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Messrs. H. O. Feiss and W. Cramer. 



[Oct. 22, 



and they play an all important part in the process of nerve regeneration. 

 According to this latter view (5) the phenomena of Wallerian degeneration 

 "do not deserve the term phenomena of degeneration. They are not 

 phenomena of degeneration or death but of reorganisation or life." 



We have indicated here only some of the views which are held. But this 

 brief survey indicates sufficiently well that the various explanations of the 

 processes of Wallerian degeneration cover a field so wide as to include their 

 interpretation as phenomena of death on the one hand and of exaggerated 

 phenomena of life on the other. 



Although the question which thus arises is one of considerable importance, 

 and although it can be tested experimentally, the evidence on this point is 

 neither ample nor convincing. The importance which Eanvier attached to 

 the proliferation of the neurilemmal cells in the process of Wallerian 

 degeneration led him to study the changes which take place in a nerve after 

 the death of the organism. He found (1) that the nerve of a dead animal 

 which was allowed to lie about " somewhere in a corner of the laboratory " for 

 several days did not show in the myelin sheath anything similar to the 

 changes of Wallerian degeneration. 



The subject does not appear to have received any attention by subsequent 

 workers until it was taken up again by Monckeberg and Bethe (3). These 

 authors have apparently not been aware of Eanvier 's experiments, and the 

 observations which they record do not quite agree with those of Eanvier. 

 They found, 24 hours after the death of an animal, a certain amount of 

 disintegration in the axis-cylinder and the sheaths of the nerves, and these 

 changes were more advanced when the body was kept at 37° C. But these 

 changes were not more pronounced two and three days after death than they 

 were after the first 24 hours. Nerves removed from a living animal and kept 

 in a moist chamber for one or two days did not show the characteristic 

 changes of the Wallerian degeneration in the axis-cylinder and the myelin 

 sheath. Monckeberg and Bethe concluded from their experiments that the 

 process of Wallerian degeneration is dependent on the life of the fibre, and, 

 further, that it takes place only when the nerve is lying in a medium of 

 living tissue. The degenerative changes which do occur during the first. 

 24 hours after death are attributed to a survival of the tissues, which is stated 

 to be prolonged by keeping the dead animal at body temperature. 



Eeference must be made also to the observations of Merzbacher (4),. 

 because they have an important bearing on the problem before us. From 

 observations on nerve degeneration in hibernating animals, and on frogs 

 kept at different temperatures, he concluded that in the living animal the 

 occurrence of Wallerian degeneration is dependent upon the temperature. 



