ELECTRO-PHYSIOLOGY. 323 



placed beyond doubt, tbat the currents thus obtained do not depend on tlio 

 heterogeneity of the laminoe of the galvanometer, or on the action of the animal 

 liquids on those laminje ; in a word, the experiments with muscular batteries 

 have furnished the most indubitable proof of the existence of the proper elec- 

 tricity of the muscles of animals living or recently killed. 



Du-Bois Reymond, to whom we owe so many important experiments in electro- 

 physiology, was the first to construct and to use a galvanometer of very fine and 

 long wire which makes at least twenty thousand coils around the needles. He 

 was thus enabled to study muscular electricity without resorting to batteries — 

 that is, by operating on a single piece of muscle. The extremities of the galva- 

 nometer used by him were two laminae of platina immersed in salted water. 

 This liquid is contained in two small cups of glass, in each of which a consid- 

 erable stratum of flannel or paper passes from and beyond the cup, and is bent 

 horizontally to a short distance. These two appendages of paper or flannel, 

 called cushions, {cuscinetti,) being imbibed with the liquid of the cups, serve to 

 close the circuit when they are brought into contact, which is eff'ected by their 

 directly touching one another, or, still better, by placing upon them a third 

 similarly imbibed with the same liquid. After it is ascertained that there is no 

 current between the laminse, the third cushion is removed and the prepared frog 

 is substituted, which is done by placing it with the nerves on the cushion of one 

 cup and the legs on the cushion of the other. We shall then see a very strong 

 deviation in the needle, referrible to the usual current, which Nobili termed the 

 current of the frog, directed in the animal from the feet towards the head. 



Whichever of these methods of operating be selected, namely, the battery of 

 muscles with the less delicate galvanometer, or a single muscle with the highly 

 sensitive galvanometer, it will still be observed that the use of the laminos 

 of platina renders the experiment imperfect and sometimes erroneous. It will 

 be found, in eff'ect, especially in using a single frog and very sensitive galva- 

 nometer, that while the flrst deviation of impulsion is very great, the needle, after 

 oscillating for a brief period, establishes the ultimate amount of deviation at a 

 few degrees, and even then exhibits instability, promptly descending towards 

 zero. We may, therefore, easily satisfy ourselves that these eff'ect s do not de- 

 pend on the feebleness of the electricity of the frog, but on a physical phenomenon 

 with which we are already acquainted — that is, on the development of secondary 

 polarity in the laminae of platina, by which there is created an electro-motive 

 force contrary to that of the frog. In eff'ect if we remove the frog and close the 

 circuit by bringing the cushions into direct contact with one another, we imme- 

 diately observe a deviation in a direction opposite to that of the frog. This 

 secondary polarity, then, is an imperfection in these experiments, both because 

 it rapidly weakens the animal currents, and' because it creates heterogenity in 

 the laminae — effects which are not easily removed, and which may introduce 

 errors into succeeding experiments. Fortunately we possess at present a method • 

 in which these imperfections are avoided. I have already shown how, in causing 

 a current to pass by two electrodes of platina into a saline solution, these elec- 

 trodes, when the current of the battery ceases, give to the galvanometer a strong 

 secondary current in the opposite direction ; I also remarked that this latter 

 current was due to the products of electrization which collected on the electrodes 

 of platina, and to their chemical action on recombining within the liquid. 

 Observe now the experiment by which it is proved that a current may be trans- 

 mitted in a liquid by means of metallic electrodes without getierating secondary 

 polarity. Instead of electrodes of platina I employ strips of zinc perfectly 

 amalgamated and covered with mercury, immersed in a saturated solution of 

 sulphate of neutral zinc. By presenting the experiment we easily obtain an 

 explanation of the result. I cause the usual current to pass, and then close the 

 circuit between these strips or laminae alone ; there is now no trace of a current. 

 The sulphate of zinc is decomposed — that is, the oxygen and sulphuric acid go 



