42 ANIMAL ELECTRICITY. LECTURE II. 



scale by reason of the current of injury from T to L 

 in the nerve. What is the value of the pressure 

 difference between T and L a-ivine that current ? 

 I open K2 from the graduation coils, and find that 

 the ,-^ volt oives i degree deflection, therefore the 

 current of injury that gives 8 degrees, is by a pres- 

 sure of ,^„ volt. Now let us start the excitation by 

 which the nerve is questioned, and watch the negative 

 deflection that is its answ^er. It is a fairly good one — 

 about I i degree, i.e., 0*0015 volt. Now for the soda 

 water. I am passing air through it into the nerve- 

 chamber for one minute. The first deflection after 

 this is not much altered, but a minute later it is 

 distinctly larger, and at the third minute it is about 

 doubled. Is this greater deflection due to raised 

 pressure or lowered resistance .^ The standard pres- 

 sure of j^ volt let into the circuit by opening K, is 

 unaltered ; therefore the augmented deflection is due 

 to augmented pressure, not to diminished resistance. 



We go through the same steps with tobacco smoke 

 on a fresh nerve, and the result is precisely similar — 

 even more marked than in the previous experiment. 

 Like soda water, tobacco smoke is a stimulant. 



And now to bring these trivial experiments to a 

 close, we will try the effect of strong alcohol, driving- 

 its vapour as before into the nerve-chamber. The 

 response of the nerve is promptly abolished. The 

 nerve seems to be dead, but is in reality no more 

 than •' dead-drunk " ; I have little doubt of its 



