54 On Electricity in the Act of Muscular Contraction. 



M. Arago by M. de Humboldt, dated the 17th of May*, ex- 

 cluding however all those secondary causes which could give 

 rise to electric currents, excepting that one the action of which 

 is described. 



I shall commence by recalling to mind the observations which 

 I made in studying the electric effects obtained with a con- 

 denser, the plates of which were made of platinum or copper 

 gilt ( Traite de VElectricite et du Magneti&me, t. v. 2^ partie, 

 page 10) :— 



" The electro-chemical effects produced on the contact of 

 acid solutions with the liquids which moisten the fingers, must 

 be taken into account. In these various reactions the acids 

 acquire the positive electricity, which is transmitted to the 

 plate, and the liquids which moisten the fingers the negative 

 electricity. With the alkalies the effects are inverse." 



It follows from this, that if one of the plates is covered ex- 

 ternally by a very thin layer of hygrometric water, and that 

 it is touched with a finger moistened with perspiration, elec- 

 tric effects, resulting from the reaction of the perspiration 

 upon the water, ensue. It is also produced when a finger in 

 a great state of transpiration is applied upon one of the plates, 

 after having been previously moistened with water; in this 

 case the water acquires the positive electricity, and the con- 

 trary electricity flows into the body of the experimenter. If 

 we add to these effects those which take place when foreign 

 bodies are adherent to the skin, we must conceive that a large 

 number of complex electric effects would be produced in 

 plunging two fingers, as is done by M. Du Bois Reymond, 

 into two capsules filled with water in which are contained two 

 plates of platinum in communication with a multiplier. This 

 is not all : when, in virtue of these various causes, a current 

 has circulated in the liquid and in the wire, the two plates of 

 platinum are polarized in opposite directions, as may be shown 

 by withdrawing the fingers and establishing the communication 

 between the two capsules by means of a siphon filled with the 

 same liquid as that which they contain. This current, during 

 the first few moments, having the same intensity as the primi- 

 tive current, annuls it; but if, in the act of contraction, the 

 finger of the contracted hand become more or less immersed 

 in water, the inverse current may be less or superior to the 

 direct current. I guarded not only against the effects of the 

 inverse current, but also against the effects resulting from the 

 greater or less immersion of the fingers by smearing with fat 

 those parts of the fingers which might temporarily come into 

 contact with the liquid. By proceeding in this manner, I found 

 it impossible to observe the effects described by M. Du Bois 

 Reymond. 



* See Phil. Mag. vol. xxxiv. p. 643. 



