FECES 235 



are required: (i) a 0.05 per cent aqueous solution of hematein; (2) a 

 40 per cent solution of sodium hydroxide and (3) 3 per cent hydrogen 

 peroxide. These will keep almost indefinitely. 



The test may be performed as follows : Take 4-5 c.c. of the liquid specimen in a 

 tube and in another tube take the same amount of material known not to contain 

 blood as a control. To each add 4-5 c.c. of the sodium hydroxide solution and 

 shake. Then to each of the tubes add 2 drops of the hematein solution. A blue 

 color of about equal intensity will develop in both tubes. Then add 10 drops of 

 hydrogen peroxide to each tube and compare. If blood is present, the tube con- 

 taming it will turn very rapidly (in three or four seconds) to violet red, then in 

 twenty seconds to clear brown, in forty seconds to pale yellow while the second 

 tube will not show these changes for several minutes. The reaction is said to 

 detect blood when present in a concentration of i part in 400,000. 



(e) A loin-turpentine Test. Mix the stool very thoroughly and take about 

 5 grams of the mixture for the test. Reduce this sample to a semi-fluid mass by 

 means of distilled water and extract very thoroughly with an equal volume of ether 

 to remove any fat which may be present. Now treat the extracted feces with one- 

 third its volume of glacial acetic acid and 10 c.c. of ether and extract very thoroughly 

 as before. The acid-ether extract will rise to the top and may be removed. 



Introduce 2-3 c.c. of this acid-ether solution into a test-tube, add an equal 

 volume of a dilute solution of aloin in 70 per cent alcohol and 2-3 c.c. of ozonized 

 turpentine and shake the tube gently. If blood is present the entire volume of fluid 

 ordinarily becomes pink and finally cherry red. In some instances the color will 

 be limited to the aloin solution which sinks to the bottom. This color reaction 

 should occur within 15 minutes in order to indicate a positive test for blood, since 

 the aloin will turn red of itself if allowed to stand for a longer period. The color is 

 ordinarily light yellow in a negative test. Hydrogen peroxide is not a satisfactory 

 substitute for turpentine in the test. 



(f) Cowie's Guaiac Test. To i gram of moist feces add 4-5 c.c. of glacial 

 acetic acid and extract the mixture with 30 c.c. of ether. To 1-2 c.c. of the extract 

 add an equal volume of water, agitate the mixture, introduce a few granules of 

 powdered guaiac resin, and after bringing the resin into solution, gradually add 

 30 drops of old turpentine or hydrogen peroxide. A blue color indicates the 

 presence of blood. Cowie claims that by means of this test an intestinal hemor- 

 rhage of i gram can easily be detected by an examination of the feces. 



(g) Weber's Guaiac Test. Mix a little feces with 30 per cent acetic acid to form 

 a fluid mass. Transfer to a test-tube and extract with ether. If blood is present 

 the ether will assume a brownish-red color. Filter off the ether extract and to a 

 portion of the filtrate add an alcoholic solution of guaiac (strength about i^o), 1 

 drop by drop, until the fluid becomes turbid. Now add hydrogen peroxide or old 

 turpentine. In the presence of blood a blue color is produced (see page 258). 



(//) Acid-hematin. Examine some of the ethereal extract from Experiment (g) 

 spectroscopically. Note the typical spectrum of acid-hematin (see Absorption 

 Spectra, Plate II). 



7. Hydrobilirubin. Schmidt's Test. Rub up a small amount of feces in a 

 mortar with a concentrated aqueous solution of mercuric chloride. Transfer to a 



1 Buckmaster advises the use of an alcoholic solution of guaiaconic acid instead of an 

 alcoholic solution of guaiac resin. 



