364 



THE URINE. 



FIG. 129. 



termined : in part it is probably derived from some constitu- 

 ents of vegetable diet, though man has no hippuric acid in his 

 food, nor, commonly, any benzoic acid that might be converted 

 into it ; in part from the natural disintegration of tissues, inde- 

 pendent of vegetable food, for Weismann constantly found an 

 appreciable quantity, even when living on an exclusively ani- 

 mal diet. 



The nature and composition of the coloring matter of urine 

 are involved in some obscurity. It is probably closely related 

 to the coloring matter of the blood. 



The mucus in the urine consists principally of the epithelial 

 debris of the mucous surface of the urinary passages. Particles 



of epithelium, in greater or less 

 abundance, may be detected in 

 most samples of urine, especi- 

 ally if it has remained at rest 

 for some time, and the lower 

 strata are then examined (Fig. 

 129). As urine cools, the mu- 

 cus is sometimes seen suspended 

 in it as a delicate opaque cloud, 

 but generally it falls. In in- 

 flammatory affections of the 

 urinary passages, especially of 

 the bladder, mucus in large 

 quantities is poured forth, and 

 speedily undergoes decomposi- 

 tion. The presence of the de- 

 composing mucus excites (as already stated) chemical changes 

 in the urea, whereby ammonia, or carbonate of ammonia, is 

 formed, which, combining with the excess of acid in the super- 

 phosphates in the urine, produces insoluble neutral or alkaline 

 phosphates of lime and magnesia, and phosphate of ammonia 

 and magnesia. 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, forming a thick, tenacious sediment. 



Besides mucus and coloring matter, urine contains a consid- 

 erable quantity of animal matter, usually described under the 

 obscure name of animal extractive. The investigations of Lie- 

 big, Heintz, and others, have shown that some of this ill-defined 

 substance consists of Creatin and Creatinin, two crystallizable 

 substances derived, probably, from the metamorphosis of mus- 

 cular tissue. These substances appear to be intermediate be- 

 tween the proper elements of the muscles, and, perhaps, of 

 other azotized tissues and urea :. the first products of the dis- 



Mucus deposited from urine. 



