214 



ELECTROLYTES IN BIOLOGICAL SYSTEMS 



experiments, slowed the rate of active salt uptake down to about one third of 

 the normal value (24). The data at hand are, as yet, not extensive enough for 

 the calculation of Qw. It would seem, however, that it is not far off from 2. 



The kind of anion present in solutions of sodium salt is irrelevant with respect 

 to active salt uptake with one notable exception, namely, iodide ion (27). It 

 has been found that the addition of equivalent amounts, with reference to 

 sodium, of NaCl, NaBr, NaNOs, Na2S04 and Na2HP04 to a saline solution of 

 a given NaCl concentration leads to the same percentage increase — about 20% 



60- 



— •Ringer's solution, NoCN free 



X X Ringer's solution containing 



NoCN (0001 per Ml.) 



.^"e\ 



X— «x— bag weight ^ 



3 "-«.y'' 



^^ 3 



relative concentrotion of Ringer's sol. 



0.4 0.6 0.8 1.0 



/ 



1.5 



bag weight 



2 

 3 



^/ 



Fig. 6. Upper two graphs: concentration gradients across the skin as found at the end of 

 12 hour experiments using 'inside-out' skin bags. Lower two graphs: changes in weights of 

 the filled bags. All bags were filled with 5 ml of normal Ringer's and immersed in 2.5 1. of 

 normal Ringer's. Rana pipiens. Numbers at the graphs indicate number of experiments from 

 which the plotted average values were obtained (24). Clo is the 'outside' chloride concentra- 

 tion, Cli that of the inside. 



— of net salt uptake. If, however, an equivalent amount of Nal is added to the 

 saline solution, then net salt transport is decreased by about 15%. In general, 

 the conditions under which these experiments were carried out were such that 

 the named salts were added to a 0.4 Ringer's solution in quantities that would 

 yield a final solution equivalent to 0.6 Ringer's with respect to its sodium 

 content. This solution represented the outside bath. The inside bath was un- 

 supplemented 0.4 Ringer's solution. It has been found, furthermore, that Br~, 

 NOs"" and I~ partly replace Cl~ in active salt uptake. It was assumed that Br~, 

 NO:r and I~ enter into competition with Cl~ for transport. Whereas, in the case 



