. American journal of physiology. ns were tested by freezing point determina-tions. Their strength is ap-proximately: Urea, 1,89 percent; alcohol, per cent;dextrose, percent; canesugar, per cent.) 1. Urea. — The isosmoticurea solution was circulatedin six experiments ; the effectswere the same in all, and con-sisted in a prompt and exten-sive fall of the vein and ureter flow and of the oncometer (Fig. i).The results are also obtained in kidneys which were excised on thepreceding day. The effect on the vein flow is removed completely by sodiumchloride, sodium sulphate, or magnes
. American journal of physiology. ns were tested by freezing point determina-tions. Their strength is ap-proximately: Urea, 1,89 percent; alcohol, per cent;dextrose, percent; canesugar, per cent.) 1. Urea. — The isosmoticurea solution was circulatedin six experiments ; the effectswere the same in all, and con-sisted in a prompt and exten-sive fall of the vein and ureter flow and of the oncometer (Fig. i).The results are also obtained in kidneys which were excised on thepreceding day. The effect on the vein flow is removed completely by sodiumchloride, sodium sulphate, or magnesium chloride; the effect on theureter flow persists after sodium chloride or sulphate, but is promptlyremoved by magnesium chloride. The same phenomena (in a lesser degree) occur when the solutionof urea is mixed with solution of sodium chloride (i part, urea; 3parts, isotonic sodium chloride). The phenomena do not occur if urea in substance is added to thesodium chloride solution (as much urea as would make a half isotonic 286. Figure 1. — Isotonic urea (E.\periment 56). ^—^ denotes the vein flow; , the ureter flow. Perfusion Experime7its on Excised Kidneys. 287 solution if added to water); if anything, there is a trifling increase ofvein and ureter flow. The action of the urea on the vein and ureter flow correspondswith the effects of very hypoisotonic solutions. In other words, theurea must penetrate the renal cells in the same way as it penetratesthe blood corpuscles. The absence of the specific effects of urea,when it is added in substance to isotonic salt solution, also provesclearly that its actions are in the main based on osmotic changes;the slight increase in the latter experiment shows that the perme-ability of the renal cells to urea is not absolute. 2. Alcohol. — The effects of an isotonic solution are shown in Experi-ment 94: Exp. Perfusion with Time. Veinflow. Ureterflow. Oncometer. 94 NaCl .... I. M. 200 36 cm. 22 6 1. M. 200 34 V. M.
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