iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 239 



anatomical recovery of the cut nerve, since the newly formed 

 nerve-fibres, after passing through the cicatrised tissue and 

 repeatedly dividing into branches, rejoin the peripheral stump 

 and run through it, between the old degenerating fibres. The 

 newly formed nerve-fibres, including even the most delicate, are 

 invariably continuous from the outset, as if there were no 

 formation of nerve-fibres other than those coming from the 

 central stump of the cut nerve. 



Perroncito observed that, while the functional recovery of the 

 nerve was intimately connected with the scar formation, it may, 

 under certain conditions, be independent of it. He saw, for 



FIG. 152. Dog in which all the nerves of the right hind-leg were destroyed. After some months 

 it showed no defect in progression. (Purpura.) 



example, that the conduction of electrical excitation reappears 

 earlier in the peripheral part than at the scar, which would 

 explain Bethe's experimental results. He brings out the fact that 

 functional recovery is not exclusively and necessarily associated 

 with anatomical regeneration since it can be simulated by the 

 existence of collateral nerve paths. 



Sometimes, particularly in young animals, Purpura noticed a 

 rapid and more or less complete functional recovery, which he 

 attributed to a process of collateral compensation. In all cases 

 in which he observed slow functional recovery he attributes this 

 to regeneration of the nerve-fibres. To ascertain whether the 

 more rapid recovery is due to collateral paths, Purpura operated 

 on puppies by cutting all the nerves to the hind -limb, and 

 obtained complete, though retarded, return of function, i.e. of 

 perfect co-ordination in walking, as partially shown in Fig. 152. 



In addition to his experimental investigations into the 



