098 DR ROBERT KENNEDY ON THE 



a fairly dense appearance, being made up of a tangle of fibres. Much of this tangle is 

 composed of undoubted young nerve fibres, the stain bringing out the axis-cylinders, 

 but in addition there are present undoubted connective tissue fibres, and also fibres of 

 which it is doubtful to which category they belong. The appearances presented are, 

 in short, those of a neuroma, and this description may be applied to all three cases. 



Deductions from Experiments. 



The results of these experiments show that in the dog there is, in the case of section 

 of the sciatic nerve, no important differences in the return of function whether the two 

 ends of the nerve are sutured so as to bring the corresponding segments of the fibres 

 into accurate apposition, or whether, by rotation of the peripheral segment, the ends of 

 nerve fibres which do not correspond are brought into apposition. Provided that the 

 two ends of the divided nerve are brought into apposition, whether in the old relation- 

 ship or in a new, reunion of the nerve follows, and the normal function returns. This 

 return of function, also, not only is qualitatively the same in the two cases, but the 

 time taken for the first evidence of restoration is also the same, namely, seven days, 

 and the further improvement, which rapidly follows, runs essentially the same course 

 in both cases. Thus voluntary co-ordinated movements of the hind limb were regained 

 as soon in Exp. I. and II. as in Exp. III. This is the more striking in a nerve like the 

 sciatic, which not only is distributed to so many different structures, but which is 

 composed of nerve fibres which supply antergic muscles, or muscles with opposing 

 functions. Thus, when the animals commenced to walk on their splints, the paw was 

 always dragged along the ground with the dorsal surface down, but on the seventh day, 

 the foot being placed with the plantar surface down indicated a return of function in the 

 extensor muscles ; and it is noteworthy that in the cases of Exp. I. and II. there was 

 more control over the extensor muscles than in the case of Exp. III. at the seventh day, 

 as in the former cases the animals had the power voluntarily to readjust the paw when 

 it turned over, a power not shown in the latter case till the day following. 



Such early return of function suggests the probability of the nerve having united by 

 first intention, but as stated above such a view implies that Wallerian degeneration had 

 not taken place, having been prevented by the early reunion of the peripheral 

 segment to its trophic centres, and that the nerve fibres of the peripheral segment in 

 the reunited nerve are the identical fibres which existed before the section. That this 

 was not the case is proved by the microscopic examination ; for not only are no adult 

 nerve fibres found in the peripheral segment, their place being taken by young nerve 

 fibres (Plate III. fig. 5), but in all cases evidence of degeneration of the old fibres is 

 abundantly present. 



Vicarious nerve supply has often been suggested as an explanation of early return of 

 function, but in the experiments this possibility is quite excluded from the extensive 

 distribution of the sciatic. Thus the section of the sciatic at the level of the trochanter 



