the stone in 

 the bladder. 



46 ON THE STRUCTURE OF CALCULr. 



Sect. VI. General Inferences. 



General con- It appears from the preceding observations, that calculi 



elusions. formed in the kidnies, and immediately voided, are almost 



always composed of uric acid ; and that the phosphates are 



very frequent ingredients in calculi of the bladder, more 



especially in those, which, from their situation, have been 



exposed to a continual current of urine : they also uniformly 



are deposited upon extraneous substances introduced into 



the bladder, but appear never to form small kidney calculi. 



Fit of the ^ n wna t * s commonly called a fit of the gravel, a small 



gravel. uric calculus is formed in the kidney, and passes along the 



ureter into the bladder. 

 Formation of It is found from observation, that for some time after a 

 stone has passed from the kidney, the urine is generally un- 

 usually loaded with uric acid, and deposites that substance 

 upon the nucleus now in the bladder. When this period, 

 which is longer or shorter in different individuals, has 

 elapsed, the subsequent addition to the calculus consists 

 principally of the phosphates. 



Where the disposition therefore to form uric acid in the 

 kidnies is very great and permanent, the calculus found in 

 the bladder is principally composed of uric acid ; but where 

 this disposition is weak and of short duration, the nucleus 

 only is uric acid, and the bulk of the stone is composed of 

 the phosphates. 



W r here the increased secretion of uric acid returns at in- 

 tervals, the calculus is composed of alternate layers of uric 

 acid and the phosphates. 



Other small calculi being formed in the kidney, they 

 make their way into the bladder, and afford fresh nuclei; 

 so that several calculi are sometimes found in the same blad- 

 der, and their composition is usually nearly the same. 



In other cases it happens, that a constant increased secre- 

 tion of uric acid is going on from the kidnies, only in small 

 quantity, which will be more uniformly mixed with the 

 phosphates deposited in the bladder, and where the uric acid 

 predominates, the species of calculus, denominated impro- 

 perly urate of ammonia, will be produced. 

 F rmationof ^ e ave ent * re ly ignorant of the cause of the formation 



of 



