1912.] Contributions to the Histo- Chemistry of Nerve. 121 



If the body temperature is below a certain minimum, the processes of 

 degeneration are arrested, or, at any rate, greatly retarded. 



These observations invalidate to a certain extent the conclusions of Banvier 

 and of Monckeberg and Bethe. They might explain why the results of 

 1'anvier's experiments above referred to were negative, and why in the 

 experiments of Monckeberg and Bethe the degenerative changes in the 

 nerves of dead animals were more advanced when the body was kept at 37° 

 than when the temperature was allowed to fall to room temperature. 



Merzbacher also records some observations on the occurrence of Wallerian 

 degeneration after transplantation. He found that nerves, after auto- 

 transplantation (transplantation into another part of the same animal), and 

 after homo-transplantation (transplantation into another animal of the same 

 species), exhibited the typical changes of Wallerian degeneration, but failed 

 to show them after hetero-transplantation (transplantation into an animal of 

 a different species). These observations, as the author himself states, are 

 only of a preliminary nature, and that accounts probably for the omission to 

 state what changes, if any, take place in a nerve after hetero-transplantation. 

 Moreover, in a repetition of these experiments, Maccabruni (5) has shown 

 and illustrated by figures that hetero-transplanted nerves undergo Wallerian 

 degeneration in the same way as auto-transplanted or homo-transplanted 

 nerves. 



From the observations of Monckeberg and Bethe, and of Merzbacher, 

 far-reaching conclusions have been drawn by van Gehuchten (6), which can 

 best be stated in his own words : " There is no degeneration, and there cannot 

 be any degeneration, except where there is life ; degeneration is not only a 

 sign of life, but it is even the most striking manifestation which we can have 

 of an actual hyperactivity of normal cell life. Nerve degeneration is a 

 reaction of the organism ; it is an actual defence against the disturbances 

 which a given traumatism has induced in the normal functioning of its nerve 

 fibres." 



These considerations lead van Gehuchten to demand a modification of the 

 first part of Waller's law, which says that the peripheral segment of a cut 

 nerve undergoes degeneration. According to van Gehuchten, this law holds 

 good only if the significance of the word degeneration is altered, and if we 

 understand by it " a process of life, a process of reorganisation, which by 

 itself tends to a reconstitution of the nerve fibre." 



It will be seen that all the authors who have discussed this question are 

 agreed that the process of Wallerian degeneration is dependent upon the life 

 of the nerve fibre. But this conclusion does not necessarily follow from their 

 observations. In almost all the experiments, two different conditions — the 



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