Increased Tolerance of Mice to Lethal X-Radiation as a Result of Previous Sublethal Exposures. ∗

Summary and Conclusion

1. It has been demonstrated with a fair degree of certainty (0.05 > P_diff > 0.02) that three weekly exposures of 144 r followed by a 30 day rest period increases the resistance of mice to a subsequent lethal dose of x-radiation.

2. It is concluded that no adequate explanation for this phenomenon of increased tolerance to x-ray radiation is available at the present time.