Res Medica

VIRUSES AND CANCERThe discovery of many new tumour viruses has established beyond doubt that the virus is a common cause of neoplastic disease in plants, amphibians, birds and mammals. There is as yet no experimental proof available that any one type of human cancer is induced by a virus, although it would be strange if nature were to divide so sharply the origin of cancer in animals and man. Several reports strongly suggest the presence of tumour virus in human neoplasms. These include :-(1) Electron-microscopic findings of virus-like particles in lymph nodes of patients with acute leukaemia.(2) Isolation of nucleic acids with cytopathic properties from human tumours.(3) Development of mammary tumours in mice injected at birth with extracts of a variety of human tumours; the uninoculated controls showed an insignificant tumour incidenc