URINARY SEDIMENTS. 829 



As previously mentioned (page 674), the urine of healthy individuals 

 may sometimes, even on voiding, be cloudy on account of the phosphates 

 present, or become so after a little while because of the separation of 

 urates. As a rule, urine just voided is clear, and after cooling shows 

 only a faint cloud (nubecula) which consists of urine mucoid, a few epithe- 

 lium-cells, mucous corpuscles, and urate particles. If an acid urine is 

 allowed to stand, it will gradually change; it becomes darker and deposits 

 a sediment consisting of uric acid or urates, and sometimes also calcium- 

 oxalate crystals, in which yeast-fungi and bacteria are often to be seen. 

 This change, which the earlier investigators called "ACID FERMENTA- 

 TION OF THE URINE," is generally considered as an exchange of the dihy- 

 drogen alkali phosphates with the urates of the urine. Monohydrogen 

 phosphates besides acid urates, quadriurates (page 708) or free uric acid 

 or a mixture of both, according to conditions, 1 are thus formed. 



Sooner or later, sometimes only after several weeks, the reaction 

 of the original acid urine changes and becomes neutral or alkaline. The 

 urine has now passed into the " ALKALINE FERMENTATION," which con- 

 sists in the decomposition of the urea into carbon dioxide and ammonia 

 by means of lower organisms, micrococcus urese, bacterium ureae, and 

 other bacteria. MUSCULUS 2 has isolated an enzyme from the micro- 

 coccus ureae which decomposes urea, which is soluble in water and is called 

 mease. During the alkaline fermentation volatile fatty acids, especially 

 acetic acid, may be produced, chiefly by the fermentation of the car- 

 bohydrates of the urine (SALKOWSKI 3 ) . A fermentation by which 

 nitric acid is reduced to nitrous acid, and another where sulphuretted 

 hydrogen is produced, may sometimes occur. 



When the alkaline fermentation has advanced only so far as to render 

 the reaction neutral, there often occur in the sediment fragments of uric- 

 acid crystals, sometimes covered with prismatic crystals of alkali urate; 

 dark-colored spheres of ammonium urate, crystals of calcium oxalate, 

 and sometimes crystallized calcium phosphate are also found. Crystals 

 of ammonium-magnesium phosphate (triple phosphate) and spherical 

 ammonium urate are specially characteristic of alkaline fermentation. 

 The urine in alkaline fermentation becomes paler and is often covered 

 with a fine membrane which contains amorphous calcium phosphate 

 and glistening crystals of triple phosphate and numerous micro-organisms. 



1 See Huppert-Neubauer, 10. Aufl., and A. Ritter, Zeitschr. f. Biologie, 35. 



2 Musculus, Pfliiger's Arch., 12. 



8 Salkowski, Zeitschr. f. Physiol. Chem., 13. 



