144 



COMPARATIVE PHYSIOLOGY 



depth of narcosis (measured by the time of exposure) which 

 was just sufficient to prevent the transmission of a stimulus 



Alcohol VapOi. 



(C:^ 



Fig. 35. — (After Adrian — see text.) 



through A or B alone, through C alone, or through A and B 

 successively. 



Time to Narcosis. 



Inspection of these figures shows (i) that the degree of 

 narcosis which extinguishes a nervous impulse transmitted 

 through a region of narcosis 9 mm. long is quite inadequate 

 to extinguish it if the section is divided into two halves separated 

 by unaffected nerve, i.e. recovery of intensity occurs on 

 emergence from the region of narcosis ; (ii) that the depth of 

 narcosis which suffices to extinguish an impulse is practically 



