ANIMAL VIRUSES 487 



et al., 1955), it seems likely that the mucoproteiii of tlie virus particle (Ada 

 and Gottschalk, 1956) is also situated here. Owing to a lack of sufficient 

 material, it has not yet been possible to study the sugars in detail; however, 

 by the use of superimposed absorption curves, it was suggested that both 

 galactose and mannose are present in the virus-liemagglutinin of influenza 

 (Frisch-Niggemeyer and Hoyle, 1956). 



In contrast to virus-hemagglutinin the G antigen, of influenza and fowl 

 plague virus, consists of protein and RNA. The G antigen of influenza virus 

 contams 5.3 % RNA (Frisch-Niggemeyer and Hoyle, 1956; Ada, 1957) and 

 that of fowl plague virus 10-15 %, possibly corresponding to the higher 

 amount of RNA that is found in its infective particle (Zillig et al., 1955; 

 Schafer, 1957b). In both virus types the G antigen seems to carry all the 

 nucleic acid (ZiUig et al., 1955; Hoyle et al., 1954; Paucker et al., 1956). Thus 

 one should not expect any differences in the nucleic acid composition of the 

 infective particle and the G antigen. This has been demonstrated in influenza 

 virus, where the proportion of the bases in the nucleic acid of the infective 

 particle and of the G antigen are the same (Ada, 1957). 



There is some evidence concerning the locahzation of the two subunits in 

 the infective particle. The virus-hemagglutinin must be part of the surface, 

 since it possesses the biological surface characteristics of the infective particle. 

 These characteristics are the hemagglutinating and enzymatic activities, as 

 weU as the virus (V) antigen. On the other hand in highly purified prepara- 

 tions of infective particles the ribonucleoprotein antigenic component can 

 only be detected in appreciable amounts after the particles are carefully 

 disrupted. Thus, the G antigen and the RNA seem to be located in the 

 interior of the infective unit (Schafer and Zilhg, 1954; Schafer, 1957b; Lief 

 and Henle, 1956a,b). Further evidence favoring this structure has been 

 obtained by degrading the infective particle with various enzymes and 

 studying the results in the electron microscope. There is an external shell of 

 protein and an internal nucleoprotein ring having the RNA on its external 

 surface (Valentine and Isaacs, 1957a,b). 



Virus-specific products appearing along with the infective particles of influ- 

 enza and fowl plague are the S antigen, the incomplete and the filamentous forms. 



In both cases the S antigen canmot be serologically difterentiated from the 

 G antigen; in the case of fowl plague, where the S antigen has been isolated 

 in a relatively pure form, the physical properties of the two antigens were 

 also found to be similar. 



The S antigen of fowl plague was purified from extracts of infected chorio- 

 allantoic membranes (Schafer and Munlv, 1952a; Schafer et al., 1956). The first 

 step was the removal of the infective particles, as well as the incomplete and 

 filamentous forms, by adsorption onto red blood cells. This was followed by 

 precipitation of the antigen at pH 4.5, shaking with butanol and ether. 



