The Effect of Radiation on the Growth of Vertebrae in the Tails of Rats

SummaryVertebrae in the tails of young rats have been irradiated with single doses of cyclotron neutrons under reduced (‘anoxic’), normal and increased conditions of oxygenation. Oxygen is dose-modifying with neutrons. The oxygen-enhancement ratio is 1·44 (± 0·04) for single doses given in air. The RBE of neutrons decreases with increasing dose, and it is suggested that the neutron survival curve for epiphyseal cells in situ is exponential. This is consistent with the failure to obtain a significant sparing effect by fractionation of neutron doses given to rats breathing air.