2l8 SCIENTIFIC RECREATIONS. 



prime conductor of the electric machine, and while the nerve was touched by 

 a conductor. Galvani then suspended a number of frogs to a railing by 

 metal hooks, with a view to experiment upon them with atmospherical 

 electricity. But the frogs' limbs were again agitated when no electricity was 

 apparent, and Galvani after some consideration came to the conclusion that 

 the movement was owing to the position the animals assumed with reference 

 to the metallic bodies. Thus when muscle and nerve were in contact with 

 metallic bodies and connected by metal, the movements of the limbs were 

 observable, and the greater the surface contact the greater was the convulsion. 

 The philosopher next tried various metals, and discovered that the most 

 powerful combination was zinc and silver. 



Galvani, in 1791, published his discovery and his theory that the body 

 .acted as a Leyden jar, different parts being in a different state of electricity. 

 No sooner were his deductions published than all Europe was in a ferment, 

 and philosophers of all nations were discussing it. Fowler, Valli, Robison, 

 Wells, Humboldt, etc., all were deeply interested, but none of them appear 

 to have arrived at so correct conclusions as did Volta, the physician of Pavia. 

 " Wherever frogs were to be found," says Du Bois Reymond, " and where 

 two different kinds of metal could be procured, everybody was anxious to 

 see the mangled limbs of frogs brought to life in this wonderful way. Physi- 

 ologists believed that at length they should realize their visions of a vital 

 power, and physicians thought no cure was impossible." 



But notwithstanding the popular theory, Volta, in his letters to Carallo, 

 while giving a full and clear account of the discovery made by Galvani and 

 his own experiments, attacked and finally defeated the Professor. Volta 

 quite upset Galvani's Leyclen-jar theory ; Volta says that it was by accident 

 that Mr. Galvani discovered the phenomenon, and by which he was more 

 astonished than he ought to have been. Volta's letters will be found in the 

 Philosophical Transactions of the Royal Society (in French), and he attributes 

 the effect to the metals which produced a small amount of electricity. He 

 found that the nerve was acted upon on even parts of a. muscle laid upon 

 two different metals, and if those were united, a contraction took place. 



" Many experiments were made in all parts of Europe," says Doctor 

 Roget, and " an opinion had been very prevalent that the real source of the 

 power developed existed in the muscle and nerve which formed part of the 

 circuit, and that the metals which composed the other part acted merely as 

 the conductors by which that agency was transferred from the one to the 

 other of these animal structures. But the discoveries of Volta dispelled the 

 rror, by proving that the sources of power were derived from the galvanic 

 properties of the metals themselves when combined with certain fluids," and 

 decided that this principle was electricity. From this the " general fact " 

 was deduced viz., " that when a certain portion of a nerve which is distributed 

 to any muscle is made part of a galvanic circuit, convulsions, generally of a 

 violent and convulsive kind, are produced in that muscle." 



Volta at length made the discovery that when two metals were brought 



