290 



SCIENCE OF COMMON THINGS. 



How galvanic electricity was discovered. 



By Galvani, professor of anatomy at Bologna, Italy, 

 in 1790. 



Having occasion to dissect several frogs, he hung up their hind legs on 

 some copper hooks, until he might find^t necessary to use them for illus- 

 tration. In this manner he happened to suspend a number of the copper 

 hooks on an iron balcony, when, to his great astonishment, the limbs wero 

 thrown into violent convulsions. 



189O On investigating the phenomena what did Galvani discover ? 



He found that whenever the nerves of a frog's leg 

 were touched by one metal and the muscles by another, 

 convulsions took place on bringing the two different 

 metals in contact. 



Fig. 85. 



This is explained by reference to Fig. 85, which represents a frog's legs, 

 the upper part dissected in such a way as to exhibit the nerves of the legs-?., 

 and a portion of the spinal marrow. If we now take two thin pieces of cop- 

 per and zinc. C z, and place one under the nerves, and the other in contact 

 with the muscles of the leg, we shall find that so long as the two pieces 

 of metal are separated, so long will the limbs remain motionless, but by 

 making a connection, instantly the whole lower extremities will be thrown 

 into violent convulsions, quivering and stretching themselves in a manner 

 too singular to describe. If the wire is kept closely in contact, these 

 phenomena are of momentary duration, but are renewed every time the 



