URINARY CALCULI 385 



The fatty acids consisted of stearic, palmitic, and probably 

 myristic acid. 



Cholesterin calculi have been found in the urinary 

 bladder in a few instances, the cause being unknown. Horbac- 

 zewski l describes one weighing 25.4 grams, found in a patient 

 who had previously had cystin calculi ; it contained 95.87 per 

 cent, of cholesterin and but 0.55 per cent, of inorganic material. 

 Gall stones have been known to enter the urinary bladder 

 through a fistula between the gall-bladder and urinary bladder. 2 



Fibrin " calculi," formed from blood-clots, often more or 

 less impregnated, with urinary salts, have occasionally been 

 observed. 3 



General Properties of Urinary Concretions. The 

 hardness depends upon the chemical composition of the 

 calculus. Those composed of amorphous phosphates are the 

 softest ; next come those with some admixture of crystalline 

 phosphates. Urate concretions are harder than these, but are 

 still softer than the uric acid and crystalline phosphate calculi. 

 Oxalates are the hardest, except for the rare crystallized calcium 

 carbonate stones. Cystin and amorphous concretions can be 

 scratched with the finger-nail, while even the hardest varieties 

 of calculi can be scratched with a wire nail. Genersich 4 gives 

 the following degrees of hardness for different calculi : Choles- 

 terin, 1.5-1.6; ammonium urate, 2.5 ; soft phosphate (Mg), 

 2.6 ; hard phosphate (Ca), 2.75 ; uric-acid stones (also salivary 

 and prostatic calculi, atheromatous patches, and phleboliths, 

 2.9 ; calcium oxalate (also rhinoliths and lung stones), 3.33.5 ; 

 calcium carbonate stones of herbivora, 4.5. 



The rate of growth also varies according to composition, 

 but is, of course, much modified by other factors. Oxalate and 

 urate stones grow most slowly, phosphate stones most rapidly. 

 A urate stone has been known to increase by about two ounces 

 during seven and one half years, while a catheter fragment or 

 other foreign body may become covered with a crust several 

 millimeters thick in a few weeks. 5 



Spontaneous disintegration of urinary concretions is limited 

 almost solely to calculi composed entirely or largely of uric 



1 Loc. cit. 



2 See Finsterer, Deut. Zeit. klin. Chir., 1906 (80), 426. 



3 Systems for procedure in determining the nature of urinary calculi are 

 given by Hammarsten (Text-book of Physiol. Chern.) and by Smith (Kefer- 

 ence Handbook of Med. Sci., 1901 (3), 236). 



4 Virchow's Arch., 1893 (131), 185. 



5 Zuckerkandl, Nothnagel's System, vol. 19, pt. 2, p. 229. 



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