3() ON THE STRUCTURE OF CALCULI. 



their histories This circumstance enabled me not only to ascertain the 

 annexed. situations in which the calculi were found, but likewise many 



of the circumstances attendant on their formation. 



I have therefore endeavoured to form an arrangement 



upon these principles, with a view to render the subject more 



clear and perspicuous. 



Sect. I. Of Calculi formed in the Kidnies, and voided 

 without having afterwards undergone any Change in the uri- 

 nary Passages, 



Calculi of the These have the following properties : 



They are of a brownish yellow colour, sometimes of a 

 grayish hue, which seems to arise from a small portion of 

 dry mucus adhering to their surface. 



They are entirely soluble in a solution of pure potash, 

 and during their solution they seldom emit an odour of am- 

 monia. 



When heated to dryness, with nitric acid, the residuum is 

 of a fine and permanent colour. 

 Contain animal When exposed to the action of the blow-pipe, they black- 

 matter. en ant j em j t a gtrong odour of burning animal matter, very 

 different from that of pure uric acid. This arises from a 

 variable proportion of animal matter which they contain, 

 and which occasions the loss in the analysis of these calculi. 

 Its relative quantity is liable to much variation, as may be 

 seen from the following statements, 



A calculus from the kidney, weighing seven grains, was 

 dissolved in a solution of pure potash. A quantity of muri- 

 atic acid (rather more than sufficient for the saturation of 

 the potash) was added, ami the precipitate of uric acid 

 thus obtained weighed when dry 4'5 grains. No other 

 substance, except animal matter, which was evident on at- 

 tempting to obtain the muriate of potash, could be detect- 

 ed, consequently the composition of this calculus was as 



follows: 



Grs. 

 Uric acid • 4*5 



Animal matter 2*5 



7-0 



This 



