598 THE URINE [CH. XXXIX. 



Quantitative estimation of the salts is accomplished by the use of solutions of 

 standard strength, which are run into the urine till the formation of a precipitate 

 ceases. The standards are made of silver nitrate, barium chloride, and uranium 

 nitrate or acetate for chlorides, sulphates, and phosphates respectively. 



Urinary Deposits. 



The different substances that may occur in urinary deposits are 

 formed elements and chemical substances. 



The formed or anatomical elements may consist of blood- 

 corpuscles, pus, mucus, epithelium cells, spermatozoa, casts of the 

 urinary tubules, fungi, and entozoa. All of these, with the exception 

 of a small quantity of mucus, which forms a flocculent cloud in the 

 urine, are pathological, and the microscope is chiefly employed in 

 their detection. 



The chemical substances are uric acid, urates, calcium oxalate, 

 calcium carbonate, and phosphates. Earer forms are leucine, tyrosine, 

 xan thine, and cystine. We shall, however, here only consider the 

 commoner deposits, and for their identification the microscope and 

 chemical tests must both be employed. 



Deposit of Uric Acid. This is a sandy reddish deposit resembling 

 cayenne pepper. It may be recognised by its crystalline form (fig. 

 382, p. 591) and by the murexide reaction. The presence of these 

 crystals generally indicates an increased formation of uric acid, and, if 

 excessive, may lead to the formation of stones or calculi in the bladder. 



Deposit of Urates. This is much commoner, and may, if the 

 urine is concentrated, occur in normal urine when it cools. It is 

 generally found in the concentrated urine of fevers; and there 

 appears to be a kind of fermentation, called the acid fermentation, 

 which occurs in the urine after it has been passed, and which leads 

 to the same result. The chief constituent of the deposit is the acid 

 sodium urate, the formation of which from the normal sodium urate 

 of the urine may be represented by the equation : 



2C 6 H 2 Na 2 N 4 O 8 + H 2 O + CO, = = 2C 5 H 3 NaN 4 O 3 + Na 2 CO 3 . 



[Normal sodium [Water.] [Carbonic [Acid sodium urate.] [Sodium 



urate.] acid.] % carbonate.] 



This deposit may be recognised as follows : 



(1) It has a pinkish colour ; the pigment called uro-erythrin is one 

 of the pigments of the urine, but its relationship to the other urinary 

 pigments is not known. 



(2) It dissolves upon warming the urine. 



(3) Microscopically it is usually amorphous, but crystalline forms 

 similar to those depicted in fig. 384 may occur. Crystals of calcium 

 oxalate may be mixed with this deposit (see fig. 385). 



Deposit of Calcium Oxalate. This occurs in envelope crystals 

 (octahedra) or dumb-bells. It is insoluble in ammonia, and in acetic 



