v*« 



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84 On Electricity in Plants^ and on Veg'efo-terrestrial Currents. 



In aiming to ascertain the chemical origin of the currents pro- 

 duced in the interior of an organized body, it should be remem- 

 bered that if two different liquids, separated by a permeable mem- 

 brane are put in communication by means of two plates of 

 platinum in connection with a multiplier, the magnetic needle 

 deviates in a direction which indicates that the liquid acting as 

 the acid sets free positive electricity, and that acting as alkali, 

 negative electricity. The intervention of metallic plates is here 

 indispensable to the production of electric currents ; but it is un- 

 necessary when certain solid substances, non-conducting and per- 

 meable, and liquid conductors, are arranged as follows, as already 

 explained to the Academy.* 



If solutions of potash and nitric acid separated by a thin layer 

 of clay are put in communication by means of two plates of pla- 

 tinum, the acid liberates positive electricity as I have just said. 

 If we substitute for the plate a tube having the form of a U, one 

 decimeter in length, filled with moistened clay free from lime, 

 and so prepared that the part which is plunged into the acid 

 should be less and less acid, and that in the alkali less and less 

 alkaline, in order that there may be but a simple chemical reac- 

 tion, we have then an apparatus by the aid of which, on break- 

 ing the tube so as to have two conductors, decompositions may 

 be produced. 



Similar arrangements to this are found beyond doubt within 

 organized bodies consisting of solid parts more or less permeable, 

 and liquids which mingle only with difficulty under the opera- 

 tion of life, on account of the tissues. 



When public attention was first called to the admirable discov- 

 eries of Volta, Dr. Baccomio of Milanf endeavored to construct 



piles of organic substances of vegetable origin, as Matteucci has 



for some years done with portions of animal muscle j but no 

 true effects of the action of a pile were obtained. And how 

 did Dr. Baccomio operate ? He made a pile out of disks of tlie 

 root of the beet, five to six centimeters in diameter and disks of 

 walnut of like size, with which he caused a frog to contract, 

 using as an excitor the leaves of Cochlearia. As there was nothing 

 to prove that a similar effect would not have resulted from a 

 single pair, there is no evidence for believing that the whole 

 acted as a pile, especially if we consider the following facts. 



M. Donne has obtained currents from animals and vegetables 

 by putting in communication, by means of metallic plates or 

 wires connected with a multiplier, liquids of different composi- 

 tion belonging to one and the same body and capable of acting 

 chemically on the surrounding liquids. Having placed a plate 

 of platinum in the mouth which is commonly alkaline, and 



XXIV 



+ Ann. de Cliim. [2], Ixii, 212 



