HISTORY OF SCIENCE. 



lightning occurred but at other times when the sky was clear. He 

 attributed these effects to changes of the electric condition of the atmo- 

 sphere. One one occasion, many hours having elapsed without any 

 movements of his electroscopes having been observed, Galvani, wearied 

 of having often looked in vain to discover signs of electricity, pressed the 

 brass hooks forcibly against the iron rails, in order to see whether this 

 would operate to make the frog's legs more sensitive to the changes of 



FIG. 262. GALVANI'S EXPERIMENT. 



the atmospheric electricity, on account of the more perfect contact and 

 electrical connection. During this action he observed contractions 

 in abundance, which had no relation whatever to the electric state of 

 the atmosphere. Here, let it be observed, Galvani for the first time 

 saw the muscular contraction take place, without the presence of any 

 electrical apparatus, or of any electrical disturbance of the atmosphere. 

 It flashed instantly upon his mind that the electricity must exist in 

 the animal organs themselves, and that the metals acted merely as 

 conductors of the organic electricity. A clue appeared to have at length 



