OCCULT BLOOD TESTS 



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scopic or chemical tests. It is in connection with blood in the faces 

 that these tests for occult blood are chiefly called for. Before making 

 such tests on faeces it is advisable to have the patient on a meat-free 

 and green-vegetable-free diet for two or three days. It is chiefly in 

 carcinoma or ulcerations of the gastro-intestinal tract that such exami- 

 nations of the faeces are required. 



Haemin Crystal Test (Teichmann). Prepare a solution of o.i gram each of KI, 

 KBr, and KCL in 100 c.c. of acetic acid. This is a stable solution. Mix some of 

 the material with a few drops of the solution on a slide, apply a cover-glass and 

 warm the material until bubbles begin to appear (gentle steaming), then examine for 

 dark-brown crystals. 



Blood in the Urine. The most rapid method of detection is by using the micro- 

 spectroscope. An ordinary hand spectroscope will answer however. 



Donogany's test is very satisfactory. To 10 c.c. of urine add i c.c. ammonium 

 sulphide solution and i c.c. of pyridin. The urine will assume a more or less deep 

 orange color according to its blood content. The spectrum of alkaline methajmo- 

 globin or haemochromogen will be obtained. See illustrations under urine. 



In making the guaiac or other tests it is a good plan to repeatedly filter the blood- 

 containing urine through the filter. Then touch a spot on the moist filter with the 

 guaiac or benzidin solution and then finally drop on this so treated spot a drop or 

 two of hydrogen peroxide solution. 



Blood in Faeces or Gastric Contents. Take 5 grams of faeces and rub it up 

 thoroughly in a mortar with 15 c.c. of a mixture of equal parts of alcohol, glacial 

 acetic acid and ether. Filter through an unmoistened pleated filter-paper re- 

 peatedly until only 3 to 4 c.c. remain of the filtrate. The fasces filtrate can be 

 first tested chemically by depositing a few drops in the center of three or four 

 circles of white filter-paper placed in a Petri dish or upon an ordinary white plate. 



Weber Guaiac Test. The moistened spot is then treated with a few drops of a 

 freshly prepared alcoholic solution of guaiac resin (about 3^ gram of guaiac resin is 

 broken up into small fragments and shaken up in about 3 c.c. of alcohol) and finally 

 there is dropped upon the spot a few drops of a solution of hydrogen peroxide. 

 Waves of blue color extending out into the moistened filter-paper show a positive 

 test for blood. 



Benzidin Test. For the benzidin test pour on this faeces filtrate-moistened filter- 

 paper a few drops of the following solution: 2 c.c. of a saturated alcoholic solution of 

 benzidin 2 c.c. of solution of peroxide of hydrogen and 2 drops of glacial acetic acid. 

 (Blue.) 



If the aloin test is preferred we treat the filtrate-moistened filter-paper with a 

 few drops of a 3% solution of aloin in 70% alcohol and then treating the spot with 

 hydrogen peroxide solution. Brick-red color. 



Phenolphthalin Test. The phenolphthalin test is an extremely delicate one and 

 will show the pink color at times with certain specimens of water, hence one should 

 always make a control using the reagents without addition of the suspected blood 

 material. 



In my opinion it has great value as a negative test. 



Take 2 c.c. of the ether alcohol acetic-acid filtrate and dilute with 7 or 8 c.c. water. 



