THEORIES OF COAGULATION 121 



vessel, and then gradually extending throughout the mass. If a portion of 

 plasma, diluted or not, be whipped with a bundle of twigs the fibrin may 

 be obtained as a solid, stringy mass, just in the same way as from the entire 

 blood, and the resulting fluid no longer retains its power of spontaneous 

 coagulability. 



Theories of Coagulation. It is evident that the blood plasma contains 

 some substance or substances which take part in the formation of fibrin. 

 By numerous investigations it has been found that the direct antecedent of 

 the fibrin is the protein substance, fibrinogen. This fibrinogen exists in the 

 blood plasma at all times, but is somewhat increased under certain condi- 

 tions. The fibrinogen is reacted on by another substance known as thrombin 

 or by the historical term fibrin ferment. We shall not present the numerous 

 theories which have been held concerning blood coagulation, many of 

 which have been more or less disproven, but shall try to present the con- 

 Blood Tissue Cells 



Plasma Blood Plates. Corpuscles. 



Neutral Salts Fibrinogen Calcium Salts 



(for dissolving 

 fibrinogen) 



Fibrin-globulin 



\ 



Prothrombin Thrombokinase 



Thrombin 



Fibrin 

 FIG. 1 08. Marowitz' Schema of Coagulation. 



densed statement of the present explanations of this intricate phenomenon. 

 One may start from the statement that the fibrinogen of the plasma when acted 

 upon by the thrombin, also of the plasma, produces an insoluble substance, fibrin. 

 The chief interest centers around the origin and character of the fibrinogen, 

 the origin and nature of the thrombin, and the conditions which influence its 

 activity. 



The fibrinogen is present in blood plasma of the circulating blood of the 

 body at all times. It can be separated from plasma by various chemical 

 means, and when purified can be made to form fibrin under proper conditions. 

 All observers are agreed that this protein is the immediate precursor of the 

 insoluble fibrin. Its origin in the blood has been traced by Matthews with 

 some degree of certainty to the disintegration of the white blood corpuscles. 



