[The significance of CELO virus as a hatching egg contaminant with special reference to its oncogenic properties]

A group of young hamsters was injected subcutaneously in the neck region with allantoic fluid containing CELO virus. A second group received transplants of cells from tumours induced by CELO virus. Tumours developed in both groups. The latent period was shorter after transplantation than after virus inoculation. The tumours grew progressively, histologically resembling fibrosarcoma. It is recommended that hatching eggs infected with CELO virus should not be used in vaccine production.