498 W. SCHAFER 



absolute amounts of nucleic acid. The smaller and some medium sized in- 

 fective particles seem to have only one molecule, but the vaccinia virus 

 contains more, if one assumes a molecular weight of '^2 X 10" for UNA 

 (Gierer, 1957) and '^ 4 X 10" for DNA (see Jordan, 1955). No mmsual 

 purine and pyrimidine bases have as yet been found in animal virus nucleic 

 acids. 



The mformation concerning the composition of protein from infective 

 particles is too scanty and uncertain to enable one to make generalizations. 



As for the lipids, it has been reported that cholesterol, phospholipids, and 

 neutral fats are found with the equine encephalomyelitis and certain larger 

 viruses, but it is not always clear which of these lipids are integral parts 

 of the particles. 



The presence of carbohydrates has been proved witli some certainty for 

 fowl plague and influenza virus, where they apparently are a part of a 

 mucoprotem. 



The same viruses and probably the other viruses of the myxovirus group 

 also possess a special enzyme with the properties of a neuraminidase. Other 

 enzymatic activities associated with vaccinia virus are suspected to come 

 from adsorbed impurities. It should be mentioned, however, that the investi- 

 gation of enzymatic activities is quite incomplete for most animal viruses. 

 The presence of flavine-adenine-dmucleotide, copper, and biotin in the infec- 

 tive particle of vaccmia suggests that this agent has its place on the border 

 between virus and higher organized biological units. 



As far as one can see from tlie results at hand, the nucleic acid of infective 

 particles seems to be locahzed generally in their interior, surrounded by 

 protein. Lipids were found to be a part of the infective particle surface, in 

 those cases where there is some evidence about their localization. The neura- 

 minidase of the myxoviruses is also situated here. 



The virus-specific products designated as S antigens are not a homo- 

 geneous group from the chemical point of view. Some are proteins, like the 

 LS antigen of vaccinia and, probably, the S antigen of poliomyelitis; others 

 are nucleoproteins, such as the S antigen of fowl plague and influenza. It is 

 noteworthy that m the latter cases there exists a close relationship between 

 the S antigen and a j)articular component enclosed m the respective infective 

 particles. This observation somewhat limits speculation concerning the 

 functions of these S antigens. It is not probable that a side product of virus 

 multiplication would exhibit such behavior. 



Our knowledge concerning the chemical composition of the hemagglutinin 

 of pox viruses and the filamentous forms of myxoviruses is still very incom- 

 plete. But there are some indications that both contain protein and lipids. 



An extremely high lipid content seems to be a characteristic of the various 

 incomplete forms of the myxoviruses. One must still ascertain whether all 



