1912] On the Distribution of Potassium in Renal Cells 399 



perhaps this would account for the very large amount of energy liberated 

 in the kidney during diuresis, as calculated from the oxygen consumption 

 of the organ by Barcroft and Brodie. 



The maintenance of this difference in the tensions of the free and 

 basal surfaces of the cell would not, however, be of much service in the 

 way of explaining the mode of action of the cell if the condensation of 

 the free (lumen) surface of the cell were not affected by another force. 

 In renal activity the glomeruli, it is believed, separate from the blood 

 plasma a fluid which is more or less free from salts and metabolites, and 

 this thin watery fluid passing down the lumina of the convoluted tubules, 

 sweeps over the free surfaces of the excreting renal cells in which the 

 surface condensation of potassium and other salts obtains. The mem- 

 brane of each cell at this point is extraordinarily thin and presumably 

 permeable to water, which, however, owing to the low tension in the cell 

 at the lumen surface, would not convey the salts there condensed into 

 the interior of the cell, and they, therefore, would diffuse only into the 

 lumen. The fluid in the latter would thus, as it passed down the tubule, 

 become more and more concentrated, and in this way the higher con- 

 centration of the urine in solutes, as compared, with the blood plasma and 

 lymph, would be accounted for. This removal of the potassium and 

 other compounds in the condensation layer would not cause the latter to 

 disappear, for so long as a difference exists in the tension on the basal and 

 free surfaces of the ceU, and so long as the latter is permeable to salts on 

 its basal border, the concentration of the adsorption layer in the cell at 

 its free border would be maintained. The condensation process would 

 thus parallel the extraction process so long as the cell is in activity. 



The difference in surface tension between the free and the basal 

 borders and the surface tension in the lymph on the external surface of 

 the excreting tubule would thus, of course, be subject to the metabolic 

 activity of the renal cells and to the composition of the lymph. Any- 

 thing that affects this metabolic activity, therefore, would affect surface 

 tension in the renal cells. The difference of surface tension between the 

 basal and free surfaces of the cells would thus be diminished or enhanced. 

 In the former case the elimination of salts would be lessened, in the 

 latter case it would be increased. On the other hand, a change in the 

 composition of the lymph must influence to a greater or less degree the 

 condensation on the surface of the tubules, and this would involve a 

 lessened or increased diffusion of the condensed salts into the renal 

 cells. 



Such alterations in the surface tension of the lumen border of the 

 cell and of its basal surface may be brought about by diuretics. This 

 would explain the results obtained in the dog's kidney under the influence 



