150 PHYSIOLOGY OF NEEVE [CH. XIV. 



phenomenon they gave the name of "autogenetic regeneration." 

 The publication of these results provoked a long controversy, which 

 lasted from 1859 to 1874, and was closed at the latter date by 

 Vulpian withdrawing his new idea. He did so because in the 

 meanwhile he had repeated his experiments more carefully, and so 

 discovered that, although the ends of the divided nerve had not 

 joined up, connection with the central nervous system had neverthe- 

 less been re-established by means of fibres growing into the peripheral 

 segment from other nerves cut through in skin and muscle in the 

 course of the operation. 



The controversy has been revived within the last few years, and 

 the position of the disputants has been almost exactly the same as 

 that occupied by Waller and Vulpian half a century ago. Modern 

 investigators have, however, the advantage of being able to apply 

 new methods of research, and are provided with many histological 

 reagents of which the older workers were destitute. It is, however, 

 never safe to argue entirely from microscopic appearances, for nerve- 

 fibres may be simulated by non-nervous structures, and a 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. 



Vulpian's old doctrine of auto -regeneration has been revived in 

 this country by Ballance and Purves Stewart, and in Scotland by 

 Kennedy. The most prominent and persistent supporter of the 

 autogenetic theory is, however, a German neurologist named Bethe. 

 But none of these investigators have excluded the fallacy which 

 underlay the work of Vulpian and Philippeaux, as has been recently 

 pointed out by Langley and Anderson. These two workers at first 

 thought they also 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 really occurred. The new nerve-fibres which grow into 

 the peripheral segment from other nerves divided in the operation, 

 often do so by a devious and contorted course. If the number of 

 medullated nerve-fibres in the peripheral end is small, then the 

 connection with central fibres was found to be slight ; and in cases 

 where no connection occurred then medullated nerve-fibres were 

 entirely absent. Bethe admits a variability in the number of 

 medullated fibres, and this, though easily explicable on the view 

 that such fibres come by accident from the central ends of divided 

 nerves, is not accounted for at all by the autogenetic theory. 



Bethe's views have been contested not only by Langley and 

 Anderson, but also by Lugaro, by Kolliker, by Cajal, by Marinesco, 

 by Mott, and Edmunds in conjunction with myself, and by numerous 

 others. 



