370 HANDBOOK OF PHYSIOLOGY. 



added to the urine of patients taking these drugs. In the case of iodides 

 the liberated iodine communicates a strong mahogany color to the urine 

 thus treated. 



(5) Mucus. Mucus in the urine consists principally of the epithe- 

 lial debris from the mucous surface of the urinary passages. Particles 

 of epithelium, 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. 256). As urine cools, the 

 mucus is sometimes 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 undergoes decomposition. The presence of the decomposing 

 mucus excites chemical changes in the urea, whereby carbonate of am- 

 monium is formed, which, combining with the excess of acid in the) 

 superphosphates in the urine, produces insoluble neutral or alkaline 



FIG. 256. Mucus deposited from urine. 



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 sur- 

 face of the bladder, and is often passed with the urine, forming a thick 

 tenacious sediment. 



(6) Extractives. In addition to those already considered, urine 

 contains a considerable number of nitrogenous compounds. These are 

 usually described under the generic name of extractives. Of these, the 

 chief are: (1) Kreatinin (C 4 H 7 N 3 0), a substance derived, probably, 

 from the metamorphosis of muscular tissue, crystallizing in colorless 

 oblique rhombic prisms; a fairly definite amount of this substance, about 

 15 grains (1 grm.), appears in the urine daily, so that it must be looked 

 upon as a normal constituent: it is increased on an increase of the nitro- 

 genous constituents of the food; (2) XantMn (C 5 N 4 H 4 2 ), an amorph- 

 ous powder soluble in hot water; (3) Hypoxanthin, or sarkin (C & H 4 N 4 0); 

 (4) Oxaluric acid (C 3 H 4 N 2 4 ), in combination with ammonium in the 

 urine of the new-born child; (5) Allantoin (C 4 H 6 N 4 3 ). All these ex- 



