PHYSIOLOGICAL CHEMISTEY 447 



In any case the tests for haemoglobin can be applied. The guiac 

 test, which is very sensitive, should be applied after boiling the urine 

 to destroy oxidases. The spectroscopic examination is also very sensi- 

 tive when an adequate depth of urine is employed (see p. 344). 



Haematuria is distinguished by the smoky appearance of the urine 

 and by examination of the urine, or deposit on centrifugalising, when 

 red blood corpuscles are seen. The spectroscope nearly always shows 

 the presence of oxyhaemoglobin. Blood from the kidney is mixed 

 with the urine. That from the bladder is often present as a clot. If 

 the red corpuscles have disintegrated, the urine will present the appear- 

 ance of haemoglobinuria. If the urine is stale, methaemoglobin may 

 be present. 



In Haemoglobinuria and Methaemoglobinuria red blood corpuscles 

 are not seen, and the urine is clear, not smoky. The two conditions 

 are distinguished by the colour of the urine and by the spectroscope. 



EXPERIMENT V. Test the urine supplied for blood and haemoglobin. 



Bile in Urine. When the bile duct is blocked by a calculus, or its 

 mucous membrane is swollen from catarrh, the bile, which accumulates 

 in the bile channels, is reabsorbed into the blood-vessels and carried to 

 the tissues, which become stained with bile pigment. Under these con- 

 ditions the urine contains bile constituents, the most easily recognised 

 of which are the bile pigments. 



EXPERIMENT VI. Apply Gmelin's test (see p. 400) to the urine of a 

 jaundiced patient. Where only a small quantity of bile pigment is 

 present it is better to concentrate the pigment by proceeding as 

 follows : Add calcium chloride solution to the urine, and then sodium 

 carbonate solution, so as to form a precipitate of calcium carbonate and 

 phosphate, which carries down the pigment; filter off the precipitate 

 atfd dissolve it in as small a volume of hot dilute hydrochloric acid as 

 possible ; apply Gmelin's test to this solution. 



Also apply Matthew Hay's sulphur test for bile salts (see p. 398). 



II. Sugars in the Urine. In the disease known as diabetes mellitus, 

 the most important symptom is the presence of dextrose (or glucose) in 

 the urine, or, in other words, glycosuria. This condition can also be 

 produced experimentally: (1) By puncture of the flow of the fourth ventricle. 

 The cause of the glycosuria in this condition is an excessive conver- 

 sion of glycogen to glucose in the liver, whereby the percentage of 

 dextrose in the blood rises above the normal, the excess being excreted 

 by the kidneys. The glycosuria ceases when all the liver glycogen has 

 been used up, and it cannot be produced by a similar experiment in 

 animals which have been previously starved to remove the glycogen 

 from the liver. 



