GASTRIC ANALYSIS 171 



4. Hopkins' Thiophene Reaction. Place about 5 c.c. of concentrated sulphuric 

 acid in a test-tube and add i drop of a saturated solution of copper sulphate. 1 

 Introduce a few drops of the gastric contents, shake the tube well, and immerse it 

 in the boiling water of a beaker-water-bath for one or two minutes. Now remove 

 .the tube, cool it under running water, add 2-3 drops of a dilute alcoholic solution 2 

 of thiophene, C4H 4 S, from a pipette, replace the tube in the beaker and carefully 

 observe any color change which may occur. Lactic acid is indicated by the ap- 

 pearance of a bright cherry-red color which forms rapidly. This color may be made 

 more or less permanent by cooling the tube as soon as the color is produced. Ex- 

 cess of thiophene produces a deep yellow or brown color with sulphuric acid. The 

 test is not wholly specific though the author claims it to be more so than Uffelmann's 

 reaction. 



(f) Detection of Occult Blood. 3 i. Ortho-tolidin Test (RuttanandHardisty). 4 

 To i c.c. of a 4 per cent glacial acetic acid solution of o-tolidin 6 in a test-tube add 

 i c.c. of the gastric juice 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. 



2. Benzidine Reaction. This is one of the most delicate of the reactions for the 

 detection of blood. Different benzidine preparations vary greatly in their sensi- 

 tiveness, however. Inasmuch as benzidine solutions change readily upon contact 

 with light it is essential that they be kept in a dark place. The test is per- 

 formed 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 gastric 

 contents 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 solution under examination. 



The sensitiveness of the benzidine reaction is greater when applied 

 to aqueous solutions than when applied to the urine. According to 

 Ascarelli the benzidine reaction serves to detect blood when present in 

 a dilution of i : 300,000. (For further discussion of this test see 

 chapter on Blood.) 



(g) Detection of Bile in Stomach Contents. If we accept BoldyrefFs 

 theory as to the automatic regulation of gastric acidity 6 under normal 



1 This is added to catalyze the oxidation which follows. 



2 About 10-20 drops in 100 c.c. af 95 per cent alcohol. 



3 These tests may be made upon the strained stomach contents or upon the solid residue. 



4 Ruttan and Hardisty: Canadian Medicine Ass'n Journal, Nov., 1912; also Biochem. 

 Bull., 2, 225, 1913. 



* NH 



CH/ \CH 3 



6 Boldyreff : Quart. Jour. Exp. Med., 8, i, 1914. 



