SECRETION. 453 



sodium urates, which it colors red to form the popularly known 

 '"brickdust" sediment. Normally, it occurs in but small quantities, 

 but by reason of its strong coloring properties is intimately con- 

 cerned in the coloring of the urine. 



Three properties are characteristic of uroerythrin: (1) its 

 remarkable affinity for uric-acid compounds, (2) the ease with which 

 its solutions are decolorized by light, and (3) its color-reactions with 

 caustic alkalies and mineral acids. 



H^EMATOPORPHYRIN" exists in but very small amounts in the 

 urine normally; pathologically and after the ingestion of certain 

 drugs, as sulphonal, it may be greatly increased. 



INDICAN, OR INDOXYL. This is another pigment which colors 

 the urine intensely yellow. It is an indigo substance represented 

 by a dense, yellow-brown acid, nauseatingly bitter and very soluble 

 in water, alcohol, and ether. 



Indican is derived from indol, which is formed in the intestines 

 as a product of putrid decomposition of the pancreo-peptones. It 

 is in direct relation to the quantity of bacterial putrefaction of 

 albumins. Indican is really a conjugated indoxyl sulphate of 

 potassium. 



Test. When urine is mixed with an equal bulk of strong HC1, 

 indoxyl is liberated from the sulphate. A solution of hypochlorite 

 is now added, drop by drop, when indigo-blue will be formed by 

 oxidation of the indoxyl. Upon the addition of chloroform the blue 

 matter is precipitated, forming a layer at the bottom of the liquid. 



Pathological Pigments. BLOOD-PIGMENTS. Blood in the urine 

 (haematuria) may result from injury or disease anywhere along the 

 urinary tract. In this urine the red blood-corpuscles are found in 

 the deposit. An idea as to the probable source of the haemorrhage 

 may be gotten by careful analysis. Thus, blood from the kidney is 

 usually small in amount, gives urine a "smoky" appearance, and is 

 well mixed. Large coagula are never found in this urine. In 

 haemorrhage from the ureter it is common to find long, wormlike 

 coagula. Bladder haemorrhage is known by its numerous clots and 

 shriveled-up leucocytes. If the urine be alkaline, crystals of triple 

 phosphate will likely be found. 



In Jicemocjldbinuria, the pigments exist in solution, no corpuscles 

 being found. It is caused by the excretion of haemoglobin by the 

 kidneys when it exists as a free body in the blood-stream. Free 

 haemoglobin is due to active haemocytolysis, which is produced by the 

 injection of foreign blood, severe burns, etc. 



