 51 days after division of the roots. 



There can be no question but that the presence of these great 

 nmnbers of fine axons in the degenerated roots can only be 

 explained on the basis of their being regenerated fibers. But it 

 is not easy to decide how to regard those few fine axons that 

 extend beyond the transition point into the cord. It is possible 

 that they are efferent fibers and it is equally possible that they 

 are regenerated fibers. It is to be regretted that the spinal 



