during Muscular Contraction. 1^1 



The question now arose^ could not the effect which might be 

 due to muscular contraction coincide with that which arose from 

 the action of the cutaneous secretions ? From the results ob- 

 tained by Du Bois-Reymond*, it would appear that the direc- 

 tion of the current due to muscular contraction is inverse, i. e. 

 from the hand to the shoulder. 



Several other experiments were undertaken in which different 

 solutions were employed to moisten the hands ; the effect upon 

 the needle was now much greater. When one hand was moist- 

 ened with a weak alkaline solution and the other with water, upon 

 contracting the muscles of the arm holding the alkaline electrode, 

 this became negative to the other ; but by proper management, 

 by not having the solution too strong, we could make this arm 

 become positive, the current occurring during muscular contrac- 

 tion overcoming the influence of the alkaline solution. Feeling 

 the force of the objections that might be raised in reference to 

 the use of the metallic electrodes, we do not think it necessary 

 to relate any other experiments made with the use of these in- 

 struments. 



A galvanometer t of the following construction was now em- 

 ployed. It consisted of two coils, one placed above the other so 

 as to produce the full effect upon both needles, with an index to 

 indicate the amount of deflection. Each coil was 2 inches in 

 length and the same in breadth, consisting of 1500 turns; the 

 thickness of the wire 37 gauge. The needles were rather less 

 than 2 inches in length; the index, of ivory, 3 inches in length. 

 As our object was to ascertain, if possible, the existence of the 

 force rather than the amount, a further description of its delicacy 

 will not be necessary. 



Two copper clamps were made, each 4 inches in length, taper- 

 ing at one extremity so as to be connected with the binding- 

 screws of the galvanometer, the other extremity being bent down 

 at right angles to the extent of half an inch, presenting a surface 

 .\\ inch in breadth, and to which was also attached a piece of 

 copper by means of two screws ; by these clamps the platinum 

 electrodes were attached, and those that were generally used 

 consisted of platinum foil, each 2^ inches in length and 1 inch 

 in breadth. 



The vessels usually employed to hold the solutions were two 

 cupping-glasses, each 2;^ inches in diameter, 2| inches in depth, 

 and contained rather more than four ounces of fluid. The 



* Rapport sur les Memoires relatifs aux phenomenes electro-phyeio- 

 logiques prescrites a 1' Academic par M. E. du Bois-Reymond, Comptes 

 Rendus, vol. xxxi. p. 28. 



t V^ide Faraday's mode of employing a galvanometer. Phil. Trans. 

 Series xxviii. 1852. 



