In the past the injection of dye substances into the circulation of living animals has yielded much information about the functions of certain regions of the kidney (1-7). Recently Rous (8-11) has reported studies of the relative reaction of living cells carried out by the use of various indicator dyes. Some of his methods are well adapted to a study of the reaction within kidney cells and he has observed that litmus when segregated within the renal epithelium is in some places red, in others blue, a fact suggestive of marked functional differences. In the work here to be reported this observation has been followed up and we shall record certain changes in the reaction within cells lining the renal tubules of mammals, which changes accompany and are largely, if not entirely conditioned by alterations in the functional activities of these cells.
Previous Literature.The older literature on vital staining of the kidney has been reviewed by Cushny (12) and recently by Marshall and Crane (13). The elimination of dye substances by the glomerufi has been demonstrated by and by Bieter and Hirschfelder (17). Workers are at one concerning it, but there has been much difference of opinion as to the significance of the presence of dye substances within the tubule cells. Heidenhain (1) took their presence to indicate a removal of the dye by these cells out of the blood and into the urine, a secretory activity in other words; but many more recent workers have looked upon it (6,12) as a result of absorption from the tubule lumen. Recently Marshall and Vickers (18) and Marshall and Crane (13) have reported studies of the excretion of phenol red which they take to indicate a direct secretion of the dye by the tubular epithelium. 797 on