132 III. THE EVOLUTION OF VIRUSES 



That the phage detectable in animal feces is not originated from 

 such lysogenic strains can be shown also in the fact that there are 

 distinct differences between the phage found in feces and that produced 

 by lysogenic strains. Feces phage is much less resistant to heat than 

 the bacteriogenic phage : for example, whereas the former is inactivated 

 to such an remarkable degree as 1/1,000 to 1/10,000 on the exposure to 

 65°C. for 5 min., the latter undergoes entirely no change even when 

 heated at this temperature for 1 hour, and 75°C. for 20 min. is neces- 

 sary for its inactivation to this degree ; with several samples Ohashi (5) 

 has found without exception this distinct difference between both groups. 

 Moreover, he has confirmed that the plaques produced by bacteriogenic 

 phage are commonly uniform in size, whereas those produced by feces 

 phage tend to vary remarkably, indicating that there are much greater 

 individual differences among feces phage particles than among bacterio- 

 genic phages. 



2. The Reason for the Phage Production from 

 Healthy Bacteria 



According to the writer's theory, a virus is an assimilase similar 

 to the protoplasm or a portion of the protoplasm. A virus can act as 

 an assimilase upon a certain cell when the cell protoplasm is weaker 

 in the assimilase action than that of the virus. A virus exists usually in 

 minute particles into which the protoplasm has been disintegrated and 

 coagulated following the infection with the parent virus. Through this 

 infection the structure of the protoplasm ' is to be so changed as to 

 become identical with that of the virus. If the structure of a particle 

 is stable enough to retain the changed protoplasm structure the particle- 

 can behave as the virus towards another cell protoplasm, thus de- 

 veloping its template action. 



This theory will naturally lead to the reasoning that normal proto- 

 plasm particles or fragments of some healthy cells must likewise be- 

 able to behave as a virus to some other cells having a weaker assimi- 

 lase action, provided the structure of the former cell protoplasm capable 

 of acting as a stronger assimilase is preserved in the fragments or 

 particles. In such a case, the healthy cells may be said to have the 

 property to produce a virus acting upon certain other cells. Lysogenic 

 bacteria above cited should be recognized as such cells. 



Thus, if certain bacteria are disintegrated into minute particles, or 

 fragments and if the original protoplasm structure is held unchanged in 

 the particles or fragments, then the latter will be able to act as a 

 phage upon certain other bacteria which have a weaker assimilase- 



