THE COAGULATION OF THE BLOOD 57 



of his pupils of the Dorpat school, on the question of 

 coagulation extended from i860 to 1895. His conceptions as to 

 the nature of the process underwent modification rather than 

 destruction by other observers. Hammarsten in particular 

 showed : 



1. That all natural and artificial fluids containing fibrinogen 

 can be caused to coagulate with fibrin-ferment. 



2. That no other protein constituent of blood-plasma can be 

 considered to exert any specific action in the process of co- 

 agulation, and that where such an action is apparent it is due 

 to contamination of the substance with thrombin or fibrin- 

 ferment, since the repeated purification of any protein which 

 apparently induces a formation of fibrin abolishes this action, 

 just as a temperature of 56 to 69 destroys any ferment adhering 

 to the substance, though the substance itself is not apparently 

 physically altered. 



3. Fibrin-ferment converts fibrinogen into fibrin, a change 

 which does not occur in living blood, since the ferment appears 

 only in shed blood. In this phase of the coagulation process 

 fibrinogen passes through a stage of soluble into insoluble 

 fibrin, exactly as caseinogen passes into a soluble and then into 

 an insoluble casein — though, as will be seen subsequently, the 

 coagulation of fibrinogen-containing fluids by thrombin is in 

 no sense paralleled by the action of rennin on caseinogen, as 

 Arthus and Pages originally believed. 



4. Phases of the Coagulation Process 



Since coagulation depends on the conversion of fibrinogen 

 into fibrin in a series of steps by a ferment body which is 

 non-existent during life, the phases of coagulation must be : 



1. Formation of thrombin. 



2. Conversion of fibrinogen into fibrin where a stage of 

 soluble fibrin precedes the insoluble stage. 



The grounds for this conception of the second phase — a belief 

 that before any separation of fibrin occurs the fibrinogen suffers 

 change— depend on some remarkable observations made by 

 Hammarsten. 1 Although fibrinogen in hydrocele fluid 2 co- 



1 Quoted from Jahresb. f. Tierchemie, 1876. 

 The spontaneously non-coagulable exudation found in a pouch derived from 

 the peritoneum, which envelops the testis. 



