26 I. INTRODUCTION TO VIRUSES 



mouse brain, but that it inhibited the incorporation of glucose fragment 

 into lysine and histidine, the amounts of these two amino acids being 

 reduced in the virus-infected tissues, whereas the amount of the other 

 amino acids was unchanged, suggesting that the virus multiplication 

 was intimately associated with the change in the amount of these two 

 amino acids. 



No difference in the amino acid composition was found between 

 particles of phage and its host bacterial cells (28), but it may be 

 unreasonable to conclude from this finding that they are entirely iden- 

 tical in the chemical composition, since the finding may merely show 

 that there was no chemical difference large enough to be detected by 

 ordinary chemical methods. If there exists an antigenical difference 

 at all, there should also be a chemical difference between a virus and 

 the protoplasm protein of host cells. 



The structural change of the protoplasm protein due to a virus 

 may spread in the protoplasm as a chain reaction, since the virus does 

 proliferate in the protoplasm. This chain reaction may be brought 

 about by the protein which has been changed structurally by the virus 

 and which may affect in turn, as a newly formed virus, the proto- 

 plasm protein surrounding it. 



Fischer (59) claimed that in coagulating blood a coagulating agent 

 is produced and that such an agent produced in a blood plasm can cause 

 the coagulation of another plasm in which a similar coagulating agent 

 will in turn be produced, thus the agent multiplying indefinitely. How- 

 ever, the agent cannot be detected in the blood plasm already having 

 finished the coagulation. Fischer interpreted this fact as based upon 

 the mutual saturation of the liberated active groups with the comple- 

 tion of the coagulation. It may not be impossible to regard a virus as 

 such a coagulant, by which the protoplams protein is coagulated into 

 minute particles, in which active groups capable of acting as the virus 

 liberated during the coagulation remain unchanged. 



The coagulation of blood may occur by a physico-chemical change 

 in the plasm protein. In a similar way the coagulation of protoplasm 

 protein into virus particles may be a result of the structural change by 

 the virus, and hence it may be said that minute body formation is only 

 a result of the virus multiplication, never the essential feature of the 

 virus. 



2. Similarity between Rennin and Viruses 



Many phenomena concerning viruses appear to be readily explained, 

 as we have seen above, if viruses are regarded as denaturase or trans- 



