ANIMAL ELECTRICITY 



-LECTURE VI. 



^2>7 



— , / is -\- y e' is less +, ^ is least +. In relation to 

 each other e is 4- and e is — . Write these signs down 

 then against e' and e of the figure (fig. 65) and trace 

 the current through. You probably first give it as 

 being from e' to e, i.e., the reverse of what it is, until a 

 little reflection makes clear to you that as regards ex- 

 trapolar current, e is kathode and e is anode. So you 

 change the signs to + at ^ and — at e'. If from this 

 point you follow the change produced during excita- 



FiG. 65. 



tion, you would not go wrong whether you take + 

 and — potentials at 3 and 4 respectively, or their 

 — and + poles at the galvanometer. Still mistakes 

 are often made, and it is necessary to be carefully on 

 one's guard, for it to come out evidently that excita- 

 tion must give an effect negative to the electrotonic 

 current. 



The way in which I prefer to express it is this : e 

 is more anodic than e, i.e., less zincative, and current in 



