URINE 445 



Almen's reagent. 1 In the presence of nucleoprotein a voluminous precipitate 

 forms. 



BLOOD 



The pathological conditions in which blood occurs in the urine may 

 be classified under the two divisions hematuria and hemoglobinuria. 

 In hematuria we are able to detect not only the hemoglobin but the 

 unruptured corpuscles as well, whereas in hemoglobinuria the pig- 

 ment alone is present. Hematuria is brought about through blood 

 passing into the urine because of some lesion of the kidney or of the 

 urinary tract below the kidney. Hemoglobinuria is brought about 

 through hemolysis, i.e., the rupturing of the stroma of the erythrocyte 

 and the liberation of the hemoglobin. This may occur in scurvy, 

 typhus, pyemia, purpura, and in other diseases. It may also occur as 

 the result of a burn covering a considerable area of the body, or may 

 be brought about through the action of cerjtain poisons or by the in- 

 jection of various substances having the power of dissolving the 

 erythrocytes. Transfusion of blood may also cause hemoglobinuria. 



Even in true hematuria the erythrocytes may escape detection if 

 the urine is ammoniacal inasmuch as the cells disintegrate under these 

 conditions. 



EXPERIMENTS 



i. Benzidine Reaction. This is orue of the most delicate of the reac- 

 tions for the detection of blood. Different benzidine preparations vary 

 greatly in their sensitiveness, however. Inasmuch as benzidine solu- 

 tions change readily upon contact with light, it is essential that they 

 be kept in a dark place. 



The test is performed as follows: To a saturated solution of benzidine in 

 alcohol or glacial acetic acid add an equal volume of 3 per cent hydrogen peroxide 

 and i c.c. of the urine under examination. If the mixture is not already acid, 

 render it so with acetic acid, and note the appearance of a blue color. A 

 control test should be made substituting water for the urine. 



Often when urines containing a small amount of blood are tested by 

 this reaction, the mixture is rendered so turbid as to make it difficult to 

 decide as to the presence of a faint green color. The sensitiveness 

 of the benzidine reaction is greater when applied to aqueous solutions 

 than when applied to the urine. 



For a modification of this test and further discussion see Chapter 

 XV on Blood and Lymph. 



1 Dissolve 5 grains of tannic acid in 240 c.c. of 50 per cent alcohol and add 10 c.c. of 25 

 per cent acetic acid. 



