PHYSICS OF NINETEENTH CENT.-ELECTRICITY. 551 



been obtained to the mystery of animal movement, and Galvani pro- 

 ceeded to follow it up in the true spirit of experimental investigation. 

 In order to eliminate any effect which might be due to the magnetic 

 condition of the iron railings or to their condition, he reproduced the 

 arrangement within doors with bars of polished iron, and with these in 

 every position. He observed the same contractions as before. He had 

 now entered upon a new and untrodden path of discovery, which he 

 began to explore with eagerness, and yet with philosophic caution ; 

 for as he himself said (repeating a very old observation), we are easily 

 deceived in an experiment, and what we have wished to see we think we 

 have seen. He examined the consequence of constructing with different 

 materials the circuit connecting the nerves and the muscles of the 

 frog's legs. He found that it was necessary to form the circuit entirely 

 of substances capable of conducting electricity. The most powerful 

 contractions were obtained when the lumbar nerves were covered with 

 tinfoil, the muscles of the leg with silver leaf, and a copper wire used 

 to establish a connection between the two metals. These experiments 

 appeared to establish beyond doubt the idea with which Galvani com- 

 menced his experiments, namely, that a certain distribution of elec- 

 tricity naturally existed in the animal organism. These experimental 

 results he formulated in a theory in which the muscle was regarded as 

 a kind of Leyden jar, the nerve and the metallic connections in the 

 experiment acting as conductors through which the discharge took 

 place. In this discharge positive electricity passed, he declared, from 

 the inside of the muscle to the nerve, and from the nerve through the 

 metallic connector to the outside of the muscle. We shall see pre- 

 sently how Galvani's idea of the existence of electric currents in the 

 muscles themselves was overshadowed for a time by other theories. 

 Nevertheless years afterwards, when the progress of science had fur- 

 nished means of investigation not dreamt of in 1791, Nobili confirmed 

 (1827) the correctness of Galvani's views as to the muscular currents; 

 and at a still later period Matteuci, and especially Professor Dubois- 

 Reymond of Berlin, have made the muscular currents the subject of 

 most elaborate and thorough experimental investigations. One distinct 

 result of these modern investigations has been the establishment of 

 the law that in the muscles stall animals any outer point is electrically 

 positive with regard to any inner point in the same transverse section 

 of the muscle. This law was clearly established by Dubois-Reymond 

 in 1843, and the same distinguished observer has since greatly ex- 

 tended our knowledge of this subject. For instance, he has shown 

 that the more powerful the mechanical effect which a muscle is des- 

 tined to produce, the more intense is the electrical current in a con- 

 ductor connecting one part of the muscle with another. Portions of the 

 muscles of a dead animal properly arranged constitute, in fact, a voltaic 

 pile capable of yielding currents which will deflect a magnetic needle. 

 Galvani's fundamental experiment, as now repeated in every course 



