BLOOD AND LYMPH 269 



2. Solubility. Try the solubility of small shreds of freshly prepared fibrin 

 in water, dilute acid and alkali. 



3. Millon's Reaction. Make the test according to directions given on page 



97- 



4. Glyoxylic Acid Reaction (Hopkins-Cole). Make the test according to 

 directions given on page 98. 



5. Biuret Test. Make the test according to directions given on page 98. 



V. Detection of Blood in Stains on Cloth, Etc. 



1. Identification of Corpuscles. If the stain under examination is on cloth 

 a portion should be extracted with a few drops of glycerol or physiological (0.9 per 

 cent) sodium chloride solution. A drop of this solution should then be examined 

 under the microscope to determine if corpuscles are present. 



2. Tests on Aqueous Extract. A second portion of the stain should be 

 extracted with a small amount of water and the following tests made upon the 

 aqueous extract : 



(a) Hemochromogen. Make a small amount of the extract alkaline by 

 potassium hydroxide or sodium hydroxide, and heat until a brownish-green color 

 results. Cool and add a few drops of ammonium sulphide or Stokes' reagent 

 (see page 296) and make a spectroscopic examination. Compare the spectrum 

 with that of hemochromogen (see Absorption Spectra, Plate II). Hankin 1 has 

 suggested a test based upon the formation of cyanhemochromogen and the 

 microspectroscopical demonstration of the spectrum of this compound. 



(b) Hemin Test. Make this test upon a small drop of the aqueous extract 

 according to the directions given on page 264. 



(c) Guaiac Test. Make this test on the aqueous extract according to the 

 directions given on page 262. The guaiac solution may also be applied directly 

 to the stain without previous extraction in the f ollowing manner : Moisten the 

 stain with water, and after allowing it to stand several minutes, add an alcoholic 

 solution of guaiac (strength about i : 60) and a little hydrogen peroxide or old 

 turpentine. The customary blue color will be observed in the presence of blood. 



(d) Benzidine Reaction. Make this test according to directions given on 

 page 263. 



(e) Acid Hematin. If the stain fails to dissolve in water extract with acid 

 alcohol and examine the spectrum for absorption bands of acid hematin (see 

 Absorption Spectra, Plate II). 



1 Hankin: Brit. Med. Jour., p. 1261, 1906. 

 Sutherland and Mitra: Biochemical Journal, 8, 128, 1914. 



