COMPLEX COACER^ ATES AND PROTOPLASM 31I 



acid and protein would also combine with one another to 

 some extent in coacervates of which they were components.''^ 



The occurrence of such combinations certainly adds con- 

 siderably to the complication of all the phenomena of 

 coacervation and would seem to favour the stabilisation of 

 the coacervates. Unfortunately this is still but poorly under- 

 stood. 



As ^vell as the simple and complex coacervates, a third 

 group is often formed, the internally complex coacervates. 

 These formations arise when ions of opposite charges are 

 adsorbed on colloidal particles. A double layer of ions is 

 formed around the particles. When this happens, the degree 

 of ionisation depends on the chemical nature of both the 

 colloid and the adsorbed ions. Internally complex coacervates 

 may be obtained from solutions of proteins and carbo- 

 hydrates, sols of phosphatides and fatty acids, with the help 

 of various mineral salts. ^"^ 



Points of similarity between complex 

 coacervates and protoplasm. 



The physico-chemical properties of complex and internally 

 complex coacervates (especially those having many com- 

 ponents) are very interesting from a biological point of view 

 as they are similar in many ways to those of protoplasm. 



This resemblance has been stressed over and over again 

 by Bungenberg de Jong,^' though conflicting opinions have 

 been expressed in the scientific literature. For example, A. 

 Frey-Wissling'"* insists that protoplasm is based on solid 

 structural elements. He writes as follows: "Thus an 

 extremely fine network is formed, a molecular framework. 

 The meshes of this framework contain the interstitial sub- 

 stances: a solution of salts in water and lipids including 

 phosphatides." This point of view finds less and less support 

 and even Frey-Wissling himself admits that the structure in 

 question is very labile and can easily be disturbed, when the 

 cytoplasm turns into a typical liquid.^'' 



Indeed, as early as 1926 L. V. Heilbrunn" became firmly 

 convinced, on the basis of his extensive investigation of the 

 viscosity of protoplasm, not only that it has no visible struc- 



