CONDITIONS AFFECTING A NERVOUS IMPULSE 293 



On removing the gas or vapour by blowing air over the nerve, the 

 conductivity and excitability gradually return in the reverse order to 

 their disappearance (Fig. 110). 



FIG. 110. Tracing to show the effect of ether on excitability and conductivity of 

 nerve. Nerve excited by single induction shocks alternately within and above 

 ether chamber. The vertical lines indicate contractions of the muscle (gastroc- 

 nemius). The lower line indicates the periods during which the nerve was exposed 

 to the action of ether. 



A, disappearance of excitability ; B, reappearance of excitability ; c, disap- 

 pearance of conductivity ; D, reappearance of conductivity. (From a tracing 

 kindly lent by PKOF. GOTCH.) 



Alcohol is said to increase the excitability or leave it unaffected, 

 while diminishing the conductivity of the nerve. 



Chloroform rapidly abolishes both excitability and conductivity. 

 It is a much more severe poison than the drugs just mentioned, so 

 that in many cases its effects are permanent, and no, or only a very 

 partial, recovery of the nerve is obtained on removal of the ch ( ro- 

 form vapour from the apparatus. 



