154 THE CELL 



practically neutral. This power is conferred on the " constructed 

 cell " by the lecithin incorporated in its membrane. 



Polarisation Current. 



In all chemical processes, alterations in potential difference take 

 place. The living complex, known as a cell, is a system in which 

 chemical transformations proceed continually and, therefore, 

 electromotive force is being generated continuously. These 

 currents may be demonstrated if special arrangements are made 

 to prevent polarisation of the electrodes (Part II.). The electrodes 

 which are used to lead the current from the cell (or group of cells) 

 to the galvanometer are subject to polarisation, as explained in 

 Chap. XI. The products of electrolytic decomposition of the cell 

 substance are transported to the electrodes and accumulated there. 

 The deposition of these products at the two poles, in course of 

 time, alters the nature of the electrodes. The cathode, for instance, 

 because of the accumulation of positive ions on it, becomes more 

 and more anodal. This produces an electric tension that causes 

 a current, the so-called polarisation-current, to flow in the opposite 

 direction to the original one. As this current grows in strength 

 it reduces the value of the tissue-current, and after a short time 

 completely obliterates it. 



Further Reading 



McClendon & Medes. "Physical Chemistry in Biolog;v and Medicine." 

 Messrs. Saunders. 



