XI. THE SUMMARY OF PART III 215 



tides, SO that the increase in the strength of virus structure will 

 follow the increase in the particle size. Since virus particles as well 

 as the protoplasm, the decomposed particles of which are virus parti- 

 cles, are presumably a kind of liquid crystals, the "crystal form" will 

 be determined by the property of the protein component, which, in 

 turn, will govern the structural pattern of the virus or of the proto- 

 plasm, and therefore the pattern of a virus producing large "crystal" 

 will be transmitted to the host protoplasm ; as a result a large sized 

 virus will reproduce a similarly large sized virus. 



For the continuity of the existence various properties similar to 

 those of organisms, including size and shape, are essential for viruses. 

 Therefore viruses mostly resembling organisms will become fitter and 

 develop up to the stage of Rickettsiae until they come to get possession 

 of the faculty to assimilize even proteins present in blood which can 

 be regarded as a streaming protoplasm. Thus the faculty of multipli- 

 cation without living cells will be obtained together with the stage 

 of undoubted organisms. 



When some protoplasm particles affect certain cells which are 

 weaker than the particles in their assimilase action, and can make 

 cells fall into pathological state, then the particles will be called 

 viruses. However, particulate assimilases may not always exhibit the 

 pathogenic action. 



The presence of virus is acknowledged only by the pathogenicity ; 

 therefore the demonstration of the non-pathogenic virus must be most 

 difficult, if not impossible. Latent viruses are usually non-pathogenic, 

 but when environmental conditions are altered the pathogenic property 

 may sometimes be revealed to prove their existence. 



When a virus is developed up to the stage of Rickettsiae, its ex- 

 istence will be readily recognized, in contrast to undeveloped viruses, 

 by its peculiar form even without pathogenicity. Thus, nonpathogenic 

 groups of Rickettsiae known are much more numerous than the patho- 

 genic ones. 



For the evolution of particulate assimilase into organisms, any 

 intensive pathogenicity may not be needed. On the contrary, in most 

 cases it may prevent the evolution, because virus may be unable to 

 find any favourable condition for their multiplication in the severely 

 injured host, and, therefore, less pathogenic viruses may become fitter. 

 From this point of view, non-pathogenic viruses existing are expected 

 to be much more numerous than pathogenic ones as in Rickettsiae, 



