64 ELECTRICITY AND GALVANISM. 



by the point, and conveyed to the ground, without any 

 mischievous effects. 



Electricity has been used as a medical agent, and with 

 very beneficial results, its effect being to rouse into action 

 any dormant condition of the muscles. 



There are certain fishes that have the property of giv- 

 ing electrical shocks ; these are the torpedo, the gymnotus 

 electricus, and the silurus electricus. The shock given by 

 the gymnotus electricus, or electrical eel, is particularly 

 violent ; fishes are killed by it instantly, and occasionally 

 much larger and more powerful animals. 



An Italian professor of philosophy, named Galvani, 

 accidentally discovered, at the latter end of the last 

 century, that the action of electricity on the limbs of a 

 frog caused them to contract. As this action took place 

 in a cold-blooded animal, it was called by Galvani animal 

 electricity, he considering it a property of living matter, 

 and imagining that these contractions were caused by 

 something in the nerves and muscles of the animal. 

 Soon after he discovered that a similar effect might be 

 produced without any visible electrical agent, but by 

 the mere action of metallic substances of different kinds. 

 Volta, another eminent Italian professor at the beginning 

 of the present century, applied himself to the investiga- 

 tion of this subject ; but instead of supposing that the 

 electricity belonged to the animal, he attributed it to the 

 metals, and therefore concluded that by increasing their 

 number he should in like proportion increase their effect. 

 He therefore repeated the experiments of Galvani, and 

 found that when two pieces of metal of different kinds 

 were placed in different parts of an animal, and these 

 metals were brought into contact, or were connected by 

 a metallic arc, contraction ensued, and that as often as 

 the contact between them took place. He also found 

 that the best metals for the purpose were zinc and 

 silver, and that the effect was increased in proportion 

 to the number of pairs used, each pair being separated 

 by means of moistened cloth. A series of plates of this 

 nature is called the Voltaic Pile, and by its means various 

 chemical discoveries have been made ; in honour, there- 

 fore, of Volta, this science has received the name of 



