1861.] on the Nutrition and Reparation of Nerves. 379 



cal applications which had been founded on recent researches as to the 

 reproductive power of bone, might be rivalled by similar ones based 

 upon the reproductive energy of nerve tissue. 



With the view of explaining the nature of the researches which 

 Dr. Waller had undertaken on this subject, the speaker gave a general 

 outline of the structure and relations of the various parts of the nervous 

 system, pointing out the distinction between the nervous centres and 

 trunks, and comparing the structure of the more common form of nerve 

 fibre, — the white, to a wax taper inserted in a tightly-fitting cylinder 

 of paper, of which the wick represented the central axis filament, the 

 paper cylinder the investing nerve sheath, and the wax the intervening 

 medullary substance ; the grey variety of nerve-fibre differing from 

 the white in the absence of this medullary substance. The structure 

 of nervous ganglia was also referred to, and the relations of the cells 

 they contained to the fibres that passed through them was pointed out, 

 as well as the important fact, first discovered by Sir C. Bell, that the 

 sensory fibres of the ordinary spinal nerves alone pass through tne 

 ganglia, and are connected with its cells. 



In order to become acquainted with the means by which the nutri- 

 tion of healthy nerves was maintained and their injuries repaired, it 

 was necessary to study the effects which were produced in a nerve 

 by separating it from its centre. Fontana and Michaelis, who were 

 induced to examine the subject by Hunter, found that when a nerve 

 was divided it reunited, and that new nerve-fibres were produced at 

 the point of the union. Neither they, nor subsequent observers, how- 

 ever, had paid any attention to the lower portion of the divided nerve, 

 into the condition of which Dr. Waller was the first to examine. 

 The results of his researches had shown that the changes which took 

 place here were of a most important character, consisting, in brief, of 

 a complete disorganization of the medullary substance of nerve-fibre, 

 which was then gradually removed, and afterwards re-created, whilst 

 the axial filament and investing membrane remained intact.* Hence, 

 if we examined the fibres of the lower end of a divided nerve a short 

 time after section, we should find that they all appeared to be under- 

 going disorganization, and their medullary substance to be breaking 

 up. But if we examined it at a much later period, the nerve-fibres, 

 though rather smaller in size than before section, would have all the 

 appearance of being perfectly healthy. This fact, which Dr. Waller 

 had first attributed to a complete destruction of the old fibres and a 

 formation of new ones, he was now satisfied was owing only to the 

 changes he had just mentioned, that is, to the regeneration of the 

 medullary substance alone, and not of the whole fibre. 



This process of disorganization was accompanied by a complete 

 loss of functions in the nerve, which were only slowly recovered after 



♦ Diagrams, illustrating these changes, as well as most of the other facts 

 alluded to in the discoui-se, were exhibited ; and microscopic specimens of disor- 

 ganized nerve were afterwards shown in the Library. 



