136 SOME RECENT RESEARCHES IN PLANT PHYSIOLOGY 



solution with a smaller surface tension than 0-68 is without 

 a destructive action upon living cells, a really valid objection 

 will have been brought forward. Czapek's work, showing 

 the similarity in surface tension of fat emulsions and living 

 cells, gives much support to the view that they have 

 structurally similar surfaces. The profound influences 

 exerted by various salts upon the permeability of proto- 

 plasm, recently revealed by the researches of Osterhout, 

 seem to have their origin in the action of the solutes upon 

 the degree of dispersion of the proteid and fatty colloids 

 of the surface. It has also been pointed out that the intake 

 of salts by the living cell is regulated largely by the laws 

 of adsorption, and that in this the specific selective action 

 of the surface colloids is of the greatest importance. 



An interesting account of researches on osmotic pressure 

 and the permeability of protoplasm, carried out before 

 1903 has been given by Livingstone. 



NOTE. Osterhout (1915, 4) has since studied the effect 

 of dilution upon the isotoxicity of isotoxic mixtures, and 

 has given a correction to be applied for the change, which 

 is generally of negligible magnitude. An important research 

 by Stiles and J0rgensen (1915) has also just appeared. 

 They measured the rate of diffusion outwards of cell 

 electrolytes by determining the change in conductivity of 

 the external medium. They conclude that, within limits, 

 the rate of exosmosis is a measure of the toxicity of the 

 medium . 



