210 Brande on ihe Medico-Chemkal 



very apt to undergo a slight decomposition, in which case it be- 

 comes ammoniacal, and more or less of the phosphates will of 

 course be thrown down. This accounts for the circumstance 

 of those calculi which have attained a very large size in the 

 bladder, consisting chiefly of the phosphates ; and shews why 

 a similar deposition is often formed upon bougies, or any other 

 extraneous body ; why uric nuclei are so often incrusted by 

 phosphates ; and why in some cases of diseased kidney a si- 

 milar deposition has often gone to a great extent. 



An enlargement of the prostate gland is not only favourable 

 to the increase of the size of a calculus for the reason which 

 has just been adverted to, but in some instances becomes the 

 cause of the formation of a stone, quite independent of any 

 mischief in the kidneys, or disordered secretion of urine. " The 

 bladder never being completely emptied, the dregs of the urine, 

 if 1 may be allowed the expression, being never evacuated, a 

 calculus, formed on a nucleus of the ammoniaco-magnesian phos- 

 phate and mucus is produced, when it would not have been pro- 

 duced under other circumstances. This species of stone, or a 

 stone upon such a nucleus, can only be produced where the 

 bladder is unable to empty itself ; it may therefore be arranged 

 among the consequences of the enlargement of the middle lobe 

 of the prostate gland." (Home on the Diseases of the Prostate 

 Gland, Vol. 1. p. 40.) 



Another way in which any obstacle to the emptying of the 

 bladder becomes a source of mischief in calculous cases, is that 

 under such circumstances, the quantity of urine secreted during a 

 given time is diminished, only eight or ten ounces being in some 

 instances voided during the 24 hours. An illustrative case of 

 this kind will be found in Sir Everard Home's treatise just 

 quoted, (p. 44.) and it always happens that the specific gravity 

 of such urine is greatly above the natural standard, and that it 

 becomes very turbid on cooling, even when voided clear, which, 

 however, seldom happens. 



Having now, 1 believe, enumerated the leading circumstances 

 respecting the composition and formation of calculi of the urinary 

 bladder, it remains to make a few observations upon the 



