324 THE EQUILIBRIUM OF COLLOID AND 



the 0-1708 shown to be present by incineration. These figures are 

 completely confirmed by freezing-point determinations. 



This experimental evidence is interesting as showing that the 

 special affinities existing in each case between protein and ion 

 demand very different pressures or concentrations to preserve 

 the equilibrium. 



We can now understand why so little phosphate is required in 

 the Ringer's solution; the union of the phosphates is so strong 

 that it is not possible to run the phosphate concentration down to 

 such a level as rapidly to disintegrate the phosphatic ions of the 

 cardiac tissue. The merest trace given off from the heart to the 

 perfusing fluid suffices to stop further loss. The level for calcium 

 and potassium, though low, is somewhat higher, and traces sufficient 

 to preserve equilibrium must be added, or these ions break free from 

 the cardiac cells, producing irregularity of function. Finally, the 

 sodium and chlorine ions are but loosely held, and hence as much as 

 0-7 to 0-9 per cent, of sodium chloride must be present to preserve 

 the equilibrium and normal conditions of physiological activity. 



The facts as to the constitution of the colloidal material and 

 its relationship with electrolytes and other crystalloids which have 

 been given above, and the interpretation put upon those facts, 

 are intended to demonstrate that the living cell is a peculiarly 

 constructed energy machine or energy transformer, dependent for 

 its activity upon a delicate labile equilibrium giving stability as 

 a whole, and yet a weakness of union causing disruption and 

 oxidation of parts, and so furnishing energy. The view put forward 

 is intended as a reaction from that view which complacently re- 

 gards all the work of the cell and peculiarity in its constitution 

 as being due to the physical properties of inert membranes. 



The attempt has been made to show that something is required 

 more than membranes and osmotic pressure to explain the peculiar 

 distribution of electrolytes in cell and nutrient medium, and, going 

 farther, to give a basis for the understanding of the peculiar energy 

 exchanges of cells. It has been sought to invoke the peculiar 

 chemical constitution of protein and bioplasm, and the varying 

 equilibria of these with the materials brought in from the nutrient 

 media at varying pressures, giving rise to transient stages of asso- 

 ciation and dissociation, and an accompanying play of energy 

 changes. 



It is not intended in doing this, however, to suggest that mem- 



