APPENDIX TO URINE 



565 



2. URINARY SEDIMENTS. 



The sediment is separated by means of the centrifuge and examined under 

 the microscope. 



A. IN ACID URINE. 



Amorphous Deposits. 



(1) Urates. 



This deposit is known as " brick dust " from its pink colour (uroerythrin). 

 It may contain crystalline forms and may dissolve completely on warming, 

 the urine. 



A little of the sediment is boiled with water. It is soluble ; the hot solu- 

 tion is acidified with hydrochloric acid and cooled. Uric acid crystallises out ; 

 the crystals are examined with the microscope and tested with the murexide 

 reaction. 



Urates may deposit from concentrated urine on cooling, as is commonly 

 found in fevers. 



The chief constituent is acid sodium urate. 



(2) Calcium Oxalate. 



Calcium oxalate has the appearance of dumb-bell or spheroidal bodies (en- 

 velope crystals) under the microscope. It is insoluble in strong acetic acid 

 and ammonia, but soluble in hydrochloric acid. 



(3) Bilirubin or Haematoidin. 



Yellow granular amorphous masses, which give Gmelin's reaction, gener- 

 ally consist of bilirubin. 



Crystalline Deposits. 



(4) Uric Acid. 



This is known as cayenne pepper deposit as it is of sandy red colour. It has a 

 distinctive crystalline form under the microscope and gives the murexide reac- 

 tion "(Fig. 80). 



FIG. 80. Deposit of uric acid. 

 (After Funke.) 



FIG. 81, Deposit of calcium oxalate. 

 (After Funke.) 



(5) Calcium Oxalate. 



This sediment consists of coloui less, transparent, highly refractive octa- 

 hedral crystals (envelope shaped). It is insoluble in acetic acid, but soluble in 

 hydrochloric acid (Fig. 81). 



