PATHOLOGICAL URINE 169 



glycuronic acid (C H, O 7 ) is, however, very likely to be confused with 

 sugar by Fehling's test ; the cause of its appearance is sometimes the 

 administration of drugs (chloral, camphor, &c.) ; but sometimes it appears 

 independently of drug treatment (see p. 88). 



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, 

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

 researches of Baumann and Wolkow have identified it with homogentisinic 

 acid [C fl H 3 .(OH) 3 CH,.COOH]. 



The best confirmatory tests for sugar are the phenyl-hydrazine 

 test (see Lesson XIII.), and the fermentation test (Lesson II.). 



Sir W. Roberts introduced a method for estimating sugar in urine, by the 

 diminution in specific gravity which it undergoes on fermentation with yeast. 

 Every degree lost in the specific gravity corresponds to one grain of sugar per 

 fluid ounce. Suppose that the specific gravity of the unfermented urine is 

 1040, and that of the urine which has undergone fermentation is 1030 : the 

 number of degrees lost is ten ; i.e. the urine contained 10 grains of sugar per 

 ounce. The percentage of sugar may be ascertained by multiplying the 

 degrees of specific gravity lost by 0*22 ; thus the percentage in the example 

 just given will be 0'22 x 10 = 2*2. The method, however, is rough and has 

 dropped out of use. 



BILE IN THE URINE 



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. Hay's sulphur test (p. 79) is very trust- 

 worthy. Excess of urobilin should not be mistaken for bile pigment. 



BLOOD AND BLOOD PIGMENT IN THE URINE 



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 cor- 

 puscles, and on spectroscopic examination the bands of oxyhaemo- 

 globin 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 



