These are remedies employed for the purpose of preventing the solids of the urine from being deposited, or of causing resolution.

One of the most important is the abundant use of water, and sometimes it is advisable to use distilled water in place of ordinary water, as distilled water is free from salts of any kind. Distilled water has a disagreeable, flat taste, but it may be made quite agreeable by charging it with carbonic acid in a gasogen.

The substances which most generally are deposited from the urine are uric acid, acid urates, oxalate of calcium, and phosphates; the two former are liable to be deposited when the urine is too acid, and the two latter when it is alkaline or neutral. Oxalate of lime also may be deposited from faintly acid urine. These substances may be deposited either in the kidney or bladder, and thus give rise to renal or vesical calculi.

The lithontriptics generally employed when uric acid, or acid urates are present, are salts of lithium and potassium, as the urate of potassium is more soluble than the urate of sodium, and the urate of lithium more soluble than even that of potas-isum. On account of the low atomic weight of lithium its salts have the further advantage of combining with a much larger relative proportion of uric acid than the salts of potassium or sodium. When phosphates are present, mineral acids, such as phosphoric, are sometimes employed, but it is difficult to render the urine acid by the internal administration of mineral acids, although it is easy to render it alkaline by the administration of alkalies. Benzoic and cinnamic acids, however, in passing through the body, are converted into hippuric acid, and they render the urine acid. They may either be given alone, or in combination with ammonia, as benzoate of ammonium, because, although ammonium is alkaline, yet it appears to undergo conversion into urea in the body, and does not render the urine alkaline.

The deposition of oxalate of calcium is usually connected with disturbances in the digestive system, and I have observed, in a hospital ward, that a deposit of it is very commonly found in the urine after the patients have had cabbage for dinner. The administration of nitro-hydrochloric acid frequently tends to prevent the deposition of oxalates, and this is, perhaps, on the whole, the best remedy for the form of dyspepsia to which the name of oxalic diathesis is sometimes given. Sometimes, however, carbonate of sodium, by aiding the digestion, seems to be more beneficial.