1906.] 



Regeneration of Nerves. 



275 



length of time had elapsed, restoration of function led us to suppose that 

 regeneration had occurred. A second operation was then performed in each 

 case. The animal was anaesthetised, and the nerve was exposed ; the union 

 of the two ends was found to have been accomplished, and the nerve was 

 excitable both above and below the junction. A piece of nerve about half an 

 inch long was then excised, an inch or so below the junction. On histological 

 examination of this all traces of degenerated products were found to have 

 disappeared, and it was made up of fine nerve-fibres, many of which had 

 acquired a delicate medullary sheath. After this second operation the 

 wound was closed and the animal allowed to live 10 days longer ; it was 

 then killed and the nerve both below and above the second cut was 

 examined. No degeneration was found in the nerve-fibres above the second 

 lesion, but Wallerian degeneration was shown by the Marchi method to have 

 occurred in the medullated fibres of the peripheral portion, which was quite 

 inexcitable. The direction of degeneration is the direction of growth, so this 

 experiment shows that the growth of the nerve-fibres had not started from 

 the periphery centralwards, but in the reverse direction. 



In the monkey in which this experiment was performed, the second 

 operation took place 70 days after the first. In the case of the cats a longer 

 interval was allowed to elapse, namely, 147 and 162 days respectively ; by 

 this time myelination of the nerve-fibres was more pronounced, and so 

 degeneration was more readily seen by the method employed. 



We give below (fig. 5) a drawing of the degeneration seen in a teased 

 preparation of the peripheral segment after the second operation. 



"We noted an interesting point in these experiments which illustrates the 

 great rate at which the regenerating fibres grow. Although only 10 days 

 had elapsed between the second operation and the killing of the animal, and 

 although quite half an inch of nerve had been excised and no efforts made 

 to approximate the ends, yet there was a well-marked strand of union 

 uniting the two segments, both in the experiment on the monkey, and in 

 one of the two experiments on cats. 



We think that these experiments, taken in conjunction with the somewhat 

 similar experiment already alluded to in the work of Langley and Anderson, 

 in which, after union of the two ends of a divided nerve, degeneration in the 

 regenerated fibres set in after a second operation of dividing the central end 

 of the nerve nearer the spinal cord, conclusively prove the regenerated fibres 

 to be in anatomical continuity with the fibres in the central end, and so 

 with the central nervous system. They thus serve to prove the doctrine 

 that the regenerated fibres have grown from those in the central stump. 



At the time that we undertook these experiments we were under the 



Y 2 



