252 INTRINSIC ACTIVITY OF SECRETING CELLS 



solutions of different strengths, so as to avoid action of the water 

 upon the lecithin. 



According to Overton's view, the lecithin membrane, like the 

 cell, ought to be impermeable to the sodium chloride, and in solu- 

 tions of different strengths an osmotic pressure effect ought to have 

 been obtainable with such a membrane. 



It was found, however, when the membrane was used in an 

 osmometer (1) that no osmotic pressure whatever developed on 

 the sodium chloride solution side, or on the side of the stronger 

 solution, and (2) that sodium chloride did pass through the 

 membrane. 



Accordingly, the presence of a lecithin membrane, even were 

 such shown experimentally to exist, would not explain the osmotic 

 phenomena of the cell or the impermeability of the cell for the 

 sodium ion. 



Taking next the membrane hypothesis from the theoretical 

 point of view, the following arguments may be urged, which apply 

 not only to the lipoid membrane but to any other conceivable 

 membrane by which an attempt may be made to explain upon such 

 a passive basis the active work of the cell in maintaining a different 

 composition and concentration of the crystalloids and ions within 

 it to that which obtains in the medium in which the cell lives. It 

 is on account of this general applicability against an explanation 

 by any passive membrane theory and not merely against the 

 lipoidal membrane theory that the arguments are here given at 

 length. 



Take, first of all, the position that the cells are entirely im- 

 permeable to certain ions (and to other non-dissociated organic 

 crystalloids), and that it is on account of such perfect impermea- 

 bility that these are found only within or only without the cell, 

 or in such very different and fixed concentrations within and 

 without the cell. For example, that potassium salts are found 

 in the cell in excess, and sodium salts in the plasma in excess, and 

 that this is due to a membrane refusing passage entirely to sodium 

 and potassium ions. This then excludes all exchange of such 

 ions between cells and plasma, and there is neither any explana- 

 tion on such a basis of how the present state of affairs with such 

 an unequal distribution of potassium and sodium ions occurred 

 in the first instance when the cells were formed and growing; nor 

 any explanation of how more potassium ion is taken in and sodium 



