title: Studies on the differentiation of variola and vaccinia viruses.
mesh_terms: D000818:Animals; D002642:Chick Embryo; D003588:Cytopathogenic Effect, Viral; D066298:In Vitro Techniques; D018139:Simplexvirus / Q000254:growth & development*; D012867:Skin / Q000473:pathology; D014616:Vaccinia virus / Q000254:growth & development*; D012901:Variola virus / Q000254:growth & development*; D014776:Virus Cultivation