52 CONTRIBUTION TO THE 



son immersion dans deux liquides separes, devient un couple vol- 

 tai'que et produit un courant en sens inverse d'autant plus energique 

 que le metal est plus inalterable. On avait pense d'abord qu'une 

 polarisation moleculaire de tout 1'arc etait la cause de ce contre- 

 courant ; mais il a etc reconnu depuis qu'il n'y avait que les bouts 

 immerge's qui jouissaient de cette faculte, et qu'elle etait due a une 

 couche d'oxigene au pole positif, et une d'hydrogene au pole nega- 

 tif. La meme cause produit les memes effets sur la grenouille ; la 

 patte positive se charge d'oxigene, et la negative d'hydrogene. Le 

 contre-courant se demontre en plongeant les pattes dans deux tasses 

 ou aboutit le fil d'un galvanometre tres-sensible. . . . Plus la pile 

 sera forte, plus le temps du courant sera long, plus les pattes seront 

 charge*es. . . . Ce qui est vrai pour une grenouille entiere Test 

 encore pour un muscle, pour une portion de muscle,' &c. * 



Du Bois-E/eymond, who established the correctness of Peltier's 

 facts by investigations of his own 2 , urged against his explanation of 

 the break-contraction that it was not easy to see how it could be 

 thus explained, since these electrical charges of Peltier would seem 

 to require a complete circuit to produce a current, a condition lost in 

 the very act of interruption 3 . It may however be said, in answer 

 to this objection of du Bois-Keymond, that the equalisation of the 

 differences of tension which exist in the muscle at the moment 

 when the external circuit is broken gives rise to internal currents. 



All this holds only for the break-contraction elicited by direct 

 excitation of the muscle, but may however be applied to the break- 

 contraction resulting from stimulation of the nerve, as to all appear- 

 ance it is identical with the other. 



Peltier's view was taken up by Matteucci, but carried no further. 

 He contented himself with pointing out that the break-contraction 



1 ' We owe to M. Hitter,' he says, ' and after him to M. De La Rive, the knowledge 

 of this fact, that a metallic arc, forming a hydroelectric circuit by its immersion in 

 two separate liquids, becomes a voltaic couple and produces a current in the reverse 

 direction, which is the more energetic the more unalterable the metal. It was at 

 first thought that a molecular polarisation of the whole arc was the cause of this 

 counter-current ; but it has since been recognised that it is only the immersed ends 

 which possess this property, which is due to a layer of oxygen at the positive pole and 

 to one of hydrogen at the negative pole. The same cause produces the same effect in 

 the frog; the positive foot gets charged with oxygen, the negative with hydrogen. 

 The reverse current shows itself when the feet are plunged into two cups, in which 



the wires of a very sensitive galvanometer terminate The stronger the battery 



and the longer the duration of the current, the more highly charged the feet become. 

 .... What is true of a whole frog is true of a muscle, of part of a muscle/ &c. 



2 Du Bois-Reymond, loc. cit. i. pp. 377-382. 

 8 Ibid. loc. cit. p. 381. 



