CHAPTER I 

 THE ORIGIN OF VIRUSES 



1. The Generation of Phage 



The possibility of the spontaneous generation of some viruses has 

 long been argued by a number of authors. Among many viruses phage 

 appears to have been discussed most frequently in connection with this 

 problem. Phage is usually found in abundance in animal feces especially 

 in those of chickens. The writer's colleague, Ohashi (1) (2), has studied 

 the origin of phage in chicken feces and has come to the conclusion 

 that the phage in chicken feces is originated from the chicken itself. 



It may appear at first sight that the phage present in the feces 

 may come from the phage taken by the chicken with food and that the 

 phage, if enters undamaged the alimentary tract, may be able to mul- 

 tiply by affecting the phage-susceptible bacteria that may thrive there 

 normally. However, it has been confirmed by Ohashi that phage experi- 

 mentally fed not only failed to multiply in the chicken tract regardless 

 of the presence of phage-susceptible bacteria thriving there, but was 

 destroyed to such an extent that only its extremely small portion could 

 be defected in the feces. The phage amount detectable in the feces 

 was only of the order of 1/1,000 to 1/10,0000 of that given by the mouth, 

 showing that almost all the phage particles, far from multiplying in 

 the tract by affecting the bacteria, had been inactivated before excreted 

 with the feces. 



Thus, the conjecture that the phage in the feces may be originated 

 from the one taken with the food does not appear to be correct, in 

 spite of the fact that in the alimentary tract phage-susceptible bacteria 

 are present abundantly. It cannot be expected that phage is continuously 

 taken by chickens with their food in so large amounts. If phage is 

 actually fed in any reasonable quantities, it will either be totally inac- 

 tivated or, if its small portion can escape the inactivation, it will never 

 reach the amount which can account for the large phage amount 

 usually found in the feces. 



In addition it was found by him that phage amount in chicken 

 feces was intimately related to the kind of diet ; thus, the feeding of 

 diet, such as wheat bran, soy-bean, greens, and rice bran, resulted in 

 phage release, while the release would cease almost totally on the 



