464 CALCIFICATION, CONCRETIONS, AND INCRUSTATIONS 



Under comparable conditions it is said that those composed of amorph- 

 ous phosphates are the softest; next come those with some admixture 

 of crystalhne phosphates. Urate concretions are harder than these, 

 but are still softer than uric acid and crystalline phosphate calculi. 

 Oxalates are usually the hardest, except for the rare crystallized 

 calcium carbonate stones. Cystine and amorphous concretions can 

 be scratched with the finger-nail, while even the hardest varieties of 

 calculi can be scratched with a wire nail. Genersich^^ gives the 

 following degrees of hardness for different calculi: Cholesterol, 1,5- 

 1.6; ammonium urate, 2.5; soft phosphate (Mg), 2.6; hard phos- 

 phate (Ca), 2.75; uric-acid stones (also salivary and prostatic calculi, 

 atheromatous patches, and phleboliths), 2.9; calcium oxalate (also 

 rhinoliths and lung stones), 3.3-3.5; calcium carbonate stones of 

 herbivora, 4.5. But the hardness or gross appearance of a urinary 

 calculus give little or no indication of its chemical composition. 



The rate of growth also varies according to composition, but is, of 

 course, much modified by other factors. Oxalate and urate stones 

 grow most slowly, phosphate stones most rapidly. A urate stone has 

 been known to increase by about two ounces during seven and one 

 half years, while a catheter fragment or other foreign body may be- 

 come covered with a crust several millimeters thick in a few weeks. ^"^ 



Spontaneous disintegration of urinary concretions is limited almost solely to 

 calculi composed entirely or largely of uric acid. Out of 121 cases collected by 

 Englisch.^i in all but 7 this was the case, these being composed of calcium and 

 magnesium phosphate (5), or calcium phosphate or carbonate (1 each). The 

 disintegration is brought about through solution of the binding substance and me- 

 chanical shattering of the stone into fragments. This occurs but rarely, Bastos- 

 estimating that perhaps one calculus in ten thousand undergoes disintegration. 



Corpora Amylacea^^ 



In the case of these widely-spread concentric bodies we find the 

 name misleading, for the bodies are not a form of animal starch, as 

 was suggested by their laminated structure and iodiu reaction, nor 

 are they so closely related to amyloid material as the name implies. 

 Different authors disagree decidedly concerning the staining reactions 

 of these bodies, but it may be said that the reactions are extremely 

 inconstant. Sometimes the corpora are stained bluish or green with 

 iodin, sometimes brown, often little at all; occasionally they react 

 partly with methyl- violet, but more often they do not; sometimes por- 

 tions of one body react one way, while the remainder behaves differ- 

 ently. Seldom if ever do the ordinary concretions of the prostate 



" Virchow's Arch., 1893 (131), 185. 



20 ZuckerkandLNothnagel's System, vol. 19, pt. 2, p. 229. 



21 Arch. klin. Chir., 1905 (76), 961 (elaborate revie^v). 

 " Folia Urol., 1913 (8), 81. 



" General literature, Posner, Zeit. klin. Med., 1889 (16), 144; Lubarsch, 

 Ergeb. allg. Pathol., 1894 (lo) 180; Ophiils, Jour. Exp. Med., 1900 (5;, 111; 

 Nunokawa, Virchow's Arch., 1909 (196), 221; Brutt, ibid., 1912 (207), 412. 



