The idea that the urine is distinctly poisonous is not a new one. For a long time it has been known that it contained poisons castoff from the system, that toxic symptoms ensued if it was consumed by man in lieu of pure water, and that death followed if the kidneys failed to do their work, if both kidneys were removed, or if the ureters were obstructed. It has, however, remained for modern investigation to determine the nature of these toxic agents, the amounts in which they are harmful, and the causes which co-operate to retain them in the system. Although the kidney is very tolerant and permits surgical interference, it is subject to acute and chronic inflammations which cause those changes of structure which occasion auto-intoxication from non-excretion of the urine. Renal insufficiency comprises all those conditions in which the kidneys are for any reason unable to properly perform their work, the most common of these being loss of functionally active mass through the lesions of nephritis. The poisons of the body are not eliminated, they remain in the circulation and accumulate until present in sufficient concentration to produce the well known symptoms of uremia. The preponderance of experimental evidence shows that the toxemia is mixed, not the result of any single urinary component, but the sum total of all of them. When it is shown that nephritis may be autogenous in its genesis, it becomes evident that a curculus viciosus is formed, they causing nephritis, and this in turn an intoxication from faulty elimination.