THE COAGULATION (OF: THE BLOOD 75 
Nolfs! recent contributions can scarcely be said to simplify 
the coagulation question. Besides the salts of calcium, he 
recognises three protein bodies which are concerned in the 
formation of a clot: 
1. A protein derived from the leucocytes, termed leuco- 
thrombin. 
2. One found in the liver—hepatothrombin. 
3. Fibrinogen, which is formed by the activity of the cells of 
the same organ. 
The interaction of the first two with calcium yields fibrin- 
ferment. Thrombin arises by the formation of an envelope of 
hepatothrombin around fine particles of leucothrombin, which 
appear early in a clear, spontaneously coagulable liquid. This 
process is followed by gelatinisation of the plasma, owing to 
the further aggregation of another layer of fibrinogen upon the 
thrombin. Fibrin, therefore, originates from an agglutination 
process which becomes established in a liquid plasma which 
at first shows no morphological constituents, and the whole 
phenomenon of coagulation is to be regarded as one of aggluti- 
nation which takes place in a perfectly clear plasma which is 
originally devoid of any morphological constituents. 
1 Archiv Internat. de Phys. iv. 1906. 
