338 FUNCTIONS OF NUTRITION. 



eral hours ; and 2d. The supernatant fluid, when decanted, is found to 

 contain albumen. 



Mucus. The slight quantity of vesical mucus, normally contained 



in the urine, is at first uniformly disseminated throughout its mass, and 

 even after being left in repose is insufficient to produce any well-marked 

 or consistent deposit. The light cloudy opalescence, which it forms at 

 the bottom of the vessel, is visible only on close inspection, and is read- 

 ily disseminated again by agitation. But in inflammation of the uri- 

 nary bladder, the mucus is increased in quantity and altered in quality. 

 It then appears as a consistent mass, which does not mix uniformly 

 with the urine, but subsides to the bottom as a semifluid deposit. Mucus 

 by itself is transparent and colorless, but it frequently contains epithe- 

 lium cells from the bladder ; and when crystalline or pulverulent deposits 

 take place in the urine, they first appear in contact with the mucus, so 

 that its surface is often sprinkled with the urates or phosphates. A 

 deposit of mucus is distinguished by its viscid and semifluid consistency. 

 It is not affected by heat, but is coagulated and shrivelled by alcohol 

 and by nitric or acetic acid. Urine containing mucus is liable to rapid 

 decomposition, and often has a peculiarly offensive odor from this cause. 



Pus. When pus is contained in the urine it gradually subsides if 

 allowed to remain at rest, forming a dense, creamy-white deposit, per- 

 fectly fluid in consistency and easily disseminated by agitation. Micro- 

 scopic examination shows it to be composed of colorless, granular, nucle- 

 ated " pus-globules," identical in appearance with the white globules of 

 the blood, but distinguishable from those belonging to a deposit of blood 

 by their abundance and by the absence of red globules. If the super- 

 natant fluid be poured off, and a few drops of a solution of caustic alkali 

 added to the deposit, it loses its white color and opacity, owing to the 

 solution of its granular cells, and swells up into a transparent, colorless 

 gelatinous substance, which can no longer be poured off in drops, but 

 slides out of the vessel in a single semi-solid mass. This character will 

 serve to distinguish a purulent deposit from any other liable to occur 

 in the urine. The supernatant urine, when filtered, is found to contain 

 a small quantity of albumen, the interstitial fluid of pus being itself 

 albuminous. 



Decomposition of the Urine. 



After its discharge from the body, the urine undergoes spontaneous 

 changes, by which its organic ingredients are altered and finally disap- 

 pear. This decomposition is closely dependent on the mucus in the 

 urine, being much retarded if this be separated by immediate filtration, 

 and hastened in a corresponding degree when the mucus is abnormally 

 abundant. It is characterized by two different stages, distinguished by 

 the successive development of acid and alkaline products. They are 

 known respectively as the acid and the alkaline fermentations. 



Acid Fermentation of the Urine. This process takes place for the 

 most part within twelve, twenty-four, or forty-eight hours after the dis- 

 charge of the urine. It consists in the production of a free acid, usually 



