RELATIONSHIPS AMONG VIRUSES 167 



shown that even an inactivated virus, whether a homologous or a 

 heterologous strain, is capable of suppressing the development of the 

 influenza virus. 



Jungeblut and Sanders (483) suggested that poliomyelitis in ani- 

 mals may be aborted by the injection of another virus. A strong antago- 

 nism was observed between a murine virus mutant (virus passed 

 through mice for many generations) and the parent strain of the virus. 

 The murine virus was capable of counteracting large paralytic doses of 

 poliomyelitis j the two viruses virtually counterbalanced each other. 



Other types of antagonism between viruses include that of canine dis- 

 temper or lymphocytic chorio-meningitis virus against experimental 

 poliomyelitis (169). An intramuscular injection of a neurotropic strain 

 of yellow fever virus was found to protect animals against simultaneous 

 infection with a highly pathogenic viscerotropic strain (447). The an- 

 tagonistic agent was believed to be a chemical substance produced by the 

 murine virus, for which the term "poliomyelitis inhibition" was pro- 

 posed by Jungeblut. The "interference phenomenon" of two viruses 

 can be used to advantage in bringing about immunity reactions. 



The suppression of one strain of yellow fever virus by another, as 

 well as of equine encephalomyelitis virus and of influenza A by yellow 

 fever virus, belongs to the same group of phenomena. No neutralizing 

 antibodies or nonspecific antiviral substances were found in the yellow 

 fever virus (558). 



A similar type of antagonism is frequently observed also among plant 

 viruses. Yellow mosaic virus will not grow in the tobacco tissue cells al- 

 ready infected with the agent causing common mosaic disease (608). 

 Other antagonistic phenomena between plant viruses have been re- 

 ported (612). The virus of peach-yellow prevented invasion by the 

 virus of little-peach and the latter prevented invasion by the former 

 (540). The conclusion was reached (608), therefore, that virus domi- 

 nation in a plant may be looked upon as a type of antagonism, quantita- 

 tive in nature, the degree of domination by a given virus being influ- 

 enced by the host. 



Many other instances of virus antagonism have been reported, as 

 when one virus prevents the multiplication of another and actually re- 

 places it in plants in which it is established (37). Certain vitamins, such 



