CHAPTER X 



NEGATIVE OSMOSE AND THE POLARIZATION OF 

 MEMBRANES IN RELATION TO THE BIO- 

 ELECTRIC PHENOMENA, STIMULATION, 

 ABSORPTION AND SECRETION 



Owing to the wide hiatus yet remaining in our knowledge of 

 this subject, we need especially to guard against definitive state- 

 ments. It seems best to attempt to explain the unknown in 

 terms of the known, or at least to admit the possibility that the 

 unknown is similar to the known and the invisible of the same 

 structure as the visible. 



Of the various conceptions of osmotic membranes, two seem 

 to stand out prominently. The first is that the membrane is a 

 molecule sieve. The fact that the osmotic properties of porcelain 

 membranes increase as the pores become finer, tends to support 

 this view. On this hypothesis, the electric phenomena associated 

 with membranes become capillary electric phenomena. The sec- 

 ond conception is that an osmotic membrane is a separate phase 

 that will dissolve some of the constituents of the fluids bathing 

 it. The electric phenomena associated with such membranes are 

 called phase boundary forces by Nernst and Riesenfeld. Since 

 there must be spaces between the molecules of the membrane, 

 this phase becomes a sieve and the difference between the two 

 conceptions seems to be more quantitative than qualitative. It 

 may be asserted that from the first viewpoint we are concerned 

 with the size of pores and molecules, and with adsorption and 

 contact electricity, whereas from the second viewpoint we are 

 concerned with solution, partition coefficient, association and 

 dissociation. But owing to the state of our knowledge of the 

 forces concerned in these phenomena, it is difficult to compare 

 them. Presumably all forces are electric. The dielectric con- 

 stant of the phase membrane determines its ionizing power and 

 hence its permeability to ions, but the dielectric constant of the 



