198 



Scientific Proceedings (76). 



Fibrin. — 5 c.c. of plasma are run into a beaker containing 

 100-150 c.c. 0.8 per cent. NaCl and 2-5 c.c. of a 2.5 per cent. 

 CaCl 2 solution. The CaCl 2 may be in amounts from 2-25 

 equivalents of the oxalate, but about five equivalents are best. 

 When coagulation is complete, the fibrin is filtered, the clot washed 

 with 0.8 per cent. NaCl, and the nitrogen determined by Kjeldahl. 

 The above is an adaptation of Howell's method for determining 

 the activity of thrombin. 1 The filtrate from the clot may be 

 tested for complete precipitation by addition of a solution con- 

 taining thromboplastic substances. 



Albumin and Globulin are calculated from the following three 

 determinations: 



Total nitrogen is determined on a 1-2 c.c. sample. 



Non-protein nitrogen is determined in the filtrate obtained 

 after precipitating the plasma with nine volumes of trichloracetic 

 acid. 



Nitrogen of Globulin Filtrate: — Globulin and fibrin are pre- 

 cipitated by adding to 5 c.c. of plasma 20 c.c. of H 2 0 and 25 c.c. 

 of saturated ammonium sulfate solution. 20 c.c. of the filtrate 

 are mixed in a Kjeldahl flask with 3 gm. MgO "Merck's Reagent" 

 and 350 c.c. of 50 per cent, alcohol. The solution is distilled until 

 the distillate gives a negative test to red litmus. This takes about 

 one hour and reduces the volume to about 20 c.c. The nitrogen, 

 representing albumin plus non-protein nitrogen, is then deter- 

 mined by Kjeldahl, using 25 c.c. H 2 S0 4 . When the digestion 

 mass becomes light brown, the sides of the flask are washed down 

 with a few c.c. of water and ten more c.c. H 2 SC>4 added. 



Calculation: 



Filtrate N — Non-protein N = Albumin N. 

 Total N— (Filtrate N + Filbrin N) = Globulin N. 



1 Am. Jour. Physiol., 1910, XXVI, 453. 



