CHAP. X. §. I. DUBIKG MUSCULAB CONTRACTION. 113 



turns; the thickness of the wire 37 gauge. The 

 needles were rather less than 3 inches in length; 

 the index, of ivory, 8 inches in length. As my 

 object was to ascertain, if possible, the eadstenee of 

 the force rather than the amount, a further de- 

 scription of its delicacy will not be necessary. 



Two copper clamps were made, each 4 inches in 

 length, tapering at one extremity so as to be con- 

 nected 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 

 IJ inch in breadth, and to which was also attached a 

 piece of copper by means of two screws ; by these 

 the platinum electrodes were securely fastened, 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 2i inches in diameter, 

 2i inches in depth, and contained rather more than 

 four ounces of fluid. The glasses being half filled 

 with a weak solution of common salt, covering the 

 electrodes to the extent of an inch, two and some- 

 times three fingers of each hand were held perpen- 

 dicularly m. the vessels, the middle finger resting 

 upon the bottom of the glass vessel. When first 

 introduced, a slight tremulous motion of the needle 

 was observed; upon taking the fingers out of one 

 vessel and reintroducing them, and repeating this 

 act, a slight effect appeared, at first definite, but this 

 soon subsided. Similar effects were observed when 



