EV.OLUTION OF ELECTRICITY. 551 



operations, and the impossibility of the occurrence of any of these without 

 some disturbance of Electric equilibrium, 1 are duly considered, the wonder 

 is, not that such disturbance should be occasionally so considerable as to 

 make itself apparent, but that it should be ordinarily so obscure as only to 

 be detected by the most careful search, and with the assistance of the most 

 delicate instruments. The researches of Prof. Matteucci, M. Du Bois-Rey- 

 rnond, and others, however, have now made it apparent, that there are no 

 two parts of the body (save those which correspond on the opposite sides), 

 whose electrical condition is precisely the same ; and that the differences be- 

 tween them are greater in proportion to the diversity of the vital processes 

 which are taking place in them, and to the activity with which these are 

 being carried on. 2 It is by the comparison of the electric states of different 

 secreting surfaces, that such departures from equilibrium are most readily 

 demonstrated. Thus, Donne found that the skin and most of the internal 

 membranes are in opposite electrical states; and Matteucci observed a con- 

 siderable deflection of the needle of a delicate galvanometer, when the liver 

 and stomach of a rabbit were connected with its platinum electrodes. 3 More 

 recently, Mr. Baxter has found that if one of the electrodes be placed upon 

 any part of the intestinal surface, and the other be inserted into the branch 

 of the mesenteric vein proceeding from it, a decided deflection of the needle 

 is produced, indicating a positive condition of the blood ; but that no effect 

 is produced when the second electrode is inserted into the artery of the part, 

 instead of into its vein. These effects were found to cease after the death of 

 the animals ; and could not be attributed, therefore, to mere chemical differ- 

 ences between the blood and the secreted product ; but must have arisen from, 

 electric disturbance taking place in the very act of secretion. 4 Scoutetten 

 and Shettle, again, have found arterial blood to be positive in its relations 

 to venous blood. That the process of Nutrition, as well as of Secretion, in 

 parts which are undergoing rapid molecular change, gives rise to electric 

 disturbance, is proved by the experiments of Matteucci and Du Bois-Rey- 



1 There is probably no instance of chemical union or decomposition, in which the 

 Electric condition of the bodies concerned is not altered. Simple change of form, 

 from solid to liquid, or from liquid to gaseous, is attended with electric disturbance; 

 and this is greatly increased when any separation takes place between substances that 

 were previously united, as when water containing a small quantity of saline matter 

 is caused to evaporate and to leave it behind. Heat, again, is continually generating 

 Electricity ; for not only is a current produced by the heating of two dissimilar metals 

 in contact, but also by the unequal heating of two parts of the same bar ; and though 

 the effect is most striking in the case of metals, it is by no means limited to them. 

 And so constantly is Electricity generated by the retardation of motion, as in friction, 

 that it is not possible to rub together any two substances, excepting those which are 

 of the most perfect homogeneity (such as the fractured surfaces of a broken bar), 

 without the production of Electric change as well as of Heat. 



2 Having 'had an opportunity of witnessing some of the experiments made by M. 

 Du Bois-Reymond with a magneto-electrometer of extraordinary sensitiveness, the 

 Author can bear his personal testimony to the fact, that the electricity even of the 

 corresponding fingers of the two hands is very seldom equally balanced, and that the 

 existence of even the slightest scratch or abrasion of surface upon one of them pro- 

 duces a very marked disturbance. 



3 See M. Becquerel's Traite de 1'Electricite, torn, i, p. 327, and torn iv, p. 300. 

 From his researches on the electrical organs of the Torpedo, Prof. Babuchin (Cen- 

 tralblatt, 1870, p. 241) arrives at the conclusion that they are essentially muscles in 

 which the proper muscular or contiactile substance is absent, and conversely he re- 

 gards muscles as electrical organs, in which muscular fibres are introduced between 

 the electrical septa. Marey .(Comptes Kendus, Ixxiii, pp 918 and 9o8) found the 

 period of latent excitation of the lectrical apparatus of the torpedo to be y'jth of 

 a second, whilst that of the muscles of the frog is g^th. 



4 Philosophical Transactions, 1848, p. 243. 



5 An Essay on the Electricity of the Blood, 18G7. 



