PROPERTIES OF PROTOPLASMIC MEiMBR^VNES 147 



with the opposite faces of the partition, and (2) the 

 potential-difference between the solid or c()lloi(hd 

 material composing the partition and the Huid occu])ying 

 its interstices or pores.' The influence of these electrical 

 factors is shown with especial clearness in the phenomena 

 of electrical endosmose, and in the related phenomenon of 

 negative or anomalous osmosis. In both phenomena an 

 electrified layer of fluid (occupying the pores of the 

 partition, hence in contact with the surface of the 

 structural material) is situated within the electrical 

 field between the two surfaces of the partition; the 

 fluid is accordingly transported across the partition by 

 electrostatic attraction in one or the other direction, so 

 long as the electric conditions remain unchanged. The 

 work involved in the transport is electrical; in negative 

 osmosis the electrical field is maintained by the unequal 

 diffusion-rates of the ions of the solution bathing the 

 partition; in electrical endosmose by the external 

 current traversing the partition. 



It will be evident that under these conditions the 

 permeability of the . partition to electrified material, 

 whether water, colloidal particles, or ions, will be different 

 in the two directions. Water, for example, will diffuse 

 outward in an osmometer, i.e., from the more to the less 

 concentrated solution, when the electrical diffusion field 

 is oriented in such a way that the charged layer of fluid 

 in the pores is attracted outwardly with sufticient force 

 to overcompensate the purely osmotic effect. 'Hiis 

 condition is met when a stronger solution of IICl is 



' Girard, CompLrend., CXLVI (1908), 927; CXLVllI (1909), 1047; 

 /. de Physiol, et de Path, gen., XII (1910), 471; /. dc Chitn. d dc Phys. 

 XVII (1910), 383. 



