Papova virus group.

The papilloma, polyoma, and vacuolating agents seem to form a natural group of tumor viruses, for which the name papova virus group is proposed. Members of the group have the following properties: 45 mmicro diameter, deoxyribonucleic acid core, 42 capsomeres, absence of essential lipids, thermal resistance, slow growth cycle with multiplication within the cell nucleus, and tumorigenicity.