CHAPTER XI 

 THE SUMMARY OF PART III 



1 



Organisms may sometimes be changed in their properties when 

 acted upon by proper chemical or physical influences. The change 

 is termed mutation or variation and is probably caused by an altera- 

 tion of the protoplasm structure including genes. If an altered 

 structure thus produced is strong and retained in the protoplasm par- 

 ticles, the particles may be able to behave as a virus towards some 

 other cells having the protoplasm of a weaker structure. Special 

 case of such change involves adaptation, and the production of virus- 

 like agents in the adaptive change of microorganisms is occasionally 

 reported. 



Even protoplasm particles of normal structure, provided the struc- 

 ture is preserved in the particles, may act as a virus upon certain 

 cells having weaker protoplasm. Phage produced by some lysogenic 

 strains may be regarded as such normal particles. Similarly, phage 

 present commonly in chicken feces may be normal protoplasm particles 

 of chick cells. Many other examples can be cited showing that normal 

 protoplasm particles can behave as a virus. 



Cells affected by a virus may acquire the faculty to produce the 

 virus, even if they have not fallen into a pathological state, as a 

 result of mutation or variation due to the virus. Since the protoplasm 

 structure of a cell is to be changed into virus structure when affected 

 by a virus, the cells affected by a virus naturally produce the virus. 



If a new protoplasm structure, exhibiting assimilase action stronger 

 than that of the original structure, is produced in a cell or cells of 

 some tissues or organs the newly formed structure will spread into 

 the surrounding cells by assimilizing the protoplasm. Allergic der- 

 matitis or various tumours including cancer may occur in such a 

 way. The general failure of virus detection in these cases is presum- 

 ably due to the lability of the structure unable to be retained in 



