KIDNEY
Stone.
—Violle1 stated that of the three kinds of urinary stones, oxalatic, uretic and phosphatic, the phosphatic stones are by far the most common. The former two types are influenced by general metabolic conditions, but this is not always true of phosphatic lithiasis, since local conditions may of themselves suffice to produce it. Phosphatic lithiasis may complicate both the other types or may replace them. Then a slow and rather restrained lithogenic process may be transformed into a rapid and active one. Two conditions are necessary for such lithiasis: precipitation and the compaction of the substance precipitated. These processes occur at two different times.Precipitation is in great part a function of urinary reaction, and is chiefly a question of hydrogen ion concentration. For precipitation a certain amount of calcium diphosphate must be present, which cannot exist unless the ph rises above 6. When the urine is