URINE 125 



of urates, sulphates, and phosphates, which is removed by filtration ; 

 the filtrate is then allowed to stand for twenty-four hom-s, when the 

 precipitation of a mercuiy salt of creatinine (C4H5HgN30HCl) 

 SHgCla + SHaO occurs in the form of minute spheres, quite " typical 

 on microscopic examination. This compound lends itself very well 

 to quantitative analysis. It may be collected, dried, and weighed, 

 and one-fifth of the weight found is creatinine.' Creatinine may be 

 obtained from it by suspending it in water, decomposing it with 

 sulphuretted hydrogen, and filtering. The filtrate deposits creatinine 

 hydi-ochloride, from which lead hydrate, Pb(0H)2, hberates creatinine. 

 An important point in Johnson's process is that all the operations are 

 earned out in the cold ; if heat is applied one obtains the creatinine 

 of former writers, which has no reducing power. 



XTRINARY DEPOSITS 



The diflferent 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. Rarer forms are leucine, tyro- 

 sine, xanthine, and cystiu. 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 fonn (fig. 

 43, p. 119) and by the mm-exide 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. The way in which uric acid is split off from the urates is 

 of great interest to pathologists, and will be found fully discussed in 

 Sir W. Eoberts's Croonian Lectures.^ 



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

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



• If only a quantitative analysis is required, the process may be considerably 

 accelerated by boiling the first filtrate for ten minutes instead of letting it stand 

 for twenty-four hours. 



- Published by Smith, Elder, & Co., London, 1892. 



