COMPOSITION AND CHARACTERS OF URINE 



1125 



(2) Uric acid. Whetstone, dumb-bell, or sheaf- like aggregations of crystals, 

 generally deeply pigmented so as to resemble cayenne pepper (Fig. 523). 



(3) Calcium oxalate (Fig. 524). Colourless, transparent, highly refrac- 



FIG. 524. Urinary deposit, containing uric 

 acid, sodium urate, and calcium oxalate. 



FIG. 525. Deposit of ' triple ' phosphate 

 and ammonium urate. (FUNKE.) 



The 



tive octahedral crystals (envelope-shaped). Insoluble in acetic acid, soluble 

 in hydrochloric acid. 



(4) Ammonium magnesium phosphates (in faintly acid urine), 

 crystals have been compared to 



knife-rests or coffin-lids (Fig. 525). 

 They are soluble in acetic acid. 



(5) Calcium hydrogen phosphate. 

 CaHP0 4 . These are rare. They 

 form large prismatic crystals often 

 arranged in rosettes. Easily soluble 

 in dilute acetic acid. On adding a 

 solution of ammonium carbonate the 

 crystals are eaten away and form an 

 amorphous deposit. 



(6) Tyrosine, fine needles in star- 

 shaped bundles, and cystine, in 

 regular hexagonal plates, may occur 



under very rare circumstances. FIG. 526. Ammonium urate. 



(6) IN ALKALINE URINE 



(1) The commonest precipitate consists of earthy phosphates, amor- 

 phous, easily soluble in dilute acetic acid. 



(2) Ammonium magnesium phosphate or triple phosphate is common 

 in urine which has undergone ammoniacal fermentation. 



(3) Acid ammonium urate (Fig. 526) may also occur in alkaline urine. 

 On treatment with HC1 it is dissolved and uric acid in crystals slowly 

 separates out. 



