1913.] A Study on the Action of Surface Tension. 529 



logical phenomena has been sought for, and, as a result, attention has been 

 specially directed to the principle of surface tension. The participation of 

 this force, although considered as a factor in the causation of amoeboid and 

 contractile movement ever since 1869, was not suggested as influencing the 

 distribution of salts in living matter till 1910, when the author advanced 

 the view that surface tension plays an all-important rdle in determining the 

 localisation of salts and other solutes in cells and tissues, and in controlling 

 the diffusion through living membranes that brings about the formation of 

 excretions and secretions. 



It was the observations derived from the microchemical study of the 

 distribution of potassium salts in living cells that led to this view. The 

 compounds of this element are amongst the most soluble of all known salts. 

 Only two of its salts are under certain conditions insoluble in water, and 

 these are the triple salt, the hexani trite of cobalt, sodium and potassium, and 

 the double salt, the potassium platinum chloride. Neither of these is found 

 in the natural world, and therefore the salts of potassium found in living- 

 tissue, when aggregated in masses or layers in a cell, cannot be so localised 

 as a precipitate. Some other explanation for this localisation had to be 

 sought for, and the author, after full consideration of all the facts involved, 

 claimed that the localisation observed is a condensation due to the influence 

 of surface tension. 



How such a condensation may develop through surface tension may be 

 Tecognised on an examination of the results of the action of the Gibbs- 

 Thomson principle of surface concentration. This law or principle may be 

 .stated in a few words. It is to the effect that when a substance in solution 

 increases the surface tension of a fluid system {e.g., a drop of water) it is less 

 concentrated in the surface layer than in the rest of the system, while a 

 substance that lowers the surface tension of the system is more concentrated 

 in the siirface film than it is in the rest of the system. It has also been 

 found by Lewis and others that solutes which raise the surface tension at 

 a water-air interface as well as those which lower it, also lower it at a liquid- 

 liquid interface and at a liquid-solid interface and undergo condensation 

 there, as a result, it is understood, of the operation of the Gibbs-Thomson 

 principle. At such interfaces the degree of condensation depends on the 

 extent of the diminution of surface tension as well as on the concentration 

 of the solute throughout the fluid system, but, assuming the application of 

 the gas laws to dilute solutions, the concentration as deduced from Gibbs' 

 formula for this value would be 



S = ^ 



2 e 2 



