I. VIRUS PARTICLES 7 



alcohol, acetic acid, etc., or exposed to heat or ground up mechanically, 

 particles will appear in the cell, and sometimes some of them will be 

 discharged and found outside the cell-body (13). Under the microscope 

 this phenomenon appears to be just a coagulation of the protoplasm into 

 minute particles. When phage is added instead of such a chemical or 

 physical aggression, the bacterial cell may undergo a similar change 

 with the production of minute particles. Even without any particular 

 aggression, an incubation of coli-bacteria for a prolonged period may 

 lead to the production of particles inside the cell body. Since the bac- 

 teria in which particles have so appeared are not motile, they may be 

 in a dead state. At any rate, it should be borne in mind that the 

 particles produced by any other causes than phage never possess the 

 phage action and that only the particles which appear in the presence 

 of phage are provided with the action. 



Lepeschkin (13) emphasized the fact that the protoplasm, in general, 

 coagulates into minute bodies on the exposure to chemical or physical 

 agents, and that when the coagulation is still reversible, the particle 

 formation is not so distinct, but that when a stimulus sufficient to kill 

 the cells is given, the particles are vigorously formed, the total proto- 

 plasm being coagulated into minute bodies. Sometimes minute particle 

 thus formed are set free from the cells and exist in the surrounding 

 medium. According to him, such coagulation of the protoplasm of a 

 spirogyra-cell caused by a pressure of the cover-glass will spread suc- 

 cessively to another part of the protoplasm until the total is coagualted 

 into minute particles ; sometimes the coagulation will be transmitted to 

 another cell, not limited to a single cell. 



In view of these facts, the writer began to form the opinion that 

 viruses were a sort of denaturase of protoplasm protein, and that the 

 denaturation or the change in the protein structure would spread 

 successively in the protoplasm as a chain reaction, followed by the 

 coagulation of the protoplasm, and that a group or a structure concern- 

 ing the virus action would be produced on the structural change or the 

 denaturation of the protoplasm protein. As pointed out already, the 

 characteristic feature of viruses exists in the fact that they cannot 

 multiply without living cells. This fact may lead to the view that for 

 the generation of the structure capable of acting as a virus, the proto- 

 plasm protein is needed to be in a "living state". 



As stated above, virus-like particles can be obtained from normal 

 cells. This is, however, not always the case ; for example, while virus 

 particles may be readily isolated from the rabbit skin tissue affected by 

 vaccinia, the isolation is impossible from the normal skin. It is also 

 known that papilloma virus particles can be separated from the infected 

 skin tissue regardless of the failure of the isolation of similar particles 



