ANIMAL VIRUSES: A COMPARATIVE SURVEY O 



comparative approach to the animal viruses is the morphological and bio- 

 chemical complexity of the virus particle. Probably very few virologists 

 would dispute the legitimacy of describing vaccinia virus as a microorganism, 

 although some might regard this admission as justifying the rejection of the 

 poxvirus group as viruses at all. 



C. Herpesvirus 



It is unfortunate that the very interesting group containing the viruses of 

 herpes simplex (hominis), B (simiae), and pseudorabies (suis) has not been 

 closely studied in regard to the properties of the infective particles. It seems 

 likely to be relatively close to the poxvirus group but there is insufficient 

 evidence to justify discussion here. The same holds for another relatively large 

 virus, that of rabies. 



D. Myxovirus 



The myxovirus group includes the two classical influenza types A and B, 

 mumps virus, and a growing list of minor respiratory pathogens of man, as 

 well as two classic avian diseases, fowlplague and Newcastle disease, and 

 possibly some other avian types. There is more than a likelihood that exten- 

 sive study of domestic and wild mammals would disclose other myxoviruses. 

 It is a very interesting situation that complement-fixing antigen of influenza 

 A is known to be present in the human virus, in swine influenza virus, in 

 fowlplague virus, and in virus responsible for infection in Swedish horses 

 (Heller et al., 1956). It appears that this is a highly versatile stock. The 

 diagnostic characters of the group include the rather variable size of sjmerical 

 infective particles, around 100 m/x in diameter, and the common occurrence 

 of filamentous forms of virus. All react with mucoproteins on the surface of 

 cells and in solution under appropriate conditions and carry an enzyme 

 capable of splitting neuraminic acid or related components from the reactive 

 mucoproteins. The nucleic acid content is low and wholly RNA. 



E. Adenoviruses 



We can feel confident that within a year or two the adenoviruses will take 

 their places as one of the key groups for fundamental investigation of viral 

 function. Effective experimentation is, however, only in an early stage. The 

 group was defined in terms of the characteristic cytopathogenic effect seen in 

 tissue cultures of monkey kidney or HeLa cells, and the existence of a com- 

 plement-fixing antigen common to the group (Enders et al., 1956). Fourteen 

 serological types have been described on a basis of specific neutralization by 

 antiserum in tissue culture tests. The unique feature of the group is its pro- 

 duction of what appear to be crystalline aggregates of virus within the nucleus 

 of affected cells. 



