208 Brande on the Medico-Chemical 



It rarely, and perhaps never, happens, that a bladder calculus 

 consists of any of the above substances perfectly pure. Traces 

 of the phosphates are discoverable in the uric calculus, and of 

 uric acid in those composed of the phosphates, and the mode 

 of analysis has already been pointed out. 



It is, however, a common circumstance to find two or more of 

 the above substances in layers distinct from each other. Uric cal- 

 culi incrusted with the phosphates are of very frequent occur- - 

 rence ; they are indeed the most common of all calculi. Some- 

 times the nucleus only is uric, the bulk of the calculus being 

 of the phosphates ; at other times a comparatively large uric cal- 

 culus is incrusted with a thin coat of the phosphates ; but I 

 have never yet seen a bladder calculus with a well defined 

 nucleus of the phosphates enveloped in uric acid. 



Besides the calculi composed of uric acid and of the phos- 

 phates, two other substances have been mentioned as belonging 

 to this formation, oxalate of lime, and cystic oxide. 



The properties of oxalate of lime have been described in speaking 

 of it as of kidney origin, but its appearance when concreting into 

 calculi in the bladder is peculiar ; their exterior is rough and 

 tuberculated, and their colour deep reddish brown, so that they 

 have been termed mulberry calculi. Dr. Marcet {Essay, p. 78,) 

 has described a variety of the oxalate of lime calculus not ex- 

 ceeding the size of a pea, of a pale brown colour and crystalline 

 texture, of which he has seen three specimens. The superficial 

 crystals were very flat octoedrons. 



The nuclei of these calculi are generally oxalic, and of renal 

 origin, but uric nuclei enveloped in the oxalate also occur ; 

 they are likewise not very unfrequently found enveloped by the 

 fusible calculus. I have in my possession a calculus of which 

 the nucleus is uric, surrounded by oxalate and phosphate of 

 lime, and triple phosphate, each in a distinct layer ; and Dr. 

 Marcet has depicted a very analogous specimen. {Essay, Plate 

 VIII., fig. 8.) 



The cystic calculus is rare compared with the other varieties. 

 In appearance it most resembles the triple phosphate, but it is 



