RENAL CALCULI 4G7 







the gold count was the same before and after boiling, i.e., the colloid which 

 those urines contained was in an irreversible precipitation state. Such 

 urines may be without defense action for colloidal gold solutions. Licht- 

 witz observed a patient who passed urine four weeks without a gold count 

 with abundant uric acid sediment ; only on one day was the urine clear and 

 acted protectively on the gold solution. 



These observations show with complete clearness the dependence of 

 the solubility of uric acid and the uric acid salts upon the colloid state of 

 the solution. 



The concentration is of subsidiary importance for the precipitation of 

 uric acid and its acid sodium salts. Precipitation occurs with quite nor- 

 mal amounts and abnormal amounts remain in solution. That other con- 

 ditions being the same, a sediment occurs more readily in concentrated 

 urine is obvious. 



The reaction is of significance only in so far that only in acid 

 urines a sediment occurs. If occasionally there is a neutral reac- 

 tion in a urine, that is caused by the fact that in the crystallization pro- 

 cess hydrogen ions have left the solution and thereby reduced its acidity. 

 At any rate in very strong acid reactions ( (H) 1.10~ 5 ) the uric acid may 

 remain dissolved. The dominant factor for the solubility is the state of 

 the urine colloids. 



Since the processes of sediment formation do not depend on the uric 

 acid itself the characterization of the sediment formation as "uric acid 

 diatheses" is quite unjustified as Brugsch and Schittenhelm have so explic- 

 itly set forth. The formation of uric acid sand and its consequences, the 

 formation of uric acid stone, the urate stone diatheses should be clearly 

 distinguished from the uricemic diatheses, the gout. This distinction is 

 not always made, because gout and uric acid stone often enough occur in 

 the same subject. This combination Sydenham observed on himself 150 

 years before the discovery of uric acid. The great majority of cases of 

 urate stone diatheses occur, however, without gout. Brugsch and Schit- 

 tenhelm remark that whereas in childhood gout is extremely rare, uric 

 acid stone is most frequent. The cases in which gout and urate stone 

 combine may be explained as follows : the gout causes deposits of acid 

 uric acid sodium in the kidney, which come to the surface and there form 

 a stone nucleus. 



Xanthin Calculi 



Xanthin or 2.6-dioxypurin, C 5 H 4 O 2 N 4 was first discovered in a 

 urinary calculus weighing eight grains by Marcet in 1817. There are sev- 

 eral cases on record where it has been found in the urine as a sediment. 

 Maclagan found xanthin crystals in the urine of a supposed hysterical girl ; 

 Jackson, in a case of diabetes mellitus ; Bence-Jones in the urine of a boy ; 



