41 



Note in the clot of horse's blood the upper light colored 

 layer of leucocytes — the buffy coat. Coagulation is slow in 

 this animal and the red and white corpuscles on account of 

 the difference in their specific gravity have time to separate. 



193. Salted Plasma. Note that in the flask containing 

 the mixture of blood and sodium sulphate, no coagulation 

 has occurred. Place some of this fluid in the centrifuge to 

 separate the corpuscles and plasma, the latter mixed with 

 the saline solution is known as the salted plasma. 



194. Oxalate Plasma. Note also that the potassium oxa- 

 late blood mixture does not coagulate. Centrifuge the 

 mixture to obtain the plasma. The oxalate precipitates (as 

 the oxalate of lime) the calcium which is necessary for 

 coagulation. 



195. To a portion of the oxalate plasma add a few drops 

 of a 2% calcium chloride solution. Coagulation results 

 (more quickly at 40°). 



196. To another portion of the plasma add a little fibrin- 

 ferment prepared by the demonstrator. The fibrin ferment 

 is prepared as follows : Precipitate some blood serum with 

 about ten times its volume of alcohol. Let it stand for 

 several weeks, then extract the precipitate with water. The 

 water dissolves out the fibrin-ferment, but not the other 

 coagulated proteids. 



197. Add a drop of freshly prepared tincture of guaiacum 

 to a small amount of diluted defibrinated blood, and then 

 some hydrogen peroxide. The color changes to blue. This 

 is often used as a test for hemoglobin, but other substances 

 (oxygen carriers) give a blue color under the .same condi- 

 tions. 



198. Place some hydrogen peroxide over fibrin in a watch 

 glass ; bubbles of oxygen are given off. 



199. Immerse a flake of fibrin in freshl}'' prepared tincture 

 of guaiacum, (5% of pure re.sin in alcohol) and then im- 

 merse the flake in hydrogen peroxide. A blue color is 



