AND BLOOD PRESSURE 1V> 



venous flow increasing slightly, and the ureter flow decreasing 

 at first, and then increasing. On altering the arterial perfusion 

 pressure the venous flow and ureter flow, the volume of the kidney, 

 the maximal venous pressure and the maximal ureter pressure all 

 varied in the same sense, but the maximal venous and ureter 

 pressures were at a lower level than the injection pressure owing 

 to leakage through capsular collaterals. If the perfusion pressure 

 were made rhythmically intermittent the venous and ureter outflow 

 were increased. Obstruction of the renal vein caused swelling of 

 the kidney and almost complete cessation of the ureter flow. A 

 graduated increase in the venous pressure, produced by raising the 

 level of the venous outflow tube, diminished the venous and ureter 

 flow and expanded the kidney, especially when the pressure rose 

 above 40 to 60 mm. Hg. The venous and ureter outflow varied 

 with the molecular concentration of the perfusion fluid. Hyper- 

 tonic solutions caused lessened resistance in, and more flow from, 

 the tubules and vessels, and hypertonic solutions the opposite. 

 In volume a hypertonic solution produced at first a sharp fall, 

 followed by a rise to original level, while a hypotonic solution gave 

 a progressive diminution in renal volume. Many of these results 

 are difficult to explain, but none are in favour of filtration. Vernon 

 has shown that the fluid coming from the kidney under these 

 conditions does not correspond to that sent into the artery. The 

 kidney metabolism continues for days after death in a modified 

 form. At first we see the perfused fluid found its way through 

 the capillary-venous system, and only much more slowly made a 

 passage through the renal tubules. At the start the capillaries 

 were distended with the perfused fluid, the lumina of the capsules 

 almost obliterated ; the surface tension of the capillaries there- 

 fore was high, that of the capsules low. The surface energy of 

 the latter therefore was high. It may have been these conditions 

 which led to the transference of the fluid from one side to the other 

 of the wet film formed by the capillary and capsular epithelial 

 cells. We may suppose with justice that the epithelium retains 

 the corpuscles and the native colloidal material of the blood. We 

 know some colloids may pass. Sollmann found gum arabic, added 

 to the perfused fluid passed through, and egg albumen passes into 

 the urine of normal people if much be eaten. In the case of the 

 renal tubules at the time when the capillaries become distended 

 with fluid, the epithelium of the tubules contains stores of ex- 



