1. Five methods for the production of slow continued reabsorbtion of urine in the experimental animal are presented.
2. The effects of this prolonged reabsorption of urinary constituents on the blood chemistry and tissues are shown with special reference to the kidney.
3. Large and rapid increase of urinary constituents in the body is definitely destructive to the kidney.
4. The degenerative changes found in the experimental animal in the protected pole of the kidney showing nephritis produced by x-ray and in man in the unscarred portions of the kidney showing chronic nephritis account for the progressive nature and final renal insufficiency of these conditions and are best ascribed to the high levels of excretory products in the body.