URINARY DEPOSITS. 



123 



alteration in the composition of the urine, whilst the latter are 

 due to ammoniacal decomposition of the urine, resulting in the 

 precipitation of phosphates on stones already formed. This of 

 course has an important bearing on the treatment of calculous 



Fig. 32. a a, Leucin balls; bb, tyrosin sheaves; 

 c, double balls of ammonium urate. 



disorders. Calculi occur in acid and alkaline urine. A highly 

 acid urine favours the formation of uric acid calculi, because that 

 substance is most insoluble in very acid urine. A highly alkaline 

 urine favours the formation of calculi, consisting of calcium 

 phosphate or triple phosphate, as these substances are insoluble in 

 alkaline urine. 



4. Method of Examining a Calculus. 



(a.) Make a section in order to see if it consists of one or 

 more substances ; examine it with the naked eye, and a por- 

 tion microscopically. 



(b.) Scrape off a little, and heat it to redness on platinum 

 foil over a Bunsen burner. 



(A) If it be entirely combustible, or almost so, it may 



