146 INTRINSIC ACTIVITY OF SECRETING CELLS 



between plasma and cell protoplasm, as has been assumed by 

 Overton. Further, it has never been shown that this hypothetical 

 membrane possesses for different ions and crystalloids the per- 

 meabilities and impermeabilities ascribed to it. 



In order to attempt to test the Overton theory with regard 

 to salt solutions, the writer has prepared a lecithin membrane 

 by thoroughly impregnating a membrane of parchment paper 

 with lecithin, so that the pores of the paper were thoroughly soaked 

 with the lecithin, and there was a continuous layer of lecithin 

 on both sides of the paper, and using this as a membrane between 

 sodium chloride solution and water, or between two sodium chloride 

 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 

 solutions of different strength 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 that the argu- 

 ments 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, 



