LABORATORY MANUAL OF PHYSIOLOGY. 



plasma, giving it a transparent color. This process is known as 

 taking and the blood is said to be laked. The corpuscles will ap- 

 pear faintly outlined as ghost or shadow corpuscles. 



4. The magnesium sulphate of tube (e) prevents coagulation. 

 Let the mixture stand in a cool place until the corpuscles have set- 

 tled to the bottom of the tube. The supernatant liquid, the 

 "salted plasma," may then be pipetted or siphoned off. 



Divide this salted plasma into four portions. To each portion 

 add eight times its volume of water. To portion i add a few drops 

 of a half-per-cent solution of ammonium oxalate. To portion 2 

 add a little of the clot from tube (a). Portion 3, place in a water 

 bath heated to 38 C. Place portion 4 on a water bath heated to 

 60 C. and add a few drops of ammonium oxalate. 



Observe the presence or absence of the phenomena of coagulation 

 in the portions of salted plasma treated as above. Are calcium 

 salts necessary to coagulation ? What is the effect of tempera- 

 ture on coagulation ? Why does coagulation take place in por- 

 tion 2? 



To tubes i and 4 add a few drops of calcium chlorid. What is 

 the effect as far as coagulation is concerned ? 



There are various theories to explain the coagulation of the 

 blood. The known facts are as follows: Clotting is produced 

 through the formation of a coagulated substance, fibrin; for the 

 formation of fibrin three things are necessary: a globulin, fibrin- 

 ogen, calcium salts, and an enzyme, fibrin ferment or thrombin. 



Fibrinogen and soluble calcium salts are normally present in the 

 blood plasma. Thrombin is formed at the time of coagulation. 

 The mooted question is the origin of the thrombin. The thrombin 

 is a nucleo-proteid which seems to be formed through cell disinte- 

 gration and especially through the breaking down of leucocytes. 



5. Defibrination of Blood. To defibrinate blood, collect it 

 from a bleeding artery, in a shallow vessel. As the blood is shed, 

 whip or beat it, vigorously, with a glass rod or a bundle of twigs. 

 The fibrin, as it is formed, separates from the blood and adheres 

 to the whip as a sticky, stringy, almost colorless mass. The blood 



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