In a recent study of the literature on the etiology of urinary lithiasis and closely related subjects, the conclusions reached after careful analysis may be summarized briefly, thus:
The problem of calculus formation in the urinary tract is one of chemical precipitation. The mechanism which causes the precipitation of urates, oxalates, phosphates, and so forth, in such a way that a fused hard concretion arises, rather than the deposition of individual crystals which maintain a state of isolation in passing through the urinary tract must be determined.
Differences in reaction, as determined by the hydrogen ion concentration, and qualitative and quantitative changes in the urinary colloids (such as pigments, mucin, nebecula, albumin, and nucleo-albumin), have been shown to influence the nature of urinary sediments both chemically and physically. The microscopic and gross features of calculi would seem to show that an abnormal variation of these factors is at