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A COLLOIDAL HYPOTHESIS OF PROTOPLASMICWl -^,^ 



PERMEABILITY VSpSv •. . ^y^J 



E. E. FREE ^*'^2L5_i3^ 



United States Army 



It is generally agreed that protoplasm is of colloidal nature 

 and that the phenomena of permeability are connected with 

 alterations of some kind in the colloidal state of the surface layer 

 of the cell. During 1916 two investigators have published 

 hypotheses concerning the mechanism by which these changes are 

 brought about. Spaeth^ assumes changes in the degree of dis- 

 persion of the colloids of the surface film. Clowes^ postulates 

 phase inversions by which, for instance, an emulsoid consisting 

 of non-aqueous globules suspended in an aqueous medium, be- 

 comes one of the aqueous globules in a non-aqueous medium, the 

 internal phase becoming the external and vice versa. I shall 

 return later to the critical examination of these hypotheses. 

 First, I shall outline a third hypothesis as to the mechanism of 

 the changes, which hypothesis it is the purpose of this paper to 

 present. This hypothesis occurred independently to Prof. F. E. 

 Lloyd and me in 1914. It has been noted briefly in a publication 

 by Lloyd.^ 



The most important facts which must be explained by any 

 theory of protoplasmic permeability are those of change of 

 permeability. Not only are there marked differences between 

 different masses of protoplasm, but the same cell may change 

 in permeability either in response to alteration of external con- 

 ditions or as the result of internal changes which may be, and fre- 

 quently are, functional and normal. As examples of changes due 



1 Science 43: 502-509 (1916). 



" Science 43: 750-757 (1916); Jour, of Physical Chemistry 20: 407-450 (1916). 

 ' Rept. Dept. Botanical Research, Carnegie Inst, of Wash. Year Book, 14: 68 

 (1915). 



141 



THE PLANT WORLD, VOL. 21, NO. 6 

 JUNE, 1918 



