CHAP, in.] ELECTRICITY AND MAGNETISM. 



185 



nounces the establishment of a current by a similar 

 contraction. 1 



229. Muscular Contractions. In 1678 Swam- 

 merdam showed to the Grand Duke of Tuscany that when 

 a portion of muscle of a frog's leg hanging by a thread of 

 nerve bound with silver wire was held over a copper 

 support, so that both nerve and wire touched the copper, 

 the muscle immediately contracted. More than a cen- 



Fig. 94. 



tury later Galvani's attention was drawn to the subject 

 by his observation of spasmodic contractions in the legs 

 of freshly-killed frogs under the influence of the " return- 

 shock " experienced every time a neighbouring electric 

 machine was discharged. Unaware of Swammerdam's 

 experiment, he discovered in 1786 the fact (alluded to in 



l It will scarcely be credited that a certain Jules Alix once seriously pro- 

 posed a system of telegraphy based on this physiological phenomenon. 



