BLOOD AND LYMPH 271 



in. Blood Plasma 



i. Preparation of Oxalated Plasma. Allow arterial blood to run into an equal 

 volume of 0.2 per cent ammonium oxalate solution. 



2 Preparation of Fibrinogen. To 25 c.c. of oxalated plasma add an equal 

 volume of saturated sodium chloride solution. Note the precipitation of fibrino- 

 gen. Filter off the precipitate (reserve the filtrate) and test it by a protein color 



test (see page 97). 



3 Effect of Calcium Salts. Place a small amount of oxalated plasma in a 

 test-tube and add a few drops of a 2 per cent calcium chloride solution. What 

 occurs? Explain it. 



4 Preparation of Salted Plasma. Allow arterial blood to run into an equal 

 volume of a saturated solution of sodium sulphate or a 10 per cent solution of 

 sodium chloride. Keep the mixture in a cool place for about 24 hours. 



5. Effect of Dilution. Place a few drops of salted plasma in a test-tube 

 and dilute it with 10-15 volumes of water. What do you observe? Explain it. 



IV. Fibrin 



1. Preparation of Fibrin. Allow blood to flow directly from the animal into 

 a vessel and rapidly whip it by means of a bundle of twigs, a mass of strong cords, 

 or a specially constructed beater. If a pure fibrin is desired it is not best to 

 attempt to manipulate a large volume*of blood at one time. After the fibrin has 

 been collected it should be freed from any adhering blood clots and washed in 

 water to remove further traces of blood. The pure product should be very light 

 n color. It may be preserved under glycerol, dilute alcohol, or chloroform water. 



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 



7 ' 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 99. 



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 300) 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 cyanhempchromogen 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 267. 



