COMPOSITION AND CHARACTERS OF URINE 1257 



are derived from the food. Alcaptonurians apparently suffer no ill 

 effects as a result of their abnormal metabolism. It seems that the 

 tyrosine and phenylalanine can be absorbed and play their part in 

 building up the proteins of the tissues, but that the process or ferment 

 is wanting, which is responsible for the further break-up of the first 

 product of their oxidation, namely, 

 homogentisic acid. 



URINARY DEPOSITS 

 In addition to formed elements, 

 such as blood-corpuscles, bacteria, 

 or pus- cells, which may occur in 

 abnormal urine, the following de- 

 posits may be found : 



FIG. 521. Various forms of uric acid 

 (a) IN ACID URINE crystals. (FRBY.) 



(1) Amorphous urates occur 



generally as a brick-red amorphous deposit thrown down as the urine 

 cools. It is redissolved on warming the urine, and consists generally 

 of the quadri-urates. The acid urate of sodium and of ammonium 

 may occasionally occur in star-shaped clusters of needles or as 

 spherules with small crystals adhering to them. 



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



crystals, generally deeply pig- 

 mented so as to resemble cayenne 

 pepper (Fig. 521). 



(3) Calcium oxalate (Fig. 522). 

 Colourless, transparent, highly re- 

 fractive octahedral crystals (enve- 

 lope-shaped). Insoluble in acetic 

 acid, soluble in hydrochloric acid. 



(4) Ammonium magnesium 

 phosphates (in faintly acid urine). 

 The crystals have been compared 

 to knife - rests or coffin - lids 

 (Fig. 523). They are soluble in 

 acetic acid. 



(5) Calcium hydrogen phos- 

 phate. 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, 



FIG. 522. Urinary deposit, containing 

 uric acid, sodium urate, and calcium 

 oxalate. 



