URINARY CALCULI. 787 



lo\vish-bro\vn or cinnamon-brown in color, of medium hardness, with amorphous 

 fracture, and on rubbing appear like wax. They burn up completely when heated 

 on a platinum foil. They give the xanthine reaction with nitric acid and alkali, 

 but this must not be mistaken for the murexid test. 



Urostealith calculi have been observed only a few times. In the moist state 

 they are soft and elastic at the temperature of the body, but in the dry state they 

 are brittle, with an amorphous fracture and waxy appearance. They burn with 

 a luminous flame when heated on platinum foil and generate an odor similar to 

 resin or shellac. Such a calculus, investigated by KRUKENBERG,* consisted of 

 paraffin derived from a paraffin bougie used as a sound on the patient. Perhaps 

 the urostealith calculi observed in other cases had a similar origin, although the 

 substances of which they consisted have not been closely studied. HORBACZEW- 

 SKI has recently analyzed a case of urostealith which, to all appearances, was 

 formed in the bladder. This calculus contained 25 p. m. water, 8 p. m. inorganic 

 bodies, 117 p. m. bodies insoluble in ether, and 850 p. m. organic bodies soluble 

 in ether, among which were 515 p. m. free fatty acids, 335 p. m. fat, and traces of 

 cholesterin. The fatty acids consisted of a mixture of stearic, palmitic, and 

 probably myristic acids. 



HORBACZEWSKI 2 has also analyzed a bladder stone which contained 958.7 

 p. m. cholesterin. 



Fibrin calculi sometimes occur. They consist of more or less changed fibrin- 

 coagulum. On burning they develop an odor of burnt horn. 



The chemical investigation of urinary calculi is of great practical impor- 

 tance. To make such an examination actually instructive it is necessary 

 to investigate y separately f the different layers which constitute the cal- 

 culus. For this purpose saw the calculus, previously wrapped in paper, 

 with a fine saw so that the nucleus becomes accessible. Then peel off the 

 different layers, or, if the stone is to be kept, scrape off enough of the 

 powder from each layer for examination. This powder is then tested by 

 heating on the platinum foil. It must not be forgotten that a calculus 

 is never entirely burnt up, and also that it is never so free from organic 

 matter that on heating it does not carbonize. Do not, therefore, lay too 

 great stress on a very insignificant unburnt residue or on a very small 

 amount of organic matter, but consider the calculus in the former case 

 as completely burnt and in the latter as unaffected. 



When the powder is in great part burnt up, but a significant quantity 

 of unburnt residue remains, then the powder in question contains as a 

 rule urates mixed with inorganic bodies. In such cases remove the urate 

 with boiling water and then test the filtrate for uric acid and the sus- 

 pected bases. The residue is then tested according to the following 

 scheme of HELLER, which is well adapted to the investigation of urinary 

 calculi. In regard to the more detailed examination the reader is referred 

 to special works on the subject. 



1 Chem. Untersuch. z. wissensch. Med., 2. Cited from Maly's Jahresber., 19, 422. 

 3 Zeitschr. f. physiol. Chem., 18. 



