“…The "venereal " wart, like the common wart, is caused by a papova virus (reviewed by Rowson and Mahy, 1967), but in contrast to the double enzyme phenotypes found in the former, Muhay and associates (1971) reported single enzyme phenotypes in six common warts from as many G-6-PD heterozygotes. Assuming that the common and "venereal " wart papova viruses are the same, the finding that the former tumors may have a unicellular origin, while the latter have a multicellular origin, suggests a significant effect of local environmental conditions such, for example, as may affect ease of viral spread) or the size of the initial innoculum on the pattern of tumorigenesis.…”