Treatment of Cahulons Disorders. 207 



«pon the surface, and their fracture was somevvliat foliated. It is 

 also comparatively rare in its pure state, as an incrustation : I 

 have seen it upon an uric nucleus, in a very large calculus, in 

 the possession of Mr. Thomas. 



The fusible calculus is always more friable than the triple ; 

 it is generally white, and often much resembles chalk in texture 

 and appearance ; it often breaks into layers, and exhibits a 

 glittering appearance when broken, in consequence of the 

 crystals of triple phosphate that have formed in its inter- 

 stices. 



The analysis of fusible calculus is perhaps best performed by 

 distilled vinegar, which, when gently heated, dissolves the 

 ammonio-magnesian phosphate, but not the phosphate of lime, 

 which may be taken up by muriatic acid ; and if any uric acid 

 were present it remains as the ultimate residuum, and may 

 be recognised by solubility in caustic potassa, Sfc. (page 67) 

 Or the uric acid may, in the first instance, be separated by 

 solution of caustic potassa, which also expels the ammonia, 

 but has no action on the other ingredients of the calculus. 



Calculi, or layers of calculi, composed entirely of phosphate 

 of lime, were first described by Dr. Wollaston under the name 

 of bone-earth calculi; their surface is generally pale brown, 

 smooth, and, when sawed through, they are found of a lami- 

 nated texture, and separate easily into concentric crusts. Dr. 

 Wollaston also notices an appearance which I have often re- 

 marked, that of each lamina being striated in a direction per- 

 pendicular to the surface, as from an assemblage of crystalline 

 fibres. This calculus is of very difficult fusion. It is soluble 

 in muriatic acid, and ammonia precipitates phosphate of lime 

 from this solution. 



The aspect and chemical characters of the uric calculus have 

 already been adverted to. Their texture when formed in the 

 bladder is gene, ally laminated ; and when cut into halves, a dis- 

 tinct nucleus of uric acid is almost always perceptible. Their 

 exterior is generally smoother than that of other calculi, ex- 

 cepting those of phosphate of lime. 

 P 2 



