PROTOPLASMIC STRUCTURE 115 



Overton and other investigators to be characteristic 

 both of animal cells (blood corpuscles, muscle cells, 

 egg cells, etc.) and plant cells of the most varied kinds. 



In the partition method, as used by Hedin and others, 

 the distribution of dissolved substances between the 

 cells and the solution is measured directly (by cryoscopic 

 determinations), and its results agree closely with those 

 of the plasmolytic method. In general it has been found 

 that the above-cited conditions of permeability are highly 

 characteristic if not universal in living protoplasm.^ 



Since in general the lipoid-soluble substances which 

 penetrate living protoplasm are also highly surface- 

 active, the conclusion may be drawn that either lipoid- 

 solubiKty or surface-activity (or both) is a property 

 favorable to penetration (Overton, Traube). The 

 penetration of one substance through another may 

 depend on mutual solubility; the cases of the rubber 

 membranes used in Flusin's experiments, the water- 

 soaked bladder partitions employed by Nernst, and the 

 palladium partitions of Ramsay's experiments with 

 nitrogen and hydrogen may be cited as illustrations.^ 

 Overton explains the permeability of the plasma mem- 

 brane to lipoid-soluble substances as an expression of the 

 solubility of these substances in the lipoids of the mem- 

 brane; in general he finds a parallelism between the 

 lipoid-water partition-ratio of a given substance and 

 its ability to penetrate cells; this is illustrated by the 

 behavior of substitution-products and of the members of 



^ Cf. Hamburger's Osmotischer Druck ti. lonenlehre for an account 

 of comparative investigations in this field. 



2 Flusin, Afin. de chim. et phys., XIII (1908), 480; Nernst, Z. 

 physik. Chem., VI (1890), 37; Ramsay, Z. physik. Chem., XV (1894), 

 518. Cf. p. 144 below. 



