Carbon Dioxide From Nerve Fibres 



127 



by heat, or due to both, cannot be decided here unless we consider the 

 relation between excitation and tissue respiration. 35 



It is hoped that we may have a better understanding of this matter 

 when we study the temperature coefficient of normal respiration of the 

 nerve. At present, we are satisfied to state only that there is a strong 

 evidence to support the conclusion that heat, ,too, increases C0 2 

 production from the nerve. 



DISCUSSION OF THE RESULTS 



Comparison of Metabolism of Non-Medullated and Medullated 

 Nerve. Although it appears ridiculous to attach any significance to 

 the marked similarity in the magnitudes of C0 2 production from non- 

 medullated and medullated nerves, the temptation is irresistible to 

 comment on the high output of C0 2 from the non-medullated nerve 

 fibre. Let us study the Table following (Table VIII), in which a 

 summarized comparison is given. 



TABLE VIII 



Since I have found that injury increases the C0 2 production from 

 the nerve, the values I have obtained from cut, or isolated, fresh 

 resting nerves, such as I had to use, may be somewhat greater than 

 the output of normal uninjured nerves would be. But since Alcock 36 

 has shown that a non-medullated nerve gives a higher electrical 

 response, both in the negative variation and the injury current, the 

 C0 2 increase due to the cut alone will probably be greater in case of 

 the non-medullated nerve than in that of the medullated one. That 

 means that the value of the CO 2 production for the resting uninjured, 



35 See p. 134. 



36 ALCOCK: Proceedings of the Royal Society, 1904, Ixxiii, p. 166. 



