. PROPER CURRENT OF THE FROG. 209 



such a way that the nerves of the first animal touch the 

 legs of the second, and the nerves of the second the legs 

 of the third, and so on. I thus have a pile, one extremity 

 of which is formed by the legs, and the other by the nerves. 

 I plunge the two poles* of this pile into two cavities of the 

 tray, which contain either a very weak saline solution or 

 distilled water. Into these I also put the two extremities 

 of the wires of the galvanometer. You see that the needle 

 deviates, and indicates precisely, as in the experiment of 

 Nobili, the existence of a very energetic current which cir- 

 culates from the legs to the nerves in each of the frogs 

 which form the pile. I have repeated and varied in a thou- 

 sand different ways this experiment, which has enabled me 

 to ascertain that the variation of the needle is proportional 

 to the number of frogs composing the pile ; that it is more 

 considerable when we employ an alkaline or saline solu- 

 tion, or, better still, an acid solution, than when we em- 

 ploy distilled water; that, whatever be the liquid employed, 

 the direction of the current is constant, and circulates al- 

 ways in the pile, from the feet to the upper part of the frog. 



On repeating these experiments, you will observe that at 

 the moment when the galvanometer indicates the presence 

 and the direction of the current, the frogs contract. 



The contractions are analogous to those observed by 

 Galvani ; they take place whenever we complete the cir- 

 cuit with a conducting body, as, for example, with a wick 

 of cotton, or a piece of paper moistened with water, or any 

 conducting liquid, provided that the arrangement be such that 

 the conducting substance communicates on one side with 

 the nerves, and on the other with the muscles of the ani- 

 mal. These contractions are also observed at the moment 

 when we interrupt the circuit. 



This current was at first called the current of the frog ; 

 but for this name I afterwards substituted another, thai of 

 14 



