CONDUCTIVITY 



141 



Fig. 24. 



Curves of the changes in irritability (p) and conductivity (c) of a nerve under the influence of 



narcosis or asphyxiation. (After Frohlich.) 



increases in strength as the irritability diminishes. If the value 

 of the threshold is learned by stimulating the nerve at the elec- 

 trodes centrally placed to the chamber with minimal stimuli, it 

 would necessarily follow that this weak stimulus would bring 

 about a corresponding weak excitation of the individual fibers 

 and the wave of excitation already in the beginning of narcosis 

 would be obliterated, for it would meet with a decrement, the 

 result of the reduction in the irritability. A wave of excita- 

 tion of minimal strength could under these conditions no longer 

 reach the muscle, even in the beginning of narcosis. In spite 

 of this the excitation, even when produced with threshold 

 stimuli, passes through for a long time, even when the irri- 

 tability in the chamber is greatly reduced, as shown by testing 

 with the electrodes within the chamber. This is not consistent 

 with the assumption that a threshold stimulus brings about the 

 minimal excitation, even in the individual nerve fiber. But 

 further : with a definite decrease of irritability of the narcotized 



