Abstract
Summary and Conclusions
1. Of 134 New Zealand White rabbits in 15 experiments 65 were given an injection of 1.0 to 0.0001 g of Brown-Pearce tumor tissue (no longer viable) which had been kept frozen anaerobically for 10-296 days. Viable Brown-Pearce tumor tussue was transplanted 10-21 days later into the testes of 54 and beneath the skin in 11 of the 65 animals; also inoculated at the same time were the 69 controls, 52 subcutaneously and 17 intratesticularly.
2. The experimental animals had a significantly greater incidence of and larger primary tumors, a greater incidence and volume of, and more numerous metastases and a greater mortality from the tumor in a shorter interval after inoculation than their respective controls, by both the intratesticular and subcutaneous routes.
3. This effect (XYZ factor) was not confined to the New Zealand White breed as common rabbit hybrids of average resistance to the Brown-Pearce tumor could be rendered more susceptible than even the most susceptible breeds such as the English, Sable, Flemish and Rex. Even the relatively resistant blue-cross or Lilac cross rabbit became more susceptible upon injection of the frozen tumor tissue.
4. The mechanism of the XYZ phenomenon seems to be influenced by the inactivation or masking by prolonged freezing of inhibitory factors present in the fresh tumor. The frozen material seems to act by blocking host resistance to a specific tumor.
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