140 THE ELECTRICAL PHENOMENA OF MUSCLE. [OH. xil. 



imagined this to be due to electricity secreted by the animal 

 tissues, and this new principle was called Galvanism. But all his 

 contemporaries did not agree with this idea, and most prominent 

 among his opponents was Volta, Professor of Physics at another 

 Italian university, Pavia. He considered that the muscular con- 

 tractions were not due to animal electricity, but to artificial 

 electricity produced by contact with different metals. 



The controversy was a keen and lengthy one, and was ter- 

 minated by the death of Galvani in 1798. Before he died, how- 

 ever, he gave to the world the experiment known as " contraction 

 without metals," which we shall study presently, and which con- 

 clusively proved the existence of animal electricity. Volta, how- 

 ever, never believed in it. In his hand electricity took a physical 

 turn, and the year after Galvani's death he invented the Voltaic 

 pile, the progenitor of our modern batteries. Volta was right in 

 maintaining that galvanism can be produced independently of 

 animals, but wrong in denying that electrical currents could be 

 obtained from animal tissues. Galvani was right in maintaining 

 the existence of animal electricity, but wrong in supposing that 

 the contact of dissimilar metals with tissues proved his point. 



This conclusion has been arrived at by certain new methods of 

 investigation. In 1820 Oersted discovered electro-magnetism: 



Fig. 160. 



Fig. 161. 



that is, when a galvanic current passes along a wire near a 

 magnetic needle, the needle is deflected one way or the other, 

 according to the direction of the current. This led to the inven- 

 tion of the astatic needle and the galvanometer, an instrument by 

 which very weak electrical currents can be detected. For a long 

 time the subject of animal electricity, however, fell largely into 

 disrepute, because of the quackery that grew up around it. It is 

 not entirely free from this evil nowadays ; but the scientific in- 

 vestigation of the subject has led to a considerable increase of 



