Abstract
Summary
1. Yolk sac implants of a dba mouse mammary tumor protected the host embryos against vaccinia virus. A dosage of the virus which killed embryos of nontumor-bearing eggs in 3-4 days gave no evidence of toxicity in the embryos bearing the dba tumor 7 days after inoculation. Tests demonstrated that the virus was present in the fluids of these embryos. 2. Comparable tests with eggs bearing a C3H mammary tumor indicated the embryos were only slightly protected against the virus, and yolk sac implants of a rat sarcoma gave negative results in this respect. 3. None of the 3 tumors affected the toxicity of a strain of influenza. 4. It is suggested that the dba tumor's protective effect on the embryos was due to the neutralization of the vaccinia virus by the tumor agent.
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