ANIMAL AND VEGETABLE 78 



CHAPTER V 

 THE NATURE OF THE NERVE IMPULSE 



'* It may be supposed that some electrical function is exercised by 

 oxygen in the blood." Sir Humphrey Davy. 



THE controversy which arose years ago between the 



physiological and physical schools as to the nature of the 



nerve impulse has, so far, contributed nothing decisive 



to our knowledge of the subject. 



" Theories there are in plenty, but none of them 



adequate to explain the phenomenon." (Halliburton, 



1915.) 



The facts which, we are told, make a chemical theory 



acceptable are 



" (1) Analogy with muscle, where the propagation of 

 the muscular impulse is undoubtedly largely due 

 to the propagation of chemical disturbance. 

 " (2) Evidence that the nerve does undergo metabolic 

 changes, as shown by the necessity for oxygen, 

 and the production of minute amounts of carbon 

 dioxide. 



" (3) Arrhenius and Van't Hoff showed that a rise of 

 10 in temperature increases the velocity of a 

 chemical reaction to two or three times its original 

 rate. . . . Maxwell's recent experiments show 

 that a rise of 10 C. approximately doubles the 

 velocity of nerve conduction. . . . Woolley ob- 

 tained the same figure from the influence of 

 temperature on the rate of conduction in muscle, 

 so probably the conduction process is of a similar 

 nature in both tissues." (Halliburton, 1915.) 



