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In approximately 92 per cent of all primary urinary calculi, more than 95 per cent of the total cation content is composed of calcium (1-3). Concepts concerning the mechanism of biologic calcification have undergone a marked revision in recent years (4). Rubin and Howard (5) have presented histochemical evidence that an acid mucopolysaccharide of cartilage and bone matrix may act as a "target substance" for the deposition of calcium and the eventual formation of bone salts. The structure of urinary concretions suggests that the initial matrix may be composed of ion-binding mucopolysaccharides or other "substrates," which not only provide the architectonic framework but may actually -"extract" specific inorganic components of urine from solution. The separation and identification of the organic components of urine are essential prerequisites to an exploration of this possibility.A series of experiments, in which some subjects have been repeatedly examined over a period of two years, has demonstrated that the biocolloids of urine may be separated into three groups of substances, on the basis of their solubilities in different buffer systems. It is the purpose of this report to present the results of studies on one of these groups-those components which are soluble in molar sodium chloride and in two buffers which have been used in the electrophoretic study of serum proteins (6-8). METHODSThree female and 10 adult male subjects from the staff of the North Carolina Baptist Hospital and the Bowman 1 This investigation was supported by research grant A-259 from the National Institute of Arthritis and Metabolic Diseases, of the National Institutes of Health, Public Health Service.Gray School of Medicine were selected as a control group; all were known to have normal renal function. The test group was made up of 17 patients (7 females and 10 males) selected over a period of 20 months because they were demonstrated roentgenographically to have progressively developing calculi. Later analysis of these stones showed them to contain pure calcium phosphate or a mixture of calcium phosphate and calcium oxalate. These patients were studied prior to operation, and no individual with signs or symptoms of acute infection was included. In addition, two patients, ages 7 and 11 years, with the nephrotic syndrome and two patients, ages 16 and 18 years, with lupus erythematosus were studied as examples of altered capillary permeability. Four additional patients with bilateral obstructive urinary tract disease and bacterial pyelonephritis were studied before operation, but after the signs of pyelonephritis had subsided.Clean voided specimens of urine were collected into chemically clean containers without preservatives, and immediately refrigerated at 0°C. Hospitalized subjects were provided with bedside ice chests to insure prompt refrigeration. Each 24-hour specimen was centrifuged at 800 times gravity to remove formed elements, and then dialyzed against distilled water at 3°C. until the electrical conductivity approached 100 X 10' a...

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