BIOLOGICAL CHEMISTRY 



its interlacing, gives the rigidity to the clot, and all the cells 

 of the blood are entangled in the interstices of the network. 

 As the network shrinks the liquid portion is squeezed out, 

 forming serum, and the clot shrinks with its entangled cells. 



Fibrin is formed from a protein, fibrinogen, in solution in 

 the blood. Under the influence of an enzyme called thrombin 

 the fibrinogen is converted into fibrils of insoluble fibrin. 



Fibrinogen can be prepared from the liquid portion of the 

 blood (plasma) by precipitation with sodium chloride added 

 to half saturation. The serum obtained from clotted blood 

 is plasma minus fibrinogen. 



TABLE XIII 

 Substances that affect coagulation of the blood. 



Coagulation retarded by 

 Cooling 



Oxalates, citrates, 

 fluorides .... 



Leech extract 



Excess of neutral salts 



Probable mode of action. 



Slows chemical reac- 

 tions and retards 

 destruction of 

 blood cells 



Removes calcium 

 from the active 

 system .... 



Antithrombin 



Corresponding method of 



hastening coagulation. 

 Keeping warm at 

 about 40 C. 



Calcium 

 limits. 



salts within 



Inhibits formation of 



thrombin. 

 Prevents destruction 



of blood corpuscles. 



Thrombin such as ven- 

 om of Echis cari- 

 natus. 



Contact with foreign 

 substances, e.g., stir- 

 ring with glass rods. 



Prevent blood from 

 contact with for- 

 eign substances by 

 using paraffined 

 vessels. 



Peptone injected into Probably produces an ( ? Injection of gela- 

 blood but not out- antithrombin . . tine.) 

 outside the body . 



MILK COAGULATION 

 Rennin , Caseinogen 



T 



Casein (Soluble) 



Calcium ions 

 I 



Calcium Caseate (Insoluble) 

 BLOOD COAGULATION. 



Thrombokinase 

 I 



Calcium ions 



Thrombogen 

 I 



Thrombin 



Fibrinogen 



Fibrin. 



