CHAPTEK XV 



THE EQUILIBRIUM OF COLLOID AND CRYSTALLOID IN 

 LIVING CELLS 



THE living cell may be regarded from the physicochemical point 

 of view as a machine or mechanism through which there constantly 

 is taking place a flux of energy. The cell is continually taking 

 energy up from its surroundings in certain forms, and redistribut- 

 ing this energy in other forms, but in the process it itself under- 

 goes little or no permanent change. Certain changes, it is true, 

 do occur slowly in the cell in the course of its life-history which 

 have the effect of permanently altering the character of the energy 

 discharged through it ; but these structural changes are so slow that 

 they can be put aside in the study of the cell as an energy machine 

 acting upon the energy at any given moment. 



If the case of the green plant cell acting as an energy trans- 

 former for light energy be placed on one side, it may be stated that 

 the energy supplies of the cell always come to it in the form of 

 organic compounds capable of yielding energy in the process of 

 oxidation in the cell. 



In order that the cell may be capable of oxidising these chemical 

 compounds of organic character coming in from its environment, 

 it is, however, absolutely essential that its own integrity be pre- 

 served ; and this integrity is just as completely dependent upon the 

 presence of the ions of certain simple inorganic salts in the cell and 

 its surrounding fluid media, as the exhibition of the typical pheno- 

 mena of cell activity is upon the supply of energy in the form of the 

 organic compounds to the living cell. In fact, in point of time, the 

 physiological activity of the cell is more rapidly destroyed by 

 removing or altering the supply of inorganc ions than it is by inter- 

 fering with the supply of organic food-stuffs. For, in the latter case, 

 the cell can oxidise the combustible materials present in storage 

 within it, and even use up a portion of its own intrinsic substance 

 before its activities come to a standstill; but when the inorganic 

 ions, forming a constitutional part of the living cell, are altered, 



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