A deoxyribonucleic acid preparation which showed infectivity and tumorigenic activity in domestic rabbits was isolated from the papillomatous tissue of wild cottontail rabbits by phenolic deproteinization procedure. The activity of the preparation could be completely abolished by its exposure to a minute amount (0.02 µg/ml) of DNAase. Antisera against Shope papilloma virus did not block the tumorigenic activity of the preparation, and trypsin and chymotrypsin had no effect on it. The extraction with phenol of a partially purified virus preparation also yielded extracts with tumorigenic potency.

Extracts obtained from the domestic rabbit papilloma and submitted to phenolic deproteinization also proved infective and tumorigenic in rabbits of this sort, although the level of "tumorigenicity" was much lower than that of the cottontail preparations. Tests for intact virus, carried out with half of the extracts yielded wholly negative findings.

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