URINARY CALCULI. 835 



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. 



