264 Drs. Mott and Halliburton and Mr. Edmunds. [June 12, 



strand that looks like a nerve-fibre is not really such unless it can be 

 experimentally shown to be both excitable and capable of conducting nerve 

 impulses. In the absence of any such proof we regard it as probable that 

 these observers have mistaken for nerve-fibres the chains of neurilemmal 

 cells which undoubtedly form in the peripheral portions of cut nerves. 



Bethe* is at present the most prominent supporter of the autogenetic 

 theory, and his observations on the return of histological structure have 

 been couple^ with experimental testing. He finds that the peripheral ends 

 of cut nerves are in young animals excitable without union with the central 

 end. He does not, however, exclude the fallacy which underlay the old 

 experiments of Vulpian and Philippeaux, and which has more recently been 

 pointed out by Langley and Anderson.! These observers showed that, in 

 spite of any obvious connecting strand with the central end, new nerve- 

 fibres find their way often by devious channels into the peripheral stump 

 from nerves in skin and muscle cut through in the operation. Bethe, in fact, 

 by burying the peripheral end of a nerve in the neighbouring musculature 

 in order to prevent reunion with the central stump, provides an excellent 

 means for the muscular nerves to carry out that union with the central 

 nervous system which it was his object to avoid.J 



At the commencement of their work Langley and Anderson thought they 

 had obtained evidence of purely peripheral regeneration, and it was not 

 until they carried out careful dissections that they convinced themselves 

 that union with the central nervous system had occurred in the manner just 

 mentioned. They, therefore, once more cut the central end of the nerve, 

 and of any other nerves which might possibly have established a connection 

 with the peripheral segment of the nerve they had under observation. The 

 second operation would cause degeneration of the fibres which had estab- 

 lished a central connection and leave intact any fibres which had regenerated 

 autogenetically. Even this was not always sufficient to prevent reunion 

 once again of the peripheral end with the central nervous system. But in 

 cases of success no autogenetically formed nerve-fibres were found ; eight to 

 twelve days after the second operation, no sound medullated fibres were 

 found in the peripheral end, and the nerve was quite inexcitable. These 

 experiments, like Bethe's, were mostly performed upon young animals 

 (kittens and rabbits), and in some, after a period of nearly two years, no 

 trace of autogenetically-formecl new nerve-fibres could be detected. 



* Loc. tit. 

 t Loc. cit. 



% This view is also taken by Miinzer, 'Neurol. Centralbl.,' December 1, 1902 (p. 1090), 

 and January, 1903 (p. 63). 



