Abstract
Extract
Viruses which may cause benign or malignant tumours have been the subject of increasing study in recent years. Although the idea that viruses are capable of causing tumour formation has achieved general acceptance only quite recently, such possibilities have been demonstrated from time to time for many years. The first demonstration that a filterable transmissible agent could cause any form of malignant tumour was the demonstration in 1908 by Ellerman and Bang in Denmark that erythromyeloblastic leukemia in chickens could be transmitted by the inoculation of cell-free filtrates of leukemic tissues. Although these authors studied the phenomenon quite extensively, very little notice was taken of their findings because only very few people were prepared to consider the possibility of a viral causation of tumours.