EXAMINATION OF NORMAL AND ABNORMAL URINE. 469 



it is well to burn filter with contents in a platinum crucible, and to deduct the 

 weight of the remaining inorganic residue (less the weight of the filter ash) 

 from that of the albumin. 



Peptones may be recognized by first precipitating all albumin by 

 means of boiling the urine acidified by acetic acid, filtering, and 

 adding to the* filtrate a few drops of dilute cupric sulphate solution 

 and sodium hydroxide. Peptones will be indicated by the purple 

 color of the biuret reaction. 



Blood. The presence of blood in urine manifests itself generally, 

 unless the amount be too slight, by a blood-red or brownish color 

 with a bluish, smoky, or greenish tint, and deposits a red or reddish- 

 brown sediment after standing. As a general rule, all constituents 

 of blood, including the corpuscles, are present, but in some cases 

 haemoglobin alone has been found. 



The tests for blood depend either on the microscope or on chemical 

 changes. By the microscope is examined the deposit which forms on 

 standing ; almost unaltered blood corpuscles may be found, or they 

 may be much swollen, decolorized, and deformed ; the corpuscles are 

 generally accompanied by blood and fibrin casts. 



Whenever blood is present, there are necessarily also albuminoids, 

 which are precipitated by acidulating with acetic acid and boiling, 

 when a brownish coagulum of albumin and hsematin are precipitated. 



Haemoglobin is also tested for by means of adding to the urine a 

 few drops of freshly prepared tincture of guaiacum, a little ozonized 

 ether, and shaking well. If haemoglobin is present, the ether 

 assumes a blue color. 



Detection of sugar. The sugar found in urine is almost ex- 

 clusively glucose, C 6 H 12 O 6 . Traces of sugar, or as much as 0.01 per 

 cent., are said to occur normally in urine, and are of no significance ; 

 moreover, it is as yet doubtful whether these traces of sugar are 

 actually present in normal urine. A large amount of sugar is often 

 indicated by a high specific gravity of the urine, which then varies 

 from 1.030 to 1.050 ; the quantities found vary from mere traces to 

 10 per cent., the latter quantity, however, being a very rare occur- 

 rence, while 3 to 5 per cent, is often found in the urine of persons 

 suffering from diabetes mellitus. 



There are many tests by which sugar can be detected. They 

 depend chiefly on the following properties of sugar, viz. : 1, to act 

 as a deoxidizing or reducing agent upon certain metallic oxides 



