236 Electricity and Galvanism, 



tion, decomposed by some cause or series of causes, by which its 

 positive and negative elements are separated, their attempt at reunion 

 to reconstitute the neutral electricity giving rise to the phenomena 

 we have been investigating. Let us now review some of the proces- 

 ses going on in the body, which, from their nature, appear capable 

 of disturbing the electric equilibrium which would, without their 

 influence, exist alike in the living frame as well as in brute matter. 



It is now an incontrovertible fact that no chemical change can 

 possibly occur without a disturbance of electric equilibrium. Let us, 

 then, ask what processes of this character are going on in the body. 

 The first in point of importance that demands our attention is the 

 union of carbon with oxygen to form carbonic acid. We know that 

 in the respiratory process, this acid, in the form of gas, is, with 

 aqueous vapour, evolved from the lungs, in addition to a consider- 

 able quantity which exhales with the perspired vapours, from the 

 surface of the skin. It is nearly impossible to determine the quan- 

 tity of carbon thus evolved in combination with oxygen with any 

 great accuracy ; but it seems pretty certain that about thirteen or 

 fourteen ounces are thus got rid of in 24 hours. During this period 

 the greatest proportion is taken in with the ingesta as mere carbon, 

 and undergoes oxidation in some part of the animal frame. By this 

 union with oxygen, carbonic acid is formed and evolved. Now it is 

 demonstrable, that, if we allow a piece of charcoal to undergo com- 

 bustion in connection with the condensing-plate of a gold-leaf elec- 

 trometer, the gold leaves will soon diverge with free negative electri- 

 city, whilst the stream of carbonic acid escaping from the burning 

 charcoal carries off with it free positive electricity. This observation 

 we owe to M. Pouillet. It is true that the carbon does not, during 

 its union with oxygen in the animal frame, become red-hot and burn 

 with a visible flame ; but this does not constitute a serious objection 

 to our regarding the generation of carbonic acid as one source at 

 least of the excitation of free electricity, for the disturbance of 

 electric equilibrium does not depend upon the light and heat evolved, 

 but from the act of union of the carbon with the oxygen. It has, 

 indeed, been suggested by Mr. Wilkinson that the act of respiration 

 is essentially a galvanic operation, and that the cells of the lungs, 

 in which the chemical changes proper to this function occur, are 



