THE SITE OF ACIDIFICATION OF URINE IN THE FROG'S AND RAT'S KIDNEY

¹ Lister Institute, London

1. A method has been described by which objective records can be obtained of the pH present in cells and body fluids of living organs by taking colour photomicrographs of the fluorescence of fluorescein injected into the animals.

2. By means of this method it has been demonstrated that in the kidneys of frogs and rats the urine eliminated into the glomerular capsules is of the same acidity as the blood plasma. This preliminary urine is acidified exclusively in the distal tubules if the ultimate acidification is moderate, but in both proximal and distal tubules if the acidification of the bladder urine reaches a higher degree.

3. The mechanism of this acidification is discussed, and it is suggested that the acidification is caused probably by absorption of alkali in both sets of convoluted tubules from the content of the lumen.

I wish to express my thanks to the Lister Institute for hospitality and for a grant enabling the reproduction of the colour photomicrographs, to the Society for the Protection of Science and Learning for a Research Fellowship, and to the Ella Sachs Plotz Foundation for a grant for technical assistance. I am very much indebted to Professor R. Robison for his assistance in the preparation of the manuscript.