PHYSIOLOGICAL EFFECTS. 127 



figure, which consists of strips of zinc and copper, 

 three inches in length, separated by a cork, is sufficient 

 to produce convulsive twitchings 

 in the legs of a frog or toad. A 

 larger apparatus produces more decided effects. The 

 legs are to be employed, with a portion of the back 

 bone attached, which is grasped by the sharpened ex- 

 tremities of the galvanic tweezers. As often as the 

 circuit is completed, by bringing the other extremeties 

 into contact, by the pressure of the fingers, the legs 

 are observed to twitch, as if they were still possessed 

 of life. The leg of a grasshopper, grasped in its 

 thickest part, may also be employed in the experiment. 

 In both these cases, the moisture of the flesh or skin 

 is the exciting fluid of the galvanic pair. In view of 

 the destruction of life which they involve, these expe- 

 riments should be confined to the lecture room, or only 

 made where many persons are to be instructed by their 

 exhibition. 



301. DISCOVERY OF GALVANISM. In the 

 discovery of words of Arago, " this immortal discovery 

 galvanism g^osQ in the most immediate and direct 



made ? 



manner, from an indisposition with which 

 a Bolognese lady was affected, in 1790, for which her 

 medical adviser prescribed frog broth." The frogs had 

 been killed and skinned, and were lying on the table 

 of her husband's laboratory. Experiments were in 

 progress with an electrical machine, which stood near 

 tli em, when it was observed that the frogs' legs were 

 convulsed, as the spark passed. This was not a new 

 fact, but Galvani was not acquainted with it, and un- 



