ANIMAL VIRUSES 501 



able to induce the production of now infective particles iii suitable cells. T3y 

 treatment with phenol, fractions have been obtained from tissues infected 

 with Mengo-encephalitis- (Colter et al., 1957) and equine encephalomyelitis- 

 virus (Wecker and Schafer, 1957). These behaved, according to some tests, 

 like KNA and were infectious, but the stability of such fractions was rela- 

 tively low. 



The main fmiction of the virus protein components seems to be to protect 

 and stabilize the labile genetic material. Furthermore, they can be important 

 for the penetration of the virus into the host cell or for the release of new 

 virus. They can carry out these functions most efficiently by forming a coat 

 around the nucleic acid; it has been shown that this is actually the case for 

 several animal viruses. There are recent experiments that localize the sites 

 of formation of some of the virus proteins, but the mechanism of their forma- 

 tion is unknown. 



The evaluation of the chemical interactions between viruses and their host 

 cells will require a great deal of further painstaking work. In the long run, 

 this work will be more rewarding using animal viruses rather than plant or 

 bacterial viruses, since the animal cells possess a well-defined inner structure 

 and can now be easily cultured in vitro under specified conditions. 



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Beard, J. W., Sharp, D. G., and Eckert, E. A. (1955). Advances in Virus Research 3, 149. 

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