1912] On the Distribution of Potassium in Renal Cells 403 



observations already referred to, it would appear that some solutes in 

 such systems undergo condensations differing in concentration for each 

 solute, and potassium from its chloride condenses more than silver does 

 from its nitrate. The relation of potassium to sodium in this respect 

 was not investigated, but one may suspect there is a difference, perhaps 

 an important one. This might account for the contrast between the 

 sodium, which is 0.3175 per cent, in the serum and 0.1783 per cent, in 

 the kidney, on the one hand, and on the other, the potassium, which is 

 0.0217 per cent, in the serum and 0.2356 per cent, in the kidney. The 

 sodium is thus decreased 44 per cent., while the potassium is increased 

 over 1000 per cent. Such a difference, as suggested, in the degree of 

 condensation would furnish an explanation for the difference in the 

 quantities of sodium and potassium in the plasma or serum which are 

 in the proportion approximately of 15 to i. 



Summary. 



1. The sodium cobalt hexanitrite reagent (CoNa3(N02)+enH20), 

 as prepared by Professor Macallum, is a suitable reagent for the localiza- 

 tion of potassium in kidney tissue. 



2. It is essential that the tissue be frozen while perfectly fresh and 

 that the sections prepared from it be kept frozen until they come in 

 contact with the reagent. 



3. There is a definite localization of potassium on the external 

 surface of the convoluted tubules and frequently about their lumina 

 as well. 



4. The uniformity of this localization about the tubules tends to 

 increase in direct proportion to the state of activity of the kidney. 



5. In the resting condition or during ordinary activity the only 

 potassium demonstrable in the cytoplasm of the cells of the convoluted 

 tubules is condensed in a layer immediately adjacent to the lumen 

 border in each cell. 



6. This localization appears to be in accordance with surface tension 

 phenomena. 



7. The presence of potassium in the lumina of the tubules and 

 absence of potassium in the glomerular cavity is evidence that the 

 inorganic sales are excreted by the tubule cells. 



8. No evidence bearing on the manner in which the glomeruli 

 perform their function was obtained. 



9. In no instance was any potassium found in a cell nucleus. 



