( 111 ) 



We have not space to trace the story of Animal Electricity, but, 

 leading up to its investigation, we have the discovery of Oersted of 

 the deflection of a needle, by a galvanic current, Ampere's astatic 

 needle (1820), and Nobili's invention of a galvanometer of great 

 delicacy. 



LEOPOLDO NOBILI (1784-1834) was for a time Professor of 

 Physics in Florence. His most valuable contribution in the 

 matter that now interests us is the astatic combination of two 

 needles, by which the sensibility of the galvanometer is increased. He 

 invented his galvanometer in 1825. This opened the way to a more 

 careful study of the " frog current." He communicated his invention 

 to the Accademia di Scienze, Lettere ed Arti di Modena. He also 



. 



LEOPOLIJO NOBILI. 



S. MAKIAXIXI. 



busied himself with vegetable physiology, and studied the move- 

 ments of protoplasm in Chara. Nor must we forget Alex. v. 

 Humboldt (1769-1859), C. Matteucci (1811-1868), and S. Marianini 

 (1790-1866). MATTEUCCI, in his Traite des Plienomiines Electro- 

 pht/sioloyiques des Animaux gives an excellent short historical account 

 of this subject, and recalls the statement that Swammerdam (Biblia 

 Naturw, II., p. 849) made an experiment, in 1668, before the Grand 

 Duke of Tuscany, showing that a muscle contracted when a copper 

 wire was touched by a silver one. This experiment is shown in 

 the figure already given under kSwammerdam (p. 34). This statement 

 is incorrect, as Du Bois has shown (Elect. I., p. 43). The old 



