lO 



ANIMAL ELECTRICITY. LECTURE 



purpose of a distinct demonstration, I may hardly hope 

 to do so otherwise than by electrical stimulation — and 

 let us watch for a negative variation of our current 

 of injury. The variation is not large, but it is un- 

 mistakable ; (and while we are about it I will submit 

 it to two tests, the significance of which w^ll be 

 explained later — the test of direction and the test of 



P^iG. 5. — Nerve currents. 



The "current of injury" is from T to L in the nerve. The *' current of 

 action" (negative variation of the current of injury) is from L to T n the 

 nerve. 



distance. I have now reversed the direction of the 

 electrical stimulation, and the variation has remained 

 negative and of unaltered magnitude. I have now 

 brought the exciting electrodes much nearer to the 

 leading out electrodes, from a distance of about 3 cm. 

 to one of about i cm, and I repeat the test with both 

 directions of stimulating current ; still the negative 

 variation remains nes^ative and of unaltered maoni- 

 tude. We are thereby entitled to conclude that the 

 effect was a ''true negative variation," and not due 



