CHAP. VII., 2.] 



ELECTRICITY.- GALVANI -NOBILI VOLTA. 



163 



ability shown by the author in discussing them. 

 There was no part of Europe in which Galvani's ob- 

 servations were not held to bear out his theory ; and 

 the warmest eulogy of them is to be found in the 

 writings of Volta himself, who soon advocated a dif- 

 ferent explanation. Volta calls animal electricity " a 

 great and luminous discovery which forms an epoch 

 in the annals of physical and medical science," and as 

 " proved to demonstration (ad evidcnza) by many ex- 

 periments well contrived and accurately executed." x 

 Had there been as little novelty as has sometimes 

 been alleged in Galvani's observations, they would 

 not have been heard of at once, and repeated in every 

 civilized country, nor have given birth to a new and 

 splendid science. Nothing then in progress, either 

 in the hands of Volta or of any one else, gave the 

 slightest clue to the invention of the Pile, which, but 

 for Galvani, might have been yet undiscovered. 



Revival of Experiments on Animal Electricity. 

 The grand discovery of Oersted, which gave a fresh im- 

 pulse to so many branches of science, revived likewise 

 the subject of the proper electricity of the animal tis- 

 sues, which had been well-nigh forgotten since the 

 death of its discoverer Galvani. Twenty-nine years 

 later, in 1827,Nobili of Florence demonstrated the ex- 

 istence of what has been termed " The current of the 

 frog." We have seen that a momentary spasm is 

 produced when a circuit is completed, including the 

 muscle and nerve of the recently dead animal. But 

 by the aid of that admirable instrument the Galvan- 

 ometer, Nobili succeeded in showing that a continu- 

 ous current of positive electricity constantly passes 

 from the feet to the head of the frog. This he de- 

 tected by placing the feet of the animal in connec- 

 tion with one end of the galvanometer wire, and its 

 spine with the other (the whole being properly insu- 

 lated), when the needle of the instrument was per- 

 manently deflected to the amount of 5 or more 

 indicating the passage of a stream of electricity in the 



direction already mentioned, which continued for se- 

 veral hours after death. Strange to say, Nobili mis- 

 apprehended the nature of the phenomenon, ascrib- 

 ing it to Thermo-Electricity, though he ought to 

 have been undeceived by the singular intensity of 

 the animal current, which, feeble as it is, can force 

 its way along thousands of feet, or even some miles of 

 fine wire. 2 



These experiments were renewed in 1837 by M. (739.) 

 Matteucci of Pisa, who has the merit of reviving the MM - . Mat - 

 original and correct opinion of Galvani as to the vital D^BoiT* 1 

 source of this electricity. To his researches, and the Reymond. 

 still later ones of Dr Du Bois Reymond of Berlin, we 

 owe the knowledge of most of the facts as yet ascer- 

 tained in this most difficult and obscure branch of 

 enquiry, where the sources of error are so numerous 

 as only to be eluded by consummate skill on the part 

 of the experimenter. It appears to be established 

 that the vital electricity exists both in the muscles 

 and in the nerves of many, probably of all animals 

 when living or recently dead ; that therefore the frog 

 current of Nobili is only a single case of the general 

 muscular current, and that the latter arises from the 

 electro-motive action of even the minutest fibres of 

 which a muscle is composed the general law being 

 (according to Dr Du Bois Reymond) that positive elec- 

 tricity moves from the transverse section to the longi- 

 tudinal section of a muscle or a nerve, or any portion 

 of either. Finally, the last-named writer has shown, 

 to the satisfaction of many eminent men who have 

 witnessed his experiments, that powerful muscular 

 contraction, whether induced by stimuli or the result 

 of volition, tends to diminish the force of the natural 

 muscular current. This he demonstrated first on the 

 frog poisoned by strychnine, but afterwards on the 

 muscles of his own arm, in which by voluntary con- 

 traction he could diminish at will the force of the 

 natural current, which in the state of rest is directed 

 from the shoulder to the hand. 



2. VOLTA. Progress of Discovery in Common and Atmospheric Electricity The Electro-motive 

 Theory Voltaic Pile Chemical Analogies and Decomposition Fabbroni ; Nicholson and 

 Carlisle. 



VOLTA was the first among philosophers whose 

 career lay solely in the study of electricity. Franklin 

 and 2Epinus, Beccaria and Wilke, Cavendish and 

 Coulomb, gave it only a share of their attention; but 

 Volta was from boyhood exclusively an electrician. 

 Such devotion deserved success, and he achieved it. 

 He was already famous, and an honorary fellow of 

 the Royal Society, long before his principal discovery 

 of the Pile. A review of his career may therefore 

 be conveniently divided into two parts what con- 



cerns ordinary and atmospheric Electricity ; and the 

 new doctrine of Galvanism and the Electro-motive 

 force. 



I. ALESSANDRO VOLTA was born at Como, of a noble 

 family,in 1745. His first paper on Electricity was ad- ex p e ri- 

 dressed to Beccaria at the age of eighteen. But it was meats 



not till 1775 3 that he published a description of the ^js Electro- 

 T-,, , r . . , . . -, phorus and 



Jzlectrophorus, an ingenious instrument in which a Condenser. 



conducting body becomes electrified an indefinite num- 

 ber of times in succession by being brought near to an 



1 Opere del Volta, ii., p. 13, 14. 



2 The galvanometer of Du Bois Reymond contains 3-17 English miles of wire, in 24,160 coilfl. 



3 See the letter to Priestley in the First volume of Volta's Works. 



