GALVANISM. 



333 



balcony in front of his laboratory, when, to his inexpressible astonishment, the 

 limbs were thrown into strong convulsions. No electrical machine was now 

 present to exert any influence. 



If the supply of capital facts be occasionally due to chance, or to the Being 

 by whom what is miscalled chance is directed, it is to the operation of the fac- 

 ulties of exalted minds that the development of the laws of nature is due : if 

 rude lumps of the natural ore of science be now and then thrown under the feet 

 of philosophy, the discovery of the vein itself, its depth and direction, its qual- 

 ity and value, the separation of the precious metal it contains from its baser 

 elements, the demonstration of its connexion with the phenomena of nature, 

 and its adaptation to the uses of life, are all and severally the work of that 

 noble faculty of intellect, that image of his own essence, which the Creator 

 of the universe has impressed upon man, and which is never more worthily 

 exercised than in the investigation of those laws of the material world, in all 

 of which, whether they affect the vast bodies of the universe, or the imper- 

 ceptible molecules of those around us, there is ever conspicuous a provident 

 care for the wellbeing of his creatures. 



In the convulsions of the frog, suspended by a copper wire on an iron rail, 

 Galvani saw a new fact, and soon discovered that the circumstance on which it 

 depended was the simultaneous contact of the metals with the nerves and mus- 

 cles of the animal. He found that the effects were reproduced whenever the 

 muscles touched the iron while the nerves touched the copper, but that contact 

 with the copper alone did not produce them. He next placed the body of the 

 animal upon a plate of iron, and touching the plate with one end of a copper 

 wire, brought the other end into contact with the lumbar nerves. The convul- 

 sions followed as before. Galvani inferred from these and other similar exper- 

 iments and observations, that the conditions under which the phenomenon was 

 produced were, that a connexion should be made between the nerves of the 

 animal and the muscles with which those nerves were united by a continued 

 line or circuit composed of two different metals ; and he explained this singu- 

 lar effect by assuming, hypothetically, that, in the animal economy, there exists 

 a natural source of electricity ; that, at the junction of the nerves and muscles, 

 the natural electricity is decomposed ; that the positive fluid goes to the nerve, 

 and the negative to the muscle ; that the nerve and muscle are therefore anal- 

 ogous to the internal and external coating of a charged Leyden jar ; that the 

 metallic connexion made between the nerve and the muscle in the experiments 

 above-mentioned serves as a conductor between these opposite electricities ; 

 and that, on making the connexion, the same discharge takes place as in the 

 Leyden experiment. 



This theory fascinated for a time the physiologists. The phenomena of animal 

 life had been ascribed to an hypothetical agent, which passed under the name of 

 the " nervous fluid." The Galvanic theory consigned this term to the obsolete list ; 

 and electricity was now the great vital principle, by which the decrees of the 

 understanding, and the dictates of the will, were conveyed from the organs of 

 the brain to the obedient members of the body. Those who know how pas- 

 sionate is the love of a theory which appears to give a satisfactory account of 

 effects otherwise mysterious, and how much more gratifying to the amour- 

 propre it is to be able to connect effects with supposed causes, than to be 

 compelled to view the former as the real limits of our knowledge, will under- 

 stand the reluctance with which the Bolognese school and its distinguished 

 leader would surrender a theory so dazzling as animal electricity ; nevertheless 

 it was doomed soon to fall under the irresistible assaults of physical truth di- 

 rected against it by a giant intellect, which, though located in a little village of 

 the Milanese, belonged to mankind. 



