On the Regeneration of Nerves. 473 



of sensation must be regarded as indicating a restored conduct! vity 

 of the divided nerve. He holds that the theories which have hitherto 

 been advanced to account for early return of sensation apart from 

 reunion of the nerve, are inapplicable to cases where early return of 

 sensation occurs from suture, performed after the lapse of several 

 months from the time of section. The imperfect return of motion he 

 takes to be fully explained by the fact that the muscles have under- 

 gone great trophic change, or indeed total destruction, and that, 

 therefore, their restitution must be slow, or may even be impossible. 



IV. Microscopical examination of the portions removed previous to 

 suture. 



Both the central and peripheral ends of nerves which had not 

 reunited in any way, contained young nerve fibres grouped in bundles, 

 each bundle containing, as a rule, many fibres. The fibres contained 

 an axis-cylinder lying in the centre of a clear, well-defined zone, 

 which, again, contained a granular, myeline deposit, while spindle- 

 shaped nuclei were attached to the sides of the fibres at frequent 

 intervals. Where the ends of the nerve were united by a cicatricial 

 segment without conductivity being restored, the examination of the 

 segment showed a dense network of connective tissue containing in 

 its meshes bundles of young fibres. 



The portions excised from the nerves involved at the seat of frac- 

 ture showed at their central ends a normal structure, but elsewhere 

 no trace of old myeline fibres, nor of degenerated fibres ; but the 

 section was made up of young fibres in bandies, which bundles were 

 of only slightly greater diameter than the old myeline fibres, and 

 often surrounded by a delicate sheath. At the point of transition 

 from old to young fibres, many of the old myeline fibres contained 

 an enlarged nucleus, with one or two distinct young fibres lodged 

 between the sheath of Schwann and the myeline sheath. In other 

 cases the number of young fibres lying in a similar position was 

 greater. All stages up to complete replacement of the old myeline 

 sheath and axis-cylinder by young fibres were found. 



Y. Deductions from the microscopical examination. 



1. Degeneration : 



(a) That there is no evidence of ascending degeneration of the 

 kind described by Krause after interruption of a nerve. 



(6) That the old axis-cylinder and myeline sheath are destroyed in 

 the peripheral segment, and in the ultimate portion of the central 

 segment. 



2. Regeneration : 



(a) That young nerve fibres are developed in the peripheral seg- 

 ment, as well as in the end of the central segment, and that even 

 while there is no connexion between the two ends. 



