iv ELECTROMOTIVE ACTION IN MUSCLE 341 



muscles below the skin would appear unmistakably at the moment 

 at which both leading -off points became electrically indifferent. 

 This seemed in fact to be the case in du Bois' experiments, but 

 the P.I)., strictly speaking, was always very low, and gradually 

 diminished. This last fact indicates that the parelectronomy 

 of the subcutaneous muscles was abolished by the gractuaT 

 permeation through the skin of the ^N"aCl solution, so that we 

 seem to be a priori justified in supposing that the very first signs 

 of the normal muscle current are also due to corrosion of the 

 natural transverse section. Hence, as Hermann (10) was the 

 first to point out and demonstrate directly by corrosion with 

 silver nitrate, which perceptibly alters (darkens) the subjacent 

 muscles, this experiment cannot be held conclusive, for the theory 

 of the pre-existence of the muscle current. " If the points of 

 corrosion are so chosen that there is no subjacent aponeurotic 

 muscle-surface (e.g. the outermost points of the toes, and skin of 

 back), there is actually no deflection corresponding with the 

 muscle current, but the circuit is as free of current as is possible 

 in any circuit which contains moist conductors and metals." If 

 creosote, silver nitrate, or still better, corrosive sublimate, are 

 used on Hermann's plan, instead of the rapidly dissolving salt 

 solution, it is really possible at a given time to demonstrate 

 complete absence of current between the two principal contacts 

 with the skin, while later on corrosion sets in, and a weak 

 normal current is produced. In fishes, where the skin current is 

 usually less strongly developed than in the frog, it is generally 

 sufficient to keep them a certain time in water at the temperature 

 of the room (Hermann) to produce absence of current on leading 

 off from the immobilised uninjured animal. We have shown 

 above, when describing the parelectronomic condition, that it is 

 possible to obtain a completely isolated muscle which is absolutely 

 curreiitless, and du Bois himself observed the same repeatedly on 

 the frog's gastrocnemius. That, this notwithstanding, he should 

 still maintain the pre-existence of muscle currents, was principally 

 because, in so many other cases, the same muscle exhibits small 

 but regular differences of potential in spite of every possible pre- 

 caution. We must, however, accept Hermann's view that in such 

 cases also the electromotive action depends on the unobserved en- 

 trance of injurious, i.e. chemically disturbing, fluids (skin-secretion, 

 muscle juices, etc.), unequal rise of temperature, contact, or 



