JACQUES LOEB 473 



ished by the oppositely charged ion with a force increasing with the 

 valency of the ion; and second, that the relative effect of the oppositely 

 charged ions is not the same at different concentrations, but that at 

 low concentrations the augmenting effect of the ion with the same 

 sign of charge as the membrane increases more rapidly than the de- 

 pressing effect of the oppositely charged ion, while at high concentra- 

 tions the reverse is true. The augmenting effect of the ion with the 

 same sign of charge as that of the membrane on the transport of liquid 

 is due chiefly, if not exclusively, to the effect of the salt on the p.d. 

 across the membrane (£), which depends upon that ion which gives 

 the salt solution the opposite charge from that of the liquid inside 

 the pores. This ion is in this case the cation and hence the trans- 

 port increases with the valency of the cation (Tables I and II). 

 The depressing effect of the oppositely charged ion on the trans- 

 port of liquid is due to the effect on e. If e is determined by the 

 Donnan equilibrium between the solid gelatin salt and the bounding 

 solution, it must, according to the theory, be depressed by that ion 

 which has the opposite sign of charge as the protein ion.^ The 

 oppositely charged ions of a salt act, therefore, each on a different 

 type of P.D., the one on diffusion potentials, the other on a p.d. due 

 to an equilibrium condition. 



There are three discrepancies between the curves in Figs. 1 and 2 

 which need further explanation. First, the location of the maximum 

 of the curves in Figs. 1 and 2 is not identical, being located at m/32 

 in Fig. 1 and at m/256 or m/512 in Fig. 2. This may be partly or 

 entirely due to the fact that the concentration of the liquid was lower 

 inside the pores than in the salt solution since water was flowing 

 constantly from the side of water into the solution, thus causing a 

 considerable dilution inside the pores. 



Second, the curves in Fig. 1 do not come down to zero while those 

 in Fig. 2 come down to nearly zero at a nominal concentration of 

 m/8. For this we may have two reasons, first, that when the concen- 

 tration exceeds m/4 the transport due to osmotic forces becomes so 

 great that a drop of the transport curves to zero is no longer possible; 

 or it may mean that after the concentration exceeds m/4 a new source 

 of electrification of the gelatin inside the pores not accounted for by 

 the ionization of the protein commences. We shall return to this 



