782 URINE. 



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 w r ith the mates of the urine. Monohydrogen 

 phosphates besides acid urates 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 ureae, bacterium urea?, and 

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

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

 urease. 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. 





 NON-ORGANIZED SEDIMENTS. 



% Uric Acid. This acid occurs in acid urines as colored crystals which 

 are identified partly by their form and partly by their property of giving 

 the murexid test. On warming the urine they are not dissolved. On 

 the addition of caustic alkali to the sediment the crystals dissolve, and 

 when a drop of this solution is placed on a microscope-slide and treated 



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



2 Musculus, Pfliiger's Arch., 12. 



3 Salkowski, Zeitschr. f. physiol. Chem., 13. 



