RENAL CALCULI 465 



tions particularly with diseases of metabolism, with gout, obesity and 

 diabetes mellitus. But all recent observations have shown that neither in 

 gout nor in all of the diseases that manifest a disturbance, of purin metab- 

 olism is there an excess of oxalic acid beyond the normal in the urine. 

 The numerous observations of a normal oxalic acid content with increased 

 uric acid output (leucemia, after pneumonia) also speak for a complete 

 independence of oxalic acid formation and nucleoprotein metabolism as 

 do the data obtained in diabetes and in obesity. The reaction of the 

 urine has no influence on the solubility and precipitation. Sediments from 

 strongly acid urine containing both uric acid and calcium oxalate are 

 known to all. On the other hand, alkaline urines with a phosphate sedi- 

 ment are frequently free from oxalate crystals. Therefore, the solubility 

 is not measurably increased by an acid nor diminished by an alkaline 

 reaction. 



Every urine is supersaturated in relation to its content of calcium oxa- 

 late, and the colloidal state of the urine determines the solubility of the 

 oxalate. 



Uraturia and Uric Acid Calculi 



By uraturia we mean the precipitation of uric acid or its acid sodium 

 salt or acid ammonium urate. These occur most frequently in acid, con- 

 centrated urine. The precipitation of ammonium urate is found only 

 with a urine of high ammonium content. 



It may be taken as certain that uric acid up to a vanishing fraction 

 circulates in blood as urate ions, since the hydrogen ion concentration of 

 the blood is not sufficient to build undissociated uric acid. 



In the secretion of acid urine the urate ion joins the hydrogen ion in 

 the kidney cell to form undissociated uric acid. In acid urine the greater 

 part of the uric acid is present in an undissociated form, a. part as urate 

 ions. Through this transition from the urate of the blood into the undis- 

 sociated uric acid of the urine, uric acid like phosphate effects an elimina- 

 tion of H ions and a sparing of alkali. 



Acid urine represents a highly supersaturated solution. Magnus-Levy 

 observed a urine that contained a gram of uric acid dissolved in 39.4 liters ; 

 according to Gudzent, at 37 it is dissolved in 25 liters of water. If the 

 water be acidified to the degree of urine the solubility becomes less and uric 

 acid precipitates. The urine behaves differently. It is but seldom that 

 acidifying causes an abundant precipitate of uric acid. Most urines, even 

 when concentrated, remain clear or only after hours crystallize out a small 

 part of the uric acid. 



Acid sodium urate has a far higher solubility than the uric acid. 

 Gudzent has shown that both isomers form the urate ; the unstable lactam 

 form 



