On the Differences in the Structure of Calculi. 1 71 



The following is a statement of the composition of the dif- 

 ferent calculi found in the bladder which I have examined,, 

 16 were composed of uric acid. 



45 - — - uric acid with a small relative pro- 

 portion of the phosphates. 



66 the phosphates, with a relatively 



small proportion of uric acid. 



J 2 — — of the phosphates entirely. 



5 of uric acid, with the phosphates and 



nuclei of oxalate of lime. 

 6 — — — : — — — chiefly of oxalate of lime. 



150 



To injure these calculi as little as possible, they were care- 

 fully cut through with a fine saw, and a portion of the whole 

 cut surface removed by a file; in this way all the different 

 ingredients of the calculi were obtained. 



In the experiments upon uric calculi from the bladder, I 

 found in most instances, a far more considerable loss in 

 attempting to obtain their pure uric acid, than in the kidney 

 calculi ; which led me to suppose that thev contained urea, 

 and that the presence of this substance, with some of the 

 gaits of urine, and with small portions of the ammoniaco- 

 magnesian phosphate, was the cause of the occasional evo- 

 lution of ammonia \\hen treated with the fixed alkalis, and 

 of their easy s ti.u'bility in those substances. 



To determine his point, a small calculus. weighing twenty- 

 five grains, and of the species commonly supposed to consist 

 pf urate of ammonia^, was digested for two hours with water 

 in a very moderate heat. The water which had assumed a 

 pale yellow colour was filtered off, and fresh water added to 

 the residuum three successive times, when it appeared that 

 every thing soluble in that fluid was separated. The inso- 

 luble part of the calculus, being now carefully dried and 

 weighed, was found to have lost 5'5 grains. 



* Fourcroy observes that urate of ammonia is easily detected by its rapid 

 solubility in the fixed alkalis, arid the odour of ammonia, which is perceived 

 during its solution. — Vide Thomson's Svst, of Chem. vol. v. p. 69 1. 



The 



