PROTOPLASMIC STRUCTURE 73 



Another condition favoring stability in an emulsion 

 is a small diameter in the disperse droplets. The 

 disperse particles in suspensions and emulsions are 

 electrically charged, and if they are sufficiently minute 

 the forces due to their mutual electrostatic repulsion 

 may be sufficient to prevent contact and fusion/ We 

 must therefore qualify the statement that at least three 

 components are necessary in a permanent emulsion- 

 system by the proviso that the subdivision be not 

 excessively minute. This factor, however, is of minor 

 importance in most emulsion systems, and probably is 

 not of great importance from a biological point of view. 

 It is worthy of note, however, that in some cases mutual 

 electrostatic repulsion appears to play a part in deter- 

 mining the distribution of colloidal particles, droplets, 

 or other minute freely mobile particles in cells; e.g., 

 the distribution of the chromatin in the equatorial 

 plates and spiremes of mitotic figures shows evidence of 

 this factor.^ 



An emulsion, being a system of disperse charged 

 particles, resembles in this respect any colloidal sus- 

 pension; hence electrolytes influence the stabiHty of 

 emulsions, because of the influence of the ions on the 

 interfacial potentials, just as they influence the stabihty 

 of other colloidal systems.^ Generally speaking, any 

 mechanical, chemical, or electrical conditions which 

 alter the surface lamellae affect the stability and other* 



' Cf. Lewis, KoUoid-Z., V (1909), 91. 



2 R. S. Lillie, American Journal of Physiology, XV (1906), 46. 



3 For the action of electrolytes on the stability of emulsions cf , 

 Powis, Z. physik. Chem., LXXXIX (1914-15), 186. Cf. Northrop 

 and De Kruif, /. Gen. Physiol., IV (1921-22), 639, for an account of 

 the analogous action of electrolytes in the agglutination of bacteria. 



