URINE 43 1 



under examination and i c.c. of 3 per cent hydrogen peroxide. In the presence 

 of blood a bluish color develops (sometimes rather slowly) and persists for some- 

 time (several hours in some instances). 



This test is said to be as sensitive for the detection of occult blood 

 in feces and stomach contents as is the benzidine reaction. It is also 

 claimed to be more satisfactory for urine than any other blood test. 

 The acetic acid solution may be kept for one month with no reduction 

 in delicacy. 



9. Benzidine Reaction. This is one 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 peformed 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. Such urines should 

 be washed with water before the test is applied to it. 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. 



9. Spectroscopic Examination. Submit the urine to a spectroscopic exami- 

 nation according to the directions given on page 296, looking especially for the 

 absorption bands of oxyhemoglobin and methemoglobin (see Absorption Spectra, 

 Plate I). 



PUS 



Pus may be present in the urine in inflammatory affections of 

 various types. Such a condition is termed pyuria. Albumin always 

 accompanies the pus. In catarrh of the bladder and in inflammation 

 of the urethra or of the pelvis of the kidney pus is particularly apt to 

 be present in the urine. If a urine of high pus concentration is voided 

 it may indicate the rupturing of an abscess in some part of the genito- 

 urinary tract. Pus may be detected by one of the procedures given 

 below. 



EXPERIMENTS 



i. Microscopical Detection of Pus. The characteristic form elements of pus are 

 leucocytes. They may occur in very small number in normal urine. Examine the 



