1906.] 



Regeneration of Nerves. 



281 



sides were equally responsive to stimulation, and histological evidence of 

 any marked difference between them was also lacking. 



Finally, we still further reduced the action of innervation currents on the 

 anterior cornual neurons by cutting off the stimuli which enter by the 

 posterior roots, as well as those which descend from the brain. The latter 

 was accomplished by combining either a semisection or a complete transection 

 of the cord in the mid-thoracic region with the division of the posterior nerve 

 roots which correspond to the lower limb of one side. 



The two sciatic nerves were then divided and sutured and, as before, an 

 interval was allowed to elapse until these nerves regenerated. Here, again, 

 the result was negative. Both nerves regenerated equally well, and both were 

 equally responsive to excitation. 



It is, therefore, quite evident that the paths which even under these 

 circumstances remain open (commissural and association tracts) are sufficient 

 to maintain the activity of the anterior cornual cells in the sprouting forth of 

 new axons in a peripheral nerve, although they may be insufficient to induce 

 those cells to send effective impulses along them. 



It is also evident that in order to reduce the activity of the anterior nerve 

 cells to a sufficient degree to prevent the regeneration of their axons, it would 

 be necessary to insulate a group of them so as to prevent all impulses 

 reaching them from every part of the nervous system. We did not see our 

 way to accomplish such an operation without interfering with the blood 

 supply of such an island of cord matter. The nearest approach we have 

 obtained to such a condition of things is to be found in those early experi- 

 ments in which haemorrhages and neuroglial overgrowth occurred as a 

 complication. Here certainly the diminution in the number of regenerated 

 fibres points to a reduced activity or, it may be, destruction of some of the 

 anterior cornual elements, but in either case these experiments, so far as they 

 go, are in favour of the view that new nerve-fibres grow from central axons, 

 and are not formed autogenetically. 



General Conclusions. 



We have put forward the foregoing five sets of experiments as a 

 contribution to the discussion now in progress as to whether the regeneration 

 of nerve-fibres is autogenetic or not. These experimental methods approach 

 the subject in different ways, and in no one case was any evidence forth- 

 coming of auto-regeneration. 



The facts recorded, taken in conjunction with those published by such 

 observers as Cajal and Langley and Anderson, form on the other hand strong 

 pieces of evidence in favour of the Wallerian doctrine that new nerve-fibres 



