154 ANTAGONISMS BETWEEN NONSPECIFIC PATHOGENS 



meningitis virus against experimental poliomyelitis (162). An intra- 

 muscular injection of a neurotropic strain of yellow fever virus was 

 found to protect animals against simultaneous infection with a highly 

 pathogenic viscerotropic strain (433). The antagonistic agent was be- 

 lieved to be a chemical substance produced by the murine virus, for 

 which the term "poliomyelitis inhibition" was proposed by Jungeblut. 

 The "interference phenomenon" of two viruses can be used to advan- 

 tage in bringing about immunity reactions. 



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 (569). 

 Other antagonistic phenomena between plant viruses have been ob- 

 served by McWhorter (573). Kunkel (510) demonstrated that the 

 peach-yellow virus prevented the invasion of the virus of little-peach 

 and that the latter prevented invasion of the former. McKinney (569) 

 concluded that virus domination in a plant may be looked upon as a 

 type of antagonism, quantitative in nature, the degree of domination 

 by a given virus being influenced by the host. 



The ability of bacterial phages to interfere with the development of 

 other phages has been studied in detail by Delbriick and Luria (167, 

 546). They have shown that a certain phage, after inactivation by ultra- 

 violet radiation, retained its ability to interfere with the growth of an- 

 other phage acting upon the same host. The partly inactivated first 

 phage is adsorbed by the sensitive bacteria and inhibits their growth 

 without producing lysis. The partly inactivated phage interferes also 

 with the growth of the active phage. This interference between bac- 

 terial phages was explained as due to competition for a "key-enzyme" 

 present in limited amount in each bacterial cell. This enzyme was also 

 believed to be essential for bacterial growth. 



BACTERIA AND TUMORS 



The ability of certain bacteria to bring about hemorrhage in tumors 

 (446, 10 10) may also be classed among the antagonistic phenomena. 

 Laszlo and Leuchtenberger (515) described a rapid test for the detec- 

 tion of tumor-growth inhibitors. Inhibition was judged by comparing 



