686 DR ROBERT KENNEDY ON THE 



A nerve is thus, both from the point of view of its morphology and of its physiology, 

 a highly specialised structure, and it is, therefore, not surprising that the study of its 

 repair after division should lead to problems of great difficulty. 



Two methods of repair after division have been described, namely, that by first 

 intention, and that by regeneration of the peripheral segment. In the former case, it is 

 supposed that after the division of the fibre the two ends speedily become connected 

 again, so as to restore the fibre as before the division. After such a process of reunion, 

 the peripheral segment is still the same structure which before the division conducted 

 the impulses. This view, then, carries with it the supposition that when the nerve 

 fibres heal by this process, the Wallerian degeneration does not take place, that after the 

 section the peripheral end becomes again connected with its trophic centres before the 

 advent of degeneration, so that by the early restoration of the influence of the centres 

 the degeneration is avoided. The evidence which is advanced by those who regard this 

 as a possibility is the early return of function, but before such a process can be accepted 

 as possible, it would be necessary to have anatomical proof from microscopic preparations 

 of the peripheral end of a recently divided and reunited nerve, that the peripheral 

 segments of the fibres present the normal characters of adult medullated fibres, and that 

 degeneration remains are absent. This is what I have been unable to find satisfactorily 

 in the papers of those authors who claim that healing by first intention is possible, the 

 evidence relied on being chiefly that of early return of function. 



In the other process of repair of a nerve, after destruction of the peripheral segment 

 by Wallerian degeneration, that segment is regenerated, and the continuity of the nerve 

 to its end-organs thus restored. On the process by which this is effected there has been 

 much difference of opinion. That described by Eanvier of outgrowth from the central 

 segment of processes from the old axis-cylinders, which continue their growth till they 

 reach the end-organs, is the view which has been most widely accepted, while the other 

 view is that simultaneously with the degeneration, new fibres are formed in the peri- 

 pheral segment independently of the central segment, and that these become connected 

 with the old fibres of the central segment. The process described in the former view 

 necessarily requires for its accomplishment a considerable period of time, a period which 

 must be longer the farther the section is from the peripheral terminations of the nerve. 

 It is the acceptance of this view which gave origin and support to the view of healing 

 by first intention, as something had to be supposed to explain cases of early return of 

 function after nerve section. On this view, and on the view of development of the 

 nerve fibres advanced by Kolliker and by His, is founded the modern conception of the 

 ' neuron.' According to the second view, it is not necessary to suppose a lengthened 

 period of time, or a different period of time, according as the section is made near or far 

 removed from the peripheral terminals, until the nerve becomes again a functional 

 structure. 



Both from clinical and from experimental experience, it is established that early 

 return of function can take place, but there are certain fallacies which should be guards! 



