COLOURING MATTER : MUCUS : EXTRACTIVE. 



459 



The nature and composition of the colouring matter of 

 urine are involved in some obscurity. It is probably closely 

 related to the colouring matter of the blood. 



The mucus in the urine con- fig. 129.* 



sists principally of the epi- 

 thelial debris of the mucous 

 surface of the urinary pas- 

 sages. Particles of epithe- 

 lium, in greater or less abun- 

 dance, m aybe dectected in most 

 samples of urine, especially if 

 it has remained at rest for 

 some time, and the lower 

 strata are then examined (fig. 

 129). 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 (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 colouring matter, urine contains a 

 considerable quantity of animal matter, usually described 

 under the obscure name of animal extractive. The investi- 

 gations of Liebig, Heintz, and others, have shown that 



* Fig. 129. Mucus deposited from urine. 



