CHAPTER 12 



Viscosity, Permeability, and Protoplasmic Streaming 



M. G. Stalfelt 

 University of Stockholm, Sweden 



Influence of visible light on viscosity of protoplasm. Influence of visible light on 

 permeability of cells: Indirect influences — Direct influences. Influence of visible light 

 on protoplasmic streaming. References. 



The effects of visible light on the viscosity, permeability, and stream- 

 ing of the protoplasm can presumably be interpreted as intermediate 

 links in a chain of reactions induced by light or as secondary effects of 

 such reactions. It is probable that this chain of reactions inchides 

 changes in the structure of the protoplasm. There are many indications 

 that this is the case. If this assumption is correct, it may be presumed 

 that the structural changes are the primary manifestations and that the 

 changes in viscosity, permeability, and streaming of the protoplasm are 

 secondary to them. This would, however, also imply that — as long as 

 the knowledge of the structure of the protoplasm is incomplete or hypo- 

 thetical — the most important premises are lacking for an analysis of the 

 relation between these secondary phenomena and the influence of light. 



INFLUENCE OF VISIBLE LIGHT ON VISCOSITY IN PROTOPLASM 



The degree of viscosity and its variations are determined by the compo- 

 sition and structure of the protoplasm and the variations occurring in it. 

 Our interpretation of the cause of viscosity and of its nature is mainly 

 based on the conception of the plasmatic structure. If the protoplasm is 

 envisaged only as a system of dissolved and dispersed substances, the 

 viscosity can be explained as a result of the friction between the parti- 

 cles in this system and as being of the same nature as the viscosity in 

 solutions and colloids in general. Staudinger (1935, 1947) classified the 

 colloids according to the shape of the particles into spherical colloids, 

 which are composed of spherical particles and whose viscosity is relatively 

 low, and thread colloids, consisting of elongated particles with a high 

 viscosity. In both categories the viscosity is dependent on the concen- 

 tration, temperature, degree of dispersion, solvation, electric charge, and 



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