174 PHYSIOLOGICAL CHEMISTRY 



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 BoldyrefTs 

 theory as to the automatic regulation of gastric acidity 1 under normal 

 conditions by the regurgitation of alkaline material from the intestine, 

 then the presence of bile in the gastric juice does not possess the clinical 

 significance it has been accorded. However, if an ordinary Ewald meal 

 be fed, and bile in any considerable quantity be found throughout the 

 entire course of digestion it may indicate, pathologically, a stenosis 

 below the level of the common bile duct. Frequently samples of 

 gastric contents are encountered which are uncolored and which never- 

 theless contain bile. It is also true that bile may be adsorbed from 

 stomach contents by mucus and food rests. The regulation technic for 

 bile testing is often inadequate to demonstrate the presence of this 

 fluid in gastric contents. The following procedure based upon the 

 oxidation of the bilirubin with nitric acid forming green biliverdin is 

 delicate and easy of application. 



Procedure. Saturate 10 c.c. of the fluid portion of the stomach contents with 

 powdered ammonium sulphate. This may be accomplished by shaking for one 

 to two minutes. It generally requires about i inch of powdered sulphate in 

 the bottom of an ordinary test-tube to obtain full saturation. When the fluid is 

 saturated add 1-3 c.c. of acetone and thoroughly mix the contents of the tube by 

 inverting the tube five or six times. (It is better not to shake.) Permit 

 the tube to stand and allow the acetone to rise to the surface. This acetone con- 

 tains the bile pigment if any is present in the stomach contents. Allow a drop 



^oldyreff: Quart. Jour. Exp. Med., 8, i, 1914. 



