PHYSIOLOGICAL CHEMISTRY. 



In case the blood has been altered or is present in minute amount 

 ("occult blood"), and cannot be detected by the means just men- 

 tioned, the following tests may be tried : 



(a) Aloin-Turpentine Test. Mix the stool very thoroughly and 

 take about 5 grams of the mixture for the test. Reduce this sam- 

 ple 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 ex- 

 tract 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 al- 

 cohol 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 reel. In some instances the color will be 

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

 reaction should occur within fifteen 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 satis- 

 factory substitute for turpentine in this test. 



(b) 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 ex- 

 tract with ether. If blood is present the ether will assume a brown- 

 ish-red color. Filter off the ether extract and to a portion of the 

 filtrate, add an alcoholic solution of guaiac (strength about i : Go), 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 196). 



(c) Cozune'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 zvater, agitate 

 the mixture, introduce a few granules of powdered guaiac resin, 

 and after bringing the resin into solution, gradually add 30 droj 

 of old turpentine or hydrogen peroxide. A blue color indicates 

 the presence of blood. Cowie claims that by means of this tesl 

 an intestinal hemorrhage of i gram can easily be detected by an 

 examination of the feces. 



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

 instead of an alcoholic solution of guaiac resin. 



