Methods for the Collection of Fluid from Single Glomeruli and Tubules of the Mammalian Kidney1

In 1921 Wearn and Richards (1) demonstrated the possibility of collecting fluid from single glomerular capsules in the living frog’s kidney. In the 20 years which have succeeded this demonstration, methods have been gradually developed for the collection of fluid from single tubules of the amphibian kidney and for the quantitative analysis of the minute amounts of fluid obtained. The body of evidence accumulated by the application of these techniques has lent clear and decisive support to the filtrationreabsorption theory of urine formation (2). Glomerular fluid has been shown to have the composition of an ultrafiltrate of blood plasma in the eleven respects in which it has been examined. Reducing substances, chlorides and fluid have been shown to be reabsorbed from this filtrate as it passes through the tubules, and the locus of these reabsorptive processes has been established. The extension of this type of experimentation from the amphibian to the mammalian kidney has seemed desirable, not alone because the truth of the filtration-reabsorption theory could again be subjected to thorough examination, but also because the functional and anatomical differences between kidneys of the two types made it certain that new information would be disclosed. Progress has been made in this extension and the present paper describes methods which have proven successful in collecting fluid from single glomeruli and tubules of the mammalian kidney. Preparation for visualization of the kidney surface. A majority of the experiments have been performed on guinea pigs and rats. In both species, a unilateral (right) nephrectomy was done from 5 to 43 days before the experiment in order to produce enlargement of the nephrons in the remaining kidney. This operation was performed on 89 guinea pigs and 56