310 IV. THE PRINCIPLES OF LIFE PHENOMENA 



taking into account of the view presented by Fischer (152) who found 

 that the blood coagulation can be transmitted indefinitely in blood plasm. 

 He found that the addition of coagulating agent, which is- being pro- 

 duced in a coagulating blood plasm, to another plasm, leads to the 

 coagulation of the latter, in which cogulating agent in turn is produced, 

 thus the agent multiplying indefinitely in the plasm. This coagulating 

 agent, however, can be demonstrated only during the progress of 

 coagulation, and so Fischer considered that the active radicals of the 

 agent diappear by the mutual saturation with the completion of the 

 coagulation. 



It seems reasonable to consider that blood coagulation is caused 

 by a kind of denaturation of plasm proteins, thereby as was previously 

 mentioned protein molecules may unfold their polypeptide chains ; the 

 active groups of the coagulating agent may be produced by such an 

 unfolding. Since the polypeptide chains are to be refolded upon the 

 completion of denaturation with the disappearance of polar groups 

 liberated by the unfolding, also the active groups must disappear 

 with the finish of the blood coagulation. 



According to the writer's concept, denaturation of proteins is gen- 

 erally infective because of such polar groups liberated during the 

 denaturation process. The fact that the infection is particularly dis- 

 tinct in blood coagulation may suggest the presence, in the blood plasm, 

 of the mechanism by which the transmission of the denaturation is 

 readily brought about. Now, we shall consider in detail this mechanism. 



It seems a general concept that the process of the blood coagulation 

 consists of the following two phases (26) : 



r. .1- u- Thromboplastin +Ca ^, , . 



rrothrombm - - - > Thrombm. 



„., . Thrombin -^.. . 



r ibrmogen -- -^ r ibrm. 



The factor termed thromboplastin or thrombokinase is usually 

 found in blood platelets, and this factor appears to be vius-like protein 

 particles containing both RNA and phospholipids (153), presumably a 

 kind of elementary bodies of the protoplasm. When blood platelets 

 are disintegrated into such particles, the particles will combine with 

 prothrombin, a kind of serum globulin. By this combination the protein 

 is disturbed in its structure just as host cells are disturbed by the 

 combination of a virus. As a result prothrombin undergoes a denatu- 

 ration, with the unfolding of polypeptide chains and the liberation of 

 polar groups. The prothrombin affected by the thromboplastin particles 

 can combine with other prothrombin molecules through these polar 

 groups, causing the denaturation in the latter molecules and thus the 



