CH. xxxvil.] PATHOLOGICAL URINE. 569 



of drug treatment. The cause of this is not known, but the condition has 

 not the serious meaning one attaches to diabetes ; hence, for life assurance 

 purposes, it is most necessary to confirm the presence of sugar by other 

 tests. 



Then. too. in the rare condition called alcaptonuria. confusion may similarly 

 arise. Alcapton is a substance which probably originates from tyrosine by 

 an unusual form of metabolism. It gives the urine a brown tint, whicli 

 darkens on exposure to the air. It is an aromatic substance, and the recent 

 researches of Baumann and Wolkow have identified it with homogentisinic 

 acid (C 8 H s .(OH) a CH a .COOH). 



(e) The best confirmatory test for sugar is the fermentation test, which is 

 performed as follows : 



Half fill a test tube with the urine and add a little German yeast. Fill 

 up the tube with mercury ; invert it in a basin of mercury, and leave it in a 

 warm place for twenty-four hours. The sugar will undergo fermentation : 

 carbonic acid gas accumulates in the tube, and the liquid no longer gives the 

 tests for sugar, or only faintly, but gives those for alcohol instead. A 

 control experiment should be made with yeast and water in another test- 

 tube, as a small yield of carbonic acid is sometimes obtained from impurities 

 in the yeast. 



(/) The plienylliydrazine test (p. 389) may also be applied. 



Bile. This occurs in jaundice. The urine is dark-brown, 

 greenish, or in extreme cases almost black in colour. The most 

 readily applied test is Gmelin's test for the bile pigments. 

 Pettenkofer's test for the bile acids seldom succeeds in urine 

 if the test is done in the ordinary way. The best method is to 

 warm a thin film of urine and cane sugar solution in a flat 

 porcelain dish. Then dip a glass rod in strong sulphuric acid, 

 and draw it across the film. Its track is marked by a purplish 

 line. Excess of urobilin should not be mistaken for bile 

 pigment. 



Blood. When haemorrhage occurs in any part of the urinary 

 tract, blood appears in the urine. It is found in the acute stage 

 of Bright's disease. If a large quantity is present, the urine is 

 deep red. Microscopic examination then reveals the presence of 

 blood corpuscles, and on spectroscopic examination the bands of 

 oxyheemoglobin are seen. 



If only a small quantity of blood is present, the secretion 

 especially if acid has a characteristic reddish-brown colour, 

 which physicians term "smoky." 



The blood pigment may, under certain circumstances, appear 

 in the urine without the presence of any blood corpuscles at all. 

 This is produced by a disintegration of the corpuscles occurring 

 in the circulation, and the most frequent caxise of this is a disease 

 allied to ague, which is called paroxysmal hcemoglolrinuria. The 

 pigment is in the condition of methromoglobin mixed with more 

 or less oxyhremoglobin, and the spectroscope is the means used 

 for identifying these substances. 



