566 



VETERINARY PHYSIOLOGY 



6. Pigments. 



A brown hygroscopic substance, which gives no bands in 

 the spectrum, may be extracted from urine. This has been 

 termed urochrome. By reducing it, another pigment, urobilin, 

 is produced, which gives definite bands, and which is frequently 

 present in the urine. It is probably identical with the hydro- 

 bilirubin which has been prepared from the bile pigments, and 

 it contains C, H, 0, and N. 



The pigment that gives the pink colour to urates has been 

 called uroerythyrin, and its chemical nature is unknown. 



Hsematoporphyrin (see p. 491) is normally present in traces 

 in the urine, but in certain pathological states it is increased in 

 amount and gives a brown colour to the urine. 



7. Nucleo-Protein. 



A mucin-like nucleo-protein, derived from the urinary 

 passages, is always present in small amounts, and forms a cloud 

 when the urine stands. 



8. Carbonic Acids. 



1. Carbonic Acid. — Small amounts of this are present in 

 urine of carnivora. 



In herbivora it is present in large amounts, combined with 



1 



3 



$ 



Fig. 225. — The Three most Common Urinary Crj-stals : 1, Triple phosphate; 

 2, uric acid ; 3, calcium oxalate. 



potassium, lime, and magnesia, and also free. The carbonate of 

 lime readily crystallises out in large dumb-bell-like crystals 

 which may be confused with crystals of oxalate of lime, but 

 which are quickly soluble, with effervescence, on the addition 

 of an acid. 



