THE COAGULATION OF THE BLOOD 57 
of his pupils of the Dorpat school, on the question of 
coagulation extended from 1860 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 Pagés 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.!. Although fibrinogen in hydrocele fluid? 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. 
