720 HUBER. [Vol. XI. 



are found in this part of the nerve. In the ulnar, below the 

 middle of the forearm, no regenerated nerve fibres were found. 



The experiments of tubular suture, although not as success- 

 ful in the results obtained as are the ones reported by others, 

 notably Vanlair, seem to me to demonstrate some interesting 

 facts. In the first place, they offer a more striking proof of 

 the down-growth of the axes of the central end during the 

 process of regeneration, than do experiments of ordinary nerve 

 suture or even implantation of a nerve segment. Attention 

 has already been drawn to this fact while reviewing the results 

 obtained by Vanlair in Part I of this paper. In Exps. 

 30 and 32 new nerve fibres were found in the connective 

 tissue between the central and peripheral part of the resected 

 nerve, in larger number and more regularly arranged the 

 nearer the central stump the observations were made. The 

 peripheral part of the resected nerve of the above experiments 

 was completely degenerated, and could therefore in no way 

 contribute to the regeneration. And if the axis cylinder is a 

 process of a cell of epiblastic origin, a theory which I think is 

 now generally accepted, an independent formation of axis 

 cylinders in the connective tissue is excluded. The experi- 

 ments further show that a return of functional activity in any 

 part of the peripheral segment of a divided nerve is concomitant 

 with a histologically demonstrable presence of axis cylinders at 

 that level in the peripheral nerve, and that irritability is first 

 present near the wound and slowly extends centrifugally. 



The bone tube would play only a secondary role in regenera- 

 tion after the tubular suture. In its place there is found, at 

 the end of ten to fifteen days a loose connective tissue, which 

 offers less resistance to the down-growing axis cylinders than 

 does the fibrous tissue surrounding the implanted bone drain. 

 The growing axes follow this path of lesser resistance, and 

 some few reach the peripheral end of the nerve. An explana- 

 tion as to why the new nerve fibres have a more regular 

 arrangement in the fibrous tissue near the central wound than 

 they show in the fibrous tissue nearer the peripheral part of 

 the resected nerve, may be found in the fact that, at a time 

 when the axes are beginning to grow toward the periphery. 



