GALVANISM. 



399 



iron balcony, when, to his great astonishment, the limbs were thrown into 

 violent convulsions. On investigating the phenomenon, he found that the 

 mere contact of dissimilar metals with the moist surfaces of the muscles and 

 nerves, was all that wa3 necessary to produce the convxilsions. 



Fig. 332. 



This singular action of electricity, first noticed by Galvani, may be experi- 

 mentally exhibited without difficulty. Fig. 332 represents the extremities 

 of a frog, with 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 copper and zinc, G 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 hmbs 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 contact is made 

 and broken. 



Galvani attributed these movements of tho muscles to a 

 kind of nervous fluid pervading the animal system, similar to 

 the electric fluid, which passed from tho nerves to tho mus- 

 cles, as soon as the two wore brought in communication with 

 each other, by means of the metallic connection, in the same way as a dis- 

 charge takes place between tho external and internal coatings of a Leyden 

 jar. He therefore called the supposed fluid animal electricity. 



To what did 

 Galvani attri- 

 bute these phe- 

 nomena? 



