458 cALcii'icATiow c()\('i>'i:ti(>\s, am) /xrh'i statioxs 



enaiiu'l-like mass under the l)l()W-i)ipe, they have been called "fusible 

 calculi." 



Calcium carbonate calculi are formed freciuently in herbivora, 

 but tliey are xcry rare in the \irinary passages of man, althoufi-h oe- 

 currinw elsewhere in the body not infrequently. Occasionally these 

 are soft and chalky, but if well crystallized, they are the hardest of 

 concretions. 



Cystine calculi '" are rare but very interesting formations. Cys- 



S-CII(NIL)-C'0011 



tine I is important as the sulphur-containing por- 



S-CH(XIL)-COOH 



tion of the protein molecule. Under normal conditions all the cystine 

 taken in food is completely oxidized and none (or uncertain traces) 

 appears in the urine. In certain individuals the urine contains con- 

 siderable quantities of cystine constantly {(jjstiuuria, see Chap, xix), 

 and occasionallj" in these cases soft concretions of nearly pure cystine 

 are formed in the urinary passages. Cystine calculi may reach the 

 size of a hen's egg, are crystalline in structure, and in the urine of 

 such patients the characteristic hexagonal crystals may usually be 

 found. The cystine of calculi is identical with that from proteins.^" 



Xanthine Calculi. — Xanthine is the most abundant of the purine 

 bases normally present in urine, but the total amount is extremely 

 small. Like uric acid, it fluctuates in amount according to the 

 amount of destruction of nucleoproteins, either of the food or of the 

 tissues. Concretions consisting chiefly of xanthine, which is often 

 mixed with uric acid, are extremely rare, but a few isolated si)eci- 

 mens having been described. Rosenbloom could collect but six cases 

 in the literature, adding one himself. ^^ 



Indigo calculi, derived from the indican of the urine through oxi- 

 dation, have also been described a few times. 



Urostealith calculi, composed of fatty matter, have been occasion- 

 ally ol)served. Although some of the concretions described under 

 this head have really represented foreign bodies introduced through 

 the urethra (e. g., Kruckenberg 's concretion of paraffin from a bou- 

 gie), yet true fat concretions do occur. The origin of the fat in tliese 

 stealiths is unknown; possibly it comes from degenerated epithelium. 

 TTorbaczewski ^' analyzed such a specimen which had the following 

 percentage composition : 



Water 2..'> 



Tnoriranio matt«M" .... OS 



Orfjaiiic matter (cliiclly ])riitciii ) 11.7 



Fatty acids .')]..") 



Nculral fal :?:5..-, 



Cliolcstcnil traces 



])li()S|)lia1e, foriiiiii^ tlic liard, rlioinliic crystals known to iiiiiicralouisis as 

 "struvit." 'I'liis is an exaini)lc of a l)lios|)Iiate stone formed independent of am- 

 inf)niaea] deeom]H>8iti()ii, a raic occurrence. 



'» T>iteratnre concerniiij,' cystine, see Kricdmann, ImltcIi. der IMi\siol., ]'J()2 (iK 

 1.'): Marriott and Wolf. Am." .lour. Med. Sci., 1!1()(> (i:?!). \'M. 



'^'1 .M.dcriialden. Zcit. iilivsioi. Clicm.. 1!»07 (51), :{91. 



«i X. V. Med. .loiir., .lati. Ill, lUlf). 



