362 HAND-BOOK OF PHYSIOLOGY. 



in the urine of man, in quantity equal or rather exceeding that of the 

 uric acid. 



Pigments. The coloring matters of the urine are: (1) Uro-MUn, 

 a substance connected with the coloring matters of the blood and bile 

 (p. 275); it is especially seen in febrile urine and exists normally, but 

 to less amount; it is of a yellowish-red color; (2) Uro-clirome, which on 

 exposure undergoes oxidation, and becomes Uro-erythrin, the former 

 being yellowish and the latter sandy red; and (3) Indican is occasionally 

 present. 



Indican is not itself pigmentary, though by its decomposition indigo 

 blue and indigo red are produced. Its presence can usually be detected 

 by adding to a small quantity of urine an equal bulk of strong hydrochloric 

 acid, and gently heating the solution; on the addition of two or three 

 drops of strong nitric acid a delicate purplish tint is developed, and indigo 

 blue and red crystals separate out. 



Mucus. Mucus in the urine consists principally of the epithelial 

 debris of the mucous surface of the urinary passages. Particles of epithe- 

 lium, in greater or less abundance, may be detected in most samples of 

 urine, especially if it has remained at rest for some time and the lower 

 strata are then examined (Fig. 250). As urine cools, the mucous is some- 



FIG. 250. Mucus deposited from urine. 



times seen suspended in it as a delicate opaque cloud, but generally it 

 falls. In inflammatory affections of the urinary passages, especially of 

 the bladder, mucus in large quantities is poured .forth, and speedily un- 

 dergoes decomposition. The presence of the decomposing mucus excites 

 (as already stated, p. 356) chemical changes in the urea, whereby ammo- 

 nia, or carbonate of ammonium, is formed, which, combining with the 

 excess of acid in the super-phosphates in the urine, produces insoluble 

 neutral or alkaline phosphates of calcium and magnesium, and phosphate 

 of ammonium and magnesium. These mixing with the mucus, constitute 

 the peculiar white, viscid, mortar-like substance which collects upon the 

 mucous surface of the bladder, and is often passed with the urine, form- 

 ing a thick tenacious sediment. 



