174 GENERAL PROPERTIES OF LIVING TISSUES 



ductivity of the nerve therefore is still sufficient, 

 while the irritability has been suspended by the 

 action of the gas. Hence, conductivity and irri- 

 tability are by no means interchangeable terms. 



Their essential difference is further shown by 

 the effect of alcohol vapor, which impairs con- 

 ductivity while irritability is little changed. 



2. Alcohol. Disconnect the rubber tube from 

 .the gas generator, and blow through the gas 

 chamber until the carbon-dioxide is driven out. 

 The nerve will recover its irritability. Deter- 

 mine this by stimulating from time to time. 

 When the nerve has recovered, drop a little 

 alcohol through the long glass tube of the gas 

 chamber, being careful that only the vapor of 

 the alcohol comes into contact with the nerve. 

 Stimulate both within and central .to the chamber. 



After a time, tetanus will no longer be pro* 

 duced by stimulating central to the chamber. 

 Stimulation within the latter is still effective. 

 Thus conductivity is impaired, while irritability 

 remains intact, or at least is affected to a less 

 extent. (The electrodes within the alcohol at- 

 mosphere should not be too far from the opening 

 through which the nerve passes to the muscle, 

 else, the, loss of conductivity in this part of the 

 nerve may make difficult the demonstration of 

 irritability.): 



