38 ON THE STRUCTURE OF CALCULr. 



Phosphates in 2. Where there is less disposition to form uric acid, the 

 external laminae are composed of the ammoniaco-magnesiah 

 phosphate, and phosphate of lime. 



In one instance, a small uric calculus has been deposited 

 in the kidney in such a situation, that its upper surface was 

 exposed to a continual stream of urine, upon which beauti- 

 ful crystals of the triple phosphate had been deposited. It 

 would therefore seem, that, under common circumstances, a 

 stream of urine* passing over a calculus of uric acid has a 

 tendency to deposit the phosphate upon it. 



Sect. III. Of Calculi of the urinary Bladder. 



Calculi of the Calculi met with in the bladder are of four kinds. 

 bladder. 1# Those formed upon nuclei of uric acid from the kid- 



ney. 



2. Those formed upon nuclei of oxalate of lime from the 

 kidney. 



3. Those formed upon sand, or animal mucus, deposited 

 in the bladder. 



4. Those formed upon extraneous bodies introduced into 

 the bladder. 



They were arranged under the following divisions. 

 Calculi of uric 1# Calculi, which, from their external appearance, con- 

 acid chiefly, sist chiefly of uric acid. 



These calculi vary in colbur from a deep reddish brown, 

 to a pale yellowish brown. 



They are either entirely soluble in a solution of pure pot- 

 ash, or nearly so. 



During their solution they frequently emit the pdpur of 

 ammonia. 



When acetic acid is added to their alkaline solution, a 



precipitate possessing the properties of uric acid is obtained. 



Calculi of 2. Calculi composed chiefly of the ammoniaco-magne- 



phosphates s i an phosphate, or of phosphate of lime, or of mixtures of 



chiefly. . - 



■ the two. 



These calculi are externally of a whiter appearance than 

 the former. 



Some perfectly white, others gray, occasionally exhibit- 

 ipg small prismatic crystals upon their surface; others 

 again soft and friable, a good deal resembling chalk; They 



are, 



